The Inhibition of MyD88 and TRIF Signaling Serve Equivalent Roles in Attenuating Myocardial Deterioration Due to Acute Severe Inflammation

Myeloid differentiation factor 88 (MyD88) and Toll or interleukin-1 receptor-domain-containing adaptor-inducing interferon-β (IFN-β) (TRIF) are two pivotal downstream adaptors of Toll-like receptors. Activation of MyD88 or TRIF signaling in cardiac immune pathology of severe inflammation negatively influences heart function. In the present study, severe septic cardiac injury was induced in C57BL/6 mice by cecum ligation and puncture (CLP). A total of 64 mice were divided randomly into the following four groups (n=16/group; 8 for observation of survival rate, 8 for heart sample analysis): Sham, CLP, anti-MyD88-CLP and anti-TRIF-CLP. Anti-MyD88 and anti-TRIF antibodies were administered to the respective mice through the tail veins 2 h before CLP. Measurements of cardiac function, including M-modes, velocity vector imaging and cardiac troponin I, were performed. Myocardial inflammatory cytokines were examined by reverse transcription-polymerase chain reaction (RT-PCR), myocardial neutrophil infiltration was measured by a myeloperoxidase activity assay, intracellular adhesion molecule and vascular cell adhesion molecule mRNA expression levels were investigated, and histopathological characteristics were evaluated. Levels of mRNA transcripts encoding genes for apoptosis production and MyD88, TRIF, nuclear factor-κB and IFN regulatory factor 3 were investigated by RT-PCR. Mice challenged with CLP demonstrated deleterious cardiac function, increased levels of interleukin-1β (IL-1β), IL-6β, and tumor necrosis factor-α mRNA, increased neutrophil infiltration, and increased apoptosis. In contrast, mice in the anti-MyD88 CLP and anti-TRIF CLP groups retained cardiac function with reduced cytokine release, decreased neutrophil infiltration, and reduced apoptosis. In addition, there was no significant difference between the anti-MyD88 CLP and anti-TRIF CLP groups. Thus, the present study indicated that MyD88 and TRIF blockades serve notable and equivalent roles in protecting cardiac deterioration from severe sepsis by attenuating cytokine release, reducing neutrophil infiltration and alleviating apoptosis.