Kupffer cell depletion attenuates leptin-mediated methoxamine-stimulated portal perfusion pressure and thromboxane A₂ release in a rodent model of NASH-cirrhosis

Cirrhotic portal hypertension is characterized by increased hepatic oxidative stress, AA (arachidonic acid)-derived TXA₂ (thromboxane A₂) release and exaggerated hepatic response to the α-adrenergic agonist MTX (methoxamine). Besides promoting hepatic fibrosis, the role of hyperleptinaemia in the modulation of vascular response in NASH (non-alcoholic steatohepatitis) rat livers remains unknown. The aim of the present study was to explore the possible links between hyperleptinaemia and the disarrangement in the hepatic microcirculation. NASH-cirrhosis with hyperleptinaemia was induced in lean rats by feeding with an HF/MCD (high-fat/methionine-choline-deficient) diet. Portal haemodynamics, various substances, protein and mRNA expression and PUFA (polyunsaturated fatty acid) composition were measured. Finally, the effects of leptin pre-infusion on TXA₂ release and concentration–PPP (portal perfusion pressure) curves in response to MTX were evaluated by simultaneously pre-treatment with the Kupffer cell inactivators GdCl₃ (gadolinium chloride) or EC (encapsulated clodronate), the TXS (TXA₂ synthase) inhibitor furegrelate, the TP receptor (TXA₂ receptor) antagonist SQ29548 and the dual TXS/TP receptor antagonist BM567. In HF/MCD+leptin-lean rats, cirrhosis-induced PPP and MTX hyper-responsiveness were associated with increased hepatic TXA₂ production, TBARS (thiobarbituric acid-reacting substances) levels and the AA (arachidonic acid)/n−3 PUFA ratio, and up-regulation of hepatic leptin, FAS (fatty acid synthase), NADPH oxidase subunits, TXS, TP receptor, TGFβ₁ (transforming growth factor β₁) proteins and mRNAs. Pre-infusion of leptin significantly enhanced MTX-stimulated PPP elevation and TXA₂ release, which were attenuated by GdCl₃ and EC pre-treatment. Concomitantly pre-incubation with BM567, but not furegrelate or SQ29548, significantly abolished the leptin-enhanced MTX-stimulated increase in PPP in NASH-cirrhotic rats. Hyperleptinaemia plays an important role in hyper-responsiveness to MTX in NASH-cirrhotic rat livers with portal hypertension. The leptin-enhanced MTX-stimulated increase in PPP is mediated by increased oxidative stress and Kupffer-cell-activated AA-derived TXA₂ release in NASH-cirrhotic rats.