Effect of mitochondrial translocator protein TSPO on LPS-induced cardiac dysfunction

Abstract

Introduction: Sepsis-induced cardiac dysfunction is one of the most serious complications of sepsis. The mitochondrial translocator protein (TSPO), a mitochondrial outer membrane protein, is widely used as a diagnostic marker of inflammation-related diseases and can also lead to the release of inflammatory components. However, whether TSPO has a therapeutic effect on sepsis-induced cardiac dysfunction is unclear.

Objectives: The aim of this study is to investigate the involvement of TSPO in the pathogenesis of sepsis-induced cardiac dysfunction and elucidate its underlying mechanism, as well as develop therapeutic strategies targeting TSPO for the prevention and treatment of sepsis-induced cardiac dysfunction.

Methods: The sepsis-induced cardiac dysfunction model was established by intraperitoneal injection of lipopolysaccharide (LPS)in C57BL/6 mice (LPS-induced cardiac dysfunction, LICD). TSPO knockout mice were constructed,and the effects of TSPO was detected by survival rate, echocardiography, HE staining, mitochondrial electron microscopy, TUNEL staining. TSPO-binding proteins were identified by co-immunoprecipitation and mass spectrometry. The mechanisms underlying between TSPO and voltage-dependent anion channel (VDAC) was studied through western blot and immunofluorescence. Proteolysis-Targeting Chimeras (PROTAC) technology was used to construct TSPO-PROTAC molecules that can degrade TSPO.

Results: Our present study found that LPS increased cardiac TSPO expression. Knockout of TSPO in C57BL/6 mice with LICD attenuated the cardiac pathology, mitochondrial dysfunction, and apoptosis of cardiomyocytes and significantly improved cardiac function and survival rate. Co-immunoprecipitation and mass spectrometry identified VDAC as a TSPO binding protein.Down-regulation of TSPO reduced PKA-mediated VDAC phosphorylation and VDAC oligomerization, ameliorated mitochondrial function, and reduced cardiomyocyte apoptosis. The study has clinical translational potential, because administration of TSPO-PROTAC to degrade TSPO improved cardiac function in mice with LICD.

Conclusion: This study elucidated the effect of TSPO in LICD, providing a new therapeutic strategy to down-regulate TSPO by administration of TSPO-PROTAC for the prevention and treatment of LICD.

Keywords: Mitochondrial function; PROTAC; Sepsis-induced cardiac dysfunction; TSPO; VDAC oligomerization.