Efeitos do óleo de coco na doença de Alzheimer: uma revisão de literatura / Effects of coconut oil on Alzheimer's disease: a literature review

A doença de Alzheimer (DA), é uma enfermidade neurodegenerativa que possui como principal característica a perda progressiva das funções cognitivas, afetando milhões de pessoas no mundo. Nesse sentido, existem contínuas buscas por ferramentas terapêuticas que atuem na prevenção e no tratamento da doença. Além disso, pesquisas com a utilização do óleo de coco como ferramenta terapêutica demonstraram um potente efeito anti-inflamatório dessa substância. Dessa forma, foi elaborada uma revisão bibliográfica para investigar os possíveis efeitos do óleo de coco relacionados à DA. O presente artigo trata-se de uma revisão bibliográfica utilizando as bases: PubMed, Science Direct, SciELO e LILACS. A partir da busca com descritores específicos, foram incluídos estudos referentes aos últimos cinco anos, publicados em inglês, português e espanhol com dados pré-clínicos e clínicos. Os estudos pré-clínicos incluídos demonstraram que o óleo de coco interfere inibindo vias metabólicas importantes que atuam na promoção da neuroinflamação, na formação de placas amiloides, no desbalanço de neurotransmissores e na dinâmica de vias de sinalização. Além disso, o uso do óleo de coco aumentou os níveis de corpos cetônicos. De certa forma, muitos ensaios clínicos já se mostraram favoráveis ao uso de óleo de coco como adjuvante no tratamento da DA. Contudo, ainda são necessários mais estudos clínicos randomizados e controlados que avaliem a dosagem ideal, bem como a eficácia ou não do óleo de coco contra a doença de Alzheimer.

Alzheimer's disease (AD) is a neurodegenerative disease whose main characteristic is the progressive loss of cognitive functions, affecting millions of people worldwide. In this sense, there is a continuous search for therapeutic tools that act in the prevention and treatment of the disease. In addition, research using coconut oil as a therapeutic tool has demonstrated a potent anti-inflammatory effect of this substance. Thus, a literature review was conducted to investigate the possible effects of coconut oil on AD. This article is a literature review using the PubMed, Science Direct, SciELO and LILACS databases. From the search with specific descriptors, studies were included referring to the last five years, published in English, Portuguese and Spanish with pre-clinical and clinical data. The included preclinical studies demonstrated that coconut oil interferes by inhibiting important metabolic pathways that act in the promotion of neuroinflammation, amyloid plaque formation, neurotransmitter imbalance, and signaling pathway dynamics. In addition, the use of coconut oil increased the levels of ketone bodies. To some extent, many clinical trials have already shown favorable support for the use of coconut oil as an adjuvant in the treatment of AD. However, there is still a need for more randomized, controlled clinical trials that evaluate the optimal dosage, as well as whether or not coconut oil is effective against Alzheimer's disease.

Effect of the Aqueous Extract of Chrysobalanus icaco Leaves on Maternal Reproductive Outcomes and Fetal Development in Wistar Rats.

Toxicological studies on medicinal plants are essential to ensure their safety and effectiveness in treating various diseases. Despite the species Chrysobalanus icaco L. being popularly used in the treatment of several diseases due to the pharmacological properties of its bioactive compounds, there are few studies in the literature regarding its toxicity regarding reproduction. Therefore, the purpose of this study was to assess the potential embryotoxic and teratogenic effects of the aqueous extract of C. icaco leaves (AECi) on Wistar rats. Animals were given AECi at doses of 100, 200, and 400 mg/kg during the pre-implantation and organogenesis periods. Data were analyzed using ANOVA followed by Tukey's test and Kruskal-Wallis. Pregnant rats treated during the pre-implantation period showed no signs of reproductive toxicity. Rats that received AECi at 100, 200, and 400 mg/kg during organogenesis did not exhibit any signs of maternal systemic toxicity or significant differences in gestational and embryotoxic parameters. Some skeletal changes were observed in the treated groups. Therefore, it can be suggested that AECi at doses of 100, 200, and 400 mg/kg is safe for treated animals and does not induce reproductive toxicity under the experimental conditions applied, but it also caused low systemic toxicity.

The Use of Proteins, Lipids, and Carbohydrates in the Management of Wounds.

Despite the fact that skin has a stronger potential to regenerate than other tissues, wounds have become a serious healthcare issue. Much effort has been focused on developing efficient therapeutical approaches, especially biological ones. This paper presents a comprehensive review on the wound healing process, the classification of wounds, and the particular characteristics of each phase of the repair process. We also highlight characteristics of the normal process and those involved in impaired wound healing, specifically in the case of infected wounds. The treatments discussed here include proteins, lipids, and carbohydrates. Proteins are important actors mediating interactions between cells and between them and the extracellular matrix, which are essential interactions for the healing process. Different strategies involving biopolymers, blends, nanotools, and immobilizing systems have been studied against infected wounds. Lipids of animal, mineral, and mainly vegetable origin have been used in the development of topical biocompatible formulations, since their healing, antimicrobial, and anti-inflammatory properties are interesting for wound healing. Vegetable oils, polymeric films, lipid nanoparticles, and lipid-based drug delivery systems have been reported as promising approaches in managing skin wounds. Carbohydrate-based formulations as blends, hydrogels, and nanocomposites, have also been reported as promising healing, antimicrobial, and modulatory agents for wound management.

Perspectives of nurse preceptors on a web-based clinical pedagogy program and clinical teaching: A descriptive qualitative study.

Nurse preceptors are key stakeholders in providing quality clinical education. This study aimed to explore the perspectives of nurse preceptors on a web-based clinical pedagogy program and clinical teaching. A descriptive qualitative design was adopted. The program was made accessible to the nurse preceptors who were assigned nursing students from July 2019 to June 2020. Upon completion of clinical teaching, a total of 19 nurse preceptors participated in four focus group discussions. The discussions were audio recorded and transcribed verbatim, and thematic analysis was conducted. Five themes, with 11 subthemes, emerged: (i) Undergoing the process of self-awareness and development; (ii) Mastering newly acquired skills to refine own teaching approach; (iii) Implementing consistent evaluation and constructive feedback; (iv) Dual roles and responsibilities of preceptor; and (v) Benefits and barriers of the program. This study highlighted the knowledge and skills preceptors gained through the program which gave them newfound confidence and facilitated their clinical teaching and evaluation. As the shift towards online learning progresses, web-based learning can be a useful platform for professional development of nurse preceptors.

Prevalence, Risk Factors, and Impact of Delirium on Hospitalized Older Adults With Dementia: A Systematic Review and Meta-Analysis.

OBJECTIVES: High prevalence of delirium superimposed on dementia (DSD) was previously reported, with associated negative impact on hospitalized older adults. However, data were conflicting, and no meta-analysis has been conducted. Although dementia is the leading risk factor for delirium, risk factors for DSD have not been adequately studied. This systematic review and meta-analysis aims to elucidate the prevalence, risk factors, and impact of DSD in hospitalized older adults. Comparisons were made between older adults with DSD and persons with dementia alone (PWDs). DESIGN: Systematic review and meta-analysis. SETTING AND PARTICIPANTS: Observational studies reporting prevalence, risk factors, or impact of DSD in hospitalized older adults. METHODS: Database search was conducted till December 2020 in PubMed, Embase, CENTRAL, PsycINFO, CINAHL, Scopus, Web of Science, ProQuest, and OpenGrey for relevant primary and secondary studies. A piloted data collection form was used for data extraction, and methodological quality was assessed using Joanna Briggs Institute critical appraisal checklists. Meta-analyses, with risk ratio and mean differences as effect measures, were performed using random effects model with Review Manager software. Cochran's Q and I2 statistics were used to assess heterogeneity, which was investigated using subgroup analyses. RESULTS: A total of 81 studies were eligible. The pooled prevalence of DSD was 48.9%, with the highest prevalence found in the Americas and orthopedic wards. Risk factors, including nonmodifiable hospital-, illness-, and medication-related factors, were found to precipitate DSD. Patients with DSD had longer length of hospitalization, disclosed worse cognitive and functional outcomes, and a higher risk of institutionalization and mortality than patients with dementia. CONCLUSIONS AND IMPLICATIONS: These findings suggested high prevalence and detrimental impact of DSD in hospitalized older adults, highlighting a need for early identification, prevention, and treatments. Further research on risk factors of DSD should be conducted as data were sparse and conflicting. Future high-quality studies regarding DSD are warranted to improve knowledge of this common but under-recognized phenomenon.

Psychological impacts and online interventions of social isolation amongst older adults during COVID-19 pandemic: A scoping review.

AIM: To summarise the psychological impacts of social isolation amongst older adults during COVID-19 and review the benefits and limitations of online interventions used to combat social isolation. DESIGN: A scoping review was performed. DATA SOURCES: A systematic search was performed from October 2020 to January 2021 in seven electronic databases: China National Knowledge Infrastructure (CNKI), PubMed, EMBASE, Cumulative Index to Nursing and Allied Health Literature (CINAHL), PsycINFO, Cochrane Library and Web of Science. A hand search of the reference lists of included papers and WHO publications was performed. Grey literature search was carried out from Scopus, ProQuest Dissertation and Google Scholar. REVIEW METHODS: Studies were screened, appraised and extracted independently by two reviewers. Thematic analysis was used to synthesise data, which were presented in a descriptive manner and organised into categories and themes. RESULTS: Totally, 33 studies were included. Four themes and eight sub-themes emerged: (1) negative impacts and experiences of older adults during social isolation, (2) adopting coping behaviours in the midst of COVID-19, (3) online interventions to combat the consequences of social isolation, (4) barriers to online intervention. CONCLUSION: The COVID-19 pandemic has taken an emotional toll on older adults' psychological wellbeing and has highlighted the untapped strengths of older adults facing isolation. Online interventions, which could be a new normal in the COVID era, were beneficial in combating social isolation. Strategies by various stakeholders were recommended to tackle the barriers of online interventions. IMPACT: With the COVID-19 pandemic still in progress, this review provides insights on the psychological impacts of social isolation amongst older adults. Nurses in the community and long-term care facilities could adopt strategies and online intervention to better support the older adults, contribute to a stronger COVID-19 response and support system, and an overall better road to recovery from this crisis.

Estudos envolvendo criatividade, educação física e epistemologia genética / Studies involving creativity, physical education and genetic epistemology / Estudios sobre la creatividad, la educación física y la epistemología genética

O objetivo deste artigo é descrever e analisar os estudos que envolvem a criatividade no contexto da escola, em especial da aula de Educação Física, considerando a teoria piagetiana sobre a construção do conhecimento. Apresenta-se um levantamento de oito artigos publicados entre 2008 e 2018. A maior parte deles é composta por artigos experimentais com foco em métodos de ensino e sujeitos com idades entre 12 e 14 anos. Os instrumentos mais utilizados são a entrevista, o diário de classe e testes KORA. Os conteúdos que mais surgem são os esportes tradicionais, como futsal, voleibol e atletismo. Foi possível encontrar relações entre os artigos e as ideias de Piaget, apontando para uma aula de Educação Física que valoriza a reflexão sobre a ação e o desenvolvimento da criatividade (AU).

The objective of this article is to describe and analyze the studies that involve creativity in the school context, especially in the Physical Education class, considering Piaget's theory on the construction of knowledge. A survey of eight articles published between 2008 and 2018 is presented. Most of them are composed of experimental articles focused on teaching methods and subjects aged between 12 and 14 years. The most used instruments are the interview, the class diary and KORA tests. The most popular content is traditional sports, such as futsal, volleyball and athletics. It was possible to find relationships between Piaget's articles and ideas, pointing to a Physical Education class that values reflection on action and the development of creativity (AU).

El objetivo de este artículo es describir y analizar los estudios que involucran la creatividad en el contexto escolar, especialmente en la clase de Educación Física (EFI), considerando la teoría de Piaget sobre la construcción del conocimiento. Se presenta una encuesta de ocho artículos publicados entre 2008 y 2018. La mayoría de ellos son: artículos experimentales centrados en métodos de enseñanza y materias con edades entre los 12 y los 14 años: instrumentos como la entrevista, el diario de clase y las pruebas KORA; contenido como los deportes tradicionales (fútbol sala, voleibol y atletismo). Fue posible encontrar relaciones entre los artículos y las ideas de Piaget, apuntando a una clase de EFI que valora la reflexión sobre la acción y el desarrollo de la creatividad (AU).

Estudos envolvendo criatividade, educação física e epistemologia genética / Studies involving creativity, physical education and genetic epistemology / Estudios sobre la creatividad, la educación física y la epistemología genética

O objetivo deste artigo é descrever e analisar os estudos que envolvem a criatividade no contexto da escola, em especial da aula de Educação Física, considerando a teoria piagetiana sobre a construção do conhecimento. Apresenta-se um levantamento de oito artigos publica-dos entre 2008 e 2018. A maior parte deles é composta por artigos expe-rimentais com foco em métodos de ensino e sujeitos com idades entre 12 e 14 anos. Os instrumentos mais utilizados são a entrevista, o diário de classe e testes KORA. Os conteúdos que mais surgem são os espor-tes tradicionais, como futsal, voleibol e atletismo. Foi possível encontrar relações entre os artigos e as ideias de Piaget, apontando para uma aula de Educação Física que valoriza a reflexão sobre a ação e o desenvolvi-mento da criatividade.

The objective of this article is to describe and analyze the studies that involve creativity in the school context, especially in the Physical Education class, considering Piaget's theory on the construction of knowledge. A survey of eight articles published between 2008 and 2018 is presented. Most of them are composed of experimental articles focused on teaching methods and subjects aged between 12 and 14 years. The most used instruments are the interview, the class diary and KORA tests. The most popular content is traditional sports, such as futsal, volleyball and athletics. It was possible to find relationships between Piaget's articles and ideas, pointing to a Physical Education class that values reflection on action and the development of creativity.

El objetivo de este artículo es describir y analizar los estudios que involucran la creatividad en el contexto escolar, especialmente en la clase de Educación Física (EFI), considerando la teoría de Piaget sobre la construcción del conocimiento. Se presenta una encuesta de ocho artículos publicados entre 2008 y 2018. La mayoría de ellos son: artículos experimentales centrados en métodos de enseñanza y materias con edades entre los 12 y los 14 años: instrumentos como la entrevista, el diario de clase y las pruebas KORA; contenido como los deportes tradicionales (fútbol sala, voleibol y atletismo). Fue posible encontrar relaciones entre los artículos y las ideas de Piaget, apuntando a una clase de EFI que valora la reflexión sobre la acción y el desarrollo de la creatividad.

The Tyrosine Kinase Pyk2 Contributes to Complement-Mediated Phagocytosis in Murine Macrophages.

Proline-rich tyrosine kinase 2 (Pyk2) is a member of the focal adhesion kinase (FAK) family and is mainly expressed in neuronal and hematopoietic cells. As FAK family members are involved in signaling connections downstream of integrins, we studied the role of Pyk2 in complement-receptor 3 (CR3, also known as Mac-1, integrin αMß2, CD11b/CD18)-mediated phagocytosis, a key process in innate immunity. Using 3 independent approaches, we observed that Pyk2 contributes to CR3-dependent phagocytosis by RAW 264.7 macrophages, but is dispensable for Fcγ receptor (FcγR)-mediated uptake. Reduction of Pyk2 expression levels via siRNA, the pharmacological inhibition of Pyk2 kinase activity as well as macrophage treatment with a cell permeable TAT fusion protein containing the C-terminus of Pyk2 (TAT-PRNK) significantly impaired CR3-mediated phagocytosis without affecting FcγR-mediated uptake. In addition, Pyk2 was strongly recruited to complement opsonized Escherichia coli and the pharmacological inhibition of Pyk2 significantly decreased uptake of the bacteria. Finally, CRISPR/Cas-mediated disruption of the pyk2 gene in RAW 264.7 macrophages confirmed the role of this protein tyrosine kinase in CR3-mediated phagocytosis. Together, our data demonstrate that Pyk2 selectively contributes to the coordination of phagocytosis-promoting signals downstream of CR3, but is dispensable for FcγR-mediated phagocytosis.

PARP1 expression, activity and ex vivo sensitivity to the PARP inhibitor, talazoparib (BMN 673), in chronic lymphocytic leukaemia.

In chronic lymphocytic leukemia (CLL), mutation and loss of p53 and ATM abrogate DNA damage signalling and predict poorer response and shorter survival. We hypothesised that poly (ADP-ribose) polymerase (PARP) activity, which is crucial for repair of DNA breaks induced by oxidative stress or chemotherapy, may be an additional predictive biomarker and a target for therapy with PARP inhibitors.We measured PARP activity in 109 patient-derived CLL samples, which varied widely (192 - 190052 pmol PAR/106 cells) compared to that seen in healthy volunteer lymphocytes (2451 - 7519 pmol PAR/106 cells). PARP activity was associated with PARP1 protein expression and endogenous PAR levels. PARP activity was not associated with p53 or ATM loss, Binet stage, IGHV mutational status or survival, but correlated with Bcl-2 and Rel A (an NF-kB subunit). Levels of 8-hydroxy-2'-deoxyguanosine in DNA (a marker of oxidative damage) were not associated with PAR levels or PARP activity. The potent PARP inhibitor, talazoparib (BMN 673), inhibited CD40L-stimulated proliferation of CLL cells at nM concentrations, independently of Binet stage or p53/ATM function.PARP activity is highly variable in CLL and correlates with stress-induced proteins. Proliferating CLL cells (including those with p53 or ATM loss) are highly sensitive to the PARP inhibitor talazoparib.

Pleiotropic action of AP-1 in v-Src-transformed cells.

The activation of AP-1 is a hallmark of cell transformation by tyrosine kinases. In this study, we characterize the role of AP-1 proteins in the transformation of chicken embryo fibroblasts (CEF) by v-Src. In normal CEF, the expression of a dominant negative mutant of c-Jun (TAM67) induced senescence. In contrast, three distinct phenotypes were observed when TAM67 was expressed in v-Src-transformed CEF. While senescent cells were also present, the inhibition of AP-1 caused apoptosis in a fraction of the v-Src-transformed cells. In addition, cells containing lipid-rich vesicles accumulated, suggesting that a subpopulation of the v-Src-transformed cells underwent differentiation in response to the inhibition of AP-1. JunD and Fra-2 were the main components of this factor, while c-Jun accounted for a minor fraction of AP-1 in v-Src-transformed CEF. The downregulation of c-Jun expression by short hairpin RNA (shRNA) induced senescence in normal and v-Src-transformed cells. In contrast, a high incidence of apoptosis was caused by the downregulation of JunD, suggesting that it is required for the survival of v-Src-transformed CEF. Levels of the p53 tumor suppressor were elevated under conditions of JunD inhibition. Repression of p53 by shRNA enhanced the survival and anchorage-independent proliferation of v-Src-transformed CEF with JunD/AP-1 inhibition. The inhibition of Fra-2 had no visible phenotype in normal CEF but caused the appearance of lipid-rich vesicles in v-Src-transformed CEF. Therefore, AP-1 facilitated transformation by acting as a survival factor, by inhibiting premature entry into senescence, and by blocking the differentiation of v-Src-transformed CEF.

Cellular processes of v-Src transformation revealed by gene profiling of primary cells--implications for human cancer.

BACKGROUND: Cell transformation by the Src tyrosine kinase is characterized by extensive changes in gene expression. In this study, we took advantage of several strains of the Rous sarcoma virus (RSV) to characterize the patterns of v-Src-dependent gene expression in two different primary cell types, namely chicken embryo fibroblasts (CEF) and chicken neuroretinal (CNR) cells. We identified a common set of v-Src regulated genes and assessed if their expression is associated with disease-free survival using several independent human tumor data sets. METHODS: CEF and CNR cells were infected with transforming, non-transforming, and temperature sensitive mutants of RSV to identify the patterns of gene expression in response to v-Src-transformation. Microarray analysis was used to measure changes in gene expression and to define a common set of v-Src regulated genes (CSR genes) in CEF and CNR cells. A clustering enrichment regime using the CSR genes and two independent breast tumor data-sets was used to identify a 42-gene aggressive tumor gene signature. The aggressive gene signature was tested for its prognostic value by conducting survival analyses on six additional tumor data sets. RESULTS: The analysis of CEF and CNR cells revealed that cell transformation by v-Src alters the expression of 6% of the protein coding genes of the genome. A common set of 175 v-Src regulated genes (CSR genes) was regulated in both CEF and CNR cells. Within the CSR gene set, a group of 42 v-Src inducible genes was associated with reduced disease- and metastasis-free survival in several independent patient cohorts with breast or lung cancer. Gene classes represented within this group include DNA replication, cell cycle, the DNA damage and stress responses, and blood vessel morphogenesis. CONCLUSION: By studying the v-Src-dependent changes in gene expression in two types of primary cells, we identified a set of 42 inducible genes associated with poor prognosis in breast and lung cancer. The identification of these genes provides a set of biomarkers of aggressive tumor behavior and a framework for the study of cancer cells characterized by elevated Src kinase activity.

Differential proteomic analysis of lymphatic, venous, and arterial endothelial cells extracted from bovine mesenteric vessels.

Differential protein profiling by 2-D PAGE is generally useful in biomarker discovery, proteome analysis and routine sample preparation prior to analysis by MS. The goal of this study was to compare 2-D PAGE-resolved protein profile of lymphatic endothelial cells to those of venous, and arterial endothelial cells isolated from lymphatic and blood vessels of bovine mesentery (bm). Three 2-D PAGE electrophoretograms were produced for each of the three cell types and quantitatively analyzed. Protein identification by LC-MS/MS was performed to identify 39 proteins found to be present at statistically significantly different levels in the three cell types (p<0.05). Most of the 39 proteins have not been previously reported in EC proteomic studies of 2-D PAGE electrophoretograms. Three proteins, HSPA1B (HSP70 family member), HSPB1 (HSP27 family member), and UBE2D3 (a member of E2 ubiquitin-conjugating enzymes) found to be at highest levels in bm arterial endothelial cells, bm venous endothelial cells, and bm lymphatic endothelial cells, respectively, were validated by immunoblotting with appropriate antibodies. The lack of substantial overlap between our results and those of other groups' comparative studies are discussed. Functional implications of differences in levels of various proteins identified in the three cell types are also discussed.

Gene expression analysis of Tek/Tie2 signaling.

The elaboration of the vasculature during embryonic development involves restructuring of the early vessels into a more complex vascular network. Of particular importance to this vascular remodeling process is the requirement of the Tek/Tie2 receptor tyrosine kinase. Mouse gene-targeting studies have shown that the Tie2-deficient embryos succumb to embryonic death at midgestation due to insufficient sprouting and remodeling of the primary capillary plexus. To identify the underlying genetic mechanisms regulating the process of vascular remodeling, transcriptomes modulated by Tie2 signaling were analyzed utilizing serial analysis of gene expression (SAGE). Two libraries were constructed and sequenced using embryonic day 8.5 yolk sac tissues from Tie2 wild-type and the Tie2-null littermates. After tag extraction, 45,689 and 45,275 SAGE tags were obtained for the Tie2 wild-type and Tie2-null libraries, respectively, yielding a total of 21,376 distinct tags. Close to 62% of the tags were uniquely annotated, whereas 10% of the total tags were unknown. Using semiquantitative PCR, the differential expression of eight genes was confirmed that included Elk3, an important angiogenic switch gene which was upregulated in the absence of Tie2 signaling. The results of this study provide valuable insight into the potential association between Tie2 signaling and other known angiogenic pathways as well as genes that might have novel functions in vascular remodeling.

Opposing roles of C/EBPbeta and AP-1 in the control of fibroblast proliferation and growth arrest-specific gene expression.

Chicken embryo fibroblasts (CEF) express several growth arrest-specific (GAS) gene products in G0. In contact-inhibited cells, the expression of the most abundant of these proteins, the p20K lipocalin, is activated at the transcriptional level by C/EBPbeta. In this report, we describe the role of C/EBPbeta in CEF proliferation. We show that the expression of a dominant negative mutant of C/EBPbeta (designated Delta184-C/EBPbeta) completely inhibited p20K expression at confluence and stimulated the proliferation of CEF without inducing transformation. Mouse embryo fibroblasts nullizygous for C/EBPbeta had a proliferative advantage over cells with one or two functional copies of this gene. C/EBP inhibition enhanced the expression of the three major components of AP-1 in cycling CEF, namely c-Jun, JunD, and Fra-2, and stimulated AP-1 activity. In contrast, the over-expression of C/EBPbeta caused a dramatic reduction in the levels of AP-1 proteins. Therefore, C/EBPbeta is a negative regulator of AP-1 expression and activity in CEF. The expression of cyclin D1 and cell proliferation were stimulated by the dominant negative mutant of C/EBPbeta but not in the presence of TAM67, a dominant negative mutant of c-Jun and AP-1. CEF over-expressing c-Jun, and to a lesser extent JunD and Fra-2, did not growth arrest at high cell density and did not express p20K. Therefore, AP-1 interfered with the action of C/EBPbeta at high cell density, indicating that these factors play opposing roles in the control of GAS gene expression and CEF proliferation.

Composition and function of AP-1 transcription complexes during muscle cell differentiation.

The role of activating protein-1 (AP-1) in muscle cells is currently equivocal. While some studies propose that AP-1 is inhibitory for myogenesis, others implicate a positive role in this process. We tested whether this variation may be due to different properties of the AP-1 subunit composition in differentiating cells. Using Western analysis we show that c-Jun, Fra-2, and JunD are expressed throughout the time course of differentiation. Phosphatase assays indicate that JunD and Fra-2 are phosphorylated in muscle cells and that at least two isoforms of each are expressed in muscle cells. Electrophoretic mobility shift assays combined with antibody supershifts indicate the appearance of Fra-2 as a major component of the AP-1 DNA binding complex in differentiating cells. In this context it appears that Fra-2 heterodimerizes with c-Jun and JunD. Studying the c-jun enhancer in reporter gene assays we observed that the muscle transcription factors MEF2A and MyoD can contribute to robust transcriptional activation of the c-jun enhancer. In differentiating muscle cells mutation of the MEF2 site reduces transactivation of the c-jun enhancer and MEF2A is the predominant MEF2 isoform binding to this cis element. Transcriptional activation of an AP-1 site containing reporter gene (TRE-Luc) is enhanced under differentiation conditions compared with growth conditions in C2C12 muscle cells. Further studies indicate that Fra-2 containing AP-1 complexes can transactivate the MyoD enhancer/promoter. Thus, an AP-1 complex containing Fra-2 and c-Jun or JunD is consistent with muscle differentiation, indicating that AP-1 function during myogenesis is dependent on its subunit composition.