gms | German Medical Science

Introduction: During mucosal inflammation, a complex array of proinflammatory and protective mechanisms regulates inflammation and severity of injury. Secretion of anti-inflammatory mediators is a mechanism that is critical in controlling inflammatory responses and promoting epithelial restitution and barrier recovery. AnxA1 is a potent anti-inflammatory protein that has been implicated to play a critical immune regulatory role in models of inflammation. Although AnxA1 has been shown to be secreted in intestinal mucosal tissues during inflammation, its potential role in modulating the injury/inflammatory response is not understood.

Material and methods: Animals:Wild-type (WT) female BALB/c mice were purchased from The Jackson Laboratory. AnxA1 null mice were generated as previously described. Induction of colitis:Seven percent (w/v) DSS was dissolved in purified water and administered to mice for 7 days. For rescue studies with ALX/FPRL-1 stimulation, we used 15-epi-lipoxin A4 ((5S,6R,15R)-5,6,15-trihydroxy-7,9,13-trans-11-cis-eicosatetraenoic acid; Calbiochem) which was injected i.p. (0,4 µg/animal) daily during the course of DSS administration. Western blotting and Immunofluorescence were performed on colonic tissue samples. For each animal, histological examination was performed on three samples of the distal colon. RT-PCR analysis: Expression of murine FPR1 (NM_013521), FPR-rs2 (NM_008039), and ALX/FPRL-1 (NM_008042) was analyzed by real-time PCR using iQ SYBR mix (iCycler; Bio-Rad). Results are expressed as the mean ± SEM. One-way ANOVA with post hoc testing or paired Student’s t tests were used to compare results from different experiments.

Results: In this study, we demonstrate that AnxA1-deficient animals exhibit increased susceptibility to dextran sulfate sodium (DSS)-induced colitis with greater clinical morbidity and histopathologic mucosal injury. Furthermore, impaired recovery following withdrawal of DSS administration was observed in AnxA1 (–/–) animals compared with wild-type (WT) control mice that was independent of inflammatory cell infiltration. Since AnxA1 exerts its anti-inflammatory properties through stimulation of ALX/FPRL-1, we explored the role of this receptor-ligand interaction in regulating DSS-induced colitis. Interestingly, treatment with an ALX/FPRL-1 agonist, 15-epi-lipoxin A4 reversed the enhanced sensitivity of AnxA1 (–/–) mice to DSS colitis. In contrast, 15-epi-lipoxin A4 did not significantly improve the severity of disease in WT animals. Additionally, differential expression of ALX/FPLR-1 in control and DSS-treated WT and AnxA1-deficient animals suggested a potential role for AnxA1 in regulating ALX/FPRL-1 expression under pathophysiological conditions.

Conclusion: Together, these results support a role of endogenous AnxA1 in the protective and reparative properties of the intestinal mucosal epithelium.

(This work was supported by a grant from the German Research Foundation (Deutsche Forschungsgemeinschaft-La 2359/1-1 to M.G.L.).