Potent, selective and reversible hMAO-B inhibition by benzalphthalides: Synthesis, enzymatic and cellular evaluations and virtual docking and predictive studies

Monoaminooxidases (MAOs) are important targets for drugs used in the treatment of neurological and psychiatric disorders and particularly on Parkinson's Disease (PD). Compounds containing a trans-stilbenoid skeleton have demonstrated good selective and reversible MAO-B inhibition. Here, twenty-two (Z)-3-benzylidenephthalides (benzalphthalides, BPHs) displaying a trans-stilbenoid skeleton have been synthesised and evaluated as inhibitors of the MAO-A and MAO-B isoforms. Some BPHs have selectively inhibited MAO-B, with IC50 values ranging from sub-nM to μM. The most potent compound with IC50 = 0.6 nM was the 3',4'-dichloro-BPH 16, which showed highly selective and reversible MAO-B inhibitory activity. Furthermore, the most selective BPHs displayed a significant protection against the apoptosis, and mitochondrial toxic effects induced by 6-hydroxydopamine (6OHDA) on SH-SY5Y cells, used as a cellular model of PD. The results of virtual binding studies on the most potent compounds docked in MAO-B and MAO-A were in agreement with the potencies and selectivity indexes found experimentally. Additionally, related to toxicity risks, drug-likeness and ADME properties, the predictions found for the most relevant BPHs in this research were within those ranges established for drug candidates.

The novel cyclophilin inhibitor C105SR reduces hepatic ischaemia-reperfusion injury via mitoprotection

Background & Aims

Mitochondrial permeability transition pore (mPTP) opening is critical for mediating cell death during hepatic ischaemia-reperfusion injury (IRI). Blocking mPTP opening by inhibiting cyclophilin D (CypD) is a promising pharmacological approach for the treatment of IRI. Here, we show that diastereoisomers of a new class of small-molecule cyclophilin inhibitors (SMCypIs) have properties that make them attractive candidates for the development of therapeutic agents against liver IRI.

Methods

Derivatives of the parent SMCypI were synthesised and evaluated for their ability to inhibit CypD peptidyl-prolyl cis-trans isomerase (PPIase) activity and for their mitoprotective properties, evaluated by measuring mitochondrial swelling and calcium retention capacity in liver mitochondria. The ability of the selected compounds to inhibit mPTP opening was evaluated in cells subjected to hypoxia/reoxygenation using a calcein/cobalt assay. Their ability to inhibit cell death was evaluated in cells subjected to hypoxia/reoxygenation by measuring lactate dehydrogenase (LDH) release, propidium iodide staining, and cell viability. The compound performing best in vitro was selected for in vivo efficacy evaluation in a mouse model of hepatic IRI.

Results

The two compounds that showed the strongest inhibition of CypD PPIase activity and mPTP opening, C105 and C110, were selected. Their SR diastereoisomers carried the activity of the racemic mixture and exhibited mitoprotective properties superior to those of the known macrocyclic cyclophilin inhibitors cyclosporin A and alisporivir. C105SR was more potent than C110SR in inhibiting mPTP opening and prevented cell death in a model of hypoxia/reoxygenation. Finally, C105SR substantially protected against hepatic IRI in vivo by reducing hepatocyte necrosis and apoptosis.

Conclusions

We identified a novel cyclophilin inhibitor with strong mitoprotective properties both in vitro and in vivo that represents a promising candidate for cellular protection in hepatic IRI.

Impact and Implications

Hepatic ischaemia-reperfusion injury (IRI) is one of the main causes of morbidity and mortality during or after liver surgery. However, no effective therapies are available to prevent or treat this devastating syndrome. An attractive strategy to prevent hepatic IRI aims at reducing cell death by targeting mitochondrial permeability transition pore opening, a phenomenon regulated by cyclophilin D. Here, we identified a new small-molecule cyclophilin inhibitor, and demonstrated the enhanced mitoprotective and hepatoprotective properties of one of its diastereoisomers both in vitro and in vivo, making it an attractive lead compound for subsequent clinical development.

Rhizobia exopolysaccharides: promising biopolymers for use in the formulation of plant inoculants

Inoculants with beneficial microorganisms comprise both selected strains and carriers that ensure a favorable microenvironment for cell survival and stability. Formulations of inoculants using synthetic polymers as carriers are common. However, only a few studies are available in the literature regarding the formulation of inoculants using natural biomolecules as carriers. Exopolysaccharides (EPS) are biomolecules produced by a vast array of microbial species, including symbiotic nitrogen-fixing bacteria, commonly known as rhizobia. EPS perform several functions, such as the protection against the deleterious effects of diverse environmental soil stresses. Two Rhizobium tropici strains and one Paraburkholderia strain were selected after semiquantitative analysis by scanning electron microscopy (SEM) of their EPS production in liquid YMA medium. Their EPS were characterized through a series of analytical techniques, aiming at their use in the formulation of plant inoculants. In addition, the effect of the carbon source on EPS yield was evaluated. Multi-stage fragmentation analysis showed the presence of xylose, glucose, galactose, galacturonic acid, and glucuronic acid in EPS chemical composition, which was confirmed by FT-IR spectra and 13C NMR spectroscopy. Thermal stability (thermogravimetric) was close to 270 °C and viscosity ranged from 120 to 1053.3 mPa.s. Surface morphology (SEM) was rough and irregular, with a cross-linked spongy matrix, which, together with the hydrophilic functional groups, confers water holding capacity. The present study showed that the three EPS have potential as microorganism carriers for formulation of microbial inoculants to be applied in plants.

Regulation of Nrf2 by phosphorylation: Consequences for biological function and therapeutic implications

The transcription factor nuclear factor erythroid-derived 2-like 2 (NRF2) participates in the activation of the antioxidant cytoprotective pathway and other important physiological processes to maintain cellular homeostasis. The dysregulation of NRF2 activity plays a role in various diseases, such as cardiovascular diseases, neurodegenerative diseases, and cancer. Thus, NRF2 activity is tightly regulated through multiple mechanisms, among which phosphorylation by kinases is critical in the posttranslational regulation of NRF2. For instance, PKC, casein kinase 2, and AMP-activated kinase positively, while GSK-3 negatively regulates NRF2 activity through phosphorylation of different sites. Here, we provide an overview of the phosphorylation regulation pattern of NRF2 and discuss the therapeutic potential of interventions targeting NRF2 phosphorylation.

Lethal Factor Domain-Mediated Delivery of Nurr1 Transcription Factor Enhances Tyrosine Hydroxylase Activity and Protects from Neurotoxin-Induced Degeneration of Dopaminergic Cells

The orphan transcription factor nuclear receptor-related 1 protein (Nurr1, also known as NR4A2) plays a key role in embryonic development and maintenance of mesencephalic dopaminergic neurons in the substantia nigra. Nurr1 deficiency is associated with Parkinson’s disease where dopaminergic neurons degenerate suggesting that counter-regulation of Nurr1 activity may have therapeutic effects. Here, we bacterially expressed and isolated a human Nurr1 fusion protein containing a N-terminal cell delivery domain derived from detoxified anthrax lethal factor followed by wild type ubiquitin with deubiquitinating enzyme recognition site for intracellular cleavage. Addition of the Nurr1 fusion protein to dopaminergic SH-SY5Y cells generated a cleaved, cytosolic Nurr1-containing fragment which was associated with increased levels of tyrosine hydroxylase, the rate-limiting enzyme in dopamine synthesis. Promoter-activity assays confirmed that exposure of cells to full-length Nurr1 fusion protein activated not only its cognate human tyrosine hydroxylase promoter but also the corresponding mouse sequence, although at a reduced efficiency. Using 6-hydroxydopamine as a dopaminergic cell specific neurotoxin, we demonstrate that full-length Nurr1 fusion protein promotes a concentration-dependent protection from this toxic insult. Altogether, the enhancement of tyrosine hydroxylase in naïve dopaminergic cells and the protective effects in a cellular model of Parkinson’s disease suggest that full-length Nurr1 fusion protein may contribute to the development of a novel concept of protein-based therapy.

The single IGF-1 partial deficiency is responsible for mitochondrial dysfunction and is restored by IGF-1 replacement therapy

BACKGROUND & AIMS

We previously described in cirrhosis and aging, both conditions of IGF-1 deficiency, a clear hepatic mitochondrial dysfunction with increased oxidative damage. In both conditions, the hepatic mitochondrial function was improved with low doses of IGF-1. The aim of this work was to explore if the only mere IGF-1 partial deficiency, without any exogenous insult, is responsible for hepatic mitochondrial dysfunction.

METHODS

Heterozygous (igf1^+/-) mice were divided into two groups: untreated and treated mice with low doses of IGF-1. WT group was used as controls. Parameters of hepatic mitochondrial function were determined by flow cytometry, antioxidant enzyme activities were determined by spectrophotometry, and electron chain transport enzyme levels were determined by immunohistochemistry and immunofluorescence analyses. Liver expression of genes coding for proteins involved in mitochondrial protection and apoptosis was studied by microarray analysis and RT-qPCR.

RESULTS

Hz mice showed a significant reduction in hepatic mitochondrial membrane potential (MMP) and ATPase activity, and an increase in intramitochondrial free radical production and proton leak rates, compared to controls. These parameters were normalized by IGF-1 replacement therapy. No significant differences were found between groups in oxygen consumption and antioxidant enzyme activities, except for catalase, whose activity was increased in both Hz groups. Relevant genes coding for proteins involved in mitochondrial protection and survival were altered in Hz group and were reverted to normal in Hz+IGF-1 group.

CONCLUSIONS

The mere IGF-1 partial deficiency is per se associated with hepatic mitochondrial dysfunction sensitive to IGF-1 replacement therapy. Results in this work prove that IGF-1 is involved in hepatic mitochondrial protection, because it is able to reduce free radical production, oxidative damage and apoptosis. All these IGF-1 actions are mediated by the modulation of the expression of genes encoding citoprotective and antiapoptotic proteins.

The chemical biology of protein hydropersulfides: Studies of a possible protective function of biological hydropersulfide generation

The recent discovery of significant hydropersulfide (RSSH) levels in mammalian tissues, fluids and cells has led to numerous questions regarding their possible physiological function. Cysteine hydropersulfides have been found in free cysteine, small molecule peptides as well as in proteins. Based on their chemical properties and likely cellular conditions associated with their biosynthesis, it has been proposed that they can serve a protective function. That is, hydropersulfide formation on critical thiols may protect them from irreversible oxidative or electrophilic inactivation. As a prelude to understanding the possible roles and functions of hydropersulfides in biological systems, this study utilizes primarily chemical experiments to delineate the possible mechanistic chemistry associated with cellular protection. Thus, the ability of hydropersulfides to protect against irreversible electrophilic and oxidative modification was examined. The results herein indicate that hydropersulfides are very reactive towards oxidants and electrophiles and are modified readily. However, reduction of these oxidized/modified species is facile generating the corresponding thiol, consistent with the idea that hydropersulfides can serve a protective function for thiol proteins.