The role of endoplasmic reticulum stress in endothelial dysfunction induced by homocysteine thiolactone

Abstract

Our and other studies have reported that homocysteine thiolactone (HTL) could induce endothelial dysfunction. However, the precise mechanism was largely unknown. In this study, we tested the most possible factor-endoplasmic reticulum (ER) stress, which was demonstrated to be involved in endothelial dysfunction in cardiovascular disease. Acetylcholine (Ach)-induced endothelium-dependent relaxation (EDR) and biochemical parameters were measured in rat isolated aorta. The level of reactive oxygen species (ROS) and NO was designed by specific fluorescent probe DCFH-DA and DAF-FM DA separately. The nuclear translocation of the NF-κB was studied by immune-fluorescence. The mRNA expression and protein expression of GRP78--a key indicator for the induction of ER stress--were assessed by real-time PCR and Western blot. Two ER stress inhibitors-4-PBA (5 mm) and Tudca (500 μg/mL)--significantly prevented HTL-impaired EDR and increased NO release, endothelial nitric oxide synthase (eNOS) and SOD activity, decreased ROS production, NADPH activity, NOX-4 mRNA and MDA level. We also found that 4-PBA and Tudca blocked HTL--induced NF-κB activation thus inhibiting the downstream target gene production including TNF-α and ICAM-1. Simultaneously, HTL increased the mRNA and protein level of GRP78. HTL could induce ER stress leading to a downstream enhancement of oxidative stress and inflammation, which finally caused vascular endothelial dysfunction.

Hyperhomocysteinaemia and vascular injury: advances in mechanisms and drug targets

“…Furthermore, as previously described, the inhibition of oxidative stress or ROS production relieves ER stress, which suggests homocysteine‐induced ROS production mediates ER stress (Kil et al ., ). Interestingly, homocysteine thiolactone (Hcy‐TL) directly up‐regulates GRP78 expression and induces ER stress independent of N ‐homocysteinylation and subsequently leads to oxidative stress and endothelial inflammation (Wu et al ., ). Overall, homocysteine‐induced ER stress and oxidative stress constitute a mutually reinforcing system.…”

Homocysteine and Mitochondria in Cardiovascular and Cerebrovascular Systems

“…Moreover, the total antioxidant power was significantly attenuated in H9C2 cardiac cells treated with Hcy [ 69 ]. Homocysteine-induced decreases in antioxidant defense were documented in vascular injury [ 4 , 70 , 71 , 72 , 73 ]. Studies on aorta have shown decreased expression of thioredoxin (Trx) and peroxiredoxin (Prx) [ 74 ].…”

Vascular protective effects of Astragalus membranaceus and its main constituents in rats with chronic hyperhomocysteinemia

“…Aortic tissue was prepared as previously described (18,19). The fluorescent probes 2,7-dichlorofluorescin-diacetate (DCFH-DA) and dihydroethidium (DHE) (both from Molecular Probes, Inc., Eugene, OR, USA) were used to evaluate the amount of hydrogen peroxide and superoxide anion, respectively.…”