Abstract 14718: Using Renal-Specific Cyclo-Oxygenase-2-Deficient Mice to Understand the Pro-Thrombotic Effects of Non-Steroidal Anti-Inflammatory Drugs

Abstract

Introduction: Non-steroidal anti-inflammatory drugs (NSAIDs) work by inhibiting the enzyme cyclooxygenase (COX)2 but their use increases thrombotic risk. We have shown that COX2 inhibition increases plasma methylarginines ADMA and LNMMA in mice and man. Methylarginines are controlled in the kidney but circulate causing inhibition of anti-thrombotic vascular NO by competing with L-arginine for the active site of eNOS. However, the causative links between renal COX2 (which is expressed predominately in fibroblasts), methylarginines and thrombosis remain unproven. Hypothesis: Here we hypothesised that deletion of COX2 from fibroblasts would result in a renal-specific COX2-deficiency and be sufficient to increase methylarginine levels and drive vascular NO dysfunction and a pro-thrombotic phenotype. Methods: Fibroblast COX2-deficient mice were generated from Fsp1-Cre and Ptgs2 flox strains. COX2 levels were measured by RT-qPCR, methylarginines by LC/MS/MS, vascular NO function as acetylcholine-induced dilation by myography and thrombosis in vivo after FeCl 3 -carotid injury. Results: Fibroblast COX2-deficient mice showed reduced COX2 expression in the renal medulla (Fig A) but not renal cortex, aorta, lung, colon, thymus or brain. This was associated with increased plasma ADMA and LNMMA levels (Fig B) and reduced NO-dependent dilatation of carotid arteries (Fig C). Fibroblast COX2-deficiency accelerated thrombosis after carotid artery injury which could be reversed by pre-treating animals with L-arginine (50mg/kg; 5 days) which displaces methylarginines from eNOS (Fig D). Conclusions: These data provide the first direct demonstration that renal COX2 regulates methylarginine levels to control systemic endothelial and thrombotic function. As such, they indicate that inhibition of renal COX2 contributes to the thrombotic risk seen in patients taking NSAIDs and suggest L-arginine supplementation as a potential rescue therapy to mitigate this.