Lipids provide essential membrane components and energy sources for viral replication, playing multiple roles in viral infection. However, the mutual influence between lipid metabolism and PRRSV proliferation remains unclear. Using transcriptomics, lipidomics, BODIPY staining, and Western blot (WB) analysis, our findings revealed that PRRSV infection significantly altered the abundance of lipid-metabolism-associated genes and lipid metabolites in cells. qRT-PCR confirmed that PRRSV infection dose-dependently upregulated SREBP2 expression (p < 0.01), while BODIPY staining demonstrated a significant increase in intracellular lipid droplets post-infection (p < 0.01). Let-7f-5p significantly reduced lipid droplet accumulation and suppressed PRRSV N protein expression. Notably, 15 lipid species that were upregulated during PRRSV infection were downregulated by let-7f-5p overexpression. These lipids were enriched in pathways related to phosphatidylcholines, monounsaturated fatty acids, and C16-C18 fatty acid metabolism. Exogenous palmitic acid (C16:0) treatment reversed the inhibitory effects of let-7f-5p on SREBP2 expression and viral replication, demonstrating that viral proliferation can be regulated by modulating host lipid metabolism. This study reveals that PRRSV hijacks host lipid metabolism to facilitate viral replication, whereas let-7f-5p exerts antiviral effects through dual mechanisms. These findings provide new insights into host-directed antiviral strategies against PRRSV infection.

Background: This study aimed to elucidate the potential mechanisms through which bone marrow-derived mesenchymal stem cells (BM-MSCs) may be effective in alleviating experimental colitis induced by treatment with 2,4,6-trinitrobenzene-sulfonate acid (TNBS), specifically through autophagy modulation. Methods: BM-MSCs were collected from BALB/c mice for subsequent experiments. The study employed cell counting kits (CCK-8) to investigate the impact of the MSC-conditioned medium (M medium) on the proliferation of RAW264.7 macrophages. The GFP-mRFP-LC3 adenovirus was transfected into RAW264.7 to detect autophagic flux. The gene expression of cytokines was assessed through quantitative reverse transcription polymerase chain reaction (qRT-PCR). Western blot analysis was employed to determine the presence of a binding interaction between NOD-like receptor protein 3 (NLRP3) and autophagy. Furthermore, a colitis mouse model was established by TNBS induction. Clinical disease activity score was assessed regularly, and histological and morphometric analyses were performed on colonic tissues. Inflammatory serum cytokines were identified using an enzyme-linked immunosorbent assay. Results: BM-MSCs significantly promoted the proliferation of RAW264.7. In vitro lipopolysaccharide (LPS)-stimulated RAW264.7 cells, treated with BM-MSCs, triggered autophagy and inhibited cytokine mRNA expression. Additionally, in LPS-induced RAW264.7, BM-MSCs enhanced the Beclin1 protein expression and the microtubule-associated protein 1 light chain 3 (LC3)-II to LC3-I ratio while suppressing the protein levels of NLRP3 and apoptosis-associated speck-like protein (ASC). Nevertheless, 3-methyladenine (3-MA), an inhibitor of autophagy, prevented the impact of BM-MSCs by reducing the levels of NLRP3 and ASC proteins, suggesting that autophagy triggered the inhibition of the NLRP3 inflammasome. In comparison to the mice in the TNBS group, the mice in the TNBS+MSC group displayed a more acute form of colitis, and the IL1β and IL18 cytokines in their serum were lowered as well. In the meantime, 3-MA raised IL1β and IL18 cytokine levels and worsened TNBS-induced experimental colitis. Conclusions: BM-MSCs can suppress inflammation in TNBS-induced experimental mice by inhibiting the NLRP3 inflammasome, thereby enhancing autophagy.

In cellular biology, the extrusion of large molecular complexes from the nucleus has consistently represented a considerable challenge. In this investigation, we reveal a hitherto unexplored mechanism facilitating the efflux of nuclear lipid droplets (nLDs) from the nucleus directly into the cytoplasm, a process integral to comprehending cellular processes and nuclear dynamics. Through high-throughput sequencing, immunoprecipitation, and immunofluorescence experimentation, we demonstrated that the type I nucleoplasmic reticulum engages with nLDs, enabling the dynamic protein Rab8a’s transfer to the nLDs and fostering their translocation to the nuclear membrane. Phosphorylation of LMNA/C at the S392 site, adjacent to the nLD-nuclear membrane contact site, induces local depolymerization of lamins, creating an aperture that enables gradual nuclear exit of nLDs. Following this, nLDs, carrying DNA fragments, are released into the cytoplasm through budding and subsequently undergo autophagy-mediated degradation. Furthermore, we demonstrate that RhoA-PKC signaling enhances nLD movement and LMNA/C phosphorylation, while its inhibition impedes nuclear nLD efflux. Our groundbreaking investigation illuminates non-nuclear pore-dependent mechanisms of material exchange and offers fresh perspectives on nuclear metabolic pathways. In Brief: In this study, Jin et al. elucidate a novel mechanism for the expulsion of nuclear lipid droplets (nLDs) from the nucleus. They demonstrate that the activation of RhoA within the nucleus recruits Rab8a to the surface of nLDs. Concurrently, PKC phosphorylation triggers the phosphorylation of LMNA/C at the S392 site, leading to a localized depolymerization of lamins. This creates an aperture that allows for the gradual exit of nLDs from the nucleus. The efflux process of nLDs involves three sequential steps: rupture of the nuclear fibril layer, fusion of nLDs with the inner nuclear membrane (INM), and subsequent fusion with the outer nuclear membrane (ONM). This enables nLDs to enter the cytoplasm, shedding light on a previously unknown process of large molecular entity expulsion from the nucleus.

Aflatoxin 1. (AFB1) threatens animal health and dairy safety, but mammary-protective interventions remain poorly defined. We evaluated whether S-methylmethionine (SMM; commonly known as vitamin U) attenuates AFB1-associated injury using MAC-T bovine mammary epithelial cells, a mouse mammary model, biochemical assays, RT-qPCR, Western blotting, H&E staining, and exploratory ATAC-seq/RNA-seq analysis. Under 4 μg/mL (approximately 12.81 μM) AFB1 challenge, 1 mM SMM increased MAC-T cell viability by 14.1% (Tukey-adjusted p = 0.0387) and reduced LDH release by 38.2% (p = 0.000236) relative to the AFB1-only group. SMM also shifted selected redox markers toward a less injured state. Nrf2 protein abundance differed between the AF and AU groups (p = 0.049), although pathway activation and causal dependence were not tested. In mice, SMM co-treatment reduced serum ALT by 38.5% and mammary MDA by 56.4%, while increasing mammary T-SOD by 85.4% and GSH-Px by 100.9% relative to AF (p < 0.05 for the reported pairwise comparisons); inflammatory transcripts changed non-uniformly. The AU-versus-AF integration yielded four exploratory candidate genes (TNFSF10, NBEAL1, ENSBTAG00000054644, and ENSBTAG00000052086), and the selected RT-qPCR results were directionally consistent with the RNA-seq data. Thus, SMM attenuated selected AFB1-associated injury features under the tested conditions, while the underlying mechanism remains unresolved.