Nitro-fatty acids: New drug candidates for chronic inflammatory and fibrotic diseases

Adipocyte-specific Nrf2 deletion negates nitro-oleic acid benefits on glucose tolerance in diet-induced obesity

Obesity is commonly linked with white adipose tissue (WAT) dysfunction, setting off inflammation and oxidative stress, both key contributors to the cardiometabolic complications associated with obesity. To improve metabolic and cardiovascular health, countering these inflammatory and oxidative signaling processes is crucial. Offering potential in this context, the activation of nuclear factor erythroid 2-related factor 2 (Nrf2) by nitro-fatty acids (NO2-FA) promote diverse anti-inflammatory signaling and counteract oxidative stress. Additionally, we previously highlighted that nitro-oleic acid (NO2-OA) preferentially accumulates in WAT and provides protection against already established high fat diet (HFD)-mediated impaired glucose tolerance. The precise mechanism accounting for these protective effects remained largely unexplored until now. Herein, we reveal that protective effects of improved glucose tolerance by NO2-OA is absent when Nrf2 is specifically ablated in adipocytes (ANKO mice). NO2-OA treatment did not alter body weight between ANKO and littermate controls (Nrf2fl/fl) mice on both the HFD and low-fat diet (LFD). As expected, at day 76 (before NO2-OA treatment) and notably at day 125 (daily treatment of 15 mg/kg NO2-OA for 48 days), both HFD-fed Nrf2fl/fl and ANKO mice exhibited increased fat mass and reduced lean mass compared to LFD controls. However, throughout the NO2-OA treatment, no distinction was observed between Nrf2fl/fl and ANKO in the HFD-fed mice as well as in the Nrf2fl/fl mice fed a LFD. Glucose tolerance tests revealed impaired glucose tolerance in HFD-fed Nrf2fl/fl and ANKO compared to LFD-fed Nrf2fl/fl mice. Notably, NO2-OA treatment improved glucose tolerance in HFD-fed Nrf2fl/fl but did not yield the same improvement in ANKO mice at days 15, 30, and 55 of treatment. Unraveling the pathways linked to NO2-OA's protective effects in obesity-mediated impairment in glucose tolerance is pivotal within the realm of precision medicine, crucially propelling future applications and refining novel drug-based strategies.

Indigenous wisdom of a Kwatha to treat NASH: An insight into the mechanism

ETHNOPHARMACOLOGICAL RELEVANCE

Nonalcoholic fatty liver disease (NAFLD) is the most common severe liver disease globally, progressing further into nonalcoholic steatohepatitis (NASH) and hepatocellular carcinoma (HCC). Vasaguduchyadi Kwatha (VK) is an Ayurvedic formulation traditionally used to treat liver diseases and other metabolic complications. This study is an ethnopharmacological approach to unravel this indigenous remedy.

AIM OF THE STUDY

We aimed to discover the probable mechanism of action of VK against NASH in this study, using network pharmacology, molecular docking, in vitro study, and preclinical investigation.

METHODS AND RESULTS

Among the 55 components identified, 10 were confirmed based on mass, elution charecteristics, MS/MS analysis data, and fragmentation rules. Computational study indicated 92 targets involved in the central pathways of NASH, out of which only 15 targets and 9 VK constituents have significant docking scores. In vitro and in vivo analysis results showed that VK significantly reduces weight gain and improves insulin sensitivity, dyslipidemia, steatohepatitis and overall histological features of NASH compared to saroglitazar (SGZR).

CONCLUSION

Our detailed study yielded three signalling pathways related to NASH on which VK has maximum effect, bringing up a probable alternative treatment for NASH.

Regulation of immunomodulatory networks by Nrf2-activation in immune cells: Redox control and therapeutic potential in inflammatory diseases

Inflammatory diseases present a serious health challenge due to their widespread prevalence and the severe impact on patients' lives. In the quest to alleviate the burden of these diseases, nuclear factor erythroid 2-related factor 2 (Nrf2) has emerged as a pivotal player. As a transcription factor intimately involved in cellular defense against metabolic and oxidative stress, Nrf2's role in modulating the inflammatory responses of immune cells has garnered significant attention. Recent findings suggest that Nrf2's ability to alter the redox status of cells underlies its regulatory effects on immune responses. Our review delves into preclinical and clinical evidence that underscores the complex influence of Nrf2 activators on immune cell phenotypes, particularly in the inflammatory milieu. By offering a detailed analysis of Nrf2's role in different immune cell populations, we cast light on the potential of Nrf2 activators in shaping the immune response towards a more regulated state, mitigating the adverse effects of inflammation through modeling redox status of immune cells. Furthermore, we explore the innovative use of nanoencapsulation techniques that enhance the delivery and efficacy of Nrf2 activators, potentially advancing the treatment strategies for inflammatory ailments. We hope this review will stimulate the development and expansion of Nrf2-targeted treatments that could substantially improve outcomes for patients suffering from a broad range of inflammatory diseases.

Effect of nitro-conjugated linoleic acid on the inflammatory response of murine macrophages activated with lipopolysaccharide derived from Prevotella intermedia

Nitro-conjugated linoleic acid (NO2-CLA) has been observed to manifest salutary signaling responses, including anti-inflammatory and antioxidant properties. Here, the authors have explored the influence and underlying mechanisms of NO2-CLA on the proinflammatory reaction of murine macrophages that were challenged with lipopolysaccharide (LPS) derived from Prevotella intermedia, a putative periodontopathic bacterium. Treatment of LPS-activated RAW264.7 cells with NO2-CLA notably dampened the secretion of iNOS-derived NO, IL-1β and IL-6 as well as their gene expressions and significantly enhanced the markers for M2 macrophage polarization. NO2-CLA promoted the HO-1 expression in cells challenged with LPS, and tin protoporphyrin IX, an HO-1 inhibitor, significantly reversed the NO2-CLA-mediated attenuation of NO secretion, but not IL-1β or IL-6. We found that cells treated with NO2-CLA significantly increased mRNA expression of PPAR-γ compared to control cells, and NO2-CLA significantly reverted the decrease in PPAR-γ mRNA caused by LPS. Nonetheless, antagonists to PPAR-γ were unable to reverse the NO2-CLA-mediated suppression of inflammatory mediators. In addition, NO2-CLA did not alter the p38 and JNK activation elicited by LPS. Both NF-κB reporter activity and IκB-α degradation caused by LPS were notably diminished by NO2-CLA. NO2-CLA was observed to interrupt the nuclear translocation and DNA binding of p50 subunits caused by LPS with no obvious alterations in p65 subunits. Further, NO2-CLA attenuated the phosphorylation of STAT1/3 elicited in response to LPS. We propose that NO2-CLA could be considered as a possible strategy for the therapy of periodontal disease, although additional researches are certainly required to confirm this.

Fatty acid nitroalkenes - Multi-target agents for the treatment of sickle cell disease

Sickle cell disease (SCD) is a hereditary hematological disease with high morbidity and mortality rates worldwide. Despite being monogenic, SCD patients display a plethora of disease-associated complications including anemia, oxidative stress, sterile inflammation, vaso-occlusive crisis-related pain, and vasculopathy, all of which contribute to multiorgan dysfunction and failure. Over the past decade, numerous small molecule drugs, biologics, and gene-based interventions have been evaluated; however, only four disease-modifying drug therapies are presently FDA approved. Barriers regarding effectiveness, accessibility, affordability, tolerance, and compliance of the current polypharmacy-based disease-management approaches are challenging. As such, there is an unmet pharmacological need for safer, more efficacious, and logistically accessible treatment options for SCD patients. Herein, we evaluate the potential of small molecule nitroalkenes such as nitro-fatty acid (NO2-FA) as a therapy for SCD. These agents are electrophilic and exert anti-inflammatory and tissue repair effects through an ability to transiently post-translationally bind to and modify transcription factors, pro-inflammatory enzymes and cell signaling mediators. Preclinical and clinical studies affirm safety of the drug class and a murine model of SCD reveals protection against inflammation, fibrosis, and vascular dysfunction. Despite protective cardiac, renal, pulmonary, and central nervous system effects of nitroalkenes, they have not previously been considered as therapy for SCD. We highlight the pathways targeted by this drug class, which can potentially prevent the end-organ damage associated with SCD and contrast their prospective therapeutic benefits for SCD as opposed to current polypharmacy approaches.

Bioactive lipids in hypertension

Hypertension is a major healthcare issue that afflicts one in every three adults worldwide and contributes to cardiovascular diseases, morbidity and mortality. Bioactive lipids contribute importantly to blood pressure regulation via actions on the vasculature, kidney, and inflammation. Vascular actions of bioactive lipids include blood pressure lowering vasodilation and blood pressure elevating vasoconstriction. Increased renin release by bioactive lipids in the kidney is pro-hypertensive whereas anti-hypertensive bioactive lipid actions result in increased sodium excretion. Bioactive lipids have pro-inflammatory and anti-inflammatory actions that increase or decrease reactive oxygen species and impact vascular and kidney function in hypertension. Human studies provide evidence that fatty acid metabolism and bioactive lipids contribute to sodium and blood pressure regulation in hypertension. Genetic changes identified in humans that impact arachidonic acid metabolism have been associated with hypertension. Arachidonic acid cyclooxygenase, lipoxygenase and cytochrome P450 metabolites have pro-hypertensive and anti-hypertensive actions. Omega-3 fish oil fatty acids eicosapentaenoic acid and docosahexaenoic acid are known to be anti-hypertensive and cardiovascular protective. Lastly, emerging fatty acid research areas include blood pressure regulation by isolevuglandins, nitrated fatty acids, and short chain fatty acids. Taken together, bioactive lipids are key contributors to blood pressure regulation and hypertension and their manipulation could decrease cardiovascular disease and associated morbidity and mortality.

Meta-omics profiling of the gut-lung axis illuminates metabolic networks and host-microbial interactions associated with elevated lung elastance in a murine model of obese allergic asthma

Obesity and associated changes to the gut microbiome worsen airway inflammation and hyperresponsiveness in asthma. Obesogenic host-microbial metabolomes have altered production of metabolites that may influence lung function and inflammatory responses in asthma. To understand the interplay of the gut microbiome, metabolism, and host inflammation in obesity-associated asthma, we used a multi-omics approach to profile the gut-lung axis in the setting of allergic airway disease and diet-induced obesity. We evaluated an immunomodulator, nitro-oleic acid (NO₂-OA), as a host- and microbial-targeted treatment intervention for obesity-associated allergic asthma. Allergic airway disease was induced using house dust mite and cholera toxin adjuvant in C57BL6/J mice with diet-induced obesity to model obesity-associated asthma. Lung function was measured by flexiVent following a week of NO₂-OA treatment and allergen challenge. 16S rRNA gene (from DNA, taxa presence) and 16S rRNA (from RNA, taxa activity) sequencing, metabolomics, and host gene expression were paired with a Treatment-Measured-Response model as a data integration framework for identifying latent/hidden relationships with linear regression among variables identified from high-dimensional meta-omics datasets. Targeting both the host and gut microbiota, NO₂-OA attenuated airway inflammation, improved lung elastance, and modified the gut microbiome. Meta-omics data integration and modeling determined that gut-associated inflammation, metabolites, and functionally active gut microbiota were linked to lung function outcomes. Using Treatment-Measured-Response modeling and meta-omics profiling of the gut-lung axis, we uncovered a previously hidden network of interactions between gut levels of amino acid metabolites involved in elastin and collagen synthesis, gut microbiota, NO₂-OA, and lung elastance. Further targeted metabolomics analyses revealed that obese mice with allergic airway disease had higher levels of proline and hydroxyproline in the lungs. NO₂-OA treatment reduced proline biosynthesis by downregulation of pyrroline-5-carboxylate reductase 1 (PYCR1) expression. These findings are relevant to human disease: adults with mild-moderate asthma and BMI ≥ 25 had higher plasma hydroxyproline levels. Our results suggest that changes to structural proteins in the lung airways and parenchyma may contribute to heightened lung elastance and serve as a potential therapeutic target for obese allergic asthma.

Nitro-oleic acid regulates T cell activation through post-translational modification of calcineurin

Nitro-fatty acids (NO₂-FAs) are unsaturated fatty acid nitration products that exhibit anti-inflammatory actions in experimental mouse models of autoimmune and allergic diseases. These electrophilic molecules interfere with intracellular signaling pathways by reversible post-translational modification of nucleophilic amino-acid residues. Several regulatory proteins have been identified as targets of NO₂-FAs, modifying their activity and promoting gene expression changes that result in anti-inflammatory effects. Herein, we report the effects of nitro-oleic acid (NO₂-OA) on pro-inflammatory T cell functions, showing that 9- and 10-NOA, but not their oleic acid precursor, decrease T cell proliferation, expression of activation markers CD25 and CD71 on the plasma membrane, and IL-2, IL-4, and IFN-γ cytokine gene expressions. Moreover, we have found that NO₂-OA inhibits the transcriptional activity of nuclear factor of activated T cells (NFAT) and that this inhibition takes place through the regulation of the phosphatase activity of calcineurin (CaN), hindering NFAT dephosphorylation, and nuclear translocation in activated T cells. Finally, using mass spectrometry-based approaches, we have found that NO₂-OA nitroalkylates CaNA on four Cys (Cys129, 228, 266, and 372), of which only nitroalkylation on Cys372 was of importance for the regulation of CaN phosphatase activity in cells, disturbing functional CaNA/CaNB heterodimer formation. These results provide evidence for an additional mechanism by which NO₂-FAs exert their anti-inflammatory actions, pointing to their potential as therapeutic bioactive lipids for the modulation of harmful T cell-mediated immune responses.

Nitrated Fatty-Acids Distribution in Storage Biomolecules during Arabidopsis thaliana Development

The non-enzymatic interaction of polyunsaturated fatty acids with nitric oxide (NO) and derived species results in the formation of nitrated fatty acids (NO₂-FAs). These signaling molecules can release NO, reversibly esterify with complex lipids, and modulate protein function through the post-translational modification called nitroalkylation. To date, NO₂-FAs act as signaling molecules during plant development in plant systems and are involved in defense responses against abiotic stress conditions. In this work, the previously unknown storage biomolecules of NO₂-FAs in Arabidopsis thaliana were identified. In addition, the distribution of NO₂-FAs in storage biomolecules during plant development was determined, with phytosterol esters (SE) and TAGs being reservoir biomolecules in seeds, which were replaced by phospholipids and proteins in the vegetative, generative, and senescence stages. The detected esterified NO₂-FAs were nitro-linolenic acid (NO₂-Ln), nitro-oleic acid (NO₂-OA), and nitro-linoleic acid (NO₂-LA). The last two were detected for the first time in Arabidopsis. The levels of the three NO₂-FAs that were esterified in both lipid and protein storage biomolecules showed a decreasing pattern throughout Arabidopsis development. Esterification of NO₂-FAs in phospholipids and proteins highlights their involvement in both biomembrane dynamics and signaling processes, respectively, during Arabidopsis plant development.

The Diverse Biological Activity of Recently Synthesized Nitro Compounds

The search for new and efficient pharmaceuticals is a constant struggle for medicinal chemists. New substances are needed in order to treat different pathologies affecting the health of humans and animals, and these new compounds should be safe, effective and have the fewest side effects possible. Some functional groups are known for having biological activity; in this matter, the nitro group (NO2) is an efficient scaffold when synthesizing new bioactive molecules. Nitro compounds display a wide spectrum of activities that include antineoplastic, antibiotic, antihypertensive, antiparasitic, tranquilizers and even herbicides, among many others. Most nitro molecules exhibit antimicrobial activity, and several of the compounds mentioned in this review may be further studied as lead compounds for the treatment of H. pylori, P. aeruginosa, M. tuberculosis and S. mutans infections, among others. The NO2 moiety triggers redox reactions within cells causing toxicity and the posterior death of microorganisms, not only bacteria but also multicellular organisms such as parasites. The same effect may be present in humans as well, so the nitro groups can be considered both a pharmacophore and a toxicophore at the same time. The role of the nitro group itself also has a deep effect on the polarity and electronic properties of the resulting molecules, and hence favors interactions with some amino acids in proteins. For these reasons, it is fundamental to analyze the recently synthesized nitro molecules that show any potential activity in order to develop new pharmacological treatments that enhance human health.

Nitro-Oleic Acid-Mediated Nitroalkylation Modulates the Antioxidant Function of Cytosolic Peroxiredoxin Tsa1 during Heat Stress in Saccharomyces cerevisiae

Heat stress is one of the abiotic stresses that leads to oxidative stress. To protect themselves, yeast cells activate the antioxidant response, in which cytosolic peroxiredoxin Tsa1 plays an important role in hydrogen peroxide removal. Concomitantly, the activation of the heat shock response (HSR) is also triggered. Nitro-fatty acids are signaling molecules generated by the interaction of reactive nitrogen species with unsaturated fatty acids. These molecules have been detected in animals and plants. They exert their signaling function mainly through a post-translational modification called nitroalkylation. In addition, these molecules are closely related to the induction of the HSR. In this work, the endogenous presence of nitro-oleic acid (NO₂-OA) in Saccharomyces cerevisiae is identified for the first time by LC-MS/MS. Both hydrogen peroxide levels and Tsa1 activity increased after heat stress with no change in protein content. The nitroalkylation of recombinant Tsa1 with NO₂-OA was also observed. It is important to point out that cysteine 47 (peroxidatic) and cysteine 171 (resolving) are the main residues responsible for protein activity. Moreover, the in vivo nitroalkylation of Tsa1 peroxidatic cysteine disappeared during heat stress as the hydrogen peroxide generated in this situation caused the rupture of the NO₂-OA binding to the protein and, thus, restored Tsa1 activity. Finally, the amino acid targets susceptible to nitroalkylation and the modulatory effect of this PTM on the enzymatic activity of Tsa1 are also shown in vitro and in vivo. This mechanism of response was faster than that involving the induction of genes and the synthesis of new proteins and could be considered as a key element in the fine-tuning regulation of defence mechanisms against oxidative stress in yeast.

Nitrated fatty acid, 10-nitrooleate protects against hyperoxia-induced acute lung injury in mice

The antioxidant and anti-inflammatory effects of electrophilic nitrated fatty acid (NFA); 10-nitrooleate, have been reported. The present study investigated whether 10-nitrooleate has a protective role against hyperoxic-induced acute lung injury (HALI). Using a C57BL/6 mice model of HALI, we investigated the protective effect of 10-nitrooleate. C57BL/6 mice were administered with NFA intratracheally, exposed to hyperoxia for 48 h to induce HALI, and kept at room air for 24 h. Bronchoalveolar lavage (BAL) fluid and lung samples were collected after 24 h of post hyperoxia to analyze markers associated with HALI. Intratracheal (IT) and intraperitoneal (IP) administration of NFA notably attenuated hyperoxia-induced infiltration of inflammatory cells, alveolar-capillary leakage, upregulation of proinflammatory cytokine levels (IL-6 and TNFα) into the BAL fluid, and resolution of inflammation in the lung. Western blot analyses showed that 10-nitrooleate reduced the expression of the inflammatory transcription factor NFκB p65 subunit and increased antioxidant proteins HO-1 and NQO1 expression in the lung tissues compared to vehicle-treated animals. Moreover, 10-nitrooleate reversed the hyperoxia-induced expression of mitophagy-associated markers (PINK1 and p62/SQSTM1), thereby protecting the HALI/ acute respiratory distress syndrome (ARDS). IT and IP delivery of 10-nitrooleate reduces hyperoxia-induced ALI/ARDS by regulating the antioxidant pathways and restoring the mitochondrial homeostasis by regulating mitophagy. It is suggested that NFAs can be further evaluated as supplementary therapy for critically ill patients like COVID-19/ARDS.

Serum albumin as a primary non-covalent binding protein for nitro-oleic acid

This work explores the interaction of 9/10-nitro-oleic acid (NO₂-OA) with human serum albumin (HSA). The molecular mechanism of the biological action of NO₂-OA is to our knowledge based on a reversible covalent reaction-Michael addition of nucleophilic amino acid residues of proteins. Since HSA is an important fatty acid transporter, a key question is whether NO₂-OA can bind covalently or non-covalently to HSA, similarly to oleic acid (OA), which can interact with the FA1-FA7 binding sites of the HSA molecule. ¹H NMR studies and competition analysis with OA and the drugs ibuprofen and warfarin were used to investigate a potential non-covalent binding mode. NO₂-OA/HSA binding was confirmed to compete with warfarin for FA-7 with significantly higher affinity. NO₂-OA competes with ibuprofen for FA-3 and FA-6, however, in contrast to the situation with warfarin, the binding affinities are not significantly different. The described interactions are based exclusively on non-covalent binding. No covalent binding of NO₂-OA to HSA was detected by MS/MS. More detailed studies based on MALDI-TOF-MS and Ellman's assay indicated that HSA can be covalently modified in the presence of NO₂-OA to a very limited extent. It was also shown that NO₂-OA has a higher affinity to HSA than that of OA.

Recent Development of Probiotic Bifidobacteria for Treating Human Diseases

Bifidobacterium is a non-spore-forming, Gram-positive, anaerobic probiotic actinobacterium and commonly found in the gut of infants and the uterine region of pregnant mothers. Like all probiotics, Bifidobacteria confer health benefits on the host when administered in adequate amounts, showing multifaceted probiotic effects. Examples include B. bifidum, B. breve, and B. longum, common Bifidobacterium strains employed to prevent and treat gastrointestinal disorders, including intestinal infections and cancers. Herein, we review the latest development in probiotic Bifidobacteria research, including studies on the therapeutic impact of Bifidobacterial species on human health and recent efforts in engineering Bifidobacterium. This review article would provide readers with a wholesome understanding of Bifidobacteria and its potentials to improve human health.

Lipid nitroalkene nanoparticles for the focal treatment of ischemia reperfusion

Rationale: The treatment of microvascular obstruction (MVO) using ultrasound-targeted LNP cavitation (UTC) therapy mechanically relieves the physical obstruction in the microcirculation but does not specifically target the associated inflammatory milieu. Electrophilic fatty acid nitroalkene derivatives (nitro-fatty acids), that display pleiotropic anti-inflammatory signaling and transcriptional regulatory actions, offer strong therapeutic potential but lack a means of rapid targeted delivery. The objective of this study was to develop nitro-fatty acid-containing lipid nanoparticles (LNP) that retain the mechanical efficacy of standard LNP and can rapidly target delivery of a tissue-protective payload that reduces inflammation and improves vascular function following ischemia-reperfusion. Methods: The stability and acoustic behavior of nitro-fatty acid LNP (NO₂-FA-LNP) were characterized by HPLC-MS/MS and ultra-high-speed microscopy. The LNP were then used in a rat hindlimb model of ischemia-reperfusion injury with ultrasound-targeted cavitation. Results: Intravenous administration of NO₂-FA-LNP followed by ultrasound-targeted LNP cavitation (UTC) in both healthy rat hindlimb and following ischemia-reperfusion injury showed enhanced NO₂-FA tissue delivery and microvascular perfusion. In addition, vascular inflammatory mediator expression and lipid peroxidation were decreased in tissues following ischemia-reperfusion revealed NO₂-FA-LNP protected against inflammatory injury. Conclusions: Vascular targeting of NO₂-FA-LNP with UTC offers a rapid method of focal anti-inflammatory therapy at sites of ischemia-reperfusion injury.

Nitro Fatty Acids (NO2-FAs): An Emerging Class of Bioactive Fatty Acids

Unsaturated nitro fatty acids (NO₂-FAs) constitute a category of molecules that may be formed endogenously by the reaction of unsaturated fatty acids (UFAs) with secondary species of nitrogen monoxide and nitrite anions. The warhead of NO₂-FAs is a nitroalkene moiety, which is a potent Michael acceptor and can undergo nucleophilic attack from thiol groups of biologically relevant proteins, showcasing the value of these molecules regarding their therapeutic potential against many diseases. In general, NO₂-FAs inhibit nuclear factorκ-B (NF-κB), and simultaneously they activate nuclear factor (erythroid derived)-like 2 (Nrf2), which activates an antioxidant signaling pathway. NO₂-FAs can be synthesized not only endogenously in the organism, but in a synthetic laboratory as well, either by a step-by-step synthesis or by a direct nitration of UFAs. The step-by-step synthesis requires specific precursor compounds and is in position to afford the desired NO₂-FAs with a certain position of the nitro group. On the contrary, the direct nitration of UFAs is not a selective methodology; thus, it affords a mixture of all possible nitro isomers.

Structural Modifications Yield Novel Insights Into the Intriguing Pharmacodynamic Potential of Anti-inflammatory Nitro-Fatty Acids

Endogenous nitro-fatty acids (NFA) are potent electrophilic lipid mediators that exert biological effects in vitro and in vivo via selective covalent modification of thiol-containing target proteins. The cytoprotective, anti-inflammatory, and anti-tumorigenic effects of NFA in animal models of disease caused by targeted protein nitroalkylation are a valuable basis for the development of future anti-phlogistic and anti-neoplastic drugs. Considering the complexity of diseases and accompanying comorbidities there is an urgent need for clinically effective multifunctional drugs. NFA are composed of a fatty acid backbone containing a nitroalkene moiety triggering Michael addition reactions. However, less is known about the target-specific structure–activity relationships and selectivities comparing different NFA targets. Therefore, we analyzed 15 NFA derivatives and compared them with the lead structure 9-nitro-oleic acid (9NOA) in terms of their effect on NF-κB (nuclear factor kappa B) signaling inhibition, induction of Nrf-2 (nuclear factor erythroid 2-related factor 2) gene expression, sEH (soluble epoxide hydrolase), LO (lipoxygenase), and COX-2 (cyclooxygenase-2) inhibition, and their cytotoxic effects on colorectal cancer cells. Minor modifications of the Michael acceptor position and variation of the chain length led to drugs showing increased target preference or enhanced multi-targeting, partly with higher potency than 9NOA. This study is a significant step forward to better understanding the biology of NFA and their enormous potential as scaffolds for designing future anti-inflammatory drugs.

Fatty acid nitroalkene reversal of established lung fibrosis

Tissue fibrosis occurs in response to dysregulated metabolism, pro-inflammatory signaling and tissue repair reactions. For example, lungs exposed to environmental toxins, cancer therapies, chronic inflammation and other stimuli manifest a phenotypic shift to activated myofibroblasts and progressive and often irreversible lung tissue scarring. There are no therapies that stop or reverse fibrosis. The 2 FDA-approved anti-fibrotic drugs at best only slow the progression of fibrosis in humans. The present study was designed to test whether a small molecule electrophilic nitroalkene, nitro-oleic acid (NO₂-OA), could reverse established pulmonary fibrosis induced by the intratracheal administration of bleomycin in C57BL/6 mice. After 14 d of bleomycin-induced fibrosis development in vivo, lungs were removed, sectioned and precision-cut lung slices (PCLS) from control and bleomycin-treated mice were cultured ex vivo for 4 d with either vehicle or NO₂-OA (5 μM). Biochemical and morphological analyses showed that over a 4 d time frame, NO₂-OA significantly inhibited pro-inflammatory mediator and growth factor expression and reversed key indices of fibrosis (hydroxyproline, collagen 1A1 and 3A1, fibronectin-1). Quantitative image analysis of PCLS immunohistology reinforced these observations, revealing that NO₂-OA suppressed additional hallmarks of the fibrotic response, including alveolar epithelial cell loss, myofibroblast differentiation and proliferation, collagen and α-smooth muscle actin expression. NO₂-OA also accelerated collagen degradation by resident macrophages. These effects occurred in the absence of the recognized NO₂-OA modulation of circulating and migrating immune cell activation. Thus, small molecule nitroalkenes may be useful agents for reversing pathogenic fibrosis of lung and other organs.

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Small molecule electrophiles, pleiotropic anti-inflammatory and anti-fibrotic drugs.

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NO₂-OA inhibits activated myofibroblasts, induces dedifferentiation to fibroblasts.

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NO₂-OA activates extracellular matrix degradation by macrophages.

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NO₂-OA promotes proliferation of alveolar type 1 and 2 epithelial cells.

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NO₂-OA reverses established lung fibrosis in murine lung slices.

Is There a Glutathione Centered Redox Dysregulation Subtype of Schizophrenia?

Schizophrenia continues to be an illness with poor outcome. Most mechanistic changes occur many years before the first episode of schizophrenia; these are not reversible after the illness onset. A developmental mechanism that is still modifiable in adult life may center on intracortical glutathione (GSH). A large body of pre-clinical data has suggested the possibility of notable GSH-deficit in a subgroup of patients with schizophrenia. Nevertheless, studies of intracortical GSH are not conclusive in this regard. In this review, we highlight the recent ultra-high field magnetic resonance spectroscopic studies linking GSH to critical outcome measures across various stages of schizophrenia. We discuss the methodological steps required to conclusively establish or refute the persistence of GSH-deficit subtype and clarify the role of the central antioxidant system in disrupting the brain structure and connectivity in the early stages of schizophrenia. We propose in-vivo GSH quantification for patient selection in forthcoming antioxidant trials in psychosis. This review offers directions for a promising non-dopaminergic early intervention approach in schizophrenia.

Suppression of Vascular Macrophage Activation by Nitro-Oleic Acid and its Implication for Abdominal Aortic Aneurysm Therapy

PURPOSE

Abdominal aortic aneurysm (AAA) is one of the leading causes of death in the developed world and is currently undertreated due to the complicated nature of the disease. Herein, we aimed to address the therapeutic potential of a novel class of pleiotropic mediators, specifically a new drug candidate, nitro-oleic acid (NO2-OA), on AAA, in a well-characterized murine AAA model.

METHODS

We generated AAA using a mouse model combining AAV.PCSK9-D377Y induced hypercholesterolemia with angiotensin II given by chronic infusion. Vehicle control (PEG-400), oleic acid (OA), or NO2-OA were subcutaneously delivered to mice using an osmotic minipump. We characterized the effects of NO2-OA on pathophysiological responses and dissected the underlying molecular mechanisms through various in vitro and ex vivo strategies.

RESULTS

Subcutaneous administration of NO2-OA significantly decreased the AAA incidence (8/28 mice) and supra-renal aorta diameters compared to mice infused with either PEG-400 (13/19, p = 0.0117) or OA (16/23, p = 0.0078). In parallel, the infusion of NO2-OA in the AAA model drastically decreased extracellular matrix degradation, inflammatory cytokine levels, and leucocyte/macrophage infiltration in the vasculature. Administration of NO2-OA reduced inflammation, cytokine secretion, and cell migration triggered by various biological stimuli in primary and macrophage cell lines partially through activation of the peroxisome proliferator-activated receptor-gamma (PPARγ). Moreover, the protective effect of NO2-OA relies on the inhibition of macrophage prostaglandin E2 (PGE2)-induced PGE2 receptor 4 (EP4) cAMP signaling, known to participate in the development of AAA.

CONCLUSION

Administration of NO2-OA protects against AAA formation and multifactorial macrophage activation. With NO2-OA currently undergoing FDA approved phase II clinical trials, these findings may expedite the use of this nitro-fatty acid for AAA therapy.

Nitro-Oleic Acid Inhibits Stemness Maintenance and Enhances Neural Differentiation of Mouse Embryonic Stem Cells via STAT3 Signaling

Nitro-oleic acid (NO₂-OA), pluripotent cell-signaling mediator, was recently described as a modulator of the signal transducer and activator of transcription 3 (STAT3) activity. In our study, we discovered new aspects of NO₂-OA involvement in the regulation of stem cell pluripotency and differentiation. Murine embryonic stem cells (mESC) or mESC-derived embryoid bodies (EBs) were exposed to NO₂-OA or oleic acid (OA) for selected time periods. Our results showed that NO₂-OA but not OA caused the loss of pluripotency of mESC cultivated in leukemia inhibitory factor (LIF) rich medium via the decrease of pluripotency markers (NANOG, sex-determining region Y-box 1 transcription factor (SOX2), and octamer-binding transcription factor 4 (OCT4)). The effects of NO₂-OA on mESC correlated with reduced phosphorylation of STAT3. Subsequent differentiation led to an increase of the ectodermal marker orthodenticle homolog 2 (Otx2). Similarly, treatment of mESC-derived EBs by NO₂-OA resulted in the up-regulation of both neural markers Nestin and β-Tubulin class III (Tubb3). Interestingly, the expression of cardiac-specific genes and beating of EBs were significantly decreased. In conclusion, NO₂-OA is able to modulate pluripotency of mESC via the regulation of STAT3 phosphorylation. Further, it attenuates cardiac differentiation on the one hand, and on the other hand, it directs mESC into neural fate.

Chemoproteomic profiling reveals cellular targets of nitro-fatty acids

Nitro-fatty acids are a class of endogenous electrophilic lipid mediators with anti-inflammatory and cytoprotective effects in a wide range of inflammatory and fibrotic disease models. While these beneficial biological effects of nitro-fatty acids are mainly attributed to their ability to form covalent adducts with proteins, only a small number of proteins are known to be nitro-alkylated and the scope of protein nitro-alkylation remains undetermined. Here we describe the synthesis and application of a clickable nitro-fatty acid probe for the detection and first global identification of mammalian proteins that are susceptible to nitro-alkylation. 184 high confidence nitro-alkylated proteins were identified in THP1 macrophages, majority of which are novel targets of nitro-fatty acids, including extended synaptotagmin 2 (ESYT2), signal transducer and activator of transcription 3 (STAT3), toll-like receptor 2 (TLR2), retinoid X receptor alpha (RXRα) and glucocorticoid receptor (NR3C1). In particular, we showed that 9-nitro-oleate covalently modified and inhibited dexamethasone binding to NR3C1. Bioinformatic analyses revealed that nitro-alkylated proteins are highly enriched in endoplasmic reticulum and transmembrane proteins, and are overrepresented in lipid metabolism and transport pathways. This study significantly expands the scope of protein substrates targeted by nitro-fatty acids in living cells and provides a useful resource towards understanding the pleiotropic biological roles of nitro-fatty acids as signaling molecules or as multi-target therapeutic agents.

Cubosomal lipid formulation of nitroalkene fatty acids: Preparation, stability and biological effects

Lipid nitroalkenes – nitro-fatty acids (NO₂–FAs) are formed in vivo via the interaction of reactive nitrogen species with unsaturated fatty acids. The resulting electrophilic NO₂–FAs play an important role in redox homeostasis and cellular stress response. This study investigated the physicochemical properties and reactivity of two NO₂–FAs: 9/10-nitrooleic acid (1) and its newly prepared 1-monoacyl ester, (E)-2,3-hydroxypropyl 9/10-nitrooctadec-9-enoate (2), both synthesized by a direct radical nitration approach. Compounds 1 and 2 were investigated in an aqueous medium and after incorporation into lipid nanoparticles prepared from 1-monoolein, cubosomes 1@CUB and 2@CUB. Using an electrochemical analysis and LC-MS, free 1 and 2 were found to be unstable under acidic conditions, and their degradation occurred in an aqueous environment within a few minutes or hours. This degradation was associated with the production of the NO radical, as confirmed by fluorescence assay. In contrast, preparations 1@CUB and 2@CUB exhibited a significant increase in the stability of the loaded 1 and 2 up to several days to weeks. In addition to experimental data, density functional theory-based calculation results on the electronic structure and structural variability (open and closed configuration) of 1 and 2 were obtained. Finally, experiments with a human HaCaT keratinocyte cell line demonstrated the ability of 1@CUB and 2@CUB to penetrate through the cytoplasmic membrane and modulate cellular pathways, which was exemplified by the Keap1 protein level monitoring. Free 1 and 2 and the cubosomes prepared from them showed cytotoxic effect on HaCaT cells with IC₅₀ values ranging from 1 to 8 μM after 24 h. The further development of cubosomal preparations with embedded electrophilic NO₂–FAs may not only contribute to the field of fundamental research, but also to their application using an optimized lipid delivery vehicle.

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Nitro-fatty acids (NO₂–FAs) are bioactive electrophiles and new drug candidates.

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The study focused on endogenous NO₂-oleic acid and its glycerol ester.

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Cubosomes are lipid nanoparticles stabilizing the incorporated NO₂–FAs.

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Applicability of NO₂-FA-loaded cubosomes was tested on human HaCaT keratinocytes.

Nitro-Oleic Acid (NO2-OA) Improves Systolic Function in Dilated Cardiomyopathy by Attenuating Myocardial Fibrosis

Nitro-oleic acid (NO2-OA), a nitric oxide (NO)- and nitrite (NO2-)-derived electrophilic fatty acid metabolite, displays anti-inflammatory and anti-fibrotic signaling actions and therapeutic benefit in murine models of ischemia-reperfusion, atrial fibrillation, and pulmonary hypertension. Muscle LIM protein-deficient mice (Mlp-/-) develop dilated cardiomyopathy (DCM), characterized by impaired left ventricular function and increased ventricular fibrosis at the age of 8 weeks. This study investigated the effects of NO2-OA on cardiac function in Mlp-/- mice both in vivo and in vitro. Mlp-/- mice were treated with NO2-OA or vehicle for 4 weeks via subcutaneous osmotic minipumps. Wildtype (WT) littermates treated with vehicle served as controls. Mlp-/- mice exhibited enhanced TGFβ signalling, fibrosis and severely reduced left ventricular systolic function. NO2-OA treatment attenuated interstitial myocardial fibrosis and substantially improved left ventricular systolic function in Mlp-/- mice. In vitro studies of TGFβ-stimulated primary cardiac fibroblasts further revealed that the anti-fibrotic effects of NO2-OA rely on its capability to attenuate fibroblast to myofibroblast transdifferentiation by inhibiting phosphorylation of TGFβ downstream targets. In conclusion, we demonstrate a substantial therapeutic benefit of NO2-OA in a murine model of DCM, mediated by interfering with endogenously activated TGFβ signaling.

Olive oil-derived nitro-fatty acids: protection of mitochondrial function in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is characterized by excessive liver fat deposition in the absence of significant alcohol intake. Since extra virgin olive oil (EVOO) reduces fat accumulation, we analyzed the involvement of nitro-fatty acids (NO2-FA) on the beneficial effects of EVOO consumption on NAFLD. Nitro-fatty acids formation was observed during digestion in mice supplemented with EVOO and nitrite. Mice fed with a high-fat diet (HF) presented lower plasma NO2-FA levels than normal chow, and circulating concentrations recovered when the HF diet was supplemented with 10% EVOO plus nitrite. Under NO2-FA formation conditions, liver hemoxygenase-1 expression significantly increased while decreased body weight and fat liver accumulation. Mitochondrial dysfunction plays a central role in the pathogenesis of NAFLD while NO2-FA has been shown to protect from mitochondrial oxidative damage. Accordingly, an improvement of respiratory indexes was observed when mice were supplemented with both EVOO plus nitrite. Liver mitochondrial complexes II and V activities were greater in mice with EVOO supplementation and further improved in the presence of nitrite. Overall, our results strongly suggest a positive correlation between NO2-OA formation from EVOO and the observed improvement of mitochondrial function in NAFLD. The formation of NO2-FA can account for the health benefits associated with EVOO consumption.

Effects of fatty acid nitroalkanes on signal transduction pathways and airway macrophage activation

Fatty acid nitroalkenes are reversibly-reactive electrophiles that are endogenously detectable at nM concentrations and display anti-inflammatory, pro-survival actions. These actions are elicited through the alteration of signal transduction proteins via a Michael addition on nucleophilic cysteine thiols. Nitrated fatty acids (NO2-FAs), like 9- or 10-nitro-octadec-9-enolic acid, will act on signal transduction proteins directly or on key regulatory proteins to cause an up-regulation or down-regulation of the protein's expression, yielding an anti-inflammatory response. These responses have been characterized in many organ systems, such as the cardiovascular system, with the pulmonary system less well defined. Macrophages are one of the most abundant immune cells in the lung and are essential in maintaining lung homeostasis. Despite this, macrophages can play a role in both acute and chronic lung injury due to up-regulation of anti-inflammatory signal transduction pathways and down-regulation of pro-inflammatory pathways. Through their propensity to alter signal transduction pathways, NO2-FAs may be able to reduce macrophage activation during pulmonary injury. This review will focus on the implications of NO2-FAs on macrophage activation in the lung and the signal transduction pathways that may be altered, leading to reduced pulmonary injury.

TRP Channel Agonists Activate Different Afferent Neuromodulatory Mechanisms in Guinea Pig Urinary Bladder

Activation of TRP channels expressed in urinary bladder afferent nerves and urothelium releases neurotransmitters that influence bladder function. Experiments were undertaken to examine the mechanisms underlying effects of TRPA1 (allyl isothiocyanate, AITC), TRPV1 (capsaicin, CAPS), and TRPC (oleoyl-2-acetyl-sn-glycerol, OAG) agonists on guinea pig bladder activity. Effects of these agonists were compared with effects of nitro-oleic acid (OA-NO2), an electrophilic nitro-fatty acid, known to activate TRPV1, TRPA1 or TRPC channels in sensory neurons. AITC (100 μM) increased (231%) area of spontaneous bladder contractions (SBCs) an effect reduced by a TRPA1 antagonist (HC3-03001, HC3, 10 μM) and reversed to inhibition by indomethacin (INDO, 500 nM) a cyclooxygenase inhibitor. The post-INDO inhibitory effect of AITC was mimicked (39% depression) by calcitonin gene-related peptide (CGRP, 100 nM) and blocked by a CGRP antagonist (BIBN, 25 μM). CAPS (1 μM) suppressed SBCs by 30% in 81% of strips, an effect blocked by a TRPV1 antagonist (diarylpiperazine, 1 μM) or BIBN. SBCs were suppressed by OA-NO2 (30 μM, 21% in 77% of strips) or by OAG (50 μM, 30%) an effect blocked by BIBN. OA-NO2 effects were not altered by HC3 or diarylpiperazine. OA-NO2 also induced excitation in 23% of bladder strips. These observations raise the possibility that guinea pig bladder is innervated by at least two types of afferent nerves: [1] Type A express TRPA1 receptors that induce the release of prostaglandins and excite the detrusor, [2] Type B express TRPV1, TRPA1 and TRPC receptors and release CGRP that inhibits the detrusor.

Oxidative stress and redox signaling in CRPC progression: therapeutic potential of clinically-tested Nrf2-activators

Androgen deprivation therapy (ADT) is the mainstay regimen in patients with androgen-dependent prostate cancer (PCa). However, the selection of androgen-independent cancer cells leads to castrate resistant prostate cancer (CRPC). The aggressive phenotype of CRPC cells underscores the need to elucidate mechanisms and therapeutic strategies to suppress CRPC outgrowth. Despite ADT, the activation of androgen receptor (AR) transcription factor continues via crosstalk with parallel signaling pathways. Understanding of how these signaling cascades are initiated and amplified post-ADT is lacking. Hormone deprivation can increase oxidative stress and the resultant reactive oxygen species (ROS) may activate both AR and non-AR signaling. Moreover, ROS-induced inflammatory cytokines may further amplify these redox signaling pathways to augment AR function. However, clinical trials using ROS quenching small molecule antioxidants have not suppressed CRPC progression, suggesting that more potent and persistent suppression of redox signaling in CRPC cells will be needed. The transcription factor Nrf2 increases the expression of numerous antioxidant enzymes and downregulates the function of inflammatory transcription factors, e.g., nuclear factor kappa B. We documented that Nrf2 overexpression can suppress AR-mediated transcription in CRPC cell lines. Furthermore, two Nrf2 activating agents, sulforaphane (a phytochemical) and bardoxolone-methyl (a drug in clinical trial) suppress AR levels and sensitize CRPC cells to anti-androgens. These observations implicate the benefits of potent Nrf2-activators to suppress the lethal signaling cascades that lead to CRPC outgrowth. This review article will address the redox signaling networks that augment AR signaling during PCa progression to CRPC, and the possible utility of Nrf2-activating agents as an adjunct to ADT.

Protein Lipoxidation: Basic Concepts and Emerging Roles

Protein lipoxidation is a non-enzymatic post-translational modification that consists of the covalent addition of reactive lipid species to proteins. This occurs under basal conditions but increases in situations associated with oxidative stress. Protein targets for lipoxidation include metabolic and signalling enzymes, cytoskeletal proteins, and transcription factors, among others. There is strong evidence for the involvement of protein lipoxidation in disease, including atherosclerosis, neurodegeneration, and cancer. Nevertheless, the involvement of lipoxidation in cellular regulatory mechanisms is less understood. Here we review basic aspects of protein lipoxidation and discuss several features that could support its role in cell signalling, including its selectivity, reversibility, and possibilities for regulation at the levels of the generation and/or detoxification of reactive lipids. Moreover, given the great structural variety of electrophilic lipid species, protein lipoxidation can contribute to the generation of multiple structurally and functionally diverse protein species. Finally, the nature of the lipoxidised proteins and residues provides a frameshift for a complex interplay with other post-translational modifications, including redox and redox-regulated modifications, such as oxidative modifications and phosphorylation, thus strengthening the importance of detailed knowledge of this process.

Role of electrophilic nitrated fatty acids during development and response to abiotic stress processes in plants

Nitro-fatty acids are generated from the interaction of unsaturated fatty acids and nitric oxide (NO)-derived molecules. The endogenous occurrence and modulation throughout plant development of nitro-linolenic acid (NO2-Ln) and nitro-oleic acid (NO2-OA) suggest a key role for these molecules in initial development stages. In addition, NO2-Ln content increases significantly in stress situations and induces the expression of genes mainly related to abiotic stress, such as genes encoding members of the heat shock response family and antioxidant enzymes. The promoter regions of NO2-Ln-induced genes are also involved mainly in stress responses. These findings confirm that NO2-Ln is involved in plant defense processes against abiotic stress conditions via induction of the chaperone network and antioxidant systems. NO2-Ln signaling capacity lies mainly in its electrophilic nature and allows it to mediate a reversible post-translational modification called nitroalkylation, which is capable of modulating protein function. NO2-Ln is a NO donor that may be involved in NO signaling events and is able to generate S-nitrosoglutathione, the major reservoir of NO in cells and a key player in NO-mediated abiotic stress responses. This review describes the current state of the art regarding the essential role of nitro-fatty acids as signaling mediators in development and abiotic stress processes.

Nuclear factor erythroid 2-related factor 2 as a treatment target of kidney diseases

PURPOSE OF REVIEW

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor which regulates a wider range of downstream pathways than previously thought. This review focuses on the novel findings about the internal regulatory mechanisms of Nrf2, the expanding understanding of its role in maintaining cellular homeostasis and the attempts to broaden the clinical application of its activators.

RECENT FINDINGS

Nrf2 is in charge of the maintenance of cellular homeostasis under stress and there exist the internal regulatory mechanisms for Nrf2 which have recently been elucidated. New downstream pathways of Nrf2 have been discovered, including the defense against ferroptosis, the latest concept of cell death. Several Nrf2 activators are at various stages of clinical development and are being tested in clinical trials for chronic kidney disease (CKD) including diabetic kidney disease, Alport syndrome, autosomal dominant polycystic kidney disease and focal segmental glomerulosclerosis.

SUMMARY

Nrf2 has been gathering attention as an emerging treatment target of chronic diseases which have oxidative stress and inflammation as their pathogenesis including CKD. Basic and clinical studies are under way to establish its role as a target for treatment of those diseases.

A Nitroalkene Benzoic Acid Derivative Targets Reactive Microglia and Prolongs Survival in an Inherited Model of ALS via NF-κB Inhibition

Motor neuron degeneration and neuroinflammation are the most striking pathological features of amyotrophic lateral sclerosis (ALS). ALS currently has no cure and approved drugs have only a modest clinically therapeutic effect in patients. Drugs targeting different deleterious inflammatory pathways in ALS appear as promising therapeutic alternatives. Here, we have assessed the potential therapeutic effect of an electrophilic nitroalkene benzoic acid derivative, (E)-4-(2-nitrovinyl) benzoic acid (BANA), to slow down paralysis progression when administered after overt disease onset in SOD1G93A rats. BANA exerted a significant inhibition of NF-κB activation in NF-κB reporter transgenic mice and microglial cell cultures. Systemic daily oral administration of BANA to SOD1G93A rats after paralysis onset significantly decreased microgliosis and astrocytosis, and significantly reduced the number of NF-κB-p65-positive microglial nuclei surrounding spinal motor neurons. Numerous microglia bearing nuclear NF-κB-p65 were observed in the surrounding of motor neurons in autopsy spinal cords from ALS patients but not in controls, suggesting ALS-associated microglia could be targeted by BANA. In addition, BANA-treated SOD1G93A rats after paralysis onset showed significantly ameliorated spinal motor neuron pathology as well as conserved neuromuscular junction innervation in the skeletal muscle, as compared to controls. Notably, BANA prolonged post-paralysis survival by ~30%, compared to vehicle-treated littermates. These data provide a rationale to therapeutically slow paralysis progression in ALS using small electrophilic compounds such as BANA, through a mechanism involving microglial NF-κB inhibition.

Electrophilic characteristics and aqueous behavior of fatty acid nitroalkenes

Fatty acid nitroalkenes (NO2-FA) are endogenously-generated products of the reaction of metabolic and inflammatory-derived nitrogen dioxide (.NO2) with unsaturated fatty acids. These species mediate signaling actions and induce adaptive responses in preclinical models of inflammatory and metabolic diseases. The nitroalkene substituent possesses an electrophilic nature, resulting in rapid and reversible reactions with biological nucleophiles such as cysteine, thus supporting post-translational modifications (PTM) of proteins having susceptible nucleophilic centers. These reactions contribute to enzyme regulation, modulation of inflammation and cell proliferation and the regulation of gene expression responses. Herein, focus is placed on the reduction-oxidation (redox) characteristics and stability of specific NO2-FA regioisomers having biological and clinical relevance; nitro-oleic acid (NO2-OA), bis-allylic nitro-linoleic acid (NO2-LA) and the conjugated diene-containing nitro-conjugated linoleic acid (NO2-cLA). Cyclic and alternating-current voltammetry and chronopotentiometry were used to the study of reduction potentials of these NO2-FA. R-NO2 reduction was observed around -0.8 V (vs. Ag/AgCl/3 M KCl) and is related to relative NO2-FA electrophilicity. This reduction process could be utilized for the evaluation of NO2-FA stability in aqueous milieu, shown herein to be pH dependent. In addition, electron paramagnetic resonance (EPR) spectroscopy was used to define the stability of the nitroalkene moiety under aqueous conditions, specifically under conditions where nitric oxide (.NO) release could be detected. The experimental data were supported by density functional theory calculations using 6-311++G (d,p) basis set and B3LYP functional. Based on experimental and computational approaches, the relative electrophilicities of these NO2-FA are NO2-cLA >> NO2-LA > NO2-OA. Micellarization and vesiculation largely define these biophysical characteristics in aqueous, nucleophile-free conditions. At concentrations below the critical micellar concentration (CMC), monomeric NO2-FA predominate, while at greater concentrations a micellar phase consisting of self-assembled lipid structures predominates. The CMC, determined by dynamic light scattering in 0.1 M phosphate buffer (pH 7.4) at 25 °C, was 6.9 (NO2-LA) 10.6 (NO2-OA) and 42.3 μM (NO2-cLA), respectively. In aggregate, this study provides new insight into the biophysical properties of NO2-FA that are important for better understanding the cell signaling and pharmacological potential of this class of mediators.

Nrf2-A Molecular Target for Sepsis Patients in Critical Care

The transcription factor NF-E2 p45-related factor 2 (Nrf2) is an established master regulator of the anti-oxidative and detoxifying cellular response. Thus, a role in inflammatory diseases associated with the generation of large amounts of reactive oxygen species (ROS) seems obvious. In line with this, data obtained in cell culture experiments and preclinical settings have shown that Nrf2 is important in regulating target genes that are necessary to ensure cellular redox balance. Additionally, Nrf2 is involved in the induction of phase II drug metabolizing enzymes, which are important both in degrading and converting drugs into active forms, and into putative carcinogens. Therefore, Nrf2 has also been implicated in tumorigenesis. This must be kept in mind when new therapy approaches are planned for the treatment of sepsis. Therefore, this review highlights the function of Nrf2 in sepsis with a special focus on the translation of rodent-based results into sepsis patients in the intensive care unit (ICU).

Fatty acid nitroalkenes inhibit the inflammatory response to bleomycin-mediated lung injury

Fatty acid nitroalkenes are reversibly-reactive electrophiles, endogenously detectable at nM concentrations, displaying anti-inflammatory actions. Nitroalkenes like 9- or 10-nitro-octadec-9-enoic acid (e.g. nitro-oleic acid, OA-NO₂) pleiotropically suppress cardiovascular inflammatory responses, with pulmonary responses less well defined. C57BL/6 J male mice were intratracheally administered bleomycin (3 U/kg, ITB), to induce pulmonary inflammation and acute injury, or saline and were treated with 50 μL OA-NO₂ (50 μg) or vehicle in the same instillation and 72 h post-exposure to assess anti-inflammatory properties. Bronchoalveolar lavage (BAL) and lung tissue were collected 7d later. ITB mice lost body weight, with OA-NO₂ mitigating this loss (-2.3 ± 0.94 vs -0.4 ± 0.83 g). Histology revealed ITB induced cellular infiltration, proteinaceous debris deposition, and tissue injury, all significantly reduced by OA-NO₂. Flow cytometry analysis of BAL demonstrated loss of Siglec F⁺/F4/80⁺/CD45⁺ alveolar macrophages with ITB (89 ± 3.5 vs 30 ± 3.7%). Analysis of CD11b/CD11c expressing cells showed ITB-induced non-resident macrophage infiltration (4 ± 2.3 vs 43 ± 2.4%) was decreased by OA-NO₂ (24 ± 2.4%). Additionally, OA-NO₂ attenuated increases in mature, activated interstitial macrophages (23 ± 4.8 vs. 43 ± 5.4%) in lung tissue digests. Flow analysis of CD31^-/CD45^-/Sca-1⁺ mesenchymal cells revealed ITB increased CD44⁺ populations (1 ± 0.4 vs 4 ± 0.4MFI), significantly reduced by OA-NO₂ (3 ± 0.4MFI). Single cell analysis of mesenchymal cells by western blotting showed profibrotic ZEB1 protein expression induced by ITB. Lung digest CD45⁺ cells revealed ITB increased HMGB1⁺ cells, with OA-NO₂ suppressing this response. Inhibition of HMGB1 expression correlated with increased basal phospholipid production and SP-B expression in the lung lining. These findings indicate OA-NO₂ inhibits ITB-induced pro-inflammatory responses by modulating resident cell function.

Electrophilic nitrated fatty acids are potential therapeutic candidates for inflammatory and fibrotic lung diseases

Several types of exposures can cause acute or chronic inflammatory reactions in the lungs often leading to asthma, pulmonary fibrosis, chronic obstructive pulmonary disease (COPD), acute lung injury, lung cancer, and other deleterious health outcomes. Current therapy, with inhaled or oral glucocorticoids, successfully targets inflammation but also produces adverse effects that limit their enthusiastic use. Accordingly, the need remains for interventions that are safer and more effective. Nitrated fatty acids (NFAs) are highly electrophilic and are produced endogenously by non-enzymatic reactions of nitric oxide with conjugated unsaturated fatty acids. The literature indicates that NFAs are detected in humans at the nanomolar range and are produced more robustly under inflammatory conditions. Recent studies on novel NFAs report antiinflammatory, antioxidant, and antifibrotic effects, while also acting as partial agonists of peroxisome proliferator-activated receptor-gamma (PPAR-γ). Furthermore, these functions of NFAs occur via reversible electrophilic alkylation of cysteine residues and regulation of antiinflammatory, antioxidant signaling through modulation of transcription factors, including nuclear factor E2-related factor 2 (Nrf2), PPAR-γ, and NF-κB. Here, we review and update the role of NFA signaling mechanisms and their therapeutic potential in various lung diseases. As NFAs display strong electrophilic interaction with multimechanistic pathways, they can be considered promising drug candidates for challenging lung diseases.

NRF2 Regulation Processes as a Source of Potential Drug Targets against Neurodegenerative Diseases

NRF2 acts by controlling gene expression, being the master regulator of the Phase II antioxidant response, and also being key to the control of neuroinflammation. NRF2 activity is regulated at several levels, including protein degradation by the proteasome, transcription, and post-transcription. The purpose of this review is to offer a concise and critical overview of the main mechanisms of NRF2 regulation and their actual or potential use as targets for the treatment of neurodegenerative diseases.

Nitro-oleic acid, a ligand of CD36, reduces cholesterol accumulation by modulating oxidized-LDL uptake and cholesterol efflux in RAW264.7 macrophages

Macrophages play a pivotal role in the early stages of atherosclerosis development; they excessively accumulate cholesterol in the cytosol in response to modified Low Density Lipoprotein (mLDL). The mLDL are incorporated through scavenger receptors. CD36 is a high-affinity cell surface scavenger receptor that facilitates the binding and uptake of long-chain fatty acids and mLDL into the cell. Numerous structurally diverse ligands can initiate signaling responses through CD36 to regulate cell metabolism, migration, and angiogenesis. Nitro-fatty acids are endogenous electrophilic lipid mediators that react with and modulate the function of multiple enzymes and transcriptional regulatory proteins. These actions induce the expression of several anti-inflammatory and cytoprotective genes and limit pathologic responses in experimental models of atherosclerosis, cardiac ischemia/reperfusion, and inflammatory diseases. Pharmacological and genetic approaches were used to explore the actions of nitro-oleic acid (NO₂-OA) on macrophage lipid metabolism. Pure synthetic NO₂-OA dose-dependently increased CD36 expression in RAW264.7 macrophages and this up-regulation was abrogated in BMDM from Nrf2-KO mice. Ligand binding analysis revealed that NO₂-OA specifically interacts with CD36, thus limiting the binding and uptake of mLDL. Docking analysis shows that NO₂-OA establishes a low binding energy interaction with the alpha helix containing Lys164 in CD36. NO₂-OA also restored autophagy flux in mLDL-loaded macrophages, thus reversing cholesterol deposition within the cell. In aggregate, these results indicate that NO₂-OA reduces cholesterol uptake by binding to CD36 and increases cholesterol efflux by restoring autophagy.

Dimethyl fumarate protects thioacetamide-induced liver damage in rats: Studies on Nrf2, NLRP3, and NF-κB

The present study was designed to investigate the hepatoprotective potential of dimethyl fumarate (DMF) against thioacetamide (TAA)-induced liver damage. Wistar rats were treated with DMF (12.5, 25, and 50 mg/kg/day, orally) and TAA (200 mg/kg intraperitoneally, every third day) for 6 consecutive weeks. TAA exposure significantly reduced body weight, increased liver weight and index, and intervention with DMF did not ameliorate these parameters. DMF treatment significantly restored TAA-induced increase in the levels of aspartate aminotransferase, alanine aminotransferase, γ-glutamyl transferase, total bilirubin, uric acid, malondialdehyde, reduced glutathione, and histopathological findings such as inflammatory cell infiltration, deposition of collagen, necrosis, and bridging fibrosis. DMF treatment significantly ameliorated TAA-induced hepatic stellate cell activation, increase in inflammatory cascade markers (NACHT, LRR, and PYD domains-containing protein 3; NLRP3, apoptosis-associated speck like protein containing a caspase recruitment domain; ASC, caspase-1, nuclear factor-kappa B; NF-κB, interleukin-6), fibrogenic makers (α-smooth muscle actin; ɑ-SMA, transforming growth factor; TGF-β1, fibronectin, collagen 1) and antioxidant markers (nuclear factor (erythroid-derived 2)-like factor 2; Nrf2, superoxide dismutase-1; SOD-1, catalase). The present findings concluded that DMF protects against TAA-induced hepatic damage mediated through the downregulation of inflammatory cascades and upregulation of antioxidant status.

Historical origins of the discovery of mammalian nitric oxide (nitrogen monoxide) production/physiology/pathophysiology

The award of the 1998 Nobel Prize in Physiology or Medicine to Robert F. Furchgott, Louis J. Ignarro, and Ferid Murad "for their discoveries concerning nitric oxide as a signaling molecule in the cardiovascular system" highlighted the discovery of NO in mammals. This breakthrough also coincided with the discoveries of the role of NO as a cytotoxic effector in the immune system and as an intercellular neurotransmitter in the nervous system. This brief overview describes the chronological development of this trilinear convergence in 1986-1988, including background chemistry and history of human/nitrogen oxide interactions in general.

Nitro-Fatty Acid Logistics: Formation, Biodistribution, Signaling, and Pharmacology

In addition to supporting cellular energetic demands and providing building blocks for lipid synthesis, fatty acids (FAs) are precursors of potent signaling molecules. In particular, the presence of conjugated double bonds on the fatty-acyl chain provides a preferential target for nitration generating nitro-FAs (NO₂-FAs). The formation of NO₂-FAs is a nonenzymatic process that requires reactive nitrogen species and occurs locally at the site of inflammation or during gastric acidification. NO₂-FAs are electrophilic and display pleiotropic signaling actions through reversible protein alkylation. This review focuses on the endogenously formed NO₂-FAs' mechanism of absorption, systemic distribution, signaling, and preclinical models. Understanding the dynamics of these processes will facilitate targeted dietary interventions and further the current pharmacological development aimed at low-grade inflammatory diseases.