Copper and ROS mediation in glycoxidation of a human serum albumin (HSA) model peptide: Advanced Glycation End‐Products (AGEs) generation and damage in motor neuron cells
Authors: Cerchiaro Giselle , Marques Caroline M.S. , Nunes Emilene A. 
Published: June 2021

Glucose, in the presence of reactive oxygen species (ROS), acts as an as an oxidative agent and drives deleterious processes in Diabetes Mellitus. We have studied the mechanism and the toxicological effects of glucose‐dependent glycoxidation reactions driven by copper and ROS, using a model peptide based on the exposed sequence of Human Serum Albumin (HSA) and containing a lysine residue susceptible to copper complexation. The main products of these reactions are Advanced Glycation End‐products (AGEs).

In vitro studies of glycation and glycoxidation often use Human Serum Albumin (HSA) as a model protein. HSA has several metal‐binding sites and it is a protein useful for studies of glycation/ glycoxidation, since it has several lysine and arginine residues, which have free amino groups in their side chains. We have studied the effects of copper ions and hydroxyl radicals, on the glycoxidation of a mimetic HAS peptide that includes the lysine residue present in the three homologous domain structures repeated in the molecule (I, II and III) and in the A and B subdomains. The model peptide is based on an exposed sequence in HSA that contains a lysine residue susceptible to complexation with copper ions .

Pyrraline condensed on the model peptide, generating a Modified Peptide (MP). These products were isolated, purified, and tested on cultured motor neuron cells. We observed DNA damage, enhancement of membrane roughness, and formation of domes. We evaluated nuclear abnormalities by the cytokinesis‐blocked micronucleus assay and we measured cytostatic and cytotoxic effects, chromosomal breakage, nuclear abnormalities, and cell death. AGEs formed by glycoxidation caused large micronucleus aberrations, apoptosis, and large‐scale nuclear abnormalities, even at low concentrations. We also observed increases in many proteins by Western blot, as NF‐κB, cyclin D1 and caspase 3 and 9 during cell treatments with MP. Activation of NF‐κB generally involves phosphorylation of IκB by the IKB kinase complex (IKK), resulting in IκB degradation. The regulation of NF‐κB genes affects apoptosis, cell adhesion, proliferation, immune responses, inflammation, and cellular stress response. NF‐κB activity can be regulated by oncogenes and tumor suppressors and may contribute to the pathology of inflammatory diseases and cancers. Activation of p53 can inhibit cyclin D1 expression by inducing association of the p52 NF‐κB subunit with co‐repressor complexes. In some cell lines, p52 is recruited directly to p53‐regulated promoters, leading to repression or activation of p53 target genes. Through this route, p52 may regularize cell cycle arrest dependent on p53 and apoptosis.

We concluded that accelerated formation of AGEs through glycoxidation reactions could serve as a biomarker of neurodegeneration in oxidative conditions such as AD and possibly in carcinogenesis.

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This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.