digoxin and Nervous-System-Diseases

The recent observation that potent and sequence-specific gene silencing by injection of double-stranded RNA (dsRNA) has sparked the phenomenon known as "RNA interference" (RNAi) and has enabled the gene-specific knockdown of drug transport proteins and metabolizing enzymes. The application of small interfering RNAs (siRNAs) is broad and the potential for use as research tools is now well established in vitro. In vivo use is still a challenge that is primarily focused on the difficulty of delivering siRNAs to target cells. The potential use of siRNAs as therapeutic agents is also exciting and holds great promise for future. For the study of drug transporter function in absorption, distribution, metabolism and excretion (ADME) and in the treatment of diseases, siRNA offers a way to gather interpretable mechanistic data-a distinct advantage over the use of "specific" chemical inhibitors. This mini review provides background information on siRNA as well as examples of the use of siRNA as applied to drug transporters.

Topics: Animals; ATP Binding Cassette Transporter, Subfamily B, Member 1; Caco-2 Cells; Digoxin; Gene Targeting; Genetic Therapy; Humans; Luciferases, Renilla; Neoplasms; Nervous System Diseases; RNA Interference; RNA, Small Interfering; Transfection

Na,K-ATPase (sodium pump; EC 3.6.1.37) is present in the membrane of most eukaryotic cells and controls directly or indirectly many essential cellular functions. Regulation of this enzyme (ion transporter) and its individual isoforms is believed to play a key role in the etiology of some pathological processes. The sodium pump is the only known receptor for the cardiac glycosides. However, endogenous ligands structurally similar to digoxin or ouabain may control the activity of this important molecular complex. Here we review the structure and function of Na,K-ATPase, its expression and distribution in tissues, and its interaction with known ligands such as the cardiac glycosides and other suspected endogenous regulators. Also reviewed are various disorders, including cardiovascular, neurological, renal, and metabolic diseases, purported to involve dysfunction of Na,K-ATPase activity. The escalation in knowledge at the molecular level concerning sodium pump function foreshadows application of this knowledge in the clinical laboratory to identify individuals at risk for Na,K-ATPase-associated diseases.

Topics: Cardiac Glycosides; Cardiovascular Diseases; Digoxin; Fetus; Humans; Lung Diseases; Metabolic Diseases; Nervous System Diseases; Sodium-Potassium-Exchanging ATPase; Structure-Activity Relationship

The membrane composition and the isoprenoid pathway metabolites important in maintaining cell membrane integrity was studied in neurological and psychiatric disorders. The results indicate alteration in cholesterol:phospholipid ratio of the RBC membrane which is increased in glioma, schizophrenia, and bipolar mood disorder (MDP); decreased in multiple sclerosis and Parkinson's disease; and not significantly altered in epilepsy. The concentration of total glycosaminoglycans (GAG), hexose, and fucose decreased in the RBC membrane and increased in the serum. The RBC membrane Na+-K+ ATPase activity was reduced and serum HMG CoA reductase activity was increased. There were increased serum levels of digoxin, cholesterol, and dolichol and decreased levels of ubiquinone. The serum magnesium and tyrosine levels were reduced and tryptophan increased. The results indicate a defect in membrane formation and a decreased membrane Na+-K+ ATPase activity in all the disorders studied. The results are discussed, and a hypothesis regarding the relationship between these disorders and defective membrane architecture and membrane Na+-K+ ATPase inhibition is presented.

Topics: Adult; Cholesterol; Digoxin; Dolichols; Erythrocyte Membrane; Female; Humans; Hydroxymethylglutaryl CoA Reductases; Male; Membrane Proteins; Mental Disorders; Middle Aged; Models, Biological; Nervous System Diseases; Neurons; Phospholipids; Sodium-Potassium-Exchanging ATPase; Terpenes; Tryptophan; Tyrosine; Ubiquinone

Psychiatric abnormalities have been described in primary neurological disorders like multiple sclerosis, primary generalized epilepsy, Parkinson's disease, subacute sclerosing panencephalitis (SSPE), central nervous system glioma, and syndrome X with vascular dementia. It was therefore considered pertinent to compare monoamine neurotransmitter pattern in schizophrenia with those in the disorders described above. The end result of neurotransmission is changes in membrane Na(+)-K+ ATPase activity. Membrane Na(+)-K+ ATPase inhibition can lead to magnesium depletion, which can lead to an upregulated isoprenoid pathway. The isoprenoid pathway produces three important metabolites--digoxin, an endogenous membrane Na(+) -K+ ATPase inhibitor; ubiquinone, a membrane antioxidant and component of mitochondrial electron transport chain; and dolichol, important in N-glycosylation of protein. The serum/plasma levels of digoxin, dolichol, ubiquinone, magnesium, HMG CoA reductase activity, and RBC Na(+)-K+ ATPase activity were estimated in all these disorders. The result showed that the concentration of serum tryptophan and serotonin was high and serum tyrosine, dopamine, adrenaline, and noradrenaline low in all the disorders studied. The plasma HMG CoA reductase activity, serum digoxin, and serum dolichol levels were high and serum ubiquinone levels, serum magnesium, and RBC Na(+)-K+ ATPase activity were low in all the disorders studied. The significance of these changes in the pathogenesis of syndrome X, multiple sclerosis, primary generalized epilepsy, schizophrenia, SSPE, and Parkinson's disease is discussed in the setting of the interrelationship between these disorders documented in literature.

Topics: Adult; Analysis of Variance; Case-Control Studies; Cell Membrane; Chromatography, High Pressure Liquid; Digoxin; Dolichols; Female; Humans; Hydroxymethylglutaryl CoA Reductases; Magnesium; Male; Middle Aged; Nervous System Diseases; Neurotransmitter Agents; Sodium-Potassium-Exchanging ATPase; Ubiquinone

Two substances which are products of the isoprenoid pathway, can participate in lipid peroxidation. One is digoxin, which by inhibiting membrane Na(+)-K+ ATPase, causes increase in intracellular Ca2+ and depletion of intracellular Mg2+, both effects contributing to increase in lipid peroxidation. Ubiquinone, another products of the pathway is a powerful membrane antioxidant and its deficiency can also result in defective electron transport and generation of reactive oxygen species. In view of this and also in the light of some preliminary reports on alteration in lipid peroxidation in neuropsychiatric disorders, a study was undertaken on the following aspects in some of these disorders (primary generalised epilepsy, schizophrenia, multiple sclerosis, Parkinson's disease and CNS glioma)--1) concentration of digoxin, ubiquinone, activity of HMG CoA reductase and RBC membrane Na(+)-K+ ATPase 2) activity of enzymes involved in free radical scavenging 3) parameters of lipid peroxidation and 4) antioxidant status. The result obtained indicates an increase in the concentration of digoxin and activity of HMG CoA reductase, decrease in ubiquinone levels and in the activity of membrane Na(+)-K+ ATPase. There is increased lipid peroxidation as evidenced from the increase in the concentration of MDA, conjugated dienes, hydroperoxides and NO with decreased antioxidant protection as indicated by decrease in ubiquinone, vit E and reduced glutathione in schizophrenia, Parkinson's disease and CNS glioma. The activity of enzymes involved in free radical scavenging like SOD, catalase, glutathione peroxidase and glutathione reductase is decreased in the above diseases. However, there is no evidence of any increase in lipid peroxidation in epilepsy or MS. The role of increased operation of the isoprenoid pathway as evidenced by alteration in the concentration of digoxin and ubiquinone in the generation of free radicals and protection against them in these disorders is discussed.

Topics: Central Nervous System Neoplasms; Digoxin; Epilepsy, Generalized; Free Radicals; Glioma; Humans; Lipid Peroxidation; Multiple Sclerosis; Nervous System Diseases; Parkinson Disease; Schizophrenia; Ubiquinone

Topics: Aged; Anti-Arrhythmia Agents; Digoxin; Drug Overdose; Humans; Male; Mental Disorders; Nervous System Diseases

Topics: Digoxin; Gastrointestinal Diseases; Humans; Nervous System Diseases

Topics: Administration, Oral; Arrhythmias, Cardiac; Cardiac Glycosides; Diet Therapy; Digitoxin; Digoxin; Diuresis; Drug Tolerance; Edetic Acid; Electrocardiography; Gastrointestinal Diseases; Heart Failure; Heart Rate; Humans; Injections, Intravenous; Lanatosides; Nervous System Diseases; Phytotherapy; Plants, Medicinal; Poisoning; Potassium; Rest; Strophanthins

Topics: Arrhythmias, Cardiac; Biliary Tract; Digitalis Glycosides; Digitoxin; Digoxin; Gastrointestinal Diseases; Heart Diseases; Humans; Intestinal Absorption; Kidney; Lanatosides; Liver; Lung; Muscles; Myocardium; Nervous System Diseases; Strophanthins; Vision Disorders