Macrophage Foam Cell Formation Research Articles

Terpene Lactucopicrin Limits Macrophage Foam Cell Formation by a Reduction of Lectin-Like Oxidized Low-Density Lipoprotein Receptor-1 in Lipid Rafts.

Sustained inflammation promotes macrophage foam cell formation by promoting cholesterol influx and impairing cholesterol efflux. Terpene lactucopicrin, affluent in vegetables of the Asteraceae family (e.g., chicory, curly escarole, and lettuce) can inhibit atherogenesis in mice. However, it remains unknown whether and how lactucopicrin regulates macrophage foam cell formation. Lactucopicrin at physiologically reachable concentrations inhibits oxidized low-density lipoprotein (oxLDL)-induced foam cell formation in inflammatory mouse bone marrow derived macrophages established by 50 pg mL-1 of LPS, reachable level in patients with metabolic endotoxemia. This effect is not due to modulation of cholesterol efflux, but reliant on a reduction in lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1)-mediated cholesterol influx. Mechanistically, lactucopicrin does not affect LOX-1 expression, cellular oxidative stress, and exocytosis, known mechanisms regulating LOX-1 function in cholesterol influx. Strikingly, lactucopicrin selectively decreases LOX-1 content in lipid rafts, an effect responsible for the lactucopicrin effect on cholesterol influx. Moreover, ApoE-/- mice fed a high fat diet supplemented with lactucopicrin for 12 weeks display fewer macrophage foam cells within atherosclerotic plaques relative to the control mice. Lactucopicrin limits macrophage foam cell formation through a reduction of LOX-1 distribution in lipid rafts, thus contributing to its atheroprotective effect.

Influences of Unmodified and Carboxylated Carbon Nanotubes on Lipid Profiles in THP-1 Macrophages: A Lipidomics Study.

Since the possible roles of surface modifications in determining multi-walled carbon nanotube (MWCNT)-promoted endoplasmic reticulum (ER) stress-mediated lipid-laden macrophage foam cell formation are still in debate, we compared unmodified and carboxylated MWCNT-induced cytotoxicity, lipid profile changes, and expression of ER stress genes in THP-1 macrophages. Particularly, we focused on lipid profile changes by using lipidomics approaches. We found that unmodified and carboxylated MWCNTs significantly decreased cellular viability and appeared to damage the cellular membrane to a similar extent. Likewise, the results from Oil Red O staining showed that both types of MWCNTs slightly but significantly induced lipid accumulation. In keeping with Oil Red O staining results, lipidomics data showed that both types of MWCNTs up-regulated most of the lipid classes. Interestingly, almost all lipid classes were relatively higher in carboxylated MWCNT-exposed THP-1 macrophages compared with unmodified MWCNT-exposed cells, indicating that carboxylated MWCNTs more effectively changed lipid profiles. But in contrast to our expectation, none of the MWCNTs significantly induced the expression of ER stress genes. Even, compared with carboxylated MWCNTs, unmodified MWCNTs induced higher expression of lipid genes, including macrophage scavenger receptor 1 and fatty acid synthase. Combined, our results suggested that even though carboxylation did not significantly affect MWCNT-induced lipid accumulation, carboxylated MWCNTs were more potent to alter lipid profiles in THP-1 macrophages, indicating the need to use omics techniques to understand the exact nanotoxicological effects of MWCNTs. However, the differential effects of unmodified and carboxylated MWCNTs on lipid profiles might not be related with the induction of ER stress.

C1q Tumor Necrosis Factor-Related Protein 1: A Promising Therapeutic Target for Atherosclerosis.

Atherosclerosis serves as the pathological basis of most cardiovascular and cerebrovascular diseases. C1q tumor necrosis factor-related protein 1 (CTRP1) is a 35-kDa glycoprotein synthesized by various tissues and cells, such as adipose tissue and macrophages. As an adiponectin paralog, CTRP1 signals through adiponectin receptor 1 and participates in a variety of pathophysiological processes. Circulating CTRP1 levels are significantly increased in patients with coronary artery disease. Importantly, CTRP1 was shown to accelerate the development of atherosclerosis by promoting vascular inflammation, macrophage foam cell formation, and endothelial barrier dysfunction. This review focused on recent advances regarding the role of CTRP1 in atherogenesis with an emphasis on its potential as a novel biomarker and a promising therapeutic target for atherosclerosis-related diseases.

Abstract 11314: Trpm2 Deletion Alleviates Atherosclerosis by Inhibiting the Activation of CD36 in Macrophages

Introduction: Atherosclerosis and its complications are the leading cause of death. The central pathological features of atherosclerosis are macrophage infiltration and foam cell formation, in which CD36 is crucial in activating macrophages and mediating the uptake of cholesterol. However, mechanisms regulating the activation of CD36 remain unclear. TRPM2 is an Ca 2+ permeable channel activated by oxidative stress, which occurs in the activation of macrophages. Hypothesis: We hypothesized that during atherosclerosis, TRPM2 is critical for the activation of CD36 in macrophages. Thus, Trpm2 deletion inhibits macrophage activation and foam cell formation. Methods: ApoE -/- mice and ApoE -/- mice with Trpm2 deletion were fed with high-fat food to induce atherosclerosis. Oil red O and immunofluorescence staining were performed to evaluate lipid deposition and macrophage load in aorta. Transwell assay was used to test macrophage infiltration and emigration. Oxidized LDL (oxLDL) or thrombospondin-1 (TSP1) was used to activate CD36. Western blot was used to examine the activation of CD36 signaling. ROS and Ca 2+ imaging were performed to examine the activation of macrophages by CD36. Results: Trpm2 deletion: (1) reduced lesion ratio (0.13 ± 0.02 vs 0.36 ± 0.02) and macrophage load (20.93 ± 4.82 / mm 2 vs 60.20 ± 8.36 / mm 2 ) in aorta; (2) inhibited oxLDL uptake (32.24 ± 7.65 % vs 100 %) by macrophages; (3) suppressed macrophage infiltration (15.83 ± 2.44 / mm 2 vs 46.83 ± 4.62 / mm 2 ) and preserved macrophage emigration (15.5 ± 1.73 / mm 2 vs 5.0 ± 0.73 / mm 2 ); (4) inhibited ROS production (5.32 ± 0.61 % vs 28.82 ± 1.48 %) and increase of intracellular Ca 2+ (2.92 ± 0.86 % vs 11.95 ± 1.60 %) in macrophages induced by oxLDL (n= 6 ~ 8 for all data). Also, oxLDL and TSP1 activated TRPM2 via CD36, and TRPM2 was required for the activation of CD36 signaling in macrophages by oxLDL or TSP1. Conclusions: In summary, TRPM2 and CD36 activated each other in macrophages, which promoted the development of atherosclerosis.

Atheroprotective Effects and Molecular Mechanism of Berberine.

Cardiovascular diseases remain the leading cause of morbidity and mortality worldwide. Atherosclerosis is the main pathological basis of cardiovascular diseases and it is closely associated with hyperlipidemia, endothelial injury, macrophage-derived foam cells formation, proliferation and migration of vascular smooth muscle cells (VSMCs), platelet aggregation, and altered gut microbiota. Various symptomatic treatments, that are currently used to inhibit atherosclerosis, need to be administered in long term and their adverse effects cannot be ignored. Berberine (BBR) has beneficial effects on atherosclerosis through regulating multiple aspects of its progression. This review highlights the recent advances in understanding the anti-atherosclerosis mechanism of BBR. BBR alleviated atherosclerosis by attenuation of dyslipidemia, correction of endothelial dysfunction, inhibition of macrophage inflammation and foam cell formation, activation of macrophage autophagy, regulation of the proliferation and migration of VSMCs, attenuation of platelet aggregation, and modulation of gut microbiota. This review would provide a modern scientific perspective to further understanding the molecular mechanism of BBR attenuating atherosclerosis and supply new ideas for atherosclerosis management.

Angiotensin II induces the expression of periostin to promote foam cell formation in oxLDL-treated macrophages

A matricellular protein periostin has been documented to promote macrophage recruitment in atherosclerotic lesions. However, the role of periostin in macrophage foam cell formation is still unknown. In this study, we examined the expression and function of periostin in cholesterol homeostasis in macrophages. The role of periostin in mediating Ang II-induced foam cell formation was also investigated. The mechanism by which Ang II induced the expression of periostin was explored. It was found that oxLDL treatment significantly increased the expression and secretion of periostin in THP-1 macrophages. Knockdown of periostin blocked oxLDL-induced lipid accumulation and enhanced cholesterol efflux. In contrast, treatment with recombinant periostin protein enhanced oxLDL-induced macrophage foam cell formation. Ang II caused a time-dependent induction of periostin in THP-1 macrophages, which was ascribed to Twist2-mediated transactivation of periostin. Ang II treatment significantly augmented lipid accumulation in THP-1 macrophages, and knockdown of periostin blocked the effect of Ang II on foam cell formation. Moreover, periostin depletion restored cholesterol efflux in Ang II-treated THP-1 macrophages. Clinically, there was a significant positive correlation between serum periostin and Ang II levels in patients with atherosclerosis. Collectively, we show that periostin is essential for Ang II-induced enhancement of macrophage foam cell formation via suppression of cholesterol efflux.

The Liver and Heart: How the Two Most Beloved “Babies” in the Human Body Communicate

The Liver and Heart: How the Two Most Beloved “Babies” in the Human Body Communicate

Desmosterol suppresses macrophage inflammasome activation and protects against vascular inflammation and atherosclerosis

Cholesterol biosynthetic intermediates, such as lanosterol and desmosterol, are emergent immune regulators of macrophages in response to inflammatory stimuli or lipid overloading, respectively. However, the participation of these sterols in regulating macrophage functions in the physiological context of atherosclerosis, an inflammatory disease driven by the accumulation of cholesterol-laden macrophages in the artery wall, has remained elusive. Here, we report that desmosterol, the most abundant cholesterol biosynthetic intermediate in human coronary artery lesions, plays an essential role during atherogenesis, serving as a key molecule integrating cholesterol homeostasis and immune responses in macrophages. Depletion of desmosterol in myeloid cells by overexpression of 3β-hydroxysterol Δ24-reductase (DHCR24), the enzyme that catalyzes conversion of desmosterol to cholesterol, promotes the progression of atherosclerosis. Single-cell transcriptomics in isolated CD45+CD11b+ cells from atherosclerotic plaques demonstrate that depletion of desmosterol increases interferon responses and attenuates the expression of antiinflammatory macrophage markers. Lipidomic and transcriptomic analysis of invivo macrophage foam cells demonstrate that desmosterol is a major endogenous liver X receptor (LXR) ligand involved in LXR/retinoid X receptor (RXR) activation and thus macrophage foam cell formation. Decreased desmosterol accumulation in mitochondria promotes macrophage mitochondrial reactive oxygen species production and NLR family pyrin domain containing 3 (NLRP3)-dependent inflammasome activation. Deficiency of NLRP3 or apoptosis-associated speck-like protein containing a CARD (ASC) rescues the increased inflammasome activity and atherogenesis observed in desmosterol-depleted macrophages. Altogether, these findings underscore the critical function of desmosterol in the atherosclerotic plaque to dampen inflammation by integrating with macrophage cholesterol metabolism and inflammatory activation and protecting from disease progression.

Swiprosin-1 deficiency in macrophages alleviated atherogenesis

Macrophages play a vital role in the development of atherosclerosis. Previously, we have found that swiprosin-1 was abundantly expressed in macrophages. Here, we investigated the role of swiprosin-1 expressed in macrophages in atherogenesis. Bone marrow transplantation was performed from swiprosin-1-knockout (Swp−/−) mice and age-matched ApoE−/− mice. Atherosclerotic lesion, serum lipid, and interleukin-β (IL-β) levels were detected. In vitro, the peritoneal macrophages isolated from Swp−/− and wild-type mice were stimulated with oxidized low-density lipoprotein (ox-LDL) and the macrophage of foam degree, cellular lipid content, apoptosis, inflammatory factor, migration, and autophagy were determined. Our results showed that swiprosin-1 was mainly expressed in macrophages of atherosclerotic plaques in aorta from ApoE−/− mice fed with high-cholesterol diet (HCD). The expression of swiprosin-1 in the foaming of RAW264.7 macrophages gradually increased with the increase of the concentration and time stimulated with ox-LDL. Atherosclerotic plaques, accumulation of macrophages, collagen content, serum total cholesterol, LDL, and IL-β levels were decreased in Swp−/− → ApoE−/− mice compared with Swp+/+ → ApoE−/− mice fed with HCD for 16 weeks. The macrophage foam cell formation and cellular cholesterol accumulation were reduced, while the lipid uptake and efflux increased in macrophages isolated from Swp−/− compared to wild-type mice treated with ox-LDL. Swiprosin-1 deficiency in macrophages could inhibit apoptosis, inflammation, migration, and promote autophagy. Taken together, our results demonstrated that swiprosin-1 deficiency in macrophages could alleviate the development and progression of AS. The role of swiprosin-1 may provide a promising new target for ameliorating AS.

Candida albicans Induces Foaming and Inflammation in Macrophages through FABP4: Its Implication for Atherosclerosis.

Atherosclerosis is a chronic degenerative disorder characterized by lipid-dense plaques and low-grade inflammation affecting arterial walls. Foamy macrophages are important in the formation of atherosclerotic plaques and the induction of low-grade inflammation. The presence of lipid-laden macrophages has occurred in infections caused by opportunistic pathogens. Candida albicans is the major cause of candidiasis in immunocompromised patients, including those with diabetes mellitus. However, the role played by C. albicans in macrophage foaming and the associated inflammation is poorly understood. We investigated whether C. albicans induces foaming along with inflammation in macrophages and, if so, by which mechanism(s). We incubated THP-1 macrophages with heat-killed C. albicans (HKCA). HKCA-induced lipid accumulation in macrophages along with increased expression of inflammatory markers, including CD11b and CD11c or expression and secretion of IL-1β. HKCA also increased the expression of PPARγ, CD36, and FABP4 in macrophages. Mechanistically, we found that the foamy and inflammatory macrophage phenotype induced by HKCA requires FABP4 because disruption of FABP4 in macrophages either by chemical inhibitor BMS309404 or small interfering RNA (siRNA) abrogated foam cell formation and expression of inflammatory markers CD11b, CD11c, and IL-1β. Furthermore, HKCA-treated macrophages displayed high expression and secretion of MMP-9. Inhibition of FABP4 resulted in suppression of HCKA-induced MMP-9 production. Overall, our results demonstrate that C. albicans induces foam cell formation, inflammation, and MMP-9 expression in macrophages via the upregulation of FABP4, which may constitute a novel therapeutic target for treating C. albicans-induced atherosclerosis.

Dapagliflozin decreases atherosclerotic plaque instability via regulating macrophage pyroptosis

Abstract Background Vulnerable plaques are characterized by infiltration of inflammatory cells, playing a key role in the progression of acute coronary events. It's important to clarify the inflammatory mechanism of unstable plaque formation. Several clinical trials have demonstrated that dapagliflozin could reduce major adverse cardiac events in whether diabetic or non-diabetic patients. However, the underlying cardioprotective mechanism of dapagliflozin remains unclear. This study was aimed to investigate the role of dapagliflozin in regulating macrophage pyroptosis and vulnerable plaque formation. Methods 20 ApoE−/− mice (control) were fed with high fat diet while another 20 ApoE−/− mice were challenged with high fat diet plus dapagliflozin for 12 weeks. The extent and instability of atherosclerotic plaque was determined by oil-red staining, HE staining, immunofluorescence staining and electron microscopy. Changes in subsets of immune cells were evaluated by flow cytometry. Plasma cytokines were assessed by ELISA. Microarray analysis was applied to detect gene expressions while Western blot and real-time PCR was used to assess gene expression levels. Results Morphology studies revealed that dapagliflozin could inhibit plaque formation and reduce instability in ApoE−/− mice. FACS data showed that dapagliflozin could decrease CD11b+Ly6Chigh M1 macrophages differentiation and inhibit foam cells formation in ApoE−/− mice. Microarray analysis and in vitro studies exhibited that dapagliflozin could induce the down regulation of NLRP3, caspase-1, IL-1β, IL-18 and MMP-7/10/12/14 to retard macrophage pyroptosis and foam cell formation. Conclusions We have characterized a novel role for dapagliflozin in modulating atherosclerotic lesion development and progression. We envision that this study may provide several potential therapeutic targets for treatment of acute coronary syndromes. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): Shanghai Sailing Program

Investigation of the effective components inhibited macrophage foam cell formation in Ophiopogonis Radix

Ethnopharmacological relevanceOphiopogonis Radix, the commonly used traditional Chinese medicine in clinic for treating cardiovascular diseases, is returned to the stomach, lung and heart meridian. It is reported to nourish yin, moisten lung and is used to treat heart yin deficiency syndromes and asthenia of heart and lung, which indicated that Ophiopogonis Radix may have a protective effect on heart disorders. Atherosclerosisis is an important process in the development of cardiovascular diseases and abnormal lipid deposition induced macrophage foam cells is its crucial foundation. Our previous study showed the extract of Ophiopogonis Radix (EOR) ameliorates atherosclerosis in vitro. However, it may protect against cardiovascular diseases through inhibiting macrophage foam cell formation and its potential effective components and mechanisms are still unclear. Aim of the studyOur study aimed to investigate the effect of Ophiopogonis Radix on macrophage foam cell formation and its potential active constituents and mechanisms. Materials and methodsOx-LDL induced macrophage cells were employed to evaluate the effect of Ophiopogonis Radix on macrophage foam cell formation. Then the potential active constituents inhibited formation of macrophage foam cells were screened by biospecific cell extraction and its underlying mechanisms were also explored by Western blot. ResultsThe extract of Ophiopogonis Radix was found to significantly inhibit macrophage foam cell formation, evidenced by the decrease of TG and TC and Oil Red O staining analysis in macrophage cells, which indicated that EOR reduced the formation of macrophage foam cells. At the same time, EOR was showed to increase antioxidant capacity in macrophage cells. After treatment with EOR, two potential active components interacted with macrophage foam cells specifically were identified to inhibit macrophage foam cell formation including methylophiopogonanone A and methylophiopogonanone B. Methylophiopogonanone A was then proved to decrease the expression of CD36, Lox-1 and SREBP2, increase the expression of ABCA1 obviously, while the expression of ABCG1 and SREBP1 had no changes. ConclusionsIn our study, Ophiopogonis Radix was found to protect against atherosclerosis through suppressing ox-LDL induced macrophage foam cell formation and two potential compounds were identified by biospecific cell extraction including methylophiopogonanone A and methylophiopogonanone B. Moreover, methylophiopogonanone A was proved to inhibit foam cells through reducing uptake, synthesis and increasing efflux, which may provide guidance and reference for application of Ophiopogonis Radix and investigation of the effective components of TCMs.

The Cholinergic Anti-Inflammatory Pathway Attenuates the Development of Atherosclerosis in Apoe-/- Mice through Modulating Macrophage Functions.

(1) Background: The cholinergic anti-inflammatory pathway (CAP) has been implicated in the regulation of various diseases, including chronic inflammatory cardiovascular disorders such as atherosclerosis (AS). This study aims to explore the underlying regulatory mechanisms of CAP activity in the progression of AS. (2) Methods: The Apoe-/- mice were subjected to sham, bilateral cervical vagotomy surgery (VGX), and VGX supplemented with Gainesville Tokushima scientists (GTS)-21 (4 mg/kg/d) and then fed with a high-fat diet for 10 weeks. Atherosclerotic lesion size and inflammation levels were investigated by histology and inflammatory cytokines analysis. The blood M1/M2 macrophages were analyzed by flow cytometry. Primary mouse bone marrow-derived macrophages (BMDM), peritoneal macrophages, and RAW264.7 cells were treated with CAP agonists acetylcholine (Ach) and GTS-21 to study their effects on macrophage functions. (3) Results: Compared with the sham group, inhibition of CAP by the VGX resulted in growing aortic lipid plaque area, deteriorated inflammatory levels, and aberrant quantity of M1/M2 macrophages in Apoe-/- mice. However, these detrimental effects of VGX were significantly ameliorated by the reactivation of CAP through GTS-21 treatment. The in vitro study using macrophages revealed that stimulation with CAP agonists suppressed M1, but promoted M2 macrophage polarization through the upregulation of TNFAIP3 and phosphorylation STAT3 levels, respectively. Moreover, the activation of CAP inhibited the formation of macrophage foam cells in the peritoneal cavity by regulating genes related to cholesterol metabolism. (4) Conclusions: This study provides novel evidence and mechanisms that the CAP plays an important role in the regulation of AS development by controlling macrophage functions, implying a potential use of CAP activation as a therapeutic strategy for AS treatment.

Abstract P183: FFAR4: A Novel Target In Preventing Atherosclerosis?

Free fatty acid receptor 4 (FFAR4), also known as G-protein coupled receptor 120 (GPR120), is a long-chain unsaturated fatty acid receptor expressed in adipocytes, endothelial cells, and macrophages. Activation of FFAR4 helps maintain metabolic homeostasis by regulating adipogenesis, insulin sensitivity, and inflammation. While FFAR4 is best known for its role its role in preventing obesity and diabetes, recent studies have demonstrated that FFAR4 may also play an important role in the development of atherosclerosis and cardiovascular disease (CVD). Given FFAR4’s importance in anti-inflammatory signaling and high expression levels in macrophages, we designed experiments to test the hypothesis that FFAR4 prevents the development of atherosclerosis by reversing macrophage foam cell formation, a hallmark of early atherogenesis. In these studies, we isolated peritoneal macrophages from wild-type C57/Bl6 mice and incubated them with 20 μg/ml oxidized low-density lipoprotein (oxLDL) to generate foam cells. We then investigated the effects of FFAR4 activation on lipid accumulation, cytokine secretion, and cholesterol efflux. We found that activation of FFAR4 with synthetic agonist GW9508 reduced lipid accumulation as observed by decreased Oil Red O staining and reduced cellular cholesterol content. Activation of FFAR4 by GW9508 also decreased macrophage secretion of pro-inflammatory cytokines interleukin 1 beta (IL-1β) by 5.3-fold, interleukin 6 (IL-6) by 2.4-fold, monocyte chemoattractant protein-1 (MCP-1) by 44.1-fold, and tumor necrosis factor alpha (TNFα) by 2.4-fold. Additionally, activation of FFAR4 by GW9508 significantly increased [ 3 H] cholesterol efflux to high-density lipoprotein (HDL) from peritoneal macrophages. Taken together, our results support an exciting and novel protective role for FFAR4 in the reversal of foam cell formation and could emerge this receptor as a new target for treating CVD by preventing accumulation of atherosclerotic plaque.

Perivascular Adipose-Derived Exosomes Reduce Foam Cell Formation by Regulating Expression of Cholesterol Transporters.

Background: Accumulating evidence demonstrates that perivascular adipose tissue (PVAT) plays an important role in maintaining vascular homeostasis. The formation of macrophage foam cells is a central feature of atherosclerosis. This study aimed to evaluate the effect of PVAT-derived exosomes (EXOs) on the lipid accumulation of macrophages and verify the anti-atherogenic characteristics of PVAT.Methods and Results: We extracted EXOs from the PVAT and subcutaneous adipose tissue (SCAT) of wild-type C57BL/6J mice. After coincubation, the EXOs were taken up by RAW264.7 cells. Oil Red O staining revealed that macrophage foam cell formation and intracellular lipid accumulation were ameliorated by PVAT-EXOs. Flow cytometry showed that PVAT-EXOs significantly reduced macrophage uptake of fluorescence-labelled oxidised low-density lipoprotein (ox-LDL). In addition, high-density lipoprotein-induced cholesterol efflux was promoted by PVAT-EXOs. Western blot analysis showed the downregulation of macrophage scavenger receptor A and the upregulation of ATP-binding cassette transporter A1 and ATP-binding cassette transporter G1, which could be mediated by the overexpression of peroxisome proliferator-activated receptor γ and was independent of liver X receptor α.Conclusion: Our findings suggest that PVAT-EXOs reduce macrophage foam cell formation by regulating the expression of cholesterol transport proteins, which provides a novel mechanism by which PVAT protects the vasculature from atherosclerosis.

Fatty acid binding protein 3 deficiency limits atherosclerosis development via macrophage foam cell formation inhibition

Atherosclerosis is the underlying contributing factor of cardiovascular disease, which is a process of inflammation and lipid-rich lesion. Macrophage-derived foam cell is a key hallmark of atherosclerosis and connected with various factors of lipid metabolism. Here, we showed that fatty acid binding protein 3 (FABP3) was upregulated in the aorta of ApoE−/- mice with high-fat-diet (HFD) feeding. Knockdown of FABP3 in HFD-fed ApoE−/- mice notably facilitated cholesterol efflux, inhibited macrophage foam cell formation, and thus prevented atherogenesis. Furthermore, FABP3 silencing decreased the expression of peroxisome proliferator-activated receptor γ (PPARγ). Mechanistic studies had disclosed the involvement of PPARγ signaling in balancing cholesterol uptake and efflux and diminishing foam cell formation. These findings firstly revealed an anti-atherogenic role of FABP3 silencing in preventing foamy macrophage formation partly through PPARγ, which might be a beneficial approach for therapying atherosclerosis.

Atypical antipsychotic drugs deregulate the cholesterol metabolism of macrophage-foam cells by activating NOX-ROS-PPARγ-CD36 signaling pathway

BackgroundClinical reports indicate that schizophrenia patients taking atypical antipsychotic drugs suffer from metabolism diseases including atherosclerosis. However, the mechanisms underlying the detrimental effect of atypical antipsychotic drugs on atherosclerosis remain to be explored. MethodsIn this study, we used apolipoprotein E-deficient (apoe−/−) hyperlipidemic mice and apoe−/−cd36−/− mice to investigate the underlying mechanism of atypical antipsychotic drugs on atherosclerosis and macrophage-foam cells. ResultsIn vivo studies showed that genetic deletion of cd36 gene ablated the pro-atherogenic effect of olanzapine in apoe−/− mice. Moreover, in vitro studies revealed that genetic deletion or siRNA-mediated knockdown of cd36 or pharmacological inhibition of CD36 prevented atypical antipsychotic drugs-induced oxLDL accumulation in macrophages. Additionally, olanzapine and clozapine activated NADPH oxidase (NOX) to generate reactive oxygen species (ROS) which upregulated the activity of peroxisome proliferator-activated receptor γ (PPARγ) and subsequently elevated CD36 expression. Inhibition of NOX activity, ROS production or PPARγ activity suppressed CD36 expression and abolished the detrimental effects of olanzapine and clozapine on oxLDL accumulation in macrophages. ConclusionCollectively, our results suggest that atypical antipsychotic drugs exacerbate atherosclerosis and macrophage-foam cell formation by activating the NOX-ROS-PPARγ-CD36 pathway.

PACAP antagonizes oxldl-induced lipid-/triglyceride accumulation and VPAC1-expression in human M2-MΦ.

Background and Aims: PACAP (pituitary adenylate cyclase-activating polypeptide) deficiency is proatherogenic in hypercholesterolemic mice and inhibits oxidized-low density lipoprotein (oxLDL)-induced TNF-α release, as well as foam cell formation in macrophages (MΦ). PACAP receptors, i.e. VIP receptor type 1 and 2 (VPAC1; VPAC2) and PACAP selective receptor PAC1 have been reported in MΦ of different tissues. The aim of this study is to examine the effects of PACAP38 on oxLDL-mediated lipid accumulation with respect to PACAP-receptor VPAC1 expression in human M1/M2-MΦ.

The interplay between ER stress, inflammation, and lipid metabolism

Background and Aims: The endoplasmic reticulum (ER) stress is an important event in the pathogenesis of human diseases, including atherosclerosis. ER stress may lead to foam cell formation and pro-inflammatory cytokines production in macrophages. In atherosclerosis, several cell types can be affected by ER stress, including endothelial cells, macrophages, and smooth muscle cells. Atherogenic low-density lipoproteins and/or inflammatory cytokines can induce ER stress, which can promote lipid accumulation and cytokine production in macrophages.

Fisetin Prevents Oxidized Low-density Lipoprotein-Induced Macrophage Foam Cell Formation.

Foam cell formation is an important event in atherosclerosis. Fisetin, a bioflavonoid, has been identified to possess anti-inflammatory, antilipidemic, and anticancerous properties; however, its role as a lipid homeostasis regulator in macrophages, specifically in the presence of metabolic stressors such as oxidized low-density lipoprotein (oxLDL) is not well understood. In this study, we have investigated the role of fisetin in preventing oxLDL-induced macrophage foam cell formation. U937-derived macrophages were stimulated with oxLDL with or without fisetin for varied time points, and various parameters were assessed including cell viability by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay; reactive oxygen species (ROS) by dichlorofluorescin diacetate assay; lipid accumulation by Oil Red O staining; and expression of NLR family pyrin domain containing 3 (NLRP3), sterol regulatory element-binding protein (SREBP)-1, and associated downstream proteins 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGCR) and fatty acid synthase (FAS) by quantitative reverse transcription polymerase chain reaction (RT-qPCR) and immunoblotting. Functionality of FAS enzyme was determined using enzyme activity assay. Docking studies were performed to determine the in silico interaction between NLRP3 and fisetin. The results showed that fisetin up to the dose of 10 µM did not alter cell viability but at the same dose could decrease the accumulation of lipids in macrophages and prevented foam cell formation. Fisetin could also ameliorate and reduce oxLDL-induced upregulation of SREBP-1 and thereby the expression of its downstream lipid synthesis genes HMGCR and FAS and inhibited ROS-induced NLRP3 inflammasome activation. In conclusion, fisetin could inhibit foam cell formation by blocking oxLDL-induced ROS formation and subsequent NLRP3 activation, thereby inhibiting SREBP-1 and its downstream genes including FAS and HMGCR.