Air pollution, smoking affect Latent
Tuberculosis
Newswise — A toxic gas present in air
pollution and tobacco smoke plays a
significant role in triggering tuberculosis
infection, according to a new study from
researchers at the University of Alabama at
Birmingham (UAB).
The UAB study focused on carbon monoxide
(CO), a colorless, odorless gas present in
tobacco smoke, and vehicle and manufacturing
plant emissions. Also, CO is produced
naturally in brushfires and volcanic gas.
The study showed that CO triggers
Mycobacterium tuberculosis (Mtb),
the causative agent of tuberculosis, to
shift from active infection to a
drug-resistant dormant state. This is called
latency, a global problem that results in
tuberculosis escaping detection and
treatment, and which contributes to overall
tuberculosis transmission.
“This is the first description of a role for
CO in mycobacterial pathogenesis, and may
explain why smoking and air pollution
contributes to TB,” said Adrie Steyn, Ph.D.,
assistant professor in UAB’s Department of
Microbiology and lead author on the study.
The findings were published online in The
Journal of Biological Chemistry.
In the study, the researchers worked with
Mtb cells under biosafe laboratory
conditions and found Mtb proteins
‘sense’ CO at the molecular level, much like
the bacteria’s proteins sense other gases in
the lungs.
The CO interaction is what led to a series
of biological steps that sent Mtb
into latency.
The finding holds political and social
implications for speeding up clean-air
measures as a way to improve public health,
in addition to the environmental
significance. The study holds promise for
helping to discover new ways to fight
extreme drug-resistant tuberculosis, or XDR
TB, the UAB researchers said.
“We’re talking about huge socio-economic and
public health implications,” said Steyn. One
third of the world’s population is infected
with undetectable forms of tuberculosis,
which hinders screening and eradication
efforts.
The finding adds to a growing understanding
that exposure to high levels of CO through
air pollution and cigarette smoke plays a
role in tuberculosis infection rates. Also,
the study showed that low levels of CO
present in the body are capable of
triggering tuberculosis latency, Steyn said.
Inflammation, infection and oxidative stress
are among contributors to CO in the body.
Research published by Steyn in 2007 showed
that combined production of CO, oxygen and
nitric oxide should be used in future models
of Mtb persistence.
Tuberculosis is the leading cause of death
in the world from a single bacterial
infection, and it kills 1.5 million people
per year.
The rate of infection in Alabama is slightly
lower than the United States. Tuberculosis
infection rate: 4.3 (Alabama) per 100,000
people compared to 4.6 (U.S.) per 100,000
people.
