Evidence of air pollution-related ocular signs and altered inflammatory cytokine profile of the ocular surface in Beijing

Abstract

We evaluated how different degrees of air pollution affect the ocular surface of a cohort of human subjects in Beijing by correlating in-patient test outcomes with tear cytokines. A cross-sectional study involving 221 volunteers was carried out in different districts of Beijing. Air pollution indices were recorded for 7 d (including the visit day). The indices recorded were the air quality index (AQI), which is a dimensionless measure that quantitatively describes the state of air quality, concentrations of particulate matter smaller than 2.5 μm (PM2.5) and 10 μm (PM10), sulfur dioxide (SO2), ozone (O3), and nitrogen dioxide (NO2). The Ocular Symptom Disease Index (OSDI) questionnaire provided. Subsequently, subjects underwent slit-lamp examination, which included meibomian gland examination, conjunctival congestion score, conjunctivochalasis grade, tear meniscus height (TMH), tear breakup time (TBUT), corneal fluorescein staining (CFS), Schirmer I test, and conjunctival impression cytology. The concentrations of vascular endothelial growth factor (VEGF), interleukins (IL)-1β, IL-6 and IL-8 in tears were measured by microsphere-based immunoassay analysis. According to the value of the AQI, participants are divided into a slightly polluted (SP) group (n = 103) which the AQI value is less than or equal to 100 and a heavily polluted (HP) group (n = 118) whose AQI value is more than 100. Air pollution is related to ocular discomfort based on tear cytokine concentrations. PM2.5, PM10 and NO2 were positively correlated with OSDI, MG expressibility, meibum score, meiboscore, conjunctival congestion score, Schirmer I test value, TMH, goblet-cell density, concentrations of IL-6, and VEGF were negatively correlated with TBUT. PM2.5 and PM10 appear to be the major risk factors to the ocular surface, with NO2 being another important risk factor based on this study. The symptoms and signs of eye discomfort in the SP group were significantly less severe than those in the HP group, and tear cytokine concentrations (IL-6 and VEGF) were lower. Air pollution degrees were significantly correlated with tear cytokine concentrations, indicating an alteration of cytokine balance at the ocular surface under different degrees of air pollution.

Tear Fluid as a Matrix for Biomonitoring Environmental and Chemical Exposures

“…Based on these ndings, the ocular mucosa was proposed as a surrogate for the pulmonary mucosa to evaluate environmental toxicity in the respiratory system 132 . Interestingly, a positive association between IL-6 levels in tears and air pollution exposure is also reported in humans 120 , as described in the Proteins section of this review, further supporting the multivariate analysis we recommend in the Multi-omics and Multivariate Analysis section of this review. Acronyms: Enzyme-linked immunosorbent assay (ELISA); Liquid chromatography-mass spectrometry (LC-MS); Gas chromatography-mass spectrometry (GC-MS); Paper spray-mass spectrometry (PSMS)…”

“…exposure was signi cantly linked to IL-5 levels (p = 0.01) and IL-10 levels (p = 0.03) 118 . Tear uid cytokines concentrations have also been used to compare air pollution exposures from different urban and industrial living districts 120 . When the analysis of tear samples from 221 healthy volunteers was correlated to atmospheric levels of particulate matter, sulfur dioxide, nitrogen dioxide, and ozone, it was revealed a signi cantly higher concentration of IL-6 (p < 0.01), IL-8 (p = 0.03), and Vascular Endothelial Growth Factor (p < 0.01) is present in groups with greater exposure to these air pollutants.…”

“…Tear uid proteins and in ammatory markers can differentiate exposure groups [118][119][120][121] . For instance, cytokine levels in the tear uid of groups chronically exposed to particulate matter (PM 2.5 ) (taxi drivers/tra c controllers) have been compared groups with low air pollution exposure (Forest Institute workers) using immunoassays 118 .…”

Toxic External Exposure Leading to Ocular Surface Injury

“…The positive association between ocular surface deficits and increased air pollution was supported in two California-based studies, as air pollution was found to cause significant eye irritation [ 232 , 233 ]. A recent study from Beijing compared ocular characteristics of subjects in heavily polluted areas to those in slightly polluted regions as measured by air quality index (AQI) and specific components encompassing particulates, NO 2 , and sulfur dioxide (SO 2 ) [ 234 ]. The Ocular Symptom Disease Index (OSDI) questionnaire was used to assess eye discomfort and scores were positively correlated with AQI, PM2.5, PM10, and NO 2 levels.…”