Abstract

Recently, dead cell has also been regarded as probiotics since they exhibited the beneficial effects to health. This study investigated the adhesion to Caco-2 cell and cytokine response of various heat-killed bacteria such as heat-killed Lactobacillus acidophilus TISTR 450 (HK-LA450), heat-killed Lactobacillus casei  subsp. rhamnosusTISTR 047 (HK-LC047), heat-killed Lactobacillus sp., LCC1 (HK-LCC1) heat-killedLactobacillus sp., LCC2 (HK-LCC2) and heat-killed Escherichia coli ATCC 25922 (HK-EC). The growth profiles, which was expressed as number of cells and specific growth rate, were examined to prepare dead cell from 10⁸ log cfu of living cell. Percent adhesion of all heat-killed bacteria ranged between 5.68 ± 0.05 and 7.95 ± 0.60%. HK-LCC1 had the highest adhesive activity. HK-EC had the lowest adhesive activity. The ability of the immune cell associated with Caco-2 to respond to heat-killed bacterial was tested by the cytokine release. Heat-killed lactobacilli and HK-EC could induce cytokines including interleukine-6 (IL-6), IL-12 (proinflammatory cytokine) and IL-10 (anti-inflammatory cytokine). HK-LCC1 had the highest activity to induce IL-6 (4.63 ± 0.70 pg/ml) and IL-10 (255.59 ± 1.22 pg/ml). HK-EC could induce only IL-12 (2.45 ± 0.11 pg/ml). The percent adhesion did not relate to cytokine production of heat-killed lactobacilli (pearson‘s correlation level r = 0.39, p = 0.01). The HK-LCC1 showed a great activity to induce the immune cell response (IL-6 and IL-10). Thus, HK-LCC1 may effectively ameliorate symtoms or diseases caused by IL-10 deficiency.

Key words: Heat-killed lactobacilli, adhesion, Caco-2, cytokine, interleukin-6, interleukin-10, interleukin-12.