Macrophage surface protein Mac-2 mediates inflammatory and stromal stress pathways in doxorubicin-induced cardiac injury

Doxorubicin (DOX) cardiotoxicity is a major complication of cancer therapy and involves macrophage-driven inflammation and myocardial remodeling. The macrophage surface protein Mac-2 (galectin-3) is upregulated in cardiac injury, but its role in regulating macrophage function and downstream injury pathways remains undefined. We used CRISPR/Cas9-engineered Mac-2-null macrophages to evaluate chemotaxis, cytokine gene expression, and lysosomal stress signaling in vitro. To examine paracrine injury mechanisms, we performed co-culture assays with cardiomyocytes and fibroblasts. In vivo, we studied homozygous Mac-2-mutant mice and used CD45.1/CD45.2 bone marrow transplantation with lineage tracking to define hematopoietic versus stromal contributions to DOX-induced inflammation, apoptosis, fibrosis, and systolic dysfunction. Doxorubicin induced Mac-2 and inflammatory transcripts (Il6, Tnf, Ccl2) in wild-type macrophages, whereas Mac-2 knockout reduced DOX uptake, chemotaxis, and cytokine induction. In co-culture, DOX-treated WT macrophages increased caspase-3/7 activity in cardiomyocytes and phospho-TFEB in fibroblasts, both attenuated with Mac-2 deletion. In vivo, Mac-2-null mice exhibited less cardiac inflammation, apoptosis, and fibrosis with preserved systolic function and reduced mortality. Bone marrow transplantation demonstrated that hematopoietic Mac-2 suppressed cardiac Tfeb and upregulated Sqstm1 and Tgfb1, enhancing inflammatory and apoptotic responses, whereas Mac-2-deficient marrow restored Tfeb, limited Sqstm1/Tgfb1, and protected cardiac function. Mac-2 promotes DOX-induced cardiac injury by facilitating inflammatory activation in macrophages, driving fibroblast lysosomal stress via TFEB and SQSTM1, and augmenting caspase-3–associated apoptosis in cardiomyocytes. Loss of Mac-2 in hematopoietic cells reduces inflammation, fibrosis, and systolic dysfunction in vivo.