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An aqueous extract of Khaya senegalensis (Desv.) A. Juss. (Meliaceae) prevents seizures and reduces anxiety in kainate-treated rats: modulation of GABA neurotransmission, oxidative stress, and neuronal loss in the hippocampus. Heliyon 2022; 8:e09549. [PMID: 35663738 PMCID: PMC9160348 DOI: 10.1016/j.heliyon.2022.e09549] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 03/28/2022] [Accepted: 05/23/2022] [Indexed: 11/22/2022] Open
Abstract
Ethnopharmacological relevance Temporal lobe epilepsy is the most common form of drug-resistant epilepsy. Therefore, medicinal plants provide an alternative source for the discovery of new antiepileptic drugs. Aim of the study This study was aimed at investigating the antiepileptic- and anxiolytic-like effects of an aqueous extract of Khaya senegalensis (K. senegalensis) in kainate-treated rats. Methods Seventy-two rats received a single dose of kainate (12 mg/kg) intraperitoneally. Those that exhibited two hours of status epilepticus were selected and monitored for the first spontaneous seizure. Then, animals that developed seizures were divided into 6 groups of 8 rats each and treated twice daily for 14 days as follows: negative control group received per os (p.o.) distilled water (10 ml/kg); two positive control groups received either sodium valproate (300 mg/kg, p.o.) or phenobarbital (20 mg/kg, p.o.); and three test groups received different doses of the extract (50, 100, and 200 mg/kg, p.o.). In addition, a group of 8 normal rats (normal control group) received distilled water (10 ml/kg, p.o.). During the treatment period, the animals were video-monitored 12 h/day for behavioral seizures. At the end of the treatment period, animals were subjected to elevated plus-maze and open field tests. Thereafter, rats were euthanized for the analysis of γ-aminobutyric acid (GABA) concentration, oxidative stress status, and neuronal loss in the hippocampus. Results The aqueous extract of K. senegalensis significantly reduced spontaneous recurrent seizures (generalized tonic-clonic seizures) and anxiety-like behavior compared to the negative control group. These effects were more marked than those of sodium valproate or phenobarbital. Furthermore, the extract significantly increased GABA concentration, alleviated oxidative stress, and mitigated neuronal loss in the dentate gyrus of the hippocampus. Conclusion These findings suggest that the aqueous extract of K. senegalensis possesses antiepileptic- and anxiolytic-like effects. These effects were greater than those of sodium valproate or phenobarbital, standard antiepileptic drugs. Furthermore, these effects are accompanied by neuromodulatory and antioxidant activities that may be related to their behavioral effects. These data justify further studies to identify the bioactive molecules present in the extract for possible future therapeutic development and to unravel their mechanisms of action.
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Curcio M, Salazar IL, Mele M, Canzoniero LMT, Duarte CB. Calpains and neuronal damage in the ischemic brain: The swiss knife in synaptic injury. Prog Neurobiol 2016; 143:1-35. [PMID: 27283248 DOI: 10.1016/j.pneurobio.2016.06.001] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Revised: 03/22/2016] [Accepted: 05/09/2016] [Indexed: 12/26/2022]
Abstract
The excessive extracellular accumulation of glutamate in the ischemic brain leads to an overactivation of glutamate receptors with consequent excitotoxic neuronal death. Neuronal demise is largely due to a sustained activation of NMDA receptors for glutamate, with a consequent increase in the intracellular Ca(2+) concentration and activation of calcium- dependent mechanisms. Calpains are a group of Ca(2+)-dependent proteases that truncate specific proteins, and some of the cleavage products remain in the cell, although with a distinct function. Numerous studies have shown pre- and post-synaptic effects of calpains on glutamatergic and GABAergic synapses, targeting membrane- associated proteins as well as intracellular proteins. The resulting changes in the presynaptic proteome alter neurotransmitter release, while the cleavage of postsynaptic proteins affects directly or indirectly the activity of neurotransmitter receptors and downstream mechanisms. These alterations also disturb the balance between excitatory and inhibitory neurotransmission in the brain, with an impact in neuronal demise. In this review we discuss the evidence pointing to a role for calpains in the dysregulation of excitatory and inhibitory synapses in brain ischemia, at the pre- and post-synaptic levels, as well as the functional consequences. Although targeting calpain-dependent mechanisms may constitute a good therapeutic approach for stroke, specific strategies should be developed to avoid non-specific effects given the important regulatory role played by these proteases under normal physiological conditions.
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Affiliation(s)
- Michele Curcio
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Ivan L Salazar
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal; Doctoral Programme in Experimental Biology and Biomedicine, Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal; Institute for Interdisciplinary Research, University of Coimbra (IIIUC), 3030-789 Coimbra, Portugal
| | - Miranda Mele
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal
| | | | - Carlos B Duarte
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504 Coimbra, Portugal; Department of Life Sciences, University of Coimbra, 3000-456 Coimbra, Portugal.
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Stimulation of neural stem cell proliferation by inhibition of phosphodiesterase 5. Stem Cells Int 2014; 2014:878397. [PMID: 24550991 PMCID: PMC3914480 DOI: 10.1155/2014/878397] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Revised: 11/20/2013] [Accepted: 11/24/2013] [Indexed: 01/25/2023] Open
Abstract
The involvement of nitric oxide (NO) and cyclic GMP (cGMP) in neurogenesis has been progressively unmasked over the last decade. Phosphodiesterase 5 (PDE5) specifically degrades cGMP and is highly abundant in the mammalian brain. Inhibition of cGMP hydrolysis by blocking PDE5 is a possible strategy to enhance the first step of neurogenesis, proliferation of neural stem cells (NSC). In this work, we have studied the effect on cell proliferation of 3 inhibitors with different selectivity and potency for PDE5, T0156, sildenafil, and zaprinast, using subventricular zone-(SVZ-) derived NSC cultures. We observed that a short- (6 h) or a long-term (24 h) treatment with PDE5 inhibitors increased SVZ-derived NSC proliferation. Cell proliferation induced by PDE5 inhibitors was dependent on the activation of the mitogen-activated protein kinase (MAPK) and was abolished by inhibitors of MAPK signaling, soluble guanylyl cyclase, and protein kinase G. Moreover, sildenafil neither activated ERK1/2 nor altered p27Kip1 levels, suggesting the involvement of pathways different from those activated by T0156 or zaprinast. In agreement with the present results, PDE5 inhibitors may be an interesting therapeutic approach for enhancing the proliferation stage of adult neurogenesis.
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Martínez-Ruiz A, Araújo IM, Izquierdo-Álvarez A, Hernansanz-Agustín P, Lamas S, Serrador JM. Specificity in S-nitrosylation: a short-range mechanism for NO signaling? Antioxid Redox Signal 2013; 19:1220-35. [PMID: 23157283 PMCID: PMC3785806 DOI: 10.1089/ars.2012.5066] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
SIGNIFICANCE Nitric oxide (NO) classical and less classical signaling mechanisms (through interaction with soluble guanylate cyclase and cytochrome c oxidase, respectively) operate through direct binding of NO to protein metal centers, and rely on diffusibility of the NO molecule. S-Nitrosylation, a covalent post-translational modification of protein cysteines, has emerged as a paradigm of nonclassical NO signaling. RECENT ADVANCES Several nonenzymatic mechanisms for S-nitrosylation formation and destruction have been described. Enzymatic mechanisms for transnitrosylation and denitrosylation have been also studied as regulators of the modification of specific subsets of proteins. The advancement of modification-specific proteomic methodologies has allowed progress in the study of diverse S-nitrosoproteomes, raising clues and questions about the parameters for determining the protein specificity of the modification. CRITICAL ISSUES We propose that S-nitrosylation is mainly a short-range mechanism of NO signaling, exerted in a relatively limited range of action around the NO sources, and tightly related to the very controlled regulation of subcellular localization of nitric oxide synthases. We review the nonenzymatic and enzymatic mechanisms that support this concept, as well as physiological examples of mammalian systems that illustrate well the precise compartmentalization of S-nitrosylation. FUTURE DIRECTIONS Individual and proteomic studies of protein S-nitrosylation-based signaling should take into account the subcellular localization in order to gain further insight into the functional role of this modification in (patho)physiological settings.
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Affiliation(s)
- Antonio Martínez-Ruiz
- 1 Servicio de Inmunología, Hospital Universitario de La Princesa, Instituto de Investigación Sanitaria Princesa (IP) , Madrid, Spain
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Post-treatment with voltage-gated Na(+) channel blocker attenuates kainic acid-induced apoptosis in rat primary hippocampal neurons. Neurochem Res 2010; 35:2175-83. [PMID: 21127971 DOI: 10.1007/s11064-010-0321-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/08/2010] [Indexed: 12/22/2022]
Abstract
Injection of rats with kainic acid (KA), a non-N-methyl-D-aspartate (NMDA) type glutamate receptor agonist, induces recurrent (delayed) convulsive seizures and subsequently hippocampal neurodegeneration, which is reminiscent of human epilepsy. The protective effect of anti-epileptic drugs on seizure-induced neuronal injury is well known; however, molecular basis of this protective effect has not yet been elucidated. In this study, we investigated the effect and signaling mediators of voltage-gated Na(+) channel blockers (Lamotrigine, Rufinamide, Oxcarbazepine, Valproic Acid, and Zonisamide) on KA-induced apoptosis in rat primary hippocampal neurons. Exposure of hippocampal neurons to 10 μM KA for 24 h caused significant increases in morphological and biochemical features of apoptosis, as determined by Wright staining and ApopTag assay, respectively. Analyses showed increases in expression and activity of cysteine proteases, production of reactive oxygen species (ROS), intracellular free [Ca(2+)], and Bax:Bcl-2 ratio during apoptosis. Cells exposed to KA for 15 min were then treated with Lamotrigine, Rufinamide, Oxcarbazepine, Valproic Acid, or Zonisamide. Post-treatment with one of these anti-epileptic drugs (500 nM) attenuated production of ROS and prevented apoptosis in hippocampal neurons. Lamotrigine, Rufinamide, and Oxcarbazepine appeared to be less protective when compared with Valproic Acid or Zonisamide. This difference may be due to blockade of T-type Ca(2+) channels also by Valproic Acid and Zonisamide. Our findings thus suggest that the anti-epileptic drugs that block both Na(+) channels and Ca(2+) channels are significantly more effective than agents that block only Na(+) channels for attenuating seizure-induced hippocampal neurodegeneration.
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Oliveira LT, Louzada PR, de Mello FG, Ferreira ST. Amyloid-β decreases nitric oxide production in cultured retinal neurons: a possible mechanism for synaptic dysfunction in Alzheimer's disease? Neurochem Res 2010; 36:163-9. [PMID: 20936504 DOI: 10.1007/s11064-010-0287-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/29/2010] [Indexed: 01/21/2023]
Abstract
The neurotoxicity of the amyloid-β peptide (Aβ) appears to be, at least in part, related to pathological activation of glutamate receptors by Aβ aggregates. However, the downstream signaling pathways leading to neurodegeneration are still incompletely understood. Hyperactivation of nitric oxide synthase (NOS) and increased nitric oxide (NO) production have been implicated in excitotoxic neuronal damage caused by overactivation of glutamate receptors, and it has been suggested that increased NO levels might also play a role in neurotoxicity in Alzheimer's disease. We have examined the effect of blockade of NO production on the neurotoxicity instigated by Aβ₄₂ and by elevated concentrations of glutamate in chick embryo retinal neurons in culture. Results showed that L-nitroarginine methyl ester, a potent inhibitor of all NOS isoforms, had no protective effect against neuronal death induced by either Aβ₄₂ (20 μM) or glutamate (1 mM). Surprisingly, at short incubation times both Aβ and glutamate decreased NO production in retinal neuronal cultures in the absence of neuronal death. Thus, excitotoxic insults induced by Aβ and glutamate cause inhibition rather than activation of NO synthase in retinal neurons, suggesting that cell death induced by Aβ or glutamate is not related to increased NO production. On the other hand, considering the role of NO in long term potentiation and synaptic plasticity, the decrease in NO levels instigated by Aβ and glutamate suggests a possible mechanism leading to synaptic failure in AD.
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Affiliation(s)
- Leandro T Oliveira
- Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941-590, Brazil
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Tissue-type plasminogen activator induces plasmin-dependent proteolysis of intracellular neuronal nitric oxide synthase. Biol Cell 2010; 102:539-47. [PMID: 20636282 DOI: 10.1042/bc20100072] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND INFORMATION Despite its pro-fibrinolytic activity, tPA (tissue plasminogen activator) is a serine protease known to influence a number of physiological and pathological functions in the central nervous system. Accordingly, tPA was reported to mediate some of its functions in the central nervous system through NMDA (N-methyl-D-aspartate) receptors, LRP (low-density lipoprotein receptor-related protein) or annexin II. RESULTS We provide here both in vitro and in vivo evidence that tPA could mediate proteolysis and subsequent delocalization of neuronal nitric oxide synthase, thereby reducing endogenous neuronal nitric oxide release. We also demonstrate that although this effect is independent of NMDA receptors, LRP signalling and calpain-mediated proteolysis, it is dependent on the ability of tPA to promote the conversion of plasminogen into plasmin. CONCLUSION Altogether, these results demonstrate a new function for tPA in the central nervous system, which most likely contributes to its pleiotropic functions.
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Silva JP, Proença F, Coutinho OP. Protective role of new nitrogen compounds on ROS/RNS-mediated damage to PC12 cells. Free Radic Res 2009; 42:57-69. [DOI: 10.1080/10715760701787719] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- João P. Silva
- CBMA—Molecular and Environmental Biology Centre/Biology Department, University of Minho, Campus de Gualtar, 4710-057, Braga, Portugal
| | - Fernanda Proença
- Chemistry Department, University of Minho, Campus de Gualtar, 4710-057, Braga, Portugal
| | - Olga P. Coutinho
- CBMA—Molecular and Environmental Biology Centre/Biology Department, University of Minho, Campus de Gualtar, 4710-057, Braga, Portugal
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Sun M, Zhao Y, Gu Y, Xu C. Inhibition of nNOS reduces ischemic cell death through down-regulating calpain and caspase-3 after experimental stroke. Neurochem Int 2009; 54:339-46. [DOI: 10.1016/j.neuint.2008.12.017] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2008] [Revised: 12/19/2008] [Accepted: 12/22/2008] [Indexed: 10/21/2022]
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10
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Averna M, Stifanese R, De Tullio R, Salamino F, Pontremoli S, Melloni E. In vivo degradation of nitric oxide synthase (NOS) and heat shock protein 90 (HSP90) by calpain is modulated by the formation of a NOS-HSP90 heterocomplex. FEBS J 2008; 275:2501-11. [PMID: 18400029 DOI: 10.1111/j.1742-4658.2008.06394.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have shown previously that isolated heat shock protein 90 (HSP90) and nitric oxide synthase (NOS), once associated in a heterocomplex, become completely resistant to calpain digestion. In this study, it is shown that, in vivo, under conditions of calpain activation, the protection of NOS degradation occurs. In addition, the extent of NOS degradation is a function of the level of HSP90 expression. Thus, in rat brain, which contains a large excess of HSP90, almost all neuronal NOS is associated with the chaperone protein. In this condition, neuronal NOS retains its full catalytic activity, although limited proteolytic conversion to still active low-molecular-mass (130 kDa) products takes place. In contrast, in aorta, which contains much smaller amounts of HSP90, endothelial NOS is not completely associated with the chaperone, and undergoes extensive degradation with a loss of protein and catalytic activity. On the basis of these findings, we propose a novel role of the HSP90-NOS heterocomplex in protecting in vivo NOS from proteolytic degradation by calpain. The efficiency of this effect is directly related to the level of intracellular HSP90 expression, generating a high HSP90 to NOS ratio, which favours both the formation and stabilization of the HSP90-NOS heterocomplex. This condition seems to occur in rat brain, but not in aorta, thus explaining the higher vulnerability to proteolytic degradation of endothelial NOS relative to neuronal NOS.
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Affiliation(s)
- Monica Averna
- Department of Experimental Medicine (DIMES)-Biochemistry Section, and Centre of Excellence for Biomedical Research (CEBR), University of Genoa, Italy
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Araújo IM, Gil JM, Carreira BP, Mohapel P, Petersen A, Pinheiro PS, Soulet D, Bahr BA, Brundin P, Carvalho CM. Calpain activation is involved in early caspase-independent neurodegeneration in the hippocampus following status epilepticus. J Neurochem 2007; 105:666-76. [PMID: 18088374 DOI: 10.1111/j.1471-4159.2007.05181.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Evidence for increased calpain activity has been described in the hippocampus of rodent models of temporal lobe epilepsy. However, it is not known whether calpains are involved in the cell death that accompanies seizures. In this work, we characterized calpain activation by examining the proteolysis of calpain substrates and in parallel we followed cell death in the hippocampus of epileptic rats. Male Wistar rats were injected with kainic acid (10 mg/kg) intraperitoneally and killed 24 h later, after development of grade 5 seizures. We observed a strong Fluoro-Jade labeling in the CA1 and CA3 areas of the hippocampus in the rats that received kainic acid, when compared with saline-treated rats. Immunohistochemistry and western blot analysis for the calpain-derived breakdown products of spectrin showed evidence of increased calpain activity in the same regions of the hippocampus where cell death is observed. No evidence was found for caspase activation, in the same conditions. Treatment with the calpain inhibitor MDL 28170 significantly prevented the neurodegeneration observed in CA1. Taken together, our data suggest that early calpain activation, but not caspase activation, is involved in neurotoxicity in the hippocampus after status epilepticus.
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Affiliation(s)
- Inês M Araújo
- Center for Neuroscience and Cell Biology, Department of Zoology, University of Coimbra, Coimbra, Portugal.
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12
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Averna M, Stifanese R, De Tullio R, Salamino F, Bertuccio M, Pontremoli S, Melloni E. Proteolytic degradation of nitric oxide synthase isoforms by calpain is modulated by the expression levels of HSP90. FEBS J 2007; 274:6116-27. [PMID: 17970747 DOI: 10.1111/j.1742-4658.2007.06133.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ca2+ loading of Jurkat and bovine aorta endothelium cells induces the degradation of the neuronal and endothelial nitric oxide synthases that are selectively expressed in these cell lines. For neuronal nitric oxide synthase, this process involves a conservative limited proteolysis without appreciable loss of catalytic activity. By contrast, endothelial nitic oxide synthase digestion proceeds through a parallel loss of protein and catalytic activity. The chaperone heat shock protein 90 (HSP90) is present in a large amount in Jurkat cells and at significantly lower levels in bovine aorta endothelium cells. The differing ratios of HSP90/nitric oxide synthase (NOS) occurring in the two cell types are responsible for the conservative or nonconservative digestion of NOS isozymes. Consistently, we demonstrate that, in the absence of Ca2+, HSP90 forms binary complexes with NOS isozymes or with calpain. When Ca2+ is present, a ternary complex containing the three proteins is produced. In this associated state, HSP90 and NOS forms are almost completely resistant to calpain digestion, probably due to a structural hindrance and a reduction in the catalytic efficiency of the protease. Thus, the recruitment of calpain in the HSP90-NOS complexes reduces the extent of the proteolysis of these two proteins. We have also observed that calpastatin competes with HSP90 for the binding of calpain in reconstructed systems. Digestion of the proteins present in the complexes can occur only when free active calpain is present in the system. This process can be visualized as a novel mechanism involving the association of NOS with HSP90 and the concomitant recruitment of active calpain in ternary complexes in which the proteolysis of both NOS isozymes and HSP90 is significantly reduced.
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Affiliation(s)
- Monica Averna
- Department of Experimental Medicine (DIMES)-Biochemistry Section and Centre of Excellence for Biomedical Research (CEBR), University of Genoa, Italy
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Araújo IM, Carreira BP, Pereira T, Santos PF, Soulet D, Inácio A, Bahr BA, Carvalho AP, Ambrósio AF, Carvalho CM. Changes in calcium dynamics following the reversal of the sodium-calcium exchanger have a key role in AMPA receptor-mediated neurodegeneration via calpain activation in hippocampal neurons. Cell Death Differ 2007; 14:1635-46. [PMID: 17585341 DOI: 10.1038/sj.cdd.4402171] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Proteolytic cleavage of the Na(+)/Ca(2+) exchanger (NCX) by calpains impairs calcium homeostasis, leading to a delayed calcium overload and excitotoxic cell death. However, it is not known whether reversal of the exchanger contributes to activate calpains and trigger neuronal death. We investigated the role of the reversal of the NCX in Ca(2+) dynamics, calpain activation and cell viability, in alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptor-stimulated hippocampal neurons. Selective overactivation of AMPA receptors caused the reversal of the NCX, which accounted for approximately 30% of the rise in intracellular free calcium concentration ([Ca(2+)](i)). The NCX reverse-mode inhibitor, 2-[2-[4-(4-nitrobenzyloxy)phenyl]ethyl]isothiourea (KB-R7943), partially inhibited the initial increase in [Ca(2+)](i), and prevented a delayed increase in [Ca(2+)](i). In parallel, overactivation of AMPA receptors strongly activated calpains and led to the proteolysis of NCX3. KB-R7943 prevented calpain activation, cleavage of NCX3 and was neuroprotective. Silencing of NCX3 reduced Ca(2+) uptake, calpain activation and was neuroprotective. Our data show for the first time that NCX reversal is an early event following AMPA receptor stimulation and is linked to the activation of calpains. Since calpain activation subsequently inactivates NCX, causing a secondary Ca(2+) entry, NCX may be viewed as a new suicide substrate operating in a Ca(2+)-dependent loop that triggers cell death and as a target for neuroprotection.
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Affiliation(s)
- I M Araújo
- Center for Neuroscience and Cell Biology, Department of Zoology, University of Coimbra, Coimbra, Portugal.
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Wu HY, Lynch DR. Calpain and synaptic function. Mol Neurobiol 2007; 33:215-36. [PMID: 16954597 DOI: 10.1385/mn:33:3:215] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2005] [Revised: 11/30/1999] [Accepted: 02/20/2006] [Indexed: 01/13/2023]
Abstract
Proteolysis by calpain is a unique posttranslational modification that can change integrity, localization, and activity of endogenous proteins. Two ubiquitous calpains, mu-calpain and m-calpain, are highly expressed in the central nervous system, and calpain substrates such as membrane receptors, postsynaptic density proteins, kinases, and phosphatases are localized to the synaptic compartments of neurons. By selective cleavage of synaptically localized molecules, calpains may play pivotal roles in the regulation of synaptic processes not only in physiological states but also during various pathological conditions. Activation of calpains during sustained synaptic activity is crucial for Ca2+-dependent neuronal functions, such as neurotransmitter release, synaptic plasticity, vesicular trafficking, and structural stabilization. Overactivation of calpain following dysregulation of Ca2+ homeostasis can lead to neuronal damage in response to events such as epilepsy, stroke, and brain trauma. Calpain may also provide a neuroprotective effect from axotomy and some forms of glutamate receptor overactivation. This article focuses on recent findings on the role of calpain-mediated proteolytic processes in potentially regulating synaptic substrates in physiological and pathophysiological events in the nervous system.
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Affiliation(s)
- Hai-Yan Wu
- Department of Pediatrics, Children's Hospital of Philadelphia and the University of Pennsylvania, Philadelphia, PA, USA
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Cunha-Oliveira T, Rego AC, Garrido J, Borges F, Macedo T, Oliveira CR. Street heroin induces mitochondrial dysfunction and apoptosis in rat cortical neurons. J Neurochem 2007; 101:543-54. [PMID: 17250679 DOI: 10.1111/j.1471-4159.2006.04406.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cortical function has been suggested to be highly compromised by repeated heroin self-administration. We have previously shown that street heroin induces apoptosis in neuronal-like PC12 cells. Thus, we analysed the apoptotic pathways involved in street heroin neurotoxicity using primary cultures of rat cortical neurons. Our street heroin sample was shown to be mainly composed by heroin, 6-monoacetylmorphine and morphine. Exposure of cortical neurons to street heroin induced a slight decrease in metabolic viability, without loss of neuronal integrity. Early activation of caspases involved in the mitochondrial apoptotic pathway was observed, culminating in caspase 3 activation, Poly-ADP Ribose Polymerase (PARP) cleavage and DNA fragmentation. Apoptotic morphology was completely prevented by the non-selective caspase inhibitor z-VAD-fmk, indicating an important role for caspases in neurodegeneration induced by street heroin. Ionotropic glutamate receptors, opioid receptors and oxidative stress were not involved in caspase 3 activation. Interestingly, street heroin cytotoxicity was shown to be independent of a functional mitochondrial respiratory chain, as determined using NT-2 rho(0) cells. Nonetheless, in street heroin-treated cortical neurons, cytochrome c was released, accompanied by a decrease in mitochondrial potential and Bcl-2/Bax. Pure heroin hydrochloride similarly decreased metabolic viability but only slightly activated caspase 3. Altogether, our data suggest an important role for mitochondria in mediating street heroin neurotoxic effects.
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Parathath SR, Parathath S, Tsirka SE. Nitric oxide mediates neurodegeneration and breakdown of the blood-brain barrier in tPA-dependent excitotoxic injury in mice. J Cell Sci 2006; 119:339-49. [PMID: 16410551 DOI: 10.1242/jcs.02734] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Stroke and many neurodegenerative diseases culminate in neuronal death through a mechanism known as excitotoxicity. Excitotoxicity proceeds through a complex signaling pathway that includes the participation of the serine protease tissue plasminogen activator (tPA). tPA mediates neurotoxic effects on resident central nervous system cells as well alters blood-brain barrier (BBB) permeability, which further promotes neurodegeneration. Another signaling molecule that promotes neurodegeneration and BBB dysfunction is nitric oxide (NO), although its precise role in pathological progression remains unclear. We examine here the potentially interrelated roles of tPA, NO and peroxynitrite (ONOO-), which is the toxic metabolite of NO, in BBB breakdown and neurodegeneration following intrahippocampal injection of the glutamate analog kainite (KA). We find that NO and ONOO- production are linked to tPA-mediated excitotoxic injury, and demonstrate that NO provision suffices to restore the toxic effects of KA in tPA-deficient mice that are normally resistant to excitotoxicity. NO also promotes BBB breakdown and excitotoxicity. Interestingly, BBB breakdown in itself does not suffice to elicit neurodegeneration; a subsequent ONOO(-)-mediated event is required. In conclusion, NO and ONOO- function as downstream effectors of tPA-mediated excitotoxicity.
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Affiliation(s)
- Susana R Parathath
- Program in Molecular and Cellular Biology, Department of Pharmacological Sciences, University Medical Center at Stony Brook, Stony Brook, NY 11794-8651, USA
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Araújo IM, Verdasca MJ, Leal EC, Bahr BA, Ambrósio AF, Carvalho AP, Carvalho CM. Early calpain-mediated proteolysis following AMPA receptor activation compromises neuronal survival in cultured hippocampal neurons. J Neurochem 2005; 91:1322-31. [PMID: 15584909 DOI: 10.1111/j.1471-4159.2004.02811.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In this work, we investigated the involvement of calpains in the neurotoxicity induced by short-term exposure to kainate (KA) in non-desensitizing conditions of AMPA receptor activation (cyclothiazide present, CTZ), in cultured rat hippocampal neurons. The calpain inhibitor MDL28170 had a protective effect in cultures treated with KA plus CTZ (p < 0.01), preventing the decrease in MTT reduction caused by exposure to KA (p < 0.001). Caspase inhibition by ZVAD-fmk was not neuroprotective against the toxic effect of KA. At 1 h after treatment, we could already observe significantly increased calpain activity, which was prevented by MDL 28170 and NBQX. Western blot analysis of calpain substrates, GluR1, neuronal nitric oxide synthase (nNOS) and nonerythroid spectrin (fodrin), showed a time-dependent and MDL 28170-sensitive proteolysis of these proteins. This effect was due to calpains, but not caspases, since ZVAD-fmk was ineffective in preventing proteolytic events. Breakdown products of fodrin (BDPs) were detected as early as 15 min after exposure to KA. Overall, these results show early activation of calpains following activation of AMPA receptors as well as compromise of neuronal survival, likely due to proteolytic events that affect proteins involved in neuronal signaling.
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Affiliation(s)
- Inês M Araújo
- Center for Neuroscience and Cell Biology, Department of Zoology, University of Coimbra, Coimbra, Portugal
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Araújo IM, Verdasca MJ, Ambrósio AF, Carvalho CM. Nitric oxide inhibits complex I following AMPA receptor activation via peroxynitrite. Neuroreport 2005; 15:2007-11. [PMID: 15486472 DOI: 10.1097/00001756-200409150-00003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
We investigated the role of nitric oxide (NO) on mitochondrial complexes activity, following short-term non-desensitizing activation of AMPA receptors with kainate (KA) plus cyclothiazide (CTZ), in cultured rat hippocampal neurons. In these conditions, we observed a decrease in the activity of mitochondrial complexes I, II/III, and IV. A selective neuronal nitric oxide synthase inhibitor, 7-Nitroindazole, prevented the decrease in the activity of mitochondrial complex I, but not for the other complexes. Exposure to KA plus CTZ also increased cyclic GMP levels significantly, and led to increased levels of 3-nitrotyrosine, a biomarker for peroxynitrite production. Taken together, our results suggest that non-desensitizing activation of AMPA receptors causes inhibition of mitochondrial complex I via peroxynitrite.
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Affiliation(s)
- Inês M Araújo
- Center for Neuroscience and Cell Biology, Department of Zoology, University of Coimbra, 3004-517 Coimbra, Portugal
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Abstract
PURPOSE OF REVIEW Partial epilepsies are characterized by cell loss with consequences for neuronal organization, excitability, mnestic and cognitive functions and present with pharmaco-resistance and difficulties in clinical management. While mesial temporal lobe epilepsies present frequently with cell loss and neuronal reorganization, neocortical epilepsies frequently involve developmental alterations. RECENT FINDINGS There is increasing evidence that nerve cells in epileptic tissue become more vulnerable to excitotoxic cell death due to impairment of mitochondrial functions and that free radical formation is critically involved in these processes. Whether and to what extent such alterations contribute to pharmaco-resistance is unclear. However, at least three mechanisms may contribute to pharmaco-resistance: changes in target molecules for antiepileptic drugs, upregulation of drug transporters, and potentially reorganization processes in inhibitory networks. Upregulation of drug transporters also seems to be involved in pharmaco-resistance of developmental alterations underlying focal epilepsies. Recent data from the literature suggest that transgenic models for disturbances of cortical development may be useful models for the study of these variable forms of partial epilepsies. SUMMARY The data suggest that improvement of therapy could result from free radical scavenging and from manipulation of drug transport into the affected tissue. New models of developmental epilepsies may help us to understand mechanisms underlying increased vulnerability to seizures as well as improving strategies for treatment.
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Affiliation(s)
- Uwe Heinemann
- Johannes Müller Institute of Physiology, University of Medicine Berlin, Germany.
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