Expresion data of Raw 264.7 cells treated with violacein. Mus musculus

Violacein, an indole-derived purple-colored natural pigment isolated from Chromobacterium violaceum has shown multiple biological activities. In this study, we report that violacein activates murine macrophages through the up-regulation of TNF-α expression at non-cytotoxic concentrations (2 µmol/L). This was evaluated by measurement of TNF-α expression using real-time qRT-PCR. In addition, we obtained evidence of the molecular mechanism of activation by determining the mRNA expression pattern upon treatment with violacein. Interestingly, the mRNA expression pattern also allowed us to observe that incubation with violacein caused activation of pathways related with an immune and inflammatory response. Together, our data indicate that violacein activates the TLR8 receptor signaling pathway, and in consequence induces production of inflammatory cytokines such as TNF-α, CCL3 and CCL4 and of negative regulators of TLR signaling such as AP20, IRG1, IκBα and IκBε. Finally, we studied the interaction of TLR8 with violacein in silico, and obtained evidence that violacein could bind to TLR8 in a similar fashion to imidazoquinoline compounds. Therefore, our results indicate that violacein could be a candidate to be applied in immune therapy. Overall design: Raw 264.7 cells were treated with violacein (three positive controls) and other three samples with fresh medium (negative controls). After incubation, total RNA extraction and hybridization on Affymetrix microarrays was made.