Selective Calcium-Dependent Inhibition of ATP-Gated P2X3 Receptors by Bisphosphonate-Induced Endogenous ATP Analog ApppI

Abstract

Pain is the most unbearable symptom accompanying primary bone cancers and bone metastases. Bone resorptive disorders are often associated with hypercalcemia, contributing to the pathologic process. Nitrogen-containing bisphosphonates (NBPs) are efficiently used to treat bone cancers and metastases. Apart from their toxic effect on cancer cells, NBPs also provide analgesia via poorly understood mechanisms. We previously showed that NBPs, by inhibiting the mevalonate pathway, induced formation of novel ATP analogs such as ApppI [1-adenosin-5'-yl ester 3-(3-methylbut-3-enyl) triphosphoric acid diester], which can potentially be involved in NBP analgesia. In this study, we used the patch-clamp technique to explore the action of ApppI on native ATP-gated P2X receptors in rat sensory neurons and rat and human P2X3, P2X2, and P2X7 receptors expressed in human embryonic kidney cells. We found that although ApppI has weak agonist activity, it is a potent inhibitor of P2X3 receptors operating in the nanomolar range. The inhibitory action of ApppI was completely blocked in hypercalcemia-like conditions and was stronger in human than in rat P2X3 receptors. In contrast, P2X2 and P2X7 receptors were insensitive to ApppI, suggesting a high selectivity of ApppI for the P2X3 receptor subtype. NBP, metabolite isopentenyl pyrophosphate, and endogenous AMP did not exert any inhibitory action, indicating that only intact ApppI has inhibitory activity. Ca-dependent inhibition was stronger in trigeminal neurons preferentially expressing desensitizing P2X3 subunits than in nodose ganglia neurons, which also express nondesensitizing P2X2 subunits. Altogether, we characterized previously unknown purinergic mechanisms of NBP-induced metabolites and suggest ApppI as the endogenous pain inhibitor contributing to cancer treatment with NBPs.

Synthesis of a Biologically Important Adenosine Triphosphate Analogue, ApppD

“…For example, very recently, Ishchenko et al showed that ApppI could evoke a calcium-dependent inhibition of pain sensation. 15 In contrast, little is known about the effects of ApppD in biological systems, as this compound has been hardly available to bioscientists.…”

Integrated analysis of isopentenyl pyrophosphate (IPP) toxicity in isoprenoid-producing Escherichia coli

“…Nucleotide analogs may also be incorporated into DNA, leading to DNA damage and the inhibition of cellular division or viral replication. Though research on the physiological consequences of ApppI accumulation is still limited, preliminary evidence points to considerable bioactivity: ApppI has been shown to inhibit the Adenosine Nucleotide Transporter (ANT) (Mönkkönen et al, 2006) and ATP-gated P23X receptor (Ishchenko et al, 2017) in eukaryotes. Inhibition of ANT has been directly linked to cell death and apoptosis in osteoclasts (Mönkkönen et al, 2006).…”

The Role of the Phosphorus Atom in Drug Design

“…It was suggested that decreasing the level of extracellular Ca 2+ under bone tumor treatment with bisphosphonates might elicit the antinociceptive effect of ApppI on P2X 3 receptors. These findings might help the design of new types of antinociceptive agents to manage painful bone cancer and bone metastases . A very interesting case of phosphorus‐containing drugs is the replacement of a non‐bridging oxygen atom from 190 by a borane moiety to afford 191 , bearing a new stereogenic center (Figure ).…”

“…These findings might help the design of new types of antinociceptive agentst om anage painful bone cancer and bone metastases. [184] Av ery interesting case of phosphoruscontaining drugs is the replacement of an on-bridgingo xygen atom from 190 by ab orane moiety to afford 191,b earinga new stereogenic center ( Figure 28). In particular, the most remarkable isomer was that possessing the R p configuration.…”