Rat brain DNA transcript profile of halothane and isoflurane exposure

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.

General anesthesia, germ cells and the missing heritability of autism: an urgent need for research

Agents of general anesthesia (GA) are commonly employed in surgical, dental and diagnostic procedures to effectuate global suppression of the nervous system, but in addition to somatic targets, the subject's germ cells-from the embryonic primordial stage to the mature gametes-may likewise be exposed. Although GA is generally considered safe for most patients, evidence has accumulated that various compounds, in particular the synthetic volatile anesthetic gases (SVAGs) such as sevoflurane, can exert neurotoxic, genotoxic and epigenotoxic effects, with adverse consequences for cellular and genomic function in both somatic and germline cells. The purpose of this paper is to review the evidence demonstrating that GA, and in particular, SVAGs, may in some circumstances adversely impact the molecular program of germ cells, resulting in brain and behavioral pathology in the progeny born of the exposed cells. Further, we exhort the medical and scientific communities to undertake comprehensive experimental and epidemiological research programs to address this critical gap in risk assessment.

Effect of different anaesthetic techniques on gene expression profiles in patients who underwent hip arthroplasty

Objectives

To investigate the modulation of genes whose expression level is indicative of stress and toxicity following exposure to three anaesthesia techniques, general anaesthesia (GA), regional anaesthesia (RA), or integrated anaesthesia (IA).

Methods

Patients scheduled for hip arthroplasty receiving GA, RA and IA were enrolled at Rizzoli Orthopaedic Institute of Bologna, Italy and the expression of genes involved in toxicology were evaluated in peripheral blood mononuclear cells (PBMCs) collected before (T0), immediately after surgery (T1), and on the third day (T2) after surgery in association with biochemical parameters.

Results

All three anaesthesia methods proved safe and reliable in terms of pain relief and patient recovery. Gene ontology analysis revealed that GA and mainly IA were associated with deregulation of DNA repair system and stress-responsive genes, which was observed even after 3-days from anaesthesia. Conversely, RA was not associated with substantial changes in gene expression.

Conclusions

Based on the gene expression analysis, RA technique showed the smallest toxicological effect in hip arthroplasty.

Trial registration

ClinicalTrials.gov number NCT03585647.

Genomics and Proteomic Techniques

Although general anesthesia induced by inhaled anesthetics produces definitive phenotypes (e.g., loss of mobility, amnesia, analgesia), the underlying targets of these drugs are still not clear. Genomics and proteomic techniques are discussed for measurement of global transcriptional and translational changes after inhaled anesthetic exposures. The current discussion focuses primarily on the genomic and proteomic technical methodology. We also include a discussion of network and pathway analyses for data interpretation after identification of the targets.

Changes in rat spinal cord gene expression after inflammatory hyperalgesia of the joint and manual therapy

CONTEXT

Mobilization of a joint affects local tissue directly but may also have other effects that are mediated through the central nervous system.

OBJECTIVE

To identify differential gene expression in the spinal cords of rats with or without inflammatory joint injury after manual therapy or no treatment.

METHODS

Rats were randomly assigned to 1 of 4 treatment groups: no injury and no touch (NI/NT), injury and no touch (I/NT), no injury and manual therapy (NI/MT), and injury and manual therapy (I/MT). We induced acute inflammatory joint injury in the rats by injecting carrageenan into an ankle. Rats in the no-injury groups did not receive carrageenan injection. One day after injury, rats received manual therapy to the knee of the injured limb. Rats in the no-touch groups were anesthetized without receiving manual therapy. Spinal cords were harvested 30 minutes after therapy or no touch, and spinal cord gene expression was analyzed by microarray for 3 comparisons: NI/NT vs I/NT, I/MT vs I/NT, and NI/NT vs NI/MT.

RESULTS

Three rats were assigned to each group. Of 38,875 expressed sequence tags, 755 were differentially expressed in the NI/NT vs I/NT comparison. For the other comparisons, no expressed sequence tags were differentially expressed. Cluster analysis revealed that the differentially expressed sequence tags were over-represented in several categories, including ion homeostasis (enrichment score, 2.29), transmembrane (enrichment score, 1.55), and disulfide bond (enrichment score, 2.04).

CONCLUSIONS

An inflammatory injury to the ankle of rats caused differential expression of genes in the spinal cord. Consistent with other studies, genes involved in ion transport were among those affected. However, manual therapy to the knees of injured limbs or to rats without injury did not alter gene expression in the spinal cord. Thus, evidence for central nervous system mediation of manual therapy was not observed.

Determination of the mechanism of action of repetitive halothane exposure on rat brain tissues using a combined method of microarray gene expression profiling and bioinformatics analysis

The present study aimed to investigate the gene expression profiles of rats brain tissues treated with halothane compared with untreated controls to improve current understanding of the mechanism of action of the inhaled anesthetic. The GSE357 gene expression profile was dowloaded from the Gene Expression Omnibus database, and included six gene chips of samples repeatedly exposed to halothane and 12 gene chips of untreated controls. The differentially expressed genes (DEGs) between these two groups were identified using the Limma package in R language. Subsequently, the Database for Annotation, Visualization and Integrated Discovery was used to annotate the function of these DEGs. In addition, the most significantly upregulated gene and downregulated gene were annotated, to reveal the functional interactions with other associated genes, in FuncBase database. A total of 44 DEGs were obtained between The control and halothane exposure samples. Following Gene Ontology functional classification, these DEGs were found to be involved predominantly in the circulatory system, regulation of cell proliferation and response to endogenous stimulus and corticosteroid stimulus processes. KRT31 and HMGCS2, which were identified as the most significantly downregulated and upregulated DEGs, respectively, were associated with the lipid metabolic process and T cell activation, respectively. These results provided a basis for the development of improved inhalational anesthetics with minimal side effects and are essential for optimization of inhaled anesthetic techniques for advanced surgical procedures.

Differential impact of stress on hypothalamic-pituitary-adrenal axis: gene expression changes in Lewis and Fisher rats

The aim of the present work was to study the influence of variable stress on the expression of 11β-hydroxysteroid dehydrogenase type 1 (11HSD1) and the neuropeptides corticotropin-releasing hormone (CRH), urocortins 2 and 3(UCN2, UCN3), arginine vasopressin (AVP), oxytocin (OXT) and adenylate cyclase-activating polypeptide (PACAP) in two inbred rat strains: stress hypo-responsive Lewis (LEW) and hyper-responsive Fisher 344 (F344) rats. We found site-specific and strain-dependent differences in the basal and stress-stimulated expression of 11HSD1, CRH, UCN2, UCN3 and PACAP. In LEW rats, stress upregulated 11HSD1 in the prefrontal cortex and lateral amygdala, whereas in F344 rats 11HSD1 was upregulated in the central amygdala and hippocampal CA2 and ventral but not dorsal CA1 region; no effect was observed in the paraventricular nucleus, pituitary gland and adrenal cortex of both strains. The expression of glucocorticoid receptors did not parallel the upregulation of 11HSD1. Stress also stimulated the expression of paraventricular OXT, CRH, UCN3 and PACAP in both strains but amygdalar CRH only in LEW and UCN2/UCN3 in F344 rats, respectively. The upregulation of PACAP and CRH was paralleled only by increased expression of PACAP receptor PAC1 but not CRH receptor type 1. These observations provide evidence that inbred F344 and LEW rats exhibit not only the well-known phenotypic differences in the activity of the HPA axis but also strain- and stress-dependent differences in the expression of genes encoding 11HSD1 and neuropeptides associated with the HPA axis activity. Moreover, the differences in 11HSD1 expression suggest different local concentration of corticosterone and access to GR in canonical and noncanonical structures of the HPA axis.

PDGF-C: a new performer in the neurovascular interplay

The importance of neurovascular crosstalk in development, normal physiology, and pathologies is increasingly being recognized. Although vascular endothelial growth factor (VEGF), a prototypic regulator of neurovascular interaction, has been studied intensively, defining other important regulators in this process is warranted. Recent studies have shown that platelet-derived growth factor C (PDGF-C) is both angiogenic and a neuronal survival factor, and it appears to be an important component of neurovascular crosstalk. Importantly, the expression pattern and functional properties of PDGF-C and its receptors differ from those of VEGF, and thus the PDGF-C-mediated neurovascular interaction may represent a new paradigm of neurovascular crosstalk.

Anesthesia in presymptomatic Alzheimer's disease: a study using the triple-transgenic mouse model

BACKGROUND

Experimental evidence suggests that anesthetics accelerate symptomatic neurodegenerative disorders such as Alzheimer's disease (AD). Because AD pathology precedes symptoms, we asked ourselves whether anesthetic exposure in the presymptomatic interval accelerated neuropathology and appearance of symptoms.

METHODS

Triple-transgenic AD mice were exposed to general aesthetics, either halothane or isoflurane, at 2, 4, and 6 months of age, they then underwent water maze cognitive testing 2 months later, and subsequently their brains were analyzed using enzyme-linked immunosorbent assay, immunoblots, and immunohistochemistry for amyloid and tau pathology and biomarkers.

RESULTS

Learning and memory improved after halothane exposure in the 2-month-old group relative to controls, but no changes were noted in the isoflurane group. When gender was examined in all age groups, females exposed to halothane performed better as compared with those exposed to isoflurane or controls. Therefore, improvement in the 2-month exposure group is most likely because of a gender effect. Level of phospho-tau in the hippocampus was significantly increased 2 months after anesthesia, especially in the 6-month exposure group, but changes in amyloid, caspase, microglia, or synaptophysin levels were not detected.

CONCLUSIONS

These results indicate that exposure to two different inhalation-type anesthetics during the presymptomatic phase of AD does not accelerate cognitive decline, after 2 months, and may cause a stress response, marked by hippocampal phosphorylated tau, resulting in preconditioning against the ongoing neuropathology, primarily in female mice.

Effects of anesthesia on the response to sleep deprivation

STUDY OBJECTIVE

Slow wave activity (SWA) during NREM sleep is the best characterized marker of sleep homeostasis, and the occurrence of sleep slow waves is necessary to reduce sleep need. Recent evidence suggests that sleep slow waves may mediate several beneficial effects of sleep on performance, from the prevention of cognitive impairments to memory consolidation. However, slow waves are also triggered by low doses of many anesthetics, but very few reports have examined whether anesthesia-mediated slow waves affect the homeostatic regulation of sleep. Moreover, no study has examined how sleep is affected by higher doses of anesthetics, which lead to a predominantly "isoelectric" EEG tracing without slow waves.

DESIGN

We studied in rats whether 1 hour of a dose of isoflurane or desflurane able to induce almost continuous slow waves (ISO-sw, DES-sw), and of a dose of desflurane resulting in a predominantly isoelectric EEG (DES-iso) reduces the sleep pressure caused by 4 h of sleep deprivation. Anesthesia was compared to a mock condition in which rats were only anesthetized for 2-3 min.

SETTING

Basic sleep research laboratory.

PATIENTS OR PARTICIPANTS

Male WKY rats (n=31).

INTERVENTIONS

Total sleep deprivation by exposure to novel objects starting at light onset, followed by one hour of anesthesia or mock anesthesia.

MEASUREMENTS AND RESULTS

One hour of anesthesia (sw or iso) did not affect either sleep duration or the overall sleep pattern. Anesthesia with ISO-sw or DES-sw, both associated with the occurrence of almost continuous slow waves, reduced the SWA rebound expected following 4 h of sleep deprivation. One hour of anesthesia with DES-iso, associated with isoelectric EEG and few slow waves, also reduced the SWA rebound after sleep deprivation, and did so to an extent similar to that observed after DES-sw. However, in contrast to DES-sw, SWA after DES-iso remained chronically lower than in baseline, resulting in reduced slow wave energy (SWE, SWA × time) for at least 2 days.

CONCLUSION

The blunted SWA rebound after ISO-sw and DES-sw suggests that anesthesia slow waves may substitute for sleep slow waves. The reduced SWA rebound after DES-iso may reflect a pathological condition that results in a chronic decrease in SWA, or may suggest that anesthesia slow waves are not an absolute requirement to discharge sleep pressure.

Isoflurane anesthesia elicits protein pattern changes in rat hippocampus

Postoperative cognitive dysfunction (POCD) is a known phenomenon occurring after anesthesia with volatile anesthetics (VA), such as isoflurane. Recent reports suggest that VA interact with neurodegenerative disease-associated proteins including compounds with pathogenic relevance in Alzheimer disease (AD) and induce processes that may be linked to AD neuropathology. Unfortunately, our present understanding of the exact anesthetics' molecular mechanisms of action, their side effects on the brain, and their catenation with AD pathology is still limited. The present study analyzes the differential proteome of the hippocampus immediately after and 3 days after a 3-hour 1 minimal alveolar concentration isoflurane anesthesia in rats. Differential 2-dimensional electrophoresis, mass spectrometry, and functional network mapping were used to identify and functionally classify 12 different hippocampal proteins, which were significantly regulated after isoflurane anesthesia (6 up-regulated, 11 down-regulated with P<0.01). Induction of differential expression ranged from 0.05 (25-fold down-regulation) to 4.4 (4.4-fold up-regulation). Ten proteins were regulated immediately after and 7 proteins 3 days after isoflurane exposure. The proteome displays isoflurane-responsive protein candidates, which have also been shown to play a role in AD. They were grouped according to their key biologic activities, which showed that isoflurane affects selected biologic processes including synaptic plasticity, stress response, detoxification, and cytoskeleton in early and late recovery phases after anesthesia. These processes are also affected in AD. Results are discussed in view of AD, the toxicity mechanisms of isoflurane as well as the implications for our present understanding and conduction of clinical anesthesia.

Enhanced hypoxic preconditioning by isoflurane: signaling gene expression and requirement of intracellular Ca2+ and inositol triphosphate receptors

Neurons preconditioned with non-injurious hypoxia or the anesthetic isoflurane express different genes but are equally protected against severe hypoxia/ischemia. We hypothesized that neuroprotection would be augmented when preconditioning with isoflurane and hypoxic preconditioning are combined. We also tested if preconditioning requires intracellular Ca(2+) and the inositol triphosphate receptor, and if gene expression is similar in single agent and combined preconditioning. Hippocampal slice cultures prepared from 9 day old rats were preconditioned with hypoxia (95% N(2), 5% CO(2) for 15 min, HPC), 1% isoflurane for 15 min (APC) or their combination (CPC) for 15 min. A day later cultures were deprived of O(2) and glucose (OGD) to produce neuronal injury. Cell death was assessed 48 h after OGD. mRNA encoding 119 signal transduction genes was quantified with cDNA micro arrays. Intracellular Ca(2+) in CA1 region was measured with fura-2 during preconditioning. The cell-permeable Ca(2+) buffer BAPTA-AM, the IP(3) receptor antagonist Xestospongin C and RNA silencing were used to investigate preconditioning mechanisms. CPC decreased CA1, CA3 and dentate region death by 64-86% following OGD, more than HPC or APC alone (P<0.01). Gene expression following CPC was an amalgam of gene expression in HPC and APC, with simultaneous increases in growth/development and survival/apoptosis regulation genes. Intracellular Ca(2+) chelation and RNA silencing of IP(3) receptors prevented preconditioning neuroprotection and gene responses. We conclude that combined isoflurane-hypoxia preconditioning augments neuroprotection compared to single agents in immature rat hippocampal slice cultures. The mechanism involves genes for growth, development, apoptosis regulation and cell survival as well as IP(3) receptors and intracellular Ca(2+).

Inhaled anesthetics elicit region-specific changes in protein expression in mammalian brain

Inhaled anesthetics bind specifically to many proteins in the mammalian brain. Within the subgroup of proteins whose activity is substantially modulated by anesthetic binding, it is reasonable to expect anesthetic-induced alterations in host expression level. Thus, in an attempt to define the group of functional targets for these commonly used drugs, we examined changes in protein expression after anesthetic exposure in both intact rodent brains and in neuronal cell culture. Differential in-gel electrophoresis was used to minimize variance, in order to detect small changes. Quantitative analysis shows that 5 h exposures to 1 minimum alveolar concentration (1 MAC) halothane caused changes in the expression of approximately 2% of detectable proteins, but only at 2-24 h after awakening, and only in the cortex. An equipotent concentration of isoflurane altered the expression of only approximately 1% of detectable proteins, and only in the hippocampus. Primary cortical neurons were exposed to three-fold higher concentrations of anesthetics with no evidence of cytotoxicity. Small changes in protein expression were elicited by both drugs. Despite the fact that anesthetics produce profound changes in neurobiology and behavior, we found only minor changes in brain protein expression. A pronounced degree of regional selectivity was noted, indicating an under appreciated degree of specificity for these promiscuous drugs.

The effects of sevoflurane anesthesia on rat brain proteins: a proteomic time-course analysis

BACKGROUND

Recent studies showed changes in cerebral protein expression up to 3 days after desflurane anesthesia in rats. In the present study, we investigated the existence of persisting changes on the proteome level after sevoflurane anesthesia that persisted for as long as 28 days after anesthesia.

METHODS

Rats were anesthetized by spontaneous inhalation of 2.4% sevoflurane in air for 3 h. Animals (n = 6 for each group) were killed either directly, 72 h, or 28 days after anesthesia. Brains were removed and subjected to global protein expression profiling based on two-dimensional gel electrophoresis and mass spectrometry. Expression factors were compared to results from untreated conscious animals at each time point. Data were statistically analyzed by ANOVA (P < 0.01) and a cut of more than two-fold change in the expression factor.

RESULTS

We found 11 protein spots differentially regulated directly after anesthesia. Seventeen proteins were differentially expressed 72 h after the anesthesia. Only one spot was differentially regulated 28 days after anesthesia. The plausible targets of these differentially regulated proteins can be attributed to synaptic vesicle handling and cell-cell communication.

CONCLUSIONS

Sevoflurane induced relevant changes in protein expression profiles directly and 72 h after an anesthesia with 1 MAC. Twenty-eight days after the anesthesia, all proteins except one had returned to baseline levels of abundance.