Modulation of oxidative stress and Ca(2+) mobilization through TRPM2 channels in rat dorsal root ganglion neuron by Hypericum perforatum

Pharmacological agents targeting transient receptor potential (TRP) channels in neuropathic pain: Preclinical and clinical status

Neuropathic pain generally affects 7-10% population worldwide and an estimated ∼1 in every 20 individuals in western countries suffer and burden to society. The most limiting factor with existing therapies includes dose escalation issues, off-target side effects and poor translation of randomized trials into clinical practice. Neuropathic pain is a broad term that comprises direct injury/damage to the central and/or peripheral nervous system, leads to maladaptive changes in neuronal as well as in non-neuronal cells, which further contributes to the spontaneous pain, sensory and motor deficit along with altered sensitivity towards the noxious as well as non-noxious stimulus. Transient receptor potential (TRP) channels are polymodal, non-specific cation channels that operate as biosensors to various mechanical and chemical stimuli, including hyperosmolarity, shear stress, heat, mechanical stretch, extracellular ATP, and other products of inflammation. Modulation of these channels leads to various physiological and pathophysiological manifestations at molecular and cellular levels, leading to diseases including neuropathic pain. There are several molecules targeting TRP channels for neuropathic pain in pre-clinical studies, clinical trials and in the market. This review highlights the critical involvement of various pharmacological modulators for TRP channels targeting neuropathic pain and their possible outcomes to harness the therapeutic potential of TRP channels.

Application Potential of Plant-Derived Medicines in Prevention and Treatment of Platinum-Induced Peripheral Neurotoxicity

As observed with other chemotherapeutic agents, the clinical application of platinum agents is a double-edged sword. Platinum-induced peripheral neuropathy (PIPN) is a common adverse event that negatively affects clinical outcomes and patients’ quality of life. Considering the unavailability of effective established agents for preventing or treating PIPN and the increasing population of cancer survivors, the identification and development of novel, effective interventions are the need of the hour. Plant-derived medicines, recognized as ideal agents, can not only help improve PIPN without affecting chemotherapy efficacy, but may also produce synergy. In this review, we present a brief summary of the mechanisms of platinum agents and PIPN and then focus on exploring the preventive or curative effects and underlying mechanisms of plant-derived medicines, which have been evaluated under platinum-induced neurotoxicity conditions. We identified 11 plant extracts as well as 17 plant secondary metabolites, and four polyherbal preparations. Their effects against PIPN are focused on oxidative stress and mitochondrial dysfunction, glial activation and inflammation response, and ion channel dysfunction. Also, ten clinical trials have assessed the effect of herbal products in patients with PIPN. The understanding of the molecular mechanism is still limited, the quality of clinical trials need to be further improved, and in terms of their efficacy, safety, and cost effectiveness studies have not provided sufficient evidence to establish a standard practice. But plant-derived medicines have been found to be invaluable sources for the development of natural agents with beneficial effects in the prevention and treatment of PIPN.

Analysis of Antidepressant Activity of Huang-Lian Jie-Du Decoction Through Network Pharmacology and Metabolomics

Depressive disorder is a common mental disorder characterized by depressed mood and loss of interest or pleasure. As the Herbal medicines are mainly used as complementary and alternative therapy for depression. This study aimed at exploring antidepressant activity of Huang-lian Jie-du Decoction (HLJDD), and evaluating active components and potential depression-associated targets. HLJDD was administered on chronic unpredictable mild stress-induced (CUMS) depressive mice. Behavior evaluation was performed through force swimming test (FST), novelty-suppressed feeding test (NSF), and open field test (OFT). Active components of HLJDD, potential targets, and metabolic pathways involved in depression were explored through systemic biology-based network pharmacology assay, molecular docking and metabonomics. FST assay showed that CUMS mice administered with HLJDD had significantly shorter immobility time compared with control mice. Further, HLJDD alleviated feeding latency of CUMS mice in NSFand increased moving distance and duration in OFT. In the following network pharmacology assay, thirty-eight active compounds in HLJDD were identified based on drug-like characteristics, and pharmacokinetics and pharmacodynamics profiles. Moreover, forty-eight molecular targets and ten biochemical pathways were uncovered through molecular docking and metabonomics. GRIN2B, DRD, PRKCA, HTR, MAOA, SLC6A4, GRIN2A, and CACNA1A are implicated in inhibition of depressive symptoms through modulating tryptophan metabolism, serotonergic and dopaminergic synaptic activities, cAMP signaling pathway, and calcium signaling pathway. Further network pharmacology-based analysis showed a correlation between HLJDD and tryptophan metabolism. A total of thirty-seven active compounds, seventy-six targets, and sixteen biochemical pathways were involved in tryptophan metabolism. These findings show that HLJDD acts on potential targets such as SLC6A4, HTR, INS, MAO, CAT, and FoxO, PI3K/Akt, calcium, HIF-1, and mTOR signaling pathways, and modulates serotoninergic and dopaminergic synaptic functions. In addition, metabonomics showed that tryptophan metabolism is the primary target for HLJDD in CUMS mice. The findings of the study show that HLJDD exhibited antidepressant effects. SLC6A4 and MAOA in tryptophan metabolism were modulated by berberine, baicalein, tetrahydroberberine, candicine and may be the main antidepressant targets for HLJDD.

Ion channels as potential redox sensors in lysosomes

Lysosomes are central organelles that recycle materials and energy to maintain intracellular homeostasis. Lysosomes are capable of sensing environmental cues such as nutrition to regulate their function accordingly. Whether lysosomes can sense redox signaling, however, was unclear. Here in this review, we summarized recent evidence of lysosomal ion channel as redox sensors for this organelle. We also discussed their roles in lysosomal diseases that features imbalanced redox.

Effects of Hypericum perforatum extract on oxaliplatin-induced neurotoxicity: in vitro evaluations

Hypericum perforatum L. has been used for centuries as a natural remedy for the treatment of many disorders. Neuropathic pain is a common side effect of oxaliplatin-based chemotherapy and often the cause of therapy discontinuation. Thanks to its anti-inflammatory and analgesic effects, the use of H. perforatum may be a novel therapeutic strategy for neuropathy. The aim of this paper was to evaluate the effect of H. perforatum hydrophilic extract on an in vitro model of oxaliplatin-induced neurotoxicity. The antioxidant potential of extract was first evaluated in cell-free models by the thiobarbituric acid-reactive substances assay and nitro blue tetrazolium oxidation test; the ability of H. perforatum extract to reduce oxaliplatin-induced caspase-3 activity in rat astrocytes and its potential interference with the cytotoxic effects of oxaliplatin in a colorectal cancer in vitro model (HT-29 cells) were also evaluated. The extract showed a significant antioxidant effect and was able to reduce caspase-3 activity in rat astrocytes. Of note, the extract alone exerted a cytotoxic effect in HT-29 cells and did not reduce the cytotoxicity of oxaliplatin in HT-29 cells. These data suggest that H. perforatum could be used as a novel therapeutic strategy for counteracting chemotherapy-induced neuropathy.

5-Fluorouracil-induced mitochondrial oxidative cytotoxicity and apoptosis are increased in MCF-7 human breast cancer cells by TRPV1 channel activation but not Hypericum perforatum treatment

5-Fluorouracil (5-FU) is a widely used chemotherapy agent for breast cancer, although drug resistance is a critical issue regarding the use of this agent in the disease. Calcium signaling is a well-known main cause of proliferation and apoptosis in breast cancer cells. Although previous studies have implicated TRPV1 inhibitor, anticancer, and apoptotic roles of Hypericum perforatum (HPer) in several cells, the synergistic inhibition effects of HPer and 5-FU in cancer and the stimulation of ongoing apoptosis have not yet been clarified in MCF-7 cells. Therefore, we investigated the apoptotic and antioxidant properties of 5-FU with/without HPer through activation of TRPV1 in MCF-7 cells. The MCF-7 cells were divided into four groups: the control group, the HPer-treated group (0.3 mM), the 5-FU-treated group (25 μM), and the 5-FU+HPer-treated group. The intracellular free calcium ion concentration ([Ca²⁺]_i) increased with 5-FU treatments, but they decreased with the HPer and HPer+5-FU treatments. The [Ca²⁺]_i is further decreased in the four groups by TRPV1 channel antagonist (capsazepine and 0.01 mM) treatments. However, mitochondrial membrane depolarization and apoptosis levels, and the PARP1, caspase 3, and caspase 9 expression levels were increased by 5-FU treatment, although the values were decreased by the HPer and 5-FU+HPer treatments. Cell viability level was also decreased by 5-FU treatment. In conclusion, antitumor and apoptosis effects of 5-FU are up-regulated by activation of TRPV1 channels, but its action was down-regulated by HPer treatment. It seems that HPer cannot be used for increasing the antitumor effect of 5-FU through modulation of the TRPV1.

Inhibition of the TRPM2 and TRPV1 Channels through Hypericum perforatum in Sciatic Nerve Injury-induced Rats Demonstrates their Key Role in Apoptosis and Mitochondrial Oxidative Stress of Sciatic Nerve and Dorsal Root Ganglion

Sciatic nerve injury (SNI) results in neuropathic pain, which is characterized by the excessive Ca²⁺ entry, reactive oxygen species (ROS) and apoptosis processes although involvement of antioxidant Hypericum perforatum (HP) through TRPM2 and TRPV1 activation has not been clarified on the processes in SNI-induced rat, yet. We investigated the protective property of HP on the processes in the sciatic nerve and dorsal root ganglion neuron (DRGN) of SNI-induced rats. The rats were divided into five groups as control, sham, sham+HP, SNI, and SNI+HP. The HP groups received 30 mg/kg HP for 4 weeks after SNI induction. TRPM2 and TRPV1 channels were activated in the neurons by ADP-ribose or cumene peroxide and capsaicin, respectively. The SNI-induced TRPM2 and TRPV1 currents and intracellular free Ca²⁺ and ROS concentrations were reduced by HP, N-(p-amylcinnamoyl) anthranilic acid (ACA), and capsazepine (CapZ). SNI-induced increase in apoptosis and mitochondrial depolarization in sciatic nerve and DRGN of SNI group were decreased by HP, ACA, and CapZ treatments. PARP-1, caspase 3 and 9 expressions in the sciatic nerve, DRGN, skin, and musculus piriformis of SNI group were also attenuated by HP treatment. In conclusion, increase of mitochondrial ROS, apoptosis, and Ca²⁺ entry through inhibition of TRPM2 and TRPV1 in the sciatic nerve and DRGN neurons were decreased by HP treatment. The results may be relevant to the etiology and treatment of SNI by HP.

Hypericum perforatum L. supplementation protects sciatic nerve injury-induced apoptotic, inflammatory and oxidative damage to muscle, blood and brain in rats

Objectives

This study was conducted to explore whether Hypericum perforatum L. (HPL) as a potent antioxidant protects against oxidative stress, cytokine production and caspase expression in muscle (soleus), brain and blood of sciatic nerve injury (SNI)-induced rats.

Methods

Thirty-five rats were equally divided into five groups. The first and second were used as untreated control and sham control groups, respectively. The third, fourth and fifth were sham + HPL, SNI and SNI + HPL groups, respectively. The third and fifth groups received 30 mg/kg HPL via gastric gavage for 28 days.

Key findings

High levels of muscle, brain and red blood cell (RBC) lipid peroxidation, plasma cytokine (TNF-α, IL-1β and IL-2), muscle PARP, caspase 3 and 9 expression levels were decreased by HPL treatments. Plasma glutathione peroxidase (GPx) activity, α-tocopherol and melatonin, muscle, brain and RBC reduced glutathione (GSH) concentrations were decreased by SNI induction, whereas their values were increased by HPL treatments. β-carotene and retinol concentrations did not change in the five groups.

Conclusion

HPL may play a role in preventing SNI-induced inflammatory, oxidative and apoptotic blood, muscle and brain damages through upregulation of the GSH and GPx values but downregulation of PARP, caspase level and cytokine production in SNI-induced rats.

Hypericum perforatum (St John's wort) beyond depression: A therapeutic perspective for pain conditions

ETHNOPHARMACOLOGICAL RELEVANCE

Hypericum perforatum L. (Hypericaceae), popularly called St. John's wort (SJW), has a rich historical background being one of the oldest used and most extensively investigated medicinal herbs. Many bioactivities and applications of SJW are listed in popular and in scientific literature, including antibacterial, antiviral, anti-inflammatory. In the last three decades many studies focused on the antidepressant activity of SJW extracts. However, several studies in recent years also described the antinociceptive and analgesic properties of SJW that validate the traditional uses of the plant in pain conditions.

AIM OF THE REVIEW

This review provides up-to-date information on the traditional uses, pre-clinical and clinical evidence on the pain relieving activity of SJW and its active ingredients, and focuses on the possible exploitation of this plant for the management of pain.

MATERIALS AND METHODS

Historical ethnobotanical publications from 1597 were reviewed for finding local and traditional uses. The relevant data on the preclinical and clinical effects of SJW were searched using various databases such as PubMed, Science Direct, Scopus, and Google Scholar. Plant taxonomy was validated by the database Plantlist.org.

RESULTS

Preclinical animal studies demonstrated the ability of low doses of SJW dry extracts (0.3% hypericins; 3-5% hyperforins) to induce antinociception, to relieve from acute and chronic hyperalgesic states and to augment opioid analgesia. Clinical studies (homeopathic remedies, dry extracts) highlighted dental pain conditions as a promising SJW application. In vivo and in vitro studies showed that the main components responsible for the pain relieving activity are hyperforin and hypericin. SJW analgesia appears at low doses (5-100mg/kg), minimizing the risk of herbal-drug interactions produced by hyperforin, a potent inducer of CYP enzymes.

CONCLUSION

Preclinical studies indicate a potential use of SJW in medical pain management. However, clinical research in this field is still scarce and the few studies available on chronic pain produced negative results. Prospective randomized controlled clinical trials performed at low doses are needed to validate its potential efficacy in humans.

Nitroxidative Signaling Mechanisms in Pathological Pain

Tissue injury can initiate bidirectional signaling between neurons, glia, and immune cells that creates and amplifies pain. While the ability for neurotransmitters, neuropeptides, and cytokines to initiate and maintain pain has been extensively studied, recent work has identified a key role for reactive oxygen and nitrogen species (ROS/RNS; nitroxidative species), including superoxide, peroxynitrite, and hydrogen peroxide. In this review we describe how nitroxidative species are generated after tissue injury and the mechanisms by which they enhance neuroexcitability in pain pathways. Finally, we discuss potential therapeutic strategies for normalizing nitroxidative signaling, which may also enhance opioid analgesia, to help to alleviate the enormous burden of pathological pain.

Hypericum perforatum (St. John's Wort) as a possible therapeutic alternative for the management of trigeminal neuralgia (TN) - A case report

Hypericum perforatum (St. John's Wort) is an alternative remedy used primarily for depression but also is used for rheumatism, gastroenteritis, headache and neuralgias. The mechanism of action of Hypericum perforatum comprehends a neurotransmitter inhibitory profile, and potential anti-inflammatory and anti-oxidant effects suggesting a role for pain management. In this case report, we describe a 53-year-old Hispanic female patient who came to our orofacial pain clinical service presenting with a history of trigeminal neuralgia (TN). The patient was not able to get an appointment soon enough and decided to take an over the counter homeopathic preparation of Hypericum perforatum since she found on the internet that it was effective for nerve pain. The patient responded dramatically to the Hypericum perforatum preparation. The use of this homeopathic preparation relieved completely the TN pain. The management of TN is often a challenge. Hypericum perforatum may be a promising therapeutic option for TN that deserves to be explored further to solidly support its use in the clinical setting.

Advanced oxidation protein products sensitized the transient receptor potential vanilloid 1 via NADPH oxidase 1 and 4 to cause mechanical hyperalgesia

Oxidative stress is a possible pathogenesis of hyperalgesia. Advanced oxidation protein products (AOPPs), a new family of oxidized protein compounds, have been considered as a novel marker of oxidative stress. However, the role of AOPPs in the mechanism of hyperalgesia remains unknown. Our study aims to investigate whether AOPPs have an effect on hyperalgesia and the possible underlying mechanisms. To identify the AOPPs involved, we induced hyperalgesia in rats by injecting complete Freund's adjuvant (CFA) in hindpaw. The level of plasma AOPPs in CFA-induced rats was 1.6-fold in comparison with what in normal rats (P<0.05). After intravenous injection of AOPPs-modified rat serum albumin (AOPPs-RSA) in Sprague-Dawley rats, the paw mechanical thresholds, measured by the electronic von Frey system, significantly declined. Immunofluorescence staining indicated that AOPPs increased expressions of NADPH oxidase 1 (Nox1), NADPH oxidase 4 (Nox4), transient receptor potential vanilloid 1 (TRPV1) and calcitonin gene-related peptide (CGRP) in the dorsal root ganglia (DRG) tissues. In-vitro studies were performed on primary DRG neurons which were obtained from both thoracic and lumbar DRG of rats. Results indicated that AOPPs triggered reactive oxygen species (ROS) production in DRG neurons, which were significantly abolished by ROS scavenger N-acetyl-l-cysteine (NAC) and small-interfering RNA (siRNA) silencing of Nox1 or Nox4. The expressions of Nox1, Nox4, TRPV1 and CGRP were significantly increased in AOPPs-induced DRG neurons. And relevant siRNA or inhibitors notably suppressed the expressions of these proteins and the calcium influxes in AOPPs-induced DRG neurons. In conclusion, AOPPs increased significantly in CFA-induced hyperalgesia rats and they activated Nox1/Nox4-ROS to sensitize TRPV1-dependent Ca2+ influx and CGRP release which led to inducing mechanical hyperalgesia.

Psychiatric Disorders and TRP Channels: Focus on Psychotropic Drugs

Psychiatric and neurological disorders are mostly associated with the changes in neural calcium ion signaling pathways required for activity-triggered cellular events. One calcium channel family is the TRP cation channel family, which contains seven subfamilies. Results of recent papers have discovered that calcium ion influx through TRP channels is important. We discuss the latest advances in calcium ion influx through TRP channels in the etiology of psychiatric disorders. Activation of TRPC4, TRPC5, and TRPV1 cation channels in the etiology of psychiatric disorders such as anxiety, fear-associated responses, and depression modulate calcium ion influx. Evidence substantiates that anandamide and its analog (methanandamide) induce an anxiolytic-like effect via CB1 receptors and TRPV1 channels. Intracellular calcium influx induced by oxidative stress has an significant role in the etiology of bipolar disorders (BDs), and studies recently reported the important role of TRP channels such as TRPC3, TRPM2, and TRPV1 in converting oxidant or nitrogen radical signaling to cytosolic calcium ion homeostasis in BDs. The TRPV1 channel also plays a function in morphine tolerance and hyperalgesia. Among psychotropic drugs, amitriptyline and capsazepine seem to have protective effects on psychiatric disorders via the TRP channels. Some drugs such as cocaine and methamphetamine also seem to have an important role in alcohol addiction and substance abuse via activation of the TRPV1 channel. Thus, we explore the relationships between the etiology of psychiatric disorders and TRP channel-regulated mechanisms. Investigation of the TRP channels in psychiatric disorders holds the promise of the development of new drug treatments.

Hypericum Perforatum Hydroalcoholic Extract Mitigates Motor Dysfunction and is Neuroprotective in Intrastriatal 6-Hydroxydopamine Rat Model of Parkinson's Disease

Parkinson's disease is the second most common neurodegenerative disorder with selective and progressive decline of nigral dopaminergic neurons. Hypericum perforatum L. (H. perforatum, St. John's wort) has been traditionally used for management of different disorders, especially mild-to-moderate depression. This study was conducted to evaluate the effect of H. perforatum extract against unilateral striatal 6-hydroxydopamine (6-OHDA) toxicity and to unmask some involved mechanisms. Intrastriatal 6-OHDA-lesioned rats were treated with H. perforatum hydroalcoholic extract at a dose of 200 mg/kg/day started 1 week pre-surgery for 1 week post-surgery. The extract attenuated apomorphine-induced rotational behavior, decreased the latency to initiate and the total time on the narrow beam task, lowered striatal level of malondialdehyde and enhanced striatal catalase activity and reduced glutathione content, normalized striatal expression of glial fibrillary acidic protein, tumor necrosis factor α with no significant effect on mitogen-activated protein kinase, lowered nigral DNA fragmentation, and prevented damage of nigral dopaminergic neurons with a higher striatal tyrosine hydroxylase immunoreactivity. These findings reveal the beneficial effect of H. perforatum via attenuation of DNA fragmentation, astrogliosis, inflammation, and oxidative stress.

Diabetes enhances oxidative stress-induced TRPM2 channel activity and its control by N-acetylcysteine in rat dorsal root ganglion and brain

N-acetylcysteine (NAC) is a sulfhydryl donor antioxidant that contributes to the regeneration of glutathione (GSH) and also scavengers via a direct reaction with free oxygen radicals. Recently, we observed a modulatory role of NAC on GSH-depleted dorsal root ganglion (DRG) cells in rats. NAC may have a protective role on oxidative stress and calcium influx through regulation of the TRPM2 channel in diabetic neurons. Therefore, we investigated the effects of NAC on DRG TRPM2 channel currents and brain oxidative stress in streptozotocin (STZ)-induced diabetic rats. Thirty-six rats divided into four groups: control, STZ, NAC and STZ + NAC. Diabetes was induced in the STZ and STZ + NAC groups by intraperitoneal STZ (65 mg/kg) administration. After the induction of diabetes, rats in the NAC and STZ + NAC groups received NAC (150 mg/kg) via gastric gavage. After 2 weeks, DRG neurons and the brain cortex were freshly isolated from rats. In whole-cell patch clamp experiments, TRPM2 currents in the DRG following diabetes induction with STZ were gated by H2O2. TRPM2 channel current densities in the DRG and lipid peroxidation levels in the DRG and brain were higher in the STZ groups than in controls; however, brain GSH, GSH peroxidase (GSH-Px), vitamin C and vitamin E concentrations and DRG GSH-Px activity were decreased by diabetes. STZ + H2O2-induced TRPM2 gating was totally inhibited by NAC and partially inhibited by N-(p-amylcinnamoyl) anthranilic acid (ACA) and 2-aminoethyl diphenylborinate (2-APB). GSH-Px activity and lipid peroxidation levels were also attenuated by NAC treatment. In conclusion, we observed a modulatory role of NAC on oxidative stress and Ca(2+) entry through the TRPM2 channel in the diabetic DRG and brain. Since excessive oxidative stress and overload Ca(2+) entry are common features of neuropathic pain, our findings are relevant to the etiology and treatment of pain neuropathology in DRG neurons.

Hypericum perforatum Attenuates Spinal Cord Injury-Induced Oxidative Stress and Apoptosis in the Dorsal Root Ganglion of Rats: Involvement of TRPM2 and TRPV1 Channels

Oxidative stress and cytosolic Ca(2+) overload have important roles on apoptosis in dorsal root ganglion (DRG) neurons after spinal cord injury (SCI). Hypericum perforatum (HP) has an antioxidant property in the DRGs due to its ability to modulate NADPH oxidase and protein kinase C pathways. We aimed to investigate the protective property of HP on oxidative stress, apoptosis, and Ca(2+) entry through transient receptor potential melastatin 2 (TRPM2) and transient receptor potential vanilloid 1 (TRPV1) channels in SCI-induced DRG neurons of rats. Rats were divided into four groups as control, HP, SCI, and SCI + HP. The HP groups received 30 mg/kg HP for three concessive days after SCI induction. The SCI-induced TRPM2 and TRPV1 currents and cytosolic free Ca(2+) concentration were reduced by HP. The SCI-induced decrease in glutathione peroxidase and cell viability values were ameliorated by HP treatment, and the SCI-induced increase in apoptosis, caspase 3, caspase 9, cytosolic reactive oxygen species (ROS) production, and mitochondrial membrane depolarization values in DRG of SCI group were overcome by HP treatment. In conclusion, we observed a protective role of HP on SCI-induced oxidative stress, apoptosis, and Ca(2+) entry through TRPM2 and TRPV1 in the DRG neurons. Our findings may be relevant to the etiology and treatment of SCI by HP. Graphical Abstract Possible molecular pathways of involvement of Hypericum perforatum (HP) on apoptosis, oxidative stress, and calcium accumulation through TRPM2 and TRPV1 channels in DRG neurons of SCI-induced rats. The TRPM2 channel is activated by ADP-ribose and oxidative stress through activation of ADP-ribose pyrophosphate although it was inhibited by N-(p-amylcinnamoyl) anthranilic acid (ACA) and 2-aminoethyl diphenylborinate (2APB). The TRPV1 channel is activated by oxidative stress and capsaicin and it is blocked by capsazepine. Injury in the DRG can result in augmented ROS release, leading to Ca(2+) uptake through TRPM2 and TRPV1 channels. Mitochondria were reported to accumulate Ca(2+), provided intracellular Ca(2+) rises, thereby leading to depolarization of mitochondrial membranes and release of apoptosis-inducing factors such as caspase 3 and caspase 9. HP via regulation of NADPH oxidase and PKC inhibits TRPM2 and TRPV1 channels. The molecular pathway may be a cause of SCI-induced pain and neuronal death, and the subject should be urgently investigated.

The role of TRPM2 in hydrogen peroxide-induced expression of inflammatory cytokine and chemokine in rat trigeminal ganglia

Trigeminal ganglia (TG) contain neuronal cell bodies surrounded by satellite glial cells. Although peripheral injury is well known to induce changes in gene expression within sensory ganglia, detailed mechanisms whereby peripheral injury leads to gene expression within sensory ganglia are not completely understood. Reactive oxygen species (ROS) are an important modulator of hyperalgesia, but the role of ROS generated within sensory ganglia is unclear. Since ROS are known to affect transcription processes, ROS generated within sensory ganglia could directly influence gene expression and induce cellular changes at the soma level. In this study, we hypothesized that peripheral inflammation leads to cytokine and chemokine production and ROS generation within TG and that transient receptor potential melastatin (TRPM2), a well known oxidative sensor, contributes to ROS-induced gene regulation within TG. The masseter injection of complete Freund's adjuvant (CFA) resulted in a significantly elevated level of ROS within TG of the inflamed side with a concurrent increase in cytokine expression in TG. Treatment of TG cultures with H2O2 significantly up-regulated mRNA and protein levels of cytokine/chemokine such as interleukin 6 (IL-6) and chemokine (C-X-C motif) ligand 2 (CXCL2). TRPM2 was expressed in both neurons and non-neuronal cells in TG, and pretreatment of TG cultures with 2-aminoethoxydiphenyl borate (2-APB), an inhibitor of TRPM2, or siRNA against TRPM2 attenuated H2O2-induced up-regulation of IL-6 and CXCL2. These results suggested that activation of TRPM2 could play an important role in the modulation of cytokine/chemokine expression within TG under oxidative stress and that such changes may contribute to amplification of nociceptive signals leading to pathological pain conditions.

Wogonin prevents rat dorsal root ganglion neurons death via inhibiting tunicamycin-induced ER stress in vitro

Wogonin is a natural flavonoid isolated from the root of Scutellaria baicalensis Georgi, which has been widely used in various research areas for its anti-oxidant, anti-inflammatory, and anti-cancer activities. It also presents a neuroprotective effect in the brain while encounters stress conditions, but the mechanisms controlling the neuroprotective effect of wogonin are not clear. In this study, we investigated the biomechanism underlying the neuroprotective effect of wogonin on rat dorsal root ganglion (DRG) neurons. Wogonin pre-treatment at 75 μM significantly increased the cell viability of DRG neurons and decreased the number of the propidium iodide-positive DRG neurons before the endoplasmic reticulum (ER) stress is being induced by tunicamycin (TUN) (0.75 μg/mL). In addition, Wogonin also inhibited the release of LDH and up-regulated the level of GSH. Furthermore, wogonin decreased the activation of ER stress-related molecules, including glucose-regulated protein 78 (GRP78), GRP94, C/EBP-homologous protein, active caspase12 and active caspase3, phosphorylation of pancreatic ER stress kinase, and eukaryotic initiation factor 2 alpha (eIF2α). In summary, our results indicated that wogonin could protect DRG neurons against TUN-induced ER stress.

Protective effects of riboflavin and selenium on brain microsomal Ca2+-ATPase and oxidative damage caused by glyceryl trinitrate in a rat headache model

Migraine headaches are considered to be associated with increased mitochondrial energy metabolism. Mitochondrial oxidative stress is also important in migraine headache pathophysiology although riboflavin and selenium (Se) induced a modulator role on mitochondrial oxidative stress in the brain. The current study aimed to determine the effects of Se with/without riboflavin on the microsomal membrane Ca(2+)-ATPase (MMCA), lipid peroxidation, antioxidant, and electroencephalography (EEG) values in glyceryl trinitrate (GTN)-induced brain injury rats. Thirty-two rats were randomly divided into four groups. The first group was used as the control, and the second group was the GTN group. Se and Se plus oral riboflavin were administered to rats constituting the third and fourth groups for 10 days prior to GTN administration. The second, third, and fourth groups received GTN to induce headache. Ten hours after the administration of GTN, the EEG records and brain cortex samples were obtained for all groups. Brain cortex microsomes were obtained from the brain samples. The brain and microsomal lipid peroxidation levels were higher in the GTN group compared to the control group, whereas they were decreased by selenium and selenium + riboflavin treatments. Vitamin A, vitamin C, vitamin E, and reduced glutathione (GSH) concentrations of the brain and MMCA, GSH and glutathione peroxidase values of microsomes were decreased by the GTN administration, although the values and β-carotene concentrations were increased by Se and Se + riboflavin treatments. There was no significant change in EEG records of the four groups. In conclusion, Se with/without riboflavin administration protected against GTN-induced brain oxidative toxicity by inhibiting free radicals and the modulation of MMCA activity and supporting the antioxidant redox system.

Reduction in traumatic brain injury-induced oxidative stress, apoptosis, and calcium entry in rat hippocampus by melatonin: Possible involvement of TRPM2 channels

Melatonin, which is a very effective reactive oxygen species (ROS) scavenger, acts through a direct reaction with free radicals. Ca(2+) entry induced by traumatic brain injury (TBI) has deleterious effects on human hippocampal function. TRPM2 is a Ca(2+) permeable non-selective channel in hippocampal neurons, and its activation of during oxidative stress has been linked to cell death. Despite the importance of oxidative stress in TBI, its role in apoptosis and Ca(2+) entry in TBI is poorly understood. Therefore, we tested the effects of melatonin on apoptosis, oxidative stress, and Ca(2+) entry through the TRPM2 channel in the hippocampal neurons of TBI-induced rats. Thirty-two rats were divided into the following four groups: control, melatonin, TBI, and TBI + melatonin groups. Melatonin (5 mg/kg body weight) was intraperitoneally given to animals in the melatonin group and the TBI + melatonin group after 1 h of brain trauma. Hippocampal neurons were freshly isolated from the four groups, incubated with a nonspecific TRPM2 blocker (2-aminoethyl diphenylborinate, 2-APB), and then stimulated with cumene hydroperoxide. Apoptosis, caspase-3, caspase-9, intracellular ROS production, mitochondrial membrane depolarization and intracellular free Ca(2+) ([Ca(2+)]i) values were high in the TBI group, and low in the TBI + melatonin group. The [Ca(2+)]i concentration was decreased in the four groups by 2-APB. In our TBI experimental model, TRPM2 channels were involved in Ca(2+) entry-induced neuronal death, and the negative modulation of the activity of this channel by melatonin pretreatment may account for the neuroprotective activity of TRPM2 channels against oxidative stress, apoptosis, and Ca(2+) entry.

Electromagnetic radiation (Wi-Fi) and epilepsy induce calcium entry and apoptosis through activation of TRPV1 channel in hippocampus and dorsal root ganglion of rats

Incidence rates of epilepsy and use of Wi-Fi worldwide have been increasing. TRPV1 is a Ca(2+) permeable and non-selective channel, gated by noxious heat, oxidative stress and capsaicin (CAP). The hyperthermia and oxidant effects of Wi-Fi may induce apoptosis and Ca(2+) entry through activation of TRPV1 channel in epilepsy. Therefore, we tested the effects of Wi-Fi (2.45 GHz) exposure on Ca(2+) influx, oxidative stress and apoptosis through TRPV1 channel in the murine dorsal root ganglion (DRG) and hippocampus of pentylentetrazol (PTZ)-induced epileptic rats. Rats in the present study were divided into two groups as controls and PTZ. The PTZ groups were divided into two subgroups namely PTZ + Wi-Fi and PTZ + Wi-Fi + capsazepine (CPZ). The hippocampal and DRG neurons were freshly isolated from the rats. The DRG and hippocampus in PTZ + Wi-Fi and PTZ + Wi-Fi + CPZ groups were exposed to Wi-Fi for 1 hour before CAP stimulation. The cytosolic free Ca(2+), reactive oxygen species production, apoptosis, mitochondrial membrane depolarization, caspase-3 and -9 values in hippocampus were higher in the PTZ group than in the control although cell viability values decreased. The Wi-Fi exposure induced additional effects on the cytosolic Ca(2+) increase. However, pretreatment of the neurons with CPZ, results in a protection against epilepsy-induced Ca(2+) influx, apoptosis and oxidative damages. In results of whole cell patch-clamp experiments, treatment of DRG with Ca(2+) channel antagonists [thapsigargin, verapamil + diltiazem, 2-APB, MK-801] indicated that Wi-Fi exposure induced Ca(2+) influx via the TRPV1 channels. In conclusion, epilepsy and Wi-Fi in our experimental model is involved in Ca(2+) influx and oxidative stress-induced hippocampal and DRG death through activation of TRPV1 channels, and negative modulation of this channel activity by CPZ pretreatment may account for the neuroprotective activity against oxidative stress.

Hypericum perforatum modulates apoptosis and calcium mobilization through voltage-gated and TRPM2 calcium channels in neutrophil of patients with Behcet's disease

Behcet's disease (BD) is a chronic, inflammatory, and multisystemic condition although its pathogenesis is uncertain. Main component of St. John's wort (Hypericum perforatum, HP) is hyperforin and induces antiinflammatory and antioxidant properties. We aimed to investigate effects of HP on oxidative stress, apoptosis, and cytosolic-free Ca²⁺ [Ca²⁺](i) concentration in neutrophil of BD patients. Nine new-diagnosed active patients with BD and nine control subjects were included in the study. Disease activity was considered by clinical findings. Neutrophil samples were obtained from the patients and controls. The neutrophils from patients were divided into three subgroups and were incubated with HP, voltage-gated calcium channel (VGCC) blockers, (verapamil+dilitiazem) and non-specific TRPM2 channel blocker (2-aminoethyl diphenylborinate, 2-APB), respectively. The neutrophils were stimulated by fMLP as a Ca²⁺-concentration agonist and oxidative stress former. Caspase-3, caspase-9, apoptosis, lipid peroxidation, and [Ca²⁺](i) values were high in the patient groups, although cell viability, glutathione (GSH), and glutathione peroxidase (GSH-Px) values were low in patient group. However, the [Ca²⁺](i), caspase-3, and caspase-9 values decreased markedly in patient+HP group although GSH and GSH-Px values increased in the group. The [Ca²⁺](i) concentration was also decreased in the patient group by V+D, 2-APB, and HP incubations. In conclusion, we observed the importance of neutrophil Ca²⁺ entry, apoptosis, and oxidative stress through gating VGCC and TRPM2 channels in the neutrophils in the pathogenesis and activation of the patients with BD. HP induced protective effects on oxidative stress by modulating Ca²⁺ influx in BD patients.