Digital PCR (dPCR) Quantification of miR-155-5p as a Potential Candidate for a Tissue Biomarker of Inflammation in Rabbits Infected with Lagovirus europaeus/Rabbit Hemorrhagic Disease Virus (RHDV)

ORF3a of SARS-CoV-2 modulates PI3K/AKT signaling in human lung epithelial cells via hsa-miR-155-5p

SARS-CoV-2 infection results in cytokine burst, leading to proinflammatory responses in lungs of COVID-19 patients. SARS-CoV-2 ORF3a triggers the generation of proinflammatory cytokines. However, the underlying mechanism of dysregulation of proinflammatory responses is not well understood. We studied the role of microRNA in the generation of proinflammatory responses as a bystander effect of SARS-CoV-2 ORF3a in human lung epithelial cells. We observed upregulation of hsa-miR-155-5p in SARS-CoV-2 ORF3a transfected human lung epithelial cells, which led to the reduced expression of SHIP1. This resulted in phosphorylation of AKT and NF-κB, which further led to the increased expression of the proinflammatory cytokines IL-6 and TNF-α. Additionally, overexpression and knockdown studies of hsa-miR-155-5p were performed to confirm the role of hsa-miR-155-5p in the regulation of the SHIP1. We demonstrated that hsa-miR-155-5p modulates the proinflammatory response by activating the PI3K/AKT pathway through the inhibition of SHIP1 in SARS-CoV-2 ORF3a transfected human lung epithelial cells.

MicroRNAs participate in the regulation of apoptosis and oxidative stress-related gene expression in rabbits infected with Lagovirus europaeus GI.1 and GI.2 genotypes

MicroRNAs (miRs) are a group of small, 17-25 nucleotide, non-coding RNA that regulate gene expression at the post-transcriptional level. To date, little is known about the molecular signatures of regulatory interactions between miRs and apoptosis and oxidative stress in viral diseases. Lagovirus europaeus is a virus that causes severe disease in rabbits (Oryctolagus cuniculus) called Rabbit Hemorrhagic Disease (RHD) and belongs to the Caliciviridae family, Lagovirus genus. Within Lagovirus europaeus associated with RHD, two genotypes (GI.1 and GI.2) have been distinguished, and the GI.1 genotype includes four variants (GI.1a, GI.1b, GI.1c, and GI.1d). The study aimed to assess the expression of miRs and their target genes involved in apoptosis and oxidative stress, as well as their potential impact on the pathways during Lagovirus europaeus-two genotypes (GI.1 and GI.2) infection of different virulences in four tissues (liver, lung, kidneys, and spleen). The expression of miRs and target genes related to apoptosis and oxidative stress was determined using quantitative real-time PCR (qPCR). In this study, we evaluated the expression of miR-21 (PTEN, PDCD4), miR-16b (Bcl-2, CXCL10), miR-34a (p53, SIRT1), and miRs-related to oxidative stress-miR-122 (Bach1) and miR-132 (Nfr-2). We also examined the biomarkers of both processes (Bax, Bax/Bcl-2 ratio, Caspase-3, PARP) and HO-I as biomarkers of oxidative stress. Our report is the first to present the regulatory effects of miRs on apoptosis and oxidative stress genes in rabbit infection with Lagovirus europaeus-two genotypes (GI.1 and GI.2) in four tissues (liver, lungs, kidneys, and spleen). The regulatory effect of miRs indicates that, on the one hand, miRs can intensify apoptosis (miR-16b, miR-34a) in the examined organs in response to a viral stimulus and, on the other hand, inhibit (miR-21), which in both cases may be a determinant of the pathogenesis of RHD and tissue damage. Biomarkers of the Bax and Bax/Bcl-2 ratio promote more intense apoptosis after infection with the Lagovirus europaeus GI.2 genotype. Our findings demonstrate that miR-122 and miR-132 regulate oxidative stress in the pathogenesis of RHD, which is associated with tissue damage. The HO-1 biomarker in the course of rabbit hemorrhagic disease indicates oxidative tissue damage. Our findings show that miR-21, miR-16b, and miR-34a regulate three apoptosis pathways. Meanwhile, miR-122 and miR-132 are involved in two oxidative stress pathways.

Epigenetic alterations of miR-155 and global DNA methylation as potential mediators of ochratoxin A cytotoxicity and carcinogenicity in human lung fibroblasts

Ochratoxin A (OTA) is a well-known mycotoxin that adversely affects different human cells. Inhalational exposure to OTA and subsequent pulmonary diseases have been previously reported, yet its potential carcinogenicity and underlying molecular mechanisms have not been fully elucidated. This study aimed to evaluate the OTA-induced cytotoxicity and the epigenetic changes underlying its potential carcinogenicity in fetal lung fibroblast (WI-38) cells. OTA cytotoxicity was assessed by MTT assay; RT-qPCR was used to determine the expression of BAX, BCL-2, TP53, and miR-155, while ELISA was used for measuring 5-methyl cytosine percentage to assess global DNA methylation in OTA-treated versus control cells. WI-38 cells demonstrated sensitivity to OTA with IC50 at 22.38 μM. Though BAX and Bcl-2 were downregulated, with low BAX/BCL-2 ratio, and TP53 was upregulated, their fold changes showed decline trend with increasing OTA concentration. A significant dose-dependent miR-155 upregulation was observed, with dynamic time-related decline. Using subtoxic OTA concentrations, a significant global DNA hypermethylation with significant dose-dependent and dynamic alterations was identified. Global DNA hypermethylation and miR-155 upregulation are epigenetic mechanisms that mediate OTA toxicity on WI-38 cells. BAX downregulation, reduced BAX/BCL-2 ratio together with miR-155 upregulation indicated either the inhibition of TP53-dependent apoptosis or a tissue specific response to OTA exposure. The aforementioned OTA-induced variations present a new molecular evidence of OTA cytotoxicity and possible carcinogenicity in lung fibroblast cells.