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Purushottam Jha, Valeriy V. Lyzogubov, Puran S. Bora, Nalini S. Bora; Membrane Attack Complex Induces Apoptosis In Retinal Ganglion Cells In Chronic Ocular Hypertension Model. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6597.
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To investigate the role of membrane attack complex (MAC)- the final product of complement activation, in the induction of apoptosis of retinal ganglionic cells in chronic ocular hypertension model.
Intraocular pressure (IOP) was elevated in left eye of Lewis rats by laser photocoagulation (two treatments, 7 days apart) of episcleral and limbal veins. The right eye was left untreated and served as control. Lewis rats were injected with cobra venom factor (CVF, >30 units/rat, i.p.) at day 7, 14, 21, 28, 35 and 49 post-laser, to inhibit the MAC formation by depleting the complement system. These animals were sacrificed on day 49 post-laser. The control animals received similar treatment with equal volume of PBS. The retina was harvested from laser-treated eyes as well as untreated control eyes and processed for flatmounts and paraffin embedding. Flatmounts were used to stain for intracellular Ca2+ and MAC. Paraffin sections were used for immunostaining for glial fibrillary acidic protein (GFAP), MAC, caspase-3 and proteins involved in Ca2+ mediated signaling such as calcineurin, calpain, and cytochrome c.
Immunofluorescent staining demonstrated that the inhibition of MAC formation resulted in decreased GFAP staining in the retina of animals with elevated IOP. Reduced active caspase-3 staining in ganglionic cell layer was observed in the absence of MAC. Inhibition of MAC formation also resulted in reduced calcium influx and decreased level of proteins involved in Ca2+ mediated signaling pathways compared to PBS treated rats with increased IOP.
Increased MAC deposition causes excess Ca2+ entry, which leads to apoptosis of RGCs in glaucoma. Thus, pharmacologic inhibition of MAC formation may have therapeutic benefits in the patients with glaucoma.
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