Expression Of Peroxisomal Enzymes Research Articles

Identification and Validation of a PEX5-Dependent Signature for Prognostic Prediction in Glioma.

Gliomas, the most prevalent and lethal form of brain cancer, are known to exhibit metabolic alterations that facilitate tumor growth, invasion, and resistance to therapies. Peroxisomes, essential organelles responsible for fatty acid oxidation and reactive oxygen species (ROS) homeostasis, rely on the receptor PEX5 for the import of metabolic enzymes into their matrix. However, the prognostic significance of peroxisomal enzymes for glioma patients remains unclear. In this study, we elucidate that PEX5 is indispensable for the cell growth, migration, and invasion of glioma cells. We establish a robust prognosis model based on the expression of peroxisomal enzymes, whose localization relies on PEX5. This PEX5-dependent signature not only serves as a robust prognosis model capable of accurately predicting outcomes for glioma patients, but also effectively distinguishes several clinicopathological features, including the grade, isocitrate dehydrogenase (IDH) mutation, and 1p19q codeletion status. Furthermore, we developed a nomogram that integrates the prognostic model with other clinicopathological factors, demonstrating highly accurate performance in estimating patient survival. Patients classified into the high-risk group based on our prognostic model exhibited an immunosuppressive microenvironment. Finally, our validation reveals that the elevated expression of GSTK1, an antioxidant enzyme within the signature, promotes the cell growth and migration of glioma cells, with this effect dependent on the peroxisomal targeting signal recognized by PEX5. These findings identify the PEX5-dependent signature as a promising prognostic tool for gliomas.

Cloning and expression pattern of peroxisomal enzymes in the mussel Mytilus galloprovincialis and in the thicklip grey mullet Chelon labrosus: Generation of new tools to study peroxisome proliferation

Aquatic organisms living in coastal/estuarine areas show peroxisome proliferation after exposure to different environmentally relevant pollutants. In order to generate new tools to assess peroxisome proliferation in aquatic animals, peroxisomal enzymes were cloned using degenerate primers in the mussel Mytilus galloprovincialis and in the thicklip grey mullet Chelon labrosus. Fragments of catalase (CAT), thiolase (THIO), polyamine oxidase (POX) and xanthine oxidoreductase (XOR) were cloned and their expression pattern studied in different tissues by semi-quantitative RT-PCR. In mussels, CAT, THIO, POX and XOR were expressed in digestive gland, mantle and gills while in mullets CAT, THIO and POX were expressed in liver, spleen, brain, heart, muscle and gills. XOR was mainly expressed in liver and heart. Mature mullets showed the highest expression of peroxisomal enzymes in liver, spleen and brain, while in juveniles expression was mainly found in muscle tissues, liver and gills. Laboratory experiments of exposure to organic pollutants are being performed to study the usefulness of these tools to study peroxisome proliferation in pollution biomonitoring programmes.

Effect of dehydroepiandrosterone supplementation on fatty acid and hormone levels in patients with X‐linked adrenoleucodystrophy

In X-linked adrenoleucodystrophy (X-ALD) the peroxisomal beta-oxidation of saturated very long-chain fatty acids (VLCFAs; carbon length > 22 atoms) is impaired. These fatty acids accumulate in blood and tissues, in particular in the nervous system, adrenal cortex and testis. Most patients have a primary adrenocortical insufficiency with low levels of cortisol and dehydroepiandrosterone (DHEA) and its sulphate ester (DHEA-S), collectively called DHEA(S). Surprisingly, very low plasma levels of DHEA(S) may be found when plasma cortisol and ACTH levels are normal. In animal studies DHEA administration had a peroxisome proliferating effect and induced the expression of peroxisomal enzymes involved in the beta-oxidation of fatty acids. To study the effect of DHEA on fatty acids in X-ALD patients, we conducted a randomized double-blind study in which 14 men (age range 21-63 years) and one boy (12 years) received 50 mg of DHEA or placebo for 3 months, followed by a 1-month wash-out period, then 3 months of placebo or vice versa. A significant rise was seen in the plasma levels of DHEA-S, Delta4-androstenedione and IGF-I. The elevated saturated VLCFAs in plasma and erythrocytes did not change. However, in erythrocytes significant decreases were found in the total amount of fatty acids, in C16:0, C18:0 and in C20:4omega-6, C22:5omega-6, C18:1omega-9, C20:1omega-9 and C20:3omega-9. In plasma, decreases were found for C18:1omega-9 and increases for C20:1omega-9. Dehydroepiandrosterone supplementation for 3 months did not lower the elevated plasma levels of saturated very long-chain fatty acids in patients with X-linked adrenoleucodystrophy. Instead, a decrease in saturated and mono- and polyunsaturated fatty acids in erythrocytes and plasma was found. An increase of C20:1omega-9 was found in plasma only.

Therapeutic role of peroxisome proliferator-activated receptors in obesity, diabetes and inflammation.

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear receptor family and play a significant role in regulation of lipid metabolism, hepatic peroxisomal enzyme expression, insulin sensitivity and glucose homeostasis. PPARs have been classified into three subtypes encoded by different genes: PPARalpha (NR1C1), PPARdelta (NR1C2), and PPARgamma (NR1C3). Each subtype of PPARs appears to be differently expressed in a tissue-specific manner because of their binding to specific consensus DNA sequences, known as PPREs (peroxisome proliferator response elements). Thus, PPARs have emerged as potential molecular targets for the design and synthesis of a different class of compounds, considering the conformation of receptors for the treatment of human metabolic disorders. This review covers the rapid progress made in functional analysis of PPARs and progress made towards the identification of ligands for each subtype receptor.

Peroxisome proliferator-activated receptors (PPARs) and peroxisomes in rat cortical and cerebellar astrocytes.

Astrocytes are the most versatile cells of the neural tissue. Numerous astrocytic functions--such as protection from oxidative damage, catabolism of neuroactive D-amino acids acting as neuromodulators, synthesis and catabolism of some lipid molecules, and, possibly, gluconeogenesis--reside in peroxisomes. The expression of several peroxisomal enzymes, particularly those of the acyl-CoA beta-oxidation pathway, is regulated by a class of ligand-activated transcription factors, known as peroxisome proliferator-activated receptors (PPARs), acting on their target genes as heterodimers with the retinoid X receptors (RXRs). In this work, primary and secondary cultures of astrocytes from the cerebral cortices and cerebella of neonatal rats (2 and 7 days of postnatal age) were utilized to investigate the expression of peroxisomal enzymes, PPAR and RXR isotypes (alpha, beta and gamma), by both biochemical and immunological methods. The results obtained demonstrate that astrocytes in vitro express peroxisomal enzymes, PPARs, and RXRs and that differences dependent on brain area, animal age, and culture time are reminiscent of the in vivo situation. Therefore, primary cultures of astrocytes and, particularly, high purified subcultures may constitute a useful model for further studies aimed to gain further insights into the roles of peroxisomes and PPARs related to lipid and glucose metabolism in these cells.

Developmental and pathological expression of peroxisomal enzymes: their relationship of d-bifunctional protein deficiency and Zellweger syndrome

We present the developmental changes of peroxisomal enzymes, catalase, L-bifunctional protein (L-BF) and D-bifunctional protein (D-BF), in the normal brains, and patients with D-BF deficiency, a new peroxisomal disease. D-BF immunoreactivity was observed in controls as early as 13 gestational weeks (GW) and increased with maturation. The adult pattern with fine granule staining of somata and dendrites became apparent in adolescence. L-BF appeared at 20 GW in the cerebral cortex and Purkinje cells and positive glia appeared early in the white matter at 17 GW, and then increased with age. Catalase-positive neurons were identified in the same manner as L-BF, D-BF deficiency in both fetus and infant showed markedly diminished enzyme immunoreactivity. Patients demonstrate reduced D-BF expression. Zellweger syndrome shows decreased expression for the three proteins. This study shows that the peroxisomal enzymes may be closely related to neuronal maturation and gliogenesis in human brain and to disturbance of neuronal migration as seen in Zellweger syndrome significant. D-BF deficiency may exhibit a range of symptoms during the neonatal and early infantile periods some of which may be similar to Zellweger syndrome.

Peroxisome distribution along the crypt-villus axis of the guinea pig small intestine.

Peroxisomes and peroxisomal enzyme expression were investigated biochemically and morphometrically in guinea pig intestinal epithelial cells at different stages of their migration along the crypt-villus axis. Epithelial cells were sequentially isolated along the axis and the specific activities of the peroxisomal enzymes catalase and acyl-CoA oxidase were found to be significantly higher in differentiated and mature cells situated at the villus tip and stem than in the crypt. Conversely, 1-alk-1'enyl, 2-acyl phospholipid (plasmalogen) concentration in the crypt and middle villus was significantly higher than in villus tip cells. Assay of alkyl DHAP synthase and fatty acyl CoA reductase (enzymes responsible for the production of plasmalogen precursors) showed no correlating activity gradient with plasmalogen concentration. Morphometric analysis revealed that peroxisomes were present even in the most immature stem cells, however, their number and volume and surface densities increased as the epithelial cell developed as did the proportion of elongated and vermiform peroxisomes to spherical structures. Senescent cells at the tip of the villus, however, showed a dramatic decrease in number of peroxisomes per cell possibly due to cellular degradation. We conclude that the peroxisomal compartment of the guinea pig small intestinal epithelial cell develops as a function of cell development possibly reflecting adaptation to maximise its metabolic capacity.

Aging and the adrenal cortex.

Aging in humans is accompanied by an increase in adrenal glucocorticoid secretion and a decline in adrenal androgen synthesis and secretion. The intense interest in adrenal function in aging individuals in recent years is in large measure related to the potential impact of cortisol excess in the development of cognitive impairment and hippocampal neuronal loss, and to the desire to provide hormone replacement and healthy aging. Although the preliminary data is tantalizing, solid scientific evidence are not at hand. It is apparent that both issues are extremely complex. Dehydroepiandrosterone (DHEA) and its 3 beta-sulfate are fascinating molecules, including their synthesis and actions in the brain. Recent studies have shown that DHEA-sulfate (DHEA-S), but not DHEA, activates peroxisome proliferator-activated receptor alpha (PPAR alpha) in the liver, an intracellular receptor belonging to the steroid receptor superfamily. Thus, DHEA-S may serve as a physiological modulator of liver fatty acid metabolism and peroxisomal enzyme expression, and thereby may contribute to the anticarcinogenic and chemoprotective properties of this intriguing class of endogenous steroids. The life-sustaining role of adrenal cortisol secretion and its regulation of metabolism via catabolic actions may be modulated by its partner DHEA and DHEA-S. During the anabolic growth period (childhood and early adulthood) the body is exposed to relatively high levels of DHEA/DHEA-S but to relatively or absolutely high levels of cortisol during infancy and the aging phase. The cortisol/DHEA-S ratio during the life span follows a U-shape curve, which may be telling us to explore these two critical adrenal steroids in tandem.

Phytanic acid is a retinoid X receptor ligand.

Metabolic defects in phytanic acid catabolism have been shown to be connected with a number of human diseases which can lead to lethal defects of the nervous system and other organs. These effects are probably a result of the very high accumulation of phytanic acid in tissues throughout the body, due to defects in phytanic acid oxidation, the peroxisome being a major site for this process. The nuclear hormone receptors peroxisome proliferator-activated receptor and retinoid X receptor (RXR) have been shown to function as transcription factors in the control of the peroxisomal enzyme expression. Known activators of peroxisome proliferator-activated receptor include polyunsaturated fatty acids and, for RXR, the 9-cis isomer of retinoic acid. Here we report that phytanic acid is also a natural ligand for RXR alpha, being able to activate a RXR-responsive promoter. We present evidence that phytanic acid binds to RXR alpha, promotes formation of an RXR alpha/RXR response element complex (as detected by gel retardation), and induces a RXR alpha conformational change similar to that induced by 9-cis-retinoic acid (as detected by protease sensitivity). These results suggest an involvement of RXR alpha in the control of fatty acid metabolism and could imply that RXRs have a role in the disease effects resulting from defective phytanic acid catabolism.

Immunohistochemical expression of peroxisomal enzymes in developing human brain.

The immunohistochemistry of peroxisomes was examined in human brains from fetal to adult ages using antibodies against catalase (CAT), acyl-CoA oxidase (AOX), and 3-ketoacyl-CoA thiolase (PT) on conventional formalin-fixed paraffin-embedded sections. Positive staining neurons first appeared in the basal ganglia, thalamus, and cerebellum at 27-28 wk of gestation, and in the frontal cortex at 35-36 wk of gestation. They increased in number with gestational age and the intensity of immunostaining increased with enlargement of perikaryonal size. Positively staining glial cells first appeared in the deep white matter at 31-32 wk of gestation, their appearance showing a shift from the deep to the superficial white matter with increasing age. This developmental change in the peroxisomal immunoreactivities in glial cells corresponds with that in myelination glia. Therefore, the results suggest that peroxisomes are closely related to neuronal growth and myelinogenesis in the developing human brain. Also, our results as to myelinogenesis may explain one pathogenetic factor of dysmyelination in peroxisomal disorders.

Peroxisome through cell differentiation and neoplasia

Peroxisomes are essential in cellular metabolism as their dysgenesis or defects in single enzymes or impairment of multiple peroxisomal enzymatic functions have been found in several inherited metabolic diseases with serious clinical sequelae. The assembly and formation of these cytoplasmic organelles constitute a major and intriguing research topic. In the present study the biogenesis of peroxisomes and the developmental patterns of their enzymes have been reviewed during embryonic and/or post-embryonic ontogenesis of lower (amphibians) and higher (avians, mammals) vertebrates. In developing vertebrates, epithelial cell differentiation is accompanied by increases in frequency and size of peroxisomes. The tissue-specific expression of peroxisomal enzymes contributes substantially to the biochemical maturation of epithelial cells. The relationship between biogenesis of peroxisomes, expression of peroxisomal enzymes and structural and functional cellular phenotype has also been investigated in differentiating epithelial cells along the crypt-villus axis of the adult rat intestine. Cytochemical studies at the ultrastructural level have provided evidence that peroxisomes are already present in proliferating cells of the intestinal crypt region before they begin to differentiate. Migration and differentiation of intestinal epithelial cells from crypt to villus compartments are marked by significant increases in number and size of catalase-positive structures. Increasing activity gradients from crypt to surface areas are found for the peroxisomal oxidases examined (enzymes of the peroxisomal beta-oxidation system, D-amino acid oxidase and polyamine oxidase). Thus, peroxisomes are more and more involved in oxidative metabolic pathways as intestinal epithelial cells differentiate. Finally, we have analyzed the peroxisomal behaviour in human neoplastic epithelial cells. The presence of peroxisomes has been cytochemically revealed in human breast and colon carcinomas. Peroxisomal enzyme specific activities are significantly lower in human breast and colon carcinomas than in the adjacent healthy mucosa. Furthermore, a relationship is found between the specific activities of some peroxisomal enzymes and the histological tumour grades.

Enhancement of peroxisomal enzymes, cytochrome P-452 and DNA synthesis in putative preneoplastic foci of rat liver treated with the peroxisome proliferator nafenopin.

The peroxisome proliferator (PP) nafenopin (NAF) enhanced tumor development in rat liver through promotion of a subtype of putative preneoplastic cell foci, characterized by weak cytoplasmic basophilia. In order to elucidate the selective growth advantage of these weakly basophilic foci (WBF) we investigated the effects of NAF on their metabolic phenotype and DNA synthesis. In WBF, as well as in other foci subpopulations and in hepatocellular carcinomas the occurrence of five NAF-inducible enzymes, i.e. of peroxisomal beta-oxidation (acyl-CoA oxidase, bifunctional protein and thiolase), catalase and cytochrome P-452 was studied by immunohistochemical methods. In untreated livers almost all foci were stained with the same intensity as the surrounding tissue. When NAF was applied, most of the liver foci showed considerably less staining than the non-focal parenchyma in which pronounced enzyme induction had occurred. However, the subpopulation of WBF showed a more heterogeneous pattern of enzyme expression varying from less to even more than in the adjacent tissue. A similarly broad range of expression of peroxisomal enzymes was found in hepatocellular carcinomas. On average, however, the tumors exhibited less staining and lower activity of peroxisomal beta-oxidation than the surrounding parenchyma. WBF always showed higher rates of DNA synthesis than other foci subtypes and unaltered liver. In approximately one-third of these foci DNA synthesis was found to be enhanced concomitantly with elevated expression of peroxisomal beta-oxidation enzymes. In conclusion, WBF may have a selective growth advantage as they 'overrespond' to the inducing effects of NAF on DNA synthesis and peroxisomal enzymes.

Loss of peroxisomal enzyme expression in preneoplastic and neoplastic lesions induced by peroxisome proliferators in rat livers

Immunohistochemical staining of enoyl CoA hydratase (ECH), a key peroxisomal enzyme, revealed that the putative preneoplastic lesions induced in livers by administration of the peroxisome proliferator (PP) clofibrate (0.3% in diet) to rats for 60 weeks or more, lacked this enzyme so that they could be detected as ECH-negative foci. ECH and other peroxisomal enzymes such as acyl CoA oxidase, catalase and carnitine-dependent acetyltransferase were also either not or only weakly expressed in most hepatic hyperplastic nodules and hepatomas induced by ciprofibrate (0.025% in diet), Wy-14,643 (0.1%) or BR-931 (0.2%), while being strongly induced in surrounding hepatocytes. These results indicate that the expression of ECH and other peroxisomal enzymes is repressed in putative preneoplastic and neoplastic lesions induced by PPs in rat livers and that these peroxisomal enzymes might therefore be used as negative markers.