Daily cannabis smoking as a risk factor for progression of fibrosis in chronic hepatitis C.

Cannabinoids present in Cannabis sativa (marijuana) exert biological effects via cannabinoid receptors CB1 and CB2. We recently demonstrated that CB1 and CB2 receptors regulate progression of experimental liver fibrosis. We therefore investigated the impact of cannabis smoking on fibrosis progression rate in patients with chronic hepatitis C (CHC). Two hundred seventy consecutive untreated patients with CHC of known duration undergoing liver biopsy were studied. Demographic, epidemiological, metabolic, and virological data were recorded, and detailed histories of cannabis, alcohol, and tobacco use over the span of hepatitis C virus infection were obtained. Fibrosis stage, steatosis, and activity grades were scored according to Metavir system. Patients were categorized as noncannabis users (52.2%), occasional users (14.8%), or daily users (33.0%), and the relationship between cannabis use and fibrosis progression rate (FPR) or fibrosis stage was assessed. On multivariate analysis, six factors were independently related to a FPR greater than 0.074 (median value of the cohort): daily cannabis use (OR = 3.4 [1.5-7.4]), Metavir activity grade A2 or higher (OR = 5.4 [2.9-10.3]), age at contamination of more than 40 years (OR = 10.5 [3.0-37.1]), genotype 3 (OR = 3.4 [1.5-7.7]), excessive alcohol intake (OR = 2.2 [1.1-4.5]), and steatosis (OR = 2.0 [1.0-4.1]). Daily cannabis use was also an independent predictor of a rapid FPR (>0.15) (OR = 3.6 [1.5-7.5]). Finally, severe fibrosis (> or =F3) was also predicted by daily cannabis use (OR = 2.5 [1.1-5.6]; P = .034), independently of Metavir activity grade, excessive alcohol intake, age at liver biopsy, steatosis, and tobacco smoking. In conclusion, daily cannabis smoking is significantly associated with fibrosis progression during CHC. Patients with ongoing CHC should be advised to refrain from regular cannabis use.

Antifibrogenic role of the cannabinoid receptor CB2 in the liver.

BACKGROUND & AIMS: Hepatic myofibroblasts are central for the development of liver fibrosis associated with chronic liver diseases, and blocking their accumulation may prevent fibrogenesis. Cannabinoids are the active components of marijuana and act via 2 G-protein-coupled receptors, CB1 and CB2. Here, we investigated whether liver fibrogenic cells are a target of cannabinoids. METHODS: CB2 receptors were characterized in biopsy specimens of normal human liver and active cirrhosis by immunohistochemistry, and in cultures of hepatic stellate cells and hepatic myofibroblasts by reverse-transcription polymerase chain reaction (RT-PCR), immunocytochemistry, and GTPgammaS assays. Functional studies were performed in cultured hepatic myofibroblasts and activated hepatic stellate cells. Carbon tetrachloride-induced liver fibrosis was studied in mice invalidated for CB2 receptors. RESULTS: In liver biopsy specimens from patients with active cirrhosis of various etiologies, CB2 receptors were expressed in nonparenchymal cells located within and at the edge of fibrous septa in smooth muscle alpha-actin-positive cells. In contrast, CB2 receptors were not detected in normal human liver. CB2 receptors were also detected in cultured hepatic myofibroblasts and in activated hepatic stellate cells. Their activation triggered potent antifibrogenic effects, namely, growth inhibition and apoptosis. Growth inhibition involved cyclooxygenase-2, and apoptosis resulted from oxidative stress. Finally, mice invalidated for CB2 receptors developed enhanced liver fibrosis following chronic carbon tetrachloride treatment as compared with wild-type mice. CONCLUSIONS: These data constitute the first demonstration that CB2 receptors are highly up-regulated in the cirrhotic liver, predominantly in hepatic fibrogenic cells. Moreover, this study also highlights the antifibrogenic role of CB2 receptors during chronic liver injury.

Hepatic fibrosis: molecular mechanisms and drug targets.

Liver fibrosis is the common response to chronic liver injury, ultimately leading to cirrhosis and its complications, portal hypertension, liver failure, and hepatocellular carcinoma. Efficient and well-tolerated antifibrotic drugs are currently lacking, and current treatment of hepatic fibrosis is limited to withdrawal of the noxious agent. Efforts over the past decade have mainly focused on fibrogenic cells generating the scarring response, although promising data on inhibition of parenchymal injury and/or reduction of liver inflammation have also been obtained. A large number of approaches have been validated in culture studies and in animal models, and several clinical trials are underway or anticipated for a growing number of molecules. This review highlights recent advances in the molecular mechanisms of liver fibrosis and discusses mechanistically based strategies that have recently emerged.

Molecular mechanisms regulating the antifibrogenic protein heme-oxygenase-1 in human hepatic myofibroblasts.

BACKGROUND/AIMS: Hepatic myofibroblasts are central in liver fibrogenesis associated with chronic liver diseases. We previously showed that heme-oxygenase-1 (HO-1) displays antifibrogenic properties in human hepatic myofibroblasts. Here, we further investigated the mechanisms regulating HO-1 expression. METHODS: Expression of HO-1 was assayed in cultured human hepatic myofibroblasts by Northern and Western blot. Functional studies were also performed in cultured human hepatic myofibroblasts. RESULTS: 15-Deoxy-Delta(12,14)-prostaglandin J2 (15-d-PGJ2) elicited inhibition of proliferation and of alpha1(I) collagen mRNA expression. These effects were reproduced by the glutathione depletor diethyl maleate and blunted by the glutathione precursor N-acetyl cysteine, indicating the involvement of oxidative stress. Two consecutive events mediated inhibition of proliferation and of alpha1(I) collagen mRNA expression by 15-d-PGJ2: (i) mild oxidative stress characterized by a transient GSH decrease and (ii) activation of p38 MAPK, resulting in increased HO-1 mRNA stability. CONCLUSIONS: Our results provide new insights into the regulatory mechanisms governing HO-1 expression in human hepatic myofibroblasts and identify mild oxidative stress and p38 MAPK as two consecutive early signals promoting HO-1 induction that are crucial for its antifibrogenic properties, namely inhibition of growth and extracellular matrix gene expression.

Heme oxygenase-1 is an antifibrogenic protein in human hepatic myofibroblasts.

BACKGROUND & AIMS: Hepatic myofibroblasts play a key role in the development of liver fibrosis associated with chronic liver diseases. We have shown that oxidative stress is a messenger of 15-deoxy-delta-12,14-prostaglandin J2 (15-d-PGJ2) in human hepatic myofibroblasts. The aim of the present study was to investigate the role of a stress-inducible protein, heme oxygenase-1 (HO-1), in the action of 15-d-PGJ2. METHODS: Expression of HO-1 was characterized in biopsy specimens of normal human liver and active cirrhosis by immunohistochemistry, and in cultured human hepatic myofibroblasts by Northern and Western blot analysis. Functional studies also were performed in cultured human hepatic myofibroblasts. RESULTS: Immunohistochemistry showed that in biopsy specimens from normal livers, HO-1 protein expression was restricted to Kupffer cells. Biopsy specimens from cirrhotic patients displayed HO-1 protein both in macrophages and in myofibroblasts within fibrotic septa. HO-1 messenger RNA (mRNA) and protein also were detected in cultured human hepatic myofibroblasts and increased in response to 15-d-PGJ2 in a time- and dose-dependent manner. Induction of HO-1 in human hepatic myofibroblasts mediated 2 major antifibrogenic properties of 15-d-PGJ2, namely, inhibition of proliferation and of procollagen I mRNA expression. These effects were ascribed to bilirubin, one of the products of HO-1-mediated heme degradation. CONCLUSIONS: This study shows that HO-1 is expressed in human hepatic myofibroblasts and induced during chronic liver injury. Moreover, these data unravel HO-1 as a major antifibrogenic pathway.