Caveolin-1/Endothelial Nitric Oxide Synthase Interaction Is Reduced in Arteries From Pregnant Spontaneously Hypertensive Rats

We have investigated the role caveolae/caveolin-1 (Cav-1) plays in endothelial nitric oxide synthase (eNOS) activation and how it impacts pregnancy-induced decreased vascular reactivity in normotensive (Wistar rats) and spontaneously hypertensive rats (SHR). Wistar rats and SHR were divided into non-pregnant (NP) and pregnant (P). Nitrite levels were assessed by the Griess method in the aorta and mesenteric vascular bed. In functional studies, arteries were incubated with methyl-β-cyclodextrin (dextrin, 10mmol/L), which disrupts caveolae by depleting cholesterol, and concentration-response curves to phenylephrine (PE) and acetylcholine (ACh) were constructed. Electronic microscopy was used to determine endothelial caveolae density in the aorta and resistance mesenteric artery in the presence of vehicle or dextrin (10mmol/L). Western blot was performed to evaluate Cav-1, p-Cav-1, calmodulin (CaM), and heat shock protein 90 (Hsp90) expression. Cav-1/eNOS interaction in the aorta and mesenteric vascular bed was assessed by co-immunoprecipitation. Nitric oxide (NO) generation was greater in arteries from P groups compared to NP groups. Dextrin did not change vascular responses in the aorta from P groups or the number of caveolae in P groups compared to NP groups. Compared to NP Wistar rats, NP SHR showed smaller number of caveolae and reduced Cav-1 expression. Pregnancy did not alter Cav-1, CaM, or Hsp90 expression in the aorta or mesenteric vascular bed from Wistar rats or SHR. These results suggest that pregnancy does not alter expression of the main eNOS regulatory proteins, but it decreases Cav-1/eNOS interaction. Reduced Cav-1/eNOS interaction in the aorta and mesenteric vascular bed seems to be an important mechanism to increase eNOS activity and nitric oxide production in pregnant normotensive and hypertensive rats.

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Rapamycin Induces an eNOS (Endothelial Nitric Oxide Synthase) Dependent Increase in Brain Collateral Perfusion in Wistar and Spontaneously Hypertensive Rats

Stroke ◽

10.1161/strokeaha.120.029781 ◽

2020 ◽

Vol 51 (9) ◽

pp. 2834-2843

Author(s):

Daniel J. Beard ◽

Zhaojin Li ◽

Anna M. Schneider ◽

Yvonne Couch ◽

Marilyn J. Cipolla ◽

...

Keyword(s):

Nitric Oxide ◽

Blood Flow ◽

Cerebral Blood Flow ◽

Nitric Oxide Synthase ◽

Spontaneously Hypertensive Rats ◽

Infarct Volume ◽

Hypertensive Rats ◽

Spontaneously Hypertensive ◽

Oxide Synthase ◽

Endothelial Nitric Oxide

Background and Purpose: Rapamycin is a clinically approved mammalian target of rapamycin inhibitor that has been shown to be neuroprotective in animal models of stroke. However, the mechanism of rapamycin-induced neuroprotection is still being explored. Our aims were to determine if rapamycin improved leptomeningeal collateral perfusion, to determine if this is through eNOS (endothelial nitric oxide synthase)-mediated vessel dilation and to determine if rapamycin increases immediate postreperfusion blood flow. Methods: Wistar and spontaneously hypertensive rats (≈14 weeks old, n=22 and n=15, respectively) were subjected to ischemia by middle cerebral artery occlusion (90 and 120 minutes, respectively) with or without treatment with rapamycin at 30-minute poststroke. Changes in middle cerebral artery and collateral perfusion territories were measured by dual-site laser Doppler. Reactivity to rapamycin was studied using isolated and pressurized leptomeningeal anastomoses. Brain injury was measured histologically or with triphenyltetrazolium chloride staining. Results: In Wistar rats, rapamycin increased collateral perfusion (43±17%), increased reperfusion cerebral blood flow (16±8%) and significantly reduced infarct volume (35±6 versus 63±8 mm 3 , P <0.05). Rapamycin dilated leptomeningeal anastomoses by 80±9%, which was abolished by nitric oxide synthase inhibition. In spontaneously hypertensive rats, rapamycin increased collateral perfusion by 32±25%, reperfusion cerebral blood flow by 44±16%, without reducing acute infarct volume 2 hours postreperfusion. Reperfusion cerebral blood flow was a stronger predictor of brain damage than collateral perfusion in both Wistar and spontaneously hypertensive rats. Conclusions: Rapamycin increased collateral perfusion and reperfusion cerebral blood flow in both Wistar and comorbid spontaneously hypertensive rats that appeared to be mediated by enhancing eNOS activation. These findings suggest that rapamycin may be an effective acute therapy for increasing collateral flow and as an adjunct therapy to thrombolysis or thrombectomy to improve reperfusion blood flow.

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