Cellular signaling mechanisms underlying pharmacological action of Bak Foong Pills on gastrointestinal secretion

Activation of apical CFTR and basolateral Ca(2+)-activated K+ channels by tetramethylpyrazine in Caco-2 cell line

We have previously demonstrated that tetramethylpyrazine (TMP) could stimulate colonic and pancreatic anion secretion. The present study investigated the signaling pathways and cellular mechanisms underlying the effect of TMP using human colonic Caco-2 cells, with permeabilized apical or basolateral membranes, in conjunction with Ussing chamber technique, intracellular cAMP and Ca2+ measurements as well as competitive RT-PCR for mRNA expression of cystic fibrosis transmembrane conductance regulator (CFTR) and Ca(2+)-dependent Cl- channels (CACC). Basolateral addition of TMP induced a short circuit current (I(SC)) response, which could be mimicked by forskolin and 3-isobutyl-1-methylxanthine (IBMX). Adenylate cyclase inhibitor, MDL12330A, and intracellular Ca2+ chelator, BAPTA-AM, significantly inhibited the TMP-induced I(SC). In basolateral membrane-permeabilized cells, TMP, as well as forskolin and IBMX, induced an I(SC) response, which was sensitive to MDL-12330A, H89, and specific channel blocker CFTR(inh-172), but insensitive to apical application of 4-4'-didsothiocyanostilbene-2, 2'-disulfonic acid (DIDS) and basolateral pretreatment with BAPTA-AM. In apical membrane-permeabilized cells, TMP, similar to forskolin and IBMX, produced a very small current increase, which was sensitive to K+ channel blockers, BaCl2 and tetraethylammonium (TEA), but not Chromanol 293B and charybdotoxin (ChTX), alone or combined. However, in intact Caco-2 monolayers, the TMP-induced I(SC) could be partially inhibited by ChTX. TMP (5 mM) could stimulate intracellular cAMP production. Intracellular Ca2+ was also increased by TMP (5 mM) in both Ca(2+)-containing and Ca(2+)-free bathing solutions. RT-PCR showed that the expression of CFTR in Caco-2 cells was 5.2 fold higher than that of Ca(2+)-activated Cl- channel (CACC). In conclusion, TMP stimulates Cl- secretion by activating cAMP and [Ca2+]i signaling pathways leading to subsequent activation of apical CFTR and basolateral K+ channels.

Tetramethylpyrazine stimulates cystic fibrosis transmembrane conductance regulator-mediated anion secretion in distal colon of rodents

AIM: To investigate the effect of tetramethylpyrazine (TMP), an active compound from Ligustium Wollichii Franchat, on electrolyte transport across the distal colon of rodents and the mechanism involved

METHODS: The short-circuit current (I_SC) technique in conjunction with pharmacological agents and specific inhibitors were used in analyzing the electrolyte transport across the distal colon of rodents. The underlying cellular signaling mechanism was investigated by radioimmunoassay analysis (RIA) and a special mouse model of cystic fibrosis.

RESULTS: TMP stimulated a concentration-dependent rise in I_SC, which was dependent on both Cl^- and HCO₃^-, and inhibited by apical application of diphenylamine-2,2’-dicarboxylic acid (DPC) and glibenclamide, but resistant to 4,4’-diisothiocyanatostilbene-2,2’-disulfonic acid disodium salt hydrate (DIDS). Removal of Na⁺ from basolateral solution almost completely abolished the I_SC response to TMP, but it was insensitive to apical Na⁺ replacement or apical Na⁺ channel blocker, amiloride. Pretreatment of colonic mucosa with BAPTA-AM, a membrane-permeable selective Ca²⁺ chelator, did not significantly alter the TMP-induced I_SC. No additive effect of forskolin and 3-isobutyl-1-methylxanthine (IBMX) was observed on the TMP-induced I_SC, but it was significantly reduced by a protein kinase A inhibitor, H₈₉. RIA results showed that TMP (1 mmol/L) elicited a significant increase in cellular cAMP production, which was similar to that elicited by the adenylate cyclase activator, forskolin (10 µmol/L). The TMP-elicited I_SC as well as forskolin- or IBMX-induced I_SC were abolished in mice with homozygous mutation of the cystic fibrosis transmembrane conductance regulator (CFTR) presenting defective CFTR functions and secretions.

CONCLUSION: TMP may stimulate cAMP-dependent and CFTR-mediated Cl^- and HCO₃^- secretion. This may have implications in the future development of alternative treatment for constipation.

Effects of Bak Foong Pills and Menoease Pills on white blood cell distribution in old age female rats

This study examined the effects of Bak Foong Pills (BFP) and the new BFP-derived post-menopause formula, Menoease Pills (MBFP), on the distribution of peripheral white blood cells (WBC) between BFP/MBFP-treated and non-treated rats. Eighteen months old female SD rats were used to mimic post-menopausal and old age animal models. The percentage distribution of lymphocytes, monocytes and granulocytes were measured using flow cytometry with and without treatments of BFP or MBFP. Results showed that WBC distribution in old age rats were significantly different from that of adult rats, suggesting that as the animal aged, their WBC distributions were altered. Old age rats were observed to have much lower percentages of lymphocytes, but higher percentages of granulocytes when compared to the adult rats, indicating possible attenuated immunity. Following treatment with BFP or MBFP, WBC populations were found to be redistributed back into the ranges observed in adult animals. Furthermore, MBFP, was found to alter WBC distribution in a dose-dependent manner. When compared to estrogen (E(2)), a well documented regulator of immune function, results showed that MBFP was able to show significantly greater effects on WBC redistribution compared to E(2). However, in ovariectomised (ovx) old age rats, neither MBFP nor E(2) treated groups showed any changes in WBC redistribution. These results indicate that MBFP may share similarities to E(2). Indeed, the effect of MBFP and E(2) seems to require intact ovaries, which are believed to be necessary for the modulation of WBC distributions and immune functions. Overall, our findings suggest that BFP and MBFP may be able to regulate WBC population in old age female rats, and thus, indicate their potential role on improving the attenuated immunity evident in post-menopausal and elderly women.

Improvement of barrier function and stimulation of colonic epithelial anion secretion by Menoease Pills

AIM: Menoease Pills (MP), a Chinese medicine-based new formula for postmenopausal women, has been shown to modulate the endocrine and immune systems^[1]. The present study investigated the effects of MP and one of its active ingredients, ligustrazine, on epithelial barrier and ion transport function in a human colonic cell line, T₈₄.

METHODS: Colonic transepithelial electrophysiological characteristics and colonic anion secretion were studied using the short circuit current (I_SC) technique. RT-PCR was used to examine the expression of cytoplasmic proteins associated with the tight junctions, ZO-1 (zonula occludens-1) and ZO-2 (zonula occludens-2).

RESULTS: Pretreatment of T₈₄ cells with MP (15 μg/mL) for 72 h significantly increased basal potential difference, transepithelial resistance and basal I_SC. RT-PCR results showed that the expressions of ZO-1 and ZO-2 were significantly increased after MP treatment, consistent with improved epithelial barrier function. Results of acute stimulation showed that apical addition of MP produced a concentration-dependent (10-5000 μg/mL, EC₅₀ = 293.9 μg/mL) increase in I_SC. MP-induced I_SC was inhibited by basolateral treatment with bumetanide (100 μmol/L), an inhibitor of the Na ⁺ -K ⁺ -2Cl^- cotransporter, apical addition of Cl^- channel blockers, diphenylamine-2, 2’-dicarboxylic acid (1 mmol/L) or glibenclamide (1 mmol/L), but not 4, 4’-diisothiocyanostilbene-2, 2’-disulfonic acid or epithelial Na ⁺ channel blocker, amiloride. The effect of MP on ZO-1 and ZO-2 was mimicked by Ligustrazine and the ligustrazine-induced I_SC was also blocked by basolateral application of bumetanide and apical addition of diphenylamine-2, 2'-dicarboxylic acid or glibenclamide, and reduced by a removal of extracellular Cl^-.

CONCLUSION: The results of the present study suggest that MP and ligustrazine may improve epithelial barrier function and exert a stimulatory effect on colonic anion secretion, indicating the potential use of MP and its active ingredients for improvement of GI tract host defense and alleviation of constipation often seen in the elderly.

Differential Cl- and HCO3- mediated anion secretion by different colonic cell types in response to tetromethylpyrazine

AIM: Colonic epithelium is known to secrete both Cl^- and HCO₃^-, but the secretory mechanisms of different colonic cell types are not fully understood. The present study aimed to investigate the differential activation of Cl^- and HCO₃^-secretion by tetramethylpyrazine (TMP) in human crypt-like cell line, T84, and villus-like cell line, Caco-2, in comparison to the TMP-induced secretory response in freshly isolated rat colonic mucosa.

METHODS: Colonic epithelial anion secretion was studied by using the short circuit current (I_SC) technique. RT-PCR was used to examine the expression of Na⁺-HCO₃^-- cotranspoter in different epithelial cell types.

RESULTS: TMP produced a concentration-dependent I_SC which was increase in both T84 and Caco-2 cells. When extracellular Cl^- was removed, TMP-induced I_SC was abolished by 76.6% in T84 cells, but not in Caco-2 cells. However, after both Cl^- and HCO₃^- were removed, TMP-induced I_SC in Caco-2 cells was reduced to 10%. Bumetanide, an inhibitor of Na⁺-K⁺-Cl^--cotranspoter, inhibited the TMP-induced I_SC by 96.7% in T84 cells, but only 47.9% in Caco-2 cells. In the presence of bumetanide and 4, 4’-diisothiocyanostilbene-2, 2’-disulfonic acid, an inhibitor of Na⁺-HCO₃^- cotransporter, inhibited the TMP-induced current in Caco-2 cells by 93.3%. In freshly isolated rat colonic mucosa, TMP stimulated distinct I_SC responses similar to that observed in T84 and Caco-2 cells depending on the concentration used. RT-PCR revealed that the expression of Na⁺-HCO₃^- cotransporter in Caco-2 cells was 4-fold more greater than that in T84 cells.

CONCLUSION: TMP exerts concentration-dependent differential effects on different colonic cell types with stimulation of predominant Cl^- secretion by crypt cells at a lower concentration, but predominant HCO₃^- secretion by villus cells at a higher concentration, suggesting different roles of these cells in colonic Cl^- and HCO₃^- secretion.

Effect of Bak Foong pills on exocrine pancreatic-bile secretion

We have recently demonstrated that Bak Foong Pills (BFP), a well-known Chinese medicine widely used for treating gynecological disorders, stimulates human colonic epithelial anion secretion, which was mediated by intracellular cAMP and Ca(2+). The present study further investigated the effect of BFP on exocrine pancreatic-bile secretion using in vivo and in vitro approaches. Duodenal infusion of BFP ethanol extract (1 g/kg) in rats produced increases in the volume and protein output of pancreatic-bile juice, but did not affect its pH. Surgical ablation of vagal neural pathway slightly reduced the effect of BFP on the protein output and volume, indicating that the vagal nerve pathway was not the major player in medicating the effect of BFP on exocrine pancreatic-bile secretion. Using CAPAN-1 cell line, a human pancreatic duct cell line, in conjunction with the short-circuit current (I(SC)) measurements, we further demonstrated that BFP could directly stimulate pancreatic HCO(3)(-) secretion. Basolateral addition of BFP (600 microg/ml) produced averaged charges transported of 2100+/-382.5 microC/cm(2), which was blocked by apical addition of Cl(-) channel blocker. Removal of HCO(3)(-) from the Krebs-Henseleit (K-H) solution inhibited the BFP-induced I(SC) by more than 95%. The present results suggest that BFP could improve digestive function by stimulating pancreatic protein and HCO(3)(-) secretion.

Cardiovascular protective effects of traditional Chinese medicine bak foong pills in spontaneously hypertensive rats

The cardiovascular protective effects of the traditional Chinese medicine Bak Foong Pills (BFP) were investigated. Spontaneously hypertensive rats (SHR) were treated (3 g/kg) over a 5-month period and blood pressure measurements periodically tested with a plethysmographic tail cuff. Following treatment, blood samples were analysed for serum electrolyte levels and lipid levels and brain tissue subjected to micro-array analysis. In vitro experiments were also conducted to identify possible direct vasorelaxatory effect. The results showed that BFP was able to significantly reduce both systolic and diastolic blood pressure by about 30 mmHg in SHR following 5 months of treatment, when compared to untreated animals. Investigation for possible mechanisms of actions revealed that BFP treated rats had elevated blood serum K(+) levels, and also demonstrated decreased serum triglyceride levels. Micro-array analysis of brain tissue showed altered expression of acetylcholine and lysosphingolipid receptor genes that are known to regulate blood pressure. In vitro experiments also showed that BFP caused a concentration-dependant vasorelaxation of isolated rat aortae when contracted with phenylepherine, which was partially inhibited by nitric oxide synthase inhibitor L-NAME (100 microM). These data suggest that BFP is able to significantly reduce hypertension in SHR through mechanisms probably involving a combination of increased serum K(+), vasorelaxatory action, reduced serum triglyceride and altered gene regulation in the higher centres.

Effect of Bak Foong pills on enhancing dopamine release from the amygdala of female rats

To investigate whether Bak Foong Pills (BFP), a well-known gynaecological tonic, has a direct effect on the central nervous system, we employed the in vivo electrochemical detection technique, fast cyclic voltammetry (FCV), to measure the dopamine release from the mesolimbic structure-amygdala of both male and female rats. The results showed that intracerebroventricular BFP (0.75, 1.5 microg) treatment promoted dopamine release from the amygdala in both female and ovariectomized female rats. The BFP-induced response appeared within 5 min after addition of BFP and lasted for at least 40 min. However, no effect of BFP was observed in male rats for an observed period of up to 60 min. The results suggest that BFP may have gender-specific beneficial effect on dopaminergic functions of the amygdala.

Effects of Bak Foong Pill on blood coagulation and platelet aggregation

The effects of Bak Foong Pill (BFP, also known as Bai Feng Wan), a preparation of crude drugs in wide clinical use for treatment of gynecological disorders, on blood coagulation and platelet aggregation were investigated. The anticoagulant effect of BFP was evaluated by using thrombin time (TT), prothrombin time (PT), and activated partial thromboplastin time (APTT) assays. Results showed that BFP 70% ethanol extract (BFP-E-ext) significantly prolonged the TT in a dose-dependent manner with values of 17.6, 38.3, and 50.4 s at concentrations of 4.0, 6.0, and 12.0 mg/ml, respectively. Whereas, the BFP-E-ext did not show significant prolonging effect in PT and APTT assays. The results suggest that the anticoagulant effect of BFP is mediated by directly blocking thrombin, the key enzyme in the blood coagulation cascade. BFP-E-ext significantly inhibited platelet aggregation induced by collagen and adenosine diphosphate (ADP) with inhibition percentages of 74 and 52% at a concentration of 6.0 mg/ml, respectively, whereas, it exhibited a weak inhibitory activity on platelet aggregation induced by archidonic acid (AA). Comparing to BFP-E-ext, the effects of BFP aqueous extract (BFP-W-ext) on both anticoagulant and antiplatelet activities were significantly less potent. Moreover, the effects of the 26 ingredients of BFP on blood coagulation and platelet aggregation were separately evaluated with 19 ingredient herbs exhibiting anticoagulant effect and 10 exhibiting antiplatelet effect. The anticoagulant and antiplatelet effects of BFP were collectively demonstrated by in vivo assays showing prolonged bleeding times after BFP treatment for two weeks. The results of the present studies may provide explanations for beneficial effects of BFP on the circulation and indicate its potential use for cardiovascular diseases.