p-tert-butylcinnamaldehyde

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

June 16, 2006 to June 27, 2006

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

A valid study is available for the analogue substance 3-(4-tert-butylphenyl)propionaldehyde. It is a GLP compliant study conducted in compliance with agreed protocols, with no or minor deviations from standard testing guidelines. The read-across is considered to be suitable based on the structural and “mechanistic action” similarities between the target substance (3-(4-tert-butylphenyl)acrylaldehyde) and source substance (3-(4-tert-butylphenyl)propionaldehyde) and their similar physico-chemical properties.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2006

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.2600 (Skin Sensitisation)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of study:

mouse local lymph node assay (LLNA)

Test material

Test material information

Constituent 1

Reference substance name:

3-(4-tert-butylphenyl)propionaldehyde

EC Number:

242-016-2

EC Name:

3-(4-tert-butylphenyl)propionaldehyde

Cas Number:

18127-01-0

IUPAC Name:

3-(4-tert-butylphenyl)propanal

Test material form:

other: liquid

Details on test material:

- Name of test material (as cited in study report): Bourgeonal
- Physical state: liquid
- Analytical purity: Not specified
- Lot/batch No.: 02759TT
- Expiration date of the lot/batch: Not specified
- Molecular formula (if other than submission substance): C13H18O
- Molecular weight (if other than submission substance): 190.2814
- Smiles notation (if other than submission substance): CC(C)(C)c1ccc(CCC=O)cc1
- InChl (if other than submission substance): InChI=1/C13H18O/c1-13(2,3)12-8-6-11(7-9-12)5-4-10-14/h6-10H,4-5H2,1-3H3
- Structural formula attached as image file (if other than submission substance): see Fig. 1

In vivo test system

Test animals

Species:

mouse

Strain:

CBA

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Harlan UK Limited, Shaw's Farm, Blackthorne, Bicester, Oxon, UK
- Age at study initiation: Young adults (8-12 weeks old)
- Weight at study initiation: Ranged from 16.6 to 20.6 g
- Housing: maximum of 4 mice housed per cage, in cages suitable for animals of this strain and weight range. Environmental enrichment provided included tents, bases and nestlets.
- Diet (e.g. ad libitum): RM1, supplied by Special Diet Services Limited, Witham, Essex, UK.
- Water (e.g. ad libitum): From mains supply
- Acclimation period: At least 5 day sprior to start of dosing.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3 °C
- Humidity (%): 30-70%
- Air changes (per hr): Minimum of 15 changes per hour
- Photoperiod (hrs dark / hrs light): Artificial light, giving 12 hours light, 12 hours dark.

IN-LIFE DATES: From: June 21, 2006 To: June 27, 2006

Study design: in vivo (LLNA)

Vehicle:

other: 1:3 Ethanol/ Diethylphthalate

Concentration:

1, 2.5, 5, 10 and 25 % w/v

No. of animals per dose:

4

Details on study design:

MAIN STUDY
ANIMAL ASSIGNMENT AND TREATMENT
- Criteria used to consider a positive response: The results are expressed as disintegrations per minute (dpm) per group. The activity of each test group is then divided by the activity of the vehicle control group to give a test: control ratio known as the stimulation index (SI) for each concentration. The criterion for a positive response is that one or more concentrations of the test substance should elicit a 3-fold or greater increase in isotope incorporation relative to the vehicle control group. The assay is able to identify those materials that elicit responses in a standard Magnusson and Kligman maximisation guinea pig test for sensitisation. Consequently, a test substance which does not fulfil the criterion is designated as unlikely to be a skin sensitiser.

TREATMENT PREPARATION AND ADMINISTRATION: Groups of four female mice were used for this study. Approximately 25 µL of a 1, 2.5, 5, 10 or 25 % w/v preparation of the test substance in 1:3 EtOH: DEP was applied, using a variable volume micro-pipette, to the dorsal surface of each ear. A vehicle control group was similarly treated using 1:3 EtOH:DEP alone. The procedure was repeated daily for 3 consecutive days.
Three days after final application, all the animals were injected, via the tail vein, with approximately 250 µL of phosphate buffered saline (PBS) containing 20 µCi of a 2.0 Ci/mmol Specific activity 3H-methyl thymidine. Approximately 5 hours later, the animals were humanely killed by inhalation of halothane followed by cervical dislocation. The draining auricular lymph nodes were removed from each animal, and together with the nodes from the other animals in the group, were placed in a container with PBS.
A single cell suspension was prepared by mechanical disaggregation of lymph nodes through 200-mesh stainless steel gauze. The cell suspensions were then washed three times by centrifugation with approximately 10 mL of PBS. Approximately 3 mL of 5 % w/v trichloroacetic acid (TCA) was added and after, overnight precipitation at 4 °C, the samples were pelleted by centrifugation and the supernatant was discarded. The cells were then resuspended in approximately 1 mL of TCA.

The lymph node suspensions were transferred to scintillation vials and 10mL of scintillant (Optiphase) was added prior to ß-scintillation counting using a Packard Tri-Carb 3100TR Liquid Scintillation Counter.

Positive control substance(s):

hexyl cinnamic aldehyde (CAS No 101-86-0)

Results and discussion

Positive control results:

In a positive control study, hexylcinnamaldehyde was shown to have the capacity to cause skin sensitisation when applied as a 25 % (w/v) preparation in acetone: olive oil (4:1), confirming the validity of the protocol used for this study.
The reliability assessment of the protocol using a positive control was conducted between January 25, 2006 and January 31, 2006.

In vivo (LLNA)

Results

Results 1

Parameter:

SI

Remarks on result:

other: see Remark

Remarks:

Concentration of test substance (% w/v) Stimulation index (SI) 0 (vehicle only) N/A 1 0.9 2.5 1.4 5 3.6 10 4.2 25 9.8

Results 2

Parameter:

other: disintegrations per minute (DPM)

Remarks on result:

other: see Remark

Remarks:

Concentration of test substance (% w/v) Disintegrations per minute (dpm) Dpm per lymph node 0 (vehicle only) 4538 567 1 3930 491 2.5 6293 787 5 16372 2047 10 18948 2369 25 44444 5556

Any other information on results incl. tables

Analogue Approach Justification:

- See attached “Justification for read-across” document for full details.

- In summary, important considerations for the use of read-across for skin sensitisation are: i) 3-(4-tert-butylphenyl)acrylaldehyde (the target substance) has similar predicted physico-chemical properties to those predicted and experimentally determined for 3-(4-tert-butylphenyl)propionaldehyde (the source substance), ii) there are structural similarities between the two chemicals and iii) the OECD QSAR Toolbox indicates that the two substances are expected to have similar interactions with biological receptors.

The information reported in this summary is included to demonstrate comparability between the source (3-(4-tert-butylphenyl)propionaldehyde) and target (3-(4-tert-butylphenyl)acrylaldehyde) substance.

Applicant's summary and conclusion

Interpretation of results:

sensitising

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

The test material has the capacity to cause skin sensitisation when applied as dose levels of 5, 10 and 25 % w/v preparations in 1:3 EtOH:DEP. The EC3 value giving rise to a three-fold increase in lymphocyte proliferation was calculated to be 4.3 % w/v (1075 µg/cm²).

Executive summary:

The test material, was tested for potential skin sensitisation according to OECD guideline 429.

The application of the test substance at concentrations of 1, 2.5, 5, 10 and 25 % w/v in 1:3 EtOH:DEP resulted in an isotope incorporation, which was greater than 3 -fold at the 5, 10 and 25 % w/v concentrations. Consequently, the test substance is likely to be a skin sensitiser under the conditions of the test. The concentration giving rise to a 3 -fold increase in lymphocyte proliferation (EC3) was calculated to be 4.3 % w/v (1075 µg/cm²).

The application of a positive control, hexylcinnamaldehyde, at concentrations of 5 %, 10 % and 25 % w/v in acetone:olive oil (4:1) resulted in greater than 3 -fold increase in isotope incorporation at the 25 % w/v concentration. Therefore, hexylcinnamaldehyde was shown to be a skin sensitiser, confirming the validity of the protocol used for the study.

In conclusion, the test material in 1:3 EtOH:DEP vehicle is a skin sensitiser under the conditions of the test with an EC3 value of 4.3 % (1075 µg/cm²).