[The role of heme oxygenase-1 on oxidative stress injury induced by zinc oxide nanoparticles in human umbilical vein endothelial cells line EA.hy926 cells]

Objective: To explore the effect of heme oxygenase-1 (HO-1) on level of reactive oxygen species (ROS) induced by zinc oxide nanoparticles (ZnO-NPs) in Human umbilical vein endothelial cells line EA.hy926. Methods: The EA.hy926 cells in logarithmic growth phase were incubated with 0.0, 2.5, 5.0, 10.0 and 15.0 mg/L ZnO-NPs respectively. The ROS level, reflected by mean fluorescence intensity (MFI), was examined by flow cytometer after 4 hours exposure, the protein expression of HO-1 which was determined by Western Blot after exposed to ZnO-NPs for 24 hours. Cells incubated with 15.0 mg/L were set as the ZnO-NPs group; a blank control group was set at the same time. Cells were pretreated with HO-1 inhibitor zinc protoporphyrin (ZnPPIx) and HO-1 activator cobalt protoporphyrin (CoPPIx), they were classified as ZnPPIx group and CoPPIx group. 15 mg/L ZnO-NPs was chosen to conduct the experiment of HO-1 activation and inhibition. Cells were classified as ZnPPIX+ ZnO-NPs group and CoPPIx+ ZnO-NPs group after pretreated with 10 μmol/L ZnPPIx or CoPPIx for 1 h, added 15 mg/L ZnO-NPs to cell culture medium. In all groups ROS levels were detected after exposed to ZnO-NPs for 4 hours, the protein expression of HO-1 was detected after exposed to ZnO-NPs for 24 hours. Results: With the increased dose of ZnO-NPs, levels of ROS and HO-1 in EA.hy926 cells were clearly elevated (the MFI of 0.0, 2.5, 5.0, 10.0 and 15.0 mg/L ZnO-NPs incubated groups was 22 627.22±718.27, 24 726.47±568.52, 31 141.75±1 312.24, 39 824.82±4 774.74, 50 569.03±1 497.63 respectively, and HO-1 relative expression were 0.16±0.01, 0.19±0.02, 0.16±0.01, 0.23±0.02, 0.92±0.06 respectively). HO-1 expression in ZnPPIx pretreatment group decreased compared with ZnO-NPs group (1.05±0.05 vs. 1.12±0.01, P<0.05), meanwhile ROS level enhanced (62 683.95±2 589.59 vs. 53 654.53±2 229.01, P<0.05). However, CoPPIx pretreatment had higher HO-1 level and lower level of ROS compared with ZnO-NPs group (HO-1: 1.74±0.11 vs. 0.22±0.03, P<0.05; ROS: 32 845.04±993.48 vs. 53 654.53±2 229.01, P<0.05). Conclusions: Exposure to ZnO-NPs significantly induced ROS generation in EA.hy926 cells in a dose-dependent manner. HO-1 regulated ZnO-NPs-induced oxidative stress.

[Dual sieve-mesh collimator]

In this paper is advanced a new type of collimator-dual sieve-mesh collimator. Its principle is to use scanned electronic beam to attack 400 matrix-arranged wolfram targets of the square holes on the upper side of the main collimator and created 400 small X-ray fields sized by 10 mm x 10 mm. These X-ray fields will leave on its center 400 smaller X-ray fields sized by 5 mm x 5 mm after being further collimated by a sub-collimator. What's more, 16 different groups of such X-ray fields can be left on the center of the same field by controlling the all-round movement of the main collimator and sub-collimator in proper order and by scanning it round by round and mesh by mesh with electronic beams. It is these ting fields groups that make up various treatment fields with different energy (Dosage). This type of collimator can replace and simplify all other present collimators on accelerators and conformal-intensity modulation radiotherapy equipment. It has advantage of reducing the costs of radio-therapy equipment and making conformal and intensity modulation radiotherapy easier to perform.