Simplified bicyclic pyridinol analogues protect mitochondrial function

Multifunctional radical quenchers as potential therapeutic agents for the treatment of mitochondrial dysfunction

Mitochondrial dysfunction is associated with a wide range of human diseases, including neurodegenerative diseases, and is believed to cause or contribute to the etiology of these diseases. These disorders are frequently associated with increased levels of reactive oxygen species. One of the design strategies for therapeutic intervention involves the development of novel small molecules containing redox cores, which can scavenge reactive oxygen radicals and selectively block oxidative damage to the mitochondria. Presently, we describe recent research dealing with multifunctional radical quenchers as antioxidants able to scavenge reactive oxygen radicals. The review encompasses ubiquinone and tocopherol analogs, as well as novel pyri(mi)dinol derivatives, and their ability to function as protective agents in cellular models of mitochondrial diseases.

Oligomeric amyloid β preferentially targets neuronal and not glial mitochondrial-encoded mRNAs

INTRODUCTION

Our laboratories have demonstrated that accumulation of oligomeric amyloid β (OAβ) in neurons is an essential step leading to OAβ-mediated mitochondrial dysfunction.

METHODS

Alzheimer's disease (AD) and matching control hippocampal neurons, astrocytes, and microglia were isolated by laser-captured microdissection from the same subjects, followed by whole-transcriptome sequencing. Complementary in vitro work was performed in OAβ-treated differentiated SH-SY5Y, followed by the use of a novel CoQ₁₀ analogue for protection. This compound is believed to be effective both in suppressing reactive oxygen species and also functioning in mitochondrial electron transport.

RESULTS

We report decreases in the same mitochondrial-encoded mRNAs in Alzheimer's disease laser-captured CA1 neurons and in OAβ-treated SH-SY5Y cells, but not in laser-captured microglia and astrocytes. Pretreatment with a novel CoQ₁₀ analogue, protects neuronal mitochondria from OAβ-induced mitochondrial changes.

DISCUSSION

Similarity of expression changes in neurons from Alzheimer's disease brain and neuronal cells treated with OAβ, and the effect of a CoQ₁₀ analogue on the latter, suggests a pretreatment option to prevent OAβ toxicity, long before the damage is apparent.

Methods for determining the efficacy of radical-trapping antioxidants

Hydrocarbon autoxidation is the free radical chain reaction primarily responsible for the oxidative degradation of organic materials, including those that make up cells, tissues, and organs. The identification of compounds that slow this process (antioxidants) and the quantitation of their efficacies have long been goals of academic and industrial researchers. Antioxidants are generally divided into two types: preventive and radical-trapping (also commonly referred to as chain-breaking). Preventive antioxidants slow the rate of initiation of autoxidation, whereas radical-trapping antioxidants slow the rate of propagation by reacting with chain-propagating peroxyl radicals. The purpose of this review is to provide a comprehensive overview of different approaches to measure the kinetics of the reactions of radical-trapping antioxidants with peroxyl radicals, and their use to study the inhibition of hydrocarbon (lipid) autoxidation in homogeneous solution, as well as biphasic media (lipid bilayers) and cell culture. Direct and indirect approaches are presented and advantages and disadvantages of each are discussed in order to facilitate method selection for investigators seeking to address particular questions in this immensely popular field.

Synthesis and antiangiogenic activity of 6-amido-2,4,5-trimethylpyridin-3-ols

We recently reported that 6-aminoalkyl-2,4,5-trimethylpyridin-3-ols, novel series of 6-aminopyridin-3-ol-based antioxidants, have high antiangiogenic activities. In pursuit of wider variety in the analogues, we here report the synthesis and antiangiogenic activities of 6-amidoalkyl-2,4,5-trimethylpyridin-3-ols, which would not be considered excellent antioxidants because of the poorer electron-donating effect of the C(6)-amido group than the corresponding C(6)-amino group. The selected 6-amido compounds showed up to several fold-higher antiangiogenic activities and up to an order of magnitude better antitumor activities in the chick embryo chorioallantoic membrane (CAM) assay than SU4312, a positive control. We also found that paracetamol, as a direct phenolic analogue of our simplest 6-amidopyridin-3-ol, showed a moderate level of antiangiogenic activity. We propose this study will offer a basis for a scaffold of novel angiogenesis inhibitors that can perturb angiogenesis-related pathologies.

6-Amino-2,4,5-trimethylpyridin-3-ols: a new general synthetic route and antiangiogenic activity

A new synthetic strategy for preparation of a wide range of 6-amino-2,4,5-trimethylpyridin-3-ols from pyridoxine·HCl via a six-step sequence has been developed. This approach features an introduction of various amino groups to C(6)-position of 3-benzyloxy-6-bromo-2,4,5-trimethylpyridine (13), a key intermediate, by a Buchwald-Hartwig amination reaction using palladium(0) transition metal, which certainly renders an expanded scope of amino substituents. Some analogs prepared using the methods described here showed high level of antiangiogenic and antitumor activities in chick chorioallantoic membrane (CAM) assay, demonstrating the potential of these new aminopyridinols as antiangiogenic agents.

An optimized pyrimidinol multifunctional radical quencher

A series of aza analogues (4-9) of the experimental neuroprotective drug idebenone (1) have been prepared and evaluated for their ability to attenuate oxidative stress induced by glutathione depletion and to compensate for the decrease in oxidative phosphorylation efficiency in cultured Friedreich's ataxia (FRDA) fibroblasts and lymphocytes and also coenzyme Q10-deficient lymphocytes. Modification of the redox core of the previously reported 3 improved its antioxidant and cytoprotective properties. Compounds 4-9, having the same redox core, exhibited a range of antioxidant activities, reflecting side chain differences. Compounds having side chains extending 14-16 atoms from the pyrimidinol ring (6, 7, and 9) were potent antioxidants. They were superior to idebenone and more active than 3, 4, 5, and 8. Optimized analogue 7 and its acetate (7a) are of interest in defining potential therapeutic agents capable of blocking oxidative stress, maintaining mitochondrial membrane integrity, and augmenting ATP levels. Compounds with such properties may find utility in treating mitochondrial and neurodegenerative diseases such as FRDA and Alzheimer's disease.