Diabetes & Metabolism Journal

Original Articles

Inducible Nitric Oxide Synthase (iNOS) Expression in the Hypoxic Injury to Pancreatic Beta (MIN6) Cells.: Seung Hyun Ko, Seung Bum Kim, Kyung Ryul Ryu, Ji Won Kim, Yu Bai Ahn, Sung Dae Moon, Sung Rae Kim, Jung Min Lee, Hyuk Snag Kwon, Kun Ho Yoon, Ki Ho Song; Korean Diabetes J. 2006;30(5):336-346. Published online September 1, 2006; DOI: https://doi.org/10.4093/jkda.2006.30.5.336

2,543 View
37 Download

Abstract PDF: BACKGROUND
Islet transplantation is an alternative potential strategy to cure type 1 diabetes mellitus. However, two or more donors are usually needed for one recipient because a substantial part of the graft becomes nonfunctional due to several factors including hypoxia. Though hypoxic exposure of pancreatic beta cells has been reported to induce apoptotic cell death, the molecular processes involved in hypoxia-induced cell death are poorly understood. In type I diabetes, Nitric Oxide (NO) is known as an important cytokine, involved in the pathogenesis of beta cell dysfunction. Pancreatic beta cells are sensitive to the induction of inducible nitric oxide synthase (iNOS) when stimulated by TNF-a or IL-1beta. But contribution of iNOS in response to hypoxia is not yet fully understood. METHODS: Mouse insulinoma cells (MIN6) were incubated in an anaerobic chamber (75% N2/15% CO2/5% H2) for up to 12 hours. Cell viability was measured after AO/PI staining. Caspase-3 activation was also determined using Western blot analysis. Nitric Oxide (NO) release into culture medium was measured using a Griess reagent. The expression of iNOS and PDX-1 mRNA and iNOS protein was examined using real time PCR and Western blot analysis. RESULTS: Marked cell death was observed within 6 hours after hypoxic exposure of MIN6 cells (control, < 5%; 2 hr, 11.0+/-7.6%; 6 hr, 46.2+/-12.8%, P < 0.05). Immunoreactivity to activated caspase-3 was observed at 2, 4 and 6 hrs. NO production was increased in a time dependent manner. Expression of iNOS mRNA and protein was significantly increased at 4 and 6 hour after hypoxia. iNOS expression was confirmed by immunostaining. Of note, Pdx-1 mRNA expression was markedly attenuated by hypoxic treatment. Pretreatment with a selective iNOS inhibitor, 1400 W, significantly prevented beta cell death induced by hypoxic injury. CONCLUSION: Our data suggest that iNOS-NO play an important role in hypoxic injury to MIN6 cells. Therefore, iNOS-NO might be a potential therapeutic target for improving engraftment of the transplanted islets and suppression of iNOS would be helpful for prevention of beta cells damage to hypoxic injury.

The Effect of Nitric Oxide on Insulin Binding and Insulin Receptor Recycling in Bovine Aortic Endothelial Cells.: Hyuk Sang Kwon, Oak Kee Hong, Hee Soo Kim, Jung Min Lee, Sung Rae Kim, Sung Dae Moon, Sang Ah Jang, Hyun Shik Son, Kun Ho Yoon, Moo Il Kang, Bong Yun Cha, Kwang Woo Lee, Ho Young Son, Sung Koo Kang; Korean Diabetes J. 2003;27(3):213-227. Published online June 1, 2003

1,221 View
29 Download

Abstract PDF: BACKGROUND
The coexistence of insulin resistance and endothelial dysfunction is commonly observed in a variety of metabolic and cardiovascular disorders, including athero-sclerosis and type 2 diabetes mellitus. Because nitric oxide (NO), or nitric oxide synthase (NOS), has been suggested as a significant contributing factor in the development of endothelial dysfunction and insulin resistance, reactive NO or NOS were investigated to see if they contribute to the insulin internalization pathway. METHODS: The production of NO (Nitrite), the expression of eNOS (endothelial NOS), insulin binding and the insulin receptor internalization and recycling, following 48 hours of incubation with bradykinin (BK), acetylcholine (Ach), NG-monomethyl- L-arginine (L-NMMA) and N-nitro-L-arginine methylester (L-NAME) in Bovine aortic endothelial cells (BAECs), were examined. RESULTS: The results were as follows: 1. In relation to the time course, the production of eNOS was increased, but was decreased after 8 hours of incubation. The production of eNOS in the L-NMMA and L-NAME treated groups was significantly decreased compared with that of the controls (p<0.05). 2. The specific insulin bindings to the receptors of the endothelial cells were maximized within 20 mins, and then decreased. At 20 mins, the binding rate of the L-NMMA treated group was significantly decreased compared to that of the controls. At a concentration of 0.4ng/ml of unlabelled insulin, the specific insulin binding of the L-NMMA treated group was significantly decreased compared to that of the controls (p<0.05). 3. The internalization of 125I-insulin into the endothelial cells, as assessed by the acid washing dissociation method, occurred rapidly. The internalized radioactivity of 125I-insulin, at 20 mins, was significantly increased in the BK and Ach groups compared with the controls (p<0.05). 4. The recycling of the internalized insulin receptors showed no significant differences between the study groups, but the recycling was slightly delayed compared with controls in the Ach group. CONCLUSION: In conclusion, the NO generating substances, BK and Ach, and the inhibitory substance, L-NMMA, may influence the binding and internalization of insulin-insulin receptors. Our results suggest that NO might contribute to the transcytosis of insulin in BAECs

Effect and Mechanism of Vascular Endothelial Growth Factor on Endothelial Nitric Oxide Synthase Expression in Aortic Endothelial Cells.: Soon Hee Lee, Jung Guk Kim, Joong Yeol Park, Sung Woo Ha, Bo Wan Kim; Korean Diabetes J. 2002;26(5):396-404. Published online October 1, 2002

1,127 View
24 Download

Abstract PDF: BACKGROUND
Vascular endothelial growth factor (VEGF), a soluble angiogenic factor produced by many tumor and normal cells, is a potent angiogenic and vascular permeability factor. VEGF plays a key role in both pathological and physiological angiogenesis. There are many recent findings regarding the role of VEGF in diabetic microvascular and macrovascular diseases. Many approaches with VEGF-related therapies begin to treat and prevent these complications and have been used for the treatment of microvascular complications such as diabetic retinopathy, whereas VEGF agonists have been used to treat macrovascular complications such as myocardial infarction and peripheral limb ischemia. Nitric oxide (NO) is known to mediate many physiological and pathological functions, including modulation of vascular tone, permeability, and capillary growth. Recent reports indicate that NO may play an intimate role in VEGF signaling. Therefore, we hypothesized that the expression of eNOS may be regulated by VEGF. The objectives of the present study were to determine whether VEGF up-regulates the expression of endothelial NO synthase (eNOS) in endothelial cells and to elucidate the mechanism that mediate this response. METHODS: Endothelial cells were isolated from bovine aortae. The expression of eNOS was assessed by Northern blotting analysis. To evaluate the mechanism of VEGF-induced eNOS expression, endothelial cells were conditioned with VEGF and pretreated with phorbol-12-myristate acetate (PMA), a protein kinase C (PKC) activator, or GF109203X (GFX), a PKC inhibitor. The changes of eNOS gene expression. RESULTS: VEGF significantly increased the expression of eNOS mRNA in bovine aortic endothelial cells (BAEC) in time and dose dependent manners. PMA increased the expression of eNOS mRNA, as well as the VEGF-induced expression of eNOS mRNA in endothelial cells, while inhibition of the PKC activity, with the GFX blocked the upregulation of the VEGF-induced eNOS mRNA. CONCLUSION: The results suggest that VEGF upregulates eNOS gene expression in aortic endothelial cells, by a PKC dependent pathway and, eNOS may be important in the development of VEGF-induced angiopathy.

First
Prev
Page of 1
Next
Last

Search