Oxidative damage from elevated production of reactive oxygen species (ROS) contributes to ischemia-reperfusion injury in myocardial infarction and stroke. The mechanism by which the increase in ROS ...occurs is not known, and it is unclear how this increase can be prevented. A wide variety of nitric oxide donors and S-nitrosating agents protect the ischemic myocardium from infarction, but the responsible mechanisms are unclear. Here we used a mitochondria-selective S-nitrosating agent, MitoSNO, to determine how mitochondrial S-nitrosation at the reperfusion phase of myocardial infarction is cardioprotective in vivo in mice. We found that protection is due to the S-nitrosation of mitochondrial complex I, which is the entry point for electrons from NADH into the respiratory chain. Reversible S-nitrosation of complex I slows the reactivation of mitochondria during the crucial first minutes of the reperfusion of ischemic tissue, thereby decreasing ROS production, oxidative damage and tissue necrosis. Inhibition of complex I is afforded by the selective S-nitrosation of Cys39 on the ND3 subunit, which becomes susceptible to modification only after ischemia. Our results identify rapid complex I reactivation as a central pathological feature of ischemia-reperfusion injury and show that preventing this reactivation by modification of a cysteine switch is a robust cardioprotective mechanism and hence a rational therapeutic strategy.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Research on sterile mosquito technology from 1955 to the 1980s provided a substantial body of knowledge on propagation and release of sterile mosquitoes. Radiation sterilisation and ...chemosterilisation have been used effectively to induce dominant lethality and thereby sterilise important mosquito vectors in the laboratory. Experimental releases of chemosterilised males provided complete control of Anopheles albimanus in a small breeding population (14-15 sq km) in El Salvador. Releases of radiation sterilised males failed to control either Aedes aegypti or Anopheles quadrimaculatus in the USA. Releases of radiation-sterilised and chemosterilised male Culex quinquefasciatus in the USA and India were successful in some instances. Development of genetic sexing systems for Anopheles and improved physical separation methods for Culex have made it possible to rear and release males almost exclusively (> 99%) minimizing the release of potential vectors, the females. Factors that affected efficacy in some field programmes included reduction of competitiveness by radiation, immigration of fertilized females from outside the release zones, and inability of laboratory-bred males to perform in the wild. Despite significant progress, institutional commitments to carry the process further were generally lacking in the late 1970s and until recently. Now, with renewed interest and support for further assessment of this technology, this paper summarizes the current knowledge base, prioritizes some areas of investigation, and challenges scientists and administrators to maintain an awareness of progress, remain realistic about the interpretation of new findings, and make decisions about the sterile insect technique on the basis of informed scientific documentation. Areas recommended for priority research status include the establishment of genetic sexing mechanisms that can be transferred to other mosquito species, re-examination of radiation sterilisation, aerial release technology and mass rearing.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The structures of mitochondrial transporters and uncoupling proteins are 3-fold pseudosymmetrical, but their substrates and coupling ions are not. Thus, deviations from symmetry are to be expected in ...the substrate and ion-binding sites in the central aqueous cavity. By analyzing the 3-fold pseudosymmetrical repeats from which their sequences are made, conserved asymmetric residues were found to cluster in a region of the central cavity identified previously as the common substrate-binding site. Conserved symmetrical residues required for the transport mechanism were found at the water-membrane interfaces, and they include the three PXDEXXRK motifs, which form a salt bridge network on the matrix side of the cavity when the substrate-binding site is open to the mitochondrial intermembrane space. Symmetrical residues in three FYDEXXRK motifs are on the cytoplasmic side of the cavity and could form a salt bridge network when the substrate-binding site is accessible from the mitochondrial matrix. It is proposed that the opening and closing of the carrier may be coupled to the disruption and formation of the 2 salt bridge networks via a 3-fold rotary twist induced by substrate binding. The interaction energies of the networks allow members of the transporter family to be classified as strict exchangers or uniporters.
Nonlinear encoding of chromatic contrast by the early visual cortex predicts that anomalous trichromats will show a larger McCollough effect than normal trichromats. In Experiment 1 we employed the ...McCollough effect to probe the cortical representation of saturation in normal trichromats, and used the results to predict enhanced McCollough effects for anomalous trichromats, which we measured in Experiment 2. In Experiment 1 three participants adapted to red and green orthogonal gratings of four different saturations. Using nulling to measure aftereffect strength, we found that halving the saturation of the inducing gratings decreased aftereffect strength only slightly, consistent with a compressive coding of saturation in early visual cortex. In anomalous trichromats, cone contrasts between red and green are greatly decreased from those of normal trichromats, but induced aftereffects are only slightly decreased, because of the non-linearity in the cortical encoding of saturation. To null the aftereffect, however, the retinal color deficiency must be overcome by adding more color to the null than required by normal trichromats. We confirmed this prediction in Experiment 2 where four anomalous trichromats required nulling stimuli approximately four times more saturated than did normal trichromats. We consider two competing models to explain our results: in a ‘pigment swap’ model anomalous trichromats have an altered photopigment but process color postreceptorally in the same way as normal trichromats; in a ‘postreceptoral compensation’ model the cortical representation of red-green contrasts is amplified to compensate for reduced cone contrasts. The latter provided a better fit to our data.
Mitochondrial disorders affect 1/5,000 and have no cure. Inducing mitochondrial biogenesis with bezafibrate improves mitochondrial function in animal models, but there are no comparable human ...studies. We performed an open‐label observational experimental medicine study of six patients with mitochondrial myopathy caused by the m.3243A>G MTTL1 mutation. Our primary aim was to determine the effects of bezafibrate on mitochondrial metabolism, whilst providing preliminary evidence of safety and efficacy using biomarkers. The participants received 600–1,200 mg bezafibrate daily for 12 weeks. There were no clinically significant adverse events, and liver function was not affected. We detected a reduction in the number of complex IV‐immunodeficient muscle fibres and improved cardiac function. However, this was accompanied by an increase in serum biomarkers of mitochondrial disease, including fibroblast growth factor 21 (FGF‐21), growth and differentiation factor 15 (GDF‐15), plus dysregulation of fatty acid and amino acid metabolism. Thus, although potentially beneficial in short term, inducing mitochondrial biogenesis with bezafibrate altered the metabolomic signature of mitochondrial disease, raising concerns about long‐term sequelae.
Synopsis
There are currently no treatments for mitochondrial disorders. Bezafibrate has been shown to induce mitochondrial biogenesis and improve mitochondrial function in pre‐clinical models, but has not been systematically studied in patients.
We performed an open‐label observational study of six patients with the m.3243A>G MTTL1 mutation using 600–1,200 mg bezafibrate daily for 12 weeks.
There were no clinically significant adverse events.
We observed an increase in serum biomarkers of mitochondrial disease, including fibroblast growth factor 21 (FGF‐21), growth and differentiation factor 15 (GDF‐15).
Metabolomic analysis showed dysregulation of fatty‐acid and amino‐acid metabolism, which are signs of compromised oxidative phosphorylation.
Although potentially beneficial in short term, inducing mitochondrial biogenesis with bezafibrate worsened the metabolomic signature of mitochondrial disease, raising concerns about long‐term sequalae.
There are currently no treatments for mitochondrial disorders. Bezafibrate has been shown to induce mitochondrial biogenesis and improve mitochondrial function in pre‐clinical models, but has not been systematically studied in patients.
Whole-exome sequencing and autozygosity mapping studies, independently performed in subjects with defective combined mitochondrial OXPHOS-enzyme deficiencies, identified a total of nine ...disease-segregating FBXL4 mutations in seven unrelated mitochondrial disease families, composed of six singletons and three siblings. All subjects manifested early-onset lactic acidemia, hypotonia, and developmental delay caused by severe encephalomyopathy consistently associated with progressive cerebral atrophy and variable involvement of the white matter, deep gray nuclei, and brainstem structures. A wide range of other multisystem features were variably seen, including dysmorphism, skeletal abnormalities, poor growth, gastrointestinal dysmotility, renal tubular acidosis, seizures, and episodic metabolic failure. Mitochondrial respiratory chain deficiency was present in muscle or fibroblasts of all tested individuals, together with markedly reduced oxygen consumption rate and hyperfragmentation of the mitochondrial network in cultured cells. In muscle and fibroblasts from several subjects, substantially decreased mtDNA content was observed. FBXL4 is a member of the F-box family of proteins, some of which are involved in phosphorylation-dependent ubiquitination and/or G protein receptor coupling. We also demonstrate that FBXL4 is targeted to mitochondria and localizes in the intermembrane space, where it participates in an approximately 400 kDa protein complex. These data strongly support a role for FBXL4 in controlling bioenergetic homeostasis and mtDNA maintenance. FBXL4 mutations are a recurrent cause of mitochondrial encephalomyopathy onset in early infancy.
Mitochondrial carriers link biochemical pathways in the cytosol and mitochondrial matrix by transporting substrates across the inner mitochondrial membrane. Substrate recognition is specific for each ...carrier, but sequence similarities suggest the carriers have similar structures and mechanisms of substrate translocation. By considering conservation of amino acids, distance and chemical constraints, and by modeling family members on the known structure of the ADP/ATP translocase, we have identified a common substrate binding site. It explains substrate selectivity and proton coupling and provides a mechanistic link to carrier opening by substrate-induced perturbation of the salt bridges that seal the pathway to and from the mitochondrial matrix. It enables the substrate specificity of uncharacterized mitochondrial carriers to be predicted.
Mitochondrial diseases are frequently associated with mutations in mitochondrial DNA (mtDNA). In most cases, mutant and wild-type mtDNAs coexist, resulting in heteroplasmy. The selective elimination ...of mutant mtDNA, and consequent enrichment of wild-type mtDNA, can rescue pathological phenotypes in heteroplasmic cells. Use of the mitochondrially targeted zinc finger-nuclease (mtZFN) results in degradation of mutant mtDNA through site-specific DNA cleavage. Here, we describe a substantial enhancement of our previous mtZFN-based approaches to targeting mtDNA, allowing near-complete directional shifts of mtDNA heteroplasmy, either by iterative treatment or through finely controlled expression of mtZFN, which limits off-target catalysis and undesired mtDNA copy number depletion. To demonstrate the utility of this improved approach, we generated an isogenic distribution of heteroplasmic cells with variable mtDNA mutant level from the same parental source without clonal selection. Analysis of these populations demonstrated an altered metabolic signature in cells harbouring decreased levels of mutant m.8993T>G mtDNA, associated with neuropathy, ataxia, and retinitis pigmentosa (NARP). We conclude that mtZFN-based approaches offer means for mtDNA heteroplasmy manipulation in basic research, and may provide a strategy for therapeutic intervention in selected mitochondrial diseases.
TIMM50 is an essential component of the TIM23 complex, the mitochondrial inner membrane machinery that imports cytosolic proteins containing a mitochondrial targeting presequence into the ...mitochondrial inner compartment. Whole exome sequencing (WES) identified compound heterozygous pathogenic mutations in TIMM50 in an infant patient with rapidly progressive, severe encephalopathy. Patient fibroblasts presented low levels of TIMM50 and other components of the TIM23 complex, lower mitochondrial membrane potential, and impaired TIM23‐dependent protein import. As a consequence, steady‐state levels of several components of mitochondrial respiratory chain were decreased, resulting in decreased respiration and increased ROS production. Growth of patient fibroblasts in galactose shifted energy production metabolism toward oxidative phosphorylation (OxPhos), producing an apparent improvement in most of the above features but also increased apoptosis. Complementation of patient fibroblasts with TIMM50 improved or restored these features to control levels. Moreover, RNASEH1 and ISCU mutant fibroblasts only shared a few of these features with TIMM50 mutant fibroblasts. Our results indicate that mutations in TIMM50 cause multiple mitochondrial bioenergetic dysfunction and that functional TIMM50 is essential for cell survival in OxPhos‐dependent conditions.
Synopsis
Mitochondrial TIMM50 is an essential component of the TIM23 protein import machinery. Mutations in TIMM50 in an infant patient are associated with rapidly progressive, severe encephalopathy.
Mutations in TIMM50 drastically decreases mitochondrial protein import though the TIM23 complex.
Mitochondrial OxPhos components and oxygen consumption are decreased in TIMM50 mutant fibroblasts.
Cell viability is compromised in OxPhos‐dependent conditions in the absence of functional TIMM50.
Complementation with wild‐type TIMM50 restores or greatly improves mitochondrial import, respiration and cell viability in OxPhos‐dependent condition.
Mitochondrial TIMM50 is an essential component of the TIM23 protein import machinery. Mutations in TIMM50 in an infant patient are associated with rapidly progressive, severe encephalopathy.
The agrochemical sector operates on a large scale within a highly complex environment. Cost-effective production on an increasing scale in a sustainable fashion imposes massive constraints on the ...industry. Here we offer a perspective on flow chemistry, with literature highlights showing how the application of this technology can impact chemical processes (especially at the early stages of R&D) for agrochemicals, with clear benefits in comparison with a traditional batch vessel, be it safety, quality, or throughput. The value of flow chemistry for the business is clear, and the number of examples reported in the literature will undoubtably continue to increase in the agrochemical industry.
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