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Ethanol exposure reduces the density of the low-affinity nerve growth factor receptor (p75) on pheochromocytoma
J Luo1, J R West, N J Pantazis
1Department of Anatomy, Bowen Science Building, University of Iowa College of Medicine, University of Iowa 52242, USA.
Abstract:
Although ethanol is detrimental to the developing nervous system, the mechanism(s) by which ethanol produces neuronal damage is (are) not clear. One potential mechanism is ethanol-induced inhibition of neurotrophic support. This study utilized an in vitro model, pheochromocytoma PC12 cells, to examine the effect of ethanol on the nerve growth factor (NGF) receptor. NGF binding studies indicated that ethanol exposure (400 mg/dl for 4 days) reduced the density of the low-affinity (p75) NGF receptor on PC12 cells, but had no effect on the density of the high-affinity NGF receptor. The equilibrium dissociation constants (Kd) for both the low-affinity and high-affinity NGF receptors were unaffected by ethanol. Low-affinity NGF binding is mediated by the p75 component of the NGF receptor. Quantification of p75 by immunoprecipitation revealed that ethanol reduced the level of p75 in PC12 cells. However, Northern analysis indicated that the p75 mRNA was not reduced by ethanol exposure, raising the possibilities that ethanol inhibited translation of p75 or incorporation of the p75 protein into the plasma membrane. This work is consistent with the hypothesis that ethanol's detrimental effects may be produced in part by inhibition of neurotrophic support at the receptor level.
Insights
Ethanol exposure reduces the low-affinity nerve growth factor (NGF) receptor (p75) in developing neurons. This suggests ethanol may harm the nervous system by disrupting neurotrophic support at the receptor level.
Area of Science:
- Neuroscience
- Toxicology
- Cell Biology
Background:
- Ethanol is known to be detrimental to the developing nervous system.
- The precise mechanisms underlying ethanol-induced neurotoxicity remain unclear.
- Neurotrophic support is crucial for neuronal development and survival.
Purpose of the Study:
- To investigate the effect of ethanol on nerve growth factor (NGF) receptors in an in vitro model.
- To explore the potential role of ethanol-induced inhibition of neurotrophic support in neurotoxicity.
Main Methods:
- Utilized pheochromocytoma PC12 cells as an in vitro model.
- Performed NGF binding studies to assess receptor density and affinity.
- Quantified p75 receptor levels using immunoprecipitation.
- Analyzed p75 mRNA levels via Northern blot.
Main Results:
- Ethanol exposure (400 mg/dl for 4 days) significantly reduced the density of the low-affinity (p75) NGF receptor.
- Ethanol did not affect the density or binding affinity (Kd) of the high-affinity NGF receptor.
- Ethanol decreased p75 protein levels but not p75 mRNA levels, suggesting post-transcriptional regulation.
Conclusions:
- Ethanol's detrimental effects on the developing nervous system may be partly mediated by inhibiting neurotrophic support.
- Ethanol appears to reduce neurotrophic support by decreasing the expression or cell surface availability of the p75 NGF receptor.
- Further research is needed to elucidate the specific mechanisms of p75 regulation by ethanol.