Novel effects of nitric oxide

Caffeic Acid Derivatives: In Vitro and In Vivo Anti-inflammatory Properties

Caffeic acid and some of its derivatives such as caffeic acid phenetyl ester (CAPE) and octyl caffeate are potent antioxidants which present important anti-inflammatory actions. The present study assessed the in vitro and in vivo effects of five caffeic acid derivatives (caffeic acid methyl, ethyl, butyl, octyl and benzyl esters) and compared their actions to those of CAPE. In the model of LPS-induced nitric oxide (NO) production in RAW 264.7 macrophages, the pre-incubation of all derivatives inhibited nitrite accumulation on the supernatant of stimulated cells, with mean IC50 (microM) values of 21.0, 12.0, 8.4, 2.4, 10.7 and 4.80 for methyl, ethyl, butyl, octyl, benzyl and CAPE, respectively. The effects of caffeic acid derivatives seem to be related to the scavenging of NO, as the compounds prevented SNAP-derived nitrite accumulation and decreased iNOS expression. In addition, butyl, octyl and CAPE derivatives significantly inhibited LPS-induced iNOS expression in RAW 264.7 macrophages. Extending the in vitro results, we showed that the pre-treatment of mice with butyl, octyl and CAPE derivatives inhibited carrageenan-induced paw edema and prevented the increase in IL-1beta levels in the mouse paw by 30, 24 and 36%, respectively. Butyl, octyl and CAPE derivatives also prevented carrageenan-induced neutrophil influx in the mouse paw by 28, 49 and 31%, respectively. Present results confirm and extend literature data, showing that caffeic acid derivatives exert in vitro and in vivo anti-inflammatory actions, being their actions mediated, at least in part by the scavenging of NO and their ability to modulate iNOS expression and probably that of other inflammatory mediators.

Transcriptional profiling identifies the metabolic phenotype of gonococcal biofilms

Neisseria gonorrhoeae, the etiologic agent of gonorrhea, is frequently asymptomatic in women, often leading to chronic infections. One factor contributing to this may be biofilm formation. N. gonorrhoeae can form biofilms on glass and plastic surfaces. There is also evidence that biofilm formation may occur during natural cervical infection. To further study the mechanism of gonococcal biofilm formation, we compared transcriptional profiles of N. gonorrhoeae biofilms to planktonic profiles. Biofilm RNA was extracted from N. gonorrhoeae 1291 grown for 48 h in continuous-flow chambers over glass. Planktonic RNA was extracted from the biofilm runoff. In comparing biofilm with planktonic growth, 3.8% of the genome was differentially regulated. Genes that were highly upregulated in biofilms included aniA, norB, and ccp. These genes encode enzymes that are central to anaerobic respiratory metabolism and stress tolerance. Downregulated genes included members of the nuo gene cluster, which encodes the proton-translocating NADH dehydrogenase. Furthermore, it was observed that aniA, ccp, and norB insertional mutants were attenuated for biofilm formation on glass and transformed human cervical epithelial cells. These data suggest that biofilm formation by the gonococcus may represent a response that is linked to the control of nitric oxide steady-state levels during infection of cervical epithelial cells.

Organization of collagen bundles during tendon healing in rats treated with L-NAME

The Achilles tendon can support high tension forces and may experience lesions. The damaged tissue does not regenerate completely, with the organization and mechanical properties of the repaired tendon being inferior to those of a healthy tendon. Nitric oxide (NO) plays an important role in wound repair. We have examined the structural reorganization and repair in Achilles tendon after injury in rats treated with the NO synthase inhibitor L-NAME. The right Achilles tendon of male Wistar rats was partially transected. One group of rats was treated with L-NAME (~300 mg/kg per day, given in drinking water) for 4 days prior to tendon sectioning and throughout the post-operative period. Control rats received water without L-NAME. The tendons were excised at 7, 14, and 21 days post-injury and used to quantify hydroxyproline and for mechanical tests. Tendons were also processed for histomorphological analysis by polarized light microscopy, which showed that the collagen fibers were disorganized by day 7 in non-treated and L-NAME-treated rats. In non-treated rats, the organization of the extracellular matrix was more homogeneous by days 14 and 21 compared with day 7, although this homogeneity was less than that in normal tendon. In contrast, in injured tendons from L-NAME-treated rats, the collagen fibers were still disorganized on day 21. Tendons from treated rats had more hydroxyproline but lower mechanical properties compared with those from non-treated rats. Thus, NO modulates tendon healing, with a reduction in NO biosynthesis delaying reorganization of the extracellular matrix, especially collagen.

A role for nitric oxide-mediated glandular hypofunction in a non-apoptotic model for Sjogren's syndrome

OBJECTIVE

To investigate a role for the inflammatory mediator, nitric oxide (NO) in SS, an autoimmune condition characterized by salivary and lacrimal gland hypofunction resulting from failure of acinar cells to secrete.

METHODS

FURA-2 microfluorimetry was used to measure agonist-evoked changes of [Ca(2+)](i) in isolated mouse and human salivary acinar cells following exposure to NO donors.

RESULTS

NO had a biphasic effect on salivary acinar function. Acute exposure to NO (2 min) caused a cyclic guanosine monophosphate (GMP)-dependent, 1-H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-sensitive increase in the Ca(2+) signal elicited in response to acetylcholine (ACh) stimulation, consistent with stimulation of ryanodine receptors by cyclic adenosine diphosphate ribose. Prolonged exposure to NO (>40 min) significantly reduced the ACh-evoked Ca(2+) signal by a mechanism independent of cyclic GMP. We found no differences between the responses of human and mouse acinar cells.

CONCLUSION

Our data show that chronic exposure to NO, which is known to be elevated in SS, could have a role in salivary gland hypofunction. We note a similarity in the response to stimulation of salivary acinar exposed to NO and that which we have previously reported in salivary acinar cells isolated from patients with SS. We speculate that NO-mediated nitrosylation of one or more elements of the signal transduction pathway could underlie down-regulation of salivary function in SS.

Elevated neuronal nitric oxide synthase expression during ageing and mitochondrial energy production

This study evaluated the effect of ageing on brain mitochondrial function mediated through protein post-translational modifications. Neuronal nitric oxide synthase increased with age and this led to a discreet pattern of nitration of mitochondrial proteins. LC/MS/MS analyses identified the nitrated mitochondrial proteins as succinyl-CoA-transferase and F1-ATPase; the latter was nitrated at Tyr269, suggesting deficient ADP binding to the active site. Activities of succinyl-CoA-transferase, F1-ATPase and cytochrome oxidase decreased with age. The decreased activity of the latter cannot be ascribed to protein modifications and is most likely due to a decreased expression and assembly of complex IV. Mitochondrial protein post-translational modifications were associated with a moderately impaired mitochondrial function, as indicated by the decreased respiratory control ratios as a function of age and by the release of mitochondrial cytochrome c to the cytosol, thus supporting the amplification of apoptotic cascades.

The interaction of oxidative stress response with cytokines in the thyrotoxic rat: is there a link?

Oxidative stress is regarded as a pathogenic factor in hyperthyroidism. Our purpose was to determine the relationship between the oxidative stress and the inflammatory cytokines and to investigate how melatonin affects oxidative damage and cytokine response in thyrotoxic rats. Twenty-one rats were divided into three groups. Group A served as negative controls. Group B had untreated thyrotoxicosis, and Group C received melatonin. Serum malondialdehyde (MDA), glutathione (GSH), glutathione reductase (GR), glutathione peroxidase (GPx), and nitric oxide derivates (NO^•x), and plasma IL-6, IL-10, and TNF-alpha were measured. MDA, GSH, NO^•x, IL-10, and TNF-alpha levels increased after L-thyroxine induction. An inhibition of triiodothyronine and thyroxine was detected, as a result of melatonin administration. MDA, GSH, and NO^•x levels were also affected by melatonin. Lowest TNF-alpha levels were observed in Group C. This study demonstrates that oxidative stress is related to cytokine response in the thyrotoxic rat. Melatonin treatment suppresses the hyperthyroidism-induced oxidative damage as well as TNF-alpha response.

Analysis of nitric oxide-stabilized mRNAs in human fibroblasts reveals HuR-dependent heme oxygenase 1 upregulation

We previously observed that nitric oxide (NO) exposure increases the stability of mRNAs encoding heme oxygenase 1 (HO-1) and TIEG-1 in human and mouse fibroblasts. Here, we have used microarrays to look broadly for changes in mRNA stability in response to NO treatment. Using human IMR-90 and mouse NIH 3T3 fibroblasts treated with actinomycin D to block de novo transcription, microarray analysis suggested that the stability of the majority of mRNAs was unaffected. Among the mRNAs that were stabilized by NO treatment, seven transcripts were found in both IMR-90 and NIH 3T3 cells (CHIC2, GADD45B, HO-1, PTGS2, RGS2, TIEG, and ID3) and were chosen for further analysis. All seven mRNAs showed at least one hit of a signature motif for the stabilizing RNA-binding protein (RBP) HuR; accordingly, ribonucleoprotein immunoprecipitation analysis revealed that all seven mRNAs associated with HuR. In keeping with a functional role of HuR in the response to NO, a measurable fraction of HuR increased in the cytoplasm following NO treatment. However, among the seven transcripts, only HO-1 mRNA showed a robust increase in the level of its association with HuR following NO treatment. In turn, HO-1 mRNA and protein levels were significantly reduced when HuR levels were silenced in IMR-90 cells, and they were elevated when HuR was overexpressed. In sum, our results indicate that NO stabilizes mRNA subsets in fibroblasts, identify HuR as an RBP implicated in the NO response, reveal that HuR alone is insufficient for stabilizing several mRNAs by NO, and show that HO-1 induction by NO is regulated by HuR.

Antimicrobial activity of the iron-sulfur nitroso compound Roussin's black salt [Fe4S3(NO)7] on the hyperthermophilic archaeon Pyrococcus furiosus

The iron-sulfur nitroso compound [Fe(4)S(3)(NO)(7)](-) is a broad-spectrum antimicrobial agent that has been used for more than 100 years to combat pathogenic anaerobes. Known as Roussin's black salt (RBS), it contains seven moles of nitric oxide, the release of which was always assumed to mediate its cytotoxicity. Using the hyperthermophilic archaeon Pyrococcus furiosus, it is demonstrated through growth studies, membrane analyses, and scanning electron microscopy that nitric oxide does not play a role in RBS toxicity; rather, the mechanism involves membrane disruption leading to cell lysis. Moreover, insoluble elemental sulfur (S(0)), which is reduced by P. furiosus to hydrogen sulfide, prevents cell lysis by RBS. It is proposed that S(0) also directly interacts with the membranes of P. furiosus during its transfer into the cell, ultimately for reduction by a cytosolic NADPH sulfur reductase. RBS is proposed to be a new class of inorganic antimicrobial agent that also has potential use as an inert cell-lysing agent.

Differential effects of nitric oxide synthesis on pulmonary vascular function during lung ischemia-reperfusion injury

Lung ischemia-reperfusion (IR) injury causes alveolar, epithelial and endothelial cell dysfunction which often results in decreased alveolar perfusion, characteristic of an acute respiratory distress syndrome. Nitric oxide (NO) from endothelium-derived NO synthase (eNOS) helps maintain a low pulmonary vascular resistance. Paradoxically, during acute lung injury, overproduction of NO via inducible NO synthase (iNOS) and oxidative stress lead to reactive oxygen and nitrogen species (ROS and RNS) formation and vascular dysfunction. RNS potentiate vascular and cellular injury by oxidation, by decreasing NO bioavailability, and by regulating NOS isoforms. RNS potentiate their own production by uncoupling NO production through eNOS by oxidation and disruption of Akt-mediated phosphorylation of eNOS. This review focuses on effects of NO which cause vascular dysfunction in the unique environment of the lung and presents a hypothesis for interplay between eNOS and iNOS activation with implications for development of new strategies to treat vascular dysfunction associated with IR.

Hemoglobin conjugated with a Band 3 N-terminus derived peptide as an oxygen carrier

A peptide composed of 9 amino acids, 7 residues from N-terminus of human erythrocytic Band 3 protein (AcMEELQDD) followed by cysteine and glutamic acids, was conjugated to hemoglobin (Hb) serving as an allosteric effector for oxygen release. The activated polyethylene glycol (PEG), maleimide-PEG-N-hydroxysuccinimidyl, was used to crosslink Hb with the peptide. The putative conjugation site on Hb for effective enhancement of oxygen release was characterized as Lys-beta95 by liquid chromatography-tandem mass spectrometry. In addition, the conjugated peptide causes a rightward shift of the oxygen dissociation curve as compared to that of its parent Hb when the degree of oxygen saturation is higher than 50%. Furthermore, this conjugated peptide remains effective on lowering Hb's oxygen affinity after Hb polymerization by another PEG crosslinker. The allosteric properties of the peptide-conjugated Hb may provide a new aspect of Hb-based oxygen carriers.

Nitric oxide and cyclic nucleotides: their roles in junction dynamics and spermatogenesis

Spermatogenesis is a highly complicated process in which functional spermatozoa (haploid, 1n) are generated from primitive mitotic spermatogonia (diploid, 2n). This process involves the differentiation and transformation of several types of germ cells as spermatocytes and spermatids undergo meiosis and differentiation. Due to its sophistication and complexity, testis possesses intrinsic mechanisms to modulate and regulate different stages of germ cell development under the intimate and indirect cooperation with Sertoli and Leydig cells, respectively. Furthermore, developing germ cells must translocate from the basal to the apical (adluminal) compartment of the seminiferous epithelium. Thus, extensive junction restructuring must occur to assist germ cell movement. Within the seminiferous tubules, three principal types of junctions are found namely anchoring junctions, tight junctions, and gap junctions. Other less studied junctions are desmosome-like junctions and hemidesmosome junctions. With these varieties of junction types, testes are using different regulators to monitor junction turnover. Among the uncountable junction modulators, nitric oxide (NO) is a prominent candidate due to its versatility and extensive downstream network. NO is synthesized by nitric oxide synthase (NOS). Three traditional NOS, specified as endothelial NOS (eNOS), inducible NOS (iNOS), and neuronal NOS (nNOS), and one testis-specific nNOS (TnNOS) are found in the testis. For these, eNOS and iNOS were recently shown to have putative junction regulation properties. More important, these two NOSs likely rely on the downstream soluble guanylyl cyclase/cGMP/protein kinase G signaling pathway to regulate the structural components at the tight junctions and adherens junctions in the testes. Apart from the involvement in junction regulation, NOS/NO also participates in controlling the levels of cytokines and hormones in the testes. On the other hand, NO is playing a unique role in modulating germ cell viability and development, and indirectly acting on some aspects of male infertility and testicular pathological conditions. Thus, NOS/NO bears an irreplaceable role in maintaining the homeostasis of the microenvironment in the seminiferous epithelium via its different downstream signaling pathways.

Inflammatory networks in the control of spermatogenesis : chronic inflammation in an immunologically privileged tissue?

Spermatogenesis is a complex, organized process involving intimate interactions between the developing germ cells and supporting Sertoli cells. The process is also highly regulated. Studies suggest that regulation in the seminiferous epithelium involves molecules normally associated with either immune or inflammatory processes; in particular, interleukin 1a (IL1a), IL6, tumor necrosis factor (TNFa), activin A and nitric oxide (NO). While there is considerable evidence that these inflammatory mediators have effects on spermatogonial and spermatocyte development as well as critical supportive functions of the Sertoli cells, which are undoubtedly of considerable importance during testicular inflammation, there remains some skepticism regarding the significance of these molecules with respect to normal testicular function. Nonetheless, it is evident that expression of these regulators varies across the cycle of the seminiferous epithelium in a consistent manner, with major changes in production coinciding with key events within the cycle. This review summarizes the evidence supporting the hypothesis that inflammatory cytokines play a role in normal testicular spermatogenesis, as well as in the etiology of inflammation induced sub-fertility. The balance of data leads to the striking conclusion that the cycle of the seminiferous epithelium resembles a chronic inflammatory event. This appears to be a somewhat paradoxical assertion, since the testis is an immunologically privileged tissue based on its well-established ability to support grafts with minimal rejection responses. However, it may be argued that local immunoregulatory mechanisms, which confer protection from immunity on both transplanted tissues and the developing spermatogenic cells, are equally necessary to prevent local inflammation responses associated with the spermatogenic process from activating the adaptive immune response.

cGMP and cGMP-dependent protein kinase in platelets and blood cells

Platelets are specialized adhesive cells that play a key role in normal and pathological hemostasis through their ability to rapidly adhere to subendothelial matrix proteins (platelet adhesion) and to other activated platelets (platelet aggregation). NO plays a crucial role in preventing platelet adhesion and aggregation. In platelets, cGMP synthesis is catalyzed by sGC, whereas PDE2, PDE3 and PDE5 are responsible for cGMP degradation. Stimulation of cGK by cGMP leads to phosphorylation of multiple target substrates. These substrates inhibit elevation of intracellular calcium, integrin activation, cytoskeletal reorganization, and platelet granule secretion, events normally associated with platelet activation. The NO/cGMP pathway also plays a significant role in many other blood cell types in addition to platelets. In leukocytes, depending on the specific cell type, cGMP signaling regulates gene expression, differentiation, migration, cytokine production, and apoptosis.

Role of nitric oxide signaling components in differentiation of embryonic stem cells into myocardial cells

Nitric oxide (NO) is involved in number of physiological and pathological events. Our previous studies demonstrated a differential expression of NO signaling components in mouse and human ES cells. Here, we demonstrate the effect of NO donors and soluble guanylyl cyclase (sGC) activators in differentiation of ES cells into myocardial cells. Our results with mouse and human ES cells demonstrate an increase in Nkx2.5 and myosin light chain (MLC2) mRNA expression on exposure of cells to NO donors and a decrease in mRNA expression of both cardiac-specific genes with nonspecific NOS inhibitor and a concomitant increase and decrease in the mRNA levels of sGC alpha(1) subunit. Although sGC activators alone exhibited an increase in mRNA expression of cardiac genes (MLC2 and Nkx2.5), robust inductions of mRNA and protein expression of marker genes were observed when NO donors and sGC activators were combined. Measurement of NO metabolites revealed an increase in the nitrite levels in the conditioned media and cell lysates on exposure of cells to the different concentrations of NO donors. cGMP analysis in undifferentiated stem cells revealed a lack of stimulation with NO donors. Differentiated cells however, acquired the ability to be stimulated by NO donors. Although, 3-(4-amino-5-cyclopropylpyrimidin-2-yl)-1-(2-fluorobenzyl)-1H-pyrazolo [3,4-b]pyridine (BAY 41-2272) alone was able to stimulate cGMP accumulation, the combination of NO donors and BAY 41-2272 stimulated cGMP levels more than either of the agents separately. These studies demonstrate that cGMP-mediated NO signaling plays an important role in the differentiation of ES cells into myocardial cells.

Oxidation of guanine by carbonate radicals derived from photolysis of carbonatotetramminecobalt(III) complexes and the pH dependence of intrastrand DNA cross-links mediated by guanine radical reactions

The carbonate radical anion CO(3)(*-) is a decomposition product of nitrosoperoxycarbonate derived from the combination of carbon dioxide and peroxynitrite, an important biological byproduct of the inflammatory response. The selective oxidation of guanine in DNA by CO(3)(*-) radicals is known to yield spiroiminodihydantoin (Sp) and guanidinohydantoin (Gh) products, and also a novel intrastrand cross-linked product: 5'-d(CCATCG*CT*ACC), featuring a linkage between guanine C8 (G*) and thymine N3 (T*) atoms in the oligonucleotide (Crean et al., Nucleic Acids Res. 2008, 36, 742-755). Involvement of the T-N3 (pK(a) of N3-H is 9.67) suggests that the formation of 5'-d(CCATCG*CT*ACC) might be pH-dependent. This hypothesis was tested by generating CO(3)(*-) radicals through the photodissociation of carbonatotetramminecobalt(III) complexes by steady-state UV irradiation, which allowed for studies of product yields in the pH 5.0-10.0 range. The yield of 5'-d(CCATCG*CT*ACC) at pH 10.0 is approximately 45 times greater than at pH 5.0; this is consistent with the proposed mechanism, which requires N3(H) thymine proton dissociation followed by nucleophilic addition to the C8 guanine radical.

Morphological and physiological study of the cardiac NOS/NO system in the Antarctic (Hb-/Mb-) icefish Chaenocephalus aceratus and in the red-blooded Trematomus bernacchii

The nitric oxide synthase (NOS)/nitric oxide (NO) system integrates cellular biochemical machinery and energetics. In heart microenvironment, dynamic NO behaviour depends upon the presence of superoxide anions, haemoglobin (Hb), and myoglobin (Mb), being hemoproteins are major players disarming NO bioactivity. The Antarctic icefish, which lack Hb and, in some species, also cardiac Mb, represent a unique model for exploring Hb and Mb impact on NOS/NO function. We report in the (Hb(-)/Mb(-)) icefish Chaenocephalus aceratus the presence of cardiac NOSs activity (NADPH-diaphorase) and endothelial NOS (eNOS)/inducible NOS (iNOS) zonal immuno-localization in the myocardium. eNOS is localized on endocardium and, to a lesser extent, in myocardiocytes, while iNOS is localized exclusively in myocardiocytes. Confronting eNOS and iNOS expression in Trematomus bernacchii (Hb(+)/Mb(+)), C. hamatus (Hb(-)/Mb(+)) and C. aceratus (Hb(-)/Mb(-)) is evident a lower expression in the Mb-less icefish. NO signaling was analyzed using isolated working heart preparations. In T. bernacchii, L-arginine and exogenous (SIN-1) NO donor dose-dependently decreased stroke volume, indicating decreased inotropism. L-arginine-induced inotropism was NOSs-dependent, being abolished by NOSs-inhibitor NG-monomethyl-L-arginine (L-NMMA). A SIN-1-induced negative inotropism was found in presence of SOD. NOS inhibition by L-N5-N-iminoethyl-L-ornithine (L-NIO) and L-NMMA confirmed the NO-mediated negative inotropic influence on cardiac performance. In contrast, in C. aceratus, L-arginine elicited a positive inotropism. SIN-1 induced a negative inotropism, which disappeared in presence of SOD, indicating peroxynitrite involvement. Cardiac performance was unaffected by L-NIO and L-NIL. NO signaling acted via a cGMP-independent mechanism. This high conservation degree of NOS localization pattern and signaling highlights its importance for cardiac biology.

Mobilisation of Ca2+ stores and flagellar regulation in human sperm by S-nitrosylation: a role for NO synthesised in the female reproductive tract

Generation of NO by nitric oxide synthase (NOS) is implicated in gamete interaction and fertilisation. Exposure of human spermatozoa to NO donors caused mobilisation of stored Ca(2+) by a mechanism that did not require activation of guanylate cyclase but was mimicked by S-nitroso-glutathione (GSNO; an S-nitrosylating agent). Application of dithiothreitol, to reduce protein -SNO groups, rapidly reversed the actions of NO and GSNO on [Ca(2+)](i). The effects of NO, GSNO and dithiothreitol on sperm protein S-nitrosylation, assessed using the biotin switch method, closely paralleled their actions on [Ca(2+)](i). Immunofluorescent staining revealed constitutive and inducible NOS in human oviduct and cumulus (the cellular layer investing the oocyte). 4,5-diaminofluorescein (DAF) staining demonstrated production of NO by these tissues. Incubation of human sperm with oviduct explants induced sperm protein S-nitrosylation resembling that induced by NO donors and GSNO. Progesterone (a product of cumulus cells) also mobilises stored Ca(2+) in human sperm. Pre-treatment of sperm with NO greatly enhanced the effect of progesterone on [Ca(2+)](i), resulting in a prolonged increase in flagellar excursion. We conclude that NO regulates mobilisation of stored Ca(2+) in human sperm by protein S-nitrosylation, that this action is synergistic with that of progesterone and that this synergism is potentially highly significant in gamete interactions leading to fertilisation.

Novel therapies for cyclic GMP control of vascular smooth muscle growth

Cyclic GMP, guanosine 3',5'-cyclic monophosphate, is a critical and multifunctional second-messenger molecule that mediates diverse physiological and pathophysiological functions in cardiac and vascular tissues. Synthesized through nitric oxide, carbon monoxide, and/or natriuretic peptide-mediated guanylate cyclase stimulation and guanosine triphosphate dephosphorylation, cyclic GMP is capable of stimulating a cascade of serine/threonine kinase events, including signaling through cyclic GMP- and/or cyclic AMP-dependent protein kinases, eliciting protein kinase-independent actions such as modulation of ion channels or transporters, or undergoing hydrolytic degradation through actions of cyclic GMP-regulated phosphodiesterases. Substrates, enzymes, cofactors, and associated variables in this multifaceted system have historically been targets of vital pharmacotherapies with perhaps most common the use of vascular smooth muscle-targeting organonitrates in cardiac patients and phosphodiesterase inhibitors in individuals with erectile dysfunction. Accumulating basic science and clinical evidence, however, suggests that cyclic GMP signaling is compromised under conditions of disease or elevated physiological stresses. Moreover, nitric oxide can stimulate an array of cytotoxic effects and nitric oxide-based therapies can be limited by diminished bioactivity and the development of tachyphylaxis or tolerance after prolonged use. Consequently, an emerging area for clinical drug development and therapeutic drug evaluation for conditions of cardiovascular adversity has focused on identification of cyclic GMP signaling pathways that act under oxidized or nitric oxide-unresponsive conditions and/or that operate irrespective of nitric oxide-induced complications. The aim of this therapeutic review is to describe novel, nitric oxide-alternate avenues for cyclic GMP signaling in vascular smooth muscle growth with particular emphasis on pharmacotherapeutics of recently characterized cyclic GMP-specific approaches.

Base excision repair of oxidative DNA damage and association with cancer and aging

Aging has been associated with damage accumulation in the genome and with increased cancer incidence. Reactive oxygen species (ROS) are produced from endogenous sources, most notably the oxidative metabolism in the mitochondria, and from exogenous sources, such as ionizing radiation. ROS attack DNA readily, generating a variety of DNA lesions, such as oxidized bases and strand breaks. If not properly removed, DNA damage can be potentially devastating to normal cell physiology, leading to mutagenesis and/or cell death, especially in the case of cytotoxic lesions that block the progression of DNA/RNA polymerases. Damage-induced mutagenesis has been linked to various malignancies. The major mechanism that cells use to repair oxidative damage lesions, such as 8-hydroxyguanine, formamidopyrimidines, and 5-hydroxyuracil, is base excision repair (BER). The BER pathway in the nucleus is well elucidated. More recently, BER was shown to also exist in the mitochondria. Here, we review the association of BER of oxidative DNA damage with aging, cancer and other diseases.

cGMP produced by NO-sensitive guanylyl cyclase essentially contributes to inflammatory and neuropathic pain by using targets different from cGMP-dependent protein kinase I

A large body of evidence indicates that the release of nitric oxide (NO) is crucial for the central sensitization of pain pathways during both inflammatory and neuropathic pain. Here, we investigated the distribution of NO-sensitive guanylyl cyclase (NO-GC) in the spinal cord and in dorsal root ganglia, and we characterized the nociceptive behavior of mice deficient in NO-GC (GC-KO mice). We show that NO-GC is distinctly expressed in neurons of the mouse dorsal horn, whereas its distribution in dorsal root ganglia is restricted to non-neuronal cells. GC-KO mice exhibited a considerably reduced nociceptive behavior in models of inflammatory or neuropathic pain, but their responses to acute pain were not impaired. Moreover, GC-KO mice failed to develop pain sensitization induced by intrathecal administration of drugs releasing NO or carbon monoxide. Surprisingly, during spinal nociceptive processing, cGMP produced by NO-GC may activate signaling pathways different from cGMP-dependent protein kinase I (cGKI), whereas cGKI can be activated by natriuretic peptide receptor-B dependent cGMP production. Together, our results provide evidence that NO-GC is crucially involved in the central sensitization of pain pathways during inflammatory and neuropathic pain.

Jejunal cholinergic, nitrergic, and soluble guanylate cyclase activity in postoperative ileus

BACKGROUND

In animal models of postoperative ileus (POI), inflammation of the intestine plays an important role in the pathogenesis of POI. Changes in alpha(2)-adrenoceptors and nitrergic regulation have been proposed to be implicated. The aim of our study was to investigate the presynaptic alpha(2)-receptor-mediated control of cholinergic nerve activity, the nitrergic nerve activity, and the possible role of soluble guanylate cyclase (sGC) during the inflammatory phase of POI.

METHODS

Ileus was induced by anesthesia and manipulation of the rat jejunum. Rats were treated with the sGC inhibitors methylene blue or ODQ; nonoperated animals served as controls. After 24 h, plasma and jejunal tissue were collected for biochemical assays, nitric oxide synthase-1 (NOS-1)-immunohistochemistry, acetylcholine (Ach)-release experiments, and muscle tension experiments.

RESULTS

In all operated animal groups, myeloperoxidase activity was significantly increased, which indicates initiation of an inflammatory response. The alpha(2)-adrenoceptor agonist UK14,304 reduced electrically induced Ach-release similarly in operated and nonoperated animals. In strips of operated animals, electrically induced nitrergic relaxations were decreased, whereas relaxations induced by exogenous nitric oxide (NO) remained unchanged compared with control. The number of myenteric neurons and the percentage of NOS-1-positive neurons were not influenced. Plasmatic cyclic guanosine monophosphate (cGMP) levels were decreased in all operated groups, whereas jejunal cGMP levels were unchanged compared with nonoperated controls; treatment with sGC inhibitors did not reduce plasmatic cGMP levels.

CONCLUSIONS

This study demonstrates that presynaptic alpha(2)-receptor mediated control of intestinal cholinergic nerve activity is unchanged during manipulation-induced inflammation. However, this inflammation induces impaired nitrergic neurotransmission related to decreased NOS-1 activity in the nitrergic nerves.

Activation of inducible NOS in peripheral vessels and outcomes in heart failure patients

BACKGROUND

Activation of inducible nitric oxide synthase (iNOS) has been reported in congestive heart failure (CHF) conditions. However, it is unknown whether activation of iNOS affects prognosis of CHF patients. We prospectively studied the influence of activation of iNOS in the forearm on the outcome of CHF patients.

METHODS AND RESULTS

Forearm blood flow (FBF) responses to 3 doses of acetylcholine (ACh) and nitroglycerin (NTG), and 4 doses of a selective iNOS inhibitor (aminoguanidine: Amn) and a nonselective NOS inhibitor (L-NMMA) were examined using plethysmography in 68 patients with CHF from idiopathic dilated cardiomyopathy. Plasma brain natriuretic peptide (BNP) and tumor necrosis factor-alpha (TNF-alpha) were also measured in all patients. During the mean follow-up period of 3.8 years, 25 patients were hospitalized for worsening heart failure and 9 of these patients died. Patients with adverse events had a diminished vasodilator response to ACh (P < .001) compared to patients without adverse events. Amn significantly decreased FBF (P < .001) in patients with adverse events, but not in patients without adverse events. FBF responses to NTG and L-NMMA were not significantly different between the 2 groups. When grouped by maximum FBF responses to each drug above and below the median value, multivariate Cox proportional hazards model analyses for cardiac event showed a significance in the FBF response to Amn (adjusted hazard ratio 5.89, P < .001). FBF responses to maximum dose of Amn significantly correlated with BNP and TNF-alpha levels (both P < .001).

CONCLUSIONS

CHF patients with vascular iNOS activation, as demonstrated by a greater vasoconstrictor response to Amn, had poor outcomes. Activation of iNOS in peripheral vessels, associated with proinflammatory cytokines in accordance to the severity of heart failure, is a marker for, or contributes to, adverse events in patients with CHF.

Nitric oxide induces aspects of egg-laying behavior in Aplysia

Aplysia egg laying is a complex behavior requiring synchronized activity in many organs. Aspects of the behavior are synchronized viathe direct effects of peptide bag cell neurohormones and via stimuli arising during the behavior. Stimuli synchronizing egg laying were examined by treating A. fasciata with a nitric oxide (NO) donor. NO elicited normal appetitive and consummatory behaviors leading to the deposition of cordons containing egg capsules without eggs. The sites at which NO acts were investigated. The latency to egg deposition in response to a NO donor was shorter than that in response to other stimuli, consistent with NO acting at downstream sites from those affected by the other stimuli. The NO donor does not act on neurons in the head ganglia presynaptic to the bag cells or on the bag cells. Ligating the small hermaphroditic duct connecting the gonad to the accessory genital mass blocked egg laying in response to bag cell homogenates,but not in response to exogenous NO, indicating that NO does not act on the gonad. NO is released by transport of eggs along the small hermaphroditic duct, and NO directly acts on the accessory genital mass which packages eggs. NO also acts at a second site, independent of the effect on the accessory genital mass. A NO donor activates appetitive behaviors that normally precede egg laying even in A. californica that are unable to lay eggs.

Viral loads of cerebrospinal fluid in infants with enterovirus meningitis

For a better understanding of the role of the viral load, free radicals, and cytokines in viral meningitis, we surveyed cerebrospinal fluid (CSF) obtained from patients below 1 year of age who showed positive for enterovirus. In their first examinations interleukin (IL)-6 and free radicals increased whereas pleocytosis was rarely observed. IL-6 decreased within the short period. Viral loads and free radicals increased simultaneously. IL-6 and free radicals of CSF are helpful for diagnosis and treatment of viral meningitis at an early stage.

Theoretical investigation of nitration and nitrosation of dimethylamine by N2O4

Reactive nitrogen oxygen species (RNOS) contribute to the deleterious effects attributed to reacting with biomolecules. The mechanisms of the nitration and nitrosation of dimethylamine (DMA), which is the simplest secondary amine by N2O4, a member of RNOS, have been investigated at the CBS-QB3 level of theory. The nitration and nitrosation proceed via different pathways. The nitration of DMA follows three pathways. The first is the abstraction of the hydrogen atom of the amino group of DMA by the NO2 radical followed by a recombination reaction of the resulting aminyl radical with another NO2 radical. The second is DMA directly reacting with symmetrical O2NNO2 leading to dimethylnitramine via a concerted and a stepwise mechanism. The third is the reaction of DMA with asymmetrical ONONO2. By computation, the main pathway for the formation of dimethylnitramine in the gas phase is by DMA directly reacting with asymmetrical ONONO2. As to the nitrosation, a concerted mechanism for the reaction of DMA with asymmetrical ONONO2 plays a major role in nitrosodimethylamine (NDMA) formation. In addition, the solvent effect on these nitration and nitrosation reactions has been also studied by using the implicit polarizable continuum model. Two major pathways of the formation of dimethylnitramine in water were found, and they are the radical process involving NO2 and the concerted mechanism starting from symmetrical O2NNO2. The result of the nitrosation of DMA in water is consistent with that in the gas phase. Comparison of the energy barriers of each mechanism leads to the conclusion that the nitrosation is more favorable than the nitration in the reaction of DMA with N2O4. This conclusion is in good agreement with the experimental results. The results obtained here will help elucidate the mechanism of the lesions of biomolecules by RNOS.

Peroxiredoxin II expression and its association with oxidative stress and cell proliferation in human idiopathic pulmonary fibrosis

Oxidant burden has been suggested to be a contributor to the pathogenesis of idiopathic pulmonary fibrosis (IPF). The study focused on peroxiredoxin (Prx) II, an antioxidant that has been associated with platelet-derived growth factor (PDGF) signaling and consequent cell proliferation. Localization and expression of Prx II, PDGF receptors (PDGFRalpha, PDGFRbeta), Ki67, and nitrotyrosine were assessed in control (n=10) and IPF/usual interstitial pneumonia (UIP) (n=10) lung biopsies by immunohistochemistry and morphometry. Prx II oxidation was determined by standard and non-reducing Western blots, two-dimensional gel electrophoresis, and mass spectrometry. Prx II localized in the IPF/UIP epithelium and alveolar macrophages. Prx II-positive area in the fibroblastic foci (FF) was smaller than in other parenchymal areas (p=0.03) or in the hyperplastic epithelium (p=0.01). There was no major Prx II oxidation in IPF/UIP compared with the normal lung. The FF showed only minor immunoreactivity to the PDGFRs; Ki67, a marker of cell proliferation; and nitrotyrosine, a marker of oxidative/nitrosative stress. The results suggest that Prx II oxidation does not relate to the pathogenesis of IPF/UIP and that Prx II, PDGFRs, and proliferating cells colocalize in the IPF/UIP lung. Unexpectedly, FF represented areas of low cell proliferation.

Exercise training improves relaxation response and SOD-1 expression in aortic and mesenteric rings from high caloric diet-fed rats

Background

Obesity has been associated with a variety of disease such as type II diabetes mellitus, arterial hypertension and atherosclerosis. Evidences have shown that exercise training promotes beneficial effects on these disorders, but the underlying mechanisms are not fully understood. The aim of this study was to investigate whether physical preconditioning prevents the deleterious effect of high caloric diet in vascular reactivity of rat aortic and mesenteric rings.

Methods

Male Wistar rats were divided into sedentary (SD); trained (TR); sedentary diet (SDD) and trained diet (TRD) groups. Run training (RT) was performed in sessions of 60 min, 5 days/week for 12 weeks (70–80% VO_2max). Triglycerides, glucose, insulin and nitrite/nitrate concentrations (NO_x^-) were measured. Concentration-response curves to acetylcholine (ACh) and sodium nitroprusside (SNP) were obtained. Expression of Cu/Zn superoxide dismutase (SOD-1) was assessed by Western blotting.

Results

High caloric diet increased triglycerides concentration (SDD: 216 ± 25 mg/dl) and exercise training restored to the baseline value (TRD: 89 ± 9 mg/dl). Physical preconditioning significantly reduced insulin levels in both groups (TR: 0.54 ± 0.1 and TRD: 1.24 ± 0.3 ng/ml) as compared to sedentary animals (SD: 0.87 ± 0.1 and SDD: 2.57 ± 0.3 ng/ml). On the other hand, glucose concentration was slightly increased by high caloric diet, and RT did not modify this parameter (SD: 126 ± 6; TR: 140 ± 8; SDD: 156 ± 8 and TRD 153 ± 9 mg/dl). Neither high caloric diet nor RT modified NO_x^- levels (SD: 27 ± 4; TR: 28 ± 6; SDD: 27 ± 3 and TRD: 30 ± 2 μM). Functional assays showed that high caloric diet impaired the relaxing response to ACh in mesenteric (about 13%), but not in aortic rings. RT improved the relaxing responses to ACh either in aortic (28%, for TR and 16%, to TRD groups) or mesenteric rings (10%, for TR and 17%, to TRD groups) that was accompanied by up-regulation of SOD-1 expression and reduction in triglycerides levels.

Conclusion

The improvement in endothelial function by physical preconditioning in mesenteric and aortic arteries from high caloric fed-rats was directly related to an increase in NO bioavailability to the smooth muscle mostly due to SOD-1 up regulation.

Characterization of the human alpha1 beta1 soluble guanylyl cyclase promoter: key role for NF-kappaB(p50) and CCAAT-binding factors in regulating expression of the nitric oxide receptor

Soluble guanylyl cyclase (sGC) is the principal receptor for NO and plays a ubiquitous role in regulating cellular function. This is exemplified in the cardiovascular system where sGC governs smooth muscle tone and growth, vascular permeability, leukocyte flux, and platelet aggregation. As a consequence, aberrant NO-sGC signaling has been linked to diseases including hypertension, atherosclerosis, and stroke. Despite these key (patho)physiological roles, little is known about the expressional regulation of sGC. To address this deficit, we have characterized the promoter activity of human α₁ and β₁ sGC genes in a cell type relevant to cardiovascular (patho)physiology, primary human aortic smooth muscle cells. Luciferase reporter constructs revealed that the 0.3- and 0.5-kb regions upstream of the transcription start sites were optimal for α₁ and β₁ sGC promoter activity, respectively. Deletion of consensus sites for c-Myb, GAGA, NFAT, NF-κB(p50), and CCAAT-binding factor(s) (CCAAT-BF) revealed that these are the principal transcription factors regulating basal sGC expression. In addition, under pro-inflammatory conditions, the effects of the strongest α₁ and β₁ sGC repressors were enhanced, and enzyme expression and activity were reduced; in particular, NF-κB(p50) is pivotal in regulating enzyme expression under such conditions. NO itself also elicited a cGMP-independent negative feedback effect on sGC promoter activity that is mediated, in part, via CCAAT-BF activity. In sum, these data provide a systematic characterization of the promoter activity of human sGC α₁ and β₁ subunits and identify key transcription factors that govern subunit expression under basal and pro-inflammatory (i.e. atherogenic) conditions and in the presence of ligand NO.

Post-translational modifications induced by nitric oxide (NO): implication in cancer cells apoptosis

Post-translational modifications of proteins can regulate the balance between survival and cell death signals. It is increasingly recognized that nitric oxide (NO) and reactive oxygen species (ROS)-induced post-translational modifications could play a role in cell death. This review provides an introduction of current knowledge of NO proteins modifications promoting or inhibiting cell death with special attention in cancer cells.

Reactive oxygen species induce signals that lead to apoptotic DNA degradation in primary CD4+ T cells

Reactive oxygen species are toxic to cells but they may also have active roles in transducing apoptotic events. To study the role of reactive oxygen species in growth factor depletion induced apoptosis of human primary CD4+ T cells, we used a synthetic manganese porphyrin superoxide dismutase mimetic to detoxify superoxide anions formed during apoptosis. Apoptosis of primary CD4+ T cells was characterized by generation of superoxide anions, plasma membrane phosphatidyl-serine translocation, loss of mitochondrial membrane potential, activation of caspase 3, condensation of chromatin, as well as DNA degradation. The detoxification of superoxide anions did not influence plasma membrane phosphatidyl-serine translocation, or chromatin condensation, and only marginally inhibited the loss of mitochondrial membrane potential and the formation of DNA strand breaks. In contrast, the detoxification of superoxide anions significantly reduced caspase 3 activity and almost completely inhibited the apoptotic decrease in total cellular DNA content as measured by propidium iodide staining. Our results indicate that reactive oxygen anions induce signals leading to efficient DNA degradation after the initial formation of DNA strand breaks. Thus, reactive oxygen anions have active roles in signaling that lead to the apoptotic events.

cis- and trans-acting elements involved in regulation of norB (norZ), the gene encoding nitric oxide reductase in Neisseria gonorrhoeae

The ability of Neisseria gonorrhoeae to reduce nitric oxide (NO) may have important immunomodulatory effects on the host during infection. Therefore, a comprehensive understanding of the regulatory mechanism of the nitric oxide reductase gene (norB) needs to be elucidated. To accomplish this, we analysed the functional regions of the norB upstream region. The promoter contains an extended -10 motif (TGNTACAAT) that is required for high-level expression. Deletion and substitution analysis of the norB upstream region revealed that no sequence upstream of the -10 motif is involved in norB regulation under anaerobic conditions or in the presence of NO. However, replacement of a 29 bp inverted repeat sequence immediately downstream of the extended -10 motif gave high levels of aerobic expression of a norB : : lacZ fusion. Insertional inactivation of gonococcal nsrR, predicted to bind to this inverted repeat sequence, resulted in the loss of norB repression and eliminated NO induction capacity. Single-copy complementation of nsrR in trans restored regulation of both norB transcription and NorB activity by NO. In Escherichia coli, expression of a gonococcal nsrR gene repressed gonococcal norB; induction of norB occurred in the presence of exogenously added NO. NsrR also regulates aniA and dnrN, as well as its own expression. We also determined that Fur regulates norB by a novel indirect activation method, by preventing the binding of a gonococcal ArsR homologue, a second repressor whose putative binding site overlaps the Fur binding site.

Differential p38 mitogen-activated protein kinase-controlled hypophosphorylation of the retinoblastoma protein induced by nitric oxide in neuroblastoma cells

In this report we show that exogenous NO added to human neuroblastoma NB69 cells inhibits cell proliferation and downregulates the epidermal growth factor receptor (EGFR) and its downstream signaling pathways. These comprise the 3-phosphoinositide-dependent kinase 1/Akt/glycogen synthase kinase-3beta pathway, the mitogen-activated protein kinase (MAPK)/extracellular-regulated kinases 1 and 2 pathway, and the phospholipase Cgamma pathway. In contrast, NO enhances the EGFR-controlled p38MAPK pathway. We also show that NO enhances the activation of the cAMP-responsive element binding protein, a transcription factor controlled by p38MAPK, as demonstrated using 4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)1H-imidazole (SB202190), a p38MAPK inhibitor. These processes are accompanied by the NO-mediated hypophosphorylation of the retinoblastoma protein (pRb), preferentially at Ser795 compared to Ser780 and Ser807/811, and the downregulation of p27(KIP1), p21(CIP1/WAF1), and p16(INK4a), although NO downregulated p16(INK4a) only when the p38MAPK activity was suppressed. The p38MAPK pathway controls the phosphorylation status of pRb as SB202190 enhances the hypophosphorylation of pRb. We reverted the inhibitory action of NO on EGFR and pRb phosphorylation in living cells using cell-permeable reducing agents, which suggested that reversible S-nitrosation controls these proteins. Our results support the notion that NO negatively modulates the p38MAPK-controlled phosphorylation of pRb, inducing the subsequent arrest of the cell cycle at the G1/S transition.

Nitric oxide-induced phosphatidic acid accumulation: a role for phospholipases C and D in stomatal closure

Stomatal closure is regulated by a complex network of signalling events involving numerous intermediates, among them nitric oxide (NO). Little is known about the signalling events occurring downstream of NO. Previous studies have shown that NO modulates cytosolic calcium concentration and the activation of plasma membrane ion channels. Here we provide evidence that supports the involvement of the lipid second messenger phosphatidic acid (PA) in NO signalling during stomatal closure. PA levels in Vicia faba epidermal peels increased upon NO treatment to maximum levels within 30 min, subsequently decreasing to control levels at 60 min. PA can be generated via phospholipase D (PLD) or via phospholipase C (PLC) in concerted action with diacylglycerol kinase (DGK). Our results showed that NO-induced PA is produced via the activation of both pathways. NO-induced stomatal closure was blocked either when PLC or PLD activity was inhibited. We have shown that PLC- and PLD-derived PA represents a downstream component of NO signalling cascade during stomatal closure.

Modulation of acid-sensing ion channel activity by nitric oxide

Acid-sensing ion channels (ASICs) are a class of ion channels activated by extracellular protons and are believed to mediate the pain caused by tissue acidosis. Although ASICs have been widely studied, little is known about their regulation by inflammatory mediators. Here, we provide evidence that nitric oxide (NO) potentiates the activity of ASICs. Whole-cell patch-clamp recordings were performed on neonatal rat cultured dorsal root ganglion neurons and on ASIC isoforms expressed in CHO cells. The NO donor S-nitroso-N-acetylpenicillamine (SNAP) potentiates proton-gated currents in DRG neurons and proton-gated currents in CHO cells expressing each of the acid-sensitive ASIC subunits. Modulators of the cGMP/PKG pathway had no effect on the potentiation, but in excised patches from CHO cells expressing ASIC2a, the potentiation could be reversed by externally applied reducing agents. NO therefore has a direct external effect on the ASIC ion channel, probably through oxidization of cysteine residues. Complementary psychophysiological studies were performed using iontophoresis of acidic solutions through the skin of human volunteers. Topical application of the NO donor glyceryl trinitrate significantly increased acid-evoked pain but did not affect heat or mechanical pain thresholds. ASICs may therefore play an important role in the pain associated with metabolic stress and inflammation, where both tissue acidosis and a high level of NO are present.

Redox proteomics: basic principles and future perspectives for the detection of protein oxidation in plants

The production and scavenging of chemically reactive species, such as ROS/RNS, are central to a broad range of biotic and abiotic stress and physiological responses in plants. Among the techniques developed for the identification of oxidative stress-induced modifications on proteins, the so-called 'redox proteome', proteomics appears to be the best-suited approach. Oxidative or nitrosative stress leaves different footprints in the cell in the form of different oxidatively modified components and, using the redox proteome, it will be possible to decipher the potential roles played by ROS/RNS-induced modifications in stressed cells. The purpose of this review is to present an overview of the latest research endeavours in the field of plant redox proteomics to identify the role of post-translational modifications of proteins in developmental cell stress. All the strategies set up to analyse the different oxidized/nitrosated amino acids, as well as the different reactivities of ROS and RNS for different amino acids are revised and discussed. A growing body of evidence indicates that ROS/RNS-induced protein modifications may be of physiological significance, and that in some cellular stresses they may act causatively and not arise as a secondary consequence of cell damage. Thus, although previously the oxidative modification of proteins was thought to represent a detrimental process in which the modified proteins were irreversibly inactivated, it is now clear that, in plants, oxidatively/nitrosatively modified proteins can be specific and reversible, playing a key role in normal cell physiology. In this sense, redox proteomics will have a central role in the definition of redox molecular mechanisms associated with cellular stresses.

Airway biomarkers of the oxidant burden in asthma and chronic obstructive pulmonary disease: current and future perspectives

The pathogenesis of asthma and chronic obstructive pulmonary disease (COPD) has been claimed to be attributable to increased systemic and local oxidative stress. Detection of the oxidant burden and evaluation of their progression and phenotypes by oxidant biomarkers have proved challenging and difficult. A large number of asthmatics are cigarette smokers and smoke itself contains oxidants complicating further the use of oxidant biomarkers. One of the most widely used oxidant markers in asthma is exhaled nitric oxide (NO), which plays an important role in the pathogenesis of asthma and disease monitoring. Another oxidant marker that has been widely investigated in COPD is 8-isoprostane, but it is probably not capable of differentiating asthma from COPD, or even sensitive in the early assessment of these diseases. None of the current biomarkers have been shown to be better than exhaled NO in asthma. There is a need to identify new biomarkers for obstructive airway diseases, especially their differential diagnosis. A comprehensive evaluation of oxidant markers and their combinations will be presented in this review. In brief, it seems that additional analyses utilizing powerful tools such as genomics, metabolomics, lipidomics, and proteomics will be required to improve the specificity and sensitivity of the next generation of biomarkers.

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.

Oxidation of single-stranded oligonucleotides by carbonate radical anions: generating intrastrand cross-links between guanine and thymine bases separated by cytosines

The carbonate radical anion is a biologically important one-electron oxidant that can directly abstract an electron from guanine, the most easily oxidizable DNA base. Oxidation of the 5'-d(CCTACGCTACC) sequence by photochemically generated CO3*- radicals in low steady-state concentrations relevant to biological processes results in the formation of spiroiminodihydantoin diastereomers and a previously unknown lesion. The latter was excised from the oxidized oligonucleotides by enzymatic digestion with nuclease P1 and alkaline phosphatase and identified by LC-MS/MS as an unusual intrastrand cross-link between guanine and thymine. In order to further characterize the structure of this lesion, 5'-d(GpCpT) was exposed to CO3*- radicals, and the cyclic nature of the 5'-d(G*pCpT*) cross-link in which the guanine C8-atom is bound to the thymine N3-atom was confirmed by LC-MS/MS, 1D and 2D NMR studies. The effect of bridging C bases on the cross-link formation was studied in the series of 5'-d(GpC(n)pT) and 5'-d(TpC(n)pG) sequences with n = 0, 1, 2 and 3. Formation of the G*-T* cross-links is most efficient in the case of 5'-d(GpCpT). Cross-link formation (n = 0) was also observed in double-stranded DNA molecules derived from the self-complementary 5'-d(TTACGTACGTAA) sequence following exposure to CO3*- radicals and enzymatic excision of the 5'-d(G*pT*) product.

Life and death: metabolic rate, membrane composition, and life span of animals

Maximum life span differences among animal species exceed life span variation achieved by experimental manipulation by orders of magnitude. The differences in the characteristic maximum life span of species was initially proposed to be due to variation in mass-specific rate of metabolism. This is called the rate-of-living theory of aging and lies at the base of the oxidative-stress theory of aging, currently the most generally accepted explanation of aging. However, the rate-of-living theory of aging while helpful is not completely adequate in explaining the maximum life span. Recently, it has been discovered that the fatty acid composition of cell membranes varies systematically between species, and this underlies the variation in their metabolic rate. When combined with the fact that 1) the products of lipid peroxidation are powerful reactive molecular species, and 2) that fatty acids differ dramatically in their susceptibility to peroxidation, membrane fatty acid composition provides a mechanistic explanation of the variation in maximum life span among animal species. When the connection between metabolic rate and life span was first proposed a century ago, it was not known that membrane composition varies between species. Many of the exceptions to the rate-of-living theory appear explicable when the particular membrane fatty acid composition is considered for each case. Here we review the links between metabolic rate and maximum life span of mammals and birds as well as the linking role of membrane fatty acid composition in determining the maximum life span. The more limited information for ectothermic animals and treatments that extend life span (e.g., caloric restriction) are also reviewed.