Heterogeneity of prodromal Parkinson symptoms in siblings of Parkinson disease patients.

A prodromal phase of Parkinson's disease (PD) may precede motor manifestations by decades. PD patients' siblings are at higher risk for PD, but the prevalence and distribution of prodromal symptoms are unknown. The study objectives were (1) to assess motor and non-motor features estimating prodromal PD probability in PD siblings recruited within the European PROPAG-AGEING project; (2) to compare motor and non-motor symptoms to the well-established DeNoPa cohort. 340 PD siblings from three sites (Bologna, Seville, Kassel/Goettingen) underwent clinical and neurological evaluations of PD markers. The German part of the cohort was compared with German de novo PD patients (dnPDs) and healthy controls (CTRs) from DeNoPa. Fifteen (4.4%) siblings presented with subtle signs of motor impairment, with MDS-UPDRS-III scores not clinically different from CTRs. Symptoms of orthostatic hypotension were present in 47 siblings (13.8%), no different to CTRs (p = 0.072). No differences were found for olfaction and overall cognition; German-siblings performed worse than CTRs in visuospatial-executive and language tasks. 3/147 siblings had video-polysomnography-confirmed REM sleep behavior disorder (RBD), none was positive on the RBD Screening Questionnaire. 173/300 siblings had <1% probability of having prodromal PD; 100 between 1 and 10%, 26 siblings between 10 and 80%, one fulfilled the criteria for prodromal PD. According to the current analysis, we cannot confirm the increased risk of PD siblings for prodromal PD. Siblings showed a heterogeneous distribution of prodromal PD markers and probability. Additional parameters, including strong disease markers, should be investigated to verify if these results depend on validity and sensitivity of prodromal PD criteria, or if siblings' risk is not elevated.

A geroscience approach for Parkinson's disease: Conceptual framework and design of PROPAG-AGEING project.

Advanced age is the major risk factor for idiopathic Parkinson's disease (PD), but to date the biological relationship between PD and ageing remains elusive. Here we describe the rationale and the design of the H2020 funded project "PROPAG-AGEING", whose aim is to characterize the contribution of the ageing process to PD development. We summarize current evidences that support the existence of a continuum between ageing and PD and justify the use of a Geroscience approach to study PD. We focus in particular on the role of inflammaging, the chronic, low-grade inflammation characteristic of elderly physiology, which can propagate and transmit both locally and systemically. We then describe PROPAG-AGEING design, which is based on the multi-omic characterization of peripheral samples from clinically characterized drug-naïve and advanced PD, PD discordant twins, healthy controls and "super-controls", i.e. centenarians, who never showed clinical signs of motor disability, and their offspring. Omic results are then validated in a large number of samples, including in vitro models of dopaminergic neurons and healthy siblings of PD patients, who are at higher risk of developing PD, with the final aim of identifying the molecular perturbations that can deviate the trajectories of healthy ageing towards PD development.

Effect of bestrophin-1 on L-type Ca2+ channel activity depends on the Ca2+ channel beta-subunit.

Best's vitelliforme macular degeneration is an inherited retinal degeneration associated with a reduction of the light-peak in the patient's electro-oculogram. Bestrophin-1, the product of the disease-promoting/forming gene can function as regulator of voltage-dependent L-type Ca(2+) channels in the retinal pigment epithelium (RPE). Since mice deficient for either ß4-subunits or Ca(V)1.3 subunits show reduced light-peaks, the regulatory function of bestrophin-1 on heterologously expressed Ca(2+) channels composed of the pore-forming Ca(V)1.3 and the auxiliary ß4-subunit was analyzed. Precipitation of ß4-subunits led to co-precipitation with bestrophin-1 and subsequent analysis of subcellular localization showed co-localization of bestrophin-1, Ca(V)1.3 and ß4-subunit in the cell membrane. Ca(V)1.3 currents in the presence of ß4-subunits and bestrophin-1 showed accelerated time-dependent activation and decreased current density compared to currents measured in the absence of bestrophin-1. In the presence of the ß3-subunit, which is not expressed in the RPE bestrophin-1 did not modulate Ca(V)1.3 activity. Deletion of a cluster of proline-rich motifs in the C-terminus of bestrophin-1 reduced its co-immuno precipitation with the ß4-subunit and strongly reduced the Ca(V)1.3 activity. Cells co-expressing bestrophin-1 lacking the proline-rich motifs and Ca(V)1.3 subunits showed less efficient trafficking of bestrophin-1 into the cell membrane. In summary, we conclude that bestrophin-1 modulates L-type channels of the RPE via proline-rich motif-dependent interaction with ß4-subunits. A disturbed interaction reduces the currents of the Ca(V)1.3 subunits. This mechanism could open new ways to understand changes in the patient's electro-oculogram and functional alterations of the RPE leading to retinal degeneration.

Voltage-dependent Ca2+ channels, not ryanodine receptors, activate Ca2+-dependent BK potassium channels in human retinal pigment epithelial cells.

PURPOSE: In different tissues the activation of large conductance Ca2+-activated (BK) potassium channels has been shown to be coupled to voltage-gated Ca2+ channels as well as ryanodine receptors. As activation of BK channels leads to hyperpolarization of the cell, these channels provide a negative feedback mechanism for Ca2+-induced functions. Many cellular functions of the retinal pigment epithelium (RPE) are coupled to changes in [Ca2+]i. The aim of this study was to identify which Ca2+-entry pathway leads to the activation of BK channels in the RPE. METHODS: We used freshly isolated human RPE cells and the ARPE-19 cell line for the detection of transcripts of BK channel alpha subunits. Patch-Clamp measurements were used to characterize BK channels in ARPE-19 cells electrophysiologically. To monitor changes in [Ca2+]i ARPE-19 cells were loaded with Fura-2. RESULTS: Freshly isolated human RPE cells and ARPE-19 cells were shown to express BK channels. In ARPE-19 cells these channels were shown to be functionally active. Application of iberiotoxin led to a block of outward currents by 28.15%. At +50 mV ARPE-19 cells had a BK channel-mediated current density of 2.42 pA/pF. Activation of ryanodine receptors by caffeine led to a significant increase in [Ca2+]i by 34.16%. Nevertheless, caffeine-induced Ca2+ signals were not sufficient to activate BK channels. Instead, the activation of L-type Ca2+ channels by BayK 8644 caused a dramatic increase in BK channel activity and a shift of the reversal potential of the ARPE-19 cells by -22.6 mV. CONCLUSIONS: We have shown here for the first time that human RPE cells express BK channels. These channels are activated in RPE cells by increases in [Ca2+]i that are mediated by the opening of voltage gated L-type Ca2+ channels. As Ca2+ entering the RPE cells through these Ca2+ channels are known to be important for growth factor secretion and light-induced transepithelial transport, we speculate that BK channels coupled directly to these Ca2+ channels may provide a good tool for negative feedback control of the L-type Ca2+ channels.

The REM Sleep Behavior Disorder Screening Questionnaire is not Valid in De Novo Parkinson's Disease.

BACKGROUND: Rapid eye movement (REM) sleep behavior disorder (RBD) is one of the most specific prodromal indicators for Parkinson's disease (PD). OBJECTIVES: To test the validity of the RBD-Screening Questionnaire (RBDSQ) in assessing RBD in early PD. METHODS: The RBDSQ was completed before video-supported polysomnography (vPSG) by 134 de novo PD patients, 109 matched controls without neurological disorder (CTR) and 30 subjects with idiopathic RBD (iRBD) without clinical signs of PD; results were compared with vPSG-confirmed RBD diagnosis. RESULTS AND CONCLUSIONS: Sensitivity/specificity of the RBDSQ for the PD cohort were 0.44/0.84 at the previously published cut-off score of 6 for PD patients, and the area under the curve (AUC) 0.68 (95% CI, 0.56-0.79). By contrast, in the iRBD/CTR cohort the RBDSQ (cut-off = 5) had a sensitivity/specificity of 0.97/0.84 and an AUC of 0.95 (95% CI, 0.90-1.00). Subanalysis of question 6 only (4 subitems asking for dream enactment) at a cut-off score of 1 revealed a sensitivity of 0.74 and a specificity of 0.70 for the de novo PD cohort, AUC was 0.74 (95% CI, 0.63-0.84). RBDSQ is an insufficient screening tool for RBD in de novo PD. New screening tools for RBD assessment need to be developed.