COPPER(II)-INDUCED IgG AGGREGATES BECOME IRREVERSIBLY AGGREGATED BY HYDROGEN PEROXIDE

CHRISTIAN SAPORITO; LILA MONTAÑANA; MARIA LAURA FACIO; FABIANA LAIRION; MARISA REPETTO

Mar del Plata

Congreso; 67º Reunión Anual de la Sociedad Argentina de Investigación Clínica; 2022

Sociedad Argentina de Investigación Clínica

Proteins are prone to aggregation and free cupric ions (Cu(II)) promote this process. Suchaggregates are found in plasma as detergent resistant aggregates (DRA). Cu(II) ions are found inthe micromolar range in plasma but rise in pathologies such as Wilson Disease. We have shownthat IgGs are selectively aggregated by Cu(II). Therefore, plasma Cu(II) may be a driving forcefor IgG aggregation. Additionally, DRA have been reported to increase in elders. We speculatethat the oxidative modifications of the aggregates impair their clearance and drive theiraccumulation over the years. Methods: Optic density (OD), Lowry assay, Carbonyl content(CO), SDS-PAGE. Results: Followed by OD, Cu(II) and Zn(II) induce IgG aggregation at 5 μMand 20 μM, respectively (n=3). Zn(II) was employed as a non-redox active metal. Upon additionof H2O2, Cu(II)-induced aggregates (Cu(II)IA) become irreversibly insoluble while Zn(II)-induced aggregates (Zn(II)IA) are fully dissolved upon metal removal by EDTA. Cu(II)IA in thepresence of H2O2 are also SDS-resistant whereas Zn(II)IA are completely soluble (n=3).Cu(II)IA become irreversibly insoluble in the presence of H2O2 (4 mM). However, whenfollowed by SDS-PAGE, concentrations of 50 μM H2O2 yet yield Cu(II)IA with higher massthan monomeric IgG, indicating the formation of soluble DRA (n=3). In contrast, when Zn(II)IAwith H2O2 mixtures are assessed by SDS-PAGE, no soluble higher mass aggregates areobserved. Furthermore, the CO content significantly rises when IgGs are incubated with H2O2 inthe presence of Cu(II) when compared to H2O2 alone (p