Protecting the beneficial functionality of lipoproteins by 1-Fe, a corrole-based catalytic antioxidant

Abstract

Functionally defective HDL emerges as a main risk factor in cardiovascular diseases, on top of imbalanced serum lipoprotein ratios. We now show that 1-Fe, an iron(III) corrole catalytic antioxidant, spontaneously forms tightly-bound conjugates with LDL (secondarily) and HDL (primarily) of human serum. This is demonstrated by HPLC separation of serum/1-Fe mixtures and analysis of the corrole-containing fractions by UV-vis and circular dichroism spectroscopy. The LDL/1-Fe and HDL/1-Fe conjugates are resistant to functionality damaging events induced by oxidizing (copper salts) and nitrating species (peroxynitrite), as realized by heavily reduced formation of conjugated dienes, hydroperoxides, aldehydes, and nitrotyrosine. What is more, even already oxidized LDL becomes less atherogenic upon conjugation. Treatment with 1-Fe preserves the cardioprotective properties of HDL (cholesterol efflux, reduction of intracellular oxidative-stress, and inhibition of apoptosis), which are otherwise damaged under conditions of oxidative-stress. The novelty of 1-Fe relies in the unique bipolarity of the corrole macrocycle (responsible for its general affinity for lipoproteins), the affinity of the corrole-chelated iron(III) center to two histidine residues from (a particular subclass of) HDL-associated proteins, and the excellent catalytic activity regarding the decomposition of the most toxic naturally-occurring species/molecules.