Deleterious Effects of Remote Ischaemic Per-conditioning During Lower Limb Ischaemia-Reperfusion in Mice.

OBJECTIVE: The aim of this study was to investigate whether remote ischaemic per-conditioning might protect skeletal muscle during lower limb ischaemia-reperfusion (IR). METHODS: Twenty-three male C57BL/6 mice were randomised into three groups: sham group (n = 7), IR group (unilateral tourniquet induced three hours of ischaemia followed by 24 hours of reperfusion, n = 8), and remote ischaemic per-conditioning group (RIPerC) (three cycles of 10 minute IR episodes on the non-ischaemic contralateral hindlimb, n = 8). Oxygraphy, spectrofluorometry, and electron paramagnetic resonance spectroscopy were performed in order to determine mitochondrial respiratory chain complexes activities, mitochondrial calcium retention capacity (CRC) and reactive oxygen species (ROS) production in skeletal muscle. RESULTS: IR impaired mitochondrial respiration (3.66 ± 0.98 vs. 7.31 ± 0. 54 µmol/min/g in ischaemic and sham muscles, p = .009 and p = .003 respectively) and tended to impair CRC (2.53 ± 0.32 vs. 3.64 ± 0.66 µmol/mg in ischaemic and sham muscles respectively, p = .066). IR did not modify ROS production (0.082 ± 0.004 vs. 0.070 ± 0.004 µmol/min/mg in ischaemic and sham muscles respectively, p = .74). RIPerC failed to restore mitochondrial respiration (3.82 ± 0.40 vs. 3.66 ± 0.98 µmol/min/g in ischaemic muscles from the RIPerC group and the IR group respectively, p = .45) and CRC (2.76 ± 0.3 vs. 2.53 ± 0.32 µmol/mg in ischaemic muscles from the RIPerC group and the IR group respectively, p = .25). RIPerC even impaired contralateral limb mitochondrial respiration (3.85 ± 0.34 vs. 7.31 ± 0. 54 µmol/min/g in contralateral muscles and sham muscles respectively, -47.3%, p = .009). CONCLUSION: RIPerC failed to protect ischaemic muscles and induced deleterious effects on the contralateral non-ischaemic muscles. These data do not support the concept of RIPerC.

Building up Strain in One Step: Synthesis of an Edge-Fused Double Silacyclobutene from an Extensively Trichlorosilylated Butadiene Dianion.

The exhaustive trichlorosilylation of hexachloro-1,3-butadiene was achieved in one step by using a mixture of Si2 Cl6 and [nBu4 N]Cl (7:2 equiv) as the silylation reagent. The corresponding butadiene dianion salt [nBu4 N]2 [1] was isolated in 36 % yield after recrystallization. The negative charges of [1]2- are mainly delocalized across its two carbanionic (Cl3 Si)2 C termini (α-effect of silicon) such that the central bond possesses largely C=C double-bond character. Upon treatment with 4 equiv of HCl, [1]2- is converted into neutral 1,2,3,4-tetrakis(trichlorosilyl)but-2-ene, 3. The Cl- acceptor AlCl3 , induces a twofold ring-closure reaction of [1]2- to form a six-membered bicycle 4 in which two silacyclobutene rings are fused along a shared C=C double bond (84 %). Compound 4, which was structurally characterized by X-ray crystallography, undergoes partial ring opening to a monocyclic silacyclobutene 2 in the presence of HCl, but is thermally stable up to at least 180 °C.

Tris(trichlorosilyl)tetrelide Anions and a Comparative Study of Their Donor Qualities.

Trichlorosilylated tetrelides [(Cl3 Si)3 E]- have been prepared by adding 1 equiv of a soluble Cl- salt to (Cl3 Si)4 Si (E=Si) or 4 Si2 Cl6 /GeCl4 (E=Ge). To assess their donor qualities, the anions [(Cl3 Si)3 E]- (E=C, Si, Ge) have been treated with BCl3 , AlCl3 , and GaCl3 . Both BCl3 and GaCl3 give 1:1 adducts with the anionic centers. AlCl3 leads to Cl- abstraction from [(Cl3 Si)3 E]- with formation of (Cl3 Si)4 E (E=Si or Ge). (Cl3 Si)4 Ge is cleanly converted to the perhydrogenated (H3 Si)4 Ge by use of Li[AlH4 ]. Another case of Cl- abstraction was observed for [(Cl3 Si)3 Ge⋅GaCl3 ]- , which reacts with GaCl3 to afford the neutral dimer [(Cl3 Si)3 Ge-GaCl2 ]2 .

Critical Limb Ischaemia Exacerbates Mitochondrial Dysfunction in ApoE-/- Mice Compared with ApoE+/+ Mice, but N-acetyl Cysteine still Confers Protection.

OBJECTIVES: The current study was performed in order to determine the influence of hypercholesterolaemia on critical limb ischaemia (CLI) and whether targeting oxidative stress by antioxidant therapies such as N-acetyl cysteine (NAC), considered to be a direct scavenger of reactive oxygen species, could confer muscle protection. METHODS: Apolipoprotein E (ApoE)-/- mice (n = 9, 29 weeks old) and their genetic controls ApoE+/+ mice (n = 9, 29 weeks old) were submitted to sequential right femoral and iliac ligations; the left limb served as control. ApoE+/+ mice were divided into two groups: Group 1 (n = 4) and Group 2 (n = 5); as well as ApoE-/- mice: Group 3 (n = 3), and Group 4 (n = 6). NAC treatment was administered to Groups 2 and 4 in drinking water. Mice were sacrificed on Day 40 and gastrocnemius muscles were harvested to study mitochondrial respiration by oxygraphy, calcium retention capacity by spectrofluorometry, and production of reactive oxygen species by electron paramagnetic resonance. RESULTS: CLI associated with ApoE deficiency resulted in more severe mitochondrial dysfunction: maximum oxidative capacity and calcium retention capacity were decreased (-42.9% vs. -25.1%, p = .010; and -73.1% vs. -40.3%, p = .003 respectively) and production of reactive oxygen species was enhanced (+63.6% vs. +41.4%, p = .03) in ApoE-/- mice compared with ApoE+/+ mice respectively. Antioxidant treatment restored oxidative capacity, calcium retention capacity and decreased production of reactive oxygen species in both mice strands. CONCLUSIONS: In this small murine study, hypercholesterolaemia exacerbated mitochondrial dysfunction, as clinically expected; but antioxidant therapy appeared protective, which is counter to clinical experience. Further work is clearly needed.

Exhaustively Trichlorosilylated C1 and C2 Building Blocks: Beyond the Müller-Rochow Direct Process.

The Cl--induced heterolysis of the Si-Si bond in Si2Cl6 generates an [SiCl3]- ion as reactive intermediate. When carried out in the presence of CCl4 or Cl2C═CCl2 (CH2Cl2 solutions, room temperature or below), the reaction furnishes the monocarbanion [C(SiCl3)3]- ([A]-; 92%) or the vicinal dianion [(Cl3Si)2C-C(SiCl3)2]2- ([B]2-; 85%) in excellent yields. Starting from [B]2-, the tetrasilylethane (Cl3Si)2(H)C-C(H)(SiCl3)2 (H2B) and the tetrasilylethene (Cl3Si)2C═C(SiCl3)2 (B; 96%) are readily available through protonation (CF3SO3H) or oxidation (CuCl2), respectively. Equimolar mixtures of H2B/[B]2- or B/[B]2- quantitatively produce 2 equiv of the monoanion [HB]- or the blue radical anion [B•]-, respectively. Treatment of B with Cl- ions in the presence of CuCl2 furnishes the disilylethyne Cl3SiC≡CSiCl3 (C; 80%); in the presence of [HMe3N]Cl, the trisilylethene (Cl3Si)2C═C(H)SiCl3 (D; 72%) is obtained. Alkyne C undergoes a [4+2]-cycloaddition reaction with 2,3-dimethyl-1,3-butadiene (CH2Cl2, 50 °C, 3d) and thus provides access to 1,2-bis(trichlorosilyl)-4,5-dimethylbenzene (E1; 80%) after oxidation with DDQ. The corresponding 1,2-bis(trichlorosilyl)-3,4,5,6-tetraphenylbenzene (E2; 83%) was prepared from C and 2,3,4,5-tetraphenyl-2,4-cyclopentadien-1-one under CO extrusion at elevated temperatures (CH2Cl2, 180 °C, 4 d). All closed-shell products were characterized by 1H, 13C{1H}, and 29Si NMR spectroscopy; an EPR spectrum of [ nBu4N][B•] was recorded. The molecular structures of [ nBu4N][A], [ nBu4N]2[B], B, E1, and E2 were further confirmed by single-crystal X-ray diffraction. On the basis of detailed experimental investigations, augmented by quantum-chemical calculations, plausible reaction mechanisms for the formation of [A]-, [B]2-, C, and D are postulated.

A Highly Reactive Geminal P/B Frustrated Lewis Pair: Expanding the Scope to C-X (X=Cl, Br) Bond Activation.

The geminal frustrated Lewis pair tBu2 PCH2 B(Fxyl)2 (1; Fxyl=3,5-(CF3 )2 C6 H3 ) is accessible in 65 % yield from tBu2 PCH2 Li and (Fxyl)2 BF. According to NMR spectroscopy and X-ray crystallography, 1 is monomeric both in solution and in the solid state. The intramolecular P⋅⋅⋅B distance of 2.900(5) Šand the full planarity of the borane site exclude any significant P/B interaction. Compound 1 readily activates a broad variety of substrates including H2 , EtMe2 SiH, CO2 /CS2 , Ph2 CO, and H3 CCN. Terminal alkynes react with heterolysis of the C-H bond. Haloboranes give cyclic adducts with strong P-BX3 and weak R3 B-X bonds. Unprecedented transformations leading to zwitterionic XP/BCX3 adducts occur on treatment of 1 with CCl4 or CBr4 in Et2 O. In less polar solvents (C6 H6 , n-pentane), XP/BCX3 adduct formation is accompanied by the generation of significant amounts of XP/BX adducts. FLP 1 catalyzes the hydrogenation of PhCH=NtBu and the hydrosilylation of Ph2 CO with EtMe2 SiH.

Octanoic Acid-Enrichment Diet Improves Endurance Capacity and Reprograms Mitochondrial Biogenesis in Skeletal Muscle of Mice.

Background: Medium Chain Fatty Acids (MCFAs) are a dietary supplement that exhibit interesting properties, due to their smaller molecular size. The acute consumption of MCFAs is expected to enhance exercise performance. However, the short-term effects of MCFAs on endurance performance remains poorly understood. The aim of our study is to evaluate the octanoic acid (C8)-rich diet effect on endurance capacity, and to explore their molecular and cellular effects. Methods: C57BL/6J mice were fed with a chow diet (Control group) or an octanoic acid-rich diet (C8 diet) for 6 weeks. Spontaneous activity, submaximal and maximal exercise tests were carried out to characterize the exercise capacities of the mice. Beta-oxidation and mitochondrial biogenesis pathways were explored in skeletal muscle by RT-qPCR, Western Blot (Quadriceps) and histochemical staining (Gastrocnemius). Results: Mice fed with a C8-rich diet presented a higher spontaneous activity (p < 0.05) and endurance capacities (p < 0.05) than the control, but no effect on maximal effort was observed. They also presented changes in the skeletal muscle metabolic phenotype, with a higher number of the oxidative fibers, rich in mitochondria. At the molecular level, the C8-diet induced an AMPK activation (p < 0.05), associated with a significant increase in PGC1a and CS gene expression and protein levels. Conclusion: Our study provided evidence that C8-enrichment as a food supplementation improves endurance capacities and activates mitochondrial biogenesis pathways leading to higher skeletal muscle oxidative capacities.

The power of trichlorosilylation: isolable trisilylated allyl anions, allyl radicals, and allenyl anions.

Treatment of hexachloropropene (Cl2C[double bond, length as m-dash]C(Cl)-CCl3) with Si2Cl6 and [nBu4N]Cl (1 : 4 : 1) in CH2Cl2 results in a quantitative conversion to the trisilylated, dichlorinated allyl anion salt [nBu4N][Cl2C[double bond, length as m-dash]C(SiCl3)-C(SiCl3)2] ([nBu4N][1]). Tetrachloroallene Cl2C[double bond, length as m-dash]C[double bond, length as m-dash]CCl2 was identified as the first intermediate of the reaction cascade. In the solid state, [1]- adopts approximate C s symmetry with a dihedral angle between the planes running through the olefinic and carbanionic fragments of [1]- of C[double bond, length as m-dash]C-Si//Si-C-Si = 78.3(1)°. One-electron oxidation of [nBu4N][1] with SbCl5 furnishes the distillable blue radical 1˙. The neutral propene Cl2C[double bond, length as m-dash]C(SiCl3)-C(SiCl3)2H (2) was obtained by (i) protonation of [1]- with HOSO2CF3 (HOTf) or (ii) H-atom transfer to 1˙ from 1,4-cyclohexadiene. Quantitative transformation of all three SiCl3 substituents in 2 to Si(OMe)3 (2 OMe) or SiMe3 (2 Me) substituents was achieved by using MeOH/NMe2Et or MeMgBr in CH2Cl2 or THF, respectively. Upon addition of 2 equiv. of tBuLi, 2 Me underwent deprotonation with subsequent LiCl elimination, 1,2-SiMe3 migration and Cl/Li exchange to afford the allenyl lithium compound Me3Si(Li)C[double bond, length as m-dash]C[double bond, length as m-dash]C(SiMe3)2 (Li[4]), which is an efficient building block for the introduction of Me, SiMe3, or SnMe3 (5) groups. The trisilylated, monochlorinated allene Cl3Si(Cl)C[double bond, length as m-dash]C[double bond, length as m-dash]C(SiCl3)2 (6), was obtained from [nBu4N][1] through Cl--ion abstraction with AlCl3 and rearrangement in CH2Cl2 (1˙ forms as a minor side product, likely because the system AlCl3/CH2Cl2 can also act as a one-electron oxidant).

Hyperspectral Imaging Quantification of Mouse Limb Microcirculation Using an Ischemia Reperfusion Model with Phosphodiesterase 5 Inhibitor Preconditioning.

Background: Peripheral arterial disease has high incidence and complication rates. Vessel recanalization represents the main therapy. However, it induces reperfusion injury. Preconditioning with sildenafil has been advocated to protect against this injury. In this study, we show a real-time noninvasive quantitative assessment using hyperspectral imaging (HSI) of ischemia/reperfusion (IR) and analyzing the sildenafil effect. Materials and Methods: A one-sided hindlimb ischemia (120 minutes) followed by reperfusion (30 minutes) was created. Five mice received Sildenafil (1 mg/kg, i.p. twice before ischemia) and 5 mice served as control. The StO2 at T0, 5, 30, 60, 120 minutes after ischemia (T5, 30, 60, 120) and 5, 15, and 30 minutes after reperfusion (T125, 135, 150) were measured through HSI. Results: The control group showed a significantly lower StO2 at T120 (24.8% ± 17%) as compared with T0 (53.3% ± 7.04%) (P = .013) and T150 (76.8 ± 3.77; P = .0008). T150 showed a statistically significantly higher StO2 than T0 (P = .0134). In the sildenafil group, T120 StO2 (28.6% ± 20%) was lower than T0 (63.3% ± 8.46%; P = .0312) and T150 (73.3% ± 19.1%, P = .0075). The StO2 values did not differ statistically between sildenafil and control groups. Conclusions: HSI is a feasible tool to quantify both ischemia and reperfusion phases during lower limb IR. Preconditioning with sildenafil did not modify IR-related StO2 changes.

Aging Exacerbates Ischemia-Reperfusion-Induced Mitochondrial Respiration Impairment in Skeletal Muscle.

Cycles of ischemia-reperfusion (IR) that occur during peripheral arterial disease (PAD) are associated with significant morbi-mortality, and aging is an irreversible risk factor of PAD. However, the effects of advanced age on IR-induced skeletal muscle mitochondrial dysfunction are not well known. Young and aged mice were therefore submitted to hindlimb IR (2 h ischemia followed by 2 h reperfusion). Skeletal muscle mitochondrial respiration, calcium retention capacity (CRC) and reactive oxygen species (ROS) production were determined using high resolution respirometry, spectrofluorometry and electronic paramagnetic resonance. IR-induced impairment in mitochondrial respiration was enhanced in old animals (VADP; from 33.0 ± 2.4 to 18.4 ± 3.8 and 32.8 ± 1.3 to 5.9 ± 2.7 pmol/s/mg wet weight; -44.2 ± 11.4% vs. -82.0 ± 8.1%, in young and aged mice, respectively). Baseline CRC was lower in old animals and IR similarly decreased the CRC in both groups (from 11.8 ± 0.9 to 4.6 ± 0.9 and 5.5 ± 0.9 to 2.1 ± 0.3 µmol/mg dry weight; -60.9 ± 7.3 and -60.9 ± 4.6%, in young and aged mice, respectively). Further, IR-induced ROS production tended to be higher in aged mice. In conclusion, aging exacerbated the deleterious effects of IR on skeletal muscle mitochondrial respiration, potentially in relation to an increased oxidative stress.

Effect of the Phosphodiesterase 5 Inhibitor Sildenafil on Ischemia-Reperfusion-Induced Muscle Mitochondrial Dysfunction and Oxidative Stress.

Lower-limb ischemia-reperfusion (IR) is frequent and associated with significant morbidity and mortality. Phosphodiesterase 5 inhibitors demonstrated antioxidant and beneficial effects in several organs submitted to IR, but their effects on muscle mitochondrial functions after lower-limb IR are unknown. Unilateral hindlimb IR (2 h tourniquet followed by 2 h reperfusion) without or with sildenafil (1mg/kg ip 30 minutes before ischemia) was performed in 18 mice. Maximal oxidative capacity (VMax), relative contribution of the mitochondrial respiratory chain complexes, calcium retention capacity (CRC)-a marker of apoptosis-and reactive oxygen species (ROS) production were determined using high-resolution respirometry, spectrofluorometry, and electron paramagnetic resonance in gastrocnemius muscles from both hindlimbs. IR significantly reduced mitochondrial VMax (from 11.79 ± 1.74 to 4.65 ± 1.11 pmol/s*mg wet weight (ww), p < 0.05, -50.2 ± 16.3%) and CRC (from 2.33 ± 0.41 to 0.84 ± 0.18 µmol/mg dry weight (dw), p < 0.05; -61.1 ± 6.8%). ROS tended to increase in the ischemic limb (+64.3 ± 31.9%, p = 0.08). Although tending to reduce IR-related ROS production (-42.4%), sildenafil failed to reduce muscle mitochondrial dysfunctions (-63.3 ± 9.2%, p < 0.001 and -55.2 ± 7.6% p < 0.01 for VMax, and CRC, respectively). In conclusion, lower limb IR impaired skeletal muscle mitochondrial function, but, despite tending to reduce ROS production, pharmacological preconditioning with sildenafil did not show protective effects.