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Biomedical subjects

O Viñas

Publications and source records attributed to O Viñas.

At least 19 recordsLinked to original sources

Uncoupling protein-3 gene expression in skeletal muscle during development is regulated by nutritional factors that alter circulating non-esterified fatty acids.

Uncoupling protein-3 gene expression in skeletal muscle is up-regulated during postnatal development of mice. A high-carbohydrate diet at weaning induces a decrease in uncoupling protein-3 mRNA levels that does not occur when mice were weaned onto a high-fat diet. Uncoupling protein-3 mRNA levels do not increase in response to fasting in young pups. Only after day 15 of life, when fasting increases serum non-esterified fatty acids, uncoupling protein-3 mRNA is up-regulated by starvation. Over-nutrition or under-nutrition during lactation increases or decreases, respectively, uncoupling protein-3 mRNA expression in skeletal muscle. Regulation of uncoupling protein-3 gene expression in skeletal muscle during development is mediated by ontogenic and nutritional factors determining changes in circulating non-esterified fatty acids.

Age Factors

Activators of peroxisome proliferator-activated receptor-alpha induce the expression of the uncoupling protein-3 gene in skeletal muscle: a potential mechanism for the lipid intake-dependent activation of uncoupling protein-3 gene expression at birth.

The recently identified uncoupling protein-3 (UCP-3) gene, predicted to encode a new member of the family of uncoupling proteins, is preferentially expressed in skeletal muscle and has been related to phenotypes of obesity and type 2 diabetes. We have established that during mouse ontogeny, the expression of the UCP-3 gene is switched on in skeletal muscle just after birth. The induction of UCP-3 gene expression is dependent on the initiation of suckling and particularly on lipid intake. Treatment of newborn mice with activators of peroxisome proliferator-activated receptors (PPARs), such as clofibrate, bezafibrate, or (4-chloro-6-(2,3-xylidine)-pirimidinylthio)acetic acid (WY 14,643), mimics the action of food intake on UCP-3 gene expression. The specific ligand of PPAR-alpha WY 14,643 induces UCP-3 gene expression in a time- and dose-dependent manner, whereas the thiazolidinedione BRL 49653, specific for PPAR-gamma, has no effect. These treatments act without altering circulating free fatty acids. During development, skeletal muscle expresses constitutive levels of PPAR-delta mRNA, whereas expression of the PPAR-gamma gene is undetectable. PPAR-alpha gene expression is developmentally regulated in muscle as it is first expressed at birth, just before UCP-3 gene induction occurs. The induction of UCP-3 gene expression by WY 14,643 is impaired in skeletal muscle of premature neonates, which do not express PPAR-alpha. It is proposed that the UCP-3 gene is predominantly regulated in neonatal muscle by PPAR-alpha activation.

Animals

9-cis retinoic acid induces the expression of the uncoupling protein-2 gene in brown adipocytes.

The expression of uncoupling protein-2 (UCP2) mRNA is up-regulated during the differentiation of brown adipocytes in primary culture. When differentiation of brown adipocytes is impaired, UCP2 mRNA expression is down-regulated. 9-cis Retinoic acid causes a dose-dependent induction of UCP2 mRNA levels in brown adipocytes, whereas all-trans retinoic acid has no effect. Specific agonists of retinoid X receptors (RXR) induce UCP2 mRNA expression, whereas specific activators of retinoic acid receptors do not. 9-cis Retinoic acid, acting through RXR receptors, is identified as a major regulator of the expression of the UCP2 gene in the brown fat cell.

Adipocytes

Regulation of mitochondrial biogenesis in brown adipose tissue: nuclear respiratory factor-2/GA-binding protein is responsible for the transcriptional regulation of the gene for the mitochondrial ATP synthase beta subunit.

The regulation of transcription of the gene for the beta subunit of the FoF1 ATP synthase (ATPsynbeta) in brown adipose tissue has been studied as a model to determine the molecular mechanisms for mitochondrial biogenesis associated with brown adipocyte differentiation. The expression of the ATPsynbeta mRNA is induced during the brown adipocyte differentiation that occurs during murine prenatal development or when brown adipocytes differentiate in culture. This induction occurs in parallel with enhanced gene expression for other nuclear and mitochondrially-encoded components of the respiratory chain/oxidative phosphorylation system (OXPHOS). Transient transfection assays indicated that the expression of the ATPsynbeta gene promoter is higher in differentiated HIB-1B brown adipocytes than in non-differentiated HIB-1B cells. A major transcriptional regulatory site was identified between nt -306 and -266 in the ATPsynbeta promoter. This element has a higher enhancer capacity in differentiated brown adipocyte HIB-1B cells than in non-differentiated cells. Electrophoretic shift analysis indicated that Sp1and nuclear respiratory factor-2/GA-binding protein (NRF2/GABP) were the main nuclear proteins present in brown adipose tissue that bind this site. Double-point mutant analysis indicated a major role for the NRF2/GABP site in the enhancer capacity of this element in brown fat cells. It is proposed that NRF2/GABP plays a pivotal role in the co-ordinated enhancement of OXPHOS gene expression associated with mitochondrial biogenesis in brown adipocyte differentiation.

Adipose Tissue, Brown

Differential regulation of uncoupling protein-2 and uncoupling protein-3 gene expression in brown adipose tissue during development and cold exposure.

The expression of the two novel uncoupling proteins genes, UCP2 and UCP3, is differentially regulated during prenatal maturation of brown adipose tissue in the mouse. UCP2 gene is expressed early in prenatal development, when neither UCP1 nor UCP3 gene expression yet occurs. UCP3 mRNA is absent at any stage of fetal life; it appears suddenly at birth and reaches adult levels in a few hours. UCP2 mRNA increased after birth but more slowly than UCP3 and UCP1 mRNA. Short-time exposure of adult mice to cold caused a rise in UCP2 or UCP1 mRNA levels but not in that of UCP3. The postnatal rise in UCP2 gene expression appears to be a response to the thermic stress associated with birth, similarly to UCP1, whereas different biological signals may be responsible for the surge in UCP3 gene expression at birth.

Adipose Tissue, Brown

Muscle/heart isoform of mitochondrial adenine nucleotide translocase (ANT1) is transiently expressed during perinatal development in rat liver.

A postnatal increase in the content of mitochondrial ANT in rat liver which is related to the maturation of mitochondrial function has previously been reported [Schönfeld et al., Biochim. Biophys Acta 1144 (1993) 353-358]. In order to define the contribution of the ANT isoforms to this postnatal increase we have studied the expression of ANT1 and ANT2 isoforms in the liver during this period. The results show that in contrast to adult liver, perinatal liver expressed the ANT1 isoform at the mRNA and protein level, and that during this period the expression of ANT1 increased to a similar extent as total ANT content. It is concluded that the postnatal increase in ANT is mainly due to the ANT1 isoform and therefore, a role for the ANT1 isoform in the postnatal maturation of mitochondrial respiration in rat liver is suggested.

Animals

Dominant negative regulation by c-Jun of transcription of the uncoupling protein-1 gene through a proximal cAMP-regulatory element: a mechanism for repressing basal and norepinephrine-induced expression of the gene before brown adipocyte differentiation.

The brown fat uncoupling protein-1 (ucp-1) gene is regulated by the sympathetic nervous system, and its transcription is stimulated by norepinephrine, mainly through cAMP-mediated pathways. Overexpression of the catalytic subunit of protein kinase A stimulated a chloramphenicol acetyltransferase expression vector driven by the 4.5-kb 5'-region of the rat ucp-1 gene. Mutant deletion analysis indicated the presence of the main cAMP-regulatory element (CRE) in the proximal region between -141 and -54. This region contains an element at -139/-122 able to confer enhancer and protein kinase A (PKA)-dependent activity to the basal thymidine kinase promoter. The potency of this element was much higher in differentiated than in nondifferentiated brown adipocytes. Gel shift analyses indicated that a complex array of proteins from brown fat nuclei bind to the -139/-122 element, among which CRE-binding protein (CREB) and Jun proteins were identified. In transfected brown adipocytes, c-Jun was a negative regulator of basal and PKA-induced transcription from the ucp-1 promoter acting through this proximal CRE region. A double-point mutation in the -139/-122 element abolished both PKA- and c-Jun-dependent regulation through this site, and overexpression of CREB blocked c-Jun repression. Thus, an opposite action of these two transcription factors on the -139/-122 CRE is proposed. c-Jun content in brown adipocytes differentiating in culture correlated negatively with both ucp-1 gene expression and the acquisition of the brown adipocyte morphology. These findings indicate that c-Jun provides a molecular mechanism to repress the basal and cAMP-mediated expression of the ucp-1 gene before the differentiation of the brown adipocyte.

Adipocytes

Anti-Sia-lb (anti-Gd) cold agglutinins bind the domain NeuNAc alpha2-3Gal in sialyl Lewis(x), sialyl Lewis(a), and related carbohydrates on nucleated cells and in soluble cancer-associated mucins.

Anti-Sia-lb (formerly anti-Gd) cold agglutinins (CAs) recognize sialylated carbohydrates on both adult and neonate red blood cells (RBCs). RBC CA activity inhibition experiments reported here indicate that the domain NeuNAc alpha2-3Gal, as found in sialyllactose, synthetic sialyl(s) Lewis(Le)(x) and sLe(a), sialyllactosamine, sialyl-fucosyllactose, and nonfucosylated sLe(a), constitutes the minimal epitope for these CAs, implicating that these autoantibodies could be able to bind this domain in sLe(x) and sLe(a) and related carbohydrates expressed on nucleated cells and in soluble cancer-related mucins. The following data obtained with the previously characterized monoclonal IgMk anti-Sia-lb CA, GAS, show that this is the case. GAS epitope expression among leukocytes that lack sLe(a) parallels that of sLe(x) determinant as detected by mouse monoclonal antibodies (MoAbs), especially MoAb KM-93. It is also found on epithelial malignant cells bearing both sLe(x) and sLe(a). GAS epitope on these nucleated cells, (1) like that present on RBC, is abolished by sialidase, unaffected by proteases, and inhibited by sialyllactose; and (2) is overlapping and/or proximal to that recognized by anti-sLe(x) MoAb, CSLEX-1, and KM-93. Moreover, CAGAS binds soluble cancer-associated mucins bearing sLe(x) and sLe(a) determinants. This binding is inhibited by sialyllactose and these mucins inhibit the RBC CA activity of CAGAS. The possible significance of anti-Sia-lb (anti-Gd) CAs as autoantibodies directed to carbohydrate ligands of host adhesion molecules that might be receptors of microbial adhesins of some CA-inducing pathogens is discussed.

Agglutinins

Respiratory chain activity and mitochondrial DNA content of nonpurified and purified pancreatic islet cells.

Considerable interest has recently focused on the possible role of alterations in mitochondrial activity and mutations in the mitochondrial genome for the development of non-insulin-dependent diabetes. Our study aimed at investigating the normal mitochondrial respiratory chain activity of nonpurified and purified islet cells to further explore whether some diabetic states are associated with alterations of mitochondrial oxidative processes. For this purpose, pancreatic islets were isolated from Wistar rats. Unpurified islet cells were obtained in the presence of trypsin and DNAse, and purified beta and non-beta cells were prepared by autofluorescence-activated sorting using a flowcytometer. Intact cell respiration and substrate oxidation in digitonin-permeabilized cells were measured polarographically with a Clark oxygen electrode in a micro-water-jacketed cell. Specific activity of the individual complexes of the respiratory chain was determined spectrophotometrically in unpurified islet cells. The relative amount of mitochondrial (mtDNA) and nuclear (nDNA) DNA in all three cell populations and in rat brain and skeletal muscle was estimated by dot blotting. The intact cell respiration of unpurified islet cells corresponds to the mean of values obtained for beta and non-beta islet cells. Oxidation rates of different substrates by permeabilized beta cells were lower than those for unpurified and non-beta cells. The amount of mtDNA relative to nDNA was similar in all three groups of cells, and was also similar to that obtained from brain and skeletal muscle. In summary, we have described mitochondrial respiratory chain activity in unpurified, beta, and non-beta islet cells. Our results represent an initial step in investigating the potential pathogenic role that alterations in oxidative phosphorylation could play in some diabetic states.

Animals

Antibodies to mycobacterial 65-kD heat shock protein cross-react with the main mitochondrial antigens in patients with primary biliary cirrhosis.

Primary biliary cirrhosis (PBC) is a chronic cholestatic liver disease associated with autoimmune disorders. The aetiology is unknown, although it has been suggested that the disease may be related to infectious agents. Previous studies revealed that sera from patients with PBC react against Mycobacterium gordonae. This specific reactivity, characterized by a recognition of two membrane polypeptides of 70-65 and 55 kD, cross-react with the two major mitochondrial autoantigens of PBC. As the most immunogenic components of mycobacteria are the heat shock proteins (hsp), which have been associated with autoimmunity, this study has been undertaken to characterize whether the reacting polypeptides in PBC are hsp from M. gordonae. Cultures of M. gordonae were incubated at 37 degrees C and 46 degrees C before sonication, protein extraction and separation by SDS-PAGE. Exposure of M. gordonae to heat shock treatment resulted in membrane protein overexpression, similar to the 70-65-kD polypeptide recognized by the sera from patients with PBC. Immunoprecipitation assays with a monoclonal antibody directed against the Hsp65 kD of mycobacteria and with sera from patients with PBC revealed similar reacting profiles characterized by the precipitation of the overexpressed 65-kD polypeptide from M. gordonae. Competitive immunoblotting showed that binding of the monoclonal antibody to the Hsp65 kD protein was prevented by preincubation with sera from patients with PBC, but not with sera from healthy subjects. Furthermore, monoclonal antibody to the Hsp65 kD protein recognized the main mitochondrial autoantigens of PBC (PDH-E2 and BCKDH-E2). These data indicate the existence of cross-reacting epitopes contained on M. gordonae Hsp65 kD and the main mitochondrial antigens in patients with PBC.

Antigens, Bacterial

Stimulation through CD50 (ICAM-3) induces both activation and programmed cell death of human thymocytes.

CD50 (ICAM-3) has been identified as the third CD11a/CD18 (LFA-1) counter receptor. We investigated the expression and possible role of this molecule in the induction of early and late activation events in human thymocytes. We observed that CD50 expression is acquired by early T cell progenitors (CD34+) and maintained during thymic development, reaching the highest levels in the most mature population of thymocytes (CD3high). Neither basal nor cytokine-induced expression of CD50 was observed on untransformed human thymic epithelial cell lines. Cross-linking of CD50 expressed on the surface of human thymocytes, by using mAbs recognizing epitopes not related to the CD11a binding site, transduced transmembrane signals leading to an increase of intracellular calcium concentration. This calcium mobilization was inhibited when CD50 was co-cross-linked with CD45, suggesting that tyrosine phosphorylation is also involved in CD50 signaling. The same anti-CD50 mAbs that were able to affect intracellular calcium levels were shown to induce CD69 but not CD25 expression on human thymocytes. This effect was preferentially observed on CD3low/CD3high thymocyte subpopulations. Cross-linking of CD50 also significantly increased activation-induced cell death of human thymocytes. These results support the idea that CD50 molecule can play a role in developing functionally mature T lymphocytes.

Antibodies, Monoclonal

Co-ordinate decrease in the expression of the mitochondrial genome and nuclear genes for mitochondrial proteins in the lactation-induced mitochondrial hypotrophy of rat brown fat.

The relative abundance of the mitochondrial-encoded mRNAs for cytochrome c oxidase subunit II and NADH dehydrogenase subunit I was lower in brown adipose tissue (BAT) from lactating rats than in virgin controls. This decrease was in parallel with a significant decrease in mitochondrial 16 S rRNA levels and in the relative content of mitochondrial DNA in the tissue. BAT from lactating rats showed lowered mRNA expression of the nuclear-encoded genes for the mitochondrial uncoupling protein, subunit IV of cytochrome c oxidase and the adenine nucleotide translocase isoforms ANT1 and ANT2, whereas mRNA levels for the ATP synthase beta-subunit were unchanged. However, the relative content of this last protein was lower in BAT mitochondria from lactating rats than in virgin controls. It is concluded that lactation-induced mitochondrial hypotrophy in BAT is associated with a co-ordinate decrease in the expression of the mitochondrial genome and nuclear genes for mitochondrial proteins. This decrease is caused by regulatory events acting at different levels, including pre- and post-transcriptional regulation. BAT appears to be a useful model with which to investigate the molecular mechanisms involved in the co-ordination of the expression of the mitochondrial and nuclear genomes during mitochondrial biogenesis.

Adipose Tissue, Brown

Existence of a soluble form of CD50 (intercellular adhesion molecule-3) produced upon human lymphocyte activation. Present in normal human serum and levels are increased in the serum of systemic lupus erythematosus patients.

CD50 (ICAM-3) is a leukocyte differentiation Ag expressed almost exclusively on hemopoietic cells, with a key role in the first steps of immune response. To develop a specific sandwich ELISA to detect a soluble CD50 form (sCD50), two different mAbs (140-11 and 101-1D2) recognizing non-overlapping epitopes were used. sCD50 was detected in the supernatant of stimulated PBMCs, with the highest levels after CD3 triggering. Simultaneously, the CD50 surface expression diminished during the first 24 h. sCD50 isolated from culture supernatant and analyzed by immunoblotting showed an apparent m.w. of 95 kDa, slightly smaller than the membrane form. These data, together with Northern blot kinetics analysis, suggest that sCD50 is cleaved from cell membrane. Furthermore, we detect sCD50 in normal human sera and higher levels in sera of systemic lupus erythematosus (SLE) patients, especially in those in active phase. The sCD50 levels showed a positive correlation with sCD27 levels (r = 0.4213; p = 0.0026). Detection of sCD50, both after in vitro CD3 triggering of PBMCs and increased in SLE sera, suggests that sCD50 could be used as a marker of lymphocyte stimulation.

Adolescent

A novel regulatory pathway of brown fat thermogenesis. Retinoic acid is a transcriptional activator of the mitochondrial uncoupling protein gene.

The mitochondrial uncoupling protein (UCP) is responsible for the thermogenic function of brown fat, and it is a molecular marker of the brown adipocyte cell type. Retinoic acid (RA) increased UCP mRNA levels severalfold in brown adipocytes differentiated in culture. This induction was independent of adrenergic pathways or protein synthesis. RA stimulated ucp gene expression regardless of the stage of brown adipocyte differentiation. In transient transfection experiments RA induced the expression of chloramphenicol acetyltransferase vectors driven by 4.5 kilobases of the 5'-noncoding region of the rat ucp gene, and co-transfection of expression vectors for RA receptors enhanced the action of RA. Retinoic acid receptor alpha was more effective than retinoid X receptor in promoting RA action, whereas a mixture of the two was the most effective. The RA-responsive region in the ucp gene was located at -2469/-2318 and contains three motifs (between -2357 and -2330) of the consensus half-sites characteristic of retinoic acid response elements. This 27-base pair sequence specifically binds purified retinoic acid receptor alpha as well as related proteins from brown fat nuclei. In conclusion, a novel potential regulatory pathway of brown fat development and thermogenic function has been recognized by identifying RA as a transcriptional activator of the ucp gene.

Adipocytes

Anti-islet cell and anti-insulin antibody production by CD5+ and CD5- B lymphocytes in IDDM.

Although CD5 + B lymphocytes are mostly committed to the production of polyreactive natural autoantibodies, CD5 + B lymphocytes committed to the production of somatically mutated and monoreactive high-affinity IgM autoantibodies have been also shown. Increased proportions of CD5 + B lymphocytes in some autoimmune diseases, including insulin-dependent diabetes mellitus (IDDM), have been noticed. The present study was undertaken to analyse the differences between CD5 + and CD5- B lymphocyte subsets for production of IDDM-related autoantibodies, i.e. anti-human insulin antibodies (IA) and anti-human islet cell antibodies (ICA). For this purpose, Epstein-Barr Virus (EBV)-transformation of FACS cell-sorted CD5 + and CD5- B lymphocytes and unfractionated enriched B lymphocytes from nine IDDM patients treated exclusively with recombinant human insulin, and from four healthy control subjects was performed; a mean of 102-216 microcultures with a mean of 1,000-2,333 cells/microculture for each B-lymphocyte fraction and individual was established. Data show that both CD5 + and CD5- B-lymphocyte subsets from either normal subjects or from IDDM patients receiving recombinant human insulin, contain B lymphocytes committed to the production of IA-IgM as a common element of their repertoire. In contrast, cells committed to the production of IA-IgG were only detected among the CD5- B lymphocyte subset from some IDDM patients. Only one microculture, out of a total of 6,211 screened (from control subjects and patients), in the CD5- B-cell subset from a recently-diagnosed IDDM patient, was found to produce ICA-IgM lambda. This might suggest that the frequency of circulating B lymphocytes committed to the production of ICA is very low even in IDDM patients bearing serum ICA. EBV-transformed B cells producing the ICA-IgM lambda were stabilized and cloned by somatic hybridization technique. This ICA-IgM lambda human monoclonal antibody, designated HY1-MB91, is not polyreactive, but shows a restricted reactivity with human pancreatic islets, failing to react with other human tissues including cerebellar cortex, and lacking rheumatoid factor and anti-DNA antibody activities. It also lacks reactivity with pancreatic islets from other mammalian species (rat, mouse and monkey) as well as with other rat tissues, including cerebellar cortex. The antigen recognized by HY1-MB91 antibody in human islet cells is a cytoplasmic component mostly found in beta cells.

Adolescent

CD50 (intercellular adhesion molecule-3) is expressed at higher levels on memory than on naive human T cells but induces a similar calcium mobilization on both subsets.

CD50, the intercellular adhesion molecule-3 (ICAM-3), is expressed almost exclusively on hematopoietic cells. T lymphocytes display a bimodal distribution on CD50 expression levels. It was observed that CD45RO+ cells expressed higher levels of CD50 than CD45RA+ T lymphocytes. A similar situation was observed when CD4 and CD8 subpopulations were analyzed, with CD8+ cells expressing higher levels of CD50 than CD4+ cells. When adult T lymphocytes were analyzed by three-color flow cytometry in CD8+CD45RA+ cells both CD50low and CD50high expressing cells were detected, in accordance with several memory markers on T lymphocytes, whereas only cells with a low level of CD50 were observed in CD4+CD45RA+. The different level of CD50 expression was confirmed by analyzing purified CD45RA+ and CD45RO+ T cells. Moreover, after the comparison of CD50 expression level in thymocytes, cord blood and adult T lymphocytes, a progressive increase was observed. When T cells were sorted by their intensity of CD50 expression, only CD50high cells proliferated in response to tetanus toxoid. Therefore, the phenotypic and functional analysis of adult and cord blood T lymphocytes as well as thymocytes indicates that CD50 expression increases during the maturation process of T lymphocytes: from the lowest CD50 levels present on CD1+ thymocytes, to the highest levels of CD50 on human memory T cells. In addition, we have observed that after CD50 cross-linking on human T lymphocytes, a transient increase in intracellular calcium concentration ([Ca2+]i) is produced. When CD45RA+ and CD45RO+ T cells were analyzed, in spite of the level of CD50 expression, the stimulation through CD50 induced a similar level of Ca2+ mobilization in both subpopulations, contrasting with the higher rise in [Ca2+]i induced by CD3 stimulation on CD45RA+ versus CD45RO+. These data suggest that the signal transduction pathways activated after CD50 cross-linking are, at least partially, independent of those involved after CD3 stimulation.

Adult

ETS transcription factors regulate the expression of the gene for the human mitochondrial ATP synthase beta-subunit.

Elements responsible for the transcriptional activity of the human ATP synthase beta-subunit (ATPsyn beta) gene promoter have been studied through transient expression in HepG2 hepatoma cells of a CAT gene connected with various 5'-deletion mutants of the 5'-flanking region. Promoter activity was mostly dependent upon a single CCAAT motif as well as a nearby Ets domain binding region. This last region contains two sites that bind Ets-related proteins present in liver nuclear extracts as well as recombinant purified Ets-1 protein. The ATPsyn beta promoter was trans-activated by Ets-1 and Ets-2 expression vectors, and this effect was lost when the Ets binding region was deleted. The Ets binding region of the ATPsyn beta promoter increased basal expression and conferred Ets-1- and Ets-2-dependent trans-activation to the herpes symplex thymidine kinase minimal promoter. A double-point mutation of the main Ets-binding site, which suppresses Ets binding, blocks Ets-dependent trans-activation. It is concluded that the gene for the mitochondrial ATPsyn beta is a target of transcriptional activation by members of the Ets family of transcription factors. It is suggested that Ets transcription factors may be involved in the enhanced expression of the ATPsyn beta gene in highly proliferating cells and in the coordinate transcription of nuclear genes for mitochondrial proteins.

Base Sequence