Delayed Nrf2-regulated antioxidant gene induction in response to silica nanoparticles

Yinhuang granule alleviates carbon tetrachloride-induced liver fibrosis in mice and its mechanism

BACKGROUND

Liver fibrosis is a formidable global medical challenge, with no effective clinical treatment currently available. Yinhuang granule (YHG) is a proprietary Chinese medicine comprising Scutellariae Radix and Lonicerae Japonicae Flos. It is frequently used for upper respiratory tract infections, pharyngitis, as well as acute and chronic tonsillitis.

AIM

To investigate the potential of YHG in alleviating carbon tetrachloride (CCl4)-induced liver fibrosis in mice.

METHODS

To induce a hepatic fibrosis model in mice, this study involved intraperitoneal injections of 2 mL/kg of CCl4 twice a week for 4 wk. Meanwhile, liver fibrosis mice in the low dose of YHG (0.4 g/kg) and high dose of YHG (0.8 g/kg) groups were orally administered YHG once a day for 4 wk. Serum alanine/aspartate aminotransferase (ALT/AST) activity and liver hydroxyproline content were detected. Sirius red and Masson's trichrome staining assay were conducted. Real-time polymerase chain reaction, western-blot and enzyme-linked immunosorbent assay were conducted. Liver glutathione content, superoxide dismutase activity level, reactive oxygen species and protein carbonylation amount were detected.

RESULTS

The administration of YHG ameliorated hepatocellular injury in CCl4-treated mice, as reflected by decreased serum ALT/AST activity and improved liver histological evaluation. YHG also attenuated liver fibrosis, evident through reduced liver hydroxyproline content, improvements in Sirius red and Masson's trichrome staining, and lowered serum hyaluronic acid levels. Furthermore, YHG hindered the activation of hepatic stellate cells (HSCs) and ameliorated oxidative stress injury and inflammation in liver from CCl4-treated mice. YHG prompted the nuclear accumulation of nuclear factor erythroid 2-related factor 2 (Nrf2) and upregulated the expression of Nrf2-dependent downstream antioxidant genes. In addition, YHG promoted mitochondrial biogenesis in liver from CCl4-treated mice, as demonstrated by increased liver adenosine triphosphate content, mitochondrial DNA levels, and the expression of peroxisome proliferator-activated receptor gamma coactivator 1 alpha and nuclear respiratory factor 1.

CONCLUSION

YHG effectively attenuates CCl4-induced liver fibrosis in mice by inhibiting the activation of HSCs, reducing inflammation, alleviating liver oxidative stress damage through Nrf2 activation, and promoting liver mitochondrial biogenesis.

Advances in Nrf2 Signaling Pathway by Targeted Nanostructured-Based Drug Delivery Systems

Nanotechnology has gained significant interest in various applications, including sensors and therapeutic agents for targeted disease sites. Several pathological consequences, including cancer, Alzheimer's disease, autoimmune diseases, and many others, are mostly driven by inflammation and Nrf2, and its negative regulator, the E3 ligase adaptor Kelch-like ECH-associated protein 1 (Keap1), plays a crucial role in maintaining redox status, the expression of antioxidant genes, and the inflammatory response. Interestingly, tuning the Nrf2/antioxidant response element (ARE) system can affect immune-metabolic mechanisms. Although many phytochemicals and synthetic drugs exhibited potential therapeutic activities, poor aqueous solubility, low bioavailability, poor tissue penetration, and, consequently, poor specific drug targeting, limit their practical use in clinical applications. Also, the therapeutic use of Nrf2 modulators is hampered in clinical applications by the absence of efficient formulation techniques. Therefore, we should explore the engineering of nanotechnology to modulate the inflammatory response via the Nrf2 signaling pathway. This review will initially examine the role of the Nrf2 signaling pathway in inflammation and oxidative stress-related pathologies. Subsequently, we will also review how custom-designed nanoscale materials encapsulating the Nrf2 activators can interact with biological systems and how this interaction can impact the Nrf2 signaling pathway and its potential outcomes, emphasizing inflammation.

The possible role of nuclear factor erythroid-2-related factor 2 activators in the management of Covid-19

COVID-19 is caused by a novel SARS-CoV-2 leading to pulmonary and extra-pulmonary manifestations due to oxidative stress (OS) development and hyperinflammation. COVID-19 is primarily asymptomatic though it may cause acute lung injury (ALI), acute respiratory distress syndrome (ARDS), systemic inflammation, and thrombotic events in severe cases. SARS-CoV-2-induced OS triggers the activation of different signaling pathways, which counterbalances this complication. One of these pathways is nuclear factor erythroid 2-related factor 2 (Nrf2), which induces a series of cellular interactions to mitigate SARS-CoV-2-mediated viral toxicity and OS-induced cellular injury. Nrf2 pathway inhibits the expression of pro-inflammatory cytokines and the development of cytokine storm in COVID-19. Therefore, Nrf2 activators may play an essential role in reducing SARS-CoV-2 infection-induced inflammation by suppressing NLRP3 inflammasome in COVID-19. Furthermore, Nrf2 activators can attenuate endothelial dysfunction (ED), renin-angiotensin system (RAS) dysregulation, immune thrombosis, and coagulopathy. Thus this mini-review tries to clarify the possible role of the Nrf2 activators in the management of COVID-19. Nrf2 activators could be an effective therapeutic strategy in the management of Covid-19. Preclinical and clinical studies are recommended in this regard.

Growth differentiation factor 15 is dispensable for acetaminophen-induced liver injury in mice

Acetaminophen (APAP)-induced liver injury (AILI) has been recognized as a pivotal contributor to drug-induced liver failure in Western countries, but its molecular mechanism remains poorly understood. Growth differentiation factor 15 (GDF15) is a pleiotropic factor that alleviates non-alcoholic liver steatohepatitis, liver fibrosis and liver injury. The aim of the present study was to examine the possibility whether GDF15 confers protection against AILI. We found that the gene expression of Gdf15 was increased significantly after APAP overdose in mice. Next, the role of Gdf15 in AILI was evaluated by hepatic Gdf15 overexpression (using adeno-associated virus serotype 8), injection with recombinant human GDF15 (rhGDF15) and Gdf15 knockout mice after challenge with APAP. A marked elevation of Gdf15 was observed after AILI. However, there were no significant differences in AILI-related liver injury and JNK phosphorylation after Gdf15 overexpression, rhGDF15 injection or Gdf15 deficiency. Together, we conclude that, despite a noticeable elevation of Gdf15 level after AILI, Gdf15 is dispensable for APAP-induced AILI. Our study further suggests that genomic analysis of mRNA expression after APAP overdose is of limited relevance unless followed up by a functional analysis of candidate genes in vivo.

Varied Responses to a High m.3243A>G Mutation Load and Respiratory Chain Dysfunction in Patient-Derived Cardiomyocytes

The m.3243A>G mutation in mitochondrial tRNA-Leu(UUR) is one of the most common pathogenic mitochondrial DNA mutations in humans. The clinical manifestations are highly heterogenous and the causes for the drastic clinical variability are unknown. Approximately one third of patients suffer from cardiac disease, which often increases mortality. Why only some patients develop cardiomyopathy is unknown. Here, we studied the molecular effects of a high m.3243A>G mutation load on cardiomyocyte functionality, using cells derived from induced pluripotent stem cells (iPSC-CM) of two different m.3243A>G patients, only one of them suffering from severe cardiomyopathy. While high mutation load impaired mitochondrial respiration in both patients' iPSC-CMs, the downstream consequences varied. mtDNA mutant cells from a patient with no clinical heart disease showed increased glucose metabolism and retained cellular ATP levels, whereas cells from the cardiac disease patient showed reduced ATP levels. In this patient, the mutations also affected intracellular calcium signaling, while this was not true in the other patient's cells. Our results reflect the clinical variability in mitochondrial disease patients and show that iPSC-CMs retain tissue specific features seen in patients.

Ferroptosis in viral infection: the unexplored possibility

Virus-induced cell death has long been thought of as a double-edged sword in the inhibition or exacerbation of viral infections. The vital role of iron, an essential element for various enzymes in the maintenance of cellular physiology and efficient viral replication, places it at the crossroads and makes it a micronutrient of competition between the viruses and the host. Viruses can interrupt iron uptake and the antioxidant response system, while others can utilize iron transporter proteins as receptors. Interestingly, the unavailability of iron facilitates certain viral infections and causes cell death characterized by lipid peroxide accumulation and malfunction of the antioxidant system. In this review, we discuss how iron uptake, regulation and metabolism, including the redistribution of iron in the host defense system during viral infection, can induce ferroptosis. Fenton reactions, a central characteristic of ferroptosis, are caused by the increased iron content in the cell. Therefore, viral infections that increase cellular iron content or intestinal iron absorption are likely to cause ferroptosis. In addition, we discuss the hijacking of the iron regulatoy pathway and the antioxidant response, both of which are typical in viral infections. Understanding the potential signaling mechanisms of ferroptosis in viral infections will aid in the development of new therapeutic agents.

Reciprocal regulation of NRF2 by autophagy and ubiquitin-proteasome modulates vascular endothelial injury induced by copper oxide nanoparticles

NRF2 is the key antioxidant molecule to maintain redox homeostasis, however the intrinsic mechanisms of NRF2 activation in the context of nanoparticles (NPs) exposure remain unclear. In this study, we revealed that copper oxide NPs (CuONPs) exposure activated NRF2 pathway in vascular endothelial cells. NRF2 knockout remarkably aggravated oxidative stress, which were remarkably mitigated by ROS scavenger. We also demonstrated that KEAP1 (the negative regulator of NRF2) was not primarily involved in NRF2 activation in that KEAP1 knockdown did not significantly affect CuONPs-induced NRF2 activation. Notably, we demonstrated that autophagy promoted NRF2 activation as evidenced by that ATG5 knockout or autophagy inhibitors significantly blocked NRF2 pathway. Mechanically, CuONPs disturbed ubiquitin–proteasome pathway and consequently inhibited the proteasome-dependent degradation of NRF2. However, autophagy deficiency reciprocally promoted proteasome activity, leading to the acceleration of degradation of NRF2 via ubiquitin–proteasome pathway. In addition, the notion that the reciprocal regulation of NRF2 by autophagy and ubiquitin–proteasome was further proven in a CuONPs pulmonary exposure mice model. Together, this study uncovers a novel regulatory mechanism of NRF2 activation by protein degradation machineries in response to CuONPs exposure, which opens a novel intriguing scenario to uncover therapeutic strategies against NPs-induced vascular injury and disease.

CuONPs exposure activates NRF2 signaling in vascular endothelial cells and mouse thoracic aorta.

KEAP1 is dispensable for NRF2 activation in CuONPs-treated vascular endothelial cells.

CuONPs-induced autophagy facilitates NRF2 activation in vascular endothelial cells and mouse thoracic aorta.

Autophagy and ubiquitin–proteasome reciprocally regulate NRF2 activation in CuONPs-treated vascular endothelial cells and mouse thoracic aorta.

Iron Speciation in Respirable Particulate Matter and Implications for Human Health

Particulate matter (PM) air pollution poses a major global health risk, but the role of iron (Fe) is not clearly defined because chemistry at the particle-cell interface is often not considered. Detailed spectromicroscopy characterizations of PM_2.5 samples from the San Joaquin Valley, CA identified major Fe-bearing components and estimated their relative proportions. Iron in ambient PM_2.5 was present in spatially and temporally variable mixtures, mostly as Fe(III) oxides and phyllosilicates, but with significant fractions of metallic iron (Fe(0)), Fe(II,III) oxide, and Fe(III) bonded to organic carbon. Fe(0) was present as aggregated, nm-sized particles that comprised up to ∼30% of the Fe spectral fraction. Mixtures reflect anthropogenic and geogenic particles subjected to environmental weathering, but reduced Fe in PM originates from anthropogenic sources, likely as abrasion products. Possible mechanistic pathways involving Fe(0) particles and mixtures of Fe(II) and Fe(III) surface species may generate hydrogen peroxide and oxygen-centered radical species (hydroxyl, hydroperoxyl, or superoxide) in Fenton-type reactions. From a health perspective, PM mixtures with reduced and oxidized Fe will have a disproportionate effect in cellular response after inhalation because of their tendency to shuttle electrons and produce oxidants and electrophiles that induce inflammation and oxidative stress.

Cardiac NF-κB Acetylation Increases While Nrf2-Related Gene Expression and Mitochondrial Activity Are Impaired during the Progression of Diabetes in UCD-T2DM Rats

The onset of type II diabetes increases the heart’s susceptibility to oxidative damage because of the associated inflammation and diminished antioxidant response. Transcription factor NF-κB initiates inflammation while Nrf2 controls antioxidant defense. Current evidence suggests crosstalk between these transcription factors that may become dysregulated during type II diabetes mellitus (T2DM) manifestation. The objective of this study was to examine the dynamic changes that occur in both transcription factors and target genes during the progression of T2DM in the heart. Novel UC Davis T2DM (UCD-T2DM) rats at the following states were utilized: (1) lean, control Sprague-Dawley (SD; n = 7), (2) insulin-resistant pre-diabetic UCD-T2DM (Pre; n = 9), (3) 2-week recently diabetic UCD-T2DM (2Wk; n = 9), (4) 3-month diabetic UCD-T2DM (3Mo; n = 14), and (5) 6-month diabetic UCD-T2DM (6Mo; n = 9). NF-κB acetylation increased 2-fold in 3Mo and 6Mo diabetic animals compared to SD and Pre animals. Nox4 protein increased 4-fold by 6Mo compared to SD. Nrf2 translocation increased 82% in Pre compared to SD but fell 47% in 6Mo animals. GCLM protein fell 35% in 6Mo animals compared to Pre. Hmox1 mRNA decreased 45% in 6Mo animals compared to SD. These data suggest that during the progression of T2DM, NF-κB related genes increase while Nrf2 genes are suppressed or unchanged, perpetuating inflammation and a lesser ability to handle an oxidant burden altering the heart’s redox state. Collectively, these changes likely contribute to the diabetes-associated cardiovascular complications.

miR-182 mediated the inhibitory effects of NF-κB on the GPR39/CREB/BDNF pathway in the hippocampus of mice with depressive-like behaviors

BACKGROUND

Chronic stress is one of the most important causes of depression, accompanied by neuroinflammation and hippocampal injuries. Long-term elevation of glucocorticoid leads to activation of NF-κB and inhibition of GPR39/CREB/BDNF pathway, which is pivotal for neuroprotection and neurogenesis. The present study thus was designed to determine the relationship between NF-κB and GPR39/CREB/BDNF pathway.

METHODS

Depressive-like behaviors were induced by chronic unpredictable mild stress (CUMS) and chronic restraint stress (CRS) in mice. Corticosterone, inflammatory cytokines, and GPR39/CREB/BDNF pathway were determined by ELISA and Western Blot assays. The activation of NF-κB and inhibition of GPR39 were connected by bioinformatic analysis and experimentally validated in hippocampus cells by knock-in and knock-down techniques.

RESULTS

CUMS and CRS led to an elevation of serum corticosterone and depressive-like behaviors in mice, with activation of NF-κB subunit p65 in the hippocampus and elevations of TNFα and IL-6. The expression of GPR39/CREB/BDNF pathway in the hippocampus was inhibited. Bioinformatic analysis revealed that four miRNAs, miR-96, miR-143, miR-150, and miR-182, were potentially transcribed by NF-κB and bound with GPR39 mRNA. NF-κB overexpression increased miR-182 expression and decreased GPR39 expression in hippocampus cells. Its inhibitor led to reverse effects. miR-182 mimics or inhibitors also regulated GPR39 expression in hippocampus cells and more importantly, blocked the regulation of NF-κB on GPR39.

CONCLUSIONS

The results suggested that activation of NF-κB inhibited GPR39/CREB/BDNF pathway through increasing miR-182 in chronic stress-induced depressive-like behaviors. The negative-regulation features of miRNAs might be important for neuroinflammation-induced inhibition of neurofunction in depression.

Decoding the Complex Free Radical Cascade by Using a DNA Framework-Based Artificial DNA Encoder

DNA-based molecular communications (DMC) are critical for regulating biological networks to maintain stable organismic functions. However, the complicated, time-consuming information transmission process involved in genome-coded DMC and the limited, vulnerable decoding activity generally lead to communication impairment or failure, in response to external stimuli. Herein, we present a conceptually innovative DMC strategy mediated by the DNA framework-based artificial DNA encoder. With the free-radical cascade as a proof-of-concept study, the artificial DNA encoder shows active sensing and real-time actuation, in situ and broad free radical-decoding efficacy, as well as robust resistance to environmental noise. It can also block undesirable short-to-medium-range communications between free radicals and inflammatory networks, leading to a synergistic anti-obesity effect. The artificial DNA encoder-based DMC may be generalized to other communication systems for a variety of applications.

Bovine serum albumin aggravates macrophage M1 activation and kidney injury in heterozygous Klotho-deficient mice via the gut microbiota-immune axis

Klotho expression abnormalities induces kidney injury and chronic kidney disease, however, the underlying mechanism remains unclear. Here, Klotho^+/- mice and wild-type mice were treated with low-dose bovine serum albumin (BSA). Pathological examination demonstrated that the area of glomerular collagen deposition and fibrosis in BSA-Kl^-/+ mice was significantly larger than that in BSA-WT mice. The serum levels of superoxide dismutase, malondialdehyde, creatinine, and urea in BSA-Kl^-/+ mice were significantly increased. Sequencing of gut microbiota 16S rRNA v3-v4 region indicated that BSA-Kl^-/+ mice showed a significantly higher relative abundance of the genera Dubosiella, Akkermansia, Alloprevotella, and Lachnospiraceae and a significantly lower relative abundance of the genera Allobaculum and Muribaculaceae than BSA-WT mice. KEGG analysis revealed that the metabolic pathways of signal transduction, xenobiotic biodegradation and metabolism, and lipid metabolism increased significantly in BSA-Kl^-/+ mice. Flow cytometry showed that the proportion of CD68⁺/CD11b⁺ cells in the peripheral blood was significantly higher in BSA-KL^-/+ mice than that in BSA-WT mice. qPCR and western blot suggested that Klotho and Nrf2 expression in MΦ1 cells of BSA-KL^-/+ mice was significantly decreased. Thus, the findings suggest during the immune activation and chronic inflammation induced by the gut microbiota imbalance in Klotho-deficient mice treated to BSA, disrupted expression of proteins in the Nrf2/NF-κB signaling pathway in monocyte-derived macrophage M1 cells leads to the aggravation of inflammation and kidney injury.

Down regulation of glutathione and glutamate cysteine ligase in the inflammatory response of macrophages

Glutathione (GSH) plays critical roles in the inflammatory response by acting as the master substrate for antioxidant enzymes and an important anti-inflammatory agent. In the early phase of the inflammatory response of macrophages, GSH content is decreased due to the down regulation of the catalytic subunit of glutamate cysteine ligase (GCLC). In the current study we investigated the underlying mechanism for this phenomenon. In human THP1-differentiated macrophages, GCLC mRNA had a half-life of 4 h under basal conditions, and it was significantly reduced to less than 2 h upon exposure to lipopolysaccharide (LPS), suggesting an increased decay of GCLC mRNA in the inflammatory response. The half-life of GCLC protein was >10 h under basal conditions, and upon LPS exposure the degradation rate of GCLC protein was significantly increased. The pan-caspase inhibitor Z-VAD-FMK but not the proteasome inhibitor MG132, prevented the down regulation of GCLC protein caused by LPS. Both caspase inhibitor Z-LEVD-FMK and siRNA of caspase-5 abrogated LPS-induced degradation of GCLC protein. In addition, supplement with γ-GC, the GCLC product, efficiently restored GSH content and suppressed the induction of NF-κB activity by LPS. In conclusion, these data suggest that GCLC down-regulation in the inflammatory response of macrophages is mediated through both increased mRNA decay and caspase-5-mediated GCLC protein degradation, and γ-GC is an efficient agent to restore GSH and regulate the inflammatory response.

Mouse brain transcriptome responses to inhaled nanoparticulate matter differed by sex and APOE in Nrf2-Nfkb interactions

The neurotoxicity of air pollution is undefined for sex and APOE alleles. These major risk factors of Alzheimer's disease (AD) were examined in mice given chronic exposure to nPM, a nano-sized subfraction of urban air pollution. In the cerebral cortex, female mice had two-fold more genes responding to nPM than males. Transcriptomic responses to nPM had sex-APOE interactions in AD-relevant pathways. Only APOE3 mice responded to nPM in genes related to Abeta deposition and clearance (Vav2, Vav3, S1009a). Other responding genes included axonal guidance, inflammation (AMPK, NFKB, APK/JNK signaling), and antioxidant signaling (NRF2, HIF1A). Genes downstream of NFKB and NRF2 responded in opposite directions to nPM. Nrf2 knockdown in microglia augmented NFKB responses to nPM, suggesting a critical role of NRF2 in air pollution neurotoxicity. These findings give a rationale for epidemiologic studies of air pollution to consider sex interactions with APOE alleles and other AD-risk genes.

Surface characterization and chemical speciation of adsorbed iron(iii) on oxidized carbon nanoparticles

Carbonaceous nanomaterials represent a significant portion of ultra-fine airborne particulate matter, and iron is the most abundant transition metal in air particles. Owing to their high surface area and atmospheric oxidation, carbon nanoparticles (CNP) are enriched with surface carbonyl functional groups and act as a host for metals and small molecules. Using a synthetic model, concentration-dependent changes in the chemical speciation of iron adsorbed on oxidized carbon surfaces were investigated by a combination of X-ray and electron microscopic and spectroscopic methods. Carbon K-edge absorption spectra demonstrated that the CNP surface was enriched with carboxylic acid groups after chemical oxidation but that microporosity was unchanged. Oxidized CNP showed a high affinity for sorption of Fe(iii) from solution (75-95% uptake) and spectroscopic measurements confirmed a 3+ oxidation state of Fe on CNP irrespective of surface loading. The bonding of adsorbed Fe(iii) at variable loadings was determined by iron K-edge X-ray absorption spectroscopy. At low loadings (3 and 10 μmol Fe m-2 CNP), mononuclear Fe was octahedrally coordinated to oxygen atoms of carboxylate groups. As Fe surface coverage increased (21 and 31 μmol Fe m-2 CNP), Fe-Fe backscatters were observed at interatomic distances indicating iron (oxy)hydroxide particle formation on CNP. Electron-donating surface carboxylate groups on CNP coordinated and stabilized mononuclear Fe(iii). Saturation of high-affinity sites may have promoted hydroxide particle nucleation at higher loading, demonstrating that the chemical form of reactive metal ions may change with surface concentration and degree of CNP surface oxidation. Model systems such as those discussed here, with controlled surface properties and known chemical speciation of adsorbed metals, are needed to establish structure-activity models for toxicity assessments of environmentally relevant nanoparticles.

Genotoxicity of amorphous silica nanoparticles: Status and prospects

Amorphous silica nanoparticles (SNPs) are widely used in biomedical applications and consumer products. Little is known, however, about their genotoxicity and potential to induce gene expression regulation. Despite recent efforts to study the underlying mechanisms of genotoxicity of SNPs, inconsistent results create a challenge. A variety of factors determine particle-cell interactions and underlying mechanisms. Further, high-throughput studies are required to carefully assess the impact of silica nanoparticle physicochemical properties on induction of genotoxic response in different cell lines and animal models. In this article, we review the strategies available for evaluation of genotoxicity of nanoparticles (NPs), survey current status of silica nanoparticle gene alteration and genotoxicity, discuss particle-mediated inflammation as a contributing factor to genotoxicity, identify existing gaps and suggest future directions for this research.

The toxicity of silica nanoparticles to the immune system

Silicon-based materials and their oxides are widely used in drug delivery, dietary supplements, implants and dental fillers. Silica nanoparticles (SiNPs) interact with immunocompetent cells and induce immunotoxicity. However, the toxic effects of SiNPs on the immune system have been inadequately reviewed. The toxicity of SiNPs to the immune system depends on their physicochemical properties and the cell type. Assessments of immunotoxicity include determining cell dysfunctions, cytotoxicity and genotoxicity. This review focuses on the immunotoxicity of SiNPs and investigates the underlying mechanisms. The main mechanisms were proinflammatory responses, oxidative stress and autophagy. Considering the toxicity of SiNPs, surface and shape modifications may mitigate the toxic effects of SiNPs, providing a new way to produce these nanomaterials with less toxic impaction.

Silicon dioxide nanoparticles induce COX-2 expression through activation of STAT3 signaling pathway in HaCaT cells

Silicon dioxide nanoparticles (SiO₂-NPs) are widely used in biomedicines and consumer products, such as sunscreens and cosmetics. However, SiO₂-NPs can cause adverse effects on human health, depending on the size and concentration of nanoparticles. The present study was aimed at investigating the molecular mechanism underlying SiO₂-NPs-induced inflammation in human keratinocyte (HaCaT) cells. Incubation of HaCaT cells with SiO₂-NPs induced the expression of cyclooxygenase-2 (COX-2) mRNA and protein. Treatment of cells with SiO₂-NPs also induced the phosphorylation, DNA binding and the reporter gene activity of signal transducer and activator of transcription 3 (STAT3). Transfection of cells with STAT3 siRNA abrogated SiO₂-NPs-induced COX-2 expression. Moreover, SiO₂-NPs enhanced the phosphorylation of Janus kinase2 (JAK2), Src and Akt. Pharmacological inhibition of either JAK2, Src or Akt abrogated SiO₂-NPs-induced STAT3 transcriptional activity and the expression of COX-2. Treatment with LY294002 also attenuated SiO₂-NPs-induced Src phosphorylation, while, JAK2 phosphorylation was not changed. In addition, SiO₂-NPs generated reactive oxygen species (ROS) and treatment of N-acetyl cysteine (NAC) attenuated the phosphorylation of JAK2, Src, Akt and STAT3, as well as the expression of COX-2 in SiO₂-NPs-treated HaCaT cells. Taken together, our study provides the first report that SiO₂-NPs induce COX-2 expression in HaCaT cells by activating the STAT3 signaling through ROS-mediated phosphorylation of upstream kinases, Akt/Src and JAK2.

Protection by the Total Flavonoids from Rosa laevigata Michx Fruit against Lipopolysaccharide-Induced Liver Injury in Mice via Modulation of FXR Signaling

We previously reported the effects of the total flavonoids (TFs) from Rosa laevigata Michx fruit against carbon tetrachloride-induced liver damage, non-alcoholic fatty liver disease, and liver ischemia-reperfusion injury. However, there have been no papers reporting the role of R. laevigata TFs against lipopolysaccharide (LPS)-induced liver injury. In this paper, liver injury in mice was induced by LPS, and R. Laevigata extract was intragastrically administered to the mice for 7 days. Biochemical parameters in serum and liver tissue were examined, and pathological changes were observed by transmission electron microscopy, hematoxylin and eosin (H&E) and Oil Red O staining. The results showed that the TFs markedly reduced serum ALT (alanine transferase), AST (aspartate transaminase), TG (total triglyceride), and TC (total cholesterol) levels and relative liver weights and improved liver pathological changes. In addition, the TFs markedly decreased tissue MDA (malondialdehyde) level and increased the levels of SOD (superoxide dismutase) and GSH-Px (glutathione peroxidase). A mechanistic study showed that the TFs significantly increased the expression levels of Nrf2 (nuclear erythroid factor2-related factor 2), HO-1 (heme oxygenase-1), NQO1 (NAD(P)H dehydrogenase (quinone 1), GCLC (glutamate-cysteine ligase catalytic subunit), and GCLM (glutamate-cysteine ligase regulatory subunit) and decreased Keap1 (Kelch-like ECH-associated protein 1) level by activating FXR (farnesoid X receptor) against oxidative stress. Furthermore, the TFs markedly suppressed the nuclear translocation of NF-κB (nuclear factor-kappa B) and subsequently decreased the expression levels of IL (interleukin)-1β, IL-6, HMGB-1 (high -mobility group box 1), and COX-2 (cyclooxygenase-2) by activating FXR and FOXO3a (forkhead box O3) against inflammation. Besides, the TFs obviously reduced the expression levels of SREBP-1c (sterol regulatory element-binding proteins-1c), ACC1 (acetyl-CoA carboxylase-1), FASN (fatty acid synthase), and SCD1 (stearoyl-coenzyme A desaturase 1), and improved CPT1 (carnitine palmitoyltransferase 1) level by activating FXR to regulate lipid metabolism. Our results suggest that TFs exhibited protective effect against LPS-induced liver injury by altering FXR-mediated oxidative stress, inflammation, and lipid metabolism, and should be developed as an effective food and healthcare product for the therapy of liver injury in the future.

A critical review of assays for hazardous components of air pollution

Increased mortality and diverse morbidities are globally associated with exposure to ambient air pollution (AAP), cigarette smoke (CS), and household air pollution (HAP). The AAP-CS-HAP aerosols present heterogeneous particulate matter (PM) of diverse chemical and physical characteristics. Some epidemiological models have assumed the same health hazards by PM weight for AAP, CS, and HAP regardless of the composition. While others have recognized that biological activities and toxicity will vary with components, we focus particularly on oxidation because of its major role in assay outcomes. Our review of PM assays considers misinterpretations of some chemical measures used for oxidative activity. Overall, there is low consistency across chemical and cell-based assays for oxidative and inflammatory activity. We also note gaps in understanding how much airborne PM of various sizes enter cells and organs. For CS, the body burden per cigarette may be much below current assumptions. Synergies shown for health hazards of AAP and CS suggest crosstalk in detoxification pathways mediated by AHR, NF-κB, and Nrf2. These complex genomic and biochemical interactions frustrate resolution of the toxicity of specific AAP components. We propose further strategies based on targeted gene expression based on cell-type differences.

Bixin protects against particle-induced long-term lung injury in an NRF2-dependent manner

Scope: Particle-induced lung injury is a kind of comprehensive pulmonary disease with not only inflammation but also fibrosis. Bixin is a natural compound that is widely used as a food additive. Our previous studies demonstrated that bixin could alleviate inflammation in ventilation-induced acute lung injury as well as UV-exposure caused skin damage. But whether it could depress silica-induced long-term comprehensive lung injury and the mechanism of bixin in this protection have not yet been studied. Methods: A murine SiO2-induced long-term comprehensive lung injury model was established through silica intratracheal instillation. To elucidate the effects and mechanisms of bixin in silica-induced pulmonary inflammation and fibrosis, we treated mice with bixin following silica instillation. Results: Bixin treatment attenuated the accumulation of inflammatory cells which significantly ameliorated pathological inflammation and fibrotic development in the lungs. In addition, intraperitoneal (i.p.) injection of bixin in mice led to the upregulation of the NRF2 response in the lungs. Since alveolar macrophage activation plays a vital role in the initiation and progression of this injury, the mechanism was further studied in the THP-1 macrophage cells. Bixin activated NRF2 signals via blocking KEAP1 mediated ubiquitylation and degradation of NRF2. Conclusions: Our work has brought insights into exploring anti-particle-induced lung injury activities in the daily consumption of natural products. In addition, our study also inspires the discovery of new beneficial effects of bixin and its application in the treatment of other inflammatory diseases.

Temporal changes in glutathione biosynthesis during the lipopolysaccharide-induced inflammatory response of THP-1 macrophages

How macrophages maintain redox homeostasis in the inflammatory process, in which a large amount of oxidants are produced, remains elusive. In this study, we investigated the temporal changes in the intracellular glutathione (GSH), the master antioxidant, and the expression of glutamate cysteine ligase (GCL), the rate-limiting enzyme for GSH biosynthesis, in the inflammatory response of human macrophages (THP1 cells) to lipopolysaccharide. Intracellular GSH concentration was decreased significantly in the early phase (~6h) of LPS exposure, and then gradually went back to the basal level in the late phase (9-24h). The expression level of the catalytic subunit of GCL (GCLC) followed a similar pattern of change as GSH: its mRNA and protein levels were reduced in the early phase and then back to basal level in the late phase. In contrast, the expression of the modifier subunit of GCL (GCLM) was significantly increased in the phase of LPS exposure. Activation Nrf2, the transcription factor involved in the induction of both GCLC and GCLM, occurred at as early as 3h after LPS exposure; whereas the activation of NF-κB occurred at as early as 30min. Inhibition of NF-κB signaling with SN50 prevented the decrease of GCLC and inhibited Nrf2 activation in response to LPS. These data demonstrate time-dependent changes in the expression of GCL and Nrf2 signaling during the inflammatory response, and that the regulation of GCLC and GCLM might be through different pathways in this process.