Abstract
In practical dairy production, cows are frequently subjected to inflammatory diseases, such as high-grain diet-induced subacute ruminal acidosis (SARA) as well as mastitis and metritis. Under the circumstances, lipopolysaccharide (LPS) induces oxidative stress within the cow and in the mammary epithelial cells. It has implications in practical production to alleviate oxidative stress and to optimize the lactational function of the mammary epithelial cells. This study thus aimed to investigate the antioxidative effects of dandelion aqueous extract (DAE) on LPS-induced oxidative stress and the mechanism of DAE as an antioxidant to alleviate oxidative stress through the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway in the bovine mammary epithelial cell line MAC-T cells. The cells were cultured for 48 h in six treatments including control (without LPS and DAE), LPS (100 ng/mL), DAE10 (100 ng/mL LPS and 10 μg/mL DAE), DAE50 (100 ng/mL LPS and 50 μg/mL DAE), DAE100 (100 ng/mL LPS and 100 μg/mL DAE), and DAE200 (100 ng/mL LPS and 200 μg/mL DAE), respectively. The results showed that cell viability was reduced by LPS, and the adverse effect of LPS was suppressed with the supplementation of DAE. Lipopolysaccharide-induced oxidative stress through enhancing reactive oxygen species (ROS) production, resulted in increases in oxidative damage marker concentrations, while 10 and 50 μg/mL DAE alleviated the LPS-induced oxidative stress via scavenging cellular ROS and improving antioxidant enzyme activity. The upregulation of antioxidative gene expression in DAE treatments was promoted through activating the Nrf2 signaling pathway, with DAE at a concentration of 50 μg/mL exhibiting the highest effect. Overall, DAE acted as an effective antioxidant to inhibit LPS-induced oxidative stress and as a potential inducer of the Nrf2 signaling pathway.
Highlights
Oxidative stress is a consequence of excessive reactive oxygen species (ROS) production, inadequate antioxidant potential, or a synchronization of both
Key Contribution: The present study demonstrated that dandelion aqueous extract was an effective antioxidant to inhibit lipopolysaccharide-induced oxidative stress in bovine mammary epithelial cells due to activating the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway
Toll-like receptor 4 (TLR4) initiates the activation of nuclear factor κB (NF-κB), which enhances the production of proinflammatory cytokines and leads to subsequent oxidative stress [4,5]
Summary
Oxidative stress is a consequence of excessive reactive oxygen species (ROS) production, inadequate antioxidant potential, or a synchronization of both. The abundance of ROS under oxidative stress leads to the damage of cellular macromolecules, resulting in protein modification, lipid peroxidation and Toxins 2020, 12, 496; doi:10.3390/toxins12080496 www.mdpi.com/journal/toxins. The excessive production of cellular ROS can be promoted by the inflammatory reaction. Cows are frequently subjected to inflammatory diseases, such as high-grain diet-induced subacute ruminal acidosis (SARA) as well as mastitis and metritis. During high-grain diet-induced SARA, the oxidative stress was triggered by lipopolysaccharide (LPS) in plasma and the liver, and the milk yield as well as milk composition were impaired in SARA cows [3]. Subclinical mastitis is a prevalent disease in dairy cows worldwide, which is mainly caused by the LPS released from invading pathogens, resulting in reduced milk production and large losses to the dairy industry.
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