Cadmium contributes to cardiac metabolic disruption by activating endothelial HIF1A-GLUT1 axis.

Cadmium (Cd) is an environmental risk factor of cardiovascular diseases. Researchers have found that Cd exposure causes energy metabolic disorders in the heart decades ago. However, the underlying molecular mechanisms are still elusive. In this study, male C57BL/6 J mice were exposed to cadmium chloride (CdCl2) through drinking water for 4 weeks. We found that exposure to CdCl2 increased glucose uptake and utilization, and disrupted normal metabolisms in the heart. In vitro studies showed that CdCl2 specifically increased endothelial glucose uptake without affecting cardiomyocytic glucose uptake and endothelial fatty acid uptake. The glucose transporter 1 (GLUT1) as well as its transcription factor HIF1A was significantly increased after CdCl2 treatment in endothelial cells. Further investigations found that CdCl2 treatment upregulated HIF1A expression by inhibiting its degradation through ubiquitin-proteasome pathway, thereby promoted its transcriptional activation of SLC2A1. Administration of HIF1A small molecule inhibitor echinomycin and A-485 reversed CdCl2-mediated increase of glucose uptake in endothelial cells. In accordance with this, intravenous injection of echinomycin effectively ameliorated CdCl2-mediated metabolic disruptions in the heart. Our study uncovered the molecular mechanisms of Cd in contributing cardiac metabolic disruption by inhibiting HIF1A degradation and increasing GLUT1 transcriptional expression. Inhibition of HIF1A could be a potential strategy to ameliorate Cd-mediated cardiac metabolic disorders and Cd-related cardiovascular diseases.

Dihydroartemisinin protects blood-brain barrier permeability during sepsis by inhibiting the transcription factor SNAI1.

Blood-brain barrier (BBB) injury is involved in the pathogenesis of sepsis-associated encephalopathy. In this study, we used dihydroartemisinin (DHA), a derivative of artemisinin, to treat a cecal ligation and puncture (CLP)-induced mouse sepsis model and a tumour necrosis factor α (TNF-α)-stimulated human cerebral microvessel endothelial cells (hCMEC)/D3 cell line. We found that DHA decreased BBB permeability and increased the expression of the tight junction protein occludin (OCLN) in the CLP model. In hCMEC/D3 cells, DHA decreased TNF-α-induced hyperpermeability and increased the expression of OCLN. DHA also repressed SNAI1 expression in the CLP mouse model and in TNF-α-stimulated hCMEC/D3 cells. These data suggest that DHA protects BBB permeability during sepsis by stimulating the expression of OCLN, by downregulating the expression of the SNAI1 transcription factor.

Erg mediates downregulation of claudin-5 in the brain endothelium of a murine experimental model of cerebral malaria.

Cerebral malaria (CM) is a severe complication with brain vascular hyperpermeability. Claudin-5 is the major component of tight junctions. To investigate the expression of claudin-5 in CM, we established a murine experimental cerebral malaria (ECM) model and an in vitro model by treating murine brain endothelial cells (bEnd3) with plasma from ECM mice. Expression of claudin-5 and the ETS transcription factor Erg was reduced in the brain endothelium of ECM mice. In bEnd3 cells exposed to ECM plasma, decreased expression of claudin-5 and Erg, and increased permeability were observed. Silencing of Erg significantly reduced Cldn5 expression. ChIP assays indicated that Erg binds to the -813 ETS motif of the murine Cldn5 gene promoter, and the binding is decreased by treatment with ECM plasma.

Cadmium regulates von Willebrand factor and occludin expression in glomerular endothelial cells of mice in a TNF-α-dependent manner.

BACKGROUND: Cadmium (Cd) is an environmental pollutant that leads to nephrotoxicity. However, the mechanisms of Cd-induced glomerular injury have not been fully clarified. Von Willebrand factor (vWF) and occludin are important endothelial cell markers in renal vasculature. In this study, the effects of Cd on the vWF and occludin expression in mouse glomeruli was investigated. OBJECTIVES: The goal of this study was to analyze the expression of von Willebrand factor and occludin in glomerular endothelial cells of tumor necrosis factor-α-/- (TNF-α-/-) mice after treatment with Cd. MATERIAL AND METHODS: C57BL6/J wild-type (WT) mice and TNF-α-/- mice (n = 6) were treated with Cd, and the kidney tissues were collected. The expression of von Willebrand factor and occludin was detected by using quantitative real-time PCR, immunofluorescence, and immunohistochemistry. In vitro, Human umbilical vascular endothelial cells (HUVECs) were used to examine the regulatory role of TNF-α on expression of von Willebrand factor and occludin. RESULTS: We found that Cd significantly increases mRNA and protein expressions of von Willebrand factor and occludin in TNF-α-/- mice, but not in WT mice. In vitro, Cd significantly increased mRNA and protein expression of von Willebrand factor and occludin in HUVECs with TNF-α small interfering RNA (siRNA) transfection. CONCLUSIONS: These results suggest that TNF-α acts to balance homeostasis of glomerular endothelium after Cd treatments.

Endoglin-targeted contrast-enhanced ultrasound imaging in hepatoblastoma xenografts.

Angiogenesis is required for the growth of hepatoblastoma (HB). In the present study, an ultrasonic contrast agent, microbubbles (MB), was combined with an endoglin antibody, and then injected into nude mice with HB. This was conducted to detect specific binding to microvessels via non-linear harmonic imaging for tumor angiogenesis assessment. In addition, endoglin expression in experimental animals was measured using western blotting, reverse transcription-quantitative polymerase chain reaction and immunohistochemistry. In vitro, human umbilical vein endothelial cells (HUVECs) were co-cultured with conditioned media collected from HepG2 cells. Western blotting and reverse transcription-quantitative PCR was performed to detect the changes of endoglin expression. In targeted ultrasound imaging, it was determined that the differential targeted enhancement of MBendoglin was significantly higher than that of MBisotype. Over expression of endoglin was identified in the tumor of experimental nude mice; however, it was not present in the liver of the mice. Endoglin expression in HUVECs was significantly increased by co-culture with the conditioned media of HepG2 cells; therefore, the results suggest that endoglin is upregulated in angiogenic vessels in the HepG2 cell xenografts in nude mice. Thus, endoglin-targeted ultrasound imaging is presented as a potential approach for the diagnosis of liver carcinoma.

Ascorbic acid promotes 3T3-L1 cells adipogenesis by attenuating ERK signaling to upregulate the collagen VI.

BACKGROUND: Type VI collagen is supposed to be a regulation factor in adipogenesis. This study aimed to assess the promoting effect of vitamin C (VC) on adipogenic differentiation of preadipocytes as well as its mechanism. METHODS: Five sets of different combinations of chemicals were used to inhibit synthesis of type I to VI collagens, blocking ERK1/2 phosphorylation during adipogenesis of 3T3-L1 preadipocytes. Furthermore, to explore whether collagen VI plays a critical role during adipogenesis, specific knockdown of collagen VI was performed by using RNA interference. The morphology and expression patterns of several target factors involved in adipogenesis were assessed at various time points. RESULTS: A reduction in ERK1/2 phosphorylation and an increase in collagen VI and adipogenic-specific factors, such as C/EBPß, PPARγ and C/EBPα, were observed after treating adipogenic 3T3-L1 cells with AA2P, a stable derivative of VC. Inhibition of collagen synthesis by ethyl-3, 4-dihydroxybenzoate (EDHB) or by specific knockdown of collagen VI by RNAi could promote ERK1/2 phosphorylation. The ERK1/2 phosphorylation in both cases could be attenuated by AA2P treatment. In addition, the inhibition of ERK1/2 phosphorylation by U0126, a highly selective inhibitor of both MEK1 and MEK2 and a type of MAPK/ERK kinase, up-regulated the expression of collagen VI, while it down-regulated the adipogenic-specific factors. CONCLUSION: AA2P could up-regulate the expression of collagen VI by attenuating ERK1/2 phosphorylation, further up-regulating adipocyte-specific factors, thus finally promoting the adipogenesis of 3T3-L1 preadipocytes.