Dynamic changes in circulating leukocytes during the induction of equine laminitis with black walnut extract.
Authors: Hurley, Parks, Reber, Donovan, Okinaga, Vandenplas, Peroni, Moore
Journal: Veterinary immunology and immunopathology
Summary
Black walnut heartwood extract reliably triggers acute laminitis in experimental settings, but the precise immunological mechanisms driving this response remain poorly characterised; this study investigated whether systemic leukocyte activation and migration might explain the pathogenesis. Researchers administered either 6 litres of black walnut extract or water to healthy horses via nasogastric tube, then monitored circulating neutrophil and monocyte counts alongside reactive oxygen species (ROS) production at intervals up to the onset of Obel grade I lameness. Horses developing clinical laminitis exhibited a marked leucopenia (reduced circulating leukocytes) at 3–4 hours post-dosing, a significant decrease in absolute monocyte numbers, and notably elevated endogenous ROS production at baseline that increased further as cells emigrated from the circulation. These findings suggest that systemic leukocyte activation, migration into laminar tissues, and the associated inflammatory cascade represent critical early events in black walnut-induced laminitis—a mechanism potentially applicable to sepsis-related or other systemic inflammatory conditions that precipitate laminitis clinically. For practitioners managing laminitis secondary to conditions like colitis, pleuropneumonia or metritis, these results indicate that therapeutic interventions targeting leukocyte activation and extravasation in the acute phase might offer preventative or ameliorative benefit alongside conventional supportive care.
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Practical Takeaways
- •Acute laminitis involves systemic leukocyte activation and extravasation into laminar tissues; understanding this mechanism may improve therapeutic strategies targeting inflammatory cascade
- •Clinical laminitis cases secondary to systemic inflammatory diseases likely share common pathways of neutrophil and monocyte migration that could be potential intervention points
- •Early detection of systemic leukocyte changes and activation markers may provide prognostic indicators for laminitis development in at-risk horses
Key Findings
- •BWHE administration caused significant reduction in circulating leukocytes at 3-4 hours compared to water controls
- •Horses developing laminitis showed significantly lower circulating leukocyte counts and consistent decrease in total monocytes compared to non-lame BWHE-treated horses
- •Horses that developed laminitis had significantly higher endogenous ROS production at baseline (T=0) and production increased significantly coinciding with leukocyte reduction
- •Systemic leukocyte activation and emigration from circulation appears to be a key early pathogenic mechanism in BWHE-induced laminitis