Global deficiency in the inflammatory chemokine receptors 1,2,3 and 5 prevents vascular dysfunction in angiotensin II-induced hypertension and selectively modulates aortic myeloid cell phenotype

Abstract Background Leukocyte migration to the vasculature and the heart plays a critical role in hypertensive immune responses and is a carefully orchestrated process, regulated by the interactions of inflammatory chemokines with their receptors, notably CCR1, CCR2, CCR3, and CCR5 (collectively termed inflammatory chemokine receptors (iCCRs)). However, the inflammatory chemokine/receptor system is characterised by redundancy, ligand sharing and overlapping expression patterns. Consequently, our understanding of the specific and combinatory roles of chemokine receptors in cardiovascular inflammation remains incomplete, thus hindering the development of targeted therapies. To address this challenge, we have utilised two novel mouse models: iREP mice, carrying fluorescent reporters of inflammatory chemokine receptor expression, and TACKO mice, in which the entire iCcr locus containing Ccr1, Ccr2, Ccr3, and Ccr5 has been deleted. Purpose To evaluate the expression pattern of iCCRs in experimental hypertension and understand how the global deletion of iCCRs impacts disease progression. Methods We induced hypertension in mice by subcutaneously implanting osmotic minipumps administering angiotensin II (Ang II) for a duration of 14 days. Single-cell RNA sequencing was utilised for investigating iCCR expression in aortas during hypertension. Additionally, we employed flow cytometry and confocal microscopy to track iCCR expression and localization in aortas and hearts obtained from iREP mice. TACKO mice were utilised to assess the effect of global iCCr deficiency on hypertensive phenotypes. Blood pressure was measured via telemetry and vascular function was assessed using myography. Vascular and heart remodelling were evaluated through histology. Molecular mechanisms were analysed using Western Blotting and RT-qPCR, while immune cell changes in the aorta were evaluated through cytometry of time-of-flight (CyTOF). Results Ang II infusion induced higher iCCRs expression levels in both the aorta and the heart in comparison with sham treatment, particularly in fibrotic areas. After Ang II-treatment, global deletion of iCCRs in TACKO mice resulted in the prevention of endothelial dysfunction (n=5/group, P<0.05) and perivascular fibrosis (n=6-9, P<0.01), and a reduction in cardiomyocyte size (n=12-16, P<0.01) compared to wild type mice. However, no significant improvements were observed in other hypertensive phenotypes, including blood pressure, heart fibrosis, vascular NO synthase, and oxidative stress. CyTOF analysis revealed reductions in inflammatory monocytes and conventional type 2 dendritic cells in TACKO aorta, accompanied by a phenotypic switch in macrophages towards a less inflammatory phenotype. Conclusion Deficiency in iCCRs confers protective effects against vascular dysfunction in experimental hypertension, primarily by selectively reducing inflammatory myeloid cell homing to the aorta.