Biologic Activity of Porphyromonas endodontalis Complex Lipids

Introduction

Periapical infections secondary to pulpal necrosis are associated with bacterial contamination of the pulp. Porphyromonas endodontalis, a gram-negative organism, is considered to be a pulpal pathogen. P. gingivalis is phylogenetically related to P. endodontalis and synthesizes several classes of novel complex lipids that possess biological activity, including the capacity to promote osteoclastogenesis and osteoclast activation. The purpose of this study was to extract and characterize constituent lipids of P. endodontalis and evaluate their capacity to promote proinflammatory secretory responses in the macrophage cell line, RAW 264.7, as well as their capacity to promote osteoclastogenesis and inhibit osteoblast activity.

Methods

Constituent lipids of both organisms were fractionated by high-performance liquid chromatography and were structurally characterized using electrospray mass spectrometry or electrospray-mass spectrometry/mass spectrometry. The virulence potential of P. endodontalis lipids was then compared with known biologically active lipids isolated from P. gingivalis.

Results

P. endodontalis total lipids were shown to promote tumor necrosis factor alpha secretion from RAW 264.7 cells, and the serine lipid fraction appeared to account for the majority of this effect. P. endodontalis lipid preparations also increased osteoclast formation from RAW 264.7 cells, but osteoblast differentiation in culture was inhibited and appeared to be dependent on Toll-like receptor 2 expression.

Conclusions

These effects underscore the importance of P. endodontalis lipids in promoting inflammatory and bone cell activation processes that could lead to periapical pathology.     

Anoxia,calcium and contracture as mediators of myocardial enzyme release

The effects of anoxia and calcium-free perfusion on enzyme release, were studied in perfused rat hearts, at 37°C. In oxygenated hearts, calcium-free medium caused detachment of cells at intercalated discs, but no cell separation or enzyme release. Sixty minutes of anoxia with calcium-free medium caused striking cell separations, contracture of sarcomeres and enzyme release. Anoxia, followed by calcium-free medium, produced a sudden, energy-independent enzyme release with contracture and cell separations. Contraction bands as well as cell separations, were present in anoxic hearts reoxygenated in the absence of calcium. It is proposed that calcium-free media causes loss of integrity of intercalated disc junctions and contraction, and anoxic contracture pulls cells apart at weakened cell junctions, mediating membrane damage and enzyme release.