Symptoms of COVID-19 range from asymptomatic/mild symptoms to severe illness and death, consequence of an excessive inflammatory process triggered by SARS-CoV-2 infection. The diffuse inflammation leads to endothelium dysfunction in pulmonary blood vessels, uncoupling eNOS activity, lowering NO production, causing pulmonary physiological alterations and coagulopathy. On the other hand, iNOS activity is increased, which may be advantageous for host defense, once NO plays antiviral effects. However, overproduction of NO may be deleterious, generating a pro-inflammatory effect. In this review, we discussed the role of endogenous NO as a protective or deleterious agent of the respiratory and vascular systems, the most affected in COVID-19 patients, focusing on eNOS and iNOS roles. We also reviewed the currently available NO therapies and pointed out possible alternative treatments targeting NO metabolism, which could help mitigate health crises in the present and future CoV’s spillovers.

Malaria is a threat to human mankind and kills about half a million people every year. On the other hand, COVID‐19 resulted in several hundred thousand deaths since December 2019 and remains without an efficient and safe treatment. The antimalarials chloroquine (CQ) and its analog, hydroxychloroquine (HCQ), have been tested for COVID‐19 treatment, and several conflicting evidence has been obtained. Therefore, the aim of this review was to summarize the evidence regarding action mechanisms of these compounds against Plasmodium and SARS‐CoV‐2 infection, together with cytometry applications. CQ and HCQ act on the renin angiotensin system, with possible implications on the cardiorespiratory system. In this context, flow and image cytometry emerge as powerful technologies to investigate the mechanism of therapeutic candidates, as well as for the identification of the immune response and prognostics of disease severity. Data from the large randomized trials support the conclusion that CQ and HCQ do not provide any clinical improvements in disease severity and progression of SARS‐CoV‐2 patients, as well as they do not present any solid evidence of increased serious side effects. These drugs are safe and effective antimalarials agents, but in SARS‐CoV‐2 patients, they need further studies in the context of clinical trials. © 2020 International Society for Advancement of Cytometry

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