Zinc deficiency impairs the renewal of hippocampal neural stem cells in adult rats: involvement of FoxO3a activation and downstream p27(kip1) expression.

Zinc plays an important role in the development and maintenance of central neural system. Zinc deficiency has been known to alter normal brain function, whose molecular mechanism remains largely elusive. In the present study, we established a zinc deficiency-exposed rat model, and, using western blot and immunohistochemical analyses, found that the expression of FoxO3a and p27(kip1) was remarkably up-regulated in the rat brain hippocampus. Immunofluorescence assay showed that FOXO3a and p27(kip1) were significantly co-localized with nestin, the marker of neural stem cells (NSCs). Furthermore, we identified that the proportion of proliferating NSCs was markedly decreased in zinc-deficient rat hippocampaus. Using C17.2 neural stem cells, it was revealed that exposure to zinc chelator N,N,N',N'-tetrakis-(2-pyridylmethy) ethylenediamine induced the expression of FoxO3a and p27(kip1) , which coincided with reduced NSC proliferation. Furthermore, depletion of FoxO3a inhibited p27(kip1) expression and restored the growth of NSCs. On the basis of these data, we concluded that FoxO3a/p27(kip1) signaling might play a significant role in zinc deficiency-induced growth impairment of NSCs and consequent neurological disorders. We describe here that zinc deficiency induces the proliferative impairment of hippocampal neural stem cells partially through the activation of FOXO3a-p27 axis in rats. Neural progenitor cells exhibited significantly up-regulated expression of FOXO3a and p27 after zinc deficiency in vivo and in vitro. Depletion of FOXO3a ameliorates zinc deficiency-induced expression of p27 and growth impairment of neural stem cells. We provide novel insight into the mechanisms underlying zinc deficiency-induced neurological deficits.

Han J ，Zhao J ，Jiang J ，Ma X ，Liu X ，Wang C ，Jiang S ，Wan C ... -  《-》

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces expression of p27(kip¹) and FoxO3a in female rat cerebral cortex and PC12 cells.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a potent toxin that alters normal brain development, producing cognitive disability and motor dysfunction. Previous studies in rats have proved that female rats are more sensitive to TCDD lethality than male ones. Recent studies have shown that TCDD induces cell cycle arrest and apoptosis, but the regulatory proteins involved in these processes have yet to be elucidated. In this study, we constructed an acute TCDD injury female rat model, and investigated the effects of TCDD on apoptosis and expression of cell cycle regulators, forkhead box class O 3a (FoxO3a) and p27(kip1), in the central nervous system (CNS). Increased levels of active caspase-3 were observed in the cerebral cortex of female rats treated with TCDD, suggesting that TCDD-induced apoptosis occurs in the CNS. The terminal deoxynucleotidyl transferase-mediated biotinylated-dUTP nick-end labeling assay showed that apoptosis primarily occurred in neurons. Furthermore, Western blot analysis, reverse transcription-polymerase chain reaction, and immunohistochemistry showed a significant up-regulation of FoxO3a and p27(kip1) in the cerebral cortex. Immunofluorescent labeling indicated that FoxO3a and p27(kip1) were predominantly localized in apoptotic neurons, but not in astrocytes. In vitro experiments using PC12, a rat neuron-like pheochromocytoma cell line, also revealed that TCDD induced apoptosis and an increase in FoxO3a and p27(kip1) expression. Furthermore, knockdown of FoxO3a expression inhibited p27(kip1) transcription and TCDD-induced apoptosis. Based on our data, induction of FoxO3a may play an important role in TCDD-induced neurotoxicity.

Xu G ，Liu J ，Yoshimoto K ，Chen G ，Iwata T ，Mizusawa N ，Duan Z ，Wan C ，Jiang J ... -  《-》

Mechanisms in cardiac fibroblast growth: an obligate role for Skp2 and FOXO3a in ERK1/2 MAPK-dependent regulation of p27kip1.

Pramod S ，Shivakumar K 《-》

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 downregulation of Wnt/β-catenin signaling pathway is associated with zinc deficiency-induced proliferative deficit of C17.2 neural stem cells.

Zinc is an essential nutrient that is important for normal brain development. Zinc deficiency has been linked to aberrant neurological development and functioning. However, the molecular mechanisms underlying Zinc deficiency-induced neurological disorders remain largely elusive. In the present study, we showed that the proliferation of C17.2 neural stem cells (NSCs) was evidently impaired after exposed to low levels of Zinc chelator, N,N,N',N'-tetrakis-(2-pyridylmethy) ethylenediamine (TPEN). In addition, we found that TPEN-induced proliferative deficit of NSCs was related with significant downregulation of Wnt/β-catenin signaling. Zinc deficiency impaired the proliferation of neural stem cells in dose- and time-dependent manners. Western blot revealed that the levels of p-Ser9-glycogensynthase kinase-3β (p-GSK-3β) and β-catenin were remarkably downregulated during TPEN-induced C17.2 proliferative impairment. Moreover, immunofluorescent analysis indicated that the level of nuclear β-catenin was apparently decreased following TPEN exposure. Furthermore, application with GSK-3β inhibitor lithium chloride (LiCl) reversed TPEN-induced downregulation of β-catenin and impairment of cell proliferation. Flow cytometry analysis also showed that TPEN-induced impairment of NSC proliferation could be reversed by LiCl. Taken together, these findings suggested that the disturbance of canonical Wnt/β-catenin signaling pathway partially accounted for Zinc deficiency-induced proliferative impairment of NSCs.

Zhao J ，Han J ，Jiang J ，Shi S ，Ma X ，Liu X ，Wang C ，Nie X ，He Y ，Jiang S ，Wan C ... -  《-》