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Candesartan attenuates diabetic retinal vascular pathology by restoring glyoxalase-I function.

Miller AG, Tan G, Binger KJ, Pickering RJ, Thomas MC, Nagaraj RH, Cooper ME, Wilkinson-Berka JL - Diabetes (2010)

Bottom Line: In BREC and BRP, Ang II induced apoptosis and reduced GLO-I activity and mRNA, with a concomitant increase in nitric oxide (NO(•)), the latter being a known negative regulator of GLO-I in BRP.In BREC and BRP, candesartan restored GLO-I and reduced NO(•).Similar events occurred in vivo, with the elevated RAS of the diabetic Ren-2 rat, but not the diabetic Sprague-Dawley rat, reducing retinal GLO-I.

View Article: PubMed Central - PubMed

Affiliation: Oxidative Stress Laboratory, Diabetes Division, Baker IDI Heart and Diabetes Institute, Melbourne, Australia. antonia.miller@monash.edu

ABSTRACT

Objective: Advanced glycation end products (AGEs) and the renin-angiotensin system (RAS) are both implicated in the development of diabetic retinopathy. How these pathways interact to promote retinal vasculopathy is not fully understood. Glyoxalase-I (GLO-I) is an enzyme critical for the detoxification of AGEs and retinal vascular cell survival. We hypothesized that, in retina, angiotensin II (Ang II) downregulates GLO-I, which leads to an increase in methylglyoxal-AGE formation. The angiotensin type 1 receptor blocker, candesartan, rectifies this imbalance and protects against retinal vasculopathy.

Research design and methods: Cultured bovine retinal endothelial cells (BREC) and bovine retinal pericytes (BRP) were incubated with Ang II (100 nmol/l) or Ang II+candesartan (1 μmol/l). Transgenic Ren-2 rats that overexpress the RAS were randomized to be nondiabetic, diabetic, or diabetic+candesartan (5 mg/kg/day) and studied over 20 weeks. Comparisons were made with diabetic Sprague-Dawley rats.

Results: In BREC and BRP, Ang II induced apoptosis and reduced GLO-I activity and mRNA, with a concomitant increase in nitric oxide (NO(•)), the latter being a known negative regulator of GLO-I in BRP. In BREC and BRP, candesartan restored GLO-I and reduced NO(•). Similar events occurred in vivo, with the elevated RAS of the diabetic Ren-2 rat, but not the diabetic Sprague-Dawley rat, reducing retinal GLO-I. In diabetic Ren-2 rats, candesartan reduced retinal acellular capillaries, inflammation, and inducible nitric oxide synthase and NO(•), and restored GLO-I.

Conclusions: We have identified a novel mechanism by which candesartan improves diabetic retinopathy through the restoration of GLO-I.

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GLO-I mRNA and activity levels in BREC and BRP after treatment with Ang II and candesartan (Cand). In BREC (A and B) and BRP (C and D), GLO-I mRNA (A and C) and activity (B and D) is decreased after treatment with Ang II (100 nmol/l) for 24 h compared with control. Cand (1 μmol/l) restored GLO-I activity and mRNA in BREC and BRP co-incubated with Ang II. A, B: *P < 0.05 versus control, †P < 0.05 versus Ang II. C and D: *P < 0.03 versus control. All data were analyzed by Kruskal-Wallis test, followed by Mann-Whitney U tests. Values are the mean of N = 3–4 independent experiments with triplicate samples within each experiment.
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Figure 2: GLO-I mRNA and activity levels in BREC and BRP after treatment with Ang II and candesartan (Cand). In BREC (A and B) and BRP (C and D), GLO-I mRNA (A and C) and activity (B and D) is decreased after treatment with Ang II (100 nmol/l) for 24 h compared with control. Cand (1 μmol/l) restored GLO-I activity and mRNA in BREC and BRP co-incubated with Ang II. A, B: *P < 0.05 versus control, †P < 0.05 versus Ang II. C and D: *P < 0.03 versus control. All data were analyzed by Kruskal-Wallis test, followed by Mann-Whitney U tests. Values are the mean of N = 3–4 independent experiments with triplicate samples within each experiment.

Mentions: To determine whether Ang II induces apoptosis in retinal vascular cells, BREC and BRP were incubated with 100 nmol/l Ang II for 24 h. In BREC and BRP, Ang II treatment resulted in a 500 and 30% increase in either TUNEL or Annexin-positive cells, respectively, compared with control (Fig. 1). Given this finding, we next evaluated GLO-I in BREC and BRP and found that, in both cell types, Ang II decreased GLO-I activity and mRNA by 20% compared with controls (Fig. 2). To confirm the involvement of Ang II in the downregulation of GLO-I, we next measured GLO-I after treatment with the AT1-RB, candesartan. In both BREC and BRP, candesartan restored both GLO-I activity and mRNA to control levels in Ang II-treated cells (Fig. 2), and in the case of BREC, GLO-I mRNA was elevated above control levels (Fig. 2). Overall, BREC was more responsive to the actions of candesartan in terms of restoration of GLO-I function. Candesartan in the absence of Ang II, in almost all instances, did not influence GLO-I levels (see supplementary Fig. 1, available in the online appendix).


Candesartan attenuates diabetic retinal vascular pathology by restoring glyoxalase-I function.

Miller AG, Tan G, Binger KJ, Pickering RJ, Thomas MC, Nagaraj RH, Cooper ME, Wilkinson-Berka JL - Diabetes (2010)

GLO-I mRNA and activity levels in BREC and BRP after treatment with Ang II and candesartan (Cand). In BREC (A and B) and BRP (C and D), GLO-I mRNA (A and C) and activity (B and D) is decreased after treatment with Ang II (100 nmol/l) for 24 h compared with control. Cand (1 μmol/l) restored GLO-I activity and mRNA in BREC and BRP co-incubated with Ang II. A, B: *P < 0.05 versus control, †P < 0.05 versus Ang II. C and D: *P < 0.03 versus control. All data were analyzed by Kruskal-Wallis test, followed by Mann-Whitney U tests. Values are the mean of N = 3–4 independent experiments with triplicate samples within each experiment.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2992784&req=5

Figure 2: GLO-I mRNA and activity levels in BREC and BRP after treatment with Ang II and candesartan (Cand). In BREC (A and B) and BRP (C and D), GLO-I mRNA (A and C) and activity (B and D) is decreased after treatment with Ang II (100 nmol/l) for 24 h compared with control. Cand (1 μmol/l) restored GLO-I activity and mRNA in BREC and BRP co-incubated with Ang II. A, B: *P < 0.05 versus control, †P < 0.05 versus Ang II. C and D: *P < 0.03 versus control. All data were analyzed by Kruskal-Wallis test, followed by Mann-Whitney U tests. Values are the mean of N = 3–4 independent experiments with triplicate samples within each experiment.
Mentions: To determine whether Ang II induces apoptosis in retinal vascular cells, BREC and BRP were incubated with 100 nmol/l Ang II for 24 h. In BREC and BRP, Ang II treatment resulted in a 500 and 30% increase in either TUNEL or Annexin-positive cells, respectively, compared with control (Fig. 1). Given this finding, we next evaluated GLO-I in BREC and BRP and found that, in both cell types, Ang II decreased GLO-I activity and mRNA by 20% compared with controls (Fig. 2). To confirm the involvement of Ang II in the downregulation of GLO-I, we next measured GLO-I after treatment with the AT1-RB, candesartan. In both BREC and BRP, candesartan restored both GLO-I activity and mRNA to control levels in Ang II-treated cells (Fig. 2), and in the case of BREC, GLO-I mRNA was elevated above control levels (Fig. 2). Overall, BREC was more responsive to the actions of candesartan in terms of restoration of GLO-I function. Candesartan in the absence of Ang II, in almost all instances, did not influence GLO-I levels (see supplementary Fig. 1, available in the online appendix).

Bottom Line: In BREC and BRP, Ang II induced apoptosis and reduced GLO-I activity and mRNA, with a concomitant increase in nitric oxide (NO(•)), the latter being a known negative regulator of GLO-I in BRP.In BREC and BRP, candesartan restored GLO-I and reduced NO(•).Similar events occurred in vivo, with the elevated RAS of the diabetic Ren-2 rat, but not the diabetic Sprague-Dawley rat, reducing retinal GLO-I.

View Article: PubMed Central - PubMed

Affiliation: Oxidative Stress Laboratory, Diabetes Division, Baker IDI Heart and Diabetes Institute, Melbourne, Australia. antonia.miller@monash.edu

ABSTRACT

Objective: Advanced glycation end products (AGEs) and the renin-angiotensin system (RAS) are both implicated in the development of diabetic retinopathy. How these pathways interact to promote retinal vasculopathy is not fully understood. Glyoxalase-I (GLO-I) is an enzyme critical for the detoxification of AGEs and retinal vascular cell survival. We hypothesized that, in retina, angiotensin II (Ang II) downregulates GLO-I, which leads to an increase in methylglyoxal-AGE formation. The angiotensin type 1 receptor blocker, candesartan, rectifies this imbalance and protects against retinal vasculopathy.

Research design and methods: Cultured bovine retinal endothelial cells (BREC) and bovine retinal pericytes (BRP) were incubated with Ang II (100 nmol/l) or Ang II+candesartan (1 μmol/l). Transgenic Ren-2 rats that overexpress the RAS were randomized to be nondiabetic, diabetic, or diabetic+candesartan (5 mg/kg/day) and studied over 20 weeks. Comparisons were made with diabetic Sprague-Dawley rats.

Results: In BREC and BRP, Ang II induced apoptosis and reduced GLO-I activity and mRNA, with a concomitant increase in nitric oxide (NO(•)), the latter being a known negative regulator of GLO-I in BRP. In BREC and BRP, candesartan restored GLO-I and reduced NO(•). Similar events occurred in vivo, with the elevated RAS of the diabetic Ren-2 rat, but not the diabetic Sprague-Dawley rat, reducing retinal GLO-I. In diabetic Ren-2 rats, candesartan reduced retinal acellular capillaries, inflammation, and inducible nitric oxide synthase and NO(•), and restored GLO-I.

Conclusions: We have identified a novel mechanism by which candesartan improves diabetic retinopathy through the restoration of GLO-I.

Show MeSH
Related in: MedlinePlus