Blue light irradiation alleviated dextran sulfate sodium-induced colitis mediated by the Bmal1 pathway in macrophages

Patients with long-term or severe inflammatory bowel disease (IBD) are more likely to develop colorectal cancer. The mortality rate of patients with IBD-related colorectal cancer is also higher than that of patients with common colorectal cancer. This study focused on the effect of photobiomodulation (PBM) on dextran sulfate sodium (DSS)-induced colitis and its underlying mechanism. C57 mice were treated with monochromatic light during DSS-induced colitis. Blue light irradiation clearly alleviated DSS-induced colitis, significantly changed the proportion of the relevant immune cell population in the colon, and improved the inflammatory environment of the colon. Moreover, the rhythm gene Brain And Muscle ARNT-Like 1 (Bmal1) is involved in the progression of colitis, and its decreased expression in colitis mice was reversed by blue light irradiation. These data demonstrated that the protective effect of blue light against colitis is mediated by the Bmal1-mediated pathway in macrophages. This study proposes blue light irradiation with specific light intensities as a potential IBD therapy.