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.

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.

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.

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.

Levels of the soluble LDL receptor-relative LR11 decrease in overweight individuals with type 2 diabetes upon diet-induced weight loss.

BACKGROUND AND AIMS: Cardiovascular disease (CVD) is a major complication in patients with type 2 diabetes (T2D), especially in those with obesity. Plasma soluble low density lipoprotein receptor-relative with 11 ligand-binding repeats (sLR11) plays a role in the development of atherosclerosis and has been linked to the metabolism of triglyceride-rich lipoproteins, adiposity, and vascular complications in T2D. We aimed to determine the effect of diet-induced weight loss on plasma sLR11 levels in overweight and obese individuals with T2D. METHODS: Plasma sLR11 levels were determined in 64 individuals with T2D and BMI >27 kg/m2 before and after a 20-week weight loss diet. As a reference, sLR11 levels were also determined in 64 healthy, non-obese controls, matched as a group for age and sex. RESULTS: Median plasma sLR11 levels of the T2D study-group at baseline (15.4 ng/mL (IQR 12.9-19.5)) were higher than in controls (10.2 (IQR: 8.7-12.2) ng/mL; p = 0.001). The diet resulted in a weight loss of 9.7 ± 5.2% (p = 0.001) and improved CVD risk factors. sLR11 levels were reduced to 13.3 ng/mL (IQR 11.0-17.1; p = 0.001). Changes in sLR11 levels positively associated with changes in non-HDL cholesterol (B = 1.54, R2 = 0.17, p = 0.001) and HbA1c (B = 0.07, R2 = 0.11, p = 0.007), but not with weight loss (B = 0.04, R2 = 0.05, p = 0.076). The changes in non-HDL cholesterol and HbA1c together explained 24% of the variance of sLR11 reduction (p = 0.001). CONCLUSIONS: Weight loss dieting in overweight and obese individuals with T2D resulted in a reduction in plasma sLR11 levels that was associated with improvements in lipid-profile and glycemic state.

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.

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.

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.

Soluble LR11 is a novel biomarker for vascular lesions late after Kawasaki disease.

OBJECTIVE: Coronary artery lesions (CALs) and a risk for early onset of atherosclerosis are major concerns following Kawasaki disease (KD). Intimal smooth muscle cells (SMCs) have an important role in vascular lesions in KD. It is known that soluble LR11 (sLR11) is a novel biomarker for vascular lesions and LR11 is markedly expressed in intimal SMCs in atherosclerotic lesions. In this study, we hypothesized that sLR11 reflects the presence of vascular lesions late after KD. METHODS: Twenty-three age-matched controls (group 1) and 59 patients with a history of KD were enrolled; 36 with KD had normal coronary arteries or regressed aneurysms (group 2), and 23 had CALs (group 3). RESULTS: Serum sLR11 levels in group 3 (median, interquartile range (IQR): 11.1 ng/mL, 9.3-13.9 ng/mL) were significantly higher than those in groups 1 (8.4 ng/mL, 7.1-10.2 ng/mL, p < 0.001) and 2 (9.0 ng/mL, 7.7-10.1 ng/mL, p < 0.01). Levels of sLR11 were positively correlated with levels of high-sensitivity C-reactive protein (r = 0.480, p < 0.01) and lipoprotein (a) (r = 0.486, p < 0.01). CONCLUSION: These findings suggest that sLR11 reflects the development of vascular lesions in patients with serious CALs.

Prognostic impact of circulating soluble LR11 on long-term clinical outcomes in patients with coronary artery disease.

BACKGROUND: LR11, a member of LDL receptor family, is a novel marker of the proliferation of intimal smooth muscle cells (SMCs). LR11 is released in soluble form (sLR11) by proteolytic shedding and has biological activity toward SMC migration. We previously showed that circulating sLR11 positively correlates with carotid intima-medial thickness (IMT) independently of classical atherosclerotic risk factors and that it significantly associates with the severity of CAD. However, the association between sLR11 and long-term clinical outcomes remain uncertain. METHODS AND RESULTS: This study included 438 consecutive patients (mean age, 65.8 ± 9.6 y; male, 82.4%) who underwent coronary intervention between March 2003 and December 2004 at our institution. The patients were assigned to quartiles according to pre-procedural sLR11 values. The primary endpoints were composite cardiovascular disease (CVD) endpoints including cardiovascular death, non-fatal acute coronary syndrome and non-fatal stroke. During median follow-up of 2876 days, composite CVD endpoints occurred 97 (22.1%) patients including 41 (9.4%) with cardiovascular disease (CVD)-related death, 36 (8.2%) non-fatal ACS and 20 (4.6%) non-fatal strokes. The hazard ratio (HR) for composite CVD endpoints significantly and dose-dependently increased with sLR11 levels (p for trend = 0.0077). A higher logarithm-transformed sLR11 value was associated with a greater risk of composite CVD endpoints, and the increased number of adverse long-term clinical outcomes persisted even after adjustment for other independent variables (HR 1.87 95%CI 1.02-3.31, p = 0.0435). CONCLUSIONS: Elevated sLR11 levels were significantly associated with higher long-term adverse cardiac events in patients with CAD. Further extensive studies are expected to elucidate the mechanistic role of sLR11 and its clinical value as a prognostic marker in the development of atherosclerosis.

Unsuppressed lipolysis in adipocytes is linked with enhanced gluconeogenesis and altered bile acid physiology in Insr(P1195L/+) mice fed high-fat-diet.

High-fat diet (HFD) triggers insulin resistance and diabetes mellitus, but their link remains unclear. Characterization of overt hyperglycemia in insulin receptor mutant (Insr(P1195L/+)) mice exposed to HFD (Insr(P1195L/+)/HFD mice) revealed increased glucose-6-phosphatase (G6pc) expression in liver and increased gluconeogenesis from glycerol. Lipolysis in white adipose tissues (WAT) and lipolysis-induced blood glucose rise were increased in Insr(P1195L/+)/HFD mice, while wild-type WAT transplantation ameliorated the hyperglycemia and the increased G6pc expression. We found that the expressions of genes involved in bile acid (BA) metabolism were altered in Insr(P1195L/+)/HFD liver. Among these, the expression of Cyp7a1, a BA synthesis enzyme, was insulin-dependent and was markedly decreased in Insr(P1195L/+)/HFD liver. Reduced Cyp7a1 expression in Insr(P1195L/+)/HFD liver was rescued by WAT transplantation, and the expression of Cyp7a1 was suppressed by glycerol administration in wild-type liver. These findings suggest that unsuppressed lipolysis in adipocytes elicited by HFD feeding is linked with enhanced gluconeogenesis from glycerol and with alterations in BA physiology in Insr(P1195L/+)/HFD liver.

Soluble LR11/SorLA represses thermogenesis in adipose tissue and correlates with BMI in humans.

Thermogenesis in brown adipose tissue (BAT) is an important component of energy expenditure in mammals. Recent studies have confirmed its presence and metabolic role in humans. Defining the physiological regulation of BAT is therefore of great importance for developing strategies to treat metabolic diseases. Here we show that the soluble form of the low-density lipoprotein receptor relative, LR11/SorLA (sLR11), suppresses thermogenesis in adipose tissue in a cell-autonomous manner. Mice lacking LR11 are protected from diet-induced obesity associated with an increased browning of white adipose tissue and hypermetabolism. Treatment of adipocytes with sLR11 inhibits thermogenesis via the bone morphogenetic protein/TGFß signalling pathway and reduces Smad phosphorylation. In addition, sLR11 levels in humans are shown to positively correlate with body mass index and adiposity. Given the need for tight regulation of a tissue with a high capacity for energy wastage, we propose that LR11 plays an energy conserving role that is exaggerated in states of obesity.

LR11/SorLA links triglyceride-rich lipoproteins to risk of developing cardiovascular disease in FH patients.

OBJECTIVE: Familial Hypercholesterolemia (FH) is associated with an increased risk of cardiovascular disease (CVD). However, whether an individual heterozygous FH patient will develop CVD depends on other genetic- and environmental risk factors as well. LDL receptor-related protein with 11 ligand binding repeat (LR11) and its soluble form (sLR11) play a role in the progression of atherosclerosis. We investigated the involvement of LR11 and sLR11 in CVD development in FH patients and in LDLR deficient (Ldlr(-/-)) mice. APPROACH AND RESULTS: In statin-treated asymptomatic male heterozygous FH subjects, plasma sLR11 levels correlated with carotid intima-media thickness. Increased plasma sLR11 levels were found in Ldlr(-/-) and also in wild-type mice exclusively after high-fat feeding. Hepatic LR11 mRNA levels, however, were higher in chow-fed Ldlr(-/-) in comparison with wild-type mice and were further increased after a high fat diet. Similar results were obtained with Apoe(-/-) mice, but not with wild-type mice. LR11 mRNA and protein levels and release of sLR11 from cultured HepG2 and aortic smooth muscle cells were upregulated by postprandial triglyceride-rich lipoproteins (TGRL). Overexpression of human LR11 in CHO cells resulted in increased binding and association of 12I-labeled TGRL, but not of 12I-labeled LDL. CONCLUSION: Our data strongly suggest an involvement of LR11 in mediating the harmful effects of a high-fat diet on CVD progression. Elevated sLR11 levels may increase the CVD risk especially in subjects with delayed clearance of triglyceride-rich remnants, such as in FH patients.

Self-pMHCII complexes are variably expressed in the thymus and periphery independent of mRNA expression but dependent on the activation state of the APCs.

Self-peptide MHCII ligands are critical for selection of CD4+ T cells in the thymus, and maintenance in the periphery. To date, no investigation as to the exact thymic and peripheral expression of a naturally occurring positive selecting self-peptide MHCII (self-pMHCII) complex has taken place. We have generated a sensitive T cell hybridoma to functionally detect the endogenous presentation of a confirmed positive selecting self-pMHCII complex for a CD4+ transgenic T cell. Using this tool to survey and quantify the expression selecting of self-pMHCII, we have shown unequivocal proof that a known CD4+ selecting ligand can be presented on both positive and negative selecting thymic APCs. We also show that peripheral presentation of this same selecting ligand is affected by the activation state of the APCs. Furthermore, discrepancies between the gene expression and self-pMHCII complex presentation of this bona fide selecting ligand suggest that functional detection self-ligand complexes will be required to establish a complete view of the naturally presented endogenous self-pMHC landscape.

Circulating soluble LR11, a novel marker of smooth muscle cell proliferation, is enhanced after coronary stenting in response to vascular injury.

OBJECTIVE: Restenosis after vascular intervention remains a major clinical problem. Circulating LR11 has been shown a novel marker of intimal smooth muscle cell (SMC) proliferation in human and animal studies. The present study was performed to clarify the clinical significance of circulating LR11 in patients with stable angina pectoris after coronary stenting. METHODS AND RESULTS: We firstly investigated the circulating sLR11 levels for 28 days after arterial injury in mice, and then assessed time-dependent change in circulating sLR11 level after coronary stenting in a clinical study. Mouse sLR11 levels rapidly increased to 4.0-fold of the control value without cuff placement at postoperative day (POD) 14, and the levels gradually declined to 3.1-fold of the control value until POD 28 in mice. The circulating soluble LR11 levels were measured (before and at 14, 60 and 240 days after coronary stenting in a clinical study of 102 consecutive patients with stable angina pectoris who were treated with percutaneous coronary intervention. Circulating sLR11 levels were significantly increased on days 14 and 60 after the procedure and positively associated with the angiographic late loss index. CONCLUSIONS: Our study suggested that circulating sLR11 levels may be a potential marker for angiographic late loss in patients after coronary stenting. Further mechanistic studies are expected to know the clinical significance of sLR11 as a novel marker for intimal SMC.

Tetraspanin CD9 modulates ADAM17-mediated shedding of LR11 in leukocytes.

LR11, also known as SorLA or SORL1, is a type-I membrane protein from which a large extracellular part, soluble LR11 (sLR11), is released by proteolytic shedding on cleavage with a disintegrin and metalloproteinase 17 (ADAM17). A shedding mechanism is presumed to have a key role in the functions of LR11, but the evidence for this has not yet been demonstrated. Tetraspanin CD9 has been recently shown to regulate the ADAM17-mediated shedding of tumor necrosis factor-α and intercellular adhesion molecule-1 on the cell surface. Here, we investigated the role of CD9 on the shedding of LR11 in leukocytes. LR11 was not expressed in THP-1 monocytes, but it was expressed and released in phorbol 12-myristate 13-acetate (PMA)-induced THP-1 macrophages (PMA/THP-1). Confocal microscopy showed colocalization of LR11 and CD9 proteins on the cell surface of PMA/THP-1. Ectopic neo-expression of CD9 in CCRF-SB cells, which are LR11-positive and CD9-negative, reduced the amount of sLR11 released from the cells. In contrast, incubation of LR11-transfected THP-1 cells with neutralizing anti-CD9 monoclonal antibodies increased the amount of sLR11 released from the cells. Likewise, the PMA-stimulated release of sLR11 increased in THP-1 cells transfected with CD9-targeted shRNAs, which was negated by treatment with the metalloproteinase inhibitor GM6001. These results suggest that the tetraspanin CD9 modulates the ADAM17-mediated shedding of LR11 in various leukemia cell lines and that the association between LR11 and CD9 on the cell surface has an important role in the ADAM17-mediated shedding mechanism.

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.