Stem cells were characterized by their stemness: self-renewal and pluripotency. Mesenchymal stem cells (MSCs) are a unique type of adult stem cells that have been proven to be involved in tissue repair, immunoloregulation and tumorigenesis. Irradiation is a well-known factor that leads to functional obstacle in stem cells. However, the mechanism of stemness maintenance in human MSCs exposed to irradiation remains unknown. We demonstrated that irradiation could induce reactive oxygen species (ROS) accumulation that resulted in DNA damage and stemness injury in MSCs. Autophagy induced by starvation or rapamycin can reduce ROS accumulation-associated DNA damage and maintain stemness in MSCs. Further, inhibition of autophagy leads to augment of ROS accumulation and DNA damage, which results in the loss of stemness in MSCs. Our results indicate that autophagy may have an important role in protecting stemness of MSCs from irradiation injury.
Nanoparticles are now emerging as a novel class of autophagy activators. Functionalized single-walled carbon nanotubes (f-SWCNTs) are valuable nanomaterials in many industries. This article is designed to assess the autophagic response for f-SWCNTs exposure in vitro and in vivo. A few types of f-SWCNTs were screened in human lung adenocarcinoma A549 cells for the autophagic response and related pathways in vitro. Formation of autophagosomes and LC3-II upregulation were confirmed on the basis of electron microscopy and LC3 western blotting for COOH-CNT, but not for PABS-CNT and PEG-CNT. MTT assay showed marked increase in cell viability, when COOH-CNT was added to cells in the presence of autophagy inhibitor 3MA, ATG6 or TSC2 siRNA. Consistent with the involvement of the Akt–TSC1/2–mTOR pathway, the phosphorylation levels of mTOR, mTOR's substrate S6 and Akt were shown significantly decreased in A549 cells on treatment with COOH-CNT using western blotting. What's more, autophagy inhibitor 3MA significantly reduced the lung edema in vivo. In a word, COOH-CNT induced autophagic cell death in A549 cells through the AKT–TSC2–mTOR pathway and caused acute lung injury in vivo. Inhibition of autophagy significantly reduced COOH-CNT-induced autophagic cell death and ameliorated acute lung injury in mice, suggesting a potential remedy to address the growing concerns on the safety of nanomaterials.
H-cadherin (CDH13; also known as T-cadherin), which functions as a tumour suppressor, is frequently silenced by promoter methylation in human cancers including bladder transitional cell carcinoma (TCC). This study investigated the clinical significance of methylation of the CDH13 gene promoter in serum from patients with bladder TCC. Methylation status of CDH13 in serum samples from 127 patients with primary bladder TCC and 41 healthy volunteers (controls) was examined by methylation-specific polymerase chain reaction. CDH13 methylation was found in 39 patients with bladder TCC (30.7%) but in no controls. CDH13 methylation was significantly associated with advanced tumour stage, high-grade tumour, large tumour size, tumour recurrence and poor prognosis. The results suggested that CDH13 methylation in serum may be a potential predictive biomarker for malignancy in bladder TCC, and an independent pre-therapeutic predictor of outcome. Demonstration of CDH13 methylation in serum may facilitate in the prediction of which patients require more aggressive additional post-operative systemic therapy.
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