Peroxynitrite-An ugly biofactor?

Potential Beneficial Role of Nitric Oxide in SARS-CoV-2 Infection: Beyond Spike-Binding Inhibition

SARS-CoV-2, the causative virus for the COVID-19 disease, uses its spike glycoprotein to bind to human ACE2 as a first step for viral entry into the cell. For this reason, great efforts have been made to find mechanisms that disrupt this interaction, avoiding the infection. Nitric oxide (NO) is a soluble endogenous gas with known antiviral and immunomodulatory properties. In this study, we aimed to test whether NO could inhibit the binding of the viral spike to ACE2 in human cells and its effects on ACE2 enzymatic activity. Our results show that ACE2 activity was decreased by the NO donors DETA-NONOate and GSNO and by the NO byproduct peroxynitrite. Furthermore, we found that DETA-NONOate could break the spike-ACE2 interaction using the spike from two different variants (Alpha and Gamma) and in two different human cell types. Moreover, the same result was obtained when using NO-producing murine macrophages, while no significant changes were observed in ACE2 expression or distribution within the cell. These results support that it is worth considering NO as a therapeutic agent for COVID-19, as previous reports have suggested.

Butyrate attenuates cold-induced hypertension via gut microbiota and activation of brown adipose tissue

OBJECTIVE

Chronic exposure to cold temperature is known to elevate blood pressure, leading to a condition known as cold-induced hypertension (CIH). Our previous research suggested correlations between alterations in gut microbiota, decrease in butyrate level, and the onset and progression of CIH. However, the role of butyrate in CIH and the underlying mechanisms need further investigation.

METHODS

We exposed Specific Pathogen Free (SPF) rats to continuous cold temperature (4 ± 1 °C) for 6 weeks to establish a CIH rat model. Rats were divided into different groups by dose and duration, and the rats under cold were administered with butyrate (0.5 or 1 g/kg/day) daily. We assessed hypertension-associated phenotypes, pathological morphological changes, and endocrine-related phenotypes of brown adipose tissue (BAT). The effects of butyrate on gut microbiota and intestinal content metabolism were evaluated by 16s RNA sequencing and non-targeted metabolomics, respectively.

RESULTS

The systolic blood pressure (SBP) of rats exposed to cold after supplemented with butyrate were significantly lower than that of the Cold group. Butyrate may increase the species, abundance, and diversity of gut microbiota in rats. Specifically, butyrate intervention enriched beneficial bacterial genera, such as Lactobacillaceae, and decreased the levels of harmful bacteria genera, such as Actinobacteriota and Erysipeiotrichaceae. Cold exposure significantly increased BAT cells and the number of mitochondria. After butyrate supplementation, the levels of peroxisome proliferator-activated receptor gamma coactivator 1a and fibroblast growth factor 21 in BAT were significantly elevated (P < 0.05), and the volume and number of lipid droplets increased. The levels of ANG II and high-density lipoprotein were elevated in the Cold group but decreased after butyrate supplementation.

CONCLUSION

Butyrate may attenuate blood pressure in CIH by promoting the growth of beneficial bacteria and the secretion of beneficial derived factors produced by BAT, thus alleviating the elevation of blood pressure induced by cold. This study demonstrates the anti-hypertensive effects of butyrate and its potential therapeutic mechanisms, offering novel insights to the prevention and treatment of CIH in populations living or working in cold environments.

Role of NO in Disease: Good, Bad or Ugly

This Special Issue of Biomedicines (https://www [...].

Mechanism of Peroxynitrite Interaction with Ferric M. tuberculosis Nitrobindin: A Computational Study

Nitrobindins (Nbs) are all-β-barrel heme proteins present along the evolutionary ladder. They display a highly solvent-exposed ferric heme group with the iron atom being coordinated by the proximal His residue and a water molecule at the distal position. Ferric nitrobindins (Nb(III)) play a role in the conversion of toxic peroxynitrite (ONOO-) to harmless nitrate, with the value of the second-order rate constant being similar to those of most heme proteins. The value of the second-order rate constant of Nbs increases as the pH decreases; this suggests that Nb(III) preferentially reacts with peroxynitrous acid (ONOOH), although ONOO- is more nucleophilic. In this work, we shed light on the molecular basis of the ONOO- and ONOOH reactivity of ferric Mycobacterium tuberculosis Nb (Mt-Nb(III)) by dissecting the ligand migration toward the active site, the water molecule release, and the ligand binding process by computer simulations. Classical molecular dynamics simulations were performed by employing a steered molecular dynamics approach and the Jarzynski equality to obtain ligand migration free energy profiles for both ONOO- and ONOOH. Our results indicate that ONOO- and ONOOH migration is almost unhindered, consistent with the exposed metal center of Mt-Nb(III). To further analyze the ligand binding process, we computed potential energy profiles for the displacement of the Fe(III)-coordinated water molecule using a hybrid QM/MM scheme at the DFT level and a nudged elastic band approach. These results indicate that ONOO- exhibits a much larger barrier for ligand displacement than ONOOH, suggesting that water displacement is assisted by protonation of the leaving group by the incoming ONOOH.

Mitochondrial Toxicant-Induced Neuronal Apoptosis in Parkinson's Disease: What We Know so Far

Parkinson's disease (PD) is one of the most common progressive neurodegenerative diseases caused by the loss of dopamine-producing neuronal cells in the region of substantia nigra pars compacta of the brain. During biological aging, neuronal cells slowly undergo degeneration, but the rate of cell death increases tremendously under some pathological conditions, leading to irreversible neurodegenerative diseases. By the time symptoms of PD usually appear, more than 50 to 60% of neuronal cells have already been destroyed. PD symptoms often start with tremors, followed by slow movement, stiffness, and postural imbalance. The etiology of PD is still unknown; however, besides genetics, several factors contribute to neurodegenerative disease, including exposure to pesticides, environmental chemicals, solvents, and heavy metals. Postmortem brain tissues of patients with PD show mitochondrial abnormalities, including dysfunction of the electron transport chain. Most chemicals present in our environment have been shown to target the mitochondria; remarkably, patients with PD show a mild deficiency in NADH dehydrogenase activity, signifying a possible link between PD and mitochondrial dysfunction. Inhibition of electron transport complexes generates free radicals that further attack the macromolecules leading to neuropathological conditions. Apart from that, oxidative stress also causes neuroinflammation-mediated neurodegeneration due to the activation of microglial cells. However, the mechanism that causes mitochondrial dysfunction, especially the electron transport chain, in the pathogenesis of PD remains unclear. This review discusses the recent updates and explains the possible mechanisms of mitochondrial toxicant-induced neuroinflammation and neurodegeneration in PD.

Activity-Based Fluorescent Probes Based on Hemicyanine for Biomedical Sensing

In recent years, fluorescent probes, as an analytical tool that can target and rapidly detect analytes, have been increasingly used for applications related to medical treatment, detection, and bioimaging. Researchers are interested in hemicyanine-based fluorescent probes because of their high quantum yield, tunable spectrum characteristics, absorption and emission in the near-infrared (NIR) region, and good photo-stability. The development of these dyes and their derivatives as NIR fluorescent probes for biological applications has advanced significantly in the last ten years. This review introduces processes for making hemicyanine dyes and the methodology for creating functional activity-based fluorescent probes. A variety of hemicyanine-based probes have been systematically developed for the detection of small biomolecules in various illnesses. Finally, the potential drawbacks of hemicyanine-based functional probes, and the prospects for future research and translation into clinical medicine, are also discussed. This study is intended to provide strategies for the development and design of novel fluorescence probes.

Visualization of DNA Damage and Protection by Atomic Force Microscopy in Liquid

DNA damage is closely related to cancer and many aging-related diseases. Peroxynitrite is a strong oxidant, thus a typical DNA damage agent, and is a major mediator of the inflammation-associated pathogenesis. For the first time, we directly visualized the process of DNA damage by peroxynitrite and DNA protection by ectoine via atomic force microscopy in liquid. We found that the persistence length of DNA decreases significantly by adding a small amount of peroxynitrite, but the observed DNA chains are still intact. Specifically, the persistence length of linear DNA in a low concentration of peroxynitrite (0 µM to 200 µM) solution decreases from about 47 nm to 4 nm. For circular plasmid DNA, we observed the enhanced superhelices of plasmid DNA due to the chain soften. When the concentration of peroxynitrite was above 300 µM, we observed the fragments of DNA. Interestingly, we also identified single-stranded DNAs during the damage process, which is also confirmed by ultraviolet spectroscopy. However, if we added 500 mM ectoine to the high concentration PN solution, almost no DNA fragments due to double strand breaks were observed because of the protection of ectoine. This protection is consistent with the similar effect for DNA damage caused by ionizing radiation and oxygenation. We ascribe DNA protection to the preferential hydration of ectoine.

A novel fast-response and highly selective AIEgen fluorescent probe for visualizing peroxynitrite in living cells, C. elegans and inflammatory mice

Most of the ONOO^- fluorescent probes have restricted applications because of their aggregation-caused quenching (ACQ) effect, long response time and low fluorescence enhancement. Herein, we developed a novel AIEgen fluorescent probe (PE-XY) based on a benzothiazole and quinolin scaffold with high sensitivity and selectivity for imaging of ONOO^-. The results indicated that probe PE-XY exhibited fast response towards ONOO^- with 2000-fold enhancement of fluorescence intensity ratio in vitro. Moreover, PE-XY exhibited a relatively high sensitivity (limit of detection: 8.58 nM), rapid response (<50 s), high fluorescence quantum yield (δ = 0.81) and excellent selectivity over other analytes towards ONOO^-in vitro. Furthermore, PE-XY was successfully applied to detect endogenous ONOO^- levels in living HeLa cells, C. elegans and inflammatory mice with low cytotoxicity. Overall, this work provided a novel fast-response and highly selective AIEgen fluorescent probe for real-time monitoring ONOO^- fluctuations in living systems.

Nitric oxide-inducing Genistein elicits apoptosis-like death via an intense SOS response in Escherichia coli

Increasing prevalence of multidrug-resistant untreatable infections has prompted researchers to trial alternative treatments such as a substitute for traditional antibiotics. This study endeavored to elucidate the antibacterial mechanism(s) of this isoflavone, via analysis of relationship between genistein and Escherichia coli. Furthermore, this investigation analyzed whether genistein generates nitric oxide (NO) in E. coli as NO contributes to cell death. RecA, an essential protein for the bacterial SOS response, was detected through western blot, and the activated caspases decreased without RecA. The results showed that the NO induced by genistein affected the bacterial DNA. Under conditions of acute DNA damage, an SOS response called apoptosis-like death occurred, affecting DNA repair. These results suggested that RecA was bacterial caspase-like protein. In addition, NO was toxic to the bacterial cells and induced dysfunction of the plasma membrane. Thus, membrane depolarization and phosphatidylserine exposure were observed similarly to eukaryotic apoptosis. In conclusion, the combined results demonstrated that the antibacterial mode of action(s) of genistein was a NO-induced apoptosis-like death, and the role of RecA suggested that it contributed to the SOS response of NO defense. KEY POINTS: • Genistein generates nitric oxide in E. coli. • Genistein exhibits intense SOS response in E. coli. • Genistein-induced NO causes apoptosis-like death in E. coli.

Structural and functional properties of Antarctic fish cytoglobins-1: Cold-reactivity in multi-ligand reactions

While the functions of the recently discovered cytoglobin, ubiquitously expressed in vertebrate tissues, remain uncertain, Antarctic fish provide unparalleled models to study novel protein traits that may arise from cold adaptation. We report here the spectral, ligand-binding and enzymatic properties (peroxynitrite isomerization, nitrite-reductase activity) of cytoglobin-1 from two Antarctic fish, Chaenocephalus aceratus and Dissostichus mawsoni, and present the crystal structure of D. mawsoni cytoglobin-1. The Antarctic cytoglobins-1 display high O₂ affinity, scarcely compatible with an O₂-supply role, a slow rate constant for nitrite-reductase activity, and do not catalyze peroxynitrite isomerization. Compared with mesophilic orthologues, the cold-adapted cytoglobins favor binding of exogenous ligands to the hexa-coordinated bis-histidyl species, a trait related to their higher rate constant for distal-His/heme-Fe dissociation relative to human cytoglobin. At the light of a remarkable 3D-structure conservation, the observed differences in ligand-binding kinetics may reflect Antarctic fish cytoglobin-1 specific features in the dynamics of the heme distal region and of protein matrix cavities, suggesting adaptation to functional requirements posed by the cold environment. Taken together, the biochemical and biophysical data presented suggest that in Antarctic fish, as in humans, cytoglobin-1 unlikely plays a role in O₂ transport, rather it may be involved in processes such as NO detoxification.

AND logic gate based fluorescence probe for simultaneous detection of peroxynitrite and hypochlorous acid

Hypochlorous acid (HOCl) and peroxynitrite (ONOO^-) are two of the most important reactive species and associated with various diseases in various physiological and pathological processes. Nonetheless, many of their roles are still vague due to the shortage of methods for simultaneously detecting HOCl and ONOO^-. Herein, three simple yet useful fluorogenic probes, LG-1, LG-2 and LG-3, have been fabricated with facile synthesis route and used to monitor the coexistence of HOCl and ONOO^- as AND-based logic gate fluorescent probe firstly. LG-1 and LG-2, which consists of 1,3-oxathiolane group and boronate group respectively, were designed to verify the capacity of monitoring HOCl and ONOO^- without interference from each other. The result showed that these two groups are perfect reaction sites of detecting HOCl and ONOO^- respectively via specific analyte-induced reactions. Hence, LG-3, which is attached by these two groups to suppress the fluorophore core, can response to HOCl and ONOO^- simultaneously without mutual interference and generate the significant time-dependent fluorescence enhancement. By investigating the absorption and fluorescence properties of LG-3 towards HOCl and ONOO^- individually and collectively, the result confirmed clearly that LG-3 has the capacity of monitoring the coexistence of HOCl and ONOO^-, which could act as a two-input AND-based logic gate fluorescent probe.

Ferric nitrosylated myoglobin catalyzes peroxynitrite scavenging

Myoglobin (Mb), generally taken as the molecular model of monomeric globular heme-proteins, is devoted: (i) to act as an intracellular oxygen reservoir, (ii) to transport oxygen from the sarcolemma to the mitochondria of vertebrate heart and red muscle cells, and (iii) to act as a scavenger of nitrogen and oxygen reactive species protecting mitochondrial respiration. Here, the first evidence of ^·NO inhibition of ferric Mb- (Mb(III)) mediated detoxification of peroxynitrite is reported, at pH 7.2 and 20.0 °C. ^·NO binds to Mb(III) with a simple equilibrium; the value of the second-order rate constant for Mb(III) nitrosylation (i.e., ^·NOk_on) is (6.8 ± 0.7) × 10⁴ M^-1 s^-1 and the value of the first-order rate constant for Mb(III)-NO denitrosylation (i.e., ^·NOk_off) is 3.1 ± 0.3 s^-1. The calculated value of the dissociation equilibrium constant for Mb(III)-NO complex formation (i.e., ^·NOk_off/^·NOk_on = (4.6 ± 0.7) × 10^-5 M) is virtually the same as that directly measured (i.e., ^·NOK = (3.8 ± 0.5) × 10^-5 M). In the absence of ^·NO, Mb(III) catalyzes the conversion of peroxynitrite to NO₃^-, the value of the second-order rate constant (i.e., ^Pk_on) being (1.9 ± 0.2) × 10⁴ M^-1 s^-1. However, in the presence of ^·NO, Mb(III)-mediated detoxification of peroxynitrite is only partially inhibited, underlying the possibility that also Mb(III)-NO is able to catalyze the peroxynitrite isomerization, though with a reduced rate (^Pk_on* = (2.8 ± 0.3) × 10³ M^-1 s^-1). These data expand the multiple roles of ^·NO in modulating heme-protein actions, envisaging a delicate balancing between peroxynitrite and ^·NO, which is modulated through the relative amount of Mb(III) and Mb(III)-NO.

Coumarin-based fluorescent probe for the rapid detection of peroxynitrite ‘AND’ biological thiols

A coumarin-based novel ‘AND’ logic fluorescent probe ROS-AHC has been developed for the simultaneous detection of ONOO⁻ and biological thiols. ROS-AHC was shown to exhibit only a very small fluorescence response upon addition of a single GSH or ONOO⁻ analyte. Exposure to both analytes, however, resulted in a significant fluorescence enhancement.

A coumarin-based novel ‘AND’ logic fluorescent probe ROS-AHC has been developed for the simultaneous detection of ONOO⁻ and biological thiols.

Novel Dimethylhydrazine-Derived Spirolactam Fluorescent Chemodosimeter for Tracing Basal Peroxynitrite in Live Cells and Zebrafish

The precise cellular function of peroxynitrite (ONOO^-) in biosystems remains elusive, primarily owing to being short of ultrasensitive techniques for monitoring its intracellular distribution. In this work, a novel rhodamine B cyclic 1,2-dimethylhydrazine fluorescent chemodosimeter RDMH-PN for highly specific and ultrasensitive monitoring of basal ONOO^- in biosystems was rationally designed. The fluorescence titration experiments demonstrated that RDMH-PN was capable of quantitatively detecting 0-100 nM ONOO^- (limit of detection = 0.68 nM). In addition, RDMH-PN has outstanding performances of ultrafast measurement, naked-eye detection, and preeminent selectivity toward ONOO^- to accurately detect intracellular basal ONOO^-. Finally, it has been confirmed that RDMH-PN could not only map the intracellular basal ONOO^- level by inhibition tests but also trace the fluctuations of endogenous and exogenous ONOO^- levels with diverse stimulations in live cells and zebrafish.

ESIPT-based fluorescence probe for the rapid detection of peroxynitrite 'AND' biological thiols

An ESIPT-based 'AND' logic fluorescence probe (GSH-ABAH) was developed for the simultaneous detection of ONOO- and biological thiols. GSH-ABAH was shown to have good cell permeability and with the addition of just SIN-1 (ONOO- donor) or GSH, no fluorescence response was observed in live cells. However, in the presence of both analytes GSH-ABAH could be used to image exogenous ONOO- 'AND' GSH added to RAW264.7 cells.

Lung Ischaemia-Reperfusion Injury: The Role of Reactive Oxygen Species

Lung ischaemia-reperfusion injury (LIRI) occurs in many lung diseases and during surgical procedures such as lung transplantation. The re-establishment of blood flow and oxygen delivery into the previously ischaemic lung exacerbates the ischaemic injury and leads to increased microvascular permeability and pulmonary vascular resistance as well as to vigorous activation of the immune response. These events initiate the irreversible damage of the lung with subsequent oedema formation that can result in systemic hypoxaemia and multi-organ failure. Alterations in the production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) have been suggested as crucial mediators of such responses during ischaemia-reperfusion in the lung. Among numerous potential sources of ROS/RNS within cells, nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, xanthine oxidases, nitric oxide synthases and mitochondria have been investigated during LIRI. Against this background, we aim to review here the extensive literature about the ROS-mediated cellular signalling during LIRI, as well as the effectiveness of antioxidants as treatment option for LIRI.

The development of a novel AND logic based fluorescence probe for the detection of peroxynitrite and GSH

We have developed a novel AND logic based fluorescence probe for the simultaneous detection of ONOO^– and GSH (GSH-PF3).

We have developed a novel AND logic based fluorescence probe for the simultaneous detection of ONOO^– and GSH (GSH-PF3). The GSH-PF3 probe was synthesised over three steps starting from commercially available fluorescein. The probe was constructed by attaching the GSH reactive motif, 2,4-dinitrobenzenesulfonyl, to the previously reported boronate fluorescence based probe, PF3. GSH-PF3 produced only a small fluorescence response towards the addition of GSH or ONOO^– separately. However, when the probe was exposed to both analytes, there was a significant (40-fold) fluorescence enhancement. GSH-PF3 demonstrated an excellent selectivity towards both GSH and ONOO^–. In cellular imaging experiments the probe was shown to be cell permeable with no ‘turn-on’ response observed for the addition of either GSH or ONOO^– separately. However, in the presence of both analytes, a clear fluorescence response was observed in live cells. GSH-PF3 was further able to monitor the co-existence of metabolically produced ONOO^– and GSH by exogenous stimulation.

Excited-state intramolecular proton-transfer (ESIPT) based fluorescence sensors and imaging agents

We review recent advances in the design and application of excited-state intramolecular proton-transfer (ESIPT) based fluorescent probes. These sensors and imaging agents (probes) are important in biology, physiology, pharmacology, and environmental science.

ESIPT-based ratiometric fluorescence probe for the intracellular imaging of peroxynitrite

In this work, we set out to develop an ER directed ESIPT-based ONOO⁻ ratiometric fluorescent probe (ABAH-LW).

Kininase 1 As a Preclinical Therapeutic Target for Kinin B1 Receptor in Insulin Resistance

Kinin B1 receptor (B1R) contributes to insulin resistance, an early event in type 2 diabetes, through the upregulation and activation of the inducible form of nitric oxide synthase (iNOS), pro-inflammatory cytokines and the oxidative stress. This study addresses the hypothesis that inhibition of kininase 1 (carboxypeptidase M, CPM), the key enzyme involved in the biosynthesis of B1R agonists, could exert the same beneficial effects to B1R antagonism in insulin resistance. Male Sprague-Dawley rats were made insulin resistant with a drinking solution containing 10% D-glucose for a period of 9 weeks. Control rats received tap water. During the last week, kininase 1 was blocked with Mergetpa (1 mg kg^-1 twice daily, s.c.) and the impact was determined on insulin resistance (HOMA index), metabolic hormone levels, oxidative stress and the expression of several markers of inflammation by western blot and qRT-PCR. Glucose-fed rats displayed hyperglycemia, hyperinsulinemia, hyperleptinemia, insulin resistance, hypertension, positive body weight gain, and enhanced expression of B1R, CPM, iNOS, and IL-1β in renal cortex, aorta and liver. Markers of oxidative stress (superoxide anion and nitrotyrosine expression) were also enhanced in aorta and renal cortex. Mergetpa reversed and normalized most of those alterations, but failed to affect leptin levels and hypertension. Pharmacological blockade of kininase 1 (CPM) exerted similar beneficial effects to a 1-week treatment with a B1R antagonist (SSR240612) or an iNOS inhibitor (1,400 W). These data reinforce the detrimental role of B1R in insulin resistance and recommend CPM as a new therapeutic target.

Long-wavelength fluorescent boronate probes for the detection and intracellular imaging of peroxynitrite

Two boronate fluorescent probes have been developed for the detection of peroxynitrite (TCFB1andTCFB2).

Cellular localisation of the kinin B1R in the pancreas of streptozotocin-treated rat and the anti-diabetic effect of the antagonist SSR240612

The mechanism by which kinin B1 receptor (B1R) contributes to type 1 diabetes is addressed by determining the impact of its inhibition on diabetes and on its pancreatic expression and cellular localisation on immunocompetent cells and primary sensory C-fibres. Rats were made diabetic with streptozotocin (STZ). On day 4, they were treated daily for 7 days with a B1R antagonist (SSR240612, 10 mg/kg) or its vehicle. The surviving β-cells were measured by immunostaining. The expression of B1R, iNOS, TNF-α, macrophages, TCD4+, CGRP and TRPV1 was measured by Western blotting, qRT-PCR and immunofluorescence. Macrophages and TCD4+ lymphocytes were absent in control, but distributed abundantly in the pancreas of STZ-diabetic rats. B1R was upregulated on these immune cells infiltrating the diabetic rat pancreas while it was not expressed on primary sensory C-fibres even if the expression of TRPV1 and CGRP was enhanced. SSR240612 prevented the infiltration of macrophages and TCD4+ lymphocytes and the upregulation of B1R, iNOS, TNF-α and TRPV1. SSR240612 corrected hyperglycaemia and hypoinsulinaemia by improving the Langerhans islets survival or regeneration. It is concluded that kinin B1R antagonism exerts anti-diabetic action by preventing the infiltration of immune cells in the pancreas and by preserving the integrity of Langerhans islets β-cells.

Visualizing peroxynitrite fluxes in endothelial cells reveals the dynamic progression of brain vascular injury

Accumulating evidence suggests that formation of peroxynitrite (ONOO(-)) in the cerebral vasculature contributes to the progression of ischemic damage, while the underlying molecular mechanisms remain elusive. To fully understand ONOO(-) biology, efficient tools that can realize the real-time tracing of endogenous ONOO(-) fluxes are indispensable. While a few ONOO(-) fluorescent probes have been reported, direct visualization of ONOO(-) fluxes in the cerebral vasculature of live mice remains a challenge. Herein, we present a fluorescent switch-on probe (NP3) for ONOO(-) imaging. NP3 exhibits good specificity, fast response, and high sensitivity toward ONOO(-) both in vitro and in vivo. Moreover, NP3 is two-photon excitable and readily blood-brain barrier penetrable. These desired photophysical and pharmacokinetic properties endow NP3 with the capability to monitor brain vascular ONOO(-) generation after injury with excellent temporal and spatial resolution. As a proof of concept, NP3 has enabled the direct visualization of neurovascular ONOO(-) formation in ischemia progression in live mouse brain by use of two-photon laser scanning microscopy. Due to these favorable properties, NP3 holds great promise for visualizing endogenous peroxynitrite fluxes in a variety of pathophysiological progressions in vitro and in vivo.

Fat deposition and accumulation in the damaged and inflamed skeletal muscle: cellular and molecular players

The skeletal muscle has the capacity to repair damage by the activation and differentiation of fiber sub-laminar satellite cells. Regeneration impairment due to reduced satellite cells number and/or functional capacity leads to fiber substitution with ectopic tissues including fat and fibrous tissue and to the loss of muscle functions. Muscle mesenchymal cells that in physiological conditions sustain or directly contribute to regeneration differentiate in adipocytes in patients with persistent damage and inflammation of the skeletal muscle. These cells comprise the fibro-adipogenic precursors, the PW1-expressing cells and some interstitial cells associated with vessels (pericytes, mesoangioblasts and myoendothelial cells). Resident fibroblasts that are responsible for collagen deposition and extracellular matrix remodeling during regeneration yield fibrotic tissue and can differentiate into adipose cells. Some authors have also proposed that satellite cells themselves could transdifferentiate into adipocytes, although recent results by lineage tracing techniques seem to put this theory to discussion. This review summarizes findings about muscle resident mesenchymal cell differentiation in adipocytes and recapitulates the molecular mediators involved in intramuscular adipose tissue deposition.

Anthracyclines/trastuzumab: new aspects of cardiotoxicity and molecular mechanisms

Anticancer drugs continue to cause significant reductions in left ventricular ejection fraction resulting in congestive heart failure. The best-known cardiotoxic agents are anthracyclines (ANTHs) such as doxorubicin (DOX). For several decades cardiotoxicity was almost exclusively associated with ANTHs, for which cumulative dose-related cardiac damage was the use-limiting step. Human epidermal growth factor (EGF) receptor 2 (HER2; ErbB2) has been identified as an important target for breast cancer. Trastuzumab (TRZ), a humanized anti-HER2 monoclonal antibody, is currently recommended as first-line treatment for patients with metastatic HER2(+) tumors. The use of TRZ may be limited by the development of drug intolerance, such as cardiac dysfunction. Cardiotoxicity has been attributed to free-iron-based, radical-induced oxidative stress. Many approaches have been promoted to minimize these serious side effects, but they are still clinically problematic. A new approach to personalized medicine for cancer that involves molecular screening for clinically relevant genomic alterations and genotype-targeted treatments is emerging.

Cardiolipin-cytochrome c complex: Switching cytochrome c from an electron-transfer shuttle to a myoglobin- and a peroxidase-like heme-protein

Cytochrome c (cytc) is a small heme-protein located in the space between the inner and the outer membrane of the mitochondrion that transfers electrons from cytc-reductase to cytc-oxidase. The hexa-coordinated heme-Fe atom of cytc displays a very low reactivity toward ligands and does not exhibit significant catalytic properties. However, upon cardiolipin (CL) binding, cytc achieves ligand binding and catalytic properties reminiscent of those of myoglobin and peroxidase. In particular, the peroxidase activity of the cardiolipin-cytochrome c complex (CL-cytc) is critical for the redistribution of CL from the inner to the outer mitochondrial membranes and is essential for the execution and completion of the apoptotic program. On the other hand, the capability of CL-cytc to bind NO and CO and the heme-Fe-based scavenging of reactive nitrogen and oxygen species may affect apoptosis. Here, the ligand binding and catalytic properties of CL-cytc are analyzed in parallel with those of CL-free cytc, myoglobin, and peroxidase to dissect the potential mechanisms of CL in modulating the pro- and anti-apoptotic actions of cytc.

Iron, oxidative stress, and redox signaling in the cardiovascular system

The redox state of the cell is predominantly dependent on an iron redox couple and is maintained within strict physiological limits. Iron is an essential metal for hemoglobin synthesis in erythrocytes, for oxidation-reduction reactions, and for cellular proliferation. The maintenance of stable iron concentrations requires the coordinated regulation of iron transport into plasma from dietary sources in the duodenum, from recycled senescent red cells in macrophages, and from storage in hepatocytes. The absorption of dietary iron, which is present in heme or nonheme form, is carried out by mature villus enterocytes of the duodenum and proximal jejunum. Multiple physiological processes are involved in maintaining iron homeostasis. These include its storage at the intracellular and extracellular level. Control of iron balance in the whole organism requires communication between sites of uptake, utilization, and storage. Key protein transporters and the molecules that regulate their activities have been identified. In this field, ferritins and hepcidin are the major regulator proteins. A variety of transcription factors may be activated depending on the level of oxidative stress, leading to the expression of different genes. Major preclinical and clinical trials have shown advances in iron-chelation therapy for the treatment of iron-overload disease as well as cardiovascular and chronic inflammatory diseases.

Oxidative stress and HPV carcinogenesis

Extensive experimental work has conclusively demonstrated that infection with certain types of human papillomaviruses, the so-called high-risk human papillomavirus (HR-HPV), represent a most powerful human carcinogen. However, neoplastic growth is a rare and inappropriate outcome in the natural history of HPV, and a number of other events have to concur in order to induce the viral infection into the (very rare) neoplastic transformation. From this perspective, a number of putative viral, host, and environmental co-factors have been proposed as potential candidates. Among them oxidative stress (OS) is an interesting candidate, yet comparatively underexplored. OS is a constant threat to aerobic organisms being generated during mitochondrial oxidative phosphorylation, as well as during inflammation, infections, ionizing irradiation, UV exposure, mechanical and chemical stresses. Epithelial tissues, the elective target for HPV infection, are heavily exposed to all named sources of OS. Two different types of cooperative mechanisms are presumed to occur between OS and HPV: I) The OS genotoxic activity and the HPV-induced genomic instability concur independently to the generation of the molecular damage necessary for the emergence of neoplastic clones. This first mode is merely a particular form of co-carcinogenesis; and II) OS specifically interacts with one or more molecular stages of neoplastic initiation and/or progression induced by the HPV infection. This manuscript was designed to summarize available data on this latter hypothesis. Experimental data and indirect evidences on promoting the activity of OS in viral infection and viral integration will be reviewed. The anti-apoptotic and pro-angiogenetic role of NO (nitric oxide) and iNOS (inducible nitric oxide synthase) will be discussed together with the OS/HPV cooperation in inducing cancer metabolism adaptation. Unexplored/underexplored aspects of the OS interplay with the HPV-driven carcinogenesis will be highlighted. The aim of this paper is to stimulate new areas of study and innovative approaches.

Mitochondria as a source and target of lipid peroxidation products in healthy and diseased heart

The heart is a highly oxidative organ in which cardiomyocyte turnover is virtually absent, making it particularly vulnerable to accumulation of lipid peroxidation products (LPP) formed as a result of oxidative damage. Reactive oxygen and nitrogen species are the most common electrophiles formed during lipid peroxidation and lead to the formation of both stable and unstable LPP. Of the LPP formed, highly reactive aldehydes are a well-recognized causative factor in ageing and age-associated diseases, including cardiovascular disease and diabetes. Recent studies have identified that the mitochondria are both a primary source and target of LPP, with specific emphasis on aldehydes in cardiomyocytes and how these affect the electron transport system and Ca(2+) balance. Numerous studies have found that there are functional consequences in the heart following exposure to specific aldehydes (acrolein, trans-2-hexanal, 4-hydroxynonenal and acetaldehyde). Because these LPP are known to form in heart failure, cardiac ischaemia-reperfusion injury and diabetes, they may have an underappreciated role in the pathophysiology of these disease processes. Lipid peroxidation products are involved in the transcriptional regulation of endogenous anti-oxidant systems. Recent evidence demonstrates that transient increases in LPP may be beneficial in cardioprotection by contributing to mitohormesis (i.e. induction of anti-oxidant systems) in cardiomyocytes. Thus, exploitation of the cardioprotective actions of the LPP may represent a novel therapeutic strategy for future treatment of heart disease.

Human serum albumin: from bench to bedside

Human serum albumin (HSA), the most abundant protein in plasma, is a monomeric multi-domain macromolecule, representing the main determinant of plasma oncotic pressure and the main modulator of fluid distribution between body compartments. HSA displays an extraordinary ligand binding capacity, providing a depot and carrier for many endogenous and exogenous compounds. Indeed, HSA represents the main carrier for fatty acids, affects pharmacokinetics of many drugs, provides the metabolic modification of some ligands, renders potential toxins harmless, accounts for most of the anti-oxidant capacity of human plasma, and displays (pseudo-)enzymatic properties. HSA is a valuable biomarker of many diseases, including cancer, rheumatoid arthritis, ischemia, post-menopausal obesity, severe acute graft-versus-host disease, and diseases that need monitoring of the glycemic control. Moreover, HSA is widely used clinically to treat several diseases, including hypovolemia, shock, burns, surgical blood loss, trauma, hemorrhage, cardiopulmonary bypass, acute respiratory distress syndrome, hemodialysis, acute liver failure, chronic liver disease, nutrition support, resuscitation, and hypoalbuminemia. Recently, biotechnological applications of HSA, including implantable biomaterials, surgical adhesives and sealants, biochromatography, ligand trapping, and fusion proteins, have been reported. Here, genetic, biochemical, biomedical, and biotechnological aspects of HSA are reviewed.

Pentoxifylline alleviates vascular impairment in insulin resistance via TNF-α inhibition

Deterioration of vascular reactivity plays a pivotal role in vascular complications. Pentoxifylline (PTX) is a well-tolerated drug used to treat vascular insufficiency. We investigated the protective effect of PTX against vascular impairment in insulin resistance. Insulin resistance was induced by fructose (10%) in drinking water while PTX was concurrently administered (50 mg/kg(-1)) for 8 weeks. Serum levels of glucose, insulin, tumor necrosis factor alpha (TNF-α) were determined. Isolated aorta reactivity to phenylephrine (PE), potassium chloride (KCl), and acetylcholine (ACh) was studied, as was nitric oxide (NO) generation and histopathology. Insulin resistance was accompanied with a significant elevation in serum TNF-α level, marked leukocytes infiltration, and endothelial pyknosis. PTX inhibited insulin resistance and prevented TNF-α elevation, leukocyte infiltration and endothelial pyknosis. Vascular dysfunction was evident in insulin resistance as increased vascular contractility to PE and decreased relaxation to ACh, whereas PTX protected against this dysfunction. Notably, in vitro incubation with TNF-α (1 ng/ml(-1)) increased contractility to PE and decreased relaxation to ACh while concomitant PTX (1 mM) incubation partially restored response to ACh but not to PE. Furthermore, TNF-α reduced ACh-induced NO generation, whereeas PTX restored it. In conclusion, PTX protects from the impairment in vascular reactivity in insulin resistance, by a mechanism involving TNF-α inhibition.

Analysis of the Aspergillus fumigatus proteome reveals metabolic changes and the activation of the pseurotin A biosynthesis gene cluster in response to hypoxia

The mold Aspergillus fumigatus is the most important airborne fungal pathogen. Adaptation to hypoxia represents an important virulence attribute for A. fumigatus. Therefore, we aimed at obtaining a comprehensive overview about this process on the proteome level. To ensure highly reproducible growth conditions, an oxygen-controlled, glucose-limited chemostat cultivation was established. Two-dimensional gel electrophoresis analysis of mycelial and mitochondrial proteins as well as two-dimensional Blue Native/SDS-gel separation of mitochondrial membrane proteins led to the identification of 117 proteins with an altered abundance under hypoxic in comparison to normoxic conditions. Hypoxia induced an increased activity of glycolysis, the TCA-cycle, respiration, and amino acid metabolism. Consistently, the cellular contents in heme, iron, copper, and zinc increased. Furthermore, hypoxia induced biosynthesis of the secondary metabolite pseurotin A as demonstrated at proteomic, transcriptional, and metabolite levels. The observed and so far not reported stimulation of the biosynthesis of a secondary metabolite by oxygen depletion may also affect the survival of A. fumigatus in hypoxic niches of the human host. Among the proteins so far not implicated in hypoxia adaptation, an NO-detoxifying flavohemoprotein was one of the most highly up-regulated proteins which indicates a link between hypoxia and the generation of nitrosative stress in A. fumigatus.

Aspergillus fumigatus is a ubiquitously distributed filamentous fungus and an important human pathogen. To colonize the human lung, A. fumigatus has to adapt to low oxygen concentrations. We analyzed the cytosolic and mitochondrial proteome of A. fumigatus under normoxic in comparison to hypoxic conditions using an oxygen-controlled chemostat. Hypoxia led to an increased respiratory capacity, induction of the biosynthesis of the secondary metabolite pseurotin A and presumably nitrosative stress.

Peroxynitrite mediates active site tyrosine nitration in manganese superoxide dismutase. Evidence of a role for the carbonate radical anion

Protein tyrosine nitration has been observed in a variety of human diseases associated with oxidative stress, such as inflammatory, neurodegenerative, and cardiovascular conditions. However, the pathways leading to nitration of tyrosine residues are still unclear. Recent studies have shown that peroxynitrite (PN), produced by the reaction of superoxide and nitric oxide, can lead to protein nitration and inactivation. Tyrosine nitration may also be mediated by nitrogen dioxide produced by the oxidation of nitrite by peroxidases. Manganese superoxide dismutase (MnSOD), which plays a critical role in cellular defense against oxidative stress by decomposing superoxide within mitochondria, is nitrated and inactivated under pathological conditions. In this study, MnSOD is shown to catalyze PN-mediated self-nitration. Direct, spectroscopic observation of the kinetics of PN decay and nitrotyrosine formation (k(cat) = 9.3 × 10(2) M(-1) s(-1)) indicates that the mechanism involves redox cycling between Mn(2+) and Mn(3+), similar to that observed with superoxide. Distinctive patterns of tyrosine nitration within MnSOD by various reagents were revealed and quantified by MS/MS analysis of MnSOD trypsin digest peptides. These analyses showed that three of the seven tyrosine residues of MnSOD (Tyr34, Tyr9, and Tyr11) were the most susceptible to nitration and that the relative amounts of nitration of these residues varied widely depending upon the nature of the nitrating agent. Notably, nitration mediated by PN, in both the presence and absence of CO2, resulted in nitration of the active site tyrosine, Tyr34, while nitration by freely diffusing nitrogen dioxide led to surface nitration at Tyr9 and Tyr11. Flux analysis of the nitration of Tyr34 by PN-CO2 showed that the nitration rate coincided with the kinetics of the reaction of PN with CO2. These kinetics and the 20-fold increase in the efficiency of tyrosine nitration in the presence of CO2 suggest a specific role for the carbonate radical anion (•CO3(-)) in MnSOD nitration by PN. We also observed that the nitration of Tyr34 caused inactivation of the enzyme, while nitration of Tyr9 and Tyr11 did not interfere with the superoxide dismutase activity. The loss of MnSOD activity upon Tyr34 nitration implies that the responsible reagent in vivo is peroxynitrite, acting either directly or through the action of •CO3(-).