The Arabidopsis Mitochondrial Glutaredoxin GRXS15 Provides [2Fe-2S] Clusters for ISCA-Mediated [4Fe-4S] Cluster Maturation

Iron-sulfur (Fe-S) proteins are crucial for many cellular functions, particularly those involving electron transfer and metabolic reactions. An essential monothiol glutaredoxin GRXS15 plays a key role in the maturation of plant mitochondrial Fe-S proteins. However, its specific molecular function is not clear, and may be different from that of the better characterized yeast and human orthologs, based on known properties. Hence, we report here a detailed characterization of the interactions between Arabidopsis thaliana GRXS15 and ISCA proteins using both in vivo and in vitro approaches. Yeast two-hybrid and bimolecular fluorescence complementation experiments demonstrated that GRXS15 interacts with each of the three plant mitochondrial ISCA1a/1b/2 proteins. UV-visible absorption/CD and resonance Raman spectroscopy demonstrated that coexpression of ISCA1a and ISCA2 resulted in samples with one [2Fe-2S]²⁺ cluster per ISCA1a/2 heterodimer, but cluster reconstitution using as-purified [2Fe-2S]-ISCA1a/2 resulted in a [4Fe-4S]²⁺ cluster-bound ISCA1a/2 heterodimer. Cluster transfer reactions monitored by UV-visible absorption and CD spectroscopy demonstrated that [2Fe-2S]-GRXS15 mediates [2Fe-2S]²⁺ cluster assembly on mitochondrial ferredoxin and [4Fe-4S]²⁺ cluster assembly on the ISCA1a/2 heterodimer in the presence of excess glutathione. This suggests that ISCA1a/2 is an assembler of [4Fe-4S]²⁺ clusters, via two-electron reductive coupling of two [2Fe-2S]²⁺ clusters. Overall, the results provide new insights into the roles of GRXS15 and ISCA1a/2 in effecting [2Fe-2S]²⁺ to [4Fe-4S]²⁺ cluster conversions for the maturation of client [4Fe-4S] cluster-containing proteins in plants.     

Adventitial Tertiary Lymphoid Organs as Potential Source of MicroRNA Biomarkers for Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is an inflammatory disease associated with marked changes in the cellular composition of the aortic wall. This study aims to identify microRNA (miRNA) expression in aneurysmal inflammatory cells isolated by laser microdissection from human tissue samples. The distribution of inflammatory cells (neutrophils, B and T lymphocytes, mast cells) was evaluated in human AAA biopsies. We observed in half of the samples that adventitial tertiary lymphoid organs (ATLOs) with a thickness from 0.5 to 2 mm were located exclusively in the adventitia. Out of the 850 miRNA that were screened by microarray in isolated ATLOs (n = 2), 164 miRNAs were detected in ATLOs. The three miRNAs (miR-15a-3p, miR-30a-5p and miR-489-3p) with the highest expression levels were chosen and their expression quantified by RT-PCR in isolated ATLOs (n = 4), M1 (n = 2) and M2 macrophages (n = 2) and entire aneurysmal biopsies (n = 3). Except for the miR-30a-5p, a similar modulation was found in ATLOs and the two subtypes of macrophages. The modulated miRNAs were then evaluated in the plasma of AAA patients for their potential as AAA biomarkers. Our data emphasize the potential of miR-15a-3p and miR-30a-5p as biomarkers of AAA but also as triggers of ATLO evolution. Further investigations will be required to evaluate their targets in order to better understand AAA pathophysiology.     

Template Synthesis of Iminodiacetic Acid Polysiloxane Immobilized Ligand Systems and their Metal Uptake Capacity

Porous solid polysiloxane ligand systems bearing an iminodiacetic acid chelating ligand of the general formula P-IDA (where P- represents [Si-O] _n polysiloxane network and IDA represent an organofunctional group) were achieved in two-step reaction. The first step includes a template synthesis of 3-iodopropylpolysiloxane (P-I) or 3-aminopropylpolysiloxane (P-MA) by hydrolytic polycondensation of TEOS and the corresponding silane agent in the presence of CTAB as a surfactant. The second step includes a modification of 3-iodopropylpolysiloxane with diethyliminodiacetate or 3-aminopropylpolysiloxane with ethylchloroacetate to produce IDA-functionalized polysiloxane ligand systems P-IDA-I & P-IDA-II respectively. It was found that the modified IDA-functionalized polysiloxane ligand systems exhibited higher capacities for uptake of the metal ions (Ni ²⁺, Cu ²⁺ and Pb ²⁺) than those prepared without surfactants.     

SiOC Ceramic Monoliths with Hierarchical Porosity

SiOC glass monoliths possessing hierarchical porosity were produced by a one-pot processing method. Periodic mesoporous organosilica (PMO) particles were embedded into a foamed siloxane preceramic polymer. After pyrolysis at 1000°C in inert atmosphere, open celled, permeable SiOC ceramic monoliths with a high amount of pores, ranging in size from hundred of micrometers to a few nanometers, were obtained. The components possessed a specific surface area of 137 m²/g, indicating the retention of most of the mesopores after the pyrolytic conversion of the PMO precursor particles. These fillers converted to truncated rhombic dodecahedral SiOC mesoporous micron-sized grains, homogeneously distributed throughout the SiOC cellular matrix. The produced porous ceramics possessed compression strength of about 1.7 MPa, which is adequate for their use in several engineering applications.     

Thermal evolution and crystallisation of polydimethylsiloxane–zirconia nanocomposites prepared by the sol–gel method

Polydimethylsiloxane–zirconia nanocomposites have been prepared by hydrolysis of diethoxydimethylsilane and zirconium n-propoxide in different molar ratios. Transparent, homogeneous and non-porous xerogels have been obtained up to 70 mol% ZrO₂ content. The starting xerogels have been pyrolyzed under argon atmosphere up to 1400°C and the structural evolution of samples treated at different temperatures has been followed by X-ray diffraction, transmission electron microscopy, infrared and ²⁹Si solid state nuclear magnetic resonance spectroscopies, thermal analyses and N₂ sorption measurements. The polymer-to-ceramic conversion leads to the structural rearrangement of the siloxane component with the production at 600°C of high surface area materials with pore sizes below 3 nm. Samples are amorphous up to 800°C. At 1000°C, the structural evolution of the silicon moiety produces an amorphous oxycarbide phase whereas the primary crystallisation of tetragonal zirconia takes place, with crystallinity and crystallite sizes depending on the ZrO₂ content. At 1400°C, the silicon oxycarbide phase generates a mixture of amorphous silica and crystalline silicon carbide polymorphs. In this matrix, tetragonal and monoclinic ZrO₂ phases are present with ZrO₂ average crystallite dimensions never exceeding 20 nm, for ZrO₂ content ≤50 mol%. The tetragonal/monoclinic ratio as well as the crystallite sizes appear strictly related to the chemical composition. ©     

Modulation of Cellular Fate of Vinyl Triarylamines through Structural Fine Tuning: To Stay or Not To Stay in the Mitochondria?

Mitochondria are involved in many cellular pathways and dysfunctional mitochondria are linked to various diseases. Hence efforts have been made to design mitochondria-targeted fluorophores for monitoring the mitochondrial status. However, the factors that govern the mitochondria-targeted potential of dyes are not well-understood. In this context, we synthesized analogues of the TP-2Bzim probe belonging to the vinyltriphenylamine (TPA) class and already described for its capacity to bind nuclear DNA in fixed cells and mitochondria in live cells. These analogues ( TP-1Bzim, TPⁿ-2Bzim, TP¹⁺-2Bzim, TN-2Bzim ) differ in the cationic charge, the number of vinylbenzimidazolium branches and the nature of the triaryl core. Using microscopy, we demonstrated that the cationic derivatives accumulate in mitochondria but do not reach mtDNA. Under depolarisation of the mitochondrial membrane, TP-2Bzim and TP¹⁺-2Bzim translocate to the nucleus in direct correlation with their strong DNA affinity. This reversible phenomenon emphasizes that these probes can be used to monitor ΔΨ_m variations.     

In Silico Logical Modelling to Uncover Cooperative Interactions in Cancer

The multistep development of cancer involves the cooperation between multiple molecular lesions, as well as complex interactions between cancer cells and the surrounding tumour microenvironment. The search for these synergistic interactions using experimental models made tremendous contributions to our understanding of oncogenesis. Yet, these approaches remain labour-intensive and challenging. To tackle such a hurdle, an integrative, multidisciplinary effort is required. In this article, we highlight the use of logical computational models, combined with experimental validations, as an effective approach to identify cooperative mechanisms and therapeutic strategies in the context of cancer biology. In silico models overcome limitations of reductionist approaches by capturing tumour complexity and by generating powerful testable hypotheses. We review representative examples of logical models reported in the literature and their validation. We then provide further analyses of our logical model of Epithelium to Mesenchymal Transition (EMT), searching for additional cooperative interactions involving inputs from the tumour microenvironment and gain of function mutations in NOTCH.     

Endothelial Colony-Forming Cells Dysfunctions Are Associated with Arterial Hypertension in a Rat Model of Intrauterine Growth Restriction

Infants born after intrauterine growth restriction (IUGR) are at risk of developing arterial hypertension at adulthood. The endothelium plays a major role in the pathogenesis of hypertension. Endothelial colony-forming cells (ECFCs), critical circulating components of the endothelium, are involved in vasculo-and angiogenesis and in endothelium repair. We previously described impaired functionality of ECFCs in cord blood of low-birth-weight newborns. However, whether early ECFC alterations persist thereafter and could be associated with hypertension in individuals born after IUGR remains unknown. A rat model of IUGR was induced by a maternal low-protein diet during gestation versus a control (CTRL) diet. In six-month-old offspring, only IUGR males have increased systolic blood pressure (tail-cuff plethysmography) and microvascular rarefaction (immunofluorescence). ECFCs isolated from bone marrow of IUGR versus CTRL males displayed a decreased proportion of CD31+ versus CD146+ staining on CD45− cells, CD34 expression (flow cytometry, immunofluorescence), reduced proliferation (BrdU incorporation), and an impaired capacity to form capillary-like structures (Matrigel test), associated with an impaired angiogenic profile (immunofluorescence). These dysfunctions were associated with oxidative stress (increased superoxide anion levels (fluorescent dye), decreased superoxide dismutase protein expression, increased DNA damage (immunofluorescence), and stress-induced premature senescence (SIPS; increased beta-galactosidase activity, increased p16^INK4a, and decreased sirtuin-1 protein expression). This study demonstrated an impaired functionality of ECFCs at adulthood associated with arterial hypertension in individuals born after IUGR.     

The efficacy of linalool, a major component of freshly-milled Ocimum canum Sims (Lamiaceae), for protection against postharvest damage by certain stored product Coleoptera

Linalool was present at 8.6 ± 0.9 mg/g in the dried leaves of Ocimum canum Sims, an annual mint used in Rwanda to protect against postharvest insect damage. Direct exposure of adults of Zabrotes subfasciatus (Bohem.) to milled, dried O. canum leaves resulted in 100% mortality of males and 50% mortality of females after 48 hr. Dose-response curves for linalool were completed with adult Z. subfasciatus, Acanthoscelides obtectus (Say), Rhyzopertha dominica (F.), and Sitophilus oryzae (L.) using a filter paper bioassay. The LC₅₀ values were: 428 μg/cm² for Z. subfasciatus; 405 μg/cm² for A. obtectus; 428 μg/cm² for R. dominica; 427 μg/cm² for S. oryzae. Knockdown was occasionally followed by recovery at doses less than the LC₅₀ for all species. There are significant differences in the LC₅₀ and LT₅₀ values for male and female Z. subfasciatus. At the lower dosages hyperactivity rarely preceded moribundity and mortality where these occurred, while at higher dosages hyperactivity occurred soon after initial exposure and preceded imminent death. A concentration increase from 250 to 750 μg/cm², representing a tripling of dosage, spanned th 10–100% response mortality for all species at 24 hr. Air-exposure of linalool-treated papers (500 μg/cm²) for up to 24 hr significantly decreased toxicity to both sexes of Z. subfasciatus. Quantitative analysis showed the only significant decrease in the amount of linalool to occur after 0.25 hr, and this did not fully correlate with the resulting decrease in efficacy against both sexes of Z. subfasciatus. The results are discussed in terms of the efficacy of using O. canum for the protection against loss due to insects in the traditional food storage systems of Rwanda.     

Studies of the pulse charge of lead-acid batteries for photovoltaic applications: Part IV. Pulse charge of the negative plate

The paper discusses the influence of the state of charge and pulse charge frequency on the mechanism of the lead-acid battery recharge with pulse current. The data from the pulse charge transients of the negative plate potential at various frequencies show that a decrease of the pulse charge frequency keeping constant average pulse current can impede the charge reaction leading to earlier start of the hydrogen evolution reaction. The dependence of the electrochemical double layer (EDL) capacitance on the state of charge was estimated both during the charge and the discharge using electrochemical impedance spectroscopy measurements at open circuit, followed by equivalent circuit modelling. These data were used to derive the dependence of the average double layer current on SOC and pulse charge frequency. The results show that in the end of the charge almost all of the charge proceeds with the participation of EDL in a certain pulse frequency domain. Using the data from the impedance measurements the optimal pulse charge frequencies were predicted, considering the existence of “electrochemical resonance”. The latter appears when the pulse charge frequency approaches the characteristic frequency of the Pb electrodeposition process, given by the product between EDL capacitance and the charge transfer resistance.