A common plasma lipidomics signature of cardiometabolic and coronary risk in statin users

Funding Acknowledgements

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): European Commission in the H2020 program: Project SMARTool, “Simulation

Modeling of coronary ARTery disease: a tool for clinical decision support—SMARTool”

Background and aims

The coexistence of elevated plasma triglycerides (TG) and low high-density lipoprotein cholesterol (HDL-C) may contribute to the residual cardiometabolic risk of coronary artery disease (CAD) independently of total cholesterol and low-density lipoprotein cholesterol (LDL-C) absolute plasma levels [1]. Aim of this study is to assess whether a high TG/HDL-C ratio is characterized by a specific lipidomics signature in statin users and its relationship with the coronary risk score defined by coronary computed tomography angiography (CTA).

Methods

TG/HDL-C ratio was calculated in 132 patients (68.8±7.7 years, 85 males) with suspected or known CAD referred to coronary CTA and receiving statins treatment in the last 6.3 ± 1.4 years before enrolment. Patients were grouped according to TG/HDL-C ratio quartiles: IQ (≤1.694), IIQ (1.695-2.399), IIIQ (2.400-3.281), and IVQ (>3.282). Coronary CTA exams were analysed according to the modified 17-segment American Heart Association classification [2] and interpretable segments were visually assessed for degree of stenosis and plaque composition. A comprehensive coronary risk score (CTA score) [3], previously validated as predictor of adverse outcome, was calculated in each patient. Except for subjects with normal arteries (CTA score = 0), all patients were classified into 3 groups of CTA score severity:  low (score < 5), intermediate (score 5-20) and high (score > 20) risk [4]. Patient-specific plasma targeted lipidomics was performed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). This approach allowed to quantify 69 circulating lipids encompassing six lipid classes (triacylglycerol [TG], phosphatidylcholine [PC], phosphatidylethanolamine [PE], ceramide [Cer], sphingomyelin [SM], cholesterol ester [CE]). Differential analysis was performed using TG/HDL-C and CTA score annotation.

Results

18 altered lipid species in the group with higher TG/HDL-C ratio were also altered in the group with higher CTA risk score. This common set of lipids is composed of CE(16:0), CE(18:0), PC(38:2), 8 SM [SM(34:2), SM(38:2), SM(41:2), SM(41:1), SM(42:4), SM(42:3), SM(42:1), SM(43:3)], TG(52:1) and 6 PE [PE(34:0), PE(34:1), PE(34:2), PE(36:1), PE(36:2), PE(36:3)], and represents the lipidomics signature associating elevated plasma TG/HDL-C ratio with high CTA risk score in statin users.

Conclusion

In patients with stable CAD under statin treatment, a specific pattern of altered lipids, characterized by reduced plasma levels of cholesterol esters and sphingomyelins and increased levels of triacylglicerols and phosphatidylethanolamines, is associated with high TG/HDL-C ratio and high CTA score. This specific lipidomic signature identifies patients with higher residual cardiometabolic and coronary risk, not tackled by current lipid lowering therapy, unveiling possible new molecular targets of treatment.

Glial-fibrillary-acidic-protein (GFAP) biomarker detection in serum-matrix: Functionalization strategies and detection by an ultra-high-frequency surface-acoustic-wave (UHF-SAW) lab-on-chip

Glial-fibrillary-acidic-protein (GFAP) has recently drawn significant attention from the clinical environment as a promising biomarker. The pathologies which can be linked to the presence of GFAP in blood severely affect the human central nervous system. These pathologies are glioblastoma multiforme (GBM), traumatic brain injuries (TBIs), multiple sclerosis (MS), intracerebral hemorrhage (ICH), and neuromyelitis optica (NMO). Here, we develop three different detection strategies for GFAP, among the most popular in the biosensing field and never examined side by side within the experimental frame. We compare their capability of detecting GFAP in a clean-buffer and serum-matrix by using gold-coated quartz-crystal-microbalance (QCM) sensors. All the three detection strategies are based on antibodies, and each of them focuses on a key aspect of the biosensing process. The first is based on a polyethylene glycol (PEG) chain for antifouling, the second on a protein-G linker for controlling antibody-orientation, and the third on antibody-splitting and direct surface immobilization for high-surface coverage. Then, we select the best-performing protocol and validate its detection performance with an ultra-high-frequency (UHF) surface-acoustic-wave (SAW) based lab-on-chip (LoC). GFAP successful detection is demonstrated in a clean-buffer and serum-matrix at a concentration of 35 pM. This GFAP level is compatible with clinical diagnostics. This result suggests the use of our technology for the realization of a point-of-care biosensing platform for the detection of multiple brain-pathology biomarkers.

Fluorescence lifetime microscopy reveals the biologically-related photophysical heterogeneity of oxyblepharismin in light-adapted (blue) Blepharisma japonicum cells

The step-up photophobic response of the heterotrich ciliate Blepharisma japonicum is mediated by a hypericinic pigment, blepharismin, which is not present in any of the known six families of photoreceptors, namely rhodopsins, phytochromes, xanthopsins, cryptochromes, phototropins, and BLUF proteins. Upon irradiation, native cells become light-adapted (blue) by converting blepharismin into the photochemically stable oxyblepharismin (OxyBP). So far, OxyBP has been investigated mainly from a photophysical point of view in vitro, either alone or complexed with proteins. In this work, we exploit the vivid fluorescence of OxyBP to characterize its lifetime emission in blue B. Japonicum cells, on account of the recognized role of the fluorescence lifetime to provide physicochemical insights into the fluorophore environment at the nanoscale. In a biological context, OxyBP modifies its emission lifetime as compared to isotropic media. The phasor approach to fluorescence lifetime microscopy in confocal mode highlights that fluorescence originates from two excited states, whose relative balance changes throughout the cell body. Additionally, Cilia and kinetids, i.e., the organelles involved in photomovement, display lifetime asymmetry between the anterior and posterior part of the cell. From these data, some hypotheses on the phototransduction mechanism are proposed.

Compositional analysis of endogenous porphyrins from Helicobacter pylori

Bacteria able to accumulate porphyrins can be inactivated by visible light irradiation thanks to the photosensitizing properties of this class of aromatic pigments (photodynamic therapy, PDT). Since the bacterial resistance to antibiotic is growing, PDT is becoming a valid alternative. In this context, the pathogen Helicobacter pylori (Hp) is a suitable target for PDT since it spontaneously produces and accumulates porphyrins. It is then important to understand the spectroscopic behavior of these endogenous species to exploit them as photosensitizers, thus improving the results given by the application of PDT in the treatment of Hp infections. In this work we extracted porphyrins from both a laboratory-adapted and a virulent strain of Hp, and we performed spectroscopic and chromatographic experiments to collect information about the composition and the spectrophotometric features of the extracts. The main components of the porphyrin mixtures were identified and their relative contribution to the global red fluorescence was examined.

Nanoimaging: photophysical and pharmaceutical characterization of poly-lactide-co-glycolide nanoparticles engineered with quantum dots

Quantum dots (QDs) and polymeric nanoparticles (NPs) are considered good binomials for the development of multifunctional nanomedicines for multimodal imaging. Fluorescent imaging of QDs can monitor the behavior of QD-labeled NPs in both cells and animals with high temporal and spatial resolutions. The comprehension of polymer interaction with the metallic QD surface must be considered to achieve a complete chemicophysical characterization of these systems and to describe the QD optical properties to be used for their unequivocal identification in the tissue. In this study, by comparing two different synthetic procedures to obtain polymeric nanoparticles labeled with QDs, we investigated whether their optical properties may change according to the formulation methods, as a consequence of the different polymeric environments. Atomic force microscopy, transmission electron microscopy, confocal and fluorescence lifetime imaging microscopy characterization demonstrated that NPs modified with QDs after the formulation process (post-NPs-QDs) conserved the photophysical features of the QD probe. In contrast, by using a polymer modified with QDs to formulate NPs (pre-NPs-QDs), a significant quenching of QD fluorescence and a blueshift in its emission spectra were observed. Our results suggest that the packaging of QDs into the polymeric matrix causes a modification of the QD optical properties: these effects must be characterized in depth and carefully considered when developing nanosystems for imaging and biological applications.

Role of extracellular calcium and mitochondrial oxygen species in psychosine-induced oligodendrocyte cell death

Globoid cell leukodystrophy (GLD) is a metabolic disease caused by mutations in the galactocerebrosidase (GALC) gene. GALC is a lysosomal enzyme whose function is to degrade galacto-lipids, including galactosyl-ceramide and galactosyl-sphingosine (psychosine, PSY). GALC loss of function causes progressive intracellular accumulation of PSY. It is widely held that PSY is the main trigger for the degeneration of myelinating cells and progressive white-matter loss. However, still little is known about the molecular mechanisms by which PSY imparts toxicity. Here, we address the role of calcium dynamics during PSY-induced cell death. Using the human oligodendrocyte cell line MO3.13, we report that cell death by PSY is accompanied by robust cytosolic and mitochondrial calcium (Ca(2+)) elevations, and by mitochondrial reactive oxygen species (ROS) production. Importantly, we demonstrate that the reduction of extracellular calcium content by the chelating agent ethylenediaminetetraacetic acid can decrease intra-mitochondrial ROS production and enhance cell viability. Antioxidant administration also reduces mitochondrial ROS production and cell loss, but this treatment does not synergize with Ca(2+) chelation. Our results disclose novel intracellular pathways involved in PSY-induced death that may be exploited for therapeutic purposes to delay GLD onset and/or slow down its progression.

Ligand signature in the membrane dynamics of single TrkA receptor molecules

The neurotrophin receptor TrkA is critically involved in several physio-pathological processes. Still, a clear description of the early steps of ligand-induced TrkA responses at the cell plasma membrane is missing. Here we exploit single particle tracking (SPT) and TIRF microscopy to study TrkA membrane lateral mobility and changes of oligomerization state upon binding of diverse TrkA agonists (NGF, NGF R100E HSANV mutant, proNGF and NT-3). We show that, in the absence of ligands, most of TrkA receptors are fast moving monomers characterized by an average diffusion coefficient of 0.47 µm2/s; about 20% TrkA molecules are moving at least an order of magnitude slower and around 4% are almost immobile within regions of about 0.6 µm diameter. Ligand binding results in increased slow and/or immobile populations over the fast one, slowing down of non-immobile trajectories and reduction of confinement areas, observations which are consistent with the formation of receptor dimeric and oligomeric states. We demonstrate that the extent of TrkA lateral mobility modification is strictly ligand-dependent and that each ligand promotes distinct trajectory patterns of TrkA receptors at the cell membrane (ligand “fingerprinting” effect). This ligand-signature of receptor dynamics results from a differential combination of receptor-binding affinity, intracellular effectors recruited in the signalling platforms and formation of signalling/recycling endosome precursors. Thus, our data uncover a close correlation between the initial receptor membrane dynamics triggered upon binding and the specific biological outcomes induced by different ligands for the same receptor.