Therapeutic Mechanism of Kynurenine, a Metabolite of Probiotics, on Atopic Dermatitis in Mice

Atopic Dermatitis (AD) is a common inflammatory skin disease characterized primarily by its chronic and recurrent nature. This has a significant impact on productivity and human longevity. Dysbiosis of gut flora has been demonstrated to be significantly associated with the progression of AD. In our previous research, it was shown that Lactobacillus rhamnosus RL5-H3-005 (RL) and Pediococcus acidilactici RP-H3-006 (RP) have the ability to reduce the risk of disease in AD mice through the gut–mammary axis. Based on our previous work, this study aims to further investigate the effects of kynurenine (KYN), a metabolite of RL and RP, on AD mice induced by 2, 4-dinitrofluorobenzene (DNFB). In this study, we found that supplementing KYN in AD mice effectively alleviates the pathological symptoms of atopic dermatitis and further improves the levels of SCFAs in their intestines. Further research indicates that KYN’s therapeutic effects on AD are primarily manifested in the reduction of secretory immunoglobulin A (sIgA), immunoglobulin E (IgE), interleukin-4 (IL-4), IL-5, IL-13, and thymic stromal lymphopoietin (TSLP) levels in mice, while also repairing the intestinal barrier function of AD mice. Overall, the metabolites KYN of probiotics RL and RP can regulate the levels of SCFAs of mice, potentially improving the symptoms of AD mice through the gut–skin axis.