Atrial Natriuretic Peptide Effects on Intracellular pH Changes and ROS Production in HEPG2 Cells: Role of p38 MAPK and Phospholipase D

Carbonic anhydrases in development: morphological observations and gene expression profiling in sea urchin embryos exposed to acetazolamide

Carbonic anhydrases (CANs) are conserved metalloenzymes catalysing the reversible hydration of carbon dioxide into protons and bicarbonate, with important roles in cells physiology. Some CAN-coding genes were found in sea urchin genome, although only one involved in embryonic skeletogenesis was described in Paracentrotus lividus. Here, we investigated gene expression patterns of P. lividus embryos cultured in the presence of acetazolamide (AZ), a CAN inhibitor, to combine morphological defects with their molecular underpinning. CAN inhibition blocked skeletogenesis, affected the spatial/temporal expression of some biomineralization-related genes, inhibited embryos swimming. A comparative analysis on the expression of 127 genes in control and 3 h/24 h AZ-treated embryos, using NanoString technology, showed the differential expression of genes encoding for structural/regulatory proteins, with different embryonic roles: biomineralization, transcriptional regulation, signalling, development and defence response. The study of the differentially expressed genes and the signalling pathways affected, besides in silico analyses and a speculative 'interactomic model', leads to predicting the presence of various CAN isoforms, possibly involved in different physiological processes/activities in sea urchin embryo, and their potential target genes/proteins. Our findings provide new valuable molecular data for further studies in several biological fields: developmental biology (biomineralization, axes patterning), cell differentiation (neural development) and drug toxicology (AZ effects on embryos/tissues).

Pleiotropic Roles of Atrial Natriuretic Peptide in Anti-Inflammation and Anti-Cancer Activity

Simple Summary

The relationship between inflammation and carcinogenesis, as well as the response to anti-tumor therapy, is intimate. Atrial natriuretic peptides (ANPs) play a pivotal role in the homeostatic control of blood pressure, electrolytes, and water balance. In addition, ANPs exert immune-modulatory effects in the tissue microenvironment, thus exhibiting a fascinating ability to prevent inflammation-related tumorigenesis and cancer recurrence. In cancers, ANPs show anti-proliferative effects through several molecular pathways. Furthermore, ANPs attenuate the side effects of cancer therapy. Therefore, ANPs have potential therapeutic value in tumors. Here, we summarized the roles of ANPs in diverse aspects of the immune system and the molecular mechanisms underlying the anti-cancer effects of ANPs, contributing to the development of ANP-based anti-cancer agents.

Abstract

The atrial natriuretic peptide (ANP), a cardiovascular hormone, plays a pivotal role in the homeostatic control of blood pressure, electrolytes, and water balance and is approved to treat congestive heart failure. In addition, there is a growing realization that ANPs might be related to immune response and tumor growth. The anti-inflammatory and immune-modulatory effects of ANPs in the tissue microenvironment are mediated through autocrine or paracrine mechanisms, which further suppress tumorigenesis. In cancers, ANPs show anti-proliferative effects through several molecular pathways. Furthermore, ANPs attenuate the side effects of cancer therapy. Therefore, ANPs act on several hallmarks of cancer, such as inflammation, angiogenesis, sustained tumor growth, and metastasis. In this review, we summarized the contributions of ANPs in diverse aspects of the immune system and the molecular mechanisms underlying the anti-cancer effects of ANPs.

Atrial Natriuretic Peptide: A Potential Early Therapy for the Prevention of Multiple Organ Dysfunction Syndrome Following Severe Trauma

Trauma remains a tremendous medical burden partly because of increased expenditure for the management of multiple organ dysfunction syndrome (MODS) developed during hospital stay. The intestinal barrier injury continues to be a second insult resulting in MODS which currently lacks efficient strategies for prevention. Recent studies have uncovered multi-organ protective benefits of atrial natriuretic peptide (ANP) in cardiovascular disease. However, the role of ANP in the prevention of MODS following severe trauma has not been understood. In our laboratory study, 1-h infusion of exogenous ANP during hemorrhagic shock following severe trauma induced high-level expression of endogenous serum ANP after 24 h, this effect was related to the improved level of functional biomarkers in multiple organs. Such phenomenon has not been found in other laboratories. A thorough literature review consequently was performed to uncover the potential mechanisms, to appraise therapy safety, and to propose uncertainties. In severe trauma, short-term exogenous ANP therapy during hemorrhagic shock may promote sustained endogenous expression of ANP from intestinal epithelium through activating a positive feedback loop mechanism involving phospholipase C-γ1 and reactive oxygen species crosstalk. This feedback loop may prevent MODS through multiple signaling pathways. Administration of ANP during hemorrhagic shock is thought to be safe. Further studies are required to confirm our proposed mechanisms and to investigate the dose, duration, and timing of ANP therapy in severe trauma.

Hepatocyte-specific deletion of LASS2 protects against diet-induced hepatic steatosis and insulin resistance

Homo sapienslongevity assurance homolog 2 of yeast LAG1 (LASS2) is expressed mostly in human liver. Here, we explored roles of LASS2 in pathogenesis of hepatic steatosis. Hepatocyte-specific LASS2 knockout (LASS2^-/-) mice were generated using Cre-LoxP system. LASS2^-/- and wild-type (WT) mice were fed with chow or high-fat diet (HFD). We found LASS2^-/- mice were resistant to HFD-induced hepatic steatosis and insulin resistance. In HFD-fed mice, LASS2 deficiency significantly inhibited p38 MAPK and ERK1/ERK2 signaling in mouse liver. This effect was mediated by a significant increase of V-ATPase activity and a decrease of ROS level. We also observed that elevated expression of LASS2 in mouse hepatocyte cell line AML12 obviously decreased V-ATPase activity and increased ROS level by activation of p38 MAPK and ERK1/ERK2 signaling. Our findings indicate that LASS2 plays an important role in the pathogenesis of diet-induced hepatic steatosis and is a potential novel target for prevention and intervention of liver diseases.

Atrial natriuretic peptide: a magic bullet for cancer therapy targeting Wnt signaling and cellular pH regulators

Atrial natriuretic peptide (ANP) is a cardiac hormone playing a crucial role in cardiovascular homeostasis mainly through blood volume and pressure regulation. In the last years, the new property ascribed to ANP of inhibiting tumor growth both in vitro and in vivo has made this peptide an attractive candidate for anticancer therapy. The molecular mechanism underlying the anti-proliferative effect of ANP has been mainly related to its interaction with the specific receptors NPRs, through which this natriuretic hormone inhibits some metabolic targets critical for cancer development, including the Ras-MEK1⁄2-ERK1⁄2 kinase cascade, functioning as a multikinase inhibitor. In this review we summarize the current knowledge on this topic, focusing on our recent data demonstrating that the antitumor activity of this natriuretic hormone is also mediated by a concomitant effect on the Wnt/β-catenin pathway and on the pH regulation ability of cancer cells, through a Frizzled-related mechanism. This peculiarity of simultaneously targeting two processes crucial for neoplastic transformation and solid tumor survival reinforces the utility of ANP for the development of both preventive and therapeutic strategies.

Recombinant adeno-associated virus utilizes cell-specific infectious entry mechanisms

Understanding the entry and trafficking mechanism(s) of recombinant adeno-associated virus (rAAV) into host cells can lead to evolution in capsid and vector design and delivery methods, resulting in enhanced transduction and therapeutic gene expression. Variability of findings regarding the early entry pathway of rAAV supports the possibility that rAAV, like other viruses, can utilize more than one infectious entry pathway. We tested whether inhibition of macropinocytosis impacted rAAV transduction of HeLa cells compared to hepatocellular carcinoma cell lines. We found that macropinocytosis inhibitor cytochalasin D blocked rAAV transduction of HeLa cells (>2-fold) but enhanced (10-fold) transduction in HepG2 and Huh7 lines. Similar results were obtained with another macropinocytosis inhibitor, 5-(N-ethyl-N-isopropyl) amiloride (EIPA). The augmented transduction was due to neither viral binding nor promoter activity, affected multiple rAAV serotypes (rAAV2, rAAV2-R585E, and rAAV8), and influenced single-stranded and self-complementary virions to comparable extents. Follow-up studies using CDC42 inhibitor ML141 and p21-activated kinase 1 (PAK1) siRNA knockdown also resulted in enhanced HepG2 transduction. Microscopy revealed that macropinocytosis inhibition correlated with expedited nuclear entry of the rAAV virions into HepG2 cells. Enhancement of hepatocellular rAAV transduction extended to the mouse liver in vivo (4-fold enhancement) but inversely blocked heart tissue transduction (13-fold). This evidence of host cell-specific rAAV entry pathways confers a potent means for controlling and enhancing vector delivery and could help unify the divergent accounts of rAAV cellular entry mechanisms.

IMPORTANCE

There is a recognized need for improved rAAV vector targeting strategies that result in delivery of fewer total particles, averting untoward toxicity and/or an immune response against the vector. A critical step in rAAV transduction is entry and early trafficking through the host cellular machinery, the mechanisms of which are under continued study. However, should the early entry and trafficking mechanisms of rAAV differ across virus serotype or be dependent on host cell environment, this could expand our ability to target particular cells and tissue for selective transduction. Thus, the observation that inhibiting macropinocytosis leads to cell-specific enhancement or inhibition of rAAV transduction that extends to the organismic level exposes a new means of modulating vector targeting.

Atrial natriuretic peptide: an old hormone or a new cytokine?

Atrial natriuretic peptide (ANP) a cardiovascular hormone mainly secreted by heart atria in response to stretching forces induces potent diuretic, natriuretic and vasorelaxant effects and plays a major role in the homeostasis of blood pressure as well as of water and salt balance. The hormone can also act as autocrine/paracrine factor and modulate several immune functions as well as cytoprotective effects. ANP contributes to innate immunity being able to: (i) stimulate the host defense against extracellular microbes by phagocytosis and Reactive Oxygen Species (ROS) release; (ii) inhibit the synthesis and release of proinflammatory markers such as TNF-α, IL-1, MCP-1, nitric oxide (NO), cyclooxygenase-2 (COX-2); (iii) inhibit the expression of adhesion molecules such as ICAM-1 and E-selectin. ANP can also affect the adaptive immunity being able to: (i) reduce the number of CD4(+) CD8(+) lymphocytes as well as to increase the CD4(-) CD8(-) cells; (ii) stimulate the differentiation of naïve CD4(+) cells toward the Th2 and/or Th17 phenotype. The hormone shows protective effects during: (i) ventricular hypertrophy and myocardial injury; (ii) atherosclerosis and hypertension by the induction of antiproliferative effects; (iii) oxidative stress counteracting the dangerous effects of ROS; (iv) growth of tumors cells by the induction of apoptosis or necrosis. Since not much is known about of the role of ANP locally produced and released by non-cardiac cells, this review outlines the contribution of ANP in different aspect of innate as well as adaptive immunity also with respect to the excessive cell growth in physiological and/or pathological conditions.

Effect of atrial natriuretic peptide on reactive oxygen species-induced by hydrogen peroxide in THP-1 monocytes: role in cell growth, migration and cytokine release

Atrial natriuretic peptide (ANP), a cardiovascular hormone, elicits different biological actions in the immune system. The aim of the present study was to investigate in THP-1 monocytes the ANP effect on hydrogen peroxide (H2O2)-induced Reactive Oxygen Species (ROS), cell proliferation and migration. A significant increase of H2O2-dependent ROS production was induced by physiological concentration of ANP (10(-10)M). The ANP action was partially affected by cell pretreatment with PD98059, an inhibitor of mitogen activated-protein kinases (MAPK) as well as by wortmannin, an inhibitor of phosphatidylinositol 3-kinase (PI3K) and totally suppressed by diphenylene iodonium (DPI), an inhibitor of the enzyme nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. The hormone effect was mimicked by cANF and an ANP/NPR-C signaling pathway was studied using pertussis toxin (PTX). A significant increase of H2O2-induced cell migration was observed after ANP (10(-10)M) treatment, conversely a decrease of THP-1 proliferation, due to cell death, was found. Both ANP actions were partially prevented by DPI. Moreover, H2O2-induced release of IL-9, TNF-α, MIP-1α and MIP-1β was not counteracted by DPI, whereas no effect was observed in any experimental condition for both IL-6 and IL-1β. Our results support the view that ANP can play a key role during the inflammatory process.

Atrial natriuretic peptide and oxidative stress

Atrial natriuretic peptide (ANP) is a hormone, produced mainly by cardiomyocytes, with a major role in cardiovascular homeostatic mechanisms such as natriuresis and vasodilation, which serve to regulate blood pressure. However, ANP also acts as an autocrine/paracrine factor on other targets such as kidney, lung, thymus, liver and the immune system. ANP participates in the regulation of cell growth and proliferation, and evidence is accumulating that these effects are associated with the generation of reactive oxygen species (ROS). In vascular cells and cardiomyocytes ANP stimulates the antioxidant defense, but in other systems such as hepatoblastoma and macrophages ANP may produce either antioxidant or prooxidant effects, depending on experimental conditions and cell context. At present very little is known on the relationship between ANP and ROS production in the normal homeostatic processes or during the development of cardiovascular diseases and cancer. Our current knowledge of the role of ANP in signaling pathways leading to the generation of intracellular messengers such as diacylglycerol (DAG), and guanosine 3'-5'-cyclic monophosphate has been examined in order to clarify the mechanisms by which the hormone may counteract or contribute to the potentially dangerous effects of free radicals.

The role of signalling molecules on actin glutathionylation and protein carbonylation induced by cadmium in haemocytes of mussel Mytilus galloprovincialis (Lmk)

This study investigated the role of Na(+)/H(+) exchanger (NHE) and signalling molecules, such as cAMP, PKC, PI 3-kinase, and immune defence enzymes, NADPH oxidase and nitric oxide synthase, in the induction of protein glutathionylation and carbonylation in cadmium-treated haemocytes of mussel Mytilus galloprovincialis. Glutathionylation was detected by western blot analysis and showed actin as its main target. A significant increase of both actin glutathionylation and protein carbonylation, were observed in haemocytes exposed to micromolar concentration of cadmium chloride (5 micromol l(-1)). Cadmium seems to cause actin polymerization that may lead to its increased glutathionylation, probably to protect it from cadmium-induced oxidative stress. It is therefore possible that polymerization of actin plays a signalling role in the induction of both glutathionylation and carbonylation processes. NHE seems to play a regulatory role in the induction of oxidative damage and actin glutathionylation, since its inhibition by 2 micromol l(-1) cariporide, significantly diminished cadmium effects in each case. Similarly, attenuation of cadmium effects were observed in cells pre-treated with either 11 micromol l(-1) GF-109203X, a potent inhibitor of PKC, 50 nmol l(-1) wortmannin, an inhibitor of PI 3-kinase, 0.01 mmol l(-1) forskolin, an adenylyl cyclase activator, 10 micromol l(-1) DPI, a NADPH oxidase inhibitor, or 10 micromol l(-1) L-NAME, a nitric oxide synthase inhibitor, suggesting a possible role of PKC, PI 3-kinase and cAMP, as well as NADPH oxidase and nitric oxide synthase in the enhancement of cadmium effects on both actin glutathionylation and protein carbonylation.

Natriuretic peptides in vascular physiology and pathology

Four major natriuretic peptides have been isolated: atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), C-type natriuretic peptide (CNP), and Dendroaspis-type natriuretic peptide (DNP). Natriuretic peptides play an important role in the regulation of cardiovascular homeostasis maintaining blood pressure and extracellular fluid volume. The classical endocrine effects of natriuretic peptides to modulate fluid and electrolyte balance and vascular smooth muscle tone are complemented by autocrine and paracrine actions that include regulation of coronary blood flow and, therefore, myocardial perfusion; modulation of proliferative responses during myocardial and vascular remodeling; and cytoprotective anti-ischemic effects. The actions of natriuretic peptides are mediated by the specific binding of these peptides to three cell surface receptors: type A natriuretic peptide receptor (NPR-A), type B natriuretic peptide receptor (NPR-B), and type C natriuretic peptide receptor (NPR-C). NPR-A and NPR-B are guanylyl cyclase receptors that increase intracellular cGMP concentration and activate cGMP-dependent protein kinases. NPR-C has been presented as a clearance receptor and its activation also results in inhibition of adenylyl cyclase activity. The wide range of effects of natriuretic peptides might be the base for the development of new therapeutic strategies of great benefit in patients with cardiovascular problems including coronary artery disease or heart failure. This review summarizes current literature concerning natriuretic peptides, their receptors and their effects on fluid/electrolyte balance, and vascular and cardiac physiology and pathology, including primary hypertension and myocardial infarction. In addition, we will attempt to provide an update on important issues regarding natriuretic peptides in congestive heart failure.

Inhibition of the Na+-H+ exchanger isoform-1 and the extracellular signal-regulated kinase induces apoptosis: a time course of events

AIMS

The present study attempts to shed light on the role and the relative position of the Na(+)/H(+) exchanger isoform 1 (NHE1) and the extracellular signal-regulated kinase (ERK) in HEp-2 cell signaling pathways concerning a diverse range of cellular functions such as regulation of intracellular pH (pHi), DNA synthesis, production of reactive oxygen species (ROS) and apoptosis.

METHODS

Pharmacological inhibition with cariporide (highly specific inhibitor of NHE1) and PD98059 (specific inhibitor of the upstream activator of ERK) was implemented. Fluorescence spectrometry, atomic absorption spectrometry and ELISA methods were used in order to obtain the results.

RESULTS

NHE1 and ERK take part in all of the aforementioned cellular functions, as their inhibition had an effect on all of them. Additionally, inhibition of NHE1 resulted in ERK inhibition as well. Moreover, continuous inhibition of NHE1 or ERK for up to 24h led HEp-2 cells to apoptosis, as assessed through caspase-3 activation, DNA fragmentation and annexin-V binding levels.

CONCLUSION

Our data shows a time course of events in relation to NHE1 and ERK and suggests the existence of a positive feedback loop between NHE1 and ERK which could pose a barrier against apoptosis.

The influence of Zn on signaling pathways and attachment of Mytilus galloprovincialis haemocytes to extracellular matrix proteins

The present study investigates the cytotoxic mechanisms induced by zinc (Zn) in haemocytes of mussel Mytilus galloprovincialis. Haemocytes play a key role in the immune defence of mussels. Micromolar concentration of Zn (50 microM) play an important role in the elevation of pHi and increase in Na+ influx in haemocytes. The observed effects were inhibited by the Na+/H+ exchanger (NHE) inhibitor, ethyl-N-isopropyl-amiloride (EIPA). Furthermore, our results showed that Zn caused an increase in O(-)(2) production that was reversed after NHE inhibition. Phorbol ester (PMA) caused a significant rise both in pHi and Na+ influx as well as in O(-)(2) production. These effects were reversed by calphostin C. Our results indicated that Zn also enhanced haemocyte attachment to both BSA and laminin which was reversed by EIPA and calphostin C. The enhancement of haemocytes attachment to both BSA and laminin after Zn suggests that it is likely to play a signal role in cytoskeleton-dependent process of cell growth and migration in mussel M. galloprovincialis haemocytes. We conclude that Zn induces a signaling pathway with the involvement of NHE, PKC, O(-)(2) and alpha1- and beta-adrenergic receptors.

Requirement of an IkappaB-beta COOH terminal region protein for acidic-adaptation in CHO cells

We previously reported that an IkappaB-beta COOH terminal region protein (designated CTIB) was essential for the proliferation of CHO cells under acidic stress (Lao et al., 2005. J Cell Physiol 203(1):186-192). In order to investigate the mechanisms underlying the requirement of CTIB for acidic adaptation, CTIB was silenced with an RNAi technique in CHO cells. CTIB silencing resulted in those cells completely failing to proliferate and maintain intracellular pH (pHi) homeostasis at an extracellular pH (pHe) of 6.3. An increased activation of p38 MAP kinase was induced by CTIB silencing at the low pH value. CTIB was only present in the cytoplasm and co-immunoprecipitation of the cytoplasmic fraction revealed that the loss of CTIB led to a loss of p65 in the immunoprecipitate complex. CTIB silencing reduced both the decrease in p65 and the increase in p50 in the nucleus when the cells were incubated at pHe 6.3. In cells with CTIB silenced, the transcriptions of p65, p105, and IL1-beta were suppressed, and decreases in both the transcription and activity of MnSOD were observed at pHe 6.3. Suppression of these genes suggested a suppressed NF-kappaB activity since p105, IL1-beta, and MnSOD were target genes of NF-kappaB. Our data demonstrated that CTIB functioned to prevent the over-accumulation of p65 in the nucleus, ensuring the appropriate composition of the NF-kappaB complex in the nucleus to respond to stimuli under acidic conditions.

Cadmium effects on ros production and DNA damage via adrenergic receptors stimulation: role of Na+/H+ exchanger and PKC

The objective of the present study was to elucidate the events that are involved in reactive oxygen species (ROS) production and DNA damage after adrenergic receptors stimulation by cadmium, in relation to cAMP, protein kinase C (PKC) and Na+/H+ exchanger (NHE). Cadmium (50 microM) caused increased levels of ROS with a concomitant increase in DNA damage in digestive gland of Mytilus galloprovincialis. Either the use of EIPA, a NHE blocker, or calphostin C, the inhibitor of PKC, reduced cadmium effects. Cells treated with alpha1-, alpha2-, beta- and beta1- adrenergic antagonists together with cadmium reversed cadmium alone effects, while the respective adrenergic agonists, phenylephrine and isoprenaline, mimic cadmium effects. Moreover, cadmium caused an increase in the levels of cAMP in digestive gland cells that were reversed after NHE and PKC inhibition as well as in the presence of each type of adrenergic antagonist. The different sensitivity of alpha1-, alpha2-, beta-, beta1- adrenergic receptors on ROS, cAMP production and DNA damage possibly leads to the induction of two signaling pathways that may be interacting or to the presence of a compensatory pathway that acts in concert with the alpha- and beta- adrenergic receptors. In these signaling pathways PKC and NHE play significant role.