Particulate Matter Exposure Aggravates IL-17-Induced Eye and Nose Inflammation in an OVA/Poly(I:C) Mouse Model.

PURPOSE: Data on the effects of direct particulate matter (PM) exposure on the eyes and the nose are limited. Here, an interleukin (IL)-17/neutrophil-dominant ovalbumin (OVA)/polyinosinic-polycytidylic acid (Poly(I:C)) mouse model was used to evaluate the effect of different-sized titanium dioxide (TiO2) particles on the eyes and the nose. We also examined whether IL-17-neutralizing antibody (IL-17Ab) treatment could reverse TiO2 effects.
METHODS: The nasal cavities and conjunctival sacs of each mouse were challenged with OVA and Poly(I:C) to induce neutrophil-dominant inflammation and then exposed to micro- and nano-TiO2. Subsequently, IL-17Ab was administered to investigate the role of IL-17 and inflammatory parameters.
RESULTS: Micro- and nano-TiO2 resulted in significant decreases in tear-break-up time and increases in corneal damage. Airborne micro-TiO2 also increased nasal rubbing and sneezing counts compared with the OVA/Poly(I:C). Micro-TiO2 exposure increased infiltration of neutrophils and IL-17A+ cells in the conjunctival tissues and the nasal mucosae. In addition, these increased symptoms and inflammation in the eyes and the nose by micro-TiO2 exposure were inhibited by the IL-17Ab, suggesting IL-17 dependency.
CONCLUSIONS: TiO2 aggravated IL-17-induced eye and nose inflammation and the IL-17Ab alleviated inflammation in the OVA/Poly(I:C) mouse model. These results may help develop a therapeutic modality for PM exposure and provide evidence for PM-associated diseases.

INTRODUCTION

Air pollution induces various adverse health effects, including acute and chronic diseases of various organ systems. Furthermore, particulate matters (PMs), a complex mixture of solid and liquid particles suspended in air, are known to be the main contributor of air pollution.12 The accumulation of PM might pose different health risks, depending on the size and exposure route to the body. PMs enter the body through the following 3 main routes: inhalation via the respiratory system, ingestion via the digestive system, and absorption via the integumentary system.34 They are responsible for increased acute and chronic respiratory symptoms, cardiovascular conditions, and other related allergic reactions, resulting in more hospital admissions and emergency room visits.5

Among the health risks, acute and chronic diseases in the eyes and the nose, such as conjunctivitis and rhinitis, are the most common. They are both known to have inflammatory symptoms and be caused by different kinds of environmental factors. Recent studies suggested that PM could be a major factor exacerbating the inflammation in both conjunctivitis and rhinitis,67 triggering inflammatory responses involving numerous cytokines and chemokines. Particularly, the cytokine interleukin-17 (IL-17) is known to be a strong inducer of inflammation in conjunctivitis and rhinitis.89

Several studies have attempted to reveal the correlation between PM-related air pollution and various health issues based on clinical data.510 However, only a few in vivo studies have been conducted,1112 and therefore, the direct effect of PM exposure on the eyes and nose and its underlying mechanisms need to be studied.13

Titanium dioxide (TiO2) is a metal oxide nanoparticle which usually used in commercial products such as paints, carpets cosmetics and textiles.1415 Due to its small size, TiO2 can cause damage to the eye surface, resulting in ocular inflammation. Symptoms include dryness, burning, itching, conjunctival injection, conjunctival chemosis, and swelling of eyelids.16 TiO2 nanoparticles can also deposit to different parts of the respiratory system such as the nose and the lungs that causes inflammation.1718

In this study, the IL-17/neutrophil dominant ovalbumin (OVA)/polyinosinic-polycytidylic acid (Poly(I:C)) mouse model was used to evaluate the effect of different-sized TiO2 on the mucosa of the eyes and the nose to confirm the role of IL-17 in the inflammatory process. In addition, we examined whether treatment with the IL-17-neutralizing antibody (IL-17Ab) could reverse the effect of TiO2 on the eyes and nose.

MATERIALS AND METHODS

Protocol for mouse conjunctivitis and rhinitis model and exposure of TiO2

To evaluate the effects of TiO2 on the OVA/Poly(I:C) mouse model, 20 female BALB/c mice were divided into 4 groups.; 1) negative control group ((−) control), 2) positive control group (OVA/Poly(I:C)), 3) micro size TiO2 + OVA/Poly(I:C) group (micro-TiO2 + Poly(I:C)), and 4) nano size TiO2 + OVA/Poly(I:C) group (nano-TiO2+Poly(I:C)) (Fig. 1A). Mice with positive control and TiO2 + OVA/Poly(I:C) groups were locally sensitized with OVA (3.75 mg/mL)/Poly(I:C) (2.5 mg/mL) mixture in the conjunctival sac/or intranasally (20 μL) on day 1, 2, 3, 7 and 14. For the challenge, OVA (5 mg/mL, 20 μL/mouse) was administered into the same route from day 15 to day 20. In case of the micro size TiO2 + OVA/Poly(I:C) group, the mice were exposed to micro-sized airborne TiO2 (particulate matter less than 10 μm [PM10], 600–700 μg/m3) in a TiO2 exposure chamber for 2 hours from day 14 to 20 (about 50 μg/m3 based on 24 hours), which is similar to the short-term (24-hour) limit value (50 μg/m3) of the Air Quality Guidelines set forth by the WHO for PM10.19 Nano size TiO2 (50 μg/mL, 20 μL/mouse/day) was administered into the conjunctival sac or the nasal cavity from day 14 to 20. Mice were sacrificed via cervical dislocation on day 21. The Dankook University Institutional Animal Care & Use Committee on the use and care of animal approved all animal experiments (DKU-17-021). All animal experiments were repeated 3 times, and the number of mice in each group was 5.

Fig. 1

The influences of exposed TiO2 size on OVA/Poly(I:C) conjunctivitis mouse model. (A) Protocol for the induction of conjunctivitis and rhinitis with OVA/Poly(I:C) and micro or nano size TiO2 in mice. (B) Tear-break-up time and tear volume measurements in all groups. (C) Corneal irregularities and corneal fluorescein staining images with corneal staining scores. (D) Histological staining for IL-17A-producing cells, conjunctival neutrophil, and conjunctival eosinophil. IL-17A producing cell counts (× 400 magnification, IHC with IL-17A antibody). Conjunctival neutrophil counts (× 400 magnification, IHC with NIMP-R14 antibody). Conjunctival eosinophil counts (× 400 magnification, IHC with hematoxylin and eosin staining).

TiO2, titanium dioxide; OVA, ovalbumin; Poly(I:C), polyinosinic-polycytidylic acid; IL, interleukin; IHC, immunohistochemistry; PBS, phosphate buffered saline.

*P < 0.05.

Treatment of IL-17 neutralization antibody

An OVA/Poly(I:C) animal model and airborne micro size TiO2 treatment were the same as in Fig. 1A, except that only airborne micro size TiO2 treatment group and IL-17 neutralization antibody treatment group were added (n = 5/group). The micro TiO2 group treated only airborne micro size TiO2 without OVA/Poly(I:C) sensitization and OVA challenge, and IL-17 neutralization antibody administration was injected intraperitoneally for 7 days (day 14–20, 500 μg/mouse, 200 μL/mouse/day) in the same manner as OVA challenge and airborne micro size TiO2 treatment.

TiO2 exposure chamber

An exposure chamber with 6 fans was constructed for the exposure of TiO2 particles on the ocular surface and nasal mucosa of mouse in this study. Titanium (IV) oxide, rutile, 99.5% (metal basis) with a mean diameter of 1.0 to 2.0 μm (Alfa Aesar; Johnson Matthey GmbH, Karlsruhe, Germany) was put in the exposure chamber, and airborne particle concentration in the exposure chambers was adjusted for PM10 as measured by a MetOne 831 Aerosol Mass Monitor (Met One, Grants Pass, OR, USA). The range of airborne TiO2 particle concentration during the study period was 600–700 μg/m3.

Assessment of the ocular and nasal inflammation

The inflammation in the eyes were assessed by the standard tear break-up time (BUT) measurement,20 tear volume measurements,21 corneal irregularities,21 and corneal damage scores.22 Corneal damage was evaluated using Oxford schema, and the grades were marked as follows: 0, normal; 1–2, mild to moderate; and > 3, severe.23 The damages on the surface of the cornea were stained by the fluorescein dye and appeared green under the blue light.

For nasal symptoms, in a blind manner, the observer recorded the frequencies of sneezing and nasal rubbing for 15 minutes after the final OVA challenge.

Tissue preparations

Whole eyes of the mice were surgically excised and fixed in 4% formalin overnight. Next day, the eyes were transferred to 15% sucrose (Sigma-Aldrich, St. Louis, MO, USA) for 4 hours then, 30% sucrose overnight. They were embedded in Optimal Cutting Temperature (O.C.T.) compound (Tissue-Tek O.C.T. Compound; Sakura, Tokyo, Japan) for cryostat sectioning.

Half of the head was removed en bloc and fixed in 4% paraformaldehyde. The nasal mucosa was removed from the nasal cavity of the other half of the head using a small curette, immediately immersed in TRIzol reagent (Invitrogen, Carlsbad, CA, USA), and stored at −80°C until use for reverse transcription-quantitative polymerase chain reaction (RT-qPCR).

Eosinophils and cell aggregation in the conjunctival and nasal mucosa

Hematoxylin and eosin staining was performed to count the number of eosinophils in the conjunctival sac. The nasal septum histology was evaluated using standard Sirius red staining. The detailed procedure was described in our previous report.24

Immunohistochemistry (IHC)

Prepared conjunctival and nasal mucosa sections were immunostained with NIMP-R14 (neutrophil marker, ab2557, 1:100; Abcam, Cambridge, MA, USA), IL-17 (LS-B4912, 1:100; LSbio, Seattle, WA, USA), IL-1β (ab9722, 1:200, Abcam), TNF-α (ab6671, 1:200; Abcam), CD4 (sc-13573, 1:200; Santa Cruz Biotechnology, Santa Cruz, CA, USA), and B220 (B cell marker,14-0452-82, 1:50, eBioscience, San Diego, CA, USA) antibodies using Avidin-Biotinylated-Horseradish Peroxidase (HRP) Kits (Vector Laboratories, Burlingame, CA, USA). The detailed procedure was described in our previous report.24

Assay of IL-4, IL-17, and interferon (IFN)-γ levels in nasal mucosa

Total RNA was prepared from nasal mucosa using TRIzol reagent (Invitrogen). cDNA was synthesized from 1 μg of RNA using the iScript cDNA Synthesis Kit (Bio-Rad, Hercules, CA, USA). For analysis of IL-4 (Mm00445258_g1), IL-17 (Mm00439618_m1), IFN-γ (Mm99999071_m1), and glyceraldehyde 3-phosphate dehydrogenase (GAPDH; Mm03302249_g1), pre-developed assay reagent kits were used (Applied Biosystems, Foster City, CA, USA). Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was performed on the ABI 7500 Real-Time PCR System (Applied Biosystems). Mean transcript levels were normalized to that of GAPDH.

Serum levels of total IgE and OVA-specific IgE, IgG1, and IgG2a

The serum levels of total and OVA-specific IgE, IgG1, and IgG2a were measured by solid-phase enzyme-linked immunosorbent assay. The detailed procedure was described in our previous report.24

Statistical analysis

Statistical analysis was performed using SPSS software version 22.0 (SPSS Inc., Chicago, IL, USA). Data were tested using the Kruskal-Wallis test with Dunn multiple comparison test. A P value < 0.05 was considered as statistically significant.

RESULTS

Effect of TiO2 exposure on the OVA/Poly(I:C) conjunctivitis and rhinitis mouse models

OVA/Poly(I:C)-induced mouse models were exposed to TiO2 of different sizes to investigate its size-dependent effects in the conjunctival sac and nasal cavity.

As a result, tear BUT decreased in all case groups, compared to the (−) control. Nano-TiO2 + Poly(I:C) group had the shortest BUT, followed by micro-TiO2 + Poly(I:C) and Poly(I:C) groups, indicating that the size of TiO2 affected BUT (Fig. 1B). Tear volume measurement showed that Poly(I:C) and TiO2-exposed groups had more amount of tear than control group, as a symptom of eye irritation. Although micro-TiO2 + Poly(I:C) group had the lowest tear volume, there were no significant differences among all groups (Fig. 1B).

White ring irregularities on corneal surface were observed in all the groups except the (−) control (Fig. 1C). The degree of irregularity was more severe in nano-TiO2 + OVA/Poly(I:C) group, followed by Poly(I:C) and micro-TiO2 + OVA/Poly(I:C) groups, indicating that nano-TiO2 caused more damage on the corneal surface than micro-TiO2. In addition, corneal fluorescein staining, which represents corneal damage, showed more damage in both micro-TiO2 + Poly(I:C) and nano-TiO2 + Poly(I:C) group, however, there was no statistically significant difference between micro-TiO2 + Poly(I:C) and nano-TiO2 + Poly(I:C) groups (Fig. 1C).

IHC showed that the level of IL-17A, neutrophil, and eosinophil increased in Poly(I:C) and TiO2-exposed groups (Fig. 1D). Especially, IL-17A and neutrophil level increased significantly in micro-TiO2 + Poly(I:C) group, indicating that micro-TiO2 induced IL-17 and neutrophil related inflammatory process.

The nasal symptom score was significantly higher in the micro-TiO2 + OVA/Poly(I:C) group than in the (−) control and nano-TiO2 + OVA/Poly(I:C) groups (Fig. 2A). IL-17A mRNA expression was significantly higher in the micro-TiO2 + OVA/Poly(I:C) group than in the OVA/Poly(I:C) and nano-TiO2+OVA/Poly(I:C) groups, as determined by the qPCR (Fig. 2B). However, the IL-4, IL-17A, and IFN-γ mRNA expression in the group exposed to nano-TiO2 was not statistically significant compared with that in the OVA/Poly(I:C) group (Fig. 2B).

Fig. 2

The influences of exposed TiO2 size on OVA/Poly(I:C) rhinitis mouse model. (A) Symptom score, frequencies of sneezing and nasal rubbing after the final OVA challenge. (B) Cytokine production in the nasal mucosa, mRNA expression (IL-4, IL-17A, and IFN-γ). (C) Histological staining for IL-17A-producing cells and inflammatory cells in the nasal mucosa. IL-17A producing cell counts (× 400 magnification, IHC with IL-17A antibody). Neutrophil counts (× 400 magnification, IHC with NIMP-R14 antibody). Eosinophil counts (× 400 magnification, Sirius red staining).

TiO2, titanium dioxide; OVA, ovalbumin; Poly(I:C), polyinosinic-polycytidylic acid; IL, interleukin; IFN, interferon; IHC, immunohistochemistry.

*P < 0.05; **P < 0.01; ***P < 0.001.

Nasal mucosal histological changes were assessed by IHC and Sirius Red staining for IL-17A-producing cell infiltration, neutrophils, eosinophils, and cell aggregation (Fig. 2C and Supplementary Fig. S1E). Intense aggregation of inflammatory cells under nasal mucosa epithelial tissue was defined as cell aggregation and evaluated by Sirius Red staining. The group treated with only OVA/Poly(I:C) had, the higher numbers of IL-17A-producing cells, neutrophils, eosinophils, and cell aggregation in the nasal mucosa than the (−) control group. Meanwhile, in the nasal mucosa of groups exposed to TiO2, the counts of eosinophils and cell aggregation were not significantly increased compared with those of the OVA/Poly(I:C) group. However, the IHC results revealed that the number of IL-17A-producing cells and neutrophils in the micro-TiO2 group was statistically higher than that in the OVA/Poly(I:C) and nano-TiO2 + OVA/Poly(I:C) groups. However, micro- and nano-TiO2 were found to have no effect on serum total immunoglobulin (Ig)E, OVA-specific IgE, and IgG (Supplementary Fig. S1A).

The results of the influence of TiO2 size revealed that IL-17A-expressing cells, neutrophils, and IL-17A mRNA levels were significantly higher in the nasal mucosa of mice exposed to airborne micro-TiO2 than OVA/Poly(I:C) and nano-TiO2.This is an additional effect of airborne micro-TiO2 on the OVA/Poly(I:C) mouse model. On the contrary, nano-TiO2 did not induce significant immunological and histological changes in the OVA/Poly(I:C) mouse model.

Effect of IL-17Ab in OVA/Poly(I:C) conjunctivitis and rhinitis mouse models with micro-sized TiO2 airborne exposure

When the effects of micro- and nano-TiO2 were compared, it was confirmed that micro size TiO2 had a significant effect in IL-17 related inflammation both on the eyes and nose. To verify the role of IL-17 in the process, IL-17Abs were treated on the micro-TiO2 + Poly(I:C) group.

Animal experiments with IL-17Ab were performed to investigate whether increased inflammatory response of nasal mucosa mediated by IL-17A and neutrophils is alleviated in the OVA/Poly(I:C) mouse model after exposure to micro-TiO2 (Fig. 3A).

Fig. 3

The effects of IL-17Ab on the eyes of OVA/Poly(I:C) mouse model with micro size TiO2 airborne exposure. (A) Protocol for the induction of conjunctivitis and rhinitis with OVA/Poly(I:C) and micro size TiO2 in mice, with added IL-17Ab treatment group. (B) Tear break-up time and tear volume measurements in all groups. (C) Corneal irregularities and corneal fluorescein staining images with corneal damage scores. (D) Histological staining for IL-17A-producing cells, conjunctival neutrophil, and conjunctival eosinophil. IL-17A producing cell counts (× 400 magnification, IHC with IL-17A antibody). Conjunctival neutrophil counts (× 400 magnification, IHC with NIMP-R14 antibody). Conjunctival eosinophil counts (× 400 magnification, IHC with hematoxylin and eosin staining).

TiO2, titanium dioxide; OVA, ovalbumin; Poly(I:C), polyinosinic-polycytidylic acid; IL, interleukin; IHC, immunohistochemistry; IL-17Ab, interleukin-17 neutralizing antibody.

*P < 0.05; **P < 0.01; ***P < 0.001.

BUT significantly increased in IL-17Ab + micro-TiO2 + Poly(I:C) group when compared with micro-TiO2 + Poly(I:C) group, indicating that the decreased BUT was recovered after IL-17 blocking antibody treatment (Fig. 3B). Poly(I:C) and IL-17Ab + micro-TiO2 + Poly(I:C) groups had the lowest tear volume, with no significant differences. Tear volume in IL-17Ab + micro-TiO2 + Poly(I:C) group was lower than micro-TiO2 + Poly(I:C) group, implying the recovery of eye irritation (Fig. 3B).

Corneal irregularities were observed in Poly(I:C), micro-TiO2, and micro-TiO2 + Poly(I:C) groups, while IL-17Ab + micro-TiO2 + Poly(I:C) group had a white ring image just as seen as in (−) control group (Fig. 3C). Corneal fluorescein staining also showed the reduced green stains on corneal surface of IL-17Ab + micro-TiO2 + Poly(I:C) group when compared with micro-TiO2 + Poly(I:C) group, indicating a significant reduction in the damage after the IL-17 blocking antibody treatment (Fig. 3C). Although there were no significant differences of the corneal damage scores in all groups micro-TiO2 + Poly(I:C) group were the most severe, and the corneal condition of IL-17Ab + micro-TiO2 + Poly(I:C) group had even lower score than the negative control (Fig. 3C).

IHC also confirmed that the inflammatory reaction was significantly increased in micro-TiO2 and micro-TiO2 + Poly(I:C) groups and decreased significantly in the IL-17Ab + micro-TiO2 + Poly(I:C) group (Fig. 3D). The treatment of IL-17 blocking antibody significantly decreased the level of IL-17, neutrophil, and eosinophil, which was significantly increased with micro size TiO2 exposure.

The symptom scores of nose scratching or sneezing after the last OVA challenge were the highest in the micro-TiO2 + OVA/Poly(I:C)-treated group, which was significantly reduced by the IL-17Ab. The (−) control and micro-TiO2 only groups showed similar symptom scores (Fig. 4A).

Fig. 4

The effects of IL-17Ab on the OVA/Poly(I:C) mouse model with micro size TiO2 airborne exposure. (A) Symptom score, frequencies of sneezing and nasal rubbing after the final OVA challenge. (B) Cytokine production in the nasal mucosa, mRNA expression (IL-4, IL-17A, and IFN-γ). (C) Histological staining for IL-17A-producing cells and inflammatory cells in the nasal mucosa. IL-17A producing cell counts (× 400 magnification, IHC with IL-17A antibody). Neutrophil counts (× 400 magnification, IHC with NIMP-R14 antibody). Eosinophil counts (× 400 magnification, Sirius red staining).

TiO2, titanium dioxide; OVA, ovalbumin; IL, interleukin; IHC, immunohistochemistry; IFN, interferon; IL-17Ab, interleukin-17 neutralizing antibody.

*P < 0.05; **P < 0.01.

In mice treated with only micro-TiO2, the levels of mRNA cytokines were relatively low similar to that of the (−) control group and IL-4 mRNA expression in the nasal mucosa was not different between the groups. The highest IL-17A mRNA expression in the group treated with micro-TiO2 + OVA/Poly(I:C) was significantly reduced by the IL-17Ab treatment. However, the expression of mRNA IFN-γ was not statistically altered in the micro-TiO2 + OVA/Poly(I:C) and IL-17Ab-treated groups compared with that in the OVA/Poly(I:C) group (Fig. 4B).

With regard to the histological changes of the nasal tissues (Fig. 4C), IL-17A-producing cells were the most abundant in the group treated with micro-TiO2 + OVA/Poly(I:C), and this level decreased significantly in the IL-17Ab-treated group. The micro-TiO2 + OVA/Poly(I:C) group was found to have the highest number of cell aggregation lesions, and its level was significantly decreased by IL-17Ab treatment. Similar to the number of IL-17A positive cells, the neutrophil count, which was significantly increased in the micro-TiO2 + OVA/Poly(I:C) group compared with that in the OVA/Poly(I:C) group, was clearly reduced by IL-17Ab treatment. However, the number of eosinophils, B cells (B220+ cells), and CD4 cells was similar in the OVA/Poly(I:C), micro-TiO2 + OVA/Poly(I:C), and IL-17Ab treatment groups (Fig. 4C and Supplementary Fig. S1D). Cell aggregation was observed in the nasal mucosa epithelial tissue in the OVA/Poly(I:C) and micro-TiO2 + OVA/Poly(I:C) groups by Sirius red staining (Supplementary Fig. S1E). The micro-TiO2 + OVA/Poly(I:C) group was found to have the highest number of cell aggregation lesions, and its level was significantly decreased by IL-17Ab treatment. In the group treated with micro-TiO2 only, there was negligible change in the nasal tissue compared with that in the (−) control group.

There was no statistically significant difference among the OVA/Poly(I:C), micro-TiO2 + OVA/Poly(I:C), and IL-17Ab-treated groups in terms of total IgE, OVA-specific IgE, and IgG in the serum. The Ig level in the group treated with only TiO2 was estimated to be similar to that of the (−) control group (Supplementary Fig. S1B).

The increase in the number of IL-17A positive cells and neutrophils in cell aggregates in OVA/Poly(I:C) mouse model exposed to micro-TiO2 was significantly decreased by IL-17Ab. However, in all parameters examined, the group exposed to TiO2 alone showed a similar pattern with the (−) control group.

DISCUSSION

Studies have reported that PMs cause respiratory and cardiovascular diseases and, in severe cases, even death.525 Furthermore, PMs are known as a major cause of allergic conditions such as allergic conjunctivitis and allergic rhinitis, and the eyes and nose are the organs most affected by PMs.2627 To study the underlying mechanisms of these diseases, TiO2 has been frequently used in vivo experiments as an effective approach to evaluate the effects of PMs in various cases.2829

In this study, we identified the relationship between micro- and nano-TiO2 exposure and IL-17 inflammation in the eyes and nose of the OVA/Poly(I:C) mouse model. Poly(I:C) is a synthetic analogue of double-stranded RNA, recognized by Toll-like receptor 3 and mimics the replication intermediates present in RNA virus-infected cells.30 In a previous study, we developed an IL-17-dominant murine model of rhinitis via nasal instillation of OVA/Poly(I:C) associated with increased neutrophil counts. The OVA/Poly(I:C) mouse model had a lower Th-2 phenotype (eosinophil infiltration and Th-2 cytokine expression including IL-4 and IL-5) and a higher Th-17-associated inflammatory responses than the conventional OVA/alum model.31

In general, depending on the size of the particle, the location of the particle in the airway is different. However, unlike the airways, in the eyes, especially the conjunctival sacs, it is difficult to remove the substances or particles introduced from the outside, regardless of the size, remaining in the closed conjunctival sacs. Therefore, it is thought that both micro- and nano-sized TiO2 induce inflammation of the conjunctival tissues to a similar degree regardless of particle size in the eyes.

In the nasal cavity, the nose is the initial part of the airway and is connected to the lower respiratory tract, and when external substances enter the nasal passages, the particle’s size determines the particle’s location in the airway. It is known that most of the micrometer-sized particles remain in the nasal mucosa, but most of the nanometer-sized particles pass through the nasal passages and remain in the lungs.323334 For this reason, micro-TiO2 is thought to have a greater effect on the induction of inflammation in the nose than nano-TiO2.

From the perspective of this experimental method, nano-TiO2 was mixed with phosphate buffered saline (PBS) and treated by the intranasal route, and micro-TiO2 was suspended in the chamber for a certain period of time and then exposed to mice. Compared with nano-TiO2 mixed with PBS, micro-TiO2 introduced in solid form could give more exposure to nasal mucosa.

This PM exposure has been shown to decrease BUT and increase tear volume as a symptom of eye irritation. When TiO2 was administered to the eyes, inflammation and conjunctival hyperemia were observed and the frequency of blinking increased. BUT decrease and tear volume increase could be explained by corneal damage or imbalance in the tear film and increased blinking frequency, respectively. However, when the symptoms do occur, the tear film can be disrupted, reducing the amount of tears and eventually leading to dry eye.

IL-17, a cytokine related to T-cell activation and neutrophil mobilization and activation, is known to cause severe inflammatory diseases and maintain the condition by amplifying inflammation.3536 The results showed that the number of IL-17-producing cells and neutrophils significantly increased in both the eyes and nose in the OVA/Poly(I:C) model after micro-size TiO2 exposure. Wu et al.6 reported that micro-sized PM increased IL-17-secreting Th-17 cells and activated neutrophils to exacerbate allergic conditions, whereas nano-sized PM upregulated levels of IL-4 and IFN-γ in the respiratory system. As IL-17 and Th-17 cells are directly related to inflammatory diseases, they can be targeted to alleviate the disease symptoms.37

A significant decrease in IL-17 and neutrophils was observed after IL-17Ab treatment, indicating that IL-17 plays a significant role in the symptoms of TiO2-induced allergic inflammation. Some studies have suggested that anti-IL-17 therapies, such as IL-17 neutralization, might be effective in reversing destructive inflammation and treating inflammatory diseases.3538

In summary, this study is the first to our knowledge to compare and confirm the effects of PM exposure on both the eyes and nose using the OVA/Poly(I:C) mouse model. Micro–size PM had significant effects on the eyes and nose, resulting in IL-17 and neutrophil associated inflammation, and treatment with IL-17Ab reduced these levels of inflammation. This demonstrates that IL-17 regulation could play a key role in managing severe inflammatory symptoms in patients.