Abstract: SA-PO740
Mint3 Mitigates Renal Fibrosis After Ischemia-Reperfusion Injury Through Protection of Tubular Epithelial Cells from Apoptosis via Upregulation of NF-κB
Session Information
- CKD: Mechanisms - III
November 09, 2019 | Location: Exhibit Hall, Walter E. Washington Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: CKD (Non-Dialysis)
- 2103 CKD (Non-Dialysis): Mechanisms
Authors
- Kawakami, Takahisa, Kyorin University School of Medicine, Tokyo, Japan
- Nasu, Kahori, the University of Tokyo School of Medicine, Tokyo, Japan
- Shinohara, Akinari, the University of Tokyo School of Medicine, Tokyo, Japan
- Kaname, Shinya, Kyorin University School of Medicine, Tokyo, Japan
- Nangaku, Masaomi, the University of Tokyo School of Medicine, Tokyo, Japan
Background
Tubulointerstitial fibrosis is a hallmark of chronic kidney disease (CKD), and initiated by tubular epithelial cell (TEC) injury. Hypoxia promotes tubular cell death, fibrosis, and CKD progression. Munc18-1-interacting protein 3 (Mint3) is a molecule that activates hypoxia-inducible factors (HIFs) by binding and suppressing factor inhibiting HIF-1 (FIH). However, the role of Mint3 in tubulointerstitial fibrosis remains unknown.
Methods
We induced fibrosis of the kidney after unilateral ischemia-reperfusion injury (uIRI) in Mint3-knockout and littermate wild-type mice. The function of Mint3 was further investigated by using mouse cortical tubular (MCT) cells, which were treated with Mint3 and/or FIH siRNA and exposed to hypoxia. Apoptosis was assayed with cleaved caspase-3 and TUNEL staining, and flow cytometry with Annexin-V and 7-AAD.
Results
We found that Mint3 was mainly expressed in TECs with immunostaining of the kidney. Knockout of Mint3 did not affect the acute injury induced by uIRI, but exacerbated the tubulointerstitial fibrosis, accompanied by an increase in TEC apoptosis. Consistently, hypoxia-induced apoptosis of MCT was aggravated by Mint3 knockdown. Unexpectedly, the additional knockdown of FIH did not suppress the increase in apoptosis by Mint3 knockdown, demonstrating the irrelevance of the FIH/HIF pathway. Hence, we focused on NF-κB, a transcription factor which has an anti-apoptotic role, as well as a well-known proinflammatory role. While NF-κB forms a dimer and usually promotes transcription, a homodimer of p50 or p52, which lacks a transactivation domain, can suppress transcription. Indeed, the expression of the inhibitory NF-κB p50 and the protein in nuclei were increased by knockdown of Mint3 in the TECs and by its knockout in the kidney, along with the decreased expressions of the NF-κB-targeted anti-apoptotic genes.
Conclusion
This study demonstrated the importance of TEC injury as a primary event leading to renal fibrosis, as well as unexpected relationship of Mint3 and NF-κB. Mint3 protects the cells from apoptosis by decreasing inhibitory effects of NF-κB, leading to fibrosis suppression. This new pathophysiology of tubulointerstitial fibrosis can be a target of the future therapy for CKD.
Funding
- Government Support - Non-U.S.