Expression of interleukin-1beta in the digital laminae of horses in the prodromal stage of experimentally induced laminitis.
Authors: Fontaine, Belknap, Allen, Moore, Kroll
Journal: American journal of veterinary research
Summary
# Editorial Summary Black walnut toxicity is a well-established laminitis trigger in horses, but precisely how systemic insult initiates the inflammatory cascade within the foot remains unclear. Fontaine and colleagues used nasogastric black walnut extract administration to induce the prodromal (pre-clinical) stage of laminitis in four horses, comparing laminar tissue samples with untreated controls through in situ hybridisation to detect interleukin-1beta (IL-1beta) mRNA expression—a key marker of early inflammation. Critically, IL-1beta mRNA was detected in perivascular cells surrounding small laminar blood vessels in all four treated horses, with one animal also showing expression in interstitial cells distant from the microvasculature; no IL-1beta expression appeared in control hooves. This localisation to perivascular cell populations is particularly significant because these cells form part of the vascular barrier and regulate inflammatory cell recruitment into tissues. The findings provide direct molecular evidence that a pro-inflammatory cytokine cascade is active *before* clinical signs emerge, suggesting that local production of IL-1beta within the laminae may represent a primary trigger rather than a secondary consequence of laminar damage. For practitioners, this reinforces that the prodromal phase—before visible lameness or digital pulse changes—is when pathological mechanisms are underway, supporting the rationale for aggressive systemic and local anti-inflammatory intervention during early disease recognition.
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Practical Takeaways
- •Laminitis involves a proinflammatory cytokine cascade that begins before clinical signs appear, indicating early intervention during the prodromal phase may be critical
- •Local inflammatory responses in digital laminar tissues precede the systemic and clinical manifestations of laminitis, supporting the need for early detection and treatment strategies
- •Understanding that IL-1beta expression in perivascular cells initiates laminar inflammation provides a molecular basis for anti-inflammatory therapeutic approaches in laminitis prevention and early treatment
Key Findings
- •IL-1beta mRNA expression was detected in perivascular cells of laminar venules and capillaries in all 4 horses given black walnut extract, but not in control horses
- •One of 4 treated horses also showed IL-1beta expression in interstitial cells remote from microvasculature
- •Expression was localized to perivascular cells; digital arterioles and veins did not exhibit IL-1beta mRNA expression
- •IL-1beta mRNA expression occurs during the prodromal stage of laminitis, suggesting local proinflammatory cytokine expression may initiate the disease process