Propofol inhibits FMLP-stimulated phosphorylation of p42 mitogen-activated protein kinase and chemotaxis in human neutrophils

Propofol Ameliorates Exaggerated Human Neutrophil Activation in a LPS Sepsis Model

Background

Sepsis is a leading cause of morbidity and mortality worldwide. Many patients suffering from sepsis are treated on intensive care units and many of them require mechanical ventilation under sedation or general anesthesia. Propofol, a drug used for these purposes, is known to interact with polymorphonuclear granulocytes (PMNs). Therefore, the aim of this study was to investigate the influence of propofol on PMN functions after experimental Gram-negative induced sepsis using lipopolysaccharide (LPS) stimulation.

Methods

A total of 34 granulocyte-enriched samples were collected from healthy subjects. PMNs were isolated by density gradient centrifugation and incubated simultaneously with either 6 µg/mL or 60 µg/mL propofol, or none (control). Additionally, the experimental sepsis samples were incubated with either 40 pg/mL or 400 pg/mL LPS. Live cell imaging was conducted in order to observe granulocyte chemotactic migration, ROS production, and NETosis. Flow cytometry was used to analyze viability and antigen expression.

Results

Propofol led to significantly reduced PMN track length (p < 0.001) and track speed (p < 0.014) after LPS-induced sepsis in a dose-dependent manner. NETosis (p = 0.018) and ROS production (p = 0.039) were accelerated by propofol without LPS incubation, indicating improved immune function. Propofol also ameliorated LPS-induced increased NETosis and ROS-production. Antigen expression for CD11b, CD62l and CD66b was unaffected by propofol.

Conclusion

Propofol improves LPS-induced exaggerated PMN activation in an ex vivo model. Beneficial effects due to restored immune function in septic patients might be possible, but needs further investigation.

Immune Function following Major Spinal Surgery and General Anesthesia

There are reported differences in the effects that general anesthetics may have on immune function after minor surgery. To date, there are no prospective trials comparing total intravenous anesthesia (TIVA) with a volatile agent-based technique and its effects on immune function after major spinal surgery in adolescents. Twenty-six adolescents undergoing spinal fusion were randomized to receive TIVA with propofol-remifentanil or a volatile agent-based technique with desflurane-remifentanil. Immune function measures were based on the antigen-presenting and cytokine production capacity, and relative proportions of cell populations. Overall characteristics of the two groups did not differ in terms of perioperative times, hemodynamics, or fluid shifts, but those treated with propofol had lower bispectral index values. Experimental groups had relatively high baseline interleukin-10 values, but both showed a significant inflammatory response with similar changes in their respective immune functions. This included a shift toward a granulocytic predominance; a transient reduction in monocyte markers with significant decrease in antigen-presenting capacity and cytokine production capacity. Anesthetic choice does not appear to differentially impact immune function, but exposure to anesthetics and surgical trauma results in reproducibly measurable suppression of both innate and adaptive immunity in adolescents undergoing posterior spinal fusion. The magnitude of this suppression was modest when compared with pediatric and adult patients with critical illnesses. This study highlighted the need to evaluate immune function in a broader population of surgical patients with higher severity of illness.

Anesthetic Strategies in Oncological Surgery: Not Only a Simple Sleep, but Also Impact on Immunosuppression and Cancer Recurrence

Tumor recurrences or metastases remain a major hurdle in improving overall cancer survival. In the perioperative period, the balance between the ability of the cancer to seed and grow at the metastatic site and the ability of the patient to fight against the tumor (i.e. the host antitumor immunity) may determine the development of clinically evident metastases and influence the patient outcome. Up to 80% of oncological patients receive anesthesia and/or analgesia for diagnostic, therapeutic or palliative interventions. Therefore, anesthesiologists are asked to administer drugs such as opiates and volatile or intravenous anesthetics, which may determine different effects on immunomodulation and cancer recurrence. For instance, some studies suggest that intravenous drugs, such as propofol, may inhibit the host immunity to a lower extent as compared to volatile anesthetics. Similarly, some studies suggest that analgesia assured by local anesthetics may provide a reduction of cancer recurrence rate; whilst on the opposite side, opioids may exert negative consequences in patients undergoing cancer surgery, by interacting with the immune system response via the modulation of the hypothalamic-pituitary-adrenal axis and autonomic nervous system, or directly through the opioid receptors on the surface of immune cells. In this review, we summarize the main findings on the effects induced by different drugs on immunomodulation and cancer recurrence.

Impact of Anesthetics on Human Neutrophil Function

Anesthetics are widely used drugs administered in a multitude of clinical settings. Their impacts on various functions of the immune system have been studied but are still not fully understood. Neutrophil granulocytes are a critical first-line host defense mechanism against infections and contribute to the inflammatory phase of wound healing, but dysregulated neutrophil activation can also precipitate perioperative organ injury. A better understanding of the interactions between common anesthetics and neutrophils may reveal considerations toward optimizing treatment of our most vulnerable patients in the intensive care unit and in the perioperative setting.

Estradiol inhibits fMLP-induced neutrophil migration and superoxide production by upregulating MKP-2 and dephosphorylating ERK

Estrogen has been reported to inhibit neutrophil infiltration related inflammation and suppress neutrophils migration in vitro, but the underlying mechanism is not fully understood. By using HL-60 differentiated neutrophil-like cells (dHL-60) and human neutrophils, we examined the effect of 17-β estradiol (E₂) on cell migration and superoxide production in response to chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (fMLP) and explored the mechanisms involved. We found that fMLP significantly induced dHL-60 cell and neutrophil migration and superoxide production, which was inhibited by ERK inhibitor PD98059. E₂ significantly inhibited fMLP-induced dHL-60 cell and neutrophil migration and superoxide production at both physiological and pharmacological concentrations. Mechanistic studies showed that pretreatment of these cells with E₂ rapidly elevated the protein level of mitogen-activated protein kinase phosphatase 2 (MKP-2) and inhibited fMLP-induced ERK phosphorylation. Pretreatment of these cells with estrogen receptor (ER) antagonist ICI 182780 reversed the inhibition of fMP-induced cell migration and superoxide production, and the induction of MKP-2 expression and the suppression of fMP-induced ERK phosphorylation by E₂. However, pretreatment of cells with G-protein coupled ER antagonist G15 had no such effect. Collectively, these results demonstrate that fMLP stimulates neutrophil chemotaxis and superoxide production through activating ERK, and indicate that ER-mediated upregulation of MKP-2 may dephosphorylate ERK and contribute to the inhibitory effect of E₂ on neutrophil activation by fMLP. Our study reveals new mechanisms involved in the anti-inflammatory activity of estrogen.

Propofol specifically suppresses IL-1β secretion but increases bacterial survival in Staphylococcus aureus-infected RAW264.7 cells

Anesthetics have immunomodulatory effects, but the use of different assay systems has contributed to inconsistent results in the literature. IL-1β and reactive oxygen species (ROS) secreted by phagocytes are important factors that protect against Staphylococcus aureus infection. In this study, the effects of four intravenous anesthetics (propofol, thiamylal sodium, midazolam, and ketamine) on IL-1β secretion, ROS, and bacterial survival in S. aureus-infected RAW264.7 cells were evaluated. S. aureus-infected RAW264.7 cells with or without intravenous anesthetic treatment were established as the experimental model. Cell supernatants were subjected to ELISAs to measure secreted IL-1β. Cell pellets were subjected to qPCR and western blot analyses to analyze IL-1β mRNA and protein levels. Luminol chemiluminescence assays were used to detect ROS, and bacterial survival was determined by counting the colony forming units at the beginning and end of the infection. Compared with the levels after treatment with the other intravenous anesthetics, secreted IL-1β levels were lowest in the supernatant of S. aureus-infected RAW264.7 cell cultures after propofol treatment, but propofol did not decrease IL-1β mRNA or protein expression. However, thiamylal sodium and midazolam decreased IL-1β mRNA and protein expression in a dose-dependent manner. Additionally, propofol substantially decreased S. aureus-stimulated ROS and phagocytosis. Bacterial survival was strongly increased by propofol treatment. Of the four intravenous anesthetics, propofol was the most potent inhibitor of IL-1β secretion and ROS level in S. aureus-infected RAW264.7 cells; moreover, propofol resulted in an increase in bacterial survival by inhibiting ROS and phagocytosis.

Immunomodulatory effects of anesthetics in obese patients

Anesthesia and surgery have an impact on inflammatory responses, which influences perioperative homeostasis. Inhalational and intravenous anesthesia can alter immune-system homeostasis through multiple processes that include activation of immune cells (such as monocytes, neutrophils, and specific tissue macrophages) with release of pro- or anti-inflammatory interleukins, upregulation of cell adhesion molecules, and overproduction of oxidative radicals. The response depends on the timing of anesthesia, anesthetic agents used, and mechanisms involved in the development of inflammation or immunosuppression. Obese patients are at increased risk for chronic diseases and may have the metabolic syndrome, which features insulin resistance and chronic low-grade inflammation. Evidence has shown that obesity has adverse impacts on surgical outcome, and that immune cells play an important role in this process. Understanding the effects of anesthetics on immune-system cells in obese patients is important to support proper selection of anesthetic agents, which may affect postoperative outcomes. This review article aims to integrate current knowledge regarding the effects of commonly used anesthetic agents on the lungs and immune response with the underlying immunology of obesity. Additionally, it identifies knowledge gaps for future research to guide optimal selection of anesthetic agents for obese patients from an immunomodulatory standpoint.

Inhibitory effects of propofol on Th17 cell differentiation

Propofol (2,6-diisopropylphenol) is probably the most widely used intravenous anesthetic agent in daily practice. It has been reported to show immunomodulatory activity. However, the effect of propofol on the differention of T cells remains unclear. In this study, we demonstrated for the first time that propofol inhibited both interleukin (IL)-6 plus transforming growth factor-β (TGF-β)-induced Th17 cell differentiation in vitro and in LPS-challenged mice. Propofol also suppressed the IL-6-induced phosphorylation of Janus kinase-2 (JAK2)/signal transducer and activator of transcription (STAT3) pathway, a cytokine-activated essential transcription factor in Th17 cell development, which occurred concomitantly with the enhancement of suppressor of cytokine signaling-3 (SOCS3) expression involved in the downregulation of STAT3 phosphorylation. These data extend our knowledge of the immunosuppressive effects of propofol and their underlying mechanism.

Propofol Protects against Ischemia/Reperfusion Injury Associated with Reduced Apoptosis in Rat Liver

Propofol is an intravenous anesthetic, reported to have a protective effect against ischemia/reperfusion (I/R) injury in heart and brain, but no definite data are available concerning its effect in hepatic I/R. This work investigated the effect of propofol anesthesia on hepatic I/R injury using in vivo rat model. Four groups of rats were included: sham operated, I/R (30 min ischemia and 2 h reperfusion), I/R treated with propofol (10 mg/kg/h), and I/R treated with propofol (20 mg/kg/h). Liver enzyme leakage, TNF-α and caspase-3 levels, and antiapoptotic Bcl-xL/apoptotic Bax gene expression, together with histopathological changes, were used to evaluate the extent of hepatic I/R injury. Compared with sham-operated group, I/R group showed significant increase in serum levels of liver enzymes (ALT, AST), TNF-α, and caspase-3 and significant decrease in the Bcl-xL/Bax ratio, associated with histopathologic damage in liver. Propofol infusion significantly attenuated these changes with reduced hepatic histopathologic lesions compared with nonpreconditioned I/R group. However, no significant differences were found between two groups treated with different doses of propofol. In conclusion, propofol infusion reduced hepatic I/R injury with decreased markers of cellular apoptosis. Therefore, propofol anesthesia may provide a useful hepatic protection during liver surgery.

Propofol inhibits superoxide production, elastase release, and chemotaxis in formyl peptide-activated human neutrophils by blocking formyl peptide receptor 1

Neutrophils play a critical role in acute and chronic inflammatory processes, including myocardial ischemia/reperfusion injury, sepsis, and adult respiratory distress syndrome. Binding of formyl peptide receptor 1 (FPR1) by N-formyl peptides can activate neutrophils and may represent a new therapeutic target in either sterile or septic inflammation. Propofol, a widely used i.v. anesthetic, has been shown to modulate immunoinflammatory responses. However, the mechanism of propofol remains to be established. In this study, we showed that propofol significantly reduced superoxide generation, elastase release, and chemotaxis in human neutrophils activated by fMLF. Propofol did not alter superoxide generation or elastase release in a cell-free system. Neither inhibitors of γ-aminobutyric acid receptors nor an inhibitor of protein kinase A reversed the inhibitory effects of propofol. In addition, propofol showed less inhibitory effects in non-FPR1-induced cell responses. The signaling pathways downstream from FPR1, involving calcium, AKT, and ERK1/2, were also competitively inhibited by propofol. These results show that propofol selectively and competitively inhibits the FPR1-induced human neutrophil activation. Consistent with the hypothesis, propofol inhibited the binding of N-formyl-Nle-Leu-Phe-Nle-Tyr-Lys-fluorescein, a fluorescent analog of fMLF, to FPR1 in human neutrophils, differentiated THP-1 cells, and FPR1-transfected human embryonic kidney-293 cells. To our knowledge, our results identify, for the first time, a novel anti-inflammatory mechanism of propofol by competitively blocking FPR1 in human neutrophils. Considering the importance of N-formyl peptides in inflammatory processes, our data indicate that propofol may have therapeutic potential to attenuate neutrophil-mediated inflammatory diseases by blocking FPR1.

Sedation & immunomodulation

As the armamentarium for sedation in the critically ill expands, opportunities will develop to modulate the immune responses of patients by way of the direct immune and neural-immune interactions of the sedatives. Control of autonomic activity through the use of appropriate sedation may be critical in this matter. Likewise analgesic-based sedation, with increased opioid dosage, may not prove beneficial in the setting of infection; whether avoidance of morphine in preference for a fentanyl derivative will help is unclear. However, as the immune effects seem dependent on the m receptor, it is improbable that a significant difference would be uncovered. Similarly, the present evidence suggests benzodiazepines are deleterious in infection; further studies are required urgently to evaluate this evidence. As an alternative to benzodiazepine-based sedation, dexmedetomidine has shown a remarkable 70% mortality benefit in a small secondary analysis of septic patients from the MENDS trial. Further powered clinical studies should now be undertaken to investigate the potential benefit of the α2-adrenoceptor agonist in this setting, with comparisons with propofol.

Sedative drug modulates T-cell and lymphocyte function-associated antigen-1 function

BACKGROUND

Sedative drugs modify immune cell functions via several mechanisms. However, the effects of sedatives on immune function have been primarily investigated in neutrophils and macrophages, and to the lesser extent lymphocytes. Lymphocyte function-associated antigen-1 (LFA-1) is an adhesion molecule that has a central role in regulating immune function of lymphocytes including interleukin-2 (IL-2) production and lymphocyte proliferation. Previous clinical studies reported that propofol and isoflurane reduced IL-2 level in patients, but midazolam did not. We previously demonstrated that isoflurane inhibited LFA-1 binding to its counter ligand, intercellular adhesion molecule-1 (ICAM-1), which might contribute to the reduction of IL-2 levels. In the current study, we examined the effect of propofol, midazolam, and dexmedetomidine on LFA-1/ICAM-1 binding, and the subsequent biological effects.

METHODS

The effect of sedative drugs on T-cell proliferation and IL-2 production was measured by calorimetric assays on human peripheral blood mononuclear cells. Because LFA-1/ICAM-1 binding has an important role in T-cell proliferation and IL-2 production, we measured the effect of sedative drugs on ICAM-1 binding to LFA-1 protein (cell-free assay). This analysis was followed by flow cytometric analysis of LFA-1 expressing T-cell binding to ICAM-1 (cell-based assay). To determine whether the drug/LFA-1 interaction is caused by competitive or allosteric inhibition, we analyzed the sedative drug effect on wild-type and high-affinity LFA-1 and a panel of monoclonal antibodies that bind to different regions of LFA-1.

RESULTS

Propofol at 10 to 100 μM inhibited ICAM-1 binding to LFA-1 in cell-free assays and cell-based assays (P < 0.05). However, dexmedetomidine and midazolam did not affect LFA-1/ICAM-1 binding. Propofol directly inhibits LFA-1 binding to ICAM-1 by binding near the ICAM-1 contact area in a competitive manner. At clinically relevant concentrations, propofol, but not dexmedetomidine or midazolam, inhibited IL-2 production (P < 0.05). Additionally, propofol inhibited lymphocyte proliferation (P < 0.05).

CONCLUSIONS

Our study suggests that propofol competitively inhibits LFA-1 binding to ICAM-1 on T-cells and suppresses T-cell proliferation and IL-2 production, whereas dexmedetomidine and midazolam do not significantly influence these immunological assays.

Ketamine reduces inducible superoxide generation in human neutrophils in vitro by modulating the p38 mitogen-activated protein kinase (MAPK)-mediated pathway

Many cellular stresses and inflammatory stimuli can activate p38 mitogen-activated protein kinase (MAPK), a serine/threonine kinase in the MAPK family. The different stimuli act via different receptors or signalling pathways to induce phosphorylation of the cytosolic protein p47(phox), one subunit of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. Formyl-methionyl-leucyl-phenylalanine (fMLP) has been shown to induce the p38 MAPK phosphorylation during the respiratory burst in human neutrophils. Here, we show that treatment with S(+)-ketamine or R(-)-ketamine at different concentrations (50, 100, 200, 400 microM) reduced fMLP-induced superoxide anion generation and p47(phox) phosphorylation in neutrophils in a concentration-dependent manner (y = -0.093x + 93.35 for S(+)-ketamine and y = -0.0982x + 95.603 for R(-)-ketamine, respectively). While treatment with 50 microM ketamine inhibited fMLP-induced superoxide generation by 10%, treatment with 400 microM S(+)-ketamine and R(-)-ketamine reduced fMLP-induced superoxide generation to 60.5 +/- 8.3% and 60.0 +/- 8.5%, respectively, compared with that in neutrophils treated with fMLP alone. Furthermore, treatment with ketamine down-regulated both fMLP-induced p47(phox) and isoproterenol-induced p38 MAPK phosphorylation and superoxide production. Interestingly, treatment with SB203580, the p38 MAPK inhibitor, also mitigated fMLP-induced superoxide anion generation and p38 MAPK and p47(phox) phosphorylation as well as apoptosis in a concentration-dependent fashion in neutrophils. Therefore, ketamine racemes inhibited fMLP-induced superoxide anion generation and p47(phox) phosphorylation by modulating fMLP-mediated p38 MAPK activation in neutrophils.

Immunomodulatory activity of Toxicodendron pubescens in experimental models

BACKGROUND

Toxicodendron pubescens is a botanical name of Rhus toxicodendron (Rhus tox). This plant is widely used in its homeopathically diluted form in the treatment of inflammatory and edematous conditions. In this study, various dilutions of Rhus tox including its crude form have been evaluated for their effects on immune response in the in vivo and in vitro experimental models.

METHODS

Rhus tox in the form of mother tincture, 6cH, 30cH, 200cH and 1000cH dilutions was tested through in vivo models including sheep red blood cells (SRBCs) induced cellular and humoral immune response in C57/BL6 mice. The effects of Rhus tox dilutions were also evaluated in vitro on the functions of human polymorphonuclear (PMN) cells such as phagocytosis and intracellular killing of Candida albicans, chemotaxis, and reduction of nitroblue tetrazolium (NBT) dye.

RESULTS

Rhus tox was found to intensify SRBCs induced antibody titer and delayed type hypersensitivity response in mice. Even higher dilutions such as 200cH and 1000cH were found to affect the immune response; however, the crude form, mother tincture, 6cH and 30cH dilutions revealed more potent effects than the 200cH and 1000cH dilutions. In in vitro assays, all the dilutions exerted stimulation of phagocytosis, candidacidal activity and chemotaxis of human PMN cells. The NBT dye reduction assay revealed that oxidative processes in the PMN cells are accelerated in the presence of Rhus tox. This study shows that Rhus tox possesses immunostimulatory activity in its crude form as well as in homeopathically diluted forms. These effects appeared to be concentration dependent as higher dilutions had less potent effects.

Sedation & immunomodulation

The management of critically ill patients necessitates the use of sedatives and analgesics to provide patient comfort and cooperation. These drugs exert profound effects on all organ systems, not only the central nervous system, and this article describes the immunologic effects of the commonly used critical care sedatives: propofol, the benzodiazepines, opioids, and alpha(2)-adrenoceptor agonists. Benzodiazepines, opioids, and possibly even propofol worsen outcome in animal models of infection, whereas preliminary evidence suggests that the alpha(2)-adrenoceptor agonist, dexmedetomidine, may improve outcomes in the setting of infection. Given the burden of sepsis and secondary infections in critical care, choice of sedation may need to be carefully considered to preserve immune responses in critically ill patients.

Resistin inhibits essential functions of polymorphonuclear leukocytes

The serum levels of resistin, a 12-kDa protein primarily expressed in inflammatory cells in humans, are increased in patients with chronic kidney disease and in those with diabetes mellitus. Both groups of patients have an increased risk of infections mainly as a result of disturbed polymorphonuclear leukocyte (PMNL) functions. Therefore, we investigated the influence of resistin on human PMNLs. Serum resistin concentrations were determined with a sandwich enzyme immunoassay. Using PMNLs from healthy subjects, chemotaxis was tested by the under-agarose method. Flow cytometric assays to measure oxidative burst and phagocytosis were conducted in whole blood. The uptake of deoxyglucose was determined as measure of the PMNL activation state. The activity of intracellular kinases was assessed by Western blotting and by in vitro kinase assays. Resistin inhibited PMNL chemotaxis and decreased the oxidative burst stimulated by Escherichia coli and by PMA, but did not influence PMNL phagocytosis of opsonized E. coli and PMNL glucose uptake. The inhibition of PMNLs by resistin was observed at concentrations found in serum samples of uremic patients, but not in concentrations measured in healthy subjects. Experiments with specific signal transduction inhibitors and measurements of intracellular kinases suggest that PI3K is a major target of resistin. In conclusion, resistin interferes with the chemotactic movement and the stimulation of the oxidative burst of PMNL, and therefore may contribute to the disturbed immune response in patients with increased resistin serum levels such as uremic and diabetic subjects.

Anesthetics, immune cells, and immune responses

General anesthesia accompanied by surgical stress is considered to suppress immunity, presumably by directly affecting the immune system or activating the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system. Along with stress such as surgery, blood transfusion, hypothermia, hyperglycemia, and postoperative pain, anesthetics per se are associated with suppressed immunity during perioperative periods because every anesthetic has direct suppressive effects on cellular and neurohumoral immunity through influencing the functions of immunocompetent cells and inflammatory mediator gene expression and secretion. Particularly in cancer patients, immunosuppression attributable to anesthetics, such as the dysfunction of natural killer cells and lymphocytes, may accelerate the growth and metastases of residual malignant cells, thereby worsening prognoses. Alternatively, the anti-inflammatory effects of anesthetics may be beneficial in distinct situations involving ischemia and reperfusion injury or the systemic inflammatory response syndrome (SIRS). Clinical anesthesiologists should select anesthetics and choose anesthetic methods with careful consideration of the clinical situation and the immune status of critically ill patients, in regard to long-term mortality, morbidity, and the optimal prognosis.

Propofol attenuation of renal ischemia/reperfusion injury involves heme oxygenase-1

AIM

To examine the protective effect of propofol in renal ischemia/reperfusion (I/R) injury and the role of heme oxygenase-1 (HO-1) in this process.

METHODS

Sprague-Dawley rats were randomly divided into 3 groups: (i) sham-operated group; (ii) I/R group; and (iii) propofol group. Bilateral renal warm ischemia for 45 min was performed. After 2, 6, and 24 h reperfusion, blood samples and kidneys were collected for assessment of renal injury, and HO-1 expressions were analyzed by immunohistochemical analysis, RT-PCR and Western blotting.

RESULTS

Blood urea nitrogen and serum creatinine levels in the propofol group were significantly lower than that in the I/R group at 24 h after reperfusion. The mean histological score by Palleros standard showed that propofol significantly attenuated renal I/R injury after 6 h reperfusion. Propofol increased HO-1 mRNA and protein levels 2 h after reperfusion, whereas HO-1 expressions were present at exceedingly low levels in the I/R group and the sham-operated group at same time point. Propofol also markedly increased HO-1 mRNA and protein levels than I/R at 6 and 24 h after reperfusion.

CONCLUSION

These results suggest that propofol mitigates renal I/R injury in rats. This protection may be partly through the induction of the HO-1 expression.

Propofol attenuates Kupffer cell activation during hypoxia-reoxygenation

PURPOSE

We undertook a study to determine whether propofol may attenuate Kupffer cell (KC) activation, thus protecting the cells against hypoxia-reoxygenation injury through the modulation of intracellular calcium ([Ca2+]i).

METHODS

[Ca2+]i, the expression of tumour necrosis factor (TNF)-alpha mRNA, and KC viability were measured in response to hypoxia-reoxygenation following pretreatment with propofol 0.5 and 5 microg.mL(-1) (Groups P1 and P2, respectively) or without propofol (Group HRC). KCs were isolated and cultured from male Sprague-Dawley rats. KCs were incubated under an atmosphere of hypoxia (95% N2 + 5% CO2) for 60 min with subsequent 120 min reoxygenation (95% air + 5% CO2). [Ca2+]i for the first 12 min after reoxygenation, TNF-alpha mRNA, and KC viability at the end of reoxygenation in groups P1 and P2 were compared with those of HRC.

RESULTS

The increase of [Ca2+]i from the baseline was attenuated in P1 (96.6 +/- 6.9%) and P2 (96.1 +/- 5.4%) compared with HRC (143.8 +/- 11.5%), (P < 0.001), with no difference between P1 and P2. The expression of TNF-alpha mRNA increased only in HRC during hypoxia-reoxygenation. KC viability increased in P1 (97.5 +/- 2.6%) and P2 (94.6 +/- 2.9%), compared with HRC (89.9 +/- 1.4%), (P < 0.005), with no difference between P1 and P2.

CONCLUSION

The results indicate that propofol attenuates KC activation and protects KC from hypoxia-reoxygenation injury at clinically relevant concentrations. This attenuation seems to result from inhibition of [Ca2+]i increase in KC.

Propofol-induced calcium signalling and actin reorganization within breast carcinoma cells

BACKGROUND AND OBJECTIVE

MDA-MB-468 breast carcinoma cells respond to non-volatile anaesthetics such as propofol with an increased migration. Here we investigated the relationship between GABA-A receptor modulators, the mode of calcium oscillation and actin reorganization with regard to breast carcinoma cell migration.

METHODS

Expression of the GABA-A receptor was determined by Western blot analysis. Calcium-imaging experiments of individual MDA-MB-468 cells as well as visualization of the F-actin distribution were performed by confocal laser scanning microscopy. Cell migration was investigated in a three-dimensional collagen matrix by time-lapse video microscopy. The GABA agonist propofol was used in a final concentration of 6 microg mL(-1). GABA-A receptor antagonist bicuculline (50 micromol) and selective L-type calcium channel blocker verapamil (5 micromol) were used to modulate the propofol effects.

RESULTS

A functional GABA-A receptor is expressed by MDA-MB-468 cells. Activation with propofol resulted in sustained increased intracellular calcium concentrations concomitant with actin reorganization and induction of migration in MDA-MB-468 cells. These propofol effects were completely blocked by verapamil. Spontaneous migration of MDA-MB-468 cells (64.4 +/- 7.0%) was significantly increased by propofol to 85.0 +/- 5.0%. MDA-MB-468 cells co-treated with propofol and verapamil showed a migratory activity of 63.0 +/- 2.0% indicating that verapamil blocked the propofol effect. Similar results were achieved with the GABA-A receptor inhibitor bicuculline (control: 56.3 +/- 8.5%; propofol: 80.5 +/- 7.1%; propofol + bicuculline: 52.5 +/- 8.6%).

CONCLUSION

Activation of GABA-A receptor by propofol correlated with an increased migration of MDA-MB-468 breast carcinoma cells, mediated by calcium influx via L-type calcium channels and reorganization of the actin cytoskeleton.

Protein O-GlcNAc modulates motility-associated signaling intermediates in neutrophils

The modification of serine/threonine residues on cytoplasmic and nuclear proteins by N-acetylglucosamine (O-GlcNAc) is suggested to play a role in the regulation of a variety of signal transduction pathways. We have previously shown that glucosamine (GlcNH(2)), a metabolic precursor of O-GlcNAcylation, increases (2)O-GlcNAc and enhances motility in neutrophils. Here, we extend this correlation by showing that a mechanistically distinct means of increasing O-GlcNAc, achieved by inhibition of O-GlcNAc removal with O-(2-acetamido-2-deoxy-d-glucopyranosylidene)amino-N-phenylcarbamate (PUGNAc), increases basal cellular motility and directional migration induced by the chemoattractant formyl-methionine-leucine-phenylalanine (fMLP). Furthermore, we demonstrate that O-GlcNAc modulates the activities of signaling intermediates known to regulate neutrophil movement. GlcNH(2) and PUGNAc increase both the basal and fMLP-induced activity of a central mediator of cellular motility, the small GTPase Rac. Phosphoinositide 3-kinase, an important regulator of Rac activity and neutrophil motility, is shown to regulate the signaling pathway on which GlcNH(2) and PUGNAc act. Rac is an important upstream regulatory element in p38 and p44/42 mitogen-activated protein kinase (MAPK) signaling in neutrophils, and these MAPKs are implicated in chemotactic signal transduction. We show that GlcNH(2) and PUGNAc treatment increases p42/44 and p38 MAPK activities and that these increases are associated with activation of upstream MAPK kinases. These data indicate that O-GlcNAcylation is an important signaling element in neutrophils that modulates the activities of several critical signaling intermediates involved in the regulation of cellular movement.

The intravenous anesthetic propofol inhibits hypoxia-inducible factor 1 activity in an oxygen tension-dependent manner

Hypoxia elicits a wide range of responses that occur at different organizational levels in the body. Hypoxia is not only a signal for energy conservation and metabolic change, but triggers expression of a select set of genes. The transcription factor hypoxia-inducible factor 1 (HIF-1) is now appreciated to be a master factor of the gene induction. Although knowledge on molecular mechanisms of HIF-1 activation in response to hypoxia is accumulating, the molecular mechanism of maintenance of HIF-1 activity under normoxic conditions remains to be elucidated. We demonstrate that the intravenous anesthetic propofol reversibly inhibits HIF-1 activity and the gene expression mediated by HIF-1 by blocking the synthesis of the HIF-1alpha subunit under 20% or 5% O2 conditions, but not under 1% O2 conditions.

Azithromycin Blocks Neutrophil Recruitment inPseudomonasEndobronchial Infection

Macrolides exert their effects on the host by modulation of immune responses. In this study, we assessed the therapeutic efficacy of azithromycin in a murine model of mucoid Pseudomonas aeruginosa endobronchial infection. The clearance of Pseudomonas from the airway of mice treated with the macrolide azithromycin was not different than untreated mice challenged with Pseudomonas beads. However, the azithromycin-treated mice showed a remarkable reduction in lung cellular infiltrate in response to Pseudomonas beads, as compared with untreated mice. This effect was associated with significant decreases in lung levels of tumor necrosis factor-alpha and keratinocyte-derived chemokine in azithromycin-treated mice compared with untreated mice. Furthermore, there was a significant reduction in the response of both mouse and human neutrophils to chemokine-dependent and -independent chemoattractants when studied in vitro. Inhibition of chemotaxis correlated with azithromycin-mediated inhibition of extracellular signal-regulated kinase-1 and -2 activation. This study indicates that the azithromycin treatment in vivo results in significant reduction in airway-specific inflammation, which occurs in part by inhibition of neutrophil recruitment to the lung through reduction in proinflammatory cytokine expression and inhibition of neutrophil migration via the extracellular signal-regulated kinase-1 and -2 signal transduction pathway.

Characterization of the MEK5-ERK5 module in human neutrophils and its relationship to ERK1/ERK2 in the chemotactic response

The role of the extracellular signal-regulated kinase (ERK) 1 and ERK2 in the neutrophil chemotactic response remains to be identified since a previously used specific inhibitor of MEK1 and MEK2, PD98059, that was used to provide evidence for a role of ERK1 and ERK2 in regulating chemotaxis, has recently been reported to also inhibit MEK5. This issue is made more critical by our present finding that human neutrophils express mitogen-activated protein (MAP) kinase/ERK kinase (MEK)5 and ERK5 (Big MAP kinase), and that their activities were stimulated by the bacterial tripeptide, formyl methionyl-leucyl-phenylalanine (fMLP). Dose response studies demonstrated a bell-shaped profile of fMLP-stimulated MEK5 and ERK5 activation, but this was left-shifted when compared with the profile of fMLP-stimulated chemotaxis. Kinetics studies demonstrated increases in kinase activity within 2 min, peaking at 3-5 min, and MEK5 activation was more persistent than that of ERK5. There were some similarities as well as differences in the pattern of activation between fMLP-stimulated ERK1 and ERK2, and MEK5-ERK5 activation. The up-regulation of MEK5-ERK5 activities was dependent on phosphatidylinositol 3-kinase. Studies with the recently described specific MEK inhibitor, PD184352, at concentrations that inhibited ERK1 and ERK2 but not ERK5 activity demonstrate that the ERK1 and ERK2 modules were involved in regulating fMLP-stimulated chemotaxis and chemokinesis. Our data suggest that the MEK5-ERK5 module is likely to regulate neutrophil responses at very low chemoattractant concentrations whereas at higher concentrations, a shift to the ERK1/ERK2 and p38 modules is apparent.

Effects of general anaesthesia on inflammation

General anaesthesia accompanied by surgical stress may influence the inflammatory responses that are essential for maintaining the homeostatic state during the postoperative course. Severe dysregulation of the inflammatory process may provoke or aggravate postoperative complications, e.g. increased susceptibility to infections, inadequate stress reactions and hypercatabolism. Anaesthetics have been suspected of impairing various functions of the immune system either directly, by disturbing the functions of immune-competent cells, or indirectly by modulating the stress response. In the past, conflicting data on the possible immunological side effects of anaesthetics have been published. Potential reasons for these controversial findings include heterogeneous patient study groups with diverse pre-existing diseases, lack of standardisation of surgical procedures, major differences in the length and severity of surgical tissue injury and a small number of randomised studies. Although the immunological effects are of minor consequence in subjects with normal immune functions, the suppression of cellular and humoral immunity following surgery and general anaesthesia may be relevant in patients with pre-existing immune disorders.

Unique effect of arachidonic acid on human neutrophil TNF receptor expression: up-regulation involving protein kinase C, extracellular signal-regulated kinase, and phospholipase A2

Arachidonic acid (AA) regulates the function of many cell types, including neutrophils. Although much emphasis has been placed on agonist-induced down-regulation of TNFR, our data show that AA caused a rapid (10-20 min) and dose-dependent (0.5-30 micro M) increase in the surface expression of both classes of TNFR (TNFR1 and TNFR2) on human neutrophils. This increased TNFR expression correlated with an increase in TNF-induced superoxide production. In contrast, the omega3 fatty acids eicosapentaenoic acid, docosahexaenoic acid, and linolenic acid failed to stimulate TNFR expression. Although fMLP and LPS reduced the neutrophil expression of TNFR, when pretreated with AA, fMLP caused an increase in TNFR expression. Consistent with this result was the finding that AA prevented the fMLP-induced receptor release in neutrophil cultures. AA also caused an increase in TNFR expression in matured HL-60 cells (neutrophil-like cells), but a decrease in nonmatured cells and HUVEC. The AA effects were independent of the lipoxygenase and cyclooxygenase pathways, but dependent on protein kinase C, the extracellular signal-regulated kinases 1 and 2, and cytosolic phospholipase A(2). The data demonstrate a unique effect of AA in the inflammatory reaction, through its action on neutrophil TNFR expression, and suggest that AA may regulate the response of neutrophils to TNF by altering its receptor number.

Influence of non-volatile anesthetics on the migration behavior of the human breast cancer cell line MDA-MB-468

BACKGROUND

Anesthetic agents are known to influence functions of the immune system. Anesthetic drugs also support cancer progression by suppressing the activity of immune cells. In breast carcinoma an increase in expression of peripheral-type benzodiazepine receptors (PBR) and the gamma aminobutyl acid (GABA) level has been discovered. Therefore, an investigation of a direct influence of GABA-A agonist propofol, GABA-A and PBR-agonist etomidate, and the local anesthetic drug lidocaine, which can also bind to the GABA-A receptor and PBR, on migration of breast carcinoma cells was performed.

METHODS

MDA-MB-468 cells were incubated with anesthetic agents using clinically relevant concentrations (propofol 3, 6, 9 mg/l, etomidate 2, 3, 4 mg/l, and lidocaine 1.25, 2.5, 5 mg/l). Locomotion was investigated in a three-dimensional collagen matrix using time-lapse video microscopy and computer-assisted cell-tracking.

RESULTS

The percentage of migrating cells (57.4+/-1.9) as well as the velocity (0.22+/-0.09 microm/min) and distance migrated (89.4+/-66.8 microm/10 h) increased in the presence of propofol in a dose-dependent manner (up to 74.4+/-7.5, 0.30+/-0.09, 143.8+/-89.1, respectively) compared with the long chain triglyceride (LCT) control. In contrast, no influence of etomidate on the number of migrating cells could be observed. The velocity and distance migrated at 3 and 4 mg/l were found to be statistically significantly enhanced. Treatment with lidocaine caused an increase in the percentage of migrating cells (up to 75.0+/-5.6) in velocity dose dependently (up to 0.33+/-0.06) and in distance migrated (up to 151.5+/-92.9).

CONCLUSION

These results show that different anesthetic drugs are able to modulate the migratory machinery of human breast carcinoma cells in vitro.

The unique property of the CC chemokine regakine-1 to synergize with other plasma-derived inflammatory mediators in neutrophil chemotaxis does not reside in its NH2-terminal structure

The recently discovered CC chemokine, regakine-1, is constitutively present in bovine serum and synergizes with the CXC chemokine interleukin-8 (IL-8) to chemoattract neutrophils. Here we show that regakine-1 cooperates with the CXC chemokine receptor 2 ligand neutrophil activating protein-2 (NAP-2) and the anaphylatoxin C5a, two other mediators of inflammation present in the circulation. Neutrophil chemotaxis was 3-fold enhanced when regakine-1 (100 ng/ml) and C5a (30 ng/ml) were combined at concentrations present in bovine or human plasma, respectively. This synergy was also observed when neutrophils were preincubated with regakine-1. Plasma chemokines such as NAP-2, beta-thromboglobulin, and hemofiltrate CC-chemokine-1 did not affect C5a chemotactic activity. The capability of regakine-1 to synergize with C5a, NAP-2, or N-formyl-methionyl-leucyl-phenylalanine (fMLP) was not observed for monocyte chemotactic protein-3 (MCP-3), another CC chemokine that weakly chemoattracts neutrophils. Regakine-1 also failed to cooperate with MCP-3 and macrophage inflammatory protein-1alpha in neutrophil chemotaxis. The receptor of regakine-1 is not known yet. Competition with labeled fMLP or C5a for binding to neutrophils or receptor transfected cell lines demonstrated that regakine-1 did not alter receptor recognition. The protein kinase inhibitors 2'-amino-3'-methoxyflavone (PD98059), wortmannin and staurosporin had no effect on the synergy between C5a and regakine-1. Although NH2-terminal truncation affects the chemotactic potency of most chemokines, it did not affect the synergistic capacity of regakine-1 with C5a on neutrophils. These findings indicate that the constitutive plasma chemokine regakine-1 is a stable enhancer of the inflammatory response and that its blockade might be beneficial in acute and systemic inflammatory disorders.