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Administrative data

Endpoint:
skin irritation: in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
May - June 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:
OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method)
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Chemical structure
Reference substance name:
Isopentyl salicylate
EC Number:
201-730-4
EC Name:
Isopentyl salicylate
Cas Number:
87-20-7
Molecular formula:
C12H16O3
IUPAC Name:
3-methylbutyl salicylate

In vitro test system

Test system:
human skin model
Source species:
human
Cell type:
non-transformed keratinocytes
Cell source:
other: EpiDerm TM tissues (Epi-200-SIT Kit)
Justification for test system used:
Dermal irritation is generally defined as "the production of reversible inflammatory changes in the skin". The potential for chemical induced skin irritation is usually determined in vivo in the Draize rabbit skin irritation test as described in OECD guideline 404. However, because systemic reactions play a minor role in modulating local skin toxicity potential of chemicals, skin irritation potential may be predicted by in vitro systems, provided they are sufficiently complex to mimic human skin barrier and cell reactivity. In an international prevalidation study performed by ECVAM, the in vitro skin irritation test using the human skin model EpiDermTM and EpiSkinTM and measurement of cell viability by dehydrogenase conversion of MTT into a blue formazan salt have turned out as a sufficiently promising predictor for skin irritancy potential.
Vehicle:
unchanged (no vehicle)
Details on test system:
RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: human skin model EpiDerm™
- Tissue batch number: 23341
- Delivery date: 14 June 2016
- Date of initiation of testing: 14 June 2016 (preincubation phase)

TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment / exposure: 37 ± 1.5 °C, 5 ± 0.5% CO2
- Temperature of post-treatment incubation: 37 ± 1.5 °C, 5 ± 0.5 % CO2

REMOVAL OF TEST MATERIAL AND CONTROLS
- Volume and number of washing steps: Rinsed with DPBS at least 15 times, after the rinsing the inserts were submerged in DPBS at least three times. Afterwards the inserts were once again rinsed with sterile DPBS from the inside and the outside.
- Observable damage in the tissue due to washing: No
- Modifications to validated SOP: No

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT concentration: (1 mg/mL)
- Incubation time: 3 hours
- Spectrophotometer: Versamax® Molecular Devices, Softmax Pro, version 4.7.1
- Wavelength: 570 nm
- Filter: 570 nm

FUNCTIONAL MODEL CONDITIONS WITH REFERENCE TO HISTORICAL DATA
- Viability: Positive: 4.64%, range 4.00 - 5.90 %

NUMBER OF REPLICATE TISSUES: 3

CONTROL TISSUES USED IN CASE OF MTT DIRECT INTERFERENCE
Since the MTT solution did not turn blue/purple, the test item was not considered to reduce MTT and an additional test with freeze-killed tissues did not have to be performed.

NUMBER OF INDEPENDENT TEST SEQUENCES / EXPERIMENTS TO DERIVE FINAL PREDICTION: 1

PREDICTION MODEL / DECISION CRITERIA
- The test substance is considered to be irritant to skin if the mean tissue viability is ≤ 50 %.
- The test substance is considered to be non-irritant to skin if the mean tissue viability is > 50 %

Acceptability of the Assay
Criterion 1
Negative control: The absolute OD 570 nm of the negative control tissues in the MTT test is an indicator of tissue viability obtained after the shipping and storing procedure and under specific conditions of the assay. Tissue viability is meeting the acceptance criterion if the mean OD570 of the negative control tissues is ≥ 0.8 and ≤ 2.8.

Criterion 2
Positive control: An assay is meeting the acceptance criterion if mean relative tissue viability of the positive control is ≤ 20%.

Criterion 3
Standard deviation: The SD of 3 identical replicates should be < 18%. OD values should not be below historically established boundaries.
Control samples:
yes, concurrent negative control
yes, concurrent positive control
Amount/concentration applied:
TEST MATERIAL
- Amount applied: 30 μL (47 μL/cm2)
- Concentration: undiluted

NEGATIVE CONTROL
- Amount applied : 30 μL DPBS (MatTek)

POSITIVE CONTROL
- Amount applied: 30 μL
- Concentration: 5% SLS solution in deionised water
Duration of treatment / exposure:
1 hour
Duration of post-treatment incubation (if applicable):
approx 43 hours
Number of replicates:
3

Results and discussion

In vitro

Results
Irritation / corrosion parameter:
% tissue viability
Run / experiment:
mean of 3 tissues
Value:
100.4
Vehicle controls validity:
not applicable
Negative controls validity:
valid
Positive controls validity:
valid
Other effects / acceptance of results:
- Direct-MTT reduction: test item did not reduce MTT
- Colour interference with MTT: test item did not change colour in the colour interference test
- After treatment with the negative control the absorbance values were well in the required range of the acceptability criterion of mean OD = 0.8 and = 2.8 for the 60 minutes treatment interval, thus assuring the quality of the tissues.
- Treatment with the positive control induced a sufficient decrease in the relative absorbance as compared to the negative control for the 60 minutes treatment interval, and thus assuring the validity of the test system; the mean relative absorbance value of the positive control was 4.5% compared to the negative control.

Applicant's summary and conclusion

Interpretation of results:
GHS criteria not met
Conclusions:
The test item was determined to be not irritant to skin in the in vitro Human Skin Model Test.
Executive summary:

This in vitro study was performed to assess the irritation potential of the test item by means of the Human Skin Model Test.

The test item did not reduce MTT (test for direct MTT reduction), and it did not change colour when mixed with deionised water (test for colour interference). Also its intrinsic colour was not intensive. Consequently, additional tests with freeze-killed or viable tissues were not necessary.

Each three tissues of the human skin model EpiDerm™ were treated with the test item, the negative (DPBS) or the positive (5% SLS) control for 60 minutes. After treatment with the negative control the absorbance values were well within the required range of the acceptability criterion of mean OD ≥ 0.8 and ≤ 2.8 for the 60 minutes treatment interval, thus assuring the quality of the tissues.

Treatment with the positive control induced a sufficient decrease in the relative absorbance as compared to the negative control for the 60 minutes treatment interval, and thus assuring the validity of the test system.

After treatment with the test item the mean absorbance value did not decrease (100.4%) compared to the relative absorbance value of the negative control. This value is above the threshold for irritancy of ≤ 50%.

Therefore, the test item is not considered to possess an irritant potential.