The volume-sensitive chloride channel inhibitors prevent both contractile dysfunction and apoptosis induced by doxorubicin through PI3kinase, Akt and Erk 1/2

Attenuation of ROS/Chloride Efflux-Mediated NLRP3 Inflammasome Activation Contributes to Alleviation of Diabetic Cardiomyopathy in Rats after Sleeve Gastrectomy

Diabetic cardiomyopathy (DCM) can develop in diabetes mellitus and is a major cause of morbidity and mortality. Surgical bariatric surgery procedures, such as sleeve gastrectomy (SG), result in remission of type 2 diabetes and have benefits regarding systolic and diastolic myocardial function. The NLR family pyrin domain containing 3 (NLRP3) inflammasome appears to participate in the development of DCM. However, whether SG surgery affects myocardial NLRP3 inflammasome-related pyroptosis to improve cardiac function remains unclear. This study was aimed at investigating the effect of SG surgery on NLRP3-associated pyroptosis in rats with DCM. We also examined cellular phenotypes and molecular mechanisms in high glucose-stimulated myocytes. The rat model of DCM was established by high-fat diet feeding and low-dose streptozotocin injection. We observed a metabolic benefit of SG, including a reduced body weight, food intake, and blood glucose levels and restored glucose tolerance and insulin sensitivity postoperatively. We observed a marked decline in glucose uptake in rats with DCM, and this was restored after SG. Also, SG alleviated the dysfunction of myocardial contraction and diastole, delayed the progression of DCM, and reduced the NLRP3 inflammasome-mediated myocardial pyroptosis in vivo. H9c2 cardiomyocytes showed membrane disruption and DNA damage under a high glucose stimulus, which suggested myocardial pyroptosis. Using a ROS scavenger or chloride channel blocker in vitro restored myocardial NLRP3-mediated pyroptosis. Furthermore, we found that chloride efflux acted downstream of ROS generation. In conclusion, SG may ameliorate or even reverse the progression of DCM. Our study provides evidence that the SG operation alleviates NLRP3 inflammasome dysregulation in DCM. Clearance of ROS overburden and suppression of chloride efflux due to SG might act as the proximal event before inhibition of NLRP3 inflammasome in the myocardium, thus contributing to morphological and functional alleviation of DCM.

Morpho-functional indicators changes of rats’ myocardium in experimental doxorubicin-induced chronic heart failure and its pharmacological modulation with new 4-amino-1,2,4-triazole derivative

Bromide 1 - (β-phenylethyl)-4-amino-1,2,4-triazolium (Hypertril) has the properties of a beta-blocker and of NO-mimetic, is assigned to the IV class of toxicity. All these effects make Hypertril a promising drug for the treatment of cardiovascular diseases. The aim of this paper was to study the cardioprotective action of Hypertril in terms of the effect on the morpho-functional parameters of the myocardium in rats with experimental chronic heart failure (CHF). CHF was modeled on 80 white outbred rats weighing 190–220g by administering doxorubicin at a cumulative dose of 15 mg/kg. Hypertril and the reference drug metoprolol succinate were administered within 30 days after CHF modeling, intragastrically at doses of 3.5 mg/kg and 15 mg/kg. Morphometric analysis of the cellular structure of the myocardium was carried out on an Axioskop microscope (Zeiss, Germany), in an automatic mode using a macro program developed in a specialized programming environment VIDAS-2.5 (Kontron Elektronik, Germany). The administration of Hypertril to animals with CHF led to an increase in the density of nuclei of cardiomyocytes, the area of myocardiocyte nuclei, an increase in the nuclear cytoplasmic ratio and an increase in the concentration of RNA in the nuclei and cytoplasm of cardiomyocytes compared with the group of untreated animals, which indicated the presence of a pronounced cardioprotective effect in the drug candidate. In terms of such indicators as the density of surviving cardiomyocytes and the content of RNA in them, the nuclear-cytoplasmic ratio of Hypertril is significantly (p < 0.05) superior to metoprolol.

Regulated cell death pathways in doxorubicin-induced cardiotoxicity

Doxorubicin is a chemotherapeutic drug used for the treatment of various malignancies; however, patients can experience cardiotoxic effects and this has limited the use of this potent drug. The mechanisms by which doxorubicin kills cardiomyocytes has been elusive and despite extensive research the exact mechanisms remain unknown. This review focuses on recent advances in our understanding of doxorubicin induced regulated cardiomyocyte death pathways including autophagy, ferroptosis, necroptosis, pyroptosis and apoptosis. Understanding the mechanisms by which doxorubicin leads to cardiomyocyte death may help identify novel therapeutic agents and lead to more targeted approaches to cardiotoxicity testing.

LRRC8A contributes to angiotensin II-induced cardiac hypertrophy by interacting with NADPH oxidases via the C-terminal leucine-rich repeat domain

Cardiac hypertrophy, an important cause of heart failure, is characterized by an increase in heart weight, the ventricular wall, and cardiomyocyte volume. The volume regulatory anion channel (VRAC) is an important regulator of cell volume. However, its role in cardiac hypertrophy remains unclear. The purpose of this study was to investigate the effect of leucine-rich repeat-containing 8A (LRRC8A), an essential component of the VRAC, on angiotensin II (AngII)-induced cardiac hypertrophy. Our results showed that LRRC8A expression, NADPH oxidase activity, and reactive oxygen species (ROS) production were increased in AngII-induced hypertrophic neonatal mouse cardiomyocytes and the myocardium of C57/BL/6 mice. In addition, AngII activated VRAC currents in cardiomyocytes. The delivery of adeno-associated viral (AAV9) bearing siRNA against mouse LRRC8A into the left ventricular wall inhibited AngII-induced cardiac hypertrophy and fibrosis. Accordingly, the knockdown of LRRC8A attenuated AngII-induced cardiomyocyte hypertrophy and VRAC currents in vitro. Furthermore, knockdown of LRRC8A suppressed AngII-induced ROS production, NADPH oxidase activity, the expression of NADPH oxidase membrane-bound subunits Nox2, Nox4, and p22phox, and the translocation of NADPH oxidase cytosolic subunits p47phox and p67phox. Immunofluorescent staining showed that LRRC8A co-localized with NADPH oxidase membrane subunits Nox2, Nox4, and p22phox. Co-immunoprecipitation and analysis of a C-terminal leucine-rich repeat domain (LRRD) mutant showed that LRRC8A physically interacts with Nox2, Nox4, and p22phox via the LRRD. Taken together, the results of this study suggested that LRRC8A might play an important role in promoting AngII-induced cardiac hypertrophy by interacting with NADPH oxidases via the LRRD.

Norcepharadione B attenuates H2O2-induced neuronal injury by upregulating cellular antioxidants and inhibiting volume-sensitive Cl- channel

Oxidative stress acts as an essential culprit factor in the development of stroke and Alzheimer’s disease. Norcepharadione B possesses various pharmacologic features as an extract obtained from Houttuynia cordata. Nevertheless, the anti-apoptotic and neuroprotective characteristics of norcepharadione B remain unclear. In this study, the neuronal protection effect provided by norcepharadione B against injury caused by hydrogen peroxide (H2O2) in HT22 cell as well as the fundamental mechanism was systematically explored. The neurotoxicity assays of hippocampal cells, which were co-cultured with H2O2, showed that norcepharadione B had the ability to insulate the toxicity induced by H2O2 with significant reduced cell apoptosis. Besides, norcepharadione B potentiated the activity of superoxide dismutase (SOD), increased the level of glutathione (GSH), and decreased malondialdehyde content. The H2O2-induced apoptotic protein Bax was suppressed, and the anti-apoptotic protein Bcl-2 was boosted by norcepharadione B. Norcepharadione B promoted Akt phosphorylation and further upregulated heme oxygenase (HO-1) in cells exposed to oxidative stress. However, the inductive effect of HO-1 by norcepharadione B was shut off via the PI3K/Akt inhibitor LY294002. Furthermore, 2-h incubation with H2O2 substantially increased cell volume in HT22 cells, while norcepharadione B effectively alleviated such effect by interrupting the activation of VSOR Cl− channel. Collectively, our data revealed protective properties of norcepharadione B in resisting oxidative stress induced by H2O2 through elevation of HO-1 in the dependence of PI3K/Akt and in inhibiting H2O2-induced cell swelling by VSOR Cl− channel obstruction in HT22 cells.

Impact statement

Norcepharadione B is an aporphine alkaloid compound extracted from Chinese herb Houttuynia cordata. It was well known for its anti-inflammatory, anti-cancer, and anti-platelet aggregation outcomes. Our study demonstrated that Norcepharadione B protected hippocampal neurons against oxidative stress and the resultant cell apoptosis upon H2O2 exposure. Meanwhile, Norcepharadione B also substantially reduced cell swelling induced by H2O2 via inhibiting VSOR Cl− channel in neurons. These findings uncovered the potential mechanisms of Norcepharadione B in protecting neuron apoptosis under oxidative stress and propose that Norcepharadione B may serve as a favorable herb medicine for restoring neuronal injury in the pathogenesis of stroke together with other neurodegenerative diseases.

Altered expression and functional role of ion channels in leukemia: bench to bedside

Leukemic cells' (LCs) survival, proliferation, activation, differentiation, and invasiveness/migration can be mediated through the function of cation and anion channels that are involved in volume regulation, polarization, cytoskeleton, and extracellular matrix reorganization. This study will review the expression of ion channels in LCs and their possible function in leukemia progression. We searched relevant literature by a PubMed (2002-2019) of English-language literature using the terms "ion channels", "leukemia", "proliferation", "differentiation", "apoptosis", and "migration". Altered expression and dysfunction of ion channels can have a strong impact on hematopoietic cell and LCs physiology and signaling, which contributes to the vital processes such as proliferation, differentiation, and apoptosis. Indeed, it can be stated that changing expression of ion channels can affect the onset and progression as well as clinical features and therapeutic responses of leukemia via inducing the maintenance of LCs. Since ion channels are membrane proteins, they can be easily accessible in LCs for understanding their influence on leukemia progression. On the other hand, ion channels can be new potential targets for chemotherapeutic agents, which may open a novel clinical and pharmaceutical field in leukemia therapy.

DIDS inhibits overexpression BAK1-induced mitochondrial apoptosis through GSK3β/β-catenin signaling pathway

Bcl-2 homologous antagonist/killer (BAK1) is a critical regulator of mitochondrial apoptosis. Although upregulation of BAK1 induces apoptosis has been established, the underlying molecular mechanism is far from clear. 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), an organic anion used as a blocker of anion exchangers and chloride channels, has been proved to rescue cell apoptosis both in vitro and in vivo. However, whether DIDS can inhibit BAK1-induced mitochondrial apoptosis remains undefined. Thus, this study aimed to explore whether DIDS could protect BAK1-induced apoptosis through GSK3β/β-catenin signaling pathway. The results showed overexpression BAK1 in 293T cells induced mitochondrial apoptosis accompanied by increasing the expression levels of cleaved caspase-9, -3, poly (ADP-ribose) polymerase (PARP) and reducing the MMP. Furthermore, overexpression BAK1 decreased the expression levels of Ser9-GSK3β and β-catenin. In addition, lithium chloride (LiCl), an activator of Wnt/β-catenin signaling pathway, markedly attenuated overexpression BAK1-induced mitochondrial apoptosis by restoring the expression levels of Ser9-GSK3β and β-catenin. Finally, DIDS absolutely abolished overexpression BAK1-mediated mitochondrial apoptosis through recovering the expression levels of Ser9-GSK3β and β-catenin. Taken together, our results reveal that DIDS blocks overexpression BAK1-induced mitochondrial apoptosis through GSK3β/β-catenin pathway.

QSKL protects against myocardial apoptosis on heart failure via PI3K/Akt-p53 signaling pathway

The ancient traditional Chinese medicine Qishenkeli (QSKL) is widely used in the treatment of heart failure (HF) in China. Previous studies have shown that QSKL has definite effects on HF. The purpose of this study is to identify the regulation of QSKL on apoptosis and clarify the underlying mechanism. An apoptosis model of H9C2 cells was induced by oxygen-glucose deprivation/recovery (OGD/R). An animal model of HF was induced by ligation of left anterior descending (LAD) coronary artery in rat. We found that QSKL reduced intracellular ROS generation, increased mitochondrial membrane potential and protected H9C2 cells against OGD/R-induced apoptosis. In vivo results showed that QSKL administration could improve cardiac functions, decrease fibrotic area, infarct size and apoptotic rate in HF model. QSKL regulated the expressions of key apoptotic molecules, including increasing Bcl-2/Bax ratio, reducing the expressions of P53, Bax and Cleaved-caspase-3. Interestingly, QSKL also regulated the phosphorylated expressions of PI3K and Akt without significantly affecting PTEN. Taken together, the protective and anti-apoptotic effects of QSKL could be mediated partly through modulating the PI3K/Akt-P53 apoptotic pathway.

Subunit composition of VRAC channels determines substrate specificity and cellular resistance to Pt-based anti-cancer drugs

Although platinum‐based drugs are widely used chemotherapeutics for cancer treatment, the determinants of tumor cell responsiveness remain poorly understood. We show that the loss of subunits LRRC8A and LRRC8D of the heteromeric LRRC8 volume‐regulated anion channels (VRACs) increased resistance to clinically relevant cisplatin/carboplatin concentrations. Under isotonic conditions, about 50% of cisplatin uptake depended on LRRC8A and LRRC8D, but neither on LRRC8C nor on LRRC8E. Cell swelling strongly enhanced LRRC8‐dependent cisplatin uptake, bolstering the notion that cisplatin enters cells through VRAC. LRRC8A disruption also suppressed drug‐induced apoptosis independently from drug uptake, possibly by impairing VRAC‐dependent apoptotic cell volume decrease. Hence, by mediating cisplatin uptake and facilitating apoptosis, VRAC plays a dual role in the cellular drug response. Incorporation of the LRRC8D subunit into VRAC substantially increased its permeability for cisplatin and the cellular osmolyte taurine, indicating that LRRC8 proteins form the channel pore. Our work suggests that LRRC8D‐containing VRACs are crucial for cell volume regulation by an important organic osmolyte and may influence cisplatin/carboplatin responsiveness of tumors.

The impact of polyphenols on chondrocyte growth and survival: a preliminary report

Background

Imbalances in the functional binding of fibroblast growth factors (FGFs) to their receptors (FGFRs) have consequences for cell proliferation and differentiation that in chondrocytes may lead to degraded cartilage. The toxic, proinflammatory, and oxidative response of cytokines and FGFs can be mitigated by dietary polyphenols.

Objective

We explored the possible effects of polyphenols in the management of osteoarticular diseases using a model based on the transduction of a mutated human FGFR3 (G380R) in murine chondrocytes. This mutation is present in most cases of skeletal dysplasia and is responsible for the overexpression of FGFR3 that, in the presence of its ligand, FGF9, results in toxic effects leading to altered cellular growth.

Design

Different combinations of dietary polyphenols derived from plant extracts were assayed in FGFR3 (G380R) mutated murine chondrocytes, exploring cell survival, chloride efflux, extracellular matrix (ECM) generation, and grade of activation of mitogen-activated protein kinases.

Results

Bioactive compounds from Hibiscus sabdariffa reversed the toxic effects of FGF9 and restored normal growth, suggesting a probable translation to clinical requests in humans. Indeed, these compounds activated the intracellular chloride efflux, increased ECM generation, and stimulated cell proliferation. The inhibition of mitogen-activated protein kinase phosphorylation was interpreted as the main mechanism governing these beneficial effects.

Conclusions

These findings support the rationale behind the encouragement of the development of drugs that repress the overexpression of FGFRs and suggest the dietary incorporation of supplementary nutrients in the management of degraded cartilage.

Activation of volume-sensitive outwardly rectifying chloride channel by ROS contributes to ER stress and cardiac contractile dysfunction: involvement of CHOP through Wnt

Endoplasmic reticulum (ER) stress occurring in stringent conditions is critically involved in cardiomyocytes apoptosis and cardiac contractile dysfunction (CCD). However, the molecular machinery that mediates cardiac ER stress and subsequent cell death remains to be fully deciphered, which will hopefully provide novel therapeutic targets for these disorders. Here, we establish tunicamycin-induced model of cardiomyocyte ER stress, which effectively mimicks pathological stimuli to trigger CCD. Tunicamycin activates volume-sensitive outward rectifying Cl⁻ currents. Blockade of the volume-sensitive outwardly rectifying (VSOR) Cl⁻ channel by 4,4'-diisothiocya-natostilbene-2,2'-disulfonic acid (DIDS), a non-selective Cl⁻ channel blocker, and 4-(2-butyl-6,7-dichlor-2-cyclopentyl-indan-1-on-5-yl) oxybutyric acid (DCPIB), a selective VSOR Cl⁻ channel blocker, improves cardiac contractility, which correlates with suppressed ER stress through inhibiting the canonical GRP78/eIF2α/ATF4 and XBP1 pathways, and promotes survival of cardiomyocytes by inverting tunicamycin-induced decrease of Wnt through the CHOP pathway. VSOR activation of tunicamycin-treated cardiomyocytes is attributed to increased intracellular levels of reactive oxygen species (ROS). Our study demonstrates a pivotal role of ROS/VSOR in mediating ER stress and functional impairment of cardiomyocytes via the CHOP-Wnt pathway, and suggests the therapeutic values of VSOR Cl⁻ channel blockers against ER stress-associated cardiac anomalies.

Role of ion transport in control of apoptotic cell death

Cell shrinkage is a hallmark and contributes to signaling of apoptosis. Apoptotic cell shrinkage requires ion transport across the cell membrane involving K(+) channels, Cl(-) or anion channels, Na(+)/H(+) exchange, Na(+),K(+),Cl(-) cotransport, and Na(+)/K(+)ATPase. Activation of K(+) channels fosters K(+) exit with decrease of cytosolic K(+) concentration, activation of anion channels triggers exit of Cl(-), organic osmolytes, and HCO3(-). Cellular loss of K(+) and organic osmolytes as well as cytosolic acidification favor apoptosis. Ca(2+) entry through Ca(2+)-permeable cation channels may result in apoptosis by affecting mitochondrial integrity, stimulating proteinases, inducing cell shrinkage due to activation of Ca(2+)-sensitive K(+) channels, and triggering cell-membrane scrambling. Signaling involved in the modification of cell-volume regulatory ion transport during apoptosis include mitogen-activated kinases p38, JNK, ERK1/2, MEKK1, MKK4, the small G proteins Cdc42, and/or Rac and the transcription factor p53. Osmosensing involves integrin receptors, focal adhesion kinases, and tyrosine kinase receptors. Hyperosmotic shock leads to vesicular acidification followed by activation of acid sphingomyelinase, ceramide formation, release of reactive oxygen species, activation of the tyrosine kinase Yes with subsequent stimulation of CD95 trafficking to the cell membrane. Apoptosis is counteracted by mechanisms involved in regulatory volume increase (RVI), by organic osmolytes, by focal adhesion kinase, and by heat-shock proteins. Clearly, our knowledge on the interplay between cell-volume regulatory mechanisms and suicidal cell death is still far from complete and substantial additional experimental effort is needed to elucidate the role of cell-volume regulatory mechanisms in suicidal cell death.

Cell volume regulation in epithelial physiology and cancer

The physiological function of epithelia is transport of ions, nutrients, and fluid either in secretory or absorptive direction. All of these processes are closely related to cell volume changes, which are thus an integrated part of epithelial function. Transepithelial transport and cell volume regulation both rely on the spatially and temporally coordinated function of ion channels and transporters. In healthy epithelia, specific ion channels/transporters localize to the luminal and basolateral membranes, contributing to functional epithelial polarity. In pathophysiological processes such as cancer, transepithelial and cell volume regulatory ion transport are dys-regulated. Furthermore, epithelial architecture and coordinated ion transport function are lost, cell survival/death balance is altered, and new interactions with the stroma arise, all contributing to drug resistance. Since altered expression of ion transporters and channels is now recognized as one of the hallmarks of cancer, it is timely to consider this especially for epithelia. Epithelial cells are highly proliferative and epithelial cancers, carcinomas, account for about 90% of all cancers. In this review we will focus on ion transporters and channels with key physiological functions in epithelia and known roles in the development of cancer in these tissues. Their roles in cell survival, cell cycle progression, and development of drug resistance in epithelial cancers will be discussed.

Discovery of bufadienolides as a novel class of ClC-3 chloride channel activators with antitumor activities

ClC-3 chloride (Cl(-)) channel has been shown to be involved in cell proliferation, cell cycle, and cell migration processes. Herein, we found that a series of bufadienolides isolated from toad venom were a novel class of ClC-3 Cl(-) channel activators with antitumor activities. Bufalin, which has the most potent antitumor activity, and 15β-acetyloxybufalin, which has no antitumor activity, were chosen as representative compounds to investigate the role of the ClC-3 Cl(-) channel. It was found that bufalin rapidly elicited activation of the ClC-3 Cl(-) channel and subsequently induced apoptosis through inhibition of the PI3K/Akt/mTOR pathway. The PI3K/Akt/mTOR pathway was attenuated by pretreatment with Cl(-) channel blockers [tamoxifen and 5-nitro-2-(3-phenylpropylamino)benzoic acid, NPPB] or ClC-3 small interfereing RNA. In summary, we discovered that activation of the ClC-3 Cl(-) channel, which subsequently induced inhibition of the PI3K/Akt/mTOR signaling pathway, was involved in the antitumor activities of bufadienolides.

Effect of chloride channel inhibitors on cytosolic Ca2+ levels and Ca2+-activated K+ (Gardos) channel activity in human red blood cells

DIDS, NPPB, tannic acid (TA) and AO1 are widely used inhibitors of Cl(-) channels. Some Cl(-) channel inhibitors (NPPB, DIDS, niflumic acid) were shown to affect phosphatidylserine (PS) scrambling and, thus, the life span of human red blood cells (hRBCs). Since a number of publications suggest Ca(2+) dependence of PS scrambling, we explored whether inhibitors of Cl(-) channels (DIDS, NPPB) or of Ca(2+)-activated Cl(-) channels (DIDS, NPPB, TA, AO1) modified intracellular free Ca(2+) concentration ([Ca(2+)]i) and activity of Ca(2+)-activated K(+) (Gardos) channel in hRBCs. According to Fluo-3 fluorescence in flow cytometry, a short treatment (15 min, +37 °C) with Cl(-) channels inhibitors decreased [Ca(2+)]i in the following order: TA > AO1 > DIDS > NPPB. According to forward scatter, the decrease of [Ca(2+)]i was accompanied by a slight but significant increase in cell volume following DIDS, NPPB and AO1 treatments. TA treatment resulted in cell shrinkage. According to whole-cell patch-clamp experiments, TA activated and NPPB and AO1 inhibited Gardos channels. The Cl(-) channel blockers further modified the alterations of [Ca(2+)]i following ATP depletion (glucose deprivation, iodoacetic acid, 6-inosine), oxidative stress (1 mM t-BHP) and treatment with Ca(2+) ionophore ionomycin (1 μM). The ability of the Cl(-) channel inhibitors to modulate PS scrambling did not correlate with their influence on [Ca(2+)]i as TA and AO1 had a particularly strong decreasing effect on [Ca(2+)]i but at the same time enhanced PS exposure. In conclusion, Cl(-) channel inhibitors affect Gardos channels, influence Ca(2+) homeostasis and induce PS exposure of hRBCs by Ca(2+)-independent mechanisms.

Phytoestrogen genistein up-regulates endothelial nitric oxide synthase expression via activation of cAMP response element-binding protein in human aortic endothelial cells

We previously reported that genistein, a phytoestrogen, up-regulates endothelial nitric oxide synthase (eNOS) and prevents hypertension in rats that are independent of estrogen signaling machinery. However, how genistein regulates eNOS expression is unknown. In the present study, we show that genistein enhanced eNOS expression and NO synthesis in primary human aortic endothelial cells. Inhibition of extracellular signal regulated kinase, phosphoinositol-3 kinase, or protein kinase C did not affect genistein-enhanced eNOS expression and NO synthesis. However, chemical inhibition of protein kinase A (PKA) or adenoviral transfer of the specific endogenous PKA inhibitor gene completely abolished PKA activity and genistein-stimulated eNOS expression and NO production. Accordingly, genistein induced PKA activity and subsequent phosphorylation of cAMP response element (CRE)-binding protein (CREB) at Ser133. Suppression of CREB by small interfering RNA transfection abolished genistein-enhanced eNOS expression and NO production. Consistently, deletion of the CRE site within human eNOS promoter eliminated genistein-stimulated eNOS promoter activity. These findings provide the first evidence to our knowledge that genistein may play a beneficial role in vascular function through targeting the PKA/CREB/eNOS/NO signaling pathway.

Apoptosis in Anthracycline Cardiomyopathy

Apoptosis is a tightly regulated physiologic process of programmed cell death that occurs in both normal and pathologic tissues. Numerous in vitro or in vivo studies have indicated that cardiomyocyte death through apoptosis and necrosis is a primary contributor to the progression of anthracycline-induced cardiomyopathy. There are now several pieces of evidence to suggest that activation of intrinsic and extrinsic apoptotic pathways contribute to anthracycline-induced apoptosis in the heart. Novel strategies were developed to address a wide variety of cardiotoxic mechanisms and apoptotic pathways by which anthracycline influences cardiac structure and function. Anthracycline-induced apoptosis provides a very valid representation of cardiotoxicity in the heart, an argument which has implications for the most appropriate animal models of damaged heart plus diverse pharmacological effects. In this review we describe various aspects of the current understanding of apoptotic cell death triggered by anthracycline. Differences in the sensitivity to anthracycline-induced apoptosis between young and adult hearts are also discussed.

Ion channels in pediatric CNS Atypical Teratoid/Rhabdoid Tumor (AT/RT) cells: potential targets for novel therapeutic agents

The central nervous system Atypical Teratoid/Rhabdoid Tumor (CNS AT/RT) is a highly malignant neoplasm that commonly affects infants and young children, and has an extremely poor prognosis. Recently, a small subset of ion channels have been found to be over-expressed in a variety of malignant cells, thus emerging as potential therapeutic targets for difficult to treat tumors. We have studied the electrophysiological properties of AT/RT cell lines with particular attention to cell volume sensitive ion channels (VSC). This class of membrane proteins can play a fundamental role in cellular processes relevant to tumor development. We have found that chloride selective VSCs are particularly active in AT/RT cell lines, compared to non-tumor cells. We evaluated specific inhibitors for activity against chloride selective VSCs and consequently for their ability to inhibit the growth and survival of AT/RT cells in vitro. The results demonstrated that the extent of volume sensitive membrane current inhibition by these agents was correlated with their potency in AT/RT cell growth inhibition in vitro. In addition, we showed that ion channel inhibition enhanced the activity of certain anti-neoplastic agents, suggesting its value in effective drug combination protocols. Results presented provide preliminary in vitro data for possible evaluation of distinct ion channels as plausible therapeutic targets in the treatment of AT/RT.

Effects of diadenosine tetraphosphate on FGF9-induced chloride flux changes in achondroplastic chondrocytes

Achondroplasia, the most common type of dwarfism, is characterized by a mutation in the fibroblast growth factor receptor 3 (FGFR3). Achondroplasia is an orphan pathology with no pharmacological treatment so far. However, the possibility of using the dinucleotide diadenosine tetraphosphate (Ap(4)A) with therapeutic purposes in achondroplasia has been previously suggested. The pathogenesis involves the constitutive activation of FGFR3, resulting in altered biochemical and physiological processes in chondrocytes. Some of these altered processes can be influenced by changes in cell volume and ionic currents. In this study, the action of mutant FGFR3 on chondrocyte size and chloride flux in achondroplastic chondrocytes was investigated as well as the effect of the Ap(4)A on these processes triggered by mutant FGFR3. Stimulation with the fibroblast growth factor 9 (FGF9), the preferred ligand for FGFR3, induced an enlarged achondroplastic chondrocyte size and an increase in the intracellular chloride concentration, suggesting the blockade of chloride efflux. Treatment with the Ap(4)A reversed the morphological changes triggered by FGF9 and restored the chloride efflux. These data provide further evidence for the therapeutic potential of this dinucleotide in achondroplasia treatment.

Volume-sensitive chloride channels are involved in maintenance of basal cell volume in human acute lymphoblastic leukemia cells

Chloride channels are expressed ubiquitously in different cells. However, the activation and roles of volume-activated chloride channels under normal isotonic conditions are not clarified, especially in lymphatic cells. In this study, the activation of basal and volume-activated chloride currents and their roles in maintenance of basal cell volume under isotonic conditions were investigated in human acute lymphoblastic leukemia Molt4 cells. The patch-clamp technique and time-lapse image analysis were employed to record whole-cell currents and cell volume changes. Under isotonic conditions, a basal chloride current was recorded. The current was weakly outward-rectified and volume-sensitive and was not inactivated obviously in the observation period. A 47% hypertonic bath solution and the chloride channel blockers NPPB and tamoxifen suppressed the current. Exposure of cells to 47% hypotonic bath solution activated further the basal current. The hypotonicity-activated current possessed properties similar to those of the basal current and was inhibited by NPPB, tamoxifen, ATP and hypertonic bath solution. Furthermore, extracellular hypotonic challenges swelled the cells and induced a regulatory volume decrease (RVD). Extracellular applications of NPPB, tamoxifen and ATP swelled the cells under isotonic conditions and inhibited the RVD induced by hypotonic cell swelling. The results suggest that some volume-activated chloride channels are activated under isotonic conditions, resulting in the appearance of the basal chloride current, which plays an important role in the maintenance of basal cell volume in lymphoblastic leukemia cells. Chloride channels can be activated further to induce a regulatory volume recovery when cells are swollen.

Advances in research of interaction between hepatitis C virus nonstructural proteins and host proteins

Hepatitis C virus (HCV) is another common cause of chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma after hepatitis B virus (HBV). Up to now, the mechanisms by which HCV promotes persistent infection and cancer remain unclear, and there are neither effective drugs nor vaccines against HCV available. Interaction between virus proteins and host proteins is a hot topic in research of the pathogenesis of viral hepatitis. Recent research shows that interaction between HCV nonstructural proteins and host proteins has an important impact on viral replication, carcinogenesis, interferon resistance, and disorders of glycometabolism and lipid metabolism. This paper summarizes the recent advances in research of interaction between HCV nonstructural proteins and host proteins.

Olesoxime (TRO19622): A Novel Mitochondrial-Targeted Neuroprotective Compound

Olesoxime (TRO19622) is a novel mitochondrial-targeted neuroprotective compound undergoing a pivotal clinical efficacy study in Amyotrophic Lateral Sclerosis (ALS) and also in development for Spinal Muscular Atrophy (SMA). It belongs to a new family of cholesterol-oximes identified for its survival-promoting activity on purified motor neurons deprived of neurotrophic factors. Olesoxime targets proteins of the outer mitochondrial membrane, concentrates at the mitochondria and prevents permeability transition pore opening mediated by, among other things, oxidative stress. Olesoxime has been shown to exert a potent neuroprotective effect in various in vitro and in vivo models. In particular olesoxime provided significant protection in experimental animal models of motor neuron disorders and more particularly ALS. Olesoxime is orally active, crosses the blood brain barrier, and is well tolerated. Collectively, its pharmacological properties designate olesoxime as a promising drug candidate for motor neuron diseases.

Deregulation of apoptotic volume decrease and ionic movements in multidrug-resistant tumor cells: role of chloride channels

Changes in cell volume and ion gradients across the plasma membrane play a pivotal role in the initiation of apoptosis. Here we explore the kinetics of apoptotic volume decrease (AVD) and ion content dynamics in wild-type (WT) and multidrug-resistant (MDR) Ehrlich ascites tumor cells (EATC). In WT EATC, induction of apoptosis with cisplatin (5 μM) leads to three distinctive AVD stages: an early AVD1 (4–12 h), associated with a 30% cell water loss; a transition stage AVDT (∼12 to 32 h), where cell volume is partly recovered; and a secondary AVD2 (past 32 h), where cell volume was further reduced. AVD1 and AVD2 were coupled to net loss of Cl−, K+, Na+, and amino acids (ninhydrin-positive substances), whereas during AVDT, Na+ and Cl− were accumulated. MDR EATC was resistant to cisplatin, showing increased viability and less caspase 3 activation. Compared with WT EATC, MDR EATC underwent a less pronounced AVD1, an augmented AVDT, and a delay in induction of AVD2. Changes in AVD were associated with inhibition of Cl− loss during AVD1, augmented NaCl uptake during AVDT, and a delay of Cl− loss during AVD2. Application of the anion channel inhibitor NS3728 inhibited AVD and completely abolished the differences in AVD, ionic movements, and caspase 3 activation between WT and MDR EATC. Finally, the maximal capacity of volume-regulated anion channel was found to be strongly repressed in MDR EATC. Together, these data suggest that impairment of AVD, primarily via modulation of NaCl movements, contribute to protection against apoptosis in MDR EATC.

Volume regulation in the human airway epithelial cell line Calu-3

Cells regulate their volume in response to changes in the osmolarity of both their extracellular and their intracellular environments. We investigated the ability of the human airway epithelial cell line Calu-3 to respond to changes in extracellular osmolarity. Although switching Calu-3 cells from an isosmotic to a hyperosmotic environment resulted in cell shrinkage, there was no compensatory mechanism for the cells to return to their original volume. In contrast, switching to a hyposmotic environment resulted in an initial cell swelling response, followed by a regulatory volume decrease (RVD). Pharmacologic studies demonstrate that the voltage-activated K+ channels Kv4.1 and (or) Kv4.3 play a crucial role in mediating this RVD response, and we demonstrated expression of these channel types at the mRNA and protein levels. Furthermore, inhibition of the large- and intermediate-conductance Ca2+-activated K+ channels KCa1.1 (maxi-K) and KCa3.1 (hIK) also implicated these channels as playing a role in volume recovery in Calu-3 cells. This report describes the nature of volume regulation in the widely used model cell line Calu-3.