Identification and functional analysis of circular RNAs during mitochondrial damage induced by infectious bovine rhinotracheitis virus infection in Madin–Darby bovine kidney cells

Background : Infectious bovine rhinotracheitis virus (IBRV), a member of the Herpesviridae family, causes infectious bovine rhinotracheitis (IBR) and induces mitochondrial dysfunction in host cells. Circular RNAs (circRNAs)—a novel class of non-coding RNAs—have been implicated in various biological processes and pathologies related to mitochondrial damage. However, their role in IBRV-induced mitochondrial damage in Madin-Darby bovine kidney (MDBK) cells remains unclear. Results : Transmission electron microscopy(TEM), laser confocal microscopy, and flow cytometry confirmed that IBRV infection causes mitochondrial damage in MDBK cells. High-throughput sequencing revealed 144 differentially expressed (DE) circRNAs, 725 messenger RNAs (mRNAs), and 160 microRNAs (miRNAs) in IBRV-infected cells. We predicted that DE circRNAs regulate mitochondrial damage via source genes, circRNA-miRNA-mRNA networks, and RNA-binding proteins (RBPs). Source genes were enriched in mitochondria-related pathways like the mammalian target of rapamycin (mTOR), thyroid hormone, and Hippo signalling; 11 genes were localized to mitochondria. CircRNA-miRNA-mRNA network target genes were associated with cellular senescence, mitophagy, and ubiquitin-mediated proteolysis; 471 genes were linked to mitochondria. Additionally, 961 RBPs were enriched in pathways like nucleocytoplasmic transport and RNA degradation; 107 RBPs were localized to mitochondria. Functional validation revealed knockdown of circ_002584 reduced reactive oxygen species (ROS) accumulation ( p < 0.05) and mitochondrial membrane potential depolarization ( p < 0.05). Knockdown of circ_004326 increased both ( p < 0.01). Conclusions : CircRNAs play a regulatory role in IBRV-induced mitochondrial damage within MDBK cells. This finding is significant for virus-associated mitochondrial damage research, forming a theoretical foundation for utilizing circRNAs as diagnostic biomarkers and potential therapeutic targets for IBR.