Elsevier

Neuroscience Letters

Volume 408, Issue 1, 6 November 2006, Pages 62-67
Neuroscience Letters

Hypoxia-induced upregulation of endothelial small G protein RhoA and Rho-kinase/ROCK2 inhibits eNOS expression

https://doi.org/10.1016/j.neulet.2006.08.038Get rights and content

Abstract

The small G protein RhoA and its downstream effector Rho-kinase/ROCK2 play an important role in regulation of various vasculature cellular functions. Nitric oxide (NO) produced by endothelial NO synthase (eNOS) is an important mediator of vascular homeostasis and cerebral blood flow. Using the human endothelial cell line HUVEC, the present study investigated the role of RhoA and Rho-kinase in endothelial eNOS protein expression under hypoxic conditions as an in vitro model of ischemia. RhoA protein levels in HUVEC were low under normoxic conditions, but were significantly increased after 5 h of hypoxia. Endothelial Rho-kinase expression was not detected until after 3 h of hypoxia; such expression remained significantly increased after 5 h. On the other hand, endothelial eNOS expression was similar after 3 h of hypoxia, but was significantly decreased after 5 h. The hypoxia-induced decrease in eNOS expression was significantly enhanced by expression of the constitutively active form of RhoA and significantly inhibited by suppression of RhoA expression by small interfering RNA. The hypoxia-induced decrease in eNOS expression was significantly inhibited when endogenous Rho-kinase activation was inhibited by Rho-binding domain expression. Furthermore, the hypoxia-induced decrease in eNOS expression was significantly enhanced by expression of the constitutively active form of Rho-kinase. Since expression and activation of RhoA and Rho-kinase inhibit eNOS expression in endothelial cells, attempts to down-regulate RhoA and Rho-kinase by multiple drugs, such as statins or Rho-kinase inhibitors, might provide endothelial and cardiovascular benefits through upregulation of eNOS.

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Acknowledgement

This work was supported by grants-in-aid for the Encouragement of Young Scientists (2005, 2006) and for Scientific Research (2005, 2006) from the Japanese Ministry of Education, Culture, Sports, Science, and Technology. We thank Mrs. Y. Furuno and M. Sasanishi for technical assistance and Dr. C.J. Hurt for manuscript corrections.

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