The occurrence and development of inflammation are closely related to the intestinal inflammation of piglet weaning and many diseases.The steroids and nonsteroidal traditional drugs are commonly used as anti-inflammatory drugs to cure inflammatory diseases,which produce side-effects in human body.Thus,to find a new type of effective substance with minimal side effects is very important to cure inflammatory diseases.As a natural carotenoid,?-carotene is an important precursor of vitamin A and has a variety of biological effects including antioxidant,enhancing gap junction intercellular communication and promoting immunity.Moreover,as an important transcription factor,NF-?B can induced inflammatory cytokines when RAW264.7 cells are stimulated LPS.Thus,inflammation model of LPS-stimulated RAW264.7 cells was set up to study the possible effects of ?-carotene on the inflammatory cytokines and relationship with NF-?B pathway,and reveal the anti-inflammatory activities and possible mechanisms of ?-carotene.Firstly,to determine the most suitable concentration and time of ?-carotene and LPS,the cells viability was measured by MTT.To build inflammation model and to ensure the effects of ?-carotene on the inflammatory cytokines,the mRNA relative expression and production of IL-1?,IL-6 and TNF-? were detected by quantitative RT-PCR and ELISA.Then,the relative expression of NF-?B p65 mRNA and protein was measured by quantitative RT-PCR and Western Blot to research the effect of ?-carotene on NF-?B signaling pathway.Finally,to analyse the effects of LPS+PDTC+?-carotene group and LPS+PDTC groupon inflammatory cytokines and NF-?B p65 by above methods.The results are as follows:In the study of ?-carotene on the inflammatory cytokines,the most suitable concentration and time of ?-carotene are 20,40,80,160 ?mol/L and 3 hours,the most suitable concentration and time of LPS are 5 ?g/mL and 24 hours.RAW264.7 cells were treated with 5 ?g/mL of LPS for 24 h and then stimulated with different concentrations of ?-carotene for 3 h,which significantly reduced the mRNA relative expression of IL-1?,IL-6 and TNF-?(P<0.01),although the effect of ?-carotene on the production of inflammatory cytokines was not all significant,there was a tendency toward lower levels.These results indicated that ?-carotene caused the inhibition of inflammatory cytokines in LPS-induced RAW264.7 cells.In the study of ?-carotene on NF-?B signaling pathway,RAW264.7 cells were induced by 5 ?g/ml of LPS and different concentration of PDTC that can inhibit the expression of NF-?B specifically together for 24 h,which significantly suppressed the mRNA and protein relative expressions of NF-?B p65 compared to LPS group(P<0.01),significantly inhibited the mRNA relative expression of IL-1?,IL-6 and TNF-?(P<0.01),and reduced the production of inflammatory cytokines.These results indicated that the suppression of NF-?B p65 contributed to inhibit the expression and production of inflammatory cytokines in LPS-induced RAW264.7 cells.In the study of NF-?B signaling pathway on specificity,addition of ?-carotene significantly reduced the mRNA and protein relative expressions of NF-?B p65 in LPS-induced RAW264.7 cells(P<0.05),which suggested that ?-carotene can inhibit the expression and production of inflammatory cytokines through suppressing the expression of NF-?B p65 in LPS-induced RAW264.7 cells.The inhibition of inflammatory cytokines in LPS+PDTC+?-carotene group was more obvious than that in LPS+PDTC group,but there was little difference about the expression of NF-?B p65 between those two groups.These results comprehensively indicated that NF-?B signaling pathway was not unique one by which ?-carotene inhibited expression and production of inflammatory cytokines.In summary,?-carotene inhibits the expression and production of key inflammatory cytokines,which is regulated through NF-?B signaling pathway. |