BIOCHEMICAL-PROPERTIES OF HUMAN ORAL POLYMORPHONUCLEAR LEUKOCYTES

Polymorphonuclear leukocytes (PMN) isolated from the oral cavity of he althy human volunteers, spontaneously generated superoxide, nitric oxi de (NO) and other reactive oxygen species (ROS) which exhibited strong luminol chemiluminescence (LCL). To understand the physiological role s of oral PMN (OPMN), biochemical properties of the cells were analyze d. Biochemical analysis revealed that OPMN were already primed under p hysiological conditions. Western blot analysis revealed that they stro ngly expressed the inducible type of NO synthase (NOS II) and exhibite d the activity to catalyze tyrosine phosphorylation of various protein s including a 115 kDa protein (cbl product). OPMN also generated H2O2 and (OH)-O-. by some superoxide dismutase (SOD)-sensitive mechanism an d released myeloperoxidase (MPO). Kinetic analysis using specific inhi bitors revealed that OCl- generated by OPMN was predominantly responsi ble for the enhanced LCL. During the incubation under standard culture conditions, OPMN underwent apoptosis which proceeded more rapidly tha n that of the circulating PMN (CPMN). Immunochemical analysis revealed that expression of apoptosis-related gene products, such as Bcl-2, Bc l-xL and Bar, was below detectable levels with both cell types. Howeve r, caspase-3 but not caspase-1 was markedly activated in OPMN. These r esults indicate that the primed OPMN spontaneously generate ROS and pl ay an important role in the defense mechanism in the oral cavity and t hat the generated ROS activate caspase-3 thereby inducing apoptosis of the cells.