Kidney Week

Abstract: SA-PO1021

Effects of TGF-β1 on the Activity of NFAT5, an Osmoprotective Transcription Factor

Session Information

• Fluid and Electrolytes: Basic - II
  October 27, 2018 | Location: Exhibit Hall, San Diego Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Fluid and Electrolytes

• 901 Fluid and Electrolytes: Basic

Authors

• Izumi, Yuichiro, Kumamoto University Graduate School of Medicine, Kumamoto, Japan

Yuichiro Izumi,

• Matsuo, Naomi, Kumamoto University Graduate School of Medicine, Kumamoto, Japan

Naomi Matsuo,

• Eguchi, Koji, Kumamoto University Graduate School of Medicine, Kumamoto, Japan

Koji Eguchi,

• Hara, Akiko, Kumamoto University Graduate School of Medicine, Kumamoto, Japan

Akiko Hara,

• Ono, Makoto, Kumamoto University Graduate School of Medicine, Kumamoto, Japan

Makoto Ono,

• Nakayama, Yushi, Kumamoto University Graduate School of Medicine, Kumamoto, Japan

Yushi Nakayama,

• Inoue, Hideki, Kumamoto University Graduate School of Medicine, Kumamoto, Japan

Hideki Inoue,

• Nonoguchi, Hiroshi, Kitasato University Medical Center, Kitamoto, SAITAMA, Japan

Hiroshi Nonoguchi,

• Kakizoe, Yutaka, Kumamoto University Graduate School of Medicine, Kumamoto, Japan

Yutaka Kakizoe,

• Kuwabara, Takashige, Kumamoto University Graduate School of Medicine, Kumamoto, Japan

Takashige Kuwabara,

• Mukoyama, Masashi, Kumamoto University Graduate School of Medicine, Kumamoto, Japan

Masashi Mukoyama,

Background

NFAT5 (nuclear factor of activated T-cells 5, or TonEBP) is a transcription factor that stimulates the expression of osmoprotective genes in response to extracellular hypertonicity, resulting in cell survival even in extremely hypertonic conditions. Activated NFAT5 is translocated from the cytoplasm to nucleus, and then binds to the osmotic response element (ORE) to induce transcription. Not only hypertonicity but also hypoxia, oxidative stress, and toll-like receptor signaling, which promote fibrogenesis in the kidney, have been suggested to increase the NFAT5 activity. Transforming growth factor-β1 (TGF-β1) is an important factor that stimulates fibrogenesis, but little is known about the interaction between TGF-β and NFAT5. We evaluated the effects of TGF-β1 on the NFAT5 activity.

Methods

For in vivo experiments, mice were subjected to unilateral ureteral obstruction (UUO). After 14 days, the expression of NFAT5 and TGF-β1 in the kidney was examined by real-time PCR. For in vitro experiments, we used human embryonic kidney 293 (HEK 293) ORE-X cells which stably express the ORE-X-luciferase reporter gene. Cells were incubated in 300 mOsm/kg or 500 mOsm/kg (NaCl added) for 24 hrs, and then the luciferase activity was measured to evaluate the NFAT5 transcriptional activity. Protein expression of NFAT5 was examined by Western blotting. To examine the effect of TGF-β on nuclear translocation of NFAT5, whole cell lysate was fractionated to nucleus and cytoplasm.

Results

The expression of NFAT5 and TGF-β1 mRNAs was 2.5 and 12 times greater in the kidney in UUO mice than that in sham-operated mice, respectively. TGF-β1 suppressed tonicity-induced NFAT5 transcriptional activity and protein expression in HEK293 cells. Nuclear translocation of NFAT5 was inhibited by TGF-β1. These results suggest that TGF-β1 directly inhibits the activation and expression of NFAT5.

Conclusion

TGF-β1 inhibits NFAT5 in the kidney, which might exacerbate renal fibrogenesis during fibrotic renal disorders.

Funding

• Government Support - Non-U.S.