Acetaminophen and lipopolysaccharide act in synergy for the production of pro-inflammatory cytokines in murine RAW264.7 macrophages

Abstract

There is extensive evidence that pro-inflammatory cytokines produced by macrophages are involved in toxicity induced by drugs such as acetaminophen (APAP). We investigated the effect of subtoxic concentrations of acetaminophen in conjunction with bacterial lipopolysaccharide (LPS) on the expression of the pro-inflammatory cytokines TNFα and IL-1β using the mouse macrophage cell line RAW264.7 as a model. APAP alone induced in a dose-dependent manner the production of TNFα and IL-1β in this cell line. When LPS was added to APAP-treated cells, the increase in TNFα and IL-1β production observed was higher than the sum of cytokine amounts produced with each agent alone, suggesting a synergistic mechanism. Moreover, we found that p38MAPK, JNK, and ERK were activated by APAP or LPS alone or in association. In our model, the NFκB signaling pathway was not involved in cytokine production induced by APAP. When inhibiting MAPKs using pharmacological inhibitors, we showed that p38MAPK inhibition abrogated the synergistic effect of APAP and LPS found for TNFα production but not for IL-1β production. JNK and ERK have comparable roles in the production of the cytokines. Furafylline, a CYP1A inhibitor, and indomethacin, a PGHS inhibitor, exhibited a significant inhibitory effect on TNFα and IL-1β production induced by the APAP and LPS combination. This work suggests that in macrophages, APAP and LPS can synergistically provoke the induction of pro-inflammatory cytokines, an effect involving the MAPK pathway and APAP bioactivation by CYP and PGHS. © 2009 Informa UK Ltd.