High-density lipoprotein mimetic nano-therapeutics targeting monocytes and macrophages for improved cardiovascular care: a comprehensive review.

The prevalence of cardiovascular diseases continues to be a challenge for global health, necessitating innovative solutions. The potential of high-density lipoprotein (HDL) mimetic nanotherapeutics in the context of cardiovascular disease and the intricate mechanisms underlying the interactions between monocyte-derived cells and HDL mimetic showing their impact on inflammation, cellular lipid metabolism, and the progression of atherosclerotic plaque. Preclinical studies have demonstrated that HDL mimetic nanotherapeutics can regulate monocyte recruitment and macrophage polarization towards an anti-inflammatory phenotype, suggesting their potential to impede the progression of atherosclerosis. The challenges and opportunities associated with the clinical application of HDL mimetic nanotherapeutics, emphasize the need for additional research to gain a better understanding of the precise molecular pathways and long-term effects of these nanotherapeutics on monocytes and macrophages to maximize their therapeutic efficacy. Furthermore, the use of nanotechnology in the treatment of cardiovascular diseases highlights the potential of nanoparticles for targeted treatments. Moreover, the concept of theranostics combines therapy and diagnosis to create a selective platform for the conversion of traditional therapeutic medications into specialized and customized treatments. The multifaceted contributions of HDL to cardiovascular and metabolic health via highlight its potential to improve plaque stability and avert atherosclerosis-related problems. There is a need for further research to maximize the therapeutic efficacy of HDL mimetic nanotherapeutics and to develop targeted treatment approaches to prevent atherosclerosis. This review provides a comprehensive overview of the potential of nanotherapeutics in the treatment of cardiovascular diseases, emphasizing the need for innovative solutions to address the challenges posed by cardiovascular diseases.

Asthmatic patients with high serum amyloid A have proinflammatory HDL: Implications for augmented systemic and airway inflammation.

RATIONALE: Serum amyloid A (SAA) is bound to high-density lipoproteins (HDL) in blood. Although SAA is increased in the blood of patients with asthma, it is not known whether this modifies asthma severity. OBJECTIVE: We sought to define the clinical characteristics of patients with asthma who have high SAA levels and assess whether HDL from SAA-high patients with asthma is proinflammatory. METHODS: SAA levels in serum from subjects with and without asthma were quantified by ELISA. HDLs isolated from subjects with asthma and high SAA levels were used to stimulate human monocytes and were intravenously administered to BALB/c mice. RESULTS: An SAA level greater than or equal to 108.8 µg/mL was defined as the threshold to identify 11% of an asthmatic cohort (n = 146) as being SAA-high. SAA-high patients with asthma were characterized by increased serum C-reactive protein, IL-6, and TNF-α; older age; and an increased prevalence of obesity and severe asthma. HDL isolated from SAA-high patients with asthma (SAA-high HDL) had an increased content of SAA as compared with HDL from SAA-low patients with asthma and induced the secretion of IL-6, IL-1ß, and TNF-α from human monocytes via a formyl peptide receptor 2/ATP/P2X purinoceptor 7 axis. Intravenous administration to mice of SAA-high HDL, but not normal HDL, induced systemic inflammation and amplified allergen-induced neutrophilic airway inflammation and goblet cell metaplasia. CONCLUSIONS: SAA-high patients with asthma are characterized by systemic inflammation, older age, and an increased prevalence of obesity and severe asthma. HDL from SAA-high patients with asthma is proinflammatory and, when intravenously administered to mice, induces systemic inflammation, and amplifies allergen-induced neutrophilic airway inflammation. This suggests that systemic inflammation induced by SAA-high HDL may augment disease severity in asthma.

Anti-Inflammatory Effect of High-Density Lipoprotein Blunted by Delivery of Altered MicroRNA Cargo in Patients With Rheumatoid Arthritis.

OBJECTIVE: High-density lipoprotein (HDL) has well-characterized anti-atherogenic cholesterol efflux and antioxidant functions. Another function of HDL uncharacterized in rheumatoid arthritis (RA) is its ability to transport microRNAs (miRNAs) between cells and thus alter cellular function. The study's purpose was to determine if HDL-miRNA cargo is altered and affects inflammation in RA. METHODS: HDL-microRNAs were characterized in 30 RA and 30 control participants by next generation sequencing and quantitative polymerase chain reaction. The most abundant differentially expressed miRNA was evaluated further. The function of miR-1246 was assessed by miRNA mimics, antagomiRs, small interfering RNA knockdown, and luciferase assays. Monocyte-derived macrophages were treated with miR-1246-loaded HDL and unmodified HDL from RA and control participants to measure delivery of miR-1246 and its effect on interleukin-6 (IL-6). RESULTS: The most abundant miRNA on HDL was miR-1246; it was significantly enriched two-fold on HDL from RA versus control participants. HDL-mediated miR-1246 delivery to macrophages significantly increased IL6 expression 43-fold. miR-1246 delivery significantly decreased DUSP3 1.5-fold and DUSP3 small interfering RNA knockdown increased macrophage IL6 expression. Luciferase assay indicated DUSP3 is a direct target of miR-1246. Unmodified HDL from RA delivered 1.6-fold more miR-1246 versus control participant HDL. Unmodified HDL from both RA and control participants attenuated activated macrophage IL6 expression, but this effect was significantly blunted in RA so that IL6 expression was 3.4-fold higher after RA versus control HDL treatment. CONCLUSION: HDL-miR-1246 was increased in RA versus control participants and delivery of miR-1246 to macrophages increased IL-6 expression by targeting DUSP3. The altered HDL-miRNA cargo in RA blunted HDL's anti-inflammatory effect.

A green-inspired method to prepare non-split high-density lipoprotein (HDL) carrier with anti-dysfunctional activities superior to reconstituted HDL.

Numerous studies have demonstrated that dysfunctional high-density lipoprotein (HDL), especially oxidized HDL (OxHDL), could generate multifaceted in vivo proatherogenic effects that run counter to the antiatherogenic activities of HDL. It thereby reminded us that the in vitro reconstituted HDL (rHDL) might encountered with oxidation-induced dysfunction. Accordingly, a green-inspired method was employed to recycle non-split HDL from human plasma fraction IV. Then it was compared with rHDL formulated by an ethanol-injection method in terms of physicochemical properties and anti-dysfunctional activities. Results exhibited that rHDL oxidation extent exceeded that of non-split HDL evidenced by higher malondialdehy content, weaker inhibition on low-density lipoprotein (LDL) oxidation and more superoxide anion. The reserved paraoxonase-1 activity on non-split HDL could partially explain for above experimental results. In the targeted transport mechanism experiment, upon SR-BI receptor inhibition and/or CD36 receptor blockage, the almost unchanged non-split HDL uptake in lipid-laden macrophage indicated its negligible oxidation modification profile with regard to rHDL again. Furthermore, compared to rHDL, better macrophage biofunctions were observed for non-split HDL as illustrated by accelerated cholesterol efflux, inhibited oxidized LDL uptake and lessened cellular lipid accumulation. Along with decreased ROS secretion, obviously weakened oxidative stress damage was also detected under treatment with non-split HDL. More importantly, foam cells with non-split HDL-intervention inspired an enhanced inflammation repression and apoptosis inhibition effect. Collectively, the anti-dysfunctional activities of non-split HDL make it suitable as a potential nanocarrier platform for cardiovascular drug payload and delivery.

Swertia mussotii prevents high-fat diet-induced non-alcoholic fatty liver disease in rats by inhibiting expression the TLR4/MyD88 and the phosphorylation of NF-κB.

CONTEXT: Swertia mussotii Franch. (Gentianaceae) is a source of the traditional Tibetan medicine, ZangYinChen, and is used to treat chronic hepatitis and many types of jaundice. OBJECTIVE: This study explored the therapeutic effects and mechanism of S. mussotii on non-alcoholic fatty liver disease in diet-induced hypercholesterolaemia. MATERIALS AND METHODS: After a week of adaptive feeding, 32 Sprague-Dawley rats were divided into four groups: (1) Control, (2) Control-S, (3) Model, and (4) Model-S. During the 12 experimental weeks, we established the Model using a high-fat diet. Control-S and Model-S were given 1.0 g/kg S. mussotii water extract via gavage starting in the fifth week until the end of experiment. RESULTS: When compared with Model rats, the S. mussotii water extract led to a reduction in high-density lipoproteins (43.9%) and albumin (13.9%) and a decrease in total cholesterol (54.0%), triglyceride (45.6%), low-density lipoproteins (8.6%), aspartate aminotransferase (11.0%), alanine aminotransferase (15.5%), alkaline phosphatase (19.1%), total protein (6.4%), and glucose (20.8%) in serum. A reduction in three cytokines (IL-1ß, IL-6, and TNFα) was detected. Histopathological examination showed that liver steatosis was significantly relieved in S. mussotii-treated high-fat diet rats. S. mussotii also caused a downregulation in the expression of TLR4 (43.2%), MyD88 (33.3%), and a decrease in phosphorylation of NF-κB. DISCUSSION AND CONCLUSIONS: Our findings indicate that S. mussotii may act as a potential anti-inflammation drug via inhibition of the TLR4/MyD88/NF-κB pathway. Further in vivo and in vitro studies are needed to validate its potential in clinical medicine.

Reconstituted HDL-apoE3 promotes endothelial cell migration through ID1 and its downstream kinases ERK1/2, AKT and p38 MAPK.

INTRODUCTION: Atherosclerotic Coronary Artery Disease (ASCAD) is the leading cause of mortality worldwide. Novel therapeutic approaches aiming to improve the atheroprotective functions of High Density Lipoprotein (HDL) include the use of reconstituted HDL forms containing human apolipoprotein A-I (rHDL-apoA-I). Given the strong atheroprotective properties of apolipoprotein E3 (apoE3), rHDL-apoE3 may represent an attractive yet largely unexplored therapeutic agent. OBJECTIVE: To evaluate the atheroprotective potential of rHDL-apoE3 starting with the unbiased assessment of global transcriptome effects and focusing on endothelial cell (EC) migration as a critical process in re-endothelialization and atherosclerosis prevention. The cellular, molecular and functional effects of rHDL-apoE3 on EC migration-associated pathways were assessed, as well as the potential translatability of these findings in vivo. METHODS: Human Aortic ECs (HAEC) were treated with rHDL-apoE3 and total RNA was analyzed by whole genome microarrays. Expression and phosphorylation changes of key EC migration-associated molecules were validated by qRT-PCR and Western blot analysis in primary HAEC, Human Coronary Artery ECs (HCAEC) and the human EA.hy926 EC line. The capacity of rHDL-apoE3 to stimulate EC migration was assessed by wound healing and transwell migration assays. The contribution of MEK1/2, PI3K and the transcription factor ID1 in rHDL-apoE3-induced EC migration and activation of EC migration-related effectors was assessed using specific inhibitors (PD98059: MEK1/2, LY294002: PI3K) and siRNA-mediated gene silencing, respectively. The capacity of rHDL-apoE3 to improve vascular permeability and hypercholesterolemia in vivo was tested in a mouse model of hypercholesterolemia (apoE KO mice) using Evans Blue assays and lipid/lipoprotein analysis in the serum, respectively. RESULTS: rHDL-apoE3 induced significant expression changes in 198 genes of HAEC mainly involved in re-endothelialization and atherosclerosis-associated functions. The most pronounced effect was observed for EC migration, with 42/198 genes being involved in the following EC migration-related pathways: 1) MEK/ERK, 2) PI3K/AKT/eNOS-MMP2/9, 3) RHO-GTPases, 4) integrin. rHDL-apoE3 induced changes in 24 representative transcripts of these pathways in HAEC, increasing the expression of their key proteins PIK3CG, EFNB2, ID1 and FLT1 in HCAEC and EA.hy926 cells. In addition, rHDL-apoE3 stimulated migration of HCAEC and EA.hy926 cells, and the migration was markedly attenuated in the presence of PD98059 or LY294002. rHDL-apoE3 also increased the phosphorylation of ERK1/2, AKT, eNOS and p38 MAPK in these cells, while PD98059 and LY294002 inhibited rHDL-apoE3-induced phosphorylation of ERK1/2, AKT and p38 MAPK, respectively. LY had no effect on rHDL-apoE3-mediated eNOS phosphorylation. ID1 siRNA markedly decreased EA.hy926 cell migration by inhibiting rHDL-apoE3-triggered ERK1/2 and AKT phosphorylation. Finally, administration of a single dose of rHDL-apoE3 in apoE KO mice markedly improved vascular permeability as demonstrated by the reduced concentration of Evans Blue dye in tissues such as the stomach, the tongue and the urinary bladder and ameliorated hypercholesterolemia. CONCLUSIONS: rHDL-apoE3 significantly enhanced EC migration in vitro, predominantly via overexpression of ID1 and subsequent activation of MEK1/2 and PI3K, and their downstream targets ERK1/2, AKT and p38 MAPK, respectively, and improved vascular permeability in vivo. These novel insights into the rHDL-apoE3 functions suggest a potential clinical use to promote re-endothelialization and retard development of atherosclerosis.

Mimic Lipoproteins Responsive to Intratumoral pH and Allosteric Enzyme for Efficient Tumor Therapy.

Discoid-reconstituted high-density lipoprotein (d-rHDL) is advantageous for tumor-targeted drug delivery due to its small size, long circulation, and efficient internalization into cancer cells. Nevertheless, an allosteric reaction catalyzed by serum lecithin-cholesterol acyltransferase (LCAT) may cause drug leakage from d-rHDL and reduce its targeting efficiency. Conversely, similar "structural weakening" catalyzed by acyl-coenzyme A-cholesterol acyltransferase (ACAT) inside tumor cells can stimulate precise intracellular drug release. Therefore, we synthesized and characterized a pH-sensitive n-butyraldehyde bi-cholesterol (BCC) to substitute for cholesterol in the d-rHDL particle, and bovine serum albumin (BSA) was used as the targeting agent. This dual pH- and ACAT-sensitive d-rHDL (d-d-rHDL) was small with a disk-like appearance. Morphological transformation observation, in vitro release assays, and differences in internalization upon LCAT treatment confirmed that BCC effectively inhibited the remodeling behavior and enhanced the tumor-targeting efficiency. The accumulation of d-d-rHDL in HepG2 cells was significantly higher than that in LO2 cells, and accumulation was inhibited by free BSA. The pH sensitivity was verified, and d-d-rHDL achieved efficient drug release in vitro and inside tumor cells after exposure to acidic conditions and ACAT. Confocal laser scanning microscopy demonstrated that d-d-rHDL escaped from lysosomes and became distributed evenly throughout cells. Moreover, in vivo imaging assays in a tumor-bearing mouse model demonstrated tumor-targeting properties of d-d-rHDL, and paclitaxel-loaded d-d-rHDL showed strong anticancer activity in these mice. This dual-sensitive d-d-rHDL thus combines structural stability in plasma and an intracellular pH/ACAT-triggered drug release to facilitate inhibition of tumor growth.

Phospholipid nanoparticles: Therapeutic potentials against atherosclerosis via reducing cholesterol crystals and inhibiting inflammation.

BACKGROUND: Atherosclerosis-related cardiovascular diseases (CVDs) are the leading cause of mortality worldwide. Cholesterol crystals (CCs) induce inflammation in atherosclerosis and are associated with unstable plaques and poor prognosis, but no drug can remove CCs in the clinic currently. METHODS: We generated a phospholipid-based and high-density lipoprotein (HDL)-like nanoparticle, miNano, and determined CC-dissolving capacity, cholesterol efflux property, and anti-inflammation effects of miNano in vitro. Both normal C57BL/6J and Apoe-deficient mice were used to explore the accumulation of miNano in atherosclerotic plaques. The efficacy and safety of miNano administration to treat atherosclerosis were evaluated in the Ldlr-deficient atherosclerosis model. The CC-dissolving capacity of miNano was also detected using human atherosclerotic plaques ex vivo. FINDINGS: We found that miNano bound to and dissolved CCs efficiently in vitro, and miNano accumulated in atherosclerotic plaques, co-localized with CCs and macrophages in vivo. Administration of miNano inhibited atherosclerosis and improved plaque stability by reducing CCs and macrophages in Ldlr-deficient mice with favorable safety profiles. In macrophages, miNano prevented foam cell formation by enhancing cholesterol efflux and suppressed inflammatory responses via inhibiting TLR4-NF-κB pathway. Finally, in an ex vivo experiment, miNano effectively dissolved CCs in human aortic atherosclerotic plaques. INTERPRETATION: Together, our work finds that phospholipid-based and HDL-like nanoparticle, miNano, has the potential to treat atherosclerosis by targeting CCs and stabilizing plaques. FUNDING: This work was supported by the National Institutes of Health HL134569, HL109916, HL136231, and HL137214 to Y.E.C, HL138139 to J.Z., R21NS111191 to A.S., by the American Heart Association 15SDG24470155, Grant Awards (U068144 from Bio-interfaces and G024404 from M-BRISC) at the University of Michigan to Y.G., by the American Heart Association 19PRE34400017 and Rackham Helen Wu award to M.Y., NIH T32 GM07767 to K. H., Barbour Fellowship to D.L.

High-Density Lipoprotein Anti-Inflammatory Capacity and Incident Cardiovascular Events.

BACKGROUND: The role of high-density lipoprotein (HDL) function in cardiovascular disease represents an important emerging concept. The present study investigated whether HDL anti-inflammatory capacity is prospectively associated with first cardiovascular events in the general population. METHODS: HDL anti-inflammatory capacity was determined as its ability to suppress TNFα (tumor necrosis factor α)-induced VCAM-1 (vascular cell adhesion molecule-1) mRNA expression in endothelial cells in vitro (results expressed as achieved percent reduction by individual HDL related to the maximum TNFα effect with no HDL present). In a nested case-control design of the PREVEND (Prevention of Renal and Vascular End Stage Disease) study, 369 cases experiencing a first cardiovascular event (combined end point of death from cardiovascular causes, ischemic heart disease, nonfatal myocardial infarction, and coronary revascularization) during a median of 10.5 years of follow-up were identified and individually matched to 369 controls with respect to age, sex, smoking status, and HDL cholesterol. Baseline samples were available in 340 cases and 340 matched controls. RESULTS: HDL anti-inflammatory capacity was not correlated with HDL cholesterol or hsCRP (high-sensitivity C-reactive protein). HDL anti-inflammatory capacity was significantly lower in cases compared with controls (31.6% [15.7-44.2] versus 27.0% [7.4-36.1]; P<0.001) and was inversely associated with incident CVD in a fully adjusted model (odds ratio [OR] per 1 SD, 0.74 [CI, 0.61-0.90]; P=0.002). Furthermore, this association was approximately similar with all individual components of the cardiovascular disease end point. The HDL anti-inflammatory was not correlated with cholesterol efflux capacity (r=-0.02; P>0.05). When combining these 2 HDL function metrics in 1 model, both were significantly and independently associated with incident cardiovascular disease in a fully adjusted model (efflux: OR per 1 SD, 0.74; P=0.002; anti-inflammatory capacity: OR per 1 SD, 0.66; P<0.001). Adding HDL anti-inflammatory capacity improved risk prediction by the Framingham risk score, with a model likelihood-ratio statistic increase from 10.50 to 20.40 (P=0.002). CONCLUSIONS: The HDL anti-inflammatory capacity, reflecting vascular protection against key steps in atherogenesis, was inversely associated with incident cardiovascular events in a general population cohort, independent of HDL cholesterol and HDL cholesterol efflux capacity. Adding HDL anti-inflammatory capacity to the Framingham risk score improves risk prediction.

Identifying the role of apolipoprotein A-I in prostate cancer.

Although localized prostate cancer (PCa) can be cured by prostatectomy and radiotherapy, the development of effective therapeutic approaches for advanced prostate cancer, including castration-resistant PCa (CRPC) and neuroendocrine PCa (NEPC), is lagging far behind. Identifying a novel prognostic and diagnostic biomarker for early diagnosis and intervention is an urgent clinical need. Here, we report that apolipoprotein A-I (ApoA-I), the major component of high-density lipoprotein (HDL), is upregulated in PCa based on both bioinformatics and experimental evidence. The fact that advanced PCa shows strong ApoA-I expression reflects its potential role in driving therapeutic resistance and disease progression by reprogramming the lipid metabolic network of tumor cells. Molecularly, ApoA-I is regulated by MYC, a frequently amplified oncogene in late-stage PCa. Altogether, our findings have revealed a novel indicator to predict prognosis and recurrence, which would benefit patients who are prone to progress to metastasis or even NEPC, which is the lethal subtype of PCa.

The Anti-inflammatory and Proangiogenic Properties of High-Density Lipoproteins: An Emerging Role in Diabetic Wound Healing.

Significance: Prolonged inflammation and impaired angiogenesis are the two principal factors that prevent successful wound healing, which is exacerbated in people with diabetes. There is a significant need for new wound healing treatments that target both these factors simultaneously. This review discusses the emerging evidence that high-density lipoproteins (HDL) have pleiotropic wound healing benefits. Recent Advances: Numerous in vitro and in vivo studies have demonstrated the anti-inflammatory and proangiogenic effects of HDL. In endothelial cells, HDL mediate these effects through interaction with the scavenger receptor SR-BI, which activates the PI3K/Akt pathway, causing a decrease in inflammatory protein production and an increase in proangiogenic growth factors. In macrophages, HDL inhibit inflammation through suppression of the nuclear factor kappa B activation pathway. This review details the molecular disturbances that cause impaired wound healing in diabetes with a particular focus on inflammation and angiogenesis and the pathways in which HDL provide benefit. Critical Issues: Diabetic foot ulcers (DFUs) impose a major public health challenge worldwide. It is estimated that 20% patients with DFUs require amputation, which is accompanied by a significant social and economic burden. To date, there are no therapeutic agents with pleiotropic effects that actively improve wound healing, highlighting a therapeutic void for this complex disease.

The effects of high-density lipoprotein and oxidized high-density lipoprotein on forskolin-induced syncytialization of BeWo cells.

INTRODUCTION: The negative relationship between maternal high-density lipoprotein-cholesterol (HDL-c) level during pregnancy and infant birth weight has been found. Syncytialization (differentiation and fusion) of trophoblast cells is important to fetal development. HDL has an antioxidant effect, and has been proved to protect trophoblast functions including hormone secretion and invasion. However, HDL is susceptible to oxidation, and high concentrations of HDL impair cell growth and oxidized HDL (oxHDL) inhibits cell proliferation and migration. Moreover, the effects of HDL and oxHDL on trophoblast syncytialization have not been characterized. The aim of this study was to investigate the effects of HDL and oxHDL on trophoblast syncytialization. METHODS: Human choriocarcinoma trophoblasts (BeWo cells) were treated with human HDL or oxHDL and then induced to differentiate by forskolin in syncytialization assays. Expression levels of mRNAs and proteins regulating syncytialization were detected by real-time PCR and western blotting, respectively. RESULTS: Treatments of HDL at high concentrations reduced human chorionic gonadotropin (hCG) secretion, placental alkaline phosphatase activity and fusion rates, and decreased the expressions of GCM1 and ERVW-1 mRNA as well as phospho-MAPK1/3 (p-MAPK1/3) and total MAPK1/3 protein in the forskolin-induced syncytialization of BeWo cells. Furthermore, treatment of oxHDL (20 µg/ml) decreased hCG secretion, but increased the expression of p-MAPK1/3 protein. DISCUSSION: These data suggested that both HDL at high concentrations and oxHDL inhibited BeWo cells syncytialization, and might be harmful to placental and fetal development.

Lipoproteins LDL versus HDL as nanocarriers to target either cancer cells or macrophages.

In this work, we have explored natural unmodified low- and high-density lipoproteins (LDL and HDL, respectively) as selective delivery vectors in colorectal cancer therapy. We show in vitro in cultured cells and in vivo (NanoSPECT/CT) in the CT-26 mice colorectal cancer model that LDLs are mainly taken up by cancer cells, while HDLs are preferentially taken up by macrophages. We loaded LDLs with cisplatin and HDLs with the heat shock protein-70 inhibitor AC1LINNC, turning them into a pair of "Trojan horses" delivering drugs selectively to their target cells as demonstrated in vitro in human colorectal cancer cells and macrophages, and in vivo. Coupling of the drugs to lipoproteins and stability was assessed by mass spectometry and raman spectrometry analysis. Cisplatin vectorized in LDLs led to better tumor growth suppression with strongly reduced adverse effects such as renal or liver toxicity. AC1LINNC vectorized into HDLs induced a strong oxidative burst in macrophages and innate anticancer immune response. Cumulative antitumor effect was observed for both drug-loaded lipoproteins. Altogether, our data show that lipoproteins from patient blood can be used as natural nanocarriers allowing cell-specific targeting, paving the way toward more efficient, safer, and personalized use of chemotherapeutic and immunotherapeutic drugs in cancer.

HDL (High-Density Lipoprotein) and ApoA-1 (Apolipoprotein A-1) Potentially Modulate Pancreatic α-Cell Glucagon Secretion.

OBJECTIVE: Subjects with low levels of HDL (high-density lipoprotein) and ApoA-1 (apolipoprotein A-1) have increased risk to develop type 2 diabetes. HDL levels are an independent predictor of ß-cell function and positively modulate it. Type 2 diabetes is characterized by defects in both ß and α-cell function, but the effect of HDL and ApoA1 on α-cell function is unknown. Approach and Results: We observed a significant negative correlation (r=-0.422, P<0.0001) between HDL levels and fasting glucagon in a cohort of 132 Italian subjects. In a multivariable regression analysis including potential confounders such as age, sex, BMI, triglycerides, total cholesterol, fasting and 2-hour postload glucose, and fasting insulin, the association between HDL and fasting glucagon remained statistically significant (ß=-0.318, P=0.006). CD1 mice treated with HDL or ApoA-1 for 3 consecutive days showed a 32% (P<0.001) and 23% (P<0.05) reduction, respectively, in glucagon levels following insulin-induced hypoglycemia, compared with controls. Treatment of pancreatic αTC1 clone 6 cells with HDL or ApoA-1 for 24 hours resulted in a significant reduction of glucagon expression (P<0.04) and secretion (P<0.01) after an hypoglycemic stimulus and increased Akt (RAC-alpha serine/threonine-protein kinase) and FoxO1 (forkhead/winged helix box gene, group O-1) phosphorylation. Pretreatment with Akt inhibitor VIII, PI3K (phosphatidylinositol 3-kinase) inhibitor LY294002, and HDL receptor SCARB-1 (scavenger receptor class B type 1) inhibitor BLT-1 (block lipid transport-1) restored αTC1 cell response to low glucose levels. CONCLUSIONS: These results support the notion that HDL and ApoA-1 modulate glucagon expression and secretion by binding their cognate receptor SCARB-1, and activating the PI3K/Akt/FoxO1 signaling cascade in an in vitro α-cell model. Overall, these results raise the hypothesis that HDL and ApoA-1 may have a role in modulating glucagon secretion.

Gestational Diabetes Type 2: Variation in High-Density Lipoproteins Composition and Function.

Aims: Class A2 gestational diabetes mellitus (GDMA2) has short- and long-term effects on the mother and child. These may include abnormalities of placentation, damage to endothelial cells and cardiovascular disease. This research investigated the function and composition of high-density lipoproteins (HDL) among women with GDMA2 and their fetuses. Methods: Thirty pregnant women were recruited during admission for delivery. The function and expression of HDL, paraoxonase1 (PON1) and apolipoprotein A1 (APOA1) in the blood samples and the placental tissue were evaluated. The effect of HDL on migration of endothelial cells was measured in vitro. Results: Compared to normal pregnancy (NP), APOA1 in the maternal plasma of women with GDMA2 was decreased. More APOA1 and PON1 were released from HDL of women with GDMA2, compared to NP. Placental APOA1 and PON1 were decreased in GDMA2. For endothelial cells stimulated with TNFα, HDL cell migration was decreased when cells were evaluated with NP-HDL, as compared to GDMA2-HDL. Conclusions: GDMA2 affects the composition and function of HDL in plasma. Changes in HDL commonly seen in GDMA2 were observed in maternal and placental samples, but not in cord samples. These results might indicate a placental role in protecting the fetus by preserving the components and functions of HDL and require further investigation.

The Role of HDL and HDL Mimetic Peptides as Potential Therapeutics for Alzheimer's Disease.

The role of high-density lipoproteins (HDL) in the cardiovascular system has been extensively studied and the cardioprotective effects of HDL are well established. As HDL particles are formed both in the systemic circulation and in the central nervous system, the role of HDL and its associated apolipoproteins in the brain has attracted much research interest in recent years. Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder and the leading cause of dementia worldwide, for which there currently exists no approved disease modifying treatment. Multiple lines of evidence, including a number of large-scale human clinical studies, have shown a robust connection between HDL levels and AD. Low levels of HDL are associated with increased risk and severity of AD, whereas high levels of HDL are correlated with superior cognitive function. Although the mechanisms underlying the protective effects of HDL in the brain are not fully understood, many of the functions of HDL, including reverse lipid/cholesterol transport, anti-inflammation/immune modulation, anti-oxidation, microvessel endothelial protection, and proteopathy modification, are thought to be critical for its beneficial effects. This review describes the current evidence for the role of HDL in AD and the potential of using small peptides mimicking HDL or its associated apolipoproteins (HDL-mimetic peptides) as therapeutics to treat AD.

Low-Density Lipoproteins, High-Density Lipoproteins (HDL), and HDL-Associated Proteins Differentially Modulate Chronic Myelogenous Leukemia Cell Viability.

Cellular lipid metabolism, lipoprotein interactions, and liver X receptor (LXR) activation have been implicated in the pathophysiology and treatment of cancer, although findings vary across cancer models and by lipoprotein profiles. In this study, we investigated the effects of human-derived low-density lipoproteins (LDL), high-density lipoproteins (HDL), and HDL-associated proteins apolipoprotein A1 (apoA1) and serum amyloid A (SAA) on markers of viability, cholesterol flux, and differentiation in K562 cells-a bone marrow-derived, stem-like erythroleukemia cell model of chronic myelogenous leukemia (CML). We further evaluated whether lipoprotein-mediated effects were altered by concomitant LXR activation. We observed that LDL promoted higher K562 cell viability in a dose- and time-dependent manner and increased cellular cholesterol concentrations, while LXR activation by the agonist TO901317 ablated these effects. LXR activation in the presence of HDL, apoA1 and SAA-rich HDL suppressed K562 cell viability, while robustly inducing mRNA expression of ATP-binding cassette transporter A1 (ABCA1). HDL and its associated proteins additionally suppressed mRNA expression of anti-apoptotic B-cell lymphoma-extra large (BCL-xL), and the erythroid lineage marker 5'-aminolevulinate synthase 2 (ALAS2), while SAA-rich HDL induced mRNA expression of the megakaryocytic lineage marker integrin subunit alpha 2b (ITGA2B). Together, these findings suggest that lipoproteins and LXR may impact the viability and characteristics of CML cells.

Synthetic High-density Lipoprotein Nanodiscs for Personalized Immunotherapy Against Gliomas.

PURPOSE: Gliomas are brain tumors with dismal prognoses. The standard-of-care treatments for gliomas include surgical resection, radiation, and temozolomide administration; however, they have been ineffective in providing significant increases in median survival. Antigen-specific cancer vaccines and immune checkpoint blockade may provide promising immunotherapeutic approaches for gliomas. EXPERIMENTAL DESIGN: We have developed immunotherapy delivery vehicles based on synthetic high-density lipoprotein (sHDL) loaded with CpG, a Toll-like receptor-9 agonist, and tumor-specific neoantigens to target gliomas and elicit immune-mediated tumor regression. RESULTS: We demonstrate that vaccination with neoantigen peptide-sHDL/CpG cocktail in combination with anti-PD-L1 immune checkpoint blocker elicits robust neoantigen-specific T-cell responses against GL261 cells and eliminated established orthotopic GL261 glioma in 33% of mice. Mice remained tumor free upon tumor cell rechallenge in the contralateral hemisphere, indicating the development of immunologic memory. Moreover, in a genetically engineered murine model of orthotopic mutant IDH1 (mIDH1) glioma, sHDL vaccination with mIDH1 neoantigen eliminated glioma in 30% of animals and significantly extended the animal survival, demonstrating the versatility of our approach in multiple glioma models. CONCLUSIONS: Overall, our strategy provides a general roadmap for combination immunotherapy against gliomas and other cancer types.

HDL inhibits endoplasmic reticulum stress-induced apoptosis of pancreatic ß-cells in vitro by activation of Smoothened.

Loss of pancreatic ß-cell mass and function as a result of sustained ER stress is a core step in the pathogenesis of diabetes mellitus type 2. The complex control of ß-cells and insulin production involves hedgehog (Hh) signaling pathways as well as cholesterol-mediated effects. In fact, data from studies in humans and animal models suggest that HDL protects against the development of diabetes through inhibition of ER stress and ß-cell apoptosis. We investigated the mechanism by which HDL inhibits ER stress and apoptosis induced by thapsigargin, a sarco/ER Ca2+-ATPase inhibitor, in ß-cells of a rat insulinoma cell line, INS1e. We further explored effects on the Hh signaling receptor Smoothened (SMO) with pharmacologic agonists and inhibitors. Interference with sterol synthesis or efflux enhanced ß-cell apoptosis and abrogated the anti-apoptotic activity of HDL. During ER stress, HDL facilitated the efflux of specific oxysterols, including 24-hydroxycholesterol (OHC). Supplementation of reconstituted HDL with 24-OHC enhanced and, in cells lacking ABCG1 or the 24-OHC synthesizing enzyme CYP46A1, restored the protective activity of HDL. Inhibition of SMO countered the beneficial effects of HDL and also LDL, and SMO agonists decreased ß-cell apoptosis in the absence of ABCG1 or CYP46A1. The translocation of the SMO-activated transcription factor glioma-associated oncogene GLI-1 was inhibited by ER stress but restored by both HDL and 24-OHC. In conclusion, the protective effect of HDL to counter ER stress and ß-cell death involves the transport, generation, and mobilization of oxysterols for activation of the Hh signaling receptor SMO.

Modification of HDL by reactive aldehydes alters select cardioprotective functions of HDL in macrophages.

While increased levels of high-density lipoprotein (HDL)-cholesterol correlate with protection against cardiovascular disease, recent findings demonstrate that HDL function, rather than HDL-cholesterol levels, may be a better indicator of cardiovascular risk. One mechanism by which HDL function can be compromised is through modification by reactive aldehydes such as acrolein (Acro), 4-hydroxynonenal, and malondialdehyde (MDA). In this study, we tested the hypothesis that modification of HDL with reactive aldehydes would impair HDL's athero-protective functions in macrophages. Compared to native HDL, Acro- and MDA-modified HDL have impaired abilities to promote migration of primary peritoneal macrophages isolated from C57BL6/J mice. Incubation of macrophages with MDA-HDL also led to an increased ability to generate reactive oxygen species. Our studies revealed that the changes in HDL function following aldehyde modification are likely not through activation of canonical nuclear factor-kappa B signaling pathways. Consistent with this finding, treatment of either noncholesterol-loaded macrophages or foam cells with modified forms of HDL does not lead to significant changes in expression levels of inflammatory markers. Importantly, our data also demonstrate that changes in HDL function are dependent on the type of modification present on the HDL particle. Our findings suggest that modification of HDL with reactive aldehydes can impair some, but not all, of HDL's athero-protective functions in macrophages.