FOXO3a/p27kip1 expression and essential role after acute spinal cord injury in adult rat.

FOXO3a (Forkhead Class box O3a), as an important direct target of the phosphatidylinositol 3-kinase (PI3K)/protein B (Akt) pathway, which regulates the cell survival and the cell-cycle progression. Recent reports showed that FOXO3a could inhibit cell-cycle progression at the G1/S transition by controlling transcription of the cyclin-dependent kinase inhibitor p27(kip1) , which is also a key regulator of the mammalian neurogenesis. To elucidate the expression and role of FOXO3a in nervous system lesion and repair, we performed an acute spinal cord contusion injury (SCI) model in adult rats, which showed a temporal-spatial expression pattern of FOXO3a. Temporally, FOXO3a protein level significantly reduced day 3 after injury, and following FOXO3a down-regulation, p27(kip1) protein and mRNA levels were also decreased after injury. Spatially, decreased levels of FOXO3a and p27(kip1) were predominant in astrocytes, which were regenerating axons and largely proliferated after injury. Furthermore in vitro, Western blot analysis, RT-PCR, and immunofluorescence staining analysis demonstrated the relationship between FOXO3a and p27(kip1) in primary astrocytes. FOXO3a modulated the cell cycle by transcriptional regulation of p27(kip1) in astrocytes. Administration of the PI3K pharmacological inhibitor LY294002 abrogated this effect by regulating FOXO3a and p27(kip1) expression and subcellular localization. These results suggest that decreased levels of FOXO3a and p27(kip1) in spinal cord are involved in axonal regeneration and the proliferation of glial cells after SCI.

Zhang S ，Huan W ，Wei H ，Shi J ，Fan J ，Zhao J ，Shen A ，Teng H ... -  《-》

The inhibition of activated hepatic stellate cells proliferation by arctigenin through G0/G1 phase cell cycle arrest: persistent p27(Kip1) induction by interfering with PI3K/Akt/FOXO3a signaling pathway.

Proliferation of hepatic stellate cells (HSCs) is vital for the development of fibrosis during liver injury. In this study, we describe that arctigenin (ATG), a major bioactive component of Fructus Arctii, exhibited selective cytotoxic activity via inhibiting platelet-derived growth factor-BB (PDGF-BB)-activated HSCs proliferation and arrested cell cycle at G0/G1 phase, which could not be observed in normal human hepatocytes in vitro. The cyclin-dependent kinase (CDK) 4/6 activities could be strongly inhibited by ATG through down-regulation of cyclin D1 and CDK4/6 expression in early G1 phase arrest. In the ATG-treated HSCs, the expression level of p27(Kip1) and the formation of CDK2-p27(Kip1) complex were also increased. p27(Kip1) silencing significantly attenuated the effect of ATG, including cell cycle arrest and suppression of proliferation in activated HSCs. We also found that ATG suppressed PDGF-BB-induced phosphorylation of Akt and its downstream transcription factor Forkhead box O 3a (FOXO3a), decreased binding of FOXO3a to 14-3-3 protein, and stimulated nuclear translocation of FOXO3a in activated HSCs. Furthermore, knockdown of FOXO3a expression by FOXO3a siRNA attenuated ATG-induced up-regulation of p27(Kip1) in activated HSCs. All the above findings suggested that ATG could increase the levels of p27(Kip1) protein through inhibition of Akt and improvement of FOXO3a activity, in turn inhibited the CDK2 kinase activity, and eventually caused an overall inhibition of HSCs proliferation.

Li A ，Wang J ，Wu M ，Zhang X ，Zhang H ... -  《-》

The PI3K/Akt/FOXO3a/p27Kip1 signaling contributes to anti-inflammatory drug-suppressed proliferation of human osteoblasts.

Akt has been reported to suppress p27(Kip1) promoter activity through Forkhead box O (FOXO) in different kinds of cells. Previous studies indicated that anti-inflammatory drugs up-regulated p27(Kip1), and this effect might play an important role in anti-inflammatory drug-induced cell cycle arrest of human osteoblasts (hOBs). In this study, we hypothesized that these drugs might increase p27(Kip1) expression in hOBs by altering the Akt/FOXO signaling. We tested this hypothesis by examining the influences of three anti-inflammatory drugs on the levels and/or activities of Akt, FOXO and p27(Kip1) as well as the relationship between these factors and proliferation of hOBs. We tested the effects of indomethacin (10(-5) and 10(-4)M), celecoxib (10(-6) and 10(-5)M), and dexamethasone (10(-7) and 10(-6)M) using PI3K inhibitor, LY294002 (10(-5)M) as the basis of comparison. The three drugs suppressed the canonical level of phosphorylated Akt in hOBs. This was accompanied by elevated FOXO3a level and increased promoter activity, mRNA expression and protein level of p27(Kip1). Furthermore, the anti-inflammatory drugs suppressed the EGF-induced increases in proliferation, phosphorylation, and nucleus translocation of Akt. Simultaneously, they suppressed EGF-induced decreases of FOXO3a nucleus accumulation and p27(Kip1) mRNA expression. On the other hand, FOXO silencing significantly attenuated the drug-induced up-regulation of p27(Kip1) and suppression of proliferation in hOBs. To the best of our knowledge, this study represents the first to demonstrate that Akt/FOXO3a/p27(Kip1) pathway contributes to suppression of hOB proliferation by anti-inflammatory drugs. We suggest that anti-inflammatory drugs suppress hOB proliferation, at least partly, through inactivating Akt, activating FOXO3a, and eventually up-regulating p27(Kip1) expression.

Li CJ ，Chang JK ，Chou CH ，Wang GJ ，Ho ML ... -  《-》

The PI3K/Akt/FOXO3a pathway regulates regeneration following spinal cord injury in adult rats through TNF-α and p27kip1 expression.

Lu H ，Zhang LH ，Yang L ，Tang PF ... -  《-》

Peripheral nerve injury induces down-regulation of Foxo3a and p27kip1 in rat dorsal root ganglia.

Wang Y ，Liu Y ，Chen Y ，Shi S ，Qin J ，Xiao F ，Zhou D ，Lu M ，Lu Q ，Shen A ... -  《-》