B-227. Differential Expression of Scavenger Receptors in Murine Peritoneal Macrophages Infected with Porphyromonas gingivalis in vitro

M. T. Baer, F. C. Gibson, III;
Boston Univ. Med. Ctr., Boston, MA.

Background: Emerging epidemiological data support that chronic infections such as periodontal disease accelerate atherosclerosis. We and others have demonstrated that Porphyromonas gingivalis accelerate atherosclerosis in ApoE-/- mice and evoke macrophage foam cell formation in vitro. The mechanisms underlying conversion of P. gingivalis-challenged macrophages into foam cells remain to be defined. Methods: As macrophage cholesterol uptake is mediated by scavenger receptors (SRs) and efflux of cholesterol from macrophages is principally dependent on ABCA-1-mediated transport, we used QRT-PCR and FACS to explore relative expression of SRs and abca-1 by thioglycolate-induced murine peritoneal macrophages cultured with P. gingivalis in vitro. Results: QRT-PCR revealed that challenged macrophages up-regulated expression of msr1 (SR-A) and down-regulated expression of cd36 and abca1. Surface presentation of SR-A by macrophages in vitro appeared to double in response to P. gingivalis challenge, while CD36 was observed to halve. Purified P. gingivalis capsular polysaccharide (CPS) influenced surface expression of macrophage SRs as potently as whole bacteria. Addition of LDL during macrophage challenge did not alter the P. gingivalis-induced increase in surface expression of SR-A, but attenuated the decrease in CD36 expression. Conclusions: The observed responses of murine macrophages to P. gingivalis may shed light on the mechanisms of foam cell induction and of pathogen-accelerated atherosclerosis.