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Improvement of endothelial nitric oxide synthase activity retards the progression of diabetic nephropathy in db/db mice.

Cheng H, Wang H, Fan X, Paueksakon P, Harris RC - Kidney Int. (2012)

Bottom Line: Treatment with sepiapterin, a stable precursor of the eNOS cofactor tetrahydrobiopterin, or the nitric oxide precursor L-arginine corrected changes in eNOS dimerization and phosphorylation, corrected permeability defects, and reduced apoptosis.Sepiapterin or L-arginine, administered to db/db mice from weeks 26 to 34, did not significantly alter hyperfiltration or affect mesangial expansion, but reduced albuminuria and GBM thickness, and decreased urinary isoprostane and nitrotyrosine excretion (markers of oxidative stress).Although there was no change in glomerular eNOS monomer expression, both sepiapterin and L-arginine partially reversed the defect in eNOS dimerization and phosphorylation.

View Article: PubMed Central - PubMed

Affiliation: Division of Nephrology, Department of Medicine, George M. O'Brien Kidney and Urologic Diseases Center, Vanderbilt University School of Medicine, Nashville Veterans Affairs Hospital, Nashville, Tennessee 37232, USA.

ABSTRACT
Impaired endothelial nitric oxide synthase (eNOS) activity may be involved in the pathogenesis of diabetic nephropathy. To test this, we used the type 2 diabetic db/db mouse (BKS background) model and found impaired eNOS dimerization and phosphorylation along with moderate glomerular mesangial expansion and increased glomerular basement membrane (GBM) thickness at 34 weeks of age. Cultured murine glomerular endothelial cells exposed to high glucose had similar alterations in eNOS dimerization and phosphorylation. Treatment with sepiapterin, a stable precursor of the eNOS cofactor tetrahydrobiopterin, or the nitric oxide precursor L-arginine corrected changes in eNOS dimerization and phosphorylation, corrected permeability defects, and reduced apoptosis. Sepiapterin or L-arginine, administered to db/db mice from weeks 26 to 34, did not significantly alter hyperfiltration or affect mesangial expansion, but reduced albuminuria and GBM thickness, and decreased urinary isoprostane and nitrotyrosine excretion (markers of oxidative stress). Although there was no change in glomerular eNOS monomer expression, both sepiapterin and L-arginine partially reversed the defect in eNOS dimerization and phosphorylation. Hence, our results support an important role for eNOS dysfunction in diabetes and suggest that sepiapterin supplementation might have therapeutic potential in diabetic nephropathy.

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Sepiapterin (Sep) and L-arginine (L-arg) reversed endothelial nitric oxide synthase (eNOS) impairment in db/db mice. (a) No significant differences in glomerular eNOS expression were detected between BKS and db/db mice with or without treatment. (n=4; NS). (b) There was decreased eNOS dimerization in glomeruli from db/db mice, which was corrected by administration of Sep or L-arg (n=4, *P<0.05, compared with wild-type or treated groups). (c) There was decreased eNOS phosphorylation at Ser1179, but not at Thr479, in glomeruli from db/db mice and normalization by Sep/L-arg treatment. Representative photo was from three independent experiments.
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fig4: Sepiapterin (Sep) and L-arginine (L-arg) reversed endothelial nitric oxide synthase (eNOS) impairment in db/db mice. (a) No significant differences in glomerular eNOS expression were detected between BKS and db/db mice with or without treatment. (n=4; NS). (b) There was decreased eNOS dimerization in glomeruli from db/db mice, which was corrected by administration of Sep or L-arg (n=4, *P<0.05, compared with wild-type or treated groups). (c) There was decreased eNOS phosphorylation at Ser1179, but not at Thr479, in glomeruli from db/db mice and normalization by Sep/L-arg treatment. Representative photo was from three independent experiments.

Mentions: To investigate the potential role of eNOS in the diabetic renal injury, we determined glomerular eNOS expression. There were no differences in eNOS monomer expression between control and diabetic mice (Figure 4a), which was further confirmed by immunohistochemical staining (data not shown). However, glomerular eNOS dimerization (Figure 4b) and phosphorylation at Ser1179 (Figure 4c) decreased by ∼50% in db/db mice, whereas phosphorylation at Thr497 was unchanged (Figure 4c). HG–mediated alterations in endothelial function have been reported to be associated with reduced intracellular BH4.19, 20 In agreement with these findings, we found that glomerular BH4 in db/db mice (0.7±0.1 ng/mg pro.) was significantly lower than BKS control (2.3±0.2 ng/mg pro., n=6, P<0.05).


Improvement of endothelial nitric oxide synthase activity retards the progression of diabetic nephropathy in db/db mice.

Cheng H, Wang H, Fan X, Paueksakon P, Harris RC - Kidney Int. (2012)

Sepiapterin (Sep) and L-arginine (L-arg) reversed endothelial nitric oxide synthase (eNOS) impairment in db/db mice. (a) No significant differences in glomerular eNOS expression were detected between BKS and db/db mice with or without treatment. (n=4; NS). (b) There was decreased eNOS dimerization in glomeruli from db/db mice, which was corrected by administration of Sep or L-arg (n=4, *P<0.05, compared with wild-type or treated groups). (c) There was decreased eNOS phosphorylation at Ser1179, but not at Thr479, in glomeruli from db/db mice and normalization by Sep/L-arg treatment. Representative photo was from three independent experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3473143&req=5

fig4: Sepiapterin (Sep) and L-arginine (L-arg) reversed endothelial nitric oxide synthase (eNOS) impairment in db/db mice. (a) No significant differences in glomerular eNOS expression were detected between BKS and db/db mice with or without treatment. (n=4; NS). (b) There was decreased eNOS dimerization in glomeruli from db/db mice, which was corrected by administration of Sep or L-arg (n=4, *P<0.05, compared with wild-type or treated groups). (c) There was decreased eNOS phosphorylation at Ser1179, but not at Thr479, in glomeruli from db/db mice and normalization by Sep/L-arg treatment. Representative photo was from three independent experiments.
Mentions: To investigate the potential role of eNOS in the diabetic renal injury, we determined glomerular eNOS expression. There were no differences in eNOS monomer expression between control and diabetic mice (Figure 4a), which was further confirmed by immunohistochemical staining (data not shown). However, glomerular eNOS dimerization (Figure 4b) and phosphorylation at Ser1179 (Figure 4c) decreased by ∼50% in db/db mice, whereas phosphorylation at Thr497 was unchanged (Figure 4c). HG–mediated alterations in endothelial function have been reported to be associated with reduced intracellular BH4.19, 20 In agreement with these findings, we found that glomerular BH4 in db/db mice (0.7±0.1 ng/mg pro.) was significantly lower than BKS control (2.3±0.2 ng/mg pro., n=6, P<0.05).

Bottom Line: Treatment with sepiapterin, a stable precursor of the eNOS cofactor tetrahydrobiopterin, or the nitric oxide precursor L-arginine corrected changes in eNOS dimerization and phosphorylation, corrected permeability defects, and reduced apoptosis.Sepiapterin or L-arginine, administered to db/db mice from weeks 26 to 34, did not significantly alter hyperfiltration or affect mesangial expansion, but reduced albuminuria and GBM thickness, and decreased urinary isoprostane and nitrotyrosine excretion (markers of oxidative stress).Although there was no change in glomerular eNOS monomer expression, both sepiapterin and L-arginine partially reversed the defect in eNOS dimerization and phosphorylation.

View Article: PubMed Central - PubMed

Affiliation: Division of Nephrology, Department of Medicine, George M. O'Brien Kidney and Urologic Diseases Center, Vanderbilt University School of Medicine, Nashville Veterans Affairs Hospital, Nashville, Tennessee 37232, USA.

ABSTRACT
Impaired endothelial nitric oxide synthase (eNOS) activity may be involved in the pathogenesis of diabetic nephropathy. To test this, we used the type 2 diabetic db/db mouse (BKS background) model and found impaired eNOS dimerization and phosphorylation along with moderate glomerular mesangial expansion and increased glomerular basement membrane (GBM) thickness at 34 weeks of age. Cultured murine glomerular endothelial cells exposed to high glucose had similar alterations in eNOS dimerization and phosphorylation. Treatment with sepiapterin, a stable precursor of the eNOS cofactor tetrahydrobiopterin, or the nitric oxide precursor L-arginine corrected changes in eNOS dimerization and phosphorylation, corrected permeability defects, and reduced apoptosis. Sepiapterin or L-arginine, administered to db/db mice from weeks 26 to 34, did not significantly alter hyperfiltration or affect mesangial expansion, but reduced albuminuria and GBM thickness, and decreased urinary isoprostane and nitrotyrosine excretion (markers of oxidative stress). Although there was no change in glomerular eNOS monomer expression, both sepiapterin and L-arginine partially reversed the defect in eNOS dimerization and phosphorylation. Hence, our results support an important role for eNOS dysfunction in diabetes and suggest that sepiapterin supplementation might have therapeutic potential in diabetic nephropathy.

Show MeSH
Related in: MedlinePlus