thiourea and Neuroblastoma

The prognosis for patients with relapsed or refractory high-risk neuroblastoma remains dismal and novel therapeutic options are urgently needed. The RIST treatment protocol has a multimodal metronomic therapy design combining molecular-targeted drugs (Rapamycin and Dasatinib) with chemotherapy backbone (Irinotecan and Temozolomide), which is currently verified in a phase II clinical trial (NCT01467986). With the availability of novel and more potent ATP competitive mTOR inhibitors, we expect to improve the RIST combination therapy. By comparing the IC

Topics: Administration, Metronomic; Antineoplastic Combined Chemotherapy Protocols; Cell Line, Tumor; Cell Survival; Dasatinib; Dose-Response Relationship, Drug; Drug Screening Assays, Antitumor; Drug Synergism; Humans; Indoles; Inhibitory Concentration 50; Irinotecan; Naphthyridines; Neuroblastoma; Purines; Pyrimidines; Signal Transduction; Sirolimus; Temozolomide; Thiourea; TOR Serine-Threonine Kinases

Activation of presynatic histamine H(3) receptors (H(3)R) down-regulates norepinephrine exocytosis from cardiac sympathetic nerve terminals, in both normal and ischemic conditions. Analogous to the effects of alpha(2)-adrenoceptors, which also act prejunctionally to inhibit norepinephrine release, H(3)R-mediated antiexocytotic effects could result from a decreased Ca(2+) influx into nerve endings. We tested this hypothesis in sympathetic nerve terminals isolated from guinea pig heart (cardiac synaptosomes) and in a model human neuronal cell line (SH-SY5Y), which we stably transfected with human H(3)R cDNA (SH-SY5Y-H(3)). We found that reducing Ca(2+) influx in response to membrane depolarization by inhibiting N-type Ca(2+) channels with omega-conotoxin (omega-CTX) greatly attenuated the exocytosis of [(3)H]norepinephrine from both SH-SY5Y and SH-SY5Y-H(3) cells, as well as the exocytosis of endogenous norepinephrine from cardiac synaptosomes. Similar to omega-CTX, activation of H(3)R with the selective H(3)R-agonist imetit also reduced both the rise in intracellular Ca(2+) concentration (Ca(i)) and norepinephrine exocytosis in response to membrane depolarization. The selective H(3)R antagonist thioperamide prevented this effect of imetit. In the parent SH-SY5Y cells lacking H(3)R, imetit affected neither the rise in Ca(i) nor [(3)H]norepinephrine exocytosis, demonstrating that the presence of H(3)R is a prerequisite for a decrease in Ca(i) in response to imetit and that H(3)R activation modulates norepinephrine exocytosis by limiting the magnitude of the increase in Ca(i). Inasmuch as excessive norepinephrine exocytosis is a leading cause of cardiac dysfunction and arrhythmias during acute myocardial ischemia, attenuation of norepinephrine release by H(3)R agonists may offer a novel therapeutic approach to this condition.

Topics: Animals; Calcium; Calcium Channel Blockers; Cell Line; Dose-Response Relationship, Drug; Exocytosis; Guinea Pigs; Histamine Agonists; Humans; Imidazoles; Male; Myocardial Ischemia; Myocardium; Neuroblastoma; Neurons; Norepinephrine; omega-Conotoxins; Potassium; Receptors, Histamine H3; Thiourea; Time Factors; Transfection; Tumor Cells, Cultured

The effects of the Na+-Ca2+ exchange inhibitor 2-[2-[4-(4-nitrobenzyloxy)phenyl]ethyl]isothiourea methanesulfonate (KB-R7943) on depolarization-induced Ca2+ signal and [3H]noradrenaline release were examined in SH-SY5Y cells. KB-R7943 at 10 microM significantly inhibited high K+-induced increase in intracellular Ca2+ concentration. KB-R7943 also inhibited high K+-evoked release of [3H]noradrenaline from the cells. These findings suggest that the Na+-Ca2+ exchanger in the reverse mode is involved at least partly in depolarization-induced transmitter release.

Topics: Calcium; Enzyme Inhibitors; Humans; Intracellular Fluid; Neuroblastoma; Norepinephrine; Potassium; Sodium-Calcium Exchanger; Thiourea; Tritium; Tumor Cells, Cultured

PTU markedly enhanced the cytotoxic effects of CuCl2 on chick embryonic PECs cultured in vitro. We investigated this newly discovered effect of PTU and its analogues in relation to the toxic effects of Cu ion. Most PECs maintained in medium containing 0.5 mM PTU were lysed within 4 h by the addition of 0.1 mM CuCl2, which addition killed no PECs in the absence of PTU. The effect of PTU was not specific to PECs. All the cell lines tested, KB, N-18, N-115 and B-16, reacted against exogenous Cu in the presence of PTU as did the PECs. Analogues of PTU had effects on PECs similar to those on PTU in the presence of Cu ion. ANTU had a greater effect than PTU. MTU and TU had less effect than PTU. PTU did not affect the cytolysis induced by the addition of the divalent cations Mn, Co and Zn. About 6-fold the 64Cu-uptake by PECs was scored in the presence of PTU. The relation between this cytotoxic-enhancing effect and other biological activities of PTU are discussed.

Topics: Animals; Carcinoma, Squamous Cell; Cations, Divalent; Cell Division; Cell Line; Cell Survival; Chick Embryo; Copper; Dose-Response Relationship, Drug; Drug Interactions; Epithelium; Humans; Kinetics; Melanoma; Mice; Neuroblastoma; Phenylthiourea; Pigmentation; Thiourea