Cellular redox poise modulation; the role of coenzyme Q10, gene and metabolic regulation

In this communication, the concept is developed that coenzyme Q₁₀ has a toti-potent role in the regulation of cellular metabolism. The redox function of coenzyme Q₁₀ leads to a number of outcomes with major impacts on sub-cellular metabolism and gene regulation. Coenzyme Q₁₀'s regulatory activities are achieved in part, through the agency of its localization in the various sub-cellular membrane compartments. Its fluctuating redox poise within these membranes reflects the cell's metabolic micro-environments. As an integral part of this process, H₂O₂ is generated as a product of the normal electron transport systems to function as a mitogenic second messenger informing the nuclear and mitochondrial (chloroplast) genomes on a real-time basis of the status of the sub-cellular metabolic micro-environments and the needs of that cell. Coenzyme Q₁₀ plays a major role both in energy conservation, and energy dissipation as a component of the uncoupler protein family. Coenzyme Q₁₀ is both an anti-oxidant and a pro-oxidant and of the two the latter is proposed as its more important cellular function. Coenzyme Q₁₀ has been reported, to be of therapeutic benefit in the treatment of a wide range of age related degenerative systemic diseases and mitochondrial disease. Our over-arching hypotheses on the central role played by coenzyme Q₁₀ in redox poise changes, the generation of H₂O₂, consequent gene regulation and metabolic flux control may account for the wide ranging therapeutic benefits attributed to coenzyme Q₁₀.     

Testing optimal foraging models for air-breathing divers

Models of diving optimality qualitatively predict diving behaviours of aquatic birds and mammals. However, none of them has been empirically tested. We examined the quantitative predictions of optimal diving models by combining cumulative oxygen uptake curves with estimates of power costs during the dives of six tufted ducks, Aythya fuligula. The effects of differing foraging costs on dive duration and rate of oxygen uptake (V_O2up) at the surface were measured during bouts of voluntary dives to a food tray. The birds were trained to surface into a respirometer after each dive, so that changes in V_O2up over time could be measured. The tray held either just food or closely packed stones on top of the food to make foraging energetically more costly. In contrast to predictions from the Houston & Carbone model, foraging time (t_f) increased after dives incorporating higher foraging energy costs but surface time (t_s) remained the same. While optimal diving models have assumed that the cumulative oxygen uptake curve is fixed, V_O2up increased when the energy cost of the dive increased. The optimal breathing model quantitatively predicted ts in both conditions and oxygen consumption during foraging (m₂t_f) in the control condition, for the mean of all ducks. This offers evidence that the ducks were diving optimally and supports the fundamentals of optimal diving theory. However, the model did not consistently predictt_s or m₂t_f for individual birds. We discuss the limits of optimal foraging models for air-breathing divers caused by individual variation. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.      

Aerosol generation by metered-dose inhalers containing dimethyl ether/propane inverse microemulsions

Water soluble compounds were incorporated into metered-dose inhalers (MDIs) by using water-in-propellant lecithin microemulsions, in which dimethyl ether (DME) and propane acted as both continuous phase and propellant. Lecithin, water, and water soluble compounds were added to glass MDI containers, valves were crimped on, and propellants were added using a pressure burette. Aerosols were produced using commercially available actuators, and inertial impaction was used to determine the mass median aerodynamic diameter (MMAD), geometric standard deviation (GSD), and fine particle fraction (FPF) of the resulting aerosols. The DME/propane/lecithin, microemulsion MDIs generated aerosols with particle size distributions suitable for pulmonary delivery (eg, MMAD 3.1 μm, FPF 59% for DME with lecithin content 3%, water content 2.5% [wt/wt]). Increasing water concentration (up to 8% wt/wt) was correlated with a reduction in FPF. Freezing and rewarming had no adverse effect on MMAD, GSD, or FPF. Storage of microemulsion samples for up to 3 weeks did not adversely affect the MMAD, GSD, or FPF. This approach may enable the pulmonary delivery of water soluble therapeutic agents via MDIs.     

Some effects of ouabain on cellular ions and water in epithelial cells of toad urinary bladder

The Journal of Membrane Biology - Transepithelial sodium transport was virtually abolished when toad urinary hemibladders, mounted in chambers and short-circuited, were exposed on their serosal...     

Genetic Analyses of the Polarity Alleles in Recombinants from Mitochondrial Genetic Crosses

A number of minority recombinant and parental types from a heterosexual cross were analyzed for the omega allele they carry. It was found that recombinant progeny can be omega(-), that minority parental types among the progeny can be omega(+) rather than omega(-), and, finally, that certain of the results suggest that the omega locus may not be at the proximal end of the mitochondrial genetic map (Bolotin et al., 1971; Grivell et al., 1973) but rather may lie between the [cap1-r/cap-s] and [ery1-r/ery-s] loci.     

Plastidial Expression of Type II NAD(P)H Dehydrogenase Increases the Reducing State of Plastoquinones and Hydrogen Photoproduction Rate by the Indirect Pathway in Chlamydomonas reinhardtii

Biological conversion of solar energy into hydrogen is naturally realized by some microalgae species due to a coupling between the photosynthetic electron transport chain and a plastidial hydrogenase. While promising for the production of clean and sustainable hydrogen, this process requires improvement to be economically viable. Two pathways, called direct and indirect photoproduction, lead to sustained hydrogen production in sulfur-deprived Chlamydomonas reinhardtii cultures. The indirect pathway allows an efficient time-based separation of O₂ and H₂ production, thus overcoming the O₂ sensitivity of the hydrogenase, but its activity is low. With the aim of identifying the limiting step of hydrogen production, we succeeded in overexpressing the plastidial type II NAD(P)H dehydrogenase (NDA2). We report that transplastomic strains overexpressing NDA2 show an increased activity of nonphotochemical reduction of plastoquinones (PQs). While hydrogen production by the direct pathway, involving the linear electron flow from photosystem II to photosystem I, was not affected by NDA2 overexpression, the rate of hydrogen production by the indirect pathway was increased in conditions, such as nutrient limitation, where soluble electron donors are not limiting. An increased intracellular starch was observed in response to nutrient deprivation in strains overexpressing NDA2. It is concluded that activity of the indirect pathway is limited by the nonphotochemical reduction of PQs, either by the pool size of soluble electron donors or by the PQ-reducing activity of NDA2 in nutrient-limited conditions. We discuss these data in relation to limitations and biotechnological improvement of hydrogen photoproduction in microalgae.A number of microalgal and cyanobacterial species are able to convert solar energy into hydrogen by photobiological processes and are therefore considered promising organisms for developing clean and sustainable hydrogen production (Benemann, 2000; Ghirardi et al., 2000; Rupprecht et al., 2006). In microalgae, hydrogen photoproduction results from coupling the photosynthetic electron transport chain and a plastidial [FeFe] hydrogenase. Under most conditions, hydrogen photoproduction is a transient phenomenon that lasts from several seconds to a few minutes (Ghirardi et al., 2000; Melis and Happe, 2001). It has been considered a relic of evolution that may now serve, under certain environmental conditions, such as induction of photosynthesis in anoxia (Ghysels et al., 2013), as a safety valve that protects the photosynthetic electron transport chain from photodamage that results from overreduction of electron acceptors (Kessler, 1973; Tolleter et al., 2011). A major limitation to sustained hydrogen photoproduction is due to the oxygen sensitivity of the [FeFe] hydrogenase (Happe et al., 2002; Stripp et al., 2009). Melis et al. (2000) proposed an elegant way to overcome this oxygen sensitivity through a time-based separation of hydrogen and oxygen production phases occurring, for instance, in response to sulfur deficiency in a closed environment. Another limitation is related to the electron supply for the hydrogenase coming from the photosynthetic electron transport chain (Cournac et al., 2002). This limitation is partly due to the fact that other metabolic pathways, such as ferredoxin-NADP⁺ reductase and CO₂ fixation, compete with the hydrogenase for the use of reduced ferredoxin (Gaffron and Rubin, 1942; Hemschemeier et al., 2008). This is also due to upstream regulation of the electron transport chain, recently evidenced from the study of a Chlamydomonas reinhardtii mutant affected in proton gradient regulation-like1 (PGRL1)-mediated cyclic electron flow (CEF) around PSI. The strong enhancement of hydrogen production rates observed in the pgrl1 mutant was interpreted as the release of a control exerted by the transthylakoidal pH gradient on electron supply to the hydrogenase (Tolleter et al., 2011).Two pathways, direct or indirect, can supply electrons to the hydrogenase (Benemann, 2000; Melis and Happe, 2001; Chochois et al., 2009). In the direct pathway, the whole electron transport chain is engaged, with PSII supplying electrons to the plastoquinone (PQ) pool, the cytochrome b₆/f complex, and, in turn, PSI, ferredoxin, and the [FeFe] hydrogenase. Due to the high oxygen sensitivity of the [FeFe] hydrogenase and to the fact that O₂ is produced during photosynthesis at PSII, the direct pathway only operates when PSII activity is lower than mitochondrial respiration, thereby allowing anaerobiosis to be maintained. Such conditions can be obtained by decreasing PSII activity either by means of sulfur deprivation (Melis et al., 2000) or by decreasing light intensity in the photobioreactor (Degrenne et al., 2010). In the indirect pathway, reducing equivalents, stored as starch during the aerobic phase, are subsequently used to fuel hydrogen production. This implies a nonphotochemical reduction of the PQ pool that is at least in part mediated by NDA2, a type II NADH dehydrogenase discovered in C. reinhardtii chloroplasts (Desplats et al., 2009). RNA interference lines expressing lower levels of NDA2 show lower hydrogen production rates, and it was concluded that NDA2 is involved in hydrogen production by the indirect pathway (Jans et al., 2008; Mignolet et al., 2012). The indirect pathway allows for an efficient time-based separation of O₂- and H₂-producing phases because it does not involve PSII activity and does not produce O₂. However, the indirect pathway has a much lower rate than the direct pathway (Cournac et al., 2002; Antal et al., 2009; Chochois et al., 2009). With the aim to identify limiting steps of hydrogen production in microalgae, we attempted to overexpress NDA2 in C. reinhardtii chloroplasts. We report that algal strains displaying a 2-fold increase in NDA2 show an increased nonphotochemical reduction of PQs and an increased rate of hydrogen production by the indirect pathway, the latter being only observed in conditions where stromal reducing equivalents are available in sufficient amounts.     

New Insights into Muscle Function during Pivot Feeding in Seahorses

Seahorses, pipefish and their syngnathiform relatives are considered unique amongst fishes in using elastic recoil of post-cranial tendons to pivot the head extremely quickly towards small crustacean prey. It is known that pipefish activate the epaxial muscles for a considerable time before striking, at which rotations of the head and the hyoid are temporarily prevented to allow energy storage in the epaxial tendons. Here, we studied the motor control of this system in seahorses using electromyographic recordings of the epaxial muscles and the sternohyoideus-hypaxial muscles with simultaneous high-speed video recordings of prey capture. In addition we present the results from a stimulation experiment including the muscle hypothesised to be responsible for the locking and triggering of pivot feeding in seahorses (m. adductor arcus palatini). Our data confirmed that the epaxial pre-activation pattern observed previously for pipefish also occurs in seahorses. Similar to the epaxials, the sternohyoideus-hypaxial muscle complex shows prolonged anticipatory activity. Although a considerable variation in displacements of the mouth via head rotation could be observed, it could not be demonstrated that seahorses have control over strike distance. In addition, we could not identify the source of the kinematic variability in the activation patterns of the associated muscles. Finally, the stimulation experiment supported the previously hypothesized role of the m. adductor arcus palatini as the trigger in this elastic recoil system. Our results show that pre-stressing of both the head elevators and the hyoid retractors is taking place. As pre-activation of the main muscles involved in pivot feeding has now been demonstrated for both seahorses and pipefish, this is probably a generalized trait of Syngnathidae.     

Randomized single oral dose phase 1 study of safety,tolerability, and pharmacokinetics of Iminosugar UV-4 Hydrochloride (UV-4B) in healthy subjects

BackgroundUV-4 (N-(9’-methoxynonyl)-1-deoxynojirimycin, also called MON-DNJ) is an iminosugar small-molecule oral drug candidate with in vitro antiviral activity against diverse viruses including dengue, influenza, and filoviruses and demonstrated in vivo efficacy against both dengue and influenza viruses. The antiviral mechanism of action of UV-4 is through inhibition of the host endoplasmic reticulum-resident α-glucosidase 1 and α-glucosidase 2 enzymes. This inhibition prevents proper glycan processing and folding of virus glycoproteins, thereby impacting virus assembly, secretion, and the fitness of nascent virions.Methodology/Principal findingsHere we report a first-in-human, single ascending dose Phase 1a study to evaluate the safety, tolerability, and pharmacokinetics of UV-4 hydrochloride (UV-4B) in healthy subjects (ClinicalTrials.gov Identifier {"type":"clinical-trial","attrs":{"text":"NCT02061358","term_id":"NCT02061358"}}NCT02061358). Sixty-four subjects received single oral doses of UV-4 as the hydrochloride salt equivalent to 3, 10, 30, 90, 180, 360, 720, or 1000 mg of UV-4 (6 subjects per cohort), or placebo (2 subjects per cohort). Single doses of UV-4 hydrochloride were well tolerated with no serious adverse events or dose-dependent increases in adverse events observed. Clinical laboratory results, vital signs, and physical examination data did not reveal any safety signals. Dose-limiting toxicity was not observed; the maximum tolerated dose of UV-4 hydrochloride in humans has not yet been determined (>1000 mg). UV-4 was rapidly absorbed and distributed after dosing with the oral solution formulation used in this study. Median time to reach maximum plasma concentration ranged from 0.5–1 hour and appeared to be independent of dose. Exposure increased approximately in proportion with dose over the 333-fold dose range. UV-4 was quantifiable in pooled urine over the entire collection interval for all doses.Conclusions/SignificanceUV-4 is a host-targeted broad-spectrum antiviral drug candidate. At doses in humans up to 1000 mg there were no serious adverse events reported and no subjects were withdrawn from the study due to treatment-emergent adverse events. These data suggest that therapeutically relevant drug levels of UV-4 can be safely administered to humans and support further clinical development of UV-4 hydrochloride or other candidate antivirals in the iminosugar class.Trial registrationClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT02061358","term_id":"NCT02061358"}}NCT02061358 https://clinicaltrials.gov/ct2/show/{"type":"clinical-trial","attrs":{"text":"NCT02061358","term_id":"NCT02061358"}}NCT02061358.