Peroxisome Proliferation In Liver Research Articles

Immunotoxicity of an Electrochemically Fluorinated Aqueous Film-Forming Foam.

Aqueous film-forming foams (AFFFs) are complex per- and polyfluoroalkyl substance (PFAS)-containing mixtures used extensively as fire suppressants. AFFF-impacted groundwater and surface water have contaminated drinking water with PFASs in many communities, raising concerns about health effects from drinking water exposures. As individual PFASs have been identified as immune hazards, the immunotoxicity of complex PFAS mixtures is also a concern. Adult female and male C57BL/6 mice were given a commercial AFFF formulation for 10 days via gavage; administered dose was based on combined content of perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) measured in the formulation (0, 1.88, 3.75, 7.5, or 10 mg PFOS+PFOA/kg body weight). A PFOA positive control of 7.5 mg/kg body weight was also given. Compared with the 0 mg/kg group, the following changes were noted: Body weights of males exposed to 7.5 and 10 mg PFOS+PFOA/kg were reduced by 15%, on average; female body weights did not differ. Average relative liver weights were increased 50%-200% in males and 37.5%-193% in females and liver peroxisome proliferation was increased 2- to 12-fold in all doses of both sexes. Antigen-specific antibody production was suppressed, on average, by 13% in males and by 12.4% in females across all doses. Spleen cellularity and lymphocyte subpopulations did not differ by dose for either sex. Our data indicate that though this complex PFAS mixture contained fairly low PFOA content, it induced changes in C57BL/6 mice similar to changes induced by PFOA alone, likely due to the presence of PFOS and many other PFASs.

The offspring from rats fed a fatty diet display impairments in the activation of liver peroxisome proliferator activated receptor alpha and features of fatty liver disease

Maternal obesity programs liver derangements similar to those of NAFLD. Our main goal was to evaluate whether these liver anomalies were related to aberrant PPARα function. Obesity was induced in female Albino-Wistar rats by a fatty diet (FD rats). Several parameters related to NAFLD were evaluated in both plasma and livers from fetuses of 21 days of gestation and 140-day-old offspring. FD fetuses and offspring developed increased levels of AST and ALT, signs of inflammation and oxidative and nitrative stress-related damage. FD offspring showed dysregulation of Plin2, CD36, Cyp4A, Aco, Cpt-1, Hadha and Acaa2 mRNA levels, genes involved in lipid metabolism and no catabolic effect of the PPARα agonist clofibrate. These results suggest that the FD offspring is prone to develop fatty liver, a susceptibility that can be linked to PPARα dysfunction, and that this could in turn be related to the liver impairments programmed by maternal obesity.

Evaluation of the immunomodulatory effects of 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)-propanoate in C57BL/6 mice.

2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)-propanoate was designed to replace perfluorooctanoic acid (PFOA), which has been mostly phased out of U.S. production due to environmental persistence, detectable human and wildlife serum concentrations, and reports of systemic toxicity. In rodent models, PFOA exposure suppresses T cell-dependent antibody responses (TDAR) and vaccine responses in exposed humans. To determine replacement compound effects on TDAR and related parameters, male and female C57BL/6 mice were gavaged with 0, 1, 10, or 100 mg/kg/day for 28 days. Mice immunized with antigen on day 24 were evaluated for TDAR and splenic lymphocyte subpopulations five days later. Serum and urine were collected for test compound concentrations and liver peroxisome proliferation was measured. Relative liver weight at 10 and 100 mg/kg and peroxisome proliferation at 100 mg/kg were increased in both sexes. TDAR was suppressed in females at 100 mg/kg. T lymphocyte numbers were increased in males at 100 mg/kg; B lymphocyte numbers were unchanged in both sexes. Females had less serum accumulation and higher clearance than males, and males had higher urine concentrations than females at all times and doses. While this PFOA-replacement compound appears less potent at suppressing TDAR relative to PFOA, it produces detectable changes in parameters affected by PFOA; further studies are necessary to determine its full immunomodulatory profile and potential synergism with other per- and polyfluoroalkyl substances of environmental concern.

Antidiabetic, Lipid Normalizing, and Nephroprotective Actions of the Strawberry: A Potent Supplementary Fruit.

The study was designed to assess the effect of different strawberry extracts on glucose levels, lipid profiles, and oxidative stress in nicotinamide-streptozotocin (NIC-STZ) induced diabetic rats. The associated changes were evaluated through biochemical, molecular, and histological assays. Diabetes was induced by intraperitoneal injection of STZ to albino Wistar rats after treatment with nicotinamide. Aqueous, hydroalcoholic, and alcoholic strawberry extracts were administrated orally to diabetic rats. Treatment of strawberry extracts improved lipid profile, liver function, and serum creatinine and led to a significant increase in antioxidant status in diabetic rats. Real-time PCR expression analysis of genes from the liver of animals treated with strawberry extracts exhibited downregulation of several fatty acid synthesis genes, transcription factors, such as Sterol regulatory Element Binding Transcription factor (SREBP) and Nuclear Factor-κβ (NF-κβ), and inflammatory markers, like Interleukin 6 (IL6) and Tumor Necrosis Factor-α (TNF-α). Strawberry extracts also upregulated liver Peroxisome Proliferator Activated Receptor-γ (PPAR-γ). Histological examination confirmed the nephroprotective and β-cell regeneration/protection effects of strawberry extracts. The present study demonstrates several beneficial effects of strawberry extracts along with its probable mechanism of action.

Energy sensing pathways differentially regulate peroxisomes in skeletal muscle vs. liver

Peroxisomes in skeletal muscle have the potential to combat lipid‐induced insulin resistance by providing an alternate route for lipid disposal which could reduce buildup of lipotoxic species while concomitantly limiting mitochondrial lipid overload. While much is known about regulation of peroxisomes in liver, there is limited information defining regulation of peroxisomes in skeletal muscle. These studies were designed to gain an understanding of peroxisomal regulation in skeletal muscle. Results indicate peroxisomes in rodent skeletal muscle were virtually unresponsive to ‘traditional’ stimuli that induce peroxisome proliferation in liver, such as peroxisome proliferator‐activated receptor (PPAR) agonists and lipid exposure. Alternatively, peroxisomal markers increased in skeletal muscle in response to dietary methionine restriction and caloric restriction. Interestingly, this response was specific to skeletal muscle as peroxisomal markers in the liver were decreased in response to these dietary manipulations. Since many beneficial effects incurred by caloric restriction are reported to be mediated via activation of energy sensing pathways, we further examined whether AMPK or sirtuin 1 (Sirt1) mediate tissue‐specific peroxisomal regulation. In support of this concept, pharmacological activation of AMPK (AICAR) and Sirt1 (resveratrol) enhanced peroxisomal genes in C2C12 myotubes, but decreased genes in AML‐12 hepatocytes. Initial findings point toward PGC1a as a potential downstream integration point mediating these effects in skeletal muscle. Overall, these findings support a model wherein skeletal muscle peroxisomes are uniquely responsive to energy status signals and interventions that activate these pathways, such as caloric restriction, exercise, cold exposure, etc., may mediate some of their therapeutic action via upregulation of peroxisomes in skeletal muscle.Support or Funding InformationThis work utilized the Genomics Core facilities at PBRC which is supported in part by COBRE (NIH 8 P20‐GM103528) and NORC (NIH 2P30‐DK072476) center grants from the National Institutes of Health. This research was also supported by NIH grants R01DK103860 (R.C.N.), R01DK089641 (R.L.M.), and a pilot and feasibility grant from NORC 2P30‐DK072476 (R.C.N.). Also, S.E.F. is supported by T32 fellowship NIH T32 AT004094.

Chimeric mice with hepatocyte-humanized liver as an appropriate model to study human peroxisome proliferator-activated receptor-α.

Peroxisome proliferator (PP)-activated receptor-α (PPARα) agonists exhibit species-specific effects on livers of the rodent and human (h), which has been considered to reside in the difference of PPARα gene structures. However, the contribution of h-hepatocytes (heps) to the species-specificity remains to be clarified. In this study, the effects of fenofibrate were investigated using a hepatocyte-humanized chimeric mouse (m) model whose livers were replaced with h-heps at >70%. Fenofibrate induced hepatocellular hypertrophy, cell proliferation, and peroxisome proliferation in livers of severe combined immunodeficiency (SCID) mice, but not in the h-hep of chimeric mouse livers. Fenofibrate increased the expression of the enzymes of β- and ω-hydroxylation and deoxygenation of lipids at both gene and protein levels in SCID mouse livers, but not in the h-heps of chimeric mouse livers, supporting the studies with h-PPARα-transgenic mice, a hitherto reliable model for studying the regulation of h-PPARα in the h-liver in most respects, except the induction of the peroxisome proliferation. This study indicates the importance of not only h-PPARα gene but also h-heps themselves to correctly predict effects of fibrates on h-livers, and, therefore, suggests that the chimeric mouse is a currently available, consistent, and reliable model to obtain pharmaceutical data concerning the effects of fibrates on h-livers.

Growth, serum biochemistry, complement activity, and liver gene expression responses of Pekin ducklings to graded levels of cultured aflatoxin B1

A 14-d study was conducted to evaluate the effects of cultured aflatoxin B1 (AFB1) on performance, serum biochemistry, serum natural antibody and complement activity, and hepatic gene expression parameters in Pekin ducklings. A total of 144 male Pekin ducklings were weighed, tagged, and randomly allotted to 4 dietary treatments containing 4 concentrations of AFB1 (0, 0.11, 0.14, and 0.21 mg/kg) from 0 to 14 d of age (6 cages per diet; 6 ducklings per cage). Compared with the control group, there was a 10.9, 31.7, and 47.4% (P < 0.05) decrease in cumulative BW gain with 0.11, 0.14, and 0.21 mg of AFB1/kg of diet, respectively, but feed efficiency was not affected. Increasing concentrations of AFB1 reduced cumulative BW gain and feed intake both linearly and quadratically, and regression equations were developed with r2 ≥0.73. Feeding 0.11 to 0.21 mg of AFB1/kg reduced serum glucose, creatinine, albumin, total protein, globulin, Ca, P, and creatine phosphokinase linearly, whereas serum urea N, Cl, alkaline phosphatase, and aspartate amino transferase concentrations increased linearly with increasing AFB1 (P < 0.05). Additionally, 0.11 to 0.21 mg of AFB1/kg diets impaired classical and alternative complement pathways in the duckling serum when tested by lysis of rabbit, human type O, and horse erythrocytes, and decreased rabbit and horse agglutinins (P < 0.05). Liver peroxisome proliferator activated receptor α (PPARα) expression was linearly downregulated by AFB1 (P < 0.01). Results from this study indicate that for every 0.10 mg/kg increase in dietary AFB1, cumulative feed intake and BW gain decrease approximately 230 and 169 g per duckling from hatch to 14 d; and that AFB1 at very low concentrations can significantly impair liver function and gene expression, and innate immune dynamics in Pekin ducklings.

PPARα Activation Induces Nε‐Lys‐Acetylation of Rat Liver Peroxisomal Multifunctional Enzyme Type 1

Peroxisomes are ubiquitous subcellular organelles that participate in metabolic and disease processes, with few of its proteins undergoing posttranslational modifications. As the role of lysine-acetylation has expanded into the cellular intermediary metabolism, we used a combination of differential centrifugation, organelle isolation by linear density gradient centrifugation, western blot analysis, and peptide fingerprinting and amino acid sequencing by mass spectrometry to investigate protein acetylation in control and ciprofibrate-treated rat liver peroxisomes. Organelle protein samples isolated by density gradient centrifugation from PPARα-agonist treated rat liver screened with an anti-N(ε)-acetyl lysine antibody revealed a single protein band of 75 kDa. Immunoprecipitation with this antibody resulted in the precipitation of a protein from the protein pool of ciprofibrate-induced peroxisomes, but not from the protein pool of non-induced peroxisomes. Peptide mass fingerprinting analysis identified the protein as the peroxisomal multifunctional enzyme type 1. In addition, mass spectrometry-based amino acid sequencing resulted in the identification of unique peptides containing 4 acetylated-Lys residues (K¹⁵⁵, K¹⁷³, K¹⁹⁰, and K⁵⁸³). This is the first report that demonstrates posttranslational acetylation of a peroxisomal enzyme in PPARα-dependent proliferation of peroxisomes in rat liver.

In vivo actions of peroxisome proliferator-activated receptors: glycemic control, insulin sensitivity, and insulin secretion.

Peroxisome proliferator–activated receptors (PPARs) form a family of nuclear hormone receptors involved in energy hemostasis and lipid metabolism (1,2) and include three isotypes encoded by different genes: PPARα (chromosome 22q12–13.1), PPARβ/δ (chromosome 6p21.2–21.1), and PPARγ (chromosome 3p25). PPARα was the first discovered and causes cellular peroxisome proliferation in rodent livers (3), giving this receptor family its name. Upon activation, PPARs interact with retinoid X receptor to create heterodimers, which bind to a specific DNA sequence motif termed peroxisome proliferator response element (4). Peroxisome proliferator response element usually appears in promoter regions and is constructed from repeats of nucleotide sequence AGGTCA separated by a single nucleotide. PPARα is widely expressed in tissues with high fatty acid catabolic activity: brown fat, heart, liver, kidney, and intestine (5). Upon activation by endogenous fatty acids and their derivatives, PPARα mediates fatty acid catabolism, gluconeogenesis, and ketone body synthesis, mainly in liver (6–9). In rodents, PPARα activation also influences immune modulation (10,11) and amino acid metabolism (12), reduces plasma triglyceride, reduces muscle and liver steatosis, and ameliorates insulin resistance (IR) (13,14). Pharmacologic PPARα activation is achieved by fibrates (7) and results in reduced (30–50%) triglyceride and VLDL levels by increasing lipid uptake, lipoprotein lipase–mediated lipolysis, and β-oxidation (15). This is accompanied by a modest increase in HDL cholesterol (5–20%), secondary to transcriptional induction of apolipoprotein A-I/A-II synthesis in liver (15). In man, the primary effect of PPARα is to reduce plasma triglyceride concentration; effects on plasma free fatty acid (FFA) concentration/FFA oxidation, muscle/liver fat content, and muscle/hepatic insulin sensitivity have not been demonstrated with current PPARα agonists such as fenofibrate (16,17). Fibrates are used to treat severe hypertriglyceridemia and combined hyperlipidemia (18–20). Clinical trials to establish a role for PPARα agonists (fenofibrate, gemfibrozil) …

Comparative gene expression profiles induced by PPARγ and PPARα/γ agonists in rat hepatocytes

Species-differential toxic effects have been described with PPARα and PPARγ agonists between rodent and human liver. PPARα agonists (fibrates) are potent hypocholesterolemic agents in humans while they induce peroxisome proliferation and tumors in rodent liver. By contrast, PPARγ agonists (glitazones) and even dual PPARα/γ agonists (glitazars) have caused idiosyncratic hepatic and nonhepatic toxicities in human without evidence of any damage in rodent during preclinical studies. The mechanisms involved in such differences remain largely unknown. Several studies have identified the major target genes of PPARα agonists in rodent liver while no comprehensive analysis has been performed on gene expression changes induced by PPARγ and dual PPARα/γ agonists. Here, we investigated transcriptomes of rat hepatocytes after 24 h treatment with two PPARγ (troglitazone and rosiglitazone) and two PPARα/γ (muraglitazar and tesaglitazar) agonists. Although, hierarchical clustering revealed a gene expression profile characteristic of each PPAR agonist class, only a limited number of genes was specifically deregulated by glitazars. Functional analyses showed that many genes known as PPARα targets were also modulated by both PPARγ and PPARα/γ agonists and quantitative differences in gene expression profiles were observed between these two classes. Moreover, most major genes modulated in rat hepatocytes were also found to be deregulated in rat liver after tesaglitazar treatment. Taken altogether, these results support the conclusion that differential toxic effects of PPARα and PPARγ agonists in rodent liver do not result from transcriptional deregulation of major PPAR target genes but rather from qualitative and/or quantitative differential responses of a small subset of genes.

Soybean diet modulates acetyl-coenzyme A carboxylase expression in livers of rats recovering from early-life malnutrition

Objective The present study evaluated the effect of nutritional recovery with a soybean diet on the gene and protein expressions and protein phosphorylation of several enzymes and transcription factors involved in hepatic lipid metabolism. Methods Rats from mothers fed with 17% or 6% protein (casein) during pregnancy and lactation were maintained with a 17% casein (CC and LC groups) or soybean (CS and LS groups) diet and with a 6% casein (LL group) diet until 90 d of life. Results The soybean diet enhanced serum insulin levels but decreased body and liver weights and hepatic lipid and glycogen concentrations. Liver peroxisome proliferator receptor-α mRNA abundance was higher in the LS and CS groups than in the LC and CC groups, but the protein content was similar in all groups. Hepatic acetyl-coenzyme A carboxylase (ACC)-α and ACCβ mRNA expression was markedly lower in the LS and CS rats than in the LC and CC rats. ACC protein expression was lower in the CS group than in the CC, LC, and LS groups. Phospho-[Ser 79]2-ACC content was similar in the CS, LC, and LS groups and lower than the CC group. In the CS rats this reduction paralleled the decrease in total ACC protein. Messenger RNA and protein expression of sterol regulatory element-binding protein 1c, adenosine monophosphate-activated protein kinase, and phospho-[Thr 172]-adenosine monophosphate-activated protein kinase was not modified by the soybean diet. Conclusion Thus, the soybean diet reduced the liver lipid concentration through downregulation of the ACC gene and protein expressions rather than by phosphorylation status, which possibly resulted in decreased lipogenesis and increased β-oxidation.

Perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA) and their salts Scientific Opinion of the Panel on Contaminants in the Food chain.

Perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA) and their salts Scientific Opinion of the Panel on Contaminants in the Food chain.

PPAR alpha, more than PPAR delta, Mediates the Hepatic and Skeletal Muscle Alterations Induced by the PPAR Agonist GW0742

Therapeutic use of certain peroxisome proliferator-activated receptor (PPAR) alpha agonists (fibrates) for the treatment of dyslipidemia has infrequently been associated with the untoward side effect of myopathy. With interest in PPAR-delta as a therapeutic target, this study assessed whether a PPAR-delta agonist induced similar hepatic and skeletal muscle alterations as noted with some fibrates. PPAR-alpha null (KO) and corresponding wild-type (WT) mice were administered toxicological dosages of a potent PPAR-delta agonist tool ligand (GW0742; which also has weak PPAR-alpha agonist activity) or a potent PPAR-alpha agonist (WY-14,643) for 10 days. Increases in liver weights and clinical chemistry indicators of skeletal muscle damage and/or liver injury were more pronounced in WT mice compared with KO mice administered the PPAR-delta agonist. Likewise, the incidence and severity of skeletal myopathy were greater in WT mice given GW0742 compared with KO mice. Ultrastructural and immunohistochemical analyses revealed significant peroxisome proliferation in muscle and liver of WT mice treated with each agonist; however, KO animals showed little or no evidence of hepatic and muscle peroxisome proliferation. PMP-70 protein expression in liver was consistent with these results. The hepatomegaly, hepatic and skeletal muscle peroxisome proliferation, and skeletal myopathy induced by this PPAR-delta ligand was predominantly mediated by its cross-activation of PPAR-alpha, though PPAR-delta agonism contributed slightly to these effects.

Administration of ciprofibrate to lactating mothers induces PPAR α-signaling pathway in the liver and kidney of suckling rats

It is well known that the hypolipidemic drug ciprofibrate induces peroxisome proliferation in rodent liver, which in turn leads to the oxidative stress, and modifies some parameters related to cell proliferation and apoptosis. The administration of ciprofibrate to rats during the lactating period determined in their pups significant modifications in hepatic peroxisome enzyme activities, induction of the PPAR α-target gene, Cyp4a10, and perturbation in cell proliferation and apoptosis, which affected the size of the liver. Moreover, this modification was associated to about two-fold induction of mRNA-PPAR α. On the contrary, in the kidney, although a similar two-fold up-regulation of PPAR α was detected, the induction of both peroxisomal enzyme activities and Cyp4a10 were weak, and no alterations were detected, neither in cell cycle nor in the size of the tissue. Our results indicate that the response to ciprofibrate is stronger in the liver than in the kidney of newborn rats.

Emerging endocrine disrupters: perfluoroalkylated substances

In recent years, polyfluorinated chemicals (PFCs) have increasingly been used as surfactants in various industry- and consumer products, because of their unique properties as repellents of dirt, water and oils. The most well-known PFCs are perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA) and their derivatives belonging to the group of perfluoroalkylated substances. The PFCs are very persistent in the environment, and some of them have been discovered as global pollutants of air, water, soil and wildlife and even found in remote polar areas. Bioaccumulation occurs also in humans, and everybody in our society has traces of these PFCs in their blood and internal organs such as the liver, kidneys, spleen, gall bladder and testes. In the blood, PFOS and PFOA are bound to serum proteins. The acute toxicity of the polyfluorinated substances is moderate but some substances can induce peroxisome proliferation in rat livers and may change the fluidity of cell membranes. Some of these PFCs, such as PFOS and PFOA, are potential developmental toxicants and are suspected endocrine disruptors with effects on sex hormone levels resulting in lower testosterone levels and higher oestradiol level. Other PFCs have oestrogenic effects in cell cultures. The industrial production of PFOS and its derivatives stopped in 2000, and the European Union has banned most uses from the summer of 2008. However, hundreds of related chemicals: homologues with shorter or longer alkyl chain, PFOA and telomers, which potentially may degrade to perfluoroalkanoic (carboxylic) acids, are not regulated.

WY-14,643–Induced Cell Proliferation and Oxidative Stress in Mouse Liver are Independent of NADPH Oxidase

Long-term exposure of rodents to peroxisome proliferators leads to increases in peroxisomes, hepatocellular proliferation, oxidative damage, suppressed apoptosis, and ultimately results in the development of hepatic adenomas and carcinomas. Peroxisome proliferators-activated receptor (PPAR)alpha was shown to be required for these pleiotropic responses; however, Kupffer cells, resident liver macrophages, were also identified as playing a role in peroxisome proliferators-induced effects, independently of PPARalpha. Previous studies showed that oxidants from NADPH (nicotinamide adenine dinucleotide phosphate, reduced) oxidase mediate acute effects of peroxisome proliferators in rodent liver. To determine if Kupffer cell oxidants are also involved in chronic effects, NADPH oxidase-deficient (p47(phox)-null) mice were fed 4-chloro-6-(2,3-xylidino)-2-pyrimidinylthio acetic acid (WY-14,643)-containing diet (0.1% wt/wt) for 1 week, 5 weeks, or 5 months along with Pparalpha-null and wild type mice. As expected, no change in liver size, cell replication rates, or other phenotypic effects of peroxisome proliferators were observed in Pparalpha-null mice. Through 5 months of treatment, the p47(phox)-null and wild type mice exhibited peroxisome proliferators-induced adverse liver effects, along with increased oxidative DNA damage and increased cell proliferation, a response that is potentially mediated through nuclear factor kappa B (NFkB). Suppressed apoptosis caused by WY-14,643 was dependent on both NADPH oxidase and PPARalpha. Collectively, these findings suggest that involvement of Kupffer cells in WY-14,643-induced parenchymal cell proliferation and oxidative stress in rodent liver is an acute phenomenon that is not relevant to long-term exposure, but they are still involved in chronic apoptotic responses. These results provide new insight for understanding the mode of hepatocarcinogenic action of peroxisome proliferators.

Sustained formation of α-(4-pyridyl-1-oxide)- N-tert-butylnitrone radical adducts in mouse liver by peroxisome proliferators is dependent upon peroxisome proliferator-activated receptor-α, but not NADPH oxidase

Reactive oxygen species are thought to be crucial for peroxisome proliferator-induced liver carcinogenesis. Free radicals have been shown to mediate the production of mitogenic cytokines by Kupffer cells and cause DNA damage in rodent liver. Previous in vivo experiments demonstrated that acute administration of the peroxisome proliferator di(2-ethylhexyl) phthalate (DEHP) led to an increase in production of α-(4-pyridyl-1-oxide)- N-tert-butylnitrone (POBN) radical adducts in liver, an event that was dependent on Kupffer cell NADPH oxidase, but not peroxisome proliferator-activated receptor (PPAR)α. Here, we hypothesized that continuous treatment with peroxisome proliferators will cause a sustained formation in POBN radical adducts in liver. Mice were fed diets containing either 4-chloro-6-(2,3-xylidino)-2-pyrimidinylthioacetic acid (WY-14,643, 0.05% w/w) or DEHP (0.6% w/w) for up to 3 weeks. Liver-derived radical production was assessed in bile samples by measuring POBN radical adducts using electron spin resonance. Our data indicate that WY-14,643 causes a sustained increase in POBN radical adducts in mouse liver and that this effect is greater than that of DEHP. To understand the molecular source of these radical species, NADPH oxidase-deficient ( p47 phox -null) and PPARα-null mice were examined after treatment with WY-14,643. No increase in radicals was observed in PPARα -null mice that were treated with WY-14,643 for 3 weeks, while the response in p47 phox -nulls was similar to that of wild-type mice. These results show that PPARα, not NADPH oxidase, is critical for a sustained increase in POBN radical production caused by peroxisome proliferators in rodent liver. Therefore, peroxisome proliferator-induced POBN radical production in Kupffer cells may be limited to an acute response to these compounds in mouse liver.

Effects of dibutylphthalate and ethynylestradiol on liver peroxisomes, reproduction, and development of zebrafish (Danio rerio)

The aim of the present work was to study the effects of the peroxisome proliferator dibutylphthalate (DBP) and the xenoestrogen 17alpha-ethynylestradiol (EE2) on liver peroxisomes, reproduction, and development of zebrafish (Danio rerio). In experiment 1, newly fertilized zebrafish eggs were exposed for five weeks, covering the entire period of sexual determination, to nominal concentrations of 25 and 100 microg/L of DBP and 5 microg/L of EE2. In experiment 2, adult female zebrafish were exposed for 15 d to 100 and 500 microg/L of DBP and 5 microg/L of EE2, and afterward, they were paired with untreated males to study the effects in the resultant offspring. Ethynylestradiol provoked marked mortality (approximately 50%) and delayed development of larvae as well as sterility of adult females, possibly related to alterations in aromatase gene expression. Ethynylestradiol up-regulated vitellogenin expression in the early life stages and increased vitellogenin synthesis and accumulation in adult females. Ethynylestradiol caused liver peroxisome proliferation in early life stages but not in adult females. Dibutylphthalate caused teratogenic effects in early life stages and mortality of the larvae obtained from exposed females. Dibutylphthalate provoked liver peroxisome proliferation and up-regulation of cytochrome P450A1 in early life stages at the end of the exposure and in adult females. Dibutylphthalate also up-regulated the expression of aromatase genes. In conclusion, the xenoestrogen EE2 caused liver peroxisome proliferation in early life stages of zebrafish, but the peroxisome proliferator DBP did not behave as a typical xenoestrogen. Overall, changes in gene expression were more marked during early life stages than in adult female zebrafish.

Effects of selected xenoestrogens on liver peroxisomes, vitellogenin levels and spermatogenic cell proliferation in male zebrafish

Environmental estrogenic compounds or xenoestrogens can mimic natural estrogens and cause a variety of adverse effects on aquatic wildlife. The purpose of the present work was to investigate if xenoestrogens are able to cause proliferation of liver peroxisomes using zebrafish ( Danio rerio) as a model. Adult male zebrafish were exposed for 15 days to 17 β-estradiol (E2) and the xenoestrogens dibutylphthalate (DBP), methoxychlor (MXC), 4-tert-octylphenol (OP) and 17 α-ethynylestradiol (EE2). All five tested compounds caused significant proliferation of liver peroxisomes ( p < 0.05) as indicated by increased peroxisomal surface and numerical densities and elevated activities of the peroxisomal β-oxidation enzyme acyl-CoA oxidase (AOX). In the case of DBP, MXC and E2, positive significant correlations between peroxisomal density parameters and AOX were found. The treatments did not produce gross alterations in testis histology, but spermatogenic cell proliferation was disturbed in E2 and EE2-treated groups and vitellogenin levels increased significantly in fish exposed to MXC, OP, EE2 and E2 with respect to controls. Furthermore, a significant correlation between vitellogenin levels and AOX activity was found for MXC, OP and EE2 treatments, suggesting that for the latter xenoestrogens early estrogenic effects are associated with liver peroxisome proliferation. No such association occurred with typical peroxisome proliferators such as DBP.

Peroxisome Proliferation in Liver of Rats Fed Oxidized Frying Oil

Oxidized frying oil (OFO) activates peroxisome proliferator-activated receptor a (PPAR alpha) in vitro and in vivo. As most PPARalpha activators are also peroxisome proliferators (PP), this study was aimed at exploring whether OFO induces peroxisome proliferation in the liver of rats. Four groups of male weanling Sprague-Dawley rats were fed the following diets for 6 wk: a basal diet containing 5 g/100 g fresh soybean oil (LSB), high-fat diets containing 20 g/100 g of fresh soybean oil (HSB as a control). OFO (HO) or fish oil (HF, as a positive control). Hepatomegaly and peroxisome proliferation in the liver of the HO group of rats were higher than those of the HF group. In addition, the acyl-CoA oxidase (ACO) activity, as well as cytochrome P450 4A (CYP4A) protein content in the livers of the HO group were 6 fold those of the HSB group, but were 2.5 fold in those of the HF group. These results indicated that dietary OFO induced typical responses to PPARalpha signaling. Moreover. as a dietary source, the OFO prepared under our frying conditions appears to be a more potent peroxisome proliferator than fish oil.