Rheumatology Advance Access originally published online on January 17, 2006
Rheumatology 2006 45(6):703-710; doi:10.1093/rheumatology/kei282
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Chloroquine inhibits production of TNF-
, IL-1ß and IL-6 from lipopolysaccharide-stimulated human monocytes/macrophages by different modes
Department of Biochemistry, College of Medicine, Catholic University of Korea, Seoul, South Korea.
Correspondence to: D.-M. Jue, Department of Biochemistry, College of Medicine, Catholic University of Korea, 505 Banpo-dong, Seocho-gu, Seoul 137-701, South Korea. E-mail: dmjue{at}catholic.ac.kr
Objectives. TNF-
, IL-1 and IL-6 are known to have primary roles in the pathogenesis of rheumatoid arthritis and other inflammatory diseases. The anti-rheumatic drug chloroquine has been shown to inhibit TNF-, IL-1 and IL-6 production from mononuclear phagocytes. We examined the underlying mechanisms involved in the chloroquine-induced inhibition of cytokine production.
Methods. Human peripheral blood mononuclear cells and monocytes/macrophages and monocytic U-937 and THP-1 cells were stimulated with lipopolysaccharide, and TNF-, IL-1ß and IL-6 production was measured by ELISA. Levels of mRNA were measured by northern blotting and reverse transcription–polymerase chain reaction. Synthesis of 26-kDa TNF- precursor was measured by metabolic labelling and immunoprecipitation analysis. Transcription rate was determined by nuclear run-on assay.
Results. TNF- release from the cells was inhibited by chloroquine, whereas the steady-state level of TNF- mRNA and synthesis of 26-kDa TNF- precursor were not changed by chloroquine. In contrast, chloroquine-induced inhibition of IL-1ß and IL-6 release was accompanied by a decrease in their steady-state mRNA levels. The transcription rates of the IL-1ß and IL-6 genes were not changed by chloroquine, whereas the stability of IL-1ß and IL-6 mRNA was decreased by chloroquine. Weak-base amines such as methylamine and ammonium chloride had no effect on the production of TNF-, whereas they partially blocked the production of IL-1ß and IL-6.
Conclusions. Our results indicate that chloroquine-mediated inhibition of TNF-, IL-1ß and IL-6 synthesis occurs through different modes in lipopolysaccharide-stimulated human monocytes/macrophages: it blocks the conversion of cell-associated TNF- precursor to mature soluble protein, whereas it reduces the levels of IL-1ß and IL-6 mRNA, at least in part, by decreasing their stability and by a pH-dependent mechanism.
KEY WORDS: Chloroquine, Rheumatoid arthritis, Cytokines, Gene regulation, Monocytes/macrophages, Inflammation