Diabetes & Metabolism Journal

Original Articles

Activation of NF-kappaB and AP-1 in Peripheral Blood Mononuclear Cells Isolated from Patients with Diabetic Nephropathy.: Jisun Nam, Min Ho Cho, Jong Suk Park, Geun Taek Lee, Hai Jin Kim, Eun Seok Kang, Yu Mie Lee, Chul Woo Ahn, Bong Soo Cha, Eun Jig Lee, Sung Kil Lim, Kyung Rae Kim, Hun Joo Ha, Hyun Chul Lee; Korean Diabetes J. 2007;31(3):261-273. Published online May 1, 2007; DOI: https://doi.org/10.4093/jkda.2007.31.3.261

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Abstract PDF: BACKGROUND
We evaluated the role of oxidative stress in diabetic nephropathy by measuring intracellular reactive oxygen species (ROS) and redox-sensitive transcription factors in isolated peripheral mononuclear cells (PBMC). METHODS: From 66 diabetic patients with or without diabetic nephropathy (Group III and II, respectively) and 49 normal control subjects (Group I), spontaneous and stimulated ROS levels, activities of nuclear factor-kappa B (NF-kappaB), activator protein-1 (AP-1), and specificity protein1 (Sp1) in PBMC, urinary and PBMC TGF-beta1 (transforming growth factor-beta1), and 24-hour urinary albumin excretion (UAE) were measured. RESULTS: Spontaneous ROS was significantly higher in group III and II than group I (60.7 +/- 3.3 vs. 60.0 +/- 3.0 vs. 41.1 +/- 2.4%, respectively), and stimulated ROS were significantly higher in Group III compared to Group II (Increment of H2O2-induced ROS production: 21.8 +/- 2.2 vs. 11.1 +/- 2.0%, respectively; increment of PMA-induced ROS production 23.5 +/- 4.5 vs. 21.6 +/- 2.2%, respectively). The activities of NF-kappaB and AP-1, but not of Sp1, were significantly higher in Group III than in Group II (2.53 vs. 2.0 vs. 1.43-fold, respectively). Both PBMC- and urinary TGF-beta1 levels were higher in Group III than Group II (3.23 +/- 0.39 vs. 1.99 +/- 0.68 ng/mg in PBMCs, 16.88 +/- 6.84 vs. 5.61 +/- 1.57 ng/mL in urine, both respectively), and they were significantly correlated with activities of NF-kappaB and AP-1 and 24-hour UAE. CONCLUSIONS: Increased intracellular ROS generation in PBMCs of diabetic patients is involved in the pathogenesis of diabetic nephropathy through activation of NF-kappaB and AP-1, but not Sp1, and increased expression of TGF-beta1.

Alpha-Lipoic acid Inhibits TNF-alpha-Induced Fractalkine Expression in Rat aortic Smooth Muscle Cells.: Keun Gyu Park, Hye Soon Kim, Seong Yeol Ryu, Chang Wook Nam, Byung Kyu Chae, Eui Dal Jung, Jung Guk Kim, Bo Wan Kim, In Kyu Lee; Korean Diabetes J. 2005;29(5):409-417. Published online September 1, 2005

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Abstract PDF: BACKGOUND: The induction of vascular inflammation via the proinflammatory cytokine/ nuclear factor (NF)-kappaB pathway is one of the key mechanisms in the development and progression of atherosclerosis. Accumulating evidence suggests a recently identified chemokine, fractalkine, is involved in arterial inflammation and atherogenesis; however, few studies have examined the effects of pharmacological agents on this process. The purposes of this study were to determine if alpha-lipoic acid (ALA) inhibits the expression of tumor necrosis factor (TNF)-alpha-stimulated fractalkine in vascular smooth muscle cells(VSMCs). METHODS: Rat VSMCs were isolated and cultured. Northern and Western blot analyses were performed to evaluate the effects of ALA on the expression of TNF-alpha-stimulated fractalkine in VSMCs. A gel shift assay was performed to examine the mechanism by which ALA inhibits the expression of fractalkine. RESULTS: TNF-alpha markedly induced the expression of fractalkine in primary cultured VSMCs. ALA inhibited the expression of TNF-alpha-stimulated fractalkine in cultured VSMCs. The result of the gel shift assay suggested the inhibitory effects of AS-6 on the expression of TNF-alpha-stimulated fractalkine were mediated via the NF-kappaB pathway. CONCLUSION: This study has shown that ALA has anti-inflammatory effects on VSMCs, which are mediated by the inhibitoin, at least in part, of the NF-kappaB dependent inflammatory signal-stimulated expression of fractalkine. Our data suggest the possibility that antioxidants, such as ALA, inhibit the NF-kappaB pathway, which may be used to prevent the development and progression of atherosclerosis.

Study on the Methylglyoxal-induced Apoptosis in Bovine Retinal Pericytes.: Jaetaek Kim, Seok Hong Lee, Jang Won Son, Jeong An Lee, Yeon Sahng Oh, Soon Hyun Shinn; Korean Diabetes J. 2004;28(3):199-207. Published online June 1, 2004

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Abstract PDF: BACKGROUND
One of the histopathological hallmarks of early diabetic retinopathy is the loss of pericytes. Evidences suggest that this pericyte loss in vivo is mediated by apoptosis. However, the underlying cause of pericyte apoptosis is not fully understood. This study investigated the influence of methylglyoxal(MGO), a reactive alpha-dicarbonyl compound of glucose metabolism, on the apoptotic cell death in retinal pericytes. METHODS: Primary cultures of retinal pericytes were prepared from isolated bovine retinal microvessels. The cells were incubated under normoglycemic conditions after treatment with 200-800muM methylglyoxal for 6 hours. The cell viability was assessed using the MTT assay. The apoptosis and intracellular reactive oxygen species(ROS) generation were measured using an ELISA kit and flow cytometry, respectively. The NF-kappaB activation was detected by immunocytochemistry. RESULTS: MGO produced a progressive cytotoxic effect on the retinal pericytes. An analysis of the internucleosomal DNA fragmentation by ELISA showed that MGO(200 to 800muM) induced apoptosis in a concentration-dependent manner. ROS were generated earlier and the antioxidant, N-acetyl cysteine, inhibited the MGO-induced apoptosis. The NF-kappaB activation and increased caspase-3 activity were detected. The apoptosis was also inhibited by the caspase-3 inhibitor, Z-DEVD-fmk, or the NF-kappaB inhibitor, pyrrolidine dithiocarbamate. CONCLUSION: These results suggest that the elevated MGO levels observed in diabetes may cause apoptosis in the retinal pericytes through an oxidative stress mechanism, and suggests that the nuclear activation of NF-kappaB is involved in the apoptotic process.

The Inhibitory Effect of Epicatechin on IL-1beta -induced iNOS Expression and NO Production in RINm5F Cell.: Gyeong Ryul Ryu, Do Sik Min, Duck Joo Rhie, Shin Hee Yoon, Sang June Hahn, Myung Suk Kim, Yang Hyeok Jo, Myung Jun Kim; Korean Diabetes J. 2003;27(6):456-466. Published online December 1, 2003

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Abstract PDF: BACKGROUND
Interleukin-1beta (IL-1beta ) stimulates the expression of inducible nitric oxide synthase (iNOS) and the production of nitric oxide (NO), lead to NO-mediated insulin, which produces cell damage. Within these signal pathways, nuclear factor-kappaB (NF-kappaB) activation is crucial, with many IL-1beta -sensitive genes containing NF-kappaB binding sites in their promoter regions. The inhibitory effect of (-)epicatechin (EC), an antioxidant agent, on IL-1beta -induced NF-kappaB activation, and the subsequent iNOS expression in RINm5F cells, were examined. METHODS: RINm5F cells were pretreated with EC (0.8 mM), and then cultured with IL-1beta (10U/mL), and the iNOS mRNA and protein levels then determined by Northern and Western blots, respectively. The production of NO was measured as nitrite in the culture supernatant. The protein levels of the inhibitor of nuclear factor kappaB (IkappaB) and NF-kappaB DNA binding activity were determined by Western blot and electrophoretic mobility shift assay, respectively. Also, the promoter activity following transient transfection of the iNOS promoter-luciferase reporter genes into the cells were tested. RESULTS: EC was found to significantly reduce the IL-1beta -induced NO production, and iNOS protein and mRNA levels, and also blocked the IL-1beta -induced IkappaB protein degradation, NF-kappaB activation and iNOS promoter activity. CONCLUSION: These results suggest that EC inhibits the IL-1beta -induced iNOS expression in RINm5F cells, by interfering with the binding of the NF-kappaB to the iNOS promoter, thereby inhibiting the induction of iNOS transcription.

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