Ethyl pyruvate attenuates formalin-induced inflammatory nociception by inhibiting neuronal ERK phosphorylation

Rab11a in the spinal cord: an essential contributor to complete Freund's adjuvant-induced inflammatory pain in mice

Inflammatory pain is a commonly observed clinical symptom in a range of acute and chronic diseases. However, the mechanism of inflammatory pain is far from clear yet. Rab11a, a small molecule guanosine triphosphate enzyme, is reported to regulate orofacial inflammatory pain in our previous works. However, the mechanism of Rab11a's involvement in the regulation of inflammatory pain remains obscure. Here, we aim to elucidate the potential mechanisms through which Rab11a contributes to the development of inflammatory pain in the spinal level. It's shown that neurons, rather than glial cells, were the primary cell type expressing Rab11a in the spinal dorsal horn (SDH). After intra-plantar injection of CFA, both the number of Fos/Rab11a-immunopositive neurons and the expression of Rab11a were increased. Administration of Rab11a-shRNA into the SDH resulted in significantly analgesic effect in mice with CFA injection. Application of Rab11a-shRNA also reduced the NMDA receptor-mediated excitatory post-synaptic current (EPSC) and the spike number of neurons in lamina II of the SDH in mice with CFA injection, without affecting the presynaptic glutamate release and the postsynaptic AMPA receptor-mediated EPSC. Our results thus suggest that the enhanced expression of neuronal Rab11a may be important for the process of inflammatory pain in mice with CFA injection, which is likely mediated by Rab11a's potentiation of the competence of post-synaptic NMDAR and spiking of SDH neurons.

New dimer and trimer of chalcone derivatives from anti-inflammatory and antinociceptive extracts of Schinopsis brasiliensis roots

ETHNOPHARMACOLOGY RELEVANCE

Schinopsis brasiliensis Engl. is an endemic tree of the Brazilian semi-arid regions belonging to the Anacardiaceae family. It is the main representative of the genus Schinopsis, mostly native to Brazil and popularly known as "braúna" or "baraúna". Different parts of this plant are employed in Brazilian folk medicines to treat inflammation in general, sexual impotence, cough, and influenza.

AIM OF THE STUDY

This work describes the antinociceptive (acetic acid-induced writhing and formalin-induced nociception) and anti-inflammatory (paw edema and neutrophil migration) activities of the extract of the root of S. brasiliensis. Besides, the evaluation of total phenolic compounds and antioxidant, antimicrobial (including MRSA bacteria), and acetylcholinesterase inhibition activities were also determined.

MATERIAL AND METHODS

The pure compounds were isolated by different chromatographic techniques and their chemical structures have been unambiguously elucidated based on extensive spectroscopic methods, including 1D (¹H, ¹³C, DEPT, and NOEdiff) and 2D (HSQC, HMBC, and NOESY) NMR experiments, MS data, and comparison with the literature data of similar compounds. The antinociceptive and anti-inflammatory activities were evaluated by acid acetic writhing test, formalin paw edema, and by the investigation of neutrophil migration to the peritoneal cavities of mice. For antimicrobial evaluation were determined MIC and MBC, antioxidant activities were obtained by TPC and DPPH tests, and AChE inhibition by Elmann's methodology.

RESULTS

The extracts showed antinociceptive and anti-inflammatory activities and two unusual new compounds, a cyclobutanyl chalcone trimer (schinopsone A) and a cyclohexene-containing chalcone dimer (schinopsone B), with six known compounds were isolated from the active extracts. Additionally, the acetylcholinesterase inhibitory activity for isolated compounds was reported for the first time in this study. Molecular docking studies indicated that the isolated compounds are responsible for the interaction with anti-inflammatory targets (COX 1 and 2 and LOX) with variable binding affinities, indicating a possible mechanism of action of these compounds.

CONCLUSIONS

These findings indicate for the first time the correlation between the anti-inflammatory activity different enriched polyphenol-organic soluble fractions of S. brasiliensis, and it contributes to the understanding of the anti-inflammatory potential of S. brasiliensis.

Analgesic Effect of Combined Therapy with the Japanese Herbal Medicine "Yokukansan" and Electroacupuncture in Rats with Acute Inflammatory Pain

Background: Japanese herbal medicine, called Kampo medicine, and acupuncture are mainly used in Japanese traditional medicine. In this experiment, the analgesic effect of Yokukansan (YKS) alone and a combination of YKS and electroacupuncture (EA) on inflammatory pain induced by formalin injection were examined. Methods: Animals were divided into four groups: a control group, formalin injection group (formalin), YKS-treated formalin group (YKS), and YKS- and EA-treated formalin group (YKS + EA). The duration of pain-related behaviors and extracellular signal-regulated protein kinase (ERK) activation in the spinal cord after formalin injection in the right hind paw were determined. Results: The duration of pain-related behaviors was dramatically prolonged in the late phase (10–60 min) in the formalin group. The YKS treatment tended to reduce (p = 0.08), whereas YKS + EA significantly suppressed the pain-related behaviors (p < 0.01). Immunohistochemical and Western blot analyses revealed that the number of phosphorylated ERK1/2 (pERK1/2)-positive cells and the pERK expression level, which were increased by formalin injection, were significantly inhibited by YKS (p < 0.05) and YKS + EA (p < 0.01). Conclusions: The YKS + EA combination therapy elicited an analgesic effect on formalin-induced acute inflammatory pain.

Anti-inflammatory activity of Nectandra angustifolia (Laurel Amarillo) ethanolic extract

ETHNOPHARMACOLOGICAL RELEVANCE

Nectandra angustifolia belongs to the Lauraceae family and it is widely known in phytomedicine by local inhabitants of South America against various maladies. It is popularly used for the treatment of different types of inflammatory processes, like rheumatism, arthritis and its associated pain.

AIM OF THE STUDY

To characterize the phytochemicals in an ethanolic extract of Nectandra angustifolia and to evaluate the total antioxidant content and its anti-inflammatory effect with multiparametric analyses through in vitro assays and an in vivo model.

METHODS

Leaves and stems of Nectandra angustifolia were air-dried and an ethanolic extract (NaE) was further obtained. Total phenolic, flavonoid and tannin content were determined and the antioxidant activity was addressed by DPPH and FRAP assays. NaE was first analyzed by HPLC and then two tests were carried out as screening assays for anti-inflammatory activities: red blood cell membrane stabilization and protein denaturation. The non-cytotoxic concentration of NaE was determined for in vitro biological assays using RAW 264.7 (murine macrophages) cell cultures through cell counting with Trypan-blue and XTT assay. Subsequently, the cell cycle of RAW 264.7 cells exposed for 24 h to NaE was analyzed. Additionally, the anti-inflammatory capacity of NaE was evaluated by RT-qPCR of pro-inflammatory cytokines. Furthermore, NF-κB translocation was observed by confocal microscopy at different times. Finally, formalin-induced mice paw inflammation was used as an in vivo model.

RESULTS

The chromatographic profile of NaE showed peaks compatible with flavonoids content. NaE exhibited better membrane stabilization effect on HRBC and protection of BSA denaturation than the standard drug (diclofenac). NaE diminished mRNA levels of pro-inflammatory cytokines when added 1-h prior LPS stimulation. Moreover, NaE prevented the translocation of NF-κB to the nucleus and in formalin-induced mice paw inflammation, reduced the edema and the stimulus of inflammatory phase.

CONCLUSION

This study shows for the first time, that Nectandra angustifolia ethanolic extract has a high content of flavonoids and that possess antioxidant and anti-inflammatory biological properties as demonstrated by multiparametric analyses from in vitro assays and an in vivo model of inflammation.

NADPH oxidase1 inhibition leads to regression of central sensitization during formalin induced acute nociception via attenuation of ERK1/2-NFκB signaling and glial activation

Role of NADPH oxidase1 in the development of inflammatory pain has been demonstrated by gene knockout studies. Nevertheless, pharmacological inhibition of NOX1 is a requisite approach for therapeutic utility. Recently, we have reported the anti-nociceptive effect of newly identified NOX1 specific inhibitor ML171 (2-acetylphenothiazine). Inhibition of NOX1 resulted in attenuation of nociceptive sensitization during acute inflammatory pain via inhibition of ROS generation and its downstream ERK1/2 activation. However, glial activation accompanying inflammation is closely related to the initiation and maintenance of pain. Peripheral nociceptive inputs activate the primary afferents via release of various chemical mediators which are potentially capable of mediating signals from neuron to glia in DRG and subsequently in spinal cord dorsal horn. The subsequent interactions between neuron and glia contribute to pain hypersensitivity. Thus, the present study was focused to investigate the effect of ML171 on ERK1/2 signaling, glial activation, and crosstalk between neuron and glia in a mouse model of formalin induced acute nociception. Thus, the present study was focused to investigate the effect of ML171 on ERK1/2 signaling, glial activation, and crosstalk between neuron and glia in DRG and dorsal horn of the spinal cord of lumbar region (L3-L5) in a mouse model of formalin induced acute nociception. Intraperitoneal administration of ML171 decreased nociceptive behavioral responses, i.e. the flinch and lick counts, in formalin induced nociceptive mice. Immunofluorescence and Western blot analysis demonstrated decreased levels of nociceptive mediators like p-ERK1/2, p-NFκB p65, Iba1 and GFAP in DRG as well as in spinal cord dorsal horn; supporting anti-nociceptive potential of ML171. Further, co-localization studies showed the neuron-glia crosstalk in tissue dependent manner. ERK1/2 was found to be activated in glia and NFκB in neurons in DRG; whereas in case of spinal cord ERK1/2 was activated in neurons and NFκB in astrocytes. Decrease in nociceptive behavioral response and activation of nociceptive mediators after intraperitoneal administration of ML171 strongly advocate anti-nociceptive potential of ML171. This is the first report demonstrating modulation of ERK1/2-NFκB signaling pathway, glial activation and regulation of neuron-glia crosstalk by NADPH oxidase1 inhibition towards its anti-nociceptive action.

Propofol produces preventive analgesia via GluN2B-containing NMDA Receptor/ERK1/2 Signaling Pathway in a rat model of inflammatory pain

Abstract

Propofol, an intravenous anesthetic, has been shown to offer superior analgesic effect clinically. Whether propofol has preventive analgesic property remains unexplored. The present study investigated the antinociceptive effect of propofol and underlying molecular and cellular mechanisms via pre-emptive administration in a formalin-induced inflammatory pain model in rats. Male adult Sprague–Dawley rats were randomly allocated into four groups: naïve (Group Naïve), formalin injection only (Group Formalin), and formalin injection at 30 min (Group P-30 min) or 2 h (Group P-2 h) after intravenous infusion of propofol (0.6 mg kg−1 min−1) for 1 h. Nociceptive responses and protein expression of phosphorylated- or pan-GluN2B, ERK1/2, p38 mitogen-activated protein kinase, and c-Jun N-terminal kinase in the spinal dorsal horn were evaluated. Alteration of intracellular Ca2+ concentration induced by N-methyl-D-aspartate (NMDA) receptor agonists with or without pre-treatment of propofol was measured using fluorometry in SH-SY5Y cells while neuronal activation in the spinal dorsal horn by immunofluorescence. Pre-emptive propofol reduced pain with a delayed response to formalin and a reduction in hypersensitivity that lasted at least for 2 h. The formalin-induced activation of spinal GluN2B and ERK1/2 but not p38 or c-Jun N-terminal kinase was also diminished by propofol treatment. Preconditioning treatment with 3 µM and 10 µM of propofol inhibited Ca2+ influx mediated through NMDA receptors in SH-SY5Y cells. Propofol also reduced the neuronal expression of c-Fos and p-ERK induced by formalin. This study shows that pre-emptive administration of propofol produces preventive analgesic effects on inflammatory pain through regulating neuronal GluN2B-containing NMDA receptor and ERK1/2 pathway in the spinal dorsal horn.

Ethyl pyruvate does not require microglia for mediating neuroprotection after excitotoxic injury

AIMS

Ethyl pyruvate (EP) mediates protective effects after neuronal injury. Besides a direct conservation of damaged neurons, the modulation of indigenous glial cells has been suggested as one important mechanism for EP-related neuroprotection. However, the specific contribution of glial cells is still unknown.

METHODS

Organotypic hippocampal slice cultures (OHSC) were excitotoxically lesioned by 50 μmol/L N-methyl-D-aspartate (NMDA, for 4 hours) or left untreated. In an additional OHSC subset, microglia was depleted using the bisphosphonate clodronate (100 μg/mL) before lesion. After removal of NMDA, EP containing culture medium (0.84 μmol/L, 8.4 μmol/L, 42 μmol/L, 84 μmol/L, 168 μmol/L) was added and incubated for 72 hours. OHSC were stained with propidium iodide to visualize degenerating neurons and isolectin IB₄ -FITC to identify microglia. Effects of EP at concentrations of 0.84, 8.4, and 84 μmol/L (0-48 hours) were analyzed in the astrocytic scratch wound assay.

RESULTS

EP significantly reduced neurodegeneration following induced excitotoxicity except for 168 μmol/L. For 84 μmol/L, a reduction in the microglia cells was observed. Microglia depletion did not affect neuronal survival after EP treatment. EP decelerated astrocytic wound closure at 48 hours after injury.

CONCLUSION

EP-mediated neuroprotection seems to be mediated by astrocytes and/or neurons.

The mitogen and stress-activated protein kinase 1 regulates the rapid epigenetic tagging of dorsal horn neurons and nocifensive behaviour

Phosphorylation of histone H3 at serine 10 (p-H3S10) is a marker of active gene transcription. Using cognitive models of neural plasticity, p-H3S10 was shown to be downstream of extracellular signal-regulated kinase (ERK) signalling in the hippocampus. In this study, we show that nociceptive signalling after peripheral formalin injection increased p-H3S10 expression in the ipsilateral dorsal horn. This increase was maximal 30 minutes after formalin injection and occurred mainly within p-ERK-positive neurons. Spinal p-H3S10-enhanced expression was also observed in neurokinin 1 receptor (NK1R), c-Fos, and Zif268 positive neurons and was inhibited by ablation of serotonergic descending controls. The mitogen and stress-activated protein kinase 1 (MSK1) is downstream of ERK and can induce p-H3S10. We found that, after formalin injection, most phospho-MSK1 (p-MSK1)-positive cells (87% ± 3%) expressed p-ERK and the majority of p-H3S10-positive cells (85% ± 5%) expressed p-MSK1. Inhibition of ERK activity with the MEK inhibitor SL327 reduced formalin-induced p-ERK, p-MSK1, and p-H3S10, demonstrating that spinal p-MSK1 and p-H3S10 were at least partly downstream of ERK signalling. Crucially, pharmacological blockade of spinal MSK1 activity with the novel MSK1 inhibitor SB727651A inhibited formalin-induced spinal p-H3S10 and nocifensive behaviour. These findings are the first to establish the involvement of p-H3S10 and its main kinase, MSK1, in ERK regulation of nociception. Given the general importance of ERK signalling in pain processing, our results suggest that p-H3S10 could play a role in the response to injury.

TSG-6 secreted by human umbilical cord-MSCs attenuates severe burn-induced excessive inflammation via inhibiting activations of P38 and JNK signaling

The hMSCs have become a promising approach for inflammation treatment in acute phase. Our previous study has demonstrated that human umbilical cord-MSCs could alleviate the inflammatory reaction of severely burned wound. In this study, we further investigated the potential role and mechanism of the MSCs on severe burn-induced excessive inflammation. Wistar rats were randomly divided into following groups: Sham, Burn, Burn+MSCs, Burn+MAPKs inhibitors, and Burn, Burn+MSCs, Burn+Vehicle, Burn+siTSG-6, Burn+rhTSG-6 in the both experiments. It was found that MSCs could only down-regulate P38 and JNK signaling, but had no effect on ERK in peritoneal macrophages of severe burn rats. Furthermore, suppression of P38 and JNK activations significantly reduced the excessive inflammation induced by severe burn. TSG-6 was secreted by MSCs using different inflammatory mediators. TSG-6 from MSCs and recombinant human (rh)TSG-6 all significantly reduced activations of P38 and JNK signaling induced by severe burn and then attenuated excessive inflammations. On the contrary, knockdown TSG-6 in the cells significantly increased phosphorylation of P38 and JNK signaling and reduced therapeutic effect of the MSCs on excessive inflammation. Taken together, this study suggested TSG-6 from MSCs attenuated severe burn-induced excessive inflammation via inhibiting activation of P38 and JNK signaling.

Pyruvate dehydrogenase kinase 2 and 4 gene deficiency attenuates nociceptive behaviors in a mouse model of acute inflammatory pain

Pyruvate dehydrogenase (PDH) kinases (PDKs) 1-4, expressed in peripheral and central tissues, regulate the activity of the PDH complex (PDC). The PDC is an important mitochondrial gatekeeping enzyme that controls cellular metabolism. The role of PDKs in diverse neurological disorders, including neurometabolic aberrations and neurodegeneration, has been described. Implications for a role of PDKs in inflammation and neurometabolic coupling led us to investigate the effect of genetic ablation of PDK2/4 on nociception in a mouse model of acute inflammatory pain. Deficiency in Pdk2 and/or Pdk4 in mice led to attenuation of formalin-induced nociceptive behaviors (flinching, licking, biting, or lifting of the injected paw). Likewise, the pharmacological inhibition of PDKs substantially diminished the nociceptive responses in the second phase of the formalin test. Furthermore, formalin-provoked paw edema formation and mechanical and thermal hypersensitivities were significantly reduced in Pdk2/4-deficient mice. Formalin-driven neutrophil recruitment at the site of inflammation, spinal glial activation, and neuronal sensitization were substantially lessened in the second or late phase of the formalin test in Pdk2/4-deficient animals. Overall, our results suggest that PDK2/4 can be a potential target for the development of pharmacotherapy for the treatment of acute inflammatory pain. © 2016 Wiley Periodicals, Inc.

ERK1/2: Function, signaling and implication in pain and pain-related anxio-depressive disorders

Despite the increasing knowledge regarding pain modulation, the understanding of the mechanisms behind a complex and pathologic chronic pain condition is still insufficient. These knowledge gaps might result in ineffective therapeutic approaches to relieve painful sensations. As a result, severe untreated chronic pain frequently triggers the onset of new disorders such as depression and/or anxiety, and therefore, both the diagnosis and treatment of patients suffering from chronic pain become seriously compromised, prompting a self-perpetuating cycle of symptomatology. The extracellular signal-regulated kinases 1 and 2 (ERK1/2) are molecules strongly implicated in the somatic component of pain at the spinal cord level and have been emerging as mediators of the emotional-affective component as well. Although these molecules might represent good biomarkers, their use as pharmacological targets is still open to discussion as paradoxical information has been obtained. Here we review the current scientific literature regarding ERK1/2 signaling in the modulation of pain, depression and anxiety, including the emotional-affective spheres of the pain experience.

Korean Red Ginseng and Ginsenoside-Rb1/-Rg1 Alleviate Experimental Autoimmune Encephalomyelitis by Suppressing Th1 and Th17 Cells and Upregulating Regulatory T Cells

The effects of Korean red ginseng extract (KRGE) on autoimmune disorders of the nervous system are not clear. We investigated whether KRGE has a beneficial effect on acute and chronic experimental autoimmune encephalomyelitis (EAE). Pretreatment (daily from 10 days before immunization with myelin basic protein peptide) with KRGE significantly attenuated clinical signs and loss of body weight and was associated with the suppression of spinal demyelination and glial activation in acute EAE rats, while onset treatment (daily after the appearance of clinical symptoms) did not. The suppressive effect of KRGE corresponded to the messenger RNA (mRNA) expression of proinflammatory cytokines (tumor necrosis factor-α [TNF-α] and interleukin [IL]-1β), chemokines (RANTES, monocyte chemotactic protein-1 [MCP-1], and macrophage inflammatory protein-1α [MIP-1α]), adhesion molecules (intercellular adhesion molecule-1 [ICAM-1], vascular cell adhesion molecule-1 [VCAM-1], and platelet endothelial cell adhesion molecule [PECAM-1]), and inducible nitric oxide synthase in the spinal cord after immunization. Interestingly, in acute EAE rats, pretreatment with KRGE significantly reduced the population of CD4(+), CD4(+)/IFN-γ(+), and CD4(+)/IL-17(+) T cells in the spinal cord and lymph nodes, corresponding to the downregulation of mRNA expression of IFN-γ, IL-17, and IL-23 in the spinal cord. On the other hand, KRGE pretreatment increased the population of CD4(+)/Foxp3(+) T cells in the spinal cord and lymph nodes of these rats, corresponding to the upregulation of mRNA expression of Foxp3 in the spinal cord. Interestingly, intrathecal pretreatment of rats with ginsenosides (Rg1 and Rb1) significantly decreased behavioral impairment. These results strongly indicate that KRGE has a beneficial effect on the development and progression of EAE by suppressing T helper 1 (Th1) and Th17 T cells and upregulating regulatory T cells. Additionally, pre- and onset treatment with KRGE alleviated neurological impairment of myelin oligodendrocyte glycoprotein(35-55)-induced mouse model of chronic EAE. These results warrant further investigation of KRGE as preventive or therapeutic strategies for autoimmune disorders, such as multiple sclerosis.

Ethyl pyruvate ameliorates 3-nitropropionic acid-induced striatal toxicity through anti-neuronal cell death and anti-inflammatory mechanisms

The potential neuroprotective value of ethyl pyruvate (EP) for the treatment of the striatal toxicity is largely unknown. We investigated whether EP promotes the survival of striatal neurons in a 3-nitropropionic acid (3-NP)-induced mouse model of Huntington's disease (HD). EP (5, 10, 20, and 40mg/kg/day, i.p.) was daily injected from 30min before 3-NP intoxication (pretreatment) and from onset/progression/peak point of neurological impairment by 3-NP intoxication. EP produced a neuroprotective effect in dose- and time-dependant manners. EP pretreatment of 40mg/kg/day produced the best neuroprotective effect among other conditions. Pretreatment of EP significantly attenuated neurological impairment and lethality and prevented formation of lesion area and neuronal loss in the striatum after 3-NP intoxication. This neuroprotection afforded by EP was associated with the suppression of succinate dehydrogenase activity, apoptosis, and microglial activation. The suppressive effect of EP corresponded to the down-regulation of mitogen-activated protein kinases (MAPKs) and nuclear factor-kappa B (NF-κB) signal pathways, and mRNA expression of inflammatory mediators including tumor necrosis factor-alpha, interleukin (IL)-1β, IL-6, inducible nitric oxide synthase, and cyclooxygenase-2 in the striatum after 3-NP intoxication. Interestingly, the intrathecal introduction of inhibitors MAPKs and NF-κB into control mice decreased the lethality after 3-NP intoxication. Our findings indicate that EP may effectively alleviate 3-NP-induced striatal toxicity by inhibition of the MAPKs and NF-κB pathways in the striatum, and that EP has a wide therapeutic window, suggesting that EP may have therapeutic value in the treatment of aspects of HD's disease related to inflammation.

ERK MAP kinase activation in spinal cord regulates phosphorylation of Cdk5 at serine 159 and contributes to peripheral inflammation induced pain/hypersensitivity

Cyclin-dependent kinase 5 is a proline-directed serine/threonine kinase and its activity participates in the regulation of nociceptive signaling. Like binding with the activators (P35 or P25), the phosphorylation of Cdk5 plays a critical role in Cdk5 activation. However, it is still unclear whether Cdk5 phosphorylation (p-Cdk5) contributes to pain hyperalgesia. The aim of our current study was to identify the roles of p-Cdk5 and its upstream regulator in response to peripheral inflammation. Complete Freund's adjuvant (CFA) injection induced acute peripheral inflammation and heat hyperalgesia, which was accompanied by sustained increases in phospho-ERK1/2 (p-ERK1/2) and phospho-Cdk5^S159 (p-Cdk5^S159) in the spinal cord dorsal horn (SCDH). CFA-induced p-ERK primarily colocalized with p-Cdk5^S159 in superficial dorsal horn neurons. Levels in p-ERK and p-Cdk5 were also increased in the 2^nd phase of hyperalgesia induced by formalin injection, which can produce acute and tonic inflammatory pain. MAP kinase kinase inhibitor U0126 intrathecal delivery significantly suppressed the elevation of p-Cdk5^S159, Cdk5 activity and pain response behavior (Heat hyperalgesia, Spontaneous flinches) induced by CFA or formalin injection. Cdk5 inhibitor roscovitine intrathecal administration also suppressed CFA-induced heat hyperalgesia and Cdk5 phosphorylation, but did not attenuate ERK activation. All these findings suggested that p-Cdk5^S159 regulated by ERK pathway activity may be a critical mechanism involved in the activation of Cdk5 in nociceptive spinal neurons contributes to peripheral inflammatory pain hypersensitivity.

Effect of ethyl pyruvate on Paclitaxel-induced neuropathic pain in rats

Background

Although paclitaxel is a widely used chemotherapeutic agent for the treatment of solid cancers, side effects such as neuropathic pain lead to poor compliance and discontinuation of the therapy. Ethyl pyruvate (EP) is known to have analgesic effects in several pain models and may inhibit apoptosis. The present study was designed to investigate the analgesic effects of EP on mechanical allodynia and apoptosis in dorsal root ganglion (DRG) cells after paclitaxel administration.

Methods

Rats were randomly divided into 3 groups: 1) a control group, which received only vehicle; 2) a paclitaxel group, which received paclitaxel; and 3) an EP group, which received EP after paclitaxel administration. Mechanical allodynia was tested before and at 7 and 14 days after final paclitaxel administration. Fourteen days after paclitaxel treatment, DRG apoptosis was determined by activated caspase-3 immunoreactivity (IR).

Results

Post-treatment with EP did not significantly affect paclitaxel-induced allodynia, although it tended to slightly reduce sensitivities to mechanical stimuli after paclitaxel administration. After paclitaxel administration, an increase in caspase-3 IR in DRG cells was observed, which was co-localized with NF200-positive myelinated neurons. Post-treatment with EP decreased the paclitaxel-induced caspase-3 IR. Paclitaxel administration or post-treatment with EP did not alter the glial fibrillary acidic protein IRs in DRG cells.

Conclusions

Inhibition of apoptosis in DRG neurons by EP may not be critical in paclitaxel-induced mechanical allodynia.

Korean Red Ginseng Extract Attenuates 3-Nitropropionic Acid-Induced Huntington's-Like Symptoms

Korean red ginseng (KRG) possesses neuroprotective activity. However, the potential neuroprotective value of KRG for the striatal toxicity is largely unknown. We investigated whether KRG extract (KRGE) could have a neuroprotective effect in a 3-nitropropionic acid- (3-NP) induced (i.p.) Huntington's disease (HD) model. KRGE (50, 100, and 250 mg/kg/day, p.o.) was administrated 10 days before 3-NP injection (pre-administration), from the same time with 3-NP injection (co-administration), or from the peak point of neurological impairment by 3-NP injection (post-administration). Pre-administration of KRGE produced the greatest neuroprotective effect in this model. Pre-administration of KRGE significantly decreased 3-NP-induced neurological impairment, lethality, lesion area, and neuronal loss in the 3-NP-injected striatum. KRGE attenuated microglial activation and phosphorylation of mitogen-activated protein kinases (MAPKs) and nuclear factor-kappa B (NF-κB) signal pathway. KRGE also reduced the level of mRNA expression of tumor necrosis factor-alpha, interleukin- (IL-) 1β, IL-6, inducible nitric oxide synthase, and OX-42. Interestingly, the intrathecal administration of SB203580 (a p38 inhibitor) or PD98059 (an inhibitor of MAPK Kinase, MEK) increased the survival rate in the 3-NP-induced HD model. Pre-administration of KRGE may effectively inhibit 3-NP-induced striatal toxicity via the inhibition of the phosphorylation of MAPKs and NF-κB pathways, indicating its therapeutic potential for suppressing Huntington's-like symptoms.