MicroRNAs regulate the expression of genes related to the innate immune and inflammatory response in rabbits infected with Lagovirus europaeus GI.1 and GI.2 genotypes

Abstract

MicroRNAs (miR) are a group of small, non-coding RNAs of 17–25 nucleotides that regulategene expression at the post-transcriptional level. Dysregulation of miRNA expression or functionmay contribute to abnormal gene expression and signaling pathways, leading to disease pathology.Lagovirus europaeus (L. europaeus) causes severe disease in rabbits called rabbit hemorrhagic disease(RHD). The symptoms of liver, lung, kidney, and spleen degeneration observed during RHD aresimilar to those of acute liver failure (ALF) and multi-organ failure (MOF) in humans. In thisstudy, we assessed the expression of miRs and their target genes involved in the innate immuneand inflammatory response. Also, we assessed their potential impact on pathways in L. europaeusinfection—two genotypes (GI.1 and GI.2)—in the liver, lungs, kidneys, and spleen. The expressionof miRs and target genes was determined using quantitative real-time PCR (qPCR). We assessedthe expression of miR-155 (MyD88, TAB2, p65, NLRP3), miR-146a (IRAK1, TRAF6), miR-223 (TLR4,IKKa, NLRP3), and miR-125b (MyD88). We also examined biomarkers of inflammation: IL-1b, IL-6,TNF-a, and IL-18 in four tissues at the mRNA level. Our study shows that the main regulators ofthe innate immune and inflammatory response in L. europaeus/GI.1 and GI.2 infection, as well asRHD, are miR-155, miR-223, and miR-146a. During infection with L. europaeus/RHD, miR-155 hasboth pro- and anti-inflammatory effects in the liver and anti-inflammatory effects in the kidneys andspleen; miR-146a has anti-inflammatory effects in the liver, lungs and kidneys; miR-223 has antiinflammatoryeffects in all tissues; however, miR-125b has anti-inflammatory effects only in the liver.In each case, such an effect may be a determinant of the pathogenesis of RHD. Our research showsthat miRs may regulate three innate immune and inflammatory response pathways in L. europaeusinfection. However, the result of this regulation may be influenced by the tissue microenvironment.Our research shows that infection of rabbits with L. europaeus/GI.1 and GI.2 genotypes causes anoverexpression of two critical acute phase cytokines: IL-6 in all examined tissues and TNF-a (in theliver, lungs, and spleen). IL-1b was highly expressed only in the lungs after L. europaeus infection.These facts indicate a strong and rapid involvement of the local innate immune and inflammatoryresponse in L. europaeus infection—two genotypes (GI.1 and GI.2)—and in the pathogenesis of RHD.Profile of biomarkers of inflammation in rabbits infected with L. europaeus/GI.1 and GI.2 genotypesare similar regarding the nature of changes but are different for individual tissues. Therefore, wepropose three inflammation profiles for L. europaeus infection for both GI.1 and GI.2 genotypes(pulmonary, renal, liver, and spleen).