Infusions of tyrosine hydroxylase antisense oligodeoxynucleotide into substantia nigra of the rat: effects on tyrosine hydroxylase mRNA and protein content, striatal dopamine release and behaviour

Setting the pace for retinal development: environmental enrichment acts through insulin-like growth factor 1 and brain-derived neurotrophic factor

Environmental enrichment strongly affects visual system maturation both at retinal and cortical levels. Which molecular pathways are activated by an enriched environment (EE) to regulate visual system development has not been clarified. Here, we show that early [postnatal day 1 (P1) to P7] insulin-like growth factor 1 (IGF-1) injections in the eyes of non-EE rat pups mimic EE effects both in increasing BDNF levels in the retinal ganglion cell layer at P10 and in determining a more adult-like retinal acuity, assessed with pattern electroretinogram at P25. Blocking IGF-1 action in EE animals during the same early postnatal time window by injecting the IGF-1 receptor antagonist JB1 prevents EE effects both on BDNF expression and on retinal acuity maturation. Reducing BDNF expression in the retina of IGF-1-treated rats prevents IGF-1 effects on retinal acuity development. Finally, we show that tyrosine hydroxylase (TH) expression is increased in the retina of P10 EE and IGF-1-treated rats and that blocking TH expression in EE animals prevents EE from affecting retinal acuity development. Thus, early levels of IGF-1 play a key role in mediating EE effects on retinal development through an action that requires BDNF and involves dopaminergic amacrine cell network.

Production of functional recombinant tyrosine hydroxylase by the BPV-1 expression plasmids in the cell cultures

Bovine papilloma virus type-1 (BPV-1)-based expression plasmids TkBPVTH and CGalBPVTH encoding the rat tyrosine hydroxylase (TH) enzyme have been designed for the development of gene therapy for experimental Parkinson's disease. The aim of the present work was to examine the transfection of BPVTH plasmids to express a dopaminergic transgene in the monkey CV1-P fibroblast, rat C6 glioma and human NHA astrocyte cell cultures. The biological function of the transgene was estimated by analyzing the production of recombinant TH mRNA and protein, and the synthesis of L-dopa and dopamine. The highest transfection efficiency was obtained using TkBPVTH plasmids (5 microg). Furthermore, the expression of TkBPVTH plasmids was associated with significant synthesis of TH enzyme and L-dopa in the C6 and NHA cell cultures.

Experimental parkinsonism is associated with increased pallidal GAD gene expression and is reversed by site-directed antisense gene therapy

The levels of mRNA encoding the two isoforms of glutamic acid decarboxylase (GAD(65) and GAD(67)) were measured throughout the pallidal complex in normal and acutely (i.e., 1 month duration) and chronically (i.e., 5 years duration) parkinsonian 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride (MPTP) -treated monkeys as well as in monkeys exposed to MPTP but asymptomatic for parkinsonism. GAD(65) mRNA labeling was modestly increased in the mid/caudal internal globus pallidus (GPi) but not in the external globus pallidus (GPe) in parkinsonian monkeys, compared with normal and asymptomatic monkeys. GAD(67) mRNA expression was highly increased in the mid/caudal GPi, and modestly increased in the GPe in parkinsonian monkeys compared with normal and asymptomatic animals. Infusion of GAD(67) antisense oligodeoxynucleotides bilaterally into the GPi resulted in a transient reversal of akinesia and bradykinesia that was not produced by infusion of missense oligodeoxynucleotides. These data emphasize the role of GAD enzyme (particularly GAD(67)) and GABA in the GPi for the expression of parkinsonian motor signs and suggest that selective manipulation of GABAergic neurotransmission in the GPi may have therapeutic potential for treating parkinsonism.

Pharmacological analysis of extracellular dopamine and metabolites in the striatum of conscious as/agu rats, mutants with locomotor disorder

The as/agu rat is a spontaneously occurring mutation which exhibits locomotor abnormalities, reduced tyrosine hydroxylase levels in the substantia nigra and lower extracellular levels of dopamine. The animal could represent a model of some human locomotor disorders. High-potassium medium evoked a 460% rise of dopamine levels in control rats but double this in mutants. Amphetamine increased extracellular dopamine by 710% in controls and 1480% in mutants. Clorgyline produced a small increase of dopamine levels in controls but an 1170% increase in mutants. The uptake inhibitor nomifensine increased dopamine levels by 910% in controls but only 270% in mutants. After treatment with benserazide plus L-DOPA, an acute injection of L-DOPA evoked a release of dopamine which was twice as large in the as/agu rats compared with controls. The results show reduced extracellular dopamine in as/agu rats when the locomotor disorder is apparent, but there has been little loss of tyrosine hydroxylase. The responses to drugs are qualitatively different from those obtained using 6-hydroxydopamine.Overall, the effects of compounds affecting aminergic neurons suggest that one possible mechanism for the neuronal abnormality in as/agu rats is a defective regulation of dopamine release from striatal terminals.

Intracerebroventricular injection of antisense oligos to nNOS decreases rat ethanol intake

Nitric oxide (NO) has been implicated in alcohol drinking behavior using NO synthase (NOS) inhibitors that are nonselective of the different isoforms of NOS. In the brain, there are two constitutive isoforms of NOS, neuronal NOS (nNOS) and endothelial NOS (eNOS). We used an antisense oligodeoxynucleotide directed against nNOS in ethanol dependent male Wistar rats to examine the specific contribution of nNOS in the control of ethanol intake. Rats were subjected to a free-choice situation water/ethanol (10% v/v) after chronic ethanol intoxication by inhalation of ethanol vapor. During the free-choice situation, rats were twice daily for 4 days intracerebroventricularly injected with either saline, or end-capped phosphorothioate-protected antisense or mismatch oligodeoxynucleotide (25 microg/4 microl per injection), or acamprosate (1 mg/kg body weight) as reference product for its anticraving properties. Our results showed that the antisense treatment, but not the mismatch treatment, reduced both ethanol intake and ethanol preference during treatment and posttreatment periods (by 25-30%) without alteration of the body weight gain. The antisense treatment, but not the mismatch treatment, also down-regulated nNOS mRNA levels (by 30%) and NOS activity in the hippocampus. The anticraving drug, acamprosate reduced both ethanol intake (by 58%) and ethanol preference. All these results suggest that nNOS is involved in the regulation of alcohol dependence.

Extracellular levels of dopamine and its metabolite 3,4-dihydroxy-phenylacetic acid measured by microdialysis in the corpus striatum of conscious AS/AGU mutant rats

The AS/AGU rat is a mutant derived from the Albino Swiss (AS) strain. It is characterized by an ungainly, staggering gait, hind limb rigidity, whole body tremor and, in older animals, difficulty in initiating movement. As and AS/AGU males aged three, six and nine months (n=6 per group) were used to estimate the levels of dopamine and its metabolites in the extracellular fluid of the caudate-putamen. The results indicate a profound loss of dopamine in the extracellular fluid at all age points examined, together with an increase in the concentration of the metabolite 3,4-dihydroxyphenylacetic acid. It is suggested that these changes reflect a defect of dopaminergic neuron function which may underlie the motor disorder seen in these animals.

Antisense Oligodeoxynucleotide Technology: Potential Use for the Treatment of Malignant Brain Tumors

BACKGROUND: Antisense oligodeoxynucleotides (ODNs) have been proposed as a new therapy for patients with cancer, including malignant brain tumors. Antisense ODNs are taken up by tumor cells and selectively block gene expression. Use of ODNs for brain tumors is attractive due to their theoretical specificity, relative ease of production and, to date, paucity of reported adverse effects. This article presents current information regarding antisense ODNs and their possible future use for the treatment of brain tumors. METHODS: The available published experimental and clinical information regarding antisense ODN treatment of glioblastoma cells and administration into the central nervous system (CNS) was reviewed. Other clinically relevant information pertaining to the molecular biology of antisense ODNs was also collected and summarized. RESULTS: Targets for antisense ODN therapy in malignant glioma cells have included c-myc, c-myb, c-sis, c-erb B, CD44, p34cdc2, bFGF, PDGF, TGF-beta, IGF-1, PKC-alpha tumor necrosis factor, urokinase, and S100beta protein. Few in vivo studies of ODN treatment of brain tumors have yet been reported. Systemically administered ODNs enter the brain only in extremely small quantities; therefore, microinfusion into the brain has been recommended. CONCLUSIONS: Antisense ODNs have been used successfully to block glioblastoma gene expression in vitro and expression of multiple genes within the CNS of experimental animals. Upcoming clinical trials will address the safety of antisense ODN use against malignant brain tumors.