Inhibition by Porphyromonas gingivalis LPS of apoptosis induction in human peripheral blood polymorphonuclear leukocytes.

Many factors, such as cytokines and bacterial products, are known to affect the life-span of polymorphonuclear leukocytes (PMNs). We investigated here whether Porphyromonas gingivalis (P.gingivalis) LPS slows down the apoptotic process of PMNs. During incubation in regular culture medium, the viability of PMNs progressively declined, producing apoptotic cells, characterized by chromatin condensation, internucleosomal DNA fragmentation, cell shrinkage and blebbing of plasma membrane. P.gingivalis LPS significantly increased the viability of PMNs and reduced the production of fragmented DNA, as efficiently as E.coli LPS. The present study suggests that the retardation of PMNs apoptosis by P.gingivalis LPS may modulate the restoration of acute inflammation in the periodontal tissues, where activated PMNs accumulate.