Furanodien-6-one from Commiphora erythraea inhibits the NF-κB signalling and attenuates LPS-induced neuroinflammation.

We investigated the in vitro anti-inflammatory activity of 1(10),4-furanodien-6-one, one the most active compounds of the hexane extract of Commiphora erythraea (Ehrenb.) Engl., by exposing microglial BV-2 cells to lipopolysaccharide. We showed that furanodien-6-one pre-treatment restored cell viability and ROS to control levels while halving NO generation. Production of pro-inflammatory IL-6, IL-23, IL-17, TGF-ß, and INF-γ, significantly induced by LPS, was also markedly reduced by furanodien-6-one treatment. We further showed that furanodien-6-one protects primary neuronal cultures against the inflammatory/toxic insults of LPS-treated BV-2 conditioned media, indicating that furanodien-6-one exerts anti-inflammatory/cytoprotective effects in neuronal cells. We then investigated whether furanodien-6-one exerts anti-inflammatory properties in an in vivo model of microglial activation. In adult mice ip-injected with LPS we found that furanodien-6-one had strong cerebral anti-inflammatory properties by inhibiting liver and brain TNFα as well as IL-1ß expression. Results were not unexpected since FTIR-metabolomic analyses showed that furanodien-6-one-treated mice had a reduced dissimilarity to control animals and that the response to LPS treatment was markedly modified by furanodien-6-one. In conclusion our data provide strong evidence of the anti-inflammatory properties of furanodien-6-one that could be exploited to counteract degenerative pathologies based on neuroinflammation.

Cyclo(His-Pro) exerts anti-inflammatory effects by modulating NF-κB and Nrf2 signalling.

Cyclo(His-Pro) is an endogenous cyclic dipeptide that exerts oxidative damage protection by selectively activating the transcription factor Nrf2 signalling pathway. Given the existence of a tight interplay of the Nrf2/NF-κB systems and that the pro-inflammatory response is governed by transcription factor NF-κB, here we sought to investigate whether and how cyclo(His-Pro) interferes with the cross-talk between the antioxidant Nrf2/heme oxygenase-1 and the pro-inflammatory NF-κB pathways. By knocking down the Nrf2 gene, we confirmed that cyclo(His-Pro) inhibits NF-κB nuclear accumulation induced by paraquat in rat pheochromocytoma PC12 cells via the Nrf2/heme oxygenase-1 pathway. The protection required functional heme oxygenase-1 activity, since zinc protoporphyrin IX, a heme oxygenase-1 inhibitor, prevented NF-κB inhibition, and the presence of exogenous carbon monoxide and bilirubin afforded cytoprotection against paraquat-induced toxicity by preventing NF-κB activation. Cyclooxygenase-2 and matrix metalloproteinase 3, two gene products governed by NF-κB, were down-regulated by cyclo(His-Pro) and up-regulated in heme oxygenase-1 knock-down cells. We validated the general mechanism underlying the anti-inflammatory effects by treating PC12 and murine microglial BV2 cells with different pro-inflammatory agents. Finally, cyclo(His-Pro) reduced 12-otetradecanoylphorbol-13-acetate-induced oedema in mouse ear inflammation model. Results, by showing that cyclo(His-pro) suppresses the pro-inflammatory NF-κB signalling via the Nrf2-mediated heme oxygenase-1 activation, contribute to the understanding of essential cellular pathways and allow the proposal of cyclo(His-Pro) as an in vivo anti-inflammatory compound.