In vitro effects of nonsteroidal anti-inflammatory drugs on cyclooxygenase activity in dogs.

P Kay-Mugford, S J Benn, J LaMarre, P Conlon

Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Canada.

American journal of veterinary research 2000 Jul

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To establish an in vitro assay and determine the differential suppressive activity of non steroidal anti-inflammatory drugs (NSAID) on cyclooxygenase (COX)-1 and COX-2 isoenzymes in dogs. COX activity was evaluated in the presence and absence of 4 NSAID (meloxicam, tolfenamic acid, carprofen, and ketoprofen), using a canine monocyte/macrophage cell line that constitutively expresses COX-1, but can be induced to express COX-2 when incubated with lipopolysaccharide. Inhibition of prostaglandin E2 TPGE2) synthesis by each NSAID was measured by enzyme immunoassay and attributed to specific COX-1 or COX-2 activity through assessment of COX messenger RNA expression by use of northern blot analysis and reverse transcription-polymerase chain reaction (RT-PCR). The COX selectivity of each drug was evaluated from dose-response curves by calculating a ratio (COX-1:COX-2) of inhibitory concentration values on the basis of concentrations that reduced PGE2 by 50% in each COX model. Meloxicam and tolfenamic acid preferentially inhibited COX-2, with meloxicam inhibiting COX-2 activity 12 times more effectively than COX-1 activity. Carprofen was only 1.75 times more selective for COX-2 than for COX-1, and ketoprofen was slightly more selective for COX-1. COX-1 and COX-2 were differentially sensitive to inhibition in vitro by NSAID. Meloxicam and tolfenamic acid were selective for COX-2. Effects of carprofen and ketoprofen approached equipotency against both isoenzymes. Selective COX-2 inhibitors are a new class of drugs with anti-inflammatory effects similar to conventional NSAID but with fewer adverse effects. Development of these agents for veterinary use would be facilitated by the convenience of using a canine cell line as a model system to screen COX-1 and COX-2 inhibitor activities in vitro.

Citation

P Kay-Mugford, S J Benn, J LaMarre, P Conlon. In vitro effects of nonsteroidal anti-inflammatory drugs on cyclooxygenase activity in dogs. American journal of veterinary research. 2000 Jul;61(7):802-10