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Melatonin has various physiological effects, such as the maintenance of circadian rhythms, anti-inflammatory functions, and regulation of intestinal barriers. The regulatory functions of melatonin in gut microbiota remodeling have also been well clarified; however, the role of gut microbiota in regulating host melatonin production remains poorly understood. To address this, we studied the contribution of gut microbiota to host melatonin production using gut microbiota-perturbed models. We demonstrated that antibiotic-treated and germ-free mice possessed diminished melatonin levels in the serum and elevated melatonin levels in the colon. The influence of the intestinal microbiota on host melatonin production was further confirmed by fecal microbiota transplantation. Notably, Lactobacillus reuteri ( L. R ) and Escherichia coli ( E. coli ) recapitulated the effects of gut microbiota on host melatonin production. Mechanistically, L. R and E. coli activated the TLR2/4/MyD88/NF-κB signaling pathway to promote expression of arylalkylamine N-acetyltransferase (AANAT, a rate-limiting enzyme for melatonin production), and MyD88 deficiency in colonic epithelial cells abolished the influence of intestinal microbiota on colonic melatonin production. Collectively, we revealed a specific underlying mechanism of gut microbiota to modulate host melatonin production, which might provide novel therapeutic ideas for melatonin-related diseases.

Food allergy affects more than 500 million people in the world, and its prevalence is increasing at an alarming rate causing serious public health concerns; however, prevention and treatment methods are still under investigation and are relatively scarce so far. Insights on pathophysiology reveal a complex interplay of the immune cells (e.g., DCs, T cells, and B cells) resulting in allergy or tolerance. Studies have shown that melatonin metabolisms are altered in patients with allergic diseases, suggesting that melatonin might impact allergic diseases. Notably, melatonin can orchestrate the differentiation and function of immune cells. Additionally, the disease severities of many allergic diseases and the function of the immune system exhibit circadian rhythmicity. Therefore, melatonin, a rhythm regulator, may also act indirectly on the immune system through the circadian clock to regulate food allergies. Herein, we reviewed the impacts of melatonin on food allergy and its underlying regulatory mechanisms, providing a theoretical reference for melatonin as effective means of prevention and treatment for food allergy in the future., (© 2023 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Melatonin acts as a crucial signaling molecule with multiple physiological functions in plant response to abiotic and biotic stresses. However, the impact and regulatory mechanism of melatonin on attenuating tomato fruit fungal decay are unclear. In this study, we investigated the potential roles of melatonin in modulating fruit resistance to Botrytis cinerea and explored related physiological and molecular mechanisms. The results revealed that disease resistance was strongly enhanced by melatonin treatment, and 50 μM was confirmed as the best concentration. Melatonin treatment increased the activities of defense-related enzymes and decreased hydrogen peroxide (H 2 O 2 ) content with enhanced antioxidant enzyme activities. Moreover, we found that melatonin treatment increased methyl jasmonate (MeJA) content; up-regulated the expressions of SlLoxD, SlAOC, and SlPI II; and reduced the expressions of SlMYC2 and SlJAZ1. We postulated that melatonin played a positive role in tomato fruit resistance to Botrytis cinerea through regulating H 2 O 2 level and JA signaling pathway.