Diosgenin, a Steroidal Sapogenin, Enhances Antigen-Specific IgG_2a and Interferon-γ Expression in Ovalbumin-Sensitized BALB/c Mice

Abstract

The effect of diosgenin, the most abundant sapogenin in Chinese yam, on humoral immunity was investigated. Ovalbumin (OVA)-sensitized and challenged BALB/c mice were administered daily with diosgenin for 34 days. The production of OVA-specific serum IgG_2a was significantly enhanced by diosgenin treatment, whereas total IgE and OVA-specific IgG₁, IgG_2a and IgM were unaffected. In parallel with the enhancement of IgG_2a, OVA-induced IFN-γ secretion and mRNA expression were markedly elevated in splenocytes of diosgenin-treated mice, whereas IL-4 expression was unaltered. Furthermore, the expression of T-bet, but not of GATA-3, in splenocytes was up-regulated by diosgenin administration. However, diosgenin treatment did not modulate IL-4 mRNA expression and inflammatory cell infiltration in the lung of OVA-sensitized and challenged mice. Collectively, these data suggest that diosgenin regulates the systemic immune response towards the Th1 direction in response to OVA sensitization. The present study provides evidence to show that intake of diosgenin modulates certain aspects of acquired immunity, including the enhancement of antigen-specific IgG_2a and IFN-γ expression, which may be mediated through the up-regulation of Th1 differentiation.

Abbreviations

BW:body weight

DIO:diosgenin

ELISA:Enzyme-linked immunosorbent assay

GAPDH:glyceraldehyde-3-phosphate dehydrogenase

Ig:immunoglobulin

IL:interleukin

NA:naïve

O.D.:optical density

OVA:ovalbumin

RT-PCR:Reverse transcription-polymerase chain reaction

S.E.M.:standard error of mean

Th:T helper

TNF:tumor necrosis factor

VH:vehicle

YMP:yam mucopolysaccharide

Diosgenin - antibody - ovalbumin - interferon-γ - T-bet

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