Valproate reduces neuroinflammation and neuronal death in a rat chronic constriction injury model

Exploring the Therapeutic Potential of N-Methyl-D-Aspartate Receptor Antagonists in Neuropathic Pain Management

Neuropathic pain (NeP) is a complex and debilitating condition that impacts millions of people globally. Although various treatment options exist, their effectiveness is often limited, and they can be accompanied by significant side effects. In recent years, there has been increasing interest in targeting the N-methyl-D-aspartate receptor (NMDAR) as a potential therapeutic approach to alleviate different types of neuropathic pain. This narrative review aims to provide a comprehensive examination of NMDAR antagonists, specifically ketamine, memantine, methadone, amantadine, carbamazepine, valproic acid, phenytoin, dextromethorphan, riluzole, and levorphanol, in the management of NeP. By analyzing and summarizing current preclinical and clinical studies, this review seeks to evaluate the efficacy of these pharmacologic agents in providing adequate relief for NeP.

Protective effect of valproic acid on ischemia-reperfusion induced spinal cord injury in a rat model

PURPOSE

This study aims to determine the anti-inflammatory, antioxidant, and anti-apoptotic effects of valproic acid (VPA) on rat spinal cord tissue in ischemia-reperfusion (IR) injury model created by abdominal aorta occlusion.

MATERIALS AND METHODS

Sprague Dawley rat (male sex) weighing 190-260 g divided into four experimental groups: control only underwent laparotomy, sham group, pre-IR injury (200 mg/kg dose), and post-IR injury (300 mg/kg) VPA. We measured serum levels of TNF-α, IL-6, IL-1β, IL-18, Total Oxidant Status (TOS) and Total Antioxidant Status (TAS), and serum Oxidative Stress Index (OSI) ratio, and tissue expression of Bax and Bcl2, Caspase3, and Bax/Bcl2 ratio.

RESULTS

Serum IL-18 was higher in the sham than the control group(P = 0.001), and there were declines in the pre-IR treatment (P = 0.002) and the post-IR treatment when compared to sham (P = 0.001). Despite these reductions, IL-18 expression levels in both the pre- and post-IR treatment groups were higher than in the control group (P = 0.001 & P = 0.003). The favorable effects of pre-IR VPA administration on immunohistochemical biomarkers were superior to post-IR VPA administration.

CONCLUSIONS

Comparative analyses between prophylactic VPA administration and post-IR interventions revealed congruence in their anti-inflammatory and anti-apoptotic ramifications. VPA can reduce spinal cord IR injury in an aortic occlusion model of rats.

Effectiveness of Valproic Acid in the Treatment of Sydenham's Chorea and a Literature Review

There is still no evidence-based guideline and consensus on the treatment Sydenham's Chorea (SC). The first-line medication preference of specialists depends on personal experience and is variable. In this study, we evaluate the treatment results of pediatric patients who were treated with valproic acid (VPA). The medical records of 17 patients diagnosed with SC were reviewed retrospectively. The mean time to clinical improvement was found as approximately 5 days, the mean duration of remission as 13.60 ± 3.94 weeks and the mean duration of medication use was found as 17.96 ± 3.81 weeks. No side effects were observed in any of the patients and relapse occurred in 2 patients. A positive correlation was found between the initial C-reactive protein (CRP) level and the duration of medication use. Until evidence-based guidelines are established, VPA can be used as an effective, safe, and inexpensive first-line treatment option, especially in pediatric patients.

Integrated proteomic and genomic analysis to identify predictive biomarkers for valproate response in bipolar disorder: a 6-month follow-up study

BACKGROUND

Several genetic studies have been undertaken to elucidate the intricate interplay between genetics and drug responses in bipolar disorder (BD). However, there has been notably limited research on biomarkers specifically linked to valproate, with only a few studies investigating integrated proteomic and genomic factors in response to valproate treatment. Therefore, this study aimed to identify biological markers for the therapeutic response to valproate treatment in BD. Patients with BD in remission were assessed only at baseline, whereas those experiencing acute mood episodes were evaluated at three points (baseline, 8 ± 2 weeks, and 6 ± 1 months). The response to valproate treatment was measured using the Alda scale, with individuals scoring an Alda A score ≥ 5 categorized into the acute-valproate responder (acute-VPAR) group. We analyzed 158 peptides (92 proteins) from peripheral blood samples using multiple reaction monitoring mass spectrometry, and proteomic result-guided candidate gene association analyses, with 1,627 single nucleotide variants (SNVs), were performed using the Korean chip.

RESULTS

The markers of 37 peptides (27 protein) showed temporal upregulation, indicating possible association with response to valproate treatment. A total of 58 SNVs in 22 genes and 37 SNVs in 16 genes showed nominally significant associations with the Alda A continuous score and the acute-VPAR group, respectively. No SNVs reached the genome-wide significance threshold; however, three SNVs (rs115788299, rs11563197, and rs117669164) in the secreted phosphoprotein 2 gene reached a gene-based false discovery rate-corrected significance threshold with response to valproate treatment. Significant markers were associated with the pathophysiological processes of bipolar disorders, including the immune response, acute phase reaction, and coagulation cascade. These results suggest that valproate effectively suppresses mechanisms associated with disease progression.

CONCLUSIONS

The markers identified in this study could be valuable indicators of the underlying mechanisms associated with response to valproate treatment.

Function of GSK‑3 signaling in spinal cord injury (Review)

Spinal cord injury (SCI) is a major social problem with a heavy burden on patient physiology and psychology. Glial scar formation and irreversible neuron loss are the two key points during SCI progression. During the acute phase of spinal cord injury, glial scars form, limiting the progression of inflammation. However, in the subacute or chronic phase, glial scarring inhibits axon regeneration. Following spinal cord injury, irreversible loss of neurons leads to further aggravation of spinal cord injury. Several therapies have been developed to improve either glial scar or neuron loss; however, few therapies reach the stage of clinical trials and there are no mainstream therapies for SCI. Exploring the key mechanism of SCI is crucial for finding further treatments. Glycogen synthase kinase-3 (GSK-3) is a widely expressed kinase with important physiological and pathophysiological functions in vivo. Dysfunction of the GSK-3 signaling pathway during SCI has been widely discussed for controlling neurite growth in vitro and in vivo, improving the proliferation and neuronal differentiation of endogenous neural stem cells and functional recovery from spinal cord injury. SCI can decrease the phosphorylated (p)/total (t)-GSK-3β ratio, which leads to an increase in apoptosis, whereas treatment with GSK-3 inhibitors can promote neurogenesis. In addition, several therapies for the treatment of SCI involve signaling pathways associated with GSK-3. Furthermore, signaling pathways associated with GSK-3 also participate in the pathological process of neuropathic pain that remains following SCI. The present review summarized the roles of GSK-3 signaling in SCI to aid in the understanding of GSK-3 signaling during the pathological processes of SCI and to provide evidence for the development of comprehensive treatments.

[6]-Shogaol and [6]-Gingerol active ingredients may improve neuropathic pain by suppressing cytokine levels in an experimental model

Background/aim

Neuropathic pain (NP) is a type of chronic pain usually caused by damage to the somatosensory system. Bioactive antioxidant compounds, such as curcumin and ginger, are widely preferred in the treatment of NP. However, the ingredient-based mechanism that underlies their pain-relieving activity remains unknown. The aim of this study was to investigate the therapeutic effects of trans-[6]-Shogaol and [6]-Gingerol active ingredients of the Zingiber officinale Roscoe extract on the spinal cord and cortex in the neuroinflammatory pathway in rats with experimental sciatic nerve injury.

Materials and methods

Forty-six volatile phenolic components were identified in ginger samples using gas chromatography-mass spectrometry analysis. Thirty 3-month-old male 250-300 g Wistar Albino rats were divided into three groups as (i) sham, (ii) chronic constriction injury (CCI), and (iii) CCI+ginger. NP was induced using the CCI model. A ginger extract treatment enriched with trans-[6]-shogaol and [6]-gingerol active ingredients was administered by gavage at 200 mg/kg/day for 7 days. On the 14th day of the experiment, locomotor activity was evaluated in open field and hyperalgesia in tail flick tests.

Results

In behavioural experiments, a significant decrease was observed in the CCI group compared to the sham group, while a significant increase was observed in the CCI+ginger group compared to the CCI group (p < 0.05). In the spinal cord and cortex tissues, there was a significant increase in the TNF-α, IL-1β, and IL-18 neuroinflammation results of the CCI group compared to the sham group, while there was a significant decrease in the CCI+ginger group compared to the CCI group.

Conclusion

In this study, ginger treatment was shown to have a therapeutic effect on neuroinflammation against sciatic nerve damage.

Mitochondrial transplantation attenuates traumatic neuropathic pain, neuroinflammation, and apoptosis in rats with nerve root ligation

Traumatic neuropathic pain (TNP) is caused by traumatic damage to the somatosensory system and induces the presentation of allodynia and hyperalgesia. Mitochondrial dysfunction, neuroinflammation, and apoptosis are hallmarks in the pathogenesis of TNP. Recently, mitochondria-based therapy has emerged as a potential therapeutic intervention for diseases related to mitochondrial dysfunction. However, the therapeutic effectiveness of mitochondrial transplantation (MT) on TNP has rarely been investigated. Here, we validated the efficacy of MT in treating TNP. Both in vivo and in vitro TNP models by conducting an L5 spinal nerve ligation in rats and exposing the primary dorsal root ganglion (DRG) neurons to capsaicin, respectively, were applied in this study. The MT was operated by administrating 100 µg of soleus-derived allogeneic mitochondria into the ipsilateral L5 DRG in vivo and the culture medium in vitro. Results showed that the viable transplanted mitochondria migrated into the rats' spinal cord and sciatic nerve. MT alleviated the nerve ligation-induced mechanical and thermal pain hypersensitivity. The nerve ligation-induced glial activation and the expression of pro-inflammatory cytokines and apoptotic markers in the spinal cord were also repressed by MT. Consistently, exogenous mitochondria reversed the capsaicin-induced reduction of mitochondrial membrane potential and expression of pro-inflammatory cytokines and apoptotic markers in the primary DRG neurons in vitro. Our findings suggest that MT mitigates the spinal nerve ligation-induced apoptosis and neuroinflammation, potentially playing a role in providing neuroprotection against TNP.

Disruption of C/EBPβ-Clec7a axis exacerbates neuroinflammatory injury via NLRP3 inflammasome-mediated pyroptosis in experimental neuropathic pain

BACKGROUND

Growing evidence shows that C-Type Lectin Domain Containing 7A (Clec7a) may be involved into neuroinflammatory injury of various neurological diseases. However, its roles in neuropathic pain remain unclear.

METHODS

A chronic constriction injury (CCI) rat model was constructed, and gene expression profilings in spinal cord tissues of CCI-insulted rats were detected by both microarray and RNA-seq studies. A series of bioinformatics analyses identified C/EBPβ-Clec7a to be a candidate axis involved into neuropathic pain. Then, its roles in mechanical allodynia, and pathological and molecular changes during CCI progression were determined by various gain-of-function and loss-of-function experiments in vivo and in vitro.

RESULTS

Significant upregulation of Clec7a at both mRNA and protein levels were verified in spinal cord tissues of CCI-insulted rats. Clec7a knockdown markedly attenuated CCI-induced mechanical allodynia, obstructed Syk, ERK and JNK phosphorylation, inhibited NLRP3 inflammasome and caspase-1 activation, GSDMD cleavage, and consequently reduced the release of pro-inflammatory cytokines (all P < 0.05). Mechanically, the rat Clec7a promoter was predicted to bind with transcription factor C/EBPβ, confirmed by Luciferase assay and ChIP-qPCR. Both in vivo and in vitro assays demonstrated that C/EBPβ knockdown significantly suppressed CCI- or LPS/ATP-induced Clec7a upregulation, and subsequently reduced Syk, ERK and JNK phosphorylation, NLRP3 oligomerization, caspase-1 activation, GSDMD expression and pyroptosis, which were markedly reversed by the co-transfection of Clec7a expression vector.

CONCLUSIONS

This pre-clinical investigation reveals that C/EBPβ-Clec7a axis may be a potential target for relieving neuropathic pain through alleviating neuroinflammation, paving its way for clinical translation as a promising approach for neuropathic pain therapy.

scRNA-seq generates a molecular map of emerging cell subtypes after sciatic nerve injury in rats

Patients with peripheral nerve injury, viral infection or metabolic disorder often suffer neuropathic pain due to inadequate pharmacological options for relief. Developing novel therapies has been challenged by incomplete mechanistic understanding of the cellular microenvironment in sensory nerve that trigger the emergence and persistence of pain. In this study, we report a high resolution transcriptomics map of the cellular heterogeneity of naïve and injured rat sensory nerve covering more than 110,000 individual cells. Annotation reveals distinguishing molecular features of multiple major cell types totaling 45 different subtypes in naïve nerve and an additional 23 subtypes emerging after injury. Ligand-receptor analysis revealed a myriad of potential targets for pharmacological intervention. This work forms a comprehensive resource and unprecedented window into the cellular milieu underlying neuropathic pain and demonstrates that nerve injury is a dynamic process orchestrated by multiple cell types in both the endoneurial and epineurial nerve compartments.

The Function of NF-Kappa B During Epilepsy, a Potential Therapeutic Target

The transcriptional regulator nuclear factor kappa B (NF-κB) modulates cellular biological activity by binding to promoter regions in the nucleus and transcribing various protein-coding genes. The NF-κB pathway plays a major role in the expressing genes related to inflammation, including chemokines, interleukins, and tumor necrosis factor. It also transcribes genes that can promote neuronal survival or apoptosis. Epilepsy is one of the most common brain disorders and it not only causes death worldwide but also affects the day-to-day life of affected individuals. While epilepsy has diverse treatment options, there remain patients who are not sensitive to the existing treatment methods. Recent studies have implicated the critical role of NF-κB in epilepsy. It is upregulated in neurons, glial cells, and endothelial cells, due to neuronal loss, glial cell proliferation, blood-brain barrier dysfunction, and hippocampal sclerosis through the glutamate and γ-aminobutyric acid imbalance, ion concentration changes, and other mechanisms. In this review, we summarize the functional changes caused by the upregulation of NF-κB in the central nervous system during different periods after seizures. This review is the first to deconvolute the complicated functions of NF-κB, and speculate that the regulation of NF-κB can be a safe and effective treatment strategy for epilepsy.

Mild Hypophagia and Associated Changes in Feeding-Related Gene Expression and c-Fos Immunoreactivity in Adult Male Rats with Sodium Valproate-Induced Autism

A core yet understudied symptom of autism is aberrant eating behaviour, including extremely narrow food preferences. Autistic individuals often refuse to eat despite hunger unless preferred food is given. We hypothesised that, apart from aberrant preference, underfeeding stems from abnormal hunger processing. Utilising an adult male VPA rat, a model of autism, we examined intake of ‘bland’ chow in animals maintained on this diet continuously, eating this food after fasting and after both food and water deprivation. We assessed body weight in adulthood to determine whether lower feeding led to slower growth. Since food intake is highly regulated by brain processes, we looked into the activation (c-Fos immunoreactivity) of central sites controlling appetite in animals subjected to food deprivation vs. fed ad libitum. Expression of genes involved in food intake in the hypothalamus and brain stem, regions responsible for energy balance, was measured in deprived vs. sated animals. We performed our analyses on VPAs and age-matched healthy controls. We found that VPAs ate less of the ‘bland’ chow when fed ad libitum and after deprivation than controls did. Their body weight increased more slowly than that of controls when maintained on the ‘bland’ food. While hungry controls had lower c-Fos IR in key feeding-related areas than their ad libitum-fed counterparts, in hungry VPAs c-Fos was unchanged or elevated compared to the fed ones. The lack of changes in expression of feeding-related genes upon deprivation in VPAs was in contrast to several transcripts affected by fasting in healthy controls. We conclude that hunger processing is dysregulated in the VPA rat.

Antinociceptive and Antipruritic Effects of HSK21542, a Peripherally-Restricted Kappa Opioid Receptor Agonist, in Animal Models of Pain and Itch

Kappa opioid receptor (KOR) agonists have been promising therapeutic candidates, owing to their potential for relieving pain and treating intractable pruritus. Although lacking morphine-like central nervous system (CNS) effects, KOR agonists do elicit sedation, dysphoria and diuresis which seriously impede their development. Peripherally-restricted KOR agonists have a poor ability to penetrate into the CNS system, so that CNS-related adverse effects can be ameliorated or even abolished. However, the only approved peripherally-restricted KOR agonist CR845 remains some frequent CNS adverse events. In the present study, we aim to address pharmacological profiles of HSK21542, with an expectation to provide a safe and effective alternative for patients who are suffering from pain and pruritus. The in vitro experimental results showed that HSK21542 was a selective and potent KOR agonist with higher potency than CR845, and had a brain/plasma concentration ratio of 0.001, indicating its peripheral selectivity. In animal models of pain, HSK21542 significantly inhibited acetic acid-, hindpaw incision- or chronic constriction injury-induced pain-related behaviors, and the efficacy was comparable to CR845 at 15 min post-dosing. HSK21542 had a long-lasting analgesic potency with a median effective dose of 1.48 mg/kg at 24 h post-drug in writhing test. Meanwhile, the antinociceptive activity of HSK21542 was effectively reversed by a KOR antagonist nor-binaltorphimine. In addition, HSK21542 had powerful antipruritic activities in compound 48/80-induced itch model. On the other hand, HSK21542 had a weak ability to produce central antinociceptive effects in a hot-plate test and fewer effects on the locomotor activity of mice. HSK21542 didn't affect the respiratory rate of mice. Therefore, HSK21542 might be a safe and effective KOR agonist and promising candidate for treating pain and pruritus.

Fumagillin Attenuates Spinal Angiogenesis, Neuroinflammation, and Pain in Neuropathic Rats after Chronic Constriction Injury

Introduction: Angiogenesis in the central nervous system is visible in animal models of neuroinflammation and bone cancer pain. However, whether spinal angiogenesis exists and contributes to central sensitization in neuropathic pain remains unclear. This study analyzes the impact of angiogenesis on spinal neuroinflammation in neuropathic pain. Methods: Rats with chronic constriction injury (CCI) to the sciatic nerve underwent the implantation of an intrathecal catheter. Fumagillin or vascular endothelial growth factor-A antibody (anti-VEGF-A) was administered intrathecally. Nociceptive behaviors, cytokine immunoassay, Western blot, and immunohistochemical analysis assessed the effect of angiogenesis inhibition on CCI-induced neuropathic pain. Results: VEGF, cluster of differentiation 31 (CD31), and von Willebrand factor (vWF) expressions increased after CCI in the ipsilateral lumbar spinal cord compared to that in the contralateral side of CCI and control rats from post-operative day (POD) 7 to 28, with a peak at POD 14. Tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-6 concentrations, but not IL-10 levels, also increased in the ipsilateral spinal cord after CCI. Fumagillin and anti-VEGF-A reduced CCI-induced thermal hyperalgesia from POD 5 to 14 and mechanical allodynia from POD 3 to 14. Fumagillin reduced CCI-upregulated expressions of angiogenic factors and astrocytes. Furthermore, fumagillin decreased TNF-α and IL-6 amounts and increased IL-10 levels at POD 7 and 14, but not IL-1β concentrations. Conclusions: Fumagillin significantly ameliorates CCI-induced nociceptive sensitization, spinal angiogenesis, and astrocyte activation. Our results suggest that angiogenesis inhibitor treatment suppresses peripheral neuropathy-induced central angiogenesis, neuroinflammation, astrocyte activation, and neuropathic pain.

Matrix metalloproteinases in the pathogenesis of dengue viral disease: Involvement of immune system and newer therapeutic strategies

Globally, the burden due to dengue infection is increasing with a recent estimate of 96 million progressing to the disease every year. Dengue pathogenesis and the factors influencing it are not completely known. It is now widely speculated that there is an important role of matrix metalloproteinases (MMPs) in the initiation and progression of dengue pathogenesis; however, their exact roles are not fully understood. Overactivation of matrix metalloproteinases may contribute to the severity of dengue pathogenesis. Cytokines and various other mediators of inflammation interact with the vascular endothelium and matrix metalloproteinases may be one of the components among them. Extensive plasma leakage into tissue spaces may result in a shock. It is evident in the literature that MMP2 and MMP9 increase in dengue patients is correlated with the severity of the disease; however, the underlying mechanism is still unknown. Activation of innate cells and adaptive immune cells which include, B and T cells, macrophages or monocytes and dendritic cells also contribute to the dengue pathology. Newer therapeutic strategies include microRNAs, such as miR-134 (targets MMP3 and MMP1) and MicroRNA-320d, (targets MMP/TIMP proteolytic system). The use of antibodies-based therapeutics like (Andecaliximab; anti-matrix metalloproteinase-9 antibody) is also suggested against MMPs in dengue. In this review, we summarize some recent developments associated with the involvement of immune cells and their mediators associated with the matrix metalloproteinases mediated dengue pathogenesis. We highlight that, there is still very little knowledge about the MMPs in dengue pathogenesis which needs attention and extensive investigations.

Systemic and cerebrospinal fluid immune and complement activation in Ugandan children and adolescents with long-standing nodding syndrome: A case-control study

OBJECTIVE

Nodding syndrome is a poorly understood epileptic encephalopathy characterized by a unique seizure type-head nodding-and associated with Onchocerca volvulus infection. We hypothesized that altered immune activation in the cerebrospinal fluid (CSF) and plasma of children with nodding syndrome may yield insights into the pathophysiology and progression of this seizure disorder.

METHOD

We conducted a case-control study of 154 children (8 years or older) with long-standing nodding syndrome and 154 healthy age-matched community controls in 3 districts of northern Uganda affected by nodding syndrome. Control CSF samples were obtained from Ugandan children in remission from hematological malignancy during routine follow-up. Markers of immune activation and inflammation (cytokines and chemokines) and complement activation (C5a) were measured in plasma and CSF using ELISA or Multiplex Luminex assays. O volvulus infection was assessed by serology for anti-OV-16 IgG levels.

RESULTS

The mean (SD) age of the population was 15.1 (SD: 1.9) years, and the mean duration of nodding syndrome from diagnosis to enrollment was 8.3 (SD: 2.7) years. The majority with nodding syndrome had been exposed to O volvulus (147/154 (95.4%)) compared with community children (86/154 (55.8%)), with an OR of 17.04 (95% CI: 7.33, 45.58), P < .001. C5a was elevated in CSF of children with nodding syndrome compared to controls (P < .0001). The levels of other CSF markers tested were comparable between cases and controls after adjusting for multiple comparisons. Children with nodding syndrome had lower plasma levels of IL-10, APRIL, CCL5 (RANTES), CCL2, CXCL13, and MMP-9 compared with community controls (P < .05 for all; multiple comparisons). Plasma CRP was elevated in children with nodding syndrome compared to community children and correlated with disease severity.

SIGNIFICANCE

Nodding syndrome is associated with exposure to O. volvulus. Compared to controls, children with long-standing symptoms of nodding syndrome show evidence of complement activation in CSF and altered immune activation in plasma.

Ameliorative effects of escin on neuropathic pain induced by chronic constriction injury of sciatic nerve

ETHNOPHARMACOLOGY RELEVANCE

Escin is a natural mixture of triterpene saponins extracted from the seeds of Aesculus wilsonii Rehd. And has been reported to possess the therapeutic effects against neuropathic pain (NP). However, the underlying mechanisms remain unclear.

AIM OF THE STUDY

The present study aimed to investigate the therapeutic effects and explore the underlying mechanisms of escin on rats of NP induced by chronic constriction injury (CCI) of sciatic nerve.

MATERIALS AND METHODS

Rats were treated with escin (7, 14, and 28 mg/kg, i. g.) daily from the third day after the surgery (day 0) for consecutive 14 days. Regular behavior and thermal threshold were measured on days 0, 3, 5, 7, 10 and 14. Investigations into mechanisms involved measurement of inflammatory factors and biochemical factors in dorsal root ganglion (DRG). Inflammatory pain responses and nerve injuries were induced by the CCI model. Tonic pain model and acute inflammatory model induced by formalin or carrageenan were established to evaluated the pharmacological effects of escin on acute inflammatory pain. Corresponding behaviors were monitored and relevant gene expression such as c-fos, mu opioid receptor (MOR) and KCNK1 were detected by qRT-PCR. Investigate the neuroprotective effects of escin on PC12 cell injury induced by lipopolysaccharide (LPS). Cell morphology was observed under inverted microscope and neuroprotective effect of escin on cell activity was assessed by MTT assay.

RESULTS

Escin could widen thermal threshold, downregulate the concentration of inflammatory factors like tumor necrosis factor (TNF)-α and interleukin (IL)-1β, suppress the gene expression of toll-like receptor 4 (TLR4), nuclear factor κB (NF-κB), decrease the level of glial fibrillary acidic protein (GFAP) and nerve growth factor (NGF) remarkably. In addition, escin significantly lowered the duration of licking, numbers of flinches and increase in paw edema, showing great therapeutic effects on inflammatory pain responses. Moreover, the activity of injured PC12 cells was significantly improved after escin administrated.

CONCLUSION

Escin exerted the ameliorative effects on NP induced by CCI which may be related to downregulating the release of pro-inflammatory cytokines, suppressing TLR-4/NF-κB signal pathway, thereafter decreasing the level of GFAP and NGF.

Combined treatment with valproic acid and estrogen has neuroprotective effects in ovariectomized mice with Alzheimer's disease

Postmenopausal women with Alzheimer’s disease (AD) exhibit dramatically reduced sensitivity to estrogen replacement therapy, which is though to be related to an estrogen receptor (ER)α/ERβ ratio imbalance arising from a significantly decreased level of ERs of the brain. The aim of our study was to investigate whether valproic acid (VPA) can enhance the beneficial effects of estrogen on cognitive function through restoration of ERα and ERβ expression in the brain. We removed the ovaries of female APP/PS1 mice to simulate the low estrogen levels present in postmenopausal women and then administered VPA (30 mg/kg, intraperitoneal injection, once daily), 17β-estradiol (E2) (2.4 μg, intraperitoneal injection, once daily), liquiritigenin (LG) (50 μg/kg, intragastric infusion, once daily), VPA + E2, or VPA + LG for 4 successive weeks. Compared with treatment with a single drug, treatment with VPA + E2 or VPA + LG significantly increased the level of glycogen synthase kinase 3β, increased the expression of estrogen receptor α, reduced the expression of small ubiquitin-like modifiers, and increased the level of estrogen receptor β. This resulted in enhanced sensitivity to estrogen therapy, reduced amyloid β aggregation, reduced abnormal phosphorylation of the tau protein, reduced neuronal loss, increased dendritic spine and postsynaptic density, and significantly alleviated memory loss and learning impairment in mice. This study was approved by the Chongqing Medical University Animal Protection and Ethics Committee, China on March 6, 2013.

HDAC1 Expression, Histone Deacetylation, and Protective Role of Sodium Valproate in the Rat Dorsal Root Ganglia After Sciatic Nerve Transection

Nerve injury is an important reason of human disability and death. We studied the role of histone deacetylation in the response of the dorsal root ganglion (DRG) cells to sciatic nerve transection. Sciatic nerve transection in the rat thigh induced overexpression of histone deacetylase 1 (HDAC1) in the ipsilateral DRG at 1-4 h after axotomy. In the DRG neurons, HDAC1 initially upregulated at 1 h but then redistributed from the nuclei to the cytoplasm at 4 h after axotomy. Histone H3 was deacetylated at 24 h after axotomy. Deacetylation of histone H4, accumulation of amyloid precursor protein, a nerve injury marker, and GAP-43, an axon regeneration marker, were observed in the axotomized DRG on day 7. Neuronal injury occurred on day 7 after axotomy along with apoptosis of DRG cells, which were mostly the satellite glial cells remote from the site of sciatic nerve transection. Administration of sodium valproate significantly reduced apoptosis not only in the injured ipsilateral DRG but also in the contralateral ganglion. It also reduced the deacetylation of histones H3 and H4, prevented axotomy-induced accumulation of amyloid precursor protein, which indicated nerve injury, and overexpressed GAP-43, a nerve regeneration marker, in the axotomized DRG. Therefore, HDAC1 was involved in the axotomy-induced injury of DRG neurons and glial cells. HDAC inhibitor sodium valproate demonstrated the neuroprotective activity in the axotomized DRG.

α-Linolenic Acid-Valproic Acid Conjugates: Toward Single-Molecule Polypharmacology for Multiple Sclerosis

Multiple sclerosis (MS) is a complex inflammatory, degenerative, and demyelinating disease of the central nervous system. Although treatments exist, MS cannot be cured by available drugs, which primarily target neuroinflammation. Thus, it is feasible that a well concerted polypharmacological approach able to act at multiple points within the intricate network of inflammation, neurodegeneration, and demyelination/remyelination pathways would succeed where other drugs have failed. Starting from reported beneficial effects of α-linolenic acid (ALA) and valproic acid (VPA) in MS, and by applying a rational strategy, we developed a small set of codrugs obtained by conjugating VPA and ALA through proper linkers. A cellular profiling identified 1 as a polypharmacological tool able not only to modulate microglia polarization, but also to counteract neurodegeneration and demyelination and induce oligodendrocyte precursor cell differentiation, by acting on multiple biochemical and epigenetic pathways.

Thymus algeriensis and Thymus fontanesii exert neuroprotective effect against chronic constriction injury-induced neuropathic pain in rats

We have previously demonstrated that the Thymus algeriensis and Thymus fontanesii extracts have powerful anti-inflammatory, antipyretic, and analgesic effects against acute pain models. We profiled their chemical composition and found many phenolic acids, flavonoids, and phenolic diterpenes. In this work, we investigated their antioxidant properties on HaCaT cells exposed to UVA-induced oxidative stress and examined their effects against chronic neuropathic pain and the underlying mechanisms. Through a rat chronic constriction injury (CCI) model, we induced chronic neuropathic pain by placing 4 loose ligatures around the right sciatic nerve for 14 days. Thermal and mechanical hyperalgesia in addition to cold and dynamic allodynia were tested on the day before surgery and on the 7th and 14th post-surgery days. Key markers of the nitrosative and oxidative stresses, in addition to markers of inflammation, were measured at day 14 post surgery. Histopathological examination and immunostaining of both synaptophysin and caspase-3 of sciatic nerve and brain stem were also performed. Results of this study showed that T. algeriensis extract suppresses UVA oxidative stress in HaCaT cells via activation of the Nrf-2 pathway. Both extracts attenuated hyperalgesia and allodynia at 7- and 14-days post-surgery with more prominent effects at day 14 of surgery. Their protective effects against neuropathic pain were mediated by inhibiting NOX-1, iNOS, by increasing the enzyme activity of catalase, and inhibition of inflammatory mediators, NF-κB, TNF-α, lipoxygenase, COX-2 enzymes, and PGE2. Furthermore, they improved deleterious structural changes of the brainstem and sciatic nerve. They also attenuated the increased caspase-3 and synaptophysin. The data indicate that both extracts have neuroprotective effects against chronic constriction injury-induced neuropathic pain. The observed protective effects are partially mediated through attenuation of oxidative and nitrosative stress and suppression of both neuroinflammation and neuronal apoptosis, suggesting substantial activities of both extracts in amelioration of painful peripheral neuropathy.

Berberine reduces neuroglia activation and inflammation in streptozotocin-induced diabetic mice

We aimed to analyze the action of berberine on the neuropathic pain and neuroglia activation in experimental diabetes mellitus (DM) model. Diabetes in mice was induced by intraperitoneal injection of streptozotocin (STZ) followed by the administration of berberine. Mechanical allodynia and thermal hyperalgesia and activations of microglia and astrocytes were evaluated. The levels of pro-inflammatory cytokines and protein expressions of inflammatory proteins were assessed by enzyme-linked immunosorbent assay (ELISA) and western blot, respectively. Our results revealed the anti-nociceptive effects of berberine in DM mice, supported by the improved mechanical threshold and thermal latency. In addition, berberine suppressed the activations of microglia and astrocytes in the spinal cords of diabetic mice. Berberine inhibited the expression of pro-inflammatory cytokines including tumor necrosis factor (TNF)-α, interleukin-6 (IL-6), and interleukin-1β (IL-1β), along with inflammatory proteins including iNOS and COX-2. Berberine suppressed neuropathic pain in STZ-induced diabetic mice, and this effect is related to the reduction on the neuroglia activation and inflammation associated with DM.

HDAC Inhibition by Valproic Acid Induces Neuroprotection and Improvement of PD-like Behaviors in LRRK2 R1441G Transgenic Mice

Parkinson’s disease (PD) is one of the late-onset neurodegenerative movement disorder. Major pathological markers of PD include progressive loss of dopaminergic neurons, Lewy body formation, genetic mutations, and environmental factors. Epigenetic regulation of specific gene expression via impaired histone acetylation is associated with neuronal dysfunction in various neurodegenerative diseases. In this study, we hypothesized that histone deacetylase (HDAC) inhibitor, valproic acid (VPA), can improve motor function by enhancing cell survival in PD genetic model mice with LRRK2 R1441G mutation. To address this question, we administered VPA in LRRK2 R1441G transgenic mice to determine whether VPA affects 1) histone acetylation and HDAC expression, 2) dopaminergic neuron survival, 3) inflammatory responses, 4) motor or non-motor symptoms. As results, VPA administration increased histone acetylation level and the number of tyrosine hydroxylase (TH) positive neurons in substantia nigra of LRRK2 R1441G mice. VPA reduced iba-1 positive activated microglia and the mRNA levels of pro-inflammatory marker genes in LRRK2 R1441G mice. In addition, VPA induced the improvement of PD-like motor and non-motor behavior in LRRK2 R1441G mice. These data suggest that the inhibition of HDAC can be further studied as potential future therapeutics for PD.

Morin Alleviates Vincristine-Induced Neuropathic Pain via Nerve protective Effect and Inhibition of NF-κB Pathway in Rats

Vincristine is a toxic chemotherapeutic agent which often triggers neuropathic pain through inflammation. Morin isolated from figs (Ficus carica) exerts anti-inflammatory and neuroprotective activities. We investigated whether morin ameliorates vincristine-induced neuropathic pain and the underlying mechanism. Vincristine was injected i.p. for 10 days (day 1-5 and day 8-12). Morin was orally administered every other day from day 1 to 21. The pain behaviors were determined by measuring paw withdrawal threshold (PWT) and paw withdrawal latency (PWL). The axons of sciatic nerves were stained with toluidine blue to study the histological abnormality. Function deficit of sciatic nerves was evaluated by sciatic functional index and the sciatic nerve conduction velocity. Neuronal excitability was assessed electrophysiologically and inflammatory mediators were detected using western blotting in dorsal root ganglia. The vincristine-induced reduction in PWT, PWL, and body weight gain was attenuated by morin. Morin restored the sciatic nerve deficits both histologically and functionally in vincristine-injected rats. The vincristine-induced neuronal hyperexcitability and increase in the expression of IL-6, NF-κB, and pNF-κB were abolished after morin administration. This study suggests that morin treatment suppressed vincristine-induced neuropathic pain by protecting the sciatic nerve and inhibiting inflammation through NF-κB pathway.