AT1R blockade reduces IFN-γ production in lymphocytes in vivo and in vitro

Abstract

Background. Type 1 angiotensin II (Ang II) receptor (AT1R) signaling induces proinflammatory responses. Recent studies suggest that T lymphocytes express AT1R; yet the effects of Ang II binding to AT1R on T cells are poorly understood. We examined the effect of AT1R blockade on release of the proinflammatory cytokine, interferon-gamma (IFN-γ) by human lymphocytes in vivo and in vitro. Methods. We used an AT1R blocker losartan in a randomized clinical trial in kidney transplant recipients over a 12-month period [AT1R blocker (N = 11) and control (N = 10)]. Peripheral blood lymphocytes, isolated from both cohorts, were analyzed by enzyme-linked immunosorbent spot assays (ELISPOT) analyses and real-time reverse transcription-polymerase chain reaction (RT-PCR) to enumerate IFN-γ producing T cells and IFN-γ mRNA levels. The effects of AT1R blockade in vitro were assessed using human alloreactive T cells and an IFN-γ producing human cytotoxic T-lymphocyte line. Alloreactive T cells were treated with losartan or candesartan and enzyme-linked immunosorbant assay (ELISA) was used to measure IFN-γ protein release. The cytotoxic T-lymphocyte line also was AT 1R blocker-treated prior to determining IFN-γ producing cells by intracellular cytokine staining. Results. The AT1R blocker cohort had a significant decrease in IFN-γ producing peripheral blood lymphocytes (P ≤ 0.05 for each time point) and IFN-γ mRNA levels (P = 0.01 vs. control patients). Losartan also decreased IFN-γ production (P < 0.001) in purified alloreactive T cells in vitro as did candesartan. Moreover, Ang II amplified IFN-γ generation (P < 0.05) in alloreactive T cells while AT1R blocker treatment inhibited Ang II's effect (P < 0.04). AT1R blocker treatment furthermore also inhibited IFN-γ production in the cytotoxic T-lymphocyte line. Conclusion. AT1R blockers may have a clinically relevant immunomodulatory role by blocking IFN-γ production in T cells. © 2005 by the International Society of Nephrology.