Effects and related mechanism of flavone from Galium verum L on peroxide induced oxidative injury in human umbilical vein endothelial cells

Abstract

To investigate the effects of flavone from Galium verum L (FGVL) on hydrogen peroxide induced oxidative injury in human umbilical vein endothelial cells (HUVEC), and explore related mechanisms. HUVEC were divided into five groups: control group (1640 complete medium), injured group (HUVEC treated with 100 μmol/L hydrogen peroxide for 4 h), FGVL group (HUVEC treated with 12.5 mg/L FGVL (group F1), 25.0 mg/L (group F2), 50.0 mg/L (group F3) for 24 h before hydrogen peroxide). The nitric oxide content was measured by nitric acid reductase method. The 6-keto-Prostacyclin-F1α (6-keto-PGF1α), thromboxane B2 (TXB2), interleukin(IL)-6 and IL-22 were determined by ELISA.mRNA expression of phosphatidylinositol 3-kinase (PI3K), protein kinase B (Akt) and endothelial nitric oxide synthase (eNOS) was detected by RT-PCR.Protein expression of p-Akt (ser(473)) and p-eNOS (ser(1177)) was determined by Western blot.Cell apoptosis was observed with fluorescence microscope after Hoechst33258 staining. (1) The contents of nitric oxide were significantly lower in the injured group than in the control group ((34.11±1.78) μmol/L vs. (74.81±2.93) μmol/L, P<0.05), which was significantly increased in group F2 ((41.86±2.32) μmol/L) and group F3 ((62.79±1.16) μmol/L) compared with injured group (both P<0.05). (2)The secretion level of 6-keto-PGF1α was significantly lower in the injured group ((44.84±3.87) ng/L) than in the control group ((82.38±3.98) ng/L, P<0.05), which was significantly increased in group F1 ((52.76±1.78) ng/L), FGVL 2 group which was(56.58±1.44) ng/L and FGVL 3 group which was(67.78±2.02) ng/L than that of injured group(all P<0.05). The secretion level of TXB2 was significantly higher in the injured group((43.37±3.96) ng/L) than in the control group ((25.56±1.75) ng/L, P<0.05), which was significantly reduced group F2 group ((32.41±1.68) ng/L) and group F3 ((28.23±2.15) ng/L) than that of injured group(both P<0.05). (3) The contents of IL-6 and IL-22 were significantly higher in the injured group ((539.74±11.63) ng/L) and ((23.70±3.05) ng/L, respectively) than in the control group ((288.67±19.52) ng/L) and ((23.70±3.05) ng/L, respectively, both P<0.05). The contents of IL-6 were significantly lower in group F1, F2 and F3 compared to that of injured group(all P<0.05). The contents of IL-22 were significantly lower in group F2 and F3 than that of injured group(both P<0.05). (4)The relative levels of PI3K mRNA and eNOS mRNA in injured group (0.68±0.09 and 0.22±0.03, respectively) were significantly lower compared to control group(0.81±0.12 and 0.63±0.11, respectively, both P<0.05), PI3K mRNA in group F2 (0.76±0.03) and group F3 (PI3K mRNA 0.83±0.06) as well as eNOS mRNA in group F1 (0.37±0.08), F2 (0.53±0.04) and F3 (0.56±0.09) than those of injured group(all P<0.05). The mRNA expression of Akt was similar among groups (P>0.05). (5) The relative levels of p-Akt (ser(473)) and p-eNOS (ser(1177)) in injured group (0.48±0.05 and 0.23±0.03, respectively) were significantly lower compared to control group (0.71±0.12 and 0.66±0.05, respectively, both P<0.05), which was up-regulated in group F1, F2 and F3 groups compared to injured group(all P<0.05). (6) The cell apoptosis rate in injured groups was significantly higher compared to control group which ((63.67±11.37)% vs. (4.67±1.15)%, P<0.05) which was significantly reduced in group F1((43.33±4.16)%), F2((18.33±4.93)%) and F3((15.67±2.08)%) compared to injured group(all P<0.05). The FGVL can reduce hydrogen peroxide induced oxidative injury in HUVEC by increasing the level of nitric oxide through PI3K/Akt/eNOS pathway.