Shear stress induces hepatocyte PAI-1 gene expression through cooperative Sp1/Ets-1 activation of transcription.
Partial hepatectomy causes hemodynamic changes that increase portal blood flow in the remaining lobe, where the expression of immediate-early genes, including plasminogen activator inhibitor-1 (PAI-1), is induced. We hypothesized that a hyperdynamic circulatory state occurring in the remaining lobe induces immediate-early gene expression. In this study, we investigated whether the mechanical force generated by flowing blood, shear stress, induces PAI-1 expression in hepatocytes. When cultured rat hepatocytes were exposed to flow, PAI-1 mRNA levels began to increase within 3 h, peaked at levels significantly higher than the static control levels, and then gradually decreased. The flow-induced PAI-1 expression was shear stress dependent rather than shear rate dependent and accompanied by increased hepatocyte production of PAI-1 protein. Shear stress increased PAI-1 transcription but did not affect PAI-1 mRNA stability. Functional analysis of the 2.1-kb PAI-1 5'-promoter indicated that a 278-bp segment containing transcription factor Sp1 and Ets-1 consensus sequences was critical to the shear stress-dependent increase of PAI-1 transcription. Mutations of both the Sp1 and Ets-1 consensus sequences, but not of either one alone, markedly prevented basal PAI-1 transcription and abolished the response of the PAI-1 promoter to shear stress. EMSA and chromatin immunoprecipitation assays showed binding of Sp1 and Ets-1 to each consensus sequence under static conditions, which increased in response to shear stress. In conclusion, hepatocyte PAI-1 expression is flow sensitive and transcriptionally regulated by shear stress via cooperative interactions between Sp1 and Ets-1.
Nakatsuka
Hideki
H
Department of Digestive and General Surgery, Graduate School of Medicine, Niigata University, Niigata, Japan.
Sokabe
Takaaki
T
Yamamoto
Kimiko
K
Sato
Yoshinobu
Y
Hatakeyama
Katsuyoshi
K
Kamiya
Akira
A
Ando
Joji
J
D000818:Animals; D002478:Cells, Cultured; D005786:Gene Expression Regulation / Q000502:physiology; D022781:Hepatocytes / Q000502:physiology*; D008297:Male; D040542:Mechanotransduction, Cellular / Q000502:physiology*; D017395:Plasminogen Activator Inhibitor 1 / Q000378:metabolism*; D050784:Proto-Oncogene Protein c-ets-1 / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D033081:Shear Strength; D015398:Signal Transduction / Q000502:physiology; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D013314:Stress, Mechanical; D015533:Transcriptional Activation / Q000502:physiology*
C494043:Ets1 protein, rat; D017395:Plasminogen Activator Inhibitor 1; D050784:Proto-Oncogene Protein c-ets-1; D016329:Sp1 Transcription Factor