Biomarkers for iron metabolism among patients hospitalized with community-acquired pneumonia caused by infection with SARS-CoV-2, bacteria, and influenza

Effects of Hypoxia and Inflammation on Hepcidin Concentration in Non-Anaemic COVID-19 Patients

Background/Objectives: This study aimed to explore the influence of hypoxia, inflammation, and erythropoiesis on hepcidin and other iron status parameters in non-anaemic COVID-19 patients admitted to the emergency unit before the introduction of therapeutic interventions. Methods: Ninety-six COVID-19 patients and 47 healthy subjects were recruited. Patients were subdivided into hypoxic or normoxic groups and, after follow-up, into mild and moderate, severe or critical disease severity groups. Iron, unsaturated iron-binding capacity (UIBC), ferritin, C-reactive protein (CRP), and interleukin 6 (IL-6) were measured on automatic analysers. ELISA kits were used for hepcidin and erythropoietin (EPO) determination. We calculated total iron-binding capacity (TIBC) and ratios of hepcidin with parameters of iron metabolism (ferritin/hepcidin, hepcidin/iron), inflammation (hepcidin/CRP, hepcidin/IL-6), and erythropoietic activity (hepcidin/EPO). Results: Hepcidin, ferritin, EPO, CRP, IL-6, ferritin/hepcidin, and hepcidin/iron were increased, while UIBC, TIBC, hepcidin/CRP, and hepcidin/IL-6 were decreased in hypoxic compared to normoxic patients as well as in patients with severe or critical disease compared to those with mild and moderate COVID-19. Regarding predictive parameters of critical COVID-19 occurrence, in multivariable logistic regression analysis, a combination of EPO and ferritin/hepcidin showed very good diagnostic performances and correctly classified 88% of cases, with an AUC of 0.838 (0.749-0.906). Conclusions: The hypoxic signal in our group of patients was not strong enough to overcome the stimulating effect of inflammation on hepcidin expression. EPO and ferritin/hepcidin might help to identify on-admission COVID-19 patients at risk of developing a critical form of the disease.

Can iron chelators ameliorate viral infections?

The redox reactivity of iron is a double-edged sword for cell functions, being either essential or harmful depending on metal concentration and location. Deregulation of iron homeostasis is associated with several clinical conditions, including viral infections. Clinical studies as well as in silico, in vitro and in vivo models show direct effects of several viruses on iron levels. There is support for the strategy of iron chelation as an alternative therapy to inhibit infection and/or viral replication, on the rationale that iron is required for the synthesis of some viral proteins and genes. In addition, abnormal iron levels can affect signaling immune response. However, other studies report different effects of viral infections on iron homeostasis, depending on the class and genotype of the virus, therefore making it difficult to predict whether iron chelation would have any benefit. This review brings general aspects of the relationship between iron homeostasis and the nonspecific immune response to viral infections, along with its relevance to the progress or inhibition of the inflammatory process, in order to elucidate situations in which the use of iron chelators could be efficient as antivirals.

COVID-19 compromises iron homeostasis: Transferrin as a target of investigation

IMPORTANCE

Since the beginning of the COVID-19 pandemic, numerous metabolic alterations have been observed in individuals with this disease. It is known that SARS-CoV-2 can mimic the action of hepcidin, altering intracellular iron metabolism, but gaps remain in the understanding of possible outcomes in other pathways involved in the iron cycle.

OBJECTIVE

To profile iron, ferritin and hepcidin levels and transferrin receptor gene expression in patients diagnosed with COVID-19 between June 2020 and September 2020.

DESIGN, SETTING AND PARTICIPANTS

Cross-sectional study that evaluated iron metabolism markers in 427 participants, 218 with COVID-19 and 209 without the disease.

EXPOSURES

The primary exposure was positive diagnose to COVID-19 in general population of Santo André and São Bernardo cities. The positive and negative diagnose were determinate through RT-qPCR.

MAIN OUTCOMES AND MEASURES

Devido a evidências de alterações do ciclo do ferro em pacientes diagnosticados com COVID-19 e devido a corregulação entre hepcidina e receptor de transferrina, uma análise da expressão gênica deste último, poderia trazer insights sobre o estado de ferro celular. A hipótese foi confirmada, mostrando aumento da expressão de receptor de transferrina concomitante com redução do nível de hepcidina circulante.

RESULTS

Serum iron presented lower values in individuals diagnosed with COVID-19, whereas serum ferritin presented much higher values in infected patients. Elderly subjects had lower serum iron levels and higher ferritin levels, and men with COVID-19 had higher ferritin values than women. Serum hepcidin was lower in the COVID-19 patient group and transferrin receptor gene expression was higher in the infected patient group compared to controls.

CONCLUSIONS AND RELEVANCE

COVID-19 causes changes in several iron cycle pathways, with iron and ferritin levels being markers that reflect the state and evolution of infection, as well as the prognosis of the disease. The increased expression of the transferrin receptor gene suggests increased iron internalization and the mimicry of hepcidin action by SARS-CoV-2, reduces iron export via ferroportin, which would explain the low circulating levels of iron by intracellular trapping.

Association between iron metabolism and SARS-COV-2 infection, determined by ferritin, hephaestin and hypoxia-induced factor-1 alpha levels in COVID-19 patients

BACKGROUND

Due to the growing evidence of the importance of iron status in immune responses, the biomarkers of iron metabolism are of interest in novel Coronavirus Disease 2019 (COVID-19). The present prospective study was carried out to compare iron status indicated by levels of ferritin with the levels of two novel biomarkers related to iron homeostasis, hephaestin and hypoxia-inducible factors-1 (HIF-1α) in the serum of patients with COVID-19 in comparison with a control group.

METHODS AND RESULTS

Blood samples from 34 COVID-19 patients and from 43 healthy volunteers were collected and the levels of HEPH and HIF-1α were measured by ELISA and compared with levels of serum ferritin. COVID-19 patients had higher serum levels of ferritin than those levels in control group (P < 0.0001). Conversely levels of HIF-1α and HEPH in the COVID-19 group were significantly lower than those of control group (P < 0.0001 for both). An inverse correlation between hephaestin and ferritin as well as between HIF-1α and ferritin was found among all subjects (P < 0.0001), and among COVID-19 patients, but not to statistical significance.

CONCLUSION

Levels of hephaestin and HIF-1α were found to be inversely related levels of ferritin across all participants in the study, and to our knowledge this is the first report of hephaestin and HIF-1α as potential markers of iron status. Further studies are needed to corroborate the findings, utilizing a broader range of markers to monitor inflammatory as well as iron status.

Evaluation of Hepcidin Level in COVID-19 Patients Admitted to the Intensive Care Unit

Coronavirus disease 2019 (COVID-19) presents a clinical spectrum that ranges from a mild condition to critical illness. Patients with critical illness present respiratory failure, septic shock and/or multi-organ failure induced by the so called “cytokine storm”. Inflammatory cytokines affect iron metabolism, mainly inducing the synthesis of hepcidin, a hormone peptide not routinely measured. High levels of hepcidin have been associated with the severity of COVID-19. The aim of this study was to analyze, retrospectively, the levels of hepcidin in a group of COVID-19 patients admitted to the intensive care unit (ICU) of the Policlinico Tor Vergata of Rome, Italy. Thirty-eight patients from November 2020 to May 2021 were enrolled in the study. Based on the clinical outcome, the patients were assigned to two groups: survivors and non-survivors. Moreover, a series of routine laboratory parameters were monitored during the stay of the patients in the ICU and their levels correlated to the outcome. Statistical differences in the level of hepcidin, D-dimer, IL-6, LDH, NLR, neutrophils level, CRP, TNF-α and transferrin were observed between the groups. In particular, hepcidin values showed significantly different median concentrations (88 ng/mL vs. 146 ng/mL) between survivors and non-survivors. In addition, ROC curves analysis revealed sensitivity and specificity values of 74% and 76%, respectively, at a cut-off of 127 (ng/mL), indicating hepcidin as a good biomarker in predicting the severity and mortality of COVID-19 in ICU patients.