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P026. Vitamin D enhances macrophage function and improves killing of Crohn's associated E. coli

P. Flanagan1, B.J. Campbell1, J.M. Rhodes1, 1University of Liverpool, Gastroenterology, Liverpool, United Kingdom

Background

E. coli are increased in Crohn's disease, have an adherent invasive (AIEC) phenotype and several lines of evidence suggest a primary pathogenic role. AIEC replicate within macrophages, the function of which is known to be impaired in Crohn's disease patients [1]. Polymorphisms in the Vitamin D receptor are associated with Crohn's disease and treatment with Vitamin D reduces the risk of clinical relapse [2]. We postulate Vitamin D supplementation may be efficacious in Crohn's disease by enhancing macrophage function and improving clearance of AIEC.

Methods

We aimed to assess the effect of Vitamin D supplementation on the generation of respiratory burst and the killing of E. coli by macrophages. J774A.1 murine macrophages were infected with representative Crohn's E. coli isolates, HM605 (colonic) or LF82 (ileal), and the effect of Vitamin D on bacterial survival was assessed using the gentamicin protection assay. Intracellular respiratory burst, determined by generation of fluorescent Dihydrorhodamine from its inactive form, was measured by flow cytometry. Total respiratory burst was quantified by lucigenin mediated chemiluminescence.

Results

Compared to untreated control, intra-macrophage E. coli survival was reduced in a dose dependent manner by Vitamin D at concentrations within the normal range for serum levels (9.01%±1.25% at 80nM, p < 0.001, ANOVA, N = 3). At equimolar concentrations, the 1,25-dihydroxylated form had significantly more potent effects on bacterial survival than non-hydroxylated Vitamin D3 (4.05±0.94 fold lower survival at 80nM, p < 0.01, N = 3). Respiratory burst was significantly higher with Vitamin D supplementation compared to untreated control (44.7%±3.9% vs 32.5%±3.8%, p < 0.05, ANOVA, N = 5).

Conclusion

Vitamin D supplementation significantly enhances macrophage killing of Crohn's associated E. coli. Dihydroxylated vitamin D3 is more biologically active than the non-hydroxylated form. A significant increase in respiratory burst is observed and may explain the enhanced killing of AIEC. These findings further support the use of Vitamin D supplementation in the treatment of Crohn's disease.

1. Flanagan P, et al., (2011), Bacteria in the pathogenesis of inflammatory bowel disease, Biochem Soc Trans, 39;1067–72

2. Jorgensen S.P., et al., (2010), Clinical trial: vitamin D3 treatment in Crohn's disease – a randomized double-blind placebo-controlled study. Aliment Pharmacol Ther, 32:377–383