Cigarette smoking is the major factor responsible for chronic obstructive lung disease, but it occurs in only a minority of smokers. Smoking is associated with increased susceptibility to pulmonary infections and with a neutrophil- and macrophage-rich inflammation of the small airways. We compared concentrations of tumor necrosis factor (TNF), interleukin (IL)-6, and IL-8 in bronchoalveolar lavage fluid (BALF) and measured the capacity of BALF macrophages to release TNF and IL-6 in vitro in nine smokers (19.1 +/- 4.2 pack-years; mean +/- SE) and nine nonsmokers. Compared with nonsmokers, BALF from smokers contained more cells (65.3 +/- 13.2 versus 27.2 +/- 4.8 x 10(6); p < 0.02), but much lower concentrations of IL-6 (1.8 +/- 1.0 versus 15.9 +/- 5.8 pg/ml; p < 0.05). The two smokers with the highest number of BALF cells had increased BALF concentrations of interleukin-8 (IL-8), but there was no difference in BALF IL-8 concentrations between the two groups (p = 0.08). Compared with BALF macrophages from nonsmokers, cells from smokers released less TNF (211 +/- 77 versus 1,406 +/- 348 units per 10(8) cells; p < 0.01) and IL-6 (5.8 +/- 2.6 versus 64.9 +/- 23.3 hybridoma units per ml; p < 0.02) during a 6-h incubation with lipopolysaccharide (LPS). We conclude that even in young, healthy smokers the pulmonary microenvironment is markedly abnormal, characterized by depressed levels of IL-6, macrophages that have a markedly depressed capacity for LPS-induced cytokine release and, in some smokers, increased concentrations of IL-8.

Although considerable evidence suggests that bronchopulmonary dysplasia (BPD) is the result of prolonged inflammation and impaired healing of the immature lung, the mediators that regulate inflammation in neonatal lung injury have not been completely elucidated. We examined whether the cytokines IL-6 and tumor necrosis factor-a (TNF) interact to modulate a cascade of cell-cell signaling events involved in inflammation contributing to the development of BPD. To determine the relative activities of these cytokines in neonatal lung injury, lung lavage samples were serially obtained from 1 to 28 d from 11 infants with self-limited respiratory distress syndrome (RDS), 19 infants with evolving BPD, and 10 control infants ventilated for nonpulmonary reasons. On the first day of life, there were no differences in antigenic IL-6 concentrations in lavage fluids among the BPD, RDS, and control groups, but IL-6 activity determined by the 7TD1 proliferation assay was 15-fold and 6.6-fold higher in lung lavage of infants who developed BPD compared with activities in lavage from control and RDS infants, respectively (control, Exogenous surfactant therapy has dramatically improved survival of very-low-birth-weight infants with RDS, but it has not affected the incidence of the neonatal chronic lung disorder B P D (1). This suggests that factors in addition t o surfactant deficiency contribute t o neonatal lung injury. Pathologic findings in B P D are consistent with a process of prolonged lung inflammation and impaired healing (2, 3). In human infants with RDS (4-6) 49.4 ? 17.6; RDS, 117.3 2 59.6; BPD, 779.5 2 212.6 x 10' hybridoma units/L, mean * SEM,p = 0.02). This suggests that pathways for inactivating or inhibiting IL-6 that may be present in the lungs of RDS and control infants may be deficient in BPD infants. IL-6 activity remained elevated in lavage of BPD infants for the first 2 wk and declined to low levels by d 28. There were no differences among groups on the first day of life for TNF antigen concentration or TNF activity determined by the L929 bioassay. Detectable but low TNF activity was found in BPD samples, with peak activity found in d-14 samples. Differences in complex interactions among these and other cytokines with their receptors and inhibitors may predispose some infants with RDS to develop BPD. (Pediuh. Res 36: 244-252, 1994) Abbreviations RDS, respiratory distress syndrome BPD, bronchopulmonary dysplasia TNF, tumor necrosis factor-a PROM, prolonged rupture of membranes and in primate models of acute lung injury (7), there is a rapid influx of neutrophils into the lung during the first 48 t o 96 h after initial injury followed b y a n increase in alveolar macrophages with subsequent resolution of airw a y inflammation. In contrast, in infants w h o develop BPD, the neutrophil influx is prolonged and the alveolar macrophage entry is delayed and blunted (5). nolysis (13), the mediators that regulate neonatal lung

The pyrogenic cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) appear in the circulation during infections and injuries, but TNF-alpha and IL-6 are regulated differently in macrophages. We compared the effects of elevated temperatures within the usual febrile range on the expression of TNF-alpha and IL-6 in vitro in lipopolysaccharide (LPS)-stimulated human macrophages derived from peripheral blood monocytes (HuMoM phi). During an 18-h incubation at 37 degrees C with 5 ng/ml LPS, these cells released 5,030 +/- 1,460 pg TNF-alpha/10(6) cells (means +/- SE) and 1,380 +/- 280 pg IL-6/10(6) cells. In LPS-stimulated HuMoM phi incubated at 40 degrees C, TNF-alpha release was almost completely inhibited (76 +/- 76 pg TNF-alpha/10(6) cells; P < 0.01 compared with LPS-stimulated HuMoM phi at 37 degrees C), but release of IL-6 was preserved (1,600 +/- 780 pg IL-6/10(6) cells). Western and Northern analyses showed that levels of TNF-alpha mRNA and cell-associated and secreted TNF-alpha protein were decreased, but IL-6 expression was unchanged at 40 degrees C in LPS-stimulated macrophages. Incubating HuMoM phi at 40 degrees did not alter their viability after 18 h but induced a 75-fold increase in levels of the inducible heat-shock protein 72 (HSP-72) mRNA in the face of a 56% inhibition in total protein synthesis. Our results show that IL-6 expression persisted at incubation temperatures in the upper end of the physiological range that induced heat shock and attenuated the expression of functionally active TNF-alpha in LPS-stimulated HuMoM phi.

We have previously reported that sustained tumor necrosis factor (TNF)-alpha expression is suppressed by temperatures in the febrile range in human macrophages. In this study, we examined the mechanisms of high-temperature-induced macrophage TNF suppression in the RAW 264.7 macrophage cell line. Incubating lipopolysaccharide (LPS)-stimulated RAW 264.7 cells at 40 degrees C reduced TNF secretion by 92% and peak TNF mRNA levels by 43% compared with cells incubated at 37 degrees C (P < 0.05) but did not affect levels of glyceraldehyde-3-phosphate dehydrogenase, beta-actin, or interleukin-6 mRNA. TNF mRNA half-life, measured after transcriptional arrest with actinomycin D, was reduced from 21.8 +/- 3.6 min in LPS-stimulated RAW 264.7 cells at 37 degrees C to 16.0 +/- 1.8 min at 40 degrees C (P < 0.03), but these cells at 40 degrees C did not alter transcription rate or TNF mRNA polysome association. TNF mRNA destabilization occurred at temperatures below the threshold (43 degrees C) for the generalized heat shock response in these cells. We conclude that heating macrophages to febrile-range temperatures attenuates sustained TNF expression by modulating posttranscriptional processing, including acceleration of TNF mRNA decay.

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