Isothiocyanate-Rich Moringa Seed Extract Activates SKN-1/Nrf2 Pathway in Caenorhabditis elegans.

Abstract

Moringa oleifera is a tropical tree that has its leaves, fruits, and seeds used as medicine and food. A standardized hydroalcoholic moringa seed extract (MSE) contains up to 40% of an isothiocyanate (MIC-1; moringin), a phytochemical known to have antioxidant and anti-inflammatory properties. Animal studies suggest that MSE may help with diseases, such as edema, colitis, obesity, and diabetes. In vitro studies have shown that MIC-1 activates the Nrf2 pathway, involved in detoxification and antioxidant pathways. To broaden the understanding of the molecular pathways regulated by MSE, we hypothesized that MSE improves the health span in Caenorhabditis elegans by activating the Nrf2 homolog (SKN-1). Our whole RNA-seq data showed that MSE at 0.1 mg/mL (100 µM MIC-1) regulated the expression of a total of 1555 genes, including genes related to C. elegans cuticle, molting cycle, and glutathione metabolism. MSE upregulated several glutathione S transferases (GST), involved in the detoxification of xenobiotics, and other SKN-1 downstream targets. MSE and MIC-1 upregulate skn-1 expression and induce SKN-1 nuclear translocation, suggesting that they activate the SKN-1/Nrf2 pathway. Moreover, the regulation of glutathione metabolism is likely dependent on the SKN-1 pathway, as the gst-4 upregulation by MSE was inhibited in skn-1 knockout mutant. However, MSE decreased survivability and delayed growth rate, while purified MIC-1 increased the lifespan of C. elegans. This study shows that MIC-1 is responsible for SKN-1/Nrf2 activation by MSE; however, components other than MIC-1 within MSE likely cause detrimental effects in C. elegans.