Cigarette smoke decreases inducible nitric oxide synthase in lung epithelial cells.
Cigarette smoking has been associated with decreased exhaled nitric oxide (NO). To investigate the mechanism of this decrease, the effects of a cigarette smoke extract were evaluated a murine lung epithelial cell line (LA-4), a human lung epithelial cell line (A549), and primary cultures of human lung epithelial cells induced to produce NO by cytokines. NO production was evaluated by measuring nitrite, a stable end product of NO, in cell culture supernatant fluids. Cigarette smoke extract caused a reduction in the cytokine-induced nitrite concentrations in the culture supernatant fluids from all 3 cell types (P < .01, all comparisons). To further investigate these observations, immunohistochemistry demonstrated a decrease in cytokine-induced inducible NO synthase (iNOS) protein expression and iNOS mRNA after cigarette smoke extract exposure in LA-4 cells. However, iNOS mRNA half-life was not altered by the smoke extract, suggesting that the smoke extract decreased NO by decreasing iNOS mRNA transcription. These findings demonstrate that cigarette smoke extract decreases iNOS expression and NO production from lung epithelial cells.
Hoyt
Jeffrey C
JC
Research Service, Southern Arizona VA Health Care System, Building 52, 3601 South 6th Avenue, Tucson, AZ 85723, USA.
Robbins
Richard A
RA
Habib
Michael
M
Springall
David R
DR
Buttery
Lee D K
LD
Polak
Julia M
JM
Barnes
Peter J
PJ
D000818:Animals; D002460:Cell Line; D016207:Cytokines / Q000494:pharmacology; D004847:Epithelial Cells / Q000201:enzymology* / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008168:Lung / Q000166:cytology* / Q000201:enzymology; D009569:Nitric Oxide / Q000096:biosynthesis; D019001:Nitric Oxide Synthase / Q000096:biosynthesis* / Q000235:genetics; D052247:Nitric Oxide Synthase Type II; D020871:RNA Stability; D012333:RNA, Messenger / Q000032:analysis; D012906:Smoke / Q000009:adverse effects*; D014026:Nicotiana; D014158:Transcription, Genetic
D016207:Cytokines; D012333:RNA, Messenger; D012906:Smoke; D009569:Nitric Oxide; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II