Effects of TCPP and TCEP exposure on human corneal epithelial cells: Oxidative damage, cell cycle arrest, and pyroptosis.

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 TCPP20+TCEP20 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-1ß, 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 TCPP20+TCEP20-induced cytotoxicity and pyroptosis in HCECs. Our results suggested that TCPP20+TCEP20 co-exposure induced severer corneal damage, further illustrating its significance in estimating indoor health hazards to humans.

Organophosphorus Flame Retardant TCPP Induces Cellular Senescence in Normal Human Skin Keratinocytes: Implication for Skin Aging.

Tris (1-chloro-2-propyl) phosphate (TCPP) is one of the most frequently detected organophosphorus flames in the environment. Continuous daily exposure to TCPP may harm human skin. However, little is known about the adverse effects of TCPP on human skin. In this study, we first evaluated the detrimental effects and tried to uncover the underlying mechanisms of TCPP on human skin keratinocytes (HaCaT) after 24 h exposure. We found that TCPP caused a concentration-dependent decrease in HaCaT cell viability after exposure to 1.56-400 µg/mL for 24 h, with an IC50 of 275 µg/mL. TCPP also promoted the generation of intracellular reactive oxygen species (ROS) and triggered DNA damage, evidenced by an increase of phosphorylated histone H2A.X (γH2A.X) in the nucleus. Furthermore, the cell cycle was arrested at the G1 phase at 100 µg/mL by upregulation of the mRNA expression of p53 and p21 and downregulation of cyclin D1 and CDK4 expression. Additionally, both the senescence-associated-ß-galactosidase activity and related proinflammatory cytokine IL-1ß and IL-6 were elevated, indicating that TCPP exposure caused cellular senescence may be through the p53-dependent DNA damage signal pathway in HaCaT cells. Taken together, our data suggest that flame-retardant exposure may be a key precipitating factor for human skin aging.

Mechanisms of Cd and Cu induced toxicity in human gastric epithelial cells: Oxidative stress, cell cycle arrest and apoptosis.

Cadmium (Cd) and copper (Cu) are widely present in foods. However, their adverse effects on human gastric epithelium are not fully understood. Here, human gastric epithelial cells (SGC-7901) were employed to study the toxicity and associated mechanisms of Cd + Cu co-exposure. Their effects on cell viability, morphology, oxidative damage, cell cycle, apoptosis, and the mRNA levels of antioxidases and cell cycle regulatory genes were investigated. Co-exposure to Cd (5 µM)/Cu (10 µM) induced >40% cell viability loss, whereas little effect on cell viability at <10 µM Cd or 40 µM Cu. Compared to individual exposure, co-exposure induced greater oxidative damage by elevating ROS (3.5 folds), malondialdehyde (2.3 folds) and expression of SOD1 and HO-1 besides inhibiting CAT, GPX1 and Nrf2. A marked S cell-cycle arrest was observed in co-exposure, evidenced by more cells staying in the S phase (36%), up-regulation of cyclins-dependent kinase (CDK4) and CDKs inhibitor (p21) and down-regulation of CDK2, CDK6 and p27. Furthermore, higher apoptosis (22%) with floated and round cells occurred in co-exposure group. Our data implicate the cytotoxicity of Cd + Cu co-exposure was higher than individual exposure, and individual assessment would underestimate their potential health risk. Oxidative stress and cell cycle arrest possibly played a role in Cd + Cu induced toxicity and apoptosis in SGC-7901 cells. Our data suggest the importance to reduce Cd in foods to decrease its adverse impacts on human digestive system.

Slit2 suppresses endothelial cell proliferation and migration by inhibiting the VEGF-Notch signaling pathway.

Slit homolog 2 (Slit2) is distributed in various tissues and participates in numerous cellular processes; however, the role of Slit2 in the regulation of angiogenesis remains controversial, since it has previously been reported to exert proangiogenic and antiangiogenic activities. The present study aimed to investigate the effects of Slit2 on vascular endothelial cell proliferation and migration in vitro, and to reveal the possible underlying signaling pathway. Aortic endothelial cells were isolated from Sprague Dawley rats and cultured. Cell proliferation assay, cell migration assay, immunocytochemistry and small interfering RNA transfection were subsequently performed. The results demonstrated that exogenous Slit2 administration markedly suppressed TNF­α­induced endothelial cell proliferation and migration in vitro. In addition, TNF­α application upregulated the protein expression levels of vascular endothelial growth factor (VEGF) and Notch in RAECs, whereas Slit2 administration downregulated VEGF and Notch expression in RAECs cultured in TNF­α conditioned medium. Further studies indicated that knockdown of VEGF suppressed the effects of TNF­α on the induction of RAEC proliferation and migration. VEGF knockdown­induced inhibition of RAEC proliferation and migration in TNF­α conditioned medium was also achieved without Slit2 administration. Furthermore, VEGF knockdown markedly decreased Notch1 and Notch2 expression. These results indicated that Slit2 suppresses TNF­α­induced vascular endothelial cell proliferation and migration in vitro by inhibiting the VEGF­Notch signaling pathway. Therefore, Slit2 may inhibit the proliferation and migration of endothelial cells during vascular development.