Mitochondrial complex I defect induces ROS release and degeneration in trabecular meshwork cells of POAG patients: protection by antioxidants.
OBJECTIVE
There is growing evidence that oxidative stress contributes to the progression of primary open-angle glaucoma (POAG), a leading cause of irreversible blindness worldwide. The authors provide evidence that mitochondrial dysfunction is a possible mechanism for the loss of trabecular meshwork (TM) cells in persons with POAG.


METHODS
TM from patients with POAG (GTM) and age-matched subjects without disease (NTM) were obtained by standard surgical trabeculectomy. Primary TM cultures were treated with one of the following mitochondrial respiratory chain inhibitors: rotenone (ROT, complex I inhibitor), thenoyltrifluoroacetone (TTFA, complex II inhibitor), myxothiazol or antimycin A (MYX, AM-complex III inhibitors); mitochondrial permeability transition (MPT) inhibitor cyclosporine A (CsA); and antioxidants vitamin E (Vit E) or N-acetylcysteine (NAC). Mitochondrial function was determined by changes in mitochondrial membrane potential (DeltaPsim) and adenosine triphosphate (ATP) production with the fluorescent probes 5,5',6,6'-tetrachloro-1,1'3,3'-tetraethylbenzimid azolocarbocyanine iodide (JC-1) and a luciferin/luciferase-based ATP assay, respectively. Reactive oxygen species (ROS) level, determined by H(2)-DCF-DA, and cell death, measured by lactate dehydrogenase activity and Annexin V-FITC labeling, were also examined.


RESULTS
GTM cells have higher endogenous ROS levels, lower ATP levels, and decreased Delta Psi m and they are more sensitive to mitochondrial complex I inhibition than their normal counterparts. ROT induces a further increase in ROS production, the release of cytochrome c, and decreases in ATP level and Delta Psi m in GTM cells, eventually leading to apoptosis. Complex II and III inhibition had little effect on the cells. Antioxidants protect against ROT-induced death by inhibiting ROS generation and cytochrome c release.


CONCLUSIONS
The authors propose that a mitochondrial complex I defect is associated with the degeneration of TM cells in patients with POAG, and antioxidants and MPT inhibitors can reduce the progression of this condition.
He
Yuan
Y
State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
Leung
Kar Wah
KW
Zhang
Yue-Hong
YH
Duan
Shan
S
Zhong
Xiu-Feng
XF
Jiang
Ru-Zhang
RZ
Peng
Zhan
Z
Tombran-Tink
Joyce
J
Ge
Jian
J
D000111:Acetylcysteine / Q000627:therapeutic use; D000255:Adenosine Triphosphate / Q000378:metabolism; D000293:Adolescent; D000328:Adult; D017304:Annexin A5 / Q000378:metabolism; D000975:Antioxidants / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects*; D002478:Cells, Cultured; D016572:Cyclosporine / Q000627:therapeutic use; D045304:Cytochromes c / Q000378:metabolism; D042967:Electron Transport Complex I / Q000037:antagonists & inhibitors*; D005902:Glaucoma, Open-Angle / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial; D008875:Middle Aged; D033681:Mitochondrial Membrane Transport Proteins / Q000037:antagonists & inhibitors; D000083162:Mitochondrial Permeability Transition Pore; D018384:Oxidative Stress; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012402:Rotenone / Q000494:pharmacology; D014129:Trabecular Meshwork / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D014475:Uncoupling Agents / Q000494:pharmacology*; D014810:Vitamin E / Q000627:therapeutic use
D017304:Annexin A5; D000975:Antioxidants; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D017382:Reactive Oxygen Species; D014475:Uncoupling Agents; D012402:Rotenone; D014810:Vitamin E; D016572:Cyclosporine; D000255:Adenosine Triphosphate; D045304:Cytochromes c; D007770:L-Lactate Dehydrogenase; D042967:Electron Transport Complex I; D000111:Acetylcysteine