Mechanical stimulation is known to modulate cell physiology in a variety of different tissues. Particularly, epithelial cells are permanently exposed to mechanical stimulation generated by externally applied forces. The present in vitro study demonstrated mechanical pressure as a trigger-factor of the p38 mitogen-activated protein kinase (MAPK) pathway in epitbelial cells. Mechanical pressure applied by teflon weights (1.02g/cm(2)) led to a rapid phosphorylation of p38 peaking between 5 and 10 min. Furthermore, phosphorylation of the small heat shock protein 27 (HSP27) was shown in response to mechanical pressure. Suppression of p38 function by using specific inhibitors blocked the pressure-inediated phosphorylation of HSP27. In order to identify upstream regulators of p38, a contribution of Src and protein kinase C (PKC) in pressure-signaling was investigated. We could demonstrate that inhibition of Src or PKC suppressed the pressure-induced phosphorylation of p38. These findings suggest mechanical pressure as a new type of effector stimulus for the p38 pathway with implications to (patho-) physiological conditions. (C) 2004 Elsevier Inc. All rights reserved.