Abstract
Two cannabinoid (CB) 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 reverse transcription-polymerase chain reaction, 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 3-(1,1-dimethylbutyl)-1-deoxy-Δ8-tetrahydrocannabinol (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, α-smooth muscle actin (SMA) expression, collagen content, and matrix metalloproteinase (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 nonparenchymal cells located in the margin of the septa, and decreased fibrosis compared with cirrhotic rats treated with vehicle. This was associated with decreased α-SMA and collagen I and increased MMP-2 in the hepatic tissue of cirrhotic rats treated with the CB2 agonist compared with 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.
Footnotes
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This work was supported by Dirección General de Investigación Científica y Técnica Grants SAF03-02597 and SAF2006-07053 (to W.J.) and Grant SAF 07-63069 (to M.M.-R.). S.T. received a grant from Institut d'Investigacions Biomèdiques August Pi i Sunyer. J.M.-L. received Grant SAF03-02597 from Dirección General de Investigación Científica y Tecnológica. G.F.-V. received a Clinical Chemistry fellowship from Siemens Medical Solutions Diagnostics. S.L.F. was supported by National Institutes of Health Grant DK56621.
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.107.131896.
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ABBREVIATIONS: AEA, anandamide; CB, cannabinoid; TRP, transient receptor potential; HSC, hepatic stellate cell(s); HPRT, hypoxanthine-guanine phosphoribosyl transferase; bp, base pair(s); RT, reverse transcription; PCR, polymerase chain reaction; JWH-133, 3-(1,1-dimethylbutyl)-1-deoxy-Δ8-tetrahydrocannabinol; MAP, mean arterial pressure; MMP, matrix metalloproteinase; SMA, smooth muscle actin; TUNEL, terminal deoxynucleotidyl transferase dUTP nick-end labeling.
- Received September 19, 2007.
- Accepted November 19, 2007.
- The American Society for Pharmacology and Experimental Therapeutics
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