Abstract Body: While CD8+ T cells (CD8Ts) have recently emerged as key players in hypertension, the precise mechanisms underlying their involvement remain incompletely understood. We reported previously that CD8T-activation is critical in initiating their direct interaction with renal tubules. Here, we discovered that CD8T activation in hypertension occurs in an antigen-independent manner. In this study, we delve into the contribution of the P2X7 receptor to CD8T activation and its subsequent promotion of hypertension.
To investigate whether CD8T activation in hypertension necessitates T cell receptor (TCR) stimulation, we employed Rag2/OT1 mice, which exclusively harbor transgenic OT1 CD8Ts, recognizing only ovalbumin peptides but no other antigens. These mice, without any exposure to ovalbumin, were induced hypertension through the DOCA + salt (DOCA) model. Blood pressure was monitored using biotelemetry, and CD8T activation was confirmed using flow cytometry. In our in-vitro studies, CD8Ts were obtained from WT or P2X7-KO mice and stimulated with ATP. The endpoints include calcium influx and cytokine production as indicators of activation. Moreover, we measured the activation profiles of CD8Ts obtained from WT or P2X7-KO mice subjected to sham or DOCA treatment using RT-PCR and flow cytometry. Additionally, we conducted an adoptive transfer experiment, transferring naive WT CD8Ts to P2X7-KO mice undergoing DOCA treatment.
We found that CD8Ts from Rag2/OT1 mice become activated in response to the DOCA pressor, leading to increased IFNγ production and contributing to salt-sensitive hypertension, even in the absence of TCR-mediated antigen stimulation. Furthermore, ATP elicited calcium influx in CD8Ts via P2X7, thereby upregulated IFNγ production. In addition, CD8Ts pre-treated with ATP exhibited a higher ability to stimulate sodium retention in co-cultured renal tubule epithelial cells compared to those co-cultured with naive CD8Ts. Notably, DOCA-treated P2X7 KO CD8Ts were unable to induce an increase in blood pressure in our adoptive transfer model. However, transferring sham WT CD8Ts to DOCA-treated P2X7 KO mice successfully restored hypertension to WT levels.
Our findings reveal a novel mechanism by which ATP/P2X7 signaling leads to activation of CD8Ts as the culprit to the pathogenesis of hypertension. As such, the CD8T P2X7 receptor presents itself as a promising target for improving blood pressure management.