Leptin Enhances the Potency of Circulating Angiogenic Cells Via Src Kinase and Integrin αvβ5

Abstract

Objective-To investigate the capacity of the adipokine leptin to promote angiogenesis by modulating the function of circulating angiogenic cells (CACs). Methods and Results-In vitro, leptin specifically promoted CAC adhesion to tubular endothelial structures and migration along outgrowing sprouts of endothelial cells. In vivo, stimulation of CACs with leptin increased their capacity to promote new vessel formation in the chorioallantoic membrane of chicken embryos and to improve neovascularization of ischemic murine hind limbs. These effects required the phosphorylation of ␣v␤5 integrins, which depended on the interaction of leptin with its receptor ObR, and on Janus kinase (JAK) 2-and phospholipase C (PLC) ␥-mediated activation of Src kinase. Protein tyrosine phosphatase 1B, a negative regulator of leptin signaling, was overexpressed in CACs from obese, hyperleptinemic individuals, and this was associated with insensitivity of CACs to the angiogenic effects of leptin. Weight loss (by [meanϮSD] 30Ϯ15 kg) normalized protein tyrosine phosphatase 1B expression in CACs and restored their responsiveness to leptin. A similar dose-dependent response was found after incubation of CACs from obese subjects with a protein tyrosine phosphatase 1B inhibitor ex vivo. Key Words: angiogenesis Ⅲ circulating angiogenic cells Ⅲ leptin Ⅲ obesity Ⅲ PTP1B Ⅲ Src kinase A ngiogenesis, the formation of new blood vessels from the existing vasculature, is a complex multistep process involving the proliferation, migration, and remodeling of endothelial cells in response to growth factors and cytokines. The adipose tissue-derived cytokine leptin has been shown to exert proangiogenic effects on endothelial cells 1,2 and leptinstimulated corneal neovascularization in rats and in leptindeficient ob/ob mice. 3 On the other hand, the prevention of leptin binding to its receptor inhibited angiogenesis, 4 and leptin receptor (ObR)-deficient mice exhibited reduced basal capillary density and defective revascularization of ischemic muscles. 5 Conclusion-Our See accompanying article on page 135Angiogenesis requires the interplay of various cell types, among which circulating angiogenic cells (CACs) appear to be of particular interest. These cells, formerly considered to represent a subpopulation of endothelial progenitor cells 6 and now regarded as a distinct (progenitor) cell type, 7 are derived from the peripheral blood after expansion in culture. They have been shown to augment neovascularization after tissue ischemia 8 and promote endothelial repair after vascular injury. 9 The vasculoprotective properties of CACs and other progenitor cells are defined by their ability to adhere to molecules released from injured tissues, allowing them to home and transmigrate at sites of injury or ischemia. 10 These steps are regulated by integrins, the transmembrane receptor heterodimers connecting the extracellular matrix to cytoskeletal and signaling molecules. More important, the activation status of integrins appears to be modulated by soluble growth fact...

Childhood obesity–related endothelial dysfunction: an update on pathophysiological mechanisms and diagnostic advancements

“…In this regard, leptin enhances the migratory activity of CAC in normal-weight adults (82). In obese adults, leptin resistance of CAC can be defeated by weight loss (83). Interestingly, the migratory ability of CAC in normal-weight children cannot be improved any further upon stimulation with leptin, indicating that in normal-weight children CAC function is likely at its maximum (79).…”

Overexpression of Integrin β5 Enhances the Paracrine Properties of Circulating Angiogenic Cells via Src Kinase–Mediated Activation of STAT3

“…15,16 Based on the isolation protocol, their proliferative behavior, and surface marker expression profile, cells were characterized as CACs, in accordance with a recently proposed definition. 4,5 A detailed description of all methods used in the present study is provided in the supplemental materials (available online at http://atvb.ahajournals.org).…”

“…15 Furthermore, the angiogenic effects of leptin on CACs involved activation of integrin ␣v␤5 and downstream signaling transduction pathways. 16 Interestingly, the beneficial effects of 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors (statins) on reendothelialization after carotid balloon injury also involved upregulation of integrin ␣v␤5 on EPCs, 25 whereas oxidized low-density lipoprotein was shown to impair EPC function by downregulating integrin ␣v␤5. 26 The results of the present study confirm and extend those previous findings by showing that ex vivo stimulation of CACs with 3-hydroxy-3-methylglutarylcoenzyme A reductase inhibitors and intake of statin medication both significantly enhanced the expression of integrin ␣v␤5 on the surface of human CACs (supplemental Figure IIA and B).…”

“…10 Regarding their exact function during angiogenic processes, discrepant findings in gene-deleted mice as opposed to data obtained after integrin function blockade have left some uncertainties. [11][12][13][14] Previous findings 15,16 suggest that upregulation of ␣v␤5 integrins on (early-outgrowth) EPCs may be involved in mediating reendothelialization and neovascularization. Thus, in the present study, we began to analyze the effect of integrin ␤5 overexpression on the angiogenic properties of CACs and to determine the intracellular mechanisms mediating the effects of ␣v␤5 integrin.…”

Endothelial progenitor cells in chronic obstructive pulmonary disease

“…It is well accepted that obesity is associated with decreased numbers of EPC [39][40][41][42][43] . Tobler et al in 2010 also stated that obese individuals not only had lower levels of circulating EPC; they also have EPC with functional deficiencies 43 .…”