NF-κB-Dependent Snail Expression Promotes Epithelial-Mesenchymal Transition in Mastitis.

Haokun Liu,Yutong Yan,Ying Zhao,Baohua Ma,Qiang Wei,Yanfang Wu,Xiaoe Zhao

doi:10.3390/ani11123422

Abstract

Mastitis is a common and important clinical disease in ruminants. This may be associated with inflammatory fibrosis if not treated promptly. Inflammation-derived fibrosis is usually accompanied by epithelial-mesenchymal transition (EMT) in epithelial cells. However, the precise molecular mechanism underlying mastitis-induced fibrosis remains unclear. Nuclear factor kappa-B (NF-κB) and Snail are key regulators of EMT. In this study, primary goat mammary epithelial cells (GMECs) were treated with 10 μg/mL lipopolysaccharide (LPS) for 14 d to mimic the in vivo mastitis environment. After LPS treatment, the GMECs underwent mesenchymal morphological transformation and expressed mesenchymal cell markers. Snail expression was induced by LPS and was inhibited by suppression of the TLR4/NF-κB signaling pathway. Snail knockdown alleviated LPS-induced EMT and altered the expression of inflammatory cytokines. Finally, we found that the expression of key molecules of the TLR4/NF-κB/Snail signaling pathway was increased in mastitis tissues. These results suggest that Snail plays a vital role in LPS-induced EMT in GMECs and that the mechanism is dependent on the activation of the TLR4/NF-κB signaling pathway.

Highlights

Mastitis is one of the most common clinical diseases in dairy animals; it may result in decreased milk production or a decrease in the quality of milk produced, and it disturbs the health and welfare of animals [1]
As TGF-β signaling has been shown to play an important role in epithelial–mesenchymal transition (EMT) [24], we used TGF-β1 as a positive control to test whether LPS induced EMT in goat mammary epithelial cells (GMECs)
The immunofluorescence results revealed that treatment with LPS or TGF-β1 led to low expression levels of E-cadherin and high expression of N-cadherin and vimentin (Figure 1B–D)

Summary

Introduction

Mastitis is one of the most common clinical diseases in dairy animals; it may result in decreased milk production or a decrease in the quality of milk produced, and it disturbs the health and welfare of animals [1]. Long-term mastitis is a prerequisite for mammary fibrosis, which probably enhances the epithelial–mesenchymal transition (EMT) by inducing the expression of inflammatory factors. There are two causes of long-term mammary infections in ruminants: delayed diagnosis and treatment of clinical mastitis [2,3], and long-term infection caused by chronic subclinical mastitis [4]. The combined prevalence of clinical mastitis and chronic subclinical mastitis in dairy cows exceeds 30% in the dairy industry [5,6]. The molecular mechanisms underlying the pathologies of mammary fibrosis remain unclear. Knowledge of molecular mechanisms that may help in mastitis prevention—to benefit animal welfare and the economy—is lacking

Methods

Results

Conclusion