**5. The effects of reactive oxygen species**

#### **5.1. Oxygen free radicals – Intracellular messengers**

Before discussing the negative effect of oxygen activation on the body, we should also take into consideration their involvement in certain physiological processes, when these ROS are produced in quantities which do not exceed the antioxidant capacity. Thus, the superoxide anion is produced by leukocytes during phagocytosis and in smooth muscle cells, epithelial cells, skin fibroblasts and endothelial cells [27].

The anion produced by macrophages and endothelial cells induces conformational changes of receptors on the LDL lipoprotein surface, allowing their recognition and involvement in atherogenesis [10, 12].

It is also involved in cascade-type metabolic reactions of arachidonic acid and in achieving platelet adhesion and aggregation function.
