Finding the Triggers for ParkinsonâsDisease

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=46inding the Triggers for Parkinson=E2=80=99s Disease
Environmental engineer Kurt Pennell is investigating how pesticides and oth=
er=20
common chemicals may linger in the brain and spur the illness on
By Marjorie Howard
Could common chemicals play a role in triggering Parkinson=E2=80=99s diseas=
e? It=E2=80=99s a=20
distinct possibility, says Kurt Pennell, professor and chair of civil and=20
environmental engineering.
Parkinson=E2=80=99s disease, a degenerative disorder of the central nervous=
 system,=20
results in resting tremors, stiffness and loss of movement. Efforts to iden=
tify=20
its genetic cause have met with limited success, accounting for less than 1=
0=20
percent of the known Parkinson=E2=80=99s cases. That has led researchers to=
 consider=20
environmental culprits. Pennell suspects that that persistent organic=20
pollutants, such as pesticides, insecticides and other chemicals that remai=
n=20
in the environment and linger in the body long after exposure, play a role =
in=20
the onset and progression of Parkinson=E2=80=99s disease.=20
=20
=E2=80=9COur brains are particularly vulnerable because of their limited an=
tioxidant=20
capacity,=E2=80=9D says Kurt Pennell. Photo: Joanie Tobin=20
One of those chemicals is rotenone, a =E2=80=9Cnatural=E2=80=9D pesticide o=
nce widely used in=20
organic farming, because it was believed to be safe. Instead, it has been=20
shown in laboratory studies to induce Parkinson=E2=80=99s-like symptoms. Li=
ke other=20
chemicals that Pennell studies, including PCBs and dieldrin, which was=20
developed as an alternative to DDT, rotenone is hydrophobic, meaning it is =
not=20
attracted to water and instead is drawn to fat, where it is stored. The hum=
an=20
brain, which is two-thirds fat, is therefore a prime target for storing the=
=20
chemical.
Scientists don=E2=80=99t think these chemicals directly cause Parkinson=E2=
=80=99s, a long-term=20
disease that progresses very slowly. Rather, =E2=80=9Chaving this exposure =
or having=20
these chemicals in your system may increase the rate at which you start to=
=20
have symptoms,=E2=80=9D says Pennell. =E2=80=9CSo you may have them at a yo=
unger age or they=20
may progress more rapidly.=E2=80=9D=20
Pennell says the presence of these compounds in the brain increases oxidati=
ve=20
stress, a state in which the body is less able to fend off free radicals, w=
hich=20
cause damage to the brain and to the body. Antioxidants are molecules that=
=20
counteract the free radicals.=20
=E2=80=9COur brains are particularly vulnerable because of their limited an=
tioxidant=20
capacity and potential for radical formation,=E2=80=9D says Pennell. =E2=80=
=9CWe suspect that=20
the presence of these compounds in the brain alters how dopamine is package=
d=20
and increases oxidative stress within neurons, meaning it could both=20
predispose people to Parkinson=E2=80=99s and also accelerate the disease.=
=E2=80=9D Dopamine is=20
a chemical that acts as a neurotransmitter. In patients with Parkinson=E2=
=80=99s=20
disease, dopamine-containing neurons located in the midbrain are damaged an=
d=20
eventually die, which reduces their ability to control movements.=20
Pennell conducts his research in conjunction with the Collaborative Centers=
=20
for Parkinson=E2=80=99s Disease Environmental Research at Emory University.=
 =E2=80=9CWe expose=20
animals to dieldrin, PCBs and other chemicals, and look at their response t=
o=20
that exposure,=E2=80=9D he explains. =E2=80=9CWe look for markers of oxidat=
ive stress in the=20
brain and for concentrations of chemicals in their tissue and in their bloo=
d.=20
I measure the amount of chemicals and how long it persists in the body.=E2=
=80=9D=20
Pennell says the animals are given low concentrations of chemicals in an ef=
fort=20
to mimic dose levels that might be found in the environment.
In the last decade scientists have begun to accept the idea that common=20
chemicals can spur Parkinson=E2=80=99s along, says Pennell, but more studie=
s, such as=20
the ones he is conducting, are needed to prove it, and help understand=20
relationships between chemical exposures, genetic predisposition and lifest=
yle=20
factors in Parkinson=E2=80=99s disease. In addition, the ways in which oxid=
ative=20
stress contribute to nerve degeneration are not well understood. =E2=80=9CW=
e=E2=80=99d like to=20
identify biomarkers that may indicate that someone is more susceptible to=20
oxidative stress and eventually find therapies for people who have been exp=
osed=20
to these chemicals.=E2=80=9D=20
Tiny Particles, Big Questions
Pennell is also interested in finding out whether oxidative stress might be=
=20
caused by nano materials, manufactured particles that are less than one=20
millionth of a meter in size. Because they are so tiny, monitoring their us=
e=20
and disposal is challenging, and there are concerns they are escaping into =
the=20
environment and may pose a health hazard.
Nanotechnology, which involves the use of these tiny particles, allows=20
researchers to work on a molecular level. Nano-sized materials are 1/100=20
nanometers in diameter. For scale, think about it this way: a sheet of pape=
r=20
is about 100,000 nanometers thick.=20
The use of nano materials, says Pennell, has become increasingly common in=
=20
products such as sunscreen and cosmetics and in medical applications such a=
s=20
imaging. And scientists predict nanotechnology will also be used in=20
manufacturing, such as for aircraft, buildings and automobiles, taking=20
advantage of its lightweight properties. In health care, nanotechnology is=
=20
used when precision is key, such as delivering the right amount of medicine=
 to=20
the exact location in the body where it is needed most.=20
But the consequences of using such tiny materials are unknown, since it is=
=20
uncertain what effect they have on the environment and on the human body. T=
here=20
are concerns that nano materials could be discharged from industrial plants=
=20
into waterways or accidentally released into the air during their productio=
n.=20
Researchers are wondering if they may cause brain damage, resulting in such=
=20
diseases as Parkinson=E2=80=99s.
Researchers need to understand how nano materials behave so they can learn =
how=20
to better control them, says Pennell. In one project, he studies how carbon-
based nanoparticles move in water. He and Linda Abriola, dean of the school=
 of=20
engineering, recently received a $350,000 grant from the National Science=20
=46oundation to study the effects of metal-based nanoparticles on both the =
body=20
and the environment.=20
=E2=80=9CNo one really knows what happens if we release nanoparticles into =
the=20
environment=E2=80=94what happens and where are they going to go,=E2=80=9D s=
ays Pennell. =E2=80=9CHow=20
will they be transported and retained? What happens if they reach a body of=
=20
water or if they=E2=80=99re spilled or put into a dump? We need to understa=
nd how to=20
control them.=E2=80=9D

http://tuftsjournal.tufts.edu/2010/03_1/features/01/

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