The relationship between CR3 deficiency and neutrophil actin assembly

Polymorphonuclear leukocytes (PMN) with a deficiency of the complement receptor type 3 (CR3) membrane glycoprotein family have impairments in the ability to adhere to surfaces as well as chemotactic and phagocytic defects, processes that require a functional contractile apparatus. PMN from the patient with neutrophil actin dysfunction (NAD) displayed similar functional characteristics to those with CR3 deficiency suggesting the two disorders may be the same disease. In order to evaluate the relationship between CR3 deficiency and actin assembly, actin filament assembly was measured in PMN from six previously reported homozygotes (two severe and four moderate CR3-deficient patients) as well as five heterozygotes for CR3 deficiency. PMN from all patients had normal unstimulated concentrations of F-actin and after exposure to the chemotactic peptide FMLP (5 x 10(-7) mol/L for 5 to 40 seconds at 25 degrees C) assembled actin normally. Pretreatment of normal PMN with concentrations of monoclonal anti-alpha CR3 antibody, capable of blocking PMN adherence, also failed to impair FMLP- induced actin filament assembly. CR3 glycoprotein expression was measured in PMNs from the mother, father, and older sister of the NAD patient (N Engl J Med 291:1093, 1974). Actin filament assembly was recently shown to be defective in PMNs from all three family members. The total concentrations of the alpha and beta CR3 subunits were below normal in PMN detergent extracts from the mother (25% of simultaneous controls) and older sister (56% of control). PMN surface expression of these two subunits was also found to be depressed (mother, 50%; older sister, 63% of control). These findings suggest these two NAD family members are heterozygote carriers for CR3 deficiency as well as NAD. Simultaneous studies of the father, however, demonstrated normal total concentrations of both the alpha and beta CR3 subunits (126% of controls) as well as normal surface expression of both subunits after phorbol myristate acetate stimulation and incubation at 37 degrees C (mean, 112% of controls) but slightly lower than normal levels after FMLP stimulation (mean, 83%). These findings indicate that CR3 deficiency generally is not associated with defective actin filament assembly and support the conclusion that NAD represents a unique kindred in which PMN actin function differs from previously reported genotypes of CR3 deficiency.     

Beta 2-integrin and L-selectin are obligatory receptors in neutrophil aggregation [see comments]

We have recently found that antibodies to L-selectin, the homing receptor on neutrophils, are as effective as those to beta 2-integrin at blocking formyl peptide-stimulated aggregation. Therefore, we investigated the requirements for expression of L-selectin and beta 2- integrin on adjacent cells during aggregation. Fluorescence flow cytometry allowed characterization of aggregates on the basis of size and color, as well as antibody binding to these two adhesive molecules. Formyl peptide-stimulated aggregate formation was measured for individual populations fluorescently labeled red (LDS-751) or green (CD44-FITC), and interpopulation red-green cell conjugates. Blocking either the beta 2-integrin or L-selectin adhesive epitope with monoclonal antibody on individual cell populations resulted in an approximately 50% reduction in two-color aggregation as compared with that in unblocked samples. Shedding the L-selectin on a cell population by preincubation with complexes of lipopolysaccharide and its plasma membrane binding protein also decreased aggregation to a control population by approximately 50%. We examined the aggregation of neutrophils from patients genetically deficient in beta 2-integrin and clinically leukocyte adhesion deficient (LAD). LAD adhesion to normal neutrophils was dependent on the expression of L-selectin on LAD cells and beta 2-integrin on normal cells. Thus, the minimum requirement for adhesion between two mixed populations of neutrophils was that one population expressed the beta 2-integrin and the other expressed the L- selectin adhesive epitope.     

Size dependent platelet subpopulations: relationship of platelet volume to ultrastructure, enzymatic activity, and function

A method for the separation of platelets on the basis of their size has been developed using counterflow centrifugation. Platelets were separated, free of plasma proteins and other cells, into seven subpopulations. The smallest-sized platelets, designated as Fraction 1, had a mean platelet volume (MPV) of 3.94 ± 0.60 μm³ (SD). Each successive fraction had a progressively larger MPV. The MPV for the largest-sized platelets, designated Fraction 7, was 8.19 ± 0.64 μm³. The MPV for the original platelets prior to fractionation was 6.57 ± 0.61 μm³. The mean density of Fraction 1 platelets was 1.067 ± 0.002 g/cm³, while Fraction 7 had a mean density of 1.072 ± 0.001 g/cm³. Transmission electron microscopy demonstrated that Fraction 1 had 4.3 ± 0.9 dense bodies per platelet, and Fraction 7 had 12.6 ± 2.4 dense bodies per platelet. Platelet LDH activity showed that the Fraction 1 platelets had 4.77 ± 0.92 iu per 10¹⁰ platelets; Fraction 7 platelets had 14.88 ± 1.23 iu per 10¹⁰ platelets. The LDH activity in the platelets before separation into subpopulations was 9.47 ± 1.45 iu per 10¹⁰ platelets.     

The Role of Stigma and Medical Mistrust in the Routine Health Care Engagement of Black Men Who Have Sex With Men

Objectives. We assessed how health care–related stigma, global medical mistrust, and personal trust in one’s health care provider relate to engaging in medical care among Black men who have sex with men (MSM).Methods. In 2012, we surveyed 544 Black MSM attending a community event. We completed generalized linear modeling and mediation analyses in 2013.Results. Twenty-nine percent of participants reported experiencing racial and sexual orientation stigma from heath care providers and 48% reported mistrust of medical establishments. We found that, among HIV-negative Black MSM, those who experienced greater stigma and global medical mistrust had longer gaps in time since their last medical exam. Furthermore, global medical mistrust mediated the relationship between stigma and engagement in care. Among HIV-positive Black MSM, experiencing stigma from health care providers was associated with longer gaps in time since last HIV care appointment.Conclusions. Interventions focusing on health care settings that support the development of greater awareness of stigma and mistrust are urgently needed. Failure to address psychosocial deterrents will stymie progress in biomedical prevention and cripple the ability to implement effective prevention and treatment strategies.The HIV epidemic is one of the most critical public health issues facing the United States today. Although HIV infections are documented among all racial/ethnic and sexual risk groups, Black men who have sex with men (Black MSM) are the most affected by HIV in the United States.1 Forty-four percent of new HIV infections are among Blacks, and the rate of HIV infection among this group is 7.9 times higher than is the rate of HIV infections among Whites. Black MSM, in particular, are diagnosed with HIV at a rate 6.0 times higher than that of White MSM, and they are 3.8 times more likely to be living with HIV than are White MSM.2 The remarkable HIV-related race/ethnicity and sexual orientation disparities observed among Black MSM require urgent attention.Although surveillance regarding HIV infection highlights increases in HIV transmission among Black MSM, in particular young Black MSM, there is considerable promise in emerging and available HIV prevention and treatment options (e.g., microbicides,3 preexposure prophylaxis,4 and treatment as prevention5). However, these approaches to HIV prevention require engagement in routine medical care and HIV treatment–related care. The use of biomedical technologies in preventing the spread of HIV will fail if those in need are not connected to care that can facilitate access to and monitor the use of these strategies.6,7Within the current HIV prevention and treatment health care landscape, it is well understood that HIV-positive Black MSM who are without engagement in care suffer worse morbidities and greater mortality than do those in care and that overall rates of engagement in care must be improved.8–10 Likewise, we know very little about the routine health care of HIV-negative Black MSM.11,12 Limited previous research has found that Black MSM describe their experiences of engaging in health care as fragmented and their health care services offered as subpar.13 The inadequate screening and treatment of sexually transmitted infection and HIV are observed even for routine sexually transmitted infection and HIV care among HIV-negative Black MSM.14 Consequently, failure to engage HIV-negative Black MSM in care results in missed opportunities to provide them with prevention options.Theoretically, there are multiple factors to consider when examining the limited retention to care that we observe among Black MSM.15–18 Notably, being uninsured or underinsured, limitations because of location and transportation, and lack of available qualified health professionals are factors directly related to access.19 However, psychosocial deterrents to care are equally important and impede health care access as well.20–23 For instance, stigma, described as the social devaluation or discrediting associated with a specific characteristic or attribute,24 and trust in health care providers and medical establishments are linked to health care behaviors.25 We focused on these psychosocial factors.Research in the area of psychosocial-related deterrents to seeking health care has highlighted the need to better understand the role of stigma in health care access26–28—in particular, the role of enacted stigma (or experiences of discrimination) in health care settings. Institutions that are mandated to protect the well-being of Black MSM are in many instances perceived as threatening to them as a result of experiencing health care provider sexual-orientation and HIV-status discrimination.29,30 Furthermore, in a review of stigma and the HIV epidemic, Mahajan et al. highlight the lack of data on measuring the effects of overlapping stigmas (in the case of Black MSM, being part of a racial and sexual orientation minority) on accessing health care.25 Not only can stigma undermine access to care, but it is also associated with longer breaks in care among those who have been linked.6,9,10 Therefore, previous research warrants an assessment of the extent to which Black MSM experience enacted stigmas and how these experiences are related to accessing medical care.Medical mistrust among Black adults has also been identified as a barrier to engaging in routine health care. Beliefs regarding mistrust in the treatment of HIV in particular are especially damaging to clinicians’ abilities to engage those in need of care.31,32 Trust in health care providers has been directly linked to health outcomes such as antiretroviral adherence and good mental health.32 However, few studies have investigated the role of medical mistrust among MSM, and limited data on Black MSM exist on this topic.33 The available literature generally presents 2 focus assessments when assessing medical mistrust: (1) a system focus assessment, that is, general trust in medical establishments; and (2) an individual focus assessment, that is, trust in a provider’s ability to offer adequate care.34–37 These concepts are thought to affect one’s likelihood of seeking out (system focus) and staying in (individual focus) care. However, research on these areas is limited and exploratory in nature.We sought to understand how experiences of health care–enacted stigma relate to accessing routine medical care among HIV-negative and HIV-positive Black MSM attending a community event in Atlanta, Georgia. Furthermore, we examined the association of this relationship with global medical mistrust and personal trust in one’s health care provider. We hypothesized that experiences of enacted health care stigma would predict routine care and that this relationship would be mediated by perceptions of medical mistrust among HIV-positive and -negative Black MSM.     

Care planning for long‐term conditions – a concept mapping

Objective

This article focuses on approaches within clinical practice that seek to actively involve patients with long‐term conditions (LTCs) and how professionals may understand and implement them. Personalized care planning is one such approach, but its current lack of conceptual clarity might have impeded its widespread implementation to date. A variety of overlapping concepts coexist in the literature, which have the potential to impair both clinical and research agendas. The aim of this article is therefore to explore the meaning of the concept of care planning in relation to other overlapping concepts and how this translates into clinical practice implementation.

Methods

Searches were conducted in the Cochrane database for systematic reviews, CINHAL and MEDLINE. A staged approach to conducting the concept mapping was undertaken, by (i) an examination of the literature on care planning in LTCs; (ii) identification of related terms; (iii) locating reviews of those terms. Retrieved articles were subjected to a content analysis, which formed the basis of our concept maps. (iv) We then appraised these against knowledge and experience of the implementation of care planning in clinical practice.

Results and Conclusions

Thirteen articles were retrieved, in which the core importance of patient‐centredness, shared decision making and self‐management was highlighted. Literature searches on these terms retrieved a further 24 articles. Our concept mapping exercise shows that whilst there are common themes across the concepts, the differences between them reflect the context and intended outcomes within clinical practice. We argue that this clarification exercise will allow for further development of both research and clinical implementation agendas.     

The GLP-1 Receptor Agonist Liraglutide Increases Myocardial Glucose Oxidation Rates via Indirect Mechanisms and Mitigates Experimental Diabetic Cardiomyopathy

BackgroundType 2 diabetes (T2D) increases risk for cardiovascular disease. Of interest, liraglutide, a therapy for T2D that activates the glucagon-like peptide-1 receptor to augment insulin secretion, reduces cardiovascular-related death in people with T2D, though it remains unknown how liraglutide produces these actions. Notably, the glucagon-like peptide-1 receptor is not expressed in ventricular cardiac myocytes, making it likely that ventricular myocardium-independent actions are involved. We hypothesized that augmented insulin secretion may explain how liraglutide indirectly mediates cardioprotection, which thereby increases myocardial glucose oxidation.MethodsC57BL/6J male mice were fed either a low-fat diet (lean) or were subjected to experimental T2D and treated with either saline or liraglutide 3× over a 24-hour period. Mice were subsequently euthanized and had their hearts perfused in the working mode to assess energy metabolism. A separate cohort of mice with T2D were treated with either vehicle control or liraglutide for 2 weeks for the assessment of cardiac function via ultrasound echocardiography.ResultsTreatment of lean mice with liraglutide increased myocardial glucose oxidation without affecting glycolysis. Conversely, direct treatment of the isolated working heart with liraglutide had no effect on glucose oxidation. These findings were recapitulated in mice with T2D and associated with increased circulating insulin levels. Furthermore, liraglutide treatment alleviated diastolic dysfunction in mice with T2D, which was associated with enhanced pyruvate dehydrogenase activity, the rate-limiting enzyme of glucose oxidation.ConclusionsOur data demonstrate that liraglutide augments myocardial glucose oxidation via indirect mechanisms, which may contribute to how liraglutide improves cardiovascular outcomes in people with T2D.