Cholinergic Stimulation of Immune Cells with Nicotine Induces Renal Inflammation and Pre‐mature Development of Hypertension in Young SHR

Abstract

We have shown that nicotinic cholinergic stimulation of immune cells in vitro and in vivo exaggerates pro‐inflammatory innate immune responses and increases proliferation of a CD161a+/CD68+ macrophage population in isolated bone marrow cells and splenocytes in young pre‐hypertensive Spontaneously Hypertensive Rat (SHR). In vivo administration of nicotine also led to renal infiltration of macrophages within 24 hours, without any increase in arterial pressure and independent of renal sympathetic innervation. We also found that 2 week subcutaneous infusion of nicotine not only leads to continued CD161a+/CD68+ macrophage infiltration, but also the development of premature hypertension in young SHR. We hypothesized 1) that the nicotine induced CD161a+/CD68+ macrophage infiltration is caused by increased renal expression of Vascular Cell Adhesion Molecule‐1 (VCAM‐1) and 2) this renal macrophage infiltration results in renal damage/toxicity. Nicotine (15mg/kg/day) was infused subcutaneously for 2 weeks. Systolic blood pressures (SBP) were measured twice weekly by tail cuff and urine, serum, and kidney tissue were collected at the end of nicotine infusion. Tissues and fluid were analyzed by luminex assay. Renal lysates were also analyzed by Western blot for the presence of VCAM‐1. Nicotine infusion led to the pre‐mature development of hypertension in SHR (153.2 ± 3 mmHg vs 138.6 ± 3 mmHg in saline infused SHR, respectively, n=10, p <0.001). There was no significant increase in SBP in control Wistar Kyoto (WKY) rats infused with nicotine, compared to saline. There was a greater infiltration of the kidney with CD161a+/CD68+ macrophages with nicotine infusion (16±2 cells per 400× field), compared to saline infusion (9±1 cells per 400× field) (n=6, p<0.001). In contrast, there was no significant renal macrophage infiltration in nicotine infused WKY, compared to saline (1±1 cells vs 1±1 cells per 400× field) (n=6, p>0.05). CD161a+/CD68+ renal macrophage infiltration in the young SHR was not associated with an increase in VCAM‐1 expression. However, nicotine induced renal CD161a+/CD68+ macrophage infiltration was associated with renal damage/toxicity, as measured by an increase in urinary Interleukin −18 (IL‐18) (283±42 pg/mL vs 101±10 pg/mL, n=4, p<0.001) and Monocyte Chemoattracatant Protein‐1 (MCP‐1) (241±22 pg/mL vs 145±23 pg/mL, n=4, p<0.05). We conclude that cholinergic stimulation with nicotine leads to renal infiltration with a CD161a+/CD68+ macrophage population that is not explained by renal expression of VCAM‐1, but is associated with renal damage, as well as the pre‐mature development of hypertension. Thus, renal damage from infiltration of this CD161a+/CD68+ macrophage population is one of the mechanisms involved in nicotine induced hypertension in the young pre‐hypertensive SHR.Support or Funding InformationNIH K08 HL11958NIH PPG HL014388