Biology subjects

Giorgi, L.

Publications and source records attributed to Giorgi, L..

4 recordsLinked to original sources

bioRxiv2025

Modifications of the 22A apoA-I mimetic peptide sequence improve the anti-atherosclerotic properties of synthetic HDL

Synthetic high-density lipoprotein (sHDL) constituted of apolipoprotein A-I (apoA-I) mimetic peptides and phospholipids are nanometer-scale particles designed to recreate biological functions of HDL particles in the context of cardiovascular disease. Particularly, the therapeutic efficacy of sHDL particles is attributed to their ability to promote reverse cholesterol transport (RCT), a process where accumulated cholesterol is transported from peripheral tissues to the liver for elimination. Here, we designed two novel apoA-I mimetic peptides (22A-F and 22A-P-18A) by modifying the sequence of the well-studied apoA-I mimetic peptide 22A. These modifications were intended to improve cholesterol efflux from macrophages in vitro and structural stability of sHDL particles in human plasma while preserving their ability to activate lecithin-cholesterol acyltransferase (LCAT). We performed a systematic examination of the potency of sHDL particles made with these peptides in cellular cholesterol efflux, activation of LCAT, plasma HDL remodeling and proteolytic stability. Our study highlights that these modifications improve cholesterol efflux and, in the case of 22A-P-18A, also cholesterol esterification rate by LCAT but they do not appear to influence HDL remodeling in human plasma. Nonetheless, the LCAT activity assay conducted in human plasma suggest that intact sHDL particles are present and are likely the primary contributors to the increased cholesterol esterification rate, rather than the pre-{beta} HDL fraction generated through HDL remodeling. These findings offer new mechanistic insights into how specific peptide modifications affect key steps in RCT, laying the groundwork for future studies to explore their functional relevance in atherosclerosis and HDL-based drug delivery applications.

pharmacology and toxicology↗

bioRxiv2024

Gliflozins, sucrose and flavonoids are allosteric activators of lecithin:cholesterol acyltransferase

Lecithin:cholesterol acyltransferase (LCAT) serves as a pivotal enzyme in preserving cholesterol homeostasis via reverse cholesterol transport, a process closely associated with the onset of atherosclerosis. Impaired LCAT function can lead to severe LCAT deficiency disorders for which no pharmacological treatment exists. LCAT-based therapies, such as small molecule positive allosteric modulators (PAMs), against LCAT deficiencies and atherosclerosis hold promise, although their efficacy against atherosclerosis remains challenging. Herein we utilized a quantitative in silico metric to predict the activity of novel PAMs and tested their potencies with in vitro enzymatic assays. As predicted, sodium-glucose cotransporter 2 (SGLT2) inhibitors (gliflozins), sucrose and flavonoids activate LCAT. This has intriguing implications for the mechanism of action of gliflozins, which are commonly used in the treatment of type 2 diabetes, and for the endogenous activation of LCAT. Our results underscore the potential of molecular dynamics simulations in rational drug design.

biochemistry↗

bioRxiv2022

Mechanistic insights into the activation of lecithin-cholesterol acyltransferase in therapeutic nanodiscs composed of apolipoprotein A-I mimetic peptides and phospholipids

The mechanistic details behind the activation of lecithin-cholesterol acyltransferase (LCAT) by apolipoprotein A-I (apoA-I) and its mimetic peptides are still enigmatic. Resolving the fundamental principles behind the LCAT activation will facilitate the design of advanced HDL-mimetic therapeutic nanodiscs for LCAT deficiencies and coronary heart disease, and for several targeted drug delivery applications. Here, we have combined coarse-grained molecular dynamics simulations with complementary experiments to gain mechanistic insight into how apoA-I mimetic peptide 22A and its variants attune LCAT activity in peptide-lipid nanodiscs. Results highlight that peptide 22A forms transient antiparallel dimers in the rim of nanodiscs. The dimerization tendency considerably decreases with the removal of C-terminal lysine K22, which has also been shown to reduce the cholesterol esterification activity of LCAT. In addition, our simulations revealed that LCAT prefers to localize to the rim of nanodiscs in a manner that shields the membrane-binding domain (MBD), A-A, and the lid amino acids from the water phase, following the previous experimental evidence. Meanwhile, the location and conformation of LCAT in the rim of nanodisc are spatially more restricted when the active site covering lid of LCAT is in the open form. The average location and spatial dimensions of LCAT in its open form were highly compatible with the electron microscopy images. All peptide 22A variants studied here had a specific interaction site in the open LCAT structure flanked by the lid and MBD domain. The bound peptides showed different tendencies to form antiparallel dimers and, interestingly, the temporal binding site occupancies of the peptide variants affected their in vitro ability to promote LCAT-mediated cholesterol esterification.

biophysics↗

bioRxiv2021

Peer presence and familiarity as key factors to reduce cocaine intake: an effect mediated by the Subthalamic Nucleus

Stimulant use, including cocaine, often occurs in a social context whose influence is important to understand to decrease intake and reduce associated harms. Given the regulatory role of the subthalamic nucleus (STN) on cocaine intake and emotions, we investigate its role on such influence of social context on cocaine intake. We explored the influence of peer presence and familiarity on the frequency of self-administered cocaine and its neurobiological basis. We first compared cocaine intake in various conditions (alone or with peers with different characteristics: observing or self-administering, familiar or not, cocaine-naive or not, dominant or subordinate) in rats (n=90). The risk of drug consumption was reduced when a peer was present, observing or self-administering as well, and further diminished when the peer was unfamiliar (vs familiar). The presence of a cocaine-naive peer further decreased cocaine consumption. The presence of a non-familiar and drug-naive peer represents thus key conditions to diminish cocaine intake. We tested the effects of STN lesions in these various conditions and also conducted social experiments to validate the role of STN in social cognition. The STN lesion by itself reduced cocaine intake to the level reached in presence of a stranger naive peer and affected social cognition, positioning the STN as one neurobiological substrate of social influence on drug intake. Finally, with a translational research approach, we compared the drug intake in these conditions in human drug users (n=77). This human study confirmed the beneficial effect of social presence, especially of strangers. Our results indirectly support the use of social interventions and harm reduction strategies, in particular supervised consumption rooms for stimulant users.

neuroscience↗