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Y. Tan, O. Alcazar, F. Praddaude, C. Pecher, S. W. Cousins, M. E. Marin-Castano; Angiotensin II-Induced Hypertension Deregulates Extracellular Matrix turnover in Mouse RPE. Invest. Ophthalmol. Vis. Sci. 2008;49(13):229.
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The pathogenesis of AMD remains unclear. However, some evidences have supported the notion that systemic vascular diseases, especially hypertension (HTN), is an important risk factor for AMD. We have previously shown that RPE from C57BL/6 mice expresses angiotensin II (Ang II) receptors. This study aims to determine whether elevated circulating levels of Ang II associated with hypertension (HTN) regulates expression of these receptors and extracellular matrix (ECM) proteins.
C57BL/6 female mice of 16 months were infused with Ang II for 2 or 4 weeks with or without Ang II receptor blockers. Blood pressure was recorded using the tail-cuff plethysmography method. After treatment animals were killed and the eyes microdissected to isolate RPE. Expression of Ang II receptors was examined by using RT-PCR and Western blot analysis. The intracellular concentration of calcium, [Ca2+]i, was determined by use of the fura-2 AM. Matrix metalloproteinase (MMP)-2 expression and activity were determined by Real-Time PCR, Western blot, and zymography, and type IV collagen expression and accumulation by Real-Time PCR and ELISA.
Ang II increased expression of mRNA of AT1B receptor and decreased expression of AT1A receptor whereas AT2 receptor was not affected. This AT1 receptor regulation resulted in functional receptor expression. Ang II also increased MMP-2 mRNA and MMP-2 activity. These effects were abolished in the presence of an AT1 receptor blocker. In contrast, Ang II decreased type IV collagen via both AT1 and AT2 receptor subtypes, suggesting a synergistic effect of the two receptor subtypes.
These data support the hypothesis that Ang II may exert biological function in RPE through Ang II receptors and that Ang II may cause deregulation of molecules that influence the turnover of ECM in RPE basement membrane and Bruch’s membrane, suggesting a pathogenic mechanism to explain the link between HTN and AMD.
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