Effects Of Conjugated Linoleic Acid On The Expression Of Toll-Like Receptors 4(TLR4)-Related Genes

As a natural and fuctional fatty acid, conjugated linoleic acid (CLA) can reduce body fat deposition, improve growth performance and carcass quality. One aspect of CLA that has drawn much attention is its ability to enhance immune function. CLA has been proposed as an important pharmaco-nutrients for modulating immunity. However, the mechanism of CLA improving immune function is not clear. Toll-like receptors (TLRs) are a class of proteins that play a key role in the innate immune system, which are now counted among the key molecules that alert the immune system to the presence of microbial infections. Recent studies suggest an association of toll-like receptor 4 (TLR4) polymorphisms with increased susceptibility to some infections. One animal feeding experiment and one in vitro experiment were conducted to determined the effect of CLA on TLR4 signaling, which is strongly associated with the pathogenesis of inflammatory.(1) 60 mices at 22-23 g were randomLy allotted to feed one of two diets containing 1% CLA,1% soybean oil for 30 days. At the end of the trial, an immunological stress model was establish through injecting with LPS (4 mg/kg). Spleen were remved immediately for total RNA extraction at 0h,1.51h,3h,6h,12h post-injection. The real-time PCR was performed for TLR4,MyD88,TRIF,NFκB-p65 using TOYOBO Assay Reagent kits. For each sample, resuils were nomalized by dividing the amount of target gene by the amount of glyceraldehyde-3-phosphate dehydrogenase (GAPDH). The results indicated that the mRNA expression of the four genes increased significantly at 6h post-LPS stimulation in both groups. TLR4,MyD88,TRIF mRNA abundance from CLA group were lower than soybean oil group at 6h post-LPS (P<0.05). However, spleen from CLA group had lower NFκB-p65 mRNA expression at 3h post-LPS (P<0.05).(2) RAW264.7 cells were cultured with media containing various concentrations (0,50,100μmol/L) of CLA. On d 1 of culture, LPS (100 ng/mL) was added to establish immunological stress model. The cells were cultured at 37℃in 5%CO2. At 0,2,4,8h post-LPS stimulation, cells were collected for total RNA extraction. TLR4,MyD88,TRIF,NF-κB mRNA expression were quantified by real-time PCR assay reagent kits. The results indicated that the mRNA expression of the four genes increased significantly at 4h post-LPS stimulation in all groups. TLR4,MyD88,TRff,NFκB-p65 mRNA abundance from 100μmol/L CLA group were significantly lower than other groups (P<0.05). The results of this study demonstrate that CLA can inhibite the downstream genes MyD88,TRIF.. NFiκB-p65 expression of TLR4 signaling with the context of LPS-induced immunological stress. So we conclude that CLA exerts profound antiinflammatory effects by downregulation of TLR4 signaling.