ABSTRACT
OBJECTIVE@#To explore the expression of the RNA-binding protein tristetraprolin in lung adenocarcinoma cells and its molecular mechanism for inhibiting autophagy.@*METHODS@#Quantitative real-time PCR and Western blotting were performed to detect the expression of autophagy-related genes (including Beclin1, LC3-Ⅱ/LC3-Ⅰ and SQSTM1/p62) in cultured lung adenocarcinoma cells at 24, 48 and 72 h after transient transfection with a tristetraprolin-overexpressing plasmid and the empty plasmid. The effects of transfection with the tristetraprolin-overexpressing plasmid and empty plasmids in the presence or absence of tumor necrosis factor- (TNF-) on the expressions of nuclear factor-κB (NF-κB) p65, c-rel, and p50 were examined in lung adenocarcinoma cells using immunofluorescence assay and Western blotting. The cells were also transfected with the IκBα-mut plasmid and the tristetraprolin-overexpressing plasmid, either alone or in combination, and the changes in the expressions of tristetraprolin and autophagy-related genes were detected using RT-qPCR and Western blotting.@*RESULTS@#The expressions of tristetraprolin were significantly reduced at both the mRNA and protein levels in lung adenocarcinoma cells ( < 0.001). Overexpression of tristetraprolin in the cells significantly lowered the expressions of autophagy-related genes Beclin1 and the ratio of LC3-Ⅱ/LC3-Ⅰ at the mRNA and protein levels ( < 0.001), obviously lowered the expressions of NF-κB p65 and c-rel, and almost totally blocked the nuclear translocation of NF-κB p65 and c-rel ( < 0.05); the expression of p50, however, did not undergo significant changes in response to tristetraprolin overexpression ( > 0.05). The inhibitory effect of tristetraprolin overexpression on autophagy was abrogated by transfection of the cells with IκBα-mut plasmid, which blocked the NF-κB signaling pathway. Co-transfection of the cells with IκBα-mut also attenuated the inhibitory effect of tristetraprolin overexpression on Beclin1 and the LC3-Ⅱ/LC3-Ⅰ ratio at both the mRNA and protein levels ( < 0.05).@*CONCLUSIONS@#The expression of tristetraprolin is low in lung adenocarcinoma cells. Tristetraprolin overexpression causes inhibition of autophagy in lung adenocarcinoma cells possibly by blocking NF-κB p65 and c-rel nuclear translocation.
Subject(s)
Humans , Autophagy , Cell Line , Lung Neoplasms , NF-kappa B , Signal Transduction , TristetraprolinABSTRACT
AIM:To explore the expression level of tristetraprolin(TTP)in rats after subarachnoid hemor-rhage(SAH)as well as the potential role of TTP in the early brain injury(EBI)after SAH in rats.METHODS:In the first experiment setting,total 56 adult male SD rats were randomly divided into sham group and SAH group.The SAH mod-el was performed by endovascular perforation.The brain tissues were taken out after SAH at 5 different time points(0,12, 24,48,72 h and 1 week).The expression of TTP in the brain tissues was detected by Western blot.In the second experi-ment,a total of 60 SD rats were divided into 4 groups: sham group, SAH group, SAH +vector group and SAH +TPP group.Neurological score,brain water content and blood-brain barrier were evaluated at 48 h after SAH.TUNEL staining was performed to detect cell apoptosis in the rat brain tissue.ELISA method was used for quantitative detection of interleu-kin-6(IL-6)and tumor necrosis factor-α(TNF-α).The protein levels of TTP,Bax,Bcl-2 and cleaved caspase-3 in the rat brain tissue were detected by Western blot.RESULTS:The protein expression of TTP in the brain was downregulated markedly from 12 h after SAH,reached the lowest level at 48 h,and then had an upward trend.After modeling for 48 h, Garcia neurological score was significantly reduced,and brain water content and Evans blue(EB)content of the brain tis-sue of the rats in SAH group were significantly higher than those in sham group(P<0.05).SAH induced significant in-creases in IL-6 and TNF-αlevels in the brain tissue(P<0.05).The number of TUNEL-stained cells was increased in the subcortical brain region after SAH compared with sham group.In addition,a lower level of Bcl-2 and higher levels of Bax and cleaved caspase-3 in the rat brains were observed at 48 h after SAH.However,the neurological deficit score was signif-icantly increased,and the brain water content and EB content in the rat brains were significantly reduced in SAH +TTP group in comparison with SAH +vector group(P<0.05).Over-expression of TTP dramatically suppressed the levels of IL-6 and TNF-αin the rat brains,and reduced the number of TUNEL positive cells.Furthermore,upregulation of TTP signifi-cantly decreased the levels of cleaved caspase-3 and Bax, and evidently enhanced the expression of Bcl-2(P<0.01). CONCLUSION:The expression of TTP is significantly decreased in early period after SAH, and enhancing the level of TTP effectively inhibits EBI following SAH in rats.
ABSTRACT
PURPOSE: Overexpression of cyclooxygenase 2 (COX-2) is thought to promote survival of transformed cells. Transforming growth factor beta (TGF-beta) exerts anti-proliferative effects on a broad range of epithelial cells. In the current study, we investigated whether TGF-beta can regulate COX-2 expression in A549 human lung adenocarcinoma cells, which are TGF-beta-responsive and overexpress COX-2. MATERIALS AND METHODS: Western blotting, Northern blotting, and mRNA stability assays were performed to demonstrate that COX-2 protein and mRNA expression were suppressed by TGF-beta. We also evaluated the effects of tristetraprolin (TTP) on COX-2 mRNA using RNA interference. RESULTS: We demonstrated that COX-2 mRNA and protein expression were both significantly suppressed by TGF-beta. An actinomycin D chase experiment demonstrated that COX-2 mRNA was more rapidly degraded in the presence of TGF-beta, suggesting that TGF-beta-induced inhibition of COX-2 expression is achieved via decreased mRNA stability. We also found that TGF-beta rapidly and transiently induced the expression of TTP, a well-known mRNA destabilizing factor, before suppression of COX-2 mRNA expression was observed. Using RNA interference, we confirmed that increased TTP levels play a pivotal role in the destabilization of COX-2 mRNA by TGF-beta. Furthermore, we showed that Smad3 is essential to TTP-dependent down-regulation of COX-2 expression in response to TGF-beta. CONCLUSION: The results of this study show that TGF-beta down-regulated COX-2 expression via mRNA destabilization mediated by Smad3/TTP in A549 cells.