Abstract 153: The Differential Effects Of Weight Loss And Regain On Atherosclerosis

Heightened inflammation in obesity is a major contributor to many diseases, including atherosclerosis and other cardiovascular diseases (CVD). Although weight loss is extremely beneficial in improving many obesity-related conditions, weight regain worsens disease outcomes, including CVD, compared to maintenance of an obese state. Nonetheless, how weight loss promotes inflammation resolution and why weight regain worsens inflammation is poorly understood and was investigated here. Using high-fat high-cholesterol diet feeding of atherogenic mice (Ldlr deficient), we promoted weight loss after the establishment of atherosclerosis and obesity by using dietary restriction, e.g. reducing daily food consumption by 30% for 2 weeks, while maintaining hyperlipidemia. For weight regain, some mice were then given free access to food for 6 weeks. Strikingly, after 2 weeks of dietary restriction we observed atherosclerosis resolution, while weight regain accelerated disease re-progression. Single-cell analysis of visceral adipose and plaque leukocytes revealed enrichment in both tissues of a novel macrophage population with dietary restriction, which is distinguished by high expression of the antibody receptor Fcgr4, a known phagocytosis mediator. Conversely, Fcgr4 + macrophages disappeared from plaques and adipose following weight regain. Mechanistically, Fcgr4 + macrophages from the adipose tissue induced clearance of plaque necrotic core via enhanced efferocytosis. Moreover, we discovered that weight loss and regain differentially influence immune progenitors. Bone marrow (BM) transplantation showed that while weight loss and obese BM recipients had similar plaque inflammation, weight regain BM recipients had larger, more inflammatory plaques. In conclusion, our data are the first to directly show that initial weight loss promotes resolution of atherosclerosis, independently of plasma cholesterol changes and through the enrichment of specialized pro-resolving macrophages in adipose tissue that communicate with plaques. Conversely, weight regain accelerates disease progression via inflammatory reprogramming of immune progenitors.

Abstract 105: Chronic Stress Primes Innate Immune Responses In Mice And Humans

Psychological stress is associated with elevated circulating markers of inflammation, including inflammatory cytokines and acute phase reactants that accelerate progression of chronic inflammatory diseases (e.g., atherosclerosis, metabolic syndrome, autoimmune diseases and cancer). However, the mechanisms underlying inflammatory reactivity to stress and how it confers future health risk are poorly understood. Monocyte-derived macrophages play key roles in sustaining tissue inflammation, and recent studies show that they can maintain epigenetic memory of pathogen or sterile inflammatory insults, leading to a heightened inflammatory state upon secondary stimulation. We show herein that psychological stress induces transcriptomic and epigenomic reprogramming of monocytes which primes them for a heightened inflammatory immune response following challenge. Monocytes isolated from stressed mice or humans with high reported levels of psychological stress exhibit a common signature of heightened inflammatory gene expression and produce increased levels of proinflammatory cytokines upon ex vivo stimulation with Toll-like receptor ligands. RNA and ATAC sequencing studies revealed that monocytes from stressed mice and humans exhibit activation of cellular metabolic pathways, including mTOR and PI3Kinase pathways, and reduced chromatin accessibility at loci associated with mitochondrial respiration. Taken together, our findings suggest that psychological stress primes the reprogramming of innate immune cells resulting in a hyperresponsive inflammatory state, which may explain its deleterious association with inflammatory disease risk.

Silencing Myeloid Netrin-1 Induces Inflammation Resolution and Plaque Regression

Rationale: Therapeutic efforts to decrease atherosclerotic cardiovascular disease risk have focused largely on reducing atherogenic lipoproteins, yet lipid-lowering therapies alone are insufficient to fully regress plaque burden. We postulate that arterial repair requires resolution of a maladaptive immune response and that targeting factors that hinder inflammation resolution will facilitate plaque regression. Objective: The guidance molecule Ntn1 (netrin-1) is secreted by macrophages in atherosclerotic plaques, where it sustains inflammation by enhancing macrophage survival and blocking macrophage emigration. We tested whether silencing Ntn1 in advanced atherosclerosis could resolve arterial inflammation and regress plaques. Methods and Results: To temporally silence Ntn1 in myeloid cells, we generated genetically modified mice in which Ntn1 could be selectively deleted in monocytes and macrophages using a tamoxifen-induced CX3CR1-driven cre recombinase (Ntn1fl/flCx3cr1creERT2+) and littermate control mice (Ntn1fl/flCx3cr1WT). Mice were fed Western diet in the setting of hepatic PCSK9 (proprotein convertase subtilisin/kexin type 9) overexpression to render them atherosclerotic and then treated with tamoxifen to initiate deletion of myeloid Ntn1 (MøΔNtn1) or not in controls (MøWT). Morphometric analyses performed 4 weeks later showed that myeloid Ntn1 silencing reduced plaque burden in the aorta (−50%) and plaque complexity in the aortic root. Monocyte-macrophage tracing experiments revealed lower monocyte recruitment, macrophage retention, and proliferation in MøΔNtn1 compared with MøWT plaques, indicating a restructuring of monocyte-macrophage dynamics in the artery wall upon Ntn1 silencing. Single-cell RNA sequencing of aortic immune cells before and after Ntn1 silencing revealed upregulation of gene pathways involved in macrophage phagocytosis and migration, including the Ccr7 chemokine receptor signaling pathway required for macrophage emigration from plaques and atherosclerosis regression. Additionally, plaques from MøΔNtn1 mice showed hallmarks of inflammation resolution, including higher levels of proresolving macrophages, IL (interleukin)-10, and efferocytosis, as compared to plaques from MøWT mice. Conclusion: Our data show that targeting Ntn1 in advanced atherosclerosis ameliorates atherosclerotic inflammation and promotes plaque regression.

Copy number evolution in simple and complex tandem repeats across the C57BL/6 and C57BL/10 inbred mouse lines

Simple sequence tandem repeats are among the most rapidly evolving compartments of the genome. Some repeat expansions are associated with mammalian disease or meiotic segregation distortion, yet the rates of copy number change across generations are not well known. Here, we use 14 distinct sublineages of the C57BL/6 and C57BL/10 inbred mouse strains, which have been evolving independently over about 300 generations, to estimate the rates of copy number changes in genome-wide tandem repeats. Rates of change varied across repeats and across lines. Notably, CAG, whose expansions in coding regions are associated with many neurological and genetic disorders, was highly stable in copy number, likely indicating stabilizing selection. Rates of change were positively correlated with copy number, but the direction and magnitude of changes varied across lines. Some mouse lines experienced consistent losses or gains across most simple repeats, but this did not correlate with copy number changes in complex repeats. Rates of copy number change were similar between simple repeats and the more abundant complex repeats after normalization by copy number. Finally, the Y-specific centromeric repeat had a fourfold higher rate of change than the homologous centromeric repeat on other chromosomes. Structural differences in satellite complexity, or restriction to the Y chromosome and elevated mutation rates of the male germline, may explain the higher rate of change. Overall, our work underscores the mutational fluidity of long tandem arrays of repeats, and the correlations and constraints between genome-wide tandem repeats, which suggest that turnover is not a completely neutral process.

miR-33 Silencing Reprograms the Immune Cell Landscape in Atherosclerotic Plaques

[Figure: see text].

The Drosophila Y Chromosome Affects Heterochromatin Integrity Genome-Wide

The Drosophila Y chromosome is gene poor and mainly consists of silenced, repetitive DNA. Nonetheless, the Y influences expression of hundreds of genes genome-wide, possibly by sequestering key components of the heterochromatin machinery away from other positions in the genome. To test the influence of the Y chromosome on the genome-wide chromatin landscape, we assayed the genomic distribution of histone modifications associated with gene activation (H3K4me3) or heterochromatin (H3K9me2 and H3K9me3) in fruit flies with varying sex chromosome complements (X0, XY, and XYY males; XX and XXY females). Consistent with the general deficiency of active chromatin modifications on the Y, we find that Y gene dose has little influence on the genomic distribution of H3K4me3. In contrast, both the presence and the number of Y chromosomes strongly influence genome-wide enrichment patterns of repressive chromatin modifications. Highly repetitive regions such as the pericentromeres, the dot, and the Y chromosome (if present) are enriched for heterochromatic modifications in wildtype males and females, and even more strongly in X0 flies. In contrast, the additional Y chromosome in XYY males and XXY females diminishes the heterochromatic signal in these normally silenced, repeat-rich regions, which is accompanied by an increase in expression of Y-linked repeats. We find hundreds of genes that are expressed differentially between individuals with aberrant sex chromosome karyotypes, many of which also show sex-biased expression in wildtype Drosophila. Thus, Y chromosomes influence heterochromatin integrity genome-wide, and differences in the chromatin landscape of males and females may also contribute to sex-biased gene expression and sexual dimorphisms.

Inhibiting LXRα phosphorylation in hematopoietic cells reduces inflammation and attenuates atherosclerosis and obesity in mice

Atherosclerosis and obesity share pathological features including inflammation mediated by innate and adaptive immune cells. LXRα plays a central role in the transcription of inflammatory and metabolic genes. LXRα is modulated by phosphorylation at serine 196 (LXRα pS196), however, the consequences of LXRα pS196 in hematopoietic cell precursors in atherosclerosis and obesity have not been investigated. To assess the importance of LXRα phosphorylation, bone marrow from LXRα WT and S196A mice was transplanted into Ldlr^−/− mice, which were fed a western diet prior to evaluation of atherosclerosis and obesity. Plaques from S196A mice showed reduced inflammatory monocyte recruitment, lipid accumulation, and macrophage proliferation. Expression profiling of CD68⁺ and T cells from S196A mouse plaques revealed downregulation of pro-inflammatory genes and in the case of CD68⁺ upregulation of mitochondrial genes characteristic of anti-inflammatory macrophages. Furthermore, S196A mice had lower body weight and less visceral adipose tissue; this was associated with transcriptional reprograming of the adipose tissue macrophages and T cells, and resolution of inflammation resulting in less fat accumulation within adipocytes. Thus, reducing LXRα pS196 in hematopoietic cells attenuates atherosclerosis and obesity by reprogramming the transcriptional activity of LXRα in macrophages and T cells to promote an anti-inflammatory phenotype.

Voisin et al. show that reducing phosphorylation at serine 196 of LXRα (LXRα pS196) in hematopoietic cells attenuates atherosclerosis and obesity of mice fed a high-fat diet. They find that the transcriptional activity of LXRα is reprogrammed in macrophages and T cells to promote an anti-inflammatory phenotype, thus identifying a functional role of LXRα pS196 in immune cells.

Wnt signaling enhances macrophage responses to IL-4 and promotes resolution of atherosclerosis

Atherosclerosis is a disease of chronic inflammation. We investigated the roles of the cytokines IL-4 and IL-13, the classical activators of STAT6, in the resolution of atherosclerosis inflammation. Using Il4-/-Il13-/- mice, resolution was impaired, and in control mice, in both progressing and resolving plaques, levels of IL-4 were stably low and IL-13 was undetectable. This suggested that IL-4 is required for atherosclerosis resolution, but collaborates with other factors. We had observed increased Wnt signaling in macrophages in resolving plaques, and human genetic data from others showed that a loss-of-function Wnt mutation was associated with premature atherosclerosis. We now find an inverse association between activation of Wnt signaling and disease severity in mice and humans. Wnt enhanced the expression of inflammation resolving factors after treatment with plaque-relevant low concentrations of IL-4. Mechanistically, activation of the Wnt pathway following lipid lowering potentiates IL-4 responsiveness in macrophages via a PGE2/STAT3 axis.

Regulatory T Cells License Macrophage Pro-Resolving Functions During Atherosclerosis Regression

RATIONALE

Regression of atherosclerosis is an important clinical goal; however, the pathways that mediate the resolution of atherosclerotic inflammation and reversal of plaques are poorly understood. Regulatory T cells (Tregs) have been shown to be atheroprotective, yet the numbers of these immunosuppressive cells decrease with disease progression, and whether they contribute to atherosclerosis regression is not known.

OBJECTIVE

We investigated the roles of Tregs in the resolution of atherosclerotic inflammation, tissue remodeling, and plaque contraction during atherosclerosis regression.

METHODS AND RESULTS

Using multiple independent mouse models of atherosclerosis regression, we demonstrate that an increase in plaque Tregs is a common signature of regressing plaques. Single-cell RNA-sequencing of plaque immune cells revealed that unlike Tregs from progressing plaques that expressed markers of natural Tregs derived from the thymus, Tregs in regressing plaques lacked Nrp1 expression, suggesting that they are induced in the periphery during lipid-lowering therapy. To test whether Tregs are required for resolution of atherosclerotic inflammation and plaque regression, Tregs were depleted using CD25 monoclonal antibody in atherosclerotic mice during apolipoprotein B antisense oligonucleotide-mediated lipid lowering. Morphometric analyses revealed that Treg depletion blocked plaque remodeling and contraction, and impaired hallmarks of inflammation resolution, including dampening of the T helper 1 response, alternative activation of macrophages, efferocytosis, and upregulation of specialized proresolving lipid mediators.

CONCLUSIONS

Our data establish essential roles for Tregs in resolving atherosclerotic cardiovascular disease and provide mechanistic insight into the pathways governing plaque remodeling and regression of disease.

Neutrophil extracellular traps promote macrophage inflammation and impair atherosclerosis resolution in diabetic mice

Neutrophil extracellular traps (NETs) promote inflammation and atherosclerosis progression. NETs are increased in diabetes and impair the resolution of inflammation during wound healing. Atherosclerosis resolution, a process resembling wound healing, is also impaired in diabetes. Thus, we hypothesized that NETs impede atherosclerosis resolution in diabetes by increasing plaque inflammation. Indeed, transcriptomic profiling of plaque macrophages from NET+ and NET- areas in low-density lipoprotein receptor-deficient (Ldlr-/-) mice revealed inflammasome and glycolysis pathway upregulation, indicating a heightened inflammatory phenotype. We found that NETs declined during atherosclerosis resolution, which was induced by reducing hyperlipidemia in nondiabetic mice, but they persisted in diabetes, exacerbating macrophage inflammation and impairing resolution. In diabetic mice, deoxyribonuclease 1 treatment reduced plaque NET content and macrophage inflammation, promoting atherosclerosis resolution after lipid lowering. Given that humans with diabetes also exhibit impaired atherosclerosis resolution with lipid lowering, these data suggest that NETs contribute to the increased cardiovascular disease risk in this population and are a potential therapeutic target.

Single-cell analysis of fate-mapped macrophages reveals heterogeneity, including stem-like properties, during atherosclerosis progression and regression

Atherosclerosis is a leading cause of death worldwide in industrialized countries. Disease progression and regression are associated with different activation states of macrophages derived from inflammatory monocytes entering the plaques. The features of monocyte-to-macrophage transition and the full spectrum of macrophage activation states during either plaque progression or regression, however, are incompletely established. Here, we use a combination of single-cell RNA sequencing and genetic fate mapping to profile, for the first time to our knowledge, plaque cells derived from CX3CR1+ precursors in mice during both progression and regression of atherosclerosis. The analyses revealed a spectrum of macrophage activation states with greater complexity than the traditional M1 and M2 polarization states, with progression associated with differentiation of CXC3R1+ monocytes into more distinct states than during regression. We also identified an unexpected cluster of proliferating monocytes with a stem cell-like signature, suggesting that monocytes may persist in a proliferating self-renewal state in inflamed tissue, rather than differentiating immediately into macrophages after entering the tissue.

The chromatin landscape of Drosophila: comparisons between species, sexes, and chromosomes

The chromatin landscape is key for gene regulation, but little is known about how it differs between sexes or between species. Here, we study the sex-specific chromatin landscape of Drosophila miranda, a species with young sex chromosomes, and compare it with Drosophila melanogaster. We analyze six histone modifications in male and female larvae of D. miranda (H3K4me1, H3K4me3, H3K36me3, H4K16ac, H3K27me3, and H3K9me2), and define seven biologically meaningful chromatin states that show different enrichments for transcribed and silent genes, repetitive elements, housekeeping, and tissue-specific genes. The genome-wide distribution of both active and repressive chromatin states differs between males and females. In males, active chromatin is enriched on the X, relative to females, due to dosage compensation of the hemizygous X. Furthermore, a smaller fraction of the euchromatic portion of the genome is in a repressive chromatin state in males relative to females. However, sex-specific chromatin states appear not to explain sex-biased expression of genes. Overall, conservation of chromatin states between male and female D. miranda is comparable to conservation between D. miranda and D. melanogaster, which diverged >30 MY ago. Active chromatin states are more highly conserved across species, while heterochromatin shows very low levels of conservation. Divergence in chromatin profiles contributes to expression divergence between species, with ∼26% of genes in different chromatin states in the two species showing species-specific or species-biased expression, an enrichment of approximately threefold over null expectation. Our data suggest that heteromorphic sex chromosomes in males (that is, a hypertranscribed X and an inactivated Y) may contribute to global redistribution of active and repressive chromatin marks between chromosomes and sexes.

Treatment of primary nocturnal enuresis in children: a review

Primary nocturnal enuresis is a common childhood disorder. Treatment approaches bridge the psychological and medical fields. A substantial body of literature addresses the various ways of treating enuresis, from pharmaceuticals to behavioural interventions. The medical and psychological literatures have proceeded relatively independently from one another and there has been little interconnection between the US and international literatures, resulting in a lack of discourse and integration among researchers investigating treatment outcomes for enuresis. This review examined the evidence base for treatments of primary nocturnal enuresis in children. Psychological, pharmaceutical and multi-component interventions are discussed. This review sought to provide an integrated interdisciplinary and international perspective on treatment efficacy for nocturnal enuresis by expressly gathering publications from psychological and medical fields, as well as US and international sources. The literature supported the urine alarm as the most effective intervention for nocturnal enuresis and demonstrated the benefit of combining the urine alarm with other components, both behavioural and pharmaceutical. In particular, recent literature showed that the urine alarm, when used in conjunction with antidiuretic medication (i.e. desmopressin), leads to more dry nights earlier in the conditioning process. Disparities between the different literatures were discussed.

Phosphorus-limited growth of a green alga and a blue-green alga

The phosphorus-limited growth kinetics of the chlorophyte Scenedesmus quadricauda and the cyanophyte Synechococcus Nägeli were studied by using batch and continuous culturing techniques. The steady-state phosphate transport capability and the phosphorus storage capacity is higher in S. Nägeli than in S. quadricauda. Synechococcus Nägeli can also deplete phosphate to much lower levels than can S. quadricauda. These results, along with their morphological characteristics, were used to construct partial physiological profiles for each organism. The profiles indicate that this unicellular cyanophyte (cyanobacterium) is better suited for growth in phosphorus-limited oligotrophic niches than is this chlorophyte (green alga).

Sheen screen, a miniaturized most-probable-number method for enumeration of oil-degrading microorganisms

Sheen Screen is a miniaturized method for enumerating oil-degrading microorganisms. The technique relies on the ability of oil-degrading microorganisms to emulsify oil when provided as a sole carbon source in 24-well tissue culture plates. Sediments that actively respire hydrocarbons have high numbers of Sheen Screen-positive microorganisms.

Pregnancy-induced severe left ventricular systolic dysfunction in a patient with hypertrophic cardiomyopathy

This paper reports the first case of hypertrophic cardiomyopathy (HCM) that developed postpartum congestive heart failure (CHF) and severe left ventricular (LV) systolic dysfunction. Review of the literature and clinical implications are discussed.

Relationships between stem cell exhaustion, tumour suppression and ageing

Ageing is a complex process characterised by a variety of disorders associated with general organismal decline and an inability to maintain tissue homoeostasis. As described in this review, recent studies indicate that ageing may be caused, in part, by the depletion of stem and progenitor cells that govern tissue renewal. The potential causes of stem and progenitor cell attrition are numerous; however, a commonly accepted theory is that these cells are lost as a result of naturally occurring DNA damage and the obligate checkpoint responses that follow. Failure to launch appropriate responses to DNA damage is strongly associated with cancer initiation and progression. Therefore, it is at this nexus, the response to DNA damage, that an important organismal fate may be determined: to degrade regenerative potential for the purpose of preventing cancer. According to this viewpoint, ageing may be the unfortunate mark of successful cancer suppression in stem cells and other cell types. In this review, we will describe how degeneration of tissue renewal capacity links ageing and cancer suppression.

Determining the source of fecal contamination in recreational waters

Public health departments bear the responsibility for investigating recreational water-associated disease outbreaks. Tracking the source of the disease is often problematic, however, because routine monitoring of recreational waters (for bacterial counts) is not source specific. The intent of the project reported here was to monitor Escherichia coli levels in a small recreational lake in Iowa and to determine their source. The authors monitored water samples for E. coli and used phenotypic methods to analyze multiple samples of lake water, well water, and known fecal sources. Moderate to high levels of E. coli were found in lake water samples from the swimming area throughout the summer. The highest levels of E. coli were found after rainfall events in both lake water samples and samples taken from monitoring wells. Phenotypic analyses indicated that likely sources of E. coli in the lake included both human and wildlife (goose) fecal material. The authors also found that the phenotype used to characterize E. coli isolated from geese frequenting this lake could not be used to characterize E. coli isolated from geese in a neighboring watershed. Identifying the source of fecal material will help authorities implement the proper preventive measures to avoid fecal contamination of the lake in the future.

Inhibition of adherence of Mycobacterium avium complex and Mycobacterium tuberculosis to fibronectin on the respiratory mucosa

Mycobacterium species adhere to the respiratory mucosa via mucus and fibronectin of extracellular matrix exposed by damaged epithelium. We have investigated whether inhibiting adherence to fibronectin influences subsequent infection of human respiratory tissue by Mycobacterium avium complex and Mycobacterium tuberculosis. Human respiratory tissue was pretreated with mycobacterial fibronectin attachment proteins prior to infection with M. avium complex and M. tuberculosis and the number of recoverable bacteria over time was compared to untreated controls. Inhibition significantly reduced recovery of M. avium complex at 15min (P= 0.02), 7days (P = 0.04), and 14 days (P= 0.03); whereas recovery of M. tuberculosis was only reduced at 15 min (P = 0.01) and not at later timepoints. We conclude that M. avium complex and M. tuberculosis infection of the mucosa proceeds by different mechanisms, since M. tuberculosis infection is independent of fibronectin adherence.

Interaction of Mycobacterium tuberculosis with human respiratory mucosa

OBJECTIVE

Endobronchial infection is associated with pulmonary tuberculosis in the majority of cases. We have investigated the adherence of Mycobacterium tuberculosis to the human respiratory mucosa.

DESIGN

Organ cultures constructed with human tissue were infected with M. tuberculosis in the presence or absence of mycobacterial fibronectin attachment cell surface proteins and examined by scanning electron microscopy.

RESULTS

M. tuberculosis adhered mainly to extracellular matrix (ECM) in areas of mucosal damage, but not to ciliated mucosa, intact extruded cells, basement membrane or collagen fibres. Bacteria also adhered to fibrous but not globular mucus and occasionally to healthy unciliated mucosa, open tight junctions and to extruded cells that had degenerated, exposing their contents. There was a significant reduction (p<0.05) in the number of bacteria adhering to ECM after pre-incubation of bacteria with fibronectin and after pre-incubation of the tissue with M. avium fibronectin attachment protein (FAP) and M. bovis antigen 85B protein, in a concentration dependent manner. The combined effect of FAP and antigen 85B protein was significantly greater than either protein alone. Bacterial adherence to fibrous mucus was not influenced by fibronectin.

CONCLUSION

We conclude that M. tuberculosis adheres to ECM in areas of mucosal damage at least in part via FAP and antigen 85B protein.

Differential expression of the L-plastin gene in human colorectal cancer progression and metastasis

To identify molecular alterations in the progression of colorectal carcinoma, we analyzed gene expression profiles of colon cancer cell lines derived from primary and metastatic tumors from a single patient. Of 2280 cDNAs investigated using our in-house microarray, the expression of 6 genes (tumor-associated antigen L6, L-plastin, the human homologue of yeast ribosomal protein S28, the B-cell translocation gene, mitochondrial aspartate-aminotransferase, and HLA-A) increased, while that of 2 genes (keratin 5 and phosphoglucomutase) decreased in metastatic-tumor-derived cells compared with primary-tumor-derived cells. Of these genes, we assessed the L-plastin gene, an actin-bundling protein, at the protein level using a tissue microarray consisting of 58 clinically stratified colorectal cancer specimens. Consistent with our microarray results, the expression of L-plastin was significantly correlated with the progression of cancer staging. Therefore, our results suggest that the L-plastin gene is a potential metastatic marker. In addition, combining cDNA microarrays and tissue arrays, as shown here, is thought to facilitate the rapid characterization of candidate biomarkers.

C-terminal peptide of thrombospondin-1 induces platelet aggregation through the Fc receptor gamma-chain-associated signaling pathway and by agglutination

A peptide from the C-terminal domain of thrombospondin-1 (Arg-Phe-Tyr-Val-Val-Met-Trp-Lys; known as 4N1-1) has been reported to induce platelet aggregation and to bind to the integrin-associated protein (IAP), which is also known as CD47. In this study, it was discovered that 4N1-1 or its derivative peptide, 4N1K, induces rapid phosphorylation of the Fc receptor (FcR) gamma chain, Syk, SLP-76, and phospholipase C gamma2 in human platelets. A specific inhibitor of Src family kinases, 4-amino-4-(4-methylphenyl)-7-(t-butyl) pyrazola[3,4-d]pyrimidine, prevented phosphorylation of these proteins, abolished platelet secretion, and reduced aggregation by approximately 50%. A similar inhibition of aggregation to 4N1-1 was obtained in the presence of Arg-Gly-Asp-Ser in mouse platelets deficient in FcR gamma chain or SLP-76 and in patients with type I Glanzmann thrombasthenia. These results show that 4N1-1 signals through a pathway similar to that used by the collagen receptor glycoprotein (GP) VI. The alphaIIbbeta3-independent aggregation induced by 4N1-1 was also observed in fixed platelets and platelets from patients with Bernard-Soulier syndrome, which are deficient in GPIbalpha. Surprisingly, the ability of 4N1-1 to stimulate aggregation and tyrosine phosphorylation was not altered in platelets pretreated with anti-IAP antibodies and in IAP-deficient mice. These results show that the C-terminal peptide of thrombospondin induces platelet aggregation through the FcR gamma-chain signaling pathway and through agglutination. The latter pathway is independent of signaling events and does not use GPIbalpha or alphaIIbbeta3. Neither of these pathways is mediated by IAP.

Effects of writing about rape: evaluating Pennebaker's paradigm with a severe trauma

We examined the effect of disclosing to others an attempted or completed rape. Eighty-five undergraduate women who acknowledged attempted or completed rape wrote about their experience and read their narratives. In a 2 x 2 design, we examined the value of writing only factual information versus factual plus emotional information, and reading to oneself versus reading aloud to another woman. Before and 1-month after the task, symptoms of dysphoria, social anxiety and posttraumatic stress disorder were assessed. Greater detail and a moderate level of personalization in the description of the trauma were associated with decreased symptoms of dysphoria and social anxiety. Neither the nature of the writing task nor the presence of another woman predicted degree of symptom reduction.

Normal ligand binding and signaling by CD47 (integrin-associated protein) requires a long range disulfide bond between the extracellular and membrane-spanning domains

CD47 is a unique member of the Ig superfamily with a single extracellular Ig domain followed by a multiply membrane-spanning (MMS) domain with five transmembrane segments, implicated in both integrin-dependent and -independent signaling cascades. Essentially all functions of CD47 require both the Ig and MMS domains, raising the possibility that interaction between the two domains is required for normal function. Conservation of Cys residues among CD47 homologues suggested the existence of a disulfide bond between the Ig and MMS domains that was confirmed by chemical digestion and mapped to Cys(33) and Cys(263). Subtle changes in CD47 conformation in the absence of the disulfide were suggested by decreased binding of two anti-Ig domain monoclonal antibodies, decreased SIRPalpha1 binding, and reduced CD47/SIRPalpha1-mediated cell adhesion. Mutagenesis to prevent formation of this disulfide completely disrupted CD47 signaling independent of effects on ligand binding, as assessed by T cell interleukin-2 secretion and Ca(2+) responses. Loss of the disulfide did not affect membrane raft localization of CD47 or its association with alpha(v)beta(3) integrin. Thus, a disulfide bond between the Ig and MMS domains of CD47 is required for normal ligand binding and signal transduction.

Activation-enhanced alpha(IIb)beta(3)-integrin-cytoskeleton interactions outside of focal contacts require the alpha-subunit

Integrins link the cell's cytoskeleton to the extracellular matrix, as well as to receptors on other cells. These links occur not only at focal contacts but also at smaller integrin-containing protein complexes outside of focal contacts. We previously demonstrated the importance of focal contact-independent integrin-cytoskeleton interactions of beta(2) integrins: activation of adhesion resulted from a release of integrins from cytoskeletal constraints. To determine whether changes in integrin-cytoskeleton interactions were related to activation of the integrin, we used single particle tracking to examine focal contact-independent cytoskeletal associations of alpha(IIb)beta(3)-integrin, in which activation results in a large conformational change. Direct activation of alpha(IIb)beta(3) by mutation did not mimic activation of lymphocytes with phorbol ester, because it enhanced integrin-cytoskeleton interactions, whereas activation of lymphocytes decreased them. Using additional integrin mutants, we found that both alpha- and beta-cytoplasmic domains were required for these links. This suggests that 1) both beta(2)- and beta(3)-integrins interact with the cytoskeleton outside of focal contacts; 2) activation of a cell and activation of an integrin are distinct processes, and both can affect integrin-cytoskeleton interactions; and 3) the role of the alpha-subunit in integrin-cytoskeleton interactions in at least some circumstances is more direct than generally supposed.

The role of complement receptor 3 (CR3) in Neisseria gonorrhoeae infection of human cervical epithelia

Neisseria gonorrhoeae is an important sexually transmitted pathogen and a major cofactor in HIV-1 infection. This organism uses different mechanisms to infect male and female genital tract epithelia. Receptor-mediated endocytosis of N. gonorrhoeae is the principle mechanism of entry into male urethral epithelial cells. Infection in men leads to a pronounced inflammatory response. In contrast, N. gonorrhoeae infection in women induces ruffling of the cervical epithelia, allowing a macropinocytic mechanism of entry. Infection in women is frequently asymptomatic, suggesting suppression of the inflammatory response. N. gonorrhoeae-induced membrane ruffling and inflammation suppression are consistent with the ability of this bacterium to enter cervical epithelial cells, in vitro and in vivo, by interaction with complement receptor 3 (CR3), a receptor that does not trigger an inflammatory response. This receptor is present on cervical epithelial cells but not on male urogenital tract epithelia. N. gonorrhoeae engagement of CR3 initiates a unique mechanism of bacterial-induced membrane ruffling and internalization. These studies explain why the pathology of N. gonorrhoeae infection differs between males and females. Additionally, the observation that this receptor is present on cervical epithelia may provide insight into the pathogenesis of other sexually transmitted pathogens.

Bidirectional negative regulation of human T and dendritic cells by CD47 and its cognate receptor signal-regulator protein-alpha: down-regulation of IL-12 responsiveness and inhibition of dendritic cell activation

Proinflammatory molecules, including IFN-gamma and IL-12, play a crucial role in the elimination of causative agents. To allow healing, potent anti-inflammatory processes are required to down-regulate the inflammatory response. In this study, we first show that CD47/integrin-associated protein, a ubiquitous multispan transmembrane protein highly expressed on T cells, interacts with signal-regulator protein (SIRP)-alpha, an immunoreceptor tyrosine-based inhibition motif-containing molecule selectively expressed on myelomonocytic cells, and next demonstrate that this pair of molecules negatively regulates human T and dendritic cell (DC) function. CD47 ligation by CD47 mAb or L-SIRP-alpha transfectants inhibits IL-12R expression and down-regulates IL-12 responsiveness of activated CD4(+) and CD8(+) adult T cells without affecting their response to IL-2. Human CD47-Fc fusion protein binds SIRP-alpha expressed on immature DC and mature DC. SIRP-alpha engagement by CD47-Fc prevents the phenotypic and functional maturation of immature DC and still inhibits cytokine production by mature DC. Finally, in allogeneic MLR between mDC and naive T cells, CD47-Fc decreases IFN-gamma production after priming and impairs the development of a Th1 response. Therefore, CD47 on T cells and its cognate receptor SIRP-alpha on DC define a novel regulatory pathway that may be involved in the maintenance of homeostasis by preventing the escalation of the inflammatory immune response.

Ventricular free wall rupture in acute myocardial infarction

Despite a progressive reduction in acute myocardial infarction mortality over the years, death related to ventricular free wall rupture has not changed. This is mostly related to the catastrophic presentation and death within minutes in the majority of these patients. Once rupture is suspected, bedside echocardiography should be performed immediately, followed by pericardiocentesis and repair of the rupture site as quickly as possible. Measures to prevent cardiac rupture include the administration of beta-blockers and angiotensin-converting enzyme inhibitors unless contraindications exist, and the avoidance of steroidal and nonsteroidal anti-inflammatory agents such as ibuprofen and indomethacin.

A remarkable medical story: benefits of angiotensin-converting enzyme inhibitors in cardiac patients

The development of angiotensin-converting enzyme inhibitors (ACE inhibitors) has been one of the most remarkable stories in the treatment of cardiovascular diseases. Angiotensin converting enzyme inhibitors have several acute and sustained hemodynamic effects that are beneficial in the presence of left ventricular (LV) dysfunction. They increase cardiac output and stroke volume and reduce systemic vascular resistance as well as pulmonary capillary wedge pressure. The hemodynamic benefits are associated with improvement in the signs and symptoms of congestive heart failure (CHF) as well as decreased mortality, regardless of the severity of CHF. In patients with asymptomatic LV dysfunction, therapy with ACE inhibitors prevented the development of CHF and reduced hospitalization and cardiovascular death. They also increase survival when administered early after an acute myocardial infarction (MI). Most recently, ACE inhibition was associated with improved clinical outcomes in a broad spectrum of high-risk patients with preserved LV function. The mechanism of ACE inhibitors benefits is multifactorial and includes prevention of progressive LV remodeling, prevention of sudden death and arrhythmogenicity and structural stability of the atherosclerotic process. Evidence suggests that ACE inhibitors are underutilized in patients with cardiovascular diseases. Efforts should be directed to prescribe ACE inhibitors to appropriate patients in target doses. It is reasonable to believe that ACE inhibitors have a class effect in the management of LV dysfunction with or without CHF and acute MI. Whether the same is true for ACE inhibitors in the prevention of ischemic events is not known yet.

L-plastin peptide activation of alpha(v)beta(3)-mediated adhesion requires integrin conformational change and actin filament disassembly

L-plastin (LPL) is a leukocyte actin binding protein previously implicated in the activation of the integrin alpha(M)beta(2) on polymorphonuclear neutrophils. To determine the role for LPL in integrin activation, K562 cell adhesion to vitronectin via alpha(v)beta(3), a well-studied model for activable integrins, was examined. Cell permeant versions of peptides based on the N-terminal sequence of LPL and the LPL headpiece domain both activated alpha(v)beta(3)-mediated adhesion. In contrast to adhesion induced by treatment with phorbol 12-myristate 13-acetate (PMA), LPL peptide-activated adhesion was independent of integrin beta(3) cytoplasmic domain tyrosines and was not inhibited by cytochalasin D. Also in contrast to PMA, LPL peptides synergized with RGD ligand or Mn(2+) for generation of a conformational change in alpha(v)beta(3) associated with the high affinity state of the integrin, as determined by binding of a ligand-induced binding site antibody. Although LPL and ligand showed synergy for ligand-induced binding site expression when actin depolymerization was inhibited by jasplakinolide, LPL peptide-induced adhesion was inhibited. Thus, both actin depolymerization and ligand-induced integrin conformational change are required for LPL peptide-induced adhesion. We hypothesize that the critical steps of increased integrin diffusion and affinity enhancement may be linked via modulation of the function of the actin binding protein L-plastin.

Target outcomes for long-term oral health care in dementia: a Delphi approach

This study developed a list of target outcomes for long-term oral health care in persons with dementia. A three-round Delphi study was used to develop a list of target outcomes. Participants included 99 staff and 171 family members associated with the Dementia Special Care Unit in Bedford, MA. In Round 1 participants were asked to list five outcomes for long-term oral health care. Items were grouped, redundancies removed, and fed back in Round 2, when participants scored the items from 1 (least important) to 10 (most important). Round 2 responses were tabulated and the top 20 were fed back for scoring in Round 3. The top 10 target outcomes in decreasing order of importance were: patient will be free from oral pain, patient will not be at risk for aspiration, emergency dental treatment will be available when needed, prevent mouth infections, daily mouth care is as much a part of daily care as shaving or brushing hair, prevent discomfort from loose teeth or sore gums, teeth will be brushed thoroughly once a day, staff will be able to provide oral hygiene care as needed, provide dental care to prevent problems eating, and recognize oral problems early. Family and professional caregivers were remarkably consistent in their identification of the top 10 outcomes. Further work is needed to ensure broad international and interdisciplinary acceptance (including families and the long-term care residents themselves) of target outcomes for long-term oral health care in persons with dementia.

Renal artery stenosis in minority patients undergoing diagnostic cardiac catheterization: prevalence and risk factors

BACKGROUND

Atherosclerotic renal artery stenosis (RAS) is a frequently overlooked clinical entity that can cause progressive renal failure and uncontrolled hypertension. Revascularization of a stenosed renal artery is associated with improved clinical outcomes including the prevention of renal failure. Thus, it is important to recognize all potential candidates for renal artery revascularization. In a general population referred for diagnostic cardiac catheterization, RAS of any severity was found in 30% of patients and significant stenosis (> or = 50% diameter narrowing) was found in 15% of patients. The number of minority groups is increasing in the US population, and RAS in this population is not well investigated. Our purpose was to determine the prevalence and risk factors associated with RAS in minority patients referred for diagnostic cardiac catheterization.

METHODS

Abdominal aortography was performed in 171 consecutive minority patients referred for diagnostic cardiac catheterization (hispanics = 115, African Americans = 56). The association of clinical and angiographic variables with RAS was examined using univariate and multivariate logistic regression analyses.

RESULTS

Renal artery stenosis of any severity was identified in 13.5% of patients (unilateral 7.7%, bilateral 5.8%). Significant RAS was found in 7.7% of patients (unilateral 4.8%, bilateral 2.9%). Independent predictors of RAS included age (mean +/-1SD, 68 +/-10 vs 57 +/-12 yr, P < 0.001, for patients with vs without RAS), coronary artery disease, and elevated serum creatinine levels (> 115 micromol/L). Race/ethnicity (hispanics vs African Americans), sex, smoking, congestive heart failure, diabetes mellitus, peripheral vascular disease, and hypertension were not independent predictors.

CONCLUSIONS

Renal artery stenosis in minority patients undergoing diagnostic cardiac catheterization is less common than reported in white patients, is similar in hispanics and African Americans, and is similar in women and men. The clinical and angiographic features are helpful in predicting its presence.

Early exercise after experimental myocardial infarction: effect on left ventricular remodeling

BACKGROUND

The effect of exercise on left ventricular remodeling after myocardial infarction is unclear. The purpose of this investigation was to test whether exercise undertaken during the healing phase of an acute myocardial infarction has an adverse effect on left ventricular remodeling.

METHODS

Before surgery, rats (n = 94) were allocated randomly to one of four groups: 1) infarct, swimming exercise; 2) infarct, no exercise; 3) sham operation, swimming exercise; 4) sham operation, no exercise. Beginning 1 week after infarction or sham operation, the rats in the exercise groups swam twice daily for 2 weeks. After a deconditioning period of 5 days, the rats were re-anesthetized, hemodynamic measurements were made, and the hearts were fixed for morphometric analysis.

RESULTS

Swimming exercise had no effect on remodeling of infarcted myocardium. Rats with infarcts in the swimming and no exercise groups had similar infarct thicknesses (1.1 +/- 0.2 mm and 0.8 +/- 0.2 mm respectively; NS), and similar degrees of infarct expansion (expansion index 1.2 +/- 0.3 and 1.4 +/- 0.3 respectively; NS). Swimming exercise also had no effect on remodeling of non-infarcted myocardium. Left ventricular volumes and pressure-volume relationships were similar in exercised and non-exercised infarcted rats.

CONCLUSION

In rats, 2 weeks of swimming exercise, started 1 week after acute experimental myocardial infarction and followed by 5 days of deconditioning, does not have an adverse effect on left ventricular remodeling.

Early angiotensin converting enzyme inhibitor therapy after experimental myocardial infarction prevents left ventricular dilation by reducing infarct expansion: a possible mechanism of clinical benefits

OBJECTIVE

To examine the effects of early angiotensin-converting enzyme (ACE) inhibitor therapy after myocardial infarction on infarct expansion in an experimental rat model.

BACKGROUND

ACE inhibitor therapy within 24 h of acute myocardial infarction (AMI) reduces mortality by unknown mechanism(s).

METHODS

Rats underwent permanent coronary artery occlusion. A treated group received enalapril (1.9+/-0.2 mg/kg) daily in drinking water beginning 2 h after coronary artery occlusion, a time too late to reduce infarct size. Rats were sacrificed 2 days or 2 weeks after myocardial infarction. Hearts were arrested and fixed at a constant pressure, then sectioned and photographed for morphometric analysis.

RESULTS

Infarcts in the control group expanded between 2 days and 2 weeks after myocardial infarction (expansion index 0.7+/-0.1 versus 2.5+/-0.4, P< 0.05). However, infarct expansion remained unchanged in the enalapril group between 2 days and 2 weeks after myocardial infarction (expansion index 0.8+/-0.1 versus 1.3+/-0.1, NS). Two weeks after myocardial infarction, the enalapril group had fewer expanded infarcts than the control group (expansion index 1.3+/-0.1 versus 2.5+/-0.4, P< 0.05). While left ventricular volume increased in the control group between 2 days and 2 weeks after myocardial infarction (0.17+/-0.01 ml versus 0.36+/-0.03 ml, P< 0.05), it remained constant in the enalapril group (0.22+/-0.02 ml versus 0.25+/-0.03 ml, NS). Two weeks after myocardial infarction, the left ventricles were larger in the control group than in the enalapril group (0.36+/-0.03 ml versus 0.25+/-0.03 ml, P< 0.05).

CONCLUSIONS

Treatment with enalapril initiated 2 h after AMI prevented left ventricular dilation by limiting infarct expansion. This may explain the mechanism by which ACE inhibitor therapy started within 24 h of an AMI improves survival 5-6 weeks after infarction.

Membrane raft association of CD47 is necessary for actin polymerization and protein kinase C theta translocation in its synergistic activation of T cells

CD47 is a ubiquitously expressed membrane protein with an extracellular Ig domain and a multiple membrane-spanning domain that can synergize with antigen to induce interleukin (IL)-2 secretion by T lymphocytes. Ligation of CD47 induced actin polymerization and increased protein kinase Ctheta (PKCtheta) association with the cytoskeleton independent of antigen receptor ligation, but ligation of mutant forms of the molecule missing either the Ig domain or the multiple membrane-spanning domain did not. Simultaneous ligation of CD47 and CD3 led to additive effects on F-actin and synergistic effects on PKCtheta cytoskeletal association. Disruption of membrane rafts by removal of cholesterol with cyclodextrin blocked CD47-induced actin polymerization, and mutant forms of CD47 that localized poorly to rafts failed to effect cytoskeletal rearrangement. However, raft association alone was not sufficient, because a raft-localized CD47 Ig domain bound to the membrane by a glycan phosphoinositol anchor was unable to induce actin polymerization. A mutant form of CD47 without its Ig domain that did not induce actin polymerization or localize to rafts still enhanced T cell receptor (TCR)-dependent tyrosine phosphorylation of PLCgamma and associated Ca(2+) signaling but did not augment IL-2 secretion. Thus, CD47 synergy with TCR to increase [Ca(2+)](i) is independent of actin and rafts but is insufficient to explain CD47 cooperation with TCR in IL-2 synthesis. Full synergy with TCR requires CD47 localization to membrane rafts where ligation leads to TCR-independent signals causing actin polymerization and PKCtheta translocation.

Integrin-associated protein (CD47) and its ligands

Integrin-associated protein (IAP or CD47) is a receptor for thrombospondin family members, a ligand for the transmembrane signaling protein SIRP alpha and a component of a supramolecular complex containing specific integrins, heterotrimeric G proteins and cholesterol. Peptides containing a VVM motif in the C-terminal domain of thrombospondins are agonists for CD47, initiating heterotrimeric Gi protein signaling that augments the functions of integrins of the beta 1, beta 2 and beta 3 families, thus modulating a range of cell activities including platelet activation, cell motility and adhesion, and leukocyte adhesion, migration and phagocytosis.

Integrin-associated protein (CD47/IAP) contributes to T cell arrest on inflammatory vascular endothelium under flow

Integrin-associated protein (CD47/IAP) is a pentaspan molecule that regulates integrin functions. We prepared a CD47-deficient Jurkat T cell line to assess its role in the arrest of T cells on inflammatory endothelium. Under flow conditions, constitutive arrest of CD47-deficient cells is strongly decreased as compared to the original cell line, whereas reexpression of CD47 reestablishes their ability to stop. Moreover, cells transfected with a chimera made with the extracellular portion of CD47 and the transmembrane domain of CD7 or several truncated forms of CD47 show that the first transmembrane domain and a short cytoplasmic loop are sufficient for this process. CD47 effect is indirect and depends mainly on the alpha4beta1/VCAM-1 pathway, as shown by blocking antibodies. We detected on endothelium the two CD47 counter receptors known to date: thrombospondin and SIRP1alpha. Blocking experiments show that both are involved. Overall, CD47 participates in the constitutive arrest of T lymphocytes on inflamed vascular endothelium by up-regulating alpha 4beta1 integrins.

The hormone resistin links obesity to diabetes

Diabetes mellitus is a chronic disease that leads to complications including heart disease, stroke, kidney failure, blindness and nerve damage. Type 2 diabetes, characterized by target-tissue resistance to insulin, is epidemic in industrialized societies and is strongly associated with obesity; however, the mechanism by which increased adiposity causes insulin resistance is unclear. Here we show that adipocytes secrete a unique signalling molecule, which we have named resistin (for resistance to insulin). Circulating resistin levels are decreased by the anti-diabetic drug rosiglitazone, and increased in diet-induced and genetic forms of obesity. Administration of anti-resistin antibody improves blood sugar and insulin action in mice with diet-induced obesity. Moreover, treatment of normal mice with recombinant resistin impairs glucose tolerance and insulin action. Insulin-stimulated glucose uptake by adipocytes is enhanced by neutralization of resistin and is reduced by resistin treatment. Resistin is thus a hormone that potentially links obesity to diabetes.

A family of tissue-specific resistin-like molecules

We have identified a family of resistin-like molecules (RELMs) in rodents and humans. Resistin is a hormone produced by fat cells. RELMalpha is a secreted protein that has a restricted tissue distribution with highest levels in adipose tissue. Another family member, RELMbeta, is a secreted protein expressed only in the gastrointestinal tract, particularly the colon, in both mouse and human. RELMbeta gene expression is highest in proliferative epithelial cells and is markedly increased in tumors, suggesting a role in intestinal proliferation. Resistin and the RELMs share a cysteine composition and other signature features. Thus, the RELMs together with resistin comprise a class of tissue-specific signaling molecules.

Late coronary artery reperfusion has additive beneficial effects on infarct expansion when combined with early angiotensin converting enzyme inhibitor therapy post myocardial infarction

BACKGROUND

Individually, late coronary artery reperfusion and early angiotensin converting enzyme (ACE) inhibitor therapy prevent infarct expansion post myocardial infarction (MI).

OBJECTIVES

To examine the effect of late reperfusion on infarct expansion when added to early ACE inhibitor therapy post MI.

METHODS

Rats were randomized into two groups: Reperfusion group: rats underwent coronary artery occlusion followed by reperfusion 2 hours after MI, a time too late to reduce infarct size. A control group: rats underwent permanent coronary artery occlusion followed by a sham operation 2 hours after MI. All rats received enalapril (2.0 +/- 0.2 mg/kg) daily in drinking water, started immediately after the second operation. Rats were sacrificed 2 weeks after coronary occlusion. Hearts were arrested and fixed at a constant pressure, then sectioned and photographed for morphometric analysis.

RESULTS

Infarct size was similar in the reperfusion and control groups (23 +/- 2 vs 26 +/- 2%, p = NS). Septal thickness was also similar in both groups (1.8 +/- 0.1 vs 1.8 +/- 0.1 mm, p = NS). There was a trend towards thicker infarcts in the reperfusion group compared to the control group (0.84 +/- 0.06 vs 0.72 +/- 0.05 mm, p = 0.1). Compared to early ACE inhibition alone, late reperfusion combined with early ACE inhibition limited infarct expansion (expansion index, 1.13 +/- 0.12 vs 1.44 +/- 0.14, p < 0.05), prevented left ventricular (LV) dilation (LV volume, 0.30 +/- 0.02 vs 0.39 +/- 0.03 ml, p < 0.01) and prevented LV hypertrophy (LV weight, 0.71 +/- 0.18 vs 0.77 +/- 0.20 gm, p < 0.05).

CONCLUSIONS

Late coronary artery reperfusion prevents infarct expansion, LV dilation and hypertrophy even when added to early ACE inhibitor therapy post MI. This suggests that late reperfusion may be beneficial in patients with acute MI treated with early ACE inhibitor therapy.

CD47, a ligand for the macrophage fusion receptor, participates in macrophage multinucleation

The macrophage fusion receptor (MFR), also called P84/BIT/SIRPalpha/SHPS-1, is a transmembrane glycoprotein that belongs to the superfamily of immunoglobulins. Previously, we showed that MFR expression is highly induced at the onset of fusion in macrophages, and that MFR appears to play a role in macrophage-macrophage adhesion/fusion leading to multinucleation. The recent finding that IAP/CD47 acts as a ligand for MFR led us to hypothesize that it interacts with CD47 at the onset of cell-cell fusion. CD47 is a transmembrane glycoprotein, which, like MFR, belongs to the superfamily of immunoglobulins. We show that macrophages express the hemopoietic form of CD47, the expression of which is induced at the onset of fusion, but to a lower level than MFR. A glutathione S-transferase CD47 fusion protein engineered to contain the extracellular domain of CD47, binds macrophages, associates with MFR, and prevents multinucleation. CD47 and MFR associate via their amino-terminal immunoglobulin variable domain. Of the nine monoclonal antibodies raised against the extracellular domain of CD47, three block fusion, as well as MFR-CD47 interaction, whereas the others have no effect. Together, these data suggest that CD47 is involved in macrophage multinucleation by virtue of interacting with MFR during adhesion/fusion.

The role of Mycobacterium avium complex fibronectin attachment protein in adherence to the human respiratory mucosa

Mycobacterium avium complex (MAC) are opportunistic respiratory pathogens that infect non-immunocompromised patients with established lung disease, although they can also cause primary infections. The ability to bind fibronectin is conserved among many mycobacterial species. We have investigated the adherence of a sputum isolate of MAC to the mucosa of organ cultures constructed with human tissue and the contribution of M. avium fibronectin attachment protein (FAP) to the process. MAC adhered to fibrous, but not globular mucus, and to extracellular matrix (ECM) in areas of epithelial damage, but not to intact extruded cells and collagen fibres. Bacteria occasionally adhered to healthy unciliated epithelium and to cells that had degenerated exposing their contents, but never to ciliated cells. The results obtained with different respiratory tissues were similar. Two ATCC strains of MAC gave similar results. There was a significant reduction (P < 0.05) in the number of bacteria adhering to ECM after preincubation of bacteria with fibronectin and after preincubation of the tissue with M. avium FAP in a concentration-dependant manner. The number of bacteria adhering to fibrous mucus was unchanged. Immunogold labelling demonstrated fibronectin in ECM as well as in other areas of epithelial damage, but only ECM bound FAP. A Mycobacterium smegmatis strain had the same pattern of adherence to the mucosa as MAC. When the FAP gene was deleted, the strain demonstrated reduced adherence to ECM, and adherence was restored when the strain was transfected with an M. avium FAP expression construct. We conclude that MAC adheres to ECM in areas of epithelial damage via FAP and to mucus with a fibrous appearance via another adhesin. Epithelial damage exposing ECM and poor mucus clearance will predispose to MAC airway infection.

Comprehensive STD/HIV prevention education targeting US adolescents: review of an ethical dilemma and proposed ethical framework

Adolescents are increasingly at risk for sexually transmitted diseases (STDs), including human immunodeficiency virus (HIV) infection. The prolonged latency period, sometimes in excess of five years, and the incubation period of up to 10 years before the manifestation of symptoms, may foster adolescents' false sense of invincibility and denial as they often do not see the devastating effects of the disease in their peers until they are older. In turn, their practice of safer sex may be hindered and thereby contribute to the escalation of this public health crisis among sexually active adolescents. Prevention-focused recommendations were made in the USA as a result of this crisis. Recommendations were made to: (1) include STD/HIV education in the curricula of grades kindergarten to 12; (2) increase to at least 75% the proportion of primary care and mental health professionals who provide age-appropriate STD/HIV prevention counselling to adolescents; and (3) expand HIV prevention services to include age-appropriate HIV education curricula for students in grades 4-12 in 95% of schools. Yet, in the USA, the provision of school-based comprehensive STD/HIV education has been difficult to achieve owing to certain limitations and, in some instances, legal action. These limitations include: limited student access; restricted content; and the implementation of sporadic and/or brief educational programmes. Given these recommendations and the fact that adolescents are acquiring STDs and HIV infections at increasing rates, and despite the limitations and legal actions, do health care professionals not have an ethical obligation to provide adolescents with comprehensive STD/HIV prevention education? This ethical dilemma will be discussed using the ethical decision-making principles of 'autonomy' and 'beneficence', and a decision-making model proposed by Thompson and Thompson, and by Chally and Loric.

Late coronary artery reperfusion: benefits and mechanisms

In patients with acute myocardial infarction (AMI), coronary artery reperfusion beyond 4 to 6 h after the onset of symptoms is believed to have little or no effect on infarct size. However, benefits have been demonstrated even when reperfusion is performed late and without significant myocardial salvage. Late reperfusion prevents infarct expansion and left ventricular remodelling. The mechanism is multifactorial and partially related to salvage of small islets of still viable myocytes within the scar. Other benefits of late reperfusion are electrical stability and prevention of arrhythmias. The survival benefits of reperfusion are strongly dependent on the time after the onset of symptoms until treatment (better outcomes are obtained with earlier reperfusion). Based on the demonstration of a significant reduction in mortality, the current practice is to perform reperfusion up to 12 h after the onset of symptoms. The survival benefits of reperfusion performed 13 to 24 h after the onset of AMI are less certain; however, large AMIs, particularly anterior infarcts, have the maximum risk of remodelling. Thus, benefits of reperfusion on left ventricular remodelling, arrhythmogenicity and prevention of congestive heart failure justify reperfusion in this group of patients up to 24 h after the onset of symptoms.

African American grandmothers' perceptions of caregiver concerns associated with rearing adolescent grandchildren

In 1996, grandparents were the sole providers of care for 269,000 grandchildren. Research findings indicate that grandmothers are usually the primary caretakers of grandchildren. Previous issues associated with raising grandchildren vary, but usually relate to the grandparents' health, financial concerns, or lack of social support. This qualitative descriptive study was designed to describe African American grandmothers' perceptions about the burdens of raising adolescent grandchildren. Using this approach, the researchers were able to study the richness and diversity of the grandmothers' perceptions. Data were collected from 35 grandmothers through a focus group (n = 7) and during a 4-day intervention research study (n = 28) entitled "Grandmother-Grandchild Health Promotion Program." Numerous concerns were voiced by both groups, but those stated most frequently were associated with the well-being of grandchildren (grandchildren's sexual behavior, potential drug use, and potential risk of encountering violence) and relational conflicts with adult children. Unexpected findings were the absence of stated concerns associated with the grandmothers' financial situation or health. Recommendations for intervention, clinical practice, and research are discussed.