The role of PSMB5 in sodium arsenite-induced oxidative stress in L-02 cells

Proteomic analysis of the effects of Dictyophora polysaccharide on arsenic-induced hepatotoxicity in rats

Arsenic (As) is a highly toxic environmental toxicant and a known human carcinogen. Long-term exposure to As can cause liver injury. Dictyophora polysaccharide (DIP) is a biologically active natural compound found in the Dictyophora with excellent antioxidation, anti-inflammation, and immune protection properties. In this study, the Sprague-Dawley (SD) rat model of As toxicity was established using a feeding method, followed by DIP treatment in rats with As-induced liver injury. The molecular mechanisms of As toxicity to the rat liver and the protective effect of DIP were investigated by proteomic studies. The results showed that 172, 328 and 191 differentially expressed proteins (DEPs) were identified between the As-exposed rats versus control rats (As/Ctrl), DIP treated rats versus As-exposed rats (DIP+As/As), and DIP treated rats versus control rats (DIP+As /Ctrl), respectively. Among them, the expression of 90 DEPs in the As/Ctrl groups was reversed by DIP treatment. As exposure caused dysregulation of metabolic pathways, mitochondria, oxidative stress, and apoptosis-related proteins in the rat liver. However, DIP treatment changed or restored the levels of these proteins, which attenuated the damage to the livers of rats caused by As exposure. The results provide new insights into the mechanisms of liver injury induced by As exposure and the treatment of DIP in As poisoning.

Environmental arsenic pollution induced liver oxidative stress injury by regulating miR-155 through inhibition of AUF1

Arsenic (As), a common environmental pollutant, has become a hot topic in recent years due to its potentially harmful effects. Liver damage being a central clinical feature of chronic arsenic poisoning. However, the underlying mechanisms remain unclear. We demonstrated that arsenic can lead to oxidative stress in the liver and result in structural and functional liver damage, significantly correlated with the expression of AUF1, Dicer1, and miR-155 in the liver. Interestingly, knockdown AUF1 promoted the up-regulatory effects of arsenic on Dicer1 and miR-155 and the inhibitory effects on SOD1, which exacerbated oxidative damage in rat liver. However, overexpression of AUF1 reversed the up-regulatory effects of arsenic on Dicer1 and miR-155, restored arsenic-induced SOD1 depletion, and attenuated liver oxidative stress injury. Further, we verified the mechanism and targets of miR-155 in regulating SOD1 by knockdown/overexpression of miR-155 and nonsense mutant SOD1 3'UTR experiments. In conclusion, these results powerfully demonstrate that arsenic inhibits AUF1 protein expression, which in turn reduces the inhibitory effect on Dicer1 expression, which promotes miR-155 to act on the SOD1 3'UTR region after high expression, thus inhibiting SOD1 protein expression and enzyme activity, and inducing liver injury. This finding provides a new perspective for the mechanism research and targeted prevention of arsenic poisoning, as well as scientific evidence for formulating strategies to prevent and control environmental arsenic pollution.

The role of FGF9-mediated TGF-β1/Smad signaling in enamel hypoplasia induced by exposure to fluoride and SO2 in rats

Many geographical areas of the world are polluted by both fluoride and sulfur dioxide (SO2). However, the effects of simultaneous exposure to fluoride and SO2 on teeth are unknown. Fibroblast growth factor-9 (FGF9) and transforming growth factor-β1 (TGF-β1) are key signaling molecules in enamel development. The purpose of the study was to explore the effects of co-exposure to fluoride and sulfur dioxide on enamel and to investigate the role and mechanism of FGF9 and TGF-β1. First, sodium fluoride (NaF) and SO2 derivatives were used to construct rat models and evaluate the enamel development of rats. Then, TGF-β1 (cytokine) treatment, SIS3 (inhibitor) treatment and FGF9 gene knockdown were used to explore the mechanism of enamel damage in vitro. The results showed that enamel column crystals in the exposed group were characterized by enamel hypoplasia, as indicated by alterations such as disarrangement of enamel column crystals, space widening and breakage. Ameloblasts also showed pathological changes such as ribosome loss, mitochondrial swelling, nuclear fragmentation and chromatin aggregation. The protein expression of FGF9 was higher and the protein expression of AMBN, TGF-β1 and p-Smad2/3 protein was lower in the groups treated with fluoride and SO2 individually or in combination compared with the control group. Further studies showed that TGF-β1 significantly upregulated p-Smad2/3 and AMBN protein expression and reduced the inhibitory effects of fluoride and SO2; furthermore, SISI blocked the effect of TGF-β1. In addition, knockdown of FGF9 upregulated TGF-β1 protein expression, further activated Smad2/3 phosphorylation, eliminated the inhibitory effects of fluoride and SO2, and increased the protein expression of AMBN. In brief, the study confirms that co-exposure to fluoride and SO2 can result in enamel hypoplasia in rats and indicates that the underlying mechanism may be closely related to the effect of FGF9 on enamel matrix protein secretion through inhibition of the TGF-β1/Smad signaling pathway.

In vitro to in vivo extrapolation and high-content imaging for simultaneous characterization of chemically induced liver steatosis and markers of hepatotoxicity

Chemically induced steatosis is characterized by lipid accumulation associated with mitochondrial dysfunction, oxidative stress and nucleus distortion. New approach methods integrating in vitro and in silico models are needed to identify chemicals that may induce these cellular events as potential risk factors for steatosis and associated hepatotoxicity. In this study we used high-content imaging for the simultaneous quantification of four cellular markers as sentinels for hepatotoxicity and steatosis in chemically exposed human liver cells in vitro. Furthermore, we evaluated the results with a computational model for the extrapolation of human oral equivalent doses (OED). First, we tested 16 reference chemicals with known capacities to induce cellular alterations in nuclear morphology, lipid accumulation, mitochondrial membrane potential and oxidative stress. Then, using physiologically based pharmacokinetic modeling and reverse dosimetry, OEDs were extrapolated from data of any stimulated individual sentinel response. The extrapolated OEDs were confirmed to be within biologically relevant exposure ranges for the reference chemicals. Next, we tested 14 chemicals found in food, selected from thousands of putative chemicals on the basis of structure-based prediction for nuclear receptor activation. Amongst these, orotic acid had an extrapolated OED overlapping with realistic exposure ranges. Thus, we were able to characterize known steatosis-inducing chemicals as well as data-scarce food-related chemicals, amongst which we confirmed orotic acid to induce hepatotoxicity. This strategy addresses needs of next generation risk assessment and can be used as a first chemical prioritization hazard screening step in a tiered approach to identify chemical risk factors for steatosis and hepatotoxicity-associated events.

Role of SESTRIN2/AMPK/ULK1 pathway activation and lysosomes dysfunction in NaAsO2-induced liver injury under oxidative stress

Arsenic, a serious environmental poison to human health, is widely distributed in nature. As the main organ of arsenic metabolism, liver is easily damaged. In the present study, we found that arsenic exposure can cause liver injury in vivo and in vitro, to date the underlying mechanism of which is yet unclear. Autophagy is a process that depends on lysosomes to degrade damaged proteins and organelles. Here, we reported that oxidative stress can be induced and then activated the SESTRIN2/AMPK/ULK1 pathway, damaged lysosomes, and finally induced necrosis upon arsenic exposure in rats and primary hepatocytes, which was characterized by lipidation of LC3II, the accumulation of P62 and the activation of RIPK1 and RIPK3. Similarly, lysosomes function and autophagy can be damaged under arsenic exposure, which can be alleviated after NAC treatment and aggravated by Leupeptin treatment in primary hepatocytes. Moreover, we also found that the transcription and protein expressions of necrotic-related indicators RIPK1 and RIPK3 in primary hepatocytes were decreased after P62 siRNA. Taken together, the results revealed that arsenic can induce oxidative stress, activate SESTRIN2/AMPK/ULK1 pathway to damage lysosomes and autophagy, and eventually induce necrosis to damage liver.

LC/MS/MS-Based Liver Metabolomics to Identify Chronic Liver Injury Biomarkers Following Exposure to Arsenic in Rats

Arsenic is a widespread natural metalloid element. Long-term chronic exposure to arsenic can lead to different degrees of liver injury. Although the etiology of this disease is well known, to date, the underlying mechanism of arsenic-induced liver injury remains unclear, and no specific treatment exists because of the complexity of arsenic. In the present study, potential biomarkers and metabolic pathways in the livers of Wistar rats treated with arsenic for 24 weeks were investigated using an integrated metabolic approach with an LC-Orbitrap Q Exactive™ HF-X mass spectrometer. Markedly increased liver levels of arsenic, alanine aminotransferase (ALT), alkaline phosphatase (ALP), and total bile acid (TBA) were detected in the arsenic treatment groups (P < 0.05). Furthermore, histopathological examination of liver tissues showed obviously swollen, loose cytoplasm and increased necrosis in the arsenic treatment groups compared with those in the control group (P < 0.05). Metabonomics results showed that 109 metabolites (variable importance in the projection (VIP) > 1; fold change > 2 or < 0.5; P adjusted < 0.05) changed significantly after exposure to arsenic and included 71 upregulated metabolites and 38 downregulated metabolites. Additionally, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that 6 metabolic pathways with statistical significance-phenylalanine metabolism, pyruvate metabolism, glycolysis/gluconeogenesis, citrate cycle (TCA cycle), thiamine metabolism, and vitamin B6 metabolism-were selected, and 13 differential metabolites were detected to be involved in regulating these metabolic pathways. The present study could help identify potential biomarkers and their functions, as well as metabolic pathways, likely providing evidence for the early diagnosis, prevention, and mechanistic study of arsenism.

PSMB5 overexpression is correlated with tumor proliferation and poor prognosis in hepatocellular carcinoma

Aberrant expression of members of the proteasome subunit beta (PSMB) family (including PSMB2, PSMB4, PSMB7 and PSMB8) has been reported in hepatocellular carcinoma (HCC). However the role of PSMB5 in HCC is unclear. To address this issue, we examined the expression of PSMB5 in HCC tissues using the The Cancer Genome Atlas, International Cancer Genome Consortium and Gene Expression Omnibus databases. A quantitative real-time PCR and immunohistochemistry were performed to validate the expression of PSMB5 in HCC. The survival mutation status and immune cell infiltration of PSMB5 were also evaluated in HCC. We then examined the effect of knocking down PSMB5 expression through RNA interference in the HCC cell line Huh7. High expression of PSMB5 was observed in HCC tissues and was associated with poor prognosis. PSMB5 expression and clinical characteristics were then incorporated to build a prognostic nomogram. We observed that PSMB5 expression was closely related to the abundance of B cells, CD4⁺ T cells, CD8⁺ T cells, dendritic cell macrophages and neutrophils. Moreover silencing of PSMB5 in Huh7 significantly suppressed cell proliferation and migration at the same time as increasing apoptosis. Inhibition of the phosphatidylinositol-3-kinase/Akt/mechanistic target of rapamycin pathway was observed after PSMB5 downregulation in Huh7 cells. Our findings suggest that PSMB5 may promote the proliferation of HCC cells by inactivating the phosphatidylinositol-3-kinase/Akt/mechanistic target of rapamycin signaling pathway and thus PSMB5 may have potential as a biomarker for diagnosis and prognosis of HCC.

Mechanism underlying the targeted regulation of the SOD1 3'UTR by the AUF1/Dicer1/miR-155/SOD1 pathway in sodium arsenite-induced liver injury

Arsenic (As) is a natural hepatotoxicity inducer that is ubiquitous in water, soil, coal, and food. Studies have found that arsenite exposure elicits increased mRNA transcription and decreased protein expression of SOD1 in vivo and in vitro; however, the specific mechanisms remain unclear. Here, we established a model of arsenic-induced chronic liver injury by providing rats with drinking water containing different concentrations of sodium arsenite (NaAsO₂) and found that NaAsO₂ exposure decreased the mRNA and protein levels of AUF1 and the protein level of SOD1 and elevated the mRNA and protein levels of Dicer1 and miR-155 and the mRNA level of SOD1. Overexpression of AUF1 under NaAsO₂ stress in vitro induced Dicer1 mRNA and protein expression and decreased miR-155 levels, which could be reversed by AUF1 siRNA. In addition, miR-155 overexpression downregulated SOD1 mRNA and protein levels, although this change was inhibited after transfection with an miR-155 inhibitor. Taken together, our findings showed that NaAsO₂ could upregulate Dicer1 mRNA and protein, thereby increasing miR-155 expression by downregulating AUF1 mRNA and protein expression. A dual-luciferase reporter assay indicated that miR-155 decreased the mRNA and protein levels of SOD1 by targeting the SOD1 3'UTR, resulting in liver injury. This study provides an important research basis for further understanding the factors underlying arsenic-induced liver injury to improve the prevention and control strategies for arsenism.

PSMB5 Alleviates Ulcerative Colitis by Inhibiting ROS-Dependent NLRP3 Inflammasome-Mediated Pyroptosis

Ulcerative colitis (UC) is a chronic inflammatory disease. Intestinal mucosal injury is a significant factor in UC. Pyroptosis is a kind of programmed cell death induced by inflammatory caspases. Proteasome 20S subunit beta 5 (PSMB5) promotes cell viability. The purpose of this study was to determine the impact of PSMB5 on intestinal mucosal injury and to elucidate the underlying processes in dextran sulfate sodium- (DSS-) induced UC mice. Kunming (KM) mice received 3% DSS for 5 days to induce UC. We collected clinical symptoms, body weight, colon length, and histological changes. MDA (malondialdehyde) and SOD (superoxide dismutase) levels were determined using an ELISA assay. RT-PCR was used to assess the expression of IL-1β and IL-18. PSMB5 demonstrated a significant effect against UC by increasing body weight and colon length and decreasing DAI (disease activity index), colon macroscopic damage index (CMDI), histological injury scores, and reactive oxygen species (ROS), MDA, and SOD levels, thereby alleviating histopathological changes and inhibiting oxidative stress. HIEC-6 cells were exposed to lipopolysaccharide (LPS) condition with or without PSMB5, along with caspase-1 inhibitor (Z-VAD-FMK), NLRP3 inhibitor (MCC950), and ROS scavenger N-acetylcysteine (NAC). The viability of the cells, the release of lactate dehydrogenase (LDH), and intracellular ROS generation were determined using assay kits. Western blot analysis was used to determine the levels of NLRP3, ASC, cleaved caspase-1 (p20), pro-IL-1β, IL-1β, pro-IL-18, and IL-18. PSMB5 overexpression enhanced the inflammatory damage in LPS-treated HIEC-6 cells by activating the NLRP3 inflammasome and mediating pyroptosis, as demonstrated by increased LDH release and lower cell viability, as well as increased expression of NLRP3, ASC, cleaved caspase-1 (p20), IL-1, and IL-18. Meanwhile, NAC protected HIEC-6 cells from LPS-induced damage by reversing the activation of the NLRP3 inflammasome-mediated pyroptosis. In conclusion, PSMB5 may lower HIEC-6 cell susceptibility to LPS and ameliorate UC-induced HIEC-6 cell damage by decreasing ROS generation and hence inhibiting NLRP3-mediated pyroptosis.

Protective Effect of Dictyophora Polysaccharides on Sodium Arsenite-Induced Hepatotoxicity: A Proteomics Study

The purpose of this study is to understand the mechanism of sodium arsenite (NaAsO₂)-induced apoptosis of L-02 human hepatic cells, and how Dictyophora polysaccharide (DIP) protects L-02 cells from arsenic-induced apoptosis. The results revealed that DIP pretreatment inhibited NaAsO₂ induced L-02 cells apoptosis by increasing anti-apoptotic Bcl-2 expression and decreasing pro-apoptotic Bax expression. Proteomic analysis showed that arsenic treatment disrupted the expression of metabolism and apoptosis associated proteins, including ribosomal proteins (RPs). After pretreatment with DIP, the expression levels of these proteins were reversed or restored. For the first time, it was observed that the significant decrease of cytoplasmic RPs and the increase of mitochondrial RPs were related to human normal cell apoptosis induced by arsenic. This is also the first report that the protective effect of DIP on cells was related to RPs. The results highlight the relationship between RPs and apoptosis, as well as the relationship between RPs and DIP attenuating arsenic-induced apoptosis.