Low-density Lipoprotein Receptor-related Protein Research Articles

The Interaction of SRL-2 Peptide with LRP-1 Receptor and Identification of Breast Cancer Related Biomarkers: An In-silico Approach

Background: Breast cancer is a multifaceted disease characterized by genetic and epigenetic changes that lead to uncontrolled cell growth and metastasis. Early detection and treatment are crucial for managing diseases. Objectives: The objective of this study is to investigate the potential of chimeric peptides for drug delivery and to identify biomarkers associated with breast cancer. Recent studies have shown that the low-density lipoprotein receptor-related protein 1 (LRP-1) receptor has a significant impact on the development of breast cancer. In order to facilitate the identification of biomarkers, we have created a chimeric peptide that has been proven to bind successfully to the LRP-1 receptor. Methods: To identify biomarkers, we utilized advanced computational methods to conduct a meta-analysis of microarray data. Specifically, the g:Profiler and eXpression2Kinases (X2K) databases were utilized to identify gene ontologies and transcription factors. We then used the Human Protein Atlas to identify and assess crucial gene expressions. Results: Our results demonstrated that nucleolar and spindle-associated protein 1 (NUSAP1), melatonin receptor 1A (MELT), and cyclin-dependent kinase 1 (CDK1) are three hub genes that play pivotal roles in the pathogenesis of breast cancer. Conclusions: The research findings provide a deeper understanding of the molecular mechanisms involved in developing breast cancer. These findings have significant implications for developing novel therapies and diagnostics for this disease.

The Interaction of SRL-2 Peptide with LRP-1 Receptor and Identification of Breast Cancer Related Biomarkers: An In-silico Approach

Background: Breast cancer is a multifaceted disease characterized by genetic and epigenetic changes that lead to uncontrolled cell growth and metastasis. Early detection and treatment are crucial for managing diseases. Objectives: The objective of this study is to investigate the potential of chimeric peptides for drug delivery and to identify biomarkers associated with breast cancer. Recent studies have shown that the low-density lipoprotein receptor-related protein 1 (LRP-1) receptor has a significant impact on the development of breast cancer. In order to facilitate the identification of biomarkers, we have created a chimeric peptide that has been proven to bind successfully to the LRP-1 receptor. Methods: To identify biomarkers, we utilized advanced computational methods to conduct a meta-analysis of microarray data. Specifically, the g:Profiler and eXpression2Kinases (X2K) databases were utilized to identify gene ontologies and transcription factors. We then used the Human Protein Atlas to identify and assess crucial gene expressions. Results: Our results demonstrated that nucleolar and spindle-associated protein 1 (NUSAP1), melatonin receptor 1A (MELT), and cyclin-dependent kinase 1 (CDK1) are three hub genes that play pivotal roles in the pathogenesis of breast cancer. Conclusions: The research findings provide a deeper understanding of the molecular mechanisms involved in developing breast cancer. These findings have significant implications for developing novel therapies and diagnostics for this disease.

Antibody-mediated inhibition of tissue-type plasminogen activator binding to the low-density lipoprotein receptor-related protein 1 as a potential beneficial modulator for stroke therapy.

The acute ischemic stroke therapy of choice is the application of Alteplase, a drug containing the enzyme tissue-type plasminogen activator (tPa) which rapidly destabilizes blood clots. A central hallmark of stroke pathology is blood-brain barrier (BBB) breakdown associated with tight junction (TJ) protein degradation, which seems to be significantly more severe under therapeutic conditions. The exact mechanisms how tPa facilitates BBB breakdown are not entirely understood. There is evidence that an interaction with the lipoprotein receptor-related protein 1 (LRP1), allowing tPa transport across the BBB into the central nervous system, is necessary for this therapeutic side effect. Whether tPa-mediated disruption of BBB integrity is initiated directly on microvascular endothelial cells or other brain cell types is still elusive. In this study we could not observe any changes of barrier properties in microvascular endothelial cells after tPa incubation. However, we present evidence that tPa causes changes in microglial activation and BBB breakdown after LRP1-mediated transport across the BBB. Using a monoclonal antibody targeting the tPa binding sites of LRP1 decreased tPa transport across an endothelial barrier. Our results indicate that limiting tPa transport from the vascular system into the brain by coapplication of a LRP1-blocking monoclonal antibody might be a novel approach to minimize tPa-related BBB damage during acute stroke therapy.

The Myc Family and the Metastasis Suppressor NDRG1: Targeting Key Molecular Interactions with Innovative Therapeutics.

Cancer is a leading cause of death worldwide, resulting in ∼10 million deaths in 2020. Major oncogenic effectors are the Myc proto-oncogene family, which consists of three members including c-Myc, N-Myc, and L-Myc. As a pertinent example of the role of the Myc family in tumorigenesis, amplification of MYCN in childhood neuroblastoma strongly correlates with poor patient prognosis. Complexes between Myc oncoproteins and their partners such as hypoxia-inducible factor-1α and Myc-associated protein X (MAX) result in proliferation arrest and pro-proliferative effects, respectively. Interactions with other proteins are also important for N-Myc activity. For instance, the enhancer of zest homolog 2 (EZH2) binds directly to N-Myc to stabilize it by acting as a competitor against the ubiquitin ligase, SCFFBXW7, which prevents proteasomal degradation. Heat shock protein 90 may also be involved in N-Myc stabilization since it binds to EZH2 and prevents its degradation. N-Myc downstream-regulated gene 1 (NDRG1) is downregulated by N-Myc and participates in the regulation of cellular proliferation via associating with other proteins, such as glycogen synthase kinase-3β and low-density lipoprotein receptor-related protein 6. These molecular interactions provide a better understanding of the biologic roles of N-Myc and NDRG1, which can be potentially used as therapeutic targets. In addition to directly targeting these proteins, disrupting their key interactions may also be a promising strategy for anti-cancer drug development. This review examines the interactions between the Myc proteins and other molecules, with a special focus on the relationship between N-Myc and NDRG1 and possible therapeutic interventions. SIGNIFICANCE STATEMENT: Neuroblastoma is one of the most common childhood solid tumors, with a dismal five-year survival rate. This problem makes it imperative to discover new and more effective therapeutics. The molecular interactions between major oncogenic drivers of the Myc family and other key proteins; for example, the metastasis suppressor, NDRG1, may potentially be used as targets for anti-neuroblastoma drug development. In addition to directly targeting these proteins, disrupting their key molecular interactions may also be promising for drug discovery.

Medical Care Use Among Patients with Monogenic Osteoporosis Due to Rare Variants in LRP5, PLS3, or WNT1

Pathogenic variants in the LRP5, PLS3, or WNT1 genes can significantly affect bone mineral density, causing monogenic osteoporosis. Much remains to be discovered about the phenotype and medical care needs of these patients. The purpose of this study was to examine the use of medical care among Dutch individuals identified between 2014 and 2021 with a pathogenic or suspicious rare variant in LRP5, PLS3, or WNT1. In addition, the aim was to compare their medical care utilization to both the overall Dutch population and the Dutch Osteogenesis Imperfecta (OI) population. The Amsterdam UMC Genome Database was used to match 92 patients with the Statistics Netherlands (CBS) cohort. Patients were categorized based on their harbored variants: LRP5, PLS3, or WNT1. Hospital admissions, outpatient visits, medication data, and diagnosis treatment combinations (DTCs) were compared between the variant groups and, when possible, to the total population and OI population. Compared to the total population, patients with an LRP5, PLS3, or WNT1 variant had 1.63 times more hospital admissions, 2.0 times more opened DTCs, and a greater proportion using medication. Compared to OI patients, they had 0.62 times fewer admissions. Dutch patients with an LRP5, PLS3, or WNT1 variant appear to require on average more medical care than the total population. As expected, they made higher use of care at the surgical and orthopedic departments. Additionally, they used more care at the audiological centers and the otorhinolaryngology (ENT) department, suggesting a higher risk of hearing-related problems.

Expression of OLR1, ACAN, and LRP1 Genes in the Synovial Membrane Cells in Patients with Osteoarthritis after SARS-CoV2 Infection

Expression of OLR1, ACAN, and LRP1 Genes in the Synovial Membrane Cells in Patients with Osteoarthritis after SARS-CoV2 Infection

SerpinB3 Upregulates Low-Density Lipoprotein Receptor-Related Protein (LRP) Family Members, Leading to Wnt Signaling Activation and Increased Cell Survival and Invasiveness.

Abnormal activation of the Wnt-β-catenin signaling cascade is involved in tumor growth and dissemination. SerpinB3 has been shown to induce β-catenin, and both molecules are overexpressed in tumors, particularly in those with poor prognoses. The aim of this study was to evaluate the ability of SerpinB3 to modulate the Wnt pathway in liver cancer and in monocytic cells, the main type of inflammatory cells in the tumor microenvironment. The Wnt cascade, Wnt co-receptors, and low-density lipoprotein receptor-related protein (LRP) members were analyzed in different cell lines and human monocytes in the presence or absence of SerpinB3. The Wnt-β-catenin axis was also evaluated in liver tumors induced in mice with different extents of SeprinB3 expression. In monocytic cells, SerpinB3 induced a significant upregulation of Wnt-1/7, nuclear β-catenin, and c-Myc, which are associated with increased cell lifespan and proliferation. In liver tumors in mice, the expression of β-catenin was significantly correlated with the presence of SerpinB3. In hepatoma cells, Wnt co-receptors LRP-5/6 and LRP-1, implicated in cell survival and invasiveness, were upregulated by SerpinB3. The LRP pan-inhibitor RAP not only induced a decrease in LRP expression, but also a dose-dependent reduction in SerpinB3-induced invasiveness. In conclusion, SerpinB3 determines the activation of the Wnt canonical pathway and cell invasiveness through the upregulation of LRP family members.

Kai-Xin-San Improves Cognitive Impairment via Wnt/β-Catenin and IRE1/XBP1s Signalings in APP/PS1 Mice.

Alzheimer's disease (AD) is the most common type of dementia with an insidious onset and slow progression. Kai-Xin-San (KXS) has been reported to be effective in improving cognitive impairment in AD. However, the mechanism is still confused. In this study, we employed APP/PS1 mice to explore the neuroprotective mechanism of KXS. Forty-eight male APP/PS1 mice were randomly divided into model group, KXS groups (0.7, 1.4, and 2.8 g/kg/d, p.o.) and the wild-type mice were assigned to the normal control group (n = 12 in each group). Y-maze and novel object recognition tests were carried out after continuous intragastric administration for 2 months. The abilities of learning, memory, and new object recognition in the APP/PS1 mice were enhanced significantly after KXS treatment. KXS can reduce the deposition of Aβ40 and Aβ42 in APP/PS1 mice brain. KXS decreased the levels of serum inflammatory cytokines, tumor necrosis factor-α, interleukin-1β, and interleukin-6. KXS increased the activities of superoxide dismutase and glutathione peroxidase significantly, whereas it inhibited the contents of reactive oxygen species and malondialdehyde significantly. In addition, we also detected Wnt/β-catenin signaling related proteins, such as Wnt7a, β-catenin, low-density lipoprotein receptor-related protein 6 (LRP6), glycogen synthase kinase-3β (GSK-3β), nuclear factor kappa-B (NF-κB), postsynaptic density 95 (PSD95), microtubule associated protein-2 (MAP-2), and endoplasmic reticulum stress (IRE1 pathway) related proteins, such as inositol-requiring enzyme 1 (IRE1), phosphorylated IRE1(p-IRE1), spliced X-box-binding protein 1 (XBP1s), immunoglobulin binding protein (BIP), and protein disulfide isomerase (PDI) in the hippocampus. Results showed that KXS decreased the expression of GSK-3β, NF-kB, p-IRE1/IRE1 ratio, XBP1s, and BIP; increased the expression of Wnt7a, β-catenin, LRP6, PSD95, MAP2, and PDI. In conclusion, KXS improved cognitive impairment by activating Wnt/β-catenin signaling, inhibiting the IRE1/XBP1s pathway in APP/PS1 mice.

LRP1 Deficiency Promotes Mitostasis in Response to Oxidative Stress: Implications for Mitochondrial Targeting after Traumatic Brain Injury.

The brain undergoes oxidative stress and mitochondrial dysfunction following physiological insults such as Traumatic brain injury (TBI), ischemia-reperfusion, and stroke. Pharmacotherapeutics targeting mitochondria (mitoceuticals) against oxidative stress include antioxidants, mild uncouplers, and enhancers of mitochondrial biogenesis, which have been shown to improve pathophysiological outcomes after TBI. However, to date, there is no effective treatment for TBI. Studies have suggested that the deletion of LDL receptor-related protein 1 (LRP1) in adult neurons or glial cells could be beneficial and promote neuronal health. In this study, we used WT and LRP1 knockout (LKO) mouse embryonic fibroblast cells to examine mitochondrial outcomes following exogenous oxidative stress. Furthermore, we developed a novel technique to measure mitochondrial morphometric dynamics using transgenic mitochondrial reporter mice mtD2g (mitochondrial-specific Dendra2 green) in a TBI model. We found that oxidative stress increased the quantity of fragmented and spherical-shaped mitochondria in the injury core of the ipsilateral cortex following TBI, whereas rod-like elongated mitochondria were seen in the corresponding contralateral cortex. Critically, LRP1 deficiency significantly decreased mitochondrial fragmentation, preserving mitochondrial function and cell growth following exogenous oxidative stress. Collectively, our results show that targeting LRP1 to improve mitochondrial function is a potential pharmacotherapeutic strategy against oxidative damage in TBI and other neurodegenerative diseases.

LRP5-/6 gene polymorphisms and its association with risk of abnormal bone mass in postmenopausal women

ObjectivesTo assess LRP5-/6 gene polymorphisms and its association with risk of abnormal bone mass (ABM) in postmenopausal women.MethodsThe study recruited 166 patients with ABM (case group) and 106 patients with normal bone mass (control group) based on bone mineral density (BMD) results. Multi-factor dimensionality reduction (MDR) was used to analyze the interaction between the Low-density lipoprotein receptor-related protein 5 (LRP5) gene (rs41494349, rs2306862) and the Low-density lipoprotein receptor-related protein 6 (LRP6) gene (rs10743980, rs2302685) and the subjects’ clinical characteristics of age and menopausal years.Results(1) Logistic regression analysis showed that the subjects with the CT or TT genotype at rs2306862 had a higher risk of ABM than those with the CC genotype (OR = 2.353, 95%CI = 1.039–6.186; OR = 2.434, 95%CI = 1.071, 5.531; P < 0.05). The subjects with the TC genotype at rs2302685 had a higher risk of ABM than those with the TT genotype (OR = 2.951, 95%CI = 1.030–8.457, P < 0.05). (2) When taking the three Single-nucleotide polymorphisms (SNPs) together, the accuracy was the highest with the cross-validation consistency of 10/10 (OR = 1.504, 95%CI:1.092–2.073, P < 0.05), indicating that the LRP5 rs41494349 and LRP6 rs10743980, rs2302685 were interactively associated with the risk of ABM. (3) Linkage disequilibrium (LD) results revealed that the LRP5 (rs41494349,rs2306862) were in strong LD (D′ > 0.9, r2 > 0.3). AC and AT haplotypes were significantly more frequently distributed in the ABM group than in the control group, indicating that subjects carrying the AC and AT haplotypes were associated with an increased risk of ABM (P < 0.01). (4) MDR showed that rs41494349 & rs2302685 & rs10743980 & age were the best model for ABM prediction. The risk of ABM in “high-risk combination” was 1.00 times that of “low-risk combination”(OR = 1.005, 95%CI: 1.002–1.008, P < 0.05). (5) MDR showed that there was no significant association between any of the SNPs and menopausal years and ABM susceptibility.ConclusionThese findings indicate that LRP5-rs2306862 and LRP6-rs2302685 polymorphisms and gene–gene and gene–age interactions may increase the risk of ABM in postmenopausal women. There was no significant association between any of the SNPs and menopausal years and ABM susceptibility.

Polymorphism in autophagy-related genes LRP1 and CAPZA1 may promote gastric mucosal atrophy

BackgroundHelicobacter pylori secretes cytotoxin-associated gene A (CagA) into the gastric epithelium, causing gastric mucosal atrophy (GMA) and gastric cancer. In contrast, host cells degrade CagA via autophagy. However, the association between polymorphisms in autophagy-related genes and GMA must be fully elucidated.ResultsWe evaluated the association between single nucleotide polymorphisms (SNPs) in autophagy-related genes (low-density lipoprotein receptor-related protein 1, LRP1; capping actin protein of muscle Z-line alpha subunit 1, CAPAZ1; and lysosomal-associated membrane protein 1, LAMP1) and GMA in 200 H. pylori-positive individuals. The frequency of the T/T genotype at rs1800137 in LRP1 was significantly lower in the GMA group than in the non-GMA group (p = 0.018, odds ratio [OR] = 0.188). The frequencies of the G/A or A/A genotype at rs4423118 and T/A or A/A genotype at rs58618380 of CAPAZ1 in the GMA group were significantly higher than those in the non-GMA group (p = 0.029 and p = 0.027, respectively). Multivariate analysis revealed that C/C or C/T genotype at rs1800137, T/A or A/A genotype at rs58618380, and age were independent risk factors for GMA (p = 0.038, p = 0.023, and p = 0.006, respectively). Furthermore, individuals with the rs1800137 C/C or C/T genotype of LRP1 had a 5.3-fold higher susceptibility to GMA. These genetic tests may provide future directions for precision medicine for individuals more likely to develop GMA.ConclusionLRP1 and CAPZA1 polymorphisms may be associated with the development of GMA.

Insights into Overlappings of Fibrosis and Cancer: Exploring the Tumor-related Cardinal Genes in Idiopathic Pulmonary Fibrosis.

The pathogenesis of idiopathic pulmonary fibrosis (IPF) is quite similar to that of cancer pathogenesis, and several pathways appear to be involved in both disorders. The mammalian target of the rapamycin (mTOR) pathway harbors several established oncogenes and tumor suppressors. The same signaling molecules and growth factors, such as vascular endothelial growth factor (VEGF), contributing to cancer development and progression play a part in fibroblast proliferation, myofibroblast differentiation, and the production of extracellular matrix in IPF development as well. The expression of candidate genes acting upstream and downstream of mTORC1, as well as Vegf and low-density lipoprotein receptor related protein 1(Lrp1), was assessed using specific primers and quantitative polymerase chain reaction (qPCR) within the lung tissues of bleomycin (BLM)-induced IPF mouse models. Lung fibrosis was evaluated by histological examinations and hydroxyproline colorimetric assay. BLM-exposed mice developed lung injuries characterized by inflammatory manifestations and fibrotic features, along with higher levels of collagen and hydroxyproline. Gene expression analyses indicated a significant elevation of regulatory associated protein of mTOR (Raptor), Ras homolog enriched in brain (Rheb), S6 kinase 1, and Eukaryotic translation initiation factor 4E-binding protein 1 (4Ebp1), as well as a significant reduction of Vegfa, Tuberous sclerosis complex (Tsc2), and Lrp1; no changes were observed in the Tsc1 mRNA level. Our findings support the elevation of S6K1 and 4EBP1 in response to the TSC/RHEB/mTORC1 axis, which profoundly encourages the development and establishment of IPF and cancer. In addition, this study suggests a possible preventive role for VEGF-A and LRP1 in the development of IPF.

TIM-3 signaling hijacks the canonical Wnt/β-catenin pathway to maintain cancer stemness in acute myeloid leukemia.

The activation of β-catenin plays critical roles in normal stem cell function, and, when aberrantly activated, the maintenance and enhancement of cancer stemness in many solid cancers. Aberrant β-catenin activation is also observed in acute myeloid leukemia (AML), and crucially contributes to self-renewal and propagation of leukemic stem cells (LSCs) regardless of mutations in contrast with such solid tumors. In this study, we showed that the AML-specific autocrine loop comprised of T-cell immunoglobulin mucin-3 (TIM-3) and its ligand, galectin-9 (Gal-9), drives the canonical Wnt pathway to stimulate self-renewal and propagation of LSCs, independent of Wnt ligands. Gal-9 ligation activates the cytoplasmic Src homology 2 domain of TIM-3 to recruit hematopoietic cell kinase (HCK), a Src family kinase highly expressed in LSCs but not in HSCs, and HCK phosphorylates p120-catenin to promote formation of the LDL receptor-related protein 6 (LRP6) signalosome, hijacking the canonical Wnt pathway. This TIM-3/HCK/p120-catenin axis is principally active in immature LSCs compared with TIM-3-expressed differentiated AML blasts and exhausted T cells. These data suggest that human AML LSCs constitutively activates β-catenin via autocrine TIM-3/HCK/p120-catenin signaling, and that molecules related to this signaling axis should be critical targets for selective eradication of LSCs without impairing normal HSCs.

Wnt Signaling Activation in Gingival Epithelial Cells and Macrophages of Experimental Periodontitis.

Objective: Wingless/integrated (Wnt) signaling plays critical roles in maintaining environmental homeostasis and is also involved in the pathogenesis of inflammatory diseases. However, its role in macrophages during periodontitis is not well understood. The present study aims to investigate the interaction between Wnt signaling and macrophages in the context of periodontitis. Methods: Experimental periodontitis was induced in C57/BL6 mice using a Porphyromonas gingivalis (P.g)-associated ligature for 14 days. Immunohistochemistry was performed to study the expression of the pro-inflammatory cytokine tumor necrosis factor (TNF-α), the stabilization of β-catenin, and the macrophage marker F4/80 in the periodontal tissues. The effect of Wnt signaling on TNF-α was examined using Western blot analysis in Raw 264.7 murine macrophages stimulated by Wnt3a-conditioned medium, with or without Wnt3a antibody neutralization, and compared with primary cultured gingival epithelial cells (GECs). The effect of P.g lipopolysaccharide (LPS) on Wnt signaling was assessed by analyzing key components of the Wnt signaling pathway, including the activity of low-density lipoprotein receptor-related protein (LRP) 6 and nuclear accumulation of β-catenin in GEC and Raw 264.7 cells. Results: Over-expressions of TNF-α and activated β-catenin were presented in the macrophages in the gingiva from mice with P.g-associated ligature-induced periodontitis. The expression patterns of TNF-α and activated β-catenin were consistent with the expression of F4/80. In Raw 264.7 cells, activation of the Wnt signaling pathway led to an increase in TNF-α, but this effect was not observed in GEC. Additionally, treatment with LPS induced β-catenin accumulation and LRP6 activation in Raw 264.7 cells, which were blocked by the addition of Dickkopf-1(DKK1). Conclusions: Wnt signaling was aberrantly activated in the macrophages in experimental periodontitis. The activation of Wnt signaling in the macrophages may play a pro-inflammatory role in periodontitis. Targeting specific signaling pathways, such as the Wnt pathway, may hold promise for developing novel therapeutic interventions for periodontitis.

The Role of Thrombomodulin in Estrogen-Receptor-Positive Breast Cancer Progression, Metastasis, and Curcumin Sensitivity.

Estrogen and estrogen receptors (ER) play a key role in breast cancer progression, which can be treated with endocrine therapy. Nevertheless, resistance to endocrine therapies is developed over time. The tumor expression of thrombomodulin (TM) is correlated with favorable prognosis in several types of cancer. However, this correlation has not yet been confirmed in ER-positive (ER+) breast cancer. This study aims to evaluate the role of TM in ER+ breast cancer. Firstly, we found that lower TM expression correlates to poor overall survival (OS) and relapse-free survival (RFS) rates in ER+ breast cancer patients through Kaplan-Meier survival analysis (p < 0.05). Silencing TM in MCF7 cells (TM-KD) increased cell proliferation, migration, and invasion ability. Additionally, TM-KD MCF7 cells showed higher sensitivity (IC50 15 μM) to the anti-cancer agent curcumin than the scrambled control cells. Conversely, overexpression of TM (TM-over) in T47D cells leads to decreased cell proliferation, migration, and invasion ability. Furthermore, TM-over T47D cells showed more resistance (IC50 > 40 μM) to the curcumin treatment. The PI staining, DAPI, and tunnel assay also confirmed that the curcumin-induced apoptosis in TM-KD MCF7 cells was higher (90.34%) than in the scrambled control cells (48.54%). Finally, the expressions of drug-resistant genes (ABCC1, LRP1, MRP5, and MDR1) were determined by qPCR. We found that the relative mRNA expression levels of ABCC1, LRP1, and MDR1 genes after curcumin treatment were higher in scrambled control cells than in TM-KD cells. In conclusion, our results demonstrated that TM plays a suppressive role in the progression and metastasis of ER+ breast cancer, and it regulates curcumin sensitivity by interfering with ABCC1, LRP1, and MDR1 gene expression.

The LRP5 high-bone-mass mutation causes alveolar bone accrual with minor craniofacial alteration.

Mutations in low-density lipoprotein receptor-related protein 5 (LRP5) cause various bone diseases. Several mouse models were generated to study the role of LRP5 in bone development. But most of the studies were confined to the appendicular skeleton. The role of LRP5 in the axial skeleton, especially in the craniofacial skeleton, is largely unknown. The aim of this study was to investigate the craniofacial phenotype with the LRP5G171V mutation. To understand how LRP5 affects craniofacial bone properties, we analyzed LRP5 high-bone-mass mutant mice carrying the G171V missense mutation (LRP5HBM ). Quantitative microcomputed tomographic imaging and histomorphometric analyses were used to study craniofacial phenotypes and bone density. Histology, immunohistochemistry, and in vivo fluorochrome labeling were used to study molecular mechanisms. LRP5HBM mice showed overall minor changes in the craniofacial bone development but with increased bone mass in the interradicular alveolar bone, edentulous ridge, palatine bone, and premaxillary suture. Elevated osteocyte density was observed in LRP5HBM mice, along with increased Runx2 expression and unmineralized bone surrounding osteocytes. Meanwhile, LRP5HBM mice exhibited increased osteoprogenitors, but no significant changes were observed in osteoclasts. This led to a high-bone-mass phenotype, and an increased osteocyte density in the alveolar bone and edentulous ridge. LRP5HBM mice display increased bone mass in the alveolar bone with minor changes in the craniofacial morphology. Collectively, these data elucidated the important role of LRP5 in axial bone development and homeostasis and provided clues into the therapeutical potential of LRP5 signaling in treating alveolar bone loss.

Abstract 307: Targeted Activation Of The Tnfa Pathway Accelerates Atherosclerosis Regression In Mice

Aggressive lipid lowering in mice with established atherosclerosis induces plaque regression and is characterized by reduced monocyte recruitment and increased expression of the motility receptor C-C chemokine receptor 7 (CCR7) to promote macrophage egress from plaques to nearby lymph nodes. Notably, genetic deletion of receptors critical for the recruitment of inflammatory Ly6C high monocytes is necessary to facilitate plaque regression. Our group previously showed that deletion of macrophage LDL receptor-related protein 1 (LRP1) in mice with established atherosclerosis accelerates plaque regression after lipid lowering and is associated with increased inflammation and macrophage CCR7-mediated egress. We tested the hypothesis that targeted activation of inflammation following lipid lowering in atherosclerotic mice accelerates atherosclerosis regression. LC-MS/MS proteomics performed on murine macrophages revealed that the loss of LRP1 upregulated the inflammatory protein tumor necrosis factor alpha (TNFα) 1.48-fold (P&lt;0.05). Apoe -/- mice were fed a Western diet for 12 weeks to establish atherosclerosis and then subjected to bone marrow transplantation (BMT) using wildtype ( Apoe +/+ ) mice as donors to restore plasma APOE and reduce lipids. A cohort was sacrificed two weeks after BMT and used as baseline (N=11). The remaining mice (N=12/group) received intraperitoneal injections of recombinant murine TNFα (0.075mg/kg/day) or saline for 6 weeks on chow diet. After 6 weeks on chow diet, total plasma cholesterol levels ranged 82 -120 mg/dL with no significant differences between treatment cohorts. TNFα-treated mice had elevated spleen-to-body weight ratios compared to saline treated controls (P&lt;0.0001), confirming successful activation of the immune system. Following 6 weeks of lipid lowering, TNFα treatment reduced total plaque area and lipid content 17.0% (P&lt;0.05) and 34.4% (P&lt;0.05), respectively, compared to saline treated controls (P&lt;0.05).Herein, we show that the administration of TNFα, to stimulate inflammation after lipid lowering, significantly reduces plaque size and plaque lipid content in mice with established atherosclerosis.

Combined Application of Salinomycin and ATRA Induces Apoptosis and Differentiation of Acute Myeloid Leukemia Cells by Inhibiting WNT/β-Catenin Pathway.

All-trans retinoic acid (ATRA) is only effective in acute promyelocytic leukemia (APL), but not in other subtype of acute myeloid leukemia (AML). Salinomycin targets tumor cells rather than non-tumorigenic cells, and WNT/β-catenin pathway inhibition is one of the mechanisms of its anti-tumor activity. There is a crosstalk between RA and WNT/β-catenin pathway. Here, we investigate the effect of the combination of salinomycin and ATRA (S+RA) in non-APL AML cells. Apoptosis was evaluated by cell viability and Annexin-V assay. Cell differentiation was analyzed by CD11c expression and morphology. To explore the underlying mechanisms, Western blot analysis and mitochondrial transmembrane potentials (ΔΨm) were used. S+RA induced differentiation and apoptosis in AML cell lines and AML primary cells. S+RA inhibited the β-catenin signal pathway as determined by the decreased protein levels of β-catenin, the low-density lipoprotein receptor-related proteins 6 (LRP6), and its downstream proteins such as survivin, c-Myc, caspase-3/7, cdc25A and cyclinD1 and reduced phosphorylation level of GSK3β S9. S+RA also increased the protein levels of CCAAT/enhancer-binding proteins (C/EBPs) and PU.1 and collapsed Δψm. The above molecular and cellular changes induced by S+RA were inhibited by β-catenin specific activator and promoted by β-catenin specific inhibitor. S+RA induced differentiation by β-catenin-inhibition-mediated up-regulation of C/EBPs and PU.1 and suppression of c-Myc. S+RA triggered apoptosis through β-catenin-inhibition-regulated ΔΨm collapse and caspase-3/7 activation. Taken together, our findings may provide novel therapeutic strategies for AML patients by targeting the WNT/β-catenin pathway.

Human respiratory syncytial virus activates beta-catenin pathway in lung epithelial cells to regulate pro-inflammatory response

Abstract Respiratory Syncytial Virus (RSV) is a non-segmented negative-sense RNA virus belonging to the paramyxovirus family. RSV infects respiratory tract to cause pneumonia and bronchiolitis in infants, elderly, and immunocompromised patients. Effective clinical therapeutic options and vaccine to combat RSV infection are still lacking. Therefore, to develop effective therapeutic interventions, it is imperative to understand virus-host interactions during RSV infection. Canonical Wnt/beta-catenin pathway is a well-established signaling cascade regulating expression of Wnt target genes involved in various biological and physiological functions. Our study shows RSV infection of human lung epithelial A549 cells triggering stabilization of beta-catenin protein and subsequent activation of beta-catenin mediated transcriptional activity. Further studies with beta-catenin inhibitors and beta-catenin lacking cells revealed a role of beta-catenin in positively regulating pro-inflammatory response in RSV infected A549 cells. Activation of beta-catenin during RSV infection was mediated by cell surface receptor complex comprising of frizzled receptors and low-density lipoprotein receptor-related protein 5 and 6 (LRP5 and LRP6). Thus, our studies have revealed an involvement of beta-catenin pathway in inducing pro-inflammatory response during RSV infection. The mechanism(s) and host derived factors regulating RSV-mediated beta-catenin activation will be discussed.

Abstract 677: Short Hydrocarbon-Stapled Apolipoprotein E Mimetic Peptides Enhance Lipoprotein Uptake

ApoE facilitates the clearance of apoB-containing lipoproteins by binding to heparan sulfate proteoglycans (HSPG), low density lipoprotein receptor (LDLR) and LDLR-related protein 1 (LRP1). ApoE has a receptor binding and a lipid binding domain, which are both needed for its biological function. Several apoE-based peptides have been developed that lower plasma lipid levels in animal models and in early-stage clinical trials. However, these peptides are long (28-61 residues), costly to synthesize and are potentially immunogenic as they often contain many amino acid substitutions that vary from the native apoE sequence. We developed novel short (10-12 residues) apoE mimetic peptides based on the apoE receptor binding region (residues 141-150) containing only 2 amino acid substitutions. We used hydrocarbon stapling to stabilize the native alpha helical structure of this region and to increase the lipid binding affinity of the peptides. In addition, octanoic or myristic acid was attached to the N-terminus of the peptides to further increase lipid binding affinity. Helical conformation and lipid binding of the peptides were confirmed by circular dichroism spectroscopy and phospholipid vesicle solubilization assay. Our peptides increased the uptake of fluorescent tagged VLDL and LDL in a concentration dependent manner (0.625-20 μM peptides) in both wild-type (WT) and LDLR knockout (KO) HepG2 cells as measured by flow cytometry. In addition, an all D-amino acid version of one of the peptides had a similar effect on LDL uptake as its all L-amino acid version. Altogether, this suggests that peptide-mediated uptake is LDLR independent. Treatment of WT HepG2 cells with heparinases diminished the low-dose effect (up to 2.5 μM) of the peptides on LDL uptake, indicating that HSPGs plays a role in peptide-mediated LDL uptake. Finally, the peptides (4.6 mg/kg, IV) lowered plasma total cholesterol (37% at 3h; 29% at 6h) and triglycerides (33% at 1h) in apoE-KO mice on a standard chow diet. In summary, the novel apoE peptides are shorter than previously reported peptides, are more similar to the native sequence of apoE, and are likely resistant to proteolysis, because of hydrocarbon stapling and, therefore, could potentially be developed into an oral therapy.