ABSTRACT
Objective To evaluate the relationship between endothelin-1 (ET-1) and p38 mitogenactivated protein kinase (p38 MAPK) and phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signaling pathways during mechanical stretch-induced enhancement of adhesion of rat pulmonary microvascular endothelial cells (PMVECs).Methods Rat PMVECs were seeded in the culture plate at a density of 0.5×105 cells/ml (2 ml/well) and divided into 5 groups (n=24 each) using a random number table:control group (group C),mechanical stretch group (group MS),mechanical stretch plus specific PI3K inhibitor LY294002 group (LY group),mechanical stretch plus specific p38 MAPK inhibitor SB203580 group (SB group),and mechanical stretch plus selective ETA receptor blocker BQ123 group (BQ group).Cells were exposed to 20％ cyclic stretch at 0.3 Hz for 4 h using a sine wave.In LY,SB and BQ groups,LY294002,SB203580 and BQ123 at the final concentration of 10 μmol/L were added,respectively,after mechanical stretch,cells were incubated for 10 min,and then extracted and purified rat polymorphonuclear neutrophil leukocytes (PMNs,5× 105 cells/well) were added and co-incubated with PMVECs for 30 min and then washed out.The concentrations of ET-1 and interleukin-6 (IL-6) in the culture medium were determined using enzyme-linked immunosorbent assay.The expression of phosphorylated p38 MAPK (p-p38 MAPK) and phosphorylated Akt (p-Akt) was detected by Western blot.Adhesion of PMNs was measured by immuno-histochemistry,and the adhesion rate was calculated.The expression of P-selectin mRNA was detected using real-time polymerase chain reaction.Results Compared with group C,the concentrations of IL-6 and ET-1 in the culture medium were significantly increased,the expression of p-p38 MAPK,p-Akt and P-selectin mRNA was up-regulated,and the adhesion rate of PMNs was increased in the other four groups (P＜0.05).Compared with group MS,the concentration of IL-6 in the culture medium was significantly decreased,the expression of p-Akt and P-selectin mRNA was down-regulated,and the adhesion rate of PMNs was decreased in LY,SB and BQ groups,the concentration of ET-1 in the culture medium was significantly decreased in group BQ,and the expression of p-p38 MAPK was significantly down-regulated in SB and BQ groups (P＜0.05).Conclusion The signaling mechanism underlying ET-1-mediated enhancement of rat PMVEC adhesion may be related to activating p38 MAPK and PI3K/Akt signaling pathways.