Grantee Research Project Results
2002 Progress Report: Mechanisms of Air Pollutant-induced Pulmonary Inflammation; Effects of Zinc on EGFR Receptor Function
EPA Grant Number: R829214Title: Mechanisms of Air Pollutant-induced Pulmonary Inflammation; Effects of Zinc on EGFR Receptor Function
Investigators: Graves, Lee M. , Wu, Weidong
Institution: University of North Carolina at Chapel Hill
EPA Project Officer: Chung, Serena
Project Period: November 19, 2001 through November 18, 2004
Project Period Covered by this Report: November 19, 2001 through November 18, 2002
Project Amount: $874,125
RFA: Health Effects of Particulate Matter (2001) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Human Health , Particulate Matter , Air
Objective:
The main objective of this research project is to specifically determine the mechanism(s) by which zinc (Zn) increases the phosphorylation and activation of the epidermal growth factor receptor (EGFR), and ultimately increases inflammatory cytokine production.
Progress Summary:
We have made considerable progress completing the aims of the research project. This has resulted in the publications listed in the Publications/Presentations section of this report.
Exposure to ambient air pollution particles is associated with significant increases in both morbidity and mortality. A leading theory attributes the toxicity of ambient PM10 particles to its content of metals, which is supported by recent in vitro and in vivo findings that relate PM10 toxicity to its transition metals. Next to iron, Zn is the most abundant combustion-derived metal associated with respiratory ambient PM. It is known to produce acute airway inflammation when inhaled and, therefore, is relevant to the possible mechanisms of PM-related morbidity and mortality. Identifying the mechanism of action of Zn is relevant to the U.S. Environmental Protection Agency's mission to gain a better understanding of the effects of ambient air pollution particles on human airway function.
The general objectives of this research project are to investigate the molecular targets that are required for initiating the cellular effects to Zn exposure. Cellular surface receptors integrate a multitude of extracellular signals such as environmental stresses, growth factors, neuropeptides or hormones, thus regulating a large diversity of signaling pathways and cell responses. The EGFR family of receptor tyrosine kinases represents both key regulators of normal cellular development as well as critical players in a variety of pathophysiological phenomena. EGFR activation recently was observed to interact with NFkB signaling pathways, which was closely associated with pro-inflammatory mediator IL-8 overexpression. The excessive production of mucin is a hallmark of chronic bronchitis, and other laboratories have reported that the induction of mucin genes (MUC5AC or MUC2) by residual oil fly ash (ROFA) was dependent on signaling through signals, which may be initiated through EGFR. Therefore, EGFR activation is increasingly recognized as a critical step in the pathogenesis of pulmonary inflammation. Remodeling induced by environmental insults also may mediate the effects of exposure to combustion-derived metal contaminants such as Zn.
Zn-induced EGFR activation was examined using specific murine B82L fibroblast cell lines, which normally have no detectable EGFR proteins or have been genetically engineered to express human EGFR or modified EGFR. Using these reagents, we observed that Zn-induced Ras activation required an EGF receptor. Zn-induced Src activation was responsible for subsequent phosphorylation of EGF receptor at Y845, further resulting in Ras activation. Thus, this research has defined phosphorylation of Tyr 845 as a requirement for Zn signaling, and provided significant novel evidence for the EGFR as a target for Zn. This work was published recently (Wu, et al. Journal of Biological Chemistry 2002;277(27):24252-24257).
We also have made considerable progress in determining if Zn directly increases EGFR dimerization. Thus far, our studies suggest that this is not the mechanism by which Zn activates the EGFR and the mitogen-activated protein kinase (MAPK) cascade. Our studies using a Zn ionophore have demonstrated that intracellular, rather than extracellular, Zn is required for the effects of this metal on EGFR signaling (a paper describing these studies has been submitted to Toxicology and Applied Pharmacology). Thus, we have made major strides towards accomplishing the initial objectives of this research project. A potential practical application of these studies is that recently developed EGFR inhibitors may provide useful agents to control inflammatory responses initiated by combustion-derived metal contaminants such as Zn.
We have begun to investigate the targets for Zn signaling and this will be a major part of the emphasis of our research this year. We will not deviate from the proposed objectives. The UNC Proteomics facility recently acquired a new mass spectrometer (ABI TOF/TOF). This instrument has greatly improved sensitivity and speed, which is predicted to assist in the identification of targets for Zn-induced phosphorylation.
Future Activities:
A major part of our research this year will be to investigate the targets for Zn signaling. Meanwhile, based on our recently achieved preliminary data, the possible role of matrix metalloproteinase in Zn-induced EGFR transactivation will be studied in normal human airway epithelial cells.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
Other project views: | All 13 publications | 8 publications in selected types | All 8 journal articles |
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Type | Citation | ||
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Samet JM, Dewar BJ, Wu W, Graves LM. Mechanisms of Zn2+-induced signal initiation through the epidermal growth factor receptor. Toxicology and Applied Pharmacology 2003;191(1):86-93. |
R829214 (2002) R829214 (Final) |
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Wu W, Graves LM, Gill GN, Parsons SJ, Samet JM. Src-dependent phosphorylation of the epidermal growth factor receptor on tyrosine 845 is required for zinc-induced Ras activation. Journal of Biological Chemistry 2002;277(27):24252-24257. |
R829214 (2002) R829214 (Final) |
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Supplemental Keywords:
ambient air, particulate matter, PM, combustion-derived metal, mucin expression, biology, protein phosphorylation, signal transduction, North Carolina, NC, EPA Region 4, air toxics, air pollutant-induced pulmonary inflammation, air quality, epidermal growth factor receptor, EGFR, human health effects, pulmonary, pulmonary toxicity, EGF receptor, Ras, MAP kinase, Zn, zinc., RFA, Scientific Discipline, Air, Waste, Geographic Area, particulate matter, Toxicology, air toxics, Health Risk Assessment, State, Incineration/Combustion, EPA Region, ambient air quality, region 4, human health effects, ambient air, pulmonary toxicity, pulmonary, Zinc, epidermal growth factor receptor (EGFR), air pollutant-induced pulmonary inflammation, North Carolina (NC), pulmonary inflammation, PMProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.