Cyclooxygenase-2 inhibition increases lipopolysaccharide-induced atherosclerosis in mice

Aims: The risk of adverse cardiovascular events in humans is increased with chronic use of cyclooxygenase-2 (COX-2) inhibitors. However, the role of COX-2 in animal models of cardiovascular disease has been controversial. In humans and animal models, cardiovascular disease is increased by bacterial infection of the supporting tissue of the teeth, a condition known as periodontal disease. Periodontal disease may result in chronic exposure to pro-inflammatory mediators, such as bacterial lipopolysaccharide (LPS), thereby producing a systemic inflammatory response. The current study examined the role of COX-2 in atherosclerosis induced by LPS derived from the periodontal disease pathogen Porphyromonas gingivalis (P. gingivalis). Methods and results: Porphyromonas gingivalis LPS was administered by chronic infusion for 28 days and atherosclerosis development was examined in the aortic root of ApoE (apolipoprotein E)-deficient mice. The extent of atherosclerosis was compared between mice receiving control diet or diet containing the COX-2 inhibitor celecoxib. The role of COX-2 in P. gingivalis LPS-induced inflammatory cell activation was examined in peritoneal macrophages. Porphyromonas gingivalis LPS infusion significantly increased atherosclerosis development. In mice infused with P. gingivalis LPS, administration of the COX-2 inhibitor celecoxib further increased the extent of atherosclerotic lesion area. In peritoneal macrophages, P. gingivalis LPS increased the expression of COX-2 mRNA (messenger ribonucleic acid) and the production of prostaglandin (PG) E₂ (PGE₂), the latter of which was inhibited by celecoxib. Porphyromonas gingivalis LPS-induced expression of tumour necrosis factor alpha (TNFα) was enhanced by inactivation of COX-2 and was attenuated by treatment with PGE₂. Conclusion: The inhibition of COX-2-derived PGE₂ may enhance P. gingivalis LPS-induced atherosclerosis by increasing macrophage production of TNFα.