Methylglyoxal stimulates endoplasmic reticulum stress in vascular smooth muscle cells.

Abstract

Methylglyoxal (MGO) is considered responsible for the detrimental effects of high blood glucose. MGO is produced as a by-product of the glycolysis pathway. While the glyoxalase system removes it, the system fails in people with diabetes. MGO concentration is detected as elevated in these patients. Endoplasmic reticulum (ER) stress may play a role in atherosclerosis progression and vascular diseases. If ER stress persists, it may result in apoptosis of the cell. As a result, stabilized plaque structure by these cells may be ruptured and cause a stroke. This study aimed to investigate whether MGO can induce ER stress and apoptosis in vascular smooth muscle cells (VSMCs). Also, the effects of aminoguanidine hydrochloride (AGH), 4-phenylbutyric acid (4-PBA), and tauroursodeoxycholic acid (TUDCA) were scrutinized to relieve ER stress. VSMCs were isolated from rat aorta and cultured primary. PERK phosphorylation, IRE1α, ATF6, BiP (Grp78), and CHOP expressions were detected by the western blot technique. A caspase-3 assay kit measured the apoptosis. MGO could stimulate the main three ER stress pathways, PERK phosphorylation, IRE1α, and ATF6 expressions in a time- and concentration-dependent manner. Furthermore, AGH, 4-PBA, and TUDCA alleviated MGO-induced ER stress. However, we detected neither an increase in CHOP expression nor apoptosis in VSMCs. This study shows that MGO induces ER stress even at low concentrations in VSMCs. The impaired glyoxalase system may cause MGO accumulation and result in persisted ER stress. Supposing that ER stress is not mitigated, this table might be finalized in cell apoptosis, plaque rupture, and stroke.