FGF‐2‐mediated protection of cultured mesencephalic dopaminergic neurons against MPTP and MPP+: Specificity and impact of culture conditions, non‐dopaminergic neurons, and astroglial cells

Abstract

The protective role of basic fibroblast growth factor (FGF‐2) for 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP)‐ and methylpyridiniumion (MPP⁺)‐lesioned dopaminergic (DAergic) nigrostriatal neurons was studied, using dissociated cell cultures of embryonic day (E) 14 rat mesencephalon. Cells were grown in different culture media and received FGF‐2 (5 ng/ml) and/or the toxins (5 μM) at various schedules, but were consistently allowed to differentiate for 3 days prior to becoming exposed to the toxin. Survival of tyrosine hydroxylase (TH)‐immunoreactive cells at 7 days was only markedly impaired by MPTP, if horse serum (HS) or bovine serum albumine (BSA) were omitted from the culture medium. FGF‐2 increased the number of TH‐immunoreactive cells, and this increase not diminished by MPTP under any culture condition. Uptake of ³H‐DA was significantly reduced by MPTP in HS‐ and BSA‐containing, but not in protein‐less cultures. A protective effect by FGF‐2 was only seen in the presence of BSA. MPP⁺ caused a more pronounced reduction in ³H‐DA uptake than MPTP, and this effect was partially reversed by the addition of FGF‐2, unless cultures contained HS. Neurofilament protein (NF), an indirect measure for the total number of neurons present in the cultures, was not significantly reduced by MPTP or MPP⁺ corroborating the specificity of the toxin for DAergic neurons, which constitute only a minor fraction in these cultures. In line with the wide spectrum of target neurons of FGF‐2, this factor significantly increased NF contents under any culture condition. Quantification of the amounts of glial fibrillary acidic protein (GFAP) revealed stimulatory effects of FGF‐2 (2.5‐ to 4‐fold) and at least 10‐fold higher levels in the presence as compared to the absence of HS. These data show that FGF‐2 can protect DAergic neurons against MPTP‐ and MPP⁺‐mediated damage. However, the effects of the toxins as well as of FGF‐2 are partially dependent on culture conditions. Variations in the effectiveness of toxins and FGF‐2 are not overtly related to the total numbers of neurons or astroglial cells, but may reflect culture type‐dependent alterations of neuronal and glial metabolism.