Abstract Body: Background: Sepsis is our body’s response to infection, which can lead to multiorgan failure and death if untreated. In the US, over 1.7 million people develop sepsis annually, making it the third leading cause of death either during hospitalization or after discharge. Although survivors have a high risk of cardiovascular dysfunction, the mechanisms behind sepsis-induced cardiovascular issues are poorly understood. Emerging research demonstrates the critical role of mitochondrial dysfunction in sepsis. Our study aims to investigate mitochondrial DNA (mtDNA) damage and its association with cardiovascular dysfunction during sepsis.
Method and Result: We administered lipopolysaccharide (LPS, 2mg/kg) intraperitoneally to adult C57BL/6 mice. After 24 hours, DNA and RNA were isolated from cardiac tissue, and mtDNA damage and inflammation were evaluated using qPCR. The results showed increased mtDNA damage and inflammation in cardiac tissue of LPS-injected mice compared to controls. Additionally, peritoneal macrophages were isolated from control and LPS-injected mice, stained with Mitosox Red and anti-caspase 3/7, and were imaged using fluorescence microscopy, revealing increased production of mitochondrial reactive oxygen species (mitoROS) and elevated cell death in LPS-treated mice. For in vitro studies, human Ac16 ventricular cardiomyocytes and mouse neonatal cardiomyocytes or HL-1 cells were treated with LPS (1µg/ml) for either 24 or 72 hours for further analysis. Immunofluorescence analysis at 24 hours showed increased mitoROS production and cell death in LPS-treated cells compared to the untreated cells. In addition, qPCR analysis revealed increased mtDNA damage and inflammation in the LPS-treated cells. Interestingly, after 72 hours of LPS stimulation, we observed downregulation of NRF2, Cox5b, TFAM, MFN2, and DRP mRNA expression, along with an upregulation of MnSOD2. Furthermore, exogenous delivery of healthy mitochondria delivered to LPS-treated and control Ac16 cells increased MnSOD2 levels and reduced the expression of pro-inflammatory cytokines.
Conclusion: LPS-induced endotoxemia may enhance ROS production, leading to mtDNA damage, inflammation, and cardiomyocyte death. Introducing healthy mitochondria into LPS-stressed cells indicates a potential therapeutic approach. Further investigations are warranted to understand the role of underlying mitochondrial mechanisms and identify novel therapeutic targets in sepsis-induced cardiovascular complications.