Reactive oxygen species generation and antioxidants systems of platelets in the experimental sepsis

Abstract

Severe sepsis is important causes of death in intensive care units and it is trigged primary by gram-negative and gram-positive bacteria. Lipopolysaccharide (LPS) is a component of the outer membrane of Gram negative bacteria and has a pivotal role in inducing Gram negative sepsis. LPS may activate many types of cells leading to activation of nuclear factor kB (NF-kB) and increase of specific genes expression that encode proteins related to inflammation such as cytokines, adhesion proteins and enzymes such as cyclooxygenase 2 (COX-2 ) and inducible nitric oxide synthase (iNOS) expression. In the sepsis, occurs also the generation of large amounts of reactive oxygen species (ROS) including superoxide anion (O2-), hydrogen peroxide (H2O2) and hydroxyl radical (.OH), and reactive nitrogen species (RNS) such as nitric oxide (NO) and peroxynitrite (ONOO-) derived from the reaction between NO and O2-. The excessive production of ROS and/or reduction of antioxidants mechanisms like superoxide dismutase (SOD), catalase and reduced glutathione in sepsis are reported to contribute to the damage of vascular endothelium and multiple organ dysfunction. In addition, the first signals in sepsis are the reduction of leukocytes and platelets number in peripheral blood. In humans, the severity of sepsis correlates to number and state of platelet activation. Platelet activation leads to activation of a series of signaling pathways including those involving the Src kinase and phosphatidylinositol 3-kinase (PI3K), which contribute to firm adhesion and platelet aggregate stabilization. Studies show that Src kinase and PI3K modulate the formation of ROS in different cells. In addition, there are evidences that Src kinase and PI3K are also responsible for mediating some effects of LPS. Previous studies have described the effects of LPS on platelet adhesion and aggregation, however, no study has evaluated the effect of LPS on ROS generation and in antioxidants systems of platelets, particularly in the model of in vivo LPS. Therefore, we propose in this study investigate the sources of ROS and antioxidant systems in platelets of rats treated with LPS. Furthermore, we intend to study the modulatory role of Src and PI3K on ROS production in platelets of these animals. (AU)