[show abstract][hide abstract] ABSTRACT: The present authors previously reported that a synthetic retinoid, CD437, induces endoplasmic reticulum stress-mediated apoptosis in ovarian adenocarcinoma cells in spite of no response to natural retinoids. However, the precise mechanism of its proapoptotic action has not been fully determined. The present study herein demonstrates that apoptosis induction of ovarian adenocarcinoma SKOV3 cells by CD437 involves the upregulation of thioredoxin-binding protein 2 (TBP2) by a mechanism that is dependent on the intracellular calcium concentration. TBP2 is known to bind to and suppress thioredoxin (TRX) activity whereas TRX has an anti-apoptotic effect by inhibiting apoptosis signal-regulating kinase 1 (ASK1). The activation of ASK1 and its downstream molecule, c-Jun N-terminal kinase, was observed after induction of TBP2 by CD437. Interestingly, CD437 induced the association of TBP2 with TRX and, in turn, facilitated the dissociation of ASK1 from TRX. Moreover, blockade of TBP2 induction by small interfering RNA (siRNA) significantly attenuated the cytotoxic effect of CD437. These results suggest that TBP2 plays a critical role in the mechanism by which CD437 exerts proapoptotic action against SKOV3 cells.
Cancer Science 12/2008; 99(12):2485-90. · 3.48 Impact Factor
[show abstract][hide abstract] ABSTRACT: Retinoids play an important role in the regulation of cell growth and death. Synthetic retinoid CD437 reportedly induces apoptosis in various cancer cell lines. However, the mechanism of inducing apoptosis in hepatocellular carcinoma (HCC) cells by this agent remains to be clarified. In this study, we investigated the signaling pathway by which CD437 induces apoptosis in HCC cell lines. Apoptosis of six human HCC cell lines was induced by treatment with CD437. Caspase-3 and -9 were activated by CD437, suggesting that the apoptosis is mediated by mitochondrial pathways. Consistent with these findings, the treatment with CD437 upregulated Bax protein, downregulated Bcl-2 protein and released cytochrome c into the cytoplasm. Moreover, rhodamine123 staining revealed mitochondrial depolarization in the cells treated with CD437. These data of the present study suggest that CD437 induces apoptosis in HCC cells via mitochondrial pathways.
Biochemical and Biophysical Research Communications 07/2008; 370(4):629-33. · 2.41 Impact Factor
[show abstract][hide abstract] ABSTRACT: A synthetic retinoid, CD437, has been shown to exert potent anti-tumor activity against various types of cancer cell lines, regardless of their sensitivities to natural retinoids. We herein demonstrate that CD437 induces endoplasmic reticulum (ER) stress, including the up-regulation of CHOP, BIP and GADD34 mRNA through ER stress transducer (PERK and IRE1alpha) activation in an ovarian adenocarcinoma cell line, SKOV3. It was also shown that CD437 induced the CHOP and GADD34 expressions in another four ovarian adenocarcinoma cell lines, indicating that CD437 functions as an ER stress inducer in these cell lines. Moreover, the siRNA-mediated knockdown of inducible CHOP expression prevented the cytotoxic effect of CD437. These results suggest that ER stress plays an important role in the mechanism by which CD437 induces apoptosis in ovarian adenocarcinoma cells.
Biochemical and Biophysical Research Communications 03/2008; 366(3):840-7. · 2.41 Impact Factor
[show abstract][hide abstract] ABSTRACT: Human umbilical cord blood-derived mesenchymal stem cells (UCBMSCs) are expected to be an excellent source of cells for transplantation. In addition, the stem cell plasticity of human UCBMSCs, which can transdifferentiate into hepatocytes, has been reported. However, the mechanisms involved remain to be clarified. To identify the genes and/or signals that are important in specifying the hepatic fate of human UCBMSCs, we analyzed gene expression profiles during the hepatic differentiation of UCBMSCs with human telomerase reverse transcriptase, UCBMSCs immortalized by infection with a retrovirus carrying telomerase reverse transcriptase, but whose differentiation potential remains unchanged. Efficient differentiation was induced by 5-azacytidine (5-aza)/hepatocyte growth factor (HGF)/oncostatin M (OSM)/fibroblast growth factor 2 (FGF2) treatment in terms of function as well as protein expression: 2.5-fold increase in albumin, 4-fold increase in CCAAT enhancer-binding protein alpha, 1.5-fold increase in cytochrome p450 1A1/2, and 8-fold increase in periodic acid-Schiff staining. Consequently, we found that the expression of Wnt/beta-catenin-related genes downregulated, and the translocation of beta-catenin was observed along the cell membrane and in the cytoplasm, although some beta-catenin was still in the nucleus. Downregulation of Wnt/beta-catenin signals in the cells by Fz8-small interference RNA treatment, which was analyzed with a Tcf4 promoter-luciferase assay, resulted in similar hepatic differentiation to that observed with 5-azacytidine/HGF/OSM/FGF2. In addition, the subcellular distribution of beta-catenin was similar to that of cells treated with 5-azacytidine/HGF/OSM/FGF2. In conclusion, the suppression of Wnt/beta-catenin signaling induced the hepatic differentiation of UCBMSCs, suggesting that Wnt/beta-catenin signals play an important role in the hepatic fate specification of human UCBMSCs.
[show abstract][hide abstract] ABSTRACT: The effect of TYB-3823 on Ca2+ current (ICa) of guinea pig ventricular myocytes was investigated by means of whole-cell patch-clamp technique. TYB-3823 (100-1,000 microM) caused a concentration-dependent decrease in ICa. Furthermore, a reduction of ICa induced by TYB-3823 (1,000 microM) was progressively accentuated by repetitive membrane depolarization, indicating a rate-dependent block of ICa. However, the inhibitory potency on ICa was approximately 1/1000 of a Ca2+ antagonistic agent, verapamil hydrochloride. Considering evidence that 3-30 microM TYB-3823 decreased the maximum upstroke velocity of the action potential of guinea pig ventricular muscles, it is indicated that the drug does not show its Ca2+ antagonistic property in the usual concentration range as a class I antiarrhythmic agent.
Journal of Electrocardiology 02/1992; 25(1):53-7. · 1.09 Impact Factor
[show abstract][hide abstract] ABSTRACT: The electrophysiological effects of urapidil, a new alpha 1-adrenoceptor antagonist, were assessed in the reserpinized guinea-pig ventricular myocardium. Urapidil suppressed the maximal rate of rise (Vmax) of steady-state action potentials elicited by the fast responses at high concentrations independently of blockade of myocardial alpha-adrenoceptors, but not the Vmax of Ca(2+)-dependent slow action potentials of partially depolarized muscles in concentrations tested (up to 1.1 mM). Urapidil at high concentrations prolonged the action potential durations of the fast and slow responses in a manner similar to the quinidine-like antiarrhythmic drugs. These results suggest that the inhibitory effect of urapidil on the slow inward Ca2+ current and the Na+ current is in practice negligible.
Cardiovascular Drugs and Therapy 01/1992; 5(6):987-90. · 2.67 Impact Factor
[show abstract][hide abstract] ABSTRACT: 1. Sodium current (INa) blockade by TYB-3823, a newly synthesized antiarrhythmic agent, was investigated in isolated single ventricular myocytes by use of the whole cell patch-clamp technique. 2. TYB-3823 blocked INa under steady-state conditions (Kd,rest = 500 microM, Kd,i = 4.9 microM), findings consistent with a shift in the steady state INa availability curve to more negative potentials. 3. TYB-3823 produced use-dependent block at 2 Hz in conjunction with increase in pulse duration (5-300 ms), that was markedly enhanced at less negative holding potentials. 4. The time course of the onset of block was accelerated and the degree of use-dependent block was decreased at more negative holding potential. The time course of the onset of block was accentuated with enhancing block at more positive holding potentials. 5. The time course of recovery from use-dependent block was accelerated at more negative holding potentials but was accentuated at more positive holding potentials. 6. These results suggest that both tonic block and use-dependent block of sodium channels in cardiac tissue might result from an interaction of TYB-3832 with sodium channels mainly in the inactivated channel states and the kinetics of the interaction between drug and receptor may be modulated by the inactivation gate.
British Journal of Pharmacology 10/1991; 104(1):25-30. · 5.07 Impact Factor
[show abstract][hide abstract] ABSTRACT: One of the effects of antiarrhythmic drugs is the reduction of conduction velocity. Cable theory predicts that there is a nonlinear relationship between conduction velocity and upstroke velocity (Vmax) of action potential. By using conventional microelectrode techniques, aprindine-induced reduction of Vmax of action potential and conduction velocity in guinea-pig papillary muscles were measured. Aprindine-produced, use-dependent, and concentration-dependent changes in conduction velocity and the decline of square of conduction velocity was well fit by a single exponential. Time constants for square of conduction velocity were comparable to simultaneously measured time constants for effects of Vmax. At a concentration of 1 to 10 microM aprindine, onset changes between Vmax and conduction velocity had a log-linear relationship in a predicted fashion. Whereas, in the recovery process from aprindine-induced depression, slow recovery time course of conduction velocity was observed. In conclusion, in the presence of aprindine, only onset block of conduction velocity can be analyzed quantitatively in the relationship to observation on Vmax in vitro. These results suggested that in the presence of aprindine, the recovery of internal conductance may be slower than that of Vmax.
The Journal of Clinical Pharmacology 05/1991; 31(4):348-53. · 2.84 Impact Factor
[show abstract][hide abstract] ABSTRACT: 1. Cibenzoline, a class 1 antiarrhythmic drug, was studied on the effects upon the myocardial slow inward Ca2+ current (ICa) and the contractile force, and was compared with verapamil. 2. In voltage-clamp experiments with guinea-pig ventricular myocytes, cibenzoline caused a concentration-related inhibition of ICa (IC50 = 30 microM), whereas verapamil exerts a stronger effect (IC50 = 0.6 microM). 3. Cibenzoline also produced a concentration-related decrease in contractile force of isolated papillary muscle preparation (IC50 = 30 microM), while IC50 of verapamil was 0.8 microM. 4. Although the myocardial Ca2+ channel blocking effect of cibenzoline is about 1/50 compared to verapamil, cibenzoline possesses an inhibitory action on Ca2+ channel as well as on Na+ channel.
[show abstract][hide abstract] ABSTRACT: 1. Effect of bunazosin, an alpha 1-adrenoceptor antagonist, upon the slow inward Ca2+ current (ICa) was studied in single ventricular myocytes of the guinea-pig using a whole-cell patch-clamp technique. 2. Bunazosin (10-100 microM) decreased ICa in a concentration-dependent manner with an IC50 of 60 microM during depolarization to + 10 mV from the holding potential of -40 mV. 3. As for the inactivation process of ICa, the steady-state inactivation (f infinity) curve was shifted toward more negative potentials from -12 mV to -17 mV and -21 mV at f infinity = 0.5, by 30 microM and 70 microM bunazosin. 4. Inhibition of ICa by the compound (10 microM) was also dependent on stimulation frequency, with greater block induced at 2 Hz (50%) than at 0.33 Hz (13%). 5. It is concluded that bunazosin possesses a direct Ca2+ channel-blocking (class 4) action in a rate-dependent fashion.
Comparative Biochemistry and Physiology Part C Comparative Pharmacology and Toxicology 02/1991; 100(3):401-4.
[show abstract][hide abstract] ABSTRACT: Under whole cell patch conditions, 1389-S blocked the INa in guinea-pig ventricular myocytes under steady state conditions (Kdrest = 30 microM, Kdi = 2.4 microM) with a shift of the inactivation curve to the hyperpolarizing direction. Both brief and long conditioning pulses could produce a use-dependent block of 1389-S. These results suggest that 1389-S had a higher affinity to the inactivated than to the rested state under steady state conditions and had a higher affinity to the activated state during train pulses as well as to the inactivated state, making channels unavailable for conduction upon activation.
European Journal of Pharmacology 05/1990; 179(3):447-51. · 2.59 Impact Factor
[show abstract][hide abstract] ABSTRACT: STUDY OBJECTIVE - To examine the effect of 9-amino-1,2,3,4-tetrahydroacridine (THA), a compound similar to the K+ blocker 4-aminopyridine, on potassium channels in the sinoatrial node. DESIGN - The pacemaking portion of rabbit sinoatrial nodes was studied using the double microelectrode voltage clamp method in the presence of THA at various concentrations. MEASUREMENTS AND RESULTS - Above 1 mumol.litre-1, THA prolonged the spontaneous cycle length and the transmembrane action potential duration at 50% repolarisation. Above 10 mumol.litre-1, the compound also decreased the maximum rate of rise, the action potential amplitude, and the rate of diastolic depolarisation. Under voltage clamp conditions, THA reduced the time dependent K+ current (IK) in a dose dependent manner. Neither the decay process of IK nor its activation process were altered by THA. CONCLUSIONS - THA depresses sinoatrial node IK without changing its kinetics. Thus it may inhibit the open state of the potassium channels.
Cardiovascular Research 02/1990; 24(1):42-6. · 5.94 Impact Factor
[show abstract][hide abstract] ABSTRACT: 1. The electrophysiological effect of 9-amino-1,2,3,4-tetrahydroacridine (THA) on the rabbit sino-atrial node was studied using double-microelectrode voltage clamp methods. 2. THA (above 10 microM) caused statistically significant decreases in the maximum rate of rise, the action potential amplitude, the rate of diastolic depolarization, and increases in the spontaneous cycle length, the action potential duration at 50% repolarization. 3. On the current systems, THA obviously depressed the time-dependent outward K+ current. The compound also decreased the slow inward Ca2+ current and the hyperpolarization-activated inward current. 4. These findings indicate that THA exerts an inhibitory action on the automaticity of sino-atrial node via effects on both outward and inward current systems.
[show abstract][hide abstract] ABSTRACT: The effects of maprotiline and mianserin, tetracyclic antidepressant agents, on membrane potentials and currents of rabbit sinoatrial node cells were studied and compared to those of a tricyclic antidepressant compound, imipramine. Imipramine (10 microM), maprotiline (30 microM) and mianserin (100 microM) significantly decreased the spontaneous rate, the maximum rate of rise and the action potential amplitude. The slope of the diastolic depolarization was also decelerated by these drugs. On the current systems, imipramine (10 microM), maprotiline (10-30 microM) and mianserin (40-100 microM) decreased the slow inward current, the time-dependent potassium outward current and the hyperpolarization-activated inward current. Although all these antidepressant agents have qualitatively similar depressant effects, the inhibitory potency on the electrical activity of sinoatrial node was: imipramine greater than maprotiline greater than mianserin. These electrophysiological observations suggest that tetracyclic antidepressant agents might have less pronounced cardiotoxicity than did tricyclic antidepressants in slow response fibers.
Archives internationales de pharmacodynamie et de thérapie. 10/1987; 289(1):72-81.
[show abstract][hide abstract] ABSTRACT: The effects of cyproheptadine (0.1-10 microM) on the membrane potentials and currents of rabbit sinoatrial node were examined with the double-microelectrode voltage clamp technique. Cyproheptadine reduced the heart rate, maximum rate of depolarization and action potential amplitude. It also decreased the slope of phase 4 depolarization. On the current systems, cyproheptadine decreased the slow inward current (Isi), the time-dependent potassium outward current (Ik) and the hyperpolarization-activated current (Ih). The reduction of Isi was the major effect. Furthermore, Isi was progressively decreased by repetitive membrane depolarization during administration of cyproheptadine, an effect suggestive of frequency-dependent block of Isi. These electrophysiological observations indicate that cyproheptadine has a calcium antagonistic property, and additionally, decreases Ik and Ih in rabbit sinoatrial node.
European Journal of Pharmacology 08/1987; 139(3):307-13. · 2.59 Impact Factor
[show abstract][hide abstract] ABSTRACT: Effects of cibenzoline (0.1-30 microM) on membrane potentials and currents were investigated in rabbit sinoatrial node cells using conventional microelectrode and double microelectrode voltage clamp methods. Cibenzoline reduced the heart rate, the maximum rate of rise and the action potential amplitude in a dose-dependent manner. At the same time, the action potential duration at half-amplitude was prolonged, and the slope of phase 4 depolarization was decelerated. The voltage clamp experiment revealed that cibenzoline (7-30 microM) depressed the slow inward current, the time-dependent potassium outward current and the hyperpolarization activated current. Neither the kinetic variable of the time-dependent potassium outward current nor the decay time of the outward current tail was altered by the drug perfusion. The results suggest that cibenzoline exerts a depressant effect on the electrical activity of sinoatrial node cells and that the depression of the currents induced by cibenzoline is due to a reduction in conductances of the current systems.
Journal of Pharmacology and Experimental Therapeutics 07/1987; 241(3):982-6. · 3.89 Impact Factor