Effect of estrogen and inhibition of phosphatidylinositol-3 kinase on Akt and FOXO1 in rat uterus
Institute of Physiology, Pécs University Medical School, Szigeti út 12, Pécs H7624, Hungary. Steroids
(Impact Factor: 2.64).
06/2007; 72(5):422-8. DOI: 10.1016/j.steroids.2007.03.001
The importance of FOXO transcription factors in regulating different aspects of cellular homeostasis and apoptosis has become apparent. Akt/protein kinase B has been shown to phosphorylate and inactivate members of FOXO family of transcription factors. Akt and its upstream regulator, phosphatidylinositol-3 kinase (PI3K) are involved in rapid action of estrogen (E2) in different cells and tissues. The aim of the present study was to analyze the E2/PI3K/Akt/FOXO pathway in rat uterus. In response to E2, phosphorylation of Akt/PKB on Ser473 and FOXO1 on Ser256 and Thr24 residues increased but with distinct kinetics, regulating the activation and inactivation of Akt and FOXO1 proteins, respectively. The antiestrogen ICI 182,780 prevented E2 induced Akt activation suggesting that estrogen receptors mediate this effect of E2. Intrauterine injection of Wortmannin caused a decrease in the phosphorylation of Ser473 of Akt, and attenuated phosphorylation of its downstream target FOXO1 at Ser256 and at Thr24. However, the effect of E2 on phosphorylation of Thr24 showed a kinetic pattern distinct from that of Ser256. Our results suggest that the E2/PI3K/Akt/FOXO1 pathway in rat uterus is functioning even at the lack of ovarian hormones and responses to E2 treatment. Estradiol increases Akt phosphorylation through a Wortmannin sensitive way, presumably involving PI3K. The present work shows that PI3K plays a crucial role in the phosphorylation and inactivation of FOXO1 in vivo, indicating that the regulation of this transcription factor is a more complex event in uterine cells requiring further investigations.
Available from: PubMed Central
- "All of genes possess more than 5 edges, and many possible target genes were predicted in the estrogen-mediated signal pathways. For example, insulin-like growth factor 1 (IGF1R) shares important signaling cascades with estrogen receptor
, while forkhead box O1 (FOXO1) is involved in the estrogen mediated E2/PI3K/Akt/FOXO1 pathway
. It has been reported that cervical SCC is a hormone-associated gynecological disease
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ABSTRACT: The purpose of this study was to detect the serum microRNAs (miRNAs) that are differentially expressed in cervical squamous cell carcinoma (SCC) patients and negative controls, with a focus on the miRNA profiles of the patients before and after surgery. The aim of the study is to evaluate the potential of these miRNAs as novel markers for the post-therapeutic monitoring of cervical SCC patients.
A total of 765 serum miRNAs from 10 cervical SCC patients before surgery, 10 SCC patients after surgery, and 10 negative controls were profiled using a TaqMan MicroRNA Array. A set of selected differentially expressed miRNAs were further analyzed in the patients at different perioperative periods, including preoperative, 1 week postoperative, and one month postoperative. The results showed that several serum miRNAs were differentially expressed in the cervical SCC patients compared with the negative controls, including miR-646, miR-141* and miR-542-3p. More importantly, we found that levels of specific serum miRNAs were deregulated in the pre- and postoperative stages, and these miRNAs could be useful for post-therapeutic monitoring of disease progression. Finally, we depicted a regulatory network of differentially expressed serum miRNAs, and many possible target genes were predicted in the estrogen-mediated signal pathways, supporting the hypothesis that cervical SCC is a hormone-associated gynecological disease.
Our study demonstrated that the circulating miRNAs miR-646, miR-141* and miR-542-3p could potentially serve as non-invasive biomarkers for cervical SCC. The levels of these specific miRNAs might be useful for the post-therapeutic monitoring of disease progression. This is the first report showing that circulating miRNAs could serve as biomarkers for the therapeutic intervention of cervical SCC.
Available from: Min Guan
- "Estrogen exerts protective effects against oxidative stress in many tissues including the heart, brain, kidney and bone mainly through an anti-apoptotic mechanism , , , , , . Only recently has estrogen's anti-apoptotic effect been linked to the inhibition of the PI3K pathway via control of Foxo 1 transcription . The PR is reported to regulate the transcriptional activities of Foxos, especially Foxo1, which controls endometrial decidualization , . "
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ABSTRACT: Augmentation of the peak bone mass (PBM) may be one of the most effective interventions to reduce the risk of developing osteoporosis later in life; however treatments to augment PBM are currently limited. Our study evaluated whether a greater PBM could be achieved either in the progesterone nuclear receptor knockout mice (PRKO) or by using a nuclear progesterone receptor (nPR) antagonist, RU486 in mice. Compared to their wild type (WT) littermates the female PRKO mice developed significantly higher cancellous and cortical mass in the distal femurs, and this was associated with increased bone formation. The high bone mass phenotype was partially reproduced by administering RU486 in female WT mice from 1-3 months of age. Our results suggest that the inhibition of the nPR during the rapid bone growth period (1-3 months) increases osteogenesis, which results in acquisition of higher bone mass. Our findings suggest a crucial role for progesterone signaling in bone acquisition and inhibition of the nPR as a novel approach to augment bone mass, which may have the potential to reduce the burden of osteoporosis.
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ABSTRACT: Murine models of starvation-induced muscle atrophy demonstrate that reduced protein kinase B (AKT) function upregulates the atrophy-related gene atrogin-1/MAFbx (atrogin). The mechanism involves release of inhibition of Forkhead transcription factors, namely Foxo1 and Foxo3. Elevated atrogin mRNA also corresponds with elevated TNF in inflammatory catabolic states, including cancer and chronic heart failure. Exogenous tumor necrosis factor (TNF) increases atrogin mRNA in vivo and in vitro. We used TNF-treated C2C12 myotubes to test the hypothesis that AKT-Foxo1/3 signaling mediates TNF regulation of atrogin mRNA. Here we confirm that exposure to TNF increases atrogin mRNA (+125%). We also confirm that canonical AKT-mediated regulation of atrogin is active in C2C12 myotubes. Inhibition of phosphoinositol-3 kinase (PI3K)/AKT signaling with wortmannin reduces AKT phosphorylation (-87%) and increases atrogin mRNA (+340%). Activation with insulin-like growth factor (IGF) increases AKT phosphorylation (+126%) and reduces atrogin mRNA (-15%). Although AKT regulation is intact, our data suggest it does not mediate TNF effects on atrogin. TNF increases AKT phosphorylation (+50%) and stimulation of AKT with IGF does not prevent TNF induction of atrogin mRNA. Nor does TNF appear to signal through Foxo1/3 proteins. TNF has no effect on Foxo1/3 mRNA or Foxo1/3 nuclear localization. Instead, TNF increases nuclear Foxo4 protein (+55%). Small interfering RNA oligos targeted to two distinct regions of Foxo4 mRNA reduce the TNF-induced increase in atrogin mRNA (-34% and -32%). We conclude that TNF increases atrogin mRNA independent of AKT via Foxo4. These results suggest a mechanism by which inflammatory catabolic states may persist in the presence of adequate growth factors and nutrition.
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