The Pivotal Role of Ca2+ Homeostasis in PBDE-47-Induced Neuronal Apoptosis

Sodium p-perfluorinated noneoxybenzen sulfonate (OBS) induced neurotoxicity in zebrafish through mitochondrial dysfunction

Sodium p-perfluorous nonenoxybenzene sulfonate (OBS)-one of the main alternatives to perfluorooctane sulfonate-has been increasingly detected in both aquatic environments and human bodies. Therefore, the pathogenic risks of OBS exposure warrant attention, especially its central nervous system toxicity mechanism under long-term exposure. In this study, the effects and mechanisms of OBS on the zebrafish brain at 40 days post exposure were examined. The results demonstrated that at 3.2 μg/L, OBS had no significant effect on the zebrafish brain, but 32 μg/L OBS caused depression or poor social behavior in zebrafish and reduced both their memory and survival ability. These changes were accompanied by histological damage and cell apoptosis. Furthermore, OBS caused the accumulation of excessive reactive oxygen species in the fish brain, leading to oxidative stress and subsequently cell apoptosis. Moreover, an imbalance of both inflammatory factors (IL-6, IL-1β, IL-10, TNF-α, and NF-κB) and neurotransmitters (GABA and Glu) led to neuroinflammation. Additionally, 32 μg/L OBS induced decreases in mitochondrial membrane potential and Na+-K+-ATPase activity, leading to both mitochondrial structural damage and the emergence of mitochondrial autophagosomes, partly explaining the neurotoxicity of OBS. These results help to analyze the target sites and molecular mechanisms of OBS neurotoxicity and provide a basis for the scientific evaluation of its health risks to humans.

ZLN005 alleviates PBDE-47 induced impairment of mitochondrial translation and neurotoxicity through PGC-1α/ERRα axis

Recent studies are identified the mitochondria as critical targets of 2, 2', 4, 4'-tetrabromodiphenyl ether (PBDE-47) induced neurotoxicity. This study aimed at examining the impact of PBDE-47 exposure on mitochondrial translation, and its subsequent effect on PBDE-47 neurotoxicity. The Sprague-Dawley (SD) rat model and neuroendocrine pheochromocytoma (PC12) cells were adopted for the measurements of mitochondrial ATP levels, mitochondrial translation products, and expressions of important mitochondrial regulators, such as required meiotic nuclear division 1 (RMND1), estrogen-related receptor α (ERRα), and peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α). To delve into the role of PGC-1α/ERRα axis in mitochondrial translation, 2-(4-tert-butylphenyl) benzimidazole (ZLN005) was employed. Both cellular and animal model results shown that PBDE-47 impeded PGC-1α/ERRα axis and mitochondrial translation. PBDE-47 suppressed mitochondrial function in rat hippocampus and PC12 cells by decreasing relative mitochondrial DNA (mtDNA) content, mitochondrial translation products, and mitochondrial ATP levels. Particularly, ZLN005 reversed PBDE-47 neurotoxicity by enhancing mitochondrial translation through activation of PGC-1α/ERRα axis, yet suppressing PGC-1α with siRNA attenuates its neuroprotective effect in vitro. In conclusion, this work highlights the importance of mitochondrial translation in PBDE-47 neurotoxicity by presenting results from cellular and animal models and suggests a potential therapeutic approach through activation of PGC-1α/ERRα axis. ENVIRONMENTAL IMPLICATION: PBDEs have attracted extensive attention because of their high lipophilicity, persistence, and detection levels in various environmental media. Increasing evidence has shown that neurodevelopmental disorders in children are associated with PBDE exposure. Several studies have also found that perinatal PBDE exposure can cause long-lasting neurobehavioral abnormalities in experimental animals. Our recent studies have also demonstrated the impact of PBDE-47 exposure on mitochondrial biogenesis and dynamics, leading to memory and neurobehavioral deficits. Therefore, we explore whether the pathological mechanism of PBDE-47-induced neurotoxicity involves the regulation of mitochondrial translation through the PGC-1α/ERRα axis.

Differential binding of CREB and REST/NRSF to NMDAR1 promoter is associated with the sex-selective cognitive deficit following postnatal PBDE-209 exposure in mice

Neonatal exposure to decabromodiphenyl ether (PBDE-209), a widely used flame retardant, affects cognitive performances in the later stage of life in a sex-dependent manner. PBDE-209 interferes with glutamatergic signaling and N-methyl-D-aspartate receptor (NMDAR) subunits with unresolved regulatory mechanisms. This study exposed male and female mice pups through postnatal day (PND) 3-10 to PBDE-209 (oral dose: 0, 6, or 20 mg/kg body weight). The frontal cortex and hippocampus, collected from neonate (PND 11) and young (PND 60) mice, were analyzed for cAMP response element-binding protein (CREB) and RE1-silencing transcription factor/ Neuron-restrictive silencer factor (REST/NRSF) binding to NMDAR1 promoter and expression of NMDAR1 gene by electrophoretic mobility shift assay and semi-quantitative RT-PCR respectively. Behavioral changes were assessed using spontaneous alternation behavior and novel object recognition tests in young mice. In neonates, the binding of CREB was increased, while REST/NRSF was decreased significantly to their cognate NMDAR1 promoter sequences at the high dose of PBDE-209 in both the sexes. This reciprocal pattern of CREB and REST/NRSF interactions correlates with the up-regulation of NMDAR1 expression. Young males followed a similar pattern of CREB and REST/NRSF binding and NMDAR1 expression as in neonates. Surprisingly, young females did not show any alteration when compared to age-matched controls. Also, we found that only young males showed working and recognition memory deficits. These results indicate that early exposure to PBDE-209 interferes with CREB- and REST/NRSF-dependent regulation of the NMDAR1 gene in an acute setting. However, long-term effects persist only in young males that could be associated with cognitive impairment.

Coronal ApoE Protein Combines with LRP1 to Inactivate GSK3β That Mitigates Silica Nanoparticle-Induced Brain Lesion

Silica nanoparticles (SiO2 NPs) are widely used engineered materials that warrant their obvious environmental exposure risk. Our previous study has shown that different routes of SiO2 NP exposure on the glycogen synthase kinase 3 beta (GSK3β) activity were related to the serum proteins enriched on the surface of SiO2 NPs, which implied that a particular protein in the serum changed the inherent toxic behavior of SiO2 NPs and inhibited the activation of GSK3β by SiO2 NPs. Here, we identified that the SiO2 NP surface enriched a large amount of apolipoprotein E (ApoE), and the ApoE protein corona bound to the lipoprotein receptor-related protein 1 (LRP1) to inactivate GSK3β, thereby reducing the damage of SiO2 NPs to the brain. This work presented the first evidence that specific biocorona reduced the toxicity of SiO2 NPs at the molecular level, which helped to elucidate the role of specific corona components on nanotoxicity.

The application of human-derived cell lines in neurotoxicity studies of environmental pollutants

As industrial and societal advancements progress, an increasing number of environmental pollutants linked to human existence have been substantiated to elicit neurotoxicity and developmental neural toxicity. For research in this field, human-derived neural cell lines have become excellent in vitro models. This study examines the utilization of immortalized cell lines, specifically the SH-SY5Y human neuroblastoma cell line, and neural cells derived from human pluripotent stem cells, in the investigation of neurotoxicity and developmental neural toxicity caused by environmental pollutants. The study also explores the culturing techniques employed for these cell lines and provides an overview of the standardized assays used to assess various biological endpoints. The environmental pollutants involved include a variety of organic compounds, heavy metals, and microplastics. The utilization of cell lines derived from human sources holds significant significance in elucidating the neurotoxic effects of environmental pollutants and the underlying mechanisms. Finally, we propose the possibility of improving the in vitro model of the human nervous system and the toxicity detection methods.

Environmental risk scores of persistent organic pollutants associate with higher ALS risk and shorter survival in a new Michigan case/control cohort

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a fatal, progressive neurogenerative disease caused by combined genetic susceptibilities and environmental exposures. Identifying and validating these exposures are of paramount importance to modify disease risk. We previously reported that persistent organic pollutants (POPs) associate with ALS risk and survival and aimed to replicate these findings in a new cohort.

METHOD

Participants with and without ALS recruited in Michigan provided plasma samples for POPs analysis by isotope dilution with triple quadrupole mass spectrometry. ORs for risk models and hazard ratios for survival models were calculated for individual POPs. POP mixtures were represented by environmental risk scores (ERS), a summation of total exposures, to evaluate the association with risk (ERSrisk) and survival (ERSsurvival).

RESULTS

Samples from 164 ALS and 105 control participants were analysed. Several individual POPs significantly associated with ALS, including 8 of 22 polychlorinated biphenyls and 7 of 10 organochlorine pesticides (OCPs). ALS risk was most strongly represented by the mixture effects of OCPs alpha-hexachlorocyclohexane, hexachlorobenzene, trans-nonachlor and cis-nonachlor and an interquartile increase in ERSrisk enhanced ALS risk 2.58 times (p<0.001). ALS survival was represented by the combined mixture of all POPs and an interquartile increase in ERSsurvival enhanced ALS mortality rate 1.65 times (p=0.008).

CONCLUSIONS

These data continue to support POPs as important factors for ALS risk and progression and replicate findings in a new cohort. The assessments of POPs in non-Michigan ALS cohorts are encouraged to better understand the global effect and the need for targeted disease risk reduction strategies.

Update of the risk assessment of polybrominated diphenyl ethers (PBDEs) in food

The European Commission asked EFSA to update its 2011 risk assessment on polybrominated diphenyl ethers (PBDEs) in food, focusing on 10 congeners: BDE-28, -47, -49, -99, -100, -138, -153, -154, -183 and ‑209. The CONTAM Panel concluded that the neurodevelopmental effects on behaviour and reproductive/developmental effects are the critical effects in rodent studies. For four congeners (BDE-47, -99, -153, -209) the Panel derived Reference Points, i.e. benchmark doses and corresponding lower 95% confidence limits (BMDLs), for endpoint-specific benchmark responses. Since repeated exposure to PBDEs results in accumulation of these chemicals in the body, the Panel estimated the body burden at the BMDL in rodents, and the chronic intake that would lead to the same body burden in humans. For the remaining six congeners no studies were available to identify Reference Points. The Panel concluded that there is scientific basis for inclusion of all 10 congeners in a common assessment group and performed a combined risk assessment. The Panel concluded that the combined margin of exposure (MOET) approach was the most appropriate risk metric and applied a tiered approach to the risk characterisation. Over 84,000 analytical results for the 10 congeners in food were used to estimate the exposure across dietary surveys and age groups of the European population. The most important contributors to the chronic dietary Lower Bound exposure to PBDEs were meat and meat products and fish and seafood. Taking into account the uncertainties affecting the assessment, the Panel concluded that it is likely that current dietary exposure to PBDEs in the European population raises a health concern.

Using in vitro data to derive acceptable exposure levels: A case study on PBDE developmental neurotoxicity

BACKGROUND

Current acceptable chemical exposure levels (e.g., tolerable daily intake) are mainly based on animal experiments, which are costly, time-consuming, considered non-ethical by many, and may poorly predict adverse outcomes in humans.

OBJECTIVE

To evaluate a method using human in vitro data and biological modeling to calculate an acceptable exposure level through a case study on 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) developmental neurotoxicity (DNT).

METHODS

We reviewed the literature on in vitro assays studying BDE-47-induced DNT. Using the most sensitive endpoint, we derived a point of departure using a mass-balance in vitro disposition model and benchmark dose modeling for a 5% response (BMC05) in cells. We subsequently used a pharmacokinetic model of gestation and lactation to estimate administered equivalent doses leading to four different metrics of child brain concentration (i.e., average prenatal, average postnatal, average overall, and maximum concentration) equal to the point of departure. The administered equivalent doses were translated into tolerable daily intakes using uncertainty factors. Finally, we calculated biomonitoring equivalents for maternal serum and compared them to published epidemiological studies of DNT.

RESULTS

We calculated a BMC05 of 164 μg/kg of cells for BDE-47 induced alteration of differentiation in neural progenitor cells. We estimated administered equivalent doses of 0.925-3.767 μg/kg/day in mothers, and tolerable daily intakes of 0.009-0.038 μg/kg/day (composite uncertainty factor: 100). The lowest derived biomonitoring equivalent was 19.75 ng/g lipids, which was consistent with reported median (0.9-23 ng/g lipids) and geometric mean (7.02-26.9 ng/g lipids) maternal serum concentrations from epidemiological studies.

CONCLUSION

This case study supports using in vitro data and biological modeling as a viable alternative to animal testing to derive acceptable exposure levels.

DBP exposure induces thyroid inflammatory impairment through activating AKT/NF-κB/NLRP3 signaling

Previous studies exhibited reproductive and neurodevelopmental toxicity in rats exposed to Di-n-butyl phthalate (DBP). However, the effects of DBP exposure on the other endocrine organ are still unclear. This study aimed to assess the impact of DBP exposure on the thyroid of male rats and the associated mechanisms. Here, rats were respectively treated with DBP at 0 (control), 50 (low dose), 250 (medium dose), or 500 (high dose) mg/kg/day dissolved in 1 ml quantity of corn oil by intragastrical administration for two weeks. The results demonstrated that the proliferation and inflammatory response changes were significantly different compared to the control. In vivo DBP is mainly converted to mono-n-butyl phthalate (MBP), an active form producing untoward reactions of DBP exposure. Therefore, for in vitro experiments, we treated the thyroid follicular epithelial cell line (Nthy-ori 3-1) in a temporal gradient using 1 mM MBP. Further in vitro studies showed that MBP exposure upregulated tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), as well as interleukin-1β (IL-1β) by activating AKT/NF-κB/NLRP3 signaling. Meanwhile, we detected that Pellino2 (Peli2) played an essential role in promoting the activation of NLRP3 inflammasome. Briefly speaking, this study confirmed that DBP exposure caused impaired thyroid structure and thyroid inflammation in male rats, which offered new views into the harm of DBP exposure on the endocrine organ.

Mitochondrial Dysfunction Was Involved in Decabromodiphenyl Ethane-Induced Glucolipid Metabolism Disorders and Neurotoxicity in Zebrafish Larvae

Decabromodiphenyl ethane (DBDPE), a novel brominated flame retardant, is becoming increasingly prevalent in environmental and biota samples. While DBDPE has been shown to cause various biological adverse effects, the molecular mechanism behind these effects is still unclear. In this research, zebrafish embryos were exposed to DBDPE (50-400 μg/L) until 120 h post fertilization (hpf). The results confirmed the neurotoxicity by increased average swimming speed, interfered neurotransmitter contents, and transcription of neurodevelopment-related genes in zebrafish larvae. Metabolomics analysis revealed changes of metabolites primarily involved in glycolipid metabolism, oxidative phosphorylation, and oxidative stress, which were validated through the alterations of multiple biomarkers at various levels. We further evaluated the mitochondrial performance upon DBDPE exposure and found inhibited mitochondrial oxidative respiration accompanied by decreased mitochondrial respiratory chain complex activities, mitochondrial membrane potential, and ATP contents. However, addition of nicotinamide riboside could effectively restore DBDPE-induced mitochondrial impairments and resultant neurotoxicity, oxidative stress as well as glycolipid metabolism in zebrafish larvae. Taken together, our data suggest that mitochondrial dysfunction was involved in DBDPE-induced toxicity, providing novel insight into the toxic mechanisms of DBDPE as well as other emerging pollutants.

PBDE-47 induces impairment of mitochondrial biogenesis and subsequent neurotoxicity through miR-128-3p/PGC-1α axis

The potential adverse effects of 2,2',4,4'-tetrabromodiphenyl ether (PBDE-47) on neurons are extensively studied, and mitochondria are identified as critical targets. This study aimed to investigate whether PBDE-47 impairs mitochondrial biogenesis via the miR-128-3p/PGC-1α axis to trigger mitochondrial dysfunction-related neuronal damage. In vitro neuroendocrine pheochromocytoma (PC12) cells and in vivo Sprague Dawley rat model were adopted. In this study, biochemical methods were used to examine mitochondrial ATP content, cell viability, and expressions of key mitochondrial biogenesis regulators, including peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α), nuclear respiratory factor 1 (NRF1), and mitochondrial transcription factor A (TFAM). Mimics and inhibitors of miR-128-3p were employed to explore its role in PBDE-47-induced neurotoxicity. Both in vivo and in vitro evidences suggested that PBDE-47 suppressed PGC-1α/NRF1/TFAM signaling pathways and mitochondrial DNA (mtDNA) encoding proteins synthesis. PBDE-47 also suppressed the relative mtDNA content, mRNA levels of mtDNA-encoded subunits, and mitochondrial ATP levels in vitro. Specifically, 2-(4-tert-butylphenyl) benzimidazole (ZLN005) alleviated PBDE-47-induced neuronal death through the improvement of mitochondrial function by activating PGC-1α/NRF1/TFAM signaling pathways. Mechanistically, PBDE-47 dramatically upregulated miR-128-3p expression. Furthermore, miR-128-3p inhibition enhanced PGC-1α/NRF1/TFAM signaling and abolished PBDE-47-induced impairment of mitochondrial biogenesis. In summary, this study provides in vitro evidence to reveal the role of mitochondrial biogenesis in PBDE-47-induced mitochondrial dysfunction and related neurotoxicity and suggests that miR-128-3p/PGC-1α axis may be a therapeutic target for PBDE-47 neurotoxicity.

Phytochemical and antioxidant screening of Moringa oleifera for its utilization in the management of hepatic injury

Introduction

Phytochemicals present in Moringa oleifera (M. oleifera) leaves have performed several physiological functions in human system such as anticarcinogenic, antidiabetic, antioxidant, immunomodulatory, hepatoprotective and antiatherogenic functions.

Methods

Phytochemical and antioxidant potential of M. oleifera leaves extracts were measured. Histopathology, biochemical analysis, and gene expression tests were performed on serum, blood, and liver in animal model.

Results and discussions

The toxic dose of N-acetyl-para-aminophenol (APAP) induced severe structural and functional changes in liver. Pre-treatment with M. oleifera ameliorated organ injury by normalizing the level of liver biomarkers and serum proteins. A low expression level of MAPK-8, TRAF-4, and TRAF-6 genes was observed in the M. oleifera treated group in comparison to positive control (hepatotoxic rats). M. oleifera leaves pretreatment amended APAP induced apoptosis and replenished hepatic cells. M. oleifera leaves extract as low-cost and sustainable treatment could be used in pharmaceutical industry for reducing hepatic degenerative changes in non-communicable diseases.

The SH-SY5Y human neuroblastoma cell line, a relevant in vitro cell model for investigating neurotoxicology in human: focus on organic pollutants

Investigation of the toxicity triggered by chemicals on the human brain has traditionally relied on approaches using rodent in vivo models and in vitro cell models including primary neuronal cultures and cell lines from rodents. The issues of species differences between humans and rodents, the animal ethical concerns and the time and cost required for neurotoxicity studies on in vivo animal models, do limit the use of animal-based models in neurotoxicology. In this context, human cell models appear relevant in elucidating cellular and molecular impacts of neurotoxicants and facilitating prioritization of in vivo testing. The SH-SY5Y human neuroblastoma cell line (ATCC® CRL-2266^TM) is one of the most used cell lines in neurosciences, either undifferentiated or differentiated into neuron-like cells. This review presents the characteristics of the SH-SY5Y cell line and proposes the results of a systematic review of literature on the use of this in vitro cell model for neurotoxicity research by focusing on organic environmental pollutants including pesticides, 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD), flame retardants, PFASs, parabens, bisphenols, phthalates, and PAHs. Organic environmental pollutants are widely present in the environment and increasingly known to cause clinical neurotoxic effects during fetal & child development and adulthood. Their effects on cultured SH-SY5Y cells include autophagy, cell death (apoptosis, pyroptosis, necroptosis, or necrosis), increased oxidative stress, mitochondrial dysfunction, disruption of neurotransmitter homeostasis, and alteration of neuritic length. Finally, the inherent advantages and limitations of the SH-SY5Y cell model are discussed in the context of chemical testing.

Adrenal Corticosteroid Perturbation by the Endocrine Disruptor BDE-47 in a Human Adrenocortical Cell Line and Male Rats

Polybrominated diphenyl ethers (PBDEs) have been previously shown to alter various endocrine biosynthetic pathways. Growing epidemiological evidence suggests that PBDEs alter cardiovascular function. The goal of this study was to examine the effects of BDE-47 on adrenal corticosteroid pathways that play vital roles in cardiovascular homeostasis and pathophysiology. The effect of BDE-47 on aldosterone and cortisol secretion was characterized in a human adrenocortical cell line. HAC15 cells were exposed to various concentrations of BDE-47 (1 nM to 100 μM). Cell viability, corticosteroid secretion, gene expression of enzymes involved in corticosteroid synthesis, and metabolic activity was examined. Additionally, Sprague Dawley male rats were orally exposed to BDE-47 (10 or 100 µg/kg), 5 days per week for 16 weeks. Organ weights and plasma corticosteroid levels were measured. In HAC15 cells, basal and stimulated aldosterone and cortisol secretion was significantly increased by BDE-47. Gene expression of several enzymes involved in corticosteroid synthesis and mitochondrial metabolism also increased. In Sprague Dawley rats, adrenal but not heart, kidney, or liver weights, were significantly increased in BDE-47 treatment groups. Plasma corticosterone levels were significantly increased in the 100 µg BDE-47/kg treatment group. No change in plasma aldosterone levels were observed with BDE-47 exposure. These data indicate that BDE-47 disrupts the regulation of corticosteroid secretion and provides further evidence that PBDEs are potential endocrine disruptors. Future studies will determine the underlying molecular mechanism of altered corticosteroid production and examine whether these alterations result in underlying cardiovascular disease in our rodent model of 16-week BDE-47 exposure.

Nucleophilic and redox properties of polybrominated diphenyl ether derived-quinone/hydroquinone metabolites are responsible for their neurotoxicity

Polybrominated diphenyl ethers (PBDEs) are a category of brominated flame retardants, which were widely used in industrial products since the 1970 s. Our previous studies indicated quinone-type metabolites of PBDEs (PBDE-Qs) cause neurotoxicity, however, their inherent toxicological mechanism remains unclear. Here, we first synthesized PBDE-Qs and corresponding reduced hydroquinone homologous (PBDE-HQs) with different pattern of bromine substitution. Their nucleophilic and redox properties were investigated. PBDE-Qs react with reduced glutathione (GSH) via Michael addition and bromine displacement reaction, whilst PBDE-HQs lack the ability of reacting with GSH. Of note, the displacement reaction only occurs with bromine on the quinone ring of PBDE-Qs but not phenyl ring. Next, electron paramagnetic resonance (EPR) analysis revealed the generation of SQ^•-, along with their downstream hydroxyl radical (HO^•) and methyl radical (^•CH₃) through a PBDE quinone/semiquinone/hydroquinone (Q/SQ^•-/HQ) futile cycle. In addition, a structure-dependent cytotoxicity pattern was found, the exposure of PBDE-Q/HQ with bromine substitution on the quinone ring resulted in higher level of apoptosis and autophagy in BV2 cells. In conclusion, this work clearly demonstrated that the nucleophilic and redox properties of PBDE-Qs/HQs are responsible for their neurotoxicity, and this finding provide better understanding of neurotoxicity of PBDEs.

BDE-47 induces nephrotoxicity through ROS-dependent pathways of mitochondrial dynamics in PK15 cells

2,2',4,4'-tetrabromodiphenyl ether (BDE-47)-induced nephrotoxicity is closely associated with oxidative stresses and mitochondrial abnormalities. Mitochondrial fusion and fission dynamics are crucial for maintaining mitochondrial and cellular physiological homeostasis. However, the detailed mechanisms through which BDE-47 disrupts this dynamic and contributes to renal injuries are still not fully understood. The porcine kidney-15 (PK15) cell line, a well-defined in vitro animal renal toxicological model, was exposed to BDE-47 with concentrations of 12.5, 25, 50, and 100 μM, respectively. Cell viability, the levels of reactive oxygen species (ROS) and adenosine triphosphate (ATP), the mitochondrial membrane potential (MMP), and the expression levels of key mitochondrial fusion and fission proteins were assessed. BDE-47 reduced cell viability and disrupted mitochondrial dynamics by inhibiting mitochondrial fusion and fission simultaneously, leading to MMP decreases, ROS overgeneration, ATP depletion, and cellular disintegration in a dose-dependent manner. Additionally, the mitochondrial division inhibitor (Mdivi-1) with the concentration of 20 μM observed to restore the downregulation of mitochondrial fusion and fission proteins, alleviate damages in mitochondrial morphology and functionality, correct ROS overproduction, and enable cell survival. The antioxidant N-acety-L-cysteine (NAC) with the concentration of 1 mM also simultaneously reversed the imbalance of mitochondrial dynamics, decreased ROS production, and restored mitochondrial morphology in PK15 cells exposed to BDE-47. Our data provide new insights indicating that BDE-47 disrupts mitochondrial fusion/fission dynamics to induce mitochondrial abnormalities, triggering oxidative stresses and thus contributing to PK15 cell dysfunction. ROS-dependent pathways in mitochondrial dynamics may provide a new avenue for developing effective strategies to protect cells against BDE-47-induced nephrotoxicity.

Interaction of BDE-47 with nuclear receptors (NRs) based on the cytotoxicity: In vitro investigation and molecular interaction

Polybrominated diphenyl ethers (PBDEs) are endocrine-disrupting chemicals that possess neuroendocrine and reproductive toxicity to humans and disturb thyroid hormone homeostasis, neurobehavior, and development. The most predominant congener of PBDEs in humans and other organisms is 2,2',4,4'-tetrabromodiphenyl ether (BDE-47); however, the molecular mechanisms underlying its cytotoxicity remain largely unknown. Here, we evaluated the toxic effect and underlying mechanism of nuclear receptors (NRs) induced by BDE-47 in SK-N-SH human neuroblastoma cells. The CCK-8 cell viability assay showed that the proliferation of human SK-N-SH cells exposed to BDE-47 was significantly inhibited in time- and dose-dependent manners, and flow cytometry showed that cell cycle was arrested at the S phase after BDE-47 exposure. Moreover, compared with the control group, the expression of retinoic acid receptor alpha (RXRα), pregnane X receptor (PXR), thyroid hormone receptors (TRs), and peroxisome proliferator-activated receptors (PPARs) at the mRNA and protein levels was significantly increased, as determined by quantitative PCR and western blot analysis, demonstrating that BDE-47 activated the NRs in vitro. Moreover, BDE-47 could bind to all four NRs in the affinity order of PPARγ > PXR > TRβ > RXRα under molecular dynamics. Because RXR is the promiscuous dimerization partner for a large number of NRs, ZDock was used to calculate its interaction with other three NRs. Taking the number of hydrogen bonds and ZDock scores into account, the rank of docking ability between RXRα and the NRs was PXR > TRβ > PPARγ. Further analysis of the interaction between BDE-47 and dimerized-NRs, the affinity order was RXRα > TRβ > PXR > PPARγ via Glide. The results of this study demonstrated that BDE-47 interfered the cross-talk among NRs, especially the promiscuous RXRα, which might be critical for the harmonized re-adjustment of cytotoxicity and biological regulation. Our findings provide a better understanding of the mechanisms underlying toxic effects and intermolecular interaction induced by BDE-47.

2,2',4,4'-tetrabromodiphenyl ether (BDE-47) induces wide metabolic changes including attenuated mitochondrial function and enhanced glycolysis in PC12 cells

Polybrominated diphenyl ethers (PBDEs) are extensively used as brominated flame retardants in various factory products. As environmental pollutants, the adverse effects of PBDEs on human health have been receiving considerable attention. However, the precise fundamental mechanisms of toxicity induced by PBDEs are still not fully understood. In this study, the mechanism of cytotoxicity induced by 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) was investigated by combining Seahorse XFp analysis and mass spectrometry-based metabolomics and flux approaches in PC12 cells, one of the most widely used neuron-like cell lines for investigating cytotoxic effects. The Seahorse results suggest that BDE-47 significantly attenuated mitochondrial respiration and enhanced glycolysis in PC12 cells. Additionally, metabolomics results revealed the reduction of TCA metabolites such as citrate, succinate, aconitate, malate, fumarate, and glutamate after BDE-47 exposure. Metabolic flux analysis showed that BDE-47 exposure reduced the oxidative metabolic capacity of mitochondria in PC12 cells. Furthermore, various altered metabolites were found in multiple metabolic pathways, especially in glycine-serine-threonine metabolism and glutathione metabolism. A total of 17 metabolic features were determined in order to distinguish potentially disturbed metabolite markers of BDE-47 exposure. Our findings provide possible biomarkers of cytotoxic effects induced by BDE-47 exposure, and elicit a deeper understanding of the intramolecular mechanisms that could be used in further studies to validate the potential neurotoxicity of PBDEs in vivo. Based on our results, therapeutic approaches targeting mitochondrial function and the glycolysis pathway may be a promising direction against PBDE exposure.

Perinatal low-dose PBDE-47 exposure hampered thyroglobulin turnover and induced thyroid cell apoptosis by triggering ER stress and lysosomal destabilization contributing to thyroid toxicity in adult female rats

Evidence demonstrates that 2,2',4,4'-tetrabromodiphenyl ether (PBDE-47) is able to disturb thyroid hormones (THs) homeostasis, yet the mechanisms remain unknown. We sought to investigate the effects of PBDE-47 on endoplasmic reticulum (ER) and lysosomes in thyroids. Using female Sprague-Dawley rats orally administered PBDE-47 at environmentally relevant doses (0.1, 1.0, 10 mg/kg/day) beginning ten days before breeding and ending at weaning, we showed that perinatal PBDE-47 exposure resulted in a reduction in serum THs levels and relative thyroid weight in adult female rats. These were accompanied by thyroid structural abnormalities with cell apoptosis. Mechanistically, PBDE-47 caused ER stress and activation of unfolded protein response (UPR). Moreover, PBDE-47 elicited lysosomal membrane permeabilization and the release of cathepsin. Importantly, the apoptotic cells co-localized with IRE1α, a stress sensor protein of UPR branch that mediates ER stress-induced apoptosis, or cathepsin B, a lysosomal cysteine protease that is involved in thyroglobulin, the precursor of THs, degradation and apoptosis induction. Interestingly, thyroglobulin was accumulated and predominantly presented in cells harboring compromised ER or lysosomal activity. Collectively, our findings suggest that perinatal low-dose PBDE-47 exposure hampers thyroglobulin turnover and induces thyroid cell apoptosis by triggering ER stress and lysosomal destabilization contributing to thyroid toxicity in adult female rats.

Resveratrol attenuates hypoxia-induced neuronal cell death, inflammation and mitochondrial oxidative stress by modulation of TRPM2 channel

Hypoxia (HYPX) induced-overload Ca²⁺ entry results in increase of mitochondrial oxidative stress, inflammation and apoptosis in several neurons. Ca²⁺ permeable TRPM2 channel was gated by ADP-ribose (ADPR) and reactive oxygen species (ROS), although its activity was modulated in HYPX-exposed neurons by resveratrol (RSV). The aim of this study was to evaluate if a therapy of RSV can modulate the effect of HYPX in the TRPM2 expressing SH-SY5Y neuronal and HEK293 (no expression of TRPM2) cell lines. The SH-SY5Y and HEK293 cells were divided into four groups as control, RSV (50 μM and 24 hours), and HYPX and RSV + HYPX. For induction of HYPX in the cells, CoCl₂ (200 μM and 24 hours) incubation was used. HYPX-induced intracellular Ca²⁺ responses to TRPM2 activation were increased in the SH-SY5Y cells but not in the HEK293 cells from coming H₂O₂ and ADPR. RSV treatment improved intracellular Ca²⁺ responses, mitochondrial function, suppressed the generation of cytokine (IL-1β and TNF-α), cytosolic and mitochondrial ROS in the SH-SY5Y cells. Intracellular free Zn²⁺, apoptosis, cell death, PARP-1, TRPM2 expression, caspase −3 and −9 levels are increased through activating TRPM2 in the SH-SY5Y cells exposed to the HYPX. However, the values were decreased in the cells by RSV and TRPM2 blockers (ACA and 2-APB). In SH-SY5Y neuronal cells exposed to HYPX conditions, the neuroprotective effects of RSV were shown to be exerted via modulation of oxidative stress, inflammation, apoptosis and death through modulation of TRPM2 channel. RSV could be used as an effective agent in the treatment of neurodegeneration exposure to HYPX.

2, 2', 4, 4'-tetrabromodiphenyl ether (BDE-47) induces mitochondrial dysfunction and related liver injury via eliciting miR-34a-5p-mediated mitophagy impairment

2,2',4,4'-Tetrabromodiphenyl ether (BDE-47) is associated with various adverse human health effects; however, the knowledge of its toxicity is still very limited. Mitochondrial injury has been observed in liver cells exposed to BDE-47 in vitro. Mitophagy impairment causes the accumulation of dysfunctional mitochondria, contributing to the pathological mechanisms of liver injury. The aim of this study was to investigate whether BDE-47 impairs mitophagy to trigger mitochondrial dysfunction-related liver injury and the underlying mechanisms. This study revealed that BDE-47 elicited mitochondrial dysfunction and related oxidative liver injury by impairing mitophagy. Moreover, our results showed that NAD⁺ insufficiency is responsible for BDE-47-mediated mitophagy defect and mitochondrial dysfunction in mouse livers, which was associated with suppression of Sirt3/FoxO3a/PINK1 signaling. Furthermore, our results indicated a potential role of miR-34a-5p in the hepatotoxicity of BDE-47. Mechanistically, BDE-47 dramatically upregulated miR-34a-5p expression in mouse livers. The data from AAV-sponge-mediated miR-34a-5p inhibition suggested that miR-34a-5p diminished NAD⁺ level by directly targeting NAMPT expression in BDE-47-treated mouse livers, which was confirmed by luciferase reporter assay. Consequently, miR-34a-5p markedly abated Sirt3/FoxO3a/PINK1 signaling-mediated mitophagy to promote mitochondrial dysfunction in BDE-47-treated mouse livers. The present study provided in vivo evidence to reveal a potential mechanism for BDE-47-induced mitochondrial dysfunction and related liver injury and indicated that miR-34a-5p-mediated mitophagy impairment might be a therapeutic target for BDE-47 toxicity.

Promotion of mitochondrial fusion protects against developmental PBDE-47 neurotoxicity by restoring mitochondrial homeostasis and suppressing excessive apoptosis

Polybrominated diphenyl ethers (PBDEs)-induced neurotoxicity is closely associated with mitochondrial abnormalities. Mitochondrial fusion and fission dynamics are required for the maintenance of mitochondrial homeostasis. However, little is known about how PBDEs disrupt this dynamics and whether such disruption contributes to impaired neurodevelopment. Methods: We investigated the effects of 2, 2', 4, 4'-tetrabromodiphenyl ether (PBDE-47), the dominant congener in human samples, on mitochondrial fusion and fission dynamics using PC12 cells, a well-defined in vitro neurodevelopmental model. We also evaluated the effects of perinatal low-dose PBDE-47 exposure on hippocampal mitochondrial dynamics and its association with neurobehavioral changes in adult Sprague-Dawley rats. Results: In vitro, PBDE-47 disrupted mitochondrial dynamics by inhibiting mitochondrial fusion and fission simultaneously, accompanied by mitochondrial fragmentation, membrane potential dissipation, ATP loss, and apoptosis activation. Specifically, enhancing mitochondrial fusion by the chemical promoter M1 or adenovirus-mediated mitofusin 2 (Mfn2) overexpression rescued PBDE-47-caused mitochondrial dynamic, morphological and functional impairments, prevented the resultant apoptosis and promoted neuronal survival. Unexpectedly, either stimulating mitochondrial fission by adenovirus-mediated fission protein 1 (Fis1) overexpression or suppressing mitochondrial fission by the mitochondrial division inhibitor-1 (Mdivi-1) failed to reverse whereas aggravated PBDE-47-induced mitochondrial damage and neuronal death. Importantly, promoting mitochondrial fusion by Mfn2 overexpression neutralized the detrimental effects elicited by Fis1 overexpression after PBDE-47 treatment. Finally, perinatal oral administration of PBDE-47 elicited neurobehavioral deficits and hippocampal neuronal loss via apoptosis in adult rats, which were associated with mitochondrial dynamics alterations manifested as a fragmented phenotype. Conclusion: Our results suggest that PBDE-47 disrupts mitochondrial dynamics to induce mitochondrial abnormalities, triggering apoptosis and thus contributing to neuronal loss and subsequent neurobehavioral deficits. Targeting mitochondrial fusion may be a promising therapeutic intervention against PBDE-47 neurotoxicity.

Cellular metabolomics reveals glutamate and pyrimidine metabolism pathway alterations induced by BDE-47 in human neuroblastoma SK-N-SH cells

Polybrominated diphenyl ethers (PBDEs) as potential neurotoxicants in environment may possess hazards to human health. Previous studies have reported that PBDEs exposure could induce oxidative stress and disturb mitochondrial functions in mammalian cells. However, the toxicological mechanism remains to be clarified. In this work, the neurotoxic effect and underlying mechanism of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) was investigated by using human neuroblastoma SK-N-SH cells as an effective model. A liquid chromatography-mass spectrometry (LC-MS)-based metabolomics approach combined with cell viability assay was applied to elucidate the metabolic perturbations and relevant toxicological pathways upon BDE-47 exposure. Our results shown that the SK-N-SH cell viability decreased in a dose-dependent manner after exposure to BDE-47 at 24 h within the concentration range of 5-250 μM, and an IC₅₀ value of 88.8 μM was obtained. Based on the dose-response curve and cell morphological observation, the 5 and 10 μM BDE-47 doses (equal to IC₅ and IC₁₀, respectively) were used for metabolomics study to capture the sensitive metabolic response following BDE-47 exposure. After BDE-47 treatment, nine metabolites were identified as potential biomarkers, and the most disturbed metabolic pathways were mainly involved in alanine, aspartate and glutamate metabolism, glutathione metabolism, tyrosine and phenylalanine metabolism, and pyrimidine metabolism, which imply that metabolic changes related to neurotransmitters, oxidative stress, and nucleotide-mediated signal transduction systems were the sensitive pathways mostly influenced. Our findings reported here may provide potential neurotoxic effect biomarkers and prompt deep understanding of the molecular and metabolic mechanisms triggered by BDE-47 exposure.

Theaflavic acid from black tea protects PC12 cells against ROS-mediated mitochondrial apoptosis induced by OGD/R via activating Nrf2/ARE signaling pathway

Cerebral ischemic stroke is a severe disease afflicting people worldwide. Phytochemicals play a pivotal role in the discovery of novel therapeutic approaches for the prevention of ischemic stroke. In our continual search for bioactive natural products for the treatment of ischemic stroke, we have evaluated the protective effects of theaflavic acid (TFA) from black tea using PC12 cells injured by oxygen and glucose deprivation/restoration (OGD/R), and investigated the possible mechanisms. The results showed that TFA can protect PC12 cells against OGD/R through increasing cell viability and decreasing intracellular lactate dehydrogenase (LDH) release. Further investigations found that TFA could inhibit the overproduction of intracellular reactive oxygen species (ROS), reduce malondialdehyde content, and elevate superoxide dismutase activity, which implied that TFA suppresses oxidative stress in PC12 cells induced by OGD/R. In addition, overload of intracellular calcium and collapse of the mitochondrial membrane potential were improved in the presence of TFA, and the activity of caspase-3 was significantly reduced by TFA. Western blot analysis showed that the expression of Bcl-2 was up-regulated while Bax was down-regulated. Therefore, it can be concluded that TFA can inhibit mitochondria-dependent apoptosis of PC12 cells induced by OGD/R. In addition, activation of the nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant response elements (ARE) signaling pathway was explored to elucidate the mechanism by which TFA inhibits ROS-mediated apoptosis in PC12 cells. The results revealed that TFA promoted the translocation of Nrf2 into nuclei, enhanced the transcriptional activity of ARE, and up-regulated expression of downstream HO-1, which indicates that the Nrf2/ARE signaling pathway is involved in the protection by TFA of PC12 cells injured by OGD/R.

Autophagy impairment contributes to PBDE-47-induced developmental neurotoxicity and its relationship with apoptosis

Apoptosis is involved in 2,2',4,4'- tetrabromodiphenyl ether (PBDE-47)-induced developmental neurotoxicity. However, little is known about the role of autophagy, especially its relationship with apoptosis underlying such neurotoxic process.

Methods: Using female Sprague-Dawley rats exposed to low-dose PBDE-47 (0.1, 1.0 and 10 mg/kg/day) from pre-pregnancy until weaning of offspring to mimic human exposure, we investigated the effects of PBDE-47 on autophagy and apoptosis in relation to cognitive impairment of adult offspring rats. We also evaluated relationship between autophagy and apoptosis using neuroendocrine pheochromocytoma (PC12) cells, a widely used neuron-like cell line for neuronal development.

Results: In vivo, perinatal exposure to PBDE-47 induced memory deficits in adult rats. This is accompanied by hippocampal neuronal loss partly as a result of apoptosis, as evidenced by caspase-3 activation and PARP cleavage. Further study identified that PBDE-47 triggered autophagic vesicles accumulation, increased levels of microtubule-associated protein 1 light chain 3 (LC3)-II, an essential protein for autophagosomes formation, and autophagy substrate sequestosome 1 (SQSTM1/p62), but reduced levels of autophagy-related protein (ATG) 7, a key protein for autophagosomes elongation, suggestive of autophagy impairment. These findings were further demonstrated by an in vitro model of PBDE-47-treated PC12 cells. Mechanistically, autophagy alteration is more sensitive to PBDE-47 treatment than apoptosis induction. Importantly, while stimulation of autophagy by the chemical inducer rapamycin and adenovirus-mediated Atg7 overexpression aggravated PBDE-47-induced apoptosis and cell death, inhibition of autophagy by the chemical inhibitor wortmannin and siRNA knockdown of Atg7 reversed PBDE-47-produced detrimental outcomes. Interestingly, blockage of apoptosis by caspase-3 inhibitor Ac-DEVD-CHO ameliorated PBDE-47-exerted autophagy impairment and cell death, though in combination with autophagy inhibitor did not further promote cell survival.

Conclusion: Our data suggest that autophagy impairment facilitates apoptosis, which, in turn, disrupts autophagy, ultimately resulting in cell death, and that autophagy may act as a promising therapeutic target for PBDE-47-induced developmental neurotoxicity.

Perigestational exposure to low doses of PBDE-47 induces excessive ER stress, defective autophagy and the resultant apoptosis contributing to maternal thyroid toxicity

Brominated flame retardant 2,2',4,4'‑tetrabromodiphenyl ether (PBDE-47) is known to induce developmental neurotoxicity by disturbing thyroid hormones (THs). Evidence shows that maternal THs are crucial for brain development and growth of fetuses and infants. However, little is known about the effects of PBDE-47 on maternal thyroid status and its mode of action. Here, using female Sprague-Dawley rats orally exposed to low doses of PBDE-47 (0.1, 1.0, 10 mg/kg/day) from pre-pregnancy until weaning of offspring to mimic human exposure, we show that perigestational exposure to PBDE-47 elevated serum triiodothyronine and thyroxine levels in mother rats. This is accompanied by disrupted thyroid follicle structure including expanded follicles, hyperplastic epithelial cells and shed cell remnants filled in the exhausted follicular lumen. Mechanistically, PBDE-47 enhanced apoptosis in thyroid tissue, as demonstrated by Caspase-3 activation, PARP cleavage and DNA fragmentation. Further study identified that PBDE-47 upregulated the levels of GRP78, ATF4, active Caspase-12 and CHOP, suggesting endoplasmic reticulum (ER) stress and unfolded protein response activation. Moreover, PBDE-47 reduced the levels of LC3-II, an autophagy marker protein essential for the autophagosomes formation, while increased the autophagy substrate p62 accumulation, indicating autophagy defect. Importantly, the colocalization of apoptotic cells with CHOP, a key mediator of ER stress-induced apoptosis, or p62, uncovered the contribution of excessive ER stress and defective autophagy to apoptosis. Collectively, our results suggest that excessive ER stress, defective autophagy and the resultant apoptosis are implicated in maternal thyroid injury following perigestational PBDE-47 exposure, which offers insight into a better understanding of PBDE-47-induced maternal thyroid toxicity.

Integration of Ca2+ signaling regulates the breast tumor cell response to simvastatin and doxorubicin

Recent studies have suggested that the lipid-lowering agent simvastatin holds great promise as a cancer therapeutic; it inhibits the growth of multiple tumors, including triple-negative breast cancer. Doxorubicin- and simvastatin-induced cytotoxicity has been associated with the modulation of Ca2+ signaling, but the underlying mechanisms remain incompletely understood. Here we identify how Ca2+ signaling regulates the breast tumor cell response to doxorubicin and simvastatin. These two drugs inhibit cell survival while increasing apoptosis in two human breast cancer cell lines and five primary breast tumor specimens through the modulation of Ca2+ signaling. Signal transduction and functional studies revealed that both simvastatin and doxorubicin trigger persistent cytosolic Ca2+ release, thereby stimulating the proapoptotic BIM pathway and mitochondrial Ca2+ overload, which are responsible for metabolic dysfunction and apoptosis induction. Simvastatin and doxorubicin suppress the prosurvival ERK1/2 pathway in a Ca2+-independent and Ca2+-dependent manner, respectively. In addition, reduction of the Ca2+ signal by chelation or pharmacological inhibition significantly prevents drug-mediated anticancer signaling. Unexpectedly, a scratch-wound assay indicated that these two drugs induce rapid cell migration, while inhibiting cell invasion and colony formation in a Ca2+-dependent manner. Further, the in vivo data for MDA-MB-231 xenografts demonstrate that upon chelation of Ca2+, the ability of both drugs to reduce the tumor burden was significantly reduced via caspase-3 deactivation. Our results establish a calcium-based mechanism as crucial for executing the cell death process triggered by simvastatin and doxorubicin, and suggest that combining simvastatin with doxorubicin may be an effective regimen for the treatment of breast cancer.

Oxidative stress-elicited autophagosome accumulation contributes to human neuroblastoma SH-SY5Y cell death induced by PBDE-47

Polybrominated diphenyl ethers, a ubiquitous persistent organic pollutant used as brominated flame retardants, is known to damage nervous system, however the underlying mechanism is still elusive. In this study, we used human neuroblastoma SH-SY5Y cells to explore the effects of PBDE-47 on autophagy and investigate the role of autophagy in PBDE-47-induced cell death. Results showed PBDE-47 could increase autophagic level (performation of cell ultrastructure with double membrane formation, MDC-positive cells raised, autophagy-related proteins LC3-II, Beclin1 and P62 increased) after cells exposed to PBDE-47. Then cells were exposed to PBDE-47 (1, 5, 10μmol/L) respectively for 1, 3, 6, 9, 12, 18, 24h, and the results showed that PBDE-47 increased the levels of LC3-II, Beclin1 and P62 in 5, 10μmol/L (9, 12, 18, 24h) PBDE-47 exposed groups. Furthermore, ROS scavenger N-Acetyl-l-cysteine (NAC), autophagic inhibitor 3-methyladenine (3-MA) and 5μmol/L PBDE-47 treated for 9h and 24h were chosen for the follow-up research. Moreover, 3-MA significantly improved cell viability when cells exposed to 5 and 10μmol/L PBDE-47, indicating that PBDE-47-induced autophagic cell death. Importantly, NAC could decrease PBDE-47-induced LC3-II, Beclin1 and P62 expression. We concluded that autophagosome accumulation mediated by oxidative stress may contribute to SH-SY5Y cell death induced by PBDE-47.

Integrating subpathway analysis to identify candidate agents for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the second most common cause of cancer-associated death worldwide, characterized by a high invasiveness and resistance to normal anticancer treatments. The need to develop new therapeutic agents for HCC is urgent. Here, we developed a bioinformatics method to identify potential novel drugs for HCC by integrating HCC-related and drug-affected subpathways. By using the RNA-seq data from the TCGA (The Cancer Genome Atlas) database, we first identified 1,763 differentially expressed genes between HCC and normal samples. Next, we identified 104 significant HCC-related subpathways. We also identified the subpathways associated with small molecular drugs in the CMap database. Finally, by integrating HCC-related and drug-affected subpathways, we identified 40 novel small molecular drugs capable of targeting these HCC-involved subpathways. In addition to previously reported agents (ie, calmidazolium), our method also identified potentially novel agents for targeting HCC. We experimentally verified that one of these novel agents, prenylamine, induced HCC cell apoptosis using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, an acridine orange/ethidium bromide stain, and electron microscopy. In addition, we found that prenylamine not only affected several classic apoptosis-related proteins, including Bax, Bcl-2, and cytochrome c, but also increased caspase-3 activity. These candidate small molecular drugs identified by us may provide insights into novel therapeutic approaches for HCC.