ATP-P2X7-Induced Inflammasome Activation Contributes to Melanocyte Death and CD8(+) T-Cell Trafficking to the Skin in Vitiligo

Abstract

Extracellular adenosine 5'-triphosphate (ATP) is a well-known inflammasome-activating signal. Emerging evidence demonstrates a critical role for inflammasome activation in vitiligo pathogenesis. However, the specific molecular mechanism of inflammasome-dependent melanocyte degeneration in vitiligo is still not clear. This study presents how extracellular ATP, released from keratinocytes by oxidative stress, affects melanocyte survival in vitiligo skin. H2O2-induced oxidative injury increased ATP release from keratinocytes and skin tissues. The high concentration of extracellular ATP induced both ROS production and cell death in melanocytes. Treatment with ATP caused the activation of caspase-1 as well as the production of active forms of IL-1 beta and IL-18 via P2X7 receptor in keratinocytes and melanocytes. Lesional and perilesional skin of vitiligo showed higher levels of ATP as well as upregulation of active caspase-1 compared with nonlesional skin, suggesting its possible role in inflammasome activation in vitiligo. Moreover, the elevated expression of CXCL9 in keratinocytes, mediated through ATP/P2X7 receptor-dependent inflammasome activation, was responsible for CLA(+) CD8(+) T-cell chemotaxis into the skin. These results demonstrate that extracellular ATP as a danger signal activates the inflammasome pathway and increases cutaneous chemotaxis of CD8(+) T cells via CXCL9 in vitiligo. Therefore, targeting ATP-P2X7 signaling may be a potential strategy for vitiligo treatment.