title: Lamellar leukocyte infiltration and involvement of IL-6 during oligofructose-induced equine laminitis development.
abstract: Laminitis is known to involve deregulation of proteases and destruction of the lamellar basement membrane with the host inflammatory response also playing a role. Leukocyte infiltration has been well characterized in the black walnut model of laminitis induction, but not in carbohydrate induced models. Increased gene expression of multiple cytokines, including IL-6, has also been implicated in laminitis development. Using real time PCR, immunohistochemistry and zymography methods, we characterize leukocyte infiltration and IL-6 gene expression in oligofructose (OF) induced laminitis. As well, we use two in vitro models to investigate a role for IL-6 in protease regulation. Laminitis was induced in normal standardbred horses (n=5) by alimentary OF dosing and lamellar biopsies were obtained throughout the 48 h experimental period. Lamellar explants and keratinocytes were also isolated from clinically normal horses for in vitro experiments. We found infiltration of calprotectin-positive leukocytes (monocytes and neutrophils) at 18-24h post oligofructose dosing, while IL-6 gene expression was increased as early as 12h post dosing. Additionally, while we found that IL-6 did not cause significant BM damage in vitro, it did result in increased secreted proMMP-9 levels from lamellar explants. Thus, we find that leukocyte infiltration does occur during oligofructose-induced laminitis development, however, IL-6 gene expression in the lamellae may precede leukocyte infiltration. Additionally, we show IL-6 plays a role in increasing the level of proMMP-9 in vivo in a manner that does not involve keratinocytes.
authors.affiliation: The Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton 4343, Australia. michelle.visser@utoronto.ca
authors.forename: Michelle B
authors.initials: MB
authors.lastname: Visser
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Pollitt
mesh_terms: D000818:Animals; D002634:Chemotaxis, Leukocyte / Q000276:immunology* / Q000502:physiology; D005534:Foot Diseases / Q000139:chemically induced / Q000276:immunology / Q000473:pathology / Q000662:veterinary*; D006724:Hoof and Claw / Q000187:drug effects / Q000276:immunology* / Q000473:pathology; D006734:Horse Diseases / Q000139:chemically induced / Q000276:immunology* / Q000473:pathology; D006736:Horses; D015850:Interleukin-6 / Q000502:physiology*; D009844:Oligosaccharides / Q000494:pharmacology; D060888:Real-Time Polymerase Chain Reaction / Q000662:veterinary
chemical_list: D015850:Interleukin-6; D009844:Oligosaccharides; C120489:oligofructose