Sevoflurane induces endoplasmic reticulum stress mediated apoptosis in hippocampal neurons of aging rats

Effect of Ginsenoside Rh-2 via Activation of Caspase-3 and Bcl-2-Insensitive Pathway in Ovarian Cancer Cells

Ginsenoside has been reported to have therapeutic effects for some types of cancer, but its effect on ovarian cancer cells has not been evaluated. In this study, we monitored the effects of ginsenoside-Rh2 (Rh2) on the inhibition of cell proliferation and the apoptotic process in the ovarian cancer cell line SKOV3 using an MTT assay and TUNEL assay. We found that Rh2 inhibited cell proliferation and significantly induced apoptosis. We confirmed the apoptotic effects of Rh2 using western blot analysis of apoptosis-related proteins. Specifically, the levels of cleaved poly ADP ribose polymerase (PARP) and cleaved caspase-3 significantly increased in SKOV3 cells treated with Rh2. Therefore, Rh2 clearly suppressed the growth of SKOV3 cells in vitro, which was associated with induction of the apoptosis pathway. Moreover, the migration assay showed that Rh2 inhibited the invasive ability of SKOV3 cells. Taken together, our results suggest that Rh2 has anticancer effects in SKOV3 cells through inhibition of cell proliferation and induction of apoptosis. Considering the therapeutic potential of Rh2, more studies should be carried out to facilitate the future application of this natural product as a potential anti-cancer agent.

The genetics of isoflurane-induced developmental neurotoxicity

INTRODUCTION

Neurotoxicity induced by early developmental exposure to volatile anesthetics is a characteristic of organisms across a wide range of species, extending from the nematode C. elegans to mammals. Prevention of anesthetic-induced neurotoxicity (AIN) will rely upon an understanding of its underlying mechanisms. However, no forward genetic screens have been undertaken to identify the critical pathways affected in AIN. By characterizing such pathways, we may identify mechanisms to eliminate isoflurane induced AIN in mammals.

METHODS

Chemotaxis in adult C. elegans after larval exposure to isoflurane was used to measure AIN. We initially compared changes in chemotaxis indices between classical mutants known to affect nervous system development adding mutants in response to data. Activation of specific genes was visualized using fluorescent markers. Animals were then treated with rapamycin or preconditioned with isoflurane to test effects on AIN.

RESULTS

Forty-four mutations, as well as pharmacologic manipulations, identified two pathways, highly conserved from invertebrates to humans, that regulate AIN in C. elegans. Activation of one stress-protective pathway (DAF-2 dependent) eliminates AIN, while activation of a second stress-responsive pathway (endoplasmic reticulum (ER) associated stress) causes AIN. Pharmacologic inhibition of the mechanistic Target of Rapamycin (mTOR) blocks ER-stress and AIN. Preconditioning with isoflurane prior to larval exposure also inhibited AIN.

DISCUSSION

Our data are best explained by a model in which isoflurane acutely inhibits mitochondrial function causing activation of responses that ultimately lead to ER-stress. The neurotoxic effect of isoflurane can be completely prevented by manipulations at multiple points in the pathways that control this response. Endogenous signaling pathways can be recruited to protect organisms from the neurotoxic effects of isoflurane.

Sevoflurane-Induced Endoplasmic Reticulum Stress Contributes to Neuroapoptosis and BACE-1 Expression in the Developing Brain: The Role of eIF2α

Neonatal exposure to volatile anesthetics causes apoptotic neurodegeneration in the developing brain, possibly leading to neurocognitive deficits in adulthood. Endoplasmic reticulum (ER) stress might be associated with sevoflurane (sevo)-induced neuroapoptosis. However, the signaling pathway regulating sevo-induced neuroapoptosis is not understood. We investigated the effects of neonatal sevo exposure on ER signaling pathway activation. Seven-day-old mouse pups were divided into control (C) and sevo (S; 3 % sevo exposure, 6 h) groups. ER stress marker [protein kinase RNA-like ER kinase (PERK), eukaryotic translation initiation factor 2α (eIF2α), activating transcription factor 4 (ATF4), CHOP, and caspase-12] levels were determined by western blotting. To understand the role of eIF2α in sevo-induced ER stress and caspase-3 activation, pups were pretreated with an eIF2α dephosphorylation inhibitor, salubrinal, and a potent and selective inhibitor of PERK, GSK2656157, before sevo exposure, and the effects on ER stress signaling and neuroapoptosis were examined. We investigated whether neonatal exposure to sevo increased β-site APP-cleaving enzyme 1 (BACE-1) expression. Neonatal sevo exposure elevated caspase-3 activation. ER stress signaling was activated, along with increased PERK and eIF2α phosphorylation, and upregulation of proapoptotic proteins (ATF4 and CHOP) in the cerebral cortex of the developing brain. Pretreatment with salubrinal augmented sevo-induced eIF2α phosphorylation, which inhibited ER stress-mediated ATF4 and caspase-3 activation. Inhibition of PERK phosphorylation due to GSK2656157 pretreatment reduced the sevo-induced increase in eIF2α phosphorylation. Sevo increased BACE-1 expression, which was attenuated by GSK2656157 and salubrinal pretreatment. Our data suggested that neonatal sevo exposure-induced neuroapoptosis is mediated via the PERK-eIF2α-ATF4-CHOP axis of the ER stress signaling pathway. Modulation of eIF2α phosphorylation may play a key role in sevo-induced neurotoxicity in the developing brain.

Single and repeated exposures to the volatile anesthetic isoflurane do not impair operant performance in aged rats

Postoperative Cognitive Dysfunction (POCD) is a complication that can occur in the elderly after anesthesia and surgery and is characterized by impairments in information processing, memory, and executive function. Currently, it is unclear whether POCD is due to the effects of surgery, anesthesia, or perhaps some interaction between these or other perioperative variables. Studies in rodents suggest that the development of POCD may be related directly to anesthesia-induced neuroactivity. Volatile anesthetics have been shown to increase cellular inflammation and apoptosis within the hippocampus of aged rodents, while producing corresponding impairments in hippocampal-dependent brain functions. However, it is unclear whether volatile anesthetics can affect additional aspects of cognition that do not primarily depend upon the hippocampus. The purpose of this study was to use established operant tests to examine the effects of isoflurane on aspects of behavioral inhibition, learning, and motivation in aged rats. Twenty-one adult Sprague-Dawley rats (11 male, 10 female) were trained to perform fixed consecutive number (FCN), incremental repeated acquisition (IRA), and progressive ratio (PR) tasks for a minimum of 15 months prior to receiving anesthesia. At 23 months of age, rats were exposed to 1.3% isoflurane or medical grade air for 2h. Initial results revealed that a 2h exposure to isoflurane had no effect on IRA, FCN, or PR performance. Thus, rats received 3 additional exposures to 1.3% isoflurane or medical grade air: 2, 4 and 6h exposures with 2 weeks elapsing before exposure two, 3 weeks elapsing between exposures two and three, and 2 weeks elapsing between exposures three and four. These additional exposures had no observable effects on performance of any operant task. These results suggest that single and repeated exposures to isoflurane do not impair the performance of aged rats in tasks designed to measure behavioral inhibition, learning, and motivation. This lack of significant effect suggests that the impairments associated with isoflurane exposure may not generalize to all aspects of cognition, but may be selective to tasks that primarily measure spatial memory processes.

Effects of calpain on sevoflurane-induced aged rats hippocampal neuronal apoptosis

BACKGROUND

Sevoflurane is one of the most commonly used volatile anesthetics and it has been shown to induce widespread apoptotic neurodegeneration in aged rat. Calpain is also activated during apoptosis in several types of cells. We hypothesized that calpain resulted in apoptosis under long time sevoflurane exposure, and it might play a role in the sevoflurane-induced memory impairment in aged rats.

METHODS

Seventy-two 18-month-old male Sprague-Dawley rats were randomly divided into three groups (n = 24): Control group rats were exposed to simply humid 50 % O2 balanced by N2 for 3 h; While M group rats received calpain inhibitor 10 mg/kg via the tail vein intravenously at 30 min before the animals inhaled 3 % sevoflurane for 3 h, subsequently received MDL 28170 3.33 mg/kg/h for 3 h. Sev group rats were only exposed to 3 % sevoflurane for 3 h without calpain inhibitor. Morris Water Maze was used to test the ability of learning and memory. Cytosolic calcium concentration was measured by using flow cytometry. Annexin-V labeled with a fluorophore or biotin can identify apoptotic cells by binding to PS. The expression of calpain in the hippocampus of rats was tested by Western blots.

RESULTS

The results showed that the M group had a shorter latency and had a larger number of times crossing over the previous platform site than that of the Sev group. Compared with Sev group, apoptosis rate and 76/80 kDa ratio of μ-calpain were significantly decreased in M group on the 1st day.

CONCLUSIONS

Sevoflurane might induce apoptosis through increasing [Ca(2+)]c and the activity of μ-calpain, which might be identified at least partially the molecular mechanism by which sevoflurane induces apoptosis.

The 2A2 protein of Duck hepatitis A virus type 1 induces apoptosis in primary cell culture

Duck hepatitis A virus type 1, (DHAV-1) 2A2^pro, is one of the most highly conserved viral proteins within the DHAV serotypes. However, its effect on host cells is unclear. We predicted that DHAV-1 2A2^pro was a GTPase-like protein based on the results of multiple sequence alignment and homologous modeling analysis. Upon transfection of a recombinant plasmid expressing DHAV-1 2A2, cells displayed fragmented nuclei, chromatin condensation, oligonucleosome-sized DNA ladder, and positive terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling staining; hence, cell death has the characteristics of apoptosis. By staining cells with fluorescein Annexin V-FITC and PI, it is possible to distinguish and quantitatively analyze nonapoptotic cells, early apoptotic cells, late apoptotic/necrotic cells, and dead cells through flow cytometry and fluorescence microscopy. The percentage of apoptotic cells gradually increased and reached a maximum after 48 h of transfection. In conclusion, apoptosis induced by this GTPase-like protein may contribute to DHAV-1 pathogenesis.

Decreased PSD95 expression in medial prefrontal cortex (mPFC) was associated with cognitive impairment induced by sevoflurane anesthesia

OBJECTIVE

Though sevoflurane has been widely used as an anesthetic in surgery, recent studies have shown that exposure to sevoflurane alone could lead to postoperative cognitive dysfunction (POCD), of which the mechanisms still remain largely unknown. The medial prefrontal cortex (mPFC) is known to be implicated in various cognitive impairments, including working memory and attentional processes. In the present study, we tried to identify dysregulated gene expression in mPFC and investigate the underlying mechanisms involved in POCD.

METHODS

Behavioral tests, including elevated plus-maze, O-maze, and Y-maze tests, were performed on Wistar rats exposed to sevoflurane. Whole-genome mRNA profiling of mPFC from Wistar rats after exposure to sevoflurane was carried out. Real-time polymerase chain reaction (PCR) was done to verify the differentially expressed genes.

RESULTS

Significant impairment of working memory of rats after exposure to sevoflurane was observed. A total of 119 of 7319 detected mRNAs showed significantly different expression between rats with and without sevoflurane exposure (fold change (FC)>2.0, P<0.05, and false discovery rate (FDR)<0.05), among which 74 mRNAs were down-regulated and 45 mRNAs were up-regulated. Postsynaptic density-95 (PSD95, also named DLG4) showed the most significantly decreased expression in mPFC and further investigation indicated that PSD95 expression level was correlated with spatial working memory performance.

CONCLUSIONS

Our study revealed that PSD95 might be involved in the mechanism of POCD, which could provide clues for preventing POCD in clinical operations.

Autophagy activation prevents sevoflurane-induced neurotoxicity in H4 human neuroglioma cells

AIM

The inhaled anesthetic sevoflurane may induce cognitive impairment in both animals and humans. Previous study has shown that sevoflurane triggers ER stress and may lead to apoptosis in rat hippocampal neurons. In this study, we examined whether sevoflurane caused autophagy and its contributions to sevoflurane induced neuronal cell injury.

METHODS

H4 human neuroglioma cells were exposed to 4.1% sevoflurane for 6 h. Cell viability and apoptosis ratio were assessed using a CCK8 kit and flow cytometry, respectively. Autophagosomes in the cells were detected using GFP-LC3 plasmid transfection or transmission electronic microscopy. The expression of LC3B, p62/SQSTM, C/EBP homologous protein (CHOP) and glucose-related protein 78 (GRP78) was assessed with Western blotting.

RESULTS

Sevoflurane treatment induced apoptosis and markedly increased the LC3-II level and GFP-LC3 puncta number, decreased p62 expression in H4 cells. Activation of autophagy by rapamycin (1 μmol/L) significantly reduced sevoflurane-induced apoptosis and increased cell viability, whereas inhibition of autophagy with 3-MA (5 mmol/L) caused the opposite effects. Furthermore, sevoflurane treatment markedly increased the expression of CHOP and GRP78, two hallmark proteins of ER stress. Inhibition of ER stress by 4-phenylbutyrate (500 μmol/L) abrogated sevoflurane-induced autophagy and apoptosis, and improved the viability. Moreover, sevoflurane-stimulated expression of CHOP and GRP78 was inhibited by rapamycin, but further enhanced by 3-MA.

CONCLUSION

Sevoflurane treatment induces ER stress and activates autophagy, which antagonizes sevoflurane-induced apoptosis in H4 human neuroglioma cells. The results suggest that autophagy may be a potential therapeutic target in preventing sevoflurane-induced neurotoxicity.

Autophagy Is Involved in the Sevoflurane Anesthesia-Induced Cognitive Dysfunction of Aged Rats

Autophagy is associated with regulation of both the survival and death of neurons, and has been linked to many neurodegenerative diseases. Postoperative cognitive dysfunction is commonly observed in elderly patients following anesthesia, but the pathophysiological mechanisms are largely unexplored. Similar effects have been found in aged rats under sevoflurane anesthesia; however, the role of autophagy in sevoflurane anesthesia-induced hippocampal neuron apoptosis of older rats remains elusive. The present study was designed to investigate the effects of autophagy on the sevoflurane-induced cognitive dysfunction in aged rats, and to identify the role of autophagy in sevoflurane-induced neuron apoptosis. We used 20-month-old rats under sevoflurane anesthesia to study memory performance, neuron apoptosis, and autophagy. The results demonstrated that sevoflurane anesthesia significantly impaired memory performance and induced hippocampal neuron apoptosis. Interestingly, treatment of rapamycin, an autophagy inducer, improved the cognitive deficit observed in the aged rats under sevoflurane anesthesia by improving autophagic flux. Rapamycin treatment led to the rapid accumulation of autophagic bodies and autophagy lysosomes, decreased p62 protein levels, and increased the ratio of microtubule-associated protein light chain 3 II (LC3-II) to LC3-I in hippocampal neurons through the mTOR signaling pathway. However, administration of an autophagy inhibitor (chloroquine) attenuated the autophagic flux and increased the severity of sevoflurane anesthesia-induced neuronal apoptosis and memory impairment. These findings suggest that impaired autophagy in the hippocampal neurons of aged rats after sevoflurane anesthesia may contribute to cognitive impairment. Therefore, our findings represent a potential novel target for pro-autophagy treatments in patients with sevoflurane anesthesia-induced neurodegeneration.

Sevoflurane anesthesia induces neither contextual fear memory impairment nor alterations in local population connectivity of medial prefrontal cortex local field potentials networks in aged rats

Sevoflurane has been found to increase apoptosis and pathologic markers associated with Alzheimer disease, provoking concern over their potential contribution to postoperative cognitive dysfunction. This study aimed to determine the effects of sevoflurane on contextual fear memory of aged rats and to characterize local population connectivity of local field potentials (LFPs) in medial prefrontal cortex (mPFC) of aged rats during contextual fear memory. Eighteen-month-old male SD rats were implanted with one multichannel electrode array in mPFC. The aged rats were divided into control group, sevoflurane group (1 MAC sevoflurane for 2 h) and surgical group with 1.0 MAC sevoflurane for 2 h. We then assessed the effect of the anesthesia on contextual fear memory, and alterations in the local population connectivity of mPFC LFP networks by partial directed coherence (PDC). Surgery impaired contextual fear memory and reduced local population connectivity of mPFC LFP networks in aged rats at day 1 after the surgery and anesthesia. 1 MAC Sevoflurane anesthesia induced neither contextual fear memory impairment nor alterations in local population connectivity of mPFC LFP networks in aged rats when tested 1, 7, 15 and 30 days after exposure (P > 0.05). PDC values of theta band mPFC LFPs became strongly increased during contextual fear memory at 1, 7, 15, and 30 days after anesthesia. Our results suggest that 1 MAC sevoflurane anesthesia does not induce contextual fear memory impairment in aged rats and suggest that the increased local population connectivity in theta bands LFPs of mPFC plays a role in contextual fear memory.

NADPH oxidase 2-derived reactive oxygen species in the hippocampus might contribute to microglial activation in postoperative cognitive dysfunction in aged mice

Microglial activation plays a key role in the development of postoperative cognitive dysfunction (POCD). Nox2, one of the main isoforms of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase in the central nervous system, is a predominant source of reactive oxygen species (ROS) overproduction in phagocytes including microglia. We therefore hypothesized that Nox2-induced microglial activation is involved in the development of POCD. Sixteen-month-old C57BL/6 mice were subjected to exploratory laparotomy with isoflurane anesthesia to mimic the clinical human abdominal surgery. Behavioral tests were performed at 6 and 7 d post-surgery with open field and fear conditioning tests, respectively. The levels of Nox2, 8-hydroxy-2'-deoxyguanosine (8-OH-dG, a marker of DNA oxidation), CD11b (a marker of microglial activation), interleukin-1β (IL-1β), and brain-derived neurotrophic factor (BDNF) were determined in the hippocampus and prefrontal cortex at 1 d and 7 d post-surgery, respectively. For the interventional study, mice were treated with a NADPH oxidase inhibitor apocynin (APO). Our results showed that exploratory laparotomy with isoflurane anesthesia impaired the contextual fear memory, increased expression of Nox2, 8-OH-dG, CD11b, and IL-1β, and down-regulated BDNF expression in the hippocampus at 7 d post-surgery. The surgery-induced microglial activation and neuroinflammation persisted to 7 d after surgery in the hippocampus, but only at 1 d in the prefrontal cortex. Notably, administration with APO could rescue these surgery-induced cognitive impairments and associated brain pathology. Together, our data suggested that Nox2-derived ROS in hippocampal microglia, at least in part, contributes to subsequent neuroinflammation and cognitive impairments induced by surgery in aged mice.

Rationale and Design of the Balanced Anesthesia Study: A Prospective Randomized Clinical Trial of Two Levels of Anesthetic Depth on Patient Outcome After Major Surgery

BACKGROUND

An association between relatively deep anesthesia, as guided by the bispectral index (BIS), and increased postoperative mortality has been demonstrated in 6 of 8 published observational studies, but association does not necessarily mean causality. Small clinical trials of anesthetic depth have demonstrated increased delirium and postoperative cognitive dysfunction in patients who were relatively deeply anesthetized, but have been inadequately powered to study mortality. A large-scale randomized study is required to determine whether causality exists.

METHODS

The primary hypothesis of our study is that "light" anesthesia, defined as a BIS target of 50, will reduce all-cause mortality within 1 year of surgery in comparison with "deep" anesthesia, defined as a BIS target of 35, in patients aged ≥60 years presenting for major surgery under general anesthesia. The trial is an international multicenter, randomized, parallel-group, double-blind (patients and investigators) prospective, intention-to-treat, safety and efficacy study. The relative reduction in mortality in the light anesthesia group is expected to be 20%, giving an absolute risk reduction from 10% to 8%. Power analysis using a = 0.049 and b = 0.2 indicates that 3250 patients are required in each group.

RESULTS

The study is underway, and 1325 patients have been recruited in 40 centers in 5 countries. It is anticipated that the study will be completed in 3 years.

CONCLUSIONS

This randomized controlled trial should definitively answer the question of whether titrating anesthetic depth makes a difference to patient outcome in a vulnerable patient group.

Elevation of Sestrin-2 expression attenuates Sevoflurane induced neurotoxicity

Sevoflurane, one of the most commonly used volatile anesthetics in clinical treatment, has been shown to induce a widespread increase in brain apoptosis. However, the underlying mechanism is still unknown. Sestrin 2 has been recently shown to regulate intracellular reactive oxygen species (ROS) levels and play a crucial role in p53-dependent antioxidant defenses. In this study, our results indicated that administration of Sevoflurane elevated the gene and protein expression of Sestrin-2 in a dose dependent manner in human neuroblastoma M17 cells. It was shown that silence of Sestrin-2 by small RNA interference (siRNA) ominously exacerbated the increase in intracellular ROS and reduction of SOD activity induced by Sevoflurane treatment. Notably, knockdown of Sestrin-2 in M17 cells significantly increases the number of apoptotic cells after treatment with Sevoflurane. Mechanistically, we also found that Sevoflurane treatment resulted in a reduced amount of the cytosolic anti-apoptotic protein Bcl-2 but an increased amount of Bax, which was exacerbated by knockdown of Sestrin-2. In addition, knockdown of Sestrin-2 remarkably increased the elevated cleaved Caspase-3 expression. Finally, we showed that the induction of Sestrin-2 by Sevoflurane was mediated by p53. These results suggest that the suppressive effects of Sestrin-2 on neuroapoptosis against the Sevoflurane anesthesia in neuronal cells might be associated with modulation of mitochondrial pathway.

Prior infection exacerbates postoperative cognitive dysfunction in aged rats

Older patients may experience persisting postoperative cognitive dysfunction (POCD), which is considered to largely depend on surgery-induced (neuro)inflammation. We hypothesize that inflammatory events before surgery could predispose patients to POCD. When part of our aged rats developed Mycoplasma pulmonis, this presented the unique opportunity to investigate whether a pulmonary infection before surgery influences surgery-induced neuroinflammation and POCD. Male 18-mo-old Wistar rats that had recovered from an active mycoplasma infection (infection) and control rats (healthy) were subjected to abdominal surgery and jugular vein catheterization under general anesthesia (surgery) or remained naïve (control). In postoperative week 2, behavioral tests were performed to assess cognitive performance and exploratory behavior. The acute systemic inflammatory response was investigated by measuring plasma IL-6 and IL-12. In the hippocampus, prefrontal cortex and striatum, microglial activity, neurogenesis, and concentrations of IL-6, IL-12, IL1B, and brain-derived neurotropic factor on postoperative day 14 were determined. Rats still showed signs of increased neuroinflammatory activity, as well as cognitive and behavioral changes, 3 wk after the symptoms of infection had subsided. Rats that had experienced infection before surgery exhibited a more generalized and exacerbated postoperative cognitive impairment compared with healthy surgery rats, as well as a prolonged increase in systemic cytokine levels and increased microglial activation in the hippocampus and prefrontal cortex. These findings support the hypothesis that an infection before surgery under general anesthesia exacerbates POCD. Future studies are necessary to determine whether the found effects are aging specific and to investigate the magnitude and time course of this effect in a controlled manner.

Assessing apoptosis gene expression profiling with a PCR array in the hippocampus of Ts65Dn mice

It is well known that Down syndrome (DS) is a condition in which extra genetic material causes delays in the way a child develops, both mentally and physically. Intellectual disability is the foremost and most debilitating trait, which caused loss of cognitive abilities and the development of early onset Alzheimer's disease (AD). Ts65Dn mice were used in this study. We isolated the hippocampus. First, we used transmission scanning electron microscopy to directly observe the hippocampus and confirm if apoptosis had occurred. Second, we customized a PCR array with 53 genes, including several important genes related to cell apoptosis. Gene expression was detected by RT-PCR. There were varying degrees of changes characteristic of apoptosis in the hippocampus of Ts65Dn mice, which mainly included the following: nuclear membrane thinning, unevenly distributed chromosomes, the production of chromatin crescents, and pyknosis of the nuclei with some nuclear fragmentation. Meanwhile, three genes (API5, AIFM1, and NFκB1) showed changes of expression in the hippocampus of Ts65Dn mice compared with normal mice. Only NFκB1 expression was significantly increased, while the expressions of API5 and AIFM1 were notably decreased. The fold changes in the expression of API5, AIFM1, and NFκB1 were 11.55, 5.94, and 3.11, respectively. However, some well-known genes related to cell apoptosis, such as the caspase family, Bcl-2, Bad, Bid, Fas, and TNF, did not show changes in expression levels. The genes we found which were differentially expressed in the hippocampus of Ts65Dn mice may be closely related to cell apoptosis. PCR array technology can assist in the screening and identification of genes involved in apoptosis.

Involvement of the blood-brain barrier opening in cognitive decline in aged rats following orthopedic surgery and high concentration of sevoflurane inhalation

The underlying causes of postoperative cognitive decline (POCD) in old patients remained unelucidated, and there are little descriptions on mechanisms associated with the blood-brain barrier (BBB) disruption during POCD. We therefore tested the effects of orthopedic surgery with different concentrations of sevoflurane for 2 h on the behavior test and the BBB permeability in aged rats. 18-month rats were divided into control group and surgical group with propofol anesthesia (0.7 mgkg(-1) min(-1)) and 1.0 MAC, 1.3 MAC, and 1.5 MAC sevoflurane inhalation for 2 h. We assessed their cognitive function via Y-maze and fear conditioning test on day 1, 3, and 7 after experiments. Animals were then assigned to control group, propofol (2 h, 0.7 mgkg(-1) min(-1)) group, surgery plus propofol group and surgery plus 1.5 MAC sevoflurane inhalation for 2h. Their hippocampal BBB permeability was detected with Evans blue quantification. Alterations of tight junctions in hippocampus were measured with occludin and claudin-5 western blot. Then we assessed matrix metalloproteinase-2,9 (MMP-2,9) via western blot and immunohistochemistry staining at day 1, 3, 7, and 14 after experiments. Surgery impaired cognitive function and increased Evans blue leakage into the hippocampus in aged rats while 2 h of 1.5 MAC sevoflurane inhalation potentiated these effects. Surgery induced occludin protein expression decreases and MMP-2,9 proteins increase and these influences can be enhanced by high concentration of sevoflurane inhalation. In conclusion, 1.5 MAC sevoflurane for 2 h exacerbated cognitive impairment induced by orthopedic surgery in aged rats and the breach in BBB may be involved in this process.

Disturbance of endogenous hydrogen sulfide generation and endoplasmic reticulum stress in hippocampus are involved in homocysteine-induced defect in learning and memory of rats

Homocysteine (Hcy) is a risk factor for Alzheimer's disease (AD). Hydrogen sulfide (H2S) acts as an endogenous neuromodulator and neuroprotectant. It has been shown that endoplasmic reticulum (ER) stress is involved in the pathological mechanisms of the learning and memory dysfunctions and that H2S exerts its neuroprotective role via suppressing ER stress. In the present work, we explored the effects of intracerebroventricular injection of Hcy on the formation of learning and memory, the generation of endogenous H2S, and the expression of ER stress in the hippocampus of rats. We found that intracerebroventricular injection of Hcy in rats leads to learning and memory dysfunctions in the Morris water maze and novel of object recognition test and decreases in the expression of cystathionine-β-synthase, the major enzyme responsible for endogenous H2S generation, and the generation of endogenous H2S in the hippocampus of rats. We also showed that exposure of Hcy could up-regulate the expressions of glucose-regulated protein 78 (GRP78), CHOP, and cleaved caspase-12, which are the major mark proteins of ER stress, in the hippocampus of rats. Taken together, these results suggest that the disturbance of hippocampal endogenous H2S generation and the increase in ER stress in the hippocampus are related to Hcy-induced defect in learning and memory.

Inhibition of serine/threonine protein phosphatase PP1 protects cardiomyocytes from tunicamycin-induced apoptosis and I/R through the upregulation of p-eIF2α

The serine/threonine protein phosphatase PP1 mediates the dephosphorylation of phosphorylated eukaryotic translation initiation factor 2 subunit α (p-eIF2α), which is a central regulator of protein synthesis. In the present study, we examined the protective effects of PP1-12 (an inhibitor of the serine/threonine protein phosphatase PP1) against tunicamycin (TM)-induced apoptosis in cultured cardiomyocytes in vitro, as well as in an in vivo model of ischemia/reperfusion (I/R) injury in rat hearts. Neonatal cardiomyocytes cultured from the ventricles of the hearts of 1-day-old Wistar rats were exposed to various concentrations of PP1-12 (0.3, 1 and 3 µmol/l) for 30 min, followed by treatment with TM for 36 h. Cell viability was assessed by adenosine triphosphate (ATP) bioluminescence, and the results revealed that pre-treatment with PP1-12 protected cell viability. Western blot analysis revealed that PP1-12 induced eIF2α phosphorylation and immuncytochemistry indicated that PP1-12 downregulated the expression of C/EBP homologous protein (CHOP), which is related to apoptosis. PP1-12 suppressed cell apoptosis, with maximum protective effects displayed at the concentration of 3 µmol/l. For the in vivo experiments, male Sprague-Dawley rats were randomly divided into 5 groups: i) sham-operated; ii) vehicle (I/R + DMSO); iii) I/R + 1 mg/kg/day PP1-12; iv) I/R + 3 mg/kg/day PP1-12; and v) I/R + 10 mg/kg/day PP1-12. PP1-12 reduced the expression of cleaved caspase-12 and increased the phosphorylation of eIF2α, as revealed by western blot analysis. By calculating the apoptotic index (AI), we found that 10 mg/kg/day PP1-12 exerted the most pronounced anti-apoptotic effect. The infarction area was significantly decreased following treatment with this concentration of PP1-12, as revealed by 2,3,5-triphenyltetrazolium chloride (TTC) staining. Taken together, these data suggest that PP1-12 protects cardiomyocytes from TM- and I/R-induced apoptosis, and this effect is achieved at least in part through the inhibition of cell apoptosis and the induction of eIF2α phosphorylation.

The protective role of Bax inhibitor-1 against chronic mild stress through the inhibition of monoamine oxidase A

The anti-apoptotic protein Bax inhibitor-1 (BI-1) is a regulator of apoptosis linked to endoplasmic reticulum (ER) stress. It has been hypothesized that BI-1 protects against neuron degenerative diseases. In this study, BI-1⁻/⁻ mice showed increased vulnerability to chronic mild stress accompanied by alterations in the size and morphology of the hippocampi, enhanced ROS accumulation and an ER stress response compared with BI-1⁺/⁺ mice. BI-1⁻/⁻ mice exposed to chronic mild stress showed significant activation of monoamine oxidase A (MAO-A), but not MAO-B, compared with BI-1⁺/⁺ mice. To examine the involvement of BI-1 in the Ca²⁺-sensitive MAO activity, thapsigargin-induced Ca²⁺ release and MAO activity were analyzed in neuronal cells overexpressing BI-1. The in vitro study showed that BI-1 regulates Ca²⁺ release and related MAO-A activity. This study indicates an endogenous protective role of BI-1 under conditions of chronic mild stress that is primarily mediated through Ca²⁺-associated MAO-A regulation.

Regulation of autophagy and apoptosis in response to angiotensin II in HL-1 cardiomyocytes

BACKGROUND

Autophagy and apoptosis are two important regulators of cell survival, and are often observed simultaneously in response to noxious stimuli. Anoxia is a known stimulus for autophagy and apoptosis, and angiotensin (Ang) II is a major mediator of anoxic injury. However, specific responses to anoxia and Ang II in terms of occurrence of autophagy and apoptosis have still not been delineated.

METHODS AND RESULTS

We observed that autophagy (measured as LC3 staining, and Beclin-1 and p62 Western blotting) was an early response and apoptosis (measured as TUNEL staining, and Annexin V and Smac/Diablo Western blotting) became dominant as the duration of anoxia was prolonged. Autophagy also occurred quickly in response to low concentrations of Ang II. When exposed to high concentrations of Ang II, a significant number of cells developed apoptosis, while autophagy response decreased. Ang II-mediated apoptosis was blocked by Ang II type 1 receptor (AT1R) blocker losartan as well as by the AT2R blocker PD123319. Ang II-induced autophagy was blocked by losartan, but not by PD123319.

CONCLUSION

Exposure to Ang II, a mediator of anoxic injury, initiates a rapid autophagy response, perhaps in an attempt to protect tissues from the impending noxious effects. However, when anoxia (and thereby release of Ang II) is prolonged, the process of apoptosis dominates. These processes will determine the outcome of cardiomyocyte well-being in states of hypoxia.

7,8-dihydroxycoumarin may promote sciatic nerve regeneration by suppressing NF-κB expression in mice

Nuclear factor (NF)-κB expression occurs during sciatic injury. In addition, 7,8-dihydroxycoumarin exhibits a neurotrophic effect on peripheral nerve regeneration. To investigate the effects of 7,8-dihydroxycoumarin on the expression levels of NF-κB in L4-6 spinal cord segments of the injured sciatic nerve in mice and on the functional recovery and regeneration following nerve injury, a total of 160 healthy adult male BALB/c mice underwent unilateral sciatic nerve interruption and anastomosis. The mice were separated into groups and subsequently treated with physiological saline (control) or high, medium or low doses of 7,8-dihydroxycoumarin. NF-κB levels were detected by western blot analysis and quantitative polymerase chain reaction (qPCR), and the sciatic functional index (SFI) was measured. Neuronal apoptosis was detected by terminal-deoxynucleotidyl transferase dUTP-mediated nick-end labeling (TUNEL) staining. The results revealed that NF-κB was activated in the L4-6 spinal cord connected to the injured sciatic nerve. qPCR and western-blot analysis results showed that the expression levels of NF-κB in the high- and medium-dose groups were significantly lower compared with the low-dose and control groups at 12 h, one day, three days, five days and one week (P<0.05 for each). SFI and TUNEL results demonstrated that the high- and medium-dose groups exhibited improved functional nerve regeneration and reduced apoptosis compared with the low-dose and control groups. In conclusion, 7,8-dihydroxycoumarin is capable of suppressing the immune activation of NF-κB in the neurons of the L4-6 spinal cord connected with the injured sciatic nerve, thereby reducing the focal filtration of inflammatory cells, producing the optimum environment for nerve regeneration.