Soluble analog of ApoER2 targeting beta2-glycoprotein I in immune complexes counteracts hypertension in lupus-prone mice with spontaneous antiphospholipid syndrome

Essentials (NZWxBXSB)F1 male mice develop antibodies beta2-glycoprotein I (β2GPI) and hypertension. A1-A1 is a soluble analogue of ApoE receptor 2 with a high affinity for β2GPI/antibody complexes. A1-A1 improved blood pressure and arterial elastance in (NZWxBXSB)F1 male mice. A1-A1 had no adverse effects on the hemodynamics of healthy mice.

SUMMARY

Background Antiphospholipid syndrome (APS) is diagnosed based on the presence of antiphospholipid antibodies and clinical thrombosis or fetal loss during pregnancy. Lupus-prone (NZWxBXSB)F1 male mice are the mouse model of spontaneous APS. They develop anti-β2GPI antibodies, microinfarcts and hypertension. ApoER2 is a receptor that contributes to anti-β2GPI-dependent thrombosis in APS by down-regulating endothelial nitric oxide synthase activation. Objectives A1-A1 is a small protein constructed from two identical ligand-binding modules from ApoER2, containing the binding site for β2GPI. We studied how treatment with A1-A1 affects the development of hypertension in (NZWxBXSB)F1 male mice. Methods We treated (NZWxBXSB)F1 male mice with A1-A1 for up to 4 weeks and examined changes in hemodynamics by left ventricular pressure-volume loop measurements. Results We observed improvements in blood pressure in the A1-A1 treated mice. A1-A1 prevented the deterioration of arterial elastance by decreasing systemic resistance and improving vessel compliance. We did not detect any adverse effects of the treatment in either male mice or in apparently healthy female (NZWxBXSB)F1 mice. Conclusions We demonstrated that A1-A1, which is a soluble analog of ApoER2 that binds pathological β2GPI/anti-β2GPI complexes, has a positive impact on hemodynamics in lupus-prone mice with spontaneous anti-β2GPI antibodies and hypertension.

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.

Enhanced circulating soluble LR11 in patients with diabetic retinopathy

PURPOSE

To investigate the relationship of circulating levels of soluble form of LR11 (sLR11; also called SorLA or SORL1), with the progression of proliferative diabetic retinopathy (PDR) in patients with type 2 diabetes mellitus.

DESIGN

Cross-sectional study.

METHODS

Fifty-four patients with type 2 diabetes mellitus were divided into 2 sex- and age-matched groups: one with PDR (n = 29) and the other with nonproliferative diabetic retinopathy (n = 25). The serum sLR11 levels were measured with an immunodetection system followed by chemifluorescence quantification.

RESULTS

The serum sLR11 levels were higher in the PDR group than in the nonproliferative diabetic retinopathy group (5.8 ± 1.2 U vs 3.7 ± 1.3 U; P < .01). A multivariate regression analysis showed that circulating sLR11 is a factor contributing to the prediction of PDR independent of other classical risk factors, and an area under the receiver operating characteristic curve analysis revealed that the sensitivity and the specificity were equivalent to or more than those of other factors. Among the classical risk factors for PDR, glycosylated hemoglobin levels showed the highest correlation coefficient (P < .01) for the sLR11 concentrations.

CONCLUSIONS

Serum sLR11 concentration may reflect the progression of PDR in patients with type 2 diabetes mellitus. sLR11, released from immature vascular cells and indicating the development of atherosclerosis, is expected to be a novel candidate biomarker indicating diabetic retinopathy in patients with type 2 diabetes mellitus.

[Novel biomarker for pathological immature cells--soluble form of LR11]

LR11 (also called SorLA or SORL1), a member of the LDL receptor family, was originally discovered in 1996 from genes specifically expressed in the intimal smooth muscle cells of atherosclerotic plaques. The soluble form of LR11 (sLR11) as well as the membrane-bound form plays a key role in the phenotype conversion of medial smooth muscle cells into intimal smooth muscle cells through the activation of urokinase receptor/integrin-mediated intracellular pathways. The levels of sLR11 in serum or CSF are increased in patients with atherosclerotic diseases, Alzheimer's disease or malignant diseases including acute leukemias. The recently developed ELISA system using two specific antibodies against LR11 made it possible to measure sLR11 quantitatively and stably for many samples. Thus, a novel clinical examination is expected to detect the pathological immature cells important for the pathophysiology of the above diseases. The soluble receptor-based clinical approach, together with basic studies about the structure-function relationship, may shed light on the development of novel target therapy against pathological immature cells in the science fields of so far independently categorized diseases.

A Mediterranean-style, low-glycemic-load diet decreases atherogenic lipoproteins and reduces lipoprotein (a) and oxidized low-density lipoprotein in women with metabolic syndrome

The objective was to assess the impact of a Mediterranean-style, low-glycemic-load diet (control group, n = 41) and the same diet plus a medical food (MF) containing phytosterols, soy protein, and extracts from hops and Acacia (MF group, n = 42) on lipoprotein atherogenicity in women with metabolic syndrome. Plasma lipids, apolipoproteins (apos), lipoprotein subfractions and particle size, low-density lipoprotein (LDL) oxidation, and lipoprotein (a) were measured at baseline, week 8, and week 12 of the intervention. Three-day dietary records were collected at the same time points to assess compliance. Compared with baseline, women decreased energy intake from carbohydrate (P < .001) and fat (P < .001), whereas they increased energy intake from protein (P < .001). A significant increase in energy from monounsaturated fatty acids was also observed as well as increases in eicosapentaenoic acid and docosahexaenoic acid, whereas trans-fatty acid intake was reduced (P < .00001). The atherogenic lipoproteins, large very low-density lipoprotein (P < .0001) and small LDL (P < .0001), were reduced, whereas the ratio of large high-density lipoprotein to smaller high-density lipoprotein particles was increased (P < .0001). Apolipoprotein B was reduced for all women (P < .0001), with a greater reduction in the MF group (P < .025). Oxidized LDL (P < .05) and lipoprotein (a) (P < .001) were reduced in both groups at the end of the intervention. Consumption of a Mediterranean-style diet reduces the risk for cardiovascular disease by decreasing atherogenic lipoproteins, oxidized LDL, and apo B. Inclusion of an MF may have an additional effect in reducing apo B.

Chylomicron remnant uptake in the livers of mice expressing human apolipoproteins E3, E2 (Arg158→Cys), and E3-Leiden

Apolipoprotein E2 (apoE2) and apoE3-Leiden cause chylomicron remnant accumulation (type III hyperlipidemia). However, the degree of dyslipidemia and its penetrance are different in humans and mice. Remnant uptake by isolated liver from apoE-/- mice transgenic for human apoE2, apoE3-Leiden, or apoE3 was measured. In the presence of both LDL receptor (LDLR) and LDL receptor-related protein (LRP), remnant uptake was apoE3>E3-Leiden>E2 mice. Absence of LDLR reduced uptake in apoE3 and apoE3-Leiden-secreting livers but not in apoE2-secreting livers. LRP inhibition with receptor-associated protein reduced uptake in apoE3- and apoE2-secreting livers, but not in apoE3-Leiden-secreting livers, regardless of the presence of LDLR. Fluorescently labeled remnants clustered with LRP in apoE3-secreting livers only in the absence of LDLR, but clustered in livers that expressed apoE2 even in the presence of LDLR, and did not cluster with LRP in livers of apoE3-Leiden even in the absence of LDLR. Remnants were reconstituted with the three human apoE isoforms. Removal by liver of mApoe-/-/mldlr-/- mice expressing the human LDLR was slightly greater than removal in the previous experiments with apoE3>E2> E3-Leiden. Thus, in vivo, human apoE2 is cleared primarily by LRP, apoE3-Leiden is cleared only by the LDLR, and apoE3 is cleared by both.

Clearance of coagulation factor VIII in very low-density lipoprotein receptor knockout mice

Low-density lipoprotein receptor-related protein (LRP) contributes to factor VIII (FVIII) catabolism in vivo. Besides LRP, FVIII also interacts with very low-density lipoprotein receptor (VLDLR) in vitro. We investigated the physiological role of VLDLR in FVIII catabolism, using knockout mouse models for VLDLR and LRP, alone and in combination. VLDLR(-/-) mice displayed normal plasma FVIII, whereas VLDLR(-/-) LRP(-) double-knockout mice had slightly increased FVIII compared with LRP-deficient mice. Remarkably, VLDLR deficiency slightly accelerated FVIII clearance. Adenovirus-mediated overexpression of VLDLR did not lower plasma FVIII in LRP-deficient mice. We conclude that VLDLR does not act in concert with LRP in FVIII clearance in vivo.