ER Proteotoxic Stress Drives Mitochondrial Dysfunction in Heat-Stressed Intestinal Epithelial Cells

Global climate change has increased the frequency and intensity of heat waves, posing a significant threat to livestock production. During heat exposure, the disruption of intestinal barrier integrity is a pivotal event in the pathogenesis of heat stress-induced intestinal injury. Endoplasmic reticulum (ER) stress and mitochondrial dysfunction are key consequences of heat stress at the cellular level. However, direct causal evidence linking ER stress to mitochondrial dysfunction in heat-stressed enterocytes remains limited. To investigate this, we used an integrated transcriptomic, metabolomic, and functional validation strategy to assess mitochondrial bioenergetics and cellular ultrastructure in porcine intestinal epithelial (IPEC-J2) cells under acute heat stress. Transcriptomic analysis revealed extensive reprogramming, highlighting the significant enrichment of pathways related to protein processing in the endoplasmic reticulum, apoptosis, and MAPK signaling. Untargeted metabolomics identified significant perturbations in amino acid and energy metabolism, as well as altered bile acid profiles. Functional assessments confirmed that heat stress severely impaired mitochondrial bioenergetics, as evidenced by reduced maximal respiration and ATP production, and induced ultrastructural damage to mitochondria. The pharmacological inhibition of ER stress by 4-phenylbutyric acid (4-PBA) significantly attenuated the mitochondrial bioenergetic impairment and ultrastructural damage, whereas ER stress induction recapitulated these defects. We demonstrate that heat stress induces profound transcriptional and metabolic remodeling characterized by ER stress activation, which critically mediates subsequent mitochondrial bioenergetic dysfunction and ultrastructural damage. Our findings suggest that targeting ER stress may represent a promising therapeutic strategy to ameliorate enterocyte mitochondrial dysfunction and mitigate heat stress-induced intestinal injury in livestock.