Evaluating a novel protective agent against radiation-induced acute intestinal injury

Objective

To develop and synthesize a novel derivative of ethyl pyruvate, named TZC02, and investigate its radioprotective effects against ionizing radiation (IR)-induced intestinal injury in mice.

Methods

Male C57BL/6J mice weighing (20 ​± ​2) g in the survival experiment were randomly divided into five groups (n ​= ​10 in each): control group, IR group, IR ​+ ​TZC02 (50 ​mg/kg) group, IR ​+ ​TZC02 (100 ​mg/kg) group, and IR ​+ ​TZC02 (200 ​mg/kg) group. Mice's survival rates were monitored for 7 ​d. In other experiments, the male mice were randomly divided into three groups (n ​= ​5 per group): control group, IR group, and IR ​+ ​TZC02 (100 ​mg/kg) group. TZC02 was intragastrically administered 1 ​h before 12 ​Gy abdominal γ-ray irradiation (ABI) and 24 h, 48 h after irradiation, respectively. Three days after IR exposure, small intestinal tissues were collected and the number of small intestinal crypts was determined using hematoxylin & eosin (H&E) staining. Immunohistochemical analysis was used to assess the regenerative capacity of the small intestine (SI) and radiation-induced damage, stemness markers or DNA repair surrogates, including Ki67, lysozyme, and villus. The expressions of histone H2AX phosphorylation (γH2AX) and caspase-3 were evaluated through immunofluorescence analyses. Additionally, in vitro cultured small intestinal organoids were employed to investigate the effects of TZC02 on SI regeneration after irradiation.

Results

The administration of TZC02 significantly improved the 7 ​d- survival rate of mice exposed to 12 ​Gy ABI (P ​< ​0.05). Compared to the IR group, TZC02 treatment attenuated the decrease of SI Ki67-positive cells [(59.60 ​± ​6.33) vs. (37.70 ​± ​7.82), t ​= ​11.89, P ​< ​0.0001) and Paneth cells [(9.90 ​± ​1.37) vs.(5.50 ​± ​1.71) , t ​= ​6.02, P ​< ​0.001) in five crypts, and reduced structural damage to the SI [villus height, (349.49 ​± ​60.17) μm vs. (294.72 ​± ​40.09) ​μm; t ​= ​3.39; P < ​0.05]. TZC02 also significantly decreased the crypt apoptosis detected by caspase-3 [(10.75 ​± ​1.26) vs. ​(29.83 ​± ​2.56), t ​= ​13.39, P ​< ​0.0001) and DNA damage detected by gH2AX [(10.40 ​± ​1.14) vs. ​(29.60 ​± ​2.70), t ​= ​10.13, P ​< ​0.0001)]. The organoid survival 7 ​d post-irradiation further confirmed the protective effects of TZC02 (area of organoids, (0.119 ​± ​0.081) ​mm² vs. ​(0.080 ​± ​0.037) ​mm²; t ​= ​2.30; P ​< ​0.05).

Conclusions

This study demonstrate that TZC02 can offer effective protection against IR-induced intestinal injury, suggesting its potential as a promising protective compound for patients treated with radiotherapy.