[Protective effects of estrogen on mitochondria in human umbilical vascular endothelial cells].

OBJECTIVE: To investigate the protective effects of estrogen on the mitochondria in human umbilical vascular endothelial cells (HUVECs). METHODS: HUVECs were exposed to H2O2 at 250 micromol/L for 4 h with or without pretreatment with 17-estradiol (E2) and ICI182780. Complex IV activity of the cells was measured with chromometry, and 2, 7-dichlorofluorescein diacetate (DCFH-DA) was used to determine intracellular reactive oxygen species (ROS). Intracellular adenosine triphosphate (ATP) level was quantified with a luciferin- and luciferase-based assay. RESULTS: Compared to the blank control group, H2O2 caused a decrease in complex IV activity, intracellular ATP level, and the cell viability, but elevated intracellular ROS. E2 pretreatment of cells significantly attenuated these effects of H2O2 exposure. ICI182780 administered prior to E2 pretreatment antagonized the protective effects of E2 against H2O2 exposure. CONCLUSION: E2 offers mitochondrial protective effects on HUVECs, which is mediated by the estrogen receptors.

[A new synthetic tripeptide inhibits L-arginine transport in macrophages].

OBJECTIVE: To observe the effect of a new synthetic tripeptide [Arg(NO(3))- Lys(OCH(3))- Arg(NO(3))] on L-arginine/NO pathway in the macrophage cell strain RAW246.7. METHODS: The cultured macrophages exposed to lipopolysaccharide (LPS, 1 microg/L) treatment were randomly divided into 3 groups (n=6) and treated with distilled water, 1x10(-4) mol/L tripeptide and 1x10(-4) mol/L L-arginine, NG-monomethyl-L-arginine (L-NMMA) for 24 h, respectively. The macrophages were incubated for 24 h with LPS (1 microg/L) and in the presence of different concentrations of L-arginine (0 to 2 mmol/L), or in normal culture medium (containing 0.5 mmol/L L-arginine) for 24 h with LPS (1 microg/L) and in the presence of tripeptide of 0 to 10x10(-4) mol/L. The changes of [(3)H]-L-arginine transport and NO production from the macrophages were measured. RESULT: NO release from macrophages incubated in the LPS-containing culture medium was 50 folds, and [(3)H]-L-arginine uptake 2.7 folds that in cells in normal culture medium. Tripeptide (1x10(-4) mol/L) inhibited [(3)H]-L-arginine transport and NO production by 67% and 71% respectively. The effect of tripeptide was stronger than L-NMMA (P<0.05). Extracellular L-arginine caused a concentration-dependent increase in nitrite production, which reached the maximum at concentrations above 0.5 mmol/L Km for nitrite production of 0.162+/-0.015 mmol/L and Vmax of 91.2+/-2.3 micromol/(24h.10(6) cells). L-arginine transport and NO production were inhibited by tripeptide, but their dose-dependent pattern of changes was different with EC50 of 0.21x10(-4) mol/L and 1.27x10(-4) mol/L, respectively. CONCLUSIONS: Activation of macrophages with LPS induces nitrite accumulation in the culture medium, which is dependent on the presence of extracellular L-arginine. The tripeptide induces dysfunction of L-arginine/NO pathway in macrophages, potently inhibits L-arginine transport and competitively combine the active sites of nitric oxide synthase.