Cerebrospinal fluid concentration gradients of catechols in synucleinopathies.

The synucleinopathies Parkinson disease (PD), multiple system atrophy (MSA), and the Lewy body form of pure autonomic failure (PAF) entail intra-cytoplasmic deposition of the protein alpha-synuclein and pathogenic catecholaminergic neurodegeneration. Cerebrospinal fluid (CSF) levels of catecholamines and their metabolites are thought to provide a "neurochemical window" on central catecholaminergic innervation and can identify specific intra-neuronal dysfunctions in synucleinopathies. We asked whether there are CSF concentration gradients for catechols such as 3,4-dihydroxyphenylacetic acid (DOPAC), the main neuronal metabolite of dopamine, and if so whether the gradients influence neurochemical differences among synucleinopathies. In a retrospective cohort study, we reviewed data about concentrations of catechols in the first, sixth, and twelfth 1-mL aliquots from 33 PD, 28 MSA, and 15 PAF patients and 41 controls. There were concentration gradients for DOPAC, dopamine, norepinephrine, and 3,4-dihydroxyphenylglycol (the main neuronal metabolite of norepinephrine) and gradients in the opposite direction for 5-S-cysteinyldopa and 5-S-cysteinyldopamine. In all 3 aliquots, CSF DOPAC was low in PD and MSA compared with controls (p < 0.0001 each) and normal in PAF. Synucleinopathies differ in CSF catechols regardless of concentration gradients. Concentration gradients for 5-S-cysteinyl derivatives in opposite directions from the parent catechols may provide biomarkers of spontaneous oxidation in the CSF space.

A pathophysiological biomarker combination separates Lewy body from non-Lewy body neurogenic orthostatic hypotension ​.

PURPOSE: Neurogenic orthostatic hypotension (nOH) results from deficient reflexive delivery of norepinephrine to cardiovascular receptors in response to decreased cardiac venous return. Lewy body (LB) forms of nOH are characterized by low 18F-dopamine-derived radioactivity (a measure of cardiac noradrenergic deficiency), olfactory dysfunction by the University of Pennsylvania Smell Identification Test (UPSIT), and increased deposition of alpha-synuclein (α-syn) in dermal sympathetic noradrenergic nerves by the α-syn-tyrosine hydroxylase (TH) colocalization index. This observational, cross-sectional study explored whether combinations of these biomarkers specifically identify LB forms of nOH. METHODS: Clinical laboratory data were reviewed from patients referred for evaluation at the National Institutes of Health for chronic autonomic failure between 2011 and 2023. The cutoff value for low myocardial 18F-dopamine-derived radioactivity was 6000 nCi-kg/cc-mCi, for olfactory dysfunction an UPSIT score ≤ 28, and for an increased α-syn-TH colocalization index ≥ 1.57. RESULTS: A total of 44 patients (31 LB, 13 non-LB nOH) had data for all three biomarkers. Compared to the non-LB group, the LB nOH group had low myocardial 18F-dopamine-derived radioactivity, low UPSIT scores, and high α-syn-TH colocalization indexes (p < 0.0001 each). Combining the three biomarkers completely separated the groups. Cluster analysis identified two distinct groups (p < 0.0001) independently of the clinical diagnosis, with one cluster corresponding exactly to LB nOH. CONCLUSION: LB forms of nOH feature cardiac noradrenergic deficiency, olfactory dysfunction, and increased α-syn-TH colocalization in skin biopsies. Combining the data for these variables efficiently separates LB from non-LB nOH. Independently of the clinical diagnosis, this biomarker triad identifies a pathophysiologically distinct cluster of nOH patients.

Cardiac 18F-dopamine positron emission tomography predicts the type of phenoconversion of pure autonomic failure.

PURPOSE: Pure autonomic failure (PAF) is a rare disease characterized by neurogenic orthostatic hypotension (nOH), no known secondary cause, and lack of a neurodegenerative movement or cognitive disorder. Clinically diagnosed PAF can evolve ("phenoconvert") to a central Lewy body disease [LBD, e.g., Parkinson's disease (PD) or dementia with Lewy bodies (DLB)] or to the non-LBD synucleinopathy multiple system atrophy (MSA). Since cardiac 18F-dopamine-derived radioactivity usually is low in LBDs and usually is normal in MSA, we hypothesized that patients with PAF with low cardiac 18F-dopamine-derived radioactivity would be more likely to phenoconvert to a central LBD than to MSA. METHODS: We reviewed data from all the patients seen at the National Institutes of Health Clinical Center from 1994 to 2023 with a clinical diagnosis of PAF and data about 18F-dopamine positron emission tomography (PET). RESULTS: Nineteen patients (15 with low 18F-dopamine-derived radioactivity, 4 with normal radioactivity) met the above criteria and had follow-up data. Nine (47%) phenoconverted to a central synucleinopathy over a mean of 6.6 years (range 1.5-18.8 years). All 6 patients with low cardiac 18F-dopamine-derived radioactivity who phenoconverted during follow-up developed a central LBD, whereas none of 4 patients with consistently normal 18F-dopamine PET phenoconverted to a central LBD (p = 0.0048), 3 evolving to probable MSA and 1 upon autopsy having neither a LBD nor MSA. CONCLUSION: Cardiac 18F-dopamine PET can predict the type of phenoconversion of PAF. This capability could refine eligibility criteria for entry into disease-modification trials aimed at preventing evolution of PAF to symptomatic central LBDs.

Is 18F-DOPA a valid cardiac sympathetic neuroimaging agent?

PURPOSE: 18F-Dopamine positron emission tomography is a validated method for identifying cardiac noradrenergic deficiency, a characteristic feature of Lewy body forms of neurogenic orthostatic hypotension; however, 18F-dopamine is a research drug. Brain 18F-DOPA positron emission tomography is FDA-approved. Since 18F-DOPA is converted to 18F-dopamine in the heart, 18F-DOPA might be useful for cardiac sympathetic neuroimaging. We compared 18F-DOPA with 18F-dopamine in patients who either had or did not have low 18F-dopamine-derived radioactivity. METHODS: Brain and cardiac 18F-DOPA scanning and cardiac 18F-dopamine scanning were done on separate days in patient groups with neurogenic orthostatic hypotension or Parkinsonism or control subjects across a range of values for 18F-dopamine-derived radioactivity. The lower limit of normal for myocardial 18F-dopamine-derived radioactivity was 6000 Bq-kg/cc-MBq. We also examined inter-relationships among cardiac 18F-DOPA-derived radioactivity, cardiac 18F-dopamine-derived radioactivity, putamen/occipital cortex ratios of 18F-DOPA-derived radioactivity, and Unified Parkinson Disease Rating Scale scores in patients with or without Parkinsonism. For putamen/occipital cortex ratios, the cutoff value was 2.70. RESULTS: Twelve subjects had severely decreased and eight normal cardiac 18F-dopamine-derived radioactivity. Cardiac 18F-DOPA-derived radioactivity did not distinguish the two groups and was unrelated to 18F-dopamine-derived radioactivity. Left ventricular myocardial 18F-DOPA-derived radioactivity was poorly resolved from that in the chamber. Putamen/occipital cortex ratios of 18F-DOPA-derived radioactivity were negatively correlated with Unified Parkinson Disease Rating Scale scores (- 0.67, p = 0.0015). CONCLUSIONS: 18F-DOPA does not seem to be a valid cardiac sympathetic neuroimaging agent, although brain 18F-DOPA scanning provides a biomarker of Parkinsonism.

Differential abnormalities of cerebrospinal fluid dopaminergic versus noradrenergic indices in synucleinopathies.

The synucleinopathies Parkinson's disease (PD), multiple system atrophy (MSA), and pure autonomic failure (PAF) are characterized by intra-cytoplasmic deposition of the protein alpha-synuclein and by catecholamine depletion. PAF, which manifests with neurogenic orthostatic hypotension (nOH) and no motor signs of central neurodegeneration, can evolve into PD+nOH. The cerebrospinal fluid (CSF) levels of catecholamine metabolites may indicate central catecholamine deficiency in these synucleinopathies, but the literature is inconsistent and incomplete. In this retrospective cohort study we reviewed data about CSF catecholamines, the dopamine metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), and the norepinephrine metabolites 3,4-dihydroxyphenylglycol (DHPG) and 3-methoxy-4-hydroxyphenylglycol (MHPG). The compounds were measured in 36 patients with PD, 37 patients with MSA, and 19 patients with PAF and in 38 controls. Compared to the control group, the PD, MSA, and PAF groups had decreased CSF MHPG (p < .0001 each by Dunnett's post hoc test), DHPG (p = .004; p < .0001; p < .0001) and norepinephrine (p = .017; p = .0003; p = .044). CSF HVA and DOPAC were decreased in PD (p < .0001 each) and MSA (p < .0001 each) but not in PAF. The three synucleinopathies therefore have in common in vivo evidence of central noradrenergic deficiency but differ in the extents of central dopaminergic deficiency-prominent in PD and MSA, less apparent in PAF. Data from putamen 18 F-DOPA and cardiac 18 F-dopamine neuroimaging in the same patients, post-mortem tissue catecholamines in largely separate cohorts, and review of the neuropathology literature fit with these distinctions. The results suggest a 'norepinephrine first' ascending pathogenetic sequence in synucleinopathies, with degeneration of pontine locus ceruleus noradrenergic neurons preceding the loss of midbrain substantia nigra dopaminergic neurons.

Do indices of baroreflex failure and peripheral noradrenergic deficiency predict the magnitude of orthostatic hypotension in Lewy body diseases?

INTRODUCTION: Patients with neurogenic orthostatic hypotension in the setting of Lewy body diseases (LBnOH) typically have baroreflex failure and peripheral noradrenergic deficiency. Either or both of these abnormalities might determine the magnitude of OH in individual patients. We retrospectively correlated the orthostatic fall in systolic blood pressure (∆BPs) during active standing or 5 min of head-up tilt at 90° from horizontal as a function of several baroreflex and sympathetic noradrenergic indices. METHODS: Physiological, neurochemical, and sympathetic neuroimaging data from the Valsalva maneuver, head-up tilt table testing, and thoracic 18F-dopamine positron emission tomographic scanning (18F-DA PET) were analyzed from 72 patients with LBnOH [44 with Parkinson disease (PD) and nOH, 28 with pure autonomic failure]. Comparison subjects had PD without OH (N = 44) or PD risk factors without parkinsonism or OH (N = 28) or were healthy volunteers (N = 8). Indices of baroreflex function included the Valsalva maneuver-associated baroreflex areas in Phase II (BRA-II) and IV (BRA-IV), the pressure recovery time (PRT), and baroreflex-cardiovagal and adrenergic sensitivities (BRS-V and BRS-A). The fractional orthostatic increment in plasma norepinephrine (Fx∆NE) provided a neurochemical index of baroreflex-sympathoneural function. RESULTS: As expected, the LBnOH group had baroreflex-sympathoneural and baroreflex-cardiovagal impairment and low cardiac 18F-DA-derived radioactivity. Among patients, values for ∆BPs correlated with BRA-II, BRA-IV, BRS-V, and Fx∆NE but not with values for PRT, BRS-A, supine plasma NE, or 18F-DA-derived radioactivity. CONCLUSION: Across individual patients with LBnOH, quantitative indices of baroreflex dysfunctions and peripheral noradrenergic deficiency are inconsistently associated with the magnitude of OH, even under controlled laboratory conditions.

Substantial renal conversion of L-threo-3,4-dihydroxyphenylserine (droxidopa) to norepinephrine in patients with neurogenic orthostatic hypotension.

BACKGROUND: The pressor effect of L-threo-3,4-dihydroxyphenylserine (L-DOPS, droxidopa, Northera™) results from conversion of L-DOPS to norepinephrine (NE) in cells expressing L-aromatic-amino-acid decarboxylase (LAAAD). After L-DOPS administration the increase in systemic plasma NE is too small to explain the increase in blood pressure. Renal proximal tubular cells abundantly express LAAAD. Since NE generated locally in the kidneys could contribute to the pressor effect of L-DOPS, in this study we assessed renal conversion of L-DOPS to NE. METHODS: Ten patients who were taking L-DOPS for symptomatic orthostatic hypotension had blood and urine sampled about 2 h after the last L-DOPS dose. L-DOPS and NE were assayed by alumina extraction followed by liquid chromatography with electrochemical detection. Data were compared in patients off vs. on levodopa/carbidopa. RESULTS: In patients off levodopa/carbidopa the ratio of NE/L-DOPS in urine averaged 63 times that in plasma (p = 0.0009 by t test applied to log-transformed data). In marked contrast, in the three patients on levodopa/carbidopa the ratio of NE/L-DOPS in urine did not differ from that in plasma. CONCLUSION: There is extensive renal production of NE from L-DOPS. Carbidopa seems to attenuate the conversion of L-DOPS to NE in the kidneys. Further research is needed to assess whether the proposed paracrine effect of L-DOPS in the kidneys contributes to the systemic pressor response.

Clinical Outcomes of Oral Suspension versus Delayed-Release Tablet Formulations of Posaconazole for Prophylaxis of Invasive Fungal Infections.

Posaconazole is used for prophylaxis for invasive fungal infections (IFIs) among patients with hematologic malignancies. We compared the incidence of breakthrough IFIs and early discontinuation between patients receiving delayed-release tablet and oral suspension formulations of posaconazole. This was a retrospective cohort study of patients receiving posaconazole between 1 January 2010 and 30 June 2016. We defined probable or proven breakthrough IFIs using the European Organization for Research and Treatment of Cancer (EORTC) criteria. Overall, 547 patients received 860 courses of posaconazole (53% received the oral suspension and 48% received the tablet); primary indications for prophylaxis were acute myeloid leukemia (69%), graft-versus-host disease (18%), and myelodysplastic syndrome (3%). There were no significant differences in demographics or indications between patients receiving the different formulations. The incidence and incidence rate of probable or proven IFIs were 1.6% and 3.2 per 10,000 posaconazole days, respectively. There was no significant difference in the rate of IFIs between suspension courses (2.8 per 10,000 posaconazole days) and tablet courses (3.7 per 10,000 posaconazole days) (rate ratio = 0.8, 95% confidence interval [CI] = 0.3 to 2.3). Of the 14 proven or probable cases of IFI, 8/14 had posaconazole serum concentrations measured, and the concentrations in 7/8 were above 0.7 µg/ml. Posaconazole was discontinued early in 15.5% of courses; however, the frequency of discontinuation was also not significantly different between the tablet (16.5%) and oral suspension (14.6%) formulations (95% CI for difference = -0.13 to 0.06). In conclusion, the incidence of breakthrough IFIs was low among patients receiving posaconazole prophylaxis and not significantly different between patients receiving the tablet formulation and those receiving the oral suspension formulation.

Pure autonomic failure without synucleinopathy.

Pure autonomic failure is a rare form of chronic autonomic failure manifesting with neurogenic orthostatic hypotension and evidence of sympathetic noradrenergic denervation unaccompanied by signs of central neurodegeneration. It has been proposed that pure autonomic failure is a Lewy body disease characterized by intra-neuronal deposition of the protein alpha-synuclein in Lewy bodies and neurites. A middle-aged man with previously diagnosed pure autonomic failure experienced a sudden, fatal cardiac arrest. He was autopsied, and tissues were harvested for neurochemical and immunofluorescence studies. Post-mortem microscopic neuropathology showed no Lewy bodies, Lewy neurites, or alpha-synuclein deposition by immunohistochemistry anywhere in the brain. The patient had markedly decreased immunofluorescent tyrosine hydroxylase in sympathetic ganglion tissue without detectable alpha-synuclein even in rare residual nests of tyrosine hydroxylase-containing ganglionic fibers. In pure autonomic failure, sympathetic noradrenergic denervation can occur without concurrent Lewy bodies or alpha-synuclein deposition in the brain or sympathetic ganglion tissue.

Autoimmunity-associated autonomic failure with sympathetic denervation.

We report a case of autoimmunity-associated autonomic failure in a young adult woman who developed arthritis followed 3 years later by pandysautonomia. There was early recovery of parasympathetic functions but persistent neurogenic orthostatic hypotension from post-ganglionic sympathetic denervation. Clinical laboratory testing indicated variable amounts of sympathetic neuronal re-sprouting in the heart, kidneys, eyes, and body as a whole upon follow-up evaluation after 1.5 years.

Comparison of Monoamine Oxidase Inhibitors in Decreasing Production of the Autotoxic Dopamine Metabolite 3,4-Dihydroxyphenylacetaldehyde in PC12 Cells.

According to the catecholaldehyde hypothesis, the toxic dopamine metabolite 3,4-dihydroxyphenylacetaldehyde (DOPAL) contributes to the loss of nigrostriatal dopaminergic neurons in Parkinson's disease. Monoamine oxidase-A (MAO-A) catalyzes the conversion of intraneuronal dopamine to DOPAL and may serve as a therapeutic target. The "cheese effect"-paroxysmal hypertension evoked by tyramine-containing foodstuffs-limits clinical use of irreversible MAO-A inhibitors. Combined MAO-A/B inhibition decreases DOPAL production in rat pheochromocytoma PC12 cells, but whether reversible MAO-A inhibitors or MAO-B inhibitors decrease endogenous DOPAL production is unknown. We compared the potencies of MAO inhibitors in attenuating DOPAL production and examined possible secondary effects on dopamine storage, constitutive release, synthesis, and auto-oxidation. Catechol concentrations were measured in cells and medium after incubation with the irreversible MAO-A inhibitor clorgyline, three reversible MAO-A inhibitors, or the MAO-B inhibitors selegiline or rasagiline for 180 minutes. Reversible MAO-A inhibitors were generally ineffective, whereas clorgyline (1 nM), rasagiline (500 nM), and selegiline (500 nM) decreased DOPAL levels in the cells and medium. All three drugs also increased dopamine and norepinephrine, decreased 3,4-dihydroxyphenylalanine, and increased cysteinyl-dopamine concentrations in the medium, suggesting increased vesicular uptake and constitutive release, decreased dopamine synthesis, and increased dopamine spontaneous oxidation. In conclusion, clorgyline, rasagiline, and selegiline decrease production of endogenous DOPAL. At relatively high concentrations, the latter drugs probably lose their selectivity for MAO-B. Possibly offsetting increased formation of potentially toxic oxidation products and decreased formation of DOPAL might account for the failure of large clinical trials of MAO-B inhibitors to demonstrate slowing of neurodegeneration in Parkinson's disease.

3,4-Dihydroxyphenylethanol (Hydroxytyrosol) Mitigates the Increase in Spontaneous Oxidation of Dopamine During Monoamine Oxidase Inhibition in PC12 Cells.

The catecholaldehyde hypothesis predicts that monoamine oxidase (MAO) inhibition should slow the progression of Parkinson's disease, by decreasing production of the autotoxic dopamine metabolite 3,4-dihydroxyphenylacetaldehyde (DOPAL). Inhibiting MAO, however, diverts the fate of cytoplasmic dopamine toward potentially harmful spontaneous oxidation products, indicated by increased 5-S-cysteinyl-dopamine (Cys-DA) levels. 3,4-Dihydroxyphenylethanol (hydroxytyrosol) is an abundant anti-oxidant phenol in constituents of the Mediterranean diet. Whether hydroxytyrosol alters enzymatic or spontaneous oxidation of dopamine has been unknown. Rat pheochromocytoma PC12 cells were incubated with hydroxytyrosol (10 µM, 180 min) alone or with the MAO-A inhibitor clorgyline (1 nM) or the MAO-B inhibitors rasagiline or selegiline (0.5 µM). Hydroxytyrosol decreased levels of DOPAL by 30 % and Cys-DA by 49 % (p < 0.0001 each). Co-incubation with hydroxytyrosol prevented the increases in Cys-DA seen with all 3 MAO inhibitors. Hydroxytyrosol therefore inhibits both enzymatic and spontaneous oxidation of endogenous dopamine and mitigates the increase in spontaneous oxidation during MAO inhibition.

Plasma biomarkers of decreased vesicular storage distinguish Parkinson disease with orthostatic hypotension from the parkinsonian form of multiple system atrophy.

BACKGROUND: Parkinson disease with orthostatic hypotension (PD + OH) and the parkinsonian form of multiple system atrophy (MSA-P) can be difficult to distinguish clinically. Recent studies indicate that PD entails a vesicular storage defect in catecholaminergic neurons. Although cardiac sympathetic neuroimaging by (18)F-dopamine positron emission tomography can identify decreased vesicular storage, this testing is not generally available. We assessed whether plasma biomarkers of a vesicular storage defect can separate PD + OH from MSA-P. METHODS: We conceptualized that after F-dopamine injection, augmented production of F-dihydroxyphenylacetic acid (F-DOPAC) indicates decreased vesicular storage, and we therefore predicted that arterial plasma F-DOPAC would be elevated in PD + OH but not in MSA-P. We measured arterial plasma F-DOPAC after (18)F-dopamine administration (infused i.v. over 3 min) in patients with PD + OH (N = 12) or MSA-P (N = 21) and in healthy control subjects (N = 26). Peak F-DOPAC:dihydroxyphenylglycol (DHPG) was also calculated to adjust for effects of denervation on F-DOPAC production. RESULTS: Plasma F-DOPAC accumulated rapidly after initiation of (18)F-dopamine infusion. Peak F-DOPAC (5-10 min) in PD + OH averaged three times that in MSA-P (P < 0.0001). Among MSA-P patients, none had peak F-DOPAC > 300 nCi-kg/cc-mCi, in contrast with 7 of 12 PD + OH patients (χ(2) = 16.6, P < 0.0001). DHPG was lower in PD + OH (3.83 ± 0.36 nmol/L) than in MSA-P (5.20 ± 0.29 nmol/L, P = 0.007). All MSA-P patients had peak F-DOPAC:DHPG < 60, in contrast with 9 of 12 PD + OH patients (χ(2) = 17.5, P < 0.0001). Adjustment of peak F-DOPAC for DHPG increased test sensitivity from 58 to 81% at similar high specificity. INTERPRETATION: After F-dopamine injection, plasma F-DOPAC and F-DOPAC:DHPG distinguish PD + OH from MSA-P.

A vesicular sequestration to oxidative deamination shift in myocardial sympathetic nerves in Parkinson's disease.

In Parkinson's disease (PD), profound putamen dopamine (DA) depletion reflects denervation and a shift from vesicular sequestration to oxidative deamination of cytoplasmic DA in residual terminals. PD also involves cardiac sympathetic denervation. Whether PD entails myocardial norepinephrine (NE) depletion and a sequestration-deamination shift have been unknown. We measured apical myocardial tissue concentrations of NE, DA, and their neuronal metabolites 3,4-dihydroxyphenylglycol (DHPG), and 3,4-dihydroxyphenylacetic acid (DOPAC) from 23 PD patients and 23 controls and ascertained the extent of myocardial NE depletion in PD. We devised, validated in VMAT2-Lo mice, and applied 5 neurochemical indices of the sequestration-deamination shift-concentration ratios of DOPAC:DA, DA:NE, DHPG:NE, DOPAC:NE, and DHPG:DOPAC-and used a kinetic model to estimate the extent of the vesicular storage defect. The PD group had decreased myocardial NE content (p < 0.0001). The majority of patients (70%) had severe NE depletion (mean 2% of control), and in this subgroup all five indices of a sequestration-deamination shift were increased compared to controls (p < 0.001 for each). Vesicular storage in residual nerves was estimated to be decreased by 84-91% in this subgroup. We conclude that most PD patients have severe myocardial NE depletion, because of both sympathetic denervation and decreased vesicular storage in residual nerves. We found that the majority (70%) of Parkinson's disease (PD) patients have profound (98%) myocardial norepinephrine depletion, because of both cardiac sympathetic denervation and a shift from vesicular sequestration to oxidative deamination of cytoplasmic catecholamines in the residual nerves. This shift may be part of a final common pathogenetic pathway in the loss of catecholaminergic neurons that characterizes PD.

Intra-neuronal alpha-synuclein deposition is related to cardiac noradrenergic deficiency and olfactory dysfunction in neurogenic orthostatic hypotension.

Purpose: Neurogenic orthostatic hypotension (nOH) results from deficient reflexive delivery of norepinephrine to cardiovascular receptors in response to decreased cardiac venous return. Lewy body (LB) forms of nOH entail low 18F-dopamine-derived radioactivity (a measure of cardiac noradrenergic deficiency), olfactory dysfunction by the University of Pennsylvania Smell Identification Test (UPSIT), and increased deposition of alpha-synuclein (ɑ-syn) in dermal sympathetic noradrenergic nerves by the ɑ-syn-tyrosine hydroxylase (TH) colocalization index. This observational, cross-sectional study explored whether combinations of these biomarkers specifically identify LB forms of nOH. Methods: Clinical laboratory data were reviewed from patients referred for evaluation at the National Institutes of Health for chronic autonomic failure between 2011 and 2023. The cutoff value for low myocardial 18F-dopamine-derived radioactivity was 6,000 nCi-kg/cc-mCi, for olfactory dysfunction an UPSIT score ≤ 28, and for an increased ɑ-syn-TH colocalization index ≥ 1.57. Results: A total of 44 patients (31 LB, 13 non-LB nOH) had data for all 3 biomarkers. Compared to the non-LB group, the LB nOH group had low myocardial 18F-dopamine-derived radioactivity, low UPSIT scores, and high ɑ-syn-TH colocalization indexes (p<0.0001 each). Combining the 3 biomarkers completely separated the groups. Cluster analysis identified 2 distinct groups (p<0.0001) independently of the clinical diagnosis, 1 cluster corresponding exactly to LB nOH. Conclusion: LB forms of nOH feature cardiac noradrenergic deficiency, olfactory dysfunction, and increased ɑ-syn-TH colocalization in skin biopsies. Combining the data for these variables efficiently separates LB from non-LB nOH. Independently of the clinical diagnosis, this biomarker triad identifies a pathophysiologically distinct cluster of nOH patients.

Cardiac noradrenergic deficiency revealed by 18F-dopamine positron emission tomography identifies preclinical central Lewy body diseases.

BACKGROUND: In Lewy body diseases (LBDs) Parkinson disease (PD), and dementia with Lewy bodies (DLB), by the time parkinsonism or cognitive dysfunction manifests clinically, substantial neurodegeneration has already occurred. Biomarkers are needed to identify central LBDs in a preclinical phase, when neurorescue strategies might forestall symptomatic disease. This phase may involve catecholamine deficiency in the autonomic nervous system. We analyzed data from the prospective, observational, long-term PDRisk study to assess the predictive value of low versus normal cardiac 18F-dopamine positron emission tomography (PET), an index of myocardial content of the sympathetic neurotransmitter norepinephrine, in at-risk individuals. METHODS: Participants self-reported risk factor information (genetics, olfactory dysfunction, dream enactment behavior, and orthostatic intolerance or hypotension) at a protocol-specific website. Thirty-four with 3 or more confirmed risk factors underwent serial cardiac 18F-dopamine PET at 1.5-year intervals for up to 7.5 years or until PD was diagnosed. RESULTS: Nine participants had low initial myocardial 18F-dopamine-derived radioactivity (<6,000 nCi-kg/cc-mCi) and 25 had normal radioactivity. At 7 years of follow-up, 8 of 9 with low initial radioactivity and 1 of 11 with normal radioactivity were diagnosed with a central LBD (LBD+) (P = 0.0009 by Fisher's exact test). Conversely, all 9 LBD+ participants had low 18F-dopamine-derived radioactivity before or at the time of diagnosis of a central LBD, whereas among 25 participants without a central LBD only 1 (4%) had persistently low radioactivity (P < 0.0001 by Fisher's exact test). CONCLUSION: Cardiac 18F-dopamine PET highly efficiently distinguishes at-risk individuals who are diagnosed subsequently with a central LBD from those who are not. CLINICALTRIALS: gov NCT00775853. FUNDING: Division of Intramural Research, NIH, NINDS.

Determinants of buildup of the toxic dopamine metabolite DOPAL in Parkinson's disease.

Intra-neuronal metabolism of dopamine (DA) begins with production of 3,4-dihydroxyphenylacetaldehyde (DOPAL),which is toxic. According to the 'catecholaldehyde hypothesis', DOPAL destroys nigrostriatal DA terminals and contributes to the profound putamen DA deficiency that characterizes Parkinson's disease (PD). We tested the feasibility of using post-mortem patterns of putamen tissue catechols to examine contributions of altered activities of the type 2 vesicular monoamine transporter (VMAT2) and aldehyde dehydrogenase(ALDH) to the increased DOPAL levels found in PD. Theoretically, the DA : DOPA concentration ratio indicates vesicular uptake, and the 3,4-dihydroxyphenylacetic acid: DOPAL ratio indicates ALDH activity. We validated these indices in transgenic mice with very low vesicular uptake VMAT2-Lo) or with knockouts of the genes encoding ALDH1A1 and ALDH2 (ALDH1A1,2 KO), applied these indices in PD putamen, and estimated the percent decreases in vesicular uptake and ALDH activity in PD. VMAT2-Lo mice had markedly decreased DA:DOPA (50 vs. 1377, p < 0.0001),and ALDH1A1,2 KO mice had decreased 3,4-dihydroxyphenylacetic acid:DOPAL (1.0 vs. 11.2, p < 0.0001). In PD putamen, vesicular uptake was estimated to be decreased by 89% and ALDH activity by 70%. Elevated DOPAL levels in PD putamen reflect a combination of decreased vesicular uptake of cytosolic DA and decreased DOPAL detoxification by ALDH.

A fluorescent peptoid pH-sensor.

Peptoids, N-substituted glycine oligomers, can adopt stable three-dimensional structures and have found diverse application as peptide surrogates and as nanomaterials. In this report, we have expanded peptoid function to include pH sensing by coupling pH-induced peptoid conformational changes with fluorescence intensity changes. We report two new peptoids (2 and 3) that comprise carboxylic-acid functionalized side chains and undergo conformational rearrangement in response to pH. Peptoids 2 and 3 are also labeled at one side-chain with an environmentally sensitive fluorophore, 4-N,N-dimethylamino-1,8-naphthalimide (4DMN). The fluorescence intensity of 2 varies 24-fold over the pH range studied. These spectroscopic properties make 2 a sensitive, biocompatible pH sensor.

Cerebrospinal fluid biomarkers of central catecholamine deficiency in Parkinson's disease and other synucleinopathies.

Central catecholamine deficiency characterizes α-synucleinopathies such as Parkinson's disease. We hypothesized that cerebrospinal fluid levels of neuronal metabolites of catecholamines provide neurochemical biomarkers of these disorders. To test this hypothesis we measured cerebrospinal fluid levels of catechols including dopamine, norepinephrine and their main respective neuronal metabolites dihydroxyphenylacetic acid and dihydroxyphenylglycol in Parkinson's disease and two other synucleinopathies, multiple system atrophy and pure autonomic failure. Cerebrospinal fluid catechols were assayed in 146 subjects-108 synucleinopathy patients (34 Parkinson's disease, 54 multiple system atrophy, 20 pure autonomic failure) and 38 controls. In 14 patients cerebrospinal fluid was obtained before or within 2 years after the onset of parkinsonism. The Parkinson's disease, multiple system atrophy and pure autonomic failure groups all had lower cerebrospinal fluid dihydroxyphenylacetic acid [0.86 ± 0.09 (SEM), 1.00 ± 0.09, 1.32 ± 0.12 nmol/l] than controls (2.15 ± 0.18 nmol/l; P < 0.0001; P < 0.0001; P = 0.0002). Dihydroxyphenylglycol was also lower in the three synucleinopathies (8.82 ± 0.44, 7.75 ± 0.42, 5.82 ± 0.65 nmol/l) than controls (11.0 ± 0.62 nmol/l; P = 0.009, P < 0.0001, P < 0.0001). Dihydroxyphenylacetic acid was lower and dihydroxyphenylglycol higher in Parkinson's disease than in pure autonomic failure. Dihydroxyphenylacetic acid was 100% sensitive at 89% specificity in separating patients with recent onset of parkinsonism from controls but was of no value in differentiating Parkinson's disease from multiple system atrophy. Synucleinopathies feature cerebrospinal fluid neurochemical evidence for central dopamine and norepinephrine deficiency. Parkinson's disease and pure autonomic failure involve differential dopaminergic versus noradrenergic lesions. Cerebrospinal fluid dihydroxyphenylacetic acid seems to provide a sensitive means to identify even early Parkinson's disease.

Cardiac 18F-Dopamine Positron Emission Tomography Predicts the Type of Phenoconversion of Pure Autonomic Failure.

Background: Pure autonomic failure (PAF) is a rare disease characterized clinically by neurogenic orthostatic hypotension (nOH) and biochemically by peripheral noradrenergic deficiency. Clinically diagnosed PAF can evolve ("phenoconvert") to a central Lewy body disease (LBD, e.g., Parkinson's disease (PD) or dementia with Lewy bodies (DLB)) or to the non-LBD synucleinopathy multiple system atrophy (MSA). We examined whether cardiac 18F-dopamine positron emission tomography (PET) predicts the trajectory of phenoconversion in PAF. Since cardiac 18F-dopamine-derived radioactivity always is decreased in LBDs with nOH and usually is normal in MSA, we hypothesized that PAF patients with low cardiac 18F-dopamine-derived radioactivity may phenoconvert to a central LBD but do not phenoconvert to MSA. Methods: We reviewed data from all the patients seen at the National Institutes of Health Clinical Center from 1994 to 2023 with a clinical diagnosis of PAF and data about serial 18F-dopamine PET. Results: Twenty patients met the above criteria. Of 15 with low cardiac 18F-dopamine-derived radioactivity, 6 (40%) phenoconverted to PD or DLB and none to MSA. Of 5 patients with consistently normal 18F-dopamine PET, 4 phenoconverted to MSA, and the other at autopsy had neither a central LBD nor MSA. Conclusion: In this case series, 40% of patients with nOH and low cardiac 18F-dopamine-derived radioactivity phenoconverted to PD or DLB during follow-up; none phenoconverted to MSA. Cardiac 18F-DA PET therefore can predict the type of phenoconversion in PAF. This capability could refine eligibility criteria for entry into disease-modification trials aiming to prevent evolution of PAF to symptomatic central LBDs.