Lipoxins Regulate Intercalated Disk-Associated Signaling and Immune Remodeling in Dilated Cardiomyopathy
We investigated whether pro-resolving lipid mediators of the lipoxin family can attenuate fibrosis and inflammation in muscle LIM protein knockout (MLPko) mice, a model of dilated cardiomyopathy (DCM). Male and female MLPko mice received either vehicle or a mix of lipoxin-A4 and lipoxin-B4 three times per week for six weeks. Cardiac function was assessed using echocardiography, and fibrosis and DCM-associated cardiac signaling was evaluated through histology, immunofluorescence and immunoblot analyses. Flow cytometry and RNA sequencing (RNAseq) was performed to identify changes in cardiac gene expression and characterize macrophage subpopulations, respectively. Flow cytometry showed increased inflammatory CD11c+ M1-like macrophages and reduction of CD206+ M2-like macrophages in MLPko hearts compared to wild-type controls. Lipoxin treatment partially reversed the macrophage imbalance and showed mild improvements in cardiac physiology in MLPko males. RNAseq analyses revealed sex-dependent alterations in the expression of pro-fibrotic and inflammation-related genes, suggesting changes in extracellular matrix (ECM) integrity and composition, and to the adaptive immune response. Intriguingly, several ECM proteins showed unexpected localizations at cardiac intercalated disks, which are known to be involved in DCM etiology. Further analysis identified lipoxin-dependent reduction in the DCM-associated expression of intercalated disk components only in lipoxin-treated MLPko males. Lipoxins also modulated key cardiac signaling pathways in a sex-specific manner, including Erk1/2 and PKC-linked Ankrd1/Carp1, which is associated with DCM development in MLPko mice. While lipoxins do not directly reverse cardiac dysfunction or fibrosis in MLPko mice, they may provide sex-specific protective effects by modulating DCM-related cardiac signaling pathways and by influencing immune-cell populations.