Plasma concentrations of endotoxin and platelet activation in the developmental stage of oligofructose-induced laminitis.
Authors: Bailey, Adair, Reinemeyer, Morgan, Brooks, Longhofer, Elliott
Journal: Veterinary immunology and immunopathology
Summary
# Editorial Summary: Endotoxin and Platelet Activation in Oligofructose-Induced Laminitis Carbohydrate overload triggers laminitis through poorly characterised mechanisms in the hindgut, but whether circulating endotoxin (lipopolysaccharide) plays a direct role has remained unclear. Bailey and colleagues investigated the temporal relationship between plasma endotoxin levels, platelet activation, and vasoactive mediator release in six horses administered 10 g/kg bodyweight of oligofructose, measuring lipopolysaccharide, phosphorylated p38 MAP kinase (a marker of platelet activation), serotonin, and thromboxane B₂ at four-hourly intervals. Endotoxin peaked at 8 hours (2.4 pg/ml), whilst platelet p38 MAPK phosphorylation increased progressively to peak at 12 hours (3.8-fold), followed by substantial increases in plasma serotonin and thromboxane as lameness developed 20–30 hours post-challenge. The findings suggest that modest quantities of endotoxin entering the circulation from the compromised caecal epithelium may preferentially activate equine platelets—which are more LPS-sensitive than immune cells—initiating a cascade of vasoactive mediator release that contributes to the early inflammatory pathology of acute laminitis. For practitioners managing at-risk horses, this underscores the importance of preventing sharp pH crashes in the hindgut and supports investigation of antiplatelet or anti-inflammatory strategies during the critical developmental phase when these mechanisms are active.
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Practical Takeaways
- •High-carbohydrate feeds causing rapid fermentation and pH drop in the cecum can trigger a cascade leading to laminitis within 20-30 hours; careful feed management is critical for at-risk horses
- •Platelet activation appears to be a key early event in carbohydrate-overload laminitis, occurring 12 hours post-insult before clinical lameness, suggesting antiplatelet or anti-inflammatory interventions during this window may be protective
- •Small quantities of endotoxin from the colon enter circulation during laminitis development but do not cause disease alone; the interaction with platelet activation is the likely pathogenic mechanism
Key Findings
- •Plasma LPS increased above detection limit (0.6 pg/ml) to peak at 2.4±1.0 pg/ml at 8 hours following oligofructose administration
- •Platelet p38 MAPK phosphorylation peaked at approximately 12 hours (3.8±1.3 fold increase) before lameness onset at 20-30 hours
- •Plasma serotonin and thromboxane B2 increased 2.9±0.6 and 11.3±5.0 fold respectively following platelet activation
- •Clinical laminitis and histopathologic changes occurred in 5 of 6 horses, suggesting endotoxin may initiate early inflammatory cascades via platelet activation