Case of levodopa toxicity from ingestion of Mucuna gigantea.

Hawai'i is home to 1000 native species of flowering plants. Mucuna gigantea is one such Hawaiian species which has been studied as affordable sustenance and as a cover crop in developing countries. Mucuna gigantea and other Mucuna species (spp.) in general, are known to contain natural levodopa and its utility in the treatment of Parkinson's Disease has also been evaluated. Levodopa is converted in the periphery into dopamine which can then act on dopamine receptors to cause nausea, vomiting, arrhythmias, and hypotension. We describe a case in which a patient presents with abdominal pain, nausea, and vomiting after legume ingestion. The bean was ultimately identified as Mucuna gigantea and the patient was diagnosed with levodopa-induced gastrointestinal toxicity from consumption of the legume. A literature review was conducted using the database search engines, Biological Abstracts and PubMed, with a broad combination of keywords of which include "mucuna, "gigantean," "levodopa," "l-dopa," "toxicity," and the association between Mucuna gigantea ingestion and levodopa toxicity is discussed. These findings expand the differential diagnosis of abdominal pain associated with nausea and vomiting in the correct clinical context.

Parkinsonism in patients with a history of amphetamine exposure.

We recently found a higher rate of prolonged amphetamine exposure in patients diagnosed with Parkinson's disease (PD) than in spouse/caregiver controls. Since distinguishing features have been described in some patients with parkinsonism due to environment exposures (e.g., manganese), we sought to compare the clinical features of patients with PD with prolonged amphetamine exposure with unexposed patients with PD. Prolonged exposure was defined as a minimum of twice a week for >or=3 months, or weekly use >or=1 year. We reviewed the clinical records of patients with PD who had participated in a telephone survey of drug and environmental exposures and compared the clinical features of patients with a history of prolonged amphetamine exposure to patients who had no such exposure. Records were available for 16 of 17 (94%) patients with prior amphetamine exposure and 127 of 137 (92%) of those unexposed. Age at diagnosis was younger in the amphetamine-exposed group (49.8 +/- 8.2 years vs. 53.1 +/- 7.4 years; P < 0.05), but other features, including presenting symptoms, initial and later treatments, development of motor fluctuations, and MRI findings were similar between these groups. Because we did not detect clinical features that differentiate parkinsonism in patients with prolonged amphetamine exposure, research to determine whether amphetamine exposure is a risk factor for parkinsonism will require detailed histories of medication and recreational drug use.

Obstructive acute renal failure related to amantadine intoxication.

We report the case of a 69-year-old woman with seizures and acute renal failure with hyperkalemia. She presented with bladder turgescence and hydronephrosis on admission and was diagnosed as obstructive acute renal failure. Urethral catheterization was performed after a single-session hemodialysis. It resulted in immediate improvement of renal function and consciousness, and subsequent disappearance of seizures. Improvement of serum creatinine level to 0.7 from 10.6 mg/dL was associated with a fall in blood level of amantadine hydrochloride from 4.40 to 0.47 microg/mL. Physicians should be aware of urinary retention in patients treated with amantadine as a first sign of intoxication that could lead if untreated to obstructive acute renal failure. And we recommend to check the overdose symptoms, even those with normal renal function, treated with amantadine.

Status epilepticus in a pediatric patient with amantadine overdose.

A 2-year-old boy who ingested 0.8-1.5 g of amantadine developed status epilepticus. One hour later, the child presented with agitation, diaphoresis, and vomiting. He was admitted to the pediatric emergency department 2 hours later. Generalized seizures evolved to status epilepticus, with alternating generalized tonic-clonic and partial seizures, over a period of 7 hours. Other initial clinical signs were sinusal tachycardia and reactive bilateral mydriasis. All symptoms resolved within 20 hours, with a good recovery; the child was released from the hospital on day 3.

A new model to study compensatory mechanisms in MPTP-treated monkeys exhibiting recovery.

The cardinal symptoms in Parkinson's disease (PD), akinesia, rigidity and tremor, are only observed when the striatal level of dopamine is decreased by 60-80%. During the preclinical phase of PD, compensatory mechanisms are probably involved in delaying the appearance of motor symptoms. In a MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) monkey model of PD, a spontaneous recovery has been reported after initial intoxication suggesting that compensatory mechanisms are activated in this model as well. Assuming that mechanisms are similar in these phenomena, the study of recovery in monkeys following MPTP intoxication may enable identification of compensatory mechanisms involved in the preclinical phase of PD. In order to maximize the temporal similarity between PD and the MPTP model, we assessed a new progressive monkey model in which spontaneous recovery is expressed systematically and to characterize it based on (1) its behavioural features, and (2) the presence of compensatory mechanisms revealed by an immunohistological approach comparing dopaminergic and serotoninergic innervation between monkeys either exhibiting behavioural recovery or stable motor symptoms. This immunohistological study focused on the substantia nigra, striatum and pallidum, and their anatomical and functional subdivisions: sensorimotor, associative and limbic. The behavioural analysis revealed that with progressive MPTP intoxication motor symptoms were initially expressed in all monkeys. Observable recovery from these symptoms occurred in all monkeys (7/7) within 3-5 weeks after the last MPTP injection, and most exhibited a full recovery. In contrast, acute intoxication induced stable motor symptoms. Despite this obvious behavioural difference, immunohistological methods revealed that the loss of dopaminergic cell bodies in substantia nigra was substantial and similar in both MPTP-treated groups. However, quantification of fibres revealed that recovered monkeys displayed more dopaminergic and serotoninergic fibres than those with stable motor symptoms in sensorimotor and associative territories of striatum and more dopaminergic fibres in internal pallidum. This study provides a new model of PD where all monkeys expressed functional recovery from motor symptoms despite a large dopaminergic neuronal loss. The immunohistological results suggest that both dopamine and serotonin could be implicated in the compensatory mechanisms.

A novel systemically active caspase inhibitor attenuates the toxicities of MPTP, malonate, and 3NP in vivo.

Molecular machinery involved in apoptosis plays a role in neuronal death in neurodegenerative disorders such as Parkinson's disease (PD) and Huntington's disease (HD). Several caspase inhibitors, such as the well-known peptidyl inhibitor carbobenzoxy-Val-Ala-Asp-fluoromethylketone (zVADfmk), can protect neurons from apoptotic death caused by mitochondrial toxins. However, the poor penetrability of zVADfmk into brain and toxicity limits its use therapeutically. In the present study, a novel peptidyl broad-spectrum caspase inhibitor, Q-VD-OPH, which offers improvements in potency, stability, and toxicity over zVADfmk, showed significant protection against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), 3-nitropropionic acid (3NP), and malonate toxicities. Q-VD-OPH significantly reduced dopamine depletion in striatum produced by MPTP administration and prevented MPTP-induced loss of dopaminergic neurons in the substantia nigra. It significantly reduced the size of striatal lesions produced by intrastriatal malonate injections and systemic administration of 3NP. Western blots performed on tissues from the midbrain following administration of MPTP or the striatum in 3NP-treated animals showed increases of the active forms of caspase-9 and caspase-8, as well as the caspase-8-mediated proapoptotic protein Bid, which were inhibited Q-VD-OPH treatment. These findings suggest that systematically active broad-spectrum caspase inhibitors maybe useful in the treatment of neurodegenerative diseases such as PD and HD.

Role of dopamine transporter against MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) neurotoxicity in mice.

We investigated the alterations of dopamine transporter (DAT)-immunopositive cells against MPTP neurotoxicity, in comparison with tyrosine hydroxylase (TH)-immunopositive neurons and glial fibrillary acidic protein (GFAP)-immunopositive cells. This study showed that DAT and TH immunoreactivity was decreased gradually in the striatum and substantia nigra of mice after MPTP treatment. The patterns of the intense TH-immunoreactive fibers and cell bodies were similar to those of DAT-immunoreactive fibers and cell bodies in the striatum and substantia nigra of mice after MPTP treatment. In contrast, GFAP immunoreactivity was increased gradually in the striatum and substantia nigra after MPTP treatment. In our double-labeled immunostaining with anti-DAT and anti-GFAP antibodies, DAT immunoreactivity was observed only in the nigral dopaminergic neurons, but not in the reactive astrocytes. The present results provide further evidence that the functional damage of DAT may precede dopaminergic neuronal death after MPTP treatment, although the decrease in the number of TH-immunopositive neurons was more pronounced than that in the number of DAT-immunopositive neurons. Furthermore, our findings demonstrate that MPTP can selectively injure the dopaminergic neurons which DAT proteins are predominantly distributed on the striatum and substantia nigra. The results provide beneficial information for MPTP-induced neurodegeneration of the nigrostriatal dopaminergic neuronal pathway.

Alpha-synuclein up-regulation in substantia nigra dopaminergic neurons following administration of the parkinsonian toxin MPTP.

Mutations in alpha-synuclein cause a form of familial Parkinson's disease (PD), and wild-type alpha-synuclein is a major component of the intraneuronal inclusions called Lewy bodies, a pathological hallmark of PD. These observations suggest a pathogenic role for alpha-synuclein in PD. Thus far, however, little is known about the importance of alpha-synuclein in the nigral dopaminergic pathway in either normal or pathological situations. Herein, we studied this question by assessing the expression of synuclein-1, the rodent homologue of human alpha-synuclein, in both normal and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-intoxicated mice. In normal mice, detectable levels of synuclein mRNA and protein were seen in all brain regions studied and especially in ventral midbrain. In the latter, there was a dense synuclein-positive nerve fiber network, which predominated over the substantia nigra, and only few scattered synuclein-positive neurons. After a regimen of MPTP that kills dopaminergic neurons by apoptosis, synuclein mRNA and protein levels were increased significantly in midbrain extracts; the time course of these changes paralleled that of MPTP-induced dopaminergic neurodegeneration. In these MPTP-injected mice, there was also a dramatic increase in the number of synuclein-immunoreactive neurons exclusively in the substantia nigra pars compacta; all synuclein-positive neurons were tyrosine hydroxylase-positive, but none coexpressed apoptotic features. These data indicate that synuclein is highly expressed in the nigrostriatal pathway of normal mice and that it is up-regulated following MPTP-induced injury. In light of the synuclein alterations, it can be suggested that, by targeting this protein, one may modulate MPTP neurotoxicity and, consequently, open new therapeutic avenues for PD.

Novel free radical spin traps protect against malonate and MPTP neurotoxicity.

Both malonate and 1-methyl-4-phenyl-1,2,5,6 tetrahydropyridine (MPTP) are neurotoxins which cause energy depletion, secondary excitotoxicity, and free radical generation. Malonate is a reversible inhibitor of succinate dehydrogenase, while MPTP is metabolized to 1-methyl-4-phenylpyridinium, an inhibitor of mitochondrial complex I. We examined the effects of pretreatment with the cyclic nitrone free radical spin trap MDL 101,002 on malonate and MPTP neurotoxicity. MDL 101,002 produced dose-dependent neuroprotection against malonate-induced striatal lesions. MDL 101, 002 produced significant protection against MPTP induced depletions of dopamine and its metabolites. MDL 101,002 also significantly attenuated MPTP-induced increases in striatal 3-nitrotyrosine concentrations. The free radical spin trap tempol also produced significant protection against MPTP neurotoxicity. These findings provide further evidence that free radical spin traps produce neuroprotective effects in vivo and suggest that they may be useful in the treatment of neurodegenerative diseases.

Creatine and cyclocreatine attenuate MPTP neurotoxicity.

Systemic administration of 1-methyl-4-phenyl-1,2,3, 6-tetrahydropyridine (MPTP) produces parkinsonism in experimental animals by a mechanism involving impaired energy production. MPTP is converted by monoamine oxidase B to 1-methyl-4-phenylpyridinium (MPP+), which blocks complex I of the electron transport chain. Oral supplementation with creatine or cyclocreatine, which are substrates for creatine kinase, may increase phosphocreatine (PCr) or cyclophosphocreatine (PCCr) and buffer against ATP depletion and thereby exert neuroprotective effects. In the present study we found that oral supplementation with either creatine or cyclocreatine produced significant protection against MPTP-induced dopamine depletions in mice. Creatine protected against MPTP-induced loss of Nissl and tyrosine hydroxylase immunostained neurons in the substantia nigra. Creatine and cyclocreatine had no effects on the conversion of MPTP to MPP+ in vivo. These results further implicate metabolic dysfunction in MPTP neurotoxicity and suggest a novel therapeutic approach, which may have applicability for Parkinson's disease.

Methamphetamine-induced changes in antioxidant enzymes and lipid peroxidation in copper/zinc-superoxide dismutase transgenic mice.

The present study was conducted to investigate the effects of methamphetamine (METH)-induced toxicity on brain cortical and striatal antioxidant defense systems. Because METH-induced toxicity is attenuated in copper/zinc-superoxide dismutase transgenic (Cu/Zn-SOD-Tg) mice, we sought to determine if METH had differential effect on antioxidant enzymes on these mice in comparison to non-Tg mice. METH (4 x 1) mg/kg) induced a significant decrease in Cu/Zn-SOD activity in the cortical region without altering striatal enzymatic activity in non-Tg mice; whereas homozygous SOD-Tg mice showed a significant increase in the striatum. In addition, METH caused decrease in catalase (CAT) activity in the striatum of non-Tg mice and significant increase in the cortex of homozygous SOD-Tg mice. METH also induced decreases in glutathione peroxidase (GSH-Px) in both cortical and striatal regions of non-Tg mice and in the striatum of heterozygous SOD-Tg mice. Lipid peroxidation was increased in both cortices and striata of non-Tg and heterozygous SOD-Tg, mice, whereas the homozygous SOD-Tg mice were not affected. These results are discussed in terms of their substantiation of a role for oxygen-based radicals in METH-induced toxicity in rodents.

Glia protect fetal midbrain dopamine neurons in culture from L-DOPA toxicity through multiple mechanisms.

Mesencephalic glia produce soluble factors that protect dopamine neurons from L-DOPA toxicity. The chemical composition of these soluble factors is unknown. We investigated the protective effect against L-DOPA neurotoxicity in midbrain dopamine neurons of fractions of different molecular size of glia conditioned medium and candidate neuroprotective agents produced by glia including neurotrophic factors and antioxidants. Protective effects were evaluated according to the number of tyrosine hydroxylase immunoreactive cells, high affinity dopamine uptake and levels of quinones. Both fractions of glia conditioned medium, smaller and larger than 10kD, protected against L-DOPA, but the fraction of smaller molecular size, that contains small free radical scanvenger molecules, was more effective than the fraction of larger molecular size, that contains large neurotrophic peptides. Among the neurotrophic factors GDNF and BDNF totally prevented L-DOPA neurotoxicity, while NGF and bFGF were less effective. However, only NGF significantly reduced the elevation of quinones induced by L-DOPA. Ascorbic acid, at the concentration found in glia conditioned medium, provided partial protective effect against L-DOPA toxicity. Glutathione, had neurotrophic effects on untreated midbrain dopamine neurons and prevented the effect of L-DOPA. In conclusion, the protective effect against L-DOPA neurotoxicity by glia conditioned medium is mediated by several compounds including neurotrophic factors and small antioxidants.

Effects of L-DOPA-therapy on dopamine D2 receptor mRNA expression in the striatum of MPTP-intoxicated parkinsonian monkeys.

The cellular expression of dopamine D2 receptor mRNA was examined in striatal (caudate nucleus and putamen) neurones of 9 Macaca fascicularis monkeys rendered parkinsonian by systemic injection of MPTP. Messenger RNA abundance was determined by quantitative in situ hybridization using human-specific 35S-labelled oligonucleotides. Control monkeys were untreated and received neither MPTP nor L-DOPA while the rest were rendered parkinsonian and received chronic levodopa therapy to induce dyskinesia. In the control brains a strong dopamine D2 receptor hybridization signal was detected overlying medium-sized and some large neurons in both the caudate nucleus and putamen. Neurons from the lateral and medial regions of the caudate nucleus, and from the dorsal and ventral regions of the putamen were analysed separately. A significant increase in the cellular abundance of dopamine D2 receptor mRNA was seen in the striatum of MPTP-treated monkeys; this increase being restricted to the population of medium-sized striatal cells. No such increase in dopamine D2 receptor mRNA was observed in (dyskinetic) L-DOPA-treated monkeys suggesting that levodopa-therapy normalises D2 receptor expression in post-synaptic striatal cells. The cellular abundance of dopamine D2 receptor mRNA expressed by large striatal neurons (putative cholinergic cells) was unaffected by either MPTP treatment or levodopa therapy. The implications of these findings for the development of levodopa-induced dyskinesias is discussed.

Acute overdose of a new dopamine agonist, CV 205-502.

CV 205-502 is a new dopamine agonist used for hyperprolactinaemia. We report a case of acute overdose (one month treatment, i.e. 2.25 mg) in a 25-year-old male patient. Clinical symptoms were restricted to nausea and mild hypotension. Treatment consisting of ipeca cuanha, charcoal and intravenous fluids allowed a rapid, successful outcome. This case illustrates the particular features of CV 205-502 intoxication when compared to other dopamine agonists, pointing out the tolerance of the drug which can be considered for wider indications and safer prescriptions.