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Circulating cell-free mtDNA release is associated with the activation of cGAS-STING pathway and inflammation in
Xutong Zhao1, Meng Yu1, Yawen Zhao1
1Department of Neurology, Peking University First Hospital, #8 Xishiku St, Xicheng District, Beijing, 100034, China.
Background:
There is increasing evidence for the role of inflammation in the pathogenesis of mitochondrial diseases (MDs). However, the mechanisms underlying mutation-induced inflammation in MD remain elusive. Our previous study suggested that mitophagy is impaired in the skeletal muscle of those with MD, likely causing mitochondrial DNA (mtDNA) release and thereby triggering inflammation. We here aimed to decipher the role of the cGAS-STING pathway in inflammatory process in MDs.
Methods:
We investigated the levels of circulating cell-free mtDNA (ccf-mtDNA) in the serum of 104 patients with MDs. Immunofluorescence was performed in skeletal muscles in MDs and control. Biochemical analysis of muscle biopsies was conducted with western blot to detect cGAS, STING, TBK1, IRF3 and phosphorylated IRF3 (p-IRF3). RT-qPCR was performed to detect the downstream genes of type I interferon in skeletal muscles. Furthermore, a protein microarray was used to examine the cytokine levels in the serum of patients with MDs.
Results:
We found that ccf-mtDNA levels were significantly increased in those with MDs compared to the controls. Consistently, the immunofluorescent results showed that cytosolic dsDNA levels were increased in the muscle samples of MD patients. Biochemical analysis of muscle biopsies showed that cGAS, IRF3, and TBK1 protein levels were significantly increased in those with MDs, indicating that there was activation of the cGAS-STING pathway. RT-qPCR showed that downstream genes of type I interferon were upregulated in muscle samples of MDs. Protein microarray results showed that a total of six cytokines associated with the cGAS-STING pathway were significantly increased in MD patients (fold change > 1.2, p value < 0.05).
Conclusions:
These findings suggest that increases in ccf-mtDNA levels is associated with the activation of the cGAS-STING pathway, thereby triggering inflammation in MDs.
Insights
Inflammation in mitochondrial diseases (MDs) is linked to increased cell-free mitochondrial DNA (mtDNA). This study shows elevated mtDNA activates the cGAS-STING pathway, triggering inflammation in MD patients.
Area of Science:
- Mitochondrial Biology
- Immunology
- Genetics
Background:
- Inflammation plays a key role in mitochondrial diseases (MDs), but the underlying mechanisms are not fully understood.
- Impaired mitophagy in MDs may lead to mitochondrial DNA (mtDNA) release and subsequent inflammation.
- This study investigates the involvement of the cGAS-STING pathway in MD-associated inflammation.
Purpose of the Study:
- To determine the role of the cGAS-STING pathway in the inflammatory process of mitochondrial diseases.
- To investigate the association between circulating cell-free mtDNA (ccf-mtDNA) levels and cGAS-STING pathway activation in MD patients.
Main Methods:
- Measured serum ccf-mtDNA levels in 104 MD patients and controls.
- Analyzed skeletal muscle biopsies using immunofluorescence and western blot for cGAS-STING pathway components.
- Assessed type I interferon gene expression and serum cytokine levels via RT-qPCR and protein microarray.
Main Results:
- MD patients exhibited significantly higher serum ccf-mtDNA and cytosolic dsDNA levels in muscle tissue.
- Increased protein levels of cGAS, IRF3, and TBK1 indicated activation of the cGAS-STING pathway.
- Upregulation of type I interferon downstream genes and elevated levels of six cGAS-STING-associated cytokines were observed in MD patients.
Conclusions:
- Elevated ccf-mtDNA levels are associated with cGAS-STING pathway activation in mitochondrial diseases.
- The cGAS-STING pathway activation contributes to the inflammatory process in MDs.
- These findings elucidate a key mechanism linking mitochondrial dysfunction to systemic inflammation.
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