Inhibition of neutrophil activation by volatile anesthetics decreases adhesion to cultured human endothelial cells

Neutrophils and Anesthetic Drugs: Implications in Onco-Anesthesia

Apart from being a significant line of defense in the host defense system, neutrophils have many immunological functions. Although there are not many publications that accurately present the functions of neutrophils in relation to oncological pathology, their activity and implications have been studied a lot recently. This review aims to extensively describe neutrophils functions'; their clinical implications, especially in tumor pathology; the value of clinical markers related to neutrophils; and the implications of neutrophils in onco-anesthesia. This review also aims to describe current evidence on the influence of anesthetic drugs on neutrophils' functions and their potential influence on perioperative outcomes.

The immune response to systemically administered endotoxin in the murine intestinal microcirculation under pentobarbital versus isoflurane anesthesia

BACKGROUND

Pentobarbital and isoflurane are commonly used veterinary anesthetics. Due to the dangers of overdose by repeat-bolus regimen of pentobarbital, isoflurane has been recommended. However, literature suggests isoflurane-induced inhibition of cytokine and adhesion molecule release, impacting leukocyte adhesion.

OBJECTIVE

This study aims to characterize the impacts of pentobarbital versus isoflurane on leukocyte interactions within the intestinal microcirculation with and without endotoxin challenge.

METHODS

Female BALB/c mice were subjected to pentobarbital or isoflurane (N = 20) and challenged with endotoxin or saline by intraperitoneal injection. The mice were kept under anesthesia for 2 hours. Fluorochromes, rhodamine-6 G and fluorescein isothiocyanate, were injected intravenously. To visualize leukocyte adhesion within the intestinal microcirculation, laparotomy and intravital microscopy was performed. Leukocyte rolling and adhesion was quantified offline in a blinded fashion.

RESULTS

Within collecting venules, leukocyte rolling and adhesion showed no significant differences between pentobarbital and isoflurane anesthesia under basal conditions. Endotoxin challenge caused a similar response in both anesthetic groups. Within postcapillary venules, no statistical differences between the two anesthetics were found for adhering leukocytes under basal conditions or following endotoxin challenge either. However, leukocyte rolling after LPS-challenge was significantly decreased in postcapillary venules during isoflurane anesthesia compared to pentobarbital anesthesia.

CONCLUSIONS

Isoflurane anesthesia showed only minor differences in the immune response to endotoxin within the intestinal microcirculation compared to pentobarbital anesthesia. Due to the superior safety profile of volatile anesthetics, immunological studies may choose isoflurane over pentobarbital as the veterinary anesthetic of choice.

Molecular Aspects of Volatile Anesthetic-Induced Organ Protection and Its Potential in Kidney Transplantation

Ischemia reperfusion injury (IRI) is inevitable in kidney transplantation and negatively impacts graft and patient outcome. Reperfusion takes place in the recipient and most of the injury following ischemia and reperfusion occurs during this reperfusion phase; therefore, the intra-operative period seems an attractive window of opportunity to modulate IRI and improve short- and potentially long-term graft outcome. Commonly used volatile anesthetics such as sevoflurane and isoflurane have been shown to interfere with many of the pathophysiological processes involved in the injurious cascade of IRI. Therefore, volatile anesthetic (VA) agents might be the preferred anesthetics used during the transplantation procedure. This review highlights the molecular and cellular protective points of engagement of VA shown in in vitro studies and in vivo animal experiments, and the potential translation of these results to the clinical setting of kidney transplantation.

HDAC1 and HDAC2 regulate anti-inflammatory effects of anesthetic isoflurane in human monocytes

Pre-exposure to volatile anesthetics inhibits inflammation induced by various stimuli, including surgical procedures and ischemia. We hypothesize that volatile anesthetics may induce anti-inflammatory effects via a mechanism involving regulation of histone deacetylases (HDACs). Pre-exposure of 1.5% isoflurane for 0.5 h induced anti-inflammatory effects [measured by cytokine production of tumor necrosis factor-ɑ, interleukin-8 (IL-8) and IL-1β] in both human THP-1 cells and primary human peripheral blood monocytes stimulated by lipopolysaccharide. In human THP-1 cells, coadministration of the HDAC inhibitor trichostatin A (TSA) blocked the isoflurane-induced anti-inflammatory effects. TSA also blocked isoflurane-upregulated HDAC1-3 expression and isoflurane-reduced nuclear translocation of p65 and p50 subunits of nuclear factor-κB (NF-κB). The ability of isoflurane to reduce NF-κB nuclear translocation and proinflammatory responses in the cell line was blocked by gene silencing of HDAC1 and HDAC2, but not by gene silencing of HDAC3. A coimmunoprecipitation assay demonstrated that the decreased interaction between HDAC1 and HDAC2 through lipopolysaccharide was restored by isoflurane pretreatment. These findings were validated in primary human peripheral blood monocytes  wherein gene silencing of HDAC1 and HDAC2 resulted in increased cytokine production and NF-κB nuclear translocation induced by isoflurane pre-exposure and lipopolysaccharide stimulation. These results indicate that anti-inflammatory effects of the volatile anesthetic isoflurane in human monocytes involve regulation of HDAC1 and HDAC2.

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.

Sevoflurane Promotes Bactericidal Properties of Macrophages through Enhanced Inducible Nitric Oxide Synthase Expression in Male Mice

BACKGROUND

Sevoflurane with its antiinflammatory properties has shown to decrease mortality in animal models of sepsis. However, the underlying mechanism of its beneficial effect in this inflammatory scenario remains poorly understood. Macrophages play an important role in the early stage of sepsis as they are tasked with eliminating invading microbes and also attracting other immune cells by the release of proinflammatory cytokines such as interleukin-1β, interleukin-6, and tumor necrosis factor-α. Thus, the authors hypothesized that sevoflurane mitigates the proinflammatory response of macrophages, while maintaining their bactericidal properties.

METHODS

Murine bone marrow-derived macrophages were stimulated in vitro with lipopolysaccharide in the presence and absence of 2% sevoflurane. Expression of cytokines and inducible NO synthase as well as uptake of fluorescently labeled Escherichia coli (E. coli) were measured. The in vivo endotoxemia model consisted of an intraperitoneal lipopolysaccharide injection after anesthesia with either ketamine and xylazine or 4% sevoflurane. Male mice (n = 6 per group) were observed for a total of 20 h. During the last 30 min fluorescently labeled E. coli were intraperitoneally injected. Peritoneal cells were extracted by peritoneal lavage and inducible NO synthase expression as well as E. coli uptake by peritoneal macrophages was determined using flow cytometry.

RESULTS

In vitro, sevoflurane enhanced lipopolysaccharide-induced inducible NO synthase expression after 8 h by 466% and increased macrophage uptake of fluorescently labeled E. coli by 70% compared with vehicle-treated controls. Inhibiting inducible NO synthase expression pharmacologically abolished this increase in bacteria uptake. In vivo, inducible NO synthase expression was increased by 669% and phagocytosis of E. coli by 49% compared with the control group.

CONCLUSIONS

Sevoflurane enhances phagocytosis of bacteria by lipopolysaccharide-challenged macrophages in vitro and in vivo via an inducible NO synthase-dependent mechanism. Thus, sevoflurane potentiates bactericidal and antiinflammatory host-defense mechanisms in endotoxemia.

Evaluation of Sevoflurane Anesthesia in Donkeys (Equus asinus) Premedicated With Xylazine and Induced With Thiopental

Sevoflurane is a volatile anesthetic agent that has become popular in the field of large animal anesthesia. The aim of this study was to evaluate the use of sevoflurane in adult healthy donkeys. Six male, adult, healthy donkeys were premedicated with xylazine (1 mg/kg IV), induced with thiopental (5 mg/kg IV), and then maintained for 90 minutes with sevoflurane in 100% oxygen at a flow rate of 6 L/min with spontaneous breathing. Rectal temperature (RT), respiratory rate, heart rate (HR), oxygen hemoglobin saturation (OHS), and mean arterial blood pressure (MBP) were measured before and 20 minutes after the administration of xylazine, 10 minutes after the injection of thiopental, and then continuously every 10 minutes until recovery. Times for various signs of recovery, total duration of recovery, and quality of recovery were recorded. Jugular blood samples were collected from each donkey and complete blood counts and venous blood gases including concentrations of oxygen (PO₂) and carbon dioxide (PCO₂) were measured. In addition, the concentrations of sodium, potassium, calcium, lactate, bicarbonate, and glucose in venous blood were measured. Results showed that during the anesthesia maintained with sevoflurane, there was a significant decrease in HR, MBP, RT, red blood corpuscles, hematocrit, total white blood cells, neutrophils, and lymphocytes, whereas the levels of OHS and glucose significantly increased. The concentrations of PO₂, PCO₂, and lactate in venous blood significantly increased, whereas the pH significantly decreased. The levels of calcium significantly decreased immediately following the recovery. Sternal recumbency and standing occurred 15.8 ± 2.6 minutes and 28.2 ± 2.2 minutes, respectively, after turning off the vaporizer. Overall, the quality of recovery was good and relatively quick. It was concluded that sevoflurane appears to provide safe and effective anesthesia in donkeys, with relatively rapid induction and recovery.

Volatile Anesthetics and Immunity

Historically, volatile anesthetics have demonstrated interesting interactions with both the innate and adaptive immune systems. This review organizes these interactions into four phases: recognition, recruitment, response, and resolution. These phases represent a range of proinflammatory, inflammatory, and innate and adaptive immune regulatory responses. The interaction between volatile anesthetics and the immune system is discussed in the context of pathogenesis of infectious disease.

Shedding Light on Anesthetic Mechanisms: Application of Photoaffinity Ligands

Anesthetic photoaffinity ligands have had an increasing presence within anesthesiology research. These ligands mimic parent general anesthetics and allow investigators to study anesthetic interactions with receptors and enzymes; identify novel targets; and determine distribution within biological systems. To date, nearly all general anesthetics used in medicine have a corresponding photoaffinity ligand represented in the literature. In this review, we examine all aspects of the current methodologies, including ligand design, characterization, and deployment. Finally we offer points of consideration and highlight the future outlook as more photoaffinity ligands emerge within the field.

Mechanisms of the Immunological Effects of Volatile Anesthetics: A Review

Volatile anesthetics (VAs) have been in clinical use for a very long time. Their mechanism of action is yet to be fully delineated, but multiple ion channels have been reported as targets for VAs (canonical VA targets). It is increasingly recognized that VAs also manifest effects outside the central nervous system, including on immune cells. However, the literature related to how VAs affect the behavior of immune cells is very limited, but it is of interest that some canonical VA targets are reportedly expressed in immune cells. Here, we review the current literature and describe canonical VA targets expressed in leukocytes and their known roles. In addition, we introduce adhesion molecules called β2 integrins as noncanonical VA targets in leukocytes. Finally, we propose a model for how VAs affect the function of neutrophils, macrophages, and natural killer cells via concerted effects on multiple targets as examples.

Isoflurane prevents acquired epilepsy in rat models of temporal lobe epilepsy

OBJECTIVE

Acquired epilepsy is a devastating long-term risk of various brain insults, including trauma, stroke, infections, and status epilepticus (SE). There is no preventive treatment for patients at risk. Attributable to the complex alterations involved in epileptogenesis, it is likely that multitargeted approaches are required for epilepsy prevention. We report novel preclinical findings with isoflurane, which exerts various nonanesthetic effects that may be relevant for antiepileptogenesis.

METHODS

The effects of isoflurane were investigated in two rat models of SE-induced epilepsy: intrahippocampal kainate and systemic administration of paraoxon. Isoflurane was either administered during (kainate) or after (paraoxon) induction of SE. Magnetic resonance imaging was used to assess blood-brain barrier (BBB) dysfunction. Positron emission tomography was used to visualize neuroinflammation. Long-term electrocorticographic recordings were used to monitor spontaneous recurrent seizures. Neuronal damage was assessed histologically.

RESULTS

In the absence of isoflurane, spontaneous recurrent seizures were common in the majority of rats in both models. When isoflurane was administered during kainate injection, duration and severity of SE were not affected, but only few rats developed spontaneous recurrent seizures. A similar antiepileptogenic effect was found when paraoxon-treated rats were exposed to isoflurane after SE. Moreover, in the latter model, isoflurane prevented BBB dysfunction and neurodegeneration, whereas isoflurane reduced neuroinflammation in the kainate model.

INTERPRETATION

Given that isoflurane is a widely used volatile anesthetic, and is used for inhalational long-term sedation in critically ill patients at risk to develop epilepsy, our findings hold a promising potential to be successfully translated into the clinic. Ann Neurol 2016;80:896-908.

Immune Modulation by Volatile Anesthetics

Volatile general anesthetics continue to be an important part of clinical anesthesia worldwide. The impact of volatile anesthetics on the immune system has been investigated at both mechanistic and clinical levels, but previous studies have returned conflicting findings due to varied protocols, experimental environments, and subject species. While many of these studies have focused on the immunosuppressive effects of volatile anesthetics, compelling evidence also exists for immunoactivation. Depending on the clinical conditions, immunosuppression and activation due to volatile anesthetics can be either detrimental or beneficial. This review provides a balanced perspective on the anesthetic modulation of innate and adaptive immune responses as well as indirect effectors of immunity. Potential mechanisms of immunomodulation by volatile anesthetics are also discussed. A clearer understanding of these issues will pave the way for clinical guidelines that better account for the impact of volatile anesthetics on the immune system, with the ultimate goal of improving perioperative management.

Different phosphoinositide 3-kinase isoforms mediate carrageenan nociception and inflammation

PI3K-α, -δ, and -γ all participate in inflammation induction. Antagonism of only PI3K-γ blocks nociception, which is indicative of a role for this isoform within the afferent.

Phosphoinositide 3-kinases (PI3Ks) participate in signal transduction cascades that can directly activate and sensitize nociceptors and enhance pain transmission. They also play essential roles in chemotaxis and immune cell infiltration leading to inflammation. We wished to determine which PI3K isoforms were involved in each of these processes. Lightly anesthetized rats (isoflurane) were injected subcutaneously with carrageenan in their hind paws. This was preceded by a local injection of 1% DMSO vehicle or an isoform-specific antagonist to PI3K-α (compound 15-e), -β (TGX221), -δ (Cal-101), or -γ (AS252424). We measured changes in the mechanical pain threshold and spinal c-Fos expression (4 hours after injection) as indices of nociception. Paw volume, plasma extravasation (Evans blue, 0.3 hours after injection), and neutrophil (myeloperoxidase; 1 hour after injection) and macrophage (CD11b+; 4 hour after injection) infiltration into paw tissue were the measured inflammation endpoints. Only PI3K-γ antagonist before treatment reduced the carrageenan-induced pain behavior and spinal expression of c-Fos (P ≤ 0.01). In contrast, pretreatment with PI3K-α, -δ, and-γ antagonists reduced early indices of inflammation. Plasma extravasation PI3K-α (P ≤ 0.05), -δ (P ≤ 0.05), and -γ (P ≤ 0.01), early (0-2 hour) edema -α (P ≤ 0.05), -δ (P ≤ 0.001), and -γ (P ≤ 0.05), and neutrophil infiltration (all P ≤ 0.001) were all reduced compared to vehicle pretreatment. Later (2-4 hour), edema and macrophage infiltration (P ≤ 0.05) were reduced by only the PI3K-δ and -γ isoform antagonists, with the PI3K-δ antagonist having a greater effect on edema. PI3K-β antagonism was ineffective in all paradigms. These data indicate that pain and clinical inflammation are pharmacologically separable and may help to explain clinical conditions in which inflammation naturally wanes or goes into remission, but pain continues unabated.

Differential effects of volatile anesthetics on leukocyte integrin macrophage-1 antigen

Macrophage-1 antigen (Mac-1, αMβ2) is a leukocyte adhesion molecule that plays a significant role in leukocyte crawling and phagocytosis, and is homologous to its sister protein leukocyte function-associated antigen-1 (LFA-1, αLβ2). The authors have previously demonstrated that volatile anesthetics isoflurane and sevoflurane bound to and inhibited LFA-1. Here, the hypothesis tested was that isoflurane and sevoflurane would inhibit Mac-1. A binding assay of Mac-1 to its ligand inter-cellular adhesion molecule-1 (ICAM-1) using V-bottom plates was established. The effect of isoflurane and sevoflurane on Mac-1 was examined using this ICAM-1 binding assay and by probing exposure of activation-sensitive epitopes. The docking program Glide was used to predict anesthetic binding site(s) on Mac-1. The functional role of this predicted binding site was then assessed by introducing point mutations in this region. Lastly, the effect of anesthetic on activating mutants was evaluated. The results indicated that isoflurane inhibited binding of Mac-1 to ICAM-1, but sevoflurane did not. Isoflurane also attenuated the exposure of the activation-sensitive epitopes. The docking simulation predicted the isoflurane binding site to be at the cavity underneath the α7 helix of the ligand binding domain (the αM I domain). Point mutants at this predicted binding site contained both activating and deactivating mutants, suggesting its functional significance. The binding of activating mutants αM-Y267A β2-WT and αM-L312A β2-WT to ICAM-1 was not affected by isoflurane, but binding of another activating mutant αM-WT β2-L132A was inhibited supporting the binding of isoflurane to this cavity. The conclusion reached from these findings was that isoflurane inhibited Mac-1 binding to ICAM-1 by binding to the cavity underneath the α7 helix of the αM I domain, but sevoflurane did not. Thus, because these common clinical volatile anesthetics demonstrated different effects on Mac-1, this implied their effects on the immune system might differ.

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.

Evaluation of neutrophil function during hemodialysis treatment in healthy dogs under anesthesia with sevoflurane

This study evaluated the number and function of neutrophils during 3 hr of hemodialysis in healthy dogs under anesthesia. Isolated neutrophils were used to assess neutrophil adhesion, phagocytosis and the oxidative burst. At 0.5 and 3 hr after the start of hemodialysis treatment, there was a decrease in neutrophil number. The phagocytic ability of neutrophils was decreased 3 hr after the start of hemodialysis. In conclusion, this study demonstrated that hemodialysis reduces the number and phagocytic ability of neutrophils during treatment. However, these changes recover within 24 hr of hemodialysis.

The volatile anesthetic isoflurane increases endothelial adenosine generation via microparticle ecto-5'-nucleotidase (CD73) release

Endothelial dysfunction is common in acute and chronic organ injury. Isoflurane is a widely used halogenated volatile anesthetic during the perioperative period and protects against endothelial cell death and inflammation. In this study, we tested whether isoflurane induces endothelial ecto-5′-nucleotidase (CD73) and cytoprotective adenosine generation to protect against endothelial cell injury. Clinically relevant concentrations of isoflurane induced CD73 activity and increased adenosine generation in cultured human umbilical vein or mouse glomerular endothelial cells. Surprisingly, isoflurane-mediated induction of endothelial CD73 activity occurred within 1 hr and without synthesizing new CD73. We determined that isoflurane rapidly increased CD73 containing endothelial microparticles into the cell culture media. Indeed, microparticles isolated from isoflurane-treated endothelial cells had significantly higher CD73 activity as well as increased CD73 protein. In vivo, plasma from mice anesthetized with isoflurane had significantly higher endothelial cell-derived CD144+ CD73+ microparticles and had increased microparticle CD73 activity compared to plasma from pentobarbital-anesthetized mice. Supporting a critical role of CD73 in isoflurane-mediated endothelial protection, a selective CD73 inhibitor (APCP) prevented isoflurane-induced protection against human endothelial cell inflammation and apoptosis. In addition, isoflurane activated endothelial cells Rho kinase evidenced by myosin phosphatase target subunit-1 and myosin light chain phosphorylation. Furthermore, isoflurane-induced release of CD73 containing microparticles was significantly attenuated by a selective Rho kinase inhibitor (Y27632). Taken together, we conclude that the volatile anesthetic isoflurane causes Rho kinase-mediated release of endothelial microparticles containing preformed CD73 and increase adenosine generation to protect against endothelial apoptosis and inflammation.

Intravenous pretreatment with emulsified isoflurane preconditioning protects kidneys against ischemia/reperfusion injury in rats

Background

Emulsified isoflurane (EIso) is a novel intravenous general anesthetic, which can provide rapid anesthetic induction and recovery. EIso preconditioning could attenuate heart, lung and liver ischemia/reperfusion (I/R) injury. We tested the hypothesis that intravenous pretreatment with EIso would protect kidneys against I/R injury by inhibiting systemic inflammatory responses and improving renal antioxidative ability.

Methods

Rats were randomly divided into these six groups: sham, I/R, intralipid, 1, 2 or 4 ml/kg EIso. Rats were subjected to 45 min left renal pedicle occlusion followed by 3 h reperfusion after right nephrectomy. Rat were treated with intravenous 8% EIso with 1, 2 or 4 ml/kg, or 30% intralipid with 2 ml/kg for 30 min before ischemia, respectively. After reperfusion, renal functional parameters, serum mediator concentrations and markers of oxidative stress in kidney tissues were determined, and renal histopathological analysis were performed.

Results

Serum creatinine, blood urea nitrogen, cystatin c, tumor necrosis factor-α, interleukin-6, and interleukin-10 concentrations were significantly increased after renal I/R as compared to the sham group. So was renal tissue MDA content and histological scores, but renal tissue SOD activity was decreased. Additionally, severe morphological damages were observed in these study groups. In contrast, 2 or 4 ml/kg EIso reduced serum creatinine, blood urea nitrogen, cystatin c, tumor necrosis factor-α, and interleukin-6 levels, decreased renal tissue MDA content and histological scores, increased serum interleukin-10 level and tissue SOD activity as compared to the I/R, intralipid and 1 ml/kg EIso groups. Renal morphological damages were alleviated after pretreatment of 2 or 4 ml/kg EIso.

Conclusions

Intravenous EIso produces preconditioning against renal I/R injury in rats, which might be mediated by attenuating inflammation and increasing antioxidation ability.

Effects of inhalational anaesthetics in experimental allergic asthma

We evaluated whether isoflurane, halothane and sevoflurane attenuate the inflammatory response and improve lung morphofunction in experimental asthma. Fifty-six BALB/c mice were sensitised and challenged with ovalbumin and anaesthetised with isoflurane, halothane, sevoflurane or pentobarbital sodium for one hour. Lung mechanics and histology were evaluated. Gene expression of pro-inflammatory (tumour necrosis factor-α), pro-fibrogenic (transforming growth factor-β) and pro-angiogenic (vascular endothelial growth factor) mediators, as well as oxidative process modulators, were analysed. These modulators included nuclear factor erythroid-2 related factor 2, sirtuin, catalase and glutathione peroxidase. Isoflurane, halothane and sevoflurane reduced airway resistance, static lung elastance and atelectasis when compared with pentobarbital sodium. Sevoflurane minimised bronchoconstriction and cell infiltration, and decreased tumour necrosis factor-α, transforming growth factor-β, vascular endothelial growth factor, sirtuin, catalase and glutathione peroxidase, while increasing nuclear factor erythroid-2-related factor 2 expression. Sevoflurane down-regulated inflammatory, fibrogenic and angiogenic mediators, and modulated oxidant-antioxidant imbalance, improving lung function in this model of asthma.

Ischemia-reperfusion injury and volatile anesthetics

Ischemia-reperfusion injury (IRI) is induced as a result of reentry of the blood and oxygen to ischemic tissue. Antioxidant and some other drugs have protective effect on IRI. In many surgeries and clinical conditions IRI is counteract inevitable. Some anesthetic agents may have a protective role in this procedure. It is known that inhalational anesthetics possess protective effects against IRI. In this review the mechanism of preventive effects of volatile anesthetics and different ischemia-reperfusion models are discussed.

Mechanisms revealed through general anesthetic photolabeling

General anesthetic photolabels are used to reveal molecular targets and molecular binding sites of anesthetic ligands. After identification, the relevance of anesthetic substrates or binding sites can be tested in biological systems. Halothane and photoactive analogs of isoflurane, propofol, etomidate, neurosteroids, anthracene, and long chain alcohols have been used in anesthetic photolabeling experiments. Interrogated protein targets include the nicotinic acetylcholine receptor, GABA_A receptor, tubulin, leukocyte function-associated antigen-1, and protein kinase C. In this review, we summarize insights revealed by photolabeling these targets, as well as general features of anesthetics, such as their propensity to partition to mitochondria and bind voltage-dependent anion channels. The theory of anesthetic photolabel design and the experimental application of photoactive ligands are also discussed.

Isoflurane prevents acute lung injury through ADP-mediated platelet inhibition

BACKGROUND

Growing evidence suggests platelets are essential in posttraumatic, acute lung injury (ALI). Halogenated ethers interfere with the formation of platelet-granulocyte aggregates. The potential benefit of halogenated ethers has not been investigated in models of trauma/hemorrhagic shock (T/HS). Therefore, we hypothesized that isoflurane decreases T/HS-mediated ALI through platelet inhibition.

METHODS

Sprague-Dawley rats (n = 47) were anesthetized by either pentobarbital or inhaled isoflurane and placed into (1) control, (2) trauma (laparotomy) sham shock, (3) T/HS (mean arterial pressure, 30 mmHg × 45 min), (4) pretreatment with an ADP receptor antagonist, or (5) T/HS with isoflurane initiated during resuscitation groups. ALI was determined by protein and pulmonary immunofluorescence bronchoalveolar lavage (BAL) fluid. Platelet Mapping specifically evaluated thrombin-independent inhibition of the ADP and AA pathways of platelet activation.

RESULTS

Pretreatment with isoflurane abrogated ALI as measured by both BAL fluid protein and pulmonary immunofluorescence (P < .001). Platelet Mapping revealed specific inhibition of the platelet ADP-pathway with isoflurane (P < .001). Pretreatment with an ADP receptor antagonist decreased ALI to sham levels, confirming that specific platelet ADP inhibition decreases ALI. Isoflurane initiated during resuscitation also decreased ALI (P < .001).

CONCLUSION

Isoflurane attenuates ALI through an antiplatelet mechanism, in part, through inhibition of the platelet ADP pathway. Isoflurane given postinjury also protects against ALI, and highlights the potential applications of this therapy in various clinical scenarios of ischemia/reperfusion.

Isoflurane binds and stabilizes a closed conformation of the leukocyte function-associated antigen-1

We previously demonstrated that isoflurane targets lymphocyte function-associated antigen-1 (LFA-1), a critical adhesion molecule for leukocyte arrest. However, it remains to be determined how isoflurane interacts with the full ectodomain LFA-1 and modulates its conformation and function. Isoflurane binding sites on the full ectodomain LFA-1 were probed by photolabeling using photoactivatable isoflurane (azi-isoflurane). The adducted residues were determined by liquid chromatography/mass spectrometry analysis. Separately, docking simulations were performed to predict binding sites. Point mutations were introduced around isoflurane binding sites. The significance of isoflurane's effect was assessed in both intracellular adhesion molecule-1 (ICAM-1) binding assays and epitope mapping of activation-sensitive antibodies using flow cytometry. Two isoflurane binding sites were identified using photolabeling and were further validated by the docking simulation: one at the hydrophobic pocket in the ICAM-1 binding domain (the αI domain); the other at the βI domain. Mutagenesis of the α'1 helix showed that isoflurane binding sites at the βI domain were significantly important in modulating LFA-1 function and conformation. Epitope mapping using activation-sensitive antibodies suggested that isoflurane stabilized LFA-1 in the closed conformation. This study suggested that isoflurane binds to both the αI and βI domains allosteric to the ICAM-1 binding site, and that isoflurane binding stabilizes LFA-1 in the closed conformation.

The effects of anesthetic preconditioning with sevoflurane in an experimental lung autotransplant model in pigs

BACKGROUND

Ischemia-reperfusion lung injury is doubly important in thoracic surgery because of the associated ventilation damage to 1 lung. In this study we evaluated the cytoprotective effects of sevoflurane in a pulmonary autotransplant model in pigs.

METHODS

Twenty Large White pigs undergoing pneumonectomy plus lung autotransplant were divided into 2 10-member groups on the basis of the anesthetic received (propofol or sevoflurane). Proinflammatory mediators, oxidative stress, nitric oxide metabolism, and hemodynamic and blood variables were measured at 5 different time points.

RESULTS

There was an increase of oxidative stress markers and proinflammatory mediators in the propofol group, whereas the hemodynamic variables were similar in both groups.

CONCLUSIONS

We demonstrated that sevoflurane decreased the inflammatory response and oxidative stress in a live ischemia-reperfusion lung model.

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.

Crystal structure of isoflurane bound to integrin LFA-1 supports a unified mechanism of volatile anesthetic action in the immune and central nervous systems

Volatile anesthetics (VAs), such as isoflurane, induce a general anesthetic state by binding to specific targets (i.e., ion channels) in the central nervous system (CNS). Simultaneously, VAs modulate immune functions, possibly via direct interaction with alternative targets on leukocytes. One such target, the integrin lymphocyte function-associated antigen-1 (LFA-1), has been shown previously to be inhibited by isoflurane. A better understanding of the mechanism by which isoflurane alters protein function requires the detailed information about the drug-protein interaction at an atomic level. Here, we describe the crystal structure of the LFA-1 ligand-binding domain (I domain) in complex with isoflurane at 1.6 A. We discovered that isoflurane binds to an allosteric cavity previously implicated as critical for the transition of LFA-1 from the low- to the high-affinity state. The isoflurane binding site in the I domain involves an array of amphiphilic interactions, thereby resembling a "common anesthetic binding motif" previously predicted for authentic VA binding sites. These results suggest that the allosteric modulation of protein function by isoflurane, as demonstrated for the integrin LFA-1, might represent a unified mechanism shared by the interactions of volatile anesthetics with targets in the CNS.

Central nervous system inflammation

Activation of inflammation is the hallmark of pathological processes that follow acute injury. This process is mediated by inflammatory cytokines and adhesion molecules that reside on the surface of endothelium, leucocyte and inflammatory cells. Attenuation of the adhesion cascade has been the subject of several basic science and clinical trials in the management of neurological injury. This review will highlight the role of adhesion molecules in the evolution of secondary injury after cerebral ischaemia and trauma. Potential therapeutic avenues will then be discussed.

The volatile anesthetic isoflurane perturbs conformational activation of integrin LFA-1 by binding to the allosteric regulatory cavity

The molecular and structural basis of anesthetic interactions with conformations and functionalities of cell surface receptors remains to be elucidated. We have demonstrated that the widely used volatile anesthetic isoflurane blocks the activation-dependent conformational conversion of integrin lymphocyte function associated antigen-1 (LFA-1), the major leukocyte cell adhesion molecule, to a high-affinity configuration. Perturbation of LFA-1 activation by isoflurane at clinically relevant concentrations leads to the inhibition of T-cell interactions with target cells as well as ligand-triggered intracellular signaling. Nuclear magnetic resonance spectroscopy reveals that isoflurane binds within a cavity in the LFA-1 ligand-binding domain, which is a previously identified drug-binding site for allosteric small-molecule antagonists that stabilize LFA-1 in a low-affinity conformation. These results provide a potential mechanism for the immunomodulatory properties of isoflurane.

Preconditioning, but not postconditioning, with Sevoflurane reduces pulmonary neutrophil accumulation after lower body ischaemia/reperfusion injury in rats

BACKGROUND AND OBJECTIVES

Aortic ischaemia and reperfusion may induce pulmonary sequestration of neutrophil granulocytes. Preconditioning and postconditioning with volatile anaesthetics confer protection against reperfusion injury in various organs, such as heart, kidneys or brain. We tested the hypothesis that pre- or postconditioning with Sevoflurane attenuates pulmonary neutrophil accumulation after ischaemia/reperfusion injury of the aorta.

METHODS

Anaesthetized and mechanically ventilated Wistar rats underwent laparotomy and were randomly assigned to one of the following groups: Sham (n = 10), ischaemia/reperfusion (n = 8, lower body ischaemia by clamping of the infrarenal aorta for 2 h followed by 3 h of reperfusion), preconditioning (n = 10, 2.0% Sevoflurane administered over 30 min prior to ischaemia) and postconditioning (n = 9, 2.0% Sevoflurane during reperfusion). Following reperfusion, the lungs were removed for microscopic determination of neutrophil accumulation.

RESULTS

Ischaemia/reperfusion induced a significant increase in pulmonary neutrophil accumulation (mean +/- SD, 29.9 +/- 7.4 vs. 15.8 +/- 6.6 neutrophils per microscopic field in ischaemia/reperfusion vs. Sham, respectively, P < 0.001). Sevoflurane preconditioning resulted in a lower neutrophil count (20.3 +/- 7.1 neutrophils, P < 0.001 vs. ischaemia/reperfusion), while postconditioning showed no effects (25.8 +/- 9.8 neutrophils vs. ischaemia/reperfusion, not significant).

CONCLUSIONS

Preconditioning, but not postconditioning, with Sevoflurane reduces pulmonary neutrophil accumulation after ischaemia/reperfusion injury of the lower body. Since neutrophil accumulation plays a major role in the pathophysiology of acute lung injury, our data suggest a protective effect of Sevoflurane preconditioning on remote pulmonary ischaemia/reperfusion injury.

Isoflurane protects against renal ischemia and reperfusion injury and modulates leukocyte infiltration in mice

Inflammation after renal ischemia-reperfusion (IR) injury is a major contributor to renal cell death. We previously demonstrated that several volatile anesthetics protect against renal IR injury and necrosis in rats in vivo. We subsequently showed that volatile anesthetics produced direct anti-inflammatory and anti-necrotic effects in cultured proximal tubule cells in vitro. In this study, we wanted to determine whether the volatile anesthetic isoflurane protects against renal IR injury by producing anti-inflammatory effects in mice. C57BL/6 mice subjected to renal IR under isoflurane anesthesia demonstrated improved renal function and reduced necrosis compared with mice subjected to renal IR under pentobarbital anesthesia. Mice subjected to renal IR under isoflurane anesthesia also showed a reduction in inflammation evidenced by a reduced renal influx of neutrophils and macrophages, reduced ICAM-1 expression, less upregulation of proinflammatory mRNAs (TNF-alpha, ICAM-1, KC, and IL-1beta) as well as reduced nuclear translocation of NF-kappaB 24 h after renal IR injury. Analysis of specific lymphocyte subset trafficking to the kidney using flow cytometry demonstrated that isoflurane anesthesia reduced intrarenal influx of CD3+, CD4+, CD8+, and NK1.1+ lymphocytes at 3 h after renal ischemia compared with pentobarbital anesthesia. However, only the differential reduction of NK1.1+ lymphocytes persisted 24 h after renal ischemia. Therefore, we conclude that isoflurane anesthesia significantly attenuated renal IR injury in mice by reducing inflammation and modulating leukocyte influx. In particular, neutrophil, macrophage, and NK1.1+ lymphocyte cell modulation may play a significant role in renal protection by isoflurane anesthesia.

Preconditioning and protection against ischaemia-reperfusion in non-cardiac organs: a place for volatile anaesthetics?

There is an increasing body of evidence that volatile anaesthetics protect myocardium against ischaemic insult by a mechanism termed 'anaesthetic preconditioning'. Anaesthetic preconditioning and ischaemic preconditioning share several common mechanisms of action. Since ischaemic preconditioning has been demonstrated in organs other than the heart, anaesthetic preconditioning might also apply in these organs and have significant clinical applications in surgical procedures carrying a high risk of ischaemia-reperfusion injury. After a brief review on myocardial preconditioning, experimental and clinical data on preconditioning in non-cardiac tissues will be presented. Potential benefits of anaesthetic preconditioning during non-cardiac surgery will be addressed.

Effects of sevoflurane and propofol on ischaemia–reperfusion injury after thoracic-aortic occlusion in pigs

BACKGROUND

Thoraco-abdominal-aneurysm surgery predicts high mortality. Propofol and sevoflurane are commonly used anaesthetics for this procedure. Halogenated anaesthetics induce organ protection similar to ischaemic preconditioning. We investigated which anaesthetic regimen would lead to a better protection against ischaemia-reperfusion injury induced by temporary thoracic-aortic occlusion.

METHODS

Following initial fentanyl-midazolam anaesthesia for surgical preparation, 18 pigs were randomly assigned to two groups: group one received propofol (n=9) and group two sevoflurane (n=9) before, during, and after lower body ischaemia in an investigator blinded fashion. Ten animals without aortic occlusion served as time controls (propofol, n=5; sevoflurane, n=5). For induction of ischaemia, the thoracic aorta was occluded by a balloon-catheter for 90 min. After 120 min of reperfusion, the study anaesthetics were discontinued and fentanyl-midazolam re-established for an additional 180 min. Goal-directed therapy was performed during reperfusion. Fluid and catecholamine requirements were assessed. Serum samples and intestinal tissue specimens were obtained.

RESULTS

Severe declamping shock occurred in both study groups. While norepinephrine requirements in the sevoflurane group were significantly reduced during reperfusion (P<0.05), allowing cessation of catecholamine support in 4/9 animals, all 9/9 animals were still catecholamine dependent at the end of the experiment in the propofol group. Serum activities of lactate dehydrogenase, aspartate transaminase, and alanine aminotransferase were lower with sevoflurane (P<0.05). Small intestine tissue specimens did not differ histologically.

CONCLUSIONS

Use of sevoflurane compared with propofol attenuated the haemodynamic sequelae of reperfusion injury in our model. Release of serum markers of cellular injury was also attenuated.

Halothane affects focal adhesion proteins in the A 549 cells

Halothane is a volatile anaesthetic, which is known to induce alterations in cellular plasma membranes, modulating the physical state of the membrane lipids and/or interacting directly with membrane-bound proteins, such as integrin receptors. Integrin-mediated cell adhesion is a general property of eukaryotic cells, which is closely related to cell viability. Our previous investigations showed that halothane is toxic for A 549 lung carcinoma cells when applied at physiologically relevant concentrations and causes inhibition of adhesion to collagen IV. The present study is focused on the mechanisms underlying halothane toxicity. Our results imply that physiologically relevant concentrations of halothane disrupt focal adhesion contacts in A 549 cells, which is accompanied with suppression of focal adhesion kinase activity and paxillin phosphorylation, and not with proteolytic changes or inhibition of vinculin and paxillin expression.We suggest that at least one of the toxic effects of halothane is due to a decreased phosphorylation of the focal contact proteins.

Quantitative analysis of influence of sevoflurane on the reactivity of microglial cells in the course of the experimental model of intracerebral haemorrhage

BACKGROUND

Microglial cells play an important role in the pathophysiology of intracerebral haemorrhage. We have examined the possible influence of sevoflurane on the reactivity of microglial cells during intracranial haemorrhage.

METHODS

Forty adult male rats were divided into two groups. All animals were anaesthetized with fentanyl, dehydrobenzperidol and midazolam. In the experimental group animals additionally received sevoflurane 2.2 vol% end-tidal concentration. Intracranial haemorrhage was produced through infusion of blood into the striatum. The microglial cell population (numerical density of immunoreactive cells and their distribution) was assessed on days 1, 3, 7, 14 and 21 after producing a haematoma using antibodies OX42 and OX6.

RESULTS

In the control group significant differences in the density of OX42-ir cells between 3rd and 7th (81.86 vs. 129.99) (95% CI: -77.99 to -18.25, P = 0.0035) and between 14th and 21st (105.36 vs. 63.81) (95% CI: 13.21 to 69.89, P = 0.006) survival days were observed. However, significant increase of percentage of amoeboid OX42-ir cells between 3rd and 7th (0.98 vs. 48.71) (95% CI: -52.17 to -43.30, P = 0.0001) and between 7th and 14th (48.71 vs. 58.47) (95% CI: -13.96 to -5.55, P = 0.0002) and then their decrease - between 14th and 21st (58.47 vs. 31.74) (95% CI: 22.52 to 30.93, P = 0.0001) days of observation were noted. In the sevoflurane groups OX42-ir cells were not found. On the 3rd day the density of OX6-ir cells in the sevoflurane group was significantly lower than that in the control group (12.39 vs. 34.57) (95% CI: -49.78 to -2.96, P = 0.02). The percentage of an amoeboid form of OX6-ir cells was significantly lower in the sevoflurane group than that in the control group (27.31 vs. 82.03) (95% CI: -72.52 to -36.92, P = 0.0001) (58.76 vs. 82.37) (95% CI: -38.81 to -8.41, P = 0.003) (42.87 vs. 81.55) (95% CI: -53.23 to -24.10, P = 0.0001) respectively for 3rd, 7th and 14th days of survival.

CONCLUSION

Administration of sevoflurane during anaesthesia in animals with intracerebral haemorrhage evoked a decrease of activation of the microglial cells.

Inclusion of Sevoflurane in Cardioplegia Reduces Neutrophil Activity During Cardiopulmonary Bypass

OBJECTIVE

The purpose of this study was to examine the effects of sevoflurane cardioplegia on neutrophil response and complement activation after cardiopulmonary bypass (CPB).

DESIGN

A prospective, randomized clinical investigation.

SETTING

University-affiliated hospital; single institutional.

PARTICIPANTS

Twenty-one male patients undergoing coronary bypass surgery using CPB.

INTERVENTIONS

Eleven patients were randomly assigned to receive sevoflurane 2% as a part of the cardioplegic mixture (SEV). The control group (n = 10) received no sevoflurane in their cardioplegia (control).

MEASUREMENTS AND MAIN RESULTS

Myeloperoxidase activity (MPO) was assayed in coronary sinus blood as a surrogate for neutrophilic response at the termination of CPB. MPO activity in the coronary sinus blood was lower in the patients who received sevoflurane compared with controls. MPO activity was higher in patients with cardiac events at 4-year follow-up when compared with asymptomatic patients. IL-8, C4b, C3d, C5a, and CH50 were assessed in coronary sinus and peripheral blood at time of CPB initiation (T0) and upon the termination of CPB (T2). Peripheral blood sampling occurred at the sixth hour after T0 (T6). IL-8 levels were significantly inhibited in the SEV group when compared with controls at T2 and T6. CH50 (an index of global activation of complement system) decreased 30% at T2 and 52% at T6. The classic component of the complement pathway (C4b) was effectively inhibited in the SEV group, whereas the common pathway (C3d and C5a) was similar in both groups.

CONCLUSIONS

The addition of sevoflurane to cardioplegia is associated with an inhibition of neutrophils after CPB. A major component of the neutrophil response appears to be IL-8 mediated, although the classic complement pathway is also inhibited by sevoflurane.

Differences in the Leukocyte Response to Incision During Upper Abdominal Surgery with Epidural Versus General Anesthesia

Epidural anesthesia attenuates surgical stress responses, such as the immune reaction and the pituitary hormone response. In the present study, we investigated the leukocyte response to initial surgical stimulation during upper abdominal surgery. Twenty adult patients (American Society of Anesthesiologists physical status I approximately II) undergoing elective upper abdominal surgery were randomly assigned to an epidural anesthesia group or a general anesthesia group. An epidural catheter for postoperative pain relief was inserted into all patients before induction. In the epidural anesthesia group, patients obtained preemptive analgesia from Th4 to Th12 with 2% mepivacaine, whereas general anesthesia was maintained with 2 L of oxygen, 4 L of nitrous oxide, and 1% to 3% isoflurane. Changes in the leukocyte count and leukocyte subset distribution were determined before induction (baseline), immediately after induction, 5 minutes after induction, 5 minutes after skin incision, and 5 minutes after peritoneal incision. The changes were significantly different between the groups throughout the observation period (p<0.0001). The general anesthesia group demonstrated an increase in the leukocyte count compared with the baseline data 5 minutes after skin incision and 5 minutes after peritoneal incision (p<0.01). Moreover, these counts were significantly higher in the general anesthesia group than in the epidural anesthesia group (p<0.05). The subset distributions were also significantly different between the groups throughout the observation period (p<0.0001). In the general anesthesia group, neutrophils decreased and lymphocytes increased significantly compared with baseline (p<0.05). Moreover, lymphocyte distribution was significantly higher in the general anesthesia group than in the epidural anesthesia group 5 minutes after peritoneal incision. Thus, anesthesia modifies the early response of leukocytes to surgical stress. The link between the early leukocyte response to surgery and postoperative outcome is the next subject of investigation.

Isoflurane Prevents Platelets from Enhancing Neutrophil-Induced Coronary Endothelial Dysfunction

We evaluated whether platelets can enhance polymorphonuclear neutrophil-induced coronary endothelial dysfunction, and, after observing this, whether isoflurane can prevent the effect. Neutrophils, coronary artery segments, and platelets were obtained from 25 healthy dogs. Coronary artery rings were exposed to neutrophils activated with platelet-activating factor (1.0 microM), and after washing and preconstriction with U46619, were evaluated for concentration-related responses to acetylcholine, an endothelium-dependent vasorelaxing drug. Superoxide production by activated neutrophils was measured spectrophotometrically. Adherence of the activated neutrophils to the endothelium of coronary segments was assessed by direct counting of neutrophils labeled with fluorescent dye. Measurements were performed in absence and presence of isoflurane (1 minimum alveolar concentration) both with and without platelets. The presence of platelets enhanced the neutrophil-induced rightward shift in the concentration-vasorelaxation response curve to acetylcholine (the concentration of acetylcholine required to elicit 50% of maximal relaxation (-log M) was increased from 6.78 +/- 0.7 to 5.26 +/- 0.6), and it increased superoxide oxide production from 45.0 +/- 4.2 to 54.3 +/- 4.2 nM O2-/5 x 10(6) neutrophils and adherence of activated neutrophils from 204 +/- 10 to 268 +/- 5 neutrophils/mm2. Isoflurane abolished these effects of platelets. In conclusion, platelets enhanced the ability of neutrophils to cause coronary endothelial dysfunction. This effect was prevented by isoflurane. This may be attributable to an inhibitory action on superoxide production by the neutrophils leading to reduced expression of endothelial adhesion molecules and, in turn, reduced neutrophil adherence.

The in vitro effect of desflurane preconditioning on endothelial adhesion molecules and mRNA expression

Lower expression of intercellular adhesion molecule-1 (ICAM-1), vascular adhesion molecule-1 (VCAM-1), and E-selectin may be responsible for attenuated ischemic-reperfusion neutrophil adhesion to vascular endothelium. Desflurane reduces ischemia-reperfusion injury. Therefore, we assessed whether desflurane affects the protein expression of ICAM-1 and E-selectin and mRNA expression of ICAM-1 and VCAM-1 of human umbilical venous endothelial cells (HUVEC) stimulated with tumor necrosis factor-alpha (TNF-alpha). HUVEC were preconditioned for 60 min with 1 minimum alveolar concentration desflurane before stimulating with TNF-alpha. Protein expression of adhesion molecules ICAM-1 and E-selectin of HUVEC were evaluated via immunocytochemical techniques combined with image cytometry. ICAM-1 and VCAM-1 mRNA expression of HUVEC were determined via reverse transcription-polymerase chain reaction. Desflurane not only reduced the protein expression of ICAM-1 and E-selectin but also ICAM-1 and VCAM-1 mRNA expression of the HUVEC. The adhesion rate of neutrophils with desflurane-treated HUVEC was slower. The decreased neutrophil adhesion on the desflurane-treated HUVEC correlated well with the decrease in adhesion molecule expression. These results show that desflurane affects the expression of adhesion molecules involved in the multistep process of neutrophil recruitment. Desflurane related ischemia-reperfusion injury reduction correlates well with expression inhibition of ICAM-1, VCAM-1, and E-selectin that mediates neutrophil rotation and firm adhesion on the vascular endothelium.

Isoflurane pretreatment supports hemodynamics and leukocyte rolling velocities in rat mesentery during lipopolysaccharide-induced inflammation

We hypothesized that the protective effects of isoflurane (ISO) pretreatment on the vasculature may be attributed, in part, to altered leukocyte-endothelial interactions. Rats were anesthetized with pentobarbital and then randomized into four groups: control, ISO-control (pretreatment with 30 min of 1.4% ISO), lipopolysaccharide (LPS; 10 mg/kg IV), and ISO-LPS (ISO pretreatment and then LPS). The mesentery was prepared for intravital videomicroscopy. Mean arterial blood pressure (MAP), along with microcirculatory variables that included postcapillary venular and arteriolar blood flow velocity and leukocyte dynamics (number of rolling and adherent leukocytes and individual rolling leukocyte velocities), were measured hourly (baseline and at 0-4 h). In LPS rats, ISO pretreatment significantly (P < 0.05) attenuated the decrease in MAP at 2 and 4 h after LPS and increased leukocyte rolling velocities after 2-4 h. Four hours after LPS, leukocyte rolling velocities were >200% more rapid (63.7 +/- 27.6 microm/s versus 19.8 +/- 6.4 micro m/s) in ISO-LPS versus LPS rats. In control rats, ISO pretreatment had no effect on MAP or leukocyte rolling velocities but increased the number of rolling leukocytes. ISO pretreatment had no effect on arteriolar and postcapillary venular blood flow velocity in LPS rats or leukocyte adherence in LPS or control rats. In conclusion, ISO pretreatment supported hemodynamics and increased leukocyte rolling velocities but did not alter the number of rolling or adherent leukocytes in the mesenteric microcirculation during LPS-induced inflammation.

IMPLICATIONS

Isoflurane pretreatment supported hemodynamics and increased leukocyte rolling velocities in the mesenteric microcirculation during lipopolysaccharide-induced inflammation. Faster rolling velocities may reduce the incidence of inflammation by decreasing leukocyte-endothelial interactions and cellular injury.

Effect of isoflurane on monocyte adhesion molecule expression in human whole blood

BACKGROUND

Recruitment of monocytes to inflamed tissue is a crucial step in the acute inflammatory reaction. Adherence of monocytes to endothelial cells followed by transmigration depends on monocyte surface adhesion molecules, inflammatory cytokines and chemoattractant chemokines. In the present study, we determined the effect of isoflurane on monocyte adhesion receptor expression in vitro.

METHODS

Citrated whole blood was incubated for 60 min with either 0.5 or 1 MAC isoflurane. In unstimulated blood samples and after stimulation with N-formyl-methionyl-leucyl-phenylalanine (FMLP) monocyte cell-surface expression of the selectins PSGL-1 and L-selectin, and the beta2-integrins CD11a and CD11b were evaluated by flow cytometry.

RESULTS

Isoflurane reduced significantly the expression of PSGL-1 on unstimulated monocytes, whereas the remaining selectins and beta2-integrins were not affected. At both concentrations, the FMLP-induced removal of PSGL-1 from the monocyte surface was increased. Furthermore, at 1 MAC isoflurane the FMLP-induced increase in CD11a expression was significantly inhibited. The surface expression of L-selectin and CD11b was not affected following exposure to isoflurane.

CONCLUSION

Isoflurane increases the removal of the selectin PSGL-1 from the monocyte surface. Since PSGL-1 is important during the initial step of monocyte adhesion to endothelial P-selectin, the decrease in monocyte surface PSGL-1 may have profound effects on monocyte-endothelial interactions. Furthermore, the effects of isoflurane on monocyte adhesion molecule expression are different from those reported for neutrophils.

The effects of sevoflurane and desflurane in vitro on platelet-leukocyte adhesion in whole blood

The interaction between platelets and leukocytes plays an important role in inflammatory and thrombotic processes. We investigated whether the volatile anaesthetics sevoflurane and desflurane alter the formation of platelet-leukocyte aggregates and the expression of P-selectin on platelets. Whole blood was incubated with 1 and 2 minimum alveolar concentration (MAC) sevoflurane or desflurane. Unstimulated and adenosine diphosphate, or thrombin receptor agonist peptide-6-stimulated samples were stained with fluorochrome-conjugated antibodies. The formation of platelet-leukocyte conjugates and the expression of P-selectin on platelets were measured using flow cytometry. Sevoflurane was found to enhance the binding of platelets to lymphocytes, neutrophils and monocytes, it also increased the expression of P-selectin on platelets especially in the stimulated samples. Desflurane decreased the percentage of lymphocyte-platelet, neutrophil-platelet and monocyte-platelet conjugates principally in unstimulated samples. The results show that these two volatile anaesthetics have differing effects on the formation of platelet-leukocyte conjugates in vitro. Sevoflurane also enhanced the expression of P-selectin on platelets.