Serum levels of vascular endothelial growth factor in patients with acute myocardial infarction undergoing reperfusion therapy

Vascular endothelial growth factor induces activation and subcellular translocation of focal adhesion kinase (p125FAK) in cultured rat cardiac myocytes

Vascular endothelial growth factor (VEGF) has been proposed to be among the candidate factors with the most potential to play a role in ischemia-induced collateral vessel formation. Recently, we found that VEGF activated the mitogen-activated protein kinase cascade in cultured rat cardiac myocytes. To elucidate how VEGF affects adhesive interaction of cardiac myocytes with the extracellular matrix (ECM), one of the important cell functions, we investigated the molecular mechanism of activation of focal adhesion-related proteins, especially focal adhesion kinase (p125(FAK)), in cultured rat cardiac myocytes. We found that the 2 VEGF receptors, KDR/Flk-1 and Flt-1, were expressed in cardiac myocytes and that KDR/Flk-1 was significantly tyrosine phosphorylated on VEGF stimulation. VEGF induced tyrosine phosphorylation and activation of p125(FAK) as well as tyrosine phosphorylation of paxillin; this was accompanied by subcellular translocation of p125(FAK) from perinuclear sites to the focal adhesions. This VEGF-induced activation of p125(FAK) was inhibited partially by the tyrosine kinase inhibitors genistein and tyrphostin. Activation of p125(FAK) was accompanied by its increased association with adapter proteins GRB2, Shc, and nonreceptor type tyrosine kinase p60(c-src). Furthermore, we confirmed that VEGF induced a significant increase in adhesive interaction between cardiac myocytes and ECM using an electric cell-substrate impedance sensor. These results strongly suggest that p125(FAK) is one of the most important components in VEGF-induced signaling in cardiac myocytes, playing a critical role in adhesive interaction between cardiac myocytes and ECM.

Pulsatile stretch activates mitogen-activated protein kinase (MAPK) family members and focal adhesion kinase (p125(FAK)) in cultured rat cardiac myocytes

Recently, we demonstrated that pulsatile mechanical stretch induced rapid secretion of vascular endothelial growth factor (VEGF) by cultured rat cardiac myocytes in vitro. To investigate whether pulsatile stretch activates intracellular signaling in cardiac myocytes, we examined the activation of mitogen-activated protein kinase (MAPK) family members and focal adhesion kinase (p125(FAK)) in cultured rat cardiac myocytes. We found that pulsatile stretch rapidly phosphorylated p44/p42 MAPKs (extracellular signal-regulated protein kinase [ERK] 1/2), stress-activated protein kinase (SAPK), p38MAPK, and p125(FAK). The stretch-induced activation of ERKs was at least partly mediated by VEGF, which was shown to be induced by transforming growth factor (TGF)-beta, and was also partly dependent on tyrosine kinases as well as protein kinase C (PKC). These data provide the direct evidence that pulsatile stretch can activate intracellular signaling in cardiac myocytes and that this was at least partly mediated by VEGF, which may play a role in cardiac adaptation to mechanical overload.

Elevated circulating levels of basic fibroblast growth factor and vascular endothelial growth factor in patients with acute myocardial infarction

Basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) have both shown strong angiogenetic effects in ischemic animal models and it has been reported that these growth factors were increased after acute myocardial ischemia. However, there have been few reports on the serum levels of bFGF and VEGF after acute myocardial infarction (AMI), in particular there has not been a comparative study of bFGF and VEGF in human subjects. The time course of circulating levels of bFGF and VEGF was examined in 36 patients with AMI who were within 24h of the onset of the AMI. The serum bFGF and VEGF levels of 50 age- and sex-matched healthy volunteers served as the baseline value. All the patients had undergone coronary angiography on the day of admission (Day 0), but prior to that the serum bFGF and VEGF levels were examined by enzyme-linked immunoassay. The serum bFGF and VEGF levels were also evaluated on Days 7, 14 and 28. Creatine kinase, myosin light chain I and troponin-T were measured subsequently and radionuclide examinations were performed during the early phase of AMI to determine the infarct size. The serum bFGF levels were significantly increased at Day 0 and were maintained until Days 7 and 14. Although serum VEGF levels at Day 0 were similar to the baseline values, they showed a remarkable increase by Days 7 and 14. A high serum level of bFGF was detected in the acute phase of AMI, and a later increase in VEGF was determined in the sub-acute phase, which suggest that these 2 growth factors play an important role at different time points of the reconstructing process of infarcted myocardial tissue.

Pulsatile stretch stimulates vascular endothelial growth factor (VEGF) secretion by cultured rat cardiac myocytes

Evidence has accumulated that vascular endothelial growth factor (VEGF) is expressed in the heart, and its expression is markedly increased in response to hypoxia. Recently, it was shown that pulsatile myocardial stretch in vivo markedly enhanced VEGF mRNA level in the heart. To investigate whether pulsatile mechanical stretch really stimulates VEGF expression by cardiac myocytes, using an in vitro preparation, we examined the secretion of VEGF into the culture media from cardiac myocytes subjected to pulsatile stretch. We found that pulsatile mechanical stretch induced rapid secretion of VEGF by cultured rat cardiac myocytes and mRNA expression of VEGF and VEGF receptors in the cardiac myocytes. We also found that the stretch-induced secretion of VEGF was at least in part mediated by TGF-beta. These data provide the direct evidence that mechanical overload itself can induce VEGF secretion by cardiac myocytes, which may play a role in ameliorating the relative myocardial hypoxia.