Skin commensals shape the clock-ferroptosis axis to preserve barrier function in psoriasis.

Psoriasis ranks among the most prevalent chronic inflammatory dermatoses worldwide and is accompanied by significant alterations in the skin microbiota. In this study, we confirmed microbial dysbiosis in psoriatic lesions and observed a reduction in Lactobacillus. Further functional screening showed that topical administration of Lactobacillus plantarum alleviated psoriatic lesions. Mechanistically, L. plantarum produces indole-3-lactic acid, which restores circadian rhythmicity in keratinocytes, thereby suppressing ferroptosis and promoting epidermal barrier repair. These findings highlight the contribution of the cutaneous microbiota to epidermal barrier restoration in psoriasis and support the therapeutic potential of L. plantarum and its metabolite ILA as clinical interventions.