Effects of lipoxygenase on primary periodontitis

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<Purpose>It has been demonstrated that 12-hydroxyeicosatetraenoic acid(12-HETE), which is 12-lipoxygenase(12-HETE)metabolites of arachidonic acid, is produced in gingival tissues. 12-HETE, which has many biological activities, i. e. degranulation, chemotactic activity and bone resorption. In this study, we investisted the effects of 12-HETE on human leukocytes, especially, the mechanisms of 12-HETE induced increase of intracellular Ca^<2+> concentration([Ca2, ]i).<Methods & Results>12-Lipoxygenase activity of various tissues in rat was measured by thin layer autoradlogram. The chemokinetic activity of 12-HETE for human peripheral blood polymorphonuclear leukocytes(PMNS)was examined in modified Boyden chamber assay. Intracellular free calcium was monitored using the fluorescent probe fura-2.12-Lipoxygenase activity in rat gingiva was much higher than any other tissues. Both 12-HETE and N-formyl-methionyl-leucyl-phenylalanine(FMLP)stimulated chemokinetic movement of hurffan PMNs in a dose dependent manner. However, 12-HETE suppressed chemokinetic movement stimulated by fMLP in a dose dependent manner. 12HETE induced the increase of[Ca^<2+>i in human PMNs in a dose dependent manner and suppressed the[Ca^<2+>]i increase induced by fMLP. N-BOC-MLP(10^<-5>M), FMLP receptor antagonist, inhibited the increase of[Ca^<2+>]i by fMLP, but not by 12-HETE. 12-HETEinduced the increase of[Ca^<2+>], Was abolished by pretreatment with pertussis toxin. The increase in[Ca^<2+>, ]i induced by 12-HETE was inhibited by U-73122, a specific phospholipase C(PLC)inhibitor. 12-HETE stimulated the production of inositol 1, 4, 5trisphosphate.<Conclusions>These results suggest that 12-HETE has chemokinetic activity for human PMNs and have interaction with another chemotactic factor. The mechanisms for 12-HETE to increase[Ca^<2+>]i may involve PLC activation through the guanin-nucleotide-binding protein, resulting in an increase in the phosphatidylinositol turnover.