Vestn Oftalmol. 2010 May-Jun;126(3):59-64.
Molecular mechanisms of retinal ischemia.[Article in Russian]
Neroev VV, Zueva MV, Kalamkarov GR.
Abstract
The review discusses the molecular mechanisms of retinal damage, which are associated with retinal ischemia. Ischemia is one of the key factors determining the pathophysiology of many retinal diseases, such as diabetic retinopathy, glaucoma, anterior ischemic optic neuropathy, age-related macular degeneration, retinopathy of prematurity.
Hypoxia and ischemia impair retinal neuronal energy metabolism, by launching a cascade of trigger reactions resulting in cell death.
Oxidative stress, excitotoxicity, cell acidosis, inflammation, and others mechanisms acting in tandem are of considerable importance in ischemia.
Neuronal apoptosis and neovascularization are the most important sequels of ischemia.
Among all retinal neurons, ganglion cells are most susceptible to ischemia, which determines their early structural and functional changes in many ischemia-associated retinal diseases.
The molecular mechanisms underlying the pathophysiology of ischemia-associated retinal diseases should be understood to substantiate and develop new therapy modalities.
PMID:20608206[PubMed – indexed for MEDLINE]

Prog Retin Eye Res. 2007 Nov;26(6):674-87. Epub 2007 Oct 10.
Dinucleoside polyphosphates in the eye: from physiology to therapeutics.
Guzmán-Aranguez A, Crooke A, Peral A, Hoyle CH, Pintor J.
Source
Departamento de Bioquímica, E.U. de Optica, Universidad Complutense de Madrid (UCM), C/Arcos de Jalón s/n, 28037 Madrid, Spain.
Abstract
Diadenosine polyphosphates are a family of dinucleotides with emerging biochemical, physiological, pharmacological and therapeutic properties in the eye and other tissues.
These compounds are formed by two adenosine moieties linked by their ribose 5′-ends to a variable number of phosphates.
Diadenosine polyphosphates are present as active components of ocular secretions such as tears and aqueous humour and they can activate P2 purinergic receptors present on the ocular surface, anterior segment and retina. Both metabotropic and ionotropic actions mediated by P2Y and P2X receptors, respectively are responsible for the control of processes such as induction of tear secretion, lysozyme production or acceleration of corneal wound healing.
Inside the eye the dinucleotide Ap(4)A can reduce intraocular pressure by acting on P2Y(1) receptors present in trabecular meshwork cells and on P2X(2) receptors present on the cholinergic terminals located in the ciliary muscle.
In the retina, derivatives of diadenosine polyphosphates can improve the re-absorption of fluids in retinal detachment.
Altogether, diadenosine polyphosphates are not only dinucleotides with roles in the physiology of the eye but it is also possible that their properties may serve to help in the treatment of some ocular pathologies.
PMID:17931952[PubMed – indexed for MEDLINE]

J Pharmacol Exp Ther. 2005 Dec;315(3):1036-45. Epub 2005 Sep 6.
The glucocorticoid triamcinolone acetonide inhibits osmotic swelling of retinal glial cells via stimulation of endogenous adenosine signaling.
Uckermann O, Kutzera F, Wolf A, Pannicke T, Reichenbach A, Wiedemann P, Wolf S, Bringmann A.
Source
Paul Flechsig Institute of Brain Research, University of Leipzig, Liebigstrasse 10-14, D-04103 Leipzig, Germany.
Abstract
The glucocorticoid triamcinolone acetonide is clinically used for the treatment of macular edema. However, the edema-resolving mechanisms of triamcinolone are incompletely understood.
Since cell swelling is a central cause of cytotoxic edema in the brain and retina, we determined the effects of triamcinolone acetonide on the swelling of retinal ganglion and Müller glial cells in acutely isolated retinas from rats and guinea pigs in situ. Triamcinolone acetonide (100 microM) had no effect on the swelling of ganglion cells that was evoked in isolated whole mounts of the guinea pig retina by acute application of glutamate (1 mM) or high K+ (50 mM). However, triamcinolone reversed the osmotic swelling of Müller glial cells in retinas of the rat that was observed under various experimental conditions: in retinas isolated at 3 days after transient retinal ischemia, in retinas of eyes with lipopolysaccharide-induced ocular inflammation, and in control retinas in the presence of Ba2+ (1 mM), H2O2 (200 microM), arachidonic acid (10 microM), or prostaglandin E2 (30 nM).
The inhibiting effect of triamcinolone on osmotic glial cell swelling was mediated by stimulation of transporter-mediated release of endogenous adenosine and subsequent A1 receptor activation, resulting in an elevation of the intracellular cAMP level and activation of the protein kinase A, and, finally, in an opening of extrusion pathways for K+ and Cl- ions.
The inhibitory effect on the cytotoxic swelling of glial cells may contribute to the fast edema-resolving effect of vitreal triamcinolone observed in human patients.
PMID:16144977[PubMed – indexed for MEDLINE]

Exp Eye Res. 2008 Oct;87(4):385-93.
Purinergic receptor activation inhibits osmotic glial cell swelling in the diabetic rat retina.
Wurm A, Iandiev I, Hollborn M, Wiedemann P, Reichenbach A, Zimmermann H, Bringmann A, Pannicke T.
Source
Paul Flechsig Institute of Brain Research, University of Leipzig, Jahnallee 59, 04109 Leipzig, Germany. antje.wurm@medizin.uni-leipzig.de
Abstract
The anti-inflammatory glucocorticoid, triamcinolone acetonide, is used clinically for the rapid resolution of diabetic macular edema. Osmotic swelling of glial cells may contribute to the development of retinal edema. Triamcinolone inhibits the swelling of retinal glial cells of diabetic rats. Here, we determined whether the effect of triamcinolone is mediated by a receptor-dependent mechanism. Hyperglycemia was induced in rats with streptozotocin injection. After 6-10 months, the swelling properties of glial cells in retinal slices upon hypotonic challenge were determined. Nucleotide-degrading ecto-enzymes were immunostained in retinal slices and glial cells. Hypotonic challenge did not change the size of glial cell bodies from control retinas but induced swelling of cells from diabetic animals. Triamcinolone inhibited glial cell swelling; this effect was prevented by a selective antagonist of adenosine A1 receptors, an inhibitor of nucleoside transporters, inhibitors of adenylyl cyclase and protein kinase A activation, and inhibitors of potassium and chloride channels. In diabetic (but not control) retinas, the effect of triamcinolone apparently involves extracellular nucleotide degradation. Glial cells from diabetic retinas displayed immunolabeling against nucleoside triphosphate diphosphohydrolase-1 (NTPDase1) which was not observed in control retinas. The mRNA expression for NTPDase1 was significantly increased in the retina of diabetic rats. It is suggested that triamcinolone induces the release and formation of endogenous adenosine that subsequently activates A1 receptors resulting in ion efflux through potassium and chloride channels and prevention of osmotic swelling.
Whereas adenosine is liberated via facilitated transport in control retinas, an extracellular formation of adenosine contributes to the effect of triamcinolone in diabetic retinas.
PMID:18687327[PubMed – indexed for MEDLINE]

Klin Oczna. 2009;111(4-6):168-73.
Role of oxidative mechanisms in the pathogenesis of age-related macular degeneration.
[Article in Polish]
Janik-Papis K, Ulińska M, Krzyzanowska A, Stoczyńska E, Borucka AI, Woźniak K, Małgorzata Z, Szaflik JP, Blasiak J.
Source
Z Katedry Genetyki Molekularnej Uniwersytetu Łodzkiego.
Abstract
Oxidative stress is a major factor in the pathogenesis of age-related macular degeneration (AMD). Retinal pigment epithelial (RPE) cells are prone to reactive oxygen species (ROS) arising during the stress due to intense oxygen metabolism and a high oxygen pressure. Additionally, the cells can be exposed to ROS as a consequence of accumulation of iron ions in these cells, sunlight exposure and tobacco smoke. There are several defense systems against RTF in the cell, including antioxidant enzymes, low-molecular weight antioxidants and DNA repair pathways. RPE cells display phagocytic activity towards outer segments of photoreceptors and this activity can be associated with additional oxidative stress since the segments are rich in long chain, polyunsaturated fatty acids (PUFA). The oxidation of PUFA leads to the production of additional ROS. Moreover, oxidized PUFA are not correctly cleaved in the lysosomes of RPE and are accumulated in the form of lipofuscin, which is deposited in Bruch’s membrane in the form of drusen and in this way it stimulates immune responses, including phagocytosis, associated with the recruiting of macrophages and dendritic cells. In this time, RPE cells are exposed to ROS, produced in oxygen burst associated with phagocytosis. Further studies, both clinical/epidemiological and in vitro, are needed to better understand relationship between AMD and oxidative stress.
PMID:19673452[PubMed – indexed for MEDLINE]

Mol Med Rep. 2013 Jun;7(6):1723-5.
Targeting the A3 adenosine receptor for glaucoma treatment (review).
Fishman P, Cohen S, Bar-Yehuda S.
Source
Can-Fite BioPharma, Petach-Tikva 49170, Israel. pnina@canfite.co.il
Abstract
Glaucoma is a worldwide disease and the second leading cause of blindness. Current treatments are associated with a number of side-effects and poor compliance, due to the requirement for treatment administration several times a day. These treatments typically aim to lower intraocular pressure (IOP); however, they are unable to protect retinal ganglion cells (RGCs) from undergoing apoptosis, which is the main cause of vision loss.
A3 adenosine receptor (A3AR) agonists have been found to protect normal cells from undergoing apoptosis via the downregulation of death signals.
Furthermore, A3AR agonists have been reported to have several ophthalmological effects, including the prevention of ganglion cell apoptosis in vitro and in vivo and anti‑inflammatory effects in experimental models of autoimmune uveitis.
CF101, an orally bioavailable A3AR agonist, has been analyzed in dry eye syndrome phase II clinical trials and was identified to be safe and well tolerated. The anti‑inflammatory effect of CF101 was shown to significantly improve corneal staining, tear meniscus and tear break‑up time in dry eye patients. In addition, CF101 was found to decrease IOP in patients. The safety and efficacy of CF101, together with its suitability for oral administration, indicates that it has potential as a candidate drug for the treatment of glaucoma.
PMID:23563604[PubMed – in process]

Am J Pathol. 2011 May;178(5):2136-45.
A(2A) adenosine receptor (A(2A)AR) as a therapeutic target in diabetic retinopathy.
Ibrahim AS, El-Shishtawy MM, Zhang W, Caldwell RB, Liou GI.
Source
Department of Ophthalmology, Medical College of Georgia, Augusta, Georgia, USA.
Abstract
In diabetic retinopathy (DR), abnormalities in vascular and neuronal function are closely related to the local production of inflammatory mediators whose potential source is microglia.
A(₂A) adenosine receptor (A(₂A)AR) has been shown to possess anti-inflammatory properties that have not been studied in DR.
Here, we evaluate the role of A(₂A)AR and its underlying signaling in retinal complications associated with diabetes. Initial studies in wild-type mice revealed that the treatment with the A(₂A)AR agonist resulted in marked decreases in hyperglycemia-induced retinal cell death and tumor necrosis factor (TNF)-α release. To further assess the role of A(₂A)AR in DR, we studied the effects of A(₂A)AR ablation on diabetes-induced retinal abnormalities. Diabetic A(₂A)AR(-/-) mice had significantly more terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive cells, TNF-α release, and intercellular adhesion molecule-1 expression compared with diabetic wild-type mice. To explore a potential mechanism by which A(₂A)AR signaling regulates inflammation in DR, we performed additional studies using microglial cells treated with Amadori-glycated albumin, a risk factor in diabetic disorders. The results showed that activation of A(₂A)AR attenuated Amadori-glycated albumin-induced TNF-α release in a cAMP/exchange protein directly activated by cAMP-dependent mechanism and significantly repressed the inflammatory cascade, C-Raf/extracellular signal-regulated kinase (ERK), in activated microglia. Collectively, this work provides pharmacological and genetic evidence for A(₂A)AR signaling as a control point of cell death in DR and suggests that the retinal protective effect of A(2A)AR is mediated by abrogating the inflammatory response that occurs in microglia via interaction with C-Raf/ERK pathway.
Copyright © 2011 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.
PMID:  21514428  [PubMed – in process]   PMCID: PMC3081155

Brain Res. 2010 Feb 26;1316:129-38. Epub 2009 Dec 23.
High glucose enhances intracellular Ca2+ responses triggered by purinergic stimulation in
retinal neurons and microglia.
Pereira Tde O, da Costa GN, Santiago AR, Ambrósio AF, dos Santos PF.
Source
Center for Neuroscience and Cell Biology, Faculty of Sciences and Technology University of Coimbra, Portugal.
Abstract
Activation of purinergic P2 receptors, which are expressed in neurons and microglial cells, normally induces an increase in intracellular calcium concentration ([Ca(2+)](i)) and some of the inflammatory mediators and excitatory neurotransmitters found to be implicated in neuronal cell death observed in diabetic retinas are released in response to an increase in the [Ca(2+)](i). However, it is unknown whether hyperglycemia/high glucose has an effect in the [Ca(2+)](i) changes triggered by the activation of P2 receptors in retinal cells.
Using single-cell calcium imaging studies, we found that [Ca(2+)](i) changes triggered by purinergic receptors activation, both in retinal neurons and microglial cells, were potentiated in cells that had been cultured in high glucose conditions. In retinal neurons the increase in [Ca(2+)](i) was mostly due to Ca(2+) influx through voltage sensitive calcium channels, whereas in microglial cells Ca(2+) influx occurred mainly through P2X receptor channels, while there was also a smaller component of [Ca(2+)](i) rise dependent on calcium release from intracellular stores, probably due to P2Y receptor activation. In conclusion, our results show that rat retinal neural cells cultured in high glucose conditions show increased calcium responses to P2 receptors activation.
This augmented calcium response might account for the increase in the release of neurotransmitters and inflammatory mediators found in diabetic retinas and, therefore, be responsible for retinal cell death observed in the early stages of diabetic retinopathy.
(c) 2009 Elsevier B.V. All rights reserved.
PMID:20034478[PubMed – indexed for MEDLINE]

Trans Am Ophthalmol Soc. 1998;96:881-923.
Acquired mitochondrial impairment as a cause of optic nerve disease.
Sadun A.Source
Doheny Eye Institute, Department of Ophthalmology, University of Southern California School of Medicine, Los Angeles, USA.
Abstract
BACKGROUND:
Blindness from an optic neuropathy recently occurred as an epidemic affecting 50,000 patients in Cuba (CEON) and had clinical features reminiscent of both tobacco-alcohol amblyopia (TAA) and Leber’s hereditary optic neuropathy (Leber’s; LHON). Selective damage to the papillomacular bundle was characteristic, and many patients also developed a peripheral neuropathy. Identified risk factors included vitamin deficiencies as well as exposure to methanol and cyanide. In all 3 syndromes, there is evidence that singular or combined insults to mitochondrial oxidative phosphorylation are associated with a clinically characteristic optic neuropathy.
PURPOSE:
First, to test the hypothesis that a common pathophysiologic mechanism involving impairment of mitochondria function and, consequently, axonal transport underlies both genetic optic nerve diseases such as Leber’s and acquired toxic and nutritional deficiency optic neuropathies. According to this hypothesis, ATP depletion below a certain threshold leads to a blockage of orthograde axonal transport of mitochondria, which, in turn, leads to total ATP depletion and subsequent cell death. Second, to address several related questions, including (1) How does impaired energy production lead to optic neuropathy, particularly since it seems to relatively spare other metabolically active tissues, such as liver and heart? (2) Within the nervous system, why is the optic nerve, and most particularly the papillomacular bundle, so highly sensitive? Although there have been previous publications on the clinical features of the Cuban epidemic of blindness, the present hypothesis and the subsequent questions have not been previously addressed.
METHODS:
Patients in Cuba with epidemic optic neuropathy were personally evaluated through a comprehensive neuro-ophthalmologic examination. In addition, serum, lymphocytes for DNA analysis, cerebrospinal fluid (CSF), sural nerves, and eyes with attached optic nerves were obtained from Cuban patients, as well as from Leber’s patients, for study. Finally, we developed an animal model to match the low serum folic acid and high serum formate levels found in the CEON patients, by administering to rats low doses of methanol after several months of a folic acid-deficient diet. Optic nerves and other tissues obtained from these rats were analyzed and compared with those from the Cuban patients.
RESULTS:
Patients from the Cuban epidemic of optic neuropathy with clinical evidence of a selective loss of the papillomacular bundle did much better once their nutritional status was corrected and exposure to toxins ceased. Patients with CEON often demonstrated low levels of folic acid and high levels of formate in their blood. Histopathologic studies demonstrated losses of the longest fibers (in the sural nerve) and those of smallest caliber (papillomacular bundle) in the optic nerve, with intra-axonal accumulations just anterior to the lamina cribrosa. Our animal model duplicated the serologic changes (low folic acid, high formate) as well as these histopathologic changes. Furthermore, ultrastructural examination of rat tissues demonstrated mitochondrial changes that further matched those seen on ultrastructural examination of tissues from patients with Leber’s.
CONCLUSION:
Mitochondria can be impaired either genetically (as in Leber’s) or through acquired insults (such as nutritional or toxic factors). Either may challenge energy production in all cells of the body. While this challenge may be met through certain compensatory mechanisms (such as in the size, shape, or number of the mitochondria), there exists in neurons a threshold which, once passed, leads to catastrophic changes.
This threshold may be that point at which mitochondrial derangement leads to such ATP depletion that axonal transport is compromised, and decreased mitochondrial transport results in even further ATP depletion.
Neurons are singularly dependent on the axonal transport of mitochondria.
PMID:10360310[PubMed – indexed for MEDLINE] PMCID: PMC1298416

Biochim Biophys Acta. 2009 May;1787(5):518-28.
Retinal ganglion cell neurodegeneration in mitochondrial inherited disorders.
Carelli V, La Morgia C, Valentino ML, Barboni P, Ross-Cisneros FN, Sadun AA.
Source
Department of Neurological Sciences, University of Bologna, Via Ugo Foscolo 7, 40123, Bologna, Italy. valerio.carelli@unibo.it
Abstract
Since the early days of mitochondrial medicine, it has been clear that optic atrophy is a very common and sometimes the singular pathological feature in mitochondrial disorders.
The first point mutation of mitochondrial DNA (mtDNA) associated with the maternally inherited blinding disorder, Leber’s hereditary optic neuropathy (LHON), was recognized in 1988.
In 2000, the other blinding disorder, dominant optic atrophy (DOA) Kjer type, was found associated with mutations in the nuclear gene OPA1 that encodes a mitochondrial protein. Besides these two non-syndromic optic neuropathies, optic atrophy is a prominent feature in many other neurodegenerative diseases that are now recognized as due to primary mitochondrial dysfunction. We will consider mtDNA based syndromes such as LHON/dystonia/Mitochondrial Encephalomyopahty Lactic Acidosis Stroke-like (MELAS)/Leigh overlapping syndrome, or nuclear based diseases such as Friedreich ataxia (mutations in FXN gene), deafness-dystonia-optic atrophy (Mohr-Tranebjerg) syndrome (mutations in TIMM8A), complicated hereditary spastic paraplegia (mutations in SPG7), DOA “plus” syndromes (mutations in OPA1), Charcot-Marie-Tooth type 2A (CMT2A) with optic atrophy or hereditary motor and sensory neuropathy type VI (HMSN VI) (mutations in MFN2), and Costeff syndrome and DOA with cataract (mutations in OPA3). Thus, genetic errors in both nuclear and mitochondrial genomes often lead to retinal ganglion cell death, a specific target for mitochondrial mediated neurodegeneration. Many mechanisms have been studied and proposed as the bases for the pathogenesis of mitochondrial optic neuropathies including bioenergetic failure, oxidative stress, glutamate toxicity, abnormal mitochondrial dynamics and axonal transport, and susceptibility to apoptosis.
PMID:19268652[PubMed – indexed for MEDLINE]

Prog Retin Eye Res. 2004 Jan;23(1):53-89.
Mitochondrial dysfunction as a cause of optic neuropathies.
Carelli V, Ross-Cisneros FN, Sadun AA.
Source
Doheny Eye Institute and Department of Ophthalmology, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA. carelli@neuro.unibo.it
Abstract
Mitochondria are increasingly recognized as central players in the life and death of cells and especially of neurons.
The energy-dependence of retinal ganglion cells (RGC) and their axons, which form the optic nerve, is singularly skewed. In fact, while mitochondria are very abundant in the initial, unmyelinated part of the axons anterior to the lamina cribrosa, their number suddenly decreases as the myelin sheath begins more posteriorly. The vascular system also presents different blood-brain barrier properties anterior and posterior to the lamina, possibly reflecting the different metabolic needs of the optic nerve head (unmyelinated) and of the retrobulbar optic nerve (myelinated). Mitochondrial biogenesis occurs within the cellular somata of RGC in the retina. It needs the coordinated interaction of nuclear and mitochondrial genomes. Mitochondria are then transported down the axons and distributed where they are needed. These locations are along the unmyelinated portion of the nerve, under the nodes of Ranvier in the retrobulbar nerve, and at the synaptic terminals. Efficient transportation of mitochondria depends on multiple factors, including their own energy production, the integrity of the cytoskeleton and its protein components (tubulin, etc.), and adequate myelination of the axons. Any dysfunction of these systems may be of pathological relevance for optic neuropathies with primary or secondary involvement of mitochondria. Leber’s hereditary optic neuropathy (LHON) is the paradigm of mitochondrial optic neuropathies where a primary role for mitochondrial dysfunction is certified by maternal inheritance and association with specific mutations in the mitochondrial DNA (mtDNA). Clinical phenocopies of this pathology are represented by the wide array of optic neuropathies associated with vitamin depletion, toxic exposures, alcohol and tobacco abuse, and use of certain drugs. Moreover, the recent identification of mutations in the nuclear gene OPA1 as the causative factor in dominant optic atrophy (DOA, Kjer’s type) brought the unexpected finding that this gene encodes for a mitochondrial protein, suggesting that DOA and LHON may be linked by similar pathogenesis. Polymorphisms in this very same gene may be associated with normal tension glaucoma (NTG), which might be considered a genetically determined optic neuropathy that again shows similarities with both LHON and DOA. Exciting new developments come from first examples of mitochondrial optic neuropathies in animal models that are genetically determined or are the result of ingenious engineering of mitochondrial gene expression, or from biochemical manipulations of the respiratory complexes. Even more exciting is the first successful attempt to correct the LHON-related complex I dysfunction by the allotopic nuclear expression of the recoded mitochondrial gene. There is hope that the genetic complexities, biochemical dysfunctions, and integrated anatomical-physiological cellular relationships will soon be precisely delineated and that promising therapeutic and prophylactic strategies will be proposed.
PMID:14766317[PubMed – indexed for MEDLINE]

Invest Ophthalmol Vis Sci. 2010 Jun;51(6):3291-9.
Reduced nitro-oxidative stress and neural cell death suggests a protective role for microglial cells in TNFalpha-/- mice in ischemic retinopathy.
Stevenson L, Matesanz N, Colhoun L, Edgar K, Devine A, Gardiner TA, McDonald DM.
Source Centre for Vision and Vascular Sciences, Queen’s University Belfast, Belfast, Northern Ireland, United Kingdom.
Abstract  PURPOSE:
Neovascularization occurs in response to tissue ischemia and growth factor stimulation.
In ischemic retinopathies, however, new vessels fail to restore the hypoxic tissue; instead, they infiltrate the transparent vitreous. In a model of oxygen-induced retinopathy (OIR), TNFalpha and iNOS, upregulated in response to tissue ischemia, are cytotoxic and inhibit vascular repair. The aim of this study was to investigate the mechanism for this effect.
METHODS:
Wild-type C57/BL6 (WT) and TNFalpha(-/-) mice were subjected to OIR by exposure to 75% oxygen (postnatal days 7-12). The retinas were removed during the hypoxic phase of the model. Retinal cell death was determined by TUNEL staining, and the microglial cells were quantified after Z-series capture with a confocal microscope. In situ peroxynitrite and superoxide were measured by using the fluorescent dyes DCF and DHE. iNOS, nitrotyrosine, and arginase were analyzed by real-time PCR, Western blot analysis, and activity determined by radiolabeled arginine conversion. Astrocyte coverage was examined after GFAP immunostaining.
RESULTS:
The TNFalpha(-/-) animals displayed a significant reduction in TUNEL-positive apoptotic cells in the inner nuclear layer of the avascular retina compared with that in the WT control mice. The reduction coincided with enhanced astrocytic survival and an increase in microglial cells actively engaged in phagocytosing apoptotic debris that displayed low ROS, RNS, and NO production and high arginase activity.
CONCLUSIONS:
Collectively, the results suggest that improved vascular recovery in the absence of TNFalpha is associated with enhanced astrocyte survival and that both phenomena are dependent on preservation of microglial cells that display an anti-inflammatory phenotype during the early ischemic phase of OIR.
PMID:20107169[PubMed – indexed for MEDLINE] PMCID: PMC2891480

Invest Ophthalmol Vis Sci. 2007 Jan;48(1):361-7.
Retinal ischemia and reperfusion causes capillary degeneration: similarities to diabetes.
Zheng L, Gong B, Hatala DA, Kern TS.
Source
Department of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA.
Abstract
PURPOSE:
Retinal neurons and vasculature interact with each other under normal conditions, and occlusion
of the retinal vasculature can result in damage to retinal neurons.
Whether damage to the neural retina will damage the vasculature, however, is less clear. This study was conducted to explore the relationship between vascular and nonvascular cells of the retina. The response of the retinal vasculature to an injury (ischemia and reperfusion; I/R) that is known to cause neuronal degeneration was studied.
METHODS:
I/R injury to the retinas was induced in Lewis rats and C57BL/6J mice by elevating intraocular pressure (IOP), and reperfusion was established immediately afterward. Some rats were pretreated with aminoguanidine (AMG, 50 mg/Kg BW in drinking water) before the procedure. Poly(ADP-ribose) polymerase (PARP) activity and expression of inducible nitric oxide synthase (iNOS), and cycloxygenase-2 (COX-2) were measured by Western blot analysis, and levels of TNF-alpha and intercellular adhesion molecule (ICAM)-1 mRNA were measured by qPCR at 2 and 7 days after the procedure. Also at 2 and 7 days after the I/R injury, apoptosis of retinal neural cells (demonstrated by TUNEL assay), density of cells in the ganglion cell layer, and thickness of retinas were quantitated, and the number of TUNEL-positive capillary cells and degenerated capillaries were assessed. Retinal neurodegeneration and capillary degeneration were also examined in C57BL/6J mice 2, 5, 8, and 14 days after I/R injury.
RESULTS:
As expected, loss of cells in the retinal ganglion cell layer was apparent 2 days after I/R injury in the rat and mouse models. In contrast, the retinal vasculature had essentially no pathology at this time in either model. Surprisingly, the number of degenerated capillaries increased greatly by 7 to 8 days after the injury. Administration of aminoguanidine significantly inhibited the I/R-induced capillary degeneration as well as neurodegeneration in the rat model. Retinal I/R caused increased PARP activity (detected by poly(ADP-ribosy)lated proteins), as well as upregulation of iNOS, COX-2, TNF-alpha, and ICAM-1 levels in rats, consistent with an inflammatory process.
CONCLUSIONS:
Capillary degeneration is an unrecognized component of acutely elevated IOP and develops only after neurodegeneration is severe. Thus, this finding raises the possibility that damage to the neural retina contributes to capillary degeneration. Aminoguanidine, a nonspecific inhibitor of iNOS, inhibited I/R-induced degeneration of both neuronal and vascular cells of the retina. The model of retinal ischemia and reperfusion will be a useful tool for investigating the relationship between neuronal damage and vascular damage in glaucoma and other diseases such as diabetic retinopathy.
PMID:17197555[PubMed – indexed for MEDLINE]

Nihon Ganka Gakkai Zasshi. 1999 Dec;103(12):910-22.
[In vivo evaluation of leukocyte dynamics in the retinal and choroidal circulation].
[Article in Japanese]
Ogura Y.
Source
Department of Ophthalmology, Nagoya City University Medical School, Japan.
Abstract
We have developed a new method to visualize leukocytes and evaluate their kinetics in the chorioretinal microcirculation of the living eyes. Nuclear staining dyes and a scanning laser ophthalmoscope were used to image leukocytes in the fundus. Acridine orange was used to visualize leukocytes in the retinal microcirculation. For imaging leukocytes in the choroid, indocyanine green was injected intravenously. Dynamics of leukocytes in the capillaries of the retina and choroid were quantitatively estimated in monkeys and rats. This method also allowed evaluation of leukocyte-endothelial interactions, such as rolling or firm adhesion, in vivo. Acridine orange leukocyte fluography was used to study leukocyte dynamics in the following experimentally induced microcirculatory disturbances of the retina: 1) interferon-associated retinopathy, 2) ischemia-reperfusion injury of the retina, and 3) experimental diabetes mellitus. 1) Interferon-associated retinopathy Systemic administration of interferon alpha enhanced leukocyte-endothelial interactions in the retina, which resulted in leukocyte rolling and entrapment in the retinal capillary beds. Leukocyte accumulation was also detected in the lung. The entrapment or accumulation of leukocytes in the microcirculation was inhibited by simultaneous administration of corticosteroids or other agents. These results suggested that leukocytes play a major role in the development of adverse effects of interferon, such as retinopathy or interstitial pneumonia. 2) Ischemia-reperfusion injury of the retina During reperfusion period after transient (60 min) retinal ischemia by optic nerve ligation, the rolling of leukocytes in the retinal veins was prominent and numerous leukocytes were trapped in the retinal capillaries. The number of rolling leukocytes was at a maximum 12 hours after reperfusion. Leukocyte entrapment peaked at 24 hours after reperfusion. By blocking adhesion molecules on the vascular endothelium, these leukocyte-endothelial interactions were effectively inhibited. Postischemic retinal atrophy was also inhibited by blocking adhesion molecules. These results suggested that leukocytes may be major players in the pathophysiology of ischemia reperfusion injury of the retina. 3) Experimental diabetes mellitus Leukocyte dynamics in the retina were studied in streptozotocin-induced diabetes and spontaneous diabetes (OLETF rats). In both diabetic models, leukocyte entrapment in the retinal capillaries was increased even in the early stages of diabetes.
Fluorescein angiography revealed that trapped leukocytes disturbed the regional capillary blood flow in the downstream. Enhanced expression of adhesion molecules was observed in the capillary endothelium of the retina in the diabetic rats.
Leukocyte entrapment in the retinal capillaries might cause microvascular occlusions and dysfunction, in turn causing diabetic retinopathy.
PMID:10643293[PubMed – indexed for MEDLINE

Circ Res. 2007 Mar 16;100(5):703-11. Epub 2007 Feb 9.
Diabetes downregulates large-conductance Ca2+-activated potassium beta 1 channel subunit in retinal arteriolar smooth muscle.
McGahon MK, Dash DP, Arora A, Wall N, Dawicki J, Simpson DA, Scholfield CN, McGeown JG, Curtis TM.
Source
Centre for Vision Sciences, School of Biomedical Sciences, The Queen’s University of Belfast, Institute of Clinical Sciences, The Royal Victoria Hospital, Grosvenor Road, Belfast BT12 6BA, Northern Ireland.
Abstract
Retinal vasoconstriction and reduced retinal blood flow precede the onset of diabetic retinopathy. The pathophysiological mechanisms that underlie increased retinal arteriolar tone during diabetes remain unclear. Normally, local Ca(2+) release events (Ca(2+)-sparks), trigger the activation of large-conductance Ca(2+)-activated K(+)(BK)-channels which hyperpolarize and relax vascular smooth muscle cells, thereby causing vasodilatation. In the present study, we examined BK channel function in retinal vascular smooth muscle cells from streptozotocin-induced diabetic rats. The BK channel inhibitor, Penitrem A, constricted nondiabetic retinal arterioles (pressurized to 70mmHg) by 28%. The BK current evoked by caffeine was dramatically reduced in retinal arterioles from diabetic animals even though caffeine-evoked [Ca(2+)](i) release was unaffected. Spontaneous BK currents were smaller in diabetic cells, but the amplitude of Ca(2+)-sparks was larger. The amplitudes of BK currents elicited by depolarizing voltage steps were similar in control and diabetic arterioles and mRNA expression of the pore-forming BKalpha subunit was unchanged. The Ca(2+)-sensitivity of single BK channels from diabetic retinal vascular smooth muscle cells was markedly reduced. The BKbeta1 subunit confers Ca(2+)-sensitivity to BK channel complexes and both transcript and protein levels for BKbeta1 were appreciably lower in diabetic retinal arterioles. The mean open times and the sensitivity of BK channels to tamoxifen were decreased in diabetic cells, consistent with a downregulation of BKbeta1 subunits. The potency of blockade by Pen A was lower for BK channels from diabetic animals. Thus, changes in the molecular composition of BK channels could account for retinal hypoperfusion in early diabetes, an idea having wider implications for the pathogenesis of diabetic hypertension.
PMID:17293477[PubMed – indexed for MEDLINE]  PMCID: PMC2596350

CNS Neurol Disord Drug Targets. 2011 Feb 1;10(1):44-56.
Ion channels on microglia: therapeutic targets for neuroprotection.
Skaper SD.
Source
Department of Pharmacology and Anesthesiology, University of Padova, Largo “E. Meneghetti” 2, 35131 Padova, Italy. Stephen.skaper@unipd.it
Abstract
Under pathological conditions microglia (resident CNS immune cells) become activated, and produce reactive oxygen and nitrogen species and pro-inflammatory cytokines: molecules that can contribute to axon demyelination and neuron death.
Because some microglia functions can exacerbate CNS disorders, including stroke, traumatic brain injury, progressive neurodegenerative disorders such as Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis, and multiple sclerosis, and several retinal diseases, controlling their activation might ameliorate immune-mediated CNS disorders.
A growing body of evidence now points to ion channels on microglia as contributing to the above neuropathologies. For example, the ATP-gated P2X7 purinergic receptor cation channel is up-regulated around amyloid β-peptide plaques in transgenic mouse models of Alzheimer’s disease and co-localizes to microglia and astrocytes. Upregulation of the P2X7 receptor subtype on microglia occurs also following spinal cord injury and after ischemia in the cerebral cortex of rats, while P2X7 receptor-like immunoreactivity is increased in activated microglial cells of multiple sclerosis and amyotrophic lateral sclerosis spinal cord.
Utilizing neuron/microglia co-cultures as an in vitro model for neuroinflammation, P2X7 receptor activation on microglia appears necessary for microglial cell-mediated injury of neurons.
A second example can be found in the chloride intracellular channel 1 (CLIC1), whose expression is related to macrophage activation, undergoes translocation from the cytosol to the plasma membrane (activation) of microglia exposed to amyloid β-peptide, and participates in amyloid β-peptide-induced neurotoxicity through the generation of reactive oxygen species. A final example is the small-conductance Ca2+/calmodulin-activated K+ channel KCNN4/KCa3.1/SK4/IK1, which is highly expressed in rat microglia. Lipopolysaccharide-activated microglia are capable of killing adjacent neurons in co-culture, and show markedly reduced toxicity when treated with an inhibitor of KCa3.1 channels. Moreover, blocking KCa3.1 channels mitigated the neurotoxicity of amyloid β-peptide-stimulated microglia. Excessive microglial cell activation and production of potentially neurotoxic molecules, mediated by ion channels, may thus constitute viable targets for the discovery and development of neurodegenerative disease therapeutics. This chapter will review recent data that reflect the prevailing approaches targeting neuroinflammation as a pathophysiological process contributing to the onset or progression of neurodegenerative diseases, with a focus on microglial ion channels and their neuroprotective potential.
PMID:21143139[PubMed – indexed for MEDLINE]

J Glaucoma. 2009 Feb;18(2):93-100.
Mitochondrial dysfunction and glaucoma.
Kong GY, Van Bergen NJ, Trounce IA, Crowston JG.
Source
Centre for Eye Research Australia, University of Melbourne and Royal Victorian Eye and Ear Hospital, Australia.
Abstract
Glaucoma is increasingly recognized as a neurodegenerative disorder, characterized by the accelerated loss of retinal ganglion cells (RGCs) and their axons. Open angle glaucoma prevalence and incidence increase exponentially with increasing age, yet the pathophysiology underlying increasing age as a risk factor for glaucoma is not well understood.
Accumulating evidence points to age-related mitochondrial dysfunction playing a key role in the etiology of other neurodegenerative disorders including amyotrophic lateral sclerosis, Alzheimer and Parkinson disease.
The 2 major functions of mitochondria are the generation of ATP through oxidative phosphorylation and the regulation of cell death by apoptosis.
This review details evidence to support our hypothesis that age-associated mitochondrial dysfunction renders RGCs susceptible to glaucomatous injury by reducing the energy available for repair processes and predisposing RGCs to apoptosis. Eliciting the role of mitochondria in glaucoma pathogenesis may uncover novel therapeutic targets for protecting the optic nerve and preventing vision loss in glaucoma.
PMID:19225343[PubMed – indexed for MEDLINE

Am J Pathol. 2011 May;178(5):2136-45.
A(₂A) adenosine receptor (A(₂A)AR) as a therapeutic target in diabetic retinopathy.
Ibrahim AS, El-Shishtawy MM, Zhang W, Caldwell RB, Liou GI.
Source
Department of Ophthalmology, Medical College of Georgia, Augusta, Georgia, USA.
Abstract
In diabetic retinopathy (DR), abnormalities in vascular and neuronal function are closely related to the local production of inflammatory mediators whose potential source is microglia.
A(₂A) adenosine receptor (A(₂A)AR) has been shown to possess anti-inflammatory properties that have not been studied in DR.
Here, we evaluate the role of A(₂A)AR and its underlying signaling in retinal complications associated with diabetes. Initial studies in wild-type mice revealed that the treatment with the A(₂A)AR agonist resulted in marked decreases in hyperglycemia-induced retinal cell death and tumor necrosis factor (TNF)-α release. To further assess the role of A(₂A)AR in DR, we studied the effects of A(₂A)AR ablation on diabetes-induced retinal abnormalities. Diabetic A(₂A)AR(-/-) mice had significantly more terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive cells, TNF-α release, and intercellular adhesion molecule-1 expression compared with diabetic wild-type mice. To explore a potential mechanism by which A(₂A)AR signaling regulates inflammation in DR, we performed additional studies using microglial cells treated with Amadori-glycated albumin, a risk factor in diabetic disorders. The results showed that activation of A(₂A)AR attenuated Amadori-glycated albumin-induced TNF-α release in a cAMP/exchange protein directly activated by cAMP-dependent mechanism and significantly repressed the inflammatory cascade, C-Raf/extracellular signal-regulated kinase (ERK), in activated microglia. Collectively, this work provides pharmacological and genetic evidence for A(₂A)AR signaling as a control point of cell death in DR and suggests that the retinal protective effect of A(2A)AR is mediated by abrogating the inflammatory response that occurs in microglia via interaction with C-Raf/ERK pathway.
Copyright © 2011 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved. PMID: 21514428 [PubMed – indexed for MEDLINE]  PMCID: PMC3081155 [Available on 2012/5/1]

Antioxid Redox Signal. 2005 Nov-Dec;7(11-12):1581-87.
Diabetic retinopathy: mitochondrial dysfunction and retinal capillary cell death.
Kowluru RA.
Source
Kresge Eye Institute, Wayne State University, Detroit, MI 48201, USA. rkowluru@med.wayne.edu
Abstract
Oxidative stress is increased in the retina in diabetes; the levels of oxidatively modified DNA and nitrosylated proteins are elevated, and antioxidant defense enzymes are impaired.
The levels of superoxides are elevated in the retina, and the mitochondria become dysfunctional with proapoptotic protein, Bax, translocating from the cytosol into the mitochondria, and cytochrome c leaking out from the mitochondria. This is accompanied by increased retinal capillary cell apoptosis, and the formation of acellular capillaries and pericyte ghosts, the early signs of retinopathy in animal models of diabetic retinopathy. Inhibition of superoxides inhibits glucose -induced mitochondrial dysfunction, activation of caspase-3, and cell death in retinal capillary cells. In animal models, long-term administration of lipoic acid or other antioxidants inhibits the development of diabetic retinopathy via inhibition of accumulation of oxidatively modified DNA and nitrotyrosine and capillary cell apoptosis in the retina. Understanding the role of mitochondria in the development of retinopathy in diabetes should help identify therapies that can neutralize superoxides and inhibit their dysfunction and, ultimately, the development of retinopathy.
Antioxid. Redox Signal. 7, 1581-1587.
PMID:16356121[PubMed – indexed for MEDLINE]

Neurosci Bull. 2009 Feb;25(1):27-32.
Therapeutic potential of extracellular ATP and P2 receptors in nervous system diseases.
Tu J, Wang LP.
Source
Research Center for Neural Engineering, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518067, China. tujie79@yahoo.com.
Abstract
Extracellular adenosine 5 inch-triphosphate (ATP) is a key signaling molecule present in the central nervous system (CNS), and now is receiving greater attention due to its role as a messenger in the CNS during different physiological and pathological events. ATP is released into the extracellular space through vesicular exocytosis or from damaged and dying cells. Once in the extracellular environment, ATP binds to the specific receptors termed P2, which mediate ATP effects and are present broadly in both neurons and glial cells. There are P2X, the ligand-gated ionotropic receptors, possessing low affinity for ATP and responsible for fast excitatory neurotransmission, and P2Y, the metabotropic G-protein-coupled receptors, possessing high affinity for ATP. Since massive extracellular release of ATP often occurs after stress, brain ischemia and trauma, the extracellular ATP is considered relating to or involving in the pathological processes of many nervous system diseases. Conversely, the trophic functions have also been extensively described for the extracellular ATP. Therefore, extracellular ATP plays a very complex role in the CNS and its binding to P2 receptors can be related to toxic and/or beneficial effects. In this review, we described the extracellular ATP acting via P2 receptors as a potent therapeutic target for treatment of nervous system diseases.
PMID:19190686[PubMed – indexed for MEDLINE

Invest Ophthalmol Vis Sci. 2003 Mar;44(3):1088-96.
Optic neuropathy induced by reductions in mitochondrial superoxide dismutase.
Qi X, Lewin AS, Hauswirth WW, Guy J.
Source
Department of Ophthalmology, Center for Vision Science, University of Florida, College of Medicine, Gainesville, Florida32610-0284, USA.
Abstract
PURPOSE:
Reactive oxygen species (ROS) are suspected to play a pivotal role in the pathogenesis of Leber hereditary optic neuropathy (LHON), caused by mutated complex I subunit genes. It seems surprising that optic neuropathy has not been described in animals with a knockout of genes encoding critical anti-ROS defenses. If ROS have a role in the optic nerve injury of LHON, then increasing mitochondrial levels of ROS should induce optic neuropathy.
METHODS:
To develop an animal model system for study of oxidative injury to the optic nerve, mitochondrial defenses were decreased against ROS by designing hammerhead ribozymes to degrade SOD2 mRNA. Several potential ribozymes were analyzed in vitro. The one with the best kinetic characteristics was cloned into a recombinant adeno-associated virus (rAAV) vector for delivery and testing in cells and animals. The effects of the AAV-expressing ribozyme on murine cell growth, SOD2 mRNA and protein, cellular ROS levels, and apoptosis were evaluated by RNase protection assay, immunoblot analysis, and ROS- and apoptosis-activated fluorescent probes. The rAAV-ribozyme was then injected into the eyes of DBA/1J mice, and the effect on the optic nerve was evaluated by ocular histopathologic examination.
RESULTS:
The AAV-expressing ribozyme decreased SOD2 mRNA and protein levels by as much as 85%, increased cellular superoxide, reduced mitochondrial membrane potential, and culminated in the death of infected cell lines by apoptosis without significantly altering complex I and III activity, somewhat spared in the most common LHON mutation (G11778A), although adenosine triphosphate (ATP) synthesis is markedly reduced. When inoculated into the eyes of mice, the AAV-expressing ribozyme led to loss of axons and myelin in the optic nerve and ganglion cells in the retina, the hallmarks of optic nerves examined at autopsy of patients with LHON.
CONCLUSIONS:
The striking similarity of the optic neuropathy to the histopathology of LHON is powerful evidence supporting ROS as a key factor in the pathogenesis of LHON.
PMID:12601034[PubMed – indexed for MEDLINE]

Invest Ophthalmol Vis Sci. 2007 Feb;48(2):681-91.
Suppression of mitochondrial oxidative stress provides long-term neuroprotection in experimental optic neuritis.
Qi X, Lewin AS, Sun L, Hauswirth WW, Guy J.
Source
Department of Ophthalmology, University of Florida, College of Medicine, Gainesville, FL 32610-0284, USA.
Abstract
PURPOSE:
Axonal loss is thought to contribute to the persistence of visual loss in optic neuritis and multiple sclerosis (MS).
The mechanisms of injury are poorly understood. The authors investigated the contribution of mitochondrial oxidative stress and the effects of modulating mitochondrial antioxidant gene expression in the optic nerves of mice induced with experimental allergic encephalomyelitis (EAE), with a focus on long-term neuroprotection.
METHODS:
Optic nerves from mice with EAE were probed for reactive oxygen species (ROS) with the use of dichlorofluorescein diacetate (DCFDA), dihydroethidium, and cerium chloride. To modulate mitochondrial oxidative stress, recombinant AAV containing the human SOD2 gene or a ribozyme targeting murine SOD2 was injected into the vitreous. Control eyes received the recombinant virus without a therapeutic gene. Mice were sensitized for EAE and were monitored by serial contrast-enhanced MRI. The effects of SOD2 modulation on the EAE optic nerve were gauged by computerized analysis of optic nerve volume, myelin fiber area, and retinal ganglion cell loss at 1, 3, and 12 months after sensitization for EAE.
RESULTS:
ROS were detected in the EAE optic nerve as early as 3 days after antigenic sensitization. Colocalization suggested mitochondria as the source of ROS activity in the absence of inflammation. The ribozyme suppressing SOD2 gene expression increased myelin fiber injury by 27%. Increasing SOD2 levels twofold in the optic nerve by virally mediated gene transfer ameliorated myelin fiber injury by 51% and RGC loss fourfold, limiting it to 7% in EAE at 1 year.
CONCLUSIONS:
Amelioration of mitochondrial oxidative stress by SOD2 gene delivery may be a therapeutic strategy for suppressing neurodegeneration in optic neuritis.
PMID:17251466[PubMed – indexed for MEDLINE]

Prog Retin Eye Res. 2004 Jan;23(1):53-89.
Mitochondrial dysfunction as a cause of optic neuropathies.
Carelli V, Ross-Cisneros FN, Sadun AA.
Source
Doheny Eye Institute and Department of Ophthalmology, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA. carelli@neuro.unibo.it
Abstract
Mitochondria are increasingly recognized as central players in the life and death of cells and especially of neurons.
The energy-dependence of retinal ganglion cells (RGC) and their axons, which form the optic nerve, is singularly skewed. In fact, while mitochondria are very abundant in the initial, unmyelinated part of the axons anterior to the lamina cribrosa, their number suddenly decreases as the myelin sheath begins more posteriorly. The vascular system also presents different blood-brain barrier properties anterior and posterior to the lamina, possibly reflecting the different metabolic needs of the optic nerve head (unmyelinated) and of the retrobulbar optic nerve (myelinated). Mitochondrial biogenesis occurs within the cellular somata of RGC in the retina. It needs the coordinated interaction of nuclear and mitochondrial genomes. Mitochondria are then transported down the axons and distributed where they are needed. These locations are along the unmyelinated portion of the nerve, under the nodes of Ranvier in the retrobulbar nerve, and at the synaptic terminals. Efficient transportation of mitochondria depends on multiple factors, including their own energy production, the integrity of the cytoskeleton and its protein components (tubulin, etc.), and adequate myelination of the axons. Any dysfunction of these systems may be of pathological relevance for optic neuropathies with primary or secondary involvement of mitochondria. Leber’s hereditary optic neuropathy (LHON) is the paradigm of mitochondrial optic neuropathies where a primary role for mitochondrial dysfunction is certified by maternal inheritance and association with specific mutations in the mitochondrial DNA (mtDNA). Clinical phenocopies of this pathology are represented by the wide array of optic neuropathies associated with vitamin depletion, toxic exposures, alcohol and tobacco abuse, and use of certain drugs. Moreover, the recent identification of mutations in the nuclear gene OPA1 as the causative factor in dominant optic atrophy (DOA, Kjer’s type) brought the unexpected finding that this gene encodes for a mitochondrial protein, suggesting that DOA and LHON may be linked by similar pathogenesis. Polymorphisms in this very same gene may be associated with normal tension glaucoma (NTG), which might be considered a genetically determined optic neuropathy that again shows similarities with both LHON and DOA. Exciting new developments come from first examples of mitochondrial optic neuropathies in animal models that are genetically determined or are the result of ingenious engineering of mitochondrial gene expression, or from biochemical manipulations of the respiratory complexes. Even more exciting is the first successful attempt to correct the LHON-related complex I dysfunction by the allotopic nuclear expression of the recoded mitochondrial gene. There is hope that the genetic complexities, biochemical dysfunctions, and integrated anatomical-physiological cellular relationships will soon be precisely delineated and that promising therapeutic and prophylactic strategies will be proposed.
PMID:14766317[PubMed – indexed for MEDLINE