SFPQ is involved in regulating arsenic-induced oxidative stress by interacting with the miRNA-induced silencing complexes

Urolithin A attenuates hexavalent chromium-induced small intestinal injury by modulating PP2A/Hippo/YAP1 pathway

Hexavalent chromium (Cr(VI)) exposure has been linked with gastrointestinal toxicity, whereas the molecular pathways and key targets remain elusive. Computational toxicology analysis predicted the correlation between protein phosphatase 2A (PP2A) and genes regarding Cr(VI)-induced intestinal injury. Here, we generated a mouse model with intestinal epithelium-specific knock-out of Ppp2r1a (encoding PP2A Aα subunit) to investigate the mechanisms underlying Cr(VI)-induced small intestinal toxicity. Heterozygous mice (HE) and matched wild-type (WT) littermates were administrated with Cr(VI) at 0, 5, 20, 80 mg/L for 28 successive days. Cr(VI) treatment led to crypt hyperplasia, epithelial cell apoptosis, and intestinal barrier dysfunction, accompanied by the decline of goblet cell counts and Occludin expression in WT mice. Notably, these effects were aggravated in HE mice, indicating that PP2A Aα deficiency conferred mice with susceptibility to Cr(VI)-induced intestinal injury. Integrated data analysis and biological experiments revealed Cr(VI) exposure could decrease YAP1 phosphorylation at Ser127 but increase protein expression and activity, together with elevated TAZ protein driving epithelial crypt cells proliferation following damage, suggesting the involvement of Hippo/YAP1 signaling pathway in Cr(VI)-induced intestinal toxicity. Nevertheless, the enhanced phosphorylation of YAP1 in HE mice resulted in proliferation/repair defects in intestinal epithelium, thereby exacerbating Cr(VI)-induced gut barrier dysfunction. Notably, by molecular docking and further studies, we identified Urolithin A, a microbial metabolite, attenuated Cr(VI)-induced disruption of intestinal barrier function, partly by modulating YAP1 expression and activity. Our findings reveal the novel molecular pathways participated in Cr(VI)-caused small intestinal injury and urolithin A could potentially protect against environmental hazards-induced intestinal diseases.

The role of exosome-shuttled miRNAs in heavy metal-induced peripheral tissues and neuroinflammation in Alzheimer's disease

Heavy metal-induced neuroinflammation is a significant pathophysiologic mechanism in Alzheimer's disease (AD). Microglia-mediated neuroinflammation plays a crucial role in the pathogenesis of AD. Multiple miRNAs are differentially expressed in peripheral tissues after heavy metal exposure, and increasing evidence suggests that they are involved in AD progression by regulating microglial homeostasis. Exosomes, which are capable of loading miRNAs and crossing the bloodbrain barrier, serve as mediators of communication between peripheral tissues and the brain. In this review, we summarize the current evidence on the link between miRNAs in peripheral tissues and neuroinflammation in AD after heavy metal exposure and propose a role for miRNAs in the microglial neurodegenerative phenotype (MGnD) of AD. This study will help to elucidate the link between peripheral tissue damage and MGnD-mediated neuroinflammation in AD after heavy metal exposure. Additionally, we summarize the regulatory effects of natural compounds on peripheral tissue-derived miRNAs, which could be potential therapeutic targets for natural compounds to regulate peripheral tissue-derived exosomal miRNAs to ameliorate heavy metal-induced MGnD-mediated neuroinflammation in patients with AD after heavy metal exposure.

The Role of microRNAs in Arsenic-Induced Human Diseases: A Review

MicroRNAs (miRNAs) are noncoding RNAs with 20-22 nucleotides, which are encoded by endogenous genes and are capable of targeting the majority of human mRNAs. Arsenic is regarded as a human carcinogen, which can lead to many adverse health effects including diabetes, skin lesions, kidney disease, neurological impairment, male reproductive injury, and cardiovascular disease (CVD) such as cardiac arrhythmias, ischemic heart failure, and endothelial dysfunction. miRNAs can act as tumor suppressors and oncogenes via directly targeting oncogenes or tumor suppressors. Recently, miRNA dysregulation was considered to be an important mechanism of arsenic-induced human diseases and a potential biomarker to predict the diseases caused by arsenic exposure. Endogenic miRNAs such as miR-21, the miR-200 family, miR-155, and the let-7 family are involved in arsenic-induced human disease by inducing translational repression or RNA degradation and influencing multiple pathways, including mTOR/Arg 1, HIF-1α/VEGF, AKT, c-Myc, MAPK, Wnt, and PI3K pathways. Additionally, exogenous miRNAs derived from plants, such as miR-34a, miR-159, miR-2911, miR-159a, miR-156c, miR-168, etc., among others, can be transported from blood to specific tissue/organ systems in vivo. These exogenous miRNAs might be critical players in the treatment of human diseases by regulating host gene expression. This review summarizes the regulatory mechanisms of miRNAs in arsenic-induced human diseases, including cancers, CVD, and other human diseases. These special miRNAs could serve as potential biomarkers in the management and treatment of human diseases linked to arsenic exposure. Finally, the protective action of exogenous miRNAs, including antitumor, anti-inflammatory, anti-CVD, antioxidant stress, and antivirus are described.

A Novel Quinazoline Derivative Prevents and Treats Arsenic-Induced Liver Injury by Regulating the Expression of RecQ Family Helicase

Arsenic is a carcinogenic metalloid toxicant widely found in the natural environment. Acute or prolonged exposure to arsenic causes a series of damages to the organs, mainly the liver, such as hepatomegaly, liver fibrosis, cirrhosis, and even hepatocellular carcinoma. Therefore, it is imperative to seek drugs to prevent arsenic-induced liver injury. Quinazolines are a class of nitrogen heterocyclic compounds with biological and pharmacological effects in vivo and in vitro. This study was designed to investigate the ameliorating effects of quinazoline derivatives on arsenic-induced liver injury and its molecular mechanism. We investigated the mechanism of the quinazoline derivative KZL-047 in preventing and ameliorating arsenic-induced liver injury in vitro by cell cycle and apoptosis. We performed real-time fluorescence quantitative polymerase chain reaction (qPCR) and Western blotting combined with molecular docking. In vivo, the experiments were performed to investigate the mechanism of KZL-047 in preventing and ameliorating arsenic-induced liver injury using arsenic-infected mice. Physiological and biochemical indices of liver function in mouse serum were measured, histopathological changes in liver tissue were observed, and immunohistochemical staining was used to detect changes in the expression of RecQ-family helicases in mouse liver tissue. The results of in vitro experiments showed that sodium arsenite (SA) inhibited the proliferation of L-02 cells, induced apoptosis, blocked the cell cycle at the G1 phase, and decreased the expression of RecQ family helicase; after KZL-047 treatment in arsenic-induced L-02 cells, the expression of RecQ family helicase was upregulated, and the apoptosis rate was slowed, leading to the restoration of the cell viability level. KZL-047 inhibited arsenic-induced oxidative stress, alleviated oxidative damage and lipid peroxidation in vivo, and ameliorated arsenic toxicity-induced liver injury. KZL-047 restored the expression of RecQ family helicase proteins, which is consistent with the results of in vitro studies. In summary, KZL-047 can be considered a potential candidate for the treatment of arsenic-induced liver injury.

Exposure to enriched environment ameliorated chronic unpredictable mild stress-induced depression-like symptoms in rats via regulating the miR-92a-3p/kruppel-like factor 2 (KLF2) pathway

BACKGROUND

Silencing of miR-92a-3p may be beneficial in relieving depression of chronically stressed rats. The level of kruppel-like factor 2 (KLF2) was increased in the striatum of depressed rats after ketamine treatment. Enriched environment (EE) ameliorated depression-like behaviors in rats. However, the specific mechanism of EE treatment on depression induced by chronic unpredictable mild stress (CUMS) remains unclear.

METHODS

After CUMS-induced male Sprague Dawley rats were treated under EE or/and Adeno-Associated Virus (AAV)-miR-92a-3p, depression-like behaviors, cognitive ability, dendritic spine density, as well as levels of miR-92a-3p and KLF2 were detected by the behavioral tests, morris water maze test, Golgi staining, and quantitative real-time polymerase chain reaction (qRT-PCR) as needed. The body weight of rats was also measured. Next, primary hippocampal neurons were cultivated. The targeting relationship between miR-92a-3p and KLF2 was analyzed by TargetScan v7.2 and dual-luciferase reporter assay. After hippocampal neurons were transfected with miR-92a-3p mimic or/and overexpressed KLF2 vector, the cell viability, and apoptosis, together with the levels of KLF2, brain-derived neurotrophic factor (BDNF), phosphorylated (p)-tropomysin related kinase B (p-TrkB) and TrkB were determined by MTT assay, flow cytometry, qRT-PCR, and western blot as needed.

RESULTS

EE ameliorated CUMS-induced depression-like behaviors and cognitive ability, and elevated the neuronal dendritic spine density and KLF2 level, but reduced miR-92a-3p level in hippocampal tissues, while the above effects were reversed by AAV-miR-92a-3p. MiR-92a-3p mimic restrained cell viability, along with p-TrkB/ TrkB and BDNF levels, but promoted apoptosis in hippocampal neurons, which were reversed by overexpressed KLF2.

CONCLUSION

EE ameliorates CUMS-induced depression-like symptoms in rats via regulating the miR-92a-3p/KLF2 pathway.

Arsenic Induces Blood‒Brain Barrier Disruption and Regulates T Lymphocyte Subpopulation Differentiation in the Cerebral Cortex and Hippocampus Associated with the Nrf2 Pathway In Vivo

Increasing evidence has confirmed that the nervous system shows innate and adaptive immunity, which also participates in nerve damage. This study aimed to explore the neuroimmune imbalance induced by arsenic and its possible mechanism. Mice were exposed to NaAsO₂ (0, 5, 10, 25, and 50 mg/L) for 1 month by drinking water. Y-maze and Morris water maze tests revealed that arsenic impaired learning and memory. The optical density of Evans blue showed a marked dose-dependent increase in the brain, and the mRNA and protein levels of the BBB tight junctions (TJs), occludin at 25 and 50 mg/L arsenic, and claudin-5 at 50 mg/L arsenic, were markedly decreased in the cerebral cortex. Arsenic downregulated occludin and claudin-5 mRNA expression at 50 mg/L and protein expression at 25 and 50 mg/L in the hippocampus. Immunohistochemical staining showed that 50 mg/L arsenic increased corticocerebral and hippocampal CD3⁺ T, CD4⁺ T, and CD8⁺ T cells; CD4 and CD8 proteins were increased with 25 and 50 mg/L arsenic. Arsenic decreased the corticocerebral and hippocampal Th1, Th17, and regulatory Treg transcription factors T-bet, Rorγt, and Foxp3 and the cytokine IFN-γ, IL-17, and TGF-β mRNA levels and increased the Th2 transcription factor GATA3 and cytokine IL-4 mRNA levels. Moreover, arsenic enhanced the expression of nuclear factor E2-related factor (Nrf2) and its downstream enzymes heme oxygenase-1 (HO-1) and glutathione-S-transferase (GST). In conclusion, these results demonstrate that arsenic exposure induces BBB dysfunction and T lymphocyte infiltration and affects CD4⁺ T lymphocyte differentiation, which may be associated with Nrf2 activation.

Epigenetic modifications from arsenic exposure: A comprehensive review

Arsenic is a notorious element with the potential to harm exposed individuals in ways that include cancerous and non-cancerous health complications. Millions of people across the globe (especially in South and Southeast Asian countries including China, Vietnam, India and Bangladesh) are currently being unknowingly exposed to precarious levels of arsenic. Among the diverse effects associated with such arsenic levels of exposure is the propensity to alter the epigenome. Although a large volume of literature exists on arsenic-induced genotoxicity, cytotoxicity, and inter-individual susceptibility due to active research on these subject areas from the last millennial, it is only recently that attention has turned on the ramifications and mechanisms of arsenic-induced epigenetic changes. The present review summarizes the possible mechanisms involved in arsenic induced epigenetic alterations. It focuses on the mechanisms underlying epigenome reprogramming from arsenic exposure that result in improper cell signaling and dysfunction of various epigenetic components. The mechanistic information articulated from the review is used to propose a number of novel therapeutic strategies with a potential for ameliorating the burden of worldwide arsenic poisoning.

The Interplay of RNA Binding Proteins, Oxidative Stress and Mitochondrial Dysfunction in ALS

RNA binding proteins fulfil a wide number of roles in gene expression. Multiple mechanisms of RNA binding protein dysregulation have been implicated in the pathomechanisms of several neurodegenerative diseases including amyotrophic lateral sclerosis (ALS). Oxidative stress and mitochondrial dysfunction also play important roles in these diseases. In this review, we highlight the mechanistic interplay between RNA binding protein dysregulation, oxidative stress and mitochondrial dysfunction in ALS. We also discuss different potential therapeutic strategies targeting these pathways.

Association of low blood arsenic exposure with level of malondialdehyde among Chinese adults aged 65 and older

High environmental arsenic exposure can increase chronic oxidative stress in experimental studies and in occupational epidemiology studies. Many regulatory agencies have put forth arsenic exposure limits, it is still unclear that whether low environmental arsenic exposure was associated with adverse health outcome in general population. This study aimed to explore the association of low blood arsenic with malondialdehyde in community-dwelling older adults. We used a cross-sectional study of 2384 older adult individuals aged ≥65 years (mean age: 85 years) from the Healthy Aging and Biomarkers Cohort Study in 2017. The median blood arsenic level was 1.41 μg/L. High oxidative stress was categorized according to the 95th percentile of MDA levels (7.47 nmol/mL). Restricted cubic spline models showed that blood arsenic levels were positively associated with malondialdehyde levels (P < 0.01); and the risk of high oxidative stress was no longer significantly increased when blood arsenic level up to 8.74 μg/L. After adjusting for potential confounders, the odds ratios of high oxidative stress for the second, third, and fourth quartiles of blood arsenic were 2.35 (1.11-4.96), 3.87 (1.90-7.91), and 4.18 (2.00-8.72) (P_trend < 0.01), compared with the first quartile. We concluded that even low arsenic exposure was associated with higher risk of oxidative stress, in a nonlinear dose-response.

Application of the in vivo oxidative stress reporter Hmox1 as mechanistic biomarker of arsenic toxicity

Inorganic arsenic (iAs) is a naturally occurring metalloid present in drinking water and polluted air exposing millions of people globally. Epidemiological studies have linked iAs exposure to the development of numerous diseases including cognitive impairment, cardiovascular failure and cancer. Despite intense research, an effective therapy for chronic arsenicosis has yet to be developed. Laboratory studies have been of great benefit in establishing the pathways involved in iAs toxicity and providing insights into its mechanism of action. However, the in vivo analysis of arsenic toxicity mechanisms has been difficult by the lack of reliable in vivo biomarkers of iAs's effects. To address this issue we have applied the use of our recently developed stress reporter models to study iAs toxicity. The reporter mice Hmox1 (oxidative stress/inflammation; HOTT) and p21 (DNA damage) were exposed to iAs at acute and chronic, environmentally relevant, doses. We observed induction of the oxidative stress reporters in several cell types and tissues, which was largely dependent on the activation of transcription factor NRF2. We propose that our HOTT reporter model can be used as a surrogate biomarker of iAs-induced oxidative stress, and it constitutes a first-in-class platform to develop treatments aimed to counteract the role of oxidative stress in arsenicosis. Indeed, in a proof of concept experiment, the HOTT reporter mice were able to predict the therapeutic utility of the antioxidant N-acetyl cysteine in the prevention of iAs associated toxicity.

LncRNA H19-mediated M2 polarization of macrophages promotes myofibroblast differentiation in pulmonary fibrosis induced by arsenic exposure

Arsenic is a potent toxicant, and long-term exposure to inorganic arsenic causes lung damage. M2 macrophages play an important role in the pathogenesis of pulmonary fibrosis. However, the potential connections between arsenic and M2 macrophages in the development of pulmonary fibrosis are elusive. C57BL/6 mice were fed with drinking water containing 0, 10 and 20 ppm arsenite for 12 months. We have found that, in lung tissues of mice, arsenite, a biologically active form of arsenic, elevated H19, c-Myc, and Arg1; decreased let-7a; and caused pulmonary fibrosis. For THP-1 macrophages (THP-M) and bone-marrow-derived macrophages (BMDMs), 8 μM arsenite increased H19, c-Myc, and Arg1; decreased let-7a; and induced M2 polarization of macrophages, which caused secretion of the fibrogenic cytokine, TGF-β1. Down-regulation of H19 or up-regulation of let-7a reversed the arsenite-induced M2 polarization of macrophages. Arsenite-treated THP-M and BMDMs co-cultured with MRC-5 cells or primary lung fibroblasts (PLFs) elevated levels of p-SMAD2/3, SMAD4, α-SMA, and collagen I in lung fibroblasts and resulted in the activation of lung fibroblasts. Knockout of H19 or up-regulation of let-7a in macrophages reversed the effects. The results indicated that H19 functioned as an miRNA sponge for let-7a, which was involved in arsenite-induced M2 polarization of macrophages and induced the myofibroblast differentiation phenotype by regulation of c-Myc. In the sera of arseniasis patients, levels of hydroxyproline and H19 were higher, and levels of let-7a were lower than levels in the controls. These observations elucidate a possible mechanism for arsenic exposure-induced pulmonary fibrosis.

Glycochenodeoxycholic acid impairs transcription factor E3 -dependent autophagy-lysosome machinery by disrupting reactive oxygen species homeostasis in L02 cells

Cholestasis represents pathophysiologic syndromes defined as impaired bile flow from the liver. As an outcome, bile acids accumulate and promote hepatocyte injury, followed by liver cirrhosis and liver failure. Glycochenodeoxycholic acid (GCDCA) is relatively toxic and highly concentrated in bile and serum after cholestasis. However, the mechanism underlying GCDCA-induced hepatotoxicity remains unclear. In this study, we found that GCDCA inhibits autophagosome formation and impairs lysosomal function by inhibiting lysosomal proteolysis and increasing lysosomal pH, contributing to defects in autophagic clearance and subsequently leading to the death of L02 human hepatocyte cells. Notably, through tandem mass tag (TMT)-based quantitative proteomic analysis and database searches, 313 differentially expressed proteins were identified, of which 71 were increased and 242 were decreased in the GCDCA group compared with those in the control group. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that GCDCA suppressed the signaling pathway of transcription factor E3 (TFE3), which was the most closely associated with autophagic flux impairment. In contrast, GCDCA-inhibited lysosomal function and autophagic flux were efficiently attenuated by TFE3 overexpression. Specifically, the decreased expression of TFE3 was closely related to the disruption of reactive oxygen species (ROS) homeostasis, which could be prevented by inhibiting intracellular ROS with N-acetyl cysteine (NAC). In summary, our study is the first to demonstrate that manipulation of ROS/TFE3 signaling may be a therapeutic approach for antagonizing GCDCA-induced hepatotoxicity.