Esaxerenone inhibits renal macrophage proliferation through MR/TGF-β1 pathway in db/db mice

To investigate the effect of mineralocorticoid receptor (MR) blockade esaxerenone on renal macrophage proliferation in db/db mice and its potential role in the progression of diabetic kidney disease (DKD).

Eight-week-old db/db mice were administered esaxerenone at a dose of 1 mg/kg/day for six weeks. The origin of macrophages (resident versus recruited) and their phenotypic subtypes (M1 vs. M2) were evaluated using molecular markers, including F4/80, Ki-67, Ly6C, iNOS, and CD206. Immunohistochemistry, flow cytometry, and single-cell RNA sequencing were utilized to evaluate these parameters. The inhibitory effects of esaxerenone and the TGF-β1 inhibitor LY2109761 on the proliferation of bone marrow-derived macrophages (BMDMs) under high-glucose conditions were examined in vitro.

Marked increases in macrophage infiltration and proliferation were observed in the kidneys of db/db mice. Both recruited and resident macrophages exhibited significant proliferative activity, with recruited macrophages predominantly adopting an M1 phenotype and resident macrophages primarily exhibiting an M2 phenotype. Proliferating macrophages displayed enhanced pro-inflammatory and pro-fibrotic responses compared to non-proliferating counterparts. In vivo, esaxerenone treatment significantly suppressed macrophage proliferation. In vitro studies demonstrated that high glucose activated MR, upregulated TGF-β1 expression, and subsequently promoted BMDMs proliferation, particularly within the M1 subtype. TGF-β1 alone also induced BMDMs proliferation, an effect attenuated by LY2109761.

Esaxerenone inhibits renal macrophage proliferation mediated by high glucose-induced activation of MR and downstream TGF-β1 signaling pathways, thereby mitigating inflammatory and fibrotic damage. These findings suggest that MR blockade may directly target macrophage proliferation and inflammation in DKD.