Resveratrol-decreased hyperalgesia mediated by the P2X7 receptor in gp120-treated rats

Phytochemical Modulation of Ion Channels in Oncologic Symptomatology and Treatment

Modern chemotherapies offer a broad approach to cancer treatment but eliminate both cancer and non-cancer cells indiscriminately and, thus, are associated with a host of side effects. Advances in precision oncology have brought about new targeted therapeutics, albeit mostly limited to a subset of patients with an actionable mutation. They too come with side effects and, ultimately, 'self-resistance' to the treatment. There is recent interest in the modulation of ion channels, transmembrane proteins that regulate the flow of electrically charged molecules in and out of cells, as an approach to aid treatment of cancer. Phytochemicals have been shown to act on ion channels with high specificity regardless of the tumor's genetic profile. This paper explores the use of phytochemicals in cancer symptom management and treatment.

Satellite glial cells in sensory ganglia play a wider role in chronic pain via multiple mechanisms

Satellite glial cells are unique glial cells that surround the cell body of primary sensory neurons. An increasing body of evidence suggests that in the presence of inflammation and nerve damage, a significant number of satellite glial cells become activated, thus triggering a series of functional changes. This suggests that satellite glial cells are closely related to the occurrence of chronic pain. In this review, we first summarize the morphological structure, molecular markers, and physiological functions of satellite glial cells. Then, we clarify the multiple key roles of satellite glial cells in chronic pain, including gap junction hemichannel Cx43, membrane channel Pannexin1, K channel subunit 4.1, ATP, purinergic P2 receptors, and a series of additional factors and their receptors, including tumor necrosis factor, glutamate, endothelin, and bradykinin. Finally, we propose that future research should focus on the specific sorting of satellite glial cells, and identify genomic differences between physiological and pathological conditions. This review provides an important perspective for clarifying mechanisms underlying the peripheral regulation of chronic pain and will facilitate the formulation of new treatment plans for chronic pain.

Progress in Pathological and Therapeutic Research of HIV-Related Neuropathic Pain

HIV-related neuropathic pain (HRNP) is a neurodegeneration that gradually develops during the long-term course of acquired immune deficiency syndrome (AIDS) and manifests as abnormal sock/sleeve-like symmetrical pain and nociceptive hyperalgesia in the extremities, which seriously reduces patient quality of life. To date, the pathogenesis of HRNP is not completely clear. There is a lack of effective clinical treatment for HRNP and it is becoming a challenge and hot spot for medical research. In this study, we conducted a systematic review of the progress of HRNP research in recent years including (1) the etiology, classification and clinical symptoms of HRNP, (2) the establishment of HRNP pathological models, (3) the pathological mechanisms underlying HRNP from three aspects: molecules, signaling pathways and cells, (4) the therapeutic strategies for HRNP, and (5) the limitations of recent HRNP research and the future research directions and prospects of HRNP. This detailed review provides new and systematic insight into the pathological mechanism of HRNP, which establishes a theoretical basis for the future exploitation of novel target drugs. HIV infection, antiretroviral therapy and opioid abuse contribute to the etiology of HRNP with symmetrical pain in both hands and feet, allodynia and hyperalgesia. The pathogenesis involves changes in cytokine expression, activation of signaling pathways and neuronal cell states. The therapy for HRNP should be patient-centered, integrating pharmacologic and nonpharmacologic treatments into multimodal intervention.

Spinal P2X4 Receptors Involved in Visceral Hypersensitivity of Neonatal Maternal Separation Rats

Recent studies have demonstrated the vital role of P2X4 receptors (a family of ATP-gated non-selective cation channels) in the transmission of neuropathic and inflammatory pain. In this study, we investigated the role of spinal P2X4 receptors in chronic functional visceral hypersensitivity of neonatal maternal separation (NMS) rats. A rat model of irritable bowel syndrome was established by neonatal maternal separation. Visceral sensitivity was assessed by recording the response of the external oblique abdominal muscle to colorectal distension. P2X4 receptor antagonist and agonist were administrated intrathecally. The expression of P2X4 receptor was examined by Western Blot and immunofluorescence. The effect of P2X4 receptor antagonist on expression of brain-derived neurotrophic factor (BDNF) was assessed by Western Blot. We found neonatal maternal separation enhanced visceral hypersensitivity and increased the expression of P2X4 receptor in spinal thoracolumbar and lumbosacral segments of rats. Pharmacological results showed that visceral sensitivity was attenuated after intrathecal injection of P2X4 receptor antagonist, 5-BDBD, at doses of 10 nM or 100 nM, while visceral sensitivity was enhanced after intrathecal injection of P2X4 receptor agonist C5-TDS at doses of 10 μM or 15 μM. In addition, the spinal expression of BDNF significantly increased in NMS rats and intrathecal injection of 5-BDBD significantly decreased the expression of BDNF especially in NMS rats. C5-TDS failed to increase EMG amplitude in the presence of ANA-12 in control rats. Our results suggested the spinal P2X4 receptors played an important role in visceral hypersensitivity of NMS rats through BDNF.

Plant-derived natural products targeting ion channels for pain

Chronic pain affects approximately one-fifth of people worldwide and reduces quality of life and in some cases, working ability. Ion channels expressed along nociceptive pathways affect neuronal excitability and as a result modulate pain experience. Several ion channels have been identified and investigated as potential targets for new medicines for the treatment of a variety of human diseases, including chronic pain. Voltage-gated channels Na⁺ and Ca²⁺ channels, K⁺ channels, transient receptor potential channels (TRP), purinergic (P2X) channels and acid-sensing ion channels (ASICs) are some examples of ion channels exhibiting altered function or expression in different chronic pain states. Pharmacological approaches are being developed to mitigate dysregulation of these channels as potential treatment options. Since natural compounds of plant origin exert promising biological and pharmacological properties and are believed to possess less adverse effects compared to synthetic drugs, they have been widely studied as treatments for chronic pain for their ability to alter the functional activity of ion channels. A literature review was conducted using Medline, Google Scholar and PubMed, resulted in listing 79 natural compounds/extracts that are reported to interact with ion channels as part of their analgesic mechanism of action. Most in vitro studies utilized electrophysiological techniques to study the effect of natural compounds on ion channels using primary cultures of dorsal root ganglia (DRG) neurons. In vivo studies concentrated on different pain models and were conducted mainly in mice and rats. Proceeding into clinical trials will require further study to develop new, potent and specific ion channel modulators of plant origin.

Neurological disorders of COVID-19: insights to applications of natural products from plants and microorganisms

In addition to the typical respiratory manifestations, various disorders including involvement of the nerve system have been detected in COVID-19 ranging from 22 to 36%. Although growing records are focusing on neurological aspects of COVID-19, the pathophysiological mechanisms and related therapeutic methods remain obscure. Considering the increased concerns of SARS-CoV-2 potential for more serious neuroinvasion conditions, the present review attempts to focus on the neuroprotective effects of natural compounds as the principle source of therapeutics inhibiting multiple steps of the SARS-CoV-2 infection cycle. The great majority of the natural products with anti-SARS-CoV-2 activity mainly inhibit the attachment, entry and gene expression rather than the replication, assembly, or release. Although microbial-derived natural products comprise 38.5% of the known natural products with neuroprotective effects following viral infection, the neuroprotective potential of the majority of microorganisms is still undiscovered. Among natural products, chrysin, huperzine A, ginsenoside Rg1, pterostilbene, and terrein have shown potent in vitro neuroprotective activity and can be promising for new or repurpose drugs for neurological complications of SARS-CoV-2.

Neuropathogenesis of HIV and emerging therapeutic targets

INTRODUCTION

HIV infection causes a wide range of neurological complications, many of which are among the most common complications of chronic HIV infection in the era of combined antiretroviral therapy. These neurological conditions arise due to complex interactions between HIV viral proteins and neuronal and glial cells that lead to the activation of various inflammatory and neurotoxic pathways across the nervous system.

AREAS COVERED

This review summarizes the current literature on the pathogenesis and clinical manifestations of neurological injuries associated with HIV in the brain, spinal cord, and peripheral nervous system. Molecular pathways relevant for possible therapeutic targets or advancements are emphasized. Gaps in knowledge and current challenges in therapeutic design are also discussed.

EXPERT OPINION

Several challenges exist in the development of therapeutic targets for HIV-associated cognitive impairments. However, recent developments in drug delivery systems and treatment strategies are encouraging. Treatments for HIV-associated pain and peripheral sensory neuropathies currently consist of symptomatic management, but a greater understanding of their pathogenesis can lead to the development of targeted molecular therapies and disease-modifying therapies. HIV-associated autonomic dysfunction may affect the course of systemic disease via disrupted neuro-immune interactions; however, more research is needed to facilitate our understanding of how these processes present clinically.

Bioactive compounds for neuropathic pain: An update on preclinical studies and future perspectives

Among different types of chronic pain, neuropathic pain (NP), arising from damage to the nervous system, including peripheral fibers and central neurons, is notoriously difficult to treat and affects 7-10% of the general population. Currently available treatment options for NP are limited and opioid analgesics have severe side effects and can result in opioid use disorder. Recent studies have exhibited the role of dietary bioactive compounds in the mitigation of NP. Here, we assessed the effects of commonly consumed bioactive compounds (ginger, curcumin, omega-3 polyunsaturated fatty acids, epigallocatechin gallate, resveratrol, soy isoflavones, lycopene, and naringin) on NP and NP-related neuroinflammation. Cellular studies demonstrated that these bioactive compounds reduce inflammation via suppression of NF-κB and MAPK signaling pathways that regulate apoptosis/cell survival, antioxidant, and anti-inflammatory responses. Animal studies strongly suggest that these regularly consumed bioactive compounds have a pronounced anti-NP effect as shown by decreased mechanical allodynia, mechanical hyperalgesia, thermal hyperalgesia, and cold hyperalgesia. The proposed molecular mechanisms include (1) the enhancement of neuron survival, (2) the reduction of neuronal hyperexcitability by activation of antinociceptive cannabinoid 1 receptors and opioid receptors, (3) the suppression of sodium channel current, and (4) enhancing a potassium outward current in NP-affected animals, triggering a cascade of chemical changes within, and between neurons for pain relief. Human studies administered in this area have been limited. Future randomized controlled trials are warranted to confirm the findings of preclinical efficacies using bioactive compounds in patients with NP.

The role of Pannexin-1 channels and extracellular ATP in the pathogenesis of the human immunodeficiency virus

Only recently, the role of large ionic channels such as Pannexin-1 channels and Connexin hemichannels has been implicated in several physiological and pathological conditions, including HIV infection and associated comorbidities. These channels are in a closed stage in healthy conditions, but in pathological conditions including HIV, Pannexin-1 channels and Connexin hemichannels become open. Our data demonstrate that acute and chronic HIV infection induces channel opening (Pannexin and Connexin channels), ATP release into the extracellular space, and subsequent activation of purinergic receptors in immune and non-immune cells. We demonstrated that Pannexin and Connexin channels contribute to HIV infection and replication, the long-term survival of viral reservoirs, and comorbidities such as NeuroHIV. Here, we discuss the available data to support the participation of these channels in the HIV life cycle and the potential therapeutic approach to prevent HIV-associated comorbidities.

Targeting P2 receptors in purinergic signaling: a new strategy of active ingredients in traditional Chinese herbals for diseases treatment

Adenosine triphosphate (ATP) and its metabolites adenosine diphosphate, adenosine monophosphate, and adenosine in purinergic signaling pathway play important roles in many diseases. Activation of P2 receptors (P2R) channels and subsequent membrane depolarization can induce accumulation of extracellular ATP, and furtherly cause kinds of diseases, such as pain- and immune-related diseases, cardiac dysfunction, and tumorigenesis. Active ingredients of traditional Chinese herbals which exhibit superior pharmacological activities on diversified P2R channels have been considered as an alternative strategy of disease treatment. Experimental evidence of potential ingredients in Chinese herbs targeting P2R and their pharmacological activities were outlined in the study.

Resveratrol rescued the pain related hypersensitivity for Cntnap2-deficient mice

Contactin-associated protein-like 2 (CNTNAP2 or CASPR2) is a neuronal transmembrane protein of the neurexin superfamily which is correlated with pain related hypersensitivity. Recent results indicated that the hyperactive phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling pathway may be a promising therapeutic target for pain-related hypersensitivity in patients with dysfunction of CNTNAP2. Resveratrol is one of the most widely studied polyphenols with several beneficial properties. In the present study, we investigated the effects of resveratrol on the pain related hypersensitivity. And we found that the up-regulated phosphorylation of S6 could be suppressed by resveratrol. The nocifensive behavior duration time to heat and chemical algogens stimulation in Cntnap2-deficiency (Cntnap2-/-) mice could be attenuated by resveratrol. Our results indicated that resveratrol could rescue the pain related hypersensitivity for Cntnap2-/- mice may be via mTOR signaling pathway.

Compounds of traditional Chinese medicine and neuropathic pain

Neuropathic pain (NP) has become a serious global health issue and a huge clinical challenge without available effective treatment. P2 receptors family is involved in pain transmission and represents a promising target for pharmacological intervention. Traditional Chinese medicine (TCM) contains multiple components which are effective in targeting different pathological mechanisms involved in NP. Different from traditional analgesics, which target a single pathway, TCMs take the advantage of multiple components and multiple targets, and can significantly improve the efficacy of treatment and contribute to the prediction of the risks of NP. Compounds of TCM acting at nucleotide P2 receptors in neurons and glial cells could be considered as a potential research direction for moderating neuropathic pain. This review summarized the recently published data and highlighted several TCMs that relieved NP by acting at P2 receptors.

The Actions and Mechanisms of P2X7R and p38 MAPK Activation in Mediating Bortezomib-Induced Neuropathic Pain

The proteasome inhibitor bortezomib (BTZ) is a potent first-line anticancer drug for multiple myeloma; nonetheless, it induced peripheral neuropathy. It has been suggested that many cytokines may play a role in mediating neuropathic pain, but the underlying molecular mechanism is not fully understood. Recent studies have shown that neuropathic pain is closely related to the purinergic ligand-gated ion channel 7 receptor (P2X7R), one of the P2X receptors, which is richly expressed in glial cells. P2X7-p38 pathway is correlated with microglia- and satellite glial cell- (SGC-) mediated neuropathic pain. However, the association of P2X7R and p38MAPK in mediating BTZ-induced neuropathic pain remains unclear. In this study, the relationship between P2X7R activation and p38 phosphorylation in the dorsal root ganglion (DRG) and spinal dorsal horn (SDH) in the development and maintenance of BTZ-induced neuropathic pain was elucidated. The results showed that BTZ increased mechanical thresholds in rats, accompanied with upregulation of P2X7R expression and p38MAPK phosphorylation, indicating that P2X7R and p38MAPK are key molecules in the development and maintenance of BTZ-induced neuropathic pain. Inhibiting p38MAPK phosphorylation with SB203580 resulted in downregulation of P2X7R expression levels. Inhibition of P2X7R with Brilliant Blue G (BBG) reversed neuropathic pain might decrease through the expression of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-6 via inhibiting p38MAPK phosphorylation. The P2X7R/p38MAPK signaling pathway in SGCs of DRG and microglia of SDH might be a potential pharmacological target behind this mechanism as an opportunity to relieve BTZ-induced neuropathic pain.

The Gut Microbiota Links Dietary Polyphenols With Management of Psychiatric Mood Disorders

The pathophysiology of depression is multifactorial yet generally aggravated by stress and its associated physiological consequences. To effectively treat these diverse risk factors, a broad acting strategy is required and is has been suggested that gut-brain-axis signaling may play a pinnacle role in promoting resilience to several of these stress-induced changes including pathogenic load, inflammation, HPA-axis activation, oxidative stress and neurotransmitter imbalances. The gut microbiota also manages the bioaccessibility of phenolic metabolites from dietary polyphenols whose multiple beneficial properties have known therapeutic efficacy against depression. Although several potential therapeutic mechanisms of dietary polyphenols toward establishing cognitive resilience to neuropsychiatric disorders have been established, only a handful of studies have systematically identified how the interaction of the gut microbiota with dietary polyphenols can synergistically alleviate the biological signatures of depression. The current review investigates several of these potential mechanisms and how synbiotics, that combine probiotics with dietary polyphenols, may provide a novel therapeutic strategy for depression. In particular, synbiotics have the potential to alleviate neuroinflammation by modulating microglial and inflammasome activation, reduce oxidative stress and balance serotonin metabolism therefore simultaneously targeting several of the major pathological risk factors of depression. Overall, synbiotics may act as a novel therapeutic paradigm for neuropsychiatric disorders and further understanding the fundamental mechanisms of gut-brain-axis signaling will allow full utilization of the gut microbiota's as a therapeutic tool.

Dihydromyricetin Alleviates Diabetic Neuropathic Pain and Depression Comorbidity Symptoms by Inhibiting P2X7 Receptor

Diabetic neuropathic pain (DNP) and major depressive disorder (MDD) are common complications of diabetes mellitus and mutually affect each other. As a member of the ATP-gated ion channel family, P2X₇ receptor is associated with the transduction of pain signal and the onset of depression. The aim of this study was to investigate the effects of dihydromyricetin (DHM) on rats with comorbid DNP and MDD. After the comorbid model was established, rat behavior changes were monitored by measuring the mechanical withdrawal threshold, thermal withdrawal latency, sugar water preference, immobility time in the forced-swim test, and open-field test parameters. The expressions of P2X₇ receptor in the dorsal root ganglia (DRGs), spinal cord, and hippocampus were assessed by quantitative real-time PCR, Western blotting, and double immunofluorescence. We found that hyperalgesia, allodynia, and depressive behaviors of rats with comorbid DNP and MDD were relieved by treatment with DHM or application of a short-hairpin RNA for P2X₇ receptor. The expression levels of P2X₇, phosphorylated extracellular signal-regulated kinase 1/2, tumor necrosis factor α, and interleukin 1ß were increased in the DRGs, spinal cord, and hippocampus of rats in the model group but restored after DHM or P2X₇ short-hairpin RNA treatment. In conclusion, P2X₇ receptor in the DRGs, spinal cord, and hippocampus participates in the transduction of DNP and MDD signals. DHM seems to relieve comorbid DNP and MDD by reducing the expression of P2X₇ receptor in the DRGs, spinal cord, and hippocampus and may be an effective new drug for the treatment of patients with both DNP and MDD.

The antinociceptive effect of resveratrol in bone cancer pain is inhibited by the Silent Information Regulator 1 inhibitor selisistat

Objectives

To study the antinociceptive effect of single and repeated doses of resveratrol in a bone cancer pain model, and whether this effect is prevented by the Silent Information Regulator 1 (SIRT1) inhibitor selisistat.

Methods

The femoral intercondylar bone of BALB/c mice was injected with 1 000 000 BJ3Z cancer cells. Bone resorption and tumour mass growth (measured by in vivo X-ray and fluorescence imaging), as well as mechanical nociceptive thresholds (von Frey device) and dynamic functionality (rotarod machine), were evaluated during the following 4 weeks. Acute resveratrol (100 mg/kg i.p.) and/or selisistat (10 mg/kg s.c.) were administered on day 14. Chronic resveratrol (100 mg/kg i.p., daily) and/or selisistat (0.5 μg/h s.c., Alzet pump) were administered between days 14 and 20.

Key findings

Tumour growth gradually incremented until day 31, while mechanical hyperalgesia started on day 3 after cancer cell injection. Acute resveratrol increased the mechanical threshold of pain (peaking at 1.5 h), while the dynamic functionality decreased. Chronic resveratrol produced a sustained antinociceptive effect on mechanical hyperalgesia and improved the loss of dynamic functionality induced by the bone cancer tumour. Selisistat prevented all the effects of resveratrol.

Conclusions

Acute and chronic resveratrol induces antinociceptive effect in the model of metastatic osseous oncological pain, an effect that would be mediated by SIRT1 molecular signalling.

Recent development in antihyperalgesic effect of phytochemicals: anti-inflammatory and neuro-modulatory actions

INTRODUCTION

Pain is an unpleasant sensation triggered by noxious stimulation. It is one of the most prevalent conditions, limiting productivity and diminishing quality of life. Non steroidal anti inflammatory drugs (NSAIDs) are widely used as pain relievers in present day practice as pain is mostly initiated due to inflammation. However, due to potentially serious side effects, long term use of these antihyperalgesic drugs raises concern. Therefore there is a demand to search novel medicines with least side effects. Herbal products have been used for centuries to reduce pain and inflammation, and phytochemicals are known to cause fewer side effects. However, identification of active phytochemicals of herbal medicines and clear understanding of the molecular mechanism of their action is needed for clinical acceptance.

MATERIALS AND METHODS

In this review, we have briefly discussed the cellular and molecular changes during hyperalgesia via inflammatory mediators and neuro-modulatory action involved therein. The review includes 54 recently reported phytochemicals with antihyperalgesic action, as per the literature available with PubMed, Google Scholar and Scopus.

CONCLUSION

Compounds of high interest as potential antihyperalgesic agents are: curcumin, resveratrol, capsaicin, quercetin, eugenol, naringenin and epigallocatechin gallate (EGCG). Current knowledge about molecular targets of pain and their regulation by these phytochemicals is elaborated and the scope of further research is discussed.

Resveratrol enhances IL-4 receptor-mediated anti-inflammatory effects in spinal cord and attenuates neuropathic pain following sciatic nerve injury

Resveratrol has been showed to relieve neuropathic pain through its anti-inflammatory effects on the peripheral nerve system. However, it is not clear whether resveratrol, especially when administered systemically, is effective in alleviating the peripheral neuropathy-induced imbalance between pro- and anti-inflammatory responses in the central nervous system. To test this, we used a rat neuropathic pain model resulting from chronic constriction injury of the sciatic nerve. Resveratrol (200 mg/kg) or vehicle (dimethylsulfoxide) were administered intraperitoneally once daily for 14 consecutive days after chronic constriction injury. We found that resveratrol attenuated mechanical allodynia and thermal hyperalgesia in rats with chronic constriction injury. After 14 days of resveratrol treatment, expression of several anti-inflammatory cytokine receptors, including IL-1RA and IL-1R2, was increased in the dorsal spinal cord of rats with chronic constriction injury, and IL-4Rα was increased in dorsal spinal cord neurons. Knockdown of IL-4Rα in a neuronal cell line reversed the resveratrol-induced upregulation of IL-1RA and IL-1R2. These results indicate that resveratrol enhances IL-4 receptor-mediated anti-inflammatory responses in the spinal cord and thus might contribute to the alleviation of central sensitization following peripheral nerve injury.

Andrographolide Inhibits Mechanical and Thermal Hyperalgesia in a Rat Model of HIV-Induced Neuropathic Pain

Aim: In this study, we investigated whether andrographolide (Andro) can alleviate neuropathic pain induced by HIV gp120 plus ddC treatment and the mechanism of its action. Methods: The paw withdrawal threshold and the paw withdrawal latency were observed to assess pain behaviors in all groups of the rats, including control group, control combined with Andro treatment group, sham group, gp120 combined with ddC treatment group, gp120 plus ddC combined with A438079 treatment group, and gp120 plus ddC combined with Andro treatment by intrathecally injecting at a dose of 25 μg/20 μl group. The protein expression levels of the P2X7 receptor, tumor necrosis factor-α-receptor (TNFα-R), interleukin-1β (IL-1β), IL-10, phospho-extracellular regulated protein kinases (ERK) (p-ERK) in the L4-L6 dorsal root ganglia (DRG) were measured by western blotting. Real-time quantitative polymerase chain reaction was used to test the mRNA expression level of the P2X7 receptor. Double-labeling immunofluorescence was used to identify the co-localization of the P2X7 receptor with glial fibrillary acidic protein (GFAP) in DRG. Molecular docking was performed to identify whether the Andro interacted perfectly with the rat P2X7 (rP2X7) receptor. Results: Andro attenuated the mechanical and thermal hyperalgesia in gp120+ddC-treated rats and down-regulated the P2X7 receptor mRNA and protein expression in the L4-L6 DRGs of gp120+ddC-treated rats. Additionally, Andro simultaneously decreased the expression of TNFα-R and IL-1β protein, increased the expression of IL-10 protein in L4-L6 DRGs, and inhibited the activation of ERK signaling pathways. Moreover, Andro decreased the co-expression of GFAP and the P2X7 receptor in the SGCs of L4-L6 DRG on 14th day after surgery. Conclusion: Andro decreased the hyperalgesia induced by gp120 plus ddC.