Selective inhibition of leukotriene receptor BLT-2 reduces vascular oxidative stress and improves endothelial function in ApoE-/- mice

Atherosclerosis is a chronic inflammatory disease and represents the main cause of death in the industrialized world. Metabolites of the arachidonic acid derived from the 5-lipoxygenase pathway are known as leukotrienes that mediate various inflammatory processes during atherogenesis. Leukotriene B4 elicits the overexpression of several proinflammatory proteins, promotes chemotaxis and foam cell formation via BLT receptors. Currently, little is known about the implications of the BLT2 receptor in atherogenesis. Here, we tested whether selective inhibition of this receptor influences the progression of atherosclerosis in mice. Apolipoprotein-E deficient mice were fed a high-fat, cholesterol-rich diet to create atherosclerotic conditions (each group n = 9). Simultaneously, mice received the pharmacologic BLT2 inhibition (Ly) by intraperitoneal injection every second day 5 mg/kg bw or vehicle. After 8 weeks, mice were killed and experiments were performed. Vascular superoxide release was diminished in mice treated with Ly compared with the control group (68 +/- A 15 vs 131 +/- A 20 RLU, P = 0.01), as measured by L012 assay. Next, endothelial function was assessed by organ chamber experiments. Endothelial-dependent relaxation was improved in mice treated with the BLT2 receptor antagonist. To determine whether selective inhibition of the BLT2 receptor affects the atherosclerotic plaque growth, immunohistochemical stainings of the aortic root were performed. Oil red O staining revealed no significant differences between both groups (36 +/- A 3% vs 38 +/- A 3%). Monocyte infiltration into the vessel wall was analyzed using Moma-2 staining. No significant differences were observed between both groups (31 +/- A 3% vs 34 +/- A 2%). Selective inhibition of the BLT2 receptor in mice reduces the release of vascular reactive oxygen species and improves endothelial function in mice. Further experiments are necessary in order to obtain tissue-specific and mechanistical insights.