Abstract:

The effect of natto lyophilized powder (NLP) on antibiotics-mediated immunomodulation and cytokine secretion
in SPF mice was explored in the present study. Totally 128 healthy mice were selected and divided randomly into 8 groups:
control group (C), four regulation groups (RN0, 1, 2 and 3), two prevention groups (P0 and PN), and model group (M).
The mice in all groups except C were administered with antibiotic solution for 3 days. Thereafter, the mice from group R0
were gavaged with normal saline, while those from group RN1, 2 and 3 were given NLP solution at three different dosages,
respectively. The mice from the two prevention groups were continuously daily administered with antibiotic solution; 8 hour
later, groups P0 and PN were respectively lavaged with normal saline and NLP solution. The mice in group M were simply
given antibiotic solution during the entire administration period of 30 days. Immunomodulatory effects of NLP in mice and its
effect on cytokine secretion were determined. Results showed that low-dose NLP resulted in a significant elevation in spleen
and thymus indices in mice compared with the model group (P < 0.01). The production of serum IL-2, IL-10, TNF-alpha,
and IFN-gamma extremely significantly increased in groups RN1, RN2 and RN3 compared with the model group
(P < 0.01). In addition, the mice from the three prevention groups showed an extremely significant increase in inducible
nitric oxide synthase (iNOS) activity in serum (P < 0.01), and serum albumin and globulin concentrations and their ratio
as well as serum NO level were significantly or extremely significantly higher in the mice from groups RN1 and RN3
(P < 0.05 or P < 0.01). The serum hemolysin levels in mice from the control, regulation and prevention groups were
significantly higher than those in the group N (P < 0.01). The phagocytic capacity of peritoneal macrophages from mice in
groups RN1, RN2, RN3 and PN was significantly higher than that of group M. Compared with the control group, the half
value of hemolysis (HC50) in groups RN1, RN2 and RN3 was significantly or extremely significantly increased (P < 0.05
or P < 0.01). Groups RN3 and PN exhibited an extremely significant increase in the percentage of macrophages engaged
in phagocytosis and the percent phagocytosis of chicken red blood cells (P < 0.01). Therefore, NLP can enhance immune
function and increase the secretion of cytokines.

Key words: natto lyophilized powder (NLP), antibiotics, immunomodulatory effect