Mitochondrial Damage and Activation of the STING Pathway Lead to Renal Inflammation and Fibrosis.

Cell Metab. 2019 Oct 1;30(4):784-799.e5.

Ki Wung Chung¹, Poonam Dhillon¹, Shizheng Huang¹, Xin Sheng¹, Rojesh Shrestha¹, Chengxiang Qiu¹, Brett A Kaufman², Jihwan Park¹, Liming Pei³, Joseph Baur⁴, Matthew Palmer⁵, Katalin Susztak⁶

1. Renal, Electrolyte, and Hypertension Division, Department of Medicine, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA 19104, USA; Institute for Diabetes, Obesity, and Metabolism, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA 19104, USA.
2. Center for Metabolism and Mitochondrial Medicine, Division of Cardiology, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
3. Institute for Diabetes, Obesity, and Metabolism, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA 19104, USA; Center for Mitochondrial and Epigenomic Medicine, Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA; Department of Pathology and Laboratory Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA.
4. Institute for Diabetes, Obesity, and Metabolism, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA 19104, USA; Department of Physiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA.
5. Department of Pathology and Laboratory Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA.
6. Renal, Electrolyte, and Hypertension Division, Department of Medicine, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA 19104, USA; Institute for Diabetes, Obesity, and Metabolism, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA 19104, USA. Electronic address: ksusztak@pennmedicine.upenn.edu.

Abstract

Fibrosis is the final common pathway leading to end-stage renal failure. By analyzing the kidneys of patients and animal models with fibrosis, we observed a significant mitochondrial defect, including the loss of the mitochondrial transcription factor A (TFAM) in kidney tubule cells. Here, we generated mice with tubule-specific deletion of TFAM (Ksp-Cre/Tfamflox/flox). While these mice developed severe mitochondrial loss and energetic deficit by 6 weeks of age, kidney fibrosis, immune cell infiltration, and progressive azotemia causing death were only observed around 12 weeks of age. In renal cells of TFAM KO (knockout) mice, aberrant packaging of the mitochondrial DNA (mtDNA) resulted in its cytosolic translocation, activation of the cytosolic cGAS-stimulator of interferon genes (STING) DNA sensing pathway, and thus cytokine expression and immune cell recruitment. Ablation of STING ameliorated kidney fibrosis in mouse models of chronic kidney disease, demonstrating how TFAM sequesters mtDNA to limit the inflammation leading to fibrosis.

Presented by Poonam Dhillon