Evaluation of the effect and mechanism of action of slow release hydrogen sulfide (H2S) donor GYY4137 on vascular response in in vitro ischemia-reperfusion model

Ischemia-reperfusion (IR) injury of autologous vascular grafts used during coronary artery bypass surgery may adversely affect surgical success. In this study, the protective effects of GYY4137, a slow-release hydrogen sulfide (H2S) donor, on vascular tissue in an in vitro rat model of IR injury were investigated. The thoracic aorta of twenty male (21-22 months, 378.2 ± 45.5 g) Sprague-Dawley rats were divided into 4 ring preparation and randomized into experimental groups: Control, IR, IR + GYY4137 100 µM, IR + GYY4137 300 µM. For the IR model, the aortic ring was kept in 0.9% saline gassed with nitrogen at 4°C for 24 hours, placed in an organ bath containing Krebs-Henseleit solution at 37°C, gassed with 95% O2+5% CO2 and exposed to sodium hypochlorite (200 μM) for 30 minutes. In GYY4137 groups, GYY4137 was added to saline. Vascular function was evaluated in the isolated organ bath setup and tissue malondialdehyde, glutathione and caspase-3 activity were measured biochemically. IR injury decreased KCl (80 mM) response (Control 1815 ± 140 mg, IR 842 ± 160 mg, p = 0.0003), increased Emax in phenylephrine concentration-response curve (Control 144.1 ± 2.64%, IR 202.3% ± 4.9%, p < 0.0001), increased Emax in acetylcholine concentration-response curve (Control 78.4% ± 1.4%, IR 32.6 ± 3.4%, p < 0.0001) and decreased pD2 (Control 7.24 ± 0.05, IR 5.18 ± 0.17, p < 0.0001), while sodium nitroprusside concentration-response curve increased Emax (Control 101,4% ± 1.47%, IR 113.6% ± 2.3%, p = 0.0009) and decreased pD2 (Control 8.4 ±0.03, IR 8.23 ± 0.04, p = 0.00025). GYY4137 did not correct these IR-induced functional changes. On the other hand, in biochemical analysis, malondialdehyde level (Control 8.4±0.9 nmol/g, IR 12.6 ± 1.0 nmol/g, p = 0.02), which increased with IR, decreased to control level with 100 μM and 300 μM GYY4137 (8.7 ± 0.9 nmol/g, p = 0.008 and 7.6 ± 1.1 nmol/g, p = 0.012, respectively). Decreased glutathione level (Control 785 ± 61 nmol/g, IR 506 ± 45 nmol/g, p = 0.012) returned to normal in the presence of 300 μM GYY4137 (709 ± 45 nmol/g, p = 0.004); Increased tissue caspase-3 levels (Control 2.4 ± 1.3 ng/g, IR 8.4 ± 1.2 ng/g, p = 0.02) were recovered by 100 μM and 300 μM GYY4137 (2.3 ± 1.3 ng/g, p = 0.004 and 3.2 ± 1.1 ng/g, p = 0.02, respectively). These findings suggest that GYY4137 provides cellular protection against oxidative stress and apoptosis following IR injury, but does not significantly improve vascular dysfunction. Further studies should focus on understanding the mechanisms of the presented findings and developing potential prevention and treatment strategies against IR injury.