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M.A. Reinoso, D.G. Espinosa–Heidmann, P. Catanuto, M.E. Marin–Castano, I.J. Suner, K.G. Csaky, S.W. Cousins; Periocular Injection of the Cigarette Smoke–Related Oxidant, Hydroquinone (HQ), Induces Nonlethal RPE Blebbing and subRPE Deposits in vivo . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3016. doi: https://doi.org/.
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Purpose: Age–related macular degeneration (AMD) is characterized by the accumulation of specific subRPE deposits. Cigarette smoking is associated with AMD, and HQ is an abundant oxidant associated with smoke. We have previously demonstrated that mice chronically exposed to cigarette smoke or to oral HQ develop subRPE deposits consistent with early AMD. Also, we have shown that incubation of cultured RPE with HQ induces a specific injury response called nonlethal blebbing, a process that we propose is related to deposit formation in AMD. Nonlethal blebbing is characterized by the formation of cytoplasmic actin aggregates and extrusion of cell membrane vesicles, but without programmed cell death. We sought to determine if direct ocular exposure to HQ could induce features of nonlethal blebbing in vivo. Methods: C57BL/6 mice were injected subconjunctivally with PBS or with various concentrations of HQ, then were enucleated for examination 1 to 72 hrs later. RPE flatmounts were stained with phalloidin to evaluate actin cytoskeleton and actin aggregates by confocal microscopy. Transmission electron microscopy (TEM) was performed to evaluate the RPE for blebs and subRPE deposits. Results: PBS injected mice demonstrated normal RPE morphology and cortical actin cytoskeleton at all times. Occasional cells revealed stress fibers. In contrast, HQ injected eyes demonstrated significant induction of stress fibers with abundant actin cytoplasmic aggregates within 6 hours, similar to the time course observed for similar changes in vitro. At 6 hrs, TEM revealed many vesicular structures along the basal and basal lateral surface of the RPE. Homogeneous subRPE deposits accumulated in many eyes, consistent with early basal laminar deposits. After 72 hours, most of the changes disappeared and the RPE resumed normal morphology. Conclusions: Acute local ocular exposure to HQ induces transient nonlethal bleb injury and subRPE deposits in vivo similar to the responses observed in vitro. Oxidant–induced RPE blebbing may be a general mechanism for drusen formation in AMD.
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