The protective role of isorhamnetin on human brain microvascular endothelial cells from cytotoxicity induced by methylglyoxal and oxygen–glucose deprivation

As the first target of stroke, cerebral endothelial cells play a key role in brain vascular repair and maintenance, and their function is impeded in diabetes. Methylglyoxal (MGO), a reactive dicarbonyl produced during glucose metabolism, accumulates in diabetic patients. MGO and MGO‐induced advanced glycation end‐products (AGEs) could ameliorate stroke‐induced brain vascular damage, closely related with ECs dysfunction. Using MGO plus oxygen–glucose deprivation (OGD) to mimic diabetic stroke, we reported the protective effect of isorhamnetin on OGD‐induced cytotoxicity after MGO treatment on primary human brain microvascular endothelial cells (HBMEC) and explored the underlying mechanisms. Treatment of MGO for 24 h significantly enhanced 3‐h OGD‐induced HBMEC toxic effect, which was inhibited by pretreatment of isorhamnetin (100 μmol/L). Moreover, the protective effect of isorhamnetin is multiple function dependent, which includes anti‐inflammation, anti‐oxidative stress and anti‐apoptosis effects. Besides its well‐known inhibition on the mitochondria‐dependent or intrinsic apoptotic pathway, isorhamnetin also reduced activation of the extrinsic apoptotic pathway, as characterized by the decreased expression and activity of caspase 3 and caspase 8. Furthermore, pretreatment with isorhamnetin specifically inhibited FAS/FASL expression and suppressed nuclear factor‐kappa B nuclear translocation. Taken together, our results indicated that isorhamnetin protected against OGD‐induced cytotoxicity after MGO treatment in cultured HBMEC due to its multiple protective effects and could inhibit Fas‐mediated extrinsic apoptosis. Therefore, isorhamnetin is a promising reagent for the treatment of hyperglycemia and ischemia‐induced cerebral vascular degeneration. A proposed model of the potential protective mechanism of isorhamnetin, a metabolite of quercetin, on methylglyoxal (MGO) treatment plus oxygen–glucose deprivation (OGD) exposure‐induced cytotoxicity in cultured human brain microvascular endothelial cells. Isorhamnetin inhibits FasL‐mediated extrinsic apoptosis and neurotrophic factor κB (NF‐κB) nuclear translocation, which can induce the cell DNA damage. Therefore, the protective effect of isorhamnetin occurs through multiple functions, including anti‐inflammation, anti‐oxidative stress and anti‐apoptosis. Therefore, isorhamnetin is a promising reagent for the treatment of hyperglycemia and ischemia‐induced cerebral vascular degeneration. A proposed model of t