Mammalian STE20-Like Kinase 2 Promotes Lipopolysaccharides-Mediated Cardiomyocyte Inflammation and Apoptosis by Enhancing Mitochondrial Fission.

Weichao Shan,Wei Qin,Zhenjiang Ding,Haijiu Song,Yanan Tian,Dapeng Jin,Ying Zhang

doi:10.3389/fphys.2020.00897

Weichao Shan, Wei Qin

Open Access

https://doi.org/10.3389/fphys.2020.00897

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Abstract

In this study, we analyzed the role of mammalian STE20-like protein kinase 2 (Mst2), a serine-threonine protein kinase, in Lipopolysaccharides (LPS)-mediated inflammation and apoptosis in the H9C2 cardiomyocytes. Mst2 mRNA and protein levels were significantly upregulated in the LPS-treated H9C2 cardiomyocytes. LPS treatment induced expression of IL-2, IL-8, and MMP9 mRNA and proteins in the H9C2 cardiomyocytes, and this was accompanied by increased caspase-3/9 mediating H9C2 cardiomyocyte apoptosis. LPS treatment also increased mitochondrial reactive oxygen species (ROS) and the levels of antioxidant enzymes, such as GSH, SOD, and GPX, in the H9C2 cardiomyocytes. The LPS-treated H9C2 cardiomyocytes showed lower cellular ATP levels and mitochondrial state-3/4 respiration but increased mitochondrial fragmentation, including upregulation of the mitochondrial fission genes Drp1, Mff, and Fis1. LPS-induced inflammation, mitochondrial ROS, mitochondrial fission, and apoptosis were all significantly suppressed by pre-treating the H9C2 cardiomyocytes with the Mst2 inhibitor, XMU-MP1. However, the beneficial effects of Mst2 inhibition by XMU-MP1 were abolished by carbonyl cyanide-4-(trifluoromethoxy) phenylhydrazone (FCCP), a potent activator of mitochondrial fission. These findings demonstrate that Mst2 mediates LPS-induced cardiomyocyte inflammation and apoptosis by increasing mitochondrial fission.

Highlights

Myocardial inflammation is the hallmark of several cardiovascular disorders, such as myocardial infarction, myocardial ischemia-reperfusion injury, diabetic cardiomyopathy, and sepsis-related myocardial damage (Gebhard et al, 2018; Zhong et al, 2019)
Immunofluorescence assays confirmed that mammalian STE20-like protein kinase 2 (Mst2) protein expression was significantly higher in the LPS-treated H9C2 cells compared to the controls (Figures 1B,C). These results demonstrate that LPS-mediated inflammation induces Mst2 mRNA and protein expression in H9C2 cardiomyocytes
Quantitative Real Time PCR (QRT-PCR) analysis showed that LPS-induced upregulation of IL-2, IL-8, and MMP9 mRNA levels in the H9C2 cardiomyocytes was blocked by pre-treatment with XMU-MP1 (Figures 1D–F)

Summary

Introduction

Myocardial inflammation is the hallmark of several cardiovascular disorders, such as myocardial infarction, myocardial ischemia-reperfusion injury, diabetic cardiomyopathy, and sepsis-related myocardial damage (Gebhard et al, 2018; Zhong et al, 2019). Mitochondria play a central role in the regulation of cardiomyocyte viability and function (Wider et al, 2018). They are the main source of ATP production in the cardiomyocytes through oxidative phosphorylation and are essential for regulating cardiomyocyte contractility (Santin et al, 2019). Inflammation-related metabolic changes in the mitochondria have been reported. SIRT3 overexpression promotes mitochondrial function and attenuates vascular inflammation, endothelial dysfunction, vascular hypertrophy, and angiosteosis. Inflammation-related spinal cord injury (SCI) is caused by excessive production of mitochondrial reactive oxygen species (ROS). The relationship between mitochondrial dysfunction and inflammation-related cardiomyocyte damage has not been explored so far

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