Nicotinamide Glycolates Antagonize CXCR2 Activity through an Intracellular Mechanism
作者:Dean Y. Maeda、Mark T. Quinn、Igor A. Schepetkin、Liliya N. Kirpotina、John A. Zebala
DOI:10.1124/jpet.109.159020
日期:2010.1
The chemokine receptors CXCR1/2 are involved in a variety of inflammatory diseases, including chronic obstructive pulmonary disease. Several classes of allosteric small-molecule CXCR1/2 antagonists have been developed. The data presented here describe the cellular pharmacology of the acid and ester forms of the nicotinamide glycolate pharmacophore, a potent antagonist of CXCR2 signaling by the chemokines CXCL1 and CXCL8. Ester forms of the nicotinamide glycolate antagonized CXCL1-stimulated chemotaxis (IC50 = 42 nM) and calcium flux (IC50 = 48 nM) in human neutrophils, but they were inactive in cell-free assays of 125I-CXCL8/CXCR2 binding and CXCL1-stimulated guanosine 5′- O -(3-[35S]thio)triphosphate ([35S]GTPγS) exchange. Acid forms of the nicotinamide glycolate were inactive in whole-cell assays of chemotaxis and calcium flux, but they inhibited 125I-CXCL8/CXCR2 binding and CXCL1-stimulated [35S]GTPγS exchange. The 3H ester was internalized by neutrophils and rapidly converted to the 3H acid in a concentrative process. The 3H acid was not internalized by neutrophils but was sufficient alone to inhibit CXCL1-stimulated calcium flux in neutrophils that were permeabilized by electroporation to permit its direct access to the cell interior. Neutrophil efflux of the acid was probenecid-sensitive, consistent with an organic acid transporter. These data support a mechanism wherein the nicotinamide glycolate ester serves as a lipophilic precursor that efficiently translocates into the intracellular neutrophil space to liberate the active acid form of the pharmacophore, which then acts at an intracellular site. Rapid inactivation by plasma esterases precluded use in vivo, but the mechanism elucidated provided insight for new nicotinamide pharmacophore classes with therapeutic potential.
趋化因子受体 CXCR1/2 与包括慢性阻塞性肺病在内的多种炎症性疾病有关。目前已开发出几类异构小分子 CXCR1/2 拮抗剂。本文提供的数据描述了烟酰胺羟基乙酸药源体的酸和酯形式的细胞药理学,它是趋化因子 CXCL1 和 CXCL8 对 CXCR2 信号传导的强效拮抗剂。烟酰胺羟基乙酸酯能拮抗人中性粒细胞中 CXCL1 刺激的趋化作用(IC50 = 42 nM)和钙通量(IC50 = 48 nM),但在 125I-CXCL8/CXCR2 结合和 CXCL1 刺激的鸟苷酸 5′- O -(3-[35S]硫代)三磷酸([35S]GTPγS)交换的无细胞检测中却不起作用。烟酰胺羟基酸的酸性形式在全细胞趋化性和钙通量试验中没有活性,但它们抑制 125I-CXCL8/CXCR2 结合和 CXCL1 刺激的 [35S]GTPγS 交换。3H 酯被中性粒细胞内化,并在浓缩过程中迅速转化为 3H 酸。3H 酸不能被中性粒细胞内化,但足以单独抑制中性粒细胞中 CXCL1 刺激的钙离子通量。中性粒细胞的酸外流对丙磺舒敏感,这与有机酸转运体一致。这些数据支持这样一种机制,即烟酰胺羟基乙酸酯作为一种亲脂性前体,有效地转运到细胞内的中性粒细胞空间,释放出药效源的活性酸形式,然后在细胞内发挥作用。血浆酯酶的快速灭活排除了它在体内的应用,但阐明的机制为具有治疗潜力的新烟酰胺药源类别提供了启示。