Immune checkpoint VISTA regulates DNA sensing and repair pathways that contribute to type I interferon (IFN-I) production in the skin

Abstract

Abstract Skin sterile injury by ultraviolet (UV) light stimulates production of type I interferons. While in healthy skin IFN-I response to UV returns to baseline over time, the IFN-I signature persists in photosensitive diseases like lupus. The pathways that downregulate IFN-I production in healthy skin, and fail to do so in lupus skin, are unknown. Previous studies showing that activating VISTA suppresses the IFN-I signature in monocytes suggest a role for this immune checkpoint in the regulation of the IFN-I response. Indeed, we showed that the skin IFN-I signature is elevated in mice globally deficient in VISTA (Vsir−/−), as well as in mice with a conditional deletion of VISTA in keratinocytes. Having confirmed its expression in keratinocytes, we tested if VISTA regulates UV-triggered IFN-I production in the skin. Expression analysis of IFN-I stimulated genes in skin biopsies collected prior to and 3h after a single dose of UVB, revealed ~10-fold higher IFN-I score in Vsir−/− vs. B6 skin after UV. RNAseq studies showed DNA sensors, ZBP1, cGAS, and IFI204 were upregulated, while nucleotide excision repair genes, Polɛ and DNA Ligase1, were suppressed in Vsir−/− skin, both at baseline and 3h after UV. Moreover, Polɛ protein levels were lower in Vsir−/− skin by immunoblot. Relevant to its role in keratinocytes, IFN-k protein levels were higher in VISTA-deficient epidermal keratinocytes ex vivo, accompanied by elevated mRNA levels of ZBP1 and IFI204 before and after UV. Together, this study identifies VISTA as a novel regulator of IFN-I production, by modulating DNA damage repair and sensing. The keratinocyte-intrinsic role of VISTA is therapeutically relevant as lupus keratinocytes express high IFN-k and are direct targets of UV-induced DNA damage. 1R21AR079661 – 01, Hitchcock Foundation, DOD lupus award