Background/aim: Endotoxaemia can complicate hepatic ischaemia–reperfusion (IR) injury. Endocannabinoids appear to modulate the haemodynamic alterations and cytokine response induced by lipopolysaccharide (LPS). Thus, we aimed to determine the effect of the endocannabinoid CB1-receptor antagonist Rimonabant in a model of hepatic IR injury complicated by endotoxaemia.
Methods: Sprague–Dawley rats pre-treated with Rimonabant 3 or 10 mg/kg or vehicle underwent partial hepatic IR and lipopolysaccharide (LPS) injection at reperfusion. Liver injury was evaluated by serum alanine aminotransferase (ALT) and necrotic-cell count. The inflammatory response was investigated by assessing hepatic neutrophil infiltration, tumour necrosis factor α (TNFα), interferon γ (IFNγ), interleukin 6 (IL6), and suppressor of cytokine signalling (SOCS) 1 and SOCS3 gene expression by real-time polymerase chain reaction (RT-PCR). Systolic blood pressure and hepatic blood flow were measured as haemodynamic parameters. Finally, lipid peroxidation, glutathione status, and immunoreactive CB1 receptor expression in the liver were also determined.
Results: Liver injury and neutrophil infiltration occurring in the late-phase of LPS-enhanced IR were significantly reduced by CB1-receptor antagonism. Rimonabant-treated rats showed significantly higher gene expression of IFNγ, IL6, SOCS1 and SOCS3 in “early” reperfusion, while that of TNFα was reduced. These findings were associated with increased STAT3 phosphorylation. Furthermore, CB1-receptor antagonism significantly improved the oxidative injury and haemodynamic alterations occurring during reperfusion in untreated rats. Finally, CB1-receptor immunoreactivity was upregulated early after reperfusion.
Conclusions: This study demonstrates that CB1-receptor antagonism protects the liver against LPS-enhanced IR injury by interfering with the inflammatory response that causes the late, neutrophil-dependent phase of reperfusion injury, although the prevention of the transient endotoxin-related hypotension occurring early during reperfusion may be also involved.
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Competing interests: PC has served as a consultant for Sanofi-Aventis (France). MD, PC and MB were recipients of the research grant by Sanofi-Aventis (Milan, Italy) which partially supported this study. TC is an employee of Sanofi-Aventis Research Laboratories, Milan, Italy. The other authors have no competing interests.
Funding: This study was supported in part by the Ministero dell’Istruzione, dell’Università e della Ricerca (M.I.U.R.) – Progetto di ricerca di interesse nazionale 2001 (ex-40%), by the Fondazione Cassa di Risparmio in Bologna, Italy, and by a research grant from Sanofi-Aventis, Milan, Italy.
Ethics approval: All procedures involving rats were conducted in accordance with internationally accepted principles for care of laboratory animals (EEC Council Directive 86/609) and the guidelines for the care and use of laboratory animals approved by the ethics committee of our university.
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