Hydrogen peroxide generation in peroxisome proliferator-induced oncogenesis

Biological responses in Danio rerio by the disinfectant SDBS in SARS-CoV-2 pandemic

The use of disinfectants, such as Sodium Dodecylbenzene Sulfonic acid salt (SDBS), has grown since the SARS-CoV-2 pandemic, with environmentally unknown consequences. The present study analyzed SDBS effects in the fish species Danio rerio, using a combination of biomarkers. Our data reported that larvae had their total locomotor activity increased when exposed to 1 mg/L of SDBS, but this parameter was decreased in fish exposed to 5 mg/L. A significant increment of erratic movements was reported in fish exposed to 1 and 5 mg/L of SDBS. These concentrations inhibited CYP1A1/CYP1A2, and of GSTs inhibition, suggesting SDBS is not preferentially biotransformed by these routes. Results concerning the antioxidant defense biomarkers (CAT and GPx) showed no straightforward pattern, suggesting SDBS exposure may have resulted in changes in redox balance. Finally, acetylcholinesterase activity increased. In summary, increased use of SDBS in a near future may result in deleterious effects in environmentally exposed fish.

Artificial Peroxisome hNiPt@Co-NC with Tetra-enzyme Activities for Colorimetric Glutathione Sensing

Artificial peroxisome plays an important part in protocell system construction and disease therapy. However, it remains an enormous challenge to exploit a practicable artificial peroxisome with multiple and stable activities. Nanozymes with multienzyme mimetic activities stand out for artificial peroxisome preparation. Herein, a novel nanozyme─Co-nanoparticle-embedded N-enriched carbon nanocubes (Co,N-CNC) decorated by hollow NiPt nanospheres (hNiPt@Co-NC) with featured tetra-enzyme mimetic activities of natural peroxisome─was prepared. Due to the synergistic effect of hollow NiPt nanospheres (hNiPtNS) and cubic porous Co,N-CNC support, hNiPt@Co-NC exhibited oxidase (OXD), peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD)-like activities with comparable catalytic efficiency, enabling it to be a competitive candidate for artificial peroxisome investigation. Based on the high OXD-mimetic activity of hNiPt@Co-NC, a facile colorimetric platform was proposed for reduced glutathione (GSH) detection with a wide linear range (0.1-5 μM, 5-100 μM) and a low detection limit (27 nM). Thus, the hNiPt@Co-NC with tetra-enzyme mimetic activities possessed bright prospects in diversified biotechnological applications, including artificial organelles, biosensing, and medical diagnostics.

Loss of ACOX1 in clear cell renal cell carcinoma and its correlation with clinical features

Clear cell renal cell carcinoma (ccRCC) is a major pathological type of kidney cancer with a poor prognosis due to a lack of biomarkers for early diagnosis and prognosis prediction of ccRCC. In this study, we investigated the aberrant expression of Acyl-coenzyme A oxidase 1 (ACOX1) in ccRCC and evaluated its potential in diagnosis and prognosis. ACOX1 is the first rate-limiting enzyme in the peroxidation β-oxidation pathway and is involved in the regulation of fatty acid oxidative catabolism. The mRNA and protein levels of ACOX1 were significantly downregulated in ccRCC, and its downregulation was closely associated with the tumor-node-metastasis stage of patients. The ROC curves showed that ACOX1 possesses a high diagnostic value for ccRCC. The OS analysis suggested that lower expression of ACOX1 was closely related to the worse outcome of patients. In addition, gene set enrichment analysis suggested that expression of ACOX1 was positively correlated with CDH1, CDH2, CDKL2, and EPCAM, while negatively correlated with MMP9 and VIM, which strongly indicated that ACOX1 may inhibit the invasion and migration of ccRCC by reversing epithelial-mesenchymal transition. Furthermore, we screened out that miR-16-5p is upregulated at the mRNA transcript level in ccRCC and negatively correlated with ACOX1. In conclusion, our results showed that ACOX1 is abnormally low expressed in ccRCC, suggesting that it could serve as a diagnostic and prognostic biomarker for ccRCC. Overexpression of miR-16-5p may be responsible for the inactivation of ACOX1.

p53 promotes peroxisomal fatty acid β-oxidation to repress purine biosynthesis and mediate tumor suppression

The metabolic pathways through which p53 functions as a potent tumor suppressor are incompletely understood. Here we report that, by associating with the Vitamin D receptor (VDR), p53 induces numerous genes encoding enzymes for peroxisomal fatty acid β-oxidation (FAO). This leads to increased cytosolic acetyl-CoA levels and acetylation of the enzyme 5-Aminoimidazole-4-Carboxamide Ribonucleotide Formyltransferase/IMP Cyclohydrolase (ATIC), which catalyzes the last two steps in the purine biosynthetic pathway. This acetylation step, mediated by lysine acetyltransferase 2B (KAT2B), occurs at ATIC Lys 266, dramatically inhibits ATIC activity, and inversely correlates with colorectal cancer (CRC) tumor growth in vitro and in vivo, and acetylation of ATIC is downregulated in human CRC samples. p53-deficient CRCs with high levels of ATIC is more susceptible to ATIC inhibition. Collectively, these findings link p53 to peroxisomal FAO, purine biosynthesis, and CRC pathogenesis in a manner that is regulated by the levels of ATIC acetylation.

AMACR Expression is a Potential Diagnostic Marker in Apocrine Lesions of Breast, and is Associated with High Histologic Grade and Lymph Node Metastases in Some Invasive Apocrine Breast Cancers

BACKGROUND

Carcinoma with apocrine differentiation (AC) is a subtype of breast carcinoma with apocrine features in >90% of the tumor. Molecular studies demonstrate AC has high expression of androgen receptor (AR) mRNA. Pure AC lack estrogen receptor (ER), progesterone receptor (PR), and express AR, with variable human epidermal growth factor 2 (HER2) status. Currently, in triple negative AC, no targetable therapies or specific diagnostic markers exist.

MATERIALS AND METHODS

α-Methylacyl CoA racemase (AMACR) expression was investigated as a marker of apocrine differentiation using a single-plex immunoperoxidase stain, and a novel AMACR/p63 dual stain in a subset of cases, across 1) benign apocrine lesions (apocrine metaplasia, adenosis) 2) apocrine DCIS (ADCIS), 3) AC/ invasive ductal carcinoma (IDC) with apocrine features, 4) non-apocrine triple negative breast cancer (TNBC) and 5) IDC, no special type. A sub-set of cases were evaluated by tissue microarray.

RESULTS

AMACR expression was increased in both AC and ADCIS, with minimal expression in benign breast tissue, TNBC and IDC, NST cases. In invasive cases, those with positive AMACR (>5% positivity) were significantly associated with higher histologic grade (P = .006), initial N stage (chi squared 0.044), and lack of ER or PR expression (both P < .001), with no correlation with overall survival. Analysis of TCGA breast cancer datasets revealed AMACR expression was significantly higher in molecularly defined apocrine carcinomas relative to basal and luminal subtypes. Moreover, high AMACR expression predicted worse relapse-free and distant-metastasis free survival, among both ER-/PR-/Her2- and ER-/PR-/Her2+ breast cancer cohorts (log-rank P = .081 and .00011, respectively).

CONCLUSION

AMACR represents a promising diagnostic and prognostic marker in apocrine breast lesions. Further study is needed to determine the biologic and clinical significance of this protein in AC.

A novel artificial peroxisome candidate based on nanozyme with excellent catalytic performance for biosensing

Artificial peroxisome is of critical importance to supersede natural peroxisome in fabricating protocell system and disease treatment. Nevertheless, developing feasible artificial peroxisome with various stable functions remains a monumental challenge. Nanozyme with multiple enzyme-like activities can mimic natural enzymes in peroxisome, which make it a prospective candidate for artificial peroxisome design. Herein, we prepared a nanozyme with multiple peroxisomal-like activities - Pd nanoparticles functionalized nitrogen-doped porous carbon-reduced graphene oxide (PdNPs/N-PC-rGO). Due to its sandwich-like structure, the incorporation of N heteroatoms and the synergistic effect between PdNPs and N-PC-rGO bi-support, the PdNPs/N-PC-rGO exhibited triple peroxisomal-like activities including oxidase (OXD), peroxidase (POD) and catalase (CAT), leading it a promising alternative for artificial peroxisome exploration. Furthermore, the PdNPs/N-PC-rGO showed high electrocatalytic activity, which could be employed for the detection of electrochemical active substances reduced glutathione (GSH). The PdNPs/N-PC-rGO modified electrode displayed a wide concentration range from 70 nM to 1500 μM, with a very low detection limit of 9.8 nM (S/N = 3). Therefore, PdNPs/N-PC-rGO was a promising nanozyme for various biotechnological applications such as artificial organelles, biosensing, cytoprotection, disease diagnosis and treatment.

Enigmatic mechanism of the N-vinylpyrrolidone hepatocarcinogenicity in the rat

N-vinyl pyrrolidone (NVP) is produced up to several thousand tons per year as starting material for the production of polymers to be used in pharmaceutics, cosmetics and food technology. Upon inhalation NVP was carcinogenic in the rat, liver tumor formation is starting already at the rather low concentration of 5 ppm. Hence, differentiation whether NVP is a genotoxic carcinogen (presumed to generally have no dose threshold for the carcinogenic activity) or a non-genotoxic carcinogen (with a potentially definable threshold) is highly important. In the present study, therefore, the existing genotoxicity investigations on NVP (all showing consistently negative results) were extended and complemented with investigations on possible alternative mechanisms, which also all proved negative. All tests were performed in the same species (rat) using the same route of exposure (inhalation) and the same doses of NVP (5, 10 and 20 ppm) as had been used in the positive carcinogenicity test. Specifically, the tests included an ex vivo Comet assay (so far not available) and an ex vivo micronucleus test (in contrast to the already available micronucleus test in mice here in the same species and by the same route of application as in the bioassay which had shown the carcinogenicity), tests on oxidative stress (non-protein-bound sulfhydryls and glutathione recycling test), mechanisms mediated by hepatic receptors, the activation of which had been shown earlier to lead to carcinogenicity in some instances (Ah receptor, CAR, PXR, PPARα). No indications were obtained for any of the investigated mechanisms to be responsible for or to contribute to the observed carcinogenicity of NVP. The most important of these exclusions is genotoxicity. Thus, NVP can rightfully be regarded and treated as a non-genotoxic carcinogen and threshold approaches to the assessment of this chemical are supported. However, the mechanism underlying the carcinogenicity of NVP in rats remains unclear.

Analysis of Peganum harmala, Melia azedarach and Morus alba extracts against six lethal human cancer cells and oxidative stress along with chemical characterization through advance Fourier Transform and Nuclear Magnetic Resonance spectroscopic methods towards green chemotherapeutic agents

Traditional medicines implicate consumption of plant crude extracts, which may consist of extensive phytochemical diversity. Overall, the most biologically active extract of Peganum harmala (seeds) exhibited significant cytotoxic activity on Artemia salina with LC50 value of 61.547 µg/mL, while P. harmala (roots) [LC50 = 124.229 µg/mL] and M. azedarach (fruits) [LC50 = 147.813 µg/mL] showed moderate cytotoxic potential. P. harmala (seeds) extract also showed the maximum antitumor potential with 52.278 µg/mL LC50. Branches of P. harmala and Morus alba were not active in both bioassays. These outcomes were further reinforced by the levels of phenolics and flavonoids checked against gallic acid and quercetin equivalents, respectively, by standard curves. Current study aims to isolate, structurally characterize and analyze the bioactive compound from plant extracts by using chromatographic and spectrophotometric techniques. Bioactivity guided isolation of extracts led to the isolation of PH-HM-16 from ethyl acetate fraction P. harmala seeds. Chemical structure of PH-HM-16 was elucidated by ESI-MS, 1H NMR, 13C NMR, HSQC and IR spectrum. The results demonstrated significant positive anticancer activities against six human cancer cell lines assessed through MTT cancer cell growth inhibition assay. PH-HM-16 was most effective against prostate cancer cell lines [IC50 = 17.63 µg/mL] followed by breast cancer cell line MCF7 [IC50 value of 41.81 µg/mL]. IC50 value of PH-HM-16 against human myeloid leukemia cell line HL-60 and human colorectal tumor cells HCT-116 was observed as 68.77 µg/mL and 71.54 µg/mL respectively. The IC 50 value of PH-HM-16 compound was not significant against human gastric cancer SGC-7901 (111.89 µg/mL) and human lung adenocarcinoma epithelial cell line A549 (176.04 µg/mL). Isolated bioactive metabolite PH-HM-16 possesses significant antitumor potential so this could be the first step to develop an effective anticancer agent. Hence, this compound represents a promising potential to be chemically standardized or developed into pharmaceuticals for the chemoprevention and/or the treatment of certain types of cancer, especially as adjuvant phytotherapeutics in conventional chemotherapy.

The combination of sesamol and clofibric acid moieties leads to a novel potent hypolipidemic agent with antioxidant, anti-inflammatory and hepatoprotective activity

Oxidative stress and inflammation have been considered the main factors in the liver injury of clofibrate (CF). To obtain a novel antihyperlipidemic agent with antioxidant, anti-inflammation and hepatoprotection, the combination of sesamol and clofibric acid moieties was performed and achieved sesamol-clofibrate (CF-Sesamol). CF-Sesamol showed significant hypolipidemia effects in hyperlipidemia mice induced by Triton WR 1339, reducing TG by 38.8% (P < 0.01) and TC by 35.1% (P < 0.01). CF-Sesamol also displayed an alleviating effect on hepatotoxicity. The hepatic weight and hepatic coefficient were decreased. The amelioration of liver function was observed, such as aspartate and lactate transaminases (AST and ALT), alkaline phosphatase (ALP) and total proteins (TP) levels. Liver histopathological examination showed that hepatocyte necrosis, cytoplasmic loosening, nuclear degeneration and inflammatory cell infiltration reduced obviously by treatment with CF-Sesamol. Related molecular mechanisms on hepatoprotection showed that CF-Sesamol up-regulated Nrf2 and HO-1 expression and down-regulated p-NF-κB p65 expression in hepatic tissues. CF-Sesamol has significant antioxidant and anti-inflammatory effects. Plasma antioxidant enzymes such as SOD and CAT increased, anti-lipid peroxidation product MDA decreased. The expression of TNF-α and IL-6 inflammatory cytokines in liver was significantly lower than that in the CF group. The results indicated that CF-Sesamol exerted more potent antihyperlipidemic effects and definite hepatoprotective activity partly through the Nrf2/NF-κB-mediated signaling pathway.

Autophagy and organelle homeostasis in cancer

Beginning with the earliest studies of autophagy in cancer, there have been indications that autophagy can both promote and inhibit cancer growth and progression; autophagy regulation of organelle homeostasis is similarly complicated. In this review we discuss pro- and antitumor effects of organelle-targeted autophagy and how this contributes to several hallmarks of cancer, such as evading cell death, genomic instability, and altered metabolism. Typically, the removal of damaged or dysfunctional organelles prevents tumor development but can also aid in proliferation or drug resistance in established tumors. By better understanding how organelle-specific autophagy takes place and can be manipulated, it may be possible to go beyond the brute-force approach of trying to manipulate all autophagy in order to improve therapeutic targeting of this process in cancer.

Curcumin promotes AApoAII amyloidosis and peroxisome proliferation in mice by activating the PPARα signaling pathway

Curcumin is a polyphenol compound that exhibits multiple physiological activities. To elucidate the mechanisms by which curcumin affects systemic amyloidosis, we investigated amyloid deposition and molecular changes in a mouse model of amyloid apolipoprotein A-II (AApoAII) amyloidosis, in which mice were fed a curcumin-supplemented diet. Curcumin supplementation for 12 weeks significantly increased AApoAII amyloid deposition relative to controls, especially in the liver and spleen. Liver weights and plasma ApoA-II and high-density lipoprotein concentrations were significantly elevated in curcumin-supplemented groups. RNA-sequence analysis revealed that curcumin intake affected hepatic lipid metabolism via the peroxisome proliferator-activated receptor (PPAR) pathway, especially PPARα activation, resulting in increased Apoa2 mRNA expression. The increase in liver weights was due to activation of PPARα and peroxisome proliferation. Taken together, these results demonstrate that curcumin is a PPARα activator and may affect expression levels of proteins involved in amyloid deposition to influence amyloidosis and metabolism in a complex manner.

Oxidative Damage and Antioxidant Response in Frontal Cortex of Demented and Nondemented Individuals with Alzheimer's Neuropathology

Alzheimer's disease (AD) is characterized by progressive neurodegeneration in the cerebral cortex, histopathologically hallmarked by amyloid β (Aβ) extracellular plaques and intracellular neurofibrillary tangles, constituted by hyperphosphorylated tau protein. Correlation between these pathologic features and dementia has been challenged by the emergence of "nondemented with Alzheimer's neuropathology" (NDAN) individuals, cognitively intact despite displaying pathologic features of AD. The existence of these subjects suggests that some unknown mechanisms are triggered to resist Aβ-mediated detrimental events. Aβ accumulation affects mitochondrial redox balance, increasing oxidative stress status, which in turn is proposed as a primary culprit in AD pathogenesis. To clarify the relationship linking Aβ, oxidative stress, and cognitive impairment, we performed a comparative study on AD, NDAN, and aged-matched human postmortem frontal cortices of either sex. We quantitatively analyzed immunofluorescence distribution of oxidative damage markers, and of SOD2 (superoxide dismutase 2), PGC1α [peroxisome proliferator-activated receptor (PPAR) γ-coactivator 1α], PPARα, and catalase as key factors in antioxidant response, as well as the expression of miRNA-485, as a PGC1α upstream regulator. Our results confirm dramatic redox imbalance, associated with impaired antioxidant defenses in AD brain. By contrast, NDAN individuals display low oxidative damage, which is associated with high levels of scavenging systems, possibly resulting from a lack of PGC1α miRNA-485-related inhibition. Comparative analyses in neurons and astrocytes further highlighted cell-specific mechanisms to counteract redox imbalance. Overall, our data emphasize the importance of transcriptional and post-transcriptional regulation of antioxidant response in AD. This suggests that an efficient PGC1α-dependent "safety mechanism" may prevent Aβ-mediated oxidative stress, supporting neuroprotective therapies aimed at ameliorating defects in antioxidant response pathways in AD patients.

Acute and chronic effects of environmental realistic concentrations of clofibric acid in Danio rerio: Behaviour, oxidative stress, biotransformation and lipid peroxidation endpoints

Due to their widespread use, pharmaceuticals can be metabolized, excreted and ultimately discarded in the environment, thereby affecting aquatic organisms. Lipid-regulating drugs are among the most prescribed medications around the world, controlling human cholesterol levels, in more than 20 million patients. Despite this growing use of lipid-regulating drugs, particularly those whose active metabolite is clofibric acid, the potential toxicological effects of these pharmaceuticals in the environment is not fully characterized. This work intended to characterize the toxicity of an acute (120 hours post-fertilization) and chronic (60 days post-fertilization) exposures to clofibric acid in concentrations of 10.35, 20.7, 41.4, 82.8, and 165.6 μg L^-1 in zebrafish (Danio rerio). The concentrations which were implemented in both exposures were based on predicted environmental concentrations for Portuguese surface waters. The acute effects were analysed focusing on behavioural endpoints (small and large distance travelled, swimming time and total distance travelled), biomarkers of oxidative stress (activity of the enzymes superoxide dismutase, Cu/Zn- and Mn SOD; catalase, CAT; glutathione peroxidase, Se- and total GPx), biotransformation (activity of glutathione S-transferases, GSTs) and lipid peroxidation (thiobarbituric acid reactive substances, TBARS). Chronically exposed individuals were also histologically analysed for sex determination and gonadal developmental stages. In terms of acute exposure, significant alterations were reported, in terms of behavioural alterations (hypoactivity), followed by an overall increase in all tested biomarkers. Chronically exposed organisms did not show alterations in terms of sex ratio and maturation stages, suggesting that clofibric acid did not act as an endocrine disruptor. Moreover, the metabolism of clofibric acid resulted in increased levels of both forms of SOD activity, especially for animals exposed to higher levels of this drug. An increase of CAT activity was observed in fish exposed to low levels, and a decrease in those exposed to higher amounts of clofibric acid. Both GPx forms had their activities increased. The enzyme of biotransformation GSTs were increased at low levels of clofibric acid but inhibited at higher amounts of this substance. Lipid peroxidation levels were also changed, with an induction of this parameter with increasing amounts of clofibric acid. Changes also occurred in behavioural endpoints and patterns for control organisms and for those exposed to clofibric acid were significantly distinct, for all types (light and darkness) of exposure, and for the two analysed endpoints (small and large distance). Results from this assay allow inferring that clofibric acid can have an ecologically relevant impact in living organisms exposed to this substance, with putative effects on the metabolism of individuals, affecting their behaviour and ultimately their survival.

Gynura divaricata exerts hypoglycemic effects by regulating the PI3K/AKT signaling pathway and fatty acid metabolism signaling pathway

OBJECTIVES

The study aimed to examine the anti-diabetic effects of Gynura divaricata (GD) and the underlying mechanism.

METHODS

Information about the chemical compositions of GD was obtained from extensive literature reports. Potential target genes were predicted using PharmMapper and analyzed using Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO). To validate the results from bioinformatics analyses, an aqueous extract of GD was administered to type 2 diabetic rats established by feeding a high-fat and high-sugar diet followed by STZ injection. Key proteins of the PI3K/AKT signaling pathway and fatty acid metabolism signaling pathway were investigated by immunoblotting.

RESULTS

The blood glucose of the rats in the GD treatment group was significantly reduced compared with the model group without treatment. GD also showed activities in reducing the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), blood urea nitrogen (BUN), and creatinine (CREA). The levels of urine sugar (U-GLU) and urine creatinine (U-CREA) were also lowered after treatment with GD. Bioinformatics analysis showed that some pathways including metabolic pathways, insulin resistance, insulin signaling pathway, PPAR signaling pathway, bile secretion, purine metabolism, etc. may be regulated by GD. Furthermore, GD significantly increased the protein expression levels of PKM1/2, p-AKT, PI3K p85, and GLUT4 in the rat liver. In addition, the expression levels of key proteins in the fatty acid metabolism signaling pathway including AMPK, p-AMPK, PPARα, and CPT1α were significantly upregulated. The anti-apoptotic protein BCL-2/BAX expression ratio in rats was significantly upregulated after GD intervention. These results were consistent with the bioinformatics analysis results.

CONCLUSIONS

Our study suggests that GD can exert hypoglycemic effects in vivo by regulating the genes at the key nodes of the PI3K/AKT signaling pathway and fatty acid metabolism signaling pathway.

Peroxisome Metabolism in Cancer

Peroxisomes are metabolic organelles involved in lipid metabolism and cellular redox balance. Peroxisomal function is central to fatty acid oxidation, ether phospholipid synthesis, bile acid synthesis, and reactive oxygen species homeostasis. Human disorders caused by genetic mutations in peroxisome genes have led to extensive studies on peroxisome biology. Peroxisomal defects are linked to metabolic dysregulation in diverse human diseases, such as neurodegeneration and age-related disorders, revealing the significance of peroxisome metabolism in human health. Cancer is a disease with metabolic aberrations. Despite the critical role of peroxisomes in cell metabolism, the functional effects of peroxisomes in cancer are not as well recognized as those of other metabolic organelles, such as mitochondria. In addition, the significance of peroxisomes in cancer is less appreciated than it is in degenerative diseases. In this review, I summarize the metabolic pathways in peroxisomes and the dysregulation of peroxisome metabolism in cancer. In addition, I discuss the potential of inactivating peroxisomes to target cancer metabolism, which may pave the way for more effective cancer treatment.

Effects of diets high in corn oil or in extra virgin olive oil on oxidative stress in an experimental model of breast cancer

Experimental evidence highlights the importance of dietetic factors on breast cancer. In this work we aimed to analyze the effects two oils, corn oil (rich in n-6 polyunsaturated fatty acids -PUFA-) and extra virgin olive oil (EVOO), on oxidative stress in an animal model of breast carcinogenesis. Female rats were fed a low-fat control, a high-corn oil, or a high-EVOO diet from weaning or after induction with 7,12-dimethylbenz[a]anthracene at 53 days. Animals were euthanized at 36, 51, 100 and 246 days of age. We analyzed antioxidant enzymes (mRNA and activity of superoxide dismutase, glutathione peroxidase and catalase), non-enzymatic capacity (oxidized and reduced glutathione) and DNA damage (8-oxo-dG) in tumors and mammary gland at different ages. We also analyzed lipid peroxidation (isoprostanes in serum and lipofuscin in liver). Results indicated a decrease in the enzymatic antioxidant capacity and increased oxidative stress in mammary gland of healthy young animals after a short period of high-fat diets intake, followed by an adaptation to chronic dietary intervention. After induction both diets, especially the one high in n-6 PUFA, increased the oxidized glutathione. In tumors no clear effects of the high-fat diets were observed, although in the long-term lipofuscin and 8-oxo-dG suggested greater oxidative damage by effect of the n-6 PUFA-rich diet. Considering the differential effects of these diets on mammary carcinogenesis that we have previously reported, this study suggests that these high-fat diets could have an effect on oxidative stress that would lead to different signaling pathways.

Genomic Identification of RNA Editing Through Integrating Omics Datasets and the Clinical Relevance in Hepatocellular Carcinoma

RNA editing is a widespread post-transcriptional mechanism to introduce single nucleotide changes to RNA in human cancers. Here, we characterized the global RNA editing profiles of 373 hepatocellular carcinoma (HCC) and 50 adjacent normal liver samples from The Cancer Genome Atlas (TCGA) and revealed that most editing events tend to occur in minor percentage of samples with moderate editing degrees (20–30%). Moreover, these RNA editing prefer to be A-to-I RNA editing in protein coding genes, especially in 3′UTR regions. Considering the association between DNA mutation and RNA editing, our analysis found that RNA editing maybe a complementary event for DNA mutation of HCC risk genes in HCC patients. We next identified 454 HCC-related editing sites, and many locate on the same genes with the same editing patterns. The functional consequences of editing revealed 2,086 functional editing sites and demonstrated that most editing in coding regions are non-synonymous variations. Furthermore, our results showed that editing in the 3′UTR regions tend to influence miRNA–target binding, and the editing degree seems to be negatively correlated with gene expression. Finally, we found that 46 HCC-related editing sites with consequence are able to distinguish the prognosis differences of HCC patients, suggesting their clinical relevance. Together, our results highlight RNA editing as a valuable molecular resource for investigating HCC mechanisms and clinical treatments.

Gene Expression Profiles Induced by a Novel Selective Peroxisome Proliferator-Activated Receptor α Modulator (SPPARMα) Pemafibrate

Pemafibrate is the first clinically-available selective peroxisome proliferator-activated receptor α modulator (SPPARMα) that has been shown to effectively improve hypertriglyceridemia and low high-density lipoprotein cholesterol (HDL-C) levels. Global gene expression analysis reveals that the activation of PPARα by pemafibrate induces fatty acid (FA) uptake, binding, and mitochondrial or peroxisomal oxidation as well as ketogenesis in mouse liver. Pemafibrate most profoundly induces HMGCS2 and PDK4, which regulate the rate-limiting step of ketogenesis and glucose oxidation, respectively, compared to other fatty acid metabolic genes in human hepatocytes. This suggests that PPARα plays a crucial role in nutrient flux in the human liver. Additionally, pemafibrate induces clinically favorable genes, such as ABCA1, FGF21, and VLDLR. Furthermore, pemafibrate shows anti-inflammatory effects in vascular endothelial cells. Pemafibrate is predicted to exhibit beneficial effects in patients with atherogenic dyslipidemia and diabetic microvascular complications.

Peroxisomes as Modulators of Cellular Protein Thiol Oxidation: A New Model System

AIMS

Peroxisomes are ubiquitous, single-membrane-bounded organelles that contain considerable amounts of enzymes involved in the production or breakdown of hydrogen peroxide (H₂O₂), a key signaling molecule in multiple biological processes and disease states. Despite this, the role of this organelle in cross-compartmental H₂O₂ signaling remains largely unclear, mainly because of the difficulty to modulate peroxisomal H₂O₂ production in a selective manner. This study aimed at establishing and validating a cellular model suitable to decipher the complex signaling processes associated with peroxisomal H₂O₂ release.

RESULTS

Here, we report the development of a human cell line that can be used to selectively generate H₂O₂ inside peroxisomes in a time- and dose-controlled manner. In addition, we provide evidence that peroxisome-derived H₂O₂ can oxidize redox-sensitive cysteine residues in multiple proteins within (e.g., peroxiredoxin-5 [PRDX5]) and outside (e.g., nuclear factor kappa B subunit 1 [NFKB1] and subunit RELA proto-oncogene [RELA], phosphatase and tensin homolog [PTEN], forkhead box O3 [FOXO3], and peroxin 5 [PEX5]) the peroxisomal compartment. Furthermore, we show that the extent of protein oxidation depends on the subcellular location of the target protein and is inversely correlated to catalase activity and cellular glutathione content. Finally, we demonstrate that excessive H₂O₂ production inside peroxisomes does not induce their selective degradation, at least not under the conditions examined.

INNOVATION

This study describes for the first time a powerful model system that can be used to examine the role of peroxisome-derived H₂O₂ in redox-regulated (patho)physiological processes, a research area in need of further investigation and innovative approaches.

CONCLUSION

Our results provide unambiguous evidence that peroxisomes can serve as regulatory hubs in thiol-based signaling networks.

Redox Signaling from and to Peroxisomes: Progress, Challenges, and Prospects

SIGNIFICANCE

Peroxisomes are organelles that are best known for their role in cellular lipid and hydrogen peroxide (H₂O₂) metabolism. Emerging evidence suggests that these organelles serve as guardians and modulators of cellular redox balance, and that alterations in their redox metabolism may contribute to aging and the development of chronic diseases such as neurodegeneration, diabetes, and cancer. Recent Advances: H₂O₂ is an important signaling messenger that controls many cellular processes by modulating protein activity through cysteine oxidation. Somewhat surprisingly, the potential involvement of peroxisomes in H₂O₂-mediated signaling processes has been overlooked for a long time. However, recent advances in the development of live-cell approaches to monitor and modulate spatiotemporal fluxes in redox species at the subcellular level have opened up new avenues for research in redox biology and boosted interest in the concept of peroxisomes as redox signaling platforms.

CRITICAL ISSUES

This review first introduces the reader to what is known about the role of peroxisomes in cellular H₂O₂ production and clearance, with a focus on mammalian cells. Next, it briefly describes the benefits and drawbacks of current strategies used to investigate the complex interplay between peroxisome metabolism and cellular redox state. Furthermore, it integrates and critically evaluates literature dealing with the interrelationship between peroxisomal redox metabolism, cell signaling, and human disease.

FUTURE DIRECTIONS

As the precise molecular mechanisms underlying many of these associations are still poorly understood, a key focus for future research should be the identification of primary targets for peroxisome-derived H₂O₂.

Protective roles of fenofibrate against cisplatin-induced ototoxicity by the rescue of peroxisomal and mitochondrial dysfunction

Cisplatin is an alkylating agent that interferes with DNA replication and kills proliferating carcinogenic cells. Several studies have been conducted to attenuate the side effects of cisplatin; one such side effect in cancer patients undergoing cisplatin chemotherapy is ototoxicity. However, owing to a lack of understanding of the precise mechanism underlying cisplatin-induced side effects, management of cisplatin-induced ototoxicity remains unsolved. We investigated the protective effects of fenofibrate, a PPAR-α activator, on cisplatin-induced ototoxicity. Fenofibrate prevented cisplatin-induced loss of hair cells and improved cell viability; moreover, fenofibrate significantly attenuated the threshold of auditory brainstem responses (ABR) in cisplatin-injected mice. Fenofibrate significantly increased PPAR-α, PPAR-γ, and PGC-1α expression, which consequently resulted in increased number and functional enzyme levels of peroxisomes and mitochondria, and markedly decreased phospho-p53 (S15), activated caspase-3, cleaved-PARP, and NF-κB p65 nuclear translocation, which reduced NADPH oxidase isoform (NOX3 and NOX4) expression, thereby decreasing reactive oxygen species (ROS) production in cisplatin-treated tissues ex vivo. Taken together, these results indicate that fenofibrate rescues cisplatin-induced ototoxicity by maintaining peroxisome and mitochondria number and function, reducing inflammation, and decreasing ROS levels. Our findings suggest that fenofibrate administration might serve as an effective therapeutic agent against cisplatin-induced ototoxicity.

SIRT5 inhibits peroxisomal ACOX1 to prevent oxidative damage and is downregulated in liver cancer

Peroxisomes account for ~35% of total H₂O₂ generation in mammalian tissues. Peroxisomal ACOX1 (acyl-CoA oxidase 1) is the first and rate-limiting enzyme in fatty acid β-oxidation and a major producer of H₂O₂ ACOX1 dysfunction is linked to peroxisomal disorders and hepatocarcinogenesis. Here, we show that the deacetylase sirtuin 5 (SIRT5) is present in peroxisomes and that ACOX1 is a physiological substrate of SIRT5. Mechanistically, SIRT5-mediated desuccinylation inhibits ACOX1 activity by suppressing its active dimer formation in both cultured cells and mouse livers. Deletion of SIRT5 increases H₂O₂ production and oxidative DNA damage, which can be alleviated by ACOX1 knockdown. We show that SIRT5 downregulation is associated with increased succinylation and activity of ACOX1 and oxidative DNA damage response in hepatocellular carcinoma (HCC). Our study reveals a novel role of SIRT5 in inhibiting peroxisome-induced oxidative stress, in liver protection, and in suppressing HCC development.

Hydroxytyrosol nicotinate, a new multifunctional hypolipidemic and hypoglycemic agent

Hydroxytyrosol (HT) is a natural polyphenol antioxidant that exists in olive oil. In the study of multifunctional hypolipidemic of nicotinic derivatives, we found that hydroxytyrosol nicotinate (HT-N) incorporation of niacin with HT displayed ?-glucosidase inhibitory activities in vitro, such as yeast ?-glucosidase (IC₅₀?=?117.72??M) and rat intestinal ?-glucosidases maltase (IC₅₀?=?31.86??M) and sucrase (IC₅₀?=?22.99??M), and had a good control of postprandial blood glucose (PBG). HT-N shown significantly hypoglycemic action by 16.9% and protection of pancreatic tissue in type 2 diabetic mellitus (T2DM) mouse model. HT-N also shown a potent antioxidant activity and property of anti-glycation in vitro, which were benefit for ameliorating diabetic complications. Moreover, HT-N exhibited much significant hypolipidemia, lowering plasma triglyceride (TG), total cholesterol (TC), and malonaldehyde (MDA) by 34.6%, 45.8% and 32.1% respectively, in hyperlipidemic mice induced by Triton WR 1339. The results indicated that HT-N has hypolipidemic, hypoglycemic and antioxidant actions. All these properties could be conducive to amelioration of oxidative stress, hyperlipidemia, and diabetes that HT-N may serve as a multifunctional potential therapeutic strategy in diabetic patients with hyperlipidemia.

Fenofibrate induced PPAR alpha expression was attenuated by oestrogen receptor alpha overexpression in Hep3B cells

The physiological regulation of Oestrogen receptor α (ERα) and peroxisome proliferator-activated receptor alpha (PPARα) in Hepatocellular carcinoma (HCC) remains unknown. The present study we first treat the cells with fenofibrate and further investigated the possible mechanisms of 17β-estradiol (E₂ ) and/or ERα on regulating PPARα expression. We also found higher PPARα expression in the tumor area than adjacent areas and subsequently compared PPARα expression in four different hepatic cancer cell lines. Hep3B cells were found to express more PPARα than the other cell lines. Using the PPARα agonist fenofibrate, we found that fenofibrate increased Hep3B cell proliferation efficiency by increasing cell cycle proteins, such as cyclin D1 and PCNA, and inhibiting p27 and caspase 3 expressions. Next, we performed transient transfections and immuno-precipitation studies using the pTRE2/ERα plasmid to evaluate the interaction between ERα and PPARα. ERα interacted directly with PPARα and negatively regulated its function. Moreover, in Tet-on ERα over-expressed Hep3B cells, E₂ treatment inhibited PPARα, its downstream gene acyl-CoA oxidase (ACO), cyclin D1 and PCNA expression and further increased p27 and caspase 3 expressions. However, over-expressed ERα plus 17-β-estradiol (10^-8 M) reversed the fenofibrate effect and induced apoptosis, which was blocked in ICI/melatonin/fenofibrate-treated cells. This study illustrates that PPARα expression and function were negatively regulated by ERα expression in Hep3B cells.

The PPARα-dependent rodent liver tumor response is not relevant to humans: addressing misconceptions

A number of industrial chemicals and therapeutic agents cause liver tumors in rats and mice by activating the nuclear receptor peroxisome proliferator-activated receptor α (PPARα). The molecular and cellular events by which PPARα activators induce rodent hepatocarcinogenesis have been extensively studied elucidating a number of consistent mechanistic changes linked to the increased incidence of liver neoplasms. The weight of evidence relevant to the hypothesized mode of action (MOA) for PPARα activator-induced rodent hepatocarcinogenesis is summarized here. Chemical-specific and mechanistic data support concordance of temporal and dose-response relationships for the key events associated with many PPARα activators. The key events (KE) identified in the MOA are PPARα activation (KE1), alteration in cell growth pathways (KE2), perturbation of hepatocyte growth and survival (KE3), and selective clonal expansion of preneoplastic foci cells (KE4), which leads to the apical event-increases in hepatocellular adenomas and carcinomas (KE5). In addition, a number of concurrent molecular and cellular events have been classified as modulating factors, because they potentially alter the ability of PPARα activators to increase rodent liver cancer while not being key events themselves. These modulating factors include increases in oxidative stress and activation of NF-kB. PPARα activators are unlikely to induce liver tumors in humans due to biological differences in the response of KEs downstream of PPARα activation. This conclusion is based on minimal or no effects observed on cell growth pathways and hepatocellular proliferation in human primary hepatocytes and absence of alteration in growth pathways, hepatocyte proliferation, and tumors in the livers of species (hamsters, guinea pigs and cynomolgus monkeys) that are more appropriate human surrogates than mice and rats at overlapping dose levels. Despite this overwhelming body of evidence and almost universal acceptance of the PPARα MOA and lack of human relevance, several reviews have selectively focused on specific studies that, as discussed, contradict the consensus opinion and suggest uncertainty. In the present review, we systematically address these most germane suggested weaknesses of the PPARα MOA.

Salvia fruticosa Modulates mRNA Expressions and Activity Levels of Xenobiotic Metabolizing CYP1A2, CYP2E1, NQO1, GPx, and GST Enzymes in Human Colorectal Adenocarcinoma HT-29 Cells

Natural products have gained considerable interests because of their use in some industrial areas including nutrition, cosmetic, pharmacy, and medicine. Salvia fruticosa M. (Lamiaceae) is known for its antioxidant, antimicrobial, and antiproliferative activities. Phase I xenobiotic metabolizing enzymes, CYP1A2 and CYP2E1, produce reactive metabolites which are eliminated by the action of phase II enzymes, NQO1, GPx, and glutathione S-transferases (GSTs). In this study, in vitro modulatory effects of S. fruticosa and its major phenolic compound rosmarinic acid (RA) on CYP1A2, CYP2E1, NQO1, GPx, and GSTm1 mRNA expressions and enzyme activities of GPx and GSTs were investigated in HT-29 cells. An mRNA expression analysis revealed that CYP1A2 and CYP2E1 levels were decreased while those of NQO1, GPx, and GSTm1 increased after S. fruticosa and RA treatments. In parallel to gene expressions, enzyme activities of GPx and GSTs by S. fruticosa increased 1.68- and 1.48-fold, respectively. Moreover, RA increased GPx and GSTs activities 1.67- and 1.94-fold, respectively. The results of this preliminary study show that metabolism of xenobiotics may be altered due to changes in the expression and activity of the investigated enzymes by S. fruticosa.

Perfluorooctanoic acid induces oxidative damage and mitochondrial dysfunction in pancreatic β-cells

Several environmental contaminants have been linked to the development of diabetes and increased diabetes‑associated mortality. Perfluorooctanoic acid (PFOA) is a widely used perfluoroalkane found in surfactants and lubricants, and in processing aids used in the production of polymers. Furthermore, PFOA has been detected in humans, wildlife and the environment. The present study investigated the toxic effects of PFOA on rat pancreatic β‑cell‑derived RIN‑m5F cells. Cell viability, apoptosis, reactive oxygen and nitrogen species, cytokine release and mitochondrial parameters, including membrane potential collapse, reduced adenosine triphosphate levels, cardiolipin peroxidation and cytochrome c release were assessed. PFOA significantly decreased RIN‑m5F cell viability and increased apoptosis. Exposure to PFOA increased the formation of reactive oxygen species, mitochondrial superoxide, nitric oxide and proinflammatory cytokines. Furthermore, PFOA induced mitochondrial membrane potential collapse and reduced adenosine triphosphate levels, cardiolipin peroxidation and cytochrome c release. These results indicate that PFOA is associated with the induction of apoptosis in RIN-m5F cells, and induces cytotoxicity via increased oxidative stress and mitochondrial dysfunction.

Hepatotoxic Effects of Fenofibrate in Spontaneously Hypertensive Rats Expressing Human C-Reactive Protein

Dyslipidemia and inflammation play an important role in the pathogenesis of cardiovascular and liver disease. Fenofibrate has a well-known efficacy to reduce cholesterol and triglycerides. Combination with statins can ameliorate hypolipidemic and anti-inflammatory effects of fibrates. In the current study, we tested the anti-inflammatory and metabolic effects of fenofibrate alone and in combination with rosuvastatin in a model of inflammation and metabolic syndrome, using spontaneously hypertensive rats expressing the human C-reactive protein transgene (SHR-CRP transgenic rats). SHR-CRP rats treated with fenofibrate alone (100 mg/kg body weight) or in combination with rosuvastatin (20 mg/kg body weight) vs. SHR-CRP untreated controls showed increased levels of proinflammatory marker IL6, increased concentrations of ALT, AST and ALP, increased oxidative stress in the liver and necrotic changes of the liver. In addition, SHR-CRP rats treated with fenofibrate, or with fenofibrate combined with rosuvastatin vs. untreated controls, exhibited increased serum triglycerides and reduced HDL cholesterol, as well as reduced hepatic triglyceride, cholesterol and glycogen concentrations. These findings suggest that in the presence of high levels of human CRP, fenofibrate can induce liver damage even in combination with rosuvastatin. Accordingly, these results caution against the possible hepatotoxic effects of fenofibrate in patients with high levels of CRP.

E2/ERβ Inhibits PPARα to Regulate Cell-Proliferation and Enhance Apoptosis in Hep3B-Hepatocellular Carcinoma

Peroxisome proliferator-activated receptor-α (PPARα) is a member of the nuclear receptor superfamily involved in hepatocarcinogenesis in rodents. In previous studies on liver tumor tissues, PPARα mRNA expression was found to be significantly higher and overexpression of ERα inhibited the PPARα expression, cell-proliferation and also induced apoptosis in Hep3B cell. However, the role of ERβ is not known yet. Therefore, the aim of this study is to define the role of ERβ on PPARα in Hep3B cells. The effect of PPARα signaling cascade were monitored by inducing Hep3B cells by fenofibrate. Further the cells were transfected with pCMV-ERβ and the consequences of ERβ-overexpression on the PPARα induced changes such as enhanced cell-proliferation and suppressed apoptosis were determined using western blot analysis and TUNEL assay. The EMSA was used to identify whether ERβ modulates PPARα expression by binding to PPARα promoter region to repress PPARα promoter activity. In addition, the direct interaction between ERβ and PPARα proteins was verified by co-immunoprecipitation assay. Our results show that the overexpressed ERβ not only attenuated the effects of fenofibrate to induce the levels of apoptosis protein such as Cyt.c, Caspase 9 and Caspase 3 but also inhibited the levels of survival protein such Bcl-xL, p-Bad, cyclin A and cyclin E. All these effects of E₂/ERβ resulted in the enhancement of mitochondria dependent apoptotic pathway and the attenuation of cell proliferation. Moreover, the overexpressed ERβ reduced the mRNA and protein levels of PPARα and its downstream Acyl-CoA oxidase (ACO). EMSA results show that ERβ directly binds to PPRE and inhibit PPARα gene expression and according to immunoprecipitation assay ERβ also binds strongly with PPARα. The E₂/ERβ further inhibited the fenofibrate-induced nuclear translocation of PPARα. Taken together, ERβ might directly downregulate PPARα gene expression and inhibit the nuclear translocation to suppress the proliferation and induce the apoptosis of Hep3B cells.

Inhibition of p38 Mitogen-Activated Protein Kinase Enhances the Apoptosis Induced by Oxidized Low-Density Lipoprotein in Endothelial Progenitor Cells

Oxidized low-density lipoprotein (oxLDL) is an important risk factor in the development of atherosclerosis. oxLDL has been shown to decrease endothelial progenitor cell (EPC) number by inducing apoptosis. p38 mitogen-activated protein kinase (MAPK) was shown to be activated by oxLDL and participated in the regulation of EPC number and function. However, the role of p38 remains unknown. Here, we show that oxLDL-induced p38 phosphorylation in EPCs is time and dose dependent. Treatment with antioxidant N-acetyl cysteine restored oxLDL-induced p38 phosphorylation to basal levels. LOX-1-blocking antibody also significantly decreased oxLDL-induced p38 phosphorylation. Interestingly, TUNEL staining showed that pretreatment with the p38 inhibitor SB203580 further increased oxLDL-induced apoptosis in EPCs. In accordance with these findings, pretreatment with SB203580 further attenuated Akt phosphorylation in EPCs challenged with oxLDL, indicating an interaction between Akt and p38 MAPK pathways. In agreement, inhibition of p38 MAPK further attenuated Akt phosphorylation and increased apoptosis in EPCs isolated from hypercholesterolemic ApoE-/- mice. In conclusion, p38 MAPK serves as an anti-apoptotic pathway by supporting Akt activity when EPCs are challenged with oxLDL.

Contaminant-induced oxidative stress in fish: a mechanistic approach

The presence of reactive oxygen species (ROS) in living organisms was described more than 60 years ago and virtually immediately it was suggested that ROS were involved in various pathological processes and aging. The state when ROS generation exceeds elimination leading to an increased steady-state ROS level has been called "oxidative stress." Although ROS association with many pathological states in animals is well established, the question of ROS responsibility for the development of these states is still open. Fish represent the largest group of vertebrates and they inhabit a broad range of ecosystems where they are subjected to many different aquatic contaminants. In many cases, the deleterious effects of contaminants have been connected to induction of oxidative stress. Therefore, deciphering of molecular mechanisms leading to such contaminant effects and organisms' response may let prevent or minimize deleterious impacts of oxidative stress. This review describes general aspects of ROS homeostasis, in particular highlighting its basic aspects, modification of cellular constituents, operation of defense systems and ROS-based signaling with an emphasis on fish systems. A brief introduction to oxidative stress theory is accompanied by the description of a recently developed classification system for oxidative stress based on its intensity and time course. Specific information on contaminant-induced oxidative stress in fish is covered in sections devoted to such pollutants as metal ions (particularly iron, copper, chromium, mercury, arsenic, nickel, etc.), pesticides (insecticides, herbicides, and fungicides) and oil with accompanying pollutants. In the last section, certain problems and perspectives in studies of oxidative stress in fish are described.

The peroxisome as a cell signaling organelle

Peroxisomes participate in lipid metabolism, and are a major source of ROS in the cell. Their importance in cellular energy balance and redox homeostasis is well-established, as is the need to maintain peroxisome homeostasis to prevent pathologies associated with too few, or too many, of these organelles. How cells regulate peroxisome number has remained somewhat elusive. Recently, the tumor suppressors ATM and TSC, which regulate mTORC1 signaling, have been localized to peroxisomes. When activated by peroxisomal ROS, ATM signals to TSC to repress mTORC1 signaling and increase autophagic flux in cells, and also phosphorylates the peroxisomal protein PEX 5 to target peroxisomes for selective autophagy (pexophagy), providing a mechanism for regulation of peroxisomal homeostasis using ROS as a rheostat.

Di(2-ethylhexyl) phthalate exacerbates non-alcoholic fatty liver in rats and its potential mechanisms

Di(2-ethylhexyl) phthalate (DEHP) may be responsible for inducing alterations similar to those encountered in nonalcoholic fatty liver disease (NAFLD). The aim of the present study was to investigate the detrimental effects and possible mechanisms of DEHP on fatty liver rats directly through triggering the disorder of liver lipid metabolism or indirectly by hepatotoxic effect. Considering these effects, DEHP may play a significant role in the pathogenesis of NAFLD. In this study, high-fat diet was used to induce NAFLD in rats for eight weeks. DEHP treated groups received (0.05, 5, 500 mg/kg daily, respectively) dose by gavage during the whole experiment period. Our results indicated that the detrimental effects of DEHP on high-fat diet induced NAFLDs were mediated via increasing lipid accumulation in the liver and causing lipid peroxidation and inflammation.

Acyl-coenzyme A oxidases 1 and 3 in brown trout (Salmo trutta f. fario): Can peroxisomal fatty acid β-oxidation be regulated by estrogen signaling?

Acyl-coenzyme A oxidases 1 (Acox1) and 3 (Acox3) are key enzymes in the regulation of lipid homeostasis. Endogenous and exogenous factors can disrupt their normal expression/activity. This study presents for the first time the isolation and characterization of Acox1 and Acox3 in brown trout (Salmo trutta f. fario). Additionally, as previous data point to the existence of a cross-talk between two nuclear receptors, namely peroxisome proliferator-activated receptors and estrogen receptors, it was here evaluated after in vitro exposures of trout hepatocytes the interference caused by ethynylestradiol in the mRNA levels of an inducible (by peroxisome proliferators) and a non-inducible oxidase. The isolated Acox1 and Acox3 show high levels of sequence conservation compared to those of other teleosts. Additionally, it was found that Acox1 has two alternative splicing isoforms, corresponding to 3I and 3II isoforms of exon 3 splicing variants. Both isoforms display tissue specificity, with Acox1-3II presenting a more ubiquitous expression in comparison with Acox1-3I. Acox3 was expressed in almost all brown trout tissues. According to real-time PCR data, the highest estrogenic stimulus was able to cause a down-regulation of Acox1 and an up-regulation of Acox3. So, for Acox1 we found a negative association between an estrogenic input and a directly activated PPARα target gene. In conclusion, changes in hormonal estrogenic stimulus may impact the mobilization of hepatic lipids to the gonads, with ultimate consequences in reproduction. Further studies using in vivo assays will be fundamental to clarify these issues.

The Anti-Oxidant and Antitumor Properties of Plant Polysaccharides

Oxidative stress has been increasingly recognized as a major contributing factor in a variety of human diseases, from inflammation to cancer. Although certain parts of signaling pathways are still under investigation, detailed molecular mechanisms for the induction of diseases have been elucidated, especially the link between excessive oxygen reactive species (ROS) damage and tumorigenesis. Emerging evidence suggests anti-oxidant therapy can play a key role in treating those diseases. Among potential drug resources, plant polysaccharides are natural anti-oxidant constituents important for human health because of their long history in ethnopharmacology, wide availability and few side effects upon consumption. Plant polysaccharides have been shown to possess anti-oxidant, anti-inflammation, cell viability promotion, immune-regulation and antitumor functions in a number of disease models, both in laboratory studies and in the clinic. In this paper, we reviewed the research progress of signaling pathways involved in the initiation and progression of oxidative stress- and cancer-related diseases in humans. The natural sources, structural properties and biological actions of several common plant polysaccharides, including Lycium barbarum, Ginseng, Zizyphus Jujuba, Astragalus lentiginosus, and Ginkgo biloba are discussed in detail, with emphasis on their signaling pathways. All of the mentioned common plant polysaccharides have great potential to treat oxidative stress and cancinogenic disorders in cell models, animal disease models and clinical cases. ROS-centered pathways (e.g. mitochondrial autophagy, MAPK and JNK) and transcription factor-related pathways (e.g. NF-[Formula: see text]B and HIF) are frequently utilized by these polysaccharides with or without the further involvement of inflammatory and death receptor pathways. Some of the polysaccharides may also influence tumorigenic pathways, such as Wnt and p53 to play their anti-tumor roles. In addition, current problems and future directions for the application of those plant polysaccharides are also listed and discussed.

Interplay between oxidant species and energy metabolism

It has long been recognized that energy metabolism is linked to the production of reactive oxygen species (ROS) and critical enzymes allied to metabolic pathways can be affected by redox reactions. This interplay between energy metabolism and ROS becomes most apparent during the aging process and in the onset and progression of many age-related diseases (i.e. diabetes, metabolic syndrome, atherosclerosis, neurodegenerative diseases). As such, the capacity to identify metabolic pathways involved in ROS formation, as well as specific targets and oxidative modifications is crucial to our understanding of the molecular basis of age-related diseases and for the design of novel therapeutic strategies.

Herein we review oxidant formation associated with the cell's energetic metabolism, key antioxidants involved in ROS detoxification, and the principal targets of oxidant species in metabolic routes and discuss their relevance in cell signaling and age-related diseases.

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Energy metabolism is both a source and target of oxidant species.

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Reactive oxygen species are formed in redox reactions in catabolic pathways.

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Sensitive targets of oxidant species regulate the flux of metabolic pathways.

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Metabolic pathways and antioxidant systems are regulated coordinately.

Redox regulation of FoxO transcription factors

Transcription factors of the forkhead box, class O (FoxO) family are important regulators of the cellular stress response and promote the cellular antioxidant defense. On one hand, FoxOs stimulate the transcription of genes coding for antioxidant proteins located in different subcellular compartments, such as in mitochondria (i.e. superoxide dismutase-2, peroxiredoxins 3 and 5) and peroxisomes (catalase), as well as for antioxidant proteins found extracellularly in plasma (e.g., selenoprotein P and ceruloplasmin). On the other hand, reactive oxygen species (ROS) as well as other stressful stimuli that elicit the formation of ROS, may modulate FoxO activity at multiple levels, including posttranslational modifications of FoxOs (such as phosphorylation and acetylation), interaction with coregulators, alterations in FoxO subcellular localization, protein synthesis and stability. Moreover, transcriptional and posttranscriptional control of the expression of genes coding for FoxOs is sensitive to ROS. Here, we review these aspects of FoxO biology focusing on redox regulation of FoxO signaling, and with emphasis on the interplay between ROS and FoxOs under various physiological and pathophysiological conditions. Of particular interest are the dual role played by FoxOs in cancer development and their key role in whole body nutrient homeostasis, modulating metabolic adaptations and/or disturbances in response to low vs. high nutrient intake. Examples discussed here include calorie restriction and starvation as well as adipogenesis, obesity and type 2 diabetes.

PPARα signaling in the hippocampus: crosstalk between fat and memory

Major functions of the hippocampus are to generate, organize and store memory. This is a complex process, which is orchestrated by a group of molecules, called plasticity-related molecules. To control these various plasticity-related molecules at the transcriptional level, we have been endowed with cAMP response element-binding protein (CREB), also known as a master regulator of memory. Interestingly, we have seen that this master regulator is regulated at the transcriptional level in the hippocampus by peroxisome proliferator-activated receptor α (PPARα), a nuclear hormone receptor family transcription factor that is known to control the metabolism of fatty acids in the liver, underlying a possible crosstalk between fat and memory. Although liver PPARα does not directly control hippocampal CREB, this opens up an important possibility to improve hippocampal functions and to be resistant to memory loss by PPARα ligands and maintaining normal levels of PPARα in the hippocampus.

Correlation of antiangiogenic, antioxidant and cytotoxic activities of some Sudanese medicinal plants with phenolic and flavonoid contents

BACKGROUND

Consumption of medicinal plants to overcome diseases is traditionally belongs to the characteristics of most cultures on this earth. Sudan has been a host and cradle to various ancient civilizations and developed a vast knowledge on traditional medicinal plants. The present study was undertaken to evaluate the antioxidant, antiangiogenic and cytotoxic activities of six Sudanese medicinal plants which have been traditionally used to treat neoplasia. Further the biological activities were correlated with phytochemical contents of the plant extracts.

METHODS

Different parts of the plants were subjected to sequential extraction method. Cytotoxicity of the extracts was determined by dimethylthiazol-2-yl)- 2,5diphenyl tetrazolium bromide (MTT) assay on 2 human cancer (colon and breast) and normal (endothelial and colon fibroblast) cells. Anti-angiogenic potential was tested using ex vivo rat aortic ring assay. DPPH (1,1-diphenyl-2-picrylhydrazyl) assay was conducted to screen the antioxidant capabilities of the extracts. Finally, total phenolic and flavonoid contents were estimated in the extracts using colorimetric assays.

RESULTS

The results indicated that out of 6 plants tested, 4 plants (Nicotiana glauca, Tephrosia apollinea, Combretum hartmannianum and Tamarix nilotica) exhibited remarkable anti-angiogenic activity by inhibiting the sprouting of microvessels more than 60%. However, the most potent antiangiogenic effect was recorded by ethanol extract of T. apollinea (94.62%). In addition, the plants exhibited significant antiproliferative effects against human breast (MCF-7) and colon (HCT 116) cancer cells while being non-cytotoxic to the tested normal cells. The IC50 values determined for C. hartmannianum, N. gluaca and T. apollinea against MCF-7 cells were 8.48, 10.78 and 29.36 μg/ml, respectively. Whereas, the IC50 values estimated for N. gluaca, T. apollinea and C. hartmannianum against HCT 116 cells were 5.4, 20.2 and 27.2 μg/ml, respectively. These results were more or less equal to the standard reference drugs, tamoxifen (IC50 = 6.67 μg/ml) and 5-fluorouracil (IC50 = 3.9 μg/ml) tested against MCF-7 and HCT 116, respectively. Extracts of C. hartmannianum bark and N. glauca leaves demonstrated potent antioxidant effect with IC50s range from 9.4-22.4 and 13.4-30 μg/ml, respectively. Extracts of N. glauca leaves and T apollinea aerial parts demonstrated high amount of flavonoids range from 57.6-88.1 and 10.7-78 mg quercetin equivalent/g, respectively.

CONCLUSIONS

These results are in good agreement with the ethnobotanical uses of the plants (N. glauca, T. apollinea, C. hartmannianum and T. nilotica) to cure the oxidative stress and paraneoplastic symptoms caused by the cancer. These findings endorse further investigations on these plants to determine the active principles and their mode of action.

Energy metabolism during anchorage-independence. Induction by osteopontin-c

The detachment of epithelial cells, but not cancer cells, causes anoikis due to reduced energy production. Invasive tumor cells generate three splice variants of the metastasis gene osteopontin, the shortest of which (osteopontin-c) supports anchorage-independence. Osteopontin-c signaling upregulates three interdependent pathways of the energy metabolism. Glutathione, glutamine and glutamate support the hexose monophosphate shunt and glycolysis and can feed into the tricarboxylic acid cycle, leading to mitochondrial ATP production. Activation of the glycerol phosphate shuttle also supports the mitochondrial respiratory chain. Drawing substrates from glutamine and glycolysis, the elevated creatine may be synthesized from serine via glycine and supports the energy metabolism by increasing the formation of ATP. Metabolic probing with N-acetyl-L-cysteine, L-glutamate, or glycerol identified differential regulation of the pathway components, with mitochondrial activity being redox dependent and the creatine pathway depending on glutamine. The multiple skewed components in the cellular metabolism synergize in a flow toward two mechanisms of ATP generation, via creatine and the respiratory chain. It is consistent with a stimulation of the energy metabolism that supports anti-anoikis. Our findings imply a coalescence in cancer cells between osteopontin-a, which increases the cellular glucose levels, and osteopontin-c, which utilizes this glucose to generate energy.

Med1 subunit of the mediator complex in nuclear receptor-regulated energy metabolism, liver regeneration, and hepatocarcinogenesis

Several nuclear receptors regulate diverse metabolic functions that impact on critical biological processes, such as development, differentiation, cellular regeneration, and neoplastic conversion. In the liver, some members of the nuclear receptor family, such as peroxisome proliferator-activated receptors (PPARs), constitutive androstane receptor (CAR), farnesoid X receptor (FXR), liver X receptor (LXR), pregnane X receptor (PXR), glucocorticoid receptor (GR), and others, regulate energy homeostasis, the formation and excretion of bile acids, and detoxification of xenobiotics. Excess energy burning resulting from increases in fatty acid oxidation systems in liver generates reactive oxygen species, and the resulting oxidative damage influences liver regeneration and liver tumor development. These nuclear receptors are important sensors of exogenous activators as well as receptor-specific endogenous ligands. In this regard, gene knockout mouse models revealed that some lipid-metabolizing enzymes generate PPARα-activating ligands, while others such as ACOX1 (fatty acyl-CoA oxidase1) inactivate these endogenous PPARα activators. In the absence of ACOX1, the unmetabolized ACOX1 substrates cause sustained activation of PPARα, and the resulting increase in energy burning leads to hepatocarcinogenesis. Ligand-activated nuclear receptors recruit the multisubunit Mediator complex for RNA polymerase II-dependent gene transcription. Evidence indicates that the Med1 subunit of the Mediator is essential for PPARα, PPARγ, CAR, and GR signaling in liver. Med1 null hepatocytes fail to respond to PPARα activators in that these cells do not show induction of peroxisome proliferation and increases in fatty acid oxidation enzymes. Med1-deficient hepatocytes show no increase in cell proliferation and do not give rise to liver tumors. Identification of nuclear receptor-specific coactivators and Mediator subunits should further our understanding of the complexities of metabolic diseases associated with increased energy combustion in liver.

Mode of action framework analysis for receptor-mediated toxicity: The peroxisome proliferator-activated receptor alpha (PPARα) as a case study

Several therapeutic agents and industrial chemicals induce liver tumors in rodents through the activation of the peroxisome proliferator-activated receptor alpha (PPARα). The cellular and molecular events by which PPARα activators induce rodent hepatocarcinogenesis has been extensively studied and elucidated. This review summarizes the weight of evidence relevant to the hypothesized mode of action (MOA) for PPARα activator-induced rodent hepatocarcinogenesis and identifies gaps in our knowledge of this MOA. Chemical-specific and mechanistic data support concordance of temporal and dose-response relationships for the key events associated with many PPARα activators including a phthalate ester plasticizer di(2-ethylhexyl) phthalate (DEHP) and the drug gemfibrozil. While biologically plausible in humans, the hypothesized key events in the rodent MOA, for PPARα activators, are unlikely to induce liver tumors in humans because of toxicodynamic and biological differences in responses. This conclusion is based on minimal or no effects observed on growth pathways, hepatocellular proliferation and liver tumors in humans and/or species (including hamsters, guinea pigs and cynomolgous monkeys) that are more appropriate human surrogates than mice and rats at overlapping dose levels. Overall, the panel concluded that significant quantitative differences in PPARα activator-induced effects related to liver cancer formation exist between rodents and humans. On the basis of these quantitative differences, most of the workgroup felt that the rodent MOA is "not relevant to humans" with the remaining members concluding that the MOA is "unlikely to be relevant to humans". The two groups differed in their level of confidence based on perceived limitations of the quantitative and mechanistic knowledge of the species differences, which for some panel members strongly supports but cannot preclude the absence of effects under unlikely exposure scenarios.