Protection against Hydrogen Peroxide-Mediated Cytotoxicity in Friedreich's Ataxia Fibroblasts Using Novel Iron Chelators of the 2-Pyridylcarboxaldehyde Isonicotinoyl Hydrazone Class

Abstract

Iron-loading diseases remain an important problem because of the toxicity of iron-catalyzed redox reactions. Iron loading occurs in the mitochondria of Friedreich's ataxia (FA) patients and may play a role in its pathogenesis. This suggests that iron chelation therapy could be useful. We developed previously the lipophilic iron chelators known as the 2-pyridylcarboxaldehyde isonicotinoyl hydrazone (PCIH) ligands and identified 2-pyridylcarboxaldehyde 2-thiophenecarboxyl hydrazone (PCTH) as the most promising analog. Hence, this study assessed the efficacy of PCTH and other PCIH analogs compared with various chelators, including deferiprone and desferrioxamine (DFO). Ageand sex-matched control and FA fibroblasts were preincubated with iron chelators and subsequently challenged with 50 M H 2 O 2 for up to 24 h. The current study demonstrates an interesting structure-activity relationship among the closely related PCIH series of ligands, with only PCTH being highly effective at preventing H 2 O 2 -induced cytotoxicity. PCTH increased FA fibroblast cell viability by up to 70%, whereas DFO rescued viability by 1 to 5% only. Hence, PCTH, which was well tolerated by cells was far more effective than DFO at preventing oxidative stress. It is noteworthy that kinetic studies demonstrated PCTH to rapidly penetrate cells to induce 59 Fe efflux, whereas DFO, PCIH, 2-pyridylcarboxaldehyde benzoyl hydrazone, and 2-pyridylcarboxaldehyde m-bromobenzoyl hydrazone were far slower, indicating it is the rate of chelator permeation that is crucial for protection against H 2 O 2 . In addition, PCTH was found to be as effective as or more effective than conventional radical scavengers or the antioxidant idebenone (which has undergone clinical trials) at protecting cells against H 2 O 2 -mediated cytotoxicity. These findings further indicate the potential of PCTH for treatment of iron overload.

The Novel Multifunctional, Iron-Chelating Drugs M30 and HLA20 Protect Pancreatic β-Cell Lines from Oxidative Stress Damage

“…Previous studies have shown that the prototype iron chelator DFO captures the labile iron pool, resulting in decreased cell death arising from several types of oxidant challenge (Ollinger and Brunk, 1995;Winterbourn, 1995). However, DFO, suffers from several problems that are due, in part, to its hydrophilicity (Kalinowski and Richardson, 2005), leading to poor absorption from the gut and poor penetration of cell membranes that prevents access to intracellular Fe 2ϩ pools (Lim et al, 2008). The protective effect of M30 and HLA20 on ␤-cells was accompanied by decreased formation of intracellular ROS after acute H 2 O 2 exposure and an enhanced activity of the antioxidant detoxifying enzyme catalase.…”

Brain Iron Homeostasis: From Molecular Mechanisms To Clinical Significance and Therapeutic Opportunities

“…The first aroylhydrazones were derived from pyridoxal isonicotinoyl hydrazone, highly effective and lipophilic molecules that prevent iron uptake while mobilizing intracellular iron (268). Subsequently, new iron chelators known as the 2-pyridylcarboxaldehyde isonicotinoyl hydrazone analogs were developed.…”

“…Subsequently, new iron chelators known as the 2-pyridylcarboxaldehyde isonicotinoyl hydrazone analogs were developed. Initial studies revealed that isonicotinoyl hydrazone was not a selective iron chelator and instead, formed a more stable complex with copper (268,344). This led to subsequent derivatives, of which 2-pyridylcarboxaldehyde 2-thiophenecarboxyl hydrazone (PCTH) was the most effective (465).…”

“…This led to subsequent derivatives, of which 2-pyridylcarboxaldehyde 2-thiophenecarboxyl hydrazone (PCTH) was the most effective (465). Experiments conducted on FA fibroblasts treated with PCTH revealed significant improvement in cell viability (70%) when compared with cells treated with DFO (1%-5%) (268). The effectiveness of PCTH in rescuing cells from hydrogen peroxide-induced cytotoxicity could be attributed to its more efficient rate of penetration.…”

Mitochonic Acid 5 (MA-5), a Derivative of the Plant Hormone Indole-3-Acetic Acid, Improves Survival of Fibroblasts from Patients with Mitochondrial Diseases

“…Idebenone inhibits ROS accumulation and prevents H 2 O 2 -induced cytotoxicity (Lim et al 2008). On the other hand, our direct monitoring of the ROS levels revealed that MA-5 had no effect on the cellular ROS levels under basal and H 2 O 2 -treated conditions (Fig.…”