The peroxisome in oxidative stress

Imperative connotation of SODs in cancer: Emerging targets and multifactorial role of action

Superoxide dismutase (SOD) is a crucial enzyme responsible for the redox homeostasis inside the cell. As a part of the antioxidant defense system, it plays a pivotal role in the dismutation of the superoxide radicals (O 2 - $$ {{\mathrm{O}}_2}^{-} $$ ) generated mainly by the oxidative phosphorylation, which would otherwise bring out the redox dysregulation, leading to higher reactive oxygen species (ROS) generation and, ultimately, cell transformation, and malignancy. Several studies have shown the involvement of ROS in a wide range of human cancers. As SOD is the key enzyme in regulating ROS, any change, such as a transcriptional change, epigenetic remodeling, functional alteration, and so forth, either activates the proto-oncogenes or aberrant signaling cascades, which results in cancer. Interestingly, in some cases, SODs act as tumor promoters instead of suppressors. Furthermore, SODs have also been known to switch their role during tumor progression. In this review, we have tried to give a comprehensive account of SODs multifactorial role in various human cancers so that SODs-based therapeutic strategies could be made to thwart cancers.

Redox regulation in lifespan determination

One of the major challenges that remain in the fields of aging and lifespan determination concerns the precise roles that reactive oxygen species (ROS) play in these processes. ROS, including superoxide and hydrogen peroxide, are constantly generated as byproducts of aerobic metabolism, as well as in response to endogenous and exogenous cues. While ROS accumulation and oxidative damage were long considered to constitute some of the main causes of age-associated decline, more recent studies reveal a signaling role in the aging process. In fact, accumulation of ROS, in a spatiotemporal manner, can trigger beneficial cellular responses that promote longevity and healthy aging. In this review, we discuss the importance of timing and compartmentalization of external and internal ROS perturbations in organismal lifespan and the role of redox regulated pathways.

Mitochondrial cholesterol: Metabolism and impact on redox biology and disease

Cholesterol is a crucial component of membrane bilayers by regulating their structural and functional properties. Cholesterol traffics to different cellular compartments including mitochondria, whose cholesterol content is low compared to other cell membranes. Despite the limited availability of cholesterol in the inner mitochondrial membrane (IMM), the metabolism of cholesterol in the IMM plays important physiological roles, acting as the precursor for the synthesis of steroid hormones and neurosteroids in steroidogenic tissues and specific neurons, respectively, or the synthesis of bile acids through an alternative pathway in the liver. Accumulation of cholesterol in mitochondria above physiological levels has a negative impact on mitochondrial function through several mechanisms, including the limitation of crucial antioxidant defenses, such as the glutathione redox cycle, increased generation of reactive oxygen species and consequent oxidative modification of cardiolipin, and defective assembly of respiratory supercomplexes. These adverse consequences of increased mitochondrial cholesterol trafficking trigger the onset of oxidative stress and cell death, and, ultimately, contribute to the development of diverse diseases, including metabolic liver diseases (i.e. fatty liver disease and liver cancer), as well as lysosomal disorders (i.e. Niemann-Pick type C disease) and neurodegenerative diseases (i.e. Alzheimer's disease). In this review, we summarize the metabolism and regulation of mitochondrial cholesterol and its potential impact on liver and neurodegenerative diseases.

Toxic effects of a mixture of pharmaceuticals in Mytilus galloprovincialis: The case of 17α-ethinylestradiol and salicylic acid

The impact of pharmaceuticals on marine invertebrates has been a topic of rising concern, with an increasing number of studies regarding the impacts on bivalves. However, very few investigated the toxicity of mixtures of pharmaceuticals. This knowledge gap was investigated in the present study, where the toxicity of 17α-ethinylestradiol (EE2) and salicylic acid (SA) mixture was evaluated. To this end, Mytilus galloprovincialis mussels were chronically subjected to both pharmaceuticals, acting alone and in combination, and the effects at the cellular level were measured. The Independent Action (IA) model was performed aiming to compare obtained with predicted responses. The integrated biomarker response (IBR) index was used to assess the overall biochemical response given by mussels. The results obtained revealed that the most stressful condition was caused by the combined effect of EE2 and SA, with the highest metabolic capacity, antioxidant (catalase activity) and biotransformation (carboxylesterases activity) activation and cellular damage in organisms exposed to the mixture of both drugs in comparison to responses observed when each drug was acting alone. Predicted responses obtained from the IA model indicate that caution should be paid as frequent deviations to observed responses were found. This study highlights the need for future studies considering the mixture of pollutants, mimicking the actual environmental conditions.

Manipulation of Oxidative Stress Responses by Non-Thermal Plasma to Treat Herpes Simplex Virus Type 1 Infection and Disease

Herpes simplex virus type 1 (HSV-1) is a contagious pathogen with a large global footprint, due to its ability to cause lifelong infection in patients. Current antiviral therapies are effective in limiting viral replication in the epithelial cells to alleviate clinical symptoms, but ineffective in eliminating latent viral reservoirs in neurons. Much of HSV-1 pathogenesis is dependent on its ability to manipulate oxidative stress responses to craft a cellular environment that favors HSV-1 replication. However, to maintain redox homeostasis and to promote antiviral immune responses, the infected cell can upregulate reactive oxygen and nitrogen species (RONS) while having a tight control on antioxidant concentrations to prevent cellular damage. Non-thermal plasma (NTP), which we propose as a potential therapy alternative directed against HSV-1 infection, is a means to deliver RONS that affect redox homeostasis in the infected cell. This review emphasizes how NTP can be an effective therapy for HSV-1 infections through the direct antiviral activity of RONS and via immunomodulatory changes in the infected cells that will stimulate anti-HSV-1 adaptive immune responses. Overall, NTP application can control HSV-1 replication and address the challenges of latency by decreasing the size of the viral reservoir in the nervous system.

The Effect of β-Carotene, Tocopherols and Ascorbic Acid as Anti-Oxidant Molecules on Human and Animal In Vitro/In Vivo Studies: A Review of Research Design and Analytical Techniques Used

Prolonged elevated oxidative stress (OS) possesses negative effect on cell structure and functioning, and is associated with the development of numerous disorders. Naturally occurred anti-oxidant compounds reduce the oxidative stress in living organisms. In this review, antioxidant properties of β-carotene, tocopherols and ascorbic acid are presented based on in vitro, in vivo and populational studies. Firstly, environmental factors contributing to the OS occurrence and intracellular sources of Reactive Oxygen Species (ROS) generation, as well as ROS-mediated cellular structure degradation, are introduced. Secondly, enzymatic and non-enzymatic mechanism of anti-oxidant defence against OS development, is presented. Furthermore, ROS-preventing mechanisms and effectiveness of β-carotene, tocopherols and ascorbic acid as anti-oxidants are summarized, based on studies where different ROS-generating (oxidizing) agents are used. Oxidative stress biomarkers, as indicators on OS level and prevention by anti-oxidant supplementation, are presented with a focus on the methods (spectrophotometric, fluorometric, chromatographic, immuno-enzymatic) of their detection. Finally, the application of Raman spectroscopy and imaging as a tool for monitoring the effect of anti-oxidant (β-carotene, ascorbic acid) on cell structure and metabolism, is proposed. Literature data gathered suggest that β-carotene, tocopherols and ascorbic acid possess potential to mitigate oxidative stress in various biological systems. Moreover, Raman spectroscopy and imaging can be a valuable technique to study the effect of oxidative stress and anti-oxidant molecules in cell studies.

Autophagy: A Key Player in Pancreatic Cancer Progression and a Potential Drug Target

Simple Summary

With the mortality rate of pancreatic cancer predicted to rise over the coming years, it is essential that effective treatment strategies are developed as soon as possible. Pancreatic cancer has always proven very difficult to treat due to its fast growing and aggressive nature. Chemotherapeutic treatment has struggled to increase the survival rate of pancreatic cancer patients due to effective chemo-resistant properties that derive from the supporting tumor microenvironment and autophagy, a vital survival pathway. This review will explore how the autophagy pathway and tumor microenvironment help to sustain tumor survival under stress and expand into a metastatic state. Due to the comprehensive understanding of the autophagy pathway, we will highlight the potential chinks in the pancreatic tumor’s armor and identify potential targets to overcome chemo-resistance in pancreatic cancer. We will also present novel autophagy inhibitors that could reduce tumor survival and how they could be most effectively conceived.

Abstract

Pancreatic cancer is known to have the lowest survival outcomes among all major cancers, and unfortunately, this has only been marginally improved over last four decades. The innate characteristics of pancreatic cancer include an aggressive and fast-growing nature from powerful driver mutations, a highly defensive tumor microenvironment and the upregulation of advantageous survival pathways such as autophagy. Autophagy involves targeted degradation of proteins and organelles to provide a secondary source of cellular supplies to maintain cell growth. Elevated autophagic activity in pancreatic cancer is recognized as a major survival pathway as it provides a plethora of support for tumors by supplying vital resources, maintaining tumour survival under the stressful microenvironment and promoting other pathways involved in tumour progression and metastasis. The combination of these features is unique to pancreatic cancer and present significant resistance to chemotherapeutic strategies, thus, indicating a need for further investigation into therapies targeting this crucial pathway. This review will outline the autophagy pathway and its regulation, in addition to the genetic landscape and tumor microenvironment that contribute to pancreatic cancer severity. Moreover, this review will also discuss the mechanisms of novel therapeutic strategies that inhibit autophagy and how they could be used to suppress tumor progression.

Organelle Engineering in Yeast: Enhanced Production of Protopanaxadiol through Manipulation of Peroxisome Proliferation in Saccharomyces cerevisiae

Isoprenoids, which are natural compounds with diverse structures, possess several biological activities that are beneficial to humans. A major consideration in isoprenoid production in microbial hosts is that the accumulation of biosynthesized isoprenoid within intracellular membranes may impede balanced cell growth, which may consequently reduce the desired yield of the target isoprenoid. As a strategy to overcome this suggested limitation, we selected peroxisome membranes as depots for the additional storage of biosynthesized isoprenoids to facilitate increased isoprenoid production in Saccharomyces cerevisiae. To maximize the peroxisome membrane storage capacity of S.cerevisiae, the copy number and size of peroxisomes were increased through genetic engineering of the expression of three peroxisome biogenesis-related peroxins (Pex11p, Pex34p, and Atg36p). The genetically enlarged and high copied peroxisomes in S.cerevisiae were stably maintained under a bioreactor fermentation condition. The peroxisome-engineered S.cerevisiae strains were then utilized as host strains for metabolic engineering of heterologous protopanaxadiol pathway. The yields of protopanaxadiol from the engineered peroxisome strains were ca 78% higher than those of the parent strain, which strongly supports the rationale for harnessing the storage capacity of the peroxisome membrane to accommodate the biosynthesized compounds. Consequently, this study presents in-depth knowledge on peroxisome biogenesis engineering in S.cerevisiae and could serve as basic information for improvement in ginsenosides production and as a potential platform to be utilized for other isoprenoids.

Mycobacterium tuberculosis Acetyltransferase Suppresses Oxidative Stress by Inducing Peroxisome Formation in Macrophages

Mycobacterium tuberculosis (Mtb) inhibits host oxidative stress responses facilitating its survival in macrophages; however, the underlying molecular mechanisms are poorly understood. Here, we identified a Mtb acetyltransferase (Rv3034c) as a novel counter actor of macrophage oxidative stress responses by inducing peroxisome formation. An inducible Rv3034c deletion mutant of Mtb failed to induce peroxisome biogenesis, expression of the peroxisomal β-oxidation pathway intermediates (ACOX1, ACAA1, MFP2) in macrophages, resulting in reduced intracellular survival compared to the parental strain. This reduced virulence phenotype was rescued by repletion of Rv3034c. Peroxisome induction depended on the interaction between Rv3034c and the macrophage mannose receptor (MR). Interaction between Rv3034c and MR induced expression of the peroxisomal biogenesis proteins PEX5p, PEX13p, PEX14p, PEX11β, PEX19p, the peroxisomal membrane lipid transporter ABCD3, and catalase. Expression of PEX14p and ABCD3 was also enhanced in lungs from Mtb aerosol-infected mice. This is the first report that peroxisome-mediated control of ROS balance is essential for innate immune responses to Mtb but can be counteracted by the mycobacterial acetyltransferase Rv3034c. Thus, peroxisomes represent interesting targets for host-directed therapeutics to tuberculosis.

Redox regulation of DUBs and its therapeutic implications in cancer

Reactive oxygen species (ROS) act as a double-edged sword in cancer, where low levels of ROS are beneficial but excessive accumulation leads to cancer progression. Elevated levels of ROS in cancer are counteracted by the antioxidant defense system. An imbalance between ROS generation and the antioxidant system alters gene expression and cellular signaling, leading to cancer progression or death. Post-translational modifications, such as ubiquitination, phosphorylation, and SUMOylation, play a critical role in the maintenance of ROS homeostasis by controlling ROS production and clearance. Recent evidence suggests that deubiquitinating enzymes (DUBs)-mediated ubiquitin removal from substrates is regulated by ROS. ROS-mediated oxidation of the catalytic cysteine (Cys) of DUBs, leading to their reversible inactivation, has emerged as a key mechanism regulating DUB-controlled cellular events. A better understanding of the mechanism by which DUBs are susceptible to ROS and exploring the ways to utilize ROS to pharmacologically modulate DUB-mediated signaling pathways might provide new insight for anticancer therapeutics. This review assesses the recent findings regarding ROS-mediated signaling in cancers, emphasizes DUB regulation by oxidation, highlights the relevant recent findings, and proposes directions of future research based on the ROS-induced modifications of DUB activity.

Peroxisome proliferator-activated receptor δ rescues xCT-deficient cells from ferroptosis by targeting peroxisomes

Ferroptosis is a recently recognized process of cell death characterized by accumulation of iron-dependent lipid peroxides. Herein, we demonstrate that peroxisome proliferator-activated receptor δ (PPARδ) inhibits ferroptosis of mouse embryonic fibroblasts (MEFs) derived from cysteine/glutamate transporter (xCT)-knockout mice. Activation of PPARδ by the specific ligand GW501516 led to a dose-dependent decrease in ferroptotic cell death triggered by xCT deficiency, along with decreased levels of intracellular iron accumulation and lipid peroxidation. These effects of GW501516 were abolished by PPARδ-targeting small interfering RNA (siRNA) and the PPARδ inhibitor GSK0660, indicating that PPARδ inhibits xCT deficiency-induced ferroptosis. In addition, GW501516-activated PPARδ time- and dose-dependently upregulated catalase expression at both the mRNA and protein levels. This PPARδ-mediated upregulation of catalase was markedly attenuated in cells treated with PPARδ-targeting siRNA and GSK0660, indicating that expression of catalase is dependent on PPARδ. Consistently, the effects of GW501516 on ferroptosis of xCT-deficient MEFs were counteracted in the presence of 3-amino-1,2,4-triazole, a specific inhibitor of catalase, suggesting that catalase is essential for the effect of PPARδ on ferroptosis triggered by xCT deficiency. GW501516-activated PPARδ stabilized peroxisomes through catalase upregulation by targeting peroxisomal hydrogen peroxide-mediated lysosomal rupture, which led to ferroptosis of xCT-deficient MEFs. Collectively, these results demonstrate that PPARδ modulates ferroptotic signals in xCT-deficient MEFs by regulating catalase expression.

Peroxisome proliferator-activated receptor-δ-mediated upregulation of catalase helps to reduce ultraviolet B-induced cellular injury in dermal fibroblasts

BACKGROUND

Previous studies suggested that the nuclear receptor peroxisome proliferator-activated receptor (PPAR)-δ plays an essential role in cellular responses against oxidative stress.

OBJECTIVE

To investigate how PPAR-δ elicits cellular responses against oxidative stress in primary human dermal fibroblasts (HDFs) exposed to ultraviolet B (UVB).

METHODS

The present study was undertaken in HDFs by performing real-time polymerase chain reaction, gene silencing, cytotoxicity and reporter gene assay, analyses for catalase and reactive oxygen species, and immunoblot analyses.

RESULTS

The PPAR-δ activator GW501516 upregulated expression of catalase and this upregulation was attenuated by PPAR-δ-targeting siRNA. GW501516-activated PPAR-δ induced catalase promoter activity through a direct repeat 1 response element. Mutation of this response element completely abrogated transcriptional activation, indicating that this site is a novel type of PPAR-δ response element. In addition, GW501516-activated PPAR-δ counteracted the reductions in activity and expression of catalase induced by UVB irradiation. These recovery effects were significantly attenuated in the presence of PPAR-δ-targeting siRNA or the specific PPAR-δ antagonist GSK0660. GW501516-activated PPAR-δ also protected HDFs from cellular damage triggered by UVB irradiation, and this PPAR-δ-mediated reduction of cellular damage was reversed by the catalase inhibitor or catalase-targeting siRNA. These effects of catalase blockade were positively correlated with accumulation of reactive oxygen species in HDFs exposed to UVB. Furthermore, GW501516-activated PPAR-δ targeted peroxisomal hydrogen peroxide through catalase in UVB-irradiated HDFs.

CONCLUSION

The gene encoding catalase is a target of PPAR-δ, and this novel catalase-mediated pathway plays a critical role in the cellular response elicited by PPAR-δ against oxidative stress.

Interactions of zinc- and redox-signaling pathways

Zinc and cellular oxidants such as reactive oxygen species (ROS) each participate in a multitude of physiological functions. There is considerable overlap between the affected events, including signal transduction. While there is no obvious direct connection between zinc and ROS, mainly because the bivalent cation zinc does not change its oxidation state in biological systems, these are linked by their interaction with sulfur, forming the remarkable triad of zinc, ROS, and protein thiols. First, zinc binds to reduced thiols and can be released upon oxidation. Thereby, redox signals are translated into changes in the free zinc concentration, which can act as zinc signals. Second, zinc affects oxidation of thiols in several ways, directly as well as indirectly. A protein incorporating many of these interactions is metallothionein (MT), which is rich in cysteine and capable of binding up to seven zinc ions in its fully reduced state. Zinc binding is diminished after (partial) oxidation, while thiols show increased reactivity in the absence of bound metal ions. Adding still more complexity, the MT promoter is controlled by zinc (via metal regulatory transcription factor 1 (MTF-1)) as well as redox (via nuclear factor erythroid 2-related factor 2 (NRF2)). Many signaling cascades that are important for cell proliferation or apoptosis contain protein thiols, acting as centers for crosstalk between zinc- and redox-signaling. A prominent example for shared molecular targets for zinc and ROS are active site cysteine thiols in protein tyrosine phosphatases (PTP), their activity being downregulated by oxidation as well as zinc binding. Because zinc binding also protects PTP thiols form irreversible oxidation, there is a multi-faceted reciprocal interaction, illustrating that zinc- and redox-signaling are intricately linked on multiple levels.

The Potential Benefit of Monitoring Oxidative Stress and Inflammation in the Prevention of Non-Communicable Diseases (NCDs)

The significant increase in worldwide morbidity and mortality from non-communicable diseases (NCDs) indicates that the efficacy of existing strategies addressing this crisis may need improvement. Early identification of the metabolic irregularities associated with the disease process may be a key to developing early intervention strategies. Unhealthy lifestyle behaviours are well established drivers of the development of several NCDs, but the impact of such behaviours on health can vary considerably between individuals. How can it be determined if an individual's unique set of lifestyle behaviours is producing disease? Accumulating evidence suggests that lifestyle-associated activation of oxidative and inflammatory processes is primary driver of the cell and tissue damage which underpins the development of NCDs. However, the benefit of monitoring subclinical inflammation and oxidative activity has not yet been established. After reviewing relevant studies in this context, we suggest that quantification of oxidative stress and inflammatory biomarkers during the disease-free prodromal stage of NCD development may have clinical relevance as a timely indicator of the presence of subclinical metabolic changes, in the individual, portending the development of disease. Monitoring markers of oxidative and inflammatory activity may therefore enable earlier and more efficient strategies to both prevent NCD development and/or monitor the effectiveness of treatment.

Effects of Single and Repeated Oral Doses of Ochratoxin A on the Lipid Peroxidation and Antioxidant Defense Systems in Mouse Kidneys

Ochratoxin-A (OTA) is a carcinogenic and nephrotoxic mycotoxin, which may cause health problems in humans and animals, and it is a contaminant in foods and feeds. The purpose of the present study is to evaluate the effect of oral OTA exposure on the antioxidant defense and lipid peroxidation in the kidney. In vivo administration of OTA in CD1, male mice (1 or 10 mg/kg body weight in a single oral dose for 24 h and repeated daily oral dose for 72 h or repeated daily oral dose of 0.5 mg/kg bodyweight for 21 days) resulted in a significant elevation of OTA levels in blood plasma. Some histopathological alterations, transcriptional changes in the glutathione system, and oxidative stress response-related genes were also found. In the renal cortex, the activity of the glutathione-system-related enzymes and certain metabolites of the lipid peroxidation (conjugated dienes, trienes, and thiobarbituric reactive substances) also changed.

In situ visualization of peroxisomal viscosity in the liver of mice with non-alcoholic fatty liver disease by near-infrared fluorescence and photoacoustic imaging

Non-alcoholic fatty liver disease (NAFLD) can gradually develop into hepatic failure, and early diagnosis is crucial to improve treatment efficiency. The occurrence of NAFLD is closely related to lipid metabolism. Peroxisomes act as the first and main site for lipid metabolism in the hepatocytes, so abnormal lipid metabolism might directly affect peroxisomal viscosity. Herein, we developed a new near-infrared fluorescence (NIRF) and photoacoustic (PA) imaging probe (PV-1) for the real-time visualization of peroxisomal viscosity in vivo. This PV-1 encompasses the malononitrile group as the rotor, which emits strong NIRF (at 705 nm) and PA (at 680 nm) signals when rotation is hindered as viscosity increases. Through dual-mode imaging, we discovered distinctly higher viscosity in the liver of NAFLD mice for the first time. We further found the remarkable amelioration of NAFLD upon treatment with N-acetylcysteine (NAC). Therefore, we anticipate that the PV-1 imaging method is promising for the early diagnosis and prognostic evaluation of NAFLD.

Oxalato bridged coordination polymer of manganese(iii) involving unconventional O⋯π-hole(nitrile) and antiparallel nitrile⋯nitrile contacts: antiproliferative evaluation and theoretical studies

Unconventional O⋯π-hole(nitrile) and antiparallel nitrile⋯nitrile contacts have been theoretically investigated for a Mn(iii) coordination polymer considering cytotoxicity, apoptosis, ROS generation, molecular docking and pharmacophore features.

ROS Generation and Antioxidant Defense Systems in Normal and Malignant Cells

Reactive oxygen species (ROS) are by-products of normal cell activity. They are produced in many cellular compartments and play a major role in signaling pathways. Overproduction of ROS is associated with the development of various human diseases (including cancer, cardiovascular, neurodegenerative, and metabolic disorders), inflammation, and aging. Tumors continuously generate ROS at increased levels that have a dual role in their development. Oxidative stress can promote tumor initiation, progression, and resistance to therapy through DNA damage, leading to the accumulation of mutations and genome instability, as well as reprogramming cell metabolism and signaling. On the contrary, elevated ROS levels can induce tumor cell death. This review covers the current data on the mechanisms of ROS generation and existing antioxidant systems balancing the redox state in mammalian cells that can also be related to tumors.

Reactive Oxygen Species: A Key Constituent in Cancer Survival

BACKGROUND

Cancer is one of the major heterogeneous disease with high morbidity and mortality with poor prognosis. Elevated levels of reactive oxygen species (ROS), alteration in redox balance, and deregulated redox signaling are common hallmarks of cancer progression and resistance to treatment. Mitochondria contribute mainly in the generation of ROS during oxidative phosphorylation. Elevated levels of ROS have been detected in cancers cells due to high metabolic activity, cellular signaling, peroxisomal activity, mitochondrial dysfunction, activation of oncogene, and increased enzymatic activity of oxidases, cyclooxygenases, lipoxygenases, and thymidine phosphorylases. Cells maintain intracellular homeostasis by developing an immense antioxidant system including catalase, superoxide dismutase, and glutathione peroxidase. Besides these enzymes exist an important antioxidant glutathione and transcription factor Nrf2 which contribute in balancing oxidative stress. Reactive oxygen species-mediated signaling pathways activate pro-oncogenic signaling which eases in cancer progression, angiogenesis, and survival. Concomitantly, to maintain ROS homeostasis and evade cancer cell death, an increased level of antioxidant capacity is associated with cancer cells.

CONCLUSIONS

This review focuses the role of ROS in cancer survival pathways and importance of targeting the ROS signal involved in cancer development, which is a new strategy in cancer treatment.

Expression enhancement in brown adipose tissue of genes related to thermogenesis and mitochondrial dynamics after administration of pepsin egg white hydrolysate

Pepsin egg white hydrolysate enhanced mitochondria proliferation on brown adipose tissue and thermogenesis. Reduced body weight and adiposity were observed.

The Impact of Di(2-ethylhexyl)phthalate on Cancer Progression

Di(2-ethylhexyl)phthalate (DEHP), a widely used plasticizer, mainly serves as an additive to render polyvinyl chloride (PVC) soft and flexible. PVC plastics have become ubiquitous in our modern society. Yet, the leaching of DEHP from PVC-based consumables ultimately results in the deposition in certain tissues via inadvertent applications. Health risks for human populations exposed to DEHP has been assumed by studies on rodents and other species, including the DEHP-induced developmental dysregulation, reproductive impairments, tumorigenesis, and diseases in a transgenerational manner. In this review, we comprehensively summarize the accumulated literature regarding the multifaceted roles of DEHP in the activation of the nuclear receptors, the alteration of the redox homeostasis, epigenetic modifications and the acquisition of chemoresistance.

Reduced SOD2 expression is associated with mortality of hepatocellular carcinoma patients in a mutant p53-dependent manner

The development and progression of hepatocellular carcinoma (HCC) is accompanied with persistent oxidative stress, but the molecular basis is not well defined. Superoxide dismutase 2 (SOD2) is an important mitochondrial antioxidant and a key aging factor. Here we investigated the expression and clinical significance of SOD2 in a large cohort of HBV-positive HCC tumors. Both SOD2 mRNA and protein are reduced in human primary HCCs compared with matching liver tissues. Consistently, the SOD2 DNA copy numbers are decreased in HCCs, providing a genetic basis for the decrease in SOD2 mRNA expression. Reduced SOD2 expression in HCCs is correlated with older age, larger tumor size, multiple tumor nodules and tumor emboli, and cancer recurrence. Moreover, low SOD2 expression is strongly associated with poor overall survival (OS) and recurrence-free survival (RFS). Univariate and multivariate Cox regression analyses indicates that SOD2 is an independent prognostic predictor for OS and RFS. Intriguingly, reduced SOD2 mRNA is strongly associated with poor survival in a separate cohort of HCC patients carrying mutant p53. Altogether, our results provide clinical evidence for the importance of SOD2 in tumor progression and mortality, and the close relationship of SOD2 and p53 in HCC.

Magnetic Fields and Reactive Oxygen Species

Reactive oxygen species (ROS) ubiquitously exist in mammalian cells to participate in various cellular signaling pathways. The intracellular ROS levels are dependent on the dynamic balance between ROS generation and elimination. In this review, we summarize reported studies about the influences of magnetic fields (MFs) on ROS levels. Although in most cases, MFs increased ROS levels in human, mouse, rat cells, and tissues, there are also studies showing that ROS levels were decreased or not affected by MFs. Multiple factors could cause these discrepancies, including but not limited to MF type/intensity/frequency, exposure time and assay time-point, as well as different biological samples examined. It will be necessary to investigate the influences of different MFs on ROS in various biological samples systematically and mechanistically, which will be helpful for people to get a more complete understanding about MF-induced biological effects. In addition, reviewing the roles of MFs in ROS modulation may open up new scenarios of MF application, which could be further and more widely adopted into clinical applications, particularly in diseases that ROS have documented pathophysiological roles.

ROS-modulated therapeutic approaches in cancer treatment

PURPOSE

Reactive oxygen species (ROS) are produced in cancer cells as a result of increased metabolic rate, dysfunction of mitochondria, elevated cell signaling, expression of oncogenes and increased peroxisome activities. Certain level of ROS is required by cancer cells, above or below which lead to cytotoxicity in cancer cells. This biochemical aspect can be exploited to develop novel therapeutic agents to preferentially and selectively target cancer cells.

METHODS

We searched various electronic databases including PubMed, Web of Science, and Google Scholar for peer-reviewed english-language articles. Selected articles ranging from research papers, clinical studies, and review articles on the ROS production in living systems, its role in cancer development and cancer treatment, and the role of microbiota in ROS-dependent cancer therapy were analyzed.

RESULTS

This review highlights oxidative stress in tumors, underlying mechanisms of different relationships of ROS and cancer cells, different ROS-mediated therapeutic strategies and the emerging role of microbiota in cancer therapy.

CONCLUSION

Cancer cells exhibit increased ROS stress and disturbed redox homeostasis which lead to ROS adaptations. ROS-dependent anticancer therapies including ROS scavenging anticancer therapy and ROS boosting anticancer therapy have shown promising results in vitro as well as in vivo. In addition, response to cancer therapy is modulated by the human microbiota which plays a critical role in systemic body functions.

Herpes simplex virus 1 infection dampens the immediate early antiviral innate immunity signaling from peroxisomes by tegument protein VP16

Background

Herpes simplex virus 1 (HSV-1) is an archetypal member of the alphaherpesvirus subfamily with a large genome encoding over 80 proteins, many of which play a critical role in virus-host interactions and immune modulation. Upon viral infections, the host cells activate innate immune responses to restrict their replications. Peroxisomes, which have long been defined to regulate metabolic activities, are reported to be important signaling platforms for antiviral innate immunity. It has been verified that signaling from peroxisomal MAVS (MAVS-Pex) triggers a rapid interferon (IFN) independent IFN-stimulated genes (ISGs) production against invading pathogens. However, little is known about the interaction between DNA viruses such as HSV-1 and the MAVS-Pex mediated signaling.

Results

HSV-1 could activate the MAVS-Pex signaling pathway at a low multiplicity of infection (MOI), while infection at a high MOI dampens MAVS-Pex induced immediately early ISGs production. A high-throughput screen assay reveals that HSV-1 tegument protein VP16 inhibits the immediate early ISGs expression downstream of MAVS-Pex signaling. Moreover, the expression of ISGs was recovered when VP16 was knockdown with its specific short hairpin RNA.

Conclusion

HSV-1 blocks MAVS-Pex mediated early ISGs production through VP16 to dampen the immediate early antiviral innate immunity signaling from peroxisomes.

Nanotechnology promotes the R&D of new-generation micronutrient foliar fertilizers

New generation foliar fertilizers are expected to be sheet-like nanocrystals and provide a sustainable supply of metal ions at a suitable concentration.

Expanding roles of superoxide dismutases in cell regulation and cancer

Reactive oxygen species (ROS) have important roles in normal physiology and diseases, particularly cancer. Under normal physiological conditions, they participate in redox reactions and serve as second messengers for regulatory functions. Owing to aberrant metabolism, cancer cells accumulate excessive ROS, thus requiring a robustly active antioxidant system to prevent cellular damage. Superoxide dismutases (SODs) are enzymes that catalyze the removal of superoxide free radicals. There are three distinct members of this metalloenzyme family in mammals: SOD1 (Cu/ZnSOD), SOD2 (MnSOD) and SOD3 (ecSOD). SODs are increasingly recognized for their regulatory functions in growth, metabolism and oxidative stress responses, which are also crucial for cancer development and survival. Growing evidence shows that SODs are also potentially useful anticancer drug targets. This review will focus on recent research of SODs in cellular regulation, with emphasis on their roles in cancer biology and therapy.

Endosomes: guardians against [Ru(Phen)3]2+ photo-action in endothelial cells during in vivo pO2 detection?

Phototoxicity is a side-effect of in vitro and in vivo oxygen partial pressure (pO2) detection by luminescence lifetime measurement methods. Dichlorotris(1,10-phenanthroline)-ruthenium(ii) hydrate ([Ru(Phen)3]2+) is a water soluble pO2 probe associated with low phototoxicity, which we investigated in vivo in the chick's chorioallantoic membrane (CAM) after intravenous or topical administration and in vitro in normal human coronary artery endothelial cells (HCAEC). In vivo, the level of intravenously injected [Ru(Phen)3]2+ decreases within several minutes, whereas the maximum of its biodistribution is observed during the first 2 h after topical application. Both routes are followed by convergence to almost identical "intra/extra-vascular" levels of [Ru(Phen)3]2+. In vitro, we observed that [Ru(Phen)3]2+ enters cells via endocytosis and is then redistributed. None of the studied conditions induced modification of lysosomal or mitochondrial membranes without illumination. No nuclear accumulation was observed. Without illumination [Ru(Phen)3]2+ induces changes in endoplasmic reticulum (ER)-to-Golgi transport. The phototoxic effect of [Ru(Phen)3]2+ leads to more marked ultrastructural changes than administration of [Ru(Phen)3]2+ only (in the dark). These could lead to disruption of Ca2+ homeostasis accompanied by mitochondrial changes or to changes in secretory pathways. In conclusion, we have demonstrated that the intravenous injection of [Ru(Phen)3]2+ into the CAM model mostly leads to extracellular localization of [Ru(Phen)3]2+, while its topical application induces intracellular localization. We have shown in vivo that [Ru(Phen)3]2+ induces minimal photo-damage after illumination with light doses larger by two orders of magnitude than those used for pO2 measurements. This low phototoxicity is due to the fact that [Ru(Phen)3]2+ enters endothelial cells via endocytosis and is then redistributed towards peroxisomes and other endosomal and secretory vesicles before it is eliminated via exocytosis. Cellular response to [Ru(Phen)3]2+, survival or death, depends on its intracellular concentration and oxidation-reduction properties.

Role of the tumor suppressor IQGAP2 in metabolic homeostasis: Possible link between diabetes and cancer

Deficiency of IQGAP2, a scaffolding protein expressed primarily in liver leads to rearrangements of hepatic protein compartmentalization and altered regulation of enzyme functions predisposing development of hepatocellular carcinoma and diabetes. Employing a systems approach with proteomics, metabolomics and fluxes characterizations, we examined the effects of IQGAP2 deficient proteomic changes on cellular metabolism and the overall metabolic phenotype. Iqgap2^-/- mice demonstrated metabolic inflexibility, fasting hyperglycemia and obesity. Such phenotypic characteristics were associated with aberrant hepatic regulations of glycolysis/gluconeogenesis, glycogenolysis, lipid homeostasis and futile cycling corroborated with corresponding proteomic changes in cytosolic and mitochondrial compartments. IQGAP2 deficiency also led to truncated TCA-cycle, increased anaplerosis, increased supply of acetyl-CoA for de novo lipogenesis, and increased mitochondrial methyl-donor metabolism necessary for nucleotides synthesis. Our results suggest that changes in metabolic networks in IQGAP2 deficiency create a hepatic environment of a 'pre-diabetic' phenotype and a predisposition to non-alcoholic fatty liver disease (NAFLD) which has been linked to the development of hepatocellular carcinoma.

Liver proteomic response to hypertriglyceridemia in human-apolipoprotein C-III transgenic mice at cellular and mitochondrial compartment levels

BACKGROUND

Hypertriglyceridemia (HTG) is defined as a triglyceride (TG) plasma level exceeding 150 mg/dl and is tightly associated with atherosclerosis, metabolic syndrome, obesity, diabetes and acute pancreatitis. The present study was undertaken to investigate the mitochondrial, sub-mitochondrial and cellular proteomic impact of hypertriglyceridemia in the hepatocytes of hypertriglyceridemic transgenic mice (overexpressing the human apolipoproteinC-III).

METHODS

Quantitative proteomics (2D-DIGE) analysis was carried out on both "low-expressor" (LE) and "high-expressor" (HE) mice, respectively exhibiting moderate and severe HTG, to characterize the effect of the TG plasma level on the proteomic response.

RESULTS

The mitoproteome analysis has revealed a large-scale phenomenon in transgenic mice, i.e. a general down-regulation of matricial proteins and up-regulation of inner membrane proteins. These data also demonstrate that the magnitude of proteomic changes strongly depends on the TG plasma level. Our different analyses indicate that, in HE mice, the capacity of several metabolic pathways is altered to promote the availability of acetyl-CoA, glycerol-3-phosphate, ATP and NADPH for TG de novo biosynthesis. The up-regulation of several cytosolic ROS detoxifying enzymes has also been observed, suggesting that the cytoplasm of HTG mice is subjected to oxidative stress. Moreover, our results suggest that iron over-accumulation takes place in the cytosol of HE mice hepatocytes and may contribute to enhance oxidative stress and to promote cellular proliferation.

CONCLUSIONS

These results indicate that the metabolic response to HTG in human apolipoprotein C-III overexpressing mice may support a high TG production rate and that the cytosol of hepatocytes is subjected to an important oxidative stress, probably as a result of FFA over-accumulation, iron overload and enhanced activity of some ROS-producing catabolic enzymes.

Oxidative stress and HPV carcinogenesis

Extensive experimental work has conclusively demonstrated that infection with certain types of human papillomaviruses, the so-called high-risk human papillomavirus (HR-HPV), represent a most powerful human carcinogen. However, neoplastic growth is a rare and inappropriate outcome in the natural history of HPV, and a number of other events have to concur in order to induce the viral infection into the (very rare) neoplastic transformation. From this perspective, a number of putative viral, host, and environmental co-factors have been proposed as potential candidates. Among them oxidative stress (OS) is an interesting candidate, yet comparatively underexplored. OS is a constant threat to aerobic organisms being generated during mitochondrial oxidative phosphorylation, as well as during inflammation, infections, ionizing irradiation, UV exposure, mechanical and chemical stresses. Epithelial tissues, the elective target for HPV infection, are heavily exposed to all named sources of OS. Two different types of cooperative mechanisms are presumed to occur between OS and HPV: I) The OS genotoxic activity and the HPV-induced genomic instability concur independently to the generation of the molecular damage necessary for the emergence of neoplastic clones. This first mode is merely a particular form of co-carcinogenesis; and II) OS specifically interacts with one or more molecular stages of neoplastic initiation and/or progression induced by the HPV infection. This manuscript was designed to summarize available data on this latter hypothesis. Experimental data and indirect evidences on promoting the activity of OS in viral infection and viral integration will be reviewed. The anti-apoptotic and pro-angiogenetic role of NO (nitric oxide) and iNOS (inducible nitric oxide synthase) will be discussed together with the OS/HPV cooperation in inducing cancer metabolism adaptation. Unexplored/underexplored aspects of the OS interplay with the HPV-driven carcinogenesis will be highlighted. The aim of this paper is to stimulate new areas of study and innovative approaches.

Peroxisome-generated hydrogen peroxide as important mediator of lipotoxicity in insulin-producing cells

OBJECTIVE

Type 2 diabetes is a complex disease that is accompanied by elevated levels of nonesterified fatty acids (NEFAs), which contribute to β-cell dysfunction and β-cell loss, referred to as lipotoxicity. Experimental evidence suggests that oxidative stress is involved in lipotoxicity. In this study, we analyzed the molecular mechanisms of reactive oxygen species-mediated lipotoxicity in insulin-producing RINm5F cells and INS-1E cells as well as in primary rat islet cells.

RESEARCH DESIGN AND METHODS

The toxicity of saturated NEFAs with different chain lengths upon insulin-producing cells was determined by MTT and propidium iodide (PI) viability assays. Catalase or superoxide dismutase overexpressing cells were used to analyze the nature and the cellular compartment of reactive oxygen species formation. With the new H₂O₂-sensitive fluorescent protein HyPer H₂O₂ formation induced by exposure to palmitic acid was determined.

RESULTS

Only long-chain (>C14) saturated NEFAs were toxic to insulin-producing cells. Overexpression of catalase in the peroxisomes and in the cytosol, but not in the mitochondria, significantly reduced H₂O₂ formation and protected the cells against palmitic acid-induced toxicity. With the HyPer protein, H₂O₂ generation was directly detectable in the peroxisomes of RINm5F and INS-1E insulin-producing cells as well as in primary rat islet cells.

CONCLUSIONS

The results demonstrate that H₂O₂ formation in the peroxisomes rather than in the mitochondria are responsible for NEFA-induced toxicity. Therefore, we propose a new concept of fatty acid-induced β-cell lipotoxicity mediated via reactive oxygen species formation through peroxisomal β- oxidation.

Role of metabolically generated reactive oxygen species for lipotoxicity in pancreatic β-cells

Chronically elevated concentrations of non-esterified fatty acids (NEFAs) in type 2 diabetes may be involved in β-cell dysfunction and apoptosis. It has been shown that long-chain saturated NEFAs exhibit a strong cytotoxic effect upon insulin-producing cells, while short-chain as well as unsaturated NEFAs are well tolerated. Moreover, long-chain unsaturated NEFAs counteract the toxicity of palmitic acid. Reactive oxygen species (ROS) formation and gene expression analyses together with viability assays in different β-cell lines showed that the G-protein-coupled receptors 40 and 120 do not mediate lipotoxicity. This is independent from the role, which these receptors, specifically GPR40, play in the potentiation of glucose-induced insulin secretion by saturated and unsaturated long-chain NEFAs. Long-chain NEFAs are not only metabolized in the mitochondria but also in peroxisomes. In contrast to mitochondrial β-oxidation, the acyl-coenzyme A (CoA) oxidases in the peroxisomes form hydrogen peroxide and not reducing equivalents. As β-cells almost completely lack catalase, they are exceptionally vulnerable to hydrogen peroxide generated in peroxisomes. ROS generation in the respiratory chain is less important because overexpression of catalase and superoxide dismutase in the mitochondria do not provide protection. Thus, peroxisomally generated hydrogen peroxide is the likely ROS that causes pancreatic β-cell dysfunction and ultimately β-cell death.

Reactive oxygen species in cancer

Elevated rates of reactive oxygen species (ROS) have been detected in almost all cancers, where they promote many aspects of tumour development and progression. However, tumour cells also express increased levels of antioxidant proteins to detoxify from ROS, suggesting that a delicate balance of intracellular ROS levels is required for cancer cell function. Further, the radical generated, the location of its generation, as well as the local concentration is important for the cellular functions of ROS in cancer. A challenge for novel therapeutic strategies will be the fine tuning of intracellular ROS signalling to effectively deprive cells from ROS-induced tumour promoting events, towards tipping the balance to ROS-induced apoptotic signalling. Alternatively, therapeutic antioxidants may prevent early events in tumour development, where ROS are important. However, to effectively target cancer cells specific ROS-sensing signalling pathways that mediate the diverse stress-regulated cellular functions need to be identified. This review discusses the generation of ROS within tumour cells, their detoxification, their cellular effects, as well as the major signalling cascades they utilize, but also provides an outlook on their modulation in therapeutics.

Peroxisomal plant 3-ketoacyl-CoA thiolase structure and activity are regulated by a sensitive redox switch

The breakdown of fatty acids, performed by the beta-oxidation cycle, is crucial for plant germination and sustainability. beta-Oxidation involves four enzymatic reactions. The final step, in which a two-carbon unit is cleaved from the fatty acid, is performed by a 3-ketoacyl-CoA thiolase (KAT). The shortened fatty acid may then pass through the cycle again (until reaching acetoacetyl-CoA) or be directed to a different cellular function. Crystal structures of KAT from Arabidopsis thaliana and Helianthus annuus have been solved to 1.5 and 1.8 A resolution, respectively. Their dimeric structures are very similar and exhibit a typical thiolase-like fold; dimer formation and active site conformation appear in an open, active, reduced state. Using an interdisciplinary approach, we confirmed the potential of plant KATs to be regulated by the redox environment in the peroxisome within a physiological range. In addition, co-immunoprecipitation studies suggest an interaction between KAT and the multifunctional protein that is responsible for the preceding two steps in beta-oxidation, which would allow a route for substrate channeling. We suggest a model for this complex based on the bacterial system.

Peroxidases of trypanosomatids

This article provides an overview about the recent advances in the dissection of the peroxide metabolism of Trypanosomatidae. This family of protozoan organisms comprises the medically relevant parasites Trypanosoma brucei, Trypanosoma cruzi, and Leishmania spp. Over the past 10 years, three major families of peroxidases have been identified in these organisms: (a) 2-cysteine peroxiredoxins, (b) nonselenium glutathione peroxidases, and (c) ascorbate peroxidases. In trypanosomatids, these enzymes display the unique feature of using reducing equivalents derived from trypanothione, a dithiol found exclusively in these protozoa. The electron transfer between trypanothione and the peroxidases is mediated by a redox shuttle, which can either be tryparedoxin, ascorbate, or even glutathione. The preference for the intermediate molecule differs among each peroxidase and so does the specificity for the peroxide substrate. These observations, added to the fact that these peroxidases are distributed throughout different subcellular compartments, point to the existence of an elaborate peroxide metabolism in trypanosomatids. With the completion of the trypanosomatids genome, other molecules displaying peroxidase activity might be added to this list in the future.

Cellular responses to reactive oxygen species-induced DNA damage and aging

Oxidative stress in cells and tissues can occur during pathophysiological developments, e.g., during inflammatory and allergic diseases or during ischemic or toxic and hyperglycemic conditions via the generation of reactive oxygen species (ROS). Moreover, ROS can be generated by radiation (UV, X-rays) and pharmacologically, e.g., by anthracyclins as chemotherapeutic compounds for treatment of a variety of tumors to induce 'stress or aberrant signaling-inducing senescence' (STASIS). Although STASIS is distinguished from intracellular replicative senescence, a variety of cellular mechanisms appear similar in both aging pathways. It is generally accepted that oxidative stress and ROS eventually cause DNA damage, whereby insufficient cellular repair mechanisms may contribute to premature aging and apoptosis. Conversely, ROS-induced imbalances of the signaling pathways for metabolic protein turnover may also result in opposite effects to recruit malfunctioning aberrant proteins and compounds that trigger tumorigenic processes. Consequently, DNA damage plays a role in the development of carcinogenesis, but is also associated with an aging process in cells and organisms.

Peroxisomal ABC transporters

Peroxisomes perform a range of different functions, dependent upon organism, tissue type, developmental stage or environmental conditions, many of which are connected with lipid metabolism. This review summarises recent research on ATP binding cassette (ABC) transporters of the peroxisomal membrane (ABC subfamily D) and their roles in plants, fungi and animals. Analysis of mutants has revealed that peroxisomal ABC transporters play key roles in specific metabolic and developmental functions in different organisms. A common function is import of substrates for beta-oxidation but much remains to be determined concerning transport substrates and mechanisms which appear to differ significantly between phyla.

Peroxisomal participation in psychosine-mediated toxicity: implications for Krabbe's disease

Psychosine (galactosylsphingosine) accumulation in globoid cell leukodystrophy (Krabbe's disease) results in the loss of myelin and oligodendrocytes. To understand the role of psychosine toxicity in Krabbe's disease, we examined the effects of psychosine on peroxisomal functions and their relationship with reactive oxygen species. Rat C(6) glial cells were treated with psychosine with and without cytokines. Peroxisomal beta-oxidation was significantly inhibited and very long chain fatty acid levels and free radicals were increased in treated cells. Furthermore, psychosine treatment decreased glutathione and ATP levels, plasmalogen content, and expression of alkyl-DHAP synthase. Brain tissue of twitcher mice (animal model of Krabbe's) had decreased beta-oxidation activity, low glutathione, and reduced plasmalogens. Psychosine treatment of rat primary oligodendrocytes inhibited peroxisomal activities. Psychosine-mediated loss of peroxisomal function and free radical production was inhibited with the antioxidant N-acetylcysteine in glial cells. Our results suggest that inhibition of peroxisomal functions and increased free radical production by psychosine may be partly responsible for oligodendrocyte and myelin loss observed in the Krabbe's brain, and that antioxidant therapy may be useful in the treatment of Krabbe's disease.

Molecular mechanisms of organelle biogenesis and related metabolic diseases

Organelle biogenesis is regulated by transcriptional networks that modulate expression of specific genes encoding organellar proteins. Structural and functional specificity of organelles requires not only the transcription of specific genes and translation of resulting mRNAs, but also the transfer of encoded polypeptides to their site of function through signaling peptides. A defect in targeting of proteins to their subcellular site of function may not necessarily prevent biogenesis of the organelle, but would definitely lead to formation of a defective organelle with respect to that specific function. Several metabolic diseases are associated with dysfunction or defects in organelle biogenesis; among these, peroxisome biogenesis disorders, mitochondrial biogenesis defects and lysosomal storage disorders are an extensively studied group of genetic diseases where biogenesis of the organelle is compromised either due to a defect in assembly of the organelle itself or impaired import of matrix proteins into the organelle. Recent advances in biochemical and molecular aspects of biogenesis of subcellular organelles have not only unraveled the mechanisms for organization of cellular networks, but have also provided new insights into the development of metabolic diseases that are caused by disruption of organelle biogenesis. This article reviews the molecular mechanisms of biogenesis of mitochondria, lysosomes and peroxisomes in relation to the metabolic diseases of genetic or nongenetic origin.

Differential gene expression in the kidney of sickle cell transgenic mice: upregulated genes

The S+S-Antilles transgenic mouse used in this study has renal defects similar to those seen in sickle cell anemia patients: congested glomeruli, medullary fibrosis, renal enlargement, vasoocclusion, and a urine concentrating defect. We used gene expression microarrays to identify genes highly up-regulated in the kidneys of these mice and validated their expression by real-time PCR. Kidney hypoxia, as demonstrated by the presence of deoxyhemoglobin, was detected by blood oxygen dependent magnetic resonance imaging (BOLD-MRI). Some of the up-regulated genes included cytochrome P450 4a14, glutathione-S-transferase alpha-1, mitochondrial hydroxymethylglutaryl CoA synthase, cytokine inducible SH-2 containing protein, retinol dehydrogenase type III, arginase II, glycolate oxidase, Na/K ATPase, renin-1, and alkaline phosphatase 2. An increase in enzyme activity was also demonstrated for one of the up-regulated genes (arginase II). These genes can be integrated into several different pathophysiological processes: a hypoxia cascade, a replacement cascade, or an ameliorating cascade, one or all of which may explain the phenotype of this disease. We conclude that microarray technology is a powerful tool to identify genes involved in renal disease in sickle cell anemia and that the identification of various metabolic pathways may open new avenues for therapeutic interventions.

Regulation of sterol carrier protein gene expression by the forkhead transcription factor FOXO3a

The SCP gene encodes two proteins, sterol carrier protein X (SCPx) and SCP2, that are independently regulated by separate promoters. SCPx has been shown to be the thiolase involved in the breakdown of branched-chain fatty acids and in the biosynthesis of bile acids. The in vivo function of SCP2 however remains to be established. The transcriptional regulation of SCPx and SCP2 is unclear, but their promoter regions contain several putative regulatory domains. We show here that both SCPx and SCP2 are upregulated by the daf-16-like Forkhead transcription factor FOXO3a (also known as FKHRL1) on the level of promoter activity. It was recently described that Forkheads regulate protection against (oxidative) stress in both Caenorhabditis elegans and mammalian cells. We looked into a role for SCP2 in the cellular defense against oxidative damage and found that a fluorescent fatty acid analog bound to SCP2 is protected against H2O2/Cu2+-induced oxidative damage. We propose a model for the way in which SCP2 could protect fatty acids from peroxidation.

Evidence for increased oxidative stress in peroxisomal D-bifunctional protein deficiency

Peroxisome biogenesis disorders (PBDs) and D-bifunctional protein (D-BP) deficiency are two types of inherited peroxisomal disorders. Patients with a PBD lack functional peroxisomes and patients with D-BP deficiency lack the enzyme, which is responsible for the second and third step of the peroxisomal beta-oxidation. The clinical presentation of these peroxisomal disorders is severe and includes several neurological abnormalities. The pathological mechanisms underlying these disorders are not understood and no therapies are available. Because peroxisomes have been associated with oxidative stress, as oxygen radicals are both produced and scavenged in peroxisomes, we have investigated whether oxidative stress is involved in the pathogenesis of PBDs and D-BP deficiency. We found in D-BP-deficient patients increased levels of thiobarbituric acid-reactive substances (TBARS) and 8-hydroxydeoxyguanosine (8-OHdG), which are markers for lipid peroxidation and oxidative DNA damage, respectively, whereas the levels of the lipophilic antioxidants alpha-tocopherol and coenzyme Q(10) were decreased. In addition, we found in skin fibroblasts from D-BP-deficient patients an imbalance between the activities of the peroxisomal H(2)O(2)-generating straight-chain acyl-CoA oxidase (SCOX) and the peroxisomal H(2)O(2)-degrading enzyme catalase. In conclusion, we have found clear evidence for the presence of increased oxidative stress in patients with D-BP deficiency, but not in patients with a PBD.