Retinoids, which are commonly used to combat acne, have several side effects, including the development of inflammatory bowel disease (IBD). To investigate the effect of retinoids on the gastrointestinal system in vivo, Oehlers et al. developed a model of IBD by immersing zebrafish larvae in dextran sodium sulfate (DSS), a chemical commonly used to induce colitis in rodents. As occurs in individuals with IBD, DSS exposure induced a protective mucosecretory response in zebrafish larvae. Both endogenous and DSS-induced mucus secretion were suppressed by exogenous retinoic acid, which promoted inflammation and exacerbated enterocolitis. These findings introduce a new model of IBD and provide evidence for how the disease might be triggered in patients treated with retinoids. Page 457

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