Organophosphorus flame retardant TDCPP-induced cytotoxicity and associated mechanisms in normal human skin keratinocytes
Graphical abstract
Introduction
Flame retardants are frequently added to various consumer products to prevent fire flame propagation. In recent years, due to their potential health effects, brominated flame retardants including polybrominated diphenyl ethers (PBDEs) have been phased out (Stapleton et al., 2012; Dishaw et al., 2014). As an alternative, organophosphorus flame retardants (OPFR) have been used in consumer products, including building materials, furniture, foam, plastics, electronics, and baby products (Stapleton et al., 2011; Hoffman et al., 2015). At present, OPFR are widely used, with global consumption reaching ~680,000 tons in 2015 (van der Veen and de Boer, 2012; Wang et al., 2015). In China, their production reached 300,000 tons in 2013, increasing ~15% annually (Ou, 2011).
Because OPFR are added to the materials physically, they can be easily released into the environment by volatilization and abrasion. Among OPFR, tris(1,3-dichloro-2-propyl) phosphate (TDCPP) is one of the most widely used and has been frequently detected in indoor dust with concentrations at 56.1–326 μg/g (Stapleton et al., 2009; Carignan et al., 2013). Moreover, it was also detected in many human samples like breast milk (Sundkvist et al., 2010; Kim et al., 2014), and blood and urine (Butt et al., 2014; Zhang et al., 2018). As such, studies have focused on the potential adverse effects of TDCPP on human health. Abou-Elwafa Abdallah et al. (2015) reported that skin absorption may be a main route for human exposure to OPFR including TDCPP. This is because human skin is the largest body organ of the integumentary system, with a total surface area of ~2 m2 in adults (Godin and Touitou, 2007). However, little is known about TDCPP-induced effects on human skin.
Animals and cell models have been widely employed to study TDCPP-induced toxicity. Yin et al. (2019) showed that TDCPP disturbed mouse embryonic development by triggering abnormal DNA methylation and apoptosis. TDCPP at 1–86 μg/mL induced neurotoxicity and cytotoxicity in pheochromocytoma neuronal cells and neuroblastoma cells (Li et al., 2017). Xiang et al. (2017a) reported that, in primary normal human corneal epithelial cells, exposure to ≥2 μg/mL TDCPP induced apoptosis, and deregulated the mRNA expression associated with endoplasmic reticulum stress and mitochondrial apoptotic pathway. However, its toxicity on human skin cells is largely unknown. The outermost cell layer of human skin (epidermis) mainly consists of keratinocytes, which acts as a barrier to protect vascular dermis from exposure to contaminants including OPFR. Cequier et al. (2014) found that dermal absorption contributed ~50% to the intake of TDCPP from indoor dust, suggesting that skin absorption may be an important route for human exposure to TDCPP.
To better understand its toxicity, the effects of TDCPP on human skin cells were evaluated using normal human skin keratinocytes (HaCaT). Changes in cell viability, morphology, apoptosis and cycle arrest were determined after 48 h exposure to TDCPP. Besides, the expression of cell apoptosis and cell cycle regulatory genes at mRNA levels were assessed to explore the underlying molecular mechanisms associated with TDCPP-induced adverse effects.
Section snippets
Chemicals and cell exposure
Tris(1,3-dichloro-2-propyl) phosphate (TDCPP, purity 99%) was from Dr. Ehrenstorfer GmbH (Augsburg, Germany). Various kits and reagents including cell counting kit-8 (CCK-8), Annexin V-FITC and propidine iodide (PI) double staining, cell cycle and apoptosis detection, total RNA extraction reagent, and SYBR green qPCR master mix were from Yi Fei Xue Biotech, Ltd. (Nanjing, China). The cDNA synthesis kit was from TaKaRa Biotech, Ltd. (Dalian, China). Roswell Park Memorial Institute (RPMI) 1640
TDCPP suppressed cell viability and changed cell morphology
Cell viability is critical for assessing cellular responses to contaminants as it reflects cell survival and proliferation (Crump et al., 2012). Several studies have determined the impacts of TDCPP on the viability of human cells. For example, Liu et al. (2012) showed decrease of cell viability by >20% in human adrenocarcinoma cells after exposing to 10 μg/mL TDCPP for 2 d. In contrast, Dishaw et al. (2011) found no detrimental effect on cell viability in rat pheochromocytoma cells after
Credit authorship contribution statement
Daolei Cui: Investigation, Writing - original draft. Jue Bi: Investigation. Zhen-Ning Zhang: Investigation. Meng-Ying Li: Investigation. Yi-Shu Qin: Investigation. Ping Xiang: Investigation, Writing - review & editing. Lena Q. Ma: Investigation, Writing - review & editing.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This work was supported in part by the National Key Research and Development Program of China (2018YFC1800504), National Natural Science Foundation of China (21906134 and 41967026), the Basic Research Program of Yunan Province (2019FB014), Yunnan Thousand Youth Talent Program (YNQR-QNRC-2018-049), Yunnan Agricultural Joint Foundation Projects (2018FG001-048), the Research Foundation of Southwest Forestry University (111819), the Key Disciplines (Ecology) Project of Yunnan Education Department,
References (44)
- et al.
Differential role of D cyclins in the regulation of cell cycle by influencing Ki67 expression in HaCaT cells
Exp. Cell Res.
(2019) - et al.
Predictors of tris(1,3-dichloro-2-propyl) phosphate metabolite in the urine of office workers
Environ. Int.
(2013) - et al.
Oxidative stress, cell cycle arrest, DNA damage and apoptosis in adult zebrafish (Danio rerio) induced by tris(1,3-dichloro-2-propyl) phosphate
Aquat. Toxicol.
(2018) - et al.
Is the PentaBDE replacement, tris (1,3-dichloro-2-propyl) phosphate (TDCPP), a developmental neurotoxicant? Studies in PC12 cells
Toxicol. Appl. Pharmacol.
(2011) - et al.
Exposures, mechanisms, and impacts of endocrine-active flame retardants
Curr. Opin. Pharmacol.
(2014) - et al.
Transdermal skin delivery: predictions for humans from in vivo, ex vivo and animal models
Adv. Drug Deliv. Rev.
(2007) - et al.
Organophosphorus flame retardants (PFRs) in human breast milk from several Asian countries
Chemosphere
(2014) - et al.
Tris (1,3-dichloro-2-propyl) phosphate-induced apoptotic signaling pathways in SH-SY5Y neuroblastoma cells
Neuro Toxicol.
(2017) - et al.
Endocrine disruption potentials of organophosphate flame retardants and related mechanisms in H295R and MVLN cell lines and in zebrafish
Aquat. Toxicol.
(2012) - et al.
Analysis of relative gene expression data using real-time quantitative PCR and the 2(−Delta Delta C (T)) method
Methods
(2001)
Cell cycle checkpoint signaling
Toxicology
Phosphorus flame retardants: properties, production, environmental occurrence, toxicity and analysis
Chemosphere
Bioconcentration, metabolism and neurotoxicity of the organophorous flame retardant 1,3-dichloro 2-propyl phosphate (TDCPP) to zebrafish
Aquat. Toxicol.
Thapsigargin induces apoptosis when autophagy is inhibited in HepG2 cells and both processes are regulated by ROS-dependent pathway
Environ. Toxicol. Pharmacol.
Effects of organophosphorus flame retardant TDCPP on normal human corneal epithelial cells: implications for human health
Environ. Pollut.
Effects of novel brominated flame retardant TBPH and its metabolite TBMEHP on human vascular endothelial cells: implication for human health risks
Environ. Res.
Cellular responses of normal (HL-7702) and cancerous (HepG2) hepatic cells to dust extract exposure
Chemosphere
Nitidine chloride induces S phase cell cycle arrest and mitochondria-dependent apoptosis in HaCaT cells and ameliorates skin lesions in psoriasis-like mouse models
Eur. J. Pharmacol.
Urinary metabolites of organophosphate flame retardants in 0-5-year-old children: potential exposure risk for inpatients and home-stay infants
Environ. Pollut.
Exposure to tris(1,3dichloro-2-propyl) phosphate (TDCPP) induces vascular toxicity through Nrf2-VEGF pathway in zebrafish and human umbilical vascular endothelial cells
Environ. Pollut.
Human dermal absorption of chlorinated organophosphate flame retardants; implications for human exposure
Toxicol. Appl. Pharmacol.
Biochemical pathways of caspase activation during apoptosis
Annu. Rev. Cell Dev. Biol.
Cited by (17)
VR-10 polypeptide interacts with CD36 to induce cell apoptosis and autophagy in choroid-retinal endothelial cells: Identification of VR-10 as putative novel therapeutic agent for choroid neovascularization (CNV) treatment
2022, PeptidesCitation Excerpt :Then, the SYBR Preminx Ex Taq reagent (Takara, Otsu, Japan) and the Real-Time qPCR machine (BD Bioscience, USA) were employed to quantify genes expression at mRNA levels. The primer sequences for PEDF, VEGF, HIF-1, IL-17, CDK2, CDK4, CDK6, Cyclin D1, Cyclin D2 and β-actin were designed by Sangon Biotech (Shanghai, China) according to the published literatures [37,38]. Gene expressions at protein levels were determined by Western Blot analysis as previously reported [36].
Dermal bioaccessibility and cytotoxicity of heavy metals in urban soils from a typical plateau city: Implication for human health
2022, Science of the Total EnvironmentCitation Excerpt :HaCaT cells were maintained in MEM supplemented with 10% FBS and 1% penicillin-streptomycin solution in an incubator with a humidified atmosphere of 5% CO2 and 95% air at 37 °C. Before cell treatments, HaCaT cells were reseeded into 6/96-well plates or Petri dishes at 2.5 × 104 cells per cm2 density overnight to allow cell attachment as our provious study (Cui et al., 2020). Artificial perspiration solutions of soil samples were sterilized by a 0.22 μm filter.
Mechanisms of Cd and Cu induced toxicity in human gastric epithelial cells: Oxidative stress, cell cycle arrest and apoptosis
2021, Science of the Total EnvironmentCitation Excerpt :Changes in cyclin-dependent kinases (CDK2 and CDK4) expression in SGC-7901 cells is an important mechanism for metal-induced cell cycle arrest (Chen et al., 2018). Up-regulation of CDK4 and inhibition of CDK2 and CDK6 expression might result in cell transition from G1 to S phase since CDK4 plays a crucial role in accelerating the timing of G1-S transition, so overexpressing CDK4 promoted cell transition from G1 to S phase (Cui et al., 2020). The p27, a crucial regulator of cell cycle, inhibits various CDKs to negatively modulate G1-S transition (Xiang et al., 2017).