The effects of interleukin-8 on airway smooth muscle contraction in cystic fibrosis.
BACKGROUND
Many cystic fibrosis (CF) patients display airway hyperresponsiveness and have symptoms of asthma such as cough, wheezing and reversible airway obstruction. Chronic airway bacterial colonization, associated with neutrophilic inflammation and high levels of interleukin-8 (IL-8) is also a common occurrence in these patients. The aim of this work was to determine the responsiveness of airway smooth muscle to IL-8 in CF patients compared to non-CF individuals.


METHODS
Experiments were conducted on cultured ASM cells harvested from subjects with and without CF (control subjects). Cells from the 2nd to 5th passage were studied. Expression of the IL-8 receptors CXCR1 and CXCR2 was assessed by flow cytometry. The cell response to IL-8 was determined by measuring intracellular calcium concentration ([Ca2+](i)), cell contraction, migration and proliferation.


RESULTS
The IL-8 receptors CXCR1 and CXCR2 were expressed in both non-CF and CF ASM cells to a comparable extent. IL-8 (100 nM) induced a peak Ca2+ release that was higher in control than in CF cells: 228 +/- 7 versus 198 +/- 10 nM (p < 0.05). IL-8 induced contraction was greater in CF cells compared to control. Furthermore, IL-8 exposure resulted in greater phosphorylation of myosin light chain (MLC20) in CF than in control cells. In addition, MLC20 expression was also increased in CF cells. Exposure to IL-8 induced migration and proliferation of both groups of ASM cells but was not different between CF and non-CF cells.


CONCLUSIONS
ASM cells of CF patients are more contractile to IL-8 than non-CF ASM cells. This enhanced contractility may be due to an increase in the amount of contractile protein MLC20. Higher expression of MLC20 by CF cells could contribute to airway hyperresponsiveness to IL-8 in CF patients.
Govindaraju
Vasanthi
V
Seymour Heisler Laboratory of the Montreal Chest Institute Research Center and Meakins Christie Laboratories, McGill University, Montreal, Quebec, Canada. Vasanthi.govindaraju@mcGill.ca
Michoud
Marie-Claire
MC
Ferraro
Pasquale
P
Arkinson
Janine
J
Safka
Katherine
K
Valderrama-Carvajal
Hector
H
Martin
James G
JG
D002478:Cells, Cultured; D003550:Cystic Fibrosis / Q000473:pathology / Q000503:physiopathology*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D016209:Interleukin-8 / Q000008:administration & dosage*; D008168:Lung / Q000187:drug effects / Q000503:physiopathology*; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000503:physiopathology*; D023062:Receptors, Interleukin-8A / Q000378:metabolism*; D023063:Receptors, Interleukin-8B / Q000378:metabolism*
D016209:Interleukin-8; D023062:Receptors, Interleukin-8A; D023063:Receptors, Interleukin-8B