On 2021-05-13 15:56:02, user Tatiana Araujo Pereira wrote:
It has been more than one year since the Coronavirus Disease 2019 (COVID-19) outbreak started. We already have effective vaccines around the world, but the imbalance between supply and demand allows Sars-CoV-2 to spread and mutate faster than mass immunization, especially in less developed countries. The arise of more transmissible variants is very worrying and motivates the search for biomarkers that enable early assessment of possible critical cases as well as therapeutic targets for the disease. In this sense Flora et al [1] performed laboratory and proteomic analysis of the plasma sample from a cohort of 163 COVID-19 patients admitted to Bauru State Hospital (São Paulo, Brasil) divided in three groups: “a) patients with mild symptoms that were discharged without admission to an ICU; b) patients with severe symptoms that were discharged after admission to an ICU; c) critical patients, who were admitted to an ICU and died”. The results point to a high concentration of ferritin (FTN) and absence of the IREB2 protein in volunteers exhibiting severe and critical symptoms, indicating that iron homeostasis would be a possible therapeutic target. These results are in line with previous researches, which also identified FTN levels directly related to the severity of the disease [2-5]. Ferritin is an iron reservoir protein, keeping it in its core shell to protect cells against oxidative stress. There are other proteins inhibiting iron redox reactivity in the body, helping with metal ions transport (Transferrin), import to (Divalent Metal Transport) and export from (Ferroportin) the cell [6, 7]. Due to its role in iron homeostasis, FTN is used to indirectly assess iron status in the body. Ordinarily, high levels of FTN mean iron overload [8]. However, circulating ferritin can be elevated independently of iron overload in inflammatory processes, in which it acts as immunosuppressant and proinflamatory modulator [4, 9, 10]. IREB2 is an Iron Regulatory Protein (IRP). When iron levels are low these proteins are able to attach to an untranslated region of mRNA known as Iron Responsive Elements (IRE). Through this mechanism it regulates expression of transferrin receptor and ferritin. In iron overload conditions the affinity of IRP for IRE is not enough to keep the attachment and the protein degrades or takes another role. IREB2 represses ferritin translation when bounded to IRE in FTN-mRNA and degrades in iron overload conditions [6, 11-13].<br />
Because of observed data, Flora et al [1] concluded that “increasing the expression of IREB2 might be a therapeutic possibility to reduce ferritin levels and, in turn, the severity of COVID-19”. Nonetheless, there is no data about iron status in the plasma of the subjects. So it is impossible to be sure whether the high levels of FTN and absence of IREB2 are associated with iron overload. In this case, suppressing ferritin production could culminate in greater oxidative damage, and even increase the risk of opportunistic infections, since intracellular segregation of iron is one of the main strategies to defend host against parasites [14]. In macrophages, this mechanism induces production of nitrogen and oxygen reactive species helping immune defenses [15, 16], but in chronic inflammation it affects iron recycling [17]. Another way to limit iron availability involves its main regulatory hormone hepcidin, which inhibits iron exit from the cell [18]. Hepcidin expression is induced by interleukine-6 (IL-6), which is produced in Sars-CoV-2 infection [19]. Also, Sepehr Ehsani identified a hepcidin mimetic in protein S region that plays a fundamental role in membrane fusion [20]. In this context it is important to verify the possibility that high levels of FTN are not associated with iron overload and only then consider increasing in IREB2 expression as a therapeutic strategy against COVID-19.
AUTHORS<br />
Pereira, T A and Espósito, B P.<br />
Institute of Chemistry – Univesity of São Paulo.
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