Differential Expression of Striatal ΔFosB mRNA and FosB mRNA After Different Levodopa Treatment Regimens in a Rat Model of Parkinson's Disease.

Levodopa-induced dyskinesia (LID) is the main side effect associated with levodopa treatment and represents the biggest challenge for Parkinson's disease therapy. While the overexpression of ΔFosB transcription factor is related to the development of LID, few studies have been undertaken on fosB gene transcriptional regulation induced by levodopa in vivo. The aim of this study is to evaluate the expression of ΔFosB mRNA and FosB mRNA in the striatum after acute, chronic, and subchronic levodopa treatment in rats with unilateral 6-OHDA-lesion in the medial forebrain bundle. qRT-PCR was used to compare the levels of ΔFosB and FosB mRNA expression in the dopamine-denervated striatum following levodopa treatment. While the results obtained after a single levodopa dose indicate a significant increase of ∆FosB mRNA expression in the striatum 1 h post-injection, the levels returned to baseline values after 24 h. After subchronic levodopa treatment, the levels of ∆FosB and FosB mRNA expression were lower 1 h post-administration of levodopa in comparison with acute effect. However, after chronic levodopa treatment, ∆FosB mRNA expression in the striatum persisted in dyskinetic rats only, and positive correlation was found between the levels of ∆FosB mRNA expression 1 h after levodopa administration and the level of dyskinetic severity. In summary, acute levodopa treatment led to highly increased levels of ∆FosB mRNA expression in the striatum. While repeated administration induced a partial desensitization of the fosB gene in the striatum, it did not suppress its activity completely, which could explain why dyskinesia appears after chronic levodopa treatment.

Effects of acute post-treatment with dipyridamole in a rat model of focal cerebral ischemia.

Dipyridamole (DP) is a platelet inhibitor with known antithrombotic benefits in stroke prevention. In addition to its anti-aggregant properties, recent studies have reported that DP promotes anti-inflammatory, anti-oxidative and neuroprotective effects. We aimed to test whether post-treatment with DP may exert protection after ischemic cerebral injury in the rat. For this purpose, rats were subjected to 120 min or 90 min of middle cerebral artery occlusion (MCAO) followed by 24 or 48 h of reperfusion, respectively. Either DP (100mg/kg) or vehicle was administered i.v. at the onset of reperfusion; rats subjected to 90 min MCAO also received additional doses of DP orally (60 mg/kg) at 24 and 36 h after ischemia. Matrix metalloproteinases, extravasated hemoglobin content and IL-6, MIP-1α and MCP-1 cytokine level were examined in brain tissue by zymography, western blot and multiple ELISA, respectively. DP post-treatment led to a neurological improvement in both models (p < 0.05) and a significant reduction in the infarct volume of rats subjected to 90 min of ischemia, as compared to vehicle group (7.9% vs. 24.4%, p = 0.03). This neuroprotection was accompanied by a modest increase in expression of MMP-9 pro-form and a significant attenuation of MIP-1α levels in the infarcted hemisphere. These results provide support for the development of novel therapies based on DP for acute treatment of stroke. In selected animals, intravenous administration of high dose DP induced an adverse hypotensive effect leading to rapid death. Thus, alternative ways of acute administration must be examined in order to avoid this unfavorable effect.

Plasma VAP-1/SSAO activity predicts intracranial hemorrhages and adverse neurological outcome after tissue plasminogen activator treatment in stroke.

BACKGROUND AND PURPOSE: Vascular adhesion protein-1 (VAP-1) is a cell surface and circulating enzyme involved in recruitment of lymphocytes and neutrophils through its semicarbazide-sensitive amine oxidase (SSAO) activity. We aimed to study plasma VAP-1/SSAO activity in relation to the risk for intracranial bleeding complications in patients with stroke treated with tissue plasminogen activator (tPA), the greatest safety concern with this treatment. METHODS: In 141 patients with ischemic stroke, we measured VAP-1/SSAO activity in plasma taken before tPA administration. Hemorrhagic events were classified according to brain CT criteria and functional outcomes evaluated using the National Institutes of Health Stroke Scale. We also assessed the potential therapeutic effect of blocking VAP-1/SSAO activity in a rat embolic stroke model treated with tPA. RESULTS: We saw significantly higher levels of plasma VAP-1/SSAO activity in patients who subsequently experienced hemorrhagic transformation. Elevated plasma VAP-1/SSAO activity also predicted worse neurological outcome in these patients. In the rat model, we confirmed that use of the inhibitor semicarbazide prevented adverse effects caused by delayed tPA administration, leading to a smaller infarct volume. CONCLUSIONS: Our data demonstrate that baseline VAP-1/SSAO activity predicts parenchymal hemorrhage after tPA, suggesting the safety of thrombolytic agents could be improved by considering VAP-1/SSAO activity. Furthermore, anti-VAP-1/SSAO drugs given with tPA may prevent neurological worsening in patients with ischemic stroke.

Noradrenergic modulation of the motor response induced by long-term levodopa administration in Parkinsonian rats.

A decrease in noradrenergic activity in Parkinson's disease might play a critical role in long-term motor complications associated with chronic dopaminergic replacement. Using the rat model of parkinsonism with an additional noradrenergic degeneration induced by the N-(-2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) toxin we evaluated whether the circling motor activity and dose-failure episodes induced by levodopa (L-DOPA) differ between single (6-OHDA) and double (6-OHDA + DSP-4) denervated animals challenged with a single daily dose of L-DOPA. While single-lesioned animals showed a sensitization-desensitization turning response with a significant increase on day 15 and a decrease on day 22, in double-lesioned animals, the turning activity was maximal from day 1 and did not decay on day 22. Double-lesioned rats exhibited significantly higher number of turns on days 15 and 22 and a significantly lower percentage of dose-failure episodes during treatment. Noradrenergic denervation appears to be associated with prolonged long-term dopaminergic sensitization. This type of response appears to be comparable to that in the clinical setting with intermittent L-DOPA administration where no desensitization occurs once the abnormal response is established.

Modulation of the motor response to dopaminergic drugs in a parkinsonian model of combined dopaminergic and noradrenergic degeneration.

Besides dopaminergic deficiency, other neurotransmitter systems such as noradrenergic nuclei are affected in Parkinson's disease. Locus coeruleus degeneration might influence the response to dopamine replacement and the presence of long-term complications such as dyskinesias. In this scenario of noradrenergic and dopaminergic neurodegeneration, behavioural effects induced by dopaminergic-interacting drugs are incompletely known. We investigated whether noradrenergic lesion modulates the levodopa (l-DOPA) response and modifies the response to adenosine antagonists and its interaction with l-DOPA. We examined the motor behaviour induced by: 1) subthreshold doses of l-DOPA (2mg/kg, i.p.), 2) the adenosine-receptor antagonist caffeine (10mg/kg), and 3) the combination of l-DOPA (2mg/kg) and caffeine (10mg/kg). Each study was done in two experimental conditions: a) rats with unilateral 6-OHDA lesion and b) rats with a lesion of the nigrostriatal pathway (6-OHDA) combined with selective denervation of locus coeruleus-noradrenergic terminal fields by N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4). While only 28% of the 6-OHDA-lesioned animals presented circling behaviour after l-DOPA challenge, all (100%) double-denervated animals rotated after the same l-DOPA dose (p<0.05). No statistical differences in the percentage of rotating animals were observed between single- and double-denervated rats after caffeine challenge. Combined l-DOPA-caffeine challenge produced rotational behaviour in all (100%) single- and double-denervated rats. No differences in total turns were observed between single- and double-denervated animals in each treatment condition. These findings suggest that additional noradrenergic denervation selectively decreases the motor threshold to l-DOPA treatment without modifying the magnitude or the pattern of the motor response to adenosinergic antagonism.