The role of unfolded protein response and ER-phagy in quantum dots-induced nephrotoxicity: an in vitro and in vivo study

Abstract

Unfolded protein response (UPR) and endoplasmic reticulum (ER)-phagy are essential for cell homeostasis. Quantum dots (QDs), which have been widely used for biomedical applications, can accumulate in the kidney tissues and may cause renal dysfunction. However, the molecular mechanism of QDs-induced nephrotoxicity is still obscure. The present study was aimed to elucidate the role and mechanism of UPR and ER-phagy in QDs-induced nephrotoxicity. Herein, human embyronic kidney (HEK) cells were exposed to 15, 30, 45, and 60 nM cadmium telluride (CdTe)-QDs for 12 and 24 h. And CdTe-QDs (30-60 nM) inhibited the HEK cell viability. The clathrin-dependent endocytosis was determined as the main pathway of CdTe-QDs cellular uptake. Within cells, CdTe-QDs disrupted ER ultrastructure and induced UPR and FAM134B-dependent ER-phagy. Blocking UPR with inhibitors or siRNA rescued the FAM134B-dependent ER-phagy, which was triggered by CdTe-QDs. Moreover, suppression of UPR or FAM134B-dependent ER-phagy restored the cell vability. In vivo, mice were intravenously injected with 8 and 16 nmol/kg body weight CdTe-QDs for 24 h. Kidney was shown as one of highest distributed organs of CdTe-QDs, resulting in renal dysfunction, as well as UPR and FAM134B-dependent ER-phagy in it. Thus, for the first time, we demonstrated that ER-phagy can be triggered by nanomaterials both in vitro and in vivo. In addition, blocking of UPR and ER-phagy showed protective effects against CdTe-QDs-induced toxicity in kideny cells. Notably, a secreted alkaline phosphatase reporter gene system has been developed as a sensitive and rapid method for evaluating the ER quality under the exposure of nanomaterials.

ToxTracker Reporter Cell Lines as a Tool for Mechanism-Based (Geno)Toxicity Screening of Nanoparticles—Metals, Oxides and Quantum Dots

“…The activation of UPR observed in response to CdTe QDs in this study is in line with findings of Jiang et al [50], demonstrating low concentrations of CdTe QDs to be distributed at ER, resulting in ER expansion and UPR activation in HEK kidney cells. These findings were further confirmed in the kidneys of mice exposed to CdTe QDs, demonstrating that UPR mediates the toxicity of CdTe QDs both in vitro and in vivo [50]. CdTe QDs have also been shown to target endothelial ER in human umbilical vein endothelial cells (HUVECs) by causing ER stress, activating the UPR pathway and all of the three downstream ER stress-mediated apoptosis pathways, and ultimately triggered ER stress-induced apoptotic cell death [51].…”

“…Furthermore, the addition of the antioxidant NAC has been reported to reduce CdTe QD cytotoxicity and preserve mitochondrial morphology [20,21]. The activation of UPR observed in response to CdTe QDs in this study is in line with findings of Jiang et al [50], demonstrating low concentrations of CdTe QDs to be distributed at ER, resulting in ER expansion and UPR activation in HEK kidney cells. These findings were further confirmed in the kidneys of mice exposed to CdTe QDs, demonstrating that UPR mediates the toxicity of CdTe QDs both in vitro and in vivo [50].…”

“…When comparing effects observed in ToxTracker between the QDs and the soluble CdCl 2 salt, based on Cd-content, CdCl 2 induced cytotoxicity at a lower concentration of Cd compared to that of CdTe QDs sized 1.5 nm. This is somewhat in conflict with previous findings demonstrating CdTe QDs to be more cytotoxic compared to CdCl 2 at similar concentrations of Cd in HepG2 [52] and HEK cells [50]. Cho et al [53] report no dose-dependent correlation between cell viability and intracellular [Cd 2+ ] following exposure to CdTe QDs, implying the cytotoxicity observed in MCF-7 cell not solely to be related to free Cd ions or Cd-complexes in solution.…”

Stem cell-based test methods

“…Recently, Agapios Sachinidis and colleagues from the University of Cologne published a review about possibilities and limitations of stem cell-based test methods in pharmacology and toxicology (Sachinidis et al, 2019[ 18 ]). In recent years, much progress has been achieved concerning in vitro techniques of liver (Godoy et al, 2013[ 7 ]; Grinberg et al, 2014[ 10 ]; Leist et al, 2017[ 15 ]; Ghallab et al, 2016[ 6 ]), kidney (Sjögren et al, 2018[ 24 ]; Jiang et al, 2018[ 11 ]; Su et al, 2016[ 25 ]; Valente et al, 2012[ 26 ]; Lee et al, 2017[ 14 ]), neuronal (Keil et al, 2018[ 12 ]; Yang et al, 2018[ 28 ]; Colaianna et al, 2017[ 5 ]; Sisnaiske et al, 2014[ 23 ]) and developmental toxicity (Adam et al, 2019[ 2 ]; Bridges et al, 2019[ 3 ]; Abbott, 2019[ 1 ]). Particularly, in developmental and reproductive toxicity testing, large numbers of animals are needed for analysis of a single compound (Krug et al, 2013[ 13 ]).…”

Highlight report: role of HNF4α in stem-cell differentiation to hepatocytes

“…Currently, there is a need of in vitro systems with cells that closely resemble mature human cells, such as hepatocytes (Godoy et al 2013(Godoy et al , 2016Ghallab et al 2016;Hewitt et al 2007), kidney epithelial tubular cells (Sjögren et al 2018;Jiang et al 2018;Leist et al 2017), and neuronal cells (Krug et al 2013;Waldmann et al 2014;Rempel et al 2015). Human hepatic differentiation protocols have been developed and optimized (Cameron et al 2015;Rashidi et al 2018;Sullivan et al 2010), but the problem remains that stem-cell-derived hepatocyte-like cells still show major differences compared to primary human hepatocytes.…”