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Abstract
Acute-on-chronic liver disease is a clinical syndrome characterized by decompensated liver fibrosis, portal hypertension and splanchnic hyperdynamic circulation. We aimed to determine whether the alpha-1 agonist phenylephrine (Phe) facilitates endothelial nitric oxide (NO) release by mesenteric resistance arteries (MRA) in rats subjected to an experimental microsurgical obstructive liver cholestasis model (LC). Sham-operated (SO) and LC rats were maintained for eight postoperative weeks. Phe-induced vasoconstriction (in the presence/absence of the NO synthase –NOS- inhibitor L-NAME) and vasodilator response to NO donor DEA-NO were analysed. Phe-induced NO release was determined in the presence/absence of either H89 (protein kinase –PK- A inhibitor) or LY 294002 (PI3K inhibitor). PKA and PKG activities, alpha-1 adrenoceptor, endothelial NOS (eNOS), PI3K, AKT and soluble guanylate cyclase (sGC) subunit expressions, as well as eNOS and AKT phosphorylation, were determined. The results show that LC blunted Phe-induced vasoconstriction, and enhanced DEA-NO-induced vasodilation. L-NAME increased the Phe-induced contraction largely in LC animals. The Phe-induced NO release was greater in MRA from LC animals. Both H89 and LY 294002 reduced NO release in LC. Alpha-1 adrenoceptor, eNOS, PI3K and AKT expressions were unchanged, but sGC subunit expression, eNOS and AKT phosphorylation and the activities of PKA and PKG were higher in MRA from LC animals. In summary, these mechanisms may help maintaining splanchnic vasodilation and hypotension observed in decompensated LC.
Highlights
Liver diseases are among the ten most frequent causes of death in the Western world[1]
The PKA and PI3K/AKT signalling pathways are both reported to be enhanced in liver pathologies[28,29,30,31]. In view of these results, we aimed to determine whether activating alpha-1 adrenoceptors with Phe facilitates the release of endothelial nitric oxide (NO) in mesenteric resistance arteries (MRA) from rats subjected to microsurgical liver cholestasis (LC), a model of acute-on-chronic liver disease, as well as the possible enzymatic pathways implicated
We found an increase in total and direct bilirubin (TB; DB), alkaline phosphatase (AP), bile acids (BA), and aspartate aminotransferase (AST) in serum from LC rats
Summary
Liver diseases are among the ten most frequent causes of death in the Western world[1]. Rat experimental models of hepatic fibrosis resulting from obstructive cholestasis cause an inflammatory activation of hepatic stellate cells, which express different, sometimes overlapping, phenotypes during the course of the disease; initially they develop a functional contractile phenotype that is responsible for the triggering of portal hypertension They can transform themselves into fibroblasts, which synthetize and release collagen, causing liver fibrosis, a portal blood flow obstruction, and enhancing portal hypertension. The PKA and PI3K/AKT signalling pathways are both reported to be enhanced in liver pathologies[28,29,30,31] In view of these results, we aimed to determine whether activating alpha-1 adrenoceptors with Phe facilitates the release of endothelial NO in MRA from rats subjected to microsurgical liver cholestasis (LC), a model of acute-on-chronic liver disease, as well as the possible enzymatic pathways implicated
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