PAN-811 (3-Aminopyridine-2-carboxaldehyde thiosemicarbazone), a novel neuroprotectant, elicits its function in primary neuronal cultures by up-regulating Bcl-2 expression

Protective effects of N(1)-2,4-dihydroxybenzylidene-N(4)-2-hydroxybenzylidene-S-methyl-thiosemicarbazidato-oxovanadium (IV) on oxidative brain injury in streptozotocin-induced diabetic rats

Diabetes is usually accompanied by increased production of free radicals or impaired antioxidant defenses. The brain is a target tissue of the oxidative attacks caused by diabetes, and there are observed changes in the biochemical parameters of this tissue in the hyperglycemic state. In this study, we aimed to show the effect of N(1)-2,4-dihydroxybenzylidene-N(4)-2-hydroxybenzylidene-S-methyl-thiosemicarbazidato-oxovanadium (IV) (VOL) compound on diabetic damaged brain tissue, induced by streptozotocin (STZ) on 3.0-3.5-month-old male rats. Single dose of STZ at 65 mg/kg was used to make rats diabetic. Four groups were created randomly. Group (i): control (intact) animals; Group (ii): VOL given control animals; Group (iii): STZ-induced diabetic animals; and Group (iv): orally VOL administered STZ-induced diabetic rats. VOL (0.2 mM/kg/day) administration to control and diabetic animals was performed for a period of 12 days. At the end of day 12, the brain tissues were taken and homogenized. The clear supernatants were used for the determination of glutathione (GSH), lipid peroxidation (LPO), nonenzymatic glycosylation (NEG), and protein levels. Alanine and aspartate transaminases and acetylcholinesterase (AChE), myeloperoxidase (MPO), xanthine oxidase (XO), and oxidative stress marker enzymes activities were also estimated from the homogenates. According to the obtained results, there is found significant elevation of MDA and NEG levels and activities of transaminases, MPO and XO; whereas the GSH content and the activities of AChE and antioxidant enzymes were strongly decreased in the STZ-induced diabetic brain tissues in comparison to control group animals. Twelve days of administration of VOL complex to the diabetic animals reversed all biochemical parameters significantly in diabetic brain tissues. Our findings suggest that the VOL complex may be an ideal candidate to be used as an anti diabetic agent to improve oxidative injury and protect the brain tissue against damage caused by diabetes. This healing effect of the VOL complex may be due to its antioxidant activity and the insulin-mimetic effects of vanadium.

Four copper(II) compounds synthesized by anion regulation: Structure, anticancer function and anticancer mechanism

Copper (Cu) compounds are a promising candidate for next generation metal anticancer drugs. Therefore, we regulated anions to synthesize four mononuclear and binuclear Cu(II) compounds derived from thiosemicarbazone Schiff base ligands and characterized them. Four of these compounds showed very high cytotoxicity to cancer cell lines in vitro. These Cu(II) compounds strongly promoted the apoptosis of BEL-7404 cells and had a capacity to arrest the cell cycle at S phase of those cells. Furthermore, reactive oxygen species (ROS), mitochondrial membrane potential and Western blot analyses revealed that these Cu(II) compounds exert their cytotoxicity through an ROS-mediated intrinsic mitochondrial pathway accompanied by the regulation of Bcl-2 family proteins.

Thiosemicarbazone p-Substituted Acetophenone Derivatives Promote the Loss of Mitochondrial Δψ, GSH Depletion, and Death in K562 Cells

A series of thiosemicarbazone (TSC) p-substituted acetophenone derivatives were synthesized and chemically characterized. The p-substituents appended to the phenyl group of the TSC structures were hydrogen, fluor, chlorine, methyl, and nitro, producing compounds named TSC-H, TSC-F, TSC-Cl, TSC-Me, and TSC-NO₂, respectively. The TSC compounds were evaluated for their capacity to induce mitochondrial permeability, to deplete mitochondrial thiol content, and to promote cell death in the K562 cell lineage using flow cytometry and fluorescence microscopy. TSC-H, TSC-F, and TSC-Cl exhibited a bell-shaped dose-response curve for the induction of apoptosis in K562 cells due to the change from apoptosis to necrosis as the principal mechanism of cell death at the highest tested doses. TSC-Me and TSC-NO₂ exhibited a typical dose-response profile, with a half maximal effective concentration of approximately 10 µM for cell death. Cell death was also evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, which revealed lower toxicity of these compounds for peripheral blood mononuclear cells than for K562 cells. The possible mechanisms leading to cell death are discussed based on the observed effects of the new TSC compounds on the cellular thiol content and on mitochondrial bioenergetics.

Microwave assisted synthesis and solid-state characterization of lithocholyl amides of isomeric aminopyridines

Microwave (MW) assisted synthesis and solid state structural characterizations of novel lithocholyl amides of 2-, 3-, and 4-aminopyridine are reported. It is shown that the MW technique is a proper method in the preparation of N-lithocholyl amides of isomeric aminopyridines. It offers many advantages compared to conventional heating. The molecular and crystal structures as well as the polymorphic and hydrated forms of prepared conjugates with their thermodynamic stabilities have been characterized by means of high resolution liquid- and solid-state NMR spectroscopy, single crystal and powder X-ray diffraction, and thermogravimetric analysis. Owing to the many biological functions of bile acids and amino substituted nitrogen heterocycles, knowledge of the crystal packing of these novel conjugates may have relevance for potential pharmaceutical applications.

Identification and characterization of thiosemicarbazones with antifungal and antitumor effects: cellular iron chelation mediating cytotoxic activity

Thiosemicarbazones derived from acetylpyrazines were prepared by condensing an acetylpyrazine or a ring-substituted acetylpyrazine with thiosemicarbazide. Using the same procedure, N, N-dimethylthiosemicarbazones were synthesized from acetylpyrazines and N, N-dimethylthiosemicarbazide. A total of 20 compounds (16 novel) were chemically characterized and then tested for antifungal effects on eight strains of fungi and also for antitumor activity against SK-N-MC neuroepithelioma cells. The most effective compound identified in terms of both antifungal and antitumor activity was N, N-dimethyl-2-(1-pyrazin-2-ylethylidene)hydrazinecarbothioamide (5a). The mechanism of action of this and its related thiosemicarbazones was due, at least in part, to its ability to act as a tridentate ligand that binds metal ions. This was deduced from preparation of the related thiosemicarbazones [acetophenone thiosemicarbazone (6) and acetophenone N, N-dimethylthiosemicarbazone (7)] that do not possess a coordinating ring-N, which plays a vital role in metal ion chelation. Furthermore, 5a and several other thiosemicarbazones that showed high antiproliferative activity were demonstrated to have marked iron (Fe) chelation efficacy. In fact, these agents were highly effective at mobilizing (59)Fe from prelabeled SK-N-MC cells and preventing (59)Fe uptake from the serum Fe transport protein, transferrin. In contrast, compounds 6 and 7 that do not possess a tridentate metal-binding site showed little activity. Further studies examining ascorbate oxidation demonstrated that the Fe complexes of the most effective compounds were redox-inactive. Thus, in contrast to other thiosemicarbazones with potent antiproliferative activity, Fe chelation and mobilization rather than free radical generation played a significant role in the cytotoxic effects of the current ligands.

Pinocembrin prevents glutamate-induced apoptosis in SH-SY5Y neuronal cells via decrease of bax/bcl-2 ratio

Pinocembrin is the most abundant flavonoids in propolis, and has been proven to have antioxidant, antibacterial and anti-inflammatory property. To assess the protective effects of pinocembrin on neurons, SH-SY5Y neuronal cells were pretreated with pinocembrin for 2 h followed by co-treatment with glutamate (2 mM) for 12 h. Cell viability was determined by(3,4,5-dimethylthiazol-2-yl)-2,5-diphenylte-trazolium bromide assay, and apoptosis was confirmed by cell morphology, capillary zone electrophoresis and flow cytometry assay. Cell morphology was evaluated with Hoechst33258/PI dye. Treatment with pinocembrin (10(-5), 10(-6), 10(-7) mol/l) increased cell viability dose-dependently, inhibited LDH release and attenuated apoptosis. Intracellular free [Ca(2+)] was increased after glutamate exposure, and this increase was attenuated in cells treated with pinocembrin. bax mRNA expression increased remarkably following glutamate exposure and pinocembrin treatment manifested a reduction effect. bcl-2 mRNA expression changes were not detected in groups with or without pinocembrin. Western blotting results indicated that pinocembrin treatment reduced the expression of Bax and had no effect on Bcl-2, thus decreased the Bax-Bcl-2 ratio, which is in consistent with the gene expression result. Pinocembrin could also down-regulate the expression of p53 protein, and inhibit the release of cytochrome c from mitochondria to cytosol. Thus we conclude that pinocembrin exerts its neuroprotective effects in glutamate injury model partly by inhibiting p53 expression, thus Bax-Bcl-2 ratio, and the release of cytochrome c.

PAN-811 provides neuroprotection against glutamate toxicity by suppressing activation of JNK and p38 MAPK

In an earlier study, we demonstrated that PAN-811 (3-aminopyridine-2-carboxaldehyde thiosemicarbazone), a novel neuroprotectant, provides protection against glutamate, staurosporine, veratridine, or hypoxia/hypoglycemia toxicities in primary cortical neuronal cultures by upregulating Bcl-2 expression [R.-W. Chen, C. Yao, X.C. Lu, Z.-G. Jiang, R. Whipple, Z. Liao, H.A. Ghanbari, B. Almassian, F.C. Tortella, J.R. Dave. PAN-811 (3-aminopyridine-2-carboxaldehyde thiosemicarbazone), a novel neuroprotectant, elicits its function in primary neuronal cultures by upregulating Bcl-2 expression. Neuroscience 135 (2005) 191-201]. Both JNK (c-Jun N-terminal kinase) and p38 MAP (mitogen-activated protein) kinase activation have a direct inhibitory action on Bcl-2 by phosphorylation. In the present study, we continued to explore the mechanism of PAN-811 neuroprotection. Our results indicate that treatment of cultured cortical neurons with glutamate (100 microM) induces phosphorylation of both JNK and p38 MAPK. Specifically, pretreatment of neurons with 10 microM PAN-811 (an optimal neuroprotective concentration) for 1h, 4h, or 24h significantly suppresses glutamate-mediated activation of both JNK and p38 MAPK. Furthermore, the p38 MAPK-specific inhibitor SB203580 and the JNK-specific inhibitor SP600125 prevented glutamate-induced neuronal death in these primary cultures. Our results demonstrate that glutamate-induced phosphorylation of JNK and p38 MAPK is suppressed by PAN-811, which might contribute to Bcl-2 upregulation and PAN-811 neuroprotection.

Broad spectrum neuroprotection profile of phosphodiesterase inhibitors as related to modulation of cell-cycle elements and caspase-3 activation

Cellular injury can involve the aberrant stimulation of cell cycle proteins in part through activation of phosphodiesterases (PDEs) and downstream expression of cell-cycle components such as cyclin D1. In mature non-proliferating cells activation of the cell cycle can lead to the induction of programmed cell death. In the present study, we investigated the in vitro neuroprotective efficacy and mechanism of action of vinpocetine (PDE1 inhibitor), trequinsin (PDE3 inhibitor), and rolipram (PDE4 inhibitor) in four mechanistically-distinct models of injury to primary rat cortical neurons as related to cell cycle regulation and apoptosis. Cellular injury was induced by hypoxia/hypoglycemia, veratridine (10 microM), staurosporine (1 microM), or glutamate (100 microM), resulting in average neuronal cell death rates of 43-48% as determined by MTT assay. Treatment with each PDE inhibitor (PDEI) resulted in a similar concentration-dependent neuroprotection profile with maximal effective concentrations of 5-10 microM (55-77% neuroprotection) in all four neurotoxicity models. Direct cytotoxicity due to PDE inhibition alone was not observed at concentrations below 100 microM. Further studies indicated that PDEIs can suppress the excitotoxic upregulation of cyclin D1 similar to the effects of flavopiridol, a cyclin-dependent kinase inhibitor, including suppression of pro-apoptotic caspase-3 activity. Overall, these data indicate that PDEIs are broad-spectrum neuroprotective agents acting through modulation of cell cycle elements and may offer a novel mode of therapy against acute injury to the brain.

Evaluation of gabapentin and ethosuximide for treatment of acute nonconvulsive seizures following ischemic brain injury in rats

Acute seizures following brain injury have been associated with a worsening of patient outcome, but they are often undiagnosed and untreated when they occur without motor convulsions. Here, we sought to compare the antiseizure profile of ethosuximide (EXM; 125-312.5 mg/kg i.v.) and gabapentin (GBP; 0.3-50 mg/kg. i.v.) in a rat model of nonconvulsive seizures (NCS) induced by brain ischemia. Seizures were detected by continuous electroencephalographic monitoring for 24 h following permanent middle cerebral artery occlusion (MCAo). Both "preseizure" and "postseizure" treatment effects were evaluated. Control rats experienced a 91% incidence of NCS (averaging 10-11 NCS/rat), which was significantly reduced following preseizure treatment (delivered 20 min post-MCAo) with either EXM (ED(50) = 161 mg/kg) or GBP (ED(50) = 10.5 mg/kg). In contrast to preseizure treatment effects, only GBP reduced NCS when given after the first seizure event. A further, albeit nonsignificant, 20% reduction in NCS incidence was measured when given in combination postseizure. Drug treatment also reduced infarct volume, which was positively correlated to the number of NCS events (r = 0.475; P < 0.001). EXM and GBP treatment of cultured neurons exposed to neurotoxic or ischemic insults showed no neuroprotective effects, suggesting that in vivo neuroprotection can be attributed to anti-seizure effects. We conclude that EXM and GBP significantly attenuate NCS in a dose-related manner and may help to improve patient outcome from brain ischemia-induced seizure activity.

Neuroprotective activity of 3-aminopyridine-2-carboxaldehyde thiosemicarbazone (PAN-811), a cancer therapeutic agent

3-aminopyridine-2-carboxaldehyde thiosemicarbazone (3-AP) is a highly-hydrophobic small molecule that was originally developed for cancer therapy (Triapine, Vion Pharmaceuticals) due to its ability to inhibit ribonucleotide reductase, a key enzyme required for DNA synthesis. 3-AP has a high affinity for divalent cations, chelating the Fe(2+) at the R2 subunit of the enzyme and inhibiting formation of a tyrosyl radical essential for ribonucleotide reduction. We have demonstrated that 3-AP is also a potent neuroprotectant (as such, it is referred to as "PAN-811"). In vitro it completely blocks ischemic neurotoxicity at a concentration of 0.5 microM (EC(50) approximate, equals 0.35 microM) and hypoxic toxicity at 1.2 microM (EC(50) approximate, equals 0.75 microM). Full protection of primary cortical and striatal neurons can be achieved with 3-AP when it is added to the medium at up to six hours after an ischemic insult. 3-AP also suppresses cell death induced by neurotoxic agents, including staurosporine, veratridine and glutamate, indicating activity against a central target(s) in the neurodegenerative process. 3-AP acts via neutralization of two important intracellular effectors of excitatory neurotoxicity; calcium and free radicals. Its reported ability to elevate anti-apoptotic proteins is likely to be a consequence of the suppression of excessive intracellular free calcium. In a rat model of transient ischemia, a single bolus delivery of 3-AP 1 h after the initiation of ischemic attack reduced infarct volume by 59% when administered i.c.v. (50 mug per rat) and by 35% when administered i.v. (1 mg/kg). In Phase I clinical trials in cancer therapy 3-AP had no cardiovascular, CNS or other major adverse effects. Thus, 3-AP has a high potential for development as a novel, potent neuroprotectant for the treatment of neurodegenerative diseases.