The PPARγ-dependent effect of flavonoid luteolin against damage induced by the chemotherapeutic irinotecan in human intestinal cells

Irinotecan (CPT-11) is one of the main agents used to treat colorectal cancer; unfortunately, it is associated with increased intestinal mucositis developing. Luteolin has been shown to prevent damage induced by this chemotherapeutic in mice; thus, in this research, we have investigated luteolin's action mechanism in human intestinal epithelial cells. The potential of luteolin in reducing inflammation and oxidative stress induced by irinotecan in Caco-2 cells was evaluated by PCR through mRNA expression of inflammatory and oxidative genes and by ELISA at the protein level. To assess whether luteolin's ability to control irinotecan-induced damage occurs in a PPAR gamma dependent manner, experiments were performed on PPAR gamma downregulated cells. Irinotecan downregulated PPAR gamma expression and upregulated inflammatory and oxidative genes, while luteolin upregulated PPAR gamma, HO-1, SOD and decreased expression of IL-1 beta and iNOS. Interestingly, when the cells were co-stimulated with luteolin and irinotecan, the flavonoid reversed the inflammation and oxidative imbalance evoked by the chemotherapeutic. However, when these experiments were performed in cells downregulated for PPAR gamma, luteolin lost the capacity to increase PPAR gamma and reverse the effect of irinotecan in all tested genes, except by IL-1 beta. The present study showed that the protective effect of luteolin against irinotecan is PPAR gamma dependent.

Automated summary

Luteolin can reduce inflammation and oxidative stress induced by irinotecan in Caco-2 cells by upregulating the expression of PPAR gamma, HO-1, and SOD genes, and decreasing the expression of IL-1 beta and iNOS. However, when PPAR gamma expression is downregulated, luteolin loses this effect.