Thiopental inhibits global protein synthesis by repression of eukaryotic elongation factor 2 and protects from hypoxic neuronal cell death

Protecting the injured central nervous system: Do anesthesia or hypothermia ameliorate secondary injury?

Traumatic injury to the central nervous system (CNS) and stroke initiate a cascade of processes that expand the area of tissue loss. The current review considers recent studies demonstrating that the induction of an anesthetic state or cooling the affected tissue (hypothermia) soon after injury can have a therapeutic effect. We first provide an overview of the neurobiological processes that fuel tissue loss after traumatic brain injury (TBI), spinal cord injury (SCI) and stroke. We then examine the rehabilitative effectiveness of therapeutic anesthesia across a variety of drug categories through a systematic review of papers in the PubMed database. We also review the therapeutic benefits hypothermia, another treatment that quells neural activity. We conclude by considering factors related to the safety, efficacy and timing of treatment, as well as the mechanisms of action. Clinical implications are also discussed.

Anesthesia may alter mRNA expression of certain wound healing-associated genes in dermal wound environment of the rats

Some anesthetics including ketamine/xylazine and thiopental have been shown to alter the expression of genes related with inflammatory cytokines and chemokines in previous studies unassociated with wound healing, arising the question of whether commonly used anesthetics in wound healing models could interfere with the transcriptional responses of the genes associated with skin wound healing. The gene expression profile in wound biopsies of rats who received widely used anesthetics doses of intraperitoneal ketamine/xylazine (50 mg/kg and 10 mg/kg) or thiopental (50 mg/kg) in comparison with control rats was analyzed by monitoring the expression of genes effective on various phases of wound healing. The expression levels of 84 genes were determined on 3rd, 7th and 14th days of post-wounding using a qPCR array system. Of the genes either up or downregulated fivefolds or more, three (Egf, Col5a1 and Cxcl3) and two (Tgfa and Il2) genes were found to be the most responsive ones to ketamine/xylazine or thiopental anesthesia respectively in a period of 14 days after correction for multiple testing. However, up to 22 and 24 genes for ketamine/xylazine and thiopental were found to be differentially expressed in the same period without correction for multiple-comparisons testing (p < 0.05). In conclusion, our data suggest that ketamine/xylazine and thiopental may alter the transcriptional responses of some genes associated with wound healing in rats. We strongly suggest to consider the possible alteration effect of these anesthetics on gene expression in animal models of dermal wound healing.

Cellular stress and AMPK links metformin and diverse compounds with accelerated emergence from anesthesia and potential recovery from disorders of consciousness

The neural correlates of consciousness and the mechanisms by which general anesthesia (GA) modulate such correlates to induce loss of consciousness (LOC) has been described as one of the biggest mysteries of modern medicine. Several cellular targets and neural circuits have been identified that play a critical role in LOC induced by GA, including the GABAA receptor and ascending arousal nuclei located in the basal forebrain, hypothalamus, and brain stem. General anesthetics (GAs) including propofol and inhalational agents induce LOC in part by potentiating chloride influx through the GABAA receptor, leading to neural inhibition and LOC. Interestingly, nearly all GAs used clinically may also induce paradoxical excitation, a phenomenon in which GAs promote neuronal excitation at low doses before inducing unconsciousness. Additionally, emergence from GA, a passive process that occurs after anesthetic removal, is associated with lower anesthetic concentrations in the brain compared to doses associated with induction of GA. AMPK, an evolutionarily conserved kinase activated by cellular stress (e.g. increases in calcium [Ca2+] and/or reactive oxygen species [ROS], etc.) increases lifespan and healthspan in several model organisms. AMPK is located throughout the mammalian brain, including in neurons of the thalamus, hypothalamus, and striatum as well as in pyramidal neurons in the hippocampus and cortex. Increases in ROS and Ca2+ play critical roles in neuronal excitation and glutamate, the primary excitatory neurotransmitter in the human brain, activates AMPK in cortical neurons. Nearly every neurotransmitter released from ascending arousal circuits that promote wakefulness, arousal, and consciousness activates AMPK, including acetylcholine, histamine, orexin-A, dopamine, and norepinephrine. Several GAs that are commonly used to induce LOC in human patients also activate AMPK (e.g. propofol, sevoflurane, isoflurane, dexmedetomidine, ketamine, midazolam). Various compounds that accelerate emergence from anesthesia, thus mitigating problematic effects associated with delayed emergence such as delirium, also activate AMPK (e.g. nicotine, caffeine, forskolin, carbachol). GAs and neurotransmitters also act as preconditioning agents and the GABAA receptor inhibitor bicuculline, which reverses propofol anesthesia, also activates AMPK in cortical neurons. We propose the novel hypothesis that cellular stress-induced AMPK activation links wakefulness, arousal, and consciousness with paradoxical excitation and accelerated emergence from anesthesia. Because AMPK activators including metformin and nicotine promote proliferation and differentiation of neural stem cells located in the subventricular zone and the dentate gyrus, AMPK activation may also enhance brain repair and promote potential recovery from disorders of consciousness (i.e. minimally conscious state, vegetative state, coma).

Intraoperative care for aortic surgery using circulatory arrest

The total circulatory arrest (CA) is necessary to achieve optimal surgical conditions in certain aortic pathologies, especially in those affecting the ascending aorta and aortic arch. During this procedure it is necessary to protect all the organs of ischemia, especially those of the central nervous system and for this purpose several strategies have been developed. The first and most important protective method is systemic hypothermia. The degree of hypothermia and the route of application have been evolving and currently tend to use moderate hypothermia (MH) (20.1-28 °C) associated with unilateral or bilateral selective cerebral perfusion methods. In this way the neurological results are better, the interval of security is greater and the times of extracorporeal circulation are smaller. Even so, it is necessary to take into account that there is the possibility of ischemia in the lower part of the body, especially of the abdominal viscera and the spinal cord, therefore the time of circulatory stop should be limited and not to exceed 80 minutes. Evidence of possible neurological drug protection is very weak and only mannitol, magnesium, and statins can produce some benefit. Inhalational anesthetics and some intravenous seem to have advantages, but more studies would be needed to test their long-term benefit. Other important parameters to be monitored during these procedures are blood glucose, anemia and coagulation disorders and acid-base balance. The recommended monitoring is common in complex cardiovascular procedures and it is of special importance the neurological monitoring that can be performed with several techniques, although currently the most used are Bispectral Index (BIS) and Near-Infrared Spectroscopy (NIRS). It is also essential to monitor the temperature routinely at the nasopharyngeal and bladder level and it is important to control coagulation with rotational thromboelastometry (ROTEM).

Gravireceptors in eukaryotes-a comparison of case studies on the cellular level

We have selected five evolutionary very different biological systems ranging from unicellular protists via algae and higher plants to human cells showing responses to the gravity vector of the Earth in order to compare their graviperception mechanisms. All these systems use a mass, which may either by a heavy statolith or the whole content of the cell heavier than the surrounding medium to operate on a gravireceptor either by exerting pressure or by pulling on a cytoskeletal element. In many cases the receptor seems to be a mechanosensitive ion channel activated by the gravitational force which allows a gated ion flux across the membrane when activated. This has been identified in many systems to be a calcium current, which in turn activates subsequent elements of the sensory transduction chain, such as calmodulin, which in turn results in the activation of ubiquitous enzymes, gene expression activation or silencing. Naturally, the subsequent responses to the gravity stimulus differ widely between the systems ranging from orientational movement and directed growth to physiological reactions and adaptation to the environmental conditions.

Neuroprotective Effects of Pregabalin on Cerebral Ischemia and Reperfusion

BACKGROUND

Stroke is one of the most common causes of death and the leading cause of disability in adults. Cerebral ischemia/reperfusion injury causes cerebral edema, hemorrhage, and neuronal death.

AIMS

In post-ischemic reperfusion, free radical production causes brain tissue damage by oxidative stress. Pregabalin, an antiepileptic agent was shown to have antioxidant effects. The aim of this study was to evaluate the neuroprotective and antioxidant effects of pregabalin on ischemia and reperfusion in rat brain injury.

STUDY DESIGN

Animal experimentation.

METHODS

Male Wistar rats weighing (250-300 g) were randomly divided into six groups, each consisting of 6 rats: control (C), pregabalin (P), ischemia (I), pregabalin + ischemia (PI), ischemia + reperfusion (IR) and ischemia + reperfusion + pregabalin (PIR). Rats were initially pre-treated with 50 mg/kg/d pregabalin orally for two days. Then, animals that applied ischemia in I, PI, IR and PIR groups were exposed to carotid clamping for 30 minutes and 20 minutes reperfusion was performed in the relevant reperfusion groups.

RESULTS

NR2B receptor levels were significantly lower in the PIR group in comparison to the IR group. In the PIR group, Thiobarbituric acid reactive substance (TBARS) level had statistically significant decrease compared with IR group. Glutathione peroxidase (GSH-PX) levels were also significantly increased in the PIR group compared with I, IR and control groups. In the PI and PIR groups, catalase (CAT) levels were also significantly increased compared with I and IR groups (p=0.03 and p=0.07, respectively).

CONCLUSION

Pregabalin may protect the damage of oxidative stress after ischemia + reperfusion. This result would illuminate clinical studies in the future.

Sevoflurane and thiopental preconditioning attenuates the migration and activity of MMP-2 in U87MG glioma cells

BACKGROUND

Tumor cell migration and diffuse infiltration into brain parenchyma are known causes of recurrence after treatment in glioblastoma (GBM), mediated in part by the interaction of glioma cells with the extracellular matrix, followed by degradation of matrix by tumor cell derived proteases, particularly the matrix metalloproteinases (MMP). Sevoflurane and thiopental are anesthetics commonly used in cancer surgery. However, their effect on the progression of glioma cells remains unclear. The aim of this study was to explore the role of these anesthetics on the migration and activity of MMP-2 in glioma cells.

METHODOLOGY

Cultured U87MG cells were pretreated with sevoflurane or thiopental and in vitro wound healing scratch assay was carried out to analyze their effect on migration of these cells. Gelatin zymography was carried out to examine the effect of these anesthetics on tumor cell MMP-2 activity using the conditioned media 24 h after pretreatment. Cell viability was analyzed using 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay.

RESULTS

U87MG cells exposed to 2.5% sevoflurane or different concentrations of thiopental significantly decreased migration and activity of MMP-2 compared to control. No effect was seen on the viability of these cells after pretreatment with sevoflurane or thiopental.

CONCLUSION/SIGNIFICANCE

These results suggest that both sevoflurane and thiopental have inhibitory effect on the migration and MMP-2 activity in glioma cells. Thus, it is important that the choice of anesthetics to be used during glioma surgery takes into account their inhibitory properties against the tumor cells.

Effects of Experimental Coma on the Expression of Bcl-2 Protein and Caspases 3 and 9 in Rat Brain

We performed immunohistochemical analysis of the expression of caspases 3, 9 and bcl-2 protein in rat brain at various terms after administration of LD50 of sodium thiopental. Expression of the specified apoptosis markers was found in the sensorimotor cortex and hippocampus (dentate gyrus and CA2 region).