HIF-1 regulates pathogenic cytotoxic T cells in lupus skin disease.

Cutaneous lupus erythematosus (CLE) is a disfiguring autoimmune skin disease characterized by an inflammatory infiltrate rich in T cells, which are strongly implicated in tissue damage. How these cells adapt to the skin environment and promote tissue inflammation and damage is not known. In lupus nephritis, we have previously identified an inflammatory gene program in kidney-infiltrating T cells that is dependent on hypoxia-inducible factor-1 (HIF-1), a transcription factor critical for the cellular and developmental response to hypoxia as well as inflammation-associated signals. In our current studies using a mouse model of lupus skin disease, we find that skin-infiltrating CD4+ and CD8+ T cells also express high levels of HIF-1. Skin-infiltrating T cells demonstrate a strong cytotoxic signature at the transcript and protein level, and HIF-1 inhibition abrogates skin and systemic disease in association with decreased T cell cytotoxic activity. We also demonstrate in human CLE tissue that the T cell rich inflammatory infiltrate exhibits increased amounts of HIF-1 and a cytotoxic signature. Granzyme B-expressing T cells are concentrated at sites of skin tissue damage in CLE, suggesting relevance of this pathway to human disease.