Lactobacillus casei Zhang Ameliorates Blood-Milk Barrier Disruption and
Suppresses the Inflammatory Response during Escherichia coli-induced
Mastitis
Abstract
Background and Purpose: Escherichia coli is a common mastitis-causing
pathogens and is destructive to the blood-milk barrier. Oral
administration of Lactobacillus casei Zhang (LCZ) could alleviate mice
mastitis. However, its prophylactic effect and mechanism through
intramammary injection on E. coli-induced mastitis is unclear now. Here,
we investigate this using E. coli-induced mastitis model. Experimental
Approach: Prophylactic effects and mechanism of intramammary injection
of LCZ on blood-milk barrier and inflammation were studied in both
bovine mammary epithelial cells (BMECs) and pregnant mice. Key Results:
In vitro tests revealed that LCZ significantly inhibited the adhesion of
E. coli to monolayer cells, reduce the damage of cell desmosomes,
up-regulated the expression of tight junction proteins (claudin-1,
claudin-4, occludin, and ZO-1), and down-regulated the expression of
inflammatory cytokines (TNF-α, IL-1β, and IL-6) thereby enhancing the
trans-epithelial electric resistance of monolayer BMECs and effectively
protecting cells from damage caused by E. coli. In vivo experiments
suggested that LCZ significantly promoted the expression of tight
junction proteins (claudin-3, occludin, and ZO-1) but significantly
inhibited the expression of inflammatory cytokines (TNF-α, IL-1β, and
IL-6) in mouse mammary tissue, thereby decreased disruption in mammary
tissues, infiltration of inflammatory cells in E. coli-induced mastitis.
Conclusions and Implications: In our study, LCZ ameliorates blood-milk
barrier disruption and suppresses the inflammatory response during E.
coli-induced mastitis, indicating LCZ may serve as a effective
prophylactic agent to preserve the blood-milk barrier function during
mastitis.