Activation of cultured astrocytes by amphotericin B: stimulation of NO and cytokines production and changes in neurotrophic factors production.

Amphotericin B (AmB) is a polyene antibiotic and reported to be one of a few reagents having therapeutic effects on prion diseases, such as the delay in the appearing of the clinical signs and the prolongation of the survival time. In prion diseases, glial cells have been suggested to play important roles by proliferating and producing various factors such as nitric oxide, proinflammatory cytokines, and neurotrophic factors. However, the therapeutic mechanism of AmB on prion diseases remains elusive. We have previously reported that AmB changed the expression of neurotoxic and neurotrophic factors in microglia (Motoyoshi et al., 2008, Neurochem. Int. 52, 1290-1296). In the present study, we examined the effects of AmB on cellular functions of rat cultured astrocytes. We found that AmB could activate astrocytes to produce nitric oxide via inducible nitric oxide synthase induction. AmB also induced mRNA expression of interleukin-1β and tumor necrosis factor-α, and productions of their proteins in astrocytes. Moreover, AmB changed levels of neurotrophic factor mRNAs and proteins. Among three neurotrophic factors examined here, neurotrophin-3 mRNA expression and its protein production in the cells were down-regulated by AmB stimulation. On the other hand, AmB significantly enhanced the amounts of glial cell line-derived neurotrophic factor and brain-derived neurotrophic factor proteins in the cells and the medium. These results suggest that AmB might show therapeutic effects on prion diseases by controlling the expression and production of such mediators in astrocytes.