- NEW YORK (Reuters
Health) - Particular infection-fighting proteins act as natural antibiotics
in the skin of mice, according to US scientists. It is the first evidence
in mammals that such proteins, known as antimicrobial peptides, can perform
like antibiotic drugs.
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- Since humans also have these types of proteins, the researchers
say their findings suggest people can churn out their own antibiotics in
the face of a germ invasion.
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- The study looked at the role of cathelicidins in the
innate immune defenses of mice. Cathelicidins, or caths, are small pieces
of protein that dwell in certain cells in mammals, including humans. While
caths have been known to aid in the body's defenses--such as helping wound
healing--it has been unclear whether they can kill infectious bugs.
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- In the November 22nd issue of Nature, Dr. Richard L.
Gallo and his colleagues report that caths are indeed a type of natural
antibiotic.
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- Gallo's team studied a mouse cathelicidin called CRAMP,
which has a human counterpart called LL-37. This suggests that the human
cath is also an innate antibiotic, according to Gallo, a researcher at
the University of California, San Diego and the Veterans Affairs San Diego
Healthcare System.
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- This is important for several reasons, Gallo told Reuters
Health in an interview.
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- For one, he explained, ``this makes us wonder if people
who get infections easily don't have proper function in their (caths).''
Further research, according to Gallo, should look into that question.
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- In addition, if humans harbor their own antibiotics,
these natural-born germ killers could be used as models for drug development.
Gallo pointed out that, unlike man-made antibiotics, caths have persisted
throughout time without a wide range of bacteria becoming resistant to
them.
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- In their study, Gallo's team created mice lacking the
gene for CRAMP, then compared their susceptibility to skin infection from
streptococcus bacteria with that of normal mice. They found that the CRAMP-deficient
mice developed more severe infections than the normal animals did.
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- Similarly, in a second round of experiments, mice that
were infected with mutant strep bacteria resistant to CRAMP had longer-lasting,
more extensive skin infections than those infected with normal strep.
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- Caths are located in various tissues other than skin,
including the lungs and intestines, and in white blood cells called neutrophils.
According to Gallo, they jump into action when necessary, increasing their
levels in tissue under assault.
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- Unlike antibiotic drugs, which are notoriously overused,
he noted, ``the body doles out caths only when needed.''
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- SOURCE: Nature 2001;414:454-457.
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