Abstract Body: Background: Exercise augments hemodynamic shear to activate mechano-sensitive molecular transducers in the vascular endothelium. Recently, we and others observed that the central nervous system mediates 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.
Methods and Results: 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 β2-adrenergic receptor positive macrophages in the AA. This Ang II-mediated sympathetic nerve and macrophage interaction activated fibroblasts to increase vascular fibrotic remodeling, aortic pulse wave velocity (PWV), and blood pressure. Sympathetic denervation with celiac ganglionectomy or 6-hydroxydopamine treatment abrogated Ang II-mediated TH⁺, reducing 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 ECM deposition in fibroblasts. Macrophage depletion with Ki20227 (colony stimulating factor-1 receptor inhibitor) reduced Ang II-mediated synapsin⁺ macrophages. Using the Ccr2 knock-in (Ccr2^gfp) / knock-out (Ccr2^KO) mice, we observed that Ang II-mediated increases in Ccr2⁺ macrophages were expressed in Ccr2^GFP mice but were absent in Ccr2^KO mice. Also, Ang II-induced increases in synapsin expression, neighboring Ccr2⁺ cells, AA thickness, and PWV were reduced in Ccr2^KOmice. Both Ki20227 (colony-stimulating factor 1 receptor inhibitor) and Ccr2^KO significantly reduced the Ang II-mediated increase in TH levels. scRNAseq results also revealed that four weeks of VWR further abrogated Ang II-mediated macrophage-to-fibroblast communication via IL-1β signaling in AA, and this communication was supported by using human macrophage and aortic adventitia fibroblast cell lines.
Conclusions: Exercise mitigates Ang II-mediated sympathetic nerve axons interaction with the macrophages in the AA to ameliorate vascular fibrotic remodeling and aortic stiffness.