We previously showed that inflammation, and not hyperlipidemia alone, was necessary for CD36 dependent atherogenesis. Chronic periodontal disease is characterized by a persistent inflammatory state and is epidemiologically associated with cardiovascular disease. We hypothesize that CD36 is an essential link between periodontal disease and atherosclerosis.
Low density lipoprotein receptor knock out (LDLR KO) mice and CD36/LDLR double KO mice were infected with the periodontal disease associated bacteria, Porphyromonas gingivalis (Pg), by oral lavage and fed a Western diet for 12 weeks (n = 7-14/group). We assessed periodontal disease, risk factors associated with atherosclerosis, and lesion burden. We conducted studies in isolated macrophages to understand mechanistic differences between the groups.
Wild type and CD36 KO macrophages equally phagocytosed bacteria. We measured the cemento-enamel junction of each molar to assess periodontal disease and found that it was significantly increased in infected mice compared with uninfected controls. Histological analysis showed neutrophil, osteoclast and macrophage infiltrates in the alveolar bone of infected mice. Differences in plasma cholesterol, triacylglycerol, insulin resistance and weight gain did not necessarily track with atherosclerosis burden, however blood neutrophils and cytokines were increased in infected LDLR KO mice compared with all other groups. Infected LDLR KO mice had significantly increased atherosclerotic lesion burden compared with uninfected LDLR KO mice, and all of the increased lesion was CD36 dependent. PCR analysis found no evidence for direct infection of atherosclerotic lesions by Pg. In vitro macrophage studies showed that heat killed Pg, lipopolysaccharide (LPS) derived from Pg, oxidatively modified LDL or plasma from infected mice, could not activate the NALP3 inflammasome. Combining heat killed Pg or Pg LPS with oxidatively modified LDL or plasma from infected mice, however, led to significant IL-1 beta secretion that was CD36 and NFkB dependent. Our data suggest that atherosclerosis associated with periodontal disease is mediated by cellular inflammatory responses involving both CD36 and Toll-like receptor.
Significance of Autoantibodies to Oxidatively Modified LDL in Plasma of Children with Down Syndrome
