A thiolate-bridged ruthenium-molybdenum complex featuring terminal nitrido and bridging amido ligands derived from the N-H and N-N bond cleavage of hydrazine.

Biomimetic di- or multimetallic complexes featuring NxHy species in a sulfur-rich coordination sphere have attracted considerable attention in modelling the possible scenarios of biological nitrogen fixation by nitrogenases. Although the active site of nitrogenases is a complex heterometallic sulfur cluster, the feasibility of NxHy species on different metal sites is scarcely investigated. Herein, we report an unprecedented thiolate-bridged ruthenium-molybdenum complex featuring bridging amido and terminal nitrido ligands obtained by cleaving the N-N and N-H bonds of hydrazine. Remarkably, this RuMo complex is also capable of catalyzing the reduction of hydrazine to ammonia. Overall, this rare activation pattern of hydrazine on a thiolate-bridged RuMo platform provides new insight into the heterometallic cooperativity in nitrogenase.

A Bioinspired Iron-Molybdenum µ-Nitrido Complex and Its Reactivity toward Ammonia Formation.

Multimetallic nitride species, especially those containing biologically related iron or molybdenum, are fundamentally important to understand the nitrogen reduction process catalysed by FeMo-nitrogenase. However, until now, there remains no report about the construction of structurally well-defined FeMo heteronuclear nitrido complex and its reactivity toward ammonia formation. Herein, a novel thiolate-bridged FeII MoVI complex featuring a bent Fe-N≡Mo fragment is synthesized and structurally characterized, which can be easily protonated to form a µ-imido complex. Subsequently, through the proton-coupled electron transfer (PCET) process, this imido species can smoothly convert into the µ-amido complex, which can further undergo reductive protonation to afford the FeMo complex containing an ammine ligand. Overall, we present the first well-defined {Fe(µ-S)2 Mo} platform that can give a panoramic picture for the late stage (N3- →NH2- →NH2- →NH3 ) of biological nitrogen reduction by the heterometallic cooperativity.

Methylene insertion into an Fe2S2 cluster: formation of a thiolate-bridged diiron complex containing an Fe-CH2-S moiety.

Reduction of a thiolate-bridged FeIIFeIII complex leads to the cleavage of an Fe-S bond by the insertion of the methylene unit from CH2Cl2 to give a neutral FeIIFeIII complex with a novel Fe-CH2-S fragment. The structural and electrochemical differences of the alkylated and the non-alkylated Fe2S2 complexes are also examined.

Uncoupling Protein 2 Inhibits Myointimal Hyperplasia in Preclinical Animal Models of Vascular Injury.

BACKGROUND: Intracoronary stent restenosis, characterized by excessive smooth muscle cell (SMC) proliferation and myointimal hyperplasia, remains a clinical challenge. Mitochondrial membrane potential has been linked to the proliferative rate of SMCs. This study aimed to screen a critical gene regulating mitochondrial potential and to confirm its effects on myointimal formation in preclinical animal models. METHODS AND RESULTS: We performed transcriptome screening for genes differentially expressed in ligated versus unligated mouse carotid arteries. We observed that uncoupling protein 2 gene (Ucp2) mRNA, encoding UCP2, was transiently upregulated during the first 3 days after ligation and then significantly downregulated from day 7 through day 21, during which time neointima formed remarkably. The UCP2 protein level also declined after day 7 of ligation. In ligated carotid arteries, Ucp2-/- mice, compared with wild-type littermates, exhibited accelerated myointimal formation, which was associated with increased superoxide production and can be attenuated by treatment with antioxidant 4-hydroxy-2,2,6,6-tetramethyl-piperidinoxyl (TEMPOL). Knockdown of UCP2 enhanced human aortic SMC migration and proliferation that can also be attenuated by TEMPOL, whereas UCP2 overexpression inhibited SMC migration and proliferation, along with decreased activity of nuclear factor-κB. Moreover, nuclear factor-κB inhibitor attenuated UCP2 knockdown-enhanced SMC proliferation. Adenovirus-mediated overexpression of UCP2 inhibited myointimal formation in balloon-injured carotid arteries of rats and rabbits and in-stent stenosis of porcine coronary arteries. Moreover, UCP2 overexpression also suppressed neointimal hyperplasia in cultured human saphenous vein ex vivo. CONCLUSIONS: UCP2 inhibits myointimal hyperplasia after vascular injury, probably through suppressing nuclear factor-κB-dependent SMC proliferation and migration, rendering UCP2 a potential therapeutic target against restenosis.

Perivascular radiofrequency renal denervation lowers blood pressure and ameliorates cardiorenal fibrosis in spontaneously hypertensive rats.

BACKGROUND: Catheter-based renal denervation (RDN) is a promising approach to treat hypertension, but innervation patterns limit the response to endovascular RDN and the post-procedural renal artery narrowing or stenosis questions the endovascular ablation strategy. This study was performed to investigate the anti-hypertensive and target organ protective effects of perivascular RDN in spontaneously hypertensive rats (SHR). METHODS: SHR and normotensive Wistar-Kyoto (WKY) rats were divided into sham group (n = 10), radiofrequency ablation group (n = 20) in which rats received bilateral perivascular ablation with radiofrequency energy (2 watts), and chemical (10% phenol in 95% ethanol) ablation group (n = 12). The tail-cuff blood pressure was measured before the ablation and on day 14 and day 28 after the procedure. The plasma levels of creatinine, urea nitrogen, and catecholamines, urinary excretion of electrolytes and protein, and myocardial and glomerular fibrosis were analyzed and compared among the groups on day 28 after the procedure. RESULTS: We identified that 2-watt is the optimal radiofrequency power for perivascular RDN in rats. Perivascular radiofrequency and chemical ablation achieved roughly comparable blood pressure reduction in SHR but not in WKY on day 14 and day 28 following the procedure. Radiofrequency-mediated ablation substantially destroyed the renal nerves surrounding the renal arteries of both SHR and WKY without damaging the renal arteries and diminished the expression of tyrosine hydroxylase, the enzyme marker for postganglionic sympathetic nerves. Additionally, perivascular radiofrequency ablation also decreased the plasma catecholamines of SHR. Interestingly, both radiofrequency and chemical ablation decreased the myocardial and glomerular fibrosis of SHR, while neither increased the plasma creatinine and blood urea nitrogen nor affected the urinary excretion of electrolytes and protein when compared to sham group. CONCLUSIONS: Radiofrequency-mediated perivascular RDN may become a feasible procedure against hypertension, and provide similar anti-hypertensive and target organ protective effects as does the chemical ablation.

Activation of transient receptor potential vanilloid 1 accelerates re-endothelialization and inhibits neointimal formation after vascular injury.

OBJECTIVE: Transient receptor potential vanilloid 1 (TRPV1) is an important regulator of endothelial function, but the effects of TRPV1 on endothelial recovery and neointimal formation after vascular injury remain elusive. We tested the effects of activating TRPV1 using capsaicin on re-endothelialization and neointimal formation after wire-induced injury of the carotid artery in mice. METHODS: The human umbilical vein endothelial cells (HUVECs) were treated with the TRPV1 agonist capsaicin, its antagonist capsazepine, intracellular calcium chelator BAPTA, or mitofusin 2 (Mfn2)-specific short interfering RNA (siRNA). The migration, proliferation, mitochondrial morphology, membrane potential, and adenosine triphosphate production were measured. The carotid artery wire injury procedure was performed in male TRPV1 knockout mice and C57BL/6J wild-type (WT) mice that were then treated with or without Mfn2 siRNA. The re-endothelialization and neointimal formation were evaluated. RESULTS: Capsaicin significantly enhanced the migration and proliferation of HUVECs. Both capsazepine and BAPTA abolished capsaicin-induced migration and proliferation of HUVECs. In addition, capsaicin stimulated the formation of reticular mitochondria, augmented mitochondrial membrane potential, increased adenosine triphosphate production, and upregulated Mfn2. However, these effects were attenuated by knockdown of Mfn2 with specific siRNA. Dietary capsaicin markedly accelerated re-endothelialization and inhibited neointimal formation in WT mice but not in TRPV1 knockout mice. Moreover, Mfn2 siRNA also attenuated capsaicin-induced enhancement of endothelial recovery and suppression of neointimal hyperplasia in WT mice. CONCLUSIONS: Activation of TRPV1 with capsaicin attenuates neointimal formation by accelerating re-endothelialization through upregulation of Mfn2.

A Novel Swine Model of Spontaneous Hypertension With Sympathetic Hyperactivity Responds Well to Renal Denervation.

BACKGROUND: The large animal model of arterial hypertension is very valuable to test the antihypertensive drugs and devices. We characterized a novel swine model of spontaneous hypertension and investigated its response to renal denervation (RDN). METHODS: The blood pressure (BP), levels of plasma catecholamines and urine vanillylmandelic acid, and the protein expressions of angiotensin-converting enzyme (ACE) and angiotensin II type 1 (AT1), and type 2 (AT2) receptors in the rostral ventrolateral medulla (RVLM) were compared between domestic pigs and Guizhou mini-pigs. Twelve-month-old Guizhou mini-pigs were divided into sham (n = 7) and ablation (n = 7) groups. The mini-pigs in ablation group received bilateral percutaneous RDN with a saline-irrigated Sniper ablation catheter. Three months after the procedure, the BP was measured and the histology of renal nerves and arteries was analyzed. RESULTS: The mini-pigs spontaneously developed hypertension by the age of 6 months and the BP (162.2 ± 11.4/111.8 ± 9.2mm Hg) was significantly higher than age-matched domestic pigs (137.5 ± 1.9/80.2 ± 4.1mm Hg, P < 0.05). The levels of plasma catecholamines and urine vanillylmandelic acid were higher in mini-pigs than domestic pigs. The expressions of ACE and AT1 were increased, but the AT2 was decreased, in RVLM from mini-pigs compared with domestic pigs. Three months after the procedure, the BP was sharply reduced in ablation group (113.8 ± 14.4/79.4 ± 11.7 mm Hg) compared with sham group (192.4 ± 10.5/141.2 ± 5.9 mm Hg, P < 0.01). Renal nerves were substantially destroyed, while renal arteries and function were not significantly affected by ablation. CONCLUSIONS: The Guizhou mini-pig is a novel spontaneous hypertensive animal model with sympathetic hyperactivity and responds well to RDN.

Apolipoprotein E-deficient rats develop atherosclerotic plaques in partially ligated carotid arteries.

BACKGROUND: The goal of this study was to establish an apolipoprotein E-deficient (ApoE(-/-)) rat model. METHODS: The ApoE(-/-) rat was created by TALEN-mediated gene targeting in the genetic background of Sprague Dawley rat. Six-to eight-week-old male rats were used in the experiments (n = 10 in each group). RESULTS: After fed with high-cholesterol diet (HCD) for 12 weeks, the ApoE(-/-) rats displayed typical dyslipidemia. In contrast, HCD failed to induce hypercholesterolemia in wild-type rats. However, there was no obvious atherosclerotic lesion in oil red O-stained en face aortas and the aortic root sections in both genetic types of rats. Interestingly, partial ligation caused the formation of plaques consist of lipid and macrophages in carotid arteries from ApoE(-/-) rats, but induced the neointimal hyperplasia in wild-type rats. Additionally, we found that HCD slightly increased the expression of adhesion molecules, while partial ligation dramatically upregulated these molecules. CONCLUSIONS: The ApoE(-/-) rat is a novel model for dyslipidemia and could also be used in the research of atherosclerosis.

Synthesis and Electrocatalytic Property of Diiron Hydride Complexes Derived from a Thiolate-Bridged Diiron Complex.

Interaction of a diiron thiolate-bridged complex, [Cp*Fe(µ-η(2):η(4)-bdt)FeCp*] (1) (Cp* = η(5)-C5Me5; bdt = benzene-1,2-dithiolate) with a proton gives an Fe(III)Fe(III) hydride bridged complex, [Cp*Fe(µ-bdt)(µ-H)FeCp*][BF4] (3[BF4]). According to in situ variable temperature (1)H NMR studies, the formation of 3[BF4] was evidenced to occur through a stepwise pathway: protonation occurring at an iron center to produce terminal hydride [Cp*Fe(µ-bdt)(t-H)FeCp*][BF4] (2) and subsequent intramolecular isomerization to bridging hydride 3[BF4]. A one-electron reduction of 3[BF4] by CoCp2 affords a paramagnetic mixed-valent Fe(II)Fe(III) hydride complex, [Cp*Fe(µ-η(2):η(2)-bdt)(µ-H)FeCp*] (4). Further, studies on protonation processes of diruthenium and iron-ruthenium analogues of 1, [Cp*M1(µ-bdt)M2Cp*] (M1 = M2 = Ru, 5; M1 = Fe, M2 = Ru, 8), provide experimental evidence for terminal hydride species at these bdt systems. Importantly, diiron or diruthenium hydride bridged complexes 3[BF4], 7[BF4] and iron-ruthenium heterodinuclear complex 8[PF6] can realize electrocatalytic hydrogen evolution.

Over-expression of calpastatin inhibits calpain activation and attenuates post-infarction myocardial remodeling.

BACKGROUND: Calpain is activated following myocardial infarction and ablation of calpastatin (CAST), an endogenous inhibitor of calpains, promotes left ventricular remodeling after myocardial infarction (MI). The present study aimed to investigate the effect of transgenic over-expression of CAST on the post-infarction myocardial remodeling process. METHOD: We established transgenic mice (TG) ubiquitously over-expressing human CAST protein and produced MI in TG mice and C57BL/6J wild-type (WT) littermates. RESULTS: The CAST protein expression was profoundly upregulated in the myocardial tissue of TG mice compared with WT littermates (P < 0.01). Overexpression of CAST significantly reduced the infarct size (P < 0.01) and blunted MI-induced interventricular hypertrophy, global myocardial fibrosis and collagen I and collagen III deposition, hypotension and hemodynamic disturbances at 21 days after MI. Moreover, the MI-induced up-regulation and activation of calpains were obviously attenuated in CAST TG mice. MI-induced down-regulation of CAST was partially reversed in TG mice. Additionally, the MI-caused imbalance of matrix metalloproteinases and their inhibitors was improved in TG mice. CONCLUSIONS: Transgenic over-expression of CAST inhibits calpain activation and attenuates post-infarction myocardial remodeling.

[Simulating experimental study on ultrasonic elastography based monitoring of cryosurgery].

Noticing the phenomenon that biological tissues will change its elasticity by orders of magnitude after it was frozen, we proposed in principle the strategy of using ultrasound elastography to monitor the formation and thawing of the iceball when performing a cryosurgery. Following our former theoretical evaluation, conceptual experiments were designed to apply ultrasound elastography to monitor three kinds of testing samples which includes: phantom embedded with glass block, phantom with tissues at normal temperature and phantom with frozen tissues inside. It was demonstrated for the first time that the ultrasound elastography could provide a high contrast picture on the ice ball during cryosurgery. The measurement errors involved in the application of the method was preliminarily analyzed and approaches to further improve the method were pointed out. With a much different value in elastography than that of water, monitoring the ice ball, the imaging target in clinics, is expected to be an important area for the application of ultrasound elastography.