Search

Atopic dermatitis (AD) is a common chronic relapsing inflammatory skin disease, of which the pathogenesis is a complex interplay between genetics and environment. Although the exact mechanisms of the disease pathogenesis remain unclear, the immune dysregulation primarily involving the Th2 inflammatory pathway and accompanied with an imbalance of multiple immune cells is considered as one of the critical etiologies of AD. Tryptophan metabolism has long been firmly established as a key regulator of immune cells and then affect the occurrence and development of many immune and inflammatory diseases. But the relationship between tryptophan metabolism and the pathogenesis of AD has not been profoundly discussed throughout the literatures. Therefore, this review is conducted to discuss the relationship between tryptophan metabolism and the complex network of skin inflammatory response in AD, which is important to elucidate its complex pathophysiological mechanisms, and then lead to the development of new therapeutic strategies and drugs for the treatment of this frequently relapsing disease., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Huang, Chen, Liu, Xiong, Ouyang and Deng.)

Background: The depletion of beneficial bacteria in the gut has been found in patients with acne vulgaris, and in previous studies, the supplement of Lactobacillus rhamnosus led to the improvement of adult acne. Nevertheless, the potential mechanism of L. rhamnosus in the amelioration of acne vulgaris has not been elucidated yet., Methods: To mimic the human intestinal environment, a pseudo-germ-free rat model was used, and then gut microbiota from healthy individuals and acne patients were transplanted into rats. The effects of L. rhamnosus and tryptophan (Trp) metabolites on a rat acne model were investigated by gavage. Then, 16S rRNA analysis and targeted measurement of metabolites were performed to discover the differences in gut microbiota and metabolites between groups. Finally, HaCaT cells pretreated with Cutibacterium acnes were employed to validate the effect and mechanism of Trp metabolites on acne., Results: L. rhamnosus significantly improved acne-like symptoms in rats by suppressing the level of inflammatory cytokines such as IL-1β , IL-6 , and TNF-α . L. rhamnosus induced an increase in the production of indole-3-acetic acid (IAA) and indole via targeted Trp metabolic analyses. Furthermore, L. rhamnosus promoted bacterial diversity and also enhanced the Firmicutes/Bacteroidota (F/B) ratio, which was positively related to both IAA and indole. Finally, the roles of IAA and indole in alleviating acne vulgaris were confirmed both in vitro and in vivo , which could be reversed by AhR inhibitors., Conclusion: Our study demonstrated that L. rhamnosus could exert its therapeutic effects on acne vulgaris by modulating the gut microbiota and regulating associated Trp metabolites., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Huang, Huang, Xia, Liu, Xiong, Ouyang and Deng.)