AMP‐activated protein kinase mediates erythropoietin‐induced activation of endothelial nitric oxide synthase

Abstract

We investigated whether AMP-activated protein kinase (AMPK), a multi-functional regulator of energy homeostasis, participates in the regulation of erythropoietin (EPO)-mediated activation of endothelial nitric oxide synthase (eNOS) in endothelial cells (ECs) and mice. In ECs, treatment with EPO increased the phosphorylation of AMPK, acetyl-CoA carboxylase (ACC), and eNOS, as revealed by Western blot analysis. Inhibition of AMPK activation by compound C or dominant-negative AMPK mutant abrogated the EPO-induced increase in the phosphorylation of AMPK, ACC, and eNOS, as well as nitric oxide (NO) production. Additionally, suppression of AMPK activation abolished EPO-induced EC proliferation, migration and tube formation. Immunoprecipitation analysis demonstrated that AMPK mediated the EPO-induced increase in the phosphorylation of β common receptor (βCR) and the formation of a βCR-AMPK-eNOS complex. In mice, inhibition of AMPK activation by compound C markedly decreased EPO-elicited angiogenesis in Matrigel plugs. Furthermore, the phosphorylation of AMPK and eNOS was significantly higher in aortas from EPO transgenic mice than wild-type mice. Moreover, treatment with EPO neutralizing antibody greatly reduced the exercise training-induced increase in phosphorylation of AMPK and eNOS in aortas of wild-type mice. Taken together, EPO may trigger AMPK-dependent signaling, which leads to enhanced phosphorylation of βCR and eNOS, increased βCR-AMPK-eNOS complex formation, NO production, and, ultimately, angiogenesis.

Activation of AMP-Activated Protein Kinase Inhibits the Proliferation of Human Endothelial Cells

“…In the latter study, AMPK activation was shown to block basal endothelial cell growth, but the underlying mechanism was not explored. It is noteworthy that our results are in contrast with investigations showing that AMPK activation is required in mediating the mitogenic response of endothelial cells to vascular endothelial growth factor and erythropoietin (Reihill et al, 2011;Su et al, 2012). Thus, the capacity of AMPK to regulate endothelial cell growth may be stimulus-dependent.…”

“…Alternatively, the kinetics of AMPK activation may dictate the nature of the proliferative response. In particular, chronic, sustained activation of AMPK that was observed in our study may favor endothelial cell growth arrest, whereas acute, transient activation of AMPK in response to angiogenic factors promotes a proliferative response (Ouchi et al, 2004;Stahmann et al, 2010;Su et al, 2012). The ability of AMPK to repress endothelial cell growth, an ATP-consuming process, provides another mechanism by which this kinase conserves energy during periods of prolonged metabolic stress.…”

Apelin-13 stimulates angiogenesis by promoting cross-talk between AMP-activated protein kinase and Akt signaling in myocardial microvascular endothelial cells

“…Notably, although the AMPK inhibitor suppressed the endogenous Akt phosphorylation, the Akt inhibitor had no effect on the endogenous phosphorylation of AMPK in MMVECs. The present data suggest that apelin-13 exerts pro-angiogenic effects in MMVECs through the modulation of AMPK and Akt signaling and the activation of eNOS, which is in accordance with previous studies (28,29,30). A study by Nagata et al (11) demonstrated that AMPK did not exhibit an effect on endothelial cell migration, tube formation and NO production under normoxia, which suggests that further in vitro and in vivo studies are required to gain a greater understanding of the role of endothelial cell AMPK in angiogenesis.…”

Implication of AMP-Activated Protein Kinase in Transient Receptor Potential Vanilloid Type 1-Mediated Activation of Endothelial Nitric Oxide Synthase

“…For instance, shear stress, the major physiological stimulation in the vascular system, was found to activate AMPK, which in turn phosphorylated eNOS at Ser635 and Ser1179, thus leading to enhanced NO bioavailability (27,36). Additionally, several cytokines such as vascular endothelial growth factor and erythropoietin have been postulated to promote endothelial progenitor cell differentiation, EC survival and angiogenesis through an AMPK signaling pathway (37)(38)(39)(40)(41). In addition to the beneficial effects of AMPK in the endothelium, activation of AMPK by the pharmacological activator aminoimidazole-carboxamideribonucleotide (AICAR) profoundly inhibited platelet-derived growth factoror angiotensin II-induced smooth muscle cell proliferation (42).…”