Increased isolevuglandin-modified proteins in glaucomatous astrocytes

PURPOSE: Lipid oxidation has been proposed to be a factor in the pathophysiology of glaucoma. We investigated whether elevated levels of isolevuglandin (iso[4]LGE(2)) protein adducts are associated with astrocytes derived from the glaucomatous optic nerve head. In addition, we examined whether the iso[4]LGE(2) protein adducts are altered following exposure of astrocytes to elevated pressure. METHODS: Astrocytes were isolated from rat brain cortex and human optic nerve and were subjected to pressure treatments, western blot analyses, liquid chromatography tandem mass spectrometry, and immunocytochemistry. RESULTS: Elevated levels of isolevuglandin (iso[4]LGE(2)) protein adducts were associated with astrocytes derived from the glaucomatous (n=10) optic nerve head when compared to those from controls (n=6). Astrocytes subjected to in vitro pressure treatment resulted in increased levels of iso[4]LGE(2) protein adducts. Pressure exposure and the recovery period affect iso[4]LGE(2) protein modification, and pyridoxamine was effective in decreasing the appearance of iso[4]LGE(2) protein adduct immunoreactivity when applied immediately after pressure treatment. CONCLUSIONS: These results suggest that the elevated iso[4]LGE(2) protein adduct immunoreactivity observed in glaucomatous astrocytes may be due to chronic and/or prolonged exposure to pressure, and pyridoxamine may have prophylactic utility against such oxidative protein modification.