Aryl hydrocarbon receptor mediates laminar fluid shear stress-induced CYP1A1 activation and cell cycle arrest in vascular endothelial cells.
OBJECTIVE
We investigated the mechanisms of shear stress (SS)-induced activation of cytochrome P450 (CYP) 1A1 and cell cycle arrest with regard to the role of the aryl hydrocarbon receptor (AhR), since AhR mediates the expression of CYP1A1 induced by polycyclic aromatic hydrocarbons (PAHs) and is thought to be involved in the regulation of cell growth and differentiation.


RESULTS
Human umbilical vein endothelial cells (ECs) were exposed to laminar SS and thereafter collected to evaluate the expression, activity, and transcription of CYP1A1 and the expression of AhR and cell cycle-related proteins. A physiological level of laminar SS (15 dynes/cm(2)) markedly increased the expression level and enzymatic activity of CYP1A1. SS stimulated CYP1A1 promoter activity without influencing mRNA stability. Loss of two functional xenobiotic response elements (XREs) in the 5'-flanking region of the CYP1A1 gene suppressed the SS-induced transcription of CYP1A1. Laminar SS stimulated the expression and nuclear translocation of AhR. alpha-Naphthoflavone, an AhR antagonist, and a small interfering RNA (siRNA) for AhR significantly suppressed SS-induced CYP1A1 expression. The siRNA also abolished SS-induced cell cycle arrest, the expression of the cyclin-dependent kinase inhibitor p21(Cip1), and dephosphorylation of retinoblastoma protein.


CONCLUSIONS
Laminar SS stimulated the transcription of CYP1A1 through the activation of AhR in a way that is similar to the effects of PAHs. AhR was also involved in cell cycle arrest induced by SS. Our results suggest that sustained activation of AhR exposed to blood flow plays an important role in the regulation of EC functions.
Department of Clinical Pharmacology, Faculty of Medical Sciences, Kyushu University, Fukuoka, Japan.
Zhiyi
Z
Han
Yoshikazu
Y
Miwa
Hiyo
H
Obikane
Masako
M
Mitsumata
Fumi
F
Takahashi-Yanaga
Sachio
S
Morimoto
Toshiyuki
T
Sasaguri
D021581:Active Transport, Cell Nucleus; D051792:Basic Helix-Loop-Helix Proteins; D001571:Benzoflavones / Q000494:pharmacology; D002453:Cell Cycle / Q000187:drug effects; D002478:Cells, Cultured; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D019363:Cytochrome P-450 CYP1A1 / Q000096:biosynthesis* / Q000235:genetics; D042783:Endothelial Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D004789:Enzyme Activation; D004790:Enzyme Induction; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011673:Pulsatile Flow; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D018336:Receptors, Aryl Hydrocarbon / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D020218:Response Elements; D016160:Retinoblastoma Protein / Q000378:metabolism; D013314:Stress, Mechanical; D013997:Time Factors; D014158:Transcription, Genetic; D015533:Transcriptional Activation
D051792:Basic Helix-Loop-Helix Proteins; D001571:Benzoflavones; D050759:Cyclin-Dependent Kinase Inhibitor p21; D019363:Cytochrome P-450 CYP1A1; D020928:Mitogen-Activated Protein Kinases; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D018336:Receptors, Aryl Hydrocarbon; D016160:Retinoblastoma Protein; C111235:AHR protein, human; C493956:CDKN1A protein, human; C011512:alpha-naphthoflavone