The mechanism of CD8+ T cell activation in promoting salt-sensitive hypertension

Abstract

Background and Hypothesis: T cells play a critical role in hypertension; however, the molecules driving this interaction were unclear. We recently showed that CD8Ts are activated during the initial phase of blood pressure elevation and directly interact with the distal convoluted tubule (DCT) through the interferon gamma (IFNγ)-PDL1 pathway. Here we identified that these CD8Ts are activated during this initial phase via pro-inflammatory extracellular ATP stimulating their P2X7 receptors, leading to enhanced IFNγ production and increased sodium retention in tubular cells that interacted with these CD8Ts. We predict the CD8T P2X7 receptor is contributing to hypertension and abrogating this receptor on CD8Ts will block CD8T-tubular interaction and lower blood pressure. Methods: To determine whether CD8Ts activation in hypertension requires T cell receptor (TCR) stimulation, we used transgenic OT1 mice and induced hypertension via the DOCA + salt (DOCA) model, measuring blood pressure and confirming enhanced CD8T activation despite no exposure to ovalbumin. In in-vitro studies, we co-cultured DCTs with pre-stimulated CD8Ts and measured PDL1 expression and sodium retention in DCTs via flow cytometry. CD8Ts were obtained from WT or P2X7 KO mice and stimulated with BZATP or ATP using calcium influx (intracellular calcium indicator Fluo-4), IFNγ transcription, and glycolytic activity (Seahorse) as activation endpoints. To confirm in-vivo, the activation profiles of CD8Ts obtained from sham or DOCA treated WT and P2X7 KO mice were measured using rt-qPCR and flow cytometry. To confirm the role of P2X7 receptors on CD8Ts, we performed adoptive transfer of DOCA CD8Ts (WT or P2X7 KO) to the alternative model and transferred naive WT CD8Ts to P2X7 KO mice receiving DOCA treatment. All blood pressure was measured via radio-biotelemetry. Results: We found OT1 CD8Ts become activated to the DOCA presser, produce more IFNγ, and contribute to salt-sensitive hypertension without antigen-mediated TCR stimulation. P2X7 receptor agonists BZATP and ATP drove CD8T calcium influx, increased IFNγ transcription, and increased glycolytic activity in CD8Ts – indicative of T cell activation; as such, CD8Ts pre-stimulated with the P2X7 agonist BZATP increased tubular PDL1 expression and sodium retention more than naive CD8Ts in our co-culture model. DOCA treated P2X7 KO CD8Ts were unable to increase blood pressure in our adoptive transfer model; however, transferring sham WT CD8Ts to DOCA P2X7 KO mice restored blood pressure response to the presser to WT levels. Conclusion: Stimulation of the P2X7 receptor contributes to CD8T activation in the pathogenesis of hypertension, resulting in enhanced sodium retention. Deficiency of this receptor on CD8Ts prevents activation by ATP and results in blunted blood pressure elevation in two models of hypertension; as such, the CD8T P2X7 receptor may be a promising target for improving blood pressure management. NIH R01-HL146713, AHA 15BGIA25730047, SPaT 5T32GM106999-09 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.