Titanium dioxide

Toxicity to reproduction: other studies

Administrative data

Endpoint:

toxicity to reproduction: other studies

Type of information:

experimental study

Adequacy of study:

disregarded due to major methodological deficiencies

Reliability:

other: not rated acc. to Klimisch

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

The publication is not relevant for human health risk assessment due to irrelevant route of test item application. In addition only one dose was tested and the frequency of treatment is not according a guideline. Test item insufficiently characterised, the given particle size of 2570nm (2.57µm) does not fall under the nano-definition and also does not correspond with the suface area of 2025m²/g (which is also unrealistic high for any commercially available titanium dioxide form).

Data source

Reference

Reference Type:

publication

Title:

Maternal exposure to nanoparticulate titanium dioxide during the prenatal period alters gene expression related to brain development in the mouse.

Author:

Shimizu, M. et al.

Year:

2009

Bibliographic source:

Part. Fibre Toxicol. 2009, 6: 20.

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

The purpose of this study was to investigate the effects of maternal exposure to nano-sized anatase titanium dioxide (TiO2) on gene expression in the brain during the developmental period using cDNA microarray analysis combined with Gene Ontology (GO) and Medical Subject Headings (MeSH) terms information. A 100 μL volume of TiO2 suspended at 1 μg/μL was injected subcutaneously into pregnant mice on gestational days 6, 9, 12, and 15 for the exposure group, while 100 μL of vehicle alone was injected into pregnant mice as a control group. Brain tissue was obtained from male foetuses on embryonic day 16 and from male pups on postnatal days 2, 7, 14, and 21.

GLP compliance:

not specified

Type of method:

in vivo

Test material

Test material information

Constituent 1

Reference substance name:

Titanium dioxide

EC Number:

236-675-5

EC Name:

Titanium dioxide

Cas Number:

13463-67-7

Molecular formula:

O2Ti

IUPAC Name:

dioxotitanium

Test material form:

solid: particulate/powder

Remarks:

migrated information: powder

Details on test material:

- Name of test material (as cited in study report): TiO2 nanopowder (purchased from Sigma-Aldrich Japan Inc. (Tokyo, Japan))
- Particle size: 2570 nm
- Surface area: 2025 m²/g
- Crystal form: anatase

Test animals

Species:

mouse

Strain:

ICR

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Japan SLC Inc. (Shizuoka, Japan)
- Diet (ad libitum): food
- Water (ad libitum):

ENVIRONMENTAL CONDITIONS
- Temperature: 23 ± 1°C
- Humidity: 55 ± 5%
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

subcutaneous

Vehicle:

other: saline with 0.05% (v/v) Tween 80

Details on exposure:

A 100 μL volume of TiO2 suspended at 1 μg/μL was injected subcutaneously into pregnant mice for the exposure group, while 100 μL of vehicle alone was injected into pregnant mice as a control group.

Analytical verification of doses or concentrations:

not specified

Details on analytical verification of doses or concentrations:

no data

Duration of treatment / exposure:

Gestational days 6, 9, 12, and 15

Frequency of treatment:

not stated

Duration of test:

Test ended on postnatal day 21

Doses / concentrations

Remarks:

Doses / Concentrations:
100 μL volume of TiO2 suspended at 1 μg/μL
Basis:
other: injected subcutaneously

No. of animals per sex per dose:

Treatment group: 15 mice
Control group: 14 mice

Control animals:

yes, concurrent vehicle

Details on study design:

Brain tissue was obtained from male foetuses on embryonic day (ED) 16 (n = 8/group) and from male pups on postnatal days 2 (n = 10/group), 7 (n = 10/group), 14 (n = 9/group), and 21 (n = 9/group).
Whole brain was frozen and tissue were homogenized. Total RNA was isolated from the brain tissue for complementary DNA microarray analysis and a functional analysis of microarray data with gene annotation. .

Statistics:

Complementary DNA microarray analysis: statistical analysis was done with analysis of variance (ANOVA) and the level of statistical significance was set at P < 0.05.
Functional analysis of microarray data: statistical analysis was performed using Fisher's exact test with hypergeometric distribution and the level of statistical significance was set at P < 0.05.

Results and discussion

Effect levels

Basis for effect level:

other: Maternal exposure to test item caused changes in gene expression assoc. w/ brain developm., cell death, response to oxidative stress, & mitochondria in brain during perinatal period, & those associated with inflammation & neurotransmitter in later stage.

Remarks on result:

not measured/tested

Remarks:

Effect level not specified (migrated information)

Observed effects

Analysis of cDNA microarrays:
In the maternal TiO2 exposure group, the expression levels of 462 genes were changed significantly in the brain of the foetus at ED 16 (upregulation 229 genes; downregulation 233 genes), and those of 864 (upregulation 234; downregulation 630), 417 (upregulation 351; downregulation 66), 738 (upregulation 450; downregulation 288), and 1887 (upregulation 613; downregulation 1274) were changed significantly in the brain of offspring 2, 7, 14, and 21 days old, respectively. The number of genes differentially expressed between groups was increased remarkably in the brain of 21 days old pups.

Functional categorization of microarray data:
Of the genes expressed differentially in the maternal TiO2 exposure group, 3, 2, 8, and 4 GO categories were enriched significantly in the brain at 2, 7, 14, and 21 days after birth, respectively, while 6, 2, 36, and 28 MeSH categories were enriched significantly at 2, 7, 14, and 21 days after birth. Eight MeSH categories were also enriched significantly in the foetal brain at ED 16. The largest group of GO categories enriched was those related to cell death 2 21 days after birth; 121 and 64 genes linked to apoptosis at 2 and 7 days after birth, respectively, and 92 and 173 genes linked to "cell death" were identified at 14 and 21 days after birth. "Brain development" was also a large category at 2 (34 genes) and 14 (43 genes) days after birth. GO categories related to oxidative stress, such as "superoxide dismutase activity", were also enriched significantly at 14 and 21 days after birth. The largest MeSH categories enriched were "Mitochondria" at ED 16 (31 genes) and 2 days (56 genes) after birth and "Apoptosis" at 14 (118 genes) and 21 (230 genes) days after birth. The "Mitochondria" category was persistently enriched at 14 (60 genes) and 21 (109 genes) days after birth. MeSH categories related to oxidative stress, such as "Glutathione", "Lipid Peroxidation", and "Reactive Oxygen Species", were also enriched significantly at ED 16 and 14 and 21 days after birth. MeSH categories related to inflammation and neurotransmitters including "Epinephrine", "Norepinephrine", "Serotonin", and "Glutamic Acid" were also highly enriched at 14 and 21 days after birth.

Applicant's summary and conclusion

Conclusions:

According to the authors, this study showed that maternal exposure to anatase TiO2 nanoparticle caused the changes in the expression of genes associated with brain development, cell death, response to oxidative stress, and mitochondria in the brain during the perinatal period, and those associated with inflammation and neurotransmitters in the later stage.