Antioxidants and phase 2 enzymes in macrophages: regulation by Nrf2 signaling and protection against oxidative and electrophilic stress

Preclinical studies of natural flavonoids in inflammatory bowel disease based on macrophages: a systematic review with meta-analysis and network pharmacology

Flavonoid is a category of bioactive polyphenolic compounds that are extensively distributed in plants with specific pharmacological properties, such as anti-inflammatory and anti-oxidant. Importantly, natural flavonoids have shown the protected function on the dextran sulfate sodium (DSS)-induced colitis in animals and lipopolysaccharides (LPS)-induced inflammatory response in macrophages. The purpose of this systematic review is to explore the efficacy of natural flavonoids in animal models of IBD (inflammatory bowel disease) and potential mechanisms in macrophages by meta-analysis and network pharmacology in preclinical studies. Relevant foundation studies were searched from January 2010 to November 2023 in databases like PubMed, Elsevier ScienceDirect, and Web of Science. Then, OriginPro software was used to extract values from images, and the analysis was performed using Review Manager 5.3. The retrieved data was analyzed according to the fixed-effects model and random-effects model. Subsequently, heterogeneity was evaluated using the I2 statistics. Lastly, network pharmacology was applied to confirm mechanisms of natural flavonoids on IBD. According to the results of meta-analysis, we found the natural flavonoids exhibited powerful therapeutic effects against IBD, which not only reversed colonic shortness (WMD = 1.33, 95% CI (1.07, 1.59), P < 0.00001), but also reduced histological score (SMD =  - 2.66, 95% CI (- 3.77, - 1.95), P < 0.00001) between natural flavonoid treatment groups compared with the experimental IBD model. Furthermore, treatment with natural flavonoids decreased the levels of tumor necrosis factor-α (TNF-α) in macrophages. Mechanistically, our summarized data substantiate that natural flavonoids alleviate LPS-induced M1 macrophage polarization, anti-oxidant, anti-inflammatory, maintain intestinal barrier, and inhibit the activation of the NLR family pyrin domain containing 3 (NLRP3) inflammasome in macrophages. Moreover, the results of network pharmacology also support this. This systematic review demonstrated the efficiency of natural flavonoids in treating IBD in preclinical research by meta-analysis and network pharmacology, which offered supporting evidence for clinical trial implementation. However, some limitations remain present, such as technique quality shortage, missed reports on account of negative results, failure to count sample size, and the risk of bias.

Vanillin Has Potent Antibacterial, Antioxidant, and Anti-Inflammatory Activities In Vitro and in Mouse Colitis Induced by Multidrug-Resistant Escherichia coli

A large number of cases of infectious colitis caused by multidrug-resistant (MDR) bacteria, such as Escherichia coli, can result in colon damage and severe inflammation. Vanilla, a widely utilized flavor and fragrance compound, is extensively used in various food. However, the effect of vanilla on MDR E. coli-induced infectious colitis has received less attention. In this study, the antibacterial activity of vanillin against MDR E. coli and other bacteria was determined by the microtiter broth dilution method. The antioxidant and anti-inflammatory capacity of vanillin was assessed in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells and MDR E. coli-induced mouse colitis. The results demonstrated that vanillin exhibited potent antibacterial activity against various strains of MDR E. coli, Salmonella, and Staphylococcus aureus, with a minimal inhibitory concentration (MIC) of 1.25-2.5 mg/mL and a minimum bactericidal concentration (MBC) of 5-10 mg/mL; it effectively inhibited cell division in E. coli. Vanillin also displayed remarkable antioxidant activity by suppressing the levels of malondialdehyde (MDA), superoxide dismutase (SOD), and reactive oxygen species (ROS) in LPS-stimulated RAW 264.7 cell; it significantly reduced the production of inflammatory mediators including nitroxide (NO), tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), and interleukin 1β (IL-1β), while increasing interleukin 10 (IL-10). In an MDR E. coli-induced mouse colitis model, vanillin effectively inhibited inflammation by suppressing inflammatory cytokines, mitogen-activated protein kinase (MAPK), and nuclear factor κ-B (NF-κB) cell signaling pathway activation; it ameliorated changes in intestinal microflora characterized by decreased Firmicutes richness alongside increased Bacteroides richness, rebalancing the dysbiosis caused by E. coli. These findings highlight the potential pharmacological applicability of vanillin as a promising bioactive molecule for treating infectious colitis.

Targeting catalase in cancer

Healthy cells have developed a sophisticated network of antioxidant molecules to prevent the toxic accumulation of reactive oxygen species (ROS) generated by diverse environmental stresses. On the opposite, cancer cells often exhibit high levels of ROS and an altered levels of antioxidant molecules compared to normal cells. Among them, the antioxidant enzyme catalase plays an essential role in cell defense against oxidative stress through the dismutation of hydrogen peroxide into water and molecular oxygen, and its expression is often decreased in cancer cells. The elevation of ROS in cancer cells provides them proliferative advantages, and leads to metabolic reprogramming, immune escape and metastasis. In this context, catalase is of critical importance to control these cellular processes in cancer through various mechanisms. In this review, we will discuss the major progresses and challenges in understanding the role of catalase in cancer for this last decade. This review also aims to provide important updates regarding the regulation of catalase expression, subcellular localization and discuss about the potential role of microbial catalases in tumor environment. Finally, we will describe the different catalase-based therapies and address the advantages, disadvantages, and limitations associated with modulating catalase therapeutically in cancer treatment.

Comparison of the protective effects of chitosan oligosaccharides and chitin oligosaccharide on apoptosis, inflammation and oxidative stress

Chitin degradation products, especially chitosan oligosaccharides (COSs), are highly valued in various industrial fields, such as food, medicine, cosmetics and agriculture, for their rich resources and high cost-effectiveness. However, little is known about the impact of acetylation on COS cellular bioactivity. The present study aimed to compare the differential effects of COS and highly N-acetylated COS (NACOS), known as chitin oligosaccharide, on H2O2-induced cell stress. MTT assay showed that pretreatment with NACOS and COS markedly inhibited H2O2-induced RAW264.7 cell death in a concentration-dependent manner. Flow cytometry indicated that NACOS and COS exerted an anti-apoptosis effect on H2O2-induced oxidative damage in RAW264.7 cells. NACOS and COS treatment ameliorated H2O2-induced RAW264.7 cell cycle arrest. Western blotting revealed that the anti-oxidation effects of NACOS and COS were mediated by suppressing expression of proteins involved in H2O2-induced apoptosis, including Bax, Bcl-2 and cleaved PARP. Furthermore, the antagonist effects of NACOS were greater than those of COS, suggesting that acetylation was essential for the protective effects of COS.

SLC15A3 plays a crucial role in pulmonary fibrosis by regulating macrophage oxidative stress

Idiopathic pulmonary fibrosis (IPF) is a fatal and irreversible disease with few effective treatments. Alveolar macrophages (AMs) are involved in the development of IPF from the initial stages due to direct exposure to air and respond to external oxidative damage (a major inducement of pulmonary fibrosis). Oxidative stress in AMs plays an indispensable role in promoting fibrosis development. The oligopeptide histidine transporter SLC15A3, mainly expressed on the lysosomal membrane of macrophages and highly expressed in the lung, has proved to be involved in innate immune and antiviral signaling pathways. In this study, we demonstrated that during bleomycin (BLM)- or radiation-induced pulmonary fibrosis, the recruitment of macrophages induced an increase of SLC15A3 in the lung, and the deficiency of SLC15A3 protected mice from pulmonary fibrosis and maintained the homeostasis of the pulmonary microenvironment. Mechanistically, deficiency of SLC15A3 resisted oxidative stress in macrophages, and SLC15A3 interacted with the scaffold protein p62 to regulate its expression and phosphorylation activation, thereby regulating p62-nuclear factor erythroid 2-related factor 2 (NRF2) antioxidant stress pathway protein, which is related to the production of reactive oxygen species (ROS). Overall, our data provided a novel mechanism for targeting SLC15A3 to regulate oxidative stress in macrophages, supporting the therapeutic potential of inhibiting or silencing SLC15A3 for the precautions and treatment of pulmonary fibrosis.

SeMet alleviates AFB1-induced oxidative stress and apoptosis in rabbit kidney by regulating Nrf2//Keap1/NQO1 and PI3K/AKT signaling pathways

The purpose of this study was to explore the protective effect of SeMet on renal injury induced by AFB1 in rabbits and its molecular mechanism. Forty rabbits of 35 days old were randomly divided into control group, AFB1 group (0.3 mg AFB1/kg b.w), 0.2 mg/kg Se + AFB1 group (0.3 mg AFB1/kg b.w + 0.2 mg SeMet/kg feed) and 0.4 mg/kg Se + AFB1 group (0.3 mg AFB1/kg b.w + 0.4 mg SeMet/kg feed). The SeMet treatment group was fed different doses of SeMet diets every day for 21 days. On the 17-21 day, the AFB1 treatment group, the 0.2 mg/kg Se + AFB1 group and the 0.4 mg/kg Se + AFB1 group were administered 0.3 mg AFB1 /kg b.w by gavage (dissolved in 0.5 ml olive oil) respectively. The results showed that AFB1 poisoning resulted in the changes of renal structure, the increase of renal coefficient and serum biochemical indexes, the ascent of ROS and MDA levels, the descent of antioxidant enzyme activity, and the significant down-regulation of Nrf2, HO-1 and NQO1. Besides, AFB1 poisoning increased the number of renal apoptotic cells, rised the levels of PTEN, Bax, Caspase-3 and Caspase-9, and decreased the levels of PI3K, AKT, p-AKT and Bcl-2. In summary, SeMet was added to alleviate the oxidative stress injury and apoptosis of kidney induced by AFB1, and the effect of 0.2 mg/kg Se + AFB1 is better than 0.4 mg/kg Se + AFB1.

Inhibition of NLRP3 Inflammasome Activation by 3H-1,2-Dithiole-3-Thione: A Potential Therapeutic Approach for Psoriasis Treatment

Psoriasis is a chronic autoimmune skin disease with a significant impact on quality of life and potential for severe comorbidities. Inflammation in the skin is induced by immune cells that overexpress pro-inflammatory cytokines, with the Th17 cell playing a crucial role. NLRP3 inflammasome activation is associated with inflammatory diseases and abnormal T cell differentiation. 3H-1,2-dithiole-3-thione (D3T), isolated from cruciferous vegetables, has anti-inflammatory effects and inhibits Th17 differentiation. This study aimed to investigate how D3T reduces skin inflammation and modulates Th17 cell differentiation by inhibiting NLRP3 inflammasome activation. In an imiquimod-induced psoriasis mouse model, D3T treatment demonstrated significant reductions in ear thickness, skin redness, and scaling compared to a control group. Our study also observed decreased expression of ki-67, NLRP3 inflammasome, and cleaved caspase-1 in skin samples, reduced levels of IL-6 and IL-17A in serum samples, and inhibition of Th17 differentiation after D3T application. D3T could also inhibit the expression of NLRP3, caspase-1, and IL-1β in TNF-α stimulated HaCaT cells. The mechanical study also revealed that D3T could inhibit NLRP3 inflammasome activation by inhibiting the JNK pathway in HaCaT cells. These results indicate that targeting NLRP3 inflammasome activation is a promising strategy in the treatment of psoriasis.

Macrophage Activity under Hyperglycemia: A Study of the Effect of Resveratrol and 3H-1,2-Dithiole-3-thione on Potential Polarization

Currently, research is focused on bioactive compounds with the potential to promote macrophage polarization with the aim of reducing the development of inflammatory-related diseases. However, the effect of bioactive compounds under oxidative-stress-induced hyperglycemia on macrophage polarization has been scarcely investigated. RAW 264.7 macrophages were incubated under standard (SG) or high glucose (HG) conditions and stimulated with lipopolysaccharide (LPS) (10, 60 and 100 ng/mL) to monitor macrophage polarization after resveratrol (RSV) or 3H-1,2-dithiole-3-thione (D3T) supplementation (2.5, 5, 10 and 20 µM). Under SG and HG conditions without LPS stimulation, RSV significantly decreased macrophage viability at the highest concentration (20 µM), whereas D3T had no or low effect. LPS stimulation at 60 and 100 ng/mL, under SG and HG conditions, increased significantly macrophage viability. Both RSV and D3T significantly decreased NO production in LPS-stimulated macrophages under HG condition, whereas only D3T increased GSH levels at 100 ng/mL and normalized MDA values at 60 ng/mL of LPS under HG condition. Under 60 ng/mL LPS stimulation and HG, mRNA IL-1 and IL-6 were higher. Interestingly, RSV decreased pro-inflammatory interleukins; meanwhile, D3T increased Arg1 and IL-10 relative expression. Overall, our results indicate that hyperglycemia plays a fundamental role in the modulation of macrophage-induced inflammation in response to bioactive compounds.

Cross-talk between energy and redox metabolism in astrocyte-neuron functional cooperation

Astrocytes show unique anatomical, morphological, and metabolic features to take up substrates from the blood and metabolize them for local delivery to active synapses to sustain neuron function. In the present review, we specifically focus on key molecular aspects of energy and redox metabolism that facilitate this astrocyte-neuronal coupling in a controlled manner. Basal glycolysis is co-ordinated by the anaphase-promoting complex/cyclosome (APC/C)-Cdh1, a ubiquitin ligase that targets the proglycolytic enzyme 6-phosphofructokinase-2,6-bisphosphastate-3 (PFKFB3) for degradation. APC/C-Cdh1 activity is more robust in neurons than in astrocytes, which determine that PFKFB3 abundance and glycolytic rate are weaker in neurons. The low PFKFB3 activity in neurons facilitates glucose-6-phosphate oxidation via the pentose-phosphate pathway, which promotes antioxidant protection. Conversely, the high PFKFB3 activity in astrocytes allows the production and release of glycolytic lactate, which is taken up by neurons that use it as an oxidizable substrate. Importantly, the mitochondrial respiratory chain is tighter assembled in neurons than in astrocytes, thus the bioenergetic efficiency of mitochondria is higher in neurons. Because of this, the production of reactive oxygen species (mROS) by mitochondrial complex I is very low in neurons and very high in astrocytes. Such a naturally occurring high abundance of mROS in astrocytes physiologically determines a specific transcriptional fingerprint that contributes to sustaining cognitive performance. We conclude that the energy and redox metabolism of astrocytes must complementarily match that of neurons to regulate brain function and animal welfare.

Targeting Nrf2 with 3 H-1,2-dithiole-3-thione to moderate OXPHOS-driven oxidative stress attenuates IL-17A-induced psoriasis

Psoriasis, a chronic autoimmune disease characterized by the hyperproliferation of keratinocytes in the epidermis and parakeratosis, significantly impacts quality of life. Interleukin (IL)- 17A dominates the pathogenesis of psoriasis and facilitates reactive oxygen species (ROS) accumulation, which exacerbates local psoriatic lesions. Biologic treatment provides remarkable clinical efficacy, but its high cost and unignorable side effects limit its applications. 3 H-1,2-Dithiole-3-thione (D3T) possesses compelling antioxidative capacities against several diseases through the nuclear factor erythroid 2-related factor 2 (Nrf2) cascade. Hence, we aimed to evaluate the effect and mechanism of D3T in psoriasis. We found that D3T attenuates skin thickening and scaling by inhibiting IL-17A-secreting γδT cells in imiquimod (IMQ)-induced psoriatic mice. Interleukin-17A markedly enhanced IL-6 and IL-8 expression, lipid peroxidation, the contents of nitric oxide and hydrogen peroxide, oxidative phosphorylation and the MAPK/NF-κB pathways in keratinocytes. IL-17A also inhibited the Nrf2-NQO1-HO-1 axis and the activities of superoxide dismutase and glutathione peroxidase. D3T significantly reversed these parameters in IL-17A-treated keratinocytes. ML-385, a Nrf2 neutralizer, failed to improve D3T-induced anti-inflammatory and antioxidative effects in IL-17A-treated keratinocytes. We conclude that targeting Nrf2 with D3T to diminish oxidative and inflammatory damage in keratinocytes may attenuate psoriasis.

Ammonium sulfate-based prefractionation improved proteome coverage and detection of carbonylated proteins in Arabidopsis thaliana leaf extract

Ammonium sulfate is well known to salt out proteins at high concentrations. The study revealed that it can serve to increase by 60% the total number of identified carbonylated proteins by LC-MS/MS. Protein carbonylation is a significant post-translational modification associated with reactive oxygen species signaling in animal and plant cells. However, the detection of carbonylated proteins involved in signaling is still challenging, as they only represent a small subset of the proteome in the absence of stress. In this study, we investigated the hypothesis that a prefractionation step with ammonium sulphate will improve the detection of the carbonylated proteins in a plant extract. For this, we extracted total protein from the Arabidopsis thaliana leaves and subjected the extract to stepwise precipitation with ammonium sulfate to 40%, 60%, and 80% saturation. The protein fractions were then analyzed by liquid chromatography-tandem mass spectrometry for protein identification. We found that all the proteins identified in the non-fractionated samples were also found in the prefractionated samples, indicating no loss was incurred during the prefractionation. About 45% more proteins were identified in the fractionated samples compared to the non-fractionated total crude extract. When the prefractionation steps were combined with the enrichment of carbonylated proteins labeled with a fluorescent hydrazide probe, several carbonylated proteins, which were unseen in the non-fractionated samples, became visible in the prefractionated samples. Consistently, the prefractionation method allowed to identify 63% more carbonylated proteins by mass spectrometry compared to the number of carbonylated proteins identified from the total crude extract without prefractionation. These results indicated that the ammonium sulfate-based proteome prefractionation can be used to improve proteome coverage and identification of carbonylated proteins from a complex proteome sample.

Nanodrug rescues liver fibrosis via synergistic therapy with H2O2 depletion and Saikosaponin b1 sustained release

Hypoxia and hydrogen peroxide (H₂O₂) accumulation form the profibrogenic liver environment, which involves fibrogenesis and chronic stimulation of hepatic stellate cells (HSCs). Catalase (CAT) is the major antioxidant enzyme that catalyzes H₂O₂ into oxygen and water, which loses its activity in different liver diseases, especially in liver fibrosis. Clinical specimens of cirrhosis patients and liver fibrotic mice are collected in this work, and results show that CAT decrease is closely correlated with hypoxia-induced transforminmg growth factor β1 (TGF-β1). A multifunctional nanosystem combining CAT-like MnO₂ and anti-fibrosis Saikosaponin b1 (Ssb1) is subsequently constructed for antifibrotic therapy. MnO₂ catalyzes the accumulated H₂O₂ into oxygen, thereby ameliorating the hypoxic and oxidative stress to prevent activation of HSCs, and assists to enhance the antifibrotic pharmaceutical effect of Ssb1. This work suggests that TGF-β1 is responsible for the diminished CAT in liver fibrosis, and our designed MnO₂@PLGA/Ssb1 nanosystem displays enhanced antifibrotic efficiency through removing excess H₂O₂ and hypoxic stress, which may be a promising therapeutic approach for liver fibrosis treatment.

Surfactant protein D inhibits lipid-laden foamy macrophages and lung inflammation in chronic obstructive pulmonary disease

Increased levels of surfactant protein D (SP-D) and lipid-laden foamy macrophages (FMs) are frequently found under oxidative stress conditions and/or in patients with chronic obstructive pulmonary disease (COPD) who are also chronically exposed to cigarette smoke (CS). However, the roles and molecular mechanisms of SP-D and FMs in COPD have not yet been determined. In this study, increased levels of SP-D were found in the bronchoalveolar lavage fluid (BALF) and sera of ozone- and CS-exposed mice. Furthermore, SP-D-knockout mice showed increased lipid-laden FMs and airway inflammation caused by ozone and CS exposure, similar to that exhibited by our study cohort of chronic smokers and COPD patients. We also showed that an exogenous recombinant fragment of human SP-D (rfhSP-D) prevented the formation of oxidized low-density lipoprotein (oxLDL)-induced FMs in vitro and reversed the airway inflammation and emphysematous changes caused by oxidative stress and CS exposure in vivo. SP-D upregulated bone marrow-derived macrophage (BMDM) expression of genes involved in countering the oxidative stress and lipid metabolism perturbations induced by CS and oxLDL. Our study demonstrates the crucial roles of SP-D in the lipid homeostasis of dysfunctional alveolar macrophages caused by ozone and CS exposure in experimental mouse emphysema, which may provide a novel opportunity for the clinical application of SP-D in patients with COPD.

NRF2 in dermatological disorders: Pharmacological activation for protection against cutaneous photodamage and photodermatosis

The skin barrier and its endogenous protective mechanisms cope daily with exogenous stressors, of which ultraviolet radiation (UVR) poses an imminent danger. Although the skin is able to reduce the potential damage, there is a need for comprehensive strategies for protection. This is particularly important when developing pharmacological approaches to protect against photocarcinogenesis. Activation of NRF2 has the potential to provide comprehensive and long-lasting protection due to the upregulation of numerous cytoprotective downstream effector proteins that can counteract the damaging effects of UVR. This is also applicable to photodermatosis conditions that exacerbate the damage caused by UVR. This review describes the alterations caused by UVR in normal skin and photosensitive disorders, and provides evidence to support the development of NRF2 activators as pharmacological treatments. Key natural and synthetic activators with photoprotective properties are summarized. Lastly, the gap in knowledge in research associated with photodermatosis conditions is highlighted.

Antioxidant Activity of Acanthopanax senticosus Flavonoids in H2O2-Induced RAW 264.7 Cells and DSS-Induced Colitis in Mice

The redox reaction is a normal process of biological metabolism in the body that leads to the production of free radicals. Under conditions such as pathogenic infection, stress, and drug exposure, free radicals can exceed normal levels, causing protein denaturation, DNA damage, and the oxidation of the cell membrane, which, in turn, causes inflammation. Acanthopanax senticosus (A. senticosus) flavonoids are the main bioactive ingredients with antioxidant function. H₂O₂-treated RAW 264.7 cells and DSS-induced colitis in mice were used to evaluate the antioxidant properties of A. senticosus flavonoids. The results show that A. senticosus flavonoids can significantly downregulate the levels of ROS and MDA in H₂O₂-treated RAW 264.7 cells and increase the levels of CAT, SOD, and GPx. A. senticosus flavonoids can also increase the body weights of DSS-induced colitis mice, increase the DAI index, and ameliorate the shortening of the colon. ELISA experiments confirmed that A. senticosus flavonoids could reduce the level of MDA in the mouse serum and increase the levels of SOD, CAT, and GPx. Histopathology showed that the tissue pathological changes in the A. senticosus flavonoid group were significantly lower than those in the DSS group. The Western blot experiments showed that the antioxidant capacity of A. senticosus flavonoids was accomplished through the Nrf2 pathway. In conclusion, A. senticosus flavonoids can relieve oxidative stress in vivo and in vitro and protect cells or tissues from oxidative damage.

Shedding a New Light on Skin Aging, Iron- and Redox-Homeostasis and Emerging Natural Antioxidants

Reactive oxygen species (ROS) are necessary for normal cell signaling and the antimicrobial defense of the skin. However excess production of ROS can disrupt the cellular redox balance and overwhelm the cellular antioxidant (AO) capacity, leading to oxidative stress. In the skin, oxidative stress plays a key role in driving both extrinsic and intrinsic aging. Sunlight exposure has also been a major contributor to extrinsic photoaging of the skin as its oxidising components disrupt both redox- and iron-homeostasis, promoting oxidative damage to skin cells and tissue constituents. Upon oxidative insults, the interplay between excess accumulation of ROS and redox-active labile iron (LI) and its detrimental consequences to the skin are often overlooked. In this review we have revisited the oxidative mechanisms underlying skin damage and aging by focussing on the concerted action of ROS and redox-active LI in the initiation and progression of intrinsic and extrinsic skin aging processes. Based on these, we propose to redefine the selection criteria for skin antiaging and photoprotective ingredients to include natural antioxidants (AOs) exhibiting robust redox-balancing and/or iron-chelating properties. This would promote the concept of natural-based or bio-inspired bifunctional anti-aging and photoprotective ingredients for skincare and sunscreen formulations with both AO and iron-chelating properties.

3H-1,2-dithiole-3-thione suppresses LPS-induced proinflammatory responses in macrophages: potential involvement of antioxidant induction, NF-κB, and Nrf2

Previously, we reported that 3H-1,2-dithiole-3-thione (D3T), an Nrf2 activator, acted as a potential chemoprotectant against lipopolysaccharide (LPS)-induced mortality in mice. In view of the critical involvement of macrophages in the pathogenesis of LPS-induced endotoxemia, in the present study, we investigated the protective effects of D3T on LPS-induced proinflammatory responses in cultured murine RAW 264.7 macrophage cell line and primary peritoneal macrophages and the potential involvement of antioxidant induction, NF-κB, and Nrf2. We showed that treatment with D3T resulted in increased levels of a series of antioxidants in RAW 264.7 cells in a concentration-dependent manner. These included the reduced form of glutathione, glutathione peroxidase, glutathione reductase, glutathione S-transferase, and NADPH:quinone oxidoreductase 1. Catalase was also potently induced by D3T which, however, did not show a concentration dependency. Concurrent with the ability to induce the above cellular antioxidants, D3T pretreatment of RAW 264.7 cells also led to a concentration-dependent suppression of LPS-induced interleukin-1beta (IL-1β) production and nitric oxide release. LPS-stimulated tumor necrosis factor-alpha (TNF-α) production was also suppressed by D3T, but to a much lesser extent. Using NF-κB reporter gene-expressing RAW 264.7 cells, we further showed that D3T pretreatment also suppressed LPS-induced NF-κB activation. To investigate the potential involvement of Nrf2, a chief regulator of cellular antioxidant genes, we used peritoneal macrophages isolated from Nrf2^+/+ and Nrf2^-/- mice. Our results showed that D3T pretreatment suppressed LPS-induced proinflammatory responses in Nrf2^+/+ macrophages, and this inhibitory effect of D3T was completely lost in Nrf2^-/- macrophages. Collectively, the results of the present study demonstrated that D3T acted as a potent suppressor of LPS-induced proinflammatory responses in macrophages. Antioxidant induction, NF-κB suppression, and Nrf2 activation appeared to contribute to the anti-proinflammatory activity of D3T in macrophages.

Environmental exposure to cadmium reduces the primary antibody-mediated response of wood mice (Apodemus sylvaticus) from differentially polluted locations in the Netherlands

The Wood mouse (Apodemus sylvaticus) is a widespread mammalian species that acts as a reservoir host for multiple infections, including zoonotic diseases. Exposure to immunotoxins, like for instance trace metals, may reduce the ability of the host to mount proper responses to pathogens, potentially increasing the transmission and prevalence of infections. Antibody-mediated responses are crucial in preventing and limiting infections, and the quantification of the primary antibody response is considered a sensitive predictor of immunosuppression. The current study aims to investigate effects of cadmium exposure on the antibody-mediated responses of wood mice inhabiting polluted and non-polluted areas in the Netherlands. Wood mice were captured alive at different locations and immunized to sheep red blood cells (SRBC) to induce a primary antibody response. SRBC-specific antibody-producing cells, or plaque forming cells (PFC), were quantified and related to kidney cadmium levels. Differential circulating main leukocyte populations were also characterised. Cadmium concentrations in mice kidneys differed between mice captured at different locations, and increased with individual body mass, likely associated with age-related time of exposure. Effect of cadmium was apparent on the percentages of B cell counts in blood. Because of potential natural immune heterogeneity between wild rodent populations, mice immune responses were analysed and compared grouped by captured locations. Capture location had significant effect on the total counts of white blood cells. Increasing cadmium exposure in wood mice captured from polluted sites was associated with a decrease of splenic PFC counts. This field research shows that wood mice antibody responses can be impaired by cadmium exposure, even at low environmental levels, by affecting B cell functioning mainly. Impaired B cell function can make exposed mice more susceptible to infections, potentially increasing the reservoir function of their populations. It also shows that immunomodulatory effects in the field should be assessed site specifically.

Xeroderma Pigmentosum C: A Valuable Tool to Decipher the Signaling Pathways in Skin Cancers

Xeroderma pigmentosum (XP) is a rare autosomal genodermatosis that manifests clinically with pronounced sensitivity to ultraviolet (UV) radiation and the high probability of the occurrence of different skin cancer types in XP patients. XP is mainly caused by mutations in XP-genes that are involved in the nucleotide excision repair (NER) pathway that functions in the removal of bulky DNA adducts. Besides, the aggregation of DNA lesions is a life-threatening event that might be a key for developing various mutations facilitating cancer appearance. One of the key players of NER is XPC that senses helical distortions found in damaged DNA. The majority of XPC gene mutations are nonsense, and some are missense leading either to the loss of XPC protein or to the expression of a truncated nonfunctional version. Given that no cure is yet available, XPC patients should be completely protected and isolated from all types of UV radiations (UVR). Although it is still poorly understood, the characterization of the proteomic signature of an XPC mutant is essential to identify mediators that could be targeted to prevent cancer development in XPC patients. Unraveling this proteomic signature is fundamental to decipher the signaling pathways affected by the loss of XPC expression following exposure to UVB radiation. In this review, we will focus on the signaling pathways disrupted in skin cancer, pathways modulating NER's function, including XPC, to disclose signaling pathways associated with XPC loss and skin cancer occurrence.

Protein Carbonylation: Emerging Roles in Plant Redox Biology and Future Prospects

Plants are sessile in nature and they perceive and react to environmental stresses such as abiotic and biotic factors. These induce a change in the cellular homeostasis of reactive oxygen species (ROS). ROS are known to react with cellular components, including DNA, lipids, and proteins, and to interfere with hormone signaling via several post-translational modifications (PTMs). Protein carbonylation (PC) is a non-enzymatic and irreversible PTM induced by ROS. The non-enzymatic feature of the carbonylation reaction has slowed the efforts to identify functions regulated by PC in plants. Yet, in prokaryotic and animal cells, studies have shown the relevance of protein carbonylation as a signal transduction mechanism in physiological processes including hydrogen peroxide sensing, cell proliferation and survival, ferroptosis, and antioxidant response. In this review, we provide a detailed update on the most recent findings pertaining to the role of PC and its implications in various physiological processes in plants. By leveraging the progress made in bacteria and animals, we highlight the main challenges in studying the impacts of carbonylation on protein functions in vivo and the knowledge gap in plants. Inspired by the success stories in animal sciences, we then suggest a few approaches that could be undertaken to overcome these challenges in plant research. Overall, this review describes the state of protein carbonylation research in plants and proposes new research avenues on the link between protein carbonylation and plant redox biology.

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.

Oxidative Stress in Ischemic Heart Disease

One of the novel interesting topics in the study of cardiovascular disease is the role of the oxidation system, since inflammation and oxidative stress are known to lead to cardiovascular diseases, their progression and complications. During decades of research, many complex interactions between agents of oxidative stress, oxidation, and antioxidant systems have been elucidated, and numerous important pathophysiological links to na number of disorders and diseases have been established. This review article will present the most relevant knowledge linking oxidative stress to vascular dysfunction and disease. The review will focus on the role of oxidative stress in endotheleial dysfunction, atherosclerosis, and other pathogenetic processes and mechanisms that contribute to the development of ischemic heart disease.

Neuronal Activity and Its Role in Controlling Antioxidant Genes

Forebrain neurons have relatively weak intrinsic antioxidant defenses compared to astrocytes, in part due to hypo-expression of Nrf2, an oxidative stress-induced master regulator of antioxidant and detoxification genes. Nevertheless, neurons do possess the capacity to auto-regulate their antioxidant defenses in response to electrical activity. Activity-dependent Ca²⁺ signals control the expression of several antioxidant genes, boosting redox buffering capacity, thus meeting the elevated antioxidant requirements associated with metabolically expensive electrical activity. These genes include examples which are reported Nrf2 target genes and yet are induced in a Nrf2-independent manner. Here we discuss the implications for Nrf2 hypofunction in neurons and the mechanisms underlying the Nrf2-independent induction of antioxidant genes by electrical activity. A significant proportion of Nrf2 target genes, defined as those genes controlled by Nrf2 in astrocytes, are regulated by activity-dependent Ca²⁺ signals in human stem cell-derived neurons. We propose that neurons interpret Ca²⁺ signals in a similar way to other cell types sense redox imbalance, to broadly induce antioxidant and detoxification genes.

Effect of Acacia Polyphenol Supplementation on Exercise-Induced Oxidative Stress in Mice Liver and Skeletal Muscle

The purpose of this study was to investigate the effects of acacia polyphenol (AP) supplementation on exercise-induced oxidative stress in mouse liver and skeletal muscle. Plasma aspartate aminotransferase (AST), liver and skeletal muscle levels of thiobarbituric acid reactive substance (TBARS), and levels of skeletal muscle protein carbonyls increased immediately after exhaustive exercise. Exhaustive exercise also decreased liver glutathione (GSH). These results suggest that the exhaustive exercise used in this study induced tissue damage and oxidative stress. Contrary to our expectations, AP supplementation increased plasma AST and alanine aminotransferase activities, liver levels of TBARS, and protein carbonyls. Furthermore, AP supplementation decreased glutathione and glutathione peroxidase activity in the liver. On the other hand, AP supplementation decreased TBARS levels in skeletal muscle. These results suggest that oral high-dose AP administration decreased oxidative stress in skeletal muscle but induced oxidative stress in the liver and increased hepatotoxicity.

Nrf2, NF-κB and PPARβ/δ mRNA Expression Profile in Patients with Coronary Artery Disease

BACKGROUND

Oxidative stress and inflammation are present in coronary artery disease (CAD) and are linked to the activation of the transcription nuclear factor kappa B (NF-κB). To attenuate these complications, transcription factors like nuclear factor erythroid 2-related factor 2 (Nrf2) and peroxisome proliferator-activated receptor-β/δ (PPARβ/δ) can be activated to inhibit NF-κB. However, the available data on expression of NF-κB, Nrf2 and PPARβ/δ in CAD patients are limited.

OBJECTIVE

To evaluate the expression of the transcription factors NF-κB and Nrf2 and PPAR𝛽/𝛿 in CAD patients.

METHODS

Thirty-five patients (17 men, mean age 62.4 ? 7.55 years) with CAD and twelve patients (5 men, mean age 63.50 ? 11.46 years) without CAD were enrolled. Peripheral blood mononuclear cells (PBMCs) were isolated and processed for mRNA expression of Nrf2, NF-κB, NADPH: quinone oxidoreductase 1 (NQO1) and PPARβ/δ mRNAs using quantitative real-time polymerase chain reaction (qPCR). p < 0.05 was considered statistically significant.

RESULTS

There was no difference in the mRNA expressions of Nrf2 (1.35 ? 0.57), NF-κB (1.08 ? 0.50) or in the antioxidant enzyme NQO1 (1.05 ? 0.88) in the CAD group compared to the group without CAD (1.16 ? 0.76, 0.95 ? 0.33, 0.81 ? 0.55, respectively). However, PPARβ/δ was highest expressed in the CAD group (1.17 ? 0.86 vs. 0.56 ? 0.34, p = 0.008).

CONCLUSION

The main finding of this study was the PPARβ/δ being more expressed in the PBMC of patients with CAD compared to the control group, whereas no differences were observed in Nrf2 or NF-κB mRNA expressions.

Biomechanical Forces and Oxidative Stress: Implications for Pulmonary Vascular Disease

Significance: Oxidative stress in the cell is characterized by excessive generation of reactive oxygen species (ROS). Superoxide (O₂^-) and hydrogen peroxide (H₂O₂) are the main ROS involved in the regulation of cellular metabolism. As our fundamental understanding of the underlying causes of lung disease has increased it has become evident that oxidative stress plays a critical role. Recent Advances: A number of cells in the lung both produce, and respond to, ROS. These include vascular endothelial and smooth muscle cells, fibroblasts, and epithelial cells as well as the cells involved in the inflammatory response, including macrophages, neutrophils, eosinophils. The redox system is involved in multiple aspects of cell metabolism and cell homeostasis. Critical Issues: Dysregulation of the cellular redox system has consequential effects on cell signaling pathways that are intimately involved in disease progression. The lung is exposed to biomechanical forces (fluid shear stress, cyclic stretch, and pressure) due to the passage of blood through the pulmonary vessels and the distension of the lungs during the breathing cycle. Cells within the lung respond to these forces by activating signal transduction pathways that alter their redox state with both physiologic and pathologic consequences. Future Directions: Here, we will discuss the intimate relationship between biomechanical forces and redox signaling and its role in the development of pulmonary disease. An understanding of the molecular mechanisms induced by biomechanical forces in the pulmonary vasculature is necessary for the development of new therapeutic strategies.

Signaling Pathways, Chemical and Biological Modulators of Nucleotide Excision Repair: The Faithful Shield against UV Genotoxicity

The continuous exposure of the human body's cells to radiation and genotoxic stresses leads to the accumulation of DNA lesions. Fortunately, our body has several effective repair mechanisms, among which is nucleotide excision repair (NER), to counteract these lesions. NER includes both global genome repair (GG-NER) and transcription-coupled repair (TC-NER). Deficiencies in the NER pathway underlie the development of several DNA repair diseases, such as xeroderma pigmentosum (XP), Cockayne syndrome (CS), and trichothiodystrophy (TTD). Deficiencies in GG-NER and TC-NER render individuals to become prone to cancer and neurological disorders, respectively. Therefore, NER regulation is of interest in fine-tuning these risks. Distinct signaling cascades including the NFE2L2 (NRF2), AHR, PI3K/AKT1, MAPK, and CSNK2A1 pathways can modulate NER function. In addition, several chemical and biological compounds have proven success in regulating NER's activity. These modulators, particularly the positive ones, could therefore provide potential treatments for genetic DNA repair-based diseases. Negative modulators, nonetheless, can help sensitize cells to killing by genotoxic chemicals. In this review, we will summarize and discuss the major upstream signaling pathways and molecules that could modulate the NER's activity.

Potential Photoprotective Effect of Dietary Corn Silk Extract on Ultraviolet B-Induced Skin Damage

Ultraviolet B (UVB) irradiation causes adverse effects on the skin. Corn silk contains flavonoids and other bioactive compounds and antioxidants, which may prevent skin photoaging through antioxidant and anti-inflammatory effects. We aimed to investigate the potential photoprotective effects of dietary corn silk on UVB-induced skin damage in mice and the mechanisms behind these effects on human skin cells. Oral administration of corn silk water extract (CS) (2 or 4 g/kg/day) for 19 weeks decreased epidermal thickness, wrinkle formation, and positive staining for PCNA, Ki67, and 8-OHdG, and increased collagen staining in UVB-irradiated SKH-1 hairless mice compared with controls. The pro-inflammatory NF-κB target genes (IL-1β, iNOS, and COX-2) and MMP-9 expressions were lower in the CS groups, and TGF-β/Smad signaling increased. Low skin lipid peroxidation and blood DNA oxidation levels and high blood glutathione were detected. Antioxidant transcription factor Nrf2-related catalase and SOD1 proteins and glutaredoxin mRNA levels increased. The results of CS extract treatment and UVB irradiation in HaCaT cells showed the same results in Nrf2 and NF-κB target genes. An LC-MS/MS analysis showed that the CS extract contained potential antioxidants, which might have contributed to its anti-photoaging effects in tissues and cells. CS extract may reduce UVB-induced skin damage through antioxidant and anti-inflammatory mechanisms.

3H-1,2-Dithiole-3-Thione as a Potentially Novel Therapeutic Compound for Sepsis Intervention

Through the history of modern medicine, bioactive components in natural products have been either employed directly as medicines or used as prototypes for synthetic drug development. This brief Research Highlights paper considers 3H-1,2-dithiole-3-thione (D3T), a member of the 1,2-dithiole-3-thiones-compounds which may naturally occur in cruciferous vegetables. Among 1,2-dithiole-3-thiones, D3T is the most potent member with regard to the capacity of inducing tissue defenses against oxidative and inflammatory stress. Oxidative and inflammatory stress is a major pathophysiological process involved in numerous human disorders, including cancer, cardiovascular diseases, neurodegeneration, and sepsis, to name just a few. This article surveys recent major research findings on D3T as an inducer of tissue antioxidative and antiinflammatory defenses and as a potential therapeutic modality for sepsis intervention.

Curcumin attenuates oxidative stress in RAW264.7 cells by increasing the activity of antioxidant enzymes and activating the Nrf2-Keap1 pathway

Large-scale breeding environments often lead to oxidative stress. Macrophages play an important role in the immune system and are vulnerable to reactive oxygen species (ROS), which result in macrophage death. Curcumin is the main active component of turmeric and exerts antioxidant effects. Here, we measured the activity of some antioxidant enzymes and chose the Nrf2-Keap1 signaling pathway to study the protective effects of curcumin on macrophages under oxidative stress in vitro. We used RAW264.7 cells as a research model, and oxidative damage was induced by hydrogen peroxide (H₂O₂). Cell viability was measured by an MTT assay. Flow cytometry was used to measure cellular ROS and apoptosis. The effect of curcumin on Nrf2-Keap1 signaling pathway-related genes was analyzed by qRT-PCR. Furthermore, the translocation of Nrf2 protein was also investigated by Western blot analysis of total and nuclear proteins. All curcumin-treated groups exhibited increased activity of catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX). Low- and middle-dose curcumin decreased malondialdehyde (MDA) and ROS levels, but high-dose curcumin increased MDA and ROS production. We found that low-dose curcumin protected cells from apoptosis, while apoptosis in the middle- and high-dose curcumin-treated groups were stagnant in the early stage. Furthermore, middle-dose curcumin upregulated Nrf2 expression after H₂O₂ treatment for 4 h. Low- and middle-dose curcumin could activate Nrf2 and promote it to migrate into nuclei. The translocation of Nrf2 to the nucleus to upregulate the expression of haemoxygenase-1 (HO-1) was promoted in the low- and middle-dose curcumin-treated groups. The middle-dose curcumin-treated group also exhibited enhanced expression of glutamate-cysteine ligase, a modifier subunit (GLCM), but inhibited transcription of glutamate-cysteine ligase, a catalytic subunit (GCLC). Curcumin resisted oxidants by increasing the activity of antioxidant enzymes and activating the Nrf2-Keap1 pathway, which could potentially promote cell survival.

Common skin bacteria protect their host from oxidative stress through secreted antioxidant RoxP

Cutibacterium acnes is an abundant skin commensal with several proposed mutualistic functions. A protein with strong antioxidant activity was recently identified from the C. acnes secretome. This protein, termed RoxP, facilitated aerobic bacterial growth in vitro and ex vivo. As reducing events naturally occurred outside of the bacterial cell, it was further hypothesized that RoxP could also serve to modulate redox status of human skin. The biological function of RoxP was here assessed in vitro and in vivo, through oxidatively stressed cell cultures and through protein quantification from skin affected by oxidative disease (actinic keratosis and basal cell carcinoma), respectively. 16S rDNA amplicon deep sequencing and single locus sequence typing was used to correlate bacterial prevalence to cutaneous RoxP abundances. We show that RoxP positively influence the viability of monocytes and keratinocytes exposed to oxidative stress, and that a congruent concentration decline of RoxP can be observed in skin affected by oxidative disease. Basal cell carcinoma was moreover associated with microbial dysbiosis, characterized by reduced C. acnes prevalence. C. acnes's secretion of RoxP, an exogenous but naturally occurring antioxidant on human skin, is likely to positively influence the human host. Results furthermore attest to its prospective usability as a biopharmaceutical.

Cell-specific immune-modulation of cadmium on murine macrophages and mast cell lines in vitro

Toxic trace metals are widespread contaminants that are potentially immunotoxic even at environmentally low exposure levels. They can modulate the immunity to infections, e.g., in wildlife species living in contaminated areas. The diverse immune cell types can be differentially affected by the exposure leading to the modulation of specific protective mechanisms. Macrophages and mast cells, part of the innate immune system, trigger immune responses and perform particular effector functions. The present study compared toxicological and functional effects of cadmium in two models of murine macrophages (RAW264.7 and NR8383 cell lines) and two models of murine mast cells (MC/9 and RBL-2H3 cell lines). Cadmium was selected as a model compound because its known potential to induce reactive oxygen species and its relevance as an environmental contaminant. Mechanisms of toxicity, such as redox imbalance and apoptosis induction were measured in stationary cells, while functional outcome effects were measured in activated cells. Cadmium-depleted glutathione antioxidant in all four cell lines tested although reactive oxygen species was not significantly increased. Mast cells had full dose-response depletion of glutathione below cytotoxic levels while in macrophages the depletion was not complete. Functional endpoints tumour necrosis factor-alpha and nitrite production in lipopolysaccharide-activated macrophages were increased by cadmium exposure. In contrast, mast cell lipopolysaccharide-induced tumour necrosis factor-alpha and IgE-mediated histamine release were reduced by cadmium. These data indicate potentially differential effects of cadmium among murine innate immune cell types, where mast cells would be more susceptible to oxidative stress and their function might be at a higher risk to be modulated compared to macrophages.

Omega 3 rich diet modulates energy metabolism via GPR120-Nrf2 crosstalk in a novel antioxidant mouse model

With obesity rates reaching epidemic proportions, more studies concentrated on reducing the risk and treating this epidemic are vital. Redox stress is an important metabolic regulator involved in the pathophysiology of cardiovascular disease, Type 2 diabetes, and obesity. Oxygen and nitrogen-derived free radicals alter glucose and lipid homeostasis in key metabolic tissues, leading to increases in risk of developing metabolic syndrome. Oxidants derived from dietary fat differ in their metabolic regulation, with numerous studies showing benefits from a high omega 3 rich diet compared to the frequently consumed "western diet" rich in saturated fat. Omega 3 (OM3) fatty acids improve lipid profile, lower inflammation, and ameliorate insulin resistance, possibly through maintaining redox homeostasis. This study is based on the hypothesis that altering endogenous antioxidant production and/or increasing OM3 rich diet consumption will improve energy metabolism and maintain insulin sensitivity. We tested the comparative metabolic effects of a diet rich in saturated fat (HFD) and an omega 3-enriched diet (OM3) in the newly developed 'stress-less' mice model that overexpresses the endogenous antioxidant catalase. Eight weeks of dietary intervention showed that mice overexpressing endogenous catalase compared to their wild-type controls when fed an OM3 enriched diet, in contrast to HFD, activated GPR120-Nrf2 cross-talk to maintain balanced energy metabolism, normal circadian rhythm, and insulin sensitivity. These findings suggest that redox regulation of GPR120/FFAR4 might be an important target in reducing risk of metabolic syndrome and associated diseases.

Protective effects of p-coumaric acid against oxidant and hyperlipidemia-an in vitro and in vivo evaluation

Dietary phenols are antioxidants with diverse physiological functions that are beneficial for human health. The objective of this research work was to investigate antioxidant activity of p-coumaric acid (p-CA) using four in vitro methods, the protective effects against oxidative stress in PC12 cells, and hypolipidemic effects on High fat-diet (HFD) mice model. The p-CA exhibited moderate antioxidant activity in the selected in vitro assay. The highest chelating activity of p-CA at 50 μg/mL was found to be 52.22%. Pretreatment with p-CA significantly enhanced cell viability of PC12 cell and suppressed AAPH-induced intracellular ROS generation and AAPH-induced LDH release. The hypolipidemic effects of p-CA (100 mg/kg BW) was directly linked to the increased expression of nuclear factor erythroid 2-related factor (Nrf2) by 2.0-fold, Glutathione peroxidase (Gpx) by 3.8-fold, Superoxide dismutase (SOD-1) by 1.6-fold, Heme oxygenase (HO-1) by 1.72-fold and NAD(P)H Quinone Dehydrogenase 1 (NQO-1) by 1.5-fold compared with HFD group. In addition to these effects, p-CA decreased total cholesterol and atherosclerosis index levels, and increased catalase (CAT) level in serum, total antioxidant capacity (T-AOC) and glutathione peroxidase (GSH-Px) levels in liver as compared HFD group. Administration of p-CA also promoted the recovery of hyperlipidemia steatohepatitis in mice by ameliorating lipid peroxidation. These results suggested that p-CA is a potent antioxidant with potential therapeutic efficacy for treating hyperlipidemia symptoms.

Catalase and nonalcoholic fatty liver disease

Obesity and insulin resistance are considered the main causes of nonalcoholic fatty liver disease (NAFLD), and oxidative stress accelerates the progression of NAFLD. Free fatty acids, which are elevated in the liver by obesity or insulin resistance, lead to incomplete oxidation in the mitochondria, peroxisomes, and microsomes, leading to the production of reactive oxygen species (ROS). Among the ROS generated, H₂O₂ is mainly produced in peroxisomes and decomposed by catalase. However, when the H₂O₂ concentration increases because of decreased expression or activity of catalase, it migrates to cytosol and other organelles, causing cell injury and participating in the Fenton reaction, resulting in serious oxidative stress. To date, numerous studies have been shown to inhibit the pathogenesis of NAFLD, but treatment for this disease mainly depends on weight loss and exercise. Various molecules such as vitamin E, metformin, liraglutide, and resveratrol have been proposed as therapeutic agents, but further verification of the dose setting, clinical application, and side effects is needed. Reducing oxidative stress may be a fundamental method for improving not only the progression of NAFLD but also obesity and insulin resistance. However, the relationship between NAFLD progression and antioxidants, particularly catalase, which is most commonly expressed in the liver, remains unclear. Therefore, this review summarizes the role of catalase, focusing on its potential therapeutic effects in NAFLD progression.

Aging attenuates redox adaptive homeostasis and proteostasis in female mice exposed to traffic-derived nanoparticles ('vehicular smog')

Environmental toxicants are catalysts for protein damage, aggregation, and the aging process. Fortunately, evolution selected adaptive homeostasis as a system to mitigate such damage by expanding the normal capacity to cope with toxic stresses. Little is known about the subcellular degradative responses to proteins oxidatively damaged by air pollution. To better understand the impact of environmental toxicants upon the adaptive homeostatic response, female C57BL/6 mice were exposed for 10 weeks to filtered air or reaerosolized vehicular-derived nano-scale particulate matter (nPM), at which point tissues from young (6 month) and middle-aged (21 month) mice were studied. We found significant increases of proteolytic capacity in lung, liver, and heart. Up to two-fold increases were seen in the 20S Proteasome, the Immunoproteasome, the mitochondrial Lon protease, and NF-E2-related factor 2 (Nrf2), a major transcriptional factor for these and other stress-responsive genes. The responses were equivalent in all organs, despite the indirect input of inhaled particles to heart and liver which are downstream of lung. To our knowledge, this is the first exploration of proteostatic responses to oxidative damage by air pollution. Although, middle-aged mice had higher basal levels, their Nrf2-responsive-genes exhibited no response to nanoparticulate exposure. We also found a parallel age-associated rise in the Nrf2 transcriptional inhibitors, Bach1 and c-Myc which appear to attenuate adaptive responses in older mammals, possibly explaining the 'age-ceiling effect.' This report extends prior findings in male mice by demonstrating the involvement of proteolytic responses to traffic-related air pollution in lung, liver, and heart of female mice, with an age-dependent loss of adaptive homeostasis.

Oxidative Stress in Cardiovascular Diseases: Involvement of Nrf2 Antioxidant Redox Signaling in Macrophage Foam Cells Formation

Oxidative stress is an important risk factor contributing to the pathogenesis of cardiovascular diseases. Oxidative stress that results from excessive reactive oxygen species (ROS) production accounts for impaired endothelial function, a process which promotes atherosclerotic lesion or fatty streaks formation (foam cells). Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor involved in cellular redox homeostasis. Upon exposure to oxidative stress, Nrf2 is dissociated from its inhibitor Keap-1 and translocated into the nucleus, where it results in the transcriptional activation of cell defense genes. Nrf2 has been demonstrated to be involved in the protection against foam cells formation by regulating the expression of antioxidant proteins (HO-1, Prxs, and GPx1), ATP-binding cassette (ABC) efflux transporters (ABCA1 and ABCG1) and scavenger receptors (scavenger receptor class B (CD36), scavenger receptor class A (SR-A) and lectin-type oxidized LDL receptor (LOX-1)). However, Nrf2 has also been reported to exhibit pro-atherogenic effects. A better understanding on the mechanism of Nrf2 in oxidative stress-induced cardiac injury, as well as the regulation of cholesterol uptake and efflux, are required before it can serve as a novel therapeutic target for cardiovascular diseases prevention and treatment.

Oxidative Stress in Cardiovascular Diseases: Involvement of Nrf2 Antioxidant Redox Signaling in Macrophage Foam Cells Formation

Oxidative stress is an important risk factor contributing to the pathogenesis of cardiovascular diseases. Oxidative stress that results from excessive reactive oxygen species (ROS) production accounts for impaired endothelial function, a process which promotes atherosclerotic lesion or fatty streaks formation (foam cells). Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor involved in cellular redox homeostasis. Upon exposure to oxidative stress, Nrf2 is dissociated from its inhibitor Keap-1 and translocated into the nucleus, where it results in the transcriptional activation of cell defense genes. Nrf2 has been demonstrated to be involved in the protection against foam cells formation by regulating the expression of antioxidant proteins (HO-1, Prxs, and GPx1), ATP-binding cassette (ABC) efflux transporters (ABCA1 and ABCG1) and scavenger receptors (scavenger receptor class B (CD36), scavenger receptor class A (SR-A) and lectin-type oxidized LDL receptor (LOX-1)). However, Nrf2 has also been reported to exhibit pro-atherogenic effects. A better understanding on the mechanism of Nrf2 in oxidative stress-induced cardiac injury, as well as the regulation of cholesterol uptake and efflux, are required before it can serve as a novel therapeutic target for cardiovascular diseases prevention and treatment.

In Vivo Bioluminescence Imaging of Nuclear Factor kappaB Activation: A Valuable Model for Studying Inflammatory and Oxidative Stress in Live Mice

The nuclear factor kappaB (NF-κB) is a redox-sensitive transcription factor that plays a critical role in inflammation among other biological functions. This ROS Protocol article describes an in vivo bioluminescence imaging assay for assessing NF-κB activation using the commercially available transgenic mice carrying NF-κB response element-luciferase reporter gene (NF-κB-RE-Luc). Using the highly sensitive Berthold NightOwl LB981 in vivo bioluminescence imaging system, we are able to visualize the NF-κB activation in live mice under basal conditions, suggesting constitutive activation of NF-κB as a part of its fundamental biology. Treatment of mice with lipopolysaccharides (LPS) results in a drastic increase in bioluminescence, proving the validity of the model in assessing inflammatory stress. Treatment of mice with 3H-1,2-dithiole-3-thione (D3T), an activator of nuclear factor E-2 related factor 2 (Nrf2), led to a significant reduction in both basal and LPS-induced activation of NF-κB in the live mice, suggesting a value of this model in assessing drug efficacy in suppressing NF-κB activation and inflammatory stress. The protocols of this valuable model are detailed in this article along with a discussion of its potential use in studying disease conditions involving inflammatory and oxidative stress mechanisms and in assessing therapeutic modalities targeting the NF-κB signaling for disease intervention.

TLR2 activation induces antioxidant defence in human monocyte-macrophage cell line models

When monocytes are recruited to inflammation/infection sites, extravasate and differentiate into macrophages, they encounter increasing levels of oxidative stress, both from exogenous and endogenous sources. In this study, we aimed to determine whether there are specific biochemical mechanisms responsible for an increase in oxidative stress resistance in differentiating macrophages. We performed experiments on in vitro cell line models of the monocyte-macrophage differentiation axis (less differentiated THP-1 cells and more differentiated Mono Mac 6 cells). At the same time, we verified the hypothesis that activating monocyte/macrophage innate immune response by pathogens (exemplified by stimulating the TLR2 pattern recognition receptor) would further strengthen cellular antioxidant defences. We found that resistance to exogenous oxidative stress increased substantially both during differentiation and upon activation of TLR2. This increase in antioxidant resistance was accompanied by decrease in free radical damage to cellular proteins. On the molecular level, this resistance was mediated especially by increased levels and activity of glutathione, glutathione-related antioxidant enzymes and Mn superoxide dismutase, as shown by gene expression assays, Western blotting and enzyme activity assays. Moreover, upon TLR2 activation additional molecular mechanisms came into play, conferring additional resistance levels even upon differentiated macrophage-like cells, mainly related to thioredoxin-linked antioxidant enzymes.

The Nrf2/Keap1/ARE Pathway and Oxidative Stress as a Therapeutic Target in Type II Diabetes Mellitus

Despite improvements in awareness and treatment of type II diabetes mellitus (TIIDM), this disease remains a major source of morbidity and mortality worldwide, and prevalence continues to rise. Oxidative damage caused by free radicals has long been known to contribute to the pathogenesis and progression of TIIDM and its complications. Only recently, however, has the role of the Nrf2/Keap1/ARE master antioxidant pathway in diabetic dysfunction begun to be elucidated. There is accumulating evidence that this pathway is implicated in diabetic damage to the pancreas, heart, and skin, among other cell types and tissues. Animal studies and clinical trials have shown promising results suggesting that activation of this pathway can delay or reverse some of these impairments in TIIDM. In this review, we outline the role of oxidative damage and the Nrf2/Keap1/ARE pathway in TIIDM, focusing on current and future efforts to utilize this relationship as a therapeutic target for prevention, prognosis, and treatment of TIID.

3H-1,2-dithiole-3-thione as a novel therapeutic agent for the treatment of experimental autoimmune encephalomyelitis

3H-1,2-dithiole-3-thione (D3T), the simplest member of the sulfur-containing dithiolethiones, is found in cruciferous vegetables, and has been previously reported to be a potent inducer of antioxidant genes and glutathione biosynthesis by activation of the transcription factor Nrf2. D3T is a cancer chemopreventive agent and possesses anti-inflammatory properties. Although D3T has been shown to protect against neoplasia, the effect of D3T in the autoimmune inflammatory disease multiple sclerosis/experimental autoimmune encephalomyelitis (EAE) is unknown. The present study is the first report of the therapeutic effect of D3T in EAE. Our results show D3T, administered post immunization, not only delays disease onset but also dramatically reduces disease severity in EAE. Strikingly, D3T, administered post disease onset of EAE, effectively prevents disease progression and exacerbation. Mechanistic studies revealed that D3T suppresses dendritic cell activation and cytokine production, inhibits pathogenic Th1 and Th17 differentiation, represses microglia activation and inflammatory cytokine expression, and promotes microglia phase II enzyme induction. In summary, these results indicate that D3T affects both innate and adaptive immune cells, and the protective effect of D3T in EAE might be attributed to its effects on modulating dendritic cell and microglia activation and pathogenic Th1/Th17 cell differentiation.

A comparative assessment of the cytotoxicity and nitric oxide reducing ability of resveratrol, pterostilbene and piceatannol in transformed and normal mouse macrophages

The present study investigated the pharmacological effects of three stilbenoids, resveratrol (RES), pterostilbene (PTR) and piceatannol (PIC), in transformed and normal macrophages. Our first aim was to comparatively assess the cytotoxicity of RES, PTR and PIC in unstimulated transformed mouse macrophages (RAW 264.7 cells) and primary peritoneal macrophages (PMs) harvested from both wild type and Nrf2 (nuclear factor erythroid 2-related factor 2)-deficient female mice. Our second aim was to investigate whether the inhibitory effect of RES, PTR and PIC on nitric oxide (NO) release from stimulated PMs depends on the status of the transcription factor Nrf2. The rationale for investigating Nrf2 status was based upon recent reports showing that certain compounds (sulforaphane and linalool) suppress LPS-induced inflammation in an Nrf2-dependent manner. Cell viability studies confirmed our prior work in unstimulated RAW 264.7 cells, with cytotoxic potency decreasing in the order of PTR > PIC > RES. Unstimulated PMs, regardless of Nrf2 status, were less sensitive to stilbenes, requiring at least a threefold higher stilbene concentration to inhibit cell viability, with cytotoxic potency again decreasing in the order of PTR > PIC > RES. In studies focused on our second aim, IC₅₀ values for NO inhibition (measured as [Formula: see text]) in wild type PMs were similar for all three stilbenes (∼10 μM). In Nrf2-deficient PMs, the IC₅₀ for NO inhibition by PIC did not change; however, a rightward shift in the concentration effect curve was observed for both RES and PTR, indicating a role for Nrf2 in the suppression of LPS-induced [Formula: see text] accumulation by these particular stilbenes.

Nrf2 Signaling in Macrophages

The nuclear factor E2-related factor 2 (Nrf2) is known as the chief regulator of cellular antioxidant defenses as well as a suppressor of inflammation. Macrophages act as major players in inflammatory responses. Because oxidative stress and inflammation are two intertwined processes, the anti-inflammatory activity of Nrf2 signaling is believed to result from its upregulation of cellular antioxidant defenses via the antioxidant response element-driven transcription. In a recent article published in Nature Communications (May 23, 2016; doi: 10.1038/ncomms11624), Kobayashi et al. reported that Nrf2 suppresses transcriptional upregulation of pro-inflammatory cytokines independent of its role in regulating cellular antioxidants and redox status. This study by Kobayashi et al. provides novel insights into the molecular basis of Nrf2 acting as a suppressor of inflammation.

Regulation of catalase expression in healthy and cancerous cells

Catalase is an important antioxidant enzyme that dismutates hydrogen peroxide into water and molecular oxygen. The catalase gene has all the characteristics of a housekeeping gene (no TATA box, no initiator element sequence, high GC content in promoter) and a core promoter that is highly conserved among species. We demonstrate in this review that within this core promoter, the presence of DNA binding sites for transcription factors, such as NF-Y and Sp1, plays an essential role in the positive regulation of catalase expression. Additional transcription factors, such as FoxO3a, are also involved in this regulatory process. There is strong evidence that the protein Akt/PKB in the PI3K signaling pathway plays a major role in the expression of catalase by modulating the activity of FoxO3a. Over the past decade, other transcription factors (PPARγ, Oct-1, etc.), as well as genetic, epigenetic, and posttranscriptional processes, have emerged as crucial contributors to the regulation of catalase expression. Altered expression levels of catalase have been reported in cancer tissues compared to their normal counterparts. Deciphering the molecular mechanisms that regulate catalase expression could, therefore, be of crucial importance for the future development of pro-oxidant cancer chemotherapy.

PMI: a ΔΨm independent pharmacological regulator of mitophagy

Mitophagy is central to mitochondrial and cellular homeostasis and operates via the PINK1/Parkin pathway targeting mitochondria devoid of membrane potential (ΔΨ_m) to autophagosomes. Although mitophagy is recognized as a fundamental cellular process, selective pharmacologic modulators of mitophagy are almost nonexistent. We developed a compound that increases the expression and signaling of the autophagic adaptor molecule P62/SQSTM1 and forces mitochondria into autophagy. The compound, P62-mediated mitophagy inducer (PMI), activates mitophagy without recruiting Parkin or collapsing ΔΨ_m and retains activity in cells devoid of a fully functional PINK1/Parkin pathway. PMI drives mitochondria to a process of quality control without compromising the bio-energetic competence of the whole network while exposing just those organelles to be recycled. Thus, PMI circumvents the toxicity and some of the nonspecific effects associated with the abrupt dissipation of ΔΨ_m by ionophores routinely used to induce mitophagy and represents a prototype pharmacological tool to investigate the molecular mechanisms of mitophagy.

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PMI stabilizes Nrf2 and upregulates the dependent gene product P62

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The increased P62 level drives mitochondrial autophagy

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PMI acts downstream of the PINK1/Parkin pathway leaving the ΔΨ_m intact