Different accumulation of activated extracellular signal-regulated kinases (ERK 1/2) and role in cell-cycle alterations by epidermal growth factor, hydrogen peroxide, or asbestos in pulmonary epithelial cells

Our plain-English summary of Different accumulation of activated extracellular signal-regulated kinases (ERK 1/2) and role in cell-cycle alterations by epidermal growth factor, hydrogen peroxide, or asbestos in pulmonary epithelial cells, by S. Buder-Hoffmann, C. Palmer, P. Vacek, et al (American Journal of Respiratory Cell and Molecular Biology, 2001).

The study

• Authors: S. Buder-Hoffmann, C. Palmer, P. Vacek, D. Taatjes, B. Mossman
• Journal: American Journal of Respiratory Cell and Molecular Biology
• Published: 2001;24(4):405-13
• Cited by: 76 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The extracellular signal-regulated kinase (ERK) pathway is induced by cytokines and oxidative stress. In this study we examined the patterns of localization of phosphorylated ERK proteins in relationship to subsequent phenotypic responses by the mitogenic agent epidermal growth factor (EGF) (5 ng/ ml); hydrogen peroxide (H(2)O(2)) (100 to 300 microM), an inducer of apoptosis; and crocidolite asbestos (5 microg/cm(2) dish) in a nontransformed murine alveolar type II epithelial cell line (C10). Laser scanning cytometry and flow cytometry were used to determine: (1) whether expression of phosphorylated ERKs was cell cycle-related; and (2) whether cell-cycle alterations by agents could be modified after addition of the mitogen-activated protein kinase/ERK kinase (MEK) 1 inhibitor PD98059. In contrast to other stimuli which induced transient increases in phosphorylated ERKs, asbestos caused fiber-associated localization of phosphorylated ERKs that were elevated from 1 to 24 h (P < or = 0.05), and striking apoptosis followed by increased numbers of cells in the S phase at 72 h. In both control and asbestos-exposed cells, the percentage of phosphorylated ERK-positive cells was greatest in cells in the G(2)/M and S phases of the cell cycle. All stimuli caused increased proportions of cells in G(2)/M at 24 h that were inhibited by PD98059 (30 microM). Increases in G(2)/M cells by H(2)O(2) and asbestos also were decreased at 48 h by the MEK1 inhibitor. In addition, PD98059 abrogated elevations in S-phase cells by EGF and H(2)O(2) at 24 h and by asbestos at 72 h. Our results suggest that ERKs mediate cell-cycle alterations during the development of epithelial cell apoptosis or proliferation by diverse ERK stimuli.

In plain English

This was a laboratory study of a mouse lung cell line (C10), not a study of people. The authors exposed the cells to crocidolite asbestos, to epidermal growth factor (EGF, a growth signal) or to hydrogen peroxide. They then tracked activated ERKs (signaling proteins), apoptosis (a form of cell death), DNA synthesis and cell-cycle stages. EGF and hydrogen peroxide caused short-lived ERK activation that peaked at 15 and 30 minutes. Asbestos caused delayed, persistent ERK activation from 1 to 24 hours, and the pattern of ERK accumulation in the cytoplasm was restricted to areas of fiber deposition. Asbestos produced striking increases in apoptosis at all time periods. At 72 hours it also increased the number of cells making DNA, with no change in total cell numbers. At 2 and 8 hours, asbestos-exposed groups showed roughly threefold increases in the percentage of cells with activated ERKs compared with unexposed cells. A drug that blocks the ERK pathway (PD98059) reduced the cell-cycle shifts caused by all three agents. The authors concluded that their results suggest ERKs mediate cell-cycle changes as these cells develop apoptosis or proliferation.

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 laboratory experiment on a cultured cell line, using microscopy, Western blot, laser scanning cytometry and flow cytometry
• Who was studied: A nontransformed mouse (murine) alveolar type II epithelial cell line (C10), studied at the University of Vermont College of Medicine; no human subjects
• Exposure: Crocidolite asbestos (NIEHS reference sample) at 5 per square centimeter of culture dish; epidermal growth factor at 5 ng/ml; hydrogen peroxide at 100 to 300. The scanned text prints the asbestos dose as 'mg/cm2' and the hydrogen peroxide dose as 'mM'; the PubMed abstract gives micrograms per square centimeter and micromolar. Comparison cultures were sham controls given medium without agents.
• Main results:
  • EGF and hydrogen peroxide caused significant increases in ERK phosphorylation that peaked at 15 and 30 minutes (P less than 0.05, Western blot)
  • Asbestos caused delayed and persistent ERK activation, from 1 to 24 hours
  • In asbestos-exposed cells, the pattern of ERK accumulation in the cytoplasm was restricted to areas where fibers were deposited and accumulated
  • Asbestos-exposed cells showed striking increases in apoptosis at all time periods, and increases in PCNA-positive (DNA-synthesizing) cells at 72 hours without changes in total cell numbers
  • Hydrogen peroxide caused a dose-dependent increase in apoptosis
  • In EGF-exposed cells, ERK activation preceded increased numbers of cells in S phase and cell proliferation, shown by higher total cell numbers
  • At 2 and 8 hours, asbestos-exposed groups had approximately threefold increases in the percentage of cells expressing activated ERKs compared with sham controls (laser scanning cytometry)
  • In sham control cells, activated ERKs were found in less than 10% of cells in the subdiploid and G0/G1 fractions and in 27 to 35% of cells in the G2/M and S fractions
  • In asbestos-exposed groups, 40 to 57% of cells in G2/M or S showed activated ERKs, while less than 10% of cells with a subdiploid DNA content did
  • All three agents increased the percentage of cells in the G2/M phase at 24 hours, and the ERK pathway blocker PD98059 significantly inhibited these increases (P less than 0.05)
  • PD98059 also abolished the more persistent G2/M increases seen at 48 hours after hydrogen peroxide or asbestos
  • PD98059 abolished S-phase increases caused by EGF and hydrogen peroxide at 24 hours and by asbestos at 72 hours
• The authors' conclusion: The authors concluded that their results suggest ERKs mediate cell-cycle alterations as epithelial cells develop apoptosis or proliferation in response to diverse ERK stimuli

Topics

Medical terms in this study, explained in our Lexicon: Cytokine, Oxidative Stress, Apoptosis, Crocidolite.

Related studies

• The duration of nuclear extracellular signal-regulated kinase 1 and 2 signaling during cell cycle reentry distinguishes proliferation from apoptosis in response to asbestos — Z. Yuan, D.J. Taatjes, et al. (2004)
• Role of extracellular signal-regulated protein kinases in apoptosis by asbestos and H2O2 — L.A. Jiménez, C. Zanella, et al. (1997)
• Persistent localization of activated extracellular signal-regulated kinases (ERK1/2) is epithelial cell-specific in an inhalation model of asbestosis — A.B. Cummins, C. Palmer, et al. (2003)
• Increased phosphorylated extracellular signal-regulated kinase immunoreactivity associated with proliferative and morphologic lung alterations after chrysotile asbestos inhalation in mice — R.F. Robledo, S.A. Buder-Hoffmann, et al. (2000)
• Effect of insulin and epidermal growth factors on the synthesis of glycosaminoglycans/proteoglycans in cultured human malignant mesothelioma cells of different phenotypic morphology — G.N. Tzanakakis, N.K. Karamanos, et al. (1996)
• Asbestos inhalation induces tyrosine nitration associated with extracellular signal-regulated kinase 1/2 activation in the rat lung — A. Iwagaki, N. Choe, et al. (2003)

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