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Inactivation of fatty acid amide hydrolase exacerbates experimental fibrosis by enhanced endocannabinoid-mediated activation of CB1


Palumbo-Zerr, Katrin; Horn, Angelika; Distler, Alfiya; Zerr, Pawel; Dees, Clara; Beyer, Christian; Selvi, Enrico; Cravatt, Benjamin F; Distler, Oliver; Schett, Georg; Distler, Jörg H W (2012). Inactivation of fatty acid amide hydrolase exacerbates experimental fibrosis by enhanced endocannabinoid-mediated activation of CB1. Annals of the Rheumatic Diseases, 71(12):2051-2054.

Abstract

BACKGROUND: Selective targeting of the cannabinoid receptors CB1 and CB2 by synthetic compounds has revealed opposing roles of both receptors in fibrosis.
OBJECTIVES: To characterise the role of endogenous cannabinoids (endocannabinoids) and their predominant receptor in fibrosis.
METHODS: The levels of endocannabinoids in mice were modulated by pharmacological or genetic inactivation of the enzyme fatty acid amide hydrolase (FAAH). The predominant receptor for endocannabinoids was determined by selective inhibition of either CB1 or CB2. The extent of fibrosis upon challenge with bleomycin was determined by quantification of dermal thickness, hydroxyproline content and myofibroblast counts.
RESULTS: The expression of FAAH is decreased in systemic sclerosis fibroblasts. FAAH-deficient mice with strongly increased levels of endocannabinoids were more sensitive to bleomycin. Consistently, pharmacological inhibition of FAAH significantly exacerbated bleomycin-induced fibrosis. Inhibition of CB1 completely abrogated the profibrotic effects of FAAH inactivation. In contrast, inhibition of CB2 only modestly enhanced fibrosis, indicating that CB1 is the predominant receptor for endocannabinoids in experimental fibrosis.
CONCLUSIONS: Increased levels of endocannabinoids induced by inactivation of FAAH worsen experimental fibrosis via activation of CB1. These findings highlight the profibrotic effects of endocannabinoids and suggest that CB1 maybe a more promising candidate for targeted treatments in fibrotic diseases than CB2.

Abstract

BACKGROUND: Selective targeting of the cannabinoid receptors CB1 and CB2 by synthetic compounds has revealed opposing roles of both receptors in fibrosis.
OBJECTIVES: To characterise the role of endogenous cannabinoids (endocannabinoids) and their predominant receptor in fibrosis.
METHODS: The levels of endocannabinoids in mice were modulated by pharmacological or genetic inactivation of the enzyme fatty acid amide hydrolase (FAAH). The predominant receptor for endocannabinoids was determined by selective inhibition of either CB1 or CB2. The extent of fibrosis upon challenge with bleomycin was determined by quantification of dermal thickness, hydroxyproline content and myofibroblast counts.
RESULTS: The expression of FAAH is decreased in systemic sclerosis fibroblasts. FAAH-deficient mice with strongly increased levels of endocannabinoids were more sensitive to bleomycin. Consistently, pharmacological inhibition of FAAH significantly exacerbated bleomycin-induced fibrosis. Inhibition of CB1 completely abrogated the profibrotic effects of FAAH inactivation. In contrast, inhibition of CB2 only modestly enhanced fibrosis, indicating that CB1 is the predominant receptor for endocannabinoids in experimental fibrosis.
CONCLUSIONS: Increased levels of endocannabinoids induced by inactivation of FAAH worsen experimental fibrosis via activation of CB1. These findings highlight the profibrotic effects of endocannabinoids and suggest that CB1 maybe a more promising candidate for targeted treatments in fibrotic diseases than CB2.

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14 citations in Web of Science®
13 citations in Scopus®
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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > University Hospital Zurich > Rheumatology Clinic and Institute of Physical Medicine
Dewey Decimal Classification:610 Medicine & health
Language:English
Date:2012
Deposited On:14 Feb 2013 16:28
Last Modified:05 Apr 2016 16:27
Publisher:BMJ Publishing Group
ISSN:0003-4967
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1136/annrheumdis-2012-201823
PubMed ID:22915616

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