REGRESSION OF FIBROSIS AFTER CHRONIC STIMULATION OF CANNABINOID CB2 RECEPTOR IN CIRRHOTIC RATS.

The Journal of pharmacology and experimental therapeutics 2007 Nov 20; In press

Munoz-Luque J J, Ros J J, Fernandez-Varo G G, Tugues S S, Morales-Ruiz M M, Alvarez C CE, Friedman S SL, Arroyo V V, Jimenez W W

Hospital Clinic.

Two cannabinoid receptor subtypes, CB1 and CB2, have been cloned and characterized. Among other activities, receptor activation by cannabinoid ligands may result in pro or antifibrogenic effects depending on their interaction with CB1 or CB2, respectively. In the current study we investigated whether selective activation of hepatic CB2 modifies collagen abundance in cirrhotic rats with ascites. mRNA and protein expression of CB receptors in the liver of control and cirrhotic rats was assessed by RT-PCR, Western blot and immunohistochemistry. The effect of chronically activating the CB2 receptor was investigated in cirrhotic rats with ascites treated daily (9 days) with the CB2 receptor selective agonist JWH-133. At the end of treatment, mean arterial pressure and portal pressure were measured and liver samples were obtained to evaluate infiltrate of mononuclear cells, hepatic apoptosis, alpha-SMA expression, collagen content and MMP-2 abundance in all animals. JWH-133 improved arterial pressure, decreased the inflammatory infiltrate, reduced the number of activated stellate cells, increased apoptosis in non-parenchymal cells located in the margin of the septa, and decreased fibrosis as compared to cirrhotic rats treated with vehicle. This was associated with decreased alpha-SMA and collagen I and increased MMP-2 in the hepatic tissue of cirrhotic rats treated with the CB2 agonist compared to untreated cirrhotic animals. Therefore, selective activation of hepatic CB2 receptors significantly reduces hepatic collagen content in rats with pre-existing cirrhosis, thus raising the possibility of using selective CB2 agonists for the treatment of hepatic fibrosis in human cirrhosis.

Keywords: FIBROSIS CANNABINOID