Phospholipase A2-IIA Is Associated With Oral Dysbiosis and Bone Loss

Objectives: Antimicrobial proteins (AMPs) are endogenous innate components that play an important role in shaping and maintaining homeostatic interactions between the microbiome and host mucosal surfaces. Phospholipase A2 group IIA (PLA2-IIA) is an AMP with bactericidal activity mainly against Gram-positive bacteria. We have shown in vitro that P. gingivalis is able to enhance bactericidal activity of human oral epithelial cells (OECs) through upregulation of PLA2-IIA and gingival PLA2-IIA expression was elevated during initiation and progression of periodontitis in non-human primates. However, whether expression of PLA2-IIA in vivo could lead to oral dysbiosis and periodontitis remain unknown.
Methods: Transgenic mice overexpressing human PLA2-IIA (Tg-hPLA2-IIA) and their wild-type (WT) littermates were co-caged. Gingival expression of hPLA2-IIA was determined by ELISA and immunofluorescence. Oral swabs, gingival tissues, and fixed hemimaxillae were evaluated using 16s next generation sequencing, RT-PCR, Luminex, and micro-CT to determine oral microbiome, innate gene expression changes, cytokine/chemokine levels, and alveolar bone loss (ABL). Bactericidal properties of gingival lysates were evaluated through their effect in colony forming units (CFUs) of susceptible bacteria and antibody-mediated neuralization experiments.
Results: Gingival hPLA2-IIA levels were between 2,000-2500 pg/µg total protein. Beta diversity was significantly decreased in the oral microbiome of Tg-hPLA2-IIA with respect to WT (p=0.0011). Overexpression of hPLA2-IIA was associated with decrease in firmicutes and fusobacteria species and increase in proteobacteria species. Gingival tissues from hPLA2-IIA but not WT showed bactericidal activity linked to hPLA2-IIA expression. Expression of classical AMPs (beta defensins, calprotectin) and cytokines/chemokines was similar in hPLA2-IIA and WT gingival tissues. ABL was greater in hPLA2-IIA compared to WT mice (p≤0.01).
Conclusions: Increased hPLA2-IIA expression is associated with oral dysbiosis and periodontal disease. hPLA2-IIA could have a direct and indirect antimicrobial effect on specific oral microbiome species and direct effect in alveolar bone loss regardless of inflammation.