Targeting NUPR1-dependent stress granules formation to induce synthetic lethality in KrasG12D-driven tumors

We find that NUPR1, a stress-associated intrinsically disordered protein, induced droplet formation via liquid-liquid phase separation (LLPS). NUPR1-driven LLPS was crucial for the creation of NUPR1-dependent stress granules (SGs) in pancreatic cancer cells since genetic or pharmacological inhibition by ZZW-115 of NUPR1 activity impeded SGs formation. The KrasG12D mutation induced oncogenic stress, NUPR1 overexpression, and promoted SGs development. Notably, enforced NUPR1 expression induced SGs formation independently of mutated KrasG12D. Mechanistically, KrasG12D expression strengthened sensitivity to NUPR1 inactivation, inducing cell death, activating caspase 3 and releasing LDH. Remarkably, ZZW-115-mediated SG-formation inhibition hampered the development of pancreatic intraepithelial neoplasia (PanINs) in Pdx1-cre;LSL-KrasG12D (KC) mice. ZZW-115-treatment of KC mice triggered caspase 3 activation, DNA fragmentation, and formation of the apoptotic bodies, leading to cell death, specifically in KrasG12D-expressing cells. We further demonstrated that, in developed PanINs, short-term ZZW-115 treatment prevented NUPR1-associated SGs presence. Lastly, a four-week ZZW-115 treatment significantly reduced the number and size of PanINs in KC mice. This study proposes that targeting NUPR1-dependent SGs formation could be a therapeutic approach to induce cell death in KrasG12D-dependent tumors.

Intrinsically Disordered Chromatin Protein NUPR1 Binds to the Enzyme PADI4

The nuclear protein 1 (NUPR1) is an intrinsically disordered protein involved in stress-mediated cellular conditions. Its paralogue nuclear protein 1-like (NUPR1L) is p53-regulated, and its expression down-regulates that of the NUPR1 gene. Peptidyl-arginine deiminase 4 (PADI4) is an isoform of a family of enzymes catalyzing arginine to citrulline conversion; it is also involved in stress-mediated cellular conditions. We characterized the interaction between NUPR1 and PADI4 in vitro, in silico, and in cellulo. The interaction of NUPR1 and PADI4 occurred with a dissociation constant of 18 ± 6 μM. The binding region of NUPR1, mapped by NMR, was a hydrophobic polypeptide patch surrounding the key residue Ala33, as pinpointed by: (i) computational results; and, (ii) site-directed mutagenesis of residues of NUPR1. The association between PADI4 and wild-type NUPR1 was also assessed in cellulo by using proximity ligation assays (PLAs) and immunofluorescence (IF), and it occurred mainly in the nucleus. Moreover, binding between NUPR1L and PADI4 also occurred in vitro with an affinity similar to that of NUPR1. Molecular modelling provided information on the binding hot spot for PADI4. This is an example of a disordered partner of PADI4, whereas its other known interacting proteins are well-folded. Altogether, our results suggest that the NUPR1/PADI4 complex could have crucial functions in modulating DNA-repair, favoring metastasis, or facilitating citrullination of other proteins.

Stroma-targeting strategies in pancreatic cancer: a double-edged sword

Pancreatic ductal adenocarcinoma (PDAC) is a type of cancer with limited treatment options and terrible long-term survival, and it is expected to become the second leading cause of cancer-related death by 2030. One reason why this cancer is so aggressive and resistant is the formation of dense stroma that surrounds the neoplastic epithelium, which promotes tumor progression, invasion, metastasis, and resistance. The three major components of PDAC stroma are extracellular matrix (ECM), cancer-associated fibroblasts (CAFs), and vasculature. The dense ECM acts as a natural physical barrier, impeding drug penetration to PDAC tumor cells. Consequently, the method that combines stroma-targeting with anticancer therapy may be a viable alternative for increasing drug penetration. Additionally, blood vessels are key entities of the tumor stroma, serving as a pathway for nutrition as well as the only way for chemical medicines and immune cells to act. Finally, PDAC CAFs and tumor cells have crosstalk effects in the tumor microenvironment, where they are responsible for enhanced matrix deposition. In this review, we aim to provide an overview of our current comprehension of the three key components of PDAC stroma and the new promising therapeutic targets for PDAC.

Melatonin controls cell proliferation and modulates mitochondrial physiology in pancreatic stellate cells

We have investigated the effects of melatonin on major pathways related with cellular proliferation and energetic metabolism in pancreatic stellate cells. In the presence of melatonin (1 mM, 100 µM, 10 µM, or 1 µM), decreases in the phosphorylation of c-Jun N-terminal kinase and of p44/42 and an increase in the phosphorylation of p38 were observed. Cell viability dropped in the presence of melatonin. A rise in the phosphorylation of AMP-activated protein kinase was detected in the presence of 1 mM and 100 µM melatonin. Treatment with 1 mM melatonin decreased the phosphorylation of protein kinase B, whereas 100 µM and 10 µM melatonin increased its phosphorylation. An increase in the generation of mitochondrial reactive oxygen species and a decrease of mitochondrial membrane potential were noted following melatonin treatment. Basal and maximal respiration, ATP production by oxidative phosphorylation, spare capacity, and proton leak dropped in the presence of melatonin. The expression of complex I of the mitochondrial respiratory chain was augmented in the presence of melatonin. Conversely, in the presence of 1 mM melatonin, decreases in the expression of mitofusins 1 and 2 were detected. The glycolysis and the glycolytic capacity were diminished in cells treated with 1 mM or 100 µM melatonin. Increases in the expression of phosphofructokinase-1 and lactate dehydrogenase were noted in cells incubated with 100 µM, 10 µM, or 1 µM melatonin. The expression of glucose transporter 1 was increased in cells incubated with 10 µM or 1 µM melatonin. Conversely, 1 mM melatonin decreased the expression of all three proteins. Our results suggest that melatonin, at pharmacological concentrations, might modulate mitochondrial physiology and energy metabolism in addition to major pathways involved in pancreatic stellate cell proliferation.

NUPR1 protects against hyperPARylation-dependent cell death

Proteomic, cellular and biochemical analysis of the stress protein NUPR1 reveals that it binds to PARP1 into the nucleus and inhibits PARP1 activity in vitro. Mutations on residues Ala33 or Thr68 of NUPR1 or treatment with its inhibitor ZZW-115 inhibits this effect. PARylation induced by 5-fluorouracil (5-FU) treatment is strongly enhanced by ZZW-115 and associated with a decrease of NAD⁺/NADH ratio and rescued by the PARP inhibitor olaparib. Cell death induced by ZZW-115 treatment of pancreas cancer-derived cells is rescued by olaparib and improved with PARG inhibitor PDD00017273. The mitochondrial catastrophe induced by ZZW-115 treatment or by genetic inactivation of NUPR1 is associated to a hyperPARylation of the mitochondria, disorganization of the mitochondrial network, mitochondrial membrane potential decrease, and with increase of superoxide production, intracellular level of reactive oxygen species (ROS) and cytosolic levels of Ca²⁺. These features are rescued by olaparib or NAD⁺ precursor nicotinamide mononucleotide in a dose-dependent manner and partially by antioxidants treatments. In conclusion, inactivation of NUPR1 induces a hyperPARylation, which in turn, induces a mitochondrial catastrophe and consequently a cell death through a non-canonical Parthanatos, since apoptosis inducing-factor (AIF) is not translocated out of the mitochondria.

Iron-Sensitive Prodrugs That Trigger Active Ferroptosis in Drug-Tolerant Pancreatic Cancer Cells

Persister cancer cells represent rare populations of cells resistant to therapy. Cancer cells can exploit epithelial-mesenchymal plasticity to adopt a drug-tolerant state that does not depend on genetic alterations. Small molecules that can interfere with cell plasticity or kill cells in a cell state-dependent manner are highly sought after. Salinomycin has been shown to kill cancer cells in the mesenchymal state by sequestering iron in lysosomes, taking advantage of the iron addiction of this cell state. Here, we report the chemo- and stereoselective synthesis of a series of structurally complex small molecule chimeras of salinomycin derivatives and the iron-reactive dihydroartemisinin. We show that these chimeras accumulate in lysosomes and can react with iron to release bioactive species, thereby inducing ferroptosis in drug-tolerant pancreatic cancer cells and biopsy-derived organoids of pancreatic ductal adenocarcinoma. This work paves the way toward the development of new cancer medicines acting through active ferroptosis.

Design of Inhibitors of the Intrinsically Disordered Protein NUPR1: Balance between Drug Affinity and Target Function

Intrinsically disordered proteins (IDPs) are emerging as attractive drug targets by virtue of their physiological ubiquity and their prevalence in various diseases, including cancer. NUPR1 is an IDP that localizes throughout the whole cell, and is involved in the development and progression of several tumors. We have previously repurposed trifluoperazine (TFP) as a drug targeting NUPR1 and, by using a ligand-based approach, designed the drug ZZW-115 starting from the TFP scaffold. Such derivative compound hinders the development of pancreatic ductal adenocarcinoma (PDAC) in mice, by hampering nuclear translocation of NUPR1. Aiming to further improve the activity of ZZW-115, here we have used an indirect drug design approach to modify its chemical features, by changing the substituent attached to the piperazine ring. As a result, we have synthesized a series of compounds based on the same chemical scaffold. Isothermal titration calorimetry (ITC) showed that, with the exception of the compound preserving the same chemical moiety at the end of the alkyl chain as ZZW-115, an increase of the length by a single methylene group (i.e., ethyl to propyl) significantly decreased the affinity towards NUPR1 measured in vitro, whereas maintaining the same length of the alkyl chain and adding heterocycles favored the binding affinity. However, small improvements of the compound affinity towards NUPR1, as measured by ITC, did not result in a corresponding improvement in their inhibitory properties and in cellulo functions, as proved by measuring three different biological effects: hindrance of the nuclear translocation of the protein, sensitization of cells against DNA damage mediated by NUPR1, and prevention of cancer cell growth. Our findings suggest that a delicate compromise between favoring ligand affinity and controlling protein function may be required to successfully design drugs against NUPR1, and likely other IDPs.

NUPR1: A Critical Regulator of the Antioxidant System

Simple Summary

Nuclear protein 1 (NUPR1) is activated in cellular stress and is expressed at high levels in cancer cells. Much evidence has been gathered supporting its critical role in regulating the antioxidant system. Our review aims to summarize the literature data on the impact of NUPR1 on the oxidative stress response via such a regulatory role and how its inhibition induces reactive oxygen species-mediated cell death, such as ferroptosis.

Abstract

Nuclear protein 1 (NUPR1) is a small intrinsically disordered protein (IDP) activated in response to various types of cellular stress, including endoplasmic reticulum (ER) stress and oxidative stress. Reactive oxygen species (ROS) are mainly produced during mitochondrial oxidative metabolism, and directly impact redox homeostasis and oxidative stress. Ferroptosis is a ROS-dependent programmed cell death driven by an iron-mediated redox reaction. Substantial evidence supports a maintenance role of the stress-inducible protein NUPR1 on cancer cell metabolism that confers chemotherapeutic resistance by upregulating mitochondrial function-associated genes and various antioxidant genes in cancer cells. NUPR1, identified as an antagonist of ferroptosis, plays an important role in redox reactions. This review summarizes the current knowledge on the mechanism behind the observed impact of NUPR1 on mitochondrial function, energy metabolism, iron metabolism, and the antioxidant system. The therapeutic potential of genetic or pharmacological inhibition of NUPR1 in cancer is also discussed. Understanding the role of NUPR1 in the antioxidant system and the mechanisms behind its regulation of ferroptosis may promote the development of more efficacious strategies for cancer therapy.

NUPR1 interacts with eIF2α and is required for resolution of the ER stress response in pancreatic tissue

Nuclear protein 1 (NUPR1) is a stress response protein overexpressed upon cell injury in virtually all organs including the exocrine pancreas. Despite NUPR1's well-established role in the response to cell stress, the molecular and structural machineries triggered by NUPR1 activation remain largely debated. In this study, we uncover a new role for NUPR1, participating in the unfolded protein response (UPR) and the integrated stress response. Biochemical results and ultrastructural morphological observations revealed alterations in the UPR of acinar cells of germline-deleted NUPR1 murine models, consistent with the inability to restore general protein synthesis after stress induction. Bioinformatic analysis of NUPR1-interacting partners showed significant enrichment in translation initiation factors, including eukaryotic initiation factor (eIF) 2α. Co-immunoprecipitation and proximity ligation assays confirmed the interaction between NUPR1 and eIF2α and its phosphorylated form (p-eIF2α). Furthermore, our data suggest loss of NUPR1 in cells results in maintained eIF2α phosphorylation and evaluation of nascent proteins by click chemistry revealed that NUPR1-depleted PANC-1 cells displayed a slower poststress protein synthesis recovery when compared to wild-type. Combined, these data propose a novel role for NUPR1 in the integrated stress response pathway, at least partially through promoting efficient PERK branch activity and resolution through a unique interaction with eIF2α.

Targeting Fibrosis: The Bridge That Connects Pancreatitis and Pancreatic Cancer

Pancreatic fibrosis is caused by the excessive deposits of extracellular matrix (ECM) and collagen fibers during repeated necrosis to repair damaged pancreatic tissue. Pancreatic fibrosis is frequently present in chronic pancreatitis (CP) and pancreatic cancer (PC). Clinically, pancreatic fibrosis is a pathological feature of pancreatitis and pancreatic cancer. However, many new studies have found that pancreatic fibrosis is involved in the transformation from pancreatitis to pancreatic cancer. Thus, the role of fibrosis in the crosstalk between pancreatitis and pancreatic cancer is critical and still elusive; therefore, it deserves more attention. Here, we review the development of pancreatic fibrosis in inflammation and cancer, and we discuss the therapeutic strategies for alleviating pancreatic fibrosis. We further propose that cellular stress response might be a key driver that links fibrosis to cancer initiation and progression. Therefore, targeting stress proteins, such as nuclear protein 1 (NUPR1), could be an interesting strategy for pancreatic fibrosis and PC treatment.

Intrinsically disordered protein NUPR1 binds to the armadillo-repeat domain of Plakophilin 1

Plakophilin 1 (PKP1), a member of the armadillo repeat family of proteins, is a scaffold component of desmosomes, which are key structural components for cell-cell adhesion. However, PKP1 can be also found in the nucleus of several cells. NUPR1 is an intrinsically disordered protein (IDP) that localizes throughout the whole cell, and intervenes in the development and progression of several cancers. In this work, we studied the binding between PKP1 and NUPR1 by using several in vitro biophysical techniques and in cellulo approaches. The interaction occurred with an affinity in the low micromolar range (~10 μM), and involved the participation of at least one of the tryptophan residues of PKP1 (as shown by fluorescence and molecular docking). The binding region of NUPR1, mapped by NMR and molecular modelling, was a polypeptide patch at the 30s region of its sequence. The association between PKP1 and NUPR1 also occurred in cellulo and was localized in the nucleus, as tested by protein ligation assays (PLAs). We hypothesize that NUPR1 plays an active role in carcinogenesis modulating the function of PKP1.

ZZW-115-dependent inhibition of NUPR1 nuclear translocation sensitizes cancer cells to genotoxic agents

Establishing the interactome of the cancer-associated stress protein Nuclear Protein 1 (NUPR1), we found that it binds to several hundreds of proteins, including proteins involved in nuclear translocation, DNA repair, and key factors of the SUMO pathway. We demonstrated that the NUPR1 inhibitor ZZW-115, an organic synthetic molecule, competes with importins for the binding to the NLS region of NUPR1, thereby inhibiting its nuclear translocation. We hypothesized, and then proved, that inhibition of NUPR1 by ZZW-115 sensitizes cancer cells to DNA damage induced by several genotoxic agents. Strikingly, we found that treatment with ZZW-115 reduced SUMOylation of several proteins involved in DNA damage response (DDR). We further report that the presence of recombinant NUPR1 improved the SUMOylation in a cell-free system, indicating that NUPR1 directly stimulates the SUMOylation machinery. We propose that ZZW-115 sensitizes cancer cells to genotoxic agents by inhibiting the nuclear translocation of NUPR1 and thereby decreasing the SUMOylation-dependent functions of key proteins involved in the DDR.

The ZZW-115-dependent inhibition of NUPR1 nuclear translocation sensitizes cancer cells to genotoxic agents by affecting SUMOylation.

Targeting NUPR1 with the small compound ZZW-115 is an efficient strategy to treat hepatocellular carcinoma

HCC is a highly lethal malignancy with Sorafenib as the only molecularly targeted drug. The multifunctional stress-associated protein, NUPR1, plays an essential role in controlling cell growth, migration, invasion and Sorafenib resistance in HCC. We report here that NUPR1 expression is absent in healthy liver and it is progressively upregulated in HCC premalignant lesions such as hepatitis and cirrhosis with a maximum expression in HCC samples, highlighting that NUPR1 is a potential drug target for HCC. We therefore assessed in this work, ZZW-115, a strong inhibitor of NUPR1, as a promising candidate for the treatment of HCC. We validated its extraordinary antitumor effect on HCC by using two HCC cell lines, HepG2-and Hep3B, both in cell based experiments and xenografted mice. We further revealed that ZZW-115 treatment induced cell death by apoptosis and necroptosis mechanisms, with a concomitant mitochondrial metabolism failure that triggers lower ATP production. Furthermore, the ATP depletion cannot be rescued by the apoptosis inhibitor Z-VAD-FMK and/or the necrosis inhibitor Necrostatin-1, indicating that ZZW-115 induces cell death through the mitochondrial failure.

Melatonin modulates red-ox state and decreases viability of rat pancreatic stellate cells

In this work we have studied the effects of pharmacological concentrations of melatonin (1 µM-1 mM) on pancreatic stellate cells (PSC). Cell viability was analyzed by AlamarBlue test. Production of reactive oxygen species (ROS) was monitored following CM-H₂DCFDA and MitoSOX Red-derived fluorescence. Total protein carbonyls and lipid peroxidation were analyzed by HPLC and spectrophotometric methods respectively. Mitochondrial membrane potential (ψ_m) was monitored by TMRM-derived fluorescence. Reduced (GSH) and oxidized (GSSG) levels of glutathione were determined by fluorescence techniques. Quantitative reverse transcription-polymerase chain reaction was employed to detect the expression of Nrf2-regulated antioxidant enzymes. Determination of SOD activity and total antioxidant capacity (TAC) were carried out by colorimetric methods, whereas expression of SOD was analyzed by Western blotting and RT-qPCR. The results show that melatonin decreased PSC viability in a concentration-dependent manner. Melatonin evoked a concentration-dependent increase in ROS production in the mitochondria and in the cytosol. Oxidation of proteins was detected in the presence of melatonin, whereas lipids oxidation was not observed. Depolarization of ψ_m was noted with 1 mM melatonin. A decrease in the GSH/GSSG ratio was observed, that depended on the concentration of melatonin used. A concentration-dependent increase in the expression of the antioxidant enzymes catalytic subunit of glutamate-cysteine ligase, catalase, NAD(P)H-quinone oxidoreductase 1 and heme oxygenase-1 was detected in cells incubated with melatonin. Finally, decreases in the expression and in the activity of superoxide dismutase were observed. We conclude that pharmacological concentrations melatonin modify the redox state of PSC, which might decrease cellular viability.

Dissecting the Anticancer Mechanism of Trifluoperazine on Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive cancers with almost no curative chemotherapeutic treatment. Besides the development of new compounds, repurposing of approved drugs to treat cancer, alone or in combination, has become an attractive strategy, showing many therapeutic and economic advantages. However, it is necessary to improve our knowledge about the mechanism of cell death elicited by approved drugs itself, but also to rationally develop more powerful multidrug treatments. In this work, we focus our attention on determining the mechanism promoting cell death following trifluoperazine (TFP) treatment, which is an antipsychotic drug with strong anticancer activity in PDAC. We demonstrate that TFP induces cell death by apoptosis and necroptosis, which can be partially inhibited by Z-VAD-FMK as well as necrostatin-1, respectively. This cell death promotion is triggered by a poor ATP content, observed in TFP-treated cells as a consequence of a dramatic decrease in OXPHOS metabolism due to mitochondrial stress. Remarkably, mitochondrial homeostasis was seriously affected, and a loss of mitochondrial membrane potential and ROS overproduction was observed. Moreover, this mitochondrial stress was coupled with an ER stress and the activation of the endoplasmic-reticulum-associated protein degradation (ERAD) and the unf olded protein response (UPR) pathways. We took advantage of this information and inhibited this process by using the proteasome inhibitors MG-132 or bortezomib compounds in combination with TFP and found a significant improvement of the anticancer effect of the TFP on primary PDAC-derived cells. In conclusion, this study not only uncovers the molecular mechanisms that are triggered upon TFP-treatment but also its possible combination with bortezomib for the future development of therapies for pancreatic cancer.

Targeting the Stress-Induced Protein NUPR1 to Treat Pancreatic Adenocarcinoma

Cancer cells activate stress-response mechanisms to adapt themselves to a variety of stressful conditions. Among these protective mechanisms, those controlled by the stress-induced nuclear protein 1 (NUPR1 ) belong to the most conserved ones. NUPR1 is an 82-residue-long, monomeric, basic and intrinsically disordered protein (IDP), which was found to be invariably overexpressed in some, if not all, cancer tissues. Remarkably, we and others have previously showed that genetic inactivation of the Nupr1 gene antagonizes the growth of pancreatic cancer as well as several other tumors. With the use of a multidisciplinary strategy by combining biophysical, biochemical, bioinformatic, and biological approaches, a trifluoperazine-derived compound, named ZZW-115, has been identified as an inhibitor of the NUPR1 functions. The anticancer activity of the ZZW-115 was first validated on a large panel of cancer cells. Furthermore, ZZW-115 produced a dose-dependent tumor regression of the tumor size in xenografted mice. Mechanistically, we have demonstrated that NUPR1 binds to several importins. Because ZZW-115 binds NUPR1 through the region around the amino acid Thr68, which is located into the nuclear location signal (NLS) region of the protein, we demonstrated that treatment with ZZW-115 inhibits completely the translocation of NUPR1 from the cytoplasm to the nucleus by competing with importins.

Designing and repurposing drugs to target intrinsically disordered proteins for cancer treatment: using NUPR1 as a paradigm

Intrinsically disordered proteins (IDPs) do not have a well-defined structure, but they have key biological tasks in cancer development. By using the disordered cancer-related protein NUPR1 as a proof-of-concept, we have developed a new multidisciplinary approach to tackle drug-design against IDPs, using it to repurpose drugs for treating pancreatic adenocarcinoma (PDAC).

Ligand-based design identifies a potent NUPR1 inhibitor exerting anticancer activity via necroptosis

Intrinsically disordered proteins (IDPs) are emerging as attractive drug targets by virtue of their prevalence in various diseases including cancer. Drug development targeting IDPs is challenging because they have dynamical structure features and conventional drug design is not applicable. NUPR1 is an IDP playing an important role in pancreatic cancer. We previously reported that Trifluoperazine (TFP), an antipsychotic agent, was capable of binding to NUPR1 and inhibiting tumors growth. Unfortunately, TFP showed strong central nervous system side-effects. In this work, we undertook a multidisciplinary approach to optimize TFP, based on the synergy of computer modeling, chemical synthesis, and a variety of biophysical, biochemical and biological evaluations. A family of TFP-derived compounds was produced and the most active one, named ZZW-115, showed a dose-dependent tumor regression with no neurological effects and induced cell death mainly by necroptosis. This study opens a new perspective for drug development against IDPs, demonstrating the possibility of successful ligand-based drug design for such challenging targets.

Melatonin induces reactive oxygen species generation and changes in glutathione levels and reduces viability in human pancreatic stellate cells

In this study, the effects of pharmacological concentrations of melatonin (1 μM-1 mM) on human pancreatic stellate cells (HPSCs) have been examined. Cell type-specific markers and expression of melatonin receptors were analyzed by western blot analysis. Changes in intracellular free Ca²⁺ concentration were followed by fluorimetric analysis of fura-2-loaded cells. Reduced glutathione (GSH) and oxidized glutathione (GSSG) levels were determined by fluorescence techniques. Production of reactive oxygen species (ROS) was monitored following 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate acetyl ester and MitoSOX™ Red-derived fluorescence. Cell viability was studied using the AlamarBlue^® test. Cultured cells expressed markers typical of stellate cells. However, cell membrane receptors for melatonin could not be detected. Thapsigargin, bradykinin, or melatonin induced changes in intracellular free Ca²⁺ concentration. In the presence of the indole, a decrease in the GSH/GSSG ratio was observed that depended on the concentration of melatonin used. Furthermore, the indole evoked a concentration-dependent increase in ROS production in the mitochondria and in the cytosol. Finally, melatonin decreased HPSC viability in a time and concentration-dependent manner. We conclude that melatonin, at pharmacological concentrations, induces changes in the oxidative state of HPSC. This might regulate cellular viability and could not involve specific plasma membrane receptors.

α-lipoic acid reduces postreperfusion syndrome in human liver transplantation - a pilot study

A double-blind randomized controlled trial was performed to compare the safety and efficacy of α-lipoic acid (ALA) in liver transplantation (LT). The grafts were randomized to receive ALA or placebo before the cold ischemia time. Furthermore, patients transplanted with the ALA-perfused graft received 600 mg of intravenous ALA, while patients with the nonperfused graft received the placebo just before graft reperfusion. Hepatic biopsy was performed 2 h postreperfusion. Blood samples were collected before, during and 1 and 2 days after reperfusion. Quantitative polymerase chain reaction (qPCR) analysis was performed on biopsies to assess genes involved in the response to hypoxia, apoptosis, cell growth, survival and proliferation, cytokine production and tissue damage protection. Nine of 40 patients developed postreperfusion syndrome (PRS), but seven of them belonged to the control group. There was a decrease in PHD2 and an increase in alpha subunit of hypoxia-inducible factor-1 (HIF-1α) and baculoviral IAP repeat containing 2 (Birc2) transcript levels in the biopsies from the ALA-treated versus the control group of patients. Additionally, plasma levels of alarmins were lower in ALA-treated patients than control patients, which suggests that ALA-treated grafts are less inflammatory than untreated grafts. These results showed that ALA is safe for use in LT, induces gene changes that protect against hypoxia and oxidative stress and reduces the appearance of PRS.

E2F signature is predictive for the pancreatic adenocarcinoma clinical outcome and sensitivity to E2F inhibitors, but not for the response to cytotoxic-based treatments

The main goal of this study was to find out strategies of clinical relevance to classify patients with a pancreatic ductal adenocarcinoma (PDAC) for individualized treatments. In the present study a set of 55 patient-derived xenografts (PDX) were obtained and their transcriptome were analyzed by using an Affymetrix approach. A supervised bioinformatics-based analysis let us to classify these PDX in two main groups named E2F-highly dependent and E2F-lowly dependent. Afterwards their characterization by using a Kaplan-Meier analysis demonstrated that E2F high patients survived significantly less than E2F low patients (9.5 months vs. 16.8 months; p = 0.0066). Then we tried to establish if E2F transcriptional target levels were associated to the response to cytotoxic treatments by comparing the IC50 values of E2F high and E2F low cells after gemcitabine, 5-fluorouracil, oxaliplatin, docetaxel or irinotecan treatment, and no association was found. Then we identified an E2F inhibitor compound, named ly101-4B, and we observed that E2F-higly dependent cells were more sensitive to its treatment (IC50 of 19.4 ± 1.8 µM vs. 44.1 ± 4.4 µM; p = 0.0061). In conclusion, in this work we describe an E2F target expression-based classification that could be predictive for patient outcome, but more important, for the sensitivity of tumors to the E2F inhibitors as a treatment. Finally, we can assume that phenotypic characterization, essentially by an RNA expression analysis of the PDAC, can help to predict their clinical outcome and their response to some treatments when are rationally selected.

Ebselen impairs cellular oxidative state and induces endoplasmic reticulum stress and activation of crucial mitogen-activated protein kinases in pancreatic tumour AR42J cells

Ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one) is an organoselenium radical scavenger compound, which has strong antioxidant and anti-inflammatory effects. However, evidence suggests that this compound could exert deleterious actions on cell physiology. In this study, we have analyzed the effect of ebselen on rat pancreatic AR42J cells. Cytosolic free-Ca²⁺ concentration ([Ca²⁺ ]_c ), cellular oxidative status, setting of endoplasmic reticulum stress, and phosphorylation of major mitogen-activated protein kinases were analyzed. Our results show that ebselen evoked a concentration-dependent increase in [Ca²⁺ ]_c . The compound induced an increase in the generation of reactive oxygen species in the mitochondria. We also observed an increase in global cysteine oxidation in the presence of ebselen. In the presence of ebselen an impairment of cholecystokinin-evoked amylase release was noted. Moreover, involvement of the unfolded protein response markers, ER chaperone and signaling regulator GRP78/BiP, eukaryotic translation initiation factor 2α and X-box binding protein 1 was detected. Finally, increases in the phosphorylation of SAPK/JNK, p38 MAPK, and p44/42 MAPK in the presence of ebselen were also observed. Our results provide evidences for an impairment of cellular oxidative state and enzyme secretion, the induction of endoplasmic reticulum stress and the activation of crucial mitogen-activated protein kinases in the presence of ebselen. As a consequence ebselen exerts a potential toxic effect on AR42J cells.

Modulation of copper accumulation and copper-induced toxicity by antioxidants and copper chelators in cultured primary brain astrocytes

Copper is essential for several important cellular processes, but an excess of copper can also lead to oxidative damage. In brain, astrocytes are considered to play a pivotal role in the copper homeostasis and antioxidative defence. To investigate whether antioxidants and copper chelators can modulate the uptake and the toxicity of copper ions in brain astrocytes, we used primary astrocytes as cell culture model. These cells accumulated substantial amounts of copper during exposure to copper chloride. Copper accumulation was accompanied by a time- and concentration-dependent loss in cell viability, as demonstrated by a lowering in cellular MTT reduction capacity and by an increase in membrane permeability for propidium iodide. During incubations in the presence of the antioxidants ascorbate, trolox or ebselen, the specific cellular copper content and the toxicity in copper chloride-treated astrocyte cultures were strongly increased. In contrast, the presence of the copper chelators bathocuproine disulfonate or tetrathiomolybdate lowered the cellular copper accumulation and the copper-induced as well as the ascorbate-accelerated copper toxicity was fully prevented. These data suggest that predominantly the cellular content of copper determines copper-induced toxicity in brain astrocytes.

Melatonin induces the expression of Nrf2-regulated antioxidant enzymes via PKC and Ca2+ influx activation in mouse pancreatic acinar cells

The goal of this study was to evaluate the potential activation of the nuclear factor erythroid 2-related factor and the antioxidant-responsive element (Nrf2-ARE) signaling pathway in response to melatonin in isolated mouse pancreatic acinar cells. Changes in intracellular free Ca(2+) concentration were followed by fluorimetric analysis of fura-2-loaded cells. The activations of PKC and JNK were measured by Western blot analysis. Quantitative reverse transcription-polymerase chain reaction was employed to detect the expression of Nrf2-regulated antioxidant enzymes. Immunocytochemistry was employed to determine nuclear location of phosphorylated Nrf2, and the cellular redox state was monitored following MitoSOX Red-derived fluorescence. Our results show that stimulation of fura-2-loaded cells with melatonin (1 µM to 1 mM), in the presence of Ca(2+) in the extracellular medium, induced a slow and progressive increase of [Ca(2+)](c) toward a stable level. Melatonin did not inhibit the typical Ca(2+) response induced by CCK-8 (1 nM). When the cells were challenged with indoleamine in the absence of Ca(2+) in the extracellular solution (medium containing 0.5 mM EGTA) or in the presence of 1 mM LaCl(3), to inhibit Ca(2+) entry, we could not detect any change in [Ca(2+)](c). Nevertheless, CCK-8 (1 nM) was able to induce the typical mobilization of Ca(2+). When the cells were incubated with the PKC activator PMA (1 µM) in the presence of Ca(2+) in the extracellular medium, we observed a response similar to that noted when the cells were challenged with melatonin 100 µM. However, in the presence of Ro31-8220 (3 µM), a PKC inhibitor, stimulation of cells with melatonin failed to evoke changes in [Ca(2+)]c. Immunoblots, using an antibody specific for phospho-PKC, revealed that melatonin induces PKCα activation, either in the presence or in the absence of external Ca(2+). Melatonin induced the phosphorylation and nuclear translocation of the transcription factor Nrf2, and evoked a concentration-dependent increase in the expression of the antioxidant enzymes NAD(P)H-quinone oxidoreductase 1, catalytic subunit of glutamate-cysteine ligase, and heme oxygenase-1. Incubation of MitoSOX Red-loaded pancreatic acinar cells in the presence of 1 nM CCK-8 induced a statistically significant increase in dye-derived fluorescence, reflecting an increase in oxidation, that was abolished by pretreatment of cells with melatonin (100 µM) or PMA (1 µM). On the contrary, pretreatment with Ro31-8220 (3 µM) blocked the effect of melatonin on CCK-8-induced increase in oxidation. Finally, phosphorylation of JNK in the presence of CCK-8 or melatonin was also observed. We conclude that melatonin, via modulation of PKC and Ca(2+) signaling, could potentially stimulate the Nrf2-mediated antioxidant response in mouse pancreatic acinar cells.

Interferences of resveratrol with fura-2-derived fluorescence in intracellular free-Ca(2+) concentration determinations

Resveratrol (3,4',5-trihydroxy-trans-stilbene) is an antioxidant widely employed in cell physiology studies. It has been reported that it interferes with fura-2-derived fluorescence, making the employment of this dye nonviable. In this work, the interference of resveratrol with fura-2 determinations of intracellular free-Ca(2+) concentration ([Ca(2+)]c) was examined. Solutions containing different concentrations of resveratrol, with or without fura-2, in the presence or in the absence of Ca(2+), were analyzed by spectrofluorimetry. AR42J tumor cells were employed to study the influence of resveratrol on fura-2 fluorescence in living cells, by single cell fluorimetry. Resveratrol impaired the detection of fura-2-fluorescence emission (510 nm) at the 340, 360 and 380 nm excitation wavelengths. Resveratrol emitted fluorescence at 510 nm when lighted at all three excitation wavelengths. In addition, resveratrol emitted fluorescence at 380 nm when excited at 340 nm. Our observations suggest that the employment of the ratiometric properties of fura-2 to follow changes in [Ca(2+)]c in the presence of resveratrol is not viable. However, we think that the 380 nm excitation light could be employed. Results could be expressed as F0/F380, where F0 is the resting fluorescence and F380 is the value of fluoresce at a certain time point. We could follow changes in [Ca(2+)]c evoked by CCK-8, and we also detected Ca(2+) mobilization by 100 µM resveratrol in AR42J cells. This investigation presents evidence demonstrating that resveratrol interferes with fura-2 fluorescence spectra. Nevertheless, a chance still exists if the 380 nm excitation wavelength is employed in the middle or low micromolar concentrations of resveratrol.

Astrocyte NMDA receptors' activity sustains neuronal survival through a Cdk5-Nrf2 pathway

Neurotransmission unavoidably increases mitochondrial reactive oxygen species. However, the intrinsic antioxidant defense of neurons is weak and hence the mechanism whereby these cells are physiologically protected against oxidative damage is unknown. Here we found that the antioxidant defense of neurons is repressed owing to the continuous protein destabilization of the master antioxidant transcriptional activator, nuclear factor-erythroid 2-related factor-2 (Nrf2). By contrast, Nrf2 is highly stable in neighbor astrocytes explaining their robust antioxidant defense and resistance against oxidative stress. We also show that subtle and persistent stimulation of N-methyl-d-aspartate receptors (NMDAR) in astrocytes, through a mechanism not requiring extracellular Ca²⁺ influx, upregulates a signal transduction pathway involving phospholipase C-mediated endoplasmic reticulum release of Ca²⁺ and protein kinase Cδ activation. Active protein kinase Cδ promotes, by phosphorylation, the stabilization of p35, a cyclin-dependent kinase-5 (Cdk5) cofactor. Active p35/Cdk5 complex in the cytosol phosphorylates Nrf2 at Thr(395), Ser(433) and Thr(439) that is sufficient to promote Nrf2 translocation to the nucleus and induce the expression of antioxidant genes. Furthermore, this Cdk5-Nrf2 transduction pathway boosts glutathione metabolism in astrocytes efficiently protecting closely spaced neurons against oxidative damage. Thus, intercellular communication through NMDAR couples neurotransmission with neuronal survival.

Melatonin modulates Ca2+ mobilization and amylase release in response to cholecystokinin octapeptide in mouse pancreatic acinar cells

In the present work, we have evaluated the effect of an acute addition of melatonin on cholecystokinin octapeptide (CCK-8)-evoked Ca(2+) signals and amylase secretion in mouse pancreatic acinar cells. For this purpose, freshly isolated mouse pancreatic acinar cells were loaded with fura-2 to study intracellular free Ca(2+) concentration ([Ca(2+)](c)). Amylase release and cell viability were studied employing colorimetric methods. Our results show that CCK-8 evoked a biphasic effect on amylase secretion, finding a maximum at a concentration of 0.1 nM and a reduction of secretion at higher concentrations. Pre-incubation of cells with melatonin (1 μM-1 mM) significantly attenuated enzyme secretion in response to high concentrations of CCK-8. Stimulation of cells with 1 nM CCK-8 led to a transient increase in [Ca(2+)](c), followed by a decrease towards a constant level. In the presence of 1 mM melatonin, stimulation of cells with CCK-8 resulted in a smaller [Ca(2+)](c) peak response, a faster rate of decay of [Ca(2+)](c) and lower values for the steady state of [Ca(2+)](c), compared with the effect of CCK-8 alone. Melatonin also reduced the oscillatory pattern of Ca(2+) mobilization evoked by a physiological concentration of CCK-8 (20 pM), and completely inhibited Ca(2+) mobilization induced by 10 pM CCK-8. On the other hand, Ca(2+) entry from the extracellular space was not affected in the presence of melatonin. Finally, melatonin alone did not change cell viability. We conclude that melatonin, at concentrations higher than those found in blood, might regulate exocrine pancreatic function via modulation of Ca(2+) signals.

Ebselen alters mitochondrial physiology and reduces viability of rat hippocampal astrocytes

The seleno-organic compound and radical scavenger ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one) have been extensively employed as an anti-inflammatory and neuroprotective compound. However, its glutathione peroxidase activity at the expense of cellular thiols groups could underlie certain deleterious actions of the compound on cell physiology. In this study, we have analyzed the effect of ebselen on rat hippocampal astrocytes in culture. Cellular viability, the intracellular free-Ca(2+) concentration ([Ca(2+)]c), the mitochondrial free-Ca(2+) concentration ([Ca(2+)]m), and mitochondrial membrane potential (ψm) were analyzed. The caspase-3 activity was also assayed. Our results show that cell viability was reduced by treatment of cells with ebselen, depending on the concentration employed. In the presence of ebselen, we observed an initial transient increase in [Ca(2+)]c that was then followed by a progressive increase to an elevated plateau. We also observed a transient increase in [Ca(2+)]m in the presence of ebselen that returned toward a value over the prestimulation level. The compound induced depolarization of ψm and altered the permeability of the mitochondrial membrane. Additionally, a disruption of the mitochondrial network was observed. Finally, we did not detect changes in caspase-3 activation in response to ebselen treatment. Collectively, these data support the likelihood of ebselen, depending on the concentration employed, reduces viability of rat hippocampal astrocytes via its action on the mitochondrial activity. These may be early effects that do not involve caspase-3 activation. We conclude that, depending on the concentration used, ebselen might exert deleterious actions on astrocyte physiology that could compromise cell function.

Cinnamtannin B-1, a natural antioxidant that reduces the effects of H(2)O(2) on CCK-8-evoked responses in mouse pancreatic acinar cells

This work was designed in order to gain an insight on the mechanisms by which antioxidants prevent pancreatic disorders. We have examined the properties of cinnamtannin B-1, which belongs to the class of polyphenols, against the effect of hydrogen peroxide (H(2)O(2)) in mouse pancreatic acinar cells. We have studied Ca(2+) mobilization, oxidative state, amylase secretion, and cell viability of cells treated with cinnamtannin B-1 in the presence of various concentrations of H(2)O(2). We found that H(2)O(2) (0.1-100 μM) increased CM-H(2)DCFDA-derived fluorescence, reflecting an increase in oxidation. Cinnamtannin B-1 (10 μM) reduced H(2)O(2)-induced oxidation of CM-H(2)DCFDA. CCK-8 induced oxidation of CM-H(2)DCFDA in a similar way to low micromolar concentrations of H(2)O(2), and cinnamtannin B-1 reduced the oxidant effect of CCK-8. In addition, H(2)O(2) induced a slow and progressive increase in intracellular free Ca(2+) concentration ([Ca(2+)](c)). Cinnamtannin B-1 reduced the effect of H(2)O(2) on [Ca(2+)](c), but only at the lower concentrations of the oxidant. H(2)O(2) inhibited amylase secretion in response to cholecystokinin, and cinnamtannin B-1 reduced the inhibitory action of H(2)O(2) on enzyme secretion. Finally, H(2)O(2) reduced cell viability, and the antioxidant protected acinar cells against H(2)O(2). In conclusion, the beneficial effects of cinnamtannin B-1 appear to be mediated by reducing the intracellular Ca(2+) overload and intracellular accumulation of digestive enzymes evoked by ROS, which is a common pathological precursor that mediates pancreatitis. Our results support the beneficial effect of natural antioxidants in the therapy against oxidative stress-derived deleterious effects on cellular physiology.

Ethanol reduces kainate-evoked glutamate secretion in rat hippocampal astrocytes

In this study we have used rat hippocampal astrocytes in culture to investigate the effect of ethanol on kainate-induced glutamate secretion. Our results show that kainate (10 μM to 500 μM) stimulated glutamate release from astrocytes. Preincubation of astrocytes in the presence of ethanol induced a concentration-dependent (1mM-50mM) inhibition of glutamate release caused by stimulation of cells with 100 μM kainate. Inhibition of alcohol-dehydrogenase, by preincubation of astrocytes in the presence of 4-methylpyrazole (1mM), abolished ethanol-induced inhibition of glutamate release in response to kainate. On the other hand, preincubation of astrocytes in the presence of the antioxidant cinnamtannin B-1 (10 μM) also blocked ethanol inhibitory action on glutamate release in response to kainate. Ethanol (50mM) reduced Ca(2+) mobilization in response to kainate, whereas cinnamtannin B-1 reversed the inhibitory action of ethanol on Ca(2+) mobilization by kainate. Our results are consistent with an inhibitory action of ethanol on glutamate secretion from hippocampal astrocytes. The inhibitory effects of ethanol are probably due to its oxidative metabolization, involves reactive oxygen species production, and a lower Ca(2+) mobilization by kainate. Taking into account the pivotal role that astrocytes play within the central nervous system, especially in relation to neurons, the negative effects of ethanol on the release of glutamate might affect neuron-glia communication in the hippocampus, which might lead to functional defects in the brain.