Inducers of oxidative stress block ciliary neurotrophic factor activation of Jak/STAT signaling in neurons

Generation of reactive oxygen species (ROS) with the accumulation of oxidative damage has been implicated in neurodegenerative disease and in the degradation of nervous system function with age. Here we report that ROS inhibit the activity of ciliary neurotrophic factor (CNTF) in nerve cells. Treatment with hydrogen peroxide (H₂O₂) as a generator of ROS inhibited CNTF-mediated Jak/STAT signaling in all cultured nerve cells tested, including chick ciliary ganglion neurons, chick neural retina, HMN-1 motor neuron hybrid cells, and SH-SY5Y and BE(2)-C human neuroblastoma cells. H ₂O₂ treatment of non-neuronal cells, chick skeletal muscle and HepG2 hepatoma cells, did not inhibit Jak/STAT signaling. The H ₂O₂ block of CNTF activity was seen at concentrations as low as 0.1 mM and within 15 min, and was reversible upon removal of H ₂O₂ from the medium. Also, two other mediators of oxidative stress, nitric oxide and rotenone, inhibited CNTF signaling. Treatment of neurons with H₂O₂ and rotenone also inhibited interferon-γ-mediated activation of Jak/STAT1. Depleting the intracellular stores of reduced glutathione by treatment of BE(2)-C cells with nitrofurantoin inhibited CNTF activity, whereas addition of reduced glutathione protected cells from the effects of H₂O₂. These results suggest that disruption of neurotrophic factor signaling by mediators of oxidative stress may contribute to the neuronal damage observed in neurodegenerative diseases and significantly affect the utility of CNTF-like factors as therapeutic agents in preventing nerve cell death.