Duplicated CCAAT/enhancer-binding protein β (C/EBPβ) gene: transcription and methylation changes in response to dietary betaine in Landes goose liver

The CCAAT/enhancer-binding protein β gene (C/EBPβ) is one of the key regulating factors of lipid metabolic balance in the liver. To better understand how C/EBPβ affects lipid accumulation in the Landes goose liver, its DNA was cloned. The goose C/EBPβ DNA sequence (2,075 bp) contains a 984-bp open reading frame and part of the 5'-flanking region, and shares 96.66 and 62.07% similarity with the chicken and human sequences at the amino acid level, respectively. Tissue expression profiling showed that the relative expression level was high in the liver and adipose tissue. To understand the effect of betaine on C/EBPβ in goose liver, the relative expression levels of C/EBPβ were detected under different treatments. Compared with the control group, C/EBPβ expression increased in the high-carbohydrate group (P < 0.01) and decreased in the betaine treatment group (P > 0.05). Using bisulfite sequencing PCR, the gene methylation status was analyzed among the different treatment groups. None of the 54 CpG sites in the promoter region or the 28 CpG sites in the structural domain of the coding region showed any significantly different methylation patterns among the groups. Taken together, the results showed that betaine decreased the goose C/EBPβ gene expression, but did not directly regulate its methylation. The data may form the basis for further investigation of the mechanisms of the effect of C/EBPβ on the regulation of lipometabolism in the goose liver and the effect of betaine on lipid metabolic genes at the molecular level.

Isoflurane affects the cytoskeleton but not survival, proliferation, or synaptogenic properties of rat astrocytes in vitro

BACKGROUND

More than half of the cells in the brain are glia and yet the impact of general anaesthetics on these cells is largely unexamined. We hypothesized that astroglia, which are strongly implicated in neuronal well-being and synapse formation and function, are vulnerable to adverse effects of isoflurane.

METHODS

Cultured rat astrocytes were treated with 1.4% isoflurane in air or air alone for 4 h. Viability, proliferation, and cytoskeleton were assessed by colorimetric assay, immunocytochemistry, or a migration assay at the end of treatment or 2 days later. Also, primary rat cortical neurones were treated for 4 days with conditioned medium from control [astrocyte-conditioned media (ACM)], or isoflurane-exposed astrocytes (Iso-ACM) and synaptic puncta were assessed by synapsin 1 and PSD-95 immunostaining.

RESULTS

By several measures, isoflurane did not kill astrocytes. Nor, based on incorporation of a thymidine analogue, did it inhibit proliferation. Isoflurane had no effect on F-actin but reduced expression of α-tubulin and glial fibrillary acidic protein both during exposure (P<0.05 and P<0.001, respectively) and 2 days later (P<0.01), but did not impair astrocyte motility. ACM increased formation of PSD-95 but not synapsin 1 positive puncta in neuronal cultures, and Iso-ACM was equally effective.

CONCLUSIONS

Isoflurane decreased expression of microtubule and intermediate filament proteins in astrocytes in vitro, but did not affect their viability, proliferation, motility, and ability to support synapses.

Anaesthetic neurotoxicity and neuroplasticity: an expert group report and statement based on the BJA Salzburg Seminar

Although previously considered entirely reversible, general anaesthesia is now being viewed as a potentially significant risk to cognitive performance at both extremes of age. A large body of preclinical as well as some retrospective clinical evidence suggest that exposure to general anaesthesia could be detrimental to cognitive development in young subjects, and might also contribute to accelerated cognitive decline in the elderly. A group of experts in anaesthetic neuropharmacology and neurotoxicity convened in Salzburg, Austria for the BJA Salzburg Seminar on Anaesthetic Neurotoxicity and Neuroplasticity. This focused workshop was sponsored by the British Journal of Anaesthesia to review and critically assess currently available evidence from animal and human studies, and to consider the direction of future research. It was concluded that mounting evidence from preclinical studies reveals general anaesthetics to be powerful modulators of neuronal development and function, which could contribute to detrimental behavioural outcomes. However, definitive clinical data remain elusive. Since general anaesthesia often cannot be avoided regardless of patient age, it is important to understand the complex mechanisms and effects involved in anaesthesia-induced neurotoxicity, and to develop strategies for avoiding or limiting potential brain injury through evidence-based approaches.

First Report of Crown Gall, Caused by Agrobacterium tumefaciens on Soapberry (Sapindus delavayi) in China

Soapberry (Sapindus delavayi (Franch.) Radlk.,) plants are widely grown as shade trees in the subtropical to tropical regions of China. In July 2011, large, aerial galls were observed on the above-ground trunks of 5-year-old soapberry plants in two commercial nursery gardens located in Zhejiang Province. Disease incidence was estimated to be 75%. The galls varied in weight from 2 to 24 g and in texture from soft and spongy to hard, and in some cases, the galls completely girdled the trunk. The trees with galls exhibited poor growth compared with healthy trees. Isolations from the grinded and macerated galls yielded nearly pure white, circular, and glistening bacterial colonies on Roy Sauer medium (2). Six random colonies from different galls were selected for bacterial identification, and showed the same morphological, physiological, and biochemical characters and 16S rDNA sequences. All six isolates (isolate SD01 to SD06) were gram negative, rod-shaped bacteria. Carbon source utilization testing with the Biolog GN Bacterial Identification System (version 3.50) confirmed the bacteria as Agrobacterium tumefaciens with a similarity of 0.90. The most-parsimonious tree from the maximum parsimony analysis (PHYLIP package, version 3.68, 500 replicates) of bacterial 16S rDNA gene sequences showed that A. tumefaciens SD01 (GenBank Accession No. JX997939) clustered phylogenetically most closely (99.5% similarity) with A. tumefaciens C58 (AE007870.2). Pathogenicity was confirmed by injecting 3- to 5-week old tomato and sunflower plants and 2-year-old soapberry with approximately 5 μl of the bacterial suspension (10⁸ CFU/ml) in sterile, distilled water. Sterile distilled water was used as a negative control. Ten plants of each treatment were inoculated. Inoculated plants were then transferred to a greenhouse at 25°C. Typical tumors developed at the inoculation sites on tomatoes and sunflower plants 3 weeks after inoculation and on soapberry 6 weeks after inoculation. No symptoms were observed on the control plants. The bacteria that were readily reisolated from the inoculated plants exhibited the same morphological, physiological characters and 16S rDNA sequence as the original culture and were confirmed as A. tumefaciens, fulfilling Koch's postulates. A. tumefaciens is endemic to China and has a very wide host range (1). However, crown gall of soapberry has never been found in China and other countries. To our knowledge, this is the first report of A. tumefaciens on soapberry plants in China. References: (1) M. A. Escobar and A. M. Dandekar. Trends Plant Sci. 8:380, 2003. (2) L. W. Moore et al. Page 17 in: Laboratory Guide for Identification of Plant Pathogenic Bacteria. 3rd ed. N. W. Schaad et al., eds. The American Phytopathological Society, St. Paul, MN, 2001.

Isoflurane and sevoflurane increase interleukin-6 levels through the nuclear factor-kappa B pathway in neuroglioma cells

BACKGROUND

Isoflurane can increase pro-inflammatory cytokine interleukin (IL)-6 levels. However, the up-stream mechanism remains unknown. Nuclear factor-kappa B (NF-κB) promotes the generation of pro-inflammatory cytokines. We examined the effects of isoflurane and sevoflurane on the NF-κB signalling pathway and its association with IL-6 levels in cultured cells.

METHODS

H4 human neuroglioma cells (H4 cells), and mouse primary neurones and microglia were treated with 2% isoflurane or 4.1% sevoflurane for 6 h, for analysis of IL-6 and NF-κB. Pyrrolidine dithiocarbamate (an NF-κB inhibitor) or 2-deoxy-d-glucose (2-DG) (an inhibitor of glucose glycolysis) was applied 1 h before anaesthetic treatment.

RESULTS

Isoflurane or sevoflurane treatment increased the levels of IL-6 [isoflurane: 410% (54); sevoflurane: 290% (24)], the nuclear levels of NF-κB [isoflurane: 170% (36); sevoflurane: 320% (30)], and the transcription activity of NF-κB in H4 cells. Moreover, isoflurane enhanced the transcription activity of NF-κB in mouse microglia, but not primary neurones. Finally, pyrrolidine dithiocarbamate and 2-DG attenuated isoflurane-induced increases in IL-6 and NF-κB, and the transcription activity of NF-κB.

CONCLUSIONS

These studies in H4 cells suggest that the NF-κB signalling pathway could contribute to isoflurane or sevoflurane-induced neuroinflammation. This could lead to the targeted intervention of anaesthetic-induced neuroinflammation.

Abstract P5-10-10: The miR-34a is down-regulated in breast cancer and breast stem cells and a potential to eradicating breast cancer via a systemic delivery of a VISA –miR-34a nanoparticle system

Breast cancer is the most common disease in women around the world and the current treatment strategies are not potent enough for the patients, especially those who are the triple-negative type of molecular classifications. Therefore, novel and more effective treatments are pressingly needed. Of the current methods, target therapy, which not only retains cancer-specific expression but also limits toxicity, is a new strategy for treatment of cancers. In this study, it was to investigate miR-34a expression in breast caner specimen and its relationship with patient's clinical status, and develop targeted miR-34a delivery system as a potential method for breast cancer therapy. miR-34a expression was investigated by qRT-PCR and related to clinicopathologic significance and found to be down-regulated in breast cancer as compared with normal adjacent tissues and involved in breast cancer stem cell through down-regulation of CD44, ZEB1, and Bmi1. We designed targeted miR-34a expression using T-VISA system (hTERT promoter driven VP16-Gal4-WPRE Integrated Systemic Amplifier) liposomed-based nanoparticles and evaluated the antitumor effect in breast cancer cells in vitro and in orthotopic animal model as well as its systemic toxicity. The T-VISA-miR-34a system robust targeted to breast cancer cells and breast cancer stem cells and prolonged duration expression of miR-34a. Furthermore, a systemic delivery of a VISA –miR-34a nanoparticle system targeted efficiently expression of miR-34a to tumors and could significantly inhibit tumor growth and prolong mouse survival in multiple living imaging xenograft and syngeneic models of orthotopic breast cancer and without toxicity in intact mice. Our study demonstrated that miR-34a expression was down-regulated in breast cancer and breast cancer stem cells through down-regulation of CD44, ZEB1, and Bmi1. The T-VISA-miR-34a nanoparticle system showed robust antitumor effects in breast cancer and could be a potential therapeutic approach to eradicating breast cancer.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-10-10.

PIKE mediates EGFR proliferative signaling in squamous cell carcinoma cells

One of the key drivers for squamous cell carcinoma (SCC) proliferation is activation of the epidermal growth factor receptor (EGFR), a known proto-oncogene. However, the mechanism of EGFR-dependent SCC proliferation remains unclear. Our previous studies indicate that epidermal growth factor (EGF)-induced SCC cell proliferation requires the SH3 domain of phospholipase C-γ1 (PLC-γ1), but not its catalytic activity. The SH3 domain of PLC-γ1 is known to activate the short form of nuclear phosphatidylinositol 3-kinase enhancer (PIKE) that enhances the activity of nuclear class Ia phosphatidylinositol 3-kinase (PI3K) required for proliferation. However, PIKE has been described for more than a decade to be present exclusively in neuronal cells. In the present study, we found that PIKE was highly expressed in malignant human keratinocytes (SCC4 and SCC12B2) but had low expression in normal human keratinocytes. Immunohistochemical analysis showed strong nuclear staining of PIKE in human epidermal and tongue SCC specimens but little staining in the adjacent non-cancerous epithelium. Treatment of SCC4 cells with EGF-induced translocation of PLC-γ1 to the nucleus and binding of PLC-γ1 to the nuclear PIKE. Knockdown of PLC-γ1 or PIKE blocked EGF-induced activation of class Ia PI3K and protein kinase C-ζ and phosphorylation of nucleolin in the nucleus as well as EGF-induced SCC cell proliferation. However, inhibition of the catalytic activity of PLC-γ1 had little effect. These data suggest that PIKE has a critical role in EGF-induced SCC cell proliferation and may function as a proto-oncogene in SCC.

Hippocampal glutamate level and glutamate aspartate transporter (GLAST) are up-regulated in senior rat associated with isoflurane-induced spatial learning/memory impairment

Postoperative cognitive decline is a clinical concern especially for senior patients. It is generally recognized that glutamatergic system plays a crucial role in the physiopathologic process of neurocognitive deterioration. However, alterations of glutamatergic system in prolonged isoflurane-induced learning/memory decline are still unclear. This study investigates the question whether glutamate concentration and corresponding transporters or receptors display any alternations in aged rat suffering from isoflurane-induced learning/memory impairment. 111 male Sprague-Dawley rats (>18 months) were randomly divided into two main groups: hippocampal microdialysis group (n = 38) and western blotting group (n = 73). Each group was subdivided into three subgroups including (1) control subgroup (n = 6 and 10, receiving no behavioral trial, anesthesia or air exposure); (2) air-exposed subgroup (n = 7 and 15, receiving behavioral trial and air exposure but not anesthesia); (3) isoflurane anesthesia subgroup (n = 25 and 48, receiving both behavioral trial and anesthesia). The isoflurane-exposed rats were further divided into a learning/memory-impaired subgroup and a non-learning/memory-impaired subgroup according to their behavioral performance, which was measured using Morris water maze. Hippocampal glutamate concentrations in microdialysates were determined by high-performance liquid chromatography. Expression levels of GLAST, GLT-1, NMDAR1, NMDAR2A/B, AMPAR and tau in hippocampus were assessed via quantitative Western blotting. The incidences of learning/memory impairment of isoflurane-exposed rats in hippocampal microdialysis group and western blotting group were 12.0 (3/25) and 10.4 % (5/48) respectively. The intra-anesthesia hippocampal glutamate levels were significantly lower than those of non-anesthesized rats. The learning/memory-impaired rats showed a long-lasting increased glutamate level from 24 h after isoflurane exposure to the end of the study, but the other 22 isoflurane-exposed rats did not. The learning/memory-impaired subgroup displayed a significantly higher GLAST level than the other three subgroups (p = 0.026, 0.02 and 0.032 respectively). The expression levels of GLT-1, NMDAR1, NMDAR2A/B and AMPAR of every subgroup were comparable. We found a continuous raised hippocampal glutamate and an up-regulation of GLAST rather than GLT-1, NMDAR1, NMDAR2A/B, AMPAR or tau in hippocampus of aged rats associated with isoflurane-induced learning/memory impairment.

Propofol and magnesium attenuate isoflurane-induced caspase-3 activation via inhibiting mitochondrial permeability transition pore

Background

The inhalation anesthetic isoflurane has been shown to open the mitochondrial permeability transition pore (mPTP) and induce caspase activation and apoptosis, which may lead to learning and memory impairment. Cyclosporine A, a blocker of mPTP opening might attenuate the isoflurane-induced mPTP opening, lessening its ripple effects. Magnesium and anesthetic propofol are also mPTP blockers. We therefore set out to determine whether propofol and magnesium can attenuate the isoflurane-induced caspase activation and mPTP opening.

Methods

We investigated the effects of magnesium sulfate (Mg²⁺), propofol, and isoflurane on the opening of mPTP and caspase activation in H4 human neuroglioma cells stably transfected to express full-length human amyloid precursor protein (APP) (H4 APP cells) and in six day-old wild-type mice, employing Western blot analysis and flowcytometry.

Results

Here we show that Mg²⁺ and propofol attenuated the isoflurane-induced caspase-3 activation in H4-APP cells and mouse brain tissue. Moreover, Mg²⁺ and propofol, the blockers of mPTP opening, mitigated the isoflurane-induced mPTP opening in the H4-APP cells.

Conclusion

These data illustrate that Mg²⁺ and propofol may ameliorate the isoflurane-induced neurotoxicity by inhibiting its mitochondrial dysfunction. Pending further studies, these findings may suggest the use of Mg²⁺ and propofol in preventing and treating anesthesia neurotoxicity.

Sleep disturbance induces neuroinflammation and impairment of learning and memory

Hospitalized patients can develop cognitive function decline, the mechanisms of which remain largely to be determined. Sleep disturbance often occurs in hospitalized patients, and neuroinflammation can induce learning and memory impairment. We therefore set out to determine whether sleep disturbance can induce neuroinflammation and impairment of learning and memory in rodents. Five to 6-month-old wild-type C57BL/6J male mice were used in the studies. The mice were placed in rocking cages for 24 h, and two rolling balls were present in each cage. The mice were tested for learning and memory function using the Fear Conditioning Test one and 7 days post-sleep disturbance. Neuroinflammation in the mouse brain tissues was also determined. Of the Fear Conditioning studies at one day and 7 days after sleep disturbance, twenty-four hour sleep disturbance decreased freezing time in the context test, which assesses hippocampus-dependent learning and memory; but not the tone test, which assesses hippocampus-independent learning and memory. Sleep disturbance increased pro-inflammatory cytokine IL-6 levels and induced microglia activation in the mouse hippocampus, but not the cortex. These results suggest that sleep disturbance induces neuroinflammation in the mouse hippocampus, and impairs hippocampus-dependent learning and memory in mice. Pending further studies, these findings suggest that sleep disturbance-induced neuroinflammation and impairment of learning and memory may contribute to the development of cognitive function decline in hospitalized patients.

Neurotoxicity of general anesthetics: an update

Though general anesthetics have now been used clinically for well over a century, both their mechanisms of action as well as the nature of any potentially neurotoxic side effects remain elusive. With roughly 234 million people undergoing surgery each year worldwide, it remains imperative that any potentially deleterious effects of anesthetics be investigated and addressed. The issue of anesthetic- induced neurotoxicity in certain subsets of patients has continued to garner attention over the past decade, as more pre-clinical and clinical studies released are suggesting that inhalational and intravenous anesthetics may both cause and mitigate existing significant neuropathology. Pre-clinically, both cell-culture and animal studies suggest that anesthetics may cause neuroapoptosis, caspase activation, neurodegeneration, β-amyloid protein (Aβ) accumulation and oligomerization, and ultimately, deficits in neurocognition. Interestingly, however, newer data suggest that certain volatile anesthetics, such as desflurane, may have a less harmful neurotoxic profile compared to others in the pre-clinical and clinical settings. Continued pre-clinical investigation may have significant impact on clinical practice in the near future. Clinically, recent studies have raised awareness that exposure to general anesthetics during childhood may be associated with an increased risk for subsequent deficits in learning, memory, and cognition. Furthermore, retrospective studies continue to allude to the potential effects of surgery and anesthesia on cognitive trajectory, and more specifically, post-operative cognitive dysfunction (POCD) in the elderly. Studies to date regarding both of these clinical topics, however, are fraught with confounders, and many are underpowered statistically. The aim of this review is to examine the current data (both pre-clinical and clinical) on anesthetic-induced neurotoxicity and argue that further data are needed to either support or refute the potential connection between anesthetics and neurotoxicity.

Anesthetic isoflurane increases phosphorylated tau levels mediated by caspase activation and Aβ generation

Anesthetic isoflurane has been shown to promote Alzheimer’s disease (AD) neuropathogenesis by inducing caspase activation and accumulation of β-amyloid (Aβ). Phosphorylation of tau protein is another important feature of AD neuropathogenesis. However, the effects of isoflurane on phosphorylated tau levels remain largely to be determined. We therefore set out to determine whether isoflurane can increase phosphorylated tau levels. 5 to 8 month-old wild-type and AD transgenic mice [B6.Cg-Tg (APPswe, PSEN1dE9)85Dbo/J] were treated with 1.4% isoflurane for two hours. The mice brain tissues were harvested at six, 12 and 24 hours after the anesthesia. For the in vitro studies, primary neurons from wild-type and the AD transgenic mice were exposed to 2% isoflurane for six hours, and were harvested at the end of anesthesia. The harvested brain tissues and neurons were subjected to Western blot analysis by which the levels of phosphorylated tau protein at Serine 262 (Tau-PS262) were determined. Here we show that the isoflurane anesthesia increased Tau-PS262 levels in brain tissues and primary neurons from the wild-type and AD transgenic mice. Moreover, the isoflurane anesthesia may induce a greater increase in Tau-PS262 levels in primary neurons and brain tissues from the AD transgenic mice. Finally, caspase activation inhibitor Z-VAD and Aβ generation inhibitor L-685,458 attenuated the isoflurane-induced increases in Tau-PS262 levels. In conclusion, clinically relevant isoflurane anesthesia increases phosphorylated tau levels, which may result from the isoflurane-induced caspase activation and Aβ generation. These findings will promote more studies to determine the effects of anesthetics on tau phosphorylation.

Assessment of immunochemotherapy and stem cell transplantation on EBV-associated hemophagocytic lymphohistiocytosis in children: a systematic review and meta analysis

BACKGROUND AND OBJECTIVES

Although immunochemotherapy had been reported to be effective initial treatment for patients with Epstein Barr virus-associated hemophagocytic lymphohistiocytosis (EBV-HLH), and stem cell transplantation (SCT) was employed for patients with refractory disease, the long-term outcome of these patients underwent such treatment remained uncertain. The main purpose of this study was to make a primary system review on the outcome of EBV-HLH patients treated with immunochemotherapy and/or SCT.

MATERIAL AND METHODS

A system review and meta analysis was conducted on studies which collected from published PubMed and China Knowledge Resource Integrated Database (CNKI). The analysis was based on clinical characteristics and follow-up. Search strategy and selection criteria were identified by relevant articles, the period was defined from January 1990 to October 2010. Search terms included all relevant terms. English and Chinese language papers were reviewed.

RESULTS

A total of 11 articles include 342 EBV-HLH patients that were identified with our search terms fulfilled the eligibility criteria. Overall 104/342 patients (30.4%) died at the end of respective study. In 288 patients who did not receive SCT, 93/288 patients (32.3%) patients died. While in 54 patients who underwent SCT, 11/54 patients (20.4%) died at the end of respective study. Four articles had the contents both of immunochemotherapy and SCT. When using a meta analysis compared the mortality between immunochemotherapy and SCT groups, there was no statistical significance could be found, the Odds Ratio is 1.10 (0.43-2.84), (p = 0.84). When compared the mortality between SCT group and total EBV-HLH patients, there was still no statistical significance could be found, the Odds Ratio is 0.99 (0.39-2.53), (p = 0.98).

CONCLUSION

Etoposide-containing immunochemotherapy and SCT both decreased the mortality in EBV-HLH patients in the past decade. There was not enough evidence to suggest that SCT is better than immunochemotherapy in children with EBV-HLH. And such result may justify further research.

Anesthetics isoflurane and desflurane differently affect mitochondrial function, learning, and memory

OBJECTIVE

There are approximately 8.5 million Alzheimer disease (AD) patients who need anesthesia and surgery care every year. The inhalation anesthetic isoflurane, but not desflurane, has been shown to induce caspase activation and apoptosis, which are part of AD neuropathogenesis, through the mitochondria-dependent apoptosis pathway. However, the in vivo relevance, underlying mechanisms, and functional consequences of these findings remain largely to be determined.

METHODS

We therefore set out to assess the effects of isoflurane and desflurane on mitochondrial function, cytotoxicity, learning, and memory using flow cytometry, confocal microscopy, Western blot analysis, immunocytochemistry, and the fear conditioning test.

RESULTS

Here we show that isoflurane, but not desflurane, induces opening of mitochondrial permeability transition pore (mPTP), increase in levels of reactive oxygen species, reduction in levels of mitochondrial membrane potential and adenosine-5'-triphosphate, activation of caspase 3, and impairment of learning and memory in cultured cells, mouse hippocampus neurons, mouse hippocampus, and mice. Moreover, cyclosporine A, a blocker of mPTP opening, attenuates isoflurane-induced mPTP opening, caspase 3 activation, and impairment of learning and memory. Finally, isoflurane may induce the opening of mPTP via increasing levels of reactive oxygen species.

INTERPRETATION

These findings suggest that desflurane could be a safer anesthetic for AD patients as compared to isoflurane, and elucidate the potential mitochondria-associated underlying mechanisms, and therefore have implications for use of anesthetics in AD patients, pending human study confirmation.

Isoflurane-induced spatial memory impairment by a mechanism independent of amyloid-beta levels and tau protein phosphorylation changes in aged rats

OBJECTIVES

The molecular mechanism of postoperative cognitive dysfunction is largely unknown. Isoflurane has been shown to promote Alzheimer's disease neuropathogenesis. We set out to determine whether the effect of isoflurane on spatial memory is associated with amyloid-beta (A-beta) levels and tau phosphorylation in aged rats.

METHODS

Eighteen-month-old male Sprague-Dawley rats were randomly assigned as anesthesia group (n = 31, received 1.4% isoflurane for 2 hours and had behavioral testing), training group (n = 20, received no anesthesia but had behavioral testing), and control group (n = 10, received no anesthesia and had no behavioral testing). Spatial memory was measured before and 2 days after the anesthesia by the Morris water maze. We divided the anesthesia group into an isoflurane-induced severe memory impairment group (SIG, n = 6) and a no severe memory impairment group (NSIG, n = 25), according to whether the escape latency was more than 1.96 stand deviation of that from the training group. Levels of A-beta and tau in the hippocampus were determined by enzyme-linked immunosorbent assay and quantitative western blot at the end of behavioral testing.

RESULTS

We found that isoflurane increased the escape latency in the SIG as compared to that in the training group and NSIG without affecting swimming speed. However, there were no differences in the levels of A-beta and tau among SIG, NSIG, training, and control groups.

CONCLUSIONS

Isoflurane may induce spatial memory impairment through non-A-beta or tau neuropathogenesis mechanisms in aged rats.

The potential dual effects of anesthetic isoflurane on Aβ-induced apoptosis

β-amyloid protein (Aβ)-induced neurotoxicity is the main component of Alzheimer's disease (AD) neuropathogenesis. Inhalation anesthetics have long been considered to protect against neurotoxicity. However, recent research studies have suggested that the inhalation anesthetic isoflurane may promote neurotoxicity by inducing apoptosis and increasing Aβ levels. We therefore set out to determine whether isoflurane can induce dose- and time-dependent dual effects on Aβ-induced apoptosis: protection versus promotion. H4 human neuroglioma cells, primary neurons from naive mice, and naive mice were treated with Aβ and/or isoflurane, and levels of caspase-3 cleavage (activation), apoptosis, Bcl-2, Bax, and cytosolic calcium were determined. Here we show for the first time that the treatment with 2% isoflurane for six hours or 30 minutes potentiated, whereas the treatment with 0.5% isoflurane for six hours or 30 minutes attenuated, the Aβ-induced caspase-3 activation and apoptosis in vitro. Moreover, anesthesia with 1.4% isoflurane for two hours potentiated, whereas the anesthesia with 0.7% isoflurane for 30 minutes attenuated, the Aβ-induced caspase-3 activation in vivo. The high concentration isoflurane potentiated the Aβ-induced reduction in Bcl-2/Bax ratio and caused a robust elevation of cytosolic calcium levels. The low concentration isoflurane attenuated the Aβ-induced reduction in Bcl-2/Bax ratio and caused only a mild elevation of cytosolic calcium levels. These results suggest that isoflurane may have dual effects (protection or promotion) on Aβ-induced toxicity, which potentially act through the Bcl-2 family proteins and cytosolic calcium. These findings would lead to more systematic studies to determine the potential dual effects of anesthetics on AD-associated neurotoxicity.