T-type calcium channels as therapeutic targets in essential tremor and Parkinson's disease

Tremor in Spinocerebellar Ataxia: A Scoping Review

Background

Spinocerebellar ataxia (SCA) denotes an expanding list of autosomal dominant cerebellar ataxias. Although tremor is an important aspect of the clinical spectrum of the SCAs, its prevalence, phenomenology, and pathophysiology are unknown.

Objectives

This review aims to describe the various types of tremors seen in the different SCAs, with a discussion on the pathophysiology of the tremors, and the possible treatment modalities.

Methods

The authors conducted a literature search on PubMed using search terms including tremor and the various SCAs. Relevant articles were included in the review after excluding duplicate publications.

Results

While action (postural and intention) tremors are most frequently associated with SCA, rest and other rare tremors have also been documented. The prevalence and types of tremors vary among the different SCAs. SCA12, common in certain ethnic populations, presents a unique situation, where the tremor is typically the principal manifestation. Clinical manifestations of SCAs may be confused with essential tremor or Parkinson's disease. The pathophysiology of tremors in SCAs predominantly involves the cerebellum and its networks, especially the cerebello-thalamo-cortical circuit. Additionally, connections with the basal ganglia, and striatal dopaminergic dysfunction may have a role. Medical management of tremor is usually guided by the phenomenology and associated clinical features. Deep brain stimulation surgery may be helpful in treatment-resistant tremors.

Conclusions

Tremor is an elemental component of SCAs, with diverse phenomenology, and emphasizes the role of the cerebellum in tremor. Further studies will be useful to delineate the clinical, pathophysiological, and therapeutic aspects of tremor in SCAs.

Updates in essential tremor

Essential tremor (ET) is one of the most common tremor disorders and can be disabling in its affect on daily activities. There have been major breakthroughs in the treatment of tremor and ET is the subject of important ongoing research. This review will present recent advancements in the epidemiology, genetics, pathophysiology, diagnosis, comorbidities, and imaging of ET. Current and future treatment options in the management of ET will also be reviewed. The need for continued innovation and scientific inquiry to address the unmet needs of persons of ET will be highlighted.

Identification of Novel Quinolone and Quinazoline Alkaloids as Phosphodiesterase 10A Inhibitors for Parkinson's Disease through a Computational Approach

Phosphodiesterases (PDEs) are vital in signal transduction, specifically by hydrolyzing cAMP and cGMP. Within the PDE family, PDE10A is notable for its prominence in the striatum and its regulatory function over neurotransmitters in medium-spiny neurons. Given the dopamine deficiency in Parkinson's disease (PD) that affects striatal pathways, PDE10A inhibitors could offer therapeutic benefits by modulating D1 and D2 receptor signaling. This study was motivated by the successful history of quinazoline/quinazoline scaffolds in the inhibition of PDE10A. This study involved detailed in silico evaluations through docking followed by pharmacological, pharmacophoric, and pharmacokinetic analyses, prioritizing central nervous system (CNS)-active drug criteria. Seven cyclic peptides, those featuring the quinazoline/quinazoline moiety at both termini, exhibited notably enhanced docking scores compared to those of the remaining alkaloids within the screened library. We identified 7 quinolines and 1 quinazoline including Lepadin G, Aspernigerin, CJ-13536, Aurachin A, 2-Undecyl-4(1H)-quinolone, Huajiaosimuline 3-Prenyl-4-prenyloxyquinolin-2-one, and Isaindigotone that followed the standard CNS active drug criteria. The dominant quinoline ring in our study and its related quinazoline were central to our evaluations; therefore, the pharmacophoric features of these scaffolds were highlighted. The top alkaloids met all CNS-active drug properties; while nonmutagenic and without PAINS alerts, many indicated potential hepatotoxicity. Among the compounds, Huajiaosimuline was particularly significant due to its alignment with lead-likeness and CNS-active criteria. Aspernigerin demonstrated its affinity for numerous dopamine receptors, which signifies its potential to alter dopaminergic neurotransmission that is directly related to PD. Interestingly, the majority of these alkaloids had biological targets primarily associated with G protein-coupled receptors, critical in PD pathophysiology. They exhibit superior excretion parameters and toxicity end-points compared to the standard. Notably, selected alkaloids demonstrated stability in the binding pocket of PDE10A according to the molecular dynamic simulation results. Our findings emphasize the potential of these alkaloids as PDE10A inhibitors. Further experimental studies may be necessary to confirm their actual potency in inhibiting PDE10A before exploring their therapeutic potential in PD.

The function of previously unappreciated exerkines secreted by muscle in regulation of neurodegenerative diseases

The initiation and progression of neurodegenerative diseases (NDs), distinguished by compromised nervous system integrity, profoundly disrupt the quality of life of patients, concurrently exerting a considerable strain on both the economy and the social healthcare infrastructure. Exercise has demonstrated its potential as both an effective preventive intervention and a rehabilitation approach among the emerging therapeutics targeting NDs. As the largest secretory organ, skeletal muscle possesses the capacity to secrete myokines, and these myokines can partially improve the prognosis of NDs by mediating the muscle-brain axis. Besides the well-studied exerkines, which are secreted by skeletal muscle during exercise that pivotally exert their beneficial function, the physiological function of novel exerkines, e.g., apelin, kynurenic acid (KYNA), and lactate have been underappreciated previously. Herein, this review discusses the roles of these novel exerkines and their mechanisms in regulating the progression and improvement of NDs, especially the significance of their functions in improving NDs' prognoses through exercise. Furthermore, several myokines with potential implications in ameliorating ND progression are proposed as the future direction for investigation. Elucidation of the function of exerkines secreted by skeletal muscle in the regulation of NDs advances the understanding of its pathogenesis and facilitates the development of therapeutics that intervene in these processes to cure NDs.

Analgesic Buxus alkaloids with Enhanced Selectivity for the Low-Voltage-Gated Calcium Channel Cav 3.2 over Cav 3.1 through a New Binding Mode

Low-voltage-gated calcium channels (LVGCCs; Cav 3.1-3.3) represent promising drug targets for epilepsy, pain, and essential tremor. At present, modulators with heightened selectivity for a subtype of LVGCCs are still highly desired. In this study we explored three classes of Buxus alkaloids and identified 9(10/19)abeo-artanes Buxusemine H and Buxusemine L (BXSL) as an unprecedented type of Cav 3.2 inhibitors. Particularly, BXSL exhibited Cav 3.2 inhibition comparable to Z944, a non-subtype-selective LVGCCs inhibitor under clinical trial. While lacking specificity for Cav 3.3, BXSL showed a 30-fold selectivity of Cav 3.2 over Cav 3.1. As compared to several well-known inhibitors, the experimental and computational studies suggested BXSL exhibits a distinct binding mode to Cav 3.2, notably through the essential interaction with serine-1543 in domain III. Furthermore, BXSL showed minimal impact on various recombinant and native nociceptive ion channels, while significantly reducing the excitability of isolated mouse dorsal root ganglion neurons. Animal studies in wild-type and Cav 3.2 knock-out mice revealed that BXSL (5 mg/kg), by inhibiting Cav 3.2, exhibits an analgesic effect equivalent to Z944 (10 mg/kg) or mibefradil (10 mg/kg). Moreover, we proposed a structural rationale for the high selectivity of 9(10/19)abeo-artane-type alkaloids towards Cav 3.2 over Cav 3.1. This study introduces a novel analgesic agent and valuable molecular insight for structure-based innovative Cav 3.2 drug development.

AAV-compatible optogenetic tools for activating endogenous calcium channels in vivo

Calcium ions (Ca2+) play pivotal roles in regulating diverse brain functions, including cognition, emotion, locomotion, and learning and memory. These functions are intricately regulated by a variety of Ca2+-dependent cellular processes, encompassing synaptic plasticity, neuro/gliotransmitter release, and gene expression. In our previous work, we developed 'monster OptoSTIM1' (monSTIM1), an improved OptoSTIM1 that selectively activates Ca2+-release-activated Ca2+ (CRAC) channels in the plasma membrane through blue light, allowing precise control over intracellular Ca2+ signaling and specific brain functions. However, the large size of the coding sequence of monSTIM1 poses a limitation for its widespread use, as it exceeds the packaging capacity of adeno-associated virus (AAV). To address this constraint, we have introduced monSTIM1 variants with reduced coding sequence sizes and established AAV-based systems for expressing them in neurons and glial cells in the mouse brain. Upon expression by AAVs, these monSTIM1 variants significantly increased the expression levels of cFos in neurons and astrocytes in the hippocampal CA1 region following non-invasive light illumination. The use of monSTIM1 variants offers a promising avenue for investigating the spatiotemporal roles of Ca2+-mediated cellular activities in various brain functions. Furthermore, this toolkit holds potential as a therapeutic strategy for addressing brain disorders associated with aberrant Ca2+ signaling.