Influence of LPS stimulation on NO production from NPFs. NPFs at a concentration of 5 × 105 cells were stimulated with various concentrations of LPS. After 24 hours, culture supernatants were obtained and assayed for NO (NO2-/NO3-) levels by the Griess method. Data are the mean ± SE of five different subjects. LPS, lipopolysaccharide; NO, nitric oxide; NPFs, nasal polyp fibroblasts. NS, not significant (P > 0.05).