Neurochemical, neurobehavioral and histochemical effects of therapeutic dose of l-dopa on striatal neurons in rats: Protective effect of virgin coconut oil.

Despite the fact that levodopa has proven its effectiveness in treating the symptoms of Parkinson's disease (PD), increasing concerns have emerged about its possible long-term toxic effects on dopamine (DA) neurons. The study investigated the possible ameliorative effect of virgin coconut oil against l-dopa- induced neurotoxicity in adult rats. A total number of 40 rats were divided into four groups. Briefly, the first served as control, the second was orally administered virgin coconut oil (1.42 mL/kg), the third group was administered a single daily dose of l-dopa/carbidopa (100/10 mg/kg/day, p.o) and the fourth group pre-treated with virgin coconut oil then administered a single daily dose of l-dopa/carbidopa. The different treatments were extended for 30 days. l-dopa treated group exhibited aggressive behavior and behavioral abnormalities in open field test compared to control group. In addition, l-dopa treatment caused significant increase in the levels of striatal dopamine and norepinephrine and their metabolites with concomitant decrease of serotonin and its metabolite. Moreover, l-dopa treatment increased histamine and GABA levels. In addition, l-dopa treatment induced oxidative stress and energy crisis. The histological and immunohistochemical studies showed that l-dopa caused a remarkable neurodegeneration and increased glial fibrillary acidic protein (GFAP) immunoexpression in the striatal area. Virgin coconut oil co-treatment significantly minimized the harmful effects of l-dopa. In conclusion, the present study revealed that virgin coconut oil provided a notable protection against l-dopa's untoward effects.

Ninety-day Local Tolerability and Toxicity Study of ND0612, a Novel Formulation of Levodopa/Carbidopa, Administered by Subcutaneous Continuous Infusion in Minipigs.

A 90-day study in Göttingen minipigs was conducted to test the local tolerability and systemic toxicity of ND0612, a novel aqueous solution of carbidopa (CD)/levodopa (LD) intended for the treatment of Parkinson's disease by continuous subcutaneous administration using a discrete infusion pump. To evaluate tissue site reactions, we used a unique study design involving multiple infusion sites to evaluate the effect of dose per site (270/63, 360/45, and 360/84 mg LD/CD), volume of infusion per site (4.5 and 6 ml per site), formulation concentration (60/14 and 60/7.5 mg/ml LD/CD), daily rate of infusion per site (240 µl/hr for16 hr and 80 µl/hr for 8 hr, 320 µl/hr for 16 hr and 100 µl/hr for 8 hr, or 750 µl/hr for 8 hr), frequency (once every 5, 10, 15, or 20 days), and number of infusions (4, 6, or 9) to the same infusion site. No systemic adverse effects were observed. Histopathological changes at infusion sites started with localized minimal necrosis and acute inflammation that progressed to subacute and chronic inflammatory and reparative changes with evidence of progressive recovery following the final infusion. None of the infusion site effects were judged to be adverse, and clinical exposures to ND0612 are not expected to result in adverse responses.

In vivo protective effect of Uridine, a pyrimidine nucleoside, on genotoxicity induced by Levodopa/Carbidopa in mice.

Parkinson's disease (PD) is a common neurodegenerative disorder that affects millions of people all over the world. Motor symptoms of PD are most commonly controlled by L-3,4-dihydroxyphenylalanine (Levodopa, L-DOPA), a precursor of dopamine, plus a peripherally-acting aromatic-L-amino-acid decarboxylase (dopa decarboxylase) inhibitor, such as carbidopa. However, chronic treatment with a combination of Levodopa plus carbidopa has been demonstrated to cause a major complication, namely abnormal involuntary movements. On the other hand, the effect of this treatment on bone marrow cells is unknown. Therefore, in this study, we aimed to investigate possible genotoxic effects of Levodopa and Carbidopa using male Balb/C mice. Our results showed that Levodopa alone or in combination with carbidopa caused genotoxicity in in vivo micronucleus test (mouse bone marrow) and Comet assay (blood cells). Furthermore, we showed that simultaneous administration of uridine, a pyrimidine nucleoside, reversed the genotoxic effect of Levodopa and Carbidopa in both assays. Our data show for the first time that Levodopa plus carbidopa combination causes genotoxicity which is reversed by uridine treatment. These findings might enhance our understanding for the complications of a common Parkinson's treatment and confer benefit in terms of reducing a possible genotoxic effect of this treatment.

Evaluation of levodopa and carbidopa antioxidant activity in normal human lymphocytes in vitro: implication for oxidative stress in Parkinson's disease.

The main pathochemical hallmark of Parkinson's disease (PD) is the loss of dopamine in the striatum of the brain, and the oral administration of levodopa (L-dopa) is a treatment that partially restores the dopaminergic transmission. In vitro assays have demonstrated both toxic and protective effects of L-dopa on dopaminergic cells, while in vivo studies have not provided any convincing data. The peripheral metabolic pathways significantly decrease the amount of L-dopa reaching the brain; therefore, all of the current commercial formulations require an association with an inhibitor of dopa-decarboxylase, such as carbidopa. However, the dosage and the actual effectiveness of carbidopa have not yet been well defined. PD patients exhibit a reduced efficiency of the endogenous antioxidant system, and peripheral blood lymphocytes (PBLs) represent a dopaminergic system for use as a cellular model to study the pharmacological treatments of neurodegenerative disorders in addition to analysing the systemic oxidative stress. According to our previous studies demonstrating a protective effect of both L-dopa and carbidopa on neuroblastoma cells in vitro, we used the PBLs of healthy donors to evaluate the modulation of DNA damage by different concentrations of L-dopa and carbidopa in the presence of oxidative stress that was exogenously induced by H2O2. We utilised a TAS assay to evaluate the in vitro direct scavenging activity of L-dopa and carbidopa and analysed the expression of genes that were involved in cellular oxidative metabolism. Our data demonstrate the antioxidant capacity of L-dopa and carbidopa and their ability to protect DNA against oxidative-induced damage that derives from different mechanisms of action.

Oxidation of carbidopa by tyrosinase and its effect on murine melanoma.

Oxidation of the anti-Parkinsonian agent carbidopa by tyrosinase was investigated. The products of this reaction were identified as 3-(3,4-dihydroxyphenyl)-2-methylpropanoic acid and 6,7-dihydroxy-3-methylcinnoline. These results demonstrate that after oxidation of the catechol moiety to an o-quinone either a redox exchange with the hydrazine group or a cyclization reaction occur. The cyclization product underwent additional oxidation reactions leading to aromatization. The cyclization reaction is undesired in the case of hydrazine-containing anti-melanoma prodrugs and will have to be taken into account in designing such compounds. Carbidopa was tested against B16(F10) melanoma cells in culture and showed cytotoxicity significantly higher than either of its oxidation products and l-dopa. This effect, however, was not specific to this cell line.

Reversible Pisa syndrome in patients with Parkinson's disease on dopaminergic therapy.

BACKGROUND: The wide variability of dystonic postures manifested in the clinical course of Parkinson's disease (PD) represents a complicated on-going issue. Several recently published reports of Pisa syndrome (PS) in parkinsonian patients on dopaminergic therapy have described a variable means of onset and clinical course of this truncal dystonia. OBJECTIVE: To describe PD patients with PS, with the aim of stressing the frequent iatrogenic origin and potential reversibility of this syndrome during the initial stages of its appearance. SUBJECTS AND METHODS: Eight consecutive PD patients who developed a PS after modifications of antiparkinson therapy were studied. All patients underwent detailed clinical assessment, [(123)I]FP-CIT-SPECT being performed in three cases. Four patients were videotaped. RESULTS: All patients developed PS within a variable time-span ranging from 15 days to 3 months after adjustment of treatment. Seven cases of PS were manifested following an increase and one a decrease of dopaminergic treatment. A marked reversal of dystonia was produced in the first seven patients by the withdrawal or dose decrease of dopaminergic PS priming drug, and in the eighth patient an increase of dopaminergic therapy was necessary. CONCLUSIONS: In our opinion, the recognition of reversibility of PS during the initial stages of its appearance may be of considerable clinical importance. Indeed, it may facilitate the rapid withdrawal or reintroduction of dopaminergic treatment, thus avoiding an initial veering towards the subchronic variant and, subsequently into a chronic irreversible variant.

Hydrogen peroxide degradation and selective carbidopa-induced cytotoxicity against human tumor lines.

The carcinoid tumor, an uncommon neuroendocrine neoplasm, is associated with serotonin overproduction as is more common small cell lung carcinoma (SCLC). alpha-Methyl-dopahydrazine (carbidopa), an inhibitor of the serotonin synthetic enzyme aromatic-L-amino acid decarboxylase, proved lethal to NCI-H727 lung carcinoid cells as well as NCI-H146 and NCI-H209 SCLC cells, but not to five other human tumor cell lines of differing origins [Gilbert JA, Frederick LM, Ames MM. The aromatic-L-amino acid decarboxylase inhibitor carbidopa is selectively cytotoxic to human pulmonary carcinoid and small cell lung carcinoma cells. Clin. Cancer Res. 2000;6:4365-72]. The mechanism of carbidopa cytotoxicity remained an unanswered question. We present data here that incubation of the catechol carbidopa (100 microM) in RPMI and DMEM culture media yielded molar equivalents of hydrogen peroxide (H2O2) within 2-4 h. Alkaline elution studies revealed carbidopa-dependent single-strand DNA breaks in sensitive carcinoid cells comparable to those induced by similar concentrations of H2O2. Neither compound induced significant DNA damage in carbidopa-resistant NCI-H460 large cell lung carcinoma cells. Furthermore, when carbidopa was incubated with a variety of tumor cell types, not only were decreased media H2O2 concentrations detected in the presence of cells, but cell lines least sensitive to carbidopa degraded exogenous H2O2 more rapidly than did sensitive cells. Implicated in these studies, pyruvate degraded H2O2 in RPMI in a dose- and time-dependent manner and reversed carbidopa-induced cytotoxicity to carcinoid cells. Extracellular pyruvate levels produced per h by resistant large cell lung carcinoma cells averaged four-fold that of sensitive carcinoid cells plated at equal density (24 h time course). Finally, carbidopa exposure (100 microM, 24 h) depleted extracellular pyruvate from sensitive carcinoid cells, but reduced pyruvate levels from resistant NCI-H460 cells less than 17%.

Internal globus pallidus discharge is nearly suppressed during levodopa-induced dyskinesias.

The functional status of the globus pallidus internal segment (GPi) plays a key role in mediating the effects of antiparkinsonian drugs. During long-term levodopa therapy, patients develop abnormal movements, dyskinesias, the pathophysiological basis of which is poorly understood. We recorded single cells in the GPi of parkinsonian monkeys continuously through the "off" and "on" states, and 10 to 15 minutes later during "on with or without dyskinesias," depending on two doses of levodopa. The transition from the "off" to the "on" state was characterized by a decrease (most cells), no change, or an increase in firing rate of individual cells. During dyskinesias, firing rates declined profoundly in almost all cells, with decrements as low as 97% in individual cells. These changes occurred only when dyskinesias were present. The difference in GPi activity between "on" and "on with dyskinesias" suggests that normal motor function in Parkinson's disease critically depends on fine tuning of the basal ganglia output. Dyskinesias result from an imbalanced low GPi discharge, a circumstance that may be susceptible to development of new therapeutic approaches.

Glial cell line-derived neurotrophic factor-levodopa interactions and reduction of side effects in parkinsonian monkeys.

Glial cell line-derived neurotrophic factor (GDNF) stimulates the nigrostriatal dopaminergic pathway and improves motor functions in animal models of parkinsonism. Sinemet is currently the most widely used drug for treating Parkinson's disease. The present study has evaluated GDNF-Sinemet interactions in parkinsonian rhesus monkeys. Both GDNF and Sinemet, when given alone, significantly improved total parkinsonian scores. The response to Sinemet did not change after intracerebroventricular vehicle injections. In contrast, there was a functional interaction between GDNF and levodopa. When comparing the levodopa dose response before and after GDNF treatment, significant behavioral improvements were seen after trophic factor administration at every levodopa dose level except 500 mg. Adverse responses to Sinemet treatment alone in parkinsonian animals included vomiting, dykinesias, dystonias, and stereotypic movements. Combined GDNF-Sinemet treatment significantly reduced the occurrence of these levodopa-induced side effects, with a >90% decrease in adverse responses seen at the mid-Sinemet (250 mg levodopa-25 mg carbidopa) dose level. The only side effect from GDNF treatment was a transitory weight loss. Thus, combined GDNF-Sinemet treatment could be of therapeutic value in treating parkinsonism, by producing a greater functional response and by mitigating adverse responses to Sinemet treatment.

Chronic L-DOPA administration induces dyskinesias in the 1-methyl-4- phenyl-1,2,3,6-tetrahydropyridine-treated common marmoset (Callithrix Jacchus).

Dyskinesias occur in the majority of patients with Parkinson's disease chronically treated with L-DOPA and also occur in several nonhuman primate species after 1-methyl-4phenyl-1,2,3,6-tetrahydropyridine (MPTP) and L-DOPA treatment. The common marmoset (Callithrix jacchus) shows parkinsonian motor deficits after MPTP administration, and we now report dyskinesias occurring in this species during chronic L-DOPA exposure. Marmosets rendered chronically parkinsonian after MPTP administration were treated orally with L-DOPA plus carbidopa for 3 weeks. After several days the animals began to display chorea, choreoathetosis, and dystonia. The severity of dyskinesias varied between the animals, with the most severely parkinsonian animals displaying the most dyskinetic movements. Each animal showed an idiosyncratic pattern of dyskinesias, which was highly reproducible. These L-DOPA-primed animals also received other D2 D1, and mixed D1/D2 agonist drugs. Quinpirole, bromocriptine, pergolide, apomorphine, and A-77636 all produce dyskinesias that were identical in character to those seen after L-DOPA administration, but the D1 agonist A-77636 gradually abolished dyskinesias while preserving its antiparkinsonian activity. The MPTP-treated marmoset provides a useful model in which to study dyskinesias in Parkinson's disease and to examine new therapeutic strategies aimed at alleviating this common side effect of chronic dopamine replacement therapy.

Oral levodopa dose-response study in MPTP-induced hemiparkinsonian monkeys: assessment with a new rating scale for monkey parkinsonism.

Quantitative measures for the severity of MPTP-induced parkinsonism and response to antiparkinsonian interventions in monkeys have been lacking. We carried out an oral levodopa dose-response study in two rhesus monkeys whose left hemiparkinsonism was induced by intracarotid administration of MPTP. A newly developed clinical rating scale of monkey parkinsonism showed a consistent dose-response relationship for levodopa over the dosage range of 50-3,500 mg/day. Antiparkinsonian effects appeared at 200 mg/day and were optimal at 1,000-2,000 mg/day. Levodopa also reversed rotational behavior, improved movement times for both the impaired and opposite upper limb, and produced dyskinesias at high dosages. Thus, MPTP-induced hemiparkinsonism in monkeys closely resembles the human disease condition, is associated with sensitive response measures, and should prove valuable for assessing novel antiparkinsonian therapies.

Genetic toxicity of several antihypertensive drugs possessing a hydrazine group.

Mutagenicity and genotoxicity of antihypertensive drugs, ecarazine, budralazine, benzerazide, and carbidopa were compared with those of hydralazine whose genetic toxicity and carcinogenicity were well established. Ecarazine and budralazine as well as hydralazine showed apparent mutagenicity in Salmonella/microsome test using a strain TA 100 and weak mutagenicity in strains TA 97 and 2637. Benzerazide and carbidopa showed merely weak mutagenicity in TA 100. None of tested drugs except hydralazine exerted any positive result in hepatocyte primary culture (HPC)/DNA repair test, indicating no genotoxic activity of these hydrazine drugs.

Influence of carbidopa, an aromatic amino acid decarboxylase inhibitor, on the development of autoimmune hemolytic anemia in NZB mice.

Causal relationships of carbidopa and its related drugs on the development of spontaneous autoimmune hemolytic anemia (AIHA) in NZB mice were studied, and the following results were obtained: 1) Long term treatment with carbidopa (3 mg/kg/day) and levodopa (30 mg/kg/day) neither accelerated nor suppressed the development of spontaneous AIHA in NZB mice. 2) In mice treated with carbidopa/levodopa (3/30 mg/kg/day), microhematocrit levels were lower than those in the control mice on and after 20 weeks of age and showed a significant decrease at 66 weeks of age (P less than 0.05). The average anti-RBC antibody titers reached the maximum level 8 weeks earlier than the control group. 3) Microhematocrit levels in the alpha-methyldopa (60 mg/kg/day)-treated group were higher than those in the control group, and at 66 weeks of age, they were decreased below that in the control group. The elevation of anti-RBC antibody titers was slower than that in the control group. As the reason for the weak effectiveness of alpha-methyldopa on the incidence of AIHA, it might be considered that the dosage employed was not sufficiently high enough and/or it may be due to the species difference between man and animals. Further studies are necessary in order to draw a conclusion on the AIHA-inducing ability of carbidopa.