Cyclooxygenase expression in the early stages of equine laminitis: a cytologic study.
BACKGROUND
Recent reports indicate increased amounts of mRNA from inflammation-related genes in the prodromal stage of laminitis.


OBJECTIVE
Cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) undergo distinct patterns of expression in equine laminae in the developmental stage (DEV) and acute clinical stage (LAM) of laminitis.


METHODS
Horses selected from an outbred population were placed into 1 of 4 groups: DEV (n = 5), CON-3h (control group for DEV, n = 5), LAM (n = 5) and CON-10h (control group for LAM, n = 5).


METHODS
Laminar and skin samples were obtained from (1) animals either undergoing leukopenia (DEV) or the onset of clinical signs of laminitis (LAM) after black walnut extract (BWE) administration and (2) animals either 3 (CON-3h) or 10 (CON-10h) hours after administration of water. Real-time quantitative polymerase chain reaction (RT-qPCR), immunoblotting, and immunohistochemical analysis were performed for COX-1 and COX-2.


RESULTS
Upon immunohistochemical analysis of all 4 groups, COX-2 was expressed by most viable epithelial cells in both laminae and skin. COX-1 exhibited similar epithelial expression to COX-2 in skin epidermis, but was expressed exclusively in the basal layer of laminar epidermis. COX-1 protein was not detectable in dermal vasculature of equine skin or laminae, whereas COX-2 was present in endothelial and vascular smooth muscle cells of dermal vasculature in both skin and laminae in all groups. A marked increase in laminar COX-2 protein concentrations was detected on immunoblotting in the DEV group, although a lesser increase was observed in the LAM group.


CONCLUSIONS
COX-2 protein expression is markedly increased in the resident laminar cell types in the developmental stage of BWE-induced laminitis.
Blikslager
Anthony T
AT
Department of Clinical Sciences, North Carolina State University, Raleigh, USA.
Yin
Cailing
C
Cochran
Anna M
AM
Wooten
Jenna G
JG
Pettigrew
Amanda
A
Belknap
James K
JK
D000818:Animals; D051545:Cyclooxygenase 1 / Q000096:biosynthesis* / Q000235:genetics; D051546:Cyclooxygenase 2 / Q000096:biosynthesis* / Q000235:genetics; D004195:Disease Models, Animal; D005534:Foot Diseases / Q000201:enzymology / Q000235:genetics / Q000662:veterinary*; D006734:Horse Diseases / Q000201:enzymology* / Q000235:genetics; D006736:Horses; D015151:Immunoblotting / Q000662:veterinary; D007150:Immunohistochemistry / Q000662:veterinary; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D012871:Skin Diseases / Q000201:enzymology / Q000235:genetics / Q000662:veterinary*
D012333:RNA, Messenger; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2