Choice of Oral Anticoagulant: Outcomes in Atrial Fibrillation Patients Post-Stroke Despite Direct Oral Anticoagulant Use.

Background: For patients with atrial fibrillation who have an ischemic stroke or transient ischemic attack (TIA) despite taking direct oral anticoagulants (DOACs), the optimal strategy for ongoing anticoagulation is unknown. Methods: Using provincial administrative databases in Alberta, Canada, we compared anticoagulant use before/after the breakthrough stroke/TIA and assessed recurrence of stroke/TIA or bleeding, with consideration of medication adherence. Adherence was defined as the proportion of days covered (PDC) being ≥ 80%. Results: Among 985 patients, the median age was 80 years (interquartile range 13), with a mean CHADS2 score of 1.7± 1 prior to the index event. Patients were followed for a median of 643 days (interquartile range 836). Following the index stroke/TIA event, 623 patients (63%) filled a prescription for the same DOAC regimen, 83 (8%) filled a prescription for a different dose, 155 (16%) switched DOAC agents, 51 (5%) switched to warfarin, and 73 (7%) filled no oral anticoagulant prescription. Patients who kept the same regimen more commonly had TIA index events (59%); patients who changed dose or drug more often had stroke index events (55%-78%). During follow-up, 135 (14%) had stroke/TIA recurrence, and 46 (5%) had bleeding; rates of each did not differ between prescribing patterns. Post-index event, the proportion of patients with a proportion of days covered ≥ 80% improved from 55% to 80%. Conclusions: Although most maintained the same DOAC regimen after stroke/TIA, rates of recurrent stroke/TIA and bleeding were similar across prescribing patterns. Stroke/TIA severity may have influenced prescribing practices. DOAC prescription adherence improved poststroke/TIA and signals an opportunity for optimization in patients with atrial fibrillation.

Contexte: Chez les patients atteints de fibrillation auriculaire qui subissent un accident vasculaire cérébral (AVC) ischémique ou un accident ischémique transitoire (AIT) malgré la prise d'anticoagulants oraux directe (AOD), la stratégie optimale pour la poursuite de l'anticoagulation est inconnue. Méthodologie: À partir des bases de données administratives provinciales en Alberta, au Canada, nous avons comparé l'utilisation d'anticoagulants avant/après l'AVC/AIT survenu pendant l'anticoagulothérapie et avons évalué la récurrence d'un AVC/AIT ou d'un saignement, en tenant compte de l'adhésion au traitement médicamenteux. L'adhésion a été définie comme une proportion de jours couverts (PJC) de 80 % ou plus. Résultats: Chez 985 patients, l'âge médian était de 80 ans (écart interquartile de 13) et le score CHADS2 moyen, de 1,7 ± 1 avant l'événement de référence. Les patients ont été suivis pendant une médiane de 643 jours (écart interquartile de 836). Après l'AVC/AIT de référence, 623 patients (63 %) ont fait exécuter une ordonnance du même schéma d'AOD, 83 (8 %) ont fait exécuter une ordonnance d'une dose différente, 155 (16 %) sont passés à d'autres AOD, 51 (5 %) sont passés à la warfarine et 73 (7 %) n'ont fait exécuter aucune ordonnance d'anticoagulant oral. Chez les patients qui ont continué à recevoir le même schéma, la plupart (59 %) avaient eu un AIT comme événement de référence; chez les patients qui ont changé de dose ou de médicament, la plupart (55 à 78 %) avaient eu un AVC comme événement de référence. Durant le suivi, 135 (14 %) ont connu un AVC/AIT récurrent et 46 (5 %) ont présenté un saignement; les taux de chaque manifestation ont été similaires pour les différents schémas de prescription. Après l'événement de référence, le pourcentage de patients ayant une PJC ≥ 80 % a augmenté, passant de 55 à 80 %. Conclusions: Malgré le maintien du même schéma d'AOD chez la plupart des patients après l'AVC/AIT, les taux d'AVC/AIT récurrent et de saignement ont été similaires avec tous les schémas de prescription. La gravité d'un AVC/AIT pourrait avoir influencé les pratiques de prescription. L'adhésion aux AOD prescrits s'est améliorée après un AVC/AIT et témoigne d'une possibilité d'optimisation chez les patients atteints de fibrillation auriculaire.

People living with moderate-to-severe COPD prefer improvement of daily symptoms over the improvement of exacerbations: a multicountry patient preference study.

Introduction: This patient preference study sought to quantify the preferences of people living with COPD regarding symptom improvement in the UK, USA, France, Australia and Japan. Methods: The inclusion criteria were people living with COPD aged 40 years or older who experienced ≥1 exacerbation in the previous year with daily symptoms of cough and excess mucus production. The study design included: 1) development of an attributes and levels grid through qualitative patient interviews; and 2) implementation of the main online quantitative survey, which included a discrete choice experiment (DCE) to allow assessment of attributes and levels using hypothetical health state profiles. Preference weights (utilities) were derived from the DCE using hierarchical Bayesian analysis. A preference simulator was developed that enabled different health state scenarios to be evaluated based on the predicted patient preferences. Results: 1050 people living with moderate-to-severe COPD completed the survey. All attributes were considered important when patients determined their preferences in the DCE. In a health state preference simulation, two hypothetical health states (comprising attribute levels) with qualitatively equivalent improvements in A) cough and mucus and B) shortness of breath (SOB) resulted in a clear preference for cough and mucus improved profile. When comparing two profiles with C) daily symptoms improved and D) exacerbations improved, there was a clear preference for the daily symptoms improved profile. Conclusions: People living with moderate-to-severe COPD prefer to reduce cough and mucus production together over improvement of SOB and would prefer to reduce combined daily symptoms over an improvement in exacerbations.

Maintaining quality of life in patients with chronic obstructive pulmonary disease (COPD) by extending the maintenance phase of community-based pulmonary rehabilitation: protocol for a randomised controlled trial (ComEx3 Study).

INTRODUCTION: Pulmonary rehabilitation is a core component of the treatment of people with chronic obstructive pulmonary disease (COPD); however, the benefits gained diminish in the ensuing months. The optimal strategy for maintaining the benefits is unclear with weekly supervised maintenance exercise programmes proposed as one strategy. However, the long-term future of maintenance programs is dependent on quality evidence. METHODS AND ANALYSIS: The ComEx3 randomised controlled trial will investigate the efficacy of extending a weekly supervised maintenance programme for an additional 6 months following an initial 10-week maintenance programme (intervention) by comparing with a control group who receive the same 10-week maintenance programme followed by 6 months of usual care. 120 participants with COPD will be recruited. Primary objective is to determine health-related quality of life over 12 months. Secondary objectives are to determine functional exercise capacity trajectory and to perform an economic evaluation of the intervention to the health system. Outcomes will be analysed for superiority according to intention-to-treat and per-protocol approaches. ETHICS AND DISSEMINATION: Approval has been received from the relevant ethics committees. Findings will be disseminated in peer-reviewed journals and conferences, targeting those involved in managing people with COPD as well as those who develop policies and guidelines. CLINICAL TRIAL REGISTRATION: ANZCTR 12618000933257.

Clinical Characteristics Of Patients With Asthma COPD Overlap (ACO) In Australian Primary Care.

Purpose: Many older adults with a history of smoking and asthma develop clinical features of both asthma and COPD, an entity sometimes called asthma-COPD overlap (ACO). Patients with ACO may be at higher risk of poor health outcomes than those with asthma or COPD alone. However, understanding of ACO is limited in the primary care setting and more information is needed to better inform patient management. We aimed to compare the characteristics of patients with ACO or COPD in Australian general practices. Patients and methods: Data were from the RADICALS (Review of Airway Dysfunction and Interdisciplinary Community-based care of Adult Long-term Smokers) trial, an intervention study of an interdisciplinary community-based model of care. Baseline demographic and clinical characteristics, pre- and post-bronchodilator spirometry, dyspnoea and St. George's Respiratory Questionnaire scores were compared between 60 ACO patients and 212 with COPD alone. Results: Pre-bronchodilator Forced Expiratory Volume in 1 second (mean±SD 58.4±14.3 vs 67.5±20.1% predicted) and Forced Vital Capacity (mean 82.1±16.9 v 91.9±17.2% predicted) were significantly lower in the ACO group (p<0.001), but no difference was found in post-bronchodilator spirometry. Demographic and clinical characteristics, dyspnoea, quality of life, comorbidities and treatment prescribed did not differ significantly between groups. Conclusion: This is the first study describing the clinical characteristics of ACO patients in Australian general practices. Our finding of lower pre-bronchodilator lung function in the ACO group compared to those with COPD reinforces the importance of spirometry in primary care to inform management. Trial registration: Australian New Zealand Clinical Trials Registry ACTRN12614001155684.

Evaluation of an innovative mobile health programme for the self-management of chronic obstructive pulmonary disease (MH-COPD): protocol of a randomised controlled trial.

INTRODUCTION: Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death globally. In outpatient care, the self-management of COPD is essential, but patient adherence to this remains suboptimal. The objective of this study is to examine whether an innovative mobile health (mHealth)-enabled care programme (MH-COPD) will improve the patient self-management and relevant health outcomes. METHODS AND ANALYSIS: A prospective open randomised controlled trial has been designed. In the trial, patients with COPD will be recruited from The Prince Charles Hospital, Brisbane, Australia. They will then be randomised to participate in either the MH-COPD intervention group (n=50 patients), or usual care control group (UC-COPD) (n=50 patients) for 6 months. The MH-COPD programme has been designed to integrate an mHealth system within a clinical COPD care service. In the programme, participants will use a mHealth application at home to review educational videos, monitor COPD symptoms, use an electronic action plan, modify the risk factors of cigarette smoking and regular physical activity, and learn to use inhalers optimally. All participants will be assessed at baseline, 3 months and 6 months. The primary outcomes will be COPD symptoms and quality of life. The secondary outcomes will be patient adherence, physical activity, smoking cessation, use of COPD medicines, frequency of COPD exacerbations and hospital readmissions, and user experience of the mobile app. ETHICS AND DISSEMINATION: The clinical trial has been approved by The Prince Charles Hospital Human Research Ethics Committee (HREC/16/QPCH/252). The recruitment and follow-up of the trial will be from January 2019 to December 2020. The study outcomes will be disseminated according to the Consolidated Standards of Reporting Trials statement through a journal publication, approximately 6 months after finishing data collection. TRIAL REGISTRATION NUMBER: ACTRN12618001091291.

Interdisciplinary COPD intervention in primary care: a cluster randomised controlled trial.

We evaluated the effectiveness of an interdisciplinary, primary care-based model of care for chronic obstructive pulmonary disease (COPD).A cluster randomised controlled trial was conducted in 43 general practices in Australia. Adults with a history of smoking and/or COPD, aged ≥40 years with two or more clinic visits in the previous year were enrolled following spirometric confirmation of COPD. The model of care comprised smoking cessation support, home medicines review (HMR) and home-based pulmonary rehabilitation (HomeBase). Main outcomes included changes in St George's Respiratory Questionnaire (SGRQ) score, COPD Assessment Test (CAT), dyspnoea, smoking abstinence and lung function at 6 and 12 months.We identified 272 participants with COPD (157 intervention, 115 usual care); 49 (31%) out of 157 completed both HMR and HomeBase. Intention-to-treat analysis showed no statistically significant difference in change in SGRQ at 6 months (adjusted between-group difference 2.45 favouring intervention, 95% CI -0.89-5.79). Per protocol analyses showed clinically and statistically significant improvements in SGRQ in those receiving the full intervention compared to usual care (difference 5.22, 95% CI 0.19-10.25). No statistically significant differences were observed in change in CAT, dyspnoea, smoking abstinence or lung function.No significant evidence was found for the effectiveness of this interdisciplinary model of care for COPD in primary care over usual care. Low uptake was a limitation.

Diagnosing COPD and supporting smoking cessation in general practice: evidence-practice gaps.

OBJECTIVES: To review the accuracy of diagnoses of chronic obstructive pulmonary disease (COPD) in primary care in Australia, and to describe smokers' experiences with and preferences for smoking cessation. DESIGN, SETTING AND PARTICIPANTS: Patients were invited to participate if they were at least 40 years old and had visited participating general practice clinics in Melbourne at least twice during the previous 12 months, reported being current or ex-smokers with a smoking history of at least 10 pack-years, or were being managed for COPD. Interviews based on a structured questionnaire and case finding (FEV1/FEV6 measurement) were followed, when appropriate, by spirometry testing and assessment of health-related quality of life, dyspnoea and symptoms. RESULTS: 1050 patients attended baseline interviews (February 2015 - April 2017) at 41 practices. Of 245 participants managed for COPD, 130 (53.1%) met the spirometry-based definition (post-bronchodilator FEV1/FVC < 0.7) or had a clinical correlation; in 37% of cases COPD was not confirmed, and no definitive result was obtained for 9.8% of patients. Case finding and subsequent spirometry testing identified 142 new COPD cases (17.6% of participants without prior diagnosis; 95% CI, 15.1-20.5%). 690 participants (65.7%) were current smokers, of whom 360 had attempted quitting during the previous 12 months; 286 (81.0% of those attempting to quit) reported difficulties during previous quit attempts. Nicotine replacement therapy (205, 57.4%) and varenicline (110, 30.8%) were the most frequently employed pharmacological treatments; side effects were common. Hypnotherapy was the most popular non-pharmacological option (62 smokers, 17%); e-cigarettes were tried by 38 (11%). 187 current smokers (27.6%) would consider using e-cigarettes in future attempts to quit. CONCLUSIONS: COPD was both misdiagnosed and missed. Case finding and effective use of spirometry testing could improve diagnosis. Side effects of smoking cessation medications and difficulties during attempts to quit smoking are common. Health professionals should emphasise evidence-based treatments, and closely monitor quitting difficulties and side effects of cessation aids. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry ACTRN12614001155684.

Pharmacists as Care Providers for Stroke Patients: A Systematic Review.

BACKGROUND: Pharmacists have become an integral member of the multidisciplinary team providing clinical patient care in various healthcare settings. Although evidence supporting their role in the care of patients with other disease states is well-established, minimal literature has been published evaluating pharmacist interventions in stroke patients. The purpose of this systematic review is to summarize the evidence evaluating the impact of pharmacist interventions on stroke patient outcomes. METHODS: Study abstracts and full-text articles evaluating the impact of a pharmacist intervention on outcomes in patients with an acute stroke/transient ischemic attack (TIA) or a history of an acute stroke/TIA were identified and a qualitative analysis performed. RESULTS: A total of 20 abstracts and full-text studies were included. The included studies provided evidence supporting pharmacist interventions in multiple settings, including emergency departments, inpatient, outpatient, and community pharmacy settings. In a significant proportion of the studies, pharmacist care was collaborative with other healthcare professionals. Some of the pharmacist interventions included participation in a stroke response team, assessment for thrombolytic use, medication reconciliation, participation in patient rounds, identification and resolution of drug therapy problems, risk-factor reduction, and patient education. Pharmacist involvement was associated with increased use of evidence-based therapies, medication adherence, risk-factor target achievement, and maintenance of health-related quality of life. CONCLUSIONS: Available evidence suggests that a variety of pharmacist interventions can have a positive impact on stroke patient outcomes. Pharmacists should be considered an integral member of the stroke patient care team.

COPD-X Australian and New Zealand guidelines for the diagnosis and management of chronic obstructive pulmonary disease: 2017 update.

INTRODUCTION: Chronic obstructive pulmonary disease (COPD) is characterised by persistent respiratory symptoms and chronic airflow limitation, and is associated with exacerbations and comorbidities. Advances in the management of COPD are updated quarterly in the national COPD guidelines, the COPD-X plan, published by Lung Foundation Australia in conjunction with the Thoracic Society of Australia and New Zealand and available at http://copdx.org.au. Main recommendations: Spirometry detects persistent airflow limitation (post-bronchodilator FEV1/FVC < 0.7) and must be used to confirm the diagnosis.Non-pharmacological and pharmacological therapies should be considered as they optimise function (ie, improve symptoms and quality of life) and prevent deterioration (ie, prevent exacerbations and reduce decline).Pulmonary rehabilitation and regular exercise are highly beneficial and should be provided to all symptomatic COPD patients.Short- and long-acting inhaled bronchodilators and, in more severe disease, anti-inflammatory agents (inhaled corticosteroids) should be considered in a stepwise approach.Given the wide range of inhaler devices available, inhaler technique and adherence should be checked regularly.Smoking cessation is essential, and influenza and pneumococcal vaccinations reduce the risk of exacerbations.A plan of care should be developed with the multidisciplinary team. COPD action plans reduce hospitalisations and are recommended as part of COPD self-management.Exacerbations should be managed promptly with bronchodilators, corticosteroids and antibiotics as appropriate to prevent hospital admission and delay COPD progression.Comorbidities of COPD require identification and appropriate management.Supportive, palliative and end-of-life care are beneficial for patients with advanced disease.Education of patients, carers and clinicians, and a strong partnership between primary and tertiary care, facilitate evidence-based management of COPD. Changes in management as result of the guideline: Spirometry remains the gold standard for diagnosing airflow obstruction and COPD. Non-pharmacological and pharmacological treatment should be used in a stepwise fashion to control symptoms and reduce exacerbation risk.

Interdisciplinary model of care (RADICALS) for early detection and management of chronic obstructive pulmonary disease (COPD) in Australian primary care: study protocol for a cluster randomised controlled trial.

INTRODUCTION: Up to half of all smokers develop clinically significant chronic obstructive pulmonary disease (COPD). Gaps exist in the implementation and uptake of evidence-based guidelines for managing COPD in primary care. We describe the methodology of a cluster randomised controlled trial (cRCT) evaluating the efficacy and cost-effectiveness of an interdisciplinary model of care aimed at reducing the burden of smoking and COPD in Australian primary care settings. METHODS AND ANALYSIS: A cRCT is being undertaken to evaluate an interdisciplinary model of care (RADICALS - Review of Airway Dysfunction and Interdisciplinary Community-based care of Adult Long-term Smokers). General practice clinics across Melbourne, Australia, are identified and randomised to the intervention group (RADICALS) or usual care. Patients who are current or ex-smokers, of at least 10 pack years, including those with an existing diagnosis of COPD, are being recruited to identify 280 participants with a spirometry-confirmed diagnosis of COPD. Handheld lung function devices are being used to facilitate case-finding. RADICALS includes individualised smoking cessation support, home-based pulmonary rehabilitation and home medicines review. Patients at control group sites receive usual care and Quitline referral, as appropriate. Follow-ups occur at 6 and 12 months from baseline to assess changes in quality of life, abstinence rates, health resource utilisation, symptom severity and lung function. The primary outcome is change in St George's Respiratory Questionnaire score of patients with COPD at 6 months from baseline. ETHICS AND DISSEMINATION: This project has been approved by the Monash University Human Research Ethics Committee and La Trobe University Human Ethics Committee (CF14/1018 - 2014000433). Results of the study will be disseminated in peer-reviewed journals and research conferences. If the intervention is successful, the RADICALS programme could potentially be integrated into general practices across Australia and sustained over time. TRIAL REGISTRATION NUMBER: ACTRN12614001155684; Pre-results.

Critical international normalized ratio results after hours: To call or not to call?

OBJECTIVE: To determine whether the timing of notification of critical international normalized ratio (INR) results (during or after clinic hours) altered the clinician's ability to affect same-day patient care. DESIGN: Retrospective chart review. SETTING: The Anticoagulation Management Service at the University of Alberta Hospital in Edmonton. PARTICIPANTS: A total of 276 patients with critical INR results (> 5.0) separated by at least 30 days were identified to have 200 critical INR results reported during clinic hours and 200 reported after hours. MAIN OUTCOME MEASURES: Differences in the proportion of patients with critical INR results having same-day care altered (by changing warfarin dose, administering vitamin K, or referring for assessment) between those with results reported during clinic hours compared with those with results reported after clinic hours. Differences by highly critical INR results (> 9.0 vs ≤ 9.0) and whether patients experienced thromboembolism or bleeding within 30 days were also assessed. RESULTS: Same-day patient care was affected for 174 out of 200 (87.0%) critical INR results reported during clinic hours compared with 101 out of 200 (50.5%) reported after clinic hours (P < .001). The most common reason for not being able to intervene was that warfarin had already been taken. Warfarin dose alteration was the most frequent change (97.1% during clinic hours and 96.0% after hours). When patients with INRs greater than 9.0 were assessed separately, the ability to affect care increased for INRs reported both during and after clinic hours (92.9% and 63.6%, respectively), largely attributable to oral vitamin K use. Overall, thromboembolic and major bleeding event rates were low and were similar in both groups. CONCLUSION: Same-day care was less likely to be affected by critical INR results communicated after hours, most commonly because the patient had already taken their daily warfarin dose. However, after-hours care was still affected for 1 out of 2 patients, which is meaningful and supports current practice.

Molecular interactions in the insulin-like growth factor (IGF) axis: a surface plasmon resonance (SPR) based biosensor study.

This review describes a comprehensive analysis of a surface plasmon resonance (SPR)-based biosensor study of molecular interactions in the insulin-like growth factor (IGF) molecular axis. In this study, we focus on the interaction between the polypeptide growth factors IGF-I and IGF-II with six soluble IGF binding proteins (IGFBP 1-6), which occur naturally in various biological fluids. We have describe the conditions required for the accurate determination of kinetic rate constants for these interactions and highlight the experimental and theoretical pitfalls, which may be encountered in the early stages of such a study. We focus on IGFBP-5 and describe a site-directed mutagenesis study, which examines the contribution of various residues in the protein to high affinity interaction with IGF-I and -II. We analyse the interaction of IGFBP-5 (and IGFBP-3) with heparin and other biomolecules and describe experiments, which were designed to monitor multi-protein complex formation in this molecular axis.

Use of low-molecular-weight heparin to bridge therapy in obese patients and in patients with renal dysfunction.

OBJECTIVE: To recommend strategies to bridge therapy with low-molecular-weight heparin (LMWH) in obese patients and in patients with renal dysfunction. METHODS: A MEDLINE search was performed of the literature from January 1966-November 2005. Published material dealing with bridging of anticoagulation therapy or short-term use of LMWH therapy in patients with renal dysfunction or obesity was reviewed. The manufacturers of enoxaparin, dalteparin, and tinzaparin were contacted for the references used to determine dosing recommendations. RESULTS: Although LMWH has been commonly used to bridge therapy, our search revealed no trials that specifically examined LMWH bridge therapy in obese patients or in patients with renal dysfunction. However, nine trials using LMWH in obese patients and 14 trials using LMWH in patients with renal dysfunction were identified. When compared with normal-weight individuals, obese patients receiving enoxaparin and dalteparin based on total body weight did not demonstrate higher hemorrhage rates or antifactor Xa levels. Subtherapeutic antifactor Xa levels were more common with once-daily dosing of enoxaparin than with dosing every 12 hours. Enoxaparin accumulates in patients with a creatinine clearance of 30 ml/minute or less; in this population, enoxaparin dosage adjustments have been attempted. Tinzaparin does not accumulate in patients with a creatinine clearance of 20 ml/minute or greater after at least 10 days of dosing. CONCLUSION: Obese patients, weighing 90-150 kg, receiving LMWH for bridge therapy should receive dosages based on total body weight. Unfractionated heparin is recommended in patients weighing more than 150 kg; however, if LMWH is used, antifactor Xa levels should be monitored. Bridging with enoxaparin should be limited to patients with a creatinine clearance greater than 30 ml/minute. The use of enoxaparin 1 mg/kg once/day for patients with a creatinine clearance of 30 ml/minute or less is not recommended for anticoagulation bridge therapy. Tinzaparin may be considered for cross-coverage of high-risk patients with recent or recurrent venous thromboembolism who have a creatinine clearance of at least 20 ml/minute.

Insulin-like growth factor binding protein (IGFBP)-5 is upregulated during both differentiation and apoptosis in primary cultures of mouse mammary epithelial cells.

We have previously demonstrated that insulin-like growth factor binding protein-5 (IGFBP-5) is upregulated following treatment of the mouse mammary epithelial cell line HC11 with lactogenic hormones (dexamethasone, insulin, and prolactin-DIP). In addition, we have also shown that IGFBP-5 is upregulated in mammary epithelial cells in vivo during involution of the rodent mammary gland. We have, therefore, postulated that there may be a dual regulation of IGFBP-5 expression during the temporally separated processes of differentiation and apoptosis of mammary epithelial cells. To test this hypothesis further, we have used a phenotypically differentiated model, which comprises primary cultures of mouse mammary epithelial cells grown on a layer of EHS (Engelbreth-Holm-Swarm) extracellular matrix. We show that lactogenic hormone treatment (hydrocortisone, insulin, and prolactin-HIP) of these cultures induces the upregulation of IGFBP-5 thus replicating the results obtained with the HC11 cell line. In addition, following the induction of apoptosis in primary cultures of mammary epithelial cells by treatment with TGFbeta-3, IGFBP-5 expression is also upregulated. In parallel with this upregulation of IGFBP-5, there is also an increase in the levels of cleaved caspase-3, a well-characterized marker of cellular apoptosis. These findings confirm previous in vivo work demonstrating an increase in IGFBP-5 expression during involution of the mouse mammary gland. When HC11 cells are cultured under serum-free conditions (a well-characterized apoptotic insult in cell culture), there is also an increase in cleaved caspase-3 levels. Unexpectedly, in the presence of TGFbeta-3, caspase-3 levels are attenuated. In the presence of DIP, caspase-3 levels are also decreased in HC11 cells. As described previously, TGFbeta-3 inhibits beta-casein synthesis in HC11 cells. In the HC11 cell line (in contrast to primary cultures of mammary epithelial cells), there is no evidence for TGFbeta-3 induction of IGFBP-5 under either serum-free or DIP-supplemented conditions. We believe our data with primary cultures of mammary epithelial cells support the hypothesis of dual regulation of IGFBP-5 expression during both differentiation and apoptosis in the mammary gland and emphasizes the importance of using appropriate cell culture models to investigate such phenomena in this tissue. We discuss the possible implications of our observations in relation to the physiological processes of pregnancy, lactation, and involution in the mammary gland and the associated changes in mammary epithelial cell function.

Cumulative mutagenesis of the basic residues in the 201-218 region of insulin-like growth factor (IGF)-binding protein-5 results in progressive loss of both IGF-I binding and inhibition of IGF-I biological action.

We have reported previously that mutation of two conserved nonbasic amino acids (G203 and Q209) within the highly basic 201-218 region in the C-terminal domain of IGF-binding protein-5 (IGFBP-5) decreases binding to IGFs. This study reveals that cumulative mutagenesis of the 10 basic residues in this region, to create the C-Term series of mutants, ultimately results in a 15-fold decrease in the affinity for IGF-I and a major loss in heparin binding. We examined the ability of mutants to inhibit IGF-mediated survival of MCF-7 cells and were able to demonstrate that this depended not only upon the affinity for IGF-I, but also the kinetics of this interaction, because IGFBP-5 mutants with similar affinity constants (K(D)) values, but with different association (Ka) and dissociation (Kd) rate values, had markedly different inhibitory properties. In contrast, the affinity for IGF-I provided no predictive value in terms of the ability of these mutants to enhance IGF action when bound to the substratum. Instead, these C-Term mutants appeared to enhance the actions of IGF-I by a combination of increased dissociation of IGF-IGFBP complexes from the substratum, together with dissociation of IGF-I from IGFBP-5 bound to the substratum. These effects of the IGFBPs were dependent upon binding to IGF-I, because a non-IGF binding mutant (N-Term) was unable to inhibit or enhance the actions of IGF-I. These results emphasize the importance of the kinetics of association/dissociation in determining the enhancing or inhibiting effects of IGFBP-5 and demonstrate the ability to generate an IGFBP-5 mutant with exclusively IGF-enhancing activity.

Molecular recognition characteristics in the insulin-like growth factor (IGF)-insulin-like growth factor binding protein -3/5 (IGFBP-3/5) heparin axis.

Insulin-like growth factor binding proteins (IGFBPs) -3 and -5 are known to interact with various components of the extracellular matrix (ECM; e.g. heparin and heparan sulphate) and this interaction is believed to affect the affinity of both IGFBP species for their cognate ligands--IGF-I and -II. There is little detail on the nature of the molecular complex formed between ECM components, IGFBPs and IGFs although the glycosaminoglycan (GAG) heparin has been reported to reduce the affinity of IGFBP-5 for IGF-I. In order to investigate this phenomenon further, we have undertaken an extensive surface plasmon resonance based biosensor study to report the affinity of IGFBP-3 and -5 for binding heparin (22 and 7 nM respectively). We have also shown that pre-complexation of IGFBP with IGF-I and -II inhibits the subsequent association of IGFBP with heparin and conversely that heparin complexation of IGFBP-3 and -5 inhibits IGFBP binding to biosensor surfaces containing immobilised IGF-I. In addition we have used both IGF-I and heparin coated biosensor surfaces in an attempt to build ternary IGF-IGFBP-heparin complexes in order to gain some insight into the nature of inhibition by heparin of IGFI-IGFBP complex formation. Our data lead us to conclude that the inhibition by heparin is partly competitive in nature, and that ternary complexes of IGF-IGFBP-heparin are either unable to form, or only form unstable transient complexes. The potential biological significance of our data is highlighted by the demonstration that IGF-I and IGF-II can displace endogenous IGFBP-5 from monolayer cultures of the mouse mammary epithelial cell line HC11.

Specific amino acid substitutions determine the differential contribution of the N- and C-terminal domains of insulin-like growth factor (IGF)-binding protein-5 in binding IGF-I.

We have previously reported that two highly conserved amino acids in the C-terminal domain of rat insulin-like growth factor-binding protein (IGFBP)-5, Gly(203) and Gln(209), are involved in binding to insulin-like growth factor (IGF)-1. Here we report that mutagenesis of both amino acids simultaneously (C-Term mutant) results in a cumulative effect and an even greater reduction in IGF-I binding: 30-fold measured by solution phase IGF binding assay and 10-fold by biosensor analysis. We compared these reductions in ligand binding to the effects of specific mutations of five amino acids in the N-terminal domain (N-Term mutant), which had previously been shown by others to cause a very large reduction in IGF-I binding (). Our results confirm this as the major IGF-binding site. To prove that the mutations in either N- or C-Term were specific for IGF-I binding, we carried out CD spectroscopy and showed that these alterations did not lead to gross conformational changes in protein structure for either mutant. Combining these mutations in both domains (N+C-Term mutant) has a cumulative effect and leads to a 126-fold reduction in IGF-I binding as measured by biosensor. Furthermore, the equivalent mutations in the C terminus of rat IGFBP-2 (C-Term 2) also results in a significant reduction in IGF-I binding, suggesting that the highly conserved Gly and Gln residues have a conserved IGF-I binding function in all six IGFBPs. Finally, although these residues lie within a major heparin-binding site in IGFBP-5 and -3, we also show that the mutations in C-Term have no effect on heparin binding.

Sensitivity of hybrid ovine/rat GH receptors to oGH and rat GH in transfected FDC-P1 mouse myeloid cells in vitro.

We have described previously the properties of two mutant ovine growth hormone receptor extracellular domain (oGHR-ECD) proteins which were created by substituting sequences from the rat GHR at two different locations within the framework of the oGHR-ECD. The first mutation occurred at a region close to the N-terminus of oGHR-ECD between residues Thr 28 and Leu34 and created the protein T28E/N29S/N33K/L34P-oGHR-ECD, where the ovine specific residues T, N, N and L are replaced by their equivalent residues E, S, K and P from the rat protein. This site lies N-terminal to the first element of beta-strand structure in the GHR-ECD and we designated this protein as Site-A mutant. The second mutation was made between residues Serl21 andAsp 124 of oGHR-ECD to produce the protein S121T/E123D/D124E-oGHR-ECD where ovine specific residues are again replaced with the equivalent residues from the rat GHR-ECD. This region lies in a loop structure which joins the two beta-barrel domains of the GHR-ECD. This protein is designated as Site-B mutant. A subsequent analysis confirmed the N-terminal region between residues 28-34 of oGHR-ECD as an important epitope defined by antiserum raised to oGHR-ECD. Also of interest was the finding that mutation at both Sites A and B in oGHR-ECD compromised the affinity of the protein for bovine GH (50-fold for Site-A and 4-fold for Site-B). A comparison of the affinity of wild type oGHR for the highly homologous bovine GH with its affinity for rat GH indicated a 10-fold higher affinity for the ruminant GH than for rat GH. Mutation at Site-A of oGHR-ECD reduced the affinity for rat GH a further 3-fold. However, mutation at Site-B of oGHR-ECD increased the affinity for rat GH 2-3 fold. This indicated that the substitution of rat GHR residues for ovine GHR residues in this part of the protein had a beneficial effect in relation to affinity for rat GH and that this region of the GHR-ECD may contain important specificity determinants. In order to test whether these observed differences in affinity for bovine and rat GH affinities have any biological relevance, we have produced the same ovine --> rat mutations in the context of the full length ovine GHR. Transfection of the cDNAs encoding the wt or mutant GHRs into the mouse myeloid pre-B cell line FDC-P1 to create stably transfected clonal lines, has allowed an examination of the relative activities of ovine and rat GH, using a robust and high throughput bio-assay based on the reduction of a cell permeable tetrazolium salt. In the current manuscript, we report that the decrease in binding affinity previously reported for Site-A and Site-B mutant oGHR extracellular domain proteins is not reflected in compromised biological activities when the same mutations are expressed in the context of the full length oGHR protein. We discuss these findings in the context of the relationships between affinity and activity at the GHR.