Radiosensitizing the Vasculature of Primary Brainstem Gliomas Fails to Improve Tumor Response to Radiation Therapy.

PURPOSE: Diffuse intrinsic pontine gliomas (DIPGs) arise in the pons and are the leading cause of death from brain tumors in children. DIPGs are routinely treated with radiation therapy, which temporarily improves neurological symptoms but generally fails to achieve local control. Because numerous clinical trials have not improved survival from DIPG over standard radiation therapy alone, there is a pressing need to evaluate new therapeutic strategies for this devastating disease. Vascular damage caused by radiation therapy can increase the permeability of tumor blood vessels and promote tumor cell death. METHODS AND MATERIALS: To investigate the impact of endothelial cell death on tumor response to radiation therapy in DIPG, we used dual recombinase (Cre + FlpO) technology to generate primary brainstem gliomas which lack ataxia telangiectasia mutated (Atm) in the vasculature. RESULTS: Here, we show that Atm-deficient tumor endothelial cells are sensitized to radiation therapy. Furthermore, radiosensitization of the vasculature in primary gliomas triggered an increase in total tumor cell death. Despite the observed increase in cell killing, in mice with autochthonous DIPGs treated with radiation therapy, deletion of Atm specifically in tumor endothelial cells failed to improve survival. CONCLUSIONS: These results suggest that targeting the tumor cells, rather than endothelial cells, during radiation therapy will be necessary to improve survival among children with DIPG.

Prenatal overexpression of platelet-derived growth factor receptor A results in central nervous system hypomyelination.

BACKGROUND: Platelet-derived growth factor (PDGF) signaling, through the ligand PDGF-A and its receptor PDGFRA, is important for the growth and maintenance of oligodendrocyte progenitor cells (OPCs) in the central nervous system (CNS). PDGFRA signaling is downregulated prior to OPC differentiation into mature myelinating oligodendrocytes. By contrast, PDGFRA is often genetically amplified or mutated in many types of gliomas, including diffuse midline glioma (DMG) where OPCs are considered the most likely cell-of-origin. The cellular and molecular changes that occur in OPCs in response to unregulated PDGFRA expression, however, are not known. METHODS: Here, we created a conditional knock-in (KI) mouse that overexpresses wild type (WT) human PDGFRA (hPDGFRA) in prenatal Olig2-expressing progenitors, and examined in vivo cellular and molecular consequences. RESULTS: The KI mice exhibited stunted growth, ataxia, and a severe loss of myelination in the brain and spinal cord. When combined with the loss of p53, a tumor suppressor gene whose activity is decreased in DMG, the KI mice failed to develop tumors but still exhibited hypomyelination. RNA-sequencing analysis revealed decreased myelination gene signatures, indicating a defect in oligodendroglial development. Mice overexpressing PDGFRA in prenatal GFAP-expressing progenitors, which give rise to a broader lineage of cells than Olig2-progenitors, also developed myelination defects. CONCLUSION: Our results suggest that embryonic overexpression of hPDGFRA in Olig2- or GFAP-progenitors is deleterious to OPC development and leads to CNS hypomyelination.

A template for physical resilience research in older adults: Methods of the PRIME-KNEE study.

BACKGROUND: Older adults with similar health conditions often experience widely divergent outcomes following health stressors. Variable recovery after a health stressor may be due in part to differences in biological mechanisms at the molecular, cellular, or system level, that are elicited in response to stressors. We describe the PRIME-KNEE study as an example of ongoing research to validate provocative clinical tests and biomarkers that predict resilience to specific health stressors. METHODS: PRIME-KNEE is an ongoing, prospective cohort study that will enroll 250 adults ≥60 years undergoing total knee arthroplasty. Data are collected at baseline (pre-surgery), during surgery, daily for 7 days after surgery, and at 1, 2, 4, and 6 months post-surgery. Provocative tests include a cognition-motor dual-task walking test, cerebrovascular reactivity assessed by functional near-infrared spectroscopy, peripheral blood mononuclear cell reactivity ex vivo to lipopolysaccharide toxin and influenza vaccine, and heart rate variability during surgery. Cognitive, psychological, and physical performance batteries are collected at baseline to estimate prestressor reserve. Demographics, medications, comorbidities, and stressor characteristics are abstracted from the electronic medical record and via participant interview. Blood-based biomarkers are collected at baseline and postoperative day 1. Repeated measures after surgery include items from a delirium assessment tool and pain scales administered daily by telephone for 7 days and cognitive change index (participant and informant), lower extremity activities of daily living, pain scales, and step counts assessed by Garmin actigraphy at 1, 2, 4, and 6 months after surgery. Statistical models use these measures to characterize resilience phenotypes and evaluate prestressor clinical indicators associated with poststressor resilience. CONCLUSION: If PRIME-KNEE validates feasible clinical tests and biomarkers that predict recovery trajectories in older surgical patients, these tools may inform surgical decision-making, guide pre-habilitation efforts, and elucidate mechanisms underlying resilience. This study design could motivate future geriatric research on resilience.

A Scoping Review of International Barriers to Asthma Medication Adherence Mapped to the Theoretical Domains Framework.

BACKGROUND: Internationally, adult asthma medication adherence rates are low. Studies characterizing variations in barriers by country are lacking. OBJECTIVE: To conduct a scoping review to characterize international variations in barriers to asthma medication adherence among adults. METHODS: MEDLINE, EMBASE, Web of Science (WOS), and CINAHL were searched from inception to February 2017. English-language studies employing qualitative methods (eg, focus groups, interviews) were selected to assess adult patient- and/or caregiver-reported barriers to asthma medication adherence. Two investigators independently identified, extracted data, and collected study characteristics, methodologic approach, and barriers. Barriers were mapped using the Theoretical Domains Framework and findings categorized according to participants' country of residence, countries' gross national income, and the presence of universal health care (World Health Organization definitions). RESULTS: Among 2942 unique abstracts, we reviewed 809 full texts. Among these, we identified 47 studies, conducted in 12 countries, meeting eligibility. Studies included a total of 2614 subjects, predominately female (67%), with the mean age of 19.1 to 70 years. Most commonly reported barriers were beliefs about consequences (eg, medications not needed for asthma control, N = 29, 61.7%) and knowledge (eg, not knowing when to take medication, N = 27, 57.4%); least common was goals (eg, asthma not a priority, N = 1, 2.1%). In 27 studies conducted in countries classified as high income (HIC) with universal health care (UHC), the most reported barrier was participants' beliefs about consequences (N = 17, 63.3%). However, environmental context and resources (N = 12, 66.7%) were more common in HIC without UHC. CONCLUSION: International adherence barriers are diverse and may vary with a country's sociopolitical context. Future adherence interventions should account for trends.

Tumor genotype dictates radiosensitization after Atm deletion in primary brainstem glioma models.

Diffuse intrinsic pontine glioma (DIPG) kills more children than any other type of brain tumor. Despite clinical trials testing many chemotherapeutic agents, palliative radiotherapy remains the standard treatment. Here, we utilized Cre/loxP technology to show that deleting Ataxia telangiectasia mutated (Atm) in primary mouse models of DIPG can enhance tumor radiosensitivity. Genetic deletion of Atm improved survival of mice with p53-deficient but not p53 wild-type gliomas after radiotherapy. Similar to patients with DIPG, mice with p53 wild-type tumors had improved survival after radiotherapy independent of Atm deletion. Primary p53 wild-type tumor cell lines induced proapoptotic genes after radiation and repressed the NRF2 target, NAD(P)H quinone dehydrogenase 1 (Nqo1). Tumors lacking p53 and Ink4a/Arf expressed the highest level of Nqo1 and were most resistant to radiation, but deletion of Atm enhanced the radiation response. These results suggest that tumor genotype may determine whether inhibition of ATM during radiotherapy will be an effective clinical approach to treat DIPGs.

Biomarkers Associated with Physical Resilience After Hip Fracture.

BACKGROUND: Clinically similar older adults demonstrate variable responses to health stressors, heterogeneity attributable to differences in physical resilience. However, molecular mechanisms underlying physical resilience are unknown. We previously derived a measure of physical resilience after hip fracture-the expected recovery differential (ERD)-that captures the difference between actual recovery and predicted recovery. Starting with biomarkers associated with physical performance, morbidity, mortality, and hip fracture, we evaluated associations with the ERD to identify biomarkers of physical resilience after hip fracture. METHODS: In the Baltimore Hip Studies (N = 304) sera, we quantified biomarkers of inflammation (TNFR-I, TNFR-II, sVCAM-1, and IL-6), metabolic and mitochondrial function (non-esterified fatty acids, lactate, ketones, acylcarnitines, free amino acids, and IGF-1), and epigenetic dysregulation (circulating microRNAs). We used principal component analysis, canonical correlation, and least absolute shrinkage and selection operator regression (LASSO) to identify biomarker associations with better-than-expected recovery (greater ERD) after hip fracture. RESULTS: Participants with greater ERD were more likely to be women and less disabled at baseline. The complete biomarker set explained 37% of the variance in ERD (p < .001) by canonical correlation. LASSO regression identified a biomarker subset that accounted for 27% of the total variance in the ERD and included a metabolic factor (aspartate/asparagine, C22, C5:1, lactate, glutamate/mine), TNFR-I, miR-376a-3p, and miR-16-5p. CONCLUSIONS: We identified a set of biomarkers that explained 27% of the variance in ERD-a measure of physical resilience after hip fracture. These ERD-associated biomarkers may be useful in predicting physical resilience in older adults facing hip fracture and other acute health stressors.

The MARBLE Study Protocol: Modulating ApoE Signaling to Reduce Brain Inflammation, DeLirium, and PostopErative Cognitive Dysfunction.

BACKGROUND: Perioperative neurocognitive disorders (PND) are common complications in older adults associated with increased 1-year mortality and long-term cognitive decline. One risk factor for worsened long-term postoperative cognitive trajectory is the Alzheimer's disease (AD) genetic risk factor APOE4. APOE4 is thought to elevate AD risk partly by increasing neuroinflammation, which is also a theorized mechanism for PND. Yet, it is unclear whether modulating apoE4 protein signaling in older surgical patients would reduce PND risk or severity. OBJECTIVE: MARBLE is a randomized, blinded, placebo-controlled phase II sequential dose escalation trial designed to evaluate perioperative administration of an apoE mimetic peptide drug, CN-105, in older adults (age≥60 years). The primary aim is evaluating the safety of CN-105 administration, as measured by adverse event rates in CN-105 versus placebo-treated patients. Secondary aims include assessing perioperative CN-105 administration feasibility and its efficacy for reducing postoperative neuroinflammation and PND severity. METHODS: 201 patients undergoing non-cardiac, non-neurological surgery will be randomized to control or CN-105 treatment groups and receive placebo or drug before and every six hours after surgery, for up to three days after surgery. Chart reviews, pre- and postoperative cognitive testing, delirium screening, and blood and CSF analyses will be performed to examine effects of CN-105 on perioperative adverse event rates, cognition, and neuroinflammation. Trial results will be disseminated by presentations at conferences and peer-reviewed publications. CONCLUSION: MARBLE is a transdisciplinary study designed to measure CN-105 safety and efficacy for preventing PND in older adults and to provide insight into the pathogenesis of these geriatric syndromes.

Two Approaches to Classifying and Quantifying Physical Resilience in Longitudinal Data.

BACKGROUND: Approaches for quantifying physical resilience in older adults have not been described. METHODS: We apply two conceptual approaches to defining physical resilience to existing longitudinal data sets in which outcomes are measured after an acute physical stressor. A "recovery phenotype" approach uses statistical methods to describe how quickly and completely a patient recovers. Statistical methods using a recovery phenotype approach can consider multiple outcomes simultaneously in a composite score (eg, factor analysis and principal components analysis) or identify groups of patients with similar recovery trajectories across multiple outcomes (eg, latent class profile analysis). An "expected recovery differential" approach quantifies how patients' actual outcomes are compared to their predicted outcome based on a population-derived model and their individual clinical characteristics at the time of the stressor. RESULTS: Application of the approaches identified different participants as being the most or least physically resilient. In the viral respiratory cohort (n = 186) weighted kappa for agreement across resilience quartiles was 0.37 (0.27-0.47). The expected recovery differential approach identified a group with more comorbidities and lower baseline function as highly resilient. In the hip fracture cohort (n = 541), comparison of the expected recovery differentials across 10 outcome measures within individuals provided preliminary support for the hypothesis that there is a latent resilience trait at the whole-person level. CONCLUSIONS: We posit that recovery phenotypes may be useful in clinical applications such as prediction models because they summarize the observed outcomes across multiple measures. Expected recovery differentials offer insight into mechanisms behind physical resilience not captured by age and other comorbidities.

Resiliency Groups Following Hip Fracture in Older Adults.

OBJECTIVES: Defining common patterns of recovery after an acute health stressor (resiliency groups) has both clinical and research implications. We sought to identify groups of patients with similar recovery patterns across 10 outcomes following hip fracture (stressor) and to determine the most important predictors of resiliency group membership. DESIGN: Secondary analysis of three prospective cohort studies. SETTING: Participants were recruited from various hospitals in the Baltimore Hip Studies network and followed for up to 1 year in their residence (home or facility). PARTICIPANTS: Community-dwelling adults aged 65 years or older with recent surgical repair of a hip fracture (n = 541). MEASUREMENTS: Self-reported physical function and activity measures using validated scales were collected at baseline (within 15-22 d of fracture), 2, 6, and 12 months. Physical performance tests were administered at all follow-up visits. Stressor characteristics, comorbidities, and psychosocial and environmental factors were collected at baseline via participant report and chart abstraction. Latent class profile analysis was used to identify resiliency groups based on recovery trajectories across 10 outcome measures and logistic regression models to identify factors associated with those groups. RESULTS: Latent profile analysis identified three resiliency groups that had similar patterns across the 10 outcome measures and were defined as "high resilience" (n = 163 [30.1%]), "medium resilience" (n = 242 [44.7%]), and "low resilience" (n = 136 [25.2%]). Recovery trajectories for the outcome measures are presented for each resiliency group. Comparing highest with the medium- and low-resilience groups, self-reported pre-fracture function was by far the strongest predictor of high-resilience group membership with area under the curve (AUC) of .84. Demographic factors, comorbidities, stressor characteristics, environmental factors, and psychosocial characteristics were less predictive, but several factors remained significant in a multivariable model (AUC = .88). CONCLUSION: These three resiliency groups following hip fracture may be useful for understanding mediators of physical resilience. They may provide a more detailed description of recovery patterns in multiple outcomes for use in clinical decision making. J Am Geriatr Soc 67:2519-2527, 2019.

Gabapentin for Perioperative Pain Management for Uterine Aspiration: A Randomized Controlled Trial.

OBJECTIVE: To evaluate the effect of oral gabapentin in conjunction with usual oral pain management regimens of lorazepam, ibuprofen, oxycodone, and acetaminophen for surgical abortion on pain 5 minutes postprocedure. METHODS: This was a randomized, double-blind, placebo-controlled trial of patients from 6 0/7-14 6/7 weeks of gestation scheduled to undergo surgical abortion at the Duke Family Planning Clinic. Participants were administered 600 mg of oral gabapentin compared with placebo with usual oral pain management. Pain score was assessed using a 100-mm visual analog scale, with the primary outcome being pain score 5 minutes after the procedure. The effect of gabapentin was assessed using a linear regression model controlling for baseline pain. We also measured pain perception 24 hours after the procedure. Secondary outcome measures included anxiety, side effects, and usage of opiate pain medication in the 24-hour postoperative period. RESULTS: Out of 113 women screened for this study; 96 women were recruited, enrolled, and randomized to study treatment arm from August 2016 to June 2018. Pain at 5 minutes after the procedure was similar between the gabapentin and placebo groups ((Equation is included in full-text article.)=3.40; 95% CI -8.20 to 15.0; P=.56). Gabapentin and placebo were well tolerated, with no statistically significant difference in side effects or anxiety levels. Although prescription of opioids after the procedure was not standardized among patients, 73% of women received a short-term prescription for oxycodone. A lower percentage of women in the gabapentin group self-reported taking opioids in the 24 hours postprocedure (18% vs 47%; odds ratio 0.26; 95% CI 0.09-0.75). CONCLUSION: The addition of gabapentin to usual oral pain management regimens with paracervical block did not reduce postoperative pain for patients undergoing outpatient surgical abortion. Although the addition of gabapentin was well tolerated and reduced oral opiate use 24 hours postprocedure, it did not affect the experience of pain during and immediately after the procedure. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov, NCT02725710.

The relationship between obesity and body compositions with respect to the timing of puberty in Chongqing adolescents: a cross-sectional study.

BACKGROUND: It is well known that excess adiposity during childhood may influence pubertal development. However, the extent to which body compositions vary in throughout puberty in boys and girls is currently unknown. The aim of this study was to investigate whether obesity and body compositions correlate with the timing of puberty in boys and girls. METHODS: By random cluster sampling, our study analyzed data from 1472 students (690 girls, 782 boys) aged 6-17 years from two schools in the Chongqing area. Data were collected by physical examination of weight, height, and skinfold thicknesses. Testicular volume was measured in boys and breast development in girls. By which we got the indicators of obesity, timing of puberty and body compositions. Probit regression analysis was used to group subjects into early puberty (>P25), on-time puberty (P25 ~ P75), and delayed puberty ( 0.05). CONCLUSIONS: In girls, delayed puberty was negatively correlated with Obesity, percentage of body fat, fat mass and fat-free mass, and positively correlated with body density. But in boys, delayed puberty was only negatively correlated with Obesity, the relation between puberty and body compositions was not found.

ABCG2 and ABCB1 Limit the Efficacy of Dasatinib in a PDGF-B-Driven Brainstem Glioma Model.

Dasatinib is a multikinase inhibitor in clinical trials for glioma, and thus far has failed to demonstrate significant efficacy. We investigated whether the ABC efflux transporters ABCG2 and ABCB1 expressed in the blood-brain barrier (BBB), are limiting the efficacy of dasatinib in the treatment of glioma using genetic and pharmacologic approaches. We utilized a genetic brainstem glioma mouse model driven by platelet-derived growth factor-B and p53 loss using abcg2/abcb1 wild-type (ABC WT) or abcg2/abcb1 knockout mice (ABC KO). First, we observed that brainstem glioma tumor latency is significantly prolonged in ABC KO versus ABC WT mice (median survival of 47 vs. 34 days). Dasatinib treatment nearly doubles the survival of brainstem glioma-bearing ABC KO mice (44 vs. 80 days). Elacridar, an ABCG2 and ABCB1 inhibitor, significantly increases the efficacy of dasatinib in brainstem glioma-bearing ABC WT mice (42 vs. 59 days). Pharmacokinetic analysis demonstrates that dasatinib delivery into the normal brain, but not into the tumor core, is significantly increased in ABC KO mice compared with ABC WT mice. Surprisingly, elacridar did not significantly increase dasatinib delivery into the normal brain or the tumor core of ABC WT mice. Next, we demonstrate that the tight junctions of the BBB of this model are compromised as assessed by tissue permeability to Texas Red dextran. Finally, elacridar increases the cytotoxicity of dasatinib independent of ABCG2 and ABCB1 expression in vitro In conclusion, elacridar improves the efficacy of dasatinib in a brainstem glioma model without significantly increasing its delivery to the tumor core. Mol Cancer Ther; 15(5); 819-29. ©2016 AACR.

Modulation of PICALM Levels Perturbs Cellular Cholesterol Homeostasis.

PICALM (Phosphatidyl Inositol Clathrin Assembly Lymphoid Myeloid protein) is a ubiquitously expressed protein that plays a role in clathrin-mediated endocytosis. PICALM also affects the internalization and trafficking of SNAREs and modulates macroautophagy. Chromosomal translocations that result in the fusion of PICALM to heterologous proteins cause leukemias, and genome-wide association studies have linked PICALM Single Nucleotide Polymorphisms (SNPs) to Alzheimer's disease. To obtain insight into the biological role of PICALM, we performed gene expression studies of PICALM-deficient and PICALM-expressing cells. Pathway analysis demonstrated that PICALM expression influences the expression of genes that encode proteins involved in cholesterol biosynthesis and lipoprotein uptake. Gas Chromatography-Mass Spectrometry (GC-MS) studies indicated that loss of PICALM increases cellular cholesterol pool size. Isotopic labeling studies revealed that loss of PICALM alters increased net scavenging of cholesterol. Flow cytometry analyses confirmed that internalization of the LDL receptor is enhanced in PICALM-deficient cells as a result of higher levels of LDLR expression. These findings suggest that PICALM is required for cellular cholesterol homeostasis and point to a novel mechanism by which PICALM alterations may contribute to disease.

A high-throughput in vitro drug screen in a genetically engineered mouse model of diffuse intrinsic pontine glioma identifies BMS-754807 as a promising therapeutic agent.

Diffuse intrinsic pontine gliomas (DIPGs) represent a particularly lethal type of pediatric brain cancer with no effective therapeutic options. Our laboratory has previously reported the development of genetically engineered DIPG mouse models using the RCAS/tv-a system, including a model driven by PDGF-B, H3.3K27M, and p53 loss. These models can serve as a platform in which to test novel therapeutics prior to the initiation of human clinical trials. In this study, an in vitro high-throughput drug screen as part of the DIPG preclinical consortium using cell-lines derived from our DIPG models identified BMS-754807 as a drug of interest in DIPG. BMS-754807 is a potent and reversible small molecule multi-kinase inhibitor with many targets including IGF-1R, IR, MET, TRKA, TRKB, AURKA, AURKB. In vitro evaluation showed significant cytotoxic effects with an IC50 of 0.13 µM, significant inhibition of proliferation at a concentration of 1.5 µM, as well as inhibition of AKT activation. Interestingly, IGF-1R signaling was absent in serum-free cultures from the PDGF-B; H3.3K27M; p53 deficient model suggesting that the antitumor activity of BMS-754807 in this model is independent of IGF-1R. In vivo, systemic administration of BMS-754807 to DIPG-bearing mice did not prolong survival. Pharmacokinetic analysis demonstrated that tumor tissue drug concentrations of BMS-754807 were well below the identified IC50, suggesting that inadequate drug delivery may limit in vivo efficacy. In summary, an unbiased in vitro drug screen identified BMS-754807 as a potential therapeutic agent in DIPG, but BMS-754807 treatment in vivo by systemic delivery did not significantly prolong survival of DIPG-bearing mice.

Over-expression of an inactive mutant cathepsin D increases endogenous alpha-synuclein and cathepsin B activity in SH-SY5Y cells.

Parkinson's disease is a neurodegenerative movement disorder. The histopathology of Parkinson's disease comprises proteinaceous inclusions known as Lewy bodies, which contains aggregated α-synuclein. Cathepsin D (CD) is a lysosomal protease previously demonstrated to cleave α-synuclein and decrease its toxicity in both cell lines and mouse brains in vivo. Here, we show that pharmacological inhibition of CD, or introduction of catalytically inactive mutant CD, resulted in decreased CD activity and increased cathepsin B activity, suggesting a possible compensatory response to inhibition of CD activity. However, this increased cathepsin B activity was not sufficient to maintain α-synuclein degradation, as evidenced by the accumulation of endogenous α-synuclein. Interestingly, the levels of LC3, LAMP1, and LAMP2, proteins involved in autophagy-lysosomal activities, as well as total lysosomal mass as assessed by LysoTracker flow cytometry, were unchanged. Neither autophagic flux nor proteasomal activities differs between cells over-expressing wild-type versus mutant CD. These observations point to a critical regulatory role for that endogenous CD activity in dopaminergic cells in α-synuclein homeostasis which cannot be compensated for by increased Cathepsin B. These data support the potential need to enhance CD function in order to attenuate α-synuclein accumulation as a therapeutic strategy against development of synucleinopathy.

Dopamine and its metabolites in cathepsin D heterozygous mice before and after MPTP administration.

Cathepsin D (CD) is a lysosomal aspartyl protease which plays an important role in α-synuclein degradation, and neuronal survival. CD knockout mice die by post-natal day 25±1 due to intestinal necrosis. We analyzed the young adult male heterozygous mice, and found no behavior abnormalities in the heterozygous mice compared to wildtype littermates. LC3-II, p62, and α-synuclein levels are similar, while LAMP1 is higher in the striatum in CD heterozygous compared to wildtype mice. Interestingly, we found that dopamine and metabolites in the striatum and olfactory bulbs are at higher levels than wildtype littermates, while the DOPAC/DA and HVA/DA ratio remain similar between wildtype and CD heterozygous mice. In response to sub-chronic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration, dopamine, DOPAC, and HVA are depleted to similar levels in the striatum in both heterozygous and wildtype mice. Dopamine synthesizing enzyme tyrosine hydroxylase, metabolic enzyme monoamine oxidase, and catechol-O-methyltransferase (COMT) levels are similar in the striatum in wildtype and heterozygous mice. These studies provide valuable information regarding how lysosomal function may contribute to neurochemical homeostasis in animal models.

Genetically engineered mouse models of Parkinson's disease.

Parkinson's disease (PD) is the most common neurodegenerative movement disorder, affecting more than 1% of the population over age 60. The most common feature of PD is a resting tremor, though there are many systemic neurological effects, such as incontinence and sleep disorders. PD is histopathologically identified by the presence of Lewy bodies (LB), proteinaceous inclusions constituted primarily by α-synuclein. To date, there is no effective treatment to slow or stop disease progression. To help understand disease pathogenesis and identify potential therapeutic targets, many genetic mouse models have been developed. By far the most common of these models are the wildtype and mutant α-synuclein transgenic mice, because α-synuclein was the first protein shown to have a direct effect on PD pathogenesis and progression. There are many other gene-disrupted or -mutated models currently available, which are based on genetic anomalies identified in the human disease. In addition, there are also models which examine genes that may contribute to disease onset or progression but currently have no identified causative PD mutations. These genes are part of signaling pathways important for maintaining neuronal function in the nigrostriatal pathway. This review will summarize the most commonly used of the genetic mouse models currently available for PD research. We will examine how these models have expanded our understanding of PD pathogenesis and progression, as well as aided in identification of potential therapeutic targets in this disorder.

Lysosomal enzyme cathepsin D protects against alpha-synuclein aggregation and toxicity.

α-synuclein (α-syn) is a main component of Lewy bodies (LB) that occur in many neurodegenerative diseases, including Parkinson's disease (PD), dementia with LB (DLB) and multi-system atrophy. α-syn mutations or amplifications are responsible for a subset of autosomal dominant familial PD cases, and overexpression causes neurodegeneration and motor disturbances in animals. To investigate mechanisms for α-syn accumulation and toxicity, we studied a mouse model of lysosomal enzyme cathepsin D (CD) deficiency, and found extensive accumulation of endogenous α-syn in neurons without overabundance of α-syn mRNA. In addition to impaired macroautophagy, CD deficiency reduced proteasome activity, suggesting an essential role for lysosomal CD function in regulating multiple proteolytic pathways that are important for α-syn metabolism. Conversely, CD overexpression reduces α-syn aggregation and is neuroprotective against α-syn overexpression-induced cell death in vitro. In a C. elegans model, CD deficiency exacerbates α-syn accumulation while its overexpression is protective against α-syn-induced dopaminergic neurodegeneration. Mutated CD with diminished enzymatic activity or overexpression of cathepsins B (CB) or L (CL) is not protective in the worm model, indicating a unique requirement for enzymatically active CD. Our data identify a conserved CD function in α-syn degradation and identify CD as a novel target for LB disease therapeutics.