Low-dose tributyltin exposure induces an oxidative stress-triggered JNK-related pancreatic β-cell apoptosis and a reversible hypoinsulinemic hyperglycemia in mice

Antimony induces mitochondria-dependent and ER stress-triggered apoptosis via the oxidative stress-activated JNK signaling pathway in pancreatic islet β-cells

Antimony (Sb), a silvery-white metal, is a heavy metal of particular prevalence that has the ability to result in adverse effects in humans through environmental exposure resulting from natural processes and human activities. Epidemiological studies have suggested that Sb has an association with the potential for diabetes mellitus (DM) development. However, the mechanisms by which Sb exerts toxicological effects on pancreatic islet β-cells are still not clear. In this investigation, Sb exposure significantly inhibited rat pancreatic islet β-cell-derived RIN-m5F cell viability and insulin secretion, while inducing mitochondria-dependent apoptotic signals, inclusive of increased apoptotic cell populations, caspase-3 activity, the expression of PARP and caspase-3/-7/-9, and mitochondrial dysfunction. RIN-m5F cells exposure to Sb also led to the triggering of endoplasmic reticulum (ER) stress via the induction of a number of vital molecules, including CHOP, XBP-1s, and caspase-12. In Sb-exposed RIN-m5F cells, 4-PBA pretreatment (an inhibitor of ER stress) significantly suppressed protein expression related to ER stress and events of an apoptotic nature. Furthermore, exposure to Sb resulted in the significant activation of AMPKα, ERK1/2, and JNK signaling, as well as reactive oxygen species (ROS) generation. Pretreatment with SP600125 (an inhibitor of JNK) and antioxidant NAC, but not PD98059 (an inhibitor of ERK) or compound C (an inhibitor of AMPK), effectively abrogated the cytotoxicity, ER stress responses, mitochondrial dysfunction, apoptotic events, insulin secretion inhibition, and JNK activation in Sb-exposed rat pancreatic islet β-cells. However, SP600125 did not prevent ROS generation, which was inhibited by the antioxidant NAC. Collectively, the results demonstrate exposure to Sb to exert β-cell cytotoxicity through oxidative stress-activated JNK signaling downstream-regulated mitochondria-dependent and ER stress-triggered cell apoptotic pathways, eventually resulting in the death of rat pancreatic islet β-cells.

Roles of oxidative stress/JNK/ERK signals in paraquat-triggered hepatic apoptosis

Paraquat (PQ), a toxic and nonselective bipyridyl herbicide, is one of the most extensively used pesticides in agricultural countries. In addition to pneumotoxicity, the liver is an important target organ for PQ poisoning in humans. However, the mechanism of PQ in hepatotoxicity remains unclear. In this study, we found that exposure of rat hepatic H4IIE cells to PQ (0.1-2 mM) induced significant cytotoxicity and apoptosis, which was accompanied by mitochondria-dependent apoptotic signals, including loss of mitochondrial membrane potential (MMP), cytosolic cytochrome c release, and changes in the Bcl-2/Bax mRNA ratio. Moreover, PQ (0.5 mM) exposure markedly induced JNK and ERK1/2 activation, but not p38-MAPK. Blockade of JNK and ERK1/2 signaling by pretreatment with the specific pharmacological inhibitors SP600125 and PD98059, respectively, effectively prevented PQ-induced cytotoxicity, mitochondrial dysfunction, and apoptotic events. Additionally, PQ exposure stimulated significant oxidative stress-related signals, including reactive oxygen species (ROS) generation and intracellular glutathione (GSH) depletion, which could be reversed by the antioxidant N-Acetylcysteine (NAC). Buffering the oxidative stress response with NAC also effectively abrogated PQ-induced hepatotoxicity, MMP loss, apoptosis, and phosphorylation of JNK and ERK1/2 protein, however, the JNK or ERK inhibitors did not suppress ROS generation in PQ-treated cells. Collectively, these results demonstrate that PQ exposure induces hepatic cell toxicity and death via an oxidative stress-dependent JNK/ERK activation-mediated downstream mitochondria-regulated apoptotic pathway.

Endoplasmic Reticulum Stress and Autophagy Are Involved in Hepatotoxicity Induced by Tributyltin

Tributyltin (TBT), a common contaminant in aquatic ecosystems, has severe toxic effects on multiple tissues and organs, especially the liver. Previous toxicogenomic analysis has indicated that the main mechanism of TBT-induced hepatotoxicity is related to the activation of the apoptotic pathway. However, the mechanism of action occurring before the activation of apoptosis is still unclear. Herein, we applied proteomic technology to explore the protein expression profile of TBT-treated HL7702 normal human liver cells. The ultrastructural changes in cells were observed by transmission electron microscopy. After low dose (2 μΜ) TBT treatment, activation of the unfolded protein response and endoplasmic reticulum stress were observed; the expression levels of PERK, ATF6, BiP, and CHOP were significantly elevated, and splicing of XBP1 mRNA was initiated. When the TBT concentration increased to 4 μΜ, the protein levels of Beclin1, Atg3, Atg5, Atg7, and Atg12-Atg5 were significantly elevated, and the protein level of LC3Ⅰ decreased while that of LC3Ⅱ increased, suggesting the activation of autophagy. As the TBT concentration continued to increase, autophagy could not eliminate the damage, and apoptosis eventually occurred. These results indicate novel pathways of hepatotoxicity induced by TBT and provide insights for future studies.

Application of In Vitro Models for Studying the Mechanisms Underlying the Obesogenic Action of Endocrine-Disrupting Chemicals (EDCs) as Food Contaminants-A Review

Obesogenic endocrine-disrupting chemicals (EDCs) belong to the group of environmental contaminants, which can adversely affect human health. A growing body of evidence supports that chronic exposure to EDCs can contribute to a rapid increase in obesity among adults and children, especially in wealthy industrialized countries with a high production of widely used industrial chemicals such as plasticizers (bisphenols and phthalates), parabens, flame retardants, and pesticides. The main source of human exposure to obesogenic EDCs is through diet, particularly with the consumption of contaminated food such as meat, fish, fruit, vegetables, milk, and dairy products. EDCs can promote obesity by stimulating adipo- and lipogenesis of target cells such as adipocytes and hepatocytes, disrupting glucose metabolism and insulin secretion, and impacting hormonal appetite/satiety regulation. In vitro models still play an essential role in investigating potential environmental obesogens. The review aimed to provide information on currently available two-dimensional (2D) in vitro animal and human cell models applied for studying the mechanisms of obesogenic action of various industrial chemicals such as food contaminants. The advantages and limitations of in vitro models representing the crucial endocrine tissue (adipose tissue) and organs (liver and pancreas) involved in the etiology of obesity and metabolic diseases, which are applied to evaluate the effects of obesogenic EDCs and their disruption activity, were thoroughly and critically discussed.

Screening of Metabolism-Disrupting Chemicals on Pancreatic α-Cells Using In Vitro Methods

Metabolism-disrupting chemicals (MDCs) are endocrine disruptors with obesogenic and/or diabetogenic action. There is mounting evidence linking exposure to MDCs to increased susceptibility to diabetes. Despite the important role of glucagon in glucose homeostasis, there is little information on the effects of MDCs on α-cells. Furthermore, there are no methods to identify and test MDCs with the potential to alter α-cell viability and function. Here, we used the mouse α-cell line αTC1-9 to evaluate the effects of MDCs on cell viability and glucagon secretion. We tested six chemicals at concentrations within human exposure (from 0.1 pM to 1 µM): bisphenol-A (BPA), tributyltin (TBT), perfluorooctanoic acid (PFOA), triphenylphosphate (TPP), triclosan (TCS), and dichlorodiphenyldichloroethylene (DDE). Using two different approaches, MTT assay and DNA-binding dyes, we observed that BPA and TBT decreased α-cell viability via a mechanism that depends on the activation of estrogen receptors and PPARγ, respectively. These two chemicals induced ROS production, but barely altered the expression of endoplasmic reticulum (ER) stress markers. Although PFOA, TPP, TCS, and DDE did not alter cell viability nor induced ROS generation or ER stress, all four compounds negatively affected glucagon secretion. Our findings suggest that αTC1-9 cells seem to be an appropriate model to test chemicals with metabolism-disrupting activity and that the improvement of the test methods proposed herein could be incorporated into protocols for the screening of diabetogenic MDCs.

Combinatorial pathway disruption is a powerful approach to delineate metabolic impacts of endocrine disruptors

The prevalence of metabolic diseases, such as obesity, diabetes, metabolic syndrome and chronic liver diseases among others, has been rising for several years. Epidemiology and mechanistic (in vivo, in vitro and in silico) toxicology have recently provided compelling evidence implicating the chemical environment in the pathogenesis of these diseases. In this review, we will describe the biological processes that contribute to the development of metabolic diseases targeted by metabolic disruptors, and will propose an integrated pathophysiological vision of their effects on several organs. With regard to these pathomechanisms, we will discuss the needs, and the stakes of evolving the testing and assessment of endocrine disruptors to improve the prevention and management of metabolic diseases that have become a global epidemic since the end of last century.

Tributyltin chloride exposure to post-ejaculatory sperm reduces motility, mitochondrial function and subsequent embryo development

CONTEXT

Male exposure to environmental toxicants can disrupt spermatogenesis and sperm function. However, consequences of environmentally relevant organotin exposure to post-ejaculatory mammalian spermatozoa on fertility are poorly understood.

AIMS

Determine the consequences of tributyltin chloride (TBT) exposure on post-ejaculatory sperm function and subsequent embryo development.

METHODS

Frozen-thawed bovine sperm were exposed to TBT (0.1-100nM) for 90min (acute) and 6h (short-term) followed by quantification of multiple sperm kinematics via computer aided sperm analysis. JC-1 dye was used to measure mitochondrial membrane potential. Sperm were then exposed to TBT for 90min in non-capacitating conditions, washed several times by centrifugation and applied to gamete co-incubation for in vitro embryo production to the blastocyst stage.

KEY RESULTS

100nM TBT decreased total motility (88 vs 79%), progressive motility (80 vs 70%) curvilinear velocity and beat-cross frequency for 90min with similar phenotypes at 6h (P<0.05). Sperm mitochondrial membrane potential was lower in 10 and 100nM groups after 6h (P≤0.05). Embryos fertilised from TBT-exposed sperm had reduced cleavage rate (80 vs 62%) and 8-16 cell morula development (55 vs 24%) compared to development from unexposed sperm.

CONCLUSIONS

Exposure of post-ejaculatory mammalian sperm to TBT alters sperm function through lowered motility and mitochondrial membrane potential. Fertilisation of oocytes with TBT-exposed sperm reduces embryo development through mechanisms of paternal origin.

IMPLICATIONS

Acute and short-term environmental exposure of post-ejaculatory sperm to organotins and endocrine disrupting chemicals such as TBT contribute to idiopathic subfertility and early embryo loss.

Exposure to perfluorooctane sulfonate reduced cell viability and insulin release capacity of β cells

Per- and polyfluoroalkyl substances (PFAS) are found to have multiple adverse outcomes on human health. Recently, epidemiological and toxicological studies showed that exposure to PFAS had adverse impacts on pancreas and showed association with insulin abnormalities. To explore how PFAS may contribute to diabetes, we studied impacts of perfluorooctane sulfonate (PFOS) on cell viability and insulin release capacity of pancreatic β cells by using in vivo and in vitro methods. We found that 28-day administration with PFOS (10 mg/(kg body weight•day)) caused reductions of pancreas weight and islet size in male mice. PFOS administration also led to lower serum insulin level both in fasting state and after glucose infusion among male mice. For cell-based in vitro bioassay, we used mouse β-TC-6 cancer cells and found 48-hr exposure to PFOS decreased the cell viability at 50 μmol/L. By measuring insulin content in supernatant, 48-hr pretreatment of PFOS (100 μmol/L) decreased the insulin release capacity of β-TC-6 cells after glucose stimulation. Although these concentrations were higher than the environmental concentration of PFOS, it might be reasonable for high concentration of PFOS to exert observable toxic effects in mice considering mice had a faster removal efficiency of PFOS than human. PFOS exposure (50 μmol/L) to β-TC-6 cells induced intracellular accumulation of reactive oxidative specie (ROS). Excessive ROS induced the reactive toxicity of cells, which eventually invoke apoptosis and necrosis. Results in this study provide evidence for the possible causal link of exposure to PFOS and diabetes risk.

In Vitro Assays to Identify Metabolism-Disrupting Chemicals with Diabetogenic Activity in a Human Pancreatic β-Cell Model

There is a need to develop identification tests for Metabolism Disrupting Chemicals (MDCs) with diabetogenic activity. Here we used the human EndoC-βH1 β-cell line, the rat β-cell line INS-1E and dispersed mouse islet cells to assess the effects of endocrine disruptors on cell viability and glucose-stimulated insulin secretion (GSIS). We tested six chemicals at concentrations within human exposure (from 0.1 pM to 1 µM). Bisphenol-A (BPA) and tributyltin (TBT) were used as controls while four other chemicals, namely perfluorooctanoic acid (PFOA), triphenylphosphate (TPP), triclosan (TCS) and dichlorodiphenyldichloroethylene (DDE), were used as “unknowns”. Regarding cell viability, BPA and TBT increased cell death as previously observed. Their mode of action involved the activation of estrogen receptors and PPARγ, respectively. ROS production was a consistent key event in BPA-and TBT-treated cells. None of the other MDCs tested modified viability or ROS production. Concerning GSIS, TBT increased insulin secretion while BPA produced no effects. PFOA decreased GSIS, suggesting that this chemical could be a “new” diabetogenic agent. Our results indicate that the EndoC-βH1 cell line is a suitable human β-cell model for testing diabetogenic MDCs. Optimization of the test methods proposed here could be incorporated into a set of protocols for the identification of MDCs.

Methylmercury Induces Mitochondria- and Endoplasmic Reticulum Stress-Dependent Pancreatic β-Cell Apoptosis via an Oxidative Stress-Mediated JNK Signaling Pathway

Methylmercury (MeHg), a long-lasting organic pollutant, is known to induce cytotoxic effects in mammalian cells. Epidemiological studies have suggested that environmental exposure to MeHg is linked to the development of diabetes mellitus (DM). The exact molecular mechanism of MeHg-induced pancreatic β-cell cytotoxicity is still unclear. Here, we found that MeHg (1-4 μM) significantly decreased insulin secretion and cell viability in pancreatic β-cell-derived RIN-m5F cells. A concomitant elevation of mitochondrial-dependent apoptotic events was observed, including decreased mitochondrial membrane potential and increased proapoptotic (Bax, Bak, p53)/antiapoptotic (Bcl-2) mRNA ratio, cytochrome c release, annexin V-Cy3 binding, caspase-3 activity, and caspase-3/-7/-9 activation. Exposure of RIN-m5F cells to MeHg (2 μM) also induced protein expression of endoplasmic reticulum (ER) stress-related signaling molecules, including C/EBP homologous protein (CHOP), X-box binding protein (XBP-1), and caspase-12. Pretreatment with 4-phenylbutyric acid (4-PBA; an ER stress inhibitor) and specific siRNAs for CHOP and XBP-1 significantly inhibited their expression and caspase-3/-12 activation in MeHg-exposed RIN-mF cells. MeHg could also evoke c-Jun N-terminal kinase (JNK) activation and reactive oxygen species (ROS) generation. Antioxidant N-acetylcysteine (NAC; 1mM) or 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (trolox; 100 μM) markedly prevented MeH-induced ROS generation and decreased cell viability in RIN-m5F cells. Furthermore, pretreatment of cells with SP600125 (JNK inhibitor; 10 μM) or NAC (1 mM) or transfection with JNK-specific siRNA obviously attenuated the MeHg-induced JNK phosphorylation, CHOP and XBP-1 protein expression, apoptotic events, and insulin secretion dysfunction. NAC significantly inhibited MeHg-activated JNK signaling, but SP600125 could not effectively reduce MeHg-induced ROS generation. Collectively, these findings demonstrate that the induction of ROS-activated JNK signaling is a crucial mechanism underlying MeHg-induced mitochondria- and ER stress-dependent apoptosis, ultimately leading to β-cell death.

Resveratrol ameliorates polycystic ovary syndrome via transzonal projections within oocyte-granulosa cell communication

Rationale: Polycystic ovary syndrome (PCOS) is closely linked to follicular dysplasia and impaired bidirectional oocyte-granulosa cell (GC) communication. Given that PCOS is a heterogeneous, multifactorial endocrine disorder, it is important to clarify the pathophysiology of this ovarian disease and identify a specific treatment.

Methods: We generated PCOS rat models based on neonatal tributyltin (TBT) exposure and studied the therapeutic effect and mechanism of resveratrol (RSV), a natural plant polyphenol. Transcriptome analysis was conducted to screen the significantly changed pathways, and a series of experiments, such as quantitative real-time polymerase chain reaction (PCR), Western blot and phalloidin staining, were performed in rat ovaries. We also observed similar changes in human PCOS samples using Gene Expression Omnibus (GEO) database analysis and quantitative real-time PCR.

Results: We first found that injury to transzonal projections (TZPs), which are specialized filopodia that mediate oocyte-GC communication in follicles, may play an important role in the etiology of PCOS. We successfully established PCOS rat models using TBT and found that overexpressed calcium-/calmodulin-dependent protein kinase II beta (CaMKIIβ) inhibited TZP assembly. In addition, TZP disruption and CAMK2B upregulation were also observed in samples from PCOS patients. Moreover, we demonstrated that RSV potently ameliorated ovarian failure and estrus cycle disorder through TZP recovery via increased cytoplasmic calcium levels and excessive phosphorylation of CaMKIIβ.

Conclusions: Our data indicated that upregulation of CaMKIIβ may play a critical role in regulating TZP assembly and may be involved in the pathogenesis of PCOS associated with ovarian dysfunction. Investigation of TZPs and RSV as potent CaMKIIβ activators provides new insight and a therapeutic target for PCOS, which is helpful for improving female reproduction.

The ameliorative effect of Moringa oleifera oil on tributyltin-induced brain toxicity in albino rats

Tributyltin (TBT) is an organotin compound widely used as a biocide in antifouling paints. Moringa oleifera oil (MOO) has a promising antioxidant potential, which necessitates further exploration. This study was conducted to investigate the potential protective effect of MOO against TBT-induced brain toxicity. The 30 rats were grouped into five groups (six each), Group I negative control, Group II positive control (vehicle), Group III MOO (5 ml/kg body weight [b.wt.]), Group IV TBT (10 mg/kg b.wt.), and Group V TBT & MOO. All treatments were given orally for 28 days. Thereafter, brains were exposed to oxidative stress and neurological parameters analyses. Histopathological and immunohistochemical (caspase-3, Bax, Bcl-2) examinations were also carried out. In rats administered TBT, increased malondialdehyde level, decreased reduced glutathione, and low total antioxidant capacity levels were in support of oxidative stress mechanism. Neurotoxicity was indicated by high nitric oxide level and increased acetylcholinestrase activity. Along with the histopathological alterations, the dysregulated expression of caspase-3, Bax, and Bcl-2 were indicative of the apoptotic mechanism mediated by TBT. Co-administration of MOO with TBT ameliorated the aforementioned toxic effects. In conclusion, TBT causes brain toxicity via oxidative, nitrosative, and apoptotic mechanisms. MOO demonstrates protective effect against TBT-induced brain toxicity mostly via potent antioxidant and antiapoptotic properties.

CHIP-overexpressing Wharton's jelly-derived mesenchymal stem cells attenuate hyperglycemia-induced oxidative stress-mediated kidney injuries in diabetic rats

Accumulating studies have demonstrated the protective roles of mesenchymal stem cells against several disorders. However, one of their crucial limitations is reduced viability under stress conditions, including the hyperglycemia induced by diabetes. The molecular mechanisms involved in diabetes-induced kidney injuries are not fully elucidated. In this study, we found that high glucose (HG) reduced human proximal tubular epithelial cell viability. Further, hyperglycemia induced oxidative stress-mediated apoptosis and fibrosis in HK-2 cells via activation of the mitogen-activated protein kinases (MAPKs) including c-Jun N-terminal kinase JNK and p38 kinase. Carboxyl terminus of HSP70 interacting protein (CHIP) overactivation considerably rescued cell viability under HG stress. Moreover, Western blot analysis, flow cytometry, and MitoSOX staining revealed that hyperglycemia-induced mitochondrial oxidative stress production and apoptosis were attenuated in CHIP-overexpressing Wharton's jelly-derived mesenchymal stem cells (WJMSCs). Co-culture with CHIP-expressing WJMSCs maintained HK-2 cell viability, and inhibited apoptosis and fibrosis by attenuating HG-induced ROS-mediated MAPK activation. CHIP-overexpressing WJMSCs also rescued the decreased kidney weight and hyperglycemia-induced kidney damage observed in streptozotocin-induced diabetic rats. Cumulatively, the current research findings demonstrate that CHIP suppresses hyperglycemia-induced oxidative stress and confers resistance to MAPK-induced apoptosis and fibrosis, and suggests that CHIP protects WJMSCs and the high quality WJMSCs have therapeutic effects against diabetes-induced kidney injuries.

N-Acetylcysteine Reduces the Pro-Oxidant and Inflammatory Responses during Pancreatitis and Pancreas Tumorigenesis

Pancreatitis, an inflammation of the pancreas, appears to be a main driver of pancreatic cancer when combined with Kras mutations. In this context, the exact redox mechanisms are not clearly elucidated. Herein, we treated mice expressing a Kras^G12D mutation in pancreatic acinar cells with cerulein to induce acute pancreatitis. In the presence of Kras^G12D, pancreatitis triggered significantly greater redox unbalance and oxidative damages compared to control mice expressing wild-type Kras alleles. Further analyses identified the disruption in glutathione metabolism as the main redox event occurring during pancreatitis. Compared to the wild-type background, Kras^G12D-bearing mice showed a greater responsiveness to treatment with a thiol-containing compound, N-acetylcysteine (NAC). Notably, NAC treatment increased the pancreatic glutathione pool, reduced systemic markers related to pancreatic and liver damages, limited the extent of pancreatic edema and fibrosis as well as reduced systemic and pancreatic oxidative damages. The protective effects of NAC were, at least, partly due to a decrease in the production of tumor necrosis factor-α (TNF-α) by acinar cells, which was concomitant with the inhibition of NF-κB(p65) nuclear translocation. Our data provide a rationale to use thiol-containing compounds as an adjuvant therapy to alleviate the severity of inflammation during pancreatitis and pancreatic tumorigenesis.

4-Methyl-2,4-bis(4-hydroxyphenyl)pent-1-ene, a Major Active Metabolite of Bisphenol A, Triggers Pancreatic β-Cell Death via a JNK/AMPKα Activation-Regulated Endoplasmic Reticulum Stress-Mediated Apoptotic Pathway

4-methyl-2,4-bis(4-hydroxyphenyl)pent-1-ene (MBP), a major active metabolite of bisphenol A (BPA), is generated in the mammalian liver. Some studies have suggested that MBP exerts greater toxicity than BPA. However, the mechanism underlying MBP-induced pancreatic β-cell cytotoxicity remains largely unclear. This study demonstrated the cytotoxicity of MBP in pancreatic β-cells and elucidated the cellular mechanism involved in MBP-induced β-cell death. Our results showed that MBP exposure significantly reduced cell viability, caused insulin secretion dysfunction, and induced apoptotic events including increased caspase-3 activity and the expression of active forms of caspase-3/-7/-9 and PARP protein. In addition, MBP triggered endoplasmic reticulum (ER) stress, as indicated by the upregulation of GRP 78, CHOP, and cleaved caspase-12 proteins. Pretreatment with 4-phenylbutyric acid (4-PBA; a pharmacological inhibitor of ER stress) markedly reversed MBP-induced ER stress and apoptosis-related signals. Furthermore, exposure to MBP significantly induced the protein phosphorylation of JNK and AMP-activated protein kinase (AMPK)α. Pretreatment of β-cells with pharmacological inhibitors for JNK (SP600125) and AMPK (compound C), respectively, effectively abrogated the MBP-induced apoptosis-related signals. Both JNK and AMPK inhibitors also suppressed the MBP-induced activation of JNK and AMPKα and of each other. In conclusion, these findings suggest that MBP exposure exerts cytotoxicity on β-cells via the interdependent activation of JNK and AMPKα, which regulates the downstream apoptotic signaling pathway.

Tributyltin triggers lipogenesis in macrophages via modifying PPARγ pathway

Tributyltin (TBT), a bioaccumulative and persistent environmental pollutant, has been proposed as a metabolism disruptor and obesogen through targeting peroxisome proliferator-activated receptor gamma (PPARγ) receptor pathway. However, it remains unknown whether this biological effect occurs in macrophage, a cell type which cooperates closely with hepatocytes and adipocytes to regulate lipid metabolism. This study for the first time investigated the effect of TBT on PPARγ pathway in macrophages. Our results indicated that nanomolar levels of TBT was able to strongly activate PPARγ in human macrophages. TBT treatment also markedly increased the intracellular lipid accumulation, and enhanced the expression of lipid metabolism-related genes in macrophages, while these effects were all significantly down-regulated in PPARγ-deficient macrophages, confirming the involvement of PPARγ in TBT-induced lipogenesis. Next, a mouse model that C57BL/6 mice were orally exposed to TBT with the doses (250 and 500 μg/kg body weight) lower than NOAEL (no observed adverse effect level) was used to further investigate the in vivo mechanisms. And the in vivo results were consistent with cellular assays, confirming the induction of PPARγ and the increased expression of lipogenesis-regulating and lipid metabolism-related genes by TBT in vivo. In conclusion, this study not only provided the first evidence that TBT stimulated lipogenesis, activated PPARγ and related genes in human macrophages, but also provided insight into the mechanism of TBT-induced metabolism disturbance and obesity through targeting PPARγ via both in vitro cellular assays and in vivo animal models.

Alleviation of tributyltin-induced toxicity by diet and microplastics in the marine rotifer Brachionus koreanus

To determine the effects of tributyltin (TBT) upon multiple exposures of diet and microplastic in rotifer, in vivo life parameters were measured. In 10 μg/L TBT-exposed rotifer, the 1 and 0.5 x diet groups resulted in reproduction reduction. However, 10 x diet treatment showed no significant changes in the total fecundity, despite a decrease in daily reproduction. Besides, differences in the lifespan were observed in response to different diet regimens. TBT and/or MP-exposed parental rotifer (F0) showed a significant delay in the pre-reproductive day under 0.5 x diet regimen. In all dietary regimens, exposure to TBT and MP induced an increase in reactive oxygen species, but antioxidant activities were perturbed. To further verify the carryover effect of TBT toxicity, progeny rotifer (F1) obtained from 24 h TBT and/or MP-exposed F0 was used. Interestingly, the faster hatching rate was observed only in F1 obtained from 1 x diet regimen-exposed F0. However, in the 0.5 x diet, the total fecundity was reduced and the pattern of the daily reproduction was collapsed. Thus, the toxicity of TBT can be alleviated by MP and nutrition status, but TBT-induced toxicity and its carryover effect are inevitable.

Estrogens counteract tributyltin-induced toxicity in the rat islets of Langerhans

Background

Tributyltin (TBT) is known as an endocrine disruptor able to interfere with estrogen receptors (ERs) leading to toxic effects on the related endocrine pathways. TBT is an obesogen, reported to disrupt glucose homeostasis leading to diabetes. The aim of this study was to assess the influence of TBT and β-estradiol on the pancreatic islets of Langerhans in simultaneous exposures.

Experimental

Pancreatic islets of 15 male rat were isolated and exposed to TBT (10 μM), β-estradiol, and TBT plus β-estradiol for 24 h. Therewith, cellular viability, oxidative stress, apoptosis, and insulin secretion markers were investigated.

Results

TBT decreased the viability and increased the apoptosis, reactive oxygen species, and insulin secretion TBT led to increased amounts of apaptosis, reactive oxygen species (ROS), and insulin secretion in pancreatic islets; however, cellular viability was reduced. Co-exposure with β-estradiol ameliorated the entire mentioned variables near to the control level.

Conclusion

These results showed that β-estradiol protect pancreatic islets of Langerhans against TBT-induced toxicity by counteracting oxidative stress and apoptosis as well as insulin secretion. In this way, it is postulated that pancreatic ER pathways particularly in β-cells might be the determinant target of toxic effects of xenoestrogens like TBT. Hence, evaluation of xenoestrogens-induced ER dysfunction in the endocrine pancreas can be helpful in diabetic risk assessment of these contaminants. Pharmacological modifications of ER pathway in the β-cells seems promising for better management of diabetes.

Relevant dose of the environmental contaminant, tributyltin, promotes histomorphological changes in the thyroid gland of male rats

Organotin compounds, such as tributyltin (TBT), are common environmental contaminants and suspected endocrine-disrupting chemicals. Tributyltin is found in antifouling paints, widely used in ships and other vessels. The present study evaluated whether a 15-day treatment with TBT at a dose of 100 ng/kg/day could induce histomorphological changes in the thyroid gland of rats. TBT promoted relevant alterations in the thyroid architecture, being the most relevant histological findings the presence of increased number of small-size follicles in the treated group. In qualitative analyses, colloid vacuolization, papillary budging structures, cystic degeneration and chronic thyroiditis, were observed. Moreover, histomorphometric analysis showed statistically significant changes in the follicular architecture of TBT-treated rats, mainly a decrease in the follicle area (colloid) and an increased epithelial height that resulted in an increased epithelial height/colloid ratio. Augmented collagen deposition was also seen in the thyroids of treated groups. In immunohistochemical (IHC) analyses, the localization of NIS protein was described and a significant increased proliferation index (evaluated by Ki67 positive cells) in the treated group was reported. As an indirect measurement of oxidative stress, mitochondrial protein SDHA was also analyzed by IHC analysis. Although the cytoplasmic expression of SDHA was observed in both groups, the staining intensity score was higher in TBT-treated group. Our results suggest that besides causing histomorphological changes, environmental relevant dose of TBT treatment can also induce oxidative alterations.

Contribution of Oxidative Stress and Impaired Biogenesis of Pancreatic β-Cells to Type 2 Diabetes

Significance: Type 2 diabetes development involves multiple changes in β-cells, related to the oxidative stress and impaired redox signaling, beginning frequently by sustained overfeeding due to the resulting lipotoxicity and glucotoxicity. Uncovering relationships among the dysregulated metabolism, impaired β-cell "well-being," biogenesis, or cross talk with peripheral insulin resistance is required for elucidation of type 2 diabetes etiology. Recent Advances: It has been recognized that the oxidative stress, lipotoxicity, and glucotoxicity cannot be separated from numerous other cell pathology events, such as the attempted compensation of β-cell for the increased insulin demand and dynamics of β-cell biogenesis and its "reversal" at dedifferentiation, that is, from the concomitantly decreasing islet β-cell mass (also due to transdifferentiation) and low-grade islet or systemic inflammation. Critical Issues: At prediabetes, the compensation responses of β-cells, attempting to delay the pathology progression-when exaggerated-set a new state, in which a self-checking redox signaling related to the expression of Ins gene expression is impaired. The resulting altered redox signaling, diminished insulin secretion responses to various secretagogues including glucose, may lead to excretion of cytokines or chemokines by β-cells or excretion of endosomes. They could substantiate putative stress signals to the periphery. Subsequent changes and lasting glucolipotoxicity promote islet inflammatory responses and further pathology spiral. Future Directions: Should bring an understanding of the β-cell self-checking and related redox signaling, including the putative stress signal to periphery. Strategies to cure or prevent type 2 diabetes could be based on the substitution of the "wrong" signal by the "correct" self-checking signal.

Environmental neglect: endocrine disruptors as underappreciated but potentially modifiable diabetes risk factors

Type 2 diabetes prevalence is increasing dramatically across the globe, imposing a tremendous toll on individuals and healthcare systems. Reversing these trends requires comprehensive approaches to address both classical and emerging diabetes risk factors. Recently, environmental toxicants acting as endocrine-disrupting chemicals (EDCs) have emerged as novel metabolic disease risk factors. EDCs implicated in diabetes pathogenesis include various inorganic and organic molecules of both natural and synthetic origin, including arsenic, bisphenol A, phthalates, polychlorinated biphenyls and organochlorine pesticides. Indeed, evidence implicates EDC exposures across the lifespan in metabolic dysfunction; moreover, specific developmental windows exhibit enhanced sensitivity to EDC-induced metabolic disruption, with potential impacts across generations. Importantly, differential exposures to diabetogenic EDCs likely also contribute to racial/ethnic and economic disparities. Despite these emerging links, clinical practice guidelines fail to address this underappreciated diabetes risk factor. Comprehensive approaches to stem the tide of diabetes must include efforts to address its environmental drivers.

DNA fragmentation factor 40 expression in T cells confers sensibility to tributyltin-induced apoptosis

DNA fragmentation factor 40 (DFF40), an endonuclease, mediates the final and irreversible step of apoptosis by conducting oligonucleosomal DNA fragmentation. New emerging studies have proposed a role of DFF40 in genomic stability, besides its nuclease activity. Overexpression of DFF40 in tumoral cells increases their sensitivity to chemotherapeutic drugs. In this study, we sought to determine if DFF40 expression influences the toxicity of tributyltin (TBT), a well-known immunotoxic and apoptosis-inducing compound. The strategy used was to knockout DFF40 expression by CRISPR-cas9 method in Jurkat T cells and to determine the toxicity of TBT in DFF40 KO cells and DFF40 WT Jurkat cells. DFF40 KO Jurkat cells show an increase of cell viability following a 24-h TBT exposure (p < 0.05). There is a resistance to TBT-induced apoptosis determined by annexin V/PI am labeling (p < 0.05). Interestingly, the basal level of ROS rises in DFF40 KO Jurkat cells, but ROS production levels after TBT exposure remains at the same basal level. Other apoptosis or DNA damage makers (procaspase-3, caspase-6, and PARP cleavage) are significantly delayed and decreased. DFF40 deficient cells do not present histone H2AX phosphorylation, whereas wild-type cells present a phosphorylation following a 6-h exposure to TBT (p < 0.001). The re-expression of DFF40 in DFF40 KO cells restores the cytotoxic effects of TBT. Overall, these data suggest a role of DFF40 in cells sensitivity to TBT and possibly in DNA stability.

The protective effects of Nile tilapia (Oreochromis niloticus) scale collagen hydrolysate against oxidative stress induced by tributyltin in HepG2 cells

Oxidative stress is regarded as one of the most important factors associated with many diseases, such as atherosclerosis, cancer, and diabetes. Various chemicals are released into the environment, causing environmental pollution. Importantly, many of them may cause damage to organisms through oxidative stress. In this work, we investigated the possible protective effects of Nile tilapia (Oreochromis niloticus) scale collagen hydrolysate (TSCH) (molecular weight approximately 4 kDa) against tributyltin (TBT)-induced oxidative stress in vitro. The results showed that pretreatment with TSCH protected against decreases in cell viability and changes in cell morphology in HepG2 cells exposed to TBT. Treatment with TSCH reduced the TBT-induced elevation in malondialdehyde (MDA) levels in HepG2 cells in a dose-dependent manner. Pretreatment with TSCH increased glutathione reductase (GR) and superoxide dismutase (SOD) activity. Moreover, TSCH decreased the expression of the proapoptotic protein Bax, reducing apoptosis. These results suggest that the protective mechanism of TSCH may be associated with its ability to scavenge MDA, increase antioxidant enzyme activity and downregulate the expression of Bax.

The Protective Effects of Levo-Tetrahydropalmatine on ConA-Induced Liver Injury Are via TRAF6/JNK Signaling

AIMS

Levo-tetrahydropalmatine (L-THP) is an active ingredient of Corydalis yanhusuo W. T. Wang, which has many bioactive properties. Herein, we investigated the protective effects of L-THP on concanavalin A- (ConA-) induced hepatitis in mice and explored its possible mechanisms of these effects.

MAIN METHODS

Balb/c mice were intravenously injected with 25 mg/kg ConA to generate a model of acute autoimmune hepatitis, and L-THP (20 or 40 mg/kg) was administered orally once daily for 5 d before the ConA injection. The liver enzyme levels, proinflammatory cytokine levels, and other marker protein levels were determined 2, 8, and 24 h after ConA injection.

RESULTS

L-THP could decrease serum liver enzymes and pathological damage by reducing the release of inflammatory factors like IL-6 and TNF-α. The results of Western Blot and PCR indicated that L-THP could ameliorate liver cell apoptosis and autophagy. L-THP could suppress T lymphocyte proliferation and the production of TNF-α and IL-6 induced by ConA in a dose-dependent manner in vitro. Additionally, the protective functions of L-THP depended on downregulating TRAF6/JNK signaling. Conclusion. The present study indicated that L-THP attenuated acute liver injury in ConA-induced autoimmune hepatitis by inhibiting apoptosis and autophagy via the TRAF6/JNK pathway.

Mitochondria as target of endocrine-disrupting chemicals: implications for type 2 diabetes

Type 2 diabetes is a chronic, heterogeneous syndrome characterized by insulin resistance and pancreatic β-cell dysfunction or death. Among several environmental factors contributing to type 2 diabetes development, endocrine-disrupting chemicals (EDCs) have been receiving special attention. These chemicals include a wide variety of pollutants, from components of plastic to pesticides, with the ability to modulate endocrine system function. EDCs can affect multiple cellular processes, including some related to energy production and utilization, leading to alterations in energy homeostasis. Mitochondria are primarily implicated in cellular energy conversion, although they also participate in other processes, such as hormone secretion and apoptosis. In fact, mitochondrial dysfunction due to reduced oxidative capacity, impaired lipid oxidation and increased oxidative stress has been linked to insulin resistance and type 2 diabetes. Herein, we review the main mechanisms whereby metabolism-disrupting chemical (MDC), a subclass of EDCs that disturbs energy homeostasis, cause mitochondrial dysfunction, thus contributing to the establishment of insulin resistance and type 2 diabetes. We conclude that MDC-induced mitochondrial dysfunction, which is mainly characterized by perturbations in mitochondrial bioenergetics, biogenesis and dynamics, excessive reactive oxygen species production and activation of the mitochondrial pathway of apoptosis, seems to be a relevant mechanism linking MDCs to type 2 diabetes development.

The obesogen tributyltin induces features of polycystic ovary syndrome (PCOS): a review

Polycystic ovary syndrome (PCOS) is a heterogeneous syndrome characterized by abnormal reproductive cycles, irregular ovulation, and hyperandrogenism. This complex disorder has its origins both within and outside the hypothalamic-pituitary-ovarian axis. Cardio-metabolic factors, such as obesity and insulin resistance, contribute to the manifestation of the PCOS phenotype. Polycystic ovary syndrome is one of the most common endocrine disorders among women of reproductive age. Growing evidence suggested an association between reproductive and metabolic features of PCOS and exposure to endocrine-disrupting chemicals (EDC), such as bisphenol A. Further, the environmental obesogen tributyltin (TBT) was shown to induce reproductive, metabolic and cardiovascular abnormalities resembling those found in women and animal models of PCOS. However, the causal link between TBT exposure and PCOS development remains unclear. The objective of this review was to summarize the most recent research findings on the potential association between TBT exposure and development of PCOS-like features in animal models and humans.

Novel curcumin analogue hybrids: Synthesis and anticancer activity

In this study, twenty curcumin analogue hybrids as potential anticancer agents through regulation protein of TrxR were designed and synthesized. Results of anticancer activity showed that 5,7-dimethoxy-3-(3-(2-((1E, 4E)-3-oxo-5-(pyridin-2-yl)penta-1,4-dien-1- yl)phenoxy)propoxy)-2-(3,4,5-trimethoxyphenyl)-4H-chromen-4-one (compound 7d) could induce gastric cancer cells apoptosis by arresting cell cycle, break mitochondria function and inhibit TrxR activity. Meanwhile, western blot revealed that this compound could dramatically up expression of Bax/Bcl-2 ratio and high expression of TrxR oxidation. These results preliminarily show that the important role of ROS mediated activation of ASK1/MAPK signaling pathways by this title compound.