Effects of α-Lipoic Acid on Phagocytosis of Oligomeric Beta-Amyloid1–42 in BV-2 Mouse Microglial Cells

Background and objectives: This study aimed to investigate the enhancing effect of vitamin-like alpha-lipoic acid (ALA) on phagocytosis of oligomeric beta-amyloid (oAβ)1–42 in BV-2 mouse microglial cells.Methods: An in vitro model was established to investigate phagocytosis of oAβ1–42 in BV-2 cells. Transmission electron microscopy images indicated that the morphology of prepared oAβ1–42 was spherical particles. BV-2 cells treated with ALA were incubated with 5(6)-carboxyfluorescein-labeled oAβ1–42 (FAM-oAβ1–42) for 24 h, followed by flow cytometer analysis, western blotting, real-time quantitative PCR, and immunocytochemistry (ICC) analysis to assess the in vitro phagocytosis ability of oAβ1–42.Results: Alpha-lipoic acid significantly increased messenger RNA (mRNA) expression of the CD36 receptor in BV-2 cells. ICC analysis showed that ALA significantly elevated CD36 protein expression in BV-2 cells both with and without oAβ1–42 treatment. Results from the flow cytometry analysis indicated that the CD36 receptor inhibitor significantly attenuated ALA-promoted phagocytosis of FAM-oAβ1–42 in BV-2 cells. Moreover, ICC analysis revealed that ALA caused the translocation of peroxisome proliferator-activated receptor-γ (PPAR-γ), which is known to regulate the expression of CD36 mRNA in BV-2 cells. ALA also elevated both the mRNA and protein expression of cyclooxygenase-2 (COX-2), which is a key enzyme involved in the synthesis of 15-deoxy-Δ12,14-prostaglandin J2 in BV-2 cells.Conclusion: We postulated that ALA enhances oAβ1–42 phagocytosis by upregulating the COX-2/15-deoxy-Δ12,14-prostaglandin J2/PPAR-γ/CD36 pathway in BV-2 cells. Finally, future studies should be conducted with an in vivo study to confirm the findings.

Rapamycin-Loaded Polymeric Nanoparticles as an Advanced Formulation for Macrophage Targeting in Atherosclerosis

Recently, rapamycin (Rapa) represents a potential drug treatment to induce regression of atherosclerotic plaques; however, its use requires site-specific accumulation in the vessels involved in the formation of the plaques to avoid the systemic effects resulting from its indiscriminate biodistribution. In this work, a stable pharmaceutical formulation for Rapa was realized as a dried powder to be dispersed extemporaneously before administration. The latter was constituted by mannitol (Man) as an excipient and a Rapa-loaded polymeric nanoparticle carrier. These nanoparticles were obtained by nanoprecipitation and using as a starting polymeric material a polycaprolactone (PCL)/α,β-poly(N-2-hydroxyethyl)-dl-aspartamide (PHEA) graft copolymer. To obtain nanoparticles targeted to macrophages, an oxidized phospholipid with a high affinity for the CD36 receptor of macrophages, the 1-(palmitoyl)-2-(5-keto-6-octene-dioyl) phosphatidylcholine (KOdia-PC), was added to the starting organic phase. The chemical–physical and technological characterization of the obtained nanoparticles demonstrated that: both the drug loading (DL%) and the entrapment efficiency (EE%) entrapped drug are high; the entrapped drug is in the amorphous state, protected from degradation and slowly released from the polymeric matrix; and the KOdia-PC is on the nanoparticle surface (KP-Nano). The biological characterization demonstrated that both systems are quickly internalized by macrophages while maintaining the activity of the drug. In vitro studies demonstrated that the effect of KP-Nano Rapa-loaded, in reducing the amount of the Phospo-Ser757-ULK1 protein through the inhibition of the mammalian target of rapamycin (mTOR), is comparable to that of the free drug.

Dietary fatty acids and CD36-mediated cholesterol homeostasis: potential mechanisms

Currently, the prevention and treatment of CVD have been a global focus since CVD is the number one cause of mortality and morbidity. In the pathogenesis of CVD, it was generally thought that impaired cholesterol homeostasis might be a risk factor. Cholesterol homeostasis is affected by exogenous factors (i.e. diet) and endogenous factors (i.e. certain receptors, enzymes and transcription factors). In this context, the number of studies investigating the potential mechanisms of dietary fatty acids on cholesterol homeostasis have increased in recent years. As well, the cluster of differentiation 36 (CD36) receptor is a multifunctional membrane receptor involved in fatty acid uptake, lipid metabolism, atherothrombosis and inflammation. CD36 is proposed to be a crucial molecule for cholesterol homeostasis in various mechanisms including absorption/reabsorption, synthesis, and transport of cholesterol and bile acids. Moreover, it has been reported that the amount of fatty acids and fatty acid pattern of the diet influence the CD36 level and CD36-mediated cholesterol metabolism principally in the liver, intestine and macrophages. In these processes, CD36-mediated cholesterol and lipoprotein homeostasis might be impaired by dietary SFA and trans-fatty acids, whereas ameliorated by MUFA in the diet. The effects of PUFA on CD36-mediated cholesterol homeostasis are controversial depending on the amount of n-3 PUFA and n-6 PUFA, and the n-3:n-6 PUFA ratio. Thus, since the CD36 receptor is suggested to be a novel nutrient-sensitive biomarker, the role of CD36 and dietary fatty acids in cholesterol metabolism might be considered in medical nutrition therapy in the near future. Therefore, the novel nutritional target of CD36 and interventions that focus on dietary fatty acids and potential mechanisms underlying cholesterol homeostasis are discussed in this review.

PCSK9 Regulates Nox2-Mediated Platelet Activation via CD36 Receptor in Patients with Atrial Fibrillation

Background: High levels of proprotein convertase subtilisin/kexin 9 (PCSK9) is predictive of cardiovascular events (CVEs) in atrial fibrillation (AF). We hypothesized that PCSK9 may directly induce platelet activation (PA). Methods: We measured platelet aggregation, recruitment, Thromboxane B2 (TxB2) formation and soluble P-selectin levels as markers of PA and soluble Nox2-derived peptide (sNox2-dp), H2O2, isoprostanes and oxidized Low-Density-Lipoprotein (oxLDL) to analyze oxidative stress (OS) in 88 patients having PCSK9 values < (n = 44) or > (n = 44) 1.2 ng/mL, balanced for age, sex and cardiovascular risk factors. Furthermore, we investigated if normal (n = 5) platelets incubated with PCSK9 (1.0–2.0 ng/mL) alone or with LDL (50 µg/mL) displayed changes of PA, OS and down-stream signaling. Results: PA and OS markers were significantly higher in patients with PCSK9 levels > 1.2 ng/mL compared to those with values < 1.2 ng/mL (p < 0.001). Levels of PCSK9 significantly correlated with markers of PA and OS. Platelets incubation with PCSK9 increased PA, OS and p38, p47 and Phospholipase A2 (PLA2) phosphorylation. These changes were amplified by adding LDL and blunted by CD36 or Nox2 inhibitors. Co-immunoprecipitation analysis revealed an immune complex of PCSK9 with CD36. Conclusions: We provide the first evidence that PCSK9, at concentration found in the circulation of AF patients, directly interacts with platelets via CD36 receptor and activating Nox2: this effect is amplified in presence of LDL.

SERS analysis of carcinoma-associated fibroblasts in a tumor microenvironment based on targeted 2D nanosheets

Ligand-grafted 2D SERS substrate is applied for monitoring the evolution of CAFs in TME by specifically recognizing the CD36 receptor on cytomembrane of the fibroblasts.