Volatile anesthetics isoflurane and sevoflurane directly target and attenuate Toll-like receptor 4 system

Toll-like receptors and integrins crosstalk

Immune system recognizes invading microbes at both pathogen and antigen levels. Toll-like receptors (TLRs) play a key role in the first-line defense against pathogens. Major functions of TLRs include cytokine and chemokine production. TLRs share common downstream signaling pathways with other receptors. The crosstalk revolving around TLRs is rather significant and complex, underscoring the intricate nature of immune system. The profiles of produced cytokines and chemokines via TLRs can be affected by other receptors. Integrins are critical heterodimeric adhesion molecules expressed on many different cells. There are studies describing synergetic or inhibitory interplay between TLRs and integrins. Thus, we reviewed the crosstalk between TLRs and integrins. Understanding the nature of the crosstalk could allow us to modulate TLR functions via integrins.

Mechanism of isoflurane‑mediated breast cancer growth in vivo

Use of volatile anesthetics is associated with worse outcome following tumor resection surgery compared with the use of intravenous anesthetics. However, the underlying mechanism has not been clearly delineated yet in vivo. The EO771 cell-based congenic breast cancer model was used in the present study. Isoflurane directly binds to and inhibits two adhesion molecules, leukocyte function-associated antigen-1 (LFA-1) and macrophage-1 antigen (Mac-1). Similarly, exposure to sevoflurane, another volatile anesthetic and LFA-1 inhibitor, is associated with an increase in breast cancer size compared with non-exposure. Thus, the present study first examined the role of LFA-1 and Mac-1 in the EO771 breast cancer model. Both LFA-1 deficiency and inhibition enhanced tumor growth, which was supported by cytokine and eicosanoid data profiles. By contrast, Mac-1 deficiency did not affect tumor growth. The exposure to isoflurane and sevoflurane was associated with an increase in breast cancer size compared with non-exposure. These data suggested that isoflurane enhanced tumor growth by interacting with LFA-1. Isoflurane exposure did not affect tumor growth in LFA-1-deficient mice. In summary, the present data showed that LFA-1 deficiency facilitated breast cancer growth, and isoflurane, an LFA-1 inhibitor, also increased breast cancer growth.

The landscape of immune dysregulation in pediatric sepsis at a single-cell resolution

Recognizing immune dysregulation as a hallmark of sepsis pathophysiology, leukocytes have attracted major attention of investigation. While adult and pediatric sepsis are clinically distinct, their immunological delineation remains limited. Single cell technologies facilitated the characterization of immune signatures. We tackled to delineate immunological profiles of pediatric sepsis at a single-cell level by analyzing blood samples from six septic children, at both acute and recovery phases, and four healthy children. 16 single-cell transcriptomic datasets were analyzed and compared to adult sepsis dataset. We showed a unique shift in neutrophil subpopulations and functions between acute and recovery phases, along with the regulatory role of resistin. Neutrophil signatures were comparable between adult and pediatric sepsis. Innate-like CD4 T cells were predominantly and uniquely observed in acute phase of pediatric sepsis. Our study serves as a rich source of information about the phenotypic diversity and trajectory of circulating immune cells during pediatric sepsis.

Cystic Fibrosis Mice Are Highly Susceptible to Repeated Acute Pseudomonas aeruginosa Pneumonia after Intranasal Inoculation

Cystic fibrosis (CF) is a genetic disorder caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) that controls chloride current. A number of different CFTR transgenic mouse lines have been developed and subjected to both acute and chronic infection models. However, prior studies showed no substantial differences in bacterial clearance between CF and non-CF mice after single inoculations. Here, using F508del transgenic CF mice, we examined the role of repeated acute Pseudomonas aeruginosa (PA) infection, with the second inoculation 7 days after the first. We found that CF mice were more susceptible to PA infection than non-CF mice following the second inoculation, with non-CF mice showing better neutrophil recruitment and effector functions. We further investigated the characteristics of lung immune cells using single-cell RNA sequencing, finding that non-CF lung neutrophils had more prominent upregulation of adhesion molecules including intercellular adhesion molecule-1 (ICAM-1) compared to CF lung neutrophils. Although people with CF are often colonized with bacteria and have high numbers of neutrophils in the airways during chronic infection, these data suggest that CF neutrophils have deficient effector functions in the setting of repeated acute infection.

The landscape of immune dysregulation in pediatric sepsis at a single-cell resolution

Recognizing immune dysregulation as a hallmark of sepsis pathophysiology, leukocytes have attracted major attention of investigation. While adult and pediatric sepsis are clinically distinct, their immunological delineation remains limited. Breakthrough of single cell technologies facilitated the characterization of immune signatures. We tackled to delineate immunological profiles of pediatric sepsis at a single-cell level by analyzing blood samples from six septic children, at both acute and recovery phases, and four healthy children. 16 single-cell transcriptomic datasets (96,156 cells) were analyzed and compared to adult sepsis dataset. We showed a unique shift in neutrophil subpopulations and functions between acute and recovery phases, along with examining the regulatory role of resistin. Neutrophil signatures were comparable between adult and pediatric sepsis. Innate-like CD4 T cells were predominantly and uniquely observed in acute phase of pediatric sepsis. Our study provides a thorough and comprehensive understanding of immune dysregulation in pediatric sepsis.

Isoflurane and Pentobarbital Anesthesia for Pulmonary Studies Requiring Prolonged Mechanical Ventilation in Mice

Mechanical ventilation can be used in mice to support high-risk anesthesia or to create clinically relevant, intensive care models. However, the choice of anesthetic and inspired oxygen concentration for prolonged procedures may affect basic physiology and lung inflammation. To characterize the effects of anesthetics and oxygen concentration in mice experiencing mechanical ventilation, mice were anesthetized with either isoflurane or pentobarbital for tracheostomy followed by mechanical ventilation with either 100% or 21% oxygen. Body temperature, oxygen saturation, and pulse rate were monitored continuously. After 6 h, mice were euthanized for collection of blood and bronchoalveolar lavage fluid for evaluation of biomarkers of inflammation and lung injury, including cell counts and cytokine levels. Overall, both isoflurane and pentobarbital provided suitable anesthesia for 6 h of mechanical ventilation with either 21% or 100% oxygen. We found no differences in lung inflammation biomarkers attributable to either oxygen concentration or the anesthetic. However, the combination of pentobarbital and 100% oxygen resulted in a significantly higher concentration of a biomarker for lung epithelial cell injury. This study demonstrates that the combination of anesthetic agent, mechanical ventilation, and inspired oxygen concentrations can alter vital signs and lung injury biomarkers during prolonged procedures. Their combined impact may influence model development and the interpretation of research results, warranting the need for preliminary evaluation to establish the baseline effects.

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.

Pro-Con Debate: Should All General Anesthesia Be Done Using Target-Controlled Propofol Infusion Guided by Objective Monitoring of Depth of Anesthesia?

In this Pro-Con commentary article, we discuss whether all general anesthesia should be done using target-controlled propofol anesthesia guided by monitoring of depth of anesthesia. This is an ongoing debate since more than 25 years, representing a scientific, cultural as well as geographical divide in the anesthesia community. The Pro side argues that total intravenous anesthesia causes less postoperative nausea and higher patient satisfaction than anesthesia using volatile anesthetics. Target-controlled infusion (TCI) of anesthetic agents allows for better titration of intravenous anesthesia using pharmacokinetic models. Processed EEG monitors, such as bispectral index monitoring, allows for better assessing the effect of TCI anesthesia than solely assessment of clinical parameters, such as ECG or blood pressure. The combination of TCI propofol and objective depth of anesthesia monitoring allows creating a pharmacokinetic-pharmacodynamic profile for each patient. Finally, anesthesia using volatile anesthetics poses health risks for healthcare professionals and contributes to greenhouse effect. The Con side argues that for procedures accompanied with ischemia and reperfusion injury of an organ or tissue and for patients suffering from a severe inflammation' the use of volatile anesthetics might well have its advantages above propofol. In times of sudden shortage of drugs, volatile anesthetics can overcome the restriction in the operating theater or even on the intensive care unit, which is another advantage. Volatile anesthetics can be used for induction of anesthesia when IV access is impossible, end-tidal measurements of volatile anesthetic concentration allows confirmation that patients receive anesthetics. Taking environmental considerations into account, both propofol and volatile anesthetics bear certain harm to the environment, be it as waste product or as greenhouse gases. The authors therefore suggest to carefully considering advantages and disadvantages for each patient in its according environment. A well-balanced choice based on the available literature is recommended. The authors recommend careful consideration of advantages and disadvantages of each technique when tailoring an anesthetic to meet patient needs. Where appropriate, anesthesia providers are encouraged to account for unique features of anesthetic drug behavior, patient-reported and observed postoperative outcomes, and economic and environmental considerations when choosing any of the 2 described techniques.

Bupivacaine inhibits the TLR4- and TLR2-Myd88/NF-κB pathways in human leukocytes

Local anesthetics have anti-inflammatory effects. Because most previous experiments were performed with supra-therapeutic concentrations, we measured the effects of clinically relevant concentrations of bupivacaine on the Toll like receptor 4 (TLR4)- and TLR2-myeloid differentiation primary response 88 (MyD88)-nuclear factor kappa-light-chain-enhancer of activated B cell (NF-κB) pathways. We measured tumor necrosis factor alpha (TNF-α) and prostaglandin E2 (PGE2) release, p38 mitogen-activated protein kinase (MAP-kinase) phosphorylation and translocation of NF-κB in human peripheral blood mononuclear cells (hPBMCs) and human monocytes challenged with lipopolysaccharide (LPS) or tripalmitoylated lipopeptide Pam3CysSerLys4 (Pam3CSK4) in the presence or absence of bupivacaine. Similarly, we measured the effect of bupivacaine on HEK293 cells expressing the hTLR4 and the hTLR2 genes and challenged with LPS or Pam3CSK4. Finally, molecular docking simulations of R(+)- and S(-)-bupivacaine binding to the TLR4-myeloid differentiation protein 2 (MD-2) complex and to the TLR2/TLR1 heterodimer were performed. In PBMCs, bupivacaine from 0.1 to 100 μM inhibited LPS-induced TNF-α and PGE2 secretion, phosphorylation of p38 and nuclear translocation of NF-κB in monocytes. Bupivacaine similarly inhibited the effects of Pam3CSK4 on TNF-α secretion. Bupivacaine inhibited the effect of LPS on HEK293 cells expressing the human TLR4 receptor and the effect of Pam3CSK4 on HEK293 cells expressing the human TLR2 receptor. Molecular docking showed that bupivacaine binds to the MD-2 co-receptor of TLR4 and to the TLR2 receptor. Contrary to numerous experiments performed with supratherapeutic doses, our results were obtained with concentrations of bupivacaine as low as 0.1 μM. We conclude that bupivacaine modulates the inflammatory reactions such as those observed after surgery or trauma, at least partly by inhibiting the TLR4- and TLR2-NF-κB pathways.

Narrative review of systemic inflammatory response mechanisms in cardiac surgery and immunomodulatory role of anesthetic agents

Although surgical techniques and perioperative care have made significant advances, perioperative mortality in cardiac surgery remains relatively high. Single- or multiple-organ failure remains the leading cause of postoperative mortality. Systemic inflammatory response syndrome (SIRS) is a common trigger for organ injury or dysfunction in surgical patients. Cardiac surgery involves major surgical dissection, the use of cardiopulmonary bypass (CPB), and frequent blood transfusions. Ischemia-reperfusion injury and contact activation from CPB are among the major triggers for SIRS. Blood transfusion can also induce proinflammatory responses. Here, we review the immunological mechanisms of organ injury and the role of anesthetic regimens in cardiac surgery.

Optimized flow cytometry assays to monitor neutrophil activation in human and mouse whole blood samples

Polymorphonuclear neutrophils (PMNs) protect the host from invading microorganisms. However, excessively activated PMNs can also cause damage to host tissues under inflammatory conditions. Here we developed simple assays to determine the activation state of PMNs in human whole blood that contains soluble mediators known to influence PMN functions. Because mouse models are widely used to study the role of PMNs in infectious and inflammatory diseases, we adapted these assays for the rapid and reliable assessment of PMN functions in murine blood samples. Freshly collected whole blood samples were stimulated with agonists of the formyl peptide receptors (FPR) of PMNs and changes in reactive oxygen species (ROS) production and the expression of CD11b, CD62L (L-selectin), CD66b, and CD63 on the cell surface were analyzed with flow cytometry. We optimized these assays to minimize inadvertent interferences such as cell stress generated during sample handling and the loss of plasma mediators that regulate PMN functions. Human PMNs readily responded to the FPR agonist N-formyl-methionyl-leucyl-phenylalanine (fMLP). The most sensitive responses of human PMNs to fMLP were CD11b, CD62L, and CD66b expression with half maximal effective concentrations (EC₅₀) of 5, 8, and 6 nM fMLP, respectively. CD63 expression and ROS production required markedly higher fMLP concentrations with EC₅₀ values of 19 and 50 nM fMLP, respectively. Mouse PMNs did not respond well to fMLP and required significantly higher concentrations of the FPR agonist WKYMVm (W-peptide) to achieve equivalent cell activation. The most sensitive response of mouse PMNs was ROS production with an EC₅₀ of 38 nM W-peptide. Because mice do not express CD66b, we only assessed the expression of CD62L, CD11b, and CD63 with EC₅₀ values of 54, 119, and 355 nM W-peptide, respectively. Validation of our optimized assays showed that they sensitively detect the responses of human PMNs to priming with endotoxin in vitro as well as the corresponding responses of murine PMNs to bacterial infection in a sepsis model. We conclude that these optimized assays could be useful tools for the monitoring of patients with infections, sepsis, and other inflammatory conditions as well as for the design and interpretation of preclinical studies of these diseases in mouse models.

αDβ2 as a novel target of experimental polymicrobial sepsis

Since sepsis was defined three decades ago, it has been a target of intensive study. However, there is no specific sepsis treatment available, with its high mortality and morbidity. αDβ2 (CD11d/CD18) is one of the four β2 integrin members. Its role in sepsis has been limitedly studied. Using an experimental polymicrobial sepsis model, we found that the deficiency of αDβ2 was associated with less lung injury and better outcome, which was in sharp contrast to other β2 integrin member αLβ2 (CD11a/CD18), and αMβ2 (CD11b/CD18). This phenotype was supported by a reduction of bacterial loads in αDβ2 knockout mice. Further analysis showed that the deficiency of αDβ2 led to a reduction of neutrophil cell death as well as an increase in neutrophil phagocytosis in both murine and human systems. Our data showed a unique role of αDβ2 among the β2 integrin members, which would serve as a potential target to improve the outcome of sepsis.

Volatile sedation in sepsis: a promising therapeutic approach or a venture doomed to fail?

Preclinical strategies targeting sepsis often had a single target and could not be translated into the clinical setting. Volatile sedation modulates multiple aspects of inflammation and improves sepsis-related survival in animal models. Whether a similar effect can be achieved in humans is unclear. Only a prospective clinical trial will be able to answer this question. The implementation of such a study in times when volatile anaesthetics are the focus of attention because of their greenhouse effect and their carbon dioxide emission will be a challenge, even though the alternative, i.v. sedation, is still insufficiently investigated in this respect.

Propofol directly binds to and inhibits TLR7

Sedatives/anesthetics are important medical tools to facilitate medical care and increase patients' comfort. Increasingly, there is recognition that sedatives/anesthetics can modulate immune functions. Toll-like receptors (TLRs) are major pattern recognition receptors involved in the recognition of microbial components. TLR7 recognizes single-strand RNA virus such as influenza and SARS-CoV2 viruses and initiates interferon (IFN) responses. IFN production triggered by TLR7 stimulation is a critical anti-viral response. For example, patients with TLR7 variants including loss-of- function variants were associated with severe COVID-19. Taken together, it is important to determine if sedatives/anesthetics mitigate TLR7 function. We have previously showed that TLR7-mediated activation was not affected by volatile anesthetics. However, we found that propofol attenuated TLR7 activation among intravenous sedatives in the reporter assay. TLR7 agonist R837 stimulation increased TNF-α, IL-1β, IL-6, IL-10, and IFN-β mRNA levels in bone marrow-derived dendritic cells, while these levels were attenuated by propofol. Our murine lung slice experiments showed that propofol attenuated IFN production. R837 increased IFN-β expression in the lungs, and propofol attenuated IFN-β expression in an in vivo model of R837 intranasal instillation. We also found that propofol directly bound to and hindered its association of TLR7 with MyD88. Our analysis using fropofol, propofol derivative showed that the hydroxyl group in propofol was important for propofol-TLR7 interaction.

Isoflurane attenuates sepsis-associated lung injury

Acute lung injury is one of major complications associated with sepsis, responsible for morbidity and mortality. Patients who suffer from acute lung injury often require respiratory support under sedations, and it would be important to know the role of sedatives in lung injury. We examined volatile anesthetic isoflurane, which is commonly used in surgical setting, but also used as an alternative sedative in intensive care settings in European countries and Canada. We found that isoflurane exposure attenuated neutrophil recruitment to the lungs in mice suffering from experimental polymicrobial abdominal sepsis. We found that isoflurane attenuated one of major neutrophil chemoattractants LTB4 mediated response via its receptor BLT1 in neutrophils. Furthermore, we have shown that isoflurane directly bound to BLT1 by a competition assay using newly developed labeled BLT1 antagonist, suggesting that isoflurane would be a BLT1 antagonist.

Sevoflurane Dampens Acute Pulmonary Inflammation via the Adenosine Receptor A2B and Heme Oxygenase-1

Acute respiratory distress syndrome is a life-threatening disease associated with high mortality. The adenosine receptor A2B (Adora2b) provides anti-inflammatory effects, which are also associated with the intracellular enzyme heme oxygenase-1 (HO-1). Our study determined the mechanism of sevoflurane’s protective properties and investigated the link between sevoflurane and the impact of a functional Adora2b via HO-1 modulation during lipopolysaccharide (LPS)-induced lung injury. We examined the LPS-induced infiltration of polymorphonuclear neutrophils (PMNs) into the lung tissue and protein extravasation in wild-type and Adora2b−/− animals. We generated chimeric animals, to identify the impact of sevoflurane on Adora2b of hematopoietic and non-hematopoietic cells. Sevoflurane decreased the LPS-induced PMN-infiltration and diminished the edema formation in wild-type mice. Reduced PMN counts after sevoflurane treatment were detected only in chimeric mice, which expressed Adora2b exclusively on leukocytes. The Adora2b on hematopoietic and non-hematopoietic cells was required to improve the permeability after sevoflurane inhalation. Further, sevoflurane increased the protective effects of HO-1 modulation on PMN migration and microvascular permeability. These protective effects were abrogated by specific HO-1 inhibition. In conclusion, our data revealed new insights into the protective mechanisms of sevoflurane application during acute pulmonary inflammation and the link between sevoflurane and Adora2b, and HO-1 signaling, respectively.

Effect of sevoflurane preconditioning on sleep reintegration after alteration by lipopolysaccharide

Despite extensive evidence on the organ protective effects of sevoflurane, its effect on disturbed sleep remains unclear. We hypothesised that sevoflurane preconditioning positively impacts disturbed sleep caused by systemic inflammation. A prospective, randomised laboratory investigation was conducted in C57BL/6J mice. A mouse model of lipopolysaccharide (LPS)-induced systemic inflammation was employed to investigate the effects of sevoflurane on sleep recovery. Symptom recovery was evaluated through electroencephalography/electromyography (EEG/EMG) and histological studies. The mice were exposed to 2% sevoflurane before and after peritoneal injection of LPS. The EEG and EMG were recorded for 24 h after the procedure. Brain tissue was harvested after the sevoflurane/LPS procedure and was immunostained using individual antibodies against choline acetyltransferase (ChAT) and Fos. The ChAT-positive and ChAT/Fos double-positive cells were analysed quantitatively in the pedunculopontine tegmental nucleus and laterodorsal tegmental nucleus (PPTg/LDTg). Compared with control mice, mice preconditioned with sevoflurane but not post-conditioned showed a significant increase in rapid eye movement (REM) sleep during EEG recording following the LPS challenge. They also demonstrated a shorter REM latency, indicating an early recovery from LPS-altered sleep. The bouts of REM episodes were retained with sevoflurane preconditioning. More ChAT/Fos double-positive cells were observed in the PPTg/LDTg in the sevoflurane preconditioning plus LPS group than in the LPS-only group. Sevoflurane preconditioning promotes recovery from altered sleep induced by systemic inflammation. Activation of PPTg/LDTg is considered a mechanism underlying sleep reintegration. The recovery phenomenon shows potential for clinical application in cases of sleep disturbances induced by systemic inflammation.

Isoflurane Attenuates Cerebral Ischaemia-Reperfusion Injury via the TLR4-NLRP3 Signalling Pathway in Diabetic Mice

Ischaemic stroke is a severe disease worldwide. Restoration of blood flow after ischaemic stroke leads to cerebral ischaemia-reperfusion injury (CIRI). Various operations, such as cardiac surgery with deep hypothermic circulatory arrest, predictably cause cerebral ischaemia. Diabetes is related to the occurrence of perioperative stroke and exacerbates neurological impairment after stroke. Therefore, the choice of anaesthetic drugs has certain clinical significance for patients with diabetes. Isoflurane (ISO) exerts neuroprotective and anti-neuroinflammatory effects in patients without diabetes. However, the role of ISO in cerebral ischaemia in the context of diabetes is still unknown. Toll-like receptor 4 (TLR4) and NOD-like receptor pyrin domain-containing protein 3 (NLRP3) inflammasome activation play important roles in microglia-mediated neuroinflammatory injury. In this study, we treated a diabetic middle cerebral artery occlusion mouse model with ISO. We found that diabetes exacerbated cerebral ischaemia damage and that ISO exerted neuroprotective effects in diabetic mice. Then, we found that ISO decreased TLR4-NLRP3 inflammasome activation in microglia and the excessive autophagy induced by CIRI in diabetic mice. The TLR4-specific agonist CRX-527 reversed the neuroprotective effects of ISO. In summary, our study indicated that ISO exerts neuroprotective effects against the neuroinflammation and autophagy observed during diabetic stroke via the TLR4-NLRP3 signalling pathway.

The immunomodulatory mechanism of dexmedetomidine

Dexmedetomidine has been increasingly introduced into the perioperative care of surgical patients. Because a subset of anesthetics/sedatives are immunomodulatory, it is critical to understand the role of dexmedetomidine in our host immune functions. Here we reviewed the role of dexmedetomidine in different immune cells. We also reviewed published clinical articles that described the role of dexmedetomidine in organ injury, cancer surgery, and infection. In animal studies, dexmedetomidine attenuated organ injury. In clinical studies, dexmedetomidine was associated with an improvement in outcomes in cardiac surgery and transplant surgery. However, there is a paucity in research examining how dexmedetomidine is associated with these outcomes. Further studies are needed to understand its clinical application from immunological standpoints.

Anesthetics isoflurane and sevoflurane attenuate flagellin-mediated inflammation in the lung

Isoflurane and sevoflurane are volatile anesthetics (VA) widely used in clinical practice to provide general anesthesia. We and others have previously shown that VAs have immunomodulatory effects and may have a significant impact on the progression of disease states. Flagellin is a component of Gram negative bacteria and plays a significant role in the pathophysiology of bacterial pneumonia through its binding to Toll-like Receptor 5 (TLR5). Our results showed that VAs, not an intravenous anesthetic, significantly attenuated the activation of TLR5 and the release of the neutrophil chemoattractant IL-8 from lung epithelial cells. Furthermore, flagellin-induced lung injury was significantly attenuated by VAs by inhibiting neutrophil migration to the bronchoalveolar space. The lungs of cystic fibrosis (CF) patients are highly colonized by Pseudomonas aeruginosa, which causes inflammation. The retrospective study of oxygenation in patients with CF who had received VA versus intravenous anesthesia suggested that VAs might have the protective effect for gas exchange. To understand the interaction between VAs and TLR5, a docking simulation was performed, which indicated that isoflurane and sevoflurane docked into the binding interphase between TLR5 and flagellin.

Surgical Site Infections and Perioperative Optimization of Host Immunity by Selection of Anesthetics

Surgical site infections are significant health care issues, and efforts to mitigate their occurrence have been ongoing worldwide, mainly focusing to reduce the spillage of microbes to the otherwise sterile tissues. Optimization of host immunity has been also recognized including temperature regulation (normothermia), adequate oxygenation, and glucose management. A number of papers have described the role of anesthetics in host immunity. The role of anesthetics in postoperative outcomes including surgical site infections has been also studied. We will review the current literature and propose the importance of anesthetic selection to potentially mitigate surgical site infections.

Comparative Effect of Propofol and Volatile Anesthetics on Postoperative Pulmonary Complications After Lung Resection Surgery: A Randomized Clinical Trial

BACKGROUND

The effect of general anesthetics (propofol and volatile anesthetics) on pulmonary outcome after lung resection surgery with one-lung ventilation (OLV) is yet undetermined. We evaluated the effect of intravenous anesthesia (propofol) and volatile anesthesia (sevoflurane or desflurane) regimens on postoperative pulmonary complications (PPCs) in patients undergoing lung resection surgery.

METHODS

This prospective, randomized controlled trial enrolled 555 adult patients scheduled for lung resection surgery with OLV. Participants were randomized to 1 of 3 general anesthetic regimens (propofol, sevoflurane, or desflurane). Standard anesthesia and ventilation protocols were followed in all groups. The primary outcome was a composite of PPCs in the first 7 postoperative days. Secondary outcomes included the severity of PPCs and major postoperative complications classification. Intergroup difference in the primary outcome was assessed for significance using the Pearson χ2 test.

RESULTS

Of 837 patients who were assessed for eligibility, 555 were randomized and 545 were analyzed. One hundred and seventy-nine patients were assigned to the propofol group, 182 in the sevoflurane group, and 184 in the desflurane group. The incidence of PPCs did not differ between the combined volatile anesthetics (sevoflurane and desflurane) group and the propofol group (21.9% vs 24.0%; odds ratio, 0.89; 95% confidence interval, 0.58-1.35; P = .570). The PPCs grade and Clavien-Dindo scores did not differ significantly across groups.

CONCLUSIONS

In patients undergoing lung resection surgery with OLV, general anesthesia with volatile anesthetics (sevoflurane or desflurane) did not reduce PPCs compared with propofol. No difference in secondary outcomes was observed.

The Microbial Flora in an Experimental Polymicrobial Abdominal Sepsis Model Probed by 16S rRNA Sequencing

BACKGROUND

Cecal ligation and puncture (CLP) surgery is a widely used preclinical model to induce and study sepsis because it is considered to recapitulate the course of human sepsis the most. This model is highly dependent on the polymicrobial gut flora and represents polymicrobial abdominal sepsis. While the majority of studies using CLP model have focused on the delineation of host immune responses, a limited number of reports have described the composition of microbial strains in this model, although microbial composition can significantly affect the outcome of sepsis in general.

METHODS

CLP surgery was performed in mice on C57BL6/J from the Jackson laboratory. We examined the composition of microbes at the peritoneal cavity using 16S rRNA sequencing after CLP surgery at 12 and 24 hours. Baseline cecal microbial flora was also analyzed.

RESULTS

The bacteria strains from the initial cecum flora consisted of mixed aerobic and anaerobic flora. There was a significant change of bacteria flora from the peritoneal cavity between 12 and 24 hours following CLP surgery. Particularly a significantly increased proportion of anaerobic microbes were noted at 24 hours after CLP surgery. We also tested bacterial composition of cecal flora of mice on the same background from the same vendor 6 months later. Baseline cecal microbial flora was different from earlier mice, showing that baseline cecal flora could be different depending on the batch of mice.

CONCLUSION

There was a dynamical chance of peritoneal microbes during CLP sepsis. Potential difference in baseline cecal flora should be kept in mind upon CLP surgery even when using mice from the same vendor.

Mechanistic consideration of the effect of perioperative volatile anesthetics on phagocytes

A growing literature has shown that volatile anesthetics are promiscuous molecules targeting multiple molecules, some of which are critical for immunological functions. We focused on studies that delineated target molecules of volatile anesthetics on immune cells and summarized the effects of volatile anesthetics on immune functions. We also presented the perspectives of studying volatile anesthetics-mediated immunomodulation.

The Role of Anesthetic Management in Surgical Site Infections After Pediatric Intestinal Surgery

BACKGROUND

Although surgical site infections (SSIs) remain a significant health care issue, a limited number of studies have analyzed risk factors for SSIs in children, particularly the role of intraoperative anesthetic management. Pediatric patients are less likely to have major adult risk factors for SSIs such as smoking and diabetes. Thus children may be more suitable as a cohort for examining the role of intraoperative anesthetics in SSIs.

AIM

We examined an association between SSI incidence and anesthetic management in children who underwent elective intestinal surgery in a single institution.

METHODS

We performed a retrospective study of 621 patients who underwent elective intestinal surgery under general anesthesia between January 2017 and September 2019, with primary outcome as the incidence of SSIs. We compared patients who were dichotomized in accordance with the median of the sevoflurane dose. We used propensity score (PS) pairwise matching of these patients to avoid selection biases. PS matching yielded 204 pairs of patients.

RESULTS

We found that higher doses of sevoflurane were associated with a higher incidence of SSIs (9.8% versus 3.9%, P = 0.019). We adjusted for intraoperative factors that were not included in the PS adjustment factors, and multivariate regression analysis after PS matching showed compatible results (odds ratio: 2.58, 95% confidence interval: 1.11-6.04, P = 0.028).

CONCLUSIONS

Higher doses of sevoflurane are associated with increased odds of SSIs after pediatric elective intestinal surgery. A randomized controlled study of volatile anesthetic-based versus intravenous anesthetic-based anesthesia will be needed to further determine the role of anesthetic drugs in SSI risk.

The effect of anesthetics on toll like receptor 9

Toll like receptors (TLRs) are critical receptors to respond to danger signals, and their functions are relevant in the perioperative period. We previously reported that volatile anesthetics directly bound to TLR2 and TLR4 and attenuated their functions. Given that TLR9 can respond to mitochondrial DNA, a danger signal that is released upon tissue injury, we examined the role of anesthetics on TLR9 function. Our reporter assay showed that volatile anesthetics isoflurane and sevoflurane increased the activation of TLR9, while propofol attenuated it. TLR9 activation occurs via its dimerization. The dimerization is facilitated by unmethylated cytosine-phosphate-guanine (CpG) DNA as well as DNA containing cytosine at the second position from 5'-end (5'-xCx DNA). Our structural analysis using photoactivable anesthetics and rigid docking simulation showed that isoflurane and sevoflurane bound to both TLR9 dimer interface and 5'-xCx DNA binding site. Propofol bound to the TLR9 antagonist binding site. This is the first illustration that anesthetics can affect the binding of nucleic acids to their receptor. This study sets the foundation for the effect of anesthetics on TLR9 and will pave the way for future studies to determine the significance of such interactions in the clinical setting.

Sevoflurane-induced cognitive decline in aged mice: Involvement of toll-like receptors 4

Toll-like receptors 4 (TLR4) contributes to the pathogenesis of some neurodegenerative diseases. However, little is known about whether TLR4 is associated with sevoflurane-induced cognitive decline. This investigation aims to address the effect of global TLR4 gene knockout on cognitive decline following sevoflurane exposure to mice. Wild-type and TLR4^-/- mice were exposed to 3% sevoflurane. Novel object recognition test and Y-maze test were used to analyze cognitive function. Tumor necrosis factor α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) in plasma and hippocampus were measured by ELISA. Peripheral administration of recombinant TNF-α to TLR4^-/- mice was used to observed the role of TNF-α in cognitive function following sevoflurane. Our results showed that, in contrast to wild-type mice, TLR4 deficiency protected against the cognitive function impairment following sevoflurane exposure, and abrogated IL-1β, IL-6 and TNF-α response to sevoflurane in the system and the hippocampus. Subcutaneous administration of recombinant TNF-α elevated these cytokine levels in the hippocampus, and resulted in cognitive decline in TLR4^-/- mice exposed to sevoflurane. Taken together, our results identify the crucial role of TLR4 in sevoflurane-induced cognitive decline, and showed that TLR4 mediated pro-inflammatory cytokine response to sevoflurane, and consequent cognitive decline in aged mice exposed to sevoflurane, and imply a novel target for improvement and therapy of sevoflurane-associated cognitive decline.

Volatile Anesthetic Sevoflurane Attenuates Toll-Like Receptor 1/2 Activation

BACKGROUND

Although immunomodulatory effects of anesthetics have been increasingly recognized, their underlying molecular mechanisms are not completely understood. Toll-like receptors (TLRs) are one of the major receptors to recognize invading pathogens and danger signals from damaged host tissues to initiate immune responses. Among the TLR family, TLR2 and TLR4 recognize a wide range of ligands and are considered to be important players in perioperative pathophysiology. Based on our recent finding that volatile anesthetics modulate TLR4 function, we tested our hypothesis that they would also modulate TLR2 function.

METHODS

The effect of anesthetics isoflurane, sevoflurane, propofol, and dexmedetomidine on TLR2 activation was examined by reporter assays. An anesthetic that affected the activation was subjected to in silico rigid docking simulation on TLR2. To test our prediction that sevoflurane and a TLR1/TLR2 ligand Pam3CSK4 would compete for the same pocket of TLR2, we performed Pam3CSK4 competitive binding assay to TLR2 using HEK cells stably transfected with TLR2 (HEK-TLR2) with or without sevoflurane. We examined the effect of different anesthetics on the functions of human neutrophils stimulated with TLR2 ligands. Kruskal-Wallis test and Mann-Whitney U test were used for statistical analysis.

RESULTS

We observed that the attenuation of TLR1/TLR2 activation was seen on sevoflurane exposure but not on isoflurane, propofol, or dexmedetomidine exposure. The attenuation of TLR2/TLR6 activation was not seen in any of the anesthetics tested. The rigid docking simulation predicted that sevoflurane and Pam3CSK4 bound to the same pocket of TLR1/TLR2 complex. The binding of Pam3CSK4 to HEK-TLR2 cells was impaired in the presence of sevoflurane, indicating that sevoflurane and Pam3CSK4 competed for the pocket, as predicted in silico. The stimulation of neutrophils with Pam3CSK4 induced L-selection shedding but did not affect phagocytosis and reactive oxygen species production. L-selectin shedding from neutrophils was attenuated only by sevoflurane, consistent with the result of our reporter assays.

CONCLUSIONS

We found that TLR1/TLR2 activation was attenuated by sevoflurane, but we found no evidence for attenuation by isoflurane, propofol, or dexmedetomidine at clinically relevant concentrations. Our structural analysis and competition assay supported that sevoflurane directly bound to TLR2 at the interphase of the TLR1/TLR2 complex. Sevoflurane attenuated neutrophil L-selectin shedding, an important step for neutrophil migration.

Desflurane and sevoflurane concentrations in blood passing through the oxygenator during cardiopulmonary bypass: a randomized prospective pilot study

Purpose

Volatile anesthetics (VAs) protect myocardial cells in cardiovascular surgery. A recent clinical trial of cardiopulmonary bypass (CPB) surgery reported no significant difference in mortality rates between the use of VAs and total intravenous anesthetics at 1 year postoperatively. However, oxygenator function may affect the VA pharmacokinetics. Thus, we measured the VA blood concentrations during CPB in patients managed with four different microporous polypropylene hollow fiber membrane oxygenators.

Methods

Twenty-four patients scheduled for elective CPB were randomly allocated to one of the two VA groups (desflurane and sevoflurane groups) and, then, randomly divided into one of four oxygenator groups: Terumo, LivaNova, Medtronic, and Senko (n = 3). Additionally, in each VA group, three patients were randomly selected and redundantly allocated to the human lung group (for control blood VA concentration without oxygenator). Blood samples collected 20 min after starting 6.0 vol% desflurane or 1.7 vol% sevoflurane were analyzed using gas chromatography. Oxygenator-related complications and structural changes in the membrane surface of each oxygenator after surgery were evaluated.

Results

The mean (standard deviation) concentrations of desflurane and sevoflurane in the human lung were 182.4 (23.2) and 54.0 (9.6) μg/ml, respectively; not significantly different from those in the four oxygenator groups. No oxygenator-related complications occurred. Structural changes in membrane fibers did not occur after clinical use, except for difficulty in image acquisition with Senko products.

Conclusion

Our results demonstrated that the blood concentrations of desflurane and sevoflurane passing through oxygenators used during CPB were similar to those in the human lung control.

Electronic supplementary material

The online version of this article (10.1007/s00540-020-02844-1) contains supplementary material, which is available to authorized users.

Neurovascular and immune mechanisms that regulate postoperative delirium superimposed on dementia

Objective

The present work evaluates the relationship between postoperative immune and neurovascular changes and the pathogenesis of surgery‐induced delirium superimposed on dementia.

Background and rationale

Postoperative delirium is a common complication in many older adults and in patients with dementia including Alzheimer's disease (AD). The course of delirium can be particularly debilitating, while its pathophysiology remains poorly defined.

Historical evolution

As of 2019, an estimated 5.8 million people of all ages have been diagnosed with AD, 97% of whom are >65 years of age. Each year, many of these patients require surgery. However, anesthesia and surgery can increase the risk for further cognitive decline. Surgery triggers neuroinflammation both in animal models and in humans, and a failure to resolve this inflammatory state may contribute to perioperative neurocognitive disorders as well as neurodegenerative pathology.

Updated hypothesis

We propose an immunovascular hypothesis whereby dysregulated innate immunity negatively affects the blood‐brain interface, which triggers delirium and thereby exacerbates AD neuropathology.

Early experimental data

We have developed a translational model to study delirium superimposed on dementia in APPSwDI/mNos2^−/− AD mice (CVN‐AD) after orthopedic surgery. At 12 months of age, CVN‐AD showed distinct neuroimmune and vascular impairments after surgery, including acute microgliosis and amyloid‐β deposition. These changes correlated with attention deficits, a core feature of delirium‐like behavior.

Future experiments and validation studies

Future research should determine the extent to which prevention of surgery‐induced microgliosis and/or neurovascular unit dysfunction can prevent or ameliorate postoperative memory and attention deficits in animal models. Translational human studies should evaluate perioperative indices of innate immunity and neurovascular integrity and assess their potential link to perioperative neurocognitive disorders.

Major challenges for the hypothesis

Understanding the complex relationships between delirium and dementia will require mechanistic studies aimed at evaluating the role of postoperative neuroinflammation and blood‐brain barrier changes in the setting of pre‐existing neurodegenerative and/or aging‐related pathology.

Linkage to other major theories

Non‐resolving inflammation with vascular disease that leads to cognitive impairments and dementia is increasingly important in risk stratification for AD in the aging population. The interdependence of these factors with surgery‐induced neuroinflammation and cognitive dysfunction is also becoming apparent, providing a strong platform for assessing the relationship between postoperative delirium and longer term cognitive dysfunction in older adults.

The role of propofol hydroxyl group in 5-lipoxygenase recognition

Propofol is a clinically important intravenous anesthetic. We previously reported that it directly inhibited 5-lipoxygenase (5-LOX), a key enzyme for leukotriene biosynthesis. Because the hydroxyl group in propofol (propofol 1-hydroxyl) is critical for its anesthetic effect, we examined if its presence would be inevitable for 5-lipoxygenase recognition. Fropofol is developed by substituting the hydroxy group in propofol with fluorine. We found that propofol 1-hydroxyl was important for 5-lipoxygenase recognition, but it was not absolutely necessary. Azi-fropofol bound to 5-LOX at one of the two propofol binding sites of 5-LOX (pocket around Phe-187), suggesting that propofol 1-hydroxyl is important for 5-LOX inhibition at the other propofol binding site (pocket around Val-431). Interestingly, 5-hydroperoxyeicosatetraenoic acid (5-HpETE) production was significantly increased by stimulation with calcium ionophore A23187 in HEK293 cells expressing 5-LOX, suggesting that the fropofol binding site is important for the conversion from 5-HpETE to leukotriene A₄. We also indicated that propofol 1-hydroxyl might have contributed to interaction with wider targets among our body.