Inhibition of the spinal astrocytic JNK/MCP-1 pathway activation correlates with the analgesic effects of tanshinone IIA sulfonate in neuropathic pain

Ethnomedicine, phytochemistry, pharmacology, pharmacokinetics, and clinical application of Salvia miltiorrhiza Bunge (Lamiaceae): A comprehensive review

ETHNOPHARMACOLOGICAL RELEVANCE

Salvia miltiorrhiza Bunge (Lamiaceae), known as Danshen in China, is a widely utilized traditional Chinese medicine (TCM). Danshen is classified within the heart and liver meridians and renowned for its ability to activate collaterals and blood vessels, facilitate the removal of blood stasis without compromising vital Qi. It plays a pivotal role in promoting blood circulation and alleviating blood stasis. Clinically, it is commonly used to treat uterine bleeding, irregular menstruation, blood stasis, and abdominal pain, among other symptoms.

AIM OF THE STUDY

This paper reviews the traditional use, botany, phytochemistry, pharmacology, toxicity, pharmacokinetics and clinical application of Danshen from 1981 to 2024. The goal is to offer valuable reference materials that can inform and guide future research related to Danshen.

MATERIALS AND METHODS

A literature search was performed on Danshen based on classic books about Chinese herbal medicine and different electronic databases including Web of Science, PubMed, Elsevier, ScienceDirect, Google Scholar, SciFinder, TPL, and CNKI.

RESULTS

Traditional uses of Danshen have been documented in China for centuries. A large number of studies have shown that Danshen is rich in chemical components. To date, more than 318 chemical compounds have been isolated and identified, including diterpenoid quinones, phenolic acids, triterpenes, essential oils, neolignans, alkaloids, flavonoids, saccharides, and others. Crude extracts and pure compounds isolated from Danshen exhibit a wide range of pharmacological effects, including anti-atherosclerotic, anti-arrhythmic, anti-thrombotic, anti-hypertensive, anti-myocardial ischemia-reperfusion injury, endothelial dysfunction protection, sedative and analgesic, neuroprotective, anti-depressive, anti-hepatic fibrosis, anti-pulmonary fibrosis, anti-renal fibrosis, anti-inflammatory, anti-oxidative, anti-tumor, anti-diabetic effects. The results of pharmacokinetic studies showed that the presence of various compounds within the extract of Danshen can significantly influence the pharmacokinetic characteristics of individual constituents through several mechanisms. These mechanisms may include enhanced bioavailability, reduced potential for toxicity, and alterations in the distribution of metabolites.

CONCLUSIONS

Danshen has been demonstrated to be a valuable medicinal resource in TCM. This paper provides a comprehensive review of the ethnopharmacology, chemical composition, pharmacological effects, toxicology, pharmacokinetics and clinical applications of Danshen, aiming to serve as a thorough reference for its further development and utilization. Additionally, further research in pharmacokinetics and toxicology is essential to enhance our understanding of its clinical applications and quality control.

Duhuo Jisheng Mixture attenuates neuropathic pain by inhibiting S1PR1/P2Y1R pathway after Chronic Constriction Injury in mice

BACKGROUND

The pathogenesis of neuropathic pain is complex and lacks effective clinical treatment strategies. Medical plants and herbal extracts from traditional Chinese medicine with multi-target comprehensive effects have attracted great attention from scientists.

PURPOSE

To investigate the pharmacological active components and mechanism underlying the anti-neuralgia effect of classic analgesic formulas Duhuo Jisheng Mixture (DJM).

STUDY DESIGN AND METHODS

Chronic Constriction Injury (CCI) surgery was used to assess the efficiency of DJM in treating neuropathic pain. Forty-two C57BL/6 mice were evenly divided into seven groups: sham-operated, sham treatment with DJM (20 ml/kg), CCI treatment with DJM (0, 10, 20, or 40 ml/kg) and CCI treatment with Morphine (3 mg/kg). DJM irrigation stomach was implemented from post-operative day (POD) 0 to POD 21. Paw withdrawal threshold and Thermal latency were conducted on POD 0, 1, 3, 5, 7, 14 and 21. On POD 14, eEPSP in spinal dorsal horn neurons was recorded by patch-clamp. mRNA transcription in spinal cord was also monitored to screen molecular targets and signaling pathways on POD 14. To further validate the influence of DJM on the S1PR1 signaling pathway, 1 mg/kg W146 was infused into mice intrathecally and delivered to the cerebral spinal fluid through one 30 G needle with a whole 20 μl intervertebral between the L5 and L6. Furthermore, the active ingredients of DJM were identified through LC/MS equipment and predicted through Molecular Docking.

RESULTS

We demonstrated that DJM treatment reversed CCI-induced pain sensitivity and the excitability of neurons, decreased up-regulation of astrocyte S1PR1, inhibited astrocyte activation, and further inhibited the expression of Purinergic P2Y1R and its downstream molecule p-JNK in mouse spinal cord, as well as the release of inflammatory factors. Interestingly, due to the regulatory role of astrocytes on neurons, the effects of DJM on astrocytes ultimately manifest in pain-effector neurons, resulting in decreased p-ERK, p-CREB, and pain-marking protein c-fos in neurons. S1PR1 Antagonist W146 possessed an equivalent analgesic effect as DJM and inhibited S1PR1 and c-fos expression. According to LC/MS analysis results, a total of 33 active ingredients were screened, of which 20 active ingredients had good binding activity with S1PR1 and were considered to be the main active ingredients for analgesia.

CONCLUSION

This study is the first to clarify the effect and molecular mechanism of DJM for anti-neuralgia in particular, which confirms the clinical value of DJM in relieving neuropathic pain. Furthermore, this study innovatively identifies the potential pharmacological components of DJM through LC/MS and Bioinformatics technology, which forms a framework for people's understanding of DJM treatment for neuropathic pain and provides a sufficient theoretical basis of DJM for clinical application.

Epitranscriptomic reader YTHDF2 regulates SEK1(MAP2K4)-JNK-cJUN inflammatory signaling in astrocytes during neurotoxic stress

As the most abundant glial cells in the central nervous system (CNS), astrocytes dynamically respond to neurotoxic stress, however, the key molecular regulators controlling the inflammatory status of these sentinels during neurotoxic stress are many and complex. Herein, we demonstrate that the m6A epitranscriptomic mRNA modification tightly regulates the pro-inflammatory functions of astrocytes. Specifically, the astrocytic neurotoxic stressor, manganese (Mn), downregulated the m6A reader YTHDF2 in human and mouse astrocyte cultures and in the mouse brain. Functionally, YTHDF2 knockdown augmented, while its overexpression dampened, the neurotoxic stress-induced proinflammatory response, suggesting YTHDF2 serves as a key upstream regulator of inflammatory responses in astrocytes. Mechanistically, YTHDF2 RIP-sequencing identified MAP2K4 (MKK4; SEK1) mRNA as a YTHDF2 target influencing inflammatory signaling. Our target validation revealed that Mn-exposed astrocytes mediate proinflammatory responses by activating the phosphorylation of SEK1, JNK, and cJUN signaling. Collectively, YTHDF2 serves as a key upstream 'molecular switch' controlling SEK1(MAP2K4)-JNK-cJUN proinflammatory signaling in astrocytes.

Peripheral and central pathogenesis of postherpetic neuralgia

BACKGROUND

Postherpetic neuralgia (PHN) is a classic chronic condition with multiple signs of peripheral and central neuropathy. Unfortunately, the pathogenesis of PHN is not well defined, limiting clinical treatment and disease management.

OBJECTIVE

To describe the peripheral and central pathological axes of PHN, including peripheral nerve injury, inflammation induction, central nervous system sensitization, and brain functional and structural network activity.

METHODS

A bibliographic survey was carried out, selecting relevant articles that evaluated the characterization of the pathogenesis of PHN, including peripheral and central pathological axes.

RESULTS

Currently, due to the complexity of the pathophysiological mechanisms of PHN and the incomplete understanding of the exact mechanism of neuralgia.

CONCLUSION

It is essential to conduct in-depth research to clarify the origins of PHN pathogenesis and explore effective and comprehensive therapies for PHN.

Inhibiting the JNK Signaling Pathway Attenuates Hypersensitivity and Anxiety-Like Behavior in a Rat Model of Non-specific Chronic Low Back Pain

Low back pain (LBP) has become a leading cause of disability worldwide. Astrocyte activation in the spinal cord plays an important role in the maintenance of latent sensitization of dorsal horn neurons in LBP. However, the role of spinal c-Jun N-terminal kinase (JNK) in astrocytes in modulating pain behavior of LBP model rats and its neurobiological mechanism have not been elucidated. Here, we investigate the role of the JNK signaling pathway on hypersensitivity and anxiety-like behavior caused by repetitive nerve growth factor (NGF) injections in male non-specific LBP model rats. LBP was produced by two injections (day 0, day 5) of NGF into multifidus muscle of the low backs of rats. We observed prolonged mechanical and thermal hypersensitivity in the low backs or hindpaws. Persistent anxiety-like behavior was observed, together with astrocyte, p-JNK, and neuronal activation and upregulated expression of monocyte chemoattractant protein-1 (MCP-1), and chemokine (C-X-C motif) ligand 1 (CXCL1) proteins in the spinal L2 segment. Second, the JNK inhibitor SP600125 was intrathecally administrated in rats from day 10 to day 12. It attenuated mechanical and thermal hypersensitivity of the low back or hindpaws and anxiety-like behavior. Meanwhile, SP600125 decreased astrocyte and neuronal activation and the expression of MCP-1 and CXCL1 proteins. These results showed that hypersensitivity and anxiety-like behavior induced by NGF in LBP rats could be attenuated by the JNK inhibitor, together with downregulation of spinal astrocyte activation, neuron activation, and inflammatory cytokines. Our results indicate that intervening with the spinal JNK signaling pathway presents an effective therapeutic approach to alleviating LBP.

Sodium tanshinone IIA sulfonate suppresses microglia polarization and neuroinflammation possibly via regulating miR-125b-5p/STAT3 axis to ameliorate neuropathic pain

The spinal cord microglia play a pivotal role in neuroinflammation and neuropathic pain (NP). Sodium tanshinone IIA sulfonate (STS), a derivative of tanshinone IIA, has anti-inflammatory and anti-hyperalgesic effects. However, its underlying mechanism in NP remains unclear. This study aimed to investigate the effect of STS and elucidate possible mechanisms in a rat model of spared nerve injury. In vivo experiments, STS and AG490 were administered intraperitoneally once daily for 14 consecutive days after surgery. The results showed that the expression of miR-125b-5p in the spinal dorsal horn was substantially reduced, whereas signal transducer and activator of transcription 3 (STAT3) signaling was increased. After treatment with STS, the mechanical thresholds, expression of miR-125b-5p, and microglial M2 marker such as Arg-1 in the spinal cord horn increased significantly, whereas multiple pro-inflammatory cytokines and apoptosis were significantly reduced. Moreover, STAT3 pathway-related proteins and expression of the microglial M1 marker, CD68, were appreciably inhibited. In vitro, lipopolysaccharide (LPS) was used to induce an inflammatory response in BV-2 microglial cells. STS pretreatment inhibited LPS-stimulated pro-inflammatory cytokine secretion, reduced STAT3 pathway related-proteins and apoptosis, increased miR-125b-5p and proopiomelanocortin expression, and enhanced microglia transformation from M1 to M2 phenotype in BV-2 cells. These effects were reversed after the inhibition of miR-125b-5p expression in BV-2 cells. A dual-luciferase reporter assay confirmed that STAT3 binds to miR-125b-5p. In summary, these results suggest that STS exerts anti-hyperalgesic and anti-neuroinflammatory effects in rats with NP possibly via the miR-125b-5p/STAT3 axis.

Treatment of neuropathic pain by traditional Chinese medicine: An updated review on their effect and putative mechanisms of action

Neuropathic pain (NP) is a common chronic pain with heterogeneous clinical features, and consequent lowering of quality of life. Currently, although conventional chemical drugs can effectively manage NP symptoms in the short term, their long-term efficacy is limited, and they come with significant side effects. In this regard, traditional Chinese medicine (TCM) provides a promising avenue for treating NP. Numerous pharmacological and clinical studies have substantiated the effectiveness of TCM with multiple targets and mechanisms. We aimed to outline the characteristics of TCM, including compound prescriptions, single Chinese herbs, active ingredients, and TCM physical therapy, for NP treatment and discussed their efficacy by analyzing the pathogenesis of NP. Various databases, such as PubMed, Web of Science, China National Knowledge Infrastructure, and Wanfang database, were searched. We focused on recent research progress in NP treatment by TCM. Finally, we proposed the future challenges and emerging trends in the treatment of NP. TCM demonstrates significant clinical efficacy in NP treatment, employing multi-mechanisms. Drawing from the theory of syndrome differentiation, four types of dialectical treatments for NP by compound TCM prescriptions were introduced: promoting blood circulation and removing blood stasis; promoting blood circulation and promote Qi flow; warming Yang and benefiting Qi; soothing the liver and regulating Qi. Meanwhile, 33 single Chinese herbs and 25 active ingredients were included. In addition, TCM physical therapy (e.g., acupuncture, massage, acupoint injection, and fumigation) also showed good efficacy in NP treatment. TCM, particularly through the use of compound prescriptions and acupuncture, holds bright prospects in treating NP owing to its diverse holistic effects. Nonetheless, the multi-targets of TCM may result in possible disadvantages to NP treatment, and the pharmacological mechanisms of TCM need further evaluation. Here, we provide an overview of NP treatment via TCM, based on the pathogenesis and the potential therapeutic mechanisms, thus providing a reference for further studies.

SPOCK2 modulates neuropathic pain by interacting with MT1-MMP to regulate astrocytic MMP-2 activation in rats with chronic constriction injury

BACKGROUND

Neuropathic pain (NP) is a kind of intractable pain. The pathogenesis of NP remains a complicated issue for pain management practitioners. SPARC/osteonectin, CWCV, and Kazal-like domains proteoglycan 2 (SPOCK2) are members of the SPOCK family that play a significant role in the development of the central nervous system. In this study, we investigated the role of SPOCK2 in the development of NP in a rat model of chronic constriction injury (CCI).

METHODS

Sprague-Dawley rats were randomly grouped to establish CCI models. We examined the effects of SPOCK2 on pain hpersensitivity and spinal astrocyte activation after CCI-induced NP. Paw withdrawal threshold (PWT) and paw withdrawal latency (PWL) were used to reflects the pain behavioral degree. Molecular mechanisms involved in SPOCK2-mediated NP in vivo were examined by western blot analysis, immunofluorescence, immunohistochemistry, and co-immunoprecipitation. In addition, we examined the SPOCK2-mediated potential protein-protein interaction (PPI) in vitro coimmunoprecipitation (Co-IP) experiments.

RESULTS

We founded the expression level of SPOCK2 in rat spinal cord was markedly increased after CCI-induced NP, while SPOCK2 downregulation could partially relieve pain caused by CCI. Our research showed that SPOCK2 expressed significantly increase in spinal astrocytes when CCI-induced NP. In addition, SPOCK2 could act as an upstream signaling molecule to regulate the activation of matrix metalloproteinase-2 (MMP-2), thus affecting astrocytic ERK1/2 activation and interleukin (IL)-1β production in the development of NP. Moreover, in vitro coimmunoprecipitation (Co-IP) experiments showed that SPOCK2 could interact with membrane-type 1 matrix metalloproteinase (MT1-MMP/MMP14) to regulate MMP-2 activation by the SPARC extracellular (SPARC_EC) domain.

CONCLUSIONS

Research shows that SPOCK2 can interact with MT1-MMP to regulate MMP-2 activation, thus affecting astrocytic ERK1/2 activation and IL-1β production to achieve positive promotion of NP.

From Plant to Chemistry: Sources of Antinociceptive Non-Opioid Active Principles for Medicinal Chemistry and Drug Design

Pain is associated with many health problems and a reduced quality of life and has been a common reason for seeking medical attention. Several therapeutics are available on the market, although side effects, physical dependence, and abuse limit their use. As the process of pain transmission and modulation is regulated by different peripheral and central mechanisms and neurotransmitters, medicinal chemistry continues to study novel ligands and innovative approaches. Among them, natural products are known to be a rich source of lead compounds for drug discovery due to their chemical structural variety and different analgesic mechanisms. Numerous studies suggested that some chemicals from medicinal plants could be alternative options for pain relief and management. Previously, we conducted a literature search aimed at identifying natural products interacting either directly or indirectly with opioid receptors. In this review, instead, we have made an excursus including active ingredients derived from plants whose mechanism of action appears from the literature to be other than the modulation of the opioid system. These substances could, either by themselves or through synthetic and/or semi-synthetic derivatives, be investigated in order to improve their pharmacokinetic characteristics and could represent a valid alternative to the opioid approach to pain therapy. They could also be the basis for the study of new mechanisms of action in the approach to this complex and disabling pathology.

Epitranscriptomic Reader YTHDF2 Regulates SEK1( MAP2K4 )-JNK-cJUN Inflammatory Signaling in Astrocytes during Neurotoxic Stress

As the most abundant glial cells in the CNS, astrocytes dynamically respond to neurotoxic stress, however, the key molecular regulators controlling the inflammatory status of these sentinels during neurotoxic stress have remained elusive. Herein, we demonstrate that the m6A epitranscriptomic mRNA modification tightly regulates the pro-inflammatory functions of astrocytes. Specifically, the astrocytic neurotoxic stresser, manganese (Mn), downregulated the m6A reader YTHDF2 in human and mouse astrocyte cultures and in the mouse brain. Functionally, YTHDF2 knockdown augmented, while its overexpression dampened, neurotoxic stress induced proinflammatory response, suggesting YTHDF2 serves as a key upstream regulator of inflammatory responses in astrocytes. Mechnistically, YTHDF2 RIP-sequencing identified MAP2K4 ( MKK4; SEK1) mRNA as a YTHDF2 target influencing inflammatory signaling. Our target validation revealed Mn-exposed astrocytes mediates proinflammatory response by activating the phosphorylation of SEK1, JNK, and cJUN signaling. Collectively, YTHDF2 serves a key upstream 'molecular switch' controlling SEK1( MAP2K4 )-JNK-cJUN proinflammatory signaling in astrocytes.

Shenqisherong pill ameliorates neuronal apoptosis by inhibiting the JNK/caspase-3 signaling pathway in a rat model of cervical cord compression

ETHNOPHARMACOLOGICAL RELEVANCE

The Shenqisherong (SQSR) pill is an empirical prescription of traditional Chinese medicine (TCM), which originated from the National Chinese Medical Science Master, Shi Qi. It has been widely used in the treatment of cervical spondylotic myelopathy (CSM) and promote the recovery of spinal cord function, but underlying molecular mechanism remains unclear.

AIM OF THE STUDY

The objective of this study was to confirm the neuroprotective effects of the SQSR pill.

MATERIALS AND METHODS

A rat model of chronic compression at double-level cervical cord was used in vivo. The protective role of SQSR pill on CSM rats was measured by Basso, Beattie, and Bresnahan (BBB) locomotor scale, inclined plane test, forelimb grip strength assessment, hindlimb pain threshold assessment, and gait analysis. The levels of reactive oxygen species (ROS) were examined by Dihydroethidium (DHE) staining and 2',7'-Dichlorofluorescein (DCF) assay, and apoptosis was detected by TdT-mediated dUTP nick-end labeling (TUNEL) assay. The expression of apoptosis proteins was evaluated by immunofluorescence staining and Western blot.

RESULTS

SQSR pill could facilitate locomotor function recovery in rats with chronic cervical cord compression, reduce local ROS in the spinal cord and downregulate the c-Jun-N-terminal kinase (JNK)/caspase-3 signaling pathway. In addition, the SQSR pill could protect primary rat cortical neurons from glutamate-treated toxicity in vitro by reducing the ROS and downregulating the phosphorylation of JNK and its downstream factors related to neuronal apoptosis meditated by the caspase cascade. Then, the neuroprotective effect was counteracted by a JNK activator.

CONCLUSIONS

Together, SQSR pill could ameliorate neuronal apoptosis by restraining ROS accumulation and inhibiting the JNK/caspase-3 signaling pathway, indicating that SQSR pill could be a candidate drug for CSM.

Advances in Neuropathic Pain Research: Selected Intracellular Factors as Potential Targets for Multidirectional Analgesics

Neuropathic pain is a complex and debilitating condition that affects millions of people worldwide. Unlike acute pain, which is short-term and starts suddenly in response to an injury, neuropathic pain arises from somatosensory nervous system damage or disease, is usually chronic, and makes every day functioning difficult, substantially reducing quality of life. The main reason for the lack of effective pharmacotherapies for neuropathic pain is its diverse etiology and the complex, still poorly understood, pathophysiological mechanism of its progression. Numerous experimental studies, including ours, conducted over the last several decades have shown that the development of neuropathic pain is based on disturbances in cell activity, imbalances in the production of pronociceptive factors, and changes in signaling pathways such as p38MAPK, ERK, JNK, NF-κB, PI3K, and NRF2, which could become important targets for pharmacotherapy in the future. Despite the availability of many different analgesics, relieving neuropathic pain is still extremely difficult and requires a multidirectional, individual approach. We would like to point out that an increasing amount of data indicates that nonselective compounds directed at more than one molecular target exert promising analgesic effects. In our review, we characterize four substances (minocycline, astaxanthin, fisetin, and peimine) with analgesic properties that result from a wide spectrum of actions, including the modulation of MAPKs and other factors. We would like to draw attention to these selected substances since, in preclinical studies, they show suitable analgesic properties in models of neuropathy of various etiologies, and, importantly, some are already used as dietary supplements; for example, astaxanthin and fisetin protect against oxidative stress and have anti-inflammatory properties. It is worth emphasizing that the results of behavioral tests also indicate their usefulness when combined with opioids, the effectiveness of which decreases when neuropathy develops. Moreover, these substances appear to have additional, beneficial properties for the treatment of diseases that frequently co-occur with neuropathic pain. Therefore, these substances provide hope for the development of modern pharmacological tools to not only treat symptoms but also restore the proper functioning of the human body.

Effects and mechanisms of tanshinone IIA on PTSD-like symptoms

BACKGROUND

In recent years, Salvia miltiorrhiza and its active substances have remarkably progressed in treating central neurological disorders. Tanshinone IIA (TSA) is an active ingredient derived from the rhizome of Salvia miltiorrhiza that has been found to alleviate the symptoms of several psychiatric illnesses. Post-traumatic stress disorder (PTSD) is a mental disorder that results after experiencing a serious physical or psychological injury. The currently used drugs are not satisfactory for the treatment of PTSD. However, it has been reported that TSA can improve PTSD-like symptoms like learning and memory, cognitive disorder, and depression through multi-target regulation.

PURPOSE

This paper discusses the ameliorative effects of TSA on PTSD-like symptoms and the possible mechanisms of action in terms of inhibition of neuronal apoptosis, anti-neuroinflammation, and anti-oxidative stress. Based on the pathological changes and clinical observations of PTSD, we hope to provide some reference for the clinical transformation of Chinese medicine in treating PTSD.

METHODS

A large number of literatures on tanshinone in the treatment of neurological diseases and PTSD were retrieved from online electronic PubMed and Web of Science databases.

CONCLUSION

TSA is a widely studied natural active ingredient against mental illness. This review will contribute to the future development of TSA as a new clinical candidate drug for improving PTSD-like symptoms.

Mirogabalin Decreases Pain-like Behaviors by Inhibiting the Microglial/Macrophage Activation, p38MAPK Signaling, and Pronociceptive CCL2 and CCL5 Release in a Mouse Model of Neuropathic Pain

Neuropathic pain is a chronic condition that significantly reduces the quality of life of many patients as a result of ineffective pain relief therapy. For that reason, looking for new analgesics remains an important issue. Mirogabalin is a new gabapentinoid that is a specific ligand for the α2σ-1 and α2σ-2 subunits of voltage-gated calcium channels. In the present study, we compared the analgesic effect of pregabalin and mirogabalin in a neuropathic pain chronic constriction injury (CCI) of the sciatic nerve in a mouse model. The main purpose of our study was to determine the effectiveness of mirogabalin administered both once and repeatedly and to explain how the drug influences highly activated cells at the spinal cord level in neuropathy. We also sought to understand whether mirogabalin modulates the selected intracellular pathways (p38MAPK, ERK, JNK) and chemokines (CCL2, CCL5) important for nociceptive transmission, which is crucial information from a clinical perspective. First, our study provides evidence that a single mirogabalin administration diminishes tactile hypersensitivity more effectively than pregabalin. Second, research shows that several indirect mechanisms may be responsible for the beneficial analgesic effect of mirogabalin. This study reports that repeated intraperitoneally (i.p.) mirogabalin administration strongly prevents spinal microglia/macrophage activation evoked by nerve injury, slightly suppresses astroglia and neutrophil infiltration, and reduces the p38MAPK levels associated with neuropathic pain, as measured on Day 7. Moreover, mirogabalin strongly diminished the levels of the pronociceptive chemokines CCL2 and CCL5. Our results indicate that mirogabalin may represent a new strategy for the effective pharmacotherapy of neuropathic pain.

Analgesic Effects of Fisetin, Peimine, Astaxanthin, Artemisinin, Bardoxolone Methyl and 740 Y-P and Their Influence on Opioid Analgesia in a Mouse Model of Neuropathic Pain

Treatment of neuropathic pain remains a challenge for modern medicine due to the insufficiently understood molecular mechanisms of its development and maintenance. One of the most important cascades that modulate the nociceptive response is the family of mitogen-activated protein (MAP) kinases and phosphatidylinositol-3-kinase (PI3K), as well as nuclear factor erythroid 2-related factor 2 (Nrf2). The aim of this study was to determine the effect of nonselective modulators of MAP kinases-fisetin (ERK1/2 and NFκB inhibitor, PI3K activator), peimine (MAPK inhibitor), astaxanthin (MAPK inhibitor, Nrf2 activator) and artemisinin (MAPK inhibitor, NFκB activator), as well as bardoxolone methyl (selective activator of Nrf2) and 740 Y-P (selective activator of PI3K)-in mice with peripheral neuropathy and to compare their antinociceptive potency and examine their effect on analgesia induced by opioids. The study was performed using albino Swiss male mice that were exposed to chronic constriction injury of the sciatic nerve (CCI model). Tactile and thermal hypersensitivity was measured using von Frey and cold plate tests, respectively. Single doses of substances were administered intrathecally on day 7 after CCI. Among the tested substances, fisetin, peimine, and astaxanthin effectively diminished tactile and thermal hypersensitivity in mice after CCI, while artemisinin did not exhibit analgesic potency in this model of neuropathic pain. Additionally, both of the activators tested, bardoxolone methyl and 740 Y-P, also showed analgesic effects after intrathecal administration in mice exposed to CCI. In the case of astaxanthin and bardoxolone methyl, an increase in analgesia after combined administration with morphine, buprenorphine, and/or oxycodone was observed. Fisetin and peimine induced a similar effect on tactile hypersensitivity, where analgesia was enhanced after administration of morphine or oxycodone. In the case of 740 Y-P, the effects of combined administration with each opioid were observed only in the case of thermal hypersensitivity. The results of our research clearly indicate that substances that inhibit all three MAPKs provide pain relief and improve opioid effectiveness, especially if they additionally block NF-κB, such as peimine, inhibit NF-κB and activate PI3K, such as fisetin, or activate Nrf2, such as astaxanthin. In light of our research, Nrf2 activation appears to be particularly beneficial. The abovementioned substances bring promising results, and further research on them will broaden our knowledge regarding the mechanisms of neuropathy and perhaps contribute to the development of more effective therapy in the future.

RNA regulation of inflammatory responses in glia and its potential as a therapeutic target in central nervous system disorders

A major hallmark of neuroinflammation is the activation of microglia and astrocytes with the induction of inflammatory mediators such as IL-1β, TNF-α, iNOS, and IL-6. Neuroinflammation contributes to disease progression in a plethora of neurological disorders ranging from acute CNS trauma to chronic neurodegenerative disease. Posttranscriptional pathways of mRNA stability and translational efficiency are major drivers for the expression of these inflammatory mediators. A common element in this level of regulation centers around the adenine- and uridine-rich element (ARE) which is present in the 3' untranslated region (UTR) of the mRNAs encoding these inflammatory mediators. (ARE)-binding proteins (AUBPs) such as Human antigen R (HuR), Tristetraprolin (TTP) and KH- type splicing regulatory protein (KSRP) are key nodes for directing these posttranscriptional pathways and either promote (HuR) or suppress (TTP and KSRP) glial production of inflammatory mediators. This review will discuss basic concepts of ARE-mediated RNA regulation and its impact on glial-driven neuroinflammatory diseases. We will discuss strategies to target this novel level of gene regulation for therapeutic effect and review exciting preliminary studies that underscore its potential for treating neurological disorders.

New advances in Nrf2-mediated analgesic drugs

BACKGROUND

Oxidative stress is an inevitable process that occurs during life activities, and it can participate in the development of inflammation. Although great progress has been made according to research examining analgesic drugs and therapies, there remains a need to develop new analgesic drugs to fill certain gaps in both the experimental and clinical space.

PURPOSE

This review reports the research and preclinical progress of this class of analgesics by summarizing known nuclear factor E-2-related factor-2 (Nrf2) pathway-modulating substances.

STUDY DESIGN

We searched and reported experiments that intervene in the Nrf2 pathway and its various upstream and downstream molecules for analgesic therapy.

METHODS

The medical literature database (PubMed) was searched for experimental studies examining the reduction of pain in animals through the Nrf2 pathway, the research methods were analyzed, and the pathways were classified and reported according to the pathway of these experimental interventions.

RESULTS

Humans have identified a variety of substances that can fight pain by regulating the expression of Nrf2 and its upstream and downstream pathways.

CONCLUSION

The Nrf2 pathway exerts anti-inflammatory activity by regulating oxidative stress, thereby playing a role in the fight against pain.

The role and pharmacological properties of P2Y12 receptor in cancer and cancer pain

The G protein-coupled P2Y12 receptor (P2Y12R) was cloned in platelets and found to play a key role in maintaining platelet function in hemostasis and thrombosis, and these effects could be mediated by the P2Y12R. However, it has recently been found that P2Y12R-mediated the progression of tumor through interactions between platelets and tumor and stromal cells, as well as through products secreted by platelets. During tumor progression, tumor cells or other cells in the tumor microenvironment (such as immune cells) can secrete large amounts of ATP into the extracellular matrix, and extracellular ATP can be hydrolyzed into ADP. ADP is a P2Y12R activator and plays an important regulatory role in the proliferation and metastasis of tumor cells. P2Y12R is involved in platelet-cancer cell crosstalk and become a potential target for anticancer therapy. Moreover, tumor progression can induce pain, which seriously affects the quality of life of patients. P2Y12R is expressed in microglia and mediates the activities of microglial and participates in the occurrence of cancer pain. Conversely, inhibiting P2Y12R activation and down-regulating its expression has the effect of inhibiting tumor progression and pain. Therefore, P2Y12R can be a common therapeutic target for both. In this article, we explored the potential link between P2Y12R and cancer, discussed the intrinsic link of P2Y12R in cancer pain and the pharmacological properties of P2Y12R antagonists in the treatment of both.

Inhibition of the RNA Regulator HuR by SRI-42127 Attenuates Neuropathic Pain After Nerve Injury Through Suppression of Neuroinflammatory Responses

Microglial activation with the production of pro-inflammatory mediators such as IL-6, TNF-α, and IL-1β, is a major driver of neuropathic pain (NP) following peripheral nerve injury. We have previously shown that the RNA binding protein, HuR, is a positive node of regulation for many of these inflammatory mediators in glia and that its chemical inhibition or genetic deletion attenuates their production. In this report, we show that systemic administration of SRI-42127, a novel small molecule HuR inhibitor, attenuates mechanical allodynia, a hallmark of NP, in the early and chronic phases after spared nerve injury in male and female mice. Flow cytometry of lumbar spinal cords in SRI-42127-treated mice shows a reduction in infiltrating macrophages and a concomitant decrease in microglial populations expressing IL-6, TNF-α, IL-1β, and CCL2. Immunohistochemistry, ELISA, and qPCR of lumbar spinal cord tissue indicate suppression of these cytokines and other inflammatory mediators. ELISA of plasma samples in the acute phase also shows attenuation of inflammatory responses. In summary, inhibition of HuR by SRI-42127 leads to the suppression of neuroinflammatory responses and allodynia after nerve injury and represents a promising new direction in the treatment of NP.

Tanshinone IIA improves contextual fear- and anxiety-like behaviors in mice via the CREB/BDNF/TrkB signaling pathway

Posttraumatic stress disorder (PTSD) is one of the most common psychiatric diseases, which is characterized by the typical symptoms such as re-experience, avoidance, and hyperarousal. However, there are few drugs for PTSD treatment. In this study, conditioned fear and single-prolonged stress were employed to establish PTSD mouse model, and we investigated the effects of Tanshinone IIA (TanIIA), a natural product isolated from traditional Chinese herbal Salvia miltiorrhiza, as well as the underlying mechanisms in mice. The results showed that the double stress exposure induced obvious PTSD-like symptoms, and TanIIA administration significantly decreased freezing time in contextual fear test and relieved anxiety-like behavior in open field and elevated plus maze tests. Moreover, TanIIA increased the spine density and upregulated synaptic plasticity-related proteins as well as activated CREB/BDNF/TrkB signaling pathway in the hippocampus. Blockage of CREB remarkably abolished the effects of TanIIA in PTSD model mice and reversed the upregulations of p-CREB, BDNF, TrkB, and synaptic plasticity-related protein induced by TanIIA. The molecular docking simulation indicated that TanIIA could interact with the CREB-binding protein. These findings indicate that TanIIA ameliorates PTSD-like behaviors in mice by activating the CREB/BDNF/TrkB pathway, which provides a basis for PTSD treatment.

The analgesic effects of β-elemene in rats with neuropathic pain by inhibition of spinal astrocytic ERK activation

Neuropathic pain takes a heavy toll on individual well-being, while current therapy is far from desirable. Herein, we assessed the analgesic effect of β-elemene, a chief component in the traditional Chinese medicine Curcuma wenyujin, and explored the underlying mechanisms at the level of spinal dorsal horn (SDH) under neuropathic pain. A spared nerve injury (SNI)-induced neuropathic pain model was established in rats. Intraperitoneal injection (i.p.) of β-elemene was administered for 21 consecutive days. Mechanical allodynia was explored by von Frey filaments. The activation of the mitogen-activated protein kinase (MAPK) family (including ERK, p38, and JNK) in spinal neurons, astrocytes, and microglia was evaluated using immunostaining 29 days after SNI surgery. The expression of GFAP, Iba-1, p-ERK, p-JNK, and p-p38 within the SDH was measured using immunoblotting. The levels of proinflammatory cytokines (including TNF-α, IL-1β, and IL-6) were measured with ELISA. The levels of oxidative stress indicators (including MDA, SOD, and GSH-PX) were detected using biochemical tests. Consecutive i.p. administration of β-elemene relieved SNI-induced mechanical allodynia (with an EC50 of 16.40 mg/kg). SNI significantly increased the expression of p-ERK in spinal astrocytes but not microglia on day 29. β-elemene reversed spinal astrocytic ERK activation and subsequent upregulation of proinflammatory cytokines in SNI rats, with no effect on the expression of p38 and JNK in spinal glia. β-elemene also exerted antioxidative effects by increasing the levels of SOD and GSH-PX and decreasing the level of MDA. Our results suggest that SNI induces robust astrocytic ERK activation within the SDH in the late phase of neuropathic pain. β-elemene exerts remarkable analgesic effects on neuropathic pain, possibly by inhibiting spinal astrocytic ERK activation and subsequent neuroinflammatory processes. Our findings suggest that β-elemene might be a promising analgesic for the treatment of chronic pain.

Role of Microglia and Astrocytes in Spinal Cord Injury Induced Neuropathic Pain

Background:

Spinal cord injuries incite varying degrees of symptoms in patients, ranging from weakness and incoordination to paralysis. Common amongst spinal cord injury (SCI) patients, neuropathic pain (NP) is a debilitating medical condition. Unfortunately, there remain many clinical impediments in treating NP because there is a lack of understanding regarding the mechanisms behind SCI-induced NP (SCINP). Given that more than 450,000 people in the United States alone suffer from SCI, it is unsatisfactory that current treatments yield poor results in alleviating and treating NP.

Summary:

In this review, we briefly discussed the models of SCINP along with the mechanisms of NP progression. Further, current treatment modalities are herein explored for SCINP involving pharmacological interventions targeting glia cells and astrocytes.

Key message:

The studies presented in this review provide insight for new directions regarding SCINP alleviation. Given the severity and incapacitating effects of SCINP, it is imperative to study the pathways involved and find new therapeutic targets in coordination with stem cell research, and to develop a new gold-standard in SCINP treatment.

Sodium tanshinone IIA sulfonate ameliorates cerebral ischemic injury through regulation of angiogenesis

Vascular remodeling and neuroprotection are two major adaptable methods for treating ischemic stroke. Edaravone is a protective agent for the treatment of stroke and was used as a positive control in the present study. Sodium tanshinone IIA sulfonate (STS) has demonstrated therapeutic clinical effects in cerebral infarction in China, while its mechanisms of action in ischemic stroke have remained elusive. The angiogenesis and neuroprotective effects of STS were evaluated in a rat model induced by middle cerebral artery occlusion and 3 days of reperfusion. When used at the same dose, the magnitude of the therapeutic effect of STS was similar to that of edaravone in terms of decreased blood-brain barrier damage as indicated by reduced Evans blue leakage, improved neurological deficits, alleviated cerebral edema and inhibition of histopathological changes caused by ischemia/reperfusion. The TUNEL assay demonstrated that the ability of STS to inhibit neuronal apoptosis was equivalent to that of edaravone. Immunofluorescence detection of CD31 and α-smooth muscle actin indicated that the vascular density was significantly reduced in the vehicle group compared with that in the sham operation group, STS increased the microvessel density in the ischemic area. Furthermore, in the vehicle group the protein expression of vascular endothelial growth factor (VEGF) and VEGF receptor 2 (VEGFR) as determined by fluorescence microscopy and immunohistochemistry was significantly reduced compared with that in the sham group. However, STS promoted their expression compared to the vehicle group respectively, and increaed the mRNA expression of VEGF, VEGFR, CD31 and angiopoietin-1 as determined by reverse transcription-quantitative PCR, but these changes were not significant or not present for edaravone apart from Ang-1. In conclusion, STS protected against ischemic brain injury by promoting angiogenesis in ischemic areas and inhibiting neuronal apoptosis. These results provide a potential treatment for stroke recovery.

Reactive Astrocytes: Critical Players in the Development of Chronic Pain

Chronic pain is associated with long term plasticity of nociceptive pathways in the central nervous system. Astrocytes can profoundly affect synaptic function and increasing evidence has highlighted how altered astrocyte activity may contribute to the pathogenesis of chronic pain. In response to injury, astrocytes undergo a shift in form and function known as reactive astrogliosis, which affects their release of cytokines and gliotransmitters. These neuromodulatory substances have been implicated in driving the persistent changes in central nociceptive activity. Astrocytes also release lactate which neurons can use to produce energy during synaptic plasticity. Furthermore, recent research has provided insight into lactate's emerging role as a signaling molecule in the central nervous system, which may be involved in directly modulating neuronal and astrocytic activity. In this review, we present evidence for the involvement of astrocyte-derived tumor necrosis factor alpha in pain-associated plasticity, in addition to research suggesting the potential involvement of gliotransmitters D-serine and adenosine-5'-triphosphate. We also discuss work implicating astrocyte-neuron metabolic coupling, and the possible role of lactate, which has been sparsely studied in the context of chronic pain, in supporting pathological changes in central nociceptive activity.

Astrocytic NDRG2 is critical in the maintenance of neuropathic pain

Activation of astrocytes and abnormal synaptic glutamate metabolism are closely associated with the induction and maintenance of neuropathic pain (NP), but the exact mechanism underlying this association remains unclear. N-myc downstream-regulated gene 2 (NDRG2), a novel tumor-suppressor protein and stress-response gene, is involved in the pathogenesis of several neurodegenerative diseases. However, its role in nociceptive transduction has rarely been investigated. Here, we found that NDRG2, which was mainly expressed in the astrocytes in the central nervous system (CNS), was increased in the spinal cord of a spinal nerve ligation (SNL) rat model for NP. Suppression of NDRG2 by intrathecal injection of an NDRG2-RNAi-adenovirus significantly alleviated SNL-induced mechanical and thermal hypersensitivity, as well as elevated astrocytic glutamate transporter 1 (GLT-1) expression and downregulated pro-inflammatory cytokine levels, in the spinal dorsal horn of rats on Day 10 after SNL. Furthermore, in lipopolysaccharide (LPS)-stimulated primary astrocytic cultures derived from neonatal rats, inhibition of NDRG2 significantly reversed both the LPS-induced activation of astrocytes and decreased expression of GLT-1. By contrast, overexpression of NDRG2 by an adenoviral vector carrying NDRG2 resulted in astrocytic activation, aberrant glutamatergic neurotransmission, and spontaneous nociceptive responses in rats. Intrathecal injection of AG490, which is an inhibitor of the Janus tyrosine kinase and signal transducer and activator of the transcription 3 (JAK/STAT3) signaling pathway, significantly attenuated both mechanical and thermal hyperalgesia, as well as inhibited reactive astrocytes and restored normal expression levels of astrocytic GLT-1, in the spinal dorsal horn of NDRG2-overexpression rats. In conclusion, spinal astrocytic NDRG2 is critical in the maintenance of NP. Moreover, NDRG2 modulates astrocytic activation and inflammatory responses via regulating GLT-1 expression through the JAK/STAT3 signaling pathway. Our findings suggested that NDRG2 could be a novel therapeutic target for the treatment of NP.

Regulation of the KATP-JNK gap junction signaling pathway by immunomodulator astragaloside IV attenuates neuropathic pain

BACKGROUND AND OBJECTIVES

Gap junctions play a pivotal role in contributing to the formation of astroglial networks and in chronic pain. However, the mechanisms underlying the dysfunction of astroglial gap junctions in chronic pain have not been fully elucidated.

METHODS

Chronic constriction injury (CCI) of the sciatic nerve was used to establish rat neuropathic pain model. C6 cells were used to perform experiments in vitro. Von Frey hairs and Hargreave's method were used to determine the withdrawal threshold of rats. Protein expression was detected by immunofluorescence and western blotting.

RESULTS

Astragaloside IV (AST IV) significantly attenuated neuropathic pain and suppressed the excitation of spinal astrocytes in rats with CCI. The antinociceptive effect of AST IV was reversed by the gap junction decoupler carbenoxolone (CBX). AST IV inhibited the high expression of phosphorylated connexin 43 (p-Cx43) and p-c-Jun N-terminal kinase (p-JNK) in spinal cord of rats with CCI. JNK inhibitor alleviated neuropathic pain, which was reversed by CBX. JNK inhibitor decreased the high expression of p-Cx43 in both rats with CCI and tumor necrosis factor-alpha (TNF-α)-treated C6 cells. Additionally, the analgesic effect of AST IV was reversed by the adenosine triphosphate-sensitive potassium (K_ATP) channel blocker, glibenclamide (Glib). Glib abolished the inhibitory effects of AST IV on p-JNK and p-Cx43 both in vivo and in vitro. K_ATP channel opener (KCO) mimicked the inhibitory effects of AST IV on p-JNK and p-Cx43 in TNF-α-treated C6 cells.

CONCLUSION

Our results indicate that the sciatic nerve CCI induces the dysfunction of gap junctions in the spinal cord by activating K_ATP/JNK signaling to contribute to neuropathic pain. AST IV attenuates neuropathic pain via regulating the K_ATP-JNK gap junction axis.

Osthole alleviates neuropathic pain in mice by inhibiting the P2Y1-receptor-dependent JNK signaling pathway

There are many reports about natural products relieving neuralgia. Osthole is the main component of Angelica biserrata Yuan et Shan, a natural product that treats rheumatism through the elimination of inflammation and the alleviation of pain that has a long history in the clinic. The analgesic mechanism of osthole is complicated and confusing. Astrocytes have attracted increasing attention from pain researchers. Inhibitors targeting astrocytes are thought to be promising treatments for neuropathic pain. Whether osthole can alleviate neuropathic pain through astrocytes has not been elucidated in detail. In this study, CCI surgery was used to establish the neuropathic pain model in mice. The CCI mice were treated with osthole (5, 10, or 20 mg/kg/day) for 14 days in vivo. Mechanical allodynia and heat hyperalgesia were measured to evaluate the therapeutic effect of osthole. In mechanism research, the activation of astrocytes; the protein expression of P2Y₁R and p-JNK in astrocytes; the release of inflammatory factors; the variations in mEPSPs and eEPSPs; and the levels of GluA1, GluN2B, p-ERK, p-CREB and c-Fos in neurons were observed. The P2Y₁R inhibitor MRS2179 and the p-JNK inhibitor SP600125 were used to demonstrate how osthole works in neuropathic pain. In addition, astrocytes and neurons were used to estimate the direct effect of osthole on astrocyte-neuron interactions and signal transmission in vitro. Our findings suggest that osthole treatment obviously relieved mechanical allodynia and heat hyperalgesia in CCI mice. P2Y₁R is involved in CCI-induced pain hypersensitivity, and P2Y₁R is required for osthole-induced p-JNK downregulation in the spinal cord. Osthole inhibited astrocyte activation and reduced inflammatory factor expression. After osthole treatment, mEPSP frequency and eEPSP amplitude were decreased in spinal lamina I-II neurons. Downstream signaling molecules such as pGluA1, pGluN2B, p-ERK, p-CREB and c-Fos were also reduced very quickly in osthole-treated neuralgic mice. Our conclusion is that osthole alleviates neuropathic pain in mice via the P2Y₁-receptor-dependent JNK signaling pathway in spinal astrocytes, and osthole could be considered a potential pharmacotherapy to alleviate neuropathic pain.

The Importance of Natural Antioxidants in the Treatment of Spinal Cord Injury in Animal Models: An Overview

Patients with spinal cord injury (SCI) face devastating health, social, and financial consequences, as well as their families and caregivers. Reducing the levels of reactive oxygen species (ROS) and oxidative stress are essential strategies for SCI treatment. Some compounds from traditional medicine could be useful to decrease ROS generated after SCI. This review is aimed at highlighting the importance of some natural compounds with antioxidant capacity used in traditional medicine to treat traumatic SCI. An electronic search of published articles describing animal models of SCI treated with natural compounds from traditional medicine was conducted using the following terms: Spinal Cord Injuries (MeSH terms) AND Models, Animal (MeSH terms) AND [Reactive Oxygen Species (MeSH terms) AND/OR Oxidative Stress (MeSH term)] AND Medicine, Traditional (MeSH terms). Articles reported from 2010 to 2018 were included. The results were further screened by title and abstract for studies performed in rats, mice, and nonhuman primates. The effects of these natural compounds are discussed, including their antioxidant, anti-inflammatory, and antiapoptotic properties. Moreover, the antioxidant properties of natural compounds were emphasized since oxidative stress has a fundamental role in the generation and progression of several pathologies of the nervous system. The use of these compounds diminishes toxic effects due to their high antioxidant capacity. These compounds have been tested in animal models with promising results; however, no clinical studies have been conducted in humans. Further research of these natural compounds is crucial to a better understanding of their effects in patients with SCI.

Danshen: a phytochemical and pharmacological overview

Danshen, the dried root or rhizome of Salvia miltiorrhiza Bge., is a traditional and folk medicine in Asian countries, especially in China and Japan. In this review, we summarized the recent researches of Danshen in traditional uses and preparations, chemical constituents, pharmacological activities and side effects. A total of 201 compounds from Danshen have been reported, including lipophilic diterpenoids, water-soluble phenolic acids, and other constituents, which have showed various pharmacological activities, such as anti-inflammation, anti-oxidation, anti-tumor, anti-atherogenesis, and anti-diabetes. This article intends to provide novel insight information for further development of Danshen, which could be of great value to its improvement of utilization.

Astrocyte activation in the periaqueductal gray promotes descending facilitation to cancer-induced bone pain through the JNK MAPK signaling pathway

Descending nociceptive modulation from the supraspinal structures has an important role in cancer-induced bone pain (CIBP). Midbrain ventrolateral periaqueductal gray (vlPAG) is a critical component of descending nociceptive circuits; nevertheless, its precise cellular and molecular mechanisms involved in descending facilitation remain elusive. Our previous study has shown that the activation of p38 MAPK in vlPAG microglia is essential for the neuropathic pain sensitization. However, the existence of potential connection between astrocytes and c-Jun N-terminal kinase (JNK) pathway in CIBP has not yet been elucidated. The following study examines the involvement of astrocyte activation and upregulation of p-JNK in vlPAG, using a CIBP rat model. Briefly, CIBP was mimicked by an intramedullary injection of Walker 256 mammary gland carcinoma cells into the animal tibia. A significant increase in expression levels of astrocytes in the vlPAG of CIBP rats was observed. Furthermore, stereotaxic microinjection of the astrocytic cytotoxin L-α-aminoadipic acid decreased the mechanical allodynia as well as established and reversed the astrocyte activation in CIBP rats. A significant increase in expression levels of p-JNK in astrocytes in vlPAG of CIBP rats was also observed. Moreover, the intrathecal administration of JNK inhibitors SP600125 reduced the expression of glial fibrillary acidic protein, while microinjection of the SP600125 decreased the mechanical allodynia of CIBP rats. These results suggested that CIBP is associated with astrocyte activation in the vlPAG that probably participates in driving descending pain facilitation through the JNK MAPK signaling pathway. To sum up, these findings reveal a novel site of astrocytes modulation of CIBP.

Retracted: Long noncoding RNA THRIL contributes in lipopolysaccharide-induced HK-2 cells injury by sponging miR-34a

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease with unknown etiology. Nowadays, several long noncoding RNAs (lncRNAs) have been reported as molecular alterations involved in SLE. This study aimed to reveal the function of TNF-related and HNRNPL-related immunoregulatory lncRNA (THRIL) in SLE. Human epithelial HK-2 cells were exposed to lipopolysaccharide (LPS) to mimic an in vitro SLE model. Then, the functions of THRIL, miR-34a, and monocyte chemoattractant protein-1 (MCP-1), as well as their correlations were detected. LncRNA THRIL was highly expressed in the LPS-stimulated cells, and THRIL overexpression aggravated LPS-induced cell damage as cell viability was decreased, and apoptosis and the release of proinflammatory cytokines were increased. THRIL worked as a sponge of microRNA-34a (miR-34a) and it could directly target MCP-1. Furthermore, MCP-1-activated JNK and Wnt/β-catenin signaling pathways. In conclusion, this study suggested that lncRNA THRIL might be a key regulator participating in LPS-induced injury in HK-2 cells. THRIL overexpression aggravated LPS-induced injury possibly via sponging miR-34a, and thus preventing MCP-1 from degradation by miR-34a. The THRIL/miR-34a/MCP-1 axis might play critical roles in SLE.

Decreased HCN2 channel expression attenuates neuropathic pain by inhibiting pro-inflammatory reactions and NF-κB activation in mice

Hyperpolarization-activated cyclic nucleotide-gated 2 (HCN2) ion channel activity plays a crucial role in the progress of peripheral neuropathic pain (PNP). However, the mechanism of HCN2 channels on PNP remains unclear. Here, we investigated the effects of HCN2 channel expression on the mechanical allodynia and thermal hyperalgesia, the local inflammatory response, the activation of astrocytes, microglia and transcription factor NF-κB in mice with spared sciatic nerve injury (SNI). The present study showed that the expression of HCN2 channels was increased in L4-L5 ipsilateral spinal dorsal horns, accompanied by a decreased paw mechanical withdrawal threshold (MWT) and paw withdrawal latency (PWL) in SNI mice. After intrathecal injection of ZD-7288 and si-HCN2, both MWT and PWL were significantly increased, while the level of pro-inflammatory factors TNF-α, IL-1β and MCP-1 were decreased in L4-L5 ipsilateral spinal dorsal horn. Furthermore, the inhibition of HCN2 channels reduces the activated astrocytes and microglia, and suppressed NF-κB p65 activation and nuclear translocation. In conclusion, the present study suggests that decreased HCN2 channel expression attenuates neuropathic pain by inhibiting pro-inflammatory reactions and NF-κB activation.

Correlation of TGN-020 with the analgesic effects via ERK pathway activation after chronic constriction injury

Extracellular regulated protein kinase (ERK) pathway activation in astrocytes and neurons has been reported to be critical for neuropathic pain development after chronic constriction injury. TGN-020 was found to be the most potent aquaporin 4 inhibitor among the agents studied. The present study aimed to assess whether the inhibition of aquaporin 4 had an analgesic effect on neuropathic pain and whether the inhibition of astrocytic activation and ERK pathway was involved in the analgesic effect of TGN-020. We thus found that TGN-020 upregulated the threshold of thermal and mechanical allodynia, downregulated the expression of interleukin-1β, interleukin-6, and tumor necrosis factor-α, attenuated the astrocytic activation and suppressed the activation of mitogen-activated protein kinase pathways in the spinal dorsal horn and dorsal root ganglion. Additionally, TGN-020 suppressed ERK phosphorylation in astrocytes and neurons after injury. The findings suggested that the analgesic effects of TGN-020 in neuropathic pain were mediated mainly by the downregulation of chronic constriction injury-induced astrocytic activation and inflammation, which is via the inhibition of ERK pathway in the spinal dorsal horn and dorsal root ganglion.

The synergistic effect of treatment with triptolide and MK-801 in the rat neuropathic pain model

Triptolide (T10), an active component of Tripterygium wilfordii Hook F, is reported to have potent anti-inflammatory and analgesic effects. Additionally, MK-801, a noncompetitive N-methyl-D-aspartate receptor antagonist, can reduce glutamate toxicity and has a significant analgesic effect on chronic pain. In this study, we tested the possible synergistic analgesic ability by intrathecal administration of T10 and MK-801 for the treatment of neuropathic pain. Single T10 (3, 10, or 30 µg/kg), MK-801 (10, 30, or 90 µg/kg), or a combination of them were intrathecally administrated in rats with spinal nerve ligation. We found that single administration of T10 caused a slow-acting but long-term analgesic effect, while single administration of MK-801 caused a fast-acting but short-term effect. Administration of their combination showed obviously synergic analgesia and the 1:3 ratio of T10 to MK-801 reached the peak effect. Furthermore, application of T10 and/or MK-801 significantly inhibited the activation of microglia and astrocyte and phosphorylation of STAT₃ and NR2B in the spinal dorsal horn induced by chronic neuropathic pain. Our data suggest that the combination of T10 and MK-801 may be a potentially novel strategy for treatment of neuropathic pain.

Neuroprotective effect of tanshinone IIA weakens spastic cerebral palsy through inflammation, p38MAPK and VEGF in neonatal rats

As one of main active ingredients of salvia miltiorrhizae, which is a traditional Chinese medicine, tanshinone IIA is the basis of its pharmacological activities. In the present study, the effect of tanshinone IIA on weakening spastic cerebral palsy (SCP) in neonatal rats was investigated. Radial arm water maze and holding tests were used to measure the alterations of spastic cerebral palsy, inflammation was measured using an ELISA kit, and western blot analysis was used to analyze the protein expression of p‑p38 mitogen‑activated protein kinase (MAPK) and vascular endothelial growth factor (VEGF). The central mechanisms involved in the mediation or modulation of inflammation, p‑p38 MAPK and VEGF were also investigated. Treatment with tanshinone IIA effectively inhibited spastic cerebral palsy, and the activities of interleukin (IL)‑1β, IL‑6, tumor necrosis factor‑α, monocyte chemoattractant protein 1, cyclooxygenase‑2 and prostaglandin E2 in a neonatal rat model of SCP. Tanshinone IIA effectively suppressed the protein expression of inducible nitric oxide synthase (NOS), phosphorylated (p‑) nuclear factor (NF)‑κB, p‑p38MAPK and VEGF, and activated the phosphorylation of inhibitor of NF‑κB and the protein expression of neuronal NOS in the SCP rat model. These results suggested that the neuroprotective effect of tanshinone IIA weakened SCP through inflammation, p38MAPK and VEGF in the neonatal rats.

Peripheral Neuropathy and Nerve Compression Syndromes in Burns

Peripheral neuropathy and nerve compression syndromes lead to substantial morbidity following burn injury. Patients present with pain, paresthesias, or weakness along a specific nerve distribution or experience generalized peripheral neuropathy. The symptoms manifest at various times from within one week of hospitalization to many months after wound closure. Peripheral neuropathy may be caused by vascular occlusion of vasa nervorum, inflammation, neurotoxin production leading to apoptosis, and direct destruction of nerves from the burn injury. This article discusses the natural history, diagnosis, current treatments, and future directions for potential interventions for peripheral neuropathy and nerve compression syndromes related to burn injury.

Neuron-restrictive silencer factor-mediated downregulation of μ-opioid receptor contributes to the reduced morphine analgesia in bone cancer pain

Neuron-restrictive silencer factor–induced downregulation of μ-opioid receptor is involved in the reduction of morphine analgesia in sarcoma-induced bone cancer pain.

Bone cancer pain has been reported to have unique mechanisms and is resistant to morphine treatment. Recent studies have indicated that neuron-restrictive silencer factor (NRSF) plays a crucial role in modulating the expression of the μ-opioid receptor (MOR) gene. The present study elucidates the regulatory mechanisms of MOR and its ability to affect bone cancer pain. Using a sarcoma-inoculated murine model, pain behaviors that represent continuous or breakthrough pain were evaluated. Expression of NRSF in the dorsal root ganglion (DRG) and spinal dorsal horn was quantified at the transcriptional and translational levels, respectively. Additionally, chromatin immunoprecipitation assays were used to detect NRSF binding to the promoter of MOR. Furthermore, NRSF was genetically knocked out by antisense oligodeoxynucleotide, and the expression of MOR and the effect of morphine were subsequently analyzed. Our results indicated that in a sarcoma murine model, NRSF expression is upregulated in dorsal root ganglion neurons, and the expression of NRSF mRNA is significantly negatively correlated with MOR mRNA expression. Additionally, chromatin immunoprecipitation analysis revealed that NRSF binding to the neuron-restrictive silencer element within the promoter area of the MOR gene is promoted with a hypoacetylation state of histone H3 and H4. Furthermore, genetically knocking down NRSF with antisense oligodeoxynucleotide rescued the expression of MOR and potentiated the systemic morphine analgesia. The present results suggest that in sarcoma-induced bone cancer pain, NRSF-induced downregulation of MOR is involved in the reduction of morphine analgesia. Epigenetically, up-regulation of MOR could substantially improve the effect of system delivery of morphine.

Analgesic effect of coumarins from Radix angelicae pubescentis is mediated by inflammatory factors and TRPV1 in a spared nerve injury model of neuropathic pain

ETHNOPHARMACOLOGICAL RELEVANCE

Coumarins from Radix angelicae pubescentis (CRAP) are a major active component that are isolated from dried roots of Angelica biserrata Yuan et Shan, which has been used clinically to cure headaches for a long period of time, and it is an effective treatment for pain. The aim of the present study was to investigate the analgesic effect of CRAP on a spared nerve injury (SNI) model of neuropathy.

MATERIALS AND METHODS

Antinociceptive effects of CRAP were assessed in Sprague-Dawley male rats using a spared nerve injury model of neuropathic pain. Inflammatory factors were determined by Enzyme-linked immunosorbent assay (ELISA). Transient receptor potential cation channel 1 (TRPV1) and Phosphorylated extracellular regulated protein kinases (pERK) were detected by Immunofluorescence and Western blotting, respectively.

RESULTS

The high performance liquid chromatography (HPLC) analysis showed the presence of osthole and columbianadin in Radix angelicae pubescentis. CRAP induced the dose-dependent effect of on attenuating the development of mechanical hypersensitivity. Molecular profiling revealed that CRAP reduced the levels of pro-inflammatory cytokines tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) and significantly attenuated the expression of TRPV1 and pERK in damaged DRG neurons.

CONCLUSION

This results demonstrate that CRAP possess remarkable antinociceptive activities which may be due to osthole and columbianadin at least in part, supporting the folkloric usage of the plant to treat various pain diseases.

Necrostatin-1 attenuates early brain injury after subarachnoid hemorrhage in rats by inhibiting necroptosis

Necroptosis is programmed cell death that has been recently proposed and reported to be involved in several neurologic diseases. However, the role of necroptosis in early brain injury after subarachnoid hemorrhage (SAH) is still unknown. The purpose of this study was to investigate whether necroptosis was involved in SAH-induced early brain injury, and to assess the possible neuroprotective effect of necrostatin-1 using an endovascular perforation rat model of SAH. Our results showed that the expression levels of necroptosis-related proteins including RIP1, RIP3 and MLKL in the basal cortex all increased at 3 hours after SAH (P<0.05) and peaked at 48 hours after SAH (P<0.05). However, they were greatly reduced after treatment with necrostatin-1 (P<0.05). Concurrently, neurologic outcomes were significantly improved after necrostatin-1 treatment (P<0.05). Furthermore, brain edema, blood-brain barrier disruption, necrotic cell death and neuroinflammation were also greatly inhibited after necrostatin-1 treatment. These results indicate that necroptosis is an important mechanism of cell death involved in the early brain injury after experimental SAH. Necrostatin-1 perhaps can serve as a promising neuroprotective agent for SAH treatment.

Tanshinones and mental diseases: from chemistry to medicine

The prevalence of mental diseases, especially neurodegenerative disorders, is ever-increasing, while treatment options for such disorders are limited and insufficient. In this scarcity of available medication, it is a feasible strategy to search for potential drugs among natural compounds, such as those found in plants. One such plant source is the root of Chinese sage, Salvia miltiorrhiza Bunge (Labiatae), which contains several compounds reported to possess neuroprotective activities. The most important of these compounds are tanshinones, which have been reported to possess ameliorative activity against a myriad of mental diseases such as Alzheimer’s disease, cerebral ischemia/reperfusion injury, and glioma, along with promoting neuronal differentiation and manifesting antinociceptive and anticonvulsant outcomes. This review offers a critical evaluation of the utility of tanshinones to treat mental illnesses, and sheds light on the underlying mechanisms through which these naturally occurring compounds confer neuroprotection.

Spinal astrocytic activation contributes to mechanical allodynia in a rat model of cyclophosphamide-induced cystitis

BACKGROUND

Previous studies have demonstrated that glial cells play an important role in the generation and maintenance of neuropathic pain. Activated glial cells produce numerous mediators such as proinflammatory cytokines that facilitate neuronal activity and synaptic plasticity. Similarly, bladder pain syndrome/interstitial cystitis shares many characteristics of neuropathic pain. However, related report on the involvement of spinal glia in bladder pain syndrome/interstitial cystitis-associated pathological pain and the underlying mechanisms are still lacking. The present study investigated spinal glial activation and underlying molecular mechanisms in a rat model of bladder pain syndrome/interstitial cystitis.

RESULTS

A rat model of bladder pain syndrome/interstitial cystitis was established via systemic injection with cyclophosphamide. Mechanical allodynia was tested with von Frey monofilaments and up-down method. Moreover, Western blots and double immunofluorescence were used to detect the expression and location of glial fibrillary acidic protein, OX42/Iba1, P-P38, NeuN, interleukin (IL)-1β, phosphorylation of N-methyl-D-aspartate receptor 1 (P-NR1), and IL-1 receptor I (IL-1RI) in the L6-S1 spinal cord. We found that glial fibrillary acidic protein rather than OX42/Iba1 or P-P38 was significantly increased in the spinal cord of cyclophosphamide-induced cystitis. L-alpha-aminoadipate but not minocycline markedly attenuated the allodynia. Furthermore, we found that spinal IL-1β was dramatically increased in cyclophosphamide-induced cystitis, and activated astrocytes were the only source of IL-1β release, which contributed to allodynia in cystitis rats. Besides, spinal P-NR1 was statistically increased in cyclophosphamide-induced cystitis and only localized in IL-1RI positive neurons in spinal dorsal horn. Additionally, NR antagonist significantly attenuated the cystitis-induced pain. Interestingly, the time course of the P-NR1 expression paralleled to that of IL-1β or glial fibrillary acidic protein.

CONCLUSIONS

Our results demonstrated that astrocytic activation but not microglial activation contributed to the allodynia in cyclophosphamide-induced cystitis and IL-1β released from astrocytes might bind to its endogenous receptor on the neurons inducing the phosphorylation of NR1 subunit, leading to sensory neuronal hyperexcitability and pathological pain.

The analgesic effect of rolipram is associated with the inhibition of the activation of the spinal astrocytic JNK/CCL2 pathway in bone cancer pain

Bone cancer pain (BCP) is one of the most difficult and intractable tasks for pain management, which is associated with spinal 'neuron-astrocytic' activation. The activation of the c-Jun N-terminal kinase (JNK)/chemokine (C-C motif) ligand (CCL2) signaling pathway has been reported to be critical for neuropathic pain. Rolipram (ROL), a selective phosphodiesterase 4 inhibitor, possesses potent anti-inflammatory and anti-nociceptive activities. The present study aimed to investigate whether the intrathecal administration of ROL has an analgesic effect on BCP in rats, and to assess whether the inhibition of spinal JNK/CCL2 pathway and astrocytic activation are involved in the analgesic effects of ROL. The analgesic effects of ROL were evaluated using the Von Frey and Hargreaves tests. Immunofluorescence staining was used to determine the number of c-Fos immunoreactive neurons, and the expression of spinal astrocytes and microglial activation on day 14 after tumor cell inoculation. Enzyme-linked immunosorbent assay (ELISA) was used to detect the expression of pro-inflammatory cytokines [interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α] and chemokines (CCL2), and western blot analysis was then used to examine the spinal phosphodiesterase 4 (PDE4), ionized calcium binding adapter molecule-1 (IBA-1) and JNK levels on day 14 after tumor cell inoculation. The results revealed that ROL exerted a short-term analgesic effect in a dose-dependent manner, and consecutive daily injections of ROL exerted continuous analgesic effects. In addition, spinal 'neuron-astrocytic' activation was suppressed and was associated with the downregulation of spinal IL-1β, IL-6 and TNF-α expression, and the inhibition of PDE4B and JNK levels in the spine was also observed. In addition, the level of CCL2 was decreased in the rats with BCP. The JNK inhibitor, SP600125, decreased CCL2 expression and attenuated pain behavior. Following co-treatment with ROL and SP600125, no significant increases in thermal hyperalgesia and CCL2 expression were observed compared with the ROL group. Thus, our findings suggest that the analgesic effects of ROL in BCP are mainly mediated through the inhibition of 'neuron-astrocytic' activation, which occurs via the suppression of spinal JNK/CCL2 signaling.

MCP-1-mediated activation of microglia promotes white matter lesions and cognitive deficits by chronic cerebral hypoperfusion in mice

Microglia activation played a vital role in the pathogenesis of white matter lesions (WMLs) by chronic cerebral hypoperfusion. In addition, hypoxia induced up-regulated expression of MCP-1, promotes the activation of microglia. However, the role of MCP-1-mediated microglia activation in chronic cerebral ischemia is still unknown. To explore that, chronic cerebral hypoperfusion model was established by permanent stenosis of bilateral common carotid artery in mice. The activation of microglia and the related signal pathway p38MAPK/PKC in white matter, and working memory of mice were observed. We found that stenosis of common carotid arteries could induce MCP-1-mediated activation of microglia through p38MAPK/PKC pathway and white matter lesions. Taken together, our findings represent a novel mechanism of MCP-1 involved in activation of microglia and provide a novel therapeutical strategy for chronic cerebral hypoperfusion.

Targeting glia for bone cancer pain

INTRODUCTION

Bone cancer pain (BCP) remains to be a clinical challenge with limited pharmaceutical interventions. Therefore, novel therapeutic targets for the management of BCP are in desperate need. Recently, a growing body of evidence has suggested that glial cells may play a pivotal role in the pathogenesis of BCP. Areas covered: This review summarizes the recent progress in the understanding of glia in BCP and reveals the potential therapeutic targets in glia for BCP treatment. Expert opinion: Pharmacological interventions inhibiting the activation of glial cells, suppressing glia-derived proinflammatory cytokines, cell surface receptors, and the intracellular signaling pathways may be beneficial for the pain management of advanced cancer patients. However, these pharmacological interventions should not disrupt the normal function of glia cells since they play a vital supportive and protective role in the central nervous system.

Upregulation of CCL2 via ATF3/c-Jun interaction mediated the Bortezomib-induced peripheral neuropathy

Bortezomib (BTZ) is a frequently used chemotherapeutic drug for the treatment of refractory multiple myeloma and hematological neoplasms. The mechanism by which the administration of BTZ leads to painful peripheral neuropathy remains unclear. In present study, we found that application of BTZ at 0.4 mg/kg for consecutive 5 days significantly increased the expression of CCL2 in DRG, and intrathecal administration of neutralizing antibody against CCL2 inhibited the mechanical allodynia induced by BTZ. We also found an increased expression of c-Jun in DRG, and that inhibition of c-Jun signaling prevented the CCL2 upregulation and mechanical allodynia in the rats treated with BTZ. Furthermore, the results with luciferase assay in vitro and ChIP assay in vivo showed that c-Jun might be essential for BTZ-induced CCL2 upregulation via binding directly to the specific position of the ccl2 promoter. In addition, the present results showed that an upregulated expression of ATF3 was co-expressed with c-Jun in the DRG neurons, and the enhanced interaction between c-Jun and ATF3 was observed in DRG in the rats treated with BTZ. Importantly, pretreatment with ATF3 siRNA significantly inhibited the recruitment of c-Jun to the ccl2 promoter in the rats treated with BTZ. Taken together, these findings suggested that upregulation of CCL2 resulting from the enhanced interaction between c-Jun and ATF3 in DRG contributed to BTZ-induced mechanical allodynia.

Targeting the Microglial Signaling Pathways: New Insights in the Modulation of Neuropathic Pain

The microglia, once thought only to be supporting cells of the central nervous system (CNS), are now recognized to play essential roles in many pathologies. Many studies within the last decades indicated that the neuro-immune interaction underlies the generation and maintenance of neuropathic pain. Through a large number of receptors and signaling pathways, the microglial cells communicate with neurons, astrocytes and other cells, including those of the immune system. A disturbance or loss of CNS homeostasis causes rapid responses of the microglia, which undergo a multistage activation process. The activated microglia change their cell shapes and gene expression profiles, which induce proliferation, migration, and the production of pro- or antinociceptive factors. The cells release a large number of mediators that can act in a manner detrimental or beneficial to the surrounding cells and can indirectly alter the nociceptive signals. This review discusses the most important microglial intracellular signaling cascades (MAPKs, NF-kB, JAK/STAT, PI3K/Akt) that are essential for neuropathic pain development and maintenance. Our objective was to identify new molecular targets that may result in the development of powerful tools to control the signaling associated with neuropathic pain.

Diphenylarsinic Acid Induced Activation of Cultured Rat Cerebellar Astrocytes: Phosphorylation of Mitogen-Activated Protein Kinases, Upregulation of Transcription Factors, and Release of Brain-Active Cytokines

Diphenylarsinic acid (DPAA) was detected as the primary compound responsible for the arsenic poisoning that occurred in Kamisu, Ibaraki, Japan, where people using water from a well that was contaminated with a high level of arsenic developed neurological (mostly cerebellar) symptoms and dysregulation of regional cerebral blood flow. To understand the underlying molecular mechanism of DPAA-induced cerebellar symptoms, we focused on astrocytes, which have a brain-protective function. Incubation with 10 µM DPAA for 96 h promoted cell proliferation, increased the expression of antioxidative stress proteins (heme oxygenase-1 and heat shock protein 70), and induced the release of cytokines (MCP-1, adrenomedullin, FGF2, CXCL1, and IL-6). Furthermore, DPAA overpoweringly increased the phosphorylation of three major mitogen-activated protein kinases (MAPKs) (ERK1/2, p38MAPK, and SAPK/JNK), which indicated MAPK activation, and subsequently induced expression and/or phosphorylation of transcription factors (Nrf2, CREB, c-Jun, and c-Fos) in cultured rat cerebellar astrocytes. Structure-activity relationship analyses of DPAA and other related pentavalent organic arsenicals revealed that DPAA at 10 µM activated astrocytes most effective among organic arsenicals tested at the same dose. These results suggest that in a cerebellum exposed to DPAA, abnormal activation of the MAPK-transcription factor pathway and irregular secretion of these neuroactive, glioactive, and/or vasoactive cytokines in astrocytes can be the direct/indirect cause of functional abnormalities in surrounding neurons, glial cells, and vascular cells: This in turn might lead to the onset of cerebellar symptoms and disruption of cerebral blood flow.