Methylglyoxal-induces multiple stable changes in human serum albumin before forming nephrotoxic advanced glycation end-products: Injury demonstration in human embryonic kidney cells.

The minor fraction of methylglyoxal that is not metabolized in healthy humans reacts with macromolecules to form AGEs. In diabetics, the formation of MG is accelerated; its level may be enhanced multifold. The glyoxalase enzymes responsible for the regular and effective clearance of excess methylglyoxal may become defective in diabetes mellitus leading to its retention in cells and plasma. The methylglyoxal-modified-HSA was prepared, characterised by multiple biophysical techniques and biochemical (s) and its damaging effect was examined on embryonic kidney cell line HEK 293. The UV results showed hyperchromicity in MG-modified-HSA while nitroblue tetrazolium and fluorescence data suggested AGEs formation in comparison to control HSA. Upward shift of negative peaks in CD suggested reduction in α-helicity. Accelerated mobility and diffused broad bands observed in native and SDS polyacrylamide gel, respectively suggest neutralization of some of the positive charges on MG-modified-HSA as well as generation of cross-links. As observed by trypan blue assay, MTT, LDH activity assay, acridine orange, propidium iodide, ethidium bromide, 4',6-diamidino-2-phenylindole (DAPI) staining and ROS measurements, the MG-HSA AGEs caused damage to human embryonic kidney cells. The data suggest that MG-HSA AGEs may trigger powerful inflammatory responses at cellular level which might set the stage for nephrotoxicity in diabetics.

Impact of endogenous stress on albumin structure in systemic lupus erythematosus (SLE) patients.

Systemic lupus erythematosus (SLE) is an inflammatory, autoimmune disorder of unknown etiology. The inflammatory stress in SLE patients may modify macromolecules and produce structural/functional abnormalities. The present study is aimed at examining the consequences of stresses on the structure of albumin in SLE patients. Albumin was isolated from the sera of SLE/healthy subjects. Multiple physicochemical techniques were used to elucidate, structure of albumin. Advanced glycation end products in SLE patients' albumin were identified by the AGE specific fluorescence. Quenching of tryptophan, tyrosine fluorescence and surface protein hydrophobicity was observed in SLE patients' albumin. Protein-bound carbonyls were elevated while free thiol, lysine, arginine, and alpha helicity was found to be decreased in SLE albumin. Furthermore, changes in the secondary structure of SLE albumin were observed as shift in the position of amide I/II bands. Functionality of SLE albumin was also compromised as its cobalt-binding ability was substantially declined. Adduction of moieties was detected by dynamic light scattering (DLS) and confirmed by matrix assisted laser desorption/ionization. DLS, thioflavin T and transmission electron microscopy results confirmed aggregates in SLE patients' albumin. This study may be helpful in understanding the role of modified albumin in the cofounding pathologies associated with SLE.