The role of the RhoA/Rho-kinase signaling pathway in renal vascular reactivity in endothelial nitric oxide synthase null mice.
BACKGROUND
Smooth muscle contraction is regulated by the small GTPase RhoA and its target, Rho-kinase and recent evidence indicates that nitric oxide (NO) causes vasodilation through inhibition of the RhoA/Rho-kinase (ROCK) signaling pathway.


OBJECTIVE
This study tested the hypothesis that the enhanced renal vascular tone and systemic hypertension in endothelial nitric oxide synthase (eNOS) null mice is due to disinhibition of the ROCK signaling pathway.


METHODS
Systolic blood pressure (SBP) was measured by tail-cuff plethysmography and the isolated Krebs-perfused kidney preparation was used to evaluate renal vascular responses in C57BL/6 (wild type, WT) and eNOS knockout (KO) mice treated with Y-27632, a ROCK inhibitor.


RESULTS
Compared with the WT mice, Rho kinase activity was higher in eNOS KO mice (37 +/- 8%, P < 0.05) as was SBP (33 +/- 4%, P < 0.05), basal renal perfusion pressure (31 +/- 4%, P < 0.05) and renal vascular resistance (35 +/- 4%, P < 0.05). Y-27632 abolished these differences. Vasoconstriction elicited by angiotensin II (Ang II) or phenylephrine (PE), G-protein-coupled receptor (GPCR) agonists, but not that elicited by arachidonic acid or KCl, was greater in eNOS KO mice. Y-27632 eliminated the amplified vasoconstriction elicited by Ang II or phenylephrine but to a greater extent in eNOS KO mice. Similarly, responses elicited by guanosine 5'-gamma-thiotriphosphate (GTPgammaS), a non-hydrolyzable GTP analog, or sodium tetrafluoride (NaF4), an activator of G-proteins, was greater in eNOS KO mice, 53 +/- 14 and 50 +/- 3%, respectively. Y-27632 normalized the difference. Y-27632 also elicited a dose-dependent renal vasodilation that was greater in eNOS KO mice.


CONCLUSIONS
These results show that the ROCK signaling pathway is amplified in the eNOS KO mouse kidney and that the enhanced renal vascular tone and selective increase in reactivity to GPCR agonists supports a role for ROCK in the hypertension and vascular dysfunction in the eNOS KO mice.
Williams
Janae
J
Center for Cardiovascular Diseases, College of Pharmacy and Health Sciences, Texas Southern University, Houston, Texas 77004, USA.
Bogwu
Justin
J
Oyekan
Adebayo
A
D000577:Amides / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000502:physiology*; D019204:GTP-Binding Proteins / Q000502:physiology; D047908:Intracellular Signaling Peptides and Proteins / Q000502:physiology*; D007668:Kidney / Q000098:blood supply*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D023421:Models, Animal; D009125:Muscle Relaxants, Central / Q000494:pharmacology; D009129:Muscle Tonus / Q000187:drug effects / Q000502:physiology; D009569:Nitric Oxide / Q000502:physiology*; D052250:Nitric Oxide Synthase Type III / Q000172:deficiency / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology; D054460:rho-Associated Kinases
D000577:Amides; D047908:Intracellular Signaling Peptides and Proteins; D009125:Muscle Relaxants, Central; D011725:Pyridines; D014662:Vasoconstrictor Agents; C108830:Y 27632; D009569:Nitric Oxide; D052250:Nitric Oxide Synthase Type III; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D019204:GTP-Binding Proteins