Linked Life Data

9387186

Source:http://linkedlifedata.com/resource/pubmed/id/9387186

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
3
pubmed:dateCreated
1998-1-27
pubmed:abstractText
The purpose of this study was to investigate the possibility of direct toxic effects of nicotine (Nic) on human bronchial epithelial cells (BEC) suggested by our previous findings of functional nicotinic acetylcholine receptors (nAChRs) in the epithelial cells lining mucocutaneous membranes. We now demonstrate for the first time that human and murine BEC both in vivo and in vitro express functional nAChRs, and that classic alpha 3, alpha 4, alpha 5 and alpha 7 subunits can contribute to formation of these acetylcholine-gated ion channels. In human bronchial and mouse lung tissues, and in cultures of human BEC, the nAChRs were visualized by subunit-specific antibodies on the cell membranes, particularly at the sites of cell-to-cell contacts. The epithelial cells of submucosal glands abundantly expressed alpha 7 nAChRs. Smoking significantly (p < 0.05) increased the relative numbers of nAChRs, and this effects could be reproduced in cultures of BEC exposed to 10 microM Nic. At a higher dose, Nic decreased the relative numbers of alpha 5-containing nAChRs, suggesting a role for receptor desensitization. The function of the nAChR channels expressed by BEC was demonstrated by biphasic increase in the concentrations of intracellular calcium ([Ca++]i) in response to activation of the channel by Nic and fluctuations of [Ca++]i due to channel blockade by mecamylamine (Mec). Long-term exposure to milimolar concentrations of Nic resulted in a steady increase of [Ca++]i, which may lead to cell damage. The biological roles of epithelial nAChRs apparently involve regulation of cell-to-cell communications, adhesion and motility, because Mec caused rapid and profound changes in these cell functions which were reversible by Nic. An over exposure of BEC to Nic, however, produced an antagonist-like effect, suggesting that the pathobiological effects of Nic toxicity might result from both activation of nAChR channels and nAChR desensitization. We conclude that medical consequences of smoking can be mediated by direct toxic effects of inhaled Nic on the respiratory tissues wherein Nic specifically binds to and activates the nicotinic ion channels present on the cell surfaces of BEC. We believe that outside the neural system Nic interferes with functioning of non-neuronal cholinergic networks by displacing from nAChR its natural ligand acetylcholine which acts as a local hormone or cytokine in a variety of non-neuronal locations.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Sep
pubmed:issn
1078-0297
pubmed:author
pubmed:issnType
Print
pubmed:volume
97
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
243-62
pubmed:dateRevised
2004-11-17
pubmed:meshHeading
pubmed:year
1997
pubmed:articleTitle
Nicotine enhances expression of the alpha 3, alpha 4, alpha 5, and alpha 7 nicotinic receptors modulating calcium metabolism and regulating adhesion and motility of respiratory epithelial cells.
pubmed:affiliation
Department of Dermatology, School of Medicine, University of California, Davis 95616, USA.
pubmed:publicationType
Journal Article