Effect Of Aldose Reductase Inhibitor Research Articles

Enhancement of glucose uptake by Ficus hispida methanolic extract through phosphatidylinositol 3 kinase and inhibiting aldose reductase – An in vitro analysis

IntroductionType 2 diabetes mellitus is a polygenic metabolic syndrome characterized by impaired carbohydrate and lipid metabolism. Diabetes mellitus is commonly associated with secondary disorders such as obesity and genetic predisposition. Prolonged hyperglycemia can also lead to secondary complications such as cataractogenesis, retinopathy and nephropathy through the induction of the polyol pathway. Ficus hispida (FH) is a medium size tree found in India, Sri Lanka and the Andaman Islands in damp localities. Traditionally, different parts of the FH plant have been used in the treatment of various diseases and disorders. MethodologyFH bark was sequentially extracted using different organic solvents ranging from non polar to polar. Glucose uptake assays were performed using 2-deoxy-d-1-[3H] for the FH extracts. Fluorimetric analysis was adopted to assess the aldose reductase inhibitory effect. The gene and protein level expression of the markers were analyzed using RT-PCR and Western blot analysis. ResultsF. hispida methanolic extract (FHME) showed an enhancement in the glucose uptake and upregulated the gene and protein level expression of IRβ, IRS-1, PI3K, GLUT4 and PPARγ. Comparison with wortmannin, a specific PI3K inhibitor confirmed that the active FHME recruits glucose uptake through a PI3K dependent pathway. Subsequently, FHME possesses a significant aldose reductase inhibitory activity. ConclusionThe current study emphasizes the cellular level mechanism of FHME on glucose transport in L6 myotubes and the inhibition of aldose reductase activity.

Anti-neuroinflammatory efficacy of the aldose reductase inhibitor FMHM via phospholipase C/protein kinase C-dependent NF-κB and MAPK pathways

Aldose reductase (AR) has a key role in several inflammatory diseases: diabetes, cancer and cardiovascular diseases. Therefore, AR inhibition seems to be a useful strategy for anti-inflammation therapy. In the central nervous system (CNS), microglial over-activation is considered to be a central event in neuroinflammation. However, the effects of AR inhibition in CNS inflammation and its underlying mechanism of action remain unknown. In the present study, we found that FMHM (a naturally derived AR inhibitor from the roots of Polygala tricornis Gagnep.) showed potent anti-neuroinflammatory effects in vivo and in vitro by inhibiting microglial activation and expression of inflammatory mediators. Mechanistic studies showed that FMHM suppressed the activity of AR-dependent phospholipase C/protein kinase C signaling, which further resulted in downstream inactivation of the IκB kinase/IκB/nuclear factor-kappa B (NF-κB) inflammatory pathway. Therefore, AR inhibition-dependent NF-κB inactivation negatively regulated the transcription and expression of various inflammatory genes. AR inhibition by FMHM exerted neuroprotective effects in lipopolysaccharide-induced neuron–microglia co-cultures. These findings suggested that AR is a potential target for neuroinflammation inhibition and that FMHM could be an effective agent for treating or preventing neuroinflammatory diseases.

The expression of aldose reductase and therapeutic benefits of their inhibition in rats injuried spinal cord

Objective To discuss the expression of Aldose reductase in acute spinal cord injury and the effect of Aldose reductase inhibitor on spinal cell apoptosis.Methods One hundred and fifty SD adult rats were randomly assigned to sham group (n =50),acute spinal cord injury (n =50 ),Aldose reductase inhibitor (Epalrestat Tablets) group (n =50),each group is divided into five sub- groups(6,12,24,48,72 h sub-groups).In the sham group,only laminectomy was applied; In the SCI group and the ARI group,the model were made by Allen' s method.The pathological changes in injured spinal cord were observed with hematoxylin and eosin staining.The aldose reductase was detected by Elisa methods.The TdTmediated dUTP nick end labeling (TUNEL) method was employed to determine neuronal apoptosis.Results After injury 6,12,24,48 and 72 h,the grey and white matter structure of damage area were damaged,with cavity forming and inflammatory cells infiltrating.The degree of ARI group was lighted than SCI group.The content of aldose reductase in the sham operation group after injury 3,12,24,48,72 h were (10.75 ±0.47),(10.61 ±0.44),(10.62±0.55),(10.92±0.49),(10.57±0.52) U/L,the AR contents of SCI group at corresponding time were ( 12.17 ± 0.65 ),( 14.09 ± 0.61 ),( 14.58 ± 0.72 ),( 15.45 ±0.47 ),( 15.33 ± 0.29 ) U/L,and the AR content of the ARI group at corresponding time were ( 10.84 ±0.21),(12.70±0.47),(12.84±0.55),(12.28±0.54),(11.95±0.90) U/L.The AR content of the SCI group at each time point were significantly higher than the shame operation group and ARI group ( P ＜0.05 ).The spinal cord apoptotic cells were rarely seen in the sham operation group at each time point.The apoptotic rates (％) of SCI group after injuried 3,12,24,48,72 h were were 8.45±0.51,27.38 ± 3.19,32.59 ±3.36,39.04 ±4.51,23.48 ±2.40,and the rates of the ARI group at corresponding time were 8.21 ±0.52,18.69 ±1.63,22.64 ±2.18,25.61 ±3.53,16.48 ± 2.23.The neuron apoptosis rates of SCI group at 12,24 、48and 72 h were higher than that of the ARI group (P ＜ 0.05 ).Conclusion After acute spinal cord injury the expression of the AR increased,ARI may reduce the spinal cord neurons cell apoptosis. Key words: Spinal cord injury; Aldose reductase; Cell apoptosis

Abstract 247: Aldose reductase inhibition sensitizes colon cancer cells to TRAIL-induced apoptosis

Abstract Sensitization of cancer cells to tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), particularly TRAIL-resistant cancer cells, could improve the effectiveness of TRAIL as a potential chemotherapy drug. Therefore, development of safe novel pharmacological agents that could sensitize the tumor cells to TRAIL should be an effective strategy to kill the chemotherapy resistance cancer cells. We have recently shown that inhibition of polyol pathway enzyme, aldose reductase (AR) that mediates NF-kB-dependent expression of inflammatory markers, prevents human colon cancer cell growth and metastasis in culture as well in nude mouse models. We now have investigated the role of AR in sensitizing cancer cells to TRAIL and potentiating TRAIL-induced apoptosis of human colon cancer cells. Our results demonstrate that inhibition of AR potentiates TRAIL-induced apoptosis in colon cancer cells (HT-29, HCT-116) by upregulation of both death receptor (DR)-5 and DR4. Specific siRNAs -mediated knockdown of DR5 and DR4 significantly (>85%) reduced the sensitizing effect of AR inhibition by pharmacological agent, fidarestat, on TRAIL-induced apoptosis. AR inhibition also down-regulated TRAIL-induced cell survival proteins such as Bcl-xL, Bcl-2, survivin, XIAP, and cFLIP, and up-regulated the expression of pro-apoptotic proteins such as Bax. Further, AR inhibition also altered the mitochondrial membrane potential leading to cytochrome c release, caspases-3 activation and PARP cleavage. Furthermore, our results indicate that AR inhibition regulates AKT/PI3K-dependent activation of forkhead transcription factor FOXO3a. Knockdown of FOXO3a significantly (>80%) abolished AR inhibition-induced upregulation of DR5 and DR4 and apoptosis in colon cancer cells. Overall, our results show that AR inhibition potentiates TRAIL-induced apoptosis through down-regulation of cell survival proteins and upregulation of death receptors and thus AR inhibitors along with TRAIL could be effective therapy for the treatment of colon cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 247. doi:1538-7445.AM2012-247

Amelioration of experimental autoimmune uveoretinitis by aldose reductase inhibition in Lewis rats.

Recently, the authors showed that the inhibition of aldose reductase (AR) prevents bacterial endotoxin-induced uveitis in rats. They have now investigated the efficacy of AR inhibitors in the prevention of experimental autoimmune-induced uveitis (EAU) in rats. Lewis rats were immunized with bovine interphotoreceptor retinoid-binding peptide (IRBP) to develop EAU. Two or 8 days after immunization, the rats started receiving the AR inhibitor fidarestat (7 mg/kg/d; intraperitoneally). They were killed when the disease was at its peak; aqueous humor (AqH) was collected from one eye, and the other eye of each rat was used for histologic studies. The protein concentration and the levels of inflammatory markers were determined in AqH. Immunohistochemical analysis of eye sections was performed to determine the expression of inflammatory markers. The effect of AR inhibition on immune response was investigated in isolated T lymphocytes. Immunization of rats by IRBP peptide resulted in a significant infiltration of leukocytes in the posterior and the anterior chambers of the eye. Further, EAU caused an increase in the concentration of proteins, inflammatory cytokines, and chemokines in AqH, and the expression of inflammatory markers such as inducible-nitric oxide synthase and cycloxygenase-2 in the rat eye ciliary bodies and retina. Treatment with fidarestat significantly prevented the EAU-induced ocular inflammatory changes. AR inhibition also prevented the proliferation of spleen-derived T cells isolated from EAU rats in response to the IRBP antigen. These results suggest that AR could be a novel mediator of bovine IRBP-induced uveitis in rats.

糖尿病性神経障害患者の自覚症状, 振動覚, 自律神経機能に対するアルドース還元酵素阻害薬フィダレスタット (SNK-860) の効果

糖尿病性神経障害患者の自覚症状, 振動覚, 自律神経機能に対するアルドース還元酵素阻害薬フィダレスタット (SNK-860) の効果

Abstract 5669: Aldose reductase is a novel therapeutic target to prevent oxidative stress-induced inflammatory signals in prostate cancer

Abstract Prostate Cancer (PC) is one of the most common cancers in American men, especially as they age. Although PC initially responds to androgen therapy, as the cancer progresses it usually becomes androgen-independent and prone to metastasis and multi-drug resistance, which kills the majority of patients within 5 years of diagnosis. Therefore, it is necessary to develop better therapeutic strategies which could prevent both early and late stage PC. Our recent studies demonstrate that Aldose Reductase (AR) is the main mediator of inflammatory signals induced by growth factors, cytokines, chemokines, carcinogens etc. Since inflammation is known to play a central role in PC, we investigated the possible role of AR in heterogenous androgen-dependent, -independent, and multi-drug resistant PC cells. Using androgen -dependent LNCaP and -independent PC-3 cells, we have determined the effect of AR inhibition on growth factors such as IGF- and EGF -induced proliferation, cell cycle progression, and generation of reactive oxygen species (ROS). We also determined the effect of AR inhibition on the phosphorylation/expression of androgen receptor, PSA, AKT/PI3K, NF-kB etc in PC cells. Our results show that inhibition of AR by fidarestat significantly prevented the IGF -and EGF-induced proliferation and generation of ROS in both androgen -dependent (LNCaP) and -independent (PC3) PC cells. Cell cycle analysis suggested that inhibition of AR prevents IGF-induced entry of cells from G1 to S phase in PC3 cells. Inhibition of AR also prevented IGF-induced activation of AKT/PI3K and NF-kB. Results with androgen-dependent LNCaP cells showed that inhibition of AR prevented the phosphorylation of androgen receptor, and secretion and expression of PSA when cells were cultured in 5% serum. Further, inhibition of AR increased the drug-sensitivity of multi-drug-resistant PC3 cells against chemotherapeutic agents such as cisplatin, docetaxel, doxorubicin, and methotrexate. These results indicate that AR mediates oxidative stress -induced inflammatory signals in prostate carcinogenesis. Hence, AR inhibition could be a potential therapeutic target against prostate cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5669.

Abstract 424: Invasion and metastasis of human colon cancer cells is prevented by aldose reductase inhibition

Abstract Worldwide colorectal cancer (CRC) is the third most common cause of cancer and is the second leading cause of cancer deaths in the USA. Although therapeutic options for patients with CRC have increased substantially, including earlier diagnosis, improved surgery as well as chemo- and radiation therapies, ∼61% of patients have metastatic disease and of these, 90% die within 5 years of diagnosis. Hence better therapeutic interventions to manage the metastatic process in CRC patients are mandatory. We have recently shown that inhibition of aldose reductase (AR), an enzyme that catalyzes reduction of lipid aldehydes and their glutathione conjugates, prevents human colon cancer cell growth in culture as well as in nude mice xenografts by inhibiting the NF-kB-dependent activation of inflammatory and carcinogenic markers. We have now investigated the effect of AR inhibition in metastatic spread of human CRC cells in nude mice and the molecular mechanisms by which AR inhibition prevents colon cancer cell invasion, migration, adhesion and metastasis. Our results indicate that AR inhibition prevents growth factors-induced migration and invasion of HT-29 CRC cells in a dose-dependent manner. AR inhibition also significantly inhibited adhesion of CRC cells to endothelial cells and inhibited the expression of ICAM-1, VCAM-1 and VE-cadherin. Further, we injected KM20 cells, transfected with a plasmid containing green fluorescent protein (GFP), into the spleen of athymic nude mice to establish liver metastases. The mice were treated with AR inhibitor or siRNA for 30 days. Our results indicate that AR inhibition or ablation prevents in vivo invasion and metastasis of CRC cells by reducing levels of AR, MMP2, cyclin D1, and CD34 and suppresses the activation of NF-kB. Since AR inhibitor fidarestat aggressively prevents human tumor growth and metastasis in nude mice and cellular models, and has already undergone phase-iii clinical studies for diabetic neuropathy, it is an excellent candidate for clinical application in preventing colon cancer tumorigenesis and metastasis. Funding Support: NIH/NCI CA129383 (SKS). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 424.

Abstract 1384: Prevention of angiogenesis by aldose reductase inhibition

Abstract We have recently shown that Aldose Reductase (AR) known to be involved in oxidative stress-signaling, initiated by inflammatory markers, prevents human colon cancer cell growth in culture as well as in nude mice xenografts. Inhibition of AR also prevents azoxymethane-induced aberrant crypt foci formation in mice. In order to understand the chemopreventive mechanism of AR inhibition in colon cancer, we have investigated the role of AR in the mediation of angiogenic signals in vitro and in vivo models. Using human umbilical vein endothelial cells (HUVEC), we have investigated the effect of AR inhibition on VEGF- and bFGF- induced tube as well as spheroid formation in in vitro angiogenesis. We have also determined the invasion and migration of HUVEC by inhibition of AR. Further, to determine the in vivo efficacy of AR inhibition on angiogenesis, matrigel plug assay was performed using a rat model. Our results show that inhibition of AR significantly prevented the VEGF- and bFGF -induced proliferation and generation of reactive oxygen species in HUVEC. Further, AR inhibition also prevented the VEGF- and bFGF- induced secretion/expression of IL-6, MMP1, MMP9, ICAM, and VCAM. Matrigel plug model of angiogenesis in rats showed that inhibition of AR prevented the infiltration of blood cells, invasion, migration and formation of capillary like structures, and expression of blood vessels markers CD31 and vWF. Thus, our results demonstrate that AR inhibitors could be novel drugs for cancer chemoprevention by inhibiting angiogenesis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1384.

Aldose Reductase Inhibitor Ameliorates Renal Vascular Endothelial Growth Factor Expression in Streptozotocin-Induced Diabetic Rats

PurposeThe vascular endothelial growth factor (VEGF) expression of podocyte is one of the well-known major factors in development of diabetic nephropathy. In this study, we investigated the effects of aldose reductase inhibitor, fidarestat on diabetic nephropathy, and renal VEGF expression in a type 1 diabetic rat model.Materials and MethodsTwenty four Sprague-Dawley male rats which were performed intraperitoneal injection of streptozotocin and normal six rats were divided into four groups including a normal control group, untreated diabetic control group, aldose reductase (AR) inhibitor (fidarestat, 16 mg · kg-1 · day-1) treated diabetic group, and angiotensin receptor blocker (losartan, 20 mg · kg-1 · day-1) treated diabetic group. We checked body weights and blood glucose levels monthly and measured urine albumin-creatinine ratio (ACR) at 8 and 32 weeks. We extracted the kidney to examine the renal morphology and VEGF expressions.ResultsThe ACR decreased in fidarestat and losartan treated diabetic rat groups than in untreated diabetic group (24.79 ± 11.12, 16.11 ± 9.95, and 84.85 ± 91.19, p < 0.05). The renal VEGF messenger RNA (mRNA) and protein expression were significantly decreased in the fidarestat and losartan treated diabetic rat groups than in the diabetic control group.ConclusionWe suggested that aldose reductase inhibitor may have preventive effect on diabetic nephropathy by reducing renal VEGF overexpression.

Anti-ischaemic activity of an antioxidant aldose reductase inhibitor on diabetic and non-diabetic rat hearts

Many observations report the cardioprotective effects of inhibitors of aldose reductase in different models of ischaemia-reperfusion injury in diabetic myocardium. In this paper, the inhibitory effects of the new pyrido[1,2-a]-pyrimidin-4-one derivative PPO, whose aldose reductase-inhibitory and antioxidant effects were shown in a previous study, were evaluated. The effect of PPO was evaluated on aldose reductase from hearts of diabetic and non-diabetic rats, and compared with that of the reference drug epalrestat. Moreover, the two drugs were tested on isolated and Langendorff-perfused diabetic and non-diabetic hearts submitted to ischaemia-reperfusion cycle. Epalrestat showed equivalent levels of potency in inhibiting the activity of the enzyme in the diabetic and in the non-diabetic hearts. On the contrary, the inhibitory potency of PPO was decreased in the diabetic organs. In the diabetic hearts submitted to ischaemia-reperfusion, an increased level of heart aldose reductase activity was recorded, and both PPO and epalrestat produced cardioprotective effects, suggesting that aldose reductase is deeply involved in the process of ischaemia-reperfusion injury in diabetic myocardium. In non-diabetic hearts, where aldose reductase has a lower activity, epalrestat failed to produce significant protection, while PPO still maintained cardioprotective effects, which may be reasonably attributed to useful 'ancillary' effects - such as antioxidant activity - independent from the aldose reductase inhibition. Therefore PPO, a new molecule endowed with both aldose reductase-inhibitory effects and antioxidant activity, may represent the prototype of a new class of multitarget drugs, focused on two different steps deeply involved in the pathogenesis of ischaemic injury of diabetic hearts.

Aldose reductase inhibitory activity and anti catraract potential of some traditionally acclaimed antidiabetic medicinal plants

Aldose reductase (AR) has been reported to play an important role in sugar-induced cataract. In the present study, the AR inhibitory activity of Enicostemma hyssopifolium (EH), Gymnema sylvestre, Eclipta alba, and Tinospora cordifolia (TC) were studied along with their effect on sugar-induced cataractogenic changes in sheep lenses in vitro. AR inhibitory activity of the aqueous extracts of plants and their anticataract potentials were evaluated in vitro in sheep lenses, considering the activity of normal sheep lenses as 100%. The concentration of the plant extract that showed maximum activity was selected to further study its effect on galactose-induced polyol accumulation in vitro. The <TEX>$IC_50$</TEX> values of EH and TC were calculated to be 102 and 85 <TEX>${\mu}g$</TEX>/ml, respectively. EH showed a significant inhibition (61.3%) in polyol accumulation followed by TC (53.1%). EH and TC possesses a significant anticataract activity in vitro and its anticataract potential could be related with its AR inhibitory effect.

Aldose reductase inhibitor counteracts the attenuated adhesion of human corneal epithelial cells induced by high glucose through modulation of MMP-10 expression

Aims We investigated the preventive effect of aldose reductase inhibitor (ARI) on the adhesion of SV40-transformed human corneal epithelial cells (HCECs) exposed to high glucose, and the underlying mechanism focusing on the role of matrix metalloproteinase (MMP)-10. Methods HCECs were cultured in medium containing a normal (5.5 mM) or high (31.2 mM) concentration of d-glucose in the presence or absence of ARI, fidarestat. Cell attachment ability was evaluated by short-term adhesion assay. The levels of intracellular polyol were measured by liquid-gas chromatography. Real-time reverse transcriptase-polymerase chain reaction (RT-PCR), and Western blotting were used to determine the expression levels. Results Decreased attachment activity and increased accumulation of polyol induced by exposure to high glucose were abrogated by ARI. Supply of recombinant MMP-10 decreased integrin α3β1-expression and cell adhesion. The expression level of MMP-10 was enhanced at both protein and mRNA levels by exposure to high glucose, while that of integrin α3β1 was decreased at the protein level, but remained unchanged at the mRNA level. These alterations in the expression levels of MMP-10 and integrin α3β1 were normalized by ARI. Conclusions ARI counteracts the decreased adhesion of HCECs induced by high glucose exposure, through the modulation of the expression of MMP-10.

Anti-inflammatory effect of aldose reductase inhibition in murine polymicrobial sepsis

Aim: Increased production of cytokines and chemokines in serum and tissues upon oxidative stress caused by severe systemic infections are the major cause of sepsis. Aldose reductase (AR) known to mediate oxidative stress-induced NF-κB activation and transcription of cytokines and chemokines are the main mediator of bacterial endotoxin-induced inflammatory response. Our aim is to investigate the effect of AR inhibitors on the prevention of inflammatory cytokines in the cecum ligation and puncture (CLP) model of polymicrobial sepsis which closely mimics the sepsis syndrome in humans. Results: Mice were rendered septic by CLP in the absence and presence of AR inhibitor, sorbinil. The levels of cytokines, chemokines and other inflammatory markers in the plasma, peritoneal fluid and heart of mice were significantly inhibited by sorbinil. Inhibition of AR also prevented CLP-induced COX-2, iNOS and HMGB-1 in heart, kidney and spleen. Conclusions: Our results showed that the inhibition of AR significantly prevented the polymicrobial sepsis-induced increase in inflammatory markers and thus indicate the use of AR inhibitors as anti-inflammatory agents.

The inhibitory effect on aldose reductase by an extract of Ganoderma lucidum

The human aldose reductase inhibitory effects of the methanol extracts of 17 medicinal and edible mushrooms were examined. Ganoderma lucidum showed the highest aldose reductase inhibitory activity compared with the other mushrooms. The effect of an ethanol extract of G. lucidum on the galactitol level in the eye lens was studied in a galactosemic rat model in vivo. This mushroom significantly decreased the galactitol accumulation.

Prevention of Posterior Capsular Opacification through Aldose Reductase Inhibition

The purpose of this study was to evaluate the effect of aldose reductase (AR) inhibition on posterior capsular opacification (PCO) with the use of a pig eye capsular bag model. Pig eye capsular bags were prepared by capsulorhexis and cultured in medium without or with AR inhibitors for 7 days. Immunostaining was performed in paraformaldehyde-fixed capsular bags to determine the expression of proliferating cell nuclear antigen (PCNA), alpha-smooth muscle actin (SMA), beta-crystallin, and intercellular adhesion molecule (ICAM)-1. The effect of AR inhibition on basic fibroblast growth factor (BFGF)-induced mitogenic signaling in cultured human lens epithelial cells (HLECs) was examined. Cell growth was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and cell counting, the expression of alpha-SMA, beta-crystallin, and ICAM-1 by Western blot and immunocytochemical analysis, protein kinases by Western blot analysis, and NF-kappaB activation by gel shift and reporter assays. During culture of pig eye capsular bags, residual cells on both the anterior and the posterior capsule showed vigorous growth. Treatment with AR inhibitors significantly prevented the lens epithelial cell growth in capsular bags and expression of alpha-SMA, beta-crystallin, and ICAM-1. HLECs showed a dose-dependent response to BFGF, proliferation at lower concentrations (<20 ng/mL) and differentiation/transdifferentiation at higher concentrations (>50 ng/mL). Inhibition of AR also prevented the BFGF-induced activation of ERK1/2, JNK, and NF-kappaB in HLECs. Results suggest that AR is required for lens epithelial cell growth and differentiation/transdifferentiation in the capsular bags, indicating that inhibition of AR could be a potential therapeutic target in the prevention of PCO.

Aldose Reductase Inhibitor, Epalrestat, Reduces Lipid Hydroperoxides in Type 2 Diabetes

The increased flux of polyol pathway induced by hyperglycemia is implicated in the pathogenesis of various complications associated with diabetic, which results in increased oxidative stress. Because oxidative stress causes tissue damage in patients with diabetes, searching for an effective strategy to reduce oxidative stress in clinical setting is important in order to prevent diabetic complications. The aim of this study was to evaluate the effects of aldose reductase inhibition on oxidative stress in patients with type 2 diabetes mellitus. The subjects of this study were 21 patients with type 2 diabetes. We compared the levels of various oxidative stress markers and antioxidants including plasma thiobarbituric acid-reactive substances, malondialdehyde-modified low-density lipoprotein, vitamin E, beta-carotene and lipid hydroperoxides in erythrocytes at baseline with those measured after a 3-month course of epalrestat (150 mg/day), an aldose reductase inhibitor. While administration of epalrestat did not result in significant changes in plasma thiobarbituric acid-reactive substances, malondialdehyde-modified low-density lipoprotein, vitamin E, or beta-carotene, it significantly reduced lipid hydroperoxides in erythrocytes. Given the importance of measuring lipid hydroperoxides in erythrocytes as an index of oxidative stress, these results highlight the potential usefulness of epalrestat in reducing oxidative stress in type 2 diabetes mellitus.

Attenuation of aldose reductase gene suppresses high-glucose-induced apoptosis and oxidative stress in rat lens epithelial cells

Aims A major contributory factor to diabetic cataract formation is increased aldose reductase (AR) activity in the polyol pathway. We investigated the effects of aldose reductase inhibition by RNA interference (RNAi) of the aldose reductase gene and administration of an aldose reductase inhibitor (ARI) on the changes induced by high glucose levels in rat lens epithelial cells (RLECs). Methods Small interfering RNAs (siRNAs) were designed to target the coding sequence of rat AR-siRNA. RLECs were cultured in either normal or high d-glucose. Western analysis was performed to monitor AR expression. MTS (3-(4-5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium salt) and TUNEL assays were used to detect apoptotic cell death. Intracellular reactive oxygen species (ROS) were assessed by using DCFH-DA. Activation of nuclear factor-κB (NF-κB) was measured by an ELISA-based detection method. Results Both siRNA and ARI suppressed increased levels of ROS, activation of NF-κB, and apoptotic cell death induced by high glucose levels. Inhibition of rAR expression by siRNA and inhibition of AR activity by ARI also suppressed sorbitol accumulation. Conclusions Both inhibition of rAR expression by rAR siRNA and inhibition of rAR activity by an ARI appeared effective in diminishing the changes of RLECs associated with high glucose levels.

Elevated lipid peroxidation and DNA oxidation in nerve from diabetic rats: effects of aldose reductase inhibition, insulin, and neurotrophic factors

We investigated the effect of treatment with an aldose reductase inhibitor, insulin, or select neurotrophic factors on the generation of oxidative damage in peripheral nerve. Rats were either treated with streptozotocin to induce insulin-deficient diabetes or fed with a diet containing 40% d-galactose to promote hexose metabolism by aldose reductase. Initial time course studies showed that lipid peroxidation and DNA oxidation were significantly elevated in sciatic nerve after 1 week or 2 weeks of streptozotocin-induced diabetes, respectively, and that both remained elevated after 12 weeks of diabetes. The increase in nerve lipid peroxidation was completely prevented or reversed by treatment with the aldose reductase inhibitor, ICI 222155, or by insulin, but not by the neurotrophic factors, prosaptide TX14(A) or neurotrophin-3. The increase in nerve DNA oxidation was significantly prevented by insulin treatment. In contrast, up to 16 weeks of galactose feeding did not alter nerve lipid peroxidation or protein oxidation, despite evidence of ongoing nerve conduction deficits. These observations demonstrate that nerve oxidative damage develops early after the onset of insulin-deficient diabetes and that it is not induced by increased hexose metabolism by aldose reductase per se, but rather is a downstream consequence of flux through this enzyme. Furthermore, the beneficial effect of prosaptide TX14(A) and neurotrophin-3 on nerve function and structure in diabetic rats is not due to amelioration of increased lipid peroxidation.

QSAR prediction of inhibition of aldose reductase for flavonoids

We performed a predictive analysis based on quantitative structure–activity relationships (QSAR) of an important property of flavonoids, which is the inhibition (IC 50) of aldose reductase (AR). The importance of AR inhibition is that it prevents cataract formation in diabetic patients. The best linear model constructed from 55 molecular structures incorporated six molecular descriptors, selected from more than a thousand geometrical, topological, quantum-mechanical, and electronic types of descriptors. As a practical application, we used the obtained QSAR model to predict the AR inhibitory effect of newly synthesized flavonoids that present 2-, 7-substitutions in the benzopyrane backbone.