Kidney Week

Abstract: FR-PO1030

DNA Double-Strand Breaks in Proximal Tubular Epithelial Cells Induce a Systemic Lipodystrophy-Like Phenotype

Session Information

• CKD Mechanisms: From Mendel to Mars
  November 03, 2023 | Location: Exhibit Hall, Pennsylvania Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: CKD (Non-Dialysis)

• 2303 CKD (Non-Dialysis): Mechanisms

Authors

• Nishimura, Erina Sugita, Keio Gijuku Daigaku Igakubu Daigakuin Igaku Kenkyuka, Shinjuku-ku, Tokyo, Japan

Erina Sugita Nishimura,

• Hishikawa, Akihito, Keio Gijuku Daigaku Igakubu Daigakuin Igaku Kenkyuka, Shinjuku-ku, Tokyo, Japan

Akihito Hishikawa,

• Nakamichi, Ran, Keio Gijuku Daigaku Igakubu Daigakuin Igaku Kenkyuka, Shinjuku-ku, Tokyo, Japan

Ran Nakamichi,

• Hama, Eriko Yoshida, Keio Gijuku Daigaku Igakubu Daigakuin Igaku Kenkyuka, Shinjuku-ku, Tokyo, Japan

Eriko Yoshida Hama,

• Hayashi, Kaori, Keio Gijuku Daigaku Igakubu Daigakuin Igaku Kenkyuka, Shinjuku-ku, Tokyo, Japan

Kaori Hayashi,

Group or Team Name

• Division of Endocrinology, Metabolism and Nephrology, Dept of Internal Medicine.

Background

We have recently reported that podocyte DNA double strand breaks (DSBs) induce alteration in DNA methylation of CD8 memory T cells which exacerbates severe podocyte injuries (Cell Rep 2023). We next investigated the pathophysical significance of DNA DSBs in PTECs.

Methods

To investigate the significance of DNA double-strand breaks (DSBs) in PTECs, we generated PTEC-specific I-PpoI-expressing mice (I-PpoI mice) which express homing endonuclease I-PpoI inducing non-mutagenic DNA DSBs.

Results

I-PpoI mice showed only mild elevation of tubular markers, but presented weight loss, increased liver free fatty acid content, decreased epidermal fat mass and impaired glucose tolerance at 16 weeks of age, which was consistent with the phenotype of systemic lipodystrophy.
Metabolomic analysis showed mitochondrial dysfunction with impaired fatty acid metabolism in kidney cortex and liver. Single-cell RNA seq analysis revealed a marked expansion of inflammatory Ly6C^hi monocytes and Ccr2^hi CD11c⁺macrophages in renal cortex of I-PpoI mice, which is reported to play an important role on metabolic derangement in adipocytes and insulin resistance.
In vitro analysis of cultured PTECs overexpressing I-PpoI showed mitochondrial dysfunction as observed in I-PpoI mice measured by Seahorse Extracellular Flux Analyzer. In addition, culture medium of PTECs overexpressing I-PpoI caused an activation of macrophages.
Next, methylated DNA Immunoprecipitation (MeDIP)-Sequencing of peripheral blood cells in wild type and I-PpoI mice was performed. Interestingly, the motif analysis showed hypomethylated regions in binding sites of KLF9, which is reported to be associated with diabetic complications in humans (Nat Metab 2020). It was also confirmed that downstream genes of KLF9 was hypomethylated, including PFKFB3, which is reported to promote the proliferation and infiltration of inflammatory Ly6C^hi monocytes into tissues and its differentiation into macrophages.

Conclusion

DNA damage in PTECs activated a different population of immune cells and caused quite different phenotypes from that in podocytes. PTEC DNA damage causes systemic metabolic alterations, associated with altered DNA methylation in peripheral blood cells.