PROJECT SUMMARY / ABSTRACT Hypertension is a prominent public health problem and a major risk factor for other cardiovascular diseases. Major clinical challenges in the management of hypertension are insufficient blood pressure control and the recurrence of hypertension after discontinuing medications. Thus, it is important to identify the unknown mechanisms that drive its pathogenesis. Immune cells, particularly CD8+ T cells (CD8Ts), play a crucial role in hypertension. Our recent findings revealed inappropriate activation and infiltration of CD8Ts into the kidneys during the initial elevation of blood pressure, which exacerbated hypertension by enhancing renal salt retention. However, the underlying mechanisms driving this "inappropriate CD8T activation in hypertension" remain unclear, hindering the development of effective treatment strategies. Our initial studies showed that CD8T activation in hypertension does not necessitate specific antigens, suggesting an antigen-independent mechanism. Building on this premise, we hypothesize in this competing renewal application that P2X7-mediated calcium influx activates CD8Ts during the onset of hypertension, and this event is sustained by an extracellular ATP autocrine positive feedback loop. Moreover, this process promotes the formation of kidney resident memory CD8Ts (kidney-CD8Trms), thereby intensifying the progression of hypertension and hypertensive memory of salt sensitivity. Specifically, Aim 1 will test the mechanism of P2X7-mediated antigen-independent activation of CD8Ts in hypertension and the critical role of the autocrine positive feedback loop in maintaining this CD8T activation to become long-lasting. Aim 2 will determine the underlying mechanisms and critical molecular pathways that mediate the establishment of CD8Trms in the kidney during the development of hypertension. Proof-of-principle studies in Aim 2 will determine whether kidney-CD8Trms contribute to the memory of salt sensitivity that underlies the recurrence of hypertension. Our experiments will rely on genetically modified animals including a knockout of purinergic receptor P2X7, CD8T-specific gene deletion of pannexin 1 (Panx1), and T cell-specific knockout of transforming growth factor β (TGFβ) to implicate these molecules in the activation and establishment of kidney-CD8Trms that fuel the progression of hypertension and hypertensive memory of salt sensitivity. Vertical integration of complementary in vitro and in vivo studies are further incorporated into this proposal to elucidate the important molecular mechanisms that cause T cell activation and homing to the kidney, thus impairing salt and volume homeostasis to cause hypertension and its recurrence. We propose that salt- sensitive hypertension is caused and maintained, at least in part, by a resident memory immune disorder in the kidney. Moreover, the key molecules identified in this study may represent novel targets for future immunotherapies to mitigate hypertensi...