Regulation of β-cell mass and function by the Akt/protein kinase B signalling pathway

The insulin receptor substrate-2/phosphoinositide 3-kinase (PI3K) pathway plays a critical role in the regulation of β-cell mass and function, demonstrated both in vitro and in vivo . The serine threonine kinase Akt is one of the promising downstream molecules of this pathway that has been identified as a potential target to regulate function and induce proliferation and survival of β cells. Here we summarize some of the molecular mechanisms, downstream signalling pathways and critical components involved in the regulation of β-cell mass and function by Akt.     

The activity of letrozole in patients with advanced or recurrent endometrial cancer and correlation with biological markers – a study of the National Cancer Institute of Canada Clinical Trials Group

A multicenter phase II trial was conducted to define the activity of letrozole in postmenopausal women with recurrent or advanced endometrial carcinoma, who had no more than one prior line of progestins and never had chemotherapy (except adjuvant). Archival paraffin-embedded tumor samples were retrieved to determine the expression level of estrogen (ER) and progesterone receptor (PgR), p53, HER-2, bcl-2 and PTEN protein, and phosphorylation status of protein kinase B (PKB/Akt). Thirty-two eligible patients were treated with letrozole at 2.5 mg daily continuously, of whom 10 (31%) had prior progestins. Of the 28 patients evaluated for response, one complete and two partial responses were noted; overall response was 9.4% (95% confidence interval 2-25%). Eleven patients had stable disease for a median duration of 6.7 months (range 3.7-19.3 months). Amongst 22 patients who had tumor blocks available, the proportion showing positive expression of the following markers includes: PgR (86%), ER (86%), PTEN (82%), phosphorylated PKB/Akt (59%), bcl-2 (45%), p53 (32%), and HER-2 (0%). None of these markers correlated with response to letrozole or disease progression. In conclusion, letrozole is well tolerated but has little overall activity in this cohort of women with endometrial cancer.     

Extracellular HIV-1 Tat protein activates phosphatidylinositol 3- and Akt/PKB kinases in CD4+ T lymphoblastoid Jurkat cells

The biological basis for the pleiotropic activity of extracellular human immunodeficiency virus (HIV)-1 Tat protein on lymphoid T cell survival is not well understood. We have here demonstrated that the addition in culture of 0.1–10 nM Tat protein to 36-h serum-starved lymphoblastoid Jurkat T cells rapidly stimulates the catalytic activity of phosphatidylinositol 3-kinase (PI 3-K). The peak of activation was observed 30 min after Tat addition. Extracellular Tat also stimulated the catalytic activity of the Akt/PKB kinase, a major target of PI 3-K lipid products. Pretreatment of serum-starved Jurkat cells with 100 nM wortmannin (WT) or 10 μM LY294002, two unrelated pharmacological inhibitors of PI 3-K, markedly suppressed the catalytic activity of both PI 3-K and Akt/PKB in Jurkat cells. Moreover, at low concentrations (0.1–1 nM), extracellular Tat showed a small but reproducible protection of Jurkat cells from apoptosis induced by serum deprivation (p < 0.05), while the combination of Tat plus 100 nM WT significantly (p < 0.05) increased the percentage of apoptosis with respect to cells left untreated or treated with Tat alone. Taken together, these data suggest that the anti-apoptotic activity of low concentrations of Tat protein on Jurkat cells is mediated by a PI 3-kinase/Akt pathway.     

Akt对哮喘小鼠肺组织VEGF表达的上调作用

目的探讨在哮喘发病机制中,PKB/Akt对哮喘小鼠肺组织VEGF表达的调节作用。方法BALB/c小鼠30只,按随机数字表法均分为正常对照组、哮喘组、PKB/Akt阻断组,免疫荧光、Western blot方法检测各组小鼠肺组织VEGF的表达。结果免疫荧光结果显示:哮喘组肺组织内VEGF阳性产物的平均光密度(MOD)显著高于正常对照组(P<0.01),而PKB/Akt阻断组与哮喘组相比,上述部位VEGF阳性反应产物的MOD值明显降低(P<0.05)。Western blot结果显示:与正常对照组比较,哮喘组小鼠肺组织内VEGF的IDV( integrated density value)与内参照IDV的比值均明显升高(P<0.01),而PKB/Akt阻断组上述部位IL-1β目标带的IDV与内参照IDV的比值均明显低于哮喘组(P<0.05)。结论在NGF介导的哮喘发病机制中,Akt能上调哮喘小鼠肺组织内VEGF的表达。     

PI3K/PKB信号通路在TGF-β_1诱导人肝星状细胞表达骨桥蛋白中的作用

目的:研究磷脂酰肌醇3-激酶/蛋白激酶B(PI3K/PKB)信号通路在转化生长因子β1(TGF-β1)诱导人肝星状细胞表达骨桥蛋白(OPN)的调控作用。方法:体外培养LX-2人肝星状细胞株,予TGF-β1(终浓度2.5、5、10、20μg/L)刺激24 h或予TGF-β1(终浓度10μg/L)刺激12 h、24 h、48 h;先经PI3K/PKB信号通路特异性抑制剂wortmannin(0.1μmol/L)预处理1 h,再予10μg/L TGF-β1刺激24 h,收集细胞,采用real-time PCR及Western blotting法检测OPN表达情况。结果:TGF-β1能够促进LX-2细胞表达OPN,在一定浓度和时间范围内,其表达量随着TGF-β1浓度和时间的增加而增加,呈剂量和时间依赖性关系;经wortmannin预处理再予TGF-β1刺激的LX-2细胞,与对照组相比,OPN表达受到明显抑制(P0.01)。结论:TGF-β1对LX-2人肝星状细胞OPN表达具有诱导作用,此作用可能受PI3K/PKB信号通路的调控。     

ShcC proteins: Brain aging and beyond

To date, most studies of Shc family of signaling adaptor proteins have been focused on the near-ubiquitously expressed ShcA, indicating its relevance to age-related diseases and longevity. Although the role of the neuronal ShcC protein is much less investigated, accumulated evidence suggests its importance for neuroprotection against such aging-associated conditions as brain ischemia and oxidative stress. Here, we summarize more than decade of studies on the ShcC expression and function in normal brain, age-related brain pathologies and immune disorders with a focus on the interactions of ShcC with signaling proteins/pathways, and the possible implications of these interactions for changes associated with aging.     

茶多酚对卵巢癌SKOV3细胞自噬水平的影响及相关机制研究

目的研究茶多酚(EGCG)对人卵巢癌SKOV3细胞自噬水平的影响及相关机制。方法用EGCG处理SKOV3细胞,Western blot检测自噬相关蛋白LC3-II及蛋白激酶B(PKB)信号通路相应蛋白表达变化。结果 EGCG处理SKOV3细胞后,自噬相关蛋白LC3-II表达上调,并呈一定的时间浓度依赖性。EGCG处理SKOV3细胞后,AKT的磷酸化水平下调,AKT激活剂胰岛素样生长因子1(IGF-1)预处理后,自噬相关蛋白LC3-II高表达被抑制。结论 EGCG通过AKT介导的信号通路诱导SKOV3细胞自噬水平升高。     

Antioxidant marine algae phlorotannins and radioprotection: A review of experimental evidence

Radiation has been widely used for cancer therapy in human medicine. However, the side effects of radiation are problematic and can limit its application. Radiation generates reactive oxygen species, leading to cell death via multiple signaling pathways. The blocking of certain signaling cascades using antioxidants represents a compensatory therapy of radiation-induced tissue injury. Although synthetic chemicals have been investigated in recent decades, anti-oxidants from natural resources have been searched for continuously. Among them, phlorotannins from marine algae, including Ecklonia cava, have been shown to protect cells from radiation-induced injury as well as oxidative stress. In the present review, the radioprotective capacity of phlorotannins derived from marine algae and the mechanisms involved are discussed.     

肌醇多磷酸5-磷酸酶(PIPP)在人下咽癌组织的表达及临床意义

目的研究肌醇多磷酸5-磷酸酶(PIPP)在人下咽癌中的表达,探讨其临床意义。方法对15例人下咽癌组织学标本和15例正常的癌旁组织进行免疫荧光和免疫印迹检测。结果 PIPP的表达量及荧光强度在下咽癌组织中明显低于正常组织。结论 PIPP在下咽癌组织中低表达可能为临床提供新的诊断指标。     

The role of hypothalamic estrogen receptors in metabolic regulation

Estrogens regulate key features of metabolism, including food intake, body weight, energy expenditure, insulin sensitivity, leptin sensitivity, and body fat distribution. There are two ‘classical’ estrogen receptors (ERs): estrogen receptor alpha (ERS1) and estrogen receptor beta (ERS2). Human and murine data indicate ERS1 contributes to metabolic regulation more so than ESR2. For example, there are human inactivating mutations of ERS1 which recapitulate aspects of the metabolic syndrome in both men and women. Much of our understanding of the metabolic roles of ERS1 was initially uncovered in estrogen receptor α-null mice (ERS1^−/−); these mice display aspects of the metabolic syndrome, including increased body weight, increased visceral fat deposition and dysregulated glucose intolerance. Recent data further implicate ERS1 in specific tissues and neuronal populations as being critical for regulating food intake, energy expenditure, body fat distribution and adipose tissue function. This review will focus predominantly on the role of hypothalamic ERs and their critical role in regulating all aspects of energy homeostasis and metabolism.