Emphysema Treatment
The
word emphysema is derived from the Greek word for inflation, is an anatomic
alteration of the lung characterized by an abnormal enlargement of the air
spaces distal to the terminal, non-respiratory bronchiole, accompanied by destructive
changes of the alveolar walls. Pulmonary emphysema has been defined as
enlargement and destruction of the alveolar containing portions of the lung.
The disease occurs most commonly in smokers and people exposed to polluted air,
dust or irritants.
Disorders
of this protein include alpha 1-antitrypsin deficiency, a hereditary disorder
in which a deficiency of alpha 1-antitrypsin leads to a chronic uninhibited
tissue breakdown. This causes the degradation especially of lung tissue, and
eventually leads to characteristic manifestations of pulmonary emphysema.
Evidence has shown that cigarette smoke can lead to oxidation of methionine 358
of α1-antitrypsin, a residue essential for binding elastase; Elastase
is an enzyme that digests and degrades a number of proteins including elastin,
an elastic substance in the lungs and some other organs that supports their
structural framework. Elastase is specifically inhibited by alpha-1
antitrypsin. This is thought to be one of the primary mechanisms by which
cigarette smoking can lead to emphysema. Lungs of smokers who developed
emphysema seem more prone to the central lobular form, where patients with
alpha 1-antitrypsin deficiency usually demonstrate the Panlobular form.
A
deficiency in a protein in the liver called alpha 1- antitrypsin has been found
in some patients to produce emphysema. Antitrypsin counteracts trypsin, an
enzyme produced by many types of bacteria that destroy tissue. Oxidation of the
methionine active center in the 1-alpha antitrypsin molecule results in a loss
of inhibitory function of the protein for elastase. Patients exposed to tobacco
smoke could inactivate the alpha 1-antitrypsin in the alveolar lining and
thereby increase the elastase burden on alveolar septal tissue. The level of
alpha 1- antitrypsin may be a factor when smoke is involved to developed
emphysema.
Emphysema
in humans takes several different forms and can be classified as Centrilobular,
Panlobular, Paraseptal, and airspace enlargement with fibrosis. The two main
types of emphysema are Panlobular, involving all of a secondary lobule, and
Centrilobular, involving the central area of a secondary lobule. Panlobular
emphysema is relatively unusual, with no more than 1 individual for every 20
with Centrilobular emphysema. Centrilobular emphysema is the more common form
of emphysema and is more severe in the upper lobes and is much more common in
men than women.
Centrilobular
emphysema is associated with cigarette smoking because the products of
cigarette smoke produce a reaction that release proteolytic enzymes increasing
elastase activity in the airways. Cigarette smoke destroys the delicate
structure of the air sacs in the lung, preventing the efficient exchange of
oxygen and carbon dioxide. Cigarette smoke contains carcinogens that damaged
and distended the air sacs in the lungs. As a result, the lungs are less able
to supply the oxygen that the body requires. Alveoli are the tiny sacs at the
end of the bronchioles where blood gives up carbon dioxide and takes on fresh
oxygen from inhaled air. As the alveoli become less efficient the air is
trapped in the lungs decreasing the volume of fresh air that can be inhaled. In
emphysema the patient's greatest problem is to exhale enough residual air
because the lungs are partially inflated all the time.
Cigarette
smoke produce irritants that stimulate mucus production and impair ciliary
function. Excess mucus production increases an individual's vulnerability to
respiratory tract infection and interferes with recovery from infection. The
great quantity of mucus leads to persistent coughing and a greater
susceptibility to colds, which can lead to chess infections. It is clear that
cigarette smoke produce an impairment of gas distribution related to long term
smoking.
Cigarette
smoking is associated with a marked increase in the number of alveolar
macrophages and phagocytes. Macrophages participate in a variety of phagocytic,
immune, and inflammatory processes and play a role in the degradation and
remodeling of the extracellular matrix.
The
lung has developed a sophisticated defense system to deal with inhaled antigens
and bacteria. When the bacterial load entering the lung is small these
organisms are removed by mechanism including mucociliary clearance, local
immunoglobulin binding, and ingestion by resident phagocytes. However, as the
bacterial rises, the organisms are able to overcome these defense mechanisms
and a symptomatic infection results. This is characterized by inflammatory
response associated with recruitment and activation of circulating phagocytes
such as monocytes and neutrophils, increased transudation of plasma proteins,
and often the expectoration of purulent secretions. A major consequence of
inhaled particles is an increase of macrophages in the lung. Then, if normal
pulmonary defenses are limited and an increasing level of proteolytic enzymes
is not activated, alveolar destruction may occur.
Macrophages
promote elastin degradation through the production and release of elastolytic
enzymes. Elastin is a protein in connective tissue that is elastic and allows
many tissues in the body to resume their shape after stretching or contracting.
Phagocytes
express a changing profile of proteinases that may participate in the
degradation of elastin and other extracellular matrix components. Elastin
degradation is an important component of the alveolar destruction in emphysema,
and once the destruction of elastin had occurred, the anatomic and physiologic
abnormalities might remain because of an inability to restore elastin
continuity.
Pulmonary
emphysema, characterized by destruction of alveolar structures, is the result
of an unrestrained in the lung of proteinases, especially elastase originating
from neutrophils. Recent findings suggest that cigarette smoking causes
retention of neutrophils in the lung and that these cells contain at least two
enzymes that affect the normal proteinase inhibitor defense mechanism and
destroy lung tissue. Cigarette smoking recruits neutrophils into the airways,
increase human neutrophil elastase from neutrophils, and inactivate proteinase
inhibitor. Neutrophils are found in increased number in the alveolar region of
individuals who smoke cigarettes, and the release of proteinase by these cells
in the alveolar region is considered to play an important role in the
subsequent development of emphysema in a proportion of individuals who smoke.
The increase in the number of neutrophils in the lung and in the number of
alveolar macrophages produces an increase in the concentration of proteinases,
including neutrophil elastase.
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