Hypoxia signaling in the equine small intestine: Expression and distribution of hypoxia inducible factors during experimental ischemia.
Authors: Verhaar Nicole, de Buhr Nicole, von Köckritz-Blickwede Maren, Dümmer Katrin, Hewicker-Trautwein Marion, Pfarrer Christiane, Dengler Franziska, Kästner Sabine
Journal: Frontiers in veterinary science
Summary
# Hypoxia Signalling and Equine Intestinal Ischaemia: What the Evidence Shows Hypoxia inducible factors (HIFs) regulate cellular responses to oxygen deprivation and are implicated in ischaemic injury across multiple organ systems, yet their role in equine intestinal ischaemia remained unexplored until this 2023 investigation. Fourteen horses underwent experimental jejunal ischaemia (90% blood flow reduction) with tissues sampled before, during, and after the insult; half received ischaemic postconditioning (delayed reperfusion) whilst controls underwent immediate reperfusion, with HIF1α and HIF2α expression quantified via immunohistochemistry, ELISA, and quantitative real-time PCR. HIF1α demonstrated significant dynamic changes, with cytoplasmic staining in crypt and villus enterocytes increasing substantially after reperfusion alongside increased nuclear immunoreactivity in villus epithelium, whilst protein levels paradoxically decreased in control animals but remained elevated in the postconditioning group throughout ischaemia and reperfusion phases. HIF2α showed minimal enterocyte nuclear activity and no temporal variation, suggesting HIF1α dominates the equine intestinal hypoxic response. The findings indicate that HIF1α activation is integral to how equine small intestinal mucosa responds to ischaemic stress, though ischaemic postconditioning did not significantly modulate HIF signalling—implying either that the protective effects of delayed reperfusion operate through different molecular pathways or that timing and protocol optimisation warrant further investigation in clinical colic management.
Read the full abstract on PubMed
Practical Takeaways
- •HIF1α activation appears to be a key cellular response to intestinal ischemia-reperfusion in horses, suggesting it may be a therapeutic target for colic management
- •Ischemic postconditioning as tested here did not enhance the protective HIF response, so current evidence does not support this as a beneficial intervention for small intestinal ischemia
- •Understanding hypoxia signaling pathways may inform future strategies to protect intestinal tissue during colic surgery, though clinical translation requires further research
Key Findings
- •HIF1α cytoplasmic and nuclear immunoreactivity significantly increased in enterocytes after reperfusion following 90% blood flow reduction
- •HIF1α protein levels decreased significantly in control group at reperfusion but remained elevated in ischemic postconditioning group
- •HIF2α showed only mild to moderate cytoplasmic staining with no nuclear immunoreactivity and no significant changes over time
- •Ischemic postconditioning did not produce detectable differences in HIF distribution or expression patterns compared to standard reperfusion