Oxidative stress increases angiotensin receptor type I responsiveness by increasing receptor degree of aggregation using image correlation spectroscopy

Oxidative stress and hyper-functioning of angiotensin II receptor type I (AT(1)R) are commonly observed in hypertensive patients but the relationship between oxidative stress and AT(1)R function is still unclear. We investigated the effects of H2O2 treatment on A-FIR-mediated intracellular calcium [Ca2+](i); signaling and its cell surface distribution pattern in HEK cells stably expressing EGFP-tagged rat AT(1)R using image correlation spectroscopy (ICS). Following H2O2 treatment (50-800 mu M), [Ca2+](i) was significantly increased upon angiotensin II stimulation. Similarly ICS revealed a significant increase in degree of AT(1)R aggregation in H2O2 treated group during Ang II activation but no difference in cluster density compared with untreated control cells or those with N-acetyl cysteine pretreatment. Thus, oxidative stress-induced AT(1)R hyper-responsiveness can be attributed by an increase in cell surface receptor aggregation state, possibly stemming in part from oxidant-related increase receptor-receptor interactions. (C) 2011 Elsevier B.V. All rights reserved.