Volatile anesthetics-induced neuroinflammatory and anti-inflammatory responses

Effects of Volatile Anaesthetics and Iron Dextran on Chronic Inflammation and Antioxidant Defense System in Rats

Iron, as an essential microelement, is involved in cell proliferation, metabolism, and differentiation. It also modulates the fate and function of macrophages in hematopoiesis and macrophage-mediated inflammatory responses. On the other hand, anesthetics can affect the inflammatory process by modulating the response to stress or the functions of immune cells. The aim of this paper is to understand how excessive iron intake alters physiological, functional characteristics of peripheral tissues and whether different anesthetics can alter cell metabolism regarding oxidative stress (OS) and inflammation through regulation of macrophage polarization. Y59 rats were injected intraperitoneally with iron dextran solution at a dose of 50 mg/kg or were exposed to inhaled anesthetics sevoflurane and isoflurane and their combination for 28 days every other day. The results show that the use of anesthetics reduces the rat’s organ weight and increases OS in peripheral tissues, leading to M1 macrophage polarization. Excessive iron intake leads to increased OS, inflammation, and an increased ratio of IL-12/IL-10 cytokines to the M1 macrophage phenotype. Iron, in combination with sevoflurane, has a protective effect in tissues showing the M2 phenotype of macrophages. The combination of iron dextran and isoflurane in rats leads to an increase in the erythropoiesis process made possible through the induction of hypoxia.

Neurite orientation dispersion and density imaging in a rodent model of acute mild traumatic brain injury

BACKGROUND AND PURPOSE

Identification of changesin brain microstructure following mild traumatic brain injury (mTBI) could be instrumental in understanding the underlying pathophysiology. The purpose of this study was to apply neurite orientation dispersion and density imaging (NODDI) to a rodent model of mTBI to determine whether microstructural changes could be detected immediately following injury.

METHODS

Fifteen adult male Wistar rats were scanned on a Bruker 9.4 Tesla small animal MRI using a multi-shell acquisition (30 b = 1000 s/mm² and 60 b = 2000 s/mm² ). Nine animals experienced a single closed head controlled cortical impact followed by NODDI from 1 to 4 h post injury. Region of interest analysis focused on the corpus callosum and hippocampus. A mixed analysis of variance (ANOVA) was used to determine statistically significant interactions in neurite density index (NDI), orientation dispersion index (ODI), fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity. Follow up repeated-measures ANOVAs were used to determine individual changes over time.

RESULTS

NDI showed a significant increase in the hippocampus and corpus callosum following injury, while ODI showed increases in the corpus callosum. No significant changes were observed in the sham control animals. No changes were found in FA, MD, AD, or RD. Histological analysis revealed increased glial fibrillary acidic protein staining relative to controls in both the hippocampus and corpus callosum, with evidence of activated astrocytes in these regions.

CONCLUSIONS

Changes in NODDI metrics were detected as early as 1 h following mTBI. No changes were detected with conventional diffusion tensor imaging (DTI) metrics, suggesting that NODDI provides greater sensitivity to microstructural changes than conventional DTI.

Immunomodulators in anesthesia

PURPOSE OF REVIEW

Anesthetics are known to have immunomodulatory effects. These can be detrimental, inducing immunosuppression and facilitating the development of opportunistic infections, especially when used at high doses, for prolonged periods, or in patients with preexisting immune deficiency; or beneficial, modulating the inflammatory response, particularly in critical illness and systemic hyperinflammatory states.

RECENT FINDINGS

Anesthetics can have microbicidal properties, and both anti- and pro-inflammatory effects. They can act directly on immune cells as well as modulate immunity through indirect pathways, acting on the neuroimmune stress response, and have recently been described to interact with the gut microbiota.

SUMMARY

Anesthesiologists should take into consideration the immunomodulatory properties of anesthetic agents in addition to their hemodynamic, neuroprotective, and other impacts. In future, patient stratification according to the perioperative assessment of serum biomarkers associated with postoperative complications may be used to guide anesthetic agent selection based on their immunomodulatory properties.

Transcriptomic response of brain tissue to focused ultrasound-mediated blood-brain barrier disruption depends strongly on anesthesia

Focused ultrasound (FUS) mediated blood-brain barrier disruption (BBBD) targets the delivery of systemically-administered therapeutics to the central nervous system. Preclinical investigations of BBBD have been performed on different anesthetic backgrounds; however, the influence of the choice of anesthetic on the molecular response to BBBD is unknown, despite its potential to critically affect interpretation of experimental therapeutic outcomes. Here, using bulk RNA sequencing, we comprehensively examined the transcriptomic response of both normal brain tissue and brain tissue exposed to FUS-induced BBBD in mice anesthetized with either isoflurane with medical air (Iso) or ketamine/dexmedetomidine (KD). In normal murine brain tissue, Iso alone elicited minimal differential gene expression (DGE) and repressed pathways associated with neuronal signaling. KD alone, however, led to massive DGE and enrichment of pathways associated with protein synthesis. In brain tissue exposed to BBBD (1 MHz, 0.5 Hz pulse repetition frequency, 0.4 MPa peak-negative pressure), we systematically evaluated the relative effects of anesthesia, microbubbles, and FUS on the transcriptome. Of particular interest, we observed that gene sets associated with sterile inflammatory responses and cell-cell junctional activity were induced by BBBD, regardless of the choice of anesthesia. Meanwhile, gene sets associated with metabolism, platelet activity, tissue repair, and signaling pathways, were differentially affected by BBBD, with a strong dependence on the anesthetic. We conclude that the underlying transcriptomic response to FUS-mediated BBBD may be powerfully influenced by anesthesia. These findings raise considerations for the translation of FUS-BBBD delivery approaches that impact, in particular, metabolism, tissue repair, and intracellular signaling.

Roflumilast Ameliorates Isoflurane-Induced Inflammation in Astrocytes via the CREB/BDNF Signaling Pathway

Background and purpose: Astrocyte-mediated neuroinflammation plays an important role in anesthetic isoflurane-induced cognitive impairment. Roflumilast, a selective inhibitor of phosphodiesterase-4 (PDE-4) used for the treatment of chronic obstructive pulmonary disease (COPD), has displayed a wide range of anti-inflammatory capacity in different types of cells and tissues. In the current study, we aimed to investigate whether roflumilast possesses a protective effect against isoflurane-induced insults in mouse primary astrocytes. Methods: Primary astrocytes were isolated from the cerebral cortices of immature rats. The production of NO was determined using DAF-FM DA staining assay. QRT-PCR and western blot were used to evaluate the expression levels of iNOS, COX-2, and BDNF in the astrocytes treated with different therapies. The gene expressions and concentrations of IL-6 and MCP-1 released by the astrocytes were detected using qRT-PCR and ELISA, respectively. The expression levels of phosphorylated CREB and PGE₂ were determined using western blot and ELISA, respectively. H89 was introduced to evaluate the function of CREB. Recombinant human BDNF and ANA-12 were used to verify the role of BDNF. Results: The upregulated iNOS, excessive production of NO, IL-6, and MCP-1, and activated COX-2/PGE₂ signaling pathways in the astrocytes induced by isoflurane were significantly reversed by the introduction of roflumilast, in a dose-dependent manner. Subsequently, we found that BDNF could be upregulated by roflumilast, which was verified to be related to the activation of CREB and blocked by H89 (a CREB inhibitor). In addition, the COX-2/PGE₂ signaling pathway activated by isoflurane can be inactivated by recombinant human BDNF. Finally, the regulatory effect of roflumilast against the isoflurane-activated COX-2/PGE₂ signaling pathway was significantly blocked by ANA-12, which is a BDNF inhibitor. Conclusion: Roflumilast might ameliorate isoflurane-induced inflammation in astrocytes via the CREB/BDNF signaling pathway.

An extracellular cold-inducible RNA-binding protein-derived small peptide targeting triggering receptor expressed on myeloid cells-1 attenuates hemorrhagic shock

BACKGROUND

Extracellular cold-inducible RNA-binding protein (eCIRP) is a damage-associated molecular pattern, which is released into the circulation after hemorrhagic shock (HS). Recently, we discovered that triggering receptor expressed on myeloid cells-1 (TREM-1) serves as a new receptor of eCIRP to exaggerate inflammation. Here, we hypothesize that by inhibiting the interaction between eCIRP and TREM-1 with the use of a novel short peptide derived from human eCIRP known as M3, we can inhibit the inflammatory response and acute lung injury in HS.

METHODS

Hemorrhagic shock was induced using C57BL/6 mice by cannulating both femoral arteries. One femoral artery was used for removal of blood while the other was used for continuous monitoring of mean arterial blood pressure. The mean arterial pressure of 25 mm Hg to 30 mm Hg was maintained for 90 minutes, followed by a resuscitation phase of 30 minutes with 1 mL of normal saline. The treatment group was given 10 mg/kg of M3 during the resuscitation phase. Four hours after resuscitation, serum and lungs were collected and analyzed for various injury and inflammatory markers by using colorimetry, real-time polymerase chain reaction, and enzyme-linked immunosorbent assay.

RESULTS

There was an increase in the serum levels of tissue injury markers (alanine aminotransferase, aspartate aminotransferase, and lactate dehydrogenase) as well as cytokines (TNF-α and IL-6) when comparing the vehicle group versus the sham group. This increase was significantly inhibited in the M3-treated group. The mRNA expression of proinflammatory cytokines TNF-α, IL-6, and IL-1β and the chemokines MIP-2 and KC in lungs was significantly increased in the vehicle-treated HS mice, while their expression was significantly decreased in M3-treated HS mice. Finally, M3 treatment significantly decreased the lung injury score compared with vehicle-treated HS mice.

CONCLUSION

The novel eCIRP-derived TREM-1 antagonist (M3) can be a potential therapeutic adjunct in the management of hemorrhagic shock.

Intravital imaging of immune cells and their interactions with other cell types in the spinal cord: Experiments with multicolored moving cells

Intravital imaging of the immune system is a powerful technique for studying biology of the immune response in the spinal cord using a variety of disease models ranging from traumatic injury to autoimmune disorders. Here, we will discuss specific technical aspects as well as many intriguing biological phenomena that have been revealed with the use of intravital imaging for investigation of the immune system in the spinal cord. We will discuss surgical techniques for exposing and stabilizing the spine that are critical for obtaining images, visualizing immune and CNS cells with genetically expressed fluorescent proteins, fluorescent labeling techniques and briefly discuss some of the challenges of image analysis.

Involvement of leukotriene pathway in the development of sevoflurane-induced pica in rats

We previously reported that sevoflurane-induced pica, kaolin ingestion behavior, in rats has the potential to reflect postoperative nausea and vomiting (PONV) in humans. It is well-known that corticosteroids, which inhibit both prostaglandin and leukotriene syntheses due to phospholipase A₂ inhibition, are effective for reducing PONV; however, the precise mechanisms remain unclear. We investigated the involvement of the prostaglandin or leukotriene pathway in the development of sevoflurane-induced pica. We found that sevoflurane-induced pica was effectively inhibited by pretreatment with a leukotriene receptor antagonist (montelukast) or an inhibitor of 5-lipoxygenase (zileuton), rather than an inhibitor of cyclooxygenase (flurbiprofen). Furthermore, we observed that sevoflurane significantly increased urinary leukotriene excretion and 5-lipoxygenase mRNA expression in the spleen, but not hypothalamus. These results suggest that the production of leukotriene may lead to the development of sevoflurane-induced pica in rats, and that inhibition of the leukotriene pathway could be potentially useful for the treatment of PONV.

Melatonin Alleviates Intracerebral Hemorrhage-Induced Secondary Brain Injury in Rats via Suppressing Apoptosis, Inflammation, Oxidative Stress, DNA Damage, and Mitochondria Injury

Intracerebral hemorrhage (ICH) is a cerebrovascular disease with high mortality and morbidity, and the effective treatment is still lacking. We designed this study to investigate the therapeutic effects and mechanisms of melatonin on the secondary brain injury (SBI) after ICH. An in vivo ICH model was induced via autologous whole blood injection into the right basal ganglia in Sprague-Dawley (SD) rats. Primary rat cortical neurons were treated with oxygen hemoglobin (OxyHb) as an in vitro ICH model. The results of the in vivo study showed that melatonin alleviated severe brain edema and behavior disorders induced by ICH. Indicators of blood-brain barrier (BBB) integrity, DNA damage, inflammation, oxidative stress, apoptosis, and mitochondria damage showed a significant increase after ICH, while melatonin reduced their levels. Meanwhile, melatonin promoted further increasing of expression levels of antioxidant indicators induced by ICH. Microscopically, TUNEL and Nissl staining showed that melatonin reduced the numbers of ICH-induced apoptotic cells. Inflammation and DNA damage indicators exhibited an identical pattern compared to those above. Additionally, the in vitro study demonstrated that melatonin reduced the apoptotic neurons induced by OxyHb and protected the mitochondrial membrane potential. Collectively, our investigation showed that melatonin ameliorated ICH-induced SBI by impacting apoptosis, inflammation, oxidative stress, DNA damage, brain edema, and BBB damage and reducing mitochondrial membrane permeability transition pore opening, and melatonin may be a potential therapeutic agent of ICH.

Anti-inflammatory properties of anesthetic agents

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2017. Other selected articles can be found online at http://ccforum.com/series/annualupdate2017. Further information about the Annual Update in Intensive Care and Emergency Medicine is available from http://www.springer.com/series/8901.

Effect of propofol and sevoflurane on the inflammatory response of patients undergoing craniotomy

BACKGROUND

The purpose of this randomised, single-centre study was to prospectively investigate the impact of anaesthetic techniques for craniotomy on the release of cytokines IL-6, IL-8, IL-10, and to determine whether intravenous anaesthesia compared to inhalational anaesthesia attenuates the inflammatory response.

METHODS

The study enroled 40 patients undergoing craniotomy, allocated into two equal groups to receive either sevoflurane (n = 20) or propofol (n = 20) in conjunction with remifentanil and rocuronium. The lungs were ventilated mechanically to maintain normocapnia. Remifentanil infusion was adjusted according to the degree of surgical manipulation and increased when mean arterial pressure and the heart rate increased by more than 30 % from baseline. The depth of anaesthesia was adjusted to maintain a bispectral index (BIS) of 40-60. Invasive haemodynamic monitoring was used. Serum levels of IL-6, IL-8 and IL-10 were measured before surgery and anaesthesia, during tumour removal, at the end of surgery, and at 24 and 48 h after surgery. Postoperative complications (pain, vomiting, changes in blood pressure, infection and pulmonary, cardiovascular and neurological events) were monitored during the first 15 days after surgery.

RESULTS

Compared with patients anaesthetised with sevoflurane, patients who received propofol had higher levels of IL-10 (p = 0.0001) and lower IL-6/IL-10 concentration ratio during and at the end of surgery (p = 0.0001). Both groups showed only a minor response of IL- 8 during and at the end of the surgery (p = 0.57).

CONCLUSIONS

Patients who received propofol had higher levels of IL-10 during surgery. Neither sevoflurane nor propofol had any significant impact on the occurrence of postoperative complications. Our findings should incite future studies to prove a potential medically important anti-inflammatory role of propofol in neuroanaesthesia.

CLINICAL TRIAL REGISTRATION

Identified as NCT02229201 at www.clinicaltrials.gov.

Dexmedetomidine Postconditioning Reduces Brain Injury after Brain Hypoxia-Ischemia in Neonatal Rats

Perinatal asphyxia can lead to death and severe disability. Brain hypoxia-ischemia (HI) injury is the major pathophysiology contributing to death and severe disability after perinatal asphyxia. Here, seven-day old Sprague-Dawley rats were subjected to left brain HI. Dexmedetomidine was given intraperitoneally after the brain HI. Yohimbine or atipamezole, two α2 adrenergic receptor antagonists, were given 10 min before the dexmedetomidine injection. Neurological outcome was evaluated 7 or 28 days after the brain HI. Frontal cerebral cortex was harvested 6 h after the brain HI. Left brain HI reduced the left cerebral hemisphere weight assessed 7 days after the brain HI. This brain tissue loss was dose-dependently attenuated by dexmedetomidine. Dexmedetomidine applied within 1 h after the brain HI produced this effect. Dexmedetomidine attenuated the brain HI-induced brain tissue and cell loss as well as neurological and cognitive dysfunction assessed from 28 days after the brain HI. Dexmedetomidine postconditioning-induced neuroprotection was abolished by yohimbine or atipamezole. Brain HI increased tumor necrosis factor α and interleukin 1β in the brain tissues. This increase was attenuated by dexmedetomidine. Atipamezole inhibited this dexmedetomidine effect. Our results suggest that dexmedetomidine postconditioning reduces HI-induced brain injury in the neonatal rats. This effect may be mediated by α2 adrenergic receptor activation that inhibits inflammation in the ischemic brain tissues.

Transfusion of Old RBCs Induces Neuroinflammation and Cognitive Impairment

OBJECTIVES

Transfusing RBCs stored for longer than 14 days (old RBC) in humans is common. This transfusion can injure organs, such as lungs and kidneys. We determined whether transfusion with old RBC injured brain.

DESIGN

Prospective, controlled animal study.

SETTING

University research laboratory.

SUBJECTS

Adult male Sprague-Dawley rats.

INTERVENTIONS

Six-month-old Sprague-Dawley rats lost 20% total blood volume and then received RBC prepared from equal volume of the lost blood. RBC was stored for 1 day (fresh RBC) or 7 days (old RBC, storage lesions similar to those of human RBC stored for 28 d). Some rats received IV cell-free hemoglobin. These rats were not subjected to hemorrhage and RBC transfusion.

MEASUREMENTS AND MAIN RESULTS

Rats were subjected to Barnes maze and fear conditioning tests from 1 week after blood transfusion. Rats transfused with old RBC but not fresh RBC took a longer time to identify the target hole in the Barnes maze and had less context-related fear conditioning behavior than control rats. Old RBC significantly increased interleukin 6 and ionized calcium-binding adapter molecule 1 in the hippocampus at 24 hours after the transfusion. These effects were attenuated by sulforaphane and minocycline, an antibiotic with anti-inflammatory property. Old RBC solution had a higher concentration of cell-free hemoglobin. Sulforaphane increased haptoglobin, a chelator of cell-free hemoglobin. Rats that received cell-free hemoglobin had a pattern of neuroinflammation and impairment of learning and memory similar to that of rats that received old RBC.

CONCLUSIONS

These results provide initial evidence to suggest that transfusion of old RBC induces neuroinflammation and impairment of learning and memory. These effects may be mediated by cell-free hemoglobin.

A Mitochondrion-Targeted Antioxidant Ameliorates Isoflurane-Induced Cognitive Deficits in Aging Mice

Isoflurane possesses neurotoxicity and can induce cognitive deficits, particularly in aging mammals. Mitochondrial reactive oxygen species (mtROS) have been linked to the early pathogenesis of this disorder. However, the role of mtROS remains to be evaluated due to a lack of targeted method to treat mtROS. Here, we determined in aging mice the effects of the mitochondrion-targeted antioxidant SS-31, on cognitive deficits induced by isoflurane, a general inhalation anesthetic. We further investigated the possible mechanisms underlying the effects of SS-31 on hippocampal neuro-inflammation and apoptosis. The results showed that isoflurane induced hippocampus-dependent memory deficit, which was associated with mitochondrial dysfunction including reduced ATP contents, increased ROS levels, and mitochondrial swelling. Treatment with SS-31 significantly ameliorated isoflurane-induced cognitive deficits through the improvement of mitochondrial integrity and function. Mechanistically, SS-31 treatment suppressed pro-inflammatory responses by decreasing the levels of NF-κB, NLRP3, caspase 1, IL-1β, and TNF-α; and inhibited the apoptotic pathway by decreasing the Bax/Bcl-2 ratio, reducing the release of cytochrome C, and blocking the cleavage of caspase 3. Our results indicate that isoflurane-induced cognitive deficits may be attenuated by mitochondrion-targeted antioxidants, such as SS-31. Therefore, SS-31 may have therapeutic potentials in preventing injuries from oxidative stresses that contribute to anesthetic-induced neurotoxicity.

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

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