Interference with Histone Deacetylase 4 Regulates c-Jun N-terminal Kinase/Activating Protein-1 Signaling to Ameliorate Sepsis-induced Alveolar Epithelial Cell Injury.

Sepsis is a syndrome of systemic inflammatory response resulting from infection, which can lead to severe lung injury. Histone deacetylase 4 (HDAC4) is a key protein known to regulate a wide range of cellular processes. This study was designed to investigate the role of HDAC4 in lipopolysaccharide (LPS)-induced alveolar epithelial cell injury as well as to disclose its potential molecular mechanisms. The alveolar epithelial cell injury model was established by inducing A549 cells with LPS. A549 cell viability was detected by cell counting kit-8 assay and the transfection efficiency of small interfering RNA targeting HDAC4 was appraised utilizing Western blot. The levels of inflammatory cytokines and oxidative stress markers were detected using corresponding assay kits. Dichloro-dihydro-fluorescein diacetate assay was used for the measurement of reactive oxygen species (ROS) content. Flow cytometry, 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethyl-benzimidazolyl-carbocyanine iodide-1 staining, adenosine triphosphate (ATP) assay kits, and MitoSOX Red assay kits were employed to estimate cell apoptosis, mitochondrial membrane potential, ATP level, and mitochondrial ROS level, respectively. The oxygen consumption rate of A549 cells was evaluated with XF96 extracellular flux analyzer. Western blot was applied for the evaluation of HDAC4, apoptosis- and c-Jun N-terminal kinase (JNK)/activating protein-1 (AP-1) signaling pathway-related proteins. HDAC4 expression was found to be increased in LPS-induced A549 cells and HDAC4 silence inhibited inflammatory damage, repressed oxidative stress, alleviated cell apoptosis, improved mitochondrial function, and blocked JNK/AP-1 signaling in A549 cells stimulated by LPS, which were all reversed by JNK activator anisomycin. Collectively, the interference with HDAC4 could ameliorate LPS-induced alveolar epithelial cell injury, and such protective effect may be potentially mediated through the JNK/AP-1 signaling pathway.