Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0011570 (depression)
 172,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Alzheimer's disease (AD) is the most common form of dementia, as least in western countries. It has been estimated that the cost to society for caring for AD patients will consume the entire gross national product of the U.S.A. by the middle of this century if left unabated. Until recently, the only available drugs for this condition were cholinergic treatments, which symptomatically enhance cognitive state to some degree, but they were not neuroprotective. In fact, many potential neuroprotective drugs tested in clinical trials failed because they were poorly tolerated. However, after our discovery of its clinically-tolerated mechanism of action, one neuroprotective drug, memantine, was recently approved by the European Union and the U.S. Food and Drug Administration (FDA) for the treatment of Alzheimer's disease. Recent phase 3 clinical trials have shown that memantine is effective in the treatment of moderate-to-severe Alzheimer's disease and possibly vascular dementia (multi-infarct dementia). Here we review the molecular mechanism of memantine's action and also the basis for the drug's use in these neurological diseases, which are mediated at least in part by excitotoxicity. Excitotoxicity is defined as excessive exposure to the neurotransmitter glutamate or overstimulation of its membrane receptors, leading to neuronal injury or death. Excitotoxic neuronal cell death is mediated in part by overactivation of N-methyl-d-aspartate (NMDA)-type glutamate receptors, which results in excessive Ca(2+) influx through the receptor's associated ion channel. Physiological NMDA receptor activity, however, is also essential for normal neuronal function. This means that potential neuroprotective agents that block virtually all NMDA receptor activity will very likely have unacceptable clinical side effects. For this reason many previous NMDA receptor antagonists have disappointingly failed advanced clinical trials for a number of neurodegenerative disorders. In contrast, studies in our laboratory have shown that the adamantane derivative, memantine, preferentially blocks excessive NMDA receptor activity without disrupting normal activity. Memantine does this through its action as an uncompetitive, low-affinity, open-channel blocker; it enters the receptor-associated ion channel preferentially when it is excessively open, and, most importantly, its off-rate is relatively fast so that it does not substantially accumulate in the channel to interfere with normal synaptic transmission. Clinical use has corroborated the prediction that memantine is thus well tolerated. Besides Alzheimer's disease, memantine is currently in trials for additional neurological disorders, including other forms of dementia, depression, glaucoma, and severe neuropathic pain. A series of second-generation memantine derivatives are currently in development and may prove to have even greater neuroprotective properties than memantine. These second-generation drugs take advantage of the fact that the NMDA receptor has other modulatory sites in addition to its ion channel that potentially could also be used for safe but effective clinical intervention.
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PMID:Paradigm shift in NMDA receptor antagonist drug development: molecular mechanism of uncompetitive inhibition by memantine in the treatment of Alzheimer's disease and other neurologic disorders. 1566 16

In western countries, Alzheimer's disease (AD) is the most common form of dementia. In fact, if left uncurbed, the economic cost of caring for AD patients could consume the entire gross national product of the USA by the middle of this century. Until recently, the only available drugs for this condition were cholinergic treatments, which symptomatically enhance cognitive state to some degree, but they were not neuroprotective. In fact, many potential neuroprotective drugs tested in clinical trials failed because they were poorly tolerated. However, after our discovery of its clinically-tolerated mechanism of action, one neuroprotective drug, memantine, was recently approved by the European Union and the U.S. Food and Drug Administration (FDA) for the treatment of Alzheimer's disease. Recent phase 3 clinical trials have shown that memantine is effective in the treatment of both mild and moderate-to-severe Alzheimer's disease and possibly vascular dementia (multi-infarct dementia). Here we review the molecular mechanism of memantine's action and also the basis for the drug's use in these neurological diseases, which are mediated at least in part by excitotoxicity. Excitotoxicity is defined as excessive exposure to the neurotransmitter glutamate or overstimulation of its membrane receptors, leading to neuronal injury or death. Excitotoxic neuronal cell death is mediated in part by overactivation of N-methyl-d-aspartate (NMDA)-type glutamate receptors, which results in excessive Ca2+ influx through the receptor's associated ion channel. Physiological NMDA receptor activity, however, is also essential for normal neuronal function. This means that potential neuroprotective agents that block virtually all NMDA receptor activity will very likely have unacceptable clinical side effects. For this reason many previous NMDA receptor antagonists have disappointingly failed advanced clinical trials for a number of neurodegenerative disorders. In contrast, studies in our laboratory have shown that the adamantane derivative, memantine, preferentially blocks excessive NMDA receptor activity without disrupting normal activity. Memantine does this through its action as an uncompetitive, low-affinity, open-channel blocker; it enters the receptor-associated ion channel preferentially when it is excessively open, and, most importantly, its off-rate is relatively fast so that it does not substantially accumulate in the channel to interfere with normal synaptic transmission. Clinical use has corroborated the prediction that memantine is thus well tolerated. Besides Alzheimer's disease, memantine is currently in trials for additional neurological disorders, including other forms of dementia, depression, glaucoma, and severe neuropathic pain. A series of second-generation memantine derivatives are currently in development and may prove to have even greater neuroprotective properties than memantine. These second-generation drugs take advantage of the fact that the NMDA receptor has other modulatory sites in addition to its ion channel that potentially could also be used for safe but effective clinical intervention.
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PMID:The molecular basis of memantine action in Alzheimer's disease and other neurologic disorders: low-affinity, uncompetitive antagonism. 1597 13

Many researchers have questioned whether new potential therapies aimed at reversing Alzheimer's disease (AD) are indeed scientifically feasible. A number of approved therapies already exist for Alzheimer's disease, yet these drugs only slow the disease progression for a period of time and treat the symptoms of this devastating disease. New therapies intended to reverse the disease would necessarily need to replace dead, dying and dysfunctional neurons in affected regions of the brain. This complex drug discovery problem is further complicated by the knowledge that AD is mainly an aging disorder and that aging, though not considered a disease, causes biological changes that may also need to be overcome [1]. The requirement for new, functional neurons under neurodegenerative diseases, as seen in AD and stroke suggests that an inhibitor of neuronal death, like Memantine, is insufficient to reverse the cognitive and physical loss. New neurons, or neurogenesis, may be required for real improvement or reversal of the cognitive deficit. Adult neurogenesis, first described by Altman in the early 1960s [2, 3], has more recently been observed as a response to injury or disease. Of interest was the finding that new neurons appear to migrate to disease/injury-affected areas in the brain not normally neurogenic in the adult. This pathological-stimulation of neurogenesis does not appear sufficient to stave off the disease and subsequent behavioral decline. Therefore, the desire to amplify and improve upon the neurogenesis-response to neurodegenerative disease appears warranted, if not yet feasible. The key to doing so lies in identifying what signals are required to promote neurogenesis and neuron survival, either in injury and disease or under environmental stimuli. This could provide clues for how to pharmacologically induce neurogenesis under neurodegenerative conditions. Currently, progress in identifying therapeutics that appear to promote ameliorative neurogenesis for AD is lagging behind the pharmacological induction of neurogenesis as a therapy for depression.
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PMID:Discovery of neurogenic, Alzheimer's disease therapeutics. 1647 4

Glutamate receptors of the N-methyl-D-asparate (NMDA-) subtype are tetrameric allosteric and ligand-gated calcium channels. They are modulated by a variety of endogenous ligands and ions and play a pivotal role in memory-related signal transduction due to a voltage-dependent block by magnesium, which makes them Hebbian coincidence detectors. On the structural level NMDA receptors have an enormous flexibility due to seven genes (NR1, NR2A-D and NR3A-B), alternative splicing, RNA-editing and extensive posttranslational modifications, like phosphorylation and glycosylation. NMDA receptors are thought to be responsible for excitotoxicity and subsequent downstream events like neuroinflammation and apoptosis and thus have been implicated in many important human pathologies, ranging from amyotrophic lateral sclerosis, Alzheimer's and Parkinson' disease, depression, epilepsy, trauma and stroke to schizophrenia. This fundamental significance of NMDA receptor-related excitotoxicity is discussed in the context of the developing clinical success of Memantine, but moreover set into relation to various proteomic and genetic markers of said diseases. The very complex localisational and functional regulation of NMDA receptors appears to be dependent on neuregulins and receptor tyrosine kinases in cholesterol-rich membrane domains (lipid rafts), calcium-related mitochondrial feedback-loops and subsynaptic structural elements like PSD-95 (post-synaptic density protein of 95 kD). The flexibility and multitude of interaction partners and possibilities of these highly dynamic molecular systems are discussed in terms of drug development strategies, in particular comparing high affinity and sub-type specific ligands to currently successful or promising therapies.
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PMID:NMDA receptors are not alone: dynamic regulation of NMDA receptor structure and function by neuregulins and transient cholesterol-rich membrane domains leads to disease-specific nuances of glutamate-signalling. 1671 8

Spreading depression (SD) has long been associated with the underlying pathophysiology of migraine. Evidence that the N-methyl-D-aspartate (NMDA) glutamate receptor (NMDA-R) is implicated in the generation and propagation of SD has itself been available for more than 15 years. However, to date, there are no reports of NMDA-R antagonists being developed for migraine therapy. In this study, an uncompetitive, pan-NMDA-R blocker, memantine, approved for clinical use, and two antagonists with selectivity for NMDA-R containing the NR2B subunit, (1S,2S)-1-(4-hydroxyphenyl)-2-(4-hydroxy-4-phenylpiperidino)-1-propanol (CP-101,606) and (+/-)-(R*,S*)-alpha-(4-hydroxyphenyl)-beta-methyl-4-(phenylmethyl)-1-piperidine propanol (Ro 25-6981), were investigated to assess their protective effects against SD in the rat. Under isoflurane anesthesia, d.c. potential and the related cortical blood flow and partial pressure of O2 (pO2) were recorded simultaneously at separate cortical sites. Drugs (1, 3, and 10 mg/kg i.p.) were given 1 h or 30 min before KCl application to the brain surface. Core temperature and arterial pCO2,pO2, and pH measurements confirmed physiological stability. KCl induced 7.7+/-1.8 (mean+/-S.D.) SD events with d.c. amplitude of 14.9+/-2.8 mV. Memantine and CP-101,606 dose-dependently decreased SD event number (to 2.0+/-1.8 and 2.3+/-2.9, respectively) and SD amplitude at doses relevant for therapeutic use. Ro 25-6981 also decreased SD events significantly, but less effectively (to 4.5+/-1.6), without affecting amplitude. These results indicate that NR2B-containing NMDA receptors are key mediators of SD, and as such, memantine- and NR2B-selective antagonists may be useful new therapeutic agents for the treatment of migraine and other SD-related disorders (e.g., stroke and brain injury). Whether chronic, rather than acute, treatment may improve their efficacy remains to be determined.
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PMID:Effects of pan- and subtype-selective N-methyl-D-aspartate receptor antagonists on cortical spreading depression in the rat: therapeutic potential for migraine. 1726 80

Alzheimer's disease (AD) and Vascular dementia represent the most common forms of dementia. If left unabated, the economic cost of caring for patients with these maladies would consume the entire gross national product of the industrialized world by the middle of this century. Until recently, the only available drugs for this condition were cholinergic treatments, which symptomatically enhance cognitive state to some degree, but they were not neuroprotective. Many potential neuroprotective drugs tested in clinical trials failed because of intolerable side effects. However, after our discovery of its clinically-tolerated mechanism of action, one putatively neuroprotective drug, memantine, was recently approved by the European Union and the U.S. Food and Drug Administration (FDA) for the treatment of dementia. Recent phase 3 clinical trials have shown that memantine is effective in the treatment of both mild and moderate-to-severe Alzheimer's disease and possibly Vascular dementia (multi-infarct dementia). Here we review the molecular mechanism of memantine's action and also the basis for the drug's use in these neurological diseases, which are mediated at least in part by excitotoxicity. Excitotoxicity is defined as excessive exposure to the neurotransmitter glutamate or overstimulation of its membrane receptors, leading to neuronal injury or death. Excitotoxic neuronal cell damage is mediated in part by overactivation of N-methyl-D-aspartate (NMDA)-type glutamate receptors, which results in excessive Ca(2+) influx through the receptor associated ion channel and subsequent free radical formation. Physiological NMDA receptor activity, however, is also essential for normal neuronal function. This means that potential neuroprotective agents that block virtually all NMDA receptor activity will very likely have unacceptable clinical side effects. For this reason many previous NMDA receptor antagonists have disappointingly failed advanced clinical trials for a number of neurodegenerative disorders. In contrast, studies in our laboratory have shown that the adamantane derivative, memantine, preferentially blocks excessive NMDA receptor activity without disrupting normal activity. Memantine does this through its action as an uncompetitive, low-affinity, open-channel blocker; it enters the receptor-associated ion channel preferentially when it is excessively open, and, most importantly, its off-rate is relatively fast so that it does not substantially accumulate in the channel to interfere with subsequent normal synaptic transmission. Clinical use has corroborated the prediction that memantine is well tolerated. Besides Alzheimer's disease, memantine is currently in trials for additional neurological disorders, including HIV-associated dementia, depression, glaucoma, and severe neuropathic pain. A series of second-generation memantine derivatives are currently in development and may prove to have even greater neuroprotective properties than memantine. These second-generation drugs take advantage of the fact that the NMDA receptor has other modulatory sites in addition to its ion channel that potentially could also be used for safe but effective clinical intervention.
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PMID:Pathologically-activated therapeutics for neuroprotection: mechanism of NMDA receptor block by memantine and S-nitrosylation. 1750 5

Recent data points to glutamatergic dysfunction in mood disorders, anxiety disorders, obsessive-compulsive disorder, and schizophrenia. Memantine, a drug approved by the FDA for the treatment of moderate to severe Alzheimer's disease that acts at the N-methyl-d-aspartate receptor, has been used off-label for various psychiatric disorders. Although promising, the available data for the use of memantine in these disorders is limited. Given this data, the routine use of memantine for depression, schizophrenia, obsessive-compulsive disorder, substance abuse, pervasive developmental disorders, bipolar disorder, and binge eating disorder cannot be recommended at this time.
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PMID:A systematic review of off-label uses of memantine for psychiatric disorders. 1826 2

Memantine, an uncompetitive antagonist of glutamate receptors of the N-methyl-D-aspartate type is approved for the treatment of moderate to severe Alzheimer's disease. A growing body of evidence supports a link between the glutamatergic neurotransmission and schizophrenia. The purpose of this study (MEM-MD-29) was to examine the efficacy and safety of memantine as an adjunctive treatment to atypical antipsychotics in patients with persistent residual psychopathology of schizophrenia. In this double-blind, placebo-controlled study, participants were assigned to receive 20 mg/day memantine (n=70) or placebo (n=68), in addition to continuing treatment with atypical antipsychotics, for 8 weeks. The primary efficacy measure was the total score on the Positive and Negative Symptom Scale (PANSS). Secondary measures were positive and negative PANSS scores, PANSS responders, Calgary Depression Scale for Schizophrenia (CDSS), Clinical Global Impression of Severity (CGI-S), Clinical Global Impression of Improvement (CGI-I), and Brief Assessment of Cognition in Schizophrenia (BACS). Missing data were imputed using the last observation carried forward (LOCF) approach. Safety was assessed by means of physical examination, clinical laboratory evaluation, recording of adverse events (AEs), and measures of extrapyramidal symptoms. At end point, total PANSS scores did not differ between the memantine and the placebo group (p=0.570, LOCF). A similar outcome was observed for all secondary measures. The frequency of serious AEs in the memantine vs placebo group was 8.7 vs 6.0%; treatment discontinuations because of AEs occurred in 11.6 and 3.0% of patients in these groups, respectively. Memantine showed no efficacy as an adjunctive therapy in schizophrenia patients with residual psychopathology and was associated with a higher incidence of AEs than placebo.
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PMID:A randomized, placebo-controlled study of memantine as adjunctive treatment in patients with schizophrenia. 1900 65

Neuropathic pain is common in the palliative care population; unless adequately treated, the pain can lead to chronic anxiety, depression, and social impairment. Many treatments have been proposed for neuropathic pain; however, it remains underdiagnosed, under-treated, and often requires long-term therapy with risk of adverse effects. Memantine (Namenda), an N-Methyl, D-aspartate receptor inhibitor currently marketed for the treatment of dementia, has been proposed as a medication for the treatment of neuropathic pain for its mechanism, safety, lack of serious adverse effects, and relatively rapid onset of action. However, clinical trials have not been promising so far and its routine use in neuropathic pain is not currently recommended.
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PMID:Memantine (Namenda) for neuropathic pain. 1919 60

There are currently no Food and Drug Administration-approved treatments for frontotemporal lobar degeneration (FTLD). The objectives of this study were to explore the tolerability of memantine treatment in FTLD and to monitor for possible effects on behavior, cognition, and function. Forty-three individuals who met clinical criteria for FTLD [21 with frontotemporal dementia (FTD), 13 with semantic dementia (SD), and 9 with progressive nonfluent aphasia (PA)] received 26 weeks of open-label treatment with memantine at a target dose of 20 mg daily. Concurrent treatment with acetylcholinesterase inhibitors was prohibited. Cognitive and functional outcome measures included the Mini Mental State Examination, Alzheimer's Disease Assessment Scale-Cognitive (ADAS-cog), clinical dementia rating-sum of boxes, Neuropsychiatric Inventory (NPI), Frontal Behavior Inventory, Executive Interview (EXIT25), Texas Functional Living Scale (TFLS), Geriatric Depression Scale, and Unified Parkinson's Disease Rating Scale-motor scale. Most subjects were able to tolerate the target dose of memantine. A transient improvement was observed on the total NPI score primarily in the FTD group. Variable declines were observed on the ADAS-cog, EXIT25, Frontal Behavior Inventory, NPI, TFLS, and UPDRS scores. The FTD and SD groups declined on most of the cognitive and behavioral outcome measures, but remained stable on the UPDRS, whereas the progressive nonfluent aphasia group remained relatively stable on the ADAS-cog, NPI, and TFLS, but declined on the UPDRS. Memantine was well-tolerated in these subjects. Future placebo-controlled trials of memantine in FTLD are warranted and may have greater power to detect behavioral and cognitive effects if focused on the FTD and SD clinical syndromes.
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PMID:An open-label study of memantine treatment in 3 subtypes of frontotemporal lobar degeneration. 1981 61


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