EIPA mg The receptor binding assay used in

The receptor binding assay used in our previous study demonstrated that propofol competitively binds to FPR1, thus blocking the downstream signal transduction of FPR1 and inhibiting neutrophil immune activities [8]. In this study, we assessed the pharmacological action of fMMYALF in the presence of propofol. Cellular inflammatory responses, including ROS generation, elastase release, and cell EIPA mg were assessed at different concentrations of the stimulant (fMMYALF) and constant concentration of the inhibitor (propofol). The addition of propofol (50 μM) causes a parallel rightward shift of the fMMYALF response curve, which represents an increase in the EC50 of the agonist (fMMYALF). In other words, propofol reduces the potency but not the maximal response of fMMYALF. In clinical condition, the plasma concentration of propofol is kept between 1 μg/mL to 30 μg/mL [42]. the dosage of propofol used in our in vitro studies ranges from are 5 μM (about 0.891 μg/mL) to 100 μM (about 17.83 μg/mL). Therefore, the propofol dosage used in our in vitro studies are corresponding to clinical practice. FPRs is a member of Gi/o protein-coupled receptor. Ligand interaction with FPRs initiates the dissociation of the Gα subunit from the Gβγ subunit. Intracellular Ca2+ mobilization occurs downstream of G-protein activation and is crucial to respiratory burst in human neutrophils [43], [44]. Our data demonstrated that propofol reduced the fMMYALF-induced mobilization of intracellular Ca2+. The activation of PI3K and the subsequent production of phosphatidylinositol (3,4,5) P3 (PIP3) and AKT are other major signal transduction event associated with FPRs and mediated by Gβγ dimers [45]. Furthermore, the p38 and ERK MAPKs are downstream mediators of the FPR signaling pathway [46], [47]. They are strongly activated on neutrophil stimulation with FPR1 agonists. The p38 promotes the chemotactic migration of neutrophils [48]. Western blot analysis in our experiments revealed that propofol reduced fMMYALF-induced phosphorylation of ERK, p38, JNK, and AKT. Taken together, the preceding evidence demonstrates that propofol can effectively reduce fMMYALF-induced human neutrophil inflammatory responses by directly interfering with the binding of fMMYALF to FPR1, thereby blocking the subsequent signal transduction. Despite considerable progress in elucidating the mechanisms of sepsis and sepsis-associated ALI as well as the development of novel intervention therapies in ICUs, sepsis and sepsis-induced ALI remain leading causes of mortality in critically ill patients [49]. Oxidative stress is a dangerous pathogenic factor in sepsis and sepsis-associated ALI [50]. Oxidative burst by neutrophil NADPH oxidase can produce huge amounts of superoxide and associated ROS at the site of inflammation. Prolonged and uncontrolled oxidative stress by activated neutrophils impairs surrounding cells and results in inflammatory disorders [51]. Recruitment and infiltration of neutrophils is considered as a critical process in ALI [52], [53]. Because FPR1 plays a vital role in the process of neutrophil migration during acute and chronic inflammation [54], researchers have carefully investigated the importance of FPR1 in neutrophil recruitment during the development of LPS-induced ALI [55]. Specifically, a prior study demonstrated that the lung infiltration of neutrophils was markedly reduced in the FPR1−/− mice [56]. Moreover, we and other researchers have shown that cyclosporine H, an FPR1 antagonist, can pharmacologically reduce the neutrophils recruitment, thus affording protection effect against LPS-induced ALI [56], [57]. In the present study, propofol was shown to reduce pulmonary edema, neutrophil infiltration, and MPO activity in our experimental murine model of LPS-induced ALI. Additionally, propofol reduces the mortality rate of mice with endotoxemic ALI. Taken together, this evidence shows that FPR1 is an important target of anti-inflammatory strategies and provides protection against LPS-induced ALI. We suggest that the mechanism of action of propofol in animal model is mediated through blocking the interaction of mitochondria formylated peptide and FPR.