Detection of periodontal bacteria in atherosclerotic plaque

Abstract

This study aims to examine the role infection plays in the pathogenesis of atherosclerosis through the molecular identification of latent bacterial species present in atherosclerotic plaque tissue from the carotid artery. Immunohistological examination of the atherosclerotic plaque tissue revealed widespread localisation of the bacterial cell wall constituent peptidoglycan (PGN). Targeted PCR amplification of the 16S rRNA gene permitted identification of a diverse collection of 16S rDNA sequences within atherosclerotic plaque samples. Thirteen of 21 (61.9%) plaques contained bacterial 16S rDNA relating to periodontal (P. gingivalis and T. forsythia), oral (Streptococcus spp.), and respiratory (Klebsiella pneumoniae and Mycobacterium tuberculosis) and commensal (Propionibacterium acnes and Staphylococcus epidermidis) species. Of the 160 isolates recovered P acnes (91%) was most frequently detected, followed by Lactobacillus spp. (3%), S. epidermidis (3%), S. mitis (3%) and S. sanguinis (1%). Challenge of THP-1 cells with a P. acnes isolate recovered from atherosclerotic plaque, resulted in significant temporal up-regulation the major cholesterogenic transcriptions factor, SREBP2 and its two target transcripts, LDLR and HMGR. Similarly, the cholesterol transporter gene ABCA1 was highly expressed in P. acnes-infected THP-1 cells in addition to inflammatory cytokines/chemokines TNFα, IL-1β, CCL3 (MIP-1α), cell adhesion molecule ICAM-1. Anti-apoptotic gene BCL2A1 showed the greatest increase in mRNA compared to all tested genes. Expression of the same panel of genes direct in atherosclerotic plaque tissue resulted in similar expression patterns.