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All-Trans Retinoic Acid Exhibits Antiviral Effect against SARS-CoV-2 by Inhibiting 3CLpro Activity

Morita et al., Viruses, doi:10.3390/v13081669

Aug 2021

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Vitamin A for COVID-19

42nd treatment shown to reduce risk in June 2023, now with p = 0.021 from 14 studies.

Lower risk for recovery and cases.

No treatment is 100% effective. Protocols combine treatments.

5,100+ studies for 109 treatments. c19early.org

In Vitro and In Silico study showing that all-trans retinoic acid is a potent SARS-CoV-2 3CL^pro inhibitor, inhibits SARS-CoV-2 replication in VeroE6/TMPRSS2 cells, and is effective against alpha, beta, gamma, and delta variants in Calu-3 cells.

10 preclinical studies support the efficacy of vitamin A for COVID-19:

4 In Silico studies1-4

5 In Vitro studies1,5-8

1 In Vivo animal study9

Vitamin A has been identified by the European Food Safety Authority (EFSA) as having sufficient evidence for a causal relationship between intake and optimal immune system function10-12. Vitamin A has potent antiviral activity against SARS-CoV-2 in both human cell lines and human organoids of the lower respiratory tract (active metabolite all-trans retinoic acid, ATRA)7, is predicted to bind critical host and viral proteins for SARS-CoV-2 and may compensate for gene expression changes related to SARS-CoV-21-3, may be beneficial for COVID-19 via antiviral, anti-inflammatory, and immunomodulatory effects according to network pharmacology analysis4, reduces barrier compromise caused by TNF-α in Calu-3 cells6, inhibits mouse coronavirus replication9, may stimulate innate immunity by activating interferon responses in an IRF3-dependent manner (ATRA)9, may reduce excessive inflammation induced by SARS-CoV-21, shows SARS-CoV-2 antiviral activity In Vitro1,5,8, is effective against multiple SARS-CoV-2 variants in Calu-3 cells8, and inhibits the entry and replication of SARS-CoV-2 via binding to ACE2 / 3CLpro / RdRp / helicase / 3′-to-5′ exonuclease1.

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1. Huang et al., All-trans retinoic acid acts as a dual-purpose inhibitor of SARS-CoV-2 infection and inflammation, Computers in Biology and Medicine, doi:10.1016/j.compbiomed.2024.107942.sciencedirect.com, doi.org.

2. Chakraborty et al., In-silico screening and in-vitro assay show the antiviral effect of Indomethacin against SARS-CoV-2, Computers in Biology and Medicine, doi:10.1016/j.compbiomed.2022.105788.sciencedirect.com, doi.org.

3. Pandya et al., Unravelling Vitamin B12 as a potential inhibitor against SARS-CoV-2: A computational approach, Informatics in Medicine Unlocked, doi:10.1016/j.imu.2022.100951.sciencedirect.com, doi.org.

4. Li et al., Revealing the targets and mechanisms of vitamin A in the treatment of COVID-19, Aging, doi:10.18632/aging.103888.aging-us.com, doi.org.

5. Moatasim et al., Potent Antiviral Activity of Vitamin B12 against Severe Acute Respiratory Syndrome Coronavirus 2, Middle East Respiratory Syndrome Coronavirus, and Human Coronavirus 229E, Microorganisms, doi:10.3390/microorganisms11112777.mdpi.com, doi.org.

6. DiGuilio et al., The multiphasic TNF-α-induced compromise of Calu-3 airway epithelial barrier function, Experimental Lung Research, doi:10.1080/01902148.2023.2193637.tandfonline.com, doi.org.

7. Tong et al., A Retinol Derivative Inhibits SARS-CoV-2 Infection by Interrupting Spike-Mediated Cellular Entry, mBio, doi:10.1128/mbio.01485-22.asm.org, doi.org.

8. Morita et al., All-Trans Retinoic Acid Exhibits Antiviral Effect against SARS-CoV-2 by Inhibiting 3CLpro Activity, Viruses, doi:10.3390/v13081669.mdpi.com, doi.org.

9. Franco et al., Retinoic Acid-Mediated Inhibition of Mouse Coronavirus Replication Is Dependent on IRF3 and CaMKK, Viruses, doi:10.3390/v16010140.mdpi.com, doi.org.

10. Galmés et al., Suboptimal Consumption of Relevant Immune System Micronutrients Is Associated with a Worse Impact of COVID-19 in Spanish Populations, Nutrients, doi:10.3390/nu14112254.mdpi.com, doi.org.

11. Galmés (B) et al., Current State of Evidence: Influence of Nutritional and Nutrigenetic Factors on Immunity in the COVID-19 Pandemic Framework, Nutrients, doi:10.3390/nu12092738.mdpi.com, doi.org.

12. EFSA, Scientific Opinion on the substantiation of health claims related to vitamin A and cell differentiation (ID 14), function of the immune system (ID 14), maintenance of skin and mucous membranes (ID 15, 17), maintenance of vision (ID 16), maintenance of bone (ID 13, 17), maintenance of teeth (ID 13, 17), maintenance of hair (ID 17), maintenance of nails (ID 17), metabolism of iron (ID 206), and protection of DNA, proteins and lipids from oxidative damage (ID 209) pursuant to Article 13(1) of Regulation (EC) No 1924/2006, EFSA Journal, doi:10.2903/j.efsa.2009.1221.europa.eu, doi.org.

Morita et al., 23 Aug 2021, peer-reviewed, 9 authors.

In Vitro studies are an important part of preclinical research, however results may be very different in vivo.

This Paper Vitamin A All

All-Trans Retinoic Acid Exhibits Antiviral Effect against SARS-CoV-2 by Inhibiting 3CLpro Activity

Takeshi Morita, Kei Miyakawa, Sundararaj Stanleyraj Jeremiah, Yutaro Yamaoka, Mitsuru Sada, Tomoko Kuniyoshi, Jinwei Yang, Hirokazu Kimura, Akihide Ryo

Viruses, doi:10.3390/v13081669

The pandemic of COVID-19 caused by SARS-CoV-2 continues to spread despite the global efforts taken to control it. The 3C-like protease (3CLpro), the major protease of SARS-CoV-2, is one of the most interesting targets for antiviral drug development because it is highly conserved among SARS-CoVs and plays an important role in viral replication. Herein, we developed high throughput screening for SARS-CoV-2 3CLpro inhibitor based on AlphaScreen. We screened 91 natural product compounds and found that all-trans retinoic acid (ATRA), an FDA-approved drug, inhibited 3CLpro activity. The 3CLpro inhibitory effect of ATRA was confirmed in vitro by both immunoblotting and AlphaScreen with a 50% inhibition concentration (IC 50 ) of 24.7 ± 1.65 µM. ATRA inhibited the replication of SARS-CoV-2 in VeroE6/TMPRSS2 and Calu-3 cells, with IC 50 = 2.69 ± 0.09 µM in the former and 0.82 ± 0.01 µM in the latter. Further, we showed the anti-SARS-CoV-2 effect of ATRA on the currently circulating variants of concern (VOC); alpha, beta, gamma, and delta. These results suggest that ATRA may be considered as a potential therapeutic agent against SARS-CoV-2.

Supplementary Materials: The following are available online at https://www.mdpi.com/article/ 10.3390/v13081669/s1, Figure S1 : The comparison of FRET and AlphaScreen, Figure S2 : Graphical determination of the type pf inhibition, Figure S3 : Cytotoxicity of ATRA, Figure S4 : Protein expression in ATRA treated Calu-3 cells during SARS-CoV-2 infection, Figure S5 : Amino acid sequence alignment of 3CLpro, Table S1 : The list of compounds screened by the enzyme assay. Conflicts of Interest: The authors declare no competing financial interest. Y.Y. is a current employee of Kanto Chemical Co., Inc. T.K. and J.Y. are a current employee of TOKIWA Phytochemical Co., Ltd.

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