Neuropathic pain is a highly debilitating chronic pain state that is a consequence of nerve injury or of diseases such as diabetes, cancer, infection, autoimmune disease, or trauma. Neuropathic pain is often resistant to currently available analgesics. There is a rapidly growing body of evidence indicating that signalings from spinal microglia play crucial roles in the pathogenesis of neuropathic pain. After peripheral nerve injury, microglia transform to reactive states through the expression of various genes such as cell-surface receptors (including purinergic receptors) and proinflammatory cytokines that enhance synaptic transmission in dorsal horn neurons. Inhibiting function or expression of these microglial molecules strongly suppresses pain hypersensitivity to innocuous mechanical stimuli (tactile allodynia), a hallmark symptom of neuropathic pain. A recent study also reveals that the transcription factor IRF8 (interferon regulatory factor 8) is a critical regulator of the nerve injury–induced gene expression in microglia. The present review article highlights the recent advances in our understanding of spinal microglia in neuropathic pain.

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We examined the effects of angiotensin II AT₁–receptor blockade with olmesartan on high fat (HF) diet–induced vascular oxidative stress and endothelial dysfunction in normal salt (NS) diet–fed Dahl salt-sensitive (DSS) rats. Treatment with NS + HF diet (32% crude fat, 0.3% NaCl) for 20 weeks significantly increased blood pressure in DSS rats. NS + HF diet–fed DSS rats also showed higher plasma levels of thiobarbituric acid–reactive substances, aortic superoxide production, and mRNA levels of p22^phox and gp91^phox in aortic tissues than NS diet–fed DSS rats. Furthermore, acetylcholine-induced vasorelaxation of aorta from NS + HF diet–fed DSS rats was significantly reduced. In NS + HF diet–fed DSS rats, treatment with olmesartan medoxomil (10 mg/kg per day, p.o.) and hydralazine (25 mg/kg per day, p.o.) similarly decreased blood pressure. However, in these animals, only olmesartan normalized plasma levels of thiobarbituric acid–reactive substances, vascular superoxide in aortic tissues, and acetylcholine-induced vasorelaxation. These data indicate that HF diet–induced hypertension is associated with vascular oxidative stress and endothelial dysfunction in NS diet–treated DSS rats. Inhibition of angiotensin II AT₁ receptors may elicit beneficial effects on HF-induced hypertension and vascular injury in subjects that have genetically enhanced sodium-sensitive blood pressure.

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Differentiation-inducing factor-1 (DIF-1), a morphogen for Dictyostelium discoideum, inhibits the proliferation of human cancer cell lines by suppressing the Wnt/β-catenin signaling pathway. In this study, we examined the effect of DIF-1 on c-Myc, a target gene product of the Wnt/β-catenin signaling pathway, mainly using HCT-116 colon cancer cells. DIF-1 strongly reduced the amount of c-Myc protein in time- and concentration-dependent manners and reduced c-Myc mRNA expression by inhibiting promoter activity through the TCF binding sites. The effect of DIF-1 on c-Myc was also confirmed using the human cervical cell line HeLa. Pretreatment with the proteasome inhibitor MG132 or glycogen synthase kinase-3β (GSK-3β) inhibitors (LiCl and SB216763) attenuated the effect of DIF-1, suggesting that DIF-1 induced c-Myc protein degradation through GSK-3β activation. Furthermore, we examined whether c-Myc was involved in the anti-proliferative effect of DIF-1 using c-Myc–overexpressing cells and found that c-Myc was associated with the anti-proliferative effect of this compound. These results suggest that DIF-1 inhibits c-Myc expression by inhibiting promoter activity and inducing protein degradation via GSK-3β activation, resulting in the inhibition of cell proliferation. Since c-Myc seems to be profoundly involved in accelerated proliferation of various malignant tumors, DIF-1 may have a potential to develop into a novel anti-cancer agent.

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Oral mucositis induced by chemotherapy or radiotherapy has an impact upon quality-of-life, is dose-limiting for chemotherapy, and causes considerable morbidity. We evaluated the effect of royal jelly (RJ) on 5-fluorouracil (5-FU)-induced oral mucositis in hamsters. Oral mucositis was induced in hamsters through a combination of 5-FU treatment and mild abrasion of the cheek pouch. RJ was contained in chitosan–sodium alginate film (RJ film). Films were attached to the oral mucosa and the healing process examined by measuring the area of mucositis, myeloperoxidase (MPO) activity, microscopic aspects, and RT-PCR for detection of pro-inflammatory cytokines (tumor necrosis factor-α, interleukin-1β). Furthermore, we evaluated the radical-scavenging activity of RJ and generation of keratinocyte growth factor from human periodontal ligament fibroblasts. RJ films (10%, 30%) significantly improved recovery from 5-FU–induced damage, reduced MPO activity and the production of pro-inflammatory cytokines. Additionally, RJ showed radical-scavenging activity. These data suggest that topical application of films that contain RJ had a healing effect on the severe oral mucositis induced by 5-FU and that the effect was caused by the anti-inflammatory or anti-oxidative activities of RJ.

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Microglial-mediated neuroinflammation has recently been implicated as one of the important mechanisms responsible for the progression of neurodegenerative diseases. Activated microglia cells produce various neurotoxic factors that are harmful to neurons. Therefore, suppression of the inflammatory response elicited by activated microglia is considered a potential therapeutic target for neurodegenerative diseases. The cannabinoid (CB) system is widespread in the central nervous system and is very crucial for modulating a spectrum of neurophysiological functions such as pain, appetite, and cognition. In the present study, we synthesized and investigated a novel CB derivative (CD-101) for its ability to suppress lipopolysaccharide (LPS)-mediated activation of BV-2 microglial cells and subsequent release of various inflammatory mediators. CD-101 significantly inhibited the production of inflammatory markers such as nitric oxide, cyclooxygenase-2, and pro-inflammatory cytokines such as tumor necrosis factor-α, interleukin-1β, and interleukin-6. The anti-neuroinflammatory effect of this novel cannabinoid derivative occurred by inhibiting p38MAPK phosphorylation and by decreasing nuclear translocation of p65 subunit of nuclear factor kappa-B in LPS-stimulated BV-2 microglial cells. These results suggest that the use of the cannabinoid derivative CD-101 might be a potential therapeutic target against neuroinflammatory disorders.

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Our previous study has shown that the corrected QT (QTc) interval of the electrocardiogram is longer during the dark period than during the light period in telemetered common marmosets. In the present study, we investigated the involvement of sympathetic and parasympathetic nervous activities in the changes of QTc interval associated with the light–dark cycle.Telemetry transmitters were implanted in six common marmosets to continuously record the electrocardiogram. The QT intervals obtained were corrected for the RR interval by applying individual probabilistic QT-rate correction formulae. Power spectral analysis of heart rate variability was performed to quantify each autonomic nervous function. Changes in QTc intervals and autonomic nervous tones were associated with the light–dark cycle. Parasympathetic nervous activity and QTc intervals significantly increased by approximately 10 ms during the dark period.Atropine, a muscarinic receptor antagonist, suppressed the increased parasympathetic tone and QTc prolongation during the dark period. In contrast, propranolol, a β-adrenoceptor antagonist, decreased the sympathetic activity and increased QTc intervals during the light period. These results suggest that the parasympathetic nerve functions prolong QTc intervals during the dark period, while the sympathetic nerve functions shorten them during the light period in common marmosets.

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(±)-Pentazocine (PTZ), a non-narcotic analgesic, is used for the clinical management of moderate to severe pain. To study the effect of PTZ on the descending noradrenergic inhibitory system, in the present study we examined the effect of [³H]norepinephrine (NE) uptake by cultured bovine adrenal medullary cells and human neuroblastoma SK-N-SH cells. (−)-PTZ and (+)-PTZ inhibited [³H]NE uptake by adrenal medullary cells in a concentration-dependent (3 – 100 μM) manner. Eadie-Hofstee analysis of [³H]NE uptake showed that both PTZs caused a significant decrease in the V_max with little change in the apparent K_m, suggesting non-competitive inhibition. Nor-Binaltorphimine and BD-1047, κ-opioid and σ-receptor antagonists, respectively, did not affect the inhibition of [³H]NE uptake induced by (−)-PTZ and (+)-PTZ, respectively. PTZs suppressed specific [³H]nisoxetine binding to intact SK-N-SH cells, but not directly to the plasma membranes isolated from the bovine adrenal medulla. Scatchard analysis of [³H]nisoxetine binding to SK-N-SH cells revealed that PTZs reduced the B_max without changing the apparent K_d. Western blot analysis showed a decrease in biotinylated cell-surface NE transporter (NET) expression after the treatment with (−)-PTZ. These findings suggest that PTZ inhibits the NET function by reducing the amount of NET in the cell surface membranes through an opioid and σ-receptor–independent pathway.

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Baicalin from Scutellaria baicalensis is a major flavonoid constituent found in the traditional Chinese medicinal herb Baikal skull cap. It has been widely used for the treatment of various diseases such as pneumonia, diarrhea, and hepatitis. Recent studies have demonstrated that baicalin possesses a wide range of pharmacological and biological activities, including anti-inflammatory, anti-microbial, anti-oxidant, and anti-tumor properties. Specifically, its anti-inflammatory activity has been estimated in various animal models of acute and chronic inflammation; however, its effects on dendritic cells (DCs) maturation and immuno-stimulatory activities are still unknown. In this study, we attempted to determine whether baicalin could influence DC surface molecule expression, antigen uptake capacity, cytokine production, and capacity to induce T-cell differentiation. Baicalin was shown to significantly suppress the expression of surface molecules CD80, CD86, major histocompatibility complex (MHC) class I, and MHC class II as well as the levels of interleukin-12 production in lipopolysaccharide stimulated DCs. Moreover, baicalin-treated DCs showed an impaired induction of the T helper type 1 immune response and a normal cell-mediated immune response. These findings provide important understanding of the immunopharmacological functions of baicalin and have ramifications for the development of therapeutic adjuvants for the treatment of DCs-related acute and chronic diseases.

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2-Arachidonoylglycerol (2-AG) is recognized as a potent endocannabinoid, which reduces synaptic transmission through cannabinoid CB₁ receptors, and is hydrolyzed by monoacylglycerol lipase (MGL) to arachidonic acid (AA), a cyclooxygenase substrate. We already reported that centrally administered MGL and cyclooxygenase inhibitors each reduced the intracerebroventricularly (i.c.v.) administered bombesin-induced secretion of adrenal catecholamines, while a centrally administered CB₁-antagonist potentiated the response, indirectly suggesting bidirectional roles of brain 2-AG (stimulatory and inhibitory roles) in the bombesin-induced response. In the present study, we separately examined these bidirectional roles using 2-AG and 2-AG ether (2-AG-E) (stable 2-AG analog for MGL) in rats. 2-AG (0.5 μmol/animal, i.c.v.), but not 2-AG-E (0.5 μmol/animal, i.c.v.), elevated basal plasma catecholamines with JZL184 (MGL inhibitor)- and indomethacin (cyclooxygenase inhibitor)-sensitive brain mechanisms. 2-AG-E (0.1 μmol/animal, i.c.v.) effectively reduced the bombesin (1 nmol/animal, i.c.v.)-induced elevation of plasma catecholamines with rimonabant (CB₁ antagonist)-sensitive brain mechanisms. Immunohistochemical studies demonstrated the bombesin-induced activation of diacylglycerol lipase α (2-AG-producing enzyme)-positive spinally projecting neurons in the hypothalamic paraventricular nucleus, a control center of central adrenomedullary outflow. These results directly indicate bidirectional roles of brain 2-AG, a stimulatory role as an AA precursor and an inhibitory role as an endocannabinoid, in the bombesin-induced central adrenomedullary outflow in rats.

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We investigated in vivo efficacies of the newly synthesized VLA-4 antagonist Compound A {trans-4-[1-[[2,5-Dichloro-4-(1-methyl-3-indolylcarboxamido)phenyl]acetyl]-(4S)methoxy-(2S)-pyrrolidinylmethoxy]cyclohexanecarboxylic acid} on Ascaris antigen–induced airway inflammation and hyperresponsiveness in a murine asthmatic model. Oral administration of Compound A significantly inhibited eosinophil infiltration into BALF and airway hyperresponsiveness 48 h after the antigen challenge. Histologic analysis of the lung sections confirmed the BALF result and revealed suppression of edema and mucus hyperplasia at 8 and 48 h after the challenge, respectively. These findings clearly show that orally active Compound A has therapeutic potential for treatment of asthma.

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