Inhibition of Schwann cell pannexin 1 attenuates neuropathic pain through the suppression of inflammatory responses.

BACKGROUND: Neuropathic pain is still a challenge for clinical treatment as a result of the comprehensive pathogenesis. Although emerging evidence demonstrates the pivotal role of glial cells in regulating neuropathic pain, the role of Schwann cells and their underlying mechanisms still need to be uncovered. Pannexin 1 (Panx 1), an important membrane channel for the release of ATP and inflammatory cytokines, as well as its activation in central glial cells, contributes to pain development. Here, we hypothesized that Schwann cell Panx 1 participates in the regulation of neuroinflammation and contributes to neuropathic pain. METHODS: A mouse model of chronic constriction injury (CCI) in CD1 adult mice or P0-Cre transgenic mice, and in vitro cultured Schwann cells were used. Intrasciatic injection with Panx 1 blockers or the desired virus was used to knock down the expression of Panx 1. Mechanical and thermal sensitivity was assessed using Von Frey and a hot plate assay. The expression of Panx 1 was measured using qPCR, western blotting, and immunofluorescence. The production of cytokines was monitored through qPCR and enzyme-linked immunosorbent assay (ELISA). Panx1 channel activity was detected by ethidium bromide (EB) uptake. RESULTS: CCI induced persistent neuroinflammatory responses and upregulation of Panx 1 in Schwann cells. Intrasciatic injection of Panx 1 blockers, carbenoxolone (CBX), probenecid, and Panx 1 mimetic peptide (10Panx) effectively reduced mechanical and heat hyperalgesia. Probenecid treatment of CCI-induced mice significantly reduced Panx 1 expression in Schwann cells, but not in dorsal root ganglion (DRG). In addition, Panx 1 knockdown in Schwann cells with Panx 1 shRNA-AAV in P0-Cre mice significantly reduced CCI-induced neuropathic pain. To determine whether Schwann cell Panx 1 participates in the regulation of neuroinflammation and contributes to neuropathic pain, we evaluated its effect in LPS-treated Schwann cells. We found that inhibition of Panx 1 via CBX and Panx 1-siRNA effectively attenuated the production of selective cytokines, as well as its mechanism of action being dependent on both Panx 1 channel activity and its expression. CONCLUSION: In this study, we found that CCI-related neuroinflammation correlates with Panx 1 activation in Schwann cells, indicating that inhibition of Panx 1 channels in Schwann cells reduces neuropathic pain through the suppression of neuroinflammatory responses.

TAT-Gap19 and Carbenoxolone Alleviate Liver Fibrosis in Mice.

Although a plethora of signaling pathways are known to drive the activation of hepatic stellate cells in liver fibrosis, the involvement of connexin-based communication in this process remains elusive. Connexin43 expression is enhanced in activated hepatic stellate cells and constitutes the molecular building stone of hemichannels and gap junctions. While gap junctions support intercellular communication, and hence the maintenance of liver homeostasis, hemichannels provide a circuit for extracellular communication and are typically opened by pathological stimuli, such as oxidative stress and inflammation. The present study was set up to investigate the effects of inhibition of connexin43-based hemichannels and gap junctions on liver fibrosis in mice. Liver fibrosis was induced by administration of thioacetamide to Balb/c mice for eight weeks. Thereafter, mice were treated for two weeks with TAT-Gap19, a specific connexin43 hemichannel inhibitor, or carbenoxolone, a general hemichannel and gap junction inhibitor. Subsequently, histopathological analysis was performed and markers of hepatic damage and functionality, oxidative stress, hepatic stellate cell activation and inflammation were evaluated. Connexin43 hemichannel specificity of TAT-Gap19 was confirmed in vitro by fluorescence recovery after photobleaching analysis and the measurement of extracellular release of adenosine-5'-triphosphate. Upon administration to animals, both TAT-Gap19 and carbenoxolone lowered the degree of liver fibrosis accompanied by superoxide dismutase overactivation and reduced production of inflammatory proteins, respectively. These results support a role of connexin-based signaling in the resolution of liver fibrosis, and simultaneously demonstrate the therapeutic potential of TAT-Gap19 and carbenoxolone in the treatment of this type of chronic liver disease.

Carbenoxolone as a novel therapy for attenuation of cancer-induced bone pain.

Pain is a major complication for patients with cancer significantly compromising their quality of life. Current treatment is far from optimal and particularly bone-related cancer pain poses an increasing clinical and socioeconomical problem. Connexins, key proteins in cell-cell communication, have the potential to affect cancer-induced bone pain at multiple levels, including nociceptive signaling and bone degradation. This study tested the analgesic potential of carbenoxolone, a broad-acting connexin blocker, in a mouse model of cancer-induced bone pain. In addition, a pharmacological approach was used to elucidate the underlying mechanisms using the 2 specific blockers Gap27 and Gap26. Compared with vehicle treatment, chronic systemic administration of 20 or 40 mg/kg carbenoxolone caused a significantly later onset and attenuation of movement-evoked and on-going pain, assessed with limb use and weight bearing, respectively. In addition, the carbenoxolone-treated groups demonstrated a significant delay in time to reach the humane endpoint. Acute intrathecal administration of Gap27 significantly attenuated both limb use and weight bearing, whereas Gap26 had a less pronounced effect. Carbenoxolone treatment had a minor effect on the bone degradation in the early phase of disease progression, whereas no effect was observed in the late phase. Surprisingly, connexin43 was downregulated in the cancer-bearing animals compared with shams. The results suggest that connexins are involved in cancer-induced bone pain, and that carbenoxolone could be a novel analgesic treatment for the pain state.

Acute anti-obesity effects of intracerebroventricular 11ß-HSD1 inhibitor administration in diet-induced obese mice.

The hypothalamus is the regulatory centre of both appetite and energy balance and endoplasmic reticulum (ER) stress in the hypothalamus is involved in the pathogenesis of obesity. Recently, inhibition of 11 ß hydroxysteroid dehydrogenase type1 (11ß-HSD1) was reported to have an anti-obesity effect by reducing fat mass. However, the link between the role of 11ß-HSD1 in the hypothalamus and obesity has yet to be determined. In the present study, embryonal primary hypothalamic neurones and high-fat diet (HFD) fed mice were used to investigate the anorexigenic effects of 11ß-HSD1 inhibitors both in vitro and in vivo. In hypothalamic neurones, carbenoxolone (a non selecitve 11ß-HSD inhibitor) alleviated ER stress and ER stress-induced neuropeptide alterations. In HFD mice, i.c.v. administration of carbenoxolone or KR67500 (nonselective and selective 11ß-HSD1 inhibitors, respectively) was associated with less weight gain compared to control mice for 24 hours after treatment, presumably by reducing food intake. Furthermore, glucose regulated protein (Grp78), spliced X-box binding protein (Xbp-1s), c/EBP homologous protein (chop) and ER DnaJ homologue protein (Erdj4) expression was decreased in the hypothalami of mice administrated 11ß-HSD1 inhibitors compared to controls. Conversely, the phosphorylation of protein kinase B (PKB/Akt), signal transducer and activator of transcription 3 (Stat3), mitogen-activated protein kinase (MAPK/ERK) and S6 kinase1 (S6K1) in the hypothalamus was induced more in mice treated using the same regimes. In conclusion, acute 11ß-HSD1 inhibition in the hypothalamus could reduce food intake by decreasing ER stress and increasing insulin, leptin, and mammalian target of rapamycin complex 1 (mTORC1) signalling.

Effects of inhibiting connexin43 on expression of fibroblast growth factor in prolactinomas in rats.

OBJECTIVE: The aim of this study was to investigate the effect of connexin43(Cx43) on basic fibroblast growth factor (bFGF) expression by inhibiting Cx43 expression in prolactinomas in rats. METHODS: An experimental rat model of prolactinoma induced by estradiol (E2) treatment was used. Gap junction inhibitor was applied in through the arachnoid space by injection of carbenoxolone (CBX). Cx43 and bFGF expression was examined by both western blotting, respectively. RESULTS: Pituitaries treated with E2 were hypertrophic, but this was reduced by CBX treatment. Estradiol induced Cx43 and bFGF expression, which decreased following CBX treatment. CONCLUSIONS: Altered Cx43 expression modulates bFGF expression, which correlates with prolactinoma development.

Pannexin 1: a novel participant in neuropathic pain signaling in the rat spinal cord.

Pannexin 1 (panx1) is a large-pore membrane channel expressed in many tissues of mammals, including neurons and glial cells. Panx1 channels are highly permeable to calcium and adenosine triphosphatase (ATP); on the other hand, they can be opened by ATP and glutamate, two crucial molecules for acute and chronic pain signaling in the spinal cord dorsal horn, thus suggesting that panx1 could be a key component for the generation of central sensitization during persistent pain. In this study, we examined the effect of three panx1 blockers, namely, 10panx peptide, carbenoxolone, and probenecid, on C-reflex wind-up activity and mechanical nociceptive behavior in a spared nerve injury neuropathic rat model involving sural nerve transection. In addition, the expression of panx1 protein in the dorsal horn of the ipsilateral lumbar spinal cord was measured in sural nerve-transected and sham-operated control rats. Sural nerve transection resulted in a lower threshold for C-reflex activation by electric stimulation of the injured hindpaw, together with persistent mechanical hypersensitivity to pressure stimuli applied to the paw. Intrathecal administration of the panx1 blockers significantly depressed the spinal C-reflex wind-up activity in both neuropathic and sham control rats, and decreased mechanical hyperalgesia in neuropathic rats without affecting the nociceptive threshold in sham animals. Western blotting showed that panx1 was similarly expressed in the dorsal horn of lumbar spinal cord from neuropathic and sham rats. The present results constitute the first evidence that panx1 channels play a significant role in the mechanisms underlying central sensitization in neuropathic pain.

The contribution of satellite glial cells to chemotherapy-induced neuropathic pain.

BACKGROUND: Chemotherapy-induced peripheral neuropathy is a serious side effect in cancer treatment, a major manifestation being neuropathic pain that can be debilitating and can reduce the quality of life of the patient. Oxaliplatin and taxol are common anti-cancer drugs that induce neuropathic pain by an unknown mechanism. We tested the hypothesis that satellite glial cells in dorsal root ganglia (DRGs) are altered in chemotherapy-induced peripheral neuropathy models and contribute to neuropathic pain. METHODS: Mice were injected with either oxaliplatin or taxol and examined at 7-30 days. Glial fibrillary acidic protein (glial activation marker) expression was determined by immunohistochemistry. Satellite glial cells in isolated DRG were injected with the fluorescent dye Lucifer yellow and the incidence of dye coupling among these cells that surround different neurons was quantified. RESULTS: Taxol or oxaliplatin increased glial fibrillary acidic protein expression in satellite glial cells. Gap junction-mediated coupling between satellite glial cells was increased by up to fivefold after oxaliplatin and by up to twofold after taxol. This is consistent with work on other pain models showing that augmented satellite glial cell coupling contributes to chronic pain. Administration of the gap junction blocker carbenoxolone to chemotherapy-treated mice produced an analgesic-like effect. CONCLUSIONS: We propose that increased coupling by gap junctions is part of satellite glial cell activation, and that augmented coupling contributes to the lowering of pain threshold in oxaliplatin- and taxol-treated mice. We further propose that gap junction blockers may have potential in treating chemotherapy-induced neuropathic pain.

Aphthous ulcers (recurrent).

INTRODUCTION: Most people with recurrent aphthous ulcers develop a few ulcers less than 1 cm in diameter, that heal after 5-14 days without scarring. The causes are unknown, but risks of recurrence may decrease if the person gives up smoking. Local physical trauma may trigger ulcers in susceptible people. In 10% of sufferers, lesions are more than 1 cm in diameter, and can cause scarring. METHODS AND OUTCOMES: We conducted a systematic review and aimed to answer the following clinical question: What are the effects of treatments for recurrent aphthous ulcers? We searched: Medline, Embase, The Cochrane Library and other important databases up to August 2006 (Clinical Evidence reviews are updated periodically, please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA). RESULTS: We found 18 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions. CONCLUSIONS: In this systematic review we present information relating to the effectiveness and safety of the following interventions: analgesics (local), carbenoxolone mouthwash, chlorhexidine (and similar agents), corticosteroids (topical), and tetracycline antibiotic mouthwash.

The effects of carbenoxolone, a semisynthetic derivative of glycyrrhizinic acid, on peripheral and central ischemia-reperfusion injuries in the skeletal muscle and hippocampus of rats.

As carbenoxolone, a semisynthetic derivative of glycyrrhizinic acid, has a free radical scavenging property, thus the effects of carbenoxolone during ischemia-reperfusion was evaluated on an animal model of ischemia-reperfusion injury in the rat hind limb and hippocampus. Peripheral and central ischemia were induced by free-flap surgery in skeletal muscle and four-vessel-occulation (4VO) of rat, respectively. Carbenoxolone (50-200 mg/kg) and normal saline (10 ml/ kg) were administered intraperitoneally. In peripherlal ischemia, during preischemia, ischemia and reperfusion conditions the electromyographic (EMG) potentials in the muscles were recorded. The malondialdehyde (MDA) was measured by the thiobarbituric acid (TBA) test after reperfusion in peripheral and central ischemia. In peripheral ischemia, the average peak-to-peak amplitude during ischemic-reperfusion was found to be significantly larger in carbenoxolone group (100-200mg/kg) in comparison to control group. The MDA levels were recovered significantly upon carbenoxolone (100-200 mg/kg) therapy in the skeletal muscle and hippocampus of ischemic rats. These results suggest that carbenoxolone can salvage the skeletal muscle and hippocampus from acute ischemia-reperfusion injury.

[Glycyrrhizic acid]. / Glitsirrizinovaya kislota

The specific properties, chemical transformations, and biological activity of glycyrrhizic acid and its derivatives are discussed. Particular attention is paid to investigations that hold promise for the development of important drugs for clinical use.

Cytoprotection and stress ulceration.

The stomach possesses many mechanisms for protection against stress ulceration. The gastric microcirculation, prostaglandins, mucus secretion, epithelial cell renewal, and muscle tone are factors involved in gastric cytoprotection. Therapy is partially directed at augmenting these natural physiologic defense mechanisms to prevent and promote healing of stress ulceration. Drugs such as sucralfate, carbenoxalone, colloidal bismuth, and prostaglandins are used. Stress ulceration is an important cause of upper gastrointestinal tract hemorrhage in postoperative and critically ill patients in the intensive care unit setting. Preventive therapy includes neutralization of gastric acid by antacids, suppression of gastric acid secretion by H2-receptor blockers, administration of cytoprotective agents, and correction of the underlying stress state. Active bleeding requires accurate diagnosis by gastroscopy. Additional therapy may be necessary, including intra-arterial administration of vasopressin and occasionally surgery. Dieulafoy's lesion is an unusual stress-related cause for upper gastrointestinal bleeding. The area of mucosal injury is minute but underneath lies a large submucosal gastric artery. It can cause massive bleeding and is often missed at initial gastroscopy. The pathogenesis of Dieulafoy's lesion is complex and the mainstay of therapy has been surgical. Ligation of the vessel, wedge resection, or proximal gastric resection is performed. Therapeutic endoscopy with endoscopic cauterization or injection has changed the approach to this lesion.

Conduta na doença ulcerosa / Peptic ulcer managment

Relata sobre as causas e formas de tratamentos da úlcera gastroduodenal. Aconselha avaliaçäo criteriosa nos casos cronicos visando uma opçäo entre o tratamento continuo de manutençäo ou a opçäo cirurgica

Effects of 12-sulfodehydroabietic acid monosodium salt (TA-2711), a new anti-ulcer agent, on gastric secretion and experimental ulcers in rats.

Effects of 12-sulfodehydroabietic acid monosodium salt (TA-2711), a new anti-ulcer agent, on gastric secretion and experimental ulcers were investigated in rats. Oral administration of TA-2711 at doses of 25 to 100 mg/kg immediately after pyloric ligation markedly reduced pepsin activity and slightly lowered acid concentration without affecting the volume of gastric juice. Addition of TA-2711 (0.25-16 mg/ml) directly to gastric juice also reduced pepsin activity in vitro. Oral TA-2711 dose-relatedly inhibited the formation of pylorus-ligated ulcers (50-200 mg/kg), aspirin-induced gastric erosions (25-100 mg/kg) and cysteamine-induced duodenal ulcers (100-800 mg/kg). In addition, this drug prevented both the formation of gastric lesions (6.3-100 mg/kg, p.o.) and the fall in gastric potential difference (100 mg/kg, p.o.) induced by ethanol. The preventive effect against ethanol-induced lesions was suppressed by pretreatment with indomethacin (10 mg/kg, s.c.). Intravenous dosing of TA-2711 (10-100 mg/kg) never produced such effects on ethanol-induced lesions and pepsin activity as observed by oral administration. These results indicate that TA-2711 exerts its anti-ulcer effect by a local action, and it is suggested that both reduction of pepsin activity and a mucosal prostaglandin-mediated process are involved in the anti-ulcer action of TA-2711.

Treatment of reflux oesophagitis with a carbenoxolone/antacid/alginate preparation. A double-blind controlled trial.

Twenty-nine patients were treated with a carbenoxolone/antacid/alginate preparation (Pyrogastrone) and 30 with antacid/alginate alone four times each day for 8 weeks, in a double-blind study, to ascertain the value of carbenoxolone in the treatment of patients with endoscopically confirmed reflux oesophagitis. Symptom review every 2 weeks and endoscopic findings every 4 weeks were converted to a 6-point grading system to facilitate statistical comparison, using a stochastic model for predicting the rate of change in grades during treatment. Carbenoxolone-treated patients showed an 82% improvement in symptom grades over 8 weeks and improved 50% faster (P less than 0.01) than did control patients, who showed a 63% improvement. Endoscopic improvement was not significantly different in the first 4 weeks, although healing was better maintained in carbenoxolone-treated patients during the second 4 weeks (P less than 0.05). At the low doses used (5 X 20 mg daily) no significant side effects of carbenoxolone were encountered. Pyrogastrone should be considered as a therapeutic alternative in patients who fail to respond to routine management with antacids.

Farmacoterapia de la úlcera péptica / Pharmacotherapy in peptic ulcer

Siendo la úlcera péptica una enfermedad de alta prevalencia, la industria farmacéutica ha introducido en los últimos años un gran número de fármacos potencialmente útiles en su tratamiento. En este artículo se revisan los fármacos actualmente disponibles y otros en fase de investigación en las variedades de antisecretores o protectores de mucosa. Se discute las ventajas, desventajas, dosis propuestas y eficacia de cada uno de ellos. Finalmente se plantea algunas interrogantes de problemas aún no resueltos en la fármacoterapia de esta enfermedad

Comparison of pirenzepine and carbenoxolone in the treatment of chronic gastric ulcer. A double-blind endoscopic trial.

The purpose of the present study was to compare the effectiveness of pirenzepine and carbenoxolone in accelerating the healing of chronic gastric ulcer. Sixty-six out-patients with endoscopically proven gastric ulcer, without major systemic diseases, were admitted to the study. Patients were randomly allocated to either pirenzepine, 50 mg three times a day for 6 weeks, or carbenoxolone, 100 mg three times a day for one week followed by 50 mg three times a day for the remaining five weeks. At 6 weeks, the ulcers had healed in 20 out of 34 patients (59%) treated with pirenzepine, and in 15 out of 29 patients (52%) treated with carbenoxolone. Symptomatic improvement was similar with both drugs. Some major side effects (oedema, hypokalaemia and hypertension) occurred in approximately 30% of patients treated with carbenoxolone; of those receiving pirenzepine 25% complained of minor symptoms (e.g. dry mouth, headache, tachycardia). It is concluded that pirenzepine and carbenoxolone are of similar, but rather limited, efficacy in speeding the healing of chronic gastric ulcer, but show important differences with respect to tolerability.

Factors relevant to the prognosis of chronic duodenal ulcer.

The aim of the study was to define the effects of sex, age, smoking, alcohol, analgesic ingestion, and treatment method whereby healing was initially induced on the prognosis of patients with a chronic duodenal ulcer (DU). 122 patients were assessed 1 year after the endoscopic demonstration of a DU. Two outcome variables for this 1-year period were studied - freedom from symptoms, and proven recurrence of the DU. Additionally, the outcome groups were compared to a community control population as regards the exposure variables. The results of the study indicate that each increase in smoking by 10 cigarettes daily increased the risk of DU recurrence within 1 year by 40%. Comparisons between patients and community controls revealed that smoking was significantly associated with DU and this association was present whether the ulcer was in exacerbation or in remission.

Topical carbenoxolone sodium in the management of herpes simplex infection.

Topical carbenoxolone was discovered by chance to be a highly effective anti-viral agent and was subsequently used in the management of Herpetic gingivostomatitis and recurrent Herpes labialis. A marked reduction in the healing time and pain associated with these lesions was noted. A discussion of the possible mechanisms of action of carbenoxolone is included.

Sucralfate and carbenoxolone in the treatment of functional disturbances following partial gastrectomy.

30 patients submitted to partial gastrectomy (Billroth II) who later suffered digestive complaints (pain, "heartburn", bilious vomiting) showed gastric hyperemia, oedema and some erosions of the gastric stump when examined by endoscopy, the presence of cancer having been excluded by biopsy. These patients were randomly allocated into 2 groups of 15, one of which was treated with sucralfate (1 g 4 times), and the other with carbenoxolone (50 mg 4 times), daily for 8 weeks. After sucralfate the endoscopic finding showed a clear improvement in the gastric wall, accompanied by the almost complete disappearance of the complaint symptoms, in 13 cases (86.6%). After carbenoxolone the same improvement was observed at the endoscopy in 12 cases (80%), with similar recovery from symptoms. Nevertheless, no histological changes that could be attributed to the treatments were observed. In those patients whose endoscopic pattern remained unchanged by either drug, the complaints did not show any relief. No side-effects were detected during either of these drug treatments, each of which showed a similar therapeutic efficacy.