Small molecule activators of the Nrf2-HO-1 antioxidant axis modulate heme metabolism and inflammation in BV2 microglia cells.

The nuclear factor erythroid derived 2-related factor 2 (Nrf2) and the antioxidant protein heme oxygenase-1 (HO-1) are crucial components of the cellular stress response. These two systems work together to combat oxidative stress and inflammation and are attractive drug targets for counteracting different pathologies, including neuroinflammation. We aimed to identify the most effective Nrf2/HO-1 activators that modulate the inflammatory response in microglia cells. In the present study, we searched the literature and selected 56 compounds reported to activate Nrf2 or HO-1 and analyzed them for HO-1 induction at 6 and 24h and cytotoxicity in BV2 microglial cells in vitro. Approximately 20 compounds up-regulated HO-1 at the concentrations tested (5-20 µM) with carnosol, supercurcumin, cobalt protoporphyrin-IX and dimethyl fumarate exhibiting the best induction/low cytotoxicity profile. Up-regulation of HO-1 by some compounds resulted in increased cellular bilirubin levels but did not augment the expression of proteins involved in heme synthesis (ALAS 1) or biliverdin reductase. Bilirubin production by HO-1 inducers correlated with their potency in inhibiting nitrite production after challenge with interferon-γ (INF-γ) or lipopolysaccharide (LPS). The compounds down-regulated the inflammatory response (TNF-α, PGE2 and nitrite) more strongly in cells challenged with INF-γ than LPS, and silencing HO-1 or Nrf2 with shRNA differentially affected the levels of inflammatory markers. These findings indicate that some small activators of Nrf2/HO-1 are effective modulators of microglia inflammation and highlight the chemical scaffolds that can serve for the synthesis of potent new derivatives to counteract neuroinflammation and neurodegeneration.

Isostructural nuclear and luminescent probes derived from stabilized [2 + 1] rhenium(I)/technetium(I) organometallic complexes.

A convenient method to prepare (99m)Tc analogues of a class of rhenium(I) luminophores was developed, creating isostructural pairs of nuclear and optical probes. A two-step procedure and a new one-pot procedure were used to produce a series of [2 + 1] complexes of the type [Tc(CO)3(bipy)L](+) in greater than 80% yield. The plasma stability of the reported compounds was evaluated, where the basicity of the monodentate pyridine type ligand (L) has a significant impact with half-lives ranging from 2 to 20 h. The ability to generate the radioactive complexes makes it possible to quantitate cell uptake of Re luminophores, which was demonstrated in MCF-7 breast cancer cells using (99m)Tc analogues of two Re(I)-based mitochondrial targeting dyes.

Syntheses, structural characterization and CO releasing properties of boranocarbonate [H3BCO2H]- derivatives.

CO plays an important role in biological processes and molecules which release CO in a controllable way could therefore be used for medicinal purposes. Beside organometallic carbonyl complexes, boranocarbonate [H(3)BCO(2)H](-) is one of the most promising candidates but releases CO too rapidly. In order to delay the CO release, we have prepared boranocarbamates [H(3)BCONH-R](-) from [H(3)BCO(2)H](-) which comprise histamine, morpholine, aniline and ethylene-diamine bound via amides to the {H(3)BCO} moiety. The syntheses of the new derivatives is described together with their structural characterization. These compounds release CO at a much slower rate than the parent compound and are therefore potential CO releasing molecules for biological and medicinal application.

Imidazole fused phenanthroline (PIP) ligands for the preparation of multimodal Re(I) and 99mTc(I) probes.

A small library of [2 + 1] 99mTc(i) complexes based on phenyl-imidazole-fused phenanthroline (PIP) ligands were synthesized and evaluated as multimodal molecular imaging probes. Using either a two-step or a one-pot synthesis method, 99mTc-PIP complexes containing N-methylimidazole as the monodentate ligand were prepared and isolated in good (54 to 89%) radiochemical yield, with the exception of one derivative bearing a strongly electron-withdrawing substituent. The stability of the [2 + 1] complexes was assessed in saline and in cysteine and histidine challenge studies, showing 6 hours stability, making them suitable for in vivo studies. In parallel, the Re(i) analogues were prepared as reference standards to verify the structure of the 99mTc complexes. The optical properties were consistent with other previously reported [2 + 1] type Re(i) complexes that have been used as cellular dyes and sensors. To facilitate the development of targeted derivatives, a tetrazine-PIP ligand was also synthesized. The 99mTc complex of the tetrazine PIP ligand effectively coupled to compounds containing a trans-cyclooctene (TCO) group including a TCO-albumin derivative, which was prepared as a model targeting molecule. An added benefit of the Re-PIP-Tz construct is that the emission from the metal complex was quenched by the presence of the tetrazine. Following the addition of TCO, there was a 70-fold increase in fluorescence emission, which can in future be leveraged during in vitro studies to reduce background signal.