Leukotriene B4 (LTB4) Aggravates Myocardial Ischemia-Reperfusion Injury through BLT2/JAK1/STAT1 Pathway

Abstract

Background: Myocardial ischemia-reperfusion (I/R) injury (MIRI) often occurs as a complication following myocardial infarction, resulting in inflammation and apoptosis of myocardial cells, thereby worsening cardiac dysfunction. Leukotriene B4 (LTB4) serves as an inflammatory mediator known for its regulation of various cellular functions through its receptor, leukotriene B4 receptor 2 (BLT2). This study delved into the precise role of LTB4 in MIRI and the underlying mechanisms. Methods: This study utilized LTB4-deficient mouse models and an in vitro model of cardiomyocytes overexpressing LTB4 subjected to H/R (hypoxia/reoxygenation). LTB4 expression levels were analyzed using enzyme linked immunosorbent assay (ELISA), while activation of the BLT2/janus kinase 1 (JAK1)/signal transducer and activator of transcription 1 (STAT1) pathway was assessed via western blotting. Cardiac function in mice was evaluated through echocardiographic and hemodynamic assessments. Myocardial injury was determined by hematoxylin-eosin (H&E) staining, as well as measurement of lactate dehydrogenase (LDH), creatine phosphokinase (CPK), cardiac troponin-I (CTNI), cardiac troponin-T (CTNT), and creatine kinase MB (CK-MB) levels. Inflammation was assessed by real-time reverse transcriptase-polymerase chain reaction (RT-qPCR) to determine the expression of inflammation-related genes. Terminal deoxynucleotidyl transferase (TDT) dUTP Nick-End Labeling (TUNEL) staining and analysis of apoptosis-related protein levels were employed to assess apoptosis. Additionally, selective BLT2 agonists and antagonists were utilized in targeting experiments to demonstrate that BLT2 acts upstream of JAK1/STAT1. Results: Our findings revealed a significant elevation in LTB4 expression during MIRI (p < 0.01). LTB4-deficient mice demonstrated enhanced cardiac function and markedly reduced activation of the BLT2/JAK1/STAT1 pathway, myocardial injury, inflammation, and cell apoptosis following I/R injury compared to wild-type mice (p < 0.05). Moreover, in vitro experiments indicated that LTB4 overexpression heightened activation of the BLT2/JAK1/STAT1 pathway, exacerbating inflammation and apoptosis in H/R-stimulated cardiomyocytes by activating the BLT2/JAK1/STAT1 pathway (p < 0.05). Conclusion: This study reaffirms the crucial involvement of LTB4 through the BLT2/JAK1/STAT1 signaling pathway in MIRI, potentially by promoting inflammation and apoptosis of myocardial cells. These results offer valuable insights for the exploration of novel therapeutic approaches. Future research should explore interventions aimed at modulating the LTB4/BLT2/JAK1/STAT1 signaling pathway to mitigate MIRI and enhance cardiac function.