Abstract
Mouse embryonic fibroblasts (10T1/2) and Chinese hamster ovary (AS52) cell lines that stably express murine prostaglandin G/H synthase (PGHS)-1 or -2 were used to compare the effects of exogenous and endogenous arachidonic acid (AA) on isozyme-selective inhibition by acetylsalicylic acid, indomethacin, and N-[2-cyclohexyloxyl-4-nitrophenyl] methanesulfonamide (NS-398). The rationale for developing in vitro systems that identify PGHS-2-selective inhibitors is the belief that inhibition of this isoform accounts for the therapeutic benefits of nonsteroidal anti-inflammatory drugs (NSAIDs). Conversely, inhibition of PGHS-1 is believed to cause the toxic effects of NSAIDs, such as gastric and renal damage. When exogenous AA was used, acetylsalicylic acid was a 5- to 10-fold more potent inhibitor of PGHS-1, whereas indomethacin was a 4- to 5-fold more potent inhibitor of PGHS-2. Within the dose range tested (1 × 10−6 μM to 100 μM), NS-398 was highly selective for PGHS-2. When calcium ionophore A23187 was used to mobilize endogenous AA, acetylsalicylic acid and indomethacin equipotently inhibited both PGHS-1 and PGHS-2 isozymes. NS-398 remained highly selective for PGHS-2 in 10T1/2 and AS52 cells but also effectively (100%) inhibited PGHS-1 in AS52 cells. Pharmacological data derived using endogenous AA correlated better with the anti-inflammatory efficacy of these NSAIDs in laboratory animals and with the therapeutic/toxic activities of these NSAIDs in rheumatoid arthritic patients. Therefore, screening for PGHS-selective NSAIDs may best be conducted in intact cells that express high levels of each isozyme using endogenous sources of AA.
Footnotes
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Send reprint requests to: Patricia C. Chulada, Ph.D., Laboratory of Environmental Carcinogenesis and Mutagenesis, National Institute of Environmental Health Sciences, P.O. Box 12233, Research Triangle Park, NC 27709.
- Abbreviations:
- PGHS
- prostaglandin G/H synthase: AA, arachidonic acid
- NSAID
- nonsteroidal anti-inflammatory drug
- BME
- Basal Medium Eagle
- RIA
- radioimmunoassay
- NS-398
- N-[2-cyclohexyloxy-4-nitrophenyl] methanesulfonamide
- PLA2
- phospholipase A2
- Received July 18, 1996.
- Accepted October 29, 1996.
- The American Society for Pharmacology and Experimental Therapeutics
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