Low-density Lipoprotein-related Receptor Research Articles

Agonist antibody to MuSK protects mice from MuSK myasthenia gravis

Myasthenia gravis (MG) is a chronic and severe disease of the skeletal neuromuscular junction (NMJ) in which the effects of neurotransmitters are attenuated, leading to muscle weakness. In the most common forms of autoimmune MG, antibodies attack components of the postsynaptic membrane, including the acetylcholine receptor (AChR) or muscle-specific kinase (MuSK). MuSK, a master regulator of NMJ development, associates with the low-density lipoprotein-related receptor 4 (Lrp4) to form the signaling receptor for neuronal Agrin, a nerve-derived synaptic organizer. Pathogenic antibodies to MuSK interfere with binding between MuSK and Lrp4, inhibiting the differentiation and maintenance of the NMJ. MuSK MG can be debilitating and refractory to treatments that are effective for AChR MG. We show here that recombinant antibodies, derived from MuSK MG patients, cause severe neuromuscular disease in mice. The disease can be prevented by a MuSK agonist antibody, presented either prophylactically or after disease onset. These findings suggest a therapeutic alternative to generalized immunosuppression for treating MuSK MG by selectively and directly targeting the disease mechanism.

Inhibiting histone deacetylase 6 suppresses the proliferation of microvascular endothelial cells by epigenetically activating miR-375-3p, potentially contributing to bone loss during mechanical unloading

BackgroundMechanical unloading-induced bone loss threatens prolonged spaceflight and human health. Recent studies have confirmed that osteoporosis is associated with a significant reduction in bone microvessels, but the relationship between them and the underlying mechanism under mechanical unloading are still unclear.MethodsWe established a 2D clinostat and hindlimb-unloaded (HLU) mouse model to simulate unloading in vitro and in vivo. Micro-CT scanning was performed to assess changes in the bone microstructure and mass of the tibia. The levels of CD31, Endomucin (EMCN) and histone deacetylase 6 (HDAC6) in tibial microvessels were detected by immunofluorescence (IF) staining. In addition, we established a coculture system of microvascular endothelial cells (MVECs) and osteoblasts, and qRT‒PCR or western blotting was used to detect RNA and protein expression; cell proliferation was detected by CCK‒8 and EdU assays. ChIP was used to detect whether HDAC6 binds to the miRNA promoter region.ResultsBone mass and bone microvessels were simultaneously significantly reduced in HLU mice. Furthermore, MVECs effectively promoted the proliferation and differentiation of osteoblasts under coculture conditions in vitro. Mechanistically, we found that the HDAC6 content was significantly reduced in the bone microvessels of HLU mice and that HDAC6 inhibited the expression of miR-375-3p by reducing histone acetylation in the miR-375 promoter region in MVECs. miR-375-3p was upregulated under unloading and it could inhibit MVEC proliferation by directly targeting low-density lipoprotein-related receptor 5 (LRP5) expression. In addition, silencing HDAC6 promoted the miR-375-3p/LRP5 pathway to suppress MVEC proliferation under mechanical unloading, and regulation of HDAC6/miR-375-3p axis in MVECs could affect osteoblast proliferation under coculture conditions.ConclusionOur study revealed that disuse-induced bone loss may be closely related to a reduction in the number of bone microvessels and that the modulation of MVEC function could improve bone loss induced by unloading. Mechanistically, the HDAC6/miR-375-3p/LRP5 pathway in MVECs might be a promising strategy for the clinical treatment of unloading-induced bone loss.

Low-density lipoprotein receptor-related protein 5/6 promotes endometrial cancer progression and cancer cell immune escape.

The study investigated the potential association of the low-density lipoprotein (LDL) genome with endometrial cancer progression based on the Gene Expression Omnibus data set and The Cancer Genome Atlas data set. Differential and weighted gene coexpression network analysis was performed on endometrial cancer transcriptome datasets GSE9750 and GSE106191. The protein-protein interaction network was built using LDL-receptor proteins and the top 50 tumor-associated genes. Low-density lipoprotein-related receptors 5/6 (LRP5/6) in endometrial cancer tissues were correlated with oncogenes, cell cycle-related genes, and immunological checkpoints using Spearman correlation. MethPrimer predicted the LRP5/6 promoter CpG island. LRP2, LRP6, LRP8, LRP12, low-density lipoprotein receptor-related protein-associated protein, and LRP5 were major LDL-receptor-related genes associated with endometrial cancer. LRP5/6 was enriched in various cancer-related pathways and may be a key LDL-receptor-related gene in cancer progression. LRP5/6 may be involved in the proliferation process of endometrial cancer cells by promoting the expression of cell cycle-related genes. LRP5/6 may be involved in the proliferation of endometrial cancer cells by promoting the expression of cell cycle-related genes. LRP5/6 may promote the immune escape of cancer cells by promoting the expression of immune checkpoints, promoting endometrial cancer progression. The MethPrimer database predicted that the LRP5/6 promoter region contained many CpG islands, suggesting that DNA methylation can occur in the LRP5/6 promoter region. LRP5/6 may aggravate endometrial cancer by activating the phosphoinositide 3-kinase/protein kinase B pathway.

FRI141 Dietary Salt Regulates mTORC1 Signaling In Humans And Mice With Hypertension

Abstract Disclosure: H. Aljaibeji: None. D.L. Brooks: None. A.E. Garza: None. P. Gerges: None. M. Heydarpour: None. P. Luminita: None. J.S. Williams: None. G. Williams: None. J.R. Romero: None. Raptor and the mammalian target of rapamycin (mTOR) form a complex (mTORC1) that has been proposed to play a role in aldosterone (ALDO) production. Pharmacological inhibition of mTORC1 reduces blood pressure (BP) and ALDO levels. However, the effects of environmental factors such as dietary salt on mTORC1 in humans are unclear. We studied the impact of one-week liberal Na+ (LIB, 200 mmol/day) and restricted (RES, 10 mmol/day) Na+ diets on Raptor and mTOR expression in human peripheral blood mononuclear cells (PBMC) from hypertensive subjects. Raptor and mTOR expression were higher on PBMCs from subjects on a LIB than on RES Na+ diet (n=13; P=0.036 and P=0.0008, respectively). We also studied Caucasian subjects (n=792) from the Hypertensive Pathotype (HyperPATH) cohort using the Multi-Ethnic Genotyping Array on the Illumina platform. Candidate gene association analyses showed that the single nucleotide polymorphic (SNP) Raptor gene variant, rs99001846, was associated with BP and ALDO levels. Multivariate linear regression analyses performed on hypertensive and normotensive participants showed that in hypertensives, rs99001846 risk allele carriers (AA/GA), as compared to non-risk carriers (GG), were associated with increased systolic BP levels on bothLIB and RES Na+ diets (P=0.02, P=0.01 respectively). In addition, risk allele carriers, as compared to non-risk carriers, showed increased ALDO and reduced Na+ excretion on a LIB Na+ diet (P=0.009, P=0.025, respectively). We also studied a mouse model of low nitric oxide and high AngII-mediated hypertension and observed increased cardiac Raptor and mTOR expression (n=4, P=0.0008 and P=0.03 respectively). We then performed in silico bioinformatic analyses of rat zona glomerulosa cells following 2 hr treatment with 100 nM angiotensin II (AngII) using the Gene Expression Omnibus (GEO). AngII treatment led to the activation of mTOR signaling pathways as shown by increased expression of insulin receptor substrate type 2 (P=0.00001) and Low-density lipoprotein-related receptor 5 (P=0.03). Also, AngII reduced the expression of Eukaryotic Translation Initiation Factor 4E Binding Protein 1 by 43% (P= 0.001) and increased expression of CAP-Gly Domain Containing Linker Protein 1 by 70% (P= 0.00003) - important signaling molecules that are downstream of mTOR activation. Our results suggest that in hypertension, Na+ intake and Raptor gene variants modify mTORC1. Thus, mTOR/Raptor expression are a potential biomarker of ALDO-mediated cardiovascular injury. Presentation: Friday, June 16, 2023

Probing the Interactions of LRP1 Ectodomain-Derived Peptides with Fibrillar Tau Protein and Its Impact on Cellular Internalization

Cellular internalization and the spreading of misfolded tau have become increasingly important for elucidating the mechanism of Tau pathology involved in Alzheimer’s disease (AD). The low-density lipoprotein-related receptor 1 (LRP1) has been implicated in the internalization of fibrillar tau. In this work, we utilized homology modeling to model the Cluster 2 domain of LRP1 and determined that a 23-amino-acid sequence is involved in binding to paired helical filaments (PHF) of Tau. Fourteen short peptide segments derived from this ectodomain region were then designed and docked with PHF Tau. Molecular dynamics studies of the optimal peptides bound to PHF Tau demonstrated that the peptides formed critical contacts through Lys and Gln residues with Tau. Based on the computational results, flow cytometry, AFM, SPR analysis and CD studies were conducted to examine binding and cellular internalization. The results showed that the peptide sequence TauRP (1–14) (DNSDEENCES) was not only associated with fibrillar Tau but was also able to mitigate its cellular internalization in LRP1-expressed HEK-293 cells. Preliminary docking studies with Aβ (1–42) revealed that the peptides also bound to Aβ (1–42). While this study focused on the CCR2 domain of LRP1 to design peptide sequences to mitigate Tau internalization, the work can be extended to other domains of the LRP1 receptor or other receptors to examine if the cellular internalization of fibrillar Tau can be deterred. These findings show that short peptides derived from the LRP1 receptor can alter the internalization of its ligands.

SORL1‐retromer regulates endosomal recycling and helps explain Alzheimer’s regional vulnerability

AbstractThe importance of the endosomal recycling pathway for cellular health was recognized ever since its reverse trafficking itinerary, clathrin‐dependent endocytosis, was described. Vital for synaptic function, a recent study found that neurons are endowed with a distinct unit dedicated to the recycling pathway. Akin to how endocytosis is regulated by a functional unit formed by the clathrin coat interacting with low‐density lipoprotein‐related receptors (LDLRs), recent studies will be reviewed suggesting that endosomal recycling in neurons is regulated by a functional unit comprised of a neuronal‐enriched retromer coat that interacts with the sortilin‐related receptor SORL1. Genetic studies suggest that rare truncating mutations in SORL1, inducing SORL1 haploinsuffiency, acts a causal event in triggering Alzheimer’s disease (AD). In agreement with this interpretation, recent studies will be reviewed showing that SORL1 haploinsufficiency can trigger AD’s cardinal pathologies, including showing in mice that it leads to selective atrophy in the trans‐entorhinal cortex. These studies suggest that SORL1‐retromer recycling is a causal pathway in AD that when disrupted can trigger AD’s molecular, cellular, and anatomical pathologies. When interpreted together with a collection of other studies this recent insight suggests why the trans‐entohrinal cortex is so dependent on SORL1‐retromer recycling, why the trans‐entorhinal cortex is differentially vulnerable even to ‘sporadic’ AD, and why AD anatomically ‘spreads’ over time.

PP2A and LRP‐1 targeted protection of human retinal pigment epithelial cells

Retinal pigment epithelial (RPE) cell disorders contribute to the leading causes of vision loss in the United States. Diabetic retinopathy and Age‐related macular degeneration are RPE disorders that develop as a consequence to the accumulation of toxic retinal lipids. However, the mechanism of how RPE regulates lipid homeostasis in response to intra‐retinal dysfunction of lipid metabolism is unknown. The purpose of this project is to provide new proof of principle information, toward the understanding, of how RPE regulates oxidative stress induced alteration of intracellular phosphatase/kinase signaling leading to retinal disorders. Through confocal immunofluorescence imaging, transepithelial resistance (TEER) measurement and Western Blot analysis of protein expression of primary human RPE(hRPE) cells are investigated after the treatment of lipid peroxidation products. Protein phosphatase 2A (PP2A), appears to have a pertinent role in the regulation of kinases (p‐Akt and p‐ERK ½) associated to RPE loss and TEER maintenance in response to oxidative stress induced by lipid peroxidation products. Altered PP2A signaling was found to be modulated by low density lipoprotein related receptor protein‐1 (LRP‐1) targeted peptidomimetic treatment. This project also provides potential clinical application to the treatment of retinal degeneration associated with intraretinal lipid homeostasis using a patented peptidomimetic targeting LRP‐1 and PP2A signaling.

Expression and Significance of Low-Density Lipoprotein-Related Receptors 5 and 6 in the Wnt/β-Catenin Signaling Pathway in Childhood Acute Lymphoblastic Leukemia

To investigate the significance of low-density lipoprotein receptor-related protein 5 and 6 (LRP5/6) in the Wnt/β-catenin signaling pathway in the pathogenesis and prognosis of childhood acute lymphoblastic leukemia (ALL). A total of 43 children who were newly diagnosed and achieved complete remission after remission induction therapy were enrolled. The children before treatment were included in incipient group, and after treatment when achieved complete remission included in remission group. A total of 39 children with immune thrombocytopenia were enrolled in control group. Three milliliter bone marrow samples were collected from above-mentioned each group. QRT-PCR was used to determine the mRNA expression of LRP5 and LRP6 in blood mononuclear cells of bone marrow. Western blot was used to detect the protein expression of LRP5 and LRP6. According to the protein expression levels of LRP5 and LRP6, the children were divided into low-expression group and high-expression group, and the clinical biological characteristics were compared between these two groups. Survival analysis was performed by Kaplan-Meier method. Both mRNA and protein expression levels of LRP5 and 6 were upregulated in the incipient group compared with the control and remission group (P<0.05). The mRNA and protein expressions of LRP5 and LRP6 in the high-risk group were higher than those in the medium-risk group (P<0.05), it is the same as in the medium-risk group than the low-risk group (P<0.05). The mRNA and protein expressions of LRP5 and 6 positively correlated with risk degree in the incipient group (rLRP5 mRNA=0.84, P<0.05; rLRP6 mRNA=0.66, P<0.05; rLRP5 protein=0.82, P<0.05; rLRP6 protein=0.76, P<0.05). The white blood cell count and lactate dehydrogenase in LRP5 and LRP6 high expression group were significantly higher than those in low expression group (P<0.05), while there was no significant difference in other biological characteristics. Kaplan-meier survival analysis showed that in the 43 children 3-year overall survival rate and event-free survival rate was (91.7±4.7)% and (87.6±5.2)%, respectively. The high expression of LRP5/6 may be one of the pathogenesis of childhood ALL, and the degree of LRP5/6 increase may be related to the risk level.

LDL receptor-related protein LRP6 senses nutrient levels and regulates Hippo signaling.

Controlled cell growth and proliferation are essential for tissue homeostasis and development. Wnt and Hippo signaling are well known as positive and negative regulators of cell proliferation, respectively. The regulation of Hippo signaling by the Wnt pathway has been shown, but how and which components of Wnt signaling are involved in the activation of Hippo signaling during nutrient starvation are unknown. Here, we report that a reduction in the level of low-density lipoprotein receptor-related protein 6 (LRP6) during nutrient starvation induces phosphorylation and cytoplasmic localization of YAP, inhibiting YAP-dependent transcription. Phosphorylation of YAP via loss of LRP6 is mediated by large tumor suppressor kinases 1/2 (LATS1/2) and Merlin. We found that O-GlcNAcylation of LRP6 was reduced, and the overall amount of LRP6 was decreased via endocytosis-mediated lysosomal degradation during nutrient starvation. Merlin binds to LRP6; when LRP6 is less O-GlcNAcylated, Merlin dissociates from it and becomes capable of interacting with LATS1 to induce phosphorylation of YAP. Our data suggest that LRP6 has unexpected roles as a nutrient sensor and Hippo signaling regulator.

Deletion of low-density lipoprotein-related receptor 5 inhibits liver Cancer cell proliferation via destabilizing Nucleoporin 37

BackgroundLRP5/6 are co-receptors in Wnt/β-catenin pathway. Recently, we discovered multiple β-catenin independent functions of LRP5/6 in tumor cells and in the diseased heart. Nucleoporin 37 (NUP37) is an important component of the nuclear pore complex (NPC), whose elevated expression is associated with worsened prognosis in liver cancer. Previous studies have shown that NUP37 interacted with YAP and activated YAP/TEAD signaling in liver cancer. Our preliminary findings showed a nuclear location of LRP5. We thus tested the hypothesis that LRP5 may act as a genuine regulator of YAP/TEAD signaling via modulating NUP37 in a β-catenin-independent way.MethodsWe performed siRNA knockdown of LRP5, LRP6, or β-catenin in liver cancer HepG2 cells to determine the effect on tumor cell proliferation. Protein expressions and interaction between LRP5 and NUP37 were determined using immunoprecipitation and western blot analyses.ResultsHepG2 cell proliferation was markedly inhibited by knockdown of LRP5 but not LRP6 or β-catenin, suggesting that LRP5 has a specific, β-catenin-independent role in inhibiting HepG2 cell proliferation. Knockdown of NUP37 by siRNA inhibited the proliferation of HepG2 cells, whereas overexpression of NUP37 reversed the decrease in cell proliferation induced by LRP5 knockdown. Immunoprecipitation assays confirmed that LRP5 bound to NUP37. Furthermore, LRP5 overexpression restored NUP37 knockdown-induced downregulation of YAP/TEAD pathway.ConclusionsLRP5 deletion attenuates cell proliferation via destabilization of NUP37, in a β-catenin-independent manner. LRP5 therefore acts as a genuine regulator of YAP/TEAD signaling via maintaining the integrity of the NPC, and implicates a therapeutic strategy in targeting LRP5 for inhibiting liver cancer cell proliferation.

Exploring Regulation of Protein O-Glycosylation in Isogenic Human HEK293 Cells by Differential O-Glycoproteomics

Most proteins trafficking the secretory pathway of metazoan cells will acquire GalNAc-type O-glycosylation. GalNAc-type O-glycosylation is differentially regulated in cells by the expression of a repertoire of up to twenty genes encoding polypeptide GalNAc-transferase isoforms (GalNAc-Ts) that initiate O-glycosylation. These GalNAc-Ts orchestrate the positions and patterns of O-glycans on proteins in coordinated, but poorly understood ways - guided partly by the kinetic properties and substrate specificities of their catalytic domains, as well as by modulatory effects of their unique GalNAc-binding lectin domains. Here, we provide the hereto most comprehensive characterization of nonredundant contributions of individual GalNAc-T isoforms to the O-glycoproteome of the human HEK293 cell using quantitative differential O-glycoproteomics on a panel of isogenic HEK293 cells with knockout of GalNAc-T genes (GALNT1, T2, T3, T7, T10, or T11). We confirm that a major part of the O-glycoproteome is covered by redundancy, whereas distinct O-glycosite subsets are covered by nonredundant GalNAc-T isoform-specific functions. We demonstrate that the GalNAc-T7 and T10 isoforms function in follow-up of high-density O-glycosylated regions, and that GalNAc-T11 has highly restricted functions and essentially only serves the low-density lipoprotein-related receptors in linker regions (C6XXXTC1) between the ligand-binding repeats.

Aortic carboxypeptidase-like protein, a WNT ligand, exacerbates nonalcoholic steatohepatitis.

Incidence of nonalcoholic steatohepatitis (NASH), which is considered a hepatic manifestation of metabolic syndrome, has been increasing worldwide with the rise in obesity; however, its pathological mechanism is poorly understood. Here, we demonstrate that the hepatic expression of aortic carboxypeptidase-like protein (ACLP), a glycosylated, secreted protein, increases in NASH in humans and mice. Furthermore, we elucidate that ACLP is a ligand, unrelated to WNT proteins, that activates the canonical WNT pathway and exacerbates NASH pathology. In the liver, ACLP is specifically expressed in hepatic stellate cells (HSCs). As fatty liver disease progresses, ACLP expression is enhanced via activation of STAT3 signaling by obesity-related factors in serum. ACLP specifically binds to frizzled-8 and low-density lipoprotein-related receptor 6 to form a ternary complex that activates canonical WNT signaling. Consequently, ACLP activates HSCs by inhibiting PPARγ signals. HSC-specific ACLP deficiency inhibits fibrosis progression in NASH by inhibiting canonical WNT signaling in HSCs. The present study elucidates the role of canonical WNT pathway activation by ACLP in NASH pathology, indicating that NASH can be treated by targeting ACLP-induced canonical WNT pathway activation in HSCs.

Loss of the adaptor protein ShcA in endothelial cells protects against monocyte macrophage adhesion, LDL-oxydation, and atherosclerotic lesion formation

ShcA is an adaptor protein that binds to the cytoplasmic tail of receptor tyrosine kinases and of the Low Density Lipoprotein-related receptor 1 (LRP1), a trans-membrane receptor that protects against atherosclerosis. Here, we examined the role of endothelial ShcA in atherosclerotic lesion formation. We found that atherosclerosis progression was markedly attenuated in mice deleted for ShcA in endothelial cells, that macrophage content was reduced at the sites of lesions, and that adhesion molecules such as the intercellular adhesion molecule-1 (ICAM-1) were severely reduced. Our data indicate that transcriptional regulation of ShcA by the zinc-finger E-box-binding homeobox 1 (ZEB1) and the Hippo pathway effector YAP, promotes ICAM-1 expression independently of p-NF-κB, the primary driver of adhesion molecules expressions. In addition, ShcA suppresses endothelial Akt and nitric oxide synthase (eNOS) expressions. Thus, through down regulation of eNOS and ZEB1-mediated ICAM-1 up regulation, endothelial ShcA promotes monocyte-macrophage adhesion and atherosclerotic lesion formation. Reducing ShcA expression in endothelial cells may represent an obvious therapeutic approach to prevent atherosclerosis.

Lack of Lrp5 Signaling in Osteoblasts Sensitizes Male Mice to Diet-Induced Disturbances in Glucose Metabolism

Wnt signaling through the low-density lipoprotein-related receptor 5 (Lrp5) coreceptor regulates osteoblast maturation, matrix mineralization, and intermediary metabolism. In the mature osteoblast, signals downstream of Lrp5 are required for normal long-chain fatty acid β-oxidation. Mice rendered deficient for this coreceptor in osteoblasts and osteocytes accumulate body fat with elevated serum lipid levels but retain normal insulin sensitivity. In the present study, we challenged Lrp5-mutant mice with a high-fat diet (HFD) to determine whether they were more susceptible to diet-induced disturbances in glucose homeostasis. The HFD-fed Lrp5 mutant mice maintained a low bone mass phenotype with an increase in adipose tissue mass and hypertriglyceridemia and hypercholesterolemia. Examination of glucose metabolism revealed that Lrp5 deficiency in the osteoblast also resulted in hyperglycemia and hyperinsulinemia, with reductions in glucose tolerance, insulin sensitivity, and serum undercarboxylated osteocalcin. The results from in vivo genetic epistasis and in vitro studies suggest that this phenotype proceeds via the accumulation of diacylglycerol species and impaired insulin signaling in Lrp5-deficient osteoblasts. In turn, glucose uptake and osteocalcin production are diminished in mutant osteoblasts. Taken together, these data identify a link between Wnt-Lrp5 signaling and insulin signaling in the osteoblast that has the potential to influence energy balance and compound the detrimental effects of a HFD on whole-body metabolism.

Expression of low-density lipoprotein-related receptors 5 and 6 (LRP5/6) in psoriasis skin.

Low-density lipoprotein-related receptors 5 and 6 (LRP5/6) are transmembrane receptors with key functions in canonical Wnt signalling. Wnt ligands are thought to play an important role in innate immunity and psoriasis, and recent studies assigned LRP5/6 anti-inflammatory properties. The objective of this study was to investigate the expression of LRP5 and LRP6 in lesional and non-lesional skin in peripheral blood and in mononuclear cells of patients with chronic plaque type psoriasis compared with control individuals. To investigate the effect of UV-B radiation, LRP5/6 skin gene expression was analysed before and after narrowband UV-B treatment. Our results showed significantly decreased gene expression of LRP5 and LRP6 in lesional skin and in peripheral blood from patients with psoriasis compared with non-lesional skin and healthy control skin. Immunohistochemistry did not reveal differences in protein expression of LRP5/6. Narrowband UV-B treatment induced a significant increase in LRP5 and LRP6 gene expression in lesional skin. Decreased gene expression of LRP5/6 in lesional skin and upregulation after nb UV-B treatment suggest a possible role for LRP5/6 in psoriasis.

Agrin and low-density lipoprotein-related receptor protein 4 antibodies in amyotrophic lateral sclerosis patients.

The prevalence and characteristics of agrin and low-density lipoprotein-related receptor protein 4 (LRP4) antibody-positive amyotrophic lateral sclerosis (ALS) patients were studied. We tested 82 ALS patients and 59 controls for agrin and LRP4 antibodies using enzyme-linked immunoassay (ELISA). We found that 13.8% of ALS patients had agrin antibodies, and 9.8% had LRP4 antibodies. Women with ALS are twice as likely as men to have antibodies. Agrin-positive ALS patients are younger than agrin-negative ALS patients. Antibodies to agrin and LRP4 are found in ALS patients. It must be determined whether these antibodies are pathogenic. Because antibody-positive patients have upper as well as lower motor neuron findings, the antibodies' effects cannot be explained solely by their actions at the neuromuscular junction. A breakdown in interneuronal signaling may be the cause of ALS. Further research is needed to resolve this question. Muscle Nerve, 2016 Muscle Nerve 55: 430-432, 2017.

Tissue-Type Plasminogen Activator-A296-299 Prevents Impairment of Cerebral Autoregulation After Stroke Through Lipoprotein-Related Receptor-Dependent Increase in cAMP and p38.

The sole Food and Drug Administration-approved treatment for stroke is tissue-type plasminogen activator (tPA), but its brief therapeutic window and complications of treatment constrain its use. One limitation may be its potential to exacerbate impairment of cerebral autoregulation after stroke. Vasodilation is maintained by elevations in cAMP. However, cAMP levels fall after stroke because of overactivation of N-methyl-d-aspartate receptors by toxic levels of glutamate, an effect that is exacerbated by tPA. Binding of wild-type (wt) tPA to the low-density lipoprotein-related receptor (LRP) mediates dilation. We propose that binding of wt-tPA to N-methyl-d-aspartate receptor reduces cAMP and impairs vasodilation. We hypothesize that tPA-A(296-299), a variant that is fibrinolytic but cannot bind to N-methyl-d-aspartate receptor, preferentially binds to LRP and increases cAMP and p38, limiting autoregulation impairment after stroke. Stroke was induced by photothrombosis in pigs equipped with a closed cranial window, cerebral blood flow determined by microspheres, and cerebrospinal fluid cAMP and p38 determined by ELISA. Stroke decreased cerebral blood flow. Cerebral blood flow was reduced further during hypotension, indicating impairment of autoregulation. Autoregulation was further impaired by wt-tPA, which was prevented by MK801 and tPA-A(296-299). Protection by tPA-A(296-299) was blocked by anti-LRP Ab, the LRP antagonist receptor-associated protein, and the p38 inhibitor SB 203580, but not by control IgG. Stroke reduced cerebrospinal fluid cAMP, which was reduced further by wt-tPA, but augmented by tPA-A(296-299). Cerebrospinal fluid p38 was unchanged by wt-tPA, increased by tPA-A(296-299), and decreased by anti-LRP Ab and receptor-associated protein. tPA-A(296-299) prevents impairment of cerebral autoregulation after stroke through an LRP-dependent increase in cAMP and p38.

Copper Exposure Perturbs Brain Inflammatory Responses and Impairs Clearance of Amyloid-Beta.

Copper promotes a toxic buildup of amyloid-beta (Aβ) and neurofibrillary tangle pathology in the brain, and its exposure may increase the risk for Alzheimer's disease (AD). However, underlying molecular mechanisms by which copper triggers such pathological changes remain largely unknown. We hypothesized that the copper exposure perturbs brain inflammatory responses, leading to impairment of Aβ clearance from the brain parenchyma. Here, we investigated whether copper attenuated Aβ clearance by microglial phagocytosis or by low-density lipoprotein-related receptor protein-1 (LRP1) dependent transcytosis in both in vitro and in vivo When murine monocyte BV2 cells were exposed to copper, their phagocytic activation induced by fibrillar Aβ or LPS was significantly reduced, while the secretion of pro-inflammatory cytokines, such as IL-1β, TNF-α, and IL-6, were increased. Interestingly, not only copper itself but also IL-1β, IL-6, or TNF-α were capable of markedly reducing the expression of LRP1 in human microvascular endothelial cells (MVECs) in a concentration-dependent manner. While copper-mediated downregulation of LRP1 was proteasome-dependent, the cytokine-induced loss of LRP1 was proteasome- or lysosome-independent. In the mouse model, copper exposure also significantly elevated neuroinflammation and downregulated LRP1 in the brain, consistent with our in vitro results. Taken together, our findings support the pathological impact of copper on inflammatory responses and Aβ clearance in the brain, which could serve as key mechanisms to explain, in part, the copper exposure as an environmental risk factor for AD.

Inhibitory effect of ilexpernoside C from Ilex pernyi on aggregated LDL-induced foam cells formation

The aggregation of macrophage-derived foam cells on vascular wall is considered to be a main cause of atherosclerosis. In the present study, we evaluated the inhibitory effect of the compound ilexpernoside C (IC1) extracted from Ilex pernyi (Aquifoliaceae) on foam cell formation in THP-1 macrophages cells which were induced by low density lipoproteins aggregates (LDL aggregates). Results showed that IC1 could significantly inhibit the formation of foam cells. The analysis on related receptors of foam cells indicated that IC1 could significantly decrease the expression of low density lipoprotein-related receptor 1(LRP1). Therefore, these findings indicated that IC1 inhibited the formation of foam cells by inhibiting endocytosis of macrophages, thus it may act as a potential anti-atherosclerotic agent.

Bone and the regulation of global energy balance.

The skeleton, populated by large numbers of osteoblasts and long-lived osteocytes, requires a constant supply of energy-rich molecules to fuel the synthesis, deposition and mineralization of bone matrix during bone modelling and remodelling. When these energetic demands are not met, bone acquisition is suppressed. Recent findings suggest that key developmental signals emanating from Wnt low-density lipoprotein-related receptor 5 and hypoxia-inducible factor pathways impact osteoblast bioenergetics to accommodate the energy requirements for bone cells to fulfil their function. In vivo studies in several mutant mouse strains have confirmed a link between bone cells and global metabolism, ultimately leading to the identification of hormonal interactions between the skeleton and other tissues. The hormones insulin and leptin affect postnatal bone acquisition, whilst osteocalcin produced by the osteoblast in turn stimulates insulin secretion by the pancreas. These observations have prompted additional questions regarding the nature of the mechanisms of fuel sensing and processing in the osteoblast and their contribution to overall energy utilization and homeostasis. Answers to such questions should advance our understanding of metabolic diseases and may ultimately improve management of affected patients. In this review, we highlight recent studies in this field and offer a perspective on the evolutionary implications of bone as a metabolic endocrine organ.