Modulation of postoperative cognitive decline via blockade of inflammatory cytokines outside the brain

Effects of anterior approach to quadratus lumborum block on postoperative cognitive function following hip surgery in older people: a randomized controlled clinical trial

BACKGROUND

Peripheral nerve block, including the quadratus lumborum block (QLB), has been used for postoperative analgesia in hip surgery. However, the effects of QLB on cognitive function after hip surgery remain unknown. This study aimed to assess the effects of the anterior approach to QLB on postoperative cognitive function in older people undergoing hip surgery.

METHODS

Sixty older people who underwent hip surgery from May 2021 to May 2022 were randomly divided into the QLB (n = 30) and control groups (n = 30). The Montreal Cognitive Assessment (MoCA) score (mean ± SD) was measured one day preoperatively and seven and 30 days postoperatively. The frequency (%) of postoperative cognitive dysfunction (POCD) was examined seven and 30 days postoperatively. The visual analog scale (VAS) scores at rest and Bruggrmann comfort scale (BCS) scores [Median (IQR)] 6 h (t1), 12 h (t2), 24 h (t3), and 48 h (t4) after surgery were assessed. The plasma high mobility group box protein 1 (HMGB1) and levels of interleukin-6 (IL-6) (mean ± SD) were evaluated 1 h preoperatively (baseline) and 24 h postoperatively (day 1). The requirement for rescue analgesia [Median (IQR)], time to first off-bed activity (mean ± SD), and adverse effects after surgery were also recorded.

RESULTS

Compared with the control group, the frequency of POCD was significantly lower in the QLB group seven days postoperatively (10.7% vs. 34.5%, P = 0.033), but no difference at 30 days postoperatively (3.6% vs. 10.3%, P = 0.319). There was no significant difference in MoCA scores between the two groups at one day preoperatively and 30 days postoperatively. However, the MoCA scores at seven days postoperatively were higher in the QLB group than in the control group (27.4 ± 1.81 vs. 26.4 ± 1.83, P = 0.043). In the QLB group, the VAS scores at t1, t2, and t3 were lower [3(2-4) vs. 4(3-4), P = 0.028; 3(2-3) vs. 4(3-5), P = 0.009; 2(1-3) vs. 2(2-3), P = 0.025], and the BCS scores at t1, t2, and t3 were higher than those in the control group [3(1-3) vs. 1(1-2), P = 0.006; 3(2-3) vs. 2(1-3), P = 0.011; 3(2-4) vs. 2(2-3), P = 0.041]. The patients in the QLB group reported significantly fewer requirements for rescue analgesia [0(0-1) vs. 1(0-2), P = 0.014]. The plasma levels of HMGB1 and IL-6 at 24 h postoperatively in the QLB group were significantly lower than in the control group (749.0 ± 185.7 vs. 842.1 ± 157.9, P = 0.046; 24.8 ± 8.1 vs. 31.9 ± 5.5, P < 0.001). The time to first off-bed activity from the end of surgery was shorter in the QLB group (25.3 ± 5.3 vs. 29.7 ± 6.9, P = 0.009). There was no significant difference in the incidence of postoperative complications between the two groups.

CONCLUSIONS

Anterior QLB given to older people undergoing hip surgery could promote early postoperative cognitive function recovery, provide adequate postoperative analgesia, and inhibit the release of inflammatory factors.

TRIAL REGISTRATION

Chictr.org.cn identifier ChiCTR2000040724 (Date of registry: 08/12/2020, prospectively registered).

New advances in clinical application of neostigmine: no longer focusing solely on increasing skeletal muscle strength

Neostigmine is a clinical cholinesterase inhibitor, that is, commonly used to enhance the function of the cholinergic neuromuscular junction. Recent studies have shown that neostigmine regulates the immune-inflammatory response through the cholinergic anti-inflammatory pathway, affecting perioperative neurocognitive function. This article reviews the relevant research evidence over the past 20 years, intending to provide new perspectives and strategies for the clinical application of neostigmine.

Influence of Different Sevoflurane Concentrations on Postoperative Cognitive Function in Aged Rats

BACKGROUND

Postoperative cognitive dysfunction may be associated with neuroinflammation, and sevoflurane suppresses surgery-induced inflammation. We hypothesized that low concentrations of sevoflurane would result in more impaired postoperative cognitive function compared to high concentrations.

METHODS

Aged male Sprague-Dawley rats (n = 21, 17-22 months) were randomly assigned to 1 of 3 groups: control (C), sevoflurane 2% (S2), and sevoflurane 4% (S4). Rats in the S2 and S4 groups underwent open femoral fracture and intramedullary fixation of the left hind limb under 2 hours of sevoflurane anesthesia. Neurological outcomes were evaluated using the Morris water maze (MWM) test, and histopathological outcomes were assessed 28 days after surgery.

RESULTS

The S2 group showed prolonged swimming latency compared to S4 on day 7 (difference of means, 34.4; 95% confidence interval [CI], 2.57-66.3; P = .031) and compared to the C group on day 9 (difference of means, -33.4; 95% CI, -65.3 to -1.55; P = .037). The intact CA1 cells in the S2 group were significantly less than those in the C and S4 groups (H statistic, 10.87; P = .006 versus C; P = .033 versus S4).

CONCLUSIONS

We found that low concentrations of sevoflurane prolonged the swimming latency of the MWM compared to high concentrations and reduced intact CA1 hippocampal neurons in aged rats. These results suggest that low-concentration sevoflurane anesthesia may be more detrimental than high concentration for spatial cognitive function and postoperative impairment of hippocampal CA1 cells in aged rats.

Clinically Optimal Neuropsychological Tests for Postoperative Cognitive Dysfunction in Heart Valve Surgeries

BACKGROUND

Postoperative cognitive dysfunction (POCD) is widely recognized and reported, but the lack of a uniform definition makes it difficult to evaluate its clinical impact. The aim of this study is to establish the optimal neuropsychological tests and definition of POCD relevant to clinical outcomes in heart valve surgeries.Methods and Results: Between June 2015 and December 2019, 315 patients undergoing elective heart valve surgeries (age ≥65 years) were enrolled. The Mini-Mental Status Examination, Montreal Cognitive Assessment (MoCA), and the Trail Making Test A and B were performed to evaluate cognitive function. Clinical endpoints were defined as readmission and death. The postoperative readmission and death rate were 17% and 3% (54/315 and 8/315; follow-up 266-1,889 days). By multivariable Cox hazard analysis, Short Physical Performance Battery (adjusted hazard ratio [HR]: 0.84, 95% confidence interval [CI]: 0.49-0.98, P=0.001), MoCA change rate (adjusted HR: 0.64, 95% CI: 0.01-1.22, P=0.024), and intensive care unit stay (adjusted HR: 0.55%, 95% CI: 0.99-1.12, P=0.054) were detected as independent risk factors for combined events. The cutoff value was -12% in the change rate of MoCA.

CONCLUSIONS

MoCA was the only neuropsychological test that predicted the clinical impact on complex events and has the potential to define POCD.

Inflammation From Peripheral Organs to the Brain: How Does Systemic Inflammation Cause Neuroinflammation?

As inflammation in the brain contributes to several neurological and psychiatric diseases, the cause of neuroinflammation is being widely studied. The causes of neuroinflammation can be roughly divided into the following domains: viral infection, autoimmune disease, inflammation from peripheral organs, mental stress, metabolic disorders, and lifestyle. In particular, the effects of neuroinflammation caused by inflammation of peripheral organs have yet unclear mechanisms. Many diseases, such as gastrointestinal inflammation, chronic obstructive pulmonary disease, rheumatoid arthritis, dermatitis, chronic fatigue syndrome, or myalgic encephalomyelitis (CFS/ME), trigger neuroinflammation through several pathways. The mechanisms of action for peripheral inflammation-induced neuroinflammation include disruption of the blood-brain barrier, activation of glial cells associated with systemic immune activation, and effects on autonomic nerves via the organ-brain axis. In this review, we consider previous studies on the relationship between systemic inflammation and neuroinflammation, focusing on the brain regions susceptible to inflammation.

The effects of neostigmine on postoperative cognitive function and inflammatory factors in elderly patients - a randomized trial

Background

Postoperative cognitive dysfunction is a common postoperative complication in elderly patients. In elderly patients, the decline of organ function and neuromuscular junction function make them more sensitive to muscle relaxants. They are more likely to experience residual muscle relaxation after surgery, which may cause various adverse events. Neostigmine, a commonly used muscle relaxant antagonist, can reduce the expression of inflammatory factors, thereby reducing the pro-inflammatory response and neurodegeneration of the cerebral cortex and hippocampus after surgery. The study aimed at observing the effect of different doses of neostigmine on postoperative cognitive function and peripheral inflammatory factors in elderly patients.

Methods

One hundred thirty-two elderly patients who underwent a radical section of gastrointestinal cancer at First Affiliated Hospital of Dalian Medical University were divided into neostigmine and saline groups at a 2:1 ratio. Neostigmine was intravenously injected in the post-anesthesia care unit (PACU) according to the train-of-four ratio (TOFR) T4/T1. When TOFR was ≤0.5, 0.04 mg/kg neostigmine was administered, whereas when TOFR was > 0.5, 0.02 mg/kg neostigmine was injected. The main observation indexes were cognitive function, interleukin 1 beta (IL-1β), tumor necrosis factor-alpha (TNF-α), and interleukin 6 (IL-6) in peripheral blood at the different times before and after the surgery. Secondary observation indicators include the number of atropine injection, extubating time, PACU residence time, incidence of hypoxemia, hypercapnia, and postoperative nausea and vomiting in PACU, time of exhaustion, and length of hospitalization.

Results

The extubating and PACU times in 0.04 mg/kg and 0.02 mg/kg groups were significantly shorter than those in the control group (P < 0.001). The incidence of early postoperative cognitive decline in 0.04 mg/kg and 0.02 mg/kg groups was 10 and 15.7%, respectively, which were significantly lower than those in the control group (P = 0.013).

Conclusion

In elderly patients, 0.02–0.04 mg/kg neostigmine could significantly reduce the incidence of early postoperative cognitive decline without affecting peripheral inflammatory factors.

Trial registration

Trial registration: Chinese Clinical Trial Registry, ChiCTR2000031739. Registered 8 April 2020 - Retrospectively registered, http://www.medresman.org.cn.

Influence of postoperative analgesia on systemic inflammatory response and postoperative cognitive dysfunction after femoral fractures surgery: a randomized controlled trial

BACKGROUND AND OBJECTIVES

To investigate the possible effect of postoperatively applied analgesics-epidurally applied levobupivacaine or intravenously applied morphine-on systemic inflammatory response and plasma concentration of interleukin (IL)-6 and to determine whether the intensity of inflammatory response is related to postoperative cognitive dysfunction (POCD).

METHODS

This is a randomized, prospective, controlled study in an academic hospital. Patients were 65 years and older scheduled for femoral fracture fixation from July 2016 to September 2017. Inflammatory response was assessed by leukocytes, neutrophils, C reactive protein (CRP) and fibrinogen levels in four blood samples (before anesthesia, 24 hours, 72 hours and 120 hours postoperatively) and IL-6 concentration from three blood samples (before anesthesia, 24 hours and 72 hours postoperatively). Cognitive function was assessed using the Mini-Mental State Examination preoperatively, from the first to the fifth postoperative day and on the day of discharge.

RESULTS

The study population included 70 patients, 35 in each group. The incidence of POCD was significantly lower in the levobupivacaine group (9%) than in the morphine group (31%) (p=0.03). CRP was significantly lower in the levobupivacaine group 72 hours (p=0.03) and 120 hours (p=0.04) after surgery. IL-6 values were significantly lower in the levobupivacaine group 72 hours after surgery (p=0.02). The only predictor of POCD in all patients was the level of IL-6 72 hours after surgery (p=0.03).

CONCLUSIONS

There is a statistically significant association between use of epidural levobupivacaine and a reduction in some inflammatory markers. Postoperative patient-controlled epidural analgesia reduces the incidence of POCD compared with intravenous morphine analgesia in the studied population.

TRIAL REGISTRATION NUMBER

NCT02848599.

Impact of thoracic paravertebral block combined with general anesthesia on postoperative cognitive function and serum adiponectin levels in elderly patients undergoing lobectomy

Introduction

Thoracic paravertebral block (TPVB) can improve postoperative analgesia, inhibiting perioperative stress and the inflammatory response. However, whether it can improve early postoperative cognitive dysfunction (POCD) by altering the secretion and expression of serum ADP remains unclear.

Aim

To investigate the impact of thoracic paravertebral block combined with general anesthesia (TPVB-GA) on postoperative cognitive function and serum adiponectin (ADP) levels in elderly patients undergoing lobectomy.

Material and methods

A total of 120 elderly patients undergoing elective lobectomy were randomly divided into three groups: general anesthesia (GA); TPVB-GA (PG); epidural block combined with general anesthesia (EG). Cognitive function in the three groups was evaluated 1 day before and 7 days after surgery. The serum levels of ADP and S-100β protein were evaluated before anesthesia (T0), 15 min after skin incision (T3), and 7 days after surgery (T5).

Results

Cognitive function scores in the three groups decreased by different extents at T5 (p < 0.05); scores in groups PG and EG were higher than those in group GA (p < 0.05). The serum levels of S-100β protein in the three groups at T3 were higher than those at T0 (p < 0.05); however, serum ADP concentrations were reduced (p < 0.05); the serum levels of S-100β protein in groups PG and EG were lower than those in group GA at T3, while serum ADP levels were higher.

Conclusions

Thoracic paravertebral block or epidural block combined with general anesthesia can improve early postoperative cognitive function in elderly patients undergoing lobectomy. TPVB-GA demonstrated better effects, which may be related to the secretion of ADP.

Resveratrol-loaded nanoemulsion prevents cognitive decline after abdominal surgery in aged rats

The maladaptive response of aged microglia to surgery and consequent neuroinflammation plays a key pathogenic role in postoperative cognitive dysfunction (POCD). Here, we assessed the preventive effect of resveratrol (RESV) for POCD in aged rats. The emulsified form of RESV (e-RESV) was selected to improve its oral and brain bioavailability. Animals were assigned to one of four groups: e-RESV (80 mg/kg) versus vehicle treatment by abdominal surgery versus isoflurane anesthesia alone (n = 8 in each group). The dose-dependent effects of e-RESV were also assessed in dose range of 0-60 mg/kg. Either vehicle or e-RESV was administered intragastrically 24 h before surgery. Seven days after procedure, cognitive function was evaluated using a novel object recognition test, followed by measurement of hippocampal pro-inflammatory cytokine levels. Our results showed that pre-treatment with e-RESV attenuated the surgery-induced cognitive impairment and related hippocampal neuroinflammation at 40 mg/kg or higher doses. Additionally, the ex-vivo experiments revealed that the preemptive e-RESV regimen reduced the hippocampal microglial immune reactivity to lipopolysaccharide. Furthermore, e-RESV induced neuroprotective benefits were inhibited by the concomitant administration of sirtinol, a specific SIRT1 inhibitor. Our findings imply the preventive potential of e-RESV for POCD via the SIRT1 signaling pathway.

Lentiviral-Mediated Overexpression of the 18 kDa Translocator Protein (TSPO) in the Hippocampal Dentate Gyrus Ameliorates LPS-Induced Cognitive Impairment in Mice

The 18 kDa translocator protein (TSPO) is involved in the immune/inflammatory response. However, the exact role that TSPO plays in neuroinflammation-induced cognitive impairment is still elusive. The purpose of our present study was to investigate the effects of lentiviral-mediated hippocampal overexpression of the TSPO in a mouse model of LPS-induced cognitive impairment. We established a mouse cognitive impairment model using systematic daily administration of lipopolysaccharide (LPS) (0.5 mg/kg). Microinjection of the dentate gyrus of the mouse with lentiviral vectors, which contained a cDNA targeting TSPO (Lv-TSPO), resulted in a significant increase in TSPO expression and allopregnanolone production. Mice treated with LPS showed cognitive deficits in the novel object recognition test and the Morris water maze test that could be ameliorated by TSPO overexpression. In addition, TSPO overexpression reversed LPS-induced microglial activation and accumulation of pro-inflammatory cytokines, including IL-1β, IL-6, and TNF-α. Moreover, TSPO overexpression attenuated the LPS-induced impairment of hippocampal neurogenesis. Our results suggest that local overexpression of TSPO in the hippocampal dentate gyrus alleviated LPS-induced cognitive deficits, and its effects might be mediated by the attenuation of inflammatory cytokines, inhibition of microglial activation, and promotion of neurogenesis.

The Cox-2 Inhibitor Meloxicam Ameliorates Neuroinflammation and Depressive Behavior in Adult Mice after Splenectomy

BACKGROUND

Peripheral surgical trauma may incite neuroinflammation that leads to neuronal dysfunction associated with both depression and cognitive deficits. In a previous study, we found that adult mice developed neuroinflammation and short-term working memory dysfunction in a delayed, transient manner after splenectomy that was ameliorated by the cyclooxygenase-2 inhibitor meloxicam. We tested the hypothesis that splenectomy in mice would also cause anhedonia, the diminished response to pleasure or rewarding stimuli that is a hallmark of depression, and that treatment with meloxicam would be ameliorative.

METHODS

After Institutional Animal Care and Use Committee approval, Swiss-Webster mice underwent sucrose preference training before being randomized into groups on day 0, when they had either splenectomy and anesthesia or anesthesia alone. Within each group, half were randomized to receive intraperitoneal saline at 24 hours, while the other half received intraperitoneal meloxicam at 24 hours. Sucrose preference ratios were determined on days 1, 5, 9, and 14. Additional mice were randomized into groups for brain histochemistry. Specimens were stained for glial fibrillary acidic protein (GFAP), a marker of astrocytes, and CD45, a protein tyrosine phosphatase that identifies microglial activation.

RESULTS

On day 5, mice receiving splenectomy and saline demonstrated diminished sucrose preference, which was not seen in mice receiving splenectomy and meloxicam. Semiquantitative analysis of histological slides taken from splenectomized mice treated with meloxicam revealed reduced microglial-based neuroinflammation and reactive astrocytosis compared to mice receiving saline.

CONCLUSION

Splenectomy in mice is associated with neuroinflammation and anhedonia, as evidenced by reactive microgliosis, astrocytosis, and behavioral changes. Postsurgical treatment with meloxicam attenuates both neuroinflammation and anhedonia. These findings suggest that cyclooxygenase-2-dependent mechanisms may play a role in the development of postoperative mood disorders, possibly via modulation of peripheral effects on neuroinflammation.

Plasma levels of tumor necrosis factor-α in adolescent idiopathic scoliosis patients serve as a predictor for the incidence of early postoperative cognitive dysfunction following orthopedic surgery

The aim of the present study was to evaluate whether the levels of the plasma biomarkers, cortisol, interleukin (IL)-1β, IL-6, IL-10 and tumor necrosis factor (TNF)-α, change in adolescent idiopathic scoliosis patients with postoperative cognitive dysfunction (POCD); thus, may serve as predictive factors for POCD. In total, 75 adolescent scoliosis patients, aged between 11 and 18 years and categorized as American Society of Anesthesiologists classification I or II, were scheduled for orthopedic surgery with general anesthesia. Blood samples were collected on the day of admission and at day 2 following surgery. The plasma levels of IL-1β, IL-6, IL-10 and TNF-α were measured using an enzyme-linked immunosorbent assay, while the concentrations of cortisol were determined using a radioimmunoassay. Cognitive function was assessed one day prior to and at day 7 following the surgery in a quiet room with the guidance of a Chinese version protocol. In total, 66 patients completed the sample collection and neurocognitive tests. According to the criteria for the diagnosis of POCD, 19 patients (28.8%) developed POCD within seven days of surgery. No statistically significant differences were observed in the baseline concentrations of cortisol, TNF-α, IL-1β, IL-10 or IL-6 between the POCD and non-POCD groups. However, the baseline plasma level of TNF-α on day 2 in the POCD group was found to be higher compared with the non-POCD group. In addition, at day 2 after surgery, the concentration of cortisol in the non-POCD group was higher compared with the POCD group. Therefore, the plasma level of TNF-α in adolescent idiopathic scoliosis patients at day 2 following orthopedic surgery may be a predictor for the incidence of early POCD.

Thinking outside the brain for cognitive improvement: Is peripheral immunomodulation on the way?

Cognitive impairment is a devastating condition commonly observed with normal aging and neurodegenerative disorders such as Alzheimer's Disease (AD). Although major efforts to prevent or slow down cognitive decline are largely focused within the central nervous system (CNS), it has become clear that signals from the systemic milieu are closely associated with the dysfunctional brain. In particular, the bidirectional crosstalk between the CNS and peripheral immune system plays a decisive role in shaping neuronal survival and function via neuroimmune, neuroendocrinal and bioenergetic mechanisms. Importantly, it is emerging that some neuroprotective and cognition-strengthening drugs may work by targeting the brain-periphery interactions, which could be intriguingly achieved without entering the CNS. We describe here how recent advances in dissecting cognitive deficits from a systems-perspective have contributed to a non-neurocentric understanding of its pathogenesis and treatment strategy. We also discuss the therapeutic and diagnostic implications of these exciting progresses and consider some key issues in the clinical translation. This article is part of a Special Issue entitled 'Neuroimmunology and Synaptic Function'.

Peripheral immunomodulation with ginsenoside Rg1 ameliorates neuroinflammation-induced behavioral deficits in rats

Neuroinflammatory disturbances have been closely associated with depression and many other neuropsychiatric diseases. Although targeting neuroinflammatory mediators with centrally acting drugs has shown certain promise, its translation is faced with several challenges especially drug delivery and safety concerns. Here, we report that neuroinflammation-induced behavioral abnormality could be effectively attenuated with immunomodulatory agents that need not to gain brain penetration. In a rat model with intracerebral lipopolysaccharide (LPS) challenge, we validated that ginsenoside Rg1 (Rg1), a well-established anti-inflammatory agent, was unable to produce a direct action in the brain. Interestingly, peripherally restricted Rg1 could effectively attenuate the weight loss, anorexic- and depressive-like behavior as well as neurochemical disturbances associated with central LPS challenge. Biochemical assay of neuroimmune mediators in the periphery revealed that Rg1 could mitigate the deregulation of the hypothalamic-pituitary-adrenal axis and selectively blunt the increase in circulating interleukin-6 levels. Furthermore, these peripheral regulatory effects were accompanied by dampened microglial activation, mitigated expression of pro-inflammatory mediators and neurotoxic species in the central compartment. Taken together, our work suggested that targeting the peripheral immune system may serve as a novel therapeutic approach to neuroinflammation-induced neuropsychiatric disorders. Moreover, our findings provided the rationale for employing peripherally active agents like Rg1 to combat mental disturbances.

TNF-α signalling and inflammation: interactions between old acquaintances

INTRODUCTION

Inflammation is a very important part of innate immunity and is regulated in many steps. One such regulating step is the cytokine network, where tumor necrosis factor α (TNF-α) plays one of the most important roles.

METHODS

A PubMed and Web of Science databases search was performed for studies providing evidences on the role of TNF-α in inflammation, apoptosis, and cancer.

RESULTS AND CONCLUSION

This review concisely summarizes the role of this pro-inflammatory cytokine during inflammation. It is focused mainly on TNF-α intracellular signaling and its influence on the typical inflammatory features in the organism. Being one of the most important pro-inflammatory cytokines, TNF-α participates in vasodilatation and edema formation, and leukocyte adhesion to epithelium through expression of adhesion molecules; it regulates blood coagulation, contributes to oxidative stress in sites of inflammation, and indirectly induces fever. The connection between TNF-α and cancer is mentioned as well.

Ulinastatin alleviates neuroinflammation but fails to improve cognitive function in aged rats following partial hepatectomy

Postoperative cognitive dysfunction (POCD) is very common complication of surgery in aged individuals. Accumulated evidence suggests that neuroinflammation may be the underlying cause of POCD. The aim of the present study was to investigate the effects of ulinastatin (UTI) on neuroinflammation and on learning and memory of aged rats after anesthesia and surgery. Our results showed that anesthetic isoflurane increased the hippocampal mRNA level of IL-1β, while surgery of partial hepatectomy increased the hippocampal mRNA levels of IL-1β, TNF-α, and IL-6 as well as impaired rats' spatial memory at day 7 post-surgery. UTI (10,000 U/kg, i.v.) decreased the anesthesia- and surgery-induced increases in mRNA levels of all three cytokines, but did not improve the rats' impaired working memory. In conclusion, moderate and temporary suppression of UTI-induced inflammatory cytokines in hippocampus is not sufficient to alleviate the impairment of working memory.

Meningeal and choroid plexus cells--novel drug targets for CNS disorders

The meninges and choroid plexus perform many functions in the developing and adult human central nervous system (CNS) and are composed of a number of different cell types. In this article I focus on meningeal and choroid plexus cells as targets for the development of drugs to treat a range of traumatic, ischemic and chronic brain disorders. Meningeal cells are involved in cortical development (and their dysfunction may be involved in cortical dysplasia), fibrotic scar formation after traumatic brain injuries (TBI), brain inflammation following infections, and neurodegenerative disorders such as Multiple Sclerosis (MS) and Alzheimer's disease (AD) and other brain disorders. The choroid plexus regulates the composition of the cerebrospinal fluid (CSF) as well as brain entry of inflammatory cells under basal conditions and after injuries. The meninges and choroid plexus also link peripheral inflammation (occurring in the metabolic syndrome and after infections) to CNS inflammation which may contribute to the development and progression of a range of CNS neurological and psychiatric disorders. They respond to cytokines generated systemically and secrete cytokines and chemokines that have powerful effects on the brain. The meninges may also provide a stem cell niche in the adult brain which could be harnessed for brain repair. Targeting meningeal and choroid plexus cells with therapeutic agents may provide novel therapies for a range of human brain disorders.

Senegenin attenuates hepatic ischemia-reperfusion induced cognitive dysfunction by increasing hippocampal NR2B expression in rats

Background

The root of Polygala tenuifolia, a traditional Chinese medicine, has been used to improve memory and intelligence, while the underlying mechanisms remain largely unknown. In this study, we investigated the protective effects of senegenin, an component of Polygala tenuifolia root extracts, on cognitive dysfunction induced by hepatic ischemia-reperfusion.

Methodology/Principal Findings

Initially, we constructed a rat model of hepatic ischemia-reperfusion (HIR) and found that the memory retention ability of rats in the step-down and Y maze test was impaired after HIR, paralleled by a decrease of N-methyl-D-aspartate (NMDA) receptor NR2B subunit mRNA and protein expressions in hippocampus. Furthermore, we found that administration of senegenin by gavage attenuated HIR-induced cognitive impairment in a dose and time dependent manner, and its mechanisms might partly due to the increasing expression of NR2B in rat hippocampus.

Conclusions/Significance

Cognitive dysfunction induced by HIR is associated with reduction of NR2B expression. Senegenin plays a neuroprotective role in HIR via increasing NR2B expression in rat hippocampus. These findings suggest that senegenin might be a potential agent for prevention and treatment of postoperative cognitive dysfunction (POCD) or other neurodegenerative diseases.