No abstract

Oxidative stress caused by cellular accumulation of reactive oxygen species (ROS) is a major contributor to disease and cell death. However, how induced pluripotent stem cells (iPSC) respond to different levels of oxidative stress is largely unknown. Here, we investigated the effect of H2 O2 -induced oxidative stress on iPSC function in vitro. Mouse iPSC were treated with H2 O2 (25-100 μmol/L). IPSC adhesion, migration, viability, apoptosis and senescence were analysed. Expression of adhesion-related genes, stress defence genes, and osteoblast- and adipocyte-associated genes were determined by reverse transcription polymerase chain reaction. The present study found that H2 O2 (25-100 μmol/L) decreased iPSC adhesion to matrix proteins and endothelial cells, and downregulated gene expression levels of adhesion-related molecules, such as integrin alpha 7, cadherin 1 and 5, melanoma cell adhesion molecule, vascular cell adhesion molecule 1, and monocyte chemoattractant protein-1. H2 O2 (100 μmol/L) decreased iPSC viability and inhibited the capacity of iPSC migration and transendothelial migration. iPSC were sensitive to H2 O2 -induced G2/M arrest, senescence and apoptosis when exposed to H2 O2 at concentrations above 25 μmol/L. H2 O2 increased the expression of stress defence genes, including catalase, cytochrome B alpha, lactoperoxidase and thioredoxin domain containing 2. H2 O2 upregulated the expression of osteoblast- and adipocyte-associated genes in iPSC during their differentiation; however, short-term H2 O2 -induced oxidative stress did not affect the protein expression of the pluripotency markers, octamer-binding transcription factor 4 and sex-determining region Y-box 2. The present results suggest that iPSC are sensitive to H2 O2 toxicity, and inhibition of oxidative stress might be a strategy for improving their functions.

The initial stage of atherosclerosis is characterised by recruitment of leukocytes to activate endothelial cells (ECs). MicroRNAs (miRNAs) are a class of 19 to 25 nucleotides, non-protein-coding RNAs that repress target gene expression by translational inhibition or mRNA degradation. The link between miRNA and endothelial functions is largely unknown. Northern blot showed that miR-155 and miR-221 were highly expressed in human umbilical vein endothelial cells (HUVECs) and vascular smooth muscle cells (VSMCs). Bioinformatics analysis proposed Ets-1, a key endothelial transcription factor for infl ammation and tube formation, as a candidate target for miR-155 and miR-221/222 cluster. The effect was demonstrated by luciferase reporter assay and Western blot. By using Western blot, we also confi rmed that angiotensin II type 1 receptor (AT1R) is a target of miR-155 in HUVECs. Quantitative PCR showed that Ets-1 and its downstream genes, including VCAM1, MCP1 and FLT1, were up-regulated in angiotensin II-stimulated HUVECs, and this effect was partially reversed by over-expression of miR-155 and miR-221/222. In addition, cell adhesion assay revealed over-expression of miR-155 and miR-221/222 effectively decreased the adhesion of Jurkat T cells to Ang II-stimulated HUVECs. Besides, by targeting AT1R, miR-155 can also decrease the HUVECs migration in response to Ang II. In summary, HUVECs highly expressed miR-155 may co-target AT1R and Ets-1 while miR-221/222 targets Ets-1, which indirectly regulate the expression of several infl ammatory molecules of ECs, and therefore attenuate the adhesion of Jurkat T cells to activated HUVECs and reduce HUVECs migration. These fi ndings present possible therapeutic targets in atherosclerosis.