Objective: Vascular endothelial growth factor (VEGF) plays important roles in establishing collateral circulation of ischemic myocardium. This study aimed to investigate the effect of isoflurane on VEGF expression and the potential intracellular signal transduction pathway in cultured rat myocardial cells in order to further reveal the molecular mechanism of myocardial preservation of isoflurane.
Methods: Primary myocardial cells of Sprague-Dawley rats were isolated and cultured. They were divided randomly into control group, isoflurane group, protein kinase C (PKC) inhibitor group and PKC inhibitor+isoflurane group where cells were respectively incubated without any treatment, treated by 0.5, 1.0 and 1.5 minimum alveolar concentration (MAC) of isoflurane for 6 hours, by PKC inhibitor calphostin C at a final concentration of 50 nmol/L and by 50 nmol/L calphostin C+1.0 MAC isoflurane for 6 hours. VEGF expression was detected by enzyme-linked immunosorbent assay (ELISA) and the expression levels of PKC isoforms were determined by Western immunoblotting method.
Results: Isoflurane increased the VEGF expression in myocardial cells in a dose-dependent way. VEGF levels were significantly higher in 1.0 and 1.5 MAC isoflurane groups than in the control group (both P < 0.01). The effect of isoflurane on upregulating VEGF expression was blocked by PKC inhibitor calphostin C (P < 0.01), but calphostin C did not alter VEGF expression (P > 0.05). Isoflurane induced the activation and translocation of PKCε. Immunoblotting analysis revealed that the immunoreactivity of PKC ε increased significantly in the membrane fractions and deceased significantly in the kytoplasm fractions for cells treated with 1.0 MAC isoflurane as compared with the untreated cells, but not of PKC-α, PKC-δ and PKC-ζ (P less than 0.01).
Conclusion: Isoflurane induces myocardial cells to release VEGF through activating PKC-epsilon from the endochylema to the cytomembrane, suggesting a possible novel mechanism of isoflurane protecting myocardial cells.