Endothelial [Ca2+]i and caveolin-1 antagonistically regulate eNOS activity and microvessel permeability in rat venules.
OBJECTIVE
In this study, we investigated the mechanisms by which caveolin-1 (CAV) inhibits increases in permeability induced by platelet activating factor (PAF) and elucidated the relationship between the endothelial intracellular Ca(2+) concentration ([Ca(2+)](i)) and CAV in regulating endothelial nitric oxide synthase (eNOS) activity and microvessel permeability in intact microvessels.


RESULTS
Experiments were conducted in individually perfused mesenteric venules in Sprague-Dawley rats. Permeability was determined by measuring hydraulic conductivity (Lp). Endothelial [Ca(2+)](i) and nitric oxide (NO) production were measured in fura-2- and DAF-2-loaded microvessels. Perfusion of the CAV scaffolding domain, AP-CAV, at 1 microM for 30 min did not affect PAF-induced increases in endothelial [Ca(2+)](i) but significantly attenuated PAF-induced NO production from 143 +/- 2 to 110 +/- 3% of control fluorescence intensity (FI). The PAF-induced Lp increase was correlatively reduced from a mean peak value of 7.5 +/- 0.9 to 1.9 +/- 0.5 times that of the control. Increasing extracellular [Ca(2+)] that potentiated PAF-induced peak [Ca(2+)](i) from 500 to 1225 nM augmented NO production to 193 +/- 13% and further increased Lp to 17.3 +/- 1.6 times the control value. More importantly, enhanced Ca(2+) influx restored the reduced NO production and Lp by AP-CAV with NO FI at 149% and Lp at 7.7 +/- 1.1 times the control value.


CONCLUSIONS
Our results indicate that eNOS inhibition and reduced NO production contribute to the inhibitory action of AP-CAV on PAF-induced increases in permeability. CAV and endothelial [Ca(2+)](i) antagonistically regulate eNOS activity in intact microvessels, and the level of produced NO is the key determinant of the degree of permeability increases during inflammation.
Zhou
Xueping
X
Department of Physiology and Pharmacology, School of Medicine, Health Science Center North West Virginia University, Morgantown, WV 26505-9229, USA.
He
Pingnian
P
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002199:Capillary Permeability; D051242:Caveolin 1 / Q000235:genetics / Q000378:metabolism*; D042783:Endothelial Cells / Q000201:enzymology*; D005260:Female; D066298:In Vitro Techniques; D018836:Inflammation Mediators / Q000378:metabolism; D008643:Mesentery / Q000098:blood supply*; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism*; D010477:Perfusion; D010972:Platelet Activating Factor / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013997:Time Factors; D014699:Venules / Q000201:enzymology*
D051242:Caveolin 1; D018836:Inflammation Mediators; D010972:Platelet Activating Factor; D011993:Recombinant Fusion Proteins; D009569:Nitric Oxide; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat; D002118:Calcium