MicroRNA 205-5p and COVID-19 adverse outcomes: Potential molecular biomarker and regulator of the immune response.

Coronavirus disease 2019 (COVID-19) is an acute respiratory infection caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The uncontrolled systemic inflammatory response, resulting from the release of large amounts of pro-inflammatory cytokines, is the main mechanism behind severe acute respiratory syndrome and multiple organ failure, the two main causes of death in COVID-19. Epigenetic mechanisms, such as gene expression regulation by microRNAs (miRs), may be at the basis of the immunological changes associated with COVID-19. Therefore, the main objective of the study was to evaluate whether the expression of miRNAs upon hospital admission could predict the risk of fatal COVID-19. To evaluate the level of circulating miRNAs, we used serum samples of COVID-19 patients collected upon hospital admission. Screening of differentially expressed miRNAs in fatal COVID-19 was performed by miRNA-Seq and the validation of miRNAs by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The Mann-Whitney test and receiver operating characteristic (ROC) curve were used to validate the miRNAs, whose potential signaling pathways and biological processes were identified through an in silico approach. A cohort of 100 COVID-19 patients was included in this study. By comparing the circulating levels of miRs between survivors and patients who died due to complications of the infection, we found that the expression of miR-205-5p was increased in those who died during hospitalization, and the expression of both miR-205-5p (area under the curve [AUC] = 0.62, 95% confidence interval [CI] = 0.5-0.7, P = 0.03) and miR-206 (AUC = 0.62, 95% CI = 0.5-0.7, P = 0.03) was increased in those who lately evolved to severe forms of the disease (AUC = 0.70, 95% CI = 0.6-0.8, P = 0.002)."In silico" analysis revealed that miR-205-5p has the potential to enhance the activation of NLPR3 inflammasome and to inhibit vascular endothelial growth factor (VEGF) pathways. Impaired innate immune response against SARS-CoV-2 may be explained by epigenetic mechanisms, which could form early biomarkers of adverse outcomes.