A High-Throughput Screening Identifies MICU1 Targeting Compounds

Mitochondrial Ca²⁺ uptake depends on the mitochondrial calcium uniporter (MCU) complex, a highly selective channel of the inner mitochondrial membrane (IMM). Here, we screen a library of 44,000 non-proprietary compounds for their ability to modulate mitochondrial Ca²⁺ uptake. Two of them, named MCU-i4 and MCU-i11, are confirmed to reliably decrease mitochondrial Ca²⁺ influx. Docking simulations reveal that these molecules directly bind a specific cleft in MICU1, a key element of the MCU complex that controls channel gating. Accordingly, in MICU1-silenced or deleted cells, the inhibitory effect of the two compounds is lost. Moreover, MCU-i4 and MCU-i11 fail to inhibit mitochondrial Ca²⁺ uptake in cells expressing a MICU1 mutated in the critical amino acids that forge the predicted binding cleft. Finally, these compounds are tested ex vivo, revealing a primary role for mitochondrial Ca²⁺ uptake in muscle growth. Overall, MCU-i4 and MCU-i11 represent leading molecules for the development of MICU1-targeting drugs.

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An HTS identifies MCU-i4 and MCU-i11 as negative modulators of the MCU

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MCU-i4 and MCU-i11 bind MICU1

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MICU1 is required for the activity of MCU-i4 and MCU-i11

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MCU-i4 and MCU-i11 impair muscle cell growth

Virtopsy in conjoined ischiopagus twins

PURPOSE OF INVESTIGATION

To propose a multidisciplinary protocol for postmortem disclosure of complex fetal malformations, comparing ultrasound, computed tomography (CT), magnetic resonance imaging (MRI), and autopsy in a case of conjoined ischiopagus twins.

MATERIALS AND METHODS

A screening second-trimester ultrasound diagnosed ischiopagus twins at 20 gestational weeks in a 31-year-old woman without any previous ultrasound examination. The couple decided for pregnancy termination. The formalin-fixed fetuses underwent full-body CT, MRI, and autopsy.

RESULTS

ultrasound accurately diagnosed ischiopagus twins. CT was very accurate in the description of bone components. MRI allowed better visualization of the visceral organs than CT. Only autopsy could disclose the aspect of the two gastrointestinal tracts and the external genitalia.

CONCLUSIONS

Prenatal ultrasound represents the standard diagnostic exam for conjoined twins. CT-MRI virtual autopsy (virtopsy) may be an option if the couple refuses to authorize necropsy or may be useful to plan a minimally invasive autopsy preserving the external phenotype.

Fe3O4@SiO2 core-shell nanoparticles for biomedical purposes: adverse effects on blood cells

Magnetite nanoparticles coated with silica, obtained by a sol-gel process in the reverse micelle microemulsion, were characterized and homogeneously suspended in water in order to assay their biocompatibility toward blood cells, in view of a potential medical use of this material. Their hemolytic, pro-thrombotic and pro-inflammatory properties were observed.

Rheumatoid trigger wrist

No abstract available

Histone deacetylase inhibitors in the treatment of muscular dystrophies: epigenetic drugs for genetic diseases

Histone deacetylases inhibitors (HDACi) include a growing number of drugs that share the ability to inhibit the enzymatic activity of some or all the HDACs. Experimental and preclinical evidence indicates that these epigenetic drugs not only can be effective in the treatment of malignancies, inflammatory diseases and degenerative disorders, but also in the treatment of genetic diseases, such as muscular dystrophies. The ability of HDACi to counter the progression of muscular dystrophies points to HDACs as a crucial link between specific genetic mutations and downstream determinants of disease progression. It also suggests the contribution of epigenetic events to the pathogenesis of muscular dystrophies. Here we describe the experimental evidence supporting the key role of HDACs in the control of the transcriptional networks underlying the potential of dystrophic muscles either to activate compensatory regeneration or to undergo fibroadipogenic degeneration. Studies performed in mouse models of Duchenne muscular dystrophy (DMD) indicate that dystrophin deficiency leads to deregulated HDAC activity, which perturbs downstream networks and can be restored directly, by HDAC blockade, or indirectly, by reexpression of dystrophin. This evidence supports the current view that HDACi are emerging candidate drugs for pharmacological interventions in muscular dystrophies, and reveals unexpected common beneficial outcomes of pharmacological treatment or gene therapy.

Nitric oxide deficiency determines global chromatin changes in Duchenne muscular dystrophy

The present study provides evidence that abnormal patterns of global histone modification are present in the skeletal muscle nuclei of mdx mice and Duchenne muscular dystrophy (DMD) patients. A combination of specific histone H3 modifications, including Ser-10 phosphorylation, acetylation of Lys 9 and 14, and Lys 79 methylation, were found enriched in muscle biopsies from human patients affected by DMD and in late-term fetuses, early postnatal pups, or adult mdx mice. In this context, chromatin immunoprecipitation experiments showed an enrichment of these modifications at the loci of genes involved in proliferation or inflammation, suggesting a regulatory effect on gene expression. Remarkably, the reexpression of dystrophin induced by gentamicin treatment or the administration of nitric oxide (NO) donors reversed the abnormal pattern of H3 histone modifications. These findings suggest an unanticipated link between the dystrophin-activated NO signaling and the remodeling of chromatin. In this context, the regulation of class IIa histone deacetylases (HDACs) 4 and 5 was found altered as a consequence of the reduced NO-dependent protein phosphatase 2A activity, indicating that both NO and class IIa HDACs are important for satellite cell differentiation and gene expression in mdx mice. In conclusion, this work provides the first evidence of a role for NO as an epigenetic regulator in DMD.

[Dynamic contrast-enhanced magnetic resonance imaging of the wrist in early arthritis]

OBJECTIVES

MRI has been proposed as the imaging method of choice to evaluate the long-term outcome in patients with early arthritis. The role of dynamic MRI, performed at presentation, in predicting the outcome of patients with early arthritis has been addressed in the present study.

METHODS

39 patients with early arthritis, involving at least one wrist, were studied with clinical visits and laboratory investigations, every 3 months. Dynamic MRI was performed with a low-field (0.2T), extremity-dedicated machine (Artoscan, Esaote, Genova, Italy) equipped with a permanent magnet and with a dedicated hand and wrist coil. During the intravenous injection of Gd-DTPA, twenty consecutive fast images of 3 slices of the wrist were acquired. The synovial contrast enhancement ratio was calculated both as rate of early enhancement (REE) per second during the first 55" and as relative enhancement (RE) at t seconds.

RESULTS

In our cohort of patients, REE and RE were significantly lower than those observed in a historical cohort of 36 patients with active rheumatoid arthritis. In univariate analysis, low RE predicted complete remission of arthritis. In multivariate analysis, fulfillment of RA criteria during follow-up was predicted by high RE. The need for immunosoppressive treatment at the end of follow-up was predicted by both low RE and high REE.

CONCLUSIONS

Dynamic MRI may be used to predict several outcomes of early arthritis involving the wrist.

Regenerative pharmacology in the treatment of genetic diseases: the paradigm of muscular dystrophy

Current evidence supports the therapeutic potential of pharmacological interventions that counter the progression of genetic disorders by promoting regeneration of the affected organs or tissues. The rationale behind this concept lies on the evidence that targeting key events downstream of the genetic defect can compensate, at least partially, the pathological consequence of the related disease. In this regard, the beneficial effect exerted on animal models of muscular dystrophy by pharmacological strategies that enhance muscle regeneration provides an interesting paradigm. In this review, we describe and discuss the potential targets of pharmacological strategies that promote regeneration of dystrophic muscles and alleviate the consequence of the primary genetic defect. Regenerative pharmacology provides an immediate and suitable therapeutic opportunity to slow down the decline of muscles in the present generation of dystrophic patients, with the perspective to hold them in conditions such that they could benefit of future, more definitive, therapies.

Deacetylase inhibitors increase muscle cell size by promoting myoblast recruitment and fusion through induction of follistatin

Fusion of undifferentiated myoblasts into multinucleated myotubes is a prerequisite for developmental myogenesis and postnatal muscle growth. We report that deacetylase inhibitors favor the recruitment and fusion of myoblasts into preformed myotubes. Muscle-restricted expression of follistatin is induced by deacetylase inhibitors and mediates myoblast recruitment and fusion into myotubes through a pathway distinct from those utilized by either IGF-1 or IL-4. Blockade of follistatin expression by RNAi-mediated knockdown, functional inactivation with either neutralizing antibodies or the antagonist protein myostatin, render myoblasts refractory to HDAC inhibitors. Muscles from animals treated with the HDAC inhibitor trichostatin A display increased production of follistatin and enhanced expression of markers of regeneration following muscle injury. These data identify follistatin as a central mediator of the fusigenic effects exerted by deacetylase inhibitors on skeletal muscles and establish a rationale for their use to manipulate skeletal myogenesis and promote muscle regeneration.

Cell age-related monovalent cations content and density changes in stored human erythrocytes

Conversion of erythrocyte membrane protein 4.1b to 4.1a occurs through a non-enzymatic deamidation reaction in most mammalian erythrocytes, with an in vivo half-life of approximately 41 days, making the 4.1a/4.1b ratio a useful index of red cell age [Inaba and Maede, Biochim. Biophys. Acta 944 (1988) 256-264]. Normal human erythrocytes distribute into subpopulations of increasing cell density and cell age when centrifuged in polyarabinogalactan density gradients. We have observed that, when erythrocytes were stored at 4 degrees C under standard blood bank conditions, the deamidation was virtually undetectable, as cells maintained the 4.1a/4.1b ratio they displayed at the onset of storage. By measuring the 4.1a/4.1b values in subpopulations of cells of different density at various time points during storage, a modification of the normal 'cell age/cell density' relationship was observed, as erythrocytes were affected by changes in cell volume in an age-dependent manner. This may stem from a different impact of storage on the imbalance of monovalent cations, Na(+) and K(+), in young and old erythrocytes, related to their different complement of cation transporters.

Characterization of the hypertonically induced tyrosine phosphorylation of erythrocyte band 3

Human erythrocyte band 3 becomes rapidly phosphorylated on tyrosine residues after exposure of erythrocytes to hypertonic conditions. The driving force for this phosphorylation reaction seems to be a decrease in cell volume, because (1) changes in band 3 phosphotyrosine content accurately track repeated changes in erythrocyte volume through several cycles of swelling and shrinking; (2) the level of band 3 phosphorylation is independent of the osmolyte employed but strongly sensitive to the magnitude of cell shrinkage; and (3) exposure of erythrocytes to hypertonic buffers under conditions in which intracellular osmolarity increases but volume does not change (nystatin-treated cells) does not promote an increase in tyrosine phosphorylation. We hypothesize that shrinkage-induced tyrosine phosphorylation results either from an excluded-volume effect, stemming from an increase in intracellular crowding, or from changes in membrane curvature that accompany the decrease in cell volume. Although the net phosphorylation state of band 3 is shown to be due to a delicate balance between a constitutively active tyrosine phosphatase and constitutively active tyrosine kinase, the increase in phosphorylation during cell shrinkage was demonstrated to derive specifically from an activation of the latter. Further, a peculiar inhibition pattern of the volume-sensitive erythrocyte tyrosine kinase that matched that of p72syk, a tyrosine kinase already known to associate with band 3 in vivo, suggested the involvement of this kinase in the volume-dependent response.

Erythrocyte signal transduction pathways and their possible functions

Human erythrocytes are equipped with a diversity of receptors and effectors that mediate well-characterized signal transduction pathways in nonerythroid cells. Some of these erythrocyte components may be vestiges of signaling pathways critical to the functions of the erythrocyte's precursors but no longer needed in the mature erythrocyte. Other signaling elements, however, are likely involved in enabling the erythrocyte to detect and respond to the needs of other hematopoietic and endothelial cells with which it comes in contact.

Tyrosine phosphorylation of band 3 protein in Ca2+/A23187-treated human erythrocytes

Human erythrocytes were induced to release membrane vesicles by treatment with Ca2+ and ionophore A23187. In addition to the biochemical changes already known to accompany loading of human erythrocytes with Ca2+, the present study reveals that tyrosine phosphorylation of the anion exchanger band 3 protein also occurs. The relationship between tyrosine phosphorylation of band 3 and membrane vesiculation was analysed using quinine (a non-specific inhibitor of the Ca(2+)-activated K+ channel, and the only known inhibitor of Ca(2+)-induced vesiculation) and charybdotoxin, a specific inhibitor of the apamin-insensitive K(+)-channel. Both inhibitors suppressed tyrosine phosphorylation of band 3. In the presence of quinine, membrane vesiculation was also suppressed. In contrast, at the concentration of charybdotoxin required to suppress tyrosine phosphorylation of band 3, membrane vesiculation was only mildly inhibited (16-23% inhibition), suggesting that tyrosine phosphorylation of band 3 is not necessary for membrane vesiculation. Phosphorylation of band 3 was in fact observed when erythrocytes were induced to shrink in a Ca(2+)-independent manner, e.g. by treatment with the K+ ionophore valinomycin or with hypertonic solutions. These observations suggest that band 3 tyrosine phosphorylation occurs when cell volume regulation is required.

Oxidation state of glutathione and membrane proteins in human red cells of different age

In this study the oxidation state of glutathione and membrane proteins was analyzed in red cells of different age in basal conditions. Red cells of different age were prepared by centrifugation and separated according to their density by two procedures: on self-forming gradients of autologous plasma (Murphy's procedure) and on discontinuous Stractan gradients. The efficiency of the two procedures in the isolation of senescent cells was compared. The results indicate that, despite the evidence that total cell GSH decreases with aging, its concentration, evaluated in the cell preparations of different ages, remains constant throughout the red cell life, when correlated with cell water content. Glutathione disulfide concentration increases with aging. The oxidation state of membrane proteins does not seem to change during the red cell life span.

Reduction of DABS-L-methionine-dl-sulfoxide by protein methionine sulfoxide reductase from polymorphonuclear leukocytes: stereospecificity towards the l-sulfoxide

A new synthetic substrate for protein methionine sulfoxide reductase is proposed. We show that extracts from human polymorphonuclear leukocytes can reduce 4-dimethylaminoazobenzene-4'-sulfonyl-L-methionine-dl-sulfoxide [DABS-L-Met-dl-(O)] to the corresponding methionine derivative, in the presence of dithiothreitol or dithioerythritol. The product of the reaction (DABS-Met) was separated by reversed-phase HPLC and detected by reading the absorbance at 436 nm. Due to the chirality of the sulfur atom in the sulfoxide, two diastereomers of Met(O) exist, namely Met-l-sulfoxide and Met-d-sulfoxide. After separation of the two forms and preparation of the DABS-derivatives, we observed a preferential reduction of the l-sulfoxide by polymorphonuclear leukocytes extracts. We discuss the possibility that the observed stereospecificity might have physiological relevance in the field of the oxidative modifications of proteins.

Evidence for membrane protein oxidation during in vivo aging of human erythrocytes

Oxidative lesions to membrane proteins were studied in human erythrocytes of different age and were evaluated on ghost membrane preparations by assaying thiol and methionine sulphoxide groups, and in situ on intact cells, after treating erythrocytes with the fluorochrome N-(7-dimethyl-amino-4-methyl-coumarinyl) maleimide (DACM). DACM reacts with thiol groups and the amount of this reagent bound by membrane proteins was quantified after SDS-PAGE separation. Results obtained show that during aging of normal cells the oxidative state of membrane proteins increases: this was better shown by the assay of methionine sulphoxide residues rather than by the thiol titration, when studies were carried out on ghost membranes. After separation of individual membrane proteins by SDS-PAGE, decreased accessibility of DACM to thiol groups of band 3 and of the main proteins of the membrane skeleton was evident in senescent erythrocytes. These results show that during aging, band 3 and membrane skeleton proteins undergo conformational changes and/or oxidation. Similar results were obtained when thiol distribution was studied in membrane proteins separated by SDS-PAGE in both reducing and non-reducing conditions.