Human intestinal mucosa-associated Lactobacillus and Bifidobacterium strains with probiotic properties modulate IL-10, IL-6 and IL-12 gene expression in THP-1 cells.

Lactobacilli and bifidobacteria are considered one of the permanent genera of the physiological human intestinal microbiota and represent an enormous pool of potential probiotic candidates. Approximately 450 isolates of presumptive Lactobacillus or Bifidobacterium strains were obtained from bioptic samples of colonic and ileal mucosa from 15 adolescents aged 12 to 18 years. On the basis of randomly amplified polymorphic DNA (RAPD)-PCR analysis, 20 strains were selected for further taxonomic classification and characterisation, as well as assessment of probiotic properties and safety. Importantly, selected strains showed the capability of colonising different parts of the intestine. The most frequently isolated species was Lactobacillus paracasei followed by Lactobacillus fermentum. The majority of isolates were susceptible to antimicrobials of human and veterinary importance, however, tetracycline and/or erythromycin resistance was observed in Lactobacillus plantarum and L. fermentum strains. Thirteen strains were able to ferment more than 19 different carbon sources and three out of five tested strains exerted antagonistic activity against several different indicator strains. Two Lactobacillus isolates (L. paracasei L350 and L. fermentum L930 bb) and one Bifidobacterium isolate (Bifidobacterium animalis subsp. animalis IM386) fulfilled in vitro selection criteria for probiotic strains and exhibited strong downregulation of pro-inflammatory cytokines IL-6 and IL-12 and upregulation of anti-inflammatory IL-10. The selected strains represent suitable candidates for further studies regarding their positive influence on host health and could play an important role in ameliorating the symptoms of inflammatory bowel diseases.

Acid resistance and response to pH-induced stress in two Lactobacillus plantarum strains with probiotic potential.

Two new Lactobacillus plantarum strains, KR6-DSM 28780 and M5 isolated from sour turnip and traditional dried fresh cheese, respectively, were evaluated for species identity, antibiotic susceptibility, resistance to gastrointestinal conditions and adaptive response to low pH. Resistance mechanisms involved in the adaptation to acid-induced stress in these two strains were investigated by quantitative PCR of the atpA, cfa1, mleS and hisD genes. In addition to absence of antibiotic resistance, the two L. plantarum strains showed excellent survival rates at pH values as low as 2.4. Adaptive response to low pH was clearly observed in both strains; strain KR6 was superior to M5, as demonstrated by its ability to survive during 3 h incubation at pH 2.0 upon adaptation to moderately acidic conditions. In contrast, acid adaptation did not significantly affect the survival rate during simulated passage through the gastrointestinal tract. In both strains, induction of histidine biosynthesis (hisD) was upregulated during the acid adaptation response. In addition, significant upregulation of the cfa1 gene, involved in modulation of membrane fatty acid composition, was observed during the adaptation phase in strain KR6 but not in strain M5. Cells adapted to moderately acidic conditions also showed a significantly increased viability after the lyophilisation procedure, a cross-protection phenomenon providing additional advantage in probiotic application.

Signaling pathway in nerve growth factor induced histamine release from rat mast cells.

OBJECTIVE AND DESIGN: We investigated a signal transduction pathway involved in NGF induced histamine secretion from mast cells. We compared this mechanism with the exocytosis induced by basic secretagogue compound 48/80. MATERIALS AND METHODS: Isolated rat peritoneal mast cells were obtained from male Wistar rats. Histamine release was assayed spectrofluorometrically. RESULTS: We found that tyrosine kinase inhibitor genistein, phospholipase C (PLC) inhibitor U-73122, phosphatidylinositol 3-kinase (PI-3 kinase) inhibitor wortmannin, protein kinase C (PKC) inhibitors, staurosporine and GF109203X, but not MAP kinase inhibitors, SB203580 and PD98059, reduce histamine secretion in NGF provoked mast cell degranulation. In compound 48/80 mediated degranulation, we confirmed only the involvement of tyrosine kinase and PLC, but not PI-3 kinase, PKC and MAP kinases. CONCLUSIONS: Our results indicate that release of histamine from mast cells after stimulation with NGF is regulated by tyrosine kinase, PLC, PI-3 kinase and PKC, but not by MAP kinases. This biochemical pathway differs from that provoked by compound 48/80.

Regulatory role of extracellular Na+ and Ca2+ ions in nerve growth factor induced histamine secretion from rat mast cells.

OBJECTIVE AND DESIGN: This study was aimed to investigate effects of extracellular Na+ and Ca2+ ions on nerve growth factor (NGF) induced histamine release from mast cells. MATERIAL: Isolated peritoneal mast cells were obtained from male Wistar rats. METHODS: Cells were suspended in solution with different concentration of Na+ and Ca2+ ions and stimulated with NGF. Histamine release was assayed spectrofluorometrically. RESULTS: NGF (0.001-1 microg/ml) dose-dependently releases histamine from mast cell at physiological extracellular Na+ (134 mM) and Ca2+ (1 mM) conditions. Lowering extracellular Ca2+ ions to 0.1 mM reduced histamine response to nearly basal level. However, the removal of extracellular Na+ ions significantly enhanced the secretion provoked by NGF (0.6 microg/ml) in low Ca2+ medium. Amiloride, an inhibitor of Na+/Ca2+ and Na/H+ exchangers inhibited the potentiating effect of sodium free conditions. CONCLUSIONS: Our results suggest that the activity of Na+/Ca2+ and/or Na+/H+ exchange mechanisms could be of particular importance in the secretory process of mast cells induced by NGF.