Dazheng Wu

Curcumin induces apoptosis in human gastric carcinoma AGS cells and colon carcinoma HT-29 cells through mitochondrial dysfunction and endoplasmic reticulum stress.

In the present study, we investigate the effect of curcumin, a major active component isolated from rhizomes of Curcuma longa, on the cytotoxicity of three human carcinoma cell lines (AGS, HT-29 and MGC803) in gastrointestinal tract and a normal gastric epithelial cell line GES-1, and the mechanism of curcumin-induced apoptosis. The results indicated that curcumin inhibited the gastrointestinal carcinoma cell growth in a dose-dependent manner and cytotoxicity was more towards the gastric carcinoma cell AGS and colon carcinoma cell HT-29 compared to normal gastric cell GES-1, and increased externalization of phosphatidylserine residue was observed by Annexin V/PI staining in the two cell lines. Treatment of AGS and HT-29 cells with curcumin enhanced the cleavage of procaspase-3, -7, -8 and -9. Meanwhile, curcumin induced endoplasmic reticulum (ER) stress and mitochondrial dysfunction as evidenced by up-regulation of CCAAT/enhancer binding protein homologous protein (CHOP), phosphorylation of JNK and down-regulation of SERCA2ATPase, release of cytochrome c, decrease of Bcl-2 and reduction of mitochondrial membrane potential in both AGS and HT-29 cells. Overexpression of bax, total JNK, phospho-FADD and total FADD were also observed in curcumin-treated HT-29 cells. Moreover, curcumin decreased cytosolic and ER Ca2+, but increased mitochondrial Ca2+ in the two cell lines. 2-Aminoethoxydiphenyl borate, an antagonist of inositol 1, 4, 5-triphosphate receptor, partly blocked curcumin-induced cytosolic Ca2+ decrease in AGS and HT-29 cells. Additionally, carbonyl cyanide m-chlorophenylhydrazone, an inhibitor of mitochondrial Ca2+ uptake, reversed curcumin-triggered AGS and HT-29 cells growth inhibition. siRNA to CHOP markedly reduced curcumin-induced apoptosis. These results suggest that curcumin can impact on ER stress and mitochondria functional pathways in AGS and HT-29 cells, death receptor pathway was also involved in curcumin-treated HT-29 cells, thus identifying specific well-defined molecular mechanisms that may be targeted by therapeutic strategies.

Tangeretin, a citrus polymethoxyflavonoid, induces apoptosis of human gastric cancer AGS cells through extrinsic and intrinsic signaling pathways

Tangeretin, a natural polymethoxyflavone present in citrus peel oil, is known to have anticancer activities in breast cancer, colorectal carcinoma and lung carcinoma, yet, the underlying mechanisms of tangeretin in human gastric cancer AGS cells have not been investigated to date. In the present study, the apoptotic mechanisms of tangeretin in AGS cells were explored. It was observed that tangeretin increased the apoptotic rates of AGS cells following treatment with tangeretin for 48 h in a dose-dependent manner by Annexin V-FITC and PI double staining. In addition, characteristic apoptotic morphology such as nuclear shrinkage and apoptotic bodies was observed after Hoechst 33258 staining. Flow cytometric assay showed that treatment of AGS cells with tangeretin decreased the mitochondrial membrane potential (MMP) in a dose-dependent manner, which indicated that mitochondrial dysfunction was involved in the tangeretin-induced apoptosis. Caspase-3, -8 and -9 activities were increased by tangeretin in a dose-dependent manner. Western blotting showed that the protein levels of pro-apoptotic proteins including cleaved caspase-3, cleaved caspase-8, cleaved caspase-9, Bax, Bid, tBid, p53, p21/cip1, Fas and FasL were significantly upregulated by tangeretin. In addition, PFT-α (a p53 inhibitor) reduced the apoptotic rates and the expression of p53, p21, caspase-3 and caspase-9 induced by tangeretin, indicating that tangeretin-induced apoptosis was p53-dependent. In conclusion, these results suggest that tangeretin induces the apoptosis of AGS cells mainly through p53-dependent mitochondrial dysfunction and the Fas/FasL-mediated extrinsic pathway.

Effect of jatrorrhizine on delayed gastrointestinal transit in rat postoperative ileus.

Objectivesu2002 Postoperative ileus is major cause of postoperative complication and prolonged hospitalization. Jatrorrhizine, which is a protoberberine alkaloid isolated from the medicinal plants Berberis aristata and Coptis chinensis, has been found to increase contractility of gastric antral and ileum smooth muscles of rat gastrointestinal tract. We have investigated whether jatrorrhizine could offset gastrointestinal transit in rat with postoperative ileus.

Palmatine, a protoberberine alkaloid, inhibits both Ca2+‐ and cAMP‐activated Cl− secretion in isolated rat distal colon

The protoberberine alkaloid berberine has been reported to inhibit colonic Cl− secretion. However, it is not known if other protoberberine alkaloids share these effects. We have therefore selected another protoberberine alkaloid, palmatine, to assess its effects on active ion transport across rat colonic epithelium.

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

AIM OF THE STUDYnLubricating 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.nnnMATERIALS AND METHODSnRat 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.nnnRESULTSnLGP 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.nnnCONCLUSIONSnThe 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.

The effects of jatrorrhizine on contractile responses of rat ileum.

This study was designed to evaluate the effect of jatrorrhizine on smooth muscle contractions isolated from rat ileum longitudinal muscles. Jatrorrhizine increased the amplitude of spontaneous contractions of ileum longitudinal muscles in concentration-dependent manner with an EC(50) of 30.0±8.4μM. Preincubation of ileum strips with atropine (1μM), 4-diphenyllacetoxy-N (2-chloriethyl)-piperidine (4-DAMP, 1μM) or darifenacin (1μM) significantly inhibited acetylcholine (0.1μM)- and jatrorrhizine (100μM)-induced ileum longitudinal muscle contractions, whereas they were not affected by AF-DX116 (1μM) or hexamethonium (100μM). Pretreatment with SB204070 (1μM) rather than 3-tropanyl-indole-3-carboxyleat (tropisetron, 1μM) significantly inhibited 5-HT (10μM)-induced ileum longitudinal muscle contractions. In contrast, jatrorrhizine-induced ileum longitudinal muscle contractions were not inhibited by tropisetron or SB204070. Furthermore, jatrorrhizine-induced ileum longitudinal muscle contractions were strongly inhibited by nifedipine (1μM), and also attenuated by removal of extracellular Ca(2+), U73122 (1μM), ruthenium red (50μM) or 2-aminoethoxydiphenylborate (2-APB, 10μM). Taken together, jatrorrhizine-elicited spontaneous contractions in rat ileum longitudinal muscles are mediated by activation of acetylcholine receptors, mostly the M(3) receptor. Ca(2+) influx through L-type Ca(2+) channel is significantly contributed to jatrorrhizine-elicited spontaneous contractions, and Ca(2+) release via IP(3) and ryanodine pathways are also involved.

Metabolic responses induced by thrombin in human umbilical vein endothelial cells.

Metabolic responses induced by thrombin in human umbilical vein endothelial cells (HUVECs) were investigated by using the cytosensor technique. Thrombin increased the extracellular acidification rate of endothelial cells, measured as an index of metabolic activity with a cytosensor microphysiometer, in a concentration-dependent fashion with an EC(50) of 1.27+/-0.59 IU/ml, which was abolished by the MAP kinase inhibitor PD98059. When intracellular Ca(2+) was chelated or PKC was inactivated, PD98059 failed to abolish the thrombin-induced acidification rate response in HUVECs. In addition, the tyrosine kinase inhibitor genistein, PKC inhibitor calphostin C, and Na(+)/H(+)exchanger antagonist MIA also partly inhibited thrombin-induced acidification rate responses. It is suggested that thrombin stimulated rapid metabolic responses via MAP kinase in HUVECs, which are calcium- and PKC-dependent.

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

AIM OF THE STUDYnLubricating 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.nnnMATERIALS AND METHODSnThe 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.nnnRESULTSnApplication 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.nnnCONCLUSIONSnLGP 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.

Kurarinone Synergizes TRAIL-Induced Apoptosis in Gastric Cancer Cells.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been identified as a promising anti-tumor agent against in a variety of cancers. However, gastric cancer cells are less sensitive than other cancer cells to TRAIL-induced apoptosis. Here, we combined TRAIL with kurarinone, a natural compound, to induce apoptosis in gastric cancer cell lines SGC7901. After the cells were treated with TRAIL and/or kurarinone, the cell viability and apoptosis were examined by MTT and flow cytometry, respectively. The expression of apoptosis-associated proteins was determined by western blot and q-RT-PCR. Kurarinone at low concentration significantly potentiated the cytotoxic effect of TRAIL by enhancing apoptosis as well as cell cycle arrest at G2/Mphase. The enhancement of apoptosis TRAIL induced by kurarinone involved downregulation of anti-apoptotic proteins Mcl-1 and c-FLIP as well as inhibition of STAT3 signaling. Moreover, we found that STAT3 inhibitor could synergistically enhanced TRAIL-induced apoptosis, similar to kurarinone. Kurarinone synergizes TRAIL-induced apoptosis in human gastric cancer cells. The synergistic effect between these two drugs is associated with downregulation of Mcl-1 and c-FLIP via inhibiting STAT3 signaling. The combination of TRAIL and kurarinone might be an effective regimen for the treatment of advanced gastric cancer.

Airway hyperresponsiveness induced by repeated esophageal infusion of HCl in guinea pigs.

Gastroesophageal reflux is a common disorder closely related to chronic airway diseases, such as chronic cough, asthma, chronic bronchitis, and chronic obstructive disease. Indeed, gastroesophageal acid reflux into the respiratory tract causes bronchoconstriction, but the underlying mechanisms have still not been clarified. This study aimed to elucidate functional changes of bronchial smooth muscles (BSMs) isolated from guinea pigs in an animal model of gastroesophageal reflux. The marked airway inflammation, hyperresponsiveness and remodeling were observed after guinea pigs were exposed to intraesophageal HCl infusion for 14 days. In addition, contractile responses to acetylcholine (ACh), KCl, electrical field stimulation, and extracellular Ca(2+) were greater in guinea pigs infused with HCl compared with control groups. The L-type voltage-dependent Ca(2+) channels (L-VDCC) blocker, nicardipine, significantly inhibited ACh- and Ca(2+)-enhanced BSM contractions in guinea pigs infused with HCl. The Rho-kinase inhibitor, Y27632, attenuated ACh-enhanced BSM contractions in guinea pigs infused with HCl. Moreover, mRNA and protein expressions for muscarinic M2 and M3 receptors, RhoA, and L-VDCC in BSM were detected by real-time PCR and Western blot. Expressions of mRNA and protein for muscarinic M3 receptors, RhoA, and L-VDCC were greater than in BSM of HCl-infused guinea pigs, whereas levels of muscarinic M2 receptors were unchanged. We demonstrate that acid infusion to the lower esophagus and, subsequently, microaspiration into the respiratory tract in guinea pigs leads to airway hyperresponsiveness and overactive BSM. Functional and molecular results indicate that overactive BSM is the reason for enhancement of extracellular Ca(2+) influx via L-VDCC and Ca(2+) sensitization through Rho-kinase signaling.