Formaldehyde Gas Exposure Increases Inflammation in an In Vitro Model of Dry Eye

Abstract

Dry eye (DE) is a multifactorial ocular surface disease whose incidence continues to rise. Various environmental stresses such as low air humidity and pollution are known to be involved in epithelial alterations inducing ocular discomfort. However, no experimental study assessing the combined effects of dry air and polluted atmospheres has been conducted so far. Formaldehyde (FA) is a ubiquitous pollutant present in the living spaces where humans spend most of their time. Using an in vitro DE model, we evaluated the cytotoxic and inflammatory responses of a conjunctival cell line exposed at the air-liquid interface (ALI) conditions to various controlled atmospheres combining low humidity (LH), airflow (AF), and formaldehyde gas (FG). Conjunctiva-derived cells grown onto transwell inserts were directly exposed to LH conditions without AF, with AF or with FG flow at 100 or 1200 µg/m3 for 15-30 min. Cell viability assays revealed an increase in cell death after a 15-min exposure to FG at 100 or 1200 µg/m3, whatever the recovery period. After a 1-h recovery period, an increase in IL-6 and CXCL8/IL-8 gene expression was observed with the 15-min exposure at 100 µg/m3 FG and with 30 min of exposure at 1200 µg/m3 FG. After 24 h of recovery, we also noted increased secretion of the proinflammatory cytokine MIF with 100 µg/m3 FG exposure and CXCL8/IL-8 at 1200 µg/m3, for both exposure periods. Together, these findings suggest that the exposure to FG at environmental levels aggravates cell death and inflammation observed in dry air conditions. This in vitro model of DE seems to be a relevant tool to study and explain the inflammatory responses observed in dry eye patients when exposed to combined environmental disturbances such as LH, airflow, and the presence of airborne pollutants.

The Adverse Effects of Air Pollution on the Eye: A Review

“…Indoor air pollution is associated with indoor tobacco smoking, dissipation of compounds used in building materials and decorations in buildings, cooking with oil and high heat, burning coal or biomass for cooking or heating, using pesticides, etc. [70,71]. Moreover, building products and materials, cleaning products, and consumer products emit many chemically nonreactive volatile organic compounds (VOCs) and biologically reactive compounds, such as formaldehyde (FA) and acrolein.…”

Benzalkonium chloride-induced direct and indirect toxicity on corneal epithelial and trigeminal neuronal cells: proinflammatory and apoptotic responses in vitro

“…Among the numerous causes of DED, the environmental conditions in which we are living, whether indoor or outdoor, have a major impact on the ocular surface, and can induce or aggravate symptoms of DED and ocular pain (Galor et al, 2015;Vitoux et al, 2018;Wolkoff, 2018). Indeed, the ocular surface has to deal with physical aggressions (low ambient air humidity, excessive heat, air conditioning, wind, dust and particles), but also chemical aggressions (formaldehyde gas, cooking fumes and disinfecting sprays for indoor environments; benzene and diesel particles for outdoor environments…).…”

Ocular surface assessment and morphological alterations in meibomian glands with non-contact meibography in electronic cigarette smokers

“…Additionally, overheated propylene glycol can turn into formaldehyde (16) . In their recent study, Vitoux et al (17) have demonstrated that exposure to formaldehyde gas increased inflammation in vitro dry eye model. The researchers used conjunctival cells to show that formaldehyde exacerbated cell death and inflammation, and found increased interleukin (IL)-6 and IL-8 gene expression after a 15-minute exposure.…”