The retinal pigment epithelium (RPE) is a highly specialized CNS tissue that plays crucial roles in retinal homeostasis. Age-related morphological changes in the RPE have been associated with retinal degenerative disorders; our understanding of the underlying molecular mechanisms, however, remains incomplete. Here we report on a key role of Klotho (Kl), an aging-suppressor gene, in retinal health and RPE physiology. Kl Ϫ / Ϫ mice show RPE and photoreceptor degeneration, reduced pigment synthesis in the RPE, and impaired phagocytosis of the outer segment of the photoreceptors. Klotho protein (KL) is expressed in primary cultured human RPE, and regulates pigment synthesis by increasing the expression of MITF (microphthalmia transcription factor) and TYR (tyrosinase), two pivotal genes in melanogenesis. Importantly, KL increases phagocytosis in cultured RPE by inducing gene expression of MERTK/AXL/TYRO3. These effects of KL are mediated through cAMP-PKA-dependent phosphorylation of transcription factor CREB. In cultured human RPE, KL increases the L-3,4-dihydroxyphenylalanine synthesis and inhibits vascular endothelial growth factor (VEGF) secretion from basal membrane by inhibiting IGF-1 signaling and VEGF receptor 2 phosphorylation. KL also regulates the expression of stress-related genes in RPE, lowers the production of reactive oxygen species, and thereby, protects RPE from oxidative stress. Together, our results demonstrate a critical function for KL in mouse retinal health in vivo, and a protective role toward human RPE cells in vitro. We conclude that KL is an important regulator of RPE homeostasis, and propose that an age-dependent decline of KL expression may contribute to RPE degeneration and retinal pathology.
The convergence of human molecular genetics and Lewy pathology of Parkinson’s disease (PD) have led to a robust, clinical-stage pipeline of alpha-synuclein ( α -syn)-targeted therapies that have the potential to slow or stop the progression of PD and other synucleinopathies. To facilitate the development of these and earlier stage investigational molecules, the Michael J. Fox Foundation for Parkinson’s Research convened a group of leaders in the field of PD research from academia and industry, the Alpha-Synuclein Clinical Path Working Group. This group set out to develop recommendations on preclinical and clinical research that can de-risk the development of α -syn targeting therapies. This consensus white paper provides a translational framework, from the selection of animal models and associated end-points to decision-driving biomarkers as well as considerations for the design of clinical proof-of-concept studies. It also identifies current gaps in our biomarker toolkit and the status of the discovery and validation of α -syn-associated biomarkers that could help fill these gaps. Further, it highlights the importance of the emerging digital technology to supplement the capture and monitoring of clinical outcomes. Although the development of disease-modifying therapies targeting α -syn face profound challenges, we remain optimistic that meaningful strides will be made soon toward the identification and approval of disease-modifying therapeutics targeting α -syn.
Objectives Isradipine is a dihydropyridine calcium channel inhibitor that has demonstrated concentration‐dependent neuroprotective effects in animal models of Parkinson’s disease (PD) but failed to show efficacy in a phase 3 clinical trial. The objectives of this study were to model the plasma pharmacokinetics of isradipine in study participants from the phase 3 trial; and, to investigate associations between drug exposure and longitudinal clinical outcome measures of PD progression. Methods Plasma samples from nearly all study participants randomized to immediate‐release isradipine 5‐mg twice daily (166 of 170) were collected for population pharmacokinetic modeling. Estimates of isradipine exposure included apparent oral clearance and area under the concentration‐time curve. Isradipine exposure parameters were tested for correlations with 36‐month changes in disease severity clinical assessment scores, and time‐to‐event analyses for initiation of antiparkinson therapy. Results Isradipine exposures did not correlate with the primary clinical outcome, changes in the antiparkinson therapy‐adjusted Unified Parkinson’s Disease Rating Scale parts I–III score over 36 months (Spearman rank correlation coefficient, rs: 0.09, P = 0.23). Cumulative levodopa equivalent dose at month 36 was weakly correlated with isradipine plasma clearance (rs: 0.18, P = 0.035). This correlation was sex dependent and significant in males, but not females. Those with higher isradipine exposure had decreased risk of needing antiparkinson treatment over 36 months compared with placebo (hazard ratio: 0.87, 95% CI: 0.78–0.98, P = 0.02). Interpretation In this clinical trial, higher isradipine plasma exposure did not affect clinical assessment measures of PD severity but modestly decreased cumulative levodopa equivalent dose and the time needed for antiparkinson treatment initiation. Trial Registration http://ClinicalTrials.gov NCT02168842.
The wrongful murders of Black individuals during 2020 (including George Floyd, Breonna Taylor, Ahmaud Aubery, and others), compounded by a long history of similar incidents, inspired protests around the world against racism and police brutality. The growing anti-racism movement sparked conversations within science, technology, engineering, mathematics, and medicine (STEMM) surrounding ways to combat racial bias in our respective fields. A spotlight was placed on the discriminatory history of scientific research and medical practice, as well as the problematic modern-day policies that perpetuate the lack of racial diversity and equity in STEMM.While observing and participating in recent discussions about the racism that pervades institutions, departments, and scientific discourse, we have noticed a set of standard arguments against anti-racism action within STEMM. Ten of these arguments are laid out in this manuscript and paired with evidence-based counterarguments. Notably, while this manuscript is primarily centered around a United States perspective, most of our arguments and suggested actions remain applicable to other countries as well. It is crucial for a STEMM anti-racism movement to extend beyond national borders, reflecting the international nature of scientific research and collaboration.This team of authors represents a collaboration between scientists from historically marginalized groups and their allies. By compiling published academic literature, we hope to directly
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