Reduced expression of neuronal nicotinic acetylcholine receptors during the early stages of damage by oxidative stress in PC12 cells

Abstract

The mechanism for a large loss of neuronal nicotinic acetylcholine receptors (nAChRs) in brains with neurodegenerative diseases remains unclear. Based on our previous results of [(3)H]epibatidine binding influenced by lipid peroxidation, we suggest that nAChR deficit in neurodegenerative diseases might be related to the neurons attacked by free radicals. To further understand how free radicals influence the expression of nAChRs, we detected [(125)I]alpha-bungarotoxin binding, nAChR subunit protein and mRNA during the early stage of damage by oxidative stress in PC12 cells in the present study. The results showed that free radical insult (FeSO(4)) within the concentration range (1 -100 microM) used in the study induced dose-dependent increases in lipid peroxidation and toxicity to PC12 cells, but did not result in apoptosis or necrosis. Significant reductions in [(125)I]alpha-bungarotoxin binding site, protein level for the alpha3 and alpha7 subunits, and mRNA level for the alpha7 subunit were observed in PC12 cells treated by FeSO(4) at the concentrations without inducing cell death compared to control. Pretreatment of cultural cells with antioxidant such as Vitamin E and reduced glutathione prevented the inhibiting effect of free radicals on [(125)I]alpha-bungarotoxin and [(3)H]epibatidine bindings. The present results further demonstrate that oxidative stress might reduce the number of [(125)I]alpha-bungarotoxin binding site and selectively suppress the expression of the nAChR subunits at protein and mRNA levels during the early stages of damage in PC12 cells.

Comparative developmental neurotoxicity of organophosphates in vivo: Transcriptional responses of pathways for brain cell development, cell signaling, cytotoxicity and neurotransmitter systems

“…As just one example, the significant reductions in chrna7, which encodes the α7 nAChR, is consistent with the targeting of this receptor subtype by developmental CPF exposure [95]. Although α7 nAChRs are sparse when compared to the more abundant α4β2 subtype, it is the α7 unit that is overexpressed during brain development [2,15,35,84,115] and is most clearly involved in neuritic outgrowth [19,78], neurotoxicity and neuroprotection [24,40,45,58,103,104]. In addition to the common effect on chrna7, CPF and DZN had substantially disparate actions on a large number of other nAChR genes, with much more widespread consequences for DZN.…”

Cross-talk between oxidative stress and modifications of cholinergic and glutaminergic receptors in the pathogenesis of Alzheimer's disease1

“…The pretreatment of cultural cells with antioxidants, such as vitamin E and reduced glutathione, can prevent the inhibitory effect of free radicals on The correlation between oxidative stress and the loss of the α4 nAChR subunit has been investigated in the temporal cortex from patients with AD, and the results showed a significant correlation between increased levels of lipid peroxidation and decreased numbers of the α4 nAChR subunit protein in AD brains [17] . In a recent study, we also found that lipid peroxidation induced directly by Aβ might be involved in the deficits of nAChR [48] . In this study, PC12 cells were treated by the addition of 5 mmol/L Aβ [25][26][27][28][29][30][31][32][33][34][35] and Aβ 1-40 , respectively, with or without an antioxidant, vitamin E. An increased lipid peroxidation and significant reductions in [ ]α-BTX binding sites and in the protein levels of the α3 and α7 nAChR subunits were observed in the cells treated with Aβ.…”

“…Aβs damage and kill neurons possibly through an effect on membrane lipid peroxidation, impaired ion-motive ATPases, glucose, and glutamate transporters making nerve cells vulnerable to the excitotoxic effects of glutamate [49] . These findings suggest that lipid peroxidation induced by Aβ might trigger the loss of nAChR in AD [48] . Interestingly, the α7 nAChR subtype may have an antioxidative function.…”

Evidence of alpha 7 nicotinic acetylcholine receptor expression in retinal pigment epithelial cells

“…AMD is one of the leading causes of irreversible vision loss and blindness in industrialized countries, occurring in about 10-25% of people over 65 years of age (Klein et al, 1992;Zarbin, 1998;Klaver et al, 2001;Chakravarthy et al, 2010). On the other hand, in PC12 cells, it has been demonstrated that during early stages of damage by oxidative stress, there is a reduction in a-bungarotoxin binding sites and expression of nAChRs selectively decreases (Guan et al, 2001).…”