Ciliary neurotrophic factor enhances the expression of NGF and p75 low-affinity NGF receptor in astrocytes

A functional interactions between ciliary neurotrophic factor (CNTF) and NGF has recently been demonstrated. We found that the exposure of rat cortical astrocytes to human recombinant CNTF for 3 h increased the level of mRNA for NGF as determined by reverse transcription-polymerase chain reaction (RT-PCR). The increase in NGF message was followed by corresponding increase in NGF protein secreted from the astrocytes into the culture medium as determined 6 h later. C-fos seemed to be involved in the mechanism of NGF induction since the expression of c-fos gene preceded NGF mRNA elevation. Furthermore, we found that in cultured astrocytes exogenous CNTF increased the level of mRNA coding for p75(NTR), the low affinity receptor for NGF and other neurotrophins. CNTF is highly expressed in the lesioned brain and CNTF-induced upregulation of NGF synthesis could be involved in the endogenous repair mechanisms.