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2.
Semin Dial ; 35(5): 440-445, 2022 09.
Article in English | MEDLINE | ID: mdl-35439847

ABSTRACT

Hemodiafiltration (HDF) is a renal replacement therapy that utilizes both diffusive clearance and convective transport to achieve greater clearance of middle-molecular-weight solutes. Among other factors, important prerequisites for the implementation of HDF include access to high-flux dialyzers, achievement of high blood flow rates, and availability of high volumes of sterile substitution/replacement fluids. Online hemodiafiltration (OL-HDF) is an established kidney replacement therapy, frequently used in many countries. Although in the United States, some prerequisites (e.g., access to high-flux dialyzers and achievement of high blood flow rates) for OL-HDF treatment are readily available; however, a machine capable of generating the online solution for OL-HDF is currently not available. As the clinical experience with HDF accumulates globally, it is worth examining the evidence for this kidney replacement therapy as used in routine clinical care. Such real-world evidence is increasingly recognized as valuable by clinicians and may inform regulatory decisions. In this review, we will focus on emerging global real-world data derived from routine clinical practices and examine how these data may complement those derived from clinical trials.


Subject(s)
Hemodiafiltration , Kidney Failure, Chronic , Humans , Kidney Failure, Chronic/therapy , Renal Dialysis
3.
Clin Nephrol ; 93(4): 163-171, 2020 Apr.
Article in English | MEDLINE | ID: mdl-32049627

ABSTRACT

Maintaining phosphorus balance in in-center hemodialysis (ICHD) patients is problematic despite recommended dietary restriction, dialysis, and phosphate binder use. Rarely is P content in prescribed medications considered, but this source should raise concern. Data was obtained from the Fresenius Kidney Care (FKC) electronic data warehouse Knowledge Center and MedReview-eRx accessed Surescripts, housing > 80% of US-filled prescriptions. Adult FKC ICHD patients prescribed ≥ 1 medication in the MedReview-eRx database were analyzed (695,759 prescriptions). Information collected included medication dose, dose unit, dose timing, strength, start and stop dates, refills, demographic information, admission history, and modality type. Numbers of patients, prescriptions by individual medication, and drug class were then analyzed. Medications prescribed > 100 times were reported. Median doses/day (number of tablets) were calculated for each medication (open order on randomly selected day). Phosphate content of medications taken in FKC clinics was assessed using routinely used pharmacology references, and potential resulting phosphate and pill burden were also calculated. The top five prescribed drug classes in FKC dialysis patients were calcium-channel blockers (22%), proton pump inhibitors (PPIs; 18%), acetaminophen-opioid (AO; 13%), angiotensin-converting enzyme inhibitors (ACEi; 10%), and α2-agonists (9%). The maximum phosphate added for different medications varied by manufacturer. For instance, at median daily doses, phosphate contributions from the top five medications prescribed were 112 mg for amlodipine, 116.2 mg from lisinopril, 6.7 mg from clonidine, 0 mg from acetaminophen, and 200 mg for omeprazole. Prescribing these together could increase the daily phosphate load by 428 mg, forcing the patient to exceed the recommended daily intake (RDI) with food and drink. Phosphate content in medications prescribed to HD patients can substantially contribute to the daily phosphate load and, in combination, may even exceed the daily recommended dietary phosphate intake. Healthcare providers should monitor all medications containing phosphate prescribed in order to minimize risk of uncontrolled hyperphosphatemia and poor adherence.
.


Subject(s)
Phosphates/therapeutic use , Renal Dialysis , Adult , Aged , Aged, 80 and over , Female , Humans , Hyperphosphatemia/drug therapy , Male , Middle Aged , Phosphates/administration & dosage , Phosphates/metabolism
4.
Blood Purif ; 45(1-3): 224-229, 2018.
Article in English | MEDLINE | ID: mdl-29478056

ABSTRACT

BACKGROUND/AIM: Home hemodialysis (HHD) has been associated with improved clinical outcomes vs. in-center HD (ICHD). The prevalence of HHD in the United States is still very low at 1.8%. This critical review compares HHD and ICHD outcomes for survival, hospitalization, cardiovascular (CV), nutrition, and quality of life (QoL). METHODS: Of 545 publications identified, 44 were not selected after applying exclusion criteria. A systematic review of the identified publications was conducted to compare HHD to ICHD outcomes for survival, hospitalization, CV outcomes, nutrition, and QoL. RESULTS: Regarding mortality, 10 of 13 trials reported 13-52% reduction; three trials found no differences. According to 6 studies, blood pressure and left ventricular size measurements were generally lower in HHD patients compared to similar measurements in ICHD patients. Regarding nutritional status, conflicting results were reported (8 studies); some found improved muscle mass, total protein, and body mass index in HHD vs. ICHD patients, while others found no significant differences. There were no significant differences in the rate of hospitalization between HHD and ICHD in the 6 articles reviewed. Seven studies on QoL demonstrated positive trends in HHD vs. ICHD populations. CONCLUSIONS: Despite limitations in the current data, 66% of the publications reviewed (29/44) demonstrated improved clinical outcomes in patients who chose HHD. These include improved survival, CV, nutritional, and QoL parameters. Even though HHD may not be preferred in all patients, a review of the literature suggests that HHD should be provided as a modality choice for substantially more than the current 1.8% of HHD patients in the United States.


Subject(s)
Hemodialysis, Home/methods , Kidney Failure, Chronic/mortality , Kidney Failure, Chronic/therapy , Clinical Trials as Topic , Disease-Free Survival , Female , Humans , Male , Survival Rate , United States/epidemiology
5.
Curr Med Res Opin ; 31(7): 1323-31, 2015.
Article in English | MEDLINE | ID: mdl-25942380

ABSTRACT

BACKGROUND: Inadequate removal of extracellular volume markedly increases blood pressure and contributes to high morbidity and mortality in hemodialysis patients. Advances in fluid management are needed to improve clinical outcomes. The aim of this quality improvement project was to examine the advantages of using a hematocrit-based, blood volume monitor (Crit-Line * ) for 12 months, as part of a clinic-wide, fluid management program in one dialysis facility. METHODS: Forty-five individuals were receiving hemodialysis at one facility at project initiation and are included in this analysis. Monthly averaged clinical parameters (dialysis treatment information, blood pressures, blood volume, and laboratory data) were compared from Months 1-12. Analyses were conducted overall and according to the presence/absence of hypertension at Month 1 (Baseline). Antihypertensive medication changes were assessed for patients with hypertension at Month 1. RESULTS: Average hemodialysis treatment time (+10.6 minutes, p = 0.002), eKt/V (+0.25, p < 0.001) and online clearance (+0.21, p < 0.0001) increased significantly in Month 12 versus Month 1. Average albumin levels and normalized protein catabolic rate increased from Month 1 to 12. Post-dialysis systolic blood pressure (SBP) decreased by Month 12 (p = 0.003). In hypertensive patients (SBP ≥ 140 mmHg in Month 1), there were significant differences in pre- and post-dialysis SBP between Month 1 and Month 12 (pre-hemodialysis: p = 0.02; post-hemodialysis: p = 0.0003), and antihypertensive medication use decreased in 29% of patients, while only 11% increased use. Treatment time in hypertensive patients increased by 15.4 minutes (p = 0.0005). LIMITATIONS: This was a single, clinic-wide, quality improvement project with no control group. All data analyzed were from existing clinical records, so only routinely measured clinical variables were available and missing data were possible. CONCLUSIONS: During this year-long fluid management quality improvement project, decreases in post-dialysis SBP and increases in adequacy and treatment time were observed. Patients with hypertension at Month 1 experienced reductions in pre-dialysis SBP and antihypertensive medications.


Subject(s)
Antihypertensive Agents/therapeutic use , Hypertension/drug therapy , Quality Improvement , Renal Dialysis/methods , Ambulatory Care Facilities , Blood Pressure , Blood Volume , Female , Fluid Therapy/methods , Humans , Male , Middle Aged , Renal Dialysis/adverse effects
6.
Perit Dial Int ; 32(4): 444-52, 2012.
Article in English | MEDLINE | ID: mdl-22383632

ABSTRACT

BACKGROUND: Conventional peritoneal dialysis fluids (PDFs) consist of ready-to-use solutions with an acidic pH. Sterilization of these fluids is known to generate high levels of glucose degradation products (GDPs). Although several neutral-pH, low-GDP PD solutions have been developed, none are commercially available in the United States. We analyzed pH and GDPs in Delflex Neutral pH (Fresenius Medical Care North America, Waltham, MA, USA), the first neutral-pH PDF to be approved by the US Food and Drug Administration. METHODS: We evaluated whether patients (n = 26; age range: 18 - 78 years) could properly mix the Delflex Neutral pH PDF after standardized initial training. We further analyzed the concentrations of 10 different glucose degradation products in Delflex Neutral pH PDF and compared the results with similar analyses in other commercially available biocompatible PDFs. RESULTS: All pH measurements (n = 288) in the delivered Delflex Neutral pH solution consistently fell within the labeled range of 7.0 ± 0.4. Analysis of mixing errors showed no significant impact on the pH results. Delflex Neutral pH, Balance (Fresenius Medical Care, Bad Homburg, Germany), BicaVera (Fresenius Medical Care), and Gambrosol Trio (Gambro Lundia AB, Lund, Sweden) exhibited similar low total GDP concentrations, with maximums in the 4.25% solutions of 88 µmol/L, 74 µmol/L, 74 µmol/L, and 79 µmol/L respectively; the concentration in Physioneal (Baxter Healthcare Corporation, Deerfield, IL, USA) was considerably higher at 263.26 µmol/L. The total GDP concentration in Extraneal (Baxter Healthcare Corporation) was 63 µmol/L, being thus slightly lower than the concentrations in the 4.25% glucose solutions, but higher than the concentrations in the 1.5% and 2.5% glucose solutions. CONCLUSIONS: The new Delflex Neutral pH PDF consistently delivers neutral pH with minimal GDPs.


Subject(s)
Dialysis Solutions/chemistry , Glucose/analysis , Peritoneal Dialysis/instrumentation , Peritoneum/metabolism , Adolescent , Adult , Aged , Drug Compounding , Feasibility Studies , Female , Humans , Hydrogen-Ion Concentration , Male , Middle Aged , Peritoneal Dialysis/methods , Peritoneal Dialysis/nursing , Peritoneum/chemistry , Self Administration , Young Adult
7.
Adv Perit Dial ; 28: 120-5, 2012.
Article in English | MEDLINE | ID: mdl-23311227

ABSTRACT

Although dialytic removal of phosphate significantly contributes to the management of phosphate levels in end-stage renal disease, many patients on peritoneal dialysis (PD) still do not reach optimal phosphate control. The present review discusses the impact of PD modality--continuous ambulatory (CAPD) or automated (APD)--on phosphate removal. Relevant factors are the diffusive properties of the phosphate anion and the kinetics of phosphate distribution in various body compartments. Confounders that potentially affect comparisons of phosphate clearances in CAPD and APD are differences in residual renal function, membrane transport status, and prescribed dialysis dose. The evidence reviewed here is not strong enough to clearly determine if one modality has a clear advantage with respect to phosphate removal. In the absence of final proof the data suggest that, given the same residual renal function and dialysis dose, CAPD might be slightly more effective than APD at peritoneal phosphate clearance, especially in low transporters.


Subject(s)
Kidney Failure, Chronic/metabolism , Peritoneal Dialysis, Continuous Ambulatory , Peritoneal Dialysis , Peritoneum/metabolism , Phosphates/metabolism , Humans , Kidney Failure, Chronic/therapy
8.
Adv Perit Dial ; 27: 22-6, 2011.
Article in English | MEDLINE | ID: mdl-22073823

ABSTRACT

Glucose degradation products (GDPs) are highly reactive precursors of advanced glycation end-products (AGEs). High glucose concentrations, GDPs, and AGEs can activate specific pathways, including inflammatory and oxidative stress response pathways, which may adversely affect the cardiovascular system. This review discusses the impact and possible mechanisms of action of GDPs and AGEs with regard to cardiovascular toxicity in chronic kidney disease patients. The AGE-RAGE pathway appears to be particularly important in the pathogenesis of cardiovascular diseases in dialysis patients. In the absence of definitive proof from randomized controlled trials, mounting evidence suggests that high levels of GDPs and AGEs play a role in the pathophysiology of cardiotoxicity.


Subject(s)
Cardiovascular Diseases/chemically induced , Dialysis Solutions/chemistry , Glucose/adverse effects , Glycation End Products, Advanced/adverse effects , Renal Dialysis , Animals , Glucose/metabolism , Glycation End Products, Advanced/metabolism , Humans , Kidney Failure, Chronic/therapy , Oxidative Stress , Receptor for Advanced Glycation End Products , Receptors, Immunologic/metabolism
9.
Glia ; 57(3): 320-35, 2009 Feb.
Article in English | MEDLINE | ID: mdl-18756527

ABSTRACT

Microglial phagocytosis contributes to the maintenance of brain homeostasis. Mechanisms involved, however, remain unclear. Using Abeta(42) solely as a stimulant, we provide novel insight into regulation of microglial phagocytosis by rafts. We demonstrate the existence of an Abeta(42) threshold level of 250 pg/mL, above which microglial phagocytic function is impaired. Low levels of Abeta(42) facilitate fluorescent bead uptake, whereas phagocytosis is inhibited when Abeta(42) accumulates. We also show that region-specific raft clustering occurs before microglial phagocytosis. Low Abeta(42) levels stimulated this type of raft aggregation, but high Abeta(42) levels inhibited it. Additionally, treatment with high Abeta(42) concentrations caused a redistribution of the raft structural protein flotillin1 from low to higher density fractions along a sucrose gradient. This suggests a loss of raft structural integrity. Certain non-steroidal anti-inflammatory drugs, e.g., the cyclooxygenase 2-specific nonsteroidal anti-inflammatory drugs, celecoxib, raise Abeta(42) levels. We demonstrated that prolonged celecoxib exposure can disrupt rafts in a manner similar to that seen in an elevated Abeta(42) environment: abnormal raft aggregation and Flot1 distribution. This resulted in aberrant receptor recruitment to rafts and impaired receptor-mediated phagocytosis by microglial cells. Specifically, recruitment of the scavenger receptor CD36 to rafts during active phagocytosis was affected. Thus, we propose that maintaining raft integrity is crucial for determining microglial phagocytic outcomes and disease progression.


Subject(s)
Amyloid beta-Peptides/metabolism , CD36 Antigens/metabolism , Membrane Microdomains/metabolism , Microglia/cytology , Microglia/metabolism , Peptide Fragments/metabolism , Amyloid Precursor Protein Secretases/metabolism , Amyloid beta-Peptides/pharmacology , Analysis of Variance , Animals , Animals, Newborn , CD36 Antigens/genetics , CD47 Antigen/genetics , CD47 Antigen/metabolism , Celecoxib , Cells, Cultured , Cerebral Cortex/cytology , Cyclooxygenase Inhibitors/pharmacology , Dose-Response Relationship, Drug , Enzyme-Linked Immunosorbent Assay/methods , Membrane Microdomains/drug effects , Membrane Proteins/metabolism , Mice , Microglia/drug effects , Peptide Fragments/pharmacology , Phagocytosis/physiology , Protein Transport/drug effects , Pyrazoles/pharmacology , Rats , Rats, Long-Evans , Sulfonamides/pharmacology
10.
J Lipid Res ; 50(4): 759-67, 2009 Apr.
Article in English | MEDLINE | ID: mdl-19060326

ABSTRACT

Membrane rafts are rich in cholesterol and sphingolipids and have specific proteins associated with them. Due to their small size, their identification and isolation have proved to be problematic. Their insolubility in nonionic detergents, such as Triton-X 100, at 4 degrees C has been the most common means of isolation. However, detergent presence can produce artifacts or interfere with ganglioside distribution. The direction is therefore toward the use of detergent-free protocols. We report an optimized method of raft isolation from lipid-rich brain tissue using a detergent-free method. We compared this to Triton-X 100-based isolation along sucrose or Optiprep gradients using the following endpoints: low protein content, high cholesterol content, presence of Flotillin 1 (Flot1), and absence of transferrin receptor (TfR) proteins. These criteria were met in raft fractions isolated in a detergent-free buffer along a sucrose gradient of 5%/35%/42.5%. The use of optiprep gave less consistent results with respect to protein distribution. We demonstrate that clean raft fractions with minimal myelin contamination can be reproducibly obtained in the top three low-density fractions along a sucrose step gradient.


Subject(s)
Brain Chemistry , Cell Fractionation/methods , Membrane Microdomains/chemistry , Animals , Centrifugation, Density Gradient , Cholesterol/isolation & purification , Detergents , Membrane Lipids/isolation & purification , Membrane Proteins/isolation & purification , Mice , Mice, Inbred C57BL , Myelin Sheath/chemistry , Nerve Tissue Proteins/isolation & purification , Octoxynol , Receptors, Transferrin/isolation & purification , Sucrose
11.
Pediatr Res ; 63(6): 625-31, 2008 Jun.
Article in English | MEDLINE | ID: mdl-18317235

ABSTRACT

Juvenile neuronal ceroid lipofuscinosis (JNCL) belongs to the neuronal ceroid lipofuscinoses characterized by blindness/seizures/motor/cognitive decline and early death. JNCL is caused by CLN3 gene mutations that negatively modulate cell growth/apoptosis. CLN3 protein (CLN3p) localizes to Golgi/Rab4-/Rab11-positive endosomes and lipid rafts, and harbors a galactosylceramide (GalCer) lipid raft-binding domain. Goals are proving CLN3p participates in GalCer transport from Golgi to rafts, and GalCer deficits negatively affect cell growth/apoptosis. GalCer/mutant CLN3p are retained in Golgi, with CLN3p rescuing GalCer deficits in rafts. Diminishing GalCer in normal cells by GalCer synthase siRNA negatively affects cell growth/apoptosis. GalCer restores JNCL cell growth. WT CLN3p binds GalCer, but not mutant CLN3p. Sphingolipid content of rafts/Golgi is perturbed with diminished GalCer in rafts and accumulation in Golgi. CLN3-deficient raft vesicular structures are small by transmission electron microscopy, reflecting altered sphingolipid composition of rafts. CLN1/CLN2/CLN6 proteins bind to lysophosphatidic acid/sulfatide, CLN6/CLN8 proteins to GalCer, and CLN8 protein to ceramide. Sphingolipid composition/morphology of CLN1-/CLN2-/CLN6-/CLN8- and CLN9-deficient rafts are altered suggesting changes in raft structure/lipid stoichiometry could be common themes underlying these diseases.


Subject(s)
Galactosylceramides/metabolism , Membrane Glycoproteins/metabolism , Membrane Lipids/metabolism , Membrane Microdomains/metabolism , Molecular Chaperones/metabolism , Neuronal Ceroid-Lipofuscinoses/metabolism , Animals , Apoptosis , Cell Line , Cell Proliferation , Cells, Cultured , Endoplasmic Reticulum/metabolism , Fibroblasts/metabolism , Galactosylceramides/deficiency , Golgi Apparatus/metabolism , Humans , Membrane Glycoproteins/genetics , Membrane Microdomains/ultrastructure , Membrane Proteins/genetics , Membrane Proteins/metabolism , Mice , Mice, Knockout , Molecular Chaperones/genetics , Mutation , Neuronal Ceroid-Lipofuscinoses/genetics , Neuronal Ceroid-Lipofuscinoses/pathology , Protein Binding , Protein Transport , Subcellular Fractions , Sulfoglycosphingolipids/metabolism , Tripeptidyl-Peptidase 1
12.
Pediatr Res ; 61(2): 146-52, 2007 Feb.
Article in English | MEDLINE | ID: mdl-17237713

ABSTRACT

The neuronal ceroid lipofuscinoses are pediatric neurodegenerative diseases with common clinical features. Of the nine clinical variants (CLN1-CLN9), six have been genetically identified. Most variants manifest cell death and dysregulated sphingolipid metabolism, suggesting the proteins defective in these disorders may interact along one pathway. NCL patient-derived cell lines exhibit cell growth and apoptotic defects that reverse following transfection with the wild-type gene. The membrane-bound proteins CLN3, CLN6, and CLN8 complement each other, as do CLN1 and CLN2 proteins, with respect to growth and apoptosis. The CLN2 protein also corrects growth and apoptosis in CLN3-, CLN6-, and CLN8-deficient cell lines. Neither CLN1-deficient nor CLN2-deficient growth defects are corrected by CLN3, CLN6, and CLN8 proteins. CLN2, CLN3, CLN6, and CLN8 proteins co-immunoprecipitate and co-localize to early and/or recycling endosomes and lipid rafts. Additionally, CLN2p and CLN1p co-immunoprecipitate. The work presented supports interactions between NCL proteins occurring at multiple points along one pathway.


Subject(s)
Neuronal Ceroid-Lipofuscinoses/metabolism , Signal Transduction , Animals , Apoptosis , COS Cells , Cell Line , Chlorocebus aethiops , Humans , Immunoprecipitation , Membrane Glycoproteins/analysis , Membrane Glycoproteins/genetics , Membrane Glycoproteins/metabolism , Mice , Mice, Inbred C57BL , Mice, Knockout , Models, Biological , Neuronal Ceroid-Lipofuscinoses/enzymology , Neuronal Ceroid-Lipofuscinoses/genetics , Time Factors , Transfection , Tripeptidyl-Peptidase 1
13.
J Clin Immunol ; 26(4): 406-16, 2006 Jul.
Article in English | MEDLINE | ID: mdl-16786433

ABSTRACT

Endothelial cell (EC) involvement in viral hemorrhagic fevers has been clearly established. However, virally activated mechanisms leading to endothelial activation and dysfunction are not well understood. Several different potential mechanisms such as direct viral infection, alterations in procoagulant/anticoagulant balance, and increased cytokine production have been suggested. We utilized a model of EC barrier dysfunction and vascular endothelial leakage to explore the effect of bluetongue virus (BTV), a hemorrhagic fever virus of ruminants, on human lung endothelial cell barrier properties. Infection of human lung EC with BTV induced a significant and dose-dependent decrease in trans-endothelial electrical resistance (TER). Furthermore, decreases in TER occurred in conjunction with cytoskeletal rearrangement, suggesting a direct mechanism for viral infection-mediated endothelial barrier disruption. Interestingly, double-stranded RNA (dsRNA) mimicked the effects of BTV on endothelial barrier properties. Both BTV- and dsRNA-induced endothelial barrier dysfunction was blocked by treatment with a pharmacological inhibitor of p38 MAPK. The induction of vascular permeability by dsRNA treatment or BTV infection was concomitent with induction of inflammatory cytokines. Taken together, our data suggest that the presence of dsRNA during viral infections and subsequent activation of p38 MAPK is a potential molecular pathway for viral induction of hemorrhagic fevers. Collectively, our data suggest that inhibition of p38 MAPK may be a possible therapeutic approach to alter viral-induced acute hemorrhagic diseases.


Subject(s)
Bluetongue virus/pathogenicity , Capillary Permeability/drug effects , Endothelium, Vascular/virology , RNA, Double-Stranded/pharmacology , p38 Mitogen-Activated Protein Kinases/physiology , Cells, Cultured , Cytokines/genetics , Cytoskeleton/metabolism , Endothelium, Vascular/pathology , Gene Expression Regulation , Hemorrhagic Fevers, Viral/etiology , Hemorrhagic Fevers, Viral/pathology , Humans , Lung/pathology , Lung/virology
14.
J Biol Chem ; 281(5): 2784-94, 2006 Feb 03.
Article in English | MEDLINE | ID: mdl-16303764

ABSTRACT

A new variant of a group of pediatric neurodegenerative diseases known as neuronal ceroid lipofuscinosis (NCL) or Batten disease has been identified. It is termed CLN9-deficient. CLN9-deficient fibroblasts have a distinctive phenotype of rapid growth and increased apoptosis and diminished levels of ceramide, dihydroceramide, and sphingomyelin. Transfection with CLN8 but not other NCL genes corrected growth and apoptosis in CLN9-deficient cells, although the entire CLN8 sequence was normal. CLN8 is one of the TRAM-Lag1-CLN8 proteins containing a Lag1 motif. The latter imparts (dihydro)ceramide synthase activity to yeast cells. Transfection with the yeast gene Lag1 Sc and the human homolog LASS1 increased ceramide levels and partially corrected growth and apoptosis in CLN9-deficient cells. LASS2,-4,,-5, and -6 also corrected growth and apoptosis. Dihydroceramide levels and dihydroceramide synthase activity were markedly diminished in CLN9-deficient cells. Sequencing of LASS1, LASS2, LASS4, LASS5, and LASS6 genes was normal, and expression levels were increased or normal in CLN9-deficient cells by reverse transcription-PCR. N-(4-Hydroxyphenyl)retinamide (4-HPR), a dihydroceramide synthase activator, corrected growth and apoptosis and increased dihydroceramide synthase activity. Ceramide levels dropped further, and there was no increase in de novo ceramide synthesis, probably due to the effects of 4-HPR as activator of dihydroceramide synthase and inhibitor of dihydroceramide desaturase. Fumonisin B1, a dihydroceramide synthase inhibitor, exaggerated the CLN9-deficient phenotype of accelerated growth, decreased ceramide and increased apoptosis. This was neutralized by 4-HPR. We conclude that the CLN9 protein may be a regulator of dihydroceramide synthase and that 4-HPR could be developed as a treatment for CLN9-deficient patients.


Subject(s)
Membrane Proteins/physiology , Neuronal Ceroid-Lipofuscinoses/metabolism , Oxidoreductases/metabolism , Apoptosis , Cell Line , Cell Proliferation , Ceramides/analysis , Fenretinide/pharmacology , Fibroblasts/pathology , Fumonisins/pharmacology , Humans , Membrane Proteins/genetics , Neuronal Ceroid-Lipofuscinoses/enzymology , Neuronal Ceroid-Lipofuscinoses/pathology , Saccharomyces cerevisiae Proteins/genetics , Sphingosine N-Acyltransferase
15.
Pediatr Res ; 56(3): 449-63, 2004 Sep.
Article in English | MEDLINE | ID: mdl-15240864

ABSTRACT

Juvenile neuronal ceroid lipofuscinosis (JNCL) is due to mutations in the CLN3 gene. We previously determined that CLN3 protein harbors a highly conserved motif, VYFAE, necessary for its impact on cell growth and apoptosis. Using molecular modeling we demonstrated that this motif is embedded in a stretch of amino acids that is homologous to and structurally compatible with a galactosylceramide (GalCer) binding domain. This domain is present in the V3 loop of the HIV-1 gp120 envelope protein, beta-amyloid protein, and the infectious form of prionic protein, and defines a binding site for lipid rafts. We determined the subcellular localization of CLN3 in different cell systems including human neurons, primary rat hippocampal neurons, normal human fibroblasts, and JNCL fibroblasts homozygous for the 1.02 kb deletion in genomic DNA. Wild-type CLN3 protein was present within Golgi, lipid rafts in the plasma membrane, and early recycling endosomes, but not late endosomes/lysosomes. Wild-type CLN3 internalized from the plasma membrane to the Golgi via Rab4- and Rab11-positive recycling endosomes. Wild-type CLN3 co-localized with GalCer in the Golgi and in lipid rafts at the plasma membrane in normal cells. Neither mutant CLN3 protein nor GalCer were found at the plasma membrane in JNCL fibroblasts. Mutant CLN3p was retained within the Golgi and partially mis-localized to lysosomes, failing to reach recycling endosomes, plasma membrane, or lipid rafts. These studies identify a novel CLN3 domain that may dictate localization and function of CLN3.


Subject(s)
Endosomes/metabolism , Galactosylceramides/metabolism , Golgi Apparatus/metabolism , Membrane Glycoproteins/metabolism , Membrane Microdomains/metabolism , Molecular Chaperones/metabolism , Animals , Cells, Cultured , Endosomes/chemistry , Fibroblasts/cytology , Fibroblasts/metabolism , Fluorescent Dyes/metabolism , Golgi Apparatus/chemistry , Humans , Membrane Glycoproteins/chemistry , Membrane Glycoproteins/genetics , Membrane Microdomains/chemistry , Molecular Chaperones/chemistry , Molecular Chaperones/genetics , Neuronal Ceroid-Lipofuscinoses/metabolism , Neurons/cytology , Neurons/metabolism , Protein Structure, Tertiary , Protein Transport/physiology , Rats , rab GTP-Binding Proteins/metabolism , rab4 GTP-Binding Proteins/metabolism
16.
Hum Mutat ; 21(5): 502-8, 2003 May.
Article in English | MEDLINE | ID: mdl-12673792

ABSTRACT

The neuronal ceroid lipofuscinoses (NCLs) are a heterogeneous group of autosomal recessive neurodegenerative diseases comprising Batten and other related diseases plus numerous variants. They are characterized by progressive neuronal cell death. The CLN6 gene was recently identified, mutations in which cause one of the variant late infantile forms of NCL (vLINCL). We describe four novel mutations in the CLN6 gene. This brings the total number of CLN6 mutations known to 11 in 38 families. This suggests that the CLN6 gene may be highly mutable. An American patient of Irish/French/Native American origin was heterozygous for a 4-bp insertion (c.267_268insAACG) in exon 3. The other allele had a point mutation (c.898T>C) in exon 7 resulting in a W300R amino acid change. Two Trinidadian siblings of Indian origin were homozygous for a mutation at the 5' donor splice site of exon 4 (IVS4+1G>T), affecting the first base of the invariant GT at the beginning of intron 4. The fourth novel mutation, a double deletion of 4 bp and 1 bp in exon 7 (c.829_832delGTCG;c.837delG), was identified in a Portuguese patient heterozygous for the I154del Portuguese CLN6 mutation. Four of the 11 mutations identified are in exon 4. Three Portuguese patients with clinical profiles similar to CLN6 patients without defects in CLN6 or other known NCL genes are described. We conclude the following: 1) the CLN6 gene may be a highly mutable gene; 2) exon 4 must code for a segment of the protein crucial for function; 3) vLINCL disease in Portugal is genetically heterogeneous; 4) the I154del accounts for 81.25% of affected CLN6 Portuguese alleles; and 5) three vLINCL Portuguese patients may have defects in a new NCL gene.


Subject(s)
Membrane Proteins/genetics , Neuronal Ceroid-Lipofuscinoses/genetics , Base Sequence , DNA/chemistry , DNA/genetics , DNA Mutational Analysis , Humans , Infant , Mutation
17.
Hum Mol Genet ; 11(18): 2129-42, 2002 Sep 01.
Article in English | MEDLINE | ID: mdl-12189165

ABSTRACT

Juvenile Batten disease (JNCL) is an autosomal recessive disease that results from mutations in the CLN3 gene. The wild-type CLN3 gene coding sequence has 15 exons, and the translated protein consists of 438 amino acids. The most commonly observed mutation is a 1.02 kb deletion in the genomic DNA. This deletion results in a truncated protein due to the loss of amino acids 154-438, and the introduction of 28 novel amino acids at the c-terminus. We demonstrate that, compared to normal controls, CLN3-deficient immortalization of lymphoblasts homozygous for this deletion grow at a slower rate, and show increased sensitivity to etoposide-induced apoptosis, supporting the notion that CLN3 may negatively regulate apoptosis. Using immortalized JNCL lymphoblast cell lines as a model system, we assess the effects of specific CLN3 mutations on cell growth rates and protection from etoposide-induced apoptosis. Protection from etoposide-induced apoptosis occurs and the cell growth rate is restored following transfection of JNCL lymphoblasts with mutant CLN3 cDNA that includes exons 11 or 13. We show that deletion of the glycosylation sites 71NQSH74 and 310NTSL313, and also mutations within the highly conserved amino acid stretches 184WSSGTGGAGLLG195, 291VYFAE295 and 330VFASRSSL337, result in slowed growth and susceptibility to apoptosis.


Subject(s)
Amino Acid Motifs/genetics , Apoptosis/genetics , Cell Division/genetics , Membrane Glycoproteins , Molecular Chaperones , Proteins/genetics , Apoptosis/drug effects , Cells, Cultured , DNA/biosynthesis , Etoposide/pharmacology , Glycosylation , Humans , Mutation , Neuronal Ceroid-Lipofuscinoses/genetics , Nucleic Acid Synthesis Inhibitors/pharmacology , Protein Biosynthesis
18.
Cancer Res ; 62(3): 801-8, 2002 Feb 01.
Article in English | MEDLINE | ID: mdl-11830536

ABSTRACT

Juvenile Batten disease is a neurodegenerative disease caused by accelerated apoptotic death of photoreceptors and neurons attributable to defects in the CLN3 gene. CLN3 is antiapoptotic when overexpressed in NT2 neuronal precursor cells. CLN3 negatively modulates endogenous ceramide levels in NT2 cells and acts upstream of ceramide generation. Because defects in regulation of apoptosis are involved in the development of cancer, we evaluated the expression of CLN3 on both mRNA and protein levels in a variety of cancer cell lines and solid colon cancer tissue. We also observed the effect of the blocking of CLN3 protein expression on cancer cell growth, survival, ceramide production, and apoptosis by using an adenovirus-bearing antisense CLN3 construct. We show that CLN3 mRNA and protein are overexpressed in glioblastoma (U-373G and T98g), neuroblastoma (IMR-32 and SK-N-MC), prostate (Du145, PC-3, and LNCaP), ovarian (SK-OV-3, SW626, and PA-1), breast (BT-20, BT-549, and BT-474), and colon (SW1116, SW480, and HCT 116) cancer cell lines but not in pancreatic (CAPAN and As-PC-1) or lung (A-549 and NCI-H520) cancer cell lines. CLN3 is also up-regulated in mouse melanoma and breast carcinoma cancer cell lines. We found CLN3 expression is 22-330% higher than in corresponding normal colon control tissue in 8 of 10 solid colon tumors. An adenovirus-expressing antisense CLN3 (Ad-AS-CLN3) blocks CLN3 protein expression in DU-145, BT-20, SW1116, and T98g cancer cell lines as seen by Western blot. Blocking of CLN3 expression using Ad-AS-CLN3 inhibits growth and viability of cancer cells. It also causes elevation in endogenous ceramide production through de novo ceramide synthesis and results in increased apoptosis as shown by propidium iodide and JC-1 staining. This suggests that Ad-AS-CLN3 may be an option for therapy in some cancers. More importantly these results suggest that CLN3 is a novel molecular target for cancer drug discovery.


Subject(s)
Membrane Glycoproteins , Molecular Chaperones , Proteins/antagonists & inhibitors , Proteins/genetics , Adenoviridae/genetics , Animals , Apoptosis/physiology , Ceramides/biosynthesis , Colonic Neoplasms/genetics , Colonic Neoplasms/metabolism , DNA, Antisense/genetics , DNA, Antisense/pharmacology , Gene Expression Regulation, Neoplastic , Genetic Vectors/genetics , Humans , Lymphocytes/metabolism , Lymphocytes/physiology , Male , Mice , Neuronal Ceroid-Lipofuscinoses/metabolism , Neuronal Ceroid-Lipofuscinoses/pathology , Prostatic Neoplasms/genetics , Prostatic Neoplasms/metabolism , Protein Biosynthesis , RNA, Messenger/biosynthesis , RNA, Messenger/genetics , Sphingomyelins/metabolism , Thymidine/metabolism , Transfection , Tumor Cells, Cultured
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