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Nickel (Ni) is ubiquitous in the environment and evidence has suggested that Ni can cause ocular surface inflammation, especially in fine particulate matter and personal products. Continuous daily exposure to Ni-containing dust may adversely impact the human cornea, whereas the underlying mechanism of this phenomenon remains not fully understood. Here, human corneal epithelial cells (HCEC) were employed to analyze the toxicity of Ni via detections of cell morphology, cell viability, reactive oxygen species production, cell apoptosis rate, and apoptotic gene expression levels after exposure for 24 h to uncover the damage of Ni to the cornea. A concentration-dependent inhibition of HCECs' viability and growth was observed. In particular, Ni at 100 μM significantly decreased cell viability to 76%, and many cells displayed an abnormal shape and even induced oxidative damage of HCEC by increasing ROS to 1.2 times, and further led to higher apoptosis (24%), evidenced by up-regulation of apoptotic genes Caspase-8, Caspase-9, NF-κB, IL-1β, and Caspase-3, posing a risk of dry eye. Our study suggested that Ni induces apoptosis of HCEC through oxidative damage. Therefore, Ni pollution should be comprehensively considered in health risks or toxic effects on the ocular surface. [ABSTRACT FROM AUTHOR]

Tris(2-chloroisopropyl) phosphate (TCPP) and Tris(2-chloroethyl) phosphate (TCEP) are the widely used organophosphorus flame retardants indoors and easily accessible to the eyes as the common adhesive components of dust and particle matter, however, hardly any evidence has demonstrated their corneal toxicity. In this study, the adverse effects of TCPP, TCEP, and TCPP + TCEP exposure on human corneal epithelial cells (HCECs) were investigated. The cell viability and morphology, intracellular reactive oxygen species (ROS), cell cycle, and the expressions of cell cycle and pyroptosis-related genes were assessed to explain the underlying mechanisms. Compared to individual exposure, co-exposure to TCPP 20 +TCEP 20 showed higher cytotoxicity with a sharp decrease of >30% in viability and more serious oxidative damage by increasing ROS production to 110.92% compared to the control group. Furthermore, the cell cycle arrested at the S phase (36.20%) was observed after combined treatment, evidenced by the upregulation of cyclin D1 , CDK2 , CDK4 , CDK6 , p21, and p27. Interestingly, pyroptosis-related genes GSDMD , Caspase-1 , NLRP3 , IL-1β , IL-18 , NLRP1, and NLRC4 expressions were promoted with cell swelling and glowing morphology. Oxidative stress and cell cycle arrest probably acted as a key role in TCPP 20 +TCEP 20 -induced cytotoxicity and pyroptosis in HCECs. Our results suggested that TCPP 20 +TCEP 20 co-exposure induced severer corneal damage, further illustrating its significance in estimating indoor health hazards to humans. [Display omitted] • Effects of TCPP and TCEP on human corneal epithelial cells were originally investigated. • The corneal cytotoxicity of co-exposure to TCPP and TCEP was higher than individual exposure. • TCPP + TCEP posed a potential risk of inducing cell cycle arrest and pyroptosis via oxidate damage. • TCPP + TCEP enhanced the expressions of NLRP1 , NLRC4 , NLRP3 , Caspase-1 , IL-1β , IL-18 and GSDMD. [ABSTRACT FROM AUTHOR]