Association of a genetic polymorphism (-44 C/G SNP) in the human DEFB1 gene with expression and inducibility of multiple β-defensins in gingival keratinocytes

Abstract

BackgroundHuman β-defensins (hBDs) are antimicrobial peptides with a role in innate immune defense. Our laboratory previously showed that a single nucleotide polymorphism (SNP) in the 5' untranslated region of the hBD1 gene (DEFB1), denoted -44 (rs1800972), is correlated with protection from oral Candida. Because this SNP alters the putative mRNA structure, we hypothesized that it alters hBD1 expression.MethodsTransfection of reporter constructs and evaluation of antimicrobial activity and mRNA expression levels in keratinocytes from multiple donors were used to evaluate the effect of this SNP on constitutive and induced levels of expression.ResultsTransfection of CAT reporter constructs containing the 5' untranslated region showed that the -44 G allele yielded a 2-fold increase in CAT protein compared to other common haplotypes suggesting a cis effect on transcription or translation. The constitutive hBD1 mRNA level in human oral keratinocytes was significantly greater in cells from donors with the -44 GG genotype compared to those with the common CC genotype. Surprisingly, the hBD3 mRNA level as well as antimicrobial activity of keratinocyte extracts also correlated with the -44 G allele. Induced levels of hBD1, hBD2, and hBD3 mRNA were evaluated in keratinocytes challenged with Toll-like receptor 2 and 4 ligands, interleukin-1β, TNFα, and interferon-γ (IFNγ). In contrast to constitutive expression levels, IFNγ-induced keratinocyte hBD1 and hBD3 mRNA expression was significantly greater in cells with the common CC genotype, but there was no clear correlation of genotype with hBD2 expression.ConclusionThe DEFB1 -44 G allele is associated with an increase in overall constitutive antimicrobial activity and expression of hBD1 and hBD3 in a manner that is consistent with protection from candidiasis, while the more common C allele is associated with IFNγ inducibility of these β-defensins and is likely to be more protective in conditions that enhance IFNγ expression such as chronic periodontitis. These results suggest a complex relationship between genetics and defensin expression that may influence periodontal health and innate immune responses.

Peroxisome proliferator-activated receptor gamma activation is required for maintenance of innate antimicrobial immunity in the colon

“…C. albicans colonization was significantly increased in CD patients and was identified as an immunogen for ASCA (19), a serologic marker associated mainly with colonic involvement in CD (23). In line with the findings of a recent study (20), we provide a mechanism whereby the rs1800972 G allele might be linked to transactivation of DEFB1 expression through PPARγ. It also might account for the inefficacity of PPARγ-based therapy, such as 5-aminosalicylates, in the colon of CD patients with colonic involvement compared with UC patients.…”

Caries and Innate Immunity: <b><i>DEFB1</i></b> Gene Polymorphisms and Caries Susceptibility in Genetic Isolates from North-Eastern Italy

“…β-Defensin production has been theorized as being under genetic control, with the involvement of copy number variations in DEFB4 , DEFB103 , and DEFB104 genes coding for hBD2 [Jaradat et al, 2013] as well as hBD3 and hBD4, reviewed in Cantsilieris and White [2013], or regulatory 5 ′ -untranslated region (UTR) polymorphisms in the DEFB1 gene encoding hBD1 [Sun et al, 2006;Milanese et al, 2007;Kalus et al, 2009;Nurjadi et al, 2013].…”

The oral cavity microbiota: between health, oral disease, and cancers of the aerodigestive tract

“…Parameters such as structure, expression, virulence factors, and invasive properties are being investigated. Furthermore, the infection can be influenced by the genetic variations of the host, which can result in defective peptides (Kalus et al 2009). In the intestine, AMPs are produced by epithelial cells.…”