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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:
27 November 2017 (Seeding of the cells, 1st experiment) - 08 March 2018 (Experimental completion date)
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2018
Report Date:
2018

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
other: OECD Guideline 442E (In Vitro Skin Sensitisation: human Cell Line Activation Test (h-CLAT))
GLP compliance:
yes (incl. certificate)
Type of study:
activation of dendritic cells
Justification for non-LLNA method:
The OECD TG 442 E may be used as part of an integrated approach to testing and assessment (IATA) to support the discrimination between skin sensitisers and non-sensitisers for the purpose of hazard classification and labelling.

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: particulate/powder

In vitro test system

Details on study design:
Cell line: THP-1 cells
The human monocytic leukemia cell line was obtained from “American Type Culture Collection, Manassas, USA” (ATCC, TIB202).

Results and discussion

Positive control results:
The positive control used was 1- chloro-2,4-dinitrobenzene (DNCB, CAS no.: 97-00-7), 4.0 µg/mL in 0.2% DMSO in culture medium. The positive and negative and vehicle control data is comparable to the historical data. The results can be seen in Table 2.

In vitro / in chemico

Resultsopen allclose all
Key result
Parameter:
other: Relative fluorescence intensity (RFI) %
Remarks:
RFI CD86
Run / experiment:
Experiment 1
Value:
< 150
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
other: Negative activation of dendritic cells according to OECD 442E at concentrations of 83-296 µg/mL
Remarks:
viability ≥ 50%
Key result
Parameter:
other: Relative fluorescence intensity (RFI) %
Remarks:
RFI CD54
Run / experiment:
Experiment 1
Value:
>= 150
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
other: Activation of dendritic cells positive according to OECD 442E at concentrations of 83-296 µg/mL.
Remarks:
viability ≥ 50%
Key result
Parameter:
other: Relative fluorescence intensity (RFI) %
Remarks:
RDI CD86
Run / experiment:
Experiment 3
Value:
< 150
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
other: Negative activation of dendritic cells according to OECD 442E at concentrations of 83-296 µg/mL
Remarks:
viability ≥ 50%
Key result
Parameter:
other: Relative fluorescence intensity (RFI) %
Remarks:
RFI CD54
Run / experiment:
Experiment 3
Value:
>= 200
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
other: Activation of dendritic cells positive according to OECD 442E at concentrations of 83-296 µg/mL
Remarks:
viability ≥ 50%
Other effects / acceptance of results:
DEMONSTRATION OF TECHNICAL PROFICIENCY:
Acceptance criteria
- A tested concentration is not to be further evaluated when relative viability is less than 50%.
- Cell viability of vehicle control cells must yield at least 90%.
- In the positive control (DNCB), RFI values of both CD86 and CD54 should be over the positive criteria (CD86≥ 150% and CD54 ≥ 200%) and cell viability should be ≥ 50%.
- In the negative control (LA), RFI values of both CD86 and CD54 should not exceed the positive criteria (RFI CD86< 150% and RFI CD54 < 200%) and cell viability should be ≥ 50%.
- For all vehicle controls, the MFI ratio of both CD86 and CD54 to isotype controls should be ≥ 105%.  
- The reactivity check of new thawed cells should produce the following result: - Positive response in CD86 and CD54 for NiSO4 and DNCB - Negative response in CD86 and CD54 for LA.
- In addition, positive, negative and vehicle control data should lie within the range of the historic data

Evaluation of results
- A test substance is predicted to activate monocytic THP-1 cells when CD86 expression is increased ≥ 150% and/or CD54 expression increased ≥ 200% at any concentration in relation to vehicle control that do not reduce viability below 50% and reproduced in the same cell surface marker in at least two independent experiments.
- A test substance is considered to be negative when the criteria mentioned above are not met up to the maximum concentration (= 5000 µg/mL for the vehicle culture medium or 1000 µg/mL for 0.2% DMSO in culture medium) or up to the cytotoxicity limit (viability less than 90% at the highest concentration tested).  
- To be relevant for evaluation, the cell viability must be more than 50% in at least four tested concentrations of an experiment.

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: Yes
- Acceptance criteria met for positive control: Yes
- Acceptance criteria met for variability between replicate measurements: Yes
- Range of historical values if different from the ones specified in the test guideline: Please refer to the historical control data in the 'Attached background material' section

Any other information on results incl. tables

Table 2: Summary of h-CLAT Main Experiments: mean values of RFI CD86, RFI CD54 and relative viability.

2 valid and evaluable experiments (4thand 5th) were performed. The 2ndexperiment was not evaluable due to technical error and is not included in the report.

4thexperiment

5thexperiment

Concentration (test substance)

 

[µg/mL)

RFI CD86

 

Mean

[%]

RFI CD54

 

Mean

[%]

Viability

 

Relative viability [%]

Concentration (test substance)

 

[µg/mL)

RFI CD86

 

Mean

 [%]

RFI CD54

 

Mean

[%]

Viability

 

Relative viability [%]

49

76

180

100

49

89

579

100

58

67

151

100

58

42

693

100

70

79

190

100

70

79

571

100

84

62

182

100

84

67

657

100

101

56

207

100

101

61

828

99

121

40

362

96

121

48

867

98

145

43

469

91

145

42

1599

92

174

38

725

85

174

37

1827

73

VC

100

100

100

VC

100

100

100

LA 1000 µg/mL

74

108

100

LA 1000 µg/mL

83

139

100

DNCB 4 µG/mL

303

1153

75

DNCB 4 µG/mL

275

496

85

RFI above 150% (CD86) or 200% (CD54) with relative viability ≥50% are indicated in bold.

VC: vehicle (culture medium); LA: lactic acid, negative control; DNCB: 1 -chloro-2, 4 -dinitrobenzene, positive control

None of the experiments met the ''borderline criteria'' and therefore the results were considered to be unambiguous.

Applicant's summary and conclusion

Interpretation of results:
other: positive prediction of skin sensitisation in h-CLAT assay
Conclusions:
Based on the observed results and applying the evaluation criteria in accordance with OECD Guideline 422 E, Acid Red 426 induces dendritic cell activation and is predicted to be a skin sensitiser.
Executive summary:

The skin sensitising potential of the test substance, Acid Red 426, was determined via the in vitro Human Cell Line Activation Test (h-CLAT) that evaluates that ability of Acid Red 426 to induce the expression of cell membrane markers (CD86 and CD54) and thus activate dendritic cells. The study was conducted following the OECD Guideline for Testing of Chemicals TG. 442E, adopted July 2016 (‘In vitro Skin Sensitisation: human Cell Line Activation Test (h-CLAT)’)

 

Main Assay

The test substance, Acid Red 426 was weighed and topped up with culture medium to achieve the required 2x concentration of the high concentration, Further concentrations were prepared as 2x concentrations by serial 1:1.2 dilution. The test substance was incubated with human monocytic leukemia cell line THP-1 for ca. 24 hours at 37°C and membrane marker expression (CD86 / CD54) was measured by flow cytometry. 

In order to determine the concentrations suitable for the main experiment, pre-tests (non-GLP) were performed. Cells were exposed to several concentrations of the test substance and cytotoxicity was determined thereafter by propidium iodide (PI) intercalation into the DNA. There was no cytotoxicity observed up tp the measurable and evaluable concentration of 296 µg/mL^2. Based on the maximum measurable and evaluable concentration, 296 µg/mL was chosen as the highest concentration. Additional concentrations were obtained by a 1:1.2 serial dilution series of the maximum concentration.

 

In the main test after 24-hour exposure THP-1 cells were stained with FITC labeled anti-humanCD86/ anti-human-CD54 antibody and propidium iodide and the fluorescence intensity was analyzed using flow cytometry. A total of 2 valid and evaluable experiments (1st and 3rd experiments) were performed. The 2nd experiment was not measured due to a technical error and was not included in the report. At concentrations used in the main experiment the test substance was not soluble in culture medium (2 x stock preparations and final concentrations) directly after application and after 24 hours.

The test substance was tested at a concentration range of 83 -296 µg/mL. In both the first and third experiment, a calculation of an EC150% (the concentration resulting in a RFI of 150%) for CD86 was not applicable. The calculation of an EC150% (the concentration resulting in a RFI of 150%) for CD86 was not applicable. The calculation of an EC200% (the concentration resulting in a RFI of 200%) was not applicable as fold inductions above 200% were obtained in all tested concentrations. Non eof the experiments met the ''borderline criteria'' and therefore the results were considered to be unambiguous.

 

In accordance with the evaluation of results, in the 1st experiment, Acid Red 426 induced CD86 expression < 150% with a relative viability of ≥ 50% at all concentrations tested. The test substance induced CD54 expression ≥ 200% at all concentrations tested (83 -296 µg/mL) with a relative viability of ≥ 99% at all concentrations tested. Similarly in the 3rd experiment, CD86 expression was <150% and CD54 expression was induced > 200%, both with a relative viability of ≥ 50%. This thus indicates that the test substance is predicted to activate monocytic THP-1 cells. The results are also relevant for evaluation, since the relative cell viability results are more than 90% in more than four of the test concentrations in the 1st and 3rd experiments.

 

The acceptance criteria were met in all experiments and the results for the positive, negative and vehicle controls are comparable with historic data.

 

Conclusion

Based on the observed results and taking into account the evaluation criteria, it can be concluded that after 24 hours of exposure to the test substance, Acid Red 426, CD86 and CD54 expression was induced in THP-1 cells with at least 50% viability in at least two independent experiments. Therefore, it can be concluded that Acid Red 426 induces dendritic cell activation and is predicted to be a skin sensitiser.