HIF-1α inhibits the TLR4/NF-κB signaling pathway and modulates intestinal flora in diarrhea-predominant irritable bowel syndrome.

Abstract

This study explored the regulatory effects of hypoxia-inducible factor-1α (HIF-1α) on the TLR4/NF-κB pathway and intestinal flora in diarrhea-predominant irritable bowel syndrome (IBS-D). Twenty-eight Wistar rats were randomized into four groups: model (n = 13), blank control (n = 5), HIF-1α upregulation (n = 5), and HIF-1α downregulation (n = 5). The IBS-D model group received combined acute and chronic stress stimulation for disease induction. On the basis of identical stress intervention, the HIF‑1α upregulation group was additionally exposed to a hypobaric hypoxic chamber, while the HIF‑1α downregulation group underwent intraperitoneal administration of the HIF‑1α antagonist 2‑methoxyestradiol to achieve targeted modulation of HIF‑1α expression.the control group was fed conventionally. Two model rats were euthanized on days 0, 7, 14, 21 to analyze colonic HIF-1α, TLR4 and NF-κB, and feces from the remaining 5 model rats were gathered on days 0, 7, 14, 21, 28 for 16S rRNA sequencing. Gastrointestinal symptoms, mucosal integrity and molecular expression were assessed after 28 days. An IBS-D model was successfully established. HIF-1α expression in the model group increased progressively, while TLR4/NF-κB levels fluctuated but showed an overall increase. The levels of all three markers were significantly higher than those in the control group(P < 0.05). The HIF-1α downregulation group exhibited more severe IBS-D symptoms and higher TLR4/NF-κB expressions than the upregulation group (P < 0.05). At the genus level, the abundance of Lachnospiraceae NK4A136 decreased, whereas the abundance of the Prevotellaceae NK3B31 group, Clostridia UCG - 014, UCG - 005, and Prevotellaceae UCG - 001 increased (P < 0.05). Under systemic hypobaric hypoxic stress, HIF-1α suppresses the TLR4/NF-κB signaling pathway and alleviates intestinal inflammatory responses. Concurrent intestinal hypoxia and inflammatory injury jointly interfere with normal commensal colonization, accompanied by altered gut microbial composition in IBS-D model rats. Changes in HIF-1α levels are biologically correlated with shifts in intestinal microbiota, though direct causal regulation of gut flora by HIF-1α remains to be verified in further experiments.