Sevoflurane pretreatment inhibits endotoxin-induced shock in rats

Sevoflurane Posttreatment Attenuates Lung Injury Induced by Oleic Acid in Dogs

BACKGROUND

In animal models, both sevoflurane and propofol protect against acute lung injury (ALI), especially when administered prior to ALI onset. We hypothesized that when compared to propofol, sevoflurane administration after the onset of acute respiratory distress syndrome would mitigate oleic acid (OA)-induced ALI in dogs.

METHODS

Dogs were randomly assigned to receive intravenous OA to induce ALI (n = 7 for each OA group) or saline as an OA control (n = 6 for each control). Dogs were then mechanically ventilated for 6 hours during which propofol (5 mg/kg/h) or sevoflurane (1.0 minimum alveolar concentration) was administered for sedation. Study end points included PO2/FIO2 ratio, pulmonary arterial pressure, pulmonary edema, histology, and tumor nuclear factor-α.

RESULTS

In OA-injured animals, oxygenation was worse at 1, 2, 3, and 4 hours after 6-hour mechanical ventilation in sevoflurane-sedated animals compared with propofol-sedated animals, with mean difference (95% confidence interval; propofol minus sevoflurane) of 75 (39-111), 87 (55-119), 66 (44-87), and 67 (27-107) mm Hg for the respective time points. However, sevoflurane reduced the elevated pulmonary arterial pressure and vascular resistance, attenuated pulmonary edema as evidenced by reduced extravascular lung water index, and decreased tumor nuclear factor-α and diffuse alveolar damage score compared with propofol in the OA-injured lungs.

CONCLUSIONS

When compared with propofol, sevoflurane attenuates OA-induced lung damage. However, despite this effect on lung histology and inflammation, sevoflurane worsened oxygenation in OA-induced ALI, possibly via inhibition of hypoxic pulmonary vasoconstriction.

Adenosine Receptor Adora2b Plays a Mechanistic Role in the Protective Effect of the Volatile Anesthetic Sevoflurane during Liver Ischemia/Reperfusion

Background

Liver ischemia/reperfusion (IR) injury is characterized by hepatic tissue damage and an inflammatory response. This is accompanied by the formation and vascular sequestration of platelet–neutrophil conjugates (PNCs). Signaling through Adora2b adenosine receptors can provide liver protection. Volatile anesthetics may interact with adenosine receptors. This study investigates potential antiinflammatory effects of the volatile anesthetic sevoflurane during liver IR.

Methods

Experiments were performed ex vivo with human blood and in a liver IR model with wild-type, Adora2a−/−, and Adora2b−/− mice. The effect of sevoflurane on platelet activation, PNC formation and sequestration, cytokine release, and liver damage (alanine aminotransferase release) was analyzed using flow cytometry, luminometry, and immunofluorescence. Adenosine receptor expression in liver tissue was analyzed using immunohistochemistry and real-time polymerase chain reaction.

Results

Ex vivo experiments indicate that sevoflurane inhibits platelet and leukocyte activation (n = 5). During liver IR, sevoflurane (2 Vol%) decreased PNC formation 2.4-fold in wild-type (P < 0.05) but not in Adora2b−/− mice (n ≥ 5). Sevoflurane reduced PNC sequestration 1.9-fold (P < 0.05) and alanine aminotransferase release 3.5-fold (P < 0.05) in wild-type but not in Adora2b−/− mice (n = 5). In Adora2a−/− mice, sevoflurane also inhibited PNC formation and cytokine release. Sevoflurane diminished cytokine release (n ≥ 3) and increased Adora2b transcription and expression in liver tissue of wild-types (n = 4).

Conclusions

Our experiments highlight antiinflammatory and tissue-protective properties of sevoflurane during liver IR and reveal a mechanistic role of Adora2b in sevoflurane-associated effects. The targeted use of sevoflurane not only as an anesthetic but also to prevent IR damage is a promising approach in the treatment of critically ill patients.

Deep anesthesia worsens outcome of rats with inflammatory responses

OBJECTIVE

We tested the hypothesis that deep anesthesia with sevoflurane, known as a potent immunomodulator, for 4 h would worsen the 24-h outcomes of rats through modulation of the inflammatory responses.

METHODS

Forty-nine male Wistar rats, administered low dose of lipopolysaccharide (0.5 mg/kg) intravenously to elicit moderate inflammatory responses mimicked mild surgical stress, underwent one minimum alveolar concentration (MAC) or 2 MAC sevoflurane anesthesia for 4 h. The 24-h survival rate, arterial blood gases, plasma interleukin (IL)-6 and tumor necrosis factor (TNF)-α concentrations, and rate of T lymphocyte apoptosis in spleen were evaluated. We further examined the effects of hypotension and TNF-α discharge on the survival rate.

RESULTS

The survival rate in 2 MAC group was significantly lower accompanied with decreased base excess and increased level of cytokines (IL-6, TNF-α) compared to 1 MAC group. The apoptosis rate did not differ between the two groups. Neither norepinephrine infusion to restore hypotension nor administration of anti-TNF-α antibody improved the outcome in the 2 MAC group.

CONCLUSIONS

Deep anesthesia with sevoflurane even for a short-term period augments the release of inflammatory cytokines evoked by inflammatory insults like surgical stress, impairs the acid-base balance, and subsequently deteriorates the outcomes.

The volatile anesthetic sevoflurane attenuates ventilator-induced lung injury through inhibition of ERK1/2 and Akt signal transduction

Background

Ventilator-induced lung injury (VILI) sustained during mechanical ventilator support is still a cause of a high rate of morbidity and mortality in intensive care units and in operating rooms. VILI is characterized by pulmonary inflammation that appears to be mediated by proinflammatory cytokines. This study investigates whether the volatile anesthetic sevoflurane has an anti-inflammatory effect that attenuates VILI.

Methods

Twenty one male rabbits were anesthetized and were mechanically ventilated with 50% oxygen at a peak inspiratory pressure (PIP) of 10 cmH₂O, I : E ratio of 1 : 4, and positive end expiratory pressure of 5 cmH₂O. All animals were randomly assigned to one of three groups that were ventilated for 5 h with 10 cmH₂O of PIP (Sham group, n = 7); 30 cmH₂O of PIP (Control group, n = 7); or 30 cmH₂O of PIP and 0.8 vol% sevoflurane (Sevoflurane group, n = 7). The wet/dry weight (W/D) ratio and histopathology of the lung; concentration of interleukin-8 (IL-8) in the bronchoalveolar lavage fluid; and activation of extracellular signal-regulated kinases (ERK) 1/2, p38 mitogen-activated protein kinase, and Akt were measured in the lung tissue after completing the protocol.

Results

Histopathology indicated that the sevoflurane group showed fewer inflammatory cells and architectural changes than the control group did. The W/D ratio [(5.36 ± 0.13) versus (6.61 ± 0.20)], expression of IL-8 [(144.08 ± 14.61) versus (228.56 ± 15.13) pg/ml] and phosphorylation of ERK1/2 and Akt decreased significantly in the sevoflurane group relative to the control group.

Conclusions

Sevoflurane attenuates VILI in rabbits mainly by inhibiting expression of IL-8, and Sevoflurane-induced inhibition of phosphorylated ERK1/2 and Akt might be a possible pathway for protection.

Sepsis pathophysiology and anesthetic consideration

Sepsis remains to be a significant health care issue associated with high mortality and healthcare cost, despite the extensive effort to better understand the pathophysiology of the sepsis. Recently updated clinical guideline for severe sepsis and septic shock, "Surviving Sepsis Campaign 2012", emphasizes the importance of early goal-directed therapy, which can be implemented in intraoperative management of sepsis patients. Herein, we review the updates of current guideline and discuss its application to anesthesic management. Furthermore, we review the recent advance in knowledge of sepsis pathophysiology, focusing on immune modulation, which may lead to new clinical therapeutic approach to sepsis.

Plasma kynurenic acid concentration in patients undergoing cardiac surgery: effect of anaesthesia

Increases in plasma kynurenic acid (KYNA) concentration relate to the severity of inflammation. The aim of this study was to analyse changes in plasma KYNA concentration and neutrophil/lymphocyte ratio (NLR) in cardiac surgery patients. Additionally, the effect of anaesthesia was analysed. Adult cardiac surgery patients under intravenous general anaesthesia were studied. Additionally, some patients received sevoflurane (SEV) prior to cardiopulmonary bypass. Plasma KYNA concentration and NLR were measured before anaesthesia, just after surgery and on postoperative days 1, 2 and 3. Patients were assigned to two groups: patients who did not receive SEV (NonSEV group) and patients who received SEV (SEV group). Forty-three patients were studied. Twenty-four of them received SEV. KYNA increased immediately after surgery and remained elevated through postoperative day 3 in the NonSEV group, whereas it was similar to the preoperative concentration in the SEV group. NLR increased immediately after surgery in both groups, and higher values were noted in the NonSEV group than in the SEV group at postoperative days 2 and 3. Plasma KYNA concentration correlated with NLR in the NonSEV group. Cardiac surgery caused an increase in NLR. Plasma KYNA increased in the NonSEV group and correlated with NLR. Administration of SEV inhibited the increase in KYNA, most likely due to its anti-inflammatory properties.

Sevoflurane combined with ATP activates caspase-1 and triggers caspase-1-dependent pyroptosis in murine J774 macrophages

Sevoflurane is one of the most commonly used volatile anesthetics. Recent studies have shown that sevoflurane plays an important role in modulation of inflammation and immunity. However, little is known about the related molecular mechanisms. This study was designed to investigate the effects and mechanisms of sevoflurane on inflammatory cell death pyroptosis in the murine macrophage cell line J774 cells. Sevoflurane combined with ATP could increase the level of activated caspase-1, pyroptosis, and reactive oxygen species (ROS). Furthermore, treatment of cells with the caspase-1 inhibitor Ac-YVAD-CMK dramatically decreased the percentage of pyroptosis. In addition, inhibition of ROS with N-acetyl-L-cysteine or diphenyleneiodonium significantly reduced the activated levels of caspase-1. These results demonstrated that sevoflurane combined with ATP could activate caspase-1 and trigger caspase-1-dependent pyroptosis through the modulation of ROS production.

Effects of sevoflurane postconditioning on cell death, inflammation and TLR expression in human endothelial cells exposed to LPS

Background

Sevoflurane is an anesthetic agent which also participates in protective mechanisms in sepsis, likely due to anti-inflammatory properties. A key tissue in sepsis is the endothelium, which expresses TLR2 and TLR4 receptors, known regulators of inflammatory mechanisms and potential therapeutic targets for this pathology. In this context, we explored the effect of sevoflurane postconditioning in an in vitro sepsis model.

Methods

Primary cultures of human umbilical vein endothelial cells were used for two different experiments. In the first set, cultures were placed in an airtight incubation chamber and exposed to different concentrations of sevoflurane (0,1,3 or 7% vol,) for 1 hour. In the second set, lipopolysaccharide from Escherichia coli 0111:B4 (1 μg/mL) was added to culture medium for 3 hours and cells were subsequently exposed to sevoflurane (0,1,3 or 7% vol,) for 1 hour as explained before. In both cases, cell viability was measured by MTT and Trypan blue assays, TLR2 and TLR4 expression were analyzed by flow cytometry, and TNFα and IL-6 levels were quantified in cell culture media by an immunoassay immediately after exposure, at 6 and 24 hours.

Results

Exposure to 3% sevoflurane decreased TLR2 at 24 hours and TLR4 at 6 and 24 hours (both p<0.05), whereas exposure to 7% decreased TLR4 expression at 6 hours (p<0.05). Both 3 and 7% sevoflurane decreased TNF-α and IL-6 levels at 24 hours (both p<0.05). In LPS-stimulated cultures, exposure to 3% sevoflurane was cytoprotective at 6 and 24 hours (p<0.05) compared with control, and decreased TLR2 and TLR4 expression at 24 hours (p<0.05); whereas 7% decreased TLR4 expression at 24 hours (p<0.05). Both 3% and 7% sevoflurane decreased TNF-α and IL-6 levels at 24 hours (both p<0.05).

Conclusions

Postconditioning with the halogenated anesthetic agent sevoflurane after LPS stimulation shows a cytoprotective effect in an in vitro model, decreasing cell death and reducing TLR2 and TLR4 expression as well as levels of the inflammatory mediators TNF-α and IL-6 in human endothelial cells.

Sevoflurane binds and allosterically blocks integrin lymphocyte function-associated antigen-1

BACKGROUND

Volatile anesthetics have been shown to modify immune cell functions via several mechanisms, some of which have been only partially elucidated. We demonstrated that isoflurane inhibits primary leukocyte integrin lymphocyte function-associated antigen-1 (LFA-1) by binding to the allosteric cavity critical for conformational activation to its high-affinity form. It remains to be determined whether the allosteric inhibition of LFA-1 by isoflurane can be generalized to other anesthetics such as sevoflurane.

METHODS

The effects of sevoflurane on the ability of LFA-1 to bind to its counter-ligand, intercellular adhesion molecule-1, was studied in leukocytes by flow cytometry. To examine whether sevoflurane acts directly on LFA-1, we measured ligand-binding using beads coated with purified LFA-1 protein. To distinguish between competitive versus allosteric inhibition, we analyzed the effects of sevoflurane on both wild-type and mutant-locked high-affinity LFA-1. One-way analysis of variance was employed for statistical analysis of the data. Nuclear magnetic resonance spectroscopy was used to identify sevoflurane binding site(s).

RESULTS

Sevoflurane at clinically relevant concentrations inhibited the ligand-binding function of LFA-1 in leukocytes as well as in cell-free assays (P<0.05). Sevoflurane blocked wild-type but not locked high-affinity LFA-1, thereby demonstrating an allosteric mode of inhibition. Nuclear magnetic resonance spectroscopy revealed that sevoflurane bound to the allosteric cavity, to which LFA-1 allosteric antagonists and isoflurane also bind.

CONCLUSIONS

This study suggests that sevoflurane also blocks the activation-dependent conformational changes of LFA-1 to the high-affinity form. The allosteric mode of action exemplified by sevoflurane and isoflurane via LFA-1 might represent one of the underlying mechanisms of anesthetic-mediated immunomodulation.

The effect of ketamine anesthesia on the immune function of mice with postoperative septicemia

BACKGROUND

It is unknown how ketamine anesthesia immunologically affects the outcome of patients with postoperative septicemia. We investigated the effects of ketamine anesthesia on mice with an Escherichia coli or lipopolysaccharide (LPS) challenge after laparotomy, focusing on phagocytosis by liver macrophages (Kupffer cells) and cytokine production.

METHODS

C57BL/6 mice received ketamine or sevoflurane anesthesia during laparotomy, which was followed by an E. coli or LPS challenge; thereafter, mouse survival rates and cytokine secretions were examined. The effects of a β-adrenoceptor antagonist, nadolol, on ketamine anesthesia were also assessed to clarify the mechanisms of ketamine-induced immunosuppressive effects.

RESULTS

Ketamine anesthesia increased the mouse survival rate after LPS challenge after laparotomy compared with sevoflurane anesthesia, whereas such an effect of ketamine was not observed after E. coli challenge. Ketamine suppressed tumor necrosis factor (TNF) and interferon (IFN)-γ secretion after LPS and E. coli challenge. When bacterial growth was inhibited using an antibiotic, ketamine anesthesia effectively improved mouse survival after E. coli challenge compared with sevoflurane anesthesia. Neutralization of TNF also improved survival and decreased IFN-γ secretion after bacterial challenge in antibiotic-treated mice with sevoflurane anesthesia, suggesting that ketamine's suppression of TNF may improve survival. Ketamine also suppressed in vivo phagocytosis of microspheres by Kupffer cells in LPS-challenged mice. Concomitant use of nadolol with an anesthetic dose of ketamine did not restore TNF suppression in LPS-challenged mice, suggesting a mechanism independent of the β-adrenergic pathway. However, it restored TNF secretion under low-dose ketamine (10% anesthetic dose). In contrast, nadolol restored the decrease in phagocytosis by Kupffer cells, which was induced by the anesthetic dose of ketamine via the β-adrenergic pathway, suggesting distinct mechanisms.

CONCLUSION

Ketamine suppresses TNF production and phagocytosis by Kupffer cells/macrophages. Therefore, unless bacterial growth is well controlled (by an antibiotic), postoperative infection might not improve despite reduction of the inflammatory response.

Lipopolysaccharide directly alters renal tubule transport through distinct TLR4-dependent pathways in basolateral and apical membranes

Bacterial infection of the kidney is associated with renal tubule dysfunction and dysregulation of systemic electrolyte balance. Whether bacterial molecules directly affect renal tubule transport is unknown. We examined the effects of LPS on HCO3(-) absorption in the isolated rat and mouse medullary thick ascending limb (MTAL). LPS decreased HCO3(-) absorption when added to bath or lumen. The MEK/ERK inhibitor U0126 eliminated inhibition by bath LPS but had no effect on inhibition by lumen LPS. Conversely, the mammalian target of rapamycin (mTOR) inhibitor rapamycin eliminated inhibition by lumen LPS but had no effect on inhibition by bath LPS. Inhibiting basolateral Na(+)/H(+) exchange with amiloride eliminated inhibition of HCO3(-) absorption by lumen but not bath LPS. Confocal immunofluorescence showed expression of TLR4 in basolateral and apical membrane domains. Inhibition of HCO3(-) absorption by bath and lumen LPS was eliminated in MTALs from TLR4(-/-) mice. Thus LPS inhibits HCO3(-) absorption through distinct TLR4-dependent pathways in basolateral and apical membranes. These results establish that bacterial molecules can directly impair the transport function of renal tubules, identifying a new mechanism contributing to tubule dysfunction during bacterial infection. The LPS-induced reduction in luminal acidification may contribute to Gram-negative pathogenicity by promoting bacterial adherence and growth and impairing correction of infection-induced systemic acid-base disorders.

Anti-inflammatory effects of sevoflurane and mild hypothermia in endotoxemic rats

BACKGROUND

Volatile anesthetics and hypothermia attenuate the inflammatory response. We aimed to compare the anti-inflammatory effects of sevoflurane and mild hypothermia during experimental endotoxemia in the rat.

METHODS

Anesthetized, ventilated Sprague-Dawley (SD) rats were randomly treated as follows (n = 6 per group): lipopolysaccharide (LPS) only, animals received LPS [LPS 5 mg/kg, intravenously (i.v.)] with no further treatment. In the LPS-hypothermia group, rats were cooled down to a temperature of 33 degrees C 15 min after LPS-injection (LPS 5 mg/kg i.v.). In animals of the LPS-sevoflurane group, sevoflurane inhalation (1 MAC) was initiated 15 min after induction of endotoxemia. The LPS-sevoflurane-hypothermia group received combined sevoflurane and hypothermia 15 min after induction of endotoxemia. A Sham group served as control without endotoxemia or treatment. After 4 h of endotoxemia, plasma levels of tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta) and IL-10 were measured. Alveolar macrophages (AM) were ex vivo cultured for nitrite assay.

RESULTS

Inhalation of sevoflurane significantly attenuated plasma levels of TNF-alpha (-60%, P < 0.05) and IL-1beta (-68%, P < 0.05) as compared with the LPS-only group. Hypothermia and its combination with sevoflurane significantly reduced TNF-alpha levels (-46% and -58%, each P < 0.05), but not IL-1beta. Application of mild hypothermia and also its combination with sevoflurane resulted in a significant increase in plasma IL-10 as compared with endotoxemic controls. Nitrite release from AM was found to be significantly suppressed by sevoflurane (-83%), hypothermia (-73%) and by the combination of both (-67%) (P < 0.05, each).

CONCLUSION

Our data suggest that sevoflurane and mild hypothermia attenuate the inflammatory response during endotoxemia in vivo thus contributing to their beneficial role in clinical organ protection.