Importance of toll-like receptor 2 in mitochondrial dysfunction during polymicrobial sepsis

摘要

Background: Toll-like receptor 2 (TLR2) contributes to sepsis pathogenesis such as deleterious systemic inflammation, cardiac dysfunction, and high mortality in animal studies. Mitochondrial dysfunction is a key molecular event that is associated with organ injury in sepsis. The role of TLR2 in sepsis-induced mitochondrial dysfunction remains unclear.Methods: Intracellular hydrogen peroxide (H2O2), mitochondrial superoxide (O2 -), mitochondrial membrane potential (ΔΨμm), and intracellular adenosine triphosphate (ATP) were measured in peritoneal leukocytes. A mouse model of polymicrobial sepsis was generated by cecum ligation and puncture (CLP). Wild-type and TLR2-deficient (TLR2-/-) mice were subjected to sham or CLP. Mitochondrial functions including reactive oxygen species (ROS), ΔΨμm, intracellular ATP, and complex III activity were measured.Results: TLR2/1 activation by Pam3Cys enhanced intracellular H2O2 and mitochondrial O2 - production in leukocytes, but had no effect on mitochondrial ΔΨm and ATP production. The effect was specific for TLR2/1 as TLR3 or TLR9 ligands did not induce ROS production. Polymicrobial sepsis induced mitochondrial dysfunction in leukocytes, as demonstrated by increased H2O2 and mitochondrial O2 - production (CLP vs. sham; H2O2: 3,173 ± 498, n = 5 vs. 557 ± 38, n = 4; O2 -: 707 ± 66, n = 35 vs. 485 ± 35, n = 17, mean fluorescence intensity, mean ± SEM), attenuated complex III activity (13 ± 2, n = 16 vs. 30 ± 3, n = 7, millioptical densities/min), loss of mitochondrial ΔΨm, and depletion of intracellular ATP (33 ± 6, n = 11 vs. 296 ± 29, n = 4, nmol/mg protein). In comparison, there was significant improvement in mitochondrial function in septic TLR2-/- mice as evidenced by attenuated mitochondrial ROS production, better-maintained mitochondrial ΔΨm, and higher cellular ATP production.Conclusions: TLR2 signaling plays a critical role in mediating mitochondrial dysfunction in peritoneal leukocytes during polymicrobial sepsis.