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author:("abreva, Iryna")
1.  No excess of mitochondrial DNA deletions within muscle in progressive multiple sclerosis 
Mitochondrial dysfunction is an established feature of multiple sclerosis (MS). We recently described high levels of mitochondrial DNA (mtDNA) deletions within respiratory enzyme-deficient (lacking mitochondrial respiratory chain complex IV with intact complex II) neurons and choroid plexus epithelial cells in progressive MS.
The objective of this paper is to determine whether respiratory enzyme deficiency and mtDNA deletions in MS were in excess of age-related changes within muscle, which, like neurons, are post-mitotic cells that frequently harbour mtDNA deletions with ageing and in disease.
In progressive MS cases (n=17), known to harbour an excess of mtDNA deletions in the central nervous system (CNS), and controls (n=15), we studied muscle (paraspinal) and explored mitochondria in single fibres. Histochemistry, immunohistochemistry, laser microdissection, real-time polymerase chain reaction (PCR), long-range PCR and sequencing were used to resolve the single muscle fibres.
The percentage of respiratory enzyme-deficient muscle fibres, mtDNA deletion level and percentage of muscle fibres harbouring high levels of mtDNA deletions were not significantly different in MS compared with controls.
Our findings do not provide support to the existence of a diffuse mitochondrial abnormality involving multiple systems in MS. Understanding the cause(s) of the CNS mitochondrial dysfunction in progressive MS remains a research priority.
PMCID: PMC4361476  PMID: 23787892
Mitochondria; muscle; multiple sclerosis
2.  Single-cell resolution mapping of neuronal damage in acute focal cerebral ischemia using thallium autometallography 
Neuronal damage shortly after onset or after brief episodes of cerebral ischemia has remained difficult to assess with clinical and preclinical imaging techniques as well as with microscopical methods. We here show, in rodent models of middle cerebral artery occlusion (MCAO), that neuronal damage in acute focal cerebral ischemia can be mapped with single-cell resolution using thallium autometallography (TlAMG), a histochemical technique for the detection of the K+-probe thallium (Tl+) in the brain. We intravenously injected rats and mice with thallium diethyldithiocarbamate (TlDDC), a lipophilic chelate complex that releases Tl+ after crossing the blood–brain barrier. We found, within the territories of the affected arteries, areas of markedly reduced neuronal Tl+ uptake in all animals at all time points studied ranging from 15 minutes to 24 hours after MCAO. In large lesions at early time points, areas with neuronal and astrocytic Tl+ uptake below thresholds of detection were surrounded by putative penumbral zones with preserved but diminished Tl+ uptake. At 24 hours, the areas of reduced Tl+uptake matched with areas delineated by established markers of neuronal damage. The results suggest the use of 201TlDDC for preclinical and clinical single-photon emission computed tomography (SPECT) imaging of hyperacute alterations in brain K+ metabolism and prediction of tissue viability in cerebral ischemia.
PMCID: PMC3887354  PMID: 24129748
cerebral ischemia; diethyldithiocarbamate; histochemistry; potassium; stroke; thallium
3.  Clonal Expansion of Mitochondrial DNA Deletions in Multiple Sclerosis 
Acta neuropathologica  2012;124(2):209-220.
Mitochondrial DNA deletions (Δ-mtDNA) are implicated in the pathogenesis of multiple sclerosis (MS), Parkinson’s disease (PD), Alzheimer’s disease (AD) and ageing. Given the diffuse nature of inflammation in MS, aim of this study was to determine whether Δ-mtDNA caused respiratory deficient cells in excess of age within choroid plexus (CP) and ongoing mutagenesis or clonal expansion accounted for the respiratory deficiency in MS.
Respiratory chain complex IV and complex II activity was determined sequentially using histochemistry. Δ-mtDNA were characterized using real time PCR, long range PCR, sequencing and single molecule PCR. Sources of reactive oxygen and nitrogen species (RONS) were explored using immunohistochemistry.
Respiratory deficient cells (lacking complex IV and with intact complex II activity) within CP epithelium were in excess of age in MS, PD and AD. Subunit-I of complex IV was lacking to a greater extent in MS than controls. Percentage of respiratory deficient cells harboring >50% heteroplasmy level of Δ-mtDNA was significantly greater in MS than PD, AD and controls. Long range PCR and sequencing confirmed Δ-mtDNA. Single molecule PCR identified clonally expanded Δ-mtDNA in MS, despite an increase in sources of RONS.
Our findings establish clonal expansion of Δ-mtDNA causing respiratory deficiency in MS and the extraparenchymal intracranial location indicated the potential to involve multiple cell types. Understanding factors that influence clonal expansion of Δ-mtDNA, a molecular link between inflammation and delayed cellular energy failure, may identify potential therapeutic targets for progressive forms of MS as well as other neurodegenerative disorders.
PMCID: PMC3674417  PMID: 22688405
4.  Mitochondrial changes within axons in multiple sclerosis 
Brain : a journal of neurology  2009;132(Pt 5):1161-1174.
Multiple sclerosis is the most common cause of non-traumatic neurological impairment in young adults. An energy deficient state has been implicated in the degeneration of axons, the pathological correlate of disease progression, in multiple sclerosis. Mitochondria are the most efficient producers of energy and play an important role in calcium homeostasis. We analysed the density and function of mitochondria using immunohistochemistry and histochemistry, respectively, in chronic active and inactive lesions in progressive multiple sclerosis. As shown before in acute pattern III and Balo’s lesions, the mitochondrial respiratory chain complex IV activity is reduced despite the presence of mitochondria in demyelinated axons with amyloid precursor protein accumulation, which are predominantly located at the active edge of chronic active lesions. Furthermore, the strong non-phosphorylated neurofilament (SMI32) reactivity was associated with a significant reduction in complex IV activity and mitochondria within demyelinated axons. The complex IV defect associated with axonal injury may be mediated by soluble products of innate immunity, as suggested by an inverse correlation between complex IV activity and macrophage/microglial density in chronic lesions. However, in inactive areas of chronic multiple sclerosis lesions the mitochondrial respiratory chain complex IV activity and mitochondrial mass, judged by porin immunoreactivity, are increased within approximately half of large (>2.5 μm diameter) chronically demyelinated axons compared with large myelinated axons in the brain and spinal cord. The axon-specific mitochondrial docking protein (syntaphilin) and phosphorylated neurofilament-H were increased in chronic lesions. The lack of complex IV activity in a proportion of Na+/K+ ATPase α-1 positive demyelinated axons supports axonal dysfunction as a contributor to neurological impairment and disease progression. Furthermore, in vitro studies show that inhibition of complex IV augments glutamate-mediated axonal injury (amyloid precursor protein and SMI32 reactivity). Our findings have important implications for both axonal degeneration and dysfunction during the progressive stage of multiple sclerosis.
PMCID: PMC3605917  PMID: 19293237
Mitochondria; axonal degeneration; multiple sclerosis
5.  Increased mitochondrial content in remyelinated axons: implications for multiple sclerosis 
Brain  2011;134(7):1901-1913.
Mitochondrial content within axons increases following demyelination in the central nervous system, presumably as a response to the changes in energy needs of axons imposed by redistribution of sodium channels. Myelin sheaths can be restored in demyelinated axons and remyelination in some multiple sclerosis lesions is extensive, while in others it is incomplete or absent. The effects of remyelination on axonal mitochondrial content in multiple sclerosis, particularly whether remyelination completely reverses the mitochondrial changes that follow demyelination, are currently unknown. In this study, we analysed axonal mitochondria within demyelinated, remyelinated and myelinated axons in post-mortem tissue from patients with multiple sclerosis and controls, as well as in experimental models of demyelination and remyelination, in vivo and in vitro. Immunofluorescent labelling of mitochondria (porin, a voltage-dependent anion channel expressed on all mitochondria) and axons (neurofilament), and ultrastructural imaging showed that in both multiple sclerosis and experimental demyelination, mitochondrial content within remyelinated axons was significantly less than in acutely and chronically demyelinated axons but more numerous than in myelinated axons. The greater mitochondrial content within remyelinated, compared with myelinated, axons was due to an increase in density of porin elements whereas increase in size accounted for the change observed in demyelinated axons. The increase in mitochondrial content in remyelinated axons was associated with an increase in mitochondrial respiratory chain complex IV activity. In vitro studies showed a significant increase in the number of stationary mitochondria in remyelinated compared with myelinated and demyelinated axons. The number of mobile mitochondria in remyelinated axons did not significantly differ from myelinated axons, although significantly greater than in demyelinated axons. Our neuropathological data and findings in experimental demyelination and remyelination in vivo and in vitro are consistent with a partial amelioration of the supposed increase in energy demand of demyelinated axons by remyelination.
PMCID: PMC3122369  PMID: 21705418
multiple sclerosis; axon; demyelination; mitochondria; remyelination
6.  Parkinson's disease with dementia: comparing patients with and without Alzheimer pathology 
Subjects with Parkinson's disease (PD) frequently develop dementia with greater than one-third meeting neuropathologic diagnostic criteria for Alzheimer's disease (AD). The objective is to identify clinical and neuropathological differences between PDD (PD with dementia) subjects, with and without coexistent AD pathology. Neuropathologic examination was available on subjects diagnosed by clinicopathologic criteria with PDD-AD (N = 23) and PDD+AD (N = 28). A small subset of subjects with PDD-AD and PDD+AD had received at least one standardized neuropsychological assessment. PDD+AD subjects were significantly older at age of PD onset and death, progressed to onset of dementia in less time, and had a shorter duration of PD symptoms prior to the onset of dementia. Education, responsiveness of L-Dopa and dopaminergic medications, presence of cognitive fluctuations and hallucinations, mean MMSE, GDS, FAST and UPDRS scores did not differ significantly between the two groups. The PDD+AD group had significantly greater total plaques, neuritic plaques, total tangles, and Braak stages compared to PDD-AD. This study suggests that it is difficult to distinguish PDD+AD and PDD-AD on the basis of movement, clinical, and neuropsychological assessment. PDD-AD and PDD+AD have similar degrees of dementia and approximately half of PDD subjects have enough AD pathology to attain a neuropathological diagnosis of AD. PDD can develop in the absence of significant Alzheimer pathology.
PMCID: PMC2760034  PMID: 19812474
Parkinson' disease with dementia; Alzheimer's Disease; Dementia with Lewy Bodies; assessment of dementia
7.  Mitochondrial defects in acute multiple sclerosis lesions 
Brain  2008;131(7):1722-1735.
Multiple sclerosis is a chronic inflammatory disease, which leads to focal plaques of demyelination and tissue injury in the CNS. The structural and immunopathological patterns of demyelination suggest that different immune mechanisms may be involved in tissue damage. In a subtype of lesions, which are mainly found in patients with acute fulminant multiple sclerosis with Balo's type concentric sclerosis and in a subset of early relapsing remitting multiple sclerosis, the initial myelin changes closely resemble those seen in white matter stroke (WMS), suggesting a hypoxia-like tissue injury. Since mitochondrial injury may be involved in the pathogenesis of such lesions, we analysed a number of mitochondrial respiratory chain proteins in active lesions from acute multiple sclerosis and from WMS using immunohistochemistry. Functionally important defects of mitochondrial respiratory chain complex IV [cytochrome c oxidase (COX)] including its catalytic component (COX-I) are present in Pattern III but not in Pattern II multiple sclerosis lesions. The lack of immunohistochemically detected COX-I is apparent in oligodendrocytes, hypertrophied astrocytes and axons, but not in microglia. The profile of immunohistochemically detected mitochondrial respiratory chain complex subunits differs between multiple sclerosis and WMS. The findings suggest that hypoxia-like tissue injury in Pattern III multiple sclerosis lesions may be due to mitochondrial impairment.
PMCID: PMC2442422  PMID: 18515320
multiple sclerosis; Pattern III lesion; mitochondria; cytochrome c oxidase
8.  Mitochondrial DNA deletions and neurodegeneration in multiple sclerosis 
Annals of Neurology  2011;69(3):481-492.
Objective Cerebral atrophy is a correlate of clinical progression in multiple sclerosis (MS). Mitochondria are now established to play a part in the pathogenesis of MS. Uniquely, mitochondria harbor their own mitochondrial DNA (mtDNA), essential for maintaining a healthy central nervous system. We explored mitochondrial respiratory chain activity and mtDNA deletions in single neurons from secondary progressive MS (SPMS) cases.
Methods Ninety-eight snap-frozen brain blocks from 13 SPMS cases together with complex IV/complex II histochemistry, immunohistochemistry, laser dissection microscopy, long-range and real-time PCR and sequencing were used to identify and analyze respiratory-deficient neurons devoid of complex IV and with complex II activity.
Results The density of respiratory-deficient neurons in SPMS was strikingly in excess of aged controls. The majority of respiratory-deficient neurons were located in layer VI and immediate subcortical white matter (WM) irrespective of lesions. Multiple deletions of mtDNA were apparent throughout the gray matter (GM) in MS. The respiratory-deficient neurons harbored high levels of clonally expanded mtDNA deletions at a single-cell level. Furthermore, there were neurons lacking mtDNA-encoded catalytic subunits of complex IV. mtDNA deletions sufficiently explained the biochemical defect in the majority of respiratory-deficient neurons.
Interpretation These findings provide evidence that neurons in MS are respiratory-deficient due to mtDNA deletions, which are extensive in GM and may be induced by inflammation. We propose induced multiple deletions of mtDNA as an important contributor to neurodegeneration in MS.
PMCID: PMC3580047  PMID: 21446022
9.  Injury and differentiation following inhibition of mitochondrial respiratory chain complex IV in rat oligodendrocytes 
Glia  2010;58(15):1827-1837.
Oligodendrocyte lineage cells are susceptible to a variety of insults including hypoxia, excitotoxicity, and reactive oxygen species. Demyelination is a well-recognized feature of several CNS disorders including multiple sclerosis, white matter strokes, progressive multifocal leukoencephalopathy, and disorders due to mitochondrial DNA mutations. Although mitochondria have been implicated in the demise of oligodendrocyte lineage cells, the consequences of mitochondrial respiratory chain defects have not been examined. We determine the in vitro impact of established inhibitors of mitochondrial respiratory chain complex IV or cytochrome c oxidase on oligodendrocyte progenitor cells (OPCs) and mature oligodendrocytes as well as on differentiation capacity of OPCs from P0 rat. Injury to mature oligodendrocytes following complex IV inhibition was significantly greater than to OPCs, judged by cell detachment and mitochondrial membrane potential (MMP) changes, although viability of cells that remained attached was not compromised. Active mitochondria were abundant in processes of differentiated oligodendrocytes and MMP was significantly greater in differentiated oligodendrocytes than OPCs. MMP dissipated following complex IV inhibition in oligodendrocytes. Furthermore, complex IV inhibition impaired process formation within oligodendrocyte lineage cells. Injury to and impaired process formation of oligodendrocytes following complex IV inhibition has potentially important implications for the pathogenesis and repair of CNS myelin disorders. © 2010 Wiley-Liss, Inc.
PMCID: PMC3580049  PMID: 20665559
mitochondria; oligodendrocytes; cytochrome c oxidase

Results 1-9 (9)