Prevention Of Neurodegenerative Diseases Research Articles

Molecular and cellular mechanisms of iron homeostasis and toxicity in mammalian cells

Iron is an essential metal for almost all living organisms due to its involvement in a large number of iron-containing enzymes and proteins, yet it is also toxic. The mechanisms involved in iron absorption across the intestinal tract, its transport in serum and delivery to cells and iron storage within cells is briefly reviewed. Current views on cellular iron homeostasis involving the iron regulatory proteins IRP1 and IRP2 and their interactions with the iron regulatory elements, affecting either mRNA translation (ferritin and erythroid cell δ-aminolaevulinate synthase) or mRNA stability (transferrin receptor) are discussed. The potential of Fe(II) to catalyse hydroxyl radical formation via the Fenton reaction means that iron is potentially toxic. The toxicity of iron in specific tissues and cell types (liver, macrophages and brain) is illustrated by studies with appropriate cellular and animal models. In liver, the high levels of cyoprotective enzymes and antioxidants, means that to observe toxic effects substantial levels of iron loading are required. In reticuloendothelial cells, such as macrophages, relatively small increases in cellular iron (2–3-fold) can affect cellular signalling, as measured by NO production and activation of the nuclear transcription factor NFκB, as well as cellular function, as measured by the capacity of the cells to produce reactive oxygen species when stimulated. The situation in brain, where anti-oxidative defences are relatively low, is highly regionally specific, where iron accumulation in specific brain regions is associated with a number of neurodegenerative diseases. In the brains of animals treated with either trimethylhexanoylferrocene or aluminium gluconate, iron and aluminium accumulate, respectively. With the latter compound, iron also increases, which may reflect an effect of aluminium on the IRP2 protein. Chelation therapy can reduce brain aluminium levels significantly, while iron can also be removed, but with greater difficulty. The prospects for chelation therapy in the treatment and possible prevention of neurodegenerative diseases is reviewed.

Role of Oxidative Stress and Antioxidants in Neurodegenerative Diseases

Neurodegenerative diseases (NDD) are a group of illness with diverse clinical importance and etiologies. NDD include motor neuron disease such as amyotrophic lateral sclerosis (ALS), cerebellar disorders, Parkinson's disease (PD), Huntington's disease (HD), cortical destructive Alzheimer's disease (AD) and Schizophrenia. Numerous epidemiological and experimental studies provide many risk factors such as advanced age, genetic defects, abnormalities of antioxidant enzymes, excitotoxicity, cytoskeletal abnormalities, autoimmunity, mineral deficiencies, oxidative stress, metabolic toxicity, hypertension and other vascular disorders. Growing body of evidence implicates free radical toxicity, radical induced mutations and oxidative enzyme impairment and mitochondrial dysfunction due to congenital genetic defects in clinical manifestations of NDD. Accumulation of oxidative damage in neurons either primarily or secondarily may account for the increased incidence of NDD such as AD, ALS and stroke in aged populations. The molecular mechanisms of neuronal degeneration remain largely unknown and effective therapies are not currently available. Recent interest has focused on antioxidants such as carotenoids and in particular lycopene, a potent antioxidant in tomatoes and tomato products, flavonoids and vitamins as potentially useful agents in the management of human NDD. The pathobiology of neurodegenerative disorders with emphasis on genetic origin and its correlation with oxidative stress of neurodegenerative disorders will be reviewed and the reasons as to why brain constitutes a vulnerable site of oxidative damage will be discussed. The article will also discuss the potential free radical scavenger, mechanism of antioxidant action of lycopene and the need for the use of antioxidants in the prevention of NDD.

Pharmacologie de l'aspirine

Aspirin (acetylsalicylic acid) is the best-known salicylate and belongs to the non steroid anti-inflammatory drug class. Despite wide use being made since more than 100 years, knowledge about mechanism of action and therapeutic issues continually evolves. The main mechanism of action is prostaglandin synthesis inhibition. This is achieved through inhibition of prostaglandin endoperoxide synthase (PGHS) or cyclooxygenase (COX) synthesis. Most of the therapeutic uses of aspirin are explained by this mechanism. Nevertheless aspirin uses change as time goes by: if the main one during the first fifty years was an analgesic, anti-pyretic and anti-inflammatory one, the last fifty years saw aspirin being used mainly as an anti-thrombotic agent, in primary and secondary thrombo-embolic prevention. Better knowledge of mechanism of action points today at, on one hand, more selective and therefore better tolerated molecules, and, on the other hand, at new therapeutic applications, such as anti-cancer and neurodegenerative diseases prevention.

Glutathione transferases catalyse the detoxication of oxidized metabolites (o-quinones) of catecholamines and may serve as an antioxidant system preventing degenerative cellular processes.

o-Quinones are physiological oxidation products of catecholamines that contribute to redox cycling, toxicity and apoptosis, i.e. the neurodegenerative processes underlying Parkinson's disease and schizophrenia. The present study shows that the cyclized o-quinones aminochrome, dopachrome, adrenochrome and noradrenochrome, derived from dopamine, dopa, adrenaline and noradrenaline respectively, are efficiently conjugated with glutathione in the presence of human glutathione transferase (GST) M2-2. The oxidation product of adrenaline, adrenochrome, is less active as a substrate for GST M2-2, and more efficiently conjugated by GST M1-1. Evidence for expression of GST M2-2 in substantia nigra of human brain was obtained by identification of the corresponding PCR product in a cDNA library. Glutathione conjugation of these quinones is a detoxication reaction that prevents redox cycling, thus indicating that GSTs have a cytoprotective role involving elimination of reactive chemical species originating from the oxidative metabolism of catecholamines. In particular, GST M2-2 has the capacity to provide protection relevant to the prevention of neurodegenerative diseases.

Melatonin prevents oxidative stress-induced cell death in hippocampal cells.

The pineal hormone melatonin has been suggested to be a very effective antioxidant in the brain. Oxidative stress may play a role in certain neuropathological conditions and the hippocampus is an early target of neurodegeneration. Using cells of the clonal hippocampal cell line HT22 and organotypic hippocampal rat brain slice cultures, we investigated a possible protective role of melatonin against oxidative stress-induced hippocampal cell death. Glutamate alone induced oxidative apoptotic cell death in HT22 cells as detected with Hoechst staining and DNA fragmentation analysis. Preincubation with 1 mM melatonin protected HT22 cells against glutamate-induced cell death and protected organotypic hippocampal slices against H2O2-induced cell death. These findings suggest that this neurohormone may be useful in the prevention of neurodegenerative diseases.

1218 Caged cyclic GMP induced neurite elongation of rat DRG neurons

Effective cell replacement therapies for neurological disease require neuron-restricted precursors as grafted cells. The problem of obtaining sufficient grafts for transplantation can be resolved by creating an appropriate immortalized cell line. In the present study, a thermally controlled immortalized GABAergic neuronal progenitor cell line (RMNE6) was established from E13 rat ventral mesencephalon cells immortalized using the temperature-sensitive mutant of SV40 large T antigen (ts-TAg). RMNE6 cells proliferated rapidly and expressed a neuron-like phenotype at the permissive temperature (33 °C), but eventually stopped growing at the non-permissive temperature (39 °C). Expression of the neuronal markers PSA-NCAM, β-tubulin III and MAP2 by RMNE6 cells was confirmed by RT-PCR or immunocytochemistry. Furthermore, these cells exhibited functional GABAergic neuron properties, as evidenced by the expression of glutamate decarboxylase (GAD) as well as the synthesis and release of the neurotransmitter GABA in a calcium-dependent manner. Moreover, RMNE6 cells spontaneously expressed and secreted several neurotrophic factors, such as NGF, BDNF, NT-3, NT-4/5, and GDNF. The cells survived well and kept expression of SV40 Tag, GAD65/67 and GABA in the striatum, at least 28 days after being transplanted in the rat brain. Tumorigenesis assays confirmed the safety of the immortalized cell line in vivo. Taken together, the results support the use of RMNE6 cells as an ideal cell model for transplantation research aimed at the treatment and prevention of neurodegenerative disease.