Phospholipase A₂ of Microbiota as Pathogenetic Determinant to Induce Inflammatory States in Ulcerative Colitis: Therapeutic Implications of Phospholipase A₂ Inhibitors

Abstract

Background: Attack by commensal microbiota is one component of induction of inflammatory episodes in ulcerative colitis (UC). In UC, the mucus layer is intrinsically devoid of phosphatidylcholine (PC) resulting in low hydrophobicity which facilitates bacterial invasion. Colonic ectophospholipase-carrying bacterial strains are likely candidates to further thinning the PC mucus barrier and to precipitate inflammatory episodes. Objective: To evaluate the effect of phospholipase A₂ (PLA₂) inhibitors on inflammation in a genetic UC mouse model. Methods: As PLA₂ inhibitor, we applied the bile acid-phospholipid conjugate ursodeoxycholate-lysophosphatidylethanolamide (UDCA-LPE) or as control 5% Tween 80 by oral gavage to intestine-specific kindlin 2 knockout mice. Results: Luminal UDCA-LPE reduced the PLA₂ activity in stool by 36 ± 8%. Concomitantly no inflammatory phenotype was observed when compared to kindlin 2^(–/–) mice not treated with UDCA-LPE. The improvement was documented in regard to stool consistency, calprotectin levels in stool, and macroscopic/endoscopic as well as histologic features of the mucosa. The pattern of colonic microbiota distribution obtained in the UC phenotype mice was reversed by UDCA-LPE to the control mice pattern. Conclusion: The inhibition of the bacterial ectophospholipase A₂ activity improves mucosal inflammation in a genetic mouse model of UC. It is assumed that the remaining mucus PC shield is better preserved when luminal PLA₂ is suppressed.

Milk Exosomes Prevent Intestinal Inflammation in a Genetic Mouse Model of Ulcerative Colitis: A Pilot Experiment

“…Animal studies followed the "ARRIVE" guidelines and were approved by the Heidelberg ethics committee (Ref-# 35-9185.81/ 6123/10 and 6284/11) (Ref-# S-211/2010). Tamoxifen-inducible, villin-Cre-dependent, kindlin 2 intestine-specific knockout mice were a gift of R. Faessler (Max-Planck Institute for Biochemistry, Munich) and propagated after embryonic transfer in the animal facilities of the University of Heidelberg [39,40]. Mutant kindlin 2 (−/−) mice received LasVendi Rod 18 complete diet (Soest, Germany) ad libitum and were kept in conventional caging with AB-BEDD LT-E-001 (Vienna, Austria) bedding at 22°C, with a 12-h/ 12-h light/dark cycle.…”

“…injected at 9:00 a.m. with 0.2 mg tamoxifen daily for up to 4 days before being sacrificed 1 day later. Ileal mucosal cells were isolated [43] and characterized by Western blotting using antibodies to mouse kindlin 2, to ensure complete depletion in the mutant mice [39,40]. As control, 12-week old wild-type mice were used.…”

“…For this purpose, we investigated the effects of oral exposure of bovine milk exosomes in an established genetic mouse model of UC [39]. This UC model, which operates by disruption of the tight-junction barrier between intestinal mucosal cells, employs a tamoxifen-inducible intestinal-specific deletion of intestinal expression of kindlin 2, resulting in a severe UC phenotype [39,40].…”

“…The difference of this mouse model in comparison to the human disease is (1) its rapid and severe phenotype and (2) that not only a hemorrhagic colitis but also an ileitis manifests. In previous studies, therapeutic strategies with topical PC supplementation as well as a luminally acting phospholipase inhibitor were shown to be effective [39,40].…”

The Detergent Effect of Mesalazine Interferes with Phosphatidylcholine Binding to Mucin 2

“…Accordingly, the colonic mucosa is less hydrophobic and prone to microbiota-induced inflammation which always starts in the rectum, the last lawn of mucus PC content due to the longest exposure time to bacterial ectophospholipase activity in stool [15]. Accordingly, the concept arose to supplement the mucus PC content in patients with UC by application of a delayed-release oral PC preparation.…”