Correlation between beta-defensin expression and induction profiles in gingival keratinocytes.

Human beta-defensins are antimicrobial peptides produced by epithelial cells. To date, 28 beta-defensins have been described and the expression of a select few has been classified as constitutive or inducible. Most studies have evaluated expression and regulation using a limited number of primary cell cultures or immortalized cell lines. The goal of this study was to quantitatively assess the in vitro expression and inducibility profiles of human beta-defensins, HBD-1, HBD-2, and HBD-3 across a number of primary gingival keratinocyte cultures. Cultured cells from 14 human subjects were stimulated with interleukin-1 beta (IL-1beta), IL-2, IL-6, IL-8, IL-12, tumor necrosis factor alpha (TNF-alpha), gamma interferon (IFN-gamma) or Escherichia coli lipopolysaccharide (LPS) and analyzed by reverse transcription (RT)-PCR. A subset of cultures were quantitatively assessed by real-time PCR. HBD-1 presented the highest and most heterogeneous expression at the basal level (non-stimulated) as compared to expression of HBD-2 and HBD-3, which was significantly lower and homogeneous. IFN-gamma was a primary inducer for HBD-1 and HBD-3, while IL-1beta and TNF-alpha were primary inducers for HBD-2. Sporadic induction was seen for IL-2, IL-6 and LPS. Synergistic expression was seen when various cytokines were combined. Interestingly, the induction potential of each beta-defensin was directly correlated to its basal expression. An inhibitor of JAK2 kinase (Janus kinase), down-regulated IFN-gamma-induced HBD-1 and HBD-3 expression, suggesting a role for the JAK/signal transducer and activator of transcription (STAT) signaling pathway in their expression. HBD-2 protein expression of supernatants and cell lysates paralleled mRNA expression. The results suggest that beta-defensin expression and induction in gingival keratinocytes is similar to that seen in other tissue. However, the novel finding of considerable variation among induction levels and the correlation of the induction with basal expression suggests that these innate response elements may play a key role in susceptibility or resistance to disease in the oral cavity.

Expression of beta-defensins in gingival health and in periodontal disease.

BACKGROUND: Human beta-defensins (HBDs) are epithelial-derived antimicrobial peptides. The expression of three HBDs (HBD-1, HBD-2, and HBD-3) has been reported in oral mucosa, gingiva, and salivary glands. However, their role in protection against oral infections is not well understood. This study examined the expression of HBD-1, HBD-2, and HBD-3 mRNAs in gingival health and periodontal disease. METHODS: Gingival tissue discarded from periodontal procedures was obtained from 20 periodontally healthy and 29 periodontally diseased sites. Total RNA was isolated, and expression of beta-defensins was analyzed by both 35-cycle and semiquantitative (25-cycle) reverse transcription-polymerase chain reaction (RT-PCR). The level of expression was assigned ordinal scores of no expression, low expression, or high expression. mRNA expression was compared between healthy and diseased groups using exact tests of homogeneity and Cochran-Mantel-Haenszel tests; associations among the variables were assessed using exact tests and Kendall's tau-b statistic. RESULTS: All 49 samples demonstrated basal mRNA expression of HBD-1, HBD-2, and HBD-3. Significantly higher levels of HBD-3 (P = 0.012) expression were found in the healthy tissues as compared to the diseased ones. There was also a suggestion of higher expression of HBD-2 in the healthy tissues (P = 0.12). Levels of HBD-1, HBD-2, and HBD-3 mRNA expression were correlated with one another (P < 0.001). CONCLUSIONS: High levels of HBD-3 mRNA expression in healthy tissues suggest a potentially important protective role for defensins in the host immune response to infection by periodontal pathogens.