Advanced Glycation End Products Downregulate Placental Growth Factor Expression in Endothelial Cells Via a Macrophage‐Mediated Mechanism

Abstract

In coronary artery disease, atherosclerosis chronically reduces blood flow. Placental growth factor (PLGF), a protein produced by endothelial cells (EC), can promote collateral artery remodeling to increase blood flow. However, collateral growth is impaired in people with type II diabetes. Our group has previously demonstrated that PLGF levels are reduced in a mouse model of diet‐induced type II diabetes. However, the mechanism for this reduction remains to be defined. Inflammatory cytokines and advanced glycation end products (AGE) are implicated in diabetic vascular dysfunction. We therefore hypothesized that AGE and TNFα signaling would inhibit PLGF expression in EC. Human coronary artery EC were treated with AGE, bovine serum albumin (BSA, as a control for AGE), or TNFα. AGE had no direct effect on PLGF in EC; however, TNFα reduced PLGF in EC (P<0.001). Next, murine macrophages (RAW cell line) were treated with AGE or BSA. RAW media was then transferred to murine endothelial cells (EOMA cell line). Treatment with both RAW‐BSA and RAW‐AGE media significantly reduced PLGF levels in EOMA cells compared with control RAW media (BSA, 481.75 ±21.00 pg/mL; AGE, 631.29 ±41.88 pg/mL; control, 1022.48 ±115 pg/mL; P<0.001, n=4). However, TNFα levels were only increased in RAW‐AGE media compared to RAW‐BSA media and RAW‐control media (AGE, 811.11 ±48.37 pg/mL; BSA, 305.68 ±13.95 pg/mL; control, 276.07 ± 10.40 pg/mL; P< 0.001, n=3). This finding suggests that cytokines other than TNFα may also be inhibitory for PLGF. Analysis of RAW media using a Multiplex Pro mouse 6‐panel cytokine assay revealed that TNFα was increased in RAW‐AGE media compared to RAW‐BSA and RAW‐control media (P<0.007). There was also a trend towards increased IL‐10 and IFN‐γ with AGE treatment, which approached significance (P<0.06), suggesting that these cytokines may also be important targets for future investigation. Identifying signaling pathways by which AGE and inflammatory mediators affect PLGF will give new insights into the pathology of diabetic cardiovascular disease.Support or Funding InformationNIH R56 HL084494 (PL), OSU CVM