2′-AMP and 3′-AMP Inhibit Proliferation of Preglomerular Vascular Smooth Muscle Cells and Glomerular Mesangial Cells via A_2B Receptors

Abstract

Studies show that kidneys produce 2Ј,3Ј-cAMP, 2Ј,3Ј-cAMP is exported and metabolized to 2Ј-AMP and 3Ј-AMP, 2Ј-AMP and 3Ј-AMP are metabolized to adenosine, 2Ј,3Ј-cAMP inhibits proliferation of preglomerular vascular smooth muscle cells (PGVSMCs) and glomerular mesangial cells (GMCs), and A 2B (not A 1 , A 2A , or A 3 ) adenosine receptors mediate part of the antiproliferative effects of 2Ј,3Ј-cAMP. These findings suggest that extracellular 2Ј,3Ј-cAMP attenuates proliferation of PGVSMCs and GMCs partly via conversion to corresponding AMPs, which are metabolized to adenosine that activates A 2B receptors. This hypothesis predicts that extracellular 2Ј-AMP and 3Ј-AMP should exert A 2B receptormediated antiproliferative effects. Therefore, we examined the antiproliferative effects (cell counts) of 2Ј-AMP and 3Ј-AMP. In PGVSMCs and GMCs, 2Ј-AMP and 3Ј-AMP exerted concentration-dependent antiproliferative effects. 3Ј-AMP was equipotent with and 2Ј-AMP was 3-fold less potent than 5Ј-AMP (prototypical adenosine precursor). In PGVSMCs, the effects of 2Ј-AMP and 3Ј-AMP were mimicked by adenosine, and 8-[4-[((4-cyanophenyl)carbamoylmethyl)oxy]phenyl]-1,3-di(npropyl)xanthine (MRS-1754) (A 2B receptor antagonist) equally blocked the antiproliferative effects of 2Ј-AMP, 3Ј-AMP, and adenosine but less effectively blocked the effects of 2Ј,3Ј-cAMP. Similar results were obtained in GMCs except that MRS-1754 also incompletely blocked the effects of 3Ј-AMP. We conclude that in PGVSMCs, 2Ј-AMP and 3Ј-AMP are antiproliferative, the antiproliferative effects of 2Ј-AMP and 3Ј-AMP are mediated nearly entirely by adenosine/A 2B receptors, and some of the antiproliferative effects of 2Ј,3Ј-cAMP are independent of adenosine/A 2B

Antiproliferative effects of selective adenosine receptor agonists and antagonists on human lymphocytes: evidence for receptor-independent mechanisms

“…Part of this effect may be attributed to adenosine via the activation of ARs and sustained increase in cAMP levels [5]. Besides the activation of extracellular receptors [11,[15][16][17], direct intracellular toxicity (also by adenosine metabolites) has been described [18][19][20][21]. Furthermore, adenosine is able to stimulate cell growth and proliferation and/or to induce apoptosis in various normal and tumor cell lines.…”

“…Proliferative or anti-proliferative effects appear to be dependent on the cell type, the distribution of adenosine receptor subtypes, and their expression on the cell surface [22][23][24][25]. A 3 adenosine receptors seem to play an important role [26][27][28], but recent evidence accumulates that A 2B ARs can be upregulated on malignant cells and are involved in the control of tumor growth and development [16,24,[29][30][31][32]. In contrast to these findings, adenosine and various related AR agonists as well as antagonists can trigger apoptosis by receptor-independent mechanisms that require the entry of the compounds into the cells.…”

Purinergic Signaling and Blood Vessels in Health and Disease

“…Adenosine, acting via both A 1 and A 2 receptors, stimulates DNA synthesis in rat cultured arterial smooth muscle cells (Jonzon et al, 1985). However, adenosine, via A 2B receptors, has been reported to inhibit growth of rat and human aortic smooth muscle cells (Dubey et al, 1996(Dubey et al, , 1998Jackson et al, 2011). Strong effects of adenosine on gene induction in human coronary artery vascular smooth muscle cells via A 2B receptors have been described associated with the antiproliferative effects of adenosine (White et al, 2000;Boarder et al, 2001).…”

In Vivo Cardiovascular Pharmacology of 2′,3′-cAMP, 2′-AMP, and 3′-AMP in the Rat

“…Their findings suggest rather sluggish metabolism of 29-AMP, 39-AMP, and 29,39-cAMP to adenosine. Our previous experiments demonstrate that 29,39-cAMP, 29-AMP, and 39-AMP potently and efficaciously inhibit the proliferation of microvascular smooth muscle cells (Jackson et al, 2010(Jackson et al, , 2011a, macrovascular smooth muscle cells (Jackson et al, 2011b), and glomerular mesangial cells (Jackson et al, 2010(Jackson et al, , 2011a), yet stimulate the proliferation of vascular endothelial cells (Jackson and Gillespie, 2012) and renal tubular epithelial cells (Jackson and Gillespie, 2012). All these effects are mediated mostly by conversion of 29,39-cAMP, 29-AMP, and 39-AMP to adenosine, followed by stimulation of adenosine receptors.…”

“…Although our previously published studies show that exogenous 29,39-cAMP, 29-AMP, and 39-AMP alter vascular smooth muscle cell, endothelial cell, and epithelial cell proliferation via conversion to adenosine, those experiments were performed by incubating cells in vitro for several days with these compounds (Jackson et al, 2010(Jackson et al, , 2011aJackson and Gillespie, 2012). Thus it is unknown whether conversion of 29,39-cAMP, 29-AMP, or 39-AMP to adenosine occurs rapidly enough in vivo to yield significant biologic effects.…”