Bromodichloromethane induces cell proliferation in different tissues of male F344 rats by suppression of E-cadherin expression via hypermethylation or transcriptional activation of c-myc and cyclin D1

Sphingosine-1-phosphate promotes pulmonary artery smooth muscle cells proliferation by stimulating autophagy-mediated E-cadherin/CDH1 down-regulation

It has been shown that sphingosine-1-phosphate (S1P) is elevated in patients with pulmonary arterial hypertension (PAH) and promotes the proliferation of pulmonary artery smooth muscle cells (PASMCs). Meanwhile, S1P has been found to induce the activation of autophagy in several types of human diseases including cancers. However, it is still unclear whether activation of autophagy mediates S1P-induced PASMCs proliferation, and detailed mechanisms responsible for these processes are indefinite. The aims of this study are to address these issues. S1P dose- and time-dependently reduced the expression of E-cadherin/CDH1 and stimulated PASMCs proliferation; this was accompanied with the elevation of TNF receptor-associated factor 2 (TRAF2), up-regulation and ubiquitination of BECN1 and the activation of autophagy. Prior silencing TRAF2 or BECN1 using siRNA or pre-incubation of cells with autophagy inhibitor chloroquine phosphate (CQ) suppressed S1P-induced autophagy activation and subsequent CDH1 degradation and further PASMCs proliferation. Taken together, our study indicates that S1P promotes the activation of autophagy by accelerating TRAF2-mediated BECN1 up-regulation and ubiquitination, which in turn results in CDH1 reduction and contributes to PASMCs proliferation.

Dynamic changes of global DNA methylation and hypermethylation of cell adhesion-related genes in rat kidneys in response to ochratoxin A

Ochratoxin A (OTA), which is found in a variety of food products, is associated with the development of nephrotoxicity and carcinogenicity in rats and has raised public health concerns. A previous study in our laboratory indicated that OTA exposure induced cytotoxicity by decreasing global DNA methylation in vitro. However, the relationship between OTA-induced nephrotoxicity and DNA methylation changes in vivo remains unclear. The object of this study was to investigate whether OTA can change global DNA methylation or alter the expression of several critical tumour-related genes by inducing methylation modifications before carcinogenesis. We focused on the mechanism of action of OTA in regard to DNA methylation, including the expression of DNA methyltransferases and the regulation of specific cell signalling pathways. Dynamic and dose-dependent changes of global DNA methylation were observed during OTA-induced nephrotoxicity and probably associated with the expression of DNA methyltransferase 1. 13-week exposure of OTA caused hypermethylation in the promoters of critical cell adhesion-related genes, E-cadherin and N-cadherin, leading to reduction of the corresponding mRNA expression, accompanied by transcriptional activation of the Wnt and PI3K/AKT pathways. These findings suggested that long-term OTA exposure could disrupt DNA methylation profile, which might be one of the possible mechanisms of OTA-induced nephrotoxicity.