M. Mena - Academia.edu (original) (raw)

Papers by M. Mena

Research paper thumbnail of Effects of retinoic acid on NB 69 human neuroblastoma cells and fetal rat mid brain neurons

J Neural Transm, 1994

Retinoids are chemical compounds which play important roles in ontogenetic development and cranio... more Retinoids are chemical compounds which play important roles in ontogenetic development and cranio-caudal differentiation in animals, but their effect on phenotypic expression of neurotransmitters are unknown. We studied the pharmacological and morphological effects of retinoic acid (RA) on two types of immature vertebrate neurons, the human derived neuroblastoma cells, NB69, and fetal rat mid brain neurons in culture. The pharmacological effects of RA on the cultures and their relation to catecholamine and acetylcholine neurotransmission were evaluated according the levels of catecholamines, tyrosine hydroxylase (TH) activity, TH immunostaining, and choline acetyltransferase (CAT) activity, respectively. RA reduces catecholamine levels and TH activity in NB69 cells and the number of dopamine neurons in cultures derived from rat fetal mid brain. The detrimental effect of RA on mid brain neurons is dose-dependent; limited to TH+ cells at low concentrations (100 to 500 nM) and toxic for all types of cells at high concentrations (1 to 2 ~M). RA increases CAT activity in NB 69 cells and produces phenotypic differentiation of these to a more mature neuronal phenotype with more prolonged neurite extensions. Therefore, RA may play atrophic positive role in the differentiation of immature cells to cholinergic neurons; this contrasts with the detrimental effects of RA on catecholamine neurons.

Research paper thumbnail of Thiolic antioxidants protect from nitric oxide-induced toxicity in fetal midbrain cultures

Neuropharmacology, 2002

... Permissions & Reprints. Thiolic antioxidants protect from nitric oxide-induced toxicity i... more ... Permissions & Reprints. Thiolic antioxidants protect from nitric oxide-induced toxicity in fetal midbrain cultures. E. Rodríguez-Martín, MJ Casarejos, S. Canals, S. de Bernardo and MA Mena Corresponding Author Contact Information , E-mail The Corresponding Author. ...

Research paper thumbnail of Glia-conditioned medium induces de novo synthesis of tyrosine hydroxylase and increases dopamine cell survival by differential signaling pathways

Journal of Neuroscience Research, 2003

The mesencephalic astroglia-conditioned medium (GCM) greatly increases dopamine (DA) phenotype ex... more The mesencephalic astroglia-conditioned medium (GCM) greatly increases dopamine (DA) phenotype expression, and it also protects from spontaneous and toxin-induced cell death in midbrain cultures. In this study, we have investigated the signaling pathways implicated in those effects. Genistein at 5 M, an inhibitor of tyrosine kinase receptors, and KT-5720, a protein kinase A inhibitor, blocked the GCM-induced effects on DA phenotype expression and DA cell survival but did not abolish the increased astrocytic (glial fibrillary acidic protein-positive; GFAP ϩ ) processes. We analyzed the role of phosphatidylinositol-3 kinase (PI-3K) on TH induction and cell survival, with the PI-3K inhibitors LY-294002 and wortmannin, and the role of the phosphorylation of mitogen-activated protein kinase (MAPK) with PD-98059, a p-ERK1/2 MAPK inhibitor. LY-294002 at 20 -30 M blocked the GCM-induced effects on TH expression and DA cell survival but did not abolish the increased astrocytic processes. PD-98059 at 20 and 40 M blocked the GCM-induced effects on DA phenotype, cell survival, and GFAP expression. However, staurosporine at 10 nM, a protein kinase C inhibitor, only blocked the protective effects induced by GCM on midbrain cell apoptosis. The data presented herein show that tyrosine kinase receptors, cAMP-dependent protein kinase, PI-3K, and MAPK signaling pathways are implicated in de novo synthesis of TH ϩ cells induced by GCM as well as in DA cell apoptosis and that these effects are unrelated to increased GFAP expression. PKC inhibitors only abolished the GCM-induced effects on midbrain neuronal survival, suggesting that signaling pathways for DA phenotype expression and survival may be independent.

Research paper thumbnail of Neurotrophic and neurotoxic effects of nitric oxide on fetal midbrain cultures

Journal of Neurochemistry, 2008

There is evidence suggesting that nitric oxide (NO) may play an important role in dopamine (DA) c... more There is evidence suggesting that nitric oxide (NO) may play an important role in dopamine (DA) cell death. Thus, the aim of this study was to investigate the effects of NO on apoptosis and functionality of DA neurones and glial cells. The experiments were carried out in neuronal-enriched midbrain cultures treated with the NO donor diethylamine±nitric oxide complexed sodium (DEA±NO). DEA±NO, at doses of 25 and 50 mM, exerted neurotrophic effects on dopamine cells, increasing the number of tyrosine hydroxylase positive (TH 1 ) cells, TH 1 neurite processes, DA levels and [ 3 H]DA uptake. A dose of 25 mM DEA±NO protected DA cells from apoptosis. In addition, it induced de novo TH synthesis and increased intracellular reduced glutathione (GSH) levels, indicating a possible neuroprotective role for GSH. However, in doses ranging from 200 to 400 mM, DEA±NO decreased TH 1 cells, DA levels, [ 3 H]DA uptake and the number of mature oligodendrocytes (O1 1 cells). No changes in either the amount or morphology of astrocytes and glial progenitors were detected. A dose-and time-dependent increase in apoptotic cells in the DEA±NO-treated culture was also observed, with a concomitant increase in the proapoptotic Bax protein levels and a reduction in the ratio between Bcl-xL and Bcl-xS proteins. In addition, DEA±NO induced a doseand time-dependent increase in necrotic cells. 1H-[1,2,4]oxadiazolo[4,3a]quinoxaline-1-one (ODQ, 0.5 mM), a selective guanylate cyclase inhibitor, did not revert the NO-induced effect on [ 3 H]DA uptake. Glia-conditioned medium, obtained from fetal midbrain astrocyte cultures, totally protected neuronal-enriched midbrain cultures from NO-induced apoptosis and rescued [ 3 H]DA uptake and TH 1 cell number. In conclusion, our results show that low NO concentrations have neurotrophic effects on DA cells via a cGMP-independent mechanism that may implicate up-regulation of GSH. On the other hand, higher levels of NO induce cell death in both dopamine neurones and mature oligodendrocytes that is totally reverted by soluble factors released from glia.

Research paper thumbnail of Glutathione depletion switches nitric oxide neurotrophic effects to cell death in midbrain cultures: implications for Parkinson's disease

Journal of Neurochemistry, 2002

Nitric oxide (NO) exerts neurotrophic and neurotoxic effects on dopamine (DA) function in primary... more Nitric oxide (NO) exerts neurotrophic and neurotoxic effects on dopamine (DA) function in primary midbrain cultures. We investigate herein the role of glutathione (GSH) homeostasis in the neurotrophic effects of NO. Fetal midbrain cultures were pretreated with GSH synthesis inhibitor, L-buthionine-(S,R)-sulfoximine (BSO), 24 h before the addition of NO donors (diethylamine/nitric oxide-complexed sodium and S-nitroso-N-acetylpenicillamine) at doses tested previously as neurotrophic. Under these conditions, the neurotrophic effects of NO disappeared and turned on highly toxic. Reduction of GSH levels to 50% of baseline induced cell death in response to neurotrophic doses of NO. Soluble guanylate cyclase (sGC) and cyclic GMP-dependent protein kinase (PKG) inhibitors protected from cell death for up to 10 h after NO addition; the antioxidant ascorbic acid also protected from cell death but its efficacy decreased when it was added after NO treatment (40% protection 2 h after NO addition). The pattern of cell death was characterized by an increase in chromatin condensed cells with no DNA fragmentation and with breakdown of plasmatic membrane. The inhibition of RNA and protein synthesis and of caspase activity also protected from cell death. This study shows that alterations in GSH levels change the neurotrophic effects of NO in midbrain cultures into neurotoxic. Under these conditions, NO triggers a programmed cell death with markers of both apoptosis and necrosis characterized by an early step of free radicals production followed by a late requirement for signalling on the sGC/cGMP/PKG pathway.

Research paper thumbnail of Effects of retinoic acid on NB 69 human neuroblastoma cells and fetal rat mid brain neurons

J Neural Transm, 1994

Retinoids are chemical compounds which play important roles in ontogenetic development and cranio... more Retinoids are chemical compounds which play important roles in ontogenetic development and cranio-caudal differentiation in animals, but their effect on phenotypic expression of neurotransmitters are unknown. We studied the pharmacological and morphological effects of retinoic acid (RA) on two types of immature vertebrate neurons, the human derived neuroblastoma cells, NB69, and fetal rat mid brain neurons in culture. The pharmacological effects of RA on the cultures and their relation to catecholamine and acetylcholine neurotransmission were evaluated according the levels of catecholamines, tyrosine hydroxylase (TH) activity, TH immunostaining, and choline acetyltransferase (CAT) activity, respectively. RA reduces catecholamine levels and TH activity in NB69 cells and the number of dopamine neurons in cultures derived from rat fetal mid brain. The detrimental effect of RA on mid brain neurons is dose-dependent; limited to TH+ cells at low concentrations (100 to 500 nM) and toxic for all types of cells at high concentrations (1 to 2 ~M). RA increases CAT activity in NB 69 cells and produces phenotypic differentiation of these to a more mature neuronal phenotype with more prolonged neurite extensions. Therefore, RA may play atrophic positive role in the differentiation of immature cells to cholinergic neurons; this contrasts with the detrimental effects of RA on catecholamine neurons.

Research paper thumbnail of Thiolic antioxidants protect from nitric oxide-induced toxicity in fetal midbrain cultures

Neuropharmacology, 2002

... Permissions & Reprints. Thiolic antioxidants protect from nitric oxide-induced toxicity i... more ... Permissions & Reprints. Thiolic antioxidants protect from nitric oxide-induced toxicity in fetal midbrain cultures. E. Rodríguez-Martín, MJ Casarejos, S. Canals, S. de Bernardo and MA Mena Corresponding Author Contact Information , E-mail The Corresponding Author. ...

Research paper thumbnail of Glia-conditioned medium induces de novo synthesis of tyrosine hydroxylase and increases dopamine cell survival by differential signaling pathways

Journal of Neuroscience Research, 2003

The mesencephalic astroglia-conditioned medium (GCM) greatly increases dopamine (DA) phenotype ex... more The mesencephalic astroglia-conditioned medium (GCM) greatly increases dopamine (DA) phenotype expression, and it also protects from spontaneous and toxin-induced cell death in midbrain cultures. In this study, we have investigated the signaling pathways implicated in those effects. Genistein at 5 M, an inhibitor of tyrosine kinase receptors, and KT-5720, a protein kinase A inhibitor, blocked the GCM-induced effects on DA phenotype expression and DA cell survival but did not abolish the increased astrocytic (glial fibrillary acidic protein-positive; GFAP ϩ ) processes. We analyzed the role of phosphatidylinositol-3 kinase (PI-3K) on TH induction and cell survival, with the PI-3K inhibitors LY-294002 and wortmannin, and the role of the phosphorylation of mitogen-activated protein kinase (MAPK) with PD-98059, a p-ERK1/2 MAPK inhibitor. LY-294002 at 20 -30 M blocked the GCM-induced effects on TH expression and DA cell survival but did not abolish the increased astrocytic processes. PD-98059 at 20 and 40 M blocked the GCM-induced effects on DA phenotype, cell survival, and GFAP expression. However, staurosporine at 10 nM, a protein kinase C inhibitor, only blocked the protective effects induced by GCM on midbrain cell apoptosis. The data presented herein show that tyrosine kinase receptors, cAMP-dependent protein kinase, PI-3K, and MAPK signaling pathways are implicated in de novo synthesis of TH ϩ cells induced by GCM as well as in DA cell apoptosis and that these effects are unrelated to increased GFAP expression. PKC inhibitors only abolished the GCM-induced effects on midbrain neuronal survival, suggesting that signaling pathways for DA phenotype expression and survival may be independent.

Research paper thumbnail of Neurotrophic and neurotoxic effects of nitric oxide on fetal midbrain cultures

Journal of Neurochemistry, 2008

There is evidence suggesting that nitric oxide (NO) may play an important role in dopamine (DA) c... more There is evidence suggesting that nitric oxide (NO) may play an important role in dopamine (DA) cell death. Thus, the aim of this study was to investigate the effects of NO on apoptosis and functionality of DA neurones and glial cells. The experiments were carried out in neuronal-enriched midbrain cultures treated with the NO donor diethylamine±nitric oxide complexed sodium (DEA±NO). DEA±NO, at doses of 25 and 50 mM, exerted neurotrophic effects on dopamine cells, increasing the number of tyrosine hydroxylase positive (TH 1 ) cells, TH 1 neurite processes, DA levels and [ 3 H]DA uptake. A dose of 25 mM DEA±NO protected DA cells from apoptosis. In addition, it induced de novo TH synthesis and increased intracellular reduced glutathione (GSH) levels, indicating a possible neuroprotective role for GSH. However, in doses ranging from 200 to 400 mM, DEA±NO decreased TH 1 cells, DA levels, [ 3 H]DA uptake and the number of mature oligodendrocytes (O1 1 cells). No changes in either the amount or morphology of astrocytes and glial progenitors were detected. A dose-and time-dependent increase in apoptotic cells in the DEA±NO-treated culture was also observed, with a concomitant increase in the proapoptotic Bax protein levels and a reduction in the ratio between Bcl-xL and Bcl-xS proteins. In addition, DEA±NO induced a doseand time-dependent increase in necrotic cells. 1H-[1,2,4]oxadiazolo[4,3a]quinoxaline-1-one (ODQ, 0.5 mM), a selective guanylate cyclase inhibitor, did not revert the NO-induced effect on [ 3 H]DA uptake. Glia-conditioned medium, obtained from fetal midbrain astrocyte cultures, totally protected neuronal-enriched midbrain cultures from NO-induced apoptosis and rescued [ 3 H]DA uptake and TH 1 cell number. In conclusion, our results show that low NO concentrations have neurotrophic effects on DA cells via a cGMP-independent mechanism that may implicate up-regulation of GSH. On the other hand, higher levels of NO induce cell death in both dopamine neurones and mature oligodendrocytes that is totally reverted by soluble factors released from glia.

Research paper thumbnail of Glutathione depletion switches nitric oxide neurotrophic effects to cell death in midbrain cultures: implications for Parkinson's disease

Journal of Neurochemistry, 2002

Nitric oxide (NO) exerts neurotrophic and neurotoxic effects on dopamine (DA) function in primary... more Nitric oxide (NO) exerts neurotrophic and neurotoxic effects on dopamine (DA) function in primary midbrain cultures. We investigate herein the role of glutathione (GSH) homeostasis in the neurotrophic effects of NO. Fetal midbrain cultures were pretreated with GSH synthesis inhibitor, L-buthionine-(S,R)-sulfoximine (BSO), 24 h before the addition of NO donors (diethylamine/nitric oxide-complexed sodium and S-nitroso-N-acetylpenicillamine) at doses tested previously as neurotrophic. Under these conditions, the neurotrophic effects of NO disappeared and turned on highly toxic. Reduction of GSH levels to 50% of baseline induced cell death in response to neurotrophic doses of NO. Soluble guanylate cyclase (sGC) and cyclic GMP-dependent protein kinase (PKG) inhibitors protected from cell death for up to 10 h after NO addition; the antioxidant ascorbic acid also protected from cell death but its efficacy decreased when it was added after NO treatment (40% protection 2 h after NO addition). The pattern of cell death was characterized by an increase in chromatin condensed cells with no DNA fragmentation and with breakdown of plasmatic membrane. The inhibition of RNA and protein synthesis and of caspase activity also protected from cell death. This study shows that alterations in GSH levels change the neurotrophic effects of NO in midbrain cultures into neurotoxic. Under these conditions, NO triggers a programmed cell death with markers of both apoptosis and necrosis characterized by an early step of free radicals production followed by a late requirement for signalling on the sGC/cGMP/PKG pathway.