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As the knowledge base and importance of mitochondrial physiology to human health expands, the necessity for harmonizing the terminologyconcerning mitochondrial respiratory states and rates has become increasingly apparent. Thechemiosmotic theoryestablishes the mechanism of energy transformationandcoupling in oxidative phosphorylation. Theunifying concept of the protonmotive force providestheframeworkfordeveloping a consistent theoretical foundation ofmitochondrial physiology and bioenergetics.We followguidelines of the International Union of Pure and Applied Chemistry(IUPAC)onterminology inphysical chemistry, extended by considerationsofopen systems and thermodynamicsof irreversible processes.Theconcept-driven constructive terminology incorporates the meaning of each quantity and alignsconcepts and symbols withthe nomenclature of classicalbioenergetics. We endeavour to provide a balanced view ofmitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes.Uniform standards for evaluation of respiratory states and rates will ultimatelycontribute to reproducibility between laboratories and thussupport the development of databases of mitochondrial respiratory function in species, tissues, and cells.Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery.

Valproic acid (VPA) is a well-tolerated anticonvulsant that exerts anti-tumour activity as a histone deacetylase inhibitor. This study investigated the in vitro and in vivo activity of VPA against multiple myeloma (MM) cells. In vitro exposure of interleukin-6-dependent or -independent MM cells to VPA inhibited cell proliferation in a time- and dose-dependent manner and induced apoptosis. In a cohort of severe combined immunodeficiency mice bearing human MM xenografts, VPA induced tumour growth inhibition and survival advantage in treated animals versus controls. Flow cytometric analysis performed on MM cells from excised tumours showed increase of G(0)-G(1) and a decreased G(2)/M- and S-phase following VPA treatment, indicating in vivo effects of VPA on cell cycle regulation. Gene expression profiling of MM cells exposed to VPA showed downregulation of genes involved in cell cycle progression, DNA replication and transcription, as well as upregulation of genes implicated in apoptosis and chemokine pathways. Pathfinder analysis of gene array data identified cell growth, cell cycle, cell death, as well as DNA replication and repair as the most important signalling networks modulated by VPA. Taken together, our data provide the preclinical rationale for VPA clinical evaluation as a single agent or in combination, to improve patient outcome in MM.

Recent studies have challenged the prevailing view that reduced mitochondrial function and increased oxidative stress are correlated with reduced longevity. Mice carrying a homozygous knockout (KO) of the Surf1 gene showed a significant decrease in mitochondrial electron transport chain Complex IV activity, yet displayed increased lifespan and reduced brain damage after excitotoxic insults. In the present study, we examined brain metabolism, brain hemodynamics, and memory of Surf1 KO mice using in vitro measures of mitochondrial function, in vivo neuroimaging, and behavioral testing. We show that decreased respiration and increased generation of hydrogen peroxide in isolated Surf1 KO brain mitochondria are associated with increased brain glucose metabolism, cerebral blood flow, and lactate levels, and with enhanced memory in Surf1 KO mice. These metabolic and functional changes in Surf1 KO brains were accompanied by higher levels of hypoxia-inducible factor 1 alpha, and by increases in the activated form of cyclic AMP response element-binding factor, which is integral to memory formation. These findings suggest that Surf1 deficiency-induced metabolic alterations may have positive effects on brain function. Exploring the relationship between mitochondrial activity, oxidative stress, and brain function will enhance our understanding of cognitive aging and of age-related neurologic disorders.

Hydrogen sulfide is a physiologically relevant signalling molecule. However, circulating levels of this highly biologically active substance have to be maintained within tightly controlled limits in order to avoid toxic side effects. In patients suffering from EE (ethylmalonic encephalopathy), a block in sulfide oxidation at the level of the SDO (sulfur dioxygenase) ETHE1 leads to severe dysfunctions in microcirculation and cellular energy metabolism. We used an Ethe1-deficient mouse model to investigate the effect of increased sulfide and persulfide concentrations on liver, kidney, muscle and brain proteomes. Major disturbances in post-translational protein modifications indicate that the mitochondrial sulfide oxidation pathway could have a crucial function during sulfide signalling most probably via the regulation of cysteine S-modifications. Our results confirm the involvement of sulfide in redox regulation and cytoskeleton dynamics. In addition, they suggest that sulfide signalling specifically regulates mitochondrial catabolism of FAs (fatty acids) and BCAAs (branched-chain amino acids). These findings are particularly relevant in the context of EE since they may explain major symptoms of the disease. DFG/HI 1471/1-1 Telethon grant/GPP10005 and AFM15927 Pierfranco and Luisa Mariani Foundation Italy

Background: Peripheral neuropathy is a disabling taxane-related adverse event. Genetic polymorphisms (GP) in drug transporters and drug-metabolizing enzymes (ADME) could be involved in taxane-associated neuropathy (TAN). We investigated the correlation between single nucleotide polymorphisms (SNPs) linked to ADME gene variants and >= grade 3 (G3) TAN by the drug-metabolizing enzyme and transporter (DMET) microarray Affymetrix platform. Patients and methods: Seventy-nine taxane-treated breast cancer patients, were enrolled in a case-control study: 27 experienced TAN (>= G3) while 52 were no-TAN matched controls. Peripheral blood cells DNA was genotyped by DMET Plus chip. The study primary end-point was association between ADME-related SNPs and TAN; secondary endpoints were the association between TAN-related SNPs and treatment response or Progression Free Survival (PFS). Genotype association was analyzed by Fisher exact test and relevant SNPs were analyzed through Log-Rank test and Cox proportional hazards model. Results: Nine SNPs significantly associated with TAN. After Bonferroni's correction only a SNP on NAT2 gene (rs1041983), remained significantly associated to TAN (=G3 neurotoxicity, being genotyped in 10/27 cases vs. 4/51 control patients (p=0.003, OR=6.911, 95% CI=1.9114 to 24.9939). Polymorphic variants in rs3808607 (CYP7A1) and in rs2292954 (SPG7) SNPs were associated to treatment response. The genotype A/C of the rs3808607 SNP, was found in 5/17 patients with Partial Response (PR), in 5/5 patients with Complete Response(CR) and 0/13 patients with Stable Disease (SD)/Progressive Disease (PD) (p=0.003) while the genotype A/G of rs2292954 SNP was found in 8/18 patients with PR, 4/5 with CR and 2/12 SD/PD (p=0.001). TAN did not correlate with clinical outcome. The rs562 polymorphism (genotype C/C) mapping in the ABCC5 gene was correlated to prolonged PFS (median not reached). The G/G genotype only slightly correlated with TAN, wasn't associated to response and showed an intermediate PFS (median 13.8 months). The C/G genotype was associated with a worse PFS (median 12.07 months). Conclusions: A polymorphic variant of NAT2 gene was correlated to TAN, while polymorphic variant of CYP7A1, SPG7 and ABCC5 genes were correlated to treatment response and PFS. DMET can identify GP for personalized therapeutic strategies.

A patient is reported who presented in the newborn period with an unusual combination of congenital lactic acidosis and bilateral calcifications in the adrenal medulla, visible on standard abdominal X-ray and ultrasound examination. At birth, the proband was hypotonic and dystrophic. She developed respiratory insufficiency, cardiomegaly and hepatomegaly and died at the age of 38 days. Examination of postmortem heart muscle revealed multiple areas of myocardial infarction with dystrophic calcifications. In the medulla of the adrenal glands foci of necrosis and calcifications, and in the liver multiple zones of necrosis and iron deposition were detected. Biochemical analysis in heart muscle revealed a decreased activity of complex IV of the oxidative phosphorylation (OXPHOS) and in liver a combined deficiency involving the complexes I, III, IV and V. The findings were suggestive of a defect in biosynthesis of the mitochondrially encoded subunits of the OXPHOS complexes. Extensive analysis of the proband's mitochondrial DNA revealed neither pathogenic deletions, point mutations nor copy number alterations. Relative amounts of mitochondrial transcripts for the ribosomal 12S and 16S were significantly increased suggesting a compensatory mechanism involving the transcription machinery to low levels of translation. The underlying molecular defect has not been identified yet.

A patient is reported who presented in the newborn period with an unusual combination of congenital lactic acidosis and bilateral calcifications in the adrenal medulla, visible on standard abdominal X-ray and ultrasound examination. At birth, the proband was hypotonic and dystrophic. She developed respiratory insufficiency, cardiomegaly and hepatomegaly and died at the age of 38 days. CerebralMRI showed small cystic lesions in the thalamus. Postmortem examination of postmortem heart muscle revealed multiple areas of myocardial infarction with dystrophic calcifications, and in the brain cystic lesions were seen in the thalamus. In the medulla of the adrenal glands foci of necrosis and calcifications, and in the liver multiple zones of necrosis and iron deposition were detected. Biochemical analysis in heart muscle revealed a decreased activity of complex IV of the oxidative phosphorylation (OXPHOS) and in liver a combined deficiency involving the complexes I, III, IV and V. The findings were suggestive of a defect in biosynthesis of the mitochondrially encoded subunits of the OXPHOS complexes. Extensive analysis of the proband's mitochondrial DNA revealed neither pathogenic deletions, point mutations nor copy number alterations. Relative amounts of mitochondrial transcripts for the ribosomal 12S and 16S were significantly increased suggesting a compensatory mechanism involving the transcription machinery to low levels of translation. The underlying molecular defect has not been identified yet.

Kcv (K+ Chlorella virus) is a miniature virus-encoded K+ channel. Its predicted membrane–pore–membrane structure lacks a cytoplasmic C-terminus and it has a short 12 amino acid (aa) cytoplasmic N-terminus. Kcv forms a functional channel when expressed in human HEK 293 cells. Deletion of the 14 N-terminal aa results in no apparent differences in the subcellular location and expression level of the Kcv protein. However, the truncated protein does not induce a measurable current in transfected HEK 293 cells or Xenopus oocytes. We conclude that the N-terminus controls functional properties of the Kcv channel, but does not influence protein expression.

1. The effect of the antiarrhythmic drug dronedarone on the Acetylcholine-activated K(+) current (I(K(ACh))) was investigated in single cells isolated from sinoatrial node (SAN) tissue of rabbit hearts. 2. Externally perfused dronedarone (0.001 - 1 microM) caused a potent, voltage independent block of I(K(ACh)). Fitting of the dose response curve of I(K(ACh)) block yielded an IC(50) value of 63 nM, a value over one order of magnitude lower than those reported for dronedarone block of other cardiac currents. 3. I(K(ACh)) block was not due to an inhibitory action of dronedarone on the muscarinic M2 receptor activation, since the drug was effective on I(K(ACh)) constitutively activated by intracellular perfusion with GTP-gammaS. 4. External cell perfusion with dronedarone inhibited the activity of I(K(ACh)) channels recorded from cell-attached patches by reducing the channel open probability (from 0.56 to 0.11) without modification of the single-channel conductance. 5. These data suggest that dronedarone blocks I(K(ACh)) channels either by disrupting the G-protein-mediated activation or by a direct inhibitory interaction with the channel protein.