Role of endoplasmic reticulum stress and oxidative stress in vinyl chloride-induced hepatic steatosis in mice

Vinyl chloride enhances high-fat diet-induced proteome alterations in the mouse pancreas related to metabolic dysfunction

Alterations in physiological processes in pancreas have been associated with various metabolic dysfunctions and can result from environmental exposures, such as chemicals and diet. It was reported that environmental vinyl chloride (VC) exposure, a common industrial organochlorine and environmental pollutant, significantly exacerbated metabolic-related phenotypes in mice fed concurrently with high-fat diet (HFD) but not low-fat diet (LFD). However, little is known about the role of the pancreas in this interplay, especially at a proteomic level. The present study was undertaken to examine the protein responses to VC exposure in pancreas tissues of C57BL/6J mice fed LFD or HFD, with focus on the investigation of protein expression and/or phosphorylation levels of key protein biomarkers of carbohydrate, lipid, and energy metabolism, oxidative stress and detoxification, insulin secretion and regulation, cell growth, development, and communication, immunological responses and inflammation, and biomarkers of pancreatic diseases and cancers. We found that the protein alterations may indicate diet-mediated susceptibility in mouse pancreas induced by HFD to concurrent exposure of low levels of inhaled VC. These proteome biomarkers may lead to a better understanding of pancreas-mediated adaptive or adverse response and susceptibility to metabolic disease.

Metabolism-Disrupting Chemicals Affecting the Liver: Screening, Testing, and Molecular Pathway Identification

The liver is the central metabolic organ of the body. The plethora of anabolic and catabolic pathways in the liver is tightly regulated by physiological signaling but may become imbalanced as a consequence of malnutrition or exposure to certain chemicals, so-called metabolic endocrine disrupters, or metabolism-disrupting chemicals (MDCs). Among different metabolism-related diseases, obesity and non-alcoholic fatty liver disease (NAFLD) constitute a growing health problem, which has been associated with a western lifestyle combining excessive caloric intake and reduced physical activity. In the past years, awareness of chemical exposure as an underlying cause of metabolic endocrine effects has continuously increased. Within this review, we have collected and summarized evidence that certain environmental MDCs are capable of contributing to metabolic diseases such as liver steatosis and cholestasis by different molecular mechanisms, thereby contributing to the metabolic syndrome. Despite the high relevance of metabolism-related diseases, standardized mechanistic assays for the identification and characterization of MDCs are missing. Therefore, the current state of candidate test systems to identify MDCs is presented, and their possible implementation into a testing strategy for MDCs is discussed.

Angiopoietin-like protein 4 treated bone marrow-derived mesenchymal stem cells alleviate myocardial injury of patients with myocardial infarction

Bone marrow‐derived mesenchymal stem cells (BMSCs) and their exosomes are of great significance for the recovery of cardiac function in patients with myocardial infarction (MI). However, the underlying mechanisms of BMSCs applied to MI treatment remain unclear. Fluorescence‐activated cell sorting (FACs) are performed to assess the apoptosis, reactive oxygen species levels and glucose uptake capacity of BMSCs. Reverse transcription polymerase chain reaction is conducted to detect the levels of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), hepatocyte growth factor (HGF), insulin‐like growth factor (IGF), transforming growth factor‐beta 1, connective tissue growth factor, and platelet‐derived growth factor. The levels of apoptosis‐related proteins were detected by Western blot. The levels of VEGF, bFGF, HGF, and IGF were assessed by enzyme‐linked immunosorbent assay. The biochemical kits are applied to detect the levels of malondialdehyde, superoxide dismutase, and adenosine triphosphate/adenosine diphosphate. 2,3,5‐triphenyltetrazolium and Masson staining and immunofluorescence are performed to assess myocardial function of rats. Angiopoietin‐like protein 4 (ANGPTL4) alleviates apoptosis and oxidative stress of BMSCs induced by serum deprivation and hypoxia; ANGPTL4 activates paracrine and accelerate metabolic energy of BMSCs; and ANGPTL4 treated‐BMSCs alleviate myocardial injury of rats with MI. ANGPTL4 treated‐BMSCs alleviate myocardial injury in rats with MI, indicating the combination therapy of ANGPTL4 and BMSCs may alleviate myocardial injury in rats with MI.

Environmental toxicant-induced maladaptive mitochondrial changes: A potential unifying mechanism in fatty liver disease?

Occupational and environmental exposures to industrial chemicals are well known to cause hepatotoxicity and liver injury. However, despite extensive evidence showing that exposure can lead to disease, current research approaches and regulatory policies fail to address the possibility that subtle changes caused by low level exposure to chemicals may also enhance preexisting conditions. In recent years, the conceptual understanding of the contribution of environmental chemicals to liver disease has progressed significantly. Mitochondria are often target of toxicity of environmental toxicants resulting in multisystem disorders involving different cells, tissues, and organs. Here, we review persistent maladaptive changes to mitochondria in response to environmental toxicant exposure as a mechanism of hepatotoxicity. With better understanding of the mechanism(s) and risk factors that mediate the initiation and progression of toxicant-induced liver disease, rational targeted therapy can be developed to better predict risk, as well as to treat or prevent this disease.

Mechanism of subchronic vinyl chloride exposure combined with a high-fat diet on hepatic steatosis

Vinyl chloride (VC) is a common industrial organic chlorine and environmental pollutant. In recent years, the dietary structure of residents especially Chinese has gradually shifted to western dietary patterns. VC aggravates dietary fatty acid-induced hepatic steatosis, but its mechanism is still unclear. And if the risk factors for steatosis persist, more severe diseases such as fibrosis and cirrhosis will occur. Therefore, we studied the effects and mechanisms of VC (160 and 800 mg/m³ ) and its metabolite (chloroacetaldehyde, 2.25, 4.5, and 9 μM) on hepatic steatosis of high-fat diet (HFD)-fed mice and palmitic acid (PA, 100 μM) treated HepG2 cells. Liver and serum biochemical indicators and pathological staining of the liver showed that the hepatic steatosis of VC combined with HFD groups was more severe than that of single-exposure groups (HFD group, low-dose VC group, and high-dose VC group). Moreover, VC enhanced HFD-induced oxidative stress (OS) and endoplasmic reticulum stress (ERS) and further upregulated the expression of sterol regulatory element-binding protein 1 (SREBP-1) and FAS. Besides, antioxidants and ERS inhibitors reduced the steatosis of HepG2 cells induced by VC metabolites and PA. These results suggest that VC exposure can enhance the degree of hepatic steatosis in HFD-fed mice. VC combined with HFD led to OS and ERS and upregulated the expression of de novo lipogenesis-related proteins, which may be related to the occurrence of hepatic steatosis. And the increased expression of CYP2E1 induced by VC combined with HFD may be the cause of OS.

Hepatic Injury Caused by the Environmental Toxicant Vinyl Chloride is Sex-Dependent in Mice

Vinyl chloride (VC), a common industrial chemical, has been associated with hemangiosarcoma and toxicant-associated steatohepatitis (TASH) in men working at rubber-production plants. Our group previously demonstrated that chronic VC inhalation at environmentally relevant levels (< 1 ppm) in male mice exacerbated hepatic injury caused by high-fat diet (HFD) feeding. Because VC studies on TASH have only been performed in male models, the objective of this study is to examine VC inhalation in female mice in the context of TASH mechanisms. Male and female C57Bl/6 mice were fed either a low-fat diet or HFD and exposed to VC or room air using an inhalation chamber, for 12 weeks (6 h, 5 days/week); and plasma and liver samples were collected after euthanasia. Compared with males, females were less susceptible to HFD+VC-induced obesogenic effects demonstrated by lower body weight and fat composition. Histological analysis revealed that whereas VC exacerbated HFD-induced steatosis in males, this effect was absent in females. In addition, females were more resistant to VC-induced hepatic inflammation whereas males had increased liver weights and higher hepatic Tnfα mRNA levels. Systemic markers of hepatic injury, namely alanine aminotransaminase and thrombin/antithrombin levels were increased by HFD+VC co-exposures only in males. In addition, females did not show significant cell death as previously reported in males. Taken together, the results suggested that VC inhalation led to sex-dependent liver and metabolic toxicity. This study implicated the importance of assessing sex differences in environmental basic science and epidemiologic studies to better identify at-risk populations in both men and women.