Role of Pigment Epithelium-Derived Factor in Arsenic-Induced Vascular Endothelial Dysfunction in a Rat Model

AMPKα is active in autophagy of endothelial cells in arsenic-induced vascular endothelial dysfunction by regulating mTORC1/p70S6K/ULK1

Cardiovascular disease (CVD) is the most common cause of death, environmental factors, such as arsenic, playing an important role in the progress of CVD. Vascular endothelial dysfunction (VED) is a crucial early feature for CVD, inorganic arsenic (iAs) can induce autophagy in various cells. However, the role of endothelial autophagy has rarely been studied in VED triggered by arsenic. Total of one hundred and twenty healthy male C57BL/6J mice weighing 18-22 g were randomly divided into an arsenic-exposure group and a control group for 3, 6, 9, and 12 weeks. The results showed that, independent of the exposure period, autophagy markers of p-ATG16L1 levels and Beclin 1 contents in the aortic arch endothelium increased significantly compared with those of the corresponding control group. And different exposure duration decreased NO contents in the serum significantly. Combined with the histological changes that endothelial injury aggravated gradually with the increasing exposure period, suggesting that under exposure to iAs over 9 weeks, VED was remarkably induced, and consistant high levels of endothelial autophagy may play an important role. Additionally, levels of p-AMPKα/AMPKα increased significantly and p-mTORC1/mTORC1 levels decreased remarkably in the aortic arch endothelium. Then, a NaAsO2-induced-VED in vitro model was used to explore the mechanism of arsenic-induced endothelial autophagy. Similarly, p-AMPKα/AMPKα level significantly increased, and p-mTORC1/mTORC1 level remarkably decreased induced by 30 μmol/L NaAsO2 in HUAECs. Further, an AMPK inhibitor (Compound C) pre-treatment prior to arsenic exposure reversed the increased autophagy level, and alleviated the endothelial dysfunction in HUVECs, as shown by the significant increase in the intracellular NO content and the cell vitality. Mechanistically, we revealed that AMPKα is active in autophagy of endothelial cells in arsenic-induced VED by regulating mTORC1/p70S6K/ULK1. The present study provide a new promising target for prevention and control arsenic-associated CVD.

Subchronic Arsenite Exposure Induced Atrophy and Erythropoietin Sensitivity Reduction in Skeletal Muscle Were Relevant to Declined Serum Melatonin Levels in Middle-Aged Rats

Arsenic is a kind of widespread environmental toxicant with multiorgan-toxic effects, and arsenic exposure is associated with the occurrence and development of many chronic diseases. The influence of environmental arsenic exposure on skeletal muscle, which is a vital organ of energy and glucose metabolism, has received increasing attention. This study aimed to investigate the types of inorganic arsenic-induced skeletal muscle injury, and the potential regulatory effects of melatonin (MT) and erythropoietin (EPO) in young (3-month-old) and middle-aged (12-month-old) rats. Our results showed that 1 mg/L sodium arsenite exposure for 3 months could accelerate gastrocnemius muscle atrophy and promote the switch of type II fibers to type I fibers in middle-aged rats; however, it did not cause significant pathological changes of gastrocnemius muscle in young rats. In addition, arsenite could inhibit serum MT levels, and promote serum EPO levels but inhibit EPO receptor (EPOR) expression in gastrocnemius muscle in middle-aged rats, while serum MT levels and EPOR expression in gastrocnemius muscle showed an opposite effect in young rats. Importantly, exogenous MT antagonized the arsenite-induced skeletal muscle toxic effect and restored serum EPO and gastrocnemius muscle EPOR expression levels in middle-aged rats. There was a positive correlation among gastrocnemius muscle index, serum MT level, and gastrocnemius muscle EPOR protein level in arsenite-exposed rats. This study demonstrated that inorganic arsenic could accelerate skeletal muscle mass loss and type II fiber reduction in middle-aged rats, which may be related to decreased MT secretion and declined EPO sensitivity in skeletal muscle.

Arsenic-Induced, Mitochondria-Mediated Apoptosis Is Associated with Decreased Peroxisome Proliferator-Activated Receptor γ Coactivator α in Rat Brains

Chronic exposure to arsenic in drinking water damages cognitive function, and nerve cell apoptosis is one of the primary characteristics. The damage to mitochondrial structure and/or function is one of the main characteristics of apoptosis. Peroxisome proliferator-activated receptor γ coactivator α (PGC-1α) is involved in the regulation of mitochondrial biogenesis, energy metabolism, and apoptosis. In this study, we aimed to study the role of PGC-1α in sodium arsenite (NaAsO₂)-induced mitochondrial apoptosis in rat hippocampal cells. We discovered that increased arsenic-induced apoptosis in rat hippocampus increased with NaAsO₂ (0, 2, 10, and 50 mg/L, orally via drinking water for 12 weeks) exposure by TUNEL assay, and the structure of mitochondria was incomplete and swollen and had increased lysosomes, lipofuscins, and nuclear membrane shrinkage observed via transmission electron microscopy. Furthermore, NaAsO₂ reduced the levels of Bcl-2 and PGC-1α and increased the levels of Bax and cytochrome C expression. Moreover, correlation analysis showed that brain arsenic content was negatively correlated with PGC-1α levels and brain ATP content; PGC-1α levels were negatively correlated with apoptosis rate; and brain ATP content was positively correlated with PGC-1α levels, but no significant correlation between ATP content and apoptosis has been observed in this study. Taken together, the results of this study indicate that NaAsO₂-induced mitochondrial pathway apoptosis is related to the reduction of PGC-1α, accompanied by ATP depletion.

The mechanism of low-level arsenic exposure-induced hypertension: Inhibition of the activity of the angiotensin-converting enzyme 2

It is now well-established that arsenic exposure induces hypertension in humans. Although arsenic-induced hypertension is reported in many epidemiological studies, the underlying molecular mechanism of arsenic-induced hypertension is not fully characterized. In the human body, blood pressure is primarily regulated by a well-known physiological system known as the renin-angiotensin system (RAS). Hence, we explored the potential molecular mechanisms of arsenic-induced hypertension by investigating the regulatory roles of the RAS. Adult C57BL/6JJcl male mice were divided into four groups according to the concentration of arsenic in drinking water (0, 8, 80, and 800 ppb) provided for 8 weeks. Arsenic significantly raised blood pressure in arsenic-exposed mice compared to the control group, and significantly raised plasma MDA and Ang II and reduced Ang (1-7) levels. RT-PCR results showed that arsenic significantly downregulated ACE2 and MasR in mice aortas. In vitro studies of endothelial HUVEC cells treated with arsenic showed increased level of MDA and Ang II and lower levels of Ang (1-7), compared with the control. Arsenic significantly downregulated ACE2 and MasR expression, as well as those of Sp1 and SIRT1; transcriptional activators of ACE2, in HUVECs. Arsenic also upregulated markers of endothelial dysfunction (MCP-1, ICAM-1) and inflammatory cytokines (IL-6, TNF-α) in HUVECs. Our findings suggest that arsenic-induced hypertension is mediated, at least in part, by oxidative stress-mediated inhibition of ACE2 as well as by suppressing the vasoprotective axes of RAS, in addition to the activation of the classical axis.

The molecular mechanism of Ang II induced-AAA models based on proteomics analysis in ApoE-/- and CD57BL/6J mice

Apolipoprotein knockout (ApoE^-/-) and CD57BL/6J mouse models of angiotensin II (Ang II)-induced abdominal aortic aneurysm (AAA) are commonly used in AAA research. However, the similarities and differences in the molecular mechanisms of AAA in these two genotypes have not been reported. In our study, we analyzed proteomics data from ApoE^-/- and CD57BL/6J mouse models of Ang II-induced AAA and control mice by LC-MS/MS. Gene set enrichment analysis (GSEA) of differentially abundance proteins (DAPs) in the ApoE^-/- or CD57BL/6J mouse groups was performed in R software, and infiltration of immune cells in groups was assessed. DAP that showed the same trend in abundance in ApoE^-/- and CD57BL/6J mice (S-DAP) were identified and subjected to GO enrichment, KEGG pathway, and connectivity map (CMap) analyses. The protein-protein interaction (PPI) network of the S-DAP was drawn, the key S-DAP were identified by MCODE, and the transcription factors (TFs) of crucial S-DAP were predicted by iRegulon in Cytoscape. Male ApoE^-/- and CD57BL/6J mouse models of Ang II-induced AAA are commonly used in AAA research, and extracellular matrix organization is associated with AAA in both of these models. However, there are some differences between the mechanisms underlying AAA in these two genotypes, and these differences need to be considered when studying AAA and selecting models. SIGNIFICANCE: Our research provided the first insight into the similarity and differential mechanisms of Ang II infused AAA models using ApoE^-/- and CD57BL/6J mice. This study might provide the some advises for the selection of Ang II infused AAA models for further AAA researches.

Pigment epithelium-derived factor (PEDF) ameliorates arsenic-induced vascular endothelial dysfunction in rats and toxicity in endothelial EA.hy926 cells

Although the harmful effects of arsenic exposure on the cardiovascular system have received great attention, there is still no effective treatment. Vascular endothelial dysfunction (VED) is the initial step of cardiovascular diseases, where pigment epithelium-derived factor (PEDF) plays an important role in maintaining endothelial function. Here, we explored the protective role of PEDF in VED induced by arsenic, and its underlying molecular mechanism, designing an in vivo rat model of arsenic exposure recovery and in vitro endothelial EA. hy926 cell-based assays. The edema of aortic endothelial cells in rats significantly improved during recovery from arsenite exposure compared with rats exposed to 10 and 50 mg/L arsenite continuously. In addition, serum levels of nitric oxide (NO), von Willebrand factor, and nitric oxide synthase (inducible and total activities) in rats, which were greatly affected by arsenite exposure, returned to levels similar to those in the control group after recovery with distilled water. The recovery from arsenite exposure was associated with increased levels of PEDF; decreased protein levels of Fas, FasL, P53, and phospho-p38; and inhibited apoptosis in aortic endothelial cells in vivo. Recombinant human PEDF treatment (100 nM) prevented the toxic effects of arsenite (50 μM) on endothelial cells in vitro by increasing NO content, decreasing reactive oxygen species (ROS) levels, and inhibiting apoptosis, as well as increasing cell viability and decreasing levels of P53 and phospho-p38. Our findings suggest that PEDF protects endothelial cells from arsenic-induced VED by increasing NO release and inhibiting apoptosis, where P53 and p38MAPK are its main targets.