Octyl Gallate Inhibits ATP-induced Intracellular Calcium Increase in PC12 Cells by Inhibiting Multiple Pathways

Mango Fruit Extracts Differentially Affect Proliferation and Intracellular Calcium Signalling in MCF-7 Human Breast Cancer Cells

The assessment of human cancer cell proliferation is a common approach in identifying plant extracts that have potential bioactive effects. In this study, we tested the hypothesis that methanolic extracts of peel and flesh from three archetypal mango cultivars, Irwin (IW), Nam Doc Mai (NDM), and Kensington Pride (KP), differentially affect proliferation, extracellular signal-regulated kinase (ERK) activity, and intracellular calcium ([Ca2+]I) signalling in MCF-7 human breast cancer cells. Mango flesh extracts from all three cultivars did not inhibit cell growth, and of the peel extracts only NDM reduced MCF-7 cell proliferation. Mango cultivar peel and flesh extracts did not significantly change ERK phosphorylation compared to controls; however, some reduced relative maximal peak[Ca2+]Iafter adenosine triphosphate stimulation, with NDM peel extract having the greatest effect among the treatments. Our results identify mango interfruit and intrafruit (peel and flesh) extract variability in antiproliferative effects and[Ca2+]Isignalling in MCF-7 breast cancer cells and highlight that parts of the fruit (such as peel and flesh) and cultivar differences are important factors to consider when assessing potential chemopreventive bioactive compounds in plants extracts.

Cyanidin-3-glucoside Inhibits ATP-induced Intracellular Free Ca(2+) Concentration, ROS Formation and Mitochondrial Depolarization in PC12 Cells

Flavonoids have an ability to suppress various ion channels. We determined whether one of flavonoids, cyanidin-3-glucoside, affects adenosine 5'-triphosphate (ATP)-induced calcium signaling using digital imaging methods for intracellular free Ca(2+) concentration ([Ca(2+)]i), reactive oxygen species (ROS) and mitochondrial membrane potential in PC12 cells. Treatment with ATP (100µM) for 90 sec induced [Ca(2+)]i increases in PC12 cells. Pretreatment with cyanidin-3-glucoside (1µ g/ml to 100µg/ml) for 30 min inhibited the ATP-induced [Ca(2+)]i increases in a concentration-dependent manner (IC50=15.3µg/ml). Pretreatment with cyanidin-3-glucoside (15µg/ml) for 30 min significantly inhibited the ATP-induced [Ca(2+)]i responses following removal of extracellular Ca(2+) or depletion of intracellular [Ca(2+)]i stores. Cyanidin-3-glucoside also significantly inhibited the relatively specific P2X2 receptor agonist 2-MeSATP-induced [Ca(2+)]i responses. Cyanidin-3-glucoside significantly inhibited the thapsigargin or ATP-induced store-operated calcium entry. Cyanidin-3-glucoside significantly inhibited the ATP-induced [Ca(2+)]i responses in the presence of nimodipine and ω-conotoxin. Cyanidin-3-glucoside also significantly inhibited KCl (50 mM)-induced [Ca(2+)]i increases. Cyanidin-3-glucoside significantly inhibited ATP-induced mitochondrial depolarization. The intracellular Ca(2+) chelator BAPTA-AM or the mitochondrial Ca(2+) uniporter inhibitor RU360 blocked the ATP-induced mitochondrial depolarization in the presence of cyanidin-3-glucoside. Cyanidin-3-glucoside blocked ATP-induced formation of ROS. BAPTA-AM further decreased the formation of ROS in the presence of cyanidin-3-glucoside. All these results suggest that cyanidin-3-glucoside inhibits ATP-induced calcium signaling in PC12 cells by inhibiting multiple pathways which are the influx of extracellular Ca(2+) through the nimodipine and ω-conotoxin-sensitive and -insensitive pathways and the release of Ca(2+) from intracellular stores. In addition, cyanidin-3-glucoside inhibits ATP-induced formation of ROS by inhibiting Ca(2+)-induced mitochondrial depolarization.

Low-level laser therapy (810 nm) protects primary cortical neurons against excitotoxicity in vitro

Excitotoxicity describes a pathogenic process whereby death of neurons releases large amounts of the excitatory neurotransmitter glutamate, which then proceeds to activate a set of glutamatergic receptors on neighboring neurons (glutamate, N-methyl-D-aspartate (NMDA), and kainate), opening ion channels leading to an influx of calcium ions producing mitochondrial dysfunction and cell death. Excitotoxicity contributes to brain damage after stroke, traumatic brain injury, and neurodegenerative diseases, and is also involved in spinal cord injury. We tested whether low level laser (light) therapy (LLLT) at 810 nm could protect primary murine cultured cortical neurons against excitotoxicity in vitro produced by addition of glutamate, NMDA or kainate. Although the prevention of cell death was modest but significant, LLLT (3 J/cm(2) delivered at 25 mW/cm(2) over 2 min) gave highly significant benefits in increasing ATP, raising mitochondrial membrane potential, reducing intracellular calcium concentrations, reducing oxidative stress and reducing nitric oxide. The action of LLLT in abrogating excitotoxicity may play a role in explaining its beneficial effects in diverse central nervous system pathologies.

Low-level laser therapy (810 nm) protects primary cortical neurons against excitotoxicity in vitro

Excitotoxicity describes a pathogenic process whereby death of neurons releases large amounts of the excitatory neurotransmitter glutamate, which then proceeds to activate a set of glutamatergic receptors on neighboring neurons (glutamate, N-methyl-D-aspartate (NMDA), and kainate), opening ion channels leading to an influx of calcium ions producing mitochondrial dysfunction and cell death. Excitotoxicity contributes to brain damage after stroke, traumatic brain injury, and neurodegenerative diseases, and is also involved in spinal cord injury. We tested whether low level laser (light) therapy (LLLT) at 810 nm could protect primary murine cultured cortical neurons against excitotoxicity in vitro produced by addition of glutamate, NMDA or kainate. Although the prevention of cell death was modest but significant, LLLT (3 J/cm(2) delivered at 25 mW/cm(2) over 2 min) gave highly significant benefits in increasing ATP, raising mitochondrial membrane potential, reducing intracellular calcium concentrations, reducing oxidative stress and reducing nitric oxide. The action of LLLT in abrogating excitotoxicity may play a role in explaining its beneficial effects in diverse central nervous system pathologies.

Inhibitory effects of acorn extract on glutamate-induced calcium signaling in cultured rat hippocampal neurons

Various effects of acorn extract have been reported including antioxidant activity, cytotoxicity against cancer cells, and the levels of acetylcholine and its related enzyme activities in the dementia mouse models. However, it is unclear whether acorn extract inhibits glutamate-induced calcium signaling in hippocampal neurons. This study was an investigation into the effect of acorn extract on intracellular free Ca concentrations ([Ca]) in cultured rat hippocampal neurons using fura-2-based digital calcium imaging and photometry. Hippocampal neurons were used between 10 and 14 d in culture from embryonic day-18 rats. Treatment with acorn extract (1 µg/mL to 1 mg/mL) for 30 min inhibited glutamate (100 µM)-induced [Ca] increases in a dose-dependent manner (IC=46.9 µg/mL). After depletion of intracellular Ca stores by treatment with the inhibitor endoplasmic reticulum Ca-ATPase, thapsigargin (1 µM), treatment with acorn extract (50 µg/mL) for 30 min decreased the subsequent glutamate-induced [Ca] increases. Acorn extract significantly inhibited (S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) (30 µM)-induced [Ca] increases. In addition, acorn extract inhibited the AMPA-induced [Ca] responses in the presence of 1 µM nimodipine. Acorn extract also significantly inhibited N-methyl-D-aspartate (100 µM)-induced [Ca] increases. Acorn extract significantly inhibited 50 mM KCl -induced [Ca] increases. Acorn extract significantly inhibited (S)-3,5-dihydroxyphenylglycine-induced [Ca] responses. Moreover, acorn extract almost completely blocked synaptically mediated [Ca] spikes induced by decreasing extracellular Mg concentration to 0.1 mM. These results suggest that acorn extract inhibits synaptically induced frequent [Ca] spikes through multiple pathways such as ionotropic glutamate receptors, voltage-gated Ca channels and metabotropic glutamate receptors in cultured rat hippocampal neurons.

Physiological and cellular aspects of phytotoxicity tolerance in plants: the role of membrane transporters and implications for crop breeding for waterlogging tolerance

Waterlogging affects large areas of agricultural land, resulting in severe economic penalties because of massive losses in crop production. Traditionally, plant breeding for waterlogging tolerance has been based on the field assessment of a range of agronomic and morphological characteristics. This review argues for a need to move towards more physiologically based approaches by targeting specific cellular mechanisms underling key components of waterlogging tolerance in plants. Also, while the main focus of researchers was predominantly on plant anoxia tolerance, less attention was given to plant tolerance to phytotoxins under waterlogged conditions. This paper reviews the production of major elemental and organic phytotoxins in waterlogged soils and describes their adverse effects on plant performance. The critical role of plasma membrane transporters in plant tolerance to secondary metabolite toxicity is highlighted, and ionic mechanisms mediating the this tolerance are discussed. A causal link between the secondary metabolite-induced disturbances to cell ionic homeostasis and programmed cell death is discussed, and a new ethylene-independent pathway for aerenchyma formation is put forward. It is concluded that plant breeding for waterlogging tolerance may significantly benefit from targeting mechanisms of tolerance to phytotoxins.

Functional Expression of P2Y Receptors in WERI-Rb1 Retinoblastoma Cells

P2Y receptors are metabotropic G-protein-coupled receptors, which are involved in many important biologic functions in the central nervous system including retina. Subtypes of P2Y receptors in retinal tissue vary according to the species and the cell types. We examined the molecular and pharmacologic profiles of P2Y purinoceptors in retinoblastoma cell, which has not been identified yet. To achieve this goal, we used Ca(2+) imaging technique and western blot analysis in WERI-Rb-1 cell, a human retinoblastoma cell line. ATP (10 µM) elicited strong but transient [Ca(2+)](i) increase in a concentration-dependent manner from more than 80% of the WERI-Rb-1 cells (n=46). Orders of potency of P2Y agonists in evoking [Ca(2+)](i) transients were 2MeS-ATP>ATP>>UTP=αβ-MeATP, which was compatible with the subclass of P2Y(1) receptor. The [Ca(2+)](i) transients evoked by applications of 2MeS-ATP and/or ATP were also profoundly suppressed in the presence of P2Y(1) selective blocker (MRS 2179; 30 µM). P2Y(1) receptor expression in WERI-Rb-1 cells was also identified by using western blot. Taken together, P2Y(1) receptor is mainly expressed in a retinoblastoma cell, which elicits Ca(2+) release from internal Ca(2+) storage sites via the phospholipase C-mediated pathway. P2Y(1) receptor activation in retinoblastoma cell could be a useful model to investigate the role of purinergic [Ca(2+)](i) signaling in neural tissue as well as to find a novel therapeutic target to this lethal cancer.