Nicotinic Acetylcholine Receptors are Sensors for Ethanol in Lung Fibroblasts
Article first published online: 19 FEB 2013
Copyright © 2013 by the Research Society on Alcoholism
Alcoholism: Clinical and Experimental Research
Volume 37, Issue 6, pages 914–923, June 2013
How to Cite
Ritzenthaler, J. D., Roser-Page, S., Guidot, D. M. and Roman, J. (2013), Nicotinic Acetylcholine Receptors are Sensors for Ethanol in Lung Fibroblasts. Alcoholism: Clinical and Experimental Research, 37: 914–923. doi: 10.1111/acer.12044
- Issue published online: 28 MAY 2013
- Article first published online: 19 FEB 2013
- Manuscript Accepted: 9 OCT 2012
- Manuscript Received: 27 AUG 2012
- National Institutes of Health. Grant Number: AA013757
- Veterans Affairs Grant
- Nicotinic Acetylcholine Receptor;
Chronic ethanol (EtOH) abuse in humans is known to independently increase the incidence of and mortality due to acute lung injury in at-risk individuals. However, the mechanisms by which EtOH affects lung cells remain incompletely elucidated. In earlier work, we reported that EtOH increased the expression in lung fibroblasts of fibronectin, a matrix glycoprotein implicated in lung injury and repair. This effect was blocked by α-bungarotoxin, a neurotoxin that binds certain nicotinic acetylcholine receptors (nAChRs) thereby implicating nAChRs in this process. Here, we examine the identity of these receptors.
Mouse lung fibroblasts were stimulated with EtOH (60 mM) or acetylcholine (100 to 500 μM) and evaluated for the expression of fibronectin and nAChRs. Inhibitors to nAChRs or the antioxidant N-acetyl cysteine (NAC) were used to assess changes in fibronectin expression. Animals exposed to EtOH for up to 6 weeks were used to evaluate the expression of nAChRs in vivo.
First, in EtOH-treated fibroblasts, we observed increased expression of α4 and α9 nAChR subunits. Second, we found that acetylcholine, a natural ligand for nAChRs, mimicked the effects of EtOH. Dihydro-β-erythroidin hydrobromide, a competitive inhibitor of α4 nAChR, blocked the increase in fibronectin expression and cell proliferation. Furthermore, EtOH-induced fibronectin expression was inhibited in cells silenced for α4 nAChR. However, EtOH-treated cells showed increased α-bungarotoxin binding suggesting that α4 nAChR mediates the effects of EtOH via a ligand-independent pathway. Knowing there are several important cysteine residues near the ligand-binding site of α4 nAChRs, we tested the antioxidant NAC and found that it too blocked the induction of fibronectin expression by EtOH. Also, fibroblasts exposed to oxidant stress showed increased fibronectin expression that was blocked with α-bungarotoxin. Finally, we showed increased expression of α4 nAChRs in the lung tissue of mice and rats exposed to EtOH suggesting a role for these receptors in vivo.
Altogether, our observations suggest that α4 nAChRs serve as sensors for EtOH-induced oxidant stress in lung fibroblasts, thereby revealing a new mechanism by which EtOH may affect lung cells and tissue remodeling and pointing to nAChRs as potential targets for intervention.