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Toxicological information

Skin sensitisation

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Administrative data

Endpoint:
skin sensitisation: in vitro
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
2 May - 8 Jul 2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2016
Report date:
2016

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
other: Draft OECD Guideline 442E (In Vitro Skin Sensitisation: human Cell Line Activation Test)
Version / remarks:
December 2015
Deviations:
yes
Remarks:
cytotoxicity measurement and estimation of the CV75 value was performed by XTT test instead of flow cytometry
GLP compliance:
yes (incl. QA statement)
Remarks:
Hess. Ministerium für Umwelt, Klimaschutz, Landwirtschaft und Verbraucherschutz, Wiesbaden, Germany
Type of study:
activation of dendritic cells

Test material

Constituent 1
Chemical structure
Reference substance name:
Hex-3-en-1-yl acetate
EC Number:
911-593-9
Molecular formula:
C8H14O2
IUPAC Name:
Hex-3-en-1-yl acetate

In vitro test system

Details on the study design:
TEST CELL LINE
- Strain: THP-1 cells (human monocytic leukemia cell line)
- Source: American Type Culture Collection
- Passage number: 24 (XTT test); 8, 10 and 14 (h-CLAT)

CELL CULTURE CONDITIONS
- Type and identity of media: RPMI-1640 supplemented with 10% (v/v) FBS, 100 U/mL penicillin, 100 µg/mL streptomycin, 0.05 mM 2-mercaptoethanol, 4.5 g/L glucose, 1% (v/v) pyruvate and 1% (v/v) L-glutamine
- Temperature (°C): 37 ± 1.5
- CO2 (%): 5.0 ± 0.5

DOSE FINDING ASSAY BY CYTOTOXICITY MEASUREMENT (XTT TEST)
The doses investigated in the main experiment (h-CLAT) were determined with a XTT test. The XTT test is a method to investigate the cytotoxicity of a test substance. The test is based on the cleavage of the yellow tetrazolium salt, sodium 3'-(1-phenylaminocarbonyl)-(3,4 - tetrazolium)-bis-(4–methoxy-6-nitro)-benzenesulfonic acid hydrate (XTT), to form an orange water soluble formazan dye by dehydrogenase activity in active mitochondria. Two independent cytotoxicity experiments were performed with different cell cultures and on different days to obtain a reliable concentration showing 75% cell viability (CV75).

CONTROLS
Negative control
- Substance: culture medium
Vehicle control
- Substance: dimethyl sulfoxide (DMSO)
- Concentration: 0.2 - 0.5%

EXPOSURE CONDITIONS
- Exposure duration: 24 ± 1 h

TEST CONCENTRATIONS
- Justification for top dose: The test substance was soluble in DMSO up to and including 1000 µg/mL, as tested by a solubility test.
7.81, 15.63, 31.25, 62.5, 125, 250, 500 and 1000 µg/mL

NUMBER OF REPLICATIONS: quadruplicates per concentration in two independent experiments

MEASUREMENT
- Device: microplate reader (Versamax Molecular Devices)
- Wavelength: 450 nm
- Reference wavelength: 690 nm

EVALUATION CRITERIA
A decrease in number of living cells results in a decrease in the overall activity of mitochondrial dehydrogenases in the sample. This decrease directly correlates to the amount of orange formazan formed, as monitored by the absorbance. The relative absorbance as compared to the solvent control is calculated using the formula:
Relative absorbance = 100 x [(mean absorbance test substance) - (absorbance blank)] / [(mean absorbance vehicle control) - (absorbance blank)]

To calculate the concentration of test substance needed to reduce the relative absorbance to 75% of the vehicle control (CV75) the following formula is used:
CV75 = Conc. > 75 - ([(Conc. > 75) - (Conc. < 75)] x [(% > 75) - 75] / [(% > 75) - (% < 75)])
a) Conc. > 75: max. measured concentration with the % of vehicle control > 75%
b) Conc. < 75: min. measured concentration with the % of vehicle control < 75%
c) % > 75: relative absorbance at a) in %
d) % < 75: relative absorbance at b) in %

ACCEPTANCE CRITERIA
The XTT test is considered to be acceptable if it meets the following criteria:
- mean absorbance of the negative control is ≥ 0.5
- mean viability of the vehicle control is ≥ 70%


h-CLAT (main study)
The h-CLAT method is an in vitro method which quantifies changes of cell surface marker expression (CD86 and CD54) on a human cell line, THP-1 cells, following 24 h exposure to the test substance. The changes of surface marker expression are measured by flow cytometry following cell staining with fluorescein isothiocyanate (FITC)-labelled antibodies. The relative fluorescence intensity of surface markers compared to vehicle control are calculated and used in the prediction model to support the discrimination between sensitisers and non-sensitisers.

CONTROLS
Negative control
- Substance: culture medium
Vehicle control
- Substance: dimethyl sulfoxide (DMSO)
- Concentration: 0.2%
Positive control
- Substance: 2,4-dinitrochlorobenzene (DNCB) in DMSO
- Concentration: 2 and 3 µg/mL

EXPOSURE CONDITIONS
- Exposure duration: 24 ± 1 h

TEST CONCENTRATIONS
- Justification for top dose: Since a CV75 value could not be determined in the XTT test, the highest soluble test substance concentration was used as highest concentration for the h-CLAT runs.
279.1, 334.9, 401.9, 482.3, 578.7, 694.4, 833.3 and 1000 µg/mL

NUMBER OF REPLICATIONS: at least in triplicates for the different stainings in two independent experiments

STAINING
- Antibodies: FITC anti-CD54 (Clone: Fun-1); FITC anti-CD86 (Clone: 6.5B5); FITC mouse IgG1 (isotype control)
- Temperature: 2 - 8 °C
- Duration: 30 ± 5 min

MEASUREMENT
- Device: flow cytometer FACSCalibur (Becton Dickinson)

EVALUATION CRITERIA
The relative fluorescence intensity (RFI) is used as an indicator of CD86 and CD54 expression, and is calculated as follows for each concentration:
RFI (%) = [(MFI of test substance treated cells) - (MFI of test substance treated isotype control cells) / (MFI of vehicle control cells) - (MFI of vehicle isotype control cells)] x 100
MFI: geometric mean fluorescence intensity (GeoMean)

The cell viability is calculated as follows for each concentration:
Cell viability (%) = (mean cytotox of vehicle control cells) / (mean cytotox of test substance treated cells) x 100
Where the mean cytotox is the mean of GeoMean (7-AAD) isotype control, GeoMean (7-AAD) CD54 and GeoMean (7-AAD) CD86.

The test substance is tested in 2 independent runs. If the RFI of CD86 is ≥ 150% or if the RFI of CD54 is ≥ 200% in both independent run data, the test substance is considered to be a sensitizer. Otherwise it is considered to be a non-sensitizer. In case of different results in both runs, a third run has to be performed. If the RFI of CD86 is ≥ 150% at any dose in at least 2 of 3 independent run data, or if the RFI of CD54 is ≥ 200% in at least 2 of 3 independent run data, the test substance is considered to be a sensitizer. Otherwise it is considered to be a non-sensitizer.

ACCEPTANCE CRITERIA
The study is considered as valid, if the following criteria are met:
- Cell viability of negative control is adjusted to 100% and the cell viability of the vehicle control should be more than 90% in comparison to the negative control.
- In the positive control, RFI values of both CD86 and CD54 should exceed the positive criteria (CD86 ≥ 150% and CD54 ≥ 200%) and the cell viability should be > 50%.
- In the vehicle control, RFI values compared to the negative control of both CD86 and CD54 should not exceed the positive criteria (CD86 ≥ 150% and CD54 ≥ 200%).
- For negative and vehicle controls, the MFI ratio of CD86 and CD54 to isotype control should be > 105%.
- For the test substance resulting in negative outcome, the cell viability at the 1.2 × CV75 value should be less than 90%. If the cell viability at the 1.2 × CV75 value is more than 90% for a positive tested test substance, the data will be acceptable. If 5 mg/mL in saline, 1 mg/mL in DMSO or the highest soluble dose will be used as the maximal test concentration instead of CV75-based dose, the data for test substance are accepted independent by the cell viability.
- The cell viability of at least 4 doses in each experiment should be ≥50%.

Results and discussion

In vitro / in chemico

Resultsopen allclose all
Key result
Run / experiment:
other: 24 h incubation
Parameter:
other: relative fluorescence intensity of CD54 (%)
Value:
200
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
other: in 2 out of 3 independent runs
Key result
Run / experiment:
other: 24 h incubation
Parameter:
other: relative fluorescence intensity of CD86 (%)
Value:
150
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
other: in 1 out of 3 independent runs
Other effects / acceptance of results:
ADDITIONAL INFORMATION ON CYTOTOXICITY:
XTT test
Cytotoxic effects were not observed following incubation with the test substance up to the highest soluble concentration (1000 µg/mL). The viability of the cells spaced within a range of 75.1 to 98.72% in the first experiment and within a range of 85.16 to 96.75% in the second experiment (threshold of cytotoxicity: < 75%). Due to the lack of cytotoxicity, a CV75 value could not be calculated.
h-CLAT
The cell viability was not negatively affected (viability > 92%) in the 3 independent experiments.

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for vehicle control: In the vehicle control, RFI values compared to the negative control of both CD86 and CD54 did not exceed the positive criteria (CD86 ≥150% and CD54 ≥200%).
- Acceptance criteria met for positive control: The RFI values of the positive control for CD86 and CD54 exceeded the positive criteria (CD86 >150% and CD54 >200%) and the cell viability was >50%.

Any other information on results incl. tables

Table 1: Results of the first XTT test

 

Concentration [µg/mL]

Mean absorbance*

Blank

Absorbance in % of vehicle control**

Medium control

-

0.872 ± 0.029

0.273

81.46

Vehicle control

-

1.021 ± 0.053

0.286

100.00

Test substance

7.81

0.885 ± 0.083

0.281

82.10

15.63

0.922 ±0.033

0.292

85.63

31.25

0.933 ± 0.075

0.298

86.34

62.5

1.031 ± 0.058

0.305

98.72

125

0.887 ± .0450

0.301

79.59

250

0.927 ± 0.027

0.307

84.29

500

0.870 ± 0.066

0.317

75.10

1000

0.937 ± 0.094

0.324

83.39

*: mean absorbance (absolute) of 4 wells

**: relative absorbance

 

Table 2: Results of the second XTT test

 

Concentration [µg/mL]

Mean absorbance*

Blank

Absorbance in % of vehicle control**

Medium control

-

0.958 ± 0.023

0.317

109.86

Vehicle control

-

0.917 ± 0.080

0.333

100.00

Test substance

7.81

0.885 ± 0.062

0.320

96.75

15.63

0.856 ± 0.056

0.317

92.33

31.25

0.822 ± 0.090

0.325

85.16

62.5

0.824 ± 0.037

0.321

86.05

125

0.866 ± 0.031

0.325

92.56

250

0.837 ± 0.065

0.331

86.70

500

0.854 ± 0.025

0.330

89.83

1000

0.873 ± 0.036

0.333

92.60

*: mean absorbance (absolute) of 4 wells

**: relative absorbance

 

Table 3. Results of the first h-CLAT run

 

Concentration [µg/mL]

Antibody / ISO

MFI GeoMean (FITC)

MFI - ISO

Csto(Geo) GeoMean (7-AAD)

Mean Cyto

RFI (%)

Viability (%)

Medium control

-

ISO

2.23

-

2.16

2.0

-

100.0

CD54

2.98

0.75

1.98

100.0

CD86

3.72

1.49

1.82

100.0

Vehicle control

-

ISO

2.29

-

2.08

2.0

-

100.0

CD54

3.08

0.79

1.95

100

CD86

3.44

1.15

1.86

100

Positive control

2

ISO

2.67

-

2.45

2.1

-

94.1

CD54

6.09

3.42

1.89

432.9*

CD86

6.16

3.49

1.92

303.5*

3

ISO

2.46

-

2.49

2.2

-

89.9

CD54

10.00

7.54

2.12

954.4*

CD86

10.65

8.19

1.94

712.2*

Test substance

279.1

ISO

2.27

-

2.27

2.1

-

93.8

CD54

3.27

1.00

2.09

126.6

CD86

3.85

1.58

1.92

137.4

334.9

ISO

2.33

-

2.29

2.1

-

94.2

CD54

3.24

0.91

2.02

115.2

CD86

3.47

1.14

1.94

99.1

401.9

ISO

2.31

-

2.25

2.1

-

94.7

CD54

3.12

0.81

2.02

102.5

CD86

3.50

1.19

1.95

103.5

482.3

ISO

2.41

-

2.20

1.9

-

102.1

CD54

3.51

1.10

1.94

139.2

CD86

4.98

2.57

1.63

223.5*

578.7

ISO

2.32

-

2.19

1.9

-

102.3

CD54

3.40

1.08

1.91

136.7

CD86

4.43

2.11

1.66

183.5*

694.4

ISO

2.31

-

2.16

1.9

-

101.0

CD54

3.51

1.20

1.91

151.9

CD86

4.16

1.85

1.76

160.9*

833.3

ISO

2.37

-

2.26

2.0

-

97.2

CD54

3.57

1.20

2.00

151.9

CD86

4.08

1.71

1.80

148.7

1000

ISO

2.40

-

2.39

2.1

-

94.1

CD54

3.69

1.29

2.05

163.3

CD86

4.27

1.87

1.82

162.6*

*: RFI value of CD86 or CD54 exceeded the criteria for a positive response (CD86 ≥ 150% and CD54 ≥ 200%).

 

Table 4. Results of the second h-CLAT run

 

Concentration [µg/mL]

Antibody / ISO

MFI GeoMean (FITC)

MFI - ISO

Csto(Geo) GeoMean (7-AAD)

Mean Cyto

RFI (%)

Viability (%)

Medium control

-

ISO

2.51

-

2.35

2.1

-

100.0

CD54

3.16

0.65

2.00

100.0

CD86

4.37

1.86

1.94

100.0

Vehicle control

-

ISO

2.35

-

2.26

2.0

-

100.0

CD54

3.17

0.82

2.06

100.0

CD86

4.32

1.97

1.82

100.0

Positive control

2

ISO

2.73

-

2.61

2.0

-

104.6

CD54

9.45

6.72

1.74

819.5*

CD86

12.57

9.84

1.52

499.5*

3

ISO

2.67

-

2.88

2.1

-

98.7

CD54

11.36

8.69

1.77

1059.8*

CD86

13.66

10.99

1.57

557.9*

Test substance

279.1

ISO

2.49

-

2.50

2.2

-

92.6

CD54

3.56

1.07

2.17

130.5

CD86

4.90

2.41

1.96

122.3

334.9

ISO

2.47

-

2.17

2.0

-

105.0

CD54

3.38

0.91

1.96

111.0

CD86

4.77

2.30

1.72

116.80

401.9

ISO

2.45

-

2.23

2.0

-

102.7

CD54

3.54

1.09

1.99

132.9

CD86

4.55

2.10

1.76

106.6

482.3

ISO

2.41

-

2.34

2.1

-

96.8

CD54

3.57

1.16

2.09

141.5

CD86

4.48

2.07

1.91

105.1

578.7

ISO

2.43

-

2.44

2.2

-

94.2

CD54

3.67

1.24

2.15

151.2

CD86

5.12

2.69

1.93

136.5

694.4

ISO

2.48

-

2.28

2.0

-

102.2

CD54

3.84

1.36

1.98

165.9

CD86

4.99

2.51

1.75

127.4

833.3

ISO

2.42

-

2.30

2.0

-

100.0

CD54

3.72

1.30

2.00

158.5

CD86

4.89

2.47

1.84

125.4

1000

ISO

2.45

-

2.39

2.1

-

97.9

CD54

4.16

1.71

1.99

208.5*

CD86

5.09

2.64

1.89

134.0

*: RFI value of CD86 or CD54 exceeded the criteria for a positive response (CD86 ≥150% and CD54 ≥200%).

 

Table 5. Results of the third h-CLAT run

 

Concentration [µg/mL]

Antibody / ISO

MFI GeoMean (FITC)

MFI - ISO

Csto(Geo) GeoMean (7-AAD)

Mean Cyto

RFI (%)

Viability (%)

Medium control

-

ISO

2.26

-

2.80

2.5

-

100.0

CD54

2.98

0.72

2.59

100.0

CD86

4.46

2.20

2.18

100.0

Vehicle control

-

ISO

2.69

-

3.38

2.5

-

101.3

CD54

10.72

8.03

2.04

1115.3*

CD86

10.71

8.02

2.05

364.5*

Positive control

2

ISO

2.60

-

3.58

2.5

-

100.7

CD54

12.91

10.31

1.97

1431.9*

CD86

11.43

8.83

1.97

401.40*

3

ISO

2.30

-

2.87

2.5

-

101.1

CD54

3.43

1.13

2.47

156.9

CD86

4.36

2.06

2.15

93.60

Test substance

279.1

ISO

2.30

-

2.74

2.4

-

105.9

CD54

3.24

0.94

2.35

130.6

CD86

4.24

1.94

2.06

88.20

334.9

ISO

2.30

-

2.74

2.4

-

105.1

CD54

3.23

0.93

2.41

129.2

CD86

4.47

2.17

2.05

98.6

401.9

ISO

2.25

-

2.64

2.3

-

110.5

CD54

3.47

1.22

2.30

169.4

CD86

4.75

2.50

1.91

113.6

482.3

ISO

2.23

-

2.60

2.2

-

112.6

CD54

3.29

1.06

2.28

147.2

CD86

4.92

2.69

1.84

122.3

578.7

ISO

2.27

-

2.54

2.2

-

114.0

CD54

3.34

1.07

2.20

148.6

CD86

4.47

2.20

1.90

100.0

694.4

ISO

2.39

-

2.60

2.3

-

109.6

CD54

3.33

0.94

2.29

130.6

CD86

4.12

1.73

2.02

78.6

833.3

ISO

2.24

-

2.95

2.5

-

100.5

CD54

3.78

1.54

2.46

213.9*

CD86

5.08

2.84

2.12

129.1

1000

ISO

2.26

-

2.80

2.5

-

100.0

CD54

2.98

0.72

2.59

100.0

CD86

4.46

2.20

2.18

100.0

*: RFI value of CD86 or CD54 exceeded the criteria for a positive response (CD86 ≥150% and CD54 ≥200%).

The RFI of CD86 was greater than 150% in at least one concentration in only 1 out of 3 independent runs. Furthermore, the RFI of CD54 was greater than 200% in one concentration (1000 µg/mL) in 2 out of 3 independent runs. Therefore, the test substance is considered to be a sensitizer.

Applicant's summary and conclusion

Interpretation of results:
other: activation of dendritic cells positive according to OECD 442E
Conclusions:
Under the conditions of the Human Cell Line Activation Test the test substance increased the expression of CD54, a cell surface marker associated with the process of activation of monocytes and dendritic cells. Based on this result, the h-CLAT prediction is considered positive for skin sensitisation.
Executive summary:

Dendritic cell response of the test substance was investigated ina Human Cell Line Activation Test according to OECD Guideline 442E and in compliance with GLP (2016). The test substance increased the expression ofthe cell surface markerCD54to more than 200% in one concentration (1000 µg/mL) in 2 out of 3 independent runs.Thus, the h-CLAT predictionfor activation of dendritic cellsis considered positive.

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