Karam F.A. Soliman

In vitro Attenuation of Nitric Oxide Production in C6 Astrocyte Cell Culture by Various Dietary Compounds

Abstract Excessive nitric oxide (NO) production in the brain has been correlated with neurotoxicity and the pathogenesis of several neurodegenerative diseases. NO production from neuroglial cells surrounding neurons contributes significantly to the pathogenesis of these diseases. The suppression of NO production in these cells may be beneficial in retarding many of these disorders. The present study was designed to evaluate the capacity of dietary-derived polyphenolic compounds, flavonoids, crude extracts, oils, and other food constituents in suppressing the release of NO from lipopolysaccharide (LPS)/gamma-interferon (IFN-γ) stimulated C6 astrocyte cells. In this experiment, 61 compounds were tested, and 36 showed significant suppressive effects of NO production. The results indicate that the following compounds exhibited a dose-dependent suppressive effect of NO production with an IC50 less than 10–3 M: quercetin, (–)-epigallocatechin gallate, morin, curcumin, apigenin, sesamol, chlorogenic acid, fisetin, (+)-taxifolin, (+)-catechin, ellagic acid, and caffeic acid. Compounds, which reduce NO production at less than 300 ppm, include milk thistle, silymarin, grapenol, and green tea. These results demonstrate a possible value for dietary compounds to inhibit the excessive production of NO.

Basic concepts of epigenetics: impact of environmental signals on gene expression.

Through epigenetic modifications, specific long-term phenotypic consequences can arise from environmental influence on slowly evolving genomic DNA. Heritable epigenetic information regulates nucleosomal arrangement around DNA and determines patterns of gene silencing or active transcription. One of the greatest challenges in the study of epigenetics as it relates to disease is the enormous diversity of proteins, histone modifications and DNA methylation patterns associated with each unique maladaptive phenotype. This is further complicated by a limitless combination of environmental cues that could alter the epigenome of specific cell types, tissues, organs and systems. In addition, complexities arise from the interpretation of studies describing analogous but not identical processes in flies, plants, worms, yeast, ciliated protozoans, tumor cells and mammals. This review integrates fundamental basic concepts of epigenetics with specific focus on how the epigenetic machinery interacts and operates in continuity to silence or activate gene expression. Topics covered include the connection between DNA methylation, methyl-CpG-binding proteins, transcriptional repression complexes, histone residues, histone modifications that mediate gene repression or relaxation, histone core variant stability, H1 histone linker flexibility, FACT complex, nucleosomal remodeling complexes, HP1 and nuclear lamins.

In Vitro Screening for the Tumoricidal Properties of International Medicinal Herbs

There is growing use of anticancer complementary and alternative medicines (CAMs) worldwide. The purpose of the current study is to assess a sizeable variety of natural and plant sources of diverse origin, to ascertain prospective research directives for cancer treatment and potential new chemotherapy drug sources. In this study, 374 natural extracts (10 µg/mL–5 mg/mL) were evaluated for dose‐dependent tumoricidal effects using immortal neuroblastoma of spontaneous malignant origin. The findings indicate no pattern of tumoricidal effects by diverse plants with similar families/genus under the classes Pinopsida, Equisetopsida, Lycopodiosida, Filicosida, Liliopsida Monocotyledons or Magnoliopsida Dicotyledons. The results indicate that many of the most commonly used CAMs exhibited relatively weak tumoricidal effects including cats claw, astragalus, ginseng, echinacea, mistletoe, milk thistle, slippery elm, cayenne, chamomile, don quai, meadowsweet, motherwort and shepherds purse. The data demonstrate that the most potent plant extracts were randomly dispersed within the plantae kingdom (LC50 = 31–490 µg/mL) in order of the lowest LC50 Dioscorea villosa (Dioscoreaceae) > Sanguinaria canadensis (Papaveraceae) > Dipsacus asper (Dipsacaceae) > Populus balsamifera (Salicaceae) > Boswellia carteri (Burseraceae) > Cyamopsis psoralioides (Fabaceae) > Rhamnus cathartica (Rhamnaceae) > Larrea tridentate (Zygophyllaceae) > Dichroa febrifuga (Hydrangeaceae) > Batschia canescens (Boraginaceae) > Kochia scoparia (Chenopodiaceae) > Solanum xanthocarpum (Solanaceae) > Opoponax chironium (Umbelliferae) > Caulophyllum thalictroides (Berberidaceae) > Dryopteris crassirhizoma (Dryopteridaceae) > Garcinia cambogia (Clusiaceae) > Vitex agnus‐castus (Verbenaceae) > Calamus draco (Arecaceae). These findings show tumoricidal effect by extracts of wild yam root, bloodroot, teasel root, bakuchi seed, dichroa root, kanta kari, garcinia fruit, mace, dragons blood and the biblically referenced herbs: balm of gilead bud, frankincense and myrrh gum. Copyright

The role of oxidative stress, impaired glycolysis and mitochondrial respiratory redox failure in the cytotoxic effects of 6-hydroxydopamine in vitro.

The neurotoxin, 6-hydroxydopamine (6-OHDA) has been implicated in the neurodegenerative process of Parkinsons disease. The current study was designed to elucidate the toxicological effects of 6-OHDA on energy metabolism in neuroblastoma (N-2A) cells. The toxicity of 6-OHDA corresponds to the total collapse of anaerobic/aerobic cell function, unlike other mitochondrial toxins such as MPP+ that target specific loss of aerobic metabolism. The toxicity of 6-OHDA paralleled the loss of mitochondrial oxygen (O2) consumption (MOC), glycolytic activity, ATP, H+ ion gradients, membrane potential and accumulation of the autoxidative product, hydrogen peroxide (H2O2). Removing H2O2 with nonenzymatic stoichiometric scavengers, such as carboxylic acids, glutathione and catalase yielded partial protection. The rapid removal of H2O2 with pyruvate or catalase restored only anaerobic glycolysis, but did not reverse the loss of MOC, indicating mitochondrial impairment is independent of H2O2. The H2O2 generated by 6-OHDA contributed toward the loss of anaerobic glycolysis through lipid peroxidation and lactic acid dehydrogenase inhibition. The ability of 6-OHDA to maintain oxidized cytochrome c (CYT-C-OX) in its reduced form (CYT-C-RED), appears to play a role in mitohondrial impairment. The reduction of CYT-C by 6-OHDA, was extensive, occurred within minutes, preceded formation of H2O2 and was unaffected by catalase or superoxide dismutase. At similar concentrations, 6-OHDA readily altered the valence state of iron [Fe(III)] to Fe(II), which would also theoretically sustain CYT-C in its reduced form. In isolated mitochondria, 6-OHDA had negligible effects on complex I, inhibited complex II and interfered with complex III by maintaining the substrate, CYT-C in a reduced state. 6-OHDA caused a transient and potent surge in isolated cytochrome oxidase (complex IV) activity, with rapid recovery as a result of 6-OHDA recycling CYT-C-OX to CYT-C-RED. Typical mitochondrial toxins such as MPP+, azide and antimycin appeared to inhibit the catalytic activity of ETC enzymes. In contrast, 6-OHDA alters the redox of the cytochromes, resulting in loss of substrate availability and obstruction of oxidation-reduction events. Complete cytoprotection against 6-OHDA toxicity and restored MOC was achieved by combining catalase with CYT-C (horse heart). In summary, CYT-C reducing properties are unique to catecholamine neurotransmitters, and may play a significant role in selective vulnerability of dopaminergic neurons to mitochondrial insults.

Ibuprofen and apigenin induce apoptosis and cell cycle arrest in activated microglia

In case of injury or disease, microglia are recruited to the site of the pathology and become activated as evidenced by morphological changes and expression of pro-inflammatory cytokines. Evidence suggests that microglia proliferate by cell division to create gliosis at the site of pathological conditions such as the amyloid plaques in Alzheimers disease and the substantia nigra of Parkinsons disease patients. The hyperactivation of microglia contributes to neurotoxicity. In the present study we tested the hypothesis that anti-inflammatory compounds modulate the progression of cell cycle and induce apoptosis of the activated cells. We investigated the effects of ibuprofen (non-steroidal anti-inflammatory drug) and apigenin (a flavonoid with anti-inflammatory and anti-proliferative properties) on the cell cycle of the murine microglial cell line BV-2. The findings indicate that apigenin-induced cell cycle arrest preferentially in the G2/M phase and ibuprofen caused S phase arrest. The binding of annexin V-FITC to the membranes of cells which indicates the apoptotic process were examined, whereas the DNA was stained with propidium iodide. Both apigenin and ibuprofen induced apoptosis significantly in early and late stages. The induction of apoptosis by ibuprofen and apigenin was confirmed using TUNEL assay, revealing that 25 microM apigenin and 250 microM ibuprofen significantly increased apoptosis in BV-2 cells. The results from the present study suggest that anti-inflammatory compounds might inhibit microglial proliferation by modulating the cell cycle progression and apoptosis.

Acetyl-l-carnitine cytoprotection against 1-methyl-4-phenylpyridinium toxicity in neuroblastoma cells

Acetyl-L-carnitine (ALCAR) plays an integral role in the transport of long chain fatty acids across the inner mitochondrial membrane for oxidative phosphorylation. In non-human primates, administration of ALCAR was reported to prevent 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurological injury to the substantia nigra. The present study investigates the effects of ALCAR against the toxicity of 1-methyl-4-phenylpyridinium (MPP(+)), the neurotoxic metabolite of MPTP, in murine brain neuroblastoma cells. MPP(+), a potent mitochondrial toxin, induced a dose-dependent reduction in mitochondrial oxygen consumption and cell viability, corresponding to an accelerated rate of cellular glucose utilization. Treatment with ALCAR, but not L-carnitine, prevented MPP(+) toxicity and partially restored intracellular ATP concentrations, but did not reverse the MPP(+)-induced loss of mitochondrial oxygen consumption. These data indicate that protective effects are independent of oxidative phosphorylation. ALCAR had a substantial glucose sparing effect in both controls and MPP(+)-treated groups, demonstrating a potential role in enhancing glucose utilization through glycolysis. Antagonizing the entry of fatty acids into the mitochondria, with either insulin or malonyl CoA, did not interfere with ALCAR protection against MPP(+). On the contrary, insulin potentiated the protective effects of ALCAR. In conclusion, these data indicate that ALCAR protects against MPP(+) toxicity, independent of mitochondrial oxidative capacity or beta-oxidation of fatty acids. In contrast, the protective effects of ALCAR appear to involve potentiation of energy derived from glucose through anaerobic glycolysis.

Manganese-induced oxidative DNA damage in neuronal SH-SY5Y cells: Attenuation of thymine base lesions by glutathione and N-acetylcysteine

Manganese (Mn) is an essential trace element required for normal function and development. However, exposure to this metal at elevated levels may cause manganism, a progressive neurodegenerative disorder with neurological symptoms similar to idiopathic Parkinsons disease (IPD). Elevated body burdens of Mn from exposure to parental nutrition, vapors in mines and smelters and welding fumes have been associated with neurological health concerns. The underlying mechanism of Mn neurotoxicity remains unclear. Accordingly, the present study was designed to investigate the toxic effects of Mn(2+) in human neuroblastoma SH-SY5Y cells. Mn(2+) caused a concentration dependent decrease in SH-SY5Y cellular viability compared to controls. The LD50 value was 12.98 μM Mn(2+) (p<0.001 for control vs. 24h Mn treatment). Both TUNEL and annexin V/propidium iodide (PI) apoptosis assays confirmed the induction of apoptosis in the cells following exposure to Mn(2+) (2 μM, 62 μM or 125 μM). In addition, Mn(2+) induced both the formation and accumulation of DNA single strand breaks (via alkaline comet assay analysis) and oxidatively modified thymine bases (via gas chromatography/mass spectrometry analysis). Pre-incubation of the cells with characteristic antioxidants, either 1mM N-acetylcysteine (NAC) or 1mM glutathione (GSH) reduced the level of DNA strand breaks and the formation of thymine base lesions, suggesting protection against oxidative cellular damage. Our findings indicate that (1) exposure of SH-SY5Y cells to Mn promotes both the formation and accumulation of oxidative DNA damage, (2) SH-SY5Y cells with accumulated DNA damage are more likely to die via an apoptotic pathway and (3) the accumulated levels of DNA damage can be abrogated by the addition of exogenous chemical antioxidants. This is the first known report of Mn(2+)-induction and antioxidant protection of thymine lesions in this SH-SY5Y cell line and contributes new information to the potential use of antioxidants as a therapeutic strategy for protection against Mn(2+)-induced oxidative DNA damage.

Cytoprotection of Pyruvic Acid and Reduced β-Nicotinamide Adenine Dinucleotide Against Hydrogen Peroxide Toxicity in Neuroblastoma Cells

Elevated production of hydrogen peroxide (H2O2) in the central nervous system has been implicated in the pathogenesis of several neurodegenerative diseases, including Parkinsons disease, ischemic reperfusion, stroke, and Alzheimers disease. Pyruvic acid has a critical role in energy metabolism and a capability to nonenzymatically decarboxylate H2O2 into H2O. This study examined the effects of glycolytic regulation of pyruvic acid on H2O2 toxicity in murine neuroblastoma cells. Glycolytic energy substrates including D-(+)-glucose, D-(−) fructose and the adenosine transport blocker dipyridamole, were not effective in providing protection against H2O2 toxicity, negating energy as a factor. On the other hand, pyruvic acid completely prevented H2O2 toxicity, restoring the loss of ATP and cell viability. H2O2 toxicity was also attenuated by d-fructose 1,6 diphosphate (FBP), phospho (enol) pyruvate (PEP), niacinamide, β-nicotinamide adenine dinucleotide (β-NAD+), and reduced form (β-NADH). Both FBP and PEP exerted positive kinetic effects on pyruvate kinase (PK) activity. Interestingly, only pyruvic acid and β-NADH exhibited powerful stoichiometric H2O2 antioxidant properties. Further, β-NADH may exert positive effects on PK activity. Subsequent pyruvic acid accumulation can lead to the recycling of β-NAD1 through lactate dehydrogenase and β-NADH through glyceraldehyde-3-phosphate dehydrogenase. It was concluded from these studies that intracellular pyruvic acid and β-NADH appear to act in concert through glycolysis, to enhance H2O2 intracellular antioxidant capacity in neuroblastoma cells. Future research will be required to examine whether similar effects are observed in primary neuronal culture or intact tissue.

Pyruvic acid cytoprotection against 1-methyl-4-phenylpyridinium, 6-hydroxydopamine and hydrogen peroxide toxicities in vitro.

The neuropathology of Parkinsons disease (PD) involves a reduction of endogenous antioxidant enzyme systems, heightened oxidative stress and mitochondrial aberrations in the region of the substantia nigra. Similarly, neurotoxins commonly used to investigate PD pathology include 6-hydroxydopamine (6-OHDA), a powerful hydrogen peroxide (H(2)0(2)) pro-oxidant and 1-methyl-4-phenylpyridinium ion (MPP+), a mitochondrial complex I inhibitor that exerts detrimental effects on cellular energy production. Pyruvic acid is a neuronal metabolic energy fuel that can also rapidly undergo decarboxylation to diffuse H(2)0(2) into H(2)0. In this study, we investigated the effect of pyruvic acid against 6-OHDA, MPP+ and H(2)0(2) toxicity in murine brain neuroblastoma cells. The results obtained indicated that the toxicity of 6-OHDA was inversely related to the autoxidative formation of H(2)0(2). Pyruvic acid exhibited powerful non-enzymatic stoichiometric H(2)0(2) trapping properties, and protected against both 6-OHDA and H(2)0(2) toxicity. While both sodium pyruvate and pyruvate were highly protective against oxidative stress, pyruvate in its free acid form only was protective against MPP+, indicating a requirement for effective transport in order to fuel glycolysis. The protective properties of glucose were compared to pyruvic acid, and the data indicated that glucose did not exhibit antioxidant properties and was effective in blocking MPP+, but not 6-OHDA or H(2)0(2) toxicity. On the other hand, pyruvic acid was protective against all three toxins, and unlike glucose, completely blocked MPP+ toxicity in a combination insult model with up to 500 microM of H(2)0(2). Moreover, the data obtained indicate that pyruvic acid exerts powerful neuroprotective properties by providing simultaneous resistance to oxidative stress and mitochondrial insult. These protective effects are the result of a unique dual property of pyruvic acid with concurrent ability to serve as an effective neuronal energy substrate for glycolysis and to act as an exceptionally powerful antioxidant.

Behavioral and neurochemical changes in the dopaminergic system after repeated cocaine administration

In order to determine whether repeated cocaine administration produced persistent changes in dopamine (DA) receptor binding and release consistent with behavioral sensitization, rats were treated with either cocaine (25 mg/kg ip) or saline twice daily for 14 consecutive days followed by a 3-d withdrawal period. The DA transporter site was assayed using [3H]GBR 12935, whereas D1 and D2 sites were assayed using [3H]SCH 23390 and [3H]spiperone, respectively. The density (Bmax) of the DA transporter binding sites in the ST of the cocaine-treated group increased significantly (p<0.05) over controls 3 d after the last injection, whereas the density of striatal D1 and D2 binding sites remained unchanged. The DA transporter in the nucleus accumbens (NA) was also studied with [3H]GBR 12935 and was unchanged following drug treatment. D1 and D2 binding parameters for the NA were not determined in this study. Furthermore, cocaine administration did not affect the affinities (Kd) of the radioligands used to label the transporter, D1, or D2 sites in any of the studies performed. In addition, striatal DA release was measured using in vivo microdialysis in anesthetized rats. Linear regression analysis on maximal decreases in DA release after apomorphine (0.02, 0.2, and 2.0 mg/kg sc) injection showed no difference in the functional capacity of the ST to modulate DA transmission between control and treated groups. Moreover, animals pretreated with cocaine showed a significant (p<0.01) decrease in locomotor activity (LA) after a presynaptic, autoregulating dose of apomorphine (0.03 mg/kg sc) was given. These results suggest that the effects seen after repeated exposure to cocaine may be regulated, in part, by changes in striatal DA transporter binding site densities and not necessarily by DA-releasing mechanisms or D1 and D2 receptor modification.