114 Application of small molecule inhibition for grouping of nanomaterials by activated inflammatory signalling pathways in-vitro

Abstract Extensive evidence shows that nanomaterials (NMs) stimulate pro-inflammatory responses, and previous studies investigating the pulmonary toxicity of NMs have identified the redox-sensitive transcription factors (TFs) NF-κB and AP-1 as key mediators of NM-induced pro-inflammatory signalling. However, to date few studies have addressed the up-stream signalling pathways that regulate the activation of these TFs by NMs. Gaining additional insight into the underlying mechanisms and pathways that mediate NM-induced pro-inflammatory signalling is not only vital for understanding the hazards NMs present but also provides an additional way to group NMs to predict their potential hazard. In this study we propose the use of selective Small Molecule Inhibitors (SMIs) to block key signalling pathways that are likely mediators of NM-induced pro-inflammatory signalling. As proof of concept for this method we selected four selective SMIs that target enzymes in the NF-κB and MAPK signalling pathways as the TFs they regulate (NF-κB and AP-1, respectively) have been shown to be key mediators of NM-induced pro-inflammatory activity. We observed that inhibition of IKK elicited a significant decrease in Ag (P < 0.001) and ZnO (P < 0.01) NM induced pro-inflammatory cytokine release, however it did not cause a significant decrease in CuO NM induced pro-inflammatory cytokine production. The SMIs targeting other sections of the NF-κB and MAPK pathways did not elicit any significant change in NM induced pro-inflammatory cytokine production. Indicating that NMs of different physico-chemical properties elicit pro-inflammatory responses via different signalling pathways. Suggesting that it may be possible to group NMs by the signalling pathways they activate.