β-Carotene Inhibits Activation of NF-κB, Activator Protein-1, and STAT3 and Regulates Abnormal Expression of Some Adipokines in 3T3-L1 Adipocytes

BACKGROUND: Oxidative stress occurs in white adipose tissue and dysregulates the expression of adipokines secreted from adipocytes. Since adipokines influence inflammation, supplementation with antioxidants might be beneficial for preventing oxidative stress-mediated inflammation in adipocytes and inflammation-associated complications. β-Carotene is the most prominent antioxidant carotenoid and scavenges reactive oxygen species in various tissues. The purpose of this study was to determine whether β-carotene regulates the expression of adipokines, such as adiponectin, monocyte chemoattractant protein-1 (MCP-1), and regulated on activation, normal T cell expressed and secreted (RANTES) in 3T3-L1 adipocytes treated with glucose/glucose oxidase (G/GO). METHODS: 3T3-L1 adipocytes were cultured with or without β-carotene and treated with G/GO, which produces H2O2. mRNA and protein levels in the medium were determined by a real-time PCR and an ELISA. DNA binding activities of transcription factors were assessed using an electrophoretic mobility shift assay. RESULTS: G/GO treatment increased DNA binding affinities of redox-sensitive transcription factors, such as NF-κB, activator protein-1 (AP-1), and STAT3. G/GO treatment reduced the expression of adiponectin and increased the expression of MCP-1 and RANTES. G/GO-induced activations of NF-κB, AP-1, and STAT3 were inhibited by β-carotene. G/GO-induced dysregulation of adiponectin, MCP-1, and RANTES were significantly recovered by treatment with β-carotene. CONCLUSIONS: β-Carotene inhibits oxidative stress-induced inflammation by suppressing pro-inflammatory adipokines MCP-1 and RANTES, and by enhancing adiponectin in adipocytes. β-Carotene may be beneficial for preventing oxidative stress-mediated inflammation, which is related to adipokine dysfunction.

alpha-Lipoic Acid Inhibits Expression of IL-8 by Suppressing Activation of MAPK, Jak/Stat, and NF-kappaB in H. pylori-Infected Gastric Epithelial AGS Cells

The epithelial cytokine response, associated with reactive oxygen species (ROS), is important in Helicobacter pylori (H. pylori)-induced inflammation. H. pylori induces the production of ROS, which may be involved in the activation of mitogen-activated protein kinases (MAPK), janus kinase/signal transducers and activators of transcription (Jak/Stat), and oxidant-sensitive transcription factor, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kappaB), and thus, expression of interleukin-8 (IL-8) in gastric epithelial cells. alpha-lipoic acid, a naturally occurring thiol compound, is a potential antioxidant. It shows beneficial effects in treatment of oxidant-associated diseases including diabetes. The present study is purposed to investigate whether alpha-lipoic acid inhibits expression of inflammatory cytokine IL-8 by suppressing activation of MAPK, Jak/Stat, and NF-kappaB in H. pylori-infected gastric epithelial cells. Gastric epithelial AGS cells were pretreated with or without alpha-lipoic acid for 2 h and infected with H. pylori in a Korean isolate (HP99) at a ratio of 300:1. IL-8 mRNA expression was analyzed by RT-PCR analysis. IL-8 levels in the medium were determined by enzyme-linked immunosorbent assay. NF-kappaB-DNA binding activity was determined by electrophoretic mobility shift assay. Phospho-specific and total forms of MAPK and Jak/Stat were assessed by Western blot analysis. ROS levels were determined using dichlorofluorescein fluorescence. As a result, H. pylori induced increases in ROS levels, mRNA, and protein levels of IL-8, as well as the activation of MAPK [extracellular signal-regulated kinase 1/2 (ERK1/2), c-Jun NH2-terminal kinase 1/2 (JNK1/2), p38], Jak/Stat (Jak1/2, Stat3), and NF-kappaB in AGS cells, which was inhibited by alpha-lipoic acid. In conclusion, alpha-lipoic acid may be beneficial for prevention and/or treatment of H. pylori infection-associated gastric inflammation.

Diphenyleneiodonium Inhibits Apoptotic Cell Death of Gastric Epithelial Cells Infected with Helicobacter pylori in a Korean Isolate

NADPH oxidase produces a large amount of reactive oxygen species (ROS) in Helicobacter pylori (H. pylori)-induced gastric epithelial cells. Even though ROS mediate apoptotic cell death, direct involvement of NADPH oxidase on H. pylori-induced apoptosis remains unclear. Besides, H. pylori isolates show a high degree of genetic variability. The predominant genotype of H. pylori in Korea has been reported as cagA+, vacA s1b, m2, iceA genotype. Present study aims to investigate whether NADPH oxidase-generated ROS mediate apoptosis in human gastric epithelial AGS cells infected with H. pylori in a Korean isolate. AGS cells were pretreated with or without an NADPH oxidase inhibitor diphenyleneiodonium (DPI) and cultured in the presence of H. pylori at a bacterium/cell ratio of 300:1. Cell viability, hydrogen peroxide level, DNA fragmentation, and protein levels of p53, Bcl-2, and Bax were determined. Results showed that H. pylori inhibited cell viability with the density of H. pylori added to the cells. Inhibition of NADPH oxidase by DPI suppressed H. pylori-induced cell death, increased hydrogen peroxide, DNA fragmentation, and the ratio of Bax/Bcl-2, and p53 induction in AGS cells dose-dependently. The results suggest that targeting NADPH oxidase may prevent the development of gastric inflammation associated with H. pylori infection by suppressing abnormal apoptotic cell death of gastric epithelial cells.