Fecal microbiota transplantation alleviated heat-induced colonic tissue damage, epithelial apoptosis, and oxidative stress.

Exposure to high ambient temperatures can cause significant damage to the gastrointestinal tract; however, the therapeutic potential of fecal microbiota transplantation (FMT) in this context remains largely unexplored. We investigated whether FMT could alleviate heat-induced colonic injury in C57BL/6J mice. Mice were randomly divided into four groups: normal control (22°C only), normal-FMT (NF, 22 °C+ FMT), heat exposure (HE, 39°C only), and HE-FMT (HF, 39°C + FMT). The HE and HF groups were exposed to 39°C for 2 hours daily over 15 consecutive days. FMT (100 µL/day) was administered by oral gavage to the NF and HF groups for 15 days, starting after the first HE. Our results showed that FMT significantly modulated gut microbiota composition, increasing the relative abundance of Alistipes, Citrobacter, Parasutterella, Bifidobacterium, Lachnospiraceae_UCG-001, Raoultella, Woeseia, Prevotellaceae_UCG-001, and Christensenellaceae, while decreasing Clostridium_sensu_stricto_1, Eubacterium_xylanophilum_group, Clostridioides, Bilophila, GCA-900066575, and Peptococcus. Notably, FMT markedly restored epithelial integrity and enhanced mucus production, as shown by hematoxylin-eosin and periodic acid-Schiff staining. Moreover, FMT attenuated heat-induced epithelial cell apoptosis, evidenced by reduced apoptotic cells and downregulation of mitochondrial apoptotic markers, including Bax, Bak, cleaved Caspase-3, cleaved Caspase-9, and the phospho-P53/P53 ratio. In addition, FMT mitigated oxidative stress induced by HE, indicated by decreased 3-nitrotyrosine levels and normalization of antioxidant-related proteins, such as Nrf2, Sod1, Cat, and Gpx4. Collectively, these findings demonstrate that FMT alleviates heat-induced colonic injury by restoring mucosal barrier integrity, inhibiting apoptosis, and reducing oxidative stress, highlighting its potential as a promising therapeutic strategy for heat-related gastrointestinal disorders. IMPORTANCE: This study is the first to demonstrate the protective role of fecal microbiota transplantation (FMT) against heat-induced colonic injury in a mouse model. We show that FMT mitigates colonic damage by restoring gut microbiota balance, preserving mucosal barrier integrity, inhibiting epithelial cell apoptosis, and reducing oxidative stress. These findings underscore the essential role of the gut microbiota in maintaining intestinal homeostasis under heat stress and highlight the therapeutic potential of microbiota-targeted strategies, such as FMT, in preventing or treating heat-related intestinal injury.