oxLDL Incubation Research Articles

Huanglian Jiedu decoction inhibits vascular smooth muscle cell-derived foam cell formation by activating autophagy via suppressing P2RY12

Ethnopharmacological relevanceHuanglian Jiedu Decoction (HLJDD) is a Chinese medicine with a long history of therapeutic application. It is widely used in treating atherosclerosis (AS) in Chinese medicine theory and clinical practice. However, the mechanism of HLJDD in treating AS remains unclear. Aim of the studyTo investigate the efficacy and mechanism of HLJDD in treating AS. Materials and methodsAS was induced on high-fat diet-fed ApoE−/− mice, with the aorta pathological changes evaluated with lipid content and plaque progression. In vitro, foam cells were induced by subjecting primary mouse aortic vascular smooth muscle cells (VSMCs) to oxLDL incubation. After HLJDD intervention, VSMCs were assessed with lipid stack, apoptosis, oxidative stress, and the expression of foam cell markers. The effects of P2RY12 were tested by adopting clopidogrel hydrogen sulfate (CDL) in vivo and transfecting P2RY12 over-expressive plasmid in vitro. Autophagy was inhibited by Chloroquine or transfecting siRNA targeting ATG7 (siATG7). The mechanism of HLJDD treating atherosclerosis was explored using network pharmacology and validated with molecular docking and co-immunoprecipitation. ResultsHLJDD exhibited a dose-dependent reduction in lipid deposition, collagen loss, and necrosis within plaques. It also reversed lipid accumulation and down-regulated the expression of foam cell markers. P2RY12 inhibition alleviated AS, while P2RY12 overexpression enhanced foam cell formation and blocked the therapeutic effects of HLJDD. Network pharmacological analysis suggested that HLJDD might mediate PI3K/AKT signaling pathway-induced autophagy. P2RY12 overexpression also impaired autophagy. Similarly, inhibiting autophagy counteracted the effect of CDL, exacerbated AS in vivo, and promoted foam cell formation in vitro. However, HLJDD treatment mitigated these detrimental effects by suppressing the PI3K/AKT signaling pathway. Immunofluorescence and molecular docking revealed a high affinity between P2RY12 and PIK3CB, while co-immunoprecipitation assays illustrated their interaction. ConclusionsHLJDD inhibited AS in vivo and foam cell formation in vitro by restoring P2RY12/PI3K/AKT signaling pathway-suppressed autophagy. This study is the first to reveal an interaction between P2RY12 and PI3K3CB.

Oxidized LDL Regulates Endothelin-1 and Oxidative Stress in Vascular Endothelial Cells: Role of Extracellular Regulated Kinase1/2 (ERK1/2)

Article Oxidized LDL Regulates Endothelin-1 and Oxidative Stress in Vascular Endothelial Cells: Role of Extracellular Regulated Kinase1/2 (ERK1/2) Haishan Xu 1,#, Jinhong Duan 1,#, Jun Tao 2, Wen Wang 3, Yunqing Wu 1,^, Shunling Dai 1,*, and Jun Ren 4,5, 1 Faculty of Basic Medicine, Peking Union Medical College, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, Beijing 100005 China 2 Department of Cardiovascular Surgery, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou 510000 China 3 Department of Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, China 4 Department of Cardiology, Zhongshan Hospital Fudan University, Shanghai 200032, China 5 National Clinical Research Center for Interventional Medicine, Shanghai 200032, China # These two authors contributed equally to this work ^ Deceased * Correspondence: daishunling@aliyun.com (Shunling Dai); corresponding author:jren_aldh2@outlook.com (Jun Ren) Abstract: It is perceived that oxidized low density lipoprotein (oxLDL) perturbs endothelial function and fosters endothelin-1 (ET-1) secretion although the underlying mechanism remains elusive. This study was designed to decipher potential mechanisms underscoring oxLDL-evoked regulation of ET-1 and signaling pathways involved in endothelial cells. ET-1 mRNA expression, secretion and promoter function were determined using RT-PCR, enzyme immunometric and luciferase assays, respectively. GO and GSEA bioinformatics analyses depicted differentially expressed genes (DEGs) mainly associated with cell proliferation, cell division, cellular structure, energy supply, and apoptosis in oxLDL-challenged endothelial cells. Incubation of oxLDL overtly increased ROS production, apoptosis, mRNA level, secretion and promoter activity of ET-1 in human umbilical vein endothelial cells (HUVECs), the effects were mitigated by N-Acetyl Cysteine (NAC). Moreover, oxLDL challenge evoked phosphorylation of extracellular signal-regulated kinase1/2 (ERK1/2) in HUVECs, the effect was reversed by NAC and MEK inhibitor PD98059. NAC and PD98059 nullified oxLDL- induced rises in mRNA expression, secretion and promoter activity of ET-1. Truncation of 5’-flanking sequence of ET-1 (–566 bpLuc to –250 bpLuc) displayed elevated luciferase activity with 24-h oxLDL incubation. Fusion plasmid from –233 and –185 bp Luc drastically dampened luciferase activity in basal and oxLDL-challenged HUVECs. Transfection of reporter construct –250 bp Luc with a 2 bp mutation at AP-1 locus, removed basal and oxLDL- evoked rises in ET-1 promoter activity. Collectively, our findings support that oxLDL evoked activation of ERK1/2 signaling likely through ROS production, en route to upregulation of endothelial transcriptional factor AP-1, resulting in expression and secretion of ET-1.

OxLDL as an Inducer of a Metabolic Shift in Cancer Cells.

Recent evidence established a link between disturbed lipid metabolism and increased risk for cancer. One of the most prominent features related to disturbed lipid metabolism is an increased production of oxidized low-density-lipoproteins (oxLDL), which results from elevated oxidative stress. OxLDL is known to have detrimental effects on healthy cells and plays a primary role in diseases related to the metabolic syndrome. Nevertheless, so far, the exact role of oxLDL in cancer cell metabolism is not yet known. To examine changes in metabolic profile induced by oxLDL, pancreatic KLM-1 cells were treated with oxLDL in a concentration- (25 or 50 µg/ml) and/or time-dependent (4 hr or 8 hr) manner and the impact of oxLDL on oxygen consumption rates (OCR) as well as extracellular acidification rates (ECAR) was analyzed using Seahorse technology. Subsequently, to establish the link between oxLDL and glycolysis, stabilization of the master regulator hypoxia-inducible factor 1-alpha (HIF-1α) was measured by means of Western blot. Furthermore, autophagic responses were assessed by measuring protein levels of the autophagosomal marker LC3B-II. Finally, the therapeutic potential of natural anti-oxLDL IgM antibodies in reversing these effects was tested. Incubation of KLM-1 cells with oxLDL shifted the energy balance towards a more glycolytic phenotype, which is an important hallmark of cancer cells. These data were supported by measurement of increased oxLDL-mediated HIF-1α stabilization. In line, oxLDL incubation also increased the levels of LC3B-II, suggesting an elevated autophagic response. Importantly, antibodies against oxLDL were able to reverse these oxLDL-mediated metabolic effects. Our data provides a novel proof-of-concept that oxLDL induces a shift in energy balance. These data not only support a role for oxLDL in the progression of cancer but also suggest the possibility of targeting oxLDL as a therapeutic option in cancer.

Myricetin ameliorates atherosclerosis in the low-density-lipoprotein receptor knockout mice by suppression of cholesterol accumulation in macrophage foam cells

BackgroundMyricetin, a major flavonoid found in several foods including berries, grapes and wine, exhibited strong antioxidant potency, yet the effect on atherosclerosis is not fully understood. In this study, we examined the effect of myricetin on lipid accumulation in macrophage and atherosclerosis in atherosclerosis-prone low density lipoprotein receptor-deficient (Ldlr−/−) mice.MethodsLdlr−/− mice were fed an atherogenic diet supplemented with myricetin (0.15% in the diet, v/v) for 8 weeks. Body weight, adipose tissue weight, food intake, serum biochemical parameters were measured. Atherosclerosis lesions and macrophages accumulaton in lesions were analyzed and quantified. Macrophages were exposed to 20 μM of myricetin before incubated with oxidized low-density lipoprotein (ox-LDL) (25μg/mL) or Dil-ox-LDL for the indicated time. Lipid uptake and foam cell formation were evaluated by flow cytometry and microscopy. The intracellular lipids were extracted and measured. mRNA expression and protein of cholesterol metabolism related receptors were analyzed.ResultsMyricetin administration reduced the weight, plasma lipid levels but not food intake in Ldlr−/− mice when fed an atherogenic diet. Myceritin-treated Ldlr−/− mice displayed significantly less atherosclerotic areas and macrophages in the cross sections of the aortic root. There were also less lipophilic areas in En face Oil red O staining of aorta from myceritin-treated Ldlr−/− mice. Myceritin treatment also markedly ameliorated ox-LDL-induced cholesterol accumulation in macrophages. The expression of CD36 were decreased in myricetin treated macrophages with ox-LDL incubation, while scavenger receptors class A (SR-A) and scavenger receptors class B (SR-BI) expression was not altered, indicating that these effect of myricetin were dependent on CD36 pathway.ConclusionsOur findings indicated that myricetin suppressed cholesterol accumulation in macrophage foam cells by inhibition of CD36-mediated ox-LDL uptake, and suggested myricetin may have an important therapeutic function for atherosclerosis.

MTOR-Dependent Oxidative Stress Regulates oxLDL-Induced Trained Innate Immunity in Human Monocytes.

Introduction: Cells of the innate immune system particularly monocytes and macrophages have been recognized as pivotal players both during the initial insult as well as the chronic phase of atherosclerosis. It has recently been shown that oxidized low-density lipoprotein (oxLDL) induces a long-term pro-inflammatory response in monocytes due to epigenetic and metabolic reprogramming, an emerging new concept called trained innate immunity. Changes in the cellular redox state are crucial events in the regulation of many physiologic functions in macrophages including transcription, differentiation and inflammatory response. Here we have analyzed the role of reactive oxygen species (ROS) in regulating this proinflammatory monocyte priming in response to oxLDL-treatment.Methods and Results: Human monocytes were isolated and incubated with oxLDL for 24 h. After 5 days of resting, oxLDL treated cells produced significantly more inflammatory cytokines upon restimulation with the TLR2-agonist Pam3cys. Furthermore, oxLDL incubation induced persistent mTOR activation, ROS formation, HIF1α accumulation and HIF1α target gene expression, while pharmacologic mTOR inhibition or siRNA mediated inhibition of the mTORC1 subunit Raptor prevented ROS formation and proinflammatory priming. mTOR dependent ROS formation was associated with increased expression of NAPDH oxidases and necessary for the emergence of the primed phenotype as antioxidant treatment blocked oxLDL priming. Inhibition of cytosolic ROS formation could also block mTOR activation and HIF1α accumulation suggesting a positive feedback loop between mTOR and cytosolic ROS. Although mitochondrial ROS scavenging did not block HIF1α-accumulation at an early time point (24 h), it was persistently reduced on day 6. Therefore, mitochondrial ROS formation appears to occur initially downstream of the mTOR-cytoROS-HIF1α feedback loop but seems to be a crucial factor that controls the long-term activation of the mTOR-HIF1α-axis.Conclusion: In summary, our data demonstrate that mTOR dependent ROS production controls the oxLDL-induced trained innate immunity phenotype in human monocyte derived macrophages. Pharmacologic modulation of these pathways might provide a potential approach to modulate inflammation, associated with aberrant monocyte activation, during atherosclerosis development.

FSD-C10 Shows Therapeutic Effects in Suppressing oxidized low-density lipoprotein (ox-LDL)-Induced Human Brain Microvascular Endothelial Cells Apoptosis via Rho-Associated Coiled-Coil Kinase (ROCK)/Mitogen-Activated Protein Kinase (MAPK) Signaling.

Backgroundox-LDL-induced injury of brain microvascular endothelial cells (BMECs) is strongly associated with cerebral vascular diseases such as cerebral arterial atherosclerosis. ROCK inhibitor was proved to be anti-apoptotic and has been used in treating cerebral vascular diseases. Research on the neuroprotective effects of a novel ROCK inhibitor, FSD-C10, is still limited. The present study investigated the anti-apoptotic effect and underlying molecular mechanism of FSD-C10 in ox-LDL-mediated apoptosis of BMECs.Material/Methodsox-LDL and/or FSD-C10 were used to incubate immortalized human BMECs. MTT assay was used to assess cell viability. Cell apoptosis was evaluated by TUNEL assay. A colorimetric method was used to assess ROCK activity. Western blot analysis was used to examine the expression and phosphorylation levels of proteins.Resultsox-LDL incubation reduced the viability of BMECs by inducing cell apoptosis in a concentration-dependent manner. ROCK activity was also elevated by ox-LDL incubation in BMECs in a concentration-dependent manner. Expression level of Bcl2 was reduced while expression levels of Bax and active caspase3 were increased by ox-LDL treatment in a concentration-dependent manner. ox-LDL also increased the phosphorylation levels of p38, JNK, and ERK1/2 in a concentration-dependent manner. FSD-C10 treatment increased the cell viability by reducing apoptosis of BMECs exposed to ox-LDL. Moreover, FSD-C10 was found to suppress the phosphorylation levels of p38, JNK, and ERK1/2 and the expression levels of Bax and active caspase3 in ox-LDL treated BMECs.ConclusionsFSD-C10 increases cell viability in ox-LDL-treated BMECs by reducing cell apoptosis. ROCK/MAPKs-mediated apoptosis appears to be the underlying molecular mechanism.

Neat1 regulates oxidized low-density lipoprotein-induced inflammation and lipid uptake in macrophages via paraspeckle formation.

Oxidized low-density lipoprotein (oxLDL) induces macrophage inflammation and lipid uptake, and serves important roles in the development of atherosclerosis. The long non-coding RNA (lncRNA) nuclear paraspeckle assembly transcript 1 (neat1) has two isoforms; the longer isoform, neat1_2, mediates the formation of subnuclear structures called paraspeckles. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR), western blotting and RNA protein immunoprecipitation (RIP), revealed that oxLDL induced paraspeckle formation in the THP-1 cell line. Additionally, the nuclear factor-κB and p38 pathways were observed to be involved in neat1 transcription. To investigate the role of paraspeckles in oxLDL-induced macrophage inflammation and lipid uptake, macrophages were transfected with small interfering RNAs against NEAT1, NEAT1_2, non-POU domain-containing octamer-binding (NONO) and splicing factor proline and glutamine rich prior to oxLDL incubation. In addition, inflammation-associated pathways and scavenger receptors were analyzed by performing western blotting and RT-qPCR. p65 phosphorylation and cluster of differentiation 36 (CD36) were demonstrated to serve roles in paraspeckle-mediated inflammation and lipid uptake, respectively. To determine the underlying mechanism, RIP was preformed, which revealed that NONO binds CD36 mRNA to decrease its expression. In conclusion, oxLDL induced neat1_2-mediated paraspeckle formation. Paraspeckles participate in oxLDL-induced macrophage inflammation and lipid uptake by regulating p65 phosphorylation and CD36 mRNA.

Role of Rab5 in the formation of macrophage-derived foam cell

BackgroundFoam cells play a key role in the occurrence and pathogenesis of atherosclerosis. Its formation starts with the ingestion of oxidized low-density lipoprotein (oxLDL). The process is associated with Ras related protein in brain 5 (Rab5) which plays a critical role in regulating endocytosis and early endosomal trafficking. Base on this, we presumed that Rab5 might participate in the maturation of foam cell. The aim of this study is to investigate the effect of Rab5 on macrophage cholesterol during the evolvement of macrophage when induced by oxLDL to the formation of foam cell.MethodsImmunohistochemistry was performed to analyze the distribution of macrophages and Rab5 in atherosclerotic plaque. RNA inteference study and transfection of inactive mutant (GFP-Rab5-S34N) and active mutant (GFP-Rab5-Q79L) in U937-derived macrophage were utilized to investigate the impact of Rab5 on the process of macrophage cholesterol, which could be detected by oil red O staining, determination of intracellular lipid content, filipin staining, nile red staining and the costaining of early endosome antigen-1 (EEA-1) and 1,1′-dioctadecyl-3,3,3′,3′-tetramethylin dicarbocyanine (Dil)-labelled oxLDL (Dil-oxLDL).ResultsRab5 was found abundantly localized in macrophage rich areas of human atherosclerotic lesions. On the foam cell study, the expression of Rab5 was increased after the incubation of oxLDL. The inteference study indicated the depletion of Rab5 led to the decreases of oil red O staining areas, total cholesterol and cholesterol esters in U937-derived marophages. Moreover, the fluorescence intensity of filipin and nile red staining were lower in GFP-Rab5-S34N as compared with GFP-Rab5-Q79L. The confocal study demonstrated less Dil-oxLDL was internalized in GFP-Rab5-S34N as compared with GFP-Rab5-Q79L; the result showed also the decrease in colocalization of internalized Dil-oxLDL and EEA-1 for GFP-Rab5-S34N as compared with GFP-Rab5-Q79L.ConclusionsRab5 plays an important role in modulating the intracellular cholesterol of macrophages and consequently mediating the formation of foam cells.

Effect of oxidized LDL on erythrocyte nitric oxide metabolism

Oxidized low density lipoprotein (ox-LDL) has been reported as an inhibitor of nitric oxide (NO)-mediated dilatation in microcirculation. Oxidized LDL effect on NO metabolism of erythrocytes is not known. Therefore, this study aims to evaluate the effect of ox-LDL on erythrocytes NO metabolism. The effect of different concentrations of human purified ox-LDL (25, 50 and 100 μg/mL) on NO metabolism was evaluated on blood of healthy subjects. An inhibitory effect of higher concentrations of ox-LDL on erythrocyte NO efflux levels was verified. Concentrations of NO efflux from erythrocytes were lower as consequence of treatments with 50 μg/mL ox-LDL treatment (1.6±0.27 nM) and 100 μg/mL ox-LDL treatment (1.3±0.22 nM) than control (1.9±0.28 nM). Opposite, ox-LDL incubation has apositive effect on GSNO content of erythrocytes. That effect is proportional to concentrations of ox-LDL treatments (10.8±1.4 nM for 25 μg/mL, 12.9±1.5 nM for 50 μg/mL and 12.1±1.9 nM for 100 μg/mL) and is significant relative to control (8.56±0.76 μM) and ACh (8.9±0.52 μM) aliquots. Presence of oxidized LDL in erythrocyte NO metabolism induces adecrease of NO efflux amount and an increase on intra-erythrocyte GSNO concentrations. These results suggest arole of ox-LDL in mobilization of NO between NO derivatives molecules in dependence of oxidized LDL concentration. An anti - reactive nitrogene role can be attributed to ox-LDL for its contribution in the erythrocyte scavenged ability for nitric oxide.

Lp-PLA2 silencing protects against ox-LDL-induced oxidative stress and cell apoptosis via Akt/mTOR signaling pathway in human THP1 macrophages

Atherosclerosis is a disease of the large- and medium-size arteries that is characterized by the formation of atherosclerotic plaques, in which foam cells are the characteristic pathological cells. However, the key underlying pathomechanisms are still not fully elucidated. In this study, we investigated the role of lipoprotein-associated phospholipase A2 (Lp-PLA2) in ox-LDL-induced oxidative stress and cell apoptosis, and further, elucidated the potential machanisms in human THP1 macrophages. Flow cytometry and western blot analyses showed that both cell apoptosis and Lp-PLA2 expression were dose-dependently elevated after ox-LDL treatment for 24 h and also time-dependently increased after 50 mg/L ox-LDL incubation in THP1 macrophages. In addition, Lp-PLA2 silencing decreased ox-LDL-induced Lp-PLA2 and CD36 expression in THP1 macrophages. We also found that the levels of oil red O-staining, triglyceride (TG) and total cholesterol (TC) were significantly upregulated in ox-LDL-treated THP1 cells, but inhibited by Lp-PLA2 silencing. Furthermore, ox-LDL treatment resulted in significant increases of ROS and MDA but a marked decrease of SOD, effects that were reversed by Lp-PLA2 silencing in THP1 cells. Lp-PLA2 silencing reduced ox-LDL-induced cell apoptosis and caspase-3 expression in THP1 cells. Moreover, Lp-PLA2 siRNA transfection dramatically lowered the elevated levels of p-Akt and p-mTOR proteins in ox-LDL-treated THP1 cells. Both PI3K inhibitor LY294002 and mTOR inhibitor rapamycin decreased the augmented caspase-3 expression and TC content induced by ox-LDL, respectively. Taken together, these results revealed that Lp-PLA2 silencing protected against ox-LDL-induced oxidative stress and cell apoptosis via Akt/mTOR signaling pathway in human THP1 macrophages.

Effects of activation of dopamine type I receptor on the produc-tion of NO/NOS in ox-LDL activated THP-1 cells

To study the effect of excited dopamine type I receptor on the production of nitric oxide/nitric oxide synthase(NO/NOS)in ox-LDL activated THP-1 cells and the possible mechanism. Cultured THP-1 cells activated by PMA were randomly assigned in the following groups:control group (control), oxidized low density lipoprotein group (ox-LDL), dopamine receptor 1(DR1) agonist group (SKF), DR1 antagonist group (SCH), ERK blocker group (PD98059). Oil Red O staining was used to identify the accumulation of cellular lipid. The levels of NO and NOS in the supernatant of THP-1 were assayed by nitrate reductase method. The protein expression of DR1, p-ERK and ERK were obtained by Western blot and immunity fluorescence. After 48 h of incubation of ox-LDL, accumulation of lipid in the cytoplasm was found in most THP-1 cells. Compared with control group, DR1 protein expression was reduced in ox-LDL-induced cells(P<0.01). Activation of DR1 agonist decrease the production of NO and iNOS(P<0.01), and PD98059 partly reversed the above effect. Activation of DR1 can inhibit the production of NO/NOS in ox-LDL-induced THP-1 cells, which may be related with ERK pathway.

OxLDL induce endothelial cell stiffening through Rho/ROCK signaling pathway

Our lab demonstrated that Oxidized LDL (OxLDL) induce endothelial cell stiffening. The signal transduction pathways leading to this increase in stiffness remain poorly understood. We hypothesize that the Rho/ROCK pathway plays a role in oxLDL induced endothelial cell stiffening. To test our hypothesis, human aortic endothelial cells (HAEC) were treated with 50µg/ml oxLDL and Rho/ROCK signaling was probed by western‐blot. First, our results show that RhoA is significantly activated by 50ug/ml oxLDL stimulation. The activated RhoA level increased 1.9 times vs control after 15 minutes incubation with oxLDL, and activated RhoA level return to control level after 60 minutes of incubation with oxLDL. Second, incubation with oxLDL increase phospho‐myosin phosphatase target subunit 1 (p‐MYPT1 (Thr853)) and phosphor‐Myosin ligh chain 2 (p‐MLC2 (Thr18/Ser19) expression level vs control. We further test that if oxLDL could affect myosin phosphorylation. Our data showed p‐MLC2 increased 1.7 times vs control after 15 minutes incubation with oxLDL, and increased 2.6 times vs control after 60 minutes incubation. The level of p‐MYPT1, which indicate the inhibition of myosin phosphatase, increased to 1.7 times vs control after 15 minutes incubation with oxLDL. Third, to further test our hypothesis, we treated HAECs with RhoA inhibitor (C3) or ROCK inhibitor (Y27632) before oxLDL incubation. Our data showed that both C3 and Y27632 attenuate oxLDL induced increase of p‐MLC2 and p‐MYPT1. Lastly, our data showed that increase of cell stiffening is also attenuated by C3 or Y27632 when treated with oxLDL.ConclusionoxLDL induce cell stiffening through increase RhoA activity, active Rho/ROCK pathway, inhibition myosin phosphatase, thereby increasing phosphorylation of myosin and leading to cell stiffening.

Evaluation of Atorvastatin effect on oxLDL induced inflammatory response and oxidative stress in human endothelial cells: a role for nNOS (851.17)

Human endothelial cells incubation with oxidized LDL (oxLDL; 6 and 24 h) increased reactive oxygen species (ROS) and NO production associated to an increase in iNOS and eNOS expression. eNOS activation was compromised at 6h but increased after 24h, suggesting eNOS uncoupling. nNOS expression and activity as well as SOD2 expression were reduced and catalase showed increased expression after 6 and 24h. Atorvastatin (Ator; 1uM) reduced oxidative stress by restoring NOS, SOD2 and catalase expression associated to superoxide and NO reduction levels. Ator reduced catalase and increased SOD2 expression. This treatment showed increase eNOS activation and nNOS expression up to control levels in the first 6 h, while its inactivation was reduced after 6 and 24 h. iNOS expression was reduced by atorvastatin treatment indicating NO unbalance regulation and possible anti‐inflammatory effect. oxLDL incubation increased pro‐inflammatory cytokines TNF‐α, IL‐6, CCL‐2 and IL‐1β production and reduced anti‐inflammatory cytokines TGF‐β and IL‐10. Ator reduced production of pro‐inflammatory cytokines (except TNF‐ α) and increased anti‐inflammatory cytokines. These effects could be related to a reduction in oxLDL uptake by endothelial cells during atorvastatin co‐incubation. In addition, nNOS inhibition increased oxLDL uptake after 6 and 24 h. These Results suggest nNOS involvement in atorvastatin protective effects.Grant Funding Source: CAPES, FAPEMIG, CNPq

Macrophage Specific Caspase-1/11 Deficiency Protects against Cholesterol Crystallization and Hepatic Inflammation in Hyperlipidemic Mice

Background & AimsWhile non-alcoholic steatohepatitis (NASH) is characterized by hepatic steatosis combined with inflammation, the mechanisms triggering hepatic inflammation are unknown. In Ldlr-/- mice, we have previously shown that lysosomal cholesterol accumulation in Kupffer cells (KCs) correlates with hepatic inflammation and cholesterol crystallization. Previously, cholesterol crystals have been shown to induce the activation of inflammasomes. Inflammasomes are protein complexes that induce the processing and release of pro-inflammatory cytokines IL-1b and IL-18 via caspase-1 activation. Whereas caspase-1 activation is independent of caspase-11 in the canonical pathway of inflammasome activation, caspase-11 was found to trigger caspase-1-dependent IL-1b and IL-18 in response to non-canonical inflammasome activators. So far, it has not been investigated whether inflammasome activation stimulates the formation of cholesterol crystals. We hypothesized that inflammasome activation in KCs stimulates cholesterol crystallization, thereby leading to hepatic inflammation.Methods Ldlr -/- mice were transplanted (tp) with wild-type (Wt) or caspase-1/11-/- (dKO) bone marrow and fed either regular chow or a high-fat, high-cholesterol (HFC) diet for 12 weeks. In vitro, bone marrow derived macrophages (BMDM) from wt or caspase-1/11-/- mice were incubated with oxLDL for 24h and autophagy was assessed. ResultsIn line with our hypothesis, caspase-1/11-/--tp mice had less severe hepatic inflammation than Wt-tp animals, as evident from liver histology and gene expression analysis in isolated KCs. Mechanistically, KCs from caspase-1/11-/--tp mice showed less cholesterol crystals, enhanced cholesterol efflux and increased autophagy. In wt BMDM, oxLDL incubation led to disturbed autophagy activity whereas BMDM from caspase-1/11-/- mice had normal autophagy activity.ConclusionAltogether, these data suggest a vicious cycle whereby disturbed autophagy and decreased cholesterol efflux leads to newly formed cholesterol crystals and thereby maintain hepatic inflammation during NASH by further activating the inflammasome.

Abstract 454: Cationic Peptides Neutralize Ox-LDL and Acetyl LDL Negative Charge and Prevent Their Uptake by Macrophages

Background Apoprotein (Apo A1) and apoprotein E mimetic peptides are known to reduce atherosclerosis. Antioxidant, anti-inflammatory, and hypolipidemic properties have been suggested to contribute to the anti-atherosclerotic effects. In this study, we tested whether three distinct and unrelated cationic peptides would inhibit the oxidation of lipoproteins and whether they would counteract and neutralize the negatively charged modified lipoproteins and inhibit their uptake by macrophages. Methods 5F-mimetic peptide of apoA1, LL27 derived from the anti-microbial peptide CAMP, and a human glycodelin derived peptide were commercially synthesized. The number of positively charged amino acid residues (K+R) and negatively charged residues (D+E) were 4/4, 7/4, 6/2 respectively. Their abilities to reduce lipid peroxides (LOOH), inhibit the oxidation low density lipoprotein (LDL) and high density lipoprotein (HDL), interact with modified lipoproteins, and to inhibit macrophage uptake of modified LDL were measured. Results Cationic peptides decomposed the peroxide content of 13-HPODE and inhibited the oxidation of LDL and HDL by copper in a lysine dependent manner. Incubation of Ox-LDL and Ac-LDL with the peptides resulted in charge neutralization as noted by agarose gel electrophoresis. Pre-incubation of the peptides with modified lipoproteins reduced the uptake of the latter by macrophages and foam cell formation as detected by Oil-Red O staining. Conclusions Based on these studies, we postulate that cationic peptides may have properties that may affect a) events that are unrelated to lipid lowering, b) may play additional role in immune competent cells, including macrophages, and c) may interact with other biologically important anionic molecules, including lipids and proteins. These results also suggest there may be other cationic proteins that may influence the atherogenic processes.

Abstract 183: Oxidized LDL Cholesterol Induces Endothelial Dysfunction in the Aorta and Lox-1 Expression in Macrophages

Elevated plasma cholesterol is one of the major risk factors in the development of atherosclerotic lesions. Oxidation of native LDL cholesterol (nLDL) by reactive oxygen species leads to the formation of oxidized LDL (oxLDL). An important receptor for the cellular uptake of oxLDL is the lectin-like oxidized low-density lipoprotein receptor-1 (Lox-1). Lox-1 is highly expressed on macrophages, but also present on arterial endothelial and vascular smooth muscle cells. Especially the uptake by macrophages leads to the formation of foam cells in atherosclerotic lesions. Aim of the present study was to analyze the impact of oxLDL on endothelial function in murine aortas and on Lox-1 expression in human macrophages. In addition, we analyzed the effect of a high-fat diet on vascular function in mice with an endothelial Lox-1 overexpression. First, we incubated aortic rings of wild-type mice for 2 h with 100 μg/mL oxLDL and analyzed the endothelial function using a Mulvany myograph. Compared to basal conditions, oxLDL significantly impaired endothelium-dependent vasodilation. Next, we fed mice with an endothelial overexpression of Lox-1 for 20 weeks a high-fat diet and analyzed the endothelial function in the thoracic aorta. Interestingly, these mice had no impaired endothelium-dependent relaxation after high-fat diet feeding. To get further insight into Lox-1 regulation by oxLDL, we analyzed the impact of oxLDL on Lox-1 expression in human macrophages. Monocytic THP-1 cells were differentiated with phorbol myristate acetate into macrophages and stimulated for 24 h with nLDL or oxLDL. We found a significant induction of Lox-1 mRNA expression after oxLDL incubation, whereas nLDL had no effect. Our data suggest an increased oxLDL uptake in oxLDL-treated macrophages by increased Lox-1 receptor expression. In conclusion, our data support an important role of oxLDL as a proatherosclerotic risk factor by its ability to induce endothelial dysfunction and Lox-1 expression in macrophages. Both processes may be involved in the development of atherosclerotic lesions but the physiological significance and functional role of Lox-1 in contributing to the human disease warrants further investigations.

Individual Variation of Scavenger Receptor Expression in Human Macrophages with Oxidized Low-Density Lipoprotein Is Associated with a Differential Inflammatory Response

Atherosclerosis is an inflammatory disease in which oxidized low-density lipoprotein (oxLDL) plays important roles. Scavenger receptors (SR) CD36, SR-A, and LOX-1 uptake over 90% of the oxLDL leading to foam cell formation and secretion of inflammatory cytokines. To investigate whether the interindividual differences in macrophage SR gene expression could determine the inflammatory variability in response to oxLDL, we quantified the gene and protein expression of SR and inflammatory molecules from macrophages isolated from 18 volunteer subjects and incubated with oxLDL for 1, 3, 6, and 18 h. The individual gene expression profile of the studied SR at 1 h of incubation was highly variable, showing a wide fold-change range: CD36: -3.57-4.22, SR-A: -5.0-4.43, and LOX-1: -1.56-75.32. We identified subjects as high and low responders depending on whether their SR gene expression was above or below the median, showing a different inflammation response pattern. CD36 and LOX-1 gene expression correlated positively with IL-1beta; SR-A correlated negatively with IL-8 and positively with PPARgamma and NF-kappaBIotaA. These results were confirmed in the same subjects 3 mo after the first sampling. Furthermore, a negative correlation existed between CD36 and SR-A at protein level after 18 h of oxLDL incubation (R = -0.926, p = 0.024). These data would suggest that the type of SR could determine the macrophage activation: more proinflammatory when associated to CD36 and LOX-1 than when associated with SR-A.

Disruption of hedgehog signalling in ApoE − /− mice reduces plasma lipid levels, but increases atherosclerosis due to enhanced lipid uptake by macrophages

Embryonic pathways are often re-expressed in adult pathology. Here we investigated the role of the morphogen hedgehog (hh), which we found to be re-expressed in atherosclerotic plaques. Male ApoE - /- mice were treated for 12 weeks with an anti-hh antibody (5E1) or a control IgG (1E6) starting at the age of 6 or 18 weeks. Inhibition of hh signalling induced a significant increase in total plaque area in the aortic arch, a result of an increase (54% and 36%, respectively) in the area of advanced plaques (atheromata). In mice treated with anti-hh, plaques contained large (18-35% > ctrl), lipid-filled, sometimes multinucleated macrophage foam cells. Plasma cholesterol levels decreased after anti-hh treatment. In bone marrow-derived macrophages, foam cell formation was enhanced after inhibition of hh signalling. Anti-hh treatment caused a 54-75% increase in early oxLDL uptake (10-240 min), which was scavenger receptor-mediated. After 3-24 h of oxLDL incubation, intense Oil red O staining as well as increased amounts of cholesterol esters were present in these macrophages after anti-hh treatment. Activation of the HH-signalling cascade by recombinant Shh induced a decrease in oxLDL uptake. Here we show that the hh-signalling pathway is one of the morphogenic pathways that regulate plasma lipid levels and atherosclerosis development and progression.

Protective effects of magnolol against oxidized LDL-induced apoptosis in endothelial cells

Magnolol, a compound extracted from the Chinese medicinal herb Magnolia officinalis, has several biological effects. However, its protective effects against endothelial injury remain unclear. In this study, we examined whether magnolol prevents oxidized low density lipoprotein (oxLDL)-induced vascular endothelial apoptosis. Incubation of oxLDL with magnolol (2.5-20 microM) inhibited copper-induced oxidative modification via diene formation, thiobarbituric acid reactive substances (TBARS) assay and electrophoretic mobility assay. Apoptotic cell death as characterized by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) stain. We measured the production of reactive oxygen species (ROS) by using the fluorescent probe 2',7'-dichlorofluorescein acetoxymethyl ester (DCF-AM), and observed the activity of antioxidant enzymes. Furthermore, several apoptotic signaling pathways which showed NF-kappaB activation, increased cytosolic calcium, alteration of mitochondrial membrane potential, cytochrome c release and activation of caspase 3 were also investigated. We demonstrated that magnolol prevented the copper-induced oxidative modification of LDL. Magnolol attenuated the oxLDL-induced ROS generation and subsequent NF-kappaB activation. Furthermore, intracellular calcium accumulation and subsequent mitochondrial membrane potential collapse, cytochome c release and activation of caspase 3 caused by oxLDL were also inhibited by magnolol. Our results suggest that magnolol may have clinical implications in the prevention of atherosclerotic vascular disease through decreasing the oxLDL-induced ROS production.

Protective effects of honokiol against oxidized LDL-induced cytotoxicity and adhesion molecule expression in endothelial cells

Honokiol, a compound extracted from Chinese medicinal herb Magnolia officinalis, has several biological effects. However, its protective effects against endothelial injury remain unclarified. In this study, we examined whether honokiol prevented oxidized low-density lipoprotein (oxLDL)-induced vascular endothelial dysfunction. Incubation of oxLDL with honokiol (2.5–20 μM) inhibited copper-induced oxidative modification as demonstrated by diene formation, thiobarbituric acid reactive substances (TBARS) assay and electrophoretic mobility assay. Expression of adhesion molecules (ICAM, VCAM and E-selectin) and endothelial NO synthase (eNOS) affected by oxLDL was investigated by flow cytometry and Western blot. We also measured the production of reactive oxygen species (ROS) using the fluorescent probe 2′,7′-dichlorofluorescein acetoxymethyl ester (DCF-AM). Furthermore, several apoptotic phenomena including increased cytosolic calcium, alteration of mitochondrial membrane potential, cytochrome c release and activation of caspase-3 were also investigated. Apoptotic cell death was characterized by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) stain. The results showed that honokiol prevented the copper-induced oxidative modification of LDL. Honokiol also ameliorated the oxLDL-diminished eNOS protein expression and reduced the oxLDL-induced adhesion molecules and the adherence of THP-1 cells to HUVECs. Furthermore, honokiol attenuated the oxLDL-induced cytotoxicity, apoptotic features, ROS generation, intracellular calcium accumulation and the subsequent mitochondrial membrane potential collapse, cytochrome c release and activation of caspase-3. Our results suggest that honokiol may have clinical implications in the prevention of atherosclerotic vascular disease.