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Biomedical subjects

F Solano

Publications and source records attributed to F Solano.

At least 19 recordsLinked to original sources
PubMed2006

Hypomethylation of DNA and resistance to apoptosis in tonsillar hypertrophy in children.

We analyzed the hypomethylation of DNA and the sensitivity to apoptosis of tonsillar cells and peripheral blood lymphocytes (PBL) in twenty children with either recurrent tonsillitis (RT) or tonsillar hypertrophy (TH). We found no significant differences in DNA methylation of PBL obtained from RT and TH groups. Hypomethylation of DNA extracted from tonsillar tissue was higher in TH than in RT and was associated with lower spontaneous and thapsigargin-induced apoptosis. By contrast, RT showed a low level of DNA hypomethylation and was associated with high sensitivity to spontaneous and thapsigargin-induced apoptosis.

Apoptosis↗
PubMed2002

Regulation of ornithine decarboxylase in B16 mouse melanoma cells: synergistic activation of melanogenesis by alphaMSH and ornithine decarboxylase inhibition.

Ornithine decarboxylase (ODC) is the rate-limiting enzyme in the biosynthesis of polyamines, a family of cationic compounds required for optimal cell proliferation and differentiation. Within mammalian melanocytes, the expression of genes regulating cell growth and/or differentiation can be controlled by alpha-melanocyte-stimulating hormone (alphaMSH) and other melanogenesis modulating agents. In the B16 mouse melanoma model, alphaMSH stimulates melanogenesis by upmodulation of tyrosinase (tyr) activity, whereas the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) inhibits melanin synthesis. Therefore, we analyzed the regulation of ODC by these agents, as related to changes in the melanogenic pathway. Treatment of B16 cells with TPA or alphaMSH rapidly stimulated ODC activity. The effect was stronger for TPA and appeared mainly posttranslational. Irreversible inhibition of ODC with the active site-directed inhibitor alpha-difluoromethylornithine (DFMO) did not block TPA-mediated inhibition of tyr. Conversely, prolonged treatment of B16 cells with DFMO stimulated tyr activity by a posttranslational mechanism, probably requiring polyamine depletion. Combination treatment with alphaMSH and DFMO synergistically activated tyr. Therefore, ODC induction is not involved in the melanogenic response of B16 cells to alphaMSH. Rather, increased intracellular concentrations of polyamines following ODC induction might constitute a feedback mechanism to limit melanogenesis activation by alphaMSH.

Animals↗
PubMed2002

Molecular characterization of the CCR 5 gene in seronegative individuals exposed to human immunodeficiency virus (HIV).

BACKGROUND: Both clinical and laboratory evidence in exposed seronegative (ESN) individuals to human HIV-1 has suggested the existence of mechanisms of natural resistance to the infection. A 32 base-pair deletion in the gene that codes for the CCR5, which is the main coreceptor for HIV-1, confers a high degree of resistance to HIV-1 infection. However, the genotype Delta32/Delta32 is present only in 2-4% of Caucasoid ESN individuals suggesting the existence of other mechanisms of protection. Mutations different from Delta32 have also been proposed as playing a role in resistance/susceptibility to this infection. OBJECTIVE: To screen for different mutations along the entire coding region of the ccr5 gene that can potentially explain the persistent seronegativity in a group of ESN individuals. STUDY DESIGN: Of a total of 86 individuals analyzed for Delta32 mutation by the PCR technique, 36 scored HIV seropositive (SP) and 50 were ESN. The entire group of ESN individuals was screened for other mutations in the ccr5 gene by single strand conformational polymorphism (SSCP) and DNA sequencing. RESULTS: The frequency of the mutant allele Delta32 was 4% (4/100) for ESN individuals and 4.2% (3/72) for SP individuals. The homozygous mutant genotype (Delta32/Delta32) was found in only 2% (1/50) of ESN individuals, but in no SP individuals. The heterozygous genotype was found in 8.3% (3/36) of SP individuals and in 4% (2/50) of ESN individuals. The differences in the allelic and genotypic frequencies among the groups were not statistically significant. A comparison between the observed and the expected genotypic frequencies showed that they were significantly different for the ESN group, suggesting a protective, yet indirect effect of the mutant genotype. CONCLUSIONS: The screening of the entire coding region of the ccr5 gene in all ESN did not revealed no other mutations that could account for resistance to HIV-1 infection. Although the CCR5 molecule is the most important coreceptor for HIV-1, mutations in this gene do not account for most of the cases of natural resistance to this virus that have so far been reported.

Alleles↗
PubMed2001

Dimethoxyphenol oxidase activity of different microbial blue multicopper proteins.

2,6-Dimethoxyphenol is a versatile substrate for Pyricularia oryzae laccase, PpoA from Marinomonas mediterranea, phenoxazinone synthase from Streptomyces antibioticus and mammalian ceruloplasmin. In addition, in cellular extracts of microorganisms expressing other blue multicopper proteins with no enzymatic activity previously described, such as Escherichia coli (copper resistance CueO), Pseudomonas syringae and Xanthomonas campestris (copper resistance CopA), Bacillus subtilis (sporulation protein CotA) and Saccharomyces cerevisiae (iron transporter Fet3p), laccase activity is detected under appropriate conditions. This oxidase activity can be spectrophotometrically followed by the oxidation of 2,6-dimethoxyphenol. Specific staining after SDS-PAGE is also possible for some of these proteins. This detection assay can facilitate the study of the multiple functions that such proteins seem to carry out in a variety of microorganisms.

Amino Acid Sequence↗
PubMed2001

Association of a CA repeat polymorphism upstream of the Fas ligand gene with multiple sclerosis.

We have analyzed a CA repeat polymorphism localized 46-kb upstream of the Fas ligand gene in Spanish and American populations that include 139 healthy controls and a cohort of 177 unrelated relapsing and remitting multiple sclerosis (MS) patients. The MS patients consisted of two groups, one with a family history of MS and one without. The frequency of the 13 CA repeats (allele B) was lower (p=0.01) in MS patients than in controls, 0.45 and 0.55 respectively. The odds ratio (BB vs. AB/AA) for MS patients vs. healthy controls was 0.51 (95% CI 0.3-0.9; p=0.01). The odds ratio (BB vs. AB/AA) for MS patients extracted from multiply affected families vs. healthy controls was 0.22 (95% CI 0.07-0.62; p=0.002). The HLA DRB1*1501-DQB1*0602 haplotype is associated with B allele with a relative frequency higher than A allele (0.52 and 0.48 in patients vs. 0.68 and 0.32 in controls). The results suggest that chromosomes with B allele have a genetic background that reduces susceptibility to MS, particularly in the familial forms.

Alleles↗
PubMed2001

Molecular cloning and functional characterization of a unique multipotent polyphenol oxidase from Marinomonas mediterranea.

Marinomonas mediterranea is a recently isolated melanogenic marine bacterium containing laccase and tyrosinase activities. These activities are due to the expression of two polyphenol oxidases (PPOs), a blue multicopper laccase and an SDS-activated tyrosinase. The gene encoding the first one, herein denominated M. mediterranea PpoA, has been isolated by transposon mutagenesis, cloned and expressed in Escherichia coli. Its predicted amino acid sequence shows the existence of a signal peptide and four copper-binding sites characteristic of the blue multicopper proteins, including all fungal laccases. In addition, two additional putative copper-binding sites near its N-terminus are also present. Recombinant expression in E. coli of this protein clearly demonstrates its multipotent capability, showing both laccase-like and tyrosinase-like activities. This is the first prokaryotic laccase sequenced and the first PPO showing such multipotent catalytic activity. The expression of several truncated products indicates that the four copper-binding sites typical of blue multicopper proteins are essential for the laccase activity of this enzyme. However, the last two of these sites are not necessary for tyrosine hydroxylase activity as this activity is retained in a truncated product containing the first two sites as well as the extra histidine-rich clusters close to the N-terminus of the protein.

Amino Acid Sequence↗
PubMed2001

The 5,6-dihydroxyindole-2-carboxylic acid (DHICA) oxidase activity of human tyrosinase.

Melanin synthesis in mammals is catalysed by at least three enzymic proteins, tyrosinase (monophenol dihydroxyphenylalanine:oxygen oxidoreductase, EC 1.14.18.1) and tyrosinase-related proteins (tyrps) 1 and 2, whose genes map to the albino, brown and slaty loci in mice, respectively. Tyrosinase catalyses the rate-limiting generation of L-dopaquinone from L-tyrosine and is also able to oxidize L-dopa to L-dopaquinone. Conversely, mouse tyrp1, but not tyrosinase, catalyses the oxidation of the indolic intermediate 5,6-dihydroxyindole-2-carboxylic acid (DHICA) into the corresponding 5,6-indolequinone-2-carboxylic acid, thus promoting the incorporation of DHICA units into eumelanin. The catalytic activities of the human melanogenic enzymes are still debated. TYRP1 has been reported to lack DHICA oxidase activity, whereas tyrosinase appears to accelerate DHICA consumption, thus raising the question of DHICA metabolism in human melanocytes. Here we have used two different approaches, comparison of the catalytic activities of human melanocytic cell lines expressing the full set of melanogenic enzymes or deficient in TYRP1, and transient expression of TYR and tyr genes in COS7 cells, to demonstrate that human tyrosinase actually functions as a DHICA oxidase, as opposed to the mouse enzyme. Therefore, human tyrosinase displays a broader substrate specificity than its mouse counterpart, and might be at least partially responsible for the incorporation of DHICA units into human eumelanins.

Amino Acid Sequence↗
PubMed2001

Inhibition of melanogenesis in response to oxidative stress: transient downregulation of melanocyte differentiation markers and possible involvement of microphthalmia transcription factor.

H(2)O(2) and other reactive oxygen species are key regulators of many intracellular pathways. Within mammalian skin, H(2)O(2) is formed as a byproduct of melanin synthesis, and following u.v. irradiation. We therefore analyzed its effects on melanin synthesis. The activity of the rate-limiting melanogenic enzyme, tyrosinase, decreased in H(2)O(2)-treated mouse and human melanoma cells. This inhibition was concentration- and time-dependent in the B16 melanoma model. Maximal inhibition (50-75%) occurred 8-16 hours after a 20 minute exposure to 0.5 mM H(2)O(2). B16 cells withstand this treatment adequately, as shown by a small effect on glutathione levels and a rapid recovery of basal lipid peroxidation levels. Enzyme activities also recovered, beginning to increase 16-20 hours after the treatment. Inhibition of enzyme activities reflected decreased protein levels. mRNAs for tyrosinase, tyrosinase-related protein 1, dopachrome tautomerase, silver protein and melanocortin 1 receptor also decreased after H(2)O(2) treatment, and recovered at different rates. Downregulation of melanocyte differentiation markers mRNAs was preceded by a decrease in microphthalmia transcription factor (Mitf) gene expression, which was quantitatively similar to the decrease achieved using 12-O-tetradecanoylphorbol-13-acetate. Recovery of basal Mitf mRNA levels was also observed clearly before that of tyrosinase. Therefore, oxidative stress may lead to hypopigmentation by mechanisms that include a microphthalmia-dependent downregulation of the melanogenic enzymes.

Animals↗
PubMed2001

Germline mutations in the CCM1 gene, encoding Krit1, cause cerebral cavernous malformations.

Mutations in the Kritl gene have been recently discovered as the cause of hereditary cerebral cavernous angioma. We sought the possibility that de novo, noninherited mutations of Kritl also cause cavernous angioma. A patient with two cerebral malformations carries a heterozygous deletion of two base pairs (741delTC) in exon VI of the Kritl gene. The deletion initiates a frameshift mutation that, 23 amino acids downstream, encodes a TAA stop triplet replacing a CAT triplet of histidine at exon VII (H271X). Magnetic resonance images of the parents were normal, neither parent carries the 741delTC mutation, and both bear the wild-type sequence of exon VI. These findings document a de novo germline mutation in Kritl gene that causes cerebral cavernous malformations.

Brain Neoplasms↗
PubMed2001

[The retinoic acid syndrome, a complication of acute promyelocytic leukemia therapy].

OBJECTIVE: To describe the retinoic acid syndrome, a complication of therapy with all-trans retinoic acid (ATRA) in acute promyelocitic leukemia (APL). PATIENTS AND METHODS: Retrospective study of five patients with a morphologic diagnosis of APL by the French-American-British (FAB) classification that were treated for remission induction with ATRA and developed the ATRA syndrome. RESULTS: Three patients in newly diagnosed APL and two in leukemia relapse were analyzed. All patients received with ATRA 45 mgrs/m2/day, and three of them also received chemotherapy. Patients developed fever, respiratory distress, pulmonary infiltrates, weight gain and edemas. The onset of this symptom complex occurred from 1 to 11 days after starting treatment and was preceded by an increased in peripheral blood leukocytes. Infections or congestive heart failure were ruled out. The clinical course progressed while patients being treated with wide spectrum antibiotics. Four patients were treated with high doses corticosteroid therapy (dexametasone 10 mgrs intravenously every 12 hours), in three of them full recovery was attained and one died. One patient that did not received steroids died. CONCLUSIONS: The use of all-trans retinoic acid to induce hematologic remission in APL patients is associated in same patients with the development of ATRA syndrome, a life threatening complication. Symptoms begin in the first days of treatment. If this syndrome is suspected, early treatment with high dose steroids should be initiated.

Adolescent↗
PubMed2000

Neurotoxicity due to o-quinones: neuromelanin formation and possible mechanisms for o-quinone detoxification.

o-Quinones are easily formed by oxidation of physiologically relevant catechols. These reactions mainly occur in two specialized cells, catecholaminergic neurons and melanocytes. Both types of cells are related ontogenetically, as they arise from the neural crest during the developmental differentiation. o-Quinones are used to form melanin, a protective pigment formed by different mechanisms in melanocytes and catecholaminergic neurons. However, the reactivity of these quinones makes their presence in the cytosol dangerous for the cell survival and these compounds have been proposed as degenerative and apoptotic agents. Thus, melanin-producing cells show several potential mechanisms to protect themselves against the noxious effects of o-quinones. In melanocytes, the most effective autoprotecting mechanisms are the existence of malanosomes as a confined site for melano-synthesis and the action of tyrosinase-related protein 2 (TRP2) to drive L-dopachrome to 5,6-dihydroxyindole-2-carboxylic acid minimizing the formation of 5,6-dihydroxyindole. In catecholaminergic neurons, recent data suggest that glutathione transferase (GST M2-2 isoenzyme) and macrophage migration inhibitory factor (MIF) are very effective in preventing long-lived formation of dopaminechrome and noradrenochrome, although the detoxification reactions are different (conjugation to GSH or isomerization respectively). These mechanisms are less efficient for adrenochrome, although MIF and GST M1-1 could also catalyze similar reactions using this compound as substrate. In addition, the formation of adrenochrome is still under discussion, and adrenolutin formation could contribute to deactivate its harmful effects. The contribution of D-dopachrome tautomerase to these mechanisms is yet unknown, although in contrast to MIF, that enzyme does not recognize catecholaminechromes as substrates. Diaphorase could also be protective against quinones, since this enzyme catalyzes their bielectronic reduction back to catechols, thus preventing the formation of chrome species. This activity has been described in melanocytes and neurons, so that its contribution should be further investigated. In contrast to diaphorase, cytochrome P450 reductase should not be considered a protective enzyme, since its monoelectronic reduction of quinones leads to formation of semiquinones, that is, even more noxious than the quinones.

Journal Article↗
PubMed2000

Serum endothelial adhesion molecules levels correlate with lesion burden in multiple sclerosis patients treated with interferon beta-1b.

The levels of serum-soluble intracellular adhesion molecule-1 and soluble endothelial-leukocyte adhesion molecule-1, and the Gadolinium-enhanced T1-weighted MRI were studied in a group of patients with relapsing-remitting multiple sclerosis treated with interferon beta-1b and compared to a non-treated control group. The levels of serum-soluble intracellular adhesion molecule-1 and soluble endothelial-leukocyte adhesion molecule-1 increased, after three months treatment, as compared to baseline and the non-treated MS patients. A significant correlation was found in the treated group between serum-soluble endothelial-leukocyte adhesion molecule-1 and the lesion area in the Gadolinium-enhancing (T2 weighted scan) MRI.

Adult↗
PubMed2000

Regulation of the murine silver locus product (gp87) by the hypopigmenting cytokines TGF-beta1 and TNF-alpha.

The melanosomal proteins encoded by the silver (si, SILV, or PMEL17) locus play important roles in melanogenesis and are actively investigated as targets for melanoma immunotherapy. The human silver locus yields two proteins, gp100 and PMEL17, by alternative splicing of a common mRNA precursor. Mouse melanocytes exclusively express the gp100 orthologue, here termed gp87, thus providing a simpler model with which to study the silver locus products. We have analyzed the effects of [Nle4, D-Phe7]-alpha melanocyte-stimulating hormone (alphaMSH) and two hypopigmenting cytokines, tumor necrosis factor (TNF)-alpha and transforming growth factor (TGF)-beta1, on the expression of gp87 in B16 mouse melanoma cells. TNF-alpha and TGF-beta1 (at saturating doses for 48 hr) decreased gp87 mRNA by 50%. The gp87 protein was almost undetectable by Western immunoblotting after TNF-alpha treatment, but was not affected by TGF-beta1. alphaMSH increased the mRNA and the gp87 protein approximately 2-fold. Moreover, the amount of gp87 was not reduced by TNF-alpha in the presence of the hormone, in spite of a 50%, decrease in its mRNA. Therefore, the levels of mRNA and gp87 protein did not correlate after treatment with the cytokines. Overall, our data suggest that the silver locus product is not regulated exclusively at the transcriptional level, and highlight the importance of still-uncharacterized regulatory translational and/or post-translational events.

Animals↗
PubMed2000

New insights on the structure of the mouse silver locus and on the function of the silver protein.

The melanosomal proteins encoded by the silver locus play important roles in melanogenesis. The human locus yields two proteins, PMEL17 and GP100, by alternative mRNA splicing. The mouse si locus was reported to encode a Pmel17 protein, and later gp87, a GP100 homologue. When we re-examined the products of wild-type and silver-mutant mouse si loci, RT-PCR of wild-type RNA and genomic DNA sequence accounted for gp87 but excluded the occurrence of Pmel17. Analysis of cDNA from the silver (si/si) melanocyte line, melan-si, showed that the pathogenic mutation is a G to A substitution at nt 1808, which yields a premature stop codon and a predicted protein truncated in the C-terminus. This was confirmed by reaction of a specific anti-gp87 antiserum with si/si melanocyte extracts. To further explore gp87 function, we compared the DHICA oxidase activity of extracts from B16, melan-si (heterozygous for the brown mutation and homozygous for the silver mutation) and Cloudman S91 cells (homozygous for the brown mutation), since both TRP1 and gp87 are thought to be involved in DHICA oxidation/polymerization. Cloudman extracts do not oxidize significantly DHICA and its methyl ester, supporting the involvement of native mouse TRP1 in DHICA oxidation. Extracts from B16 and melan-si do not show significant differences for the oxidation of free acid and methylated dihydroxyindoles, indicating that the mechanism is not decarboxylative. Melan-si extracts are very efficient in catalyzing dihydroxyindole oxidation, in spite of being heterozygous for the TRP1 mutation, consistent with a stablin effect for the wild-type gp87 protein. On the other hand, aggregated and degraded forms of that mutant gp87 protein are found in the cytosolic fraction of melan-si, suggesting that misrouting and aberrant processing of the gp87 and tyrosinase may also be related to the high DHICA oxidase activity of these melanocytes.

Alternative Splicing↗
PubMed2000

Marinomonas mediterranea MMB-1 transposon mutagenesis: isolation of a multipotent polyphenol oxidase mutant.

Marinomonas mediterranea is a melanogenic marine bacterium expressing a multifunctional polyphenol oxidase (PPO) able to oxidize substrates characteristic for laccases and tyrosinases, as well as produce a classical tyrosinase. A new and quick method has been developed for screening laccase activity in culture plates to detect mutants differentially affected in this PPO activity. Transposon mutagenesis has been applied for the first time to M. mediterranea by using different minitransposons loaded in R6K-based suicide delivery vectors mobilizable by conjugation. Higher frequencies of insertions were obtained by using mini-Tn10 derivatives encoding kanamycin or gentamycin resistance. After applying this protocol, a multifunctional PPO-negative mutant was obtained. By using the antibiotic resistance cassette as a marker, flanking regions were cloned. Then the wild-type gene was amplified by PCR and was cloned and sequenced. This is the first report on cloning and sequencing of a gene encoding a prokaryotic enzyme with laccase activity. The deduced amino acid sequence shows the characteristic copper-binding sites of other blue copper proteins, including fungal laccases. In addition, it shows some extra copper-binding sites that might be related to its multipotent enzymatic capability.

Base Sequence↗
PubMed2000

Melanization stimulating factors in the integument of the Mugil cephalus and Dicertranchus labrax.

The pigment pattern expression resides in the chromatoblasts of the embryonic skin. The differentiation of these chromatoblasts is influenced by specific local factors such a melanization inhibiting factor (MIF) and a melanization-stimulating factor (MSF). We reveal the presence of these factors by means of a series of experiments on the skin of the marine species of fish Dicertranchus labrax and Mugil cephalus, each with different pigment pattern, the former having a light skin and the latter a darker one. Media conditioned by exposure to dorsal and/or ventral skin, stimulates the melanization of Xenopus laevis neural crest cells throughout a 3 day assay period. Similarly conditioned culture media tested on B16-F10 murine malignant melanocytes, revealed a considerable influence in enzymatic activities: dopachrome tautomerase (DCT), tyrosine hydroxylase and dopa oxidase. The use of media in a dose response basis suggests that the conditioned media may contain both melanophore stimulating and inhibiting factors. The results obtained may actually reflect the resultant activity of the two factors present.

Animals↗
PubMed1999

Enzyme activity of macrophage migration inhibitory factor toward oxidized catecholamines.

Macrophage migration inhibitory factor (MIF) is a relatively small, 12.5-kDa protein that is structurally related to some isomerases and for which multiple immune and catalytic roles have been proposed. MIF is widely expressed in tissues with particularly high levels in neural tissues. Here we show that MIF is able to catalyze the conversion of 3,4-dihydroxyphenylaminechrome and norepinephrinechrome, toxic quinone products of the neurotransmitter catecholamines 3,4-dihydroxyphenylamine and norepinephrine, to indoledihydroxy derivatives that may serve as precursors to neuromelanin. This raises the possibility that MIF participates in a detoxification pathway for catecholamine products and could therefore have a protective role in neural tissues, which as in Parkinson's disease, may be subject to catecholamine-related cell death.

Aging↗