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Toxicological information

Skin sensitisation

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Administrative data

Endpoint:
skin sensitisation: in vitro
Type of information:
experimental study
Adequacy of study:
key study
Study period:
September-October 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2017
Report date:
2017

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 442D (In Vitro Skin Sensitisation: ARE-Nrf2 Luciferase Test Method)
GLP compliance:
yes
Type of study:
other: in vitro Keratinosens
Justification for non-LLNA method:
The objective of the KeratinoSens assay is to evaluate the potential of the test item to activate the Nrf2 transcription factor. This test is part of a tiered strategy for the evaluation of skin sensitisation potential. Thus, data generated with the present Test Guideline should be used to support the discrimination between skin sensitizers and non sensitizers in the context of an integrated approach to testing and assessment. It is an alternative method in order to avoid animal study

Test material

Constituent 1
Chemical structure
Reference substance name:
2-hydroxyethanesulphonic acid, compound with 4,4'-[hexane-1,6-diylbis(oxy)]bis[benzenecarboxamidine] (2:1)
EC Number:
211-533-5
EC Name:
2-hydroxyethanesulphonic acid, compound with 4,4'-[hexane-1,6-diylbis(oxy)]bis[benzenecarboxamidine] (2:1)
Cas Number:
659-40-5
Molecular formula:
C20H26N4O2.2C2H6O4S
IUPAC Name:
4-[6-(4-carbamimidoylphenoxy)hexoxy]benzenecarboximidamide;2-hydroxyethanesulfonic acid
Test material form:
solid: particulate/powder
Details on test material:
Appearance: White to slightly yellow powder
Specific details on test material used for the study:
Batch No.: . 42964
Storage conditions: . At room temperature. Protected from humidity.
Correction factor: . No correction factor
Expiry (or re-test) date: January 2019

In vitro test system

Details on the study design:
Methods
The KeratinoSens cells were first plated on 96-well plates and grown for 24 hours at 37°C. Then the medium was removed and the cells were exposed to the vehicle control or to different concentrations of test item and of positive controls. The treated plates were then incubated for 48 hours at 37°C. At the end of the treatment, cells were washed and the luciferase production was measured by flash luminescence. In parallel, the cytotoxicity was measured by a MTT reduction test and was taken into consideration in the interpretation of the sensitisation results. Two independent runs were performed as part of this study.

PRINCIPLE OF THE ASSAY
This in vitro test uses Human adherent HaCaT keratinocytes, an immortalized cell line. The KeratinoSens is a stably transfected cell line with a plasmid containing a luciferase gene under the transcriptional control of the SV40 origin of replication promoter. This promoter is fused with an ARE sequence.
Potential skin sensitizers are applied to the cells at 12 different concentrations for a period of 48 hours. Sensitizers with electrophilic properties provoke the dissociation of Keap-1 from the transcription factor Nrf2. The free Nrf2 binds to the ARE sequence contained in the plasmid and therefore induces transcription of firefly luciferase. The luciferase reporter gene is under control of a single copy of the ARE-element of the human AKR1C2. The luciferase production is measured by flash luminescence.
In parallel, cytotoxicity is measured by a MTT reduction and is taken into consideration in the interpretation of the sensitisation results. This evaluation is performed in at least two independent runs.

Results and discussion

Positive control results:
Cinnamic Aldehyde (positive control item)
Gene induction values, Imax and EC1.5 values obtained with the positive control for each run:
run 1: Imax=6.71 and EC1.5=4.29
run 2: Imax=7.44 and EC1.5=8.22

In vitro / in chemico

Resultsopen allclose all
Key result
Run / experiment:
other: 1
Parameter:
other: Imax
Value:
1.27
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
no indication of skin sensitisation
Key result
Run / experiment:
other: 1
Parameter:
other: IC50
Value:
6.67
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
no indication of skin sensitisation
Key result
Run / experiment:
other: 1
Parameter:
other: IC30
Value:
5.47
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
no indication of skin sensitisation
Key result
Run / experiment:
other: 2
Parameter:
other: Imax
Value:
1.14
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
no indication of skin sensitisation
Run / experiment:
other: 2
Parameter:
other: IC50
Value:
9.97
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
no indication of skin sensitisation
Key result
Run / experiment:
other: 2
Parameter:
other: IC30
Value:
8.1
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
no indication of skin sensitisation
Other effects / acceptance of results:
All acceptance criteria were fulfilled for the positive and negative controls in each run. Both runs were therefore considered to be valid.

Any other information on results incl. tables

KERATINOSENS RUN

The Imax, IC30, IC50, EC1.5 and viability values obtained for cells treated with test item in each run as well as the mean and SD values are presented in Appendix 2 of the report. The viability values (%), induction values, Imax, IC30, IC50 and EC1.5 values obtained with the positive control are presented in Appendix 3 of the report. In addition the luminescence values of all negative control wells and the %CV between these values for each run are also presented in Appendix 3 of the report.

All acceptance criteria were fulfilled for the positive and negative controls in each run. Both runs were therefore considered to be valid.

First run

This run was performed using the following concentrations: 0.98, 1.95, 3.91, 7.81, 15.63, 31.25, 62.5, 125, 250, 500, 1000 and 2000 μM in culture medium containing 1% DMSO.

At these tested concentrations:

. a slight precipitate was observed at the highest concentration of 2000 μM at the end of the 48-hour treatment period,

. a high decrease in cell viability (i.e. cell viability < 70%) was noted at concentrations ≥ 7.81 μM,

. the corresponding calculated IC30 and IC50 were 5.47 and 6.67 μM, respectively,

. no statistically significant gene-fold induction above the threshold of 1.5 was noted in comparison to the negative control at any tested concentrations. Moreover, the Imax value was < 1.5 (i.e. 1.27).

The evaluation criteria for a negative response were met in this run.

Second run

Due to the cytotoxicity observed in the first run, a lower and narrower range of concentrations was used in the second run. This run was therefore performed using the following concentrations: 0.23, 0.32, 0.45, 0.64, 0.90, 1.3, 1.8, 2.5, 3.6, 5.0, 7.1, 10 μM in culture medium containing 1% DMSO.

At these tested concentrations:

. no precipitate was observed in any test item-treated wells at the end of the 48-hour treatment period,

. a decrease in cell viability (i.e. cell viability < 70%) was only noted at the highest concentration of 10 μM,

. the corresponding calculated IC30 and IC50 were 8.10 and 9.97 μM, respectively,

. no statistically significant gene-fold induction above the threshold of 1.5 was noted in comparison to the negative control at any tested concentrations. Moreover, the Imax value was again < 1.5 (i.e. 1.14). The evaluation criteria for a negative response were also met in this run.

Applicant's summary and conclusion

Interpretation of results:
GHS criteria not met
Conclusions:
The test item HEXAMIDINE DIISETHIONATE, noted as highly cytotoxic at concentrations ≥ 10 μM, was considered as negative in the KeratinoSens assay up to the highest analyzable concentration of 7.1 μM. Therefore, the test item HEXAMIDINE DIISETHIONATE was considered to have no potential to activate the Nrf2 transcription factor, under the experimental conditions of this study.
Executive summary:

All acceptance criteria were fulfilled for the positive and negative controls in each run. Both runs were therefore considered to be valid.

First run

This run was performed using the following concentrations: 0.98, 1.95, 3.91, 7.81, 15.63, 31.25, 62.5, 125, 250, 500, 1000 and 2000 μM in culture medium containing 1% DMSO.

At these tested concentrations:

. a slight precipitate was observed at the highest concentration of 2000 μM at the end of the 48-hour treatment period, in test item-treated wells,

. a high decrease in cell viability (i.e. cell viability < 70%) was noted at concentrations ≥ 7.81 μM,

. the corresponding calculated IC30 and IC50 were 5.47 and 6.67 μM, respectively,

. no statistically significant gene-fold induction above the threshold of 1.5 was noted in comparison to the negative control at any tested concentrations. Moreover, the Imax value was < 1.5 (i.e. 1.27).

The evaluation criteria for a negative response were met in this run.

CiToxLAB France/Study No. 45434 TIK/HEXAMIDINE DIISETHIONATE/LA MESTA Chimie Fine

10/32

Second run

Due to the cytotoxicity observed in the first run, a lower and narrower range of concentrations was used in the second run. This run was therefore performed using the following concentrations 0.23, 0.32, 0.45, 0.64, 0.90, 1.27, 1.8, 2.5, 3.6, 5.0, 7.1, 10 μM in culture medium containing 1% DMSO.

At these tested concentrations:

. no precipitate was observed in any test item-treated wells at the end of the 48-hour treatment period,

. a decrease in cell viability (i.e. cell viability < 70%) was only noted at the highest concentration of 10 μM,

. the corresponding calculated IC30 and IC50 were 8.10 and 9.97 μM, respectively,

. no statistically significant gene-fold induction above the threshold of 1.5 was noted in comparison to the negative control, at any tested concentrations. Moreover, the Imax value was again < 1.5 (i.e. 1.14).

The evaluation criteria for a negative response were also met in this run.

The evaluation criteria for a negative response were met in both runs, the final outcome is therefore negative. This negative result can be used to support the discrimination between skin sensitizers and non-sensitizers in the context of an integrated approach to testing and assessment. It cannot be used on its own to conclude on a skin sensitisation potential.