Heme Oxygenase Inhibition Sensitizes Neuroblastoma Cells to Carfilzomib

Novel Acetamide-Based HO-1 Inhibitor Counteracts Glioblastoma Progression by Interfering with the Hypoxic-Angiogenic Pathway

Glioblastoma multiforme (GBM) represents the deadliest tumor among brain cancers. It is a solid tumor characterized by uncontrolled cell proliferation generating the hypoxic niches in the cancer core. By inducing the transcription of hypoxic inducible factor (HIF), hypoxia triggers many signaling cascades responsible for cancer progression and aggressiveness, including enhanced expression of vascular endothelial growth factor (VEGF) or antioxidant enzymes, such as heme oxygenase-1 (HO-1). The present work aimed to investigate the link between HO-1 expression and the hypoxic microenvironment of GBM by culturing two human glioblastoma cell lines (U87MG and A172) in the presence of a hypoxic mimetic agent, deferoxamine (DFX). By targeting hypoxia-induced HO-1, we have tested the effect of a novel acetamide-based HO-1 inhibitor (VP18/58) on GBM progression. Results have demonstrated that hypoxic conditions induced upregulation and nuclear expression of HO-1 in a cell-dependent manner related to malignant phenotype. Moreover, our data demonstrated that the HO-1 inhibitor counteracted GBM progression by modulating the HIFα/HO-1/VEGF signaling cascade in cancer cells bearing more malignant phenotypes.

Cytoprotective Role of Heme Oxygenase-1 in Cancer Chemoresistance: Focus on Antioxidant, Antiapoptotic, and Pro-Autophagy Properties

Chemoresistance remains the foremost challenge in cancer therapy. Targeting reactive oxygen species (ROS) manipulation is a promising strategy in cancer treatment since tumor cells present high levels of intracellular ROS, which makes them more vulnerable to further ROS elevation than normal cells. Nevertheless, dynamic redox evolution and adaptation of tumor cells are capable of counteracting therapy-induced oxidative stress, which leads to chemoresistance. Hence, exploring the cytoprotective mechanisms of tumor cells is urgently needed to overcome chemoresistance. Heme oxygenase-1 (HO-1), a rate-limiting enzyme of heme degradation, acts as a crucial antioxidant defense and cytoprotective molecule in response to cellular stress. Recently, emerging evidence indicated that ROS detoxification and oxidative stress tolerance owing to the antioxidant function of HO-1 contribute to chemoresistance in various cancers. Enhanced HO-1 expression or enzymatic activity was revealed to promote apoptosis resistance and activate protective autophagy, which also involved in the development of chemoresistance. Moreover, inhibition of HO-1 in multiple cancers was identified to reversing chemoresistance or improving chemosensitivity. Here, we summarize the most recent advances regarding the antioxidant, antiapoptotic, and pro-autophagy properties of HO-1 in mediating chemoresistance, highlighting HO-1 as a novel target for overcoming chemoresistance and improving the prognosis of cancer patients.

Epigenetics and Metabolism Reprogramming Interplay into Glioblastoma: Novel Insights on Immunosuppressive Mechanisms

The central nervous system represents a complex environment in which glioblastoma adapts skillfully, unleashing a series of mechanisms suitable for its efficient development and diffusion. In particular, changes in gene expression and mutational events that fall within the domain of epigenetics interact complexly with metabolic reprogramming and stress responses enacted in the tumor microenvironment, which in turn fuel genomic instability by providing substrates for DNA modifications. The aim of this review is to analyze this complex interaction that consolidates several conditions that confer a state of immunosuppression and immunoevasion, making glioblastoma capable of escaping attack and elimination by immune cells and therefore invincible against current therapies. The progressive knowledge of the cellular mechanisms that underlie the resistance of the glioblastoma represents, in fact, the only weapon to unmask its weak points to be exploited to plan successful therapeutic strategies.

IGFBP-6 Alters Mesenchymal Stromal Cell Phenotype Driving Dasatinib Resistance in Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML), BCR-ABL1-positive, is classified as a myeloproliferative characterized by Philadelphia chromosome/translocation t(9;22) and proliferating granulocytes. Despite the clinical success of tyrosine kinase inhibitors (TKi) agents in the treatment of CML, most patients have minimal residual disease contained in the bone marrow microenvironment, within which stromal cells assume a pro-inflammatory phenotype that determines their transformation in cancer-associated fibroblasts (CAF) which, in turn can play a fundamental role in resistance to therapy. Insulin-like Growth Factor Binding Protein-6 (IGFBP-6) is expressed during tumor development, and is involved in immune-escape and inflammation as well, providing a potential additional target for CML therapy. Here, we aimed at investigating the role of IGFBP-6/SHH/TLR4 axis in TKi response. We used a CML cell line, LAMA84-s, and healthy bone marrow stromal cells, HS-5, in mono- or co-culture. The two cell lines were treated with Dasatinib and/or IGFBP-6, and the expression of inflammatory markers was tested by qRT-PCR; furthermore, expression of IGFBP-6, TLR4 and Gli1 were evaluated by Western blot analysis and immumocytochemistry. The results showed that both co-culture and Dasatinib exposure induce inflammation in stromal and cancer cells so that they modulate the expression of TLR4, and these effects were more marked following IGFBP-6 pre-treatment suggesting that this molecule may confer resistance through the inflammatory processes. This phenomenon was coupled with sonic hedgehog (SHH) signaling. Indeed, our data also demonstrate that HS-5 treatment with PMO (an inducer of SHH) induces significant modulation of TLR4 and overexpression of IGFPB-6 suggesting that the two pathways are interconnected with each other and with the TLR-4 pathway. Finally, we demonstrated that pretreatment with IGFBP-6 and/or PMO restored LAMA-84 cell viability after treatment with Dasatinib, suggesting that both IGFBP-6 and SHH are involved in the resistance mechanisms induced by the modulation of TLR-4, thus indicating that the two pathways may be considered as potential therapeutic targets.

Lactate Rewrites the Metabolic Reprogramming of Uveal Melanoma Cells and Induces Quiescence Phenotype

Uveal melanoma (UM), the most common primary intraocular cancer in adults, is among the tumors with poorer prognosis. Recently, the role of the oncometabolite lactate has become attractive due to its role as hydroxycarboxylic acid receptor 1 (HCAR1) activator, as an epigenetic modulator inducing lysine residues lactylation and, of course, as a glycolysis end-product, bridging the gap between glycolysis and oxidative phosphorylation. The aim of the present study was to dissect in UM cell line (92.1) the role of lactate as either a metabolite or a signaling molecule, using the known modulators of HCAR1 and of lactate transporters. Our results show that lactate (20 mM) resulted in a significant decrease in cell proliferation and migration, acting and switching cell metabolism toward oxidative phosphorylation. These results were coupled with increased euchromatin content and quiescence in UM cells. We further showed, in a clinical setting, that an increase in lactate transporters MCT4 and HCAR1 is associated with a spindle-shape histological type in UM. In conclusion, our results suggest that lactate metabolism may serve as a prognostic marker of UM progression and may be exploited as a potential therapeutic target.

Neuroprotective Role of α-Lipoic Acid in Iron-Overload-Mediated Toxicity and Inflammation in In Vitro and In Vivo Models

Hemoglobin and iron overload is considered the major contributor to intracerebral hemorrhage (ICH)-induced brain injury. Accumulation of iron in the brain leads to microglia activation, inflammation and cell loss. Current available treatments for iron overload-mediated disorders are characterized by severe adverse effects, making such conditions an unmet clinical need. We assessed the potential of α-lipoic acid (ALA) as an iron chelator, antioxidant and anti-inflammatory agent in both in vitro and in vivo models of iron overload. ALA was found to revert iron-overload-induced toxicity in HMC3 microglia cell line, preventing cell apoptosis, reactive oxygen species generation and reducing glutathione depletion. Furthermore, ALA regulated gene expression of iron-related markers and inflammatory cytokines, such as IL-6, IL-1β and TNF. Iron toxicity also affects mitochondria fitness and biogenesis, impairments which were prevented by ALA pre-treatment in vitro. Immunocytochemistry assay showed that, although iron treatment caused inflammatory activation of microglia, ALA treatment resulted in increased ARG1 expression, suggesting it promoted an anti-inflammatory phenotype. We also assessed the effects of ALA in an in vivo zebrafish model of iron overload, showing that ALA treatment was able to reduce iron accumulation in the brain and reduced iron-mediated oxidative stress and inflammation. Our data support ALA as a novel approach for iron-overload-induced brain damage.

Mutual Prodrugs of 5-Fluorouracil: From a Classic Chemotherapeutic Agent to Novel Potential Anticancer Drugs

The development of potent antitumor agents with a low toxicological profile against healthy cells is still one of the greatest challenges facing medicinal chemistry. In this context, the “mutual prodrug” approach has emerged as a potential tool to overcome undesirable physicochemical features and mitigate the side effects of approved drugs. Among broad‐spectrum chemotherapeutics available for clinical use today, 5‐fluorouracil (5‐FU) is one of the most representative, also included in the World Health Organization model list of essential medicines. Unfortunately, severe side effects and drug resistance phenomena are still the primary limits and drawbacks in its clinical use. This review describes the progress made over the last ten years in developing 5‐FU‐based mutual prodrugs to improve the therapeutic profile and achieve targeted delivery to cancer tissues.

Novel mutual prodrug of 5-fluorouracil and heme oxygenase-1 inhibitor (5-FU/HO-1 hybrid): design and preliminary in vitro evaluation

In this work, the first mutual prodrug of 5-fluorouracil and heme oxygenase1 inhibitor (5-FU/HO-1 hybrid) has been designed, synthesised, and evaluated for its in vitro chemical and enzymatic hydrolysis stability. Predicted in silico physicochemical properties of the newly synthesised hybrid (3) demonstrated a drug-like profile with suitable Absorption, Distribution, Metabolism, and Excretion (ADME) properties and low toxic liabilities. Preliminary cytotoxicity evaluation towards human prostate (DU145) and lung (A549) cancer cell lines demonstrated that 3 exerted a similar effect on cell viability to that produced by the reference drug 5-FU. Among the two tested cancer cell lines, the A549 cells were more susceptible for 3. Of note, hybrid 3 also had a significantly lower cytotoxic effect on healthy human lung epithelial cells (BEAS-2B) than 5-FU. Altogether our results served as an initial proof-of-concept to develop 5-FU/HO-1 mutual prodrugs as potential novel anticancer agents.

Clinical Significance of Heme Oxygenase 1 in Tumor Progression

Heme oxygenase 1 (HO-1) plays a key role in cell adaptation to stressors through the antioxidant, antiapoptotic, and anti-inflammatory properties of its metabolic products. For these reasons, in cancer cells, HO-1 can favor aggressiveness and resistance to therapies, leading to poor prognosis/outcome. Genetic polymorphisms of HO-1 promoter have been associated with an increased risk of cancer progression and a high degree of therapy failure. Moreover, evidence from cancer biopsies highlights the possible correlation between HO-1 expression, pathological features, and clinical outcome. Indeed, high levels of HO-1 in tumor specimens often correlate with reduced survival rates. Furthermore, HO-1 modulation has been proposed in order to improve the efficacy of antitumor therapies. However, contrasting evidence on the role of HO-1 in tumor biology has been reported. This review focuses on the role of HO-1 as a promising biomarker of cancer progression; understanding the correlation between HO-1 and clinical data might guide the therapeutic choice and improve the outcome of patients in terms of prognosis and life quality.

Mitochondrial Bioenergetics at the Onset of Drug Resistance in Hematological Malignancies: An Overview

The combined derangements in mitochondria network, function and dynamics can affect metabolism and ATP production, redox homeostasis and apoptosis triggering, contributing to cancer development in many different complex ways. In hematological malignancies, there is a strong relationship between cellular metabolism, mitochondrial bioenergetics, interconnections with supportive microenvironment and drug resistance. Lymphoma and chronic lymphocytic leukemia cells, e.g., adapt to intrinsic oxidative stress by increasing mitochondrial biogenesis. In other hematological disorders such as myeloma, on the contrary, bioenergetics changes, associated to increased mitochondrial fitness, derive from the adaptive response to drug-induced stress. In the bone marrow niche, a reverse Warburg effect has been recently described, consisting in metabolic changes occurring in stromal cells in the attempt to metabolically support adjacent cancer cells. Moreover, a physiological dynamic, based on mitochondria transfer, between tumor cells and their supporting stromal microenvironment has been described to sustain oxidative stress associated to proteostasis maintenance in multiple myeloma and leukemia. Increased mitochondrial biogenesis of tumor cells associated to acquisition of new mitochondria transferred by mesenchymal stromal cells results in augmented ATP production through increased oxidative phosphorylation (OX-PHOS), higher drug resistance, and resurgence after treatment. Accordingly, targeting mitochondrial biogenesis, electron transfer, mitochondrial DNA replication, or mitochondrial fatty acid transport increases therapy efficacy. In this review, we summarize selected examples of the mitochondrial derangements in hematological malignancies, which provide metabolic adaptation and apoptosis resistance, also supported by the crosstalk with tumor microenvironment. This field promises a rational design to improve target-therapy including the metabolic phenotype.

Heme Oxygenase-1 in Central Nervous System Malignancies

Central nervous system tumors are the most common pediatric solid tumors and account for 20–25% of all childhood malignancies. Several lines of evidence suggest that brain tumors show altered redox homeostasis that triggers the activation of various survival pathways, leading to disease progression and chemoresistance. Among these pathways, heme oxygenase-1 (HO-1) plays an important role. HO-1 catalyzes the enzymatic degradation of heme with the simultaneous release of carbon monoxide (CO), ferrous iron (Fe²⁺), and biliverdin. The biological effects of HO-1 in tumor cells have been shown to be cell-specific since, in some tumors, its upregulation promotes cell cycle arrest and cellular death, whereas, in other neoplasms, it is associated with tumor survival and progression. This review focuses on the role of HO-1 in central nervous system malignancies and the possibility of exploiting such a target to improve the outcome of well-established therapeutic regimens. Finally, several studies show that HO-1 overexpression is involved in the development and resistance of brain tumors to chemotherapy and radiotherapy, suggesting the use of HO-1 as an innovative therapeutic target to overcome drug resistance. The following keywords were used to search the literature related to this topic: nuclear factor erythroid 2 p45-related factor 2, heme oxygenase, neuroblastoma, medulloblastoma, meningioma, astrocytoma, oligodendroglioma, glioblastoma multiforme, and gliomas.

α-Lipoic acid induces Endoplasmic Reticulum stress-mediated apoptosis in hepatoma cells

Hepatocellular carcinoma (HCC) is the most common liver cancer and a major cause of adult death. The current treatments for HCC suffer from drug resistance and poor prognosis; therefore, novel therapeutic agents are urgently needed. Phytochemicals have been proposed to treat a range of cancers. Among them, α-lipoic acid (α-LA), a naturally synthesized antioxidant found in various dietary animal and plant sources, prevents oxidant-mediated cell death in normal cells while inducing apoptosis in several cancer cell lines. Previously, we demonstrated that the treatment of hepatoma cells with α-LA induced apoptosis, which was preceded by the generation of reactive oxygen species (ROS) and activation of the p53 protein, a known inducer of mitochondria-mediated apoptosis. Several studies have shown that ROS-induced apoptosis is associated with endoplasmic reticulum (ER) stress and Unfolded Protein Response (UPR) activation. Herein, we investigated if α-LA-induced apoptosis in hepatoma cell lines was ER stress- and UPR-mediated by gene expression profiling analyses. UPR and ER stress pathways were the most up-regulated after treatment with α-LA. This finding, which has been confirmed by expression analyses of ER- and UPR-associated proteins, provides a better understanding of the molecular mechanisms behind the anti-tumoral action of α-LA on hepatoma cells.

Chromatograpic resolution of phenylethanolic-azole racemic compounds highlighted stereoselective inhibition of heme oxygenase-1 by (R)-enantiomers

Heme oxygenase-1 (HO-1) has been recognized as extensively involved in the development and aggravation of cancer, cell propagation and at in the mechanism of chemoresistance development. Low micromolar HO-1 inhibitors selective towards HO-2 has been recently reported, wherein the azole core and the hydrophobic residues are linked through a phenylethanolic spacer bearing a chiral center. Since less information are known about the stereoselective requirements for HO-1 inhibition, here we report the enantiomeric resolution of 1-(biphenyl-3-yl)-2-(1H-imidazol-1-yl)ethanol (1) and 1-[4-[(4-bromobenzyl)oxy]phenyl]-2-(1H-imidazol-1-yl)ethanol (2), two among the most potent and selective HO-1 inhibitors known thus far when tested as racemates. The absolute configuration was established for 1 by a combination of experimental and in silico derived electronic circular dichroism spectra, while docking approaches were useful in the case of compound 2. Biological evaluation of pure enantiomers highlighted higher HO-1 inhibitory activity of (R)-enantiomers. Docking studies demonstrated the importance of hydrogen bond interaction, more pronounced for the (R)-enantiomers, with a consensus water molecule within the binding pocket. The present study demonstrates that differences in three-dimensional structure amongst compounds 1 and 2 enantiomers affect significantly the selectivity of these HO-1 inhibitors.

New Arylethanolimidazole Derivatives as HO-1 Inhibitors with Cytotoxicity against MCF-7 Breast Cancer Cells

In this paper, a novel series of imidazole-based heme oxygenase-1 (HO-1) inhibitors is reported. These compounds were obtained by modifications of previously described high potent and selective arylethanolimidazoles. In particular, simplification of the central linker and repositioning of the hydrophobic portion were carried out. Results indicate that a hydroxyl group in the central region is crucial for the potency as well as the spatial distribution of the hydrophobic portion. Docking studies revealed a similar interaction of the classical HO-1 inhibitors with the active site of the protein. The most potent and selective compound (5a) was tested for its potential cytotoxic activity against hormone-sensitive and hormone-resistant breast cancer cell lines (MCF-7 and MDA-MB-231).

Role of 17β-Estradiol on Cell Proliferation and Mitochondrial Fitness in Glioblastoma Cells

Gliomas are the most common primary tumors of the central nervous system (CNS) in the adult. Previous data showed that estrogen affects cancer cells, but its effect is cell-type-dependent and controversial. The present study aimed to analyze the effects of estradiol (E2, 5 nM) in human glioblastoma multiforme U87-MG cells and how it may impact on cell proliferation and mitochondrial fitness. We monitored cell proliferation by xCELLigence technology and mitochondrial fitness by assessing the expression of genes involved in mitochondrial biogenesis (PGC1α, SIRT1, and TFAM), oxidative phosphorylation (ND4, Cytb, COX-II, COX IV, NDUFA6, and ATP synthase), and dynamics (OPA1, MNF2, MNF1, and FIS1). Finally, we evaluated Nrf2 nuclear translocation by immunocytochemical analysis. Our results showed that E2 resulted in a significant increase in cell proliferation, with a significant increase in the expression of genes involved in various mechanisms of mitochondrial fitness. Finally, E2 treatment resulted in a significant increase of Nrf2 nuclear translocation with a significant increase in the expression of one of its target genes (i.e., heme oxygenase-1). Our results suggest that E2 promotes proliferation in glioblastoma cells and regulate the expression of genes involved in mitochondrial fitness and chemoresistance pathway.

Ginseng and heme oxygenase-1: The link between an old herb and a new protective system

Ginseng is an ancient herb, belonging to Asian traditional medicine, that has been considered as a restorative to enhance vitality for centuries. It has been demonstrated that the antioxidant action of ginseng may be mediated through activation of different cellular signaling pathways involving the heme oxygenase (HO) system. Several compounds derived from ginseng have been studied for their potential role in brain, heart and liver protection, and the Nrf2 pathway seems to be the most affected by these natural molecules to exert this effect. Ginseng is also popularly used in cancer patients therapy for the demonstrated capability to defend tissues from chemotherapy-induced damage. Reported results suggest that the effect of ginseng is primarily associated with ROS scavenging, mainly exerted through the activation of Nrf2 pathway, and the consequent induction of HO-1 levels. This review aims to discuss the connection between the antioxidant properties of ginseng and the activation of the HO system, as well as to outline novel therapeutic applications of this medicinal plant to human health.

Inhibition of Heme Oxygenase Antioxidant Activity Exacerbates Hepatic Steatosis and Fibrosis In Vitro

The progression of non-alcoholic fatty liver disease (NAFLD) and the development of hepatic fibrosis is caused by changes in redox balance, leading to an increase of reactive oxygen species (ROS) levels. NAFLD patients are at risk of progressing to non-alcoholic steatohepatitis (NASH), associated to cardiovascular diseases (CVD), coronary heart disease and stroke. Heme Oxygenase-1 (HO-1) is a potent endogenous antioxidant gene that plays a key role in decreasing oxidative stress. The present work was directed to determine whether use of an inhibitor of HO-1 activity affects lipid metabolism and fibrosis process in hepatic cells. Oil Red assay and mRNA analysis were used to evaluate the triglycerides content and the lipid metabolism pathway in HepG2 cells. ROS measurement, RT-PCR and Soluble collagen assay were used to assess the intracellular oxidant, the fibrosis pathway and the soluble collagen in LX2 cells. The activity of HO-1 was inhibited using Tin Mesoporphyrin IX (SnMP). Our study demonstrates that a non-functional HO system results in an increased lipid storage and collagen release in hepatocytes. Consequently, an increase of HO-1 levels may provide a therapeutic approach to address the metabolic alterations associated with NAFLD and its progression to NASH.

Heme Oxygenase-1 Inhibition Sensitizes Human Prostate Cancer Cells towards Glucose Deprivation and Metformin-Mediated Cell Death

High levels of heme oxygenase (HO)-1 have been frequently reported in different human cancers, playing a major role in drug resistance and regulation of cancer cell redox homeostasis. Metformin (MET), a drug widely used for type 2 diabetes, has recently gained interest for treating several cancers. Recent studies indicated that the anti-proliferative effects of metformin in cancer cells are highly dependent on glucose concentration. The present work was directed to determine whether use of a specific inhibitor of HO-1 activity, alone or in combination with metformin, affected metastatic prostate cancer cell viability under different concentrations of glucose. MTT assay and the xCELLigence system were used to evaluate cell viability and cell proliferation in DU145 human prostate cancer cells. Cell apoptosis and reactive oxygen species were analyzed by flow cytometry. The activity of HO-1 was inhibited using a selective imidazole-based inhibitor; genes associated with antioxidant systems and cell death were evaluated by qRT-PCR. Our study demonstrates that metformin suppressed prostate cancer growth in vitro and increased oxidative stress. Disrupting the antioxidant HO-1 activity, especially under low glucose concentration, could be an attractive approach to potentiate metformin antineoplastic effects and could provide a biochemical basis for developing HO-1-targeting drugs against solid tumors.

Protective Effects of Caffeic Acid Phenethyl Ester (CAPE) and Novel Cape Analogue as Inducers of Heme Oxygenase-1 in Streptozotocin-Induced Type 1 Diabetic Rats

Type 1 diabetes mellitus (T1D) is a chronic autoimmune disease resulting in the destruction of insulin producing β-cells of the pancreas, with consequent insulin deficiency and excessive glucose production. Hyperglycemia results in increased levels of reactive oxygen species (ROS) and nitrogen species (RNS) with consequent oxidative/nitrosative stress and tissue damage. Oxidative damage of the pancreatic tissue may contribute to endothelial dysfunction associated with diabetes. The aim of the present study was to investigate if the potentially protective effects of phenethyl ester of caffeic acid (CAPE), a natural phenolic compound occurring in a variety of plants and derived from honeybee hive propolis, and of a novel CAPE analogue, as heme oxygenase-1 (HO-1) inducers, could reduce pancreatic oxidative damage induced by excessive amount of glucose, affecting the nitric oxide synthase/dimethylarginine dimethylaminohydrolase (NOS/DDAH) pathway in streptozotocin-induced type 1 diabetic rats. Our data demonstrated that inducible nitric oxide synthase/gamma-Glutamyl-cysteine ligase (iNOS/GGCL) and DDAH dysregulation may play a key role in high glucose mediated oxidative stress, whereas HO-1 inducers such as CAPE or its more potent derivatives may be useful in diabetes and other stress-induced pathological conditions.

Antiproliferative Effects of Ellagic Acid on DU145 Cells

Background:

Prostate Cancer (PC) represents a leading cause of tumor-related death among men in the Western world. Above all, DU145 cell line represents the most particular cells model of PC, derived from a central nervous system metastasis. In recent years, functional and healthy diet has gained a pivotal role in society, allowing the possibility to deal with cancer before its emergence or progression, profiting by anti-tumor properties of dietary phytochemicals. Among them, Ellagic Acid (EA) is found in several fruits and vegetables, whose juice demonstrated antioxidant, anti-carcinogenic and anti-fibrotic properties.

Methods:

DU145 prostate cancer cell line was used to determine the effects of ellagic acid on cell viability. In order to evaluate metastatic feature of DU145, VEGF-A and OPG levels by ELISA assay were assessed. Expression of β-catenin, HO-1, HO-2 and SIRT1, markers of proliferative and defense capacities, were determined by western blotting. To strengthen the study, cell transfection with siRNA β-catenin was performed.

Results:

In the presence of EA, the viability of DU145 cells was reduced by about 40 and 50%, respectively after the exposure to 50 and 100 μM concentrations. We also observed a reduction of both levels of VEGF-A and OPG, confirming the important role of EA in facing the metastasis development. EA treatment (50 μM) induced a significant reduction of β-catenin and SIRT1 levels and, similarly, there was a decrease of HO protein expression, more pronounced for HO-2, showing EA activity on the proliferative feature of DU145 cells. Knockdown of β-catenin by siRNA, in the presence of EA treatment, inhibited cell proliferation.

Conclusion:

Ellagic acid exhibits significant antiproliferative effects in ourin vitromodel of prostate cancer’s metastasis, suggesting that, the use of EA as a multitarget natural compound, may represent a possible strategy for cancer chemoprevention.

Fourfold Filtered Statistical/Computational Approach for the Identification of Imidazole Compounds as HO-1 Inhibitors from Natural Products

Over-regulation of Heme oxygenase 1 (HO-1) has been recently identified in many types of human cancer, and in these cases, poor clinical outcomes are normally reported. Indeed, the inhibition of HO-1 is being considered as an anticancer approach. Imidazole scaffold is normally present in most of the classical HO-1 inhibitors and seems indispensable to the inhibitory activity due to its strong interaction with the Fe(II) of the heme group. In this paper, we searched for new potentially HO-1 inhibitors among three different databases: Marine Natural Products (MNP), ZINC Natural Products (ZNP) and Super Natural II (SN2). 484,527 compounds were retrieved from the databases and filtered through four statistical/computational filters (2D descriptors, 2D-QSAR pharmacophoric model, 3D-QSAR pharmacophoric model, and docking). Different imidazole-based compounds were suggested by our methodology to be potentially active in inhibiting the HO-1, and the results have been rationalized by the bioactivity of the filtered molecules reported in the literature.

Progress in the development of selective heme oxygenase-1 inhibitors and their potential therapeutic application

Heme oxygenases (HOs) are a family of enzymes involved in the selective catabolism of free circulating heme. While HO-2 is constitutively expressed, HO-1 is strongly overexpressed under stressful stimuli (e.g., oxidative stress). Under these conditions, HO-1 exerts its strong cytoprotective activities and plays a crucial role in stimulating cell survival by removing the pro-oxidant heme and by producing carbon monoxide and biliverdin (promptly reduced to bilirubin). Unfortunately, the broad spectrum of HO-1 cytoprotective effects has been well experimentally documented both in normal and tumor cells, where the enzyme can be overexpressed, making it an exciting target in the management of some type of tumors. Development of non-competitive HO-1 inhibitors dates back in 2002 with the discovery of Azalanstat. Since then, many efforts have been devoted to the identification of selective HO-1 and HO-2 inhibitors and to unravel the molecular determinants responsible for selectivity. Molecular modeling studies supported the identification of chemical features involved in the recognition and inhibition of these enzymes. Herein, medicinal chemistry aspects and in silico studies related to the development of HO inhibitors will be discussed. The purpose of this review is to highlight recent advances in the development of new selective HO-1 and HO-2 inhibitors and covers the last six years (2013-2018).

Heme oxygenase 1 regulates apoptosis induced by heat stress in bovine ovarian granulosa cells via the ERK1/2 pathway

Heat stress can inhibit follicular development in dairy cows, and thus can affect their reproductive performance. Follicular granulosa cells can synthesize estrogen, that affects the development and differentiation of follicles by apoptosis. Heme oxygenase 1 (HO-1/heat shock protein 32) plays an antiapoptotic and cytoprotective role in various cells during stress-induced apoptosis, but little is known about its definitive function in bovine (ovarian) granulosa cells (bGCs). In our study, the roles and mechanism of HO-1 on the heat stress-induced apoptosis of bGCs were studied. Our results show that the expression of HO-1 was significantly increased under heat stress. Moreover, HO-1 silencing increased apoptosis, whereas its overexpression dampened apoptosis by regulating the expression of Bax/Bcl-2 and the levels of cleaved caspase-3. In addition, HO-1 can also play a cytoprotective role by affecting estrogen levels and decomposing heme to produce biologically active metabolite carbon monoxide (CO). Meanwhile, CO significantly increased the level of HO-1, decreased Bax/Bcl-2 levels, and inhibited the activation of extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway. The apoptosis of ovarian GCs can affect the secretion of estrogen and lead to disorder of the ovarian microenvironment, thus affecting the normal function of the ovary. Our results indicate that HO-1 acts as a cytoprotective enzyme and plays a protective role in heat-induced apoptosis of bGCs. In conclusion, HO-1 and its metabolite CO inhibit the apoptosis of bGCs induced by heat stress through the ERK1/2 pathway. The results of this study provide a valuable clue for improving the fertility of heat stressed cows in summer.

Development of new HO-1 inhibitors by a thorough scaffold-hopping analysis

HO-1 inhibition is considered a valuable anticancer approach. In fact, up-regulation of HO-1 had been repeatedly reported in many types of human malignancies, and in these clinical cases, poor outcomes are reported. To identify novel HO-1 inhibitors suitable for drug development, a scaffold-hopping strategy calculation was utilized to design novel derivatives. Different parts of the selected molecule were analyzed and the different series of novel compounds were virtually evaluated. The calculation for the linker moiety of the classical HO-1 inhibitors structure led us to compounds 5 and 6. A synthetic pathway for the two molecules was designed and the compounds were synthesized. The biological activity revealed an HO-1 inhibition of 0.9 and 54 μM for molecules 5 and 6 respectively. This study suggested that our scaffold-hopping approach was successful and these results are ongoing for further development.