Our long term objective is to understand the molecular basis for intraindividual differences in susceptibility to Gram-negative periodontal infections. There is increasing data which link a hyperresponsive monocyte secretion trait (Macrophage+) and susceptibility to periodontal disease. A monocytic Macrophage+ phenotype is characterized by a hypersecretion of PGE2 in response to stimuli such as lipopolysaccharide (LPS, endotoxin). Since PGE2 is a potent mediator of periodontal tissue destruction, we hypothesize that the macrophage+ trait may be a marker for susceptibility to severe forms of disease. This concept is supported by an observation that this macrophage+ trait is present in many patients with early onset periodontitis (EOP), refractory periodontitis (Ref) and insulin-dependent diabetes mellitus associated periodontium. The purpose of this investigation is to focus on understanding the intracellular biochemical pathways that distinguish the macrophage+ trait. We will examine and compare differences in monocytic secretory responses to lPS comparing monocytes from normal (macrophage) patients and the 3 groups of patients with the macrophage+ trait. We will measure the secretion of PGE2, IL-1beta and TNFalpha. We will examine for molecular differences to explain differences in PGE2 secretory patterns by studying lPS receptor (CD14) density and binding affinities, phospholipid turnover, arachidonic acid metabolism, PKC activation and G protein activation. We will measure the levels of cyclooxygenase (COX) enzyme in resting and stimulated macrophage+ and macrophage cells and the levels of COX-1 and COX-2 mRNA. We will examine the role of PKC in modulating COX-2 mRNA expression and determine whether differences in COX-2 gene expression are due to differential regulation by the NF-kappaB promoter/I-kappaB inhibitor systems. The data should provide new insight into host susceptibility to periodontal destruction.
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