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Nicotine activates and up-regulates nicotinic acetylcholine receptors in bronchial epithelial cells.

ABSTRACT: Prenatal nicotine exposure impairs normal lung development and leads to diminished pulmonary function after birth. Previous work from our laboratory has demonstrated that nicotine alters lung development by affecting a nonneuronal cholinergic autocrine loop that is expressed in lung. Bronchial epithelial cells (BECs) express choline acetyltransferase, the choline high-affinity transporter and nicotinic acetylcholine (ACh) receptor (nAChR) subunits. We now demonstrate through a combination of morphological and electrophysiological techniques that nicotine affects this autocrine loop by up-regulating and activating cholinergic signaling. RT-PCR showed the expression of alpha 3, alpha 4, alpha 7, alpha 9, alpha 10, beta2, and beta 4 nAChR mRNAs in rhesus monkey lung and cultured BECs. The expression of alpha 7, alpha 4, and beta2 nAChR was confirmed by immunofluorescence in the cultured BECs and lung. The electrophysiological characteristics of nAChR in BECs were determined using whole-cell patch-clamp on cultured BECs. Both ACh and nicotine evoked an inward current, with a rapid desensitizing current. Nicotine induced inward currents in a concentration-dependent manner, with an EC(50) of 26.7 microM. Nicotine-induced currents were reversibly blocked by the nicotinic antagonists, mecamylamine, dihydro-beta-erythroidine, and methyllcaconitine. Incubation of BECs with 1 microM nicotine for 48 hours enhanced nicotine-induced currents by roughly 26%. The protein tyrosine phosphorylation inhibitor, genistein, increased nicotine-induced currents by 58% and enhanced methyllcaconitine-sensitive currents (alpha 7 nAChR activities) 2.3-fold, whereas the protein tyrosine phosphatase inhibitor, pervanadate, decreased the effects of nicotine. These results demonstrate that chronic nicotine exposure up-regulates nAChR activity in developing lung, and that nAChR activity can be further modified by tyrosine phosphorylation.

SUBMITTER: Fu XW

PROVIDER: S-EPMC2701964 | biostudies-literature | 2009 Jul

REPOSITORIES: biostudies-literature

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Nicotine activates and up-regulates nicotinic acetylcholine receptors in bronchial epithelial cells.

Fu Xiao Wen XW Lindstrom Jon J Spindel Eliot R ER

American journal of respiratory cell and molecular biology 20081218 1

Prenatal nicotine exposure impairs normal lung development and leads to diminished pulmonary function after birth. Previous work from our laboratory has demonstrated that nicotine alters lung development by affecting a nonneuronal cholinergic autocrine loop that is expressed in lung. Bronchial epithelial cells (BECs) express choline acetyltransferase, the choline high-affinity transporter and nicotinic acetylcholine (ACh) receptor (nAChR) subunits. We now demonstrate through a combination of mor ...[more]

PMID: 19097990

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Project description:Allelic variation in CHRNA3, the gene encoding the α3 nicotinic acetylcholine receptor (nAChR) subunit, increases vulnerability to tobacco dependence and smoking-related diseases, but little is known about the role for α3-containing (α3*) nAChRs in regulating the addiction-related behavioral or physiological actions of nicotine. α3* nAChRs are densely expressed by medial habenula (mHb) neurons, which project almost exclusively to the interpeduncular nucleus (IPn) and are known to regulate nicotine avoidance behaviors. We found that Chrna3tm1.1Hwrt hypomorphic mice, which express constitutively low levels of α3* nAChRs, self-administer greater quantities of nicotine (0.4 mg kg-1 per infusion) than their wild-type littermates. Microinfusion of a lentivirus vector to express a short-hairpin RNA into the mHb or IPn to knock-down Chrna3 transcripts markedly increased nicotine self-administration behavior in rats (0.01-0.18 mg kg-1 per infusion). Using whole-cell recordings, we found that the α3β4* nAChR-selective antagonist α-conotoxin AuIB almost completely abolished nicotine-evoked currents in mHb neurons. By contrast, the α3β2* nAChR-selective antagonist α-conotoxin MII only partially attenuated these currents. Finally, micro-infusion of α-conotoxin AuIB (10 μm) but not α-conotoxin MII (10 μm) into the IPn in rats increased nicotine self-administration behavior. Together, these data suggest that α3β4* nAChRs regulate the stimulatory effects of nicotine on the mHb-IPn circuit and thereby regulate nicotine avoidance behaviors. These findings provide mechanistic insights into how CHRNA3 risk alleles can increase the risk of tobacco dependence and smoking-related diseases in human smokers.SIGNIFICANCE STATEMENT Allelic variation in CHRNA3, which encodes the α3 nicotinic acetylcholine receptor (nAChR) subunit gene, increases risk of tobacco dependence but underlying mechanisms are unclear. We report that Chrna3 hypomorphic mice consume greater quantities of nicotine than wild-type mice and that knock-down of Chrna3 gene transcripts in the habenula or interpeduncular nucleus (IPn) increases nicotine intake in rats. α-Conotoxin AuIB, a potent antagonist of the α3β4 nAChR subtype, reduced the stimulatory effects of nicotine on habenular neurons, and its infusion into the IPn increased nicotine intake in rats. These data suggest that α3β4 nAChRs in the habenula-IPn circuit regulate the motivational properties of nicotine.

Dataset Information

Nicotine activates and up-regulates nicotinic acetylcholine receptors in bronchial epithelial cells.

Publications

Nicotine activates and up-regulates nicotinic acetylcholine receptors in bronchial epithelial cells.

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