Rutaecarpine induces chloride secretion across rat isolated distal colon

The Role of Traditional Chinese Herbal Medicines and Bioactive Ingredients on Ion Channels: A Brief Review and Prospect

Traditional Chinese Medicines (TCMs), particularly the Chinese herbal medicines, are valuable sources of medicines and have been used for centuries. The term "TCMs" both represents to the single drug agent like Salvia miltiorrhiza, Ligusticum chuanxiong and Angelica sinensis, and those herbal formulas like Jingshu Keli, Wenxin Keli and Danzhen powder. In recent years, the researches of TCMs developed rapidly to understand the scientific basis of these herbs. In this review, we collect the studies of TCM and their containing bioactive compounds, and attempt to provide an overview for their regulatory effects on different ion channels including Ca2+, K+, Na+, Cl- channels and TRP, P2X receptors. The following conditions are used to limit the range of our review. (i) Only the herbal materials are included in this review and the animal- and mineral-original TCMs are excluded. (ii) The major discussions in this review focus on single TCM agent and the herbal formulas are only discussed for a little. (iii) Those most famous herbal medicines like Capsicum annuum (pepper), Curcuma longa (ginger) and Cannabis sativa (marijuana) are excluded. (iv) Only those TCM herbs with more than 5 research papers confirming their effects on ion channels are discussed in this review. Our review discusses recently available scientific evidences for TCMs and related bioactive compounds that have been reported with the modulatory effects on different ion channels, and thus provides a new ethnopharmacological approach to understand the usage of TCMs.

Regulation of Cl- Electrolyte Permeability in Epithelia by Active Traditional Chinese Medicine Monomers for Diarrhea

The epithelial layer, lining the inner surface of the mammalian alveolar, kidney, brain and colon, is a typical electrolyte transporting tissue. Large quantities of salt and fluid are actively moved from the mucosal side toward the blood vessel. Transepithelial salt re-absorption in epithelial tissues plays an important role in maintaining fluid homeostasis. In absorptive epithelium, fluid and salt flux is controlled by the machinery mainly composed of epithelial sodium channel, cystic fibrosis transmembrane conductance regulator, Na+-K+-2Cl- cotransporter, Na+/H+ exchanger, and Na+/K+-ATPase. Dysregulation of salt permeability across epithelium contributes to the pathogenesis of organ edema. In numerous ion transporters, epithelial Cl- transportation plays an important role in water secretion across epithelial tissues and regulation of body fluid content. Many traditional Chinese medicines treat diarrhea by regulating the Cl- electrolyte transport. We systematically summarized the recent progress regarding the traditional Chinese medicine on Cl- electrolyte transport in the intestinal epithelial tissues. The pharmaceutical relevance of developing advanced strategies to mitigate edematous disorders is also implicated. In conclusion, the crosstalk between Cl- electrolyte transport and active traditional Chinese medicine monomers may lead to the development of new strategies for diarrhea by manipulating the function and expression of ion channels.

How Phosphorylation and ATPase Activity Regulate Anion Flux though the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR)

The cystic fibrosis transmembrane conductance regulator (CFTR, ABCC7), mutations of which cause cystic fibrosis, belongs to the ATP-binding cassette (ABC) transporter family and works as a channel for small anions, such as chloride and bicarbonate. Anion channel activity is known to depend on phosphorylation by cAMP-dependent protein kinase A (PKA) and CFTR-ATPase activity. Whereas anion channel activity has been extensively investigated, phosphorylation and CFTR-ATPase activity are still poorly understood. Here, we show that the two processes can be measured in a label-free and non-invasive manner in real time in live cells, stably transfected with CFTR. This study reveals three key findings. (i) The major contribution (≥90%) to the total CFTR-related ATP hydrolysis rate is due to phosphorylation by PKA and the minor contribution (≤10%) to CFTR-ATPase activity. (ii) The mutant CFTR-E1371S that is still conductive, but defective in ATP hydrolysis, is not phosphorylated, suggesting that phosphorylation requires a functional nucleotide binding domain and occurs in the post-hydrolysis transition state. (iii) CFTR-ATPase activity is inversely related to CFTR anion flux. The present data are consistent with a model in which CFTR is in a closed conformation with two ATPs bound. The open conformation is induced by ATP hydrolysis and corresponds to the post-hydrolysis transition state that is stabilized by phosphorylation and binding of chloride channel potentiators.

Decreased basal chloride secretion and altered cystic fibrosis transmembrane conductance regulatory protein, Villin, GLUT5 protein expression in jejunum from leptin-deficient mice

Patients with diabetes and obesity are at increased risk of developing disturbances in intestinal function. In this study, we characterized jejunal function in the clinically relevant leptin-deficient ob/ob mouse, a model of diabetes and obesity. We measured transepithelial short circuit current (Isc), across freshly isolated segments of jejunum from 12-week-old ob/ob and lean C57BL/6J (female and male) mice. The basal Isc was significantly decreased (~30%) in the ob/ob mice (66.5±5.7 μA/cm(2) [n=20]) (P< 0.05) compared with their lean counterparts (95.1±9.1 μA/cm(2) [n=19]). Inhibition with clotrimazole (100 μM, applied bilaterally) was significantly reduced in the ob/ob mice (-7.92%±3.67% [n=15]) (P<0.05) compared with the lean mice (10.44%±7.92% [n=15]), indicating a decreased contribution of Ca(2+)-activated K(+) (KCa) channels in the ob/ob mice. Inhibition with ouabain (100 μM, applied serosally) was significantly reduced in the ob/ob mice (1.40%±3.61%, n=13) (P< 0.05) versus the lean mice (18.93%±3.76% [n=18]), suggesting a potential defect in the Na(+)/K(+)-adenosine triphosphate (ATP)ase pump with leptin-deficiency. Expression of cystic fibrosis transmembrane conductance regulatory protein (CFTR) (normalized to glyceraldehyde-3-phosphate dehydrogenase [GAPDH]) was significantly decreased ~twofold (P<0.05) in the ob/ob mice compared with the leans, whilst crypt depth was unchanged. Villi length was significantly increased by ~25% (P<0.05) in the ob/ob mice compared with the leans and was associated with an increase in Villin and GLUT5 expression. GLUT2 and SGLT-1 expression were both unchanged. Our data suggests that reduced basal jejunal Isc in ob/ob mice is likely a consequence of reduced CFTR expression and decreased activity of the basolateral KCa channel and Na(+)/K(+)-ATPase. Understanding intestinal dysfunctions in ob/ob jejunum may allow for the development of novel drug targets to treat obesity and diabetes.

Antidiarrheal properties of different extracts of Chinese herbal medicine formula Bao-Xie-Ning

OBJECTIVE

Bao-Xie-Ning (BXN), a traditional Chinese herbal medicine (CHM) formula composed of Fructus Evodiae, Flos Caryophylli and Cortex Cinnamomi, and used for the treatment of infant diarrheal illness, was subject to systematic assessment for its putative multiple pharmacodynamic effects and pharmacological antidiarrheal mechanisms.

METHODS

High-performance liquid chromatography-diode array detector-electrospray ionization-mass spectrometric/mass spectrometry was developed and validated for identification and quantification of the main constituents in different extracts of BXN. Male Kunming mice weighing 20 to 25 g were used for detecting the antidiarrheal activity of the extracts. Ethanolic extract (EE), volatile oil extract (VOE), and aqueous extract (AE) of BXN were respectively subjected to pharmacodynamic and pharmacological comparison in assessing antidiarrheal effects with senna-induced diarrhea, castor oil-induced diarrhea, acetic acid-induced writhing assay, and isolated duodenum test.

RESULTS

The highest yields of three detected components of BXN, rutaecarpine, eugenol and cinnamaldehyde were observed in EE. EE showed the most remarkable antidiarrheal activity in dose-dependent and time-dependent manners in both senna- and castor oil-induced diarrhea models, and presented dose-dependent analgesic activity in acetic acid-induced algesthesia model. In addition, EE extract of BXN also exhibited strong antimobility action on the intestine and strongest depression on spontaneous contraction of isolated duodenum.

CONCLUSION

Ethanol extraction is an efficient method to extract the active constituents of BXN. BXN extract demonstrated multiple pharmacological activities affecting the main mechanisms of diarrhea, which validated BXN's usage in the comprehensive clinical treatment of diarrhea.

Stimulation of murine intestinal secretion by daily genistein injections: gender-dependent differences

BACKGROUND/AIMS

The effect of daily injections with genistein (naturally occurring phytoestrogen) on intestinal chloride (Cl(-)) secretion was measured with Ussing chamber short circuit current (I(sc), μA/cm(2)), in C57BL/6J male and female mice, using 600 mg/kg genistein/day (600G), 300 mg/kg genistein/day (300G), 150 mg/kg genistein/day (150G) or genistein-free vehicle control (0G) for 1- or 2-weeks.

METHODS AND RESULTS

Injecting with 600G elicited significant increases in basal I(sc) in females after 1-week (ñ70 μA/cm(2), n=15, p < 0.05) and in males after 2-weeks (ñ80 μA/cm(2), n=5, p < 0.05) compared to their 0G counterparts. Chloride-free ringer significantly reduced basal I(sc) by 65% in 600G males and 72% in 600G females, suggesting that Cl(-) was the major anion comprising the genistein-stimulated secretion. The forskolin-stimulated (10 μM) I(sc) was significantly inhibited by the CFTR chloride channel inhibitors, glibenclamide (500 μM) and CFTR(inh)-172 (100 μM) in 600G males and females, suggesting some contribution by genistein-dependent CFTR-mediated Cl(-) secretion. We found no associated changes in intestinal morphology, nor change in total CFTR protein with 600G. There was a 5% increase in apical/subapical ratio in 600G males compared to controls (no change in females).

CONCLUSION

These data suggest that male and female mice both exhibit increased Cl- secretion with 600G, however, the mechanisms mediating this are gender-dependent.

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

AIM

To clarify whether CFTR is a molecular target of intestinal fluid secretion caused by the anthraquinone compounds from laxative herbal plants.

METHODS

A cell-based fluorescent assay to measure I(-) influx through CFTR chloride channel. A short-circuit current assay to measure transcellular Cl(-) current across single layer FRT cells and freshly isolated colon mucosa. A closed loop experiment to measure colon fluid secretion in vivo.

RESULTS

Anthraquinone compounds rhein, aloe-emodin and 1,8-dihydroxyanthraquinone (DHAN) stimulated I(-) influx through CFTR chloride channel in a dose-dependent manner in the presence of physiological concentration of cAMP. In the short-circuit current assay, the three compound enhanced Cl(-) currents in epithelia formed by CFTR-expressing FRT cells with EC(50) values of 73 ± 1.4, 56 ± 1.7, and 50 ± 0.5 μmol/L, respectively, and Rhein also enhanced Cl(-) current in freshly isolated rat colonic mucosa with a similar potency. These effects were completely reversed by the CFTR selective blocker CFTR(inh)-172. In in vivo closed loop experiments, rhein 2 mmol/L stimulated colonic fluid accumulation that was largely blocked by CFTR(inh)-172. The anthraquinone compounds did not elevate cAMP level in cultured FRT cells and rat colonic mucosa, suggesting a direct effect on CFTR activity.

CONCLUSION

Natural anthraquinone compounds in vegetable laxative drugs are CFTR potentiators that stimulated colonic chloride and fluid secretion. Thus CFTR chloride channel is a molecular target of vegetable laxative drugs.

Traditional Chinese formula, lubricating gut pill, stimulates cAMP-dependent CI(−) secretion across rat distal colonic mucosa

AIM OF THE STUDY

Lubricating gut pill (LGP), a traditional Chinese formula, had been conformed to improve the loperamide-induced rat constipation by stimulation of Cl(-) secretion, but its mechanism has not been fully explored. Thus, the purpose of this study was to identify the action sites of LGP-stimulated Cl(-) secretion across rat distal colonic mucosa.

MATERIALS AND METHODS

Rat distal colonic mucosa was mounted in Ussing chambers and short circuit current (I(SC)), apical Cl(-) current and basolateral K(+) current were recorded. Intracellular cyclic adenosine monophosphate (cAMP) content and protein kinase A (PKA) activity were determined with ELISA kit and the non-radioactive PepTag test, respectively.

RESULTS

LGP at 800μg/ml elicited a sustained increase in Cl(-) secretory response, which was inhibited by CFTR(inh)172, a cystic fibrosis transmembrane conductance regulator (CFTR) inhibitor. Permeabilizing apical membrane with nystatin revealed that LGP-stimulated basolateral K(+) current was significantly inhibited by KCNQ1 K(+) channel inhibitor chromanol 293B. LGP-stimulated I(SC) was markedly reduced by pretreatment with cis-N-[2-phenylcyclopentyl]-azacyclotridec-1-en-2amine (MDL-12,330A) and N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide (H-89), but not with inhibitors of Ca(2+)-dependent signaling pathway. Treatment of tissue with LGP resulted in an increase in intracellular cAMP level and the activation in protein kinase A. The E-prostanoid(4) (EP)(4) receptor antagonist L-161,982 completely eliminated LGP-induced response.

CONCLUSIONS

The results showed that LGP enhances Cl(-) and fluid secretion via prostanoid receptor signaling and also cAMP and protein kinase A pathway, subsequently triggering the activation of apical Cl(-) channels mostly CFTR and basolateral cAMP-dependent K(+) channel.

Traditional Chinese formula, lubricating gut pill, improves loperamide-induced rat constipation involved in enhance of Cl- secretion across distal colonic epithelium

AIM OF THE STUDY

Lubricating gut pill (LGP), a traditional Chinese formula, was widely used for the treatment of chronic constipation, especially in the elderly, in China. However, it is unclear whether LGP-induced laxative and/or lubricating effect is involved in water and electrolytes transport in distal colonic epithelium.

MATERIALS AND METHODS

The present study was designed to evaluate the effect of LGP on Cl(-) secretion across rat distal colonic epithelium mounted in Ussing chambers, and on a rat constipation model induced by loperamide, respectively.

RESULTS

Application of LGP in the apical side elicited a sustained increase in short circuit current (I(SC)) response in a concentration-dependent manner. Evidence that LGP-stimulated I(SC) was due to Cl(-) secretion is based on inhibition of current by (a) a Na(+)-K(+)-2Cl(-) cotransporter inhibitor bumetanide, (b) removal of Cl(-) ions in bath solution, and (c) the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel blocker DPC, suggesting that a apical cAMP-dependent Cl(-) channel was activated. LGP-stimulated I(SC) was also strongly inhibited by pretreatment with clotrimazole, indicating that the basolateral K(+) channel was also involved in maintaining this cAMP-dependent Cl(-) secretion. Pretreatment of tissues with indomethacin, but not atropine, tetrodotoxin or hexamethonium, inhibited LGP-induced response. In a rat constipation model, oral administration with LGP was significantly restored number of fecal pellets, water content and mucus secretion compared with loperamide-treated group alone.

CONCLUSIONS

LGP enhances Cl(-) secretion that is mostly mediated through the release of cyclooxygenase metabolites, by which provided an osmotic force for the subsequent laxative action observed in the rat constipation model.