Figure 1: Effect of xylazine, cocaine, 6-monoacetylmorphine, and their combination on ROS production in human umbilical vein endothelial cells (EA.hy926). ROS levels in EA.hy926 cells, after 24 h of exposure to negative control (vehicle), xylazine (XYL, 60 M), cocaine (COC, 160 M), 6-monoacetylmorphine (6-MAM, 160 M), camptothecin (positive control, 50 M), XYL/COC (50 M), XYL/6-MAM (50 M), and XYL/COC/6-MAM (40 M), were determined. Cells exposed to XYL and 6-MAM showed increased ROS levels. Cells exposed to COC and XYL in combination with COC and 6-MAM showed diminished ROS levels in comparison to negative control as determined by ANOVA. The experiment was repeated for at least three times in replicates and expressed as change from negative control (%). All values are expressed as mean SD of 6–9 replicates, from 2 to 3 experiments. Statistical analysis performed was a one-way ANOVA, with Tukey post hoc test, where was considered to be significant. summary; significantly higher in contrast to the negative control (), ### significantly lower in contrast to the negative control ().