Investigation of the circulatory microRNAs and their involvement in regulation of inflammation in patients with COVID-19.

Background: Dysregulated levels of cytokines may lead to cytokine storm, which has been implicated in the immunopathogenesis of coronavirus disease 2019 (COVID-19). Here in the current study, the role of microRNA (miR)-155-5p, miR-146a, and miR-221-3p in the regulation of the immune responses and inflammatory state in patients with COVID-19 was investigated.

Methods: In this case-control study, peripheral blood samples were obtained from 75 COVID-19 subjects and 100 healthy controls. From the plasma samples, RNA was extracted and cDNA was synthesized, and subsequently the transcript level of miRNAs was measured by Real-time PCR. The plasma levels of interleukin (IL)-4 and interferon (IFN)-γ were determined using ELISA.

Results: miR-155-5p (fold change = 1.87, P = 0.020) and miR-221-3p (fold change = 2.26, P = 0.008), but not miR-146a, was upregulated in the plasma sample of COVID-19 cases compared to controls. The level of IFN-γ (but not IL-4) was significantly higher in the plasma samples of COVID-19 patients compared to control group. The expression level of miR-155-5p (r = 0.35, corrected P = 0.066) and miR-221-3p (r = 0.25, corrected P = 0.066) had positive correlation with the plasma levels of IFN-γ.

Conclusions: IFN-γ pathway in involved in the pathogenesis of COVID-19 that is regulated through miR-155-5p and miR-221-3p. These miRNAs showed potential utility as biomarkers for predicting the severity of COVID-19.