Utilize este identificador para referenciar este registo: http://hdl.handle.net/10451/36920
Título: Molecular characterization of the fibrinogen-erythrocyte interaction as a cardiovascular risk
Autor: Guedes, Ana Filipa Barata Duarte 1986-
Orientador: Santos, Nuno C., 1972-
Carvalho, Filomena A., 1976-
Palavras-chave: Teses de doutoramento - 2018
Doenças cardiovasculares
Microscopia de força atómica
Data de Defesa: 2018
Resumo: Cardiovascular diseases (CVD) are the major cause of death worldwide. The evaluation of new risk factors can help to identify individuals at higher risk. Erythrocyte aggregation is one of the indicators of cardiovascular risk, which seems to be influenced by high plasma fibrinogen levels. This acute plasma protein has an alternatively spliced γchain variant (γ’ fibrinogen) that has been particularly associated with altered structure or properties of the clots and with increased cardiovascular risk. However, this association has been controversial and the molecular mechanisms are not clear. Based on these findings, we studied how fibrinogen and its variants interact with erythrocytes, and how this binding influences erythrocyte aggregation and fibrin clot properties. After the evaluation and characterization of the fibrinogen-erythrocyte binding in healthy subjects, the main goal of this Thesis was the study of fibrinogen-erythrocyte binding in patients with different cardiovascular and cerebrovascular diseases, as a clinical risk factor, trying to understand the impact of the presence of fibrinogen on erythrocyte aggregation. Clinical and hemorheological profiles, and the changes on γ’ fibrinogen levels associated to CVDs were also evaluated. To reach our goals, different experimental approaches were performed, including atomic force microscopy-based force spectroscopy, magnetic tweezers, ELISA assays, confocal and scanning electron microscopy, hemorheological methodologies and clot permeability studies. Patients with chronic heart failure (CHF), essential arterial hypertension (EAH) and stroke were enrolled in this study. Results were correlated with patient’s clinical profile. Our conclusions are that erythrocytes triggered variability in the fibrin network structure, in the individual fiber characteristics and overall clot properties. The presence of γ’ chain on the fibrinogen molecule, even combined with γA chain, altered the clot structure. Thus, clots with γAγ’ fibrinogen might interact differently with erythrocytes, potentially increasing the risk of thrombosis. Addressing our main goal, we found, at the single-molecule level, that fibrinogenerythrocyte binding forces were higher in EAH, CHF and stroke patients, when compared with the control group, despite of a lower binding frequency. This transient binding is not enough to form a clot, but it could lead to changes on whole blood flow, representing a cardiovascular risk factor. Moreover, a 12-month clinical follow-up showed that CHF patients with higher fibrinogen-erythrocyte binding forces had a significantly higher probability of being hospitalized due to cardiovascular complications in the following year, pointing out the value of this approach for clinical prognosis. Importantly, we also showed that erythrocytes from EAH patients adhere more than those from the control group. Upon increasing fibrinogen concentration, there was an increase in the work and force necessary for cell-cell detachment, both on healthy donors and EAH patients, showing the importance of this plasma protein on the adhesion between these cells. Changes on hemorheological profiles were found in patients compared to the control group. γ’ fibrinogen levels were higher in patients than in healthy donors, which is indicative of an increased cardiovascular risk. Thus, these results are relevant to conclude on the degree of pathophysiological relevance of fibrinogen and erythrocyte aggregation, since an increment on both might induce a state of microcirculatory slower flow, increasing the probability of cardiovascular complications. Moreover, it was concluded that the specific receptor of fibrinogen on erythrocyte membrane is the integrin αvβ3 and the 94RGD97 sequence on the Aα-chain of the fibrinogen is one of the essential binding sites. These results, together with future studies, will be important to discover therapeutic drugs in order to overcome the erythrocyte aggregation promoted by the fibrinogen-erythrocyte binding and, thus, reduce the possibility of cardiovascular events.
Descrição: Tese de doutoramento, Ciências Biomédicas (Bioquímica Médica), Universidade de Lisboa, Faculdade de Medicina, 2018
URI: http://hdl.handle.net/10451/36920
Designação: Doutoramento em Ciências Biomédicas
Aparece nas colecções:FM - Teses de Doutoramento

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