Lipossomas como nanocarreadores de angiotensina-(1-7) para o Sistema Nervoso Central e o tratamento de Acidente Vascular Encefálico

Abstract

Stroke is one of the leading causes of death and serious long-term disability worldwide. The only therapeutic agent available is tissue-type plasminogen activator (t-PA), however the number of potential patients is limited because of its side effects and narrow therapeutic window. Angiotensin-(1-7) [Ang-(1-7)], an endogenous peptide from the renin-angiotensin system, has shown neuroprotective effects in in vitro and in vivo ischemia models. Ang-(1-7) is rapidly metabolized and to overcome this issue liposome nanoparticle encapsulation is a valuable approach to prevent degradation of the peptide. Liposomes are vesicles consisting of one or more lipid bilayers surrounding an aqueous compartment. Liposomes are biodegradable, biocompatible, and are able to increase drug efficacy in models of stroke, therefore the use of liposomes as Ang-(1-7) carriers to the Central Nervous System is an asset for ischemic stroke therapy. In this study, liposomes were labeled with the fluorescent probe Dil (1,1'-dioctadecyl-3,3,3 ', 3'-tetramethyl-indocarbocyanine perchlorate), followed by Ang-(1-7) encapsulation. Biodistribution and kinetics analyses were performed using CD1 mouse, at 1.5h, 4h and 24h after intravenous injection of empty and loaded liposomes. In parallel, CD1 mice underwent temporary middle cerebral artery occlusion (MCAO) surgery. Immediately after reperfusion, liposomes were intravenously injected. To analyze the biodistribution of the liposomes in the chosen organs and in the MCAo mice brain fluorescent images were made. The in vivo experiments demonstrated that fluorescence was detected in the plasma and in the brain after 24h of injection, that liposome possibly underwent liver and spleen metabolism and that the fluorescent label was eliminated by the kidneys. In addition, liposomes were observed in the ischemic region of MCAO mice brain. Overall the results showed that this type of delivery system can cross the blood brain barrier (biodistribution) and accumulate in the ischemic core of MCAo animals, thereby presenting high potential for stroke treatment.