Cytosolic DNA Triggers Inflammasome Activation in Keratinocytes in Psoriatic Lesions

The proinflammatory cytokine interleukin-1 beta (IL-1 beta) plays a central role in the pathogenesis and the course of inflammatory skin diseases, including psoriasis. Posttranscriptional activation of IL-1 beta is mediated by inflammasomes; however, the mechanisms triggering IL-1 beta processing remain unknown. Recently, cytosolic DNA has been identified as a danger signal that activates inflammasomes containing the DNA sensor AIM2. In this study, we detected abundant cytosolic DNA and increased AIM2 expression in keratinocytes in psoriatic lesions but not in healthy skin. In cultured keratinocytes, interferon-g induced AIM2, and cytosolic DNA triggered the release of IL-1 beta via the AIM2 inflammasome. Moreover, the antimicrobial cathelicidin peptide LL-37, which can interact with DNA in psoriatic skin, neutralized cytosolic DNA in keratinocytes and blocked AIM2 inflammasome activation. Together, these data suggest that cytosolic DNA is an important disease-associated molecular pattern that can trigger AIM2 inflammasome and IL-1 beta activation in psoriasis. Furthermore, cathelicidin LL-37 interfered with DNA-sensing inflammasomes, which thereby suggests an anti-inflammatory function for this peptide. Thus, our data reveal a link between the AIM2 inflammasome, cathelicidin LL-37, and autoinflammation in psoriasis, providing new potential targets for the treatment of this chronic skin disease.