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Review

Reaction Cycles of Halogen Species in the Immune Defense: Implications for Human Health and Diseases and the Pathology and Treatment of COVID-19

Department of Physics and Astronomy and Department of Biology, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada
Cells 2020, 9(6), 1461; https://doi.org/10.3390/cells9061461
Received: 1 May 2020 / Revised: 1 June 2020 / Accepted: 10 June 2020 / Published: 13 June 2020
There is no vaccine or specific antiviral treatment for COVID-19, which is causing a global pandemic. One current focus is drug repurposing research, but those drugs have limited therapeutic efficacies and known adverse effects. The pathology of COVID-19 is essentially unknown. Without this understanding, it is challenging to discover a successful treatment to be approved for clinical use. This paper addresses several key biological processes of reactive oxygen, halogen and nitrogen species (ROS, RHS and RNS) that play crucial physiological roles in organisms from plants to humans. These include why superoxide dismutases, the enzymes to catalyze the formation of H2O2, are required for protecting ROS-induced injury in cell metabolism, why the amount of ROS/RNS produced by ionizing radiation at clinically relevant doses is ~1000 fold lower than the endogenous ROS/RNS level routinely produced in the cell and why a low level of endogenous RHS plays a crucial role in phagocytosis for immune defense. Herein we propose a plausible amplification mechanism in immune defense: ozone-depleting-like halogen cyclic reactions enhancing RHS effects are responsible for all the mentioned physiological functions, which are activated by H2O2 and deactivated by NO signaling molecule. Our results show that the reaction cycles can be repeated thousands of times and amplify the RHS pathogen-killing (defense) effects by 100,000 fold in phagocytosis, resembling the cyclic ozone-depleting reactions in the stratosphere. It is unraveled that H2O2 is a required protective signaling molecule (angel) in the defense system for human health and its dysfunction can cause many diseases or conditions such as autoimmune disorders, aging and cancer. We also identify a class of potent drugs for effective treatment of invading pathogens such as HIV and SARS-CoV-2 (COVID-19), cancer and other diseases, and provide a molecular mechanism of action of the drugs or candidates. View Full-Text
Keywords: respiratory burst; phagocytosis; reactive oxygen species; reactive halogen species; reactive nitrogen species; signaling; antitumor agents; antiviral agents; HIV; COVID-19 respiratory burst; phagocytosis; reactive oxygen species; reactive halogen species; reactive nitrogen species; signaling; antitumor agents; antiviral agents; HIV; COVID-19
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MDPI and ACS Style

Lu, Q.-B. Reaction Cycles of Halogen Species in the Immune Defense: Implications for Human Health and Diseases and the Pathology and Treatment of COVID-19. Cells 2020, 9, 1461. https://doi.org/10.3390/cells9061461

AMA Style

Lu Q-B. Reaction Cycles of Halogen Species in the Immune Defense: Implications for Human Health and Diseases and the Pathology and Treatment of COVID-19. Cells. 2020; 9(6):1461. https://doi.org/10.3390/cells9061461

Chicago/Turabian Style

Lu, Qing-Bin. 2020. "Reaction Cycles of Halogen Species in the Immune Defense: Implications for Human Health and Diseases and the Pathology and Treatment of COVID-19" Cells 9, no. 6: 1461. https://doi.org/10.3390/cells9061461

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