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The central pathophysiological mechanisms underlying irritable bowel syndrome (IBS), a female-predominant gastrointestinal disorder characterized by abdominal pain and abnormal bowel habits, remain poorly understood. IBS patients often report that chronic stress exacerbates their symptoms. Brain imaging studies have revealed that the amygdala, a stress-responsive brain region, of IBS patients is overactive when compared to healthy controls. Previously, we demonstrated that downregulation of the glucocorticoid receptor (GR) in the central nucleus of the amygdala (CeA) underlies stress-induced visceral hypersensitivity in female rats. In the current study, we aimed to evaluate in the CeA of female rats whether chronic water avoidance stress (WAS) alters DNA methylation of the GR exon 1 promoter region, a region homologous to the human GR promoter. As histone deacetylase (HDAC) inhibitors are able to change DNA methylation, we also evaluated whether administration of the HDAC inhibitor trichostatin A (TSA) directly into the CeA prevented WAS-induced increases in DNA methylation of the GR exon 1 promoter. We found that WAS increased overall and specific CpG methylation of the GR promoter in the CeA of female rats, which persisted for up to 28 days. Administration of the TSA directly into the CeA prevented these stress-induced changes of DNA methylation at the GR promoter. Our results suggest that, in females, changes in DNA methylation are involved in the regulation of GR expression in the CeA. These changes in DNA methylation may contribute to the central mechanisms responsible for stress-induced visceral hypersensitivity.
Learn More >The present study aimed to design and synthesize a series of 2-hydroxy-3-(4-aryl-1-piperazinyl)propyl phthalimide derivatives, which are analogs of 1H-pyrrolo[3,4-c]pyridine-1,3(2H)-dione derivatives with proven analgesic effect. In accordance with the basic principle proposed by Lipinski's rule, the probable bioavailabilities of the F1-F4 phthalimides were assessed. The obtained values indicate good absorption after oral administration and the ability to cross the blood-brain barrier. The four compounds F1-F4 differing in the type of pharmacophore in the phenyl group of the 2-hydroxy-3-(4-aryl-1-piperazinyl)propyl on the imide nitrogen atom (R, F1-F3) and the 4-benzhydryl analog (F4) were selected for in vitro and in vivo studies. Based on the in vitro studies, the effects of compounds F1-F4 on cell viability/proliferation and COX-2 levels were evaluated. Moreover, using in vivo methods, the compounds were tested for antinociceptive activity in models of acute pain (the writhing and the hot-plate tests) in mice. Their influence on the motor coordination effect and locomotor activity was also tested. The obtained results revealed that the compounds F1-F4 strongly suppress the pain of peripheral origin and to a lesser extent (F1-F3) pain of central/supraspinal origin. In the in vitro studies, F1-F4 reduced the COX-2 level in lipopolysaccharide-activated RAW 264.7 cells, which suggests their anti-inflammatory activity.
Learn More >Noxious pain signals are transduced in the peripheral nervous system as action potentials, which rely on the activities of voltage-gated sodium channels (NaVs). Blocking NaVs is thus a valuable strategy for pain treatment. Here, we report the characterization of a novel NaVs antagonist, 2-(2-(diethylamino)ethyl)indeno[1,2,3-de]phthalazin-3(2H)-one (C65780), and investigation of its action mechanisms. C65780 inhibited the resting NaV1.7, NaV1.8, and NaV1.9 channels with IC50s of 11.3 ± 0.4 μM, 2.7 ± 0.3 μM and 19.2 ± 2.3 μM, respectively. Mechanistic analysis revealed that C65780 quickly bound to its high-affinity receptor site in NaV1.7 as formed by the fast inactivation process and stabilized the channels in a slowly recovering state, for which it facilitated NaV1.7 channels' inactivation by shifting their inactivation-voltage relationship in the hyperpolarizing direction, increasing the plateau proportion of inactivated channels, and blunting their time-dependent recovery. The slow inactivation of NaV1.7, however, is not involved in the action of C65780. In DRG neurons, C65780 also inhibited activity of NaVs, thus dampening neuronal excitability. These effects parlayed into a broad efficacy of orally administrated C65780 in various models of pain, with an efficacy comparable to the antidepressant/neuropathic pain drug Amitriptyline. Excitingly, C65780 demonstrated weaker inactivated state inhibition of related NaV1.4 and NaV1.5 channels compared to amitriptyline, and no toxicity or inhibition of locomotion in a forced-swimming test was observed in mice at pain-relieving doses. These results demonstrate that C65780 acts by trapping NaVs in the inactivated and slowly-recovering state to produce pain relief and may represent an excellent starting compound for developing analgesics.
Learn More >Spinal cord injury (SCI) may cause structural alterations in brain due to pathophysiological processes, but the effects of SCI treatment on brain have rarely been reported. Here, voxel-based morphometry is employed to investigate the effects of SCI and neurotrophin-3 (NT3) coupled chitosan-induced regeneration on brain and spinal cord structures in rhesus monkeys. Possible association between brain and spinal cord structural alterations is explored. The pain sensitivity and stepping ability of animals are collected to evaluate sensorimotor functional alterations. Compared with SCI, the unique effects of NT3 treatment on brain structure appear in extensive regions which involved in motor control and neuropathic pain, such as right visual cortex, superior parietal lobule, left superior frontal gyrus (SFG), middle frontal gyrus, inferior frontal gyrus, insula, secondary somatosensory cortex, anterior cingulate cortex, and bilateral caudate nucleus. Particularly, the structure of insula is significantly correlated with the pain sensitivity. Regenerative treatment also shows a protective effect on spinal cord structure. The associations between brain and spinal cord structural alterations are observed in right primary somatosensory cortex, SFG, and other regions. These results help further elucidate secondary effects on brain of SCI and provide a basis for evaluating the effects of NT3 treatment on brain structure.
Learn More >This study explored the role of P2X7 receptors in spinal cord astrocytes in the electroacupuncture-induced inhibition of visceral hypersensitivity (VH) in rats with irritable bowel syndrome (IBS). Visceral hypersensitivity of IBS was intracolonically induced by 2,4,6-trinitrobenzene sulfonic acid (TNBS). Visceromotor responses to colorectal distension (CRD-20,40,60,80 mmHg) and abdominal withdrawal reflex scoring (AWRs) were recorded after electroacupuncture at bilateral Zusanli (ST36) and Sanyinjiao (SP6) acupoints to evaluate the analgesic effect of electroacupuncture on visceral pain in rats with IBS. Fluorocitric acid (FCA), an astrocyte activity inhibitor, was injected intrathecally before electroacupuncture intervention and AWRs were recorded. Western blot and real-time qPCR were used to detect the expression of NMDA and P2X7 receptor to observe the regulation effect of electroacupuncture on NMDA receptor in the spinal cord of rats with visceral hypersensitivity. Intrathecal injection of P2X7 agonist or antagonist was administered before electroacupuncture treatment. To observe the effect of P2X7 receptor in spinal astrocytes on the inhibition of visceral hyperalgesia by electroacupuncture, the changes of AWR score, NMDA receptor in the spinal cord, and GFAP expression in astrocytes were detected. Inflammation of the colon had basically subsided at day 21 post-TNBS; persistent visceral hypersensitivity could be suppressed by electroacupuncture. This analgesic effect could be inhibited by FCA. The analgesic effect, downregulation of NMDA receptor NR1 subunit, and P2X7 protein of electroacupuncture were all reversed by FCA. P2X7 receptor antagonist A740003 can cooperate with EA to carry out analgesic effect in rats with visceral pain and downregulate the expression of NR1, NR2B, and GFAP in spinal dorsal horn. However, the P2X7 receptor agonist BzATP could partially reverse the analgesic effect of EA, inhibiting the downregulatory effect of EA on the expression of NR1, NR2B, and GFAP. These results indicate that EA may downregulate the expression of the NMDA receptor by inhibiting the P2X7 receptor in the spinal cord, thereby inhibiting spinal cord sensitization in IBS rats with visceral pain, in which astrocytes are an important medium.
Learn More >Low back pain (LBP) management is an important clinical issue. Inadequate LBP control has consequences on the mental and physical health of patients. Thus, acquiring new information on LBP mechanism would increase the available therapeutic tools. Resveratrol is a natural compound with many beneficial effects. In this study, we investigated the role of resveratrol on behavioral changes, inflammation and oxidative stress induced by LBP. Ten microliters of Complete Freund's adjuvant (CFA) was injected in the lumbar intervertebral disk of Sprague Dawley rats to induce degeneration, and resveratrol was administered daily. Behavioral analyses were performed on day zero, three, five and seven, and the animals were sacrificed to evaluate the molecular pathways involved. Resveratrol administration alleviated hyperalgesia, motor disfunction and allodynia. Resveratrol administration significantly reduced the loss of notochordal cells and degenerative changes in the intervertebral disk. From the molecular point of view, resveratrol reduced the 5th/6th lumbar (L5-6) spinal activation of the WNT pathway, reducing the expression of WNT3a and cysteine-rich domain frizzled (FZ)8 and the accumulation of cytosolic and nuclear β-catenin. Moreover, resveratrol reduced the levels of TNF-α and IL-18 that are target genes strictly downstream of the WNT/β-catenin pathway. It also showed important anti-inflammatory activities by reducing the activation of the NFkB pathway, the expression of iNOS and COX-2, and the levels of PGE2 in the lumbar spinal cord. Moreover, resveratrol reduced the oxidative stress associated with inflammation and pain, as shown by the observed reduced lipid peroxidation and increased GSH, SOD, and CAT activities. Therefore, resveratrol administration controlled the WNT/β-catenin pathway and the related inflammatory and oxidative alterations, thus alleviating the behavioral changes induced by LBP.
Learn More >P2X7 receptor antagonists have potential for treating various CNS diseases, including neuropathic pain, although none have been approved for clinical use. Reasons may include insufficient understanding of P2X7 receptor signaling in pain and the lack of a corresponding preclinical mechanistic biomarker.
Learn More >KIAA1199 has a strong hyaluronidase activity in inflammatory arthritis. This study aimed to identify a drug that could reduce KIAA1199 activity and clarify its effects on inflammatory arthritis. Rat chondrosarcoma (RCS) cells were strongly stained with Alcian blue (AB). Its stainability was reduced in RCS cells, which were over-expressed with the KIAA1199 gene (RCS-KIAA). We screened the drugs that restore the AB stainability in RCS-KIAA. The effects of the drug were evaluated by particle exclusion assay, HA ELISA, RT-PCR, and Western blotting. We further evaluated the HA accumulation and the MMP1 and three expressions in fibroblast-like synoviocytes (FLS). In vivo, the effects of the drug on symptoms and serum concentration of HA in a collagen-induced arthritis mouse were evaluated. Ipriflavone was identified to restore AB stainability at 23%. Extracellular matrix formation was significantly increased in a dose-dependent manner ( = 0.006). Ipriflavone increased the HA accumulation and suppressed the MMP1 and MMP3 expression on TNF-α stimulated FLS. In vivo, Ipriflavone significantly improved the symptoms and reduced the serum concentrations of HA. Conclusions: We identified Ipriflavone, which has inhibitory effects on KIAA1199 activity. Ipriflavone may be a therapeutic candidate based on its reduction of KIAA1199 activity in inflammatory arthritis.
Learn More >Paclitaxel is a widely used anticancer drug that induces dose-limiting peripheral neuropathy. Mitochondrial dysfunction has been implicated in paclitaxel-induced neuronal damage and in the onset of peripheral neuropathy. We have previously shown that the expression of PINK1, a key mediator of mitochondrial quality control, ameliorated the paclitaxel-induced thermal hyperalgesia phenotype and restored mitochondrial homeostasis in larvae. In this study, we show that the small-molecule PINK1 activator niclosamide exhibits therapeutic potential for paclitaxel-induced peripheral neuropathy. Specifically, niclosamide cotreatment significantly ameliorated the paclitaxel-induced thermal hyperalgesia phenotype in larvae in a PINK1-dependent manner. Paclitaxel-induced alteration of the dendrite structure of class IV dendritic arborization (C4da) neurons was not reduced upon niclosamide treatment. In contrast, paclitaxel treatment-induced increases in both mitochondrial ROS and aberrant mitophagy levels in C4da neurons were significantly suppressed by niclosamide. In addition, niclosamide suppressed paclitaxel-induced mitochondrial dysfunction in human SH-SY5Y cells in a PINK1-dependent manner. These results suggest that niclosamide alleviates thermal hyperalgesia by attenuating paclitaxel-induced mitochondrial dysfunction. Taken together, our results suggest that niclosamide is a potential candidate for the treatment of paclitaxel-induced peripheral neuropathy with low toxicity in neurons and that targeting mitochondrial dysfunction is a promising strategy for the treatment of chemotherapy-induced peripheral neuropathy.
Learn More >Neuroinflammation in spinal dorsal horn (SDH) plays an important role in the pathogenesis of interstitial cystitis/bladder pain syndrome (IC/BPS). Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) exert potent anti-inflammatory activities in the treatment of various diseases. This study aimed to determine the therapeutic effects of MSC-EVs on IC and furtherly investigate the potential mechanism to attenuate neuroinflammation.
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