Wuzi Yanzong pill attenuates MPTP-induced Parkinson’s Disease via PI3K/Akt signaling pathway

Metabolic Brain Disease - Wuzi Yanzong Pill (WYP) was found to play a protective role on nerve cells and neurological diseases, however the molecular mechanism is unclear. To understand the...     

The role of Akt/GSK-3β signaling in familial hypertrophic cardiomyopathy

Mutations in cardiac troponin T (TnT) are a cause of familial hypertrophic cardiomyopathy (FHC). Transgenic mice expressing a missense mutation (R92Q) or a splice site donor mutation (Trunc) in the cardiac TnT gene have mutation-specific phenotypes but mice of both models have smaller hearts compared to wild type and exhibit hemodynamic dysfunction. Because growth-related signaling pathways in the hearts of mice expressing TnT mutations are not known, we evaluated the impact of increased Akt or glycogen synthase kinase-3β (GSK-3β) activity in both mutant TnT mice; molecules that increase heart size via physiologic pathways and block pathologic growth, respectively. Expression of activated Akt dramatically augments heart size in both R92Q and Trunc mice; however, this increase in heart size is not beneficial, since Akt also increases fibrosis in both TnT mutants and causes some pathologic gene expression shifts in the R92Q mice. Activated GSK-3β results in further decreases in left ventricular size in both R92Q and Trunc hearts, but this decrease is associated with significant mutation-specific phenotypes. Among many pathologic consequences, activating GSK-3β in R92Q hearts decreases phosphorylation of troponin I and results in early mortality. In contrast, increased GSK-3β activity in Trunc hearts does not significantly impact cardiac phenotypes. These findings demonstrate that increased Akt and its downstream target, GSK-3β can impact both cardiac size and phenotype in a mutation-specific manner. Moreover, increased activity of these molecules implicated in beneficial cardiac phenotypes exacerbates the progression of disease in the R92Q TnT mutant.     

PI3K/Akt and GSK-3β prevents in a differential fashion the malignant phenotype of colorectal cancer cells

Purpose  

During colorectal cancer progression, the loss of differentiation and cell–cell adhesion as well as a higher migratory potential are well-defined features; however, the signaling mechanism governing these events is not fully elucidated. The aim of this study was to investigate the role that PI3K and downstream effectors play in controlling colon cancer malignant phenotypes.     

Inhibitory effect of ubiquitin-proteasome pathway on proliferation of esophageal carcinoma cells

AIM:To investigate the inhibitory effect of ubiquitin-proteasome pathway(UPP)on proliferation of esophagealcarcinoma cells.METHODS:Esophageal carcinoma cell strain EC9706 wastreated with MG-132 to inhibit its UPP specificity.Cell growthsuppression was evaluated with 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium bromide(MTT)assay.DNAsynthesis was evaluated by ~3H-thymidine(~3H-TdR)incorporation.Morphologic changes of cells were observedunder microscope.Activity of telomerase was examinedby telomeric repeat amplification protocol(TRAP)of PCR-ELISA.Cell cycle and apoptosis were detected by flowcytometry(FCM).DNA fragment analysis was used toconfirm the presence of apoptosis.Expression of p27~(kip1)was detected by immunocytochemical technique.RESULTS:After exposed to MG-132,the growth and valueof ~3H-TdR incorporation of EC9706 cells were obviouslyinhibited.Cells became round,small and exfoliative undermicroscope.TRAP PCR-ELISA showed that light absorptionof cells gradually decreased after exposed to 5μmol/L ofMG-132 for 24,48,72 and 96 h(P<0.01).The percentageof cells at G_0/G_1 phase was increased and that at S andG_2/M was decreased(P<0.01).The rate of apoptotic cellstreated with 5 μmol/L of MG-132 for 48 and 96 h was 31.7%and 66.4%,respectively.Agarose electrophoresis showedmarked ladders.In addition,the positive signals of p27~(kip1)were located in cytoplasm and nuclei in MG-132 group incontrast to cytoplasm staining in control group.CONCLUSION:MG-132 can obviously inhibit proliferationof EC9706 cells and induce apoptosis.The mechanismsinclude upregulation of p27~(kip1) expression,G_1 arrest anddepression of telomerase activity.The results indicate thatinhibiting UPP is a novel strategy for esophageal carcinomatherapy.     

Interferon-γ attenuates the survival activity of G-CSF through PI3K/Akt signaling pathway in mouse multipotent progenitor cells

Apoptosis plays an important role in the injury to stem and progenitor compartments associated with aberrant interferon-gamma (IFN-γ) in aplastic anemia (AA), which is characterized by the loss of stem cells; however, its molecular mechanism is poorly understood. In this study, we have addressed the mechanism of the apoptotic function of IFN-γ against hematopoietic stem and/or progenitors. Although granulocyte colony-stimulating factor (G-CSF) augmented survival and proliferative and differentiating activity in 32D cells, mouse multipotent progenitor cells, these effects were abolished by IFN-γ and were susceptible to apoptosis with IFN-γ. IFN-γ attenuated Akt phosphorylated by G-CSF in a dose- and time-dependent manner. Wortmannin, a specific inhibitor of phosphatidylinositol 3-kinase (PI3K), enhanced the inhibitory effect on Akt phosphorylated by G-CSF in collaboration with IFN-γ, suggesting that the activity of IFN-γ might converge on the PI3K pathway. We examined the expression of Bcl-2-associated death (Bad), which works downstream of Akt. IFN-γ increased the Bad protein reduced by G-CSF. IFN-γ induced apoptosis in 32D cells through the caspase pathway. Taken together, these results suggest that IFN-γ could exert inhibitory action on stem cells and/or progenitors by interference with the PI3K/Akt signaling pathway. Our findings may contribute to understanding the decreased number of stem cells characteristic of AA.     

Morphine peripheral analgesia depends on activation of the PI3Kγ/AKT/nNOS/NO/KATP signaling pathway

Morphine is one of the most prescribed and effective drugs used for the treatment of acute and chronic pain conditions. In addition to its central effects, morphine can also produce peripheral analgesia. However, the mechanisms underlying this peripheral action of morphine have not yet been fully elucidated. Here, we show that the peripheral antinociceptive effect of morphine is lost in neuronal nitric-oxide synthase null mice and that morphine induces the production of nitric oxide in primary nociceptive neurons. The activation of the nitric-oxide pathway by morphine was dependent on an initial stimulation of PI3Kγ/AKT protein kinase B (AKT) and culminated in increased activation of K_ATP channels. In the latter, this intracellular signaling pathway might cause a hyperpolarization of nociceptive neurons, and it is fundamental for the direct blockade of inflammatory pain by morphine. This understanding offers new targets for analgesic drug development.     

Targeting the PI3K/Akt signaling pathway in gastric carcinoma: A reality for personalized medicine?

Frequent activation of phosphatidylinositol-3 kinases (PI3K)/Akt/mTOR signaling pathway in gastric cancer (GC) is gaining immense popularity with identification of mutations and/or amplifications of PIK3CA gene or loss of function of PTEN, a tumor suppressor protein, to name a few; both playing a crucial role in regulating this pathway. These aberrations result in dysregulation of this pathway eventually leading to gastric oncogenesis, hence, there is a need for targeted therapy for more effective anticancer treatment. Several inhibitors are currently in either preclinical or clinical stages for treatment of solid tumors like GC. With so many inhibitors under development, further studies on predictive biomarkers are needed to measure the specificity of any therapeutic intervention. Herein, we review the common dysregulation of PI3K/Akt/mTOR pathway in GC and the various types of single or dual pathway inhibitors under development that might have a superior role in GC treatment. We also summarize the recent developments in identification of predictive biomarkers and propose use of predictive biomarkers to facilitate more personalized cancer therapy with effective PI3K/Akt/mTOR pathway inhibition.     

Inhibitory effect of oxymatrine on serum hepatitis B virus DNA in HBV transgenic mice

AIM:To study the inhibitory effect of oxymatrine on serumhepatitis B virus (HBV) DNA in HBV transgenic mice.METHODS:HBV transgenic mice model was establishedby microinjection,and identified by HBV DNA integrationand replication.Transgenic mice with replicating HBV weredivided into 3 groups,and injected with normal saline(group A,n=9),50 mglkg (group B,n=8) and 100 mg/kg(group C,n=9) oxymatrine intraperitoneally once a dayfor 30d,respectively.Quantitation of serum HBV DNA inHBV transgenic mice was performed by competitivepolymerase chain reaction (PCR) in combination with DNAhybridization quantitative detection technique before andafter treatment.RESULTS:Compared with pre-treatment,the serum HBVDNA in group A (F=1.04,P=0.9612) and group B (F=1.13,P=0.8739) had no changes after treatment.However,in groupC serum HBV DNA was significantly decreased (F=13.97,P=0.0012).The serum HBV DNA after treatment was lowerin group C than in groups B and A (F=8.65,P=0.0068;F=12.35,P=0.0018;respectively).The serum HBV DNAafter treatment was lower in group B than in group A,butthere was no statistical significance (F=1.43,P=0.652).CONCLUSION:Oxymatrine has inhibitory effects on serumHBV DNA in HBV transgenic mice.     

Protection of endothelial cells against Ang II-induced impairment: Involvement of both PPARα and PPARγ via PI3K/Akt pathway

The aim of our study is to explore the involvement of PPARα and PPARγ in Ang II-induced endothelial injury. We found that Ang II significantly elevated the oxidative stress in HUVECs, causing apoptosis and cellular impairment in a time-dependent pattern. Activation of either PPARα by docosahexaenoic acid (DHA) or PPARγ by rosiglitazone protected the endothelial cells. Interestingly, a more significant effect was observed when DHA and rosiglitazone were administrated together. Moreover, we found that this protection was mediated through the PI3K/Akt pathway. Our study may help to understand the mechanism of endothelial dysfunction, contributing to the treatment of hypertension and other endothelial-related diseases.     

Pigment epithelium–derived factor down regulates hyperglycemia-induced apoptosis via PI3K/Akt activation in goat retinal pericytes

Pigment epithelium–derived factor (PEDF) is a well-known protease inhibitor for angiogenesis in the eye, suggesting that loss of PEDF in eye is implicated in the pathogenesis of proliferative diabetic retinopathy. Since the role of PEDF in diabetic retinopathy is unclear, the effect of PEDF on different types of cells constituting the blood vessel has to be checked. Here, we have investigated the effects of PEDF under hyperglycemic conditions in retinal pericytes, isolated from goat’s eye and used to analyze the signaling pathway involved. High glucose increased the apoptotic cell death and intracellular reactive oxygen species generation, which was blocked on the addition of PEDF. PEDF was found to inhibit the apoptotic cell death and protect the cells via activating the PI3K/Akt pathway, which was analyzed with dominant negative Akt and constitutively active Akt–transfected cells. These results demonstrate that PEDF protects pericytes against the high glucose–induced apoptosis and dysfunction.     

Testicular orphan receptor 4 induced hepatic stellate cells activation via the regulation of TGF-β receptor Ⅰ/Smad2/3 signaling pathway

Introduction and ObjectivesLiver fibrosis is a common pathological change in many chronic liver diseases. Activation of hepatic stellate cells (HSCs) is the core event in liver fibrosis. This study aimed to investigate the role of testicular orphan receptor 4 (TR4) in the activation of HSCs.Materials and MethodsIn vivo, bile duct ligation (BDL)-induced rat liver fibrosis model was established, and the expressions of TR4 and α-smooth muscle actin (α-SMA) in liver tissues were detected. In vitro, TR4 knockdown and overexpression in JS-1 cells using lentiviral vectors were constructed, and the expressions of TR4, α-SMA, Col-I, and TGF-β1/smads and retinoid X receptor (RXR) pathway-related genes were detected.ResultsTR4 was highly expressed in BDL-induced fibrotic liver, accompanied by increased expression of α-SMA. Knockdown of TR4 significantly inhibited the expressions of α-SMA, Col-I, p-TβRI, and p-Smad2/3, and up-regulated the expression of RXRα in HSCs in vitro. In contrast, TR4 overexpression significantly increased the expressions of α-SMA, Col-I, p-TβRI, and p-Smad2/3, and inhibited the expression of RXRα.ConclusionsTR4 may promote the activation of HSCs by up-regulating TβR I/Smad2/3 signaling pathway and down-regulating RXRα signaling, thereby promoting the progression of liver fibrosis. Our findings may provide a new therapeutic target against hepatic fibrosis.     

Angiotensin type 1 receptor mediates thyroid hormone-induced cardiomyocyte hypertrophy through the Akt/GSK-3β/mTOR signaling pathway

Several studies have implicated the renin angiotensin system in the cardiac hypertrophy induced by thyroid hormone. However, whether Angiotensin type 1 receptor (AT₁R) is critically required to the development of T₃-induced cardiomyocyte hypertrophy as well as whether the intracellular mechanisms that are triggered by AT₁R are able to contribute to this hypertrophy model is unknown. To address these questions, we employed a selective small interfering RNA (siRNA, 50 nM) or an AT₁R blocker (Losartan, 1 μM) to evaluate the specific role of this receptor in primary cultures of neonatal cardiomyocytes submitted to T₃ (10 nM) treatment. The cardiomyocytes transfected with the AT₁R siRNA presented reduced mRNA (90%, P < 0.001) and protein (70%, P < 0.001) expression of AT₁R. The AT₁R silencing and the AT₁R blockade totally prevented the T₃-induced cardiomyocyte hypertrophy, as evidenced by lower mRNA expression of atrial natriuretic factor (66%, P < 0.01) and skeletal α-actin (170%, P < 0.01) as well as by reduction in protein synthesis (85%, P < 0.001). The cardiomyocytes treated with T₃ demonstrated a rapid activation of Akt/GSK-3β/mTOR signaling pathway, which was completely inhibited by the use of PI3K inhibitors (LY294002, 10 μM and Wortmannin, 200 nM). In addition, we demonstrated that the AT₁R mediated the T₃-induced activation of Akt/GSK-3β/mTOR signaling pathway, since the AT₁R silencing and the AT₁R blockade attenuated or totally prevented the activation of this signaling pathway. We also reported that local Angiotensin I/II (Ang I/II) levels (120%, P < 0.05) and the AT₁R expression (180%, P < 0.05) were rapidly increased by T₃ treatment. These data demonstrate for the first time that the AT₁R is a critical mediator to the T₃-induced cardiomyocyte hypertrophy as well as to the activation of Akt/GSK-3β/mTOR signaling pathway. These results represent a new insight into the mechanism of T₃-induced cardiomyocyte hypertrophy, indicating that the Ang I/II-AT₁R-Akt/GSK-3β/mTOR pathway corresponds to a potential mediator of the trophic effect exerted by T₃ in cardiomyocytes.     

PI3K/Akt信号转导通路与甲状腺结节

近年来研究发现,磷脂酰肌醇3激酶(PDK)/蛋白激酶B(Akt)信号转导通路在细胞的增殖、分化、生存和凋亡过程中起重要调节作用.结节性甲状腺肿、甲状腺腺瘤、甲状腺癌及桥本甲状腺炎病变中存在着PI3K/Akt信号转导通路的过度激活.PI3K/Akt信号转导通路的活化使甲状腺细胞增殖指数和生长指数明显升高,刺激甲状腺滤泡持续生长,促进甲状腺结节的发生、发展.研究此通路中相关分子的表达,对探索甲状腺结节的病因、发病机制和防治策略具有重要意义.     

PI3K/Akt信号通路与肝纤维化

PI3K/AKT信号通路可以通过调控基因表达,从而在细胞的存活、分化、生长、运动和凋亡等多种生理和病理过程中起到重要作用。尤其在肝纤维化的进展中,此信号通路发挥了重要的调节作用。本文将对目前有关PI3K/AKT信号通路在参与肝纤维化形成中,如何调控细胞外基质的降解、影响HSC的活化及调节肝窦毛细血管化等作用机制作一综述。这些资料不仅可以揭示相关疾病条件下,多个细胞与信号因子之间复杂的相互作用机制,而且能够突出通过阻断PI3K/AKT信号通路可以保护和治疗肝纤维化这一潜在的临床意义。     

PI3K/Akt信号通路与神经保护

PI3K/Akt通路是由磷脂酰肌醇3-激酶(phosphatidylinositol 3-kinase,PI3K)始动的生物信号转导通路,在细胞增殖、细胞周期调控、凋亡启动、血管生成等方面发挥着关键作用.此外,PI3K/Akt通路还与中枢神经系统损伤的保护机制密切相关.深入研究PI3K/Akt、下游分子及其调控机制可能为脑损伤的治疗提供新的思路和方法.     

Urocortin-induced cardiomyocytes hypertrophy is associated with regulation of the GSK-3β pathway

Urocortin-1 (UCN), a member of the corticotropin-releasing factor, is a cardioprotective peptide, and is also involved in cardiac hypertrophy. The involvement of GSK-3β, a pivotal kinase in cardiac hypertrophy, in response to UCN is not yet documented. Cardiomyocytes from adult rats were stimulated for 48 h with UCN. Cell size, protein, and DNA contents were determined. Phosphorylated and total forms GSK-3β and the total amount of β-catenin were quantified by Western immunoblots. The effects of astressin, a UCN competitive receptor antagonist, were also evaluated. UCN increased cell size and the protein-to-DNA ratio, in accordance with a hypertrophic response. This effect was associated with increased phosphorylation of GSK-3β and marked accumulation of β-catenin, a downstream element to GSK-3β. All these effects were prevented by astressin and LY294002, an inhibitor of the phosphatidyl-inositol-3-kinase. UCN-induced cardiomyocytes hypertrophy is associated with regulation of GSK-3β, a pivotal kinase involved in cardiac hypertrophy, in a PI3K-dependent manner. Furthermore, the pharmacological blockade of UCN receptors was able to prevent UCN-induced hypertrophy, which leads to inhibition of the Akt/GSK-3β pathway.     

Could changes in the regulation of the PI3K/PKB/Akt signaling pathway and cell cycle be involved in astrocytic tumor pathogenesis and progression?

The most frequent alterations found in astrocytomas are two major groups of signaling proteins: the cell cycle and the growth factor-regulated signaling pathways. The aim of our study was to detect changes in expression of the following proteins: the tumor suppressors PTEN, p53, and p21Waf1/Cip1, glial fibrillary acidic protein (GFAP, as a marker of astroglial differentiation), the phosphorylated form of protein kinase B/Akt (PKB/Akt), which is downstream to the epidermal growth factor receptor (EGFR), and MDM2, which degrades p53. Paraffin-embedded astrocytoma tissue samples from 89 patients were divided into low grade (grade I-II; 42 samples) and high grade astrocytomas (grade III-IV; 47 samples). Mouse monoclonal antibodies against GFAP, PTEN, PKB/Akt phosphorylated on serine 473, EGFR, p53, p21Waf1/Cip1 and MDM2 were used, followed by standard indirect immunohistochemical method. EGFR protein was detected in 29 % of low grade and in 60 % of high grade astrocytomas. The expression of phosphorylated PKB/Akt was found in roughly the same proportions: in 86% of low grade and in 79% of high grade astrocytomas. PTEN was not found in most of astrocytomas, 64% of low grade and 74% of high grade tumors showed no PTEN staining. Overexpression of the mutated form of p53 or loss of p53 expression, however, was found in about 63% in both groups of astrocytomas with no differences between them. GFAP expression was decreased in tumor astrocytes compared to normal astrocytes and this decreased with grading. GFAP positive tumor cells were detected in only 50% of low grade, and 32% of high grade astrocytomas. The level of MDM2 expression was similar in both grades. Loss of p21Waf1/Cip1 expression was shown in 20% of low and in 45% of high grade tumors. In the subgroup of high grade tumors with wild type p53, 86% showed p21Waf1/Cip1 expression, whereas in the subgroup of high grade tumors with altered p53, only 35% displayed p21Waf1/Cip1. We conclude that EGFR expression increases with astrocytoma grading. EGFR activation may subsequently lead to stimulation of the PKB/Akt survival pathway. PTEN defects may also participate in aggressive tumor behaviour through activation of the PKB/Akt pathway. The alteration of p53 supports the finding that the cell cycle regulation is also disrupted during development of astrocytomas. The changes in PTEN and p53 expression, and activation of PKB/Akt are events in the early stages of astrocytomagenesis. EGFR is one of the factors, which drives the progression of astrocytomas from low to high grade stage.     

PI3K/Akt/mTOR信号转导途径与消化系统肿瘤

雷帕霉素靶蛋白（target of rapamycin,TOR）是一种从酵母到哺乳动物高度保守的丝氨酸／苏氨酸蛋白激酶,是细胞内多种重要信号传导通路的枢纽,参与基因转录、蛋白质翻译、核糖体合成、细胞凋亡等多种生物学功能。近年来的多项研究显示,mTOR的功能失调与多种肿瘤发生密切相关。mTOR信号转导途径在细胞的增殖、生长、分化和生存的调节中起到重要作用,是肿瘤治疗的一个重要靶点。