Asbestos-induced activation of cell signaling pathways in human bronchial epithelial cells

Our plain-English summary of Asbestos-induced activation of cell signaling pathways in human bronchial epithelial cells, by X. Wang, J.M. Samet, A.J. Ghio (Experimental Lung Research, 2006).

The study

• Authors: X. Wang, J.M. Samet, A.J. Ghio
• Journal: Experimental Lung Research
• Published: 2006;32(6):229-43
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Using respiratory epithelial cells transfected with either superoxide dismutase (SOD) or catalase, the authors tested the hypothesis that the activation of the epidermal growth factor (EGF) receptor signal pathway after asbestos exposure involves an oxidative stress. Western blotting using phospho-specific antibodies demonstrated that the EGF receptor kinase inhibitor PD153035 decreased both the phosphorylation of extracellular signal-regulated kinase (ERK)1/2 and its upstream signal pathway, including mitogen-activate protein kinase/ERK kinase (MEK)1/2. Similarly, the MEK1/2 kinase inhibitor PD98059 also demonstrated the ability to decrease phosphorylation of ERK1/2. Crocidolite-induced phosphorylation of EGF receptor, ERK1/2, and MEK1/2 was reduced by transfection of BEAS-2B cells with a catalase vector, supporting a participation of oxidative stress in this pathway. These results show that crocidolite can activate the phosphorylation of EGF receptor and its downstream cell signal pathway in BEAS-2B cells and this is associated with the oxidative stress presented by the fibers.

In plain English

This was a laboratory cell-culture experiment in BEAS-2B cells, an immortalized line of normal human bronchial epithelium. Cells were exposed to crocidolite asbestos (100 micrograms per mL) or to EGF for 30 or 120 minutes, and protein phosphorylation was measured by Western blotting with phospho-specific antibodies. Crocidolite increased DCF fluorescence within an hour, indicating oxidative stress, and overexpression of superoxide dismutase (SOD) or catalase significantly decreased this signal. Crocidolite produced phosphorylation of ERK1/2 and MEK1/2 at 30 minutes that persisted at 2 hours, while JNK and p38 phosphorylation were weak. The EGF receptor was phosphorylated at several tyrosine sites, with Y1068 greatest and Y992 not detectable. The EGF receptor kinase inhibitor PD153035 and a blocking antibody against the receptor's ligand-binding domain (LA-1) each reduced receptor, MEK1/2 and ERK1/2 phosphorylation; the MEK inhibitor PD98059 reduced ERK1/2 but not MEK1/2 phosphorylation. Densitometry of the lower phospho-ERK1/2 band, with each group's medium-only exposure assigned a value of 1.0, gave relative values after asbestos of 3.1 plus or minus 1.3 in control-vector cells, 1.4 plus or minus 0.7 with SOD and 1.3 plus or minus 0.7 with catalase. The authors concluded that oxidative stress participates in this signaling.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: in vitro cell-culture experiment using a human bronchial epithelial cell line with adenoviral antioxidant transfection and kinase inhibitors
• Who was studied: BEAS-2B human bronchial epithelial cells (passages 68 to 80) grown in culture; some infected with adenovirus SOD or catalase vectors or a control CMV vector
• Exposure: Crocidolite (an amphibole asbestos), final concentration 100 micrograms per mL, for 30 or 120 minutes; EGF 100 ng/mL used as a comparison stimulus
• Main results:
  • Crocidolite increased oxidative stress measured by DCF fluorescence in BEAS-2B cells within an hour; SOD and catalase overexpression significantly decreased the signal
  • Crocidolite (100 micrograms per mL) induced ERK1/2 phosphorylation at 30 minutes, persisting at 2 hours; JNK and p38 phosphorylation were weak
  • Crocidolite also increased phospho-MEK1/2 at 30 minutes in BEAS-2B cells, persisting for 2 hours
  • EGF receptor phosphorylation after crocidolite occurred at multiple sites, greatest at Y1068 and not detectable at Y992
  • The EGF receptor kinase inhibitor PD153035 decreased crocidolite-induced EGF receptor phosphorylation (total and at Y845, Y1068, Y1173)
  • PD153035 and the MEK inhibitor PD98059 both reduced asbestos-induced ERK1/2 phosphorylation
  • PD153035 blocked MEK1/2 phosphorylation after asbestos, whereas PD98059 did not reduce MEK1/2 phosphorylation
  • A blocking antibody (LA-1) against the EGF receptor ligand-binding domain decreased phospho-ERK1/2 and phospho-MEK1/2 after asbestos, in addition to attenuating receptor phosphorylation
  • Densitometry was performed on the lower phospho-ERK1/2 band and on the phospho-MEK1/2 band, with each group's medium exposure set at 1.0; Table 1 reports after asbestos 3.1 plus or minus 1.3 (CMV), 1.4 plus or minus 0.7 (SOD) and 1.3 plus or minus 0.7 (catalase) for phospho-ERK1/2, and 3.8 plus or minus 1.8 (CMV), 1.8 plus or minus 0.5 (SOD) and 1.5 plus or minus 0.8 (catalase) for phospho-MEK1/2
• The authors' conclusion: The authors concluded that increased SOD and catalase expression decreased EGF receptor activation and ERK1/2 and MEK1/2 phosphorylation after asbestos exposure, supporting a role of oxidative stress in cell signaling after fiber exposure

Topics

The National Library of Medicine indexes this study under subjects our site covers: Crocidolite.

Medical terms in this study, explained in our Lexicon: Superoxide, Asbestos Exposure, Oxidative Stress, Crocidolite.

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