Caracterização da ativação plaquetária e interação plaquetaleucócitos na obesidade

Abstract

Obesity is a global health problem associated with chronic low-grade inflammation that supports comorbidities such as diabetes and cardiovascular disease. However, the thromboinflammatory mechanisms related to cardiometabolic risk are not fully known. Platelets are effector cells of hemostasis as well as immunity and inflammation. Activated platelets secrete inflammatory mediators and interact with leukocytes modulating responses such as secretion, migration, antibody class switching and T cell polarization. Nonetheless, the mechanisms and functional responses of platelets and platelet-leukocyte aggregates in obesity remain poorly understood. Our hypothesis is that platelet activation contributes to immunoregulation in obesity, participating in mechanisms of inflammation and high cardiometabolic risk. The main goal of the present project is to investigate the role of platelet activation and platelet-leukocyte interaction in immunoregulation and inflammation in obesity. Blood samples were obtained from obese and eutrophic individuals and analyzed to thromboinflammatory mediators in plasma and platelet activation by flow cytometry. Individuals with obesity have increased levels of thromboinflammation markers and platelet activation with greater secretion of dense granules. Platelets from patients with grade III to IV obesity have higher activation and hyper-responsive to thrombin. Leukocyte subpopulations and circulating platelet-leukocyte aggregates were characterized in whole blood samples by flow cytometry. We demonstrated that obesity induces the formation of platelet-monocyte aggregates, but not platelets with and T, B, NK and NKT lymphocytes and neutrophils interaction. Circulating platelet-monocyte aggregates in obese individuals is associated with CD16+ monocyte subpopulations and increased expression of TF (tissue factor), the main activator of the extrinsic cascade of coagulation. Furthermore, we investigated the role of leptin, a classic inflammatory mediator increased in obesity, in the formation of platelet-leukocyte aggregates and TF expression in monocytes. Leptin partially reproduces the phenotype observed in obese individuals, inducing TF expression in monocytes associated with platelet interaction. To investigate the role of platelet-monocyte interaction in the reciprocal activation of platelets and monocytes in obesity, we initially used an autologous platelet-monocyte interaction model from obese or eutrophic individuals and measured mediators secreted by ELISA. Platelets and monocytes from obese patients are more activated with secretion of inflammatory mediators TNF-α, IL-10, sCD62P e CCL5/RANTES. Considering that higher activation of platelets and monocytes from patients with obesity, we investigated whether the platelet-monocyte interaction contributes to reciprocal activation of platelets and monocytes in obesity, using an ex vivo heterologous co-culture model. The platelet-monocyte interaction induced TF expression in monocytes, as well as potentiating the reciprocal activation of platelets and monocytes, amplifying the secretion of thromboinflammatory mediators such as CCL2/MCP-1, IL-1β and sCD62P. Together, the data highlight the participation of both cells in the reprogramming of their responses during platelet-monocyte interaction in obesity. All these cell interaction events are potentially involved in thromboinflammation mechanisms in obesity.