Glycyrrhizin attenuates isoflurane-induced cognitive deficits in neonatal rats via its anti-inflammatory activity

Glycyrrhizin Production in Licorice Hairy Roots Based on Metabolic Redirection of Triterpenoid Biosynthetic Pathway by Genome Editing

Glycyrrhizin, a type of the triterpenoid saponin, is a major active ingredient contained in the roots of the medicinal plant licorice (Glycyrrhiza uralensis, G. glabra and G. inflata), and is used worldwide in diverse applications, such as herbal medicines and sweeteners. The growing demand for licorice threatens wild resources and therefore a sustainable method of supplying glycyrrhizin is required. With the goal of establishing an alternative glycyrrhizin supply method not dependent on wild plants, we attempted to produce glycyrrhizin using hairy root culture. We tried to promote glycyrrhizin production by blocking competing pathways using CRISPR/Cas9-based gene editing. CYP93E3 CYP72A566 double-knockout (KO) and CYP93E3 CYP72A566 CYP716A179 LUS1 quadruple-KO variants were generated, and a substantial amount of glycyrrhizin accumulation was confirmed in both types of hairy root. Furthermore, we evaluated the potential for promoting further glycyrrhizin production by simultaneous CYP93E3 CYP72A566 double-KO and CYP88D6-overexpression. This strategy resulted in a 3-fold increase (∼1.4 mg/g) in glycyrrhizin accumulation in double-KO/CYP88D6-overexpression hairy roots, on average, compared with that of double-KO hairy roots. These findings demonstrate that the combination of blocking competing pathways and overexpression of the biosynthetic gene is important for enhancing glycyrrhizin production in G. uralensis hairy roots. Our findings provide the foundation for sustainable glycyrrhizin production using hairy root culture. Given the widespread use of genome editing technology in hairy roots, this combined with gene knockout and overexpression could be widely applied to the production of valuable substances contained in various plant roots.

Neobaicalein prevents isoflurane anesthesia-induced cognitive impairment in neonatal mice via regulating CREB1

OBJECTIVES

Isoflurane (ISO) is widely used in the clinic and research. The authors aimed to explore whether Neobaicalein (Neob) could protect neonatal mice from ISO-induced cognitive damage.

METHOD

The open field test, Morris water maze test, and tail suspension test was performed to assess the cognitive function in mice. Enzyme-linked immunosorbent assay was used to evaluate inflammatory-related protein concentrations. Immunohistochemistry was used to assess Ionized calcium-Binding Adapter molecule-1 (IBA-1) expression. Hippocampal neuron viability was detected using the Cell Counting Kit-8 assay. Double immunofluorescence staining was employed to confirm the interaction between proteins. Western blotting was used to assess protein expression levels.

RESULTS

Neob notably improved cognitive function and exhibited anti-inflammatory effects; moreover, under iso-treatment, it exhibited neuroprotective effects. Furthermore, Neob suppressed interleukin-1β, tumor necrosis factor-α, and interleukin-6 levels and upregulated interleukin-10 levels in ISO-treated mice. Neob significantly mitigated iso-induced increases in IBA-1-positive cell numbers of the hippocampus in neonatal mice. Furthermore, it inhibited ISO-induced neuronal apoptosis. Mechanistically, Neob was observed to upregulate cAMP Response Element Binding protein (CREB1) phosphorylation and protected hippocampal neurons from ISO-mediated apoptosis. Moreover, it rescued ISO-induced abnormalities of synaptic protein.

CONCLUSIONS

Neob prevented ISO anesthesia-induced cognitive impairment by suppressing apoptosis and inflammation through upregulating CREB1.

Prenatal Sevoflurane Exposure Impairs the Learning and Memory of Rat Offspring via HMGB1-Induced NLRP3/ASC Inflammasome Activation

The neurotoxic effects of sevoflurane anesthesia on the immature nervous system have aroused public concern, but the specific effects and mechanism remain poorly understood. Pyroptosis caused by the activation of the NLRP3 inflammasome is pivotal for cell survival and acts as a key player in cognitive impairment. This study was carried out to determine the critical role of the NLRP3 inflammasome and high-mobility group box 1 (HMGB1) in sevoflurane-induced cognitive impairment. On gestational day 20 (G20), 3% sevoflurane was administered for 4 h to pregnant rats. The hippocampus and cerebral cortex of the offspring were harvested at postnatal day 1 (P1) for Western blotting and immunofluorescence staining. Pregnant rat sevoflurane exposure increased the protein levels of NLRP3, ASC, cleaved-caspase 1 (p20), mature-IL-1β (m-IL-1β), and HMGB1 in the cerebral cortex and hippocampus of offspring rats. More microglial cells of offspring were also observed after sevoflurane anesthesia. The Morris water maze (MWM) test was implemented to evaluate cognitive function from postnatal day 30 (P30) to postnatal 35 (P35) of offspring. The sevoflurane-treated offspring took longer than the control rats to find the MWM platform during the learning phase. Furthermore, they had a longer travel distance and less time in the target quadrant than the control rats in the probe trial. Maternal intraperitoneal injection of glycyrrhizin (an inhibitor of HMGB1) attenuated the sevoflurane-induced microglia and NLRP3/ASC inflammasome activation and cognitive impairment of offspring. Simultaneously, the sevoflurane-induced increase in Toll-like receptors (TLR4) and nuclear factor-κB (NF-κB) was significantly reduced by glycyrrhizin. We concluded that the HMGB1 inhibitor may repress the sevoflurane-induced activation of the NLRP3/ASC inflammasome and cognitive dysfunction and that TLR4/NF-κB signaling maybe the key pathway, at least in part.

A mechanistic review of pharmacological activities of homeopathic medicine licorice against neural diseases

The use of medicinal plants has grown in popularity in recent decades because, as natural ingredients, they have fewer adverse effects and are more effective than synthetic alternatives. As a small perennial herb, Glycyrrhiza glabra L. (Licorice) has been investigated for its therapeutic efficacy against neural disorders mainly ischemic stroke as well as the neurodegenerative diseases such as dementia and Alzheimer's disease, and Parkinson's disease which has been attributed to its HMGB inhibitory function, reactive oxygen scavenging and anti-inflammatory activity. The objective of current review is to review the evidence for the pharmacological effects of licorice and its vital active components on neurological disorders and the underlying signaling networks. We reviewed Papers published from 2000.1.1 up to 2 January 2023 in web of science, Google Scholar and PubMed data bases using key words including "Licorice," "Glycyrrhiza glabra L.," "Glycyrrhizic acid," "brain," "neurodegenerative disease," "Alzheimer's," and "Parkinson" were used to search in title/abstracts. Licorice extract and/or its active components can be used safely in therapeutic doses for optimizing the management of a multiple neurodegenerative disorders, and hampering the extent of neural tissue injury and neurologic deficits subsequent to cerebrovascular accidents.

Targeting neuroinflammation as a preventive and therapeutic approach for perioperative neurocognitive disorders

Perioperative neurocognitive disorders (PND) is a common postoperative complication associated with regional or general anesthesia and surgery. Growing evidence in both patient and animal models of PND suggested that neuroinflammation plays a critical role in the development and progression of this problem, therefore, mounting efforts have been made to develop novel therapeutic approaches for PND by targeting specific factors or steps alongside the neuroinflammation. Multiple studies have shown that perioperative anti-neuroinflammatory strategies via administering pharmacologic agents or performing nonpharmacologic approaches exert benefits in the prevention and management of PND, although more clinical evidence is urgently needed to testify or confirm these results. Furthermore, long-term effects and outcomes with respect to cognitive functions and side effects are needed to be observed. In this review, we discuss recent preclinical and clinical studies published within a decade as potential preventive and therapeutic approaches targeting neuroinflammation for PND.

Long Non-Coding RNA maternally expressed 3 (MEG3) regulates isoflurane-induced cognitive dysfunction by targeting miR-7-5p

This study aimed to investigate the role and mechanism of long non-coding RNA maternally expressed gene 3 (MEG3) in cognitive dysfunction induced by isoflurane (ISO). Morrier water maze analysis was performed to evaluate the cognitive function of rats. Modified modified neurological severity score (mNSS) scores were assessed for neurological damage. The levels of MEG3 in hippocampal tissues of rats and hippocampal neuron cell lines HT22 were examined by reverse transcription-quantitative polymerase chain reaction (qRT-PCR). Moreover, the cell viability and apoptosis were assessed by the Cell Counting Kit-8 (CCK-8) and flow cytometry assay. Indicators of inflammation and oxidative stress were determined using enzyme-linked immunosorbent assay (ELISA) and commercial assay kits. Relationship between MEG3 and microRNA (miR)-7-5p was verified by the dual-luciferase reporter gene assay. MEG3 was increased in hippocampal tissues and HT22 after ISO treatment (P < 0.05). MEG3 downregulation alleviated the increase in neurological severity score and cognitive dysfunction caused by ISO treatment (P < 0.05). In vitro, MEG3 downregulation alleviates the decrease in cell activity and increased apoptosis induced by ISO. What's more, MEG3 reduction eliminated activation of neuroinflammation and oxidative stress promoted by ISO treatment in rats and HT22 (P < 0.05). MEG3 was confirmed to specifically bind to miR-7-5p. Inhibition of miR-7-5p eliminated the alleviating effects of MEG3 downregulation on cognitive dysfunction caused by ISO treatment. Decreased MEG3 alleviates cognitive dysfunction caused by ISO by targeting miR-7-5p and play a neuroprotective effect. We present a strategy for MEG3 as a potential target for brain protection during anesthesia.

The genus Glycyrrhiza (Fabaceae family) and its active constituents as protective agents against natural or chemical toxicities

Licorice is the dried roots and rhizomes of various species of the genus Glycyrrhiza (Fabaceae) that have been used in folk medicine from ancient times. Many important research projects have established several beneficial effects for this medicinal herb, including antiinflammatory, antimicrobial, antiviral, antiprotozoal, antioxidant, antihyperglycemic, antihyperlipidemic, hepatoprotective, and neuroprotective. Licorice contains important bioactive components, such as glycyrrhizin (glycyrrhizic, glycyrrhizinic acid), liquiritigenin, liquiritin, and glycyrrhetinic acid. The protective effects of licorice and its main chemical components against toxins and toxicants in several organs including the brain, heart, liver, kidney, and lung have been shown. In this comprehensive review article, the protective effects of these constituents against natural, industrial, environmental, and chemical toxicities with attention on the cellular and molecular mechanism are introduced. Also, it has been revealed that this plant and its main compounds can inhibit the toxicity of different toxins by the antioxidant, antiinflammatory, and anti-apoptotic properties as well as the modulation of Inhibitor of kappaB kinase (IKK), Extracellular signal-regulated protein kinase1/2 (ERK1/2), p38, inducible nitric oxide synthase, and nuclear factor-κB (NF-κB) signaling pathways. More high-quality investigations in both experimental and clinical studies need to firmly establish the efficacy of licorice and its main constituents against toxic agents.

Intranasal levosimendan prevents cognitive dysfunction and apoptotic response induced by repeated isoflurane exposure in newborn rats

Anesthetic-induced toxicity in early life may lead to risk of cognitive decline at later ages. Notably, multiple exposures to isoflurane (ISO) cause acute apoptotic cell death in the developing brain and long-term cognitive dysfunction. This study is the first to investigate whether levosimendan (LVS), known for its protective myocardial properties, can prevent anesthesia-induced apoptotic response in brain cells and learning and memory impairment. Postnatal day (P)7 Wistar albino pups were randomly assigned to groups consisting of an equal number of males and females in this laboratory investigation. We treated rats with LVS (0.8 mg/kg/day) intranasally 30 min before each ISO exposure (1.5%, 3 h) at P7+9+11. We selected DMSO as the drug vehicle. Also, the control group at P7+9+11 received 50% O2 for 3 h instead of ISO. Neuroprotective activity of LVS against ISO-induced cognitive dysfunction was evaluated by Morris water maze. Expression of apoptotic-related proteins was detected in the whole brain using western blot. LVS pretreatment significantly prevented anesthesia-induced deficit in spatial learning (at P28-32) and memory (at P33, P60, and P90). No sex-dependent difference occurred on any day of the training and probe trial. Intranasal LVS was also found to significantly prevent the ISO-induced apoptosis by reducing Bax and cleaved caspase-3, and by increasing Bcl-2 and Bcl-xL. Our findings support pretreatment with intranasal LVS application as a simple strategy in daily clinical practice in pediatric anesthesia to protect infants and children from the risk of general anesthesia-induced cell death and cognitive declines.

Repeated Neonatal Isoflurane Exposure is Associated with Higher Susceptibility to Chronic Variable Stress-induced Behavioural and Neuro-inflammatory Alterations

Numerous studies have reported that prolonged or multiple exposures to anaesthetics in early life lead to detrimental effects on brain function, most having focused on neurocognitive function, and relatively few on long term neuropsychiatric performance. The present study investigated the impact of repeated neonatal isoflurane exposure on chronic variable stress (CVS)-induced psychiatric and behavioural outcomes together with CVS-related neuronal activity and neuro-inflammatory reactivity in relevant brain circuits. In the present study, C57BL/6J mice received either three exposures to isoflurane at postnatal days 7, 8, and 9 or a control exposure. From postnatal day 45, mice were exposed to a mild, 3-week, CVS paradigm or none and the CVS-related neuropsychiatric performance was evaluated using a series of behavioural tests. The neuronal activity in relevant brain regions was measured by ΔFosB immunopositivity and CVS-related neuroinflammation was assessed by analysing levels of pro-inflammatory cytokines IL-1α, IL-1β, IL-6, and TNF-α. In mice experiencing serial neonatal isoflurane exposure, we detected a significant enhancement in anxiety levels following CVS procedures, together with enhanced neuronal activity, and exacerbated neuroinflammation in the basolateral amygdaloid nuclei (BLA) and hippocampal dentate gyrus (DG) regions. No such change was found in control mice. These results indicate an association between early multiple isoflurane exposures in infant mice and susceptibility to a CVS-evoked anxious phenotype accompanied by enhanced neuronal activity in BLA and DG regions and high inflammatory reactivity in response to CVS.

Advances in Pharmacological Activities and Mechanisms of Glycyrrhizic Acid

Licorice (Glycyrrhiza glabra L.) is widely regarded as an important medicinal plant and has been used for centuries in traditional medicine because of its therapeutic properties. Studies have shown that metabolites isolated from licorice have many pharmacological activities, such as antiinflammatory, anti-viral, participation in immune regulation, anti-tumor and other activities. This article gives an overview of the pharmacological activities and mechanisms of licorice metabolites and the adverse reactions that need attention. This review helps to further investigate the possibility of licorice as a potential drug for various diseases. It is hoped that this review can provide a relevant theoretical basis for relevant scholars' research and their own learning.

The neurotoxic effect of isoflurane on age-defined neurons generated from tertiary dentate matrix in mice

INTRODUCTION

Recent animal studies showed that isoflurane exposure may lead to the disturbance of hippocampal neurogenesis and later cognitive impairment. However, much less is known about the effect of isoflurane exposure on the neurons generated form tertiary dentate matrix, even though a great increase of granule cell population during the infantile period is principally derived from this area.

METHODS

To label the new cells originated from the tertiary dentate matrix, the mice were injected with BrdU on postnatal day 6 (P6). Then, the mice were exposed to isoflurane for 4 hr at 1, 8, 21, and 42 days after BrdU injection, and the brains were collected 24 hr later. The loss of newly generated cells/neurons with different developmental stage was assessed by BrdU, BrdU + DCX, BrdU + NeuN, or BrdU + Prox-1 staining, respectively.

RESULTS

We found that the isoflurane exposure significantly decreased the numbers of nascent cells (1 day old) and mature neurons (42 days old), but had no effect on the immature (8 days old) and early mature neurons (8 and 21 days old, respectively).

CONCLUSION

The results suggested isoflurane exposure exerts the neurotoxic effects on the tertiary dentate matrix-originated cells with an age-defined pattern in mice, which partly explain the cognitive impairment resulting from isoflurane exposure to the young brain.

The differential effects of isoflurane and sevoflurane on neonatal mice

Previous research has shown that exposure to volatile anesthetics can induce acute neuroinflammation and neuroapoptopsis in neonatal rodents and that these events can lead to cognitive dysfunction at later stages. Isoflurane and sevoflurane are two of the most popular anesthetics used in the field of pediatrics. However, the relative impact of these two anesthetics on the developing brain at distinct time points after the induction of anesthesia has not been compared. In the present study, we exposed 7-day-old mice to clinically equivalent doses of isoflurane (1.5%) and sevoflurane (2.5%) for 4 h and then investigated consequential changes in the brains of these mice at six different time points. We analyzed the levels of proteins that are directly related to neuroapoptosis, neuroinflammation, synaptic function, and memory, in the brains of neonatal mice. Exposure of neonatal mice to isoflurane and sevoflurane resulted in acute neuronal apoptosis. Our analysis observed significant levels of neuroinflammation and changes in the expression levels of proteins associated with both synaptic transmission and memory in mice from the isoflurane group but not the sevoflurane group. Our results therefore indicate that isoflurane and sevoflurane induce differential effects in the brains of neonatal mice.

The performance of the alarmin HMGB1 in pediatric diseases: From lab to clinic

INTRODUCTION

The ubiquitously expressed nonhistone nuclear protein high-mobility group box protein 1 (HMGB1) has different functions related to posttranslational modifications and cellular localization. In the nucleus, HMGB1 modulates gene transcription, replication and DNA repair as well as determines chromosomal architecture. When the post-transcriptional modified HMGB1 is released into the extracellular space, it triggers several physiological and pathological responses and initiates innate immunity through interacting with its reciprocal receptors (i.e., TLR4/2 and RAGE). The effect of HMGB1-mediated inflammatory activation on different systems has received increasing attention. HMGB1 is now considered to be an alarmin and participates in multiple inflammation-related diseases. In addition, HMGB1 also affects the occurrence and progression of tumors. However, most studies involving HMGB1 have been focused on adults or mature animals. Due to differences in disease characteristics between children and adults, it is necessary to clarify the role of HMGB1 in pediatric diseases.

METHODS AND RESULTS

Through systematic database retrieval, this review aimed to first elaborate the characteristics of HMGB1 under physiological and pathological conditions and then discuss the clinical significance of HMGB1 in the pediatric diseases according to different systems.

CONCLUSIONS

HMGB1 plays an important role in a variety of pediatric diseases and may be used as a diagnostic biomarker and therapeutic target for new strategies for the prevention and treatment of pediatric diseases.

Tetramethylpyrazine ameliorates isoflurane-induced cognitive dysfunction by inhibiting neuroinflammation via miR-150 in rats

Tetramethylpyrazine (TMP) has neuroprotective effects in the pathogenesis of some human diseases, such as Parkinson's disease. The present study aimed to investigate the role of TMP in isoflurane-induced cognitive dysfunction in rats, and further identify the mechanisms involved in the protective effects of TMP. The Morris water maze test was used to evaluate the cognitive function of rats exposed to isoflurane or treated with TMP. ELISA was conducted to evaluate the effects of isoflurane or TMP on neuroinflammation. The expression of microRNA-150 (miR-150) was measured using reverse transcription-quantitative PCR, and the potential target genes of miR-150 were predicted and verified. The impaired cognitive function induced by isoflurane in the rats was significantly ameliorated by treatment with TMP. In addition, TMP treatment in rats attenuated neuroinflammation caused by isoflurane. The expression of miR-150 was inhibited by isoflurane exposure, but was enhanced by TMP treatment in rats. Furthermore, the overexpression of miR-150 alleviated the isoflurane-induced cognitive dysfunction and neuroinflammation, while the neuroprotective effects of TMP were significantly abrogated by the knockdown of miR-150. AKT3 was a direct target of miR-150, and its mRNA expression was significantly decreased by the overexpression of miR-150 in isoflurane- and TMP-treated rats. These results demonstrated the protective effects of TMP against isoflurane-induced cognitive dysfunction, which were achieved by attenuating neuroinflammation via the regulation of the miR-150/AKT3 pathway. In addition, miR-150 may serve as a novel therapeutic target for the alleviation of cognitive dysfunction induced by anesthetics.

Potential Neuroprotective Effect of the HMGB1 Inhibitor Glycyrrhizin in Neurological Disorders

Glycyrrhizin (glycyrrhizic acid), a bioactive triterpenoid saponin constituent of Glycyrrhiza glabra, is a traditional medicine possessing a plethora of pharmacological anti-inflammatory, antioxidant, antimicrobial, and antiaging properties. It is a known pharmacological inhibitor of high mobility group box 1 (HMGB1), a ubiquitous protein with proinflammatory cytokine-like activity. HMGB1 has been implicated in an array of inflammatory diseases when released extracellularly, mainly by activating intracellular signaling upon binding to the receptor for advanced glycation end products (RAGE) and toll-like receptor 4 (TLR4). HMGB1 neutralization strategies have demonstrated disease-modifying outcomes in several preclinical models of neurological disorders. Herein, we reveal the potential neuroprotective effects of glycyrrhizin against several neurological disorders. Emerging findings demonstrate the therapeutic potential of glycyrrhizin against several HMGB1-mediated pathological conditions including traumatic brain injury, neuroinflammation and associated conditions, epileptic seizures, Alzheimer's disease, Parkinson's disease, and multiple sclerosis. Glycyrrhizin's effects in neurological disorders are mainly attributed to the attenuation of neuronal damage by inhibiting HMGB1 expression and translocation as well as by downregulating the expression of inflammatory cytokines. A large number of preclinical findings supports the notion that glycyrrhizin might be a promising therapeutic alternative to overcome the shortcomings of the mainstream therapeutic strategies against neurological disorders, mainly by halting disease progression. However, future research is warranted for a deeper exploration of the precise underlying molecular mechanism as well as for clinical translation.

NR2B receptor- and calpain-mediated KCC2 cleavage resulted in cognitive deficiency exposure to isoflurane

BACKGROUND

During brain development, volatile anesthetic can rapidly interfere with physiologic patterns of dendritic development and synaptogenesis and impair the formation of precise neuronal circuits. KCC2 plays vital roles in spine development and synaptogenesis through its Cl- transport function and structural interactions with the spine cytoskeleton protein 4.1 N. The aim of this study was to dissect the mechanism of volatile anesthetics, which impair dendritic development and synaptogenesis via mediation of KCC2 cleavage.

METHODS

Westernblotting was employed to assess the expression change of NR2B, NR2A, calpain-1, calpain-2, KCC2, and 4.1 N protein of rat (PND 5). Co-immunoprecipitation was applied to demonstrate the interaction between KCC2 and 4.1 N protein. Long-term cognitive deficiency was assessed by MWM. Lentivirus-calpain-2 was administered by hippocampus stereotaxic injection.

RESULTS

There was a significant increase in the level of NR2B instead of NR2A exposure to isoflurane. Calpain-2 was excessively activated via NR2B after 6 h of isoflurane exposure. The expression of plasmalemmal KCC2 and 4.1 N protein was significantly decreased treated with isoflurane. The isoflurane group showed longer traveled distance, prolonged escape latency, less time spent in the target quadrant, and decreased platform crossings. Pretreatment with ifenprodil and downregulated calpain-2 expression significantly alleviated these neurotoxicity responses and cognitive deficiency after isoflurane exposure.

CONCLUSIONS

A significant increase in NR2B, excessive activation of calpain-2 and increased cleavage of plasmalemmal KCC2, are involved in isoflurane-induced neurotoxicity and long-term cognitive deficiency. Blocking NR2B and calpain-2 activity significantly attenuated these responses. The KCC2 cleavage mediated by NR2B and calpain-2 is a major determinant of isoflurane-induced long-term cognitive deficiency.

Hemin treatment protects neonatal rats from sevoflurane-induced neurotoxicity via the phosphoinositide 3-kinase/Akt pathway

AIMS

Anaesthesia-related neurotoxicity in the developing brain is a controversial issue that has recently attracted much attention. Hemin plays a protective role in hypoxic and ischemic brain damage; however, its effects on sevoflurane-induced neurotoxicity remain unclear. Our aim was to investigate the mechanisms of sevoflurane neurotoxicity and potential neuroprotective roles of hemin upon sevoflurane exposure.

MAIN METHODS

Hippocampi were harvested 18 h after sevoflurane exposure. Haem oxygenase 1 (HMOX1), superoxide dismutase 2 (SOD2), discs large MAGUK scaffold protein 4 (DLG4), phosphorylated Akt, Akt, cleaved caspase 3, and neuroglobin were detected by western blotting. A water maze test was used to assess learning and memory ability in P30 rats.

KEY FINDINGS

Sevoflurane inhalation increased cleaved caspase 3 levels. Hemin treatment enhanced the antioxidant defence response, protecting rats from oxidative stress injury. Hemin plays its neuroprotective role via phosphoinositide 3-kinase (PI3K)/Akt signalling. A single inhalation of sevoflurane did not affect DLG4 expression, while hemin treatment did. Platform crossing increased in rats treated with hemin as well, which may be related to increased DLG4. Neuroglobin expression was not affected, suggesting that it may act upstream of PI3K/Akt signalling.

SIGNIFICANCE

Our study demonstrates that hemin plays a protective role in anaesthesia-induced neurotoxicity by both inhibiting apoptosis via the PI3K/Akt pathway and increasing the expression of antioxidant enzymes, reducing oxidative damage. The results provide mechanistic insight into the effects of sevoflurane anaesthesia on the developing brain and suggest that hemin could help avoid these effects.

High mobility group box-1 mediates hippocampal inflammation and contributes to cognitive deficits in high-fat high-fructose diet-induced obese rats

High-fat high-sugar diet-induced obesity can lead to hippocampal inflammation and cognitive deficits, but the detailed underlying mechanism is still not clear. We aim to investigate the role of HMGB1 in hippocampal inflammatory responses and cognitive impairment in high-fat high-fructose diet (HFHFD)-induced obesity. Rats were fed with a normal control diet or an HFHFD diet for 14 weeks. In the last 6 weeks on the diets, the rats were treated with control, or an HMGB1 inhibitor glycyrrhizin, or an anti-HMGB1 neutralizing monoclonal antibody (mAb). Obesity was induced in the HFHFD-fed rats, which had higher body weight, epididymal white adipose tissue (EWAT) weight and caloric efficiency, and lower brain/body weight ratio, glucose tolerance and insulin sensitivity than the ones on normal diets. In the HFHFD-induced obese rats, the HMGB1 levels in plasma and hippocampus were increased, and the nucleus-to-cytoplasm translocation of HMGB1 was promoted. The hippocampal inflammatory responses were enhanced in the HFHFD-induced obesity, including the activation of TLR4 and NF-κB, the production of IL-1β, TNF-α and IL-6, as well as the activation of microglia and astrocytes. In addition, the hippocampal cell apoptosis and cognitive impairment were observed in the HFHFD-fed rats. The treatment with glycyrrhizin or HMGB1 mAb successfully decreased the HMGB1 levels in plasma and hippocampus, and prevented the HMGB1 translocation from the nucleus to cytoplasm. Inhibiting HMGB1 by glycyrrhizin or HMGB1 mAb suppressed the hippocampal inflammatory, alleviated the apoptosis and ameliorated the cognitive impairment in HFHFD-fed rats. These findings indicate that HMGB1 mediates the hippocampal inflammation and contributes to the cognitive deficits in HFHFD-induced obesity. Therefore, inhibition of HMGB1 may have beneficial effect in protecting against hippocampal inflammation and cognitive deficits in dietary obesity.

Detrimental Effects of HMGB-1 Require Microglial-Astroglial Interaction: Implications for the Status Epilepticus -Induced Neuroinflammation

Temporal Lobe Epilepsy (TLE) is the most common form of human epilepsy and available treatments with antiepileptic drugs are not disease-modifying therapies. The neuroinflammation, neuronal death and exacerbated plasticity that occur during the silent period, following the initial precipitating event (IPE), seem to be crucial for epileptogenesis. Damage Associated Molecular Patterns (DAMP) such as HMGB-1, are released early during this period concomitantly with a phenomenon of reactive gliosis and neurodegeneration. Here, using a combination of primary neuronal and glial cell cultures, we show that exposure to HMGB-1 induces dendrite loss and neurodegeneration in a glial-dependent manner. In glial cells, loss of function studies showed that HMGB-1 exposure induces NF-κB activation by engaging a signaling pathway that involves TLR2, TLR4, and RAGE. In the absence of glial cells, HMGB-1 failed to induce neurodegeneration of primary cultured cortical neurons. Moreover, purified astrocytes were unable to fully respond to HMGB-1 with NF-κB activation and required microglial cooperation. In agreement, in vivo HMGB-1 blockage with glycyrrhizin, immediately after pilocarpine-induced status epilepticus (SE), reduced neuronal degeneration, reactive astrogliosis and microgliosis in the long term. We conclude that microglial-astroglial cooperation is required for astrocytes to respond to HMGB-1 and to induce neurodegeneration. Disruption of this HMGB-1 mediated signaling pathway shows beneficial effects by reducing neuroinflammation and neurodegeneration after SE. Thus, early treatment strategies during the latency period aimed at blocking downstream signaling pathways activated by HMGB-1 are likely to have a significant effect in the neuroinflammation and neurodegeneration that are proposed as key factors in epileptogenesis.

The Molecular Evolution and Functional Divergence of Lamprey Programmed Cell Death Genes

The programmed cell death (PDCD) family plays a significant role in the regulation of cell survival and apoptotic cell death. However, the evolution, distribution and role of the PDCD family in lampreys have not been revealed. Thus, we identified the PDCD gene family in the lamprey genome and classified the genes into five subfamilies based on orthologs of the genes, conserved synteny, functional domains, phylogenetic tree, and conserved motifs. The distribution of the lamprey PDCD family and the immune response of the PDCD family in lampreys stimulated by different pathogens were also demonstrated. In addition, we investigated the molecular function of lamprey PDCD2, PDCD5, and PDCD10. Our studies showed that the recombinant lamprey PDCD5 protein and transfection of the L-PDCD5 gene induced cell apoptosis, upregulated the expression of the associated X protein (BAX) and TP53 and downregulated the expression of B cell lymphoma 2 (BCL-2) independent of Caspase 3. In contrast, lamprey PDCD10 suppressed apoptosis in response to cis-diaminedichloro-platinum (II) stimuli. Our phylogenetic and functional data not only provide a better understanding of the evolution of lamprey PDCD genes but also reveal the conservation of PDCD genes in apoptosis. Overall, our results provide a novel perspective on lamprey immune regulation mediated by the PDCD family.

Pioglitazone prevents sevoflurane‑induced neuroinflammation and cognitive decline in a rat model of chronic intermittent hypoxia by upregulating hippocampal PPAR‑γ

Post‑operative cognitive dysfunction is a common complication after anesthesia and surgery. Sevoflurane (SEV), a widely used inhalational anesthetic, can exaggerate neuroinflammation and cause cognitive dysfunction under chronic intermittent hypoxia (CIH) conditions by downregulating hippocampal peroxisome proliferator‑activated receptor‑γ (PPAR‑γ). In the present study, it was examined whether treatment with PPAR‑γ agonist pioglitazone (PIO) is beneficial in counteracting SEV‑induced neuroinflammation and cognitive decline in a rat model of CIH. Rats were exposed to CIH for 4 weeks. After 2 weeks of CIH, these animals underwent either 2.6% SEV or control (CON) exposure for 4 h. PIO (60 mg/kg) or vehicle (VEH) was administered orally twice daily for 2 weeks, starting one day prior to SEV or CON exposure. Compared with CIH‑CON+VEH rats, CIH‑SEV+VEH rats exhibited significant cognitive decline as indicated by increased latency to locate the hidden platform and shorter dwell‑time in the goal quadrant in the Morris Water Maze task. Molecular studies revealed that CIH‑SEV+VEH rats had increased proinflammatory cytokine expression and microglial activation in the hippocampus, which were associated with decreased PPAR‑γ activity. Notably, SEV‑induced cognitive decline and increases in proinflammatory cytokine expression and microglial activation were prevented by PIO, which increased hippocampal PPAR‑γ activity. PIO also increased hippocampal PPAR‑γ activity in CIH‑CON rats but did not alter proinflammatory cytokine expression and microglial activation as well as cognitive function. Additionally, expression of hippocampal PPAR‑α and PPAR‑β, two other PPAR isotypes, were comparable among the groups. These data suggest that PIO prevents SEV‑induced exaggeration of neuroinflammation and cognitive decline under CIH conditions by upregulating hippocampal PPAR‑γ. PIO may have the potential to prevent anesthetic SEV‑induced cognitive decline in surgical patients with obstructive sleep apnea.

Cytosolic HMGB1 Mediates Autophagy Activation in an Emulsified Isoflurane Anesthesia Cell Model

Inhalation anesthetic isoflurane may cause an increased risk of cognitive impairment. Previous studies have indicated that this cognitive decline is associated with neuroinflammation mediated by high mobility group box 1 (HMGB1). HMGB1 is released from cells and acts as a damage-associated molecule in neurodegenerative diseases. However, the effect of intracellular HMGB1 during emulsified isoflurane (EI) exposure is poorly understood. The purpose of this study was to investigate the effect of autophagy on neuroprotection, evaluate variation of HMGB1, and determine its role in autophagic flux after EI exposure in vitro. We observed that EI decreased cell viability in a concentration-dependent manner, accompanied by an increase in autophagic flux. EI exposure also elevates the HMGB1 level in cytoplasm. Further, cytosolic HMGB1 was necessary for autophagy by perturbing the beclin1-Bcl-2 interaction. Most importantly, autophagy induction by rapamycin alleviated EI-provoked cell injury, and HMGB1 knockdown induced autophagy inhibition, which exacerbated cell damage. Based on these findings, we propose that autophagic flux is sustained and upregulated in response to EI exposure by increased cytosolic HMGB1, and that autophagy activation serves as a protective mechanism against EI-induced cytotoxicity. Thus, the complex roles of HMGB1 make it pivotal in reducing EI-induced neuronal damage.

Beneficial Effects of Gagam-Palmultang on Scopolamine-Induced Memory Deficits in Mice

From text mining of Dongeuibogam, the 7 herbs in Palmultang can be considered effective candidates for memory enhancement. We sought to determine whether Gagam-Palmultang, comprising these 7 herbs, ameliorates scopolamine-induced memory impairment in mice, by focusing on the central cholinergic system and memory-related signaling molecules. Behavioral tests were performed after inducing memory impairment by scopolamine administration. The cholinergic system activity and memory-related molecules were examined in the hippocampus by enzyme-linked immunosorbent, western blot, and immunofluorescence assays. Gagam-Palmultang ameliorated scopolamine-induced memory impairment in the Morris water maze test, producing a significant improvement in the mean time required to find the hidden platform. Treatment with Gagam-Palmultang reduced acetylcholinesterase activity and expression in the hippocampus induced by scopolamine. The diminished phosphorylated phosphatidylinositide 3-kinase (PI3K), extracellular signal-regulated kinase (ERK), cAMP response element-binding protein (CREB), and mature brain-derived neurotrophic factor (mBDNF) expressions caused by scopolamine administration were attenuated by treatment with Gagam-Palmultang. This treatment also promoted neuronal cell proliferation in the hippocampus. Gagam-Palmultang has beneficial effects against scopolamine-induced memory impairments, which are exerted via modulation of the cholinergic system as well as the PI3K and ERK/CREB/BDNF signaling pathway. Therefore, this multiherb formula may be a useful therapeutic agent for diseases associated with memory impairments.

Sevoflurane Induces Exaggerated and Persistent Cognitive Decline in a Type II Diabetic Rat Model by Aggregating Hippocampal Inflammation

Recent studies show that a moderate duration of sevoflurane, one of the most commonly used volatile anesthetics in clinical practice, does not induce cognitive impairment in animals under physiological conditions. However, the influence of sevoflurane on cognitive function under diabetic conditions remains unclear. The aim of this study was to determine whether sevoflurane causes cognitive decline in a rat model of type 2 diabetes mellitus (DM) and if so, to explore a possible underlying mechanism. Diabetic Goto–Kakizaki (GK) rats and non-diabetic Wistar rats underwent 2.6% sevoflurane for 4 h or sham (control) exposure. Cognitive function and hippocampal inflammation were assessed 1 week and 5 months after sevoflurane or sham exposure. Compared with Wistar control rats, GK control rats exhibited shorter freezing times in Trace fear conditioning task 1 week after exposure, took longer to locate the submerged platform and had shorter dwell-time in the target quadrant in Morris Water Maze task 5 months after exposure. GK rats that received sevoflurane not only exhibited less freezing times 1 week after exposure, but also spent more time to locate the submerged platform and had less dwell-time in the target quadrant, compared with GK control rats. Molecular studies revealed that the levels of pro-inflammatory cytokines and activated microglia in the hippocampus were higher in GK control rats than those in Wistar control rats at both time points and were further increased in GK rats receiving sevoflurane. Wistar rats that received sevoflurane and Wistar control rats did not differ in any cognitive performance and molecular assessment. The results suggest that diabetic GK rats exhibit cognitive dysfunction probably due to increased hippocampal inflammation, and that sevoflurane induces exaggerated and persistent cognitive decline in GK rat by aggregating hippocampal inflammation.

18α-Glycyrrhetinic acid monoglucuronide as an anti-inflammatory agent through suppression of the NF-κB and MAPK signaling pathway

Based on the SAR analysis of glycyrrhizin, 18α-glycyrrhetinic acid monoglucuronide (18α-GAMG) with strong inhibition against LPS-induced NO and IL-6 production in RAW264.7 cells was discovered. Western blotting and immunofluorescence results showed that 18α-GAMG reduced the expression of iNOS, COX-2, and MAPKs, as well as activation of NF-κB in the LPS-stimulated RAW264.7 cells. Further in vivo results showed that 18α-GAMG could significantly improve the pathological changes of CCl4-induced hepatic fibrosis.

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.