Oxidative stress-responsive transcription factor ATF3 potentially mediates diabetic angiopathy

Type 2 diabetic mellitus related osteoporosis: focusing on ferroptosis

With the aging global population, type 2 diabetes mellitus (T2DM) and osteoporosis(OP) are becoming increasingly prevalent. Diabetic osteoporosis (DOP) is a metabolic bone disorder characterized by abnormal bone tissue structure and reduced bone strength in patients with diabetes. Studies have revealed a close association among diabetes, increased fracture risk, and disturbances in iron metabolism. This review explores the concept of ferroptosis, a non-apoptotic cell death process dependent on intracellular iron, focusing on its role in DOP. Iron-dependent lipid peroxidation, particularly impacting pancreatic β-cells, osteoblasts (OBs) and osteoclasts (OCs), contributes to DOP. The intricate interplay between iron dysregulation, which comprises deficiency and overload, and DOP has been discussed, emphasizing how excessive iron accumulation triggers ferroptosis in DOP. This concise overview highlights the need to understand the complex relationship between T2DM and OP, particularly ferroptosis. This review aimed to elucidate the pathogenesis of ferroptosis in DOP and provide a prospective for future research targeting interventions in the field of ferroptosis.

Therapeutic targeting of cellular senescence in diabetic macular edema: preclinical and phase 1 trial results

Compromised vascular endothelial barrier function is a salient feature of diabetic complications such as sight-threatening diabetic macular edema (DME). Current standards of care for DME manage aspects of the disease, but require frequent intravitreal administration and are poorly effective in large subsets of patients. Here we provide evidence that an elevated burden of senescent cells in the retina triggers cardinal features of DME pathology and conduct an initial test of senolytic therapy in patients with DME. In cell culture models, sustained hyperglycemia provoked cellular senescence in subsets of vascular endothelial cells displaying perturbed transendothelial junctions associated with poor barrier function and leading to micro-inflammation. Pharmacological elimination of senescent cells in a mouse model of DME reduces diabetes-induced retinal vascular leakage and preserves retinal function. We then conducted a phase 1 single ascending dose safety study of UBX1325 (foselutoclax), a senolytic small-molecule inhibitor of BCL-xL, in patients with advanced DME for whom anti-vascular endothelial growth factor therapy was no longer considered beneficial. The primary objective of assessment of safety and tolerability of UBX1325 was achieved. Collectively, our data suggest that therapeutic targeting of senescent cells in the diabetic retina with a BCL-xL inhibitor may provide a long-lasting, disease-modifying intervention for DME. This hypothesis will need to be verified in larger clinical trials. ClinicalTrials.gov identifier: NCT04537884 .

Biological macromolecules-based nanoformulation in improving wound healing and bacterial biofilm-associated infection: A review

A chronic wound is a serious complication associated with diabetes mellitus and is difficult to heal due to high glucose levels, oxidative stress, and biofilm-associated microbial infection. The structural complexity of microbial biofilm makes it impossible for antibiotics to penetrate the matrix, hence conventional antibiotic therapies became ineffective in clinical settings. This demonstrates an urgent need to find safer alternatives to reduce the prevalence of chronic wound infection associated with microbial biofilm. A novel approach to address these concerns is to inhibit biofilm formation using biological-macromolecule based nano-delivery system. Higher drug loading efficiency, sustained drug release, enhanced drug stability, and improved bioavailability are advantages of employing nano-drug delivery systems to prevent microbial colonization and biofilm formation in chronic wounds. This review covers the pathogenesis, microbial biofilm formation, and immune response to chronic wounds. Furthermore, we also focus on macromolecule-based nanoparticles as wound healing therapies to reduce the increased mortality associated with chronic wound infections.

Effects of Atherogenic Factors on Endothelial Cells: Bioinformatics Analysis of Differentially Expressed Genes and Signaling Pathways

(1) Background: Atherosclerosis is a serious medical condition associated with high morbidity and mortality rates. It develops over many years as a complex chain of events in the vascular wall involving various cells and is influenced by many factors of clinical interest. (2) Methods: In this study, we performed a bioinformatic analysis of Gene Expression Omnibus (GEO) datasets to investigate the gene ontology of differentially expressed genes (DEGs) in endothelial cells exposed to atherogenic factors such as tobacco smoking, oscillatory shear, and oxidized low-density lipoproteins (oxLDL). DEGs were identified using the limma R package, and gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment, and protein-protein interaction (PPI) network analysis were performed. (3) Results: We studied biological processes and signaling pathways involving DEGs in endothelial cells under the influence of atherogenic factors. GO enrichment analysis demonstrated that the DEGs were mainly involved in cytokine-mediated signaling pathway, innate immune response, lipid biosynthetic process, 5-lipoxygenase activity, and nitric-oxide synthase activity. KEGG pathway enrichment analysis showed that common pathways included tumor necrosis factor signaling pathway, NF-κB signaling pathway, NOD-like receptor signaling pathway, lipid and atherosclerosis, lipoprotein particle binding, and apoptosis. (4) Conclusions: Atherogenic factors such as smoking, impaired flow, and oxLDL contribute to impaired innate immune response, metabolism, and apoptosis in endothelial cells, potentially leading to the development of atherosclerosis.

Pretreatment of human retinal pigment epithelial cells with sterculic acid forestalls fenretinide-induced apoptosis

The ratio of saturated to monounsaturated fatty acids, thought to play a critical role in many cellular functions, is regulated by stearoyl-CoA desaturase (SCD), a rate-limiting enzyme in the biosynthesis of monounsaturated fatty acids. Previously, we observed a decrease in both SCD protein and enzymatic activity in apoptosis induced by fenretinide, a synthetic analog of retinoic acid, in the human retinal pigment epithelial (RPE) cell line ARPE-19. Here, we investigated the effect of pretreating ARPE-19 with sterculic acid, a cyclopropenoic fatty acid inhibitor of SCD, on preventing fenretinide-induced apoptosis, given the role of SCD in cell proliferation and apoptosis. We show that sterculic acid pretreatment prevents the effects of fenretinide-induced apoptosis shown by changes in cell morphology, viability, and caspase-3 activation. Analysis of endoplasmic reticulum (ER)-associated proteins shows that sterculic acid pretreatment reduced the fenretinide-induced upregulation of heme oxygenase-1, ATF3 and GADD153 expression that are in response to reactive oxygen species (ROS) generation. Sterculic acid is as effective as allopurinol in inhibition of xanthine oxidase (XDH), and this may play a role in reducing the potential role of XDH in fenretinide-induced ROS generation. Sterculic acid pretreatment also results in a reduction in SOD2 mRNA expression. Dihydroceramide accumulation, compared to ceramide, and ROS generation indicate that a ceramide-independent pathway mediates fenretinide-induced apoptosis, and ROS mediation is borne out by activation of the NF-κBp50 and NF-κBp65 downstream signaling cascade. Its prevention by sterculic acid pretreatment further indicates the latter's antioxidant/anti-inflammatory effect. Taken together, our results suggest that sterculic acid pretreatment can mitigate ROS-mediated fenretinide-induced apoptosis. Thus, sterculic acid may serve as a potential antioxidant and therapeutic agent. These effects may be independent of its effects on SCD activity.

ATF3 in atherosclerosis: a controversial transcription factor

Atherosclerosis, the pathophysiological basis of most malignant cardiovascular diseases, remains a global concern. Transcription factors play a key role in regulating cell function and disease progression in developmental signaling pathways involved in atherosclerosis. Activated transcription factor (ATF) 3 is an adaptive response gene in the ATF/cAMP response element binding (CREB) protein family that acts as a transcription suppressor or activator by forming homodimers or heterodimers with other ATF/CREB members. Appropriate ATF3 expression is vital for normal physiological cell function. Notably, ATF3 exhibits distinct roles in vascular endothelial cells, macrophages, and the liver, which will also be described in detail. This review provides a new perspective for atherosclerosis therapy by summarizing the mechanism of ATF3 in atherosclerosis, as well as the structure and pathophysiological properties of ATF3. KEY MESSAGES: • In endothelial cells, ATF3 overexpression aggravates oxidative stress and inflammation. • In macrophages and liver cells, ATF3 can act as a negative regulator of inflammation and promote cholesterol metabolism. • ATF3 can be used as a potential therapeutic factor in the treatment of atherosclerosis.

ATF3 Regulates Osteogenic Function by Mediating Osteoblast Ferroptosis in Type 2 Diabetic Osteoporosis

PURPOSE

Osteoporosis is a complication of type 2 diabetes, and it is characterized by reduced bone mass, augmented bone fragility, and increased risk of fracture, thus reducing patient quality of life, especially in the elderly. Ferroptosis has been implicated in the pathological process of type 2 diabetic osteoporosis (T2DOP), but the specific underlying mechanisms remain largely unknown. This study clarified the role of activating transcription factor 3 (ATF3) in T2DOP and explored its specific regulatory mechanism, providing a new treatment target for T2DOP.

METHODS

We cultured hFob1.19 cells in high glucose (HG, 35 mM) and knocked down ATF3 using short hairpin RNA (shRNA). We then measured cell viability, assessed morphology, quantified the expression of ATF3 and glutathione peroxidase 4 (GPX4), detected the levels of reactive oxygen species (ROS) and lipid peroxides, and determined the osteogenic function of osteoblasts. Cystine/glutamate antiporter (system Xc-) activity was evaluated by determining the expression of SLC7A11 and the levels of glutathione (GSH) and extracellular glutamate. We constructed a T2DOP rat model and observed the effect of ATF3 on ferroptosis and T2DOP by knocking down ATF3 using small interfering RNA (siRNA). Then, we evaluated the levels of iron metabolism, lipid peroxidation, and bone turnover in serum, detected the expression of ATF3, SLC7A11, and GPX4 in bone tissues, and assessed bone microstructure using microcomputed tomography.

RESULTS

ATF3 expression was increased in osteoblasts under HG condition and in T2DOP rats. Inhibiting the function of ATF3 increased GPX4 levels and reduced the accumulation of ROS and lipid peroxides. These changes inhibited the ferroptosis of osteoblasts and improved osteogenic function. In addition, HG induced ATF3 upregulation, resulting in decreased SLC7A11 expression and lower levels of intracellular GSH and extracellular glutamate.

CONCLUSION

Osteoblast ferroptosis under HG conditions is induced by ATF3-mediated inhibition of system Xc- activity, and these events contribute to T2DOP pathogenesis.

ATF3 promotes ferroptosis in sorafenib-induced cardiotoxicity by suppressing Slc7a11 expression

Sorafenib is the unique recommended molecular-targeted drug for advanced hepatocellular carcinoma, but its clinical use is limited due to cardiotoxicity. As sorafenib is an efficient ferroptosis inducer, the pathogenesis of this compound to ferroptosis-mediated cardiotoxicity is worth further study. Mice were administered 30 mg/kg sorafenib intraperitoneally for 2 weeks to induce cardiac dysfunction and Ferrostatin-1 (Fer-1) was used to reduce ferroptosis of mice with sorafenib-induced cardiotoxicity. Sorafenib reduced levels of anti-ferroptotic markers involving Slc7a11 and glutathione peroxidase 4 (GPX4), increased malonaldehyde malondialdehyde, apart from causing obvious mitochondria damage, which was alleviated by Fer-1. In vitro experiments showed that Fer-1 inhibited lipid peroxidation and injury of H9c2 cardiomyoblasts induced by sorafenib. Both in vitro and in vivo experiments confirmed that the expression of Slc7a11 was down regulated in sorafenib-induced cardiotoxicity, which can be partially prevented by treatment with Fer-1. Overexpression of Slc7a11 protected cells from ferroptosis, while knock-down of Slc7a11 made cardiomyoblasts sensitive to ferroptosis caused by sorafenib. Finally, by comparing data from the GEO database, we found that the expression of ATF3 was significantly increased in sorafenib treated human cardiomyocytes. In addition, we demonstrated that ATF3 suppressed Slc7a11 expression and promoted ferroptosis. Based on these findings, we concluded that ATF3/Slc7a11 mediated ferroptosis is one of the key mechanisms leading to sorafenib-induced cardiotoxicity. Targeting ferroptosis may be a novel therapeutic approach for preventing sorafenib-induced cardiotoxicity in the future.

The role of NUPR1 in response to stress and cancer development

Stress contributes to the development of many human diseases, including cancer. Based on the source of stress, it can be divided into external stress, such as environmental carcinogens, chemicals, and radiation, and internal stress, like endoplasmic reticulum (ER) stress, hypoxia, and oxidative stress. Nuclear Protein 1 (NUPR1, p8 or Com-1) is a small, highly basic transcriptional regulator that participates in regulating a variety of cellular processes including DNA repair, ER stress, oxidative stress response, cell cycle, autophagy, apoptosis, ferroptosis and chromatin remodeling. A large number of studies have reported that NUPR1 expression can be stimulated rapidly in response to various stresses. Thus, NUPR1 is also known as a stress-response gene. Since the role of NUPR1 in breast cancer was identified in 1999, an increasing number of studies sought to reveal its function in cancer. High expression of NUPR1 has been identified in oral squamous cell carcinoma, breast cancer, lung cancer, multiple myeloma, liver cancer and renal cancer. In this review, we summarize current studies of NUPR1 in response to multiple external stressors and internal stressors, and its role in mediating stressors to cause different cell signaling responses. In addition, this review discusses the function of NUPR1 in carcinogenesis, tumorigenesis, metastasis, and cancer therapy. Thus, this review gives a comprehensive insight into the role of NUPR1 in mediating signals from stress to different cell responses, and this process plays a role in the development of cancer.

Regulatory pathways and drugs associated with ferroptosis in tumors

Ferroptosis is a type of cell death that depends on iron and reactive oxygen species (ROS). The accumulation of iron and lipid peroxidation primarily initiates oxidative membrane damage during ferroptosis. The core molecular mechanism of ferroptosis includes the regulation of oxidation and the balance between damage and antioxidant defense. Tumor cells usually contain a large amount of H₂O₂, and ferrous/iron ions will react with excessive H₂O₂ in cells to produce hydroxyl radicals and induce ferroptosis in tumor cells. Here, we reviewed the latest studies on the regulation of ferroptosis in tumor cells and introduced the tumor-related signaling pathways of ferroptosis. We paid particular attention to the role of noncoding RNA, nanomaterials, the role of drugs, and targeted treatment using ferroptosis drugs for mediating the ferroptosis process in tumor cells. Finally, we discussed the currently unresolved problems and future research directions for ferroptosis in tumor cells and the prospects of this emerging field. Therefore, we have attempted to provide a reference for further understanding of the pathogenesis of ferroptosis and proposed new targets for cancer treatment.

A new platform for ultra-high dose rate radiobiological research using the BELLA PW laser proton beamline

Radiotherapy is the current standard of care for more than 50% of all cancer patients. Improvements in radiotherapy (RT) technology have increased tumor targeting and normal tissue sparing. Radiations at ultra-high dose rates required for FLASH-RT effects have sparked interest in potentially providing additional differential therapeutic benefits. We present a new experimental platform that is the first one to deliver petawatt laser-driven proton pulses of 2 MeV energy at 0.2 Hz repetition rate by means of a compact, tunable active plasma lens beamline to biological samples. Cell monolayers grown over a 10 mm diameter field were exposed to clinically relevant proton doses ranging from 7 to 35 Gy at ultra-high instantaneous dose rates of 10⁷ Gy/s. Dose-dependent cell survival measurements of human normal and tumor cells exposed to LD protons showed significantly higher cell survival of normal-cells compared to tumor-cells for total doses of 7 Gy and higher, which was not observed to the same extent for X-ray reference irradiations at clinical dose rates. These findings provide preliminary evidence that compact LD proton sources enable a new and promising platform for investigating the physical, chemical and biological mechanisms underlying the FLASH effect.

Exercise-induced angiogenesis is dependent on metabolically primed ATF3/4+ endothelial cells

Exercise is a powerful driver of physiological angiogenesis during adulthood, but the mechanisms of exercise-induced vascular expansion are poorly understood. We explored endothelial heterogeneity in skeletal muscle and identified two capillary muscle endothelial cell (mEC) populations that are characterized by differential expression of ATF3/4. Spatial mapping showed that ATF3/4⁺ mECs are enriched in red oxidative muscle areas while ATF3/4^low ECs lie adjacent to white glycolytic fibers. In vitro and in vivo experiments revealed that red ATF3/4⁺ mECs are more angiogenic when compared with white ATF3/4^low mECs. Mechanistically, ATF3/4 in mECs control genes involved in amino acid uptake and metabolism and metabolically prime red (ATF3/4⁺) mECs for angiogenesis. As a consequence, supplementation of non-essential amino acids and overexpression of ATF4 increased proliferation of white mECs. Finally, deleting Atf4 in ECs impaired exercise-induced angiogenesis. Our findings illustrate that spatial metabolic angiodiversity determines the angiogenic potential of muscle ECs.

NUPR1: A Critical Regulator of the Antioxidant System

Simple Summary

Nuclear protein 1 (NUPR1) is activated in cellular stress and is expressed at high levels in cancer cells. Much evidence has been gathered supporting its critical role in regulating the antioxidant system. Our review aims to summarize the literature data on the impact of NUPR1 on the oxidative stress response via such a regulatory role and how its inhibition induces reactive oxygen species-mediated cell death, such as ferroptosis.

Abstract

Nuclear protein 1 (NUPR1) is a small intrinsically disordered protein (IDP) activated in response to various types of cellular stress, including endoplasmic reticulum (ER) stress and oxidative stress. Reactive oxygen species (ROS) are mainly produced during mitochondrial oxidative metabolism, and directly impact redox homeostasis and oxidative stress. Ferroptosis is a ROS-dependent programmed cell death driven by an iron-mediated redox reaction. Substantial evidence supports a maintenance role of the stress-inducible protein NUPR1 on cancer cell metabolism that confers chemotherapeutic resistance by upregulating mitochondrial function-associated genes and various antioxidant genes in cancer cells. NUPR1, identified as an antagonist of ferroptosis, plays an important role in redox reactions. This review summarizes the current knowledge on the mechanism behind the observed impact of NUPR1 on mitochondrial function, energy metabolism, iron metabolism, and the antioxidant system. The therapeutic potential of genetic or pharmacological inhibition of NUPR1 in cancer is also discussed. Understanding the role of NUPR1 in the antioxidant system and the mechanisms behind its regulation of ferroptosis may promote the development of more efficacious strategies for cancer therapy.

Targeting HDL in tumor microenvironment: New hope for cancer therapy

Epidemiological studies have shown that plasma HDL-C levels are closely related to the risk of prostate cancer, breast cancer, and other malignancies. As one of the key carriers of cholesterol regulation, high-density lipoprotein (HDL) plays an important role in tumorigenesis and cancer development through anti-inflammation, antioxidation, immune-modulation, and mediating cholesterol transportation in cancer cells and noncancer cells. In addition, the occurrence and progression of cancer are closely related to the alteration of the tumor microenvironment (TME). Cancer cells synthesize and secrete a variety of cytokines and other factors to promote the reprogramming of surrounding cells and shape the microenvironment suitable for cancer survival. By analyzing the effect of HDL on the infiltrating immune cells in the TME, as well as the relationship between HDL and tumor-associated angiogenesis, it is suggested that a moderate increase in the level of HDL in vivo with consequent improvement of the function of HDL in the TME and induction of intracellular cholesterol efflux may be a promising strategy for cancer therapy.

Overexpression of Activating Transcription Factor 3 Alleviates Cardiac Microvascular Ischemia/Reperfusion Injury in Rats

Activating transcription factor 3 (ATF3) has been confirmed to be responsive to oxidative stress and to negatively regulate the activity of Toll-like receptor 4 (TLR4). However, the effect of ATF3 on cardiac microvascular ischemia/reperfusion (I/R) injury remains unknown. The GEO2R online tool was employed to obtain differentially expressed genes GSE4105 and GSE122020, in two rat I/R injury microarray datasets. We established a rat myocardial I/R model in vivo, and also generated an in vitro hypoxia/reoxygenation (H/R) model of cardiomyoblast H9c2 cells. Overexpression of ATF3 was achieved by adenoviral-mediated gene transfer (Ad-ATF3). Rats were randomly divided into four groups: sham, I/R, I/R + Ad-Lacz (as a control), and I/R + Ad-ATF3. ELISA, CCK-8, DCFH-DA probe, qRT-PCR and Western blotting were used to determine the expression of ATF3, oxidative indices, cellular injury and TLR4/NF-κB pathway-associated proteins. Transmission electron microscopy, immunohistochemistry and immunofluorescence were used to detect the leukocyte infiltration and the alteration of microvascular morphology and function in vivo. Echocardiographic and hemodynamic data were also obtained. Bioinformatics analysis revealed that ATF3 was upregulated in I/R myocardia in two independent rat myocardial I/R models. Cardiac microvascular I/R injury included leukocyte infiltration, microvascular integrity disruption, and microvascular perfusion defect, which eventually resulted in the deterioration of hemodynamic parameters and heart function. Ad-ATF3 significantly restored microvascular function, increased cardiac microvascular perfusion, and improved hemodynamic parameters and heart function. Mechanistically, Ad-ATF3 ameliorated oxidative stress, inhibited TLR4/NF-κB pathway activation and down-regulated the expression of downstream proinflammatory cytokines in I/R myocardium in vivo and in H/R H9c2 cells in vitro. ATF3 overexpression protects against cardiac microvascular I/R injury in part by inhibiting the TLR4/NF-κB pathway and oxidative stress.

Protective Effect of Quercetin against H2O2-Induced Oxidative Damage in PC-12 Cells: Comprehensive Analysis of a lncRNA-Associated ceRNA Network

Quercetin is a bioflavonoid with potential antioxidant properties. However, the mechanisms underlying its effects remain unclear. Herein, we focused on integrating long noncoding RNA (lncRNA), microRNA (miRNA), and messenger RNA (mRNA) sequencing of PC-12 cells treated with quercetin. We treated PC-12 cells with hydrogen peroxide to generate a validated oxidative damage model. We evaluated the effects of quercetin on PC-12 cells and established the lncRNA, miRNA, and mRNA profiles of these cells. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses of these RNAs were conducted to identify the key pathways. Quercetin significantly protected PC-12 neuronal cells from hydrogen peroxide-induced death. We identified 297, 194, and 14 significantly dysregulated lncRNAs, miRNAs, and mRNAs, respectively, associated with the antioxidant effect of quercetin. Furthermore, the phosphatidylinositol-3-kinase/protein kinase B pathway was identified as the crucial signalling pathway. Finally, we constructed a lncRNA-associated competing endogenous RNA (ceRNA) network by utilizing oxidative damage mechanism-matched miRNA, lncRNA, and mRNA expression profiles and those changed by quercetin. In conclusion, quercetin exerted a protective effect against oxidative stress-induced damage in PC-12 cells. Our study provides novel insight into ceRNA-mediated gene regulation in the progression of oxidative damage and the action mechanisms of quercetin.

Cardiolipin Synthase 1 Ameliorates NASH Through Activating Transcription Factor 3 Transcriptional Inactivation

BACKGROUND AND AIMS

NASH is an increasingly prevalent disease that is the major cause of liver dysfunction. Previous research has indicated that adipose cardiolipin synthase 1 (CRLS1) levels are associated with insulin sensitivity; however, the precise roles of CRLS1 and underlying mechanisms involving CRLS1 in the pathological process of NASH have not been elucidated.

APPROACH AND RESULTS

Here, we discovered that CRLS1 was significantly down-regulated in genetically obese and diet-induced mice models. In vitro studies demonstrated that overexpression of CRLS1 markedly attenuated hepatic steatosis and inflammation in hepatocytes, whereas short hairpin RNA-mediated CRLS1 knockdown aggravated these abnormalities. Moreover, high-fat diet-induced insulin resistance and hepatic steatosis were significantly exacerbated in hepatocyte-specific Crls1-knockout (Crls1-HKO) mice. It is worth noting that Crls1 depletion significantly aggravated high-fat and high-cholesterol diet-induced inflammatory response and fibrosis during NASH development. RNA-sequencing analysis systematically demonstrated a prominently aggravated lipid metabolism disorder in which inflammation and fibrosis resulted from Crls1 deficiency. Mechanically, activating transcription factor 3 (ATF3) was identified as the key differentially expressed gene in Crls1-HKO mice through transcriptomic analysis, and our investigation further showed that CRLS1 suppresses ATF3 expression and inhibits its activity in palmitic acid-stimulated hepatocytes, whereas ATF3 partially reverses lipid accumulation and inflammation inhibited by CRLS1 overexpression under metabolic stress.

CONCLUSIONS

In conclusion, CRLS1 ameliorates insulin resistance, hepatic steatosis, inflammation, and fibrosis during the pathological process of NASH by inhibiting the expression and activity of ATF3.

The mRNA levels of heat shock factor 1 are regulated by thermogenic signals via the cAMP-dependent transcription factor ATF3

Heat shock factor 1 (HSF1) regulates cellular adaptation to challenges such as heat shock and oxidative and proteotoxic stresses. We have recently reported a previously unappreciated role for HSF1 in the regulation of energy metabolism in fat tissues; however, whether HSF1 is differentially expressed in adipose depots and how its levels are regulated in fat tissues remain unclear. Here, we show that HSF1 levels are higher in brown and subcutaneous fat tissues than in those in the visceral depot and that HSF1 is more abundant in differentiated, thermogenic adipocytes. Gene expression experiments indicated that HSF1 is transcriptionally regulated in fat by agents that modulate cAMP levels, by cold exposure, and by pharmacological stimulation of β-adrenergic signaling. An in silico promoter analysis helped identify a putative response element for activating transcription factor 3 (ATF3) at -258 to -250 base pairs from the HSF1 transcriptional start site, and electrophoretic mobility shift and ChIP assays confirmed ATF3 binding to this sequence. Furthermore, functional assays disclosed that ATF3 is necessary and sufficient for HSF1 regulation. Detailed gene expression analysis revealed that ATF3 is one of the most highly induced ATFs in thermogenic tissues of mice exposed to cold temperatures or treated with the β-adrenergic receptor agonist CL316,243 and that its expression is induced by modulators of cAMP levels in isolated adipocytes. To the best of our knowledge, our results show for the first time that HSF1 is transcriptionally controlled by ATF3 in response to classic stimuli that promote heat generation in thermogenic tissues.

ATF3 promotes erastin-induced ferroptosis by suppressing system Xc

The amino acid antiporter system Xc⁻ is important for the synthesis of glutathione (GSH) that functions to prevent lipid peroxidation and protect cells from nonapoptotic, iron-dependent death (i.e., ferroptosis). While the activity of system Xc⁻ often positively correlates with the expression level of its light chain encoded by SLC7A11, inhibition of system Xc⁻ activity by small molecules (e.g., erastin) causes a decrease in the intracellular GSH level, leading to ferroptotic cell death. How system Xc⁻ is regulated during ferroptosis remains largely unknown. Here we report that activating transcription factor 3 (ATF3), a common stress sensor, can promote ferroptosis induced by erastin. ATF3 suppressed system Xc⁻, depleted intracellular GSH, and thereby promoted lipid peroxidation induced by erastin. ATF3 achieved this activity through binding to the SLC7A11 promoter and repressing SLC7A11 expression in a p53-independent manner. These findings thus add ATF3 to a short list of proteins that can regulate system Xc⁻ and promote ferroptosis repressed by this antiporter.

Roles of EphA1/A2 and ephrin-A1 in cancer

The biological functions of the Eph/ephrin system have been intensively investigated and well documented so far since its discovery in 1987. Although the Eph/ephrin system has been implicated in pathological settings such as Alzheimer's disease and cancer, the molecular mechanism of the Eph/ephrin system in those diseases is not well understood. Especially in cancer, recent studies have demonstrated that most of Eph and ephrin are up‐ or down‐regulated in various types of cancer, and have been implicated in tumor progression, tumor malignancy, and prognosis. However, they lack consistency and are in controversy. The localization patterns of EphA1 and EphA2 in mouse lungs are very similar, and both knockout mice showed similar phenotypes in the lungs. Ephrin‐A1 that is a membrane‐anchored ligand for EphAs was co‐localized with EphA1 and EphA2 in lung vascular endothelial cells. We recently uncovered the molecular mechanism of ephrin‐A1‐induced lung metastasis by understanding the physiological function of ephrin‐A1 in lungs. This review focuses on the function of EphA1, EphA2, and ephrin‐A1 in tumors and an establishment of pre‐metastatic microenvironment in the lungs.

Activating transcription factor 3 in cardiovascular diseases: a potential therapeutic target

Cardiovascular diseases (CVDs) are the primary causes of death worldwide. Among the numerous signaling molecules involved in CVDs, transcriptional factors directly influence gene expression and play a critical role in regulating cell function and the development of diseases. Activating transcription factor (ATF) 3 is an adaptive-response gene in the ATF/cAMP responsive element-binding (CREB) protein family of transcription factors that acts as either a repressor or an activator of transcription via the formation of homodimers or heterodimers with other ATF/CREB members. A appropriate ATF3 expression is important for the normal physiology of cells, and dysfunction of ATF3 is associated with various pathophysiological responses such as inflammation, apoptosis, oxidative stress and endoplasmic reticulum stress, and diseases, including CVDs. This review focuses on the role of ATF3 in cardiac hypertrophy, heart failure, atherosclerosis, ischemic heart diseases, hypertension and diabetes mellitus to provide a novel therapeutic target for CVDs.

Oxidation of heat shock protein 60 and protein disulfide isomerase activates ERK and migration of human hepatocellular carcinoma HepG2

Hepatocyte growth factor (HGF) and its receptor c-Met were frequently deregulated in hepatocellular carcinoma (HCC). Signaling pathways activated by HGF-c-Met are promising targets for preventing HCC progression. HGF can induce the reactive oxygen species (ROS) signaling for cell adhesion, migration and invasion of tumors including HCC. On the other hand, extracellular signal-regulated kinases (ERK), member of mitogen activated kinase, can be activated by ROS for a lot of cellular processes. As expected, HGF-induced phosphorylation of ERK and progression of HCC cell HepG2 were suppressed by ROS scavengers. By N-(biotinoyl)-N'-(iodoacetyl)-ethylenediamine (BIAM) labeling method, a lot of cysteine (-SH)-containing proteins with M.W. 50-75 kD were decreased in HepG2 treated with HGF or two other ROS generators, 12-O-tetradecanoyl-phorbol-13-acetate (TPA) and phenazine methosulfate. These redox sensitive proteins were identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry. Among them, two chaperones, heat shock protein 60 (HSP60) and protein disulfide isomerase (PDI), were found to be the most common redox sensitive proteins in responding to all three agonists. Affinity blot of BIAM-labeled, immunoprecipitated HSP60 and PDI verified that HGF can decrease the cysteine (-SH) containing HSP60 and PDI. On the other hand, HGF and TPA increased cysteinyl glutathione-containing HSP60, consistent with the decrease of cysteine (-SH)-containing HSP60. Moreover, depletion of HSP60 and PDI or expression of dominant negative mutant of HSP60 with alteration of Cys, effectively prevented HGF-induced ERK phosphorylation and HepG2 migration.In conclusion, the redox sensitive HSP60 and PDI are required for HGF-induced ROS signaling and potential targets for preventing HCC progressions.

Gene expression differences in Longissimus muscle of Nelore steers genetically divergent for residual feed intake

Residual feed intake (RFI), a measure of feed efficiency (FE), is defined as the difference between the observed and the predictable feed intake considering size and growth of the animal. It is extremely important to beef production systems due to its impact on the allocation of land areas to alternative agricultural production, animal methane emissions, food demand and cost of production. Global differential gene expression analysis between high and low RFI groups (HRFI and LRFI: less and more efficient, respectively) revealed 73 differentially expressed (DE) annotated genes in Longissimus thoracis (LT) muscle of Nelore steers. These genes are involved in the overrepresented pathways Metabolism of Xenobiotics by Cytochrome P450 and Butanoate and Tryptophan Metabolism. Among the DE transcripts were several proteins related to mitochondrial function and the metabolism of lipids. Our findings indicate that observed gene expression differences are primarily related to metabolic processes underlying oxidative stress. Genes involved in the metabolism of xenobiotics and antioxidant mechanisms were primarily down-regulated, while genes responsible for lipid oxidation and ketogenesis were up-regulated in HRFI group. By using LT muscle, this study reinforces our previous findings using liver tissue and reveals new genes and likely tissue-specific regulators playing key-roles in these processes.

Camel whey protein improves lymphocyte function and protects against diabetes in the offspring of diabetic mouse dams

The prevalence of health problems in the offspring of pregnant diabetic mothers has recently been verified. Therefore, the present study was designed to investigate the influence of dietary camel whey protein (CWP), administered as a supplement to streptozotocin (STZ)-induced diabetic pregnant mice, on the efficiency of the immune system of the offspring. Three groups of female mice (n = 10) were used: non-diabetic control mice, diabetic mice, and diabetic mice orally administered CWP during the pregnancy and lactation periods. We then tested the immune response of B and T cells in adult male offspring (n = 15 in each group) by using flow cytometry, western blotting, and ELISAs. Our data demonstrated that the offspring of diabetic dams exhibited several postpartum complications, such as significant aberrant overexpression of activating transcription factor-3 (ATF-3), significant elevation of the plasma levels of pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) and reactive oxygen species (ROS), marked decreases in the plasma levels of IL-2 and IL-7, significant inhibition of CCL21- and CXCL12-mediated chemotaxis of B- and T-lymphocytes, and a marked decrease in the proliferative capacity of antigen-stimulated B- and T-lymphocytes. Interestingly, administration of CWP to diabetic dams substantially restored the expression of ATF-3 and the levels of ROS, pro-inflammatory cytokines, IL-2, and IL-7 in the offspring. Furthermore, the chemotaxis of B- and T-lymphocytes toward CCL21 and CXCL12 and the proliferative capacities of these lymphocytes were restored in the male offspring of diabetic mice administered CWP. Our data provide evidence of a protective role of CWP in decreasing the tendency of the offspring of diabetic mothers to develop diabetes and related complications.

Bee Venom Accelerates Wound Healing in Diabetic Mice by Suppressing Activating Transcription Factor-3 (ATF-3) and Inducible Nitric Oxide Synthase (iNOS)-Mediated Oxidative Stress and Recruiting Bone Marrow-Derived Endothelial Progenitor Cells

Multiple mechanisms contribute to impaired diabetic wound healing including impaired neovascularization and deficient endothelial progenitor cell (EPC) recruitment. Bee venom (BV) has been used as an anti-inflammatory agent for the treatment of several diseases. Nevertheless, the effect of BV on the healing of diabetic wounds has not been studied. Therefore, in this study, we investigated the impact of BV on diabetic wound closure in a type I diabetic mouse model. Three experimental groups were used: group 1, non-diabetic control mice; group 2, diabetic mice; and group 3, diabetic mice treated with BV. We found that the diabetic mice exhibited delayed wound closure characterized by a significant decrease in collagen production and prolonged elevation of inflammatory cytokines levels in wounded tissue compared to control non-diabetic mice. Additionally, wounded tissue in diabetic mice revealed aberrantly up-regulated expression of ATF-3 and iNOS followed by a marked elevation in free radical levels. Impaired diabetic wound healing was also characterized by a significant elevation in caspase-3, -8, and -9 activity and a marked reduction in the expression of TGF-β and VEGF, which led to decreased neovascularization and angiogenesis of the injured tissue by impairing EPC mobilization. Interestingly, BV treatment significantly enhanced wound closure in diabetic mice by increasing collagen production and restoring the levels of inflammatory cytokines, free radical, TGF-β, and VEGF. Most importantly, BV-treated diabetic mice exhibited mobilized long-lived EPCs by inhibiting caspase activity in the wounded tissue. Our findings reveal the molecular mechanisms underlying improved diabetic wound healing and closure following BV treatment. J. Cell. Physiol. 231: 2159-2171, 2016. © 2016 Wiley Periodicals, Inc.

Loss of ATF3 promotes hormone-induced prostate carcinogenesis and the emergence of CK5(+)CK8(+) epithelial cells

Steroid sex hormones can induce prostate carcinogenesis, and are thought to contribute to the development of prostate cancer during aging. However, the mechanism for hormone-induced prostate carcinogenesis remains elusive. Here we report that activating transcription factor 3 (ATF3) – a broad stress sensor – suppressed hormone-induced prostate carcinogenesis in mice. While implantation of testosterone and estradiol (T+E₂) pellets for 2 months in wild-type mice rarely induced prostatic intraepithelial neoplasia (PIN) in dorsal prostates (1 out of 8 mice), loss of ATF3 led to the appearance of not only PIN but also invasive lesions in almost all examined animals. The enhanced carcinogenic effects of hormones on ATF3-deficient prostates did not appear to be caused by a change in estrogen signaling, but were more likely a consequence of elevated androgen signaling that stimulated differentiation of prostatic basal cells into transformation-preferable luminal cells. Indeed, we found that hormone-induced lesions in ATF3-knockout mice often contained cells with both basal and luminal characteristics, such as p63⁺ cells (a basal cell marker) showing luminal-like morphology, or cells double-stained with basal (CK5⁺) and luminal (CK8⁺) markers. Consistent with these findings, low ATF3 expression was found to be a poor prognostic marker for prostate cancer in a cohort of 245 patients. Our results thus support that ATF3 is a tumor suppressor in prostate cancer.

Indole-3-carbinol and its N-alkoxy derivatives preferentially target ERα-positive breast cancer cells

Indole-3-carbinol (I3C) is a natural anti-carcinogenic compound found at high concentrations in Brassica vegetables. I3C was recently reported to inhibit neutrophil elastase (NE) activity, while consequently limiting the proteolytic processing of full length cyclin E into pro-tumorigenic low molecular weight cyclin E (LMW-E). In this study, we hypothesized that inhibition of NE activity and resultant LMW-E generation is critical to the anti-tumor effects of I3C. LMW-E was predominately expressed by ERα-negative breast cancer cell lines. However, ERα-positive cell lines demonstrated the greatest sensitivity to the anti-tumor effects of I3C and its more potent N-alkoxy derivatives. We found that I3C was incapable of inhibiting NE activity or the generation of LMW-E. Therefore, this pathway did not contribute to the anti-tumor activity of I3C. Gene expression analyzes identified ligand-activated aryl hydrocarbon receptor (AhR), which mediated sensitivity to the anti-tumor effects of I3C in ERα-positive MCF-7 cells. In this model system, the reactive oxygen species (ROS)-induced upregulation of ATF-3 and pro-apoptotic BH3-only proteins (e.g. NOXA) contributed to the sensitivity of ERα-positive breast cancer cells to the anti-tumor effects of I3C. Overexpression of ERα in MDA-MB-231 cells, which normally lack ERα expression, increased sensitivity to the anti-tumor effects of I3C, demonstrating a direct role for ERα in mediating the sensitivity of breast cancer cell lines to I3C. Our results suggest that ERα signaling amplified the pro-apoptotic effect of I3C-induced AhR signaling in luminal breast cancer cell lines, which was mediated in part through oxidative stress induced upregulation of ATF-3 and downstream BH3-only proteins.

The role of high-density lipoproteins in the regulation of angiogenesis

Angiogenesis is important for postnatal physiological processes including tissue neovascularization in response to an ischaemic injury. Conversely, uncontrolled inflammatory-driven angiogenesis can accelerate atherosclerotic plaque and tumour growth. Angiogenesis-associated diseases are highly prevalent globally, with cardiovascular-related disorders and cancer being the leading causes of mortality worldwide. A vast amount of research has been conducted on the vasculoprotective effects of high-density lipoproteins (HDLs) and while current HDL-raising therapies to date have not yielded the desired benefits clinically, its role in angiogenesis is yet to be fully elucidated. Epidemiological studies report positive correlations between elevated HDL levels and improved prognosis in both ischaemia- and inflammatory-driven pathologies, in which angiogenesis plays a key role. This review focuses on current evidence from epidemiological and prospective studies, coupled with animal models and mechanistic studies that highlight the ability of HDL to conditionally regulate angiogenesis.

ATF3-mediated NRF2/HO-1 signaling regulates TLR4 innate immune responses in mouse liver ischemia/reperfusion injury

Activating transcription factor 3 (ATF3) is a stress-induced transcription factor that has been shown to repress inflammatory gene expression in multiple cell types and diseases. However, little is known about the roles and mechanisms of ATF3 in liver ischemia/reperfusion injury (IRI). In warm and cold liver IRI models, we showed that ATF3 deficiency significantly increased ischemia/reperfusion (IR)-stressed liver injury, as evidenced by increased serum alanine aminotransferase levels, histological liver damage, and hepatocellular apoptosis. These may correlate with inhibition of the intrahepatic nuclear factor erythroid-derived 2-related factor 2/heme oxygenase-1 (NRF2/HO-1) signaling pathway leading to enhancing Toll-like receptor 4/nuclear factor kappa beta (TLR4/NF-κB) activation, pro-inflammatory programs and macrophage/neutrophil trafficking, while simultaneously repressing anti-apoptotic molecules in ischemic liver. Interestingly, activation of NRF2/HO-1 signaling using an NRF2 activator, oltipraz (M2), during hepatic IRI-rescued ATF3 anti-inflammatory functions in ATF3-deficient mice. For in vitro studies, ATF3 ablation in lipopolysaccharide (LPS)-stimulated bone marrow-derived macrophages (BMMs) depressed levels of NRF2/HO-1 and PI3K/AKT, resulting in enhanced TLR4/NF-κB activation. Pretreatment of LPS-stimulated BMMs with M2 increased NRF2/HO-1 expression, promoted PI3K/AKT, which in turn suppressed TLR4/NF-κB-mediated proinflammatory mediators. Thus, our results first demonstrate ATF3-mediated NRF2/HO-1 signaling in the regulation of TLR4-driven inflammatory responses in IR-stressed livers. Our findings provide a rationale for a novel therapeutic strategy for managing IR-induced liver injury.

Interleukin-18 has antipermeablity and antiangiogenic activities in the eye: reciprocal suppression with VEGF

Interleukin-18 (IL-18) is increased along with IL-1β by activation of the inflammasome and has been implicated in inflammatory and autoimmune diseases, but its role in the eye is uncertain. In patients with macular edema due to retinal vein occlusion, intraocular IL-18 levels increased significantly (P < 0.001) after treatment with ranibizumab particularly in patients with high baseline IL-18 which correlated with good visual outcome (P < 0.05). In mice with ischemic retinopathy, suppression of VEGF caused an increase in IL18 mRNA due to an increase in IL-18-positive myeloid cells. VEGF significantly and specifically inhibited IL-18 production by myeloid cells stimulated with lipopolysaccharide (P < 0.001). Intraocular injection of IL-18 reduced VEGF-induced leakage and neovascularization, and reversed VEGF-induced suppression of Claudin5 expression and Claudin 5 labeling of vascular tight junctions. Injection of IL-18 also increased expression of Thrombospondin 1 and reduced ischemia-induced retinal neovascularization relevant to diabetic retinopathy and subretinal neovascularization relevant to neovascular age-related macular degeneration. Thus, VEGF and IL-18 suppress each other's production and effects on the vasculature suggesting that IL-18 may provide benefit in multiple retinal/choroidal vascular diseases.

Integrative transcriptome analysis reveals dysregulation of canonical cancer molecular pathways in placenta leading to preeclampsia

We previously suggested links between specific XPD mutations in the fetal genome and the risk of placental maldevelopment and preeclampsia, possibly due to impairment of Transcription Factor (TF)IIH-mediated functions in placenta. To identify the underlying mechanisms, we conducted the current integrative analysis of several relevant transcriptome data sources. Our meta-analysis revealed downregulation of TFIIH subunits in preeclamptic placentas. Our overall integrative analysis suggested that, in the presence of hypoxia and oxidative stress, EGFR signaling deficiency, which can be caused by TFIIH impairment as well as by other mechanisms, results in ATF3 upregulation, inducing mediators of clinical symptoms of preeclampsia such as FLT1 and ENG. EGFR- and ATF3-dependent pathways play prominent roles in cancer development. We propose that dysregulation of these canonical cancer molecular pathways occurs in preeclampsia and delineate the relevance of TFIIH, providing etiologic clues which could eventually translate into a therapeutic approach.

Chronic ethanol consumption decreases serum sulfatide levels by suppressing hepatic cerebroside sulfotransferase expression in mice

Epidemiological studies demonstrate a possible relationship between chronic ethanol drinking and thrombotic diseases, such as myocardial infarction and stroke. However, the precise mechanism for this association remains unclear. Sulfatides are endogenous glycosphingolipids composed of ceramide, galactose, and sulfate, known to have anti-thrombotic properties. Low (0.5 g/kg/day), middle (1.5 g/kg/day), and high (3.0 g/kg/day) doses of ethanol were administered for 21 days intraperitoneally to female wild-type mice, and serum/liver sulfatide levels were measured. No significant changes in cholesterol and triglycerides were seen in serum and liver by ethanol treatment. However, serum/liver sulfatide levels were significantly decreased by middle- and high-dose ethanol treatment, likely due to downregulation of hepatic cerebroside sulfotransferase (CST) levels. Marked decreases in the expression of catalase and superoxide dismutases and ensuing increases in lipid peroxides were also observed in the livers of mice with middle- and high-dose ethanol treatment, suggesting the association between the suppression of hepatic CST expression and enhancement of oxidative stress. Furthermore, serum levels of tissue factor, a typical pro-coagulant molecule, were significantly increased in the mice with middle- and high-dose ethanol treatment showing decreases in serum sulfatide levels. Collectively, these results demonstrate that chronic ethanol consumption reduces serum sulfatide levels by increasing oxidative stress and decreasing the expression of CST in the liver. These findings could provide a mechanism by which chronic ethanol drinking increases thrombotic events.

Activation of TLR4 signaling promotes gastric cancer progression by inducing mitochondrial ROS production

Chronic infection, such as Helicobacter pylori infection, has been associated with the development of gastric cancer (GC). Pathogen-associated molecular patterns can trigger inflammatory responses via Toll-like receptors (TLRs) in GC. Here we showed that Toll-like receptor 4 (TLR4) was highly expressed in GC cells and was associated with the aggressiveness of GC. The binding of lipopolysaccharide (LPS) to TLR4 on GC cells enhanced proliferation without affecting apoptosis. Higher level of reactive oxygen species (ROS) was induced after activation of TLR4 signaling in GC. Using oxidase inhibitors and antioxidants, we found that mitochondrial ROS (mROS) was major source of TLR4-stimulated ROS generation. This elevated mROS production can be inhibited by diphenylene iodonium (DPI), and the blocking of the mROS production rather than ROS neutralization resulted in cell cycle arrest and the loss of mitochondrial potential, which were plausible reason for decreased cell viability. Furthermore, the increased mROS owing to TLR4 signaling resulted in the activation of Akt phosphorylation and NF-κB p65 nuclear translocation. Altogether, these results reveal a novel pathway linking innate immune signaling to GC cell proliferation, implicate mROS as an important component of cell survival signals and further establish mitochondria as hubs for GC therapies.

Current status of NADPH oxidase research in cardiovascular pharmacology

The implications of reactive oxygen species in cardiovascular disease have been known for some decades. Rationally, therapeutic antioxidant strategies combating oxidative stress have been developed, but the results of clinical trials have not been as good as expected. Therefore, to move forward in the design of new therapeutic strategies for cardiovascular disease based on prevention of production of reactive oxygen species, steps must be taken on two fronts, ie, comprehension of reduction-oxidation signaling pathways and the pathophysiologic roles of reactive oxygen species, and development of new, less toxic, and more selective nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitors, to clarify both the role of each NADPH oxidase isoform and their utility in clinical practice. In this review, we analyze the value of NADPH oxidase as a therapeutic target for cardiovascular disease and the old and new pharmacologic agents or strategies to prevent NADPH oxidase activity. Some inhibitors and different direct or indirect approaches are available. Regarding direct NADPH oxidase inhibition, the specificity of NADPH oxidase is the focus of current investigations, whereas the chemical structure-activity relationship studies of known inhibitors have provided pharmacophore models with which to search for new molecules. From a general point of view, small-molecule inhibitors are preferred because of their hydrosolubility and oral bioavailability. However, other possibilities are not closed, with peptide inhibitors or monoclonal antibodies against NADPH oxidase isoforms continuing to be under investigation as well as the ongoing search for naturally occurring compounds. Likewise, some different approaches include inhibition of assembly of the NADPH oxidase complex, subcellular translocation, post-transductional modifications, calcium entry/release, electron transfer, and genetic expression. High-throughput screens for any of these activities could provide new inhibitors. All this knowledge and the research presently underway will likely result in development of new drugs for inhibition of NADPH oxidase and application of therapeutic approaches based on their action, for the treatment of cardiovascular disease in the next few years.

Subamolide a induces mitotic catastrophe accompanied by apoptosis in human lung cancer cells

This study investigated the anticancer effects of subamolide A (Sub-A), isolated from Cinnamomum subavenium, on human nonsmall cell lung cancer cell lines A549 and NCI-H460. Treatment of cancer cells with Sub-A resulted in decreased cell viability of both lung cancer cell lines. Sub-A induced lung cancer cell death by triggering mitotic catastrophe with apoptosis. It triggered oxidant stress, indicated by increased cellular reactive oxygen species (ROS) production and decreased glutathione level. The elevated ROS triggered the activation of ataxia-telangiectasia mutation (ATM), which further enhanced the ATF3 upregulation and subsequently enhanced p53 function by phosphorylation at Serine 15 and Serine 392. The antioxidant, EUK8, significantly decreased mitotic catastrophe by inhibiting ATM activation, ATF3 expression, and p53 phosphorylation. The reduction of ATM and ATF3 expression by shRNA decreased Sub-A-mediated p53 phosphorylation and mitotic catastrophe. Sub-A also caused a dramatic 70% reduction in tumor size in an animal model. Taken together, cell death of lung cancer cells in response to Sub-A is dependent on ROS generation, which triggers mitotic catastrophe followed by apoptosis. Therefore, Sub-A may be a novel anticancer agent for the treatment of nonsmall cell lung cancer.

Metabolic syndrome influences cardiac gene expression pattern at the transcript level in male ZDF rats

BACKGROUND

Metabolic syndrome (coexisting visceral obesity, dyslipidemia, hyperglycemia, and hypertension) is a prominent risk factor for cardiovascular morbidity and mortality, however, its effect on cardiac gene expression pattern is unclear. Therefore, we examined the possible alterations in cardiac gene expression pattern in male Zucker Diabetic Fatty (ZDF) rats, a model of metabolic syndrome.

METHODS

Fasting blood glucose, serum insulin, cholesterol and triglyceride levels were measured at 6, 16, and 25 wk of age in male ZDF and lean control rats. Oral glucose tolerance test was performed at 16 and 25 wk of age. At week 25, total RNA was isolated from the myocardium and assayed by rat oligonucleotide microarray for 14921 genes. Expression of selected genes was confirmed by qRT-PCR.

RESULTS

Fasting blood glucose, serum insulin, cholesterol and triglyceride levels were significantly increased, glucose tolerance and insulin sensitivity were impaired in ZDF rats compared to leans. In hearts of ZDF rats, 36 genes showed significant up-regulation and 49 genes showed down-regulation as compared to lean controls. Genes with significantly altered expression in the heart due to metabolic syndrome includes functional clusters of metabolism (e.g. 3-hydroxy-3-methylglutaryl-Coenzyme A synthase 2; argininosuccinate synthetase; 2-amino-3-ketobutyrate-coenzyme A ligase), structural proteins (e.g. myosin IXA; aggrecan1), signal transduction (e.g. activating transcription factor 3; phospholipase A2; insulin responsive sequence DNA binding protein-1) stress response (e.g. heat shock 70kD protein 1A; heat shock protein 60; glutathione S-transferase Yc2 subunit), ion channels and receptors (e.g. ATPase, (Na+)/K+ transporting, beta 4 polypeptide; ATPase, H+/K+ transporting, nongastric, alpha polypeptide). Moreover some other genes with no definite functional clusters were also changed such as e.g. S100 calcium binding protein A3; ubiquitin carboxy-terminal hydrolase L1; interleukin 18. Gene ontology analysis revealed several significantly enriched functional inter-relationships between genes influenced by metabolic syndrome.

CONCLUSIONS

Metabolic syndrome significantly alters cardiac gene expression profile which may be involved in development of cardiac pathologies in the presence of metabolic syndrome.

Attenuation of kidney injuries maintains serum sulfatide levels dependent on hepatic synthetic ability: a possible involvement of oxidative stress

Serum sulfatides are the major glycosphingolipids in lipoproteins. Although serum sulfatides are mainly synthesized and secreted by the liver, they are significantly decreased when the kidneys are impaired. Our recent experimental study using a murine protein-overload nephropathy model suggested a hypothetical mechanism whereby serum sulfatides were reduced due to kidney dysfunction. This was the result of decreased hepatic expression of a sulfatide synthetic enzyme, cerebroside sulfotransferase (CST), which is associated with systemic enhancement of oxidative stress. However, there is a possibility that the experimental process, protein-overload itself, directly affected the sulfatide metabolism and oxidative stress in the liver. To determine whether kidney dysfunction actually reduces the hepatic synthesis of sulfatides via oxidative stress, we examined sulfatide levels, the hepatic content of metabolic sulfatide enzymes, and the degree of oxidative stress in protein-overload mice subjected to renoprotective therapy using clofibrate, a representative hypolipidemic medicine. Protein-overload mice exhibited marked kidney injuries, enhancement of hepatic oxidative stress, decreased levels of serum and hepatic sulfatides, and decreased expression of hepatic CST. The clofibrate treatment attenuated kidney damage and hepatic oxidative stress while maintaining serum/hepatic sulfatide levels and hepatic CST content in the mice. Because clofibrate monotherapy without protein-overload treatment only minimally affected these hepatic parameters, the hepatic synthesis of sulfatides appeared to be strongly influenced by kidney dysfunction and subsequent oxidative stress. This study suggests that the crosstalk between kidney dysfunction and hepatic sulfatide metabolism is mediated by oxidative stress. These results should help to understand the phenomenon in patients with end-stage kidney disease.

ATF3 protects against atherosclerosis by suppressing 25-hydroxycholesterol-induced lipid body formation

The transcription factor ATF3 inhibits lipid body formation in macrophages during atherosclerosis in part by dampening the expression of cholesterol 25-hydroxylase.

Atherosclerosis is a chronic inflammatory disease characterized by the accumulation of lipid-loaded macrophages in the arterial wall. We demonstrate that macrophage lipid body formation can be induced by modified lipoproteins or by inflammatory Toll-like receptor agonists. We used an unbiased approach to study the overlap in these pathways to identify regulators that control foam cell formation and atherogenesis. An analysis method integrating epigenomic and transcriptomic datasets with a transcription factor (TF) binding site prediction algorithm suggested that the TF ATF3 may regulate macrophage foam cell formation. Indeed, we found that deletion of this TF results in increased lipid body accumulation, and that ATF3 directly regulates transcription of the gene encoding cholesterol 25-hydroxylase. We further showed that production of 25-hydroxycholesterol (25-HC) promotes macrophage foam cell formation. Finally, deletion of ATF3 in Apoe^−/− mice led to in vivo increases in foam cell formation, aortic 25-HC levels, and disease progression. These results define a previously unknown role for ATF3 in controlling macrophage lipid metabolism and demonstrate that ATF3 is a key intersection point for lipid metabolic and inflammatory pathways in these cells.

Hydrogen saline treatment attenuates hyperoxia-induced retinopathy by inhibition of oxidative stress and reduction of VEGF expression

OBJECTIVE

Retinal neovascularization or retinopathy is a proliferative disorder of the retinal capillaries and is the primary cause of blindness. Some studies have shown that oxidative stress plays an important role in hyperoxia-induced retinal neovascularization. Previous reports have indicated that hydrogen has a therapeutic, antioxidant activity by selectively reducing hydroxyl radicals. This study examined the therapeutic effect of hydrogen saline on retinopathy in an established mouse model of hyperoxia-induced retinopathy.

METHODS

Mouse pups were exposed to 75% O(2) from postnatal day 7 (P7) to P12. Hydrogen saline was administered by intraperitoneal injection (5 ml/kg) daily for 5 days. On P17, the pups were decapitated, and retinal neovascularization was assessed using fluorescence imaging and histopathological examination. Vascular endothelial growth factor (VEGF) expression was evaluated using real-time polymerase chain reaction and fluorescence immunohistochemistry. Oxidative stress was quantified based on the malondialdehyde (MDA) level.

RESULTS

Hydrogen saline decreased retinal neovascularization, reduced the mRNA and protein expression of VEGF, and suppressed the MDA levels.

CONCLUSIONS

Hydrogen saline may be a potential treatment for hyperoxia-induced retinopathy that acts via the inhibition of oxidative stress and the reduction of VEGF expression.

Early transcriptional regulation by C-peptide in freshly isolated rat proximal tubular cells

BACKGROUND

Clinical studies have shown that proinsulin C-peptide exerts renoprotective effects in type 1 diabetes, although the underlying mechanisms are poorly understood. As C-peptide has been shown to induce several intracellular events and to localize to nuclei, we aimed to determine whether gene transcription is affected in proximal tubular kidney cells, and if so, whether the genes with altered transcription include those related to protective mechanisms.

METHODS

The effect of C-peptide incubation (2 h) on gene expression was investigated in freshly isolated proximal tubular cells from streptozotocin-diabetic Sprague-Dawley rats using global gene expression profiling and real-time quantitative polymerase chain reaction. Protein expression was assayed using western blotting. Different bioinformatic strategies were employed.

RESULTS

Gene transcription profiling demonstrated differential transcription of 492 genes (p < 0.01) after 2 h of C-peptide exposure, with the majority of these genes repressed (83%). Real-time quantitative polymerase chain reaction validation supported a trend of several G protein-coupled receptors being activated, and certain transcription factors being repressed. Also, C-peptide repressed the transcription of genes associated with the pathways of circulatory and inflammatory diseases.

CONCLUSION

This study shows that C-peptide exerts early effects on gene transcription in proximal tubular cells. The findings also bring further knowledge to the renoprotective mechanisms of C-peptide in type 1 diabetes, and support a transcriptional activity for C-peptide. It is suggested that C-peptide may play a regulatory role in the gene expression of proximal tubular cells.

Activating transcription factor 3 regulates survivability and migration of vascular smooth muscle cells

Activating transcription factor 3 (ATF3) is a member of the ATF/CREB (CAMP responsive element binding protein) family of transcription factors. The expression and the function of ATF3 in vascular smooth muscle cells (VSMCs) remain unknown. The aim of this work is to determine the expression and possible function of ATF3 in VSMCs. We found that VSMCs expressed ATF3, and expression of ATF3 in VSMCs was induced by a variety of stimuli including serum, angiotensin II, and H(2)O(2). Knockdown of ATF3 induced apoptosis of VSMCs, caspase-3 cleavage, and cytochrome c release. The results suggest that ATF3 regulates survivability of VSMCs. Moreover, we found that overexpression of ATF3 promoted migration of VSMCs and induced expression of matrix metalloproteinase 1, 3, and 13. These results suggest that ATF3 plays a role in regulating migration of VSMCs. In addition, we found that the expression of ATF3 was upregulated in smooth muscle cells in the injured mouse femoral arteries compared with the uninjured control group. These results suggest that ATF3 is relevant to disease physiology.

Unforeseen decreases in dissolved oxygen levels affect tube formation kinetics in collagen gels

The availability of oxygen (O(2)) is a critical parameter affecting vascular tube formation. In this study, we hypothesize that dissolved oxygen (DO) levels in collagen gels change during the three-dimensional (3D) culture of human umbilical vein endothelial cells (HUVECs) in atmospheric conditions and that such changes affect the kinetics of tube formation through the production of reactive oxygen species (ROS). We demonstrate a decrease in O(2) tension during 3D cultures of HUVECs. Noninvasive measurements of DO levels during culture under atmospheric conditions revealed a profound decrease that reached as low as 2% O(2) at the end of 24 h. After media replacement, DO levels rose rapidly and equilibrated at ∼15% O(2), creating a reoxygenated environment. To accurately estimate DO gradients in 3D collagen gels, we developed a 3D mathematical model and determined the Michaelis-Menten parameters, V(max) and K(m), of HUVECs in collagen gels. We detected an increase in ROS levels throughout the culture period. Using diphenyliodonium to inhibit ROS production resulted in the complete inhibition of tube formation. Interference RNA studies further showed that hypoxia-inducible factors (HIFs)-1α and -2α are not involved in the formation of 3D tubes in collagen gels. We conclude that ROS affect the tubulogenesis process through HIFα-independent pathways, where the levels of ROS are influenced by the uncontrolled variations in DO levels. This study is the first demonstration of the critical and unexpected role of O(2) during 3D in vitro culture models of tubulogenesis in atmospheric conditions.

Mechanistic Study on Hepatocarcinogenesis of Piperonyl Butoxide in Mice

To clarify the mechanism of piperonyl butoxide (PBO)-induced hepatocarcinogenesis in mice, male mice were subjected to a two-thirds partial hepatectomy, N-diethylnitrosamine (DEN) initiation, and a diet containing 0.6% PBO for eight weeks. The incidence of γ-glutamyl transpeptidase (GGT)-positive foci and PCNA-positive cells was significantly increased in the DEN + PBO group compared with the DEN-alone group. Real-time reverse transcription-polymerase chain reaction (RT-PCR) analysis showed up-regulation of genes related to metabolism, such as cytochrome P450 1A1 and 2B10, and metabolic stress, such as Por, Nqo1, Nrf2, abcc3, and abcc4. Early responsive genes downstream of mitogen-activated protein kinase (MAPK), such as c-fos, c-jun, c-myc, and activating transcription factor 3 ( ATF3), were also up-regulated in this group. Positive immunohistochemical staining for ATF3 was diffusely observed in nonproliferating hepatocytes of the DEN + PBO group, but altered foci were negative or weakly positive for ATF3. The nuclei of hepatocytes within ATF3-negative foci were positive for cyclin D. Thus PBO can induce oxidative stress, activate the MAPK pathway, and increase ATF3 transcript levels in hepatocytes outside the altered foci during the early stage of PBO-induced hepatocarcinogenesis in mice.

Oxidative stress promotes ocular neovascularization

Mice deficient in superoxide dismutase 1 (Sod1(-/-) mice) develop many features seen in patients with age-related macular degeneration (AMD) including choroidal neovascularization (NV). We sought to determine if the absence of SOD1 contributes to the pro-angiogenic environment in the subretinal space or whether it is completely secondary to other changes in Bruch's membrane and the retinal pigmented epithelium (RPE) that precede the development of choroidal NV. In an ischemic retinopathy model or a transgenic model in which the rhodopsin promoter drives expression of vascular endothelial growth factor (VEGF) in photoreceptor there was significantly more NV in Sod1(-/-) compared to Sod1(+/+) mice. The compromised antioxidant defense system in Sod1(-/-) mice contributes to the pro-angiogenic environment, because treatment of Sod1(-/-) mice with a mixture of antioxidants caused a significant reduction in ischemia-induced retinal NV. Wild-type mice treated with the same antioxidants also showed reduced ischemia-induced retinal NV, reduced VEGF-induced subretinal NV, and reduced choroidal NV at Bruch's membrane rupture sites. These data suggest that reactive oxygen species contribute to several types of ocular NV. This could explain why in the Age-Related Eye Disease Trial, antioxidant treatment reduced conversion from non-neovascular to neovascular AMD and severe vision loss, and suggest that potent antioxidants should be considered for other diseases complicated by ocular NV. J. Cell. Physiol. 219: 544-552, 2009. (c) 2009 Wiley-Liss, Inc.

Mammals reduce methionine-S-sulfoxide with MsrA and are unable to reduce methionine-R-sulfoxide, and this function can be restored with a yeast reductase

Methionine is an essential amino acid in mammals at the junction of methylation, protein synthesis, and sulfur pathways. However, this amino acid is highly susceptible to oxidation, resulting in a mixture of methionine-S-sulfoxide and methionine-R-sulfoxide. Whether methionine is quantitatively regenerated from these compounds is unknown. Here we report that SK-Hep1 hepatocytes grew on methionine-S-sulfoxide and consumed this compound by import and methionine-S-sulfoxide reductase (MsrA)-dependent reduction, but methionine-R-sulfoxide reductases were not involved in this process, and methionine-R-sulfoxide could not be used by the cells. However, SK-Hep1 cells expressing a yeast free methionine-R-sulfoxide reductase proliferated in the presence of either sulfoxide, reduced them, and showed increased resistance to oxidative stress. Only methionine-R-sulfoxide was detected in the plasma of wild type mice, but both sulfoxides were in the plasma of MsrA knock-out mice. These results show that mammals can support methionine metabolism by reduction of methionine-S-sulfoxide, that this process is dependent on MsrA, that mammals are inherently deficient in the reduction of methionine-R-sulfoxide, and that expression of yeast free methionine-R-sulfoxide reductase can fully compensate for this deficiency.

Acute hypoxia to endothelial cells induces activating transcription factor 3 (ATF3) expression that is mediated via nitric oxide

Endothelial cells (ECs) play an important role in hypoxia-induced vascular disorders. We investigated the acute hypoxia effect on endothelial expression of activating transcription factor 3 (ATF3), a stress-inducible transcription factor playing significant roles in cellular responses to stress. Bovine aortic ECs were subjected to acute hypoxia (1% O(2), pO(2)=8 mmHg) and ATF3 expression was examined. ECs exposed to hypoxia transiently induced ATF3 expression. A transient increase in the activation of c-Jun-NH(2)-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) in ECs was observed; however, only ECs pretreated with a specific inhibitor to JNK suppressed the hypoxia-induced ATF3 expression. ECs exposed to acute hypoxia transiently increased endothelial nitric oxide (eNOS) activity. Pre-treating ECs with a specific inhibitor to eNOS (l-NAME) or PI3-kinase significantly inhibited the hypoxia-induced JNK activation and ATF3 expression. ATF3 induction has been shown to inhibit matrix metalloproteinase-2 (MMP-2) expression. Consistently, ECs exposed to hypoxia attenuated the MMP-2 expression. This hypoxia-attenuated MMP-2 expression can be rescued by pre-treating ECs with an inhibitor of eNOS. These results suggest that the ATF3 induction by acute hypoxia is mediated by nitric oxide and the JNK pathway in ECs. Our findings provide a molecular basis for the mechanism in which ECs respond to acute hypoxia.