Bioactive eicosanoids: Role of prostaglandin F2α and F2-isoprostanes in inflammation and oxidative stress related pathology

Oxidative stress and inflammation are supposed to be the key players of several acute and chronic diseases, and also for progressive aging process. Eicosanoids, especially prostaglandin F_2α (PGF_2α) and F₂-isoprostanes are endogenous compounds that are involved both in physiology and the above mentioned pathologies. These compounds are biosynthesized mainly from esterified arachidonic acid through both enzymatic and non-enzymatic free radical-catalysed reactions in vivo, respectively. They have shown to possess potent biological activities in addition to their application as biomarkers of oxidative stress and inflammation. Recent advancement of methodologies has made it possible to quantify these compounds more reliably and apply them in various in vivo studies successfully. Today, experimental and clinical studies have revealed that both PGF_2α and F₂-isoprostanes are involved in severe acute or chronic inflammatory conditions such as rheumatic diseases, asthma, risk factors of atherosclerosis, diabetes, ischemia-reperfusion, septic shock and many others. These evidences promote that assessment of bioactive PGF_2α and F₂-isoprostanes simultaneously in body fluids offers unique non-invasive analytical opportunity to study the function of these eicosanoids in physiology, oxidative stress-related and inflammatory diseases, and also in the determination of potency of various radical scavengers, anti-inflammatory compounds, drugs, antioxidants and diet.     

Isoprostanes and asthma

Isoprostanes are prostaglandin (PG)-like compounds generated in vivo following oxidative stress by non-enzymatic peroxidation of polyunsaturated fatty acids, including arachidonic acid. They are named based on their prostane ring structure and by the localization of hydroxyl groups on the carbon side chain; these structural differences result in a broad array of isoprostane molecules with varying biological properties. Generation of specific isoprostanes is also regulated by host cell redox conditions; reducing conditions favor F₂-isoprostane production while under conditions with deficient antioxidant capacity, D₂- and E₂-isoprostanes are formed. F₂-isoprostanes (F₂-isoP) are considered reliable markers of oxidative stress in pulmonary diseases including asthma. Importantly, F₂-isoP and other isoprostanes function as ligands for PG receptors, and potentially other receptors that have not yet been identified. They have been reported to have important biological properties in many organs. In the lung, isoprostanes regulate cellular processes affecting airway smooth muscle tone, neural secretion, epithelial ion flux, endothelial cell adhesion and permeability, and macrophage adhesion and function. In this review, we will summarize the evidence that F₂-isoP functions as a marker of oxidative stress in asthma, and that F₂-isoP and other isoprostanes exert biological effects that contribute to the pathogenesis of asthma. This article is part of a Special Issue entitled Biochemistry of Asthma.     

Imaging in vivo redox status in high spatial resolution with OMRI

Abstract

Redox-reactions are playing a significant role in regulation of homeostasis of organism. Disorder of the redox-status is related with the onset and/or propagation of oxidative diseases such as lifestyle-related diseases, including cancers and cardiac diseases, etc. In vivo imaging of redox-status is thereby important in the analysis of mechanisms of oxidative diseases and developments of new medicines for the diseases. Aminoxyl radicals are redox-sensitive reporter molecules, which lose their paramagnetic moiety by reactions of free radicals or reducing compounds. Electron spin resonance (ESR) technique has been used to measure the molecules in vivo. In vivo spatial resolution in ESR imaging is in the range of a few millimeters and is not sufficient for the detailed diagnosis of disease models. Overhauser enhanced MRI (OMRI) is an emerging free radical imaging technique, which utilised electron–proton coupling to image the distribution of free radicals. In vivo imaging of redox-status is applicable with OMRI/aminoxyl radical technique. The detailed imaging analysis was demonstrated in oxidative diseases, such as tumour-bearing, neurodegeneration or gastric ulcer models. The OMRI/aminoxyl radical technique has a large potential as a diagnostic system for biomedical applications in the future.     

Calcium-independent phospholipase A2γ (iPLA2γ) and its roles in cellular functions and diseases

Calcium-independent phospholipase A₂γ (iPLA₂γ)/patatin-like phospholipase domain-containing lipase 8 (PNPLA8) is one of the iPLA₂ enzymes, which do not require Ca²⁺ ion for their activity. iPLA₂γ is a membrane-bound enzyme with unique features, including the utilization of four distinct translation initiation sites and the presence of mitochondrial and peroxisomal localization signals. This enzyme is preferentially distributed in the mitochondria and peroxisomes and is thought to be responsible for the maintenance of lipid homeostasis in these organelles. Thus, both the overexpression and the deletion of iPLA₂γ in vivo caused mitochondrial abnormalities and dysfunction. Roles of iPLA₂γ in lipid mediator production and cytoprotection against oxidative stress have also been suggested by in vitro and in vivo studies. The dysregulation of iPLA₂γ can therefore be a critical factor in the development of many diseases, including metabolic diseases and cancer. In this review, we provide an overview of the biochemical properties of iPLA₂γ and then summarize the current understanding of the in vivo roles of iPLA₂γ revealed by knockout mouse studies.     

Significance of Antioxidant Potential of Plants and its Relevance to Therapeutic Applications

Oxidative stress has been identified as the root cause of the development and progression of several diseases. Supplementation of exogenous antioxidants or boosting endogenous antioxidant defenses of the body is a promising way of combating the undesirable effects of reactive oxygen species (ROS) induced oxidative damage. Plants have an innate ability to biosynthesize a wide range of non-enzymatic antioxidants capable of attenuating ROS- induced oxidative damage. Several in vitro methods have been used to screen plants for their antioxidant potential, and in most of these assays they revealed potent antioxidant activity. However, prior to confirming their in vivo therapeutic efficacy, plant antioxidants have to pass through several physiopharmacological processes. Consequently, the findings of in vitro and in vivo antioxidant potential assessment studies are not always the same. Nevertheless, the results of in vitro assays have been irrelevantly extrapolated to the therapeutic application of plant antioxidants without undertaking sufficient in vivo studies. Therefore, we have briefly reviewed the physiology and redox biology of both plants and humans to improve our understanding of plant antioxidants as therapeutic entities. The applications and limitations of antioxidant activity measurement assays were also highlighted to identify the precise path to be followed for future research in the area of plant antioxidants.     

The roles of strawberry and honey phytochemicals on human health: A possible clue on the molecular mechanisms involved in the prevention of oxidative stress and inflammation

BackgroundOxidative stress and inflammation contribute to the etiopathogenesis of several human chronic diseases, such as cancer, diabetes, cardiovascular diseases and metabolic syndrome. Besides classic stimuli, such as reactive oxidant species, endotoxins (i.e., bacteria lipopolysaccharide), cytokines or carcinogens, oxidative stress and inflammation can be triggered by a poor diet and an excess of body fat and energy intake. Strawberry and honey are common rich sources of nutrients and bioactive compounds, widely studied for their roles exerted in health maintenance and disease prevention.PurposeThis review aims to summarize and update the effects of strawberry and honey against oxidative stress and inflammation, with emphasis on metabolism and on the main molecular mechanisms involved in these effects.MethodsA wide range of literature, published in the last 10 years, elucidating the effects of strawberry and honey in preventing oxidative stress and inflammation both in vitro (whole matrix and digested fractions) and in vivo was collected from online electronic databases (PubMed, Scopus and Web of Science) and reviewed.ResultsStrawberry and honey polyphenols may potentially prevent the chronic diseases related to oxidative stress and inflammation. Several in vitro and in vivo studies reported the effects of these foods in suppressing the oxidative stress, by decreasing ROS production and oxidative biomarkers, restoring the antioxidant enzyme activities, ameliorating the mitochondrial antioxidant status and functionality, among others, and the inflammatory process, by modulating the mediators of acute and chronic inflammation essential for the onset of several human diseases. These beneficial properties are mediated in part through their ability to target multiple signaling pathways, such as p38 MAPK, AMPK, PI3K/Akt, NF-κB and Nrf2.ConclusionsAvailable scientific literature show that strawberry and honey may be effective in preventing oxidative stress and inflammation. The deep evaluation of the factors that affect their metabolism as well as the assessment of the main molecular mechanisms involved are of extreme importance for the possible therapeutic and preventive benefit against the most common human diseases. However, published literature is still scarce so that deeper studies should be performed in order to evaluate the bioavailability of these food matrices and their effects after digestion.     

Spectroscopic studies on free radical coalescing antioxidants and brain protein cystatin

Cystatins are the inhibitors of thiol proteinases and are ubiquitously present in mammalian system. In brain, they put off unwanted proteolysis and are also involved in several neurodegenerative diseases. In the present study, it was demonstrated that photo-activated HOCl-induced modifications in brain cystatin leading to its inactivation and degradation due to hydroxyl radicals. It has been shown that oxidation of cystatin by ROS in vivo leads to oxidative modification which may direct the damage of this significant protein, as it is so well pronounced in vitro. The interplay between free radicals, antioxidants and co-factors is important in maintaining health, aging and age-related diseases. Body’s endogenous antioxidant systems stabilize free radical-induced oxidative stress by the ingestion of exogenous antioxidants. If the generation of free radicals goes beyond the protective effect of antioxidants, this can cause oxidative damage which accumulates during the life cycle and has been implicated in aging and age-related diseases such as cardiovascular disease, cancer, neurodegenerative disorders and other chronic conditions. Activation of neutrophils in certain diseases (e.g., inflammatory conditions and atherosclerosis) results in the production of highly reactive species, such as OH^? and the release of the enzyme myeloperoxidase. Stimulated monocytes and neutrophils generate hypochlorite (HOCl) via the release of the enzyme myeloperoxidase and hydrogen peroxide. Hypochlorous acid (HOCl) is a potent oxidant formed by myeloperoxidase that causes aggregation of many proteins and damage of proteins by reaction with amino-acid side-chains or backbone cleavage.

Communicated by Ramaswamy H. Sarma     

The isoprostanes: Unique bioactive products of lipid peroxidation

The development of a specific, reliable and noninvasive method for measuring oxidative stress in humans is essential for establishing the role of free radicals in human diseases. Currently, accurate techniques to assess oxidant injury in vivo are extremely limited although a number of approaches are being investigated. Of these, the measurement of specific products of nonenzymatic lipid peroxidation, the F₂-isoprostanes (F₂-IsoPs), appears to be a more accurate marker of oxidative stress in vivo in humans than other available methods. The purpose of this brief review is to acquaint the reader with the IsoPs from a biochemical perspective and to provide information regarding the utility of quantifying these compounds as indicators of oxidant stress.     

Persistent response of Fanconi anemia haematopoietic stem and progenitor cells to oxidative stress

Oxidative stress is considered as an important pathogenic factor in many human diseases including Fanconi anemia (FA), an inherited bone marrow failure syndrome with extremely high risk of leukemic transformation. Members of the FA protein family are involved in DNA damage and other cellular stress responses. Loss of FA proteins renders cells hypersensitive to oxidative stress and cancer transformation. However, how FA cells respond to oxidative DNA damage remains unclear. By using an in vivo stress-response mouse strain expressing the Gadd45β-luciferase transgene, we show here that haematopoietic stem and progenitor cells (HSPCs) from mice deficient for the FA gene Fanca or Fancc persistently responded to oxidative stress. Mechanistically, we demonstrated that accumulation of unrepaired DNA damage, particularly in oxidative damage-sensitive genes, was responsible for the long-lasting response in FA HSPCs. Furthermore, genetic correction of Fanca deficiency almost completely abolished the persistent oxidative stress-induced G₂/M arrest and DNA damage response in vivo. Our study suggests that FA pathway is an integral part of a versatile cellular mechanism by which HSPCs respond to oxidative stress.     

Overlapping and Complementary Oxidative Stress Defense Mechanisms in Nontypeable Haemophilus influenzae

The Gram-negative commensal bacterium nontypeable Haemophilus influenzae (NTHI) can cause respiratory tract diseases that include otitis media, sinusitis, exacerbations of chronic obstructive pulmonary disease, and bronchitis. During colonization and infection, NTHI withstands oxidative stress generated by reactive oxygen species produced endogenously, by the host, and by other copathogens and flora. These reactive oxygen species include superoxide, hydrogen peroxide (H₂O₂), and hydroxyl radicals, whose killing is amplified by iron via the Fenton reaction. We previously identified genes that encode proteins with putative roles in protection of the NTHI isolate strain 86-028NP against oxidative stress. These include catalase (HktE), peroxiredoxin/glutaredoxin (PgdX), and a ferritin-like protein (Dps). Strains were generated with mutations in hktE, pgdX, and dps. The hktE mutant and a pgdX hktE double mutant were more sensitive than the parent to killing by H₂O₂. Conversely, the pgdX mutant was more resistant to H₂O₂ due to increased catalase activity. Supporting the role of killing via the Fenton reaction, binding of iron by Dps significantly mitigated the effect of H₂O₂-mediated killing. NTHI thus utilizes several effectors to resist oxidative stress, and regulation of free iron is critical to this protection. These mechanisms will be important for successful colonization and infection by this opportunistic human pathogen.     

Effect of copper on pro- and antioxidative reactions in radish (Raphanus sativus L.) in vitro and in vivo

The generation of superoxide radicals, lipid peroxidation (as measured by malone dialdehyde formation) and the activity of selected antioxidant enzymes (superoxide dismutase, catalase, ascorbate peroxidase) were assessed in radish (Raphanus sativus L.), in response to elevated concentrations of copper ions in the culture medium in vitro and in vivo. Experiments were performed on 7-day-old seedlings and 5-week-old calluses grown on media supplemented with CuSO₄ in concentrations of 10, 100 and 1000 μМ. The exposure to elevated Cu concentrations in the medium significantly reduced both callogenesis and the proliferation of radish calluses in vitro. Cu treatment resulted in the increased generation of the superoxide radical (O₂⁻) in radish seedlings and calluses indicating the occurrence of oxidative stress in radish cells, whereas the level of lipid peroxidation (LPO) remained unchanged. Both in calluses and in radish seedlings in vivo, the relative level of oxidative stress was maximal at micromolar Cu concentrations and became attenuated with increasing Cu concentrations. Stronger oxidative stress occurred in the radish seedlings in vivo, compared with radish calluses in vitro. The observed lower sensitivity of calluses to Cu-induced oxidative stress and their ability to proliferate upon exposure to Cu concentrations of up to 1000 μМ demonstrate the potential of in vitro cell-selection to obtain metal-tolerant radish plant lines.     

Reactive oxygen species in cardiovascular disease

Based on the “free radical theory” of disease, researchers have been trying to elucidate the role of oxidative stress from free radicals in cardiovascular disease. Considerable data indicate that reactive oxygen species and oxidative stress are important features of cardiovascular diseases including atherosclerosis, hypertension, and congestive heart failure. However, blanket strategies with antioxidants to ameliorate cardiovascular disease have not generally yielded favorable results. However, our understanding of reactive oxygen species has evolved to the point at which we now realize these species have important roles in physiology as well as pathophysiology. Thus, it is overly simplistic to assume a general antioxidant strategy will yield specific effects on cardiovascular disease. Indeed, there are several sources of reactive oxygen species that are known to be active in the cardiovascular system. This review addresses our understanding of reactive oxygen species sources in cardiovascular disease and both animal and human data defining how reactive oxygen species contribute to physiology and pathology.     

The preventive and therapeutic effects of molecular hydrogen in ocular diseases and injuries where oxidative stress is involved

Oxidative stress initiates, accompanies and contributes to the development of several human diseases and injuries, including ocular diseases. Reactive oxygen species (ROS) can generate oxidative stress via excessive ROS production and/or decreased physiologically occurring antioxidants. To replace these weakened antioxidants, substances with effective antioxidant properties are needed in order to suppress oxidative stress and enable healing. Molecular hydrogen (H₂) is very suitable for this purpose due to its unique properties. H₂ is the only antioxidant that crosses the blood–brain and blood-ocular barriers. It quickly penetrates through tissue due to its small molecular size and effectively removes ROS, mainly hydroxyl radicals and peroxynitrite. Apart from its antioxidant effects, H₂ also displays anti-inflammatory, antiapoptotic, cytoprotective and mitohormetic properties. A significant advantage of H₂ is its nontoxicity, even when applied at high concentrations. In this review, we present the results of studies utilising H₂ in the treatment of ocular diseases involving oxidative stress. These results, obtained in experimental animals as well as in human clinical studies, show that the suppression of oxidative stress by H₂ treatment leads to the prevention or improvement of ocular diseases. In severe degenerative diseases, H₂ slows disease progression.     

Action of 6-amino-3-pyridinols as novel antioxidants against free radicals and oxidative stress in solution,plasma, and cultured cells

Free radical-mediated lipid peroxidation has been implicated in the pathogenesis of various diseases. Lipid peroxidation products are cytotoxic and they modify proteins and DNA bases, leading eventually to degenerative disorders. Various synthetic antioxidants have been developed and assessed for their capacity to inhibit lipid peroxidation and oxidative stress induced by free radicals. In this study, the capacity of novel 6-amino-2,4,5-trimethyl-3-pyridinols for scavenging peroxyl radicals, inhibiting plasma lipid peroxidation in vitro, and preventing cytotoxicity induced by glutamate, 6-hydroxydopamine, 1-methyl-4-phenylpyridium (MPP⁺ ), and hydroperoxyoctadecadienoic acid was assessed. It was found that they exerted higher reactivity toward peroxyl radicals and more potent activity for inhibiting the above oxidative stress than α-tocopherol, the most potent natural antioxidant, except against the cytotoxicity induced by MPP⁺. These results suggest that the novel 6-amino-3-pyridinols may be potent antioxidants against oxidative stress.     

Effect of natural exogenous antioxidants on aging and on neurodegenerative diseases

Abstract

Aging and neurodegenerative diseases share oxidative stress cell damage and depletion of endogenous antioxidants as mechanisms of injury, phenomena that are occurring at different rates in each process. Nevertheless, as the central nervous system (CNS) consists largely of lipids and has a poor catalase activity, a low amount of superoxide dismutase and is rich in iron, its cellular components are damaged easily by overproduction of free radicals in any of these physiological or pathological conditions. Thus, antioxidants are needed to prevent the formation and to oppose the free radicals damage to DNA, lipids, proteins, and other biomolecules. Due to endogenous antioxidant defenses are inadequate to prevent damage completely, different efforts have been undertaken in order to increase the use of natural antioxidants and to develop antioxidants that might ameliorate neural injury by oxidative stress. In this context, natural antioxidants like flavonoids (quercetin, curcumin, luteolin and catechins), magnolol and honokiol are showing to be the efficient inhibitors of the oxidative process and seem to be a better therapeutic option than the traditional ones (vitamins C and E, and β-carotene) in various models of aging and injury in vitro and in vivo conditions. Thus, the goal of the present review is to discuss the molecular basis, mechanisms of action, functions, and targets of flavonoids, magnolol, honokiol and traditional antioxidants with the aim of obtaining better results when they are prescribed on aging and neurodegenerative diseases.     

Oxidation of glycosaminoglycans by free radicals and reactive oxidative species: A review of investigative methods

Abstract

Glycosaminoglycans, in particular hyaluronan (HA), and proteoglycans are components of the extracellular matrix (ECM). The ECM plays a key role in the regulation of cellular behaviour and alterations to it can modulate both the development of human diseases as well as controlling normal biochemical processes such as cell signalling and pro-inflammatory responses. For these reasons, in vitro fragmentation studies of glycosaminoglycans by free radicals and oxidative species are seen to be relevant to the understanding of in vivo studies of damage to the ECM. A wide range of investigative techniques have therefore been applied to gain insights into the relative fragmentation effects of several reactive oxidative species with the ultimate goal of determining mechanisms of fragmentation at the molecular level. These methods are reviewed here.     

A water-soluble manganese(II) octanediaoate/phenanthroline complex acts as an antioxidant and attenuates alpha-synuclein toxicity

The overproduction of reactive oxygen species (ROS) induces oxidative stress, a well-known process associated with aging and several human pathologies, such as cancer and neurodegenerative diseases. A large number of synthetic compounds have been described as antioxidant enzyme mimics, capable of eliminating ROS and/or reducing oxidative damage. In this study, we investigated the antioxidant activity of a water-soluble 1,10-phenantroline-octanediaoate Mn²⁺-complex on cells under oxidative stress, and assessed its capacity to attenuate alpha-synuclein (aSyn) toxicity and aggregation, a process associated with increased oxidative stress. This Mn²⁺-complex exhibited a significant antioxidant potential, reducing intracelular oxidation and increasing oxidative stress resistance in S. cerevisiae cells and in vivo, in G. mellonella, increasing the activity of the intracellular antioxidant enzymes superoxide dismutase and catalase. Strikingly, the Mn²⁺-complex reduced both aSyn oligomerization and aggregation in human cell cultures and, using NMR and DFT/molecular docking we confirmed its interaction with the C-terminal region of aSyn. In conclusion, the Mn²⁺-complex appears as an excellent lead for the design of new phenanthroline derivatives as alternative compounds for preventing oxidative damages and oxidative stress - related diseases.     

Separation and identification of F2-isoprostane regioisomers and diastereomers by novel liquid chromatographic/mass spectrometric methods

Isoprostanes are isomers of prostaglandins that are generated from free radical-initiated autoxidation of arachidonic acid. Quantification of F(2)-isoprostanes is regarded as the "gold standard" to assess oxidative stress in various human diseases. There are 32 possible racemic isoprostane isomers that exist as four sets of regioisomers. Each regioisomer is composed of eight diastereomers. We report liquid chromatographic/mass spectrometric methods to separate and identify F(2)-isoprostane stereoisomers. These methods have been applied to the analysis of F(2)-isoprostanes derived from tissues of rats exposed to an oxidative stress and are useful to assess the relative formation of various regioisomers and stereoisomers generated in vitro and in vivo. The delineation of the more abundant isomers formed will allow for studies to examine the biological relevance of selected compounds in vivo.     

Omeprazole as a potent activator of human cytosolic aldehyde dehydrogenase ALDH1A1

BackgroundAccumulation of lipid aldehydes plays a key role in the etiology of human diseases where high levels of oxidative stress are generated. In this regard, activation of aldehyde dehydrogenases (ALDHs) prevents oxidative tissue damage during ischemia-reperfusion processes. Although omeprazole is used to reduce stomach gastric acid production, in the present work this drug is described as the most potent activator of human ALDH1A1 reported yet.MethodsDocking analysis was performed to predict the interactions of omeprazole with the enzyme. Recombinant human ALDH1A1 was used to assess the effect of omeprazole on the kinetic properties. Temperature treatment and mass spectrometry were conducted to address the nature of binding of the activator to the enzyme. Finally, the effect of omeprazole was evaluated in an in vivo model of oxidative stress, using E. coli cells expressing the human ALDH1A1.ResultsOmeprazole interacted with the aldehyde binding site, increasing 4–6 fold the activity of human ALDH1A1, modified the kinetic properties, altering the order of binding of substrates and release of products, and protected the enzyme from inactivation by lipid aldehydes. Furthermore, omeprazole protected E. coli cells over-expressing ALDH1A1 from the effects of oxidative stress generated by H₂O₂ exposure, reducing the levels of lipid aldehydes and preserving ALDH activity.ConclusionOmeprazole can be repositioned as a potent activator of human ALDH1A1 and may be proposed for its use in therapeutic strategies, to attenuate the damage generated during oxidative stress events occurring in different human pathologies.     

Tat-glyoxalase protein inhibits against ischemic neuronal cell damage and ameliorates ischemic injury

Methylglyoxal (MG), a metabolite of glucose, is the major precursor of protein glycation and induces apoptosis. MG is associated with neurodegeneration, including oxidative stress and impaired glucose metabolism, and is efficiently metabolized to S-D-lactoylglutathione by glyoxalase (GLO). Although GLO has been implicated as being crucial in various diseases including ischemia, its detailed functions remain unclear. Therefore, we investigated the protective effect of GLO (GLO1 and GLO2) in neuronal cells and an animal ischemia model using Tat-GLO proteins. Purified Tat-GLO protein efficiently transduced into HT-22 neuronal cells and protected cells against MG- and H₂O₂-induced cell death, DNA fragmentation, and activation of caspase-3 and mitogen-activated protein kinase. In addition, transduced Tat-GLO protein increased D-lactate in MG- and H₂O₂-treated cells whereas glycation end products (AGE) and MG levels were significantly reduced in the same cells. Gerbils treated with Tat-GLO proteins displayed delayed neuronal cell death in the CA1 region of the hippocampus compared with a control. Furthermore, the combined neuroprotective effects of Tat-GLO1 and Tat-GLO2 proteins against ischemic damage were significantly higher than those of each individual protein. Those results demonstrate that transduced Tat-GLO protein protects neuronal cells by inhibiting MG- and H₂O₂-mediated cytotoxicity in vitro and in vivo. Therefore, we suggest that Tat-GLO proteins could be useful as a therapeutic agent for various human diseases related to oxidative stress including brain diseases.