Isoflurane increases neuronal cell death vulnerability by downregulating miR-214

Luteolin protects mouse hippocampal neuronal cells against isoflurane-induced neurotoxicity through miR-214/PTEN/Akt pathway

Isoflurane is one of the most commonly used anaesthetic agents in surgery procedures. During the past decades, isoflurane has been found to cause impairment in neurological capabilities in new-borns and elderly patients. Luteolin is a flavonoid that has been documented to possess a neuroprotective effect. Here we investigated the putative neuroprotective effects of luteolin on isoflurane-induced neurotoxicity in mouse hippocampal neuronal HT22 cells and explored the potential mechanisms. We demonstrated that luteolin improved mitochondrial dysfunction and reduced oxidative stress and apoptosis in isoflurane-treated HT22 cells, and thus inhibiting the isoflurane-induced neuronal injury. Further investigations showed that isoflurane exposure caused miR-214 downregulation, which could be mitigated by treatment with luteolin. Knockdown of miR-214 attenuated the neuroprotection of luteolin on isoflurane-induced neuronal injury. More importantly, luteolin inhibited isoflurane-caused regulation of the PTEN/Akt pathway, while miR-214 knockdown altered the regulatory effect of luteolin on the PTEN/Akt pathway. Furthermore, the effects of miR-214 knockdown on the neuroprotection of luteolin could also be prevented by knockdown of PTEN, implying that the neuroprotective effect of luteolin was mediated by miR-214/PTEN/Akt signaling pathway. These findings provided evidence for the potential application of luteolin in preventing isoflurane-induced neurotoxicity.

The role of anesthesia in peri‑operative neurocognitive disorders: Molecular mechanisms and preventive strategies

Peri-operative neurocognitive disorders (PNDs) include postoperative delirium (POD) and postoperative cognitive dysfunction (POCD). Children and the elderly are the two populations most vulnerable to the development of POD and POCD, which results in both high morbidity and mortality. There are many factors, including neuroinflammation and oxidative stress, that are associated with POD and POCD. General anesthesia is a major risk factor of PNDs. However, the molecular mechanisms of PNDs are poorly understood. Dexmedetomidine (DEX) is a useful sedative agent with analgesic properties, which significantly improves POCD in elderly patients. In this review, the current understanding of anesthesia in PNDs and the protective effects of DEX are summarized, and the underlying mechanisms are further discussed.

Recent progress on the role of non-coding RNA in postoperative cognitive dysfunction

Postoperative cognitive dysfunction (POCD), especially in elderly patients, is a serious complication characterized by impairment of cognitive and sensory modalities after surgery. The pathogenesis of POCD mainly includes neuroinflammation, neuronal apoptosis, oxidative stress, accumulation of Aβ, and tau hyperphosphorylation; however, the exact mechanism remains unclear. Non-coding RNA (ncRNA) may play an important role in POCD. Some evidence suggests that microRNA, long ncRNA, and circular RNA can regulate POCD-related processes, making them promising biomarkers in POCD diagnosis, treatment, and prognosis. This article reviews the crosstalk between ncRNAs and POCD, and systematically discusses the role of ncRNAs in the pathogenesis and diagnosis of POCD. Additionally, we explored the possible mechanisms of ncRNA-associated POCD, providing new knowledge for developing ncRNA-based treatments for POCD.

Pro-Apoptotic Activity of the Marine Sponge Dactylospongia elegans Metabolites Pelorol and 5-epi-Ilimaquinone on Human 501Mel Melanoma Cells

The natural environment represents an important source of drugs that originates from the terrestrial and, in minority, marine organisms. Indeed, the marine environment represents a largely untapped source in the process of drug discovery. Among all marine organisms, sponges with algae represent the richest source of compounds showing anticancer activity. In this study, the two secondary metabolites pelorol (PEL) and 5-epi-ilimaquinone (EPI), purified from Dactylospongia elegans were investigated for their anti-melanoma activity. PEL and EPI induced cell growth repression of 501Mel melanoma cells in a concentration- and time-dependent manner. A cell cycle block in the G1 phase by PEL and EPI was also observed. Furthermore, PEL and EPI induced significant accumulation of DNA histone fragments in the cytoplasmic fraction, indicating a pro-apoptotic effect of both compounds. At the molecular level, PEL and EPI induced apoptosis through the increase in pro-apoptotic BAX expression, confirmed by the decrease in its silencing miR-214-3p and the decrease in the anti-apoptotic BCL-2, MCL1, and BIRC-5 mRNA expression, attested by the increase in their silencing miRNAs, i.e., miR-193a-3p and miR-16-5p. In conclusion, our data indicate that PEL and EPI exert cytotoxicity activity against 501Mel melanoma cells promoting apoptotic signaling and inducing changes in miRNA expression and their downstream effectors. For these reasons could represent promising lead compounds in the anti-melanoma drug research.

MicroRNA-Target Interaction Regulatory Network in Alzheimer's Disease

Alzheimer’s Disease (AD) is a progressive neurodegenerative disorder and the most common cause of dementia; however, early diagnosis of the disease is challenging. Research suggests that biomarkers found in blood, such as microRNAs (miRNA), may be promising for AD diagnostics. Experimental data on miRNA–target interactions (MTI) associated with AD are scattered across databases and publications, thus making the identification of promising miRNA biomarkers for AD difficult. In response to this, a list of experimentally validated AD-associated MTIs was obtained from miRTarBase. Cytoscape was used to create a visual MTI network. STRING software was used for protein–protein interaction analysis and mirPath was used for pathway enrichment analysis. Several targets regulated by multiple miRNAs were identified, including: BACE1, APP, NCSTN, SP1, SIRT1, and PTEN. The miRNA with the highest numbers of interactions in the network were: miR-9, miR-16, miR-34a, miR-106a, miR-107, miR-125b, miR-146, and miR-181c. The analysis revealed seven subnetworks, representing disease modules which have a potential for further biomarker development. The obtained MTI network is not yet complete, and additional studies are needed for the comprehensive understanding of the AD-associated miRNA targetome.

MicroRNA-214-5p involves in the protection effect of Dexmedetomidine against neurological injury in Alzheimer's disease via targeting the suppressor of zest 12

OBJECTIVE

Alzheimer's disease (AD) is a neurological disease. Dexmedetomidine (Dex) has been evidenced to exert neuroprotective effects on multiple neurological diseases, while the function of microRNA(miR)- 214-5p on Dex-mediated AD progression via targeting the suppressor of zest 12 (SUZ12) remains unclear. This study obligates to investigate the regulatory functions of Dex, miR-214-5p and SUZ12 on AD.

METHODS

The expression of miR-214-5p and SUZ12 in APPswe/PS1dE9 mice (hereinafter referred to as AD mice) was examined. Thereafter, the AD mice were treated with Dex or increased miR-214-5p or reduced SUZ12 to determine the spatial memory ability, apoptosis of hippocampal neurons and the contents of serum inflammatory and oxidative stress factors of AD mice. Finally, the target relationship between miR-214-5p and SUZ12 was detected.

RESULTS

MiR-214-5p was reduced and SUZ12 was elevated in AD mice. Dex administration reduced the apoptosis of hippocampal neurons, the contents of serum inflammatory factor and oxidative stress, and attenuated the cognitive impairment of AD mice accompanied by up-regulated miR-214-5p and down-regulated SUZ12, and the overexpression of miR-214-5p or reduction of SUZ12 could effectively enhance the Dex-treated effects on AD mice. MiR-214-5p targeted SUZ12.

CONCLUSION

Dex may have a potential neuroprotective effect on AD via the miR-214-5p/SUZ12 axis. This study provides novel therapeutic targets for AD treatment.

Longitudinal impact on rat cardiac tissue transcriptomic profiles due to acute intratracheal inhalation exposures to isoflurane

Isoflurane (ISO) is a widely used inhalation anesthetic in experiments with rodents and humans during surgery. Though ISO has not been reported to impart long-lasting side effects, it is unknown if ISO can influence gene regulation in certain tissues, including the heart. Such changes could have important implications for use of this anesthetic in patients susceptible to heart failure/other cardiac abnormalities. To test if ISO could alter gene regulation/expression in heart tissues, and if such changes were reversible, prolonged, or late onset with time, SHR (spontaneously hypertensive) rats were exposed by intratracheal inhalation to a 97.5% air/2.5% ISO mixture on two consecutive days (2 hr/d). Control rats breathed filtered air only. On Days 1, 30, 240, and 360 post-exposure, rat hearts were collected and total RNA was extracted from the left ventricle for global gene expression analysis. The data revealed differentially-expressed genes (DEG) in response to ISO (compared to naïve control) at all post-exposure timepoints. The data showed acute ISO exposures led to DEG associated with wounding, local immune function, inflammation, and circadian rhythm regulation at Days 1 and 30; these effects dissipated by Day 240. There were other significantly-increased DEG induced by ISO at Day 360; these included changes in expression of genes associated with cell signaling, differentiation, and migration, extracellular matrix organization, cell-substrate adhesion, heart development, and blood pressure regulation. Examination of consistent DEG at Days 240 and 360 indicated late onset DEG reflecting potential long-lasting effects from ISO; these included DEG associated with oxidative phosphorylation, ribosome, angiogenesis, mitochondrial translation elongation, and focal adhesion. Together, the data show acute repeated ISO exposures could impart variable effects on gene expression/regulation in the heart. While some alterations self-resolved, others appeared to be long-lasting or late onset. Whether such changes occur in all rat models or in humans remains to be investigated.

Overexpression of miR-133b protects against isoflurane-induced learning and memory impairment

A number of microRNAs (miRs) have been identified as being involved in the regulation of anesthesia-induced cognitive impairment. The aim of the present study was to investigated the role and potential mechanism of miR-133b in isoflurane-induced learning and memory impairment. An animal model of isoflurane exposure was established using neonatal Sprague-Dawley rats. The rats were trained for Morris water maze (MWM) testing to assess their spatial learning and memory ability. Reverse transcription-quantitative polymerase chain reaction was used for the measurement of miR-133b expression in hippocampal tissues and primary hippocampal neuron cultures. Cell viability was assessed using a Cell Counting Kit-8 assay, and flow cytometric analysis was used to determine the rate of apoptosis. The MWM test results indicated that during the training period, the time required to locate the platform was significantly increased for rats exposed to isoflurane, and this increased time was reduced by the overexpression of miR-133b. The results of a probe trial indicated that isoflurane exposure increased escape latency and decreased the time spent in the platform area for isoflurane-treated rats; however, these effects were reversed by the injection of miR-133b agomir. The in vitro experiments demonstrated that the overexpression of miR-133b attenuated the reduction of neuronal cell viability induced by isoflurane, and inhibited the isoflurane-induced apoptosis of hippocampal neurons. In conclusion, the present study revealed that the overexpression of miR-133b attenuated isoflurane-induced learning and memory impairment in rats. Furthermore, miR-133b overexpression promoted the viability of hippocampal neurons and their resistance to apoptosis when exposed to isoflurane.

MiR-191 downregulation protects against isoflurane-induced neurotoxicity through targeting BDNF

BACKGROUND

Isoflurane inhalation can cause nerve damage, and miR-191 is abnormally expressed in nerve crush injuries. This study aimed to explore the effect of miR-191 on isoflurane-induced cognition impairment and neurotoxicity in vivo and in vitro, as well as its potential mechanism.

METHODS

Sprague-Dawley male rats and primary hippocampal neurons were applied and exposed to 2% isoflurane. The level of miR-191 was regulated both in vitro and in vivo to investigate the role of miR-191 in isoflurane-induced neurotoxicity. Morris water maze assay was used to evaluate the neurological function of rats. The level of miR-191 was measured by qRT-PCR. CCK-8 assay and Flow cytometry were applied to detect the cell viability and apoptosis. Dual luciferase reporter gene detection was used for the target gene analysis.

RESULTS

miR-191 was up-regulated in the hippocampal tissues of rats exposed to isoflurane. Downregulation of miR-191 ameliorated isoflurane-induced cognition impairment, including the increase of the neurological score and the escape latency, and the decrease of the time spent in the original quadrant for the rats exposed to isoflurane. Isoflurane exposure inhibited hippocampal neuron viability and promoted cell apoptosis, which was reversed by down-regulation of miR-191. BDNF is a target gene of miR-191.

CONCLUSIONS

Isoflurane causes some neurotoxic effect which is mediated through miR-191 abnormal expression targeting BDNF. Downregulation of miR-191 has a protective role against isoflurane-induced neurotoxicity, regulates the vitality and slows down neuronal cell apoptosis.

GABAergic neurons are susceptible to BAX-dependent apoptosis following isoflurane exposure in the neonatal period

Exposure to volatile anesthetics during the neonatal period results in acute neuron death. Prior work suggests that apoptosis is the dominant mechanism mediating neuron death. We show that Bax deficiency blocks neuronal death following exposure to isoflurane during the neonatal period. Blocking Bax-mediated neuron death attenuated the neuroinflammatory response of microglia following isoflurane exposure. We find that GABAergic interneurons are disproportionately overrepresented among dying neurons. Despite the increase in neuronal apoptosis induced by isoflurane exposure during the neonatal period, seizure susceptibility, spatial memory retention, and contextual fear memory were unaffected later in life. However, Bax deficiency alone led to mild deficiencies in spatial memory and contextual fear memory, suggesting that normal developmental apoptotic death is important for cognitive function. Collectively, these findings show that while GABAergic neurons in the neonatal brain undergo elevated Bax-dependent apoptotic cell death following exposure to isoflurane, this does not appear to have long-lasting consequences on overall neurological function later in life.

Long Non-Coding RNA BACE1-AS Modulates Isoflurane-Induced Neurotoxicity to Alzheimer's Disease Through Sponging miR-214-3p

Isoflurane, an anesthetic, can aggravate the progression of Alzheimer's disease (AD). Long non-coding RNA β-secretase 1 (BACE1)-antisense transcript (BACE1-AS) and miR-214-3p are related to AD progression. Nevertheless, it is unclear whether BACE1-AS is involved in the development of isoflurane-mediated AD via miR-214-3p. Amyloid beta peptide (Aβ) was employed to construct the AD cell model. The expression of BACE1-AS and miR-214-3p in the plasma of AD patients and SK-N-SH and SK-N-AS cells treated with Aβ and isoflurane was assessed through quantitative reverse transcription polymerase chain reaction (qRT-PCR). The proliferation and apoptosis of Aβ-treated SK-N-SH and SK-N-AS cells were determined via 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) or flow cytometry assays, respectively. Protein levels of B cell lymphoma 2 (Bcl-2), Bcl-2-associated X (Bax), CyclinD1, microtubule-associated protein A1/1B-light chain3 (LC3 I/LC3 II), p62 and Beclin1 were detected via western blot analysis. The relationship between BACE1-AS and miR-214-3p was verified by dual-luciferase reporter assay. We found that BACE1-AS was upregulated and miR-214-3p was downregulated in the plasma of AD patients and SK-N-SH and SK-N-AS cells treated with Aβ and isoflurane. Both BACE1-AS depletion and miR-214-3p augmentation restored the suppression of proliferation and the facilitation of apoptosis and autophagy of Aβ-treated SK-N-SH and SK-N-AS cells induced by isoflurane. Importantly, BACE1-AS acted as a sponge for miR-214-3p. Additionally, miR-214-3p silencing reversed the influence of BACE1-AS knockdown on isoflurane-mediated proliferation, apoptosis and autophagy in Aβ-induced SK-N-SH and SK-N-AS cells. In conclusion, BACE1-AS aggravated isoflurane-induced neurotoxicity to AD via sponging miR-214-3p.

Prediction and analysis of weighted genes in isoflurane induced general anesthesia based on network analysis

Purpose: Isoflurane is still wildly used in the developing countries and isoflurane-induced general anesthesia gives rise to serious side effects. The aim of the present study was to investigate the molecular mechanism on isoflurane-induced general anesthesia.Materials and methods: The microarray data of GSE64617 dataset was downloaded from Gene Expression Omnibus (GEO) database. A total of 755 DEGs were identified using the limma package in the R programming language. Gene Ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes, and Genomes (KEGG) pathways enrichment were conducted for DEGs. A protein-protein interaction (PPI) network was constructed for DEGs and sensory perception related genes. A global miRNA-mRNA regulatory network was constructed to reveal the interactions in miRNA and mRNA in isoflurane treated samples. Degree was used to evaluate the importance of a gene in the PPI network and miRNA-mRNA regulatory network.Results and conclusions: HMBOX1, CSNK2A1, PNN, SRRM1, PRPF40A, APCNTRK1, MAPK1, hsa-miR-16-5p, hsa-miR-424-5p, hsa-miR-497-5p and hsa-miR-17-5p were selected as weighted genes. The expression changes were further vitrificated in the rat models by performing quantitative real-time PCR (qPCR) analysis. In conclusion, we find several weighted mRNAs and miRNAs involved in isoflurane induced general anesthesia through bioinformatics analysis.

Puerarin attenuates hypoxia-resulted damages in neural stem cells by up-regulating microRNA-214

Puerarin has been reported to be useful in protection against hypoxia-induced injury. In our current study, we attempted to explore the protective effects of puerarin against hypoxia-caused damages in neural stem cells (NSCs). Additionally, the relative molecular underpinning studies preliminarily proceeded. NSCs were pre-incubated with puerarin before the hypoxic stimulus. MicroRNA-214 (miR-214) inhibitor was transfected into NSCs. Subsequently, the viability of NSCs was assessed by CCK-8 assay. Flow cytometry was employed to detect apoptotic cells after staining. qRT-PCR was performed to quantify miR-214. Western blot was applied for analyzing the expression of apoptosis-relative proteins and regulators. We found that puerarin alleviated hypoxia-induced apoptosis and maintained cell viability. Hypoxia-evoked up-regulation of miR-214 was further enhanced by puerarin. By contrast, miR-214-deficient NSCs showed the reduction in cell viability and the facilitation in apoptosis progress after pre-treatment with puerarin and stimulation in a hypoxia circumstance. Additionally, puerarin restored the phosphorylation of relative regulators, which was originally blunted by hypoxia. However, puerarin did not evidently restore the phosphorylation for response to hypoxia in miR-214-silenced NSCs. In conclusion, puerarin might be applied as a novel agent to ameliorate hypoxia-evoked damages in NSCs. Molecularly, miR-214 might be implicated in the protective roles of puerarin.

Role of MicroRNAs in Anesthesia-Induced Neurotoxicity in Animal Models and Neuronal Cultures: a Systematic Review

Exposure to anesthetic agents in early childhood or late intrauterine life might be associated with neurotoxicity and long-term neurocognitive decline in adulthood. This could be attributed to induction of neuroapoptosis and inhibition of neurogenesis by several mechanisms, with a pivotal role of microRNAs in this milieu. MicroRNAs are critical regulators of gene expression that are differentially expressed in response to internal and external environmental stimuli, including general anesthetics. Through this systematic review, we aimed at summarizing the current knowledge apropos of the roles and implications of deregulated microRNAs pertaining to anesthesia-induced neurotoxicity in animal models and derived neuronal cultures. OVID/Medline and PubMed databases were lastly searched on April 1st, 2019, using the Medical Subject Heading (MeSH) or Title/Abstract words ("microRNA" and "anesthesia"), to identify all published research studies on microRNAs and anesthesia. During the review process, data abstraction and methodological assessment was done by independent groups of reviewers. In total, 29 studies were recognized to be eligible and were thus involved in this systematic review. Anesthetic agents studied included sevoflurane, isoflurane, propofol, bupivacaine, and ketamine. More than 40 microRNAs were identified to have regulatory roles in anesthesia-induced neurotoxicity. This field of study still comprises several gaps that should be filled by conducting basic, clinical, and translational research in the future to decipher the exact role of microRNAs and their functions in the context of anesthesia-induced neurotoxicity.

A Systematic Review of MicroRNA Expression as Biomarker of Late-Onset Alzheimer's Disease

Late-onset Alzheimer's disease (LOAD) is a high-occurrence neurological disorder but the difficulty in identifying precise and early biomarkers has complicated the understanding of the disease and the development of new treatments. In this sense, important knowledge is emerging regarding novel molecular and biological candidates with diagnostic potential, including microRNAs (miRNAs), which have a key role in gene repression. The aim of this systematic review was to define the role of miRNAs' expression as biomarkers for LOAD both in brain tissues, which could help understand the biology of the disease, and circulating tissues, which could serve as non-invasive markers of the pathology. A systematic search was performed in Web of Science and PubMed using the keywords ((Alzheimer or Alzheimer's) and (microRNA or microRNAs or miRNA or miRNAs or miR)) until August 2018 to retrieve all articles that presented independent original data evaluating the impact of miRNA expression on the development of LOAD in human population. A total of 90 studies investigating the role of miRNAs' expression in the development of LOAD were identified. While other widely studied miRNAs such as hsa-miR-146a presented contradictory results among studies, deregulation in brain tissue of seven miRNAs, hsa-miR-16-5p, hsa-miR-34a-5p, hsa-miR-107, hsa-miR-125-5p, hsa-miR-132-3p, hsa-miR-181-3p, and hsa-miR-212-3p, was consistently identified in LOAD patients. Their role in the disease could be mediated through the regulation of key pathways, such as axon guidance, longevity, insulin, and MAPK signaling pathway. However, regarding their role as non-invasive biomarkers of LOAD in fluids, although the limited results available are promising, further studies are required.

Interaction of Isoflurane, Tumor Necrosis Factor-α and β-Amyloid on Long-term Potentiation in Rat Hippocampal Slices

BACKGROUND

The relationship between inhalational anesthetics such as isoflurane and cognitive impairment in the elderly is controversial. Both β-amyloid peptide (Aβ), associated with Alzheimer disease, and tumor necrosis factor-α (TNF-α), a proinflammatory stress-related peptide, impair the synaptic function. We hypothesized that transient exposure to isoflurane and these peptides would impair synaptic function, manifest as a depression of long-term potentiation (LTP) and paired pulse facilitation (PPF), in the rat hippocampus.

METHODS

Hippocampal slices were prepared from 3- to 4-week-old male Wistar rats. Preliminary experiments identified minimal concentrations of Aβ1-42 peptide and TNF-α that produced statistically detectable suppressing effects on LTP (600 nM Aβ1-42 and 5 ng/mL TNF-α). These concentrations of peptides were applied to slices alone, with 1.5% isoflurane, or in combination for 1 hour and then washed out. Measurements of LTP (field excitatory postsynaptic potentials [fEPSPs]) from neurons in the CA1 area by stimulation of the Schaffer-Collateral pathway were made after high-frequency stimulation (100 Hz, 1 second). Analysis of variance with correction for multiple comparisons was used to compare LTP under steady-state conditions and averaged for the 40- to 60-minute period after LTP induction.

RESULTS

EPSP amplitude after LTP induction was 155% ± 9% of baseline and was not affected by isoflurane exposure and washout (150% ± 4% of baseline, P = .47). Both Aβ1-42 and TNF-α reduced LTP by approximately 15% compared with control (129% ± 7% and 131% ± 11% of baseline respectively, means ± SD, both P < .001). When Aβ1-42 was combined with isoflurane, LTP was not impaired (151% ± 9% of control, P = .85), but isoflurane had no effect on LTP depression caused by TNF-α or a combination of Aβ and TNF-α.

CONCLUSIONS

Brief exposure to isoflurane prevents rather than impairs the decrease in LTP caused by Aβ1-42 in rat hippocampus. In contrast, isoflurane had no effect on synaptic impairment caused by TNF-α or a combination of TNF-α and Aβ. Although this is an in vitro study and translation to clinical medicine requires additional work, the interactions of isoflurane, Aβ, and TNF-α revealed here could have implications for patients with Alzheimer disease or perioperative neuroinflammation.

miR-365 targets β-arrestin 2 to reverse morphine tolerance in rats

Morphine tolerance is a challenging clinical problem that limits its clinical application in pain treatment. Non-coding microRNAs (miRNAs) modulate gene expression in a post transcriptional manner, and their dysregulation causes various diseases. However, the significance of miRNAs in morphine tolerance is still poorly understood. In the present study, we hypothesized that microRNA-365 (miR-365) is a key functional small RNA that reverses morphine tolerance through regulation of β-arrestin 2 in rats. Here, microarray analysis and quantitative real-time PCR showed that miR-365 was robustly decreased in the spinal cord after chronic morphine administration. In situ hybridization and immunochemistry double staining showed that miR-365 was expressed in neurons of the spinal cord. We identified β-arrestin 2 as the target gene of miR-365 by bioinformatics analysis and luciferase reporter assay. The data showed that overexpression of miR-365 prevented and reversed established morphine tolerance, and increased expression of miR-365 caused a decrease in expression of β-arrestin 2 protein. miR-365 downregulation is involved in the development and maintenance of morphine tolerance through regulation of β-arrestin 2, and miR-365 upregulation provides a promising and novel approach for treatment of morphine tolerance.

Emerging Roles for MicroRNAs in Perioperative Medicine

MicroRNAs (miRNAs) are small, non-protein-coding, single-stranded RNAs. They function as posttranscriptional regulators of gene expression by interacting with target mRNAs. This process prevents translation of target mRNAs into a functional protein. miRNAs are considered to be functionally involved in virtually all physiologic processes, including differentiation and proliferation, metabolism, hemostasis, apoptosis, and inflammation. Many of these functions have important implications for anesthesiology and critical care medicine. Studies indicate that miRNA expression levels can be used to predict the risk for eminent organ injury or sepsis. Pharmacologic approaches targeting miRNAs for the treatment of human diseases are currently being tested in clinical trials. The present review highlights the important biological functions of miRNAs and their usefulness as perioperative biomarkers and discusses the pharmacologic approaches that modulate miRNA functions for disease treatment. In addition, the authors discuss the pharmacologic interactions of miRNAs with currently used anesthetics and their potential to impact anesthetic toxicity and side effects.

TNF-α receptor antagonist attenuates isoflurane-induced cognitive impairment in aged rats

Postoperative cognitive dysfunction (POCD), a common clinical in aged patients, is characterized by deficits in cognitive functions in patients following anesthesia and surgery. It has been demonstrated that isoflurane may lead to cognitive impairment in aged rats; however, effective clinical interventions for preventing this disorder are limited. Tumor necrosis factor (TNF)-α has been suggested to be involved in neuroinflammation as well as the development of POCD. Accordingly, the present study aimed to investigate whether TNF-α signaling is involved in the isoflurane-induced cognitive impairment in aged rats, and whether TNF-α receptor antagonist are able to attenuate isoflurane-induced cognitive impairment in aged rats. A population of 20-month-old rats were administered TNF-α receptor antagonist R-7050 or an equal volume of saline by intraperitoneal injection 12 h prior to exposure to isoflurane to model cognitive impairment following anesthesia in old patients. Then the rats were exposed to 1.3% isoflurane for 4 h. In the control group, rats showed impaired cognitive functions evaluated by Morris water maze assay after isoflurane exposure. Furthermore, isoflurane exposure induced marked upregulation of proinflammatory cytokines, including interleukin (IL)-1β, TNF-α, IL-6 and IL-8 in the hippocampus tissue. In the experimental group, intracisternal administration of TNF-α receptor antagonist R-7050 significantly attenuated isoflurane-induced cognitive impairment and upregulation of proinflammatory cytokines. Further investigation revealed that intracisternal administration of TNF-α receptor antagonist R-7050 notably suppressed isoflurane-induced activation of NF-κB and MAPK signaling. Collectively, the present results suggest that TNF-α receptor antagonist may serve as a potential agent for the prevention of anesthesia-induced cognitive decline in aged patients.

MicroRNA-214 suppresses gluconeogenesis by targeting activating transcriptional factor 4

Although the gluconeogenesis pathway is already a target for the treatment of type 2 diabetes, the potential role of microRNAs (miRNAs) in gluconeogenesis remains unclear. Here, we investigated the physiological functions of miR-214 in gluconeogenesis. The expression of miR-214 was suppressed by glucagon via protein kinase A signaling in primary hepatocytes, and miR-214 was down-regulated in the livers of fasted, high fat diet-induced diabetic and leptin receptor-mutated (db/db) mice. The overexpression of miR-214 in primary hepatocytes suppressed glucose production, and silencing miR-214 reversed this effect. Gluconeogenesis was suppressed in the livers of mice injected with an adenovirus expressing miR-214 (Ad-miR-214). Additionally, Ad-miR-214 alleviated high fat diet-induced elevation of gluconeogenesis and hyperglycemia. Furthermore, we found that activating transcription factor 4 (ATF4), a reported target of miR-214, can reverse the suppressive effect of miR-214 on gluconeogenesis in primary hepatocytes, and this suppressive effect was blocked in liver-specific ATF4 knock-out mice. ATF4 regulated gluconeogenesis via affecting forkhead box protein O1 (FOXO1) transcriptional activity. Finally, liver-specific miR-214 transgenic mice exhibited suppressed gluconeogenesis and reduced expression of ATF4, phosphoenolpyruvate carboxykinase, and glucose-6-phosphatase in liver. Taken together, our results suggest that the miR-214-ATF4 axis is a novel pathway for the regulation of hepatic gluconeogenesis.

Downregulation of miR-23a and miR-27a following experimental traumatic brain injury induces neuronal cell death through activation of proapoptotic Bcl-2 proteins

MicroRNAs (miRs) are small noncoding RNAs that negatively regulate gene expression at the post-transcriptional level. To identify miRs that may regulate neuronal cell death after experimental traumatic brain injury (TBI), we profiled miR expression changes during the first several days after controlled cortical impact (CCI) in mice. miR-23a and miR-27a were rapidly downregulated in the injured cortex in the first hour after TBI. These changes coincided with increased expression of the proapoptotic Bcl-2 family members Noxa, Puma, and Bax. In an etoposide-induced in vitro model of apoptosis in primary cortical neurons, miR-23a and miR-27a were markedly downregulated as early as 1 h after exposure, before the upregulation of proapoptotic Bcl-2 family molecules. Administration of miR-23a and miR-27a mimics attenuated etoposide-induced changes in Noxa, Puma, and Bax, reduced downstream markers of caspase-dependent (cytochrome c release and caspase activation) and caspase-independent (apoptosis-inducing factor release) pathways, and limited neuronal cell death. In contrast, miRs hairpin inhibitors enhanced etoposide-induced neuronal apoptosis and caspase activation. Importantly, administration of miR-23a and miR-27a mimics significantly reduced activation of Puma, Noxa, and Bax as well as attenuated markers of caspase-dependent and -independent apoptosis after TBI. Furthermore, miR-23a and miR-27a mimics significantly attenuated cortical lesion volume and neuronal cell loss in the hippocampus after TBI. These findings indicate that post-traumatic decreases in miR-23a and miR-27a contribute to neuronal cell death after TBI by upregulating proapoptotic Bcl-2 family members, thus providing a novel therapeutic target.

Desflurane accelerates neuronal cytotoxicity of Aβ by downregulating miR-214

Since more and more evidence suggests anesthetics serve as a risk factor of Alzheimer's disease (AD), we examine the neurotoxicity of a commonly used inhalational anesthetics, desflurane, and its potential toxicity mechanism in primary rat hippocampal neurons. Here we show that desflurane increase the cytotoxicity of intracellular and extracellular amyloid β (Aβ) in the presence or absence of serum. It is also demonstrated that the cytotoxicity of desflurane is caused by the reduction of miR-214 which binds to Bax 3'UTR and results in the increased expression of Bax. Therefore, we conclude that desflurane accelerates neuronal cytotoxicity of Aβ by downregulating miR-214. Our study sheds a light on the therapy of cytotoxicity induced by inhaled anesthetics, especially in patients of AD.

Halothane increases neuronal cell death vulnerability by downregulating miR-214 and upregulating Bax

Inhalational general anesthesia is widely used in clinical practice, but there have been plenty of evidence shows that application of inhalational anesthetics may increase the risk of Alzheimer's disease (AD). Halothane is a common inhalational anesthetics. We cultured rat primary neurons as study model to investigate cytotoxicity of halothane in neurons. We found that halothane could enhance the cytotoxicity induced by intracellular or extracellular amyloid β (Aβ) with or without serum deprivation. In addition, halothane induced the enhanced cytotoxicity through downregulation of miR-214 level which can lead to increasing expression of Bax. Therefore our data suggest that halothane increases cell death induced by Aβ through increasing Bax level by downregulating miR-214. Our study indicates a probable connection between anesthetic application and AD, while provides a new perspective for the studies of inhalational anesthetics cytotoxicity.