RESUMEN
AIMS: Unintentional injuries in the home contribute substantially to preschool child morbidity and mortality. Practitioners such as health visitors, family mentors and children's centre staff are well-positioned to facilitate child injury prevention by providing home safety advice to families, and training may enhance their ability to do so. We aimed to assess the impact of child home safety training for these practitioners. METHODS: An explanatory mixed-methods design was used. Practitioners completed questionnaires before, and up to 7 months after, receiving child home safety training and took part in interviews. Seventy-eight health visitors, 72 family mentors and 11 children's centre staff members completed questionnaires. Items were used to calculate scores on home safety knowledge, confidence to provide home safety advice and belief that child home safety promotion is important. Thematic analysis of interviews with seven health visitors and nine family mentors, open-ended responses to the questionnaires and an additional evaluation form was conducted to explore attendees' perceptions of the training and its impact. In addition, seven health visitors and six children's centre staff who had received no training were interviewed. RESULTS: Knowledge was greater post-training than pre-training across all participants (p < .001). When practitioner groups were analysed separately, there were significant increases in family mentors' knowledge (p < .001) and belief (p = .016), and health visitors' confidence (p = .0036). Qualitative findings indicated that most training session attendees valued the training, believed their practice relating to child home safety had improved as a result, and felt further similar training sessions would be beneficial. Those who had not attended the sessions described a need for more child home safety training. CONCLUSIONS: Delivering training to practitioners providing child home safety promotion to families with preschool children can enhance injury prevention knowledge, beliefs and confidence and positively impact on home safety promotion by practitioners.
RESUMEN
OBJECTIVES: Falls in older adults cause significant morbidity and mortality and incur cost to health and care services. The Falls Management Exercise (FaME) programme is a 24-week intervention for older adults that, in clinical trials, improves balance and functional strength and leads to fewer falls. Similar but more modest outcomes have been found when FaME is delivered in routine practice. Understanding the degree to which the programme is delivered with fidelity is important if 'real-world' delivery of FaME is to achieve the same magnitude of outcome as in clinical trials. The objective of this study was to examine the implementation fidelity of FaME when delivered in the community to inform quality improvement strategies that maximise programme effectiveness. STUDY DESIGN: A mixed methods implementation study of FaME programme delivery. METHODS: Data from programme registers, expert observations of FaME classes, and semistructured interviews with FaME instructors were triangulated using a conceptual framework for implementation fidelity. Quantitative data were analysed using descriptive statistics. Interviews were transcribed verbatim and analysed using thematic analysis. RESULTS: In total, 356 participants enrolled on 29 FaME programmes, and 143 (40%) participants completed at least 75% of the classes within a programme. Observations showed that 72%-78% of programme content was delivered, and 80%-84% quality criteria were met. Important content that was most often left out included home exercises, Tai Chi moves, and floor work, whereas quality items most frequently missed out included asking about falls in the previous week, following up attendance absence and explaining the purpose of exercises. Only 24% of class participants made the expected strength training progression. Interviews with FaME instructors helped explain why elements of programme content and quality were not delivered. Strategies for improving FaME delivery were established and helped to maintain quality and fidelity. CONCLUSIONS: FaME programmes delivered in the 'real world' can be implemented with a high degree of fidelity, although important deviations were found. Facilitation strategies could be used to further improve programme fidelity and maximise participant outcomes.
Asunto(s)
Ejercicio Físico , Entrenamiento de Fuerza , Anciano , Terapia por Ejercicio , Humanos , Evaluación de Programas y Proyectos de SaludRESUMEN
BACKGROUND: Childhood falls, poisonings and scalds, occurring predominantly in the home, are an important public health problem, yet there is limited evidence on the costs of these injuries to individuals and society. OBJECTIVES: To estimate National Health Service (NHS) and child and family costs of falls, poisonings and scalds. METHODS: We undertook a multicentre longitudinal study of falls, poisonings and scalds in children under 5â years old, set in acute NHS Trusts across four UK study centres. Data from parental self-reported questionnaires on health service resource use, family costs and expenditure were combined with unit cost data from published sources to calculate average cost for participants and injury mechanism. RESULTS: 344 parents completed resource use questionnaires until their child recovered from their injury or until 12â months, whichever came soonest. Most injuries were minor, with >95% recovering within 2â weeks, and 99% within 1â month of the injury. 61% emergency department (ED) attendees were not admitted, 35% admitted for ≤1â day and 4% admitted for ≥2 days. The typical healthcare cost of an admission for ≥2 days was estimated at £2000-3000, for an admission for ≤1â day was £700-1000 and for an ED attendance without admission was £100-180. Family costs were considerable and varied across injury mechanisms. Of all injuries, scalds accrued highest healthcare and family costs. CONCLUSIONS: Falls, poisonings and scalds incur considerable short-term healthcare and family costs. These data can inform injury prevention policy and commissioning of preventive services.
Asunto(s)
Accidentes por Caídas/economía , Accidentes Domésticos/economía , Quemaduras/economía , Hospitalización/economía , Tiempo de Internación/economía , Intoxicación/economía , Medicina Preventiva , Accidentes por Caídas/prevención & control , Accidentes por Caídas/estadística & datos numéricos , Accidentes Domésticos/prevención & control , Quemaduras/prevención & control , Quemaduras/rehabilitación , Preescolar , Inglaterra/epidemiología , Femenino , Costos de la Atención en Salud , Hospitalización/estadística & datos numéricos , Humanos , Lactante , Recién Nacido , Tiempo de Internación/estadística & datos numéricos , Estudios Longitudinales , Masculino , Padres , Intoxicación/prevención & control , Intoxicación/rehabilitación , Formulación de Políticas , Medicina Preventiva/economía , Medicina Preventiva/métodos , Encuestas y CuestionariosRESUMEN
Old age is associated with a higher prevalence of cardiovascular disease and diabetes mellitus. Vascular smooth muscle cells (VSMC) play a role in the pathogenesis of vascular diseases, often a complication of diabetes mellitus. We examined in explanted aortic VSMC from young vs. older rats glucose-related activation of nuclear factor kappaB (NF-kappaB), a transcription factor induced by many oxidants. Data demonstrate that old age is associated with enhanced NF-kappaB activity in unstimulated VSMC that is further increased after exposure to high glucose medium. Furthermore, VSMC from old animals exhibit increased levels of protein carbonyls, an indicator of oxidative stress, and less apoptosis in response to glucose than VSMC isolated from young animals. These changes are accompanied by increased expression of NF-kappaB-related genes, gamma-glutamylcysteine synthetase, inhibitor of apoptosis protein-1 (IAP-1), and inducible nitric oxide synthase (iNOS). Results suggest that high glucose, a putative oxidative stress, causes apoptosis in VSMC from young animals and is associated with greater induction of NF-kappaB in VSMC from older animals. Increases in IAP-1 and decreased apoptosis implicate NF-kappaB as a survival factor in VSMC.
Asunto(s)
Apoptosis , Senescencia Celular/fisiología , Glucosa/farmacología , Músculo Liso Vascular/efectos de los fármacos , Animales , Aorta/citología , Glutamato-Cisteína Ligasa/biosíntesis , Glutamato-Cisteína Ligasa/genética , Proteínas Inhibidoras de la Apoptosis , Masculino , Músculo Liso Vascular/citología , Músculo Liso Vascular/metabolismo , FN-kappa B/metabolismo , Óxido Nítrico Sintasa/biosíntesis , Óxido Nítrico Sintasa/genética , Óxido Nítrico Sintasa de Tipo II , Estrés Oxidativo/efectos de los fármacos , Estrés Oxidativo/fisiología , Biosíntesis de Proteínas , Proteínas/genética , RatasRESUMEN
Crystalline silica has been classified as a group 1 human carcinogen in the lung. However, its mechanisms of action on pulmonary epithelial cells which give rise to lung cancers are unclear. Using a nontransformed alveolar type II epithelial cell line (C10), we show that alpha-quartz silica causes persistent dose-related increases in phosphorylation of c-Jun-NH2-terminal amino kinases (JNKs) that are inhibited by antioxidants (P < or = 0.05). Increases in activator protein-1 (AP-1) binding to DNA and transactivation of AP-1-dependent gene expression by silica were accompanied by increases in steady-state mRNA levels of the AP-1 family members, c-jun, junB, fra-1, and c-fos at 8 h and elevated mRNA levels of fra-1 at 24 h (P < or = 0.05). Addition of tetramethylthiourea inhibited silica-associated increases infra-1 and proportions of cells in S-phase (P < or = .05). Our findings indicate that silica induces JNK activity, AP-1-dependent gene expression, ie., fra-1, and DNA synthesis via oxidative stress. Moreover, they suggest that silica may act mechanistically as a mitogen or tumor promoter, rather than a genotoxic carcinogen, in the development of lung cancers.
Asunto(s)
Regulación de la Expresión Génica/efectos de los fármacos , Proteínas Quinasas Activadas por Mitógenos/metabolismo , Estrés Oxidativo/fisiología , Proteínas Proto-Oncogénicas c-fos/biosíntesis , Alveolos Pulmonares/efectos de los fármacos , Fase S/efectos de los fármacos , Dióxido de Silicio/toxicidad , Tiourea/análogos & derivados , Animales , Línea Celular , ADN/metabolismo , Relación Dosis-Respuesta a Droga , Activación Enzimática/efectos de los fármacos , Células Epiteliales/citología , Células Epiteliales/efectos de los fármacos , Células Epiteliales/metabolismo , Depuradores de Radicales Libres/farmacología , Radical Hidroxilo/metabolismo , Proteínas Quinasas JNK Activadas por Mitógenos , Sistema de Señalización de MAP Quinasas/efectos de los fármacos , Ratones , Fosforilación/efectos de los fármacos , Proto-Oncogenes Mas , Proteínas Proto-Oncogénicas c-fos/genética , Alveolos Pulmonares/citología , Alveolos Pulmonares/metabolismo , ARN Mensajero/biosíntesis , ARN Mensajero/genética , Dióxido de Silicio/antagonistas & inhibidores , Tiourea/farmacología , Factor de Transcripción AP-1/metabolismoRESUMEN
High levels of ambient air pollution are associated with exacerbation of asthma and respiratory morbidity, yet little is known concerning the mechanisms of inflammation and toxicity by components of inhaled particulate matter (PM). Brief inhalation of PM(2.5) (particles of an aerodynamic diameter of < 2.5 microns) (300 microg/m(3) air for 6 h followed by a period of 24 h in clean air) by either C3H/HeJ or C57/BL6 mice caused significant (P
Asunto(s)
Contaminantes Atmosféricos/farmacología , Regulación de la Expresión Génica/efectos de los fármacos , FN-kappa B/efectos de los fármacos , Oxidantes/fisiología , Animales , Carbono/farmacología , Línea Celular , ADN/metabolismo , Células Epiteliales/efectos de los fármacos , Células Epiteliales/metabolismo , Fluoresceínas/metabolismo , Exposición por Inhalación , Interferón gamma/genética , Interleucina-6/genética , Pulmón/citología , Pulmón/efectos de los fármacos , Pulmón/metabolismo , Linfotoxina-alfa/genética , Masculino , Ratones , Ratones Endogámicos C3H , Ratones Endogámicos C57BL , FN-kappa B/metabolismo , Oxidantes/metabolismo , Tamaño de la Partícula , Unión Proteica/efectos de los fármacos , ARN Mensajero/efectos de los fármacos , ARN Mensajero/genética , ARN Mensajero/metabolismo , Activación Transcripcional/efectos de los fármacos , Factor de Crecimiento Transformador beta/genética , Factor de Necrosis Tumoral alfa/genéticaRESUMEN
Cell signaling by pathogenic minerals may initiate the transactivation of genes that are critical to carcinogenesis and fibroproliferative diseases of the lung and pleura. We have shown previously that stimulation of the mitogen-activated protein kinase (MAPK) cascade by asbestos fibers leads to phosphorylation events involved in transactivation of lun and Fos proteins that comprise the activator protein-1 (AP-1) transcription factor. Recently, we have also used AP-1 luciferase reporter transgenic mice and immunocytochemistry to show that transactivation of AP-1 occurs in bronchiolar and alveolar epithelial cells after inhalation of asbestos fibers. After inhalation of asbestos, epithelial cells of the lung also show increased immunoreactivity of pliosphorylated extracellular signal regulated kinases (ERKs 1/2) at sites of fibrogenesis. The availability of lung epithelial cell-specific promoters has allowed the creation of transgenic mice with mutations in the transactivation domains of key receptors and protein intermediates that comprise the MAPK signaling cascade. These rodent models may reveal whether cell signaling events initiated by mineral dusts in epithelial cells are critical to the development of cell proliferation, apoptosis, and lung disease.
RESUMEN
Aging is characterized by an accumulation of oxidative injury to DNA, RNA, proteins, lipids, and carbohydrates. In addition to damage, oxidative stress can initiate cell signaling cascades that modulate cell function, growth, and death. Aging and two common age-related diseases, diabetes mellitus and atherosclerosis, may share common oxidant-related signaling pathways that lead to abnormal transcription factor activation and ultimately to cellular dysfunction, degeneration, or death. This review will focus on approaches to evaluate key redox-sensitive signaling pathways and the transcription factors altered by diabetes, atherosclerosis, and aging.
Asunto(s)
Envejecimiento , Transducción de Señal , Factores de Transcripción/metabolismo , Arteriosclerosis/metabolismo , Diabetes Mellitus/metabolismo , Humanos , Modelos Biológicos , Estrés Oxidativo , Oxígeno/metabolismoRESUMEN
We examined the mechanisms of interaction of crocidolite asbestos fibers with the epidermal growth factor (EGF) receptor (EGFR) and the role of the EGFR-extracellular signal-regulated kinase (ERK) signaling pathway in early-response protooncogene (c-fos/c-jun) expression and apoptosis induced by asbestos in rat pleural mesothelial (RPM) cells. Asbestos fibers, but not the nonfibrous analog riebeckite, abolished binding of EGF to the EGFR. This was not due to a direct interaction of fibers with ligand, inasmuch as binding studies using fibers and EGF in the absence of membranes showed that EGF did not adsorb to the surface of asbestos fibers. Exposure of RPM cells to asbestos caused a greater than twofold increase in steady-state message and protein levels of EGFR (P < 0.05). The tyrphostin AG-1478, which inhibits the tyrosine kinase activity of the EGFR, but not the tyrphostin A-10, which does not affect EGFR activity, significantly ameliorated asbestos-induced increases in mRNA levels of c-fos but not of c-jun. Pretreatment of RPM cells with AG-1478 significantly reduced apoptosis in cells exposed to asbestos. Our findings suggest that asbestos-induced binding to EGFR initiates signaling pathways responsible for increased expression of the protooncogene c-fos and the development of apoptosis. The ability to block asbestos-induced elevations in c-fos mRNA levels and apoptosis by small-molecule inhibitors of EGFR phosphorylation may have therapeutic implications in asbestos-related diseases.
Asunto(s)
Apoptosis/fisiología , Asbesto Crocidolita/farmacología , Receptores ErbB/metabolismo , Proteínas Proto-Oncogénicas c-fos/metabolismo , Animales , Células Cultivadas , Factor de Crecimiento Epidérmico/antagonistas & inhibidores , Factor de Crecimiento Epidérmico/metabolismo , Factor de Crecimiento Epidérmico/farmacología , Células Epiteliales/metabolismo , Receptores ErbB/genética , Receptores ErbB/fisiología , Regulación de la Expresión Génica/fisiología , Homeostasis/efectos de los fármacos , Fosforilación , Pleura/citología , Pleura/metabolismo , Proteínas Proto-Oncogénicas c-fos/genética , ARN Mensajero/metabolismo , Ratas , Ratas Endogámicas F344 , Transducción de Señal/fisiologíaRESUMEN
Numerous epidemiological studies have demonstrated a positive association between ambient air pollution and adverse health effects including respiratory morbidity, asthma, and lung cancer. It has been suggested in some experimental studies that airborne particulate matter (PM) can produce inflammatory effects, but nothing is known about the possible proliferative and carcinogenic effects of these particles on cells of the lung. We show here that exposure of pulmonary epithelial cells, a cell type affected in acute lung injury, asthma, and lung carcinomas, to nontoxic concentrations of PM in vitro results in increases in c-jun kinase activity, levels of phosphorylated cJun immunoreactive protein, and transcriptional activation of activator protein-1-dependent gene expression. These changes are accompanied by elevations in numbers of cells incorporating 5'-bromodeoxyuridine, a marker of unscheduled DNA synthesis and/or cell proliferation. Data here are the first to demonstrate that interaction of ambient PM with target cells of the lung initiates a cell signaling cascade related causally to aberrant cell proliferation and carcinogenesis.
Asunto(s)
Contaminación del Aire/efectos adversos , Proteínas Quinasas Dependientes de Calcio-Calmodulina/fisiología , ADN/biosíntesis , Pulmón/metabolismo , Proteínas Quinasas Activadas por Mitógenos , Animales , Bromodesoxiuridina/metabolismo , División Celular , Activación Enzimática , Células Epiteliales/metabolismo , Proteínas Quinasas JNK Activadas por Mitógenos , Fosforilación , Ratas , Factor de Transcripción AP-1/fisiologíaRESUMEN
Oxidants are important in the regulation of signal transduction and gene expression. Multiple classes of genes are transcriptionally activated by oxidants and are implicated in different phenotypic responses. In the present study, we performed differential mRNA display to elucidate genes that are induced or repressed after exposure of rat lung epithelial (RLE) cells to H2O2 or crocidolite asbestos, a pathogenic mineral that generates oxidants. After 8 or 24 hr of exposure, RNA was extracted, reverse transcribed, and amplified by polymerase chain reaction with degenerate primers to visualize alterations in gene expression. The seven clones obtained were sequenced and encoded the mitochondrial genes, NADH dehydrogenase subunits ND5 and ND6, and 16S ribosomal RNA. Evaluation of their expression by Northern blot analysis revealed increased expression of 16S rRNA after 1 or 2 hr of exposure to H2O2. At later time periods (4 and 24 hr), mRNA levels of 16S rRNA and NADH dehydrogenase were decreased in H2O2-treated RLE cells when compared to sham controls. Crocidolite asbestos caused increases in 16S rRNA levels after 8 hr of exposure, whereas after 24 hr of exposure to asbestos, 16S rRNA levels were decreased in comparison to sham controls. In addition to these oxidants, the nitric oxide generator spermine NONOate caused similar decreases in NADH dehydrogenase mRNA levels after 4 hr of exposure. The present data and previous studies demonstrated that all oxidants examined resulted in apoptosis in RLE cells during the time frame where alterations of mitochondrial gene expression were observed. As the mitochondrion is a major organelle that controls apoptosis, alterations in expression of mitochondrial genes may be involved in the regulation of apoptosis.
Asunto(s)
Pulmón/efectos de los fármacos , Pulmón/metabolismo , Mitocondrias/genética , Oxidantes/toxicidad , Animales , Apoptosis , Asbesto Crocidolita/toxicidad , Línea Celular , Células Epiteliales/efectos de los fármacos , Células Epiteliales/metabolismo , Expresión Génica/efectos de los fármacos , Peróxido de Hidrógeno/toxicidad , Pulmón/citología , NADH Deshidrogenasa/genética , Alveolos Pulmonares/citología , Alveolos Pulmonares/efectos de los fármacos , Alveolos Pulmonares/metabolismo , ARN Mensajero/genética , ARN Mensajero/metabolismo , ARN Ribosómico 16S/genética , RatasRESUMEN
Erionite, a naturally occurring fibrous zeolite, is associated with the development of nonmalignant and malignant lung diseases and is more carcinogenic than asbestos fibers in man and rodent inhalation models of disease. To investigate the possible molecular mechanisms of erionite-induced toxicity and carcinogenesis and whether cationic content of erionite fibers was important, we examined c-fos and c-jun mRNA levels, activator protein-1 (AP-1) binding to DNA, and changes in cell proliferation and apoptosis in rat pleural mesothelial (RPM) cells exposed to different cation-substituted erionite fibers or crocidolite asbestos at various concentrations (1, 5, or 10 microg/cm2 dish) at time periods from 8 to 48 h after addition of minerals. c-fos mRNA levels in cells exposed to equal weight concentrations of various erionites and crocidolite fibers were increased comparably. When compared to other fibers, Na-erionite caused significantly increased levels of c-jun mRNA at lower mass concentrations (1 and 5 microg/cm2) than crocidolite asbestos, but comparable AP-1 binding to DNA. In comparison to untreated controls, numbers of RPM cells incorporating 5'-bromodeoxyuridine (BrdU) were increased dramatically after exposure to asbestos or Na-erionite at 5 and 10 microg/cm2. Significant dose-dependent increases in apoptosis were observed with asbestos at all time points, whereas erionites failed to induce apoptosis at 8 or 24 h, with minimal induction at higher concentrations than asbestos at 48 h. These data suggest that erionite increases the balance between cell proliferation (and/or abnormal DNA repair) and apoptosis, a normal mechanism of elimination of transformed or proliferating cells.
Asunto(s)
Apoptosis/efectos de los fármacos , Amianto/toxicidad , Carcinógenos/toxicidad , Pleura/efectos de los fármacos , Proteínas Proto-Oncogénicas c-fos/biosíntesis , Proteínas Proto-Oncogénicas c-jun/biosíntesis , Factor de Transcripción AP-1/metabolismo , Zeolitas/toxicidad , Animales , Apoptosis/genética , Northern Blotting , División Celular/efectos de los fármacos , Células Cultivadas , Proteínas de Unión al ADN , Células Epiteliales/efectos de los fármacos , Citometría de Flujo , Pleura/metabolismo , Pleura/patología , Proteínas Proto-Oncogénicas c-fos/genética , Proteínas Proto-Oncogénicas c-jun/genética , ARN Mensajero/biosíntesis , Ratas , Ratas Endogámicas F344RESUMEN
To evaluate the contribution of reactive nitrogen species to inflammation by asbestos, Fischer 344 rats were exposed to crocidolite or chrysotile asbestos by inhalation to determine whether increases occurred in nitric oxide (NO.) metabolites from alveolar macrophages (AMs). AMs from animals inhaling asbestos showed significant elevations (p < .05) in nitrite/nitrate levels which were ameliorated by NG-monomethyl-L-arginine (NMMA), an inhibitor of inducible nitric oxide synthase (iNOS) activity. Temporal patterns of NO. generation from AMs correlated with neutrophil influx in bronchoalveolar lavage samples after asbestos inhalation or bleomycin instillation, another model of pulmonary fibrosis. To determine the molecular mechanisms and specificity of iNOS promoter activation by asbestos, RAW 264.7 cells, a murine macrophage-like line, and AMs isolated from control rats were exposed to crocidolite asbestos in vitro. These cells showed increases in steady-state levels of iNOS mRNA in response to asbestos and more dramatic increases in both iNOS mRNA and immunoreactive protein after addition of lipopolysaccharide (LPS). After transfection of an iNOS promoter/luciferase reporter construct, RAW 264.7 cells exposed to LPS, crocidolite asbestos and its nonfibrous analog, riebeckite, revealed increases in luciferase activity whereas cristobalite silica had no effects. Studies suggest that NO. generation may be important in cell injury and inflammation by asbestos.
Asunto(s)
Amianto/toxicidad , Macrófagos Alveolares/efectos de los fármacos , Nitratos/metabolismo , Óxido Nítrico/biosíntesis , Nitritos/metabolismo , Administración por Inhalación , Animales , Bleomicina/farmacología , Líquido del Lavado Bronquioalveolar/citología , Células Cultivadas , Radicales Libres , Inmunohistoquímica , Macrófagos Alveolares/metabolismo , Masculino , Oxidación-Reducción , Fibrosis Pulmonar/etiología , Fibrosis Pulmonar/metabolismo , Ratas , Ratas Endogámicas F344RESUMEN
Occupational exposure to crocidolite asbestos is associated with the development of nonmalignant and malignant pulmonary disease. Considerable evidence indicates that the mechanisms of asbestos-induced toxicity involve the production of active oxygen species (AOS). Production of AOS in excess of cellular defenses creates an environment of oxidative stress and stimulates the expression of a number of different genes whose products may be involved in mediating responses from oxidant injury. To further investigate the mechanisms of asbestos-induced pathogenicity, we have examined by Western blot analyses the induction of the stress response proteins GRP78 and HSP72/73 in rat lung epithelial cells (RLE) exposed to crocidolite asbestos. In comparative studies, we also examined GRP78, HSP72/73, and cJun expression in RLE cells exposed to equitoxic concentrations of cadmium chloride (CdCl2) and hydrogen peroxide (H2O2). Our results demonstrate that asbestos and H2O2 do not alter GRP78 or HSP72/73 protein levels in RLE cells, but do increase levels of cJun protein. Increases by asbestos and H2O2 were not accompanied by alterations in cellular glutathione levels in this cell type, but asbestos caused elevations in protein levels of manganese-containing superoxide dismutase (MnSOD), an indirect indicator of oxidant stress. In contrast, exposure of cells to CdCl2 led to no changes in MnSOD protein levels, but increases in GRP78, HSP72/73, and cJun proteins as well as significant increases in oxidized and reduced thiol pools. Results suggest that environmental agents causing oxidative injury to lung epithelium elicit different patterns of stress responses.
Asunto(s)
Amianto/toxicidad , Cloruro de Cadmio/toxicidad , Proteínas HSP70 de Choque Térmico , Proteínas de Choque Térmico/metabolismo , Peróxido de Hidrógeno/toxicidad , Pulmón/efectos de los fármacos , Estrés Oxidativo , Animales , Proteínas Portadoras/metabolismo , Chaperón BiP del Retículo Endoplásmico , Células Epiteliales/metabolismo , Glutatión/metabolismo , Proteínas del Choque Térmico HSC70 , Proteínas del Choque Térmico HSP72 , Pulmón/metabolismo , Chaperonas Moleculares/metabolismo , Proteínas Proto-Oncogénicas c-jun/metabolismo , Ratas , Superóxido Dismutasa/metabolismoRESUMEN
In recent years, it has become apparent that minerals can trigger alterations in gene expression by initiating signaling events upstream of gene transactivation. These cascades may be initiated at the cell surface after interaction of minerals with the plasma membrane either through receptorlike mechanisms or integrins. Alternatively, signaling pathways may be stimulated by active oxygen species generated both during phagocytosis of minerals and by redox reactions on the mineral surface. At least two signaling cascades linked to activation of transcription factors, i.e., DNA-binding proteins involved in modulating gene expression and DNA replication, are stimulated after exposure of lung cells to asbestos fibers in vitro. These include nuclear factor kappa B (NF kappa B) and the mitogen-activated protein kinase (MAPK) cascade important in regulation of the transcription factor, activator protein-1 (AP-1). Both NF kappa B and AP-1 bind to specific DNA sequences within the regulatory or promoter regions of genes that are critical to cell proliferation and inflammation. Unraveling the cell signaling cascades initiated by mineral dusts and pharmacologic inhibition of these events may be important for the control and treatment of mineral-associated occupational diseases.
Asunto(s)
Amianto/toxicidad , Carcinógenos/toxicidad , Comunicación Celular/efectos de los fármacos , Transducción de Señal/efectos de los fármacos , Animales , Asbesto Crocidolita/toxicidad , Proteínas Quinasas Dependientes de Calcio-Calmodulina/metabolismo , División Celular/efectos de los fármacos , Línea Celular , Cricetinae , Electroforesis en Gel de Poliacrilamida , Células Epiteliales/efectos de los fármacos , Receptores ErbB/genética , FN-kappa B/efectos de los fármacos , Fenotipo , Factor de Transcripción AP-1/biosíntesis , Factor de Transcripción AP-1/genéticaRESUMEN
We developed in situ dual-fluorescence detection techniques for measuring apoptosis and proliferation simultaneously in single dishes of cells. The deoxyribonucleic acid (DNA)-specific labeling method, terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine triphosphate nick-end labeling (TUNEL), first was used in conjunction with a 4',6-diamidino-2-phenylindole (DAPI) counterstain to detect and measure morphologic characteristics of apoptotic rat pleural mesothelial (RPM) cells isolated from Fischer 344 rats and exposed to 300 microM hydrogen peroxide (H2O2). For this purpose, 100 TUNEL-positive nuclei were measured while being viewed with DAPI counterstaining for area, perimeter, longest diameter, and average diameter, using imaging software and an image-collection apparatus. We then exposed cells to a range of concentrations of crocidolite asbestos and putative apoptotic and mitogenic agents. Exposure to crocidolite asbestos (5 microg/cm2) caused a striking dose-dependent apoptotic response at 24 h, 48 h, and 72 h. The nonfibrous crocidolite analogue riebeckite failed to induce apoptosis. At 24 h, tumor necrosis factor-alpha (TNF-alpha) (10 ng/ml) caused an increase in apoptotic nuclei. A second method, utilizing an antibody to 5'-bromodeoxyridine (BrdU) and oxazole yellow homodimer (YOYO), showed a dose-dependent increase in proliferation occurring in cells exposed to asbestos (5 microg/cm2) at 48 h and 72 h. In addition, increased numbers of rat pleural mesothelial (RPM) cells exposed to 12-O-tetradecanoylphorbol-13-acetate (TPA), TNF-alpha, and epidermal growth factor (EGF) exhibited incorporation of BrdU at these time points, although total numbers of cells per unit area were unchanged. Results indicate a dynamic balance between apoptosis and increased DNA synthesis after exposure of mesothelial cells to asbestos.
Asunto(s)
Apoptosis/efectos de los fármacos , Asbesto Crocidolita/farmacología , Carcinógenos/farmacología , Citometría de Imagen/métodos , Pleura/citología , Animales , Benzoxazoles , Biotina , Bromodesoxiuridina , División Celular/fisiología , Fragmentación del ADN , Nucleótidos de Desoxiuracil , Factor de Crecimiento Epidérmico/farmacología , Células Epiteliales , Colorantes Fluorescentes , Procesamiento de Imagen Asistido por Computador/métodos , Indoles , Microscopía Fluorescente/métodos , Mitógenos/farmacología , Compuestos de Quinolinio , Ratas , Ratas Endogámicas F344 , Coloración y Etiquetado , Acetato de Tetradecanoilforbol/farmacología , Factor de Necrosis Tumoral alfa/farmacologíaRESUMEN
Asbestos and the phorbol ester tumor promoter, 12-O-tetradecanoylphorbol-13-acetate (TPA), increase c-fos and c-jun mRNA levels and AP-1 DNA binding activity in rat pleural mesothelial (RPM) cells, a target cell of asbestos-induced mesotheliomas (N. H. Heintz et al., Proc. Natl. Acad. Sci. USA, 90: 3299-3303, 1993). Because protein kinase C (PKC) is the intracellular receptor of phorbol ester tumor promoters and asbestos is a putative tumor promoter in the respiratory tract, we hypothesized that PKC might play a critical role in asbestos-induced cell signaling pathways associated with regulation of proto-oncogenes. Using a panel of PKC antibodies, we identified PKC alpha as the major PKC isozyme in RPM cells. We then pretreated cells with phorbol ester dibutyrate to down-modulate PKC or with calphostin C, a specific PKC inhibitor, to determine if depletion of PKC alpha could block asbestos-induced c-fos/c-jun expression. Quantitation of Northern blots showed that fiber-associated c-fos/c-jun mRNA levels were significantly lower either after PKC alpha down-modulation or pretreatment with calphostin C. In addition, to determine whether tyrosine kinases also were involved in proto-oncogene activation by asbestos, tyrphostin AG82 or herbimycin A was added to RPM cells before exposure to asbestos. These inhibitors decreased crocidolite-induced c-fos but not c-jun levels, suggesting that tyrosine kinases have different regulatory roles in asbestos-induced c-fos versus c-jun signaling pathways. The ability to block induction of asbestos-induced proto-oncogene expression using pharmacological intervention may be important in prevention and treatment of asbestos-induced proliferative diseases including lung cancers, mesothelioma, and pulmonary fibrosis.
Asunto(s)
Amianto/farmacología , Epitelio/enzimología , Proteína Quinasa C/fisiología , Proteínas Proto-Oncogénicas c-fos/metabolismo , Proteínas Proto-Oncogénicas c-jun/metabolismo , Animales , Benzoquinonas , Epitelio/efectos de los fármacos , Expresión Génica , Isoenzimas , Lactamas Macrocíclicas , Naftalenos/farmacología , Forbol 12,13-Dibutirato/farmacología , Proteínas Tirosina Quinasas/antagonistas & inhibidores , Proteínas Tirosina Quinasas/metabolismo , Proteínas Proto-Oncogénicas c-fos/genética , Proteínas Proto-Oncogénicas c-jun/genética , Quinonas/farmacología , ARN Mensajero/análisis , Ratas , Ratas Endogámicas F344 , Rifabutina/análogos & derivados , Factores de TiempoRESUMEN
Asbestos causes persistent increases in c-jun mRNA and AP-1 DNA binding activity in hamster tracheal epithelial (HTE) cells, the progenitor cell type of asbestos-induced bronchogenic carcinoma. Studies here were designed to determine mechanisms of c-jun induction by asbestos and the phenotypic consequences of Jun expression in HTE cells. To examine whether asbestos or H2O2 induced transcription of c-jun, we transiently transfected HTE cells with a plasmid containing a fragment of the c-jun promoter coupled to a luciferase reporter gene. In addition, c-jun was overexpressed in cells using a full-length human c-jun construct, and effects on proliferation and transformation were examined. HTE cells transfected with the jun-luciferase construct showed increased luciferase activity when exposed to crocidolite asbestos or H2O2. These results demonstrate that asbestos and H2O2 activate AP-1-dependent gene transcription. Overexpression of c-jun led to increased proliferation and enhanced ability of HTE cells to grow in soft agar, an indication of cellular transformation. Data suggest that overexpression of c-jun may contribute to asbestos and oxidant-induced proliferation and carcinogenesis.