CFTR chloride channel as a molecular target of anthraquinone compounds in herbal laxatives

CFTR and Gastrointestinal Cancers: An Update

Cystic Fibrosis (CF) is a disease caused by mutations in the CFTR gene that severely affects the lungs as well as extra-pulmonary tissues, including the gastrointestinal (GI) tract. CFTR dysfunction resulting from either mutations or the downregulation of its expression has been shown to promote carcinogenesis. An example is the enhanced risk for several types of cancer in patients with CF, especially cancers of the GI tract. CFTR also acts as a tumor suppressor in diverse sporadic epithelial cancers in many tissues, primarily due to the silencing of CFTR expression via multiple mechanisms, but especially due to epigenetic regulation. This review provides an update on the latest research linking CFTR-deficiency to GI cancers, in both CF patients and in sporadic GI cancers, with a particular focus on cancer of the intestinal tract. It will discuss changes in the tissue landscape linked to CFTR-deficiency that may promote cancer development such as breakdowns in physical barriers, microbial dysbiosis and inflammation. It will also discuss molecular pathways and mechanisms that act upstream to modulate CFTR expression, such as by epigenetic silencing, as well as molecular pathways that act downstream of CFTR-deficiency, such as the dysregulation of the Wnt/β-catenin and NF-κB signaling pathways. Finally, it will discuss the emerging CFTR modulator drugs that have shown promising results in improving CFTR function in CF patients. The potential impact of these modulator drugs on the treatment and prevention of GI cancers can provide a new example of personalized cancer medicine.

Treatment of Gastrointestinal Disorders-Plants and Potential Mechanisms of Action of Their Constituents

The worldwide prevalence of gastrointestinal diseases is about 40%, with standard pharmacotherapy being long-lasting and economically challenging. Of the dozens of diseases listed by the Rome IV Foundation criteria, for five of them (heartburn, dyspepsia, nausea and vomiting disorder, constipation, and diarrhoea), treatment with herbals is an official alternative, legislatively supported by the European Medicines Agency (EMA). However, for most plants, the Directive does not require a description of the mechanisms of action, which should be related to the therapeutic effect of the European plant in question. This review article, therefore, summarizes the basic pharmacological knowledge of synthetic drugs used in selected functional gastrointestinal disorders (FGIDs) and correlates them with the constituents of medicinal plants. Therefore, the information presented here is intended as a starting point to support the claim that both empirical folk medicine and current and decades-old treatments with official herbal remedies have a rational basis in modern pharmacology.

Visualizing spatial distribution of small molecules in the rhubarb stalk (Rheum rhabarbarum) by surface-transfer mass spectrometry imaging

Laser desorption/ionization mass spectrometry imaging (LDI-MSI) with gold nanoparticle-enhanced target (AuNPET) was used for visualization of small molecules in the rhubarb stalk (Rheum rhabarbarum L.). Analysis was focused on spatial distribution of biologically active compounds which are found in rhubarb species. Detected compounds belong to a very wide range of chemical compound classes such as anthraquinone derivatives and their glucosides, stilbenes, anthocyanins, flavonoids, polyphenols, organic acids, chromenes, chromanones, chromone glycosides and vitamins. The analysis of the spatial distribution of these compounds in rhubarb stalk with the nanoparticle-rich surface of AuNPET target plate has been made without additional matrix and with minimal sample preparation steps.

Mashiningan Improves Opioid-Induced Constipation in Rats by Activating Cystic Fibrosis Transmembrane Conductance Regulator Chloride Channel

Opioid receptor stimulants are analgesics used in patients with and without cancer; however, they often cause constipation, resulting in poor adherence and deterioration of the quality of life. Hence, suitable treatments for constipation are required. In this study, we investigated the pharmacological mechanisms of action of mashiningan (MNG), a Kampo medicine used to treat constipation, and evaluated the effect of MNG on opioid-induced constipation in rats. MNG (100 or 300 mg/kg) was orally administered to normal or codeine phosphate (CPH)-induced constipation in rats, and its effect was evaluated on the basis of fecal counts, characteristics, and weight. Small intestinal fluid secretion was measured after treatment with MNG alone or coadministration with a cystic fibrosis transmembrane conductance regulator (CFTR)-specific inhibitor (CFTRinh-172). The effects of MNG on the CFTR and type-2 chloride channel were determined using patch-clamp or short-circuit current experiments, respectively. MNG increased the fecal weight and proportion of soft feces in normal rats. CPH-induced constipation in rats decreased fecal counts and weight, whereas MNG prevented these effects and increased the proportion of soft feces. MNG increased the electronic chloride current, and this effect was inhibited by the CFTRinh-172 in the CFTR assay. Furthermore, MNG increased small intestinal fluid secretion, and this effect was abolished by coadministration with the CFTRinh-172. MNG improved opioid-induced constipation in rats, and this improvement may have been mediated by increasing intestinal fluid secretion via CFTR chloride channel activation. Therefore, MNG is expected as a medicine of the treatment of constipation in patients taking opioids.

Dehydrocostuslactone, a sesquiterpene lactone activates wild-type and ΔF508 mutant CFTR chloride channel

Cystic fibrosis transmembrane conductance regulator (CFTR) represents the main cAMP-activated Cl⁻ channel expressed in the apical membrane of serous epithelial cells. Both deficiency and overactivation of CFTR may cause fluid and salt secretion related diseases. The aim of this study was to identify natural compounds that are able to stimulate wild-type (wt) and ΔF508 mutant CFTR channel activities in CFTR-expressing Fischer rat thyroid (FRT) cells. We found that dehydrocostuslactone [DHC, (3aS, 6aR, 9aR, 9bS)-decahydro-3,6,9-tris (methylene) azuleno [4,5-b] furan-2(3H)-one)] dose dependently potentiates both wt and ΔF508 mutant CFTR-mediated iodide influx in cell-based fluorescent assays and CFTR-mediated Cl⁻ currents in short-circuit current studies, and the activations could be reversed by the CFTR inhibitor CFTRinh-172. Maximal CFTR-mediated apical Cl⁻ current secretion in CFTR-expressing FRT cells was stimulated by 100 μM DHC. Determination of intracellular cAMP content showed that DHC modestly but significantly increased cAMP level in FRT cells, but cAMP elevation effects contributed little to DHC-stimulated iodide influx. DHC also stimulated CFTR-mediated apical Cl⁻ current secretion in FRT cells expressing ΔF508-CFTR. Subsequent studies demonstrated that activation of CFTR by DHC is forskolin dependent. DHC represents a new class of CFTR potentiators that may have therapeutic potential in CFTR-related diseases.

Anti-inflammatory properties of anthraquinones and their relationship with the regulation of P-glycoprotein function and expression

There is a growing interest in natural products that potentially have anti-inflammatory properties and inhibit P-glycoprotein (P-gp) function. In this report, we assessed the effects of anthraquinone derivatives from rhubarb on LPS-induced RAW 264.7 macrophages to determine their anti-inflammatory potential. The derivatives were also tested in Caco-2 cell lines to evaluate the inhibition of the drug efflux function of P-gp. The transport abilities were examined and the cellular accumulation of rhodamine-123 (R-123) was also measured. Electorphoretic mobility shift assay (EMSA) was performed to check the activator protein-1 (AP-1) DNA binding affinity. Five anthraquinones were tested to determine their inhibitory activities on NO production and the protein and mRNA expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Furthermore, the level of prostaglandin E(2) (PGE(2)) was determined in LPS-induced RAW264.7 macrophages. Emodin was found to be the most potent inhibitor, and it also reduced paw swelling in the mouse model of carrageenan-induced paw edema. In Caco-2 cells, emodin elevated the accumulation of R-123 and decreased the efflux ratio of R-123, which indicates the inhibition of P-gp function. The inhibition of COX-2 protein by emodin paralleled the decrease in P-gp expression. In addition, mitogen-activated protein kinase (MAPK) expression was decreased through the prevention of AP-1 DNA binding, which leads to downregulation in the expression of P-gp. Our data indicate that the decrease of P-gp expression is caused by the decreased expression of COX-2 through the MAPK/AP-1 pathway. Based on our results, we suggest that anti-inflammatory drugs with COX-2 inhibitory activity might be used to modulate P-gp function and expression.

Emodin potentiates spontaneous contraction of gastric antral smooth muscle in guinea pigs

AIM: To investigate the effect of emodin on spontaneous contraction of gastric antral smooth muscle in guinea pigs and to explore the possible mechanisms involved.

METHODS: The spontaneous contraction of gastric antral circular muscle of guinea pigs was recorded by a 4-channel physiograph. The whole cell patch-clamp technique was introduced to record L-type calcium currents in gastric myocytes isolated with collagenase. The effect of emodin on spontaneous contraction of gastric antral circular smooth muscle was observed.

RESULTS: Emodin potentiated spontaneous contraction of gastric antral circular smooth muscle in a dose-dependent manner. At concentrations of 5, 10, 15, 20, 25 and 50 μmol/L, emodin increased the amplitude of spontaneous contraction to 108.2% ± 6.2%, 150.6% ± 8.3%, 198.2% ± 7.6%, 200.2% ± 8.6%, 160% ± 6.8%, and 81.2% ± 6.2% of control levels, respectively. Nifedipine (10 μmol/L) blocked emodin-induced increase in the amplitude of spontaneous contraction. At concentrations of 10 and 20 μmol/L, emodin increased I_Ba in gastric myocytes of guinea pigs. I_Ba peak current tended to be stable 200 s after perfusing 10 μmol/L emodin or 170 s after perfusing 20 μmol/L emodin. The peak current amplitude increased to 137.88% ± 5.79% and 158.69% ± 6.11% of control levels, respectively.

CONCLUSION: Emodin potentiates spontaneous contraction of gastric antral smooth muscle in guinea pigs, at least partly due to augmented entry of calcium into cell via L-type calcium channel.