A novel pro-inflammatory protein of Streptococcus suis 2 induces the Toll-like receptor 2-dependent expression of pro-inflammatory cytokines in RAW 264.7 macrophages via activation of ERK1/2 pathway.

Qiang Zhang,Yajing Song,Shuxian Yan,Meilin Jin,Zhongmin Xu,Jiantao Liu,Junping Yu,Anding Zhang,Yujie Yang

doi:10.3389/fmicb.2015.00178

Qiang Zhang, Yajing Song + Show 7 more

Open Access

https://doi.org/10.3389/fmicb.2015.00178

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Journal: Frontiers in microbiology	Publication Date: Mar 9, 2015
Citations: 20	License type: cc-by

Affiliation: Huazhong Agricultural University

Abstract

Streptococcus suis 2 is an important swine pathogen and an emergent zoonotic pathogen. Excessive inflammation caused by S. suis is responsible for the high levels of early mortality observed in septic shock-like syndrome cases. However, the mechanisms through which S. suis 2 (SS2) causes excessive inflammation remain unclear. Thus, this study aimed to identify novel pro-inflammatory mediators that play important roles in the development of therapies against SS2 infection. In this study, the novel pro-inflammatory protein HP0459, which was encoded by the SSUSC84_0459 gene, was discovered. The stimulation of RAW 264.7 macrophages with recombinant HP0459 protein induced the expression of pro-inflammatory cytokines (IL-1β, MCP-1 and TNF-α). Compared with the wild-type (WT) strain, the isogenic knockout of HP0459 in SS2 led to reduced production of pro-inflammatory cytokines in RAW264.7 macrophages and in vivo. The pro-inflammatory activity of HP0459 was significantly reduced by an antibody against Toll-like receptor 2 (TLR2) in RAW264.7 macrophages and was lower in TLR2-deficient (TLR2-/-) macrophages than in WT macrophages. Furthermore, specific inhibitors of the extracellular signal-regulated kinase 1/2 (ERK1/2) pathways significantly decreased the HP0459-induced pro-inflammatory cytokine production, and a western blot assay showed that HP0459 stimulation induced the activation of the ERK1/2 pathway. Taken together, our data indicate that HP0459 is a novel pro-inflammatory mediator of SS2 and induces TLR2-dependent pro-inflammatory activity in RAW264.7 macrophages through the ERK1/2 pathway.

Highlights

Streptococcus suis is a major pathogen responsible for important economic losses to the swine industry worldwide, during the past 20 years (Gottschalk et al, 2010)
Cytokine Secretion from RAW264.7 Cells Stimulated with HP0459 After purification by Ni-NTA agarose chromatography, the SDSPAGE (Figure 1A) and western blot analysis (Figure 1B) of HP0459 revealed that the HP0459 protein was successfully purified
To determine the pro-inflammatory role of HP0459, RAW264.7 cells were stimulated with HP0459 at a concentration of 10 μg ml−1 for 10 h and analyzed by quantitative polymerase chain reaction (qPCR) and enzyme-linked immunosorbent assay (ELISA) respectively

Summary

Introduction

Streptococcus suis is a major pathogen responsible for important economic losses to the swine industry worldwide, during the past 20 years (Gottschalk et al, 2010). S. suis is considered one of the most important causes of meningitis in humans in various locations, including Vietnam, Thailand, and Hong Kong (Suankratay et al, 2004; Hui et al, 2005; Ip et al, 2007; Mai et al, 2008). These findings emphasize the importance of S. suis as an emerging zoonosis and indicate that S. suis represents a significant public health concern (Fittipaldi et al, 2012). The increased severity of S. suis infection in humans underscores the critical need to better understand the factors associated with the pathogenesis of S. suis infection (Gottschalk and Segura, 2000)

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