Tryptophan metabolism in psoriasis and its complications: Future opportunities

Tryptophan (Trp) metabolism encompasses primary three pathways: the kynurenine pathway, the serotonin pathway, and the indole pathway. These pathways are intricately involved in the physiological and pathological processes underlying psoriasis, exerting broad regulatory effects on immune function, inflammation responses, keratinocytes proliferation, angiogenesis, and intestinal homeostasis. Key enzymes and metabolites within the Trp metabolic pathway have been implicated in the development and progression of psoriasis. Disruptions in Trp metabolism have been observed in psoriasis and its associated complications, with alterations in certain metabolite levels noted following improvements in disease symptoms. Emerging evidence indicates that targeted therapies modulating Trp metabolism have demonstrated efficacy in clinical applications, offering valuable insights for medication selection in psoriasis treatment. This review aims to summarize the most recent research findings regarding the role of Trp metabolism in psoriasis and its comorbidities, as well as the therapeutic potential of targeting Trp metabolic pathways.