Supplements For COVID-19: In Vitro Study Shows That Copper Gluconate Supplementation Could Inhibit SARS-CoV-2 Infection
Supplements For COVID-19
: A new study by researchers from CIRI (Centre International de Recherche en Infectiologie)-France and the University Hospital of St-Etienne-France have shown that copper gluconate is able to inhibit SARS-CoV-2 coronavirus infection n vitro and has the potential to be used as a supplement to help in controlling COVID-19 infections in the role as an adjuvant.
The SARS-CoV-2 coronavirus that emerged late in 2019 is the etiologic agent of the COVID-19 disease. There is an urgent need to develop curative and preventive therapeutics to limit the current pandemic and to prevent the re-emergence of COVID-19.
This study was aimed to assess the in vitro activity of copper gluconate against SARS-CoV-2.
For the study, Vero E6 cells were treated with copper gluconate 18 hours before infection. Cells were infected with a recombinant GFP expressing SARS-CoV-2. Infected cells were maintained in fresh medium containing copper gluconate for an additional 48-hour period. The infection level was measured by the confocal microscopy-based high content screening method. The cell viability in presence of copper gluconate was assessed by XTT assay.
The study findings found that the viability of Vero E6 cells treated with copper gluconate up to 200 µM was found to be similar to that of untreated cells, but it dropped below 40% with 400 µM of this agent. The infection rate was 23.8%, 18.9%, 20.6%, 6.9%, 5.3%,5.2% in cells treated with 0, 2, 10, 25, 50 and 100 µM of copper gluconate respectively. As compared to untreated cells, the number of infected cells was reduced by 71%, 77%, and 78% with 25, 50, and 100 µM of copper gluconate respectively (p < 0.05).
The study findings showed that Copper gluconate was found to mitigate SARS-CoV-2 infection in Vero E6 cells. However furthers studies are needed to determine whether copper homeostasis could play a role in SARS-CoV-2 infection.
The study findings were published on a preprint server and are currently being peer reviewed. https://www.biorxiv.org/content/10.1101/2020.12.13.422548v1
The current second wave of the COVID-19 pandemic has affected many countries, costing thousands of lives and dealing further heavy blows to already reeling economies.
Researchers have been working hard to bring out new drugs and repurpose older ones to stop the virus in its tracks and help the world return to something resembling normality.
The extremely infectious nature of the SARS-CoV-2 virus, and the significant percentage of individuals who develop severe or critical disease following infection, has placed a heavy or overwhelming burden on healthcare providers and public health authorities.
The dire search for pharmaceutical control measures requires in vitro
studies of drug efficacy, for which not all laboratories are equipped.
To date most predicted lead compounds have come from computational studies. Thus, there is little actual in vitro information on the efficacy of drugs thought to have potential activity against the virus, beyond a handful comprising remdesivi
r, hydroxychloroquine, lopinavir-ritonavir, favipiravir, interferon, camostat mesylate, tocilizumab, and other immunomodulators.
Disappointingly among these, the SOLIDARITY and RECOVERY trials, which are still ongoing, have reported in preliminary findings that these drugs have no significant effect on the number of deaths or duration of hospitalization following SARS-CoV-2 infection. https://www.nejm.org/doi/full/10.1056/NEJMoa2023184
It has long been known that copper exerts antimicrobial and antiviral actions. SARS-CoV-2 can be eradicated from a copper surface within 4 hours while it can survive up to 72 hours on stainless steel and plastic surface
Hence copper could be helpful to inactivate the virus on hospital door handles, face masks, and other surfaces that face contamination and there are already commercial applications of this.
Copper is also known to have antimicrobial and antiviral effects in living organisms and humans. https://www.mdpi.com/1999-4915/12/10/1179
Thailand Medical News had done an earlier article proposing the potential benefits of copper supplements to help with COVID-19 treatments. https://www.thailandmedical.news/news/covid-19-supplements-can-copper-supplements-help-in-covid-19
It is also already known that copper is a cofactor essential for the activity of multiple enzymes that take part in redox reactions. The concentration of copper within the cell must be high enough to prevent metabolic breakdown.
Typically in adults, this would range from 650 to 1850 μg/L. Copper is bound by many proteins, including ceruloplasmin, albumin, and alpha-2-macroglobulin.
This study explores the use of copper to block cell infection by SARS-CoV-2. Copper gluconate could be a viral inhibitor, preventing SARS-CoV-2 infection.
The study team decided to use a novel confocal microscopy-based high content screening (HCS) technique to evaluate the effect of pre-and post-treatment with copper gluconate on cell infection with this virus.
The team used a cell system exposed to synthetic SARS-CoV-2, with a green fluorescent protein (GFP) as the reporter. The reporter facilitates the rapid detection of the virus by fluorescence.
The utilization of this method helps achieve separate analysis of each cell, with high reliability due to the simultaneous counting of thousands of cells at each well.
The complete automation of this process eliminates multiple sources of bias. In short, this model is suitable for drug screening, as shown by its use for remdesivir.
The researchers used the GFP-SARS-CoV-2 which was combined with the confocal microscopy method to evaluate the antiviral activity of copper gluconate. It can be further refined to examine other potential antiviral drugs in mammalian cell lines.
The study team tested for toxicity of copper gluconate using Vero E6 cells treated with copper gluconate at concentrations of 0 to 1600 μM for 24 hours. They measured the amount of XIT converted to formazan, yielding an orange color, with the CyQUANT XTT assay.
The team found that at up to 200 μM, Vero cell viability remained intact. After this, it fell sharply from 400 μM onwards to 800 μM, being measured at <40 percent and almost zero, respectively.
The study team next treated Vero E6 cells with copper gluconate from 0 to 100 μM at 18 hours and then infected them with the virus. After a one-hour gap to allow adsorption of the virus the cells were again exposed to a fresh culture medium with the same copper gluconate concentration for 48 hours more. At this point, confocal microscopy was performed to assess the level of infection and viral replication.
The study results showed that cells treated with copper gluconate at 25 μM or more had 70 percent lower infection rates (number of cells infected). This dosage was the lowest to achieve a marked reduction in infection. Moreover, the mean intensity of GFP fluorescence was inversely proportional to the concentration of copper gluconate, indicating the limiting effect of copper on viral replication.
However, even at 100 μM, copper gluconate did not achieve complete viral inhibition. Concentrations beyond this were not assayed, even though it seems to be non-cytotoxic even at concentrations of 200 μM. The tissue concentration of copper is a thousand times lower than the serum concentration, at 1 to 12 μg/g vs. 1000 μg/ (15 μM). For this reason, the scientists chose to evaluate the effect of up to 25 μM of copper gluconate, even though the observed effect fell far short of antiviral drugs in efficacy.
The team called attention to the presence of copper in all eukaryotic cells. This could explain and predict a complex antiviral effect of copper in vivo rather than just reducing the infection rate.
The study team said that copper gluconate may damage the viral membranes and denature the viral genome through a direct effect since, in this experiment; the copper concentration was kept steady throughout the experiment. Secondly, rising copper gluconate levels up to 100 μM were linked to a fall in mean fluorescent intensity, MFI. Interestingly, GFP in the recombinant SARS-CoV-2 is fused to the non-structural protein nsp7.
Hence reduced MFI could indicate that copper disrupts the production of viral proteins.
Earlier modeling studies predicted an inhibitory role for metals like cobalt or copper in ionic form on the main protease of SARS-CoV-2. More research will confirm this to be the case. https://chemrxiv.org/articles/Copper_II_Inhibition_of_the_SARS-CoV-2_Main_Protease/12673436
Interestingly another mechanism could be increased Cu/Zn superoxide dismutase 1 (SOD1) expression, which has been shown to be linked to reduced viral replication in vitro. Finally, coronavirus replication requires a replication complex that depends on cellular components associated with autophagy. https://pubs.rsc.org/en/content/articlelanding/2016/MT/C6MT00103C#!divAbstract
It must also be noted that copper is known to alter the rate of autophagy and could thus reduce or prevent the formation of this complex. Which of these potential mechanisms is most important in the antiviral effect of copper remains to be teased out in future research. https://www.jbc.org/content/279/11/10136
Further studies are required to understand what role copper plays in acute viral infection, beginning from copper ion concentrations in blood, nails, hair, and other tissues at all stages and at different levels of clinical severity of COVID-19.
The study team concluded that the current study shows that copper gluconate administration can reduce infection rates with SARS-CoV-2 in vitro.
Furthers studies are however needed to determine whether copper homeostasis could play a role in SARS-CoV-2 infection.
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