Implementing a Palliative Care Junior Faculty Visiting Professor Program: Pearls and Pitfalls

MOTIVATION

Palliative Care (PC) is a small, relatively young interprofessional sub-specialty; hence mentorship for early-career research faculty is widely dispersed across schools and universities. We developed the Junior Visiting Professor Program (JVPP) to provide junior faculty in palliative care (PC) with opportunities to meet multidisciplinary PC researchers from other institutions and to advance their research through networking and presenting their work. We describe how we designed and implemented the program, and we report on the first cohort of participants.

METHODS

We invited PC research groups from US schools of medicine and nursing to participate in this 5-year interprofessional exchange program by nominating junior faculty and serving as hosts. We matched nominees to host institutions based on nominee training experiences, nominee research interests, and host institution faculty expertise. In addition, we provided logistical guidance on visit planning. Post-visit, we surveyed both hosts and junior visiting professors (JVPs) regarding their satisfaction, perceived value, and suggestions regarding the program.

RESULTS

We recruited 13 schools to participate and matched 10 nominees to host institutions in our first year. Nine JVPs completed their visit; 6 JVPs and 8 host faculty/staff responded to the post-visit survey. Overall, JVPs were highly satisfied with their matches and the visiting professor experience. Hosts were generally satisfied with their matches and believed the program to be mutually beneficial. The most frequent suggestion was for greater administrative support to plan visits.

CONCLUSIONS

Structured, well-supported opportunities for networking across institutions is beneficial for emerging PC researchers and for building PC research capacity.

Associations of Health Care Utilization and Therapeutic Alliance in Patients with Advanced Cancer

Introduction: Therapeutic alliance (TA), or the extent to which patients feel a sense of caring and trust with their physician, may have an impact on health care utilization. We sought to determine if TA is associated with: (1) emergency department (ED) visits within 30 days of death and (2) hospice enrollment. Methods and Materials: This is a secondary analysis of data from a randomized clinical trial. We used restricted cubic splines to assess the relationship between TA scores and health care utilization. Results: Six hundred seventy-two patients were enrolled in the study, with 331 (49.3%) dying within 12 months. Patients with higher TA were less likely to have an ED visit in the last 30 days of life, but there was no evidence of a relationship between TA and enrollment in hospice. Conclusions: Higher TA was associated with decreased ED visits within 30 days of death. There was no association between TA and rates of hospice enrollment. Clinical Registration Number: NCT02712229.

Longitudinal Analysis of Caregiver Burden in Head and Neck Cancer

Importance

Despite the critical role of caregivers in head and neck cancer (HNC), there is limited literature on caregiver burden (CGB) and its evolution over treatment. Research is needed to address evidence gaps that exist in understanding the causal pathways between caregiving and treatment outcomes.

Objective

To evaluate the prevalence of and identify risk factors for CGB in HNC survivorship.

Design, Setting, and Participants

This longitudinal prospective cohort study took place at the University of Pittsburgh Medical Center. Dyads of treatment-naive patients with HNC and their caregivers were recruited between October 2019 and December 2020. Eligible patient-caregiver dyads were 18 years or older and fluent in English. Patients undergoing definitive treatment identified a caregiver as the primary, nonprofessional, nonpaid person who provided the most assistance to them. Among 100 eligible dyadic participants, 2 caregivers declined participation, resulting in 96 enrolled participants. Data were analyzed from September 2021 through October 2022.

Main Outcomes and Measures

Participants were surveyed at diagnosis, 3 months postdiagnosis, and 6 months postdiagnosis. Caregiver burden was evaluated with the 19-item Social Support Survey (scored 0-100, with higher scores indicating more support), Caregiver Reaction Assessment (CRA; scored 0-5, with higher scores on 4 subscales [disrupted schedule, financial problems, lack of family support, and health problems] indicating negative reactions, and higher scores on the fifth subscale [self-esteem] indicating favorable influence); and 3-item Loneliness Scale (scored 3-9, with higher scores indicating greater loneliness). Patient health-related quality of life was assessed using the University of Washington Quality of Life scale (UW-QOL; scored 0-100, with higher scores indicating better QOL).

Results

Of the 96 enrolled participants, half were women (48 [50%]), and a majority were White (92 [96%]), married or living with a partner (81 [84%]), and working (51 [53%]). Of these participants, 60 (63%) completed surveys at diagnosis and at least 1 follow-up. Of the 30 caregivers, most were women (24 [80%]), White (29 [97%]), married or living with a partner (28 [93%]), and working (22 [73%]). Caregivers of nonworking patients reported higher scores on the CRA subscale for health problems than caregivers of working patients (mean difference, 0.41; 95% CI, 0.18-0.64). Caregivers of patients with UW-QOL social/emotional (S/E) subscale scores of 62 or lower at diagnosis reported increased scores on the CRA subscale for health problems (UW-QOL-S/E score of 22: CRA score mean difference, 1.12; 95% CI, 0.48-1.77; UW-QOL-S/E score of 42: CRA score mean difference, 0.74; 95% CI, 0.34-1.15; and UW-QOL-S/E score of 62: CRA score mean difference, 0.36; 95% CI, 0.14-0.59). Woman caregivers had statistically significant worsening scores on the Social Support Survey (mean difference, -9.18; 95% CI, -17.14 to -1.22). The proportion of lonely caregivers increased over treatment.

Conclusions and Relevance

This cohort study highlights patient- and caregiver-specific factors that are associated with increased CGB. Results further demonstrate the potential implications for negative health outcomes for caregivers of patients who are not working and have lower health-related quality of life.

Who Engages and Why It Matters?

While the use and benefits of serious games in health care are increasingly recognized, the impact of individuals' game engagement remains understudied, limiting the potential for impact. This pilot study aims to describe game engagement and its associations with learning outcomes, sociodemographics, and health factors in women with advanced cancer receiving a 12-week self-advocacy serious game intervention. Game engagement was collected from study tablets and weekly self-reported surveys. Participants' game engagement was overall high but with large amounts of variation and did not differ by their sociodemographics and health factors. Participants with lower baseline symptom severity were more likely to repeat game scenarios, and those who engaged in all scenarios had higher connected strength post-intervention. Knowing what prevents patients with advanced cancer from engaging in the serious game enlightens ways to refine the gamified interventions. Future research is suggested to evaluate patients' engagement to deepen understanding of its impacts on learning outcomes.

Testing the effects of the Strong Together self-advocacy serious game among women with advanced cancer: Protocol for the STRONG randomized clinical trial

BACKGROUND

Women with advanced cancer experience significant barriers to achieving high-quality care and maximizing their physical and emotional health. Our novel serious game, Strong Together, aims to teach women with advanced cancer self-advocacy skills needed to improve their symptom burden, quality of life, and patient-centered care.

METHODS

This is a single-center, multi-site randomized clinical trial of the Strong Together intervention among 336 women within three months of an advanced breast or gynecologic cancer diagnosis. Randomization occurs to the 3-month Strong Together serious game or enhanced care as usual group. The aims are to: (1) evaluate the effects of the intervention on patient self-advocacy (primary outcome); (2) evaluate the effects of the intervention on quality of life, symptom burden, and patient-centered care (secondary outcomes); and (3) evaluate the behavioral and game mechanisms that influence the efficacy of the intervention.

ELIGIBILITY CRITERIA

female, age ≥ 18 years; diagnosis of advanced breast or gynecologic cancer within the past 3 months; Eastern Cooperative Oncology Group score of 0-2; English literacy; and ≥ 6-month life expectancy. Patient-reported outcome measures are collected at baseline, 3-months, and 6-months.

CONCLUSION

This protocol is the first large-scale intervention aimed at promoting self-advocacy in women with advanced cancer. Understanding the ability of serious games to impact patient outcomes provides critical information for researchers, clinicians, and stakeholders aiming to improve patient-centered care.

TRIAL REGISTRATION

NCT04813276.

Effects of the WRITE Symptoms Interventions on Symptoms and Quality of Life Among Patients With Recurrent Ovarian Cancers: An NRG Oncology/GOG Study (GOG-0259)

PURPOSE

GOG-259 was a 3-arm randomized controlled trial of two web-based symptom management interventions for patients with recurrent ovarian cancer. Primary aims were to compare the efficacy of the nurse-guided (Nurse-WRITE) and self-directed (SD-WRITE) interventions to Enhanced Usual Care (EUC) in improving symptoms (burden and controllability) and quality of life (QOL).

METHODS

Patients with recurrent or persistent ovarian, fallopian, or primary peritoneal cancer with 3+ symptoms were eligible for the study. Participants completed baseline (BL) surveys (symptom burden and controllability and QOL) before random assignment. WRITE interventions lasted 8 weeks to develop symptom management plans for three target symptoms. All women received EUC: monthly online symptom assessment with provider reports; online resources; and every 2-week e-mails. Outcomes were evaluated at 8 and 12 weeks after BL. Repeated-measures modeling with linear contrasts evaluated group by time effects on symptom burden, controllability, and QOL, controlling for key covariates.

RESULTS

Participants (N = 497) reported mean age of 59.3 ± 9.2 years. At BL, 84% were receiving chemotherapy and reported a mean of 14.2 ± 4.9 concurrent symptoms, most commonly fatigue, constipation, and peripheral neuropathy. Symptom burden and QOL improved significantly over time (P < .001) for all three groups. A group by time interaction (P < .001) for symptom controllability was noted whereby both WRITE intervention groups had similar improvements from BL to 8 and 12 weeks, whereas EUC did not improve over time.

CONCLUSION

Both WRITE Intervention groups showed significantly greater improvements in symptom controllability from BL to 8 and BL to 12 weeks compared with EUC. There were no significant differences between Nurse-WRITE and SD-WRITE. SD-WRITE has potential as a scalable intervention for a future implementation study.

Effects of an Oncology Nurse-Led, Primary Palliative Care Intervention (CONNECT) on Illness Expectations Among Patients With Advanced Cancer

PURPOSE

Patients with advanced cancer often have unrealistic expectations about prognosis and treatment. This study assessed the effect of an oncology nurse-led primary palliative care intervention on illness expectations among patients with advanced cancer.

METHODS

This study is a secondary analysis of a cluster-randomized trial of primary palliative care conducted at 17 oncology clinics. Adult patients with advanced solid tumors for whom the oncologist would not be surprised if died within 1 year were enrolled. Monthly visits were designed to foster realistic illness expectations by eliciting patient concerns and goals for their medical care and empowering patients and families to engage in discussions with oncologists about treatment options and preferences. Baseline and 3-month questionnaires included questions about life expectancy, treatment intent, and terminal illness acknowledgment. Odds of realistic illness expectations at 3 months were adjusted for baseline responses, patient demographic and clinical characteristics, and intervention dose.

RESULTS

Among 457 primarily White patients, there was little difference in realistic illness expectations at 3 months between intervention and standard care groups: 12.8% v 11.4% for life expectancy (adjusted odds ratio [aOR] = 1.15; 95% CI, 0.59 to 2.22; P = .684); 24.6% v 33.3% for treatment intent (aOR = 0.76; 95% CI, 0.44 to 1.27; P = .290); 53.6% v 44.7% for terminal illness acknowledgment (aOR = 1.28; 95% CI, 0.81 to 2.00; P = .288). Results did not differ when accounting for variation in clinic sites or intervention dose.

CONCLUSION

Illness expectations are difficult to change among patients with advanced cancer. Additional work is needed to identify approaches within oncology practices that foster realistic illness expectations to improve patient decision making.

The cost of cure: Examining objective and subjective financial toxicity in head and neck cancer survivors

BACKGROUND

Little is documented regarding objective financial metrics and their impact on subjective financial toxicity in head and neck cancer (HNC) survivors.

METHODS

In a cross-sectional analysis, 71 survivors with available claims data for HNC-specific out-of-pocket expenses (OOPE) completed a survey including patient-reported, subjective financial toxicity outcome tools: the Comprehensive Score for financial Toxicity (COST) and the Financial Distress Questionnaire (FDQ).

RESULTS

Worse COST scores were significantly associated with lower earnings at survey administration (coefficient = 3.79; 95% CI 2.63-4.95; p < 0.001); loss of earnings after diagnosis (coefficient = 6.03; 95% CI 0.53-11.52; p = 0.032); and greater annual OOPE as a proportion of earnings [log10(Annual OOPE:Earnings at survey): coefficient = -5.66; 95% CI -10.28 to -1.04; p = 0.017]. Similar results were found with FDQ.

CONCLUSION

Financial toxicity is associated with particular socioeconomic characteristics which, if understood, would assist the development of pre-treatment screening tools to detect at-risk individuals and intervene early in the HNC cancer survivorship trajectory.

Exploring caregiver burden and financial toxicity in caregivers of tracheostomy-dependent children

OBJECTIVE

Measure the prevalence of and factors associated with financial toxicity (FT) and caregiver burden in families of tracheostomy-dependent children. FT is defined as the objective and subjective patient-level impact of the costs of medical care and has been associated with lower quality of life, decreased compliance with treatment, and increased mortality.

METHODS

A medical record review was performed on all children with a tracheostomy tube placed from 2009 to 2018 at a tertiary children's hospital to identify and include children younger than 18 years old, not deceased, and not decannulated at the time of review. Eligible children's caregivers were contacted to fill out a 36-item questionnaire and three validated instruments: The Comprehensive Score for Financial Toxicity (COST) and the Financial Distress Questionnaire (FDQ), both addressed to the parent/primary caregiver, and the Burden Scale for Family Caregivers - short version (BSFC-s).

RESULTS

Of the 140 eligible tracheostomy patients identified, 45 caregivers (32.1%) returned the survey. The average COST score was 18 ± 1.7 with 73.3% of caregivers reporting high toxicity based on FDQ, and 75.6% having severe-to-very severe caregiver burden. Significant increase in FT was seen in households where an adult had to leave a paid position (p = 0.047) or work less (p = 0.002) because of their child's condition; or needed to omit some of the child's medical services or medications due to cost-prohibitive reasons (p<0.001). Financial toxicity was associated with caregiver burden (by BSFC-s) [r = -596; beta coefficient = -0.95, t(43) = -4.87, p<0.001] and financial distress (by FDQ; p<0.001).

CONCLUSION

Caregivers of children with medically complex, tracheostomy-dependent conditions suffer from FT and caregiver burden. As a result, harmful financial coping mechanisms such as missing necessary care components or forgoing prescribed treatments, may be adopted for cost-prohibitive reasons.

Gynecologic Cancers

Gynecologic cancer, which includes cancers of the ovary, endometrium, uterus, cervix, vagina, and vulva and trophoblastic disease, is the third most common cancer and the third leading cause of cancer deaths among women in the United States. Gynecologic cancer and treatment lead to a wide range of physical, psychological, and social challenges. Disparities based on race/ethnicity, socioeconomic status, and healthcare access are also prevalent for cervical cancer. Impairments in reproductive and sexual function are some of the most distressing consequences of gynecologic cancers. There is some evidence to support the use of psychological interventions, psycho-education to promote self-management of psychological and physical symptoms, sexuality counseling, and social support interventions.

A Conceptual Framework of Self-advocacy in Women With Cancer

Researchers define self-advocacy as the ability of an individual with cancer to overcome challenges in getting their preferences, needs, and values met. While imperative in all health care settings, self-advocacy is especially important in cancer care. The goal of this article is to present a conceptual framework for self-advocacy in cancer. We review foundational studies in self-advocacy, define the elements of the conceptual framework, discuss underlying assumptions of the framework, and suggest future directions in this research area. This framework provides an empirical and conceptual basis for studies designed to understand and improve self-advocacy among women with cancer.

Integrating Family Caregiver Support Into a Gynecologic Oncology Practice: An ASCO Quality Training Program Project

PURPOSE:

A needs assessment of family caregivers (CGs) in our gynecologic oncology clinic found that 50% of CGs report nine or more distressing unmet needs, but only 19% of patients had a documented CG. We conducted an ASCO Quality Training Program project with the following aims: (1) to identify and document primary CGs for 85% of patients within two clinic visits of a gynecologic cancer diagnosis, and (2) assess the needs of and provide interventions to 75% of identified family CGs.

METHODS:

Plan-Do-Study-Act (PDSA) methodology and tools endorsed by the ASCO Quality Training Program were used. An interprofessional team reviewed baseline data (ie, any mention of a family CG in the electronic health record visit note; CG distress survey), defined the problem and project aims, created process maps, and identified root causes of poor CG identification and documentation. Eight successive PDSA cycles were implemented between October 2018 and March 2019 to address identified root causes.

RESULTS:

For aim 1, CG identification increased from 19% at baseline to 57% postimplementation, whereas for aim 2, assessment improved from 28% at baseline to 60% postimplementation. Results fell somewhat short of initial goals, but they represent an important initial improvement in care. The core team has begun additional PDSA cycles to improve CG identification rates and extend the momentum of the project.

CONCLUSION:

This project demonstrated that a CG assessment protocol can be implemented in a large, academic, gynecologic oncology clinic. Additional efforts to integrate CG identification, assessment, and intervention more fully within the clinic and electronic health record are under way.

Understanding financial toxicity in head and neck cancer survivors

OBJECTIVES

(1) Describe financial toxicity (FT) in head and neck cancer (HNC) survivors and assess its association with personal/health characteristics and health-related quality of life (HRQOL); (2) examine financial coping mechanisms (savings/loans); (3) assess relationship between COmprehensive Score for financial Toxicity (COST) and Financial Distress Questionnaire (FDQ).

PATIENTS AND METHODS

Cross-sectional survey from January - April 2018 of insured patients at a tertiary multidisciplinary HNC survivorship clinic who completed primary treatment for squamous cell carcinoma of the oral cavity, oropharynx, or larynx/hypopharynx.

RESULTS

Of 104 survivors, 30 (40.5%) demonstrated high FT. Patients with worse FT were more likely (1) not married (COST, 25.33 ± 1.87 vs. 30.61 ± 1.34, p = 0.008); (2) of lower education levels (COST, 26.12 ± 1.47 vs. 34.14 ± 1.47, p < 0.001); and (3) with larynx/hypopharynx primaries (COST, 22.86 ± 2.28 vs. 30.27 ± 1.50 vs. 32.72 ± 1.98, p = 0.005). Younger age (4.23, 95%CI 2.20 to 6.26, p < 0.001), lower earnings at diagnosis (1.17, 95%CI 0.76 to 1.58, p < 0.001), and loss in earnings (-1.80, 95%CI -2.43 to -1.16, p < 0.001) were associated with worse FT. COST was associated with HRQOL (0.08, p = 0.03). Most survivors (63/102, 60%) reported using savings and/or loans. Worse FT was associated with increased likelihood of using more mechanisms (COST, OR1.06, 95%CI 1.02 to 1.10, p = 0.004). Similar results were found with FDQ.

CONCLUSIONS

We found differences in FT by primary site, with worst FT in larynx/hypopharynx patients. This finding illuminates potential site-specific factors, e.g. workplace discrimination or inability to return to work, that may contribute to increased risk. FDQ correlates strongly with COST, encouraging further exploration as a clinically-meaningful screening tool.

Defining Essential Elements of Caregiver Support in Gynecologic Cancers Using the Modified Delphi Method

PURPOSE

Family caregivers are instrumental to patients with gynecologic cancer and can be deeply affected by the demands of caregiving. Our aims were as follows: (1) increase awareness of unmet needs of caregivers and (2) identify and prioritize the unmet needs of caregivers and essential support services to be provided in gynecologic cancer centers.

METHODS

From July 2017 to June 2018, a 16-person steering committee and 40 stakeholders, including caregivers, patients, and clinicians, participated in a modified Delphi approach to generate, review, and prioritize a set of essential elements for caregiver support. Stakeholders prioritized caregiver needs and brainstormed, discussed, and prioritized essential support services to meet those needs, using three rounds of a consensus-building protocol. Basic descriptive statistics were performed to feed means and rankings back to stakeholders before each round.

RESULTS

The top three caregiver needs were as follows: (1) to obtain information about their loved one's cancer, (2) how to provide support and comfort to their loved one, and (3) how to maintain their own emotional health and well-being. Fifteen essential elements of support for caregivers of patients with gynecologic cancer were identified and ranged from elements currently attainable (eg, information on managing symptoms, skilled-care training, a point person to help navigate the system) to more aspirational elements (eg, integrative services to promote caregiver well-being).

CONCLUSION

To ensure comprehensive quality care, clinicians and health care providers should strive to provide caregivers with the identified essential elements of support. Health care settings should work to incorporate caregiver needs into cancer care delivery.

Integrating Political Philosophy Into Health Policy Education

Twenty-first century America is marked by deep and seemingly incommensurable divisions in terms of public policy solutions to our most intractable issues. Health policy challenges are not immune to these deep divisions, as the debate during and since the passage of the Affordable Care Act illustrates. Positions on key public policy issues are driven by largely implicit and unarticulated philosophical presuppositions that guide individuals' notions of the nature of government, individuals' moral obligations to each other, how society assesses quality of life, and what it means to be a community. If faculty in schools of nursing are to prepare graduate nurses to enter into these heated public policy debates, we must help students understand, identify, and articulate the philosophical presuppositions that undergird reasoning related to health policy issues. In this article, we present a working taxonomy that can help faculty members provide students with a basic understanding of core philosophical principles. We attempt to categorize all of western political philosophy into four distinct traditions or "impulses," describing each of these four traditions in detail. We illustrate each tradition's approach to political reasoning using a specific health policy case study. We conclude with some guidance about how to implement this content within a doctoral-level public policy curriculum.

Abnormal glyceraldehyde-3-phosphate dehydrogenase binding and glycolytic flux in Autosomal Dominant Polycystic Kidney Disease after a mild oxidative stress

AIM

The aim of this study was, a) to investigate the effect of mild oxidative stress on glycolytic flux and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) binding in erythrocytes from patients with autosomal dominant polycystic kidney disease (ADPKD), and b) to examine whether the modulation of GAPDH-binding to the red cell membrane leads to changes in glycolytic flux.

PATIENTS AND METHODS

The rate of lactate production in intact erythrocytes and the GAPDH/actin ratio in erythrocyte ghost membranes were measured before and after treating cells with t-butyl hydroperoxide or N-ethylmaleimide (NEM) in 13 ADPKD patients and 12 controls.

RESULTS

t-bytyl hydro-peroxide had a significant effect on both lactate production and GAPDH/actin ratio in healthy subjects, but it had essentially no effect on ADPKD patients in which both parameters already resembled those of the peroxide-treated controls. NEM treatment after 300 sec had a very significant effect on both lactate production and GAPDH/actin ratio in both patient and control cells. However, after 10 sec the effect on GAPDH/actin ratio was only significant in the erythrocytes of ADPKD patients. In every experiment glycolytic lactate production correlated negatively with membrane-bound GAPDH/actin ratio.

CONCLUSIONS

We conclude that glycolytic flux and GAPDH binding in erythrocytes from ADPKD patients respond abnormally to both a mild oxidative stress and brief exposure to NEM.

Inflammation in cardiovascular disease and regulation of the actin cytoskeleton in inflammatory cells: the actin cytoskeleton as a target

Cardiovascular disease is prevalent in developed countries causing very large burdens to health services. The underlying pathology is atheromatous plaque in the sub-endothelial region of the vascular wall. High levels of low density lipoprotein cholesterol and high blood pressure cause endothelial damage. Atheroma develop from a response to this injury that is perpetuated to chronic inflammation. The invasion of inflammatory leukocytes into atheroma during its development and in the precipitation of acute thrombotic events is mediated by adhesion molecules on the cell surface. These are regulated by the actin filament cytoskeleton which also mediates intracellular signalling from them. The actin cytoskeleton is central to NADPH oxidase activation that produces superoxide which is an intracellular signalling molecule for the hypertensive and inflammatory actions of angiotensin II. There are polymorphisms in actin filament proteins such as adducin and caldesmon and in the promoter regions of tropomyosins that may cause individual variation in these processes. Many signalling molecules in the actin filament response to inflammatory stimuli and in signalling downstream from actin filaments are small G-proteins that require post-transcriptional modification by isoprenoids from the cholesterol synthetic pathway. Statins deplete the isoprenoids and so down regulate G-proteins that mediate the inflammatory response. Angiotensin converting enzyme inhibitors and angiotensin II receptor type 1 antagonists decrease angiotensin II stimulated superoxide production thus decreasing not only blood pressure but also inflammation. The anti-inflammatory effects of these drugs, involving altered actin filament function, are a major contributor to their benefits in the treatment of cardiovascular disease. The feasibility of modifying the behaviour of actin filament proteins as a therapeutic approach for cardiovascular disease is considered.

Increasing neutrophil F-actin corrects CD11b exposure in Type 2 diabetes

BACKGROUND

Leukocyte dysfunction contributes to the pathogenesis of diabetic vascular complications. Neutrophils adhere to the endothelium through the beta(2)integrin CD11b/CD18. In Type 2 diabetes, neutrophil surface CD11b expression is increased and is associated with impaired actin polymerization. This study aimed to determine whether increasing neutrophil actin polymerization could correct the defect in CD11b exposure.

DESIGN

Neutrophil actin polymerization was stimulated with the tyrosine phosphatase inhibitor phenylarsine oxide (PAO), and cytoskeletal phosphotyrosine was monitored by immunoblotting Triton X-100 insoluble fractions of cells. Neutrophil F-actin was measured with phalloidin-FITC staining, and surface CD11b expression was determined with anti-CD11b-PE before analysis with flow cytometry.

RESULTS

Phenylarsine oxide caused an increase in phosphotyrosine in neutrophils from both patients with Type 2 diabetes (DM) and controls (NC) (-fold increase: NC, 1.43 +/- 0.16; DM, 1.46 +/- 0.10). The response to PAO in terms of phalloidin-binding was impaired in neutrophils from patients [phalloidin-FITC MFI area under the curve, NC 200 +/- 5 (x 10(3)), DM 124 +/- 9 (x 10(3)), P < 0.0001]. Phenylarsine oxide at concentrations < 10 micro mol L(-1) also caused loss of CD11b from neutrophil surfaces that was impaired in samples from patients [CD11b sites area under the curve NC 90 +/- 6 (x 10(3)), DM 121 +/- 9 (x 10(3)), P < 0.002]. However, in neutrophils from patients, incubation with PAO at a concentration of > 10 micro mol L(-1) caused a significant increase in intracellular F-actin and CD11b down-regulation equivalent to that observed in controls.

CONCLUSION

In Type 2 diabetes, impaired neutrophil actin polymerization even in response to increasing cytoskeletal phophotyrosine suggests a downstream defect. Furthermore, increasing actin polymerization, above a minimum threshold level, corrects the defect in integrin exposure. Correction of the actin polymerization defect in Type 2 diabetes could improve the prognosis of diabetic vascular complications.

Impaired neutrophil store-mediated calcium entry in Type 2 diabetes

BACKGROUND

In Type 2 diabetes impaired neutrophil function leads to increased bacterial infection and cardiovascular disease. Many neutrophil functions depend on calcium signalling, which involves release of calcium from intracellular stores and subsequently translocation of stores via the cytoskeleton to the plasma membrane, causing store-mediated calcium entry (SMCE) into the cell. We hypothesized that in Type 2 diabetes there would be a defect in SMCE.

MATERIALS AND METHODS

Neutrophils were prepared from patients with Type 2 diabetes (DM, n=15) and controls (NC, n=15). Free cytosolic calcium [Ca2+]i was measured with Fura-2 in resting cells and after stimulation of calcium release with fMLP and thapsigargin.

RESULTS

Baseline [Ca2+]i was higher in neutrophils from the patients than the controls (NC 65 +/- 5 nm, DM 80 +/- 4 nm, P<0.05). However, after fMLP-treatment [Ca2+]i was significantly lower in the patients (NC 301 +/- 28 nm, DM 210 +/- 20 nm, P<0.01). The greater increase in controls was not observed when cells were treated with fMLP in the absence of extracellular calcium (-fold increase NC 2.9 +/- 0.5, DM 2.7 +/- 0.3). Treatment of cells with thapsigargin caused a similar greater increase in [Ca2+]i in the controls than in the patients that was not seen in the absence of extracellular calcium (-fold increase with Ca2+ NC 5.2 +/- 1.0, DM 3.0 +/- 0.4, P<0.05; fold increase without Ca2+ NC 2.5 +/- 0.4, DM 2.2 +/- 0.2).

CONCLUSIONS

In Type 2 diabetes there is a defect in neutrophil calcium signalling which results in a lesser increase in free cytosolic calcium owing to impaired influx across the plasma membrane. Abnormal calcium signalling is likely to be important in the pathogenesis of diabetic complications.

Impaired neutrophil actin assembly causes persistent CD11b expression and reduced primary granule exocytosis in Type II diabetes

AIMS/HYPOTHESIS

Neutrophil dysfunction has a role in the pathogenesis of complications in Type II (non-insulin-dependent) diabetes mellitus. Neutrophils adhere through expression of the beta(2)integrin CD11b/CD18 which closely associates with the actin cytoskeleton. The aim of this study was to investigate the effect of actin polymerisation on CD11b expression and exocytosis of the primary granule marker CD69 in neutrophils from patients with Type II diabetes.

METHODS

Neutrophils were activated with fMLP or PMA, actin polymerisation was inhibited with cytochalasin D. Cells were stained for CD11b and CD69 expression and intracellular F-actin was measured with phalloidin-FITC. Cellular fluorescence was measured by flow cytometry. Actin content of Triton X-100 fractions of cells was measured by SDS-PAGE and Coomassie blue staining.

RESULTS

PMA caused an increase in neutrophil F-actin that was greater in control subjects than in patients with Type II diabetes (50.8% vs 33.4%, p<0.001) and correlated with actin integrated optical density (IOD) by SDS-PAGE ( r=0.74, p=0.01). Loss of CD11b from cell surfaces only occurred in neutrophils with high F-actin. The proportion of cells losing CD11b was lower in patients than in control subjects (23.1% vs 37.5%, p<0.001) and lowest in patients with additional cardiovascular risk markers (20.1% vs 27.7%; p<0.05). Cytochalasin D prevented loss of CD11b ( p<0.001). CD69 expression was reduced in patients with Type II diabetes (22.6% vs 36.4%, p<0.001) and correlated with F-actin content ( r=0.78, p<0.0001).

CONCLUSION/INTERPRETATION

In Type II diabetes impaired neutrophil actin polymerisation leads to persistent expression of CD11b and reduced exocytosis of primary granules and could contribute to the pathogenesis of diabetic complications.

Rapid fusion of granules with neutrophil cell membranes in hypertensive patients may increase vascular damage

In essential hypertension (EHT) the presence of a metabolic syndrome increases the risk of cardiovascular disease. A cell membrane abnormality is implicated but its role in cardiovascular disease is unclear. Neutrophil accumulation, which occurs by beta2-integrin (CD11b/CD18) expression, followed by release of proinflammatory factors from primary vesicles is an important factor in vascular damage. CD11b and CD69 expression on neutrophils from normal controls and EHT patients was determined by fluorescence-activated cell scanning. Neutrophils were activated with phorbol myristate acetate (PMA). Protein kinase C (PKC) and calpain were inhibited with bisindolylmaleimide and E64d, respectively. In EHT patients CD11b was not increased on neutrophils at rest. However, EHT neutrophils more readily expressed CD11b on incubation in phosphate-buffered saline and more cells went on to exocytose primary granules indicated by expression of CD69. Stimulation with PMA caused more rapid activation in EHT neutrophils with expression of CD11b, followed rapidly by exocytosis of primary granules. Bisindolylmaleimide slowed but did not prevent CD11b expression, which, together with primary granule exocytosis, continued to be faster in EHT neutrophils. E64d also slowed but did not prevent either CD11b expression or primary granule exocytosis, but this inhibitor did abolish the difference between NC and EHT neutrophils. The membrane abnormality in EHT may contribute to cardiovascular risk by increasing the rate of vesicle fusion with the cell membrane to increase neutrophil accumulation and release of inflammatory agents at sites of vascular damage. Calpain activation may be the rate-limiting component that is abnormal.

Abnormal thiol reactivity of tropomyosin in essential hypertension and its association with abnormal sodium-lithium countertransport kinetics

OBJECTIVES

To identify a thiol protein that is abnormal in a subgroup of essential hypertensive (EHT) patients who have a strong family history of hypertension and cardiovascular disease and have a low Km of erythrocyte Na/Li countertransport (CT).

METHODS

To detect biotin maleimide labelling of a key thiol protein to investigate its reaction with N-ethylmaleimide (NEM) in normal and EHT erythrocytes.

RESULTS

The thiol protein of 33 kDa apparent molecular weight (p33) identified by the loss of labelling with biotin maleimide was identified as tropomyosin due to its retarded running in 6 mol/l urea gels and immunoblotting. The NEM reaction with p33 detected by loss of subsequent biotin maleimide labelling is biphasic in normal control erythrocytes with the rate in the first 30 s double that after 30 s. In EHT erythrocytes NEM reaction (1) after 30 s is faster than normal and (2) in the first 30 s causes a paradoxical increase in apparent biotin maleimide labelling. In normal control erythrocytes, the loss of biotin maleimide labelling with NEM reaction or the faster phenylmaleimide reaction follows the same time course as the decrease in Km of Na/Li CT.

CONCLUSIONS

NEM reaction with p33 requires two thiols. Only the cytoskeletal form of tropomyosin from the TM3 gene has more than one thiol group and agrees with SDS-PAGE mobility. Tropomyosin is a strong candidate to explain the familial abnormality in EHT with abnormal Na/ Li CT and it could explain many of the characteristics of this disease.

Na/Li countertransport abnormalities in type 1 diabetes with and without nephropathy are familial

OBJECTIVE

To determine whether there is a familial abnormality in erythrocyte Na/Li countertransport (CT) kinetics in the approximate one-third of type 1 diabetic patients that succumb to a familial predisposition to nephropathy.

RESEARCH DESIGN AND METHODS

Erythrocyte Na/Li CT kinetics were measured in nondiabetic first-degree relatives of type 1 diabetic patients with nephropathy (DNrel) (n = 32) or without nephropathy (DCrel) (n = 22) and normal control subjects ( n = 25).

RESULTS

Increases in outside-site Na ion association rate constant and turnover rate of Na/Li countertransport (CT) in DNrels caused increases in Vmax/Km and Vmax, respectively. Thiol alkylation with N-ethy]maleimide (NEM) modifies these kinetic parameters abnormally in nephropathy. With Na ions at the outside site of the transporter, thiol alkylation causes a large decrease in Vmax; but in their absence, Vmax is decreased in normal control subjects, unchanged in DCrels, or increased in DNrels. The relationship between Vmax values after thiol alkylation with or without Na ions was different in DNrels (P < 0.001). Kinetic parameters with and without thiol alkylation identified 60% of DNrels and 20% of DCrels as abnormal. The single-flux rate assay of Na/Li CT did not give this discrimination, and its use may cause discrepancy between studies.

CONCLUSIONS

Clinically normal untreated DNrels have the same abnormality in Na/Li CT as the affected patients. DNrels had a metabolic syndrome with increased BMI and plasma triglycerides, but no elevation in blood pressure. Na/Li CT can detect those type 1 diabetic patients at risk of nephropathy who have a familial abnormality in a membrane thiol protein.

Abnormal thiol group modulation of sodium-lithium countertransport and membrane fluidity is associated with a disturbed relationship between serum triacylglycerols and membrane function in type II diabetes

In essential hypertension and diabetic nephropathy, sodium-lithium countertransport (Na-Li CT) is an inherited marker, subject to metabolic influences, of cardiovascular risk. Studies in Type II diabetes, taking clinical phenotypes as their starting point, are conflicting. We sought to identify Na-Li CT kinetic abnormalities in Type II diabetes, and only subsequently to seek relationships with clinical variables. Na-Li CT kinetics, membrane fluidity and their modulation by thiol proteins were measured in erythrocytes from 38 patients with Type II diabetes and in 16 normal control subjects. In untreated erythrocytes, Na-Li CT kinetics were similar. Thiol protein alkylation with N-ethylmaleimide generally caused both V(max) and K(m) to fall, but caused K(m) to rise in erythrocytes from 13 out of 38 diabetic subjects, whose native K(m) was low (P=0. 0013 compared with control). V(max) and serum triacylglycerol levels were related in normal controls (r(s)=0.54, P=0.038) and in diabetic subjects whose K(m) fell after N-ethylmaleimide (n=25, r(s)=0.62, P=0.001). Where the K(m) rose after N-ethylmaleimide, V(max) and triacylglycerol levels were not related (n=13, r(s)=-0.39, P=0.183) and membrane fluidity did not increase after N-ethylmaleimide. However, these subgroups were indistinguishable in terms of blood pressure, albuminuria, glycaemia or lipid profiles. Thus abnormalities in the regulation of Na-Li CT and membrane fluidity by key thiol proteins, resembling those seen in essential hypertension and diabetic nephropathy, were apparent in one-third of subjects with Type II diabetes. Membrane abnormalities may indicate a common pathological mechanism. The prognostic significance of Na-Li CT kinetic abnormalities in Type II diabetes must now be confirmed.

Thiol protein defect in sodium-lithium countertransport in subset of essential hypertension

There is probably a heterogeneous etiology for essential hypertension (EHT), and abnormal erythrocyte sodium-lithium countertransport (Na/Li CT) is common in a subgroup of patients with a strong family history of hypertension and cardiovascular disease (EHT-FH patients). The aim of this study was to test the hypothesis that altering a membrane thiol protein could mimic the abnormal Na/Li CT observed in the patients and that a more refined understanding of the mechanism of abnormal Na/Li CT would facilitate a clearer identification of a subgroup of patients with a homogeneous biochemical abnormality. Na/Li CT kinetics were determined in untreated erythrocytes and after thiol group alkylation with N-ethylmaleimide (NEM). Compared with normal control erythrocytes, untreated erythrocytes from EHT-FH patients had a low K(m) of Na/Li CT, with a high ratio of maximum velocity to K(m). This kinetic pattern was reproduced in normal erythrocytes by treatment with NEM in sodium-free medium. The same treatment in EHT-FH erythrocytes caused a markedly abnormal effect with an increase in maximum velocity, indicating an increase in transporter turnover in contrast to the increase in sodium affinity seen in normal control erythrocytes. Frequency distributions of these kinetic changes showed a subgroup of approximately 75% of EHT-FH patients with abnormal kinetic changes with NEM. Therefore, the key Na/Li CT thiol group that is very reactive to NEM and causes the abnormal Na/Li CT in a subgroup of hypertensive patients may be a useful intermediate phenotype for a disease group within the syndrome of EHT. The single flux assay of Na/Li CT at 140 mmol/L sodium poorly discriminates this group. Identification of the thiol protein involved may lead to a molecular explanation of the altered membrane function in this subgroup of patients.

Effect of age on plasma membrane asymmetry and membrane fluidity in human leukocytes and platelets

BACKGROUND

We determined whether ageing changes in plasma membrane phospholipid asymmetry were related to changes in membrane physical characteristics.

METHODS

Plasma membrane asymmetry was determined in polymorphonuclear leukocytes (PMN), lymphocytes, and platelets from 45 healthy young (mean 29 years, 26 male) and 28 healthy elderly (mean 70 years, 15 male) subjects by flow cytometric measurement of annexin V binding to cell surface phosphatidylserine. Membrane fluidity in lymphocytes and platelets from young and elderly subjects was determined by fluorescence polarization of 1,6-diphenyl- 1,3,5-hexatriene (DPH) and (4-trimethylammonium)-DPH (TMA).

RESULTS

In elderly subjects, a higher proportion of lymphocytes had specific annexin V binding to phosphatidylserine (PS) than in young subjects (young: median percentage of cells with specific annexin V binding to PS 5.3 [second to fourth quintiles range 3.8-8.7]; elderly: 8.5 [5.2-17.2]; p = .028). No ageing change in annexin V binding to PMN was observed (young: 35.0% [21.8-53.5]; elderly: 39.6% [27.4-69.8]; p = .42). Platelets had no specific annexin V binding (young: median molecules of annexin V specific binding 3.8 [0.4-11.3]; elderly: -1.4 [-4.8-1.7]; p = .23). Superficial membrane fluidity was increased in lymphocytes (TMA anisotropy, young: 0.271 [0.259-0.289]; elderly: 0.262 [0.242-0.279];p = .004), but not in platelets (young: 0.273 [0.259-0.293]; elderly: 0.269 [0.248-0.284]; p = .12). Lymphocyte annexin V binding correlated with TMA (r = -.65, p = .022), but not DPH anisotropy (r = -.39, p = .18).

CONCLUSIONS

Plasma membrane asymmetry is decreased with age in human lymphocytes, but not in human PMN or platelets. The increased proportion of lymphocytes with loss of plasma membrane asymmetry corresponds to the ageing changes in superficial membrane fluidity observed in lymphocytes. Such alterations in lymphocyte plasma membrane structure with age could account for changes in membrane-bound receptor function described with ageing, and may contribute to alterations in immune responsiveness and vascular thrombosis seen in older humans.

Effect of aging on CD11b and CD69 surface expression by vesicular insertion in human polymorphonuclear leucocytes

The exocytosis of intracellular vesicles is an important function of the plasma membrane, which is responsible for hormone secretion, cell surface expression of antigens, ion transporters and receptors, and intracellular and intercellular signalling. Human aging is associated with many physiological and cellular changes, many of which are due to alterations in plasma membrane functioning. Alterations in vesicle externalization with age could account for many of these changes. We investigated whether alterations in vesicle exocytosis occur with increasing age by flow-cytometric determination of CD11b and CD69 expression on the surface of human polymorphonuclear leucocytes (PMN) stimulated with phorbol myristate acetate (PMA), a tumour promoter which binds to and activates protein kinase C (PKC) directly, or with formyl-Met-Leu-Phe (fMLP), which activates PKC indirectly via interactions with a cell surface receptor and G-protein, and subsequent inositol phosphate hydrolysis. Following stimulation with PMA, a decrease in the proportion of PMN expressing CD69 at high levels was observed in elderly compared with young subjects (young, 55.3%; elderly, 43.9%; P=0.01). No aging-related differences in the proportion of PMN expressing CD11b (young, 73.7%; elderly, 68.4%; P=0.15), or in the number of molecules of CD69 or CD11b expressed per cell, were observed. Stimulation with fMLP or low PMA concentrations resulted in full CD11b expression but minimal CD69 expression in both young and elderly subjects. Cells which expressed CD69 had no CD11b expression, while those cells expressing CD11b had minimal CD69 expression. Thus the PMA-induced expression of CD11b and CD69 in human PMN represents two separate processes, only one of which is affected in aging. CD11b expression appears to require a lesser degree of PKC stimulation compared with that required for CD69 expression. The age-associated reduction in PMA-stimulated CD69 expression may occur either at or distal to PKC activation. Such a decrease may contribute to the age-associated impairments in PMN function that contribute, in turn, to immunosenescence.

Dysregulation of PMN antigen expression in Type 2 diabetes may reflect a generalized defect of exocytosis: influence of hypertension and microalbuminuria

Defective exocytosis could underlie clinical and metabolic abnormalities in Type 2 diabetes. Because many SNARE proteins appear to be common mediators of exocytosis, we examined phorbol myristate acetate-stimulated expression of CD11b and CD69 on polymorphonuclear leukocytes (PMN) from Type 2 diabetic subjects with hypertension and microalbuminuria (D-htma), hypertension only (D-ht) or uncomplicated (D-uc), and normal controls (NC) by flow cytometry. CD11b expression was rapid (half maximal by 7 min), initially on all PMN. CD69 expression took place subsequently but on PMN that did not express CD11b. The proportion of CD11b-positive PMN at 30 min was higher in all diabetic groups than in NC. Expression of CD11b was higher and CD69 lower in D-uc and D-htma but were similar in NC and D-ht. In Type 2 diabetes the transition from the CD11b-positive to CD69-positive state is impaired. The defect in the process of CD69 expression appeared most marked in diabetic subjects with hypertension and microalbuminuria.

Erythrocyte membrane thiol proteins associated with changes in the kinetics of Na/Li countertransport: a possible molecular explanation of changes in disease

BACKGROUND

Abnormal erythrocyte Na/Li countertransport is associated with diseases such as essential hypertension and diabetic renal disease. Although it seems unlikely that Na/Li countertransport contributes to any disease process, it may be abnormal because of a change in the cell membrane that is part of the disease process.

METHODS

We have shown that Na/Li countertransport kinetics are modified by two types of thiol group. One of these, which we have called 'type 1', is rapidly alkylated by N-ethylmaleimide to give a kinetic pattern similar to that in the above diseases.

RESULTS

AtpH 6 and 2 degrees C, both N-ethylmaleimide and iodoacetamide cause the K(m) of Na/Li countertransport to decrease to completion in 300s, with 78% (SEM 6%) of the decrease occurring in 30s. Using these reaction conditions, N-ethylmaleimide reacted with a unique thiol group on a 33-kD protein, blocking its subsequent reaction with biotin maleimide. This 33-kD protein was present in rabbit erythrocytes, which have high levels of Na/Li countertransport, but absent from rat erythrocytes, which have no Na/Li countertransport. Iodoacetyl biotin labelled a 60-kD protein that was specifically blocked by iodoacetamide.

CONCLUSION

We suggest that these proteins are members of a cluster of membrane proteins that can modify Na/Li countertransport and may have a functional role in the disease processes.

Abnormal regulation of cell membrane fluidity in diabetic nephropathy

An abnormality of the physical properties of the cell membrane may underlie the defect that unites the clinical and biochemical abnormalities found in subjects with diabetic nephropathy. The cell membrane is linked both structurally and functionally with the cytoskeleton. The fluorescence anisotropy, a measure of membrane fluidity, was studied at baseline and after modulation of cytoskeletal proteins by thiol group alkylation with N-ethylmaleimide (NEM). 1,6-diphenyl-1,3,5-hexatriene (DPH) was used to assess anisotropy in the deep hydrophobic regions of the lipid bilayer and trimethylammonium-diphenylhexatriene (TMA-DPH) was used to assess the superficial, relatively hydrophilic regions. We compared 17 subjects with insulin-dependent diabetes mellitus (IDDM) and nephropathy with 17 control subjects with IDDM and 24 non-diabetic control subjects. Median TMA-DPH anisotropy (0.271 (0.239-0.332) vs 0.269 (0.258-0.281) vs 0.275 (0.246-0.287)) and DPH anisotropy (0.221 (0.193-0.261) vs 0.227 (0.197-0.253) vs 0.226 (0.193-0.245)) were similar in erythrocytes from the three groups. However after alkylation of protein thiol groups with NEM clear differences emerged. In the control subjects with and without IDDM there was a significant fall in TMA-DPH anisotropy compared to the subjects with diabetic nephropathy in whom the addition of NEM had no effect (deltaTMA-DPH anisotropy -0.005 (-0.020 - +0.006) vs -0.005 (-0.011 - +0.016) vs +0.002 (-0.010 - +0.008) p < 0.001). This finding was confirmed when the deep regions of the lipid bilayer were assessed using DPH (deltaDPH anisotropy -0.017 (-0.029 - -0.007.) vs -0.015 (-0.029 - +0.001) vs + 0.003 (-0.021 - +0.018) p < 0.001). We conclude that cytoskeletal modulation of the physical properties of the cell membrane lipids by proteins is abnormal in subjects with diabetic nephropathy. Such an abnormality could explain some of the clinical and metabolic abnormalities found in this condition.

Sodium-lithium countertransport: physiology and function

Current opinions on the relationships between erythrocyte sodium-lithium countertransport kinetics and primary hypertension, hyperlipidaemia and diabetic nephropathy are reviewed. Problems associated with the assay are analysed. Some possible mechanisms that could modify the kinetics of ion exchange are examined. The question of what catalyses sodium-lithium countertransport is discussed, but not answered. Some models are put forward showing how a study of sodium-lithium countertransport kinetics could further our understanding of important disease processes.

Lack of function of an N-ethylmaleimide-sensitive thiol protein in erythrocyte membrane of autosomal dominant polycystic kidney disease

The polycystic kidney disease 1 (PKD1) gene product polycystin has been predicted to be an integral membrane protein involved in cell-cell and cell-matrix interactions. The erythrocyte membrane fluidity in autosomal dominant polycystic kidney disease (ADPKD) patients is increased, and this may be due to a membrane cytoskeletal abnormality. The abnormal erythrocyte sodium-lithium countertransport kinetics in-ADPKD are related to an altered thiol protein in the cytoskeleton. The possibility that a similar thiol protein abnormality causes the increased erythrocyte membrane fluidity in ADPKD was investigated. The membrane fluidity of intact erythrocytes from 12 ADPKD patients and 12 healthy control subjects was assessed from the fluorescence anisotropies of 1,6-diphenyl-1,3,5-hexatriene (DPH) and trimethylammonium-diphenyl-hexatriene (TMA-DPH). The effect on membrane fluidity of N-ethylmaleimide (NEM), cytochalasin D, heating at 48 degrees C for 20 min, or more specifically, liposomes containing antibodies to actin or ankyrin, was determined. In erythrocytes from healthy control subjects, the fluorescence anisotropy of DPH (mean +/- SEM: 0.223 +/- 0.001) was decreased after treatment with NEM (0.200 +/- 0.003, P < 0.001), cytochalasin D (0.206 +/- 0.006, P < 0.001), heating (0.199 +/- 0.002, P < 0.001), and antibodies to actin (0.194 +/- 0.002, P < 0.001) or ankyrin (0.196 +/- 0.002, P < 0.001). The TMA-DPH anisotropy (0.279 +/- 0.001) was also decreased after treatment with NEM (0.264 +/- 0.001, P < 0.001), cytochalasin D (0.264 +/- 0.001, P < 0.001), heating (0.265 +/- 0.001, P < 0.001), and antibodies to actin (0.262 +/- 0.002, P < 0.001) or ankyrin (0.262 +/- 0.002, P < 0.001). NEM had no additional effect on the other treatments, suggesting that its target thiol protein was associated with the cytoskeleton. In untreated erythrocytes from ADPKD patients, fluorescence anisotropies of both DPH and TMA-DPH were reduced, and none of the treatments altered the anisotropy of either DPH or TMA-DPH. In ADPKD, a cytoskeletal thiol protein is abnormal and possibly explains abnormal lipid bilayer properties and transport protein function in erythrocytes in this disease.

Na-Li countertransport kinetics in the relatives of hypertensive patients with abnormal Na-Li countertransport activity

Familial factors are believed to be important in determining the high sodium-lithium countertransport activity (defined as >0.40 mmol Li/(h x l cell) at external sodium concentration of 140 mmol/L (Nae 140)) which is observed in a proportion of patients with essential hypertension. However, environmental factors such as pregnancy and dyslipidemia also affect activity. High sodium-lithium countertransport activity (Nae 140) in essential hypertension is mainly due to a low Michaelis constant (Km) and is associated with a high Vmax/Km ratio. In contrast, dyslipidemias affect Vmax. This study aimed to determine if there was evidence that Km and Vmax/Km ratios are influenced by familial factors. Sodium-lithium countertransport kinetics were measured in the 47 first degree relatives of 12 hypertensive probands with abnormal sodium-lithium countertransport kinetics and 35 normotensive control subjects. Sodium-lithium countertransport was measured as Na-stimulated Li efflux from lithium loaded erythrocytes. The relatives had significantly reduced Km and increased Vmax/Km compared to normal subjects. Eleven relatives had high sodium-lithium countertransport activity (Nae 140), associated with low Km and high Vmax/Km. The 14 relatives that were hypertensive had abnormalities of sodium-lithium countertransport kinetics. The results of this study suggest that familial factors are important in determining the Km and Vmax/Km of sodium-lithium countertransport activity. Studies aimed at determining the inheritance of sodium-lithium countertransport and its use as an intermediate phenotype of essential hypertension must measure its kinetic determinants to reduce the risk of confounding effects from other variables.

Thiol group modulation of sodium-lithium countertransport kinetics in diabetic nephropathy

Abnormal erythrocyte sodium-lithium countertransport (Na-Li CT) activity, traditionally measured at a single sodium concentration of 140 mmol.l-1 (V140), may represent an inherited risk marker for diabetic nephropathy. The membrane defect underlying this association is poorly understood, though modulation by key protein thiol groups appears to be important in essential hypertension. To improve understanding of this abnormality, Na-Li CT kinetics in untreated erythrocytes and after thiol group alkylation with N-ethylmaleimide were investigated in 18 subjects with diabetic nephropathy, 20 normoalbuminuric insulin-dependent diabetic (IDDM) subjects and 18 non-diabetic individuals. Using the traditional assay, V140 was similar in subjects with diabetic nephropathy compared to IDDM control subjects vs 0.311 (0.152-0.475) (0.247 (0.111-0.498) mmol Li.h-1.l erythrocytes-1). Kinetic parameters were abnormal in subjects with diabetic nephropathy compared with diabetic and non-diabetic control subjects with both Vmax (maximal Na-Li CT activity) (0.454 (0.257-0.963) vs 0.338 (0.183-0.972) vs 0.332 (0.213-0.603) mmol Li.h-1.l erythrocytes-1, p < 0.05), and Vmax/Km(So) ratio, reflecting ion association (6.03 (2.3-9.6) vs 4.73 (2.0-10.4) vs 4.48 (1.5-7.1), p < 0.01), significantly higher. N-ethylmaleimide decreased K(m)(So) and Vmax abolishing differences in Vmax/Km(So) ratio between groups (2.45 (1.18-4.21) vs 2.23 (0.96-4.3) vs 2.44 (1.4-3.7), but enhancing the differences in Vmax (0.186 (0.090-0.315) vs 0.120 (0.051-0.256) vs 0.128 (0.080-0.206) mmol Li.h-1.l erythrocytes-1, p < 0.0001). Of subjects with diabetic nephropathy, 78% were outside the 75th percentile of the non-diabetic control subjects when Vmax and Vmax/Km(So) ratio were combined, compared to 20% of the normoalbuminuric control subjects. We conclude that the traditional assay, V140, is poor at detecting individuals with diabetic nephropathy. Study of the kinetic parameters of the transporter, including thiol group modulation, suggests that increased ion association, Vmax/Km(So) ratio may represent the inherited defect and improves identification of subjects with diabetic nephropathy.

Insulin resistance in adult polycystic kidney disease

Adult polycystic kidney disease (APKD) is a common hereditary disease with renal and extra-renal manifestations. There are at least three genes responsible for this disease. The polycystic kidney disease 1 (PKD1) gene product is a membrane protein involved in cell-cell and cell-matrix interactions and has a widespread tissue distribution. Abnormal membrane fluidity in erythrocytes from APKD patients is due to altered membrane proteins. Membrane fluidity of mononuclear cells is related to whole body insulin sensitivity. Insulin sensitivity might therefore be disturbed in APKD if the erythrocyte membrane abnormality is also present in other cells. Therefore, we investigated insulin sensitivity in 15 APKD patients and 20 normal subjects matched for age and sex. Insulin sensitivity was assessed by a short insulin tolerance test to derive the first-order rate constant for the disappearance of glucose (Kitt) and mononuclear leukocyte membrane fluidity was measured by fluorescence anisotropy. The Kitt value (% mmol.liter-1.min-1) was lower in APKD patients than in normal subjects [median (range) 2.2 (1.5 to 6.3) vs. 4.1 (2.0 to 5.4). P < 0.001]. Fasting plasma insulin concentrations were negatively correlated with the Kitt values (r = -0.66, P < 0.001). Core region anisotropy was significantly lower (higher fluidity) in leukocytes from APKD patients [mean (SEM) 0.164 (0.003) vs. 0.174 (0.001), P < 0.001]. Insulin sensitivity was positively correlated with the fluorescence anisotropy of the core region of leukocyte membranes (r = 0.81, P = 0.0001). In conclusion, APKD patients were insulin resistant and some patients were hyperinsulinemic, which may indicate increased cardiovascular risk. The cellular basis of the insulin resistance may be directly related to the proteins causing the disease or to the general change in membrane properties.

Erythrocyte ion and water balance and membrane potential in the puerperium of normal pregnancy

OBJECTIVE

To examine the balance of erythrocyte ions and water during the rapid changes in plasma osmolality in the early puerperium, and during the subsequent period of sustained readjustment.

DESIGN

A serial study from the third trimester of pregnancy to 20 weeks after delivery.

PARTICIPANTS

Thirty-five primiparous women who had experienced no antenatal complications.

MAIN OUTCOME MEASURES

Plasma osmolality, erythrocyte hydration, potassium, chloride and sodium were measured and nondiffusible ion content and erythrocyte membrane potential calculated. Plasma sodium, potassium and chloride were also measured.

RESULTS

During the first week after delivery plasma osmolality increased (280 (SEM 0.52)-289 (SEM 0.64) mosmol/kg; P < 0.001) but erythrocyte hydration did not decrease (2.060 (SEM 0.018)-2.067 (SEM 0.021) 1/kg dry cells) because of an increase in total cell osmole content (577 (SEM 5.31)-597 (SEM 6.15) mosmol/kg dry cells; P = 0.001). This increase included nondiffusible anions, chloride and potassium. These changes in ionic balance did not affect membrane potential. After the first week of the puerperium and up to the 20th week, plasma osmolality was stable but erythrocyte osmole content and hydration both decreased. This was due to a decrease in nondiffusible anions and potassium with a smaller increase in chloride leading to a decrease in membrane potential (-14.31 (SEM 0.34)mV to -12.66 (SEM 0.28)mV; P < 0.001).

CONCLUSIONS

A rapid increase in intracellular osmoles can occur in the mature erythrocyte and probably precedes the decrease in plasma osmolality in the puerperium. Changes in erythrocyte homeostasis in the first week of the puerperium can be accounted for by alterations in nondiffusible anions. After the first week of the puerperium it appears that the functional organisation of the membrane is changing.

Abnormal sodium-lithium countertransport kinetics in immunoglobulin A nephropathy patients and the families: association with hypertension

Immunoglobulin A nephropathy (IgAN) is the most common primary glomerulonephritis worldwide. There is an increased prevalence of hypertension, which is an important risk factor for progressive renal impairment, in patients with IgAN. Changes in sodium-lithium countertransport (Na/Li CT) kinetics, particularly high Vmax/Km, have been shown in familial essential hypertension. In this study a high Vmax/Km was observed in IgA probands with hypertension and/or progressive renal impairment. Mean blood pressure was higher in the first-degree relatives of patients with IgAN compared with relatives of normotensive IgAN probands. These hypertensive relatives had an increased Vmax/Vm ratio and a low Km of Na/Li CT. There is a strong correlation of Vmax/Vm (r = 0.82) between the IgA probands and their first degree relatives, suggesting strong familial factors contributing to this Na/Li CT kinetic parameter. An increased Vmax/Km ratio of Na/Li CT seems to be a better marker for familial hypertension than Km alone and may be useful in identifying those patients who are at a greater risk of developing hypertension.

Increased mononuclear cell membrane fluidity and increased B lymphocyte HLA class I expression in IgA nephropathy

BACKGROUND

The functions of membrane bound proteins are regulated by the physical properties of the cell membrane. Lymphocyte dysfunction in IgA nephropathy may therefore be related to abnormal cell membrane fluidity. In this study we have examined peripheral blood mononuclear cell membrane fluidity and the expression of HLA antigens on the surface of lymphocytes in IgA nephropathy subjects compared to normal controls and disease controls.

METHODS

Twenty-two IgA nephropathy subjects with normal or mildly elevated serum creatinine (serum creatinine

RESULTS

Fluorescence anisotropy for diphenylhexatriene of mononuclear cells from IgA nephropathy subjects was significantly lower compared to mononuclear cells from normal control subjects and disease control subjects, indicating higher membrane fluidity (median values, IgA nephropathy 0.161; normal control 0.175; disease control 0.175; P<0.001 and P<0.001). Fluorescence anisotropy for trimethylammonium-DPH was lower in the IgA nephropathy groups compared to the normal control group (median values, IgA nephropathy 0.268; normal control 0.274; P<0.001), but not significantly different compared to the disease control group (0.272). HLA class I expression on the surface of B lymphocytes was significantly higher in the IgA nephropathy group compared to the normal control and disease control groups (median values, IgA nephropathy 30364, normal control 15495; disease control 16907; P=0.0001 and P=0.002 respectively).

CONCLUSION

This study provides evidence of abnormal cell membrane architecture and increased HLA class I expression in Iga nephropathy.

Erythrocyte membrane fluidity in adult polycystic kidney disease: difference between intact cells and ghost membranes

In adult polycystic kidney disease (APCKD) the cytoskeleton of renal tubular cells is abnormal. In erythrocytes the cytoskeleton affects the fluidity of membrane lipids. The authors determined fluorescence anisotropy in intact erythrocytes and erythrocyte ghosts in 12 APCKD patients and 12 normal subjects. In APCKD whole erythrocytes had a much lower core-region anisotropy, which indicated higher membrane fluidity than normal (mean 0 center dot 175 vs. 0 center dot 224, P < 0 center dot 01). This abnormality was not detected in erythrocyte ghosts, which suggests that preparation of ghosts altered membrane lipid organization. This could be directly due to ghosting or secondary to the loss of cytoskeletal effects, which may be abnormal in APCKD.

Thiol group control of sodium-lithium countertransport kinetics in uraemia: evidence of a membrane abnormality affected by haemodialysis

Uraemia affects erythrocyte metabolism and membrane function but no consistent effect on Na/Li countertransport (CT) has been reported. We report only small differences in Na/Li CT at 150 mmol/l Na over haemodialysis, but major differences in other properties of Na/Li CT. The Km for external sodium and Vmax both increased during haemodialysis but the Vmax/Km ratio, which was greater than normal, was not affected. The thiol reagent, N-ethylmaleimide (NEM), which causes a decrease in Km and Vmax in normal subjects, had no effect on Km in the predialysis erythrocytes. After haemodialysis, the sensitivity of Na/Li CT to NEM was improved. The changes in Na/Li CT kinetics were not related to changes in membrane lipid fluidity or plasma lipids. These observations suggest that uraemia affects a thiol group that controls Na/Li CT kinetics and that haemodialysis temporarily improves this aspect of membrane function.

Increased susceptibility to membrane lipid peroxidation in renal failure

The susceptibility of membrane lipids to peroxidation in renal failure was investigated. A fluorescent polyunsaturated fatty acid probe, cis-parinaric acid, showed that mononuclear leucocytes from both chronic renal failure and haemodialysis patients had increased susceptibility to membrane lipid peroxidation compared with normal controls. The effect of oxidant stress on the physical properties of the cell membrane was also investigated by measuring fluidity with the probes diphenylhexatriene and trimethylaminodiphenylhexatriene. Oxidant stress caused a significant increase in membrane fluidity of mononuclear leucocytes from normal controls, which was greater than that seen in renal failure. The effect of oxidant stress on the physical properties of the cell membrane was not simply determined by the susceptibility of the membrane lipids to peroxidation.

Abnormal effect of thiol groups on erythrocyte Na/Li countertransport kinetics in adult polycystic kidney disease

BACKGROUND

Evidence suggests that in adult polycystic kidney disease (APCKD) there is abnormal membrane organisation that involves cytoskeletal proteins and affects ion-transport proteins. The possibility of detecting a membrane organisation defect in erythrocytes from APCKD patients was investigated.

METHODS

Na/Li countertransport (CT) kinetics were measured in erythrocytes from APCKD patients compared with normal controls. The modulation of Na/Li CT kinetics by key membrane thiol groups and by dissociation of spectrin by heating was studied.

RESULTS

In erythrocytes from APCKD compared to normal subjects the Km of Na/Li CT was lower (64 SEM 3v 90 SEM 3 mmol Na/l, P < 0.001) and Vmax/Km was higher (6.8 SEM 0.6v 5.3 SEM 0.4 (x 19(-3)), P < 0.05). In erythrocytes from normal subjects, after N-ethylmaleimide (NEM) treatment in choline medium, Km of Na/Li CT was reduced and Vmax/Km increased (59 SEM 5, 8.2 SEM 0.4 (x 10(-3)), P < 0.001) but there was no effect on these kinetic parameters in erythrocytes from APCKD. The effect of heating was similar to that of NEM in choline medium. In normal controls after NEM treatment in sodium medium both Km and Vmax were reduced whereas in APCKD Vmax was reduced but Km was unchanged.

CONCLUSIONS

In APCKD the effect of a key membrane thiol group on Na association with Na/Li CT was absent and the effect of spectrin dissociation was similarily abnormal. A second thiol group effect on the Vmax of Na/Li CT was normal. The results are consistent with a thiol-protein linked to the spectrin cytoskeleton that modulates Na/Li CT and is abnormal in APCKD.

Modification of erythrocyte Na+/Li+ countertransport kinetics by two types of thiol group

Erythrocyte Na+/Li+ countertransport activity is decreased by reagents that react with thiol groups. An understanding of the role of these groups in control of Na+/Li+ countertransport may help to explain its association with disease states. The effect of thiol reactive agents on the kinetic parameters of Na+/Li+ countertransport has not previously been described. In choline medium, N-ethylmaleimide (NEM) and iodoacetamide (IAamide) cause a rapid decrease of about 40% in Km for external sodium (Km(So)) that is complete in 10 s with a much smaller change in Vmax and an increase in the Vmax/Km ratio. In Na medium, NEM and IAamide both cause a rapid decrease in Km(So) and Vmax. With NEM the partial reduction in Vmax is complete in 100s although the NEM is sufficient to reduce Vmax up to 15 min. With IAamide the decrease in Vmax is initially slower but it continues apparently towards complete inhibition. These results indicate at least two types of thiol group controlling Na+/Li+ countertransport kinetics. The type 1 thiol reaction is Na independent and causes an increase in the apparent rate constant for Na association with the unloaded carrier so that Vmax/Km rises and Km(So) decreases. The type 2 thiol reaction is facilitated by Na at the outside ion-binding site and causes a decrease in Vmax, possibly by total blockage of carriers with IAamide but by a different mechanism with NEM such as reduced turnover rate.

Sulphydryl group control of sodium-lithium countertransport kinetics: a membrane protein control abnormality in essential hypertension

Erythrocyte sodium-lithium countertransport (SLC) is an obligatorily coupled equimolar exchange of intracellular sodium or lithium with extracellular sodium or lithium. SLC is partially inhibited by N-ethylmaleimide (NEM) but only when a transported ion (sodium of lithium) is present in the extracellular medium. In essential hypertensive patients with a strong family history of hypertension the Km of SLC for extracellular sodium was lower and Vmax tended to be higher than in normal controls, but the ratio Vmax/Km gave a much clearer distinction between the two groups. After NEM treatment, the remaining SLC activity in normal individuals had a lower Vmax and Km for sodium but Vmax/Km was not affected. In essential hypertensives the remaining SLC activity after NEM again had lowered Vmax and Km but in these patients the Vmax/Km was much lower than in untreated erythrocytes and was then the same as in normal controls. On the assumption that NEM reacts with a -SH group on a membrane protein that regulates SLC, and that the ratio Vmax/Km reflects a rate constant for binding extracellular sodium to the unloaded carrier, the results suggest that (a) essential hypertensives have an increased rate of sodium binding to the transporter and (b) this is due to abnormal behaviour of a membrane -SH group.