LPS pretreatment of mouse peritoneal macrophages differentially modulates TNFα and iNOS expression

Many studies have established that pretreatment of mouse macrophages with LPS will alter subsequent responsiveness of these cells to stimulation either with LPS or other stimuli. Incubation of C3Heb/FeJ mouse macrophages with low sub-stimulatory (e.g. 0.10 ng/ml) LPS for 6 h, followed by activation with 100 ng/ml of LPS results in up-regulation of LPS-dependent TNFα production and suppression of the ability of these cells to secrete nitric oxide (NO). To assess whether these two responses might be co-ordinately regulated, immunocytochemical analyses of LPS-pretreated macrophages were carried out using anti-TNFα and anti-iNOS antibodies, both with and without a period of LPS pretreatment. As anticipated, the detection of individual iNOS-expressing macrophages in LPS-stimulated cultures accurately reflected threshold doses of LPS required for detection of NO in culture supernatants in terms of frequency of percentage of the total population positive for expression of iNOS protein. Pretreatment with sub-stim...