Frontiers in Pharmacology (Aug 2022)
Luteolin induces pyroptosis in HT-29 cells by activating the Caspase1/Gasdermin D signalling pathway
Abstract
Luteolin, which is a natural flavonoid, has anti-inflammatory, antioxidant, and anticancer properties. Numerous studies have proven that luteolin inhibits the growth of many types of cancer cells by promoting apoptosis, autophagy, and cell cycle arrest in tumour cells. However, in vivo research on this topic has been limited. In addition, other studies have shown that luteolin exerts a good inhibitory effect on apoptosis-resistant cancer cells. While existing studies have not completely elucidated the mechanism underlying this phenomenon, we assume that luteolin, which is a natural compound that exerts its effects through various mechanisms, may have the potential to inhibit tumour growth. In our study, we proved that luteolin exerted a good inhibitory effect on the proliferation of colon cancer cells according to CCK8 and EdU fluorescence assays, and the same conclusion was drawn in animal experiments. In addition, we found that luteolin, which is an antioxidant, unexpectedly promoted oxidative stress as shown by measuring the levels of oxidative balance-related indicators, such as reactive oxygen species (ROS), SOD, H2O2 and GSH. However, the decreased oxidation of luteolin-treated HT-29 cells after treatment with the active oxygen scavenger NAC did not reverse the inhibition of cell growth. However, the Caspase1 inhibitor VX765 did reverse the inhibition of cell growth. Western blotting analysis showed that luteolin treatment increased the expression of Caspase1, Gasdermin D and IL-1β, which are members of the pyroptosis signalling pathway, in colon cancer cells. We further intuitively observed NLRP3/Gasdermin D colocalization in luteolin-treated HT-29 cells and mouse tumour tissues by immunofluorescence. These results suggest that luteolin inhibits the proliferation of colon cancer cells through a novel pathway called pyroptosis. This study provides a new direction for the development of natural products that inhibit tumour growth by inducing pyroptosis.
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