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Elevated intraocular pressure (IOP) is considered as the major risk factor for the loss of retinal ganglion cells (RGCs) and their axons in glaucoma. Emerging evidence suggests elevated IOP can induce Drp1 upregulation and mitochondrial fission, which is involved in cell death. However, the underlying mechanism for these effects remains unknown. The present study used RNAi screening to investigate the effects of 24 kinases associated with mitochondrial activities on DRP1 expression under hydrostatic pressure. We identified, for the first time, that glycogen synthase kinase 3 beta (GSK3β) knockdown suppressed the upregulation of DRP1 induced by elevated pressure. Use of the pharmacological inhibitor of GSK3β inhibitor, lithium chloride (LiCl), confirmed this result. Furthermore, we demonstrated that one of the mechanisms of lithium chloride neuroprotection might be via inhibition of mitochondrial fission through downregulation of Drp1.

Chronic organophosphorus pesticides (OP) exposure is associated with an increased risk of depression, and there is an urgent need to find an effective treatment for the depressive-like symptoms caused by OP. The main purpose of this study was to investigate whether combined lithium chloride (LiCl) and astaxanthin (AST) treatment would manifest synergetic antidepressant effects on mice with chronic OP exposure, and to determine the role of the Akt/GSK3β/CREB signaling pathway. Our results showed that chronic omethoate exposure significantly increased immobility time in behavioral tests and induced neuron damage in HE staining. The expression of p-GSK3β, p-CREB, p-PI3K and p-Akt in hippocampus after OP exposure were significantly down-regulated, while the influences were reversed by LiCl and AST treatment. Moreover, the combined application of AST and LiCl had synergistic therapeutic effects compared to LiCl and AST treatment alone, the expression of p-GSK3β, p-CREB, p-PI3K and p-Akt after combined LiCl-AST treatment were significantly higher than that with single drug application. These results showed that the combination of LiCl and AST could efficiently ameliorate depressive-like behavior induced by omethoate, and Akt/GSK3β/CREB signaling pathway might be responsible for the neuroprotective effect.

In recent years, the widespread use of chlorpyrifos (CPF) has aroused concerns regarding its potential neurotoxic effects, especially in developing individuals. One of the major consequences of CPF exposure is mood disorders such as depression. Epidemiological studies have demonstrated susceptibility to depression in populations with a history of CPF exposure. Our previous study indicated that repeated CPF exposure in doses from 10 to 160 mg/kg elicits depression- and anxiety-like alterations. However, whether this alteration is due to persistent inhibition of acetylcholinesterase (AChE) was not determined. In this study, we used lower doses of CPF to avoid evident inhibition of AChE to investigate other potential target systems that contribute to CPF's neurotoxic effect. Four-week-old adolescent male rats were repeatedly exposed to CPF at doses of 2.5, 5, or 10mg/kg (s.c., 10 days) and then were subjected to either neurobehavioral testing or immunoblot analysis. Depression-like behaviors as manifested by increased immobility time was observed in force swimming test, while immunoblot analysis revealed a dramatically increased phosphorylation of glycogen synthase kinase-3β (GSK-3β) in the hippocampus and striatum, with no effect on the levels of Wnt2, GSK-3β, or β-catenin. These results suggest a noncholinergic mechanism, the hyper-phosphorylation of GSK-3β, which may contribute to the cellular neurotoxicity of CPF, thus increasing the susceptibility to mood disorders.

Glycogen synthase kinase 3 beta (GSK3β) plays a critical role in signal transductions concerning neuronal death. In the present study, we investigated the potential role of GSK3β in 6-hydroxydopamine (6-OHDA)-induced toxicity in human neuroblastoma cell line SH-SY5Y. We assessed the apoptotic proteins and the relative levels of pGSK3β (Ser9) and pGSK3β (Tyr216) to GSK3β in 6-OHDA-treated SH-SY5Y. Furthermore, we downregulated the expression of GSK3β by short hairpin RNA (shRNA) interference and compared the cell viability and expression of apoptotic proteins in knockdown group with those in control group under the treatment of 6-OHDA. We found that 6-OHDA increased the expression of caspase-3 and caspase-9 but not caspase-8. Additionally, 6-OHDA decreased the ratio of pGSK3β (Ser9)/GSK3β and increased the ratio of pGSK3β (Tyr216)/GSK3β. Moreover, 6-OHDA induced less cell viability loss and lower expression of caspase-9 and caspase-3 in GSK3β knockdown group compared with control. The present data indicate that 6-OHDA may induce apoptosis in SH-SY5Y via the intrinsic death pathway and GSK3β knockdown can partly attenuate 6-OHDA-induced neuronal death and apoptosis, suggesting that GSK3β may have the potential to serve as a therapeutic target for PD.

Understanding the mechanisms that regulate postnatal neurogenesis is becoming increasingly relevant since its modulation has been implicated in the pathogenesis of certain neuropsychiatric disorders. Lithium is a mood stabilizer known to increase hippocampal neurogenesis. Lithium also results in increased levels of the angiogenic factor vascular endothelial growth factor (VEGF). Since VEGF was recently shown to have neurogenic properties, we were interested to examine whether lithium administration might also be accompanied by alterations in VEGF expression in the hippocampus of normal and stressed rats; the latter treatment was introduced to reproduce some of the psychopathological signs for which lithium is used therapeutically. The expression of VEGF in the hippocampus in stressed animals was lower than that in controls, but the effect of stress was significantly attenuated in animals concomitantly receiving lithium. Double staining for VEGF and specific markers for immature neurons, mature neurons and astroglia revealed that immature neurons were most sensitive to the VEGF-inhibiting effects of stress. Confirming the involvement of a known regulatory pathway in these actions of lithium, we demonstrated that lithium co-administration prevented the stress-induced upregulation of glycogen synthase kinase-3beta (GSK-3beta) and down-regulation of beta-catenin expression; GSK-3beta is a known primary lithium target and its inhibition by this mood stabilizer leads to an upregulation of beta-catenin and subsequently, an increase of VEGF. Our results suggest that the actions of lithium, and possibly its therapeutic efficacy as a mood stabilizer also, are mediated by VEGF., Rui Silva is a pre-doctoral fellow of the Portuguese Foundation for Science and Technology (SFRH/BD/9756/2003). This work was supported by a grant (JG0495) from the Gulbenkian Foundation.

Estradiol prevents neuronal cell death through the activation of cell survival signals and the inhibition of apoptotic signals. This study investigated whether estradiol modulates the anti-apoptotic signal through the phosphorylation of Akt and its downstream target, glycogen synthase kinase 3beta (GSK3beta). Adult female rats were ovariectomized and treated with estradiol prior to middle cerebral artery occlusion (MCAO). Brains were collected 24 h after MCAO and infarct volumes were analyzed. Estradiol administration significantly reduced infarct volume and decreased the positive cells of TUNEL staining in the cerebral cortex. Potential activation was measured by phosphorylation of Akt at Ser(473) and GSK3beta at Ser(9) using Western blot analysis and immunohistochemistry. Estradiol prevented the injury-induced decrease of pAkt and pGSK3beta. Furthermore, pretreatment with estradiol decreased glutamate toxicity-induced cell death in a hippocampal cell line (HT22). Also, estradiol prevented the glutamate toxicity-induced decrease of pAkt and pGSK3beta in HT22 cells. Our findings suggest that estradiol plays a potent protective role against brain injury and that phosphorylation of Akt and GSK3beta by estradiol mediated these protective effects.

Recent studies have suggested the involvement of Glycogen synthase kinase-3 beta (GSK-3 beta) in pathogenesis and treatment target of schizophrenia and bipolar disorder, which led to consider GSK-3 beta as one of the candidate genes for those disorders. However, the association analysis between GSK-3 beta and either schizophrenia or bipolar disorder is yet to be reported in Korean population. Along with 350 healthy individuals, a sample of 138 schizophrenia and 120 bipolar patients was analyzed for two common SNPs at position -1727 A/T and -50 C/T polymorphism localized in intron 1 of the gene. The results showed that allele, genotype and haplotype distributions for the two SNPs do not differ between the controls and neither schizophrenia nor bipolar disorder patients. We also analyzed the association between the controls and the combined samples of schizophrenia and bipolar disorder, but no association was found. In conclusion, these results suggest that the GSK-3 beta is not associated with the development of schizophrenia and bipolar disorder in Korean population.

Alzheimer's disease (AD) is a neurodegenerative disorder that results in cognitive impairment. It has been proposed that deposits of beta-amyloid (Aβ) form the cores of the plaque and, subsequently, induce the activation of GSK-3β and the hyperphosphorylation of tau, resulting in cognitive impairment. Oxidative stress has been proposed to be an important factor in the pathogenesis of AD. Cyanidin 3-O-glucoside (Cy3G) is a neuroprotective antioxidant. However, the effects of Cy3G on cognition are unclear. In this paper, we show that Cy3G is protective against the Aβ-induced impairment of learning and memory, but has no effect on normal learning and memory. Moreover, we found that Gy3G attenuated the Aβ-induced tau hyperphosphorylation and GSK-3β hyperactivation observed in AD. Taken together, these results demonstrated that Cy3G can rescue the cognitive impairments that are induced by Aβ via the modulation of GSK-3β/tau, suggesting a potential therapeutic role of Cy3G in AD.

The axons of the adult mammalian brain and spinal cord fail to regenerate after injury, and it has been suggested that Nogo-66 could prevent CNS axon repair. However, the mechanism of Nogo-66 inhibiting neurite outgrowth remains unknown. Our previous results indicated that protein kinase B (PKB) is involved in the inhibition of the neurite outgrowth by Nogo-66. Glycogen synthase kinase-3β (GSK-3β) is implicated in many processes in the nervous system, including differentiation, specification, polarity, plasticity and axon growth. In addition, GSK-3β is one of the most important molecules downstream of PKB. In the present study, we report on the role of GSK-3β signaling on Nogo-66-treated mouse neuroblastoma N2a cells. Nogo-66 reduced the phosphorylation of GSK-3β at Ser9 in N2a cells. In contrast, pretreatment with SB216763, a specific inhibitor of GSK-3β, resulted in an amelioration of neurite outgrowth by Nogo-66, compared with the Nogo-66 alone group (P

We have previously demonstrated that Leptin reduces extracellular amyloid beta (Abeta) protein both in vitro and in vivo, and intracellular tau phosphorylation in vitro. Further, we have shown that these effects are dependent on activation of AMP-activated protein kinase (AMPK) in vitro. Herein, we investigated downstream effectors of AMPK signaling directly linked to tau phosphorylation. One such target, of relevance to Alzheimer's disease (AD), may be GSK-3beta, which has been shown to be inactivated by Leptin. We therefore dissected the role of GSK-3beta in mediating Leptin's ability to reduce tau phosphorylation in neuronal cells. Our data suggest that Leptin regulates tau phosphorylation through a pathway involving both AMPK and GSK-3beta. This was based on the following: Leptin and the cell-permeable AMPK activator, 5-aminoimidazole-4-carboxyamide ribonucleoside (AICAR), reduced tau phosphorylation at AD-relevant sites similarly to the GSK-3beta inhibitor, lithium chloride (LiCl). Further, this reduction of tau phosphorylation was mimicked by the downregulation of GSK-3beta, achieved using siRNA technology and antagonized by the ectopic overexpression of GSK-3beta. These studies provide further insight into Leptin's mechanism of action in suppressing AD-related pathways.

Amyloid precursor protein (APP) is expressed ubiquitously but its wrong cleavage only occurs in central nervous system. In this research, overexpression of wild type human APP695 was found to stimulate the adhesion and migration of N2a cells. In the cells co-transfected by familial Alzheimer's disease (FAD)-linked Swedish mutant of APP695 gene plus big up tri, openE9 deleted presenilin1 gene (N2a/Swe. big up tri, open9), however, this stimulating function was impaired compared to that in the cells co-transfected by Swedish mutant of APP695 gene plus dominant negative mutant of presenilin1 D385A gene (N2a/Swe.385). Furthermore, it was also found that the phosphorylation of FAK Tyr-861 and GSK-3beta Ser-9 was reduced in N2a/Swe.Delta9 cells, which can be possibly taken as a reasonable explanation for the underlying mechanism. Our results suggest that impaired cell adhesion and migration induced by abnormal cleavage of APP could contribute to the pathological effects in FAD brain.

Hyperphosphorylated tau is the prominent component of paired helical filaments, which are the major component of neurofibrillary tangles associated with Alzheimer's disease (AD). Glycogen synthase kinase 3beta (GSK3beta) is implicated to phosphorylate tau in normal and AD brain. Previously, we isolated a large multiprotein complex containing tau, Ser9-phosphorylated GSK3beta and 14-3-3zeta from bovine brain microtubules. We showed that within the complex, 14-3-3zeta binds to tau and GSK3beta and mediates GSK3beta-catalyzed tau phosphorylation. A recent report however indicated that 14-3-3zeta does not bind to tau or GSK3beta and does not increase tau phosphorylation by GSK3beta in cell models [T.A. Matthews, G.V.W. Johnson, Neurosci. Lett. 384 (2005) 211-216]. In the current study we have thoroughly analyzed the binding of 14-3-3zeta with tau and GSK3beta and evaluated the effect of 14-3-3zeta on tau phosphorylation by GSK3beta in HEK-293 cells. We found that 14-3-3zeta binds to tau and Ser9-phosphorylated GSK3beta. Nonphosphorylated GSK3beta phosphorylates tau without being influenced by 14-3-3zeta. Ser9-phosphorylated GSK3beta on the other hand phosphorylates tau significantly only in the presence of 14-3-3zeta. Our data demonstrate that 14-3-3zeta mediates tau phosphorylation by Ser9-phosphorylated GSK3beta in HEK-293 cells.