Podocyte derived TNF-α mediates monocyte differentiation and contributes to glomerular injury.

Abstract

Diabetes shortens the life expectancy by more than a decade, and the excess mortality in diabetes is correlated with the incidence of kidney disease. Diabetic kidney disease (DKD) is the leading cause of end-stage kidney disease. Macrophage accumulation predicts the severity of kidney injury in human biopsies and experimental models of DKD. However, the mechanism underlying macrophage recruitment in diabetes glomeruli is unclear. Elevated plasma growth hormone (GH) levels in type I diabetes and acromegalic individuals impaired glomerular biology. In this study, we examined whether GH-stimulated podocytes contribute to macrophage accumulation. RNA-seq analysis revealed elevated TNF-α signaling in GH-treated human podocytes. Conditioned media from GH-treated podocytes (GH-CM) induced differentiation of monocytes to macrophages. On the other hand, neutralization of GH-CM with the TNF-α antibody diminished GH-CM's action on monocytes. The treatment of mice with GH resulted in increased macrophage recruitment, podocyte injury, and proteinuria. Furthermore, we noticed the activation of TNF-α signaling, macrophage accumulation, and fibrosis in DKD patients' kidney biopsies. Our findings suggest that podocytes could secrete TNF-α and contribute to macrophage migration, resulting in DKD-related renal inflammation. Inhibition of either GH action or TNF-α expression in podocytes could be a novel therapeutic approach for DKD treatment.