Regulation of caveolin-1 expression, nitric oxide production and tissue injury by tumor necrosis factor-alpha following ozone inhalation.
Alveolar macrophages (AM) and inflammatory mediators including nitric oxide and peroxynitrite contribute to ozone-induced lung injury. The generation of these mediators is regulated, in part, by the transcription factor NF-kappaB. We previously demonstrated a critical role for NF-kappaB p50 in ozone-induced injury. In the present studies mechanisms regulating NF-kappaB activation in the lung after ozone inhalation were analyzed. Treatment of wild type (WT) mice with ozone (0.8 ppm, 3 h) resulted in a rapid increase in NF-kappaB binding activity in AM, which persisted for at least 12 h. This was not evident in mice lacking TNFalpha which are protected from ozone-induced injury; there was also no evidence of nitric oxide or peroxynitrite production in lungs from these animals. These data demonstrate that TNFalpha plays a role in NF-kappaB activation and toxicity. TNFalpha signaling involves PI-3-kinase (PI3K)/protein kinase B (PKB), and p44/42 MAP kinase (MAPK) which are important in NF-kappaB activation. Ozone Inhalation resulted in rapid and transient increases in p44/42 MAPK and PI3K/PKB in AM from WT mice, which was evident immediately after exposure. Caveolin-1, a transmembrane protein that negatively regulates PI3K/PKB and p44/42 MAPK signaling, was downregulated in AM from WT mice after ozone exposure. In contrast, ozone had no effect on caveolin-1, PI3K/PKB or p44/42 MAPK expression in AM from TNFalpha knockout mice. These data, together with our findings that TNFalpha suppressed caveolin-1 expression in cultured AM, suggest that TNFalpha and downstream signaling mediate activation of NF-kappaB and the regulation of inflammatory genes important in ozone toxicity, and that this process is linked to caveolin-1.
Fakhrzadeh
Ladan
L
Department of Pharmacology and Toxicology, Rutgers University, 160 Frelinghuysen Road, Piscataway, NJ 08854, USA.
Laskin
Jeffrey D
JD
Laskin
Debra L
DL
D000818:Animals; D051242:Caveolin 1 / Q000235:genetics / Q000378:metabolism*; D005260:Female; D001239:Inhalation; D016676:Macrophages, Alveolar / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D010126:Ozone / Q000633:toxicity*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011014:Pneumonia / Q000139:chemically induced* / Q000235:genetics / Q000473:pathology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism*
D051242:Caveolin 1; D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; D009569:Nitric Oxide; D010126:Ozone; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3