Nicotinamide suppresses bevacizumab-induced epithelial-mesenchymal transition of ARPE-19 cells by attenuating oxidative stress.

AIM: To investigate the effects of nicotinamide (NAM) on bevacizumab (BEV)-induced epithelial-mesenchymal transition (EMT) of human retinal pigment epithelial cells (ARPE-19) and the underling mechanisms. METHODS: ARPE-19 cells were treated with BEV for 24, 48, and 72h, and the variation degrees of EMT-related markers (fibronectin, α-SMA, vimentin, and ZO-1) were assessed by Western blotting to select the optimal treatment time point which exhibited the most obvious changes of EMT-related markers for the subsequent experiments. Furthermore, NAM was added to the medium, the mRNA and protein levels of the EMT-related markers were then measured. The accumulation of reactive oxygen species (ROS) and H2O2 and the total antioxidant capacity (TAC) of the cells were also measured to evaluate the level of oxidative stress. RESULTS: After being treated with BEV for 72h, the protein expression levels of EMT-related markers in ARPE-19 cells showed significant changes. Meanwhile the levels of ROS and H2O2 were obviously increased, and the TAC of ARPE-19 cells was decreased. Totally 72h was chosen to be the optimal treatment time point in subsequent experiments. Furthermore, NAM inhibited BEV-induced EMT by downregulating fibronectin, α-SMA, and vimentin and upregulating ZO-1, decreased the accumulation of ROS and H2O2, and enhanced TAC in BEV-treated ARPE-19 cells. CONCLUSION: This study demonstrates that NAM suppressed BEV-induced EMT in ARPE-19 cells by attenuating oxidative stress. Hence, NAM may be a potential therapeutic agent for alleviating neovascular fibrosis of the ocular fundus after anti-vascular endothelial growth factor therapy.

LRG1 promotes epithelial-mesenchymal transition of retinal pigment epithelium cells by activating NOX4.

AIM: To investigate the effect of leucine-rich-alpha-2-glycoprotein 1 (LRG1) on epithelial-mesenchymal transition (EMT) in retinal pigment epithelium (RPE) cells, and to explore the role of NADPH oxidase 4 (NOX4). METHODS: RPE cells (ARPE-19 cell line) were treated with transforming growth factor-ß1 (TGF-ß1) to induce EMT. Changes of the mRNA and protein expression levels of LRG1 were tested in the TGF-ß1 treated cells. The recombinant human LRG1 protein (rLRG1) and siRNA of LRG1 were used to establish accumulation of exogenous LRG1 model and the down-regulation of LRG1 model in ARPE-19 cells respectively, and to detect EMT-related markers including fibronectin, α-smooth muscle actin (α-SMA) and zonula occludens-1 (ZO-1). The mRNA and protein expression level of NOX4 were measured according to the above treatments. VAS2870 was used as a NOX4 inhibitor in rLRG1-treated cells. EMT-related markers were detected to verify the effect of NOX4 in the process of EMT. RESULTS: TGF-ß1 promoted the expression of LRG1 at both the mRNA and protein levels during the process of EMT which showed the up-regulation of fibronectin and α-SMA, as well as the down-regulation of ZO-1. Furthermore, the rLRG1 promoted EMT of ARPE-19 cells, which manifested high levels of fibronectin and α-SMA and low level of ZO-1, whereas knockdown of LRG1 prevented EMT by decreasing the expressions of fibronectin and α-SMA and increasing the expression of ZO-1 in ARPE-19 cells. Besides, the rLRG1 activated and LRG1 siRNA suppressed NOX4 expression. EMT was inhibited when VAS2870 was used in the rLRG1-treated cells. CONCLUSION: These results for the first time demonstrate that LRG1 promotes EMT of RPE cells by activating NOX4, which may provide a novel direction to explore the mechanisms of subretinal fibrosis.

Anion exchange induced tunable catalysis properties of an uncommon butterfly-like tetranuclear copper(II) cluster and magnetic characterization.

An uncommon butterfly-like tetranuclear copper(ii) cluster with the formula {[Cu(4)(µ(3)-OH)(2)(µ(4)-Cl)(H(2)O)(2)(L)(2)]·Cl(H(2)O)(7)}(n) (1) (H(2)L = 1,2-bis[3-(1,2,4-triazolyl)-4-amino-5-carboxylmethylthio]ethane) has been synthesized. Compound 1 exhibits interesting anion exchange characteristics, in which both guest and coordinated Cl(-) can be replaced by I(-) or NO(3)(-) in water. Furthermore, a high catalytic selectivity to produce poly(phenylene ether) by the oxidative coupling of 2,6-dimethylphenol in water is found to be 74% for 1 and 87% for the anion-exchanged product 1-MI(x), respectively. Additionally, the antiferromagnetic interaction among Cu ions for compound 1 is also found.