Co-expression of nAChRs and molecules of the bitter taste transduction pathway by epithelial cells of intrapulmonary airways.
OBJECTIVE
The ability to sense the bitter taste of nicotine is an important component of addiction to, and withdrawal from, cigarette smoking. alpha-Gustducin and phospholipase C-beta2 (PLC-beta2), molecules involved in the taste transduction pathway, have been identified in airway epithelial solitary chemosensory cells (SCCs). Airway epithelial cells also express multiple nicotinic acetylcholine receptors (nAChRs). However, the relationship between nAChRs and molecules of taste transduction in response to nicotine is not known. This study was designed to determine whether nAChRs and the taste transduction molecules alpha-gustducin, PLC-beta2 and bitter taste receptors (T2R38) reside at sites of the intrapulmonary airways where interaction with the nicotine components of cigarette smoke is likely.


METHODS
We used the reverse transcription-polymerase chain reaction (RT-PCR) to detect alpha-gustducin, PLC-beta2 and T2R38 mRNA and immunohistochemistry to localize expression of these proteins by nAChR expressing cells of the airway.


RESULTS
RT-PCR demonstrated the presence of mRNA for alpha-gustducin, PLC-beta2 and T2R38. Immunohistochemistry showed the expression of alpha-gustducin, PLC-beta2 and T2R38 by subsets of epithelial cells at all levels of the intrapulmonary airways including bronchi, terminal and respiratory bronchioles. Double labeling demonstrated the co-expression of alpha-gustducin with alpha3, alpha4, alpha5, alpha7 and beta2, as well as, PLC-beta2 and T2R38 with alpha4, alpha5 and beta2 nAChR subunits.


CONCLUSIONS
These findings provide morphological evidence for the presence of molecules of the bitter taste transduction pathway in nAChR expressing SCCs of the intrapulmonary airways. These SCCs may, thus, constitute a peripheral component of the bitter taste signal transduction pathway for nicotine.
Dehkordi
Ozra
O
Department of Surgery, Howard University Hospital, Washington DC 20060, United States. odehkordi@howard.edu
Rose
Jed E
JE
Balan
Kannan V
KV
Millis
Richard M
RM
Bhatti
Babur
B
Jayam-Trouth
Annapurni
A
D000818:Animals; D004847:Epithelial Cells / Q000378:metabolism*; D005786:Gene Expression Regulation; D008297:Male; D009538:Nicotine / Q000494:pharmacology*; D018722:Nicotinic Agonists / Q000494:pharmacology*; D054799:Phospholipase C beta / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D043562:Receptors, G-Protein-Coupled / Q000096:biosynthesis; D011978:Receptors, Nicotinic / Q000096:biosynthesis*; D020545:Respiratory Mucosa / Q000378:metabolism*; D015398:Signal Transduction; D012907:Smoking / Q000235:genetics / Q000378:metabolism; D016540:Smoking Cessation; D013649:Taste; D015293:Transducin / Q000096:biosynthesis; D000098706:Taste Receptors, Type 2
D018722:Nicotinic Agonists; D043562:Receptors, G-Protein-Coupled; D011978:Receptors, Nicotinic; D000098706:Taste Receptors, Type 2; C075192:gustducin; D009538:Nicotine; D054799:Phospholipase C beta; D015293:Transducin