Potential Therapeutic Targets to Modulate the Endocannabinoid System in Alzheimer's Disease.

Alzheimer's disease (AD), the most common neurodegenerative disease (NDD), is characterized by chronic neuronal cell death through progressive loss of cognitive function. Amyloid beta (Aß) deposition, neuroinflammation, oxidative stress, and hyperphosphorylated tau proteins are considered the hallmarks of AD pathology. Different therapeutic approaches approved by the Food and Drug Administration can only target a single altered pathway instead of various mechanisms that are involved in AD pathology, resulting in limited symptomatic relief and almost no effect in slowing down the disease progression. Growing evidence on modulating the components of the endocannabinoid system (ECS) proclaimed their neuroprotective effects by reducing neurochemical alterations and preventing cellular dysfunction. Recent studies on AD mouse models have reported that the inhibitors of the fatty acid amide hydrolase (FAAH) and monoacylglycerol (MAGL), hydrolytic enzymes for N-arachidonoyl ethanolamine (AEA) and 2-arachidonoylglycerol (2-AG), respectively, might be promising candidates as therapeutical intervention. The FAAH and MAGL inhibitors alone or in combination seem to produce neuroprotection by reversing cognitive deficits along with Aß-induced neuroinflammation, oxidative responses, and neuronal death, delaying AD progression. Their exact signaling mechanisms need to be elucidated for understanding the brain intrinsic repair mechanism. The aim of this review was to shed light on physiology and pathophysiology of AD and to summarize the experimental data on neuroprotective roles of FAAH and MAGL inhibitors. In this review, we have also included CB1R and CB2R modulators with their diverse roles to modulate ECS mediated responses such as anti-nociceptive, anxiolytic, and anti-inflammatory actions in AD. Future research would provide the directions in understanding the molecular mechanisms and development of new therapeutic interventions for the treatment of AD.

Low incidence of nephrotoxicity following intravenous administration of iodinated contrast media: a prospective study.

OBJECTIVES: To estimate the incidence of contrast-induced acute kidney injury (CI-AKI) after intravenous (iv) iodinated contrast material (ICM) exposure. METHODS: This prospective cohort study included all consecutive patients who underwent radiological investigations using low-osmolar iopamidol 370 mg/ml in a regional hospital over a period of 36 months, without any exclusion criteria. The estimated glomerular filtration rate (eGFR) was evaluated using the MRDR equation before (2-10 days) and after (24-36 h) radiological investigations. CI-AKI was defined as a ≥ 25% decrease in eGFR from baseline. CI-AKI incidence was estimated using a binomial distribution. The association between CI-AKI and demographic and clinical characteristics was modeled using logistic regression. RESULTS: The study included 1541 patients with a median age of 68 (1st-3rd quartiles 58-76) years with various comorbidities, 30% of whom had pre-existing CKD. Patients affected by stage III or IV chronic kidney disease (CKD) received an infusion of 0.9% normal saline (1.0-1.5 ml/kg/h) before and after iso-osmolar iodixanol administration. CI-AKI was observed in 33 patients (2.1%, 95% CI 1.5-3.0). The logistic regression analysis showed that antibiotic and statin therapies were significantly associated with CI-AKI. The probability of developing CI-AKI decreased by 80% in patients taking statins (OR = 0.20, 95% CI 0.03; 0.68) and increased approximately three times in patients with antibiotic therapy compared with those who did not take statins and antibiotics (OR = 2.92, 95% CI 1.21; 6.36). CONCLUSIONS: Our data suggest that low-osmolar iopamidol carries a low incidence of nephrotoxicity, even in subjects with various comorbid conditions or reduced renal function. KEY POINTS: • IV administration of ICM carries a low incidence of nephrotoxicity, which was transient in observed patients. • Statin therapy is negatively associated with AKI in patients exposed to ICM. • Pre-existing impairment of renal function is not associated with AKI in patients exposed to ICM.

Diagnostic Methods in Forensic Pathology: Autoptic Findings and Immunohistochemical Study in Cases of Sudden Death Due to a Colloid Cyst of the Third Ventricle.

The colloid cyst is a non-malignant tumor growth made of a gelatinous material covered by a membrane of epithelial tissue. It is usually located posterior to the foramen of Monro, in the anterior aspect of the third ventricle of the brain. Due to its location, it can cause obstructive hydrocephalus, increased intracranial pressure, and sudden cardiac death, catecholamine-mediated, through hypothalamus compression. All the mechanisms are still controversial, but the role of catecholamine has been confirmed with histological findings that highlighted myocardial injury (coagulative myocytolysis and contraction band necrosis, CBN). This study presents a case of sudden death in a previously healthy 22-year-old male due to a colloid cyst of the third ventricle. A complete autopsy was performed, highlighting in the brain an abundant quantity of cerebrospinal fluid (CSF) and a 2 cm pale grayish-green rounded cyst formation partially filling and distending the third ventricle. The diagnosis was confirmed through immunohistochemical investigation: positivity for Periodic acid-Schiff (PAS) staining and CK7 expression. In cases such as the one reported here, a combined approach of autopsy, histology, and immunohistochemistry is mandatory in order to identify the neoformation's location and morpho-structural characteristics for a correct differential diagnosis, as well as to identify the cause of death.

Calcium Deregulation in Neurodegeneration and Neuroinflammation in Parkinson's Disease: Role of Calcium-Storing Organelles and Sodium-Calcium Exchanger.

Parkinson's disease (PD) is a progressive neurodegenerative disorder that lacks effective treatment strategies to halt or delay its progression. The homeostasis of Ca2+ ions is crucial for ensuring optimal cellular functions and survival, especially for neuronal cells. In the context of PD, the systems regulating cellular Ca2+ are compromised, leading to Ca2+-dependent synaptic dysfunction, impaired neuronal plasticity, and ultimately, neuronal loss. Recent research efforts directed toward understanding the pathology of PD have yielded significant insights, particularly highlighting the close relationship between Ca2+ dysregulation, neuroinflammation, and neurodegeneration. However, the precise mechanisms driving the selective loss of dopaminergic neurons in PD remain elusive. The disruption of Ca2+ homeostasis is a key factor, engaging various neurodegenerative and neuroinflammatory pathways and affecting intracellular organelles that store Ca2+. Specifically, impaired functioning of mitochondria, lysosomes, and the endoplasmic reticulum (ER) in Ca2+ metabolism is believed to contribute to the disease's pathophysiology. The Na+-Ca2+ exchanger (NCX) is considered an important key regulator of Ca2+ homeostasis in various cell types, including neurons, astrocytes, and microglia. Alterations in NCX activity are associated with neurodegenerative processes in different models of PD. In this review, we will explore the role of Ca2+ dysregulation and neuroinflammation as primary drivers of PD-related neurodegeneration, with an emphasis on the pivotal role of NCX in the pathology of PD. Consequently, NCXs and their interplay with intracellular organelles may emerge as potentially pivotal players in the mechanisms underlying PD neurodegeneration, providing a promising avenue for therapeutic intervention aimed at halting neurodegeneration.

Glutamate-induced ATP synthesis: relationship between plasma membrane Na+/Ca2+ exchanger and excitatory amino acid transporters in brain and heart cell models.

It is known that glutamate (Glu), the major excitatory amino acid in the central nervous system, can be an essential source for cell energy metabolism. Here we investigated the role of the plasma membrane Na(+)/Ca(2+) exchanger (NCX) and the excitatory amino acid transporters (EAATs) in Glu uptake and recycling mechanisms leading to ATP synthesis. We used different cell lines, such as SH-SY5Y neuroblastoma, C6 glioma and H9c2 as neuronal, glial, and cardiac models, respectively. We first observed that Glu increased ATP production in SH-SY5Y and C6 cells. Pharmacological inhibition of either EAAT or NCX counteracted the Glu-induced ATP synthesis. Furthermore, Glu induced a plasma membrane depolarization and an intracellular Ca(2+) increase, and both responses were again abolished by EAAT and NCX blockers. In line with the hypothesis of a mutual interplay between the activities of EAAT and NCX, coimmunoprecipitation studies showed a physical interaction between them. We expanded our studies on EAAT/NCX interplay in the H9c2 cells. H9c2 expresses EAATs but lacks endogenous NCX1 expression. Glu failed to elicit any significant response in terms of ATP synthesis, cell depolarization, and Ca(2+) increase unless a functional NCX1 was introduced in H9c2 cells by stable transfection. Moreover, these responses were counteracted by EAAT and NCX blockers, as observed in SH-SY5Y and C6 cells. Collectively, these data suggest that plasma membrane EAAT and NCX are both involved in Glu-induced ATP synthesis, with NCX playing a pivotal role.

Altered regulation of glutamate release and decreased functional activity and expression of GLT1 and GLAST glutamate transporters in the hippocampus of adolescent rats perinatally exposed to Delta(9)-THC.

The long-term effects of perinatal Delta(9)-tetrahydrocannabinol (Delta(9)-THC) exposure - from gestational day (GD) 15 to postnatal day (PND) 9 - on hippocampal glutamatergic neurotransmission were studied in slices from the 40-day-old offspring of Delta(9)-THC exposed (Delta(9)-THC-rats) and vehicle-exposed (control) dams. Basal and in K+-evoked endogenous hippocampal glutamate outflow were both significantly decreased in Delta(9)-THC-rats. The effect of short Delta(9)-THC exposure (0.1microM) on K(+)-evoked glutamate release disclosed a loss of the stimulatory effect of Delta(9)-THC on hippocampal glutamate release in Delta(9)-THC-rats, but not in controls. In addition, l-[(3)H]-glutamate uptake was significantly lower in hippocampal slices from Delta(9)-THC-rats, where a significant decrease in glutamate transporter 1 (GLT1) and glutamate/aspartate transporter (GLAST) protein was also detected. Collectively, these data demonstrate that perinatal exposure to cannabinoids induces long-term impairment in hippocampal glutamatergic neurotransmission that persist into adolescence.

Gateways for Glutamate Neuroprotection in Parkinson's Disease (PD): Essential Role of EAAT3 and NCX1 Revealed in an In Vitro Model of PD.

Increasing evidence suggests that metabolic alterations may be etiologically linked to neurodegenerative disorders such as Parkinson's disease (PD) and in particular empathizes the possibility of targeting mitochondrial dysfunctions to improve PD progression. Under different pathological conditions (i.e., cardiac and neuronal ischemia/reperfusion injury), we showed that supplementation of energetic substrates like glutamate exerts a protective role by preserving mitochondrial functions and enhancing ATP synthesis through a mechanism involving the Na+-dependent excitatory amino acid transporters (EAATs) and the Na+/Ca2+ exchanger (NCX). In this study, we investigated whether a similar approach aimed at promoting glutamate metabolism would be also beneficial against cell damage in an in vitro PD-like model. In retinoic acid (RA)-differentiated SH-SY5Y cells challenged with α-synuclein (α-syn) plus rotenone (Rot), glutamate significantly improved cell viability by increasing ATP levels, reducing oxidative damage and cytosolic and mitochondrial Ca2+ overload. Glutamate benefits were strikingly lost when either EAAT3 or NCX1 expression was knocked down by RNA silencing. Overall, our results open the possibility of targeting EAAT3/NCX1 functions to limit PD pathology by simultaneously favoring glutamate uptake and metabolic use in dopaminergic neurons.

NCX and EAAT transporters in ischemia: At the crossroad between glutamate metabolism and cell survival.

Energy metabolism impairment is a central event in the pathophysiology of ischemia. The limited availability of glucose and oxygen strongly affects mitochondrial activity, thus leading to ATP depletion. In this setting, the switch to alternative energy sources could ameliorate cells survival by enhancing ATP production, thus representing an attractive strategy for ischemic treatment. In this regard, some studies have recently re-evaluated the metabolic role of glutamate and its potential to promote cell survival under pathological conditions. In the present review, we discuss the ability of glutamate to exert an "energizing role" in cardiac and neuronal models of hypoxia/reoxygenation (H/R) injury, focusing on the Na+/Ca2+ exchanger (NCX) and the Na+-dependent excitatory amino acid transporters (EAATs) as key players in this metabolic pathway.

Selective inhibition of mitochondrial sodium-calcium exchanger protects striatal neurons from α-synuclein plus rotenone induced toxicity.

Progressive accumulation of α-synuclein (α-syn) and exposure to environmental toxins are risk factors that may both concur to Parkinson's disease (PD) pathogenesis. Electrophysiological recordings of field postsynaptic potentials (fEPSPs) and Ca2+ measures in striatal brain slices and differentiated SH-SY5Y cells showed that co-application of α-syn and the neurotoxic pesticide rotenone (Rot) induced Ca2+ dysregulation and alteration of both synaptic transmission and cell function. Interestingly, the presence of the mitochondrial NCX inhibitor CGP-37157 prevented these alterations. The specific involvement of the mitochondrial NCX was confirmed by the inability of the plasma membrane inhibitor SN-6 to counteract such phenomenon. Of note, using a siRNA approach, we found that NCX1 was the isoform specifically involved. These findings suggested that NCX1, operating on the mitochondrial membrane, may have a critical role in the maintenance of ionic Ca2+ homeostasis in PD and that its inhibition most likely exerts a protective effect in the toxicity induced by α-syn and Rot.

Atypical gating of M-type potassium channels conferred by mutations in uncharged residues in the S4 region of KCNQ2 causing benign familial neonatal convulsions.

Heteromeric assembly of KCNQ2 and KCNQ3 subunits underlie the M-current (I(KM)), a slowly activating and noninactivating neuronal K(+) current. Mutations in KCNQ2 and KCNQ3 genes cause benign familial neonatal convulsions (BFNCs), a rare autosomal-dominant epilepsy of the newborn. In the present study, we describe the identification of a novel KCNQ2 heterozygous mutation (c587t) in a BFNC-affected family, leading to an alanine to valine substitution at amino acid position 196 located at the N-terminal end of the voltage-sensing S(4) domain. The consequences on KCNQ2 subunit function prompted by the A196V substitution, as well as by the A196V/L197P mutation previously described in another BFNC-affected family, were investigated by macroscopic and single-channel current measurements in CHO cells transiently transfected with wild-type and mutant subunits. When compared with KCNQ2 channels, homomeric KCNQ2 A196V or A196V/L197P channels showed a 20 mV rightward shift in their activation voltage dependence, with no concomitant change in maximal open probability or single-channel conductance. Furthermore, current activation kinetics of KCNQ2 A196V channels displayed an unusual dependence on the conditioning prepulse voltage, being markedly slower when preceded by prepulses to more depolarized potentials. Heteromeric channels formed by KCNQ2 A196V and KCNQ3 subunits displayed gating changes similar to those of KCNQ2 A196V homomeric channels. Collectively, these results reveal a novel role for noncharged residues in the N-terminal end of S(4) in controlling gating of I(KM) and suggest that gating changes caused by mutations at these residues may decrease I(KM) function, thus causing neuronal hyperexcitability, ultimately leading to neonatal convulsions.

Glutamate as a potential "survival factor" in an in vitro model of neuronal hypoxia/reoxygenation injury: leading role of the Na+/Ca2+ exchanger.

In brain ischemia, reduction in oxygen and substrates affects mitochondrial respiratory chain and aerobic metabolism, culminating in ATP production impairment, ionic imbalance, and cell death. The restoration of blood flow and reoxygenation are frequently associated with exacerbation of tissue injury, giving rise to ischemia/reperfusion (I/R) injury. In this setting, the imbalance of brain bioenergetics induces important metabolic adaptations, including utilization of alternative energy sources, such as glutamate. Although glutamate has long been considered as a neurotoxin, it can also be used as intermediary metabolite for ATP synthesis, and both the Na+/Ca2+ exchanger (NCX) and the Na+-dependent excitatory amino-acid transporters (EAATs) are essential in this pathway. Here we analyzed the role of NCX in the potential of glutamate to improve metabolism and survival of neuronal cells subjected to hypoxia/reoxygenation (H/R). In SH-SY5Y neuroblastoma cells differentiated into a neuron-like state, H/R produced a significant cell damage, a decrease in ATP cellular content, and intracellular Ca2+ alterations. Exposure to glutamate at the onset of the reoxygenation phase attenuated H/R-induced cell damage and evoked a significant raise in intracellular ATP levels. Furthermore, we found that in H/R cells NCX reverse-mode activity was reduced, and that glutamate limited such reduction. All the effects induced by glutamate supplementation were lost when cells were transfected with small interfering RNA against NCX1 and EAAT3, suggesting the need of a specific functional interplay between these proteins for glutamate-induced protection. Collectively, our results revealed the potential beneficial effect of glutamate in an in vitro model of H/R injury and focused on the essential role exerted by NCX1. Although preliminary, these findings could be a starting point to further investigate in in vivo systems such protective effect in ischemic settings, shedding a new light on the classical view of glutamate as detrimental factor.

The Biological Effects of Kambo: Is There a Relationship Between its Administration and Sudden Death?

Kambo is a substance obtained from the skin secretions of a frog, Phyllomedusa bicolor, popular in the Amazon region, which is administered via the transdermal route. We report a case of 42-year-old man found dead in his house. Near the corpse, a plastic box labeled as "Kambo sticks" was found. The man was a chronic consumer of Kambo and no previous pathology or genetic disease emerged in clinical history from the declaration of his general practitioner. Autopsy investigations and toxicological analysis were performed. The histopathological examination showed left ventricular hypertrophy. Toxicological screening was negative for ethanol and other drugs. Phyllocaerulein, phyllokinin, and deltorphin A were isolated from the Kambo sticks but, only deltorphin A was detected in blood sample. We describe the first forensic case of death associated with Kambo administration. We attempt to explain how its use could be related to the cause of sudden death in this case.

Cellular and subcellular localization of Na+-Ca2+ exchanger protein isoforms, NCX1, NCX2, and NCX3 in cerebral cortex and hippocampus of adult rat.

Na(+)-Ca(2+) exchanger (NCX) controls cytosolic Ca(2+) and Na(+) concentrations ([Ca(2+)](i) and [Na(+)](i)) in eukaryotic cells. Here we investigated by immunocytochemistry the cellular and subcellular localization of the three known NCX isoforms, NCX1, NCX2 and NCX3, in adult rat neocortex and hippocampus. NCX1-3 were widely expressed in both brain areas: NCX1 immunoreactivity (ir) was exclusively associated to neuropilar puncta, while NCX2-3 were also detected in neuronal somata and dendrites. NCX1-3 ir was often identified around blood vessels. In both neocortex and hippocampus, all NCX isoforms were prominently expressed in dendrites and dendritic spines contacted by asymmetric axon terminals, whereas they were poorly expressed in presynaptic boutons. In addition, NCX1-3 ir was detected in astrocytes, notably in distal processes ensheathing excitatory synapses. All NCXs were expressed in perivascular astrocytic endfeet and endothelial cells. The robust expression of NCX1-3 in heterogeneous cell types in the brain in situ emphasizes their role in handling Ca(2+) and Na(+) in both excitable and non-excitable cells. Perisynaptic localization of NCX1-3 in dendrites and spines indicates that all isoforms are favourably located for buffering [Ca(2+)](i) in excitatory postsynaptic sites. NCX1-3 expressed in perisynaptic glial processes may participate in shaping astrocytic [Ca(2+)](i) transients evoked by ongoing synaptic activity.

Prenatal exposure to the cannabinoid receptor agonist WIN 55,212-2 increases glutamate uptake through overexpression of GLT1 and EAAC1 glutamate transporter subtypes in rat frontal cerebral cortex.

Prenatal exposure to the CB1 receptor agonist (R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)-pyrrolo[1,2,3-de]-1,4-benzoxazinyl]-(1-naphthalenyl)methanone) mesylate (WIN) at a daily dose of 0.5 mg/kg, and Delta9-tetrahydrocannabinol (Delta9-THC) at a daily dose of 5 mg/kg, reduced dialysate glutamate levels in frontal cerebral cortex of adolescent offspring (40-day-old) with respect to those born from vehicle-treated mothers. WIN treatment induced a statistically significant enhancement of Vmaxl-[3H]glutamate uptake, whereas it did not modify glutamate Km, in frontal cerebral cortex synaptosomes of adolescent rats. Western blotting analysis, performed either in membrane proteins derived from homogenates and in proteins extracted from synaptosomes of frontal cerebral cortex, revealed that prenatal WIN exposure enhanced the expression of glutamate transporter 1 (GLT1) and excitatory amino acid carrier 1 (EAAC1). Moreover, immunocytochemical analyses of frontal cortex area revealed a more intense GLT1 and EAAC1 immunoreactivity (ir) distribution in the WIN-treated group. Collectively these results show that prenatal exposure to the cannabinoid CB1 receptor agonist WIN increases expression and functional activity of GLT1 and EAAC1 glutamate transporters (GluTs) associated to a decrease of cortical glutamate outflow, in adolescent rats. These findings may contribute to explain the mechanism underlying the cognitive impairment observed in the offspring of mothers who used marijuana during pregnancy.

Essential role of the Na+-Ca2+ exchanger (NCX) in glutamate-enhanced cell survival in cardiac cells exposed to hypoxia/reoxygenation.

Myocardial ischemia culminates in ATP production impairment, ionic derangement and cell death. The provision of metabolic substrates during reperfusion significantly increases heart tolerance to ischemia by improving mitochondrial performance. Under normoxia, glutamate contributes to myocardial energy balance as substrate for anaplerotic reactions, and we demonstrated that the Na+/Ca2+ exchanger1 (NCX1) provides functional support for both glutamate uptake and use for ATP synthesis. Here we investigated the role of NCX1 in the potential of glutamate to improve energy metabolism and survival of cardiac cells subjected to hypoxia/reoxygenation (H/R). Specifically, in H9c2-NCX1 myoblasts, ATP levels, mitochondrial activities and cell survival were significantly compromised after H/R challenge. Glutamate supplementation at the onset of the reoxygenation phase significantly promoted viability, improved mitochondrial functions and normalized the H/R-induced increase of NCX1 reverse-mode activity. The benefits of glutamate were strikingly lost in H9c2-WT (lacking NCX1 expression), or in H9c2-NCX1 and rat cardiomyocytes treated with either NCX or Excitatory Amino Acid Transporters (EAATs) blockers, suggesting that a functional interplay between these transporters is critically required for glutamate-induced protection. Collectively, these results revealed for the first time the key role of NCX1 for the beneficial effects of glutamate against H/R-induced cell injury.

Na+/Ca2+ exchanger 1 inhibition abolishes ischemic tolerance induced by ischemic preconditioning in different cardiac models.

Ca2+-handling disturbances play an important role in the genesis of myocardial ischemia/reperfusion (I/R) injury. Ischemic preconditioning (IPC) is a powerful strategy to induce tolerance against subsequent ischemic episodes. IPC signaling pathways may be triggered by Ca2+ ion. Since Na+/Ca2+ exchanger 1 (NCX1) participates in modulating intracellular Ca2+ homeostasis, here we further defined its role in I/R and investigated its potential involvement in IPC-induced cardioprotection. In isolated ventricular cardiomyocytes, perfused rat heart and H9c2 cardiomyoblasts, I/R produced a significant cell injury, assessed by measuring extracellular lactate dehydrogenase (LDH) and, for the whole heart, also by estimating myocardial infarct size area. Characterization of cell death revealed the involvement of apoptotic processes. Interestingly, I/R challenge induced NCX1 protein upregulation. In NCX1-transfected H9c2 cells, exchanger protein upregulation was accompanied by an increase in its reverse mode activity. The effects of I/R on extracellular LDH and infarct size area were drastically reduced by 1µM SN-6, a selective NCX1 inhibitor. Moreover, SN-6 also prevented I/R-induced increase of NCX1 reverse-mode activity and protein upregulation. These results suggested a deleterious role of NCX1 in I/R-induced cell damage. In both isolated cardiomyocytes and perfused heart, IPC followed by I/R afforded cardioprotection, reducing extracellular LDH release and limiting ischemic area extent. Interestingly, NCX1 blockade (1µM SN-6) completely abolished IPC protection against I/R, leading to exacerbation of cell injury, massive infarct size area and restoration of NCX1 protein expression. These findings suggest that NCX1 is deleterious in I/R, whereas it may be beneficial in promoting IPC-induced cardioprotection.

Antiproliferative effects of tocopherols (vitamin E) on murine glioma C6 cells: homologue-specific control of PKC/ERK and cyclin signaling.

Chemoprevention strategies for brain tumors (specifically gliomas) are few and surprisingly poorly investigated. We have studied the effects of tocopherols (TOCs; vitamin E) on proliferation and death processes of murine glioma C6 cells. These vitamers showed different cell uptake and concentration- and time-dependent inhibitory effects on cell growth that were significant at the lowest concentrations tested (1-10 microM). However, the inhibitory potency of TOCs seemed to reflect at least in part their actual cell concentrations at steady state, with the order of magnitude gamma-TOC >or= alpha-TOC > delta-TOC approximately or = beta-TOC. Moreover, for extracellular concentrations >or=10 microM, TOCs also showed a significant cytotoxic effects due mainly to necrosis, while apoptosis was negligible. Gamma-TOC (the form showing preferential cell uptake and lowest unspecific cytotoxicity) was the most effective inhibitor of cell cycle progression (arrest in G0/G1 phase) leading to lowered expression of cyclin E and cyclin-dependent kinases 2 and 4 and overexpression of p27 (specific inhibitor of S-phase entering). According to these signals, activated ERK1/2 and PKC upstream and Rb phosphorylation downstream were decreased. In conclusion, within TOCs the gamma form exerts the most potent and specific control of cell cycle progression in C6 cells (cytostatic effect). This suggests a chemopreventive role of this form of vitamin E in gliomas.

Intracellular Calcium Dysregulation: Implications for Alzheimer's Disease.

Alzheimer's Disease (AD) is a neurodegenerative disorder characterized by progressive neuronal loss. AD is associated with aberrant processing of the amyloid precursor protein, which leads to the deposition of amyloid-ß plaques within the brain. Together with plaques deposition, the hyperphosphorylation of the microtubules associated protein tau and the formation of intraneuronal neurofibrillary tangles are a typical neuropathological feature in AD brains. Cellular dysfunctions involving specific subcellular compartments, such as mitochondria and endoplasmic reticulum (ER), are emerging as crucial players in the pathogenesis of AD, as well as increased oxidative stress and dysregulation of calcium homeostasis. Specifically, dysregulation of intracellular calcium homeostasis has been suggested as a common proximal cause of neural dysfunction in AD. Aberrant calcium signaling has been considered a phenomenon mainly related to the dysfunction of intracellular calcium stores, which can occur in both neuronal and nonneuronal cells. This review reports the most recent findings on cellular mechanisms involved in the pathogenesis of AD, with main focus on the control of calcium homeostasis at both cytosolic and mitochondrial level.

M channels containing KCNQ2 subunits modulate norepinephrine, aspartate, and GABA release from hippocampal nerve terminals.

KCNQ subunits encode for the M current (I(KM)), a neuron-specific voltage-dependent K+ current with a well established role in the control of neuronal excitability. In this study, by means of a combined biochemical, pharmacological, and electrophysiological approach, the role of presynaptic I(KM) in the release of previously taken up tritiated norepineprine (NE), GABA, and d-aspartate (d-ASP) from hippocampal nerve terminals (synaptosomes) has been evaluated. Retigabine (RT) (0.01-30 microm), a specific activator of I(KM), inhibited [3H]NE, [3H]d-ASP, and [3H]GABA release evoked by 9 mm extracellular K+ ([K+]e). RT-induced inhibition of [3H]NE release was prevented by synaptosomal entrapment of polyclonal antibodies directed against KCNQ2 subunits, an effect that was abolished by antibody preabsorption with the KCNQ2 immunizing peptide; antibodies against KCNQ3 subunits were ineffective. Flupirtine (FP), a structural analog of RT, also inhibited 9 mm [K+]e-induced [3H]NE release, although its maximal inhibition was lower than that of RT. Electrophysiological studies in KCNQ2-transfected Chinese hamster ovary cells revealed that RT and FP (10 microm) caused a -19 and -9 mV hyperpolarizing shift, respectively, in the voltage dependence of activation of KCNQ2 K+ channels. In the same cells, the cognition enhancer 10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone (XE-991) (10 microm) blocked KCNQ2 channels and prevented their activation by RT (1-10 microm). Finally, both XE-991 (10-100 microm) and tetraethylammonium ions (100 microm) abolished the inhibitory effect of RT (1 microm) on [3H]NE release. These findings provide novel evidence for a major regulatory role of KCNQ2 K+ channel subunits in neurotransmitter release from rat hippocampal nerve endings.

Benign familial neonatal convulsions caused by altered gating of KCNQ2/KCNQ3 potassium channels.

The muscarinic-regulated potassium current (M-current), formed by the heteromeric assembly of subunits encoded by the KCNQ2 and KCNQ3 genes, is a primary regulator of neuronal excitability; this regulation is accomplished by impeding repetitive firing and causing spike-frequency adaptation. Mutations in KCNQ2 or KCNQ3 cause benign familial neonatal convulsions (BFNC), a rare autosomal-dominant generalized epilepsy of newborns, by reducing the maximal current carried by the M-channels without affecting ion selectivity or gating properties. Here we show that KCNQ2/KCNQ3 channels carrying a novel BFNC-causing mutation leading to an arginine to tryptophan substitution in the voltage-sensing S4 domain of KCNQ2 subunits (R214W) displayed slower opening and faster closing kinetics and a decreased voltage sensitivity with no concomitant changes in maximal current or plasma membrane expression. These results suggest that mutation-induced gating alterations of the M-current may cause epilepsy in neonates.