Levodopa, Parkinson's disease, and hypotension

Convolutional neural networks can detect orthostatic hypotension in Parkinson's disease using resting-state functional near-infrared spectroscopy data

Neurological disorders such as Parkinson's disease (PD) often adversely affect the vascular system, leading to alterations in blood flow patterns. Functional near-infrared spectroscopy (fNIRS) is used to monitor hemodynamic changes via signal measurement. This study investigated the potential of using resting-state fNIRS data through a convolutional neural network (CNN) to evaluate PD with orthostatic hypotension. The CNN demonstrated significant efficacy in analyzing fNIRS data, and it outperformed the other machine learning methods. The results indicate that judicious input data selection can enhance accuracy by over 85%, while including the correlation matrix as an input further improves the accuracy to more than 90%. This study underscores the promising role of CNN-based fNIRS data analysis in the diagnosis and management of the PD. This approach enhances diagnostic accuracy, particularly in resting-state conditions, and can reduce the discomfort and risks associated with current diagnostic methods, such as the head-up tilt test.

Effect of acute levodopa challenge test on cerebral blood flow in Parkinson's disease with the supine-to-standing transcranial Doppler test

BACKGROUND

Levodopa, a common drug that improves symptoms of Parkinson's disease (PD), can induce a reduction in blood pressure (BP); however, the effect of levodopa on cerebral blood flow (CBF) remains unclear.

OBJECTIVES

To observe the changes in BP and CBF during active standing before and after the acute levodopa challenge test (ALCT) and analyse the influencing factors of CBF in patients with PD.

METHODS

BP and CBF velocity were simultaneously recorded by continuous beat-to-beat non-invasive BP monitoring and transcranial Doppler at supine and orthostatic positions twice, before and after ALCT. The patients were divided into two groups according to those with increased and decreased CBF at baseline after ALCT to analyse the influencing factors.

RESULTS

We examined 64 patients with PD (59.2 ± 11.6 years, 33 males). BP decreased at all timepoints after ALCT, while there was no significant change in the magnitude of the drop in BP induced by standing. CBF was reduced after ALCT, especially within 15 s to 1 min of standing (15 s: 48.95 ± 13.50 vs. 44.93 ± 13.26, p < 0.001; 30 s: 52.46 ± 12.06 vs. 50.11 ± 12.56, p = 0.033; 1 min: 52.19 ± 11.83 vs. 50.17 ± 13.21, p = 0.044). Lower body mass index (β = -0.280, p = 0.027) was an independent factor associated with CBF reduction after ALCT.

CONCLUSIONS

Additional attention should be paid to changes in CBF and BP within 1 min after standing in patients with PD taking levodopa, especially in those with low bodyweight.

Levodopa-Carbidopa Intestinal Gel Improves Symptoms of Orthostatic Hypotension in Patients with Parkinson’s Disease—Prospective Pilot Interventional Study

Parkinson’s disease (PD) is currently considered progressive neurodegeneration of both the central and peripheral nervous systems. Widespread neuropathological changes lead to a complex clinical presentation with typical motor (hypokinesia, tremor, and rigidity) and various nonmotor symptoms. Orthostatic hypotension is one of the most disabling nonmotor features contributing to increased morbidity and mortality and decreased quality of life (QoL). Our study aimed to disclose the effect of a continuous infusion of levodopa-carbidopa intestinal gel (LCIG) on symptoms of orthostatic hypotension. Nine patients indicated for LCIG and eight matched patients on optimized medical treatment (OMT) were examined with scales for orthostatic symptoms (SCOPA-AUT), nonmotor symptoms and motor fluctuations (MDS-UPDRS), and QoL (PDQ39) at both baseline and after six months. The scores of “light-headedness after standing” and “fainting” decreased in the LCIG group compared to the OMT group. Treatment with LCIG was associated with a significantly higher decrease in the score of “light-headedness after standing”. Change in the PDQ39 correlated positively with fluctuation improvement and with change in the scores of both “light-headedness” and “fainting”. LCIG treatment improved symptoms of orthostatic hypotension in patients with PD mainly by a reduction in motor complications. Decreased severity in both motor and nonmotor fluctuations was connected also with improved QoL. Continuous treatment with LCIG should be considered not only in the case of severe motor fluctuation but also in patients with nonmotor fluctuations responsive to dopaminergic treatment.

Insights into the Molecular Mechanisms of Alzheimer's and Parkinson's Diseases with Molecular Simulations: Understanding the Roles of Artificial and Pathological Missense Mutations in Intrinsically Disordered Proteins Related to Pathology

Amyloid-β and α-synuclein are intrinsically disordered proteins (IDPs), which are at the center of Alzheimer's and Parkinson's disease pathologies, respectively. These IDPs are extremely flexible and do not adopt stable structures. Furthermore, both amyloid-β and α-synuclein can form toxic oligomers, amyloid fibrils and other type of aggregates in Alzheimer's and Parkinson's diseases. Experimentalists face challenges in investigating the structures and thermodynamic properties of these IDPs in their monomeric and oligomeric forms due to the rapid conformational changes, fast aggregation processes and strong solvent effects. Classical molecular dynamics simulations complement experiments and provide structural information at the atomic level with dynamics without facing the same experimental limitations. Artificial missense mutations are employed experimentally and computationally for providing insights into the structure-function relationships of amyloid-β and α-synuclein in relation to the pathologies of Alzheimer's and Parkinson's diseases. Furthermore, there are several natural genetic variations that play a role in the pathogenesis of familial cases of Alzheimer's and Parkinson's diseases, which are related to specific genetic defects inherited in dominant or recessive patterns. The present review summarizes the current understanding of monomeric and oligomeric forms of amyloid-β and α-synuclein, as well as the impacts of artificial and pathological missense mutations on the structural ensembles of these IDPs using molecular dynamics simulations. We also emphasize the recent investigations on residual secondary structure formation in dynamic conformational ensembles of amyloid-β and α-synuclein, such as β-structure linked to the oligomerization and fibrillation mechanisms related to the pathologies of Alzheimer's and Parkinson's diseases. This information represents an important foundation for the successful and efficient drug design studies.

Exosomes in Parkinson's Disease

Exosomes, nano-sized extracellular vesicles secreted by most cell types, are found in all kinds of biological fluids and tissues, including the central nervous system (CNS). The proposed functions of these vesicles include roles in cell-cell signaling, removal of cellular debris, and transfer of pathogens between cells. Many studies have revealed that exosomes derived from the CNS occur in the cerebrospinal fluid and peripheral body fluids, and their contents are altered during disease, making them an appealing target for biomarker development in Parkinson's disease (PD). Exosomes have been shown to spread toxic α-synuclein (αsyn) between cells and induce apoptosis, which suggests a key mechanism underlying the spread of αsyn aggregates in the brain and the acceleration of pathology in PD. However, potential neuroprotective roles of exosomes in PD have also been reported. On the treatment side, as drug delivery vehicles, exosomes have been used to deliver small interfering RNAs and catalase to the brain, and have shown clear therapeutic effects in a mouse model of PD. These features of exosomes in PD make them extremely interesting from the point of view of developing novel diagnostic and therapeutic approaches.

Neuroprotective and Therapeutic Strategies against Parkinson's Disease: Recent Perspectives

Parkinsonism is a progressive motor disease that affects 1.5 million Americans and is the second most common neurodegenerative disease after Alzheimer’s. Typical neuropathological features of Parkinson’s disease (PD) include degeneration of dopaminergic neurons located in the pars compacta of the substantia nigra that project to the striatum (nigro-striatal pathway) and depositions of cytoplasmic fibrillary inclusions (Lewy bodies) which contain ubiquitin and α-synuclein. The cardinal motor signs of PD are tremors, rigidity, slow movement (bradykinesia), poor balance, and difficulty in walking (Parkinsonian gait). In addition to motor symptoms, non-motor symptoms that include autonomic and psychiatric as well as cognitive impairments are pressing issues that need to be addressed. Several different mechanisms play an important role in generation of Lewy bodies; endoplasmic reticulum (ER) stress induced unfolded proteins, neuroinflammation and eventual loss of dopaminergic neurons in the substantia nigra of mid brain in PD. Moreover, these diverse processes that result in PD make modeling of the disease and evaluation of therapeutics against this devastating disease difficult. Here, we will discuss diverse mechanisms that are involved in PD, neuroprotective and therapeutic strategies currently in clinical trial or in preclinical stages, and impart views about strategies that are promising to mitigate PD pathology.

The management of orthostatic hypotension in Parkinson's disease

Orthostatic hypotension (OH) is a common and disabling symptom affecting Parkinson's disease (PD) patients. We present the effect of the different therapies commonly used to manage PD on this clinical manifestation. For this purpose, we describe the relationship between OH and the current treatments employed in PD, such as L-DOPA, dopaminergic agonists, and continuous dopaminergic stimulation therapies. Additionally, we review the therapeutic measures that could be used to ameliorate OH. There are different approaches to deal with this manifestation, including pharmacological and non-pharmacological treatments, although none of them is specifically aimed for treating OH in PD.

Impaired cardiovascular autonomic control in newly and long-term-treated patients with Parkinson's disease: involvement of L-dopa therapy

In idiopathic Parkinson's disease (PD), autonomic dysfunction is frequent, causing orthostatic hypotension. The respective roles of disease progression and dopaminergic treatment remain unclear. In this study, we investigated the autonomic control of cardiovascular functions and its relation to L-dopa therapy in both newly diagnosed (ND) and long-term-treated (LT) patients. Study subjects were: (1) nine ND patients never having undergone treatment with L-dopa; (2) 18 LT patients who had been receiving L-dopa treatment for a long period. ND patients were investigated before L-dopa treatment and after stabilization of their L-dopa dosage. LT patients were investigated once with their regular treatment and once after a 12-h interruption of L-dopa treatment; (3) nine healthy subjects served as controls. At each test session, blood pressure (BP), heart rate (HR), plasma catecholamines, heart rate variability (HRV), and spontaneous baroreflex sensitivity were assessed in the supine and upright positions. Before receiving L-dopa medication, ND patients had reduced E/I ratios (HR response/deep breathing) and lowered HRV when compared to controls; this was evidence of early effects of the disease on autonomic HR control. Introduction of L-dopa treatment reduced BP, HR, and plasma levels of adrenaline and noradrenaline. Similar changes were found in LT patients when contrasting the short-term treatment interruption and the usual L-dopa dosage. The treatment-linked increase in plasma dopamine also correlated with the decrease in noradrenaline. These results showed that mild impairment of autonomic cardiovascular control occurred early in the course of PD. They also provided evidence that the side effects of L-dopa aggravated the impairment of the autonomic control of BP and HR.

Autonomic Nervous System Dysfunction in Parkinson's Disease

Autonomic nervous system (ANS) dysfunction is common in Parkinson's disease (PD), affects 70% to 80% of patients, and causes significant morbidity and discomfort. Autonomic nervous system dysfunction symptoms in PD include sexual dysfunction, swallowing and gastrointestinal disorders, bowel and bladder abnormalities, sleep disturbances, and derangements of cardiovascular regulation, particularly, orthostatic hypotension. Autonomic nervous system dysfunction in PD may be caused by an underlying degenerative process that affects the autonomic ganglia, brainstem nuclei, and hypothalamic nuclei. Anti-parkinsonian medications can cause or worsen symptoms of ANS dysfunction. The care of a PD patient with ANS dysfunction relies on its recognition and directed treatment, including coordinated care between the neurologist and appropriate subspecialist. Pharmacotherapy may be useful to treat orthostasis, gastrointestinal, urinary, and sexual dysfunction.

Selegiline in the treatment of Parkinson's disease: its impact on orthostatic hypotension

Less than a consensus exists as to whether chronic treatment with selegiline in combination with levodopa/carbidopa in patients with Parkinson's disease, is associated with more pronounced orthostatic hypotension than treatment with levodopa/carbidopa alone. To resolve this issue, we compared orthostatic tolerance and autonomic reflexes in 95 patients with Parkinson's disease treated chronically with either selegiline alone (n = 10), levodopa/carbidopa alone (n = 49) or both agents combined (n = 36). Supine heart rate and blood pressure, autonomic cardiovascular reflexes and the frequency and magnitude of orthostatic hypotension were similar in all three treatment groups.

Decreased myocardial 123I-MIBG uptake in Parkinson's disease

We studied myocardial 123I-metaiodobenzylguanidine (MIBG) accumulation in 12 patients with Parkinson's disease (PD). MIBG is an analog of norepinephrine (NE) and a tracer for sympathetic neuron integrity and function. MIBG uptake of the myocardium was significantly lower in PD than in controls. The heart to mediastinum ratio (H/M) was calculated by using the average count per pixel for the heart and mediastinum. In PD, H/M was lower than in controls (P<0.0001), while the washout ratio of the heart was higher (P<0.001). A decrease in myocardial accumulation of MIBG was observed in the early stage of PD. This suggests that the measurement of MIBG may help the diagnosis of early PD, and the causative factor underlying in PD may be operating the NE neuron as well as dopamine neuron.

Sympathetic vasoconstrictor reflexes in Parkinson's disease with autonomic dysfunction

Centrally and locally elicited sympathetic vasoconstrictor responses were examined in 12 patients with symptoms and signs of cardiovascular autonomic dysfunction due to Parkinson's disease. The sympathetic reflex mechanisms were measured in skeletal muscle and subcutaneous tissue of the arm and leg using the 133-Xenon washout technique. This method allows differentiation between local and central sympathetic reflexes in different tissues. The results indicate an abolished centrally mediated vasoconstrictor response in skeletal muscle in the arm and a decreased response in skeletal muscle in the leg and in subcutaneous tissue. This is in agreement with an autonomic dysfunction located in the central nervous system. A possible spinal sympathetic reflex controlling blood flow in subcutaneous tissue and leg muscles is considered. The sympathetic vasoconstrictor responses in parkinsonian patients without autonomic failure were of normal magnitude and the responses were not affected by long-term levodopa treatment.

Amine accumulation: a possible precursor of Lewy body formation in Parkinson's disease

It is now well recognized that the hypothalamus is an important site of neuropathology in Parkinson's disease (PD). Lewy bodies, a marker of nerve cell degeneration and a pathological hallmark of PD, have been observed frequently in the hypothalamus of PD patients by Lewy (1923) and other investigators and confirmed by more recent systematic studies by Langston & Forno (1978). Both Lewy and Langston & Forno found a predilection of Lewy body formation in specific hypothalamic nuclei with the tuberomammillary, lateral, and posterior areas containing by far the highest average counts per nucleus. Selective vulnerability of the tuberomammillary, lateral, and posterior hypothalamic cell groups to degeneration has been observed also in aging, postencephalitic Parkinsonism, Alzheimer's disease, and schizophrenia. The susceptibility of these particular nuclei to degenerative changes including Lewy body formation is not presently understood nor are the mechanisms by which Lewy bodies are formed in PD and other CNS disorders. Accumulation of amines, a pathological process which follows degeneration of catecholamine-containing neurons in experimental animals, also occurs most frequently in the lateral and posterior hypothalamic areas. In the present communication we propose that in PD, amine accumulation may be a precursor to Lewy body formation and that the susceptibility of certain hypothalamic areas to Lewy body formation may be related to their propensity to accumulate amines. Furthermore, the frequent co-existence of Lewy bodies and Alzheimer's neurofibrillary tangles in the lateral and posterior hypothalamic nuclei suggest that they may share a common pathogenetic etiology. If confirmed, this hypothesis may provide an experimental model by which the formation of Lewy bodies and neurofibrillary tangles may be investigated.

Cerebral autoregulation in patients with orthostatic hypotension

The present study was conducted to determine the relationship between autonomic nervous function and cerebral autoregulation in 17 patients with vertigo or dizziness. Autonomic nervous function was examined by measuring systolic blood pressure response and dynamic electrocardiogram R-peak to R-peak response upon standing up. Regional cerebral autoregulation was examined by comparing cerebral blood flow in both supine and standing positions with single photon emission computed tomography. Moreover, the relationship of each of these three measures to postural provocation of symptoms was studied. The findings indicated that autonomic nervous dysfunction does not influence cerebral autoregulation, but autonomic nervous dysfunction was related to postural provocation of symptoms. This might indicate that impaired autoregulation in the brain stem or the peripheral vestibule, which could not be detected by the single photon emission computed tomography, played a role in inducing vertigo or dizziness in patients with orthostatic hypotension.

Cardiovascular reflexes and autonomic dysfunction in Parkinson's disease

Cardiovascular reflexes were analysed in a group of 20 patients suffering from Parkinson's disease and in 12 age-matched healthy subjects, in order to ascertain the incidence and degree of autonomic dysfunction. The following were measured: heart rate variation during normal breathing, postural change (30/15 ratio) and during the Valsalva manoeuvre: blood pressure variation after standing. These measurements were taken at least 12 h after therapy had been withdrawn and were repeated after therapy had been resumed. Significant changes in the different heart rate variation indices were found in the parkinsonian patients which correlated with the duration and severity of the extrapyramidal symptomatology. After standing the patients showed a significant drop in blood pressure, when compared respectively with their base values and with the response in controls. Anticholinergic drugs had no significant effect on the heart rate variation indices, whereas antiparkinsonian therapy seems to have contributed to the drop in blood pressure after standing.

Autonomic involvement in extrapyramidal and cerebellar disorders

We reviewed the clinical and autonomic features of all patients with extrapyramidal and cerebellar disorders studied in the Mayo Autonomic Reflex Laboratory from 1983 to 1989. Patients were grouped into the following categories (number in parentheses): Parkinson's disease (35); parkinsonism-plus (54); multiple system atrophy (75); hereditary multisystem degenerations (eleven); progressive supranuclear palsy (32); non-familial cerebellar degeneration (eleven); nonspecific sporadic multisystem degeneration (73). Severe autonomic failure occurred in 97% of patients with multiple system atrophy and 53% of the nonspecific sporadic multisystem degeneration patients respectively. Autonomic involvement was mild or absent in Parkinson's disease while parkinsonism-plus and non-familial cerebellar degeneration patients had moderate autonomic failure. Orthostatic blood pressure reduction, percentage of anhidrosis on thermoregulatory sweat test, quantitative sudomotor axon reflex test, forearm response and heart rate response to deep breathing strongly regressed with severity. A response to levodopa treatment in patients with parkinsonism was more likely if cerebellar signs and cognitive deficits were absent. The presence of levodopa induced dyskinesia was also a marker for a clinically favourable levodopa response. We conclude that there is a spectrum of autonomic involvement in these degenerative disorders and that autonomic studies are useful in separating them and monitoring their course.

Autonomic dysfunction in recent onset and advanced Parkinson's disease

Cardiovascular autonomic nerve function and its relation to the clinical variables of untreated recent onset and levodopa-treated advanced disease parkinsonian patients were studied. Heart rate variations were diminished in both groups when compared with age-matched controls. An orthostatic blood pressure drop was found in both disease groups. The drop was stronger and related to the levodopa dose in the advanced disease group. In conclusion, 1) in Parkinson's disease a parasympathetic damage occurs which worsens during the course of the disease, 2) the orthostatic fall in blood pressure, indicating a sympathetic dysfunction, is partly due to the disease itself and partly due to levodopa treatment.

The hypothalamus in Parkinson disease

It is currently believed that Parkinson disease (PD) is due to a degenerative process that independently damages multiple areas of the central and peripheral nervous system. Loss of nigrostriatal dopamine is now widely recognized as being directly related to the motor symptoms in Parkinson's disease. Parkinsonian patients also exhibit symptoms and signs suggestive of hypothalamic dysfunction (e.g. dysautonomia, impaired heat tolerance). The latter clinical features are supported by pathological, biochemical and endocrinological findings. Lewy body formation has been demonstrated in every nucleus of the hypothalamus, specifically the tuberomamillary and posterior hypothalamic. Preferential involvement of the hypothalamus was also noted in patients after post-encephalitic parkinsonism. Loss of dopamine (30-40%) in the hypothalamus of affected patients has been shown in recent studies, and is compatible with the reported abnormalities of growth hormone release in response to L-dopa administration, elevated plasma levels of MSH, and reduced CSF levels of somatostatin and beta-endorphins in these patients. Deranged immunological mechanisms have been found in PD patients including the presence of autoantibodies against sympathetic ganglia neurons, adrenal medulla and caudate nucleus. On the evidence of on pathological studies demonstrating the early vulnerability of the hypothalamus in aging and PD, and the known role of the hypothalamus in immune modulation, we expect that it will be shown that primary damage of the hypothalamus leads to subsequent secondary degeneration of structures receiving direct projections from the hypothalamus. Within this framework, the dopaminergic systems may be damaged, since striatal dopamine synthesis and receptor sensitivity have been shown to be regulated by ACTH and alpha-MSH through direct arcuate nucleus-striatal projections.(ABSTRACT TRUNCATED AT 250 WORDS)

Autonomic cardiovascular responses in parkinsonism: effect of levodopa with dopa-decarboxylase inhibition

Autonomically mediated cardiovascular responses to certain manoeuvres were studied in 20 parkinson patients, 24 h off levodopa-decarboxylase inhibitor medication and again one h after medication. Results were compared with 15 healthy control subjects. The heart rate at rest was higher in parkinson, the respiratory sinus arrhythmia was lower, while the Valsalva ratio, the heart rate and blood pressure responses during an orthostatic test and the heart rate response to a dive reflex test were normal. These findings indicate a normal function of peripheral autonomic nerves and a possible central parasympathetic dysfunction. There were significantly attenuated responses of heart rate, blood pressure and contralateral forearm blood flow to an isometric handgrip. Since the peripheral autonomic nerves seemed to be normal, these results could be related to a reduced central command and/or diminished stimulation of postulated peripheral ergoreceptors in parkinsonism. There was no major effect on the cardiovascular responses by the acutely administered medication.

DL-3,4-threo-DOPS in Parkinson's disease: effects on orthostatic hypotension and dizziness

Parkinsonian patients with orthostatic hypotension and dizziness due to usual antiparkinson therapy have been treated with the precursor amino-acid of noradrenaline, DL-3,4-threo-dihydroxyphenylserine (DL-3,4-threo-DOPS). Oral and intravenous administration improved these side effects significantly. A combined treatment of L-dopa, peripheral decarboxylase inhibitor and DL-3,4-threo-DOPS seems to be of benefit with respect to akinesia and orthostatic hypotension.

Interaction between levodopa and methyldopa

The interaction between methyldopa and levodopa was studied in 18 patients with Parkinsonism. Together they produced a fall in blood pressure in doses which when given alone had no effect or only a slight hypotensive effect. Severe hypotension never occurred. It is reasonable to give methyldopa to hypertensive patients on levodopa but the regimen should be initiated in hospital.

Modification of the cardiovascular effects of L-dopa in anesthetized dogs by inhibitors of enzymes involved in catecholamine metabolism

The influence of various enzyme inhibitors on the cardiovascular effects of L -dopa (methylester) has been studied to determine the sites of action of the drug or a responsible metabolite. L -Dopa, 10 mg/kg, iv, had minor early effects on heart rate and blood pressure in normal dogs, but in animals with inhibition of monoamine oxidase (MAO), it caused tachycardia and severe hypotension of gradual onset. When MAO was inhibited, earlier doses of a dopamine β-oxidase inhibitor (FLA 63) did not significantly modify the effects of L -dopa; prior administration of a decarboxylase inhibitor, NSD 1055 or Ro 4-4602, prevented all but the initial effects; selective extracerebral decarboxylase inhibition with MK 486 ( L -α-hydrazino-α-methyldopa) prevented the tachycardia but not the hypotension. DL - threo -Dihydroxyphenylserine caused an initial rise in blood pressure in dogs with MAO inhibition, had less pressor activity when peripheral decarboxylase was also inhibited, and in both cases did not cause the hypotension characteristic of L -dopa. L -Dopa enhanced pressor responses and especially associated bradycardic responses to norepinephrine in dogs with MAO inhibition. This action was prevented by all decarboxylase inhibitors but not FLA 63. Responses to angiotensin were similarly augmented. Thus, MAO inhibition enabled L -dopa to induce severe hypotension, which appeared to rely on a central conversion to dopamine; the other effects were probably mediated by peripherally formed dopamine.