Putative Protective Role of hBD1 SNP in Gingival Epithelial Cells

Objective: Human beta-defensins (hBDs) are antimicrobial peptides secreted by oral epithelia. hBD1 is constituitively expressed while other members of the defensin family are induced by bacteria and inflammatory cytokines. This innate immune response protects the oral cavity against periopathogenic bacteria, yeast and viruses. hBD1-2 are well characterized in gingival epithelial cells (GECs), however little is known about hBD3-9 expression. Previous studies have shown the G allele of the -44 C/G SNP in hBD1 5' untranslated region is associated with protection from Candida. Here we evaluated the effect of the -44 hBD1 SNP genotype on hBD1-9 expression in GECs stimulated with endotoxins and pro-inflammatory cytokines. Methods: GEC from 6 different donors (n=2 each C/C, C/G, G/G) were stimulated for 24h with Escherichia coli lipopolysaccharide, PAM3CSK4, IL-1beta, TNF-alpha, INF-gamma and PMA along with an unstimulated control. Gene expression levels of hBD1-9 were analyzed by quantitative real-time PCR. Each GEC donor was stimulated in duplicate and subsequently analyzed in duplicate.  Results: There was negligible difference in hBD1 expression levels between the three SNP genotypes. All cytokines enhanced expression of hBD2 in the C/C and C/G SNP donors but not in the G/G donors. hBD3 expression also increased in the C/C and C/G genotypes but only with TNR-alpha and INF-gamma stimulation. Endotoxins produced minimal effect on both hBD2 and hBD3 expression for all SNP genotypes. For hBD4-9, only hBD9 had detectable expression and the levels were similar between all SNP genotypes. Conclusion: Our data suggest that an hBD1 SNP may enhance the ability of the oral epithelium to prepare itself against infection and inflammation by producing more hBD2 and hBD3 in the presence of periopathogens. Due to our small sample size, further SNP donor analysis is needed to elucidate this relationship between genotype and beta-defensin expression.

Supported by NIDCR R01DE16961 and DE13573