AGEs/RAGE Promote Osteogenic Differentiation in Rat Bone Marrow-Derived Endothelial Progenitor Cells via MAPK Signaling.

Systemic vascular impairment is the most common complication of diabetes. Advanced glycation end products (AGEs) can exacerbate diabetes-related vascular damage by affecting the intima and media through a variety of mechanisms. In the study, we demonstrated that AGEs and their membrane receptor RAGE could induce the differentiation of EPCs into osteoblasts under certain circumstances, thereby promoting accelerated atherosclerosis. Differentiation into osteoblasts was confirmed by positive staining for DiI-acetylated fluorescently labeled low-density lipoprotein and FITC-conjugated Ulex europaeus agglutinin. During differentiation, expression of receptor for AGE (RAGE) was significantly upregulated. This upregulation was attenuated by transfection with RAGE-targeting small interfering (si)RNA. siRNA-mediated knockdown of RAGE expression significantly inhibited the upregulation of AGE-induced calcification-related proteins, such as runt-related transcription factor 2 (RUNX2) and osteoprotegerin (OPG). Additional experiments showed that AGE induction of EPCs significantly induced ERK, p38MAPK, and JNK activation. The AGE-induced upregulation of osteoblast proteins (RUNX2 and OPG) was suppressed by treatment with a p38MAPK inhibitor (SB203580) or JNK inhibitor (SP600125), but not by treatment with an ERK inhibitor (PD98059), which indicated that AGE-induced osteoblast differentiation from EPCs may be mediated by p38MAPK and JNK signaling, but not by ERK signaling. These data suggested that AGEs may bind to RAGE on the EPC membrane to trigger differentiation into osteoblasts. The underlying mechanism appears to involve the p38MAPK and JNK1/2 pathways, but not the ERK1/2 pathway.

AGEs promote calcification of HASMCs by mediating Pi3k/AKT-GSK3ß signaling.

This study aimed to investigate the effects of advanced glycation end products (AGEs) on the calcification of human arterial smooth muscle cells (HASMCs) and to explore whether AGEs can promote the calcification of HASMCs by activating the phosphoinositide 3-kinase (PI3K)/AKT-glycogen synthase kinase 3 beta (GSK3-ß) axis. Cultured HASMCs were divided into five groups: blank control group, dimethyl sulfoxide (vehicle) group, AGEs group, LY294002 (AKT inhibitor) group, and TWS119 (GSK3-ß inhibitor) group. Cells were pretreated with either vehicle, LY294002, or TWS119 for 2 hours followed by incubation with AGEs (25 µg/mL) for 5 days, and the expression levels of proteins in each group were analyzed by western blotting. AGE treatment promoted HASMC calcification, which coincided with increased expression of p-AKT and p-GSK3-ß (serine 9). Also, AGEs upregulated the expression of osteoprotegerin and bone morphogenetic protein, and these effects were suppressed by LY294002 but enhanced by TWS119. In conclusion, AGEs promote calcification of HASMCs, and this effect is ameliorated by inhibition of AKT activity but potentiated by inhibition of GSK3-ß activity. Hence, AGEs trigger HASMC calcification by regulating PI3K/AKT-GSK3-ß signaling.

Advanced Glycation End Products Induce Proliferation and Migration of Human Aortic Smooth Muscle Cells through PI3K/AKT Pathway.

Advanced glycation end products (AGEs) have been widely regarded as an important inducing factor in the pathogenesis of diabetic arteriosclerosis, and the proliferation and migration of vascular smooth muscle cells (VSMCs) are also involved in this process. However, it is not clear whether AGEs promote atherosclerosis by inducing the proliferation and migration of VSMCs. To figure out this question, this study investigated the effects of AGEs on the proliferation and migration of human aorta vascular smooth muscle cells (HASMCs) and the underlying mechanisms. This study evaluated the effects of different concentrations of AGEs on cell proliferation and migration. CCK8, transwell, and western blotting assays demonstrated that AGEs significantly increased cell proliferation and migration in a concentration-dependent manner and that the optimal proproliferative and promigratory concentrations of AGEs were 10 mg/L and 20 mg/L, respectively. AGE-induced cell proliferation, migration, and expression of filament actin (F-actin) were markedly attenuated by a PI3K inhibitor (LY2940002). Additionally, the phosphorylation of AKT was reduced when the receptor of advanced glycation end product (RAGE) gene was silenced by lentivirus transfection, which led to a concomitant reduction of the expression of proliferation and migration-related proteins. These data indicate that AGEs may activate the PI3K/AKT pathway through RAGE and thus facilitate the proliferation and migration of HASMCs.