General anesthesia delays the inflammatory response and increases survival for mice with endotoxic shock

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.

Evaluating the effect of post-traumatic hypoxia on the development of axonal injury following traumatic brain injury in sheep

Damage to the axonal white matter tracts within the brain is a key cause of neurological impairment and long-term disability following traumatic brain injury (TBI). Understanding how axonal injury develops following TBI requires gyrencephalic models that undergo shear strain and tissue deformation similar to the clinical situation and investigation of the effects of post-injury insults like hypoxia. The aim of this study was to determine the effect of post-traumatic hypoxia on axonal injury and inflammation in a sheep model of TBI. Fourteen male Merino sheep were allocated to receive a single TBI via a modified humane captive bolt animal stunner, or sham surgery, followed by either a 15 min period of hypoxia or maintenance of normoxia. Head kinematics were measured in injured animals. Brains were assessed for axonal damage, microglia and astrocyte accumulation and inflammatory cytokine expression at 4 hrs following injury. Early axonal injury was characterised by calpain activation, with significantly increased SNTF immunoreactivity, a proteolytic fragment of alpha-II spectrin, but not with impaired axonal transport, as measured by amyloid precursor protein (APP) immunoreactivity. Early axonal injury was associated with an increase in GFAP levels within the CSF, but not with increases in IBA1 or GFAP+ve cells, nor in levels of TNFα, IL1β or IL6 within the cerebrospinal fluid or white matter. No additive effect of post-injury hypoxia was noted on axonal injury or inflammation. This study provides further support that axonal injury post-TBI is driven by different pathophysiological mechanisms, and detection requires specific markers targeting multiple injury mechanisms. Treatment may also need to be tailored for injury severity and timing post-injury to target the correct injury pathway.

Autonomic Regulation of Inflammation in Conscious Animals

Bioelectronic medicine is a novel field in modern medicine based on the specific neuronal stimulation to control organ function, cardiovascular, and immune homeostasis. However, most studies addressing neuromodulation of the immune system have been conducted on anesthetized animals, which can affect the nervous system and neuromodulation. Here, we review recent studies involving conscious experimental rodents (rats and mice) to better understand the functional organization of neural control of immune homeostasis. We highlight typical experimental models of cardiovascular regulation, such as electrical activation of the aortic depressor nerve or the carotid sinus nerve, bilateral carotid occlusion, the Bezold-Jarisch reflex, and intravenous administration of the bacterial endotoxin lipopolysaccharide. These models have been used to investigate the relationship between neuromodulation of the cardiovascular and immune systems in conscious rodents (rats and mice). These studies provide critical information about the neuromodulation of the immune system, particularly the role of the autonomic nervous system, i.e., the sympathetic and parasympathetic branches acting both centrally (hypothalamus, nucleus ambiguus, nucleus tractus solitarius, caudal ventrolateral medulla, and rostral ventrolateral medulla), and peripherally (particularly spleen and adrenal medulla). Overall, the studies in conscious experimental models have certainly highlighted to the reader how the methodological approaches used to investigate cardiovascular reflexes in conscious rodents (rats and mice) can also be valuable for investigating the neural mechanisms involved in inflammatory responses. The reviewed studies have clinical implications for future therapeutic approaches of bioelectronic modulation of the nervous system to control organ function and physiological homeostasis in conscious physiology.

Galvanic vestibular stimulation-induced activation of C1 neurons in medulla oblongata protects against acute lung injury

Autonomic nerves, including the sympathetic and parasympathetic nerves, control the immune system along with their physiological functions. On the peripheral side, the interaction between the splenic sympathetic nerves and immune cells is important for the anti-inflammatory effects. However, the central mechanism underlying these anti-inflammatory effects remains unclear. C1 neurons respond to stressors and subsequently determine the outflow of the autonomic nervous system. We have previously shown that C1 neurons protect against acute kidney injury and found a signaling connection between peripheral vestibular organs and C1 neurons. Thus, we hypothesized that hypergravity load or galvanic vestibular stimulation (GVS) might protect against acute lung injury. We showed that C1 neurons are histologically and functionally activated by stimulating the peripheral vestibular organs. Protection against acute lung injury that was induced by a 2 G load disappeared due to vestibular lesions or the deletion of C1 neurons. This GVS-induced protective effect was also eliminated by the deletion of the C1 neurons. Furthermore, GVS increased splenic sympathetic nerve activity in conscious mice, and splenic sympathetic denervation abolished the GVS-induced protection against acute lung injury. Therefore, the activated pathway between C1 neurons and splenic sympathetic nerves is indispensable for GVS-induced protection against acute lung injury.

Cardiomyocyte-specific disruption of soluble epoxide hydrolase limits inflammation to preserve cardiac function

Endotoxemia elicits a multiorgan inflammatory response that results in cardiac dysfunction and often leads to death. Inflammation-induced metabolism of endogenous N-3 and N-6 polyunsaturated fatty acids generates numerous lipid mediators, such as epoxy fatty acids (EpFAs), which protect the heart. However, EpFAs are hydrolyzed by soluble epoxide hydrolase (sEH), which attenuates their cardioprotective actions. Global genetic disruption of sEH preserves EpFA levels and attenuates cardiac dysfunction in mice following acute lipopolysaccharide (LPS)-induced inflammatory injury. In leukocytes, EpFAs modulate the innate immune system through the NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome. However, the mechanisms by which both EpFAs and sEH inhibition exert their protective effects in the cardiomyocyte are still elusive. This study investigated whether cardiomyocyte-specific sEH disruption attenuates inflammation and cardiac dysfunction in acute LPS inflammatory injury via modulation of the NLRP3 inflammasome. We use tamoxifen-inducible CreER recombinase technology to target sEH genetic disruption to the cardiomyocyte. Primary cardiomyocyte studies provide mechanistic insight into inflammasome signaling. For the first time, we demonstrate that cardiomyocyte-specific sEH disruption preserves cardiac function and attenuates inflammatory responses by limiting local cardiac inflammation and activation of the systemic immune response. Mechanistically, inhibition of cardiomyocyte-specific sEH activity or exogenous EpFA treatment do not prevent upregulation of NLRP3 inflammasome machinery in neonatal rat cardiomyocytes. Rather, they limit downstream activation of the pathway leading to release of fewer chemoattractant factors and recruitment of immune cells to the heart. These data emphasize that cardiomyocyte sEH is vital for mediating detrimental systemic inflammation.NEW & NOTEWORTHY The cardioprotective effects of genetic disruption and pharmacological inhibition of sEH have been demonstrated in a variety of cardiac disease models, including acute LPS inflammatory injury. For the first time, it has been demonstrated that sEH genetic disruption limited to the cardiomyocyte profoundly preserves cardiac function and limits local and systemic inflammation following acute LPS exposure. Hence, cardiomyocytes serve a critical role in the innate immune response that can be modulated to protect the heart.

Azadirachta indica A. Juss bark extract and its Nimbin isomers restrict β-coronaviral infection and replication

Emerging mutations in the SARS-CoV-2 genome pose a challenge for vaccine development and antiviral therapy. The antiviral efficacy of Azadirachta indica bark extract (NBE) was assessed against SARS-CoV-2 and m-CoV-RSA59 infection. Effects of in vivo intranasal or oral NBE administration on viral load, inflammatory response, and histopathological changes were assessed in m-CoV-RSA59-infection. NBE administered inhibits SARS-CoV-2 and m-CoV-RSA59 infection and replication in vitro, reducing Envelope and Nucleocapsid gene expression. NBE ameliorates neuroinflammation and hepatitis in vivo by restricting viral replication and spread. Isolated fractions of NBE enriched in Nimbin isomers shows potent inhibition of m-CoV-RSA59 infection in vitro. In silico studies revealed that NBE could target Spike and RdRp of m-CoV and SARS-CoV-2 with high affinity. NBE has a triterpenoids origin that may allow them to competitively target panoply of viral proteins to inhibit mouse and different strains of human coronavirus infections, suggesting its potential as an antiviral against pan-β-Coronaviruses.

Magnetic resonance imaging under isoflurane anesthesia alters cortical cyclooxygenase-2 expression and glial cell morphology during sepsis-associated neurological dysfunction in rats

Background

Magnetic resonance imaging (MRI) of rodents combined with histology allows to determine what mechanisms underlie functional and structural brain changes during sepsis-associated encephalopathy. However, the effects of MRI performed in isoflurane-anesthetized rodents on modifications of the blood-brain barrier and the production of vasoactive prostaglandins and glia cells, which have been proposed to mediate sepsis-associated brain dysfunction, are unknown.

Methods

This study addressed the effect of MRI under isoflurane anesthesia on blood-brain barrier integrity, cyclooxygenase-2 expression, and glial cell activation during cecal ligature and puncture-induced sepsis-associated brain dysfunction in rats.

Results

Cecal ligature and puncture reduced food intake and the righting reflex. MRI under isoflurane anesthesia reduced blood-brain barrier breakdown, decreased circularity of white matter astrocytes, and increased neuronal cyclooxygenase-2 immunoreactivity in the cortex 24 hours after laparotomy. In addition, it annihilated cecal ligature and puncture-induced increased circularity of white matter microglia. MRI under isoflurane anesthesia, however, did not alter sepsis-associated perivascular cyclooxygenase-2 induction.

Conclusion

These findings indicate that MRI under isoflurane anesthesia of rodents can modify neurovascular and glial responses and should, therefore, be interpreted with caution.

AAV9 transduction mediated by systemic delivery of vector via retro-orbital injection in newborn, neonatal and juvenile mice

Adeno-associated virus (AAV)-based gene therapy is gaining popularity owing to its excellent safety profile and effective therapeutic outcomes in a number of diseases. Intravenous (IV) injection of AAV into the tail vein, facial vein and retro-orbital (RO) venous sinus have all been useful strategies to infuse the viral vector systemically. However, tail vein injection is technically challenging in juvenile mice, and injection at young ages (≤ postnatal day-(P)21) is essentially impossible. The temporal or facial vein is localized anterior to the ear bud and is markedly visible in the first couple of days postnatally. However, this method is age-dependent and requires a dissecting microscope. Retro-orbital injection (ROI), on the other hand, is suitable for all murine ages, including newborn and older mice, and is relatively less stressful to animals compared to tail vein injection. Although many reports have shown ROI as an effective route of AAV delivery, herein we aim to highlight and summarize the methods and benefits of ROI. To capture the full spectrum of transduction efficiency mediated by ROI, we transduced the editing-dependent reporter mice (Ai9 Cre reporter mice) with the AAV9 vector, which targets a wide range of peripheral tissues with exceptional brain tropism. We also provide a comprehensive description of the ROI technique to facilitate viral vector administration without complications.

Regulation of the Nfkbiz Gene and Its Protein Product IkBζ in Animal Models of Sepsis and Endotoxic Shock

Sepsis is a life-threatening condition that arises from a poorly regulated inflammatory response to pathogenic organisms. Current treatments are limited to antibiotics, fluid resuscitation, and other supportive therapies. New targets for monitoring disease progression and therapeutic interventions are therefore critically needed. We previously reported that lipocalin-2 (Lcn2), a bacteriostatic mediator with potent proapoptotic activities, was robustly induced in sepsis. Other studies showed that Lcn2 was a predictor of mortality in septic patients. However, how Lcn2 is regulated during sepsis is poorly understood. We evaluated how IkBζ, an inducer of Lcn2, was regulated in sepsis using both the cecal ligation and puncture (CLP) and endotoxemia (lipopolysaccharide [LPS]) animal models. We show that Nfkbiz, the gene encoding IkBζ, was rapidly stimulated but, unlike Lcn2, whose expression persists during sepsis, mRNA levels of Nfkbiz decline to near basal levels several hours after its induction. In contrast, we observed that IkBζ expression remained highly elevated in septic animals following CLP but not LPS, indicating the occurrence of a CLP-specific mechanism that extends IkBζ half-life. By using an inhibitor of IkBζ, we determined that the expression of Lcn2 was largely controlled by IkBζ. Altogether, these data indicate that the high IkBζ expression in tissues likely contributes to the elevated expression of Lcn2 in sepsis. Since IkBζ is also capable of promoting or repressing other inflammatory genes, it might exert a central role in sepsis.

N‑acetylcysteine inhibits atherosclerosis by correcting glutathione‑dependent methylglyoxal elimination and dicarbonyl/oxidative stress in the aorta of diabetic mice

In diabetic animal models, high plasma/tissue levels of methylglyoxal (MG) are implicated in atherosclerosis. N-acetylcysteine (NAC) is a cysteine prodrug that replenishes intracellular glutathione (GSH) levels, which can increase the elimination of MG in diabetes mellitus (DM). The present study investigated the anti-atherosclerotic role of NAC in DM and aimed to determine whether the mechanism involved GSH-dependent MG elimination in the aorta. Apolipoprotein-E knockdown (ApoE^−/−) mice injected with streptozotocin for 5 days exhibited enhanced atherosclerotic plaque size in the aortic root; notably, a high-lipid diet aggravated this alteration. NAC treatment in the drinking water for 12 weeks decreased the size of the atherosclerotic lesion, which was associated with a reduction in MG-dicarbonyl stress and oxidative stress, as indicated by decreased serum malondialdehyde levels, and increased superoxide dismutase-1 and glutathione peroxidase-1 levels in the diabetic aorta. Endothelial damage was also corrected by NAC, as indicated by an increase in the expression levels of phosphorylated (p-)Akt and p-endothelial nitric oxide synthase (eNOS) in the aorta, as well as nitric oxide (NO) in the serum. In addition, MG-treated human umbilical vein endothelial cells (HUVECs) exhibited increased reactive oxygen species and decreased antioxidant enzyme expression levels. NAC treatment corrected the alteration in HUVECs induced by MG, whereas the protective role of NAC was blocked via inhibition of GSH. These findings indicated that the diabetic aorta was more susceptible to atherosclerotic lesions compared with non-diabetic ApoE^−/− mice. Furthermore, NAC may offer protection against atherosclerotic development in DM by altering aortic and systemic responses via correcting GSH-dependent MG elimination, leading to decreased oxidative stress and restoration of the p-Akt/p-eNOS pathway in the aorta.

Comparison of response to LPS-induced sepsis in three DBA/2 stocks derived from different sources

Sepsis, one of the most fatal diseases in the world, is known to culminate in multiple organ failure due to an uncontrolled inflammatory response. Hence, the use of animal models in sepsis research is very important to study complex immune responses. The current study was undertaken to compare commercial stocks with KFDA stocks of DBA/2 mice as an animal model for sepsis study. To compare responses of DBA/2 mice to lipopolysaccharides (LPS)-induced sepsis, we measured altered characteristics of various factors associated with sepsis, including survival curves, organ failure and inflammatory response, in DBA/2Korl stock and two commercial stocks (DBA/2A and DBA/2B). Survival rates after LPS exposure were similar for DBA/2Korl and DBA/2B; however, for times over 20 h, survival rates were reduced and concentration dependent in DBA/2A. In order to evaluate multiple organ failure caused by sepsis, H&E stains were evaluated for liver and spleen tissues obtained in the early (2 h) and later (20 h) stages after exposure to LPS; no significant differences were observed between the three stocks. mRNA and protein levels of proinflammatory cytokines were assessed for evaluating inflammatory reactions, and were found to increase in a dose-dependent manner in most DBA/2 mice after LPS treatment. However, no changes were observed in the mRNA levels of proinflammatory cytokines at 20 h after LPS exposure in the DBA/2A stock. The induction of inflammation-mediated factors by LPS exposure did not induce alterations in the mRNA levels of COX-2 and iNOS in all three DBA/2 stocks. Our results indicate that response of DBA/2Korl to LPS-induced sepsis is similar to the two commercial DBA/2 stocks, thus representing its potential as a useful biological resource established in Korea.

Electrostimulation of the carotid sinus nerve in mice attenuates inflammation via glucocorticoid receptor on myeloid immune cells

BACKGROUND

The carotid bodies and baroreceptors are sensors capable of detecting various physiological parameters that signal to the brain via the afferent carotid sinus nerve for physiological adjustment by efferent pathways. Because receptors for inflammatory mediators are expressed by these sensors, we and others have hypothesised they could detect changes in pro-inflammatory cytokine blood levels and eventually trigger an anti-inflammatory reflex.

METHODS

To test this hypothesis, we surgically isolated the carotid sinus nerve and implanted an electrode, which could deliver an electrical stimulation package prior and following a lipopolysaccharide injection. Subsequently, 90 min later, blood was extracted, and cytokine levels were analysed.

RESULTS

Here, we found that carotid sinus nerve electrical stimulation inhibited lipopolysaccharide-induced tumour necrosis factor production in both anaesthetised and non-anaesthetised conscious mice. The anti-inflammatory effect of carotid sinus nerve electrical stimulation was so potent that it protected conscious mice from endotoxaemic shock-induced death. In contrast to the mechanisms underlying the well-described vagal anti-inflammatory reflex, this phenomenon does not depend on signalling through the autonomic nervous system. Rather, the inhibition of lipopolysaccharide-induced tumour necrosis factor production by carotid sinus nerve electrical stimulation is abolished by surgical removal of the adrenal glands, by treatment with the glucocorticoid receptor antagonist mifepristone or by genetic inactivation of the glucocorticoid gene in myeloid cells. Further, carotid sinus nerve electrical stimulation increases the spontaneous discharge activity of the hypothalamic paraventricular nucleus leading to enhanced production of corticosterone.

CONCLUSION

Carotid sinus nerve electrostimulation attenuates inflammation and protects against lipopolysaccharide-induced endotoxaemic shock via increased corticosterone acting on the glucocorticoid receptor of myeloid immune cells. These results provide a rationale for the use of carotid sinus nerve electrostimulation as a therapeutic approach for immune-mediated inflammatory diseases.

Minimum Information in In Vivo Research

Data quality, reproducibility and reliability are a matter of concern in many scientific fields including biomedical research. Robust, reproducible data and scientific rigour form the foundation on which future studies are built and determine the pace of knowledge gain and the time needed to develop new and innovative drugs that provide benefit to patients. Critical to the attainment of this is the precise and transparent reporting of data. In the current chapter, we will describe literature highlighting factors that constitute the minimum information that is needed to be included in the reporting of in vivo research. The main part of the chapter will focus on the minimum information that is essential for reporting in a scientific publication. In addition, we will present a table distinguishing information necessary to be recorded in a laboratory notebook or another form of internal protocols versus information that should be reported in a paper. We will use examples from the behavioural literature, in vivo studies where the use of anaesthetics and analgesics are used and finally ex vivo studies including histological evaluations and biochemical assays.

An Effective Method for Acute Vagus Nerve Stimulation in Experimental Inflammation

Neural reflexes regulate inflammation and electrical activation of the vagus nerve reduces inflammation in models of inflammatory disease. These discoveries have generated an increasing interest in targeted neurostimulation as treatment for chronic inflammatory diseases. Data from the first clinical trials that use vagus nerve stimulation (VNS) in treatment of rheumatoid arthritis and Crohn’s disease suggest that there is a therapeutic potential of electrical VNS in diseases characterized by excessive inflammation. Accordingly, there is an interest to further explore the molecular mechanisms and therapeutic potential of electrical VNS in a range of experimental settings and available genetic mouse models of disease. Here, we describe a method for electrical VNS in experimental inflammation in mice.

Impact of general anaesthesia on endoplasmic reticulum stress: propofol vs. isoflurane

Background: This study investigated the effects of propofol and isoflurane on endoplasmic reticulum (ER) stress in an animal model under general anaesthesia. Methods: Rats were randomly divided into Propofol and Isoflurane groups. Anaesthesia was maintained with propofol for Propofol group or isoflurane for Isoflurane group during 3 h. ER stress from lymphocytes in blood and tissues was evaluated between two groups after euthanasia. Reactive oxygen species (ROS) from lymphocytes in blood and tissues, and cytokines in blood were also checked. An immunohistochemical assay for ER stress marker from tissues was performed. Results: After anaesthesia, the levels of CCAAT-enhancer-binding protein homologous proteins (CHOP) in blood and liver were significantly higher in Isoflurane group, compared to Propofol group [blood, 31,499 ± 4,934 (30,733, 26,441-38,807) mean fluorescence intensity (MFI) in Isoflurane group vs. 20,595 ± 1,838 (20,780, 18,866-22,232) MFI in Propofol group, p = 0.002; liver, 28,342 ± 5,535 (29,421, 23,388-32,756) MFI in Isoflurane group vs. 20,004 ± 2,155 (19,244, 18,197-22,191) MFI in Propofol group, p = 0.020]. ROS in blood was significantly higher in Isoflurane group, compared to Propofol group. However, cytokines in blood and immunohistochemical assays in tissues were similar between groups. Conclusion: Significant higher of ER stress from blood and liver were observed in rats under anaesthesia with isoflurane, compared to those that received propofol. ROS from blood also showed significant higher under anaesthesia with isoflurane. However, these findings were not associated with any changes in cytokines in blood or immunohistochemical assay in tissues.

Why Antibiotic Treatment Is Not Enough for Sepsis Resolution: an Evaluation in an Experimental Animal Model

Sepsis remains a major health problem at the levels of mortality, morbidity, and economic burden to the health care system, a condition that is aggravated by the development of secondary conditions such as septic shock and multiple-organ failure. Our current understanding of the etiology of human sepsis has advanced, at least in part, due to the use of experimental animal models, particularly the model of cecum ligation and puncture (CLP). Antibiotic treatment has been commonly used in this model to closely mirror the treatment of human septic patients. However, whether their use may obscure the elucidation of the cellular and molecular mechanisms involved in the septic response is questionable. The objective of the present study was to determine the effect of antibiotic treatment in the outcome of a fulminant model of CLP. Various dosing strategies were used for the administration of imipenem, which has broad-spectrum coverage of enteric bacteria. No statistically significant differences in the survival of mice were observed between the different antibiotic dosing strategies and no treatment, suggesting that live bacteria may not be the only factor inducing septic shock. To further investigate this hypothesis, mice were challenged with sterilized or unsterilized cecal contents. We found that exposure of mice to sterilized cecal contents also resulted in a high mortality rate. Therefore, it is possible that bacterial debris, apart from bacterial proliferation, triggers a septic response and contributes to mortality in this model, suggesting that additional factors are involved in the development of septic shock.

Carotid sinus nerve electrical stimulation in conscious rats attenuates systemic inflammation via chemoreceptor activation

Recent studies demonstrated a critical functional connection between the autonomic (sympathetic and parasympathetic) nervous and the immune systems. The carotid sinus nerve (CSN) conveys electrical signals from the chemoreceptors of the carotid bifurcation to the central nervous system where the stimuli are processed to activate sympathetic and parasympathetic efferent signals. Here, we reported that chemoreflex activation via electrical CSN stimulation, in conscious rats, controls the innate immune response to lipopolysaccharide attenuating the plasma levels of inflammatory cytokines such as tumor necrosis factor (TNF), interleukin 1β (IL-1β) and interleukin 6 (IL-6). By contrast, the chemoreflex stimulation increases the plasma levels of anti-inflammatory cytokine interleukin 10 (IL-10). This chemoreflex anti-inflammatory network was abrogated by carotid chemoreceptor denervation and by pharmacological blockade of either sympathetic - propranolol - or parasympathetic - methylatropine – signals. The chemoreflex stimulation as well as the surgical and pharmacological procedures were confirmed by real-time recording of hemodynamic parameters [pulsatile arterial pressure (PAP) and heart rate (HR)]. These results reveal, in conscious animals, a novel mechanism of neuromodulation mediated by the carotid chemoreceptors and involving both the sympathetic and parasympathetic systems.

Combined administration of a sedative dose sevoflurane and 60% oxygen reduces inflammatory responses to sepsis in animals and in human PMBCs

Our study aims to investigate the effects of the inhalation of subanesthestic doses of sevoflurane combined with oxygen on sepsis. Male Sprague-Dawley rats or Male ICR/Km mice underwent caecal ligation and puncture (CLP) or intraperitoneal injection of lipopolysccharide (LPS) to induce sepsis, while sham rats were used as control. Then, rats were treated with the inhalation of sevoflurane in oxygen; and air or 100% oxygen was used as control. Seven-day survival, lung injury and inflammatory factors were assessed. In this in vitro experiment, we obtained RAW264.7 macrophages and human peripheral blood mononuclear cells (PBMCs) incubated by LPS or plasma from septic patients to explore the NF-κB pathway in the effect of the inhalation of sevoflurane combined with oxygen in sepsis. In this study, we found that the inhalation of 0.5 MAC of sevoflurane in 60% oxygen was the best protocol for protecting against lethality resulting from sepsis and ALI, and there was a time window for these protective effects. We also founded that 0.5 MAC of sevoflurane in 60% oxygen inhibited the nuclear translocation of NF-κB in human PBMCs induced by LPS or plasma from septic patients. The subanesthesia dose sevoflurane in 60% oxygen may reduce sepsis-induced inflammatory responses in animals and in PBMCs, and the inhibition to the activation of the NF-κB pathway may contribute to this protection.

Sub-anesthesia Dose of Isoflurane in 60% Oxygen Reduces Inflammatory Responses in Experimental Sepsis Models

BACKGROUND

Sepsis is a major cause of mortality in Intensive Care Units. Anesthetic dose isoflurane and 100% oxygen were proved to be beneficial in sepsis; however, their application in septic patients is limited because long-term hyperoxia may induce oxygen toxicity and anesthetic dose isoflurane has potential adverse consequences. This study was scheduled to find the optimal combination of isoflurane and oxygen in protecting experimental sepsis and its mechanisms.

METHODS

The effects of combined therapy with isoflurane and oxygen on lung injury and sepsis were determined in animal models of sepsis induced by cecal ligation and puncture (CLP) or intraperitoneal injection of lipopolysaccharide (LPS) or zymosan. Mouse RAW264.7 cells or human peripheral blood mononuclear cells (PBMCs) were treated by LPS to probe mechanisms. The nuclear factor kappa B (NF-κB) signaling molecules were examined by Western blot and cellular immunohistochemistry.

RESULTS

The 0.5 minimum alveolar concentration (MAC) isoflurane in 60% oxygen was the best combination of oxygen and isoflurane for reducing mortality in experimental sepsis induced by CLP, intraperitoneal injection of LPS, or zymosan. The 0.5 MAC isoflurane in 60% oxygen inhibited proinflammatory cytokines in peritoneal lavage fluids (tumor necrosis factor-alpha [TNF-β]: 149.3 vs. 229.7 pg/ml, interleukin [IL]-1β: 12.5 vs. 20.6 pg/ml, IL-6: 86.1 vs. 116.1 pg/ml, and high-mobility group protein 1 [HMGB1]: 323.7 vs. 449.3 ng/ml; all P< 0.05) and serum (TNF-β: 302.7 vs. 450.7 pg/ml, IL-1β: 51.7 vs. 96.7 pg/ml, IL-6: 390.4 vs. 722.5 pg/ml, and HMGB1: 592.2 vs. 985.4 ng/ml; all P< 0.05) in septic animals. In vitro experiments showed that the 0.5 MAC isoflurane in 60% oxygen reduced inflammatory responses in mouse RAW264.7 cells, after LPS stimulation (all P< 0.05). Suppressed activation of NF-κB pathway was also observed in mouse RAW264.7 macrophages and human PBMCs after LPS stimulation or plasma from septic patients. The 0.5 MAC isoflurane in 60% oxygen also prevented the increases of phospho-IKKβ/β, phospho-IκBβ, and phospho-p65 expressions in RAW264.7 macrophages after LPS stimulation (all P< 0.05).

CONCLUSION

Combined administration of a sedative dose of isoflurane with 60% oxygen improves survival of septic animals through reducing inflammatory responses.

Renal sympathetic nerve activity and vascular reactivity to phenylephrine after lipopolysaccharide administration in conscious rats

It has been proposed that sympathoexcitation is responsible for vascular desensitization to α₁-adrenoceptor stimulation during lipopolysaccharide (LPS)-induced systemic inflammation. The present study tested this hypothesis by examining the effects of sympatho-deactivation with the α₂-adrenoceptor agonist, dexmedetomidine, on mean arterial pressure (MAP), renal sympathetic nerve activity (RSNA), and vascular reactivity to phenylephrine in conscious rats with cardiac autonomic blockade (methylatropine and atenolol) following LPS administration. In male, adult Sprague-Dawley rats (n = 5 per group), RSNA and MAP were continuously recorded over 1-h periods, before and after LPS administration (20 mg/kg iv), and finally after infusion of either saline or dexmedetomidine (5 μg/kg, then 5 μg/kg/h iv). A full dose-response curve to phenylephrine was constructed under each condition. After pooling data from both groups of rats (n = 10), LPS significantly (P = 0.005) decreased MAP (from 115 ± 1 to 107 ± 2 mmHg), increased RSNA (to 403 ± 46% of baseline values) and induced 4 to 5-fold increases in the half-maximal effective dose (ED₅₀) of phenylephrine (from 1.02 ± 0.09 to 4.76 ± 0.51 μg/kg). During saline infusion, RSNA progressively decreased while vascular reactivity did not improve. Treatment with dexmedetomidine decreased MAP, returned RSNA to near pre-endotoxemic levels, but only partially restored vascular reactivity to phenylephrine (ED₅₀ was still threefold increased as compared with baseline values). These findings indicate that only part of the decrease in vascular reactivity to α₁-adrenoceptor stimulation during endotoxemia can be accounted for by sympathetic activation, at least on a short-term basis.

Chloral Hydrate Treatment Induced Apoptosis of Macrophages via Fas Signaling Pathway

BACKGROUND There are recent reports on several anesthetics that have anti-inflammatory and anti-infective effects apart from their uses for pain relief and muscle relaxation. Chloral hydrate is a clinical anesthetic drug and sedative that has also been reported to attenuate inflammatory response, but the mechanisms are not clearly understood. MATERIAL AND METHODS This study investigated the effect of chloral hydrate treatment on the apoptosis of macrophages and explored the underlying mechanisms. RAW264.7 macrophages were treated with various concentrations of chloral hydrate for various lengths of time. Morphological changes were observed under a light microscope and apoptosis was detected with annexin-V-FITC/PI double-staining assay, Hochest 33258 and DNA ladder assay, the expression of Fas/FasL was detected with a flow cytometer, and the Fas signaling pathway was assessed by Western blotting. RESULTS The results showed that chloral hydrate treatment induced the morphology of RAW264.7 macrophages to change shape from typical fusiform to round in a concentration- and time-dependent manner, and was finally suspended in the supernatant. For the induction of apoptosis, chloral hydrate treatment induced the apoptosis of RAW264.7 macrophages from early-to-late stage apoptosis in a concentration- and time-dependent manner. For the mechanism, chloral hydrate treatment induced higher expression of Fas on RAW264.7 macrophages, and was also associated with changes in the expression of proteins involved in Fas signaling pathways. CONCLUSIONS Chloral hydrate treatment can induce the apoptosis of RAW264.7 macrophages through the Fas signaling pathway, which may provide new options for adjunctive treatment of acute inflammation.

The splanchnic anti-inflammatory pathway: could it be the efferent arm of the inflammatory reflex?

What is the topic of this review? We review the current literature on the neural reflex termed the 'inflammatory reflex' that inhibits an excessive release of inflammatory mediators in response to an immune challenge. What advances does it highlight? The original model proposed that the inflammatory reflex is a vago-vagal reflex that controls immune function. We posit that, in the endotoxaemic animal model, the vagus nerves do not appear to play a role. The evidence suggests that the efferent motor pathway, termed here the 'splanchnic anti-inflammatory pathway', is purely sympathetic, travelling via the greater splanchnic nerves to regulate the ensuing inflammatory response to immune challenges. Exposure to immune challenges results in the development of inflammation. An insufficient inflammatory response can be life-threatening, whereas an exaggerated response is also detrimental because it causes tissue damage and, in extreme cases, septic shock that can lead to death. Hence, inflammation must be finely regulated. It is generally accepted that the brain inhibits inflammation induced by an immune challenge in two main ways: humorally, by activating the hypothalamic-pituitary-adrenal axis to release glucocorticoids; and neurally, via a mechanism that has been termed the 'inflammatory reflex'. The efferent arm of this reflex (the neural-to-immune link) was thought to be the 'cholinergic anti-inflammatory pathway'. Here, we discuss data that support the hypothesis that the vagus nerves play no role in the control of inflammation in the endotoxaemic animal model. We have shown and posit that it is the greater splanchnic nerves that are activated in response to the immune challenge and that, in turn, drive postganglionic sympathetic neurons to inhibit inflammation.

Anesthesia and Monitoring in Small Laboratory Mammals Used in Anesthesiology, Respiratory and Critical Care Research: A Systematic Review on the Current Reporting in Top-10 Impact Factor Ranked Journals

RATIONALE

This study aimed to investigate the quality of reporting of anesthesia and euthanasia in experimental studies in small laboratory mammals published in the top ten impact factor journals.

METHODS

A descriptive systematic review was conducted and data was abstracted from the ten highest ranked journals with respect to impact factor in the categories 'Anesthesiology', 'Critical Care Medicine' and 'Respiratory System' as defined by the 2012 Journal Citation Reports. Inclusion criteria according to PICOS criteria were as follows: 1) population: small laboratory mammals; 2) intervention: any form of anesthesia and/or euthanasia; 3) comparison: not specified; 4) primary outcome: type of anesthesia, anesthetic agents and type of euthanasia; secondary outcome: animal characteristics, monitoring, mechanical ventilation, fluid management, postoperative pain therapy, animal care approval, sample size calculation and performed interventions; 5) study: experimental studies. Anesthesia, euthanasia, and monitoring were analyzed per performed intervention in each article.

RESULTS

The search yielded 845 articles with 1,041 interventions of interest. Throughout the manuscripts we found poor quality and frequency of reporting with respect to completeness of data on animal characteristics as well as euthanasia, while anesthesia (732/1041, 70.3%) and interventions without survival (970/1041, 93.2%) per se were frequently reported. Premedication and neuromuscular blocking agents were reported in 169/732 (23.1%) and 38/732 (5.2%) interventions, respectively. Frequency of reporting of analgesia during (117/610, 19.1%) and after painful procedures (38/364, 10.4%) was low. Euthanasia practice was reported as anesthesia (348/501, 69%), transcardial perfusion (37/501, 8%), carbon dioxide (26/501, 6%), decapitation (22/501, 5%), exsanguination (23/501, 5%), other (25/501, 5%) and not specified (20/501, 4%, respectively.

CONCLUSIONS

The present systematic review revealed insufficient reporting of anesthesia and euthanasia methods throughout experimental studies in small laboratory mammals. Specific guidelines for anesthesia and euthanasia regimens should be considered to achieve comparability, quality of animal experiments and animal welfare. These measures are of special interest when translating experimental findings to future clinical applications.

A Systematic Review of Rhubarb (a Traditional Chinese Medicine) Used for the Treatment of Experimental Sepsis

Sepsis is a global major health problem in great need for more effective therapy. For thousands of years, Rhubarb had been used for various diseases including severe infection. Pharmacological studies and trials reported that Rhubarb may be effective in treating sepsis, but the efficacy and the quality of evidence remain unclear since there is no systematic review on Rhubarb for sepsis. The present study is the first systematic review of Rhubarb used for the treatment of experimental sepsis in both English and Chinese literatures by identifying 27 studies from 7 databases. It showed that Rhubarb might be effective in reducing injuries in gastrointestinal tract, lung, and liver induced by sepsis, and its potential mechanisms might include reducing oxidative stress and inflammation, ameliorating microcirculatory disturbance, and maintaining immune balance. Yet the positive findings should be interpreted with caution due to poor methodological quality. In a word, Rhubarb might be a promising candidate that is worth further clinical and experimental trials for sepsis therapy.

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.

Reflex control of inflammation by the splanchnic anti-inflammatory pathway is sustained and independent of anesthesia

Following an immune challenge, there is two-way communication between the nervous and immune systems. It is proposed that a neural reflex--the inflammatory reflex--regulates the plasma levels of the key proinflammatory cytokine TNF-α, and that its efferent pathway is in the splanchnic sympathetic nerves. The evidence for this reflex is based on experiments on anesthetized animals, but anesthesia itself suppresses inflammation, confounding interpretation. Here, we show that previous section of the splanchnic nerves strongly enhances the levels of plasma TNF-α in conscious rats 90 min after they received intravenous LPS (60 μg/kg). The same reflex mechanism, therefore, applies in conscious as in anesthetized animals. In anesthetized rats, we then determined the longer-term effects of splanchnic nerve section on responses to LPS (60 μg/kg iv). We confirmed that prior splanchnic nerve section enhanced the early (90 min) peak in plasma TNF-α and found that it reduced the 90-min peak of the anti-inflammatory cytokine IL-10; both subsequently fell to low levels in all animals. Splanchnic nerve section also enhanced the delayed rise in two key proinflammatory cytokines IL-6 and interferon γ. That enhancement was undiminished after 6 h, when other measured cytokines had subsided. Finally, LPS treatment caused hypotensive shock in rats with cut splanchnic nerves but not in sham-operated animals. These findings demonstrate that reflex activation of the splanchnic anti-inflammatory pathway has a powerful and sustained restraining influence on inflammatory processes.

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.

Chloral hydrate-dependent reduction in the peptidoglycan-induced inflammatory macrophage response is associated with lower expression levels of toll-like receptor 2

The aim of this study was to investigate the effect and mechanism of action of chloral hydrate on the peptidoglycan (PGN)-induced inflammatory macrophage response. The effect of chloral hydrate on the production of tumor necrosis factor α (TNF-α) and interleukin-6 (IL-6) by murine peritoneal macrophages with PGN-stimulation was investigated. In addition, RAW264.7 cells transfected with a nuclear factor-κB (NF-κB) luciferase reporter plasmid stimulated by PGN were used to study the effect of chloral hydrate on the levels NF-κB activity. Flow cytometry and western blotting were performed to investigate the expression levels of toll-like receptor 2 (TLR2) in the treated RAW264.7 cells. It was identified that chloral hydrate reduced the levels of IL-6 and TNF-α produced by the peritoneal macrophages stimulated with PGN. The levels of NF-κB activity of the RAW264.7 cells stimulated by PGN decreased following treatment with chloral hydrate, which was associated with a reduction in the expression levels of TLR2 and reduced levels of TLR2 signal transduction. These data demonstrate that chloral hydrate reduced the magnitude of the PGN-induced inflammatory macrophage response associated with lower expression levels of TLR2.

Volatile anesthetics-induced neuroinflammatory and anti-inflammatory responses

Volatile anesthetics have been the major anesthetics used clinically for more than 150 years. They provide all components of general anesthesia and are easy to be applied and monitored with modern equipment and technology. In addition to having anesthetic property, volatile anesthetics have multiple other effects. Many studies have clearly shown that volatile anesthetics can reduce systemic and local inflammatory responses induced by various stimuli in humans and animals. On the other hand, recent animal studies have shown that volatile anesthetics may induce mild neuroinflammation. These dual effects on inflammation may have significant biological implications and are briefly reviewed here.

Inflammatory immune responses in a reproducible mouse brain death model

BACKGROUND

Brain death impairs donor organ quality and accelerates immune responses after transplantation. Detailed aspects of immune activation following brain death remain unclear. We have established a mouse model and investigated the immediate consequences of brain death and anesthesia on immune responses.

METHODS

C57JBl/6 mice (n=6/group) were anesthetized with isoflurane (ISF) or ketamine/xylazine (KX); subsequently, animals underwent brain death induction and were followed for 3h under continuous ventilation. Blood pressure was monitored continuously and animals were resuscitated with normal saline to achieve normotension. Immune activation in brain dead animals was analyzed by IFNγ-ELispot, MLR, and flow-cytometry. Sham-operated and naïve animals served as controls.

RESULTS

Blood pressure remained stable in both BD/KX and BD/ISF animals during the 3h observation time. Brain death was linked to systemic immune activation: IFNγ-expression of splenocytes and lymphocyte proliferation rates was significantly elevated subsequent to brain death (p<0.02, <0.01); T-cell activation markers CD28 and CD69 had increased in brain dead animals (p<0.03, <0.02). Isoflurane treatment in sham controls throughout the observation period (3.5h) revealed anesthesia associated IFNγ-expression and lymphocyte activation which were not observed when animals were treated with ketamine/xylazine (p<0.04, <0.009).

CONCLUSIONS

This study reports on a reproducible and hemodynamically stable brain death mouse model. Hemodynamic stability was not impacted through either isoflurane or ketamine/xylazine induction. Of clinical relevance, prolonged anesthesia with isoflurane had been linked to pro-inflammatory cytokine activation. Brain death caused systemic immune activation in organ donors.

Delayed treatment with lidocaine reduces mouse microglial cell injury and cytokine production after stimulation with lipopolysaccharide and interferon γ

BACKGROUND

Neuroinflammation is an important pathological process for almost all acquired neurological diseases. Microglial cells play a critical role in neuroinflammation. We determined whether lidocaine, a local anesthetic with anti-inflammatory property, protected microglial cells and attenuated cytokine production from activated microglial cells.

METHODS

Mouse microglial cultures were incubated with or without 1 μg/mL lipopolysaccharide and 10 U/mL interferon γ (IFNγ) for 24 hours in the presence or absence of lidocaine for 1 hour started at 2, 3, or 4 hours after the onset of lipopolysaccharide and IFNγ stimulation. Lactate dehydrogenase release and cytokine production were determined after the cells were stimulated by lipopolysaccharide and IFNγ for 24 hours.

RESULTS

Lidocaine dose-dependently reduced lipopolysaccharide and IFNγ-induced microglial cell injury as measured by lactate dehydrogenase release. This effect was apparent with lidocaine at 2 μg/mL (30.3% ± 5.8% and 23.1% ± 9.7%, respectively, for stimulation alone and the stimulation in the presence of lidocaine, n = 18, P = 0.025). Lidocaine applied at 2, 3, or 4 hours after the onset of lipopolysaccharide and IFNγ stimulation reduced the cell injury. This lidocaine effect was not affected by the mitochondrial K(ATP) channel inhibitor 5-hydroxydecanoate. Similar to lidocaine, QX314, a permanently charged lidocaine analog that usually does not permeate through the plasma membrane, reduced lipopolysaccharide and IFNγ-induced microglial cell injury. QX314 also attenuated the stimulation-induced interleukin-1β production.

CONCLUSIONS

Delayed treatment with lidocaine protects microglial cells and reduces cytokine production from these cells. These effects may involve action site(s) on the cell surface.

CXCL5 mediates UVB irradiation-induced pain

Many persistent pain states (pain lasting for hours, days, or longer) are poorly treated because of the limitations of existing therapies. Analgesics such as nonsteroidal anti-inflammatory drugs and opioids often provide incomplete pain relief and prolonged use results in the development of severe side effects. Identification of the key mediators of various types of pain could improve such therapies. Here, we tested the hypothesis that hitherto unrecognized cytokines and chemokines might act as mediators in inflammatory pain. We used ultraviolet B (UVB) irradiation to induce persistent, abnormal sensitivity to pain in humans and rats. The expression of more than 90 different inflammatory mediators was measured in treated skin at the peak of UVB-induced hypersensitivity with custom-made polymerase chain reaction arrays. There was a significant positive correlation in the overall expression profiles between the two species. The expression of several genes [interleukin-1β (IL-1β), IL-6, and cyclooxygenase-2 (COX-2)], previously shown to contribute to pain hypersensitivity, was significantly increased after UVB exposure, and there was dysregulation of several chemokines (CCL2, CCL3, CCL4, CCL7, CCL11, CXCL1, CXCL2, CXCL4, CXCL7, and CXCL8). Among the genes measured, CXCL5 was induced to the greatest extent by UVB treatment in human skin; when injected into the skin of rats, CXCL5 recapitulated the mechanical hypersensitivity caused by UVB irradiation. This hypersensitivity was associated with the infiltration of neutrophils and macrophages into the dermis, and neutralizing the effects of CXCL5 attenuated the abnormal pain-like behavior. Our findings demonstrate that the chemokine CXCL5 is a peripheral mediator of UVB-induced inflammatory pain, likely in humans as well as rats.

Xylazine-/diazepam-ketamine and isoflurane differentially affect hemodynamics and organ injury under hemorrhagic/traumatic shock and resuscitation in rats

Most experimental studies on hemorrhage and trauma are performed under anesthesia. We determined the effects of three commonly used anesthetic regimens on hemodynamics and organ damage under normal and hemorrhagic/traumatic shock (HTS) conditions in rats. Animals were anesthetized with ketamine/diazepam (K/D), ketamine/xylazine (K/X), or isoflurane (ISO). Hemorrhagic/traumatic shock was induced by a midline laparotomy, bleeding to a mean arterial pressure of 30 to 35 mmHg until decompensation, followed by restrictive and adequate phases of resuscitation. The experiment was terminated 120 min after the completion of resuscitation. Under normal conditions, K/D anesthesia resulted in higher mean arterial pressure and heart rate than K/X and higher systemic vascular resistance index (SVRI) than ISO. Stroke volume was significantly lower in K/D group than in K/X and ISO groups. Under normal conditions, ISO anesthesia was accompanied by the highest cardiac index. During shock and resuscitation, heart rate remained higher in the K/D than K/X. During shock, SVRI decreased in the K/D group but increased in K/X and ISO groups. After resuscitation, SVRI was lower, and cardiac index was higher in the ISO group than in the K/D group. Despite higher shed blood volume, the rats anesthetized with ISO did not decompensate within the time frame compared with other groups. Cellular damage (plasma creatine kinase, lactate dehydrogenase, uric acid) was more pronounced with K/D compared with ISO. Histological examinations revealed frequent HTS-induced damage to adrenals, kidney, and liver of animals anesthetized with K/D and K/X but not with ISO. Anesthetics differentially affect HTS-induced hemodynamic alterations and organ injury. Thus, when interpreting data from HTS models, the individual effect of anesthetics should be considered.

The effects of isoflurane anesthesia and mechanical ventilation on renal function during endotoxemia

BACKGROUND

Isoflurane is a common anesthetic agent used in human surgery and in animal models of sepsis. It has been suggested to have beneficial anti-inflammatory properties and to protect kidney function. Here, we investigated the effect of isoflurane on the development of kidney injury and dysfunction during 48-h endotoxemia in sheep.

METHODS

Before the experiments, the sheep (n=16) were surgically equipped with transit-time flowprobes around the renal, femoral and superior mesenteric artery. The animals were randomized to either be anesthetized with isoflurane and mechanically ventilated or to remain conscious while they received intravenous Escherichia coli lipopolysaccharide (LPS) for 48 h (25 ng/kg/min). In two animals in each group, the LPS was excluded to investigate any effect of isoflurane per se over time.

RESULTS

Endotoxemia caused cardiovascular changes typical for hyperdynamic sepsis and, although renal hyperemia occurred, impaired renal function in both groups. Compared with conscious animals, isoflurane significantly (P<0.05) reduced urine output, renal creatinine clearance, fractional sodium excretion and renal blood flow during endotoxemia. Furthermore, the plasma concentrations of urea and creatinine increased more in the anesthetized animals. Isoflurane anesthesia also enhanced neutrophil activity and accumulation in the kidney during endotoxemia. N-acetyl-β-D-glucosaminidase was significantly increased, with no inter-group difference as an indication of tubular injury.

CONCLUSIONS

The results of the current study suggest that isoflurane anesthesia (minimum alveolar concentration 1.0) with mechanical ventilation aggravates renal dysfunction during 48 h of endotoxemia and does not significantly reduce the inflammatory response or signs of tubular damage.

Impact of anesthesia, analgesia, and euthanasia technique on the inflammatory cytokine profile in a rodent model of severe burn injury

Anesthetics used in burn and trauma animal models may be influencing results by modulating inflammatory and acute-phase responses. Accordingly, we determined the effects of various anesthetics, analgesia, and euthanasia techniques in a rodent burn model. Isoflurane (ISO), ketamine-xylazine (KX), or pentobarbital (PEN) with or without buprenorphine were administered before scald-burn in 72 rats that were euthanized without anesthesia by decapitation after 24 h and compared with unburned shams. In a second experiment, 120 rats underwent the same scald-burn injury using KX, and 24 h later were euthanized under anesthesia or carbon dioxide (CO2). In addition, we compared euthanasia by exsanguination with that of decapitation. Serum cytokine levels were determined by an enzyme-linked immunosorbent assay. In the first experiment, ISO was associated with elevation of cytokine-induced neutrophil chemoattractant 2 (CINC-2) and monocyte chemotactic protein 1 (MCP-1), and KX and PEN was associated with elevation of CINC-1,CINC-2, IL-6, and MCP-1. Pentobarbital also decreased IL-1". IL-6 increased significantly when ISO or PEN were combined with buprenorphine. In the second experiment, euthanasia performed by exsanguination under ISO was associated with reduced levels of IL-1", CINC-1, CINC-2, and MCP-1, whereas KX reduced CINC-2 and increased IL-6 levels. Meanwhile, PEN reduced levels of IL-1" and MCP-1, and CO2 reduced CINC-2 and MCP-1. In addition,decapitation after KX, PEN, or CO2 decreased IL-1" and MCP-1, although we found no significant difference between ISO and controls. Euthanasia by exsanguination compared with decapitation using the same agent also led to modulation of several cytokines. Differential expression of inflammatory markers with the use of anesthetics and analgesics should be considered when designing animal studies and interpreting results because these seem to have a significant modulating impact. Our findings indicate that brief anesthesia with ISO immediately before euthanasia by decapitation exerted the least dampening effect on the cytokines measured. Conversely, KX with buprenorphine may offer a better balance during longer procedures to avoid significant modulation. Standardization across all experiments that are compared and awareness of these findings are essential for those investigating the pathophysiology of inflammation in animal models.

The impact of the perioperative period on neurocognitive development, with a focus on pharmacological concerns

Mounting evidence from animal studies has implicated that all commonly used anaesthetics and sedatives may induce widespread neuronal cell death and result in long-term neurological abnormalities. These findings have led to serious questions regarding the safe use of these drugs in young children. In humans, recent findings from retrospective, epidemiological studies do not exclude the possibility of an association between surgery with anaesthesia early in life and subsequent learning abnormalities. These results have sparked discussions regarding the appropriate timing of paediatric surgery and the safe management of paediatric anaesthesia. However, important questions need to be addressed before findings from laboratory studies and retrospective clinical surveys can be used to guide clinical practice. This article summarises the currently available preclinical and clinical information regarding the impact of anaesthetics, sedatives, opioids, pain and stress, inflammation, hypoxia-ischaemia, co-morbidities and genetic predisposition on brain structure and long-term neurological function. Moreover, this article outlines the putative mechanisms of anaesthetic neurotoxicity, and the phenomenon's implications for clinical practice in this rapidly emerging field.

Anesthesia aggravates lung damage and precipitates hypotension in endotoxemic sheep

Beneficial anti-inflammatory properties have been ascribed to volatile anesthetics in septic conditions, but no studies have compared anesthesia to the conscious state in a large-animal model. The aim of this study was to investigate the effect of isoflurane anesthesia on cardiovascular and respiratory function, leukocyte activation, and lung damage in a model of endotoxemia in sheep. Conscious (n = 6) and anesthetized (n = 6) sheep were made endotoxemic by continuous infusion of LPS for 48 h. Central hemodynamics were monitored continuously, and blood samples were collected regularly. Activation of leukocytes was assessed by surface expression of CD11b and plasma myeloperoxidase concentration. Lung damage was determined by electron microscopy, cell count in bronchoalveolar lavage fluid, and analysis of lung vascular permeability. Four additional animals (two conscious and two anesthetized) went through the same protocol but did not receive LPS. LPS infusion induced a hyperdynamic sepsis. The drop in total peripheral resistance was compensated by an increase in heart rate and cardiac output in the conscious group, whereas anesthetized sheep failed to compensate in this way. Endotoxemic isoflurane-anesthetized sheep also showed signs of aggravated lung edema formation and tissue damage together with enhanced neutrophil activation and lung tissue accumulation. Our data suggest that isoflurane in conjunction with mechanical ventilation blunts cardiovascular compensatory mechanisms in sepsis and enhances leukocyte activation, which may contribute to lung edema formation and tissue damage.

Comparison of the effects of tramadol, codeine, and ketoprofen alone or in combination on postoperative pain and on concentrations of blood glucose, serum cortisol, and serum interleukin-6 in dogs undergoing maxillectomy or mandibulectomy

OBJECTIVE

To compare analgesic effects of tramadol, codeine, and ketoprofen administered alone and in combination and their effects on concentrations of blood glucose, serum cortisol, and serum interleukin (IL)-6 in dogs undergoing maxillectomy or mandibulectomy.

ANIMALS

42 dogs with oral neoplasms.

PROCEDURES

30 minutes before the end of surgery, dogs received SC injections of tramadol (2 mg/kg), codeine (2 mg/kg), ketoprofen (2 mg/kg), tramadol+ketoprofen, or codeine+ketoprofen (at the aforementioned dosages). Physiologic variables, analgesia, and sedation were measured before (baseline) and 1, 2, 3, 4, 5, and 24 hours after surgery. Blood glucose, serum cortisol, and serum IL-6 concentrations were measured 1, 3, 5, and 24 hours after administration of analgesics.

RESULTS

All treatments provided adequate postoperative analgesia. Significant increases in mean+/-SD blood glucose concentrations were detected in dogs receiving tramadol (96+/-14 mg/dL), codeine (120+/-66 mg/dL and 96+/-21 mg/dL), ketoprofen (105+/-22 mg/dL), and codeine+ketoprofen (104+/-16 mg/dL) at 5, 1 and 3, 5, and 3 hours after analgesic administration, respectively, compared with preoperative (baseline) values. There were no significant changes in physiologic variables, serum IL-6 concentrations, or serum cortisol concentrations. Dogs administered codeine+ketoprofen had light but significant sedation at 4, 5, and 24 hours.

CONCLUSIONS AND CLINICAL RELEVANCE

Opioids alone or in combination with an NSAID promoted analgesia without adverse effects during the 24-hour postoperative period in dogs undergoing maxillectomy or mandibulectomy for removal of oral neoplasms.

Traumatic brain injury and intestinal dysfunction: uncovering the neuro-enteric axis

Traumatic brain injury (TBI) can lead to several physiologic complications including gastrointestinal dysfunction. Specifically, TBI can induce an increase in intestinal permeability, which may lead to bacterial translocation, sepsis, and eventually multi-system organ failure. However, the exact mechanism of increased intestinal permeability following TBI is unknown. We hypothesized that expression of tight junction protein ZO-1 and occludin, responsible for intestinal architectural and functional integrity, will decrease following TBI and increase intestinal permeability. BALB/c mice underwent a weight drop TBI model following anesthesia. Brain injury was confirmed by a neurologic assessment and gross brain pathology. Six hours following injury, FITC-dextran (25 mg 4.4 kDa FITC-dextran) was injected into the intact lumen of the isolated ileum. Intestinal permeability was measured in plasma 30 min following injection, by using spectrophotometry to determine plasma FITC-dextran concentrations. Whole ileum extracts were used to measure expression of tight junction proteins ZO-1 and occludin by Western blot. TBI caused a significant increase in intestinal permeability (110.0 microg/mL +/-22.2) compared to sham animals (29.4 microg/mL +/- 9.7) 6 h after injury (p = 0.016). Expression of ZO-1 was decreased by 49% relative to sham animals (p < 0.02), whereas expression of occludin was decreased by 73% relative to sham animals (p < 0.001). An increase in intestinal permeability corresponds with decreased expression of tight junction proteins ZO-1 and occludin following TBI. Expression of intestinal tight junction proteins may be an important factor in gastrointestinal dysfunction following brain injury.

Traumatic brain injury and intestinal dysfunction: uncovering the neuro-enteric axis

Traumatic brain injury (TBI) can lead to several physiologic complications including gastrointestinal dysfunction. Specifically, TBI can induce an increase in intestinal permeability, which may lead to bacterial translocation, sepsis, and eventually multi-system organ failure. However, the exact mechanism of increased intestinal permeability following TBI is unknown. We hypothesized that expression of tight junction protein ZO-1 and occludin, responsible for intestinal architectural and functional integrity, will decrease following TBI and increase intestinal permeability. BALB/c mice underwent a weight drop TBI model following anesthesia. Brain injury was confirmed by a neurologic assessment and gross brain pathology. Six hours following injury, FITC-dextran (25 mg 4.4 kDa FITC-dextran) was injected into the intact lumen of the isolated ileum. Intestinal permeability was measured in plasma 30 min following injection, by using spectrophotometry to determine plasma FITC-dextran concentrations. Whole ileum extracts were used to measure expression of tight junction proteins ZO-1 and occludin by Western blot. TBI caused a significant increase in intestinal permeability (110.0 microg/mL +/-22.2) compared to sham animals (29.4 microg/mL +/- 9.7) 6 h after injury (p = 0.016). Expression of ZO-1 was decreased by 49% relative to sham animals (p < 0.02), whereas expression of occludin was decreased by 73% relative to sham animals (p < 0.001). An increase in intestinal permeability corresponds with decreased expression of tight junction proteins ZO-1 and occludin following TBI. Expression of intestinal tight junction proteins may be an important factor in gastrointestinal dysfunction following brain injury.

Effects of sevoflurane on collagen production and growth factor expression in rats with an excision wound

BACKGROUND

Sevoflurane is a widely used inhalation anesthetic, but there are no studies on its effect on the wound-healing process. This study was undertaken to evaluate the effect of exposure time to sevoflurane on wound healing.

METHOD

Male Sprague-Dawley rats were used. Two circular full-thickness skin defects 8 mm in diameter were made on the dorsum of the rats. The animals were divided into six groups according to exposed gas type and time: S1 (sevoflurane, 1 h), S4 (sevoflurane, 4 h), S8 (sevoflurane, 8 h), O1 (oxygen, 1 h), O4 (oxygen, 4 h), and O8 (oxygen, 8 h). The surface area of the wounds was measured 0, 1, 3, and 7 days after surgery. Separately, the mean blood pressures (MBP) and arterial oxygen pressures (PaO(2)) were monitored during the sevoflurane exposure. Collagen type I production and transforming growth factor-beta1 (TGF-beta1) and basic fibroblast growth factor (bFGF) expression on the wound surface were analyzed. Routine histological analysis was also performed.

RESULT

Exposure duration to sevoflurane had no influence on MBP and PaO(2). The reduction in wound size and collagen type I production was delayed in S8. The expression of TGF-beta1 and bFGF on the wound surface in S8 was significantly attenuated in S8. The histology of the S8 demonstrated a delayed healing status.

CONCLUSIONS

Prolonged exposure to sevoflurane might alter the inflammatory phase of the wound-healing process by attenuation of growth factor expression such as TGF-beta1 and bFGF and subsequently by reduced collagen production.

Protective effect of chloral hydrate against lipopolysaccharide/D-galactosamine-induced acute lethal liver injury and zymosan-induced peritonitis in mice

In recent years, certain anesthetics have been shown to have protective effects against acute inflammation in experimental animals, an observation that may yield new options for adjunctive treatment of acute inflammation. In this study, we investigated the effects of chloral hydrate (CH) on the acute inflammatory response in BALB/c mice using lipopolysaccharide/D-galactosamine (LPS/D-GalN)-induced acute lethal liver injury and zymosan A-induced peritonitis models. The survival of mice following LPS/D-GalN treatment was significantly improved by a single injection with chloral hydrate, which could be administered simultaneously or as late as 3h after challenge with LPS/D-GalN; liver injury was also attenuated. A sharp rise in serum levels of MCP-1, IL-6 and TNF-alpha was attenuated or delayed after chloral hydrate treatment. Furthermore, the mechanism by which chlorate hydrate inhibits inflammation was associated with an attenuated increase in nuclear factor kappaappaB (NF-kappaB) activity in NF-kappaB-RE-luc mice upon LPS/D-GalN treatment. In mice with acute peritonitis, leukocyte number and protein concentration in peritoneal exudates peaked with a 16h lag, and serum levels of MCP-1, IL-6 and TNF-alpha were significantly lower at certain time points in the chloral hydrate-treated group compared to those in the normal saline (NS)-treated control group. In addition, chloral hydrate treatment in vitro attenuated the upregulation of TNF-alpha and IL-6 by peritoneal macrophages and NF-kappaB activity in RAW264.7 cells stimulated with LPS, suggesting that monocytes/macrophages may be a target of chloral hydrate. These results indicate that chloral hydrate has a protective effect against LPS/D-GalN-induced acute lethal liver injury in mice, which may be associated with an inhibition of NF-kappaB activity and delays in proinflammatory cytokine production. However, this phenomenon was not associated with levels of serum corticosterone. Chloral hydrate also attenuated the inflammatory response in zymosan A-induced acute peritonitis, a model of mild inflammation. In conclusion, treatment with only a single injection of chloral hydrate could significantly attenuate acute inflammation in mice treated with LPS/D-GalN and zymosan A. These effects are also likely associated with the inhibition of NF-kappaB activity.

Murine pulmonary inflammation model: a comparative study of anesthesia and instillation methods

Various techniques have been utilized historically to generate acute pulmonary inflammation in the murine system. Crystalline silica exposure results in acute inflammation followed by pulmonary fibrosis. Methods of exposure are varied in their techniques, as well as types of anesthesia. Therefore, the current study sought to compare the effects of two major anesthesia (isoflurane and ketamine) and three routes of instillation, intranasal (IN), intratracheal (IT), and trans-oral (TO), on markers of inflammation. Mice were anesthetized with isoflurane or ketamine and instilled IN with silica or phosphate-buffered saline (PBS). Mice were sacrificed and lavaged after 3 days. To assess inflammation, alveolar cells were assessed by cytospin and lavage fluid was analyzed for inflammatory cytokines and total protein. While all parameters were increased in silica-exposed groups, regardless of anesthesia type, there were significant increases in neutrophils and total protein in mice anesthetized with ketamine, compared to isoflurane. In comparing instillation techniques, mice were anesthetized with isoflurane and instilled IN, IT, or TO with silica. Increases were observed in all parameters, except tumor necrosis factor-alpha, following IT silica instillation as compared to the IN and TO instillation groups. In addition, fluorescent microsphere uptake by alveolar macrophages supported the notion that all methods of instillation were uniform, but IT had significantly greater dispersion. Taken together, these data show that each method of exposure tested generated significant inflammation among the silica groups, and any differences in parameters or techniques should be taken into consideration when developing an animal model to study pulmonary diseases.

Delayed treatment with isoflurane attenuates lipopolysaccharide and interferon gamma-induced activation and injury of mouse microglial cells

BACKGROUND

Isoflurane pretreatment can induce protection against lipopolysaccharide and interferon gamma (IFNgamma)-induced injury and activation of mouse microglial cells. This study's goal was to determine whether delayed isoflurane treatment is protective.

METHODS

Mouse microglial cells were exposed to various concentrations of isoflurane for 1 h immediately after the initiation of lipopolysaccharide (10 or 1000 ng/ml) and IFNgamma (10 U/ml) stimulation or to 2% isoflurane for 1 h at various times after initiation of the stimulation. Nitrite production, lactate dehydrogenase release, and cell viability measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay were assessed after stimulation with lipopolysaccharide and IFNgamma for 24 h. Inducible nitric oxide synthase (iNOS) protein expression was quantified by Western blotting. The iNOS expression in mouse brain was also studied.

RESULTS

Isoflurane applied 0 and 2 h after the initiation of lipopolysaccharide and IFNgamma stimulation improved cell viability. Isoflurane at 2%, but not at 1 or 3%, reduced the lipopolysaccharide and IFNgamma-induced nitrite production and decreased cell viability. Aminoguanidine, an iNOS inhibitor, also attenuated this decreased cell viability. Chelerythrine and bisindolylmalemide IX, protein kinase C inhibitors, abolished isoflurane effects on cell viability and iNOS expression after lipopolysaccharide and IFNgamma application. Isoflurane also decreased lipopolysaccharide-induced iNOS expression in mouse brain. Late isoflurane application to microglial cells reduced lipopolysaccharide and IFNgamma-induced lactate dehydrogenase release that was not inhibited by aminoguanidine.

CONCLUSIONS

These results suggest that delayed isoflurane treatment can reduce lipopolysaccharide and IFNgamma-induced activation and injury of microglial cells. These effects may be mediated by protein kinase C.

Tumor necrosis factor-alpha induces renal vasoconstriction as well as natriuresis in mice

Tumor necrosis factor-α (TNF-α) has been implicated in the pathogenesis of hypertension and renal injury. However, the direct effects of TNF-α on renal hemodynamic and excretory function are not yet clearly defined. We examined the renal responses to infusion of TNF-α (0.33 ng·g⁻¹·min⁻¹) in anesthetized mice. Renal blood flow (RBF) and glomerular filtration rate (GFR) were determined by PAH and inulin clearance. The urine was collected from a cannula inserted into the bladder. Following the 60-min control clearance period, TNF-α infusion was initiated and 15 min were given for stabilization followed by another 60-min clearance period. TNF-α alone (n = 7) caused decreases in RBF (7.9 ± 0.3 to 6.4 ± 0.3 ml·min⁻¹·g⁻¹) and GFR (1.04 ± 0.06 to 0.62 ± 0.08 ml·min⁻¹·g⁻¹) as well as increases in absolute (0.8 ± 0.3 to 1.4 ± 0.3 μmol·min⁻¹·g⁻¹) and fractional excretion of sodium (0.5 ± 0.2 to 1.5 ± 0.4%) without affecting arterial pressure. TNF-α also increased 8-isoprostane excretion (8.10 ± 1.09 to 11.13 ± 1.34 pg·min⁻¹·g⁻¹). Pretreatment with TNF-α blocker etanercept (5 mg/kg sc; 24 and 3 h before TNF-α infusion; n = 6) abolished these responses. However, TNF-α induced an increase in RBF and caused attenuation of the GFR reduction in mice pretreated with superoxide (O₂⁻) scavenger tempol (2 μg·g⁻¹·min⁻¹; n = 6). Pretreatment with nitric oxide (NO) synthase inhibitor nitro-l-arginine methyl ester (0.1 μg·g⁻¹·min⁻¹; n = 6) resulted in further enhancement in vasoconstriction while natriuresis remained unaffected in response to TNF-α. These data suggest that TNF-α induces renal vasoconstriction and hypofiltration via enhancing the activity of O₂⁻ and thus reducing the activity of NO. The natriuretic response to TNF-α is related to its direct effects on tubular sodium reabsorption.