[4-[p,p'-bis(dimethylamino)benzhydrylidene]cyclohexa-2,5-dien-1-ylidene]dimethylammonium m-[[p-anilinophenyl]azo]benzenesulphonate

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 2011-12-07 to 2011-12-19

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2011

Report date:

2011

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

: Use of the lymph node cell count for measurement of the cell proliferation instead of the determination of DNA synthetis (3H-thymidine incorporation into the lymph node cells).

Principles of method if other than guideline:

Lymph node cell count is more direct measurement of cell proliferation than determination of DNA synthesis and therefore considered an appropriate parameter for evaluation of cell proliferation in the assay. In this case, the cut-off value is much lower and it is fixed at 1.4 times increase of stimulation index (instead of 3 for the 3H-thymidine method). This is understandable by the facts that cell count indices have:
- Lower individual variance compared to 3H-thymidine incorporation
- Lower maximum stimulation indices compared to radioactive labelling.

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:

[4-[p,p'-bis(dimethylamino)benzhydrylidene]cyclohexa-2,5-dien-1-ylidene]dimethylammonium m-[[p-anilinophenyl]azo]benzenesulphonate

EC Number:

265-449-9

EC Name:

[4-[p,p'-bis(dimethylamino)benzhydrylidene]cyclohexa-2,5-dien-1-ylidene]dimethylammonium m-[[p-anilinophenyl]azo]benzenesulphonate

Cas Number:

65113-55-5

Molecular formula:

C25H30N3.C18H14N3O3S

IUPAC Name:

[4-[p,p'-bis(dimethylamino)benzhydrylidene]cyclohexa-2,5-dien-1-ylidene]dimethylammonium m-[[p-anilinophenyl]azo]benzenesulphonate

Test material form:

solid: particulate/powder

In vivo test system

Test animals

Species:

mouse

Strain:

CBA

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Elevage Janvier (F-53941 Le Genest Saint Isle)
- Age at study initiation: 8 to 9 weeks old
- Weight at study initiation: 18.8 to 22.1 g
- Housing: Individually housed in suspended solid-floor polypropylene cages furnished with softwood woodflakes.
- Diet : Food (M20, SDS) ad libitum
- Water : Tap water ad libitum
- Acclimation period: At least 5 days under stabling and nutritional conditions identical to those of the test

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22+/-3°C
- Humidity (%): 30 to 70%
- Air changes (per hr): approximately 15 changes /hr
- Photoperiod (hrs dark / hrs light): 12 hrs dark / 12 hrs light

Study design: in vivo (LLNA)

Vehicle:

dimethylformamide

Concentration:

Test item diluted at concentrations of 50% (v/v), 25% (v/v), 10% (v/v), 5 (v/v) and 2.5 (v/v) in the dimethylformamide (DMF).

No. of animals per dose:

4 animals per dose + 4 animals for the vehicle control (vehicle alone) : Pooled lymph nodes approach.

(An additional mouse was treated in each group in case of problem which may occur during the study, in particular during the excision of lymph nodes. As the excision of lymph nodes was doubtful for one animal in groups 5 and 6, the lymph nodes of the additional mouse were collected and only the data concerning the 4 selected animals of each group were used in the study)

Details on study design:

RANGE FINDING TESTS
- Concentration: 25 µL of the test item diluted at 50% in DMF to the dorsal surface of each ear for three consecutive days (D1, D2 and D3).
- Irritation: Daily examination. Ear thickness recorded on D1, D3 and D6.
- Lymph node proliferation response: Not performed.

MAIN STUDY
ANIMAL ASSIGNMENT AND TREATMENT
- Name of test method: Pooled approach with the lymph node cell count method.
- Criteria used to consider a positive response: In order to assess any posible irritant effect 1) Ear thickness measurements of the right ear of each animal (vehicle and treated groups), by a micrometer were performed on D1, D3 and D6; 2) Any local reactions (irritation reaction or any other observation) were recorded. 3) On D6, punch biopsies of 8 mm in diameter of the apical area of both ears were prepared and weighed and the two lymph nodes per mouse were weighed. In fact, possible irritancy may be involved in false positive lymphoproliferative responses.

In order to assess the skin sensisation of the test item, animals were anaesthetised on D6. The draining auricular lymph nodes from the four mice were excised and pooled for each experimental group. The proliferation response of lymph node cells was expressed as the stimulation index :

SI = Cell count of treated group / Cell count of control group

The test item will be regarded as a sensitiser if at least one concentration of the test item results is greater than 1.4 compared to control values. The irritation level were also taken into account for the interpretation of the results. Any test item failing to produce a SI<1.4 will be classified as a "non-sensitiser".

TREATMENT PREPARATION AND ADMINISTRATION: 25 µL of the appropriate concentration of the test item (2.5%, 5%, 10%, 25% , 50% or the vehicule) was applied to the dorsal surface of each ear, using an automatic micropipette and spread over the dorsal surface of the ear using the tip of the pipette. The application was repeated on days 2 and 3. On D6, the draining auricular lymph nodes from mouses were excised and pooled for each experimental group after anaesthetisia. Then, a single cell suspension of the lymph node cells of 4 mice of each group was prepared by gentle mechanical tissue disaggregation through a 200-mesh cell strainers in 4 mL of PBS containing 0.5% BSA into a 6-well multiwell plate. 10 µL of this cell suspension was diluted in 10 mL of physiological saline solution (NaCl 0.9%). The lymphocyte cells were counted using a cell counter. For the run, the lower size selected was 5 µM and the upper size selected was 15 µm (the average size of a lymphocyte is 8 µm).

Positive control substance(s):

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

Results and discussion

Positive control results:

CURRENT POSITIVE CONTROL STUDY

Groups Test item Cell count/groups Stimulation Index Result
concentration (x106 cells/mL) (S.I.)
1 AOO 22.26 n.a. n.a.
2 2.5% 26.04 1.17 Negative
3 5% 29.66 1.33 Negative
4 10% 34.00 1.53 Positive

The EC1.4 value = 6.75%

In conclusion, in view of these results, under these experimental conditions, the positive control must be classified R43 "may cause sensitisation by skin contact" in accordance with the criteria for classification, packaging and labelling of dangerous substances and preparations of the E.E.C. Directives 67/548, 2001/59 and 99/45. This substance must be characterised by the symbol "Xi" and the warning label "Irritant". In accordance with the regulation (EC) n°1272/2008, the test item must be classified in category 1 "Skin sensitisation". The signal word "Warning" and hazard statement H317 "May cause an allergic skin reaction" are required.

In vivo (LLNA)

Results

Results 1

Key result

Parameter:

other: EC1.4

Value:

ca. 2.98

Results 2

Key result

Parameter:

SI

Value:

1.35

Test group / Remarks:

2.5%

Results 3

Key result

Parameter:

SI

Value:

1.61

Test group / Remarks:

5%

Results 4

Key result

Parameter:

SI

Value:

2.1

Test group / Remarks:

10%

Results 5

Key result

Parameter:

SI

Value:

2.34

Test group / Remarks:

25%

Results 6

Key result

Parameter:

SI

Value:

3.41

Test group / Remarks:

50%

Any other information on results incl. tables

Cell count, stimulation index and calculation of EC1.4

Groups	Test item	Cell count/groups (x10^6cells/mL)	Stimulation Index (SI)	Results	EC1.4value
1	DMF	21.58	n.a	n.a	n.a
2	2.5%	29.03	1.35	Negative	2.98 %
3	5%	34.67	1.61	Positive
4	10%	45.40	2.10	Positive
5	25%	50.48	2.34	Positive
6	50%	73.68	3.41	Positive

 

The EC_1.4 value is determined by linear interpolation of points on the dose-response curve, immediately above and below the 1.4-fold threshold, according the equation:

EC_1.4= c + [(1.4 – d) / (b – d)] x (a – c)

a= the lowest concentration giving stimulation index > 1.4

b= the actual stimulation index caused by a.

c= the highest concentration failing to produce a stimulation index of 1.4

d= the actual stimulation index caused by c.

So,

EC_1.4= 2.5 + [(1.4 – 1.35) / (1.61 – 1.35)] x (5 – 2.5) = 2.98 %

Applicant's summary and conclusion

Interpretation of results:

Category 1B (indication of skin sensitising potential) based on GHS criteria

Conclusions:

In view of these results, under these experimental conditions, the test item must be classified as a skin sensitiser. In, accordance with the criteria for classification, packaging and labelling of dangerous substances and preparations of the E.E.C. Directives 67/548, 2001/59 and 99/45, this item must be characterised by the symbol "Xi" and the warning label "Irritant" with the risk sentence R43 "May cause sensitisation by skin contact". In accordance with the regulation with the Regulation EC N° 1272/2008, the test item must be classified in category 1 "Skin sensitisation". The signal word "Warning" and hazard statement H317 "May cause an allergic skin reaction" are required.

Executive summary:

The test was performed to assess the skin sensitisation potential of the test item in the CBA/J strain mouse following topical applications to the dorsal surface of the ear.

 

A preliminary study was performed using one mouse, treated daily (on D1, D2 and D3) with 25 µL per ear of the test item diluted at 50% in dimethylformamide (DMF). After a daily examination until D6, any signs of toxicity or excessive local irritation observed during this period were recorded. Therefore, the concentration of 50% was chosen as the highest concentration for the main study.

 

For the main test, five groups of four animals, were treated for three consecutive days (D1, D2 and D3) with 25 µL per ear of the test item diluted in dimethylformamide (DMF) at concentrations of 2.5%, 5%, 10%, 25% and 50% (v/v). A further group of four animals was treated with DMF.

On D6, the proliferation of lymphocytes in the draining auricular lymph nodes was determined by cell counting. The experimental protocol was established according the OECD guideline N° 429 dated 22 july 2010 and the test method B.42 of the council regulation N° 440/2008.

 

No mortality and no signs of systemic toxicity were noted in the test and control animals during the test.

No cutaneous reaction was noted in the treated animals. Remaining test item, associated with a blue coloration of the treatment site, was noted in animals treated at 2.5%, 5%, 10%, 25% and 50% from day 2 or day 3 to day 6.

No significant increase in ear thickness and in ear weight was noted in none of groups.

Therefore, the test item must be considered as not excessively irritant at the five concentrations.

 

The stimulation index (SI) calculated by pooled approach was 1.35, 1.61, 2.10, 2.34 and 3.41 for the treated groups at 2.5%, 5%, 10%, 25% and 50% respectively.

The EC_1.4 determined by linear regression was 2.98%.

 

In view of these results, under these experimental conditions, the test item must be classified as a skin sensitiser. In accordance with the criteria for classification, packaging and labelling of dangerous substances and preparation of the E.E.C. Directives 67/548, 2001/59 and 99/45, this item must be characterised by the symbol "Xi" and the warning label "Irritant" with the risk sentence R43 "May cause sensitisation by skin contact".

In accordance with the Regulation EC N°1272/2008, the test item must be classified in category 1 "Skin sensitisation" and in subcategory 1B. The signal word "Warning" and hazard statement H317 "May cause an allergic skin reaction" are required.