Habitual Exercise Modulates Neuro-Immune Interaction to Mitigate Aortic Stiffness
Exercise augments hemodynamic shear to activate mechano-sensitive molecular transducers in the vascular endothelium. Recently, the central nervous system has been reported to mediate neuro-immune interaction in the aortic adventitia (AA). Whether exercise modulates the sympathetic nerve interaction with the immune cells to mitigate aortic stiffness remains unknown. Four weeks of Angiotensin II (Ang II) infusion to C57BL/6 mice increased neural activation to increase the expression of tyrosine hydroxylase (TH) for sympathetic nerve axons and norepinephrine levels along with the colocalization of synapsin and ß2-adrenergic receptor (ß2-AR) positive macrophages in the AA. This Ang II-mediated sympathetic nerve and macrophage interaction activated fibroblasts to increase vascular fibrosis and arterial pulse wave velocity (PWV). Sympathetic denervation with celiac ganglionectomy or 6-hydroxydopamine treatment abrogated Ang II-mediated TH+, AA thickness, and PWV. scRNAseq analyses of the AA revealed that Ang II increased the circulating monocyte-derived macrophages (Ccr2+CD80) but reduced the resident macrophages (Lyve1+CD163). Gene ontology analysis of differentially expressed genes unveiled that voluntary wheel running (VWR) mitigated Ang II-mediated increase in Ccr2+CD80 macrophages, cytokines-mediated signaling pathways in macrophages, and extracellular matrix deposition in fibroblasts. Macrophage depletion with Ki20227 (colony stimulating factor-1 receptor inhibitor) reduced Ang II-mediated synapsin+ macrophages. Using the Ccr2 knock-in (Ccr2GFP) / knock-out (Ccr2KO) mice, we observed that Ang II-mediated increases in Ccr2+ macrophages were expressed in Ccr2GFP mice but were absent in Ccr2KO mice. Also, Ang II-induced increases in synapsin expression, neighboring Ccr2+ cells, AA thickness, and PWV were reduced in Ccr2KO mice. Both Ki20227 and Ccr2KO reduced the Ang II-mediated increase in TH levels. Furthermore, VWR-mediated reduction in vascular fibrosis and aortic stiffness were mitigated by a ß2-AR agonist, terbutaline, indicating ß2-AR in neuro-immune modulation. Exercise mitigates Ang II-mediated sympathetic axon interaction with the circulating monocyte-derived macrophages in the AA to attenuate vascular fibrosis and aortic stiffness. Overall design: Single-cell RNA sequencing (scRNA-seq) was performed on aortic adventitial from 9 total mice (n = 3 for saline (Vehicle), n = 3 for angiotensin II (AngII), and n = 3 for AngII + voluntary wheel running (VWR))