Dihydropyridines Potentiate ATP-Induced Currents Mediated by the Full-Length Human P2X5 Receptor.

Ida C Schiller,Fritz Markwardt,Günther Schmalzing,Kenneth A Jacobson,Zhiwei Wen,Aparna Malisetty

doi:10.3390/molecules27061846

Abstract

The P2X5 receptor, an ATP-gated cation channel, is believed to be involved in tumor development, inflammatory bone loss and inflammasome activation after bacterial infection. Therefore, it is a worthwhile pharmacological target to treat the corresponding diseases, especially in minority populations that have a gene variant coding for functional homotrimeric P2X5 channels. Here, we investigated the effects of dihydropyridines on the human full-length P2X5 receptor (hP2X5FL) heterologously expressed in Xenopus oocytes using the two-microelectrode voltage clamp method. Agonist dependency, kinetics and permeation behavior, including Cl− permeability, were similar to hP2X5FL expressed in HEK293 or 1321N1 cells. Additionally, 1,4-dihydropyridines have been shown to interact with various other purinergic receptors, and we have examined them as potential hP2X5 modulators. Of seven commercially available and four newly synthesized dihydropyridines tested at hP2X5FL, only amlodipine exerted an inhibitory effect, but only at a high concentration of 300 µM. Isradipine and—even more—nimodipine stimulated ATP-induced currents in the low micromolar range. We conclude that common dihydropyridines or four new derivatives of amlodipine are not suitable as hP2X5 antagonists, but amlodipine might serve as a lead for future synthesis to increase its affinity. Furthermore, a side effect of nimodipine therapy could be a stimulatory effect on inflammatory processes.

Highlights

The ATP-activated P2X receptors represent emerging pharmaceutical targets for a variety of conditions [1]
1,4-dihydropyridines have been shown to interact with various other purinergic receptors, and we have examined them as potential Human P2X5 (hP2X5) modulators
We conclude that common dihydropyridines or four new derivatives of amlodipine are not suitable as hP2X5 antagonists, but amlodipine might serve as a lead for future synthesis to increase its affinity

Summary

Introduction

The ATP-activated P2X receptors represent emerging pharmaceutical targets for a variety of conditions [1]. X-ray and cryo-EM structures of various P2X receptors with agonist or antagonist bounds have been reported [6], which has led to structure-based approaches to understanding the ligand recognition and drug discovery. Despite its unique expression profile and dynamic mRNA regulation, the P2X5 receptor is an outlier in the field of drug development, as no definitive ligand tools have yet been reported [1]. One possible reason is that due to a prevailing T > G SNP (G-allele) at the 3 -splice site of exon 10, most humans express only an apparently non-functional splice variant (see Supplementary Figure S1), designated as hP2X5∆328–349 [7,15,16]. The rare T-allele, at the 3 -splice site of exon 10 results in a transcript encoding the 444-residues long, full-length hP2X5 (hP2X5FL) subunit, which is capable of assembling into a functional ATP-gated receptor channel [16–18]. The rare T-allele has only been detected in tissue samples obtained from African Americans, but not in people of other ethnicities [15]

Methods

Results

Conclusion