Regulation of interleukin-8 expression in porcine alveolar macrophages by bacterial lipopolysaccharide

• Published in: The Journal of biological chemistry 1994-01, Vol.269 (1), p.77-85
• Main Authors: Lin, G, Pearson, A E, Scamurra, R W, Zhou, Y, Baarsch, M J, Weiss, D J, Murtaugh, M P
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Analysis of the immune response. Humoral and cellular immunity; Animals; Base Sequence; Biological and medical sciences; Cloning, Molecular; Dexamethasone - pharmacology; DNA, Complementary; Fundamental and applied biological sciences. Psychology; Fundamental immunology; Gene Expression Regulation - drug effects; Humans; Immunobiology; Interleukin-4 - pharmacology; Interleukin-8 - biosynthesis; Interleukin-8 - genetics; Lipopolysaccharides - pharmacology; Lymphokines, interleukins ( function, expression); Macrophages, Alveolar - metabolism; Molecular Sequence Data; Regulatory factors and their cellular receptors; Sequence Homology, Amino Acid; Swine; Transcription, Genetic
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/s0021-9258(17)42316-7

Interleukin (IL)-8 is a macrophage-derived neutrophil chemotactic factor that plays an important role in the recruitment of neutrophils to inflammatory loci. Hence, expression of IL-8 by alveolar macrophages may be a significant factor in host defense in the lung and in the pathogenesis of pneumonia in swine. To initiate molecular studies of IL-8 regulation in pigs, we cloned IL-8 cDNA and examined the regulation of its mRNA in alveolar macrophages. The porcine IL-8 cDNA consists of 1491 base pairs including a coding region of 309 base pairs. The deduced amino acid sequence was 75 and 81% similar to human and rabbit IL-8, respectively. Resting macrophages contained low levels of IL-8 mRNA, which increased markedly after exposure to bacterial lipopolysaccharide (LPS). LPS induction of IL-8 was direct, not mediated through elevation of tumor necrosis factor or interleukin-1. The effect of LPS on IL-8 expression was dose dependent, and induction was observed at a concentration of 10 pg/ml. IL-8 mRNA expression was detectable within 0.5 h after stimulation with LPS, peaked at 3-6 h at about 30-fold higher levels than in resting cells, and was maintained for 24 h. Secreted IL-8, measured by neutrophil chemotaxis, was induced within 4 h by LPS, and accumulated in the media throughout the 24-h period. The mechanism of induction of IL-8 mRNA appeared to involve transcription and RNA processing. Nuclear run-on analysis showed that the IL-8 gene was actively transcribed in noninduced cells; upon stimulation with LPS, the rate of IL-8 transcription was increased about 4-fold. A single mature mRNA species was detected by primer extension analysis. The half-life of IL-8 mRNA transcripts in aveolar macrophages was approximately 2 h and did not change after LPS stimulation. The ability of LPS to induce IL-8 expression was suppressed by recombinant human IL-4 and dexamethasone in a concentration-dependent manner. These observations indicate that the expression of IL-8 is an early event in the sequelae to bacterial infection in the lung.