Activin A Contribution to Diabetic Kidney Disease Injury and Effects of Activin A Antagonism In-Vitro

Abstract

Diabetic kidney disease (DKD) is the worldwide leader in end-stage kidney failure and has limited treatment options. Cellular senescence abundance and inflammation contribute to DKD pathogenesis. We previously demonstrated that activin A, an inflammatory mediator of pro-fibrotic kidney injury and cellular senescence, is increased in DKD and correlates with DKD injury and kidney function. We hypothesized that activin A contributes to DKD injury causing pro-fibrotic, pro-inflammatory, and cellular senescence effects in vitro, and that antagonism of activin A is achieved with follistatin. An in vitro model of DKD injury was applied with high-glucose (HG) and transforming growth factor-β (TGFβ) exposure for 24 hours in U-937-derived macrophages and renal epithelial (HK2) cells. Prior to exposure, U-937 cells were converted to M0 macrophages with phorbol myristate acetate (PMA). To examine the potential of reducing activin A release by DKD injured cells, follistatin, an activin A antagonist, was added to the media of cells at the time of injury for 24 hours. Additionally, an activin A neutralizing antibody was added to the collected supernatant of DKD injured cells. Activin A, senescence (p16), pro-fibrotic (collagen I), and pro-inflammatory (monocyte chemoattractant protein [MCP]-1, tumor necrosis factor [TNF]-alpha, interleukin [IL]-6) markers were measured through qPCR, ELISA (activin A), and immunofluorescence staining (activin A). DKD injury in renal epithelial cells increased protein expression of activin A, increased gene expression of activin A, p16, and collagen I, but did not significantly increase MCP-1 expression at 24 hour exposure (Figure 1). Furthermore, DKD injury led to increased activin A release in conditioned medium vs. control renal epithelial cells. Administration of follistatin reduced activin A release by renal epithelial cells. Application of neutralizing antibody reduced activin A levels in collected medium after cell injury. After DKD injury in U-937 derived macrophages, activin A gene expression was increased. Injured macrophages had increased gene expression of TNF-alpha and IL-6, demonstrating a pro-inflammatory phenotype. In conclusion, diabetic kidney injury increases activin A release, inflammation markers, and senescence markers in kidney cells and macrophages, therein contributing to downstream effects that further propagate disease. As shown, follistatin antagonism reduces activin A release by injured cells. Additional studies are needed to explore activin A as a promising therapeutic target and follistatin as a possible treatment in DKD. NIH 5TL1TR002380-07, AG076537, DK123492, DK109134. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.