P141 Engineered probiotics treat inflammatory bowel disease by releasing all trans retinoic acid in the intestine

Abstract

Abstract Background All trans retinoic acid (ATRA) is a potential candidate drug for the treatment of inflammatory bowel disease (IBD). ATRA can affect multiple pathways involved in the pathogenesis of IBD by binding to retinoic acid receptors. However, the shortcomings of poor compliance and significant side effects in patients who directly use ATRA limit its clinical application. Methods Here, we have developed a live biotherapeutic products (ELBPRA) based on synthetic biology methods for controllable delivery of ATRA on the gut. We first expressed four enzyme genes required for the synthesis of β-carotene, a precursor of retinoic acid, in Escherichia coli Nissle 1917 (EcN). In addition, we introduced the exogenous synthesis pathway of isopentane pyrophosphate into EcN to increase the yield of β-carotene. Then, β-carotene oxygenase and retinal dehydrogenase, were expressed in EcN to convert β-carotene into retinoic acid. However, considering the poor solubility of retinoic acid, we knocked out some genes related to vesicle formation in the EcN genome to increase extracellular production of retinoic acid. Finally, we investigated the therapeutic effect of ELBPRA using a colitis model induced by sodium dextran sulfate (DSS). Results ELBPRA continuously produces retinoic acid and delivers it in the form of vesicles. ELBPRA reduced weight loss and disease activity index in DSS-induced colitis. Similarly, the spleen index also demonstrates the effectiveness of ELBPRA in treating colitis. The ELBPRA intervention group reduced the degree of colon shortening in mice. In addition, ELBPRA improved crypt loss and disorder of crypt structure. Finally, we also evaluated the inflammatory cytokines in the serum. ELBPRA significantly increased the concentration of anti-inflammatory cytokine IL-10 and decreased the concentration of pro-inflammatory cytokine IL-1β and TNF-α. Conclusion Engineered probiotics ELBPRA can deliver retinoic acid in the form of vesicles to alleviate DSS-induced colitis in mice, which provides a safe and effective treatment strategy for ulcerative colitis.