AUTHOR=Zheng Yuhui , Liu Gang , Wang Wei , Wang Yajing , Cao Zhijun , Yang Hongjian , Li Shengli 

TITLE=Lactobacillus casei Zhang Counteracts Blood-Milk Barrier Disruption and Moderates the Inflammatory Response in Escherichia coli-Induced Mastitis

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.675492

DOI=10.3389/fmicb.2021.675492

ISSN=1664-302X

ABSTRACT=<p><italic>Escherichia coli</italic> is a common mastitis-causing pathogen that can disrupt the blood-milk barrier of mammals. Although <italic>Lactobacillus casei</italic> Zhang (LCZ) can alleviate mice mastitis, whether it has a prophylactic effect on <italic>E. coli</italic>-induced mastitis through intramammary infusion, as well as its underlying mechanism, remains unclear. In this study, <italic>E. coli</italic>-induced injury models of bovine mammary epithelial cells (BMECs) and mice in lactation were used to fill this research gap. <italic>In vitro</italic> tests of BMECs revealed that LCZ significantly inhibited the <italic>E. coli</italic> adhesion (<italic>p</italic> &lt; 0.01); reduced the cell desmosome damage; increased the expression of the tight junction proteins claudin-1, claudin-4, occludin, and zonula occludens-1 (ZO-1; <italic>p</italic> &lt; 0.01); and decreased the expression of the inflammatory cytokines tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 (<italic>p</italic> &lt; 0.01), thereby increasing trans-epithelial electric resistance (<italic>p</italic> &lt; 0.01) and attenuating the lactate dehydrogenase release induced by <italic>E. coli</italic> (<italic>p</italic> &lt; 0.01). <italic>In vivo</italic> tests indicated that LCZ significantly reduced the injury and histological score of mice mammary tissues in <italic>E. coli</italic>-induced mastitis (<italic>p</italic> &lt; 0.01) by significantly promoting the expression of the tight junction proteins claudin-3, occludin, and ZO-1 (<italic>p</italic> &lt; 0.01), which ameliorated blood-milk barrier disruption, and decreasing the expression of the inflammatory cytokines (TNF-α, IL-1β, and IL-6) in mice mammary tissue (<italic>p</italic> &lt; 0.01). Our study suggested that LCZ counteracted the disrupted blood-milk barrier and moderated the inflammatory response in <italic>E. coli</italic>-induced injury models, indicating that LCZ can ameliorate the injury of mammary tissue in mastitis.</p>