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Antonio L Andreu

Publications and source records attributed to Antonio L Andreu.

11 recordsLinked to original sources
PubMed2005

Free radicals-mediated damage in transmitochondrial cells harboring the T14487C mutation in the ND6 gene of mtDNA.

We have studied the production of reactive oxygen species (ROS) in transmitochondrial cells, harboring homoplasmic levels of the T14487C mtDNA mutation in the ND6 gene of mitochondrial DNA (mtDNA). Previous work has shown that this mutation causes complex I deficiency. Here, we show that this mutation causes an overproduction of ROS leading to an increase in the oxidation of lipids and mtDNA without modification of antioxidant enzyme activities. We suggest that mutations in mtDNA affecting complex I activity may result in oxidative cellular damage, and reinforce the possible role of ROS-mediated mechanisms participating in some mtDNA-related disorders.

DNA, Mitochondrial↗
PubMed2005

Enhanced ROS production and antioxidant defenses in cybrids harbouring mutations in mtDNA.

It has been suggested that mutations in mitochondrial DNA (mtDNA) can produce an increase in reactive oxygen species (ROS) and that this can play a major role in the pathogenic mechanisms of mitochondrial encephalomyopathies. Many studies exist using electron transport chain (ETC) inhibitors, however there are only a few studies that examine ROS production associated with mutations in the mtDNA. To investigate this issue, we have studied ROS production, antioxidant defences and oxidative damage to lipids and proteins in transmitochondrial cybrids carrying different mtDNA mutations. Here, we report that two different mutant cell lines carrying mutations in their mitochondrial tRNA genes (A3243G in tRNA LeuUUR and A8344G in tRNA Lys) showed an increased ROS production with a parallel increase in the antioxidant enzyme activities, which may protect cells from oxidative damage in our experimental conditions (no overt oxidative damage to lipids and proteins has been observed). In contrast, cytochrome c oxidase (COX) mutant cybrids (carrying the stop-codon mutation G6930A in the COXI gene) showed neither an increase in ROS production nor elevation of antioxidant enzyme activities or oxidative damage. These results suggest that the specific location of mutations in mtDNA has a strong influence on the phenotype of the antioxidant response. Therefore, this issue should be carefully considered when antioxidant therapies are investigated in patients with mitochondrial disorders.

Adaptation, Physiological↗
PubMed2004

Peripheral neuropathy with ataxia in childhood as a result of the G8363A mutation in mitochondrial DNA.

Peripheral neuropathy has been identified in children with mitochondrial encephalomyopathies but not as a main clinical landmark. Here we report the clinical, electrophysiologic, biochemical, and genetic findings in a family who harbors the G8363A mutation in the tRNALys gene of mitochondrial DNA. Affected individuals presented with peripheral neuropathy and ataxia as the main clinical sign. Additional involvement included muscle weakness and multiple lipomatosis. Other common clinical characteristics associated with the G8363A mutation, such as cardiomyopathy and myoclonus epilepsy, were not observed. These findings suggest that a mitochondrial disease should be considered in the differential diagnosis of children with heredoataxic syndrome and peripheral neuropathy of unknown origin.

Adolescent↗
PubMed2004

A novel exon 5 mutation (N139H) in the SOD1 gene in a Spanish family associated with incomplete penetrance.

BACKGROUND: Allelic heterogeneity and phenotype variability-especially in age at onset, penetrance and progression-are reported in ALS1 families. For this reason, SOD1 gene mutation data in ALS1 patients are currently being gathered to better understand the genotype-phenotype relationship in this disorder. Here, we report the clinical and molecular characteristics of a Spanish ALS1 family with incomplete penetrance. PATIENTS AND METHODS: Clinical data including age at onset, initial topography, progression and survival were available in three affected members. Erythrocyte SOD1 activity was measured in four individuals. Analysis of the SOD1 gene was performed by PCR and direct sequencing. RESULTS: A novel missense mutation in the exon 5 of the SOD1 gene, an A-to-C transversion at nucleotide position 1485 leading to N139H residue change, was identified in three family members. The phenotype was similar in all cases, with initial symptoms in the distal limb muscles and a mean survival time of around 4 years. Incomplete penetrance was observed in our family, as two obligate carriers did not develop any symptoms of amyotrophic lateral sclerosis (ALS). CONCLUSIONS: N139H is the fifth SOD1 gene mutation reported in Spain, and the first one presenting with incomplete penetrance. Genetic counseling for at-risk relatives in these low-penetrance families could be difficult as some individuals harbouring the mutation remain asymptomatic throughout their lives. Further genetic characterisation of ALS1 families should provide information regarding the distribution of SOD1 mutants in different ethnic groups.

Amino Acid Sequence↗
PubMed2004

Preventing in vitro lipoperoxidation in the malondialdehyde-thiobarbituric assay.

The malondialdehyde-thiobarbituric acid assay is widely used to study lipid peroxidation. Among the various methods used to perform the assay, the most widely accepted is the quantification of malondialdehyde using the thiobarbituric acid reaction, followed by reversed-phase chromatography. However, unacceptable results may be obtained as malondialdehyde can be produced in vitro. To study the conditions that inhibit in vitro lipid peroxidation, malondialdehyde levels were measured in cultured cells using different concentrations of butylated hydroxytoluene, EDTA or a combination of both. Butylated hydroxytoluene alone inhibits in vitro lipid peroxidation effectively. EDTA reduces artificially produced malondialdehyde, but not totally. Finally, the combination of EDTA and butylated hydroxytoluene does not improve the results obtained using butylated hydroxytoluene alone. The conclusion is that in the malondialdehyde-thiobarbituric acid assay it is necessary to add an inhibitor of the in vitro lipid peroxidation and assay the necessary concentration depending on the specimen used.

Butylated Hydroxytoluene↗
PubMed2003

Bilateral striatal necrosis associated with a novel mutation in the mitochondrial ND6 gene.

We report the molecular findings in two independent patients presenting with progressive generalized dystonia and bilateral striatal necrosis in whom we have identified a mutation (T14487C) in the mitochondrial ND6 gene. The mutation is heteroplasmic in all samples analyzed, and it fulfills all accepted criteria of pathogenicity. Transmitochondrial cell lines harboring 100% mutant mitochondrial DNA showed a marked decrease in the activity of complex I of the respiratory chain supporting the pathogenic role of T14487C.

Adolescent↗
PubMed2002

Mitochondrial neurogastrointestinal encephalomyopathy and thymidine metabolism: results and hypotheses.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is an autosomal recessive disease with mitochondrial DNA (mtDNA) alterations and is caused by mutations in the nuclear gene encoding thymidine phosphorylase (TP). The cardinal clinical manifestations are ptosis, ophthalmoparesis, gastrointestinal dysmotility, cachexia, peripheral neuropathy, and leukoencephalopathy. Skeletal muscle shows mitochondrial abnormalities, including ragged-red fibers and cytochrome c oxidase deficiency, together with mtDNA depletion, multiple deletions or both. In MNGIE patients, TP mutations cause a loss-of-function of the cytosolic enzyme, TP. As a direct consequence of the TP defect, thymidine metabolism is altered. High blood levels of this nucleoside are likely to lead to mtDNA defects even in cells that do not express TP, such as skeletal muscle. We hypothesize that high concentrations of thymidine affect dNTP (deoxyribonucleoside triphosphate) metabolism in mitochondria more than in cytosol or nuclei, because mitochondrial dNTPs depend mainly on the thymidine salvage pathway, whereas nuclear dNTPs depend mostly on de novo pathway. The imbalance in the mitochondrial dNTP homeostasis affects mtDNA replication, leading to mitochondrial dysfunction.

Journal Article↗
PubMed2002

A novel exon 3 mutation (D76V) in the SOD1 gene associated with slowly progressive ALS.

INTRODUCTION: Details of the mutations in the Cu/Zn superoxide dismutase (SOD1) gene in patients with the familial form of amyotrophic lateral sclerosis are currently being gathered in order better to understand the genotype-phenotype relationship in this disorder. We report on a large family with 15 affected individuals spanning five generations. RESULTS: A novel mutation in the exon 3 of the SOD1 gene, an A-to-T transversion at nucleotide position 696 in the heterozygous state leading to a D76V amino acid change, was identified in four family members. Affected individuals showed a homogeneous phenotype, characterized by initial symptoms in the lower limbs, clinical onset in the fifth decade of life, long survival and high penetrance. DISCUSSION: Our results are discussed in relation to the previously reported exon 3 SOD1 mutations, paying particular attention to the phenotypic characteristics of ALS-SOD1 patients.

Aged↗
PubMed2001

Altered thymidine metabolism due to defects of thymidine phosphorylase.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is an autosomal recessive human disease due to mutations in the thymidine phosphorylase (TP) gene. TP enzyme catalyzes the reversible phosphorolysis of thymidine to thymine and 2-deoxy-D-ribose 1-phosphate. We present evidence that thymidine metabolism is altered in MNGIE. TP activities in buffy coats were reduced drastically in all 27 MNGIE patients compared with 19 controls. All MNGIE patients had much higher plasma levels of thymidine than normal individuals and asymptomatic TP mutation carriers. In two patients, the renal clearance of thymidine was approximately 20% that of creatinine, and because hemodialysis demonstrated that thymidine is ultrafiltratable, most of the filtered thymidine is likely to be reabsorbed by the kidney. In vitro, fibroblasts from controls catabolized thymidine in medium; by contrast, MNGIE fibroblasts released thymidine. In MNGIE, severe impairment of TP enzyme activity leads to increased plasma thymidine. In patients who are suspected of having MNGIE, determination of TP activity in buffy coats and thymidine levels in plasma are diagnostic. We hypothesize that excess thymidine alters mitochondrial nucleoside and nucleotide pools leading to impaired mitochondrial DNA replication, repair, or both. Therapies to reduce thymidine levels may be beneficial to MNGIE patients.

Cells, Cultured↗