Kidney Week

Abstract: FR-PO209

Intraglomerular Cross-Talk Between Mesangial Cells and Podocytes Inhibits Normal Endoplasmic Reticulum-Associated Degradation Processes and Induces Podocyte Injury in Diabetes

Session Information

• Diabetic Kidney Disease: Basic - II
  November 08, 2019 | Location: Exhibit Hall, Walter E. Washington Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Diabetic Kidney Disease

• 601 Diabetic Kidney Disease: Basic

Authors

• Fujimoto, Daisuke, Kumamoto University, Kumamoto, Japan

Daisuke Fujimoto,

• Kuwabara, Takashige, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Japan

Takashige Kuwabara,

• Hata, Yusuke, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Japan

Yusuke Hata,

• Umemoto, Shuro, Kumamoto University Graduate School of Medicine, Kumamoto, Japan

Shuro Umemoto,

• Kanki, Tomoko, Kumamoto University, Kumamoto, Japan

Tomoko Kanki,

• Nishiguchi, Yoshihiko, Kumamoto University Hospital, Kumamoto, Japan

Yoshihiko Nishiguchi,

• Mizumoto, Teruhiko, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Japan

Teruhiko Mizumoto,

• Hayata, Manabu, Kumamoto University, Kumamoto, Japan

Manabu Hayata,

• Izumi, Yuichiro, Kumamoto University, Kumamoto, Japan

Yuichiro Izumi,

• Kakizoe, Yutaka, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Japan

Yutaka Kakizoe,

• Mukoyama, Masashi, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Japan

Masashi Mukoyama,

Background

Mesangial lesion and podocyte injury are essential for the progression of diabetic kidney disease (DKD). Although cross-communication between mesangial cells (MC) and podocytes is recently suggested by single cell RNA-seq analyses, its molecular mechanisms remain elusive. Our previous experiment on cDNA microarray of diabetic mice glomeruli suggested that ER stress might be involved in DKD progression. The aim of this study is to clarify the effects of MC-podocyte crosstalk on ER stress response of podocytes in diabetic conditions.

Methods

First, we conducted quantitative PCR array focused on ER stress-associated genes. Using cultured mouse podocytes (MPC5) and mouse macrophages (Mφ) stimulated with MC-cultured medium (MC-sup) under high-glucose condition (HG), we evaluated podocyte-specific responses. Further evaluations of ER stress responses of MPC5 were made by Western blotting, real-time PCR and TUNEL staining. The effects of an ER-associated degradation (ERAD) inhibitor Eeyarestatin I (EerI) in MPC5 and db/db mice were also examined.

Results

In vitro, stimulation with HG MC-sup suppressed ERAD-related factors (XBP1, Derlin), and enhanced apoptotic responses in both protein and mRNA levels specifically in MPC5, but not in Mφ. TUNEL staining of MPC5 also showed increased apoptotic cells by HG MC-sup. Those results were augmented by HG MC-sup compared to MC-sup under low-glucose condition. Of note, treatment with EerI recapitulated similar responses, namely suppressed IRE1α, spliced XBP1 and Derlin-2 in MPC5. In vivo, such alterations were also observed in isolated diabetic glomeruli. Administration of EerI significantly exacerbated albuminuria in db/db mice. Expression of genes related to inflammation and fibrosis increased, and immunohistochemistry showed lowered expression of Derlin-2 and nephrin in the glomeruli.

Conclusion

It is recently reported that ERAD pathway may play important roles in the maintenance of podocytes to avoid ER stress in several glomerular diseases including DKD. In this study, we first reveal that intraglomerular crosstalk between MC and podocytes inhibits normal ERAD processes, potentially causing podocyte injury in diabetic conditions.