Cis-9, Trans-11 CLA Alleviates Lipopolysaccharide-Induced Depression of Fatty Acid Synthesis by Inhibiting Oxidative Stress and Autophagy in Bovine Mammary Epithelial Cells.

Nana Ma,Xiangzhen Shen,Xiaoli Shi,Guangjun Chang,Hongzhu Zhang,Hongyu Dai,Guozhen Wei,Animesh Chandra Roy

doi:10.3390/antiox11010055

Abstract

Lipopolysaccharide (LPS) is the dominating endotoxin of Gram-negative bacteria, which can cause mastitis. Bovine mammary epithelial cells (BMECs), as major components of the mammary gland, usually suffer LPS challenge. Cis-9, trans-11 conjugated linoleic acid (CLA) has been reported to have anti-inflammatory characteristics, while its anti-oxidative ability to maintain cellular homeostasis in BMECs under LPS challenge is limited. Therefore, we studied whether cis-9, trans-11 CLA can restore the disturbance of cellular homeostasis indicated by the redox status and autophagy level caused by LPS and have an effect on cellular function- milk fat metabolism. For oxidative stress, LPS challenge promoted the formation of reactive oxygen species (ROS) and thiobarbituric acid reactive substances (TBARS) and decreased the concentration of glutathione. Anti-oxidative signaling regulated by transcription factor nuclear factor, erythroid 2 like 2 (Nrf2) was also depressed by LPS at the mRNA and protein level. However, cis-9, trans-11 CLA pretreatment downregulated the formation of ROS and TBARS and upregulated the expression of antioxidative enzymes. As a part of innate immunity, autophagy was also motivated by LPS challenge, while CLA decreased the autophagy level. LPS and H2O2 inhibited milk fat synthesis-related transcription factor sterol regulatory element binding protein (SREBP1), peroxisome proliferator activated receptor gamma (PPARG) and their downstream enzymes. Furthermore, 50 uM cis-9, trans-11 CLA promoted the mRNA and protein abundance of milk fat synthesis-related genes and lipid droplet formation in BMECs. In conclusion, LPS challenge disturbed the cellular homeostasis and depressed milk fat synthesis in BMECs; while cis-9, trans-11 CLA alleviated oxidative stress and decreased autophagy level, thus promoting milk fat synthesis, which offers a natural therapeutic strategy for mastitis.

Highlights

Mastitis is an inflammatory disease that occurs in the mammary gland, which reduces milk production and milk quality [1]
Erythroid 2 like 2 (Nrf2), a transcription factor, is the core of the antioxidant system, as it can bind to antioxidant-response elements (AREs) in the promoters of antioxidant target genes, such as superoxide dismutase (SOD), glutathione biosynthetic enzymes (GCLC and glutamate-cysteine ligase modifier subunit (GCLM)), glutathione peroxidase (GPX), glutathione Stransferases (GST) and heme oxygenase-1 (HMOX1) et al [12]
Bovine mammary epithelial cells (BMECs) were stimulated with 8 μg/mL LPS for 2, 4, 6, 8, 12 and 24 h to check the influence of LPS on the mRNA expression of the antioxidant system

Summary

Introduction

Mastitis is an inflammatory disease that occurs in the mammary gland, which reduces milk production and milk quality [1]. Toll-like receptor 4 (TLR4), and induce the key inflammatory transcript factor, nuclear factor κB (NF-κB), to translocate into the nucleus, leading to the production of a variety of pro-inflammatory cytokines, such as interleukin 1β (IL-1β), IL-6 and tumor necrosis factor α (TNF-α) [7]. The occurrence and development of oxidative stress contributes significantly to dysfunctional inflammatory response [9]. Erythroid 2 like 2 (Nrf2), a transcription factor, is the core of the antioxidant system, as it can bind to antioxidant-response elements (AREs) in the promoters of antioxidant target genes, such as superoxide dismutase (SOD), glutathione biosynthetic enzymes (GCLC and GCLM), glutathione peroxidase (GPX), glutathione Stransferases (GST) and heme oxygenase-1 (HMOX1) et al [12]. Autophagy can limit the epithelial inflammatory response to kidney injury by suppressing

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Conclusion