Ruthenium Amine Research Articles

Antioxidants and Calcium Modulators Preclude in Vitro Hepatitis B Virus-Induced Mitochondrial Damage.

Hepatitis B virus induces mitochondrial damage via the production of reactive oxygen species and concomitant with deregulation of calcium homeostasis. The current study evaluates the potential of antioxidant and calcium modulators for inhibition of hepatitis B virus-induced mitochondrial damage using in vitro cell culture models. Hepatitis B virus-induced mitochondrial fragmentation was observed by immunofluorescence confocal micros- copy in hepatitis B virus-infected cell lines (HepG2 and HepAD38). Differential protein expression of mitochondrial fragmentation mark- ers, dynamin-related protein 1 and phospho-dynamin-related protein 1, were evaluated both pre- and posttreatment with antioxidant N-acetyl-l-cysteine and calcium modulators like 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakisacetoxymethyl ester, ethylene-bis (oxyethylenenitrilo) tetraacetic acid glycol ether diamine tetraacetic acid-acetoxymethyl ester, and ruthenium amine complex by western blot analysis. A slight reduction in mitochondrial fragmentation in both cell lines was observed post-antioxidant treatment with a partial prevention observed with calcium modulators. The expression of phospho-dynamin-related protein 1 was significantly upregulated (P = .0007, P = .003) in both hepatitis B virus-infected cell lines compared to uninfected cells. In line with these observations, the expres- sion of dynamin-related protein 1 and phospho-dynamin-related protein 1 was found to be significantly downregulated with N-acetyl- l-cysteine treatment in both cell lines (P = .003, P = .002), respectively. A nonsignificant trend was observed in the case of calcium modulators treatment. Current study indicates that the mitochondrial fragmentation induced by hepatitis B virus infection can be reduced after antioxidant treatment pointing toward exploring better drug targets for the prevention of hepatitis B virus-induced mitochondrial frag- mentation and associated liver damage.

Remarkable thermal stability of light-induced Ru-ON linkage isomers in mixed salts of a ruthenium amine complex with a trans-ON-Ru-F coordinate.

Two new complexes trans-(H3O)[RuNO(NH3)4F](NO3)1.5F1.5·0.5H2O (I) and trans-[RuNO(NH3)4F](ClO4)Cl (II) are synthesized and characterized by single crystal X-ray diffraction. The complexes crystallized in the centrosymmetric space groups I4/m and P21/n due to specific intermolecular interactions; the strongest ones are represented by N-HO contacts. The irradiation of the complexes in the blue-light range induces the formation of Ru-ON isomers (MS1), determined by IR spectroscopy and differential scanning calorimetry (DSC). The subsequent excitation of MS1 by infrared light induces the formation of Ru-(η2-(NO)) (MS2) isomers, confirmed by the same techniques. Using combined IR and DSC analysis, the activation barriers (Ea) and frequency factors (lg k0) of the MS1 → GS and MS2 → GS reactions are determined. According to the kinetic parameters, the calculated lifetimes (k-1) of MS1 at 300 K are 33 and 178 min for I and II, respectively. To the best of our knowledge, the thermal stability of MS1 in II is the highest among known related complexes. The thermal stability of MS2 was found to be lower (the lifetimes are 0.12 and 0.02 s at 300 K for I and II, respectively), which is characteristic of these states. The high thermal stability of MS1 can be applied for the design of photochromic materials and to generally facilitate the investigation of the states.

Polynuclear Ruthenium Amines Inhibit K2P Channels via a “Finger in the Dam” Mechanism

The trinuclear ruthenium amine ruthenium red (RuR) inhibits diverse ion channels, including K2P potassium channels, TRPs, the calcium uniporter, CALHMs, ryanodine receptors, and Piezos. Despite this extraordinary array, there is limited information for how RuR engages targets. Here, using X-ray crystallographic and electrophysiological studies of an RuR-sensitive K2P, K2P2.1 (TREK-1) I110D, we show that RuR acts by binding an acidic residue pair comprising the "Keystone inhibitor site" under the K2P CAP domain archway above the channel pore. We further establish that Ru360, a dinuclear ruthenium amine not known to affect K2Ps, inhibits RuR-sensitive K2Ps using the same mechanism. Structural knowledge enabled a generalizable design strategy for creating K2P RuR "super-responders" having nanomolar sensitivity. Together, the data define a "finger in the dam" inhibition mechanism acting at a novel K2P inhibitor binding site. These findings highlight the polysite nature of K2P pharmacology and provide a new framework for K2P inhibitor development.

Substituent Effects on the Electrochemistry and Electronic Coupling of Terphenyl-Bridged Cyclometalated Ruthenium-Amine Conjugated Complexes.

Six terphenyl-bridged cyclometalated ruthenium–amine conjugated complexes 4(PF6)–9(PF6) were synthesized and studied. Three different substituents, methoxy, methyl, and chloro, were used to vary the electronic nature of the amine unit, and two terminal ligands 2,2′:6′,2″-terpyridine (tpy) and trimethyl-4,4′,4″-tricarboxylate-2,2′:6′,2″-terpyridine (Me3tctpy) were used to tune the electronic nature of the ruthenium component. All complexes, except 7(PF6) with the methoxy substituent and Me3tctpy ligand, display two well-separated redox waves in the potential range of +0.5 to +1.1 V versus Ag/AgCl. The regular electrochemical changes of these complexes help to establish the oxidation order of ruthenium and amine and hence of the direction of the electron transfer in odd-electron state. The degree of electronic coupling was estimated by analyzing the donor-to-acceptor charge transfer band in the near-infrared region obtained by oxidative spectroelectrochemical measurements. Electron paramagnetic resonance analyses and density functional theory calculations were performed on the one-electron oxidized forms to obtain information on the spin distribution of these complexes.

Water-soluble superbulky (η6-p-cymene) ruthenium(ii) amine: an active catalyst in the oxidative homocoupling of arylboronic acids and the hydration of organonitriles

Water-soluble superbulky (η6-p-cymene) ruthenium(ii) amine complex mediated oxidative homocoupling of arylboronic acids and the hydration of organonitriles are reported.

Transition from a Metal-Localized Mixed-Valence Compound to a Fully Delocalized and Bridge-Biased Electrophore in a Ruthenium-Amine-Ruthenium Tricenter System.

A series of cyclometalated diruthenium complexes with a redox-active amine bridge were synthesized. Depending on the terminal ligands of the ruthenium components and the substituent on the amine unit, the one-electron-oxidized state can be either in the form of a weakly or strongly coupled mixed-valence diruthenium complex, a fully charge-delocalized three-center system, or a bridge-biased electrophore. This transition among different electronic forms was supported by electrochemistry, near-infrared absorption, electron paramagnetic resonance, and density functional theory analysis.

Synthesis and characterization of new α,α′-diaminoalkane-bridged dicarbonyl(η5-cyclopentadienyl)ruthenium(II) complex salts: Antibacterial activity tests of η5-cyclopentadienyl dicarbonyl ruthenium(II) amine complexes

Bacterial resistance to antimicrobial drugs is a significant threat to humans and requires urgent intervention. There is, therefore, a clear need for the development of new types of antibacterial agents. We have thus synthesized the α,α′-diaminoalkane-bridged diruthenium complex salts [Rp2NH2(CH2)nNH2]Y2 (Rp = CpRu(CO)2 where Cp = η5–C5H5; n = 2, 3, 4 and 6; Y=BF4 (1) or SO3CF3(2)) by the reaction of [RpNCCH3]Y and NH2(CH2)nNH2 (n = 2 (DAE) (3); n = 3 (DAP) (4); n = 4 (DAB) (5) and n = 6 (DAH) (6 (BF)4, 7 (SO3CF3)) at ambient temperature and pressure. These compounds are reported for the first time and have been fully characterized by infrared spectroscopy, 1H and 13C NMR spectroscopy, elemental analyses and melting points. The crystal structures of compounds 1 and 3 were obtained by single crystal X-ray crystallography. The two compounds crystallized in the monoclinic crystal system in the P21/n space group. Antimicrobial susceptibility tests were done for the new dinuclear complexes 3–7 as well as for mononuclear ruthenium complexes, [RpBA]BF4 (8), [RpMBA]BF4 (9), [RpMeOBA]BF4 (10) and [RpAMBN]BF4 (11) (BA=NH2CH2C6H5, MBA = NH2CH(CH3)C6H5, MeOBA = NH2CH2C6H4OCH3 and AMBN = NH2CH2C6H5) against selected drug-resistant and drug-susceptible Gram-positive and Gram-negative bacteria. Some of the dinuclear and mononuclear ruthenium complexes demonstrated good potential abilities to inhibit growth of the bacteria tested, with some showing better growth inhibition ability than well-known antibiotics such as ampicillin (AMP10). The ruthenium moiety CpRu(CO)2 triggered or enhanced the ability of the coordinated ligands to inhibit bacterial growth. In vitro cytotoxicity of the complexes 8 and 10 was investigated through cell viability evaluation using human colorectal cancer (Caco-2) cells and the non-cancerous human embryonic kidney (HEK293) cells.

Solution processing of highly conductive ruthenium and ruthenium oxide thin films from ruthenium–amine complexes

Designing of ruthenium–amine complexes leads to preparation of highly conductive thin films of ruthenium (20–40 nm thick) and ruthenium oxide (50–90 nm thick) by a simple solution process.

Effect of mitochondrial calcium uniporter blocking on human spermatozoa.

Calcium (Ca(2+) ) regulates a number of essential processes in spermatozoa. Ca(2+) is taken up by mitochondria via the mitochondrial calcium uniporter (mCU). Oxygen-bridged dinuclear ruthenium amine complex (Ru360) has been used to study mCU because it is a potent and specific inhibitor of this channel. In bovine spermatozoa, it has been demonstrated that mitochondrial calcium uptake inhibition adversely affects the capacitation process. It has been demonstrated in human spermatozoa that mCU blocking, through Ru360, prevents apoptosis; however, the contribution of the mCU to normal human sperm function has not been studied. Therefore, the aim of this study was to evaluate the effect of mCU blocking on human sperm function. Spermatozoa obtained from apparently healthy donors were incubated with 5 and 10μm Ru360 for 4h at 37°C. Viability was assessed using propidium iodide staining; motility was determined by computer-aided sperm analysis, adenosine triphosphate (ATP) levels using a luminescence-based method, mitochondrial membrane potential (ΔΨm) using JC-1 staining and reactive oxygen species (ROS) production using dihydroethidium dye. Our results show that mCU blocking significantly reduced total sperm motility and ATP levels without affecting sperm viability, ΔΨm and ROS production. In conclusion, mCU contributes to the maintenance of sperm motility and ATP levels in human spermatozoa.

Electropolymerized films as a molecular platform for volatile memory devices with two near-infrared outputs and long retention time

Surface-confined molecular logic gates have great potential as memory devices. We present in this article the uses of electropolymerized films as a molecular platform for volatile memory devices. A vinyl-substituted cyclometalated ruthenium–amine hybridized compound has been polymerized by reductive electropolymerization. The resulting polymeric films display two well-defined redox processes at +0.32 and +0.68 V vs. Ag/AgCl, leading to three well-separated redox states. Characterizations of these films by XPS and TEM techniques are presented. The singly- and doubly-oxidized states of the film possess intense absorption at 1070 and 700 nm, respectively. These polymeric films exhibit promising three-stage near-infrared electrochromism and the best contrast ratios (ΔT%) of 52% at 1070 nm and 76% at 700 nm have been achieved. The colors of the film at three redox stages are purple, brown, and sky blue, respectively. The electrochromism is featured by a long retention time at all three stages (infinity at −0.20 V, 4 h at +0.55 V, and 30 min at +1.05 V, respectively). The singly- and doubly-oxidized states of a film about 10 nm thick have been used to build a surface-confined Set/Reset flip-flop memory with two electrochemical inputs and two near-infrared optical outputs. By using another intermediate state between the singly- and doubly-oxidized states a multi-valued logic system has been demonstrated.

Ruthenium-Amine Electronic Coupling Bridged through Phen-1,3-diyl Versus Phen-1,4-diyl: Reverse of the Charge Transfer Direction

Three tris-bidentate cyclometalated ruthenium complexes with a di(p-anisyl)amino [5(PF6)], di(p-tolyl)amino [6(PF6)], or di(p-chlorophenyl)amino [7(PF6)] substituent on the cyclometalating phenyl ring have been prepared, where the amine nitrogen is in the meta position to the cyclometalated site (bridged through the phen-1,3-diyl unit). The structure of 6(PF6) has been confirmed by single-crystal X-ray diffraction analysis. Two consecutive redox waves are evident at +0.48 and +0.87 V versus Ag/AgCl for 5(PF6), +0.51 and +1.02 V for 6(PF6), and +0.53 and +1.18 V for 7(PF6), respectively. The first wave is assigned to the Ru(II/III) process, and the second wave is attributed to the N(0/+) process. After one-electron oxidation using SbCl5, these complexes display distinct absorptions in the near-infrared region, which are assigned to the nitrogen-to-ruthenium intervalence charge-transfer (ICVT) transitions. The energies of the IVCT transitions vary linearly versus the potential splitting of the Ru(II/III) and N(0/+) process. The charge-transfer direction in these complexes is reversed with respect to a previously reported ruthenium–amine system where the amine nitrogen is in the para position to the cyclometalated site (bridged through the phen-1,4-diyl unit).

The In Vitro and In Vivo Antitumour Activities of Nitrosyl Ruthenium Amine Complexes

Ruthenium compounds of the type trans-[Ru(NO)(NH3)4(L)]X3, L = N-heterocyclic ligands, P(OEt)3, SO32–, X = BF4– or PF6–, or [Ru(NO)Hedta], were tested for antitumour activity in vitro against murine melanoma and human tumour cells. The ruthenium complexes induced DNA fragmentation and morphological alterations suggestive of necrotic tumour cell death. The calculated IC50 values were lower than 100 μM. Complexes for which L = isn or imN were partially effective in vivo in a syngeneic model of murine melanoma B16F10, increasing animal survival. In addition, the same ruthenium complexes effectively inhibited angiogenesis of HUVEC cells in vitro. The results suggest that these nitrosyl complexes are a promising platform to be explored for the development of novel antitumour agents.

Ruthenium–amine complexation for constructing self-assembled molecular films

A redox active self-assembled monolayer consisting of ethylenediamine moieties coordinated to Ru III ions was prepared through a vapor phase silane coupling of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AEAPS) molecules onto a SiO 2/Si substrate, followed by complexation of Ru III ions in an aqueous RuCl 3 solution. A similar SAM with 3-aminopropyltriethoxysilane did not provide surface Ru III-complex, indicating that chelation ability plays a key role in immobilizing Ru III ions at the surface. The Ru III chelated AEAPS-SAM gave a couple of Ru III/Ru IV redox peaks at +1.0 and −0.1 V vs. Ag/AgCl (3 mol dm −3 NaCl).

Intramolecular Trapping of an Intermediate in the Reduction of Imines by a Hydroxycyclopentadienyl Ruthenium Hydride: Support for a Concerted Outer Sphere Mechanism

Reduction of imines by [2,5-Ph2-3,4-Tol(2)(eta(5)-C(4)COH)]Ru(CO)2H (1) produces kinetically stable ruthenium amine complexes. Reduction of an imine possessing an intramolecular amine was studied to distinguish between inner sphere and outer sphere mechanisms. 1,4-Bn(15)NH(c-C(6)H(10))=NBn (12) was reduced by 1 in toluene-d8 to give 85% of [2,5-Ph2-3,4-Tol(2)(eta(4)-C(4)CO)](CO)(2)RuNHBn(c-C(6)H(10))(15)NHBn (16-RuN,15N), resulting from coordination of the newly formed amine to the ruthenium center, and 15% of trapping product [2,5-Ph2-3,4-Tol(2)(eta(4)-C(4)CO)](CO)(2)Ru(15)NHBn(c-C(6)H(10))NHBn (16-Ru(15)N,N), resulting from coordination of the intramolecular trapping amine. These results provide support for an outer sphere transfer of hydrogen to the imine to generate a coordinatively unsaturated intermediate, which can be trapped by the intramolecular amine. An opposing mechanism, requiring coordination of the imine nitrogen to ruthenium prior to hydrogen transfer, cannot readily explain the observation of the trapping product 16-Ru(15)N,N.

DFT Study of an Inner-Sphere Mechanism in the Hydrogen Transfer from a Hydroxycyclopentadienyl Ruthenium Hydride to Imines

A combination of the DFT method with the computational description of environmental effects by solvent was applied to a theoretical study of the hydrogen transfer to imines by [2,3,4,5-Ph4(η5-C4COH)Ru(CO)2H] (2) within a molecular model that closely mimics the authentic reaction conditions. A consistent polarizable continuum solvent model (PCM) was instrumental and necessary in achieving stability of the computational model. Environmental effects by solvent were also considered in an extended model with an addition of explicit solvent molecules within the PCM. The study elucidates an inner-sphere mechanism in detail. Intermediate complexes and transition states are characterized. Three distinct energy barriers along the reaction coordinate are predicted when solvent effects are taken into account. The imine coordinates to ruthenium via ring slippage with an energy barrier of about 15 kcal/mol. Close in energy (12 kcal/mol) is the transition state of the hydride transfer, which gives an (η2-cyclopentadienone)ruthenium amine intermediate. The presence of Ph groups on the Cp ring facilitates the ring slippage that occurs on imine coordination. This η2-intermediate finally rearranges to the corresponding (η4-cyclopentadienone)ruthenium amine complex via a transition state at 9 kcal/mol. The stable ruthenium amine complex was verified against an X-ray structure of the corresponding complex. Inclusion of the solvent (by PCM or explicit molecules) was required to stabilize low-hapticity intermediates and transition state structures.

Mechanistic Study of Hydrogen Transfer to Imines from a Hydroxycyclopentadienyl Ruthenium Hydride. Experimental Support for a Mechanism Involving Coordination of Imine to Ruthenium Prior to Hydrogen Transfer

Reaction of [2,3,4,5-Ph(4)(eta(5)-C(4)COH)Ru(CO)(2)H] (2) with different imines afforded ruthenium amine complexes at low temperatures. At higher temperatures in the presence of 2, the complexes decomposed to give [Ru(2)(CO)(4)(mu-H)(C(4)Ph(4)COHOCC(4)Ph(4))] (1) and free amine. Electron-rich imines gave ruthenium amine complexes with 2 at a lower temperature than did electron-deficient imines. The negligible deuterium isotope effect (k(RuHOH)/k(RuDOD) = 1.05) observed in the reaction of 2 with N-phenyl[1-(4-methoxyphenyl)ethylidene]amine (12) shows that neither hydride (RuH) nor proton (OH) is transferred to the imine in the rate-determining step. In the dehydrogenation of N-phenyl-1-phenylethylamine (4) to the corresponding imine 8 by [2,3,4,5-Ph(4)(eta(4)-C(4)CO)Ru(CO)(2)] (A), the kinetic isotope effects observed support a stepwise hydrogen transfer where the isotope effect for C-H cleavage (k(CHNH)/k(CDNH) = 3.24) is equal to the combined (C-H, N-H) isotope effect (k(CHNH)/k(CDND) = 3.26). Hydrogenation of N-methyl(1-phenylethylidene)amine (14) by 2 in the presence of the external amine trap N-methyl-1-(4-methoxyphenyl)ethylamine (16) afforded 90-100% of complex [2,3,4,5-Ph(4)(eta(4)-C(4)CO)]Ru(CO)(2)NH(CH(3))(CHPhCH(3)) (15), which is the complex between ruthenium and the amine newly generated from the imine. At -80 degrees C the reaction of hydride 2 with 4-BnNH-C(6)H(9)=NPh (18), with an internal amine trap, only afforded [2,3,4,5-Ph(4)(eta(4)-C(4)CO)](CO)(2)RuNH(Ph)(C(6)H(10)-4-NHBn) (19), where the ruthenium binds to the amine originating from the imine, showing that neither complex A nor the diamine is formed. Above -8 degrees C complex 19 rearranged to the thermodynamically more stable [Ph(4)(eta(4)-C(4)CO)](CO)(2)RuNH(Bn)(C(6)H(10)-4-NHPh) (20). These results are consistent with an inner sphere mechanism in which the substrate coordinates to ruthenium prior to hydrogen transfer and are difficult to explain with the outer sphere pathway previously proposed.

Reactions of [η 5:σ-Me 2C(C 5H 4)(C 2B 10H 10)]Ru(COD) with Lewis bases: Synthesis, structure, and electrochemistry of ruthenium amine, nitrile, carbene, phosphite and phosphine complexes

Treatment of [η 5:σ-Me 2C(C 5H 4)(C 2B 10H 10)]Ru(COD) ( 1) with phosphites, phosphines, amines or N-heterocyclic carbene in THF afforded the COD displacement complexes [η 5:σ-Me 2C(C 5H 4)(C 2B 10H 10)]Ru[P(OEt) 3] 2 ( 2), [η 5:σ-Me 2C(C 5H 4)(C 2B 10H 10)]Ru[PPh 2(OEt)] 2 ( 3), [η 5:σ-Me 2C(C 5H 4)(C 2B 10H 10)]Ru[NH 2CH 2CH 2Pr i ] 2 ( 4), [η 5:σ-Me 2C(C 5H 4)(C 2B 10H 10)]Ru(NH 2Pr n ) 2 ( 5), [η 5:σ-Me 2C(C 5H 4)(C 2B 10H 10)]Ru (η 2-NH 2CH 2CH 2NH 2) ( 6), [η 5:σ-Me 2C(C 5H 4)(C 2B 10H 10)]Ru[η 2-NH(CH 3)CH 2CH 2NH(CH 3)] ( 7) or [η 5:σ-Me 2C(C 5H 4)(C 2B 10H 10)]Ru[NHC] 2 ( 8, NHC = 1,3,4,5-tetramethylimidazol-2-yilidene), respectively. Ruthenium–amine complexes were much more labile than 1. Upon exposure to moisture, 5 was converted into [{η 5:σ-Me 2C(C 5H 4)(C 2B 10H 10)}Ru(μ-H 2O)] 2 ( 9). Reactions of 5 with PR 3 (R = PPh 3, Cy), TMEDA (TMEDA = N, N, N′, N′-tetramethylethylenediamine) and CH 3CN afforded the corresponding amine replacement products[η 5:σ-Me 2C(C 5H 4)(C 2B 10H 10)]Ru(NH 2Pr n )(PPh 3) ( 10), [η 5:σ-Me 2C(C 5H 4)(C 2B 10H 10)]Ru(NH 2Pr n )(PCy 3) ( 11), [η 5:σ-Me 2C(C 5H 4)(C 2B 10H 10)]Ru(TMEDA) ( 12) and [η 5:σ-Me 2C(C 5H 4)(C 2B 10H 10)]Ru(NCCH 3) 2 ( 13). These results indicated that the steric factor dominated these substitution reactions. The electrochemical studies showed that the electron richness of the Ru atom decreased in the order L 2Ru(NHC) 2 > L 2Ru(amine) 2 > L 2Ru(NCMe) 2 > L 2Ru(P) 2. All of these complexes were fully characterized by various spectroscopic techniques and elemental analyses. The molecular structures of 2, 3, 5– 10, 12 and 13 were further confirmed by single-crystal X-ray analyses.

Reduction of Imines by Hydroxycyclopentadienyl Ruthenium Hydride: Intramolecular Trapping Evidence for Hydride and Proton Transfer Outside the Coordination Sphere of the Metal

Reduction of imines by [2,5-Ph2-3,4-Tol2(eta(5)-C4COH)]Ru(CO)2H (2) produces kinetically stable ruthenium amine complexes. Reduction of an imine by 2 in the presence of an external amine trap gives only the complex of the newly generated amine. Reaction of 2 with H2N-p-C6H4N=CHPh (11), which contains an intramolecular amine trap, gave a 1:1 mixture of [2,5-Ph2-3,4-Tol2(eta(4)-C4CO)](CO)2RuNH(CH2Ph)(C6H4-p-NH2) (8), formed by coordination of the newly generated amine to the ruthenium center, and [2,5-Ph2-3,4-Tol2(eta(4)-C4CO)](CO)2RuNH2C6H4-p-NHCH2Ph (9), formed by coordination of the amine already present in the substrate. These results require transfer of hydrogen to the imine outside the coordination sphere of the metal to give a coordinatively unsaturated intermediate that can be trapped inside the initial solvent cage. Amine diffusion from the solvent cage must be much slower than coordination to the metal center. Mechanisms requiring prior coordination of the substrate to ruthenium would have led only to 8 and can be eliminated.

Inhibition of the mitochondrial calcium uniporter by the oxo‐bridged dinuclear ruthenium amine complex (Ru360) prevents from irreversible injury in postischemic rat heart

Mitochondrial calcium overload has been implicated in the irreversible damage of reperfused heart. Accordingly, we studied the effect of an oxygen-bridged dinuclear ruthenium amine complex (Ru360), which is a selective and potent mitochondrial calcium uniporter blocker, on mitochondrial dysfunction and on the matrix free-calcium concentration in mitochondria isolated from reperfused rat hearts. The perfusion of Ru360 maintained oxidative phosphorylation and prevented opening of the mitochondrial permeability transition pore in mitochondria isolated from reperfused hearts. We found that Ru360 perfusion only partially inhibited the mitochondrial calcium uniporter, maintaining the mitochondrial matrix free-calcium concentration at basal levels, despite high concentrations of cytosolic calcium. Additionally, we observed that perfused Ru360 neither inhibited Ca2+ cycling in the sarcoplasmic reticulum nor blocked ryanodine receptors, implying that the inhibition of ryanodine receptors cannot explain the protective effect of Ru360 in isolated hearts. We conclude that the maintenance of postischemic myocardial function correlates with an incomplete inhibition of the mitochondrial calcium uniporter. Thus, the chemical inhibition by this molecule could be an approach used to prevent heart injury during reperfusion.

Mitochondrial glycosidic residues contribute to the interaction between ruthenium amine complexes and the calcium uniporter

The role of glycosidic residues in the inhibitory properties of ruthenium complexes on mitochondrial calcium uptake was determined in mitoplasts. Our results showed that the binding and inhibitory properties of ruthenium amine complexes were modified when mitoplasts were exposed to N-glycosidase F action, but calcium uptake was not altered. N-linked proteins of the mitochondrial inner membrane were identified. We detected an 18-kDa protein that binds labeled Ru360 under control conditions, but failed to bind the inhibitor after deglycosilation. A relationship between this protein and the action of ruthenium amine inhibitors of the mitochondrial uniporter is proposed.