Background and purpose:
Doxorubicin causes a chronic cardiomyopathy in which reactive oxygen species (ROS) accumulate over time and are associated with genetic and functional lesions of mitochondria. ...Dexrazoxane is a cardioprotective iron chelator that interferes with ROS production. We aim to analyze the effects of dexrazoxane on mitochondria in the prevention of doxorubicin‐induced chronic myocardial lesions.
Experimental approach:
Wistar rats (11 weeks of age) were injected with intravenous doxorubicin (0.8 mg kg‐1 weekly for 7 weeks) with or without simultaneous dexrazoxane (8 mg kg‐1). Animals were killed at 48 weeks. Cardiomyopathy was scored clinically and histologically and cardiac mitochondria were analyzed.
Key results:
Compared to control rats receiving saline, rats treated with doxorubicin alone developed a clinical, macroscopic, histological and ultrastructural cardiomyopathy with low cytochrome c‐oxidase (COX) activity (26% of controls). The expression of the mtDNA‐encoded COX II subunit was reduced (64% of controls). Myocardia exhibited a high production of ROS (malondialdehyde 338% and superoxide 787% of controls). Mitochondria were depleted of mitochondrial DNA (mtDNA copy number 46% of controls) and contained elevated levels of mtDNA deletions. Dexrazoxane co‐administration prevented all these effects of doxorubicin on mitochondria, except that hearts co‐exposed to doxorubicin and dexrazoxane had a slightly lower mtDNA content (81% of controls) and mtDNA deletions at low frequency.
Conclusions and Implications:
Dexrazoxane prevented doxorubicin induced late‐onset cardiomyopathy and also protected the cardiac mitochondria from acquired ultrastructural, genetic and functional damage.
British Journal of Pharmacology (2007) 151, 771–778; doi:10.1038/sj.bjp.0707294
Objectives
HIV and antiretroviral (ART) exposure in utero may have deleterious effects on the infant, but uncertainty still exists. The objective of this study was to evaluate aspects of ...mitochondrial DNA (mtDNA) content, mitochondrial function and oxidative stress simultaneously in placenta, umbilical cord blood and infant blood in HIV/ART‐exposed infants compared with uninfected controls.
Methods
HIV‐1‐infected pregnant women and HIV‐1‐uninfected healthy pregnant controls were enrolled in the study prospectively. Placenta and umbilical cord blood were obtained at delivery and infant blood was obtained within 48 h of delivery. mtDNA content was determined for each specimen. Nuclear subunit IV of cytochrome c‐oxidase (COX IV)‐ and mitochondrial (COX II)‐encoded polypeptides of the oxidative phosphorylation enzyme cytochrome c‐oxidase were quantified in cord and infant blood. Placental mitochondria malondialdehyde (MDA) concentrations were measured as a marker of oxidative stress.
Results
Twenty HIV‐positive/HIV‐exposed and 26 control mother–infant pairs were enrolled in the study. All HIV‐infected women and their infants received ART. Placental MDA concentration and mtDNA content in placenta and cord blood were similar between groups. The cord blood COX II:IV ratio was lower in the HIV‐positive group than in the controls, whereas the infant peripheral blood mtDNA content was higher in the HIV‐exposed infants, but the infant peripheral blood COX II:IV ratio was similar. No infant had clinical evidence of mitochondrial disease or acquired HIV infection. In multivariable regression analyses, the significant findings in cord and infant blood were both most associated with HIV/ART exposure.
Conclusions
HIV‐exposed infants showed reduced umbilical cord blood mitochondrial enzyme expression with increased infant peripheral blood mitochondrial DNA levels, the latter possibly reflecting a compensatory mechanism to overcome HIV/ART‐associated mitochondrial toxicity.
Intracellular antibodies (intrabodies) and the chaperone, heat shock protein 70 (Hsp70), have each shown potential as therapeutics for neurodegenerative diseases in vitro and in vivo. Investigating ...combinational therapy in an established Drosophila model of Huntington's disease (HD), we show that Hsp70 and intrabody actually affect different aspects of the disease. Overexpression of human Hsp70 resulted in improved survival of HD flies to eclosion and prolonged adult life compared with intrabody treatment alone. An additive effect on adult survival was observed when the two therapies were combined. Intrabody was more successful at suppressing neurodegeneration in photoreceptors than was Hsp70. Furthermore, Hsp70 treatment alone did not block aggregation of mutant huntingtin, a process slowed by intrabody. Expression of each is restricted to the nervous system, which implies different neuronal populations respond distinctly to these treatments. Importantly, a role for endogenous Hsp70 in suppression of mutant huntingtin pathology was confirmed by a separate set of genetic studies in which HD flies deficient for Hsp70 showed significantly increased pathology. We conclude that a combinational approach of intrabody with enhanced Hsp70 expression is beneficial in addressing multiple pathologies associated with HD and has potential application for other neurodegenerative disorders.--McLear, J. A., Lebrecht, D., Messer, A., Wolfgang, W. J. Combinational approach of intrabody with enhanced Hsp70 expression addresses multiple pathologies in a fly model of Huntington's disease.
Background. Stavudine is widely used in developing countries. Lipoatrophy and mitochondrial toxicity have been linked to stavudine use, but it is unclear whether switching to a lower dose can reduce ...these toxicities while maintaining human immunodeficiency virus (HIV) suppression. Methods. HIV-infected subjects receiving standard-dose stavudine with undetectable HIV type 1 RNA for ⩾6 months were randomized (ratio, 3:2) to receive one-half of the stavudine dose (switch arm) or to maintain the dose (continuation arm) while continuing to receive all other prescribed antiretrovirals. The following measurements were obtained at baseline and week 48: fasting lactate, pyruvate, and lipid levels; results of whole-body dual-energy x-ray absorptiometry; and mitochondrial DNA (mtDNA) measurements in fat and peripheral blood mononuclear cells. Change from baseline to week 48 was compared within and between groups. Results. Twenty-four patients (79% of whom were men and 79% of whom were African American; median age, 45 years) were enrolled in the study, 15 were enrolled in the switch arm, and 9 were enrolled in the continuation arm. The median duration of stavudine treatment was 55 months (range, 21–126 months). The median CD4 cell count was 558 cells/mm3 (range, 207–1698 cells/mm3). At baseline, the study arms had similar demographic characteristics and laboratory indices, except for body mass index, total lean body mass, and triglyceride levels (all of which were higher in the switch arm). Three patients (2 in the switch arm) discontinued the study because of study-unrelated reasons. CD4 cell counts remained unchanged. At 48 weeks, 6 patients (4 27% in the switch arm and 2 22% in the continuation arm) had detectable HIV RNA levels (median, 972 copies/mL; range, 60–49,400 copies/mL). All patients with detectable HIV RNA levels reported significant lapses in treatment adherence; none exhibited mutations in HIV genotype. After the treatment switch, significant changes from study entry to week 48 were noted only for lactate level (median change, −0.27 mmol/L; range, −1.2 to 0.25 mmol/L; P=.02) and fat mtDNA (median change, 40 copies/cell; range, −49 to 261 copies/cell; P=.02). In the continuation arm, a significant loss of bone mineral density was seen at week 48 (median change, −1.7%; range, −6.3% to 0.8%; P=.02). The only significant between-group difference was the change in bone mineral density from baseline (P=.003). Conclusions. Reducing stavudine dose by one-half increased fat mtDNA and decreased lactate levels, suggesting improvement in mitochondrial indices while preserving HIV suppression in subjects who maintained adherence. A significant loss of bone mineral density was seen in patients receiving standard-dose stavudine but not in those receiving low-dose stavudine. These results suggest that switching to low-dose stavudine may improve mitochondrial indices while maintaining virological suppression.
Background. Doxorubicin induces a self-perpetuating nephropathy characterized by early glomerular and late-onset tubular lesions in rats. We investigated the potential role of mitochondrial injury in ...the onset of these lesions. Methods. Rats were treated with intravenous doxorubicin (1 mg kg–1 week–1) for 7 weeks and were sacrificed either 1 week (‘short-term’) or 30 weeks (‘long-term’) following the last dose. Additional rats received a single dose either 6 days or 2 h prior to euthanasia. All rats were killed at 48 weeks of age. Glomerular and tubular injury was monitored and correlated to the activity or expression of respiratory chain components. Finally, we quantified both nuclear and mitochondrial DNA (mtDNA) as well as superoxide production and the 4834 base pair ‘common’ mtDNA deletion. Results. The ‘long-term’ group had significant glomerular and tubular lesions, depressed activities of mtDNA-encoded NADH dehydrogenase and cytochrome-c oxidase (COX) and increased citrate synthase activity. In addition, expression of the mtDNA-encoded COX subunit I was reduced and mtDNA levels were decreased. In ‘short-term’ rats, there were fewer tubular lesions, but similar numbers of glomerular lesions activity. Among all animals, glomerular and tubular injury were inversely correlated with mtDNA levels, mtDNA-encoded respiratory chain activities and with the expression of the mtDNA-encoded respiratory chain subunit COX-I. Injury was positively correlated with superoxide production and the activities of nucleus-encoded mitochondrial or cytoplasmic enzymes. Kidneys from the ‘long-term’ group showed more mtDNA deletions than in ‘short-term’ animals and these were not observed in the other groups. Conclusions. These results suggest an important role for quantitative and qualitative mtDNA alterations through the reduction of mtDNA-encoded respiratory chain function and induction of superoxide in doxorubicin-induced renal lesions.
Familial myelodysplastic syndromes arise from haploinsufficiency of genes involved in hematopoiesis and are primarily associated with early-onset disease. Here we describe a familial syndrome in ...seven patients from four unrelated pedigrees presenting with myelodysplastic syndrome and loss of chromosome 7/7q. Their median age at diagnosis was 2.1 years (range, 1-42). All patients presented with thrombocytopenia with or without additional cytopenias and a hypocellular marrow without an increase of blasts. Genomic studies identified constitutional mutations (p.H880Q, p.R986H, p.R986C and p.V1512M) in the
gene on 7q21, with decreased allele frequency in hematopoiesis. The non-random loss of mutated
alleles was attained via monosomy 7, deletion 7q, UPD7q, or acquired truncating
variants p.R1188X and p.S1317RfsX21. Incomplete penetrance was noted in 30% (3/10) of mutation carriers. Long-term observation revealed divergent outcomes with either progression to leukemia and/or accumulation of driver mutations (n=2), persistent monosomy 7 (n=4), and transient monosomy 7 followed by spontaneous recovery with
-wildtype UPD7q (n=2). Dysmorphic features or neurological symptoms were absent in our patients, pointing to the notion that myelodysplasia with monosomy 7 can be a sole manifestation of SAMD9L disease. Collectively, our results define a new subtype of familial myelodysplastic syndrome and provide an explanation for the phenomenon of transient monosomy 7.
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Objectives: Uridine abrogates mitochondrial toxicities of nucleoside reverse transcriptase inhibitor in adipocyte cell culture. We aim to study the effect of uridine supplementation on human ...adipocyte mitochondrial DNA (mtDNA) levels in subjects with human immunodeficiency (HIV) lipoatrophy. Methods: Sixteen patients with lipoatrophy on stavudine-containing antiretroviral therapy were enrolled, and received NucleomaxX, a dietary supplement with a high bioavailability of uridine (36 g TID every other day for 16 weeks). Patients were then followed off-uridine for another 16 weeks. Highly active antiretroviral therapy remained unchanged during the trial. Results: Fourteen patients completed the study. Two subjects dropped out before week 4 for study-unrelated reasons. No adverse events were noted throughout the study. HIV-1 RNA, CD4 counts, liver enzymes and hemoglobin remained unchanged. Body mass index, lactate, lipids, insulin and homeostasis model assessment of insulin resistance were unaltered. Fat and peripheral blood and mononuclear cell mtDNA levels did not correlate with each other and exhibited no changes throughout the study. Lipoatrophy scores by patients and physician improved significantly at weeks 16 and 32 compared to study entry. Conclusion: In this pilot study, NucleomaxX was safe, well tolerated without apparent deleterious effect on HIV indices. In contrast to in vitro data, NucleomaxX did not lead to changes in fat or blood mtDNA levels.
Doxorubicin (adriamycin) is an effective drug in the treatment of many malignancies. Its prolonged use is, however, limited by an irreversible, dose-dependent and progressive cardiomyopathy, which ...may become evident even years after completion of therapy. Data from rats and humans show that oxidative phosphorylation is impaired rapidly after acute doxorubicin-exposure. Such respiratory chain dysfunction is known to enhance the production of reactive oxygen species and may lead to quantitative and qualitative injury of mitochondrial DNA (mtDNA) and its encoded respiratory chain subunits. MtDNA depletion, mtDNA mutations and respiratory defects then accumulate with time also in the absence of continued anthracycline exposure. Chronic cardiotoxicity then manifests, when the bioenergetic capacity of the organelles is severely impaired. The mitochondrial damage in late-onset doxorubicin cardiomyopathy is heart specific and not found in skeletal muscle. DOXO-EMCH, a 6-maleimidocaproyl hydrazone derivative of doxorubicin has evolved from the search for less cardiotoxic anthracyclines. At equieffective antitumor doses, DOXO-EMCH has a substantially lower heart toxicity than free doxorubicin.
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