Abstract:

Objective By simulating acute hypoxic conditions, an experimental model of intestinal stress injury in plateau mice was established to explore the pathogenic mechanism of acute gastrointestinal diseases in plateau, and to lay foundation for preventive and therapeutic measures. Methods Thirty-six SPF-grade adult male BALB/c mice were randomly divided into four groups: normoxic 24 h, normoxic 72 h, hypoxic 24 h, and hypoxic 72 h, based on body weight using a randomized numerical table method, with nine mice in each group. Mice in the normoxic group were kept in a conventional barrier environment, while those in the hypoxic group were placed in a hypoxic chamber within the barrier environment with oxygen concentration set at 10% to simulate plateau conditions. They were subjected to stress for 24 h and 72 h, respectively, in order to establish a model of intestinal injury induced by acute hypoxia. After modeling, the mice were weighed, anesthetized with 1% pentobarbital sodium, and then euthanized by cervical dislocation. Duodenal and colonic tissues were collected. Histopathological morphology of intestinal tissues was observed after HE staining. Western blotting and immunohistochemistry were used to detect the expression levels of tight junction-related proteins in intestinal tissues. Real-time fluorescence quantitative PCR was performed to measure the expression levels of inflammatory cytokines and chemokines. TUNEL staining was used to assess apoptotic activity of intestinal epithelial cells, thus evaluating intestinal injury-related phenotypes in this model. Results Compared with the normoxic groups, mice in the 24 h and 72 h hypoxia groups showed weight loss, shortened duodenal villi, abnormal crypt structure, and decreased villus/crypt ratio. The colonic mucosa was infiltrated with inflammatory cells and irregular crypt structure. Expression levels of Occludin and zonula occludens-1 (ZO-1) were significantly decreased in duodenal and colonic tissues of mice in the 24 h and 72 h hypoxia groups (P<0.05). The expression of pro-apoptotic protein Bax was significantly up-regulated while expression of anti-apoptotic protein Bcl-2 was significantly down-regulated in duodenal tissues (P<0.05). Apoptotic activity of intestinal epithelial cells was significantly enhanced (P<0.05). In addition, interleukin (IL)-1β, IL-6, monocyte chemoattractant protein-1 (MCP-1), and tumor necrosis factor-α (TNF-α) mRNA levels were significantly increased in duodenal tissues after 24 and 72 h of hypoxic stress(P<0.05). After 24 h of hypoxic stress, there was no significant change in the expression levels of inflammatory cytokines in colon tissues (P>0.05), but after 72 h, the expression levels of pro-inflammatory factors IL-1β, TNF-α, IL-6, MCP-1, and anti-inflammatory factor IL-10 mRNAs significantly increased in colon tissues of mice (P<0.05). Conclusion The usage of a hypoxia chamber to simulate an acute hypoxic environment in plateau can lead to abnormal intestinal tissue structure, intestinal barrier dysfunction, and induce intestinal epithelial cell apoptosis, triggering an intestinal inflammatory response in stress mice. These findings indicate the successful construction of a mouse model for an acute hypoxic stress-induced intestinal injury.

Key words: Plateau acute hypoxia, Intestinal stress injury, Apoptosis, Inflammatory response, Mice