Exposure to Traffic-Related Particulate Matter 2.5 Triggers Th2-Dominant Ocular Immune Response in a Murine Model

HMGB1 Promotes Lysosome-Dependent Cell Death Induced Via Dry Eye by Disrupting Lysosomal Homeostasis

Purpose

Hypertonic stress can induce apoptosis, inflammation, and dry eye disease (DED) through the upregulation of HMGB1 expression. However, its role in mediating and maintaining lysosomal homeostasis and suppressing DED development in living and in vitro models is unclear.

Methods

Immunofluorescence, nucleoplasmic separation, and electron microscopic analysis were used to compare the effects of hypertonic stress on lysosomal function, nuclear HGMB1 expression, and lysosomal localization in three different dry eye models. The live model was established by the subcutaneous injection of scopolamine (SCOP) into C57BL/6J female mice, and the in vitro model used human corneal epithelial cell (HCEC) cultures that were maintained at a hyperosmotic level of 450 milliosmolar (mOsm). RNAi technology was used to knockdown HMGB1 expression levels, altering hyperosmotic stress-induced changes in survival and autophagy of corneal epithelial cells in vitro. Lysosomal protease inhibitors were applied to suppress the increase of corneal tissue inflammation in the dry eye mouse model.

Results

This hypertrophic stress upregulated karyoplasmic HMGB1 expression in HCECs. This change disrupted lysosomal structural and functional integrity, which facilitated the release of HMGB1 into the cytoplasm. SiRNAs downregulated HMGB1 expression levels and reversed increases in HMGB1 transfer from the nucleus to the cytoplasm and lysosomal alkalinizing function. These changes promoted increases in cathepsin leakage from lysosomes and increased mouse corneal epithelial apoptosis, whereas autophagy decreased. In a mouse model, administration of a cathepsin inhibitor reduced both ocular inflammation and other aspects of dry eye symptomology.

Conclusions

Hyperosmotic-induced HMGB1 upregulation and increased HMGB1 transfer into the cytoplasm from the nucleus underlie the loss of lysosomal membrane integrity, which increases both cathepsin release and corneal epithelial apoptosis. HMGB1 downregulation instead ameliorated these pathogenic responses.

Association between traffic-related air pollution and risk of outpatient visits for dry eye disease in a megacity along the subtropical coast in South China

BACKGROUND

Traffic-related air pollution especially in highly socioeconomically developed megacity is usually considered as a severe problem leading to inevitable adverse health outcomes. This study aimed to investigate the associations between traffic-related air pollutants with risk of dry eye disease (DED) outpatient visits in a megacity (Guangzhou) along the subtropical coast in South China.

METHODS

Daily data on DED outpatient visits and environmental variables from 1 January 2014 to 31 December 2020 in Guangzhou were obtained. A time-series study using a quasi-Poisson generalized linear model (GLM) combined with distributed lag non-linear model (DLNM) was adopted. Subgroup analyses stratified by age, gender, and season were conducted.

RESULTS

Totally, 27, 828 DED cases were identified during the study period including 2557 days. Daily number of outpatient visits for DED ranged from 0 to 41. An increase of 10 μg/m3 in PM2.5, NO2 and SO2 concentration was associated with 3.1%, 5.9% and 17.4% increase in the risk of DED outpatient visits, respectively (RRPM2.5 = 1.031, 95%CI: 1.004-1.059, lag 0-11 day; RRNO2 = 1.059, 95% CI: 1.027-1.092, lag0-14 day; RRSO2 = 1.174, 95% CI: 1.036-1.330, lag0-13 day). Subgroup analyses indicated that the effects of PM2.5 exposure on the risk of DED outpatient visits remained significant in aged < 60 years (RR max = 1.008, 95% CI: 1.003-1.013, lag0 day) and the effects of SO2 exposure on the DED outpatient visits risk remained significant in the females (RR max = 1.025, 95% CI: 1.006-1.044, lag0 day). The associations of PM2.5 (RR = 1.010, 95% CI: 1.003-1.016, lag0 day) and SO2 (RR = 1.030, 95% CI: 1.003-1.058, lag14 day) exposure with DED outpatient visits risk remained significant in warm seasons, whereas NO2 (RR = 1.006, 95% CI: 1.002-1.009, lag14 day) exposure was significantly associated with DED outpatient visits in cold seasons. The associations of PM2.5 (first visit, RR = 1.006, 95% CI: 1.001-1.011, lag0 day; re-visit, RR = 1.002, 95% CI: 1.000-1.005, lag6 day), NO2 (first visit, RR = 1.006, 95% CI: 1.001-1.012, lag0 day; re-visit, RR = 1.007, 95% CI: 1.002-1.012, lag0 day), and SO2 (first visit, RR = 1.023, 95% CI: 1.002-1.044, lag0 day; re-visit, RR = 1.023, 95% CI: 1.000-1.045, lag0 day) exposure with risk of DED outpatient visits were significant for both first- and re-visits.

CONCLUSIONS

Our study revealed that short-term exposure to PM2.5, NO2 and SO2 were positively associated with risk of DED outpatient visits, especially for the youngers, females and during warm seasons, providing evidence for making public health policy to improve life quality in developed megacity.

Impact of particulate matter and air pollution on ocular surface disease: A systematic review of preclinical and clinical evidence

PURPOSE

Exposure to particulate matter (PM) and air pollution has been implicated in the etiology of ocular surface diseases (OSD). The purpose of this systematic review is to evaluate and synthesize peer-reviewed literature on the impact of PM exposure on the ocular surface, integrating results from preclinical in vitro and in vivo studies with clinical findings to provide a comprehensive understanding of molecular mechanisms, physiological effects, clinical implications, and potential therapies to target acute and chronic PM-induced ocular toxicity.

METHODS

A systematic literature search was performed using PubMed and EMBASE over the period from 2009 to 2024 following the recommendations for the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) reporting guidelines. 102 studies were identified that met the inclusion/exclusion criteria. All studies were assessed for the risk of bias and qualitative data were analyzed.

RESULTS

Preclinical studies using models of corneal and conjunctival cells found that exposure to PM and similar air pollutants resulted in apoptosis, primarily via inflammatory and oxidative stress pathways as well as allergic and immune responses. Animal models resulted in phenotypes reminiscent of that of dry eye disease, presenting with reduced tear volumes and ocular surface damage. These results were corroborated by clinical studies, which reported that patients commonly presented with symptoms of itching, burning, and irritation, and ocular surface signs correlated with a diagnosis of dry eye disease, conjunctivitis, and allergic eye disease.

CONCLUSIONS

This systematic review provides a comprehensive summary of our current understanding of PM exposure on the ocular surface, highlighting the correlation between exposure to PM and ocular surface dysfunction.

Air pollutant exposure is associated with visual trajectories and visual impairment in children

Air pollution is associated with vision loss in children, but the relationship with vision trajectories has not been explored. The study was conducted as a prospective cohort in 16 districts of Shanghai from 2021 to 2023, involving 5612 children with complete survey data. Each child underwent 3-4 eye tests, including unaided visual acuity and computerized refraction. Children's air pollutant exposure levels (PM2.5, PM10, O3, SO2, NO2, and CO) were assessed using school addresses and examination dates. Latent class mixture modeling was used to identify the trajectories of changes in vision-related measurements in children. Multinomial logistic regression and Cox proportional hazards regression were used to examine the association of air pollutant exposure and visual trajectories, as well as visual impairment outcomes. The study identified three trajectory categories for children's unaided visual acuity, spherical equivalent, and four trajectory categories for axial length. Increased levels of PM2.5, PM10, O3, and SO2 exposure are associated with an increased risk of categorizing vision-related measurements into the "poor" category trajectory in children. Increased exposure to PM2.5, O3, and NO2 was associated with an increased risk of visual impairment outcomes in children with normal vision at baseline, and the effect was more significant in female and older children.

Long-term effects of air pollution on daily outpatient visits for allergic conjunctivitis from 2013 to 2020: a time-series study in Urumqi, China

Introduction

This study aimed to elucidate the effects of outdoor air pollution and allergic conjunctivitis and population-based lagged effects of air pollution.

Methods

We included data on six major air pollutants, PM10, PM2.5, carbon monoxide (CO), sulfur dioxide (SO2), nitrogen dioxide (NO2), and ozone (O3), and 3325 allergic conjunctivitis outpatient visits in Urumqi, northwest China, from 1 January 2013 to 31 December 2020. We developed quasi-Poisson generalized linear regression models with distributed lagged nonlinear models (DLNM), and single and multi-pollutant models were constructed to investigate single-day and cumulative lagged effects in detail.

Results

Our results confirmed that elevated PM10 and NO2 levels are significantly associated with increased allergic conjunctivitis outpatient visits with lags of 2 and 3 days respectively, and subgroup analyses further suggest that the effects of PM10 and NO2 on allergic conjunctivitis are more pronounced during the warm season. Women are more sensitive to PM10 exposure and the effect of air pollution on allergic conjunctivitis is influenced by age (e.g., infancy and older people).

Discussion

Our work provides the first time-series study in Urumqi, the world's furthest inland city from the ocean. Further implementation of specific outdoor air pollution controls such as the burning of fossil fuels like coal, as well as special population protection policies remain necessary. Multicenter studies with larger sample sizes are needed.

Effects of Air Pollution and Meteorological Conditions on DED: Associated Manifestations and Underlying Mechanisms

This study aims to explore the associations and the underlying mechanism among dry eye disease (DED), air pollution, and meteorological conditions. DED is positively correlated with air pollutants (i.e., PM2.5, PM10, O3, NO2, CO, and SO2) and meteorological conditions (i.e., high altitude and wind speed), while negatively associated with relative humidity. Both low and high air temperatures effect DED. Atmospheric pollutants affect DED mainly through necroptosis or autophagy, inflammatory responses, and oxidative stress. Meteorological factors affect DED not only by their own affects but also by dispersing the concentration of air pollutants, and then reducing the negative exposure. In summary, this review may expand the understanding of the effects of air pollution and meteorological factors on DED and emphasize the importance of air environmental protection.

Effect of Exposure to Particulate Matter on the Ocular Surface in an Experimental Allergic Eye Disease Mouse Model

In response to the escalating concern over the effect of environmental factors on ocular health, this study aimed to investigate the impact of air pollution-associated particulate matter (PM) on ocular allergy and inflammation. C57BL/6 mice were sensitized with ovalbumin (OVA) topically and aluminum hydroxide via intraperitoneal injection. Two weeks later, the mice were challenged with OVA and exposed to PM. Three groups-naive, OVA, and OVA-sensitized with PM exposure (OVA + PM) groups-were induced to an Allergic Eye disease (AED) model. Parameters including clinical signs, histological changes, inflammatory cell infiltration, serum OVA-specific immunoglobulins E (IgE) levels, mast cells degranulation, cellular apoptosis and T-cell cytokines were studied. The results demonstrate that exposure with PM significantly exacerbates ocular allergy, evidenced by increased eye-lid edema, mast cell degranulation, inflammatory cytokines (IL-4, IL-5 and TNF-α), cell proliferation (Ki67), and serum IgE, polymorphonuclear leukocytes (PMN), and apoptosis and reduced goblet cells. These findings elucidate the detrimental impact of PM exposure on exacerbating the severity of AED. Noticeably, diminished goblet cells highlight disruptions in ocular surface integrity, while increased PMN infiltration with an elevated production of IgE signifies a systemic allergic response with inflammation. In conclusion, this study not only scientifically substantiates the association between air pollution, specifically PM, and ocular health, but also underscores the urgency for further exploration and targeted interventions to mitigate the detrimental effects of environmental pollutants on ocular surfaces.

Loliolide in Sargassum horneri Alleviates Ultrafine Urban Particulate Matter (PM 0.1)-Induced Inflammation in Human RPE Cells

Owing to increasing air pollution due to industrial development, fine dust has been associated with threatening public health. In particular, ultrafine urban particulate matter (uf-UP, PM 0.1) can easily enter our bodies, causing inflammation-related diseases. Therefore, in the present study, we evaluated the effects of hydrothermal extracts of Sargassum horneri and its bioactive compound, loliolide, on uf-UP-induced inflammation as a potential treatment strategy for retinal disorders. Human retinal pigment epithelial cells (ARPE-19) stimulated with TNF-α or uf-UPs were treated with S. horneri extract and loliolide. S. horneri extracts exhibited anti-inflammatory effects on uf-UP-induced inflammation without cell toxicity through downregulating the mRNA expression of MCP-1, IL-8, IL-6, and TNF-α. UPLC-QTOF/MS analysis confirmed that the hydrothermal extract of S. horneri contained loliolide, which has anti-inflammatory effects. Loliolide effectively reduced the mRNA expression and production of proinflammatory chemokines (IL-8) and cytokines (IL-1β and IL-6) by downregulating the MAPK/NF-ĸB signaling pathway on TNF-α-stimulated inflammatory ARPE-19 cells. These effects were further confirmed in inflammatory ARPE-19 cells after stimulation with uf-UPs. Collectively, these results suggested the application of S. horneri as a functional ingredient for treating ocular disorders caused by particular matters.

Particulate Matter Elevates Ocular Inflammation and Endoplasmic Reticulum Stress in Human Retinal Pigmented Epithelium Cells

Because of their exposure to air, eyes can come into contact with air pollutants such as particulate matter (PM), which may cause severe ocular pathologies. Prolonged ocular PM exposure may increase inflammation and endoplasmic reticulum stress in the retina. Herein, we investigated whether PM exposure induces ocular inflammation and endoplasmic reticulum (ER) stress-related cellular responses in human retinal epithelium-19 (ARPE-19) cells. To understand how PM promotes ocular inflammation, we monitored the activation of the mitogen-activated protein kinase (MAPK)/nuclear factor kappa beta (NFκB) axis and the expression of key inflammatory mRNAs. We also measured the upregulation of signature components for the ER-related unfolded protein response (UPR) pathways, as well as intracellular calcium ([Ca²⁺]_i) levels, as readouts for ER stress induction following PM exposure. Ocular PM exposure significantly elevated the expression of multiple cytokine mRNAs and increased phosphorylation levels of NFκB-MAPK axis in a PM dose-dependent manner. Moreover, incubation with PM significantly increased [Ca²⁺]_i levels and the expression of UPR-related proteins, which indicated ER stress resulting from cell hypoxia, and upregulation of hypoxic adaptation mechanisms such as the ER-associated UPR pathways. Our study demonstrated that ocular PM exposure increased inflammation in ARPE-19 cells, by activating the MAPK/NFκB axis and cytokine mRNA expression, while also inducing ER stress and stress adaptation responses. These findings may provide helpful insight into clinical and non-clinical research examining the role of PM exposure in ocular pathophysiology and delineating its underlying molecular mechanisms.

Size-specific particulate matter and outpatient visits for allergic conjunctivitis in children: a time-stratified case-crossover study in Guangzhou, China

This time-stratified case-crossover study aims to quantify the risk of allergic conjunctivitis (AC) associated with short-term exposure to PMs (i.e., PM₁, PM_2.5, PM_c, and PM₁₀) among children in Guangzhou, China. We collected data on children's daily AC outpatient visits from the Guangzhou Women and Children Medical Center during February 20, 2016 to December 31, 2018, and also extracted air pollution and meteorological data in the same time frame. We used conditional logistic regression model to estimate the associations between PMs and AC outpatient visits, and conducted subgroup analyses stratified by sex, age, and season. During the study period, we recorded 39,330 children's outpatient visits for AC, including 27,638 boys and 11,692 girls. The associations between PMs and AC were general linear with no clear threshold, which were largest at the current days but remained positive for lag 1 to 3 days. For every 10 μg/m³ increase in daily PM₁, PM_2.5, PM_c, and PM₁₀ concentrations, the estimated risks of AC outpatient visits at the current days increased by 2.5% (OR = 1.025, 95% CI: 1.011-1.039), 1.8% (OR = 1.018, 95% CI: 1.009-1.027), 2.1% (OR = 1.021, 95% CI: 1.004-1.039), and 1.3% (OR = 1.013, 95% CI: 1.007-1.020), respectively. In addition, our stratified analyses revealed that girls and children aged 1 to 6 years were more sensitive to PM exposure, and the PM-associated risks for AC were more apparent in autumn and winter. Our study suggests that short-term exposure to PMs may induce AC in children.

Smoke and the eyes: A review of the harmful effects of wildfire smoke and air pollution on the ocular surface

Wildfires are occurring worldwide with greater frequency and intensity. Wildfires, as well as other sources of air pollution including environmental tobacco smoke, household biomass combustion, agricultural burning, and vehicular emissions, release large amounts of toxic substances into the atmosphere. The ocular surface is constantly exposed to the ambient air and is hence vulnerable to damage from air pollutants. This review describes the detrimental effects of wildfire smoke and air pollution on the ocular surface and resultant signs and symptoms. The latest relevant evidence is synthesised and critically evaluated. A mechanism for the pathophysiology of ocular surface damage will be proposed considering the existing literature on respiratory effects of air pollution. Current strategies to reduce human exposure to air pollutants are discussed and specific possible approaches to protect the ocular surface and manage air pollution induced ocular surface damage are suggested. Further avenues of research are suggested to understand how acute and chronic air pollution exposure affects the ocular surface including the short and long-term implications.

TLR4-Dependent DUOX2 Activation Triggered Oxidative Stress and Promoted HMGB1 Release in Dry Eye

Dry eye disease (DED) is one of the most common ocular surface diseases worldwide. DED has been characterized by excessive accumulation of reactive oxygen species (ROS), following significant corneal epithelial cell death and ocular surface inflammation. However, the key regulatory factor remains unclear. In this study, we tended to explore whether DUOX2 contributed to DED development and the underlying mechanism. Human corneal epithelial (HCE) cells were treated with hyperosmolarity, C57BL/6 mice were injected of subcutaneous scopolamine to imitate DED. Expression of mRNA was investigated by RNA sequencing (RNA-seq) and quantitative real-time PCR (qPCR). Protein changes and distribution of DUOX2, high mobility group box 1 (HMGB1), Toll-like receptor 4 (TLR4), and 4-hydroxynonenal (4-HNE) were evaluated by western blot assays and immunofluorescence. Cell death was assessed by Cell Counting Kit-8 (CCK8), lactate dehydrogenase (LDH) release, and propidium iodide (PI) staining. Cellular ROS levels and mitochondrial membrane potential (MMP) were analyzed by flow cytometry. RNA-seq and western blot assay indicated a significant increase of DUOX2 dependent of TLR4 activation in DED both in vitro and in vivo. Immunofluorescence revealed significant translocation of HMGB1 within corneal epithelial cells under hyperosmolar stress. Interestingly, after ablated DUOX2 expression by siRNA, we found a remarkable decrease of ROS level and recovered MMP in HCE cells. Moreover, knockdown of DUOX2 greatly inhibited HMGB1 release, protected cell viability and abolished inflammatory activation. Taken together, our data here suggest that upregulation of DUOX2 plays a crucial role in ROS production, thereafter, induce HMGB1 release and cell death, which triggers ocular surface inflammation in DED.

Expression profiles of long noncoding RNAs in human corneal epithelial cells exposed to fine particulate matter

PURPOSE

The aim of this study was to investigate the expression profiles of long noncoding RNAs (lncRNAs) in human corneal epithelial cells (HCECs) exposed to fine particulate matter (PM_2.5) and to identify potential biological pathways involved in PM_2.5-induced toxicity in HCECs.

METHODS

Using RNA sequencing (RNA-seq) and hierarchy clustering analysis, lncRNA expression profiles in PM_2.5-treated and untreated HCECs were examined. Gene ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed to predict the role of altered lncRNAs in biological processes and pathways. A quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) assay was conducted to verify the RNA-seq results in HCECs and human corneal epithelial cell sheets.

RESULTS

In total, 65 lncRNAs were altered in the PM_2.5-treated HCECs, including 41 upregulated and 24 downregulated lncRNAs. The results of the qRT-PCR assay were consistent with those of the RNA-seq analysis. The expression of two significantly upregulated lncRNAs was confirmed in human corneal epithelial cell sheets. The GO analysis demonstrated that altered lncRNAs in the PM_2.5-treated HCECs were significantly enriched in three domains: cellular component, molecular function, and biological process. The KEGG pathway analysis revealed enriched pathways of lncRNA co-expressed mRNAs, including cancer, RNA transport, and Rap1 signaling.

CONCLUSIONS

Our results suggest that lncRNAs are involved in the pathogenesis of PM_2.5-induced ocular diseases, exerting their effects through biological processes and pathogenic pathways. Among the altered lncRNAs, RP3-406P24.3 and RP11-285E9.5 may play significant roles in PM_2.5-induced ocular surface injury.

Research advances in pathogenic mechanisms underlying air pollution-induced ocular surface diseases

Background

The harmful effect of aerial fine particulate matter（PM2.5）has been a serious public health issue and has attracted worldwide attention, especially in developing countries.

Main Text

Numerous previous clinical and experimental studies have demonstrated that PM2.5 has a clear pathogenic effect on diseases related to the respiratory and cardiovascular systems. Recent researches have pointed out that PM2.5 plays a pivotal role in the occurrence and progression of ocular surface diseases. The current studies have shown that PM2.5 may promote the appearance of conjunctivitis, keratitis, blepharitis, dry eye, meibomian gland dysfunction（MGD） and other ocular surface diseases through regulating a series of mechanisms such as inflammation, immune reaction, oxidative stress, autophagy, cell migration, and epigenetics.

Conclusions

This review aims to summarize the current research progress on the pathogenic mechanism of PM2.5-related ocular surface diseases.

Air pollution and meteorological conditions significantly contribute to the worsening of allergic conjunctivitis: a regional 20-city, 5-year study in Northeast China

This study is the first to explore the potential associations among allergic conjunctivitis (AC), air pollution, and meteorological conditions in Northeast China. Data of meteorology, ambient atmospheric pollutants, and the incidence of allergic conjunctivitis (IAC) in prefecture-level cities between the years 2014 and 2018 are analyzed. The results show an increasing trend in the AC of average growth rate per annum 7.6%, with the highest incidence in the provincial capitals. The IAC is positively correlated with atmospheric pollutants (i.e., PM_2.5, PM₁₀, CO, SO₂, NO₂, and O₃) and meteorological factors (i.e., air temperature and wind speed), but negatively correlated with relative humidity. These results suggest that the IAC is directly proportional to pollution level and climatic conditions, and also the precedence of air pollution. We have further obtained the threshold values of atmospheric pollutants concentration and meteorological factors, a turning point above which more AC may be induced. Compared with the air quality standard advised by China and the World Health Organization (WHO), both thresholds of PM₁₀ (70 μg m^-3) and PM_2.5 (45 μg m^-3) are higher than current standards and pose a less environmental risk for the IAC. SO₂ threshold (23 μg m^-3) is comparable to the WHO standard and significantly lower than that of China's, indicating greater environmental risks in China. Both thresholds of NO₂ (27 μg m^-3) and O₃ (88 μg m^-3) are below current standards, indicating that they are major environmental risk factors for the IAC. Our findings highlight the importance of atmospheric environmental protection and reference for health-based amendment.

The Protective Effect of Topical Spermidine on Dry Eye Disease with Retinal Damage Induced by Diesel Particulate Matter2.5

Air pollutants, especially ambient fine particulate matter2.5, may contribute to various ocular surface disorders, including dry eye disease, keratitis and conjunctivitis. A natural polyamine spermidine has a protective effect on the retina and optic nerve; however, no study has been conducted on the application of spermidine in particulate matter2.5-induced dry eye disease. In the present study, we investigated the effect of spermidine eye drops in topically exposed particulate matter2.5-induced dry eye models of Sprague-Dawley rats, by hematological, biochemical and histological evaluation. Spermidine eye drops attenuated the particulate matter2.5 exposure-induced reduction of tear secretion and corneal epithelial damage. Furthermore, spermidine protected against conjunctival goblet cell loss and retinal ganglion cell loss induced by particulate matter2.5. Additionally, spermidine markedly prevented particulate matter2.5-induced infiltration of cluster of differentiation3⁺ and cluster of differentiation4⁺ T lymphocytes and F4/80⁺ macrophages on lacrimal gland. Moreover, over expression of pro-inflammatory cytokines, including tumor necrosis factor-α, interleukin-6 and interleukin-17 in the lacrimal gland and cornea. Meanwhile, the levels of serum total cholesterol and low-density lipoprotein cholesterol were markedly increased by topical exposure to particulate matter2.5, but this change in the lipid profile was decreased by spermidine. Taken together, spermidine may have protective effects against particulate matter2.5-induced dry eye symptoms via stabilization of the tear film and suppression of inflammation and may in part contribute to improving retinal function and lipid metabolism disorder.

The Protective Effect of Oral Application of Corni Fructus on the Disorders of the Cornea, Conjunctiva, Lacrimal Gland and Retina by Topical Particulate Matter 2.5

Particulate matter 2.5 (PM_2.5) may aggravate dry eye disease (DED). Corni Fructus (CF), which is fruit of Cornus officinalis Sieb. et Zucc., has been reported to have various beneficial pharmacological effects, whereas the effect of CF on the eye is still unknown. Therefore, in this study, we investigated the effect of oral administration of water extract of CF (CFW) on the eye, hematology, and biochemistry in a DED model induced by topical exposure to PM_2.5. Furthermore, the efficacy of CFW compared with cyclosporine (CsA), an anti-inflammatory agent, and lutein, the posterior eye-protective agent. Sprague-Dawley rats were topically administered 5 mg/mL PM_2.5 in both eyes four times daily for 14 days. During the same period, CFW (200 mg/kg and 400 mg/kg) and lutein (4.1 mg/kg) were orally administered once a day. All eyes of rats in the 0.05% cyclosporine A (CsA)-treated group were topically exposed to 20 μL of CsA, twice daily for 14 days. Oral administration of CFW attenuated the PM_2.5-induced reduction of tear secretion and corneal epithelial damage. In addition, CFW protected against goblet cell loss in conjunctiva and overexpression of inflammatory factors in the lacrimal gland following topical exposure to PM_2.5. Furthermore, CFW markedly prevented PM_2.5-induced ganglion cell loss and recovered the thickness of inner plexiform layer. Meanwhile, CFW treatment decreased the levels of total cholesterol and low-density lipoprotein cholesterol in serum induced by PM_2.5. Importantly, the efficacy of CFW was superior or similar to that of CsA and lutein. Taken together, oral administration of CFW may have protective effects against PM_2.5-induced DED symptoms via stabilization of the tear film and suppression of inflammation. Furthermore, CFW may in part contribute to improving retinal function and lipid metabolism disorder.

Traffic-related particulate matter aggravates ocular allergic inflammation by mediating dendritic cell maturation

The aim of this study was to determine the effects of traffic-related particulate matter (PM) on allergic inflammation of ocular surfaces. BALB/c mice were sensitized with ovalbumin (OVA) and aluminum hydroxide via intraperitoneal injection. Two weeks later, mice were challenged with eye drops containing OVA concomitant with either traffic-related PM_2.5 or vehicle eye drops. Topical OVA challenges were administered following unilateral subconjunctival injection of magnetic-bead-sorted CD11c+ dendritic cells (DC). The following were assessed: (1) clinical signs, (2) infiltration of inflammatory cells into conjunctiva, (3) serum levels of OVA-specific IgE production, and (4) T-cell cytokine secretion with topical application of PM_2.5, compared to saline vehicle. PM_2.5 was found to increase production of OVA-specific IgE in serum and Th2 immune response-related cytokines including interleukin (IL)-4, IL-17A, and IL-13 compared to vehicle control. It is of interest that PM_2.5 treatment also elevated the population of mature DCs in draining lymph nodes (LNs). Exposure with PM_2.5 was associated with a significant rise in conjunctival expression of IL-1β, IL-6, IL-17, and TNF. After subconjunctival injection of CD11c+DCs from PM_2.5-treated allergic conjunctivitis (AC) mice into naïve mice, T cell responses and OVA-specific IgE were also enhanced. Data suggest that traffic-related PM_2.5 exacerbated allergic conjunctivitis as evidenced by increased infiltration of inflammatory cells into the conjunctiva and Th2 responses in the draining LNs associated with enhanced maturation of DCs. Our findings provide new insight into the hazardous potential of traffic-related PM_2.5 on allergic diseases, such as asthma or atopic dermatitis.