Carbenoxolone: a review of its pharmacological properties and therapeutic efficacy in peptic ulcer disease

Argel's stemmoside C as a novel natural remedy for mice with alcohol-induced gastric ulcer based on its molecular mechanistic pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Solenostemma argel is widely distributed in Africa & Asia with traditional usage in alleviating abdominal colic, aches, & cramps. This plant is rich in phytochemicals, which must be explored for its pharmacological effects.

PURPOSE

Peptic Ulcer Disease (PUD) is the digestion of the digestive tube. PUD not only interferes with food digestion & nutrient absorption, damages one of the largest defensive barriers against pathogenic micro-organisms, but also impedes drug absorption & bioavailability, rendering the oral route, the most convenient way, ineffective. Omeprazole, one of the indispensable cost-effective proton-pump inhibitors (PPIs) extensively prescribed to control PUD, is showing growing apprehensions toward multiple drug interactions & side effects. Hence, finding a natural alternative with Omeprazole-like activity & limited side effects is a medical concern.

STUDY DESIGN

Therefore, we present Stemmoside C as a new gastroprotective phytochemical agent isolated from Solenostemma argel to be tested in upgrading doses against ethanol-induced gastric ulcers in mice compared to negative, positive, & reference Omeprazole groups.

METHODS

We carried out in-depth pharmacological & histopathological studies to determine the possible mechanistic pathway.

RESULTS

Our results showed that Stemmoside C protected the stomach against ethanol-induced gastric ulcers parallel to Omeprazole. Furthermore, the mechanistic studies revealed that Stemmoside C produced its effect using an orchestrated array of different mechanisms. Stemmoside C stimulates stomach defense by increasing COX-2, PGE-2, NO, & TFF-1 healing factors, IL-10 anti-inflammatory cytokine, & Nrf-2 & HO-1 anti-oxidant pathways. It also suppresses stomach ulceration by inhibiting leucocyte recruitment, especially neutrophils, leading to subsequent inhibition of NF-κBp65, TNF-α, IL-1β, & iNOS pro-inflammatory cytokines & JAK-1/STAT-3 inflammation-induced carcinogenicity cascade in addition to MMP-9 responsible for tissue degradation.

CONCLUSION

These findings cast light on Stemmoside C's clinical application against gastric ulcer progression, recurrence, & tumorigenicity & concurrently with chemotherapy.

Unveiling the mechanisms of trichloroethylene hypersensitivity syndrome: Exploring the role of connexin 43 gap junctions in severe skin damage

Trichloroethylene (TCE), extensively used as an organic solvent in various industrial applications, has been identified as a causative factor in inducing hypersensitivity syndrome (THS). Currently, there is no specific treatment for THS, and most patients experience serious adverse outcomes due to extensive skin damage leading to severe infection. However, the pathogenesis of THS-associated skin damage remains unclear. This study aims to elucidate the mechanism underlying skin damage from the perspective of intercellular communication and gap junctions in THS. Our results verified that hyperactivation of connexin43 gap junctions, caused by the aberrantly elevated expression of connexin43, triggers a bystander effect that promotes apoptosis and inflammation in THS via the TNF-TNFRSF1B and mitochondria-associated pathways. Additionally, we identified the gap junction inhibitor Carbenoxolone disodium (CBX) as a promising agent for the treatment of skin damage in THS. CBX protects against inflammatory cell infiltration in the skin and decreases immune cell imbalance in the peripheral blood of THS mice. Furthermore, CBX reduces connexin43 expression, apoptosis and inflammation in THS mice. The study reveals new insights into the mechanisms underlying TCE-induced skin damage, offering a potential treatment strategy for the development of effective therapies targeting severe dermatitis induced by chemical exposure.

Somatic GJA4 mutation in intracranial extra-axial cavernous hemangiomas

OBJECTIVE

Extra-axial cavernous hemangiomas (ECHs) are sporadic and rare intracranial occupational lesions that usually occur within the cavernous sinus. The aetiology of ECHs remains unknown.

METHODS

Whole-exome sequencing was performed on ECH lesions from 12 patients (discovery cohort) and droplet digital polymerase-chain-reaction (ddPCR) was used to confirm the identified mutation in 46 additional cases (validation cohort). Laser capture microdissection (LCM) was carried out to capture and characterise subgroups of tissue cells. Mechanistic and functional investigations were carried out in human umbilical vein endothelial cells and a newly established mouse model.

RESULTS

We detected somatic GJA4 mutation (c.121G>T, p.G41C) in 5/12 patients with ECH in the discovery cohort and confirmed the finding in the validation cohort (16/46). LCM followed by ddPCR revealed that the mutation was enriched in lesional endothelium. In vitro experiments in endothelial cells demonstrated that the GJA4 mutation activated SGK-1 signalling that in turn upregulated key genes involved in cell hyperproliferation and the loss of arterial specification. Compared with wild-type littermates, mice overexpressing the GJA4 mutation developed ECH-like pathological morphological characteristics (dilated venous lumen and elevated vascular density) in the retinal superficial vascular plexus at the postnatal 3 weeks, which were reversed by an SGK1 inhibitor, EMD638683.

CONCLUSIONS

We identified a somatic GJA4 mutation that presents in over one-third of ECH lesions and proposed that ECHs are vascular malformations due to GJA4-induced activation of the SGK1 signalling pathway in brain endothelial cells.

Antioxidant and Gastroprotective Activity of Suaeda fruticosa Forssk. Ex J.F.Gmel

Suaeda fruticosa Forssk. Ex J.F.Gmel is traditionally used for inflammatory and digestive disorders, as a carminative, and for diarrhea. This plant is widely distributed in Asia, Africa, and the Mediterranean region. Aqueous methanolic extract of S. fruticosa (Sf.Cr) was prepared and screened for phytoconstituents through qualitative and GC-MS analysis. Quantification of total phenolic and flavonoid contents was performed, while antioxidant capacity was determined by DPPH, CUPRAC, FRAP, and ABTS assays. The gastroprotective activity was assessed in an ethanol-induced ulcer model. Gastric secretory parameters and macroscopic ulcerated lesions were analyzed and scored for ulcer severity. After scoring, histopathology was performed, and gastric mucus contents were determined. Oral pre-treatment of Sf.Cr demonstrated significant gastroprotection. The gastric ulcer severity score and ulcer index were reduced while the %-inhibition of ulcer was increased dose-dependently. The Sf.Cr significantly elevated the pH of gastric juice, while a decrease in total acidity and gastric juice volume was observed. Histopathology demonstrated less oedema and neutrophil infiltration in gastric mucosa of rats pre-treated with the Sf.Cr in comparison to ethanol-intoxicated animals. Furthermore, the gastric mucus contents were increased as determined by alcian blue binding. Sf.Cr showed marked gastroprotective activity, which can be attributed to antioxidant, antisecretory, and cytoprotective effects.

Current Evidence to Propose Different Food Supplements for Weight Loss: A Comprehensive Review

The use of food supplements for weight loss purposes has rapidly gained popularity as the prevalence of obesity increases. Navigating through the vast, often low quality, literature available is challenging, as is providing informed advice to those asking for it. Herein, we provide a comprehensive literature revision focusing on most currently marketed dietary supplements claimed to favor weight loss, classifying them by their purported mechanism of action. We conclude by proposing a combination of supplements most supported by current evidence, that leverages all mechanisms of action possibly leading to a synergistic effect and greater weight loss in the foreseen absence of adverse events. Further studies will be needed to confirm the weight loss and metabolic improvement that may be obtained through the use of the proposed combination.

Multi-walled carbon nanotubes induce IL-1β secretion by activating hemichannels-mediated ATP release in THP-1 macrophages

Multi-walled carbon nanotubes (MWCNTs) are known to induce pulmonary inflammatory effects through stimulating pro-inflammatory cytokine secretion from alveolar macrophages. Despite extensive studies on MWCNTs' pro-inflammatory reactivity, the understanding of molecular mechanisms involved is still incomplete. In this study, we investigated hemichannel's involvement in MWCNTs-induced macrophage IL-1β release. Our results showed that the unmodified and COOH MWCNTs could induce ATP release and ATP-P2X₇R axis-dependent IL-1β secretion from THP-1 macrophages. By using various inhibitors, we confirmed that the MWCNTs-induced ATP release was primarily through hemichannels. EtBr dye uptake assay detected significant hemichannels opening in MWCNTs exposed THP-1 macrophages. Inhibition of hemichannels by CBX, ⁴³Gap27, or ¹⁰Panx1 pretreatment results in decreased ATP and IL-1β release. The addition of ATP restored the reduced IL-1β secretion level from hemichannel inhibition. We also confirmed with five other types of MWCNTs that the induction of hemichannels by MWCNTs strongly correlates with their capacity to induce IL-1β secretion. Taken together, we conclude that hemichannels-mediated ATP release and subsequent NLRP3 inflammasome activation through P2X₇R may be one mechanism by which MWCNTs induce macrophage IL-1β secretion. Our findings may provide a novel molecular mechanism for MWCNTs induced IL-1β secretion.

Floating Drug Delivery Systems: An Emerging Trend for the Treatment of Peptic Ulcer

Floating drug delivery system (FDDS) is the main approach to prolonging the gastric residence time in the stomach in which the bilayer floating tablet has the main role. It is more suitable for the treatment of local infections such as peptic ulcer, gastritis, Zollinger-Ellision syndrome, indigestion, and other local infections related to the gastrointestinal tract and also used for systemic applications. FDDS provides protection for those drugs which are acid labile and have a short half-life. It also improves bioavailability, reduces drug waste, and enhances the residence time of drugs. Nowadays, various technologies are being used for the development of FDDS. Novel drug delivery systems incorporation into bilayer floating tablets have also broadened the role of FDDS. Polymers have the main role in the development of FDDS, which serve as carriers for the drug and determine the gastric retention time and drug protection. FDDS is also an easy, cheap, and more convenient method for dual drug delivery of drugs.

Encapsulated Carbenoxolone Reduces Lung Metastases

Carbenoxolone is an anti-inflammatory compound and a derivate of a natural substance from the licorice plant. We previously showed that carbenoxolone reduces the metastatic burden in the lungs of mice through its antagonistic effect on high mobility group box 1 (HMGB1). To further enhance carbenoxolone's activity and localization in the lungs, thereby reducing the potential adverse side effects resulting from systemic exposure, we developed a poly(lactic-co-glycolic acid) (PLGA) slow-release system for pulmonary delivery which maintains drug activity in-vitro, as demonstrated in the anoikis assay. Both systemic and intranasal administrations of carbenoxolone effectively minimize metastatic formation in a lung colonization model in mice. Our results show a decrease in the metastatic burden in the lung tissue. Notably, the therapeutic effect of a single intranasal administration of 25 mg/kg carbenoxolone, in the form of drug-loaded particles, had a similar effect in reducing metastatic lesions in the lungs to that of a 10-fold dose of the free drug via intraperitoneal injections, three times per week over the course of four weeks. These data offer new means to potentiate the anti-cancer activity of carbenoxolone and simultaneously reduce the requirement for high dosage administration; the upshot substantially improves therapeutic effect and avoidance of side effects.

Carbenoxolone enhances peripheral insulin sensitivity and GLUT4 expression in skeletal muscle of obese rats: Potential participation of UBC9 protein

AIM

This study investigates the insulin sensitizer effect of carbenoxolone (CBX) and potentially involved peripheral mechanisms.

MAIN METHODS

Taking glucose transporter 4 (GLUT4) as a marker of glucose disposal, we investigated the CBX effects on whole-body insulin sensitivity and solute carrier 2a4 (Slc2a4)/GLUT4 expression in visceral (VAT) and subcutaneous (SAT) adipose tissues and soleus muscle of monosodium glutamate (MSG)-induced obese rats. Sterol regulatory element binding protein (SREBP1), an enhancer of Slc2a4 expression was analyzed through mRNA content and SREBP1-binding to Slc2a4 promoter. Finally, the small ubiquitin-modifier conjugating enzyme 9 (UBC9), whose low content indicates accelerated GLUT4 degradation was analyzed in soleus.

KEY FINDINGS

Hypercorticosteronemia, hyperinsulinemia and low glucose decay rate in the insulin tolerance test of obese rats were restored by CBX (P < 0.05). Slc2a4/GLUT4 increased in SAT (P < 0.05) and decreased in VAT (P < 0.01) of obese rats. In soleus, obesity increased Slc2a4 but decreased GLUT4 (P < 0.01), possibly by accelerating GLUT4 degradation, as suggested by decreased UBC9 (P < 0.01). CBX restored both UBC9 and GLUT4 contents. SREBP1 did not participate in the Slc2a4 transcriptional regulation.

SIGNIFICANCE

The insulin sensitizer effect of CBX involves the increase of GLUT4 expression in soleus, indicating an increased glucose disposal in skeletal muscle. This observation reinforces the skeletal muscle as the main site of insulin-induced glucose uptake and sheds new light on the metabolic effects of 11βHSD1 inhibitors, since most of the studies so far have focused on its effects on liver and adipose tissues.

Analysis of carbenoxolone by ultra-high-performance liquid chromatography tandem mass spectrometry in mouse brain and blood after systemic administration

Carbenoxolone is a derivative of glycyrrhetinic acid found in the root of Glycyrrhiza glabra, colloquially known as licorice. It has been used as a treatment for peptic and oral ulcers. In recent years, carbenoxolone has been utilized in basic research for its ability to block gap junctional communication. Better understanding the distribution of carbenoxolone after systemic administration can lead to a better understanding of its potential sites of action. Presented is an ultra high-performance liquid chromatography tandem mass spectrometer (UHPLC-MS/MS) method for the identification and quantification of carbenoxolone in mouse blood and brain tissue. Twenty mice were injected intraperitoneally with 25 mg/kg carbenoxolone and brain tissue and blood were collected for analysis. Blood concentrations (mean ± SD) at 15, 30, 60 and 120 min were determined to be (n = 5) 5394 ± 778, 2636 ± 836, 1564 ± 541 and 846 ± 252 ng/mL, respectively. Brain concentrations (mean ± SD) at 15, 30, 60 and 120 mins were determined to be (n = 5) 171 ± 62, 102 ± 35, 55 ± 10 and 27 ± 9 ng/g, respectively. The analysis of these specimens at the four different time points resulted in blood and brain half-lives in mice of ~43 and 41 min, respectively. The UHPLC-MS/MS method was determined to be sensitive and robust for quantification of carbenoxolone.

Roles of astrocytic connexin-43, hemichannels, and gap junctions in oxygen-glucose deprivation/reperfusion injury induced neuroinflammation and the possible regulatory mechanisms of salvianolic acid B and carbenoxolone

Background

Glia-mediated neuroinflammation is related to brain injury exacerbation after cerebral ischemia/reperfusion (I/R) injury. Astrocytic hemichannels or gap junctions, which were mainly formed by connexin-43, have been implicated in I/R damage. However, the exact roles of astrocytic hemichannels and gap junction in neuroinflammatory responses induced by I/R injury remain unknown.

Methods

Primary cultured astrocytes were subjected to OGD/R injury, an in vitro model of I/R injury. Salvianolic acid B (SalB) or carbenoxolone (CBX) were applied for those astrocytes. Besides, Cx43 mimetic peptides Gap19 or Gap26 were also applied during OGD/R injury; Cx43 protein levels were determined by western blot and cytoimmunofluorescene staining, hemichannel activities by Ethidium bromide uptake and ATP concentration detection, and gap junction intercellular communication (GJIC) permeability by parachute assay. Further, astrocyte-conditioned medium (ACM) was collected and incubated with microglia. Meanwhile, ATP or apyrase were applied to explore the role of ATP during OGD/R injury. Microglial activation, M1/M2 phenotypes, and M1/M2-related cytokines were detected. Also, microglia-conditioned medium (MEM) was collected and incubated with astrocytes to further investigate its influence on astrocytic hemichannel activity and GJIC permeability. Lastly, effects of ACM and MCM on neuronal viability were detected by flow cytometry.

Results

We found that OGD/R induced abnormally opened hemichannels with increased ATP release and EtBr uptake but reduced GJIC permeability. WB tests showed decreased astrocytic plasma membrane’s Cx43, while showing an increase in cytoplasma. Treating OGD/R-injured microglia with ATP or OGD/R-ACM induced further microglial activation and secondary pro-inflammatory cytokine release, with the M1 phenotype predominating. Conversely, astrocytes incubated with OGD/R-MCM exhibited increased hemichannel opening but reduced GJIC coupling. Both SalB and CBX inhibited abnormal astrocytic hemichannel opening and ATP release and switched the activated microglial phenotype from M1 to M2, thus providing effective neuroprotection. Application of Gap19 or Gap26 showed similar results with CBX. We also found that OGD/R injury caused both plasma membrane p-Cx43(Ser265) and p-Src(Tyr416) significantly upregulated; application of SalB may be inhibiting Src kinase and attenuating Cx43 internalization. Meanwhile, CBX treatment induced obviously downregulation of p-Cx43(Ser368) and p-PKC(Ser729) protein levels in plasma membrane.

Conclusions

We propose a vicious cycle exists between astrocytic hemichannel and microglial activation after OGD/R injury, which would aggravate neuroinflammatory responses and neuronal damage. Astrocytic Cx43, hemichannels, and GJIC play critical roles in OGD/R injury-induced neuroinflammatory responses; treatment differentially targeting astrocytic Cx43, hemichannels, and GJIC may provide novel avenues for therapeutics during cerebral I/R injury.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1127-3) contains supplementary material, which is available to authorized users.

Marketing medicines: charting the rise of modern therapeutics through a systematic review of adverts in UK medical journals (1950-1980)

AIMS

To examine how pharmaceutical products that were first marketed between 1950 and 1980 were promoted to physicians through advertisements and briefly review advertising regulations and accuracy of the advertisements in the light of modern knowledge.

METHODS

We systematically reviewed advertisements promoting drugs for specific therapeutic areas, namely central nervous system disorders (anxiety and sleep disorders, depression, psychoses, and Parkinson's disease), respiratory disorders, cardiovascular disorders, and gastrointestinal disorders. We examined about 800 issues of the British Medical Journal (1950-1980) and about 150 issues of World Medicine (1965-1984).

RESULTS

Advertising material was minimally regulated until the mid-1970s. Many drugs were marketed with little preclinical or clinical knowledge and some with the expectation that prescribers would obtain further data. The peak of advertising occurred in parallel with the surge in the release of novel drugs during the 1960s, but declined markedly after the mid-1970s. Advertisements generally contained little useful prescribing information. The period we investigated saw the release of many novel pharmaceuticals in the therapeutic areas we examined, and many (or their class successors) still play important therapeutic roles, including benzodiazepines, tricyclic antidepressants, phenothiazines, levodopa, selective and non-selective β-adrenoceptor antagonists, thiazide diuretics, β-adrenoceptor agonists, and histamine H₂ receptor antagonists.

CONCLUSIONS

Advertising pharmaceuticals in the BMJ and World Medicine in 1950-1980 was poorly regulated and often lacked rigour. However, advertisements were gradually modified in the light of increasing clinical pharmacological knowledge, and they reflect an exciting period for the introduction of many drugs that continue to be of benefit today.

Carbenoxolone inhibits TRPV4 channel-initiated oxidative urothelial injury and ameliorates cyclophosphamide-induced bladder dysfunction

Carbenoxolone (CBX) is a clinically prescribed drug for the treatment of digestive ulcer and inflammation. It is also a widely used pharmacological inhibitor of several channels in basic research. Given that the overactivity of several channels, including those inhibitable by CBX, underlies bladder dysfunction, we tested the potential therapeutic application and mechanism of CBX in the treatment of voiding dysfunction. In a mouse model of cystitis induced by cyclophosphamide (CYP), CBX administration prevented the CYP‐elicited increase in bladder weight, oedema, haemorrhage, and urothelial injury. CBX also greatly improved micturition pattern, as manifested by the apparently decreased micturition frequency and increased micturition volume. Western blot results showed that CBX suppressed CYP‐induced increase in protein carbonyls, COX‐2, and iNOS. Further analysis using cultured urothelial cells revealed that acrolein, the major metabolite of CYP, caused protein oxidation, p38 activation, and urothelial injury. These effects of acrolein were reproduced by TRPV4 agonists and significantly prevented by antioxidant NAC, p38 inhibitor SB203580, TRPV4 antagonist RN‐1734, and CBX. Further studies showed that CBX potently suppressed TRPV4 agonist‐initiated calcium influx and subsequent cell injury. CBX attenuated CYP‐induced cystitis in vivo and reduced acrolein‐induced cell injury in vitro, through mechanisms involving inhibition of TRPV4 channels and attenuation of the channel‐mediated oxidative stress. CBX might be a promising agent for the treatment of bladder dysfunction.

Gap Junction Blockers: An Overview of their Effects on Induced Seizures in Animal Models

BACKGROUND

Gap junctions are clusters of intercellular channels allowing the bidirectional pass of ions directly into the cytoplasm of adjacent cells. Electrical coupling mediated by gap junctions plays a role in the generation of highly synchronized electrical activity. The hypersynchronous neuronal activity is a distinctive characteristic of convulsive events. Therefore, it has been postulated that enhanced gap junctional communication is an underlying mechanism involved in the generation and maintenance of seizures. There are some chemical compounds characterized as gap junction blockers because of their ability to disrupt the gap junctional intercellular communication.

OBJECTIVE

Hence, the aim of this review is to analyze the available data concerning the effects of gap junction blockers specifically in seizure models.

RESULTS

Carbenoxolone, quinine, mefloquine, quinidine, anandamide, oleamide, heptanol, octanol, meclofenamic acid, niflumic acid, flufenamic acid, glycyrrhetinic acid and retinoic acid have all been evaluated on animal seizure models. In vitro, these compounds share anticonvulsant effects typically characterized by the reduction of both amplitude and frequency of the epileptiform activity induced in brain slices. In vivo, gap junction blockers modify the behavioral parameters related to seizures induced by 4-aminopyridine, pentylenetetrazole, pilocarpine, penicillin and maximal electroshock.

CONCLUSION

Although more studies are still required, these molecules could be a promising avenue in the search for new pharmaceutical alternatives for the treatment of epilepsy.

11β-hydroxysteroid dehydrogenase inhibition as a new potential therapeutic target for alcohol abuse

The identification of new and more effective treatments for alcohol abuse remains a priority. Alcohol intake activates glucocorticoids, which have a key role in alcohol's reinforcing properties. Glucocorticoid effects are modulated in part by the activity of 11β-hydroxysteroid dehydrogenases (11β-HSD) acting as pre-receptors. Here, we tested the effects on alcohol intake of the 11β-HSD inhibitor carbenoxolone (CBX, 18β-glycyrrhetinic acid 3β-O-hemisuccinate), which has been extensively used in the clinic for the treatment of gastritis and peptic ulcer and is active on both 11β-HSD1 and 11β-HSD2 isoforms. We observed that CBX reduces both baseline and excessive drinking in rats and mice. The CBX diastereomer 18α-glycyrrhetinic acid 3β-O-hemisuccinate (αCBX), which we found to be selective for 11β-HSD2, was also effective in reducing alcohol drinking in mice. Thus, 11β-HSD inhibitors may be a promising new class of candidate alcohol abuse medications, and existing 11β-HSD inhibitor drugs may be potentially re-purposed for alcohol abuse treatment.

Antiulcer and antiproliferative properties of spent brewer's yeast peptide extracts for incorporation into foods

The main objective was to study the antiulcer and antiproliferative potential of yeast peptide extract for further incorporation into functional foods.

3-(2,6-Dichloro-benzyloxy)-11-oxo-olean-12-ene-29-oic acid, a semisynthetic derivative of glycyrrhetic acid: synthesis, antiproliferative, apoptotic and anti-angiogenesis activity

The synthesis and biological evaluation of the semisynthetic analogs of glycyrrhetic acid are described.

Spectroscopic analysis on structure-affinity relationship in the interactions of different oleanane-type triterpenoids with bovine serum albumin

Oleanane-type triterpenoids serve as an important group of plant secondary metabolites with a variety of biological activities and the C-3 position substitution pattern is a significant structural feature for their biological activities. Three selected oleanane-type triterpenoids (glycyrrhizin, glycyrrhetinic acid, and carbenoxolone) bearing different substituents (glucuronic acid dimer, hydroxyl, and succinyl groups) at the C-3 position were studied for their affinities to bind bovine serum albumin (BSA) by steady-state fluorescence, synchronous, three-dimensional fluorescence and ultraviolet-visible (UV-vis) absorption spectra. The binding mechanism of the triterpenoids to BSA is due to the formation of the triterpenoids-BSA complex and the binding affinity is strongest for carbenoxolone and ranked in the order carbenoxolone > glycyrrhetinic acid > glycyrrhizin. The thermodynamic parameters calculated at different temperatures showed that triterpenoids binding to BSA primarily depended on hydrophobic interaction and hydrogen bonding. The distance between the bound triterpenoid and BSA was determined on the basis of the Förster's energy transfer theory. Displacement experiments using phenylbutazone and ibuprofen showed the binding site of triterpenoids on BSA at subdomain IIA (Sudlow's site I). The effect of triterpenoids on BSA conformation was analyzed by UV-vis absorption, and synchronous and three-dimensional fluorescence spectra. These results revealed that the C-3 position substitution pattern significantly affects the structure-affinity relationships of oleanane-type triterpenoid binding to BSA and further affects the bioavailability of triterpenoids in the blood circulatory system.

Chemical induction of Hsp70 reduces α-synuclein aggregation in neuroglioma cells

Misfolding and aggregation of α-synuclein (α-syn) is associated with the development of a number of neurodegenerative diseases including Parkinson's disease (PD). Analyses of post mortem tissues revealed the presence of molecular chaperones within α-syn aggregates, suggesting that chaperones play a role in α-syn misfolding and aggregation. In fact, inhibition of chaperone activity aggravates α-syn toxicity, and the overexpression of chaperones, particularly 70-kDa heat shock protein (Hsp70), protects against α-syn-induced toxicity. In this study, we investigated the effect of carbenoxolone (CBX), a glycyrrhizic acid derivative previously reported to upregulate Hsp70, in human neuroglioma cells overexpressing α-syn. We report that CBX treatment lowers α-syn aggregation and prevents α-syn-induced cytotoxicity. We demonstrate further that Hsp70 induction by CBX arises from activation of heat shock factor 1 (HSF1). The Hsp70 inhibitor MAL3-101 and the Hsp70 enhancer 115-7c led to an increase or decrease in α-syn aggregation, respectively, in agreement with these findings. In summary, this study provides a proof-of-principle demonstration that chemical modulation of the Hsp70 machine is a promising strategy to prevent α-syn aggregation.

Reinvestigation of the effect of carbenoxolone on the induction of heat shock proteins

Carbenoxolone (CBX) is a semisynthetic derivative of the licorice root substance glycyrrhizinic acid and has been previously reported to induce only heat shock protein 70 [Hsp70, HSPA1A (the systematic name of heat shock protein is given in the parenthesis after each HSP, according to the recent nomenclature guidelines, Kampinga et al., Cell Stress Chaperones, 14:105-111, 2008) but not other heat shock proteins (HSPs) (Nagayama et al., Life Sci. 69:2867-2873, 2001). In this study, we reinvestigated the effect of CBX on the induction of HSPs in HeLa and human neuroblastoma (A-172) cells. CBX clearly induced not only Hsp70 but also Hsp90 (HSPC1), Hsp40 (DNAJB1), and Hsp27 (HSPB1) at concentrations of 10 to 800 microM for 16 h incubation. At higher concentrations (more than 400 microM), however, CBX appeared to be toxic. Treatment of cells with CBX resulted in enhanced phosphorylation and acquisition of DNA-binding ability of heat shock transcription factor 1 (HSF1). Furthermore, characteristic HSF1 granules were formed in the nucleus, suggesting that the induction of HSPs by CBX is mediated by the activation of HSF1. Furthermore, thermotolerance was induced by CBX treatment, as determined by clonogenic survival. Although the precise target of CBX is not known at present, these results indicate that CBX is one of the molecular chaperone inducers and suggest that some pharmacological activities of CBX might be ascribable in part to its molecular chaperone-inducing property.

18β-glycyrrhetinic acid promotes src interaction with connexin43 in rat cardiomyocytes

The mechanism by which 18beta-glycyrrhetinic acid regulates gap junction intercellular communication (GJIC) remains poorly understood. In this study, treatment of cultured rat neonatal cardiomyocytes with 18beta-glycyrrhetinic acid resulted in dose-dependent inhibition of GJIC as assessed by fluorescent dye transfer analysis. 18beta-Glycyrrhetinic acid induced time-dependent serine/threonine dephosphorylation and redistribution of connexin43 (Cx43) in cardiomyocytes and the induced Cx43 dephosphorylation was prevented by the protein phosphatase inhibitor, calyculin A. However, functional analyses showed that the inhibitory effect of 18beta-glycyrrhetinic acid on dye spreading among cardiomyocytes was not blocked by calyculin A, but was blocked by the Src-selective tyrosine kinase inhibitor, PP2. 18beta-Glycyrrhetinic acid also induced an increase in the levels of phosphorylated Src, and this effect was prevented by PP2. Immunoprecipitation using anti-Cx43 and anti-p-Src antibodies showed that 18beta-glycyrrhetinic acid increased the association between p-Src and Cx43 and induced tyrosine phosphorylation of Cx43. We conclude that the inhibitory effect of 18beta-glycyrrhetinic acid on GJIC in cardiomyocytes involves Src-mediated tyrosine phosphorylation of Cx43.

Metabolic effects of carbenoxolone in rat liver

The action of carbenoxolone on hepatic energy metabolism was investigated in the perfused rat liver and isolated mitochondria. In perfused livers, carbenoxolone (200-300 microM) increased oxygen consumption, glucose production and glycolysis from endogenous glycogen. Gluconeogenesis from lactate or fructose, an energy-dependent process, was inhibited. This effect was already evident at a concentration of 25 microM. The cellular ATP levels and the adenine nucleotide content were decreased by carbenoxolone, whereas the AMP levels were increased. In isolated mitochondria, carbenoxolone stimulated state IV respiration and decreased the respiratory coefficient with the substrates beta-hydroxybutyrate and succinate. The ATPase of intact mitochondria was stimulated, the ATPase of uncoupled mitochondria was inhibited, and the ATPase of disrupted mitochondria was not altered by carbenoxolone. These results indicate that carbenoxolone acts as an uncoupler of oxidative phosphorylation and, possibly, as an inhibitor of the ATP/ADP exchange system. The inhibitory action of carbenoxolone on mitochondrial energy metabolism could be contributing to induce the mitochondrial permeability transition (MPT), a key phenomenon in apoptosis. The results of the present study can explain, partly at least, the in vivo hepatotoxic actions of carbenoxolone that were found in a previous clinical evaluation.

Carbenoxolone induces oxidative stress in liver mitochondria, which is responsible for transition pore opening

Carbenoxolone (Cbx), a derivative of glycyrrhetinic acid, which has been found to affect mineralocorticoid and glucocorticoid receptors, induces swelling and membrane potential collapse when added to Ca(2+)-loaded liver mitochondria at 10 microM concentrations. These effects are strictly correlated with hydrogen peroxide generation, increase in oxygen uptake, and sulfhydryl and pyridine nucleotide oxidation. Cyclosporin A, bongkrekic acid, and N-ethylmaleimide completely abolish all the above-described effects, suggesting that Cbx can be considered an inducer of mitochondrial permeability transition by means of oxidative stress. Cbx can also trigger the apoptotic pathway because the above events are also correlated with the loss of cytochrome c. These effects are probably related to the conjugated carbonyl oxygen in C-11, which produces reactive oxygen species by interacting with the mitochondrial respiratory chain, mainly at the level of complex I but, most likely, also with complex III. The oxidative stress induced by Cbx, which is responsible for pore opening, excludes that this is related to a genomic effect of the compound.

Pseudohyperaldosteronism: pathogenetic mechanisms

Pseudohyperaldosteronism is characterized by a clinical picture of hyperaldosteronism with suppression of plasma renin activity and aldosterone. Pseudohyperaldosteronism can be due to a direct mineralocorticoid effect, as with desoxycorticosterone, fluorohydrocortisone, fluoroprednisolone, estrogens, and the ingestion of high amounts of glycyrrhetinic acid. A block of 11-hydroxysteroid-dehydrogenase type 2 (11HSD2), the enzyme that converts cortisol into cortisone, at the level of epithelial target tissues of aldosterone, is involved in other cases. This mechanism is related either to a mutation of the gene, which encodes 11HSD2 (apparent mineralocorticoid excess syndrome and some cases of low renin hypertension) or to an acquired reduction of the activity of the enzyme due to glycyrrhetinic acid, carbenoxolone, and grapefruit juice. In other cases saturation of 11HSD2 may be involved as in severe Cushing's syndrome and chronic therapy with some corticosteroids. Recently, an activating mutation of the mineralocorticoid receptor gene has been described. Another genetic cause of pseudohyperaldosteronism is the syndrome of Liddle, which is due to a mutation of the gene encoding for beta and gamma subunits of the sodium channels.

Liquorice and its health implications

This article presents an overview of the health implications of liquorice. Liquorice has beneficial applications in the medicinal and the confectionery sectors; the substance, therefore, is both widely available and commercially attractive. However, the ingestion of liquorice, and/or its active metabolites, can sometimes produce an acquired form of apparent mineralocorticoid excess (AME) syndrome, expressed as sodium retention, potassium loss and suppression of the renin-angiotensin-aldosterone system, in addition to clinical consequences such as raised blood pressure and oedema. Moreover, these metabolic changes, the mechanisms underlying which are highlighted in the accompanying text, are associated with a number of additional clinical symptoms. Considering the easy availability of liquorice itself and also of other products containing its active metabolites, it is quite possible that the health burden of liquorice-induced morbidity could be substantial. Healthcare practitioners need to be fully aware of the risks in view of a large number of reports in the literature concerning its toxicity.

Heart failure: lessons learned over the past 25 years

Over the past 25 years, a great deal has been learned about the pathophysiology and management of heart failure--a major health problem whose prevalence and incidence have not declined, unlike other cardiovascular disorders. Several of these lessons are reviewed herein. However, despite these advances, important issues remain to challenge both the practicing physician and the research scientist.

Haemodynamic and metabolic effects of carbenoxolone in normal subjects and patients with renal impairment

Carbenoxolone inhibits the enzyme complex 11 beta-hydroxysteroid dehydrogenase. Functional deficiency of this complex might contribute to the hypertension of renal parenchymal disease. We have compared the effects of carbenoxolone (300 mg/day for 5 days) in six normal subjects and seven patients with renal disease. Patients with renal disease had higher blood pressure, plasma creatinine concentration (0.15 +/- 0.01 mmol/L cf. 0.09 +/- 0.01 mmol/L) and urine protein excretion than normals. In normal subjects carbenoxolone increased body weight and plasma chloride and decreased initial urine sodium excretion, packed cell volume, plasma albumin, renin and aldosterone concentrations. In patients with renal disease, carbenoxolone also produced these effects, but in addition significantly increased systolic, (129 +/- 3 to 135 +/- 5 mm Hg) mean (97 +/- 3 to 101 +/- 3 mm Hg) and diastolic blood pressure (81 +/- 3 to 85 +/- 2 mm Hg) and lowered plasma potassium (4.1 +/- 0.1 to 3.8 +/- 0.1 mmol/L) and urine sodium:potassium ratio (1.57 +/- 0.22 to 2.60 +/- 0.54). These results are consistent with the notion that partial deficiency of 11 beta-hydroxysteroid dehydrogenase contributes to the hypertension of renal parenchymal disease.

Endogenous inhibitors of 11 beta-OHSD: existence and possible significance

Inhibition of 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD) by licorice-derived compounds and in cases of idiopathic impairment of this enzyme is known to result in hypermineralocorticoid syndromes, reflecting corticosteroid receptor activation by excess intracellular glucocorticoids. In this paper we address the question of whether or not endogenous inhibitors of 11 beta-OHSD exist that might cause pathological glucocorticoid metabolism. Using microsomal preparations we have demonstrated that bile acids are potent inhibitors of rat renal and human hepatic 11 beta-OHSD, with lithocholic acid exerting the strongest effect. The human renal enzyme is affected to a lesser extent. Serum of patients with cholestatic liver cirrhosis also inhibited 11 beta-OHSD activity, in parallel with total bile acid concentration. Cholesterol and its precursor lanosterol inhibited the enzymatic activity in microsomes from rat and human kidney cortex and human liver. We conclude that bile acids could contribute to the abnormalities of cortisol metabolism observed in cholestatic liver cirrhosis.

Licorice and enzymes other than 11 beta-hydroxysteroid dehydrogenase: an evolutionary perspective

Licorice has long been known to promote the healing of ulcers. In the 1950s, studies with licorice-derived compounds revealed that the anti-ulcer effects of licorice are due to inhibition of 15-hydroxyprostaglandin dehydrogenase and delta 13-prostaglandin reductase. 15-Hydroxyprostaglandin dehydrogenase converts prostaglandins E2 and F2 alpha to 15-ketoprostaglandins, which are inactive. delta 13-Prostaglandin reductase metabolizes the inactive delta 13-prostaglandin to 13,14-dihydro,15-ketoprostaglandin, which is further metabolized and excreted in urine. Thus, licorice-derived compounds have the effect of raising the local concentration of prostaglandins that promote mucous secretion and cell proliferation in the stomach, leading to healing of ulcers. 11 beta-Hydroxysteroid dehydrogenase, which also is inhibited by licorice-derived compounds, shares a common ancestor with 15-hydroxyprostaglandin dehydrogenase. Both enzymes are homologous to Streptomyces hydrogenans 3 alpha,20 beta-hydroxysteroid dehydrogenase, which also is inhibited by licorice. Thus, licorice inhibits enzymes that diverged at least 2 billion years ago from a common ancestor. Other oxidoreductases in bacteria, plants, and animals that are inhibited by licorice-derived compounds are likely to be discovered in the future.

Effects of carbenoxolone administered acutely to adrenalectomized rats (in vivo) on renal and hepatic handling of corticosterone by 11 beta-hydroxysteroid dehydrogenase

The in vivo effect(s) of carbenoxolone (CS) on renal 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD), hepatic 11 beta-OHSD, and 5 beta-reductase enzymatic activity was investigated, under conditions previously shown to confer mineralocorticoid (MC)-like activity on the glucocorticoids cortisol and corticosterone; it has been suggested that this Na+ retention is linked to inhibition of renal 11 beta-OHSD. The results show that acute administration of CS [2.5 mg/rat for 0.5 or 2 hours; and 10 or 25 mg/rat for 2 hours subcutaneously (sc)] to rats caused no inhibition of 11 beta-OHSD activity in kidney homogenates, minces, and microsomes when compared with controls. However, addition of 50 nM CS to the incubation medium completely inhibited the 11 beta-OHSD activity in kidney homogenates and microsomes (from controls or CS-injected rats). In contrast, hepatic microsomal 11 beta-OHSD was significantly inhibited after in vivo treatment with CS (P < 0.05) using 2 microM and 50 microM corticosterone, as was 5 beta-reductase (P < 0.05) using 4 microM corticosterone as substrate. However, chronic glycyrrhizin administration (15 mg/rat/day sc for 14 days) significantly inhibited renal 11 beta-OHSD activity when assayed in minces or homogenates. Thus, it appears that when CS is administered acutely, its effects are primarily on hepatic 11 beta-OHSD and 5 beta-reductase with no inhibition of renal 11 beta-OHSD.(ABSTRACT TRUNCATED AT 250 WORDS)

The pharmacological differences and similarities between stress- and ethanol-induced gastric mucosal damage

Stress- and ethanol-induced gastric mucosal damage are the two commonly used ulcer models in animals. They share some of the similarities but also have differences in the etiology of gastric ulceration. This article reviews the influences of various protective drugs on these two types of gastric damage in rats. Verapamil (a calcium antagonist) or N-ethylmaleimide (a sulfhydryl depletor) prevents cold restraint-, but potentiates ethanol-provoked gastric lesion formation. N-Acetylcysteine (a mucolytic agent) and acetaminophen (an antipyretic analgesic) have the opposite actions. Prostaglandins provide a much better antiulcer effect on ethanol-induced lesions. Cimetidine (a histamine H2-receptor antagonist) prevents only stress-induced mucosal damage. These differences in drug actions indicate that stress and ethanol may have dissimilar ulcerogenic mechanisms in rats. On the other hand, carbenoxolone (a mucus inducer), histamine H1-receptor antagonists, leukotriene inhibitors (FPL 55712 and nordihydroguaiaretic acid) and mast cell stabilizers (like zinc compounds, sodium cromoglycate, FPL 52694 and ketotifen), all protect against gastric mucosal damage by stress or ethanol in rats. However, the role of gastric sulfhydryls in both types of gastric lesions is still controversial. These findings imply that the two types of lesion formation share some of the ulcerogenic mechanisms. This communication attempts to analyze the various findings and to relate them to the etiology of stress and ethanol-induced gastric lesions. It also summarizes the uses, and the antiulcer mechanisms, of the drugs that have been studied utilizing these two animal ulcer models, and suggests their possible implications in man.

The pathogenesis of pseudohyperaldosteronism from carbenoxolone

Carbenoxolone is a derivative of glycyrrhetinic acid used for the treatment of peptic ulcer and gastritis, with salt and water retention a very common side-effect. To investigate this drug-induced pseudohyperaldosteronism we have studied 6 male volunteers before, during and after treatment with carbenoxolone for 7 days. Serum, urinary and sweat electrolytes values were consistent with a mineralocorticoid-like effect of drug administration. PRA was suppressed, and plasma cortisol and aldosterone progressively decreased over treatment. We have also determined by radioreceptor assay the plasma levels of factors which bind to mineralocorticoid receptors in rat kidney cytosol. The levels of these factors were decreased significantly at day 3 of treatment, suggesting a local renal effect of carbenoxolone to amplify endogenous steroid action. At day 7 the radioreceptor assay values were still decreased but significantly higher than at day 3, suggesting in addition a direct mineralocorticoid effect of the drug. We conclude that the drug is initially effective by amplifying the effect of endogenous steroids, and then when the plasma concentrations of the drug or its metabolites reach a higher plasma concentration, there may also be in addition a direct mineralocorticoid-like effect.

Mineralocorticoid effector mechanism of liquorice derivatives in human mononuclear leukocytes

The mineralocorticoid effector mechanism of glycyrrhetinic acid and of its ester derivative carbenoxolone was evaluated in human mononuclear leukocytes by radioreceptorassay and measurement of intracellular sodium and potassium after incubation of the cells with or without the drugs. The affinity of both compounds for mineralocorticoid receptors in this human model was also compared with that found in kidney cytosol from adrenalectomized rats. Glycyrrhetinic acid possesses a measurable affinity for mineralocorticoid receptors in mononuclear leukocytes, which is 1:3,000 that of aldosterone itself. Carbenoxolone does not bind to the receptors in mononuclear leukocytes, in contrast with kidney cytosol where the drugs show a parallel affinity. The mean intracellular content of sodium in mononuclear leukocytes from 7 volunteers was 35% higher (p less than 0.05) after incubation with 3 mumol glycyrrhetinic acid than after incubation with an equivalent amount of carbenoxolone, or in medium alone. The effect of glycyrrhetinic acid was completely reversed by addition of canrenone for the period of incubation. We conclude that the syndrome of pseudohyperaldosteronism from carbenoxolone is thus probably not related to a direct agonist effect of the drug at the level of mineralocorticoid receptors, but that any action must follow in vivo conversion into glycyrrhetinic acid by hydrolysis.

Cytoprotective action of carbenoxolone sodium on ethanol-induced gastric lesions in rats and its inhibition by indomethacin

Carbenoxolone produced a marked and dose-related inhibition of ethanol-induced gastric lesions in rats. This cytoprotective action was inhibited progressively and significantly by increasing doses of indomethacin. The evidence presented confirms previous suggestions that prostaglandin(s) are involved in the cytoprotective action of carbenoxolone.

A quantitative morphological study of the effects of carbenoxolone sodium on duodenal goblet-cells of the rat

A direct microscopic and microdensitometric examination was carried out on duodenal goblet-cells of non-fasted and fasted rats with and without carbenoxolone sodium treatment. The results of microdensitometric examination revealed a marked and significant increase of mucus production in the non-fasted and fasted rats pretreated for 2 hr with a single oral dose of carbenoxolone sodium at 100 mg/kg. Fasting alone also increased mucus production. On microscopic examination, the number of duodenal goblet-cells full of mucosubstances in the non-fasted and fasted rats receiving carbenoxolone sodium treatment was approximately 20% higher than in the controls.

Affinity of liquorice derivatives for mineralocorticoid and glucocorticoid receptors

Liquorice abuse causes a syndrome of pseudohyperaldosteronism. Much less commonly, glucocorticoid-like effects have been reported. The electrolyte-active principle of liquorice is glycyrrhizic acid (GI), which can be hydrolyzed to glycyrrhetinic acid (GE). Previous studies have reported that GE, but not GI, may occupy mineralocorticoid and glucocorticoid receptors. We here report that both GE and GI can bind to both mineralocorticoid and glucocorticoid receptors. The affinity of GI for mineralocorticoid receptors is four orders of magnitude lower than aldosterone and for glucocorticoid receptors five orders of magnitude lower than dexamethasone. The affinity, though low, is sufficient to explain the mineralocorticoid-like side effects, given the large amount of liquorice required to produce such a syndrome.

Effect of transdermally administered hyoscine methobromide on nocturnal acid secretion in patients with duodenal ulcer

Use of anticholinergic drugs in treatment of duodenal ulcers is limited by the side effects of widespread parasympathetic blockade evoked by usual therapeutic doses. A study was conducted into the effectiveness of transdermal delivery of hyoscine methobromide using a new system which releases the drug into the circulation at a controlled rate. In six patients whose duodenal ulcer had healed secretion of acid was measured over two nights, the first on placebo and the second on hyoscine methobromide. All patients responded to the active drug and showed a significant inhibition of acid secretion. Four subjects complained of a dry mouth after overnight treatment with hyoscine methobromide; no other side effects were reported. Transdermal delivery of anticholinergic drugs may be useful in maintenance treatment of duodenal ulcers and further clinical tests are indicated.