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M.E. Marin Castano, P. Catanuto, K.G. Csaky, S.W. Cousins; Angiotensin–II Enhances Oxidant–Induced RPE Blebbing but Prevents MMP–2 Loss . Invest. Ophthalmol. Vis. Sci. 2005;46(13):5290.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Cigarette smoking and hypertension (HTN) have been implicated in the pathogenesis of age–related macular degeneration (AMD). We postulate that a specific tar–associated oxidant in cigarette smoke, hydroquinone (HQ), in combination with HTN, might contribute to subretinal deposit formation. We have previously shown that RPE oxidant injury with HQ induces cell membrane blebbing but diminishes metalloproteinase–2 (MMP–2) activity, promoting subRPE deposit accumulation. We postulate that HTN–associated hormones like angiotensin II (Ang–II), through interactions with its two cell surface receptors (AT1 and AT2), will modify the HQ response by the induction of cell oxidases or altering the activity of MMPs. We have previously demonstrated that human and murine RPE express both angiotensin receptors and that Ang–II treatment upregulates MMP–2 and –9 activity.In this study, we sought to determine the impact of both HQ and Ang–II together. Methods: Confluent cultures of human ARPE–19 cell line in low serum conditions were incubated with 100 mM HQ for 6 hours followed by incubation without or with Ang–II alone (10–11 to 10–5 M) or in combination with a specific angiotensin receptor antagonists (AT1 or AT2) for 24 hours. In parallel experiments, ARPE–19 cells were first incubated with Ang–II alone or in combination with a specific AT1 or AT2 receptor antagonist for 24 hours followed by 100 mM HQ for 6 hours. Changes in F–actin structures were detected by immunostaining with rhodamine phalloidin. Cells were examined under a dual–channel laser scanning confocal microscope (Zeiss LSM–510). Supernatants were collected to assess MMP–2 activity. Results: RPE exposure to HQ for 6hrs induced bleb and focal aggregates formation and decreased MMP–2 activity. Ang–II alone did not induce aggregates formation, but did increase MMP–2 activity. Ang–II added after HQ prevented loss of MMP–2 activity but, paradoxically potentiated blebbing and focal aggregates. The AT1 antagonist, Candesartan, attenuated the Ang–II effect, but the AT2 antagonist, PD123319, may have enhanced the responses. Conclusions: HQ injury followed by exposure to Ang–II increased bleb and aggregates formation but prevented loss of MMP–2, and this effect can be prevented by AT1 blockade. These data indicate that the mechanisms for blebbing and dysregulated MMP expression are differentially regulated in the RPE. Also, the findings support the hypothesis that HTN–associated hormones like Ang–II may modify oxidant–mediated RPE injury responses that contribute to drusen formation in hypertensive patients with AMD.
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