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Thrombomodulin (TM) is expressed on the surface of monocytes and is a key regulator of actual immune capacity. Propofol is an anesthetic agent that exerts anti-inflammatory effects. The objective of this study was to determine whether propofol could modulate TM in TNF--stimulated monocytes. THP-1 cells and male New Zealand rabbits were used in this study. The results showed that TNF- decreases the TM expression by mediating posttranscriptional modification, and this inhibition may be repressed by treatment with propofol. Immunofluorescence, immunoprecipitation, and pull-down assays were used to demonstrate that Rac1-dependent nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, Cdc42, and p38 mitogen-activated protein kinase activation, as well as tristetraprolin (TTP) expression, all contributed to the downregulation of TM in TNF--treated cells. Propofol reversed the effects of TNF- on TM downregulation. Propofol mediated the expression of intracellular TTP and the distribution of cytosolic human antigen R (HuR) and changed their interactions with the 3-untranslated region of TM mRNA regulating by Cdc42 and Rac1. In addition, the animal study showed that propofol regulates TM, TTP, and HuR expression on monocytes in TNF--treated rabbits. In conclusion, the inhibition of TM expression in TNF--treated monocytes was mediated by the activation of NADPH oxidase and the expression of TTP. Propofol may inhibit the downregulation of TM by mediating NADPH oxidase and TTP inactivation and through the activation of HuR in vitroand in vivo. Utilizing TTP and HuR to control TM expression may be a promising approach for controlling systemic inflammation, and propofol may possess potential implications for the clinical immunity of monocytes after anesthesia or surgery.

Toll-like receptor 4 (TLR4) plays a major role in regulating the innate immune response, which is related to postoperative complications. Although inflammatory capacity and TNF- synthesis were altered on monocytes after cardiopulmonary bypass (CPB), whether the CPB and the CPB-induced TNF- affect TLR4 expression on monocytes have not yet clarified. We speculate that the changing of TNF- level during CPB may be involved in monocytic TLR4 expression. As previous report, our enzyme-linked immunosorbent assay showed that CPB elevated the plasma level of TNF-, whereas off-pump cardiac surgery does not. Flow cytometry reported decreased levels of monocytic TLR4 in patients undergoing CPB but not undergoing off-pump cardiac surgery. To elucidate whether the CPB-induced TNF- is related to TLR4 down-regulation, we used human monocytic THP-1 cells. Actinomycin D chase experiments demonstrated that TNF- decreased TLR4 expression and TLR4 mRNA stability on THP-1. Confocal microscopy and real-time polymerase chain reaction showed that TNF- induced intracellular tristetraprolin (TTP) expression. Transfection with TTP siRNA reversed the down-regulation of TLR4 in TNF--stimulated THP-1. Treatment with ERK1/2 inhibitor and SAPK/JNK inhibitor decreased TNF--induced TTP expression. Immunoprecipitation and Western blot analysis showed that the TNF--mediated activation of TTP might be inhibited by p38 mitogen-activated protein kinase inhibitor and by PD98059. We also demonstrated in clinical samples with confocal microscopy and flow cytometry that CPB led to an elevation of TTP in monocytes. In conclusion, CPB and TNF- decrease TLR4 expression on monocytes; TTP expression and mitogen-activated protein kinase-signaling pathways play critical roles in CPB- and TNF--mediated decreases of TLR4 on monocytes. Our results suggest that using TTP to control cytokine message decay rate may be a promising approach for controlling system inflammation and preventing post-CPB complications.