Role of reactive oxygen species in bradykinin-induced mitogen-activated protein kinase and c-fos induction in vascular cells

Bradykinin stimulates proliferation of aortic vascular smooth muscle cells (VSMCs). We investigated the action of bradykinin on the phosphorylation st ate of the mitogen-activated protein kinases p42(map lambda) and p44(mapk) in VSMCs and tested the hypothesis that reactive oxygen species (ROS) might be involved in the signal transduction pathway linking bradykinin activati on of nuclear transcription factors to the phosphorylation of p42(mapk) and p44(mapk) Bradykinin (10(-8) mol/L) rapidly increased (4- to 5-fold) the p hosphorylation of p42(mapk) and p44(mapk) in VSMCs. Preincubation of VSMCs with either N-acetyl-L-cysteine and/or alpha-lipoic acid significantly decr eased bradykinin-induced cytosolic and nuclear phosphorylation of p42(mapk) and p44(map lambda). In addition, the induction c-fos mRNA levels by brady kinin was completely abolished by N-acetyl-L-cysteine and alpha-lipoic acid . Using the cell-permeable fluorescent dye dichlorofluorescein diacetate, w e determined that bradykinin (10(-8) mol/L) rapidly increased the generatio n of ROS in VSMCs. The NADPH oxidase inhibitor diphenylene iodonium (DPI) b locked bradykinin-induced c-fos mRNA expression and p42(mapk) and p44(mapk) activation, implicating NADPH oxidase as the source for the generation of ROS. These findings demonstrate that the phosphorylation of cytosolic and n uclear p42(mapk) and p44(mapk) and the expression of c-fos mRNA in VSMCs in response to bradykinin ale mediated via the generation of ROS and implicat e ROS as important mediators in the signal transduction pathway through whi ch bradykinin promotes VSMC proliferation in states of vascular injury.