scholarly journals Hypolipidaemia among patients with PMM2-CDG is associated with low circulating PCSK9 levels: a case report followed by observational and experimental studies

2019 ◽  
Vol 57 (1) ◽  
pp. 11-17 ◽  
Author(s):  
Michael Chong ◽  
Grace Yoon ◽  
Delia Susan-Resiga ◽  
Ann Chamberland ◽  
David Cheillan ◽  
...  
Keyword(s):  
Side Effects ◽  
Experimental Studies ◽  
Ldl Receptor ◽  
Cerebellar Atrophy ◽  
Density Lipoprotein ◽  
Negative Regulator ◽  
Global Developmental Delay ◽  
Loss Of Function ◽  
Pcsk9 Inhibitors

BackgroundProprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors are novel therapeutics for reducing low-density lipoprotein cholesterol (LDLc). While serious side-effects have not been observed in short-term clinical trials, there remain concerns that long-term PCSK9 inhibition may cause neurocognitive side-effects.Methods and resultsAn adult male with childhood-onset global developmental delay, cerebellar atrophy and severe hypolipidaemia underwent extensive biochemical and genetic investigations. Initial testing revealed low circulating PCSK9 levels and a common loss-of-function PCSK9 polymorphism, but these findings did not fully account for severe hypolipidaemia. Whole-exome sequencing was subsequently performed and identified two pathogenic phosphomannose mutase 2 (PMM2) variants (p.Arg141His and p.Pro69Ser) known to cause PMM2-associated congenital disorder of glycosylation (PMM2-CDG). A diagnosis of PMM2-CDG was consistent with the proband’s neurological symptoms and severe hypolipidaemia. Given that PMM2-CDG is characterised by defective protein N-glycosylation and that PCSK9 is a negative regulator of LDLc, we postulated that loss of PCSK9 N-glycosylation mediates hypolipidaemia among patients with PMM2-CDG. First, in an independent cohort of patients with PMM2-CDG (N=8), we verified that circulating PCSK9 levels were significantly lower in patients than controls (p=0.0006). Second, we conducted in vitro experiments in hepatocyte-derived cells to evaluate the effects of PCSK9 N-glycosylation loss on LDL receptor (LDLR) activity. Experimental results suggest that defective PCSK9 N-glycosylation reduces the ability of circulating PCSK9 to degrade LDLR.ConclusionLife-long exposure to genetically lower PCSK9 per se is unlikely to cause neurocognitive impairment. Both observational and experimental findings suggest that hypolipidaemia in PMM2-CDG may be partially mediated by loss of PCSK9 N-glycosylation and/or its regulators.

scholarly journals A transient amphipathic helix in the prodomain of PCSK9 facilitates binding to low-density lipoprotein particles

2020 ◽  
Vol 295 (8) ◽  
pp. 2285-2298
Author(s):  
Samantha K. Sarkar ◽  
Alexander C. Y. Foo ◽  
Angela Matyas ◽  
Ikhuosho Asikhia ◽  
Tanja Kosenko ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Low Density Lipoprotein ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Low Density ◽  
Loss Of Function ◽  
Ldl Particles ◽  
Ldl Binding ◽  
Α Helix

Proprotein convertase subtilisin/kexin type-9 (PCSK9) is a ligand of low-density lipoprotein (LDL) receptor (LDLR) that promotes LDLR degradation in late endosomes/lysosomes. In human plasma, 30–40% of PCSK9 is bound to LDL particles; however, the physiological significance of this interaction remains unknown. LDL binding in vitro requires a disordered N-terminal region in PCSK9's prodomain. Here, we report that peptides corresponding to a predicted amphipathic α-helix in the prodomain N terminus adopt helical structure in a membrane-mimetic environment. This effect was greatly enhanced by an R46L substitution representing an atheroprotective PCSK9 loss-of-function mutation. A helix-disrupting proline substitution within the putative α-helical motif in full-length PCSK9 lowered LDL binding affinity >5-fold. Modeling studies suggested that the transient α-helix aligns multiple polar residues to interact with positively charged residues in the C-terminal domain. Gain-of-function PCSK9 mutations associated with familial hypercholesterolemia (FH) and clustered at the predicted interdomain interface (R469W, R496W, and F515L) inhibited LDL binding, which was completely abolished in the case of the R496W variant. These findings shed light on allosteric conformational changes in PCSK9 required for high-affinity binding to LDL particles. Moreover, the initial identification of FH-associated mutations that diminish PCSK9's ability to bind LDL reported here supports the notion that PCSK9-LDL association in the circulation inhibits PCSK9 activity.

PCSK9 inhibition for LDL lowering and beyond – implications for patients with peripheral artery disease

VASA ◽  
2018 ◽  
Vol 47 (3) ◽  
pp. 165-176 ◽  
Author(s):  
Katrin Gebauer ◽  
Holger Reinecke
Keyword(s):  
Cardiovascular Risk ◽  
Risk Reduction ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Past Century ◽  
Pcsk9 Inhibitors ◽  
Cardiovascular Risk Reduction ◽  
Simultaneous Application ◽  
The Past ◽  
Pcsk9 Inhibition

Abstract. Low-density lipoprotein cholesterol (LDL-C) has been proven to be a causal factor of atherosclerosis and, along with other triggers like inflammation, the most frequent reason for peripheral arterial disease. Moreover, a linear correlation between LDL-C concentration and cardiovascular outcome in high-risk patients could be established during the past century. After the development of statins, numerous randomized trials have shown the superiority for LDL-C reduction and hence the decrease in cardiovascular outcomes including mortality. Over the past decades it became evident that more intense LDL-C lowering, by either the use of highly potent statin supplements or by additional cholesterol absorption inhibitor application, accounted for an even more profound cardiovascular risk reduction. Proprotein convertase subtilisin/kexin type 9 (PCSK9), a serin protease with effect on the LDL receptor cycle leading to its degradation and therefore preventing continuing LDL-C clearance from the blood, is the target of a newly developed monoclonal antibody facilitating astounding LDL-C reduction far below to what has been set as target level by recent ESC/EAS guidelines in management of dyslipidaemias. Large randomized outcome trials including subjects with PAD so far have been able to prove significant and even more intense cardiovascular risk reduction via further LDL-C debasement on top of high-intensity statin medication. Another approach for LDL-C reduction is a silencing interfering RNA muting the translation of PCSK9 intracellularly. Moreover, PCSK9 concentrations are elevated in cells involved in plaque composition, so the potency of intracellular PCSK9 inhibition and therefore prevention or reversal of plaques may provide this mechanism of action on PCSK9 with additional beneficial effects on cells involved in plaque formation. Thus, simultaneous application of statins and PCSK9 inhibitors promise to reduce cardiovascular event burden by both LDL-C reduction and pleiotropic effects of both agents.

scholarly journals Liver X Receptor Nuclear Receptors Are Transcriptional Regulators of Dendritic Cell Chemotaxis

2018 ◽  
Vol 38 (10) ◽  
Author(s):  
Susana Beceiro ◽  
Attila Pap ◽  
Zsolt Czimmerer ◽  
Tamer Sallam ◽  
Jose A. Guillén ◽  
...  
Keyword(s):  
Nuclear Receptors ◽  
Low Density Lipoprotein ◽  
Myeloid Cells ◽  
Density Lipoprotein ◽  
Loss Of Function ◽  
Transcriptional Responses ◽  
Cd38 Expression ◽  
The Impact

ABSTRACTThe liver X receptors (LXRs) are ligand-activated nuclear receptors with established roles in the maintenance of lipid homeostasis in multiple tissues. LXRs exert additional biological functions as negative regulators of inflammation, particularly in macrophages. However, the transcriptional responses controlled by LXRs in other myeloid cells, such as dendritic cells (DCs), are still poorly understood. Here we used gain- and loss-of-function models to characterize the impact of LXR deficiency on DC activation programs. Our results identified an LXR-dependent pathway that is important for DC chemotaxis. LXR-deficient mature DCs are defective in stimulus-induced migrationin vitroandin vivo. Mechanistically, we show that LXRs facilitate DC chemotactic signaling by regulating the expression of CD38, an ectoenzyme important for leukocyte trafficking. Pharmacological or genetic inactivation of CD38 activity abolished the LXR-dependent induction of DC chemotaxis. Using the low-density lipoprotein receptor-deficient (LDLR−/−) LDLR−/−mouse model of atherosclerosis, we also demonstrated that hematopoietic CD38 expression is important for the accumulation of lipid-laden myeloid cells in lesions, suggesting that CD38 is a key factor in leukocyte migration during atherogenesis. Collectively, our results demonstrate that LXRs are required for the efficient emigration of DCs in response to chemotactic signals during inflammation.

scholarly journals Knockdown of lncRNA ENST00000609755.1 Confers Protection Against Early oxLDL-Induced Coronary Heart Disease

2021 ◽  
Vol 8 ◽  
Author(s):  
Yi Sun ◽  
Shuna Huang ◽  
Chunyu Wan ◽  
Qishuang Ruan ◽  
Xiaoxu Xie ◽  
...  
Keyword(s):  
Coronary Heart Disease ◽  
Heart Disease ◽  
Peripheral Blood ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Peripheral Blood Leukocyte ◽  
Loss Of Function ◽  
Human Coronary Artery ◽  
Injury Model

Background: This study investigated the association between long non-coding RNAs (lncRNAs) and coronary heart disease (CHD) and further elucidated the potential biological roles of lncRNAs in CHD pathogenesis.Methods: A case-control study (590 patients and 590 controls) was conducted from February 2017 and March 2019 in Fuzhou, China. Environmental factors were investigated using questionnaires and physical examinations. Five representative lncRNAs were screened using lncRNA microarray (peripheral blood in 5 cases and 5 controls) and further verified by quantitative real-time polymerase chain reaction (peripheral blood leukocyte in 100 cases and 100 controls). Oxidized low-density lipoprotein (oxLDL) was used to induce a human coronary artery endothelial cell (HCAECs) injury model, and loss of function was used to elucidate the role of lncRNA ENST00000609755.1 (lnc-MICALL2-2) in oxLDL-induced HCAECs injury.Results: A total of 320 lncRNAs were found dysregulated in CHD patients (fold change> 2, p < 0.05). The results of a discovery microarray, population verification and HCAEC experiments suggested the lnc-MICALL2-2 is upregulated in CHD subjects and in an oxLDL-induced HCAECs injury model. Conversely, lnc-MICALL2-2 inhibition in vitro attenuated the effects of oxLDL on HCAECs morphology, proliferation, and apoptosis.Conclusion: Elevated expression of lnc-MICALL2-2 is an independent risk factor for CHD, and knockdown subsequently confers protection against early pathological processes of oxLDL-induced CHD.

scholarly journals Development of an LDL Receptor-Targeted Peptide Susceptible to Facilitate the Brain Access of Diagnostic or Therapeutic Agents

Biology ◽  
2020 ◽  
Vol 9 (7) ◽  
pp. 161
Author(s):  
Séverine André ◽  
Lionel Larbanoix ◽  
Sébastien Verteneuil ◽  
Dimitri Stanicki ◽  
Denis Nonclercq ◽  
...  
Keyword(s):  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Therapeutic Agents ◽  
In Vivo Studies ◽  
Phage Display Technology ◽  
Brain Penetration ◽  
Wide Range ◽  
The Brain

Blood-brain barrier (BBB) crossing and brain penetration are really challenging for the delivery of therapeutic agents and imaging probes. The development of new crossing strategies is needed, and a wide range of approaches (invasive or not) have been proposed so far. The receptor-mediated transcytosis is an attractive mechanism, allowing the non-invasive penetration of the BBB. Among available targets, the low-density lipoprotein (LDL) receptor (LDLR) shows favorable characteristics mainly because of the lysosome-bypassed pathway of LDL delivery to the brain, allowing an intact discharge of the carried ligand to the brain targets. The phage display technology was employed to identify a dodecapeptide targeted to the extracellular domain of LDLR (ED-LDLR). This peptide was able to bind the ED-LDLR in the presence of natural ligands and dissociated at acidic pH and in the absence of calcium, in a similar manner as the LDL. In vitro, our peptide was endocytosed by endothelial cells through the caveolae-dependent pathway, proper to the LDLR route in BBB, suggesting the prevention of its lysosomal degradation. The in vivo studies performed by magnetic resonance imaging and fluorescent lifetime imaging suggested the brain penetration of this ED-LDLR-targeted peptide.

PCSK9 and inflammation: role of shear stress, pro-inflammatory cytokines, and LOX-1

2019 ◽  
Vol 116 (5) ◽  
pp. 908-915 ◽  
Author(s):  
Zufeng Ding ◽  
Naga Venkata K Pothineni ◽  
Akshay Goel ◽  
Thomas F Lüscher ◽  
Jawahar L Mehta
Keyword(s):  
Inflammatory Cytokines ◽  
Ldl Cholesterol ◽  
Vascular Endothelial Cells ◽  
Oxidized Ldl ◽  
Low Density Lipoprotein ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Pcsk9 Inhibitors ◽  
Prevention Of Atherosclerosis ◽  
Pro Inflammatory Cytokines

Abstract PCSK9 degrades low-density lipoprotein cholesterol (LDL) receptors and subsequently increases serum LDL cholesterol. Clinical trials show that inhibition of PCSK9 efficiently lowers LDL cholesterol levels and reduces cardiovascular events. PCSK9 inhibitors also reduce the extent of atherosclerosis. Recent studies show that PCSK9 is secreted by vascular endothelial cells, smooth muscle cells, and macrophages. PCSK9 induces secretion of pro-inflammatory cytokines in macrophages, liver cells, and in a variety of tissues. PCSK9 regulates toll-like receptor 4 expression and NF-κB activation as well as development of apoptosis and autophagy. PCSK9 also interacts with oxidized-LDL receptor-1 (LOX-1) in a mutually facilitative fashion. These observations suggest that PCSK9 is inter-twined with inflammation with implications in atherosclerosis and its major consequence—myocardial ischaemia. This relationship provides a basis for the use of PCSK9 inhibitors in prevention of atherosclerosis and related clinical events.

scholarly journals Human USP18 deficiency underlies type 1 interferonopathy leading to severe pseudo-TORCH syndrome

2016 ◽  
Vol 213 (7) ◽  
pp. 1163-1174 ◽  
Author(s):  
Marije E.C. Meuwissen ◽  
Rachel Schot ◽  
Sofija Buta ◽  
Grétel Oudesluijs ◽  
Sigrid Tinschert ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Genetic Disorders ◽  
Genetic Disorder ◽  
Congenital Infection ◽  
Infectious Agent ◽  
Negative Regulator ◽  
Type I ◽  
Loss Of Function

Pseudo-TORCH syndrome (PTS) is characterized by microcephaly, enlarged ventricles, cerebral calcification, and, occasionally, by systemic features at birth resembling the sequelae of congenital infection but in the absence of an infectious agent. Genetic defects resulting in activation of type 1 interferon (IFN) responses have been documented to cause Aicardi-Goutières syndrome, which is a cause of PTS. Ubiquitin-specific peptidase 18 (USP18) is a key negative regulator of type I IFN signaling. In this study, we identified loss-of-function recessive mutations of USP18 in five PTS patients from two unrelated families. Ex vivo brain autopsy material demonstrated innate immune inflammation with calcification and polymicrogyria. In vitro, patient fibroblasts displayed severely enhanced IFN-induced inflammation, which was completely rescued by lentiviral transduction of USP18. These findings add USP18 deficiency to the list of genetic disorders collectively termed type I interferonopathies. Moreover, USP18 deficiency represents the first genetic disorder of PTS caused by dysregulation of the response to type I IFNs. Therapeutically, this places USP18 as a promising target not only for genetic but also acquired IFN-mediated CNS disorders.

scholarly journals A novel peroxisome proliferator response element modulates hepatic low-density lipoprotein receptor gene transcription in response to PPARδ activation

2015 ◽  
Vol 472 (3) ◽  
pp. 275-286 ◽  
Author(s):  
Vikram R. Shende ◽  
Amar Bahadur Singh ◽  
Jingwen Liu
Keyword(s):  
Gene Transcription ◽  
Receptor Gene ◽  
Low Density Lipoprotein ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Peroxisome Proliferator ◽  
Density Lipoprotein Receptor ◽  
Peroxisome Proliferator Response Element

PPARδ activation beneficially regulates lipid metabolism. We have now identified a novel function of PPARδ that increases LDL receptor gene transcription in hepatic cells in vitro and in vivo through direct binding to a PPRE motif on LDLR promoter.

scholarly journals The efficacy of evolocumab in the management of hyperlipidemia: a systematic review

2017 ◽  
Vol 11 (5-6) ◽  
pp. 155-169 ◽  
Author(s):  
Lamia AlHajri ◽  
Asma AlHadhrami ◽  
Shama AlMheiri ◽  
Yalwah AlMutawa ◽  
Zainab AlHashimi
Keyword(s):  
Systematic Review ◽  
Side Effects ◽  
Lipid Profile ◽  
Data Extraction ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Lipoprotein Cholesterol ◽  
Pcsk9 Inhibitors ◽  
Lipid Management ◽  
Highly Effective

Background: Hyperlipidemia or dyslipidemia has been a concern for a long time, with various guidelines emphasizing the importance of managing the lipid profile to prevent cardiac incidences. Although statins have been found to be highly effective, resistance and intolerability to side effects will continue to be a stumbling block for certain patients. Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors tackle lipid profile via a novel mechanism and therefore provide an additional effective option for managing lipid profile. The overarching aim of this systematic review was to evaluate the efficacy of evolocumab among various populations with hypercholesterolemia. Methods: A comprehensive search was conducted in ProQuest Health & Medical Complete, Google Scholar, ScienceDirect, and PubMed to identify potential records; then titles, abstracts, and full texts were screened using the inclusion criteria to filter out irrelevant studies. Data extraction and quality assessment were undertaken using standardized tools and the results were narratively synthesized and presented in tables. Results: Eight studies were included in this systematic review after screening 1191 records. All studies demonstrated a statistically significant reduction in low-density lipoprotein cholesterol (LDL-C) values in the groups that received evolocumab compared with the comparator groups ( p < 0.05). The decline in LDL-C levels from baseline in the majority of studies ranged from 40% to 80%, whether used alone or in combination with other agents. Also, high-density lipoprotein cholesterol, lipoprotein (a) and apolipoprotein B were improved with the use of evolocumab. Conclusions: This study helped to collate evidence from studies that tested the effectiveness of evolocumab in the management of hyperlipidemia. Evolocumab seems to be highly effective in reducing LDL-C and other lipid parameters. Hence, it provides an excellent alternative for patients with refractory disease or patients who develop intolerable side effects, therefore helping to overcome the stumbling block to achieving optimal lipid management.

scholarly journals A Novel Approach for Generating Platelet-Delivered FVIII: Role of Transient LRP1 Expression during Megakaryopoiesis

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 1102-1102
Author(s):  
John Tkaczynski ◽  
Randolph Lyde ◽  
Hyunsook Ahn ◽  
Francis Ayombil ◽  
Sara Borst ◽  
...  
Keyword(s):  
Clinical Application ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Coagulation Factor ◽  
Induced Pluripotent Stem Cell ◽  
Human Platelets ◽  
Platelet Glycoprotein ◽  
Hemostatic Efficacy

Human platelets endocytose coagulation factor (F) V into their α-granules, in part, via low-density lipoprotein (LDL) receptor-related protein 1 (LRP1). In contrast to humans, mouse FV is endogenously expressed during megakaryopoiesis and stored in α-granules. The FV-related coagulation factor FVIII is not endogenously expressed in megakaryocytes (Mks) and thought not to be endocytosed by human or murine Mks/platelets. The lack of FVIII endocytosis is surprising as LRP1 on multiple cell types is involved in FVIII uptake and clearance. We and others have shown that FVIII can be ectopically expressed during human or murine megakaryopoiesis and stored in α-granules. These platelets are effective in the delivery of FVIII to sites of vascular injury and improve outcome in hemophilia A (HA) mice even in the presence of circulating inhibitors. Thus, it has been proposed that lentiviral bone marrow gene therapy to ectopically express FVIII during megakaryopoiesis may be a curative strategy especially for patients with HA and intractable inhibitors. However, we have shown that pFVIII has a toxic effect on Mks during intracellular processing in the endoplasmic reticulum/Golgi, limiting platelet yield and pFVIII levels. We have recently shown that exogenous FV can be taken up by in vitro differentiated CD34+- and by induced pluripotent stem cell (iPSC)-derived Mks and asked if the same can be done with FVIII. We found that Mks can take up full-length FVIII (Advate) (Fig. 1A), B-domainless (BD) FVIII (Xyntha, not shown) and BD FVIIIR1645H (not shown), a FVIII mutant we have shown is particularly effective when released by platelets. Uptake is half maximum at 0.25 IU/ml following overnight incubation. Endocytosed FVIII colocalizes with labeled fibrinogen uptake (Fig. 1A), supporting its localization to α-granules, and this FVIII uptake can be blocked by receptor-associated protein (RAP), a blocker of LDL receptor family members, including LRP1 (Fig. 1A) or by including FVIII's carrier protein von Willebrand factor (VWF) (Fig. 1B). To test the biological efficacy of endocytosed pFVIII, we took advantage of our previous studies showing that infused Mks into mice release highly functional platelets after becoming entrapped in the lungs. To focus our studies on the released human platelets and the hemostatic efficacy of the endocytosed pFVIII, we used immunodeficient NOD-scid IL2rgnull (NSG) mice that were also FVIII-deficient and that only expressed mutant VWF that binds human, but not mouse, platelet glycoprotein Ib/IX (VWFR1326H) (N/8/V mice). We infused 1x106 human FVIII-endocytosed Mks into these N/8/V mice resulting in ~1-10% being human platelets in recipient mice. We studied hemostatic efficacy by rotational thromboelastography (ROTEM) and demonstrated that the in vivo-released FVIII from released human platelets within the N/8/V blood corrected hemostasis in this system (Fig. 1C). These FVIII-containing platelets fully corrected clotting as well in a FeCl3 carotid artery injury model (Fig. 1D). In summary, we found that in vitro-grown human Mks can endocytose FVIII from the media into their α-granules in sufficient amounts to have potential clinical application in the care of HA patients. This endocytosis is likely via LRP1. FVIII is not found normally in platelets likely because of a combination of the following: 1) in plasma, FVIII it is bound to VWF, 2) circulating platelets also lack LRP1, and 3) in the marrow, there is little or no free FVIII for endocytosis by LRP1-positive Mks. We propose that endocytosed FVIII by Mks can be an important clinical application of commercial, in vitro-grown Mks for patients with HA and inhibitors who need supplemental long-lasting, hemostatic support to their emicizumab without the thrombotic risks of FVIII-bypassing agents. Disclosures Sabatino: Spark Therapeutics: Patents & Royalties. Camire:Pfizer: Research Funding.

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