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BACKGROUND: Coal-fired power plants are major contributors of ambient sulfur dioxide (SO2) air pollution. Epidemiological literature suggests an adverse association between SO2 exposure during gestation and preterm birth (PTB; <37 weeks completed gestation). PTB is strongly associated with infant mortality and increased risk for later life morbidities. OBJECTIVE: We investigated associations between SO2 and PTB in North Carolina and evaluated whether the associations were modified by race/ethnicity. METHODS: We assembled a retrospective, administrative cohort of singleton births in North Carolina from 2003-2015. We used US EPA EQUATES data to assign long-term SO2 gestational exposures to eligible births for the entire pregnancy and by trimester. We used multivariable generalized linear regression to estimate risk differences (RD (95%CI)) per 1-ppb increase in SO2, adjusted for gestational parent education, Medicaid status, marital status, and season of conception. Multi-pollutant models were additionally adjusted for other criteria air co-pollutants (O3, PM2.5, NO2). RESULTS: The median SO2 (24-hour average) across exposure windows was ~1.5 (IQR: 1.8) ppb. The overall baseline risk for PTB was 8,756 per 100,000 live births. When stratified by race/ethnicity, the baseline risk for PTB was 12215, 7824, and 7187 per 100,000 live births among non-Hispanic Black, non-Hispanic white, and Hispanic births, respectively. RDs per 1-ppb increase in SO2 averaged across the entire pregnancy were 317.0 (95%CI: 279.4, 354.5) and 568.2 (95%CI: 500.3, 636.1) per 100,000 live births for single- and multi-pollutant models, respectively. For the PTB multi-pollutant models, we observed similar RDs for non-Hispanic Black participants (669.6 [95%CI: 573.9, 765.2]) and non-Hispanic white participants (635.4 [95%CI: 557.2, 713.6]) with smaller RDs for Hispanic participants (336.8 [95%CI: 241.3, 432.2]). SIGNIFICANCE: The results for our adjusted single- and multi-pollutant models showed adverse associations between SO2 and PTB, with some evidence of effect measure modification by race/ethnicity within subcategories of PTB.
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BACKGROUND Coal combustion releases a number of airborne toxins. The North Carolina Clean Smokestacks Act (CSA) of 2002 required North Carolina coal-fired power plants (CFPP) to reduce nitrogen oxides (NOX) emissions by 2009 and sulfur dioxide (SO2) emissions to 2 benchmarks by 2009 and 2013.METHODS We utilized publicly available databases from the Energy Information Administration and the Environmental Protection Agency to characterize North Carolina's electricity generation profile from 2000 until 2019 and evaluate corresponding NOx and SO2 emissions by sector over the same time period.RESULTS Between 2000 and 2008 in North Carolina, approximately 60% of electric power was generated by CFPPs. Since then, North Carolina's electric power generation has transformed from predominant dependence on coal to approximately equal dependence on natural gas and nuclear power (each at ~ 30%), with coal close behind (~ 25%). Renewables have increased, although marginally relative to the rapid increase in natural gas. Despite the stark drop in reliance on CFPPs for energy in North Carolina and subsequent drop in emissions, CFPPs still contribute ~ 60% of SO2 air pollution as of 2017.LIMITATIONS This analysis relies upon electricity generation and emissions data self-reported by utilities and publicly available from federal agenciesCONCLUSION North Carolina's electric utilities met the 2009 and 2013 regulatory benchmarks set by the CSA, which resulted in substantial reductions in SO2 emissions from the fuel combustion electric generation sector. Still, CFPPs remain the primary utility-related and overall anthropogenic contributor of SO2 air pollution in North Carolina.
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Poluentes Atmosféricos , Poluição do Ar , Poluentes Atmosféricos/análise , Poluição do Ar/prevenção & controle , Carvão Mineral , Humanos , Gás Natural , North Carolina , Centrais ElétricasRESUMO
Environmental justice means equal access to a healthful environment for all. In North Carolina, many sources of pollution disproportionately affect low-income communities and communities of color. Clinicians who recognize effects of environmental injustices can improve patient care and community health. As an example, we present the effects of industrial-scale hog operations in North Carolina.
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Ração Animal , Saúde Ambiental , Indústria Alimentícia , Saúde Pública , Justiça Social , Suínos , Animais , Humanos , North CarolinaRESUMO
BACKGROUND: Nearly six million people residing in the United States do not have access to safely managed sanitation. Housed populations may lack access to centralized wastewater treatment systems or functioning onsite wastewater treatment systems, which subsequently places them at higher risk for adverse health outcomes associated with unsafe sanitation. OBJECTIVES: We sought to understand the various social barriers that impact access to safe sanitation in the United States. METHODS: We included peer-reviewed studies published between January 2000 and March 2023. The publication search was conducted using Scopus, ProQuest Social Science Database, and HeinOnline. We extracted data on social barriers and physical factors associated with access to sanitation. RESULTS: Twenty publications met the inclusion criteria, and data relating to 11 social barriers and two physical factors were extracted. The social barriers to safe sanitation access mentioned most frequently were found to be socioeconomic status and race-based discrimination. Studies discussed sanitation in communities in five states. DISCUSSION: Barriers pertained to lack of access to centralized wastewater treatment system, inadequate repair or replacement of septic systems, and lack of safely managed onsite sanitation systems. We discuss the intersectionality of the barriers, the underlying policy and history that leads to them, and make recommendations to address inequitable access to safe sanitation. Legislation and policy must be critically reviewed at national, state, and local levels to limit or eliminate ability for utilities to be extended on the basis of a community's income and property values or racial makeup. Policy recommendations also include additional community engagement, onsite sanitation system monitoring, and knowledge dissemination and education of septic system users. More geographically diverse research and research on sanitation in specific communities such as those of migrant farmworkers, undocumented persons, and tenants are recommended.
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Saneamento , Humanos , Estados UnidosRESUMO
PURPOSE: Oxidative stress is implicated in pancreatic ß-cell dysfunction, yet clinical outcomes of antioxidant therapies on diabetes are inconclusive. Since reactive oxygen species (ROS) can function as signaling intermediates for glucose-stimulated insulin secretion (GSIS), we hypothesize that exogenously boosting cellular antioxidant capacity dampens signaling ROS and GSIS. METHODS: To test the hypothesis, we formulated a mathematical model of redox homeostatic control circuit comprising known feedback and feedforward loops and validated model predictions with plant-derived antioxidant sulforaphane (SFN). RESULTS: SFN acutely (30-min treatment) stimulated basal insulin secretion in INS-1(832/13) cells and cultured mouse islets, which could be attributed to SFN-elicited ROS as N-acetylcysteine or glutathione ethyl ester suppressed SFN-stimulated insulin secretion. The mathematical model predicted an adapted redox state characteristic of strong induction of endogenous antioxidants but marginally increased ROS under prolonged SFN exposure, a state that attenuates rather than facilitates glucose-stimulated ROS and GSIS. We validated the prediction by demonstrating that although 24-h treatment of INS-1(832/13) cells with low, non-cytotoxic concentrations of SFN (2-10 µM) protected the cells from cytotoxicity by oxidative insult, it markedly suppressed insulin secretion stimulated by 20 mM glucose. CONCLUSIONS: Our study indicates that adaptive induction of endogenous antioxidants by exogenous antioxidants, albeit cytoprotective, inhibits GSIS in ß-cells.
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Antioxidantes/farmacologia , Glucose/metabolismo , Células Secretoras de Insulina/efeitos dos fármacos , Insulina/metabolismo , Isotiocianatos/farmacologia , Espécies Reativas de Oxigênio/metabolismo , Animais , Linhagem Celular , Células Cultivadas , Humanos , Células Secretoras de Insulina/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Modelos Biológicos , Estresse Oxidativo/efeitos dos fármacos , SulfóxidosRESUMO
Landfills pose an important public health risk, especially in historically disenfranchised communities that are disproportionately sited for landfills and in rural areas where private wells may be impacted. Landfills are major sources of perfluoroalkyl substances (PFAS) that migrate into the surrounding environment. This study characterized PFAS in surface waters adjacent to two landfills, one in Sampson County (SC) and one in Orange County (OC) in North Carolina. In addition to municipal solid waste and construction and demolition waste, the landfill in SC accepts industrial sludge from a chemical plant that produces proprietary PFAS. Over four months, 35 surface water samples were collected at upstream, landfill-adjacent, and downstream/downgradient sites. Thirty-four PFAS were analyzed using liquid chromatography with tandem mass spectroscopy. Of those, six novel and six legacy PFAS were detected. Legacy PFAS were detected in surface water near both landfills, with the highest concentrations adjacent to the landfill. Novel PFAS were only detected in surface water near the SC landfill and showed the highest concentrations adjacent to the landfill, indicating offsite migration of PFAS. These findings support the need for more comprehensive and frequent monitoring of groundwater and surface water wells near landfills and stricter regulation regarding the landfilling of industrial materials.
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Fluorocarbonos , Água Subterrânea , Eliminação de Resíduos , Poluentes Químicos da Água , Eliminação de Resíduos/métodos , North Carolina , Poluentes Químicos da Água/análise , Água Subterrânea/química , Instalações de Eliminação de Resíduos , Fluorocarbonos/análiseRESUMO
Coal-fired power plants (CFPP) are major contributors of air pollution, including the majority of anthropogenic sulfur dioxide (SO2) emissions, which have been associated with preterm birth (PTB). To address a 2002 North Carolina (NC) policy, 14 of the largest NC CFPPs either installed desulfurization equipment (scrubbers) or retired coal units, resulting in substantial reductions of SO2 air emissions. We investigated whether SO2 air emission reduction strategies at CFPPs in NC were associated with changes in prevalence of PTB in nearby communities. Methods: We used US EPA Air Markets Program Data to track SO2 emissions and determine the implementation dates of intervention at CFPPs and geocoded 2003-2015 NC singleton live births. We conducted a difference-in-difference analysis to estimate change in PTB associated with change in SO2 reduction strategies for populations living 0-<4 and 4-<10 miles from CFPPs pre- and postintervention, with a comparison of those living 10-<15 miles from CFPPs. Results: With the spatial-temporal exposure restrictions applied, 42,231 and 41,218 births were within 15 miles of CFPP-scrubbers and CFPP-retired groups, respectively. For residents within 4-<10 miles from a CFPP, we estimated that the absolute prevalence of PTB decreased by -1.5% [95% confidence interval (CI): -2.6, -0.4] associated with scrubber installation and -0.5% (95% CI: -1.6, 0.6) associated with the retirement of coal units at CFPPs. Our findings were imprecise and generally null-to-positive among those living within 0-<4 miles regardless of the intervention type. Conclusions: Results suggest a reduction of PTB among residents 4-<10 miles of the CFPPs that installed scrubbers.
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Rural communities of color in the southeastern U.S. experience a high burden of environmental hazards from concentrated industry placement. Community-engaged research and qualitative methods can improve our understanding of meaning-making in a community impacted by polluting facilities. This study applies the photovoice method to assess how a predominantly African American community in rural North Carolina, impacted by a landfill and confined animal feeding operations (CAFOs), perceives their health-related quality of life (HRQoL). Two research questions were developed with community-based partners: (a) How do environmental health concerns in this community influence residents' perceptions of their HRQoL? and (b) How do community and county factors facilitate or inhibit community organizing around these concerns? Three photo assignment sessions were held to engage participants in discussions related to the research questions. Researchers analyzed discussion audio recordings and identified themes related to concerns about the following issues: health and quality of life, the landfill industry's influence on community cohesion and self-determination, and actions to address environmental injustice in Sampson County. Photovoice benefits community-engaged researchers by providing a process for assessing the research interests of a community. Photovoice also serves community organizers by providing residents with a structured way to discuss their lived experiences and strategize ways to reduce hazard exposure.
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População Rural , Qualidade da Água , Humanos , Qualidade de Vida , North CarolinaRESUMO
Chronic human exposure to inorganic arsenic (iAs), a potent environmental oxidative stressor, is associated with increased prevalence of type 2 diabetes, where impairment of pancreatic ß-cell function is a key pathogenic factor. Nuclear factor E2-related factor 2 (Nrf2) is a central transcription factor regulating cellular adaptive response to oxidative stress. However, persistent activation of Nrf2 in response to chronic oxidative stress, including inorganic arsenite (iAs³âº) exposure, blunts glucose-triggered reactive oxygen species (ROS) signaling and impairs glucose-stimulated insulin secretion (GSIS). In the current study, we found that MIN6 pancreatic ß-cells with stable knockdown of Nrf2 (Nrf2-KD) by lentiviral shRNA and pancreatic islets isolated from Nrf2-knockout (Nrf2â»/â») mice exhibited reduced expression of several antioxidant and detoxification enzymes in response to acute iAs³âº exposure. As a result, Nrf2-KD MIN6 cells and Nrf2â»/â» islets were more susceptible to iAs³âº and monomethylarsonous acid (MMA³âº)-induced cell damage, as measured by decreased cell viability, augmented apoptosis and morphological change. Pretreatment of MIN6 cells with Nrf2 activator tert-butylhydroquinone protected the cells from iAs³âº-induced cell damage in an Nrf2-dependent fashion. In contrast, antioxidant N-acetyl cysteine protected Nrf2-KD MIN6 cells against acute cytotoxicity of iAs³âº. The present study demonstrates that Nrf2-mediated antioxidant response is critical in the pancreatic ß-cell defense mechanism against acute cytotoxicity by arsenic. The findings here, combined with our previous results on the inhibitory effect of antioxidants on ROS signaling and GSIS, suggest that Nrf2 plays paradoxical roles in pancreatic ß-cell dysfunction induced by environmental arsenic exposure.
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Arsênio/toxicidade , Poluentes Ambientais/toxicidade , Células Secretoras de Insulina/efeitos dos fármacos , Fator 2 Relacionado a NF-E2/metabolismo , Animais , Antioxidantes , Linhagem Celular , Técnicas de Silenciamento de Genes , Inativação Gênica , Células Secretoras de Insulina/patologia , Camundongos , Fator 2 Relacionado a NF-E2/genética , Espécies Reativas de Oxigênio , Reação em Cadeia da Polimerase em Tempo Real , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
There is growing evidence that chronic exposure of humans to inorganic arsenic, a potent environmental oxidative stressor, is associated with the incidence of type 2 diabetes (T2D). One critical feature of T2D is insulin resistance in peripheral tissues, especially in mature adipocytes, the hallmark of which is decreased insulin-stimulated glucose uptake (ISGU). Despite the deleterious effects of reactive oxygen species (ROS), they have been recognized as a second messenger serving an intracellular signaling role for insulin action. Nuclear factor erythroid 2-related factor 2 (NRF2) is a central transcription factor regulating cellular adaptive response to oxidative stress. This study proposes that in response to arsenic exposure, the NRF2-mediated adaptive induction of endogenous antioxidant enzymes blunts insulin-stimulated ROS signaling and thus impairs ISGU. Exposure of differentiated 3T3-L1 cells to low-level (up to 2 µM) inorganic arsenite (iAs³(+)) led to decreased ISGU in a dose- and time-dependent manner. Concomitant to the impairment of ISGU, iAs³(+) exposure significantly attenuated insulin-stimulated intracellular ROS accumulation and AKT S473 phosphorylation, which could be attributed to the activation of NRF2 and induction of a battery of endogenous antioxidant enzymes. In addition, prolonged iAs³(+) exposure of 3T3-L1 adipocytes resulted in significant induction of inflammatory response genes and decreased expression of adipogenic genes and glucose transporter type 4 (GLUT4), suggesting chronic inflammation and reduction in GLUT4 expression may also be involved in arsenic-induced insulin resistance in adipocytes. Taken together our studies suggest that prolonged low-level iAs³(+) exposure activates the cellular adaptive oxidative stress response, which impairs insulin-stimulated ROS signaling that is involved in ISGU, and thus causes insulin resistance in adipocytes.
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Adipócitos/efeitos dos fármacos , Adipogenia/efeitos dos fármacos , Arsenitos/toxicidade , Poluentes Ambientais/toxicidade , Glucose/metabolismo , Insulina/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Células 3T3-L1 , Adipócitos/metabolismo , Adipogenia/genética , Animais , Diabetes Mellitus Tipo 2/induzido quimicamente , Diabetes Mellitus Tipo 2/genética , Diabetes Mellitus Tipo 2/metabolismo , Expressão Gênica/efeitos dos fármacos , Transportador de Glucose Tipo 4/genética , Insulina/farmacologia , Camundongos , Fator 2 Relacionado a NF-E2/metabolismo , Estresse Oxidativo/genética , Espécies Reativas de Oxigênio/metabolismoRESUMO
Cells in vivo are constantly exposed to reactive oxygen species (ROS) generated endogenously and exogenously. To defend against the deleterious consequences of ROS, cells contain multiple antioxidant enzymes expressed in various cellular compartments to scavenge these toxic species. Under oxidative stresses, these antioxidant enzymes are upregulated to restore redox homeostasis. Such an adaptive response results from the activation of a redox-sensitive gene regulatory network mediated by nuclear factor E2-related factor 2. To more completely understand how the redox control system is designed by nature to meet homeostatic goals, we have examined the network from a systems perspective using engineering approaches. As with man-made control devices, the redox control system can be decomposed into distinct functional modules, including transducer, controller, actuator, and plant. Cells achieve specific performance objectives by utilizing nested feedback loops, feedforward control, and ultrasensitive signaling motifs, etc. Given that endogenously generated ROS are also used as signaling molecules, our analysis suggests a novel mode of action to explain oxidative stress-induced pathological conditions and diseases. Specifically, by adaptively upregulating antioxidant enzymes, oxidative stress may inadvertently attenuate ROS signals that mediate physiological processes, resulting in aberrations of cellular functions and adverse consequences. Lastly, by simultaneously considering the two competing cellular tasks-adaptive antioxidant defense and ROS signaling-we re-examine the premise that dietary antioxidant supplements is generally beneficial to human health. Our analysis highlights some possible adverse effects of these widely consumed antioxidants.
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Antioxidantes/metabolismo , Fator 2 Relacionado a NF-E2/metabolismo , Estresse Oxidativo , Espécies Reativas de Oxigênio/metabolismo , Transdução de Sinais , Biologia de Sistemas , Animais , Homeostase , Humanos , OxirreduçãoRESUMO
This review focuses on the emerging evidence that reactive oxygen species (ROS) derived from glucose metabolism, such as H(2)O(2), act as metabolic signaling molecules for glucose-stimulated insulin secretion (GSIS) in pancreatic beta-cells. Particular emphasis is placed on the potential inhibitory role of endogenous antioxidants, which rise in response to oxidative stress, in glucose-triggered ROS and GSIS. We propose that cellular adaptive response to oxidative stress challenge, such as nuclear factor E2-related factor 2 (Nrf2)-mediated antioxidant induction, plays paradoxical roles in pancreatic beta-cell function. On the one hand, induction of antioxidant enzymes protects beta-cells from oxidative damage and possible cell death, thus minimizing oxidative damage-related impairment of insulin secretion. On the other hand, the induction of antioxidant enzymes by Nrf2 activation blunts glucose-triggered ROS signaling, thus resulting in reduced GSIS. These two premises are potentially relevant to impairment of beta-cells occurring in the late and early stage of Type 2 diabetes, respectively. In addition, we summarized our recent findings that persistent oxidative stress due to absence of uncoupling protein 2 activates cellular adaptive response which is associated with impaired pancreatic beta-cell function.
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Antioxidantes/metabolismo , Diabetes Mellitus Tipo 2/metabolismo , Células Secretoras de Insulina/metabolismo , Fator 2 Relacionado a NF-E2/metabolismo , Estresse Oxidativo , Espécies Reativas de Oxigênio/metabolismo , Transdução de Sinais , Animais , Antioxidantes/uso terapêutico , Diabetes Mellitus Tipo 2/tratamento farmacológico , Glucose/metabolismo , Humanos , Hipoglicemiantes/farmacologia , Insulina/metabolismo , Células Secretoras de Insulina/efeitos dos fármacos , Células Secretoras de Insulina/enzimologia , Canais Iônicos/metabolismo , Proteínas Mitocondriais/metabolismo , Transdução de Sinais/efeitos dos fármacos , Proteína Desacopladora 2RESUMO
In this paper, we evaluate the PPARα signaling network in rats, examining transcriptional responses in primary hepatocytes exposed to a PPARα specific ligand, GW7647. These transcriptomic studies were complemented with ChIP-seq studies of PPARα binding and transcription binding motif identification for PPARα responsive genes. We also conducted a limited study of GW7647 dosing the in intact rat to examine differences in transcriptional responses for primary hepatocytes in vitro and in the intact liver. The rat network has a much larger number of down-regulated genes and pathways than we had found in the human and the PPARα binding motifs in rat differed for upregulated and down regulated genes. Based on these results and comparison with our previous work with the human PPARα signaling network, we identified qualitative differences in the transcriptional networks controlled by PPARα activation in the two species that provide an explanation of the interspecies differences in the responses of humans and rodents to GW7647 and likely to other PPARα agonists. These studies also allow some observations on the manner in which in vitro, fit-for-purpose assays in human hepatocytes could form the basis for risk assessment without recourse to in-life studies in rodents or other test species.
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Hepatócitos/metabolismo , PPAR alfa/metabolismo , Medição de Risco/métodos , Animais , Butiratos/farmacologia , Células Cultivadas , Regulação da Expressão Gênica/efeitos dos fármacos , Hepatócitos/efeitos dos fármacos , Humanos , Masculino , PPAR alfa/agonistas , PPAR alfa/genética , Compostos de Fenilureia/farmacologia , Ratos Sprague-Dawley , Transdução de Sinais/efeitos dos fármacosRESUMO
Hormetic responses to xenobiotic exposure likely occur as a result of overcompensation by the homeostatic control systems operating in biological organisms. However, the mechanisms underlying overcompensation that leads to hormesis are still unclear. A well-known homeostatic circuit in the cell is the gene induction network comprising phase I, II and III metabolizing enzymes, which are responsible for xenobiotic detoxification, and in many cases, bioactivation. By formulating a differential equation-based computational model, we investigated in this study whether hormesis can arise from the operation of this gene/enzyme network. The model consists of two feedback and one feedforward controls. With the phase I negative feedback control, xenobiotic X activates nuclear receptors to induce cytochrome P450 enzyme, which bioactivates X into a reactive metabolite X'. With the phase II negative feedback control, X' activates transcription factor Nrf2 to induce phase II enzymes such as glutathione S-transferase and glutamate cysteine ligase, etc., which participate in a set of reactions that lead to the metabolism of X' into a less toxic conjugate X''. The feedforward control involves phase I to II cross-induction, in which the parent chemical X can also induce phase II enzymes directly through the nuclear receptor and indirectly through transcriptionally upregulating Nrf2. As a result of the active feedforward control, a steady-state hormetic relationship readily arises between the concentrations of the reactive metabolite X' and the extracellular parent chemical X to which the cell is exposed. The shape of dose-response evolves over time from initially monotonically increasing to J-shaped at the final steady state-a temporal sequence consistent with adaptation-mediated hormesis. The magnitude of the hormetic response is enhanced by increases in the feedforward gain, but attenuated by increases in the bioactivation or phase II feedback loop gains. Our study suggests a possibly common mechanism for the hormetic responses observed with many mutagens/carcinogens whose activities require bioactivation by phase I enzymes. Feedforward control, often operating in combination with negative feedback regulation in a homeostatic system, may be a general control theme responsible for steady-state hormesis.
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Sistema Enzimático do Citocromo P-450/metabolismo , Retroalimentação Fisiológica , Homeostase , Estresse Fisiológico , Xenobióticos/metabolismo , Físico-Química , Sistema Enzimático do Citocromo P-450/química , Relação Dose-Resposta a Droga , Retroalimentação Fisiológica/efeitos dos fármacos , Retroalimentação Fisiológica/genética , Homeostase/efeitos dos fármacos , Homeostase/genética , Preparações Farmacêuticas/metabolismo , Receptores Citoplasmáticos e Nucleares/metabolismo , Estresse Fisiológico/efeitos dos fármacos , Estresse Fisiológico/fisiologia , Xenobióticos/química , Xenobióticos/farmacologiaRESUMO
Constitutive androstane receptor (CAR) and peroxisome proliferator activated receptor (PPAR)alpha are transcription factors known to be primary mediators of liver effects, including carcinogenesis, by phenobarbital-like compounds and peroxisome proliferators, respectively, in rodents. Many similarities exist in the phenotypes elicited by these two classes of agents in rodent liver, and we hypothesized that the initial transcriptional responses to the xenobiotic activators of CAR and PPARalpha will exhibit distinct patterns, but at later time-points these biological pathways will converge. In order to capture the global transcriptional changes that result from activation of these nuclear receptors over a time-course in the mouse liver, microarray technology was used. First, differences in basal expression of liver genes between C57Bl/6J wild-type and Car-null mice were examined and 14 significantly differentially expressed genes were identified. Next, mice were treated with phenobarbital (100 mg/kg by gavage for 24 h, or 0.085% w/w diet for 7 or 28 days), and liver gene expression changes with regards to both time and treatment were identified. While several pathways related to cellular proliferation and metabolism were affected by phenobarbital in wild-type mice, no significant changes in gene expression were found over time in the Car-nulls. Next, we determined commonalities and differences in the temporal response to phenobarbital and WY-14,643, a prototypical activator of PPAR alpha. Gene expression signatures from livers of wild-type mice C57Bl6/J mice treated with PB or WY-14,643 were compared. Similar pathways were affected by both compounds; however, considerable time-related differences were present. This study establishes common gene expression fingerprints of exposure to activators of CAR and PPARalpha in rodent liver and demonstrates that despite similar phenotypic changes, molecular pathways differ between classes of chemical carcinogens.
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Fígado/efeitos dos fármacos , PPAR alfa/efeitos dos fármacos , Receptores Citoplasmáticos e Nucleares/efeitos dos fármacos , Fatores de Transcrição/efeitos dos fármacos , Xenobióticos/farmacologia , Animais , Compostos Azo , Biotransformação/efeitos dos fármacos , Análise Química do Sangue , Carcinógenos/farmacologia , Receptor Constitutivo de Androstano , DNA Complementar/biossíntese , DNA Complementar/genética , Hipnóticos e Sedativos/farmacologia , Imuno-Histoquímica , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Análise de Sequência com Séries de Oligonucleotídeos , PPAR alfa/genética , Fenobarbital/farmacologia , Antígeno Nuclear de Célula em Proliferação/metabolismo , Pirimidinas/farmacologia , RNA/biossíntese , RNA/genética , Receptores Citoplasmáticos e Nucleares/genética , Fatores de Transcrição/genéticaRESUMO
Hypochlorous acid (HOCl) is potentially an important source of cellular oxidative stress. Human HOCl exposure can occur from chlorine gas inhalation or from endogenous sources of HOCl, such as respiratory burst by phagocytes. Transcription factor Nrf2 is a key regulator of cellular redox status and serves as a primary source of defense against oxidative stress. We recently demonstrated that HOCl activates Nrf2-mediated antioxidant response in cultured mouse macrophages in a biphasic manner. In an effort to determine whether Nrf2 pathways overlap with other stress pathways, gene expression profiling was performed in RAW 264.7 macrophages exposed to HOCl using whole genome mouse microarrays. Benchmark dose (BMD) analysis on gene expression data revealed that Nrf2-mediated antioxidant response and protein ubiquitination were the most sensitive biological pathways that were activated in response to low concentrations of HOCl (<0.35 mM). Genes involved in chromatin architecture maintenance and DNA-dependent transcription were also sensitive to very low doses. Moderate concentrations of HOCl (0.35 to 1.4 mM) caused maximal activation of the Nrf2 pathway and innate immune response genes, such as IL-1beta, IL-6, IL-10 and chemokines. At even higher concentrations of HOCl (2.8 to 3.5 mM) there was a loss of Nrf2-target gene expression with increased expression of numerous heat shock and histone cluster genes, AP-1-family genes, cFos and Fra1 and DNA damage-inducible Gadd45 genes. These findings confirm an Nrf2-centric mechanism of action of HOCl in mouse macrophages and provide evidence of interactions between Nrf2, inflammatory, and other stress pathways.
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Ácido Hipocloroso/toxicidade , Macrófagos/efeitos dos fármacos , Fator 2 Relacionado a NF-E2/efeitos dos fármacos , Oxidantes/toxicidade , Estresse Oxidativo/efeitos dos fármacos , Animais , Linhagem Celular , Relação Dose-Resposta a Droga , Perfilação da Expressão Gênica/métodos , Regulação da Expressão Gênica/efeitos dos fármacos , Genoma , Ácido Hipocloroso/administração & dosagem , Imunidade Inata/efeitos dos fármacos , Macrófagos/metabolismo , Camundongos , Análise em Microsséries , Fator 2 Relacionado a NF-E2/metabolismo , Oxidantes/administração & dosagem , Ubiquitinação/efeitos dos fármacosRESUMO
Reactive oxygen species are thought to be crucial for peroxisome proliferator-induced liver carcinogenesis. Free radicals have been shown to mediate the production of mitogenic cytokines by Kupffer cells and cause DNA damage in rodent liver. Previous in vivo experiments demonstrated that acute administration of the peroxisome proliferator di(2-ethylhexyl) phthalate (DEHP) led to an increase in production of alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (POBN) radical adducts in liver, an event that was dependent on Kupffer cell NADPH oxidase, but not peroxisome proliferator-activated receptor (PPAR)alpha. Here, we hypothesized that continuous treatment with peroxisome proliferators will cause a sustained formation in POBN radical adducts in liver. Mice were fed diets containing either 4-chloro-6-(2,3-xylidino)-2-pyrimidinylthioacetic acid (WY-14,643, 0.05% w/w) or DEHP (0.6% w/w) for up to 3 weeks. Liver-derived radical production was assessed in bile samples by measuring POBN radical adducts using electron spin resonance. Our data indicate that WY-14,643 causes a sustained increase in POBN radical adducts in mouse liver and that this effect is greater than that of DEHP. To understand the molecular source of these radical species, NADPH oxidase-deficient (p47phox-null) and PPARalpha-null mice were examined after treatment with WY-14,643. No increase in radicals was observed in PPARalpha-null mice that were treated with WY-14,643 for 3 weeks, while the response in p47phox-nulls was similar to that of wild-type mice. These results show that PPARalpha, not NADPH oxidase, is critical for a sustained increase in POBN radical production caused by peroxisome proliferators in rodent liver. Therefore, peroxisome proliferator-induced POBN radical production in Kupffer cells may be limited to an acute response to these compounds in mouse liver.
Assuntos
Fígado/efeitos dos fármacos , NADPH Oxidases/metabolismo , PPAR alfa/metabolismo , Proliferadores de Peroxissomos/farmacologia , Piridinas/metabolismo , Animais , Dietilexilftalato/farmacologia , Radicais Livres/metabolismo , Células de Kupffer/metabolismo , Fígado/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , NADPH Oxidases/genética , PPAR alfa/genética , Proliferadores de Peroxissomos/metabolismo , Pirimidinas/farmacologia , Espécies Reativas de Oxigênio/metabolismoRESUMO
Long-term exposure of rodents to peroxisome proliferators leads to increases in peroxisomes, hepatocellular proliferation, oxidative damage, suppressed apoptosis, and ultimately results in the development of hepatic adenomas and carcinomas. Peroxisome proliferators-activated receptor (PPAR)alpha was shown to be required for these pleiotropic responses; however, Kupffer cells, resident liver macrophages, were also identified as playing a role in peroxisome proliferators-induced effects, independently of PPARalpha. Previous studies showed that oxidants from NADPH (nicotinamide adenine dinucleotide phosphate, reduced) oxidase mediate acute effects of peroxisome proliferators in rodent liver. To determine if Kupffer cell oxidants are also involved in chronic effects, NADPH oxidase-deficient (p47(phox)-null) mice were fed 4-chloro-6-(2,3-xylidino)-2-pyrimidinylthio acetic acid (WY-14,643)-containing diet (0.1% wt/wt) for 1 week, 5 weeks, or 5 months along with Pparalpha-null and wild type mice. As expected, no change in liver size, cell replication rates, or other phenotypic effects of peroxisome proliferators were observed in Pparalpha-null mice. Through 5 months of treatment, the p47(phox)-null and wild type mice exhibited peroxisome proliferators-induced adverse liver effects, along with increased oxidative DNA damage and increased cell proliferation, a response that is potentially mediated through nuclear factor kappa B (NFkB). Suppressed apoptosis caused by WY-14,643 was dependent on both NADPH oxidase and PPARalpha. Collectively, these findings suggest that involvement of Kupffer cells in WY-14,643-induced parenchymal cell proliferation and oxidative stress in rodent liver is an acute phenomenon that is not relevant to long-term exposure, but they are still involved in chronic apoptotic responses. These results provide new insight for understanding the mode of hepatocarcinogenic action of peroxisome proliferators.
Assuntos
Fígado/efeitos dos fármacos , PPAR alfa/deficiência , Proliferadores de Peroxissomos/toxicidade , Pirimidinas/toxicidade , Acil-CoA Oxidase/metabolismo , Animais , Apoptose/efeitos dos fármacos , Peso Corporal/efeitos dos fármacos , Caspase 8/metabolismo , Caspase 9/metabolismo , Proteínas de Ciclo Celular/metabolismo , Proliferação de Células/efeitos dos fármacos , Dano ao DNA , Fígado/metabolismo , Fígado/patologia , Masculino , Camundongos , Camundongos Knockout , NADPH Oxidases/deficiência , NADPH Oxidases/genética , Tamanho do Órgão/efeitos dos fármacos , Estresse Oxidativo , PPAR alfa/genéticaRESUMO
Gene expression profiling is a widely used technique with data from the majority of published microarray studies being publicly available. These data are being used for meta-analyses and in silico discovery; however, the comparability of toxicogenomic data generated in multiple laboratories has not been critically evaluated. Using the power of prospective multilaboratory investigations, seven centers individually conducted a common toxicogenomics experiment designed to advance understanding of molecular pathways perturbed in liver by an acute toxic dose of N-acetyl-p-aminophenol (APAP) and to uncover reproducible genomic signatures of APAP-induced toxicity. The nonhepatotoxic APAP isomer N-acetyl-m-aminophenol was used to identify gene expression changes unique to APAP. Our data show that c-Myc is induced by APAP and that c-Myc-centered interactomes are the most significant networks of proteins associated with liver injury. Furthermore, sources of error and data variability among Centers and methods to accommodate this variability were identified by coupling gene expression with extensive toxicological evaluation of the toxic responses. We show that phenotypic anchoring of gene expression data is required for biologically meaningful analysis of toxicogenomic experiments.
Assuntos
Acetaminofen/toxicidade , Analgésicos não Narcóticos/toxicidade , Perfilação da Expressão Gênica/métodos , Expressão Gênica/efeitos dos fármacos , Genômica/métodos , Fígado/efeitos dos fármacos , Animais , Proteínas de Ligação a DNA/biossíntese , Proteínas de Ligação a DNA/genética , Determinação de Ponto Final , Ilhas Genômicas , Isomerismo , Fígado/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Fenótipo , Reprodutibilidade dos Testes , alfa-Amilases Salivares , Fatores de Transcrição/biossíntese , Fatores de Transcrição/genéticaRESUMO
Peroxisome proliferators are potent rodent liver carcinogens that act via a non-genotoxic mechanism. The mode of action of these agents in rodent liver includes increased cell proliferation, decreased apoptosis, secondary oxidative stress and other events; however, it is not well understood how peroxisome proliferators are triggering the plethora of the molecular signals leading to cancer. Epigenetic changes have been implicated in the mechanism of liver carcinogenesis by a number of environmental agents. Short-term treatment with peroxisome proliferators and other non-genotoxic carcinogens leads to global and locus-specific DNA hypomethylation in mouse liver, events that were suggested to correlate with a burst of cell proliferation. In the current study, we investigated the effects of long-term exposure to a model peroxisome proliferator WY-14,643 on DNA and histone methylation. Male SV129mice were fed a control or WY-14,643-containing (1000ppm) diet for one week, five weeks or five months. Treatment with WY-14,643 led to progressive global hypomethylation of liver DNA as determined by an HpaII-based cytosine extension assay with the maximum effect reaching over 200% at five months. Likewise, trimethylation of histone H4 lysine 20 and H3 lysine 9 was significantly decreased at all time points. The majority of cytosine methylation in mammals resides in repetitive DNA sequences. In view of this, we measured the effect of WY-14,643 on the methylation status of major and minor satellites, as well as in IAP, LINE1 and LINE2 elements in liver DNA. Exposure to WY-14,643 resulted in a gradual loss of cytosine methylation in major and minor satellites, IAP, LINE1 and LINE2 elements. The epigenetic changes correlated with the temporal effects of WY-14,643 on cell proliferation rates in liver, but no sustained effect on c-Myc promoter methylation was observed. Finally, WY-14,643 had no effect on DNA and histone methylation status in Pparalpha-null mice at any of the time points considered in this study. These data indicate the importance of epigenetic alterations in the mechanism of action of peroxisome proliferators and the key role of Pparalpha.