Abstract P115: Oxidized Ldl Potentiates Angiotensin Ii-induced gαQ Activation Through The At1-lox1 Receptor Complex In Kidney Cells

Introduction: In this study, we performed cell experiments to investigate how the co-treatment of oxLDL and AII activates AT1 particularly by focusing on Gαq-dependent pathway. Methods: We used CHO-cells stably transfected with AT1 (CHO-AT1), LOX-1 and AT1 (CHO-LOX-1-AT1) and two rat kidney cells (NRK49F and NRK52E). Activation of Gαq and the subsequent induction of Ca influx were quantified by accumulation of IP1 and Fura-2 AM assay, respectively. We also assessed protein expression of αSMA as a molecular marker of epithelial mesanchymal transition (EMT) after 3 days of the indicated stimulation in NRK49F and NRK52E.The proliferative activity was measured using BrdU assay in NRK49F. Results: The activation of Gαq was not observed by oxLDL treatment alone but was enhanced by the co-treatment of oxLDL and AII compared to AII alone in CHO-LOX-1-AT1 but not in CHO-AT1. Ca influx was induced not by oxLDL alone but by the co-treatment of oxLDL and a low concentration of AII that was insufficient to induce Ca influx when treated alone in CHO-LOX-1-AT1. We also found that the activation of Gαq and the induction of Ca influx were detected by the co-treatment of oxLDL and AII but not by single treatment in rat kidney cells. These phenomenons were inhibited by ARB, a Gq inhibitor or the siRNA knockdown of AT1 or LOX-1. Furthermore, the EMT was induced only by the combination treatment compared to the single treatment. These phenomenons were inhibited either by ARB or the Gq inhibitor. The combination treatment enhanced the proliferative activity of kidney fibroblasts compared with single treatment, that was inhibited by ARB, the Gq inhibitor or the siRNA knockdown of AT1 or LOX-1.. Conclusions: These findings suggest the synergistic role of the AT1-LOX-1 interaction whereby oxLDL potentiates Ang II-induced Gαq signaling, leading to the enhancement of renal injury-associated cellular response.