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

The Role of Aldose Reductase in Polyol Pathway: An Emerging Pharmacological Target in Diabetic Complications and Associated Morbidities

The expression of aldose reductase leads to a variety of biological and pathological effects. It is a multifunctional enzyme which has a tendency to reduce aldehydes to the corresponding sugar.alcohol. In diabetic conditions, the aldose reductase enzyme converts glucose into sorbitol using nicotinamide adenine dinucleotide phosphate as a cofactor. It is a key enzyme in polyol pathway which is a surrogate course of glucose metabolism. The polyol pathway has a significant impact on the aetiology of complications in individuals with end-stage diabetes. The exorbitant level of sorbitol leads to the accumulation of intracellular reactive oxygen species in diabetic heart, neurons, kidneys, eyes and other vasculatures, leading to many complications and pathogenesis. Recently, the pathophysiological role of aldose reductase has been explored with multifarious perspectives. Research on aldose reductase suggest that besides implying in diabetic complications, the enzyme also turns down the lipid-derived aldehydes as well as their glutathione conjugates. Although aldose reductase has certain lucrative role in detoxification of toxic lipid aldehydes, its overexpression leads to intracellular accumulation of sorbitol which is involved in secondary diabetic complications, such as neuropathy, cataractogenesis, nephropathy, retinopathy and cardiovascular pathogenesis. Osmotic upset and oxidative stress are produced by aldose reductase via the polyol pathway. The inhibition of aldose reductase alters the activation of transcription factors like NF-ƙB. Moreover, in many preclinical studies, aldose reductase inhibitors have been observed to reduce inflammation-related impediments, such as asthma, sepsis and colon cancer, in diabetic subjects. Targeting aldose reductase can bestow a novel cognizance for this primordial enzyme as an ingenious strategy to prevent diabetic complications and associated morbidities. In this review article, the significance of aldose reductase is briefly discussed along with their prospective applications in other afflictions.

Aberrant expression of AKR1B1 indicates poor prognosis and promotes gastric cancer progression by regulating the AKT-mTOR pathway

Gastric cancer (GC) is a common malignant tumor in the digestive tract and a major cause of global cancer death. Due to the limited access to early screening, many patients are diagnosed with advanced GC. Therefore, postoperative radiotherapy and chemotherapy possess limited efficacy in treating GC. AKR1B1 has been associated with tumorigenesis and metastasis across various tumors, becoming a potential therapeutic target for GC. However, its role and mechanism in GC remain unclear. In this study, AKR1B1 was elevated in GC tissue, depicting a poor prognosis. AKR1B1 is closely related to age, vascular and neural invasion, lymph node metastasis, and the TNM stage of GC. The developed survival prediction model suggested that AKR1B1 expression level is crucial in the prognosis of GC patients. Moreover, the expression level of AKR1B1 in GC tissues is closely associated with the AKT-mTOR pathway. In vitro and in vivo assays functional assays helped determine the oncogenic role of AKR1B1. Additionally, the knockdown of AKR1B1 expression level in GC cell lines could effectively suppress the AKT-mTOR pathway and inhibit the proliferation and migration of tumor cells. In conclusion, this study provides a theoretical basis to establish the potential association and regulatory mechanism of AKR1B1 while offering a new strategy for GC-targeted therapy.

Antioxidant and Antiproliferative activity of Basella alba against colorectal cancer

Basella alba, a green leafy vegetable with remarkable nutraceutical potential is widely used since ancient times to maintain a healthy colon. This plant has been investigated for its medicinal potential due to the increase in young adult cases of colorectal cancer each year. This study was accomplished to investigate Basella alba methanolic extract (BaME) antioxidant and anticancer properties. BaME consisted of a substantial amount of both phenolic and flavonoid compounds which exhibited significant antioxidant reactivity. Both colon cancer cell lines experienced a cell cycle arrest at the G0/G1 phase after receiving treatment with BaME, which inhibited pRb and cyclin D1 and raised p21 expression levels. This was associated with the survival pathway molecule inhibition and downregulation of E2F-1. The results of the current investigation confirm that BaME inhibits CRC cell survival and expansion. To conclude, the bioactive principles in the extract act as potential antioxidants and antiproliferative agents against colorectal cancer.

Inhibition of GSK3β Promotes Proliferation and Suppresses Apoptosis of Porcine Muscle Satellite Cells

As the global population increases, interest in cultured meat (a new research field) is gradually increasing. The main raw material for the production of cultured meat is muscle stem cells called satellite cells isolated from livestock. However, how to mass proliferate and maintain satellite cells in vitro without genetic manipulation remains unclear. In the present study, we isolated and purified porcine muscle satellite cells (PMSCs) from the femur of a 1-day-old piglet and cultured PMSCs by treating them with an inhibitor (XAV939, Tankyrase (TNKS) inhibitor) or an activator (CHIR99021, glycogen synthase kinase 3 beta (GSK3β) inhibitor) of Wnt signaling. The CHIR group treated with 3 μM CHIR99021 showed a significantly increased proliferation rate of PMSCs compared to the SC group (control), whereas the XAV group treated with 1 μM XAV939 showed a significantly decreased proliferation rate of PMSCs. CHIR99021 also inhibited the differentiation of PMSCs by reducing the expression of MyoD while maintaining the expression of Pax7 and suppressed apoptosis by regulating the expression of apoptosis-related proteins and genes. RNA sequencing was performed to obtain gene expression profiles following inhibition or activation of the Wnt signaling pathway and various signaling mechanisms related to the maintenance of satellite cells were identified. Our results suggest that inhibition of GSK3β could dramatically improve the maintenance and mass proliferation ability of PMSCs in vitro by regulating the expression of myogenic markers and the cell cycle.

Physiological and Pathological Roles of Aldose Reductase

Aldose reductase (AR) is an aldo-keto reductase that catalyzes the first step in the polyol pathway which converts glucose to sorbitol. Under normal glucose homeostasis the pathway represents a minor route of glucose metabolism that operates in parallel with glycolysis. However, during hyperglycemia the flux of glucose via the polyol pathway increases significantly, leading to excessive formation of sorbitol. The polyol pathway-driven accumulation of osmotically active sorbitol has been implicated in the development of secondary diabetic complications such as retinopathy, nephropathy, and neuropathy. Based on the notion that inhibition of AR could prevent these complications a range of AR inhibitors have been developed and tested; however, their clinical efficacy has been found to be marginal at best. Moreover, recent work has shown that AR participates in the detoxification of aldehydes that are derived from lipid peroxidation and their glutathione conjugates. Although in some contexts this antioxidant function of AR helps protect against tissue injury and dysfunction, the metabolic transformation of the glutathione conjugates of lipid peroxidation-derived aldehydes could also lead to the generation of reactive metabolites that can stimulate mitogenic or inflammatory signaling events. Thus, inhibition of AR could have both salutary and injurious outcomes. Nevertheless, accumulating evidence suggests that inhibition of AR could modify the effects of cardiovascular disease, asthma, neuropathy, sepsis, and cancer; therefore, additional work is required to selectively target AR inhibitors to specific disease states. Despite past challenges, we opine that a more gainful consideration of therapeutic modulation of AR activity awaits clearer identification of the specific role(s) of the AR enzyme in health and disease.

An Update on the Potential Roles of E2F Family Members in Colorectal Cancer

Colorectal cancer (CRC) is a major health burden worldwide, and thus, optimised diagnosis and treatments are imperative. E2F transcription factors (E2Fs) are a family of transcription factors consisting of eight genes, contributing to the oncogenesis and development of CRC. Importantly, E2Fs control not only the cell cycle but also apoptosis, senescence, DNA damage response, and drug resistance by interacting with multiple signaling pathways. However, the specific functions and intricate machinery of these eight E2Fs in human CRC remain unclear in many respects. Evidence on E2Fs and CRC has been scattered on the related regulatory genes, microRNAs (miRNAs), and competing endogenous RNAs (ceRNAs). Accordingly, some drugs targeting E2Fs have been transferred from preclinical to clinical application. Herein, we have systemically reviewed the current literature on the roles of various E2Fs in CRC with the purpose of providing possible clinical implications for patient diagnosis and prognosis and future treatment strategy design, thereby furthering the understanding of the E2Fs.

(-)-Kusunokinin as a Potential Aldose Reductase Inhibitor: Equivalency Observed via AKR1B1 Dynamics Simulation

(-)-Kusunokinin performed its anticancer potency through CFS1R and AKT pathways. Its ambiguous binding target has, however, hindered the next development phase. Our study thus applied molecular docking and molecular dynamics simulation to predict the protein target from the pathways. Among various candidates, aldo-keto reductase family 1 member B1 (AKR1B1) was finally identified as a (-)-kusunokinin receptor. The predicted binding affinity of (-)-kusunokinin was better than the selected aldose reductase inhibitors (ARIs) and substrates. The compound also had no significant effect on AKR1B1 conformation. An intriguing AKR1B1 efficacy, with respect to the known inhibitors (epalrestat, zenarestat, and minalrestat) and substrates (UVI2008 and prostaglandin H₂), as well as a similar interactive insight of the enzyme pocket, pinpointed an ARI equivalence of (-)-kusunokinin. An aromatic ring and a γ-butyrolactone ring shared a role with structural counterparts in known inhibitors. The modeling explained that the aromatic constituent contributed to π-π attraction with Trp111. In addition, the γ-butyrolactone ring bound the catalytic His110 using hydrogen bonds, which could lead to enzymatic inhibition as a consequence of substrate competitiveness. Our computer-based findings suggested that the potential of (-)-kusunokinin could be furthered by in vitro and/or in vivo experiments to consolidate (-)-kusunokinin as a new AKR1B1 antagonist in the future.

Aldo Keto Reductases AKR1B1 and AKR1B10 in Cancer: Molecular Mechanisms and Signaling Networks

Deregulation of metabolic pathways has increasingly been appreciated as a major driver of cancer in recent years. The principal cancer-associated alterations in metabolism include abnormal uptake of glucose and amino acids and the preferential use of metabolic pathways for the production of biomass and nicotinamide adenine dinucleotide phosphate (NADPH). Aldo-keto reductases (AKRs) are NADPH dependent cytosolic enzymes that can catalyze the reduction of carbonyl groups to primary and secondary alcohols using electrons from NADPH. Aldose reductase, also known as AKR1B1, catalyzes the conversion of excess glucose to sorbitol and has been studied extensively for its role in a number of diabetic pathologies. In recent years, however, high expression of the AKR1B and AKR1C family of enzymes has been strongly associated with worse outcomes in different cancer types. This review provides an overview of the catalysis-dependent and independent data emerging on the molecular mechanisms of the functions of AKRBs in different tumor models with an emphasis of the role of these enzymes in chemoresistance, inflammation, oxidative stress and epithelial-to-mesenchymal transition.

Role of aldo-keto reductase family 1 member B1 (AKR1B1) in the cancer process and its therapeutic potential

The role of aldo‐keto reductase family 1 member B1 (AKR1B1) in cancer is not totally clear but growing evidence is suggesting to have a great impact on cancer progression. AKR1B1 could participate in a complicated network of signalling pathways, proteins and miRNAs such as mir‐21 mediating mechanisms like inflammatory responses, cell cycle, epithelial to mesenchymal transition, cell survival and apoptosis. AKR1B1 has been shown to be mostly overexpressed in cancer. This overexpression has been associated with inflammatory mediators including nuclear factor kappa‐light‐chain‐enhancer of activated B cells (NFκB), cell cycle mediators such as cyclins and cyclin‐dependent kinases (CDKs), survival proteins and pathways like mammalian target of rapamycin (mTOR) and protein kinase B (PKB) or AKT, and other regulatory factors in response to reactive oxygen species (ROS) and prostaglandin synthesis. In addition, inhibition of AKR1B1 has been shown to mostly have anti‐cancer effects. Several studies have also suggested that AKR1B1 inhibition as an adjuvant therapy could render tumour cells more sensitive to anti‐cancer therapy or alleviate the adverse effects of therapy. AKR1B1 could also be considered as a potential cancer diagnostic biomarker since its promoter has shown high levels of methylation. Although pre‐clinical investigations on the role of AKR1B1 in cancer and the application of its inhibitors have shown promising results, the lack of clinical studies on AKR1B1 inhibitors has hampered the use of these drugs to treat cancer. Thus, there is a need to conduct more clinical studies on the application of AKR1B1 inhibitors as adjuvant therapy on different cancers.

A comprehensive review of the roles of E2F1 in colon cancer

E2F transcription factor 1 (E2F1) is a member of the E2F family of transcription factors. E2F1 binds to DNA with dimerization partner (DP) proteins through an E2 recognition site. The dissociation of E2F1 from retinoblastoma (Rb) protein recovers its transcriptional activity, which drives the cell cycle from the G1 to S phase. E2F1 has been shown to be involved in cellular proliferation, differentiation, and apoptosis in colon cancer. It was recently found that E2F1 also participates in the metastasis and chemoresistance of colon cancer. There are abundant experimental data regarding the actions of E2F1, which can be grouped as either pro-tumorigenic or pro-apoptotic. Despite a growing interest and plentiful data, there is currently no review that focuses on the role of E2F1 in colon cancer. Research on E2F1 and colon cancer has been scattered over various genes and microRNAs (miRNAs) that affect E2F1 expression. Here, we provide the first review that aims to consider and dissect all of the elucidated complex behaviors of E2F1 in colon cancer. This review also provides an analysis and conclusion regarding the current understanding of E2F1 in colon cancer in order to facilitate the direction of future research.

AKR1B10 Inhibitor Epalrestat Facilitates Sorafenib-Induced Apoptosis and Autophagy Via Targeting the mTOR Pathway in Hepatocellular Carcinoma

Sorafenib is the standard systemic treatment for advanced hepatocellular carcinoma (HCC), and improving its therapeutic effects is crucial for addressing cancer aggression. We previously reported that epalrestat, an aldo-keto reductase 1B10 inhibitor, enhanced sorafenib's inhibitory effects on HCC xenograft in nude mice. This study aimed to elucidate the mechanism of epalrestat's anti-tumour enhancing effects on sorafenib. HepG2 cells were treated with sorafenib, epalrestat, and their combination. Cell proliferation was assessed with Cell Counting Kit-8 and colony formation assays. AKR1B10 supernate concentration and enzyme activity were detected by ELISA assay and the decrease of optical density of NADPH at 340 nm. Cell cycle and apoptosis analyses were performed with flow cytometry. Western blots clarified the molecular mechanism underlying effects on cell cycle, apoptosis, and autophagy. The anti-tumour mechanism was then validated in vivo through TUNEL and immunohistochemistry staining of HCC xenograft sections. Epalrestat combined with sorafenib inhibited HepG2 cellular proliferation in vitro, arrested the cell cycle at G0/G1, and promoted apoptosis and autophagy. Treatment with a specific mTOR activator MHY-1485 increased mTOR phosphorylation, while suppressing apoptosis and autophagy. Consistent with in vitro results, data from the HCC-xenograft nude mouse model also indicated that combined treatment inhibited the mTOR pathway and promoted apoptosis and autophagy. In conclusion, epalrestat heightens sorafenib's anti-cancer effects via blocking the mTOR pathway, thus inducing cell cycle arrest, apoptosis, and autophagy.

Pharmacological Stimulation of Nurr1 Promotes Cell Cycle Progression in Adult Hippocampal Neural Stem Cells

Nuclear receptor related-1 (Nurr1) protein performs a crucial role in hippocampal neural stem cell (hNSC) development as well as cognitive functions. We previously demonstrated that the pharmacological stimulation of Nurr1 by amodiaquine (AQ) promotes spatial memory by enhancing adult hippocampal neurogenesis. However, the role of Nurr1 in the cell cycle regulation of the adult hippocampus has not been investigated. This study aimed to examine changes in the cell cycle-related molecules involved in adult hippocampal neurogenesis induced by Nurr1 pharmacological stimulation. Fluorescence-activated cell sorting (FACS) analysis showed that AQ improved the progression of cell cycle from G0/G1 to S phase in a dose-dependent manner, and MEK1 or PI3K inhibitors attenuated this progression. In addition, AQ treatment increased the expression of cell proliferation markers MCM5 and PCNA, and transcription factor E2F1. Furthermore, pharmacological stimulation of Nurr1 by AQ increased the expression levels of positive cell cycle regulators such as cyclin A and cyclin-dependent kinases (CDK) 2. In contrast, levels of CDK inhibitors p27KIP1 and p57KIP2 were reduced upon treatment with AQ. Similar to the in vitro results, RT-qPCR analysis of AQ-administered mice brains revealed an increase in the levels of markers of cell cycle progression, PCNA, MCM5, and Cdc25a. Finally, AQ administration resulted in decreased p27KIP1 and increased CDK2 levels in the dentate gyrus of the mouse hippocampus, as quantified immunohistochemically. Our results demonstrate that the pharmacological stimulation of Nurr1 in adult hNSCs by AQ promotes the cell cycle by modulating cell cycle-related molecules.

Signaling pathways involved in colorectal cancer progression

Colorectal cancer (CRC) is the fourth leading cause of the worldwide cancer mortality. Different molecular mechanisms have been attributed to the development and progress of CRC. In this review, we will focus on the mitogen-activated protein kinase (MAPK) cascades downstream of the epidermal growth factor receptor (EGFR), Notch, PI3K/AKT pathway, transforming growth factor-β (TGF-β), and Wnt signaling pathways. Various mutations in the components of these signaling pathways have been linked to the development of CRC. Accordingly, numerous efforts have been carried out to target the signaling pathways to develop novel therapeutic approaches. Herein, we review the signaling pathways involved in the incidence and progression of CRC, and the strategies for the therapy targeting components of signaling pathways in CRC.

Aldose reductase inhibitor, fidarestat regulates mitochondrial biogenesis via Nrf2/HO-1/AMPK pathway in colon cancer cells

Although we have shown earlier that aldose reductase (AR) inhibitors prevent colorectal cancer cell (CRC) growth in culture as well as in nude mice xenografts, the mechanism(s) is not well understood. In this study, we have investigated how AR inhibition prevents CRC growth by regulating the mitochondrial biogenesis via Nrf2/HO-1 pathway. Incubation of CRC cells such as SW-480, HT29, and HCT116 with AR inhibitor, fidarestat that non-covalently binds to the enzyme, increases the expression of Nrf2. Further, fidarestat augmented the EGF-induced expression of Nrf2 in CRC cells. Fidarestat also increased the Nrf2 -DNA binding activity as well as expression of HO-1 and NQO1 and activation of SOD and catalase in SW480 cells. Similarly, in nude mice xenograft tumor tissues, Nrf2 and HO-1 levels were significantly higher in fidarestat-treated mice compared to controls. Further, stimulation of CRC cells with EGF in the presence of fidarestat increased the mRNA levels of PGC-1α, Nrf1 and TFAM and protein levels of PGC-1α, TFAM and COX-IV and decreased the mitochondrial DNA damage as measured by 8-hydroxy-2'-deoxyguanosine levels. AR inhibitor also modulated the phosphorylations of AMPK and mTOR and expression of p53 in EGF-treated cells. Collectively, our results indicate that AR inhibitor prevents CRC growth by increasing mitochondrial biogenesis via increasing the expression of Nrf2/HO-1/AMPK/p53 and decreasing the mitochondrial DNA damage.

Opposing roles of the aldo-keto reductases AKR1B1 and AKR1B10 in colorectal cancer

PURPOSE

Aldo-keto reductases (including AKR1B1 and AKR1B10) constitute a family of oxidoreductases that have been implicated in the pathophysiology of diabetes and cancer, including colorectal cancer (CRC). Available data indicate that, despite their similarities in structure and enzymatic functions, their roles in CRC may be divergent. Here, we aimed to determine the expression and functional implications of AKR1B1 and AKR1B10 in CRC.

METHODS

AKR1B1 and AKR1B10 gene expression levels were analyzed using publicly available microarray data and ex vivo CRC-derived cDNA samples. Gene Set Enrichment Analysis (GSEA), The Cancer Genome Atlas (TCGA) RNA-seq data and The Cancer Proteome Atlas (TCPA) proteome data were analyzed to determine the effect of high and low AKR1B1 and AKR1B10 expression levels in CRC patients. Proliferation, cell cycle progression, cellular motility, adhesion and inflammation were determined in CRC-derived cell lines in which these genes were either exogenously overexpressed or silenced.

RESULTS

We found that the expression of AKR1B1 was unaltered, whereas that of AKR1B10 was decreased in primary CRCs. GSEA revealed that, while high AKR1B1 expression was associated with increased cell cycle progression, cellular motility and inflammation, high AKR1B10 expression was associated with a weak inflammatory phenotype. Functional studies carried out in CRC-derived cell lines confirmed these data. Microarray data analysis indicated that high expression levels of AKR1B1 and AKR1B10 were significantly associated with shorter and longer disease-free survival rates, respectively. A combined gene expression signature of AKR1B10 (low) and AKR1B1 (high) showed a better prognostic stratification of CRC patients independent of confounding factors.

CONCLUSIONS

Despite their similarities, the expression levels and functions of AKR1B1 and AKR1B10 are highly divergent in CRC, and they may have prognostic implications.

MicroRNAs as regulators and mediators of forkhead box transcription factors function in human cancers

Evidence has shown that microRNAs are widely implicated as indispensable components of tumor suppressive and oncogenic pathways in human cancers. Thus, identification of microRNA targets and their relevant pathways will contribute to the development of microRNA-based therapeutics. The forkhead box transcription factors regulate numerous processes including cell cycle progression, metabolism, metastasis and angiogenesis, thereby facilitating tumor initiation and progression. A complex network of protein and non-coding RNAs mediates the expression and activity of forkhead box transcription factors. In this review, we summarize the current knowledge and concepts concerning the involvement of microRNAs and forkhead box transcription factors and describe the roles of microRNAs-forkhead box axis in various disease states including tumor initiation and progression. Additionally, we describe some of the technical challenges in the use of the microRNA-forkhead box signaling pathway in cancer treatment.

Aldose reductase inhibitor increases doxorubicin-sensitivity of colon cancer cells and decreases cardiotoxicity

Anthracycline drugs such as doxorubicin (DOX) and daunorubicin remain some of the most active wide-spectrum and cost-effective drugs in cancer therapy. However, colorectal cancer (CRC) cells are inherently resistant to anthracyclines which at higher doses cause cardiotoxicity. Our recent studies indicate that aldose reductase (AR) inhibitors such as fidarestat inhibit CRC growth in vitro and in vivo. Here, we show that treatment of CRC cells with fidarestat increases the efficacy of DOX-induced death in HT-29 and SW480 cells and in nude mice xenografts. AR inhibition also results in higher intracellular accumulation of DOX and decreases the expression of drug transporter proteins MDR1, MRP1, and ABCG2. Further, fidarestat also inhibits DOX-induced increase in troponin-I and various inflammatory markers in the serum and heart and restores cardiac function in mice. These results suggest that fidarestat could be used as adjuvant therapy to enhance DOX sensitivity of CRC cells and to reduce DOX-associated cardiotoxicity.

Aldose reductase interacts with AKT1 to augment hepatic AKT/mTOR signaling and promote hepatocarcinogenesis

Marked up-regulation of aldose reductase (AR) is reportedly associated with the development of hepatocellular carcinoma (HCC). We investigated how aberrantly overexpressed AR might promote oncogenic transformation in liver cells and tissues. We found that overexpressed AR interacted with the kinase domain of AKT1 to increase AKT/mTOR signaling. In both cultured liver cancer cells and liver tissues in DEN-induced transgenic HCC model mice, we observed that AR overexpression-induced AKT/mTOR signaling tended to enhance lactate formation and hepatic inflammation to enhance hepatocarcinogenesis. Conversely, AR knockdown suppressed lactate formation and inflammation. Using cultured liver cancer cells, we also demonstrated that AKT1 was essential for AR-induced dysregulation of AKT/mTOR signaling, metabolic reprogramming, antioxidant defense, and inflammatory responses. These findings suggest that aberrantly overexpressed/over-activated hepatic AR promotes HCC development at least in part by interacting with oncogenic AKT1 to augment AKT/mTOR signaling. Inhibition of AR and/or AKT1 might serve as an effective strategy for the prevention and therapy of liver cancer.

Unveiling differentially expressed genes upon regulation of transcription factors in sepsis

In this study, we integrated the gene expression data of sepsis to reveal more precise genome-wide expression signature to shed light on the pathological mechanism of sepsis. Differentially expressed genes via integrating five microarray datasets from the Gene Expression Omnibus database were obtained. The gene function and involved pathways of differentially expressed genes (DEGs) were detected by GeneCodis3. Transcription factors (TFs) targeting top 20 dysregulated DEGs (including up- and downregulated genes) were found based on the TRANSFAC. A total of 1339 DEGs were detected including 788 upregulated and 551 downregulated genes. These genes were mostly involved in DNA-dependent transcription regulation, blood coagulation, and innate immune response, pathogenic escherichia coli infection, epithelial cell signaling in helicobacter pylori infection, and chemokine signaling pathway. TFs bioinformatic analysis of 20 DEGs generated 374 pairs of TF-target gene involving 47 TFs. At last, we found that five top ten upregulated DEGs (S100A8, S100A9, S100A12, PGLYRP1 and MMP9) and three downregulated DEGs (ZNF84, CYB561A3 and BST1) were under the regulation of three hub TFs of Pax-4, POU2F1, and Nkx2-5. The identified eight DEGs may be regarded as the diagnosis marker and drug target for sepsis.

Targeting the Warburg effect in cancer cells through ENO1 knockdown rescues oxidative phosphorylation and induces growth arrest

In the last 5 years, novel knowledge on tumor metabolism has been revealed with the identification of critical factors that fuel tumors. Alpha-enolase (ENO1) is commonly over-expressed in tumors and is a clinically relevant candidate molecular target for immunotherapy. Here, we silenced ENO1 in human cancer cell lines and evaluated its impact through proteomic, biochemical and functional approaches. ENO1 silencing increased reactive oxygen species that were mainly generated through the sorbitol and NADPH oxidase pathways, as well as autophagy and catabolic pathway adaptations, which together affect cancer cell growth and induce senescence. These findings represent the first comprehensive metabolic analysis following ENO1 silencing. Inhibition of ENO1, either alone, or in combination with other pathways which were perturbed by ENO1 silencing, opens novel avenues for future therapeutic approaches.

Cyclooxygenase-2 induced β1-integrin expression in NSCLC and promoted cell invasion via the EP1/MAPK/E2F-1/FoxC2 signal pathway

Cyclooxygenase-2 (COX-2) has been implicated in cell invasion in non-small-cell lung cancer (NSCLC). However, the mechanism is unclear. The present study investigated the effect of COX-2 on β1-integrin expression and cell invasion in NSCLC. COX-2 and β1-integrin were co-expressed in NSCLC tissues. COX-2 overexpression or Prostaglandin E2 (PGE2) treatment increased β1-integrin expression in NSCLC cell lines. β1-integrin silencing suppressed COX-2-mediated tumour growth and cancer cell invasion in vivo and in vitro. Prostaglandin E Receptor EP1 transfection or treatment with EP1 agonist mimicked the effect of PGE₂ treatment. EP1 siRNA blocked PGE₂-mediated β1-integrin expression. EP1 agonist treatment promoted Erk1/2, p38 phosphorylation and E2F-1 expression. MEK1/2 and p38 inhibitors suppressed EP1-mediated β1-integrin expression. E2F-1 silencing suppressed EP1-mediated FoxC2 and β1-integrin upregulation. ChIP and Luciferase Reporter assays identified that EP1 agonist treatment induced E2F-1 binding to FoxC2 promotor directly and improved FoxC2 transcription. FoxC2 siRNA suppressed β1-integrin expression and EP1-mediated cell invasion. Immunohistochemistry showed E2F-1, FoxC2, and EP1R were all highly expressed in the NSCLC cases. This study suggested that COX-2 upregulates β1-integrin expression and cell invasion in NSCLC by activating the MAPK/E2F-1 signalling pathway. Targeting the COX-2/EP1/PKC/MAPK/E2F-1/FoxC2/β1-integrin pathway might represent a new therapeutic strategy for the prevention and treatment of this cancer.

HSP90 inhibition downregulates thymidylate synthase and sensitizes colorectal cancer cell lines to the effect of 5FU-based chemotherapy

Cell cycle progression and DNA synthesis are essential steps in cancer cell growth. Thymidylate synthase (TS) is a therapeutic target for 5FU. We tested the hypothesis that HSP90 transcriptional and functional inhibition can inhibit cell cycle progression, downregulate TS levels and sensitize colorectal cancer (CRC) cell lines to the effects of 5FU. Treatment with ganetespib (50 nM) for 24 hours inhibited cyclin D1 and pRb at the transcriptional and translational levels and induced p21, leading to G0/G1 cell cycle arrest in both CRC cell lines (HCT-116 and HT-29). This was associated with downregulation of E2F1 and its target gene TS. In addition, ganetespib inhibited PI3K/Akt and ERK signalling pathways. Similar effects were observed with HSP90 knockdown in both cell lines. Ganetespib sensitized CRC cell lines to the effects of oxaliplatin and 5FU. Similar effects were also observed in tumors from animals treated with ganetespib, oxaliplatin and 5FU. In this study, we present in vitro and animal data supporting that the targeting of HSP90 decreases CRC cell survival and proliferation. Ganetespib sensitizes CRC cell lines to the effects of 5FU-based chemotherapy. Combining HSP90 inhibitors with chemotherapy is a rational approach for future drug development in CRC.

Sulfatase 1 (hSulf-1) reverses basic fibroblast growth factor-stimulated signaling and inhibits growth of hepatocellular carcinoma in animal model

The human sulfatase 1 (hSulf-1) gene encodes an endosulfatase that functions to inhibit the heparin-binding growth factor signaling, including the basic fibroblast growth factor (bFGF)-mediated pathway, by desulfating the cell surface heparan sulfate proteoglycans (HSPGs). bFGF could stimulate cell cycle progression and inhibit cell apoptosis, this biological effect can be reversed by hSulf-1. However, molecular mechanisms have not been fully reported. In the current study, by reactivation of hSulf-1 expression and function in the hSulf-1-negative hepatocellular carcinoma (HCC) cell lines and HCC xenograft tumors, we found that hSulf-1 blocked the bFGF effect on the promotion of cell cycle and inhibition of apoptosis. The bFGF-stimulated activation of protein kinase B (AKT) and extracellular signal-regulated kinase (ERK) pathways was suppressed by hSulf-1, which led to a decreased expression of the target genes Cyclin D1 and Survivin, then finally induced cell cycle arrest and apoptosis in HCC cells. Our data suggested that hSulf-1 may be a suitable target for cancer therapy.

4-Hydroxynonenal in the pathogenesis and progression of human diseases

Metastable aldehydes produced by lipid peroxidation act as 'toxic second messengers' that extend the injurious potential of free radicals. 4-hydroxy 2-nonenal (HNE), a highly toxic and most abundant stable end product of lipid peroxidation, has been implicated in the tissue damage, dysfunction, injury associated with aging and other pathological states such as cancer, Alzheimer, diabetes, cardiovascular and inflammatory complications. Further, HNE has been considered as a oxidative stress marker and it act as a secondary signaling molecule to regulates a number of cell signaling pathways. Biological activity of HNE depends on its intracellular concentration, which can differentially modulate cell death, growth and differentiation. Therefore, the mechanisms responsible for maintaining the intracellular levels of HNE are most important, not only in the defense against oxidative stress but also in the pathophysiology of a number of disease processes. In this review, we discussed the significance of HNE in mediating various disease processes and how regulation of its metabolism could be therapeutically effective.

Aldose reductase inhibition suppresses azoxymethane-induced colonic premalignant lesions in C57BL/KsJ-db/db mice

Type-2 diabetes and obesity-related metabolic abnormalities are major risk factors for the development of colon cancer. In the present study, we examined the effects of polyol pathway enzyme aldose reductase (AR) inhibitor, fidarestat, on the development of azoxymethane (AOM)-induced colonic premalignant lesions in C57BL/KsJ-db/db obese mice. Our results indicate that fidarestat given in the drinking water caused a significant reduction in the total number of colonic premalignant lesions in the AOM treated obese mice. Further, the expression levels of PKC-β2, AKT, COX-2 and iNOS in the colonic mucosa of AOM-treated mice were significantly decreased by fidarestat. The serum levels of IL-1α, IP-10, MIG, TNF-α and VEGF are significantly suppressed in AOM + fidarestat treated obese mice. Fidarestat also decreased the expression of COX-2, iNOS, XIAP, survivin, β-catenin and NF-κB in high glucose-treated HT29 colon cancer cells. In conclusion, our results indicate that fidarestat inhibits the development of colonic premalignant lesions in an obesity-related colon cancer and is chemopreventive to colorectal carcinogenesis in obese individuals.

Epidermal growth factor stimulates nuclear factor-κB activation and heme oxygenase-1 expression via c-Src, NADPH oxidase, PI3K, and Akt in human colon cancer cells

Previous report showed that epidermal growth factor (EGF) promotes tumor progression. Several studies demonstrated that growth factors can induce heme oxygenase (HO)-1 expression, protect against cellular injury and cancer cell proliferation. In this study, we investigated the involvement of the c-Src, NADPH oxidase, reactive oxygen species (ROS), PI3K/Akt, and NF-κB signaling pathways in EGF-induced HO-1 expression in human HT-29 colon cancer cells. Treatment of HT-29 cells with EGF caused HO-1 to be expressed in concentration- and time-dependent manners. Treatment of HT-29 cells with AG1478 (an EGF receptor (EGFR) inhibitor), small interfering RNA of EGFR (EGFR siRNA), a dominant negative mutant of c-Src (c-Src DN), DPI (an NADPH oxidase inhibitor), glutathione (an ROS inhibitor), LY294002 (a PI3K inhibitor), and an Akt DN inhibited EGF-induced HO-1 expression. Stimulation of cells with EGF caused an increase in c-Src phosphorylation at Tyr406 in a time-dependent manner. Treatment of HT-29 cells with EGF induced an increase in p47(phox) translocation from the cytosol to membranes. The EGF-induced ROS production was inhibited by DPI. Stimulation of cells with EGF resulted in an increase in Akt phosphorylation at Ser473, which was inhibited by c-Src DN, DPI, and LY 294002. Moreover, treatment of HT-29 cells with a dominant negative mutant of IκB (IκBαM) inhibited EGF-induced HO-1 expression. Stimulation of cells with EGF induced p65 translocation from the cytosol to nuclei. Treatment of HT-29 cells with EGF induced an increase in κB-luciferase activity, which was inhibited by a c-Src DN, LY 294002, and an Akt DN. Furthermore, EGF-induced colon cancer cell proliferation was inhibited by Sn(IV)protoporphyrin-IX (snPP, an HO-1 inhibitor). Taken together, these results suggest that the c-Src, NADPH oxidase, PI3K, and Akt signaling pathways play important roles in EGF-induced NF-κB activation and HO-1 expression in HT-29 cells. Moreover, overexpression of HO-1 mediates EGF-induced colon cancer cell proliferation.

Caffeic acid derivatives inhibit the growth of colon cancer: involvement of the PI3-K/Akt and AMPK signaling pathways

Background

The aberrant regulation of phosphatidylinositide 3-kinases (PI3-K)/Akt, AMP-activated protein kinase (AMPK) and mammalian target of rapamycin (m-TOR) signaling pathways in cancer has prompted significant interest in the suppression of these pathways to treat cancer. Caffeic acid (CA) has been reported to possess important anti-inflammatory actions. However, the molecular mechanisms by which CA derivatives including caffeic acid phenethyl ester (CAPE) and caffeic acid phenylpropyl ester (CAPPE), exert inhibitory effects on the proliferation of human colorectal cancer (CRC) cells have yet to be elucidated.

Methodology/Principal Findings

CAPE and CAPPE were evaluated for their ability to modulate these signaling pathways and suppress the proliferation of CRC cells both in vitro and in vivo. Anti-cancer effects of these CA derivatives were measured by using proliferation assays, cell cycle analysis, western blotting assay, reporter gene assay and immunohistochemical (IHC) staining assays both in vitro and in vivo. This study demonstrates that CAPE and CAPPE exhibit a dose-dependent inhibition of proliferation and survival of CRC cells through the induction of G₀/G₁ cell cycle arrest and augmentation of apoptotic pathways. Consumption of CAPE and CAPPE significantly inhibited the growth of colorectal tumors in a mouse xenograft model. The mechanisms of action included a modulation of PI3-K/Akt, AMPK and m-TOR signaling cascades both in vitro and in vivo. In conclusion, the results demonstrate novel anti-cancer mechanisms of CA derivatives against the growth of human CRC cells.

Conclusions

CA derivatives are potent anti-cancer agents that augment AMPK activation and promote apoptosis in human CRC cells. The structure of CA derivatives can be used for the rational design of novel inhibitors that target human CRC cells.

Development of aldose reductase inhibitors for the treatment of inflammatory disorders

INTRODUCTION

Accumulating evidence attributes a significant role to aldose reductase (ALR2) in the pathogenesis of several inflammatory pathologies. Aldose reductase inhibitors (ARIs) were found to attenuate reactive oxygen species (ROS) production both in vitro and in vivo. Thus, they disrupt signaling cascades that lead to the production of cytokines/chemokines, which induce and exacerbate inflammation. As a result, ARIs might hold a significant therapeutic potential as alternate anti-inflammatory drugs.

AREAS COVERED

The authors present a comprehensive review of the current data that support the central role of ALR2 in several inflammatory pathologies (i.e., diabetes, cancer, sepsis, asthma and ocular inflammation). Further, the authors describe the potential underlying molecular mechanisms and provide a commentary on the status of ARIs in this field.

EXPERT OPINION

It is important that future efforts focus on delineating all the steps of the molecular mechanism that implicates ALR2 in inflammatory pathologies. At the same time, utilizing the previous efforts in the field of ARIs, several candidates that have been proven safe in the clinic may be evaluated for their clinical significance as anti-inflammatory medication. Finally, structurally novel ARIs, designed to target specifically the proinflammatory subpocket of ALR2, should be pursued.

Aldose reductase inhibition enhances TRAIL-induced human colon cancer cell apoptosis through AKT/FOXO3a-dependent upregulation of death receptors

One of the major problems associated with the chemotherapy of tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) that selectively kills tumor cells is decreased drug resistance. This warranted the development of safe novel pharmacological agents that could sensitize the tumor cells to TRAIL. Herein, we examined the role of aldose reductase (AR) in sensitizing cancer cells to TRAIL and potentiating TRAIL-induced apoptosis of human colon cancer cells. We demonstrate that AR inhibition potentiates TRAIL-induced cytotoxicity in cancer cells by upregulation of both death receptor (DR)-5 and DR4. Knockdown of DR5 and DR4 significantly (>85%) reduced the sensitizing effect of the AR inhibitor fidarestat on TRAIL-induced apoptosis. Further, AR inhibition also downregulates cell survival proteins (Bcl-xL, Bcl-2, survivin, XIAP, and FLIP) and upregulates the expression of proapoptotic proteins such as Bax and alters mitochondrial membrane potential, leading to cytochrome c release, caspases-3 activation, and PARP cleavage. We found 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 fidarestat potentiates TRAIL-induced apoptosis through downregulation of cell survival proteins and upregulation of death receptors via activation of the AKT/FOXO3a pathway.

Aldose reductase inhibition suppresses colon cancer cell viability by modulating microRNA-21 mediated programmed cell death 4 (PDCD4) expression

Inhibition of polyol pathway enzyme aldose reductase (AR) has been shown to prevent colon cancer cells growth in culture and in nude mice xenografts. However, the role of AR in the mediation of growth factor-induced colon cancer cells growth is not well understood. In this study, we have investigated how AR inhibition prevents tumour growth via regulation of microRNA (miR)-21-mediated programmed cell death 4 (PDCD4) expression in colon cancer cells in in vitro and in vivo. Treatment of colon cancer cells (HT29, SW480 and Caco-2) with epidermal growth factor (EGF) caused increased expression of miR-21 and inhibition of AR prevented it. Further, AR inhibition also increased PDCD4, a putative target of miR-21 in human colon cancer cells. Inhibition of AR also prevented EGF-induced phosphorylation of PDCD4. Treatment of HT29 cells with AR inhibitor, fidarestat, prevented the EGF-induced phosphorylation of mammalian target of rapamycin (mTOR), regulatory associated protein of mTOR (Raptor), eukaryotic initiation factor 4E (eIF4E), p70 S6 kinase (S6K) and eukaryotic initiation factor 4E (eIF4E)-binding protein 1 (4E-BP1) and increased the phosphorylation of 5' adenosine monophosphate-activated protein kinase (AMPK). Similarly, in nude mice xenograft tissues, PDCD4 and 4E-BP1 levels were significantly higher in AR inhibitor-treated mice compared to controls. Collectively, these results indicate that AR inhibition prevents growth factor-induced colon cancer growth by down-regulating miR-21 expression and increasing PDCD4 levels through the reactive oxygen species (ROS)/AMPK/mTOR/AP1/4E-BP1 pathway.

Aldose reductase inhibition prevents colon cancer growth by restoring phosphatase and tensin homolog through modulation of miR-21 and FOXO3a

AIMS

We have shown earlier that inhibition of aldose reductase (AR), an oxidative stress-response protein, prevents colon cancer cell growth in vitro and in vivo. Changes in microribonucleic acid (miR) expression can contribute to cancer by modulating the functional expression of critical genes involved in cancer growth and metastasis. However, the molecular mechanisms by which AR regulates miR expression and their dependent mitogenic effects in cancer cells are not known. Therefore, we investigated how AR regulates growth factor-induced expression of miRs and growth of colon cancer cells.

RESULTS

Inhibition of AR significantly downregulated growth factor-induced miR-21 expression in human colon cancer cells, HT29, SW480, and Caco-2. Further, AR inhibition also increased phosphatase and tensin homolog (PTEN) (a direct target of miR-21) and forkhead box O3A (FOXO3a) in colon cancer cells. Our results obtained with HT29 cells ablated with FOXO3a siRNA showed increased activator protein-1 (AP-1) activation and miR-21 expression, indicating that FOXO3a represses miR-21 via AP-1 inactivation. Inhibition of AR also prevented the epidermal growth factor-induced phosphorylation of phosphatidylinositol 3-kinase (PI3K), serine/threonine kinase (AKT), c-Jun, c-Fos, PTEN, and FOXO3a, and deoxyribonucleic acid (DNA)-binding activity of AP-1. More importantly, in human colon adenocarcinoma xenograft tissues, miR-21 expression was lower, and PTEN and FOXO3a levels were significantly higher in AR inhibitor-treated mice compared to controls.

INNOVATION

These findings demonstrate a novel role of AR in the regulation of miR-21 and its target PTEN in growth factor-induced colon cancer cell growth.

CONCLUSIONS

Collectively, these results show a novel role of AR in mediation of growth factor-induced colon cancer growth by modulating miR-21, PTEN, and FOXO3a expression through reactive oxygen species (ROS)/PI3K/AKT/AP-1.

Expression of the Aldo-Ketoreductases AKR1B1 and AKR1B10 in Human Cancers

The American Cancer Society estimates that there will be more than 1.5 million new cases of cancer in 2011, underscoring the need for identification of new therapeutic targets and development of novel cancer therapies. Previous studies have implicated the human aldo-ketoreductases AKR1B1 and AKR1B10 in cancer, and therefore we examined AKR1B1 and AKR1B10 expression across all major human cancer types using the Oncomine cancer gene expression database (Compendia Biosciences, www.oncomine.com). Using this database, we found that expression of AKR1B1 and AKR1B10 varies greatly by cancer type and tissue of origin, including agreement with previous reports that AKR1B10 is significantly over-expressed in cancers of the lungs and liver. AKR1B1 is more broadly over-expressed in human cancers than AKR1B10, albeit at a generally lower magnitude. AKR1B1 over-expression was found to be associated with shortened patient survival in acute myelogenous leukemias and multiple myelomas. High AKR1B10 expression tends to predict less aggressive clinical course generally, notably within lung cancers, where it tends to be highly over-expressed compared to normal tissue. These findings suggest that AKR1B1 inhibitors in particular hold great potential as novel cancer therapeutics.

Rictor regulates FBXW7-dependent c-Myc and cyclin E degradation in colorectal cancer cells

Rictor (Rapamycin-insensitive companion of mTOR) forms a complex with mTOR and phosphorylates and activates Akt. Activation of Akt induces expression of c-Myc and cyclin E, which are overexpressed in colorectal cancer and play an important role in colorectal cancer cell proliferation. Here, we show that rictor associates with FBXW7 to form an E3 complex participating in the regulation of c-Myc and cyclin E degradation. The Rictor-FBXW7 complex is biochemically distinct from the previously reported mTORC2 and can be immunoprecipitated independently of mTORC2. Moreover, knocking down of rictor in serum-deprived colorectal cancer cells results in the decreased ubiquitination and increased protein levels of c-Myc and cyclin E while overexpression of rictor induces the degradation of c-Myc and cyclin E proteins. Genetic knockout of FBXW7 blunts the effects of rictor, suggesting that rictor regulation of c-Myc and cyclin E requires FBXW7. Our findings identify rictor as an important component of FBXW7 E3 ligase complex participating in the regulation of c-Myc and cyclin E protein ubiquitination and degradation. Importantly, our results suggest that elevated growth factor signaling may contribute to decrease rictor/FBXW7-mediated ubiquitination of c-Myc and cyclin E, thus leading to accumulation of cyclin E and c-Myc in colorectal cancer cells.

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.

ALDOSE REDUCTASE: New Insights for an Old Enzyme

In the past years aldose reductase (AKR1B1; AR) is thought to be involved in the pathogenesis of secondary diabetic complications such as retinopathy, neuropathy, nephropathy and cataractogenesis. Subsequently, a number of AR inhibitors have been developed and tested for diabetic complications. Although, these inhibitors have found to be safe for human use, they have not been successful at the clinical studies because of limited efficacy. Recently, the potential physiological role of AR has been reassessed from a different point of view. Diverse groups suggested that AR besides reducing glucose, also efficiently reduces oxidative stress-generated lipid peroxidation-derived aldehydes and their glutathione conjugates. Since lipid aldehydes alter cellular signals by regulating the activation of transcription factors such as NF-kB and AP1, inhibition of AR could inhibit such events. Indeed, a wide array of recent experimental evidence indicates that the inhibition of AR prevents oxidative stress-induced activation of NF-kB and AP1 signals that lead to cell death or growth. Further, AR inhibitors have been shown to prevent inflammatory complications such as sepsis, asthma, colon cancer and uveitis in rodent animal models. The new experimental in-vitro and in-vivo data has provided a basis for investigating the clinical efficacy of AR inhibitors in preventing other inflammatory complications than diabetes. This review describes how the recent studies have identified novel plethoric physiological and pathophysiological significance of AR in mediating inflammatory complications, and how the discovery of such new insights for this old enzyme could have considerable importance in envisioning potential new therapeutic strategies for the prevention or treatment of inflammatory diseases.

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 inhibition suppresses oxidative stress-induced inflammatory disorders

Oxidative stress-induced inflammation is a major contributor to several disease conditions including sepsis, carcinogenesis and metastasis, diabetic complications, allergic asthma, uveitis and after cataract surgery posterior capsular opacification. Since reactive oxygen species (ROS)-mediated activation of redox-sensitive transcription factors and subsequent expression of inflammatory cytokines, chemokines and growth factors are characteristics of inflammatory disorders, we envisioned that by blocking the molecular signals of ROS that activate redox-sensitive transcription factors, various inflammatory diseases could be ameliorated. We have indeed demonstrated that ROS-induced lipid peroxidation-derived lipid aldehydes such as 4-hydroxy-trans-2-nonenal (HNE) and their glutathione-conjugates (e.g. GS-HNE) are efficiently reduced by aldose reductase to corresponding alcohols which mediate the inflammatory signals. Our results showed that inhibition of aldose reductase (AKR1B1) significantly prevented the inflammatory signals induced by cytokines, growth factors, endotoxins, high glucose, allergens and auto-immune reactions in cellular as well as animal models. We have demonstrated that AKR1B1 inhibitor, fidarestat, significantly prevents tumor necrosis factor-alpha (TNF-α)-, growth factors-, lipopolysachharide (LPS)-, and environmental allergens-induced inflammatory signals that cause various inflammatory diseases. In animal models of inflammatory diseases such as diabetes, cardiovascular, uveitis, asthma, and cancer (colon, breast, prostate and lung) and metastasis, inhibition of AKR1B1 significantly ameliorated the disease. Our results from various cellular and animal models representing a number of inflammatory conditions suggest that ROS-induced inflammatory response could be reduced by inhibition of AKR1B1, thereby decreasing the progression of the disease and if the therapy is initiated early, the disease could be eliminated. Since fidarestat has already undergone phase III clinical trial for diabetic neuropathy and found to be safe, though clinically not very effective, our results indicate that it can be developed for the therapy of a number of inflammation-related diseases. Our results thus offer a novel therapeutic approach to treat a wide array of inflammatory diseases.