title: Pulsatile and steady flow induces c-fos expression in human endothelial cells.
abstract: The effects of pulsatile and steady fluid flow on the mRNA levels of proto-oncogenes c-fos, c-jun, and c-myc in cultured human umbilical vein endothelial cells (HUVEC) were investigated. c-fos mRNA levels in stationary cultures were very low. A 1 Hz pulsatile flow with an average shear stress of 16 dynes/cm2 induced a dramatic increase of c-fos mRNA levels in HUVEC 0.5 h after the onset of flow, which declined rapidly to basal levels within 1 h. Steady flow with a similar shear stress also induced a transient increase of c-fos mRNA levels, but to a lesser extent. In addition, increased c-fos mRNA levels were observed when low shear (2-6 dynes/cm2) was replaced by high shear (16-33 dynes/cm2). Pulsatile and steady flow caused a slight increase of c-jun and c-myc mRNA levels. The role of pulsatility was also investigated in platelet-derived growth factor (PDGF) expression. Pulsatile flow induced a transient increase of PDGF A- and B-chain mRNA levels with peaks at 1.5-2 h. Pulsatile flow, which was more stimulatory in mediating c-fos expression, however, was less stimulatory than steady flow in mediating PDGF expression. By using various inhibitors, protein kinase C was found to be an important mediator in flow-induced c-fos expression, with the involvement of G proteins, phospholipase C, and intracellular calcium. Protein kinase C was previously shown as a possible major mediator in flow-induced PDGF expression which, at least partly, appeared to follow the induction mechanism of c-fos, suggesting a possible connection between c-fos and PDGF induction. However, the c-fos antisense treatment, which significantly inhibited c-fos transcription, failed to block the flow-induced PDGF expression, suggesting that flow-induced c-fos expression may not play an important role in the mechanism of flow-induced PDGF expression. The difference in the induction of c-fos and PDGF expression under pulsatile as compared to steady flow indicates that a complex, flow-mediated regulatory mechanism of gene expression exists in HUVEC. The increased expression of these proto-oncogenes mediated by flow may be important in regulating long-term cellular responses.
authors.affiliation: Department of Chemical Engineering, Pennsylvania State University, University Park 16802.
authors.forename: H J
authors.initials: HJ
authors.lastname: Hsieh
authors.forename: N Q
authors.initials: NQ
authors.lastname: Li
authors.forename: J A
authors.initials: JA
authors.lastname: Frangos
mesh_terms: D001483:Base Sequence; D015152:Blotting, Northern; D002478:Cells, Cultured; D004277:DNA, Single-Stranded; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics* / Q000378:metabolism; D011673:Pulsatile Flow / Q000502:physiology*; D012039:Regional Blood Flow / Q000502:physiology*
chemical_list: D004277:DNA, Single-Stranded; D016760:Proto-Oncogene Proteins c-fos