Silencing fatty acid-binding protein 4 improved sepsis-induced myocardial dysfunction through anti-apoptotic and antioxidant effects by mammalian target of rapamycin signaling pathway.

Objective: One of the main complications of sepsis that is linked to poor clinical outcomes and high mortality is sepsis-induced myocardial dysfunction (SIMD). Fatty acid-binding protein 4 (FABP4) is a protein that is expressed in macrophages and adipose tissue and is involved in inflammation and apoptosis in various pathological processes. The purpose of this study was to investigate the role of FABP4 in SIMD.

Material and methods: The H9c2 cell model of myocardial dysfunction induced by septicemia was established by lipopolysaccharide (LPS). Measurements of cell viability, apoptosis, reactive oxygen species levels, mitochondrial activity, and proinflammatory factor expression were used to assess FABP4's involvement in SIMD. In addition, the expression level of key proteins in the mammalian target of rapamycin (mTOR) signaling pathway was analyzed using Western blot. Finally, the combination of AZD-8055 further demonstrated the possibility of mTOR as a therapeutic target for SIMD.

Results: Silencing FABP4 expression drastically increased H9c2 cell viability and mitochondrial function. In addition, by upregulating B-cell lymphoma-2 (Bcl-2) and downregulating Bcl-2 associated X protein, FABP4 silencing improved LPS-induced anti-apoptosis of H9c2 cells. Finally, silencing FABP4 alleviated SIMD through the mTOR signaling pathway. However, the therapeutic effect was inhibited when FABP4 silencing was combined with the mTOR inhibitor AZD-8055.

Conclusion: Silencing FABP4 alleviates LPS-induced inflammatory response and apoptosis in H9c2 cells and enhances mitochondrial function through the mTOR signaling pathway.