Circulating high-molecular-weight RAGE ligands activate pathways implicated in the development of diabetic nephropathy

Abstract

The accumulation of advanced glycation end products is thought to be a key factor in the initiation and progression of diabetic nephropathy. Here we determined whether the size of the ligands for the receptor for advanced glycation end products (RAGEs) that were present in the serum of patients with type 2 diabetes modulates their pathogenic potential. Serum was collected from control subjects and patients with type 2 diabetes with varying degrees of renal disease (normo-, micro-, or macroalbuminuria). The titers of the RAGE ligands N-carboxymethyllysine (CML), S100A, S100B, and high-mobility group box 1 (HMGB1) were measured by enzyme-linked immunosorbent assay in serum as well as in pooled size-fractionated serum. We also measured cellular binding of serum fractions to mesangial cells transfected with RAGE and examined the downstream signaling pathways. Circulating CML was increased in patients with type 2 diabetes, whereas HMGB1 was decreased. S100A8, S100BA9, and soluble RAGE were unchanged. The high-molecular-weight (over 50 kDa) serum fraction contained the greatest proportion of RAGE ligands, with all immunoreactivity and cellular binding observed only with serum fractions over 30 kDa. High-molecular-weight serum from macroalbuminuric patients showed greater RAGE binding capacity, modulation of cell-surface RAGE expression, increased phospho-protein kinase C-alpha, and p65 nuclear factor kappaB DNA-binding activity, which were competitively inhibited by soluble RAGE or CML neutralizing antibodies. These data show that ligands that activate RAGE present in the circulation of patients with type 2 diabetes and nephropathy are predominantly of high molecular weight.

Dipeptidyl peptidase IV inhibitor protects against renal interstitial fibrosis in a mouse model of ureteral obstruction

“…11 HMGB1, a nuclear protein that regulates gene transcription, is passively released after cell injury and has been implicated in tissue inflammation in animal models of kidney injury. 13,30 HMGB1 is a known ligand of TLR, which leads to the activation of NF-kB, ultimately increasing tissue inflammation. 12,31 We also found that renal expression of HMGB1 was decreased in mice given LC15-0444 treatment in this study.…”

“…11,12 A 2012 paper proposed HMGB-1 as a causative factor in renal damage. 13 DPPIV has high expression levels and activity in the kidney, and is found on the apical/brush border surface of proximal renal tubular cells and in the urine. 14 However, the roles of DPPIV and its inhibition are not fully understood in the pathogenesis of renal disease.…”

S-glutathionylation: relevance in diabetes and potential role as a biomarker

“…They can interact with their receptor (RAGE) and induce inflammatory responses and ROS generation (Schmidt et al, 1995), cardinal features of diabetic nephropathy. In vivo experiments have demonstrated that the AGE-RAGE interaction generates superoxide and may contribute to angiopathy development in type 2 diabetes (Penfold et al, 2010). Further, in diabetic patients, glycated albumin induces ROS production in endothelial cells (Rodino-Janeiro et al, 2010).…”

Role of advanced glycation end products in cardiovascular disease

“…RAGE activation by high serum and tissue levels of AGEs induces multiple intracellular signalling pathways (Figure 4) that have been implicated in pathogenesis of serious diabetic complications such as enhanced atherosclerosis, cardiovascular disease, nephropathy and chronic inflammation [9,10,[108][109][110] . It has been documented that circulating AGEs bind with endothelial RAGE resulting in endothelial dysfunction via activation of a number of signaling pathways, e.g., activation of nicotinamide adenine dinucleotide phosphate oxidase that enhances the production of reactive oxygen species (ROS) [108] .…”