Presence of tetrahydroisoquinoline and 1-methyl-tetrahydro-isoquinoline in foods: compounds related to Parkinson's disease

Design, synthesis, and biological evaluation of THIQ as antidepressive agents

7-substituted tetrahydroisoquinolines derivatives were designed, synthesized, and evaluated for neuroprotective properties. We summarized the preliminary structure activity relationships (SAR). Compound 3i was screened as a hit compound and its antidepressant activity was evaluated by employing the forced swimming test, tail suspension test. Additionally, ADMET profile (absorption, distribution, metabolism, excretion and toxicity properties) of the compound 3i was predicted in order to evaluate their lead-like properties and safety. The interaction of compound 3i bound to MAO-A was explored using molecular docking and molecular dynamics simulation. Results of biological studies revealed that the compound 3i exhibited almost equal antidepressant activity compared with magnoflorine. Compound 3i is predicted to possess good drug like properties and safety based on ADMET profile predictions. This work provides ideas for the drugs discovery of antidepressant agents.

Quantitative Determination of Endogenous Tetrahydroisoquinolines, Potential Parkinson's Disease Biomarkers, in Mammals

Current diagnostic options for Parkinson's disease are very limited and primarily based on characteristic clinical symptoms. Thus, there are urgent needs for reliable biomarkers that enable us to diagnose the disease in the early stages, differentiate it from other atypical Parkinsonian syndromes, monitor its progression, increase knowledge of its pathogenesis, and improve the development of potent therapies. A promising group of potential biomarkers are endogenous tetrahydroisoquinoline metabolites, which are thought to contribute to the multifactorial etiology of Parkinson's disease. The aim of this critical review is to highlight trends and limitations of available traditional and modern analytical techniques for sample pretreatment (extraction and derivatization procedures) and quantitative determination of tetrahydroisoquinoline derivatives in various types of mammalian fluids and tissues (urine, plasma, cerebrospinal fluid, brain tissue, liver tissue). Particular attention is paid to the most sensitive and specific analytical techniques, involving immunochemistry and gas or liquid chromatography coupled with mass spectrometric, fluorescence, or electrochemical detection. The review also includes a discussion of other relevant agents proposed and tested in Parkinson's disease.

Neurotoxicity and Underlying Mechanisms of Endogenous Neurotoxins

Endogenous and exogenous neurotoxins are important factors leading to neurodegenerative diseases. In the 1980s, the discovery that 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) contributes to Parkinson's disease (PD) symptoms led to new research investigations on neurotoxins. An abnormal metabolism of endogenous substances, such as condensation of bioamines with endogenous aldehydes, dopamine (DA) oxidation, and kynurenine pathway, can produce endogenous neurotoxins. Neurotoxins may damage the nervous system by inhibiting mitochondrial activity, increasing oxidative stress, increasing neuroinflammation, and up-regulating proteins related to cell death. This paper reviews the biological synthesis of various known endogenous neurotoxins and their toxic mechanisms.

Effects of Natural Monoamine Oxidase Inhibitors on Anxiety-Like Behavior in Zebrafish

Monoamine oxidases (MAO) are a valuable class of mitochondrial enzymes with a critical role in neuromodulation. In this study, we investigated the effect of natural MAO inhibitors on novel environment-induced anxiety by using the zebrafish novel tank test (NTT). Because zebrafish spend more time at the bottom of the tank when they are anxious, anxiolytic compounds increase the time zebrafish spend at the top of the tank and vice versa. Using this paradigm, we found that harmane, norharmane, and 1,2,3,4-tetrahydroisoquinoline (TIQ) induce anxiolytic-like effects in zebrafish, causing them to spend more time at the top of the test tank and less time at the bottom. 2,3,6-trimethyl-1,4-naphtoquinone (TMN) induced an interesting mix of both anxiolytic- and anxiogenic-like effects during the first and second halves of the test, respectively. TIQ was unique in having no observable effect on general movement. Similarly, a reference MAO inhibitor clorgyline—but not pargyline—increased the time spent at the top in a concentration-dependent manner. We also demonstrated that the brain bioavailability of these compounds are high based on the ex vivo bioavailability assay and in silico prediction models, which support the notion that the observed effects on anxiety-like behavior in zebrafish were most likely due to the direct effect of these compounds in the brain. This study is the first investigation to demonstrate the anxiolytic-like effects of MAO inhibitors on novel environment-induced anxiety in zebrafish.

1-Methyl-1,2,3,4-tetrahydroisoquinoline - The toxicological research on an exo/endogenous amine with antidepressant-like activity - In vivo, in vitro and in silico studies

BACKGROUND

1-Methyl-1,2,3,4-tetrahydroisoquinoline (1MeTIQ) demonstrates significant neuroprotective activity. It can interact with agonistic conformation of dopamine (DA) receptors. 1MeTIQ inhibits the formation of 3,4-dihydroxyphenylacetic acid as well as production of free radicals and shifts DA catabolism toward COMT-dependent O-methylation. 1MeTIQ inhibits both MAO-A and B enzymes activity and increases neurotransmitters levels in the brain. It shows significant antidepressant-like effect in forced swim test (FST) in rats. This compound might be effective for depression therapy in a clinical setting but its success is determined not only by good efficacy, but also by an acceptable its ADMET profile. The use of combination in silico prediction with in vivoand in vitro studies greatly simplifies the search for new, safer and effectively acting drugs.

METHODS

The aim of this study was to investigate the degree of histopathological changes in different rats tissues after acute and chronic administration of 1MeTIQ. Additionally, prediction of its properties in terms of absorption, distribution, metabolism, elimination and toxicity in the human body was performed.

RESULTS

The obtained data did not show extensive and significant toxic effects of tested substance in in vivo and in vitro studies in rats, and in silico ADMET prediction.

CONCLUSIONS

These results can help to discover a new effective and safe antidepressant substance and have important significance in the treatment of depression in clinic. Additionally, the use in the treatment of depression substance with neuroprotective, antioxidant and antidepressant-like effects in the CNS and existing endogenously might be also beneficial in controlling the adverse CNS inflammatory processes accompanying depression.

Salsolinol-neurotoxic or Neuroprotective?

Salsolinol (6,7-dihydroxy-1-methyl-1,2,3,4-tetrahydroisoquinoline), widely available in many edibles, is considered to alter the function of dopaminergic neurons in the central nervous system and thus, multiple hypotheses on its either physiological and/or pathophysiological role have emerged. The aim of our work was to revisit its potentially neurotoxic and/or neuroprotective role through a series of both in vitro and in vivo experiments. Salsolinol in the concentration range 10-250 μM did not show any significant release of lactate dehydrogenase from necrotic SH-SY5Y cells and was able in the concentration of 50 and 100 μM to rescue SH-SY5Y cells from death induced by H₂O₂. Its neuroprotective effect against neurotoxin 6-hydroxydopamine was also determined. Salsolinol was found to decrease significantly the reactive oxygen species level in SH-SY5Y cells treated by 500 μM H₂O₂ and the caspase activity induced by 300 μM of H₂O₂ or 100 μM of 6-hydroxydopamine. Serum levels of TNFα and CRP of salsolinol-treated rats were not significantly different from control animals. Both TNFα and CRP served as indirect markers of neurotoxicity and/or neuroprotection. Although the neurotoxic properties of salsolinol have numerously been emphasized, its neuroprotective properties should not be neglected and need greater consideration.

Salsolinol: an Unintelligible and Double-Faced Molecule-Lessons Learned from In Vivo and In Vitro Experiments

Salsolinol (1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline) is a tetrahydroisoquinoline derivative whose presence in humans was first detected in the urine of Parkinsonian patients on l-DOPA (l-dihydroxyphenylalanine) medication. Thus far, multiple hypotheses regarding its physiological/pathophysiological roles have been proposed, especially related to Parkinson’s disease or alcohol addiction. The aim of this review was to outline studies related to salsolinol, with special focus on in vivo and in vitro experimental models. To begin with, the chemical structure of salsolinol together with its biochemical implications and the role in neurotransmission are discussed. Numerous experimental studies are summarized in tables and the most relevant ones are stressed. Finally, the ability of salsolinol to cross the blood–brain barrier and its possible double-faced neurobiological potential are reviewed.

Mitochondrial Dysfunction in Parkinson’s Disease

Parkinson’s disease (PD) is one of the most common neurodegenerative disorders where oxidative stress and mitochondrial dysfunction have been implicated as etiological factors. Mitochondria are the major producers of reactive oxygen species (ROS) that can have damaging effects to cellular macromolecules leading to neurodegeneration. The most compelling evidence for the role of mitochondria in the pathogenesis of PD has been derived from toxicant-induced models of parkinsonism. Over the years, epidemiological studies have suggested a link between exposure to environmental toxins such as pesticides and the risk of developing PD. Data from human and experimental studies involving the use of chemical agents like paraquat, diquat, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, rotenone and maneb have provided valuable insight into the underlying mitochondrial mechanisms contributing to PD and associated neurodegeneration. In this review, we have discussed the role of mitochondrial ROS and dysfunction in the pathogenesis of PD with a special focus on environmental agent-induced parkinsonism. We have described the various mitochondrial mechanisms by which such chemicals exert neurotoxicity, highlighting some landmark epidemiological and experimental studies that support the role of mitochondrial ROS and oxidative stress in contributing to these effects. Finally, we have discussed the significance of these studies in understanding the mechanistic underpinnings of PD-related dopaminergic neurodegeneration.

The mechanism of neuroprotective action of natural compounds

Disturbance of cerebral redox homeostasis is the primary cause of human neurodegenerative disorders, such as Parkinson's disease or Alzheimer's disease. Well known experimental research demonstrates that oxidative stress is a main cause of cell death. A high concentration of reactive oxygen and nitrogen species leads to damage of a lot of proteins, lipids and also DNA. Synthetic compounds used for the treatment in the neurodegenerative diseases failed to meet the hopes they had raised and often exhibit a number of side effects. Therefore, in recent years interest in natural compounds derived from plants appears to be on the rise. This review describes a few natural compounds (1MeTIQ, resveratrol, curcumin, vitamin C and Gingko biloba) which revealed neuroprotective potential both in experimental studies and clinical trials. 1MeTIQ has a privileged position because, as opposed to the remaining compounds, it is an endogenous amine synthesized in human and animal brain. Based on evidence from research, it seems that a common protective mechanism for all the above-mentioned natural compounds relies on their ability to inhibit or even scavenge the excess of free radicals generated in oxidative and neurotoxin-induced processes in nerve cells of the brain. However, it was demonstrated that further different molecular processes connected with neurotoxicity (e.g. the inhibition of mitochondrial complex I, activation of caspase-3, apoptosis) follow later and are initiated by the reactive oxygen species. What is more, these natural compounds are able to inhibit further stages of apoptosis triggered by neurotoxins in the brain.

Bioenergetics and metabolism: a bench to bedside perspective

'Metabolism' refers to the vast collection of chemical processes that occur within a living organism. Within this broad designation, one can identify metabolism events that relate specifically to energy homeostasis, whether they occur at the subcellular, cellular, organ, or whole organism level. This review operationally refers to this type of metabolism as 'energy metabolism' or 'bioenergetics.' Changes in energy metabolism/bioenergetics have been linked to brain aging and a number of neurodegenerative diseases, and research suggests mitochondria may uniquely contribute to this. Interventions that manipulate energy metabolism/bioenergetic function and mitochondria may have therapeutic potential and efforts intended to accomplish this are playing out at basic, translational, and clinical levels. This review follows evolving views of energy metabolism's role in neurodegenerative diseases but especially Alzheimer's disease, with an emphasis on the bench-to-bedside process whose ultimate goal is to develop therapeutic interventions. It further considers challenges encountered during this process, which include linking basic concepts to a medical question at the initial research stage, adapting conceptual knowledge gained to a disease-associated application in the translational stage, extending what has been learned to the clinical arena, and maintaining support for the research at each of these fundamentally linked but functionally distinct stages. A bench-to-bedside biomedical research process is discussed that moves through conceptual, basic, translational, and clinical levels. For example, herein a case was made that bioenergetics is a valid Alzheimer's disease therapeutic target. Following this, a fundamental strategy for manipulating bioenergetics was defined, potential implications studied, and the approach extended to the clinical arena. This article is part of the 60th Anniversary special issue.

Disease-Toxicant Interactions in Parkinson's Disease Neuropathology

Human disease commonly manifests as a result of complex genetic and environmental interactions. In the case of neurodegenerative diseases, such as Parkinson's disease (PD), understanding how environmental exposures collude with genetic polymorphisms in the central nervous system to cause dysfunction is critical in order to develop better treatment strategies, therapies, and a more cohesive paradigm for future research. The intersection of genetics and the environment in disease etiology is particularly relevant in the context of their shared pathophysiological mechanisms. This review offers an integrated view of disease-toxicant interactions in PD. Particular attention is dedicated to how mutations in the genes SNCA, parkin, leucine-rich repeat kinase 2 (LRRK2) and DJ-1, as well as dysfunction of the ubiquitin proteasome system, may contribute to PD and how exposure to heavy metals, pesticides and illicit drugs may further the consequences of these mutations to exacerbate PD and PD-like disorders. Although the toxic effects induced by exposure to these environmental factors may not be the primary causes of PD, their mechanisms of action are critical for our current understanding of the neuropathologies driving PD. Elucidating how environment and genetics collude to cause pathogenesis of PD will facilitate the development of more effective treatments for the disease. Additionally, we discuss the neuroprotection exerted by estrogen and other compounds that may prevent PD and provide an overview of current treatment strategies and therapies.

Parkinson's disease: no milk today?

Several prospective epidemiological studies on large cohorts have consistently reported an association between milk intake and a higher incidence of Parkinson’s disease (PD). Pesticide contamination of milk and milk’s urate-lowering effects have been put forward as risk factors to explain epidemiological data. This has led to considerable uncertainty among physicians and avoidance of dairy products by PD patients. However, neither factor stands up to the rational and detailed examination of the literature carried out in this mini-review. We suggest that changes in eating behavior related to pre-motor PD are an alternative potential explanation of correlations observed between milk intake and PD occurrence. Despite clear-cut associations between milk intake and PD incidence, there is no rational explanation for milk being a risk factor for PD. Based on current knowledge, limiting the consumption of dairy products does not seem to be a reasonable strategy in the prevention of the development and progression of PD.

1-Methyl-1,2,3,4-tetrahydroisoquinoline, an endogenous amine with unexpected mechanism of action: new vistas of therapeutic application

This review outlines the effects of 1,2,3,4-tetrahydroisoquinoline (TIQ) and its derivative, 1-methyl-1,2,3,4-tetrahydroisoquinoline (1MeTIQ), endogenous substances imbued with high pharmacological potential and broad spectrum of action in brain. 1MeTIQ has gained special interest as a neuroprotectant, and its ability to antagonize the behavioral syndrome produced by well-known neurotoxins (e.g., MPTP; rotenone). This review is thus focused on mechanisms of action of 1MeTIQ in behavioral, neurochemical, and molecular studies in rodents; also, effects of TIQ and 1MeTIQ on dopamine metabolism; and neuroprotective properties of TIQ and 1MeTIQ in vitro and in vivo. Finally, antiaddictive properties of 1MeTIQ will be described in cocaine self-administered rats. Findings implicate TIQ and especially its methyl derivative 1MeTIQ in unique and complex mechanisms of neuroprotection in various neurodegenerative illnesses of the central nervous system. We believe that MAO inhibition, free radicals scavenging properties, and antagonism to the glutamatergic system may play an essential role in neuroprotection. In addition, the results strongly support the view that 1MeTIQ has a considerable potential as a drug for combating substance abuse, through the attenuation of craving.

Does mitochondrial DNA play a role in Parkinson's disease? A review of cybrid and other supportive evidence

SIGNIFICANCE

Mitochondria are currently believed to play an important role in the neurodysfunction and neurodegeneration that underlie Parkinson's disease (PD).

RECENT ADVANCES

While it increasingly appears that mitochondrial dysfunction in PD can have different causes, it has been proposed that mitochondrial DNA (mtDNA) may account for or drive mitochondrial dysfunction in the majority of the cases. If correct, the responsible mtDNA signatures could represent acquired mutations, inherited mutations, or population-distributed polymorphisms.

CRITICAL ISSUES AND FUTURE DIRECTIONS

This review discusses the case for mtDNA as a key mediator of PD, and especially focuses on data from studies of PD cytoplasmic hybrid (cybrid) cell lines.

Lack of association of dairy food, calcium, and vitamin D intake with the risk of Parkinson's disease: a case-control study in Japan

Three previous cohort studies in the USA reported that dairy product consumption was significantly associated with an increased risk of Parkinson's disease (PD) in men, but not in women. We examined the relationship between consumption of dairy products, calcium, and vitamin D and the risk of PD using data from a multicenter hospital-based case-control study in Japan. Included were 249 cases within 6 years of onset of PD based on the UK PD Society Brain Bank clinical diagnostic criteria. Controls were 368 inpatients and outpatients without a neurodegenerative disease. Information on dietary factors was collected using a validated self-administered diet history questionnaire. Adjustment was made for sex, age, region of residence, pack-years of smoking, years of education, body mass index, and dietary factors including cholesterol, dietary glycemic index, vitamin E, β-carotene, vitamin B(6), caffeine, iron, and alcohol. Total dairy product consumption was not materially associated with the risk of PD (P for trend = 0.62). No evident relationships were observed between intake of milk, yogurt, cheese, or ice cream and the risk of PD (P for trend = 0.75, 0.63, 0.59, and 0.35, respectively). There were no measurable associations between consumption of calcium or vitamin D and PD (P for trend = 0.37 and 0.69, respectively). No significant interactions were observed between the dietary exposures and sex regarding PD. Our results suggest that intake of dairy products, calcium, and vitamin D was not related to PD, regardless of sex. However, such null relationships might be a consequence of PD.

Effects of berberine on 6-hydroxydopamine-induced neurotoxicity in PC12 cells and a rat model of Parkinson's disease

Protoberberine isoquinoline alkaloids including berberine inhibit dopamine biosynthesis and aggravate l-DOPA-induced cytotoxicity in PC12 cells. In this study, the effects of berberine on 6-hydroxydopamine (6-OHDA)-induced cytotoxicity in PC12 cells and on unilateral 6-OHDA-lesioned rats were investigated. In PC12 cells, berberine at 10 and 30μM associated with 6-OHDA (10, 20, and 50μM) enhanced cytotoxicity at 48h compared to 6-OHDA alone, indicated by an increase in apoptotic cell death. In addition, treatment with berberine (5 and 30mg/kg, i.p.) for 21 days in 6-OHDA-lesioned rats markedly depleted tyrosine hydroxylase-immunopositive cells in the substantia nigra as compared to berberine-untreated rats. Further, the levels of dopamine and norepinephrine were also significantly decreased by berberine administration (5 and 30mg/kg) in the striatal regions of 6-OHDA-lesioned rats. These results suggested that berberine aggravated 6-OHDA-induced cytotoxicity in PC12 cells, and led to the degeneration of dopaminergic neuronal cells in the substantia nigra of 6-OHDA-lesioned rats. It is, therefore, suggested that the use of long-term l-DOPA therapy with isoquinoline derivatives including berberine may need to be examined for the presence of adverse symptoms.

Regional distribution of tetrahydroisoquinoline derivatives in rodent, human, and Parkinson's disease brain

Several members of the tetrahydroisoquinoline (TIQ) family of monoamine alkaloids can be formed from dopamine or its oxidized metabolites and may be involved in the pathogenesis of monoaminergic cell death in Parkinson's disease (PD). Using enantiomeric-selective high-performance liquid chromatography with electrochemical detection and liquid chromatography with tandem mass spectroscopy, the regional concentrations of several TIQ derivatives, including salsolinols, were determined in mouse, rat, normal human, and PD brain. TIQ derivatives were detected in all regions subjected to analysis. In general, salsolinols were present at higher concentrations than TIQ and its benzyl and methyl derivatives, especially in human brain. Moreover, salsolinols were concentrated in areas with increased dopamine synthesis and turnover such as the ventral midbrain and striatum, respectively. A possible consequence of nigrostriatal dopaminergic cell death, significantly lower levels of (R)salsolinol, (S)salsolinol, N-methyl-(R)salsolinol and N-methyl-(S)salsolinol were found in the caudate nuclei of PD in comparison with normal human brain. Our data support the hypothesis of endogenous synthesis of salsolinols and provide evidence for their accumulation in catecholaminergic neurons.

Quantification of salsolinol enantiomers by stable isotope dilution liquid chromatography with tandem mass spectrometric detection

Salsolinol, 1-methyl-6,7-dihydroxy-2,3,4,5-tetrahydroisoquinoline (SAL), is a precursor of a Parkinsonian neurotoxin, N-methysalsolinol (N-methyl-SAL). Previous studies have shown that individual enantiomers of N-methyl-SAL possess distinct neurotoxicological properties. In this work, a chiral high-performance liquid chromatography (HPLC) method with electrospray ionization tandem mass spectrometric (ESI-MS/MS) detection was developed for the quantification of (R/S)-SAL enantiomers. Enantioseparation was achieved on a beta-cyclodextrin-bonded silica gel column, and the resolved enantiomers were detected by ESI-MS/MS operated in positive ion mode. The ESI collision-induced dissociation (CID) mass spectrum of SAL was studied together with that of its deuterium-labeled analog (i.e. salsolinol-alpha,alpha,alpha,1-d(4), SAL-d(4)) so that the fragmentation pathways could be elucidated. Further, using SAL-d(4) as internal standard in HPLC/MS/MS analysis of SAL improved significantly assay accuracy and reliability. Determination of (R/S)-SAL enantiomers present in food samples such as dried banana chips was demonstrated.

Consumption of dairy products and risk of Parkinson's disease

The authors prospectively investigated the association between intake of dairy products and risk of Parkinson's disease among 57,689 men and 73,175 women from the American Cancer Society's Cancer Prevention Study II Nutrition Cohort. A total of 250 men and 138 women with Parkinson's disease were identified during follow-up (1992-2001). Dairy product consumption was positively associated with risk of Parkinson's disease: Compared with the lowest intake quintile, the corresponding relative risks for quintiles 2-5 were 1.4, 1.4, 1.4, and 1.6 (95 percent confidence interval (CI): 1.1, 2.2; p for trend = 0.05). A higher risk among dairy product consumers was found in both men and women, although the association in women appeared nonlinear. Meta-analysis of all prospective studies confirmed a moderately elevated risk of Parkinson's disease among persons with high dairy product consumption: For extreme intake categories, relative risks were 1.6 (95 percent CI: 1.3, 2.0) for both sexes, 1.8 for men (95 percent CI: 1.4, 2.4), and 1.3 for women (95 percent CI: 0.8, 2.1). These data suggest that dairy consumption may increase the risk of Parkinson's disease, particularly in men. More studies are needed to further examine these findings and to explore underlying mechanisms.

The effect of modulation of gamma-glutamyl transpeptidase and nitric oxide synthase activity on GSH homeostasis in HepG2 cells

High glutathione (GSH) level and elevated gamma-glutamyl transpeptidase (gammaGT) activity are hallmarks of tumor cells. Toxicity of drugs and radiation to the cells is largely dependent on the level of thiols. In the present studies, we attempted to inhibit gammaGT activity in human hepatoblastoma (HepG2) cells to examine whether the administration of gammaGT inhibitors, acivicin (AC) and 1,2,3,4-tetrahydroisoquinoline (TIQ) influences cell proliferation and enhances cytostatic action of doxorubicin (DOX) and cisplatin (CP) on HepG2 cells. The effects of these inhibitors were determined by 1-(4,5-dimethylthiazol-2-yl)-3,5-diphenylformazan (MTT), BrdU and lactate dehydrogenase (LDH) tests and by estimation of GSH level. Additionally, we investigated the changes in caspase-3 activity, which is a marker of apoptosis. The obtained results showed that the gammaGT inhibitors introduced to the medium alone elicited cytotoxic effect, which was accompanied by an increase in GSH level in the cells. TIQ concomitantly increased caspase-3 activity. Doxorubicin and CP proved to be cytotoxic, and both inhibitors augmented this effect. As well DOX as CP radically decreased GSH levels, whereas gammaGT inhibitors had diverse effects. Therefore, the obtained results confirm that gammaGT inhibitors can enhance pharmacological action of DOX and CP, which may permit clinicians to decrease their doses thereby alleviating side effects. Aminoguanidine (nitric oxide synthase inhibitor) given alone was little cytotoxic to HepG2 cells, while its introduction to the medium together with DOX and CP significantly increased their cytotoxicity. Aminoguanidine on its own did not show any effect on GSH level in HepG2 cells, but markedly and significantly elevated its concentration when added in combination with CP but not with DOX. This indicates that when CP was used as a cytostatic, GSH level rose after treatment with its combination with both AC and aminoguanidine.

1-Benzyl-1,2,3,4-tetrahydroisoquinoline passes through the blood–brain barrier of rat brain: An in vivo microdialysis study

Previous work has established that 1-benzyl-1,2,3,4-tetrahydroisoquinoline (1-BnTIQ) causes a parkinsonian syndrome in rats. The present study reports the blood-brain barrier (BBB) permeability of 1-BnTIQ in freely moving rats with the aid of in vivo microdialysis-based measurements. The microdialysis probe was implanted in the frontal cortex of rat brain. Brain dialysate samples were analyzed using an HPLC-MS/MS assay. 1-BnTIQ, when administered i.p., dose-dependently appeared in brain extracellular fluid (ECF), reaching a maximum concentration after about 40 min. Two other tetrahydroisoquinoline derivatives, 1,2,3,4-tetrahydroisoquinoline (TIQ) and 6,7-dihydroxy-1-methyl-1,2,3,4-tetrahydroisoquinoline [salsolinol (SAL)], served as positive and negative controls, respectively. The results confirmed an earlier report that SAL does not reach the brain after i.p. administration. In contrast, TIQ readily passed through the BBB. The brain dialysate concentration of 1-BnTIQ was about 24% that of TIQ when administered i.p. at the same dose. Both of them decreased quickly with a half-life of about 50 min.

Capillary liquid chromatography–tandem mass spectrometry of tetrahydroisoquinoline derived neurotoxins: A study on the blood–brain barrier of rat brain

Certain tetrahydroisoquinoline derivatives such as 1-benzyl-1,2,3,4-tetrahydroisoquinoline (1-BnTIQ) and N-methylsalsolinol are parkinsonian neurotoxins. This paper describes a sensitive and reliable analytical method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the determination of tetrahydroisoquinoline derivatives (TIQs) in brain dialysate. Samples (20 microL injected) were effectively stacked and cleaned up in-line on a capillary column (5 cm x 0.25 mm I.D.) packed with 5 microm phenyl reversed-phase silica particles. Under the optimized conditions, electrospray ionisation-MS/MS detection of TIQs was highly sensitive. The capillary LC-MS/MS method had a detection limit of 2 ng/ml for TIQ. The method was used in combination with in vivo microdialysis to study the blood-brain barrier (BBB) for TIQs. The microdialysis probe was implanted in the frontal cortex of rat brain. Test compounds were administered intraperitoneally (i.p.). Four TIQs including 1,2,3,4-tetrahydroisoquinoline (TIQ), 5,6,7,8-tetrahydroisoquinoline (5-TIQ), 1-BnTIQ, and salsolinol (SAL) were studied. A concentration maximum was detected in brain dialysate for TIQ, 5-TIQ, and 1-BnTIQ about 40 min after drug administration. However, SAL, the precursor of N-methylsalsolinol was found unable to cross the BBB of rat brain.

Synthesis and neurotoxicity of tetrahydroisoquinoline derivatives for studying Parkinson's disease

Parkinson's disease involves the progressive degeneration of dopaminergic neurons in the substantia nigra. However, the etiology of the disease remains to be elucidated. Endogenous amines, such as 1,2,3,4-tetrahydroisoquinoline (TIQ) derivatives present in the mammalian brain, are known to participate in the pathogenesis of Parkinson's disease. These endogenous neurotoxins have been extensively studied because of their structural resemblance to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), an agent widely used for generating animal models of Parkinson's disease-like symptoms. Investigations of the synthesis and pharmacological properties of TIQ derivatives are expected to contribute to the development of new therapeutic agents for treating Parkinson's disease. In the present study, we describe more efficient synthesis methods for TIQ derivatives via Pummerer-type cyclization of the substrate N-acyl sulfoxide. Furthermore, the modified Pummerer reaction provided a convenient and efficient method for synthesizing various TIQs. TIQ and its derivative, 1-benzyl-TIQ, can induce parkinsonism in primates and rodents. On the other hand, one TIQ derivative, 1-methyl-TIQ, has been shown to prevent MPTP, TIQ, and 1-benzyl-TIQ induced behavioral abnormalities. Therefore, TIQ derivatives are considered to play an important role in both the onset and prevention of Parkinson's disease. In this article, we focus on the synthesis and pharmacological aspects of 1,2,3,4-tetrahydroisoquinoline derivatives in Parkinson's disease.

1,2,3,4-Tetrahydroisoquinoline protects terminals of dopaminergic neurons in the striatum against the malonate-induced neurotoxicity

Malonate, a reversible inhibitor of the mitochondrial enzyme succinate dehydrogenase, is frequently used as a model neurotoxin to produce lesion of the nigrostriatal dopaminergic system in animals due to particular sensitivity of dopamine neurons to mild energy impairment. This model of neurotoxicity was applied in our study to explore neuroprotective potential of 1,2,3,4-tetrahydroisoquinoline (TIQ), an endo- and exogenous substance whose function in the mammalian brain, despite extensive studies, has not been elucidated so far. Injection of malonate at a dose of 3 mumol unilaterally into the rat left medial forebrain bundle resulted in the 54% decrease in dopamine (DA) concentration in the ipsilateral striatum and, depending on the examined striatum regions, caused 24-44% reduction in [3H]GBR12,935 binding to the dopamine transporter (DAT). TIQ (50 mg/kg i.p.) administered 4 h before malonate infusion and next once daily for successive 7 days prevented both these effects of malonate. Such TIQ treatment restored DA content and DAT binding almost to the control level. The results of the present study indicate that TIQ may act as a neuroprotective agent in the rat brain. An inhibition of the enzymatic activities of monoamine oxidase and gamma-glutamyl transpeptidase as well as an increase in the striatal levels of glutathione and nitric oxide found after TIQ administration and reported in our earlier studies are considered to be potential factors that may be involved in the TIQ-mediated protection of dopamine terminals from malonate toxicity.

Treatment with 1,2,3,4-tetrahydroisoquinolone affects the levels of nitric oxide, S-nitrosothiols, glutathione and the enzymatic activity of γ-glutamyl transpeptidase in the dopaminergic structures of rat brain

Depletion of glutathione (GSH), nitrosative stress and chronic intoxication with some neurotoxins have been postulated to play a major role in the pathogenesis of Parkinson's disease. This study aimed to examine the effects of acute and chronic treatments with 1,2,3,4-tetrahydroisoquinoline (TIQ), an endo-/exogenous substance suspected of producing Parkinsonism in human, on the levels of nitric oxide (NO), S-nitrosothiols and glutathione (GSH) in the whole rat brain and in its dopaminergic structures. TIQ administered at a dose of 50 mg/kg i.p. significantly increased the tissue concentrations of NO and GSH in the substantia nigra (SN), striatum (STR) and cortex (CTX) of rats receiving this compound both acutely and chronically. Moreover, it decreased the level of oxidized glutathione (GSSG) and enhanced GSH:GSSG ratio affecting in this way the redox state of brain cells. TIQ also increased the level of S-nitrosothiols when measured in the whole rat brain and CTX, although it markedly decreased their level in the STR after both treatments. Inhibition of the constitutive NO synthase by l-NAME in the presence of TIQ caused decreases in GSH and S-nitrosothiol levels in the brain. The latter effect shows that the TIQ-mediated increases in GSH and S-nitrosothiol concentrations were dependent on the enhanced NO level. The above-described results suggest that TIQ can act as a modulator of GSH, NO and S-nitrosothiol levels but not as a parkinsonism-inducing agent in the rat brain.

Studies on the pathogenesis of Parkinson's disease in Japan

Studies on the pathogenesis of nigral cell death in Parkinson's disease (PD) are reviewed. Discussions are focused mainly on studies performed by Japanese investigators because of the purpose of this issue. We and other groups found a decrease in complex I of the mitochondrial electron transfer complex in the substantia nigra of patients with PD, and in addition to complex I deficiency, we reported loss of alpha-ketoglutarate dehydrogenase complex of the tricarboxylic acid cycle (TCA cycle) by immunohistochemistry. Thus mitochondrial respiratory failure and resultant energy crisis appear to be one of the most important mechanisms that lead nigral neurons to cell death. The primary cause of mitochondrial respiratory failure has not been elucidated yet; however, environmental neurotoxins such as 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) may be responsible for nigral cell death in PD; in this respect a number of candidate toxins including tetrahydroisoquinolines and beta-carbolines have extensively been studied for nigral as well as mitochondrial toxicity. Recent progress in this field is also reviewed. Even if an environmental neurotoxin is involved in PD, exposure to such a neurotoxin alone may not account for its pathogenesis, as most of us are probably being exposed to the same toxin. Therefore, genetic predisposition appears to be essential for the development of PD. The genetic predisposition may involve hepatic detoxifying enzymes for such neurotoxins, the transport mechanism of those toxins to the brain, bioactivation of those toxins in the brain, the uptake mechanism to the nigral neurons, and the activity levels of target enzymes or proteins; all of these factors are being extensively studied in many laboratories at a molecular level.

Disposition of 1,2,3,4,-tetrahydroisoquinoline in the brain of male Wistar and Dark Agouti rats

Direct evidence for accumulation of 1,2,3,4-tetrahydroisoquinoline (TIQ), an endo- and exogenous substance suspected of producing Parkinsonism in humans, has not yet been shown. This study aimed to examine TIQ disposition in the whole rat brain and in the striatum and substantia nigra (SN). TIQ was administered to male Wistar and Dark Agouti rats (20, 40 and 100 mg/kg i.p.) alone or jointly with specific CYP2D inhibitor quinine (20, 40, 80 mg/kg i.p.), acutely or chronically. TIQ concentration in brain of both strains was several-fold higher than in plasma. The level of its metabolite, 4-OH-TIQ, was very low in the brain and plasma of TIQ-treated Wistar while in those receiving additionally quinine or in Dark Agouti rats, 4-OH-TIQ was absent or negligible. Inhibition of CYP2D catalyzing TIQ 4-hydroxylation in the liver had no influence on TIQ accumulation in the brain. Exogenous TIQ was actively transported from periphery into the brain by the organic cation transporter system, mainly OCT3, and quickly eliminated from it by P-glycoprotein. TIQ accumulation after chronic injection to Wistar rats was short-lasting and limited to SN. High concentration of TIQ in SN induces while in the liver inhibits the nigral and hepatic activity CYP2D, respectively.

Update on epidemiological aspects of progressive supranuclear palsy

The cause of progressive supranuclear palsy (PSP), the most common form of the atypical parkinsonian disorders, is unknown. PSP is characterized by four-repeat tau aggregates in neurons (neurofibrillary tangles) and glia in specific basal ganglia and brainstem areas. A thorough literature review led us to hypothesize that genetic and/or environmental factors contribute to its development. It is likely that inheritance of the H1/H1 tau genotype represents a predisposition to develop PSP requiring other environmental or genetic factors. Less likely, a relatively rare mutation with low penetrance could contribute to the abnormal tau aggregation present in this disorder. The possible role of chemicals in the diet or occupation, hypertension, traumatic brain injury, coffee, and inflammation or oxidative injury are reviewed.

1-Benzyl-1,2,3,4-tetrahydroisoquinoline (1BnTIQ), an endogenous neurotoxin, induces dopaminergic cell death through apoptosis

Endogenous MPTP-like neurotoxins such as 1-benzyl-1,2,3,4-tetrahydroisoquinoline (1BnTIQ) have been suspected in the etiology of Parkinson's disease (PD). 1BnTIQ was found in a concentration three times higher in cerebrospinal fluid of PD brains than control subjects [J. Neurochem. 65 (6) (1995) 2633]. In the present study, we have evaluated the mechanisms of 1BnTIQ toxicity in human dopaminergic SH-SY5Y cells and tested the neuroprotective action of SKF-38393, a dopamine receptor (D(1)) agonist. 1BnTIQ dose dependently decreased cell viability in dopaminergic SH-SY5Y cells and the extent of cell death was more pronounced when compared to MPP(+). Similar to MPP(+), 1BnTIQ significantly decreased [3H]dopamine uptake. 1BnTIQ significantly increased lipid peroxidation, Bax expression, and active caspase-3 formation. Furthermore, it decreased the expression of Bcl-xL, an anti-apoptotic protein, in these cells. SKF-38393, a dopamine receptor (D(1)) agonist (1 and 10 microM) completely prevented the cell death and significantly increased cell viability. These results strongly suggest that 1BnTIQ induces dopaminergic cell death by apoptosis and dopamine receptor agonists may be useful neuroprotective agents against 1BnTIQ toxicity.

Brain sites of movement disorder: genetic and environmental agents in neurodevelopmental perturbations

In assessing and assimilating the neurodevelopmental basis of the so-called movement disorders it is probably useful to establish certain concepts that will modulate both the variation and selection of affliction, mechanisms-processes and diversity of disease states. Both genetic, developmental and degenerative aberrations are to be encompassed within such an approach, as well as all deviations from the necessary components of behaviour that are generally understood to incorporate "normal" functioning. In the present treatise, both conditions of hyperactivity/hypoactivity, akinesia and bradykinesia together with a constellation of other symptoms and syndromes are considered in conjunction with the neuropharmacological and brain morphological alterations that may or may not accompany them, e.g. following neonatal denervation. As a case in point, the neuroanatomical and neurochemical points of interaction in Attention Deficit and Hyperactivity disorder (ADHD) are examined with reference to both the perinatal metallic and organic environment and genetic backgrounds. The role of apoptosis, as opposed to necrosis, in cell death during brain development necessitates careful considerations of the current explosion of evidence for brain nerve growth factors, neurotrophins and cytokines, and the processes regulating their appearance, release and fate. Some of these processes may possess putative inherited characteristics, like alpha-synuclein, others may to greater or lesser extents be endogenous or semi-endogenous (in food), like the tetrahydroisoquinolines, others exogenous until inhaled or injested through environmental accident, like heavy metals, e.g. mercury. Another central concept of neurodevelopment is cellular plasticity, thereby underlining the essential involvement of glutamate systems and N-methyl-D-aspartate receptor configurations. Finally, an essential assimilation of brain development in disease must delineate the relative merits of inherited as opposed to environmental risks not only for the commonly-regarded movement disorders, like Parkinson's disease, Huntington's disease and epilepsy, but also for afflictions bearing strong elements of psychosocial tragedy, like ADHD, autism and Savantism.

Diet and Parkinson's disease: a potential role of dairy products in men

Diet may play a causative role in Parkinson's disease (PD), but potential associations between diet and PD risk rarely have been assessed in prospective studies. We investigated associations between food intakes and PD risk in two large prospective cohorts in which 210 incident PD cases in men and 184 in women were documented. A positive association was found between dairy intake and PD risk in men (relative risk [RR] comparing extreme categories, 1.8; p trend = 0.004), but not in women (RR, 1.1; p trend = 0.9). No other food groups were associated with PD risk in either men or women. Further analyses among men showed significant positive associations with PD risk for intakes of several dairy foods as well as dairy calcium (RR, 1.5; p trend = 0.02), dairy vitamin D (RR, 1.6; p trend = 0.004), dairy protein (RR, 1.6; p trend = 0.01), and lactose (RR, 1.8; p trend = 0.002), but not dairy fat (RR, 1.1; p trend = 0.4). Intakes of calcium, vitamin D, and protein from other dietary or supplemental sources were not related to PD risk in men. Our results suggest that higher intake of dairy products may increase the risk of PD in men; however, this finding needs further evaluation, and the underlying active components need to be identified.

Decrease of 1-methyl-1,2,3,4-tetrahydroisoquinoline synthesizing enzyme activity in the brain areas of aged rat

1-Methyl-1,2,3,4-tetrahydroisoquinoline (1-MeTIQ), an endogenous monoamine, which prevents the neurotoxic effect of 1-methyl-4-phenylpyridinium ion (MPP(+)) and other endogenous neurotoxins, has been described as being enzymatically formed in the brain by the 1-MeTIQ synthesizing enzyme (1-MeTIQse). In this paper, we report the brain's regional distribution of this enzyme in 3- and 24-month-old rats. The results show that the activity is spread throughout the brain, the highest activity being in the dopaminergic areas (striatum and substantia nigra) and in the cortex. During aging there was a 1-MeTIQse activity reduction ( approximately 50%) in the areas implicated in the ethyology of Parkinson disease (substantia nigra, striatum) and in the cerebral cortex.

Environmental factors in Parkinson's disease

Evidence discussed in this review article lends strong support in favor of an etiologic role of environmentalfactors in Parkinson's disease. First, thanks to the discovery of MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine), it is now clear that, by targeting the nigrostriatal system, neurotoxicants can reproduce the neurochemical and pathological features of idiopathic parkinsonism. The sequence of toxic events triggered by MPTP has also provided us with intriguing clues concerning mechanisms of toxicant selectivity and nigrostriatal vulnerability. Relevant examples are (i) the role of the plasma membrane dopamine transporter in facilitating the access of potentially toxic species into dopaminergic neurons; (ii) the vulnerability of the nigrostriatal system to failure of mitochondrial energy metabolism; and (iii) the contribution of inflammatory processes to tissue lesioning. Epidemiological and experimental data suggest the potential involvement of specific agents as neurotoxicants (e.g. pesticides) or neuroprotective compounds (e.g. tobacco products) in the pathogenesis of nigrostriatal degeneration, further supporting a relationship between the environment and Parkinson's disease. A likely scenario that emerges from our current knowledge is that neurodegeneration results from multiple events and interactive mechanisms. These may include (i) the synergistic action of endogenous and exogenous toxins (e.g. the ability of the pesticide diethyldithiocarbamate to promote the toxicity of other compounds); (ii) the interactions of toxic agents with endogenous elements (e.g. the protein alpha-synuclein); (iii) the tissue response to an initial toxic insult; and, last but not least, (iv) the effects of environmental factors on the background of genetic predisposition and aging.

Effect of acute administration of 1,2,3,4-tetrahydroisoquinoline on the levels of glutathione and reactive oxygen species, and on the enzymatic activity of gamma-glutamyl transpeptidase in dopaminergic structures of rat brain

The effect of acute administration of 1,2,3,4-tetrahydroisoquinoline, an endogenous substance suspected of producing Parkinsonism in humans, on the levels of glutathione and reactive oxygen species and on the enzymatic activity of gamma-glutamyl transpeptidase was investigated in the substantia nigra, striatum and cortex of rat brain. Four hours after a single dose of 1,2,3,4-tetrahydroisoquinoline (100 mg/kg i.p.), a significant increase in tissue glutathione level was found in the dopaminergic structures studied. The most pronounced effect was observed in the substantia nigra and cortex, and the weakest in the striatum. At the same time, significant inhibition of gamma-glutamyl transpeptidase was observed in the substantia nigra, cortex and striatum whose extent strictly corresponded to the increase in glutathione levels in those structures. Moreover, in 1,2,3,4-tetrahydroisoquinoline-treated rats, the production of reactive oxygen species was significantly reduced in the substantia nigra, whereas it was markedly enhanced in the striatum.Our results suggest that the increase in tissue glutathione level in the dopaminergic structures studied results from inhibition of gamma-glutamyl transpeptidase and refers to the extracellular pool of this peptide. Moreover, it is likely that both the 1,2,3,4-tetrahydroisoquinoline-induced alterations in glutathione level and the enhanced production of reactive oxygen species in the striatum may have implications for the pathogenesis of Parkinson's disease.

N-methyl-norsalsolinol, a putative dopaminergic neurotoxin, passes through the blood-brain barrier in vivo

In earlier studies the dihydroxylated tetrahydroisoquinoline derivatives salsolinol and 2(N)-methyl-norsalsolinol (NMNorsal), a 2(N)-analogue of salsolinol, were identified as putative endogenous neurotoxins in patients with Parkinson's disease. Since a prominent blood-brain barrier (BBB) was described to exist for salsolinol, in the present study microdialysis experiments were performed to investigate the penetration of NMNorsal through the BBB into the caudate nucleus of the rat brain. After i.p. administration of NMNorsal (20 mg/kg), it could be detected in the dialysate of the caudate nucleus with a mean maximum after 40 min. There was no alteration in extracellular dopamine or 3,4-dihydroxyphenylacetic acid levels. Addition of the monoamine oxidase inhibitor pargyline (10 microM) to the perfusate did not modify NMNorsal levels in the caudate nucleus. To corroborate the microdialysis results, homogenates of the contralateral caudate nucleus were prepared and NMNorsal could also be detected. These findings indicate that NMNorsal is indeed able to pass through the blood-brain barrier of the rat brain.

Dopaminergic cell death induced by MPP(+), oxidant and specific neurotoxicants shares the common molecular mechanism

Recent etiological study in twins (Tanner et al. 1999) strongly suggests that environmental factors play an important role in typical, non-familial Parkinson's disease (PD), beginning after age 50. Epidemiological risk factor analyses of typical PD cases have identified several neurotoxicants, including MPP(+) (the active metabolite of MPTP), paraquat, dieldrin, manganese and salsolinol. Here, we tested the hypothesis that these neurotoxic agents might induce cell death in our nigral dopaminergic cell line, SN4741 (Son et al. 1999) through a common molecular mechanism. Our initial experiments revealed that treatment with both MPP(+) and the other PD-related neurotoxicants induced apoptotic cell death in SN4741 cells, following initial increases of H(2)O(2)-related ROS activity and subsequent activation of JNK1/2 MAP kinases. Moreover, we have demonstrated that during dopaminergic cell death cascades, MPP(+), the neurotoxicants and an oxidant, H(2)O(2) equally induce the ROS-dependent events. Remarkably, the oxidant treatment alone induced similar sequential molecular events: ROS increase, activation of JNK MAP kinases, activation of the PITSLRE kinase, p110, by both Caspase-1 and Caspase-3-like activities and apoptotic cell death. Pharmacological intervention using the combination of the antioxidant Trolox and a pan-caspase inhibitor Boc-(Asp)-fmk (BAF) exerted significant neuroprotection against ROS-induced dopaminergic cell death. Finally, the high throughput cDNA microarray screening using the current model identified downstream response genes, such as heme oxygenase-1, a constituent of Lewy bodies, that can be the useful biomarkers to monitor the pathological conditions of dopaminergic neurons under neurotoxic insult.

Effect of acute and chronic administration of 1,2,3,4-tetrahydroisoquinoline on muscle tone, metabolism of dopamine in the striatum and tyrosine hydroxylase immunocytochemistry in the substantia nigra, in rats

The effects of acute and chronic administration of 1,2,3,4-tetrahydroisoquinoline, an endogenous substance suspected of producing parkinsonism in humans, on the muscle tone and metabolism of dopamine in the striatum, and on the number of tyrosine hydroxylase-immunoreactive cells in the substantia nigra were investigated in rats. Muscle tone was examined using a combined mechanomyographic and electromyographic method which measured simultaneously the muscle resistance of the rat's hind foot to passive extension and flexion in the ankle joint and electromyographic activity of the antagonistic muscles of that joint: gastrocnemius and tibialis anterior. 1,2,3,4-Tetrahydroisoquinoline administered at doses of 50 and 100 mg/kg intraperitoneally for 19 days increased muscle resistance 1 h after the first injection (acute treatment), 1 h after the last injection (chronic treatment) and three days after compound withdrawal. Rigidity observed on the third day of 1,2,3,4-tetrahydroisoquinoline withdrawal was accompanied by an increased tonic (resting) electromyographic activity of the gastrocnemius and tibialis anterior muscles. At the same time, a significant reduction in the number of tyrosine hydroxylase-immunoreactive neurons in the substantia nigra and a decrease in the dopamine level in the striatum were also found. A declining number of tyrosine hydroxylase-immunoreactive neurons in the whole substantia nigra showed a significant negative correlation with the enhanced muscle resistance, as well as with the tonic electromyographic activity recorded at rest, i.e. before the start of movements, from the gastrocnemius and tibialis anterior muscles. Our results suggest that 1,2,3,4-tetrahydroisoquinoline may be one of the endogenous substances involved in the progress of Parkinson's disease.

Review of apoptosis vs. necrosis of substantia nigra pars compacta in Parkinson's disease

The discovery that melanized neurons of the pars compacta of substantia nigra (pcSN) degenerate in the midbrain of human Parkinsonians is nearly a century old, but only in this decade have we gained insights into mechanisms underlying this neuronal loss. Although it had long been assumed that pcSN neurons underwent necrosis, recent (1) in vitro studies on isolated neurons, (2) in vivo studies in animals treated with neurotoxins, and (3) postmortem study of human Parkinsonian brain provide strong evidence that pcSN cells may be lost more from apoptosis (i.e., cell suicide) than from necrosis. This paper gives some historical perspective, but focuses primarily on mechanisms involved in both necrosis and apoptosis of neurons, primarily dopaminergic, and reviews the recent literature relating to apoptosis and apoptotic factors now identified in neurons undergoing neurotoxin-induced death and in postmortem human Parkinsonian brain. The weight of evidence in favor of apoptosis and apoptotic factors in these neurons, provides us with tools needed to develop anti-apoptotic factors that can be targeted to proteins on genes, so that it may be possible to decelerate or prevent the progressive neuronal cell loss in human Parkinsonians or in humans with other neurodegenerative disorders.

Cerebral cortical blood flow maps are reorganized in MAOB-deficient mice

Cerebral cortical blood flow (CBF) was measured autoradiographically in conscious mice without the monoamine oxidase B (MAOB) gene (KO, n=11) and the corresponding wild-type animals (WILD, n=11). Subgroups of animals of each genotype received a continuous intravenous infusion over 30 min of phenylethylamine (PEA), an endogenous substrate of MAOB, (8 nmol g-1 min-1 in normal saline at a volume rate of 0.11 microl g-1 min-1) or saline at the same volume rate. Maps of relative CBF distribution showed predominance of midline motor and sensory area CBF in KO mice over WILD mice that received saline. PEA enhanced CBF in lateral frontal and piriform cortex in both KO and WILD mice. These changes may reflect a differential activation due to chronic and acute PEA elevations on motor and olfactory function, as well as on the anxiogenic effects of this amine. In addition to its effects on regional CBF distribution, PEA decreased CBF globally in KO mice (range -31% to -41% decrease from control levels) with a lesser effect in WILD mice. It is concluded that MAOB may normally regulate CBF distribution and its response to blood PEA.

Stereospecific N-methylation of the tetrahydroisoquinoline alkaloids isosalsoline and salsolidine by amine N-methyltransferase A from bovine liver

Stereospecific N-methylation of the tetrahydroisoquinoline alkaloids isosalsoline (7-hydroxy-6-methoxy-1-methyl-1,2,3,4-tetrahydroisoquinoline) and salsolidine (6,7-dimethoxy-1-methyl-1,2,3,4-tetrahydroisoquinoline) by amine N-methyltransferase A isolated from bovine liver is reported. Incubation with S-adenosylmethionine as cosubstrate revealed that in case of isosalsoline, an endogenous tetrahydroisoquinoline alkaloid, the (+)-(R)-enantiomer, is preferentially methylated, whereas in the case of salsolidine the (-)-(S)-enantiomer is preferentially methylated. The results were obtained by using two independent methods, namely a radioassay and HPLC following separate incubation experiments.