justicidin a inhibits the transport of tumor necrosis factoralpha to cell surface in lipopolysaccharidestimulated raw 2647 macrophages exposure of macrophages to lipopolysaccharide lps induces release of tumor necrosis factoralpha tnfalpha which is initially synthesized as a 26kda protnfalpha followed by proteolytic processing to a 17kda secreted form in this study justicidin a an arylnaphthalide lignan isolated from justicia procumbens was found to inhibit lpsstimulated tnfalpha release from raw 2647 macrophages in a concentration and timedependent manner and the underlying mechanism was investigated in the presence of justicidin a challenge with lps increased the steadystate level of the 26kda membranebound form of tnfalpha protein whereas justicidin a had little effect on the expression of tnfalpha mrna and on the synthesis of protnfalpha protein results of the pulsechase experiment revealed that the conversion of protnfalpha to mature tnfalpha was inhibited by justicidin a moreover justicidin a suppressed the transport of tnfalpha to cell surface as analyzed by flow cytometry the immunofluorescence analysis demonstrated that large amounts of lpsinduced tnfalpha accumulated primarily within golgi complex these results indicate that justicidin a inhibits tnfalpha release at the step of transport of protnfalpha to cell surface and this leads to the accumulation of tnfalpha in golgi complex in raw 2647 macrophages