Abstract
BackgroundBenzodiazepines are widely used for anesthesia and sedation and have immunomodulatory properties that may negatively influence clinical outcomes; however, the cellular targets and intermediary signaling pathways involved are unclear. We examined the immunomodulatory effects of the benzodiazepine midazolam on human macrophages and associated molecular mechanisms. MethodsWe analyzed effects of midazolam pretreatment on lipopolysaccharide (LPS)-induced upregulation of the costimulatory molecule CD80 and secretion of the pro-inflammatory factors interleukin-6 (IL-6), tumor necrosis factor-α, interleukin-10, and nitric oxide (NO) in the human monocyte–macrophage cell line THP-1 and in peripheral monocyte-derived macrophages (PMDMs). The effects of midazolam on NF-κB, IκBα protein, and mitogen-activated protein kinase (MAPK) activation were analyzed in THP-1 cells. We analyzed the involvement of translocator protein (TSPO) in the immunomodulatory effects of midazolam using TSPO ligands. The role of TSPO was investigated using THP-1 cells overexpressing TSPO and THP-1 cells with TSPO knockdown through transfection with small interfering RNA for TSPO. ResultsMidazolam suppressed LPS-induced upregulation of CD80 and release of IL-6 and NO in THP-1 cells and PMDMs. Additionally, midazolam suppressed the activation of NF-κB/AP-1 and MAPKs in human THP-1 cells. The assessed synthetic TSPO ligands showed the same inhibitory effects on macrophage activation as midazolam. Macrophages overexpressing TSPO exhibited enhanced susceptibility to immunosuppression by midazolam, and macrophages lacking TSPO expression exhibited reduced effects of midazolam. ConclusionMidazolam inhibits LPS-stimulated immune responses in human macrophages by activating TSPO signaling. Suppression of macrophage activity may contribute to deleterious side effects of benzodiazepines reported in critically ill patients.
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