Matrine attenuates bovine mammary epithelial cells inflammatory responses induced by Streptococcus agalactiae through inhibiting NF-κB and MAPK signaling pathways

Streptococcus agalactiae is one of the main pathogens associated with bovine mastitis. The invasion of S. agalactiae in bovine mammary epithelial cells (BMECs) has been implicated as a key event in the pathogenesis of mastitis. Matrine is known for its various pharmacological activities, such as immune response regulation and anti-inflammation. The primary aim of the research was to investigate the preventive effect of matrine on S. agalactiae-induced inflammation in BMECs along with underlying molecular mechanisms. Our data showed matrine at the concentrations of 50-100 μg/mL promoted BMECs proliferation without infection, and decreased cytotoxicity induced by S. agalactiae. Subsequently, BMECs were pre-treated with matrine (50, 75, or 100 μg/mL) for 24 h, followed by the infection with S. agalactiae for an additional 6 h. Pretreatment with matrine followed by S. agalactiae treatment decreased cell apoptosis of BMECs. Also, pretreatment of matrine to BMECs prevented the invasion of S. agalactiae. The mRNA abundances of IL-1β, IL-6, IL-8, and TNF-α were down-regulated in S. agalactiae-infected cells pretreated with matrine. In addition, the greater ratios of protein NF-κB p-p65/p65, p-IκBα/IκBα, p-38/38, and p-ERK/ERK induced by S. agalactiae were attenuated due to matrine treatment. Furthermore, pretreatment of BMECs with matrine impeded the degradation of TAK1 induced by S. agalactiae infection. These results suggest matrine could be a potential modulator in immune response of the mammary gland. In conclusion, matrine prevents cellular damage due to S. agalactiae infection by the modulation of NF-κB and MAPK signaling pathways and pro-inflammatory cytokine production.