Studies on the Potential Probiotic Strains Isolated from Korean Traditional Fermented Foods for Alleviating the Intestinal Inflammation

Abstract

Inflammatory bowel disease (IBD) including ulcerative colitis and crohns disease is caused by chronic inflammation in the digestive tract. Even though the exact pathogenesis remains unclear, dysbiosis of gut microbiota, damage of epithelial integrity, imbalance of cytokine profile and infection of specific pathogenic bacteria have been considered as the primary factors for triggering IBD. For developing probiotics which could positively modulate gut microbiota and immune response, this study aimed to screen and characterize putative probiotics with various functions to alleviate intestinal inflammation associated with IBD. First, using selective and differential media, 399 lactic acid bacteria (LAB) were isolated from 77 traditional fermented food samples produced in Gangwon province, Korea. Second, 10 strains with putative functional LAB were screened and selected based on the probiotic properties, such as resistance to intestinal conditions, safety assessment and adhesion ability for human epithelial cell line. Then, the selected bacterial strains were evaluated for their antimicrobial activities against pathogens, particularly related to IBD by disk diffusion and agar-well diffusion methods and ATP assay. Almost every strains showed inhibition activities against pathogen indicators except the strain of B4 compared to reference strain, LGG. Anti-inflammatory effects of the selected strains suppressing excessive intestinal inflammation were assessed by nitric oxide (NO) assay using murine macrophage RAW264.7 cell line. In addition, concentration of IL-8 produced by HT-29 cells and the expression levels of tight junction proteins in caco-2 cells which were both treated by 10 ng/ml of TNF-α were significantly regulated positively. After inducing colitis in mice by administration of 2.5 and 5 % DSS for 3 days, LGG, HS-2 and NG-4 strains were treated orally for 14 days to verify the attenuation effects of intestinal inflammation. The groups of NG-4 treatment showed increased average feed intake, better survival, less DAI scores, shortening of the colon length, modulating gut microbiota positively and upregulating the expression of TJ proteins compared to LGG group. In conclusion, Pediococcus acidilactici NG-4 is anticipated to have possibilities and apply as probiotics for IBD patients to alleviate the symptoms of intestinal inflammation followed by clinical tests.