Liposomal encapsulation of L-arginine and L-citrulline enhances therapeutic effects in a rat model of Preeclampsia and Fetal Growth Restriction

Background L-arginine and L-citrulline improve vascular health in Preeclampsia (PE) and Fetal growth restriction (FGR). However, the short half-life of these amino acids limits their efficacy. This study investigates pharmacokinetics, delivery, and therapeutic outcomes of liposomal encapsulation of L-arginine and L-citrulline in a rat model of PE and FGR. Method Firstly, the pharmacokinetics of liposome-encapsulated L-arginine (Encapsulated L-arg) was compared to that of free L-arginine (Free L-arg) in normal pregnant (NP) dams, following single intravenous administration. Secondly, the therapeutic effect on maternal blood pressure and fetal weight were studied in NP rats and the reduced uterine perfusion pressure (RUPP) model for PE and FGR. Treatment groups consisted of Encapsulated L-arginine and L-citrulline (Encapsulated AAs); ratio 1:1, Free L-arginine and L-citrulline (AAs), or PBS, administered intravenously for five consecutive days. Blood and organs were analyzed for amino acid concentrations and fluorescence to assess the biodistribution profile of the liposomes. Nitrite and nitrate were quantified to measure changes in endogenous nitric oxide production in the pharmacokinetic study. Results Liposomal encapsulation increased the area under the curve of blood arginine concentration-time curves >120-fold. Encapsulated AAs led to a marked increase in plasma and placental tissue concentrations compared to their free forms. Encapsulated AAs reduced maternal blood pressure in RUPP without affecting fetal weight. Enlarged spleens were observed in both Encapsulated AAs groups. Conclusions The enhanced pharmacokinetics enabled by liposomal encapsulation effectively increased placental delivery of L-arginine and L-citrulline and reduced hypertension. Optimizing composition could enhance efficacy on FGR, making Encapsulated AAs a promising strategy for managing PE and FGR. The etiology of the observed maternal splenomegaly observed warrants further research before this novel approach can be clinically implemented.