CYTOKINE EXPRESSION BY NEUTROPHILS AND MACROPHAGES IN-VIVO - ENDOTOXIN INDUCES TUMOR-NECROSIS-FACTOR-ALPHA, MACROPHAGE INFLAMMATORY PROTEIN-2, INTERLEUKIN-1-BETA, AND INTERLEUKIN-6 BUT NOT RANTES OR TRANSFORMING GROWTH FACTOR-BETA(1) MESSENGER-RNA EXPRESSION IN ACUTE LUNG INFLAMMATION

Using a rat model of acute lung inflammation induced by intratracheal instillation of lipopolysaccharide (LPS), we investigated the kinetics of mRNA expression and the potential cellular sources of tumor necrosis factor-alpha (TNF-alpha), macrophage inflammatory protein-2 (MIP-2), interleukin (IL)-1beta, IL-6, RANTES, and transforming growth factor-beta1 (TGF-beta1). By Northern blot analysis, TNF-alpha and MIP-2 mRNAs in total lung tissue increased markedly by 30 min and peaked by 1 h after LPS exposure, whereas expression of IL-1beta and IL-6 was not detected until 1 h and peaked within 6 h. In contrast, neither RANTES nor TGF-beta1 mRNA was induced by LPS throughout 72 h, although a basal expression was detected in both saline- and LPS-treated lung tissues. At 1 h after LPS, the bronchoalveolar lavage (BAL) fluid contained about 98 % alveolar macrophages (AM), whereas by 6 or 12 h, 88 % of BAL cells were polymorphonuclear neutrophils (PMN). Upon extraction of total RNA after separation of AM from PMN in BAL, Northern analysis showed that at 1 h, AM expressed pronounced signals for TNF-alpha, MIP-2, IL-1beta, and IL-6. At 6 and 12 h, however, while cytokine transcripts decreased in AM, PMN exhibited strong signals for these cytokines. A low basal noninducible signal for TGF-beta1 but not RANTES was detected in both AM and PMN. Finally, by in situ hybridization techniques, PMN in the lung tissue, particularly those located in the vicinity of the bronchiole and vasculature, were demonstrated to localize MIP-2 mRNA. Thus, our data provide strong evidence that LPS in vivo induces a selective cytokine response in the lung, and AM and PMN represent different temporal and cellular waves of cytokine expression during the course of acute inflammation.