ACETYLCHOLINE SIGNALING IN RENAL MACROPHAGES CONTRIBUTES TO HYPERTENSION DEVELOPMENT

Recent studies have revealed that the accumulation of immune cells within organs contributes to the development and maintenance of hypertension. The kidney also plays a role in immune-mediated regulation of blood pressure. CD8⁺ T cell–dependent modulation of Na⁺-Cl⁻ cotransporter activity and macrophage-mediated regulation of renin production have been reported, suggesting the presence of additional blood pressure control mechanisms governed by immune cells in the kidney. Furthermore, the autonomic nervous system is known to influence immune cell function through neurotransmitter receptors expressed on their surface. Although we previously demonstrated that activation of the neuro–immune system exerts anti-inflammatory and renal protective effects, its contribution to blood pressure regulation has not been fully elucidated. Therefore, we hypothesized that autonomic nerves regulate renal immune activity and thereby modulate systemic blood pressure.

Hypertension was induced in male C57BL/6 mice (8–10 weeks old) by continuous subcutaneous infusion of angiotensin II (1000 ng/kg/min) combined with saline intake for 14 days. Systolic blood pressure was measured using the tail-cuff method. On day 14, immune cell infiltration into major organs was analyzed by flow cytometry and immunostaining. In this model, either pharmacological macrophage depletion or macrophage-specific knockout (KO) of autonomic receptors (adrenergic and nicotinic acetylcholine receptors) was performed, and their effects on blood pressure were evaluated. Bone marrow–derived macrophages (BMDMs) treated with nicotine were transplanted into wild-type mice, and their effects on blood pressure were assessed. Furthermore, renal macrophages isolated from wild-type and KO mice were subjected to RNA sequencing to identify genes associated with blood pressure regulation.

This study reveals a novel mechanism by which parasympathetic signaling regulates renal RAAS activity through macrophage-mediated pathways, thereby contributing to hypertension development. These findings highlight a previously unrecognized neuro–immune–renal axis that may represent a potential therapeutic target for hypertension.In hypertensive mice, macrophage accumulation increased in the kidney and liver, accompanied by expansion of F4/80⁺ areas around glomeruli. Both macrophage depletion and macrophage-specific KO of the nicotinic acetylcholine receptor significantly attenuated the elevation in blood pressure. Wild-type mice transplanted with nicotine-treated BMDMs exhibited higher blood pressure compared with those receiving untreated cells. In KO mice, total renal macrophage numbers were unchanged; however, glomerular F4/80⁺ areas were significantly reduced, indicating qualitative rather than quantitative changes in macrophage distribution. qPCR analyses showed a trend toward decreased expression of Agt and Ace in the kidneys of KO mice. RNA-seq analysis identified gene clusters upregulated during hypertension but suppressed in the KO condition, suggesting transcriptional reprogramming of renal macrophages in response to parasympathetic signaling.

This study reveals a novel mechanism by which parasympathetic signaling regulates renal RAAS activity through macrophage-mediated pathways, thereby contributing to hypertension development. These findings highlight a previously unrecognized neuro–immune–renal axis that may represent a potential therapeutic target for hypertension.