Ko Suzuki

Protective effect of N-acetyl chitohexaose on Listeria monocytogenes infection in mice

A water‐soluble oligosaccharide, N‐acetyl chitohexaose (NACOS‐6) was able to enhance the protecting effect of BALB/c male mice against Listeria monocytogenes infection, when administered intraperitoneally 24 hr before the challenge with this microbe. Significant decrease in number of microbes within the peritoneal cavity, spleen, and liver from the mice of NACOS‐6‐administered group was not observed 1 day after the infection but 4 days after the infection. Administration of NACOS‐6 enhanced the delayed‐type hypersensitivity response against sheep red blood cells (SRBC) or heat‐killed L. monocytogenes. Splenic T lymphocytes from mice administered NACOS‐6 released macrophage activating factor (MAF). These results suggested that NACOS‐6 was also able to elevate the function of cellular immunity. Macrophages treated with a combination of NACOS‐6 and the culture supernatant of splenic T lymphocytes from mice administered NACOS‐6, “NACOS‐6 sup,” were found to exert a fairly strong growth‐inhibitory effect on L. monocytogenes. Interferon‐γ (IFN‐γ) and interleukin 2 (IL‐2) were able to enhance the growth‐inhibitory effect on L. monocytogenes by the NACOS‐6‐treated macrophages.

Protecting Effect of Chitin and Chitosan on Experimentally Induced Murine Candidiasis

Chitin and chitosan were found to exhibit a protective effect on mice administered these polysaccharides intraperitoneally against infection of the viable cells of Candida albicans NIH A‐207 strain. A significant difference was observed between the protective effects of chitin and chitosan, i.e., chitin was much more effective than chitosan when the C. albicans cells were challenged via the intravenous route. In intraperitoneal inoculations of C. albicans cells, however, chitosan provided stronger resistance for mice than chitin.

Effect of N-Acetylchito-Oligosaccharides on Activation of Phagocytes

Four N‐acetylchito‐oligosaccharides, from tetra‐N‐acetylchitotetraose (NACOS‐4) to hepta‐N‐acetylchitoheptaose (NACOS‐7), were found to increase the number of peritoneal exudate cells (PEC) in male BALB/c mice after 3 hr intraperitoneal administration of 50 mg/kg of each oligosaccharide. The number of attracted cells, consisting largely of polymorphonuclear leukocytes (PMN), was proportional to the molecular weights of the administered oligosaccharides, except for NACOS‐7 which displayed the same activity as NACOS‐6. In an in vitro chemotaxis assay using normal mouse leukocytes, it was found that NACOS‐6 displayed stronger effects than muramyl dipeptide. The PEC from NACOS‐6 treated mice showed a higher active oxygen‐generating activity. PMN from normal mouse peripheral blood were also shown to have enhanced active oxygen‐generating activity in vitro. PEC from NACOS‐6 treated mice were shown to possess strong candidacidal activity in vitro.

Chemotactic Response of Human Neutrophils to N -Acetyl Chitohexaose in vitro

N‐Acetyl chitohexaose (NACOS‐6) was able to display chemotactic response of human neutrophils in vitro. In order to analyze the mechanism, a series of chemotaxis studies by means of neutrophils treated with inhibitors of phospholipase A2, cyclooxygenase, or lipoxygenase to NACOS‐6 was conducted. The treatment of neutrophils with inhibitors of phospholipase A2 or cyclooxygenase resulted in decrease of number of migrated cells. However, the lipoxygenase inhibitors did not exhibit the same effect. On the other hand, the treatment of neutrophils with inhibitors of phospholipase A2 or lipoxygenase resulted in decrease of chemotactic response to Formyl‐Met‐Leu‐Phe (FMLP), although the cyclooxygenase inhibitors did not inhibit chemotaxis of neutrophils. Neutrophils added to exogenous prostaglandin E2 (PGE2) caused an enhanced chemotactic response to NACOS‐6. These results indicate that the mechanism of chemotactic response to NACOS‐6 was different from that of FMLP, and that the response was enhanced by PGE2 released from the neutrophils with stimulation of NACOS‐6.

Candidacidal Effect of Peritoneal Exudate Cells in Mice Administered with Chitin or Chitosan

Recently, several papers have been published on the mechanism of the protective effect of microbial infection and on the role of reactive oxygen intermediates (ROI) and myeloperoxidase (MPO) (2-4, 6-8), demonstrating that polymorphonuclear leukocytes (PMN) play an important role in the killing of Candida albicans by generating large amounts of ROI (2), while macrophages (MO) were able to kill the yeast form cells of C. albicans by releasing a cationic protein (4). However, the role of these phagocytes in the killing process of C. albicans cells has not been fully elucidated . In the preceding paper of this series, we reported that both chitin (poly-Nacetyl-D-glucosamine) and chitosan (de-N-acetylated product of chitin) showed

Protective effect of acidic mannan fraction of bakers' yeast on experimental candidiasis in mice.

An acidic fraction of Bakers yeast mannan, WAM025, showed a significant protective effect against Candida albicans infection in mice, but a neutral fraction of the same Bakers yeast mannan, WNM, did not exhibit this effect. Moreover, pretreatment with WAM025 resulted in a marked reduction of proliferation of C. albicans cells in the organs of the infected mice. We investigated the stimulative effect of these mannan fractions on the function of mouse peritoneal phagocytes, and found that mice administered WAM025 showed a greater increase in the number of peritoneal exudate cells, macrophages and polymorphonuclear leucocytes (PMN), than the mice treated with WNM, especially in the proportion of PMN. Peritoneal phagocytes, PMN and macrophages obtained from WAM025‐treated mice showed marked candidacidal activity. Of the phagocytes, PMN were responsible for the larger part of the candidacidal activity. The myeloperoxidase activities of PMN and macrophages in WAM025‐treated PEC were greater than in untreated macrophages. The myeloperoxidase activity of WAM025‐treated PMN was significantly greater than that of WAM025‐treated macrophages. This activity paralleled the active oxygen‐releasing activity of the phagocytes. On the other hand, the phagocytic activity of phagocytes from mice administered WNM or WAM025 for C. albicans cells was identical to that of untreated phagocytes. WAM025 seems to cause enhance elimination of the pathogen from mice, by increasing the number and candidacidal activity of phagocytic cells.