Low-density Lipoprotein Receptor-related Protein Research Articles

Peptide-drug conjugates repolarize glioblastoma-associated macrophages to resensitize chemo-immunotherapy of glioblastoma.

The prevalent tumor-supporting glioblastoma-associated macrophages (GAMs) promote glioblastoma multiforme (GBM) progression and resistance to multiple therapies. Repolarizing GAMs from tumor-supporting to tumor-inhibiting phenotype may troubleshoot. However, sufficient accumulation of drugs at the GBM site is restricted by blood-brain barrier (BBB). Herein, we designed peptide-drug conjugates (PDCs) by conjugating camptothecin or resiquimod to a tandem peptide composed of matrix metalloproteinase 2-responsive peptide and angiopep-2 via disulfonyl-ethyl carbonate/carbamate (MAPDCs). The mixed self-assembly MAPDCs could recognize low-density lipoprotein receptor-related protein 1 (LRP1) to facilitate BBB transport. Once reaching the GBM site, the responsive peptide would be cleaved to shed the angiopep-2, blocking abluminal LRP1-mediated brain-to-blood efflux and enhancing drug retention. Sequentially, drugs are released under the high level of intracellular glutathione. In vivo studies demonstrated that MAPDCs repolarized GAMs, boosted immune response, and resensitized chemotherapeutic toxicity, offering a much-improved anti-GBM effect. The effectiveness of MAPDCs validates GAMs as therapeutic target and PDCs as versatile brain delivery system with high design flexibility.

Oleandrin inhibits osteoclast differentiation by targeting the LRP4/MAPK/NF-κB signalling pathway to treat osteoporosis.

Osteoporosis is a common inflammation-related disease in which the release of proinflammatory cytokines promotes bone loss. Oleandrin is a monomer compound extracted from the leaves of the Nerium oleander plant, has been shown to exert an anti-inflammatory effect on a variety of inflammation-related diseases. However, its role in osteoporosis and the underlying mechanisms remain unclear. In this study, Oleandrin was shown to reduce bone loss in ovariectomy-induced osteoporotic mice in vivo. Additionally, Oleandrin inhibited RANKL-induced osteoclast differentiation in a concentration-dependent manner in vitro. Signalling pathway studies showed that Oleandrin could inhibit osteoclast differentiation by targeting MAPK and NF-κB signalling pathways. Further mechanistic studies showed that Oleandrin binds to low-density lipoprotein receptor-related protein 4 in osteoclast, thereby exerting inhibitory effects on osteoclast differentiation. In conclusion, this study lays the foundation for further research on the anti-inflammatory and anti-osteoporotic effects of Oleandrin on osteoporosis and its underlying mechanism and provides new possibilities for the treatment of osteoporosis.

Low-density lipoprotein receptor-related protein 6 ameliorates cardiac hypertrophy by regulating CTSD/HSP90α signaling during pressure overload.

Pressure overload induces pathological cardiac remodeling, including cardiac hypertrophy and fibrosis, resulting in cardiac dysfunction or heart failure. Recently, we observed that the low-density lipoprotein receptor-related protein 6 (LRP6), has shown potential in enhancing cardiac function by mitigating cardiac fibrosis in a mouse model subjected to pressure overload. In this study, we investigated the role of LRP6 as a potential modulator of pressure overload-induced cardiac hypertrophy and elucidated the underlying molecular mechanisms. We performed transverse aortic constriction (TAC) to induce pressure overload in cardiomyocyte-specific LRP6 overexpression mice (LRP6-overmice) and in control mice (α-myosin heavy chain (α-MHC) Mer-Cre-Mer Tg mice or namedMCM mice). Cardiac function and hypertrophy were assessed using echocardiography. LRP6-over mice showed improved cardiac function and reduced hypertrophy after TAC, compared with MCM mice. We also applied mechanical stretch to cultured neonatal rat cardiomyocytes to model pressure overload in vitro. Mass spectrometry analysis showed that LRP6 interacts with HSP90α and cathepsin D (CTSD) in cardiomyocytes under mechanical stress. Further analysis demonstrated that LRP6 facilitates CTSD-mediated degradation of HSP90α, consequently inhibiting β-cateninactivation and reducing cardiac hypertrophy post-TAC. Treatment with recombinantHSP90α protein or the CTSD inhibitor, pepstatin A, partly abolished the protective effect of LRP6 overexpression on myocardial hypertrophy and cardiac function after TAC in mice. Collectively, our data suggest that LRP6 protects against pressure overload-induced myocardial remodeling and that the CTSD/HSP90α/β-catenin axis may be a potential therapeutic target.

The LDL Receptor-Related Protein 1: Mechanisms and roles in promoting Aβ efflux transporter in Alzheimer's disease.

The LDL Receptor-Related Protein 1(LRP1), a member of the Low-density Lipoprotein (LDL) receptor family, is a multifunctional cellular transporter and signaling receptor, this includes regulation of lipid metabolism, cell migration and signaling. Abnormal accumulation of amyloid beta (Aβ) in the brain is thought to be the main pathological change in Alzheimer's disease. By binding to a variety of ligands, LRP1 is involved in the internalization and degradation of Aβ, thereby affecting the course of Alzheimer's disease (AD). Here, we discuss the main mechanisms by which LRP1 mediates Aβ degradation and clearance and several current therapeutic approaches targeting LRP1. Finally, we concluded that modulating the expression level of LRP1 is an effective way to attenuate Aβ deposition and ameliorate AD. Abbreviations: LRP1, LDL Receptor-Related Protein 1;LDL, Low Density Lipoprotein; Aβ, amyloid beta; AD, Alzheimer's disease; APP, amyloid precursor protein; ApoE, apolipoprotein E; TGF, growth factor; MMP, matrix metalloproteinase;TAT, thrombin-antithrombin complex; BBB, blood-brain barrier; MMP-9,cyclophilin A (CypA)-matrix metalloproteinase-9; VMC, Vascular Mural Cell; IDE,insulin degrading enzyme; EVs, extracellular vesicles; sLRP1,shed LRP1; BDNF, brain-derived neurotrophin; IGF-1,insulin-like growth factor 1; NGF, nerve growth factor; MAPK,mitogen-activated protein kinase; ERK1/2,exogenous signal-regulated kinase1/2;JNK, c-Jun amino-terminal kinase; TLR4, toll-like receptor 4; NF-κB,nuclear factor-κB; GCAP,guanylate cyclase-activating protein; KD, ketogenic diet;KB, ketone body; BLECs,Brain-like endothelial cell; BYHWD, Buyang Huanwu decoction; LGZG, Linguizhugan decoction;P- gp, P-glycoprotein;PPARγ, Peroxisome proliferator-activated receptor γ;SP16,SERPIN peptide 16; Asx, Astaxanthin; Bex, Bexarotene.

High-throughput microfluidic spheroid technology for early detection of colistin-induced nephrotoxicity with gradient-based analysis.

Colistin is essential for treating multidrug-resistant Gram-negative bacterial infections but has significant nephrotoxic side effects. Traditional approaches for studying colistin's nephrotoxicity are challenged by the rapid metabolism of its prodrug, colistin methanesulfonate and the difficulty of obtaining adequate plasma from critically ill patients. To address these challenges, we developed the Spheroid Nephrotoxicity Assessing Platform (SNAP), a microfluidic device that efficiently detects colistin-induced toxicity in renal proximal tubular epithelial cell (RPTEC) spheroids within 48 hours using just 200 μL of patient plasma. Our findings demonstrate that SNAP not only promotes higher expression of kidney-specific markers aquaporin-1 (AQP1) and low-density lipoprotein receptor-related protein 2 (LRP2) compared to traditional two-dimensional (2D) cultures, but also exhibits increased sensitivity to colistin, with significant toxicity detected at concentrations of 50 μg ml-1 and above. Notably, SNAP's non-invasive method did not identify nephrotoxicity in plasma from healthy donors, thereby confirming its physiological relevance and showcasing superior sensitivity over 2D cultures, which yielded false-positive results. In clinical validation, SNAP accurately identified patients at risk of colistin-induced nephrotoxicity with 100% accuracy for both early and late onset and demonstrated a 75% accuracy rate in predicting the non-occurrence of nephrotoxicity. These results underline the potential of SNAP in personalized medicine, offering a non-invasive, precise and efficient tool for the assessment of antibiotic-induced nephrotoxicity, thus enhancing the safety and efficacy of treatments against resistant bacterial infections.

Evaluation of LRP6, SFRP3, and DVL1 Protein Concentrations in Serum of Patients with Gastroenteropancreatic or Bronchopulmonary Neuroendocrine Tumors.

Introduction: Neuroendocrine tumors are a diverse group of tumors predominantly found in the gastrointestinal tract or respiratory system. Methods: This retrospective study aimed to measure the serum concentrations of LRP6 (low-density lipoprotein receptor-related protein 6), SFRP3 (secreted frizzled-related protein 3), and DVL1 (segment polarity protein dishevelled homolog) using the ELISA method in patients with NETs (N = 80) and a control group (N = 62). We evaluated the results against various demographic, clinicopathological, and biochemical characteristics. Results: Our analyses revealed that the concentration of SFRP3 in patients with neuroendocrine tumors was significantly elevated (p < 0.001) compared to the control group. Additionally, DVL1 concentrations were significantly higher (p < 0.01) in patients with BP-NETs compared to GEP-NETs. Furthermore, DVL1 analysis showed a moderate negative correlation with chromogranin A (p < 0.001) and weak negative correlations with serotonin (p < 0.05) and 5-HIAA (p < 0.05). Significant negative correlations were also observed between DVL1 and age in the control group (p < 0.01), and between LRP6 and Ki-67 in the study group. Conclusions: These results suggest that changes in the SFRP3 and DVL1 pathways play a key role in NET development. Elevated levels of these proteins highlight their importance in tumor biology, with SFRP3 and DVL1 potentially being crucial in NET molecular mechanisms. Further research is needed to explore their roles and potential in diagnosis and treatment.

LRP4 mutations promote tumour progression and resistance to anti-PD-1 therapy in recurrent hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) recurrence is a major factor limiting long-time survival and the cause of most deaths in patients with HCC. However, molecular characterisation and potential therapeutic targets of recurrent HCC remain mostly unknown. We performed whole-exome sequencing (WES) in 63 matched primary and recurrent HCC tumours and combined the data with whole-genome sequencing (WGS) results in 43 paired samples from our previous study. Sanger sequencing was used to identify all low-density lipoprotein receptor-related protein 4 (LRP4) coding exons in 203 additional patients with recurrent HCC. We identified LRP4 somatic mutations in 7.8% (24/309) of recurrent tumours and only 0.97% (3/309) of primary tumours (P<0.001). Prognosis after the second liver resection was poorer in patients with an LRP4 mutation. Biofunctional investigations demonstrated that inactivating LRP4 mutations promoted tumour progression and immunosuppression. Mechanistically, mutated LRP4 reduced intratumoural conventional type 1 dendritic cell and CD8+ T cell infiltration by repressing CCL4 expression and secretion through activation of β-catenin signalling, resulting in resistance to anti-programmed cell death protein-1 (PD-1) therapy. Patients with recurrent HCC carrying an LRP4 mutation did not benefit from anti-PD-1 treatment after their second resection surgery. A β-catenin inhibitor reversed LRP4-induced resistance to anti-PD-1 therapy in humanised tumour-bearing mice. Our results identified novel LRP4 mutations important in recurrent HCC. Inactivating LRP4 mutations were associated with resistance to anti-PD-1 therapy and could be useful biomarkers for precision therapy in patients with recurrent HCC.

Microglia internalize tau monomers and fibrils using distinct receptors but similar mechanisms.

Alzheimer's disease (AD) and other tauopathies are characterized by intracellular aggregates of microtubule-associated protein tau that are actively released and promote proteopathic spread. Microglia engulf pathological proteins, but how they endocytose tau is unknown. We measured endocytosis of different tau species by microglia after pharmacological modulation of macropinocytosis or clathrin-mediated endocytosis (CME) or antagonism/genetic depletion of known tau receptors heparan-sulfate proteoglycans (HSPGs) and low-density lipoprotein receptor-related protein 1 (LRP1). Dynamin inhibition decreased microglial endocytosis of all tested tau species. Meanwhile, HSPG antagonism blocked only fibril uptake, and LRP1 antagonism or genetic depletion inconsistently inhibited the endocytosis of fibrils and monomers. Cre recombinase robustly enhanced tau uptake with partial selectivity for fibrils. These data show that microglia take up both tau monomers and aggregates via a dynamin-dependent form of endocytosis (eg, CME) but may differ in using HSPGs for entry depending on species. Microglial endocytosis of tau monomers and fibrils is dynamin-dependent. HSPG antagonism blocks microglial uptake of tau fibrils but not monomers. LRP1 antagonism or knockdown inconsistently inhibits tau uptake. TAT-Cre stimulates semi-selective uptake of fibrils over monomers.

Possible Involvement of Hippocampal miR-539-3p/Lrp6/Igf1r Axis for Diminished Working Memory in Mice Fed a Low-Carbohydrate and High-Protein Diet.

A low-carbohydrate and high-protein (LC-HP) diet demonstrates favorable impacts on metabolic parameters, albeit it leads to a decline in hippocampal function with the decreased expression of hippocampal insulin-like growth factor-1 receptor (IGF-1R) among healthy mice. However, the precise mechanisms underlying this phenomenon remain unexplored. Eight-week-old male C57BL/6 mice were divided into the LC-HP diet-fed group (25.1% carbohydrate, 57.2% protein, and 17.7% fat as percentages of calories; n=10) and the control diet-fed group (58.9% carbohydrate, 24.0% protein, and 17.1% fat; n=10). After 4 weeks, all mice underwent the Y-maze test, followed by analyses of hippocampal mRNA and miRNA expressions. We revealed that feeding the LC-HP diet suppressed working memory function and hippocampal Igf1r mRNA levels in mice. Sequencing of hippocampal miRNA demonstrated 17 upregulated and 27 downregulated miRNAs in the LC-HP diet-fed mice. Notably, we found decreased hippocampal mRNA levels of low-density lipoprotein receptor-related protein 6 (Lrp6), a gene modulated by miR-539-3p, in mice fed the LC-HP diet. Furthermore, a significant positive correlation was observed between Lrp6 and Igf1r mRNA levels in the hippocampus. These findings suggest that LC-HP diets may suppress hippocampal function via the miR-539-3p/Lrp6/Igf1r axis.

Temperature induces brain-intake shift of recombinant high-density lipoprotein after traumatic brain injury

Traumatic brain injury (TBI) is one of the leading public health concerns in the world. Therapeutic hypothermia is routinely used in severe TBI, and pathophysiological hyperthermia, frequently observed in TBI patients, has an unclear impact on drug transport in the injured brain due to a lack of study on its effects. We investigated the effect of post-traumatic therapeutic hypothermia at 33°C and pathophysiological hyperthermia at 39°C on brain transport and cell uptake of neuroprotectants after TBI. Recombinant high-density lipoprotein (rHDL), which possesses anti-inflammatory, antioxidant activity, and blood–brain barrier (BBB) permeability, was chosen as the model drug. First, we found that mild hypothermia and hyperthermia impaired rHDL transport to the brain and lesion targeting in controlled cortical impact mice. Second, we investigated the temperature-induced rHDL uptake shift by various brain cell types. Mild hypothermia impeded the uptake of rHDL by endothelial cells, neurons, microglia, and astrocytes. Hyperthermia impeded the uptake of rHDL by endothelial cells and neurons while promoting its uptake by microglia and astrocytes. In an attempt to understand the mechanisms behind the above phenomena, it was found that temperature induced brain-intake shift of rHDL through the regulation of low-density lipoprotein receptor (LDLR) and LDLR-related protein 1 (LRP1) stability in brain cells. We therefore reported the full view of the temperature-induced brain-intake shift of rHDL after TBI for the first time. It would be of help in coordinating pharmacotherapy with temperature management in individualization and precision medicine.Graphical

LRP1B mutation is associated with lymph node metastasis in endometrial carcinoma: A clinical next-generation sequencing study.

This study aims to investigate the mutation status and protein expression of low-density lipoprotein receptor-related protein 1B (LRP1B) in endometrial cancer, and analyze its association with lymph node metastasis (LNM) in endometrial cancer. Targeted next-generation sequencing (NGS) was conducted on both tumor tissues and paired blood DNA obtained from 94 endometrial cancer patients, followed by comprehensive analysis. Additionally, immunohistochemistry (IHC) was used to explore the correlation between LRP1B protein expression levels, its gene mutation status, and LNM. LRP1B mutation was observed in 19 patients (20.2%). Our results revealed that LRP1B mutation frequencies were significantly different between endometrial cancer with or without LNM (P = 0.038). Multivariate analysis indicated that LRP1B mutation was a favorable predictor (odds ratio 0.09; 95% confidence interval 0.01-0.95; P = 0.045) for LNM in endometrial cancer. Further analysis revealed that combination of LRP1B mutation with clinical variants (LVSI and histological subtype) yielded a higher area under the curve value of 0.871) and patients harboring LRP1B mutated-type were less likely to develop LNM. On integrated analysis, the concordance between LRP1B NGS and LRP1B IHC was 73.3%. This study utilizes targeted NGS to uncover the relationship between LRP1B mutation and LNM status, contributing to the development of primary prevention and proactive treatment strategies.

A commonly inherited human PCSK9 germline variant drives breast cancer metastasis via LRP1 receptor.

Identifying patients at risk for metastatic relapse is a critical medical need. We identified a common missense germline variant in proprotein convertase subtilisin/kexin type 9 (PCSK9) (rs562556, V474I) that is associated with reduced survival in multiple breast cancer patient cohorts. Genetic modeling of this gain-of-function single-nucleotide variant in mice revealed that it causally promotes breast cancer metastasis. Conversely, host PCSK9 deletion reduced metastatic colonization in multiple breast cancer models. Host PCSK9 promoted metastatic initiation events in lung and enhanced metastatic proliferative competence by targeting tumoral low-density lipoprotein receptor related protein 1 (LRP1) receptors, which repressed metastasis-promoting genes XAF1 and USP18. Antibody-mediated therapeutic inhibition of PCSK9 suppressed breast cancer metastasis in multiple models. In a large Swedish early-stage breast cancer cohort, rs562556 homozygotes had a 22% risk of distant metastatic relapse at 15 years, whereas non-homozygotes had a 2% risk. Our findings reveal that a commonly inherited genetic alteration governs breast cancer metastasis and predicts survival-uncovering a hereditary basis underlying breast cancer metastasis.

Selection of LRP1 ligand phage-displayed single domain antibody that transmigrates BBB

Effective drug delivery to the central nervous system (CNS) remains a challenge due to the blood–brain barrier (BBB). Macromolecules such as proteins and peptides are unable to cross BBB and have poor therapeutic efficacy due to little or no drug distribution. A promising alternative is the conjugation of a drug to a shuttle molecule that can reach the CNS via receptor-mediated transcytosis (RMT). Several receptors have been described for RMT, such as low-density lipoprotein receptor-related protein 1 (LRP1). We used phage display technology combined with an in vitro BBB model to identify LRP1 ligands. A single domain antibody (dAb) library was used to enrich for species that selectively bind to immobilised LRP1 ligand. We obtained a novel nanobody, dAb D11, that selectively binds to LRP1 receptor and mediates in vitro internalisation of phage particles in brain endothelial cells, with a dissociation constant Kd of 183.1 ± 85.8 nM. The high permeability of D11 was demonstrated by an in vivo biodistribution assay in mice. We discovered D11, the first LRP1 binding dAb with BBB permeability. Our findings will contribute to the development of RMT-based drugs for the treatment of CNS diseases.

Renal Proximal Tubule Cell-Specific Megalin Deletion Does Not Affect Atherosclerosis But Induces Tubulointerstitial Nephritis in Mice Fed a Western Diet.

Pharmacological inhibition of megalin (also known as LRP2 [low-density lipoprotein receptor-related protein-2]) attenuates atherosclerosis in hypercholesterolemic mice. Since megalin is abundant in renal proximal tubule cells (PTCs), the purpose of this study was to determine whether PTC-specific deletion of megalin reduces hypercholesterolemia-induced atherosclerosis in mice. Female Lrp2 f/f mice were bred with male Ndrg1-Cre ERT2 +/0 mice to develop PTC-LRP2 +/+ and PTC-LRP2 -/- littermates. To study atherosclerosis, all mice were bred to an LDL (low-density lipoprotein) receptor -/- background and fed a Western diet to induce atherosclerosis. PTC-specific megalin deletion did not attenuate atherosclerosis in LDL receptor -/- mice in either sex. Serendipitously, we discovered that PTC-specific megalin deletion led to interstitial infiltration of CD68+ cells and tubular atrophy. The pathology was only evident in male PTC-LRP2 -/- mice fed a Western diet but not in mice fed a normal laboratory diet. Renal pathologies were also observed in male PTC-LRP2 -/- mice in an LDL receptor +/+ background fed the same Western diet, demonstrating that the renal pathologies were dependent on diet and not on hypercholesterolemia. In contrast, female PTC-LRP2 -/- mice had no apparent renal pathologies. In vivo multiphoton microscopy demonstrated that PTC-specific megalin deletion dramatically diminished ALB (albumin) accumulation in PTCs within 10 days of Western diet feeding. RNA-sequencing analyses demonstrated the upregulation of inflammation-related pathways in the kidney. PTC-specific megalin deletion does not affect atherosclerosis but leads to tubulointerstitial nephritis in mice fed a Western diet, with severe pathologies in male mice.

The co-receptor Tetraspanin12 directly captures Norrin to promote ligand-specific β-catenin signaling.

Wnt/β-catenin signaling directs animal development and tissue renewal in a tightly controlled, cell- and tissue-specific manner. In the mammalian central nervous system, the atypical ligand Norrin controls angiogenesis and maintenance of the blood-brain barrier and blood-retina barrier through the Wnt/β-catenin pathway. Like Wnt, Norrin activates signaling by binding and heterodimerizing the receptors Frizzled (Fzd) and Low-density lipoprotein receptor-related protein 5 or 6 (LRP5/6), leading to membrane recruitment of the intracellular transducer Dishevelled (Dvl) and ultimately stabilizing the transcriptional coactivator β-catenin. Unlike Wnt, the cystine-knot ligand Norrin only signals through Fzd4 and additionally requires the co-receptor Tetraspanin12 (Tspan12); however, the mechanism underlying Tspan12-mediated signal enhancement is unclear. It has been proposed that Tspan12 integrates into the Norrin-Fzd4 complex to enhance Norrin-Fzd4 affinity or otherwise allosterically modulate Fzd4 signaling. Here, we measure direct, high-affinity binding between purified Norrin and Tspan12 in a lipid environment and use AlphaFold models to interrogate this interaction interface. We find that Tspan12 and Fzd4 can simultaneously bind Norrin and that a pre-formed Tspan12/Fzd4 heterodimer, as well as cells co-expressing Tspan12 and Fzd4, more efficiently capture low concentrations of Norrin than Fzd4 alone. We also show that Tspan12 competes with both heparan sulfate proteoglycans and LRP6 for Norrin binding and that Tspan12 does not impact Fzd4-Dvl affinity in the presence or absence of Norrin. Our findings suggest that Tspan12 does not allosterically enhance Fzd4 binding to Norrin or Dvl, but instead functions to directly capture Norrin upstream of signaling.

The role of neutrophils in tPA thrombolysis after stroke: a malicious troublemaker.

Acute ischemic stroke represents a critical, life-threatening condition affecting the central nervous system. Intravenous thrombolysis with tissue plasminogen activator (tPA) remains a cornerstone for achieving vascular recanalization in such patients; however, its therapeutic utility is limited, with only approximately 10% of patients benefiting due to the narrow therapeutic window and significant risk of hemorrhagic transformation. Enhancing the efficacy of tPA thrombolysis is therefore imperative. Neutrophils have been identified as key modulators of thrombolytic outcomes, interacting with tPA post-stroke to influence treatment effectiveness. The binding of tPA to low-density lipoprotein receptor-related protein 1 (LRP-1) on neutrophil surfaces induces degranulation and formation of neutrophil extracellular traps (NETs). Conversely, neutrophils impede the thrombolytic action of tPA by obstructing its interaction with fibrin and activating platelets. These findings suggest that targeting neutrophils may hold promise for improving thrombolysis outcomes. This review explores the role of neutrophils in tPA-mediated thrombolysis following acute ischemic stroke, examines neutrophil-associated biomarkers, and outlines potential strategies for enhancing tPA efficacy.

Systemic Lipid Metabolism Dysregulation as a Possible Driving Force of Fracture Non-Unions?

Non-unions are fractures that do not heal properly, resulting in a false joint formation at the fracture site. This condition leads to major health issues and imposes a burden on national healthcare systems. The etiology of non-unions is still not fully understood; therefore, we aimed to identify potential systemic factors that may contribute to their formation. We conducted a cross-sectional concomitant proteomic and metabolomic pilot study of blood plasma in patients with non-unions (N = 11) and compared them with patients with bone fracture in the normal active healing phase (N = 12). We found five significantly upregulated proteins in the non-union group: immunoglobulin heavy variable 3-74, immunoglobulin lambda variable 2-18, low-density lipoprotein receptor-related protein 4, zinc-alpha-2-glycoprotein, and serum amyloid A-1 protein; and we found one downregulated protein: cystatin-C. The metabolomic study found differences in alanine, aspartate and glutamate metabolism pathways between two groups. The combined results of proteomic and metabolomic analyses suggest that the dysregulation of lipid metabolism may contribute to non-union formation.

ApoE Receptor-2 R952Q Variant in Macrophages Elevates Soluble LRP1 to Potentiate Hyperlipidemia and Accelerate Atherosclerosis in Mice.

apoER2 (apolipoprotein E receptor-2) is a transmembrane receptor in the low-density lipoprotein receptor (LDLR) family with unique tissue expression. A single-nucleotide polymorphism that encodes the R952Q sequence variant has been associated with elevated plasma cholesterol levels and increased myocardial infarction risk in humans. The objective of this study was to delineate the mechanism underlying the association between the apoER2 R952Q variant and increased atherosclerosis risk. An apoER2 R952Q mouse model was generated using a CRISPR/Cas9 strategy, intercrossed with LDLR knockout mice, followed by feeding a Western-type high-fat high-cholesterol diet for 16 weeks. Atherosclerosis was investigated by immunohistology. Plasma lipids and lipid distributions among the various lipoprotein classes were analyzed by colorimetric assay. Tissue-specific effects of the R952Q sequence variant on atherosclerosis were analyzed by bone marrow transplant studies. sLRP1 (soluble low-density lipoprotein receptor-related protein 1) was measured in plasma and conditioned media from bone marrow-derived macrophages by ELISA and GST-RAP (glutathione S-transferase-receptor-associated protein) pull-down, respectively. P38 MAPK (mitogen-activated protein kinase) phosphorylation in VLDL (very-low-density lipoprotein)-treated macrophages was determined by Western blot analysis. Consistent with observations in humans with this sequence variant, the apoER2 R952Q mutation exacerbated diet-induced hypercholesterolemia, via impediment of plasma triglyceride-rich lipoprotein clearance, to accelerate atherosclerosis in Western diet-fed LDLR knockout mice. Reciprocal bone marrow transplant experiments revealed that the apoER2 R952Q mutation in bone marrow-derived cells instead of non-bone marrow-derived cells was responsible for the increase in hypercholesterolemia and atherosclerosis. Additional data showed that the apoER2 R952Q mutation in macrophages promotes VLDL-induced LRP1 (low-density lipoprotein receptor-related protein 1) shedding in a p38 MAPK-dependent manner. The apoER2 R952Q mouse model recapitulates characteristics observed in human disease. The underlying mechanism is that the apoER2 R952Q mutation in macrophages exacerbates VLDL-stimulated sLRP1 production in a p38 MAPK-dependent manner, resulting in its competition with cell surface LRP1 to impede triglyceride-rich lipoprotein clearance, thereby resulting in increased hypercholesterolemia and accelerated atherosclerosis.

Lrp1 facilitates infection of neurons by Jamestown Canyon virus.

Jamestown Canyon virus (JCV) is a bunyavirus and arbovirus responsible for neuroinvasive disease in the United States. Little is known about JCV pathogenesis, and no host factors required for cellular infection have been identified. Recently, we identified low-density lipoprotein receptor related protein 1 (Lrp1) as a host entry factor for two other bunyaviruses Rift Valley fever virus (RVFV) and Oropouche virus (OROV). Here, we assessed the role of Lrp1 in mediating JCV cellular infection of neurons. Both neuronal and non-neuronal immortalized cell lines deficient for Lrp1 displayed reduction in infection with JCV, and early stages of infection such as binding and internalization were impacted by lack of Lrp1. In primary rat neurons, Lrp1 was highly expressed, and the neurons were highly permissive for JCV infection. Treatment of primary neurons with recombinant receptor-associated protein (RAP), a high affinity ligand for Lrp1, resulted in reduced infectivity with JCV. In addition, pretreatment of cells with RVFV Gn inhibited JCV infection, suggesting that the two viruses may share overlapping binding sites. These results provide compelling evidence that Lrp1 is an important cellular factor for efficient infection by JCV, and thus multiple bunyaviruses with varying clinical manifestations and tissue tropism are facilitated by the host cell Lrp1. Reliance of multiple bunyaviruses on Lrp1 makes it a promising target for pan-bunyaviral antivirals and therapeutics.

A phase I dose-escalation study of LRP5/6 antagonist BI 905677 in patients with advanced solid tumors

Aberrant Wnt pathway signaling has been implicated in the development of many cancers. Targeting of low-density lipoprotein receptor-related protein 5/6 (LRP5/6) co-receptors inhibits Wnt signaling and may be a novel therapy. BI 905677 is an LRP5/6 antagonist that has demonstrated preclinical antitumor activity. This (NCT03604445) was a phase I, dose-escalation study evaluating BI 905677 for patients with advanced solid tumors over two dosing schedules (A: i.v. infusion every 3 weeks, 3-week cycles; B: i.v. infusion every 2 weeks, 4-week cycles). Adult patients were eligible if they had exhausted treatment options and had an Eastern Cooperative Oncology Group performance status of 0-1. The primary endpoints were the maximum tolerated dose (MTD) and safety. Other endpoints were pharmacokinetics, pharmacodynamics, and efficacy. In total, 37 patients received BI 905677 over nine dose cohorts (0.05-3.6 mg/kg/every 3 weeks). Dose-limiting toxicities were only reported during cycle 1 in the 3.6 mg/kg cohort and the MTD was established at 2.8 mg/kg every 3 weeks. Enrollment for schedule B was not pursued. The most frequently reported adverse events were diarrhea (35.1%), vomiting (21.6%), and C-telopeptide increase (18.9%). All patients in the 3.6 mg/kg cohort experienced a dose-limiting toxicity, suggesting a narrow therapeutic index. Paired pre-treatment and on-treatment biopsies, where available, showed decreased Axin2 expression by reverse transcriptase polymerase chain reaction with treatment, suggesting target inhibition. Best response observed was stable disease in 14 (38%) patients. The MTD of BI 905677 was set at 2.8 mg/kg every 3 weeks. BI 905677 was well tolerated but a narrow therapeutic range and minimal efficacy led to early termination of the trial.