M.J. Anadon

Synthesis and antinociceptive activity of 9-phenyl-oxy or 9-acyl-oxy derivatives of xanthene, thioxanthene and acridine

The synthesis of 9-alkyl-oxy or 9-acyl-oxy derivatives of xanthene, thioxanthene and acridine is reported. A potent antinociceptive activity was confirmed for the 9-phenyl-9-propionyl-oxy derivative bearing an oxygen or sulfur atom in the heteroaromatic structure.Abstract The synthesis of 9-alkyl-oxy or 9-acyl-oxy derivatives of xanthene, thioxanthene and acridine is reported. A potent antinociceptive activity was confirmed for the 9-phenyl-9-propionyl-oxy derivative bearing an oxygen or sulfur atom in the heteroaromatic structure.

Alcohol Concentration Determines the Type of Atrial Arrhythmia Induced in a Porcine Model of Acute Alcoholic Intoxication

Alcohol abuse has long been suspected clinically to cause paroxysmal atrial tachyarrhythmias. However, such a relationship has never been conclusively proven, partly due to the lack of experimental evidence. Although atrial fibrillation (AF) is the most common atrial arrhythmia attributed to acute alcoholic ingestion, atrial flutter has occasionally been noted. We analyzed the possible role of alcohol in initiation and/or maintenance of a variety of atrial tachyarrhythmias in a closed‐chest porcine model. Nine pigs underwent nine endocnrdial right atrial stimulation protocols (EASP) at baseline and 17 RASPs after increasing doses of ethanol (first infusion 1,230 mg/kg, second infusion 870 mg/kg) by means of one multipolar catheter advanced under heavy sedation from the femoral vein. Each RASP included 1, 2, and 3 extrastimuli, and rapid pacing at 5 times diastolic threshold. Venous ethanol concentrations were measured (HPGC method) every 10 minutes and at the time of arrhythmia induction. Atrial tachyarrhythmias were induced in 4 of 9 baseline RASPs, and lasted for a mean of 21 seconds, and in 16 of 17 RASPs after alcohol lasting for a mean of 357 seconds. Only fibrillation was observed at the baseline RASP. The atrial tachyarrhythmias induced after alcohol were AF in 11 RASPs and atrial flutter in 5 RASPs (in 5 animals). The mean venous ethanol concentration at the time of the longest arrhythmia induced for each RASP were 200 ± 89 mg/dL for RASP inducing fibrillation and 292 ± 40 mg/dL for RASP inducing flutter (P < 0.05). Flutter tended to be sustained (> 1 minute in duration) more often than fibrillation (4 of 5 flutter vs 2 of 11 fibrillation P < 0.05). In three experiments, atrial flutter persisted for > 10 minutes and was terminated by overdrive atrial pacing. We concluded: (1) in this closed‐chest porcine model, an ethanol infusion facilitates a variety of atrial arrhythmias related to the ethanol concentration; (2) flutter tended to be sustained, and its termination by overdrive pacing suggests the possibility of an alcohol induced reentrant mechanism: and (3) the higher concentration required for atrial flutter, exceeding that usually seen in humans, may help to explain the rarity of atrial flutter in clinical alcohol intoxication.

Original paperSynthesis and antinociceptive activity of 9-phenyl-oxy or 9-acyl-oxy derivatives of xanthene, thioxanthene and acridineSynthèse et activité antinociceptive de dérivés phényl-9-alkoxy-9 ou acyl-oxy-9 de xanthène, thioxanthène et acridine

The synthesis of 9-alkyl-oxy or 9-acyl-oxy derivatives of xanthene, thioxanthene and acridine is reported. A potent antinociceptive activity was confirmed for the 9-phenyl-9-propionyl-oxy derivative bearing an oxygen or sulfur atom in the heteroaromatic structure.Abstract The synthesis of 9-alkyl-oxy or 9-acyl-oxy derivatives of xanthene, thioxanthene and acridine is reported. A potent antinociceptive activity was confirmed for the 9-phenyl-9-propionyl-oxy derivative bearing an oxygen or sulfur atom in the heteroaromatic structure.

Higher sensitivity to cadmium induced cell death of basal forebrain cholinergic neurons: a cholinesterase dependent mechanism.

Cadmium is an environmental pollutant, which is a cause of concern because it can be greatly concentrated in the organism causing severe damage to a variety of organs including the nervous system which is one of the most affected. Cadmium has been reported to produce learning and memory dysfunctions and Alzheimer like symptoms, though the mechanism is unknown. On the other hand, cholinergic system in central nervous system (CNS) is implicated on learning and memory regulation, and it has been reported that cadmium can affect cholinergic transmission and it can also induce selective toxicity on cholinergic system at peripheral level, producing cholinergic neurons loss, which may explain cadmium effects on learning and memory processes if produced on central level. The present study is aimed at researching the selective neurotoxicity induced by cadmium on cholinergic system in CNS. For this purpose we evaluated, in basal forebrain region, the cadmium toxic effects on neuronal viability and the cholinergic mechanisms related to it on NS56 cholinergic mourine septal cell line. This study proves that cadmium induces a more pronounced, but not selective, cell death on acetylcholinesterase (AChE) on cholinergic neurons. Moreover, MTT and LDH assays showed a dose dependent decrease of cell viability in NS56 cells. The ACh treatment of SN56 cells did not revert cell viability reduction induced by cadmium, but siRNA transfection against AChE partially reduced it. Our present results provide new understanding of the mechanisms contributing to the harmful effects of cadmium on the function and viability of neurons, and the possible relevance of cadmium in the pathogenesis of neurodegenerative diseases.

Cadmium-induced cell death of basal forebrain cholinergic neurons mediated by muscarinic M1 receptor blockade, increase in GSK-3β enzyme, β-amyloid and tau protein levels

Abstract Cadmium is a neurotoxic compound which induces cognitive alterations similar to those produced by Alzheimer’s disease (AD). However, the mechanism through which cadmium induces this effect remains unknown. In this regard, we described in a previous work that cadmium blocks cholinergic transmission and induces a more pronounced cell death on cholinergic neurons from basal forebrain which is partially mediated by AChE overexpression. Degeneration of basal forebrain cholinergic neurons, as happens in AD, results in memory deficits attributable to the loss of cholinergic modulation of hippocampal synaptic circuits. Moreover, cadmium has been described to activate GSK-3β, induce Aβ protein production and tau filament formation, which have been related to a selective loss of basal forebrain cholinergic neurons and development of AD. The present study is aimed at researching the mechanisms of cell death induced by cadmium on basal forebrain cholinergic neurons. For this purpose, we evaluated, in SN56 cholinergic mourine septal cell line from basal forebrain region, the cadmium toxic effects on neuronal viability through muscarinic M1 receptor, AChE splice variants, GSK-3β enzyme, Aβ and tau proteins. This study proves that cadmium induces cell death on cholinergic neurons through blockade of M1 receptor, overexpression of AChE-S and GSK-3β, down-regulation of AChE-R and increase in Aβ and total and phosphorylated tau protein levels. Our present results provide new understanding of the mechanisms contributing to the harmful effects of cadmium on cholinergic neurons and suggest that cadmium could mediate these mechanisms by M1R blockade through AChE splices altered expression.

Acute and long-term exposure to chlorpyrifos induces cell death of basal forebrain cholinergic neurons through AChE variants alteration

Chlorpyrifos (CPF) is one of the most widely used organophosphates insecticides that has been reported to induce cognitive disorders both after acute and repeated administration similar to those induced in Alzheimers disease (AD). However, the mechanisms through which it induces these effects are unknown. On the other hand, the cholinergic system, mainly basal forebrain cholinergic neurons, is involved in learning and memory regulation, and an alteration of cholinergic transmission or/and cholinergic cell loss could induce these effects. In this regard, it has been reported that CPF can affect cholinergic transmission, and alter AChE variants, which have been shown to be related with basal forebrain cholinergic neuronal loss. According to these data, we hypothesized that CPF could induce basal forebrain cholinergic neuronal loss through cholinergic transmission and AChE variants alteration. To prove this hypothesis, we evaluated in septal SN56 basal forebrain cholinergic neurons, the CPF toxic effects after 24h and 14 days exposure on neuronal viability and the cholinergic mechanisms related to it. This study shows that CPF impaired cholinergic transmission, induced AChE inhibition and, only after long-term exposure, increased CHT expression, which suggests that acetylcholine levels alteration could be mediated by these actions. Moreover, CPF induces, after acute and long-term exposure, cell death in cholinergic neurons in the basal forebrain and this effect is independent of AChE inhibition and acetylcholine alteration, but was mediated partially by AChE variants alteration. Our present results provide a new understanding of the mechanisms contributing to the harmful effects of CPF on neuronal function and viability, and the possible relevance of CPF in the pathogenesis of neurodegenerative diseases.

Toxicogenomic profile of apoptotic and necrotic SN56 basal forebrain cholinergic neuronal loss after acute and long-term chlorpyrifos exposure

Chlorpyrifos (CPF) is an organophosphate insecticide reported to induce, both after acute and repeated exposure, learning and memory dysfunctions, although the mechanism is not completely known. CPF produces basal forebrain cholinergic neuronal loss, involved on learning and memory regulation, which could be the cause of such cognitive disorders. This effect was reported to be induced through apoptotic process, partially mediated by AChE overexpression, although neuronal necrosis was also described after CPF exposure. Accordingly, we hypothesized that CPF induces apoptotic and necrotic basal forebrain cholinergic cell death. We evaluated, in septal SN56 basal forebrain cholinergic neurons, the CPF effect after 24h and 14days exposure on apoptosis and necrosis induction and the apoptotic and necrotic gene expression pathways. This study shows that CPF induces, after acute and long-term exposure, apoptosis and necrosis, partially mediated through AChE overexpression. Evaluation of cell death pathways supports the necrosis and apoptosis data and revealed that some genes are altered at lower concentrations than those at which the effects observed are produce and below the No Observed Adverse Effect Level (NOAEL). The present finding suggests that the use of gene expression profile could be a more sensitive and accurate way to determine the CPFs NOAEL.

SN56 neuronal cell death after 24 h and 14 days chlorpyrifos exposure through glutamate transmission dysfunction, increase of GSK-3β enzyme, β-amyloid and tau protein levels

Chlorpyrifos (CPF) is an organophosphate insecticide described to induce cognitive disorders, both after acute and repeated administration. However, the mechanisms through which it induces these effects are unknown. CPF has been reported to produce basal forebrain cholinergic neuronal cell death, involved on learning and memory regulation, which could be the cause of such cognitive disorders. Neuronal cell death was partially mediated by oxidative stress generation, P75NTR and α7-nAChRs gene expression alteration triggered through acetylcholinesterase (AChE) variants disruption, suggesting other mechanisms are involved. In this regard, CPF induces Aβ and tau proteins production and activation of GSK3β enzyme and alters glutamatergic transmission, which have been related with basal forebrain cholinergic neuronal cell death and development of cognitive disorders. According to these data, we hypothesized that CPF induces basal forebrain cholinergic neuronal cell death through induction of Aβ and tau proteins production, activation of GSK-3β enzyme and disruption of glutamatergic transmission. We evaluated this hypothesis in septal SN56 basal forebrain cholinergic neurons, after 24 h and 14 days CPF exposure. This study shows that CPF increases glutamate levels, upregulates GSK-3β gene expression, and increases the production of Aβ and phosphorylated tau proteins and all these effects reduced cell viability. CPF increases glutaminase activity and upregulates the VGLUT1 gene expression, which could mediate the disruption of glutamatergic transmission. Our present results provide new understanding of the mechanisms contributing to the harmful effects of CPF, and its possible relevance in the pathogenesis of neurodegenerative diseases.

Cadmium induced ROS alters M1 and M3 receptors, leading to SN56 cholinergic neuronal loss, through AChE variants disruption

Cadmium, an environmental neurotoxic compound, produces cognitive disorders, although the mechanism remains unknown. Previously, we described that cadmium induces a more pronounced cell death on cholinergic neurons from basal forebrain (BF). This effect, partially mediated by M1 receptor blockade, triggering it through AChE splices variants alteration, may explain cadmium effects on learning and memory processes. Cadmium has been also reported to induce oxidative stress generation leading to M2 and M4 muscarinic receptors alteration, in hippocampus and frontal cortex, which are necessary to maintain cell viability and cognitive regulation, so their alteration in BF could also mediate this effect. Moreover, it has been reported that antioxidant treatment could reverse cognitive disorders, muscarinic receptor and AChE variants alterations induced by cadmium. Thus, we hypothesized that cadmium induced cell death of BF cholinergic neurons is mediated by oxidative stress generation and this mechanism could produce this effect, in part, through AChE variants altered by muscarinic receptors disruption. To prove this, we evaluated in BF SN56 cholinergic neurons, whether cadmium induces oxidative stress and alters muscarinic receptors, and their involvement in the induction of cell death through alteration of AChE variants. Our results show that cadmium induces oxidative stress, which mediates partially the alteration of AChE variants and M2 to M4 muscarinic receptors expression and blockage of M1 receptor. In addition, cadmium induced oxidative stress generation by M1 and M3 receptors alteration through AChE variants disruption, leading to cell death. These results provide new understanding of the mechanisms contributing to cadmium harmful effects on cholinergic neurons.

Primary hippocampal neuronal cell death induction after acute and repeated paraquat exposures mediated by AChE variants alteration and cholinergic and glutamatergic transmission disruption

Paraquat (PQ) is a widely used non-selective contact herbicide shown to produce memory and learning deficits after acute and repeated exposure similar to those induced in Alzheimers disease (AD). However, the complete mechanisms through which it induces these effects are unknown. On the other hand, cholinergic and glutamatergic systems, mainly in the hippocampus, are involved on learning, memory and cell viability regulation. An alteration of hippocampal cholinergic or glutamatergic transmissions or neuronal cell loss may induce these effects. In this regard, it has been suggested that PQ may induce cell death and affect cholinergic and glutamatergic transmission, which alteration could produce neuronal loss. According to these data, we hypothesized that PQ could induce hippocampal neuronal loss through cholinergic and glutamatergic transmissions alteration. To prove this hypothesis, we evaluated in hippocampal primary cell culture, the PQ toxic effects after 24h and 14 consecutive days exposure on neuronal viability and the cholinergic and glutamatergic mechanisms related to it. This study shows that PQ impaired acetylcholine levels and induced AChE inhibition and increased CHT expression only after 14days exposure, which suggests that acetylcholine levels alteration could be mediated by these actions. PQ also disrupted glutamate levels through induction of glutaminase activity. In addition, PQ induced, after 24h and 14days exposure, cell death on hippocampal neurons that was partially mediated by AChE variants alteration and cholinergic and gultamatergic transmissions disruption. Our present results provide new view of the mechanisms contributing to PQ neurotoxicity and may explain cognitive dysfunctions observed after PQ exposure.