AUTHOR=Zhuang Cuicui , Liu Gang , Barkema Herman W. , Zhou Man , Xu Siyu , ur Rahman Sadeeq , Liu Yongxia , Kastelic John P. , Gao Jian , Han Bo 

TITLE=Selenomethionine Suppressed TLR4/NF-κB Pathway by Activating Selenoprotein S to Alleviate ESBL Escherichia coli-Induced Inflammation in Bovine Mammary Epithelial Cells and Macrophages

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.01461

DOI=10.3389/fmicb.2020.01461

ISSN=1664-302X

ABSTRACT=<p>Inflammation is the hallmark of extended-spectrum β-lactamase (ESBL)-producing <italic>Escherichia coli</italic>-induced bovine mastitis. Organic selenium can activate pivotal proteins in immune responses and regulate the immune system. The present study aimed to investigate whether selenomethionine (SeMet) attenuates ESBL <italic>E. coli</italic>-induced inflammation in bovine mammary epithelial cells (bMECs) and macrophages. Cells were treated with 0, 5/10, 10/20, 20/40, or 40/60 μM SeMet for 12 h and/or inoculated with ESBL<italic>-E. coli</italic> [multiplicity of infection (MOI) = 5] for 4/6 h, respectively. We assessed inflammatory responses, including selenoprotein S (SeS), Toll-like receptor 4 (TLR4), Ikappa-B (IκB), phospho-NF-κB p65 (Ser536), interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and lactate dehydrogenase (LDH) activities. Treatment with 40/60 μM SeMet promoted cell viability and inhibited LDH activities in both bMECs and macrophages. Inoculation with ESBL-<italic>E. coli</italic> reduced cell viability, which was attenuated by SeMet treatment in bMECs and macrophages. SeMet increased ESBL <italic>E. coli</italic>-induced downregulation of SeS and decreased LDH activities, TLR4, IκB, phospho-NF-κB p65 (Ser536), IL-1β, and TNF-α protein expressions in bMECs and macrophages. In addition, knockdown of SeS promoted protein expression of TLR4-mediated nuclear factor-kappa (NF-κB) pathway and BAY 11-708 inhibited TNF-α and IL-1β protein levels in bMECs and macrophages after ESBL-<italic>E. coli</italic> treatment. Moreover, ESBL-<italic>E. coli</italic> inoculation increased monocyte chemoattractant protein 1 (MCP-1), C–C motif ligand 3 (CCL-3), and CCL-5 mRNA expressions in bMECs. In conclusion, ESBL-<italic>E. coli</italic> induced expression of MCP-1, CCL-3, and CCL-5 in bMECs and then recruited and activated macrophages, whereas SeMet attenuated ESBL <italic>E. coli</italic>-induced inflammation through activated SeS-mediated TLR4/NF-κB signaling pathway in bMECs and macrophages.</p>