Hydrolysis of 2-Arachidonoglycerol by Pig Liver Esterase Enhances Inflammation Induced by Porcine Reproductive and Respiratory Syndrome Virus Infection
Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) infection induces a robust inflammation in pigs, characterized primarily by severe interstitial pneumonia. It is crucial to elucidate the mechanism of dysregulation of inflammatory mediators during PRRSV infection. This study investigated the function and molecular mechanisms of porcine liver esterase (PLE) in modulating the inflammation induced by PRRSV. Firstly, it was determined that PLE exhibits high expression levels in porcine alveolar macrophages (PAMs), mainly expressing the PLE6 which has high hydrolytic activity. Subsequent experimental investigations demonstrated that the inhibition of PLE activity or PLE knockdown significantly attenuated PRRSV-induced pro-inflammatory cytokines production. At the same time, it was found that the hydrolysis substrate of PLE, endocannabinoid-2-arachidonoglycerol (2-AG), could inhibit the expression of pro-inflammatory cytokines induced by PRRSV. Notably, this anti-inflammatory effect was abolished upon 2-AG hydrolysis, which exacerbated the inflammation. Subsequently, in vivo studies were performed to validate that the inhibition of PLE activity effectively weakened the hydrolysis of 2-AG and mitigated PRRSV-induced inflammation, alleviated lung tissue damage. Transcriptomic analysis identified the PI3K-Akt signaling pathway is important for PLE to modulate PRRSV-mediated inflammatory processes. Finally, mechanistic validation in PAMs demonstrated that both inhibition of PLE activity and 2-AG administration effectively suppressed the activating of the PI3K-Akt-NF-?B signaling cascade by PRRSV, particularly by inhibiting phosphorylation of Akt and p65. In conclusion, our findings demonstrate that PLE exacerbates PRRSV-induced inflammation through the hydrolysis of 2-AG. This study finds a novel mechanism of inflammation pathology caused by PRRSV, and can provide theoretical basis for PRRS control. Overall design: To investigate the effects of BNPP treatments on PRRSV infected pigs , we randomly divided experimental piglets into three groups (n=5 per group). Following treatment administration, PAMs were isolated from each group using standard bronchoalveolar lavage . Subsequently, total RNA was extracted from PAMs and subjected to high-throughput transcriptome sequencing  . The resulting sequencing data were processed through quality control, alignment to the porcine reference genome (Sus scrofa 11.1), and quantification of gene expression levels. Differential gene expression analysis was performed using DESeq2 (|log2FC| > 1, adjusted p-value < 0.05), followed by functional enrichment analysis (GO and KEGG) to identify significantly altered biological pathways.