Muscarinic receptors, leukotriene B4 production and neutrophilic inflammation in COPD patients.
BACKGROUND
Acetylcholine (ACh) plays an important role in smooth muscle contraction and in the development of airway narrowing; preliminary evidences led us to hypothesize that ACh might also play a role in the development of airways inflammation in chronic obstructive pulmonary disease (COPD).


METHODS
We evaluated the concentrations of leukotriene B4 (LTB4) in induced sputum, and the expression of Ach M1, M2, and M3 receptors in sputum cells (SC) obtained from 16 patients with COPD, 11 smokers, and 14 control subjects. The SC were also treated with ACh and the production of LTB4 assessed in the presence or absence of a muscarinic antagonist (oxitropium). In blood monocytes, we evaluated LTB4 release and activation of the extracellular signal-regulated kinases (ERK) pathway after treatment with Ach.


RESULTS
The LTB4 concentrations were higher in COPD than in controls (P < 0.01) and correlated with the number of neutrophil (P < 0.01). The M3 receptors expression was increased in COPD subjects when compared to smokers and control (P < 0.05 and 0.0001, respectively), while M2 expression resulted decreased (P < 0.05 and 0.01). The ACh-induced LTB(4) production was observed in peripheral blood monocytes, and was sensitive to ERK inhibition. Similarly, ACh significantly increased neutrophil chemotactic activity and LTB4 released from SC of COPD patients only, and these effects were blocked by pretreatment with the inhibitor of ERK pathway PD98059.


CONCLUSIONS
The results obtained show that muscarinic receptors may be involved in airway inflammation in COPD subjects through ACh-induced, ERK1/2-dependent LTB4 release. Muscarinic antagonism may contribute to reduce neutrophil infiltration and activation in COPD.
Profita
M
M
Institute of Biomedicine and Molecular Immunology, Italian National Research Council, Palermo, Italy.
Giorgi
R Di
RD
Sala
A
A
Bonanno
A
A
Riccobono
L
L
Mirabella
F
F
Gjomarkaj
M
M
Bonsignore
G
G
Bousquet
J
J
Vignola
A M
AM
D000109:Acetylcholine / Q000494:pharmacology; D000368:Aged; D002135:Calcium-Binding Proteins / Q000037:antagonists & inhibitors / Q000494:pharmacology; D002478:Cells, Cultured; D002634:Chemotaxis, Leukocyte; D005260:Female; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D007150:Immunohistochemistry; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000378:metabolism*; D007975:Leukotriene B4 / Q000032:analysis / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D048052:Mitogen-Activated Protein Kinase 3 / Q000187:drug effects / Q000378:metabolism; D009504:Neutrophils / Q000378:metabolism*; D015800:Protozoan Proteins / Q000037:antagonists & inhibitors / Q000494:pharmacology; D029424:Pulmonary Disease, Chronic Obstructive / Q000276:immunology* / Q000378:metabolism*; D011976:Receptors, Muscarinic / Q000378:metabolism*; D013183:Sputum / Q000166:cytology / Q000378:metabolism
D002135:Calcium-Binding Proteins; D005419:Flavonoids; D015800:Protozoan Proteins; D011976:Receptors, Muscarinic; C093239:calcium-binding protein 1, Dictyostelium discoideum; D007975:Leukotriene B4; D048052:Mitogen-Activated Protein Kinase 3; D000109:Acetylcholine; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one