| Bovine mastitis, a major disease affecting dairy cattle worldwide, always occursin postpartum lactation period. With high prevalence, it always caused huge economicloss. There are currently about220million cows around the world, a third cows sufferfrom different types of mastitis, which leading to more than40billion dollareconomic losses every year. According to the clinical symptoms, the mastitis can beclassified into clinical and chronic forms. It is always caused by nipple injury, milkdeposition, pathogen infection, and other factors. Mastitis caused by pathogenicbacteria infection is very common, and the morbidity is as high as90%. So far, it hasmade many achievements for the research of the disease, but it can’t completely solvethe problems caused by mastitis in production practice.In the research field of animal disease, S. aureus is the most common and themost important pathogen that induced mastitis. S. aureus is the environmental bacteriaand the bacteria have a variety of virulence factors. S. aureus-induced mastitis oftenbrings cows about lactation decreased, lifespan shortened. It aslo effects the quality ofmilk, causes the food hygiene safety problems and harms the health of consumers. Sohow to control and prevent dairy cow from S. aureus-induced mastitis is the firstpriority of veterinary work.The treatment of S. aureus mastitis almost completely relies on the use ofantibiotics in the world wide, although there are varieties of therapies. In general, it iseffective to prevent the mastitis by using antibiotics in antepartum cow, and theantibiotics can cure the S. aureus mastitis at a certain extent. The negative effect ofantibiotics therapies is that they promote antibiotic resistance of bacteria, and theantibiotic residual in milk can lead to food security crisis. Traditional Chinesemedicine, which has the functions of activating blood circulation, heat-clearing anddetoxifying, and supplementing qi and nourishing blood, can adjust the organismimmunity and clean the pathogens, to cure the S. aureus mastitis. Traditional Chinesemedicine therapy has become to be research hotspot in treatment of clinical dairy cow mastitis. Traditional Chinese medicine therapies are effective to S. aureus mastitis andavert the hazard of drug residues in milk and facilitating the drug resistance bacteria.Furthermore, it has the positive effects and good economic prospect to developeffective traditional Chinese medicine in the treatment of S. aureus mastitis.Baicalin is the major active constituent of the isolated root of Scutellariabaicalensis. Studies have shown that it has multiple biological properties, includinganti-inflammatory, Anti-bacteria, anti-allergic, spasmolysis, and diuresis activities. Itis used in the treatment of infectious hepatitis, acute biliary duct infection, andplumbism. Baicalin is used in medicine and maquillage. Baicalin can absorbultraviolet light, clear the oxygen free radicals, reducing melanin, is used in theproduction of cosmetics as a functional raw material. The study of mechanisms andeffect of baicalin contribute to the further application of the application in thetreatment of animal diseases.In the present study, we analyzed from various angles pharmacological effects ofbaicalin due to the variety of biological effects the most traditional Chinese medicinehas. Because of the direct use of cattle spend too much and do not fit the need ofexperimental study mechanisms, the present study, Staphylococcus aureus mastitismodel of mouse was made via perfusion Staphylococcus aureus though Milk ducts.The purpose of this study is to investigate the anti-inflammatory effects, the protectiveand antibacterial effect of baicalin in vivo experimental. The experimental resultsshowed that baicalin reduce the inflammation induce by S. aureus and protect thetissue effectively, enhance the kill effect of neutrophils to S. aureus in breast tissue. Aswe all know that, mammary glandular cell is the most important in breast tissue, inorder to confirm the experimental results, mammary cells were isolated and culturedafter stimulation with S. aureus and then added baicalin. The results were consistentwith the animal experiments.To further analyze the pharmacological mechanism of baicalin in breast, thepresent study investigate the regulation of related signaling proteins. TLR2, is themain Pattern Recognition Receptors (PRRs) to S. aureus, can also adjust thedownstream signaling pathways. The results showed that baicalin inhibit theexpression of TLR2and reduced activation of downstream signaling. Baicalin inhibited TLR2expression and reduce the corresponding nuclear transfer factor intothe nucleus by inhibiting NF-κB and phosphorylation of p38protein to inhibits theexpression of IL-1β, TNF-and IL-6and other cytokines.S. aureus infection can cause inflammation, and activate apoptotic related fatorsto induce cell death, which result from the organizational structure uncomplete anddamaged. TLR2can not only regulate inflammatory signaling pathways, but alsoregulate apoptotic protein for the S. aureus infection.The present study used TUNELfor mammary gland tissues and LIVE/DEAD staining for mammary epithelial cells,we observed that baicalin can significantly reduce cell apoptosis caused by S. aureus.Further research, we found that baicalin protected the cells by suppressing thephosphorylation of p53, increasing the ratio of Bcl-2/BAX and finally inhibiting thecleavage of casp-3to initiate the programmed cell death.The study also investigated the antibacterial mechanism of bacilin.Isloating andcultured neutrophil, we found that bacilin not only showed antibacterial activity intissue level, but showed the corresponding effect in cell level. Although the addeddose of baicalin did not reach effective bacteriostasis concentration, it is supposed thatthe baicalin regulated intracellular related bacteriocidal substance to enhance itsbactericidal action. With physical spectroscopy analysis, it is confirmed that baicalincan combine with neutrophils lysozyme. Further antibacterial experiment in vitroshowed that baicalin can enhance lysozyme to kill S. aureus.In conclusion, we utilized an animal model to investigate the effect of bacilin on S.aureus-induced mastitis and do deep analysis on the mechanism of itsanti-inflammatory, cell protection and anti-bacteria roles. Additionally, we appliedbacilin in the clinical to preliminarily determine the therapeutic effect on cows. Wewished that our results would provide theoretical guidance and help for theapplication of bacilin in veterinary clinical and the development of protective drugsfor S. aureus-induced mastitis. |
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