RESUMO
The effects of a dry extract of the roots of Angelica sinensis (Oliv.) Diels (ASE) on the growth and differentiation of granulocyte-macrophage progenitor cells (CFU-GM) in normal and Listeria monocytogenes-infected mice were studied. Myelosuppression concomitant with increased numbers of spleen CFU-GM was observed in infected mice. Prophylactic administration of ASE (10, 25, and 50 mg/kg) stimulated marrow myelopoiesis in a dose-dependent manner and reduced spleen colony formation to control values. The dose of 50 mg/kg ASE was the optimal biologically active dose in infected mice, and this dose schedule significantly increased survival of mice infected with a lethal dose of L. monocytogenes, with survival rate up to 30%. Investigation of the production of colony-stimulating factors revealed a dose-dependent increased colony-stimulating activity in the serum of infected mice, with higher response produced by the 50 mg/kg dose. Notably, no effects were observed with the 100 mg/kg dose, compared with infected nontreated controls. Further studies to investigate the production of factors such as inteferon-γ and tumor necrosis factor-α demonstrated increased levels of both cytokines in mice infected with L. monocytogenes and treated with 50 mg/kg ASE. We propose that ASE indirectly modulates immune activity and probably disengages Listeria-induced suppression of these responses by inducing a higher reserve of myeloid progenitors in the bone marrow in consequence of biologically active cytokine release (colony-stimulating factors, interferon-γ, and tumor necrosis factor-α).