Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin...
Transcript of Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin...
![Page 1: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/1.jpg)
Schrenk 2010
Dieter Schrenk
Lebensmittelchemie und Toxikologie
Technische Universität Kaiserslautern
2010
![Page 2: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/2.jpg)
Schrenk 2010
1.
Introduction
2.
‚Dioxins‘
as tumor
promoters
3.
are
‚Dioxins‘
genotoxic?
4.
what
about
non-dioxinlike
PCBs?
5.
Summary
![Page 3: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/3.jpg)
Schrenk 2010
1.
Introduction
2.
‚Dioxins‘
as tumor
promoters
3.
are
‚Dioxins‘
genotoxic?
4.
what
about
non-dioxinlike
PCBs?
5.
Summary
![Page 4: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/4.jpg)
Schrenk 2010
1. Introduction
•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC
• TCDD exerts most (if not all) toxic effects through mechanisms involving the aryl hydrocarbon receptor (AHR)
• TCDD acts as a potent liver tumour promoter in two- step rodent carcinogenesis models (Campbell et al., 1992)
• when applied to rodents without pre-treatment with an initiator, TCDD also leads to increased cancer incidences (Kociba et al., 1976)
![Page 5: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/5.jpg)
Schrenk 2010
1. Introduction
-0.5 0.0 0.5 1.0 1.5 2.0 2.5
0
10
20
30
40
50
60To
tal a
nim
als
with
neop
lasm
s(%
)
lg Dose (ng TEq/kg b.w. x day)
Aroclors
[Mayes
et al., 1998]TCDD [Kociba
et al., 1976]
Liver
neoplasms
in female
rats
treated
with
TCDD or
Aroclors
TEq
are
carcinogenic
in the
liver
of female
rats
![Page 6: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/6.jpg)
Schrenk 2010
1. Introduction
OO
O
Ligand
CytoplasmA
hR
Chaperones AhR
binding
Nucleus
Translocati
on
AR
NT
Ah
R
AR
NT
Binding to DRE
DNA DRE
Transcripti
onCYP1A1 mRNA
O
O
O
O
![Page 7: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/7.jpg)
Schrenk 2010
Signal transduction
I
AhR ARNT
XRE
CYP1A1 etc.
OO
O
OO
O
PAI-2
PAI-2fos/jun
PAI-2TGFα
PAI-2IL-1ß
transcriptional
1. Introduction
![Page 8: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/8.jpg)
Schrenk 2010
cellular
effects
and signal
transduction
II
ROS
AhR ARNT
ERα/ßERα/ß XRE
CYP1A1 etc.
OO
O
OO
O
Metabolism
c-src
Phosphorylation
of target
proteins
A. Drug metabolismB. oxidative
stress
D. Protein phosphorylation
E. growth inhibition
F. suppression
of contact
inhibition
C. antiestrogenic
effects
D
A B
C
EGFR
?
p27*
E
E
*an inhibitor of cyclin-dependent kinases
cyclinA/cdk2
F
1. Introduction
?
![Page 9: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/9.jpg)
Schrenk 2010
1.
Introduction
2.
‚Dioxins‘
as tumor
promoters
3.
are
‚Dioxins‘
genotoxic?
4.
what
about
non-dioxinlike
PCBs?
5.
Summary
![Page 10: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/10.jpg)
Schrenk 2010
2. ‚Dioxins‘
as tumor
promotors
Glutathione S-transferase
P –
positive preneoplastic
focus in rat liver (eight cell stage)
Nuclei
of normal hepatocytes
![Page 11: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/11.jpg)
Tumor promotion
(rat liver) with
PCDDs*
*Schrenk et al. (1994) Carcinogenesis
15, 509
DEN
2 weeks 2 weeks
fr. interv. PCDDs13 weeks
Schrenk 2010
2. ‚Dioxins‘
as tumor
promotors
![Page 12: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/12.jpg)
Schrenk 2010
initiation proliferati
on
apoptosis
progression
(tumor)DNA damage
hepatocyte/
hepatic
stem
cell
(?)
preneoplastic
cell
preneoplastic
focus
2. ‚Dioxins‘
as tumor
promotors
![Page 13: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/13.jpg)
Schrenk 2010
initiation proliferati
on
apoptosis
progression
(tumor)DNA damage
hepatocyte/
hepatic
stem
cell
(?)
preneoplastic
cell
preneoplastic
focus
2. ‚Dioxins‘
as tumor
promotors
+
![Page 14: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/14.jpg)
Schrenk 2010
initiation proliferati
on
apoptosis
progression
(tumor)DNA damage
hepatocyte/
hepatic
stem
cell
(?)
preneoplastic
cell
preneoplastic
focus
2. ‚Dioxins‘
as tumor
promotors
![Page 15: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/15.jpg)
Schrenk 2010
1.
(Stinchcombe
et al., 1994):
TCDD inhibits
apoptosis
in preneoplastic
rat hepatocytes
in situ
2. ‚Dioxins‘
as tumor
promotors
![Page 16: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/16.jpg)
Schrenk 2010
2. ‚Dioxins‘
as tumor
promotorsExtrinsic and intrinsic pathway of
apoptosis
![Page 17: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/17.jpg)
Schrenk 2010
2. (Wörner & Schrenk, 1994)
TCDD inhibits
apoptosis
in rat hepatocytes
in primary
culture
2. ‚Dioxins‘
as tumor
promotors
![Page 18: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/18.jpg)
Schrenk 2010
0 6 12 24
1
2
3
4
0
Time (h)
Apo
ptot
icnu
clei
(%)
control
(DMSO)
UV / TCDD 10-9
M
** *
*p<0.05
UV / DMSO
UV
2. ‚Dioxins‘
as tumor
promotors
![Page 19: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/19.jpg)
Schrenk 2010
3. (Wörner
& Schrenk, 1996):
TCDD suppresses the p53 response in rat
hepatocytes
in primary culture
2. ‚Dioxins‘
as tumor
promotors
![Page 20: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/20.jpg)
UV dose (J/m2) 0 0 90 90 120 120 150 150
TCDD (10-9
M) -
+ -
+ -
+ -
+
Rat hepatocytes
in primary
culture
were
harvested
24 h after irradiation; TCDD was added
30 min after
irradiation.
*Wörner and Schrenk, 1996
53 kD
Schrenk 2010
2. ‚Dioxins‘
as tumor
promotors
![Page 21: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/21.jpg)
Schrenk 2010
4. (Wörner
& Schrenk, 1998):
In rat hepatocytes, TCDD leads to hyper-phosphorylation
of p53. This effect shows the
same concentration-response characteristics as CYP1A1 induction.
2. ‚Dioxins‘
as tumor
promotors
![Page 22: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/22.jpg)
Schrenk 2010
[TCDD] (M) - 10-12 10-11 10-10 10-9 10-8
Rat hepatocytes
in primary
culture
were
harvested
6h after
TCDD treatment
*Woerner
and Schrenk, 1998
53 kD
2. ‚Dioxins‘
as tumor
promotors
0
200
400
600
800
-13 -12 -11 -10 -9 -8 -7
lg
[TCDD] (M)
ER
OD
act
ivity
![Page 23: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/23.jpg)
Schrenk 2010
5. (Kunz et al., 2004):
TCDD does not suppress MNNG-induced activation of caspase3 but leads to an increase in caspase3 activity without MNNG treatment.
2. ‚Dioxins‘
as tumor
promotors
![Page 24: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/24.jpg)
Schrenk 2010
Rat hepatocytes: Effect
of TCDD on UV-induced
apoptosis
2. ‚Dioxins‘
as tumor
promotors
Chopra
et al., Tox. Sci., 2009
![Page 25: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/25.jpg)
Schrenk 2010
TCDD does
not suppress
caspase
activation
in rat hepatocytes
2. ‚Dioxins‘
as tumor
promotors
![Page 26: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/26.jpg)
Schrenk 2010
Pan-caspase
inhibition suppresses apoptosis
2. ‚Dioxins‘
as tumor
promotors
Chopra
et al., Tox. Sci., 2009
![Page 27: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/27.jpg)
Schrenk 2010
TCDD does
not inhibit
PARP cleavage
2. ‚Dioxins‘
as tumor
promotors
Chopra
et al., Tox. Sci., 2009
![Page 28: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/28.jpg)
Schrenk 2010
CAD pathway
2. ‚Dioxins‘
as tumor
promotors
Apoptotic
signal
Caspa se
3
DNA fragmentati
on factor (DFF)-
complex
ICADCAD
activeCAD
Nucl eus
Bild: DNA mit
Nukleosomen
![Page 29: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/29.jpg)
Schrenk 2010
Nuclei from TCDD-treated hepatocytes
behave like untreated as CAD substrates
2. ‚Dioxins‘
as tumor
promotors
Caspase
3-
activated DFF action
is not affected by addition of TCDD in DNA
isolated from
untreated hepatocyte
s
Caspase
3-
activated DFF action
is not affected
by pretreatm
ent ofhepatocyte
s
with TCDD Chopra
et al., Tox. Sci., 2009
![Page 30: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/30.jpg)
Schrenk 2010
Caspase-dependent/independent apoptosis?
2. ‚Dioxins‘
as tumor
promotors
![Page 31: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/31.jpg)
Schrenk 2010
UV light leads to a loss of AIF from mitochondria (M); TCDD does not suppress this release
2. ‚Dioxins‘
as tumor
promotors
Chopra
et al., Tox. Sci., 2009
![Page 32: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/32.jpg)
Schrenk 2010
The AhR-antagonist CH-223191 abrogates TCDD-mediated supression
of apoptosis
2. ‚Dioxins‘
as tumor
promotors
Chopra
et al., Tox. Sci., 2009
![Page 33: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/33.jpg)
Schrenk 2010
2. ‚Dioxins‘
as tumor
promotors10 nM
TCDD reduces Huh-7 cells in sub G1
Chopra
et al., Tox. Sci., 2009
![Page 34: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/34.jpg)
Schrenk 2010
2. ‚Dioxins‘
as tumor
promotorsTCDD does not suppress caspase
activation in Huh-7 cells
Chopra
et al., Tox. Sci., 2009
![Page 35: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/35.jpg)
Schrenk 2010
2. ‚Dioxins‘
as tumor
promotors
![Page 36: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/36.jpg)
Schrenk 2010
catenin, H2A and NF-κB
p65 levels are not affected by TCDD
2. ‚Dioxins‘
as tumor
promotors
Chopra
et al., Tox. Sci., 2009
![Page 37: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/37.jpg)
Schrenk 2010
2. ‚Dioxins‘
as tumor
promotorsTCDD does
not inhibit
OTA-
or
CHX-initiated
apoptosis
Chopra
et al., Mol. Biol. Toxicol., 2009
![Page 38: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/38.jpg)
Schrenk 2010
2. ‚Dioxins‘
as tumor
promotorsOTA and CHX inhibit
protein
biosynthesis
Chopra
et al., Mol. Biol. Toxicol., 2009
![Page 39: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/39.jpg)
Schrenk 2010
2. ‚Dioxins‘
as tumor
promotorsCHX reduces
UV light-induced
apoptosis
Chopra
et al., Mol. Biol. Toxicol., 2010
![Page 40: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/40.jpg)
Schrenk 2010
1.
Introduction
2.
‚Dioxins‘
as tumor
promoters
3.
are
‚Dioxins‘
genotoxic?
4.
what
about
non-dioxinlike
PCBs?
5.
Summary
![Page 41: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/41.jpg)
Schrenk 2010
Mechanism
of dioxin
carcinogenicity–
tumor promotion
and/or
initiation?
3. Are ‚Dioxins‘
genotoxic?
![Page 42: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/42.jpg)
Schrenk 2010
Signal transduction and cellular effects
ROS
AhR ARNT
XRE
CYP1A1 etc.
OO
O
OO
O
ROS/genotoxic
metabolites?
c-srcc-src
Phosphorylation
of p53 (other
targets?)
A. Initiating
action?B. Suppression of apoptosis
A
BCaspase
3 ??
3. Are ‚Dioxins‘
genotoxic?
![Page 43: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/43.jpg)
Schrenk 2010
oxo8G per 106 dG
in hepatic
nuclear
DNA of intact
and ovariectomized female
Sprague-Dawley
rats
(Wyde
et al., Chem
Res Toxicol
14, 849, 2001)
Treatment intact
ovx ovx/estradiol
control
3.1 ±
1.5a
2.6 ±
1.4 2.8 ±
1.6
TCDDb
51 ±
22* 2.4 ±
1.5 32 ±
36*a
mean
± S.D.b
100 ng/kg per day, orally, for
30 weeks
* significantly
higher
than
control
(p<0.01)
3. Are ‚Dioxins‘
genotoxic?
![Page 44: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/44.jpg)
Schrenk 2010
HO
CH3OH
estradiol
Possible
consequences
of CYP1A1 induction: metabolic
activation
of estradiol*?
1
2
3
45
67
89
10
1112
14
13
15
16
17
18
HO
CH3OH
4-Hydroxy-estradiol
1
2
3
45
67
89
10
1112
14
13
15
16
17
18
HO[CYP1B1]
[CYP1A1?]
O
CH3OH
catechol
quinone estrogen
12
3
45
67
89
10
1112
14
13
15
16
17
18
O
.
O
CH3OH
semiquinone
radical
1
2
3
45
67
89
10
1112
14
13
15
16
17
18
OH
[Reductase]H+/e-
4-hydroxylation
oxidation
O2O2
-. reduction
*Wyde
et al., Chem. Res. Toxicol. 14, 849 (2001)
3. Are ‚Dioxins‘
genotoxic?
![Page 45: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/45.jpg)
Schrenk 2010
Possible
consequences
of CYP1A1 induction: increased
release
of superoxide?
N N
N N
FeIII
SCys
e - N N
N N
FeII
SCys
N N
N NFeII
SCys
O2
O
O
N N
N NFeIII
SCys
O
O-
e -2H+H2O
N N
N NFeV
SCys
O
N N
N NFeIII
SCys
O
HH
ROH
RH
O2- .
2H+
H2
O2
2H+
peroxo‚oxenoid‘
3. Are ‚Dioxins‘
genotoxic?
![Page 46: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/46.jpg)
Fe2+/3+
1/2 O2
O2- . OH.
SOD/Fenton
reaction
DNA (e.g. guanine) N
NH
NH2
N
N
R
HO
O
8-oxo-deoxyguanosine
CYP1A1
Schrenk 2010
3. Are ‚Dioxins‘
genotoxic?
![Page 47: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/47.jpg)
Schrenk 2010
Determination of ROS formationin-vitro in the human cell line HepG2 and in primary rat hepatocytes
• after incubation with TCDD (1 nM)
2´,7´-dihydrodichloro-fluorescein
diacetate
(H2
DCFDA) assay
Quantification of 8-oxo-2´- deoxyguanosine (8-oxo-dG) with
HPLC-MS/MS.
3. Are ‚Dioxins‘
genotoxic?
![Page 48: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/48.jpg)
Schrenk 2010
10
20
30
0
oxo8 G
per
106
dG(m
ean
±S.
D.)
control
(DMSO)
TCDD (1 nM)
oxo8G per 106
dG
and H2
DCFDA assay
in rat hepatocytes
in primary
culture*significantly
higher
than
control
(p<0.01)
3. Are ‚Dioxins‘
genotoxic?
200
600
0
400
800
rela
tive
fluor
esce
nce
(%)
**
![Page 49: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/49.jpg)
Schrenk 2010
10
20
30
0
oxo8 G
per
106
dG(m
ean
±S.
D.)
control
(DMSO)
TCDD (1 nM)
oxo8G per 106
dG
and H2
DCFDA assay
in Hep
G2 cells*significantly
higher
than
control
(p<0.01)
3. Are ‚Dioxins‘
genotoxic?
200
600
0
400
800
rela
tive
fluor
esce
nce
(%)
![Page 50: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/50.jpg)
0
50000
1E+05
2E+05
2E+05
3E+05
3E+05
200
600
0
400
800
ERO
D a
ctiv
ity(p
mol
/min
x m
g pr
otei
n)
1000
3. Are ‚Dioxins‘
genotoxic?
Hep
G2 cells
rat hepatocytes
EROD actvity
and immuno-reactive
CYP1A1 in Hep
G2 cells
and rat hepatoytes
after
treatment
with
1 nM
TCDD
Schrenk 2010
![Page 51: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/51.jpg)
Schrenk 2010
3. Are ‚Dioxins‘
genotoxic?
in-vivo: transgenic
mouse
model
(Andersson et al. 2001)
: constitutively
active
Ah-receptor
(CA-AHR):
deletion
of amino
acids
230–421 encompassing
the
minimal PAS B motif
generation of an activated
form of the
receptor
stimulates
transcription
in the absence
of ligand
schematic
representation
of the
structural
motifs
within
the
full-length
mouse
dioxin
receptor
(AHR) and the
dioxin
receptor
deletion
mutant
(CA-
AHR); (McGuire et al. 2001)
mAhR
CA-AhR
![Page 52: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/52.jpg)
3. Are ‚Dioxins‘
genotoxic?
EROD activity
in microsomes
from
wildtype
C57Bl6 mice
and CA-AHR mice
Schrenk 2010
0
50
100
150
200
250
300
350
400
vehicle control TCDD wild type CA-AhR
ER
OD
(pm
ol/m
in*m
g)
![Page 53: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/53.jpg)
3. Are ‚Dioxins‘
genotoxic?
8-oxo-dG in hepatic
DNA from
wildtype
C57Bl6 mice
and CA-AHR mice
Schrenk 2010
0
50
100
150
200
250
300
350
400
vehiclecontrol
TCDD wild type CA-AhR
8-ox
o-dG
(%)
n = 10n = 8n = 6n = 6
** unpaired t-test, one-tail p
value
![Page 54: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/54.jpg)
3. Are ‚Dioxins‘
genotoxic?
Schrenk 2010
0
50
100
150
200
250
Control TCDD 1nM E2 100nM TCDD 1nM + E2100nM
DC
F [%
of c
ontr
ol]
HepG2H4IIEHepa1
n ≥ 3*
**
*
0
50
100
150
200
250
Control TCDD 1nM E2 100nM TCDD 1nM + E2100nM
DC
F (%
of c
ontr
ol)
female-derived
male-derivedn ≥ 3
*
**
**
*
**
Effects of 1 nM
TCDD and 100 nM
17--estradiol on the formation of ROS, measured as increase in oxidized DCF in HepG2, H4IIE, and Hepa1 cells (left diagram) and in male-
and female-derived rat primary hepatocytes
(right diagram). Cells were incubated for a period of 48 h. Both TCDD and estradiol
were dissolved in DMSO. Controls represent cells treated with DMSO 0.5 % final concentration. Bars represent means ±
SD from n ≥
3 independent experiments; the asterisk indicates a significant
difference from the control. (paired t-test,; one tailed p value, *p≤
0,05, **p≤
0,001). E2, 17--estradiol; DMSO, Dimethylsulfoxide.
![Page 55: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/55.jpg)
3. Are ‚Dioxins‘
genotoxic?
Schrenk 2010
0
20
40
60
80
100
120
140
160
180
Medium DMSO E2 100nM TCDD 1nM TCDD 1nM +E2 100nM
ERO
D a
ctiv
ity (p
mol
/min
*mg)
female-derivedmale-derived
**
**
*
*n = 3
Effects of 1 nM
TCDD and 100 nM
E2 on EROD activity in male-
and female-derived rat primary hepatocytes. Cells were incubated for a period of 48 h. Both TCDD and Estradiol
were dissolved in DMSO. Bars represent means ±
SD from n = 3 independent experiments; the asterisk indicates a significant difference from the DMSO control.
![Page 56: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/56.jpg)
3. Are ‚Dioxins‘
genotoxic?
Schrenk 2010
0
0,5
1
1,5
2
2,5
3
3,5
4
4,5
rat CYP1A1 rat CYP1A2 human CYP1A1 human CYP1A2 human CYP1B1 control supersomes
DCF
form
ation
[pm
ol/m
in*pm
ol P4
50]
0
10
20
30
40
50
60
P450
redu
ctas
e ac
tivity
[nm
ol/m
in*pm
ol P4
50]
.
no compound added DMSO TCDD
B[a]P 8-MOP 8-MOP + TCDD
E2 E2 + TCDD P450 reductase activity
n = 3
Effects of adding test compounds (1 nM
TCDD, 10 μM B[a]P, 100 μM 8-MOP, 100 nM
estradiol
(E2) or 0.5 % (v/v) DMSO) to SupersomesTM
on the formation of ROS, measured as increase in oxidized DCF (bars). The curve shows cytochrome
P450 reductase
activities of individual Supersomes.
![Page 57: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/57.jpg)
Schrenk 2010
1.
Introduction
2.
‚Dioxins‘
as tumor
promoters
3.
are
‚Dioxins‘
genotoxic?
4.
what
about
non-dioxinlike
PCBs?
5.
Summary
![Page 58: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/58.jpg)
Schrenk 2010
What
about
NDL-PCBs?
ATHONAssessing
the
Toxicity
and Hazard
of Non-dioxin-like
PCBs
Present
in Food
![Page 59: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/59.jpg)
Schrenk 2010
Cl
3,3‘,4,4‘,5-Pentachlorobiphenyl (PCB 126)Cl
Cl
ClClCl
Cl
3‘2‘4‘
5‘6‘654
3 21 1‘Cl Cl Cl
Cl
2,2‘,4,4‘,5,5‘-Hexachlorobiphenyl (PCB 153)
Cl
Cl
ClCl3‘2‘
4‘5‘6‘65
43 2
1 1‘Cl
Cl
a ‚non
-
dioxinlike‘
PCB congener:
ClCl
ClCl
Cl
a ‚dioxinlike‘
PCB congener:
4. What
about
NDL-PCBs?
![Page 60: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/60.jpg)
Schrenk 2010
-0.5 0.0 0.5 1.0 1.5 2.0 2.5
0
10
20
30
40
50
60To
tal a
nim
als
with
neop
lasm
s(%
)
lg Dose (ng TEq/kg b.w. x day)
Aroclors
[Mayes
et al., 1998]TCDD [Kociba
et al., 1976]
Liver
neoplasms
in female
rats
treated
with
TCDD or
Aroclors
TEq
are
carcinogenic
in the
liver
of female
rats
4. What
about
NDL-PCBs?
![Page 61: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/61.jpg)
Schrenk 2010
1.
Introduction
2.
‚Dioxins‘
as tumor
promoters
3.
are
‚Dioxins‘
genotoxic?
4.
what
about
non-dioxinlike
PCBs?
5.
Summary
![Page 62: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/62.jpg)
Schrenk 2010
Summary
I
•The carcinogenicity of TCDD in rat liver is due (in part) to tumor promotion. Suppression of apoptosis seems to play a key role in this effect. A possible mechanism of suppression of apoptosis in irradiated rat hepatoyctes
in culture involves
suppression of the p53 response and a concomitant hyper- phosphorylation
of p53 (and other targets?)
•TCDD inhibits UV-induced apoptosis in a caspase-independent (!) manner
•TCDD-mediated suppression of apoptosis requires AhR activation and protein biosynthesis
![Page 63: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/63.jpg)
Schrenk 2010
Summary
II •In rodent liver TCDD can lead to increased oxidative DNA damage measured as 8-
oxo-dG. In rats the latter effect is strongly estrogen-dependent.
•In rat hepatocytes
in primary culture TCDD enhances formation of ROS and 8-oxo- DG. In human HepG2 cells this effect is not
observed, which is in accordance with the much lower level of CYP1A1 induction.
•In transgenic mice bearing a constitutively active AHR, hepatic 8-oxo-dG levels were significantly higher than in wildtype
C57Bl6 mice, whereas EROD activity was not markedly increased (!).
•
In hepatoma
cell lines and rat hepatocytes
estradiol
did not significantly enhance TCDD-induced ROS formation. However, in rat hepatocytes
estradiol
only increased ROS formation significantly.
•In Supersomes, human CYP1A1 was the most effective source of ROS. Addition of estradiol
reduced ROS formation.
![Page 64: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/64.jpg)
Schrenk 2010
•In rats, the carcinogenicity of techniocal
PCB mixtures is mainly, if not exclusively, due to DL-
compounds. •In mice, treatment with highly purified
PCBs 52,
101, 138, 153, and 180 induced CYP2B mRNAs indicating CAR activation ‘signature’, while PCB 28 did not. PCB 138 only (besides the DL-PCB 126) also seems to induce AhR-regulated CYP1A1.•In summary, PCBs 52 and 180 also have no DL properties in rats. PCB 138 is a ‘mixed’
DL/NDL-PCB
while PCB 28 is none of both in the mouse.
Summary
III
![Page 65: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/65.jpg)
Schrenk 2010
Acknowledgment
EU (6. FP)Deutsche ForschungsgemeinschaftFederal Ministry of Education and ResearchStates of Rheinland-Pfalz
Food Chemistry
& Toxicology, University of Kaiserslautern:Martin ChopraAndreas KamyschnikowMaike GährsManuela GöttelMonika GroßStefanie KnerrRobert RoosHans-Joachim Schmitz
Institute of Toxicology
University of Würzburg:Barbara MallyWolfgang Dekant
Karolinska
Institute, Molecular Medicine, Stockholm
Lorenz PoellingerPatrick Andersson
Athon
Partners:Patrik de Boover, VITO, Mol, BelgiumMatti Viluksela, University of Kuopio, FinlandLeo van der Ven, RIVM, Bilthoven, The
Netherlands
![Page 66: Dieter Schrenk Lebensmittelchemie und Toxikologie ......•2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been classified as a group I carcinogen by IARC • TCDD exerts most (if not](https://reader030.fdocuments.net/reader030/viewer/2022040717/5e23729c517877685014ed97/html5/thumbnails/66.jpg)
Schrenk 2010
Thank
you
for
your
attention!