H2O2 Stimulation of the Cl−/HCO3− Exchanger by Angiotensin II and Angiotensin II Type 1 Receptor Distribution in Membrane Microdomains

摘要

The present study tested the hypothesis that angiotensin II (Ang II)–induced oxidative stress and Ang II–stimulated Cl⁻/HCO3⁻ exchanger are increased and related to the differential membrane Ang II type 1 (AT1) receptor and reduced nicotinamide-adenine dinucleotide phosphate oxidase expression in immortalized renal proximal tubular epithelial (PTE) cells from the spontaneously hypertensive rat (SHR) relative to its normotensive control (Wistar Kyoto rat [WKY]). The exposure of cells to Ang II increased Cl⁻/HCO3⁻ exchanger activity with EC50s of 0.10 and 12.2 nmol/L in SHR and WKY PTE cells, respectively. SHR PTE cells were found to overexpress nicotinamide-adenine dinucleotide phosphate oxidase 2 and 4 and were endowed with an enhanced ability to generate H2O2. The reduced nicotinamide-adenine dinucleotide phosphate oxidase inhibitor apocynin reduced the production of H2O2 in SHR PTE cells and abolished their hypersensitivity to Ang II. The expression of the glycosylated form of the AT1 receptor in both lipid and nonlipid rafts were higher in SHR cells than in WKY PTE cells. Pretreatment with apocynin reduced the abundance of AT1 receptors in both microdomains, mainly the glycosylated form of the AT1 receptor in lipid rafts, in SHR cells but not in WKY PTE cells. In conclusion, differences between WKY and SHR PTE cells in their sensitivity to Ang II correlate with the higher H2O2 generation that provokes an enhanced expression of glycosylated and nonglycosylated AT1 receptor forms in lipid rafts.