Normal butanol fraction of <i>Polygonum hydropiper</i> L. flavonoids reduces inflammation caused by PCV2 infections in cell and mouse models.

Abstract

<h4>Introduction</h4>The normal butanol fraction of <i>Polygonum hydropiper</i> L. flavonoids (FNB) exhibits significant anti-inflammatory effects. This study investigated FNB's impact on inflammatory responses induced by Porcine circovirus type 2 (PCV2) in cell and mouse models.<h4>Methods</h4>An inflammatory model was established in RAW264.7 cells infected with varying PCV2 concentrations. And assigning both RAW264.7 cells and 108 SPF-grade KM mice to Control, PCV2, Rutin, and various dosages of FNB groups. Inflammatory factors such as Monocyte Chemoattractant Protein-1 (MCP-1), interleukin-6 (IL-6), IL-8, IL-10, Tumor Necrosis Factor-alpha (TNF-α), Reactive Oxygen Species (ROS), and Nitric Oxide (NO) were quantified using ELISA, RT-qPCR and immunohistochemistry.<h4>Results</h4>Results showed that a PCV2 titer of 10^4.5 TCID₅₀/0.1 mL when applied to RAW264.7 cells effectively established an <i>in vitro</i> inflammatory model at 12 and 24 h post-infection. Following PCV2 infection, all the inflammatory factors displayed a significant increased both in culture supernatant and intracellular mRNA expression levels (<i>p</i> < 0.05 or <i>p</i> < 0.01), but these levels were reduced by FNB treatment (<i>p</i> < 0.05 or <i>p</i> < 0.01). In mouse sera post-PCV2 infection also showed elevated levels of IL-6, IL-8 IL-10, TNF-α, and MCP-1 (<i>p</i> < 0.05 or <i>p</i> < 0.01). Additionally, mRNA and protein levels for TNF-α, IL-8, IL-10, IL-6, and iNOS rose significantly in lung tissues (<i>p</i> < 0.01) but decreased with FNB treatment (<i>p</i> < 0.05 or <i>p</i> < 0.01).<h4>Discussion</h4>These findings suggest that FNB reduces inflammatory factor production and modulates the inflammatory response triggered by PCV2 infection, potentially enhancing host resistance against it.