ß-Cells Different Vulnerability to the Parkinsonian Neurotoxins Rotenone, 1-Methyl-4-phenylpyridinium (MPP+) and 6-Hydroxydopamine (6-OHDA).

Neurotoxins such as rotenone, 1-methyl-4-phenylpyridinium (MPP+) and 6-hydroxydopamine (6-OHDA) are well known for their high toxicity on dopaminergic neurons and are associated with Parkinson's disease (PD) in murine models and humans. In addition, PD patients often have glucose intolerance and may develop type 2 diabetes (T2D), whereas T2D patients have higher risk of PD compared to general population. Based on these premises, we evaluated the toxicity of these three toxins on pancreatic ß-cell lines (INS-1 832/13 and MIN6) and we showed that rotenone is the most potent for reducing ß-cells viability and altering mitochondrial structure and bioenergetics in the low nanomolar range, similar to that found in dopaminergic cell lines. MPP+ and 6-OHDA show similar effects but at higher concentration. Importantly, rotenone-induced toxicity was counteracted by α-tocopherol and partially by metformin, which are endowed with strong antioxidative and cytoprotective properties. These data show similarities between dopaminergic neurons and ß-cells in terms of vulnerability to toxins and pharmacological agents capable to protect both cell types.

Striatal Dopamine Transporter Modulation After Rotigotine: Results From a Pilot Single-Photon Emission Computed Tomography Study in a Group of Early Stage Parkinson Disease Patients.

INTRODUCTION: Several in vitro data have reported negative interference by dopamine-agonists on the expression of dopamine transporter (DAT), whereas the majority of imaging studies have shown that neither L-dopa nor dopamine-agonists interfere with DAT availability. As yet, there are no in vivo studies on DAT expression after treatment with rotigotine. METHODS: We evaluated presynaptic nigrostriatal function in 8 patients with de novo Parkinson disease (age, 59 ± 6.2 years; male/female sex, 5/3) using 123-I- N-ω-fluoropropyl-2-ß-carbomethoxy-3-ß-(4-iodophenyl)nortropane (FP-CIT) single-photon emission computed tomography before and after 3 months of treatment with rotigotine (mean dose, 7.75 ± 1.98 mg). For data analysis, specific (left and right caudate, left and right putamen) to nonspecific (occipital cortex) binding ratios, putamen-to-caudate ratios, and asymmetry indices were calculated. RESULTS: After rotigotine, motor symptoms improved in all patients (Unified Parkinson Disease Rating Scale III mean score, 11.88 ± 2.59 vs 7.63 ± 1.92 on therapy; P = 0.0022). Striatal FP-CIT levels showed a significant improvement in every patient at the follow-up scan. Comparisons between before and after treatment in the whole group revealed a significant improvement in FP-CIT uptake in both caudate and putamen (P < 0.001 in each nucleus). Putamen-to-caudate ratio and asymmetry indices did not show any significant difference before and after treatment. DISCUSSION: Although the study population was small, we found DAT overexpression after chronic treatment with rotigotine, presumably related to its pharmacological profile. The DAT upregulation by rotigotine in an opposite direction with respect to early Parkinson disease compensatory mechanisms might reduce the risk of dyskinesia, but it could imply less motor benefit because of less stimulation by the dopamine itself on dopaminergic receptors.

Serum uric acid levels and different phases of illness in bipolar I patients treated with lithium.

Recent findings support the role of purinergic system dysfunction in the pathophysiology of bipolar disorder (BD). The present study aimed to evaluate the pattern of serum uric acid levels in a sample of 98 BD I patients followed-up prospectively in a naturalistic study and treated with lithium monotherapy or in association with other mood stabilizers (valproate or carbamazepine), in relation to different phases of illness and to pharmacological treatment. The results showed that uric acid levels were significantly higher in patients suffering from a manic/mixed episode, than in those euthymic or during a depressive phase. Further, these levels were related to the Clinical Global Impression-Bipolar Version (CGI-BP) scale score for the severity of manic symptoms. A positive correlation was found also with male sex and with serum lithium levels. These findings suggest that a dysregulation of the purinergic system may occur during manic/mixed episodes, and they support a possible role of serum uric acid levels as a state-dependent marker of BD manic phases.

Acetaldehyde and parkinsonism: role of CYP450 2E1.

The present review update the relationship between acetaldehyde (ACE) and parkinsonism with a specific focus on the role of P450 system and CYP 2E1 isozyme particularly. We have indicated that ACE is able to enhance the parkinsonism induced in mice by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, a neurotoxin able to damage the nigrostriatal dopaminergic pathway. Similarly diethyldithiocarbamate, the main metabolite of disulfiram, a drug widely used to control alcoholism, diallylsulfide (DAS) and phenylisothiocyanate also markedly enhance the toxin-related parkinsonism. All these compounds are substrate/inhibitors of CYP450 2E1 isozyme. The presence of CYP 2E1 has been detected in the dopamine (DA) neurons of rodent Substantia Nigra (SN), but a precise function of the enzyme has not been elucidated yet. By treating CYP 2E1 knockout (KO) mice with the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, the SN induced lesion was significantly reduced when compared with the lesion observed in wild-type animals. Several in vivo and in vitro studies led to the conclusion that CYP 2E1 may enhance the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine toxicity in mice by increasing free radical production inside the dopaminergic neurons. ACE is a good substrate for CYP 2E1 enzyme as the other substrate-inhibitors and by this way may facilitate the susceptibility of dopaminergic neurons to toxic events. The literature suggests that ethanol and/or disulfiram may be responsible for toxic parkinsonism in human and it indicates that basal ganglia are the major targets of disulfiram toxicity. A very recent study reports that there are a decreased methylation of the CYP 2E1 gene and increased expression of CYP 2E1 mRNA in Parkinson's disease (PD) patient brains. This study suggests that epigenetic variants of this cytochrome contribute to the susceptibility, thus confirming multiples lines of evidence which indicate a link between environmental toxins and PD.

[Long-term treatment of bipolar disorder: how should we use lithium salts?]. / Trattamento a lungo termine del disturbo bipolare: quale impiego dei sali di litio nella pratica clinica?

UNLABELLED: Despite the great quantity of evidence supporting the efficacy of lithium in the maintenance treatment of bipolar disorder (BD), its use has often been limited because of issues about the management of this compound. W aimed to evaluate the use of lithium in common clinical practice and to identify possible relationships between the trend over time of serum lithium levels and clinical course of the illness. METHODS: 98 patients with bipolar I and bipolar II disorder (DSM-IV-TR) on maintenance treatment with lithium salts were recruited and followed up in a naturalistic trial at the Day Hospital of Psychiatric Clinic of Pisa. Diagnosis was confirmed using a structured interview, the SCID-I. During symptom assessment, the Clinical Global Impression-Bipolar Version Scale (CGI-BP) was used. RESULTS: The sample is made up mainly of BI patients (87.8%) and lithium is used in association with anticonvulsants in 63%. Less than half of the sample (48%) presents average serum lithium levels in the therapeutic range (0.5-0.8 mEq/L); serum values of lithium within the range were seen more frequently in patients with manic/mixed episode, with manic/mixed polarity of onset, with a greater number of previous episodes, with a higher percentage of rapid cycling and in subjects treated with lithium associated with anticonvulsants. During the follow-up patients with average serum lithium levels within the therapeutic range obtained a clinical improvement in a significantly greater proportion compared to patients with average serum lithium levels lower than 0.50 mEq/L. DISCUSSION: In clinical practice, lithium is often used at doses determining serum levels at the lower limits of the therapeutic range. Preliminary data on the prospective course of the illness support the importance of maintaining serum values of lithium within the therapeutic range.

Behavioral, neurochemical, and electrophysiological changes in an early spontaneous mouse model of nigrostriatal degeneration.

In idiopathic Parkinson's disease, clinical symptoms do not emerge until consistent neurodegeneration has occurred. The late appearance of symptoms implies the existence of a relatively long preclinical period during which several disease-induced neurochemical changes take place to mask the existence of the disease and delay its clinical manifestations. The aim of this study was to examine the neurochemical, neurophysiological, and behavioral changes induced by the loss of nigrostriatal innervation in the En1+/-;En2-/- mouse, in the 10 months following degeneration, compared to En2 null mutant mice. Behavioral analysis (Pole-test, Beam-walking test, and Inverted grid test) and field potential recordings in the striatum indicated that loss of ~70% of nigrostriatal neurons produced no significant functional effects until 8 months of age, when En1+/-;En2-/- animals started to show frank motor deficits and electrophysiological alterations in corticostriatal plasticity. Similarly, alterations in dopamine homeostasis, dopamine turnover, and dopamine innervation were observed in aged animals compared to young En1+/-;En2-/- mice. These data suggests that in En1+/-;En2-/- mice nigrostriatal degeneration in the substantia nigra is functionally compensated.

Characterization of the Engrailed mutant mice as experimental models for Parkinson's disease.

Engrailed genes are homeodomain-containing transcription factors necessary for the development and maintenance of mesencephalic dopaminergic neurons. Deletion in the Engrailed genes has been shown to affect the survival of mesencephalic dopaminergic neurons both during development and in the adult. Here we describe for the first time a significant reduction in striatal dopamine levels in En1+/-;En2+/- mice compared with their En2+/- littermates, accompanied by a modest reduction in the number of nigral DA neurons. Our results strengthen previous evidence indicating Engrailed genes as survival factors for mature dopaminergic neurons. Furthermore, our data suggest a role for these transcription factors in the maintenance of synaptic dopaminergic neurotransmission in adult neurons.

TSH-Dependent expression of the LDL receptor-associated protein (RAP) in thyroid epithelial cells.

The low density lipoprotein (LDL) receptor-associated protein (RAP) is an endoplasmic reticulum (ER)-resident molecular chaperone for several LDL receptor family members and it also binds to thyroglobulin (Tg), the thyroid hormone precursor. Disruption of the RAP gene in thyrocytes results in impaired Tg secretion. To gain further insights into the function of RAP in the thyroid, we investigated whether its expression in thyrocytes is regulated by thyroid-stimulating hormone (TSH), a feature common to all proteins involved in thyroid hormone secretion. We found by immunofluorescence that in FRTL-5 cells cultured in the presence of TSH, RAP is expressed intracellularly. The levels of expression increased after exposure to TSH, beginning at 48 hours, in a concentration-dependent manner as observed by immunofluorescence and Western blotting. Expression of RAP was also increased by TSH in primary cultures of human thyrocytes as observed by Western blotting. In hypothyroid mice with high serum TSH, RAP was markedly increased compared with euthyroid mice as observed by immunohistochemistry and Western blotting. Based on these findings, we concluded that RAP is expressed by thyrocytes in a TSH-dependent manner, both in cultured thyroid cells and in vivo.

Involvement of cytochrome P450 2E1 in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced mouse model of Parkinson's disease.

Elucidation of the biochemical steps leading to the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced degeneration of the nigrostriatal dopamine (DA) pathway has provided new clues to the pathophysiology of Parkinson's disease. In line with the enhancement of MPTP toxicity by diethyldithiocarbamate (DDC), here we demonstrate how other cytochrome P450 (CYP) 2E1 inhibitors, such as diallyl sulphide (DAS) and phenylethylisothiocyanate (PIC), also potentiate the selective DA neurone degeneration in C57/bl mice. In addition, we show that CYP 2E1 is present in the brain and in the basal ganglia of this mouse strain, as measured by RT-PCR, western blot analysis and immunohistochemistry. A kinetic analysis of MPTP and its metabolites, by means of the microdialysis technique in the striatum, indicates that no detoxification metabolic pathway is affected by any of these inhibitors. This does not rule out, however, that an undetected detoxification pathway involving CYP 2E1 is operating. In order to provide direct evidence for this isozyme involvement, CYP 2E1 knockout mice were challenged with MPTP or the combined treatment. Here we show that these transgenic mice have a low sensitivity to MPTP alone, similar to their wild-type counterparts, suggesting that it is likely that transgenic mice compensate for the missing enzyme. However, DDC pretreatment completely fails to enhance MPTP toxicity in CYP 2E1 knockout mice, whereas this enhancement is regularly present in wild-type animals. This study indicates that the occurrence of CYP 2E1 in C57/bl mouse brain is relevant to MPTP toxicity, and suggests that this isozyme may have a detoxificant role related to the efflux transporter of the toxin.

Noradrenergic Modulation of Methamphetamine-Induced Striatal Dopamine Depletion.

Noradrenergic (NE) neurons belonging to the locus coeruleus (LC), much more than the A1 and A2 NE areas, are lost in Parkinson's disease (PD). In this study, we reproduced the selective pattern of NE loss involving axons arising from the LC using the selective neurotoxin N-(-2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) (50 mg/kg). In these experimental conditions, we investigated whether NE loss potentiates methamphetamine-induced striatal dopamine (DA) depletion in mice and in rats. Administration of a moderate dose of methamphetamine to C57B1/6N mice or Sprague-Dawley rats produced only a partial striatal DA depletion 7 days after drug administration. Pretreatment with DSP-4, in both animal species, significantly enhanced methamphetamine-induced striatal DA depletion. Administration of a lower dose of methamphetamine did not decrease striatal DA levels when injected alone, but produced a significant decrease in striatal DA when given to DSP-4-pretreated rodents. Moreover, we found that agents reducing the noradrenergic activity (i.e., the alpha-2 agonist clonidine) enhanced, whereas alpha-2 antagonists decreased, methamphetamine toxicity. Enhancement of methamphetamine toxicity did not occur if the noradrenergic lesion was produced 12 hr after methamphetamine administration. By contrast, exacerbation of methamphetamine toxicity in NE-depleted animals was accompanied by increased extracellular DA levels measured with brain dialysis and by a more severe acute DA depletion measured in striatal homogenates.