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1.
Clin Pharmacol Ther ; 2024 Jun 11.
Article in English | MEDLINE | ID: mdl-38860403

ABSTRACT

The global rise in polypharmacy has increased both the necessity and complexity of drug-drug interaction (DDI) assessments, given the growing potential for interactions involving more than two drugs. Leveraging large-scale healthcare claims data, we piloted a semi-automated, high-throughput case-crossover-based approach for drug-drug-drug interaction (3DI) screening. Cases were direct-acting oral anticoagulant (DOAC) users with either a major bleeding event during ongoing dispensings for potentially interacting, enzyme-inhibiting antihypertensive drugs (AHDs) (Study 1), or a thromboembolic event during ongoing dispensings for potentially interacting, enzyme-inducing antiseizure medications (ASMs) (Study 2). 3DI detection was based on screening for additional drug exposures that served as acute outcome triggers. To mitigate direct effects and confounding by concomitant drugs, self-controlled estimates were adjusted using negative cases (external "control" DOAC users with the same outcomes but co-dispensings for non-interacting AHDs or ASMs). Signal thresholds were set based on P-values and false discovery rate q-values to address multiple comparisons. Study 1: 285 drugs were examined among 3,306 episodes. Self-controlled assessments with q-value thresholds yielded 9 3DI signals (cases) and 40 DDI signals (negative cases). External adjustment generated 10 3DI signals from the P-value threshold and no signals from the q-value threshold. Study 2: 126 drugs were examined among 604 episodes. Assessments with P-value thresholds yielded 3 3DI and 26 DDI signals following self-control, as well as 4 3DI signals following adjustment. No 3DI signals met the q-value threshold. The presented self- and externally-controlled approach aimed to advance paradigms for real-world higher order drug interaction screening among high-susceptibility populations with pre-existent DDI risk.

2.
Epilepsy Behav ; 150: 109572, 2024 Jan.
Article in English | MEDLINE | ID: mdl-38070406

ABSTRACT

RATIONALE: Seizure induction techniques are used in the epilepsy monitoring unit (EMU) to increase diagnostic yield and reduce length of stay. There are insufficient data on the efficacy of alcohol as an induction technique. METHODS: We performed a retrospective cohort study using six years of EMU data at our institution. We compared cases who received alcohol for seizure induction to matched controls who did not. The groups were matched on the following variables: age, reason for admission, length of stay, number of antiseizure medications (ASM) at admission, whether ASMs were tapered during admission, and presence of interictal epileptiform discharges. We used both propensity score and exact matching strategies. We compared the likelihood of epileptic seizures and nonepileptic events in cases versus controls using Kaplan-Meier time-to-event analysis, as well as odds ratios for these outcomes occurring at any time during the admission. RESULTS: We analyzed 256 cases who received alcohol (median dose 2.5 standard drinks) and 256 propensity score-matched controls. Cases who received alcohol were no more likely than controls to have an epileptic seizure (X2(1) = 0.01, p = 0.93) or nonepileptic event (X2(1) = 2.1, p = 0.14) in the first 48 h after alcohol administration. For the admission overall, cases were no more likely to have an epileptic seizure (OR 0.89, 95 % CI 0.61-1.28, p = 0.58), nonepileptic event (OR 0.97, CI 0.62-1.53, p = 1.00), nor require rescue benzodiazepine (OR 0.63, CI 0.35-1.12, p = 0.15). Stratified analyses revealed no increased risk of epileptic seizure in any subgroups. Sensitivity analysis using exact matching showed that results were robust to matching strategy. CONCLUSIONS: Alcohol was not an effective induction technique in the EMU. This finding has implications for counseling patients with epilepsy about the risks of drinking alcohol in moderation in their daily lives.


Subject(s)
Electroencephalography , Epilepsy , Humans , Retrospective Studies , Electroencephalography/methods , Seizures/psychology , Epilepsy/complications , Epilepsy/diagnosis , Epilepsy/epidemiology , Monitoring, Physiologic , Ethanol/therapeutic use
3.
Epilepsia ; 64(2): 374-385, 2023 02.
Article in English | MEDLINE | ID: mdl-36268811

ABSTRACT

OBJECTIVE: Alprazolam administered via the Staccato® breath-actuated device is delivered into the deep lung for rapid systemic exposure and is a potential therapy for rapid epileptic seizure termination (REST). We conducted an inpatient study (ENGAGE-E-001 [NCT03478982]) in patients with stereotypic seizure episodes with prolonged or repetitive seizures to determine whether Staccato alprazolam rapidly terminates seizures in a small observed population after administration under direct supervision. METHODS: Adult patients with established diagnosis of focal and/or generalized epilepsy with a documented history of seizure episodes with a predictable pattern were enrolled. They were randomized 1:1:1 to double-blind treatment of a single seizure event with one dose of Staccato alprazolam 1.0 mg or 2.0 mg, or Staccato placebo in an inpatient unit. The primary end point of the study was the proportion of responders in each treatment group achieving seizure activity cessation within 2 min after administration of study drug and no recurrence of seizure activity within 2 h. RESULTS: A total of 273 patients were screened, and 116 randomized patients received treatment with the study drug in the double-blind part. The proportion of treated patients who were responders was 65.8% for each of Staccato alprazolam 1.0 mg (n = 38; p = .0392) and 2.0 mg (n = 38; p = .0392), compared with 42.5% for Staccato placebo (n = 40). Staccato alprazolam was well tolerated when administered as a single dose of 1.0 or 2.0 mg: cough and somnolence were the most common adverse events (AEs) (both 14.5%), followed by dysgeusia (13.2%). AEs were mostly mild or moderate in intensity; there were no treatment-related serious AEs. SIGNIFICANCE: Both 1.0 mg and 2.0 mg doses of Staccato alprazolam demonstrated efficacy in rapidly terminating seizures in an inpatient setting and were well tolerated. The next step is a Phase 3 confirmatory study to demonstrate efficacy and safety of Staccato alprazolam for rapid cessation of seizures in an outpatient setting.


Subject(s)
Alprazolam , Epilepsy , Adult , Humans , Alprazolam/therapeutic use , Anticonvulsants/adverse effects , Treatment Outcome , Seizures/drug therapy , Seizures/chemically induced , Epilepsy/drug therapy , Double-Blind Method
4.
J Clin Neurophysiol ; 39(6): 459-465, 2022 Sep 01.
Article in English | MEDLINE | ID: mdl-33298682

ABSTRACT

INTRODUCTION: The authors tested the hypothesis that the EEG feature generalized polyspike train (GPT) is associated with drug-resistant idiopathic generalized epilepsy (IGE). METHODS: The authors conducted a single-center case-control study of patients with IGE who had outpatient EEGs performed between 2016 and 2020. The authors classified patients as drug-resistant or drug-responsive based on clinical review and in a masked manner reviewed EEG data for the presence and timing of GPT (a burst of generalized rhythmic spikes lasting less than 1 second) and other EEG features. A relationship between GPT and drug resistance was tested before and after controlling for EEG duration. The EEG duration needed to observe GPT was also calculated. RESULTS: One hundred three patients were included (70% drug-responsive and 30% drug-resistant patients). Generalized polyspike train was more prevalent in drug-resistant IGE (odds ratio, 3.8; 95% confidence interval, 1.3-11.4; P = 0.02). This finding persisted when controlling for EEG duration both with stratification and with survival analysis. A median of 6.5 hours (interquartile range, 0.5-12.7 hours) of EEG recording was required to capture the first occurrence of GPT. CONCLUSIONS: The findings support the hypothesis that GPT is associated with drug-resistant IGE. Prolonged EEG recording is required to identify this feature. Thus, >24-hour EEG recording early in the evaluation of patients with IGE may facilitate prognostication.


Subject(s)
Drug Resistant Epilepsy , Epilepsy, Generalized , Case-Control Studies , Drug Resistant Epilepsy/diagnosis , Drug Resistant Epilepsy/drug therapy , Electroencephalography , Epilepsy, Generalized/diagnosis , Epilepsy, Generalized/drug therapy , Humans , Immunoglobulin E
5.
J Stroke Cerebrovasc Dis ; 30(10): 106024, 2021 Oct.
Article in English | MEDLINE | ID: mdl-34438280

ABSTRACT

OBJECTIVES: Cerebrovascular disease is the leading cause of seizures and incident epilepsy of known etiology in older adults. Statins have increasingly garnered attention as a potential preventive strategy due to their pleiotropic effects beyond lipid-lowering, which may include neuroprotective and anti-epileptogenic properties. We aim to assess the evidence on statin use for prevention of post-stroke early-onset seizures and post-stroke epilepsy. MATERIALS AND METHODS: We conducted a systematic review and meta-analysis in accordance with PRISMA guidelines, which was prospectively registered with PROSPERO (CRD42019144916). PubMed and Embase were searched from database inception to 05/2020 for English-language, full-text studies examining the association between statin use in adults and development of early-onset seizures (≤7 days post-stroke) or post-stroke epilepsy. Pooled analyses were based on random-effects models using the inverse-variance method. RESULTS: Of 182 citations identified, 175 were excluded due to duplication or ineligibility. The 7 eligible publications were all cohort studies from East Asia or South America, with a total of 53,579 patients. Pre-stroke statin use was not associated with post-stroke epilepsy (3 studies pooled: OR 1.14, CI 0.91-1.42). However, post-stroke statin use was associated with lower risk of both early-onset seizures (3 studies pooled: OR 0.36, CI 0.25-0.53), and post-stroke epilepsy (6 studies pooled: OR 0.64, CI 0.46-0.88). CONCLUSIONS: Review of 7 cohort studies suggested post-stroke, but not pre-stroke, statin use may be associated with reduced risk of early-onset seizures and post-stroke epilepsy. Further research is warranted to validate these findings in broader populations and better parse the temporal components of the associations.


Subject(s)
Anticonvulsants/therapeutic use , Brain/drug effects , Epilepsy/prevention & control , Hydroxymethylglutaryl-CoA Reductase Inhibitors/therapeutic use , Seizures/prevention & control , Stroke/drug therapy , Adult , Aged , Aged, 80 and over , Anticonvulsants/adverse effects , Brain/physiopathology , Epilepsy/diagnosis , Epilepsy/etiology , Epilepsy/physiopathology , Female , Humans , Hydroxymethylglutaryl-CoA Reductase Inhibitors/adverse effects , Male , Middle Aged , Protective Factors , Risk Assessment , Risk Factors , Seizures/diagnosis , Seizures/etiology , Seizures/physiopathology , Stroke/complications , Stroke/diagnosis , Stroke/physiopathology , Time Factors , Treatment Outcome
6.
Eur J Neurol ; 28(5): 1453-1462, 2021 05.
Article in English | MEDLINE | ID: mdl-33465822

ABSTRACT

BACKGROUND AND PURPOSE: The aim of this study was to evaluate the quality of smartphone videos (SVs) of neurologic events in adult epilepsy outpatients. The use of home video recording in patients with neurological disease states is increasing. Experts interpretation of outpatient smartphone videos of seizures and neurological events has demonstrated similar diagnostic accuracy to inpatient video-electroencephalography (EEG) monitoring. METHODS: A prospective, multicenter cohort study was conducted to evaluate SV quality in patients with paroxysmal neurologic events from August 15, 2015 through August 31, 2018. Epileptic seizures (ESs), psychogenic nonepileptic attacks (PNEAs), and physiologic nonepileptic events (PhysNEEs) were confirmed by video-EEG monitoring. Experts and senior neurology residents blindly viewed cloud-based SVs without clinical information. Quality ratings with regard to technical and operator-driven metrics were provided in responses to a survey. RESULTS: Forty-four patients (31 women, age 45.1 years [r = 20-82]) were included and 530 SVs were viewed by a mean of seven experts and six residents; one video per patient was reviewed for a mean of 133.8 s (r = 9-543). In all, 30 patients had PNEAs, 11 had ESs, and three had PhysNEEs. Quality was suitable in 70.8% of SVs (375/530 total views), with 36/44 (81.8%) patient SVs rated as adequate by the majority of reviewers. Accuracy improved with the presence of convulsive features from 72.4% to 98.2% in ESs and from 71.1% to 95.7% in PNEAs. An accurate diagnosis was given by all reviewers (100%) in 11/44 SVs (all PNEAs). Audio was rated as good by 86.2% of reviewers for these SVs compared with 75.4% for the remaining SVs (p = 0.01). Lighting was better in SVs associated with high accuracy (p = 0.06), but clarity was not (p = 0.59). Poor video quality yielded unknown diagnoses in 24.2% of the SVs reviewed. Features hindering diagnosis were limited interactivity, restricted field of view and short video duration. CONCLUSIONS: Smartphone video quality is adequate for clinical interpretation in the majority of patients with paroxysmal neurologic events. Quality can be optimized by encouraging interactivity with the patient, adequate duration of the SV, and enlarged field of view during videography. Quality limitations were primarily operational though accuracy remained for SV review of ESs and PNEAs.


Subject(s)
Epilepsy , Outpatients , Adult , Cohort Studies , Electroencephalography , Epilepsy/diagnosis , Female , Humans , Middle Aged , Prospective Studies , Smartphone
7.
Epilepsy Behav ; 113: 107550, 2020 12.
Article in English | MEDLINE | ID: mdl-33242772

ABSTRACT

Treatment considerations for epilepsy patients requiring anticoagulation are changing, and actual prescribing practices have not been characterized. We used the 2010-2018 Optum Clinformatics® Data Mart Database to estimate the annual prevalence and distinguish the patterns of oral anticoagulants (OACs) co-dispensed with antiepileptic drugs (AEDs) among adults with epilepsy. Monotonic trends were assessed using the Spearman rank correlation coefficient (ρ). Multivariable logistic regression models were built to evaluate the associations of sociodemographic characteristics. Among 345,892 adults with epilepsy (56.5% female; median age 61, IQR 46-74) on studied AEDs, the prevalence per thousand of concurrent OACs increased from 58.4 in 2010 to 92.0 in 2018 (OR 1.63, CI 1.58-1.69). Direct-acting oral anticoagulant (DOAC) use rapidly increased from 2010 to 2018 (ρ = 1.00; P < 0.001), with a corresponding decrease in warfarin use (ρ = -0.97; P < 0.001). Among OAC/AED dispensings in 2018, warfarin was more likely to be co-dispensed with potentially interacting, enzyme-inducing antiepileptic drugs (EI-AEDs) versus presumably non-interacting, non-enzyme inducing antiepileptic drugs (OR 1.48, CI 1.38-1.59). Characteristics independently associated with concurrent OAC/EI-AED use included younger age, female sex, white race, net worth <$250 K, and lower education levels. Our findings demonstrate the expanding use and evolving patterns of OAC/AED co-dispensing, and ensuing critical need to further understanding regarding postulated interactions.


Subject(s)
Anticonvulsants , Epilepsy , Administration, Oral , Adult , Anticoagulants/therapeutic use , Anticonvulsants/therapeutic use , Epilepsy/drug therapy , Epilepsy/epidemiology , Female , Humans , Male , Middle Aged , Prescriptions
8.
Epilepsia ; 61(11): 2426-2434, 2020 11.
Article in English | MEDLINE | ID: mdl-32944970

ABSTRACT

OBJECTIVE: Diazepam buccal film (DBF) is in development for treatment of patients experiencing bouts of increased seizure activity. We assessed safety, tolerability, and usability of self- or caregiver-administered DBF in the outpatient setting. METHODS: Patients aged 2-65 years needing treatment with a rescue benzodiazepine at least once monthly were eligible for the study. DBF (5-17.5 mg) was dispensed based on age and body weight. Patients/caregivers administered DBF for up to five seizure episodes per month. Adverse events (AEs) and usability assessments were recorded after the first dose, then every 3 months. RESULTS: Onehundred eighteen patients who used ≥1 DBF dose (adults, n = 82; adolescents, n = 19; children, n = 17) were enrolled. Eleven treatment-related AEs (10 being mild or moderate in severity) occurred in nine (7.6%) patients over a mean of 243 days of follow-up. No patient discontinued participation because of AEs. Mild local buccal discomfort, buccal swelling, and cheek skin sensitivity were reported by one patient each. Twenty-two serious AEs were reported; one was treatment-related. The three deaths reported, all unrelated to DBF, resulted from seizures or seizure with brain malignancy. Self-administration by adults was attempted on 23.6% (188/795) of use occasions. Administration of DBF occurred under ictal or peri-ictal conditions on 49.5% (538/1087) of use occasions, and DBF was successfully administered on a first or second attempt on 96.6% (1050/1087) of use occasions. Overall, patients received their dose of DBF on 99.2% (1078/1087) of use occasions. A second DBF dose was required within 24 hours after the first dose on 8.5% (92/1087) of use occasions. SIGNIFICANCE: In this observational study of chronic intermittent use, DBF was easy to administer, safe, and well tolerated in adult, adolescent, and pediatric patients with epilepsy experiencing seizure emergencies. DBF can be readily self-administered by adults with epilepsy, as well as successfully administered by a caregiver in seizure emergencies.


Subject(s)
Anticonvulsants/administration & dosage , Diazepam/administration & dosage , Drug Delivery Systems/methods , Epilepsy/diagnosis , Epilepsy/drug therapy , Administration, Buccal , Adolescent , Adult , Aged , Anticonvulsants/adverse effects , Anticonvulsants/metabolism , Child , Child, Preschool , Diazepam/adverse effects , Diazepam/metabolism , Drug Administration Schedule , Epilepsy/metabolism , Female , Fever/chemically induced , Humans , Male , Middle Aged , Nausea/chemically induced , Treatment Outcome , Young Adult
9.
Neurology ; 95(10): 454-457, 2020 09 08.
Article in English | MEDLINE | ID: mdl-32586898
10.
JAMA Neurol ; 77(5): 593-600, 2020 05 01.
Article in English | MEDLINE | ID: mdl-31961382

ABSTRACT

Importance: Misdiagnosis of epilepsy is common. Video electroencephalogram provides a definitive diagnosis but is impractical for many patients referred for evaluation of epilepsy. Objective: To evaluate the accuracy of outpatient smartphone videos in epilepsy. Design, Setting, and Participants: This prospective, masked, diagnostic accuracy study (the OSmartViE study) took place between August 31, 2015, and August 31, 2018, at 8 academic epilepsy centers in the United States and included a convenience sample of 44 nonconsecutive outpatients who volunteered a smartphone video during evaluation and subsequently underwent video electroencephalogram monitoring. Three epileptologists uploaded videos for physicians from the 8 epilepsy centers to review. Main Outcomes and Measures: Measures of performance (accuracy, sensitivity, specificity, positive predictive value, and negative predictive value) for smartphone video-based diagnosis by experts and trainees (the index test) were compared with those for history and physical examination and video electroencephalogram monitoring (the reference standard). Results: Forty-four eligible epilepsy clinic outpatients (31 women [70.5%]; mean [range] age, 45.1 [20-82] years) submitted smartphone videos (530 total physician reviews). Final video electroencephalogram diagnoses included 11 epileptic seizures, 30 psychogenic nonepileptic attacks, and 3 physiologic nonepileptic events. Expert interpretation of a smartphone video was accurate in predicting a video electroencephalogram monitoring diagnosis of epileptic seizures 89.1% (95% CI, 84.2%-92.9%) of the time, with a specificity of 93.3% (95% CI, 88.3%-96.6%). Resident responses were less accurate for all metrics involving epileptic seizures and psychogenic nonepileptic attacks, despite greater confidence. Motor signs during events increased accuracy. One-fourth of the smartphone videos were correctly diagnosed by 100% of the reviewing physicians, composed solely of psychogenic attacks. When histories and physical examination results were combined with smartphone videos, correct diagnoses rose from 78.6% to 95.2%. The odds of receiving a correct diagnosis were 5.45 times greater using smartphone video alongside patient history and physical examination results than with history and physical examination alone (95% CI, 1.01-54.3; P = .02). Conclusions and Relevance: Outpatient smartphone video review by experts has predictive and additive value for diagnosing epileptic seizures. Smartphone videos may reliably aid psychogenic nonepileptic attacks diagnosis for some people.


Subject(s)
Seizures/diagnosis , Smartphone , Telemedicine/methods , Video Recording , Adult , Aged , Aged, 80 and over , Female , Humans , Male , Middle Aged , Outpatients , Telemedicine/instrumentation , Young Adult
11.
Pharmacoepidemiol Drug Saf ; 28(11): 1534-1538, 2019 11.
Article in English | MEDLINE | ID: mdl-31517414

ABSTRACT

PURPOSE: To assess concordance regarding proposed interactions between enzyme-inducing antiepileptic drugs (EI-AEDs) and direct oral anticoagulants (DOACs) in leading, international drug compendia. METHODS: We measured consistency of interaction reporting for each DOAC with a group of potent EI-AEDs among eight provider and consumer-focused drug compendia. Discrepant severity ranking systems were consolidated on a 0 to 4 scale. Percent agreement (PA) and Scott/Fleiss' Kappa (к) were used to quantify inter-compendia agreement on interaction listings, with linear weighting when consolidated severity rankings were taken into account (wPA and wк, respectively). RESULTS: For dabigatran, rivaroxaban, apixaban, and edoxaban, poor inter-compendia concordance was observed for interaction listings with EI-AEDs, with and without accounting for severity rankings (wPA: 0.54-0.72/wк: -0.08-0.03, and PA 0.47-0.79/к: -0.09-0.09, respectively). Conversely, betrixaban was consistently listed as not interacting with EI-AEDs in almost all assessed compendia, despite overlap in P-glycoprotein-based transport with other DOACs. Only 6/20 (30%) EI-AED/DOAC interactions were listed in all eight databases, and even in these six cases, severity rankings were universally discordant. Extreme inconsistencies in interaction reporting (some compendia assigning the highest possible severity ranking, while others reported no interactions) were observed in half of the individually examined interactions (10/20). CONCLUSIONS: Drug compendia are highly inconsistent in the inclusion and reported severity of interactions between EI-AEDs and DOACs. Generation of high-quality, real-world evidence from large-scale outcome studies is imperative to resolve discordance and provide clarity for clinical guidelines.


Subject(s)
Anticoagulants/administration & dosage , Anticonvulsants/administration & dosage , Databases, Factual/statistics & numerical data , Drug Interactions , Administration, Oral , Anticoagulants/adverse effects , Anticonvulsants/adverse effects , Anticonvulsants/pharmacology , Databases, Factual/standards , Enzyme Induction/drug effects , Humans , Severity of Illness Index
12.
Epilepsia ; 60(8): 1602-1609, 2019 08.
Article in English | MEDLINE | ID: mdl-31268555

ABSTRACT

OBJECTIVE: Treatment options for seizure clusters are limited; the need for easy-to-administer treatments remains. The Staccato system delivers drug deep into the lung via inhalation. In this phase 2a study, we investigated the ability of three different doses of Staccato alprazolam to suppress the electroencephalographic (EEG) photoparoxysmal response (PPR) compared with placebo in participants with photosensitive seizures. METHODS: Adults (18-60 years) with a diagnosis and history of PPR on EEG with or without an epilepsy diagnosis were eligible to participate. Participants received Staccato alprazolam 0.5, 1.0, and 2.0 mg, and Staccato placebo (twice) in random order. Intermittent photic stimulation and clinical assessments were performed at one predose and seven postdose time points. The primary endpoint of the study was the change in standardized photosensitivity range (SPR) in participants receiving each dose of Staccato alprazolam. RESULTS: Fifteen participants with a prior epilepsy diagnosis were screened; five were enrolled, randomized, and completed the study. All participants were white females with a mean (SD) age of 27.2 (6.8) years. All doses of Staccato alprazolam reduced the SPR at 2 minutes; the effect was sustained through 4 hours for the 0.5-mg dose and 6 hours for the 1.0- and 2.0-mg doses. The magnitude and duration of sedation and sleepiness were dose-related. Four participants (80%) experienced ≥1 adverse event (AE); none was severe or serious. Cough, diarrhea, dysgeusia, oral dysesthesia, sedation, and somnolence were experienced by two participants (40%) each. SIGNIFICANCE: This proof-of-concept study demonstrated that Staccato alprazolam 0.5, 1.0, and 2.0 mg rapidly suppressed epileptiform activity in photosensitive participants with epilepsy. The AE profile of Staccato alprazolam was similar to what has been reported for alprazolam for other indications. The results support further development of Staccato alprazolam as a rescue medication for the acute treatment of seizures.


Subject(s)
Alprazolam/therapeutic use , Anticonvulsants/therapeutic use , Epilepsy, Reflex/drug therapy , Administration, Inhalation , Adult , Alprazolam/administration & dosage , Anticonvulsants/administration & dosage , Drug Delivery Systems , Electroencephalography , Female , Humans , Photic Stimulation/adverse effects , Treatment Outcome , Young Adult
13.
Biochemistry ; 41(34): 10646-56, 2002 Aug 27.
Article in English | MEDLINE | ID: mdl-12186550

ABSTRACT

A debilitating complication of long-term hemodialysis is the deposition of beta-2-microglobulin (beta2m) as amyloid plaques in the joint space. We have recently shown that Cu(2+) can be a contributing, if not causal, factor at concentrations encountered during dialysis therapy. The basis for this effect is destabilization and incorporation of beta2m into amyloid fibers upon binding of Cu(2+). In this work, we demonstrate that while beta2m binds Cu(2+) specifically in the native state, it is binding of Cu(2+) by non-native states of beta2m which is responsible for destabilization. Mutagenesis of potential coordinating groups for Cu(2+) shows that native state binding of Cu(2+) is mediated by residues and structures that are different than those which bind in non-native states. An increased affinity for copper by non-native states compared to that of the native state gives rise to overall destabilization. Using mass spectrometry, NMR, and fluorescence techniques, we show that native state binding is localized to H31 and W60 and is highly specific for Cu(2+) over Zn(2+) and Ni(2+). Binding of Cu(2+) in non-native states of beta2m is mediated by residues H13, H51, and H84, but not H31. Although denatured beta2m has characteristics of a globally unfolded state, it nevertheless demonstrates the following strong specificity of binding: Cu(2+) > Zn(2+) >> Ni(2+). This requires the existence of a well-defined structure in the unfolded state of this protein. As Cu(2+) effects are reported in many other amyloidoses, e.g., PrP, alpha-synuclein, and Abeta, our results may be extended to the emerging field of divalent ion-associated amyloidosis.


Subject(s)
Copper/metabolism , beta 2-Microglobulin/metabolism , Amino Acid Sequence , Animals , Binding Sites , Circular Dichroism , Cysteine/metabolism , Histidine/metabolism , Humans , Mass Spectrometry , Models, Molecular , Mutation , Nuclear Magnetic Resonance, Biomolecular , Protein Binding , Protein Conformation , Protein Denaturation , Protein Folding , Sequence Homology, Amino Acid , Structure-Activity Relationship , Thermodynamics , beta 2-Microglobulin/chemistry , beta 2-Microglobulin/genetics
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