Prevalence of Late-Stage Parkinson's Disease in the US Healthcare System: Insights from TriNetX.

BACKGROUND: Patients in late-stage Parkinson's disease (PDLS) are caregiver-dependent, have low quality of life, and higher healthcare costs. OBJECTIVE: To estimate the prevalence of PDLS patients in the current US healthcare system. METHODS: We downloaded the 2010-2022 data from the TriNetX Diamond claims network that consists of 92 US healthcare sites. PD was identified using standard diagnosis codes, and PDLS was identified by the usage of wheelchair dependence, personal care assistance, and/or presence of diagnoses of dementia. Age of PDLS identification and survival information were obtained and stratified by demographic and the disability subgroups. RESULTS: We identified 1,031,377 PD patients in the TriNetX database. Of these, 18.8% fitted our definition of PDLS (n = 194,297), and 10.2% met two or more late-stage criteria. Among all PDLS, the mean age of PDLS identification was 78.1 (±7.7) years, and 49% were already reported as deceased. PDLS patients were predominantly male (58.5%) with similar distribution across PDLS subgroups. The majority did not have race (71%) or ethnicity (69%) information, but for the available information >90% (n = 53,162) were White, 8.2% (n = 5121) Hispanic/Latino, 7.8% (n = 4557) Black, and <0.01% (n = 408) Asian. Of the PDLS cohort, 71.6% identified with dementia, 12.9% had personal care assistance, and 4.8% were wheelchair-bound. CONCLUSIONS: Late-stage patients are a significant part of the PD landscape in the current US healthcare system, and largely missed by traditional motor-based disability staging. It is imperative to include this population as a clinical, social, and research priority. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Dopamine D1 Receptor Agonists Rescue Age-related Decline in Temporal Order Memory.

Dopamine D1 receptor agonists improve spatial working memory, but their effects on temporal order memory, particularly prone to the effects of aging, have not been studied. Two D1 agonists, PF6256142 (PF) and 2-methyldihydrexidine (2MDHX), were examined for their effects in a rodent temporal order recognition task. Our results are consistent with the hypothesis that there is an age-related decline in rodent temporal order memory. The data also show that either agonist rescues the poor memory performance with a large effective size. Interestingly, the optimal effective dose varied among individual rats of different age groups. PF showed greater potency for older rats, whereas 2MDHX showed better overall population effectiveness. Both PF and 2MDHX have high intrinsic activity at rodent D1-mediated cAMP synthesis. Conversely, at D1-mediated ß-arrestin recruitment, PF has essentially no intrinsic activity, whereas 2MDHX is a super-agonist. These findings suggest that D1 agonists have potential to treat age-related cognitive decline, and the pattern of functional selectivity may be useful for developing drugs with an improved therapeutic index.

Effects of mixed metal exposures on MRI diffusion features in the medial temporal lobe.

Background: Environmental exposure to metal mixtures is common and may be associated with increased risk for neurodegenerative disorders including Alzheimer's disease. Objective: This study examined associations of mixed metal exposures with medial temporal lobe (MTL) MRI structural metrics and neuropsychological performance. Methods: Metal exposure history, whole blood metal, and neuropsychological tests were obtained from subjects with/without a history of mixed metal exposure from welding fumes (42 exposed subjects; 31 controls). MTL structures (hippocampus, entorhinal and parahippocampal cortices) were assessed by morphologic (volume, cortical thickness) and diffusion tensor imaging [mean (MD), axial (AD), radial diffusivity (RD), and fractional anisotropy (FA)] metrics. In exposed subjects, correlation, multiple linear, Bayesian kernel machine regression, and mediation analyses were employed to examine effects of single- or mixed-metal predictor(s) and their interactions on MTL structural and neuropsychological metrics; and on the path from metal exposure to neuropsychological consequences. Results: Compared to controls, exposed subjects had higher blood Cu, Fe, K, Mn, Pb, Se, and Zn levels (p's<0.026) and poorer performance in processing/psychomotor speed, executive, and visuospatial domains (p's<0.046). Exposed subjects displayed higher MD, AD, and RD in all MTL ROIs (p's<0.040) and lower FA in entorhinal and parahippocampal cortices (p's<0.033), but not morphological differences. Long-term mixed-metal exposure history indirectly predicted lower processing speed performance via lower parahippocampal FA (p=0.023). Higher whole blood Mn and Cu predicted higher entorhinal diffusivity (p's<0.043) and lower Delayed Story Recall performance (p=0.007) without overall metal mixture or interaction effects. Discussion: Mixed metal exposure predicted MTL structural and neuropsychological features that are similar to Alzheimer's disease at-risk populations. These data warrant follow-up as they may illuminate the path for environmental exposure to Alzheimer's disease-related health outcomes.

Resting-state global brain activity affects early ß-amyloid accumulation in default mode network.

It remains unclear why ß-amyloid (Aß) plaque, a hallmark pathology of Alzheimer's disease (AD), first accumulates cortically in the default mode network (DMN), years before AD diagnosis. Resting-state low-frequency ( < 0.1 Hz) global brain activity recently was linked to AD, presumably due to its role in glymphatic clearance. Here we show that the preferential Aß accumulation in the DMN at the early stage of Aß pathology was associated with the preferential reduction of global brain activity in the same regions. This can be partly explained by its failure to reach these regions as propagating waves. Together, these findings highlight the important role of resting-state global brain activity in early preferential Aß deposition in the DMN.

Student Perceptions of a New Course Using Argumentation in Medical Education.

Purpose: Critical thinking and the ability to engage with others of differing views in a civil manner is essential to the practice of medicine. A new format for medical student education ("Argue-to-Learn") that uses staged debates followed by small group discussions was introduced into the curriculum of first year medical school at the Penn State College of Medicine. The goal was to create a structured environment for spirited, civil discourse, and to encourage students to think critically about clinically controversial topics. This manuscript describes the development of the program, and presents comparative data on student perceptions of the first two mandatory sessions that focused on the treatment of post-menopausal osteoporosis and on COVID-19 vaccine mandates. Methods: Quantitative results were gathered from standardized post-block student surveys for each session and compared to cumulative results of all other courses included in the learning block. Post-block surveys of students include four session-evaluation questions scored on a 5 point Likert scale. Scores were compared using Student's t-test. Thematic analysis of qualitative data was performed on a single open-ended response from the same survey. Results: Compared to all other courses in the learning block, scores on each of the four questions were either the same or numerically higher for the Argue-to-Learn sessions, but none reached statistical significance. Two important qualitative themes were identified. First, students enjoyed the format, found it interesting and engaging and want more similar sessions. Second, students appreciated hearing opposing viewpoints and presenting their own viewpoints in a safe and supportive environment. Conclusion: These findings support evidence from educational scholarship outside of medicine showing argumentation as a learning tool is well received by students. Further work is needed to determine whether it improves critical thinking skills and enhances learning in medical education.

Characterization of behavioral changes in T-maze alternation from dopamine D1 agonists with different receptor coupling mechanisms.

RATIONALE: Dopamine D1 receptor agonists have been shown to improve working memory, but often have a non-monotonic (inverted-U) dose-response curve. One hypothesis is that this may reflect dose-dependent differential engagement of D1 signaling pathways, a mechanism termed functional selectivity or signaling bias. OBJECTIVES AND METHODS: To test this hypothesis, we compared two D1 ligands with different signaling biases in a rodent T-maze alternation task. Both tested ligands (2-methyldihydrexidine and CY208243) have high intrinsic activity at cAMP signaling, but the former also has markedly higher intrinsic activity at D1-mediated recruitment of ß-arrestin. The spatial working memory was assessed via the alternation behavior in the T-maze where the alternate choice rate quantified the quality of the memory and the duration prior to making a choice represented the decision latency. RESULTS: Both D1 drugs changed the alternate rate and the choice latency in a dose-dependent manner, albeit with important differences. 2-Methyldihydrexidine was somewhat less potent but caused a more homogeneous improvement than CY208243 in spatial working memory. The maximum changes in the alternate rate and the choice latency tended to occur at different doses for both drugs. CONCLUSIONS: These data suggest that D1 signaling bias in these two pathways (cAMP vs ß-arrestin) has complex effects on cognitive processes as assessed by T-maze alternation. Understanding these mechanisms should allow the identification or discovery of D1 agonists that can provide superior cognitive enhancement.

Quantifying network behavior in the rat prefrontal cortex: a reproducibility crisis.

The question of how consciousness and behavior arise from neural activity is fundamental to understanding the brain, and to improving the diagnosis and treatment of neurological and psychiatric disorders. There is significant murine and primate literature on how behavior is related to the electrophysiological activity of the medial prefrontal cortex and its role in working memory processes such as planning and decision-making. Existing experimental designs, however, have insufficient statistical power to unravel the complex processes of the prefrontal cortex. We therefore examined the theoretical limitations of such experiments, providing concrete guidelines for robust and reproducible science. We piloted the use of dynamic time warping and associated statistical tests to data from neuron spike trains and local field potentials, to quantify neural network synchronicity and correlate neuroelectrophysiology with rat behavior. Our results indicate the statistical limitations of existing data, making meaningful comparison between dynamic time warping with traditional Fourier and wavelet analysis currently impossible until larger and cleaner datasets are available. Significance Statement: The prefrontal cortex is important in decision-making, yet no robust method currently exists to correlate neuron firing in the PFC to behavior. We argue that existing experimental designs are ill-suited to addressing these scientific questions, and we propose a potential method using dynamic time warping to analyze PFC neural electrical activity. We conclude that careful curation of experimental controls is needed to separate true neural signals from noise accurately.

Dopamine D1 Agonists: First Potential Treatment for Late-Stage Parkinson's Disease.

Current pharmacotherapy has limited efficacy and/or intolerable side effects in late-stage Parkinson's disease (LsPD) patients whose daily life depends primarily on caregivers and palliative care. Clinical metrics inadequately gauge efficacy in LsPD patients. We explored if a D1/5 dopamine agonist would have efficacy in LsPD using a double-blind placebo-controlled crossover phase Ia/b study comparing the D1/5 agonist PF-06412562 to levodopa/carbidopa in six LsPD patients. Caregiver assessment was the primary efficacy measure because caregivers were with patients throughout the study, and standard clinical metrics inadequately gauge efficacy in LsPD. Assessments included standard quantitative scales of motor function (MDS-UPDRS-III), alertness (Glasgow Coma and Stanford Sleepiness Scales), and cognition (Severe Impairment and Frontal Assessment Batteries) at baseline (Day 1) and thrice daily during drug testing (Days 2-3). Clinicians and caregivers completed the clinical impression of change questionnaires, and caregivers participated in a qualitative exit interview. Blinded triangulation of quantitative and qualitative data was used to integrate findings. Neither traditional scales nor clinician impression of change detected consistent differences between treatments in the five participants who completed the study. Conversely, the overall caregiver data strongly favored PF-06412562 over levodopa in four of five patients. The most meaningful improvements converged on motor, alertness, and functional engagement. These data suggest for the first time that there can be useful pharmacological intervention in LsPD patients using D1/5 agonists and also that caregiver perspectives with mixed method analyses may overcome limitations using methods common in early-stage patients. The results encourage future clinical studies and understanding of the most efficacious signaling properties of a D1 agonist for this population.

A noncommutative combinatorial protein logic circuit controls cell orientation in nanoenvironments.

Single-protein-based devices that integrate signal sensing with logical operations to generate functional outputs offer exceptional promise for monitoring and modulating biological systems. Engineering such intelligent nanoscale computing agents is challenging, as it requires the integration of sensor domains into a functional protein via intricate allosteric networks. We incorporate a rapamycin-sensitive sensor (uniRapR) and a blue light-responsive LOV2 domain into human Src kinase, creating a protein device that functions as a noncommutative combinatorial logic circuit. In our design, rapamycin activates Src kinase, causing protein localization to focal adhesions, whereas blue light exerts the reverse effect that inactivates Src translocation. Focal adhesion maturation induced by Src activation reduces cell migration dynamics and shifts cell orientation to align along collagen nanolane fibers. Using this protein device, we reversibly control cell orientation by applying the appropriate input signals, a framework that may be useful in tissue engineering and regenerative medicine.

Higher hippocampal diffusivity values in welders are associated with greater R2* in the red nucleus and lower psychomotor performance.

INTRODUCTION: Chronic excessive welding exposure may be related to higher metal accumulation and structural differences in different subcortical structures. We examined how welding affected brain structures and their associations with metal exposure and neurobehavioral consequences. METHODS: Study includes 42 welders and 31 controls without a welding history. Welding-related structural differences were assessed by volume and diffusion tensor imaging (DTI) metrics in basal ganglia, red nucleus (RN), and hippocampus. Metal exposure was estimated by both exposure questionnaires and whole blood metal levels. Brain metal accumulations were estimated by R1 (for Mn) and R2* (for Fe). Neurobehavioral status was assessed by standard neuropsychological tests. RESULTS: Compared to controls, welders displayed higher hippocampal mean (MD), axial (AD), and radial diffusivity (RD) (p's < 0.036), but similar DTI or volume in other ROIs (p's > 0.117). Welders had higher blood metal levels (p's < 0.004), higher caudate and RN R2* (p's < 0.014), and lower performance on processing/psychomotor speed, executive function, and visuospatial processing tasks (p's < 0.046). Higher caudate and RN R2* were associated with higher blood Fe and Pb (p's < 0.043), respectively. RN R2* was a significant predictor of all hippocampal diffusivity metrics (p's < 0.006). Higher hippocampal MD and RD values were associated with lower Trail Making Test-A scores (p's < 0.025). A mediation analysis of both groups revealed blood Pb indirectly affected hippocampal diffusivity via RN R2* (p's < 0.041). DISCUSSION: Welding-related higher hippocampal diffusivity metrics may be associated with higher RN R2* and lower psychomotor speed performance. Future studies are warranted to test the role of Pb exposure in these findings.

Clinician-Scientist Faculty Mentoring Program (FAME) - A New Inclusive Training Model at Penn State Increases Scholarly Productivity and Extramural Grant Funding.

Purpose: Clinician-scientists have a high attrition rate at the junior-faculty level, before they gain independent funding. We identified the lack of skill set, clinician-scientist community and collaboration between clinician-scientists and clinicians with predominantly clinical duties, as key problems in our medium-size college of medicine. Methods: We designed a novel two-year educational program, the Clinician-scientist Faculty Mentoring program (FAME) specifically to target junior clinician-scientists. The program enrollment included both lab-based, "traditional" and "non-traditional" clinician-scientists, with predominantly clinical duties and limited time for research. The curriculum included the novel educational tools: Emerging technology seminars and mentored work-in-progress research seminars, integrated with mock grant review. Results: The first class enrolled 17 clinician-scientists with diverse clinical subspecialty, previous research training, and protected research time. After two years in the program, the self-assessment of FAME scholars demonstrated strong improvement in grantsmanship skills, career development, emerging technologies, and the sense of community and collaboration. Compared to the period before initiating FAME, scholars increased annual scholarly output by 65% and new extramural funding by >20-fold ($0.189 vs $4.0 million) following completion of FAME. The "traditional" clinician-scientists, who had >50% research time, increased new extramural funding by ~25-fold ($0.134 vs $3.336 million), whereas "non-traditional" clinician-scientists who had ≤50% research time increased new extramural funding by >13-fold. Conclusion: Results suggest that a training program tailored specifically to clinician-scientists leads to increased scholarly productivity and grant funding regardless of research background. Implementing this type of training program nationally, with inclusion of clinician-scientists with various amounts of protected time for research, will help both "traditional" and "non-traditional" clinician-scientists to obtain a substantial independent extramural funding, fulfill their scholarly potential, and enhance their sense of community. Our model would be particularly useful for small-to-medium sized academic institutions, who have a limited clinician-scientist workforce facing competing health care system needs.

Dose-Dependent Regulation on Prefrontal Neuronal Working Memory by Dopamine D1 Agonists: Evidence of Receptor Functional Selectivity-Related Mechanisms.

Low doses of dopamine D1 agonists improve working memory-related behavior, but high doses eliminate the improvement, thus yielding an 'inverted-U' dose-response curve. This dose-dependency also occurs at the single neuron level in the prefrontal cortex where the cellular basis of working memory is represented. Because signaling mechanisms are unclear, we examined this process at the neuron population level. Two D1 agonists (2-methyldihydrexidine and CY208,243) having different signaling bias were tested in rats performing a spatial working memory-related T-maze task. 2-Methyldihydrexidine is slightly bias toward D1-mediated ß-arrestin-related signaling as it is a full agonist at adenylate cyclase and a super-agonist at ß-arrestin recruitment, whereas CY208,243 is slightly bias toward D1-mediated cAMP signaling as it has relatively high intrinsic activity at adenylate cyclase, but is a partial agonist at ß-arrestin recruitment. Both compounds had the expected inverted U dose-dependency in modulating prefrontal neuronal activities, albeit with important differences. Although CY208,243 was superior in improving the strength of neuronal outcome sensitivity to the working memory-related choice behavior in the T-maze, 2-methyldihydrexidine better reduced neuron-to-neuron variation. Interestingly, at the neuron population level, both drugs affected the percentage, uniformity, and ensemble strength of neuronal sensitivity in a complicated dose-dependent fashion, but the overall effect suggested higher efficiency and potency of 2-methyldihydrexidine compared to CY208,243. The differences between 2-methyldihydrexidine and CY208,243 may be related to their specific D1 signaling. These results suggest that D1-related dose-dependent regulation of working memory can be modified differentially by functionally selective ligands, theoretically increasing the balance between desired and undesired effects.

Dopamine D1 receptor-mediated ß-arrestin signaling: Insight from pharmacology, biology, behavior, and neurophysiology.

The awareness of the potential importance of functional selectivity/biased signaling has led to the discovery of biased compounds as both research tools and novel drugs. A major pan-receptor focus has been to identify GPCR-selective ligands that have bias in G protein-dependent vs. ß-arrestin related signaling. Although this field has exploded during the past two decades, it is only recently that highly ß-arrestin biased ligands for the dopamine D1 receptor were reported. We now summarize important pharmacological, molecular, and cellular studies relevant to D1-mediated ß-arrestin-related signaling. It is intriguing that many results emerged from behavioral and physiological studies implying that bias toward or against D1-mediated ß-arrestin either can improve or impair functional outcomes. We discuss the importance of understanding the translatability of cell and animal models to have more precise functional targeting to harness the value of this signaling pathway.

A Dopamine D1 Agonist Versus Methylphenidate in Modulating Prefrontal Cortical Working Memory.

Methylphenidate is used widely to treat symptoms of attention-deficit/hyperactivity disorder (ADHD), but like other stimulants has significant side effects. This study used a rodent model (spontaneously hypertensive rat) of spatial working memory (sWM) to compare the effects of methylphenidate with the novel dopamine D1-like receptor agonist 2-methyldihydrexidine. Acute oral administration of methylphenidate (1.5 mg/kg) caused sWM improvement in half of the tested rats, but impairment in the others. Both improvement or impairment were eliminated by administration of the D1 antagonist SCH39266 directly into the prefrontal cortex (PFC). Conversely, 2-methyldihydrexidine showed greater sWM improvement compared with methylphenidate without significant impairment in any subject. Its effects correlated negatively with vehicle-treated baseline performance (i.e., rats with lower baseline performance improved more than rats with higher baseline performance). These behavioral effects were associated with neural activities in the PFC. Single neuron firing rate was changed, leading to the alteration in neuronal preference to correct or error behavioral responses. Overall, 2-methyldihydrexidine was superior to methylphenidate in decreasing the neuronal preference, prospectively, in the animals whose behavior was improved. In contrast, methylphenidate, but not 2-methyldihydrexidine, significantly decreased neuronal preference, retrospectively, in those animals who had impaired performance. These results suggest that a D1 agonist may be more effective than methylphenidate in regulating sWM-related behavior through neural modulation of the PFC, and thus may be superior to methylphenidate or other stimulants as ADHD pharmacotherapy. SIGNIFICANCE STATEMENT: Methylphenidate is effective in ADHD by its indirect agonist stimulation of dopamine and/or adrenergic receptors, but the precise effects on specific targets are unclear. This study compared methylphenidate to a dopamine D1 receptor-selective agonist by investigating effects on working memory occurring via neural modulation in the prefrontal cortex. The data suggest that pharmacological treatment selectively targeting the dopamine D1 may offer a superior approach to ADHD pharmacotherapy.

Dynamics of Nigral Iron Accumulation in Parkinson's Disease: From Diagnosis to Late Stage.

BACKGROUND: Higher nigral iron has been reported in Parkinson's disease (PD). OBJECTIVE: The aim is to understand the dynamics of nigral iron accumulation in PD and its association with drug treatment. METHODS: Susceptibility magnetic resonance imaging data were obtained from 79 controls and 18 drug-naive (PDDN ) and 87 drug-treated (PDDT ) PD patients. Regional brain iron in basal ganglia and cerebellar structures was estimated using quantitative susceptibility mapping. Nigral iron was compared between PDDN and PDDT subgroups defined by disease duration (early [PDE, <2 years], middle [PDM, 2-6 years], and later [PDL, >6 years]). Associations with both disease duration and types of antiparkinson drugs were explored using regression analysis. RESULTS: Compared to controls, PDDN had lower iron in the substantia nigra (P = 0.018), caudate nucleus (P = 0.038), and globus pallidus (P = 0.01) but not in the putamen or red nucleus. In contrast, PDDT had higher iron in the nigra (P < 0.001) but not in other regions, compared to either controls or PDDN . Iron in the nigra increased with disease duration (PDE > PDDN [P = 0.001], PDM > PDE [P = 0.045]) except for PDM versus PDL (P = 0.226). Levodopa usage was associated with higher (P = 0.013) nigral iron, whereas lower nigral iron was correlated with selegiline usage (P = 0.030). CONCLUSION: Nigral iron is lower before the start of dopaminergic medication and then increases throughout the disease until it plateaus at late stages, suggesting increased iron may not be an etiological factor. Interestingly, PD medications may have differential associations with iron accumulation that need further investigation. © 2022 International Parkinson and Movement Disorder Society.

Higher R2* in the Red Nucleus Is Associated With Lead Exposure in an Asymptomatic Welder Cohort.

Lead is a nonessential metal and may be a coexposure in welding fumes. Preclinical data indicate lead may affect iron regulation. The current study investigated blood lead concentrations and their association with brain iron accumulation in workers with chronic welding fume exposure, with a focus on iron-rich subcortical regions of the cerebellum and basal ganglia. Occupational exposure, whole blood metal, and brain MRI data were obtained from 29 controls and 42 welders. R2* (1/T2*) and R1 (T1 relaxation rate) values were used to estimate brain iron and manganese content, respectively. Blood metals and brain R2* (in the red nucleus [RN], dentate nucleus, caudate, putamen, globus pallidus, and substantia nigra) were compared between groups. Associations between brain R2* values and exposure metrics were tested within each group, and analyses were adjusted for potential confounders. Welders had significantly higher levels of whole blood lead, manganese, iron, and copper. Welders also had higher R2* RN (p = .002), but not R1. A 2nd-order polynomial modeled the association between R2* RN and a long-term welding exposure metric. In welders, but not controls, R2* RN was associated positively with whole blood lead (r = 0.54, p = .003), and negatively with whole blood manganese (r = -0.43, p = .02). Higher blood Pb and lower blood Mn independently accounted for variance in high RN R2*. Together, these data suggest that higher RN R2* values may mark lead exposure in welders. Because lead is a known neurotoxicant, additional studies are warranted to confirm this finding, and ascertain its scientific and public/occupational health implications.

Low plasma serotonin linked to higher nigral iron in Parkinson's disease.

A growing body of evidence suggests nigral iron accumulation plays an important role in the pathophysiology of Parkinson's disease (PD), contributing to dopaminergic neuron loss in the substantia nigra pars compacta (SNc). Converging evidence suggests this accumulation might be related to, or increased by, serotonergic dysfunction, a common, often early feature of the disease. We investigated whether lower plasma serotonin in PD is associated with higher nigral iron. We obtained plasma samples from 97 PD patients and 89 controls and MRI scans from a sub-cohort (62 PD, 70 controls). We measured serotonin concentrations using ultra-high performance liquid chromatography and regional iron content using MRI-based quantitative susceptibility mapping. PD patients had lower plasma serotonin (p < 0.0001) and higher nigral iron content (SNc: p < 0.001) overall. Exclusively in PD, lower plasma serotonin was correlated with higher nigral iron (SNc: r(58) = - 0.501, p < 0.001). This correlation was significant even in patients newly diagnosed (< 1 year) and stronger in the SNc than any other region examined. This study reveals an early, linear association between low serotonin and higher nigral iron in PD patients, which is absent in controls. This is consistent with a serotonin-iron relationship in the disease process, warranting further studies to determine its cause and directionality.

Antipsychotic drugs elicit cytotoxicity in glioblastoma multiforme in a calcium-dependent, non-D2 receptor-dependent, manner.

Dopamine D2 -like receptor antagonists have been suggested as being potential anticancer therapeutics with specific utility for central nervous system cancers due to their ability to cross the blood-brain barrier. Despite a plethora of data reporting anticancer effects for D2 R antagonists in cell or animal studies, the ligand concentrations or doses required to achieve such effects greatly exceed the levels known to cause high degrees of occupancy of the D2 receptor. To resolve this conundrum, we interrogated a panel of glioblastoma multiforme (GBM) cell lines using D2 antagonists of varying chemotype. We studied the cytotoxic effects of these compounds, and also ascertained the expression of D2 receptors (D2 R) on these cells. Although several chemotypes of D2 R antagonists, including phenothiazines and phenylbutylpiperidines, were effective against GBM cell line cultures, the highly selective antagonist remoxipride had no anticancer activity at biologically relevant concentrations. Moreover the D2 R antagonist-induced cytotoxicity in monolayer cultures was independent of whether the cells expressed D2 R. Instead, cytotoxicity was associated with a rapid, high-magnitude calcium flux into the cytoplasm and mitochondria, which then induced depolarization and apoptosis. Blocking this flux protected the GBM cell lines U87MG, U251MG, and A172. Together, these data suggest that the cytotoxicity of these D2 R antagonists involves calcium signaling mechanisms, not D2 R antagonism. Repurposing of existing drugs should focus on the former, not latter, mechanism.

Decoupling of Global Brain Activity and Cerebrospinal Fluid Flow in Parkinson's Disease Cognitive Decline.

BACKGROUND: Deposition and spreading of misfolded proteins (α-synuclein and tau) have been linked to Parkinson's disease cognitive dysfunction. The glymphatic system may play an important role in the clearance of these toxic proteins via cerebrospinal fluid (CSF) flow through perivascular and interstitial spaces. Recent studies discovered that sleep-dependent global brain activity is coupled to CSF flow, which may reflect glymphatic function. OBJECTIVE: The objective of this current study was to determine if the decoupling of brain activity-CSF flow is linked to Parkinson's disease cognitive dysfunction. METHODS: Functional and structural MRI data, clinical motor (Unified Parkinson's Disease Rating Scale), and cognitive (Montreal Cognitive Assessment [MoCA]) scores were collected from 60 Parkinson's disease and 58 control subjects. Parkinson's disease patients were subgrouped into those with mild cognitive impairment (MoCA < 26), n = 31, and those without mild cognitive impairment (MoCA ≥ 26), n = 29. The coupling strength between the resting-state global blood-oxygen-level-dependent signal and associated CSF flow was quantified, compared among groups, and associated with clinical and structural measurements. RESULTS: Global blood-oxygen-level-dependent signal-CSF coupling decreased significantly (P < 0.006) in Parkinson's disease patients showing mild cognitive impairment, compared with those without mild cognitive impairment and controls. Reduced global blood-oxygen-level-dependent signal-CSF coupling was associated with decreased MoCA scores present in Parkinson's disease patients (P = 0.005) but not in controls (P = 0.65). Weaker global blood-oxygen-level-dependent signal-CSF coupling in Parkinson's disease patients also was associated with a thinner right entorhinal cortex (Spearman's correlation, -0.36; P = 0.012), an early structural change often seen in Alzheimer's disease. CONCLUSIONS: The decoupling between global brain activity and associated CSF flow is related to Parkinson's disease cognitive impairment. © 2021 International Parkinson and Movement Disorder Society.

Nigral MRI features of asymptomatic welders.

INTRODUCTION: Manganese (Mn)-induced parkinsonism involves motor symptoms similar to those observed in Parkinson's disease (PD). Previous literature suggests that chronic Mn- exposure may increase PD risk, although Mn-induced clinical syndromes are considered atypical for PD. This study investigated whether asymptomatic welders display differences in the substantia nigra (SN), the key pathological locus of PD. METHOD: Brain MRI data and occupational exposure history were obtained in welders (N = 43) and matched controls (N = 31). Diffusion tensor imaging fractional anisotropy (FA; estimate of microstructural integrity) and R2* (estimate of iron and other PD-related brain differences) values in the SN pars compacta (SNc), SN reticulata (SNr), and globus pallidus (GP) were compared between the two groups. The MRI markers of the SN and GP within welders were related to exposure estimates. RESULTS: Compared to controls, welders who had chronic, but low-level, Mn-exposure had similar FA and R2* values in both SN regions (p's > 0.082), but significantly lower FA (p = 0.0013), although not R2* (p = 0.553), in the GP. In welders, FA values in the SN and GP showed a second-order polynomial relationship with cumulative lifetime welding exposure (p's < 0.03). CONCLUSION: Neurotoxic processes associated with Mn-exposure may be different from those in PD when the exposure-level is relatively low. Greater welding duration and level, however, were associated with FA differences in the GP and SN, indicating that welding exposures above a certain level may induce neurotoxicity in the SN, a finding that should be explored further in future studies.