Peptides
37
(2012)
309–313
Contents
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at
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Peptides
j
ourna
l
ho
me
pa
ge:
www.elsevier.com/locate/peptides
Antimicrobial–immunomodulatory
activities
of
zebrafish
phosvitin-derived
peptide
Pt5
Yunchao
Ding,
Xuemei
Liu,
Lingzhen
Bu,
Hongyan
Li,
Shicui
Zhang
∗
Laboratory
for
Evolution
&
Development,
Institute
of
Evolution
&
Marine
Biodiversity
and
Department
of
Marine
Biology,
Ocean
University
of
China,
Qingdao
266003,
China
a
r
t
i
c
l
e
i
n
f
o
Article
history:
Received
18
June
2012
Received
in
revised
form
18
July
2012
Accepted
18
July
2012
Available
online
27
July
2012
Keywords:
Zebrafish
Danio
rerio
Phosvitin
Antimicrobial
peptide
Immunomodulator
a
b
s
t
r
a
c
t
A
phosvitin
(Pv)-derived
peptide,
Pt5,
which
consists
of
the
C-terminal
55
residues
of
Pv
in
zebrafish,
has
been
shown
to
function
as
an
antimicrobial
agent
capable
of
killing
microbes
in
vitro.
However,
its
in
vivo
role
in
zebrafish
remains
unknown.
In
this
study,
we
clearly
demonstrated
that
Pt5
protected
adult
zebrafish
from
pathogenic
Aeromonas
hydrophila
attack,
capable
of
significantly
enhancing
the
survival
rate
of
zebrafish
after
the
pathogenic
challenge.
Pt5
also
caused
a
marked
decrease
in
the
numbers
of
A.
hydrophila
in
the
blood,
spleen,
kidney,
liver
and
muscle,
suggesting
that
Pt5
was
able
to
block
multipli-
cation/dissemination
of
A.
hydrophila
in
zebrafish.
Additionally,
Pt5
markedly
suppressed
the
expression
of
the
proinflammatory
cytokine
genes
IL-1ˇ,
IL-6,
TNF-˛
and
IFN-
in
the
spleen
and
head
kidney
of
A.
hydrophila-infected
zebrafish,
but
it
considerably
enhanced
the
expressions
of
the
antiinflammatory
cytokine
genes
IL-10
and
IL-4
in
the
same
tissues.
Taken
together,
these
data
indicate
that
Pt5
plays
a
dual
role
in
zebrafish
as
an
antimicrobial
and
immunomodulatory
agent,
capable
of
protecting
zebrafish
against
pathogenic
A.
hydrophila
through
its
antimicrobial
activity
as
well
as
preventing
zebrafish
from
the
detrimental
effects
of
an
excessive
inflammatory
response
via
modulating
immune
functions.
©
2012
Elsevier
Inc.
All
rights
reserved.
1.
Introduction
Antimicrobial
peptides
(AMPs)
are
an
evolutionarily
conserved
component
of
the
innate
immunity,
and
are
found
among
virtu-
ally
all
classes
of
organisms
including
plants
and
animals
[7,27].
AMPs
are
generally
12
to
50
amino
acids
in
size.
They
have
been
demonstrated
to
be
potent,
broad
spectrum
antibiotics
capable
of
killing
Gram-negative
and
Gram-positive
bacteria,
mycobacteria,
enveloped
viruses,
fungi
and
even
transformed
or
cancerous
cells
[10].
Several
hundred
AMPs
have
been
identified,
but
only
a
few
of
their
roles
in
host
immunity
have
been
studied
[12,21,23,26].
Apart
from
efficient
antimicrobial
activity,
AMPs
also
regulate
immunity
by
functioning
as
immunomodulators.
They
not
only
boost
the
immune
response
to
prevent
infection
but
also
suppress
other
proinflammatory
responses
to
avoid
uncontrolled
inflamma-
tion,
thereby
resulting
in
homeostasis
of
innate
cellular
defenses
within
an
organism
[2,18].
For
example,
human
neutrophil
peptide
HNP
1–3
binds
C1q
and
activates
the
classic
complement
pathway
[19],
increases
the
production
of
TNF-␣
and
IL-1,
and
decreases
Abbreviations:
AMPs,
antimicrobial
peptides;
Pv,
phosvitin;
LPS,
lipopolysaccha-
ride;
LTA,
lipoteichoic
acid;
PGN,
peptidoglycan;
LD
50
,
50%
lethal
dose;
RPS,
relative
percent
survival.
∗
Corresponding
author
at:
Room
205,
Ke
Xue
Guan,
5
Yushan
Road,
Ocean
Uni-
versity
of
China,
Qingdao
266003,
China.
Tel.:
+86
532
82032787.
E-mail
address:
sczhang@ouc.edu.cn
(S.
Zhang).
the
production
of
IL-10
by
monocytes
[3,8,16].
Furthermore,
some
AMPs
such
as
human
cathelicidin
LL-37
synergize
with
cytokines
and
modify
their
immunomodulatory
activity
[5,6,11].
Zebrafish
(Danio
rerio)
is
a
widely
used
model
organism
to
study
vertebrate
development
and
hematopoiesis
but
interest
in
this
model
organism
has
expanded
into
the
fields
of
human
disease,
cancer
and
immunology
in
recent
years
[9,17,28].
Accord-
ingly,
knowledge
regarding
the
immunology
of
zebrafish
has
been
increasingly
growing
[14,17].
For
example,
several
AMPs
includ-
ing
-defensin
and
hepcidin
have
been
identified
in
zebrafish
[30].
Midkine
and
pleiotrophin
in
zebrafish
have
also
been
shown
to
have
bactericidal
properties
[22].
Recently,
we
have
demonstrated
that
egg
yolk
protein
phosvitin
(Pv)
played
a
critical
role
in
the
immunity
of
zebrafish
embryos
via
acting
as
a
pattern
recognition
receptor
and
an
antimicrobial
effector
[25].
In
addition,
a
Pv-derived
peptide,
Pt5,
which
consists
of
the
C-terminal
55
residues
of
Pv,
also
dis-
played
a
remarkable
antimicrobial
activity
generally
comparable
to
that
of
Pv
as
well
as
an
affinity
to
the
microbial
signature
molecules
lipopolysaccharide
(LPS),
lipoteichoic
acid
(LTA)
and
peptidogly-
can
(PGN),
while
its
mutant,
M13,
generated
by
double
mutation
A201G/I203M,
lost
almost
all
the
antimicrobial
activity
and
the
affinity
to
LPS,
LTA
and
PGN
[25].
Despite
these
progresses,
many
questions
remain
uncertain.
We
do
not
know
if
Pt5
can
protect
adult
zebrafish
from
pathogenic
infection
in
vivo;
and
if
so,
can
it
modulate
the
immune
responses?
The
present
study
was
therefore
undertaken
to
answer
these
questions.
0196-9781/$
–
see
front
matter
©
2012
Elsevier
Inc.
All
rights
reserved.
http://dx.doi.org/10.1016/j.peptides.2012.07.014