Role of RhoA/MERK1/ERK1/2/iNOS signaling in ocular ischemic syndrome.

Purpose: To determine the molecular mechanisms underlying ocular ischemic syndrome (OIS). This study uses a rat model to evaluate the role of the RhoA/MEK1/ ERK1/2/iNOS pathways in response to OIS-associated oxidative and nitrosative stress, with a long-term goal of identifying therapeutic targets for OIS. Methods: Rats were randomly allocated to one of three groups: bilateral occlusion of the common carotid artery (BOCCA), sham surgery control, or unoperated control (n = 8/group). Three months after the procedure, retinas were analyzed anatomically, using immunohistochemistry and by enzyme-linked immunosorbent assay for RhoA, MEK1, ERK1, ERK2, iNOS. Retinal injury was assessed using TUNEL. Levels of superoxide dismutase (SOD) and malondialdehyde (MDA) were measured by WST-1 and TBA methods, respectively. Results: In BOCCA rats, occlusion of the bilateral common carotid artery induced degeneration of retinal ganglion cells, which was not observed in either control group. Retinal levels of RhoA, MEK1, ERK1, ERK2, iNOS, NOX2, and MDA were elevated in the BOCCA group, but not in either control group. In comparison, retinal levels of SOD were reduced in SOD animals. By immunofluorescent staining, RhoA was elevated in all retinal layers, while the increased levels of MEK, ERK1/1, and NOX were restricted to the INL, and that of ERK1/2 and NOX inner nuclear layer; iNOS elevations were observed in both the inner and outer nuclear layers. TUNEL labeling results showed that BOCCA group is higher staining than sham and control group. Conclusions: OIS elevates activity of the RhoA/MERK1/ERK1/2/iNOS pathways throughout the retina, likely reflecting a response to oxidative and nitrosative stress. Retinal thickness was reduced in BOCCA rats, reflecting a loss of retinal ganglion cells following the reduced blood flow to the eye. These results indicate that drugs that inhibit these pathways may be effective treatments for OIS. [ABSTRACT FROM AUTHOR]