#6817 ROLE OF THE CGAS-STING PATHWAY IN THE PROGRESSION OF DIABETIC NEPHROPATHY

Abstract

Abstract Background and Aims Diabetic kidney disease (DKD) is the leading cause of chronic renal pathology. Understanding the molecular underpinnings of DKD is critical to designing tailored therapeutic approaches. We have demonstrated previously that type 2 diabetic nephropathy (T2DN) rats develop renal and physiological abnormalities similar to clinical observations in humans with DKD, indicating these rats are an excellent model for studying the progression of renal injury in type 2 DKD [1]. Furthermore, our recent studies revealed sexual dimorphism in this model, indicating that while both male and female T2DN rats developed non-obese DKD phenotype, females had significant protection from the development of severe forms of glomerular and tubular damage [2]. The potential role of the cyclic GMP-AMP synthase (cGAS) / Stimulator of interferon genes (STING) pathway in renal inflammation and fibrosis was also uncovered [3]. Here we focused on sex differences in DKD and the potential mechanisms leading to the progression of DKD. Method To explore the sexual dimorphisms in the development of DKD, we utilized young (12-week-old) and aged (>48 weeks old) type 2 diabetic nephropathy (T2DN) rats. To delineate transcriptional changes, RNA-Seq analysis was performed in the kidney cortex of T2DN rats of both sexes at a younger and older age. Western blotting, immunohistochemistry, and flow cytometry analyses were further used to identify specific pathways contributing to sexual dimorphism and disease progression in T2DN rats. Results We have revealed that the cGAS/STING signaling pathway is upregulated in T2DN rats compared to non-diabetic Wistar rats and in type 2 diabetic human kidneys. The expression of key proteins in the cGAS-STING pathway, such as cGAS, STING, phospho-IRF, mtTFA, and TREX1, was significantly different between male and female T2DN rats and following the progression of DKD. Proinflammatory genes were also upregulated in male T2DN rats compared to female rats of the same age, and their levels were further elevated in aged rats. RNA-Seq analysis also identified significant changes in genes participating in the cGAS-STING inflammatory pathway. Flow cytometry revealed a significantly greater number of infiltrating leukocytes in the male kidneys compared to their age-matched females. Moreover, the leukocytic count was significantly higher in old males versus young males, while it was almost the same in females of different ages. Approximately 50% of the renal leukocytic population was monocytes/macrophages (CD11b/c+), with fewer CD3+ T cells, both CD3+CD4+ T helper and CD3+CD8+ cytotoxic T cells, and CD45R+ B cells. Conclusion Our study provides critical insights into the sexual dimorphism and progression of DKD and identifies the cGAS-STING pathway as an essential contributor to disease development.