Methyl α-D-mannopyranoside

Eye irritation

Administrative data

Endpoint:

eye irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2021-03-02 to 2021-03-04

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2021

Report date:

2021

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

other: EU method B.69 RECONSTRUCTED HUMAN CORNEA-LIKE EPITHELIUM (RhCE) TEST METHOD FOR IDENTIFYING CHEMICALS NOT REQUIRING CLASSIFICATION AND LABELLING FOR EYE IRRITATION OR SERIOUS EYE DAMAGE

Version / remarks:

31 July 2019

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

OECD Guideline 492 (Reconstructed Human Cornea-like Epithelium (RhCE) Test Method for Identifying Chemicals Not Requiring Classification and Labelling for Eye Irritation or Serious Eye Damage)

Version / remarks:

18 Jun 2019

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Methyl α-D-mannopyranoside

EC Number:

210-502-3

EC Name:

Methyl α-D-mannopyranoside

Cas Number:

617-04-9

Molecular formula:

C7H14O6

IUPAC Name:

(2R,3S,4S,5S,6S)-2-(hydroxymethyl)-6-methoxyoxane-3,4,5-triol

Test material form:

solid

Test animals / tissue source

Species:

human

Details on test animals or tissues and environmental conditions:

- Justification of the test method and considerations regarding applicability: The reconstructed human cornea-like epithelium (RhCE) model is an accepted in vitro method to replace animal testing. The human eye EpiOcular-model closely mimics the biochemical and physiological properties of the human eye, i.e. the cornea.
- Description of the cell system used, and the mycoplasma status of the cell live: The EpiOcular™-model is a nonkeratinized epithelium prepared from normal human keratinocytes. It models the cornea epithelium with progressively stratified, but not cornified cells. Long term antibiotic and antimycotic free culture with no contamination was applicable (result: sterile). Therefore, the QA statement from the supplier considered a pass for the sterility criterion.
- Cell line used, its source, passage number and confluence of cells used for testing: Keratinocyte strain: 4F1188; passage number: not specified; Barrier function: 14.26 min (within acceptance criteria of supplier)
- RhCE tissue or hCE cell construct used, including batch number: EpiOcular™ Tissue (OCL-200, OCL-212) from MatTek In Vitro Life Science Laboratories, Bratislava, Slovakia, Lot no: 30699

Test system

Vehicle:

unchanged (no vehicle)

Controls:

yes, concurrent positive control

yes, concurrent negative control

Amount / concentration applied:

TEST MATERIAL
- Amount applied: 50 mg/tissue

Controls
- Amount applied: 50 µL/tissue

Duration of treatment / exposure:

6 hours (± 15 minutes)

Duration of post- treatment incubation (in vitro):

18 hours (± 15 minutes)

Number of animals or in vitro replicates:

2

Details on study design:

- Details of the test procedure used
The test item was applied topically to a reconstructed human cornea-like epithelium model (EpiOcular™) followed by determination of the cell viability. Cell viability was determined by enzymatic conversion of vital dye MTT into a blue formazan salt and measurement of the formazan salt after extraction from tissues. The percent reduction of cell viability in comparison to untreated negative controls was used to predict the eye irritation potential.

- RhCE tissue construct used, including batch number
Designation: EpiOcular™ Tissue (OCL-200, OCL-212)
Lot No.: 30699
Keratinocyte strain: 4F1188
Supplier: MatTek In Vitro Life Science Laboratories

- Doses of test chemical and control substances used
Solid test item: 50 mg per tissue
Negative control: 50 µL per tissue
Positive control: 50 µL per tissue

- Duration and temperature of exposure, post-exposure immersion and post-exposure incubation periods
Exposure: 6 hours (± 15 minutes) at 37 °C and 5 % CO2
Post-exposure immersion: 25 minutes (± 2 minutes) at room temperature
Post-exposure incubation: 18 hours (± 15 minutes) at 37 °C and 5 % CO2

- Indication of controls used for direct MTT-reducers and/or colouring test chemicals
A 1.0 mg/mL MTT solution (in DMEM) was prepared. 50 mg of the test item were added to 1 mL of the MTT solution in a 6-well plate and the mixture was incubated at 37 ± 1°C and 5% CO2 and protected from light for 3 hours (± 5 minutes). Sterile deionised water (50 µL) was used as negative control concurrently. If the MTT solution colour turned blue/purple, the test item was presumed to have reduced the MTT.
The non-colored test item was tested for its ability to become colorant after contact with water or isopropanol. For this purpose, 50 mg of the test item were added to 1.0 mL of water in a 6-well plate and the mixture was incubated for 1 hour at 37 ± 1°C and 5 % CO2 protected from light. Furthermore, 50 mg were added to 2 mL isopropanol, the same amount as used for MTT extraction, and was incubated in 6-well plates for 2 to 3 hours at room temperature.
The pre-test for direct MTT-reducing capacity of the test item did not result in blue color, i.e. the test item is not a direct MTT reducer and the test item has no colorant properties. Therefore, no additional controls were used.

- Number of tissue replicates used per test chemical and controls (positive control, negative control, NSMTT, NSCliving and NSCkilled)
The test item as well as the positive and negative control were tested in batch-duplicates. Therefore, a total number of six tissues were used in this study.

- Wavelength used for quantifying MTT formazan, and linearity range of measuring device (e.g. spectrophotometer)
The OD was read using a spectrophotometer at 570 nm wavelength. A functional test of the microplate reader was performed using a filter test plate. The results of the functional test and the printout of the measurement were included in the raw data of the study.
Spectrophotometer used: ELx800, BioTek Instruments GmbH, Bad Friedrichshall, Germany

- Description of the method used to quantify MTT formazan
After the post-treatment incubation period, the treated tissues were transferred in a 24-well plate filled with 300 µL MTT solution (1.0 mg/mL MTT). Once all the tissues were placed into the 24-well plate, the plate was incubated for 180 minutes (±10 minutes) at 37 °C and 5 % CO2. The inserts were removed from the 24-well plate after 180 minutes (± 10 minutes). The bottom of the inserts was blotted on absorbent material, and then transferred to a 6-well plate containing 2 mL isopropanol so that no isopropanol was flowing into the inserts. The plate was sealed with a standard plate sealer. To extract the MTT, the plate was placed on an orbital plate shaker and shaken for 2 to 3 hours at room temperature. The corresponding negative and positive controls were treated identically. The extract solution was mixed and 2 x 200 µL were transferred into a 96-well plate.

- Description of evaluation criteria used including the justification for the selection of the cut-off point for the prediction model
The test item is identified as not requiring classification and labeling according to UN GHS (No Category) if the mean percent tissue viability is more than 60 %. In this case no further testing in other test methods is required.
If the mean percent tissue viability is less than or equal 60 %, no prediction can be made. In this case, further testing with other test methods will be required because RhCE test methods show a certain number of false positive results and cannot resolve between UN GHS Categories 1 and 2.

- Acceptable variability between tissue replicates for positive and negative controls
The results are acceptable if:
1. The negative control OD >0.8 and <2.5
2. The mean relative viability of the positive control is:
a) 30-minute exposure (treatment of liquid test items): below 50 % of control viability
b) 6-hour exposure (treatment of solid test items): below 50 % of control viability

- Acceptable variability between tissue replicates for the test chemical
The difference of viability between the two relating tissues of a single chemical is <20 % in the same run (for positive and negative control tissues and tissues of single chemicals). This applies also to the killed controls (single chemicals and negative killed control) and the colorant controls which are calculated as percent values related to the viability of the relating negative control.

- Acceptability of the Positive and Negative Control based on Historical Data of the Testing Laboratory:
The negative control data meet the acceptance criteria if the mean OD value is higher or equal than a historically established boundary at 570 nm. The boundary is two standard deviations below the current historical mean.
The positive control data meet the acceptance criteria if the mean viability value, expressed as % of the negative control, is lower than or equal to a historically established boundary. The boundary is two standard deviations above the current historical mean.

Results and discussion

In vitro

Results

Irritation parameter:

mean percent tissue viability 

Run / experiment:

Mean

Value:

89.8

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Remarks:

100

Positive controls validity:

valid

Remarks:

30.5

Remarks on result:

no indication of irritation

Other effects / acceptance of results:

OTHER EFFECTS:
- Visible damage on test system: not specified

DEMONSTRATION OF TECHNICAL PROFICIENCY: not specified

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: yes. The negative control OD is >0.8 and <2.5 (1.435 and 1.395). For laboratory: Acceptance Criterion of mean OD ≥ 1.113, Result 1.415
- Acceptance criteria met for positive control: yes. The mean relative viability of the positive control is below 50 % of the negative control viability (30.5 %). For laboratory: Acceptance Criterion of mean viability ≤ 50.1 %, Result 30.5 %
- Other: The difference of viability between the two relating tissues of a single chemical is <20 % (values between 0.4 % to 3.9 %) in the same run (for positive and negative control tissues and tissues of single chemicals).

Any other information on results incl. tables

Group	Tissue 1		Tissue 2		Mean		SD	Difference between tissue replicates
	OD	Viability	OD	Viability	OD	Viability	Viability
Negative Control	1.435	101.4%	1.395	98.6%	1.415	100.0%	1.98	2.8%
Positive Control	0.434	30.7%	0.429	30.3%	0.432	30.5%	0.28	0.4%
Test item	1.242	87.8%	1.297	91.7%	1.270	89.8%	2.76	3.9%

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

The test item did not show an eye irritating potential.

Executive summary:

A study according to OECD TG 492 was conducted to investigate the potential of the test item to induce eye irritation in an in vitro human cornea model. The test item was applied topically to a reconstructed human cornea-like epithelium model (EpiOcular) followed by determination of the cell viability. Cell viability was determined by enzymatic conversion of vital dye MTT into a blue formazan salt and measurement of the formazan salt after extraction from tissues. The percent reduction of cell viability in comparison to untreated negative controls was used to predict the eye irritation potential. Duplicates of the EpiOcular-model were treated with the test item, the negative or the positive control for 6 hours (± 15 minutes). 50 mg of the test item and 50 µL of either the negative control (sterile deionized water) or the positive control (methyl acetate) were applied to the tissues. All acceptability criteria after treatment with the negative control (sterile deionized water) and the positive control (methyl acetate) were met. Following treatment with the test item, the tissue viability was 89.8 % and, thus, higher than 60 %, i.e. according to OECD 492 the test item is identified as not requiring classification and labeling according to UN GHS (No Category). Under the conditions of the present study, the test item did not show an eye irritating potential.