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Insulin enhances nitric oxide production in trabecular meshwork cells via de novo pathway for tetrahydrobiopterin synthesis.

Kim JW - Korean J Ophthalmol (2007)

Bottom Line: To investigate the effect of insulin on the production of nitric oxide (NO) in the trabecular meshwork (TM) cells and the enzymatic synthetic pathway of tetrahydrobiopterin (BH(4)) synthesis.To evaluate the enzymatic pathway of BH(4) synthesis, 10 microM dexamethasone, 5 mM diaminopyrimidinone, 100 microM ascorbic acid, 100 microM sepiapterin, or 10 microM methotrexate were also co-administered respectively.Ascorbic acid increased NO production independent of insulin and methotrexate did not affect to the action of insulin in NO production.

View Article: PubMed Central - PubMed

Affiliation: Department of Ophthalmology, Catholic University of Daegu College of Medicine, Nam-gu, Daegu, Korea. jwkim@cu.ac.kr

ABSTRACT

Purpose: To investigate the effect of insulin on the production of nitric oxide (NO) in the trabecular meshwork (TM) cells and the enzymatic synthetic pathway of tetrahydrobiopterin (BH(4)) synthesis.

Methods: Primarily cultured human TM cells were exposed to 1, 10, and 100 microgram/ml of insulin and 0, 1, 10, 100 and 1000 nM dexamethasone for 3 days. To evaluate the enzymatic pathway of BH(4) synthesis, 10 microM dexamethasone, 5 mM diaminopyrimidinone, 100 microM ascorbic acid, 100 microM sepiapterin, or 10 microM methotrexate were also co-administered respectively. Cellular survival and NO production were measured with MTT and Griess assay.

Results: Insulin enhanced NO production in a dose-dependent manner significantly (0.05) without affecting cell viability, whereas dexamethasone inhibited NO production. With co-exposure of insulin, diaminopyrimidinone and sepiapterin inhibited insulin-induced NO production. Ascorbic acid increased NO production independent of insulin and methotrexate did not affect to the action of insulin in NO production.

Conclusions: Insulin increases NO production in TM cells via de novo synthetic pathway for BH(4) synthesis. Insulin could be involved in the regulation of trabecular outflow by enhancing NO production in TM cells.

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Effect of insulin on the production of nitric oxide on cultured human trabecular meshwork cells. Insulin increased nitric oxide production in a dose-dependent manner and inhibited by 0.5 mM L-NAME (Nω-Nitro-L-arginine methyl ester). (*; p<0.05)
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Figure 2: Effect of insulin on the production of nitric oxide on cultured human trabecular meshwork cells. Insulin increased nitric oxide production in a dose-dependent manner and inhibited by 0.5 mM L-NAME (Nω-Nitro-L-arginine methyl ester). (*; p<0.05)

Mentions: The synthetic glucocorticoid dexamethasone inhibited NO production significantly in a dose-dependent manner. Nitrite concentration was decreased from 1.60 µM of non-exposed control down to 0.89 µM of 1000 nM dexamethasone exposure (Fig. 1). On the contrary, insulin enhanced NO production significantly in a dose-dependent manner up to 2.76 µM (Fig. 2). This insulin-induced enhanced NO production was inhibited by L-NAME, indicating NO was produced by TM cells per se. With co-exposure of insulin, 10 µM dexamethasone did not affect to the insulin-induced increase of NO production (Fig. 3).


Insulin enhances nitric oxide production in trabecular meshwork cells via de novo pathway for tetrahydrobiopterin synthesis.

Kim JW - Korean J Ophthalmol (2007)

Effect of insulin on the production of nitric oxide on cultured human trabecular meshwork cells. Insulin increased nitric oxide production in a dose-dependent manner and inhibited by 0.5 mM L-NAME (Nω-Nitro-L-arginine methyl ester). (*; p<0.05)
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2629692&req=5

Figure 2: Effect of insulin on the production of nitric oxide on cultured human trabecular meshwork cells. Insulin increased nitric oxide production in a dose-dependent manner and inhibited by 0.5 mM L-NAME (Nω-Nitro-L-arginine methyl ester). (*; p<0.05)
Mentions: The synthetic glucocorticoid dexamethasone inhibited NO production significantly in a dose-dependent manner. Nitrite concentration was decreased from 1.60 µM of non-exposed control down to 0.89 µM of 1000 nM dexamethasone exposure (Fig. 1). On the contrary, insulin enhanced NO production significantly in a dose-dependent manner up to 2.76 µM (Fig. 2). This insulin-induced enhanced NO production was inhibited by L-NAME, indicating NO was produced by TM cells per se. With co-exposure of insulin, 10 µM dexamethasone did not affect to the insulin-induced increase of NO production (Fig. 3).

Bottom Line: To investigate the effect of insulin on the production of nitric oxide (NO) in the trabecular meshwork (TM) cells and the enzymatic synthetic pathway of tetrahydrobiopterin (BH(4)) synthesis.To evaluate the enzymatic pathway of BH(4) synthesis, 10 microM dexamethasone, 5 mM diaminopyrimidinone, 100 microM ascorbic acid, 100 microM sepiapterin, or 10 microM methotrexate were also co-administered respectively.Ascorbic acid increased NO production independent of insulin and methotrexate did not affect to the action of insulin in NO production.

View Article: PubMed Central - PubMed

Affiliation: Department of Ophthalmology, Catholic University of Daegu College of Medicine, Nam-gu, Daegu, Korea. jwkim@cu.ac.kr

ABSTRACT

Purpose: To investigate the effect of insulin on the production of nitric oxide (NO) in the trabecular meshwork (TM) cells and the enzymatic synthetic pathway of tetrahydrobiopterin (BH(4)) synthesis.

Methods: Primarily cultured human TM cells were exposed to 1, 10, and 100 microgram/ml of insulin and 0, 1, 10, 100 and 1000 nM dexamethasone for 3 days. To evaluate the enzymatic pathway of BH(4) synthesis, 10 microM dexamethasone, 5 mM diaminopyrimidinone, 100 microM ascorbic acid, 100 microM sepiapterin, or 10 microM methotrexate were also co-administered respectively. Cellular survival and NO production were measured with MTT and Griess assay.

Results: Insulin enhanced NO production in a dose-dependent manner significantly (0.05) without affecting cell viability, whereas dexamethasone inhibited NO production. With co-exposure of insulin, diaminopyrimidinone and sepiapterin inhibited insulin-induced NO production. Ascorbic acid increased NO production independent of insulin and methotrexate did not affect to the action of insulin in NO production.

Conclusions: Insulin increases NO production in TM cells via de novo synthetic pathway for BH(4) synthesis. Insulin could be involved in the regulation of trabecular outflow by enhancing NO production in TM cells.

Show MeSH
Related in: MedlinePlus