CXCL1-CXCR2 axis mediates angiotensin II-induced cardiac hypertrophy and remodelling through regulation of monocyte infiltration.

Aims: Chemokine-mediated monocyte infiltration into the damaged heart represents an initial step in inflammation during cardiac remodelling. Our recent study demonstrates a central role for chemokine receptor CXCR2 in monocyte recruitment and hypertension; however, the role of chemokine CXCL1 and its receptor CXCR2 in angiotensin II (Ang II)-induced cardiac remodelling remain unknown.
Methods and Results: Angiotensin II (1000 ng kg-1 min-1) was administrated to wild-type (WT) mice treated with CXCL1 neutralizing antibody or CXCR2 inhibitor SB265610, knockout (CXCR2 KO) or bone marrow (BM) reconstituted chimeric mice for 14 days. Microarray revealed that CXCL1 was the most highly upregulated chemokine in the WT heart at Day 1 after Ang II infusion. The CXCR2 expression and the CXCR2+ immune cells were time-dependently increased in Ang II-infused hearts. Moreover, administration of CXCL1 neutralizing antibody markedly prevented Ang II-induced hypertension, cardiac dysfunction, hypertrophy, fibrosis, and macrophage accumulation compared with Immunoglobulin G (IgG) control. Furthermore, Ang II-induced cardiac remodelling and inflammatory response were also significantly attenuated in CXCR2 KO mice and in WT mice treated with SB265610 or transplanted with CXCR2-deficienct BM cells. Co-culture experiments in vitro further confirmed that CXCR2 deficiency inhibited macrophage migration and activation, and attenuated Ang II-induced cardiomyocyte hypertrophy and fibroblast differentiation through multiple signalling pathways. Notably, circulating CXCL1 level and CXCR2+ monocytes were higher in patients with heart failure compared with normotensive individuals.
Conclusions: Angiotensin II-induced infiltration of monocytes in the heart is largely mediated by CXCL1-CXCR2 signalling which initiates and aggravates cardiac remodelling. Inhibition of CXCL1 and/or CXCR2 may represent new therapeutic targets for treating hypertensive heart diseases.