Background: Chronic renal disease (CKD) is characterized by complex changes in cell metabolism leading to an increased production of oxygen radicals, that, in turn has been suggested to play a key role in numerous clinical complications of this pathological condition. Several reports have focused on the identification of biological elements involved in the development of systemic biochemical alterations in CKD, but this abundant literature results fragmented and not exhaustive.Results: To better define the cellular machinery associated to this condition, we employed a high-throughput genomic approach based on a whole transcriptomic analysis associated with classical molecular methodologies. The genomic screening of peripheral blood mononuclear cells revealed that 44 genes were up-regulated in both CKD patients in conservative treatment (CKD, n = 9) and hemodialysis (HD, n = 17) compared to healthy subjects (HS, n = 8) (p < 0.001, FDR = 1%). Functional analysis demonstrated that 11/44 genes were involved in the oxidative phosphorylation system. Western blotting for COXI and COXIV, key constituents of the complex IV of oxidative phosphorylation system, performed on an independent testing-group (12 healthy subjects, 10 CKD and 14 HD) confirmed an higher synthesis of these subunits in CKD/HD patients compared to the control group. Only for COXI, the comparison between CKD and healthy subjects reached the statistical significance. However, complex IV activity was significantly reduced in CKD/HD patients compared to healthy subjects (p < 0.01). Finally, CKD/HD patients presented higher reactive oxygen species and 8-hydroxydeoxyguanosine levels compared to controls.Conclusion: Taken together these results suggest, for the first time, that CKD/HD patients may have an impaired mitochondrial respiratory system and this condition may be both the consequence and the cause of an enhanced oxidative stress.

The question of whether and to what extent thein vivo cytochrome c oxidase (COX) capacity in mammalian cells exceeds that required to support respiration is still unresolved. In the present work, to address this question, a newly developed approach for measuring the rate of COX activity, either as an isolated step or as a respiratory chain-integrated step, has been applied to a variety of human cell types, including several tumor-derived semidifferentiated cell lines, as well as specialized cells removed from the organism. KCN titration assays, carried out on intact uncoupled cells, have clearly shown that the COX capacity is in low excess (16–40%) with respect to that required to support the endogenous respiration rate. Furthermore, measurements of O₂ consumption rate supported by 0.4 mmtetramethyl-p-phenylenediamine in antimycin-inhibited uncoupled intact cells have given results that are fully consistent with those obtained in the KCN titration experiments. Similarly, KCN titration assays on digitonin-permeabilized cells have revealed a COX capacity that is nearly limiting (7–22% excess) for ADP + glutamate/malate-dependent respiration. The present observations, therefore, substantiate the conclusion that the in vivo control of respiration by COX is much tighter than has been generally assumed on the basis of experiments carried out on isolated mitochondria. This conclusion has important implications for understanding the role of physiological or pathological factors in affecting the COX threshold.

Eukaryotic cells devoid of mitochondrial DNA (ρ ⁰ cells) were originally generated under artificial growth conditions utilizing ethidium bromide. The chemical is known to intercalate preferentially with the mitochondrial double-stranded DNA thereby interfering with enzymes of the replication machinery. ρ ⁰ cell lines are highly valuable tools to study human mitochondrial disorders because they can be utilized in cytoplasmic transfer experiments. However, mutagenic effects of ethidium bromide onto the nuclear DNA cannot be excluded. To foreclose this mutagenic character during the development of ρ ⁰ cell lines, we developed an extremely mild, reliable and timesaving method to generate ρ ⁰ cell lines within 3–5 days based on an enzymatic approach. Utilizing the genes for the restriction endonuclease EcoRI and the fluorescent protein EGFP that were fused to a mitochondrial targeting sequence, we developed a CMV-driven expression vector that allowed the temporal expression of the resulting fusion enzyme in eukaryotic cells. Applied on the human cell line 143B.TK ⁻ the active protein localized to mitochondria and induced the complete destruction of endogenous mtDNA. Mouse and rat ρ ⁰ cell lines were also successfully created with this approach. Furthermore, the newly established 143B.TK ⁻ ρ ⁰ cell line was characterized in great detail thereby releasing interesting insights into the morphology and ultra structure of human ρ ⁰ mitochondria.