Phosphorylated nuclear factor erythroid 2-related factor 2 promotes the secretion of C-C motif chemokine ligand 2 and the recruitment of M2 macrophages

BACKGROUND: Nuclear factor erythroid 2-related factor 2 (Nrf2) has been shown to ameliorate early ischemia-reperfusion (I/R) injury after activation by tertiary butylhydroquinone (TBHQ). However, despite macrophage-associated inflammation being a distinguishing feature of I/R injury, the precise roles and mechanisms of Nrf2 in macrophage-associated inflammation are still poorly understood. METHODS: I/R and hypoxia/reperfusion (H/R) models were constructed in vivo using rats and in vitro using the H9C2 rat cardiomyoblast cell line, respectively. The effects of TBHQ on myocardial damage under oxidative stress were assessed using apoptosis and cell cycle assays, as well as echocardiography. The Jaspar database was used to identify the C-C motif chemokine ligand 2 (Ccl2) gene promoter as a possible binding site for Nrf2. This interaction was validated by chromatin immunoprecipitation (ChIP) assays, enzyme-linked immunosorbent assay (ELISA), immunofluorescence staining, and western blot analysis. Transwell migration assays were used to examine the migration ability of the recruited macrophages. RESULTS: The Nrf2 activator, TBHQ, induced phosphorylation of Nrf2 and promoted the secretion of Ccl2 by myocardial microvascular endothelial cells. The secreted Ccl2 induced the chemotaxis of M2 macrophages into the injury site and triggered the secretion of anti-inflammatory factors including interleukin (IL)-10 and tumor growth factor (TGF)-β1 by M2 macrophages, thereby reducing early myocardial ischemia reperfusion injury (MI/R). CONCLUSIONS: Activation of Nrf2 alleviated oxidative stress during myocardial ischemia and reperfusion by inducing the secretion of anti-inflammatory factors.