RESUMO
AIMS: SCN5A gene encodes the α-subunit of Nav1.5, mainly found in the human heart. SCN5A variants are the most common genetic alterations associated with Brugada syndrome (BrS). In rare cases, compound heterozygosity is observed; however, its functional consequences are poorly understood. We aimed to analyze the functional impact of de novo Nav1.5 mutations in compound heterozygosity in distinct alleles (G400R and T1461S positions) previously found in a patient with BrS. Moreover, we evaluated the potential benefits of quinidine to improve the phenotype of mutant Na+ channels in vitro. MATERIALS AND METHODS: The functional properties of human wild-type and Nav1.5 variants were evaluated using whole-cell patch-clamp and immunofluorescence techniques in transiently expressed human embryonic kidney (HEK293) cells. KEY FINDINGS: Both variants occur in the highly conservative positions of SCN5A. Although all variants were expressed in the cell membrane, a significant reduction in the Na+ current density (except for G400R alone, which was undetected) was observed along with abnormal biophysical properties, once the variants were expressed in homozygosis and heterozygosis. Interestingly, the incubation of transfected cells with quinidine partially rescued the biophysical properties of the mutant Na+ channel. SIGNIFICANCE: De novo compound heterozygosis mutations in SNC5A disrupt the Na+ macroscopic current. Quinidine could partially reverse the in vitro loss-of-function phenotype of Na+ current. Thus, our data provide, for the first time, a detailed biophysical characterization of dysfunctional Na+ channels linked to compound heterozygosity in BrS as well as the benefits of the pharmacological treatment using quinidine on the biophysical properties of Nav1.5.
Assuntos
Síndrome de Brugada/genética , Mutação com Perda de Função , Canal de Sódio Disparado por Voltagem NAV1.5/genética , Sequência de Aminoácidos , Síndrome de Brugada/tratamento farmacológico , Síndrome de Brugada/metabolismo , Células HEK293 , Heterozigoto , Humanos , Mutação com Perda de Função/efeitos dos fármacos , Canal de Sódio Disparado por Voltagem NAV1.5/química , Canal de Sódio Disparado por Voltagem NAV1.5/metabolismo , Mutação Puntual/efeitos dos fármacos , Quinidina/farmacologiaRESUMO
Migrating partial seizures of infancy is an early onset epileptic encephalopathy syndrome that is typically resistant to treatment. The most common cause is a gain of function mutation in the potassium channel KCNT1. The antiarrhythmic drug quinidine is a partial antagonist of KCNT1 and hence may be a candidate drug for treatment of this condition. We report the case of a child with migrating partial seizures of infancy secondary to an activating mutation in KCNT1 treated with quinidine. Treatment with quinidine was correlated with a marked reduction in seizure frequency and improved psychomotor development.
Assuntos
Antiarrítmicos/farmacologia , Epilepsias Parciais/tratamento farmacológico , Proteínas do Tecido Nervoso/antagonistas & inibidores , Quinidina/farmacologia , Antiarrítmicos/administração & dosagem , Pré-Escolar , Relação Dose-Resposta a Droga , Eletroencefalografia , Epilepsias Parciais/genética , Epilepsias Parciais/fisiopatologia , Éxons/genética , Feminino , Humanos , Mutação de Sentido Incorreto/genética , Proteínas do Tecido Nervoso/genética , Canais de Potássio/genética , Canais de Potássio Ativados por Sódio , Quinidina/administração & dosagem , Resultado do TratamentoRESUMO
Re-emergence of vector-borne diseases such as dengue and yellow fever, which are both transmitted by the Aedes aegypti mosquito, has been correlated with insecticide resistance. P-glycoproteins (P-gps) are ATP-dependent efflux pumps that are involved in the transport of substrates across membranes. Some of these proteins have been implicated in multidrug resistance (MDR). In this study, we identified a putative P-glycoprotein in the Ae. aegypti database based on its significantly high identity with Anopheles gambiae, Culex quinquefasciatus, Drosophila melanogaster and human P-gps. The basal ATPase activity of ATP-binding cassette transporters in larvae was significantly increased in the presence of MDR modulators (verapamil and quinidine). An eightfold increase in Ae. aegypti P-gp (AaegP-gp) gene expression was detected in temephos-treated larvae as determined by quantitative PCR. To analyse the potential role of AaegP-gp in insecticide efflux, a temephos larvicide assay was performed in the presence of verapamil. The results showed an increase of 24% in temephos toxicity, which is in agreement with the efflux reversing effect. RNA interference (RNAi)-mediated silencing of the AaegP-gp gene caused a significant increase in temephos toxicity (57%). In conclusion, we have demonstrated for the first time in insects that insecticide-induced P-gp expression can be involved in the modulation of insecticide efflux.
Assuntos
Aedes/efeitos dos fármacos , Larva/efeitos dos fármacos , Temefós , Subfamília B de Transportador de Cassetes de Ligação de ATP , Transportadores de Cassetes de Ligação de ATP/metabolismo , Sequência de Aminoácidos , Animais , Expressão Gênica/efeitos dos fármacos , Resistência a Inseticidas/genética , Dados de Sequência Molecular , Mortalidade , Quinidina/farmacologia , Verapamil/farmacologiaRESUMO
BACKGROUND: The parasitic trematode Schistosoma mansoni is one of the major causative agents of human schistosomiasis, which afflicts 200 million people worldwide. Praziquantel remains the main drug used for schistosomiasis treatment, and reliance on the single therapy has been prompting the search for new therapeutic compounds against this disease. Our group has demonstrated that heme crystallization into hemozoin (Hz) within the S. mansoni gut is a major heme detoxification route with lipid droplets involved in this process and acting as a potential chemotherapeutical target. In the present work, we investigated the effects of three antimalarial compounds, quinine (QN), quinidine (QND) and quinacrine (QCR) in a murine schistosomiasis model by using a combination of biochemical, cell biology and molecular biology approaches. METHODOLOGY/PRINCIPAL FINDINGS: Treatment of S. mansoni-infected female Swiss mice with daily intraperitoneal injections of QN, and QND (75 mg/kg/day) from the 11(th) to 17(th) day after infection caused significant decreases in worm burden (39%-61%) and egg production (42%-98%). Hz formation was significantly inhibited (40%-65%) in female worms recovered from QN- and QND-treated mice and correlated with reduction in the female worm burden. We also observed that QN treatment promoted remarkable ultrastructural changes in male and female worms, particularly in the gut epithelium and reduced the granulomatous reaction to parasite eggs trapped in the liver. Microarray gene expression analysis indicated that QN treatment increased the expression of transcripts related to musculature, protein synthesis and repair mechanisms. CONCLUSIONS: The overall significant reduction in several disease burden parameters by the antimalarial quinoline methanols indicates that interference with Hz formation in S. mansoni represents an important mechanism of schistosomicidal action of these compounds and points out the heme crystallization process as a valid chemotherapeutic target to treat schistosomiasis.
Assuntos
Anti-Helmínticos/farmacologia , Hemeproteínas/antagonistas & inibidores , Hemeproteínas/metabolismo , Quinacrina/farmacologia , Quinidina/farmacologia , Quinina/farmacologia , Schistosoma mansoni/efeitos dos fármacos , Animais , Feminino , Trato Gastrointestinal/parasitologia , Perfilação da Expressão Gênica , Mucosa Intestinal/efeitos dos fármacos , Mucosa Intestinal/ultraestrutura , Fígado/parasitologia , Masculino , Camundongos , Contagem de Ovos de Parasitas , Schistosoma mansoni/ultraestrutura , Esquistossomose mansoni/tratamento farmacológicoRESUMO
Metoprolol is a beta-blocker and its racemic mixture is used for the treatment of hypertension. In the present study we investigated the influence of CYP2D and CYP3A on the stereoselective metabolism of metoprolol in rats. Male Wistar rats (n = 6 per group) received racemic metoprolol (15 mg/kg) orally, with or without pretreatment with the CYP inhibitor ketoconazole (50 mg/kg), cimetidine (150 mg/kg), or quinidine (80 mg/kg). Blood samples were collected up to 48 h after metoprolol administration. The plasma concentrations of the stereoisomers of metoprolol, O-demethylmetoprolol (ODM), alpha-hydroxymetoprolol (OHM) (Chiralpak AD column), and metoprolol acidic metabolite (AODM) (Chiralcel OD-R column) were determined by HPLC using fluorescence detection (lambda(exc) = 229 nm; lambda(em) = 298 nm). CYP3A inhibition by ketoconazole reduced the plasma concentrations of ODM and AODM and favored the formation of OHM. CYP2D and CYP3A inhibition by cimetidine reduced the plasma concentrations of OHM and AODM and favored the formation of ODM. The inhibition of CYP2D by quinidine reduced the plasma concentrations of OHM and favored the formation of ODM. In conclusion, the results suggest that CYP3A is involved in the formation of ODM and CYP2D is involved in the formation of AODM.
Assuntos
Cimetidina/farmacologia , Cetoconazol/farmacologia , Metoprolol/metabolismo , Metoprolol/farmacocinética , Quinidina/farmacologia , Antagonistas Adrenérgicos beta/sangue , Antagonistas Adrenérgicos beta/metabolismo , Antagonistas Adrenérgicos beta/farmacocinética , Animais , Área Sob a Curva , Cromatografia Líquida de Alta Pressão , Inibidores do Citocromo P-450 CYP3A , Interações Medicamentosas , Inibidores Enzimáticos/farmacologia , Jejum , Concentração de Íons de Hidrogênio , Masculino , Taxa de Depuração Metabólica , Metoprolol/antagonistas & inibidores , Metoprolol/sangue , Metoprolol/química , Estrutura Molecular , Ratos , Ratos Wistar , Espectrometria de Fluorescência , EstereoisomerismoRESUMO
Citalopram (CITA) is available as a racemic mixture or as (+)-(S)-CITA. In humans, CITA is metabolized to demethylcitalopram (DCITA) by CYP2C19, CYP2D6, and CYP3A and to didemethylcitalopram by CYP2D6. There are no data regarding the enzymes involved in CITA and DCITA metabolism in rats. The present study investigated the influence of CYP inhibitors on the enantioselective metabolism of CITA in rats. Male Wistar rats (n = 6) received a single dose of 20 mg x kg-1 CITA after pretreatment with 80 mg x kg-1 quinidine, 10 mg x kg-1 fluvoxamine, 50 mg x kg-1 ketoconazole, or vehicle (control). Blood samples were collected up to 20 h after CITA administration. The CITA and DCITA enantiomers were analyzed by LC-MS/MS using a Chiralcel OD-R column. The kinetic disposition of CITA was enantioselective in rats (AUCS/R ratio = 0.4). Coadministration with quinidine resulted in non-enantioselective inhibition of the metabolism of CITA. Coadministration with fluvoxamine or ketoconazole, however, inhibited only the metabolism of (+)-(S)-CITA, but not of (-)-(R)-CITA when the racemic drug was administered to rats.
Assuntos
Antifúngicos/farmacologia , Antimaláricos/farmacologia , Citalopram/farmacocinética , Fluvoxamina/farmacologia , Cetoconazol/farmacologia , Quinidina/farmacologia , Inibidores Seletivos de Recaptação de Serotonina/farmacologia , Inibidores Seletivos de Recaptação de Serotonina/farmacocinética , Animais , Interações Medicamentosas , Masculino , Ratos , Ratos Wistar , EstereoisomerismoRESUMO
In this study, we report the effects of the quinoline derivatives quinine, its optical isomer quinidine, and chloroquine on alpha9alpha10-containing nicotinic acetylcholine receptors (nAChRs). The compounds blocked acetylcholine (ACh)-evoked responses in alpha9alpha10-injected Xenopus laevis oocytes in a concentration-dependent manner, with a rank order of potency of chloroquine (IC50 = 0.39 microM) > quinine (IC50 = 0.97 microM) approximately quinidine (IC50= 1.37 microM). Moreover, chloroquine blocked ACh-evoked responses on rat cochlear inner hair cells with an IC50 value of 0.13 microM, which is within the same range as that observed for recombinant receptors. Block by chloroquine was purely competitive, whereas quinine inhibited ACh currents in a mixed competitive and noncompetitive manner. The competitive nature of the blockage produced by the three compounds was confirmed by equilibrium binding experiments using [3H]methyllycaconitine. Binding affinities (Ki values) were 2.3, 5.5, and 13.0 microM for chloroquine, quinine, and quinidine, respectively. Block by quinine was found to be only slightly voltage-dependent, thus precluding open-channel block as the main mechanism of interaction of quinine with alpha9alpha10 nAChRs. The present results add to the pharmacological characterization of alpha9alpha10-containing nicotinic receptors and indicate that the efferent olivocochlear system that innervates the cochlear hair cells is a target of these ototoxic antimalarial compounds.
Assuntos
Antimaláricos/farmacologia , Cloroquina/farmacologia , Quinidina/farmacologia , Quinina/farmacologia , Receptores Nicotínicos/efeitos dos fármacos , Animais , Antimaláricos/toxicidade , Cloroquina/toxicidade , Células Ciliadas Auditivas Internas/efeitos dos fármacos , Quinidina/toxicidade , Quinina/toxicidade , Ensaio Radioligante , Ratos , Ratos Sprague-Dawley , Proteínas Recombinantes/efeitos dos fármacos , Xenopus laevisAssuntos
Gravidez , Criança , Adulto , Idoso , Animais , Humanos , Fibrilação Atrial , Procainamida , Procainamida/uso terapêutico , Propranolol , Propranolol/administração & dosagem , Quinidina/farmacologia , Quinidina/uso terapêutico , Taquicardia Ventricular , Complexos Cardíacos Prematuros , Flutter Atrial/diagnóstico , Lidocaína , Lidocaína/uso terapêutico , Taquicardia Supraventricular/diagnósticoRESUMO
Falciparum malaria represents a serious and an increasing world public health problem due to the acquired parasite's resistance to the most available drugs. In some endemic areas, quinidine, a diastereoisomer of the antimalarial quinine, has been employed for replacing the latter. In order to evaluate the use of quinidine as an alternative to the increasing loss of quinine effectiveness in Brazilian P. falciparum strains, as has been observed in the Amazon area, we have assayed quinidine, quinine and chloroquine. The in vitro microtechnique was employed. All isolates showed to be highly resistant to chloroquine. Resistance to quinine was not noted although high MIC (minimal inhibitory concentration) values have been observed. These data corroborate the decreasing sensitivity to quinine in strains from Brazil. Quinidine showed IC50 from 0.053 to 4.577 micromol/L of blood while IC50 from 0.053 to 8.132 micromol/L of blood was estimated for quinine. Moreover, clearance of the parasitemia was observed in concentrations lower than that used for quinidine in antiarrhythmic therapy, confirming our previous data. The results were similar to African isolate.