Cadmium induces N-cadherin cleavage via ERK-mediated γ-secretase activation in C6 astroglia cells

Hypoxia response element-directed expression of bFGF in dental pulp stem cells improve the hypoxic environment by targeting pericytes in SCI rats

Cell-based transplantation strategies possess great potential for spinal cord injury (SCI) repair. Basic fibroblast growth factor (bFGF) has been reported to have multiple neuro-promoting effects on developing and adult nervous system of mammals and considered a promising therapy for nerve injury following SCI. Human dental pulp stem cells (DPSCs) are abundant stem cells with low immune rejection, which can be considered for cell replacement therapy. The purpose of this study was to investigate the roles of DPSCs which express bFGF under the regulation of five hypoxia-responsive elements (5HRE) using an adeno-associated virus (AAV-5HRE-bFGF-DPSCs) in SCI repairing model. In this study, DPSCs were revealed to differentiate into CD13⁺ pericytes and up-regulate N-cadherin expression to promote the re-attachment of CD13⁺ pericytes to vascular endothelial cells. The re-attachment of CD13⁺ pericytes to vascular endothelial cells subsequently increased the flow rate of blood in microvessels via the contraction of protuberance. As a result, increased numbers of red blood cells carried more oxygen to the damaged area and the local hypoxia microenvironment in SCI was improved. Thus, this study represents a step forward towards the potential use of AAV-5HRE-bFGF-DPSCs in SCI treatment in clinic.

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) 5HRE-bFGF-DPSCs secrete bFGF in a hypoxia dependent manner, making the administration more precise.

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CD13+ pericyte regulate vascular diameter and promote the recovery of hypoxia microenvironment via DDC-5HT-5HT-1B in SCI.

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5HRE-bFGF-DPSCs can differentiate into CD13+ pericyte to compensate for the mass death of CD13+ pericyte after SCI.

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5HRE-bFGF-DPSCs promote CD13+ pericyte adhesion to vascular endothelial cell by secreting bFGF through N-cadherin.

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5HRE-bFGF-DPSCs promote the recovery of SCI by restoring hypoxic microenvironment and inhibit autophagy pathway.

Cadmium induces epithelial-mesenchymal transition and migration of renal cancer cells by increasing PGE2 through a cAMP/PKA-COX2 dependent mechanism

Environmental or occupational exposure of Cadmium (Cd) is concerned to be a threat to human health. The kidney is main target of Cd accumulation, which increases the risk of renal cell carcinoma (RCC). In addition, low content of Cd had been determined in kidney cancer, however, the roles of presence of Cd in renal tumors progression are still unclear. The present study is proposed to determine the effect of low-dose Cd exposure on the renal cancer cells and aimed to clarify the underlying mechanisms. The cell viability, cytotoxicity, and the migratory effect of low-dose Cd on the renal cancer cells were detected. Moreover, the roles of reactive oxygen species (ROS), Ca²⁺, and cyclic AMP (cAMP)/protein kinase A (PKA)-cyclooxygenase2 (COX2) signaling, as well as COX2 catalytic product prostaglandin E2 (PGE2) on cell migration and invasion were identified. Our results suggested that low dose Cd exposure promoted migration of renal cancer Caki-1 cells, which was not dependent on Cd-induced ROS and intracellular Ca²⁺ levels. Cd exposure induced cAMP/PKA-COX2, which mediated cell migration and invasion, and decreased expressions of epithelial-mesenchymal transition (EMT) marker, E-cadherin, but increased expressions of N-cadherin and Vimentin. Moreover, Cd-induced secretion of PGE2 feedback on activation of cAMP/PKA-COX2 signaling, also promoted EMT, migration and invasion of renal cancer Caki-1 cells. This study might contribute to understanding of the mechanism of Cd-induce progression of renal cancer and future studies on the prevention and therapy of renal cell carcinomas.

Involvement of ADAM10 in acrolein-induced astrocytic inflammation

Acrolein is a neurotoxin produced through lipid peroxidation in the brain affected by ischemic stroke, which results in neuronal cell injury and inflammation. However the mechanism underlying acrolein-induced brain inflammation remains unclear. Therefore we examined how acrolein leads to astrocytic inflammation. It was found that acrolein increased the levels of NLRP3 and cleaved caspase-1, which led to the maturation of interleukin-1β (IL-1β). ELISA assay results, which showed that acrolein increased the secreted IL-1β, further supported acrolein-induced astrocytic inflammation. Acrolein increased ADAM10 protein levels and the cleavage of N-cadherin. The ADAM10 inhibitor, GI 254023X blocked N-cadherin cleavage by acrolein, suggesting that ADAM10 is an upstream of N-cadherin. Furthermore, we found that acrolein activated p38 MAPK and NF-κB p65, while pretreatment with p38 MAPK inhibitor, SB203580 and GI 254023X inhibited NF-κB p65 activation and NLRP3 inflammasome. This suggests that p38 MAPK mediates the activation of NF-κB p65, which is associated with NLRP3 expression. Finally, we showed that acrolein induced cell toxicity and decrease of EAAT1 expression, suggesting that acrolein may induce a loss of glutamate uptake function. In conclusion, we demonstrate that acrolein induces astrocytic inflammation through NLRP3 inflammasome, which is regulated by ADAM10 and attributed to p38 MAPK-activated NF-κB p65 activity.

Different Regulation of p53 Expression by Cadmium Exposure in Kidney, Liver, Intestine, Vasculature, and Brain Astrocytes

Chronic exposure to cadmium (Cd) is known to adversely affect renal function. Our previous studies indicated that Cd induces p53-dependent apoptosis by inhibiting gene expression of the ubiquitin-conjugating enzyme (Ube) 2d family in both human and rat proximal tubular cells. In this study, the effects of Cd on protein expression of p53 and apoptotic signals in the kidney and liver of mice exposed to Cd for 12 months were examined, as well as the effects of Cd on p53 protein levels and gene expression of the Ube2d family in various cell lines. Results showed that in the kidney of mice exposed to 300 ppm Cd for 12 months, there was overaccumulation of p53 proteins in addition to the induction of apoptosis, which was triggered specifically in the proximal tubules. Interestingly, the site of apoptosis was the same as that of p53 accumulation in the proximal tubules. In the liver of mice chronically exposed to Cd, gene expression of the Ube2d family tended to be slightly decreased, together with slight apoptosis without the accumulation of p53 protein. In rat small intestine epithelial (IEC-6) cells, Cd decreased not only the p53 protein level but also gene expression of Ube2d1, Ube2d2 and Ube2d4. In human brain microvascular endothelial cells (HBMECs), Cd did not suppress gene expression of the Ube2d family, but increased the p53 protein level. In human brain astrocytes (HBASTs), Cd only increased gene expression of UBE2D3. These results suggest that Cd-induced apoptosis through p53 protein is associated with renal toxicity but not hepatic toxicity, and the modification of p53 protein by Cd may vary depending on cell type.

Calcium Signaling Involvement in Cadmium-Induced Astrocyte Cytotoxicity and Cell Death Through Activation of MAPK and PI3K/Akt Signaling Pathways

Cadmium (Cd), a highly ubiquitous toxic heavy metal, can contaminate the environment, including agricultural soil, water and air, via industrial runoff and other sources of pollution. Cd accumulated in the body via direct exposure or through the food chain results in neurodegeneration and many other diseases. Previous studies on its toxicity in the central nervous system (CNS) focused mainly on neurons. To obtain a more comprehensive understanding of Cd toxicity for the CNS, we investigated how astrocytes respond to acute and chronic Cd exposure and its toxic molecular mechanisms. When primary cultures of cerebral cortical astrocytes incubated with 1-300 μM CdCl2, morphological changes, LDH release and cell death were observed in a time and dose-dependent manner. Further studies demonstrated that acute and chronic Cd treatment phosphorylated JNK, p38 and Akt to different degrees, while ERK1/2 was only phosphorylated under low doses of Cd (10 μM) exposure. Inhibition of JNK and PI3K/Akt, but not of p38, could partially protect astrocyte from cytotoxicity in chronic and acute Cd exposure. Moreover, Cd also induced a strong calcium signal, while BAPTA, a specific intracellular calcium (Ca(2+)) chelator, prevented Cd-induced intracellular increase of calcium levels in astrocytes; inhibited the Cd-induced activation of ERK1/2, JNK, p38 and Akt; and also significantly reduced astrocyte cell death. All of these results suggested that the Cd-Ca(2+)-MAPK and PI3K/Akt signaling pathways were involved in Cd-induced toxicity in astrocytes. This toxicity involvement indicates that these pathways may be exploited as a target for the prevention of Cd-induced neurodegenerative diseases.

Dysregulation of nectin-2 in the testicular cells: an explanation of cadmium-induced male infertility

Nectin-2, a junction molecule, is found at the basal and apical ectoplasmic specializations (ES) for the formation of the blood-testis barrier (BTB) (constituted by tight junctions and basal ES) and Sertoli-spermatid adhesion. Loss of nectin-2 causes male infertility, suggesting nectin-2-based ES is crucial for spermatogenesis. Cadmium (Cd) has been known to induce severe testicular injury. Recent evidence has shown that the basal ES at the BTB and apical ES are the targets of Cd, suggesting that unique junction protein at the ES may explain why testis is more susceptible than other tissues. Since nectin-2 is expressed exclusively at the ES, it is highly possible that nectin-2 is the direct target of Cd. In this study, we investigate if nectin-2 is the target protein of Cd toxicity and the mechanism on how Cd down-regulates nectin-2 to achieve ES disruption. Our results revealed that Cd suppresses nectin-2 at transcriptional and post-translational levels. Inhibitor and shRNA knockdown have shown that Cd induces nectin-2 protein degradation via clathrin-dependent endocytosis. Immunofluorescence staining and endocytosis assays further confirmed that nectin-2 internalization is promoted upon Cd treatment. Besides, Cd directly represses nectin-2 transcription. EMSA and ChIP assays showed that Cd inhibits the binding of positive regulators to nectin-2 promoter. siRNA and overexpression analyses have demonstrated that Cd reduces the expression and binding affinity of positive regulators for transcription. Taken together, nectin-2 is the direct molecular target of Cd and its disruptive effects are mediated via direct repressing nectin-2 transcription and endocytosis of nectin-2 for degradation.

Polish natural bee honeys are anti-proliferative and anti-metastatic agents in human glioblastoma multiforme U87MG cell line

Honey has been used as food and a traditional medicament since ancient times. However, recently many scientists have been concentrating on the anti-oxidant, anti-proliferative, anti-inflammatory and other properties of honey. In this study, we investigated for the first time an anticancer effect of different honeys from Poland on tumor cell line - glioblastoma multiforme U87MG. Anti-proliferative activity of honeys and its interferences with temozolomide were determined by a cytotoxicity test and DNA binding by [H³]-thymidine incorporation. A gelatin zymography was used to conduct an evaluation of metalloproteinases (MMP-2 and MMP-9) expression in U87MG treatment with honey samples. The honeys were previously tested qualitatively (diastase activity, total phenolic content, lead and cadmium content). The data demonstrated that the examined honeys have a potent anti-proliferative effect on U87MG cell line in a time- and dose-dependent manner, being effective at concentrations as low as 0.5% (multifloral light honey - viability 53% after 72 h of incubation). We observed that after 48 h, combining honey with temozolomide showed a significantly higher inhibitory effect than the samples of honey alone. We observed a strong inhibition of MMP-2 and MMP-9 for the tested honeys (from 20 to 56% and from 5 to 58% compared to control, respectively). Our results suggest that Polish honeys have an anti-proliferative and anti-metastatic effect on U87MG cell line. Therefore, natural bee honey can be considered as a promising adjuvant treatment for brain tumors.

HBx protein promotes oval cell proliferation by up-regulation of cyclin D1 via activation of the MEK/ERK and PI3K/Akt pathways

Growing evidence has shown that hepatic oval cells, also named liver progenitor cells, play an important role in the process of liver regeneration in various liver diseases. Oval cell proliferation has been reported in hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC) and chronic liver disease. Studies have found expression of HBV surface and core antigens in oval cells in the livers of patients with HCC, suggesting that HBV infection of oval cells could be a mechanism of human hepatocarcinogenesis. In addition, there is evidence of multiplication of HBV in oval cell culture. However, little research has been performed to explore the role of HBV-encoded proteins in the proliferation of hepatic oval cells. Previously, we successfully transfected the HBV x (HBx) gene, one of the four genes in the HBV genome, into a rat LE/6 oval cell line. In this study, we tested whether or not the transfected HBx gene could affect oval cell proliferation in vitro. Our results show that overexpression of HBx promotes the proliferation of oval cells and increases cyclin D1 expression, assessed at both the mRNA and protein levels. We also found that HBx activated the PI-3K/Akt and MEK/ERK1/2 pathways in HBx-transfected oval cells. Furthermore, the HBx-induced increases in cyclin D1 expression and oval cell proliferation were completely abolished by treatment with either MEK inhibitor PD184352 or PI-3K inhibitor LY294002. These results demonstrated that HBx has the ability to promote oval cell proliferation in vitro, and its stimulatory effects on cell proliferation and expression of cyclin D1 depend on the activation of the MEK/ERK and PI3K/Akt signaling pathways in cultured oval cells.