Enhanced interleukin-8 production in THP-1 human monocytic cells by lipopolysaccharide from oral microorganisms and granulocyte-macrophage colony-stimulating factor

Granulocyte-macrophage colony-stimulating factor (GM-CSF) has been used to assist in bone marrow recovery during cancer chemotherapy. Interleukin-8 (I L-8) plays an important role in macrophage mediated inflammatory processes including exacerbation of periodontal diseases, one of the most common comp lications in GM-CSF receiving cancer patients. The effect of GM-CSF supplem entation on IL-8 production was investigated in a human monocyte cell line THP-1, stimulated with lipopolysaccharide extracted from two oral microorga nisms. Porphyromonas gingivalis and Fusobacterium nucleatum. Resting THP-1 cells were treated with lipopolysaccharide (1 mu g/ml) of P. gingivalis or F. nucleatum and/or GM-CSF (50 IU/ml) for varying time periods. The product ion of IL-8 in THP-1 cells was measured by a solid-phase enzyme-linked immu nosorbent assay (ELISA). A very low level of the cytokine IL-8 was produced constitutive in THP-1 cells, Starting from 8 h of treatment and afterwards GM-CSF alone significantly increased IL-8 production in THP-1 cells. Lipop olysaccharide (1 mu g/ml) extracts from either F, nucleatum or P. gingivali s amplified IL-8 production 500-800 times in comparison to resting THP-1 ce lls. When lipopolysaccharide of F. nucleatum or P. gingivalis was supplemen ted with 50 IU/ml of GM-CSF, there was a statistically significant enhanced production of IL-8 by THP-1 cells after 1 day to 7 days of treatment as co mpared with lipopolysaccharide treatment alone. GM-CSF (50 IU/ml) also sign ificantly increased IL-8 production from 2-7 days of treatment of THP-1 cel ls when supplemented with a positive control, phorbol-12-myristate-13 aceta te (PMA), as compared to PMA treatment alone. These investigations using th e in vitro THP-1 human monocyte cell model indicate that there may be an in crease in the response on a cellular level to oral endotoxin following GM-C SF therapy as evidenced by enhanced production of the tissue-reactive infla mmatory cytokine, IL-8.