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Therapeutic potential of Nrf2 activators in streptozotocin-induced diabetic nephropathy.

Zheng H, Whitman SA, Wu W, Wondrak GT, Wong PK, Fang D, Zhang DD - Diabetes (2011)

Bottom Line: Changes in protein expression of the Nrf2 pathway, as well as transforming growth factor-β1 (TGF-β1), fibronectin (FN), collagen IV, and p21/WAF1Cip1 (p21) were analyzed.Nrf2 activation reduced oxidative damage and suppressed the expression of TGF-β1, extracellular matrix proteins and p21 both in vivo and in HRMCs.In addition, Nrf2 activation reverted p21-mediated growth inhibition and hypertrophy of HRMCs under hyperglycemic conditions.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology and Toxicology, University of Arizona, Tucson, Arizona, USA.

ABSTRACT

Objective: To determine whether dietary compounds targeting NFE2-related factor 2 (Nrf2) activation can be used to attenuate renal damage and preserve renal function during the course of streptozotocin (STZ)-induced diabetic nephropathy.

Research design and methods: Diabetes was induced in Nrf2(+/+) and Nrf2(-/-) mice by STZ injection. Sulforaphane (SF) or cinnamic aldehyde (CA) was administered 2 weeks after STZ injection and metabolic indices and renal structure and function were assessed (18 weeks). Markers of diabetes including blood glucose, insulin, polydipsia, polyuria, and weight loss were measured. Pathological alterations and oxidative damage in glomeruli were also determined. Changes in protein expression of the Nrf2 pathway, as well as transforming growth factor-β1 (TGF-β1), fibronectin (FN), collagen IV, and p21/WAF1Cip1 (p21) were analyzed. The molecular mechanisms of Nrf2-mediated protection were investigated in an in vitro model using human renal mesangial cells (HRMCs).

Results: SF or CA significantly attenuated common metabolic disorder symptoms associated with diabetes in Nrf2(+/+) but not in Nrf2(-/-) mice, indicating SF and CA function through specific activation of the Nrf2 pathway. Furthermore, SF or CA improved renal performance and minimized pathological alterations in the glomerulus of STZ-Nrf2(+/+) mice. Nrf2 activation reduced oxidative damage and suppressed the expression of TGF-β1, extracellular matrix proteins and p21 both in vivo and in HRMCs. In addition, Nrf2 activation reverted p21-mediated growth inhibition and hypertrophy of HRMCs under hyperglycemic conditions.

Conclusions: We provide experimental evidence indicating that dietary compounds targeting Nrf2 activation can be used therapeutically to improve metabolic disorder and relieve renal damage induced by diabetes.

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Related in: MedlinePlus

Activation of Nrf2 reduces TGF-β1, ECM deposition, and p21 expression. A: Immunoblot analysis was performed on lysates from whole kidney (left panel), and band intensities were quantified (right panel, bar graphs) and reported as relative expression to control animals. STZ injection increased TGF-β1, FN, collagen IV, and p21 expression. Treatment with SF and CA reduced this expression in Nrf2+/+ only. B: Fixed kidney tissue was analyzed by IHC. STZ injection increased staining of the glomeruli for TGF-β1, FN, collagen IV, and p21. Treatment with SF and CA reduced expression of TGF-β1, FN, collagen IV, and p21 in Nrf2+/+ only. Data are expressed as mean ± SD (n = 3). *P < 0.05 compared with control. #P < 0.05 dietary treatment compared with STZ alone. (A high-quality color representation of this figure is available in the online issue.)
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Figure 4: Activation of Nrf2 reduces TGF-β1, ECM deposition, and p21 expression. A: Immunoblot analysis was performed on lysates from whole kidney (left panel), and band intensities were quantified (right panel, bar graphs) and reported as relative expression to control animals. STZ injection increased TGF-β1, FN, collagen IV, and p21 expression. Treatment with SF and CA reduced this expression in Nrf2+/+ only. B: Fixed kidney tissue was analyzed by IHC. STZ injection increased staining of the glomeruli for TGF-β1, FN, collagen IV, and p21. Treatment with SF and CA reduced expression of TGF-β1, FN, collagen IV, and p21 in Nrf2+/+ only. Data are expressed as mean ± SD (n = 3). *P < 0.05 compared with control. #P < 0.05 dietary treatment compared with STZ alone. (A high-quality color representation of this figure is available in the online issue.)

Mentions: Given that treatment with SF or CA diminished renal disorders resulting from STZ-induced diabetes, the molecular mechanisms underlying Nrf2-dependent protection of the kidney by SF or CA were explored. Previously, our laboratory reported a negative association between Nrf2 and TGF-β1. In accordance with that report, the basal expression of TGF-β1 was higher in Nrf2−/− mice compared with Nrf2+/+ mice (Fig. 4A and B). Diabetes induced by STZ significantly upregulated protein levels of TGF-β1 and its downstream effectors, FN, collagen IV, and p21, which were significantly abrogated by treatment with SF or CA in the Nrf2+/+ animals only (Fig. 4A and B). Treatment with SF and CA in the Nrf2−/− mice did not alter TGF-β1, ECM, or p21, indicating that the negative regulation of TGF-β1 and subsequent downstream effectors (ECM and p21) observed with SF and CA treatment is Nrf2 dependent.


Therapeutic potential of Nrf2 activators in streptozotocin-induced diabetic nephropathy.

Zheng H, Whitman SA, Wu W, Wondrak GT, Wong PK, Fang D, Zhang DD - Diabetes (2011)

Activation of Nrf2 reduces TGF-β1, ECM deposition, and p21 expression. A: Immunoblot analysis was performed on lysates from whole kidney (left panel), and band intensities were quantified (right panel, bar graphs) and reported as relative expression to control animals. STZ injection increased TGF-β1, FN, collagen IV, and p21 expression. Treatment with SF and CA reduced this expression in Nrf2+/+ only. B: Fixed kidney tissue was analyzed by IHC. STZ injection increased staining of the glomeruli for TGF-β1, FN, collagen IV, and p21. Treatment with SF and CA reduced expression of TGF-β1, FN, collagen IV, and p21 in Nrf2+/+ only. Data are expressed as mean ± SD (n = 3). *P < 0.05 compared with control. #P < 0.05 dietary treatment compared with STZ alone. (A high-quality color representation of this figure is available in the online issue.)
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3198067&req=5

Figure 4: Activation of Nrf2 reduces TGF-β1, ECM deposition, and p21 expression. A: Immunoblot analysis was performed on lysates from whole kidney (left panel), and band intensities were quantified (right panel, bar graphs) and reported as relative expression to control animals. STZ injection increased TGF-β1, FN, collagen IV, and p21 expression. Treatment with SF and CA reduced this expression in Nrf2+/+ only. B: Fixed kidney tissue was analyzed by IHC. STZ injection increased staining of the glomeruli for TGF-β1, FN, collagen IV, and p21. Treatment with SF and CA reduced expression of TGF-β1, FN, collagen IV, and p21 in Nrf2+/+ only. Data are expressed as mean ± SD (n = 3). *P < 0.05 compared with control. #P < 0.05 dietary treatment compared with STZ alone. (A high-quality color representation of this figure is available in the online issue.)
Mentions: Given that treatment with SF or CA diminished renal disorders resulting from STZ-induced diabetes, the molecular mechanisms underlying Nrf2-dependent protection of the kidney by SF or CA were explored. Previously, our laboratory reported a negative association between Nrf2 and TGF-β1. In accordance with that report, the basal expression of TGF-β1 was higher in Nrf2−/− mice compared with Nrf2+/+ mice (Fig. 4A and B). Diabetes induced by STZ significantly upregulated protein levels of TGF-β1 and its downstream effectors, FN, collagen IV, and p21, which were significantly abrogated by treatment with SF or CA in the Nrf2+/+ animals only (Fig. 4A and B). Treatment with SF and CA in the Nrf2−/− mice did not alter TGF-β1, ECM, or p21, indicating that the negative regulation of TGF-β1 and subsequent downstream effectors (ECM and p21) observed with SF and CA treatment is Nrf2 dependent.

Bottom Line: Changes in protein expression of the Nrf2 pathway, as well as transforming growth factor-β1 (TGF-β1), fibronectin (FN), collagen IV, and p21/WAF1Cip1 (p21) were analyzed.Nrf2 activation reduced oxidative damage and suppressed the expression of TGF-β1, extracellular matrix proteins and p21 both in vivo and in HRMCs.In addition, Nrf2 activation reverted p21-mediated growth inhibition and hypertrophy of HRMCs under hyperglycemic conditions.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology and Toxicology, University of Arizona, Tucson, Arizona, USA.

ABSTRACT

Objective: To determine whether dietary compounds targeting NFE2-related factor 2 (Nrf2) activation can be used to attenuate renal damage and preserve renal function during the course of streptozotocin (STZ)-induced diabetic nephropathy.

Research design and methods: Diabetes was induced in Nrf2(+/+) and Nrf2(-/-) mice by STZ injection. Sulforaphane (SF) or cinnamic aldehyde (CA) was administered 2 weeks after STZ injection and metabolic indices and renal structure and function were assessed (18 weeks). Markers of diabetes including blood glucose, insulin, polydipsia, polyuria, and weight loss were measured. Pathological alterations and oxidative damage in glomeruli were also determined. Changes in protein expression of the Nrf2 pathway, as well as transforming growth factor-β1 (TGF-β1), fibronectin (FN), collagen IV, and p21/WAF1Cip1 (p21) were analyzed. The molecular mechanisms of Nrf2-mediated protection were investigated in an in vitro model using human renal mesangial cells (HRMCs).

Results: SF or CA significantly attenuated common metabolic disorder symptoms associated with diabetes in Nrf2(+/+) but not in Nrf2(-/-) mice, indicating SF and CA function through specific activation of the Nrf2 pathway. Furthermore, SF or CA improved renal performance and minimized pathological alterations in the glomerulus of STZ-Nrf2(+/+) mice. Nrf2 activation reduced oxidative damage and suppressed the expression of TGF-β1, extracellular matrix proteins and p21 both in vivo and in HRMCs. In addition, Nrf2 activation reverted p21-mediated growth inhibition and hypertrophy of HRMCs under hyperglycemic conditions.

Conclusions: We provide experimental evidence indicating that dietary compounds targeting Nrf2 activation can be used therapeutically to improve metabolic disorder and relieve renal damage induced by diabetes.

Show MeSH
Related in: MedlinePlus