Associations of P2RX7 Functional Diplotypes with Localized Aggressive Periodontitis

Abstract

Aim: The purpose of this study was to test for the role of the P2X7 receptor in localized aggressive periodontitis (LAP). Methods: Peripheral blood was obtained from 95 subjects with LAP and 76 healthy unrelated controls (HUCs). Three P2RX7 single-nucleotide polymorphisms (rs1718119, rs2230911, and rs3751143) were genotyped from these subjects, and their peripheral blood samples were stimulated with lipopolysaccharide (LPS) from Escherichia coli and tested for inflammatory markers. The 3 P2RX7 single-nucleotide polymorphisms were in found to be in perfect linkage disequilibrium, and a total of 4 haplotypes and 9 diplotypes were identified among all subjects. For both subject populations, the 9 diplotypes were grouped into 4 functional groups and tested for association with subject inflammatory response. To specifically study the effects of extrinsic activation of the P2X7 receptor in LAP, peripheral blood samples from were stimulated under 3 treatments: LPS, LPS + ATP, and LPS +ATP+ P2X7 selective inhibitor. The effects of these treatments on P2X7 receptor activity were measured through Luminex protein assay. Last, to test whether receptor stimulation was related to P2RX7 expression, relative mRNA levels of P2RX7 were quantified with real-time quantitative polymerase chain reaction. Results: Several associations between the P2RX7 diplotypes and LPS-stimulated blood chemokine/cytokine levels were found between the LAP and HUC populations (P < 0.05). P2X7 activation resulted in statistically significant differences in IL-1β and IL-12p40 concentrations for both subject populations. The relative P2RX7 mRNA levels increased significantly after addition of its inhibitor for both LAP and HUC populations. Conclusions: This study detected an association between P2RX7 functional diplotypes and in vitro immune response of whole blood from subjects with LAP. In addition, we found that inhibition of the activated P2X7 receptor leads to increased P2RX7 mRNA levels, suggesting a feedback loop ( ClinicalTrials.gov NCT01330719). Knowledge Transfer Statement: The results of this study suggest that P2RX7 functional diplotypes are associated with LAP and their in vitro immune response to bacteria. Ongoing studies to uncover the mechanistic link between P2RX7 and LAP phenotypes could lead to the development of preventive approaches for susceptible subjects.

Case Report of a 4-Year-Old Girl with Stage IV Grade C Localized Periodontitis (Pre-Puberal Localized Aggressive Periodontitis) Affected by Misrecognition and Late Diagnosis

“…A rapid Stage IV grade C localized periodontitis/LPP diagnosis is essential, since the aggressive auto-immune response to bacteria can rapidly lead to a resorptive process [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 11 ]. Thus, a simple bacterial test to identify the pathogenic bacterium types would provide both diagnostic confirmation and justification for antibiotic treatment [ 2 , 3 , 11 , 12 , 13 , 14 , 15 ]. If LPP disorder is identified early, there is time to wait (i.e., usually up to two weeks) for lab test results, and only then should antibiotic therapy proceed [ 5 , 6 , 9 , 10 , 16 , 17 , 18 ].…”

“…Stage IV grade C localized periodontitis (formerly known as localized aggressive periodontitis (LAP)/localized juvenile periodontitis) is a rare form of inflammatory periodontal disease occurring in clinically healthy individuals (with a 0.06% prevalence in European white individuals and an up to 2.6% prevalence in African Americans) [ 1 , 2 , 3 , 4 , 5 ]. Early-age onset and rapid progressive bone and periodontal ligament (PDL) loss around very specific teeth (first, the molars and incisors) correlated with low/no calculus or oral plaque deposits and surrounding periodontal tissues with almost no inflamed aspects upon clinical inspection are some of the main pathognomonic signs [ 1 , 2 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ].…”

“…This rare form of periodontitis has been reported to show familial aggregation (i.e., hyperinflammatory auto-immune response when encountering periodontopathic bacteria in blood samples) [ 2 , 3 , 4 , 11 ]. LAP is a multifactorial disease, with its leading role being abnormal response to microbial communities present in the oral cavity [ 3 ]. In healthy individuals, there is a symbiotic relationship between bacterial community and oral biofilm [ 3 ].…”

“…LAP is a multifactorial disease, with its leading role being abnormal response to microbial communities present in the oral cavity [ 3 ]. In healthy individuals, there is a symbiotic relationship between bacterial community and oral biofilm [ 3 ]. However, if a genetic predisposition and/or environmental factors (not yet characterized) are met, the normal symbiotic relationship becomes abnormal and dysbiotic, producing an extremely aggressive auto-immune response leading to tissue destruction due to disruptions in bone metabolism [ 2 , 3 ].…”

“…Nevertheless, there are contradictory data related to the relationship between the response to certain bacterial types and the exaggerated immune response to any bacteria [ 2 , 11 , 15 ]. In the presence of genetic predisposition and/or environmental factors (presently unknown), the immune response becomes excessively aggressive (i.e., activating an intracellular signaling cascade with inflammatory cytokines, P2Rx7 functional diplotypes, chemokines, adhesion molecules, and growth factors) ending with tissular destruction [ 2 , 3 , 11 , 15 ].…”