Autoreactive lymphocytes that infiltrate the pancreatic islet environment and target β cells are primary drivers of type 1 diabetes. In this issue of Immunity, Srivastava et al.1 examine the role of the islet microenvironment in autoimmunity and find that the scavenging receptor CXCL16 on islet-resident macrophages uptakes oxidized low-density lipoproteins and promotes the differentiation and survival of infiltrating pathogenic CD8+ T cells.

Lipids are compounds involved in many biologic functions including cell structure, metabolism, energy storage and are involved in signaling. A prominent lipid in these functions is cholesterol. Cholesterol also plays a part in the signaling of melanocytes, which contain melanosomes. The maturation of these melanosomes happens during melanocyte growth. The deficit of melanogenesis or melanosome maturation is associated with ocular albinism in the eye. Aberrations of melanosome maturation are also associated with pigment dispersion syndrome. Albinism and pigment dispersion manifestations are systemic. Both melanogenesis and melanocyte maturation are affected by cholesterol metabolism. Cholesterol signaling is a part of many pathways in the body, and evaluating these signals can have implications in systemic disease processes of melanogenesis and melanosome maturation, like ocular albinism and pigment dispersion. Cholesterol is carried by lipoprotein particles. Low-density lipoprotein (LDL) is usually the transport vehicle for cholesterol to reach tissues and organelles. The LDL uptake on cells often sends out a cascade of internal signaling within the cells. We describe here LDL signaling related to lipase activity changes using enzymatic methods with a kit. We describe analyses of cholesterol esters and free cholesterol with liquid chromatography and gas chromatography with or in tandem with mass spectrometry (GC-MS and LC-MS/MS). These analyses will provide insight into melanosome maturation and melanogenesis. The methods described here are applicable to all melanocytes within the body of a model mammalian organism.

Lipoproteins in plasma are constituted by the least dense chylomicron, very-low-density lipoprotein (VLDL), low-density lipoprotein (LDL), and high-density lipoprotein (HDL) that can be separated using commercially available medium such as iodixanol. Iodixanol constitutes the self-generated density gradient to fractionate lipoproteins by rapid ultracentrifugation method, replacing time-consuming protocols. Filling the centrifuge tubes is technically easier and faster than layering salt gradients and is reproducible. The separated lipoproteins by this method are closest to the native state with 80 to 100% recovery possible. Low-density lipoprotein is the major carrier of cholesterol in systemic circulation. The plasma isolated LDL is purified to be used as native LDL and for the preparation of oxidized LDL (oxLDL). The oxLDL is characterized for its oxidation, by various methods based on assay of the lipid and protein oxidation products such as TBARS, conjugated diene formation, and by other methods such as agarose gel electrophoresis. Rapid isolation of LDL particles from human plasma is useful for lipid peroxidation studies, characterization of subclass for functional studies and clinical correlation especially in cardiovascular diseases apart from lipidomic, and proteomic studies. OxLDL preparations are done in vitro chiefly based on copper-induced oxidation; glucose and other prooxidants. Which are used for various studies using animal model and in vitro cell models especially to understand macrophage-mediated atheroma formation, vascular endothelial cell dysfunction, cell signaling studies has scope for extensive research in metabolic dysfunction of various cells.  This chapter deals with one of the applications in the in vitro cell models using macrophage (THP-1 cell line) and human retinal pigment epithelial cell (ARPE-19 cell line) to study the oxLDL uptake using fluorescently labeled oxidized LDL (DiI-oxLDL).

Atherosclerosis refers to a disease characterized by the formation of lipid plaque deposits within arterial walls, leading to reduced blood flow or blockage of blood outflow. The process of endothelial injury induced by oxidized low-density lipoprotein (ox-LDL) is considered the initial stage of atherosclerosis. Ferroptosis is a form of iron-dependent, non-apoptotic cell death, and current research suggests its association with coronary artery disease (CAD). In this study, we observed a correlation between reduced expression of SREBP-1 and the occurrence of stable CAD. Additionally, during the process of endothelial injury induced by ox-LDL, we also noted decreased expression of the SREBP-1/SCD1/FADS2 and involvement in the ferroptosis process. Mechanistically, ox-LDL induced endothelial injury by inhibiting the lipid biosynthesis process mediated by the SREBP-1/SCD1/FADS2, thereby inducing lipid peroxidation and ferroptosis. On the contrary, overexpression of SREBP-1 or supplementation with monounsaturated fatty acids counteracted iron accumulation, mitochondrial damage, and lipid peroxidation-induced ferroptosis, thereby improving endothelial injury. Our study indicated that the decreased expression of peripheral blood SREBP-1 mRNA is an independent risk factor for stable CAD. Furthermore, in endothelial cells, the lipid biosynthesis process mediated by SREBP-1 could ameliorate endothelial injury by resisting ferroptosis. The study has been registered with the Chinese Clinical Trial Registry, which serves as a primary registry in the World Health Organization International Clinical Trials Registry Platform (ChiCTR2300074315, August 3rd, 2023).

Proprotein convertase subtilisin/kexin type 9 (PCSK9) has emerged as a promising therapeutic target to reduce lipids. In 2020, we reported a chimeric camelid-human heavy chain antibody VHH-B11-Fc targeting PCSK9. Recently, it was verified that VHH-B11 binds one linear epitope in the PCSK9 hinge region. To enhance its druggability, we have developed a novel biparatopic B11-H2-Fc Ab herein. Thereinto, surface plasmon resonance (SPR) confirmed the epitope differences in binding-PCSK9 among VHH-B11, VHH-H2 and the approved Repatha. Additionally, SPR revealed the B11-H2-Fc exhibits an avidity of approximately 0.036 nM for PCSK9, representing a considerable increase compared to VHH-B11-Fc (~ 0.69 nM). Moreover, we found the Repatha and B11-H2-Fc exhibited > 95% PCSK9 inhibition efficiency compared to approximately 48% for the VHH-Fc at 7.4 nM (P < 0.0005). Further, we verified its biological activity using the human hepatoma cells G2 model, where the B11-H2-Fc exhibited almost 100% efficiency in PCSK9 inhibition at only 0.75 μM. The immunoblotting results of low-density lipoprotein cholesterol (LDL-c) uptake assay also demonstrated the excellent performance of B11-H2-Fc on recovering the LDL-c receptor (LDLR), as strong as the Repatha (P > 0.05). These findings provide the first evidence of the efficacy of a novel Ab targeting PCSK9 in the field of lipid-lowering drugs.

Despite data suggesting that apolipoprotein B (apoB) measurement outperforms low-density lipoprotein cholesterol level measurement in predicting atherosclerotic cardiovascular disease risk, apoB measurement has not become widely adopted into routine clinical practice. One barrier for use of apoB measurement is lack of consistent guidance for clinicians on how to interpret and apply apoB results in clinical context. Whereas guidelines have often provided clear low-density lipoprotein cholesterol targets or triggers to initiate treatment change, consistent targets for apoB are lacking. In this review, we synthesize existing data regarding the epidemiology of apoB by comparing guideline recommendations regarding use of apoB measurement, describing population percentiles of apoB relative to low-density lipoprotein cholesterol levels, summarizing studies of discordance between low-density lipoprotein cholesterol and apoB levels, and evaluating apoB levels in clinical trials of lipid-lowering therapy to guide potential treatment targets. We propose evidence-guided apoB thresholds for use in cholesterol management and clinical care.

Veterans living with HIV (VLWH) and hepatitis C virus (HCV) co-infection have an exacerbated risk of cardiovascular disease (CVD). It is unknown if HCV cure reduces CVD risk in this population. We evaluated changes in low-density lipoprotein (LDL), as a surrogate of CVD risk, 18 months after HCV cure in VLWH. We found significant increases in LDL in VLWH with advanced fibrosis, potentially increasing CVD risk. Lower LDL thresholds to initiate lipid-lowering therapies in VLWH after HCV cure may be warranted.

Arterial macrophage cholesterol accumulation and impaired cholesterol efflux lead to foam cell formation and the development of atherosclerosis. Modified lipoproteins interact with toll-like receptors (TLR), causing an increased inflammatory response and altered cholesterol homeostasis. We aimed to determine the effects of TLR antagonists on cholesterol efflux and foam cell formation in human macrophages. Stimulated monocytes were treated with TLR antagonists (MIP2), and the cholesterol efflux transporter expression and foam cell formation were analyzed. The administration of MIP2 attenuated the foam cell formation induced by lipopolysaccharides (LPS) and oxidized low-density lipoproteins (ox-LDL) in stimulated THP-1 cells (p < 0.001). The expression of ATP-binding cassette transporters A (ABCA)-1, ABCG-1, scavenger receptor (SR)-B1, liver X receptor (LXR)-α, and peroxisome proliferator-activated receptor (PPAR)-γ mRNA and proteins were increased (p < 0.001) following MIP2 administration. A concentration-dependent decrease in the phosphorylation of p65, p38, and JNK was also observed following MIP2 administration. Moreover, an inhibition of p65 phosphorylation enhanced the expression of ABCA1, ABCG1, SR-B1, and LXR-α. TLR inhibition promoted the cholesterol efflux pathway by increasing the expression of ABCA-1, ABCG-1, and SR-B1, thereby reducing foam cell formation. Our results suggest a potential role of the p65/NF-kB/LXR-α/ABCA1 axis in TLR-mediated cholesterol homeostasis.

暂无摘要。

OBJECTIVE: To explore high density lipoprotein (HDL)/low density lipoprotein (LDL) and total typeⅠcollagen amino terminal extender peptide (t-PINP)/ C-terminal peptide of typeⅠcollagen β special sequence(β-CTX)and risk of osteoporosis vertebral fractures (OPVFs) in elderly women.
METHODS: The clinical data of 446 female OPVFs patients aged above 60 years old from January 2019 to December 2020 were retrospectively analyzed. According to whether or not fracture, patients were divided into non-fracture group (186 patients) and fracture group(260 patients). Univariate analysis was performed to analysis age, body mass index(BMI), N-terminal mioldle molecular fragment of osteocalcin, N-MID OC), t-PINP, β-CTX, 25-hydroxyvitamin D[25-(OH) VitD], blood sugar (Glu), total cholesterol(TC), high-density lipoprotein (HDL), low-density lipoprotein (LDL), Ca, P, Mg, urea (UREA), creatinine (Cr) and Cystatin C(CysC), and correlation between OPVFs and the above indexes and lipid, bone metabolism indexes between two groups;Logistic regression was performed to analyze risk factors and stratification relationship between vertebral fracture and HDL/LDL, t-PINP/β-CTX. Logistic regression was used to analyze risk factors and stratification relationship between OPVFs and HDL/LDL, t-PINP/β-CTX.
RESULTS: There were no significant difference in age and BMI between non-fracture group and fracture group (P>0.05). Compared with non-fracture group, contents of HDL, t-PINP/β-CTX and HDL/LDL in fracture group were decreased, and contents of β-CTX were increased (P<0.05). OPVFs was positively correlated with β-CTX (r=0.110, P<0.05), and negatively correlated with HDL, HDL/LDL and t-PINP/β-CTX (r=-0.157, -0.175, -0.181, P<0.05). HDL and HDL/LDL were negatively correlated with β-CTX (r=-0.22, -0.12, P<0.05) and t-PINP (r=-0.13, -0.10, P<0.05). 25-(OH) VitD was positively correlated with TC and HDL (r=0.11, 0.18, P<0.05). HDL/LDL was positively correlated with t-PINP/β-CTX(r=0.11, P=0.02). t-PINP/β-CTX[OR=0.998, 95%CI(0.997, 1.000), P<0.05], HDL/LDL[OR=0.228, 95%CI(0.104, 0.499), P<0.01] were risk factors for vertebral fracture. The lower levels between two tristratified indicators, the higher the vertebral fracture rate. The risk of fracture was 2.5 and 2 times higher in the lowest stratum than in the highest stratum, with an adjusted OR was[2.112, 95%CI(1.310, 3.404)] and [2.331, 95%CI(1.453, 3.739)], respectively.
CONCLUSIONS: Serum low HDL/LDL and t-PINP /β-CTX are independent risk factors for OPVF in elderly women, and have good predictive value for OPVF risk.