yo-pro-1 and Astrocytoma

On a daily basis we are exposed to cationic nanoparticulates in many different ways. They are known to distribute to many organs of the body, and while some evidence suggests that these nanoparticles are toxic to cells, the mechanism of their toxicity is not clear. Here we apply a combination of biochemical and imaging techniques to study the mechanism by which amine-modified polystyrene nanoparticles induce cell death in a human brain astrocytoma cell line. Flow cytometry analysis of cells exposed to cationic nanoparticles revealed an increase in cell membrane permeability of the dyes YoPro-1 and propidium iodide, indicating onset of an apoptotic followed by a secondary necrotic response. Activation of caspases 3/7 and 9 and cleavage of poly(ADP-ribose) polymerase (PARP)-1 was also detected, providing clear molecular evidence of the apoptotic pathway induced by the nanoparticles. Transmission electron microscopy also revealed that these nanoparticles induce morphological changes in lysosomes and mitochondria, consistent with our observation of a rapid increase in the formation of reactive oxygen species in these cells. Together these results suggest that amine-modified polystyrene nanoparticles can mediate cell death through an apoptotic mechanism mediated by damage to the mitochondria.

Topics: Amines; Analysis of Variance; Apoptosis; Astrocytoma; Benzoxazoles; Caspases; Cations; Cell Line, Tumor; Cell Survival; Enzyme Induction; Fluorescent Dyes; Humans; Isoenzymes; Lysosomes; Mitochondria; Nanoparticles; Polystyrenes; Propidium; Quinolinium Compounds; Reactive Oxygen Species

ATP-sensitive P2X7 receptors are localized on cells of immunological origin including peripheral macrophages and glial cells in the CNS. Activation of P2X7 receptors leads to rapid changes in intracellular calcium concentrations, release of the pro-inflammatory cytokine IL-1beta, and following prolonged agonist exposure, the formation of cytolytic pores in plasma membranes. Data from gene knockout studies and recently described selective antagonists indicate a role for P2X7 receptor activation in inflammation and pain. While several species selective P2X7 antagonists exist, A-804598 represents a structurally novel, competitive, and selective antagonist that has equivalent high affinity at rat (IC50 = 10 nM), mouse (IC50 = 9 nM) and human (IC50 = 11 nM) P2X7 receptors. A-804598 also potently blocked agonist stimulated release of IL-1beta and Yo-Pro uptake from differentiated THP-1 cells that natively express human P2X7 receptors. A-804598 was tritiated ([3H]A-804598; 8.1Ci/mmol) and utilized to study recombinant rat P2X7 receptors expressed in 1321N1 cells. [3H]A-804598 labeled a single class of high affinity binding sites (Kd=2.4 nM and apparent Bmax=0.56 pmol/mg). No specific binding was observed in untransfected 1321N1 cells. The pharmacological profile for P2X antagonists to inhibit [3H]A-804598 binding correlated with their ability to block functional activation of P2X7 receptors (r=0.95, P<0.05). These data demonstrate that A-804598 is one of the most potent and selective antagonists for mammalian P2X7 receptors described to date and [3H]A-804598 is a high affinity antagonist radioligand that specifically labels rat P2X7 receptors.

Topics: Adenosine Triphosphate; Animals; Astrocytoma; Benzoxazoles; Binding, Competitive; Calcium; Cell Line, Tumor; Cell Membrane; Dose-Response Relationship, Drug; Guanidines; Humans; Inhibitory Concentration 50; Interleukin-1beta; Mice; Purinergic P2 Receptor Antagonists; Quinolines; Quinolinium Compounds; Radioligand Assay; Rats; Receptors, Purinergic P2; Receptors, Purinergic P2X7; Recombinant Proteins; Transfection; Tritium

Acute activation of P2X7 receptors rapidly opens a non-selective cation channel. Sustained P2X7 receptor activation leads to the formation of cytolytic pores, mediated by downstream recruitment of hemichannels to the cell surface. Species- and single-nucleotide polymorphism-mediated differences in P2X7 receptor activation have been reported that complicate understanding of the physiological role of P2X7 receptors. Studies were conducted to determine pharmacological differences between human, rat and mouse P2X7 receptors.. Receptor-mediated changes in calcium influx and Yo-Pro uptake were compared between recombinant mouse, rat and human P2X7 receptors. For mouse P2X7 receptors, wild-type (BALB/c) and a reported loss of function (C57BL/6) P2X7 receptor were also compared.. BzATP [2,3-O-(4-benzoylbenzoyl)-ATP] was more potent than ATP in stimulating calcium influx and Yo-Pro uptake at rat, human, BALB/c and C57BL/6 mouse P2X7 receptors. Two selective P2X7 receptor antagonists, A-740003 and A-438079, potently blocked P2X7 receptor activation across mammalian species. Several reported P2X1 receptor antagonists [e.g. MRS 2159 (4-[(4-formyl-5-hydroxy-6-methyl-3-[(phosphonooxy)methyl}-2-pyridinyl)azo]-benzoic acid), PPNDS and NF279] blocked P2X7 receptors. NF279 fully blocked human P2X7 receptors, but only partially blocked BALB/c P2X7 receptors and was inactive at C57BL/6 P2X7 receptors.. These data provide new insights into P2X7 receptor antagonist pharmacology across mammalian species. P2X7 receptor pharmacology in a widely used knockout background mouse strain (C57BL/6) was similar to wild-type mouse P2X7 receptors. Several structurally novel, selective and competitive P2X7 receptor antagonists show less species differences compared with earlier non-selective antagonists.

Topics: Animals; Astrocytoma; Benzoxazoles; Calcium; Cell Line, Tumor; Fluorescent Dyes; Humans; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Knockout; Purinergic P2 Receptor Agonists; Purinergic P2 Receptor Antagonists; Quinolinium Compounds; Rats; Receptors, Purinergic P2; Receptors, Purinergic P2X7; Species Specificity