INVASION OF AORTIC AND HEART ENDOTHELIAL-CELLS BY PORPHYROMONAS-GINGIVALIS

Invasion of host cells is believed to be an important strategy utilize d by a number of pathogens, which affords them protection from the hos t immune system. The connective tissues of the periodontium are extrem ely well vascularized, which allows invading microorganisms, such as t he periodontal pathogen Porphyromonas gingivalis, to readily enter the bloodstream. However, the ability of P. gingivalis to actively invade endothelial cells has not been previously examined. In this study, we demonstrate that P. gingivalis can invade bovine and human endothelia l cells as assessed by an antibiotic protection assay and by transmiss ion and scanning electron microscopy. P. gingivalis A7436 was demonstr ated to adhere to and to invade fetal bovine heart endothelial cells ( FBHEC), bovine aortic endothelial cells (BAEC), and human umbilical ve in endothelial cells (HUVEC). Invasion efficiencies of 0.1, 0.2, and 0 .3% were obtained with BAEC, HUVEC, and FBHEC, respectively. Invasion of FBHEC and BAEC by P. gingivalis A7436 assessed by electron microsco py revealed the formation of microvillus-like extensions around adhere nt bacteria followed by the engulfment of the pathogen within vacuoles . Invasion of BAEC by P. gingivalis A7436 was inhibited by cytochalasi n D, nocodazole, staurosporine, protease inhibitors, and sodium azide, indicating that cytoskeletal rearrangements, protein phosphorylation, energy metabolism, and P. gingivalis proteases are essential for inva sion. In contrast, addition of rifampin, nalidixic acid, and chloramph enicol had little effect on invasion, indicating that bacterial RNA, D NA, and de novo protein synthesis are not required for P. gingivalis i nvasion of endothelial cells. Likewise de novo protein synthesis by en dothelial cells was not required for invasion by P. gingivalis. P. gin givalis 381 was demonstrated to adhere to and to invade BAEC (0.11 and 0.1% efficiency, respectively). However, adherence and invasion of th e corresponding fimA mutant DPG3, which lacks the major fimbriae, was not detected. These results indicate that P. gingivalis can actively i nvade endothelial cells and that fimbriae are required for this proces s. P. gingivalis invasion of endothelial cells may represent another s trategy utilized by this pathogen to thwart the host immune response.