Correction: Inhibitory Effect of Ginsenosides Rh1 and Rg2 on Oxidative Stress in LPS-Stimulated RAW 264.7 Cells

In this article, it has been stated that this study was supported by SMtech Development Program (#2018-0006-01) and Research Fund of Chungnam National University (#2017-1794-01). This information has now been corrected as follows: This research was supported by Research Fund of Chungnam National University (#2017-1794-01).

p90RSK Activation Promotes Epithelial-Mesenchymal Transition in Cisplatin-Treated Triple-Negative Breast Cancer Cells

p90 ribosomal S6 kinase (p90RSK), one of the downstream effectors in ERK1/2 pathways, shows high expression in human breast cancer tissues. However, its role in breast cancer development and drug resistance is not fully understood. Here, we demonstrate that Cis-DDP treatment failed to increase cytotoxicity in MDA-MB-231 cells compared to MCF-7 cells and p90RSK activation was involved in Cis-DDP-resistance to MDA-MB-231 cells. In the study, we found that inhibition of p90RSK expression or activation using a small interfering RNA (siRNA) or dominant-negative kinase mutant (DN-p90RSK) plasmid overexpression increased Cis-DDP-induced cytotoxicity of MDA-MB-231 cells, respectively. Mechanistically, we found that Cis-DDP resistance was associated with up-regulation of epithelial growth factor (EGF) expression and EGF treatment induced cancer survival signaling pathway including activation of ERK1/2, p90RSK, and Akt. We also examined the expression of epithelial-mesenchymal transition (EMT)-associated proteins using a reverse transition-quantitative PCR analysis. Cis-DDP treatment induced EMT by increasing the expression levels of N-cadherin, Snail, and Twist, while decreasing the expression levels of E-cadherin. Furthermore, we examined the epithelial marker, Zonula occludens-1 (ZO-1) using immunofluorescence analysis and found that Cis-DDP-inhibited ZO-1 expression was recovered by p90RSK deactivated condition. Therefore, we conclude that Cis-DDP resistance is involved in EMT via regulating the EGF-mediated p90RSK signaling pathway in MDA-MB-231 cells.

Inhibitory Effect of Ginsenosides Rh1 and Rg2 on Oxidative Stress in LPS-Stimulated RAW 264.7 Cells

Minor ginsenosides Rh1 and Rg2 were isolated from Korean red ginseng and reported to have various biological effects on anti-inflammatory and anti-stress activities. However, the effects of Rh1 and Rg2 on antioxidant activity and their regulatory effects on the antioxidant enzymes have not been studied. Since oxidative stress is one of the major toxic inflammatory responses stimulated by lipopolysaccharides (LPS), the present study investigated the role of minor ginsenosides Rh1 and Rg2 on antioxidant effects in LPS-treated RAW 264.7 cells. In this study, we found that treatment with ginsenosides Rh1 and Rg2 strongly inhibited LPS-stimulated intracellular ROS production in cells. Luciferase assay showed that treatment with LPS reduced antioxidant response element (ARE) encoding the pARE-luc promoter activity, while ginsenosides inhibited the pARE-luc promoter activity. Moreover, ginsenosides Rh1 and Rg2 exhibited anti-oxidative activity in LPS-induced cells by upregulating antioxidant enzymes including superoxide dismutase, catalase, and glutathione peroxidase. Our results suggest that minor ginsenosides Rh1 and Rg2 may be potential bio-active compounds for antioxidative effects by inhibiting the generation of ROS in RAW 264.7 cells.

Anti-apoptotic effects of autophagy via ROS regulation in microtubule-targeted and PDGF-stimulated vascular smooth muscle cells

Autophagy has been studied as a therapeutic strategy for cardiovascular diseases. However, insufficient studies have been reported concerning the influence of vascular smooth muscle cells (VSMCs) through autophagy regulation. The aim of the present study was to determine the effects of VSMCs on the regulation of autophagy under in vitro conditions similar to vascular status of the equipped microtubule target agent-eluting stent and increased release of platelet-derived growth factor-BB (PDGF-BB). Cell viability and proliferation were measured using MTT and cell counting assays. Immunofluorescence using an anti-α-tubulin antibody was performed to determine microtubule dynamic formation. Cell apoptosis was measured by cleavage of caspase-3 using western blot analysis, and by nuclear fragmentation using a fluorescence assay. Autophagy activity was assessed by microtubule-associated protein light chain 3-II (LC-II) using western blot analysis. Levels of intracellular reactive oxygen species (ROS) were measured using H₂DCFDA. The proliferation and viability of VSMCs were inhibited by microtubule regulation. Additionally, microtubule-regulated and PDGF-BB-stimulated VSMCs increased the cleavage of caspase-3 more than only the microtubule-regulated condition, similar to that of LC3-II, implying autophagy. Inhibitory autophagy of microtubule-regulated and PDGF-BB-stimulated VSMCs resulted in low viability. However, enhancement of autophagy maintained survival through the reduction of ROS. These results suggest that the apoptosis of conditioned VSMCs is decreased by the blocking generation of ROS via the promotion of autophagy, and proliferation is also inhibited. Thus, promoting autophagy as a therapeutic target for vascular restenosis and atherosclerosis may be a good strategy.

Alleviation of ascorbic acid-induced gastric high acidity by calcium ascorbate in vitro and in vivo

Ascorbic acid is one of the most well-known nutritional supplement and antioxidant found in fruits and vegetables. Calcium ascorbate has been developed to mitigate the gastric irritation caused by the acidity of ascorbic acid. The aim of this study was to compare calcium ascorbate and ascorbic acid, focusing on their antioxidant activity and effects on gastric juice pH, total acid output, and pepsin secretion in an in vivo rat model, as well as pharmacokinetic parameters. Calcium ascorbate and ascorbic acid had similar antioxidant activity. However, the gastric fluid pH was increased by calcium ascorbate, whereas total acid output was increased by ascorbic acid. In the rat pylorus ligation-induced ulcer model, calcium ascorbate increased the gastric fluid pH without changing the total acid output. Administration of calcium ascorbate to rats given a single oral dose of 100 mg/kg as ascorbic acid resulted in higher plasma concentrations than that from ascorbic acid alone. The area under the curve (AUC) values of calcium ascorbate were 1.5-fold higher than those of ascorbic acid, and the C(max) value of calcium ascorbate (91.0 ng/ml) was higher than that of ascorbic acid (74.8 ng/ml). However, their T(max) values were similar. Thus, although calcium ascorbate showed equivalent antioxidant activity to ascorbic acid, it could attenuate the gastric high acidity caused by ascorbic acid, making it suitable for consideration of use to improve the side effects of ascorbic acid. Furthermore, calcium ascorbate could be an appropriate antioxidant substrate, with increased oral bioavailability, for patients with gastrointestinal disorders.

LPS-stimulated Macrophage Activation Affects Endothelial Dysfunction

Intestinal microbiota is involved in the atherosclerotic process by development of an atheromatous core with foam cells in carotid arteries. It has reported that lipopolysaccharide (LPS) from Escherichia coli localizes in human atherosclerotic plaque and causes inflammation via interaction with toll like receptor 4. However, there is no evidence that whether LPS-activated macrophages regulate endothelial cell (EC) function. We evaluated whether LPS-activated macrophage acts as one of the stimulants activating EC and its underlying signaling pathways. Using Western blotting and quantitative reverse transcription-polymerase chain reaction (qRT-PCR), we confirmed that intraperitoneal injection with LPS increases iNOS protein and inflammatory cytokine, TNF-α and IL-6 mRNA expressions. To determine whether LPS-mediated macrophage inflammatory condition affects EC activation and inflammation, human umbilical vein endothelial cells (HUVECs) were incubated with isolated peritoneal macrophages from LPS-injected mice. Interestingly, p90RSK Serine 380 phosphorylation and protein expression were significantly increased by macrophage treatment in EC. Messenger RNA levels of vascular cell adhesion molecule 1 and p90RSK was increased, but endothelial nitric oxide synthase was decreased. In addition, NF-κB promoter activity, which plays an important role in the pathogenesis of inflammation, was strongly enhanced by the macrophage treatment in EC. We further evaluated the effects of LPS on EC function in the mouse aorta using en face staining. In agreement with in vitro result, p90RSK expression was strongly increased in the steady laminar flow region of the mouse aorta in mice injected with LPS. Together, our study demonstrates that p90RSK might be a one of the major therapeutic candidates for the prevention of vascular diseases mediated by LPS.