Doxycycline affects diet- and bacteria-associated atherosclerosis in an ApoE heterozygote murine model: Cytokine profiling implications

BACKGROUND: - It has been postulated that increased levels of oxidized LDL and/or systemic infection with pathogens such as Porphyromonas gingivalis (Pg) elevate the inflammatory response and increase susceptibility to atherosclerosis. Doxycycline has been known to be a pluripotent drug affecting several cell functions. In particular, it is believed to affect matrix remodeling, an important process involved in the development of atherosclerosis. Thus, we hypothesized that Doxycycline would be beneficial in diet- and/or Pg-induced atherosclerosis METHODS AND RESULTS: To test the hypothesis, Apolipoprotein E heterozygous (ApoE+/-) mice were inoculated weekly with Pg and treated with either Doxycycline or saline; animals were fed either a high-fat or normal chow diet. Animals were euthanized at 14 or 24 weeks and histomorphometric analysis of atheromatous lesions in the proximal aorta, serum levels of acute phase protein Serum Amyloid A (SAA) and serum cytokine profiling were performed. Histomorphometric analysis demonstrated that in non-infected mice fed a high fat diet, administration of Doxycycline resulted in a reduction from 10.5 % +/-.49 to 1.09% +/- 0.102 (p < 0.05) in the high-fat diet non-infected groups at 14 weeks (see figures 7a, 7b, 9.) and a reduction from 10.5% +/0.49 to 1.09% +/- 0.102 (p=0.106) in the high-fat diet non-infected groups at 24 weeks. Administration of Doxycycline to chow-fed Pg mice also resulted in a reduction from 0.62% +/- 0.128 to 0.0% +/- 0.0 (p < 0.05) at 14 weeks and a reduction from 0.92% +/- 0.23 to 0.0% +/- 0.0 (p < 0.05) at 24 weeks. Administration of Doxycycline to mice fed a high fat diet and Pg-inoculated resulted in a reduction of mean percentage of proximal aorta occupied by atheromatous plaque lesion from 16.46% +/- 1.69 to 1.141% +/- 0.23 (p < 0.05) at 14 weeks and a reduction from 25.27% +/- 1.734 to 0.428% +/- 0.033 (p < 0.05) at 24 weeks. At this timepoint, there was a reduction of SAA levels in Pg-infected animals by 5-fold and 3-fold in Doxycycline-treated chow and high fat-diet groups respectively. Cytokine antibody arrays revealed a marked reduction in the levels of pro-inflammatory cytokines such as TNF alpha, VEGF, IL-1 alpha, IL-1 beta and IL-6 in Doxycycline treated groups whether Pg-infected or fed a high fat diet while anti-inflammatory cytokines were not affected. CONCLUSIONS: - Doxycycline inhibits proinflammatory cytokines and results in profound reduction in the progression of atherosclerosis in ApoE+/- Pg-inoculated and/or high fat diet fed mice.