Mechanism of enhanced hematopoietic response by soluble β-glucan SCG in cyclophosphamide-treated mice

Abstract

SCG is a major 6-branched 1,3-β-D-glucan in Sparassis crispa Fr. SCG shows antitumor activity and also enhances the hematopoietic response in cyclophosphamide (CY)-treated mice. In the present study, the molecular mechanism of the enhancement of the hematopoietic response was investigated. The levels of interferon- (IFN-) γ, tumor necrosis factor- (TNF-) α, granulocyte-macrophage-colony stimulating factor (GM-CSF), interleukin- (IL-) 6 and IL-12p70 were significantly increased by SCG in CY-treated mice. GM-CSF production in the splenocytes from the CY-treated mice was higher than that in normal mice regardless of SCG stimulation. Neutralizing GM-CSF significantly inhibited the induction of IFN-γ, TNF-α and IL-12p70 by SCG. The level of cytokine induction by SCG was regulated by the amount of endogenous GM-CSF produced in response to CY treatment in a dose-dependent manner. The expression of β-glucan receptors, such as CR3 and dectin-1, was up-regulated by CY treatment. Blocking dectin-1 significantly inhibited the induction of TNF-α and IL-12p70 production by SCG. Taken together, these results suggest that the key factors in the cytokine induction in CY-treated mice were the enhanced levels of both endogenous GM-CSF production and dectin-1 expression.