Increased tachykinin levels in induced sputum from asthmatic and cough patients with acid reflux.
BACKGROUND
Acid reflux may aggravate airway disease including asthma and chronic cough. One postulated mechanism concerns a vagally-mediated oesophageal-tracheobronchial reflex with airway sensory nerve activation and tachykinin release.


OBJECTIVE
To test the hypothesis that patients with airways disease and reflux have higher airway tachykinin levels than those without reflux.


METHODS
Thirty-two patients with airways disease (16 with mild asthma and 16 non-asthmatic subjects with chronic cough) underwent 24 h oesophageal pH monitoring. Acid reflux was defined as increased total oesophageal acid exposure (% total time pH<4 of >4.9% at the distal probe). All subjects underwent sputum induction. Differential cell counts and concentrations of substance P (SP), neurokinin A (NKA), albumin and alpha2-macroglobulin were determined.


RESULTS
SP and NKA levels were significantly higher in patients with reflux than in those without (SP: 1434 (680) pg/ml vs 906 (593) pg/ml, p=0.026; NKA: 81 (33) pg/ml vs 52 (36) pg/ml, p=0.03). Significantly higher tachykinin levels were also found in asthmatic patients with reflux than in asthmatic patients without reflux (SP: 1508 (781) pg/ml vs 737 (512) pg/ml, p=0.035; NKA: median (interquartile range 108 (85-120) pg/ml vs 75 (2-98) pg/ml, p=0.02). In patients with asthma there was a significant positive correlation between distal oesophageal acid exposure and SP levels (r=0.59, p=0.01) and NKA levels (r=0.56, p=0.02). Non-significant increases in SP and NKA were measured in patients with cough with reflux (SP: 1534.71 (711) pg/ml vs 1089 (606) pg/ml, p=0.20; NKA: 56 (43) pg/ml vs 49 (17) pg/ml, p=0.71). No significant difference in differential cell counts or any other biochemical parameter was noted between study groups.


CONCLUSIONS
This study demonstrates increased airway tachykinin levels in patients with asthma and cough patients with coexistent acid reflux. This suggests airway sensory nerve activation in this population.
Patterson
Robert N
RN
Department of Medicine, Queen's University Belfast, and Regional Respiratory Centre, Belfast City Hospital, Grosvenor Road, Belfast BT12 6BJ, UK.
Johnston
Brian T
BT
Ardill
Joy E S
JE
Heaney
Liam G
LG
McGarvey
Lorcan P A
LP
D000293:Adolescent; D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000378:metabolism; D002452:Cell Count; D003371:Cough / Q000378:metabolism*; D005764:Gastroesophageal Reflux / Q000378:metabolism*; D006801:Humans; D008875:Middle Aged; D012129:Respiratory Function Tests; D012709:Serum Albumin / Q000378:metabolism; D013183:Sputum / Q000378:metabolism*; D015320:Tachykinins / Q000378:metabolism*; D000511:alpha-Macroglobulins / Q000378:metabolism
D015415:Biomarkers; D012709:Serum Albumin; D015320:Tachykinins; D000511:alpha-Macroglobulins