Metabolic reprogramming, oxidative stress, and mitophagy in JSRV Env-transformed BEAS-2B cells: insights from integrated transcriptomics and metabolomics

BACKGROUND: Jaagsiekte sheep retrovirus (JSRV) causes ovine pulmonary adenocarcinoma (OPA), and its pathogenesis is primarily mediated by the viral envelope (Env) protein. However, the detailed oncogenic mechanisms underlying JSRV infection remain incompletely understood. In this study, we integrated transcriptomic and metabolomic analyses to characterize JSRV Env-induced alterations in human bronchial epithelial BEAS-2B (cells). RESULTS: BEAS-2B cells transfected with the pcDNA4.0myc-his-JSRV-env plasmid, those transfected with the empty pcDNA4.0myc-his vector, and untreated BEAS-2B cells served as the experimental, negative control, and blank control groups, respectively. Transcriptomic analysis identified a total of 2733 differentially expressed genes (DEGs). Specifically, relative to the blank and negative control groups, 1178 genes were upregulated and 307 were downregulated in the JSRV-env group. These DEGs were significantly enriched in pathways related to altered cellular energy metabolism, cell cycle regulation, and oncogenic signaling. Metabolomic analysis revealed 451 differentially expressed metabolites (DEMs), with 192 detected in positive ion mode and 259 in negative ion mode. Compared with both control groups, the JSRV-env group exhibited 33 upregulated and 46 downregulated DEMs in positive ion mode, as well as 22 upregulated and 55 downregulated DEMs in negative ion mode. These DEMs were significantly enriched in pathways such as cellular metabolism, purine metabolism, amino acid metabolism, and the tricarboxylic acid cycle. Notably, cellular and mitochondrial energy metabolism pathways were closely linked. Analyses of mitochondrial- and mitophagy-related genes, alongside an integrated transcriptomic and metabolomic evaluation of their interactions, suggested mitochondrial damage and the potential activation of mitophagy. Furthermore, JSRV Env-transformed BEAS-2B cells exhibited elevated reactive oxygen species, decreased mitochondrial membrane potential, and abnormal mitochondrial morphology-characterized by swelling, as well as fragmented, dissolved, or disappearing cristae-along with the presence of myelin-like mitochondrial lesions and mitophagosomes. Mitochondrial and lysosomal probe co-localization further confirmed mitochondrial degradation in the transformed cells. CONCLUSIONS: Overall, these results highlight the potential involvement of altered mitochondrial energy metabolism and mitophagy in JSRV Env-induced BEAS-2B cell transformation. These findings offer novel insights into the mechanisms of viral oncoproteins, cellular metabolic reprogramming, and mitophagy, while identifying potential targets for understanding JSRV pathogenesis.