URSOLIC ACID INTERFERES LIPID DROPLET METABOLISM AND INHIBITS ROTAVIRUS INFECTION

TOHMÉ, M. JULIETA; COLOMBO, M. ISABEL; WILKE, NATALIA; CARUSO, BENJAMÍN; DELGUI, L.R.

Virtual

Congreso; Reunión Conjunta SAIB-SAMIGE 2020. Edición ON-LINE; 2020

SAIB-SAMIGE

Rotavirus (RV) is one of the main causes of acute gastroenteritis and hospitalizations in young children, mainly affecting developing countries. Since there is no specific treatment, the development of an efficient method for RV elimination is still a priority. We demonstrated that ursolic acid (UA), a natural triterpenoid, exerts anti-RV activity, negatively affecting the early stages of the viral cycle. Moreover, UA comprises a broad anti-RV since the yields of the simian SA11, the porcine RRV, and the bovine NCDV RV strains were diminished in the presence of the compound in vitro.Once the virus reaches the cytosol, viral proteins translation and genome replication begin. Immediately after the viroplasms (VPs) formation occurs. The VPs are electrodense structures that constitute the platform for new viral particles assembly. One of the main components of the VPs are the lipid droplets (LDs), dynamic organelles mainly associated with lipid storage within the cells. We and others observed that during RV infection there is an accumulation of LDs in the cells. We analysed if the anti-RV effect of UA was due to its ability to modulate the LD metabolism and/or the thermodynamic aspects related to LDs generation and growth. To evaluate the influence of UA on LDs formation we used Langmuir monolayers as model. Monolayers of a phosphatidylcholine and triglyceride (PC-TG) mixture, two of the main LDs components, were prepared and the generation of TG-aggregates (lenses) was monitored using Brewster Angle Microscopy. Our results showed that UA exerts an effect on PC-TG mixtures, yielding membranes thermodynamically more prone to form lenses. Therefore, the number of lenses increased with UA content. However, the lenses became thinner in those conditions. These observations, translated to the cellular environment, suggest that although UA would induce the formation of ?blisters? inside the ER-membrane (the initial stage of LD biogenesis) it would interfere with their budding-off. Accordingly, we observed that short treatments with UA significantly decreased the number and size of LDs within the cells.Also, we analysed the lipolytic rate of LDs in the presence of UA. We induced the accumulation of LDs in the cells and measured them along 4 h in the presence or absence of UA. We observed a significant decrease in the number and size of LDs after 1 h UA-treatment, indicating that UA induces LDs degradation.Taken together, our results indicate that UA interferes with the lipid metabolism negatively affecting the formation of LDs and accelerating their degradation. These effects conduct to less availability of LDs within the cells, which hampers the formation of VPs, and consequently inhibits the RV amplification. Even though further experiments need to be done, we conclude that UA-interference on LD metabolism constitute, at least in part, the basis of its mechanism of action as anti-RV compound and make it an attractive option to future anti-RV treatments.