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

Abstract

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 H 2 O 2 treatment on AT 1 R-mediated intracellular calcium [Ca 2+ ] 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 H 2 O 2 treatment (50-800 μM), [Ca 2+ ] i was significantly increased upon angiotensin II stimulation. Similarly ICS revealed a significant increase in degree of AT 1 R aggregation in H 2 O 2 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. © 2011 Elsevier B.V. All rights reserved.