STING Agonist-Induced Skin Inflammation is Exacerbated with Prior Systemic Innate Immune Activation.

Activation of the Stimulator of Interferon Genes (STING) protein has paradoxical outcomes in skin disease. STING activation exacerbates psoriatic skin disease and delays wound healing in diabetic mice, yet it also facilitates wound healing in normal mice. To address the role of localized STING activation in the skin, mice were injected subcutaneously with a STING agonist, diamidobenzimidazole STING Agonist-1 (diAbZi). The effect of a prior inflammatory stimulus on STING activation was addressed by pre-treating mice intraperitoneally with poly (I:C). The skin at the injection site was evaluated for local inflammation, histopathology, immune cell infiltration, and gene expression. Serum cytokine levels were measured to assess systemic inflammatory responses. Localized diABZI injection induced severe skin inflammation with erythema, scaling, and induration. However, the lesions were self-limiting and resolved within 6 weeks. At the peak of inflammation, the skin showed epidermal thickening, hyperkeratosis, and dermal fibrosis. Neutrophils, CD3 T cells, and F4/80 macrophages were present in the dermis and subcutaneous layers. Gene expression was consistent with increased local interferon and cytokine signaling. Interestingly, the poly (I:C)-pre-treated mice showed higher serum cytokine responses and developed worse inflammation with delayed wound resolution. Our study demonstrates that prior systemic inflammation amplifies STING-mediated inflammatory responses and skin disease.