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Toxicological information

Skin irritation / corrosion

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Administrative data

Endpoint:
skin irritation: in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
Data is from experimental study report

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2018
Report Date:
2018

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method)
Principles of method if other than guideline:
The purpose of this study was to assess potential for the test article to be dermal irritants. The dermal irritation potential of test article may be predicted by measurement of their cytotoxic effect, as reflected in the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, in the MatTek EpiDerm™ model (MatTek Corp., Ashland, MA).
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Name of test material (as cited in study report): 4-methyl-1-phenylpyrazolidin-3-one
- Molecular formula: C10H12N2O
- Molecular weight: 176.218g/mol
- Substance type: Organic
- Physical state: Solid

In vitro test system

Test system:
human skin model
Source species:
human
Cell type:
non-transformed keratinocytes
Cell source:
other: EpiDerm™ 3-dimensional human tissues used in this study
Source strain:
other: Not applicable
Details on animal used as source of test system:
- Description of the cell system used:The normal human-derived keratinocytes were cultured at the air-liquid interface in a chemically defined medium on a permeable polycarbonate insert (surface 0.5 cm2). They were cultured in chemically defined serum free medium to form a multi-layered epithelium similar to that found in native epidermis. Each lot of tissues was Quality Assured by MatTek according to specific QC standards including: histology, tissue viability (MTT mean optical density), reproducibility (SD) and tissue thickness.- Test System IdentificationAll of the EpiDerm™ 3-dimensional human tissues used in this study were identified by the date of arrival and the lot number. Certificate of Analysis for the tissues are included in this report. Tissue plates were appropriately labeled with study information.
Justification for test system used:
The 3-Dimensional Human Dermal Epithelial Model (EpiDerm™, MatTek, Ashland, MA) is made up of normal human keratinocytes in serum free medium. The cells form an epithelial tissue that consists of organized basal, spinous, granular, and cornified layers analogous to those found in vivo. The EpiDerm™ model also contains epidermis-specific differentiation markers such as pro-filaggrin, the K1/K10 cytokeratin pair, involucrin, and type I epidermal transglutaminase, as well as keratohyalin granules, tonofilament bundles, desmosomes, and a multi-layered stratum corneum containing intercellular lamellar lipid layers arranged in patterns characteristic of in vivo epidermis. Each lot of tissues was Quality Assured by MatTek, Inc. according to specific QC standards including: histology (cell layers), tissue viability (MTT mean optical density) and reproducibility (SD). Tissue plates were appropriately labeled with study information. Bias was not a factor in this test system.
Vehicle:
unchanged (no vehicle)
Details on test system:
The tissues were exposed to the test article neat (undiluted) on June 28, 2017 (Run 1 of 1). EpiDerm™ tissues were purchased from MatTek. Quality control of the tissues was performed by MatTek and the Certificate of Analysis (CoA) for the tissues is provided and is kept in the study binder. Tissues were exposed for approximately 1 hour, with 35 minutes in an approximately 37°C, 5% CO2 humidified incubator and the remaining 25 minutes at room temperature. Following the exposure time, the tissues were rinsed and placed in fresh media for approximately 24 hours. The media was then changed again and the tissues were incubated in fresh media for another ~18 hours for a total of approximately 42 hour post-exposure recovery period. The tissue viability was then assessed by MTT assay. The tissue CoA was used instead of verification of barrier properties of the tissue.MTT and Color Pre-testsPretesting for MTT auto-reduction and coloring was not performed for this study but was based on the results obtained from another study (CYP1690_R1b).MTT AssayFollowing the rinsing period, the MTT assay was performed by transferring the tissues to 24-well plates containing 300 µL MTT medium (1.0 mg/mL). After 2 hours, 57 minute and 25 second MTT incubation at approximately 37°C, approximately 5% CO2 in a humidified incubator, the blue formazan salt was extracted by submerging tissues in 2 mL isopropanol in a 24-well plate. The extraction time was approximately 2 hours 04 minutes and 11 seconds with gentle shaking. The optical density of the extracted formazan (200 µL/well of a 96-well plate) was determined using a Synergy H4 spectrophotometer at 570 nm. Relative cell viability is calculated for each tissue as % of the mean negative control tissues.Evaluation of Test Article in the Cell Models:1. Cell system: Upon receipt, the MatTek EpiDerm™ tissue cultures were placed in 0.9 mL of fresh Maintenance medium (in a 6-well plate). The culture inserts are incubated for ~one hour. The tissues were then transferred to 6-well plates containing 0.9 mL fresh Maintenance medium and they were incubated overnight at ~37°C, 5% CO2 in a humidified incubator.2. Control and Test Article Exposures: On the day of dosing, the tissues are then removed from the incubator and the controls and the test article are applied topically to tissues by pipette. Tissues were exposed to controls and the test articles for one hour, with ~35 minutes in a 37°C, 5% CO2 humidified incubator and the remaining 25 minutes at room temperature.a) Controls30 µL of negative control DPBS, positive control 5% SDS was applied topically to the tissue and gently spread by placing a nylon mesh on the apical surface of each tissue, if necessary.b)Test ArticleFor solid test article, the tissues were moistened with 25 μL of ultrapure water to improve contact of the tissue surface with the test article. Approximately 25 mg of each test article was evenly applied to the apical surface of each tissue (n=3). All the tissues were placed into the ~37°C incubator with 5% CO2. The exposure times were approximately 1 hour, with ~35 minutes exposure in the incubator and ~25 minutes at room temperature. 3.Post-exposure treatmentAfter the 1 hour exposure, the tissues were rinsed 20 to 25 times with 1 mL of DPBS. The apical surface was gently blotted with a cotton swab. The tissues were placed in 0.9 mL of fresh Maintenance medium (6-well plate) for either 25 hours, 38 minutes and 23 seconds or for 24 hours, 10 minutes and 09 seconds (as there were numerous tissues, they had to be broken down into 2 sets to complete dosing in a timely manner). After this initial ~24 hour incubation, the tissues were placed in 6-well plates containing 0.9 mL fresh Maintenance medium and incubated for another 17 hours, 03 minutes and 34 seconds prior to performing the MTT assay, for a total of an approximately 42 hour post-exposure incubation.RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE- Model used: The EpiDerm™ 3 dimensional human tissue model- Tissue Lot number(s): 26459- Date of initiation of testing: 6/08/2017TEMPERATURE USED FOR TEST SYSTEM- Temperature used during treatment / exposure: 37°C- Temperature of post-treatment incubation (if applicable): 37°CREMOVAL OF TEST MATERIAL AND CONTROLS-Volume and number of washing steps: TwiceMTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE- MTT concentration: 300 µL MTT medium (1.0 mg/mL).- Incubation time: After 2 hours, 57 minute and 25 second MTT incubation- Spectrophotometer: Synergy H4 spectrophotometer - Wavelength: 570 nm- Filter: No data- Filter bandwidth: No data- Linear OD range of spectrophotometer: No dataNUMBER OF REPLICATE TISSUES: 3CALCULATIONS and STATISTICAL METHODSAll data were background subtracted before analysis. MTT data are presented as % viable compared to negative control. Data were generated as follows: MTT AssayBlanks:·        The optical density (OD) mean from all replicates for each plate (ODblank). Negative Controls (NC):·        The blank corrected value was calculated: ODNC= ODNCraw– ODblank. ·        The OD mean per NC tissue was calculated. ·        The mean OD for all tissues corresponds to 100% viability. ·        The mean, standard deviation (SD), standard error of the mean (SEM) and the percent coefficient of variation (% CV) was calculated. Positive Control (PC):·        Calculate the blank corrected value: ODPC= ODPCraw– ODblank. ·        The OD mean per PC tissue was calculated. ·        The viability per tissue was calculated: %PC = [ODPC/ mean ODNC] x 100. ·        The mean viability for all tissues was calculated: Mean PC = Σ %PC / number of tissues. ·        The standard deviation (SD), standard error of the mean (SEM) and the percent coefficient of variation (% CV) was calculated. Tested compound :·        Calculate the blank corrected value ODTT= ODTTraw– ODblank. ·        The OD mean per tissue was calculated. ·        The viability per tissue was calculated: %TT = [ODTT/ mean ODNC] x 100. ·        The mean viability for all tissues was calculated: Mean TT = Σ %TT / number of tissues. ·        The standard deviation (SD), standard error of the mean (SEM) and the percent coefficient of variation (% CV) was calculated. Data Correction Procedure for MTT Interfering Compounds (if applicable)True viability = Viability of treated tissue – Interference from test article = ODtvt– ODktwhere ODkt= (mean ODtkt– mean ODukt).ODtvt= optical density of treated viable tissueODkt= optical density of killed tissuesODtkt= optical density of treated killed tissueODukt= optical density of untreated killed tissue (NC treated tissue) Data Correction Procedure for Colored Compounds (if applicable)True viability = Viability of treated tissue incubated in MTT media – Viability of treated tissue incubated in media without MTT = ODtvt– ODvt.ODtvt= optical density of treated viable tissue incubated in MTT mediaODvt= optical density of viable tissues incubated in media alone- Evaluation of data The results of the assay was evaluated and compared to negative control.  Table: Criteria for in vitro Interpretation: In VitroResults In VivoPredictionMean tissue viability ≤50% Irritant (I), R38Mean tissue viability >50% Non-irritant (NI)- Assay quality controls- Negative Controls (NC)The Dulbecco’s phosphate buffered saline (DPBS) was used as a NC. The assay passed all acceptance criteria if the ODs of the negative control exposed tissues were between ≥0.8 and ≤2.8.  - Positive Controls (PC)5% solution of sodium dodecyl sulfate was used as a PC. The assay is meeting the acceptance criteria if the viability of the PC is ≤20% of the negative control.   - Standard Deviation (SD)The standard deviation (SD) calculated from individual percent tissue viabilities of the test article exposed replicates was ≤18.
Control samples:
yes, concurrent negative control
yes, concurrent positive control
Amount/concentration applied:
TEST MATERIAL- Amount(s) applied (volume or weight with unit): 25 mg - Concentration (if solution): neat (undiluted)VEHICLE (Not used)- Amount(s) applied (volume or weight with unit): none- Concentration (if solution): none- Lot/batch no. (if required): none- Purity: noneNEGATIVE CONTROL- Amount(s) applied (volume or weight): 30 µL- Concentration (if solution): neatPOSITIVE CONTROL- Amount(s) applied (volume or weight): 30 µL- Concentration (if solution): 5% solution of sodium dodecyl sulfate
Duration of treatment / exposure:
The exposure times were approximately 1 hour, with ~35 minutes exposure in the incubator and ~25 minutes at room temperature.
Duration of post-treatment incubation (if applicable):
For a total of an approximately 42 hour post-exposure incubation.
Number of replicates:
3 tissues will be used per test compound and control.

Results and discussion

In vitro

Results
Irritation / corrosion parameter:
% tissue viability
Run / experiment:
Run 1
Value:
99.9
Vehicle controls validity:
not specified
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
no indication of irritation
Other effects / acceptance of results:
The MTT data show the assay quality controls were met.

Any other information on results incl. tables

Code N° Tissue  Raw data   Blank corrected data mean  % of viability
  n Aliq. 1 Aliq. 2 Aliq. 1 Aliq. 2 of aliquotes  
NC 1 2.1422 2.1817 2.107 2.146 2.126 97.7
  2 2.2181 2.214 2.183 2.178 2.181 100.1
  3 2.2638 2.2585 2.228 2.223 2.226 102.2
PC 1 0.0956 0.0955 0.060 0.060 0.060 2.8
  2 0.0943 0.0956 0.059 0.060 0.059 2.7
  3 0.1508 0.1512 0.115 0.116 0.115 5.3

C2 1 2.1897 2.221 2.154 2.185 2.170 99.6
  2 1.8093 1.8534 1.774 1.818 1.796 82.5
  3 2.5781 2.6154 2.543 2.580 2.561 117.6

  mean SD mean of SD CV %
  of OD of OD viabilities [%] of viabilities [%]
NC 2.178 0.050 100.0 2.28 2.28
PC 0.078 0.032 3.6 1.48 41.12

C2 2.176 0.383 99.9 17.58 17.59

Applicant's summary and conclusion

Interpretation of results:
other: not irritating
Conclusions:
The dermal irritation potential of test article was determined according to the OECD 439 test guideline followed for this study. The mean of OD for test chemical was determined to be 2.176.The standard deviation of viabilities for test chemical were calculated to be 17.58.The Mean % tissue viability compared to negative control (n=3) of the test chemical was determined to be 99.9%. Thus, test chemical was considered to be not irritating to the human skin.
Executive summary:

The dermal irritation potential of test article was determined according to the OECD 439 test guideline for this study. The MatTek EpiDerm™ model was used to assess the potential dermal irritation of the test article by determining the viability of the tissues following exposure to the test article via MTT. Tissues were exposed to the test article and controls for ~one hour, followed by a 42 hour post-exposure recovery period. The viability of each tissue was determined by MTT assay.

The MTT data show the assay quality controls were met and passed the acceptance of criteria.

The mean of OD for test chemical was determined to be 2.176. The standard deviation of viabilities for test chemical were calculated to be 17.58.The Mean % tissue viability compared to negative control (n=3) of the test chemical was determined to be 99.9%. Hence, under the current experimental test conditions it was concluded that test chemical was considered to be non-irritating to human skin.