Abstract
Intraluminal administration of the endocannabinoidsN-arachidonoyl-ethanolamine (anandamide) and 2-arachidonoylglycerol (2-AG) causes inflammation similar to that caused by Clostridium difficile toxin A in the rat ileum. The effects of anandamide and 2-AG were significantly inhibited by pretreatment with the specific capsaicin receptor (vanilloid receptor subtype 1; VR1) antagonist capsazepine. Pretreatment with the CB1 and CB2 cannabinoid receptor antagonistsN-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-3-pyrazole-carboxamide (SR141716) andN-[1S)-endo-1,3,3-trimethylbicyclo[2.2.1]heptan-2-yl]-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)-pyrazole-3-carboxamide (SR144528) did not affect the responses to anandamide. It has previously been shown that intraluminal toxin A stimulates substance P (SP) release from primary sensory neurons and that pretreatment with SP receptor [neurokinin (NK)-1 receptor] antagonists inhibits the inflammatory effects of toxin A. Anandamide stimulated SP release and this was blocked by capsazepine pretreatment. Also, pretreatment with the specific NK-1 receptor antagonist (2S,3S)-3-([3,5-bis[trifluoromethyl)phenyl]methoxy)-2-phenylpiperidine (L-733,060) significantly inhibited the inflammatory effects of both toxin A and anandamide. Toxin A increased tissue concentrations of anandamide and 2-AG in the ileum, and these effects were enhanced after pretreatment with inhibitors of fatty acid amide hydrolase, a major endocannabinoid-degrading enzyme. The toxin A-stimulated release of anandamide but not 2-AG was selective over their congeners. These results demonstrate that the endocannabinoids anandamide and 2-AG stimulate intestinal primary sensory neurons via the capsaicin VR1 receptor to release SP, resulting in enteritis, and that endocannabinoids may mediate the inflammatory effects of toxin A.
Footnotes
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This work was supported by a Veterans Affairs Merit Review Grant (to S.R.V.), National Institutes of Health Grants DK-50265 (to S.R.V.) and GM-45741 (to H.H.O.S.), and by the Hormel Foundation (to H.H.O.S.).
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DOI: 10.1124/jpet.102.043893
- Abbreviations:
- SP
- substance P
- VR1
- vanilloid receptor subtype 1
- CB
- cannabinoid
- 2-AG
- 2-arachidonoylglycerol
- FAAH
- fatty acid amide hydrolase
- MAFP
- methyl arachidonyl fluorophosphonate
- PMSF
- phenylmethanesulfonyl fluoride
- DMSO
- dimethyl sulfoxide
- MPO
- myeloperoxidase
- NK-1R
- neurokinin-1 receptor
- NK-1R-ir
- neurokinin-1 receptor-1R-immunoreactive
- NAE
- N-acylethanolamine
- MAG
- monoacylglycerol
- tBDMS
- tert-butyldimethylsilyl
- NK-1
- neurokinin-1
- Received August 4, 2002.
- Accepted October 3, 2002.
- U.S. Government
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