Soluble LR11 as a Novel Biomarker in Acute Kawasaki Disease.

BACKGROUND: Intimal smooth muscle cells (SMCs) play an important role in the vasculitis caused by Kawasaki disease (KD). Lipoprotein receptor 11 (LR11) is a member of the low-density lipoprotein receptor family, which is expressed markedly in intimal vascular SMCs and secreted in a soluble form (sLR11). sLR11 has been recently identified as a potential vascular lesion biomarker. sLR11 is reportedly elevated in patients with coronary artery lesions long after KD, but there is no description of sLR11 in acute KD. Our aim was to determine the sLR11 dynamics in acute KD and to assess its usefulness as a biomarker.Methods and Results: 106 acute KD patients and 18 age-matched afebrile controls were enrolled. KD patients were classified into the following subgroups: intravenous immunoglobulin (IVIG) responders (n=85) and non-responders (n=21). Serum sLR11 levels before IVIG therapy were higher in non-responders (median, 19.6 ng/mL; interquartile range [IQR], 13.0-24.9 ng/mL) than in controls (11.9 ng/mL, 10.4-14.9 ng/mL, P<0.01) or responders (14.3 ng/mL, 11.7-16.5 ng/mL, P<0.01). Using a cutoff of >17.5 ng/mL, non-responders to initial IVIG therapy were identified with 66.7% sensitivity and 78.8% specificity. CONCLUSIONS: sLR11 can reflect the state of acute KD and might be a biomarker for patient response to IVIG therapy.

Deletion of LR11 Attenuates Hypoxia-Induced Pulmonary Arterial Smooth Muscle Cell Proliferation With Medial Thickening in Mice.

OBJECTIVE: We aimed to determine whether LR11 (low-density lipoprotein receptor with 11 binding repeats) is a potential key regulator of smooth muscle cell (SMC) proliferation during the progression of hypoxia-induced medial thickening in mice and whether sLR11 (soluble LR11) can serve as a biomarker in patients with pulmonary arterial hypertension. APPROACH AND RESULTS: The role of LR11 in pulmonary arterial hypertension was investigated using mouse and cell models of induced hypoxia. The expression of LR11 and of hypoxia-inducible factor-1α was significantly increased in lung tissues from C57Bl/6 mice after 3 weeks of exposure to hypoxia compared with normoxia. Serum sLR11 levels were also increased. Physiological and histochemical analyses showed that increased right ventricular systolic pressure, right ventricular hypertrophy, and medial thickening induced under hypoxia in wild-type mice were attenuated in LR11(-/-) mice. The proliferation rates stimulated by hypoxia or platelet-derived growth factor-BB were attenuated in SMC derived from LR11(-/-) mice, compared with those from wild-type mice. Exogenous sLR11 protein increased the proliferation rates of SMC from wild-type mice. The expression of LR11 and hypoxia-inducible factor-1α was increased in cultured SMC under hypoxic conditions, and hypoxia-inducible factor-1α knockdown almost abolished the induction of LR11. Serum sLR11 levels were significantly higher in patients with, rather than without, pulmonary arterial hypertension. sLR11 levels positively correlated with pulmonary vascular resistance and mean pulmonary arterial pressure. CONCLUSIONS: LR11 regulated SMC proliferation during the progression of hypoxia-induced medial thickening in mice. The findings obtained from mice, together with those in humans, indicate that sLR11 could serve as a novel biomarker that reflects the pathophysiology of proliferating medial SMC in pulmonary arterial hypertension.

Soluble form of LR11 is highly increased in the vitreous fluids of patients with idiopathic epiretinal membrane.

PURPOSE: LR11 (also called SorLA or SORL1) is a migration regulator of adherent cells with the immature proliferative phenotype. The present study investigated the clinical and pathological involvement of the soluble form of LR11 (sLR11) in the idiopathic epiretinal membrane (iERM). METHODS: The subjects were 51 patients with iERM (24 cellophane macular reflex (CMR) and 27 preretinal macular fibrosis (PMF)) and 45 patients with macular holes as age and sex-matched controls. Vitreous sLR11 and transforming growth factor (TGF)ß2 levels were measured by ELISA. RESULTS: The sLR11 levels in the vitreous fluids of patients with iERM (20.2 ± 8.1 ng/mL) were significantly higher than those in controls (11.4 ± 4.7 ng/mL). Among the patients with iERM, the vitreous sLR11 levels were significantly higher in PMF (23.6 ± 8.2 ng/mL), than those in CMR (16.5 ± 5.9 ng/mL). Multivariate regression analysis of the studied factors showed that sLR11 was a unique factor independently contributing to the discrimination of the iERM patients against the control subjects (odds ratio [OR] 1.35 per 1-ng/mL increase, 95% CI 1.09-1.67; P = 0.004). ROC analysis showed that the sensitivity and the specificity of sLR11, but not of other studied factors, categorized into the rank of moderate accuracy. Finally, there was a positive correlation (R = 0.588; P = 0.003) between the vitreous levels of sLR11 and TGFß2 using the available samples. CONCLUSIONS: sLR11 levels in vitreous fluids were specifically increased in patients with iERM, suggesting the involvement in the pathology of proliferative and migrating cells for the development of iERM.

The soluble form of LR11 protein is a regulator of hypoxia-induced, urokinase-type plasminogen activator receptor (uPAR)-mediated adhesion of immature hematological cells.

A key property of hematopoietic stem and progenitor cells (HSPCs) regarding differentiation from the self-renewing quiescent to the proliferating stage is their adhesion to the bone marrow (BM) niche. An important molecule involved in proliferation and pool size of HSPCs in the BM is the hypoxia-induced urokinase-type plasminogen activator receptor (uPAR). Here, we show that the soluble form (sLR11) of LR11 (also called SorLA or SORL1) modulates the uPAR-mediated attachment of HSPCs under hypoxic conditions. Immunohistochemical and mRNA expression analyses revealed that hypoxia increased LR11 expression in hematological c-Kit(+) Lin(-) cells. In U937 cells, hypoxia induced a transient rise in LR11 transcription, production of cellular protein, and release of sLR11. Attachment to stromal cells of c-Kit(+) Lin(-) cells of lr11(-/-) mice was reduced by hypoxia much more than of lr11(+/+) animals. sLR11 induced the adhesion of U937 and c-Kit(+) Lin(-) cells to stromal cells. Cell attachment was increased by sLR11 and reduced in the presence of anti-uPAR antibodies. Furthermore, the fraction of uPAR co-immunoprecipitated with LR11 in membrane extracts of U937 cells was increased by hypoxia. CoCl2, a chemical inducer of HIF-1α, enhanced the levels of LR11 and sLR11 in U937 cells. The decrease in hypoxia-induced attachment of HIF-1α-knockdown cells was largely prevented by exogenously added sLR11. Finally, hypoxia induced HIF-1α binding to a consensus binding site in the LR11 promoter. Thus, we conclude that sLR11 regulates the hypoxia-enhanced adhesion of HSPCs via an uPAR-mediated pathway that stabilizes the hematological pool size by controlling cell attachment to the BM niche.

G-CSF induces the release of the soluble form of LR11, a regulator of myeloid cell mobilization in bone marrow.

Granulocyte colony-stimulating factor (G-CSF) induces the mobilization of leukocytes from the bone marrow (BM) to the circulation by a yet incompletely understood mechanism. Here, we describe that the membrane-bound receptor LR11 is highly expressed in human myeloid cells and that the shed soluble form of LR11 (sLR11) is a modifier of myeloid cell migration. In the process of leukocyte mobilization by G-CSF treatment, circulating sLR11 levels are transiently elevated in humans and mice. Moreover, following G-CSF treatment, the sLR11 levels in patients show significant positive correlation with the numbers of mobilized leukocytes. The changes of LR11 levels in BM cells and of sLR11 released into the BM fluid of mice correlate tightly with the changes in circulating sLR11 levels. G-CSF dose-dependently enhanced sLR11 release from HL-60 cells, which in turn accelerated cell migration. Finally, cooperatively with tumor necrosis factor-α (TNF-α) and G-CSF, sLR11 increased the attachment of floating cells (HL-60 and U937) to endothelial cells. We propose that sLR11 is a novel candidate modifier of G-CSF-mediated mobilization of hematologic cells. Identification of sLR11 as a regulatory component of G-CSF-mediated hematologic cell mobilization may facilitate further improvement of hematologic stem cell collection for clinical applications.

Vitreous fluid and circulating levels of soluble lr11, a novel marker for progression of diabetic retinopathy.

BACKGROUND: To evaluate the vitreous fluid levels of soluble LR11 (sLR11), a novel circulating marker for proliferative diabetic retinopathy (PDR), in patients with PDR and non-PDR (NPDR) in comparison to those in patients with non-diabetic ocular diseases. METHOD: Twenty NPDR and 60 PDR cases were included. Twenty-four subjects with a macular hole were served as a control group. The sLR11 levels of vitreous fluid and serum were determined by sandwich enzyme-linked immunosorbent assay. RESULTS: The serum sLR11 levels in the PDR and NPDR groups were 12.3 ± 5.0 ng/ml and 10.0 ± 2.7 ng/ml, respectively. The sLR11 levels in the vitreous fluid in the PDR (17.8 ± 6.2 ng/ml) and NPDR (17.4 ± 7.1 ng/ml) groups were significantly higher than those in the control subjects (12.3 ± 4.5 ng /ml) (P = 0.0003 and P = 0.006, respectively). The vitreous fluid levels of sLR11 were not significantly different between the PDR and NPDR groups, and the levels were not significantly correlated with the serum levels of sLR11 in the patients with PDR or NPDR. CONCLUSION: Vitreous fluid sLR11 level may be a novel risk factor for the early development of PDR prior to the increase in circulating levels in diabetic patients.

ß-Site amyloid precursor protein-cleaving enzyme 1 activity is related to cerebrospinal fluid concentrations of sortilin-related receptor with A-type repeats, soluble amyloid precursor protein, and tau.

BACKGROUND: ß-Site amyloid precursor protein (APP)-cleaving enzyme 1 (BACE1) activity determines the rate of APP cleavage and is therefore the main driver of amyloid ß production, which is a pathological hallmark of Alzheimer's disease (AD). METHODS: The present study explored the correlation between BACE1 activity and cerebrospinal fluid (CSF) markers of APP metabolism and axonal degeneration in 63 patients with mild AD and 12 healthy control subjects. RESULTS: In the AD group, positive correlations between BACE1 activity and soluble APP ß, the APP sorting receptor sortilin-related receptor with A-type repeats (also known as SorLA or LR11), and tau were detected. BACE1 activity was not associated with amyloid ß1-42 or soluble APP α concentrations in the AD group, and no associations between BACE1 activity and any of the protein concentrations were found in the control group. CONCLUSION: Our results confirm the relevance of BACE1 and sortilin-related receptor with A-type repeats within the amyloid cascade and also provide a further piece of evidence for the link between amyloid and tau pathology in AD.

SORL1 genetic variants and cerebrospinal fluid biomarkers of Alzheimer's disease.

The neuronal sortilin-related receptor with A-type repeats (SORL1, also called LR11 or sorLA) is involved in amyloidogenesis, and the SORL1 gene is a major risk factor for Alzheimer's disease (AD). We investigated AD-related CSF biomarkers for associations with SORL1 genetic variants in 105 German patients with mild cognitive impairment (MCI) and AD. The homozygous CC-allele of single nucleotide polymorphism (SNP) 4 was associated with increased Tau concentrations in AD, and the minor alleles of SNP8, SNP9, and SNP10 and the haplotype CGT of these SNPs were associated with increased SORL1 concentrations in MCI. SNP22 and SNP23, and the haplotypes TCT of SNP19-21-23, and TTC of SNP22-23-24 were correlated with decreased Ab42 levels in AD. These results strengthen the functional role of SORL1 in AD.

Ang II-stimulated migration of vascular smooth muscle cells is dependent on LR11 in mice.

Medial-to-intimal migration of SMCs is critical to atherosclerotic plaque formation and remodeling of injured arteries. Considerable amounts of the shed soluble form of the LDL receptor relative LR11 (sLR11) produced by intimal SMCs enhance SMC migration in vitro via upregulation of urokinase-type plasminogen activator receptor (uPAR) expression. Here, we show that circulating sLR11 is a novel marker of carotid intima-media thickness (IMT) and that targeted disruption of the LR11 gene greatly reduces intimal thickening of arteries through attenuation of Ang II-induced migration of SMCs. Serum concentrations of sLR11 were positively correlated with IMT in dyslipidemic subjects, and multivariable regression analysis suggested sLR11 levels as an index of IMT, independent of classical atherosclerosis risk factors. In Lr11-/- mice, femoral artery intimal thickness after cuff placement was decreased, and Ang II-stimulated migration and attachment of SMCs from these mice were largely abolished. In isolated murine SMCs, sLR11 caused membrane ruffle formation via activation of focal adhesion kinase/ERK/Rac1 accompanied by complex formation between uPAR and integrin alphavbeta3, a process accelerated by Ang II. Overproduction of sLR11 decreased the sensitivity of Ang II-induced activation pathways to inhibition by an Ang II type 1 receptor blocker in mice. Thus, we demonstrate a requirement for sLR11 in Ang II-induced SMC migration and propose what we believe is a novel role for sLR11 as a biomarker of carotid IMT.

Development of an immunoassay for the quantification of soluble LR11, a circulating marker of atherosclerosis.

BACKGROUND: Vascular smooth muscle cells (SMCs) migrate from the arterial media to the intima in the progression of atherosclerosis, and dysfunction of SMCs leads to enhanced atherogenesis. A soluble form of the LDL receptor relative with 11 ligand-binding repeats (sLR11) is produced by the intimal SMCs, and the circulating concentrations of sLR11 likely reflect the pathophysiological condition of intimal SMCs. Furthermore, polymorphism of the LR11 gene has been found to be related to the onset of Alzheimer disease. This study describes the development of a sandwich immunoassay for quantifying sLR11 in human serum and cerebrospinal fluid. METHODS: We used synthetic peptides or DNA immunization to produce monoclonal antibodies (MAbs) A2-2-3, M3, and R14 against different epitopes of LR11. RESULTS: sLR11 was immunologically identified as a 250-kDa protein in human serum and cerebrospinal fluid by SDS-PAGE separation, and was purified from serum by use of a receptor-associated protein and MAb M3. An immunoassay for quantification of sLR11 with a working range of 0.25-4.0 microg/L was developed using the combination of MAbs M3 and R14. Treatment of serum with 5.25% n-nonanoyl-N-methyl-d-glucamine reduced the matrix effects of serum on the absorbance detection in the ELISA system. The linear dynamic range of the ELISA spanned the variation of circulating sLR11 concentrations in individuals with atherosclerosis. CONCLUSIONS: A sandwich ELISA was established for quantifying sLR11 in serum and cerebrospinal fluid. This technique provides a novel means for assessing the pathophysiology of atherosclerosis, and possibly neurodegenerative diseases.

Circulating soluble LR11, a differentiation regulator for vascular cells, is increased during pregnancy and exaggerated in patients with pre-eclampsia.

BACKGROUND: Pre-eclampsia is a pregnancy-specific disease characterized by onset of hypertension and proteinuria, sometimes progressing into damaging other organs. Here, we investigated the pathological significance of the soluble fragment of LR11 (sLR11), a cell differentiation regulator, in comparison to circulating IL-6 and TNF-α, in pre-eclampsia. METHODS: The study was conducted in a cross-sectional research design with fourteen pre-eclampsia patients and fifty healthy pregnant subjects. Pre-eclampsia was defined as hypertensive disorders in pregnancy at over 20 weeks of gestation with proteinuria. RESULTS: Plasma levels of sLR11 as well as IL-6 in pre-eclampsia were increased compared with those in the healthy pregnant subjects at the first, the second, and the third trimester. Receiver operating characteristic analysis for the detection of pre-eclampsia among third-trimester subjects showed that the areas under the curves of sLR11 and IL-6 were equivalent. sLR11 and IL-6 correlated positively with TNF-α in healthy pregnant subjects. In the pre-eclampsia patients, there was neither a correlation between sLR11 and IL-6 nor between sLR11 and TNF-α. CONCLUSIONS: sLR11 increases during pregnancy, with levels further exaggerated in pre-eclampsia, and may be related to the pathology of pre-eclampsia.

Levels of circulating soluble LR11, a regulator of smooth muscle cell migration, are highly associated with atherosclerotic plaques in patients with carotid artery stenosis.

BACKGROUND: The levels of plasma sLR11, released from intimal SMCs, are positively associated with intima-media thickness (IMT) in asymptomatic subjects. We have evaluated the yet unknown pathological significance of sLR11 for plaque conditions in patients with carotid artery stenosis. METHODS: The presence of LR11 in carotid plaques was investigated using autopsy specimens. A clinical ultrasonography study for elucidating relationships between sLR11 and plaque condition was performed in 46 patients. RESULTS: Immunohistochemistry showed high levels of LR11 in SMCs within thickened intima and at the media-intima border of atherosclerotic carotid plaques. The levels of sLR11 in patients were clearly elevated compared to healthy controls. Univariate analysis of sLR11 revealed significant positive correlation with plaque score and a tendency to correlate with the stenotic fraction. Univariate and multiple regression analyses of plaque scores showed that sLR11, maximum IMT, and HDL-cholesterol independently determined plaque score. Finally, univariate analysis of initial sLR11 levels for changes in imaging markers after one-year follow-up showed that initial sLR11 levels significantly correlated with stenotic fraction progression. CONCLUSIONS: The levels of sLR11, abundantly expressed in carotid atherosclerotic plaques, are highly associated with increased plaque score. sLR11 levels may be predictive of plaque conditions in patients with advanced carotid atherosclerosis.

Matrix metalloproteinase-3 enhances the free fatty acids-induced VEGF expression in adipocytes through toll-like receptor 2.

Infiltrated macrophages (Mphi) are believed to cause pathological changes in the surrounding adipocytes through the secretion of active molecules in visceral fat. Matrix metalloproteinase (MMP)-3 is secreted from Mphi, and enhances expression of the inflammatory cytokines through the activation of toll-like receptor (TLR) 2. Visceral adipocytes express high levels of vascular endothelial growth factor (VEGF), and the degree of visceral fat accumulation is associated with the plasma VEGF concentration in obese subjects. The aim of the study is to clarify the role of MMP-3 in the enhancement of the free fatty acids (FFAs)-induced VEGF expression through TLR2 in visceral adipocytes. One mM FFAs induced VEGF mRNA and protein expression in 3T3-L1 adipocytes. The FFAs-induced VEGF expression was mostly mediated by TLR2. A high fat intake increased the VEGF mRNA expression in visceral fat and the VEGF concentration in plasma, accompanied with the increase in the plasma FFAs concentration in mice. These increases were largely inhibited in TLR2-deficient mice. The FFAs-induced VEGF expression was increased in the presence of Mphi-conditioned medium (CM) in adipocytes, and the enhancement was inhibited by a MMP-3 inhibitor or a neutralizing antibody against MMP-3. The active form of MMP-3 induced the VEGF mRNA expression, as well as TLR2, in adipocytes. The increase in the VEGF expression by MMP-3 was inhibited by the treatment with siRNA for TLR2. The enhancement of FFAs-induced TLR2 expression by Mphi-CM was inhibited by blocking of the MMP-3. The increase in the VEGF mRNA expression by Mphi-CM or MMP-3 was partially inhibited by a neutralizing antibody against TNF-alpha. These results indicate that MMP-3 in Mphi-CM enhances the FFAs-induced VEGF expression in adipocytes through the increase in the TLR2 expression. The MMP-3 secreted from the infiltrated Mphi may be a regulator of the VEGF expression in visceral adipocytes.

A secreted soluble form of LR11, specifically expressed in intimal smooth muscle cells, accelerates formation of lipid-laden macrophages.

OBJECTIVE: Macrophages play a key role in lipid-rich unstable plaque formation and interact with intimal smooth muscle cells (SMCs) in early and progressive stages of atherosclerosis. LR11 (also called sorLA), a member of low-density lipoprotein receptor family, is highly and specifically expressed in intimal SMCs, and causes urokinase-type plasminogen activator receptor-mediated degradation of extracellular matrices. Here we investigated whether the secreted soluble form of LR11 (solLR11) enhances adhesion, migration, and lipid accumulation in macrophages using animal models and cultured systems. METHODS AND RESULTS: Immunohistochemistry showed solLR11 expression in thickened intima of balloon-denuded rat artery. Macrophage infiltration into the cuff-injured artery was markedly reduced in LR11-deficient mice. In vitro functional assays using THP-1-derived macrophages showed that solLR11 (1 microg/mL) significantly increased acetylated low-density lipoprotein uptake by THP-1 cells and cell surface levels of scavenger receptor SR-A 1.7- and 2.8-fold, respectively. SolLR11 dose-dependently increased the migration activity of THP-1 macrophages and adhesion to extracellular matrices 2.0- and 2.1-fold, respectively, at 1 microg/mL. These effects of solLR11 were almost completely inhibited by a neutralizing anti-urokinase-type plasminogen activator receptor antibody. CONCLUSION: SolLR11, secreted from intimal SMCs, regulates adhesion, migration, and lipid accumulation in macrophages through activation of urokinase-type plasminogen activator receptor. The formation of lipid-laden macrophages in atherosclerotic plaques possibly is regulated by SolLR11 of intimal SMCs.

Susceptibilities of epicardial and subcutaneous fat tissue for browning-gene expression and diet-induced volume reduction are different.

The upregulation of brown or brown-like beige adipocytes is a potential strategy for the prevention or treatment of diabetes and coronary artery diseases in obese patients. Epicardial adipose tissue (EAT) differs significantly from subcutaneous fat tissue (SAT) in metabolic properties. To investigate properties of EAT further, thermogenesis gene expression was investigated in human autopsy and murine samples, and adipocytes differentiated from EAT mesenchymal cells. Subsequently, analyzed EAT volume alterations were observed to be associated with weight reduction in obese patients by imaging. Gene expression analyses of autopsy samples revealed that UCP­1 mRNA levels in EAT were significantly increased compared with SAT, and ß3­adrenergic receptor (AR) levels tended to be increased; this finding was verified in comparing EAT with SAT in mice. Browning stimulation of human EAT­derived MCs increased uncoupling protein­1 and ß3­AR levels by 3.2 fold­ and 12.6­fold compared with SAT­derived MCs, respectively. Subsequent imaging for EAT volume measurement using multi­detector computed tomography in 10 obese patients revealed that mean EAT volumes did not significantly decrease following weight loss therapy. The EAT volume alterations were not correlated with weight changes, whereas positive correlations were observed in SAT and visceral adipose tissue. Therefore, the studies in man and mouse on EAT properties demonstrated that susceptibilities of EAT and SAT for browning­gene expression and diet­induced volume reduction were grossly different. The data suggest a potential association of EAT with local thermogenetic and metabolic homeostasis in cardiac and/or cardiovascular cells, in conjunction with systemic energy metabolism.

Soluble LR11 associates with aortic root calcification in asymptomatic treated male patients with familial hypercholesterolemia.

BACKGROUND AND AIMS: Despite statin treatment, a high prevalence of severe vascular calcification is found in patients with familial hypercholesterolemia (FH). We assessed the relation between the circulating soluble form of low-density lipoprotein receptor relative with 11 ligand-binding repeats (sLR11), a risk factor for cardiovascular disease, and vascular calcification in asymptomatic statin-treated heterozygous FH patients. METHODS: In 123 asymptomatic heterozygous FH patients (age 40-69 years), aortic root (ARC), aortic valve (AVC) and coronary artery calcification (CAC) were determined with CT-based calcium scoring expressed in Agatston units. Plasma sLR11 levels were measured by sandwich ELISA. RESULTS: Seventy-three patients displayed ARC, 48 had AVC and 96 CAC. Plasma sLR11 levels were positively correlated with the presence of ARC (r = 0.2, p = 0.03), but not with AVC or CAC. The correlation between sLR11 levels and ARC was restricted to male FH patients (r = 0.31, p = 0.006). Multivariate logistic analyses showed that the association of plasma sLR11 with the presence of ARC was independent of other determinants (Adjusted Odds Ratio, 2.01 (95% CI = 1.28-3.16) p = 0.002). CONCLUSIONS: Plasma sLR11 is associated with ARC in male FH patients and may be mechanistically involved in the differential distribution of atherosclerotic lesions in the vasculature.

LR11, an LDL receptor gene family member, is a novel regulator of smooth muscle cell migration.

LR11, a member of the LDL receptor family, is highly expressed in vascular smooth muscle cells (SMCs) of the hyperplastic intima, and induces enhanced migration of SMCs in vitro via its upregulation of urokinase-type plasminogen activator receptor (uPAR) expression. In this study, we have delineated the mechanism by which LR11 elevates the expression levels of uPAR in SMCs. Secretion of soluble LR11 is induced in SMCs during the rapidly proliferating phase, and the secreted LR11 induces the migration activities of SMCs. Both the cell-anchored and secreted forms of LR11 have the capacity to bind to and form complexes with uPAR. LR11-overexpressing cells show significantly enhanced uPAR binding, but decreased uPAR internalization. LR11 colocalizes with uPAR on the cell surface and inhibits the LDL receptor-related protein (LRP)-mediated binding and internalization of uPAR. Thus, LR11 mediates the uPAR localization to the plasma membrane. LR11 is highly expressed in the atheromatous plaque areas of apoE knockout mice, particularly in the intimal SMCs at the border between intima and media. The neutralization of LR11 function with anti-LR11 antibody reduced cuff-induced intimal thickness in mice. The novel mechanism of regulation of uPAR localization in SMCs accompanied with enhanced migration activity possibly constitutes an important factor in the process of atherosclerosis and arterial remodeling.

Circulating soluble form of LR11, a regulator of smooth muscle cell migration, is a novel marker for intima-media thickness of carotid arteries in type 2 diabetes.

BACKGROUND: Smooth muscle cell (SMC) migration from the media to the intima, a process affecting plaque stability in advanced-stage atherosclerosis, is under the control of LR11. To delineate the clinical significance of the circulating soluble form of LR11 (sLR11) in patients with type 2 diabetes (T2D), we analyzed the correlation of sLR11 levels with intima-media thickness (IMT) of carotid arteries. METHODS: Plasma sLR11 levels were measured in 165 patients with T2D (mean age 56.2±10.4 y, 58.2% males, and BMI 24.6±3.6) by ELISA. Averaged IMT levels of common carotid arteries were determined by ultrasonography. RESULTS: Circulating sLR11 levels were 9.8±3.5ng/ml, and correlated positively with the classical atherosclerosis risk factors age, sex, systolic blood pressure, low-density lipoprotein-cholesterol (LDL-C), fasting plasma-glucose (FPG), and glycosylated hemoglobin. Multivariate linear regression analysis indicated that only FPG was associated with sLR11; sLR11 correlated positively with IMT, together with age and FPG, but less with LDL-C. Among the serum risk factors for IMT, multivariate linear regression analysis uncovered that sLR11 was independently associated with IMT. Subsequent logistic analysis revealed that FPG correlated best with IMT values at a cut-off of 0.80mm and sLR11 at a cut-off of 0.90mm, respectively, while LDL-C showed lower discriminatory power at any IMT cut-off values. CONCLUSION: Increased sLR11 concentrations are highly associated with increased IMT as well as with FPG in middle-aged, non-obese patients with T2D. Circulating sLR11 may be a novel marker representing the pathophysiology of intimal SMCs in patients with T2D.

Levels of soluble LR11/SorLA are highly increased in the bile of patients with biliary tract and pancreatic cancers.

BACKGROUND: The utility of molecules derived from cancer cells as biomarkers of the pathological status in biliary tract and pancreatic cancers is still limited. Soluble LDL receptor relative with 11 ligand-binding repeats (sLR11), a molecule released from immature cells, has been shown to be a circulating biomarker for early stage hematological malignancies. METHODS: We have evaluated the pathological significance of bile sLR11 levels in 147 samples from 72 patients with biliary tract cancer (BTC), pancreatic cancer (PC), or benign diseases. RESULTS: The bile sLR11 levels in the cancer patients were significantly increased compared with those in patients without cancer, independent of cytological detection of cancer cells in bile. The average bile sLR11 levels in cancer patients were significantly higher than in those with benign diseases, while levels of bile carbohydrate antigen 19-9 (CA19-9) and carcinoembryonic antigen (CEA) were not different. LR11 protein was found to be highly expressed in the BTC and PC cells. The LR11 transcript levels in cholangiocarcinoma and pancreatic cancer cell lines were sharply induced during proliferation and significantly increased under hypoxic conditions. CONCLUSIONS: Therefore, sLR11 levels in bile may be indicative of cancer cell conditions and may serve as potential novel biomarker in patients with BTC and PC.