Angiotensin II type 2 receptor mediates programmed cell death.

Abstract

The function of the recently discovered angiotensin II type 2 (AT2) receptor remains elusive. This receptor is expressed abundantly in fetus, but scantily in adult tissues except brain, adrenal medulla, and atretic ovary. In this study, we demonstrated that this receptor mediates programmed cell death (apoptosis). We observed this effect in PC12W cells (rat pheochromocytoma cell line) and R3T3 cells (mouse fibroblast cell line), which express abundant AT2 receptor but not AT1 receptor. The cellular mechanism appears to involve the dephosphorylation of mitogen-activated protein kinase (MAP kinase (3,4) which is abundantly expressed in fetal tissues and immature brain (5) but present only at low levels in certain adult tissues (6-8). Recently, we and others have reported that the AT2 receptor mediates anti-growth effects on vascular smooth muscle (9) and endothelial (10) cells. To examine further the mechanism of the anti-growth action of the AT2 receptor, we studied its effect on programmed cell death (apoptosis). We also elucidated the biochemical signal transduction mechanism of the AT2 receptor mediating apoptosis.We first studied PC12W cells, a subline of the PC12 rat pheochromocytoma cell line (11), which express high levels of the AT2 but not the AT1 receptor. These cells differentiate into neuronal-like cells in the presence of nerve growth factor (NGF) and provide a good model for investigating programmed neural cell death (12). Second we studied R3T3 cells, a mouse fibroblast cell line whose expression of AT2 receptor is modulated by the growth state of the cells-i.e., very low in actively growing cells but increasing markedly in the confluent, quiescent state (13). This cell line is a good model for studying the growth-regulatory function of AT2 receptor. MATERIALS AND METHODSCells and Treatment. PC12W cells were grown and underwent differentiation in Dulbecco's modified Eagle's medium (DMEM) (GIBCO) plus 10% horse serum, 5% fetal bovine serum (FBS), and NGF (10 ng/ml). R3T3 cells were maintained in DMEM plus 10% FBS.The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact. FIG. 1. Ang 1I-enhanced apoptosis in PC12W cells. Hoechst 33342(blue) stains chromatin in cells with an intact cell membrane and propidium iodide (pink) stains chromatin in cells without cell membrane integrity. After cells differentiated in medium containing 10% horse serum, 5% FBS, and NGF at 10 ng/ml for 1 week, the medium was exchanged with serum-free medium containing NGF at 1 ng/ml for 2 days. No apoptotic changes were observed in this condition (A). Morphological apoptotic changes appeared 2 days after addition of Ang 11 (0.1 ,uM), showing nuclear condensation (C), fragmentation (D), and margination (E). (X400.)Staining with Chromatin-Binding Dyes. PC12W cells were seeded into six-well plates (Falcon) at 2.0 x 105 cells per well. The chromatin binding dyes Hoechst 3334...

Dose-response efficacy of valsartan, a new angiotensin II receptor blocker

“…[5][6][7][8] These agents effectively block the RAS by competitive antagonism of the action of angiotensin II at its cellular receptor site. 5,6,7,9 The AT 1 cellular receptor site appears to mediate most of the known actions of angiotensin II, although a second receptor site exists, AT 2 , 10 which appears to play an important role in apoptosis 11 and inhibition of cell growth and fibrillar collagen metabolism. 12 Valsartan is a new orally active angiotensin II antagonist which inhibits the RAS by selectively preventing the interaction of angiotensin II at its AT 1 cellular receptor site 9,13 Previous Phase I trials with valsartan have shown it to be well tolerated in single doses ranging from 10 to 400 mg once daily.…”

Receptors and their classification: focus on angiotensin II and the AT2 receptor

“…79 Apoptosis in response to Ang II through the AT 2 receptor has been reported for R3T3 cells 79,96 and for rat ovarian granulosa cells as well. 97 In the latter cell type the AT 2 binding sites are increased under apoptotic conditions.…”

“…Additional evidence for a link of the AT 2 receptor and MAP kinase activity has been obtained from R3T3, PC12W and neuronal cells. 78,79 In these cell types, AT 2 receptor stimulation results in a decrease in MAP kinase activity. The antiproliferative character of the AT 2 receptor is reflected in the inhibition of MAP kinase activity.…”

Recombinant adeno-associated virus-mediated human kallikrein gene therapy protects against hypertensive target organ injuries through inhibiting cell apoptosis

“…As shown in our study, aortas of DOCA-salt rats, SHRs and angiotensin-infused rats exhibit apoptosis [23] . Numerous inflammatory modulators are also present in the vasculature, including reactive oxygen species [24] , NO [25] , angiotensin type 2 receptors [26] and the endothelin system [27] . The present study suggests that kallikrein/kinin regulates apoptosis in the aorta through countervailing influences on anti-apoptotic and pro-apoptotic systems.…”