Biomedical subjects

Andrea Martinuzzi

Publications and source records attributed to Andrea Martinuzzi.

29 records · Page 2Linked to original sources

PubMed2004

Leber hereditary optic neuropathy mtDNA mutations disrupt glutamate transport in cybrid cell lines.

Leber hereditary optic neuropathy (LHON) is a maternally inherited form of retinal ganglion cell degeneration leading to optic atrophy which is caused by point mutations in the mitochondrial genome (mtDNA). Three pathogenic mutations (positions 11778/ND4, 3460/ND1 and 14484/ND6) account for the majority of LHON cases and they affect genes that encode for different subunits of mitochondrial complex I. Excitotoxic injury to retinal ganglion cells and the optic nerve has been previously hypothesized, especially given the high susceptibility of this neural cell type to glutamate toxicity. Osteosarcoma-derived cytoplasmic hybrids (cybrids) generated from six unrelated LHON patients, two cell lines for each pathogenic mutation, were compared with cybrids obtained from three healthy controls. Molecular and biochemical analyses showed that excitatory amino acid transporter 1 (EAAT1)/GLAST is the most active glutamate transporter in this cellular model. The glutamate uptake maximal velocity was significantly reduced in all LHON cybrids compared with control cybrids. This reduction was correlated in a mutation-specific fashion with the degree of mitochondrial production of reactive oxygen species, which is enhanced in LHON cybrids. Our findings support the hypothesis that the genetically determined mitochondrial dysfunction in LHON patients leads to impaired activity of the EAAT1 glutamate transporter. This observation is particularly relevant since EAAT1 is the major means of glutamate removal in the inner retina and this prevents retinal ganglion cells being damaged as a result of excitotoxicity.

Amino Acid Transport System X-AG↗

PubMed2004

Bioenergetics shapes cellular death pathways in Leber's hereditary optic neuropathy: a model of mitochondrial neurodegeneration.

Leber's hereditary optic neuropathy (LHON) was the first maternally inherited disease to be associated with point mutations in mitochondrial DNA and is now considered the most prevalent mitochondrial disorder. The pathology is characterized by selective loss of ganglion cells in the retina leading to central vision loss and optic atrophy, prevalently in young males. The pathogenic mtDNA point mutations for LHON affect complex I with the double effect of lowering the ATP synthesis driven by complex I substrates and increasing oxidative stress chronically. In this review, we first consider the biochemical changes associated with the proton-translocating NADH-quinone oxidoreductase of mitochondria in cybrid cells carrying the most common LHON mutations. However, the LHON cybrid bioenergetic dysfunction is essentially compensated under normal conditions, i.e. in glucose medium, but is unrevealed by stressful conditions such as growing cybrids in glucose free/galactose medium, which forces cells to rely only on respiratory chain for ATP synthesis. In fact, the second part of this review deals with the investigation of LHON cybrid death pathway in galactose medium. The parallel marked changes in antioxidant enzymes, during the time-course of galactose experiments, also reveal a relevant role played by oxidative stress. The LHON cybrid model sheds light on the complex interplay amongst the different levels of biochemical consequences deriving from complex I mutations in determining neurodegeneration in LHON, and suggests an unsuspected role of bioenergetics in shaping cell death pathways.

Animals↗

PubMed2004

International Classification of Functioning, Disability and Health in a cohort of children with cognitive, motor, and complex disabilities.

The recently endorsed World Health Organization (WHO) International Classification of Functioning, Disability and Health (ICF) is proposed as a new tool to describe human functioning and health in a multiprofessional approach for individuals of all ages. Its application to paediatric neurorehabilitation may be of great help, especially in children with complex disabilities. However, experience with its application in this field is still limited. We tested the application of ICF in 40 children (26 males, 14 females; age range 3 to 18 years; mean age 11 years 1 month, SD 5 years 3 months) with various types and degrees of disability. We tested the applicability and reliability of the classification, and studied its correlation with well-established measures of functioning (Verbal IQ; gross motor function measure; functional independence measure). The ICF proved to be applicable and reliable, and strongly correlated with established scales. However, several of the Activity and Participation components do not fully capture the developmental nature of many abilities of children. Our study, although acknowledging the universal application of the ICF, and the ICF's value as a clinical tool, calls for its specific adaptation to accommodate better the peculiarities of child functioning and disability.

Adolescent↗

PubMed2003

Novel LGI1 mutation in a family with autosomal dominant partial epilepsy with auditory features.

Autosomal dominant partial epilepsy with auditory features (ADPEAF) is a rare idiopathic epilepsy syndrome caused by mutations in the leucine-rich, glioma-inactivated 1 (LGI1) gene. The authors report that molecular genetic studies in seven affected family members identified a novel F318C substitution that alters a highly conserved residue in a predicted repeat domain of unknown function. This report suggests that this domain may participate in the development of the ADPEAF phenotype.

Aged↗

PubMed2003

Phenotype modulators in myophosphorylase deficiency.

Myophosphorylase deficiency is characterized by exercise intolerance, muscle cramps, and recurrent myoglobinuria. Some patients are severely affected, whereas others are minimally affected or asymptomatic. The molecular basis of the disease has been elucidated but does not provide an explanation for the clinical variability. In a large cohort of patients with myophosphorylase deficiency, we tested the hypothesis that polymorphic variants in either myoadenylate deaminase (MADA) or angiotensin-converting enzyme (ACE) could act as modulators of phenotype expression. Forty-seven patients were evaluated. Clinical severity was assessed according to a severity scale of four grades. MADA activity was studied by histochemical and biochemical analysis of muscle, and the Q12X mutation in the adenine monophosphate deaminase 1 gene (AMPD1) and the insertion/deletion polymorphism in the ACE gene were assessed genetically. A complete MADA defect together with the Q12X mutation was detected in one severely affected patient. Eleven patients were heterozygous for the Q12X mutation. There was no association between clinical grading and MADA status. In contrast, we found a highly significant (p < 0.01) association between ACE genotype and clinical severity, with strong correlation between severe phenotype and number of D alleles. We show that ACE insertion/deletion polymorphism may play a significant role as phenotype modulator in McArdle's disease.

AMP Deaminase↗

PubMed2003

Apoptotic cell death of cybrid cells bearing Leber's hereditary optic neuropathy mutations is caspase independent.

Leber's hereditary optic neuropathy (LHON) is a maternally inherited disease characterized by selective death of retinal ganglion cells. Three pathogenic mtDNA point mutations induce an impairment of oxidative phosphorylation. We have investigated whether the release of cytochrome c during incubation of LHON cybrids in galactose medium leads to activation of the executive caspase-3 and to alteration of the energetic status of cells. From our research, it can be concluded that apoptotic cell death induced in LHON cybrid by galactose medium is caspase independent. It remains to be explained how the significant fragmentation of intranucleosomal DNA observed in LHON cybrids could also occur in the absence of caspase activation.

Adenosine Triphosphate↗

PubMed2003

Endoscopic anatomic features of the triangular recess.

OBJECTIVE: To describe the morphological and topographic features of the triangular recess (TR) in the anterior wall of the third ventricle and the pathological conditions that allow its observation during ventricular endoscopic neuronavigation. METHODS: A systematic review of records and operative videotapes for 145 patients who underwent endoscopic third ventriculostomy was performed. RESULTS: The TR could be recognized in five cases of hydrocephalus, each caused by a different underlying pathological condition. The approach was precoronal in four cases and suboccipital in one. The morphological and topographic features of the TR and adjacent structures varied among the different cases. CONCLUSION: Although it is seldom reported in neuroanatomy handbooks and is not readily accessible under normal conditions, the TR is a characteristic structure of the third ventricle, which might become apparent in several conditions that produce hydrocephalus. Neurosurgeons who perform neuroendoscopy should be aware of this structure and of the situations that cause its deformation and allow its observation during endoscopic neuronavigation.

Adult↗

PubMed2002

Leber's hereditary optic neuropathy (LHON) pathogenic mutations induce mitochondrial-dependent apoptotic death in transmitochondrial cells incubated with galactose medium.

Leber's hereditary optic neuropathy (LHON), a maternally inherited form of central vision loss, is associated with mitochondrial DNA pathogenic point mutations affecting different subunits of complex I. We here report that osteosarcoma-derived cytoplasmic hybrids (cybrid) cell lines harboring one of the three most frequent LHON pathogenic mutations, at positions 11778/ND4, 3460/ND1, and 14484/ND6, undergo cell death when galactose replaces glucose in the medium, contrary to control cybrids that maintain some growth capabilities. This is a well known way to produce a metabolic stress, forcing the cells to rely on the mitochondrial respiratory chain to produce ATP. We demonstrate that LHON cybrid cell death is apoptotic, showing chromatin condensation and nuclear DNA laddering. Moreover, we also document the mitochondrial involvement in the activation of the apoptotic cascade, as shown by the increased release of cytochrome c into the cytosol in LHON cybrid cells as compared with controls. Cybrids bearing the 3460/ND1 and 14484/ND6 mutations seemed more readily prone to undergo apoptosis as compared with the 11778/ND4 mutation. In conclusion, LHON cybrid cells forced by the reduced rate of glycolytic flux to utilize oxidative metabolism are sensitized to an apoptotic death through a mechanism involving mitochondria.

Apoptosis↗

PubMed2002

Respiratory function in cybrid cell lines carrying European mtDNA haplogroups: implications for Leber's hereditary optic neuropathy.

The possibility that some combinations of mtDNA polymorphisms, previously associated with Leber's hereditary optic neuropathy (LHON), may affect mitochondrial respiratory function was tested in osteosarcoma-derived transmitochondrial cytoplasmic hybrids (cybrids). In this cellular system, in the presence of the same nuclear background, different exogenous mtDNAs are used to repopulate a parental cell line previously devoid of its original mtDNA. No detectable differences in multiple parameters exploring respiratory function were observed when mtDNAs belonging to European haplogroups X, H, T and J were used. Different possible explanations for the previously established association between haplogroup J and LHON 11778/ND4 and 14484/ND6 pathogenic mutations are discussed, including the unconventional proposal that mtDNA haplogroup J may exert a protective rather than detrimental effect.

Clone Cells↗

PubMed2002

Rescue of a mitochondrial deficiency causing Leber Hereditary Optic Neuropathy.

A G to A transition at nucleotide 11778 in the ND4 subunit gene of complex I was the first point mutation in the mitochondrial genome linked to a human disease. It causes Leber Hereditary Optic Neuropathy, a disorder with oxidative phosphorylation deficiency. To overcome this defect, we made a synthetic ND4 subunit compatible with the "universal" genetic code and imported it into mitochondria by adding a mitochondrial targeting sequence. For detection we added a FLAG tag. This gene was inserted in an adeno-associated viral vector. The ND4FLAG protein was imported into the mitochondria of cybrids harboring the G11778A mutation, where it increased their survival rate threefold, under restrictive conditions that forced the cells to rely predominantly on oxidative phosphorylation to produce ATP. Since assays of complex I activity were normal in G11778A cybrids we focused on changes in ATP synthesis using complex I substrates. The G11778A cybrids showed a 60% reduction in the rate of ATP synthesis. Relative to mock-transfected G11778A cybrids, complemented G11778A cybrids showed a threefold increase in ATP synthesis, to a level indistinguishable from that in cybrids containing normal mitochondrial DNA. Restoration of respiration by allotopic expression opens the door for gene therapy of Leber Hereditary Optic Neuropathy.

Adenosine Triphosphate↗

PubMed2001

Cells bearing mutations causing Leber's hereditary optic neuropathy are sensitized to Fas-Induced apoptosis.

Three prevalent mitochondrial DNA pathogenic mutations at positions 11778, 3460, and 14484, which affect different subunits of Complex I, cause retinal ganglion cell death and optic nerve atrophy in Leber's hereditary optic neuropathy (LHON). The cell death is painless and without inflammation, consistent with an apoptotic mechanism. We have investigated the possibility that the LHON mutation confers a pro-apoptotic stimulus and have tested the sensitivity of osteosarcoma-derived cybrid cells carrying the most common and severe mutations (11778 and 3460) to cell death induced by Fas. We observed that LHON cybrids were sensitized to Fas-dependent death. Control cells that bear the same mitochondrial genetic background (the J haplogroup) without the pathogenic 11778 mutation are no more sensitive than other controls, indicating that increased Fas-dependent death in LHON cybrids was induced by the LHON pathogenic mutations. The type of death was apoptotic by several criteria, including induction by Fas, inhibition by the caspase inhibitor zVAD-fmk (zVal-Ala-Asp-fluoro-methyl ketone), activation of DEVDase activity (Asp-Glu-Val-Asp protease), specific cleavage of caspase-3, DNA fragmentation, and increased Annexin-V labeling. These data indicate that the most common and severe LHON pathogenic mutations 11778 and 3460 predispose cells to apoptosis, which may be relevant for the pathophysiology of cell death in LHON, and potential therapy.

Amino Acid Chloromethyl Ketones↗