Transcript QSAR-based Prediction of Inhalation Toxicity

QSAR-based Prediction of
Inhalation Toxicity
Incorporating elements of dosimetry and
reactivity to predict biological response
Kendall B. Wallace, Eli Petkova, Gilman D. Veith
University of Minnesota – Duluth Medical School &
International QSAR Foundation
Human
Airway
Chemical disposition
(free vapor)• VP
• SolH2O
• Chemical Reactivity
Biological Response • Protein adduct immune surveillance
 Asthma, T-cell
mediated
hypersensitivity
 Irritation/inflammation
/tissue necrosis
Factors affecting pulmonary response
Chem Name
Water
Solubility
Chemical
Reactivity
Pulmonary
Toxicity
Acetaldehyde
High
Moderate
Upper airways
Ammonia
High
High
Upper airways
Chlorine
Moderate
High
Large and
intermediate
airways
Phosgene
Isocyanates
Low
High
Lower
terminal
airways
Carbon
monoxide
Low
Low
none
The QSAR Inhalation Toxicity Database
 Although inhalation toxicity data have been
compiled in selected open access databases, the
entries are limited and have seldom been subjected
to rigorous peer review.
 Thus, although these databases may suffice for
general reference purposes, the data is frequently
ambiguous and of questionable quality.
 As a result, models of inhalation toxicity derived
from these databases have largely been unsuccessful
and doubts have been cast regarding the validity of
QSAR approaches to inhalation toxicology.
The Inhalation Toxicity Database
The inhalation toxicity database (ITDB) is an
effort to compile high quality inhalation data
published in the open literature and government
reports as well as publicly available unpublished
toxicity reports using strict Q/A standards.
ITDB has a goal of eventually becoming an
international and widely distributed resource for
high quality inhalation toxicity data that can be
used to better characterize inhalation toxicity
with minimal animal testing.
Current Status of the ITDB
 We have embarked on compiling an exhaustive mammalian
inhalation toxicity database using strict standards of peer
review to insure only high-quality studies are included.
 Currently focus on acute (4 hr) inhalation by rats
 About 200 unique chemicals, 86 – tested for acute toxicity in rat/4h
 Limited short-term mouse data
 Expanding to include other species as well as repeat exposure and
chronic inhalation data
 Preliminary analyses of the database.……….
Modeling Assumptions
• Obstructive disorders
– Low vapor pressure
– High water solubility
– High chemical reactivity
• Restrictive disorders
– Low vapor pressure
– Low water solubility
– High chemical reactivity
• MoA - specific disease
• Non-specific, narcotic-like effects
– Low vapor pressure
– Low water solubility
– Low chemical reactivity
5
LC50/rat/4h vs Vapor Pressure
4
Data was compiled from the
literature.
LC50, mmol/m3
3
•From mid 50s to present *
•All chemicals tested as vapors **
LC50,mmol/m3
2
•Consistent exposure conditions ***
•Different rat strains
1
0
-2
-1
0
1
2
3
4
* Guidelines somewhat vary with time
-1
**Specified (aimed ) in the experiment
but sometimes might not be truth
-2
***Exposure time constant, number of
animals and observation periods vary
Vapor Pressure, mmHg
Vapor Pressure,
mmHg
5
y = 0.705x + 1.4719
R2 = 0.9277
LC50 /rat/4h vs Vapor
Pressure for chemicals
previously classified as
4
NON-REACTIVE
LC50, mmol
/ m3
LC50,
mmol/m3
3
2
1
0
-2
-1
0
1
-1
-2
VapormmHg
pressure, mmHg
Vapor Pressure,
2
3
4
5
HYDROCARBONS are a good
examples for narcosis
4
LC50, mmol / m3
LC50,
mmol/m3
3
Nonane, hexane, isoprene,
butadiene, isobutylene,
butane, 2-metylpentene-1,
2-metylpentene-2, styrene
2
1
0
-2
-1
0
1
-1
-2
Vapor pressure,
mmHg
Vapor Pressure,
mmHg
2
3
4
5
No similar relationship of
LC50/VP for NITRITES
4
/ m3
LC50, mmol
LC50,
mmol/m3
3
2
1
0
-2
-1
0
1
2
-1
-2
Vapor pressure, mmHg
Vapor Pressure, mmHg
3
4
5
LC50/VP relationship
4
for AMINES
LC50, mmolmmol/m3
/ m3
LC50,
3
2
Allylamine, CAS 107-11-9
1
0
-2
-1
0
1
2
-1
-2
Vapor pressure, mmHg
Vapor Pressure, mmHg
3
4
5
4
ACRYLATES &
METHACRYLATES
LC50, mmolmmol/m3
/ m3
LC50,
3
2
1
0
-2
-1
0
1
2
-1
-2
Vapor pressure, mmHg
Vapor Pressure, mmHg
3
4
For ACRYLATES & METHACRYLATES there is no relationship
with Vapor Pressure but significant correlation with GSH
reactivity
4
2.5
mmol/m3
LC50,
LogLC50,
mmol/m3
3.0
3
LC50, mmol / m3
LC50, mmol/m3
-2
5
2
2.0
1.5
1.0
1
0.5
0
0.0
-1
0
1
2
3
4
LogLC50 = 0.28logEC50 + 2.01
R2 = 0.91
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Log EC50,mM
EC50,
mM
-1
-2
Vapor pressure, mmHg
Vapor Pressure, mmHg
LC50 vs GSH reactivity
for acrylates and methacrylates
2.5
0
-1
0
1
2
Solubility in Air / LC50
-1
-2
-3
-4
-5
-6
Vapor Pressure, mmHg
3
4
Solubility in air and
Lethal Concentration
vs Vapor Pressure
for narcotics (rat/4h)
0
Sol Air
LC50,
mol/l
/ LC50
Air
in &
Solubility
-0.5
0
0.5
1
1.5
2
2.5
3
-1
-1.5
-2
-2.5
-3
-3.5
Vapor
Pressure,
Vapor
Pressure,
mmHGmmHg
3.5
4
Solubility in air and
Lethal Concentration
vs Vapor Pressure
for ethers
(mouse//15 min)
Baseline Toxicity

Fish and mammal inhalation baseline toxicity are
not directly comparable because the external media
are different
 However, blood thermodynamic activity for
LC50(nar) is the same in fish and mammal
 At steady-state, the activity in air/water equals the
activity in blood by definition :
α=Сxγ
α – activity; C- concentration; γ-activity coefficient
Baseline Toxicity
 The thermodynamic activity at any concentration can
be estimated by dividing by the solubility in the
medium
 activity for narcosis in fish = LC50(fish)/water solubility
activity for narcosis in rat = LC50 (rat)/air solubility
 if activity for narcosis in fish and rat were equal, the
plot of LC50 versus solubility in exposure medium
should be the same
Solubility in Water or Air vs LC50 in Fish or Rat (combined)
Solubility in Water or Air vs LC50 in Fish or Rat
0
-5
-4
-3
-2
-1
0
1
LC50, mol/l
-1
-2
-3
LC50 fish vs Water
Solubility
-4LC50 rat vs Air
Solubility
-5
Solubility, mol/l
LC50rat vs LC50fish*Kh
LC50rat vs LC50fish*Kh
0
-5
-4
-3
-2
-1
0
-1
Log (LC50 fish*Kh)
-2
-3
-4
-5
-6
-7
-8
log LC50 rat
LogLC50 for fish or rat vs Solubility in water or air
LogLC50 for fish or rat vs Solubility in water or air
0
-6
-5
-4
-3
-2
-1
0
1
2
-1
LC50fish vs LogWsol
LC50, mol/l
-2
-3
-4
-5
-6
Solubility, mol/l
LC50rat vs LogAirsol
Linear (LC50fish vs
LogWsol)
y = 0.7847x - 1.6059
R2 = 0.889
Concentration response curves for all
mixture components
2.5 Endocrine active industrial chemicals:
Release and occurrence in the environment
Binding Assays
4,4'-sulfonyldiphenol
110
solubility limit
100
RBA %
90
Binding (%)
80
70
60
E2 rbtER (cyto)
SDP rbtER (cyto)
0.0020
E2 hER (recomb-LBD)
SDP hER (recomb-LBD)
0.0055
50
40
30
20
10
0
-10
-11
-10
-9
-8
-7
-6
-5
-4
-3
Log Concentration (M)
-2
-1
Binding Assays
ethylparaben
solubility limit
RBA %
90
E2 rbtER (cyto)
EP rbtER (cyto)
0.0008
80
E2 hER(recomb-LBD)
EP hER (recomb-LBD)
ND
70
60
50
40
30
20
10
TL
0
CR
Binding (%)
100
-10 -9 -8 -7 -6 -5 -4
Log Concentration (M)
-3
-2
Binding Assays
resorcinol sulfide
350
RBA %
100
E2 rbtER (cyto)
RES rbtER (cyto)
325
90
300
70
275
60
250
50
225
40
30
200
20
175
10
150
CR
TL
0
-10 -9 -8 -7 -6 -5 -4
Log Concentration (M)
-3
125
-2
E2 hER (recomb-full)FP
RES hER (recomb-full)FP 0.0098
Polarization (mp)
Binding (%)
80
0.00057
1.0×10 8
110
100
90
80
1.0×10 7
70
60
50
40
1.0×10 6
30
20
10
1.0×10 5
C
TR
L
0
AAN rbtER (cyto)
-10 -9
-8
-7
-6
-5
Log Concentration (M)
AAN rbt Vtg
Control rbt Vtg
-4
-3
-2
-1
VTG mRNA copies/400 ng total RNA
[3H]-E2 Binding (%)/Fecundity (% decrease)
4-n-Amylaniline
1.0×10 8
110
100
90
80
1.0×10 7
70
60
50
40
1.0×10 6
30
20
10
1.0×10 5
C
TR
L
0
AAN rbtER (cyto)
-10 -9
-8
-7
-6
-5
Log Concentration (M)
AAN rbt Vtg
Control rbt Vtg
-4
-3
-2
-1
VTG mRNA copies/400 ng total RNA
[3H]-E2 Binding (%)/Fecundity (% decrease)
4-n-Amylaniline
1.0×10 8
110
100
90
80
1.0×10 7
70
60
50
40
1.0×10 6
30
20
10
1.0×10 5
C
TR
L
0
AAN rbtER (cyto)
-10 -9
-8
-7
-6
-5
-4
Log Concentration (M)
AAN rbt Vtg
Control rbt Vtg
In vivo Water Exposure
Medaka Fecundity
-3
-2
-1
VTG mRNA copies/400 ng total RNA
[3H]-E2 Binding (%)/Fecundity (% decrease)
4-n-Amylaniline
1.0×10 8
110
100
90
80
1.0×10 7
70
60
50
40
1.0×10 6
30
20
10
1.0×10 5
C
TR
L
0
AAN rbtER (cyto)
VTG mRNA copies/400 ng total RNA
[3H]-E2 Binding (%)/Fecundity (% decrease)
4-n-Amylaniline
-10 -9
-8
-7
-6
-5
-4
Log Concentration (M)
AAN rbt Vtg
Control rbt Vtg
In vivo Water Exposure
Medaka Fecundity
-3
-2
-1
Predicted in vivo Liver
Steady State Concentration
Medaka Fecundity