The protective effects of vitamin E on urinary bladder apoptosis and oxidative stress in streptozotocin-induced diabetic rats

Oxidative Stress Alterations in the Bladder of a Short-period Type 2 Diabetes Rat Model: Antioxidant Treatment Can Be Beneficial for the Bladder

BACKGROUND/AIM

A short-period type 2 diabetes model was established in order to identify changes in oxidative stress in the bladder at the initiation of the disease. The effect of antioxidant treatment was examined.

MATERIALS AND METHODS

Diabetes was induced in adult male Wistar rats with a single dose of streptozotocin (40 mg/kg; i.p.). Diabetic animals were then randomly separated into three groups: No treatment (DM), resveratrol treatment, and taurine treatment, and fed with a high-fat diet. Age-matched non-diabetic animals were used and fed with normal diet (control). Two weeks later, animals were sacrificed and bladders were processed for histological evaluation, and further analysis for oxidative stress markers.

RESULTS

The body weight of all diabetic animals was significantly lower compared to the controls. The DM group demonstrated a significantly higher bladder weight to body weight ratio compared to the control. The bladder in the DM group demonstrated abruption of the mucosa from the muscularis and edema in the transitional epithelium. Bladders from the resveratrol-, and taurine-treated groups did not demonstrate these histological alterations. The level of malondialdehyde (MDA) in the bladder was significantly higher in the DM group compared to all other groups. Immunohistochemistry showed that diabetes induced a moderate to strong expression of oxidative stress markers MDA and 4-hydroxynonenal, and DNA oxidative stress marker 8-deoxyguanosine in the DM group compared to the other groups.

CONCLUSION

Prompt diagnosis and treatment of diabetes is crucial in regard to disease progression. Specifically, in the bladder it appears that both mild damage at the structural level, as well as oxidative damage at the molecular level may be prevented by antioxidant treatment.

CGRP Reduces Apoptosis of DRG Cells Induced by High-Glucose Oxidative Stress Injury through PI3K/AKT Induction of Heme Oxygenase-1 and Nrf-2 Expression

Dorsal root ganglion (DRG) neurons, which are sensitive to oxidative stress due to their anatomical and structural characteristics, play a complex role in the initiation and progression of diabetic bladder neuropathy. We investigated the hypothesis that the antioxidant and antiapoptotic effects of CGRP may be partly related to the expression of Nrf2 and HO-1, via the phosphatidylinositol 3-kinase (PI3K)/AKT pathway, thus reducing apoptosis and oxidative stress responses. This study shows that CGRP activates the PI3K/AKT pathway, thereby inducing increased expression of Nrf2 and HO-1 and resulting in the decrease of reactive oxygen species and malondialdehyde levels and reduced neuronal apoptosis. These effects were suppressed by LY294002, an inhibitor of the PI3K/AKT pathway. Therefore, regulation of Nrf2 and HO-1 expression by the PI3K/AKT pathway plays an important role in the regulation of the antioxidant and antiapoptotic responses in DRG cells in a high-glucose culture model.

Smooth muscle-specific deletion of MnSOD exacerbates diabetes-induced bladder dysfunction in mice

Bladder dysfunction in diabetes progresses gradually over time. However, the mechanisms of the development are not clear. We tested the hypothesis that oxidative stress plays a key role in the development of diabetic bladder dysfunction using an inducible smooth muscle (SM)-specific superoxide dismutase 2 (Sod2) gene knockout (SM-Sod2 KO) mouse model. Eight-week-old male Sod2lox/lox, SM-CreERT2(ki)Cre/+ mice and wild-type mice were assigned to diabetic or control groups. 4-Hydroxytamoxifen was injected into Sod2lox/lox, SM-CreERT2(ki)Cre/+ mice to activate CreERT2-mediated deletion of Sod2. Diabetes was induced by injection of streptozotocin, whereas control mice were injected with vehicle. Nine weeks later, bladder function was evaluated, and bladders were harvested for immunoblot analysis. Wild-type diabetic mice presented compensated bladder function along with increased nitrotyrosine and MnSOD in detrusor muscle. Induction of diabetes in SM-Sod2 KO mice caused deteriorated bladder function and even greater increases in nitrotyrosine compared with wild-type diabetic mice. Expression levels of apoptosis regulator Bax and cleaved caspase-3 were increased, but apoptosis regulator Bcl-2 expression was decreased in detrusor muscle of both diabetic groups, with more pronounced effects in SM-Sod2 KO diabetic mice. Our findings demonstrate that exaggerated oxidative stress can accelerate the development of bladder dysfunction in diabetic mice and the enhanced activation of apoptotic pathways in the bladder may be involved in the process.

Grape Seed Proanthocyanidin Extract Ameliorates Diabetic Bladder Dysfunction via the Activation of the Nrf2 Pathway

Diabetes Mellitus (DM)-induced bladder dysfunction is predominantly due to the long-term oxidative stress caused by hyperglycemia. Grape seed proanthocyanidin extract (GSPE) has been reported to possess a broad spectrum of pharmacological and therapeutic properties against oxidative stress. However, its protective effects against diabetic bladder dysfunction have not been clarified. This study focuses on the effects of GSPE on bladder dysfunction in diabetic rats induced by streptozotocin. After 8 weeks of GSPE administration, the bladder function of the diabetic rats was improved significantly, as indicated by both urodynamics analysis and histopathological manifestation. Moreover, the disordered activities of antioxidant enzymes (SOD and GSH-Px) and abnormal oxidative stress levels were partly reversed by treatment with GSPE. Furthermore, the level of apoptosis in the bladder caused by DM was decreased following the administration of GSPE according to the Terminal Deoxynucleotidyl Transferase (TdT)-mediated dUTP Nick-End Labeling (TUNEL) assay. Additionally, GSPE affected the expression of apoptosis-related proteins such as Bax, Bcl-2 and cleaved caspase-3. Furthermore, GSPE showed neuroprotective effects on the bladder of diabetic rats, as shown by the increased expression of nerve growth factor (NGF) and decreased expression of the precursor of nerve growth factor (proNGF). GSPE also activated nuclear erythroid2-related factor2 (Nrf2), which is a key antioxidative transcription factor, with the concomitant elevation of downstream hemeoxygenase-1 (HO-1). These findings suggested that GSPE could ameliorate diabetic bladder dysfunction and decrease the apoptosis of the bladder in diabetic rats, a finding that may be associated with its antioxidant activity and ability to activate the Nrf2 defense pathway.

Grape seed extract has superior beneficial effects than vitamin E on oxidative stress and apoptosis in the hippocampus of streptozotocin induced diabetic rats

We aimed to investigate the effects of grape seed extract (GSE) and vitamin E (Vit E) on oxidative stress and apoptosis in the hippocampus of streptozotocin-induced diabetic rats. In Control, Diabetic, and Diabetic treated with GSE (Diabetic+GSE) and vitamin E (Diabetic+Vit E) groups, oxidative stress index (OSI), TUNEL staining and Bcl-2, Bcl-XL, Bax, caspase-3, -9, and -8, Cyt-c, TNF-α, and NF-κB gene expressions were evaluated. OSI was significantly increased in the plasma and hippocampus of the Diabetic compared to Control group and decreased in Diabetic+GSE and Diabetic+Vit E groups compared to Diabetic. TUNEL positive neurons significantly increased in the hippocampus of the Diabetic group compared to Control and decreased in Diabetic+GSE (more prominently) and Diabetic+Vit E groups compared to Diabetic. In the hippocampus of the Diabetic group, Bcl-2 and Bcl-XL gene expressions were significantly decreased; Bax, caspase-3, -9, and -8, Cyt-c, TNF-α, and NF-κB gene expressions were significantly increased compared to Control. In Diabetic+GSE and Diabetic+Vit E groups, Bcl-2 gene expressions were significantly increased; Bcl-XL gene expressions did not differ compared to the Diabetic group. The expression of Bax, caspase-3, -9, and -8, Cyt-c, TNF-α, and NF-κB genes in the Diabetic+GSE group and the expression of caspase-3 and -9, TNF-α, and NF-κB genes in the Diabetic+Vit E group were significantly decreased compared to Diabetic. In conclusion, GSE (more prominently) and vitamin E decreased oxidative stress and neuronal apoptosis occurring in the hippocampus of diabetic rats.

Bladder dysfunction in patients with diabetes

With diabetes mellitus (DM) reaching epidemic proportions, the identification of voiding dysfunction as a common and burdensome complication of this disease is critical. Research into diabetic voiding dysfunction significantly lags behind other complications of DM, such as retinopathy and nephropathy. Recent studies have revealed that DM predisposes patients to a wide range of lower urinary tract dysfunction, from the classic diabetic cystopathy of incomplete emptying to urgency incontinence. In this review, we discuss the current concepts of diabetic voiding dysfunction with a critical analysis of the available evidence.

Poly(ADP-ribose) polymerase is involved in the development of diabetic cystopathy via regulation of nuclear factor kappa B

OBJECTIVES

To investigate whether overactivated Poly (ADP-ribose) polymerase (PARP) and subsequent activation of nuclear factor kappa B (NF-κB) correlate with the development of diabetic cystopathy via induction of bladder apoptosis. Diabetic cystopathy as a common complication of diabetes is frequently associated with increased oxidative stress and apoptosis of the bladder. PARP is activated by hyperglycemia-induced oxidative stress and plays a critical role in cell apoptosis and the development of diabetic complications, such as retinopathy and nephropathy.

METHODS

Sprague-Dawley rats were divided into 3 groups: control, diabetic, and diabetic treated with PARP inhibitor (DM+Vit-B3). Four weeks after induction of diabetes, the DM+Vit-B3 group was treated with PARP inhibitor (nicotinamide, 400 mg/kg/d) for 3 weeks. Bladder function was then assessed by conscious cystometry. The extent of oxidative stress and apoptosis, expression of poly(ADP-ribose) (PAR), NF-κB, phosphorylated inhibitor of NF-κB (IκB)-α, Bcl-2, and Bax in the bladder were also investigated.

RESULTS

Bladder dysfunction was strongly associated with increased oxidative stress and bladder apoptosis. In addition, the amount of PAR, phosphorylated IκB-α, expression of NF-κB, and Bax were significantly increased in diabetic rat bladder. Inhibition of PARP significantly reduced PARP activation and expression of NF-κB and Bax. As a result, bladder apoptosis was attenuated and bladder function was improved.

CONCLUSIONS

These results indicate that overactivated PARP and subsequent activation of NF-κB play important roles in the development of diabetic cystopathy via induction of bladder apoptosis. These findings may be applied in the development of novel therapies for patients with diabetic cystopathy.