Ager Deletion Enhances Ischemic Muscle Inflammation, Angiogenesis, and Blood Flow Recovery in Diabetic Mice

Abstract

Objective Diabetic subjects are at higher risk of ischemic peripheral vascular disease (PVD). We tested the hypothesis that advanced glycation end products (AGEs) and their receptor (RAGE) block neoangiogenesis and blood flow recovery after hind limb ischemia induced by femoral artery ligation (FAL) through modulation of immune/inflammatory mechanisms. Approach and Results Wild type (WT) mice rendered diabetic with streptozotocin and subjected to unilateral FAL displayed increased accumulation and expression of AGEs and RAGE in ischemic muscle. In diabetic WT mice, FAL attenuated neoangiogenesis and impaired blood flow recovery, in parallel with reduced macrophage content in ischemic muscle and suppression of early inflammatory gene expression, including chemokine (C-C motif) ligand 2 (Ccl2) and early growth response gene 1 (Egr1) versus non-diabetic mice. Deletion of Ager or transgenic expression of Glo1 (reduces AGEs) restored adaptive inflammation, neoangiogenesis and blood flow recovery in diabetic mice. In diabetes, deletion of Ager increased circulating Ly6Chi monocytes and augmented macrophage infiltration into ischemic muscle tissue after FAL. In vitro, macrophages grown in high glucose display inflammation that is skewed to expression of tissue damage versus tissue repair gene expression. Further, macrophages grown in high versus low glucose demonstrate blunted macrophage-endothelial cell interactions. In both settings, these adverse effects of high glucose were reversed by Ager deletion in macrophages. Conclusions These findings indicate that RAGE attenuates adaptive inflammation in hind limb ischemia; underscore microenvironment-specific functions for RAGE in inflammation in tissue repair versus damage; and illustrate that AGE/RAGE antagonism may fill a critical gap in diabetic PVD.

RAGE impairs murine diabetic atherosclerosis regression and implicates IRF7 in macrophage inflammation and cholesterol metabolism

“…Reverse transendothelial migration assay. Collagen gels were polymerized with collagen type I (BD 354231) before WT primary MAECs were isolated and seeded (72). Primary BMDMs (4 × 10 6 cells/mL) were added to confluent endothelial cultures for 2 hours to allow accumulation of macrophages in the subendothelial collagen.…”

Dicarbonyl Stress at the Crossroads of Healthy and Unhealthy Aging

“…Although a compensatory increase of Glo1 is able to contain a transient increase of MGO flux in metabolically healthy muscle cells, the reduced efficiency of Glo1 in metabolically compromised muscle leads to intracellular MGO accumulation. This activates molecular pathways contributing to insulin-resistance, including mitochondria damage and increased ROS production [94,95], structural changes of skeletal muscle proteins [96] and inflammation mediated through RAGE activation [97,98].…”

Dicarbonyl Stress and Glyoxalase-1 in Skeletal Muscle: Implications for Insulin Resistance and Type 2 Diabetes

“…MG induces pathways known to contribute to insulin resistance including: (1) oxidative stress caused by damage to mitochondria ( 31 ) and mitochondrial DNA ( 32 ), (2) generation of AGEs [for more information on the independent effects of AGEs in diabetes and diabetic complications, the reader is directed to a recent review by Brings et al ( 33 )] and (3) inflammation mediated through the Receptor for Advanced Glycation Endproducts (RAGE) signaling ( 34 – 36 ). RAGE is highly expressed in skeletal muscle ( 37 , 38 ) and upon binding of a RAGE-ligands (i.e., MG-H1) a well characterized inflammatory signaling cascade ensues ( 39 – 41 ). Further, in vitro experiments in L6 myotubes treated with MG or MG-modified proteins, inhibit insulin-stimulated glucose uptake via impaired phosphorylation of phosphatidylinositol-4,5-bisphosphate 3-kinase (P13K) and extracellular-signal-regulated kinase 1 and 2 (ERK1/2) ( 42 – 44 ).…”