Zoledronic Acid as a Novel Dual Blocker of KIR6.1/2-SUR2 Subunits of ATP-Sensitive K+ Channels: Role in the Adverse Drug Reactions

Fatima Maqoud,Antonio Scilimati,Ciro Leonardo Pierri,Rosa Scala,Maria Grazia Perrone,Domenico Tricarico,Vincenzo Tragni

doi:10.3390/pharmaceutics13091350

Fatima Maqoud, Antonio Scilimati + Show 5 more

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https://doi.org/10.3390/pharmaceutics13091350

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Abstract

Zoledronic acid (ZOL) is used as a bone-specific antiresorptive drug with antimyeloma effects. Adverse drug reactions (A.D.R.) are associated with ZOL-therapy, whose mechanics are unknown. ZOL is a nitrogen-containing molecule whose structure shows similarities with nucleotides, ligands of ATP-sensitive K+ (KATP) channels. We investigated the action of ZOL by performing in vitro patch-clamp experiments on native KATP channels in murine skeletal muscle fibers, bone cells, and recombinant subunits in cell lines, and by in silico docking the nucleotide site on KIR and SUR, as well as the glibenclamide site. ZOL fully inhibited the KATP currents recorded in excised macro-patches from Extensor digitorum longus (EDL) and Soleus (SOL) muscle fibers with an IC50 of 1.2 ± 1.4 × 10−6 and 2.1 ± 3.7 × 10−10 M, respectively, and the KATP currents recorded in cell-attached patches from primary long bone cells with an IC50 of 1.6 ± 2.8 × 10−10 M. ZOL fully inhibited a whole-cell KATP channel current of recombinant KIR6.1-SUR2B and KIR6.2-SUR2A subunits expressed in HEK293 cells with an IC50 of 3.9 ± 2.7 × 10−10 M and 7.1 ± 3.1 × 10−6 M, respectively. The rank order of potency in inhibiting the KATP currents was: KIR6.1-SUR2B/SOL-KATP/osteoblast-KATP > KIR6.2-SUR2A/EDL-KATP >>> KIR6.2-SUR1 and KIR6.1-SUR1. Docking investigation revealed that the drug binds to the ADP/ATP sites on KIR6.1/2 and SUR2A/B and on the sulfonylureas site showing low binding energy <6 Kcal/mol for the KIR6.1/2-SUR2 subunits vs. the <4 Kcal/mol for the KIR6.2-SUR1. The IC50 of ZOL to inhibit the KIR6.1/2-SUR2A/B channels were correlated with its musculoskeletal and cardiovascular risks. We first showed that ZOL blocks at subnanomolar concentration musculoskeletal KATP channels and cardiac and vascular KIR6.2/1-SUR2 channels.

Highlights

Extensor digitorum longus (EDL) and slow-twitch Soleus (SOL) murine muscle fibers, we found that increasing concentrations of zoledronic acid (ZOL) (10−10 –10−7 M) solutions applied on the internal side of the membrane inhibited the KATP currents (Figure 1A,B)
The KATP currents were recorded in C-A patches from primary long bone cells in physiological asymmetrical K+ ions condition in the absence of CTRL, presence of glibenclamide (Glib), or increasing concentrations of ZOL solution, followed by BaCl2 solutions applied at the end of protocol period
We found that ZOL inhibits the KATP currents of soleus muscle fibers and primary bone culture at sub-nanomolar concentrations that highly express the KIR6.1 subunit and SUR2 [27,28], and it is a potent blocker of the recombinant KIR6.1-SUR2B channel, suggesting that the KIR6.1-SUR2B subunits are the drug targets in these tissues

Summary

Introduction

Bisphopshonates (BPs) are the most used antiresorptive drugs, useful for the treatment of bone diseases associated with an increased resorption rate. They include compounds without nitrogen atoms in their structure, such as etidronate and clodronate that are expected to cause osteoclast apoptosis via the formation of toxic ATP-metabolites [1], and nitrogen-containing BPs, such as pamidronic acid, alendronic acid, risedronic acid, and zoledronic acid. Once internalized into the osteoclasts, nitrogen-containing BPs can act as potent inhibitors of human farnesyl pyrophosphate synthase (hFPPS), a key enzyme in the mevalonate pathway, inducing osteoclast apoptosis [2,3,4].

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