Role of HSP-90 for increased nNOS-mediated vasodilation in mesenteric arteries in portal hypertension.
OBJECTIVE
To explore the role of heat shock protein-90 (HSP-90) for nitrergic vasorelaxation in the splanchnic circulation in rats with and without portal hypertension.


METHODS
Neuronal nitric oxide synthase (nNOS) and HSP-90 were analyzed by immunofluorescence, western blotting and co-immunoprecipitation in the mesenteric vasculature and isolated nerves of portal-vein-ligated (PVL) rats and sham operated rats. In vitro perfused de-endothelialized mesenteric arterial vasculature was preconstricted with norepinephrine (EC(80)) and tested for nNOS-mediated vasorelaxation by periarterial nerve stimulation (PNS, 2-12 Hz, 45V) before and after incubation with geldanamycin (specific inhibitor of HSP-90 signalling, 3 microg/mL) or L-NAME (non-specific NOS-blocker, 10(-4) mol/L).


RESULTS
nNOS and HSP-90 expression was significantly increased in mesenteric nerves from PVL as compared to sham rats. Moreover, nNOS and HSP-90 were visualized in mesenteric nerves by immunofluorescence and immunoprecipitation of nNOS co-immunoprecipitated HSP-90 in sham and PVL rats. PNS induced a frequency-dependent vasorelaxation which was more pronounced in PVL as compared to sham rats. L-NAME and geldanamycin markedly reduced nNOS-mediated vasorelaxation abrogating differences between the study groups. The effect of L-NAME and geldanamycin on nNOS-mediated vasorelaxation was significantly greater in PVL than in sham animals. However, no difference in magnitude of effect between L-NAME and geldanamycin was noted.


CONCLUSIONS
HSP-90 acts as a signalling mediator of nNOS-dependent nerve mediated vascular responses in mesenteric arteries, and the increased nitrergic vasorelaxation observed in portal hypertension is mediated largely by HSP-90.
Moleda
Lukas
L
Department of Internal Medicine I, University Medical Center, D-93042 Regensburg, Germany.
Jurzik
Lars
L
Froh
Matthias
M
Gäbele
Erwin
E
Hellerbrand
Claus
C
Straub
Rainer H
RH
Schölmerich
Jürgen
J
Wiest
Reiner
R
D000818:Animals; D016227:Benzoquinones / Q000494:pharmacology; D015153:Blotting, Western; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D006975:Hypertension, Portal / Q000378:metabolism / Q000473:pathology*; D047468:Immunoprecipitation; D047029:Lactams, Macrocyclic / Q000494:pharmacology; D008297:Male; D008638:Mesenteric Arteries / Q000473:pathology*; D008856:Microscopy, Fluorescence / Q000379:methods; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism*; D010477:Perfusion; D051381:Rats; D017207:Rats, Sprague-Dawley; D014664:Vasodilation
D016227:Benzoquinones; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D052248:Nitric Oxide Synthase Type I; D019331:NG-Nitroarginine Methyl Ester; C001277:geldanamycin
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