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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:
12 October 2016 - 22 November 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 guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)
Qualifier:
according to guideline
Guideline:
EU Method B.42 (Skin Sensitisation: Local Lymph Node Assay)
GLP compliance:
yes (incl. QA statement)
Type of study:
mouse local lymph node assay (LLNA)

Test material

Constituent 1
Chemical structure
Reference substance name:
Fatty acids, C18 unsatd., reaction products with triethanolamine
EC Number:
938-513-5
Cas Number:
1187872-27-0
IUPAC Name:
Fatty acids, C18 unsatd., reaction products with triethanolamine
Test material form:
liquid: viscous

In vivo test system

Test animals

Species:
mouse
Strain:
CBA/Ca
Sex:
female
Details on test animals and environmental conditions:
Housing: group
Cage Type: Makrolon Type II (pre-test) / III (main study), with wire mesh top
Bedding: granulated soft wood bedding
Feed: 2018C Teklad Global 18% protein rodent diet (certified), ad libitum
Water: tap water, ad libitum
Environment: temperature 22 ± 2°C, relative humidity approx. 45-65%, artificial light 6.00 a.m. - 6.00 p.m.

Study design: in vivo (LLNA)

Vehicle:
dimethylformamide
Concentration:
1, 2.5, and 5%
No. of animals per dose:
4
Details on study design:
Determination of Ear Thickness
In the pre-test prior to the first and third application of the test item (study days 1 and 3) and prior to treatment with 3HTdR (study day 6), the ear thickness was determined using a micrometer.
Test Item Administration
Each test group of mice was treated by (epidermal) topical application to the dorsal surface of each ear with test item concentrations of 1, 2.5, and 5% in DMF. The application volume, 25 µL/ear/day, was spread over the entire dorsal surface (  8 mm) of each ear once daily for three consecutive days. A further group of mice (control animals) was treated with an equivalent volume of the relevant vehicle alone (control animals).
Administration of 3H-methyl-thymidine
Five days after the first topical application (day 6) 250 µL of phosphate-buffered saline containing 20.5 µCi of 3H-methyl thymidine (equivalent to 81.8 µCi/mL 3HTdR) were injected into each test and control mouse via the tail vein.
Terminal Procedure
Approximately five hours after treatment with 3HTdR all mice were euthanized by using CO2, which was, after harvesting of the lymph nodes, followed by cervical dislocation to ensure death. The draining lymph nodes were rapidly excised and pooled for each experimental group (8 nodes per group).
Preparation of Single Cell Suspensions
Single cell suspensions (in phosphate buffered saline) of pooled lymph node cells were prepared by gentle mechanical disaggregation through stainless steel gauze (200 µm mesh size). After washing two times with phosphate buffered saline (approx. 10 mL) the lymph node cells were resuspended in 5 % trichloroacetic acid (approx. 3 mL) and incubated at approximately +4 °C for at least 18 hours for precipitation of macromolecules.
Determination of cellular proliferation (incorporation of 3HTdR)
The precipitates were then resuspended in 5 % trichloroacetic acid (1 mL) and transferred to scintillation vials with 10 mL of scintillation liquid and thoroughly mixed. The level of 3HTdR incorporation was then measured in a -scintillation counter. Similarly, background 3HTdR levels were also measured in two 1 mL aliquots of 5 % trichloroacetic acid. The -scintillation counter expresses 3HTdR incorporation as the number of radioactive disintegrations per minute (DPM).
Determination of Ear Weights
In the pre-test and main experiment after the lymph nodes had been excised, both ears (left and right) of mice were punched at the apical area using a biopsy punch (Ø 8 mm corresponding to 0.5 cm2). For each animal both punches were immediately weighed (pooled per animal) using an analytical balance.
Observations
Clinical Observations
All animals were observed on a daily basis, including pre- and post-dose observations on days 1, 2 and 3. Any clinical signs of systemic toxicity, local skin irritation or signs of ill health during the study were recorded.
Ear thickness: In the pre-test, the ear thickness was determined prior to the first application (day 1), on day 3, and prior to sacrifice on day 6.
Ear weights: In the pre-test and main experiment, the ear weight was determined after sacrifice (biopsy punches will be taken from each ear).
Body Weights
The body weights were recorded on day 1 (prior to dosing) and prior to sacrifice (pre-test) or prior to treatment with 3HTdR (main experiment)
Positive control substance(s):
hexyl cinnamic aldehyde (CAS No 101-86-0)

Results and discussion

Positive control results:
October 2016 (study 1792800): S.I. of 1.50, 3.84, and 11.76 were derived at tested concentrations of 5, 10, 25%, respectively and an EC3 value of 8.2% was calculated.

In vivo (LLNA)

Results
Key result
Parameter:
other: disintegrations per minute (DPM)
Remarks on result:
other: see depicted table below

Any other information on results incl. tables

 Calculation and Results of Individual Data

Vehicle: DMF

Test item concentration %

Group

Measurement DPM

Calculation

Result

DPM-BGa)

number of lymph nodes

DPM per lymph nodeb)

S.I.

---

BG I

17

---

---

---

---

---

BG II

23

---

---

---

---

0

1

10206

10186

8

1273.2

1.00

1

2

16108

16088

8

2011

1.58

2.5

3

12960

12940

8

1617.5

1.27

5

4

18294

18274

8

2284.2

1.79

1    =  Control Group

2-4=  Test Group

a)   =  The mean value was taken from the figures BG I and BG II

b)      =  Since the lymph nodes of the animals of a dose group were pooled, DPM/node was determined by dividing the measured value by the number of lymph nodes pooled

 Calculation of the EC3 value

The EC3 value could not be calculated, since all S.I.´s are below the threshold value of 3.

 Viability / Mortality

No deaths occurred during the study period.

Clinical Signs

No symptoms of local skin irritation at the ears of the animals and no signs of systemic toxicity were observed during the study period.

 Body Weights

The body weight of the animals, recordedprior to the first application and prior to treatment with3HTdR, was within the range commonly recorded for animals of this strain and age.

 Ear Weights

The measured ear weight of all animals treated was recorded on test day 6 (after necropsy). A statistically significant or biologically relevant increase in ear weights was not observed.

Applicant's summary and conclusion

Conclusions:
The test item Emulsogen TO was not a skin sensitiser under the test conditions of this study.
Executive summary:

In order to study a possible skin sensitising potential of the test item, three groups each of four female mice were treated once daily with the test item at concentrations of 1, 2.5, and 5% in DMF by topical application to the dorsum of each ear for three consecutive days. The highest concentration tested was the highest concentration that could be achieved whilst avoiding systemic toxicity and excessive local skin irritation as confirmed by three pre-experiments. A control group of four mice was treated with the vehicle (DMF) only. Five days after the first topical application the mice were injected intravenously into a tail vein with radio-labelled thymidine (3H-methyl thymidine). Approximately five hours after intravenous injection, the mice were sacrificed, the draining auricular lymph nodes excised and pooled per group. Single cell suspensions of lymph node cells were prepared from pooled lymph nodes, which were subsequently washed and incubated with trichloroacetic acid overnight. The proliferative capacity of pooled lymph node cells was determined by the incorporation of3H-methyl thymidine measured in a scintillation counter.

All treated animals survived the scheduled study period and no signs of systemic toxicity or local skin irritation were observed. A statistically relevant increase in ear weights was not observed.

A test item is regarded as a sensitiser in the LLNA if the exposure to one or more test concentration resulted in a 3-fold or greater increase in incorporation of3HTdR compared with concurrent controls, as indicated by the Stimulation Index (S.I.). The estimated concentration of test item required to produce a S.I. of 3 is referred to as the EC3 value.

In this study Stimulation Indices of 1.58, 1.27, and 1.79 were determined with the test item at concentrations of 1, 2.5, and 5% (w/w) in DMF. The EC3 value could not be calculated, since none of the tested concentrations induced a S.I. greater than the threshold value of 3.

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