Ação da ldl oxidada na ativação plaquetária durante a dengue

Abstract

Dengue is caused by the dengue virus (DENV) and transmitted mainly by the species A. aegypti. The disease can range from asymptomatic to increased vascular leakage, severe hemorrhage and organ damage, characterizing severe dengue.High concentrations of inflammatory cytokines contribute to increased vascular permeability and severity of dengue. In patients with dengue, the levels of inflammatory cytokines are significantly correlated with thrombocytopenia, which, in turn, is positively associated with the critical phase of the disease. In addition to platelet hemostatic functions, platelets also participate in inflammatory responses, by secreting cytokines and chemokines, in addition to interacting with other immune cells. Platelet activation is described in dengue, which may contribute to thrombocytopenia and also to exacerbated inflammation and severity of the disease.Platelet activation stimuli are not yet fully elucidated. Serum lipid changes, such as a reduction in low density lipoprotein - LDL, a cholesterol transporter, are observed in the course of infection and are positively associated with severity.These data corroborate the fact that cholesterol is fundamental in the replication of Flaviviruses. In addition, in an environment of immune response and exacerbated inflammation, we can consider a high risk of lipid peroxidation due to increased oxidative stress.In this sense, the formation of bioactive compounds in oxidized LDL (oxLDL) that amplify the inflammatory response when activating immune cells is well understood. Therefore, this work aimed to investigate the participation of oxLDL in the pathogenesis of dengue, identifying mechanisms of platelet activation and apoptosis and secretion of inflammatory mediators by platelets. LDL from patients with dengue were isolated by density gradient and ultracentrifugation and evaluated by T-BARS and Western Blot tests for the presence of reactive aldehydes (malondialdehyde and 4-HNE, respectively) from lipid peroxidation. There was a significant increase in oxidation in LDL in patients with dengue. Platelets from healthy volunteers were incubated with LDL from dengue patients at different concentrations (0, 5, 10, 100 and 1000ng/mL) with or without thrombin (0.02U/mL) and evaluated by flow cytometry for the expression of P-selectin, GPIIb/IIIa activation, CD36 receptor expression and apoptosis (Annexin-V+/TMRE-). Supernatants after platelet LDL stimulation from dengue patients or healthy individuals were collected and analyzed by ELISA for secretion of inflammatory mediators (IL-1α, IL-1β, PF4/CXCL4, RANTES/CCL5 and MIF). Despite the higher level of oxidation of LDLs in patients with dengue, they were not able to induce activation, apoptosis and secretion of inflammatory platelet mediators compared to LDL from healthy volunteers. Therefore, oxLDL from mild dengue patients with or without warning signs cannot be identified as contributors to platelet activation and apoptosis in dengue. Other stimuli involved in platelet activation during dengue should be elucidated.