Tubular epithelial cell-to-macrophage communication forms a negative feedback loop via extracellular vesicle transfer to promote renal inflammation and apoptosis in diabetic nephropathy

Background: Macrophage infiltration around lipotoxic tubular epithelial cells (TECs) is a hallmark of diabetic nephropathy (DN).However, how these two types of cells communicate remains obscure.We previously demonstrated that LRG1 was elevated in the process of kidney injury.Here, we demonstrated that macrophage-derived, LRG1-enriched extracellular vesicles (EVs) exacerbated DN.Methods: We induced an experimental T2DM mouse model with a HFD diet for four months.Renal primary epithelial cells and macrophage-derived EVs were isolated from T2D mice by differential ultracentrifugation.To investigate whether lipotoxic TEC-derived EV (EVe) activate macrophages, mouse bone marrow-derived macrophages (BMDMs) were incubated with EVe.To investigate whether activated macrophage-derived EVs (EVm) induce lipotoxic TEC apoptosis, EVm were cocultured with primary renal tubular epithelial cells.Subsequently, we evaluated the effect of LRG1 in EVe by investigating the apoptosis mechanism.Results: We demonstrated that incubation of primary TECs of DN or HK-2 mTECs with lysophosphatidyl choline (LPC) increased the release of EVe.Interestingly, TEC-derived EVe activated an inflammatory phenotype in macrophages and induced the release of macrophage-derived EVm.Furthermore, EVm could induce apoptosis in TECs injured by LPC.Importantly, we found that leucine-rich α-2-glycoprotein 1 (LRG1)-enriched EVe activated macrophages via a TGFβR1-dependent process and that tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-enriched EVm induced apoptosis in injured TECs via a death receptor 5 (DR5)-dependent process.Conclusion: Our findings indicated a novel cell communication mechanism between tubular epithelial cells and macrophages in DN, which could be a potential therapeutic target.