Effect of cigarette smoking on cough reflex induced by TRPV1 and TRPA1 stimulations.
BACKGROUND
Recent studies have shown that neurogenic inflammation induced by cigarette smoke is inhibited by TRPA1 antagonist, but not by TRPV1 antagonist. Since cough reflex sensitivity is known to be modified by smoking status, we investigated the effects of cigarette smoking on TRPA1- and TRPV1-induced cough and urge-to-cough in healthy males.


METHODS
Twenty-six healthy never-smokers and 30 healthy current smokers were recruited via public postings. Cough reflex thresholds and urge-to-cough were evaluated by inhalation of capsaicin, a TRPV1 agonist, and cinnamaldehyde, a TRPA1 agonist. The cough reflex thresholds were defined as the lowest concentrations of capsaicin and cinnamaldehyde that elicited two or more coughs (C(2)) and five or more coughs (C(5)), respectively. The urge-to-cough was evaluated using the modified Borg scale.


RESULTS
In capsaicin-induced cough, the cough reflex thresholds, as expressed by C(2) and C(5), in current smokers were significantly higher than those in never-smokers (p<0.01 and p<0.001, respectively). The urge-to-cough log-log slopes in current smokers were significantly lower than those of never-smokers (p<0.001). There were no significant differences in the thresholds of the urge-to-cough between never-smokers and current smokers. In cinnamaldehyde-induced cough, there were no significant differences in cough reflex thresholds in C(2) and C(5) between never-smokers and current smokers, nor were there any significant differences in urge-to-cough log-log slope between never-smokers and current smokers. There were no significant differences in the thresholds of the urge-to-cough between never-smokers and current smokers.


CONCLUSIONS
The study suggests that smoking has a differential effect on cough responses between TRPV1 and TRPA1 stimulations.
Department of Internal Medicine and Rehabilitation Science, Tohoku University Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan.
Masashi
M
Kanezaki
Satoru
S
Ebihara
Peijun
P
Gui
Takae
T
Ebihara
Masahiro
M
Kohzuki
D000171:Acrolein / Q000031:analogs & derivatives; D000293:Adolescent; D000328:Adult; D015220:Calcium Channels / Q000502:physiology*; D002211:Capsaicin; D003371:Cough / Q000139:chemically induced / Q000209:etiology / Q000503:physiopathology* / Q000523:psychology; D018592:Cross-Over Studies; D006801:Humans; D008297:Male; D009419:Nerve Tissue Proteins / Q000819:agonists / Q000502:physiology*; D012018:Reflex / Q000187:drug effects / Q000502:physiology; D012684:Sensory Thresholds / Q000187:drug effects / Q000502:physiology; D012907:Smoking / Q000009:adverse effects / Q000503:physiopathology* / Q000523:psychology; D000074025:TRPA1 Cation Channel; D050916:TRPV Cation Channels / Q000819:agonists / Q000502:physiology*; D050051:Transient Receptor Potential Channels / Q000819:agonists / Q000502:physiology*; D055815:Young Adult
D015220:Calcium Channels; D009419:Nerve Tissue Proteins; D000074025:TRPA1 Cation Channel; C473350:TRPA1 protein, human; D050916:TRPV Cation Channels; C494482:TRPV1 protein, human; D050051:Transient Receptor Potential Channels; D000171:Acrolein; D002211:Capsaicin; C012843:cinnamaldehyde