RESUMO
Lithium is the first-line mood stabilizer for the treatment of patients with bipolar disorder. However, its mechanisms of action and transport across the blood-brain barrier remain poorly understood. The contribution of lithium-7 magnetic resonance imaging (7 Li MRI) to investigate brain lithium distribution remains limited because of the modest sensitivity of the lithium nucleus and the expected low brain concentrations in humans and animal models. Therefore, we decided to image lithium distribution in the rat brain ex vivo using a turbo-spin-echo imaging sequence at 17.2 T. The estimation of lithium concentrations was performed using a phantom replacement approach accounting for B1 inhomogeneities and differential T1 and T2 weighting. Our MRI-derived lithium concentrations were validated by comparison with inductively coupled plasma-mass spectrometry (ICP-MS) measurements ([Li]MRI = 1.18[Li]MS , R = 0.95). Overall, a sensitivity of 0.03 mmol/L was achieved for a spatial resolution of 16 µL. Lithium distribution was uneven throughout the brain (normalized lithium content ranged from 0.4 to 1.4) and was mostly symmetrical, with consistently lower concentrations in the metencephalon (cerebellum and brainstem) and higher concentrations in the cortex. Interestingly, low lithium concentrations were also observed close to the lateral ventricles. The average brain-to-plasma lithium ratio was 0.34 ± 0.04, ranging from 0.29 to 0.39. Brain lithium concentrations were reasonably correlated with plasma lithium concentrations, with Pearson correlation factors ranging from 0.63 to 0.90.
Assuntos
Encéfalo/metabolismo , Lítio/farmacocinética , Espectroscopia de Ressonância Magnética/métodos , Animais , Imageamento por Ressonância Magnética , Masculino , Ratos , Ratos Sprague-DawleyRESUMO
OBJECTIVES: Lithium overdose may result in encephalopathy and electroencephalographic abnormalities. Three poisoning patterns have been identified based on the ingested dose, previous treatment duration and renal function. Whether the severity of lithium-induced encephalopathy depends on the poisoning pattern has not been established. We designed a rat study to investigate lithium-induced encephalopathy and correlate its severity to plasma, erythrocyte, cerebrospinal fluid and brain lithium concentrations previously determined in rat models mimicking human poisoning patterns. METHODS: Lithium-induced encephalopathy was assessed and scored using continuous electroencephalography. RESULTS: We demonstrated that lithium overdose was consistently responsible for encephalopathy, the severity of which depended on the poisoning pattern. Acutely poisoned rats developed rapid-onset encephalopathy which reached a maximal grade of 2/5 at 6 h and disappeared at 24 h post-injection. Acute-on-chronically poisoned rats developed persistent and slightly fluctuating encephalopathy which reached a maximal grade of 3/5. Chronically poisoned rats developed rapid-onset but gradually increasing life-threatening encephalopathy which reached a maximal grade of 4/5. None of the acutely, 20% of the acute-on-chronically and 57% of the chronically lithium-poisoned rats developed seizures. The relationships between encephalopathy severity and lithium concentrations fitted a sigmoidal Emax model based on cerebrospinal fluid concentrations in acute poisoning and brain concentrations in acute-on-chronic poisoning. In chronic poisoning, worsening of encephalopathy paralleled the increase in plasma lithium concentrations. CONCLUSIONS: The severity of lithium-induced encephalopathy is dependent on the poisoning pattern, which was previously shown to determine lithium accumulation in the brain. Our data support the proposition that electroencephalography is a sensitive tool for scoring lithium-related neurotoxicity.
Assuntos
Transtorno Bipolar/tratamento farmacológico , Eletroencefalografia/métodos , Compostos de Lítio , Lítio , Síndromes Neurotóxicas , Animais , Antimaníacos/farmacologia , Antimaníacos/toxicidade , Encéfalo/efeitos dos fármacos , Relação Dose-Resposta a Droga , Lítio/sangue , Lítio/farmacocinética , Compostos de Lítio/farmacologia , Compostos de Lítio/toxicidade , Síndromes Neurotóxicas/diagnóstico , Síndromes Neurotóxicas/etiologia , Ratos , Distribuição TecidualRESUMO
Despite the international convention on the prohibition of chemical weapons ratified in 1997, the threat of conflicts and terrorist attacks involving such weapons still exists. Among these, organophosphorus-nerve agents (OPs) inhibit cholinesterases (ChE) causing cholinergic syndrome. The reactivation of these enzymes is therefore essential to protect the poisoned people. However, these reactivating molecules, mainly named oximes, have major drawbacks with limited efficacy against some OPs and a non-negligible ChE inhibitor potential if administered at an inadequate dose, an effect that they are precisely supposed to mitigate. As a result, this project focused on assessing therapeutic efficacy, in mice, up to the NOAEL dose, the maximum dose of oxime that does not induce any observable toxic effect. NOAEL doses of HI-6 DMS, a reference oxime, and JDS364. HCl, a candidate reactivator, were assessed using dual-chamber plethysmography, with respiratory ventilation impairment as a toxicity criterion. Time-course modeling parameters and pharmacodynamic profiles, reflecting the interaction between the oxime and circulating ChE, were evaluated for treatments at their NOAEL and higher doses. Finally, the therapeutic potential against OPs poisoning was determined through the assessment of protective indices. For JDS364. HCl, the NOAEL dose corresponds to the smallest dose inducing the most significant therapeutic effect without causing any abnormality in ChE activity. In contrast, for HI-6 DMS, its therapeutic benefit was observed at doses higher than its NOAEL, leading to alterations in respiratory function. These alterations could not be directly correlated with ChE inhibition and had no adverse effects on survival. They are potentially attributed to the stimulation of non-enzymatic cholinergic targets by HI-6 DMS. Thus, the NOAEL appears to be an optimal dose for evaluating the efficacy of oximes, particularly when it can be linked to respiratory alterations effectively resulting from ChE inhibition.
Assuntos
Substâncias para a Guerra Química , Reativadores da Colinesterase , Agentes Neurotóxicos , Humanos , Camundongos , Animais , Reativadores da Colinesterase/farmacologia , Reativadores da Colinesterase/uso terapêutico , Reativadores da Colinesterase/química , Agentes Neurotóxicos/toxicidade , Nível de Efeito Adverso não Observado , Substâncias para a Guerra Química/toxicidade , Oximas/farmacologia , Oximas/uso terapêutico , Oximas/química , Compostos de Piridínio/farmacologia , Inibidores da Colinesterase/toxicidade , Inibidores da Colinesterase/química , Colinesterases , Acetilcolinesterase , Antídotos/farmacologia , Antídotos/uso terapêuticoRESUMO
In the absence of appropriate medical care, exposure to organophosphorus nerve agents, such as VX, can lead to respiratory failure, and potentially death by asphyxiation. Despite the critical role of respiratory disturbances in organophosphorus-induced toxicity, the nature and underlying mechanisms of respiratory failure remain poorly understood. This study aimed to characterize respiratory alterations by determining their type and duration in mice exposed to a subcutaneous sublethal dose of VX. Respiratory ventilation in Swiss mice was monitored using dual-chamber plethysmography for up to 7 days post-exposure. Cholinesterase activity was assessed via spectrophotometry, and levels of inflammatory biomarkers were quantified using Luminex technology in blood and tissues involved in respiration (diaphragm, lung, and medulla oblongata). Additionally, a histological study was conducted on these tissues to ensure their structural integrity. Ventilatory alterations appeared 20-25â¯minutes after the injection of 0.9 LD50 VX and increased until the end of the recording, i.e., 40â¯minutes after intoxication. Concurrent with the occurrence of apnea, increased inspiratory and expiratory times resulted in a significant decrease in respiratory rate in exposed mice compared to controls. Ventilatory amplitude and, consequently, minute volume were reduced, while specific airway resistance significantly increased, indicating bronchoconstriction. These ventilatory effects persisted up to 24 or even 72â¯hours post-intoxication, resolving on the 7th day. They were correlated with a decrease in acetylcholinesterase activity in the diaphragm, which persisted for up to 72â¯hours, and with the triggering of an inflammatory reaction in the same tissue. No significant histologic lesions were observed in the examined tissues. The ventilatory alterations observed up to 72â¯hours post-VX exposure appear to result from a functional failure of the respiratory system rather than tissue damage. This comprehensive characterization contributes to a better understanding of the respiratory effects induced by VX exposure, which is crucial for developing specific medical countermeasures.
Assuntos
Substâncias para a Guerra Química , Compostos Organotiofosforados , Animais , Substâncias para a Guerra Química/toxicidade , Camundongos , Masculino , Compostos Organotiofosforados/toxicidade , Acetilcolinesterase/metabolismo , Pulmão/efeitos dos fármacos , Pulmão/patologia , Diafragma/efeitos dos fármacosRESUMO
Recent events demonstrated that organophosphorus nerve agents are a serious threat for civilian and military populations. The current therapy includes a pyridinium aldoxime reactivator to restore the enzymatic activity of acetylcholinesterase located in the central nervous system and neuro-muscular junctions. One major drawback of these charged acetylcholinesterase reactivators is their poor ability to cross the blood-brain barrier. In this study, we propose to evaluate glucoconjugated oximes devoid of permanent charge as potential central nervous system reactivators. We determined their in vitro reactivation efficacy on inhibited human acetylcholinesterase, the crystal structure of two compounds in complex with the enzyme, their protective index on intoxicated mice, and their pharmacokinetics. We then evaluated their endothelial permeability coefficients with a human in vitro model. This study shed light on the structural restrains of new sugar oximes designed to reach the central nervous system through the glucose transporter located at the blood-brain barrier.
Assuntos
Intoxicação por Organofosfatos , Acetilcolinesterase , Animais , Antídotos/farmacologia , Antídotos/uso terapêutico , Inibidores da Colinesterase/farmacologia , Camundongos , Intoxicação por Organofosfatos/tratamento farmacológico , Compostos Organofosforados/farmacologia , Oximas/química , Oximas/farmacologia , Oximas/uso terapêutico , AçúcaresRESUMO
Islet inflammation is associated with defective ß cell function and mass in type 2 diabetes (T2D). Glycogen synthase kinase 3 (GSK3) has been identified as an important regulator of inflammation in different diseased conditions. However, the role of GSK3 in islet inflammation in the context of diabetes remains unexplored. In this study, we investigated the direct implication of GSK3 in islet inflammation in vitro and tested the impact of GSK3 inhibition in vivo, on the reduction of islet inflammation, and the improvement of glucose metabolism in the Goto-Kakizaki (GK) rat, a spontaneous model of T2D. GK rats were chronically treated with infra-therapeutic doses of lithium, a widely used inhibitor of GSK3. We analyzed parameters of glucose homeostasis as well as islet inflammation and fibrosis in the endocrine pancreas. Ex vivo, we tested the impact of GSK3 inhibition on the autonomous inflammatory response of non-diabetic rat and human islets, exposed to a mix of pro-inflammatory cytokines to mimic an inflammatory environment. Treatment of young GK rats with lithium prevented the development of overt diabetes. Lithium treatment resulted in reduced expression of pro-inflammatory cytokines in the islets. It decreased islet fibrosis and partially restored the glucose-induced insulin secretion in GK rats. Studies in non-diabetic human and rat islets exposed to inflammatory environment revealed the direct implication of GSK3 in the islet autonomous inflammatory response. We show for the first time, the implication of GSK3 in islet inflammation and suggest this enzyme as a viable target to treat diabetes-associated inflammation.
Assuntos
Diabetes Mellitus Tipo 2/metabolismo , Quinase 3 da Glicogênio Sintase/metabolismo , Ilhotas Pancreáticas/metabolismo , Animais , Modelos Animais de Doenças , Fibrose , Glucose/metabolismo , Humanos , Inflamação , Secreção de Insulina , Masculino , Ratos , Ratos WistarRESUMO
(1) Background: Human exposure to organophosphorus compounds employed as pesticides or as chemical warfare agents induces deleterious effects due to cholinesterase inhibition. One therapeutic approach is the reactivation of inhibited acetylcholinesterase by oximes. While currently available oximes are unable to reach the central nervous system to reactivate cholinesterases or to display a wide spectrum of action against the variety of organophosphorus compounds, we aim to identify new reactivators without such drawbacks. (2) Methods: This study gathers an exhaustive work to assess in vitro and in vivo efficacy, and toxicity of a hybrid tetrahydroacridine pyridinaldoxime reactivator, KM297, compared to pralidoxime. (3) Results: Blood-brain barrier crossing assay carried out on a human in vitro model established that KM297 has an endothelial permeability coefficient twice that of pralidoxime. It also presents higher cytotoxicity, particularly on bone marrow-derived cells. Its strong cholinesterase inhibition potency seems to be correlated to its low protective efficacy in mice exposed to paraoxon. Ventilatory monitoring of KM297-treated mice by double-chamber plethysmography shows toxic effects at the selected therapeutic dose. This breathing assessment could help define the No Observed Adverse Effect Level (NOAEL) dose of new oximes which would have a maximum therapeutic effect without any toxic side effects.
Assuntos
Acetilcolinesterase/metabolismo , Inibidores da Colinesterase/farmacologia , Compostos de Pralidoxima/farmacologia , Animais , Barreira Hematoencefálica/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Inibidores da Colinesterase/administração & dosagem , Inibidores da Colinesterase/química , Relação Dose-Resposta a Droga , Humanos , Injeções Intraperitoneais , Masculino , Camundongos , Estrutura Molecular , Compostos de Pralidoxima/química , Proteínas Recombinantes/metabolismoRESUMO
Severity of lithium poisoning depends on the ingested dose, previous treatment duration and renal function. No animal study has investigated neurobehavioral differences in relation to the lithium poisoning pattern observed in humans, while differences in lithium pharmacokinetics have been reported in lithium-pretreated rats mimicking chronic poisonings with enhanced brain accumulation in rats with renal failure. Our objectives were: 1)-to investigate lithium-related effects in overdose on locomotor activity, anxiety-like behavior, spatial recognition memory and anhedonia in the rat; 2)-to model the relationships between lithium-induced effects on locomotion and plasma, erythrocyte, cerebrospinal fluid and brain concentrations previously obtained according to the poisoning pattern. Open-field, elevated plus-maze, Y-maze and sucrose consumption tests were used. In acutely lithium-poisoned rats, we observed horizontal (p<0.001) and vertical hypolocomotion (p<0.0001), increased anxiety-like behavior (p<0.05) and impaired memory (p<0.01) but no altered hedonic status. Horizontal (p<0.01) and vertical (p<0.001) hypolocomotion peaked more markedly 24h after lithium injection and was more prolonged in acute-on-chronically vs. acutely lithium-poisoned rats. Hypolocomotion in chronically lithium-poisoned rats with impaired renal function did not differ from acutely poisoned rats 24h after the last injection. Interestingly, hypolocomotion/concentration relationships best fitted a sigmoidal Emax model in acute poisoning and a linear regression model linked to brain lithium in acute-on-chronic poisoning. In conclusion, lithium overdose alters rat behavior and consistently induces hypolocomotion which is more marked and prolonged in repeatedly lithium-treated rats. Our data suggest that differences between poisoning patterns regarding lithium-induced hypolocomotion are better explained by the duration of lithium exposure than by its brain accumulation.
Assuntos
Anedonia/efeitos dos fármacos , Antidepressivos/intoxicação , Comportamento Animal/efeitos dos fármacos , Compostos de Lítio/intoxicação , Atividade Motora/efeitos dos fármacos , Memória Espacial/efeitos dos fármacos , Animais , Modelos Animais de Doenças , Masculino , Ratos , Ratos Sprague-DawleyRESUMO
Lithium-induced neurotoxicity may be life threatening. Three patterns have been described, including acute, acute-on-chronic, and chronic poisoning, with unexplained discrepancies in the relationship between clinical features and plasma lithium concentrations. Our objective was to investigate differences in plasma, erythrocyte, cerebrospinal fluid, and brain lithium pharmacokinetics using a multicompartmental approach in rat models mimicking the three human intoxication patterns. We developed acute (intraperitoneal administration of 185 mg/kg Li2CO3 in naive rats), acute-on-chronic (intraperitoneal administration of 185 mg/kg Li2CO3 in rats receiving 800 mg/l Li2CO3 in water during 28 days), and chronic poisoning models (intraperitoneal administration of 74 mg/kg Li2CO3 during 5 days in rats with 15 mg/kg K2Cr2O7-induced renal failure). Delayed absorption (4.03 vs 0.31 h), increased plasma elimination (0.65 vs 0.37 l/kg/h) and shorter half-life (1.75 vs 2.68 h) were observed in acute-on-chronically compared with acutely poisoned rats. Erythrocyte and cerebrospinal fluid kinetics paralleled plasma kinetics in both models. Brain lithium distribution was rapid (as early as 15 min), inhomogeneous and with delayed elimination (over 78 h). However, brain lithium accumulation was more marked in acute-on-chronically than acutely poisoned rats [area-under-the-curve of brain concentrations (379 ± 41 vs 295 ± 26, P < .05) and brain-to-plasma ratio (45 ± 10 vs 8 ± 2, P < .0001) at 54 h]. Moreover, brain lithium distribution was increased in chronically compared with acute-on-chronically poisoned rats (brain-to-plasma ratio: 9 ± 1 vs 3 ± 0, P < .01). In conclusion, prolonged rat exposure results in brain lithium accumulation, which is more marked in the presence of renal failure. Our data suggest that differences in plasma and brain kinetics may at least partially explain the observed variability between human intoxication patterns.