Kinase experiment:

Human astrocytoma cells, 1321N1, are grown to stably express rat P2X7, human P2X4, P2X2a, P2X2/3, P2X1, P2Y1 and P2Y2 recombinant receptors. Agonist, BzATP, 2,3-O-(4-ben-zoylbenzoyl)-ATP or ATP-induced changes in intracellular Ca2+ concentrations are assessed in all of the cell lines using the Ca2+ chelating dye, Fluo-4, in conjunction with a Fluorometric Imaging Plate Reader. The cells are plated out the day before the experiment onto poly-D-lysine-coated black 96 well plates. After the agonist addition, changes in intracellular Ca2+ concentrations are recorded, per second, for 3 min. Ligands are tested at 11 half-log concentrations from 10-10 to 10-4 M. BzATP or ATP concentrations corresponds to the EC70 values for each receptor to enable comparison of antagonist potencies across the multiple P2 receptor subtypes. A 438079 is added to the cell plate and fluorescence data are collected for 3 min before the addition of agonist, subsequently, data are then collected for another 2 min. The pEC50 or pIC50 values are derived from a single curve fit.

Animal experiment:

To confirm A 438079 reach the brain after systemic administration, P10 rat pups are injected with 5 mg/kg A 438079 and killed either 10 min, 30 min, or 2 h later (n=4 per group). Blood samples are centrifuged at 1000×g for 10 min to isolate the plasma. Samples are analyzed using liquid chromatography-mass spectrometry (LC-MS/MS) by a service provider. Briefly, protein is precipitated from 50 μL aliquots of the individual plasma or brain tissue homogenate, and A 438079 is quantified by LC-MS/MS from a five-point standard curve.

A 438079 hydrochloride is a selective antagonist of P2X7 receptor with IC50 values of 100 and 300 nM in rat and human, respectively [1].

A 438079 is a derivative of the origin compound tetrazole 5 selected out as a novel P2X7 receptor antagonist. In human 1321N1 astrocytoma cells with expressing recombinant human P2X7, A 438079 treatment suppressed the Ca²⁺flux with pIC50 value of 6.9. In the pore formation assay, A 438079 blocked the pore formation of human THP-1 cells and prevented the cells from uptaking the diiodide dye YO-PRO. Moreover, in the spinal nerve ligation model, administration of A 438079 reduced the neuropathic pain induced by the application of a von Frey hair. The ED50 value was 76 μM/kg [2].

References:
1. Nelson D W, Gregg R J, Kort M E, et al. Structure-activity relationship studies on a series of novel, substituted 1-benzyl-5-phenyltetrazole P2X7 antagonists. Journal of medicinal chemistry, 2006, 49(12): 3659-3666.
2. Donnelly-Roberts D L, Jarvis M F. Discovery of P2X7 receptor-selective antagonists offers new insights into P2X7 receptor function and indicates a role in chronic pain states. British journal of pharmacology, 2007, 151(5): 571-579.