MCL protects against radiation in HIECs (A) Cell viability was significantly decreased in a dose-dependent manner following treatment with radiation (0, 5, 10, or 20 Gy) for 24, 48, or 72 h (B) LDH release increased in a time-and dose-dependent manner following radiation (0, 5, 10, or 20 Gy) (C) Cells were treated with 10 μM of the drug candidate library for 2 h and then exposed to radiation (10 Gy). Cell viability of HIECs exposed to the drug candidate library. Each point represents the percentage of cell viability of the compounds at a concentration of 10 μM (D) MCL increased cell viability following radiation (10 Gy) in a dose-dependent (0, 2.5, 5, or 10 μM) manner (E) MCL decreased LDH release following radiation (10 Gy) in a dose-dependent (0, 2.5, 5, or 10 μM) manner (F) MCL decreased cell culture supernatant IL-18 release following radiation (10 Gy) in a dose-dependent (0, 2.5, 5, or 10 μM) manner (G) MCL decreased cell culture supernatant IL-1β release following radiation (10 Gy) in a dose-dependent (0, 2.5, 5, or 10 μM) manner (H) HIECs were pretreated with different concentrations (0, 2.5, 5, or 10 μM) of MCL for 2 h and exposed to 10 Gy radiation. Representative flow cytometry scatter plots (I) HIECs were pretreated with different concentrations (0, 2.5, 5, or 10 μM) of MCL for 2 h and exposed to 10 Gy radiation. Representative propidium iodide staining fluorescence image. *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001, two-tailed Student’s t-test. HIEC, human intestinal epithelial cell; LDH, lactate dehydrogenase; MCL, micheliolide; IL, interleukin.