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J Inorg Biochem ; 231: 111777, 2022 06.
Article in English | MEDLINE | ID: covidwho-1873158


The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) pandemic is currently the major challenge to global public health. Two proteases, papain-like protease (PLpro) and the 3-chymotrypsin-like protease (3CLpro or Mpro), are indispensable for SARS-CoV-2 replication, making them attractive targets for antiviral therapy development. Here we screened a panel of essential metal ions using a proteolytic assay and identified that zinc gluconate, a widely-used zinc supplement, strongly inhibited the proteolytic activities of the two proteases in vitro. Biochemical and crystallographic data reveal that zinc gluconate exhibited the inhibitory function via binding to the protease catalytic site residues. We further show that treatment of zinc gluconate in combination with a small molecule ionophore hinokitiol, could lead to elevated intracellular Zn2+ level and thereby significantly impaired the two protease activities in cellulo. Particularly, this approach could also be applied to rescue SARS-CoV-2 infected mammalian cells, indicative of potential application to combat coronavirus infections. Our studies provide the direct experimental evidence that elevated intracellular zinc concentration directly inhibits SARS-CoV-2 replication and suggest the potential benefits to use the zinc supplements for coronavirus disease 2019 (COVID-19) treatment.

COVID-19 , SARS-CoV-2 , Animals , Antiviral Agents/chemistry , Antiviral Agents/pharmacology , COVID-19/drug therapy , Gluconates , Mammals/metabolism , Monoterpenes , Peptide Hydrolases/metabolism , Tropolone/analogs & derivatives , Zinc/pharmacology
Dalton Trans ; 50(35): 12226-12233, 2021 Sep 14.
Article in English | MEDLINE | ID: covidwho-1358359


Numerous organic molecules are known to inhibit the main protease of SARS-CoV-2, (SC2Mpro), a key component in viral replication of the 2019 novel coronavirus. We explore the hypothesis that zinc ions, long used as a medicinal supplement and known to support immune function, bind to the SC2Mpro enzyme in combination with lipophilic tropolone and thiotropolone ligands, L, block substrate docking, and inhibit function. This study combines synthetic inorganic chemistry, in vitro protease activity assays, and computational modeling. While the ligands themselves have half maximal inhibition concentrations, IC50, for SC2Mpro in the 8-34 µM range, the IC50 values are ca. 100 nM for Zn(NO3)2 which are further enhanced in Zn-L combinations (59-97 nM). Isolation of the Zn(L)2 binary complexes and characterization of their ability to undergo ligand displacement is the basis for computational modeling of the chemical features of the enzyme inhibition. Blind docking onto the SC2Mpro enzyme surface using a modified Autodock4 protocol found preferential binding into the active site pocket. Such Zn-L combinations orient so as to permit dative bonding of Zn(L)+ to basic active site residues.

COVID-19/drug therapy , Coronavirus 3C Proteases/antagonists & inhibitors , Protease Inhibitors/pharmacology , SARS-CoV-2/drug effects , Tropolone/pharmacology , Zinc/pharmacology , Antiviral Agents/chemistry , Antiviral Agents/pharmacology , COVID-19/virology , Catalytic Domain/drug effects , Coronavirus 3C Proteases/chemistry , Coronavirus 3C Proteases/metabolism , Humans , Ligands , Models, Molecular , Molecular Docking Simulation , Protease Inhibitors/chemistry , SARS-CoV-2/enzymology , Tropolone/analogs & derivatives , Zinc/chemistry
Med Hypotheses ; 145: 110333, 2020 Dec.
Article in English | MEDLINE | ID: covidwho-813777


Zinc and the combination with zinc ionophore have been reported in basic research and several clinical investigations as a potentially viable and economical preventive and therapeutic options for COVID-19 treatment. Zinc is a vital microelement that actively supports respiratory epithelium barrier integrity, innate and adaptive immune functions, and inflammatory regulations. Moreover, zinc may also prevent viral entry, suppress viral replication, and mitigate the damages due to oxidative stress and hyperinflammatory reaction in patients with respiratory infections. Hinokitiol (ß-thujaplicin) is a natural monoterpenoid and is considered as a safe zinc ionophore to help zinc transport into cells. It has been widely used in skin and oral care, and therapeutic products for its potent antiviral, antimicrobial, antifungal, anti-inflammatory, and anticancer applications. The ongoing COVID-19 pandemic and the significant morbidity and mortality exist in the high-risk group of patients associated with other respiratory infections such as influenza, respiratory syncytial virus, and dengue fever. There is an urgent need for the development of inexpensive, safe, and effective therapeutics to prevent and treat these viral infections. Considering that hydroxychloroquine (HCQ), the most studied zinc ionophore drug for COVID-19, is linked to potentially serious side effects, we propose the implementation of hinokitiol as a zinc ionophore and anti-infective agent for the prevention and treatment of COVID-19 and other viral infections.

Anti-Infective Agents/therapeutic use , COVID-19/drug therapy , COVID-19/prevention & control , Ionophores/therapeutic use , Monoterpenes/therapeutic use , Tropolone/analogs & derivatives , Zinc/chemistry , Antiviral Agents/therapeutic use , Homeostasis , Humans , Hydroxychloroquine/pharmacology , Models, Theoretical , Risk , Tropolone/therapeutic use