Activation of the canonical nuclear factor-κB pathway is involved in isoflurane-induced hippocampal interleukin-1β elevation and the resultant cognitive deficits in aged rats

Effect of General Anesthetic Agents on Microglia

The effects of general anesthetic agents (GAAs) on microglia and their potential neurotoxicity have attracted the attention of neuroscientists. Microglia play important roles in the inflammatory process and in neuromodulation of the central nervous system. Microglia-mediated neuroinflammation is a key mechanism of neurocognitive dysfunction during the perioperative period. Microglial activation by GAAs induces anti-inflammatory and pro-inflammatory effects in microglia, suggesting that GAAs play a dual role in the mechanism of postoperative cognitive dysfunction. Understanding of the mechanisms by which GAAs regulate microglia may help to reduce the incidence of postoperative adverse effects. Here, we review the actions of GAAs on microglia and the consequent changes in microglial function. We summarize clinical and animal studies associating microglia with general anesthesia and describe how GAAs interact with neurons via microglia to further explore the mechanisms of action of GAAs in the nervous system.

GLP-1 Analog Alleviated Cognitive Dysfunction in Aged Rats Anaesthetized with Sevoflurane

Postoperative cognitive dysfunction (POCD) in elderly patients undergoing general anesthesia is a major problem in the aging society. Sevoflurane is the most widely applied anesthetic in clinical practice. In this study, we investigated the effects of the GLP-1 analogue liraglutide on cognitive function in aged rats anesthetized by sevoflurane. Specifically, 48 Sprague-Dawley rats were divided into the control (C) group, the liraglutide (L) group, the sevoflurane (S) group, and the sevoflurane+liraglutide (SL) group, each group with 12 rats. In the S group and the SL group, the rats were injected subcutaneously with normal saline and liraglutide after inhalation of a mixture of 3% sevoflurane and pure oxygen. In the C group and the L group, normal saline and liraglutide were injected subcutaneously into the rats after inhalation of pure oxygen. Morris Water Maze Task was applied for the detection of spatial learning and memory in rats; HE and TUNEL for staining; and western blot for quantifying Bax, Bcl-2 expression, and examining caspase-3 activity in hippocampal tissues as well as for revealing the antiapoptotic mechanism. Besides, the accumulation of inflammatory factors NF-κB and IL-1β in the hippocampal tissue was quantitatively studied to reveal the anti-inflammatory mechanism. The protective effect of liraglutide on sevoflurane toxicity was the first to be confirmed in this study. Additionally, this study elucidated the mechanism of the above effect. The results of this study might be helpful to find an effective medical solution for the treatment of POCD caused by sevoflurane anesthesia.

Renoprotective effects of prazosin on ischemia-reperfusion injury in rats

BACKGROUND

Renal ischemia-reperfusion (IR) injury is one of the main leading causes of acute kidney injury associated with inflammation, oxidative stress and cell apoptosis. We studied the effects of prazosin, as a specific blocker of α1-AR, on renal IR injury.

METHODS

Rats were divided into normal control; untreated IR and prazosin-treated IR (1 mg/kg body weight). Prazosin was administered by intraperitoneal injection 30 min prior to IR induction. The level of urea/creatinine and oxidative factors were detected by colorimetric methods. Apoptosis-associated factors, inflammatory, and signaling proteins were analyzed in renal tissue. The abnormalities of renal histopathology were detected by immunohistochemistry.

RESULTS

Administration of prazosin to IR rats ameliorated serum urea and creatinine and IR-induced histopathological damages. Lipid peroxidation was significantly improved after treatment by prazosin in IR injury rats, however, antioxidant status was not affected. Rats subjected to IR injury activated Bax protein and NF-κB mediated inflammatory response. Moreover, treatment with prazosin inhibited renal NF-κB activation, resulting in a significant decline in pro-inflammatory cytokine of IL-6.

CONCLUSION

These findings suggest that prazosin could be a good candidate to attenuate renal IR injury due to its ability to modulate renal function, apoptosis and inflammation.

Manganese-induced reactive oxygen species activate IκB kinase to upregulate YY1 and impair glutamate transporter EAAT2 function in human astrocytes in vitro

Dysregulation of the astrocytic glutamate transporter excitatory amino acid transporter 2 (EAAT2) is associated with several neurological disorders, including Parkinson's disease, Alzheimer's disease, and manganism, the latter induced by chronic exposure to high levels of manganese (Mn). Mechanisms of Mn-induced neurotoxicity include impairment of EAAT2 function secondary to the activation of the transcription factor Yin Yang 1 (YY1) by nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). However, the upstream mechanisms by which Mn-induced NF-κB activates YY1 remain to be elucidated. In the present study, we used the H4 human astrocyte cell line to test if Mn activates YY1 through the canonical NF-κB signaling pathway, leading to EAAT2 repression. The results demonstrate that Mn exposure induced phosphorylation of the upstream kinase IκB kinase (IKK-β), leading to NF-κB p65 translocation, increased YY1 promoter activity, mRNA/protein levels, and consequently repressed EAAT2. Results also demonstrated that Mn-induced oxidative stress and subsequent TNF-α production were upstream of IKK-β activation, as antioxidants attenuated Mn-induced TNF-α production and IKK-β activation. Moreover, TNF-α inhibition attenuated the Mn-induced activation of IKK-β and YY1. Taken together, Mn-induced oxidative stress and TNF-α mediates activation of NF-κB signaling and YY1 upregulation, leading to repression of EAAT2. Thus, targeting reactive oxygen species (ROS), TNF-α and IKK-β may attenuate Mn-induced YY1 activation and consequent EAAT2 repression.

The Non-peptide Angiotensin-(1-7) Mimic AVE 0991 Attenuates Delayed Neurocognitive Recovery After Laparotomy by Reducing Neuroinflammation and Restoring Blood-Brain Barrier Integrity in Aged Rats

Delayed neurocognitive recovery (dNCR) after surgery is a common postoperative complication in older adult patients. Our previous studies have demonstrated that cognitive impairment after surgery involves an increase in the brain renin-angiotensin system (RAS) activity, including overactivation of the angiotensin 2/angiotensin receptor-1 (Ang II/AT1) axis, which provokes the disruption of the hippocampal blood-brain barrier (BBB). Nevertheless, the potential role of the counter-regulatory RAS axis, the Ang-(1–7)/Mas pathway, in dNCR remains unknown. Using an aged rat model of dNCR, we dynamically investigated the activity of both axes of the RAS following laparotomy. AVE 0991, a nonpeptide analog of Ang-(1–7), was administered intranasally immediately after laparotomy. We found that the elevation of Ang II, induced by surgery was accompanied by a decrease of Ang-(1–7) in the hippocampus, but not in the circulation. Surgery also significantly downregulated hippocampal Mas receptor expression at 24 h postsurgery. Mas activation with intranasal AVE 0991 treatment significantly improved hippocampus-dependent learning and memory deficits induced by surgery. Furthermore, it attenuated hippocampal neuroinflammation, as shown by the decreased level of the microglial activation marker cluster of differentiation 11b (CD11b) and the decreased production of several inflammatory molecules. Along with these beneficial effects, the AVE 0991 treatment also alleviated the imbalance between matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of matrix metalloproteinase-3 (TIMP-3), modulated the expression of occludin, and alleviated the IgG extravasation, thereby restoring the integrity of the BBB. In conclusion, these data indicate that activation of Mas by AVE 0991 attenuates dNCR after surgery by reducing neuroinflammation and restoring BBB integrity. Our findings suggest that the Ang-(1–7)/Mas pathway may be a novel therapeutic target for treating dNCR after surgery in older adult patients.

Neurofilament degradation is involved in laparotomy-induced cognitive dysfunction in aged rats

Excessive neuroinflammatory responses play important roles in the development of postoperative cognitive dysfunction (POCD). Neurofilaments (NFs) were essential to the structure of axon and nerve conduction; and the abnormal degradation of NFs were always accompanied with degenerative diseases, which were also characterized by excessive neuroinflammatory responses in brain. However, it is still unclear whether the NFs were involved in the POCD. In this study, the LC-MS/MS method was used to explore the neuroinflammatory response and NFs of POCD in aged rats. Moreover, trichostatin A (TSA), an inflammation-related drug, was selected to test whether it could improve the surgery-induced cognitive dysfunction, inflammatory responses and NFs. Evident cognitive dysfunction, excessive microglia activation, neuroinflammatory responses and upregulated NFs in hippocampus were observed in the POCD group. TSA pretreatment could significantly mitigate these changes. The KEGG analysis revealed that nine pathways were enriched in the TSA + surgery group (versus the surgery group). Among them, two signaling pathways were closely related with the changes of NFs proteins. In conclusion, surgery could impair the cognitive function and aggravate neuroinflammation and NFs. The TSA could significantly improve these changes which might be related to the activation of the “focal adhesion” and “ECM-receptor interaction” pathways.

Prebiotics Regulation of Intestinal Microbiota Attenuates Cognitive Dysfunction Induced by Surgery Stimulation in APP/PS1 Mice

Emerging evidence indicates that the intestinal microbiota could interact with the central nervous system and modulate multiple pathophysiological changes, including the integrity of intestinal barrier and blood-brain barrier, as well as neuroinflammatory response. In the present study, we investigated the potential role of intestinal microbiota in the pathophysiological process of postoperative cognitive dysfunction. Six-month-old APP/PS1 mice were subjected to partial hepatectomy to establish surgery model and exhibited cognitive dysfunction. The expressions of inflammatory mediators increased and tight junction proteins (ZO-1 and Occludin) levels decreased in the intestine and hippocampus. The 16S ribosomal RNA gene sequencing showed altered β diversity and intestinal microbiota richness after surgery, including genus Rodentibacter, Bacteroides, Ruminococcaceae_UCG_014 and Faecalibaculum, as well as family Eggerthellaceae and Muribaculaceae. Furthermore, prebiotics (Xylooligosaccharides, XOS) intervention effectively attenuated surgery-induced cognitive dysfunction and intestinal microbiota alteration, reduced inflammatory responses, and improved the integrity of tight junction barrier in the intestine and hippocampus. In summary, the present study indicates that intestinal microbiota alteration, the related intestinal barrier and blood-brain barrier damage, and inflammatory responses participate the pathophysiological process of postoperative cognitive dysfunction. Prebiotics intervention could be a potential preventative approach.

Genome-Wide Screen of the Hippocampus in Aged Rats Identifies Mitochondria, Metabolism and Aging Processes Implicated in Sevoflurane Anesthesia

Previous studies have shown multiple mechanisms and pathophysiological changes after anesthesia, and genome-wide studies have been implemented in the studies of brain aging and neurodegenerative diseases. However, the genome-wide gene expression patterns and modulation networks after general anesthesia remains to be elucidated. Therefore, whole transcriptome microarray analysis was used to explore the coding gene expression patterns in the hippocampus of aged rats after sevoflurane anesthesia. Six hundred and thirty one upregulated and 183 downregulated genes were screened out, then 44 enriched terms of biological process, 16 of molecular function and 18 of the cellular components were identified by Gene Ontology (GO) and KEGG analysis. Among them, oxidative stress, metabolism, aging, and neurodegeneration were the most enriched biological processes and changed functions. Thus, involved genes of these processes were selected for qPCR verification and a good consistency was confirmed. The potential signaling pathways were further constructed including mitochondrion and oxidative stress-related Hifs-Prkcd-Akt-Nfe2l2-Sod1 signaling, multiple metabolism signaling (Scd2, Scap-Hmgcs2, Aldh18a1-Glul and Igf1r), as well as aging and neurodegeneration related signaling (Spidr-Ercc4-Cdkn1a-Pmaip1 and Map1lc3b). These results provide potential therapeutic gene targets for brain function modulation and memory formation process after inhaled anesthesia in the elderly, which could be valuable for preventing postoperative brain disorders and diseases, such as perioperative neurocognitive disorders (PND), from the genetic level in the future.

Ampelopsin alleviates sevoflurane-induced cognitive dysfunction by mediating NF-κB pathway in aged rats

BACKGROUND

Cancer-induced bone pain (CIBP) is the pain caused by bone metastasis from malignant tumors, and the largest source of pain for cancer patients. miR-300 is an important miRNA in cancer. It has been shown that miR-300 regulates tumorigenesis of various tumors.

PURPOSE

This study aims to investigate the role of miR-300 in CIBP and its underlying molecular mechanisms in vitro and in vivo.

METHODS

We constructed CIBP model in rats and investigated the mechanism through which miR-300 affects CIBP. We first examined expression level of miR-300 in CIBP rats and then tested the effect of its overexpression. Next, we identified the target of miR-300 using TargetScan analysis and double luciferase assay. Finally, we studied genetic interactions between miR-300 and its target and their roles in CIBP.

RESULTS

We found that miR-300 was downregulated in CIBP rats. Overexpression of miR-300 significantly attenuated cancer-induced neuropathic pain (p < 0.01). Furthermore, TargetScan analysis and double luciferase assay show High Mobility Group Box 1 (HMGB1) is a target of miR-300. Notably, HMGB1 is overexpressed in CIBP rats, while up-regulation of miR-300 significantly suppresses expression of HMGB1 (p < 0.01). Moreover, knockdown of HMGB1 by siRNA significantly relieves cancer-induced neuropathic pain in rats (p < 0.01). On the other hand, HMGB1 overexpression partially blocked the effect of miR-300 on cancer-induced nerve pain.

CONCLUSION

miR-300 relieves cancer-induced neuropathic pain by inhibiting HMGB1 expression. These results may be beneficial for the treatment of CIBP in clinical practice.

General anesthetic neurotoxicity in the young: Mechanism and prevention

General anesthesia (GA) is usually considered to safely induce a reversible unconscious state allowing surgery to be performed without pain. A growing number of studies, in particular pre-clinical studies, however, demonstrate that general anesthetics can cause neuronal death and even long-term neurological deficits. Herein, we report our literature review and meta-analysis data of the neurological outcomes after anesthesia in the young. We also review available mechanistic and epigenetic data of GA exposure related to cognitive impairment per se and the potential preventive strategies including natural herbal compounds to attenuate those side effects. In summary, anesthetic-induced neurotoxicity may be treatable and natural herbal compounds and other medications may have great potential for such use but warrants further study before clinical applications can be initiated.

Isoflurane-Induced Postoperative Neurovascular and Cognitive Dysfunction Is Associated with VEGF Overexpression in Aged Rats

Postoperative cognitive dysfunction (POCD) is a common complication in older adults; however, its aetiology remains unclear. Although vascular endothelial growth factor (VEGF) is associated with blood-brain barrier (BBB) disorders and neurological disease, its role in POCD is unknown. Here, we investigated the effect of brain VEGF inhibition on isoflurane-induced cognitive impairment in an aged rat model of POCD. VEGF protein expression was increased in the hippocampus after isoflurane exposure, suggesting that inhalation anaesthesia induces hippocampal VEGF protein overexpression in aged rats. Pretreatment with 2 mg/kg RB-222, an anti-VEGF neutralizing antibody, may partially abolish the degradation of occludin protein in cerebral capillaries, thereby maintaining the ultrastructural and functional integrity of the hippocampal BBB. Inhibition of VEGF also significantly attenuated the isoflurane-induced cognitive deficits in the Morris water maze task. Together, our findings show, for the first time, that elevated expression of brain VEGF after isoflurane exposure contributes to POCD in aged rats. Therefore, therapeutic strategies involving VEGF should take into consideration its role in the pathogenesis of POCD.

Peripheral inflammation induces neuroinflammation that alters neurotransmission and cognitive and motor function in hepatic encephalopathy: Underlying mechanisms and therapeutic implications

Several million patients with liver cirrhosis suffer minimal hepatic encephalopathy (MHE), with mild cognitive and coordination impairments that reduce their quality of life and life span. Hyperammonaemia and peripheral inflammation act synergistically to induce these neurological alterations. We propose that MHE appearance is because of the changes in peripheral immune system, which are transmitted to brain, leading to neuroinflammation that alters neurotransmission leading to cognitive and motor alterations. We summarize studies showing that MHE in cirrhotic patients is associated with alterations in the immune system and that patients died with HE show neuroinflammation in cerebellum, with microglial and astrocytic activation and Purkinje cell loss. We also summarize studies in animal models of MHE on the role of peripheral inflammation in neuroinflammation induction, how neuroinflammation alters neurotransmission and how this leads to cognitive and motor alterations. These studies identify therapeutic targets and treatments that improve cognitive and motor function. Rats with MHE show neuroinflammation in hippocampus and altered NMDA and AMPA receptor membrane expression, which impairs spatial learning and memory. Neuroinflammation in cerebellum is associated with altered GABA transporters and extracellular GABA, which impair motor coordination and learning in a Y maze. These alterations are reversed by treatments that reduce peripheral inflammation (anti-TNFα, ibuprofen), neuroinflammation (sulphoraphane, p38 inhibitors), GABAergic tone (bicuculline, pregnenolone sulphate) or increase extracellular cGMP (sildenafil or cGMP). The mechanisms identified would also occur in other chronic diseases associated with inflammation, aging and some mental and neurodegenerative diseases. Treatments that improve MHE may also be beneficial to treat these pathologies.

Isoflurane‑induced postoperative cognitive dysfunction is mediated by hypoxia‑inducible factor‑1α‑dependent neuroinflammation in aged rats

Elderly patients are at high risk of developing postoperative cognitive dysfunction (POCD) after prolonged exposure to inhaled anesthetics. However, the pathogenesis of POCD remains unknown. Hypoxia-inducible factor-1α (HIF-1α) is activated by inhaled anesthetics. The aim of the present study was to determine the role of HIF-1α in isoflurane-induced neuroinflammation and the resulting cognitive impairment. Following a 4-h exposure to 1.5% isoflurane in 20-month-old rats, increased expression of HIF-1α protein, activation of nuclear factor (NF)-κB signaling and increased expression of TNF-1α were observed in the hippocampus of isoflurane-exposed rats compared with the control group. Pharmacological inhibition of HIF-1α activation by 5-[1-(phenylmethyl)-1H-indazol-3-yl]-2-furanmethanol (YC-1) markedly suppressed the enhanced expression of HIF-1α, disrupted NF-κB signaling pathway activity and inhibited the isoflurane-induced increase of TNF-1α expression. YC-1 pretreatment also significantly attenuated isoflurane-induced cognitive deficits according to the results of the Morris water maze task. These results suggest that hippocampal HIF-1α appears to be involved in an upstream mechanism of isoflurane-induced cognitive impairment. Further research is warranted to fully clarify the pathogenesis and investigate HIF-1α as a potential therapeutic target for POCD.

Influence of sevoflurane exposure on mitogen-activated protein kinases and Akt/GSK-3β/CRMP-2 signaling pathways in the developing rat brain

Prolonged exposure to volatile anesthetics causes neurodegeneration in developing animal brains. However, their underlying mechanisms of action remain unclear. The current study investigated the expression of proteins associated with the mitogen-activated protein kinases (MAPK) and protein kinase B (Akt)/glycogen synthase kinase-3β (GSK-3β)/collapsin response mediator protein 2 (CRMP-2) signaling pathways in the cortices of neonatal mice following exposure to sevoflurane. Seven-day-old (P7) neonatal C57BL/6 mice were randomly divided into 2 groups and either exposed to 2.6% sevoflurane or air for 6 h. Terminal deoxyribonucleotide transferase mediated dUTP nick end labeling (TUNEL) staining, as well as the expression of activated caspase-3 and α-fodrin, was used to detect neuronal apoptosis in the cortices of mice. MAPK signaling pathways were investigated by detecting the expression of phosphorylated (p-) extracellular signal-regulated kinase 1/2 (ERK1/2), p-cyclic adenosine monophosphate response element-binding protein (CREB), p-p38, p-nuclear factor (NF-κB) and p-c-Jun N-terminal kinase (p-JNK). Akt/GSK-3β/CRMP-2 signaling pathways were assessed by detecting the expression of p-Akt, p-GSK-3β and p-CRMP-2 in the cortices of P7 mice 2 h following exposure to sevoflurane. The results demonstrated that sevoflurane significantly increased the apoptosis of cells in the retrosplenial cortex (RS), frontal cortex (FC) and parietal association cortex (PtA), increased the expression of cleaved caspase-3 expression and promoted the formation of 145 kDa and 120 kDa fragments from α-fodrin. Sevoflurane inhibited the phosphorylation of ERK1/2 and CREB, stimulated the phosphorylation of p38 and NF-κB, but did not significantly affect the phosphorylation of JNK. Furthermore, sevoflurane inhibited the phosphorylation of Akt, decreased the phosphorylation of GSK-3β at ser9 and increased the phosphorylation of CRMP2 at Thr514. These results suggest that multiple signaling pathways, including ERK1/2, P38 and Akt/GSK-3β/CRMP-2 may be involved in sevoflurane-induced neuroapoptosis in the developing brain.

Repeated exposure to sevoflurane impairs the learning and memory of older male rats

AIMS

Critically ill old patients sometimes require repeated surgical interventions, and thus it is important to determine the influence of repeated exposure to anesthetics on learning and memory. Sevoflurane, a widely used inhalation anesthetic, has few neurological adverse effects and offers a rapid return to consciousness. But the long-term influence of sevoflurane exposure and the effect of repeated sevoflurane exposure on cognition have rarely been reported, and available studies are contradictory.

MATERIALS AND METHODS

In the present study, the Morris water maze test was employed to investigate the long-term influence of single (4h) or repeated (2h daily for 5 consecutive days) exposure to 1.5% or 2.5% sevoflurane on the learning ability and memory of old (16-18months old) male rats. Testing was performed from 1day to 4weeks after the last exposure. In the hippocampus, brain derived neurotrophic factor (BDNF), NF-κB mRNA, and apoptosis rate were also examined to determine whether cellular biochemical changes related to cognition and memory occurred after single or repeated exposure to sevoflurane.

KEY FINDINGS

Repeated exposure to 2.5% sevoflurane decreased hippocampal levels of BDNF protein, enhanced hippocampal levels of NF-κB mRNA, and increased the apoptosis rate of pyramidal cells. Single exposure to 2.5% sevoflurane, and repeated exposure to either 1.5% or 2.5% sevoflurane significantly compromised learning and memory of old male rats.

SIGNIFICANCE

Repeated exposure to sevoflurane impaired the learning and memory of old male rats, an impairment that was accompanied by cognition-related biochemical changes in the hippocampus.

Hypoxia-inducible factor-1α is involved in isoflurane-induced blood-brain barrier disruption in aged rats model of POCD

Prolonged exposure to inhaled anesthetics may lead to postoperative cognitive dysfunction (POCD). Nevertheless, the underlying mechanisms are not known. Hypoxia-inducible factor-1α (HIF-1α) and its target gene vascular endothelial growth factor (VEGF) were shown to be activated by inhaled anesthetics. The aim of the present study was to determine the role of HIF-1α in isoflurane-induced blood-brain barrier (BBB) disruption and resultant cognitive impairment. After a 4-h exposure to 1.5% isoflurane in 20-month-old rats, increases in vascular permeability, and disrupted BBB ultrastructure were accompanied by the degradation of tight junction proteins occludin and collagen type IV in brain blood vessels. Increases in HIF-1α and VEGF proteins and activation of MMP-2 in the hippocampus were also observed in the hippocamp of isoflurane-exposed rats compared with control rats. Pharmacological inhibition of HIF-1α activation by 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole (YC-1) markedly suppressed the expression of HIF-1α, VEGF and MMP-2, and mitigated the severity of BBB disruption.YC-1 pretreatment also significantly attenuated isoflurane-induced cognitive deficits in the Morris water maze task. Overall, our results demonstrate that hippocampal HIF-1α/VEGF signaling seems to be the upstream mechanism of isoflurane-induced cognitive impairment, and provides apotential preventive and therapeutic target for POCD.

Lasting impact of general anaesthesia on the brain: mechanisms and relevance

General anaesthesia is usually considered to safely induce a reversible brain state allowing the performance of surgery under optimal conditions. An increasing number of clinical and experimental observations, however, suggest that anaesthetic drugs, especially when they are administered at the extremes of age, can trigger long-term morphological and functional alterations in the brain. Here, we review available mechanistic data linking general-anaesthesia exposure to impaired cognitive performance in both young and mature nervous systems. We also provide a critical appraisal of the translational value of animal models and highlight the important challenges that need to be addressed to strengthen the link between laboratory work and clinical investigations in the field of anaesthesia-neurotoxicity research.

Protective effects of salidroside against isoflurane-induced cognitive impairment in rats

Postoperative cognitive dysfunction, which is associated with a wide range of cognitive functions including working memory, long-term memory, information processing, attention, and cognitive flexibility, is a major clinical issue in geriatric surgical patients. The aim of the current study was to determine the protective role and possible mechanisms of salidroside against isoflurane-induced cognitive impairment. Sprague Dawley rats were randomly assigned to five groups and were treated with or without salidroside before isoflurane exposure. Open-field and fear conditioning tests were conducted to evaluate the cognitive function of the rats. Moreover, the hippocampus tissues were obtained for biochemical analysis. The results showed that the isoflurane anesthesia decreased the freezing time to context significantly at 48 h after the isoflurane exposure in the fear conditioning test. Salidroside could ameliorate isoflurane-induced cognitive dysfunction. Further analysis demonstrated salidroside markedly suppressed the release of tumor necrosis factor-α and interleukin-1β. Moreover, salidroside reversed the decreased activity of choline acetyltransferase, superoxide dismutase, glutathione peroxidase, and content of acetylcholine, as well as the increased activity of acetylcholine esterase and content of malondialdehyde in hippocampal tissue of isoflurane-exposed rats. According to the results, we concluded that that salidroside has a protective effect against isoflurane-induced cognitive dysfunction by inhibiting excessive inflammatory responses, decreasing oxidative stress, and regulating the cholinergic system.

Enhanced neuroinflammation mediated by DNA methylation of the glucocorticoid receptor triggers cognitive dysfunction after sevoflurane anesthesia in adult rats subjected to maternal separation during the neonatal period

BACKGROUND

Mounting evidence indicates that children who experience abuse and neglect are prone to chronic diseases and premature mortality later in life. One mechanistic hypothesis for this phenomenon is that early life adversity alters the expression or functioning of the glucocorticoid receptor (GR) throughout the course of life and thereby increases sensitivity to inflammatory stimulation. An exaggerated pro-inflammatory response is generally considered to be a key cause of postoperative cognitive dysfunction (POCD). The aim of this study was to examine the effects of early life adversity on cognitive function and neuroinflammation after sevoflurane anesthesia in adult rats and to determine whether such effects are associated with the epigenetic regulation of GR.

METHODS

Wistar rat pups were repeatedly subjected to infant maternal separation (early life stress) from postnatal days 2-21. In adulthood, their behavior and the signaling of hippocampal pro-inflammatory factors and nuclear factor-kappa B (NF-κB) after sevoflurane anesthesia were evaluated. We also examined the effects of maternal separation (MS) on the expression of GR and the DNA methylation status of the promoter region of exon 1₇ of GR and whether behavioral changes and neuroinflammation after anesthesia were reversible when the expression of GR was increased by altering DNA methylation.

RESULTS

MS induced cognitive decline after sevoflurane inhalation in the Morris water maze and context fear conditioning tests and enhanced the release of cytokines and the activation of astrocyte intracellular NF-κB signaling induced by sevoflurane in the hippocampus of adult rats. Blocking NF-κB signaling by pyrrolidine dithiocarbamate (PDTC) inhibited the release of cytokines. MS also reduced the expression of GR and upregulated the methylation levels of the promoter region of GR exon 1₇, and such effects were reversed by treatment with the histone deacetylase inhibitor trichostatin A (TSA) in adult rats. Moreover, TSA treatment in adult MS rats inhibited the overactivation of astrocyte intracellular NF-κB signaling and the release of cytokines and alleviated cognitive dysfunction after sevoflurane anesthesia.

CONCLUSIONS

Early life stress induces cognitive dysfunction after sevoflurane anesthesia, perhaps due to the aberrant methylation of the GR gene promoter, which reduces the expression of the GR gene and facilitates exaggerated inflammatory responses.

Calcineurin/nuclear factor-κB signaling mediates isoflurane-induced hippocampal neuroinflammation and subsequent cognitive impairment in aged rats

It is known that inhaled anesthetics induce neuroinflammation and facilitate postoperative cognitive dysfunction (POCD) in aged individuals; however, the mechanisms by which they mediate these effects remain elusive. Inhalation of the isoflurane anesthetic leads to opening of the mitochondrial permeability transition pore and loss of mitochondrial membrane potential. Therefore, mitochondrial retrograde signaling, which is an adaptive mechanism that facilitates the transmission of signals from dysfunctional mitochondria to the nucleus to activate target gene expression, may be activated during isoflurane inhalation. Therefore, the present study was designed to investigate the role of mitochondrial retrograde signaling in isoflurane-induced hippocampal neuroinflammation and cognitive impairment in aged rats. As calcineurin (CaN) serves an important role in the initiation of mitochondrial retrograde signaling, and nuclear factor-κB (NF‑κB) is involved in CaN signaling, their effects on isoflurane‑induced hippocampal neuroinflammation and cognitive impairment were investigated. Reactive oxygen species and mitochondrial membrane potential fluorescence staining, western blotting, colorimetric analysis, ELISA, immunofluorescence and the Morris water maze test were used in the present study. The results indicate that isoflurane induced hippocampal mitochondrial dysfunction and activated CaN, which subsequently lead to the putative activation of NF‑κB. These resulted in the elevation of interleukin‑1β (IL‑1β) expression (a typical marker of neuroinflammation), and was associated with cognitive impairment in aged rats. In addition, CaN and NF‑κB inhibition attenuated isoflurane-induced neuroinflammation and subsequent cognitive impairment. In conclusion, the results of the present study demonstrate the role of mitochondrial retrograde signaling and associated protein factors in inhaled anesthetic-induced neuroinflammation and cognitive impairment. These protein factors may therefore present promising therapeutic targets for the prevention of POCD.

Anesthetic neurotoxicity: Apoptosis and autophagic cell death mediated by calcium dysregulation

A number of findings suggested that general anesthetics induced neural cell death by apoptosis in various animal models. Although clinical evidence regarding the correlation between anesthetic exposures at young age and subsequent cognitive impairments remains unclear, repeated or consistent exposures to general anesthetics may be a potential harmful risk in developing human brains. The mechanisms underlying the anesthetic neurotoxicity have received extensive attention recently. We will attempt a brief review to summarize current understanding on the role of both apoptosis and autophagic cell death mediated by calcium dysregulation in anesthetic neurotoxicity.

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.

Dexmedetomidine attenuates repeated propofol exposure-induced hippocampal apoptosis, PI3K/Akt/Gsk-3β signaling disruption, and juvenile cognitive deficits in neonatal rats

Propofol is one of the most widely used intravenous anesthetics. However, repeated exposure to propofol may cause neurodegeneration in the developing brain. Dexmedetomidine (Dex), an α2 adrenoceptor agonist, has been previously demonstrated to provide neuroprotection against neuroapoptosis and neurocognitive impairments induced by several anesthetics. Thus, the current study aimed to investigate the effect of Dex on neonatal propofol-induced neuroapoptosis and juvenile spatial learning/memory deficits. Propofol (30 mg/kg) was intraperiotoneally administered to 7‑day‑old Sprague Dawley rats (n=75) three times each day at 90 min intervals for seven consecutive days with or without Dex (75 µg/kg) treatment 20 min prior to propofol injection. Following repeated propofol exposure, reduced Akt and GSK‑3β phosphorylation, increased cleaved caspase‑3 expression levels, an increased Bax/Bcl‑2 ratio, and increased terminal deoxynucleotidyl transferase‑mediated dUTP nick‑end labeling (TUNEL)‑positive cells in the CA1 hippocampal subregion were observed. Morris Water Maze testing at postnatal day 29 also demonstrated spatial learning and memory deficits following propofol treatment compared with the control group. Notably, these changes were significantly attenuated by Dex pretreatment. The results of the current study demonstrated that Dex ameliorates the neurocognitive impairment induced by repeated neonatal propofol challenge in rats, partially via its anti‑apoptotic action and normalization of the disruption to the PI3K/Akt/GSK‑3β signaling pathway. The present study provides preliminary evidence demonstrating the safety of propofol on the neonatal brain and the potential use of dexmedetomidine pretreatment in pediatric patients.

Increased extrasynaptic GluN2B expression is involved in cognitive impairment after isoflurane anesthesia

There is increasing concern regarding the postoperative cognitive dysfunction (POCD) in the aging population, and general anesthetics are believed to be involved. Isoflurane exposure induced increased N-methyl-D-aspartic acid receptor (NMDAR) GluN2B subunit expression following anesthesia, which was accompanied by alteration of the cognitive function. However, whether isoflurane affects this expression in different subcellular compartments, and is involved in the development of POCD remains to be elucidated. The aims of the study were to investigate the effects of isoflurane on the expression of the synaptic and extrasynaptic NMDAR subunits, GluN2A and GluN2B, as well as the associated alteration of cognitive function in aged rats. The GluN2B antagonist, Ro25–6981, was given to rats exposed to isoflurane to determine the role of GluN2B in the isoflurane-induced alteration of cognitive function. The results showed that spatial learning and memory tested in the Morris water maze (MWM) was impaired at least 7 days after isoflurane exposure, and was returned to control levels 30 days thereafter. Ro25-6981 treatment can alleviate this impairment. Extrasynaptic GluN2B protein expression, but not synaptic GluN2B or GluN2A, increased significantly after isoflurane exposure compared to non-isoflurane exposure, and returned to control levels approximately 30 days thereafter. The results of the present study indicated that isoflurane induced the prolonged upregulation of extrasynaptic GluN2B expression after anesthesia and is involved in reversible cognitive impairment.

Surgery-Induced Hippocampal Angiotensin II Elevation Causes Blood-Brain Barrier Disruption via MMP/TIMP in Aged Rats

Reversible blood-brain barrier (BBB) disruption has been uniformly reported in several animal models of postoperative cognitive dysfunction (POCD). Nevertheless, the precise mechanism underlying this occurrence remains unclear. Using an aged rat model of POCD, we investigated the dynamic changes in expression of molecules involved in BBB disintegration, matrix metalloproteinase-2 (MMP-2) and -9 (MMP-9), as well as three of their endogenous tissue inhibitors of MMP (TIMP-1, -2, -3), and tried to establish the correlation between MMP/TIMP balance and surgery-induced hippocampal BBB disruption. We validated the increased hippocampal expression of angiotensin II (Ang II) and Ang II receptor type 1 (AT1) after surgery. We also found MMP/TIMP imbalance as early as 6 h after surgery, together with increased BBB permeability and decreased expression of Occludin and zonula occludens-1 (ZO-1), as well as increased basal lamina protein laminin at 24 h postsurgery. The AT1 antagonist candesartan restored MMP/TIMP equilibrium and modulated expression of Occludin and laminin, but not ZO-1, thereby improving BBB permeability. These events were accompanied by suppression of the surgery-induced canonical nuclear factor-κB (NF-κB) activation cascade. Nevertheless, AT1 antagonism did not affect nuclear receptor peroxisome proliferator-activated receptor-γ (PPARγ) expression. Collectively, these findings suggest that surgery-induced Ang II release impairs BBB integrity by activating NF-κB signaling and disrupting downstream MMP/TIMP balance via AT1 receptor.

Quantitative-profiling of neurotransmitter abnormalities in the disease progression of experimental diabetic encephalopathy rat

Diabetic encephalopathy (DE) is one of the most prevalent chronic complications of diabetes mellitus (DM), with neither effective prevention nor proven therapeutic regimen. This study aims to uncover the potential dysregulation pattern of the neurotransmitters in a rat model of streptozotocin (STZ)-induced experimental DE. For that purpose, male Sprague–Dawley (SD) rats were treated with a single intraperitoneal injection of STZ. Cognitive performance was detected with the Morris water maze (MWM) test. Serum, cerebrospinal fluid (CSF), and brain tissues were collected to measure the levels of neurotransmitters. Compared with the control rats, the acetylcholine (ACh) levels in serum, CSF, hippocampus, and cortex were all significantly down-regulated as early as 6 weeks in the STZ treatment group. In contrast, the glutamate (Glu) levels were decreased in CSF and the hippocampus, but unaffected in the serum and cortex of STZ-treated rats. As for γ-aminobutyric acid (GABA), it was down-regulated in serum, but up-regulated in CSF, hippocampus, and the cortex in the STZ-treated group. The mRNA expressions of neurotransmitter-related rate limiting enzymes (including AChE, GAD1, and GAD2) and pro-inflammatory cytokines (including IL-1β and TNF-α) were all increased in the DE rats. Our data suggest that DM induces isoform-dependent and tissue-specific neurotransmitter abnormalities, and that neuroinflammation may underlay the nervous system dysfunction observed in the progression of DE.

Sildenafil reduces neuroinflammation and restores spatial learning in rats with hepatic encephalopathy: underlying mechanisms

Background

There are no specific treatments for the neurological alterations of cirrhotic patients with minimal hepatic encephalopathy (MHE). Rats with MHE due to portacaval shunt (PCS) show impaired spatial learning. The underlying mechanisms remain unknown. The aims of this work were to assess: (a) whether PCS rats show neuroinflammation in hippocampus, (b) whether treatment with sildenafil reduces neuroinflammation and restores spatial learning in PCS rats, and (c) analyze the underlying mechanisms.

Methods

Neuroinflammation was assessed by determining inflammatory markers by Western blot. Phosphorylation of MAP-kinase p38 was assessed by immunohistochemistry. Membrane expression of GABA and glutamate receptors was analyzed using BS3 cross-linker. Spatial learning was analyzed using the radial and Morris water mazes. To assess if sildenafil reverses the alterations, rats were treated with sildenafil in the drinking water.

Results

PCS rats show increased IL-1β and TNF-α levels and phosphorylation (activity) of p38 in hippocampus. Membrane expression of subunits α1 of GABA_A receptor and GluR2 of AMPA receptor are increased in PCS rats, while subunits GluR1 of AMPA receptors and NR1 and NR2a of NMDA receptors are reduced. PCS rats show reduced spatial learning in the radial and Morris water mazes. Sildenafil treatment normalizes IL-1β and TNF-α levels, p38 phosphorylation, and membrane expression of GABA_A, AMPA, and NMDA receptors and restores spatial learning.

Conclusions

Increased IL-1β alters GABAergic and glutamatergic neurotransmission in hippocampus and impairs spatial learning in rats with MHE. Sildenafil reduces neuroinflammation and restores learning. Phosphodiesterase-5 inhibitors may be useful to improve cognitive function in patients with MHE.

A Mitochondrion-Targeted Antioxidant Ameliorates Isoflurane-Induced Cognitive Deficits in Aging Mice

Isoflurane possesses neurotoxicity and can induce cognitive deficits, particularly in aging mammals. Mitochondrial reactive oxygen species (mtROS) have been linked to the early pathogenesis of this disorder. However, the role of mtROS remains to be evaluated due to a lack of targeted method to treat mtROS. Here, we determined in aging mice the effects of the mitochondrion-targeted antioxidant SS-31, on cognitive deficits induced by isoflurane, a general inhalation anesthetic. We further investigated the possible mechanisms underlying the effects of SS-31 on hippocampal neuro-inflammation and apoptosis. The results showed that isoflurane induced hippocampus-dependent memory deficit, which was associated with mitochondrial dysfunction including reduced ATP contents, increased ROS levels, and mitochondrial swelling. Treatment with SS-31 significantly ameliorated isoflurane-induced cognitive deficits through the improvement of mitochondrial integrity and function. Mechanistically, SS-31 treatment suppressed pro-inflammatory responses by decreasing the levels of NF-κB, NLRP3, caspase 1, IL-1β, and TNF-α; and inhibited the apoptotic pathway by decreasing the Bax/Bcl-2 ratio, reducing the release of cytochrome C, and blocking the cleavage of caspase 3. Our results indicate that isoflurane-induced cognitive deficits may be attenuated by mitochondrion-targeted antioxidants, such as SS-31. Therefore, SS-31 may have therapeutic potentials in preventing injuries from oxidative stresses that contribute to anesthetic-induced neurotoxicity.

Duration-dependent regulation of autophagy by isoflurane exposure in aged rats

Current evidence suggests a central role for autophagy in many inflammatory brain disorders, including Alzheimer's disease (AD). Furthermore, it is also well accepted that some inhalation anesthetics, such as isoflurane, may cause AD-like neuropathogenesis and resultant postoperative cognitive dysfunction, especially in the elderly population. However, the impact of inhalation anesthetics on autophagic components in the brain remains to be documented. Hence, our objective was to investigate the effects of different durations of isoflurane exposure on hippocampus-dependent learning and hippocampal autophagy in aged rats. Aged Sprague-Dawley rats (20 months old) were randomly exposed to 1.5% isoflurane or 100% oxygen for 1 or 4 h. Animals were then trained in the Morris water maze (4 trials/day for 5 consecutive days). Hippocampal phagophore formation markers, beclin 1 and protein microtubule-associated protein 1 light chain-3B (LC3B), as well as p62, an indicator of autophagic flux, were quantified by western blotting. There was no significant difference in the escape latencies and time spent in the target quadrant, as well as hippocampal expression of beclin 1, LC3B-II, and p62 at 24 h post-anesthesia between the 1-h isoflurane-exposed rats and their controls (P >0.05). Four-hour exposure to isoflurane resulted in spatial learning and memory deficits, as evidenced by prolonged escape latencies on days 4 and 5 post-anesthesia and less time spent in the target quadrant than sham-exposed animals (P <0.05). These events were accompanied by a decline in hippocampal expression of LC3B-I, LC3B-II, and beclin 1 24 h after isoflurane (P <0.01 and P <0.05). Nevertheless, no significant change in p62 expression was found. Further kinetics study of autophagic changes induced by 4 h of isoflurane showed a transient upregulation of LC3B-I, LC3B-II, and beclin 1 at the end of exposure and a subsequent striking decrease within 12-24 h post-anesthesia (P <0.05). Hippocampal p62 peaked at 6 h but subsequently resolved. These results from our pilot in vivo study support a duration-dependent relationship between 1.5% isoflurane exposure, and spatial cognitive function as well as hippocampal phagophore formation.

Surgical stress induces brain-derived neurotrophic factor reduction and postoperative cognitive dysfunction via glucocorticoid receptor phosphorylation in aged mice

AIMS

This study explored whether surgical stress-induced glucocorticoid receptor (GR) phosphorylation is related to postoperative cognitive dysfunction (POCD) in aged individuals. Inhibition of GR activation could be an effective treatment for POCD.

METHODS

A laparotomy was given to C57/BL6 mice in POCD group both 20 and 6 months old. Animals in control group were treated in identical manners except for laparotomy. Cognitive function was evaluated by Morris water maze and elevated plus maze. Western blot and Elisa assay were used to detect related molecules. Mifepristone and roscovitine were treated as inhibitions of GR phosphorylation.

RESULTS

The cognitive function was impaired, and brain-derived neurotrophic factor (BDNF) was found reduced in aged POCD group. GR translocation into nucleus and elevated GR phosphorylation were found in prefrontal cortex of aged POCD mice. Cyclin-dependent Kinase 5 (CDK5), kinase for GR phosphorylation also elevated in aged POCD mice. With GR antagonist and CDK5 inhibitor, reduction of BDNF and cognitive dysfunction in aged mice were both rescued.

CONCLUSION

These results presented a mechanism that surgical stress-induced GR phosphorylation contributes to POCD in aged individuals. Inhibition of GR activation and phosphorylation might be a potential treatment target of POCD.

Redox Changes Induced by General Anesthesia in Critically Ill Patients with Multiple Traumas

The critically ill polytrauma patient is a constant challenge for the trauma team due to the complexity of the complications presented. Intense inflammatory response and infections, as well as multiple organ dysfunctions, significantly increase the rate of morbidity and mortality in these patients. Moreover, due to the physiological and biochemical imbalances present in this type of patients, the bioproduction of free radicals is significantly accelerated, thus installing the oxidative stress. In the therapeutic management of such patients, multiple surgical interventions are required and therefore they are being subjected to repeated general anesthesia. In this paper, we want to present the pathophysiological implications of oxidative stress in critically ill patients with multiple traumas and the implications of general anesthesia on the redox mechanisms of the cell. We also want to summarize the antioxidant treatments able to reduce the intensity of oxidative stress by modulating the biochemical activity of some cellular mechanisms.

Modulation of learning and memory by cytokines: signaling mechanisms and long term consequences

This review describes the role of cytokines and their downstream signaling cascades on the modulation of learning and memory. Immune proteins are required for many key neural processes and dysregulation of these functions by systemic inflammation can result in impairments of memory that persist long after the resolution of inflammation. Recent research has demonstrated that manipulations of individual cytokines can modulate learning, memory, and synaptic plasticity. The many conflicting findings, however, have prevented a clear understanding of the precise role of cytokines in memory. Given the complexity of inflammatory signaling, understanding its modulatory role requires a shift in focus from single cytokines to a network of cytokine interactions and elucidation of the cytokine-dependent intracellular signaling cascades. Finally, we propose that whereas signal transduction and transcription may mediate short-term modulation of memory, long-lasting cellular and molecular mechanisms such as epigenetic modifications and altered neurogenesis may be required for the long lasting impact of inflammation on memory and cognition.

Isoflurane preconditioning ameliorates renal ischemia-reperfusion injury through antiinflammatory and antiapoptotic actions in rats

Renal ischemia-reperfusion (I/R) injury is a major cause of acute kidney injury via inflammation and cell apoptosis. Volatile anesthetics have been shown to exert organ-protective effects against kidney damage in vivo and in vitro. In the present study, we investigated the effects of isoflurane, a commonly used volatile anesthetic, on renal I/R injury and the underlying mechanisms. Rats subjected to renal I/R displayed higher serum creatinine and blood urea nitrogen levels than sham rats as well as severe histopathological damage. Renal I/R also resulted in a nuclear factor-κB (NF-κB)-mediated inflammatory response and dysfunction of the p53-Bax-caspase-3 apoptotic pathway. Rats preconditioned with 1.5% isoflurane for 2 h had better renal function and less tubular apoptosis 24 h after I/R injury than control rats. Pretreatment with isoflurane suppressed renal NF-κB activation, leading to a reduction in proinflammatory molecules (high-mobility group box 1, interleukin-1β, and tumor necrosis factor-α) both in the kidneys and circulation. In addition, rats subjected to isoflurane preconditioning had a higher Bcl-2/Bax ratio and less cleaved caspase-3. Our findings suggest that preconditioning with a clinically relevant concentration of isoflurane attenuates renal I/R injury, based at least in part on its ability to modulate renal inflammation and apoptosis.

Subanesthetic isoflurane reduces zymosan-induced inflammation in murine Kupffer cells by inhibiting ROS-activated p38 MAPK/NF-κB signaling

Volatile anesthetic isoflurane (ISO) has immunomodulatory effects. The fungal component zymosan (ZY) induces inflammation through toll-like receptor 2 or dectin-1 signaling. We investigated the molecular actions of subanesthetic (0.7%) ISO against ZY-induced inflammatory activation in murine Kupffer cells (KCs), which are known as the resident macrophages within the liver. We observed that ISO reduced ZY-induced cyclooxygenase 2 upregulation and prostaglandin E₂ release, as determined by western blot and radioimmunoassay, respectively. ISO also reduced the production of tumor necrosis factor-α, interleukin-1β, IL-6, high-mobility group box-1, macrophage inflammatory protein-1α, macrophage inflammatory protein-2, and monocyte chemoattractant protein-1 as assessed by enzyme-linked immunosorbent assays. ISO blocked the ZY-induced nuclear translocation and DNA-binding activity of nuclear factor- (NF)-κB p65. Moreover, ISO attenuated ZY-induced p38 mitogen-activated protein kinase (MAPK) activation partly by scavenging reactive oxygen species (ROS); the interregulation that ROS activated p38 MAPK followed by NF-κB activation was crucial for the ZY-induced inflammatory responses in KCs. An in vivo study by peritoneal injection of ZY into BALB/C mice confirmed the anti-inflammatory properties of 0.7% ISO against ZY in KCs. These results suggest that ISO ameliorates ZY-induced inflammatory responses in murine KCs by inhibiting the interconnected ROS/p38 MAPK/NF-κB signaling pathways.

Both JNK and P38 MAPK pathways participate in the protection by dexmedetomidine against isoflurane-induced neuroapoptosis in the hippocampus of neonatal rats

Dexmedetomidine, a highly selective α2-adrenergic agonist, has been reported to attenuate isoflurane-induced cognitive impairment and neuroapoptosis. However, the underlying molecular mechanisms remain poorly understood. The aim of this study was to investigate whether mitogen-activated protein kinase (MAPK) pathway was involved in dexmedetomidine-induced neuroprotection against isoflurane effects. Seven-day-old (P7) neonatal Sprague-Dawley rats were pretreated with various concentrations of dexmedetomidine, and then exposed to 0.75% isoflurane or air for 6h. Terminal deoxyribonucleotide transferase-mediated dUTP nick end labeling (TUNEL) was used to detect neuronal apoptosis in their hippocampus. Activated caspase-3, extracellular signal-regulated kinase 1/2 (ERK1/2), c-Jun NH2-terminal kinases (JNK), p38, phospho-ERK1/2, phospho-JNK and phospho-p38 proteins were detected by Western blotting in the hippocampus at the end of exposure. Also, P7 rats were pretreated with 75 μg/kg dexmedetomidine alone, or given the ERK inhibitor U0126 before dexmedetomidine pretreatment, or pretreated with the p38 MAPK inhibitor SB203580 or JNK inhibitor SP600125 alone, and then exposed to 0.75% isoflurane for 6h. Isoflurane induced significant neuroapoptosis, increased the protein expression of phospho-JNK, phospho-c-Jun, phospho-p38 and phospho-nuclear factor-κB (NF-κB), decreased the level of phospho-ERK1/2 protein and reduced the ratio of Bcl-2/Bax in the hippocampus. Dexmedetomidine pretreatment inhibited isoflurane-induced neuroapoptosis and restored proteins expression of MAPK pathways and the Bcl-2/Bax ratio after isoflurane exposure. Moreover, SB203580 and SP600125 also partly attenuated the isoflurane-induced protein changes. However, U0126 did not reverse dexmedetomidine-induced neuroprotection. Our results indicate that the JNK and p38 pathways, not the ERK pathway are involved in dexmedetomidine-induced neuroprotection against isoflurane effects.

Prophylactic angiotensin type 1 receptor antagonism confers neuroprotection in an aged rat model of postoperative cognitive dysfunction

Postoperative cognitive dysfunction (POCD) is a common geriatric complication, although its exact neuropathogenesis remains elusive. Blockers of the renin-angiotensin system (RAS) ameliorate cognitive deficits in inflammatory brain disorders, with its effects on POCD not yet fully elucidated. The aim of the present study was to investigate regulation of the brain RAS and the effect of angiotensin II receptor type 1 (AT1) inhibition on surgery-induced cognitive impairment in a well-established rat POCD model. We observed upregulation of angiotensin II protein expression and AT1 subtype B transcript levels in the hippocampus after laparotomy, suggesting surgical stress activates the hippocampal RAS in aged rats. Chronic pretreatment with 0.1 mg/kg/day candesartan, an AT1 antagonist, significantly attenuated surgery-induced cognitive deficits in the Morris water maze task without altering blood pressure. Candesartan also decreased hippocampal blood-brain barrier (BBB) permeability. Concomitant with these functional benefits, we observed significant inhibition of hippocampal neuroinflammation, evidenced by decreased glial reactivity and phosphorylation of the NF-κB p65 subunit, as well as marked reductions in interleukin-1β, tumor necrosis factor-α, and cyclooxygenase-2. Our results are the first to show that activation of the brain RAS after surgery contributes to POCD in aged rats. Chronic treatment with low doses of candesartan may elicit blood pressure-independent neuroprotective effects in POCD by improving BBB function and promoting resolution of neuroinflammation.