Objective:To examine whether lipoxin A 4(LXA 4) has an inhibitory effect on tumor necrosis factor-α(TNF-α)-induced proliferation of glomerular mesangial cells of rat, and explore the molecular mechanisms of signal...Objective:To examine whether lipoxin A 4(LXA 4) has an inhibitory effect on tumor necrosis factor-α(TNF-α)-induced proliferation of glomerular mesangial cells of rat, and explore the molecular mechanisms of signal pathway in LXA 4 actions. Methods: Glomerular mesangial cells of rat were cultured and treated with TNF-α(10 ng/ml), with or without preincubation with LXA 4 at different concentrations. Cell proliferation was evaluated by monotetrazolium (MTT) colorimetric assay. The expression of cyclin E mRNA was measured by RT-PCR. Phosphorylated Akt1(Thr308) and p27 kip1 were analyzed by Western blotting. Results: TNF-α-stimulated proliferation of mesangial cells was inhibited by LXA 4 in a dose-dependent manner. The marked increments in cyclin E mRNA expression induced by TNF-α during proliferation of mesangial cells were down-regulated by LXA 4. Threonine phosphorylated Akt1 proteins at 308 site stimulated by TNF-α was reduced by LXA 4. TNF-α-induced decrements in expression of p27 kip1 proteins was ameliorated by LXA 4 in a dose-dependent manner. Conclusion: TNF-α-induced proliferation of rat mesangial cells can be inhibited by TXA 4 through the mechanism of Akt 1/p27 kip1 pathway-dependent signal transduction.展开更多
蛋白磷酸酶2A(PP2A)是由36 k Da的催化亚基C(PP2Ac)和65 k Da的结构亚基A(PP2Aα/β)一起组成PP2A的核心酶,并且和各种不同的调节亚基B形成具有不同功能的PP2A全酶复合体。在细胞中PP2A发挥着重要作用,特别是在抑制肿瘤的形成当中,编码P...蛋白磷酸酶2A(PP2A)是由36 k Da的催化亚基C(PP2Ac)和65 k Da的结构亚基A(PP2Aα/β)一起组成PP2A的核心酶,并且和各种不同的调节亚基B形成具有不同功能的PP2A全酶复合体。在细胞中PP2A发挥着重要作用,特别是在抑制肿瘤的形成当中,编码PP2Aα/β基因的突变将导致肿瘤的形成和其他疾病。当非小细胞肺癌细胞H1299中过表达PP2A-Aα时,细胞生长被抑制,细胞周期停留在G0/G1期,致瘤能力也同时被抑制。进一步研究证明当PP2A-Aα过表达时,Akt被去磷酸化失活使Skp2的表达下调,从而导致细胞周期抑制因子p27kip1的表达上调。肿瘤细胞软琼脂克隆形成实验的结果表明过表达PP2A-Aα之后H1299细胞的锚定非依赖性生长能力明显的降低,形成的克隆细胞团也较小,这些结果和裸鼠成瘤实验的结果是一致的。展开更多
Objective Cytotoxin-associated protein （CagA） of H. pylori has been confirmed to be closely associated with gastric inflammation and tumorigenesis, but the mechanism behind it is little understood. In this study, we...Objective Cytotoxin-associated protein （CagA） of H. pylori has been confirmed to be closely associated with gastric inflammation and tumorigenesis, but the mechanism behind it is little understood. In this study, we try to determine roles of CagA＋ strain in activating PI3K/Akt1 signaling pathway, and affecting expression of p21WAF1/CIP1 and p27KIP1, and also in releasing IL-8 in host cells. Methods Akt1 phosphorylation and IL-8 levels of CagA＋ and CagAˉ strain infected AGS cells were detected by ELISAs. Two quantitative RT-PCRs were established to measure p21WAF1/CIP1 and p27KIP1 mRNA levels in the CagA＋ and CagAˉ strain infected cells. LY294002, an inhibitor of PI3K/Akt pathway, was used to define effect of the pathway in IL-8 release. Results CagA＋ strain could induce an obvious elevation of Akt1 phosphorylation in the infected AGS cells while CagAˉ strain failed to do so. The CagA＋ H. pylori strain infected AGS cells showed significant drops both in p21WAF1/CIP1 and p27KIP1 mRNA levels, whereas the CagAˉ H. pylori strain caused a remarkable increase in p21WAF1/CIP1 mRNA without affecting p27KIP1 gene transcription in the AGS cells. Both the CagA＋ and CagAˉ H. pylori strains enabled AGS cells to produce close elevated levels of IL-8, and the LY294002 block resulted in unexpected elevations of IL-8 levels. Conclusion CagA can activate PI3K/Akt1 pathway that plays an inhibitory role in IL-8 release in H. pylori infected AGS cells. Activation of PI3K/Akt1 pathway and subsequent negative regulation of p21^WAF1/CIP1 and p27^KIP1 expression might be involved in CagA-associated carcinogenesis.展开更多
文摘Objective:To examine whether lipoxin A 4(LXA 4) has an inhibitory effect on tumor necrosis factor-α(TNF-α)-induced proliferation of glomerular mesangial cells of rat, and explore the molecular mechanisms of signal pathway in LXA 4 actions. Methods: Glomerular mesangial cells of rat were cultured and treated with TNF-α(10 ng/ml), with or without preincubation with LXA 4 at different concentrations. Cell proliferation was evaluated by monotetrazolium (MTT) colorimetric assay. The expression of cyclin E mRNA was measured by RT-PCR. Phosphorylated Akt1(Thr308) and p27 kip1 were analyzed by Western blotting. Results: TNF-α-stimulated proliferation of mesangial cells was inhibited by LXA 4 in a dose-dependent manner. The marked increments in cyclin E mRNA expression induced by TNF-α during proliferation of mesangial cells were down-regulated by LXA 4. Threonine phosphorylated Akt1 proteins at 308 site stimulated by TNF-α was reduced by LXA 4. TNF-α-induced decrements in expression of p27 kip1 proteins was ameliorated by LXA 4 in a dose-dependent manner. Conclusion: TNF-α-induced proliferation of rat mesangial cells can be inhibited by TXA 4 through the mechanism of Akt 1/p27 kip1 pathway-dependent signal transduction.
文摘蛋白磷酸酶2A(PP2A)是由36 k Da的催化亚基C(PP2Ac)和65 k Da的结构亚基A(PP2Aα/β)一起组成PP2A的核心酶,并且和各种不同的调节亚基B形成具有不同功能的PP2A全酶复合体。在细胞中PP2A发挥着重要作用,特别是在抑制肿瘤的形成当中,编码PP2Aα/β基因的突变将导致肿瘤的形成和其他疾病。当非小细胞肺癌细胞H1299中过表达PP2A-Aα时,细胞生长被抑制,细胞周期停留在G0/G1期,致瘤能力也同时被抑制。进一步研究证明当PP2A-Aα过表达时,Akt被去磷酸化失活使Skp2的表达下调,从而导致细胞周期抑制因子p27kip1的表达上调。肿瘤细胞软琼脂克隆形成实验的结果表明过表达PP2A-Aα之后H1299细胞的锚定非依赖性生长能力明显的降低,形成的克隆细胞团也较小,这些结果和裸鼠成瘤实验的结果是一致的。
基金supported by a grant (2008ZZ06) from the National Key Laboratory for Diagnosis and Treatment of Infectious Diseases of China
文摘Objective Cytotoxin-associated protein （CagA） of H. pylori has been confirmed to be closely associated with gastric inflammation and tumorigenesis, but the mechanism behind it is little understood. In this study, we try to determine roles of CagA＋ strain in activating PI3K/Akt1 signaling pathway, and affecting expression of p21WAF1/CIP1 and p27KIP1, and also in releasing IL-8 in host cells. Methods Akt1 phosphorylation and IL-8 levels of CagA＋ and CagAˉ strain infected AGS cells were detected by ELISAs. Two quantitative RT-PCRs were established to measure p21WAF1/CIP1 and p27KIP1 mRNA levels in the CagA＋ and CagAˉ strain infected cells. LY294002, an inhibitor of PI3K/Akt pathway, was used to define effect of the pathway in IL-8 release. Results CagA＋ strain could induce an obvious elevation of Akt1 phosphorylation in the infected AGS cells while CagAˉ strain failed to do so. The CagA＋ H. pylori strain infected AGS cells showed significant drops both in p21WAF1/CIP1 and p27KIP1 mRNA levels, whereas the CagAˉ H. pylori strain caused a remarkable increase in p21WAF1/CIP1 mRNA without affecting p27KIP1 gene transcription in the AGS cells. Both the CagA＋ and CagAˉ H. pylori strains enabled AGS cells to produce close elevated levels of IL-8, and the LY294002 block resulted in unexpected elevations of IL-8 levels. Conclusion CagA can activate PI3K/Akt1 pathway that plays an inhibitory role in IL-8 release in H. pylori infected AGS cells. Activation of PI3K/Akt1 pathway and subsequent negative regulation of p21^WAF1/CIP1 and p27^KIP1 expression might be involved in CagA-associated carcinogenesis.
