Effect of carbon black and silicon dioxide nanoparticle exposure on corona receptor ACE2 and TMPRSS2 expression in the ocular surface.

The Coronavirus disease 2019 (COVID-19) pandemic has led to a global health crisis, including ocular symptoms, primarily targeting the Angiotensin-Converting Enzyme 2 (ACE2) receptor. PM2.5 air pollution may increase infection risk by altering ACE2 expression. Silicon Dioxide (SiO) and carbon black (CB), major components of PM2.5 from sands and vehicle emissions, were studied for their effects on ACE2 and Transmembrane Protease Serine 2 (TMPRSS2) expression in corneal and conjunctival cells, and ocular tissues. Human corneal epithelial cells (HCECs) and conjunctival epithelial cells (HCjECs) were exposed to nanoparticles (NPs) for 24 hours, assessing viability via WST-8 assay. TNF-α, IL-6, and IL-1β levels in the medium were measured. An in vivo rat study administered NPs via eye drops, with Rose Bengal staining to evaluate damage. ACE2, TMPRSS2, and Angiotensin II (AngII) protein expressions were quantified by Western blot. ACE2 expression in HCjECs increased with NP exposure, while it decreased in HCECs. CB exposure increased TNF-α, IL-6, and IL-1β levels in HCECs. In vivo, corneal exposure to CB decreased ACE2 expression, whereas conjunctival exposure to SiO increased ACE2 expression. These changes suggest that SiO2 exposure may increase the risk of COVID-19 through the ocular surface, while CB exposure may decrease it.