Liver fibrosis, a consequence of chronic liver injury and a way station to cirrhosis and hepatocellular carcinoma, lacks effective treatment. Endocannabinoids acting via cannabinoid-1 receptors (CB1R) induce profibrotic gene expression and promote pathologies that predispose to liver fibrosis. CB1R antagonists produce opposite effects, but their therapeutic development was halted due to neuropsychiatric side effects. Inducible nitric oxide synthase (iNOS) also promotes liver fibrosis and its underlying pathologies, but iNOS inhibitors tested to date showed limited therapeutic efficacy in inflammatory diseases. Here, we introduce a peripherally restricted, orally bioavailable CB1R antagonist, which accumulates in liver to release an iNOS inhibitory leaving group. In mouse models of fibrosis induced by CCl4 or bile duct ligation, the hybrid CB1R/iNOS antagonist surpassed the antifibrotic efficacy of the CB1R antagonist rimonabant or the iNOS inhibitor 1400W, without inducing anxiety-like behaviors or CB1R occupancy in the CNS. The hybrid inhibitor also targeted CB1R-independent, iNOS-mediated profibrotic pathways, including increased PDGF, Nlrp3/Asc3, and integrin αvβ6 signaling, as judged by its ability to inhibit these pathways in cnr1–/– but not in nos2–/– mice. Additionally, it was able to slow fibrosis progression and to attenuate established fibrosis. Thus, dual-target peripheral CB1R/iNOS antagonists have therapeutic potential in liver fibrosis.
Resat Cinar, Malliga R. Iyer, Ziyi Liu, Zongxian Cao, Tony Jourdan, Katalin Erdelyi, Grzegorz Godlewski, Gergő Szanda, Jie Liu, Joshua K. Park, Bani Mukhopadhyay, Avi Z. Rosenberg, Jeih-San Liow, Robin G. Lorenz, Pal Pacher, Robert B. Innis, George Kunos
Attenuation of hepatic iNOS activity and protein levels in biliary fibrosis by MRI-1867 but not rimonabant.