| Selenium(Se) was considered to be a toxic substance in the early stages of discovery.But with the deepening of research and technology,it was found that Se was a kind of micronutrients necessary for many kinds of organisms,was irreplaceable to the development and physiological function of human and various animal organs.Se-deficiency can reduce the activity of glutathione peroxidase and antioxidant capacity,the large accumulation of peroxide and lipid free radicals will destroy the cells and tissues and reduce the organization’s immune capacity in the body.Se-supplement associated with the cure of systemic inflammatory response syndrome and sepsis,which is related to the intake of selenium in a sufficient individual body.Se-supplement can enhance activation and promote proliferation of T cells and increase NK cell activity with significant immunostimulatory effects.Mastitis is often caused by dairy cow inflammation of the breast tissue,occurred in the dairy cow lactation.Staphylococcus aureus(S.aureus)is the main pathogen,which caused breast swelling and reduced milk production,if dairy cow infected severely can lead to systemic inflammatory injury in clinical research.Micro RNA-155(miR-155)is a typical multi-biological functional miRNA.It affects the differentiation of hematopoietic cells and plays a key role in immune response.After inflammatory stimulation,miR-155 can be up-regulated by the TLRs via the MyD88 dependency pathway.Furthermore,miR-155 was induced by the NF-κB and the JNK/MAPK pathway to regulate the inflammatory response.However,the current biological mechanism of selenium in regulating miR-155 and inhibiting the activation of the NF-κB and MAPK to reduce inflammation in the body is unknown.In vivo study,we investigated S.aureus-induced mastitis models of SPF BALB/c mice.They were fed with diaries that contain the different selenium level: Se-deficiency chow,normal chow and Se-supplement chow.Feeding 60 days,postpartum female mice were used to establish an intramammary infusion of S.aureus to study the effect of selenium on mastitis.Histopathological analysis,selenium content in breast tissues,MPO activity,pro-inflammatory genes analysis,and the levels of TLR1,2,6 were conducted to study effects of selenium on S.aureus-induced mouse mammary mastitis.Results showed that diaries diets selenium level can affect the contain of selenium in the breast tissue.Histopathological observation of mammary gland in S.aureus-induced Se-deficient mouse mammary gland showed more infiltration of inflammatory cells,the structure of gland was destroyed.However,the structure of Se-supplement gland was complete comparatively.Pro-inflammatory genes and miR-155 expression in mammary gland of Se-deficient group were higher than Se-supplement group.All the results suggest that Se-deficiency promotes the mouse mammary gland inflammation which induced by S.aureus,but Se-supplement can inhibit the expression of TLR2 significantly.Meanwhile,Se-supplement inhibits the production of protein phosphorylation in the downstream NF-κB and MAPK inflammatory signaling pathways and promotes the repair of breast tissue from inflammatory.In addition,inflammatory model was performed by S.aureus-induced primary mouse mammary gland epithelial cells(MMECs)in vitro.MMECs were transfected with miR-155-5p mimics after CK-18 identification and MTT activity test.After miR-155 mimics transfection,MMECs was cultured 12 h with different concentration of MSC to build cell model,a control group of miR-155 mimics was established without transfection.RT-qPCR and ELISA test results showed that miR-155 mimics transfection can increase the proinflammatory cytokines and the expression of TLR2 significantly,that also can enhance the NF-κB and MAPK protein phosphorylation level in MMECs model.All the data displayed that miR-155 played pro-inflammatory role in inflammatory reaction.It is proved that the proper amount of selenium can be used to improve the immune mechanism of the body by regulating miR-155 and relieve inflammatory injury. |
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