Plasma catechols and monoamine oxidase metabolites in untreated Parkinson's and Alzheimer's diseases

A Pilot Study of Changes in the Level of Catecholamines and the Activity of α-2-Macroglobulin in the Tear Fluid of Patients with Parkinson's Disease and Parkinsonian Mice

Development of differential and early (preclinical) diagnostics of Parkinson’s disease (PD) is among the priorities in neuroscience. We searched for changes in the level of catecholamines and α-2-macroglobulin activity in the tear fluid (TF) in PD patients at an early clinical stage. It was shown that TF in patients is characterized by an increased level of noradrenaline mainly on the ipsilateral side of pronounced motor symptoms (72%, p = 0.049), a decreased level of adrenaline on both sides (ipsilateral—53%, p = 0.004; contralateral—42%, p = 0.02), and an increased α-2-macroglobulin activity on both sides (ipsilateral—53%, p = 0.03; contralateral—56%, p = 0.037) compared to controls. These changes are considered as potential biomarkers for differential diagnosis. Similar changes in the TF were found in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice when modeling clinical and preclinical stages of PD. These data show the adequacy of models to the pathogenesis of PD along the selected metabolic pathways, and also suggest that the found TF changes can be considered as potential biomarkers for preclinical diagnosis of PD. In Parkinsonian mice, the level of catecholamines also changes in the lacrimal glands, which makes it possible to consider them as one of the sources of catecholamines in the TF.

Development of early diagnosis of Parkinson's disease: Illusion or reality?

The fight against neurodegenerative diseases, Alzheimer disease and Parkinson's disease (PD), is a challenge of the 21st century. The low efficacy of treating patients is due to the late diagnosis and start of therapy, after the degeneration of most specific neurons and depletion of neuroplasticity. It is believed that the development of early diagnosis (ED) and preventive treatment will delay the onset of specific symptoms. This review evaluates methodologies for developing ED of PD. Since PD is a systemic disease, and the degeneration of certain neurons precedes that of nigrostriatal dopaminergic neurons that control motor function, the current methodology is based on searching biomarkers, such as premotor symptoms and changes in body fluids (BF) in patients. However, all attempts to develop ED were unsuccessful. Therefore, it is proposed to enhance the current methodology by (i) selecting among biomarkers found in BF in patients at the clinical stage those that are characteristics of animal models of the preclinical stage, (ii) searching biomarkers in BF in subjects at the prodromal stage, selected by detecting premotor symptoms and failure of the nigrostriatal dopaminergic system. Moreover, a new methodology was proposed for the development of ED of PD using a provocative test, which is successfully used in internal medicine.

The Noradrenergic System in Parkinson's Disease

Nowadays it is well accepted that in Parkinson’s disease (PD), the neurodegenerative process occurs in stages and that damage to other areas precedes the neuronal loss in the substantia nigra pars compacta, which is considered a pathophysiological hallmark of PD. This heterogeneous and progressive neurodegeneration may explain the diverse symptomatology of the disease, including motor and non-motor alterations. In PD, one of the first areas undergoing degeneration is the locus coeruleus (LC). This noradrenergic nucleus provides extensive innervation throughout the brain and plays a fundamental neuromodulator role, participating in stress responses, emotional memory, and control of motor, sensory, and autonomic functions. Early in the disease, LC neurons suffer modifications that can condition the effectiveness of pharmacological treatments, and importantly, can lead to the appearance of common non-motor symptomatology. The noradrenergic system also exerts anti-inflammatory and neuroprotective effect on the dopaminergic degeneration and noradrenergic damage can consequently condition the progress of the disease. From the pharmacological point of view, it is also important to understand how the noradrenergic system performs in PD, since noradrenergic medication is often used in these patients, and drug interactions can take place when combining them with the gold standard drug therapy in PD, L-3,4-dihydroxyphenylalanine (L-DOPA). This review provides an overview about the functional status of the noradrenergic system in PD and its contribution to the efficacy of pharmacological-based treatments. Based on preclinical and clinical publications, a special attention will be dedicated to the most prevalent non-motor symptoms of the disease.

Platelets: Peripheral Biomarkers of Dementia?

Dementia continues to be the most burdening neurocognitive disorder, having a negative impact on the lives of millions. The search for biomarkers to improve the clinical diagnosis of dementia is ongoing, with the focus on effective use of readily accessible peripheral markers. In this review, we concentrate on platelets as biomarkers of dementia and analyze their potential as easily-accessible clinical biomarkers for various subtypes of dementia. Current platelet protein biomarkers that have been investigated for their clinical utility in the diagnosis of dementia, in particular Alzheimer's disease, include amyloid-β protein precursor (AβPP), the AβPP secretases (BACE1 and ADAM10), α-synuclein, tau protein, serotonin, cholesterol, phospholipases, clusterin, IgG, surface receptors, MAO-B, and coated platelets. Few of them, i.e., platelet tau, AβPP (particularly with regards to coated platelets) and secreted ADAM10 and BACE1 show the most promise to be taken forward into clinical setting to diagnose dementia. Aside from protein biomarkers, changes in factors such as mean platelet volume have the potential to play a very specific role in both the dementia diagnosis and prognosis. This review raises a number of research questions for consideration before application of the above biomarkers to routine clinical setting. It is without doubt that there is a need for more clarification on the effects of dementia on platelet morphology and protein content before these changes can be clinically applied as dementia biomarkers and explored further in differentiating distinct dementia subtypes.

Upgraded Methodology for the Development of Early Diagnosis of Parkinson's Disease Based on Searching Blood Markers in Patients and Experimental Models

Numerous attempts to develop an early diagnosis of Parkinson's disease (PD) by searching biomarkers in biological fluids were unsuccessful. The drawback of this methodology is searching markers in patients at the clinical stage without guarantee that they are also characteristic of either preclinical stage or prodromal stage (preclinical-prodromal stage). We attempted to upgrade this methodology by selecting only markers that are found both in patients and in PD animal models. HPLC and RT-PCR were used to estimate the concentration of amino acids, catecholamines/metabolites in plasma and gene expression in lymphocytes in 36 untreated early-stage PD patients and 52 controls, and in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice at modeling the clinical ("symptomatic") stage and preclinical-prodromal ("presymptomatic") stage of PD. It was shown that among 13 blood markers found in patients, 7 markers are characteristic of parkinsonian symptomatic mice and 3 markers of both symptomatic and presymptomatic mice. According to our suggestion, the detection of the same marker in patients and symptomatic animals indicates adequate reproduction of pathogenesis along the corresponding metabolic pathway, whereas the detection of the same marker in presymptomatic animals indicates its specificity for preclinical-prodromal stage. This means that the minority of markers found in patients-decreased concentration of L-3,4-dihydroxyphenylalanine (L-DOPA) and dihydroxyphenylacetic acid (DOPAC) and increased dopamine D3 receptor gene expression-are specific for preclinical-prodromal stage and are suitable for early diagnosis of PD. Thus, we upgraded a current methodology for development of early diagnosis of PD by searching blood markers not only in patients but also in parkinsonian animals.

Platelets, a reliable source for peripheral Alzheimer's disease biomarkers?

Peripheral biomarkers play an indispensable role in quick and reliable diagnoses of any kind of disease. With the population ageing, the number of people suffering from age-related diseases is expected to rise dramatically over the coming decades. In particular, all types of cognitive deficits, such as Alzheimer's disease, will increase. Alzheimer's disease is characterised mainly by coexistence of amyloid plaques and neurofibrillary tangles in brain. Reliable identification of such molecular characteristics antemortem, however, is problematic due to restricted availability of appropriate sample material and definitive diagnosis is only possible postmortem. Currently, the best molecular biomarkers available for antemortem diagnosis originate from cerebrospinal fluid. Though, this is not convenient for routine diagnosis because of the required invasive lumbar puncture. As a consequence, there is a growing demand for additional peripheral biomarkers in a more readily accessible sample material. Blood platelets, due to shared biochemical properties with neurons, can constitute an attractive alternative as discussed here. This review summarises potential platelet Alzheimer's disease biomarkers, their role, implication, and alteration in the disease. For easy comparison of their performance, the Hedge effect size was calculated whenever data were available.

Monoamine oxidase inhibitors: promising therapeutic agents for Alzheimer's disease (Review)

Activated monoamine oxidase (MAO) has a critical role in the pathogenesis of Alzheimer's disease (AD), including the formation of amyloid plaques from amyloid β peptide (Aβ) production and accumulation, formation of neurofibrillary tangles, and cognitive impairment via the destruction of cholinergic neurons and disorder of the cholinergic system. Several studies have indicated that MAO inhibitors improve cognitive deficits and reverse Aβ pathology by modulating proteolytic cleavage of amyloid precursor protein and decreasing Aβ protein fragments. Thus, MAO inhibitors may be considered as promising therapeutic agents for AD.

Alzheimer disease and platelets: how's that relevant

Alzheimer Disease (AD) is the most common neurodegenerative disorder worldwide, and account for 60% to 70% of all cases of progressive cognitive impairment in elderly patients. At the microscopic level distinctive features of AD are neurons and synapses degeneration, together with extensive amounts of senile plaques and neurofibrillars tangles. The degenerative process probably starts 20-30 years before the clinical onset of the disease. Senile plaques are composed of a central core of amyloid β peptide, Aβ, derived from the metabolism of the larger amyloid precursor protein, APP, which is expressed not only in the brain, but even in non neuronal tissues. More than 30 years ago, some studies reported that human platelets express APP and all the enzymatic activities necessary to process this protein through the same pathways described in the brain. Since then a large number of evidence has been accumulated to suggest that platelets may be a good peripheral model to study the metabolism of APP, and the pathophysiology of the onset of AD. In this review, we will summarize the current knowledge on the involvement of platelets in Alzheimer Disease. Although platelets are generally accepted as a suitable model for AD, the current scientific interest on this model is very high, because many concepts still remain debated and controversial. At the same time, however, these still unsolved divergences mirror a difficulty to establish constant parameters to better defined the role of platelets in AD.

Comparative platelet proteome analysis reveals an increase of monoamine oxidase-B protein expression in Alzheimer's disease but not in non-demented Parkinson's disease patients

Monoamine oxidase-B (Mao-B) catalysing the breakdown of the neurotransmitter dopamine, is known to be involved in the pathophysiology of Parkinson's (PD) and Alzheimer's disease (AD). Increased brain Mao-B activity is associated with AD. This alteration can also be seen in platelets, albeit the cause has hitherto remained elusive. To gain a deeper understanding of the etiology of AD, the platelet proteome was characterised, (2D DIGE pH6-9, including Mao-B) from 150 individuals: 34 AD, 13 vascular dementia, 15 non-demented PD patients, 49 matched controls, 18 oldest old and 21 young individuals. One significant change was noted after applying false discovery rate with the upregulation of the Mao-B expression (30% adjusted P value<0.001; effect size 1.31) in AD compared to age- and sex-matched controls. In contrast, Mao-B levels were unchanged in PD to matched controls. Western blot and mRNA analyses verified these findings. Moreover, Mao-B concentration correlated with age in the cognitive healthy individuals (r=0.53; P<0.001) and PD patients but not in those suffering from AD (r=-0.03; P=0.874). Mao-B activity correlated with the increased Mao-B protein expression in AD (r=0.81; P=0.016). We suggest that Mao-B platelet protein level may serve as a biomarker for age-related dementia, especially AD.

Anxiety in Parkinson's disease: a critical review of experimental and clinical studies

Parkinson's disease (PD) is the second most common neurodegenerative disorder affecting about 1% of the population older than 60 years. Classically, PD is considered as a movement disorder, and its diagnosis is based on the presence of a set of cardinal motor signs that are the consequence of a pronounced death of dopaminergic neurons in the substantia nigra pars compacta. There is now considerable evidence showing that the neurodegenerative processes leading to sporadic PD begin many years before the appearance of the characteristic motor symptoms, and that additional neuronal fields and neurotransmitter systems are also involved in PD, including olfactory structures, amygdala, caudal raphe nuclei, locus coeruleus, and hippocampus. Accordingly, adrenergic and serotonergic neurons are also lost, which seems to contribute to the anxiety in PD. Non-motor features of PD usually do not respond to dopaminergic medication and probably form the major current challenge in the clinical management of PD. Additionally, most studies performed with animal models of PD have investigated their ability to induce motor alterations associated with advanced phases of PD, and some studies begin to assess non-motor behavioral features of the disease. The present review attempts to examine results obtained from clinical and experimental studies to provide a comprehensive picture of the neurobiology and current and potential treatments for anxiety in PD. The data reviewed here indicate that, despite their high prevalence and impact on the quality of life, anxiety disorders are often under-diagnosed and under-treated in PD patients. Moreover, there are currently few clinical and pre-clinical studies underway to investigate new pharmacological agents for relieving these symptoms, and we hope that this article may inspire clinicians and researchers devote to the studies on anxiety in PD to change this scenario. This article is part of a Special Issue entitled 'Anxiety and Depression'.

Simultaneous determination of catecholamines and their metabolites related to Alzheimer's disease in human urine

A simple and specific high-performance liquid chromatography method coupled with fluorescence detection (HPLC-FL) has been developed for the simultaneous determination of L-3,4-dihydroxyphenylalanine, norepinephrine, dopamine, epinephrine and 3,4-dihydroxyphenylacetic acid in human urine. The samples were derivatized by 1,2-diphenylethylenediamine with isoprenaline as internal standard. The factors affecting the fluorescence yield were investigated, including the reaction and separation conditions. The catecholamine derivatives were separated on a Kromasil C(18) column with methanol and sodium acetate buffer as mobile phase. The limits of detection for all catecholamines ranged from 0.2 to 1.1 ng/mL. The linear ranges were from 2.5 to 200 ng/mL except 3,4-dihydroxyphenylacetic acid from 5 to 200 ng/mL. The intra- and interday RSDs for all catecholamines were 1.0-8.0 and 2.1-14%, respectively. The method was successfully applied to determine the catecholamines in human urine from 14 Alzheimer's disease patients and 14 healthy volunteers. It was concluded that the mean levels of catecholamines in urine of Alzheimer's disease patients were all lower than those in healthy volunteers. The cluster analysis and independent samples T-test were used to distinguish the Alzheimer's disease patients and healthy volunteers.

Potential mechanisms underlying anxiety and depression in Parkinson's disease: consequences of l-DOPA treatment

Though the most recognizable symptoms of Parkinson's disease (PD) are motor-related, many patients also suffer from debilitating affective symptoms that deleteriously influence quality of life. Dopamine (DA) loss is likely involved in the onset of depression and anxiety in PD. However, these symptoms are not reliably improved by DA replacement therapy with l-3,4-dihydroxyphenylalanine (l-DOPA). In fact, preclinical and clinical evidence suggests that l-DOPA treatment may worsen affect. Though the neurobiological mechanisms remain unclear, recent research contends that l-DOPA further perturbs the function of the norepinephrine and serotonin systems, already affected by PD pathology, which have been intimately linked to the development and expression of anxiety and depression. As such, this review provides an overview of the clinical characteristics of affective disorders in PD, examines the utility of animal models for the study of anxiety and depression in PD, and finally, discusses potential mechanisms by which DA loss and subsequent l-DOPA therapy influence monoamine function and concomitant affective symptoms.

Platelet serotonin concentration and monoamine oxidase type B activity in female patients in early, middle and late phase of Alzheimer's disease

Alzheimer's disease (AD) is a progressive, neurodegenerative disorder with unclear aetiology. Cognitive impairment in AD might be associated with altered serotonergic system. The aim of the study was to determine platelet serotonin (5-HT) concentrations and platelet monoamine oxidase type B (MAO-B) activity in patients with different severity of AD. Platelet 5-HT concentrations and MAO-B activity were determined spectrofluorimetrically in 74 female patients with AD (NINCDS-ADRDA, DSM-IV-TR criteria), subdivided according to the Mini Mental State Examination (MMSE) scores in three groups with a) 23 patients in early (MMSE scores 19-24), b) 23 patients in middle (MMSE 10-18), and c) 28 patients in late (MMSE 0-9) phase of AD, and in 49 age-matched healthy women. Platelet 5-HT concentrations and MAO-B activity were similar between all patients with AD and healthy subjects, but were significantly lower in patients in the late phase of AD than in other phases of AD, and in healthy controls. The significant correlations were found between MMSE scores and platelet 5-HT concentrations, MAO-B activity and age. Lower platelet 5-HT concentration and MAO-B activity in the late phase of AD suggested that these markers might indicate severity and/or clinical progress of AD.

Neurocirculatory Abnormalities in Parkinson Disease With Orthostatic Hypotension

Patients with Parkinson disease often have orthostatic hypotension. Neurocirculatory abnormalities underlying orthostatic hypotension might reflect levodopa treatment. Sixty-six Parkinson disease patients (36 with orthostatic hypotension, 15 off and 21 on levodopa; 30 without orthostatic hypotension) had tests of reflexive cardiovagal gain (decrease in interbeat interval per unit decrease in systolic pressure during the Valsalva maneuver; orthostatic increase in heart rate per unit decrease in pressure); reflexive sympathoneural function (decrease in pressure during the Valsalva maneuver; orthostatic increment in plasma norepinephrine); and cardiac and extracardiac noradrenergic innervation (septal myocardial 6-[ 18 F]fluorodopamine-derived radioactivity; supine plasma norepinephrine). Severity of orthostatic hypotension did not differ between the levodopa-untreated and levodopa-treated groups with Parkinson disease and orthostatic hypotension (−52±6 [SEM] versus −49±5 mm Hg systolic). The 2 groups had similarly low reflexive cardiovagal gain (0.84±0.23 versus 1.33±0.35 ms/mm Hg during Valsalva; 0.43±0.09 versus 0.27±0.06 bpm/mm Hg during orthostasis); and had similarly attenuated reflexive sympathoneural responses (97±29 versus 71±23 pg/mL during orthostasis; −82±10 versus −73±8 mm Hg during Valsalva). In patients off levodopa, plasma norepinephrine was lower in those with (193±19 pg/mL) than without (348±46 pg/mL) orthostatic hypotension. Low values for reflexive cardiovagal gain, sympathoneural responses, and noradrenergic innervation were strongly related to orthostatic hypotension. Parkinson disease with orthostatic hypotension features reflexive cardiovagal and sympathoneural failure and cardiac and partial extracardiac sympathetic denervation, independent of levodopa treatment.

Orthostatic hypotension from sympathetic denervation in Parkinson's disease

BACKGROUND

Patients with PD often have signs or symptoms of autonomic failure, including orthostatic hypotension. Cardiac sympathetic denervation occurs frequently in PD, but this has been thought to occur independently of autonomic failure.

METHODS

Forty-one patients with PD (18 with and 23 without orthostatic hypotension) and 16 age-matched healthy volunteers underwent PET scanning to visualize sympathetic innervation after injection of 6-[(18)F]fluorodopamine. Beat-to-beat blood pressure responses to the Valsalva maneuver were used to identify sympathetic neurocirculatory failure and plasma norepinephrine to indicate overall sympathetic innervation.

RESULTS

All patients with PD and orthostatic hypotension had abnormal blood pressure responses to the Valsalva maneuver and septal and lateral ventricular myocardial concentrations of 6-[(18)F]fluorodopamine-derived radioactivity >2 SD below the normal mean. In contrast, only 6 of the 23 patients without orthostatic hypotension had abnormal Valsalva responses (p < 0.0001 compared with patients with orthostatic hypotension), and only 11 had diffusely decreased 6-[(18)F]fluorodopamine-derived radioactivity in the left ventricular myocardium (p = 0.0004). Of the 12 remaining patients without orthostatic hypotension, 7 had locally decreased myocardial radioactivity. Supine plasma norepinephrine was lower in patients with than in those without orthostatic hypotension (1.40 +/- 0.15 vs 2.32 +/- 0.26 nmol/L, p = 0.005). 6-[(18)F]fluorodopamine-derived radioactivity was less not only in the myocardium but also in the thyroid and renal cortex of patients with PD than in healthy control subjects.

CONCLUSIONS

In PD, orthostatic hypotension reflects sympathetic neurocirculatory failure from generalized sympathetic denervation.

Hypothalamic pituitary adrenocortical and sympathetic nervous system responses to the cold pressor test in Alzheimer's disease

BACKGROUND

Increased basal activity of the hypothalamic-pituitary-adrenocortical (HPA) axis has been repeatedly demonstrated in Alzheimer's disease (AD), and some studies suggest increased basal activity of the sympathetic nervous system (SNS) in this disorder; however, the effects of AD on HPA axis or SNS responses to a standardized aversive stressor have not been examined. The neuroendocrine response to aversive stress may be relevant to the pathophysiology of AD.

METHODS

Plasma adrenocorticotropic hormone (ACTH), cortisol, norepinephrine (NE), and epinephrine responses to a 1-min cold pressor test (CPT) were measured in nine medically healthy AD outpatients (age 76 +/- 2 years) and nine age- and gender-matched medically healthy cognitively normal older subjects (age 76 +/- 1 year).

RESULTS

The cortisol response to CPT was increased in the AD group but the ACTH response did not differ between groups. Basal NE concentrations were higher in the AD group. Although NE responses to CPT did not differ between groups, the blood pressure response to CPT was higher in the AD subjects.

CONCLUSIONS

These results suggest increased HPA axis responsiveness to CPT at the level of the adrenal cortex in AD. The results also suggest increased basal sympathoneural activity and increased cardiovascular responsiveness to sympathoneural stimulation in AD under the conditions of this experimental protocol. Increased SNS stimulatory modulation of the adrenal cortex is a possible mechanism contributing to the observed enhanced cortisol response to CPT in these AD subjects.

Platelet MAO-B activity and serotonin content in patients with dementia: effect of age, medication, and disease

This study aimed at determining the effect of drug therapy, age and type of dementia on biological markers. Both platelet monoamine oxidase type B (MAO-B) activity and serotonin content of 57 demented patients and 20 control subjects were determined. Platelet MAO-B activity was measured using [14C]tyramine as substrate. Serotonin content was determined by HPLC-EC method. Increased platelet serotonin content and platelet count was found in patients with dementia compared to controls. A positive correlation was experienced between platelet MAO-B activity, platelet serotonin content and age. Platelet MAO-B activity was higher in the haloperidol treated group, compared with patients treated with anxyolitics. The main original finding of the present study is that platelet serotonin content is increased in demented patients with delusions compared to dementia without complications (p = 0.006). It seems, that platelet MAO-B activity is influenced mainly by drug therapy, while serotonin content rather reflects clinical characteristics in dementia.

Decreased beta-phenylethylamine in CSF in Parkinson's disease

OBJECTIVE

To determine the concentrations of beta-phenylethylamine (PEA) in CSF in patients with Parkinson's disease, and to evaluate the relation between concentration of PEA in CSF and severity of Parkinson's disease.

METHODS

Using gas chromatography-chemical ionisation mass spectrometry, CSF concentrations of PEA were measured in 23 patients with Parkinson's disease (mean age, 64.0 (SD 8.2) years), of whom three were at Hoehn and Yahr stage II, 11 were at stage III, and nine were at stage IV. Comparison was made with eight patients with neuropathy (mean age, 57.0 (SD 19.2) years) and 12 controls without neurological disease (mean age, 57.6 (SD 4.8) years).

RESULTS

Concentrations of PEA in CSF in Parkinson's disease were significantly lower (mean 205 (SD 131) pg/ml) than in patients with peripheral neuropathy (433 (SD 254) pg/ml) and controls (387 (SD 194) pg/ml). The concentrations of PEA in CSF correlated negatively with Hoehn and Yahr stage (P<0.01).

CONCLUSIONS

There are decreased CSF concentrations of PEA in patients with Parkinson's disease.

Symptoms and duration of the prodromal phase in Parkinson's disease

To investigate the duration of a prodromal phase before the onset of the classic symptoms of idiopathic Parkinson's disease, the authors conducted a retrospective case-control study of 60 patients with Parkinson's disease and 58 age- and sex-matched control subjects, covering the decade preceding the onset of classic Parkinson's disease. The symptoms were derived from files of the patients' general practitioners. Compared with control subjects, patients pre-Parkinson's disease had more central nervous system, psychologic, musculoskeletal, and cardiovascular (i.e., autonomic) symptoms. Patients pre-Parkinson's disease also made more visits to general practitioners and medical specialists. The results indicate that the onset of classic parkinsonism is frequently preceded by a prodromal phase lasting from 4-6 years.