Gasdermin D-mediated keratinocyte pyroptosis as a key step in psoriasis pathogenesis

Gasdermin D (GSDMD)-mediated pyroptosis has a significant pro-inflammation characteristic due to dramatic secretion of pro-inflammatory substances. However, its role remains unclear in psoriasis as one chronic inflammatory skin disorder with high prevalence. We found that N-terminal GSDMD (N-GSDMD) was aberrantly expressed in epidermis of skin lesion in psoriasis patients and imiquimod-induced psoriasis-like dermatitis (IIPLD) mice. In epidermis of IIPLD mice and M5 (simulating psoriatic inflammatory challenge)-treated keratinocytes cultured in vitro, cleavage products of caspase-1, GSDMD and IL-1β were increased. M5-stimulated keratinocyte presented typical pyroptosis morphology accompanied with PI-staining. Gsdmd^-/- keratinocytes could not present pyroptosis morphology while stimulated with M5. Electroporation of recombinant N-GSDMD could make the pyroptosis morphology reappear. In Gsdmd^-/- mice or keratinocyte-specific Gsdmd conditional knockout mice, we observed the alleviation of psoriatic inflammation and epidermal aberrant expression of Ki-67 and differentiation markers (loricrin and keratin 5) after imiquimod stimulation. Transplanting skin tissue from control mice to Gsdmd^-/- mice can evoke the response to imiquimod stimulation in the background of Gsdmd^-/- mice (not limited in transplanting area). In M5-stimulated keratinocytes, disulfiram or GSDMD siRNA transfection can inhibit pyroptosis and eliminate disproportionate increases of Ki-67 and PI. We further validated that topically application of disulfiram (pyroptosis inhibitor) also alleviated IIPLD in mice. These findings indicate a novel mechanism that GSDMD-mediated keratinocyte pyroptosis facilitates hyperproliferation and aberrant differentiation induced by immune microenvironment in psoriatic skin inflammation, which contributes to pathogenesis of psoriasis. Our study provides an innovative insight that targeting pyroptosis can be considered as a therapeutic strategy against psoriasis.