Psychosis-Like Behavior and Hyperdopaminergic Dysregulation in Human α-Synuclein BAC Transgenic Rats.

BACKGROUND: Parkinson's disease psychosis is a prevalent yet underreported and understudied nonmotor manifestation of Parkinson's disease and, arguably, the most debilitating. It is unknown if α-synuclein plays a role in psychosis, and if so, this endophenotype may be crucial for elucidating the neurodegenerative process. OBJECTIVES: We sought to dissect the underlying neurobiology of novelty-induced hyperactivity, reminiscent of psychosis-like behavior, in human α-synuclein BAC rats. RESULTS: Herein, we demonstrate a prodromal psychosis-like phenotype, including late-onset sensorimotor gating disruption, striatal hyperdopaminergic signaling, and persistent novelty-induced hyperactivity (up to 18 months), albeit reduced baseline locomotor activity, that is augmented by d-amphetamine and reversed by classical and atypical antipsychotics. MicroRNA-mediated α-synuclein downregulation in the ventral midbrain rescues the hyperactive phenotype and restores striatal dopamine levels. This phenotype is accompanied by an abundance of age-, brain region- and gene dose-dependent aberrant α-synuclein, including hyperphosphorylation, C-terminal truncation, aggregation pathology, and mild nigral neurodegeneration (27%). CONCLUSIONS: Our findings demonstrate a potential role of α-synuclein in Parkinson's disease psychosis and provide evidence of region-specific perturbations prior to neurodegeneration phenoconversion. The reported phenotype coincides with the latest clinical findings that suggest a premotor hyperdopaminergic state may occur, while at the same time, premotor psychotic symptoms are increasingly being recognized. © 2020 International Parkinson and Movement Disorder Society.

Substrate reduction therapy using Genz-667161 reduces levels of pathogenic components in a mouse model of neuronopathic forms of Gaucher disease.

Most lysosomal storage diseases (LSDs) have a significant neurological component, including types 2 and 3 Gaucher disease (neuronal forms of Gaucher disease; nGD). No therapies are currently available for nGD since the recombinant enzymes used in the systemic form of Gaucher disease do not cross the blood-brain barrier (BBB). However, a number of promising approaches are currently being tested, including substrate reduction therapy (SRT), in which partial inhibition of the synthesis of the glycosphingolipids (GSLs) that accumulate in nGD lowers their accumulation. We now induce nGD in mice by injection with conduritol B-epoxide (CBE), an irreversible inhibitor of acid beta-glucosidase (GCase), the enzyme defective in nGD, with or without co-injection with Genz-667161, a prototype for SRT which crosses the BBB. Significant neuropathology, and a reduction in lifespan, was observed upon CBE injection, and this was largely reversed by co-injection with Genz-667161, along with a reduction in glucosylceramide and glucosylsphingosine levels. Analysis of gene expression by RNAseq revealed that Genz-667161 largely reversed the changes in genes and pathways that were differentially expressed upon CBE injection, specifically pathways of GSL metabolism, lipoproteins and other lipid metabolic pathways, lipid droplets, astrocyte activation, neuronal function, and to some extent, neuroinflammation. Together, this demonstrates the efficacy of SRT to reverse the effects of substrate accumulation on pathological components and pathways in nGD brain.

A new model to study cell-to-cell transfer of αSynuclein in vivo.

Parkinson's disease (PD) compromises motor control due to the loss of dopaminergic neurons in the substantia nigra pars compacta. At the histopathological level, PD is characterized by the accumulation of Lewy bodies, large protein inclusions containing aggregated αSynuclein (αSyn). The progression of PD involves the spreading of αSyn misfolding through the brain mediated by a prion-like mechanism, where the protein is transferred between cells. Here we report that αSyn internalization is a dynamic process, where the protein transits through different sub-cellular compartments. Importantly, cells incorporating αSyn develop larger protein-like inclusions when compared to αSyn producing cells. We developed a new tool to monitor cell-to-cell transfer of αSyn in vivo using an adeno-associated viral (AAV) vector expressing αSyn fused to a red fluorescent protein in addition to soluble EGFP to label donor cells. Intra-nigral delivery of this reporter AAV construct allowed the visualization of αSyn incorporation into surrounding neurons. This work provides a new tool to study αSyn cell-to-cell transfer in vivo and may open new opportunities to study PD pathogenesis.

Gene Therapy Strategies to Restore ER Proteostasis in Disease.

Proteostasis alterations are proposed as a transversal hallmark of several pathological conditions, including metabolic disorders, mechanical injury, cardiac malfunction, neurodegeneration, and cancer. Strategies to improve proteostasis aim to reduce the accumulation of specific disease-related misfolded proteins or bolster the endogenous mechanisms to fold and degrade abnormal proteins. Endoplasmic reticulum (ER) stress is a common pathological signature of a variety of diseases, which engages the unfolded protein response (UPR) as a cellular reaction to mitigate ER stress. Pharmacological modulation of the UPR is challenging considering the physiological importance of the pathway in various organs. However, local targeting of ER stress responses in the affected tissue using gene therapy is emerging as a possible solution to overcome side effects. The delivery of ER chaperones or active UPR components using adeno-associated virus (AAV) has demonstrated outstanding beneficial effects in several disease models (e.g., neurodegenerative conditions, eye disorders, and metabolic diseases). Here, we discuss current efforts to design and optimize gene therapy strategies to improve ER proteostasis in different disease contexts.

Targeting PERK signaling with the small molecule GSK2606414 prevents neurodegeneration in a model of Parkinson's disease.

Parkinson's disease (PD) is the second most common neurodegenerative disorder, leading to the progressive decline of motor control due to the loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc). Accumulating evidence suggest that altered proteostasis is a salient feature of PD, highlighting perturbations to the endoplasmic reticulum (ER), the main compartment involved in protein folding and secretion. PERK is a central ER stress sensor that enforces adaptive programs to recover homeostasis through a block of protein translation and the induction of the transcription factor ATF4. In addition, chronic PERK signaling results in apoptosis induction and neuronal dysfunction due to the repression in the translation of synaptic proteins. Here we confirmed the activation of PERK signaling in postmortem brain tissue derived from PD patients and three different rodent models of the disease. Pharmacological targeting of PERK by the oral administration of GSK2606414 demonstrated efficient inhibition of the pathway in the SNpc after experimental ER stress stimulation. GSK2606414 protected nigral-dopaminergic neurons against a PD-inducing neurotoxin, improving motor performance. The neuroprotective effects of PERK inhibition were accompanied by an increase in dopamine levels and the expression of synaptic proteins. However, GSK2606414 treated animals developed secondary effects possibly related to pancreatic toxicity. This study suggests that strategies to attenuate ER stress levels may be effective to reduce neurodegeneration in PD.

Silencing mutant huntingtin by adeno-associated virus-mediated RNA interference ameliorates disease manifestations in the YAC128 mouse model of Huntington's disease.

Huntington's disease (HD) is a fatal autosomal dominant neurodegenerative disease caused by an increase in the number of polyglutamine residues in the huntingtin (Htt) protein. With the identification of the underlying basis of HD, therapies are being developed that reduce expression of the causative mutant Htt. RNA interference (RNAi) that seeks to selectively reduce the expression of such disease-causing agents is emerging as a potential therapeutic strategy for this and similar disorders. This study examines the merits of administering a recombinant adeno-associated viral (AAV) vector designed to deliver small interfering RNA (siRNA) that targets the degradation of the Htt transcript. The aim was to lower Htt levels and to correct the behavioral, biochemical, and neuropathological deficits shown to be associated with the YAC128 mouse model of HD. Our data demonstrate that AAV-mediated RNAi is effective at transducing greater than 80% of the cells in the striatum and partially reducing the levels (~40%) of both wild-type and mutant Htt in this region. Concomitant with these reductions are significant improvements in behavioral deficits, reduction of striatal Htt aggregates, and partial correction of the aberrant striatal transcriptional profile observed in YAC128 mice. Importantly, a partial reduction of both the mutant and wild-type Htt levels is not associated with any notable overt neurotoxicity. Collectively, these results support the continued development of AAV-mediated RNAi as a therapeutic strategy for HD.

Amplicación de la respuesta contráctil a noradrenalina por serotonina en la arteria umbilical humana / Amplification of contractile response by serotonin on noradrenaline in the human umbilical artery

Durante el transcurso del embarazo, se ha observado el incremento progresivo de los niveles plasmáticos de serotonina (5-HT). Además, se ha descripto el aumento de la concentración de noradrenalina (NA) durante el parto. Por otro lado, en diferentes arterias se ha observado que concentraciones efectivas mínimas de 5-HT pueden producir un aumento o "amplificación" de la respuesta contráctil a un segundo agonista. A partir de estos trabajos, se consideró relevante determinar la existencia de una interacción sinérgica entre la 5-HT y la NA en la arteria umbilical humana (AUH), y los posibles mecanismos involucrados en este fenómeno. Para ello, se emplearon tiras de esta arteria incubadas en solución de Krebs a 37 grados Celsius, burbujeadas con carbógeno en las que se evaluó la respuesta contráctil isométrica. La máxima respuesta contráctil a NA fue del 21 por ciento con respecto a la respuesta máxima de vasoconstricción, obtenida con 5-HT. Por otro lado, cuando se administró previamente una dosis efectiva mínima de 5-HT, la respuesta a la NA resultó significativamente mayor que la control (0,53 ñ 0,06 g y 0,24 ñ 0,06, respectivamente, p < 0,01). Esta respuesta "amplificada" a NA se correlacionó inversamente con el grado de contracción previa con 5-HT, cuando ésta tenía valores entre el 3 y 30% del máximo. Además, precontracciones superiores al 40 por ciento abolieron las respuestas a la NA. En otra serie de experimentos, la incubación previa con diltiazem, bioqueante de los canales de calcio, produjo una disminución de la respuesta tanto control como amplificada a NA. En este trabajo se demuestra la existencia de un efecto amplificador de la 5-HT sobre las respuestas a NA en la AUH y se discute la posible relevancia clínica en la preeclampsia y los mecanismos involucrados en este fenómeno.

Amplicación de la respuesta contráctil a noradrenalina por serotonina en la arteria umbilical humana / Amplification of contractile response by serotonin on noradrenaline in the human umbilical artery

Durante el transcurso del embarazo, se ha observado el incremento progresivo de los niveles plasmáticos de serotonina (5-HT). Además, se ha descripto el aumento de la concentración de noradrenalina (NA) durante el parto. Por otro lado, en diferentes arterias se ha observado que concentraciones efectivas mínimas de 5-HT pueden producir un aumento o "amplificación" de la respuesta contráctil a un segundo agonista. A partir de estos trabajos, se consideró relevante determinar la existencia de una interacción sinérgica entre la 5-HT y la NA en la arteria umbilical humana (AUH), y los posibles mecanismos involucrados en este fenómeno. Para ello, se emplearon tiras de esta arteria incubadas en solución de Krebs a 37 grados Celsius, burbujeadas con carbógeno en las que se evaluó la respuesta contráctil isométrica. La máxima respuesta contráctil a NA fue del 21 por ciento con respecto a la respuesta máxima de vasoconstricción, obtenida con 5-HT. Por otro lado, cuando se administró previamente una dosis efectiva mínima de 5-HT, la respuesta a la NA resultó significativamente mayor que la control (0,53 ñ 0,06 g y 0,24 ñ 0,06, respectivamente, p < 0,01). Esta respuesta "amplificada" a NA se correlacionó inversamente con el grado de contracción previa con 5-HT, cuando ésta tenía valores entre el 3 y 30% del máximo. Además, precontracciones superiores al 40 por ciento abolieron las respuestas a la NA. En otra serie de experimentos, la incubación previa con diltiazem, bioqueante de los canales de calcio, produjo una disminución de la respuesta tanto control como amplificada a NA. En este trabajo se demuestra la existencia de un efecto amplificador de la 5-HT sobre las respuestas a NA en la AUH y se discute la posible relevancia clínica en la preeclampsia y los mecanismos involucrados en este fenómeno.(AU)