[Show abstract][Hide abstract] ABSTRACT: Despite recent improvements in treatment strategies, the results of chemotherapy in patients with advanced squamous cell carcinoma of the larynx are not satisfactory. Thus, the development of new approaches which influence specific metabolic pathways are needed. In the last decade, evidence has emerged implicating a role for glutamate as a signal mediator in tumors.
The presence of glutamate receptor subunits in two laryngeal cancer cell lines (RK33 and RK45) was evaluated by means of end-point PCR, real-time PCR, and immunocytochemistry.
Glutamate receptor subunits are differentially expressed in laryngeal cancer cell lines. In addition, we show that selected ionotropic glutamate receptor antagonists and metabotropic glutamate receptor 5 antagonist inhibit proliferation of laryngeal cancer cells. Glutamate antagonists also affected activity of extracellular signal-regulated kinases 1/2 in tumor cells.
Signaling through glutamate receptors may influence growth of laryngeal cancer cells and may constitute an adjunctive therapeutic target.
Full-text · Article · Feb 2011 · Anticancer research
[Show abstract][Hide abstract] ABSTRACT: Epilepsy, the most common neurological disorder in young humans, has its highest incidence during the first year of life. Antiepileptic drugs (AEDs) which are used to treat seizures in infants, children and pregnant women target ion channels, neurotransmitters and second messenger systems in the brain. The same targets regulate brain processes essential both for propagation of seizures and for brain development, learning, memory and emotional behavior. Here we review adverse effects of AEDs in the developing mammalian brain. In addition, we discuss mechanisms explaining adverse effects of AEDs in the developing mammalian brain including interference with cell proliferation and migration, neurogenesis, axonal arborization, synaptogenesis, synaptic plasticity and physiological apoptotic cell death.
[Show abstract][Hide abstract] ABSTRACT: Emerging evidence suggests a role for glutamate and its receptors in the biology of cancer. This study was designed to systematically analyze the expression of ionotropic and metabotropic glutamate receptor subunits in various human cancer cell lines, compare expression levels to those in human brain tissue and, using electrophysiological techniques, explore whether cancer cells respond to glutamate receptor agonists and antagonists. Expression analysis of glutamate receptor subunits NR1-NR3B, GluR1-GluR7, KA1, KA2 and mGluR1-mGluR8 was performed by means of RT-PCR in human rhabdomyosarcoma/medulloblastoma (TE671), neuroblastoma (SK-NA-S), thyroid carcinoma (FTC 238), lung carcinoma (SK-LU-1), astrocytoma (MOGGCCM), multiple myeloma (RPMI 8226), glioma (U87-MG and U343), lung carcinoma (A549), colon adenocarcinoma (HT 29), T cell leukemia cells (Jurkat E6.1), breast carcinoma (T47D) and colon adenocarcinoma (LS180). Analysis revealed that all glutamate receptor subunits were differentially expressed in the tumor cell lines. For the majority of tumors, expression levels of NR2B, GluR4, GluR6 and KA2 were lower compared to human brain tissue. Confocal imaging revealed that selected glutamate receptor subunit proteins were expressed in tumor cells. By means of patch-clamp analysis, it was shown that A549 and TE671 cells depolarized in response to application of glutamate agonists and that this effect was reversed by glutamate receptor antagonists. This study reveals that glutamate receptor subunits are differentially expressed in human tumor cell lines at the mRNA and the protein level, and that their expression is associated with the formation of functional channels. The potential role of glutamate receptor antagonists in cancer therapy is a feasible goal to be explored in clinical trials.
[Show abstract][Hide abstract] ABSTRACT: Fluoxetine (FLX) is a widely prescribed antidepressant. Concerns were raised about the potential impact of FLX on cancer growth, because FLX was shown to promote development of breast cancer in rodents. Here we studied the effect of FLX on tumor growth in lung (A549), colon (HT29), neuroblastoma (SKNAS), medulloblastoma/rhabdomyosarcoma (TE671), astrocytoma (MOGGCCM) and breast (T47D) cancer cells and explored potential mechanisms of its action. In our study, FLX reduced growth of cancer cells in vitro in a concentration dependent manner. The antiproliferative effect of FLX was already evident after 24 hours exposure and more pronounced at 96 hours. We demonstrate that FLX inhibits phosphorylation of ERK1/2 kinases in a time and concentration-dependent manner, followed by reduced phosphorylation of transcription factor c-Myc in A549 and HT29 cells. After treatment with FLX, A549 and HT29 cells demonstrated concentration-dependent decrease in the expression of c-fos, c-jun, cyclin A, cyclin D1, and increased expression of p21(waf1) and p53 genes, which resulted in slowing of the cell cycle progression. We suggest that these changes could be responsible for observed inhibition of cancer cell proliferation during FLX treatment in vitro.
Full-text · Article · Nov 2008 · Cancer biology & therapy
[Show abstract][Hide abstract] ABSTRACT: Sedative and anticonvulsant drugs, which inhibit N-methyl-D-aspartate receptor-mediated excitation or enhance GABA-mediated action, may cause apoptotic neurodegeneration in the developing mammalian brain. Here we explored whether such agents influence early postnatal neurogenesis.
The N-methyl-D-aspartate antagonist MK801 and the GABA subtype A agonists phenobarbital and diazepam were administered to infant rats, and cell proliferation and neurogenesis were studied in the brain using 5-bromo-2'-deoxyuridine and doublecortin immunohistochemistry and stereology. Using confocal microscopy, we quantified neurogenesis in the dentate gyrus on postnatal day 15 (P15) after treatment with MK801 or phenobarbital on P6 to P10. Learning and memory were assessed at the age of 6 months after early postnatal treatment with phenobarbital.
MK801, phenobarbital, and diazepam reduced numbers of newly born cells in the brain. We found no evidence that these agents caused apoptosis of 5-bromo-2'-deoxyuridine-positive cells. In the dentate gyrus, many of the newly formed cells differentiated toward a neuronal phenotype. Phenobarbital and MK801 reduced numbers of newly formed neurons in the dentate gyrus. At the age of 6 months, phenobarbital-treated rats had fewer neurons in the dentate gyrus and performed worse than saline-treated littermates in water maze learning and memory task.
These findings show that blockade of N-methyl-D-aspartate receptor-mediated excitation and enhancement of GABA subtype A receptor activation impair cell proliferation and inhibit neurogenesis in the immature rat brain. Because many sedative and antiepileptic drugs used in pediatric medicine act via these mechanisms, our findings raise concerns about their potential impact on human brain development.
No preview · Article · Oct 2008 · Annals of Neurology
[Show abstract][Hide abstract] ABSTRACT: Blockade of receptors for the excitatory neurotransmitter glutamate ameliorates neurological clinical signs in models of the CNS inflammatory demyelinating disease multiple sclerosis (MS). To investigate whether glutamate excitoxicity may play a role in MS pathogenesis, the cellular localization of glutamate and its receptors, transporters and enzymes was examined. Expression of glutamate receptor (GluR) 1, a Ca(++)-permeable ionotropic AMPA receptor subunit, was up-regulated on oligodendrocytes in active MS lesion borders, but Ca(++)-impermeable AMPA GluR2 subunit levels were not increased. Reactive astrocytes in active plaques expressed AMPA GluR3 and metabotropic mGluR1, 2/3 and 5 receptors and the GLT-1 transporter, and a subpopulation was immunostained with glutamate antibodies. Activated microglia and macrophages were immunopositive for GluR2, GluR4 and NMDA receptor subunit 1. Kainate receptor GluR5-7 immunostaining showed endothelial cells and dystrophic axons. Astrocyte and macrophage populations expressed glutamate metabolizing enzymes and unexpectedly the EAAC1 transporter, which may play a role in glutamate uptake in lesions. Thus, reactive astrocytes in MS white matter lesions are equipped for a protective role in sequestering and metabolizing extracellular glutamate. However, they may be unable to maintain glutamate at levels low enough to protect oligodendrocytes rendered vulnerable to excitotoxic damage because of GluR1 up-regulation.
[Show abstract][Hide abstract] ABSTRACT: Antagonists at alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)-type glutamate receptors limit growth of human cancers in vitro. However, the mechanism of anticancer action of AMPA antagonists is not known. Here we report that the AMPA antagonists GYKI 52466 and CFM-2 inhibit the extracellular signal regulated kinase (ERK1/2) pathway, an intracellular signaling cascade which is activated by growth factors and controls proliferation of lung adenocarcinoma cells. AMPA antagonists reduced phosphorylation of cAMP-responsive element binding protein (CREB), suppressed expression of cyclin D1, upregulated the cell cycle regulators and tumor suppressor proteins p21 and p53 and decreased number of lung adenocarcinoma cells in G2 and S phases of the cell cycle. These findings reveal potential mechanism of antiproliferative action of AMPA antagonists and indicate that this class of compounds may be useful in the therapy of human cancers.
Full-text · Article · Jan 2008 · Cancer biology & therapy
[Show abstract][Hide abstract] ABSTRACT: Epilepsy is the most common neurological disorder in young humans. Antiepileptic drugs (AEDs) which are used to treat seizures in infants, children and pregnant women can cause cognitive impairment, microcephaly and birth defects. Ion channels, neurotransmitters and second messenger systems constitute molecular targets of AEDs. The same targets regulate brain processes essential both for propagation of seizures and for learning, memory and emotional behavior. Thus, AEDs can influence brain function and brain development in undesired ways. Here we review mechanisms of action of AEDs, examine clinical evidence for their adverse effects in the developing human brain, and present studies on cognitive and behavioral effects in animal models. Furthermore, we discuss mechanisms responsible for adverse effects of AEDs in the developing mammalian brain, including interference with cell proliferation and migration, axonal arborization, synaptogenesis, synaptic plasticity and physiological apoptotic cell death.
No preview · Article · Mar 2006 · Cellular and Molecular Life Sciences CMLS
[Show abstract][Hide abstract] ABSTRACT: Glutamate antagonists limit the growth of human cancers in vitro. The mechanism of anticancer action of NMDA antagonists is not known, however. In this article, we report that the NMDA antagonist dizocilpine inhibits the extracellular signal-regulated kinase 1/2 pathway, an intracellular signaling cascade that is activated by growth factors and controls the proliferation of cancer cells. Dizocilpine reduces the phosphorylation of cAMP-responsive element binding protein, suppresses the expression of cyclin D1, up-regulates the cell cycle regulators and tumor suppressor proteins p21 and p53, and increases the number of lung adenocarcinoma cells in the G(2) and S phases of the cell cycle. Silencing of the tumor suppressor protein p21 abolishes antiproliferative action of dizocilpine. Consistent with inhibition of the extracellular signal-regulated kinase 1/2-signaling cascade, dizocilpine reverses the stimulation of proliferation induced by epidermal, insulin, and basic fibroblast growth factors in lung adenocarcinoma cells. Furthermore, dizocilpine prolongs the survival of mice with metastatic lung adenocarcinoma and slows the growth of neuroblastoma and rhabdomyosarcoma in mice. These findings reveal the mechanism of antiproliferative action of dizocilpine and indicate that it may be useful in the therapy of human cancers.
Full-text · Article · Nov 2005 · Proceedings of the National Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: To reveal whether increased Ca2+ permeability of glutamate AMPA channels triggered by the transgene for GluR-B(N) induces decline in motor functions and neurodegeneration in the spinal cord, we evaluated growth, motor coordination, and spinal reflexes in transgenic GluR-B(N) and wild-type (wt) mice. To reveal whether the transgenic GluR-B(N) expression aggravates the course of motoneuron disease in SOD1 mice, we mated heterozygous GluR-B(N) and SOD1 [C57BL6Ico-TgN(hSOD1-G93A)1Gur] mice to generate double-transgenic progeny. The phenotypic sequelae in mice carrying mutations were evaluated by monitoring growth, motor coordination, and survival. Neuronal degeneration was assessed by morphological and stereological analysis of spinal cord and brain. We found that transgenic expression in mice of GluR-B(N)-containing glutamate AMPA receptors with increased Ca2+ permeability leads to a late-onset degeneration of neurons in the spinal cord and decline of motor functions. Neuronal death progressed over the entire life span, but manifested clinically in late adulthood, resembling the course of a slow neurodegenerative disorder. Additional transgenic expression of mutated human SOD1 accelerated disease progression, aggravated severity of motor decline, and decreased survival. These observations reveal that moderate, but persistently elevated Ca2+ influx via glutamate AMPA channels causes degeneration of spinal motoneurons and motor decline over the span of life. These features resemble the course of sporadic amyotrophic lateral sclerosis (ALS) in humans and suggest that modified function of glutamate AMPA channels may be causally linked to pathogenesis of ALS.
No preview · Article · Sep 2005 · Annals of the New York Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: Under pathophysiological conditions, alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptor activation is considered to play a key role in several disorders of the central nervous system. In the search for AMPA receptor antagonists, the synthesis and pharmacological characterization of a series of novel compounds that are structurally related to GYKI 52466 (1), a well-known selective noncompetitive AMPA receptor antagonist, was performed. In vitro, 2,3-dimethyl-6-phenyl-12H-[1,3]dioxolo[4,5-h]imidazo[1,2-c][2,3]benzodiazepine (ZK 187638, 14a) antagonized the kainate-induced currents in cultured hippocampal neurons with an IC(50) of 3.4 microM in a noncompetitive fashion. When tested in a clinically predictive rat model of acute ischemic stroke, this noncompetitive AMPA receptor antagonist significantly reduced brain infarction, indicating that it is neuroprotective after permanent focal cerebral ischemia.
No preview · Article · Aug 2005 · Journal of Medicinal Chemistry
[Show abstract][Hide abstract] ABSTRACT: Amyotrophic lateral sclerosis (ALS) is a devastating disorder of the central nervous system in middle and old age that leads to progressive loss of spinal motoneurons. Transgenic mice overexpressing mutated human Cu(2+)/Zn(2+) superoxide dismutase 1 (SOD1) reproduce clinical features of the familial form of ALS. However, changes in SOD1 activity do not correlate with severity of motor decline in sporadic cases, indicating that targets unrelated to superoxide metabolism contribute to the pathogenesis of the disease. We show here that transgenic expression in mice of GluR-B(N)-containing L-alpha-amino-3-hydroxy-5-methylisoxazole-4-proprionate (AMPA) receptors with increased Ca(2+) permeability leads to late-onset degeneration of neurons in the spinal cord and decline of motor functions. Neuronal death progresses over the entire lifespan but manifests clinically in late adulthood, resembling the course of a slow neurodegenerative disorder. Additional transgenic expression of mutated human SOD1 accelerates disease progression, aggravates the severity of motor decline, and decreases survival. These observations link persistently elevated Ca(2+) influx through AMPA channels with progressive motor decline and late-onset degeneration of spinal motoneurons, indicating that functionally altered AMPA channels may be causally related to pathogenesis of sporadic ALS in humans.
Full-text · Article · May 2005 · Proceedings of the National Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: The discovery of anticancer activity of glutamate antagonists provides new challenges for cancer biologists and the pharmaceutical
industry. One crucial issue to resolve is determining whether glutamate antagonists exert similar anticancer activity in vivo. It will be important to decipher the molecular pathways that glutamate antagonists utilize to limit tumor growth, invasiveness,
and migration. The electrophysiological and binding properties of glutamate receptor/ion channels present on tumor cells will
need to be investigated as well as their subunits better characterized and sequenced. Having achieved this, hopefully it will
be possible to support existing chemotherapy armamentarium with a new class of drugs that have primarily been developed for
[Show abstract][Hide abstract] ABSTRACT: Experimental autoimmune encephalomyelitis reproduces in rodents the features of multiple sclerosis, an immune-mediated, disabling disorder of the human nervous system. No adequate therapy is available for multiple sclerosis, despite anti-inflammatory, immunosuppressive, and immunomodulatory measures. Increasingly glutamate is implicated in the pathogenesis of neurodegenerative diseases. Here we (1) review changes in the glutamatergic system in multiple sclerosis and (2) reveal the effects of glutamate AMPA antagonists in acute and chronic rodent models of multiple sclerosis. Administration of structurally diverse competitive and non-competitive AMPA antagonists reduces neurologic disability in rodents subjected to acute experimental autoimmune encephalomyelitis. In addition, AMPA antagonists are active in both the adoptive transfer and in chronic models of experimental autoimmune encephalomyelitis in rats and mice and affect both the acute and chronic relapsing phases. Moreover, short-term therapy with AMPA antagonists leads to sustained benefit well into the progressive phases. These results imply that therapeutic strategies for multiple sclerosis should be complemented by glutamate AMPA antagonists to reduce neurologic disability.
No preview · Article · Jun 2003 · Annals of the New York Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: Glutamate N-methyl-D-aspartate (NMDA) receptor antagonists (competitive receptor antagonists, ion channel blockers, and glycine antagonists)--such as selfotel, aptiganel, eliprodil, licostinel and gavestinel--failed to show efficacy in clinical trials of stroke or traumatic brain injury. This failure has been attributed to the deficient properties of the molecules that entered human trials and to inappropriate design of clinical studies. In this article we hypothesise that glutamate may be involved in the acute neurodestructive phase that occurs immediately after traumatic or ischaemic injury (excitotoxicity), but that, after this period, it assumes its normal physiological functions, which include promotion of neuronal survival. We propose that NMDA receptor antagonists failed stroke and traumatic brain injury trials in human beings because blockade of synaptic transmission mediated by NMDA receptors hinders neuronal survival.
No preview · Article · Nov 2002 · The Lancet Neurology
[Show abstract][Hide abstract] ABSTRACT: The management of malignancies in humans constitutes a major challenge for contemporary medicine. Despite progress in chemotherapy, bone marrow transplantation, surgical measures, and radiation technologies, and in immunological and immunomodulatory approaches, humans continue to succumb to cancer due to tumor recurrence and metastatic disease. The excitatory neurotransmitter glutamate, which regulates proliferation and migration of neuronal progenitors and immature neurons during the development of the mammalian nervous system, is present in peripheral cancers. Since both neuronal progenitors and tumor cells possess propensity to proliferate and to migrate, and since glutamate and glutamate receptors are known to modify these phenomena in the nervous system, we proceeded to investigate the possible influence of glutamate antagonists on the proliferation and migration of tumor cells. We found and recently reported that glutamate N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA) antagonists inhibit the proliferation of human colon adenocarcinoma, astrocytoma, breast and lung carcinoma, and neuroblastoma cells in vitro. The antiproliferative effect of glutamate antagonists is Ca(2+)-dependent and results from decreased cell division and increased cell death. Glutamate antagonists produce morphological alterations in tumor cells, which consist of reduced membrane ruffling and pseudopodial protrusions, and decrease their motility and invasive growth. Furthermore, glutamate antagonists enhance in vitro cytostatic and cytotoxic effects of common chemotherapeutic agents used in cancer therapy. These findings demonstrate the anticancer potential of glutamate antagonists and suggest that they may be used as an adjunctive measure in the treatment of cancer.
Full-text · Article · Nov 2002 · Biochemical Pharmacology