Robert A. Levine
United States Department of Veterans Affairs
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Featured researches published by Robert A. Levine.
European Journal of Neuroscience | 1997
Panagiotis Z. Anastasiadis; Laurent Bezin; Bruce A. Imerman; Donald M. Kuhn; Marisa C. Louie; Robert A. Levine
Epidermal growth factor and nerve growth factor increased the proliferation of rat phaeochromocytoma PC12 cells through obligatory elevation of intracellular (6R)‐tetrahydrobiopterin (BH4). Epidermal growth factor and nerve growth factor increased intracellular BH4 by inducing GTP‐cyclohydrolase, the rate‐limiting enzyme in BH4 biosynthesis. Specific inhibitors of BH4 biosynthesis prevented growth factor‐induced increases in BH4 levels and proliferation. The induction of GTP cyclohydrolase, BH4 and cellular proliferation by nerve growth factor was mediated by CAMP. Elevation of BH4 biosynthesis occurred downstream from CAMP in the cascade used by nerve growth factor to increase proliferation. Thus, intracellular BH4 is an essential mediator of the proliferative effects of epidermal growth factor and nerve growth factor in PC12 cells.
Neuroscience Letters | 2005
Hao Jiang; David Koubi; Lijie Zhang; Jarret Kuo; Alba I. Rodriguez; Tangella Jackson Hunter; Subhash C. Gautam; Robert A. Levine
It has been shown that deletion of the gene encoding the inducible form of nitric oxide synthase (iNOS) results in a reduction of ischemia-induced apoptotic cell death, suggesting the detrimental role of iNOS. The signaling pathways by which iNOS mediates apoptotic cell death under ischemic conditions remain unclear. Understanding the molecular mechanisms of iNOS-mediated apoptotic cell death in ischemia may offer opportunities for potential therapeutic intervention. In the current study, undifferentiated rat pheochromocytoma PC12 cells, exposed to oxygen and glucose deprivation (OGD) followed by reperfusion (adding back oxygen and glucose, OGD-R), were used as an in vitro model of ischemia. The iNOS expression and activity were increased during OGD-R. OGD-R-induced apoptosis was demonstrated by the increase of LDH release, cytosolic release of cytochrome C and caspase-3 activity. Inhibition of iNOS activity by selective iNOS inhibitors, aminoguanidine and 1400W, reduces OGD-R-induced apoptotic cell death, as demonstrated by the decrease of LDH release, cytochrome C release, and caspase-3 activity. These results suggest the critical role of iNOS in mediating apoptosis under ischemic conditions, likely through the induction of caspase-3 activity.
Brain Research | 1994
Panagiotis Z. Anastasiadis; Donald M. Kuhn; Robert A. Levine
The uptake of (6R)-5,6,7,8-tetrahydro-L-biopterin (BH4) was investigated in rat brain synaptosomes, cultured rat pheochromocytoma (PC12) cells, and rat striatum (control and depleted of dopamine neurons) following peripheral administration. A linear, non-saturable, concentration-dependent intracellular accumulation was observed when BH4 was added to either synaptosomes or PC12 cells. The uptake of BH4, in contrast to that of serotonin uptake into synaptosomes or norepinephrine (NE) uptake into PC12 cells, was not dependent on glucose or extracellular sodium. Stimulation of tryptophan hydroxylation in synaptosomes by incubation with 5 microM tryptophan (which increases utilization of BH4 in serotonergic cells) did not alter BH4 uptake. In rats with unilateral 6-hydroxydopamine (6-OHDA) lesions of dopamine neurons, BH4 uptake was the same in control and lesioned striatum following peripheral administration. These results indicate that neurons and PC12 cells do not appear to have a specific membrane carrier for BH4 and that BH4 uptake into cells is due to passive diffusion.
Neurochemistry International | 2005
David Koubi; Hao Jiang; Lijie Zhang; Wenxue Tang; Jarret Kuo; Alba I. Rodriguez; Tangella Jackson Hunter; Michael D. Seidman; George B. Corcoran; Robert A. Levine
Apoptotic cell death has been observed in many in vivo and in vitro models of ischemia. However, the molecular pathways involved in ischemia-induced apoptosis remain unclear. We have examined the role of Bcl-2 family of proteins in mediating apoptosis of PC12 cells exposed to the conditions of oxygen and glucose deprivation (OGD) or OGD followed by restoration of oxygen and glucose (OGD-restoration, OGD-R). OGD decreased mitochondrial membrane potential and induced necrosis of PC12 cells, which were both prevented by the overexpression of Bcl-2 proteins. OGD-R caused apoptotic cell death, induced cytochrome C release from mitochondria and caspase-3 activation, decreased mitochondrial membrane potential, and increased levels of pro-apoptotic Bax translocated to the mitochondrial membrane, all of which were reversed by overexpression of Bcl-2. These results demonstrate that the cell death induced by OGD and OGD-R in PC12 cells is potentially mediated through the regulation of mitochondrial membrane potential by the Bcl-2 family of proteins. It also reveals the importance of developing therapeutic strategies for maintaining the mitochondrial membrane potential as a possible way of reducing necrotic and apoptotic cell death that occurs following an ischemic insult.
Neuroscience Letters | 2001
Laurent Groc; Laurent Bezin; Hao Jiang; Tangella S Jackson; Robert A. Levine
Naturally occurring cell death via apoptosis has been reported in the substantia nigra of rats during development, culminating during the perinatal period. Cellular pathways leading to apoptotic death of developing nigral dopamine neurons remain unknown, although the apoptotic mediator, caspase 3, has been shown to be activated during this process. Our previous results demonstrated the inability of antioxidants to rescue the nigral dopamine neurons that undergo apoptosis during development. In the present study, we investigated using immunohistochemistry the expression of cyclins D1, D3, and E in the substantia nigra during pre- and postnatal development, since their re-expression in postmitotic neurons has been proposed to contribute to developmental apoptosis. We also investigated by Western blot analysis of nigral tissue isolated during the first postnatal week the expression of the anti- and pro-apoptotic proteins, Bcl-2 and Bax, respectively, since altered Bcl-2 expression during developmental apoptosis has been described. During apoptotic death of nigral dopamine neurons in development, we detected a significant increase in the Bax:Bcl-2 ratio, which is consistent with enhanced apoptosis. There were no changes in the expression of the cyclins during the same apoptotic period. These novel findings suggest that nigral dopamine neurons undergo developmental apoptotic death through a Bax:Bcl-2-sensitive pathway that does not involve cyclin mediation.
Neurochemistry International | 2001
Laurent Groc; Laurent Bezin; Jane A Foster; Hao Jiang; Tangella S Jackson; D. Weissmann; Robert A. Levine
The cellular pathways underlying naturally occurring neuronal apoptosis in the rat substantia nigra (SN) during the perinatal period remain largely unknown. Determining the mediators of this process in development may shed light on causes of premature neuronal death in adult neurodegenerative disorders, including the loss of dopamine neurons in Parkinsons disease. In the present study, we investigated whether lipid peroxidation-mediated oxidative stress mediates developmental death of nigral neurons by (1) establishing the profile of lipid peroxidation and other oxidative stress markers throughout the postnatal period both in the SN and striatum, and (2) examining whether the inhibitor of lipid peroxidation, alpha-tocopherol, protects these neurons from death. In addition to monitoring, the level of lipid peroxidation throughout development, we also measured the activities of three antioxidant enzymes, namely superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx). We have shown that lipid peroxidation and SOD activity progressively increased from postnatal day (PND) 3 to PND 42 in both SN and striatum. During this period, GPx activity remained stable, while catalase activity transiently increased at PND 8 only in the SN. Furthermore, alpha-tocopherol treatment from embryonic day 18 to PND 2 did not reduce the number of apoptotic neurons at PND 3. These results do not support the hypothesis that lipid peroxidation-mediated oxidative stress is the major mediator of nigral dopamine neuronal apoptosis during the perinatal period.
Developmental Brain Research | 2002
Laurent Groc; Tangella Jackson Hunter; Hao Jiang; Laurent Bezin; David Koubi; George B. Corcoran; Robert A. Levine
Naturally occurring cell death via apoptosis occurs in the substantia nigra pars compacta (SNc) during rat development, culminating during the perinatal period. We previously showed that lipid peroxidation-mediated oxidative stress is not involved in this cell death process. Nitric oxide (NO) has been proposed to be critical for many developmental processes in brain and has been shown to mediate cell death in neurotoxin models of neurodegenerative disorders. Here, we reported that in vivo pre- and postnatal treatment with the non-specific NO synthase (NOS) inhibitor, L-NAME (60 mg/kg), or with the neuronal NOS inhibitor, 7-NI (30 mg/kg), dramatically decreased the NOS activity as well as the NADPH-diaphorase staining in brain. However, those treatments did not rescue dopamine neurons from developmental death, suggesting that NO is not involved in vivo in developmental death of these neurons or in the overall development of the SNc.
Developmental Brain Research | 2000
Laurent Groc; Robert A. Levine; Jane A Foster; Howard J. Normile; Dinah Weissmann; Laurent Bezin
Apoptosis of dopamine neurons occurs naturally in the substantia nigra during development, culminating in approximately 30% loss of these cells during the perinatal period. Deprenyl, independent of its monoamine oxidase (MAO)-B inhibitory properties, can prevent dopamine neuronal apoptosis in models of neurodegeneration. Our current study demonstrate that apoptotic death of dopamine neurons during development is insensitive to daily treatment of pregnant mothers and then newborns with deprenyl (0.1, 1, or 10 mg/kg). This result is not due to poor crossing of the placental and blood-brain barriers, since deprenyl caused a dose-dependent inhibition of brain MAO-B activity in pups at birth. Determining the pathway(s) leading to deprenyl-insensitive apoptosis of nigral dopamine neurons in development may shed light on mechanisms underlying the premature death of dopamine neurons in neurodegenerative disorders.
Journal of Chemical Neuroanatomy | 2002
Jane A. Foster; Patricia L. Christopherson; Robert A. Levine
The cause of premature death of dopamine neurons in patients with Parkinsons disease remains unknown. It is speculated that damaging reactive species resulting from the metabolism of dopamine, nitric oxide, and tetrahydrobiopterin (BH(4)) may be involved. GTP cyclohydrolase I (GCH1) is the first and rate-limiting enzyme in the synthesis of BH(4), an essential cofactor for tyrosine hydroxylase and nitric oxide synthase in dopamine and nitric oxide production, respectively. Our studies have explored BH(4) metabolism in the nigrostriatal system following intrastriatal kainic acid lesion. We have demonstrated that 1 week following kainic acid there was an increase in striatal GCH1 mRNA, protein, and activity. There was also an elevation of BH(4) levels in the striatum. Part of the induction of GCH1 was localized in situ to astrocytes. Further, the striatal lesion caused death of both neurons and astrocytes in striatum, as shown by in situ end labeling. These novel observations suggest that the induction of GTP cyclohydrolase and BH(4) in striatal astrocytes may be mediating death of striatal neuronal and non-neuronal cells. This work supports existing and emerging reports that demonstrate the importance of dopamine metabolism in neuronal death of the nigrostriatal system.
Archive | 2002
Laurent Groc; Laurent Bezin; Hao Jiang; Tangella Jackson Hunter; Jane A. Foster; Robert A. Levine
Dopamine neurons in the substantia nigra during development undergo cell death, which has been described as apoptotic (1,2), with the main apoptotic peak occurring during the perinatal period (1). Several studies have investigated the cellular mechanisms underlying the apoptosis of these neurons, but the precise mechanisms are still poorly understood. In cultured catecholamine cells, tetrahydrobiopterin (BH4) has been shown to participate in the apoptotic cell death process (3). Both dopamine and BH4 metabolism can produce reactive oxygen species, which can cause cellular damage including lipid peroxidation, which is characterized by the formation of lipid byproducts derived from the breakdown of polyunsaturated fatty acids and related esters (6). Reactive oxygen species are actively scavenged by antioxidant enzymes, such as superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx). (−)-Deprenyl is an irreversible inhibitor of monoamine oxidase-B, which has been shown to prevent apoptosis of cultured fetal dopamine neurons through its antioxidant properties (7,8). α-Tocopherol (vitamin E) is a lipophilic antioxidant that can prevent lipid peroxidation, and has been used to reduce neuronal damage induced by neurotoxic agents (9). We have previously shown that deprenyl and α-tocopherol had no protective effects against developmental apoptosis of dopamine neurons (4,5). In present report, we investigated the effects of deprenyl and α-tocopherol on levels of antioxidant enzymes, lipid oxidation, and the locomotor and learning behaviors of rats.