EVIDENCE OF AN ASSOCIATION BETWEEN FUNCTIONAL ABNORMALITIES AND DEFECTIVE DIACYLGLYCEROL KINASE-ACTIVITY IN PERIPHERAL-BLOOD NEUTROPHILS FROM PATIENTS WITH LOCALIZED JUVENILE PERIODONTITIS

Peripheral neutrophils from patients with localized juvenile periodont itis (LJP) show functional abnormalities, such as impaired locomotion and enhanced respiratory burst activity. A defect in intracellular sig nalling mechanism has been proposed to be responsible for some changes , but direct evidence is lacking. In this study we have determined the activity of diacylglycerol (DAG) kinase, an enzyme controlling the DA G/protein kinase C (PKC)-pathway, in crude cytosolic and membrane frac tions of neutrophils from 5 LJP patients and age and gender-matched no rmal individuals. No difference was observed in the DAG kinase activit y in subcellular fractions from unstimulated cells between the 2 group s. When normal neutrophils were stimulated with N-formyl-methionyl-leu cyl-phenylalanine (FMLP), the enzyme activity was markedly increased i n both subcellular fractions. In contrast, neutrophils from 3 of the 5 LJP patients tested completely failed to rise the DAG kinase activity upon chemoattractant stimulation. These data indicate that in some LJ P patients the neutrophil DAG kinase may be defective. To examine whet her a decrease in DAG kinase activity could account for some neutrophi l abnormalities seen in LJP, normal neutrophils were treated with R590 22, a DAG kinase inhibitor, that has been shown to reduce DAG kinase a ctivity in human neutrophils. Upon stimulation with FMLP, R59022-treat ed normal neutrophils showed significantly reduced chemotactic respons e and enhanced respiratory burst activity, two typical functional abno rmalities featured by LJP cells. It is concluded that a defect in DAG kinase may cause, through an abnormal accumulation of the endogenous P KC activator DAG, some of the functional changes observed in neutrophi ls from LJP patients.