Characterization of the Modulatory Effect of Hydroxychloroquine on ACE2 Activity: New Insights in relation to COVID-19.

Juan E Tichauer,Dagoberto Soto,Max Andresen,Tariq Ismail

doi:10.1155/2021/6614000

Juan E Tichauer, Dagoberto Soto + Show 2 more

Open Access

https://doi.org/10.1155/2021/6614000

Copy DOI

Abstract

Chloroquine (CQ) and hydroxychloroquine (HCQ) have shown the ability to inhibit in vitro viral replications of coronaviridae viruses such as SARS-CoV and SARS-CoV-2. However, clinical trial outcomes have been disparate, suggesting that CQ and HCQ antiviral mechanisms are not fully understood. Based on three-dimensional structural similarities between HCQ and the known ACE2 specific inhibitor MLN-4760, we compared their modulation on ACE2 activity. Here we describe, for the first time, in a cell-free in vitro system that HCQ directly and dose-dependently inhibits the activity of recombinant human ACE2, with a potency similar to the MLN-4760. Further analysis suggests that HCQ binds to a noncompetitive site other than the one occupied by MLN-4760. We also determined that the viral spike glycoprotein segment that comprises the RBD segment has no effect on ACE2 activity but unexpectedly was able to partially reverse the inhibition induced by HCQ but not that by MLN-4760. In summary, here we demonstrate the direct inhibitory action of HCQ over the activity of the enzyme ACE2. Then, by determining the activity of ACE2, we reveal that the interaction with the spike protein of SARS-CoV-2 leads to structural changes that at least partially displace the interaction of the said enzyme with HCQ. These results may help to explain why the effectiveness of HCQ in clinical trials has been so variable. Additionally, this knowledge could be used for to develop techniques for the detection of SARS-CoV-2.

Highlights

Chloroquine (CQ) and its less toxic derivative hydroxychloroquine (HCQ) have shown in vitro to efficiently inhibit viral replication, including strains of coronaviridae virus SARS-CoV [1,2,3,4] and SARS-CoV-2 [5]
Motivated by putative structural analogies, in this cell-free model, we demonstrated that HCQ directly and dosedependently inhibited angiotensin-converting enzyme 2 (ACE2) activity
Nami et al and Teralı et al described in silico models where the binding of ACE2 to the selective inhibitor MLN-4760 predicts conformational changes, which modify the enzymatic active site and alter the binding site and residues involved in the hydrogen and hydrophobic binding between spike glycoprotein RBD domain and ACE2 [13, 14]

Summary

Introduction

Chloroquine (CQ) and its less toxic derivative hydroxychloroquine (HCQ) have shown in vitro to efficiently inhibit viral replication, including strains of coronaviridae virus SARS-CoV [1,2,3,4] and SARS-CoV-2 [5]. As coronaviridae viruses infect their target cells through an endocytic pathway [6, 7], it has been proposed that the mechanism of action of CQ and HCQ is mediated by the acidification of organelles such as the endosome, Golgi vesicles, and the lysosomes. The results of these trials have been variable, ranging from an encouraging decrease in nasopharyngeal viral load to some indifferent and even harmful clinical outcomes. This variety of results strongly suggests that the mechanics behind the antiviral action of HCQ is still not fully known. The HCQ antiviral mechanism is still awaiting to be revealed

Methods

Results

Conclusion