The effects of halothane on cultured mouse neuroblastoma cells. I. Inhibition of morphological differentiation

An In Silico Investigation of the Molecular Interactions between Volatile Anesthetics and Actin

Volatile anesthetics (VAs) are medicinal chemistry compounds commonly used to enable surgical procedures for patients who undergo painful treatments and can be partially or fully sedated, remaining in an unconscious state during the operation. The specific molecular mechanism of anesthesia is still an open issue, but scientific evidence supports the hypothesis of the involvement of both putative hydrophobic cavities in membrane receptors as binding pockets and interactions between anesthetics and cytoplasmic proteins. Previous studies demonstrated the binding of VAs to tubulin. Since actin is the other major component of the cytoskeleton, this study involves an investigation of its interactions with four major anesthetics: halothane, isoflurane, sevoflurane, and desflurane. Molecular docking was implemented using the Molecular Operating Environment (MOE) software (version 2022.02) and applied to a G-actin monomer, extrapolating the relative binding affinities and root-mean-square deviation (RMSD) values. A comparison with the F-actin was also made to assess if the generally accepted idea about the enhanced F-to-G-actin transformation during anesthesia is warranted. Overall, our results confirm the solvent-like behavior of anesthetics, as evidenced by Van der Waals interactions as well as the relevant hydrogen bonds formed in the case of isoflurane and sevoflurane. Also, a comparison of the interactions of anesthetics with tubulin was made. Finally, the short- and long-term effects of anesthetics are discussed for their possible impact on the occurrence of mental disorders.

Volatile Anesthetics Regulate Anti-Cancer Relevant Signaling

Volatile anesthetics are widely used inhalation anesthetics in clinical anesthesia. In recent years, the regulation of anti-cancer relevant signaling of volatile anesthetics has drawn the attention of investigators. However, their underlying mechanism remains unclear. This review summarizes the research progress on the regulation of anti-cancer relevant signaling of volatile anesthetics, including sevoflurane, desflurane, xenon, isoflurane, and halothane in vitro, in vivo, and clinical studies. The present review article aims to provide a general overview of regulation of anti-cancer relevant signaling and explore potential underlying molecular mechanisms of volatile anesthetics. It may promote promising insights of guiding clinical anesthesia procedure and instructing enhance recovery after surgery (ERAS) with latent benefits.

Acute toxicity testing in cultures of mouse neuroblastoma cells

Cultured mouse neuroblastoma cells (C1300) may be used as models for nerve cells since they have a number of properties in common with their normal counterparts in vivo. In order to test the possibility of using C1300 cells as alternative to experimental animals when testing for acute toxicity, cells (clone 41A3) were exposed to a number of common chemicals (CH3HgCl, CdCl2,HgCl2 ppDDT, n-butanol, benzene, dioxan, n-propanol, aceton and t-butanol). The toxic effect was quantified by measuring the degree of cell detachment in the cultures. The concentrations of chemicals that caused 25% of the total cell number to detach (TD25) were used for comparison with LD50 values. In spite of the very simplified situation in culture, where the toxicity of a substance is little or not at all influenced by factors like penetration, storage, metabolism and excretion a good correlation (corr. coeff. 0,98) was obtained between TD25 values and LD50 values. Good correlations between in vitro and in vivo tests have also been reported by others. One possible explanation to these findings could be simplified in vivo toxicokinetics of these substances when tested in high doses for general effects like animal death. If so, simple in vitro tests may be used for predicting acute toxicity of certain groups of substances.

Stimulation of cortical actin polymerization in the sea urchin egg cortex by NH4Cl, procaine and urethane: elevation of cytoplasmic pH is not the common mechanism of action

Previous studies have demonstrated that the penetrating weak base NH4Cl and the anesthetics procaine and urethane disrupt the normal attachment of cortical granules to the cortex of the sea urchin egg. Hylander and Summers (1981: Dev. Biol. 86:1-11) hypothesized that this effect may be caused by a pH-induced polymerization of cortical actin. We have tested this hypothesis by measuring the intracellular pH of eggs of the sea urchins S. purpuratus and A. punctulata treated with NH4Cl, procaine, or urethane, and determining the effects of these agents on the organization of cortical actin. Intracellular pH was determined by the ratiometric measurement of the fluorescent dye BCECF, and filamentous actin organization was examined by confocal laser scanning microscopy of BODIPY-phallocidin stained eggs. Treatment of eggs with either NH4Cl or procaine resulted in a rapid and reversible increase in cytoplasmic pH of up to 1 pH unit and a dose-dependent increase in the intensity of fluorescent staining of the cortex, indicating an increase in the content of filamentous actin. While urethane also induced a dramatic polymerization of cortical actin, no effect on cytoplasmic pH could be detected. These results demonstrate that NH4Cl, procaine and urethane all induce an increase in the amount of filamentous actin in the sea urchin egg cortex that may participate in the detachment of cortical granules. However, these compounds do not share a common mechanism of action based on the elevation of cytoplasmic pH.

The effect of halothane on cultured fibroblasts and neuroblastoma cells

Halothane exposure over the cultured cells (100 and 1,000 ppm) caused a disruption of the pattern of actin distribution in both fibroblasts and neuroblastoma cells. Neuroblastoma cells exposed to halothane also lost microspikes; however, neurite elongation was not affected by halothane. The present study suggests that halothane induces the functional disruption of actin, resulting in an interference of normal neural development in vivo.

Neurobehavioral toxicology of halothane in rats

Halothane, a commonly used general anesthetic, is considered to be relatively safe for that purpose. Chronic exposure, however, has been found to cause long-lasting damage to neural structure and impairment of behavioral function. In rats, behavioral alterations are particularly evident after developmental exposure, but they can also be seen with adult exposure, especially when halothane is given during the period of neural regrowth following a brain lesion. The pattern of neural damage includes retarded synaptogenesis, impaired dendritic branching and disruption of organelle structure. The behavioral syndrome includes learning impairment, decreased exploratory behavior and decreased nociceptive reactivity. In general, the neural pathology is more pronounced and more easily discernible than the behavioral effects. Neural damage, particularly to the hippocampus, can be clearly seen at points when behavioral impairments have not been found. This demonstrates that in some cases changes in neural structure can be more sensitive indicators of toxic damage than behavioral dysfunction. Halothane exposure has proved to be quite useful as an experimental tool in the study of neural and behavioral recovery after brain lesions. For example, after unilateral entorhinal cortical lesions, behavioral recovery and reactive synaptogenesis occur contemporaneously. It has not been demonstrated whether the behavioral recovery is due to this reinnervation. Postlesion halothane exposure almost completely suppresses reactive synaptogenesis, however, behavioral recovery of T-maze alternation behavior occurs in the halothane-treated rats as well as in controls. This suggests that recovery of spatial performance after such a lesion is not due to recovery of innervation in the dentate, but to some other process such as other neural systems taking over the functions lost with the brain lesion. The studies reviewed highlight the dangers of halothane exposure, especially during development or when recovering from brain injury. They also provide a good case study for comparing the relative sensitivity of morphological and behavioral measures in toxicology and point to the potential use of halothane as an experimental tool for examining the relationships between neural structure and behavioral function.

Suppressive effects of halothane on reactive synaptogenesis in the dentate gyrus of rats

Reactive synaptogenesis was studied in the dentate gyrus of rats exposed to 100 parts per million of halothane for 15 days starting on the day after unilateral entorhinal lesioning. Halothane exposure markedly affected the replacement of synapses. Only 17% of the lost synapses were restored by day 15 postlesion in rats exposed to halothane, while 73% of the lost synapses were recovered in rats not exposed to halothane. However, this suppression in initial reactive synaptogenesis did not result in permanent deficits in synaptic population. After halothane exposure was stopped, reactive synaptogenesis resumed, and by day 30 after the lesion, the synaptic population of the experimental group caught up to the control level. This suppressive action of halothane suggests its utility as a research tool for delaying synaptogenesis during selected developmental epochs to study the relationship between synaptic and behavioral recovery.

Ultrastructural analysis of abnormalities in the morphology of the second meiotic spindle in ethanol-induced parthenogenones

A high frequency of parthenogenetic activation occurs when ovulated mouse oocytes are briefly exposed to a dilute solution of ethanol in vitro. Cytogenetic analyses of parthenogenones at metaphase of the first cleavage division have confirmed that parthenogenetic activation, per se, does not increase the incidence of chromosome segregation errors during the completion of the second meiotic division. Ethanol-induced activation, however, significantly increases the incidence of aneuploidy. The ultrastructural changes that occur in the morphology and organization of the second meiotic spindle apparatus in ethanol- and hyaluronidase-activated oocytes is reported here. Abnormalities in the arrangement of microtubule arrays and chromosome position were principally observed in ethanol-activated oocytes at anaphase and telophase of the second meiotic division, but were only rarely observed in hyaluronidase-activated oocytes. It is proposed that the abnormalities in spindle morphology and chromosome displacement observed in ethanol-activated oocytes represent the initial events that lead to chromosome segregation errors following exposure to this agent.

Cytogenetic analysis of ethanol-induced parthenogenesis

The brief exposure of recently ovulated mouse oocytes to a dilute solution of ethanol in vitro for 1, 3, or 5 min induced a uniform high incidence of parthenogenetic activation. The majority of parthenogenones developed a single haploid pronucleus after the extrusion of a second polar body. The proportionate incidence of this parthenogenetic class was significantly reduced as the duration of ethanol exposure increased from 1 min to 5 min. There was a concomitant increase in the incidence of parthenogenones that developed two haploid pronuclei following failure of extrusion of the second polar body. Cytogenetic analysis of the ethanol-induced single-pronuclear haploid parthenogenones at metaphase of the first cleavage division clearly demonstrated that a significant proportion were aneuploid. The incidence of aneuploidy observed was directly related to the duration of ethanol exposure. G-band analysis of the aneuploid metaphases revealed that the chromosomes were not randomly involved in the malsegregation events. This observation may be a reflection of the relationship of particular chromosomes to the meiotic spindle apparatus rather than on any specific property of the agent to which they were exposed. It is believed that ethanol disrupts the organisation of cytoskeletal elements and, in particular, interferes with the processes of chromosome segregation at the second meiotic division.

Effects of halothane on the development of rat brain: a golgi study of dendritic growth

Dendritic growth was studied in rats exposed to halothane in utero for the entire gestation period and 60 days after birth. The exposure conditions were control, intermittent halothane (25 +/- 5 ppm or 100 +/- 5 ppm, 8 h/day, 5 days/week), or continuous halothane (25 +/- 5 ppm, 24 h/day, 7 days/week). Dendritic growth in terms of branch numbers and length was most advanced in the control groups, followed by those groups exposed to 25 +/- 5 ppm halothane intermittently, 25 +/- 5 ppm halothane continuously, and 100 +/- 5 ppm halothane intermittently. The latter two exposure conditions exerted identical effects on dendritic growth. The order of this dendritic growth level established at 5 postnatal days remained the same throughout the first 95 postnatal days in both the entorhinal cortex and subiculum. The effect of halothane on dendritic growth appeared to be enduring, and the delay in the initial dendritic growth caused by halothane was not compensated for by an increased rate of dendritic growth.

Prolongation of inhibitory postsynaptic currents by pentobarbitone, halothane and ketamine in CA1 pyramidal cells in rat hippocampus

Spontaneous inhibitory postsynaptic currents (i.p.s.cs) were recorded in voltage-clamped CA1 neurones in rat hippocampal slices. The exponential decay of i.p.s.cs was prolonged by concentrations of sodium pentobarbitone as low as 50 microM. With concentrations up to 100 microM, there was no change in the amplitude or rise time of the currents but current amplitude was depressed at 200 microM. The prolongation of currents increased with drug concentration within the range tested (50 to 200 microM). Halothane, at concentrations from 1 to 5%, also increased the time constant of decay of i.p.s.cs. The effect increased with concentration and was fully reversible. Ketamine, at a concentration of 0.5 mM, increased the time constant of decay of i.p.s.cs by 50 to 80% and the effect was reversible. Ethanol (10-200 mM), nitrous oxide (75-80%), and caffeine (10 microM-5 mM) had no detectable effect on the i.p.s.cs. It is suggested that pentobarbitone, halothane and ketamine increase the time constant of decay of the i.p.s.cs by stabilizing the open state of channels activated by gamma-aminobutyric acid.

An hypothesis regarding the origin of aneuploidy in man: indirect evidence from an experimental model

Recent studies have clearly demonstrated that aneuploidy may be induced in about 10 to 20% of oocytes and recently ovulated eggs when female mice are given an intragastric injection of a dilute solution of ethanol. Similar rates of aneuploidy have also been observed when recently ovulated eggs are briefly exposed in vitro to a dilute solution of ethanol in tissue culture medium. These findings are briefly reviewed, and observations made on the possible underlying mechanism of induction of chromosome malsegregation in the ethanol exposed groups. Attention is drawn to evidence from a wide range of studies on the effect of ethanol, acetaldehyde (its primary metabolite), and anaesthetics on cell division and chromosome segregation in an attempt to substantiate an hypothesis regarding the mode of action of these agents. In the light of this information, it is hypothesised that exposure to ethanol probably interferes with the normal functioning of the cytoskeletal elements of the spindle apparatus, or its precursor elements, during the first or second meiotic divisions. An attempt is also made to account for the very high incidence of aneuploid conceptuses in man, a high proportion of which are spontaneously aborted. It is hypothesised that exposure to ethanol and other spindle active agents during appropriate stages of oogenesis (in particular during the first meiotic division), and possibly also during spermatogenesis, may be important aetiological factors in a proportion of those cases of spontaneous abortion with a numerical chromosome anomaly for which no other obvious cause is recognised. If it is valid to extrapolate from these experimental findings to the clinical situation in man, it is suggested that attention should also be drawn to the potentially greater hazard to the conceptus which could result from maternal alcohol consumption at and shortly before conception.

Influence of ethanol on chromosome segregation during the first and second meiotic divisions in the mouse egg

This study was carried out to investigate the influence of ethanol on chromosome segregation during the first and second meiotic divisions. Female mice were given a single intragastric injection of a dilute solution of ethanol either just before or at various times after the HCG injection for inducing superovulation. The mice were mated, and the chromosome constitution of fertilized eggs was determined at the first cleavage mitosis. The technique employed allowed the male- and female-derived pronuclear sets to remain as two discrete groups. Exposure from 1.5 h before to 17 h after the HCG injection induced a high incidence of aneuploidy (15-25%) involving in over 90% of cases only one chromosome, so that either 19 or 21 instead of the normal complement of 20 chromosomes were present in one of the two sets (a previous study using a "marker" chromosome has demonstrated that the nondisjunction induced here invariably involves the female set). We suggest these findings draw attention to the susceptibility of chromosome segregation in female germ cells to interference by ethanol and that the mode of action is likely to be via interference with the normal functioning of the spindle apparatus. It is possible that interference with meiotic chromosome segregation by spindle-acting agents such as ethanol might account for a proportion of human spontaneous abortions with similar chromosomal defects where no other obvious cause is apparent.

The effects of halothane on the DNase I activity in an isolated enzyme preparation and in the DNase I-G actin complex

The effects of halothane on the DNase I activity in an isolated enzyme preparation and in a DNase I-globular (G) actin complex was investigated. DNase I, DNase I-G actin complexes and G actin were exposed to various (0.2-4.0 vol./%) halothane concentrations for 3 h. Thereafter, DNase I was mixed with a DNA solution and the extinction of the acid soluble supernatant of the DNase I assay was determined as a measure of DNase I activity. After 10 min of halothane exposure the DNase I activity is inhibited in direct proportion to halothane concentrations between 0.6 and 4.0 vol/%. After 10 min halothane activates inactive DNase I by inhibiting G actin, an inhibitor of DNase I. G actin, exposed to halothane, does not inhibit the activity of DNase I. The results suggest a mechanism by which halothane may contribute to chromosomal defects and disturbances of DNA metabolism in cells.

Growth cones in differentiated neuroblastoma: a time-lapse cinematographic and electron microscopic study

Growth cones of 'differentiating' neuroblastoma cells in monolayer culture were studied by time-lapse cinematography and electron microscopy. Morphological differentiation, and thus growth cone formation, was induced by the glucocorticoid dexamethasone. Growth cones lengthened gradually at an average rate of 30 microns/h, advancing in stages that involved alternating extensions and retractions of the filopodia and lamellar sheets. During neurite growth the cell body usually remained stationary. The ultrastructure of growth cones was typified by several filopodia, each containing a bundle of microfilaments, agranular endoplasmic reticulum, aggregates of large agranular vesicles lying adjacent to filopodia (previously termed vesicle-filled mounds), many dense-cored vesicles, 100-140 nm in diameter, microtubules, bizarre and distorted mitochondria, and scattered from ribosomes. Comparing the findings with previous ultrastructural accounts of growth cones of cultured ganglion cells, similarities outnumbered differences. The organization of the microfilament bundles and the abundance of free ribosomes were remarkable in the neuroblastoma cell as was the profusion of dense-cored vesicles which were most numerous in the proximal portion of the growth cone.

The effects of halothane anaesthesia on antibody-dependent cellular cytotoxicity in rats

Lymphocytes from rats killed while anaesthetized with 1-5 per cent halothane showed a significantly reduced capacity to induce lysis of antibody-coated target cells compared with those from untreated rats. This effect was short-lived however, being no longer apparent in lymphoid cells taken from rats 2 h after their recovery from such anaesthesia. Surgical procedures were not effective in extending the duration of reduced ADCC activity. The implication of these findings is that the post-operative depression of this in vitro assay of immunocompetence results from the influence of the anaesthetic agent per se or its metabolities with surgical trauma having little role.

Cell shape changes induced by cationic anesthetics

The effects of local anesthetics on cultivated macrophages were studied in living preparations and recorded in still pictures and time-lapse cine-micrographs. Exposure to 12mM lidocaine or 1.5 mM tetracaine resulted in rounding in 10-15 min. Rounding was characterized by cell contraction, marked increase in retraction fibrils, withdrawal of cell processes, and, in late stages, pulsation-like activity and zeiosis. Cells showed appreciable membrane activity as they rounded. Respreading was complete within 15 min of perfusion in drug-free medium and entailed a marked increase in surface motility over control periods. As many as eight successive cycles of rounding and spreading were obtained with lidocaine without evidence of cell damage. The effects of anesthetics were similar to those observed with EDTA, but ethylene-glycol-bis(beta-aminoethylether)-N, N'-tetraacetic acid-Mg was ineffective. Rounding was also induced by benzocaine, an anesthetic nearly uncharged at pH 7.0. Quaternary (nondischargeable) compounds were of low activity, presumably because they are slow permeants. Lidocaine induced rounding at 10 degrees C and above but was less effective at 5 degrees C and ineffective at 0 degrees C. Rounding by the anesthetic was also obtained in media depleted or Na or enriched with 10 mM Ca or Mg. The latter finding, together with the failure of tetrodotoxin to induce rounding, suggests that the anesthetic effect is unrelated to inhibition of sodium conductance. It is possible that the drugs influence divalent ion fluxes or some component of the contractile cells' machinery, but a metabolic target of action cannot yet be excluded.

Effects of local anesthetics on cell morphology and membrane-associated cytoskeletal organization in BALB/3T3 cells

Tertiary amine local anesthetics (dibucaine, tetracaine, procaine) reversibly affect the morphology of untransformed BALB/3T3 cells and the organization of membrane-associated cytoskeletal elements. In the presence of these drugs cells contract and become rounded in shape with the appearance of numerous surface "blebs." Electron microscope examination of anesthetic-treated cells revealed significant reductions in plasma membrane-associated microtubules and microfilaments and/or their plasma membrane attachment. The relationship of the findings on local anesthetic-induced changes in cellular cytoskeletal systems is discussed in relation to previous proposals on plasma membrane organization and control of cell surface receptor topography and mobility.

Cell shape changes and transmembrane receptor uncoupling induced by tertiary amine local anesthetic

Tertiary amine local anesthetics (dibucaine, tetracaine, procaine, etc.) modify cell morphology, concanavalin A (Con A)-mediated agglutinability and redistribution of Con A receptors. Con A agglutination of untransformed mouse 3T3 cells was enhanced at low concentrations of local anesthetics, and the dynamics of fluorescent-Con A indicated that ligand-induced clustering was increased in the presence of the drugs. In contast, these drugs inhibited Con A-induced receptor capping on mouse spleen cells. These effects can be duplicated by combinations of vinblastine (or colchicine) and cytochalasin B suggesting that local anesthetics act on microtubule and microfilament assemblies which are involved in the trans-membrane control of cell surface receptor mobility and distribution. It is proposed that tertiary amine local anesthetics displace plasma membrane-bound Ca2+, resulting in disengagement of microfilament systems from the plasma membrane and increased cellular Ca2+ concentration to levels which disrupt microtubular organization. The possible involvement of cellular Ca2+ in cytoskeletal destruction by local anesthetics was investigated utilizing Ca2+-specific ionophores A23187 and X537A. In media containing Ca2+ and cytochalasin B these ionophores caused effects similar to tertiary amine local anesthetics.

Reversal of morphological differentiation of mouse neuroblastoma cells by mitosis-inhibitors and anesthetics

Differentiated mouse neuroblastoma cells (C 1300) were exposed to various mitosis-inhibitors (vinblastine, colchicine and griseofulvin) and substances with anesthetic action (lidocaine, tetracaine, chlorpromazine and sodium dodecyl sulphate). All the drugs caused rapid retraction of the neurites, which was reversible in all cases but for sodium dodecyl sulphate, and showed a sigmoid dose-response relationship. The two groups of substances caused morphologically similar effects in that the microtubules disappeared and the intracellular orientation was lost. The order of potency of the anesthetics corresponded to their efficiency to cause nerve-block and antihemolysis as reported by others. Colchicine, griseofulvin, lidocaine and chlorpromazine were tested for effects of agglutination of undiffentiated cells. They inhibited agglutination at doses that were only slightly higher than those causing neurite retraction. The possibility of a close relationship between the cell membrane and microtubule system will be considered.