Simple Biological Systems for Assessing the Activity of Superoxide Dismutase Mimics

Abstract

Significance: Half a century of research provided unambiguous proof that superoxide and species derived from it-reactive oxygen species (ROS)-play a central role in many diseases and degenerative processes. This stimulated the search for pharmaceutical agents that are capable of preventing oxidative damage, and methods of assessing their therapeutic potential. Recent Advances: The limitations of superoxide dismutase (SOD) as a therapeutic tool directed attention to small molecules, SOD mimics, that are capable of catalytically scavenging superoxide. Several groups of compounds, based on either metal complexes, including metalloporphyrins, metallocorroles, Mn(II) cyclic polyamines, and Mn(III) salen derivatives, or non-metal based compounds, such as fullerenes, nitrones, and nitroxides, have been developed and studied in vitro and in vivo. Very few entered clinical trials. Critical Issues and Future Directions: Development of SOD mimics requires in-depth understanding of their mechanisms of biological action. Elucidation of both molecular features, essential for efficient ROS-scavenging in vivo, and factors limiting the potential side effects requires biologically relevant and, at the same time, relatively simple testing systems. This review discuses the advantages and limitations of genetically engineered SOD-deficient unicellular organisms, Escherichia coli and Saccharomyces cerevisiae as tools for investigating the efficacy and mechanisms of biological actions of SOD mimics. These simple systems allow the scrutiny of the minimal requirements for a functional SOD mimic: the association of a high catalytic activity for superoxide dismutation, low toxicity, and an efficient cellular uptake/biodistribution. Antioxid. Redox Signal. 20, 2416Signal. 20, -2436

SOD Therapeutics: Latest Insights into Their Structure-Activity Relationships and Impact on the Cellular Redox-Based Signaling Pathways

“…Under identical concentrations (*20 lM), MnPs were protective, while FePs were toxic (30). However, FePs were efficacious at approximately *1000-fold lower, 0.01 lM concentrations (270,273). Further, the E. coli growth pattern is different with FePs relative to MnPs.…”

“…However, the growth pattern is different (B). The growth was followed in a restricted five-amino-acid medium that better distinguishes the true SOD mimics from other redox-active compounds than rich media (270,273). Wild-type E. coli was AB1157, and SOD-deficient JI132.…”

“…Those compounds with favorable E 1/2 ( > 0 mV vs. NHE) have been subsequently tested in a simple superoxidespecific assay where SOD-deficient Escherichia coli grows aerobically as well as wild type only if supplied by true SOD mimics (270). The SOD-deficient yeast, Saccharomyces cerevisiae has been recently established as an additional model (270). Most of the published work on Mn porphyrins (MnPs) relates to our first lead, MnTE-2-PyP 5 + , which continues to be widely used for therapeutic and mechanistic purposes.…”

“…Based on the ortho effect, the di-ortho imidazolyl derivatives were subsequently synthesized and showed potency in a number of animal models of oxidative stress (26-28, 131, 211, 225, 239). In E. coli model, the Mn(III) meso-tetrakis (N,N¢-diethylimidazolium-2-yl)porphyrin, MnTDE-2-ImP 5 + (AEOL10150) is inferior relative to porphyrins bearing Nalkylpyridyl substituents (32,195,270). The N,N¢-dialkylimidazolyl substituents are positioned both above and below the porphyrin plane; in turn, the N,N¢-dialkylimidazolylporphyrins are much bulkier than N-alkylpyridyl analogs (Fig.…”

“…It is important to note that the reduction of Mn III P 5 + with ascorbate reduces a total charge of MnP from penta-to tetracationic and, thus, enhances lipopilicity and cellular and tissue accumulation (251,270). In cellular studies, the MnP/ ascorbate was added exogenously into medium where it produced peroxide outside of the cell.…”