trisodium (2S)-2,6-bis(3-carboxylatopropanamido)hexanoate

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Based on the negative results from three in vitro assays, namely an Ames study, a mammalian cell gene mutation assay and a chromosome aberration study, each performed with and without metabolic activation it is concluded that the substance is non-mutagenic and hence, not subject to classification for mutagenicity according to CLP (Regulation EC No. 127272008).

Link to relevant study records

Reference

Reference 1

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Target gene:

The phenotypic characteristics checked, were: Histidine requirement, presence or absence of R-factor plasmids where appropriate (i.e. Ampicillin resistance in strains TA 98, TA 100 and Ampicillin + Tetracycline resistance in strain TA 102); the presence of characteristic mutations as UVrB and rfa mutation.

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and TA 102

Metabolic activation:

with and without

Metabolic activation system:

Due to migration, the value was transferred to one of the current document's attachments

Test concentrations with justification for top dose:

The test sample has been tested at:
1) 5 mg/plate
2) 1.5 mg/plate
3) 0.5 mg/plate
4) 0.15 mg/plate
5) 0.05 mg/plate

Vehicle / solvent:

The test item at 50 mg/ml in water and 4 subsequent dilutions in water of semi-log intervals between them have been prepared.

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

9-aminoacridine

sodium azide

mitomycin C

other: Daunomycin

Details on test system and experimental conditions:

NUMBER OF REPLICATIONS:
- Number of cultures per concentration: triplicate
- Number of independent experiments :2

METHOD OF TREATMENT/ EXPOSURE:
- Cell density at seeding (if applicable): n/a
- Test substance added : in agar (plate incorporation)

TREATMENT AND HARVEST SCHEDULE:
- Preincubation period, if applicable:
Microbiological controls
Aliquots of maximum concentration of the assay samples, Solvent, PBS, S9 mix and Top Agar, were directly placed in TSA and MGA plates. The development of any bacterial colonies have been observed after 48-72 hours of incubation at 37°C±1°C and recorded.
- Exposure duration/duration of treatment: 37±1°C for 48-72 hours.
- Harvest time after the end of treatment (sampling/recovery times): none

METHODS FOR MEASUREMENT OF CYTOTOXICITY
- Method: background growth inhibition;
The sample toxicity assay for the test strains was determining any reduction in culture growth and number
of spontaneously reverting organisms caused by the assay sample.

Evaluation criteria:

ASSAY VALIDITY CRITERIA
In the microbiological controls performed on MGA and TSA plates, top-agar, solvent used, assay sample at the highest concentration tested, PBS and S9 Mix should not be contaminated by more than two colonies per plates.
On average, for the TA 1535, TA 1537 and TA 98 strains, the number of reverting colonies developed by the positive control should be at least 300% higher than that of the respective negative control (lower limit for positive control/negative control ratio for strains with low mutation frequency); for the TA100 and TA102 strains, the number of reverting colonies developed by the positive control should be at least 200% higher than that of the respective negative control (a 20% of variation is accepted at the lower limit of the positive control/negative control ratio in strains with high mutation frequency).
These criteria refer to internal method validation only. OECD 471 guideline doesn't give any reference thereof.
The average number of spontaneously reverting colonies per plate in the negative controls should be included between the validated limits.

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 102

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

Remarks on result:

other: not mutagenic

Assay validity criteria

Microbiological controls:the microbiological controls performed on the assay sample at maximum concentration prepared, on Top Agar supplemented, solvents, PBS and S9mix, didn't show any contamination.

Negative and positive controls: the average number of spontaneously reverting colonies in the negative control plates did not exceed the established limits and all positive controls caused a significant increase of number of reverting colonies.

Genetic characteristics of the bacterial strains: the verification of the genetic characteristics showed that the test strains maintained the required genetic properties in both the assay repetitions.

Toxicity of the test substance

On the basis of the results obtained during the test, the test substance did not show toxic effects either in

the presence or absence of the enzymatic system for metabolism activation.

Mutacienic Activity

Neither reproducible increase in the number of revertants colonies per plate in any strain with or without metabolic activation system was detected. Besides, the statistical test applied showed no significant difference between the numbers of revertants colonies for assay sample vs. negative control.

Conclusions:

On the basis of the results interpreted according to OECD 471:1997, the test substance "TRISODIUM (2S)-2,6-BIS(3-CARBOXYLATOPROPANAMIDO)HEXANOATE" tested as recommended by Standards, proved to be NOT MUTAGENIC for all the test strains, either in the presence or absence of metabolic activation.

Executive summary:

On the test item "TRISODIUM (2S)-2,6-BIS(3-CARBOXYLATOPROPANAMIDO)HEXANOATE", a genotoxicological study was carried out to evaluate its mutagenic effects. The following test was performed:

- Bacterial reverse mutation assay (Ames test).

The Bacterial reverse mutation assay was performed on five mutant strains of Salmonella typhimurium (TA 1535, TA 1537, TA 98, TA 100, TA 102).

The presumed mutagenic activity of the test substance was determined by comparing the number of reverting colonies in treated cultures with the number of the reverting organisms in the control cultures. The direct incorporation method in a plate was used both in the presence of, and without, an enzymatic system for metabolic activation.

The test item has been tested at 50 mg/mL, and 4 subsequent dilutions of semi-log intervals between them.

The assay was performed in two replicates.

On the basis of the results interpreted according to OECD 471:1997, the test substance "TRISODIUM (2S)-2,6-BIS(3-CARBOXYLATOPROPANAMIDO)HEXANOATE" tested as recommended by Standards, proved to be NOT MUTAGENIC for all the test strains, either in the presence or absence of metabolic activation.

Reference 2

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Type of information:

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

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Justification for type of information:

Justification for Read Across is detailed in the report attached to the IUCLID section 13.

Qualifier:

equivalent or similar to guideline

Guideline:

other: OECD Guideline 473 (In Vitro Mammalian Chromosomal Aberration Test) (migrated information)

Principles of method if other than guideline:

Chromosomal aberration tests were carried out using a Chinese hamster fibroblast cell line, CHL, as described elsewhere (Ishidate & Odashima, 1977).

GLP compliance:

no

Type of assay:

in vitro mammalian chromosome aberration test

Species / strain / cell type:

Chinese hamster lung fibroblasts (V79)

Details on mammalian cell type (if applicable):

The cell line was originally established from the lung of a newborn female at the Cancer Research Institute, Tokyo and was maintained by 4-day passages in Minimum Essential Medium (MEM; GIBCO) supplemented by 10 % calf serum. The modal chromosome number is 25 and the doubling time was approximately 15 hr.

Metabolic activation:

without

Test concentrations with justification for top dose:

Three dosed; the maximum dose tested 1 mg/ml

Vehicle / solvent:

- Vehicle: physiological saline solution.

Untreated negative controls:

yes

Remarks:

The experiment was carried out on 190 synthetic food additives and 52 food additives derived from natural sources. Both positive and negatve results were recorded.

Details on test system and experimental conditions:

EXPOSURE
The cells were exposed to each sample at three different doses for 24 and 48 hr.

CHROMOSOME PREPARATION
Colcemid (final concn 0.2 µg/ml) was added to the culture 2 hr before cell harvesting. The cells were then trypsinized and suspended in a hypotonic KCI solution (0.075 M) for 13 min at room temperature. After centrifugation the cells were fixed with acetic acid-methanol (1:3, v/v) and spread on clean glass slides. After air-drying, the slides were stained with Giemsa solution (1.5 %, at pH 6.8; E. Merck) for 12-15 min. A hundred well-spread metaphases were observed under the microscope (x 600 with a nocover objective lens).

EXAMINATION
The incidence of polyploid cells as well as of cells with structural chromosomal aberrations such as chromatid or chromosome gaps, breaks, exchanges, ring formations, fragmentations and others, was recorded on each culture plate.

TEST CONCENTRATION
The maximum dose of each sample was selected by a preliminary test in which the dose needed for 50 % cell-growth inhibition was estimated using a cell densitometer (Monocellater, Olympus Co., Ltd).

Evaluation criteria:

The results were considered to be negative if the incidence was less than 4.9 %, equivocal if it was between 5.0 and 9.9 %, and positive if it was more than 10.0 %. When no reasonable dose-response relationships were found, additional experiments were carried out at similar dose levels.

For a quantitative evaluation of the clastogenic potential of the positive samples, the D20 was calculated, which is the dose (mg/ml) at which structural aberrations (including gaps) were detected in 20 % of the metaphases observed. In addition, the TR value was calculated, which indicates the frequency of cells with exchange-type aberrations per unit dose (mg/ml). TR values are relatively high for chemicals that show carcinogenic potential in animals (Ishidate, Sofuni & Yoshikawa, 1981).

Key result

Species / strain:

Chinese hamster lung fibroblasts (V79)

Remarks:

all strains/cell types tested

Metabolic activation:

without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Untreated negative controls validity:

valid

Remarks:

the incidence of aberrations was usually less than 3.0 %

Additional information on results:

Incidence of polyploid cells: 0 % at 48 hrs
Structural aberration: 1.0 % at 48 hrs

Conclusions:

The substance did not induce chromosome aberration in Chinese hamster fibroblast cell line.

Executive summary:

Method

The substance was tested for mutagenic effects in vitro in using a Chinese hamster fibroblast cell line. The cell line was originally established from the lung of a newborn female at the Cancer Research Institute, Tokyo. In the present studies, no metabolic activation systems were applied.

Untreated cells and solvent-treated cells served as negative controls. The experiment was carried out on 190 synthetic food additives and 52 food additives derived from natural sources. Both positive and negatve results were recorded.

Results

Based on the results of these experiments, it is concluded that tested substance did not induce chromosome aberration in Chinese hamster fibroblast cell line.

Reference 3

Endpoint:

in vitro DNA damage and/or repair study

Type of information:

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

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Justification for type of information:

Justification for Read Across is detailed in the report attached to the IUCLID section 13.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 479 (Genetic Toxicology: In Vitro Sister Chromatid Exchange Assay in Mammalian Cells)

Principles of method if other than guideline:

Sister chromatid exchange Human peripheral blood Lymphocytes.

GLP compliance:

not specified

Type of assay:

sister chromatid exchange assay in mammalian cells

Species / strain / cell type:

lymphocytes: human peripheral blood lymphocytes

Additional strain / cell type characteristics:

not specified

Metabolic activation:

without

Test concentrations with justification for top dose:

0, 10, 50 and 100 µg/ml

Vehicle / solvent:

Saline solution

Untreated negative controls:

yes

Details on test system and experimental conditions:

METHOD OF APPLICATION
The whole-blood microculture technique was used. 0.4 ml of venous whole blood was inoculated to 5 ml of the culture medium.

CULTURE MEDIUM
- Composition: containing
41.6 mg of RPMI 1640 (JR Scientific Inc., Woodland, CA)
1 ml of fetal calf serum (purchased from Tianjin Medical College, China)
1.5 mg of PHA (produced by Guangdong Biological Product Institute, China)
10000 IU each of penicillin and streptomycin
0.1 ml of 5 % NaHCO3.
- pH: 7

INCUBATION
The mixture was incubated for 24 h. Bromodeoxyuridine (BrdU), at 10 µg/ml, was added at 24 h of culture.
At 48 h of culture, substance (dissolved in saline solution) or saline solution (for control) was added and the cultures were incubated for another 24 h.

HARVESTING
Peripheral Blood Lymphocytes (PBL) were harvested at the end of the 24 h exposure period (total culture time = 72 h) with 0.05 µg/ml colchicine being added 2 h before harvesting.
All cultures were incubated at 37 °C in the dark.
PBL, harvested after gentle centrifugation (1000 rpm, 10 min) and discarding the supernatant, were resuspended in 0.075 M KCI solution for hypotonic treatment for 20 min, centrifuged again, and finally fixed in methanolacetic acid solution (3:1) three times.

SLIDES PREPARATION
A few drops of the cell suspension were dropped onto a clean slide taken from icy water and frame-dried. The slides were incubated in 2 × SSC solution in petri dishes at 70 °C and irradiated simultaneously under a UV lamp (30 W) at a distance of 10 cm for 20 min. The preparations were stained in 3 % Giemsa solution for 10 min after being rinsed with tap water (Xing, 1990; Zhang, 1991).

SCE ANALYSIS
SCE analysis was carried out on cells having replicated for two cycles in the presence of BrdU. Ten metaphases were scored for each treatment.

Statistics:

Statistical methods for analysis of variance (AOV) based on the square roots of SCE were used (Crossen, 1977; Morgan, 1977, 1981; Vercauteren, 1984)

Key result

Species / strain:

lymphocytes: human peripheral blood lymphocytes

Metabolic activation:

without

Genotoxicity:

negative

Untreated negative controls validity:

valid

Additional information on results:

After multiple comparisons, the effects of test article on SCE in PBL are not significant.

Further substances were involved in the test and divided into two groups with each group consisting of five substances. A randomized complete-block design was used to avoid the influence of individual differences on SCE. One person's blood was used for each test and regarded as one block.

Remarks on result:

other: no mutagenic potential

 

 

Conclusions:

No mutagenic potential

Executive summary:

Effects of Target substance on SCE in PBL

The experimental data show that the treatment with test substance did not induce a significant increase in SCE. The test item is an essential substance for PBL growth. Thus, it was unexpected that the target substance can significantly induce SCE in PBL. We infer that the addition of exogenous substances might result in an imbalance among tested substances in the medium and cause metabolic disturbances in cells. This might further influence the activities of various enzymes and result in the induction of SCE.

However, this is only a hypothesis and the actual molecular mechanisms involved remain unsolved.

Reference 4

Endpoint:

in vitro gene mutation study in mammalian cells

Type of information:

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

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: official EFSA document, only short abstract available.

Justification for type of information:

Justification for Read Across is detailed in the report attached to the IUCLID section 13.

Qualifier:

according to guideline

Guideline:

OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test)

GLP compliance:

not specified

Type of assay:

other: In vitro gene mutation assay in mammalian cells

Species / strain / cell type:

mouse lymphoma L5178Y cells

Metabolic activation:

with and without

Test concentrations with justification for top dose:

The maximum tested concentration was 6500 µg/plate.

Key result

Species / strain:

mouse lymphoma L5178Y cells

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

not specified

Untreated negative controls validity:

not specified

Positive controls validity:

not specified

Conclusions:

No evidence of mutagenicity observed.

Executive summary:

Method

Gene mutation tests (in accordance with OECD Guideline 476) at the TK locus of the L5178Y cell line were performed, in both the presence and absence of metabolic activation, with concentrated liquid L-lysine HCl at doses up to 6500 µg/ml.

Results

No evidence of mutagenicity was found.

Reference 5

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Type of information:

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

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Justification for type of information:

See attached justification

Reason / purpose for cross-reference:

read-across source

Qualifier:

equivalent or similar to guideline

Guideline:

other: OECD Guideline 473 (In Vitro Mammalian Chromosomal Aberration Test) (migrated information)

Species / strain:

Chinese hamster lung fibroblasts (V79)

Metabolic activation:

without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Untreated negative controls validity:

valid

Remarks:

the incidence of aberrations was usually less than 3.0 %

Conclusions:

A reliable study investigating the chromosomal aberrations in V79 cells (according to OECD 473) has been conducted on the source substance, showing that the substance is not genotoxic.
According to the rationale explained in details in the attached read across justification, it is assumed that target and read-across substance, do share the same toxicological mechanisms and the effects of the target substance are predicted to be equal to the effects of the source substance.
The target substance has no mutagenic potential.

Reference 6

Endpoint:

in vitro DNA damage and/or repair study

Type of information:

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

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Justification for type of information:

See attachment for further details on READ across apporach

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

according to guideline

Guideline:

other: OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test) (migrated information)

Species / strain:

mouse lymphoma L5178Y cells

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

not specified

Untreated negative controls validity:

not specified

Species / strain:

lymphocytes: human peripheral blood

Metabolic activation:

without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

not specified

Untreated negative controls validity:

not specified

Conclusions:

A reliable in vitro gene mutation assay in mammalian cells study according to OECD Guideline 476 is available for the source substance, showing that the substance is not genotoxic.
According to the rationale explained in details in the attached read across justification, it is assumed that target and read-across substance, do share the same toxicological mechanisms and the effects of the target substance are predicted to be equal to the effects of the source substance.
The target substance has no mutagenic potential.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

The substance was tested for genetic toxicity on bacteria in one in-vitro study.

Two in-vitro studies (genetic toxicity on mammalian cells and Chromosomal aberration) on an analougue substance have been considered for the assessment using a read across approach.

Based on the findings in these studies, the substance is NOT classified as genotoxic according to CLP (Regulation EC No. 1272/2008).