Abstract: TH-PO026
Mitochondrial Damage Causes Inflammation via cGAS-STING Signaling in AKI
Session Information
- AKI: Mechanisms - Primary Injury and Repair - I
November 07, 2019 | Location: Exhibit Hall, Walter E. Washington Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Acute Kidney Injury
- 103 AKI: Mechanisms
Authors
- Maekawa, Hiroshi, The University of Tokyo Graduate School of Medicine, Bunkyo-ku, ToKyo, Japan
- Inoue, Tsuyoshi, The University of Tokyo Graduate School of Medicine, Bunkyo-ku, ToKyo, Japan
- Jao, Tzu-Ming, National Taiwan University Hospital, Taipei, Taiwan
- Nishi, Hiroshi, The University of Tokyo Graduate School of Medicine, Bunkyo-ku, ToKyo, Japan
- Inoue, Reiko, The University of Tokyo Graduate School of Medicine, Bunkyo-ku, ToKyo, Japan
- Haruki, Ouchi, The University of Tokyo Graduate School of Medicine, Bunkyo-ku, ToKyo, Japan
- Fujii, Rie, The University of Tokyo Graduate School of Medicine, Bunkyo-ku, ToKyo, Japan
- Uni, Rie, The University of Tokyo Graduate School of Medicine, Bunkyo-ku, ToKyo, Japan
- Tanaka, Tetsuhiro, The University of Tokyo Graduate School of Medicine, Bunkyo-ku, ToKyo, Japan
- Nangaku, Masaomi, The University of Tokyo Graduate School of Medicine, Bunkyo-ku, ToKyo, Japan
- Inagi, Reiko, The University of Tokyo Graduate School of Medicine, Bunkyo-ku, ToKyo, Japan
Background
Acute kidney injury (AKI) is characterized by mitochondrial dysfunction and activation of the immune response. The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway detects cytosolic DNA and induces innate immunity. We investigated the role of mitochondrial damage and subsequent activation of the cGAS-STING pathway in cisplatin (cis)-induced AKI.
Methods
The human proximal tubular cell line, HK-2, treated with 20 μM of cis and the renal cortex of WT (C57BL/6) or STING KO mice injected with 25 mg/kg of cis for 48 or 72 hr were analyzed. The changes in cGAS-STING activation, mitochondrial damage, mitochondrial DNA (mtDNA) leakage or neutrophil infiltration were evaluated by flux analyzer, mitochondrial membrane potential analysis, real-time PCR, western blotting, or immunostaining.The culture supernatants of cis and/or STING siRNA-treated HK-2 were used for cytokine arrays and migration assays. Ethidium bromide (EtBr) and extracted mtDNA from HK-2 were used for mtDNA depletion and mtDNA transfection (to increase cytosolic mtDNA), respectively.
Results
In cis-treated HK-2 or kidney cortex of cis-induced AKI mice, cGAS and STING were upregulated and STING translocated from the ER to the Golgi apparatus, indicating STING activation. Subsequently, the cGAS-STING axis was activated via cis-mediated phosphorylation of TBK-1 and P65, leading to induction of inflammatory cytokines (IL-6, IL-8, ICAM-1, CXCL10, and GM-CSF) and neutrophil chemotaxis. The inflammatory response by cis was ameliorated in STING-knockdowned HK-2 or STING KO mice. Cis impaired tubular mitochondrial function: reduction of mitochondrial respiration and mitochondrial fatty acid β-oxidation with subsequent decrease in ATP production. Moreover, cis permeabilized mitochondrial membrane. Following the mitochondrial dysfunction, cis-mediated mtDNA leakage to the cytosol was induced in tubular cells both in vivo and in vitro. mtDNA depletion inhibited the inflammation by cis in HK-2, whereas mtDNA transfection activated cGAS-STING axis, indicating that leaked cytosolic mtDNA acts as a ligand for the cGAS-STING pathway in cis-induced tubular inflammation.
Conclusion
Mitochondrial damage leads to mtDNA leakage, activating cGAS-STING signaling and subsequent inflammation in cis-induced AKI.