Morin suppresses inflammatory cytokine expression by downregulation of nuclear factor-κB and mitogen-activated protein kinase (MAPK) signaling pathways in lipopolysaccharide-stimulated primary bovine mammary epithelial cells

Morin, a flavonoid isolated from Chinese herbs of the Moraceae family, has been reported to possess antiinflammatory activity. However, the effects of morin on mastitis have not been investigated. The present study was conducted to elucidate the antiinflammatory properties of morin on lipopolysaccharide (LPS)-stimulated primary bovine mammary epithelial cells (bMEC). The viability of bMEC was analyzed by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium] assay. Subsequently, bMEC were stimulated with LPS in the presence or absence of morin. Gene expression of proinflammatory cytokines was determined by quantitative real-time PCR (qRT-PCR). Nuclear factor-κB (NF-κB), inhibitory kappa B (IκBα) protein, extracellular signal-regulated kinase (ERK), p38, and c-Jun N-terminal kinase (JNK) were detected by Western blotting. The results showed that cell viability was not affected by morin. Moreover, morin inhibited the gene expression of tumor necrosis factor-α (TNF-α), IL-6, and IL-1β in LPS-stimulated bMEC in a dose-dependent manner. Western blot analysis showed that morin suppressed the phosphorylation of IκBα, NF-κB unit p65, ERK, p38, and JNK in LPS-stimulated bMEC. In conclusion, the protective effects of morin on LPS-induced inflammatory response in bMEC may be due to its ability to suppress NF-κB and mitogen-activated protein kinase (MAPK) signaling pathways. These findings suggest that morin may be used as antiinflammatory drug for mastitis.