Experimental colitis in mice is attenuated by changes in the levels of endocannabinoid metabolites induced by selective inhibition of fatty acid amide hydrolase (FAAH)

Abstract

Background and aims: Pharmacological treatment and/or maintenance of remission in inflammatory bowel diseases (IBD) is currently one of the biggest challenge in the field of gastroenterology. Available therapies are mostly limited to overcoming the symptoms, but not the cause of the disease. Recently, the endocannabinoid system has been proposed as a novel target in the treatment of IBD. Here we aimed to assess the anti-inflammatory action of the novel fatty acid amide hydrolase (FAAH) inhibitor PF-3845 and its effect on the endocannabinoid and related lipid metabolism during the course of experimental colitis.

Methods: We used two models of experimental colitis in mice (TNBS- and DSS-induced) and additionally, we employed LC/MS/MS spectrometry to determine the changes in biolipid levels in the mouse colon during inflammation.

Results: We showed that the FAAH inhibitor PF-3845 reduced experimental TNBS-induced colitis in mice and its anti-inflammatory action is associated with altering the levels of selected biolipids (arachidonic and oleic acid derivatives, prostaglandins and biolipids containing glycine in the mouse colon).

Conclusions: We show that FAAH is a promising pharmacological target and the FAAH-dependent biolipids play a major role in colitis. Our results highlight and promote therapeutic strategy based on targeting FAAH-dependent metabolic pathways in order to alleviate intestinal inflammation.

Keywords: Experimental colitis; Fatty acid amide hydrolase;; Inflammatory bowel diseases;; Intestinal inflammation;; PF-3845;.

Figure 1

PF-3845 (10 mg/kg) injected twice daily over 3 days in various routes of administration attenuated TNBS-induced colitis in mice. Figure shows data for macroscopic scores and MPO activity after (A) i.p., (B) p.o. and (C) i.c. administration. *P < 0.05, **P< 0.01 ***P < 0.001, as compared to control mice. ##P < 0.01, ###P < 0.001, vs. TNBS-treated animals. Data represent mean ± SEM of 6–8 mice per group.

Figure 2

The anti-inflammatory effect of PF-3845 (10 mg/kg, p.o.) injected twice daily over 3 days in TNBS-treated mice was reversed by the CB1 antagonist AM 251 (1 mg/kg, i.p.), but not the CB2 antagonist AM 630 (1 mg/kg, i.p.). Figure shows data for macroscopic score (A), MPO activity (B), ulcer score (C), and colon length (D). &P<0.05, &&P<0.01, &&&P<0.001, as compared to control mice, *P < 0.05, **P< 0.01, as compared to TNBS-treated mice. #P < 0.05, ##P < 0.01, vs. PF-3845-treated animals. Data represent mean ± SEM of 6–8 mice per group.

Figure 3

Microscopic total damage score and representative micrographs of hematoxylin and eosin-stained sections of distal colon from (A) control, (B) TNBS, and (C) TNBS + PF-3845 (10 mg/kg, p.o., twice daily)-treated mice, (D) TNBS + PF3845 + AM 251, (D) TNBS + PF3845 + AM 630. Scale bar = 100 μm. &&&P <0.001, as compared with control mice, **P < 0.01, ***P< 0.001, as compared to TNBS-treated mice. ###P < 0.001, vs. PF-3845-treated animals. Data represent mean ± SEM of 6–8 mice per group.

Figure 4

PF-3845 (10 mg/kg, p.o.) injected twice daily over 7 days did not attenuate the DSS-induced colitis. Figure shows data for macroscopic score (A), MPO activity (B), colon weight (C), and colon length (D). ***P < 0.001, as compared to control mice. Data represent mean ± SEM of 6–8 mice per group.

Figure 5

Effect of PF-3845 on biolopid levels in control and TNBS-treated mice colon specimens. Figure shows changes in levels of A) 2-AG, B) 2-OG, C) PGE2, and D) biolipids containing glycine. *P < 0.05, **P< 0.01, ***P< 0.001 vs. control animals. #P < 0.05, vs. TNBS-treated animals. Data represent mean ± SEM of 6–8 colon samples per group.

Figure 6

Determination of FAAH mRNA levels in colon specimens from patients with diagnosed UC and CD vs. healthy subjects. There is an observable difference between control and UC as well as CD groups, but it did not reach statistical significance.