Microphotometric analysis of NADH-tetrazolium reductase deficiency in fibroblasts of patients with Leber hereditary optic neuropathy

Evaluation of Mitochondrial Dysfunction and Idebenone Responsiveness in Fibroblasts from Leber's Hereditary Optic Neuropathy (LHON) Subjects

Leber's hereditary optic neuropathy (LHON) is a disease that affects the optical nerve, causing visual loss. The diagnosis of LHON is mostly defined by the identification of three pathogenic variants in the mitochondrial DNA. Idebenone is widely used to treat LHON patients, but only some of them are responders to treatment. In our study, we assessed the maximal respiration rate (MRR) and other respiratory parameters in eight fibroblast lines from subjects carrying LHON pathogenic variants. We measured also the effects of idebenone treatment on cell growth and mtDNA amounts. Results showed that LHON fibroblasts had significantly reduced respiratory parameters in untreated conditions, but no significant gain in MRR after idebenone supplementation. No major toxicity toward mitochondrial function and no relevant compensatory effect in terms of mtDNA quantity were found for the treatment at the tested conditions. Our findings confirmed that fibroblasts from subjects harboring LHON pathogenic variants displayed impaired respiration, regardless of the disease penetrance and severity. Testing responsiveness to idebenone treatment in cultured cells did not fully recapitulate in vivo data. The in-depth evaluation of cellular respiration in fibroblasts is a good approach to evaluating novel mtDNA variants associated with LHON but needs further evaluation as a potential biomarker for disease prognosis and treatment responsiveness.

Leber's hereditary optic neuropathy is multiorgan not mono-organ

Leber's hereditary optic neuropathy (LHON) is a maternally inherited mitochondrial disorder with bilateral loss of central vision primarily due to mitochondrial DNA (mtDNA) mutations in subunits of complex I in the respiratory chain (primary LHON mutations), while other mtDNA mutations can also be causative. Since the first description, it is known that LHON is not restricted to the eyes but is a multisystem disorder additionally involving the central nervous system, ears, endocrinological organs, heart, bone marrow, arteries, kidneys, or the peripheral nervous system. Multisystem involvement may start before or after the onset of visual impairment. Involvement of organs other than the eyes may be subclinical depending on age, ethnicity, and possibly the heteroplasmy rate of the responsible primary LHON mutation. Primary LHON mutations may rarely manifest without ocular compromise but with arterial hypertension, various neurodegenerative diseases, or Leigh syndrome. Patients with LHON need to be closely followed up to detect at which point organs other than the eyes become affected. Multiorgan disease in LHON often responds more favorably to symptomatic treatment than the ocular compromise.

Morphological and enzymatic changes caused by a long-term treatment of female rats with a low dose of gonadoliberin agonist and antagonist

Background

Long-term treatment with gonadoliberin analogs is used to block the hypothalamic-pituitary-gonadal axis. The use of these agents is generally considered to be safe; however, some observations suggest the possibility of adverse effects.

Material/Methods

We investigated whether a 3-months administration of a low dose (6 μg/kg b.w.) of dalarelin – a new agonist, and cetrorelix – a known antagonist of GnRH to female rats causes morphological changes in pituitary gland, ovaries, uterus and liver (HE and VG staining); effects on pituitary, hepatic and blood enzyme activities (histochemical and kinetic methods, respectively), and on the blood lipid profile (colorimetric methods); and to what extent these changes are reversible.

Results

Applying analogs effectively inhibited ovulation, affected the uterine endometrium and changed histological appearance of the liver (e.g., steatosis). They altered activities of marker enzymes of cellular respiration, gluconeogenesis and intracellular digestion in the liver and, partially in the pituitary gland, caused undesirable changes in the activities of aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, and creatine kinase, and a concentration of cholesterol HDL fraction and triglycerides in the blood. Both morphological and enzymatic effects were more evident after antagonist administration; changes in the blood lipid profile were more evident after agonist administration. In both analogs histological and enzymatic changes persisted a relatively long time after the discontinuation of the treatment.

Conclusions

The low dose of dalarelin and cetrorelix is sufficient to cause limited damage of hepatic cells and may modify the function of pituitary, ovaries, uterus and liver as well as other organs, even after discontinuation of the treatment.

Expression of GFP in the mitochondrial compartment using DQAsome-mediated delivery of an artificial mini-mitochondrial genome

PURPOSE

We describe a novel strategy for expression of GFP in mammalian mitochondria.

METHODS

The key components of the strategy were an artificially created mitochondrial genome pmtGFP and a DQAsome transfection system.

RESULTS

Using immunofluorescence and a combination of immunohistochemical and molecular based techniques, we show that DQAsomes are capable of delivering the pmtGFP construct to the mitochondrial compartment of the mouse macrophage cell line RAW264.7, albeit at low efficiency (1-5%), resulting in the expression of GFP mRNA and protein. Similar transfection efficiencies were also demonstrated in a range of other mammalian cell lines.

CONCLUSIONS

The DQAsome-transfection technique was able to deliver the exogenous DNA into the cellular mitochondria and the pmtGFP was functional. Further optimization of this strategy would provide a flexible and rapid way to generate mutant cells and useful animal models of mitochondrial disease.

Plasma membrane NADH-oxidoreductase in cells carrying mitochondrial DNA G11778A mutation and in cells devoid of mitochondrial DNA (rho0)

The mammalian plasma membrane (PM) NADH-oxidoreductase (PMOR) system is a multi-enzyme complex located in the plasma membrane of all eukaryotic cells, harboring at least two distinct activities, the plasma membrane NADH-ferricyanide reductase and the NADH-oxidase. To assess the behaviour of the two activities of the PMOR system, we measured the NADH-ferricyanide reductase and NADH-oxidase activities in fibroblast cell lines derived from patients carrying a mitochondrial DNA (mtDNA) G11778A mutation. We also measured the two activities in other cell lines, the HL-60 and HeLa (S3) lines, as well as in rho0 cells (cells devoid of mtDNA) generated from those lines and the fibroblast cells. These rho0 cells consequently lack oxidative phosphorylation and rely on anaerobic glycolysis for their ATP need. We have proposed that in rho0 cells, at least in part, up-regulation of the PMOR is a necessity to maintain the NAD+/NADH ratio, and a pre-requisite for cell growth and viability. We show here that the PM NADH-ferricyanide reductase activity was up-regulated in HL-AV2 (HL-60 rho0) cell lines, but not in the other rho0 and mtDNA mutant lines. The plasma membrane NADH oxidase activity was found to be up-regulated in both HL-AV2 and HeLa rho0 cell lines, but not significantly in the fibroblast rho0 and G11778A lines.