Reactive oxygen species-mediated regulation of the Na+–H+ exchanger 1 gene expression connects intracellular redox status with cells' sensitivity to death triggers

A superoxide-driven redox state promotes geroconversion and resistance to senolysis in replication-stress associated senescence

Using S-phase synchronized RPE1-hTERT cells exposed to the DNA damaging agent, methyl methanesulfonate, we show the existence of a redox state associated with replication stress-induced senescence termed senescence-associated redox state (SA-redox state). SA-redox state is characterized by its reactivity with superoxide-sensing fluorescent probes such as dihydroethidine, lucigenin and mitosox and peroxynitrite or hydroxyl radical sensing probe hydroxyphenyl fluorescein (HPF) but not the hydrogen peroxide (H₂O₂) reactive fluorescent probe CM-H₂DCFDA. Measurement of GSH and GSSH also reveals that SA-redox state mitigates the level of total GSH rather than oxidizes GSH to GSSG. Moreover, supporting the role of superoxide (O₂^.-) in the SA-redox state, we show that incubation of senescent RPE1-hTERT cells with the O₂^.- scavenger, Tiron, decreases the reactivity of SA-redox state with the oxidants' reactive probes lucigenin and HPF while the H₂O₂ antioxidant N-acetyl cysteine has no effect. SA-redox state does not participate in the loss of proliferative capacity, G2/M cell cycle arrest or the increase in SA-β-Gal activity. However, SA-redox state is associated with the activation of NF-κB, dictates the profile of the Senescence Associated Secretory Phenotype, increases TFEB protein level, promotes geroconversion evidenced by increased phosphorylation of S6K and S6 proteins, and influences senescent cells response to senolysis. Furthermore, we provide evidence for crosstalk between SA redox state, p53 and p21. While p53 mitigates the establishment of SA-redox state, p21 is critical for the sustained reinforcement of the SA-redox state involved in geroconversion and resistance to senolysis.

Ethyl isopropyl amiloride decreases oxidative phosphorylation and increases mitochondrial fusion in clonal untransformed and cancer cells

Many cancer cells, regardless of their tissue origin or genetic landscape, have increased expression or activity of the plasma membrane Na-H exchanger NHE1 and a higher intracellular pH (pHi) compared with untransformed cells. A current perspective that remains to be validated is that increased NHE1 activity and pHi enable a Warburg-like metabolic reprogramming of increased glycolysis and decreased mitochondrial oxidative phosphorylation. We tested this perspective and find it is not accurate for clonal pancreatic and breast cancer cells. Using the pharmacological reagent ethyl isopropyl amiloride (EIPA) to inhibit NHE1 activity and decrease pHi, we observe no change in glycolysis, as indicated by secreted lactate and intracellular pyruvate, despite confirming increased activity of the glycolytic enzyme phosphofructokinase-1 at higher pH. Also, in contrast to predictions, we find a significant decrease in oxidative phosphorylation with EIPA, as indicated by oxygen consumption rate (OCR). Decreased OCR with EIPA is not associated with changes in pathways that fuel oxidative phosphorylation or with mitochondrial membrane potential but occurs with a change in mitochondrial dynamics that includes a significant increase in elongated mitochondrial networks, suggesting increased fusion. These findings conflict with current paradigms on increased pHi inhibiting oxidative phosphorylation and increased oxidative phosphorylation being associated with mitochondrial fusion. Moreover, these findings raise questions on the suggested use of EIPA-like compounds to limit metabolic reprogramming in cancer cells.

Reactive Oxygen Species and Antioxidants in Carcinogenesis and Tumor Therapy

Strictly regulated balance between the formation and utilization of reactive oxygen species (ROS) is the basis of normal functioning of organisms. ROS play an important role in the regulation of many metabolic processes; however, excessive content of ROS leads to the development of various disorders, including oncological diseases, as a result of ROS-induced mutations in DNA. In tumors, high levels of oxygen radicals promote cell proliferation and metastasis. On the other hand, high content of ROS can trigger cell death, a phenomenon used in the antitumor therapy. Water- and lipid-soluble antioxidants, as well as antioxidant enzyme systems, can inhibit ROS generation; however, they should be used with caution. Antioxidants can suppress ROS-dependent cell proliferation and metastasis, but at the same time, they may inhibit the death of tumor cells if the antitumor therapeutic agents stimulate oxidative stress. The data on the role of antioxidants in the death of tumor cells and on the effects of antioxidants taken as dietary supplements during antitumor therapy, are contradictory. This review focuses on the mechanisms by which antioxidants can affect tumor and healthy cells.

Redox and apoptotic potential of novel ruthenium complexes in rat blood and heart

Ruthenium(II) complexes offer the potential for lower toxicity compared with platinum(II) complexes. Our study aimed to compare cardiotoxicity of [Ru(Cl-tpy)(en)Cl][Cl], [Ru(Cl-tpy)(dach)Cl][Cl], [Ru(Cl-tpy)(bpy)Cl][Cl], cisplatin, and saline through assessment of redox status and relative expression of apoptosis-related genes. A total of 40 Wistar albino rats were divided into five groups. Ruthenium groups received a single dose of complexes intraperitoneally (4 mg/kg/week) for a 4-week period; cisplatin group received cisplatin (4 mg/kg/week) and control group received saline (4 mL/kg/week) in the same manner as ruthenium groups. In collected blood and heart tissue samples, spectrophotometric determination of oxidative stress biomarkers was performed. The relative expression of apoptosis-related genes (Bcl-2, Bax, and caspase-3) in hearts was examined by real-time polymerase chain reaction. Our results showed that systemic and cardiac pro-oxidative markers (thiobarbituric acid reactive substances and nitrite) were significantly lower in ruthenium groups compared with cisplatin group, while concentrations of antioxidative parameters (catalase, superoxide dismutase, and oxidized glutathione) were significantly higher. Ruthenium administration led to significantly lower gene expression of Bax and caspase-3 compared with cisplatin-treated rats, while Bcl-2 remained unchanged. Applied ruthenium complexes have less pronounced potential for induction of oxidative stress-mediated cardiotoxicity compared with cisplatin. These findings may help for future studies that should clarify the mechanisms of cardiotoxicity of ruthenium-based metallodrugs.

The impact of tumour pH on cancer progression: strategies for clinical intervention

Dysregulation of cellular pH is frequent in solid tumours and provides potential opportunities for therapeutic intervention. The acidic microenvironment within a tumour can promote migration, invasion and metastasis of cancer cells through a variety of mechanisms. Pathways associated with the control of intracellular pH that are under consideration for intervention include carbonic anhydrase IX, the monocarboxylate transporters (MCT, MCT1 and MCT4), the vacuolar-type H⁺-ATPase proton pump, and the sodium-hydrogen exchanger 1. This review will describe progress in the development of inhibitors to these targets.

Superoxide induced inhibition of death receptor signaling is mediated via induced expression of apoptosis inhibitory protein cFLIP

The death inhibitory proteins, cFLIP and Bcl-2, canonically act at different steps to regulate receptor-mediated apoptosis in cancer cells. Here we report that pharmacological or genetic means to effect an increase in intracellular superoxide result in cFLIP upregulation. Interestingly, Bcl-2 overexpression is associated with a concomitant increase in cFLIP, and reducing superoxide sensitizes Bcl-2 overexpressing cancer cells to receptor-mediated apoptosis via downregulation of cFLIP. Moreover, inhibiting glycolytic flux overcomes apoptosis resistance by superoxide-dependent downregulation of cFLIP. Superoxide-induced upregulation of cFLIP is a function of enhanced transcription, as evidenced by increases in cFLIP promoter activity and mRNA abundance. The positive effect of superoxide on cFLIP is mediated through its reaction with nitric oxide to generate peroxynitrite. Corroborating these findings in cell lines, subjecting primary cells derived from lymphoma patients to glucose deprivation ex vivo, as a means to decrease superoxide, not only reduced cFLIP expression but also significantly enhanced death receptor sensitivity. Based on this novel mechanistic insight into the redox regulation of cancer cell fate, modulation of intracellular superoxide could have potential therapeutic implications in cancers in which these two death inhibitory proteins present a therapeutic challenge.

The slow force response to stretch: Controversy and contradictions

When exposed to an abrupt stretch, cardiac muscle exhibits biphasic active force enhancement. The initial, instantaneous, force enhancement is well explained by the Frank-Starling mechanism. However, the cellular mechanisms associated with the second, slower phase remain contentious. This review explores hypotheses regarding this "slow force response" with the intention of clarifying some apparent contradictions in the literature. The review is partitioned into three sections. The first section considers pathways that modify the intracellular calcium handling to address the role of the sarcoplasmic reticulum in the mechanism underlying the slow force response. The second section focuses on extracellular calcium fluxes and explores the identity and contribution of the stretch-activated, non-specific, cation channels as well as signalling cascades associated with G-protein coupled receptors. The final section introduces promising candidates for the mechanosensor(s) responsible for detecting the stretch perturbation.

Changes in the blood antioxidant defense of advanced age people

Introduction: Since 1956 there have been numerous scientific articles about free radical theory of aging which both confirm and deny the theory. Due to oxygen metabolism, there are relatively high concentrations of molecular oxygen in human cells, especially in mitochondria. Under normal physiological conditions, a small fraction of oxygen is constantly converted to ROS, such as superoxide radical (O2^-•), H₂O₂, and related metabolites. Aim of the study: The aim of this work was to show the relation between the activity of main antioxidative enzymes and the age of the examined patients. Materials and methods: The analysis of antioxidant defense was performed on the blood samples from 184 "aged" individuals aged 65-90+ years, and compared to the blood samples of 37 individuals just about at the beginning of aging, aged 55-59 years. Results: The statistically significant decreases of Zn,Cu-superoxide dismutase (SOD-1), catalase (CAT), and glutathione peroxidase (GSH-Px) activities were observed in elderly people in comparison with the control group. Moreover, an inverse correlation between the activities of SOD-1, CAT, and GSH-Px and the age of the examined persons was found. No age-related changes in glutathione reductase activities and malondialdehyde concentrations were observed. Conclusion: Lower activities of fundamental antioxidant enzymes in the erythrocytes of elderly people, which indicate the impairment of antioxidant defense in the aging organism and the intensity of peroxidative lipid structures, were observed.

Cutaneous pH landscape as a facilitator of melanoma initiation and progression

Melanoma incidence is on the rise and currently causes the majority of skin cancer-related deaths. Yet, therapies for metastatic melanoma are still insufficient so that new concepts are essential. Malignant transformation of melanocytes and melanoma progression are intimately linked to the cutaneous pH landscape and its dysregulation in tumour lesions. The pH landscape of normal skin is characterized by a large pH gradient of up to 3 pH units between surface and dermis. The Na⁺ /H⁺ exchanger NHE1 is one of the major contributors of acidity in superficial skin layers. It is also activated by the most frequent mutation in melanoma, BRAF^{V 600E} , thereby causing pH dysregulation during melanoma initiation. Melanoma progression is supported by an extracellular acidification and/or NHE1 activity which promote the escape of single melanoma cells from the primary tumour, migration and metastatic spreading. We propose that viewing melanoma against the background of the acid-base physiology of the skin provides a better understanding of the pathophysiology of this disease and allows the development of novel therapeutic concepts.

Amelioration of Lipopolysaccharide-Induced Acute Lung Injury in Rats by Na-H Exchanger-1 Inhibitor Amiloride Is Associated with Reversal of ERK Mitogen-Activated Protein Kinase

Background

Na-H exchanger-1 (NHE-1) is expressed in the lung of rats. Accumulating evidence shows that Na-H exchangers are involved in inflammation. Amiloride, an inhibitor of NHE-1, inhibits the activation of macrophages and endothelial cells and reduces their production of cytokines. Since these processes have been implicated in acute lung injury (ALI) induced by lipopolysaccharide (LPS), we examined the protective effect of amiloride on ALI induced by LPS in rats.

Material and Methods

ALI in specific pathogen-free male Sprague-Dawley rats was induced by an intravenous injection of 6 mg/kg LPS. Amiloride pretreated rats received an intravenous injection of 10 mg/kg amiloride 30 min before the administration of LPS. Controls received normal saline in a similar manner. All animals were sacrificed 6 h after LPS or normal saline administration. The degree of ALI was assessed by wet-to-dry weight ratio (W/D) and lung histological examination. Neutrophilic infiltration was determined by myeloperoxidase (MPO) activity in lung tissue. Concentrations of total protein (TP), tumor necrosis factor-alpha (TNF-α), and macrophage inflammatory protein-2 (MIP-2) in bronchoalveolar lavage fluid (BALF) were also measured. Expression of NHE-1 and mitogen-activated protein kinase (MAPK) p38, p-p38, ERK, and p-ERK was evaluated by western blot analysis.

Results

Pretreatment with amiloride significantly reduced the increase in W/D, ALI score, lung tissue MPO activity, concentrations of TP, TNF-α, and MIP-2 in BALF, resulting in attenuation of ALI induced by LPS. Meanwhile, levels of NHE-1 and p-ERK proteins were reversed, whereas that of p-p38 was not.

Conclusions

These findings suggest that NHE-1 inhibitor amiloride could attenuate ALI induced by LPS in rats. This effect is mediated through reversal of ERK.

The effect of oxidative stress upon intestinal sugar transport: an in vitro study using human intestinal epithelial (Caco-2) cells

The pathogenesis of various gastrointestinal diseases, including gastrointestinal cancers and inflammatory bowel disease, is associated with increased oxidative stress levels. We aimed to investigate the effect of oxidative stress induced by tert-butylhydroperoxide (TBH) on the uptake of 3H-deoxy-d-glucose (3H-DG) and 14C-fructose by the human intestinal Caco-2 cell line. TBH (500 μM; 24 h) increased lipid peroxidation (TBARS) levels and was not cytotoxic. TBH (500 μM; 24 h) increased uptake of both low (SGLT1-mediated) and high concentrations (SGLT1- and GLUT2-mediated) of 3H-DG, but did not affect absorption of 14C-fructose (GLUT2- and GLUT5-mediated). The polyphenol chrysin abolished the increase in TBARS levels and the increase in uptake of both low and high concentrations of 3H-DG induced by TBH. On the other hand, TBH blocked the inhibitory effect of chrysin on 14C-fructose uptake. 3H-DG uptake, but not 14C-fructose uptake, was sensitive to sweet taste receptor (STRs) inhibition (with lactisole). The inhibitory effect of lactisole in relation to uptake of 3H-DG (10 nM) (SGLT1-mediated), but not in relation to uptake of 3H-DG (50 mM) (SGLT1- and GLUT2-mediated), was abolished in the presence of TBH. So, these results show that the stimulatory effect of STRs on SGLT1-mediated transport is dependent on oxidative stress levels. In conclusion, this work shows that uptake of both 3H-DG and 14C-fructose is sensitive to oxidative stress levels. Moreover, it suggests that the three distinct transporters involved in the intestinal absorption of glucose and fructose (SGLT1, GLUT2 and GLUT5) have different sensitivities to oxidative stress levels, SGLT1 being the most sensitive and GLUT5 the least.

Transcriptional response of Erwinia amylovora to copper shock: in vivo role of the copA gene

Fire blight is a devastating plant disease caused by the bacterium Erwinia amylovora, and its control is frequently based on the use of copper-based compounds whose mechanisms of action are not well known. Consequently, in this article, we investigate the response of E. amylovora to copper shock by a whole-genome microarray approach. Transcriptional analyses showed that, in the presence of copper, 23 genes were increased in expression; these genes were classified mainly into the transport and stress functional categories. Among them, the copA gene was strongly induced and regulated in a finely tuned manner by copper. Mutation of copA, soxS, arcB, yjcE, ygcF, yhhQ, galF and EAM_3469 genes revealed that tolerance to copper in E. amylovora can be achieved by complex physiological mechanisms, including: (i) the control of copper homeostasis through, at least, the extrusion of Cu(I) by a P-type ATPase efflux pump CopA; and (ii) the overcoming of copper toxicity caused by oxidative stress by the expression of several reactive oxygen species (ROS)-related genes, including the two major transcriptional factors SoxS and ArcB. Furthermore, complementation analyses demonstrated the important role of copA for copper tolerance in E. amylovora, not only in vitro, but also in inoculated pear shoots.

Electron Pathways through Erythrocyte Plasma Membrane in Human Physiology and Pathology: Potential Redox Biomarker?

Erythrocytes are involved in the transport of oxygen and carbon dioxide in the body. Since pH is the influential factor in the Bohr-Haldane effect, pHi is actively maintained via secondary active transports Na+/H+ exchange and HC3–/Cl– anion exchanger. Because of the redox properties of the iron, hemoglobin generates reactive oxygen species and thus, the human erythrocyte is constantly exposed to oxidative damage. Although the adult erythrocyte lacks protein synthesis and cannot restore damaged proteins, it is equipped with high activity of protective enzymes. Redox changes in the cell initiate various signalling pathways. Plasma membrane oxido-reductases (PMORs) are trans-membrane electron transport systems that have been found in the membranes of all cells and have been extensively characterized in the human erythrocyte. Erythrocyte PMORs transfer reducing equivalents from intracellular reductants to extracellular oxidants, thus their most important role seems to be to enable the cell respond to changes in intra- and extra-cellular redox environments.

So far the activity of erythrocyte PMORs in disease states has not been systematically investigated. This review summarizes present knowledge on erythrocyte electron transfer activity in humans (health, type 1 diabetes, diabetic nephropathy, and chronic uremia) and hypothesizes an integrated model of the functional organization of erythrocyte plasma membrane where electron pathways work in parallel with transport metabolons to maintain redox homeostasis.

The Role of pH Regulation in Cancer Progression

Frequently observed phenotypes of tumours include high metabolic activity, hypoxia and poor perfusion; these act to produce an acidic microenvironment. Cellular function depends on pH homoeostasis, and thus, tumours become dependent on pH regulatory mechanisms. Many of the proteins involved in pH regulation are highly expressed in tumours, and their expression is often of prognostic significance. The more acidic tumour microenvironment also has important implications with regard to chemotherapeutic and radiotherapeutic interventions. In addition, we review pH-sensing mechanisms, the role of pH regulation in tumour phenotype and the use of pH regulatory mechanisms as therapeutic targets.

Focal photodynamic intracellular acidification as a cancer therapeutic

Cancer cells utilize an array of proton transporters to regulate intra- and extracellular pH to thrive in hypoxic conditions, and to increase tumor growth and metastasis. Efforts to target many of the transporters involved in cancer cell pH regulation have yielded promising results, however, many productive attempts to disrupt pH regulation appear to be non-specific to cancer cells, and more effective in some cancer cells than others. Following a review of the status of photodynamic cancer therapy, a novel light-activated process is presented which creates very focal, rapid, and significant decreases in only intracellular pH (pHi), leading to cell death. The light-activation of the H⁺ carrier, nitrobenzaldehyde, has been effective at initiating pH-induced apoptosis in non-cancerous and numerous cancerous cell lines in vitro, to include breast, prostate, and pancreatic cancers. Also, this intracellular acidification technique caused significant reductions in tumor growth rate and enhanced survival in mice bearing triple negative breast cancer tumors. The efficacy of an NBA-upconverting nanoparticle to kill breast cancer cells in vitro is described, as well as a discussion of the potential intracellular mechanisms underlying the pH-induced apoptosis.

Normobaric hyperoxia stimulates superoxide and nitric oxide production in the caudal solitary complex of rat brain slices

Central CO₂-chemosensitive neurons in the caudal solitary complex (cSC) are stimulated not only by hypercapnic acidosis, but by hyperoxia as well. While a cellular mechanism for the CO₂ response has yet to be isolated, previous data show that a redox-sensitive mechanism underlies neuronal excitability to hyperoxia. However, it remains unknown how changes in Po₂ affect the production of reactive oxygen and nitrogen species (RONS) in the cSC that can lead to increased cellular excitability and, with larger doses, to cellular dysfunction and death. To this end, we used fluorescence microscopy in real time to determine how normobaric hyperoxia increases the production of key RONS in the cSC. Because neurons in the region are CO₂ sensitive, we also examined the potential effects of CO₂ narcosis, used during euthanasia before brain slice harvesting, on RONS production. Our findings show that normobaric hyperoxia (0.4 → 0.95 atmospheres absolute O₂) increases the fluorescence rates of fluorogenic dyes specific to both superoxide and nitric oxide. Interestingly, different results were seen for superoxide fluorescence when CO₂ narcosis was used during euthanasia, suggesting long-lasting changes in superoxide production and/or antioxidant activity subsequent to CO₂ narcosis before brain slicing. Further research needs to distinguish whether the increased levels of RONS reported here are merely increases in oxidative and nitrosative signaling or, alternatively, evidence of redox and nitrosative stress.

Novel targets for paclitaxel nano formulations: Hopes and hypes in triple negative breast cancer

Triple negative breast cancer is defined as one of the utmost prevailing breast cancers worldwide, possessing an inadequate prognosis and treatment option limited to chemotherapy and radiotherapy, creating a challenge for researchers as far as developing a specific targeted therapy is concerned. The past research era has shown several promising outcomes for TNBC such as nano-formulations of the chemotherapeutic agents already used for the management of the malignant tumor. Taking a glance at paclitaxel nano formulations, it has been proven beneficial in several researches in the past decade; nevertheless its solubility is often a challenge to scientists in achieving success. We have henceforth discussed the basic heterogeneity of triple negative breast cancer along with the current management options as well as a brief outlook on pros and cons of paclitaxel, known as the most widely used chemotherapeutic agent for the treatment of the disease. We further analyzed the need of nanotechnology pertaining to the problems encountered with the current paclitaxel formulations available discussing the strategic progress in various nano-formulations till date taking into account the basic research strategies required in terms of solubility, permeability, physicochemical properties, active and passive targeting. A thorough review in recent advances in active targeting for TNBC was carried out whereby the various ligands which are at present finding its way into TNBC research such as hyaluronic acid, folic acid, transferrin, etc. were discussed. These ligands have specific receptor affinity to TNBC tumor cells hence can be beneficial for novel drug targeting approaches. Conversely, there are currently several novel strategies in the research pipeline whose targeting ligands have not yet been studied. Therefore, we reviewed upon the numerous novel receptor targets along with the respective nano-formulation aspects which have not yet been fully researched upon and could be exemplified as outstanding target strategies for TNBC which is currently an urgent requirement.

JAK2V617F mediates resistance to DNA damage-induced apoptosis by modulating FOXO3A localization and Bcl-xL deamidation

The JAK2V617F mutation is found in most patients with a myeloproliferative neoplasm (MPN). This gain-of-function mutation dysregulates cytokine signaling and is associated with increased accumulation of DNA damage, a process likely to drive disease evolution. JAK2V617F inhibits NHE-1 upregulation in response to DNA damage and consequently represses Bcl-xL deamidation and apoptosis, thus giving rise to inappropriate cell survival. However, the mechanism whereby NHE-1 expression is inhibited by JAK2V617F is unknown. In this study, we demonstrate that the accumulation of reactive oxygen species (ROS) in cells expressing JAK2V617F compromises the NHE-1/Bcl-xL deamidation pathway by repressing NHE-1 upregulation in response to DNA damage. In JAK2V617F-positive cells, increased ROS levels results from aberrant PI3K signaling, which decreases nuclear localization of FOXO3A and decreases catalase expression. Furthermore, when compared with autologous control erythroblasts, clonally derived JAK2V617F-positive erythroblasts from MPN patients displayed increased ROS levels and reduced nuclear FOXO3A. However, in hematopoietic stem cells (HSCs), FOXO3A is largely localized within the nuclei despite the presence of JAK2V617F mutation, suggesting that JAK2-FOXO signaling has a different effect on progenitors compared with stem cells. Inactivation of FOXO proteins and elevation of intracellular ROS are characteristics common to many cancers, and hence these findings are likely to be of relevance beyond the MPN field.

The Na⁺/H⁺ exchanger (NHE1) as a novel co-adjuvant target in paclitaxel therapy of triple-negative breast cancer cells

Dysregulation of Na⁺ /H⁺ exchanger isoform one (NHE1) activity is a hallmark of cells undergoing tumorigenesis and metastasis, the leading cause of patient mortality. The acidic tumor microenvironment is thought to facilitate the development of resistance to chemotherapy drugs and to promote extracellular matrix remodeling leading to metastasis. Here, we investigated NHE1 as a co-adjuvant target in paclitaxel chemotherapy of metastatic breast cancer. We generated a stable NHE1-knockout of the highly invasive, triple-negative, MDA-MB-231 breast cancer cells. The NHE1-knockout cells proliferated comparably to parental cells, but had markedly lower rates of migration and invasion in vitro. In vivo xenograft tumor growth in athymic nude mice was also dramatically decreased compared to parental MDA-MB-231 cells. Loss of NHE1 expression also increased the susceptibility of knockout cells to paclitaxel-mediated cell death. NHE1 inhibition, in combination with paclitaxel, resulted in a dramatic decrease in viability, and migratory and invasive potential of triple-negative breast cancer cells, but not in hormone receptor-positive, luminal MCF7 cells. Our data suggest that NHE1 is critical in triple-negative breast cancer metastasis, and its chemical inhibition boosts the efficacy of paclitaxel in vitro, highlighting NHE1 as a novel, potential co-adjuvant target in breast cancer chemotherapy.

Modulation Effects of Curcumin on Erythrocyte Ion-Transporter Activity

Curcumin ((1E,6E)-1,7-Bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione), the yellow biphenolic pigment isolated from turmeric (Curcuma longa), has various medicinal benefits through antioxidation, anti-inflammation, cardiovascular protection, immunomodulation, enhancing of the apoptotic process, and antiangiogenic property. We explored the effects of curcumin in vitro (10⁻⁵ M to 10⁻⁸ M) and in vivo (340 and 170 mg/kg b.w., oral) on Na⁺/K⁺ ATPase (NKA), Na⁺/H⁺ exchanger (NHE) activity, and membrane lipid hydroperoxides (ROOH) in control and experimental oxidative stress erythrocytes of Wistar rats. As a result, we found that curcumin potently modulated the membrane transporters activity with protecting membrane lipids against hydro-peroxidation in control as well as oxidatively challenged erythrocytes evidenced by stimulation of NKA, downregulation of NHE, and reduction of ROOH in the membrane. The observed results corroborate membrane transporters activity with susceptibility of erythrocyte membrane towards oxidative damage. Results explain the protective mechanism of curcumin against oxidative stress mediated impairment in ions-transporters activity and health beneficial effects.

NOX signaling in molecular cardiovascular mechanisms involved in the blood pressure homeostasis

Blood pressure homeostasis is maintained by several mechanisms regulating cardiac output, vascular resistances, and blood volume. At cellular levels, reactive oxygen species (ROS) signaling is involved in multiple molecular mechanisms controlling blood pressure. Among ROS producing systems, NADPH oxidases (NOXs), expressed in different cells of the cardiovascular system, are the most important enzymes clearly linked to the development of hypertension. NOXs exert a central role in cardiac mechanosensing, endothelium-dependent relaxation, and Angiotensin-II (Ang-II) redox signaling regulating vascular tone. The central role of NOXs in redox-dependent cardiovascular cell functions renders these enzymes a promising pharmacological target for the treatment of cardiovascular diseases, including hypertension. The aim of the present review is to focus on the physiological role of the cardiovascular NOX-generating ROS in the molecular and cellular mechanisms affecting blood pressure.

Roles of oxidative stress in the development and progression of breast cancer

Oxidative stress is caused by an imbalance in the redox status of the body. In such a state, increase of free radicals in the body can lead to tissue damage. One of the most important species of free radicals is reactive oxygen species (ROS) produced by various metabolic pathways, including aerobic metabolism in the mitochondrial respiratory chain. It plays a critical role in the initiation and progression of various types of cancers. ROS affects different signaling pathways, including growth factors and mitogenic pathways, and controls many cellular processes, including cell proliferation, and thus stimulates the uncontrolled growth of cells which encourages the development of tumors and begins the process of carcinogenesis. Increased oxidative stress caused by reactive species can reduce the body's antioxidant defense against angiogenesis and metastasis in cancer cells. These processes are main factors in the development of cancer. Bimolecular reactions cause free radicals in which create such compounds as malondialdehyde (MDA) and hydroxyguanosine. These substances can be used as indicators of cancer. In this review, free radicals as oxidizing agents, antioxidants as the immune system, and the role of oxidative stress in cancer, particularly breast cancer, have been investigated in the hope that better identification of the factors involved in the occurrence and spread of cancer will improve the identification of treatment goals.

Endothelial Na+/H+ exchanger NHE1 participates in redox-sensitive leukocyte recruitment triggered by methylglyoxal

Background

Excessive levels of methylglyoxal (MG) encountered in diabetes foster enhanced leukocyte-endothelial cell interactions, mechanisms of which are incompletely understood. MG genomically upregulates endothelial serum- and glucocorticoid-inducible kinase 1 (SGK1) which orchestrates leukocyte recruitment by regulating the activation and expression of transcription factors and adhesion molecules. SGK1 regulates a myriad of ion channels and carriers including the Na⁺/H⁺ exchanger NHE1. Here, we explored the effect of MG on SGK1-dependent NHE1 activation and the putative role of NHE1 activation in MG-induced leukocyte recruitment and microvascular hyperpermeability.

Methods

Using RT-PCR and immunoblotting, we analyzed NHE1 mRNA and protein levels in murine microvascular SVEC4-10EE2 endothelial cells (EE2 ECs). NHE1 phosphorylation was detected using a specific antibody against the 14-3-3 binding motif at phospho-Ser⁷⁰³. SGK in EE2 ECs was silenced using targeted siRNA. ROS production was determined using DCF-dependent fluorescence. Leukocyte recruitment and microvascular permeability in murine cremasteric microvasculature were measured using intravital microscopy. The expression of endothelial adhesion molecules was determined by immunoblotting and confocal imaging analysis.

Results

MG treatment significantly upregulated NHE1 mRNA and dose-dependently increased total- and phospho-NHE1. Treatment with SGK1 inhibitor GSK650394, antioxidant Tempol and silencing SGK all blunted MG-triggered phospho-NHE1 upregulation in EE2 ECs. NHE1 inhibitor cariporide attenuated MG-triggered ROS production, leukocyte adhesion and emigration and microvascular hyperpermeability, without affecting leukocyte rolling. Cariporide treatment did not alter MG-triggered upregulation of P- and E-selectins, but reduced endothelial ICAM-1 expression.

Conclusion

MG elicits SGK1-dependent activation of endothelial Na⁺/H⁺ exchanger NHE1 which participates in MG-induced ROS production, upregulation of endothelial ICAM-1, leukocyte recruitment and microvascular hyperpermeability. Pharmacological inhibition of NHE1 attenuates the proinflammatory effects of excessive MG and may, thus, be beneficial in diabetes-associated inflammation.

NHE1 gene associated with avian leukosis virus subgroup J infection in chicken

As a kind of binding protein, the type 1 Na(+)/H(+) exchanger (NHE1) is a receptor for the highly pathogenic Avian leukosis viruses-J subgroup (ALV-J) in chicken. In order to investigate the potential effect of chicken NHE1 gene on leukosis, we compared its expression between ALV-J-affected and -unaffected chicken, screened variations across the whole gene, and then performed association analysis with ALV-J affected/unaffected trait in three un-related chicken populations. We found that the NHE1 gene expressed in four immune tissues including spleen, bursa fabricius, liver, and thymus, and its expression was significantly up-regulated in liver and thymus of ALV-J-affected chickens (with leukosis phenotype) compared to -unaffected ones (ALV-J-negative controls). Thirty-six single nucleotide polymorphisms (SNP) were identified in a 6,105 bp region of the chicken NHE1 gene, giving rise to every 170 bp per SNP. Two SNP of g.4405A>G and g.5886C>G were genotyped with PCR-RFLP method. Results showed that g.4405A>G was significantly associated (P < 0.05) with ALV-J infection in all of the three chicken populations, including White Recessive Rock (WRR), Dwarf Yellow (DY) and Shiki Yellow (SY), while g.5886C>G was significantly associated (P < 0.05) with ALV-J infection in SY. These results indicated that the NHE1 gene was related to ALV-J infection in chicken.

Manganese superoxide dismutase is a promising target for enhancing chemosensitivity of basal-like breast carcinoma

AIMS

Although earlier reports highlighted a tumor suppressor role for manganese superoxide dismutase (MnSOD), recent evidence indicates increased expression in a variety of human cancers including aggressive breast carcinoma. In the present article, we hypothesized that MnSOD expression is significantly amplified in the aggressive breast carcinoma basal subtype, and targeting MnSOD could be an attractive strategy for enhancing chemosensitivity of this highly aggressive breast cancer subtype.

RESULTS

Using MDA-MB-231 and BT549 as a model of basal breast cancer cell lines, we show that knockdown of MnSOD decreased the colony-forming ability and sensitized the cells to drug-induced cell death, while drug resistance was associated with increased MnSOD expression. In an attempt to develop a clinically relevant approach to down-regulate MnSOD expression in patients with basal breast carcinoma, we employed activation of the peroxisome proliferator-activated receptor gamma (PPARγ) to repress MnSOD expression; PPARγ activation significantly reduced MnSOD expression, increased chemosensitivity, and inhibited tumor growth. Moreover, as a proof of concept for the clinical use of PPARγ agonists to decrease MnSOD expression, biopsies derived from breast cancer patients who had received synthetic PPARγ ligands as anti-diabetic therapy had significantly reduced MnSOD expression. Finally, we provide evidence to implicate peroxynitrite as the mechanism involved in the increased sensitivity to chemotherapy induced by MnSOD repression.

INNOVATION AND CONCLUSION

These data provide evidence to link increased MnSOD expression with the aggressive basal breast cancer, and underscore the judicious use of PPARγ ligands for specifically down-regulating MnSOD to increase the chemosensitivity of this subtype of breast carcinoma.

Inhibition of carbonic anhydrase prevents the Na(+)/H(+) exchanger 1-dependent slow force response to rat myocardial stretch

Myocardial stretch is an established signal that leads to hypertrophy. Myocardial stretch induces a first immediate force increase followed by a slow force response (SFR), which is a consequence of an increased Ca(2+) transient that follows the NHE1 Na(+)/H(+) exchanger activation. Carbonic anhydrase II (CAII) binds to the extreme COOH terminus of NHE1 and regulates its transport activity. We aimed to test the role of CAII bound to NHE1 in the SFR. The SFR and changes in intracellular pH (pHi) were evaluated in rat papillary muscle bathed with CO2/HCO3(-) buffer and stretched from 92% to 98% of the muscle maximal force development length for 10 min in the presence of the CA inhibitor 6-ethoxzolamide (ETZ, 100 μM). SFR control was 120 ± 3% (n = 8) of the rapid initial phase and was fully blocked by ETZ (99 ± 4%, n = 6). The SFR corresponded to a maximal increase in pHi of 0.18 ± 0.02 pH units (n = 4), and pHi changes were blocked by ETZ (0.04 ± 0.04, n = 6), as monitored by epifluorescence. NHE1/CAII physical association was examined in the SFR by coimmunoprecipitation, using muscle lysates. CAII immunoprecipitated with an anti-NHE1 antibody and the CAII immunoprecipitated protein levels increased 58 ± 9% (n = 6) upon stretch of muscles, assessed by immunoblots. The p90(RSK) kinase inhibitor SL0101-1 (10 μM) blocked the SFR of heart muscles after stretch 102 ± 2% (n = 4) and reduced the binding of CAII to NHE1, suggesting that the stretch-induced phosphorylation of NHE1 increases its binding to CAII. CAII/NHE1 interaction constitutes a component of the SFR to heart muscle stretch, which potentiates NHE1-mediated H(+) transport in the myocardium.

Inside out: targeting NHE1 as an intracellular and extracellular regulator of cancer progression

The sodium hydrogen exchanger isoform one is a critical regulator of intracellular pH, serves as an anchor for the formation of cytoplasmic signaling complexes, and modulates cytoskeletal organization. There is a growing interest in the potential for sodium hydrogen exchanger isoform one as a therapeutic target against cancer. Sodium hydrogen exchanger isoform one transport drives formation of membrane protrusions essential for cell migration and contributes to the establishment of a tumor microenvironment that leads to the rearrangement of the extracellular matrix further supporting tumor progression. Here, we focus on the potential impact that an inexpensive, $100 genome would have in identifying prospective therapeutic targets to treat tumors based upon changes in gene expression and variation of sodium hydrogen exchanger isoform one regulators. In particular, we will focus on the ezrin, radixin, moesin family proteins, calcineurin B homologous proteins, Ras/Raf/MEK/ERK signaling, and phosphoinositide signaling as they relate to the regulation of sodium hydrogen exchanger isoform one in cancer progression.

Reactive oxygen species: the 2-edged sword of osteoarthritis

The degenerative joint disease osteoarthritis (OA) is the most prevalent form of chronic musculoskeletal disease worldwide, and it commonly afflicts the elderly population. OA-induced impairment of joint function can debilitate normal physical activity, and in more severe cases, it can lead to complete joint destruction and loss of independence or even mobility. The pathophysiology of OA remains to be fully elucidated, despite the extensive research efforts into this complex disease. Studies have revealed that reactive oxygen species (ROS) can contribute to the onset and progression of OA by inducing indispensable chondrocyte death and matrix degradation. However, ROS are also key components of many normal physiological processes, and at moderate levels, they act as indispensable second messengers. This review focuses on the dual role of ROS in cartilage, with the aim of gaining insights into how ROS can be regulated such that its beneficial effects are maintained and its detrimental effects are eliminated.

Therapeutic implications of targeting energy metabolism in breast cancer

PPARs are ligand activated transcription factors. PPARγ agonists have been reported as a new and potentially efficacious treatment of inflammation, diabetes, obesity, cancer, AD, and schizophrenia. Since cancer cells show dysregulation of glycolysis they are potentially manageable through changes in metabolic environment. Interestingly, several of the genes involved in maintaining the metabolic environment and the central energy generation pathway are regulated or predicted to be regulated by PPARγ. The use of synthetic PPARγ ligands as drugs and their recent withdrawal/restricted usage highlight the lack of understanding of the molecular basis of these drugs, their off-target effects, and their network. These data further underscores the complexity of nuclear receptor signalling mechanisms. This paper will discuss the function and role of PPARγ in energy metabolism and cancer biology in general and its emergence as a promising therapeutic target in breast cancer.

Computational modelling of LY303511 and TRAIL-induced apoptosis suggests dynamic regulation of cFLIP

MOTIVATION

TRAIL has been widely studied for the ability to kill cancer cells selectively, but its clinical usefulness has been hindered by the development of resistance. Multiple compounds have been identified that sensitize cancer cells to TRAIL-induced apoptosis. The drug LY303511 (LY30), combined with TRAIL, caused synergistic (greater than additive) killing of multiple cancer cell lines. We used mathematical modelling and ordinary differential equations to represent how LY30 and TRAIL individually affect HeLa cells, and to predict how the combined treatment achieves synergy.

RESULTS

Model-based predictions were compared with in vitro experiments. The combination treatment model was successful at mimicking the synergistic levels of cell death caused by LY30 and TRAIL combined. However, there were significant failures of the model to mimic upstream activation at early time points, particularly the slope of caspase-8 activation. This flaw in the model led us to perform additional measurements of early caspase-8 activation. Surprisingly, caspase-8 exhibited a transient decrease in activity after LY30 treatment, prior to strong activation. cFLIP, an inhibitor of caspase-8 activation, was up-regulated briefly after 30 min of LY30 treatment, followed by a significant down-regulation over prolonged exposure. A further model suggested that LY30-induced fluctuation of cFLIP might result from tilting the ratio of two key species of reactive oxygen species (ROS), superoxide and hydrogen peroxide. Computational modelling extracted novel biological implications from measured dynamics, identified time intervals with unexplained effects, and clarified the non-monotonic effects of the drug LY30 on cFLIP during cancer cell apoptosis.

The effect of oxidative stress upon the intestinal epithelial uptake of butyrate

Our aim was to investigate the effect of oxidative stress upon butyrate uptake at the intestinal epithelial level. For this, IEC-6 cells were treated with tert-butylhydroperoxide 3000μM (tBOOH), which increased levels of oxidative stress biomarkers, while maintaining cellular viability. The effect of tBOOH upon uptake of [(14)C]butyrate ([(14)C]BT) (10μM) can be summarized as follows: (a) it caused a reduction in the intracellular accumulation of [(14)C]BT over time, (b) it strongly reduced total [(14)C]BT uptake but did not affect Na(+)-independent uptake of [(14)C]BT, and (c) it did not affect the kinetics of [(14)C]BT uptake at 37°C, but increased uptake at 4°C. Moreover, tBOOH increased the efflux of [(14)C]BT not mediated by breast cancer resistance protein. We thus conclude that tBOOH strongly inhibits Na(+)-coupled monocarboxylate cotransporter 1 (SMCT1)-mediated, but not H(+)-coupled monocarboxylate transporter (MCT1)-mediated butyrate uptake; moreover, it increases uptake and efflux of butyrate by passive diffusion. tBOOH did not affect the mRNA expression levels of MCT1 and SMCT1 nor their cell membrane insertion. Rather, its effect was dependent on extracellular signal regulated kinase 1/2 and protein tyrosine kinase activation and on the generation of reactive oxygen species by NADPH and xanthine oxidases and was partially prevented by the polyphenols quercetin and resveratrol. In conclusion, tBOOH is an effective inhibitor of SMCT1-mediated butyrate transport in non-tumoral intestinal epithelial cells. Given the important role played by butyrate in the intestine, this mechanism may contribute to the procarcinogenic and proinflammatory effect of oxidative stress at this level.

Regulation of acid-base transporters by reactive oxygen species following mitochondrial fragmentation

Mitochondrial morphology is determined by the balance between the opposing processes of fission and fusion, each of which is regulated by a distinct set of proteins. Abnormalities in mitochondrial dynamics have been associated with a variety of diseases, including neurodegenerative conditions such as Alzheimer's disease, Parkinson's disease, and dominant optic atrophy. Although the genetic determinants of fission and fusion are well recognized, less is known about the mechanism(s) whereby altered morphology contributes to the underlying pathophysiology of these disease states. Previous work from our laboratory identified a role for mitochondrial dynamics in intracellular pH homeostasis in both mammalian cell culture and in the genetic model organism Caenorhabditis elegans. Here we show that the acidification seen in mutant animals that have lost the ability to fuse their mitochondrial inner membrane occurs through a reactive oxygen species (ROS)-dependent mechanism and can be suppressed through the use of pharmacological antioxidants targeted specifically at the mitochondrial matrix. Physiological approaches examining the activity of endogenous mammalian acid-base transport proteins in rat liver Clone 9 cells support the idea that ROS signaling to sodium-proton exchangers contributes to acidification. Because maintaining pH homeostasis is essential for cell function and viability, the results of this work provide new insight into the pathophysiology associated with the loss of inner mitochondrial membrane fusion.

Silencing of NHE-1 blunts the slow force response to myocardial stretch

Myocardial stretch induces a biphasic force response: a first abrupt increase followed by a slow force response (SFR), believed to be the in vitro manifestation of the Anrep effect. The SFR is due to an increase in Ca2+ transient of unclear mechanism. We proposed that Na+/H+ exchanger (NHE-1) activation is a key factor in determining the contractile response, but recent reports challenged our findings. We aimed to specifically test the role of the NHE-1 in the SFR. To this purpose small hairpin interference RNA capable of mediating specific NHE-1 knockdown was incorporated into a lentiviral vector (l-shNHE1) and injected into the left ventricular wall of Wistar rats. Injection of a lentiviral vector expressing a nonsilencing sequence (scramble) served as control. Myocardial NHE-1 protein expression and function (the latter evaluated by the recovery of pHi after an acidic load and the SFR) were evaluated. Animals transduced with l-shNHE1 showed reduced NHE-1 expression (45 ± 8% of controls; P < 0.05), and the presence of the lentivirus in the left ventricular myocardium, far from the site of injection, was evidenced by confocal microscopy. These findings correlated with depressed basal pHi recovery after acidosis [maxdpHi/d t 0.055 ± 0.008 (scramble) vs. 0.009 ± 0.004 (l-shNHE1) pH units/min, P < 0.05], leftward shift of the relationship between JH+ (H+ efflux corrected by the intrinsic buffer capacity), and abolishment of SFR (124 ± 2 vs. 101 ± 2% of rapid phase; P < 0.05) despite preserved ERK1/2 phosphorylation [247 ± 12 (stretch) and 263 ± 23 (stretch l-shNHE1) % of control; P < 0.05 vs. nonstretched control], well-known NHE-1 activators. Our results provide strong evidence to propose NHE-1 activation as key factor in determining the SFR to stretch.

Silencing of sodium/hydrogen exchanger in the heart by direct injection of naked siRNA

Cardiac Na+/H+ exchanger (NHE1) hyperactivity is a central factor in cardiac remodeling following hypertension, myocardial infarction, ischemia-reperfusion injury, and heart failure. Treatment of these pathologies by inhibiting NHE1 is challenging because specific drugs that have been beneficial in experimental models were associated with undesired side effects in clinical practice. In the present work, small interference RNA (siRNA) produced in vitro to specifically silence NHE1 (siRNANHE1) was injected once in vivo into the apex of the left ventricular wall of mouse myocardium. After 48 h, left ventricular NHE1 protein expression was reduced in siRNANHE1-injected mice compared with scrambled siRNA by 33.2 ± 3.4% ( n = 5; P < 0.05). Similarly, NHE1 mRNA levels were reduced by 20 ± 2.0% ( n = 4). At 72 h, siRNANHE1 spreading was evident from the decrease in NHE1 expression in three portions of the myocardium (apex, medium, base). NHE1 function was assessed based on maximal velocity of intracellular pH (pHi) recovery (dpHi/d t) after an ammonium prepulse-induced acidic load. Maximal dpHi/d t was reduced to 14% in siRNANHE1-isolated left ventricular papillary muscles compared with scrambled siRNA. In conclusion, only one injection of naked siRNANHE1 successfully reduced NHE1 expression and activity in the left ventricle. As has been previously suggested, extensive NHE1 expression reduction may indicate myocardial spread of siRNA molecules from the injection site through gap junctions, providing a valid technique not only for further research into NHE1 function, but also for consideration as a potential therapeutic strategy.

Angiopoietin-like 4 protein elevates the prosurvival intracellular O2(-):H2O2 ratio and confers anoikis resistance to tumors

Cancer is a leading cause of death worldwide. Tumor cells exploit various signaling pathways to promote their growth and metastasis. To our knowledge, the role of angiopoietin-like 4 protein (ANGPTL4) in cancer remains undefined. Here, we found that elevated ANGPTL4 expression is widespread in tumors, and its suppression impairs tumor growth associated with enhanced apoptosis. Tumor-derived ANGPTL4 interacts with integrins to stimulate NADPH oxidase-dependent production of O(2)(-). A high ratio of O(2)(-):H(2)O(2) oxidizes/activates Src, triggering the PI3K/PKBα and ERK prosurvival pathways to confer anoikis resistance, thus promoting tumor growth. ANGPTL4 deficiency results in diminished O(2)(-) production and a reduced O(2)(-):H(2)O(2) ratio, creating a cellular environment conducive to apoptosis. ANGPTL4 is an important redox player in cancer and a potential therapeutic target.

Silencing of cardiac mitochondrial NHE1 prevents mitochondrial permeability transition pore opening

Inhibition of Na(+)/H(+) exchanger 1 (NHE1) reduces cardiac ischemia-reperfusion (I/R) injury and also cardiac hypertrophy and failure. Although the mechanisms underlying these NHE1-mediated effects suggest delay of mitochondrial permeability transition pore (MPTP) opening, and reduction of mitochondrial-derived superoxide production, the possibility of NHE1 blockade targeting mitochondria has been incompletely explored. A short-hairpin RNA sequence mediating specific knock down of NHE1 expression was incorporated into a lentiviral vector (shRNA-NHE1) and transduced in the rat myocardium. NHE1 expression of mitochondrial lysates revealed that shRNA-NHE1 transductions reduced mitochondrial NHE1 (mNHE1) by ∼60%, supporting the expression of NHE1 in mitochondria membranes. Electron microscopy studies corroborate the presence of NHE1 in heart mitochondria. Immunostaining of rat cardiomyocytes also suggests colocalization of NHE1 with the mitochondrial marker cytochrome c oxidase. To examine the functional role of mNHE1, mitochondrial suspensions were exposed to increasing concentrations of CaCl(2) to induce MPTP opening and consequently mitochondrial swelling. shRNA-NHE1 transduction reduced CaCl(2)-induced mitochondrial swelling by 64 ± 4%. Whereas the NHE1 inhibitor HOE-642 (10 μM) decreased mitochondrial Ca(2+)-induced swelling in rats transduced with nonsilencing RNAi (37 ± 6%), no additional HOE-642 effects were detected in mitochondria from rats transduced with shRNA-NHE1. We have characterized the expression and function of NHE1 in rat heart mitochondria. Because mitochondria from rats injected with shRNA-NHE1 present a high threshold for MPTP formation, the beneficial effects of NHE1 inhibition in I/R resulting from mitochondrial targeting should be considered.

Superoxide anion, uncoupling proteins and Alzheimer's disease

Superoxide anion is the first generated reactive oxygen species (ROS) after oxygen enters living cells. It was once considered to be highly deleterious to cell functions and aging. Therefore, antioxidants were suggested to prevent aging and degenerative diseases. However, superoxide signaling has been shown in many physiological responses such as transcriptional regulation, protein activation, bioenergy output, cell proliferation and apoptosis. The uncoupling proteins (UCPs) are a family of mitochondrial anion-carrier proteins located in the inner mitochondrial membrane and are considered to reduce the generation of superoxide anion through the mitochondrial mild uncoupling. UCPs are important in prevention of mitochondrial excessive generation of ROS, transfer of mitochondrial substrates, mitochondrial calcium uniport and regulation of thermogenesis. Superoxide anion and uncoupling proteins are linked to Alzheimer's disease in mitochondria. Simultaneous disorders of superoxide and uncoupling proteins create the conditions for neuronal oxidative damages. On the one hand, sustained oxidative damage causes neuronal apoptosis and eventually, accumulated neuronal apoptosis, leading to exacerbations of Alzheimer's disease. On the other hand, our study has shown that UCP2 and UCP4 have important impact on mitochondrial calcium concentration of nerve cells, suggesting that their abnormal expression may involve in the pathogenesis of Alzheimer's disease.

The Anrep effect requires transactivation of the epidermal growth factor receptor

Myocardial stretch elicits a biphasic contractile response: the Frank-Starling mechanism followed by the slow force response (SFR) or Anrep effect. In this study we hypothesized that the SFR depends on epidermal growth factor receptor (EGFR) transactivation after the myocardial stretch-induced angiotensin II (Ang II)/endothelin (ET) release. Experiments were performed in isolated cat papillary muscles stretched from 92 to 98% of the length at which maximal twitch force was developed (L(max)). The SFR was 123 +/- 1% of the immediate rapid phase (n = 6, P < 0.05) and was blunted by preventing EGFR transactivation with the Src-kinase inhibitor PP1 (99 +/- 2%, n = 4), matrix metalloproteinase inhibitor MMPI (108 +/- 4%, n = 11), the EGFR blocker AG1478 (98 +/- 2%, n = 6) or the mitochondrial transition pore blocker clyclosporine (99 +/- 3%, n = 6). Stretch increased ERK1/2 phosphorylation by 196 +/- 17% of control (n = 7, P < 0.05), an effect that was prevented by PP1 (124 +/- 22%, n = 7) and AG1478 (131 +/- 17%, n = 4). In myocardial slices, Ang II (which enhances ET mRNA) or endothelin-1 (ET-1)-induced increase in O(2)() production (146 +/- 14%, n = 9, and 191 +/- 17%, n = 13, of control, respectively, P < 0.05) was cancelled by AG1478 (94 +/- 5%, n = 12, and 98 +/- 15%, n = 8, respectively) or PP1 (100 +/- 4%, n = 6, and 99 +/- 8%, n = 3, respectively). EGF increased O(2)() production by 149 +/- 4% of control (n = 9, P < 0.05), an effect cancelled by inhibiting NADPH oxidase with apocynin (110 +/- 6% n = 7), mKATP channels with 5-hydroxydecanoic acid (5-HD; 105 +/- 5%, n = 8), the respiratory chain with rotenone (110 +/- 7%, n = 7) or the mitochondrial permeability transition pore with cyclosporine (111 +/- 10%, n = 6). EGF increased ERK1/2 phosphorylation (136 +/- 8% of control, n = 9, P < 0.05), which was blunted by 5-HD (97 +/- 5%, n = 4), suggesting that ERK1/2 activation is downstream of mitochondrial oxidative stress. Finally, stretch increased Ser703 Na(+)/H(+) exchanger-1 (NHE-1) phosphorylation by 172 +/- 24% of control (n = 4, P < 0.05), an effect that was cancelled by AG1478 (94 +/- 17%, n = 4). In conclusion, our data show for the first time that EGFR transactivation is crucial in the chain of events leading to the Anrep effect.

Computational identification and experimental validation of PPRE motifs in NHE1 and MnSOD genes of human

BACKGROUND

Activation of PPARs has been reported to inhibit the proliferation of malignant cells from different lineages. They are involved in transcription regulation of genes upon activation by a ligand. The binding of PPARs to the promoter sequence either represses or activates the gene. Hence, PPARs represent promising targets for cancer treatment because of their anti-proliferative and pro-apoptotic activities. Here we computationally identified PPAR binding regions in NHE1 and MnSOD. We further validated the predictions in vitro.

RESULTS

Our results computationally predicted the presence of 2 PPRE motifs in NHE1 and 3 PPRE motifs in MnSOD. We experimentally confirmed the true motifs and their regulation by PPAR.

CONCLUSION

Our results suggest that both NHE1 and MnSOD have PPRE binding motif in their upstream/promoter region and hence are regulated by PPAR upon ligand binding.

Repression of NHE1 expression by PPARgamma activation is a potential new approach for specific inhibition of the growth of tumor cells in vitro and in vivo

Ligand-induced activation of peroxisome proliferator-activated receptor gamma (PPARgamma) inhibits proliferation in cancer cells in vitro and in vivo; however, the downstream targets remain undefined. We report the identification of a peroxisome proliferator response element in the promoter region of the Na(+)/H(+) transporter gene NHE1, the overexpression of which has been associated with carcinogenesis. Exposure of breast cancer cells expressing high levels of PPARgamma to its natural and synthetic agonists resulted in downregulation of NHE1 transcription as well as protein expression. Furthermore, the inhibitory effect of activated PPARgamma on tumor colony-forming ability was abrogated on overexpression of NHE1, whereas small interfering RNA-mediated gene silencing of NHE1 significantly increased the sensitivity of cancer cells to growth-inhibitory stimuli. Finally, histopathologic analysis of breast cancer biopsies obtained from patients with type II diabetes treated with the synthetic agonist rosiglitazone showed significant repression of NHE1 in the tumor tissue. These data provide evidence for tumor-selective downregulation of NHE1 by activated PPARgamma in vitro and in pathologic specimens from breast cancer patients and could have potential implications for the judicious use of low doses of PPARgamma ligands in combination chemotherapy regimens for an effective therapeutic response.