Anticonvulsant and Neuroprotective Effects of Dexmedetomidine on Pilocarpine-Induced Status Epilepticus in Rats Using a Metabolomics Approach

A New Mouse Model for Exploring Tranexamic Acid-Associated Seizures

BACKGROUND

Tranexamic acid (TXA) plays a central role in antifibrinolytic strategies, raising intense concerns regarding TXA-associated seizures. The aim of the study was to develop an in vivo TXA-induced seizure (TIS) model and identify its features on behavior, electroencephalograph (EEG), histology, and metabolomics.

METHODS

Adult healthy male C57BL/6J mice (n = 42) were randomized into 7 dosage groups to receive intracerebroventricular injection of TXA (vehicle, 1, 5, 7.5, 10, 25, 50 μg/μL, n = 6 each). The dose titration was based on behavioral observation according to the Racine scale. Further, continuous video-EEG was performed in another 8 TIS mice and 5 control mice with the stereotaxic implantation of electrodes and guide cannulas. Then hippocampus samples were obtained from an additional 10 TIS mice and 9 control mice for histological evaluation and metabolomic analysis.

RESULTS

Behavioral observation revealed a dose-dependent relationship between the intensity of seizures and the intraventricular gradient of the agent. A dose of 2 μL 7.5 μg/μL TXA i.c.v. was confirmed as the target scheme to establish the model with intense behavioral seizures and typical spike epileptic EEG discharges. Histological exploration illustrated necrosis and loss of neurons as well as loss of Nissl granules in the CA3 area of the hippocampus. Additionally, metabolomic analysis revealed a variety of disturbed metabolic pathways related to seizures including amino acid, energy, antioxidant stress metabolism, and nerve signal regulation.

CONCLUSIONS

The study provided an in vivo mouse TIS model with specific features on behavioral seizures, EEG discharges, histological findings, and metabolomic pathways.

Metabolomic changes in adults with status epilepticus: A human case-control study

OBJECTIVE

Status epilepticus (SE) is a life-threatening prolonged epileptic seizure that affects ~40 per 100 000 people yearly worldwide. The persistence of seizures may lead to excitotoxic processes, neuronal loss, and neuroinflammation, resulting in long-term neurocognitive and functional disabilities. A better understanding of the pathophysiological mechanisms underlying SE consequences is crucial for improving SE management and preventing secondary neuronal injury.

METHODS

We conducted a comprehensive untargeted metabolomic analysis, using liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS), on plasma and cerebrospinal fluid (CSF) samples from 78 adult patients with SE and 107 control patients without SE, including 29 with CSF for both groups. The metabolomic fingerprints were compared between patients with SE and controls. Metabolites with differences in relative abundances that could not be attributed to treatment or nutrition provided in the intensive care unit were isolated. Enrichment analysis was performed on these metabolites to identify the most affected pathways.

RESULTS

We identified 76 metabolites in the plasma and 37 in the CSF that exhibited differential expression in patients with SE compared to controls. The enrichment analysis revealed that metabolic dysregulations in patients with SE affected primarily amino acid metabolism (including glutamate, alanine, tryptophan, glycine, and serine metabolism), pyrimidine metabolism, and lipid homeostasis. Specifically, patients with SE had elevated levels of pyruvate, quinolinic acid, and keto butyric acid levels, along with lower levels of arginine, N-acetylaspartylglutamate (NAAG), tryptophan, uracil, and uridine. The tryptophan kynurenine pathway was identified as the most significantly altered in SE, resulting in the overproduction of quinolinic acid, an N-methyl-d-aspartate (NMDA) receptor agonist with pro-inflammatory properties.

SIGNIFICANCE

This study has identified several pathways that may play pivotal roles in SE consequences, such as the tryptophan kynurenine pathway. These findings offer novel perspectives for the development of neuroprotective therapeutics.

Dexmedetomidine attenuates neuroinflammation and microglia activation in LPS-stimulated BV2 microglia cells through targeting circ-Shank3/miR-140-3p/TLR4 axis

It has been shown that dexmedetomidine (Dex) could attenuate postoperative cognitive dysfunction (POCD) via targeting circular RNAs (circRNAs). Circ-Shank3 has been found to be involved in the neuroprotective effects of Dex against POCD. However, the role of circ-Shank3 in POCD remains largely unknown. Reverse transcription quantitative PCR (RT-qPCR) was performed to detect circ-Shank3 and miR-140-3p levels in lipopolysaccharide (LPS)-treated microglia BV-2 cells in the absence or presence of Dex. The relationship among circ-Shank3, miR-140-3p and TLR4 was confirmed by dual-luciferase reporter assay. Additionally, Western blot and immunofluorescence (IF) assays were conducted to evaluate TLR4, p65 and Iba-1 or CD11b levels in cells. In this study, we found that Dex notably decreased circ-Shank3 and TLR4 levels and elevated miR-140-3p level in LPS-treated BV2 cells. Mechanistically, circ-Shank3 harbor miR-140-3p, functioning as a miRNA sponge, and then miR-140-3p targeted the 3'-UTR of TLR4. Additionally, Dex treatment significantly reduced TLR4 level and phosphorylation of p65, and decreased the expressions of microglia markers Iba-1 and CD11b in LPS-treated BV2 cells. As expected, silenced circ-Shank3 further reduced TLR4, p65 and Iba-1 and CD11b levels in LPS-treated BV2 cells in the presence of Dex, whereas these phenomena were reversed by miR-140-3p inhibitor. Collectively, our results found that Dex could attenuate the neuroinflammation and microglia activation in BV2 cells exposed to LPS via targeting circ-Shank3/miR-140-3p/TLR4 axis. Our results might shed a new light on the mechanism of Dex for the treatment of POCD.

Mechanism of cell death pathways in status epilepticus and related therapeutic agents

The most severe form of epilepsy, status epilepticus (SE), causes brain damage and results in the development of recurring seizures. Currently, the management of SE remains a clinical challenge because patients do not respond adequately to conventional treatments. Evidence suggests that neural cell death worsens the occurrence and progression of SE. The main forms of cell death are apoptosis, necroptosis, pyroptosis, and ferroptosis. Herein, these mechanisms of neuronal death in relation to SE and the alleviation of SE by potential modulators that target neuronal death have been reviewed. An understanding of these pathways and their possible roles in SE may assist in the development of SE therapies and in the discovery of new agents.

Anticonvulsant effects of desvenlafaxine on modulating brain monoamine and oxidative stress in mice

Desvenlafaxine succinate (DVS) inhibits serotonin reuptake selectively and is approved for major depressive disorders. This research investigated influence of DVS on modulating brain monoamine and oxidative stress in mice. The antiepileptic potential of DVS (10, 20, or 30 mg/kg/i.p.) in pentylenetetrazole (PTZ; 85 mg/kg) with i.p. route of administration, strychnine (STR; 75 mg/kg) with i.p. route, pilocarpine (400 mg/kg) with s.c. route and maximal electroshock MES-induced convulsion in mouse models. The activities of oxidative stress, i.e. superoxide dismutase (SOD), glutathione (GSH) and lipid peroxidation (LPO) as well as gamma-aminobutyric acid (GABA) in the brains of PTZ-induced convulsive mice. Treatment with DVS increased the latency to develop siezures and declined mortalities in rodents against PTZ, STR and pilocarpine-induced convulsions. Results of MES-leaded siezures revealed that DVS reduced tonic hind limb extension duration and mortalities significantly. Brain, SOD, GSH and GABA level were significantly (P<0.01) increased and LPO reduced significantly (P<0.01) after DVS treatment. Furthermore, the DVS did not show any motor coordination signs in the rotarod test. We demonstrated that the role of DVS in convulsion genesis in mice under control condition and attenuate the PTZ-induced oxidative damage.

Knockdown of Lingo-1 by short hairpin RNA promotes cognitive function recovery in a status convulsion model

The purpose of this study was to determine the dynamic changes of the Nogo-66 receptor 1 (NgR1) pathway during epileptogenesis and the potential beneficial of leucine-rich repeat and Ig-like domain-containing Nogo receptor interacting protein 1 (Lingo-1) inhibition on epilepsy rats. The hippocampal changes of the NgR1 pathway during epileptogenesis were determined by western blot analysis of multiple proteins, including neurite outgrowth inhibitor protein A (NogoA), myelin-associated glycoprotein (MAG), oligodendrocyte-myelin glycoprotein (OMgp), Lingo-1, ras homolog family member A (RhoA) and phosphorylated RhoA (p-RhoA). Lentivirus-mediated short hairpin RNA (shRNA) was used to knockdown the hippocampal expression of Lingo-1. Novel object recognition (NOR) test and Morris Water Maze (MWM) test were employed to determine the cognitive functions of rats. Hematoxylin and eosin (H&E) staining, protein expressions of RhoA, p-RhoA, and myelin basic protein (MBP), as well as convulsion susceptibility test were additionally performed. Our results showed that the NgR1 pathway was activated during epileptogenesis, characterized by up-regulation of NogoA, MAG, OMgp, and Lingo-1, which was especially significant at the chronic phase of epilepsy. The cognitive function, convulsion susceptibility and hippocampal neuronal survival of rats were impaired at the chronic phase of epileptogenesis but all improved by Lingo-1 inhibition; besides, the hippocampal protein expressions of p-RhoA and MBP were significantly decreased at the chronic phase of SC rats but increased after Lingo-1 inhibition. Our results demonstrated that Lingo-1 shRNA can improve epilepsy-induced cognitive impairment, which may be related with the pro-myelination and neuroprotection effects of Lingo-1 inhibition.

Studies on effect of Tongfengxiaofang in HUM model mice using a UPLC-ESI-Q-TOF/MS metabolomic approach

Hyperuricemia (HUM) is a major risk factor for the development of gout. The traditional Chinese medicine (TCM) complex prescription Tongfengxiaofang (TFXF) is composed of a variety of TCMs. To study the therapeutic effect of TFXF on HUM mice and the mechanisms by which it exerts a therapeutic effect, the biochemical indices were measured and qPCR technique was used. In addition, plasma metabolomics analysis was carried out based on UPLC-Q-TOF/MS to evaluate the characteristics of the metabolic spectrum changes. TFXF significantly downregulated the contents of uric acid, urea nitrogen and creatinine in serum and the concentration of xanthine oxidase in liver of HUM mice. In addition, TFXF significantly inhibited the overexpression of uric acid transporter 1 and glucose transporter 9 and upregulated the expression of organic anion transporter 1 in the kidney. A total of 152 metabolites were identified and 11 key biomarkers were further selected from these pathways to understand the mechanism of TFXF on the arginine biosynthesis, galactose metabolism, pyrimidine metabolism, glycerophospholipid metabolism, tryptophan metabolism and the citrate cycle (TCA cycle). The results of this confirmed the effect of TFXF on HUM and revealed the metabolic activity mechanism.

TRPV1 Contributes to the Neuroprotective Effect of Dexmedetomidine in Pilocarpine-Induced Status Epilepticus Juvenile Rats

To investigate the antiepileptic and neuroprotective effects of dexmedetomidine (Dex) in pilocarpine- (Pilo-) induced status epilepticus (SE) juvenile rats, rats were randomly assigned to the following six groups (n = 20): normal, normal+Dex, SE, SE+Cap, SE+Dex, and SE+Dex+Cap. The rats were treated with either diazepam (i.p., an antiepileptic drug) or Dex after the onset of SE. The Morris water maze was used to assess rat cognitive behavior. Flow cytometry was used to detect the concentrations of Ca²⁺, mitochondrial membrane potential, and reactive oxygen species. Transmission electron microscopy was performed to evaluate specimens of brain tissue. The levels of caspase 3 and TRPV1 were examined by western blot and immunohistochemistry (IHC). Treatment with Dex significantly decreased the escape latency of the SE rats (P < 0.05). Capsaicin, a TRPV1 agonist, delivery aggravated the performance of SE rats. Pathological changes in SE rat were attenuated by Dex and deteriorated by capsaicin. Swollen mitochondria and abnormal endoplasmic reticulum were found in SE rats and were then aggravated by capsaicin and reversed by Dex. Moreover, our data showed that Dex significantly restrained calcium overload, ROS production, and mitochondrial membrane potential loss, all of which were induced by Pilo and capsaicin (P < 0.05). Dex decreased the apoptotic rate in the Model SE group (P < 0.05) and TRPV1 and caspase 3 expression in the Dex treatment group (P < 0.05). Interestingly, all these effects of Dex were partially counteracted by the TRPV1 agonist, capsaicin (P < 0.05). Our study showed that Dex exerted a neuroprotective effect in Pilo-induced SE rats by inhibiting TRPV1 expression and provided information for therapy to SE patients.