Journal Article

MAPK/AP-1 signal pathway in tobacco smoke-induced cell proliferation and squamous metaplasia in the lungs of rats

Cai-Yun Zhong, Ya-Mei Zhou, Gordon C. Douglas, Hanspeter Witschi and Kent E. Pinkerton

in Carcinogenesis

Volume 26, issue 12, pages 2187-2195
Published in print December 2005 | ISSN: 0143-3334
Published online July 2005 | e-ISSN: 1460-2180 | DOI:
MAPK/AP-1 signal pathway in tobacco smoke-induced cell proliferation and squamous metaplasia in the lungs of rats

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Overwhelming evidence has demonstrated tobacco smoke (TS) is causally associated with various types of cancers, especially lung cancer. Sustained epithelial cell hyperplasia and squamous metaplasia are considered as preneoplastic lesions during the formation of lung cancer. The cellular and molecular mechanisms leading to lung cancer due to TS are not clear. Mitogen-activated protein kinases (MAPK)/activator protein-1 (AP-1) can be activated by various stimuli and play a critical role in the control of cell proliferation and differentiation. To date, information on the response of the MAPK/AP-1 pathway during hyperplasia and squamous metaplasia induced by TS is lacking. We therefore investigated the effects of TS on the development of epithelial hyperplasia and squamous metaplasia, regulation of MAPK/AP-1 activation, and expression of AP-1-regulated cell cycle proteins and differentiation markers in the lungs of rats. Exposure of rats to TS (30 mg/m3 or 80 mg/m3, 6 h/day, 3 days/week for 14 weeks) dramatically induced cell proliferation and squamous metaplasia in a dose-dependent manner, effects that paralleled the activation of AP-1-DNA binding activity. Phosphorylated ERK1/2, JNK, p38 and ERK5 were significantly increased by exposure to TS, indicating the activation of these MAPK pathways. Expression of Jun and Fos proteins were differentially regulated by TS. TS upregulated the expression of AP-1-dependent cell cycle proteins including cyclin D1 and proliferating cell nuclear antigen (PCNA). Among the AP-1-dependent cell differentiation markers, keratin 5 and 14 were upregulated, while loricrin, filaggrin and involucrin were downregulated following TS exposure. These findings suggest the important role of MAPK/AP-1 pathway in TS-induced pathogenesis, thus providing new insights into the molecular mechanisms of TS-associated lung diseases including lung cancers.

Keywords: AP-1, activator protein-1; BrdU, bromodeoxyuridine; DAB, diaminobenzidine; EGFR, epidermal growth factor receptor; ERK, extracellular signal-regulated kinases; FA, filtered air; JNK, Jun N-terminal kinases; MAPK, mitogen-activated protein kinases; PCNA, proliferating cell nuclear antigen; SAPK, stress-activated protein kinase; TS, tobacco smoke; TSP, total suspended particulates

Journal Article.  5965 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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