Different Pathways of Cellular Cholesterol Efflux

Role of miR-128-3p and miR-195-5p as biomarkers of coronary artery disease in Indians: a pilot study

Coronary artery disease (CAD) imposes a significant economic burden in developing countries like India. Timely diagnosis and treatment should be prioritized to mitigate the disease. Current diagnostic tools being invasive and less specific raise the need to develop less invasive and more reliable molecular biomarkers. MicroRNAs (miRNAs) are an emerging class of molecules that can serve as a potential source of non-invasive biomarkers for CAD. The objective of this study was to determine the potential of circulatory miRNAs as diagnostic biomarkers in CAD. In this study, we have reported two microRNAs, miR-128-3p and miR-195-5p in the serum of CAD patients in Indian Population. A total of 124 subjects were recruited which included 89 angiographically proven CAD patients and 35 control subjects. Our results show a significant decrease in the levels of miR-128-3p in CAD patients while there were no significant changes in the levels of miR-195-5p. Further bioinformatics analysis revealed the potential role of miR-128-3p in cholesterol homeostasis. Altered homeostasis due to cholesterol accumulation in macrophages is the driving force behind formation of foam cells which in turn accelerates the progression of CAD. Here, we have shown that miR-128-3p increases cholesterol levels in macrophages by decreasing cholesterol efflux in-vitro.

Decreased expression of ATP-binding cassette protein G1 promotes abnormal adipogenesis of condylar chondrocytes in temporomandibular joint osteoarthritis

BACKGROUND

Abnormal lipid metabolism is involved in the development of osteoarthritis (OA). ATP-binding cassette protein G1 (ABCG1) is crucial in mediating the outflow of cholesterol, phosphatidylcholine and sphingomyelin and reducing intracellular lipid accumulation.

OBJECTIVE

This study aimed to evaluate whether ABCG1 participates in the abnormal adipogenesis of chondrocytes in osteoarthritic cartilage of temporomandibular joint.

METHODS

Eight-week-old female rats were subjected to unilateral anterior crossbite (UAC) to induce OA in the temporomandibular joint (TMJ). Histochemical staining, immunohistochemical (IHC) staining, and qRT-PCR were performed. Primary condylar chondrocytes of rats were transfected with ABCG1 shRNA or overexpression lentivirus and then stimulated with fluid flow shear stress (FFSS). Cells were collected for oil red O staining, immunofluorescence staining, and qRT-PCR analysis.

RESULTS

Abnormal adipogenesis, characterized by increased expression of Adiponectin, CCAAT/enhancer-binding protein α (Cebpα), fatty acid binding protein 4 (Fabp4) and Perilipin1, was enhanced in the degenerative cartilage of TMJ OA in rats with UAC, accompanied by decreased expression of ABCG1. After FFSS stimulation, we observed lipid droplets in the cytoplasm of cultured cells with increased expression of Adiponectin, Cebpα, Fabp4 and Perilipin1 and decreased expression of ABCG1. Knockdown of Abcg1 induced abnormal adipogenesis and differentiation of condylar chondrocytes. Overexpression of ABCG1 alleviated the abnormal adipogenesis and differentiation of condylar chondrocytes induced by FFSS.

CONCLUSIONS

Abnormal adipogenesis of chondrocytes and decreased ABCG1 expression were observed in degenerative cartilage of TMJ OA. ABCG1 overexpression effectively inhibits the adipogenesis of chondrocytes and thus alleviates TMJ condylar cartilage degeneration.

The Role of Phospholipid Alterations in Mitochondrial and Brain Dysfunction after Cardiac Arrest

The human brain possesses three predominate phospholipids, phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylserine (PS), which account for approximately 35-40%, 35-40%, and 20% of the brain's phospholipids, respectively. Mitochondrial membranes are relatively diverse, containing the aforementioned PC, PE, and PS, as well as phosphatidylinositol (PI) and phosphatidic acid (PA); however, cardiolipin (CL) and phosphatidylglycerol (PG) are exclusively present in mitochondrial membranes. These phospholipid interactions play an essential role in mitochondrial fusion and fission dynamics, leading to the maintenance of mitochondrial structural and signaling pathways. The essential nature of these phospholipids is demonstrated through the inability of mitochondria to tolerate alteration in these specific phospholipids, with changes leading to mitochondrial damage resulting in neural degeneration. This review will emphasize how the structure of phospholipids relates to their physiologic function, how their metabolism facilitates signaling, and the role of organ- and mitochondria-specific phospholipid compositions. Finally, we will discuss the effects of global ischemia and reperfusion on organ- and mitochondria-specific phospholipids alongside the novel therapeutics that may protect against injury.

The anti-hyperlipidemia effect of Atractylodes macrocephala Rhizome increased HDL via reverse cholesterol transfer

Aim

Atractylodes macrocephala Rhizome (AM) has been used to treat hyperlipidemia for centuries, but its functional components and mechanisms are not clear. This research aimed to investigate the active components in AM and the mechanisms that underlie its anti-hyperlipidemia effect.

Methods

SD rats were fed a high-sucrose high-fat diet in conjunction with alcohol (HSHFDAC) along with different AM extracts (AMW, AMO, AME, and AMP) for 4 weeks. AM's active components were analyzed using multiple databases, and their mechanisms were explored through network pharmacology. The relationship between AM's effect of enhancing serum HDL-c and regulating the expression of reverse cholesterol transport (RCT)-related proteins (Apo-A1, LCAT, and SR-BI) was further validated in the HSHFDAC-induced hyperlipidemic rats. The kidney and liver functions of the rats were measured to evaluate the safety of AM.

Results

AMO, mainly comprised of volatile and liposoluble components, contributed the most significant anti-hyperlipidemia effect among the four extracts obtained from AM, significantly improving the blood lipid profile. Network pharmacology analysis also suggested that volatile and liposoluble components, comprise AM's main active components and they might act on signaling pathways associated with elevated HDL-c. Validation experiments found that AMO substantially and dose-dependently increased HDL-c levels, upregulated the expression of Apo-A1, SR-BI, and LCAT, improved the pathological changes in the kidney and liver, and significantly reduced the serum creatinine levels in rats with hyperlipidemia.

Conclusion

The main anti-hyperlipidemia active components of AM are its volatile and liposoluble components, which may enhance serum HDL-c by increasing the expression of the RCT-related proteins Apo-A1, LCAT, and SR-BI.

Long-term polystyrene nanoplastic exposure disrupt hepatic lipid metabolism and cause atherosclerosis in ApoE-/- mice

Nanoplastics (NPs) exposure is usually linked with abnormal inflammation and oxidative stress, which are high-risk triggers of atherosclerosis; however, whether this exposure causes the development of atherosclerosis is vague. Here, we found that PS NPs co-exposure with ox-LDL induces significant accumulation of lipid, as well as oxidative stress and inflammation in RAW264.7 macrophages. Using an ultrasound biomicroscope (UBM), we observed the emergence of atherosclerotic plaques at the aortic arch of apolipoprotein knockout (ApoE-/-) mice after being exposed to PS NPs for three months. Oil-red O and hematoxylin-eosin (H&E) staining at the mice's aortic root also observed the deposition of lipids with plaque formation. Moreover, the development of atherosclerotic disease is associated with disturbances in lipid metabolism and oxidative stress damage in the mice liver. In conclusion, this study provides additional evidence to further understand the possible cardiovascular damage caused by NPs exposure.

Promoting reverse cholesterol transport contributes to the amelioration of atherosclerosis by paeoniflorin

Reverse cholesterol transport (RCT) offers a practical approach to mitigating atherosclerosis. Paeoniflorin, a monoterpenoid glycoside found in plants of the Paeoniaceae family, has shown various effects on cardiovascular and liver diseases. Nevertheless, its impact on atherosclerosis in vivo remains poorly understood. The objective of this study is to examine the effect of paeoniflorin on atherosclerosis using apolipoprotein E-deficient (ApoE-/-) mice and explore the underlying mechanisms, with a specific focus on its modulation of RCT. ApoE-/- mice were continuously administered paeoniflorin by gavage for three months. We assessed lipid parameters in serum and examined pathological changes and gene expressions related to RCT pathways in the aorta, liver, and intestine. In an in vitro study, we utilized RAW264.7 macrophages to investigate the inhibitory effect of paeoniflorin on foam cell formation and its potential to promote RCT. The results revealed that paeoniflorin reduced atherosclerosis, alleviated hyperlipidemia, and mitigated hepatic steatosis. Paeoniflorin may promote RCT by stimulating cholesterol efflux from macrophages via the liver X receptor alpha pathway, enhancing serum high-density lipoprotein cholesterol and apolipoprotein A-I levels, and regulating key genes in hepatic and intestinal RCT. Additionally, treatment ApoE-/- mice with paeoniflorin suppressed the expression of inflammation-related genes, including CD68, tumor necrosis factor alpha, and monocyte chemoattractant protein-1, and mitigated oxidative stress in both the aorta and liver. Our results indicated that paeoniflorin has the potential to be a more effective and safer treatment for atherosclerosis, thanks to its promotion of RCT and its anti-inflammatory and anti-oxidative effects.

Enhancement of Anti-inflammatory Effects of Synthetic High-Density Lipoproteins by Incorporation of Anionic Lipids

Phosphatidylserine (PS) is an anionic phospholipid component in endogenous high-density lipoprotein (HDL). With the intrinsic anti-inflammatory effects of PS and the correlation between PS content and HDL functions, it was hypothesized that incorporating PS would enhance the therapeutic effects of HDL mimetic particles. To test this hypothesis, a series of synthetic high-density lipoproteins (sHDLs) were prepared with an apolipoprotein A-I (ApoA-1) mimetic peptide, 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC), and 1-palmitoyl-2-oleoyl-glycero-3-phospho-l-serine (POPS). Incorporating PS was found to improve the particle stability of sHDLs. Moreover, increasing the PS content in sHDLs enhanced the anti-inflammatory effects on lipopolysaccharide-activated macrophages and endothelial cells. The incorporation of PS had no negative impact on cholesterol efflux capacity, in vivo cholesterol mobilization, and did not affect the pharmacokinetic profiles of sHDLs. Such results suggest the therapeutic potential of PS-containing sHDLs for inflammation resolution in atherosclerosis and other inflammatory diseases.

SIDT2 Associates with Apolipoprotein A1 (ApoA1) and Facilitates ApoA1 Secretion in Hepatocytes

SIDT2 is a lysosomal protein involved in the degradation of nucleic acids and the transport of cholesterol between membranes. Previous studies identified two "cholesterol recognition/interaction amino acid consensus" (CRAC) motifs in SIDT1 and SIDT2 members. We have previously shown that the first CRAC motif (CRAC-1) is essential for protein translocation to the PM upon cholesterol depletion in the cell. In the present study, we show that SIDT2 and the apolipoprotein A1 (ApoA1) form a complex which requires the second CRAC-2 motif in SIDT2 to be established. The overexpression of SIDT2 and ApoA1 results in enhanced ApoA1 secretion by HepG2 cells. This is not observed when overexpressing the SIDT2 with the CRAC-2 domain mutated to render it unfunctional. All these results provide evidence of a novel role for SIDT2 as a protein forming a complex with ApoA1 and enhancing its secretion to the extracellular space.

Differential Expression of Subsets of Genes Related to HDL Metabolism and Atherogenesis in the Peripheral Blood in Coronary Artery Disease

Differential expression of genes (DEGs) in coronary artery disease (CAD) and the association between transcript level and high-density lipoprotein cholesterol (HDL-C) were studied with 76 male patients with CAD and 63 control patients. The transcript level of genes related to HDL metabolism (24 genes) and atherosclerosis-prone (41 genes) in RNA isolated from peripheral blood mononuclear cells was measured by real-time RT-PCR. Twenty-eight DEGs were identified. The expression of cholesterol transporters, ALB, APOA1, and LCAT was down-regulated, while the expression of AMN, APOE, LDLR, LPL, PLTP, PRKACA, and CETP was up-regulated. The systemic inflammation in CAD is evidenced by the up-regulation of IL1B, TLR8, CXCL5, and TNFRSF1A. For the controls, TLR8 and SOAT1 were negative predictors of the HDL-C level. For CAD patients, PRKACG, PRKCQ, and SREBF1 were positive predictors, while PRKACB, LCAT, and S100A8 were negative predictors. For CAD patients, the efficiency of reverse cholesterol transport is 73-79%, and intracellular free cholesterol seems to accumulate at hyperalphalipoproteinemia. Both atheroprotective (via S100A8) and proatherogenic (via SREBF1, LCAT, PRKACG, PRKACB, and PRKCQ) associations of gene expression with HDL-C determine HDL functionality in CAD patients. The selected key genes and involved pathways may represent HDL-specific targets for the diagnosis and treatment of CAD and atherosclerosis.

Circular RNAs Variously Participate in Coronary Atherogenesis

Over the past decade, numerous studies have shown that circular RNAs (circRNAs) play a significant role in coronary artery atherogenesis and other cardiovascular diseases. They belong to the class of non-coding RNAs and arise as a result of non-canonical splicing of premature RNA, which results in the formation of closed single-stranded circRNA molecules that lack 5'-end caps and 3'-end poly(A) tails. circRNAs have broad post-transcriptional regulatory activity. Acting as a sponge for miRNAs, circRNAs compete with mRNAs for binding to miRNAs, acting as competing endogenous RNAs. Numerous circRNAs are involved in the circRNA-miRNA-mRNA regulatory axes associated with the pathogenesis of cardiomyopathy, chronic heart failure, hypertension, atherosclerosis, and coronary artery disease. Recent studies have shown that сirc_0001445, circ_0000345, circ_0093887, сircSmoc1-2, and circ_0003423 are involved in the pathogenesis of coronary artery disease (CAD) with an atheroprotective effect, while circ_0002984, circ_0029589, circ_0124644, circ_0091822, and circ_0050486 possess a proatherogenic effect. With their high resistance to endonucleases, circRNAs are promising diagnostic biomarkers and therapeutic targets. This review aims to provide updated information on the involvement of atherogenesis-related circRNAs in the pathogenesis of CAD. We also discuss the main modern approaches to detecting and studying circRNA-miRNA-mRNA interactions, as well as the prospects for using circRNAs as biomarkers and therapeutic targets for the treatment of cardiovascular diseases.

Obicetrapib plus ezetimibe as an adjunct to high-intensity statin therapy: A randomized phase 2 trial

BACKGROUND

Obicetrapib, a selective cholesteryl ester transfer protein (CETP) inhibitor, reduces low-density lipoprotein cholesterol (LDL-C), non-high-density lipoprotein cholesterol (non-HDL-C), lipoprotein particles, and apolipoproteins, when added to high-intensity statin in patients with dyslipidemia.

OBJECTIVE

To evaluate the safety and lipid-altering efficacy of obicetrapib plus ezetimibe combination therapy as an adjunct to high-intensity statin therapy.

METHODS

This double-blind, randomized, phase 2 trial administered 10 mg obicetrapib plus 10 mg ezetimibe (n = 40), 10 mg obicetrapib (n = 39), or placebo (n = 40) for 12 weeks to patients with LDL-C >70 mg/dL and triglycerides (TG) <400 mg/dL, on stable high-intensity statin. Endpoints included concentrations of lipids, apolipoproteins, lipoprotein particles, and proprotein convertase subtilisin kexin type 9 (PCSK9), safety, and tolerability.

RESULTS

Ninety-seven patients were included in the primary analysis (mean age 62.6 years, 63.9% male, 84.5% white, average body mass index of 30.9 kg/m2). LDL-C decreased from baseline to week 12 by 63.4%, 43.5%, and 6.35% in combination, monotherapy, and placebo groups, respectively (p<0.0001 vs. placebo). LDL-C levels of <100, <70, and <55 mg/dL were achieved by 100%, 93.5%, and 87.1%, respectively, of patients taking the combination. Both active treatments also significantly reduced concentrations of non-HDL-C, apolipoprotein B, and total and small LDL particles. Obicetrapib was well tolerated and no safety issues were identified.

CONCLUSION

The combination of obicetrapib plus ezetimibe significantly lowered atherogenic lipid and lipoprotein parameters, and was safe and well tolerated when administered on top of high-intensity statin to patients with elevated LDL-C.

Is reverse cholesterol transport regulated by active cholesterol?

This review considers the hypothesis that a small portion of plasma membrane cholesterol regulates reverse cholesterol transport in coordination with overall cellular homeostasis. It appears that almost all of the plasma membrane cholesterol is held in stoichiometric complexes with bilayer phospholipids. The minor fraction of cholesterol that exceeds the complexation capacity of the phospholipids is called active cholesterol. It has an elevated chemical activity and circulates among the organelles. It also moves down its chemical activity gradient to plasma HDL, facilitated by the activity of ABCA1, ABCG1, and SR-BI. ABCA1 initiates this process by perturbing the organization of the plasma membrane bilayer, thereby priming its phospholipids for translocation to apoA-I to form nascent HDL. The active excess sterol and that activated by ABCA1 itself follow the phospholipids to the nascent HDL. ABCG1 similarly rearranges the bilayer and sends additional active cholesterol to nascent HDL, while SR-BI simply facilitates the equilibration of the active sterol between plasma membranes and plasma proteins. Active cholesterol also flows downhill to cytoplasmic membranes where it serves both as a feedback signal to homeostatic ER proteins and as the substrate for the synthesis of mitochondrial 27-hydroxycholesterol (27HC). 27HC binds the LXR and promotes the expression of the aforementioned transport proteins. 27HC-LXR also activates ABCA1 by competitively displacing its inhibitor, unliganded LXR. § Considerable indirect evidence suggests that active cholesterol serves as both a substrate and a feedback signal for reverse cholesterol transport. Direct tests of this novel hypothesis are proposed.

Long-term exposure of molybdenum disulfide nanosheets leads to hepatic lipid accumulation and atherogenesis in apolipoprotein E deficient mice

Before their large-scale applications, it is necessary to understand the biological effects of nanomaterials. Although two-dimensional nanomaterials (2D NMs) molybdenum disulfide nanosheets (MoS₂ NSs) are promising in biomedical fields, the current knowledge regarding their toxicities is inadequate. Using apolipoprotein E deficient (ApoE^-/-) mice as a long-term exposure model, this study demonstrated that intravenous (i.v.) injection of MoS₂ NSs most accumulated in the liver and caused in situ hepatic damage. Histopathological examination indicated severe infiltration of inflammatory cells and irregular central veins in the MoS₂ NSs-treated mouse liver. Meanwhile, the overwhelming expressions of inflammatory cytokines, dyslipidemia, and dysregulated hepatic lipid metabolism implied the potential vascular toxicity of MoS₂ NSs. Indeed, our result supported that MoS₂ NSs exposure is highly associated with atherosclerotic progression. This study provided the first line of evidence on the vascular toxicity of MoS₂ NSs, which remind scientists to pay attention to the rational use of MoS₂ NSs, especially in the biomedical fields.

Highlighting In Vitro the Role of Brain-like Endothelial Cells on the Maturation and Metabolism of Brain Pericytes by SWATH Proteomics

Within the neurovascular unit, brain pericytes (BPs) are of major importance for the induction and maintenance of the properties of the blood-brain barrier (BBB) carried by the brain microvessel endothelial cells (ECs). Throughout barriergenesis, ECs take advantage of soluble elements or contact with BPs to maintain BBB integrity and the regulation of their cellular homeostasis. However, very few studies have focused on the role of ECs in the maturation of BPs. The aim of this study is to shed light on the proteome of BPs solocultured (hBP-solo) or cocultured with ECs (hBP-coc) to model the human BBB in a non-contact manner. We first generated protein libraries for each condition and identified 2233 proteins in hBP-solo versus 2492 in hBP-coc and 2035 common proteins. We performed a quantification of the enriched proteins in each condition by sequential window acquisition of all theoretical mass spectra (SWATH) analysis. We found 51 proteins enriched in hBP-solo related to cell proliferation, contractility, adhesion and extracellular matrix element production, a protein pattern related to an immature cell. In contrast, 90 proteins are enriched in hBP-coc associated with a reduction in contractile activities as observed in vivo in ‘mature’ BPs, and a significant gain in different metabolic functions, particularly related to mitochondrial activities and sterol metabolism. This study highlights that BPs take advantage of ECs during barriergenesis to make a metabolic switch in favor of BBB homeostasis in vitro.

Diterpenoids inhibit ox-LDL-induced foam cell formation in RAW264.7 cells by promoting ABCA1 mediated cholesterol efflux

Introduction: Atherosclerosis is the main cause of many cardiovascular diseases and contributes to morbidity and mortality worldwide. The formation of macrophage-derived foam cells plays a critical role in the early stage of atherosclerosis pathogenesis. Diterpenoids found in the flowers of Callicarpa rubella Lindl., a traditional Chinese medicine, have been reported to have anti-inflammatory activity. However, little is known about the effects of these diterpenoids on macrophage foam cell formation. Methods: A macrophage-derived foam cell formation model was established by treating RAW264.7 cells with oxidized low-density lipoprotein (ox-LDL) for 24 h. Oil red O staining were used to detect the intracellular lipids. The cholesterol efflux capacity was assayed by labeling cells with 22-NBD-cholesterol. Western blots and real-time PCRs were performed to quantify protein and mRNA expressions. Results: Two diterpenoid molecules, 14α-hydroxyisopimaric acid (C069002) and isopimaric acid (C069004), extracted from the flowers of Callicarpa rubella Lindl., significantly attenuated ox-LDL-induced foam cell formation in RAW264.7 macrophages. Further investigation showed that these two diterpenoids could promote cholesterol efflux from RAW264.7 macrophages to apolipoprotein A-I or high-density lipoproteins, which was associated with upregulated expression of ATP-binding cassette A1/G1 (ABCA1/G1), liver X receptor-α (LXRα), and peroxisome proliferator-activated receptor-γ (PPARγ). Unexpectedly, the diterpenoids C069002 and C069004 failed to enhance the mRNA transcription of the ABCG1 gene in macrophage-derived foam cells induced by ox-LDL. To evaluate the effects of diterpenoids on macrophage foam cell formation and determine the underlying mechanism, two drugs (lovastatin and rosiglitazone) were used as positive controls. Although both drugs could reduce macrophage foam cell formation and promote cholesterol efflux, they each had distinctive abilities to modulate the expression of cholesterol efflux-related genes. In contrast to lovastatin, rosiglitazone showed a similar influence on the expression of cholesterol efflux-related genes (including ABCA1, LXRα, and PPARγ) as the diterpenoids regardless of the presence or absence of ox-LDL, implying a similar mechanism by which they may exert atheroprotective effects. Conclusion: Our research indicates that diterpenoids effectively inhibit ox-LDL-induced macrophage foam cell formation by promoting cholesterol efflux from macrophages via the PPARγ-LXRα-ABCA1 pathway. Further investigation of diterpenoids as potential drugs for the treatment of atherosclerosis is warranted.

ISG15 Is a Novel Regulator of Lipid Metabolism during Vaccinia Virus Infection

Interferon-stimulated gene 15 (ISG15) is a 15-kDa ubiquitin-like modifier that binds to target proteins in a process termed ISGylation. ISG15, first described as an antiviral molecule against many viruses, participates in numerous cellular processes, from immune modulation to the regulation of genome stability. Interestingly, the role of ISG15 as a regulator of cell metabolism has recently gained strength. We previously described ISG15 as a regulator of mitochondrial functions in bone marrow-derived macrophages (BMDMs) in the context of Vaccinia virus (VACV) infection. Here, we demonstrate that ISG15 regulates lipid metabolism in BMDMs and that ISG15 is necessary to modulate the impact of VACV infection on lipid metabolism. We show that Isg15-/- BMDMs demonstrate alterations in the levels of several key proteins of lipid metabolism that result in differences in the lipid profile compared with Isg15+/+ (wild-type [WT]) BMDMs. Specifically, Isg15-/- BMDMs present reduced levels of neutral lipids, reflected by decreased lipid droplet number. These alterations are linked to increased levels of lipases and are independent of enhanced fatty acid oxidation (FAO). Moreover, we demonstrate that VACV causes a dysregulation in the proteomes of BMDMs and alterations in the lipid content of these cells, which appear exacerbated in Isg15-/- BMDMs. Such metabolic changes are likely caused by increased expression of the metabolic regulators peroxisome proliferator-activated receptor-γ (PPARγ) and PPARγ coactivator-1α (PGC-1α). In summary, our results highlight that ISG15 controls BMDM lipid metabolism during viral infections, suggesting that ISG15 is an important host factor to restrain VACV impact on cell metabolism. IMPORTANCE The functions of ISG15 are continuously expanding, and growing evidence supports its role as a relevant modulator of cell metabolism. In this work, we highlight how the absence of ISG15 impacts macrophage lipid metabolism in the context of viral infections and how poxviruses modulate metabolism to ensure successful replication. Our results open the door to new advances in the comprehension of macrophage immunometabolism and the interaction between VACV and the host.

Bidirectional Control between Cholesterol Shuttle and Purine Signal at the Central Nervous System

Recent studies have highlighted the mechanisms controlling the formation of cerebral cholesterol, which is synthesized in situ primarily by astrocytes, where it is loaded onto apolipoproteins and delivered to neurons and oligodendrocytes through interactions with specific lipoprotein receptors. The “cholesterol shuttle” is influenced by numerous proteins or carbohydrates, which mainly modulate the lipoprotein receptor activity, function and signaling. These molecules, provided with enzymatic/proteolytic activity leading to the formation of peptide fragments of different sizes and specific sequences, could be also responsible for machinery malfunctions, which are associated with neurological, neurodegenerative and neurodevelopmental disorders. In this context, we have pointed out that purines, ancestral molecules acting as signal molecules and neuromodulators at the central nervous system, can influence the homeostatic machinery of the cerebral cholesterol turnover and vice versa. Evidence gathered so far indicates that purine receptors, mainly the subtypes P2Y2, P2X7 and A2A, are involved in the pathogenesis of neurodegenerative diseases, such as Alzheimer’s and Niemann–Pick C diseases, by controlling the brain cholesterol homeostasis; in addition, alterations in cholesterol turnover can hinder the purine receptor function. Although the precise mechanisms of these interactions are currently poorly understood, the results here collected on cholesterol–purine reciprocal control could hopefully promote further research.