Swine IRF3/IRF7 attenuates inflammatory responses through TLR4 signaling pathway.

Guang-Ming Zha,Yan-Jing Guan,Pei-Ge Chen,Cheng-Yu Zhang,Xian-Qin Jiao,He-Ping Li,Yue-Ying Wang,He-Shui Zhu

doi:10.18632/oncotarget.18740

Abstract

To explore the role of IRF3/IRF7 during inflammatory responses, we investigated the effects of swine IRF3/IRF7 on TLR4 signaling pathway and inflammatory factors expression in porcine kidney epithelial PK15 cell lines. We successfully constructed eukaryotic vectors PB-IRF3 and PB-IRF7, transfected these vectors into PK15 cells and observed GFP under a fluorescence microscope. In addition, RT-PCR was also used to detect transfection efficiency. We found that IRF3/IRF7 was efficiently overexpressed in PK15 cells. Moreover, we evaluated the effects of IRF3/IRF7 on the TLR4 signaling pathway and inflammatory factors by RT-PCR. Transfected cells were treated with lipopolysaccharide (LPS) alone, or in combination with a TBK1 inhibitor (LiCl). We revealed that IRF3/IRF7 enhanced IFNα production, and decreased IL-6 mRNA expression. Blocking the TBK1 pathway, inhibited the changes in IFNα, but not IL-6 mRNA. This illustrated that IRF3/IRF7 enhanced IFNα production through TLR4/TBK1 signaling pathway and played an anti-inflammatory role, while IRF3/IRF7 decreased IL-6 expression independent of the TBK1 pathway. Trends in MyD88, TRAF6, TBK1 and NFκB mRNA variation were similar in all treatments. LPS increased MyD88, TRAF6, TBK1 and NFκB mRNA abundance in PBR3/PBR7 and PBv cells, while LiCl blocked the LPS-mediated effects. The levels of these four factors in PBR3/PBR7 cells were higher than those in PBv. These results demonstrated that IRF3/IRF7 regulated the inflammatory response through the TLR4 signaling pathway. Overexpression of swine IRF3/IRF7 in PK15 cells induced type I interferons production, and attenuated inflammatory responses through TLR4 signaling pathway.

Highlights

Outbreaks of catastrophic swine diseases have drawn extensive attention to the considerable economic and social losses that affect a wide range of swine farms locally and the industry worldwide
LPS increased MyD88, tumor necrosis factor receptor-associated factor-6 (TRAF6), TBK1 and NFκB mRNA abundance in PBR3/PBR7 and PBv cells, while LiCl blocked the LPS-mediated effects. The levels of these four factors in PBR3/PBR7 cells were higher than those in PBv. These results demonstrated that IRF3/IRF7 regulated the inflammatory response through the TLR4 signaling pathway
It promoted IFNα and inhibited IL-6 expression, further suppressing the inflammatory response. These results demonstrated that overexpression of swine IRF3/IRF7 could decrease the inflammatory response through TLR4 signaling pathway, and participate in type I interferons production

Summary

Introduction

Outbreaks of catastrophic swine diseases have drawn extensive attention to the considerable economic and social losses that affect a wide range of swine farms locally and the industry worldwide. Current vaccination strategies and antiviral drugs cannot effectively control swine diseases, such as porcine reproductive and respiratory syndrome (PRRS), which is mainly caused by PRRS virus (PRRSV), based on PRRSV itself is easy to mutate with time, PRRSV has the diversity of the genotypes. The innate immune response is the first line of host defense against infections. Type I interferons (IFNs) (primarily IFN-α/β) are induced to boost the immune response, protecting hosts from viral and nonviral pathogens [3]. IRF3 and IRF7 are two important members of IRFs family, having high homology. They play an important regulatory role in the expression and secretion of type I IFN for antiviral functions [5]

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Results

Conclusion