LPS-Induced Activation of the cGAS-STING Pathway is Regulated by Mitochondrial Dysfunction and Mitochondrial DNA Leakage in Endometritis

Abstract

Introduction: Chronic endometritis is a common disease in women of childbearing age and can cause pelvic inflammatory disease. The cGAS-STING pathway plays an important role in many inflammatory diseases. Purpose: The aim of this study was to investigate the relationship between the cGAS-STING pathway and endometritis. Methods: We collected endometrium samples from patients with endometritis to detect changes in the cGAS-STING pathway. In vitro, human endometrial stromal cells (HESC) were stimulated with lipopolysaccharide (LPS), and a mouse STING gene-knockout model was established by CRISPR/cas9 for STING to further explore the mechanism underlying its effects in endometritis. We used Western blotting (WB) and immunohistochemical staining to detect the variations in protein levels and real-time PCR to study the variations in gene expression. Results: We observed the activation of the cGAS-STING pathway and an increase in the expression of cytokine-encoding genes, including IL-8, IL-6, IL-1β, and IFN-β1, in endometrial tissues of patients with endometritis. Stimulation of HESCs using LPS demonstrated increase in the expression of proteins involved the cGAS-STING pathway and the gene expression of inflammatory cytokines. STING-knockdown experiments demonstrated a decrease in the gene expression levels of inflammatory cytokines. Moreover, we also identified the translocation of IRF3 and STING after LPS stimulation. Regarding mitochondrial function, LPS led to an increase in reactive oxygen species levels and a reduction in mitochondrial membrane potential. However, we observed that the mitochondrial DNA (mtDNA) leaked into the cytoplasm, upregulating the levels of proteins involved in the cGAS-STING pathway upon LPS stimulation. Furthermore, our results showed that LPS induced hyperemia, inflammatory factor production, and expression of Pho-TBK1 in wild-type mice compared with the levels in control mice, and STING gene-knockdown alleviated these effects. Conclusion: LPS induces mitochondrial dysfunction in endometrial stromal cells, resulting in mtDNA leakage and promoting endometritis by stimulating the cGAS-STING pathway.

Cecropin A Alleviates LPS-Induced Oxidative Stress and Apoptosis of Bovine Endometrial Epithelial Cells

“…Antioxidant enzymes, including SOD, SOD2, and peroxidases such as GPX and CAT, play a crucial role in antioxidant defense by regulating ROS levels [ 33 , 34 ]. A high concentration of LPS leads to abnormal ROS and MMP levels; promotes the production of inflammatory factors such as TNF-α, IL-1β, IL-6, and IL-8, causing oxidative damage and mitochondrial dysfunction [ 2 , 35 ]; and even leads to apoptosis [ 36 , 37 ]. Cecropin A has been shown to inhibit the production of TNF-α and IL-1β induced by LPS in mouse macrophage-derived RAW264.7 cells [ 18 ].…”

“…Long-term feeding of dairy cows with a high-concentrate diet poses a significant risk of sub-acute ruminal acidosis (SARA), leading to a high concentration of lipopolysaccharides (LPSs) in the circulatory system and triggering a systemic inflammatory response [ 1 ]. A previous study demonstrated that elevated LPS levels correlate with increased reactive oxygen species (ROS) and reduced mitochondrial membrane potential, ultimately causing mitochondrial dysfunction [ 2 ]. Furthermore, LPS leads to the upregulation of NADPH Oxidase (NOX), then resulting in an increase in ROS levels, which is a marker of oxidative stress [ 3 ].…”

Advances in crosstalk among innate immune pathways activated by mitochondrial DNA

“…cGAS recognizes the mtDNA and produces cGAMP, which inhibits the proliferation of endothelial cells through the downregulation of the YAP1 signaling pathway. Another study found that LPS induced mitochondrial dysfunction in endometrial mesenchymal cells through activation of the cGAS-STING pathway, induced mtDNA leakage, and promoted endometritis [ 83 ]. In addition, Interleukin-1β [ 84 ], palmitic acid (PA)-induced Lipotoxicity [ 85 ], TNF [ 86 ], and Electronic Cigarettes [ 87 ] are all involved in a variety of physiological and pathological processes through the activation of innate immune signaling pathways by mtDNA.…”

Our current understanding of the biological impact of endometrial cancer mtDNA genome mutations and their potential use as a biomarker

“…In another study using human endometrial stromal cells (HESCs) stimulated with lipopolysaccharide (LPS), cytoplasmic dsDNA, the cGAS-STING pathway, and IFN-β1 , IL-1β , IL-6 , and IL-8 gene expression were increased after LPS stimulation. Furthermore, when mtDNA was isolated and extracted from HESCs and then transfected into HESCs, the levels of cGAS-STING pathway proteins increased ( 142 ). Similarly, in a study investigating the role of the pro-inflammatory cytokine interleukin-6 (IL-6) on human endometrial adenocarcinoma MFE-296 cells, IL-6 increased the generation of ROS by enhancing NADH oxidase levels and inducing the cellular release of mtDNA.…”