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Toxicological information

Skin sensitisation

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Administrative data

Endpoint:
skin sensitisation: in vivo (LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Between 15 November 2011 and 01 December 2011
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2012
Report Date:
2012

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method B.42 (Skin Sensitisation: Local Lymph Node Assay)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
No analysis was carried out to determine the homogeneity, concentration or stability of the test item formulation. This exception is considered not to affect the purpose or integrity of the study.
Type of study:
mouse local lymph node assay (LLNA)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
other: liquid
Details on test material:
Sponsor's identification: 1,1,3,3-tetramethylbutyl 2-ethylperoxyhexanoate (CAS 22288-43-3)
Description : clear colourless liquid
Batch number : 1009442440
Purity : 90.8%
Date received : 19 July 2011
Expiry date : 01 October 2012
Storage conditions: approximately 20°C in the dark
The integrity of supplied data relating to the identity, purity and stability of the test item is the responsibility of the Sponsor.
A Certificate of Analysis supplied by the Sponsor is given in Appendix 5 (attachment 1).

In vivo test system

Test animals

Species:
mouse
Strain:
other: CBA/Ca (CBA/CaOlaHsd)
Sex:
female
Details on test animals and environmental conditions:
Female CBA/Ca (CBA/CaOlaHsd) strain mice were supplied by Harlan Laboratories UK Ltd., Oxon, UK. On receipt the animals were randomly allocated to cages. The animals were nulliparous and non pregnant. After an acclimatisation period of at least five days the animals were selected at random and given a number unique within the study by indelible ink marking on the tail and a number written on a cage card. At the start of the study the animals were in the weight range of 15 to 23 g, and were eight to twelve weeks old.
The animals were individually housed in suspended solid floor polypropylene cages furnished with softwood woodflakes. Free access to mains tap water and food (2014C Teklad Global Rodent diet supplied by Harlan Laboratories UK Ltd., Oxon, UK) was allowed throughout the study.
The temperature and relative humidity were in the range of 18 to 23°C and 47 to 59%, respectively. Any occasional deviations from these targets (temperature: 19 to 25°C and relative humidity: 30 to 70%) were considered not to have affected the purpose or integrity of the study. The rate of air exchange was approximately fifteen changes per hour and the lighting was controlled by a time switch to give twelve hours continuous light (06.00 to 18.00) and twelve hours darkness.
The animals were provided with environmental enrichment items which were considered not to contain any contaminant of a level that might have affected the purpose or integrity of the study.

Study design: in vivo (LLNA)

Vehicle:
acetone/olive oil (4:1 v/v)
Concentration:
Undiluted test item or the test item at concentrations of 50% or 25% v/v in acetone/olive oil 4:1
No. of animals per dose:
Groups of five mice were treated
Details on study design:
Preliminary Screening Test
Using available information regarding the systemic toxicity/irritancy potential of the test item, a preliminary screening test was performed using one mouse. The mouse was treated by daily application of 25 µl of the undiluted test item, to the dorsal surface of each ear for three consecutive days (Days 1, 2, 3). The mouse was observed twice daily on Days 1, 2 and 3 and once daily on Days 4, 5 and 6. Local irritation was scored daily according to the scale included as Appendix 4. Any clinical signs of toxicity, if present, were also recorded. The bodyweight was recorded on Day 1 (prior to dosing) and on Day 6.
The thickness of each ear was measured using an Oditest micrometer (Dyer, PA), pre dose on Day 1, post dose on Day 3 and on Day 6. Any changes in the ear thickness were noted. Mean ear thickness changes were calculated between time periods Days 1 to 3 and Days 1 to 6. A mean ear thickness increase of equal to or greater than 25% was considered to indicate excessive irritation and limited biological relevance to the endpoint of sensitisation.
Main Test
Test Item Administration
Groups of five mice were treated with the undiluted test item or the test item at concentrations of 50% or 25% v/v in acetone/olive oil 4:1. The preliminary screening test suggested that the test item would not produce systemic toxicity or excessive local irritation at the highest suitable concentration. The mice were treated by daily application of 25 µl of the appropriate concentration of the test item to the dorsal surface of each ear for three consecutive days (Days 1, 2, 3). The test item formulation was administered using an automatic micropipette and spread over the dorsal surface of the ear using the tip of the pipette.
A further group of five mice received the vehicle alone in the same manner.
³H-Methyl Thymidine Administration
Five days following the first topical application of the test item or vehicle (Day 6) all mice were injected via the tail vein with 250 µl of phosphate buffered saline (PBS) containing ³H methyl thymidine (3HTdR:80µCi/ml, specific activity 2.0 Ci/mmol, ARC UK Ltd) giving a total of 20 µCi to each mouse.
Observations
Clinical Observations: All animals were observed twice daily on Days 1, 2 and 3 and on a daily basis on Days 4, 5 and 6. Any signs of toxicity or signs of ill health during the test were recorded.
Bodyweights: The bodyweight of each mouse was recorded on Day 1 (prior to dosing) and Day 6 (prior to termination).
Terminal Procedures
Termination: Five hours following the administration of ³HTdR all mice were killed by carbon dioxide asphyxiation followed by cervical separation. For each individual animal of each group the draining auricular lymph nodes were excised and processed. For each individual animal 1 ml of PBS was added to the lymph nodes.
Preparation of Single Cell Suspension: A single cell suspension of the lymph node cells for each individual animal was prepared by gentle mechanical disaggregation through a 200 mesh stainless steel gauze. The lymph node cells were rinsed through the gauze with 4 ml of PBS into a petri dish labelled with the project number and dose concentration. The lymph node cells suspension was transferred to a centrifuge tube. The petri dish was washed with an additional 5 ml of PBS to remove all remaining lymph node cells and these were added to the centrifuge tube. The lymph node cells were pelleted at 1400 rpm (approximately 190 g) for ten minutes. The pellet was resuspended in 10 ml of PBS and re-pelleted. To precipitate out the radioactive material, the pellet was resuspended in 3 ml of 5% Trichloroacetic acid (TCA).
Determination of ³HTdR Incorporation: After approximately eighteen hours incubation at approximately 4°C, the precipitates were recovered by centrifugation at 2100 rpm (approximately 450 g) for ten minutes, resuspended in 1 ml of TCA and transferred to 10 ml of scintillation fluid (Optiphase 'Trisafe'). ³HTdR incorporation was measured by ß scintillation counting. The "Poly QTM" vials containing the samples and scintillation fluid were placed in the sample changer of the scintillator and left for approximately twenty minutes. The purpose of this period of time in darkness was to reduce the risk of luminescence, which has been shown to affect the reliability of the results. After approximately twenty minutes, the vials were shaken vigorously. The number of radioactive disintegrations per minute was then measured using the Beckman LS6500 scintillation system (Beckman Instruments Inc, Fullerton, CA, USA).
Positive control substance(s):
hexyl cinnamic aldehyde (CAS No 101-86-0)
Statistics:
Statistical Analysis
Data was processed to give group mean values for disintegrations per minute and standard deviations where appropriate. Individual and group mean disintegrations per minute values were assessed for dose response relationships by analysis of homogeneity of variance followed by one way analysis of variance (ANOVA). In the event of a significant result from the ANOVA, pairwise comparisons were performed between control and treated groups. For homogenous datasets Dunnett’s Multiple Comparison test was used and for non homogenous datasets Dunnett’s T3 Multiple Comparison Method was used.
Probability values (p) are presented as follows:
P<0.001 ***
P<0.01 **
P<0.05 *
P>0.05 (not significant)

Results and discussion

In vivo (LLNA)

Resultsopen allclose all
Parameter:
SI
Remarks on result:
other: The stimulation index are given in Table 4.
Parameter:
other: disintegrations per minute (DPM)
Remarks on result:
other: The radioactive disintegrations per minute per animal are given in Table 4.

Any other information on results incl. tables

Interpretation of ResultsThe proliferation response of lymph node cells was expressed as the number of radioactive disintegrations per minute per lymph nodes from each individual animal and as the ratio of 3HTdR incorporation into lymph node cells of test nodes relative to that recorded for the control nodes (Stimulation Index).

The test item will be regarded as a sensitiser if at least one concentration of the test item results in a threefold or greater increase in 3HTdR incorporation compared to control values. Any test item failing to produce a threefold or greater increase in 3HTdR incorporation will be classified as a "non‑sensitiser".

The EC3 value was also calculated. The EC3 value is the concentration of test item expected to cause a 3 fold increase in 3HTdR incorporation. The equation used for the calculation of EC3 is:

aEC3= c + [[(3-d)/(b-d)] x (a-c)]


a= lowest concentration giving stimulation index >3

b = actual stimulation index caused by ‘a’

c = highest concentration failing to produce a stimulation index of 3

d = actual stimulation index caused by ‘c’

 

Preliminary Screening Test

Clinical observations, bodyweight and mortality data are given in Table 1 and local skin irritation is given in Table 2. The ear thickness measurements and mean ear thickness changes are given in Table 3.

No signs of systemic toxicity, visual local skin irritation or irritation indicated by anequal to or greater than 25% increase in mean ear thicknesswere noted.

Based on this information the undiluted test item and the test item at concentrations of 50% and 25v/v in acetone/olive oil 4:1 were selected for the main test.

Main Test

Estimation of the Proliferative Response of Lymph Node Cells

The radioactive disintegrations per minute per animal and the stimulation index are given in Table 4.

The Stimulation Index expressed as the mean radioactive incorporation for each treatment group divided by the mean radioactive incorporation of the vehicle control group are as follows:

Concentration (%v/v) in
acetone/olive oil 4:1

Stimulation Index

Result

25

2.56

Negative

50

4.21

Positive

100

8.41

Positive

Clinical Observations and Mortality Data

Individual clinical observations and mortality data for test and control animals are given in Table 5.

There were no deaths. No signs of systemic toxicity were noted in the test or control animals during the test.

Bodyweight

Individual bodyweights and bodyweight changes for test and control animals are given in Table 6.

Bodyweight changes of the test animals between Day 1 and Day 6 were comparable to those observed in the corresponding control group animals over the same period.

Calculation of EC3 Value

EC3= c + [[(3-d)/(b-d)] x (a-c)]a

a

=

50

b

=

4.21

c

=

25

d

=

2.56

EC3= + [[(3-2.56)/(4.21-2.56)] x (50-25)] =32

The concentration of test item expected to cause a 3 fold increase in 3HTdR incorporation (EC3value) was calculated to be 32%.


a= lowest concentration giving stimulation index >3

b = actual stimulation index caused by ‘a’

c = highest concentration failing to produce a stimulation index of 3

d = actual stimulation index caused by ‘c’

Table 1              Clinical Observations, Bodyweight and Mortality Data – Preliminary Screening Test

Concentration

Animal Number

Bodyweight (g)

Day

1

2

3

4

5

6

Day 1

Day 6

Pre-Dose

Post Dose

Pre-Dose

Post Dose

Pre-Dose

Post Dose

100%

S-1

18

17

0

0

0

0

0

0

0

0

0

0 =     No signs of systemic toxicity

Table 2              Local Skin Irritation – Preliminary Screening Test

Concentration

Animal Number

Local Skin Irritation

Day 1

Day 2

Day 3

Day 4

Day 5

Day 6

pre‑dose

post dose

post dose

left

right

left

right

left

right

left

right

left

right

left

right

100%

S-1

0

0

0

0

0

0

0

0

0

0

0

0

Table 3              Measurement of Ear Thicknessand Mean Ear Thickness Changes – Preliminary Screening Test

Concentration

Animal Number

Ear Thickness Measurement (mm)

Day 1

Day 3

Day 6

pre‑dose

post dose

left

right

left

right

left

right

100%

S-1

0.235

0.230

0.240

0.240

0.235

0.230

overall mean (mm)

0.233

0.240

0.233

overall mean
ear thickness change (%)

na

3.226

0.000

na =     Not applicable

Table 4              Individual Disintegrations per Minute and Stimulation Indices

Concentration
(% v/v) in
acetone/olive oil 4:1

Animal Number

dpm/
Animala

Mean dpm/Animal
(Standard Deviation)

Stimulation Indexb

Result

Vehicle

1-1

1455.04

1361.79
(±196.98)

na

na

1-2

1250.46

1-3

1083.30

1-4

1430.81

1-5

1589.36

25

2-1

2115.65

3491.87
(±1349.23)

2.56

Negative

2-2

5563.74

2-3

2865.11

2-4

2865.89

2-5

4048.94

50

3-1

4059.93

5733.66**
(±1130.04)

4.21

Positive

3-2

6563.29

3-3

6970.56

3-4

5462.16

3-5

5612.37

100

4-1

12069.30

11446.82***
(±2388.51)

8.41

Positive

4-2

11267.62

4-3

10075.59

4-4

15080.14

4-5

8741.46

dpm=Disintegrations per minute

a=     Total number of lymph nodes per animal is 2

b=     Stimulation Index of 3.0 or greater indicates a positive result

na=     Not applicable

**=     Significantly different from control group p<0.01

***=   Significantly different from control group p<0.001

Table 5              Individual Clinical Observations and Mortality Data

Concentration
(% v/v) in
acetone/olive oil 4:1

Animal Number

Day 1

Day 2

Day 3

Day 4

Day 5

Day 6

Pre-Dose

Post Dose

Pre-Dose

Post Dose

Pre-Dose

Post Dose

Vehicle

1-1

0

0

0

0

0

0

0

0

0

1-2

0

0

0

0

0

0

0

0

0

1-3

0

0

0

0

0

0

0

0

0

1-4

0

0

0

0

0

0

0

0

0

1-5

0

0

0

0

0

0

0

0

0

25

2-1

0

0

0

0

0

0

0

0

0

2-2

0

0

0

0

0

0

0

0

0

2-3

0

0

0

0

0

0

0

0

0

2-4

0

0

0

0

0

0

0

0

0

2-5

0

0

0

0

0

0

0

0

0

50

3-1

0

0

0

0

0

0

0

0

0

3-2

0

0

0

0

0

0

0

0

0

3-3

0

0

0

0

0

0

0

0

0

3-4

0

0

0

0

0

0

0

0

0

3-5

0

0

0

0

0

0

0

0

0

100

4-1

0

0

0

0

0

0

0

0

0

4-2

0

0

0

0

0

0

0

0

0

4-3

0

0

0

0

0

0

0

0

0

4-4

0

0

0

0

0

0

0

0

0

4-5

0

0

0

0

0

0

0

0

0

0 =      No signs of systemic toxicity

Table 6              Individual Bodyweights and Bodyweight Changes

Concentration
(% v/v) in
acetone/olive oil 4:1

Animal Number

Bodyweight (g)

Bodyweight Change (g)

Day 1

Day 6

Vehicle

1-1

18

19

1

1-2

19

20

1

1-3

21

23

2

1-4

19

21

2

1-5

19

21

2

25

2-1

20

19

-1

2-2

17

18

1

2-3

18

20

2

2-4

18

19

1

2-5

18

19

1

50

3-1

19

21

2

3-2

18

19

1

3-3

19

19

0

3-4

20

19

-1

3-5

20

20

0

100

4-1

18

19

1

4-2

21

20

-1

4-3

19

20

1

4-4

18

18

0

4-5

19

18

-1

Appendix 1      Current Positive Control Study for the Local Lymph Node Assay

Introduction. A study was performed to assess the sensitivity of the strain of mouse used at these laboratories to a known sensitiser. The current positive control study was performed outside the recommended six months interval, but due to the historical data available, this deviation was considered not to affect the purpose or integrity of the study. The methodology for the LLNA is detailed in the OECD Guideline for the Testing of Chemicals, No. 429, and Method B.42 of CommissionRegulation (EC) No. 440/2008. The study described in this document is based on these test methods but has been refined in order to reduce the number of animals required. The reduced LLNA (rLLNA) has been endorsed by the non‑Commission members of the European Centre for the Validation of Alternative Methods (ECVAM) Scientific Advisory Committee (ESAC) at its 26thmeeting held on 26 – 27 April 2007 at ECVAM,,.

Test Item                   :                                  α‑Hexylcinnamaldehyde, tech., 85%

Project number       :                                  41103434

Study dates              :                                  05 October 2011 to 11 October 2011

Methods. A group of five animals was treated with 50 µl (25 µl per ear) ofα‑Hexylcinnamaldehyde, tech., 85% as a solution in acetone/olive oil 4:1at a concentration of 25% v/v. A further control group of five animals was treated with acetone/olive oil 4:1alone.

Results. The Stimulation Index expressed as the mean radioactive incorporation for the treatment group divided by the mean radioactive incorporation of the vehicle control group is as follows:

Concentration (% v/v) in
acetone/olive oil 4:1

Stimulation Index

Result

25

4.05

Positive

Conclusion. α‑Hexylcinnamaldehyde, tech., 85% was considered to be a sensitiser under the conditions of the test.

Applicant's summary and conclusion

Interpretation of results:
Category 1B (indication of skin sensitising potential) based on GHS criteria
Conclusions:
The test item was considered to be a sensitiser under the conditions of the test.
Executive summary:

Introduction. A study was performed to assess the skin sensitisation potential of the test item in the CBA/Ca strain mouse following topical application to the dorsal surface of the ear. The method was designed to be compatible withthe following:

OECD Guideline for the Testing of Chemicals No.429 "Skin Sensitisation: Local Lymph Node Assay" (adopted 22 July 2010)

Method B42 Skin Sensitisation (Local Lymph Node Assay) of Comission Regulation (EC) No.440/2008

Methods. Following a preliminary screening test in which no clinical signs of toxicity were noted at a concentration of 100%, this concentration was selected as the highest dose investigated in the main test of the Local Lymph Node Assay. Three groups, each of five animals, were treated with 50 µl (25 µl per ear) of the undiluted test item or the test item as a solution in acetone/olive oil 4:1at concentrations of 50% or 25v/v. A further group of five animals was treated with acetone/olive oil 4:1 alone.

Results. The Stimulation Index expressed as the mean radioactive incorporation for each treatment group divided by the mean radioactive incorporation of the vehicle control group are as follows:

Concentration (%v/v) in
acetone/olive oil 4:1

Stimulation Index

Result

25

2.56

Negative

50

4.21

Positive

100

8.41

Positive

The concentration of test item expected to cause a 3 fold increase in 3HTdR incorporation (EC3 value) was calculated to be 32%.

Conclusion. The test item was considered to be a sensitiser under the conditions of the test.