Berberine Protects Endothelial Function From Homocysteine By Increasing Nitric Oxide Production And Decreasing Asymmetric Dimethylarginine Level

BACKGROUND AND PURPOSE:Endothelial dysfunction is an important pathogenic mechanism and phenomenon in cardiovascular diseases.In recent years,more and more researches focus on the decrease of endothelial nitric oxide(NO)production and the subsequent impairment of endothelium-mediated vasodilation as well as vascular smooth muscle proliferation and migration.Hyperhomocysteinemia is a well-known cardiovascular risk factor.Homocysteine affects enzymes involved in asymmetric dimethylarginine(ADMA)metabolism,resulting in the accumulation of ADMA,which could competitively inhibit endothelial nitric oxide synthase(eNOS)activity and decrease endothelial production of NO.Berberine,BBR;is an isoquinoline plant alkaloi insolated from Berberis vulgaris and other plants.It has been revealed in animal models and in vitro experiments that berberine could protect endothelial function via several mechanisms like decreasing oxidative damage,increasing NO production and inhibiting apoptosis.Clinical trials also found that patients with hypertension,diabetes,post-myocardial infarction ventricular remodeling could benefit from berberine.But up until now,there is no research investigating whether berberine could protect endothelial function from homocysteine damage or if the mechanism involves ADMA metabolism.This research investigated into these two issues,trying to provide a new perspective to the endothelial protection mechanism of berberine.METHODS:Human umbilical vein endothelial cells(HUVECs)were isolated and cultured in vitro.After synchronization,HUVECs were treated with 300?M or 500?M homocysteine combined with berberine of 0?M,1.25?M,2.5?M,5.0?M,or 10.0?M.Supernatant and cells were harvested at 12h,24h,and 48h.Cell viability,supernatant NO concentration,ADMA concentration and the transcription level of endothelial nitric oxide synthase(eNOS),dimethylarginine dimethylaminohydrolase(DDAH)and proteinarginine N-methyltransferase 1(PRMT1)were examined by CCK8 kit,Griess method,liquid chromatography-mass spectrometry(LC-MS),and quantitative polymerase chain reaction(qPCR),respectively.RESULTS:HUVEC viability significantly dereased when treated with 500?M of Hcy,but not with 300?M of Hcy.Hcy suppressed eNOS and DDAH 1 transcription,increased PRMT1 transcription and increased ADMA level,thus jeopardized NO production under certain circumstances.Berberine protected cell viability,reduced ADMA accumulation and increased NO production.However,NO production may further decrease if HUVECs were treated with low-concentration berberine and high-concentration of Hcy,or with berberine and Hcy for 48h.Under certain circumstances,Berberine could increase eNOS and DDAH1 transcription and decrease PRMT1 transcription.CONCLUSION:Homocysteine decreases HUVEC viability and NO production,probably by suppressing eNOS and DDAH1 transcription,inceasing PRMT1 and increasing ADMA,but the detailed mechanism still needs confirmation and further investigation.Berberine could increase HUVEC viability,reduce ADMA accumulation and increase NO production,and this protecting effect lasts for 12?4h.If the dosage of berberine could not compensate the damaging effect of Hcy,or cultivation lasts more than 24h,berberine intervention may further reduce NO level.The protection effect of berberine may be related to its regulation of transcriptions of enzymes eNOS,DDAH1 and PRMT1,which are involved in the NO and ADMA metabolism.However,the mechanism still needs confirmation and further investigation.