Abstract 002: Activation of AT1 receptors on Dendritic Cells Restrains Angiotensin II-Dependent Hypertension Through a CCR7-dependent Mechanism

Abstract

Dendritic cells (DCs) trigger an adaptive immune response by presenting processed antigens to T lymphocytes. Given the emerging importance of adaptive immunity in hypertension, we posited that DCs may sample neoantigens in the kidney in order to prime pro-hypertensive T cells. Using CD11c-Cre mT/mG mice in which DCs fluoresce green, we detected robust green signals within the kidney after 2 wks of angiotensin (Ang) II-induced hypertension, confirming infiltration of DCs into the hypertensive kidney. As activation of type 1 angiotensin (AT1) receptors on other immune cell lineages has been shown to alter inflammatory responses, we explored the role of the DC AT1 receptor in blood pressure regulation by generating mice with DC-specific deletion of the AT1A receptor (CD11c Cre+ Agtr1aflox/flox = DC KO) and littermate controls (Agtr1aflox/flox = WT). Compared to WTs, the DC KOs had an ≈87% reduction in AT1A receptor mRNA expression in DCs (p<0.0001) but preserved AT1A expression in B and T lymphocytes, kidney, and heart (p=NS). Next, we infused uni-nephrectomized DC KO mice and wild-type (WT) controls with Ang II (500ng/kg/min) for 4 wks. At baseline, the mean arterial blood pressure (MAP) was similar in WT and DC KO mice (123±2 vs. 126±2 mm Hg; p=NS). By contrast, after the 1st week of Ang II infusion, DC KO mice had markedly exaggerated MAP elevations compared to WTs (174±4 vs. 158±5 mm Hg; p=0.026). Expression of the chemokine receptor CCR7 on mature DCs and T cells directs both cell lineages to the lymph node where the DC can display a processed antigen and activate the T cell. We detected higher levels of CCR7 mRNA in the kidneys from the Ang II-infused DC KOs compared to WTs (2.98±0.90 vs. 1.00±0.16 au; p=0.04), and posited that enhanced DC priming of T cells in the DC KOs contributed to their exaggerated hypertension. Consistent with this possibility, uni-nephrectomized CCR7-deficient (KO) mice had a significantly blunted chronic hypertensive response to Ang II (165±4 vs. 178±2 mm Hg; p=0.03) and ameliorated albuminuria (2.1±0.2 vs. 3.7±0.8 mg/24hrs; p=0.02) versus WT controls. We conclude from these data that stimulation of AT1 receptors on DCs constrains Ang II-induced blood pressure elevation, possibly by limiting the CCR7-dependent activation of T lymphocytes by DCs.