Expression of the cyclooxygenase isoforms in the prodromal stage of black walnut-induced laminitis in horses.
OBJECTIVE
To compare the levels of mRNA expression of cycooxygenase (COX)-1 and COX-2 in the digital laminae of normal horses and horses in the developmental stages of laminitis experimentally induced by administration of black walnut extract (BWE).


METHODS
Samples of mRNA extracted from the digital laminae of 5 control horses and 5 horses at the onset of leukopenia after administration of BWE.


METHODS
Specimens of laminae were collected from anesthetized horses prior to euthanasia. Expression of COX-1 and COX-2 mRNA in laminae of control and affected horses was evaluated via real-time quantitative polymerase chain reaction techniques.


RESULTS
Expression of COX-2 mRNA was significantly increased in the BWE-treated group, compared with that in control horses. In contrast to COX-2 regulation, COX-1 mRNA expression was not significantly different between groups. Interestingly, despite consistent clinical signs such as leukopenia in all BWE-treated horses, distinct differences in COX-2 mRNA expression were detected among those 5 horses (compared with values for control horses, the increase in COX-2 mRNA expression ranged from no increase to a 30-fold increase).


CONCLUSIONS
Results indicated that there was a significant upregulation of COX-2 mRNA expression during the developmental stages of laminitis, with no significant change in expression of the COX-1 isoform. These data appear to provide support for aggressive use of nonsteroidal anti-inflammatory drugs in horses at risk for laminitis; further investigation into the clinical value of selective COX-2 inhibitors for treatment of laminitis in horses appears to be warranted.
Waguespack
R Wayne
RW
Department of Clinical Science, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA.
Cochran
Anne
A
Belknap
James K
JK
D000818:Animals; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000032:analysis; D005260:Female; D005534:Foot Diseases / Q000139:chemically induced / Q000201:enzymology / Q000662:veterinary*; D005552:Forelimb / Q000201:enzymology / Q000473:pathology; D006734:Horse Diseases / Q000139:chemically induced / Q000201:enzymology* / Q000473:pathology; D006736:Horses; D007527:Isoenzymes; D031324:Juglans / Q000009:adverse effects*; D007794:Lameness, Animal / Q000139:chemically induced / Q000201:enzymology* / Q000473:pathology; D008297:Male; D016133:Polymerase Chain Reaction / Q000662:veterinary; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism*; D015854:Up-Regulation
D017931:DNA Primers; D018076:DNA, Complementary; D007527:Isoenzymes; D012333:RNA, Messenger; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases