Rhenium fac-Tricarbonyl Bisimine Chalcogenide Complexes: Synthesis, Photophysical Studies, and Confocal and Time-Resolved Cell Microscopy.

We describe the preparation, characterization, and imaging studies of rhenium carbonyl complexes with a pyta (4-(2-pyridyl)-1,2,3-triazole) or tapy (1-(2-pyridyl)-1,2,3-triazole)-based heteroaromatic N∧N ligand and thiolate or selenoate X ligand. The stability and photophysical properties of the selenolate complexes are compared with parent chloride complexes and previously described analogues with benzenethiolate ligands. Two complexes were imaged in A549 cells upon excitation at 405 nm. Colocalization studies suggest a lysosomal accumulation, while one parent chloride complex was described to localize at the Golgi apparatus. Preliminary fluorescence lifetime measurements and imaging demonstrate potential for application in time-resolved microscopy techniques due to the long and variable lifetimes observed in cellular environments, including an increase in lifetime between the solution and solid state many times larger than previously reported.

Cellular Detection of a Mitochondria Targeted Brominated Vinyl Triphenylamine Optical Probe (TP-Br) by X-Ray Fluorescence Microscopy.

Triphenylamine (TP) derivatives such as two-branch cationic vinylbenzimidazolium triphenylamine TP-2Bzim are promising turn-on fluorescent probes suitable for two-photon imaging, labelling mitochondria in live cells. Here, we designed two TP-2Bzim derivatives as bimodal probes suitable for X-ray fluorescence imaging. The conjugation of the TP core with a rhenium tricarbonyl moiety in the TP-RePyta probe altered the localisation in live cells from mitochondria to lysosomes. The introduction of bromine on the TP core generated the TP-Br probe retaining good photophysical properties and mitochondria labelling in live cells. The influence of calcium channels in the uptake of TP-Br was studied. Synchrotron Radiation X-ray Fluorescence (SXRF) imaging of bromine enabled the detection of TP-Br and suggested a negligible presence of the probe in an unbound state in the incubated cells, a crucial point in the development of these probes. This study paves the way towards the development of TP probes as specific organelle stainers suitable for SXRF imaging.

A New Manganese Superoxide Dismutase Mimetic Improves Oxaliplatin-Induced Neuropathy and Global Tolerance in Mice.

Reactive oxygen species (ROS) are produced by every aerobic cell during mitochondrial oxidative metabolism as well as in cellular response to xenobiotics, cytokines, and bacterial invasion. Superoxide Dismutases (SOD) are antioxidant proteins that convert superoxide anions (O2•-) to hydrogen peroxide (H2O2) and dioxygen. Using the differential in the level of oxidative stress between normal and cancer cells, SOD mimetics can show an antitumoral effect and prevent oxaliplatin-induced peripheral neuropathy. New Pt(IV) conjugate prodrugs (OxPt-x-Mn1C1A (x = 1, 1-OH, 2)), combining oxaliplatin and a Mn SOD mimic (MnSODm Mn1C1A) with a covalent link, were designed. Their stability in buffer and in the presence of sodium ascorbate was studied. In vitro, their antitumoral activity was assessed by the viability and ROS production of tumor cell lines (CT16, HCT 116, KC) and fibroblasts (primary culture and NIH 3T3). In vivo, a murine model of colorectal cancer was created with subcutaneous injection of CT26 cells in Balb/c mice. Tumor size and volume were measured weekly in four groups: vehicle, oxaliplatin, and oxaliplatin associated with MnSODm Mn1C1A and the bis-conjugate OxPt-2-Mn1C1A. Oxaliplatin-induced peripheral neuropathy (OIPN) was assessed using a Von Frey test reflecting chronic hypoalgesia. Tolerance to treatment was assessed with a clinical score including four items: weight loss, weariness, alopecia, and diarrhea. In vitro, Mn1C1A associated with oxaliplatin and Pt(IV) conjugates treatment induced significantly higher production of H2O2 in all cell lines and showed a significant improvement of the antitumoral efficacy compared to oxaliplatin alone. In vivo, the association of Mn1C1A to oxaliplatin did not decrease its antitumoral activity, while OxPt-2-Mn1C1A had lower antitumoral activity than oxaliplatin alone. Mn1C1A associated with oxaliplatin significantly decreased OIPN and also improved global clinical tolerance of oxaliplatin. A neuroprotective effect was observed, associated with a significantly improved tolerance to oxaliplatin without impairing its antitumoral activity.

Understanding the g-tensors of perchlorotriphenylmethyl and Finland-type trityl radicals.

The 285 GHz EPR spectra of perchlorotriphenylmethyl and tetrathiatriarylmethyl radicals in frozen solution have been accurately measured. The relationship between their molecular structures and their g-tensors has been investigated with the aid of DFT calculations, revealing that the degree of spin density delocalization away from the central methylene carbon is an important determining factor of the g-anisotropy. In particular, the small amount of spin densities on the Cl or S heteroatoms at the 2 and 6 positions with respect to the central carbon have the strongest influence. Furthermore, the amount of spin densities on these heteroatoms and thus the anisotropy can be modulated by the protonation (esterification) state of the carboxylate groups at the 4 position. These results provide unique insights into the g-anisotropy of persistent trityl radicals and how it can be tuned.

Direct Keap1-Nrf2 disruption as a potential therapeutic target for Alzheimer's disease.

Nrf2, a transcriptional activator of cell protection genes, is an attractive therapeutic target for the prevention of neurodegenerative diseases, including Alzheimer's disease (AD). Current Nrf2 activators, however, may exert toxicity and pathway over-activation can induce detrimental effects. An understanding of the mechanisms mediating Nrf2 inhibition in neurodegenerative conditions may therefore direct the design of drugs targeted for the prevention of these diseases with minimal side-effects. Our study provides the first in vivo evidence that specific inhibition of Keap1, a negative regulator of Nrf2, can prevent neuronal toxicity in response to the AD-initiating Aß42 peptide, in correlation with Nrf2 activation. Comparatively, lithium, an inhibitor of the Nrf2 suppressor GSK-3, prevented Aß42 toxicity by mechanisms independent of Nrf2. A new direct inhibitor of the Keap1-Nrf2 binding domain also prevented synaptotoxicity mediated by naturally-derived Aß oligomers in mouse cortical neurons. Overall, our findings highlight Keap1 specifically as an efficient target for the re-activation of Nrf2 in AD, and support the further investigation of direct Keap1 inhibitors for the prevention of neurodegeneration in vivo.

Labeling of Hyaluronic Acids with a Rhenium-tricarbonyl Tag and Percutaneous Penetration Studied by Multimodal Imaging.

Hyaluronic acids were labeled with a rhenium-tricarbonyl used as single core multimodal probe for imaging and their penetration into human skin biopsies was studied using IR microscopy and fluorescence imaging (labeled SCoMPI). The penetration was shown to be dependent on the molecular weight of the molecule and limited to the upper layer of the skin.

Association of a Platinum Complex to a G-Quadruplex Ligand Enhances Telomere Disruption.

Telomeres protect the ends of chromosomes against illegitimate recombination and repair. They can be targets for G-quadruplex ligands and platinum complexes due to their repeated G-rich sequences. Protection of telomeres is ensured by a complex of six proteins, including TRF2, which inhibits the DNA damage response pathway. We analyzed telomere modifications induced in cancer cells by the experimental hybrid platinum complex, Pt-MPQ, comprising both an ethylene diamine monofunctional platinum complex and a G-quadruplex recognition moiety (MPQ). Pt-MPQ promotes the displacement of two telomeric proteins (TRF2 and TRF1) from telomeres, as well as the formation of telomere damage and telomere sister losses, whereas the control compound MPQ does not. This suggests that the platinum moiety potentiates the targeting of the G-quadruplex ligand to telomeres, opening a new perspective for telomere biology and anticancer therapy. Interestingly, the chemotherapy drug cisplatin, which has no specific affinity for G-quadruplex structures, partially induces the TRF2 delocalization from telomeres but produces less telomeric DNA damage, suggesting that this TRF2 displacement could be independent of G-quadruplex recognition.

Rhenium Complexes Based on 2-Pyridyl-1,2,3-triazole Ligands: A New Class of CO2 Reduction Catalysts.

A series of [Re(N^N)(CO)3(X)] (N^N = diimine and X = halide) complexes based on 4-(2-pyridyl)-1,2,3-triazole (pyta) and 1-(2-pyridyl)-1,2,3-triazole (tapy) diimine ligands have been prepared and electrochemically characterized. The first ligand-based reduction process is shown to be highly sensitive to the nature of the isomer as well as to the substituents on the pyridyl ring, with the peak potential changing by up to 700 mV. The abilities of this class of complexes to catalyze the electroreduction and photoreduction of CO2 were assessed for the first time. It is found that only Re pyta complexes that have a first reduction wave with a peak potential at ca. -1.7 V vs SCE are active, producing CO as the major product, together with small amounts of H2 and formic acid. The catalytic wave that is observed in the CVs is enhanced by the addition of water or trifluoroethanol as a proton source. Long-term controlled potential electrolysis experiments gave total Faradaic yield close to 100%. In particular, functionalization of the triazolyl ring with a 2,4,6-tri-tert-butylphenyl group provided the catalyst with a remarkable stability.

Bimodal X-ray and Infrared Imaging of an Organometallic Derivative of Praziquantel in Schistosoma mansoni.

An organometallic derivative of praziquantel was studied directly in worms by using inductively coupled plasma-mass spectrometry (ICP-MS) for quantification and synchrotron-based imaging. X-ray fluorescence (XRF) and IR absorption spectromicroscopy were used for the first time in combination to directly locate this organometallic drug candidate in schistosomes. The detection of both CO (IR) and Cr (XRF) signatures proved that the Cr(CO)3 core remained intact in the worms. Images showed a preferential accumulation at the worm's tegument, consistent with a possible targeting of the calcium channel but not excluding other biological targets inside the worm.

A Bis-Manganese(II)-DOTA Complex for Pulsed Dipolar Spectroscopy.

High-spin gadolinium(III) and manganese(II) complexes have emerged as alternatives to standard nitroxide radical spin labels for measuring nanometric distances by using pulsed electron-electron double resonance (PELDOR or DEER) at high fields/frequencies. For certain complexes, particularly those with relatively small zero-field splitting (ZFS) and short distances between the two metal centers, the pseudosecular term of the dipolar coupling Hamiltonian is non-negligible. However, in general, the contribution from this term during conventional data analysis is masked by the flexibility of the molecule of interest and/or the long tethers connecting them to the spin labels. The efficient synthesis of a model system consisting of two [Mn(dota)](2-) (MnDOTA; DOTA(4-) =1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate) directly connected to the ends of a central rodlike oligo(phenylene-ethynylene) (OPE) spacer is reported. The rigidity of the OPE is confirmed by Q-band PELDOR measurements on a bis-nitroxide analogue. The Mn(II) -Mn(II) distance distribution profile determined by W-band PELDOR is in reasonable agreement with one simulated by using a simple rotamer analysis. The small degree of flexibility arising from the linking MnDOTA arm appears to outweigh the contribution from the pseudosecular term at this interspin distance. This study illustrates the potential of MnDOTA-based spin labels for measuring fairly short nanometer distances, and also presents an interesting candidate for in-depth studies of pulsed dipolar spectroscopy methods on Mn(II) -Mn(II) systems.

Dextrose Prolotherapy Versus Control Injections in Painful Rotator Cuff Tendinopathy.

OBJECTIVE: To compare the effect of dextrose prolotherapy on pain levels and degenerative changes in painful rotator cuff tendinopathy against 2 potentially active control injection procedures. DESIGN: Randomized controlled trial, blinded to participants and evaluators. SETTING: Outpatient pain medicine practice. PARTICIPANTS: Persons (N=73) with chronic shoulder pain, examination findings of rotator cuff tendinopathy, and ultrasound-confirmed supraspinatus tendinosis/tear. INTERVENTIONS: Three monthly injections either (1) onto painful entheses with dextrose (Enthesis-Dextrose), (2) onto entheses with saline (Enthesis-Saline), or (3) above entheses with saline (Superficial-Saline). All solutions included 0.1% lidocaine. All participants received concurrent programmed physical therapy. MAIN OUTCOME MEASURES: Primary: participants achieving an improvement in maximal current shoulder pain ≥2.8 (twice the minimal clinically important difference for visual analog scale pain) or not. Secondary: improvement in the Ultrasound Shoulder Pathology Rating Scale (USPRS) and a 0-to-10 satisfaction score (10, completely satisfied). RESULTS: The 73 participants had moderate to severe shoulder pain (7.0±2.0) for 7.6±9.6 years. There were no baseline differences between groups. Blinding was effective. At 9-month follow-up, 59% of Enthesis-Dextrose participants maintained ≥2.8 improvement in pain compared with Enthesis-Saline (37%; P=.088) and Superficial-Saline (27%; P=.017). Enthesis-Dextrose participants' satisfaction was 6.7±3.2 compared with Enthesis-Saline (4.7±4.1; P=.079) and Superficial-Saline (3.9±3.1; P=.003). USPRS findings were not different between groups (P=.734). CONCLUSIONS: In participants with painful rotator cuff tendinopathy who receive physical therapy, injection of hypertonic dextrose on painful entheses resulted in superior long-term pain improvement and patient satisfaction compared with blinded saline injection over painful entheses, with intermediate results for entheses injection with saline. These differences could not be attributed to a regenerative effect. Dextrose prolotherapy may improve on the standard care of painful rotator cuff tendinopathy for certain patients.

Nanometric distance measurements between Mn(ii)DOTA centers.

Pulse electron-electron double resonance (PELDOR) is a versatile technique for probing the structures and functions of complex biological systems. Despite the recent interest in high-spin metal-ions for high field/frequency applications, PELDOR measurements of Mn(ii) remain relatively underexplored. Here we present Mn(ii)-Mn(ii) PELDOR distance measurements at 94 GHz on polyproline II (PPII) helices doubly spin-labeled with Mn(ii)DOTA, which are distinguished by their small zero-field interaction. The measured Mn-Mn distances and distribution profiles were in good agreement with the expected values from molecular models. Additional features in the frequency-domain spectra became apparent at certain combinations of detect and pump frequencies. Spin-Hamiltonian calculations showed that they likely arose from contributions from the pseudo-secular component of the dipolar interaction that were found to be non-negligible for Mn(ii)DOTA. However, the influence of the pseudo-secular component on the distance distribution profiles apparently was limited. The results show the potential of Mn(ii)DOTA spin labels for high-field PELDOR distance measurements in proteins and other biological systems.

Influence of the side-chain length on the cellular uptake and the cytotoxicity of rhenium triscarbonyl derivatives: a bimodal infrared and luminescence quantitative study.

Rhenium triscarbonyl complexes fac-[Re(CO)3 (N^N)] with appropriate ancillary N^N ligands are relevant for fluorescent bio-imaging. Recently, we have shown that [Re(CO)3 ] cores can also be efficiently mapped inside cells using their IR signature and that they can thus be used in a bimodal approach. To describe them we have coined the term SCoMPIs for single-core multimodal probes for imaging. In the context of the use of these SCoMPIs in bio-imaging, the questions of their cellular uptake and cytotoxicity are critical. We report here a series of compounds derived from the [Re(CO)3 Cl(pyta)] core (pyta=4-(2-pyridyl)-1,2,3-triazole). The pyta ligand is of interest because it can be easily functionalized. Aliphatic side chains (C4 , C8 , and C12 ) were appended to this core. A correlative study involving IR and luminescence was performed to monitor and quantify their cellular internalization. We studied the relationship between lipophilicity (log P(o/w)), cytotoxicity (IC50 ), and cellular uptake, and we showed that both uptake and cytotoxicity increase with the length of the side chain, with a higher uptake for the C12 derivative. This study stresses the distinction that has to be made between apparent toxicity, determined as an incubation concentration IC50 , and intrinsic toxicity. Indeed, the intrinsic toxicity of a compound can remain hidden if it is not cell permeable. Therefore it must be kept in mind that IC50 values are composite values, reflecting both cellular uptake and intrinsic toxicity.

Luminescence modulations of rhenium tricarbonyl complexes induced by structural variations.

Octahedral d(6) low-spin Re(I) tricarbonyl complexes are of considerable interest as noninvasive imaging probes and have been deeply studied owing to their biological stability, low toxicity, large Stokes shifts, and long luminescence lifetimes. We reported recently the bimodal IR and luminescence imaging of a Re(I) tricarbonyl complex with a Pyta ligand (4-(2-pyridyl)-1,2,3-triazole) in cells and labeled such metal-carbonyl complexes SCoMPIs for single-core multimodal probes for imaging. Re(I) tricarbonyl complexes have unique photophysical properties allowing for their unequivocal detection in cells but also present some weaknesses such as a very low luminescence quantum yield in aqueous medium. Further optimizations would thus be desirable. We therefore developed new Re(I) tricarbonyl complexes prepared from different ancillary ligands. Complexes with benzothiadiazole-triazole ligands show interesting luminescent quantum yields in acetonitrile and may constitute valuable luminescent metal complexes in organic media. A series of complexes with bidentate 1-(2-quinolinyl)-1,2,3-triazole (Taquin) and 1-(2-pyridyl)-1,2,3-triazole (Tapy) ligands bearing various 4-substituted alkyl side chains has been designed and synthesized with efficient procedures. Their photophysical properties have been characterized in acetonitrile and in a H2O/DMSO (98/2) mixture and compared with those of the parent Quinta- and Pyta-based complexes. Tapy complexes bearing long alkyl chains show impressive enhancement of their luminescent properties relative to the parent Pyta complex. Theoretical calculations have been performed to further characterize this new class of rhenium tricarbonyl complexes. Preliminary cellular imaging studies in MDA-MB231 breast cancer cells reveal a strong increase in the luminescence signal in cells incubated with the Tapy complex substituted with a C12 alkyl chain. This study points out the interesting potential of the Tapy ligand in coordination chemistry, which has been so far underexploited.

Synthesis, properties, and remarkable 2 D Self-Assembly at the Liquid/Solid interface of a series of triskele-shaped 5,11,17-triazatrinaphthylenes (TrisK).

A series of 5,11,17-triazatrinaphthylene (TrisK) derivatives, large disk-like π-conjugated molecules with C3h symmetry, has been synthesised by following an optimised synthetic pathway. The synthesis was performed by a four-step protocol based on the N-arylation of 1,3,5-tribromobenzene with appropriate anthranilate derivatives. This strategy permits the generation of either chlorinated (TrisK-Cl-OCn) or non-chlorinated (TrisK-H-OCn) alkoxy-substituted derivatives (OCn H2n+1 with n=3, 10, 12 and 16), thus providing additional versatility in the control of the structure-property relationships. The electronic properties of the various TrisK compounds have been characterised in solution by absorption and emission spectroscopies as well as cyclic voltammetry. The crystal structure of 2,8,14-propyloxy-5,11,17-triazatrinaphthylene TrisK-H-OC3 has been determined by X-ray diffraction analysis, which revealed the presence of stabilising weak intermolecular H bonds. Scanning tunnelling microscopy (STM) at the liquid/solid interface has revealed the remarkable 2D self-assembling properties of the TrisK compounds. In particular, it has shown that TrisK-H-OC12 forms three concomitant self-organised 2D phases with different row-packing arrangements. This 2D polymorphism arises from slow ordering due to the presence of three long dodecyloxy chains on the molecular backbone. Individual molecules can be imaged with spectacular intramolecular resolution, thus providing the possibility of correlating the STM features with the calculated charge density distribution.

Chronic Low Back Pain Forced Me to Search for and Find Pain Solutions: An Autobiographical Case Report.

Lifelong, pregnancy-induced low back pain forced me to search for solutions to the problem of pain. Currently, low back pain is often diagnosed as "nonspecific" and, as a result, a multitude of tests and poorly effective, at times side effect-laden or habit-forming treatments are recommended. My quest for relief took me to first diagnose my pain as coming from the sacroiliac joints, then to prolotherapy, the first treatment which brought me prolonged relief. I then learned how to perform prolotherapy. In 2009, when I undertook a randomized controlled study of dextrose prolotherapy for rotator cuff tendinopathy, I restricted my practice to treating pain. As low back pain was a large part of my practice, I sought new ways to examine the sacroiliac joints. I conducted a consecutive patient data collection which suggested that over three-quarters of those with low back pain suffer from displaced sacroiliac joints. In a further randomized controlled study, I found that the two-minute corrective exercise I derived from this test provided immediate relief to 90% of those using it. With Dr. John Clark Lyftogt I discovered the safety and effectiveness of 5% dextrose perineural injections to provide immediate pain relief to any area supplied by a nerve I could reach with my needle. As I was treating many diabetics with peripheral neuropathy, I shifted my perineural injection material to 5% mannitol, which may be as effective, with less exposure to dextrose as a potential benefit for diabetics. As most people dislike injections, a pharmacist and I developed a mannitol-containing topical cream for pain relief. We compared a base cream to the same cream with mannitol on lips pretreated with capsaicin cream which made them burn. By 10 minutes the probability the two creams were as effective in relieving the burn was less than 0.001 in favor of mannitol. When given to 235 patients with a total of 289 different painful conditions, we found that it provided 53% relief in an average of 16 minutes with a median of four hours duration. Now retired, after 55 years of medical practice, I love to relieve the pain of friends and fellow hikers using exercise and cream. Searching for and finding solutions to chronic pain has enriched my life and that of many others.

SOD mimics: From the tool box of the chemists to cellular studies.

Superoxide dismutases (SODs) are metalloproteins that protect cells against oxidative stress by controlling the concentration of superoxide (O2-) through catalysis of its dismutation. The activity of superoxide dismutases can be mimicked by low-molecular-weight complexes having potential therapeutic applications. This review presents recent strategies for designing efficient SOD mimics, from molecular metal complexes to nanomaterials. Studies of these systems in cells reveal that some SOD mimics, designed to react directly with superoxide, may also indirectly enhance the cellular antioxidant arsenal. Finally, a good understanding of the bioactivity requires information on the cell-penetration, speciation, and subcellular location of the SOD mimics: we will describe recent studies and new techniques that open opportunities for characterizing SOD mimics in biological environments.

Recognition of G-quadruplex DNA by triangular star-shaped compounds: with or without side chains?

We report the synthesis of two new series of triangular aromatic platforms, either with three aminoalkyl side chains (triazatrinaphthylene series, TrisK: six compounds), or without side chains (triazoniatrinaphthylene, TrisQ). The quadruplex-DNA binding behavior of the two series, which differ essentially by the localization of the cationic charges, was evaluated by means of FRET-melting and G4-FID assays. For the trisubstituted triazatrinaphthylenes (TrisK), the length of the substituents and the presence of terminal hydrogen-bond-donor groups (NH(2)) were shown to be crucial for ensuring a high quadruplex affinity (ΔT(1/2) values of up to 20 °C at 1 µM for the best candidate, TrisK3-NH) and selectivity versus duplex DNA. Subsequently, comparison of data collected on both the telomeric- and c-myc-quadruplex showed that the nonsubstituted TrisQ is even more efficient than TrisK3-NH, both in terms of quadruplex affinity (ΔT(1/2)=26 °C in K(+) buffer) and selectivity versus duplex DNA. Structural considerations conducted with the c-myc quadruplex indicate that both TrisK3-NH and TrisQ stack well onto the G-quartet but in an offset position, which might be influenced by the formation of multiple hydrogen bonds with the target in the former case. Finally, the nonsubstituted TrisQ displays a binding profile very similar to some of the best quadruplex binders, BRACO-19 and bisquinolinium 360A, used herein as references, and thereby represents a highly promising novel molecular design for quadruplex recognition.