RalB degradation by dihydroartemisinin induces autophagy and IFI16/caspase-1 inflammasome depression in the human Laryngeal squamous cell carcinoma

Abstract

Background Interferon-inducible 16 (IFI16) /caspase-1 inflammasome activates and secretes IL-1β. However, whether the IFI16 inflammasome involved in human Laryngeal squamous cell carcinoma is still unclear. Autophagy directly removed inflammasome components and limited early IL-1β production. RalB is required for the crosstalk between inflammasome and autophagy in macrophages. Dihydroartemisinin (DHA), the main derived ingredient of artemisinin, has a variety of biological activities. The mechanism of DHA in regulation the crosstalk between IFI16 inflammasome and autophagy by inhibiting RalB expression was analyzed in order to provide clues for new therapeutic methods in laryngeal cancer. Methods The expression of IFI16 was analyzed by Oncomine and GEPIA databases and detected by Western blot and immunohistochemistry. The relationship between IFI16 inflammasome and autophagy was investigated by transmission electron microscopy, immunofluorescence assay, etc. in Hep-2, Cal-27 and HeLa cells with DHA treatment. Hep-2 cell xenograft tumor in nude mice were used to assess the effect of DHA on laryngeal cancer. Results The study was firstly reported that IFI16 was overexpressed and positively correlated with caspase-1 in laryngeal carcinoma tissues. DHA alone or in combination with cisplatin significantly inhibited inflammasome activation and reduced IL-1β production in the xenograft tumor microenvironment of Hep-2 cell xenograft tumor in nude mice. Mechanistically, we found that DHA degraded RalB by inhibiting USP33 expression, leading to triggered autophagy. Meanwhile, enhanced autophagy can reduce the expression of RalB and USP33. Therefore, DHA depresses RalB, resulting in formation a positive feedback loop between USP33 and autophagy. Further, DHA promotes autophagy, which suppresses the IFI16/caspase-1 inflammasome activation and IL-1β production. Conclusions Therefore, our findings demonstrate that DHA may act as a RalB inhibitor to regulate the crosstalk between autophagy and IFI16/caspase-1 inflammasome, which inhibits IL-1β production in tumor microenvironment.