OBJECTIVE: To correlate cytokine gene expression with the release of protein product by murine peritoneal macrophages rendered tolerant by sequential endotoxin stimulation in vitro. DESIGN: In vitro investigation of the regulation of endotoxin-stimulated cytokine production following endotoxin pretreatment using cytokine bioassays, polymerase chain reaction, and Northern blot analyses. SETTING: In vitro cell culture model of sequential endotoxin stimulation of murine macrophages. INTERVENTIONS: Macrophages were pretreated with 0 or 100 ng/mL of lipopolysaccharide (LPS1) for 24 hours and then stimulated with 0 or 100 ng/mL of LPS (LPS2) for 4 or 24 hours. After stimulation, supernatant tumor necrosis factor (TNF) and interleukin-1 (IL-1) levels were measured by bioassay. Total RNA was extracted and messenger RNA (mRNA) corresponding to TNF and IL-1 was amplified by reverse transcription-polymerase chain reaction or analyzed by Northern blot. RESULTS: Endotoxin pretreatment resulted in the augmentation of IL-1 (mean +/- SD, 78 +/- 9 vs 596 +/- 42 pg/mL, P < .01) and the inhibition of TNF (274 +/- 63 vs 61 +/- 3 pg/mL, P < .01) release 4 hours after stimulation with 100 ng/mL of LPS2. A similar pattern of cytokine release was observed 24 hours after LPS2 stimulation. Pretreatment produced an increased IL-1 message in response to 100 ng/mL of LPS2. The TNF message was detectable in all groups receiving LPS2 alone, but the highest levels of TNF mRNA were seen in LPS1-pretreated cells stimulated with LPS2. CONCLUSIONS: Endotoxin pretreatment produced increased IL-1 message that paralleled the augmentation of IL-1 protein, whereas abundant TNF message was present even though TNF protein release was significantly inhibited. In this model of in vitro endotoxin tolerance, pretreatment initiates divergent pathways of cytokine regulation.
OBJECTIVE: To correlate cytokine gene expression with the release of protein product by murine peritoneal macrophages rendered tolerant by sequential endotoxin stimulation in vitro. DESIGN: In vitro investigation of the regulation of endotoxin-stimulated cytokine production following endotoxin pretreatment using cytokine bioassays, polymerase chain reaction, and Northern blot analyses. SETTING: In vitro cell culture model of sequential endotoxin stimulation of murine macrophages. INTERVENTIONS: Macrophages were pretreated with 0 or 100 ng/mL of lipopolysaccharide (LPS1) for 24 hours and then stimulated with 0 or 100 ng/mL of LPS (LPS2) for 4 or 24 hours. After stimulation, supernatant tumor necrosis factor (TNF) and interleukin-1 (IL-1) levels were measured by bioassay. Total RNA was extracted and messenger RNA (mRNA) corresponding to TNF and IL-1 was amplified by reverse transcription-polymerase chain reaction or analyzed by Northern blot. RESULTS: Endotoxin pretreatment resulted in the augmentation of IL-1 (mean +/- SD, 78 +/- 9 vs 596 +/- 42 pg/mL, P < .01) and the inhibition of TNF (274 +/- 63 vs 61 +/- 3 pg/mL, P < .01) release 4 hours after stimulation with 100 ng/mL of LPS2. A similar pattern of cytokine release was observed 24 hours after LPS2 stimulation. Pretreatment produced an increased IL-1 message in response to 100 ng/mL of LPS2. The TNF message was detectable in all groups receiving LPS2 alone, but the highest levels of TNF mRNA were seen in LPS1-pretreated cells stimulated with LPS2. CONCLUSIONS: Endotoxin pretreatment produced increased IL-1 message that paralleled the augmentation of IL-1 protein, whereas abundant TNF message was present even though TNF protein release was significantly inhibited. In this model of in vitro endotoxin tolerance, pretreatment initiates divergent pathways of cytokine regulation.