The IFNγ‐PDL1 Pathway Enhances the Interaction Between CD8+ T Cells and Distal Convoluted Tubules to Promote Salt‐Sensitive Hypertension

Abstract

Background & HypothesisOur study – among others – has recently demonstrated the role of T cells in contributing to salt‐sensitive hypertension via interacting with tubular cells within the nephron. In particular, CD8+ T cells (CD8Ts) infiltrate the kidneys and stimulate distal convoluted tubular cells (DCTs), to upregulate sodium‐chloride co‐transporter (NCC) activity, leading to excessive salt retention. However, the precise molecules driving this direct interaction between CD8Ts and DCTs have not yet been identified. Here we hypothesize that gamma interferon (IFNγ), released by activated CD8Ts, primes the tubular cell to express PDL1 which functions as a co‐stimulatory ligand promoting interactions between activated CD8Ts and DCTs during the development of salt‐sensitive hypertension.We predict therapeutically blocking this molecular pathway will reduce CD8T‐homing into the kidney, thereby lowering blood pressure.MethodsIn in‐vitro studies, we co‐cultured CD8Ts (with or without pre‐activation) and DCTs. Recombinant mouse IFNγ, IFNγ neutralizing antibody, and specific siRNAs against the IFNγ‐receptor and PDL1 were used to determine the role of IFNγ‐PDL1 pathway in the interaction between CD8Ts and DCTs. To further test the in‐vitro results in‐vivo, we employed IFNγ knockout (KO) mice, mice with systemically blocked PDL1 using anti‐PDL1 antibody, and mice with renal tubule‐specific knockdown of PDL1 (mediated by siRNA containing renal tubule specific nanoparticles) in both the DOCA‐salt model, a classic model of salt‐sensitive hypertension, and the CD8T adoptive transfer model, a CD8T specific model of salt‐sensitive hypertension. Blood pressure was continuously monitored using radio‐biotelemetry. Cells were analyzed using flow cytometry, RT‐qPCR, and western blot. Kidneys were obtained at experimental endpoints and analyzed using immunohistochemistry and western blot.ResultsWe found that CD8Ts isolated from DOCA‐salt treated hypertensive mice exhibit higher activity compared to those from sham normotensive mice. Pre‐activated CD8Ts demonstrated augmented ability to interact with DCTs compared to naïve CD8Ts, and as a consequence, DCTs that had been co‐cultured with pre‐activated CD8Ts demonstrated increased expression of PDL1, NCC, and enhanced sodium retention. These effects were abolished by neutralizing IFNγ or knockdown of PDL1 in DCTs. In‐vivo results verified the in‐vitro studies. We found that in both IFNγ‐KO mice and WT mice receiving PDL1‐antagonizing antibodies, DOCA‐salt treatment failed to elevate their blood pressure and reduced T cell infiltration and NCC expression within their kidneys compared to WT/control mice receiving the same treatment (anti‐PDL1 results shown in Figure 1). Similar results were also observed in DOCA‐salt treated mice with renal tubule‐specific knockdown of PDL1.ConclusionActivated CD8Ts demonstrate enhanced ability to interact with DCTs leading to increased expression of NCC and sodium retention through a IFNγ‐PDL1 pathway mediated mechanism. Blocking the IFNγ‐PDL1 pathway prevents CD8T‐DCT interaction both in vitro and in vivo, thereby ameliorating salt‐sensitive hypertension.