Lens as a novel target of urban air pollutants: evaluation of the redox balance

Abstract

Purpose : Particulate matter (PM) present in air pollution induces adverse effects on the eye. Oxidative stress has been suggested to play a key role in the ocular surface response triggered by urban air pollutants. It is well-known that lens antioxidant system maintains the redox status of nearby ocular structures. The aim of the study was to evaluate the redox balance in mice lens after the exposure to urban air pollution.

Methods : 8-week-old Balb/c male mice were exposed to urban air or filtered air (UA-group and FA-group, respectively) in exposure chambers located in highly populated area of Buenos Aires city (average level of PM: 25.6 ± 0.8 μg/m³). The animals were exposed for 8 h/day, 5 days/week, up to 12 weeks. The local committee for animal care (CICUAL-FFYB, CUDAP 50946/16) approved the experimental model. Superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), Glutathione S-transferase (GST), and Thioredoxin reductase (TrxR) activities, levels of reduced and oxidized glutathione (GSH and GSSG) and protein oxidation (PO) were evaluated in lens lysates.

Results : After 1 and 2 weeks of exposure, UA-group presented no significant differences in all measurements compared to the FA-group, except for SOD activity that was increased after 1 week (107%, p<0.05). After 4 weeks, an increase in GR activity was shown in UA-group (47%, p<0.05). After 12 weeks, GPx activity was increased in UA-group (63%, p<0.05), meanwhile GR activity decreased (40%, p<0.05) as well as the GSH/GSSG index (62%, p<0.05), compared to FA-group. PO increased in UA-group (113%, p<0.05), and an inverse correlation was found between PO and GSH/GSSG index (r=-0.9114, p<0.001). GPx activity and GSH/GSSG index also presented an inverse correlation (r=-0.7421, p<0.001) in UA-group. There were no significant differences in GST and TrxR activities between both groups in all the time points evaluated.

Conclusions : These results suggest that urban air pollution exposure alters the redox balance of the lens, which could affect the antioxidant defenses of nearby ocular structures. The correlation between the PO and GSH/GSSG index indicates that lens GSH pool could prevent the protein oxidation, which has been suggested as one of the triggers of cataracts. Therefore, this study suggests that lens should also be considered as an important target of urban air pollution.

This is a 2020 ARVO Annual Meeting abstract.