Inhibition of aldose reductase prevents endotoxin-induced inflammation by regulating the arachidonic acid pathway in murine macrophages

The bacterial endotoxin lipopolysaccharide (LPS) is known to induce release of arachidonic acid (AA) and its metabolic products, which play important roles in the inflammatory process. We have shown earlier that LPS-induced signals in macrophages are mediated by aldose reductase (AR). Here we have investigated the role of AR in LPS-induced release of AA metabolites and their modulation using a potent pharmacological inhibitor, fidarestat, and AR siRNA ablation in RAW264.7 macrophages and AR-knockout mouse peritoneal macrophages and heart tissue. Inhibition or genetic ablation of AR prevented the LPS-induced synthesis and release of AA metabolites such as PGE2, TXB, PGI2, and LTBs in macrophages. LPS-induced activation of cPLA2 was also prevented by AR inhibition. Similarly, AR inhibition also prevented the calcium ionophore A23187-induced cPLA2 and LTB4 in macrophages. Further, AR inhibition by fidarestat prevented the expression of AA-metabolizing enzymes such as COX-2 and LOX-5 in RAW264.7 cells and AR-knockout mouse-derived peritoneal macrophages. LPS-induced expression of AA-metabolizing enzymes and their catalyzed metabolic products was significantly lower in peritoneal macrophages and heart tissue from AR-knockout mice. LPS-induced activation of redox-sensitive signaling intermediates such as MAPKs, transcription factor NF-κB, and EGR-1, a transcriptional regulator of mPGES-1, which in collaboration with COX-2 leads to the production of PGE2, was also significantly prevented by AR inhibition. Taken together, our results indicate that AR mediates LPS-induced inflammation by regulating the AA-metabolic pathway and thus provide a novel role for AR inhibition in preventing inflammatory complications such as sepsis.

Aldose reductase deficiency protects from autoimmune- and endotoxin-induced uveitis in mice

PURPOSE

To investigate the effect of aldose reductase (AR) deficiency in protecting the chronic experimental autoimmune (EAU) and acute endotoxin-induced uveitis (EIU) in c57BL/6 mice.

METHODS

The WT and AR-null (ARKO) mice were immunized with human interphotoreceptor retinoid-binding peptide (hIRPB-1-20), to induce EAU, or were injected subcutaneously with lipopolysaccharide (LPS; 100 μg) to induce EIU. The mice were killed on day 21 for EAU and at 24 hours for EIU, when the disease was at its peak, and the eyes were immediately enucleated for histologic and biochemical studies. Spleen-derived T-lymphocytes were used to study the antigen-specific immune response in vitro and in vivo.

RESULTS

In WT-EAU mice, severe damage to the retinal wall, especially to the photoreceptor layer was observed, corresponding to a pathologic score of ∼2, which was significantly prevented in the ARKO or AR inhibitor-treated mice. The levels of cytokines and chemokines increased markedly in the whole-eye homogenates of WT-EAU mice, but not in ARKO-EAU mice. Further, expression of inflammatory marker proteins such as inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2, tumor necrosis factor (TNF)-α, and vascular cell adhesion molecule (VCAM)-1 was increased in the WT-EIU mouse eyes but not in the ARKO-EIU eyes. The T cells proliferated vigorously when exposed to the hIRPB antigen in vitro and secreted various cytokines and chemokines, which were significantly inhibited in the T cells isolated from the ARKO mice.

CONCLUSIONS

These findings suggest that AR-deficiency/inhibition protects against acute as well as chronic forms of ocular inflammatory complications such as uveitis.

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

PURPOSE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

These results suggest that AR could be a novel mediator of bovine IRBP-induced uveitis in rats.

Simple facile route for the preparation of graphite oxide and graphene

A simple method is reported for the preparation of graphite oxide (GO) and graphene using KCIO3/NaNO3/H2SO4 and Na2S as oxidizing agent as oxidizing and reducing agents respectively. The formation of GO and graphene have also been confirmed by X-ray diffraction studies, UV-visible, spectroscopy, FTIR and Raman spectroscopy. The morphology, surface charge characteristic and thermal stability behaviour have been studied by SEM/TEM, Zeta potential measurements, thermogravimetric analysis.

Evidence for Serpentine as a novel antioxidant by a redox sensitive HABP1 overexpressing cell line by inhibiting its nuclear translocation of NF-κB

Herbal antioxidants are gradually gaining importance as dietary supplements considering the growing implications of oxidative stress in most degenerative diseases and aging. Thus, continuous attempts are made to search for novel herbal molecules with antioxidative properties, using chemical methods predominantly with the need arising for cell based assays. We have generated a stable cell line F-HABP07, by constitutively overexpressing human Hyaluronan Binding Protein1 (HABP1) in murine fibroblasts which accumulates in the mitochondria leading to excess ROS generation without any external stimuli. In the present study, we demonstrated the nuclear translocation of p65 subunit of NF-κB in F-HABP07 cells, an important signature of ROS induced signalling cascade providing us an opportunity to use it as a screening system for ROS scavengers. Using known antioxidants on our designer cell line, we have demonstrated a dose dependant reduction in ROS generation and observed inhibition of p65 subunit of NF-κB nuclear translocation, increase in glutathione content and down-regulation of apoptotic marker Bax establishing its antioxidant biosensing capacity. With the help of this cell line, we for the first time demonstrated serpentine, one of the active components from the roots of Rauwolfia serpentina (a traditional medicinal plant), to be a novel non-cytotoxic antioxidant. The authenticity of this cell line screening system based discovery was validated using standard chemical assays thus, opening up new therapeutic avenues for this herbal compound and the use of this designer cell line.

Inhibition of aldose reductase prevents colon cancer metastasis

Colon cancer is the third most common cause of cancer and is the second leading cause of cancer deaths in the USA. Although inhibition of aldose reductase (AR) is known to prevent human colon cancer cell growth in nude mice xenografts, the role of AR in the regulation of cancer metastasis is not known. We now demonstrate the mechanisms by which AR regulates colon cancer metastasis in vitro and in vivo. Inhibition of AR prevented the epidermal growth factor (EGF) or fibroblast growth factor (FGF)-induced migration and invasion of human colon cancer (HT29; KM20) cells by >70% and also inhibited (>80%) the adhesion of the cancer cells to endothelial cells. Treatment of endothelial cells with AR inhibitors significantly (∼85%) downregulated the EGF or FGF-induced expression of Inter-Cellular Adhesion Molecule-1, Vascular cell adhesion molecule-1 and vascular endothelial-cadherin. Furthermore, liver metastasis of green fluorescent protein-labeled KM20 cells injected into the spleen of athymic nude mice was significantly (>65%) prevented by AR inhibitor, fidarestat or ARsiRNA delivered systemically into the mice. Similar results were observed with HT29 cells. AR inhibition or ablation also prevented (70-90%) the increase in the levels of matrix metalloproteinase-2, cyclin D1, CD31, CD34 and the activation of nuclear factor-kappa-binding protein in metastatic liver. Thus, our results indicate that AR regulates cancer cell adhesion, invasion and migration events which initiate metastasis and therefore, AR inhibition could be a novel therapeutic approach for the prevention of colon cancer metastasis.

Aldose reductase inhibition prevents hypoxia-induced increase in hypoxia-inducible factor-1alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF) by regulating 26 S proteasome-mediated protein degradation in human colon cancer cells

The development of intratumoral hypoxia, a hallmark of rapidly progressing solid tumors, renders tumor cells resistant to chemotherapy and radiation therapy. We have recently shown that inhibition of aldose reductase (AR), an enzyme that catalyzes the reduction of lipid aldehydes and their glutathione conjugates, prevents human colon cancer cell growth in culture as well as in nude mouse xenografts by inhibiting the NF-κB-dependent activation of oxidative stress-mediated inflammatory and carcinogenic markers. However, the role of AR in mediating hypoxic stress signals is not known. We therefore investigated the molecular mechanisms by which AR inhibition prevents the hypoxia-induced human colon cancer cells growth and invasion. Our results indicate that AR inhibition by the pharmacological inhibitor fidarestat or ablation by AR-specific siRNA prevents hypoxia-induced proliferation of HT29, SW480, and Caco-2 colon cancer cells. Furthermore, hypoxia-induced increase in the level of HIF-1α in colon cancer cells was significantly decreased by AR inhibition. During hypoxic conditions, treatment of HT29 cells with the AR inhibitor fidarestat significantly decreased the expression of vascular endothelial growth factor, a down target of HIF-1α, at both mRNA and protein levels and also prevented the activation of PI3K/AKT, GSK3β, Snail, and lysyl oxidase. Furthermore, inhibition of hypoxia-induced HIF-1α protein accumulation by AR inhibition was abolished in the presence of MG132, a potent inhibitor of the 26 S proteasome. In addition, AR inhibition also prevented the hypoxia-induced inflammatory molecules such as Cox-2 and PGE2 and expression of extracellular matrix proteins such as MMP2, vimentin, uPAR, and lysyl oxidase 2. In conclusion, our results indicate that AR mediates hypoxic signals, leading to tumor progression and invasion.

Abstract 2052: Inhibition of aldose reductase prevents hypoxic stress signaling in human colon cancer cells

Hypoxia, a hallmark of invasive solid tumors and increased angiogenesis, is strongly associated with the progression of malignant phenotypes, poor prognosis, and resistance to chemo and radiation therapies. In a variety of cancers, hypoxic stress-induces inflammatory signaling which is mediated by specific cytokines, chemokines and growth factors. We have recently shown that inhibition of aldose reductase (AR), an enzyme that catalyzes the 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 oxidative stress-mediated inflammatory and carcinogenic markers. However, the role of AR in mediating hypoxic stress signals is not known. We therefore investigated the molecular mechanisms by which AR inhibition prevents the hypoxia-induced human colon cancer cells growth and invasion. Our results indicate that AR inhibition by pharmacological inhibitor fidarestat or ablation by AR specific siRNA prevents hypoxia-induced proliferation of HT29 colon cancer cells. Further, hypoxia- induced increase in the level of HIF1a in HT29 cells was significantly decreased by AR inhibition. During hypoxic conditions treatment of HT29 cells with AR inhibitor, fidarestat significantly decreased the expression of VEGF, a down target of HIF1a, at both mRNA and protein levels and also prevented the activation of PI3K/AKT and GSK3b. Further, AR inhibition also prevented hypoxia-induced inflammatory molecules such as Cox-2 and PGE2 and expression of extracellular matrix proteins such as MMP2, vimentin, uPAR and LOX2. In addition, AR inhibition also prevented the hypoxia -induced tube formation (angiogenesis) in vascular endothelial cells. In conclusion, our results indicate that AR mediates hypoxia -induced tumor progression, invasion and angiogenesis which can be prevented by AR inhibition or ablation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2052. doi:10.1158/1538-7445.AM2011-2052

Inhibition of aldose reductase prevents angiogenesis in vitro and in vivo

We have recently shown that aldose reductase (AR, EC 1.1.1.21) a nicotinamide adenine dinucleotide phosphate-dependent aldo-keto reductase, known to be involved in oxidative stress-signaling, 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(s) 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. Our results show that inhibition of AR significantly prevented the VEGF- and FGF -induced proliferation and expression of proliferative marker Ki67 in the human umbilical vein endothelial cells (HUVEC). Further, AR inhibition or ablation with siRNA prevented the VEGF- and FGF -induced invasion and migration in HUVEC. AR inhibition also prevented the VEGF- and FGF- induced secretion/expression of IL-6, MMP2, MMP9, ICAM, and VCAM. The anti-angiogenic feature of AR inhibition in HUVEC was associated with inactivation of PI3 K/AKT and NF-κB (p65) and suppression of VEGF receptor 2 protein levels. Most importantly, matrigel plug model of angiogenesis in rats showed that inhibition of AR prevented 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 agents to prevent angiogenesis.

Aldose reductase deficiency protects sugar-induced lens opacification in rats

Aldose reductase (AKR1B1), which catalyzes the reduction of glucose to sorbitol and lipid aldehydes to lipid alcohols, has been shown to be involved in secondary diabetic complications including cataractogenesis. Rats have high levels of AKR1B1 in lenses and readily develop diabetic cataracts, whereas mice have very low levels of AKR1B1 in their lenses and are not susceptible to hyperglycemic cataracts. Studies with transgenic mice that over-express AKR1B1 indicate that it is the key protein for the development of diabetic complications including diabetic cataract. However, no such studies were performed in genetically altered AKR1B1 rats. Hence, we developed siRNA-based AKR1B1 knockdown rats (ARKO) using the AKR1B1-siRNA-pSuper vector construct. Genotyping analysis suggested that more than 90% of AKR1B1 was knocked down in the littermates. Interestingly, all the male animals were born dead and only 3 female rats survived. Furthermore, all 3 female animals were not able to give birth to F1 generation. Hence, we could not establish an AKR1B1 rat knockdown colony. However, we examined the effect of AKR1B1 knockdown on sugar-induced lens opacification in ex vivo. Our results indicate that rat lenses obtained from AKR1B1 knockdown rats were resistant to high glucose-induced lens opacification as compared to wild-type (WT) rat lenses. Biochemical analysis of lens homogenates showed that the AKR1B1 activity and sorbitol levels were significantly lower in sugar-treated AKR1B1 knockdown rat lenses as compared to WT rat lenses treated with 50mM glucose. Our results thus confirmed the significance of AKR1B1 in the mediation of sugar-induced lens opacification and indicate the use of AKR1B1 inhibitors in the prevention of cataractogenesis.

Post-translational protein modification by carotenoid cleavage products

Carotenoids are known to generate various aldehydes, known as carotenoid-derived aldehydes (CDAs), which could efficiently react with protein or DNA. In this in vitro model study, interaction between CDA and protein has been studied. Various proteins were incubated with CDA, and protein modification and adduct formation were confirmed by using matrix-assisted laser desorption and ionization time-of-flight, amino acid analysis, and measuring enzyme activity on modification with CDA. Using radiolabeled NaB((3) H)H(4) and Raney nickel as well as sulfhydryl assay (Ellman's reagent), we confirmed that CDA could conjugate with cysteine through a thioether linkage. The carbonyl assay using 2,4-dinitrophenylhydrazine revealed the possible involvement of Schiff's base reaction between CDA and lysine. The adducts formed between β-apo-8-carotenal (BA8C) and N-acetylcysteine and BA8C and N-acetyllysine were confirmed by HPLC and ESI-MS. Our results suggest that CDA could alter protein function by post-translational interaction with cysteine and lysine by thioether linkage and by schiff's based bonds, respectively. Thus, the formation of CDA adducts with proteins could alter functional properties of proteins responsible for maintaining cell homeostasis and thereby cause cellular toxicity. In view of these observations, further studies are required to understand the delicate balance between beneficial and/or harmful effects of carotenoids as a dietary supplement to slow age-related macular degeneration progression.

Aldose reductase inhibition suppresses airway inflammation

Airway inflammation induced by reactive oxygen species (ROS)-mediated activation of redox-sensitive transcription factors is the hallmark of asthma, a prevalent chronic respiratory disease. In various cellular and animal models, we have recently demonstrated that, in response to multiple stimuli, aldose reductase (AKR1B1) regulates the inflammatory signals via NF-kappa B activation. Since NF-κB activation is implicated in asthma pathogenesis, we investigated whether AKR1B1 inhibition could prevent ovalbumin (Ova)- and ragweed pollen extract (RWE)-induced airway inflammation and hyper-responsiveness in mice models and tumor necrosis factor-alpha (TNF-α)-, lipopolysachharide (LPS)- and RWE-induced cytotoxic and inflammatory signals in primary human small airway epithelial cells (SAEC). Sensitization and challenge with Ova or RWE caused airway inflammation and production of inflammatory cytokines, accumulation of eosinophils in airways and sub-epithelial regions, mucin production in the bronchoalveolar lavage fluid, airway hyperresponsiveness, elevated IgE levels and release of Th2 cytokines in the airway and treatment with AKR1B1 inhibitors markedly reduced these pathological changes in mice. In SAEC, treatment with TNF-α, LPS or RWE induced apoptosis, reactive oxygen species generation, synthesis of inflammatory markers IL-6, IL-8, and PGE2 and activation of NF-κB and AP-1. Pharmacological inhibition prevented these changes suggesting that AKR1B1 mediates ROS induced inflammation in small airway epithelial cells. Our results indicate that AKR1B1 inhibitors may offer a novel therapeutic approach to treat inflammatory airway diseases such as asthma.

Aldose reductase inhibition prevents metaplasia of airway epithelial cells

BACKGROUND

Goblet cell metaplasia that causes mucus hypersecretion and obstruction in the airway lumen could be life threatening in asthma and chronic obstructive pulmonary disease patients. Inflammatory cytokines such as IL-13 mediate the transformation of airway ciliary epithelial cells to mucin-secreting goblet cells in acute as well as chronic airway inflammatory diseases. However, no effective and specific pharmacologic treatment is currently available. Here, we investigated the mechanisms by which aldose reductase (AR) regulates the mucus cell metaplasia in vitro and in vivo.

METHODOLOGY/FINDINGS

Metaplasia in primary human small airway epithelial cells (SAEC) was induced by a Th2 cytokine, IL-13, without or with AR inhibitor, fidarestat. After 48 h of incubation with IL-13 a large number of SAEC were transformed into goblet cells as determined by periodic acid-schiff (PAS)-staining and immunohistochemistry using antibodies against Mucin5AC. Further, IL-13 significantly increased the expression of Mucin5AC at mRNA and protein levels. These changes were significantly prevented by treatment of the SAEC with AR inhibitor. AR inhibition also decreased IL-13-induced expression of Muc5AC, Muc5B, and SPDEF, and phosphorylation of JAK-1, ERK1/2 and STAT-6. In a mouse model of ragweed pollen extract (RWE)-induced allergic asthma treatment with fidarestat prevented the expression of IL-13, phosphorylation of STAT-6 and transformation of epithelial cells to goblet cells in the lung. Additionally, while the AR-null mice were resistant, wild-type mice showed goblet cell metaplasia after challenge with RWE.

CONCLUSIONS

The results show that exposure of SAEC to IL-13 caused goblet cell metaplasia, which was significantly prevented by AR inhibition. Administration of fidarestat to mice prevented RWE-induced goblet cell metaplasia and AR null mice were largely resistant to allergen induced changes in the lung. Thus our results indicate that AR inhibitors such as fidarestat could be developed as therapeutic agents to prevent goblet cell metaplasia in asthma and related pathologies.

Layered double hydroxide as nanofiller in the development of polyurethane nanocomposites

Polyurethane (PU)/Dodecyl sulphate intercalated layered double hydroxide (DS-LDH) nanocomposites were successfully synthesized from PU prepolymer and polyol TG (mixtures of glycerol and trimethylolpropane) for the first time. Formation of partially exfoliated structures of PU/DS-LDH nanocomposites was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Analysis of tensile properties showed significant improvements in tensile strength (TS) and elongation at break (EB) of about 407% and 83% for PU/DS-LDH (3 wt%) nanocomposite. The observed excellent concurrent improvement in TS and EB is attributed to the relatively better reinforcing effect of partially exfoliated DS-LDH layers in PU making the present investigation most noteworthy. In addition, gradual improvement in thermal stability and limiting oxygen index (LOI) with increasing DS-LDH loading makes these nanocomposites versatile and hence suitable for many critical applications.

Understanding the role of aldose reductase in ocular inflammation

Aldose reductase, although identified initially as a glucose-reducing enzyme via polyol pathway, is believed to be an important component of antioxidant defense system as well as a key mediator of oxidative stress-induced molecular signaling. The dual role played by AR has made it a very important enzyme for the regulation of not only the cellular redox state by detoxifying the reactive lipid-aldehydes generated by lipid peroxidation which is crucial in the cellular homeostasis, but also in the regulation of molecular signaling cascade that may regulate oxidative stress-induced cytotoxic events. Search for the new molecular targets to restrain the oxidative stress-induced inflammation has resulted in the identification of AR as an unanticipated mediator of oxidative stress-induced signaling. Although, in last one decade or so AR has been implicated in various inflammation-related diseases conditions ranging from diabetes, sepsis, cancer, cardiovascular and ocular inflammation, however, a critical evaluation of the clinical efficacy of AR inhibitors awaits a better understanding of the role of AR in regulating inflammation, especially in ocular inflammation.

Hydrothermal synthesis of PbTe nanorods using different templates

Nanocrystalline PbTe has successfully been synthesized under hydrothermal conditions in the temperature range 125-165 degrees C for 24 h in presence of ethylene diamine tetraacetic acid (EDTA), as template from the aqueous chemical routes using lead acetate, Pb(CH3COO)2 and sodium tellurite (Na2TeO3) as precursors and hydrazine hydrate (N2H4 x H2O) as the reductant. At lower temperature (125 degrees C), predominantly PbTe cubes are formed, where at higher temperature (165 degrees C), growth of nanorods of diameter 65 nm and length ranging in microns takes place. The possible mechanisms about the formation of PbTe have also been discussed. Raman studies on the nanorods of these samples also confirmed the purity of the product. The formation of PbTe nanorods is also observed when tartaric acid (TA) and ethylene diamine (EDA) have been used at templates at 165 degrees C for 24 h.

Synthesis, quantification, characterization, and signaling properties of glutathionyl conjugates of enals

Oxidation of lipids generates large quantities of highly reactive alpha,beta-unsaturated aldehydes (enals). Enals and their protein adducts accumulate in the tissues of several pathologies. In vitro, low concentrations of enals such as HNE (4-hydroxy trans-2-nonenal) affect cell signaling whereas high concentrations of enals are cytotoxic. Direct conjugation of the C2-C3 double bond of enals with the sulfhydryl group of GSH is a major route for the metabolism and detoxification of enals. Recently, we found that glutathionyl conjugate of HNE (GS-HNE) enhances the peritoneal leukocyte infiltration and stimulates the formation of proinflammatory lipid mediators. Moreover, the reduced form of the glutathione conjugate of HNE (GS-DHN) elicits strong mitogenic signaling in smooth muscle cells. In this chapter we discuss the methods to study the metabolism of enals and the redox signaling properties of glutathionyl conjugates of HNE.

Protective role of benfotiamine, a fat-soluble vitamin B1 analogue, in lipopolysaccharide-induced cytotoxic signals in murine macrophages

This study was designed to investigate the molecular mechanisms by which benfotiamine, a lipid-soluble analogue of vitamin B1, affects lipopolysaccharide (LPS)-induced inflammatory signals leading to cytotoxicity in the mouse macrophage cell line RAW264.7. Benfotiamine prevented LPS-induced apoptosis, expression of the Bcl-2 family of proapoptotic proteins, caspase-3 activation, and PARP cleavage and altered mitochondrial membrane potential and release of cytochrome c and apoptosis-inducing factor and phosphorylation and subsequent activation of p38-MAPK, stress-activated kinases (SAPK/JNK), protein kinase C, and cytoplasmic phospholipase A2 in RAW cells. Further, phosphorylation and degradation of inhibitory kappaB and consequent activation and nuclear translocation of the redox-sensitive transcription factor NF-kappaB were significantly prevented by benfotiamine. The LPS-induced increased expression of cytokines and chemokines and the inflammatory marker proteins iNOS and COX-2 and their metabolic products NO and PGE(2) was also blocked significantly. Thus, our results elucidate the molecular mechanism of the anti-inflammatory action of benfotiamine in LPS-induced inflammation in murine macrophages. Benfotiamine suppresses oxidative stress-induced NF-kappaB activation and prevents bacterial endotoxin-induced inflammation, indicating that vitamin B1 supplementation could be beneficial in the treatment of inflammatory diseases.

Aldose reductase regulates vascular smooth muscle cell proliferation by modulating G1/S phase transition of cell cycle

Abnormal proliferation of vascular smooth muscle cells (VSMC) is a key feature of development of cardiovascular complications, atherosclerosis, and restenosis. Patients with diabetes have higher risk for restenosis after coronary angioplasty than nondiabetic patients due to hyperglycemia-induced release of cytokines such as TNF-alpha. However, the molecular mechanisms regulating VSMC proliferation remain unclear. Herein, we report that inhibition of the polyol pathway enzyme aldose reductase (AR) prevents high glucose (HG)- and/or TNF-alpha-induced VSMC proliferation by accumulating cells at the G1 phase of the cell cycle. Treatment of VSMC with AR inhibitor sorbinil prevented HG- as well as TNF-alpha-induced phosphorylation of retinoblastoma protein and activation of E2F-1. Inhibition of AR also prevented HG- and TNF-alpha-induced phosphorylation of cyclin-dependent kinase (cdk)-2 and expression of G1/S transition regulatory proteins such as cyclin D1, cyclin E, cdk-4, c-myc, and proliferative cell nuclear antigen. More importantly, inhibition of AR prevented the increased expression of E2F-1 and proliferative cell nuclear antigen in diabetic rat aorta. Treatment of VSMC with the most abundant and toxic lipid aldehyde 4-hydroxy-trans-2-nonenal (HNE) or its glutathione conjugate [glutathionyl (GS)-HNE] or AR-catalyzed product of GS-HNE, GS-1,4-dihydroxynonane, resulted in increased E2F-1 expression. Inhibition of AR prevented HNE- or GS-HNE-induced but not GS-1,4-dihydroxynonane-induced up-regulation of E2F-1. Collectively, these results show that AR could regulate HG- and TNF-alpha-induced VSMC proliferation by altering the activation of G1/S-phase proteins such as E2F-1, cdks, and cyclins. Thus, inhibition of AR may be a useful therapeutic approach in preventing vascular complications.

Abstract 3233: Inhibition of aldose reductase prevents lung cancer cell growth in vitro and in vivo

Lung cancer is the second most common cancer and the leading cause of cancer death among both men and women. Although, tobacco smoking is the dominant etiologic factor responsible for the vast majority of lung cancers, other factors such as asbestos, pollutants, polycyclic aromatic hydrocarbons, nutritional and dietary factors which can cause pulmonary inflammation can also drive carcinogenesis by altering cellular and molecular targets and pathways that are crucial to normal tissue homeostasis. However, the molecular signaling events specific to the pulmonary inflammation and their effects on pulmonary cells leading to carcinogenesis are poorly understood. Hence, we investigated the role of polyol pathway enzyme aldose reductase (AR), an oxidative stress response protein that catalyzes the reduction of lipid peroxidation -derived lipid aldehydes and their glutathione conjugates, in the mediation of carcinogenic signals leading to lung cancer. We examined the effect of pharmacological and siRNA -mediated inhibition of AR on in vitro human lung carcinoma cell line A549 growth as well as tumor growth in nude mice xenografts. We have also examined the molecular mechanisms by which AR inhibition prevents carcinogenic signaling events that cause lung cancer cell growth. Treatment of A549 cells with AR inhibitors prevented the activation of NF-kB and expression of NF-kB- dependent inflammatory markers such as iNOS and Cox-2. AR inhibition also prevented the proliferation of cultured human lung cancer cells. Further, AR inhibition significantly arrested the tumor growth in nude mice bearing lung adenocarcinoma xenografts. Similar results were observed in AR-siRNA treated nude mice xenografts. Immunohistochemical analysis of nude mice tumor cross sections indicated that AR inhibition prevents activation of iNOS, Cox-2, AR and NF-kB. Our studies thus strongly suggest that AR may be a critical regulator of signaling pathway(s) that cause lung cancer. Hence, disrupting these signals by AR inhibition could be a novel preventive approach in lung cancer progression.

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 3233.

Abstract 1384: Prevention of angiogenesis by aldose reductase inhibition

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.

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

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.

Inhibition of aldose reductase prevents growth factor-induced G1-S phase transition through the AKT/phosphoinositide 3-kinase/E2F-1 pathway in human colon cancer cells

Colon cancer is the leading cause of cancer death in both men and women worldwide. The deregulated cell cycle control or decreased apoptosis of normal epithelial cells leading to uncontrolled proliferation is one of the major features of tumor progression. We have previously shown that aldose reductase (AR), a NADPH-dependent aldo-keto reductase, has been shown to be involved in growth factor-induced proliferation of colon cancer cells. Herein, we report that inhibition of AR prevents epidermal growth factor (EGF)- and basic fibroblast growth factor (bFGF)-induced HT29 cell proliferation by accumulating cells at G(1) phase of cell cycle. Similar results were observed in SW480 and HCT-116 colon cancer cells. Treatment of HT29 cells with AR inhibitor, sorbinil or zopolrestat, prevented the EGF- and bFGF-induced DNA binding activity of E2F-1 and phosphorylation of retinoblastoma protein. Inhibition of AR also prevented EGF- and bFGF-induced phosphorylation of cyclin-dependent kinase (cdk)-2 and expression of G(1)-S transition regulatory proteins such as cyclin D1, cdk4, proliferating cell nuclear antigen, cyclin E, and c-myc. More importantly, inhibition of AR prevented the EGF- and bFGF-induced activation of phosphoinositide 3-kinase/AKT and reactive oxygen species generation in colon cancer cells. Further, inhibition of AR also prevented the tumor growth of human colon cancer cells in nude mouse xenografts. Collectively, these results show that AR mediates EGF- and bFGF-induced colon cancer cell proliferation by activating or expressing G(1)-S phase proteins such as E2F-1, cdks, and cyclins through the reactive oxygen species/phosphoinositide 3-kinase/AKT pathway, indicating the use of AR inhibitors in the prevention of colon carcinogenesis. Mol Cancer Ther; 9(4); 813-24. (c)2010 AACR.

Aldose reductase inhibition prevents lipopolysaccharide-induced glucose uptake and glucose transporter 3 expression in RAW264.7 macrophages

Macrophages which play a central role in the injury, infection and sepsis, use glucose as their primary source of metabolic energy. Increased glucose uptake in inflammatory cells is well known to be one of the responsible processes that cause inflammatory response and cytotoxicity. We have shown recently that the inhibition of aldose reductase (AR) prevents bacterial endotoxin, lipopolysaccharide (LPS)-induced cytotoxicity and inflammatory response in macrophages. However, it is not known how AR inhibition prevents LPS-induced inflammation. Here in, we examined the effect of AR inhibition on LPS-induced glucose uptake and the expression of glucose transporter 3 (GLUT-3) in RAW264.7 murine macrophages. Stimulation of macrophages with LPS-increased glucose uptake as measured by using C(14) labeled methyl-d-glucose and inhibition of AR prevented it. Similarly, ablation of AR by using AR-siRNA also prevented the LPS-induced glucose uptake in macrophages. Further, AR inhibition also prevented the LPS-induced up-regulation of GLUT-3 expression, cyclic adenosine monophosphate (cAMP) accumulation and protein kinase A (PKA) activation in RAW264.7 cells. Moreover, LPS-induced down-regulation of cAMP response element modulator (CREM), phosphorylation of cAMP response element-binding protein (CREB) and DNA-binding of CREB were also prevented by AR inhibition. Further, inhibition of AR or PKA also prevented the LPS-induced levels of GLUT-3 protein as well as mRNA in macrophages. These results indicate that AR mediates LPS-induced glucose uptake and expression of glucose transporter-3 via cAMP/PKA/CREB pathway and thus represents a novel mechanism by which AR regulates LPS-induced inflammation.