Tanshinone IIA Downregulates HMGB1 and TLR4 Expression in a Spinal Nerve Ligation Model of Neuropathic Pain

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.

Astrocyte-associated fibronectin promotes the proinflammatory phenotype of astrocytes through β1 integrin activation

Astrocytes are key players in neuroinflammation. In response to central nervous system (CNS) injury or disease, astrocytes undergo reactive astrogliosis, which is characterized by increased proliferation, migration, and glial fibrillary acidic protein (GFAP) expression. Activation of the transcription factor nuclear factor-κB (NF-κB) and upregulation of downstream proinflammatory mediators in reactive astrocytes induce a proinflammatory phenotype in astrocytes, thereby exacerbating neuroinflammation by establishing an inflammatory loop. In this study, we hypothesized that excessive fibronectin (FN) derived from reactive astrocytes would induce this proinflammatory phenotype in astrocytes in an autocrine manner. We exogenously treated astrocytes with monomer FN, which can be incorporated into the extracellular matrix (ECM), to mimic plasma FN extravasated through a compromised blood-brain barrier in neuroinflammation. We also induced de novo synthesis and accumulation of astrocyte-derived FN through tumor necrosis factor-α (TNF-α) stimulation. The excessive FN deposition resulting from both treatments initiated reactive astrogliosis and triggered NF-κB signaling in the cultured astrocytes. In addition, inhibition of FN accumulation in the ECM by the FN inhibitor pUR4 strongly attenuated the FN- and TNF-α-induced GFAP expression, NF-κB activation, and proinflammatory mediator production of astrocytes by interrupting FN-β1 integrin coupling and thus the inflammatory loop. In an in vivo experiment, intrathecal injection of pUR4 considerably ameliorated FN deposition, GFAP expression, and NF-κB activation in inflamed spinal cord, suggesting the therapeutic potential of pUR4 for attenuating neuroinflammation and promoting neuronal function restoration.

Polyphenols Targeting Oxidative Stress in Spinal Cord Injury: Current Status and Future Vision

A spinal cord injury (SCI) occurs when the spinal cord is deteriorated or traumatized, leading to motor and sensory functions lost even totally or partially. An imbalance within the generation of reactive oxygen species and antioxidant defense levels results in oxidative stress (OS) and neuroinflammation. After SCI, OS and occurring pathways of inflammations are significant strenuous drivers of cross-linked dysregulated pathways. It emphasizes the significance of multitarget therapy in combating SCI consequences. Polyphenols, which are secondary metabolites originating from plants, have the promise to be used as alternative therapeutic agents to treat SCI. Secondary metabolites have activity on neuroinflammatory, neuronal OS, and extrinsic axonal dysregulated pathways during the early stages of SCI. Experimental and clinical investigations have noted the possible importance of phenolic compounds as important phytochemicals in moderating upstream dysregulated OS/inflammatory signaling mediators and axonal regeneration's extrinsic pathways after the SCI probable significance of phenolic compounds as important phytochemicals in mediating upstream dysregulated OS/inflammatory signaling mediators. Furthermore, combining polyphenols could be a way to lessen the effects of SCI.

Salvianolic acid B ameliorates non-alcoholic fatty liver disease by inhibiting hepatic lipid accumulation and NLRP3 inflammasome in ob/ob mice

Non-alcoholic fatty liver disease (NAFLD) has high occurrence in the global world, which poses serious threats to human health. Salvianolic acid B (SalB), an extract of the root of Salvia miltiorrhiza, has the protective effect on metabolic homeostasis. However, the mechanism is still unknown. In this study, we used ob/ob mice, a model of NAFLD, to explore the hepatoprotective effects of SalB. The results showed that SalB significantly reduced the body weights and liver weights, and ameliorated plasma alanine aminotransferase (ALT), aspartate aminotransferase (AST), triglyceride (TG), hepatic free fatty acid (FFA), total cholesterol (TC) levels, and hepatic TG and TC levels in ob/ob mice. SalB reduced the number of lipid droplets and inhibited hepatic lipogenesis by regulating peroxisome proliferator-activated receptor gamma (PPARγ), fatty acid synthase (FASN), stearoyl-Co A desaturase 1 (SCD1), and cluster of differentiation 36 (CD36). Compared to ob/ob mice, the lower expressions of the pro-inflammatory cytokines, such as interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and F4/80, were observed after SalB treatment. Importantly, SalB treatment inhibited the activation of NLRP3 inflammasome and reduced the severity of liver inflammation. Our findings suggested that SalB improved NAFLD pathology in ob/ob mice by reducing hepatic lipid accumulation and NLRP3 inflammasome activation, which might be the potential hepatoprotective mechanism of SalB.

Dexmedetomidine relieved neuropathic pain and inflammation response induced by CCI through HMGB1/TLR4/NF-κB signal pathway

Neuropathic pain is one of the most intractable diseases. The lack of effective therapy measures remains a critical problem due to the poor understanding of the cause of neuropathic pain. The aim of this study was to investigate the effect of dexmedetomidine (Dex) in trigeminal neuropathic pain and the underlying molecular mechanism in order to identify possible therapeutic targets. We used a chronic constriction injury (CCI) model of mice to investigate whether Dex prevents neuropathic pain and the inflammation response. The α 2-adrenoceptors (α2AR) inhibitor BRL44408 and adenovirus for knocking down High mobility group box 1 (HMGB1) was administrated to confirm whether Dex exert its effect through targeting α2AR and HMGB1. The results indicated that Dex significantly inhibited CCI induced neuropathic pain through targeting α2AR and HMGB1. Dex inhibited the inflammatory response through decreasing the release and the mRNA expression of IL-1β, IL-6, and TNF-ɑ while increasing that of IL-10. Moreover, Dex participates in the regulation of HMGB1, Toll-like receptor 4 (TLR4), NFκb (p-65) expression and the phosphorylation of IκB-ɑ. In conclusion, Dex could relieve neuropathic pain through α2AR and HMGB1 and attenuate inflammation response.

Targeting apoptosis and autophagy following spinal cord injury: Therapeutic approaches to polyphenols and candidate phytochemicals

Spinal cord injury (SCI) is a neurological disorder associated with the loss of sensory and motor function. Understanding the precise dysregulated signaling pathways, especially apoptosis and autophagy following SCI, is of vital importance in developing innovative therapeutic targets and treatments. The present study lies in the fact that it reveals the precise dysregulated signaling mediators of apoptotic and autophagic pathways following SCI and also examines the effects of polyphenols and other candidate phytochemicals. It provides new insights to develop new treatments for post-SCI complications. Accordingly, a comprehensive review was conducted using electronic databases including, Scopus, Web of Science, PubMed, and Medline, along with the authors' expertise in apoptosis and autophagy as well as their knowledge about the effects of polyphenols and other phytochemicals on SCI pathogenesis. The primary mechanical injury to spinal cord is followed by a secondary cascade of apoptosis and autophagy that play critical roles during SCI. In terms of pharmacological mechanisms, caspases, Bax/Bcl-2, TNF-α, and JAK/STAT in apoptosis along with LC3 and Beclin-1 in autophagy have shown a close interconnection with the inflammatory pathways mainly glutamatergic, PI3K/Akt/mTOR, ERK/MAPK, and other cross-linked mediators. Besides, apoptotic pathways have been shown to regulate autophagy mediators and vice versa. Prevailing evidence has highlighted the importance of modulating these signaling mediators/pathways by polyphenols and other candidate phytochemicals post-SCI. The present review provides dysregulated signaling mediators and therapeutic targets of apoptotic and autophagic pathways following SCI, focusing on the modulatory effects of polyphenols and other potential phytochemical candidates.

Role of high-mobility group box 1 and its modulation by thrombomodulin/thrombin axis in neuropathic and inflammatory pain

High-mobility group box 1 (HMGB1), a nuclear protein, once released to the extracellular space, facilitates pain signals as well as inflammation. Intraplantar or intraspinal application of HMGB1 elicits hyperalgesia/allodynia in rodents by activating the advanced glycosylation end-product specific receptor (receptor for advanced glycation end-products; RAGE) or Toll-like receptor 4 (TLR4). Endogenous HMGB1 derived from neurons, perineuronal cells or immune cells accumulating in the dorsal root ganglion or sensory nerves participates in somatic and visceral pain consisting of neuropathic and/or inflammatory components. Endothelial thrombomodulin (TM) and recombinant human soluble TM, TMα, markedly increase thrombin-dependent degradation of HMGB1, and systemic administration of TMα prevents and reverses various HMGB1-dependent pathological pain. Low MW compounds that directly inactivate HMGB1 or antagonize HMGB1-targeted receptors would be useful to reduce various forms of intractable pain. Thus, HMGB1 and its receptors are considered to serve as promising targets in developing novel agents to prevent or treat pathological pain. LINKED ARTICLES: This article is part of a themed issue on Neurochemistry in Japan. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.4/issuetoc.

Phytochemicals against TNFα-Mediated Neuroinflammatory Diseases

Tumor necrosis factor-alpha (TNF-α) is a well-known pro-inflammatory cytokine responsible for the modulation of the immune system. TNF-α plays a critical role in almost every type of inflammatory disorder, including central nervous system (CNS) diseases. Although TNF-α is a well-studied component of inflammatory responses, its functioning in diverse cell types is still unclear. TNF-α functions through its two main receptors: tumor necrosis factor receptor 1 and 2 (TNFR1, TNFR2), also known as p55 and p75, respectively. Normally, the functions of soluble TNF-α-induced TNFR1 activation are reported to be pro-inflammatory and apoptotic. While TNF-α mediated TNFR2 activation has a dual role. Several synthetic drugs used as inhibitors of TNF-α for diverse inflammatory diseases possess serious adverse effects, which make patients and researchers turn their focus toward natural medicines, phytochemicals in particular. Phytochemicals targeting TNF-α can significantly improve disease conditions involving TNF-α with fewer side effects. Here, we reviewed known TNF-α inhibitors, as well as lately studied phytochemicals, with a role in inhibiting TNF-α itself, and TNF-α-mediated signaling in inflammatory diseases focusing mainly on CNS disorders.

Fibronectin inhibitor pUR4 attenuates tumor necrosis factor α-induced endothelial hyperpermeability by modulating β1 integrin activation

BACKGROUND

The blood-spinal cord barrier (BSCB) is composed of a monolayer of endothelium linked with tight junctions and extracellular matrix (ECM)-rich basement membranes and is surrounded by astrocyte foot processes. Endothelial permeability is regulated by interaction between endothelial cells and ECM proteins. Fibronectin (FN) is a principal ECM component of microvessels. Excessive FN deposition disrupts cell-cell adhesion in fibroblasts through β1 integrin ligation. To determine whether excessive FN deposition contributes to the disruption of endothelial integrity, we used an in vitro model of the endothelial monolayer to investigate whether the FN inhibitor pUR4 prevents FN deposition into the subendothelial matrix and attenuates endothelial leakage.

METHODS

To correlate the effects of excessive FN accumulation in microvessels on BSCB disruption, spinal nerve ligation-which induces BSCB leakage-was applied, and FN expression in the spinal cord was evaluated through immunohistochemistry and immunoblotting. To elucidate the effects by which pUR4 modulates endothelial permeability, brain-derived endothelial (bEND.3) cells treated with tumor necrosis factor (TNF)-α were used to mimic a leaky BSCB. A bEND.3 monolayer was preincubated with pUR4 before TNF-α treatment. The transendothelial electrical resistance (TEER) measurement and transendothelial permeability assay were applied to assess the endothelial integrity of the bEND.3 monolayer. Immunofluorescence analysis and immunoblotting were performed to evaluate the inhibitory effects of pUR4 on TNF-α-induced FN deposition. To determine the mechanisms underlying pUR4-mediated endothelial permeability, cell morphology, stress fiber formation, myosin light chain (MLC) phosphorylation, and β1 integrin-mediated signaling were evaluated through immunofluorescence analysis and immunoblotting.

RESULTS

Excessive FN was accumulated in the microvessels of the spinal cord after spinal nerve ligation; moreover, pUR4 inhibited TNF-α-induced FN deposition in the bEND.3 monolayer and maintained intact TEER and endothelial permeability. Furthermore, pUR4 reduced cell morphology alteration, actin stress fiber formation, and MLC phosphorylation, thereby attenuating paracellular gap formation. Moreover, pUR4 reduced β1 integrin activation and downstream signaling.

CONCLUSIONS

pUR4 reduces TNF-α-induced β1 integrin activation by depleting ECM FN, leading to a decrease in endothelial hyperpermeability and maintenance of monolayer integrity. These findings suggest therapeutic benefits of pUR4 in pathological vascular leakage treatment.

Spinal macrophage migration inhibitory factor and high mobility group box 1 mediate persistent bladder pain

Repeated intravesical PAR4 (protease activated receptor 4) activation elicits persistent bladder pain lasting 5 days after the last treatment. Persistent bladder pain was fully reversed by a systemic HMGB1 (high mobility group box 1) inhibitor while a MIF (macrophage migration inhibitory factor) antagonist partly reversed it. Since there is growing evidence that spinal MIF and HMGB1 mediate inflammatory and neuropathic pain we examined whether there were spinal changes occurring during persistent bladder pain that may be responsible for maintaining bladder pain. In addition, we tested whether we could modulate persistent bladder pain with spinal MIF or HMGB1 antagonists. Persistent bladder pain was elicited in female C57 mice by repeated (3x) intravesical instillation of PAR4-activating peptide while control animals received scramble peptide treatment. On day 4, spinal cord (L6-S1) changes in c-fos (non-specific marker of spinal activation) was assessed with immunofluorescence while MIF and HMGB1 were assessed with immunofluorescence, western blotting and real-time PCR. On day 7, mice received an intrathecal injection of a neutralizing MIF monoclonal antibody (15 μg in 5 μl PBS) or a HMGB1 inhibitor glycyrrhizin (25 μg in 5 μl of 5% alcohol in PBS) and abdominal mechanical threshold was tested. On day 9, mice were treated with vehicle or control and abdominal mechanical threshold was tested. Immunofluorescence showed that c-fos and MIF in the dorsal horn, dorsal grey commissure and intermediolateral areas significantly increased in PAR4-treated mice while HMGB1 was decreased. In addition, intrathecal treatment with MIF neutralizing mAb or glycyrrhizin significantly alleviated abdominal mechanical hypersensitivity at 1 and 2 h and the analgesic effect diminished at 6 h. Vehicle or control treatment had no effect. Persistent bladder pain is associated with spinal changes in MIF and HMGB1 levels. Furthermore, spinal treatment with MIF monoclonal antibody and HMGB1 inhibitor temporarily reversed bladder pain. Our findings suggest that spinal MIF and HMGB1 participate in persistent bladder pain induced by repeated intravesical PAR4 and may be potential therapeutic targets in chronic bladder pain conditions.

Can External Use of Chinese Herbal Medicine Prevent Cumulative Peripheral Neuropathy Induced by Oxaliplatin? A Systematic Literature Review With Meta-analysis

Background. Peripheral neurotoxicity caused by oxaliplatin (OXA) chemotherapy is the main limitation preventing continuation of chemotherapy in patients with gastrointestinal cancer. The purpose of this study was to determine the efficacy of external use of Chinese herbal medicine (CHM) on the incidence of cumulative OXA-induced peripheral neurotoxicity (OIPN). Method. Scientific literature databases were searched to identify controlled clinical trials analyzing CHM in OIPN. Clinical studies that included at least 1 relevant primary outcome were analyzed by 2 independent reviewers. Meta-analysis was performed on the software RevMan 5.3. Results. 700 cancer patients of 9 studies were reported, of whom 352 received external CHM and 348 received warm water baths, conventional medicine, or no intervention as controls. Neurotoxicity incidence (Levi grade ≥ 1) was significantly decreased in CHM group, compared with no intervention (P < .01). The incidence of cumulative neurotoxicity (Levi grade ≥2) was also significantly lower in the CHM group than in all the control groups (P < .05), and the cumulative neurotoxicity in the CHM group was significantly reduced (Levi grade ≥ 3) in comparision with no intervention (P < .01). These results were consistent with those of the subgroup analyses for preventing OIPN at each of the chemotherapy treatment cycles. There was no difference in the incidence of adverse events between groups (P > .05). Conclusion. External use of CHM may be beneficial in preventing the OXA-induced cumulative neurotoxicity. However, given the low quality of the evidence, the results should be interpreted with caution.

Lentiviral‑mediated inducible silencing of TLR4 attenuates neuropathic pain in a rat model of chronic constriction injury

An increasing body of evidence has indicated that spinal microglial Toll-like receptor 4 (TLR4) may serve a significant role in the development and maintenance of neuropathic pain (NP). In the present study, experiments were conducted to evaluate the contribution of a tetracycline inducible lentiviral-mediated delivery system for the expression of TLR4 small interfering (si)RNA to NP in rats with chronic constriction injury (CCI). Behavioral tests, including paw withdrawal latency and paw withdrawal threshold, and biochemical analysis of the spinal cord, including western blotting, reverse transcription-quantitative polymerase chain reaction and ELISA, were conducted following CCI to the sciatic nerve. Intrathecal administration of LvOn-si-TLR4 with doxycycline (Dox) attenuated allodynia and hyperalgesia. Biochemical analysis revealed that the mRNA and proteins levels of TLR4 were unregulated following CCI to the sciatic nerve, which was then blocked by intrathecal administration of LvOn-siTLR4 with Dox. The LvOn-siTLR4 was also demonstrated to have no effect on TLR4 or the pain response without Dox, which indicated that the expression of siRNA was Dox-inducible in the lentivirus delivery system. In conclusion, TLR4 may serve a significant role in neuropathy and the results of the present study provide an inducible lentivirus-mediated siRNA against TLR4 that may serve as a potential novel strategy to be applied in gene therapy for NP in the future.

Inhibiting High Mobility Group Box-1 Reduces Early Spinal Cord Edema and Attenuates Astrocyte Activation and Aquaporin-4 Expression after Spinal Cord Injury in Rats

High mobility group box-1 (HMGB1) could function as an early trigger for pro-inflammatory activation after spinal cord injury (SCI). Spinal cord edema contributes to inflammatory response mechanisms and a poor clinical prognosis after SCI, for which efficient therapies targeting the specific molecules involved remain limited. This study was designed to evaluate the roles of HMGB1 on the regulation of early spinal cord edema, astrocyte activation, and aquaporin-4 (AQP4) expression in a rat SCI model. Adult female Sprague-Dawley rats underwent laminectomy at T10, and the SCI model was induced by a heavy falling object. After SCI, rats received ethyl pyruvate (EP) or glycyrrhizin (GL) via an intraperitoneal injection to inhibit HMGB1. The effects of HMGB1 inhibition on the early spinal cord edema, astrocyte activation (glial fibrillary acidic protein [GFAP] expression), and AQP4 expression after SCI (12 h-3 days) were analyzed. The results showed that EP or GL effectively inhibited HMGB1 expression in the spinal cord and HMGB1 levels in the serum of SCI rats. HMGB1 inhibition improved motor function, reduced spinal cord water content, and attenuated spinal cord edema in SCI rats. HMGB1 inhibition decreased SCI-associated GFAP and AQP4 overexpression in the spinal cord. Further, HMGB1 inhibition also repressed the activation of the toll-like receptor 4/myeloid differentiation primary response gene 88/nuclear factor-kappa B signaling pathway. These results implicate that HMGB1 inhibition improved locomotor function and reduced early spinal cord edema, which was associated with a downregulation of astrocyte activation (GFAP expression) and AQP4 expression in SCI rats.

Tanshinone IIA alleviates lipopolysaccharide-induced acute lung injury by downregulating TRPM7 and pro-inflammatory factors

The study aimed to investigate the role of Tanshinone IIA (Tan IIA) in lipopolysaccharide (LPS)-induced acute lung injury (ALI) in its regulation of TRPM7. Wistar male rats were randomly divided into the normal saline (NS), LPS, knockout (KO) + LPS, low-dose Tan IIA (Tan-L), middle-dose Tan IIA (Tan-M), high-dose Tan IIA (Tan-H) and KO + high-dose Tan IIA (KO + Tan-H) groups. The level of tumour necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-6, TRPM7 protein expression, current density-voltage curve and Ca2+ concentration were detected through ELISA, Western blotting, electrophysiological experiment and a calcium-imaging technique, respectively. The rats in the KO + LPS, Tan-L, Tan-M, Tan-H and KO + Tan-H groups all displayed lower levels of TNF-α, IL-1β and IL-6 than the LPS group. Rats in the KO + Tan-H group exhibited lower levels of NF-α, IL-1β and IL-6 than rats in the Tan-H group. Elevated levels of TRPM7 protein expression in the LPS and Tan groups were detected in comparison with the NS group. However, TRPM7 protein expression in Tan-M and Tan-H groups was notably lower than in that of the LPS group. In comparison with the NS group, the LPS and Tan groups had a greater PIMs cell density and a higher concentration of Ca2+ . Contrary results were observed in the KO + LPS, Tan-H and KO + Tan-H groups. Tan IIA decreases calcium influx in PIMs and inhibits pro-inflammatory factors which provide an alleviatory effect in regards to LPS-induced ALI by suppressing TRPM7 expression.

Inhibition of HMGB1 reduces rat spinal cord astrocytic swelling and AQP4 expression after oxygen-glucose deprivation and reoxygenation via TLR4 and NF-κB signaling in an IL-6-dependent manner

Background

Spinal cord astrocyte swelling is an important component to spinal cord edema and is associated with poor functional recovery as well as therapeutic resistance after spinal cord injury (SCI). High mobility group box-1 (HMGB1) is a mediator of inflammatory responses in the central nervous system and plays a critical role after SCI. Given this, we sought to identify both the role and underlying mechanisms of HMGB1 in cellular swelling and aquaporin 4 (AQP4) expression in cultured rat spinal cord astrocytes after oxygen-glucose deprivation/reoxygenation (OGD/R).

Methods

The post-natal day 1–2 Sprague-Dawley rat spinal cord astrocytes were cultured in vitro, and the OGD/R model was induced. We first investigated the effects of OGD/R on spinal cord astrocytic swelling and HMGB1 and AQP4 expression, as well as HMGB1 release. We then studied the effects of HMGB1 inhibition on cellular swelling, HMGB1 and AQP4 expression, and HMGB1 release. The roles of both toll-like receptor 4 (TLR4)/nuclear factor-kappa B (NF-κB) signaling pathway and interleukin-6 (IL-6) in reducing cellular swelling resulting from HMGB1 inhibition in spinal cord astrocytes after OGD/R were studied. Intergroup data were compared using one-way analysis of variance (ANOVA) followed by Dunnett’s test.

Results

The OGD/R increased spinal cord astrocytic swelling and HMGB1 and AQP4 expression, as well as HMGB1 release. Inhibition of HMGB1 using either HMGB1 shRNA or ethyl pyruvate resulted in reduced cellular volume, mitochondrial and endoplasmic reticulum swelling, and lysosome number and decreased upregulation of both HMGB1 and AQP4 in spinal cord astrocytes, as well as HMGB1 release. The HMGB1 effects on spinal cord astrocytic swelling and AQP4 upregulation after OGD/R were mediated—at least in part—via activation of TLR4, myeloid differentiation primary response gene 88 (MyD88), and NF-κB. These activation effects can be repressed by TLR4 inhibition using CLI-095 or C34, or by NF-κB inhibition using BAY 11-7082. Furthermore, either OGD/R or HMGB1 inhibition resulted in changes in IL-6 release. IL-6 was also shown to mediate AQP4 expression in spinal cord astrocytes.

Conclusions

HMGB1 upregulates AQP4 expression and promotes cell swelling in cultured spinal cord astrocytes after OGD/R, which is mediated through HMGB1/TLR4/MyD88/NF-κB signaling and in an IL-6-dependent manner.

MicroRNA-142-3p relieves neuropathic pain by targeting high mobility group box 1

MicroRNA (miRNA) are emerging as critical regulators of neuropathic pain development. Neuroinflammation contributes to the development of neuropathic pain. miR‑142‑3p has been characterized as an inflammation‑related miRNA in various pathological processes. However, little is known about the role of miR‑142‑3p in neuroinflammation and neuropathic pain. The present study aimed to investigate the function of miR‑142‑3p in neuropathic pain by creating a murine model using spinal nerve ligation (SNL). A significant reduction in miR‑142‑3p expression was observed in the dorsal root ganglion of mice with SNL (P<0.05) compared with control mice. Overexpression of miR‑142‑3p significantly inhibited neuropathic pain and neuroinflammation in mice with SNL (P<0.05). High mobility group box 1 (HMGB1) was identified as a direct target gene of miR‑142‑3p by bioinformatic analysis and dual‑luciferase reporter assays. Overexpression of miR‑142‑3p significantly reduced the mRNA and protein expression levels of HMGB1 in vitro and in vivo (P<0.05). In addition, HMGB1 mRNA expression and miR‑142‑3p expression were inversely correlated in mice with SNL. Furthermore, overexpression of HMGB1 significantly reversed the inhibitory effect of miR‑142‑3p on neuroinflammation and neuropathic pain development (P<0.05). Overall, these results suggest that miR‑142‑3p functions as a negative regulator of neuropathic pain development through the downregulation of HMGB1, indicating that miR‑142‑3p may serve as a potential therapeutic target for neuropathic pain.

Disulfide high mobility group box-1 causes bladder pain through bladder Toll-like receptor 4

BACKGROUND

Bladder pain is a prominent symptom in several urological conditions (e.g. infection, painful bladder syndrome/interstitial cystitis, cancer). Understanding the mechanism of bladder pain is important, particularly when the pain is not accompanied by bladder pathology. Stimulation of protease activated receptor 4 (PAR4) in the urothelium results in bladder pain through release of urothelial high mobility group box-1 (HMGB1). HGMB1 has two functionally active redox states (disulfide and all-thiol) and it is not known which form elicits bladder pain. Therefore, we investigated whether intravesical administration of specific HMGB1 redox forms caused abdominal mechanical hypersensitivity, micturition changes, and bladder inflammation in female C57BL/6 mice 24 hours post-administration. Moreover, we determined which of the specific HMGB1 receptors, Toll-like receptor 4 (TLR4) or receptor for advanced glycation end products (RAGE), mediate HMGB1-induced changes.

RESULTS

Disulfide HMGB1 elicited abdominal mechanical hypersensitivity 24 hours after intravesical (5, 10, 20 μg/150 μl) instillation. In contrast, all-thiol HMGB1 did not produce abdominal mechanical hypersensitivity in any of the doses tested (1, 2, 5, 10, 20 μg/150 μl). Both HMGB1 redox forms caused micturition changes only at the highest dose tested (20 μg/150 μl) while eliciting mild bladder edema and reactive changes at all doses. We subsequently tested whether the effects of intravesical disulfide HMGB1 (10 μg/150 μl; a dose that did not produce inflammation) were prevented by systemic (i.p.) or local (intravesical) administration of either a TLR4 antagonist (TAK-242) or a RAGE antagonist (FPS-ZM1). Systemic administration of either TAK-242 (3 mg/kg) or FPS-ZM1 (10 mg/kg) prevented HMGB1 induced abdominal mechanical hypersensitivity while only intravesical TLR4 antagonist pretreatment (1.5 mg/ml; not RAGE) had this effect.

CONCLUSIONS

The disulfide form of HMGB1 mediates bladder pain directly (not secondary to inflammation or injury) through activation of TLR4 receptors in the bladder. Thus, TLR4 receptors are a specific local target for bladder pain.

Pre-conditioning with tanshinone IIA attenuates the ischemia/reperfusion injury caused by liver grafts via regulation of HMGB1 in rat Kupffer cells

OBJECTIVE

We have evaluated the protective mechanism of tanshinone IIA in ischemia/reperfusion injury (IRI) induced by liver grafts, revealing novel supplementary immunotherapy for liver transplantation.

METHODS

The tanshinone IIA preconditioning group (TP group) was pretreated with tanshinone IIA via intraperitoneal injection for 1 week before receiving orthotopic liver transplantation with hepatic arterial ischemia for 30min. The sham-operation group (SO group), control graft group (CG group) and IRI group were pretreated with an equivalent volume of normal saline. The IRI group and CG group received orthotopic liver transplantation with or without hepatic arterial ischemia. Rats were sacrificed at each time point, serum was collected for ELISA detection, and Kupffer cells (KCs) were isolated to extract total protein and RNA for western blotting and real-time PCR, respectively.

RESULTS

The levels of TNF-α and IL-4 in the TP group were significantly lower than those of in the IRI group; meanwhile the IL-10 and TGF-β levels were significantly higher than in the IRI group. The protein and mRNA expression levels of HMGB1 were significantly lower in TP group than in the IRI group at each time point. The TLR-4, Myd88, NLRP3 and p-NF-κb p65 expression levels in the TP groups were significantly lower than those in the IRI group, while the PTEN, PI3K and AKT phosphorylation levels in the TP groups were significantly higher than those in the IRI group.

CONCLUSIONS

Tanshinone IIA attenuates IRI caused by liver grafts via down-regulation of the HMGB1-TLR-4/NF-κb pathway in KCs and activation of PTEN/PI3K/AKT pathway, suggesting a potential role for prevention of liver cell IRI during liver transplantation.

The Emerging Role of HMGB1 in Neuropathic Pain: A Potential Therapeutic Target for Neuroinflammation

Neuropathic pain (NPP) is intolerable, persistent, and specific type of long-term pain. It is considered to be a direct consequence of pathological changes affecting the somatosensory system and can be debilitating for affected patients. Despite recent progress and growing interest in understanding the pathogenesis of the disease, NPP still presents a major diagnostic and therapeutic challenge. High mobility group box 1 (HMGB1) mediates inflammatory and immune reactions in nervous system and emerging evidence reveals that HMGB1 plays an essential role in neuroinflammation through receptors such as Toll-like receptors (TLR), receptor for advanced glycation end products (RAGE), C-X-X motif chemokines receptor 4 (CXCR4), and N-methyl-D-aspartate (NMDA) receptor. In this review, we present evidence from studies that address the role of HMGB1 in NPP. First, we review studies aimed at determining the role of HMGB1 in NPP and discuss the possible mechanisms underlying HMGB1-mediated NPP progression where receptors for HMGB1 are involved. Then we review studies that address HMGB1 as a potential therapeutic target for NPP.

Therapeutic Developments Targeting Toll-like Receptor-4-Mediated Neuroinflammation

Toll-like receptors (TLRs) have been shown to play an important role in the immune system, which warrants study of their remarkable potential as pharmacological targets. Activation of TLRs requires participation from specific pathogen-associated molecular patterns (PAMPs) and accessory proteins such as myeloid differentiation protein 2 (MD2), lipopolysaccharide binding protein (LBP), and cluster differentiation antigen 14 (CD14). Assembly of the TLR4-MD2-LPS complex is essential in TLR4 activation. Recent studies have revealed that TLR4 activation is a significant trigger of signal transmission pathways in the nervous system, which could result in chronic pain as well as opioid tolerance and dependence. Researchers of the molecular structure of TLRs and their accessory proteins have opened a door to syntheses of TLRs agonists and antagonists, such as eritoran. Small-molecule modulators of TLR4, such as MD2-I and tricyclic antidepressants, offer more promising prospects than peptides, given their convenience in oral administration and lower cost. Herein we mainly discuss the mechanisms and clinical prospects of TLR4 agonists and antagonists.

Inducible Lentivirus-Mediated siRNA against TLR4 Reduces Nociception in a Rat Model of Bone Cancer Pain

Although bone cancer pain is still not fully understood by scientists and clinicians alike, studies suggest that toll like receptor 4 (TLR4) plays an important role in the initiation and/or maintenance of pathological pain state in bone cancer pain. A promising treatment for bone cancer pain is the downregulation of TLR4 by RNA interference; however, naked siRNA (small interference RNA) is not effective in long-term treatments. In order to concoct a viable prolonged treatment for bone cancer pain, an inducible lentivirus LvOn-siTLR4 (tetracycline inducible lentivirus carrying siRNA targeting TLR4) was prepared and the antinociception effects were observed in bone cancer pain rats induced by Walker 256 cells injection in left leg. Results showed that LvOn-siTLR4 intrathecal injection with doxycycline (Dox) oral administration effectively reduced the nociception induced by Walker 256 cells while inhibiting the mRNA and protein expression of TLR4. Proinflammatory cytokines as TNF-α and IL-1β in spinal cord were also decreased. These findings suggest that TLR4 could be a target for bone cancer pain treatment and tetracycline inducible lentivirus LvOn-siTLR4 represents a new potential option for long-term treatment of bone cancer pain.

p38 and interleukin-1 beta pathway via toll-like receptor 4 contributed to the skin and muscle incision and retraction-induced allodynia

BACKGROUND

Persistent postsurgical pain, as an important clinical problem, seriously affects the quality of life in patients. However, the mechanism underlying persistent postsurgical pain remains largely unclear. The present study aims to elucidate the involvement of toll-like receptor 4 (TLR4) and its interaction with p38 and interleukin [IL]-1β signaling in dorsal root ganglion (DRG) in the persistent postsurgical pain.

METHODS

Skin and muscle incision and retraction (SMIR) surgery-induced paw withdrawal threshold (PWT) change was determined by applying mechanical stimuli to the plantar surface of the hind paw using von Frey hairs. The PE-10 catheter intrathecal placement was used to deliver LPS-RS, interleukin-1 receptor antagonist, or SB203580. Western blot analysis was performed to measure the expression of the TLR4, mitogen-activated protein kinases family, and IL-1β in ipsilateral L3 and L4 DRG. Immunofluorescence staining was performed to further investigate the cell type of TLR4 expression. All data were expressed as means ± standard error of the mean and analyzed using SPSS 13.0.

RESULTS

The results showed that the SMIR surgery, a rat model of persistent postoperative pain, decreased the ipsilateral 50% PWT, and the decrease lasted for at least 20 d. The expression of TLR4 and phosphorylation of p38 were upregulated in ipsilateral L3 and L4 DRG neurons after SMIR surgery. Pretreatment with LPS-RS, an established TLR4 antagonist, prevented p38 activation and attenuated mechanical allodynia induced by SMIR surgery. In addition, the expression of IL-1β was significantly increased after SMIR surgery. Blocking IL-1β by interleukin-1 receptor antagonist significantly improved the decreased PWT evoked by SMIR. Moreover, inhibition of TLR4 or p38 pathway prevented the IL-1β upregulation and mechanical allodynia induced by SMIR.

CONCLUSIONS

These findings suggest that the activation of p38 and IL-1β signaling pathway via TLR4 mediate mechanical allodynia after SMIR surgery.

The over-production of TNF-α via Toll-like receptor 4 in spinal dorsal horn contributes to the chronic postsurgical pain in rat

PURPOSE

Many patients suffer from chronic postsurgical pain (CPSP) following surgery, and the underlying mechanisms are poorly understood. In the present work, using the skin/muscle incision retraction (SMIR) model, the role of spinal TLR4/TNF-α pathway in the induction of CPSP was evaluated.

METHODS

Mechanical allodynia induced by SMIR was established in adult male Sprague-Dawley rats. The von Frey test was performed to evaluate the role of TLR4/TNF-α pathway on the mechanical allodynia. Western-blot and immunohistochemistry methods were adopted to understand the molecular mechanisms.

RESULTS

SMIR surgery decreased the ipsilateral 50 % paw withdrawal threshold, lasting for at least 20 days. Western-blot analysis and immunohistochemistry revealed that SMIR surgery significantly upregulated the expression of TLR4 (p < 0.01) in glial cells on the ipsilateral side of spinal cord and increased TLR4 occurred on day 5 and was maintained to the end of the experiment (day 20). Similarly, tumor necrosis factor-alpha (TNF-α) was significantly increased on days 5, 10, and 20 on the ipsilateral side of spinal dorsal horn following SMIR surgery. Intraperitoneal injection of an inhibitor of TNF-α synthesis thalidomide at 50 or 100 mg/kg dose (but not 10 mg/kg dose) significantly ameliorated the reduced paw withdrawal threshold induced by SMIR surgery. Importantly, intrathecal delivery of a specific TLR4 antagonist (LPS-RS) at dose of 25 μg significantly attenuated mechanical allodynia and prevented the upregulation of TNF-α induced by SMIR surgery.

CONCLUSIONS

These findings suggest that the upregulation of TNF-α via TLR4 contributes to the development of CPSP in spinal dorsal horn.