FLUID SHEAR-STRESS INDUCTION OF THE TRANSCRIPTIONAL ACTIVATOR C-FOS IN HUMAN AND BOVINE ENDOTHELIAL-CELLS, HELA, AND CHINESE-HAMSTER OVARY CELLS

The c-fos protein belongs to a family of transcriptional cofactors tha t can complex with proteins of the Jun family and activate mRNA transc ription from gene promoters containing an activator protein 1 (AP-1) b inding element. The shear stress inducibility of the c-fos protein was studied in human and animal cell lines of vastly different origins. P rimary human umbilical vein endothelial cells (HUVEC), bovine aortic e ndothelial cells (BAEC, passage 2-14), HeLa cells, and Chinese hamster ovary (CHO) cells were subjected to steady laminar shear stress using a parallel plate flow apparatus. After 1 h of flow exposure at 25 dyn /cm(2), the c-fos levels in nuclei of shear stress HUVEC, BAEC, HeLa, and CHO were 5.4 +/- 2.0 (n = 3), 2.25 +/- 1.38 (n = 6), 2.14 +/- 0.07 (n = 8), 1.92 +/- 0.58 (n = 2) times higher, respectively, than in ma tched stationary controls. Flow exposure at 4 dyn/cm(2) caused no enha ncement of c-fos levels in any of the cell lines tested, but caused si gnificant reduction in c-fos expression in the HeLa cells. The c-fos i nduction by shear stress could be blocked by pharmacological agents. F or example, the flow induction of the c-fos protein levels was blocked by 50% with the preincubation of HUVEC with a protein kinase C inhibi tor, H7 (10 mu M) and blocked completely in HeLa cells preincubated wi th the phospholipase C inhibitor, neomycin (5 mM). The minimum time of shear stress exposure required to induce the c-fos protein expression in HeLa cells was found to be as low as 1 min. By Northern analysis, the c-fos mRNA levels were found to be elevated in BAEC, CHO, and HeLa cells exposed to 25 dyn/cm(2) for 30 min. These studies indicate that c-fos induction is a consistent genetic response in a variety of mamm alian cells that may alter cellular phenotype in mechanical environmen ts. (C) 1996 John Wiley & Sons, Inc.