cis-9,trans-11-Conjugated Linoleic Acid Exerts an Anti-inflammatory Effect in Bovine Mammary Epithelial Cells after Escherichia coli Stimulation through NF-κB Signaling Pathway

The anti-inflammatory effects of cis-9,trans-11-conjugated linoleic acid (cis-9,trans-11-CLA) in diverse cells have been demonstrated in recent studies. The present study was conducted to observe the anti-inflammatory effects and involved mechanisms of CLA in bovine mammary epithelial cells (BMECs) exposed to Escherichia coli. According to the gene expression of IL-6, to optimize the treatment period and dose of CLA, 50 and 100 mu M CLA were chosen to pretreat the cells for a period of 48 h. BMECs were exposed to 1 X 10(7) /mL E. coli for 6 h (ECO group), and cells were pretreated with 50 and 100 mu M CLA for 48 h followed by E. coli challenge (C50 and C100 groups). After E. coli challenge, compared with that in the CON group (control group), the gene expressions of pro-inflammatory cytokines (IL-1 beta and IL-6), chemokines (IL-8 and CCL-20), and antimicrobial peptide BNBD5 were increased, while the gene expression of the anti-inflammatory cytokine IL-10 was decreased significantly; CLA reversed this inflammation effect. Pretreatment with CLA also repressed the secretion of IL-6, IL-8, and TNF-alpha from BMECs in the culture medium following E. coil challenge. Therefore, cis-9,trans-11-CLA exerted anti-inflammatory effects in BMECs. The cells that were pretreated with CLA expressed remarkably lower levels of phospho-p65, phospho-I kappa B, and TLR4 and a higher level of PPAR gamma after E. call challenge at the gene and protein levels. Compared to that in the ECO group, the nuclear translocation of phospho-p65 was suppressed when CLA was added. Combined with the above results, 50 mu M CLA showed a better anti-inflammatory effect. In conclusion, CLA can reduce inflammation caused by E. coli in bovine mammary epithelial cells, and this effect is mediated through the TLR4-NF-kappa B pathway and PPAR gamma participation.