Biomedical Engineering Reference
In-Depth Information
D. GM-CSF
The concentrations of granulocyte-macrophage colony stimulating factor
(GM-CSF) in BAL fluid are increased in stable COPD but markedly ele-
vated during exacerbations (138). The GM-CSF is important for neutrophil
survival and may play an enhancing role in neutrophilic inflammation. Like
other proinflammatory cytokines, it is predominantly regulated by NF-
k
B.
E.
Interleukin-10
The IL-10 is a potent anti-inflammatory cytokine that is released from
monocytes and alveolar macrophages in response to inflammatory stimuli.
The IL-10 secretion is markedly reduced in alveolar macrophages from
patients with asthma (139) and its concentrations are reduced in sputum
of patients with asthma and COPD, suggesting that a similar abnormality
may apply on COPD (140). The IL-10 production appears to be increased
in macrophages from normal smokers (141), but it is not certain whether
macrophages from COPD patients show a relatively reduced production,
as in asthma, which may help amplify inflammation.
F. Other Cytokines
Overexpression of IL-13 and also interferon-
g
in murine lungs unexpectedly
results in emphysema that is mediated by increased expression of MMPs
and cathepsins (142,143). There is also an association between a promoter
polymorphism in the IL-13 gene and COPD, as also seen for asthma
(144). The relevance of IL-13 cytokines in the pathogenesis of human
emphysema has not yet been elucidated, however. Another Th2 cytokine
IL-4 is a classical Th2 cytokine which plays a key role in asthma, but it
has been found to unexpectedly increased in chronic bronchitis, particularly
in CD8
รพ
T lymphocytes around submucosal glands, although this was not
observed in COPD (145). A third Th2 cytokine IL-9 is also increased in
airway T lymphocytes of patients with COPD (96).
The IL-17 is a cytokine that releases CXC chemokines from airway
epithelial cells (146), but is not increased in sputum of COPD patients (147).
VII. GROWTH FACTORS
Marked structural changes are found in small airways and lung parench-
yma, presumably as a result of chronic inflammation and the release of cyto-
kines, particularly growth factors that induce fibrosis and cell metaplasia.
A. Transforming Growth Factors
Transforming growth factor (TGF)-
b
1 shows increased expression in small
airway epithelial cells and alveolar macrophages of patients with COPD and
