Probiotic Lactobacillus-casei Effect on Epithelial Cell Responses to Oral Pathogens

Objective: Gingival epithelial cell has receptors, the innate immune system and cytokine secretion capabilities to recruit host defenses against bacterial infections. This study evaluated the effect of probiotic Lactobacillus casei strain Shirota on the expression of Interleukin-8 (IL-8) and human Beta-Defensin-2 (hBD-2) mRNA when bacteria interact with gingival epithelial cell. Method: This study used quantitative real time-polymerase chain reaction assay (RT-PCR) to analyze changes in gene expression related to cytokine responses and the innate immune system on HaCaT epithelial cell line. The confluent cultured HaCat cell (10⁵ cell/mL) was exposed to Streptococcus mutans ATCC 25175  (10⁷ CFU/mL) and Porphyromonas gingivalis ATCC 33277 (10⁷ CFU/mL), respectively for 24 h, at 37⁰C, CO₂ 5% and challenged with probiotic Lactobacillus casei strain Shirota (10⁷ CFU/ml). Subsequently, the transcription level of IL-8 and hBD-2 in HaCat cell were analyzed by RT-PCR. Additionally, cell viability was analyzed by MTT assay. Data was statistically evaluated by one way analysis of variance. Result: MTT assays confirmed that there were no cytotoxic effects of Lactobacillus casei on HaCat cell (viability 90.1%). Both mRNA expression of IL-8 and BD-2 increased after exposed to both bacteria species. The presence of Lactobacillus casei strain Shirota reduced the expression of IL-8, however there was no effect of the presence of Lactobacillus casei towards the transcription level on hBD-2. From the statistical evaluation, the reduced expression of IL-8 has significant difference (p < 0.05) after challenged with Lactobacillus casei whilst hBD-2 was not found to be significantly different. Conclusion: The results suggest that Lactobacillus casei may suppress expression of IL-8 and induce human Beta-Defensin 2 inflammatory genes in response of HaCat cell to S. mutans and P. gingivalis infection. There was no cytotoxic effects of Lactobacillus casei towards epithelial cell. However this result should be confirmed by using other oral bacteria.