Role of endothelial cell-derived angptl2 in vascular inflammation leading to endothelial dysfunction and atherosclerosis progression.

OBJECTIVE: Cardiovascular disease (CVD), the most common morbidity resulting from atherosclerosis, remains a frequent cause of death. Efforts to develop effective therapeutic strategies have focused on vascular inflammation as a critical pathology driving atherosclerosis progression. Nonetheless, molecular mechanisms underlying this activity remain unclear. Here, we ask whether angiopoietin-like protein 2 (Angptl2), a proinflammatory protein, contributes to vascular inflammation that promotes atherosclerosis progression. APPROACH AND RESULTS: Histological analysis revealed abundant Angptl2 expression in endothelial cells and macrophages infiltrating atheromatous plaques in patients with cardiovascular disease. Angptl2 knockout in apolipoprotein E-deficient mice (ApoE(-/-)/Angptl2(-/-)) attenuated atherosclerosis progression by decreasing the number of macrophages infiltrating atheromatous plaques, reducing vascular inflammation. Bone marrow transplantation experiments showed that Angptl2 deficiency in endothelial cells attenuated atherosclerosis development. Conversely, ApoE(-/-) mice crossed with transgenic mice expressing Angptl2 driven by the Tie2 promoter (ApoE(-/-)/Tie2-Angptl2 Tg), which drives Angptl2 expression in endothelial cells but not monocytes/macrophages, showed accelerated plaque formation and vascular inflammation because of increased numbers of infiltrated macrophages in atheromatous plaques. Tie2-Angptl2 Tg mice alone did not develop plaques but exhibited endothelium-dependent vasodilatory dysfunction, likely because of decreased production of endothelial cell-derived nitric oxide. Conversely, Angptl2(-/-) mice exhibited less severe endothelial dysfunction than did wild-type mice when fed a high-fat diet. In vitro, Angptl2 activated proinflammatory nuclear factor-κB signaling in endothelial cells and increased monocyte/macrophage chemotaxis. CONCLUSIONS: Endothelial cell-derived Angptl2 accelerates vascular inflammation by activating proinflammatory signaling in endothelial cells and increasing macrophage infiltration, leading to endothelial dysfunction and atherosclerosis progression.

Perivascular adipose tissue-secreted angiopoietin-like protein 2 (Angptl2) accelerates neointimal hyperplasia after endovascular injury.

Much attention is currently focused on the role of perivascular adipose tissue in development of cardiovascular disease (CVD). Some researchers view it as promoting CVD through secretion of cytokines and growth factors called adipokines, while recent reports reveal that perivascular adipose tissue can exert a protective effect on CVD development. Furthermore, adiponectin, an anti-inflammatory adipokine, reportedly suppresses neointimal hyperplasia after endovascular injury, whereas such vascular remodeling is enhanced by pro-inflammatory adipokines secreted by perivascular adipose, such as tumor necrosis factor-α (TNF-α). These findings suggest that extent of vascular remodeling, a pathological process associated with CVD development, depends on the balance between pro- and anti-inflammatory adipokines secreted from perivascular adipose tissue. We previously demonstrated that angiopoietin-like protein 2 (Angptl2), a pro-inflammatory factor secreted by adipose tissue, promotes adipose tissue inflammation and subsequent systemic insulin resistance in obesity. Here, we examined whether Angptl2 secreted by perivascular adipose tissue contributes to vascular remodeling after endovascular injury in studies of transgenic mice expressing Angptl2 in adipose tissue (aP2-Angptl2 transgenic mice) and Angptl2 knockout mice (Angptl2(-/-) mice). To assess the role of Angptl2 secreted by perivascular adipose tissue on vascular remodeling after endovascular injury, we performed adipose tissue transplantation experiments using these mice. Wild-type mice with perivascular adipose tissue derived from aP2-Angptl2 mice exhibited accelerated neointimal hyperplasia after endovascular injury compared to wild-type mice transplanted with wild-type tissue. Conversely, vascular inflammation and neointimal hyperplasia after endovascular injury were significantly attenuated in wild-type mice transplanted with Angptl2(-/-) mouse-derived perivascular adipose tissue compared to wild-type mice transplanted with wild-type tissue. RT-PCR analysis revealed that mouse Angptl2 expression in perivascular adipose tissue was significantly increased by aging, hypercholesterolemia, and endovascular injury, all risk factors for coronary heart disease (CHD). Immunohistochemical and RT-PCR analysis of tissues from patients with CHD and from non-CHD patients indicated that ANGPTL2 expression in epicardial adipose tissue was unchanged. Interestingly, that analysis also revealed a positive correlation in ANGPTL2 and ADIPONECTIN expression in epicardial adipose tissue of non-CHD patients, a correlation not seen in CHD patients. However, in epicardial adipose tissue from CHD patients, ANGPTL2 expression was positively correlated with that of TNF-α, a correlation was not seen in non-CHD patients. These findings suggest that pro-inflammatory adipokines cooperatively accelerate CHD development and that maintaining a balance between pro- and anti-inflammatory adipokines likely protects non-CHD patients from developing CHD. Overall, our studies demonstrate that perivascular adipose tissue-secreted Angptl2 accelerates vascular inflammation and the subsequent CVD development.

Macrophage-derived angiopoietin-like protein 2 accelerates development of abdominal aortic aneurysm.

OBJECTIVE: Recently, we reported that angiopoietin-like protein 2 (Angptl2) functions in various chronic inflammatory diseases. In the present study, we asked whether Angptl2 and its associated chronic inflammation contribute to abdominal aortic aneurysm (AAA). METHODS AND RESULTS: Immunohistochemistry revealed that Angptl2 is abundantly expressed in infiltrating macrophages within the vessel wall of patients with AAA and in a CaCl(2)-induced AAA mouse model. When Angptl2-deficient mice were used in the mouse model, they showed decreased AAA development compared with wild-type mice, as evidenced by reduction in aneurysmal size, less severe destruction of vessel structure, and lower expression of proinflammatory cytokines and matrix metalloproteinase-9. However, no difference in the number of infiltrating macrophages within the aortic aneurysmal vessel wall was observed between genotypes. AAA development was also significantly suppressed in wild-type mice that underwent Angptl2-deficient bone marrow transplantation. Expression levels of proinflammatory cytokines and metalloproteinase-9 in Angptl2-deficient macrophages were significantly decreased, and those decreases were rescued by treatment of Angptl2 deficient macrophages with exogenous Angptl2. CONCLUSIONS: Macrophage-derived Angptl2 contributes to AAA development by inducing inflammation and degradation of extracellular matrix in the vessel wall, suggesting that targeting the Angptl2-induced inflammatory axis in macrophages could represent a new strategy for AAA therapy.

Angiopoietin-like protein 2 is associated with chronic kidney disease in a general Japanese population: the Hisayama Study.

BACKGROUND: Angiopoietin-like protein 2 (Angptl2) is an adipokine that promotes inflammation and endothelial dysfunction of the vessels. The aim of this study was to investigate the relationship between serum Angptl2 level and chronic kidney disease (CKD). METHODS AND RESULTS: A total of 3,169 community-dwelling subjects aged ≥40 years were divided into quintiles by Angptl2 level. CKD was defined as the presence of albuminuria (urine albumin-creatinine ratio ≥30.0mg/g) or decreased estimated glomerular filtration rate (eGFR <60ml·min(-1)·1.73m(-2)). The odds ratio (OR) for the presence of CKD was calculated using a logistic regression model. The overall prevalence of CKD was 37.5%. The age- and sex-adjusted ORs for the presence of CKD increased with higher serum Angptl2 level. This trend remained significant after adjusting for known cardiovascular risk factors (<2.01ng/ml: OR, 1.00 (reference); 2.01-2.48ng/ml: OR, 1.67, 95% confidence interval [CI]: 1.24-2.24; 2.49-2.99ng/ml: OR, 1.70, 95% CI: 1.27-2.28; 3.00-3.65ng/ml: OR, 1.78, 95% CI: 1.32-2.39; ≥3.66ng/ml: OR, 1.79, 95% CI: 1.32-2.43; P-value for trend=0.001). Multivariate-adjusted ORs for the presence of albuminuria increased significantly with elevated serum Angptl2 (P-value for trend=0.004), while there was no evidence of a significant relationship between serum Angptl2 level and decreased eGFR (P-value for trend=0.08). CONCLUSIONS: Elevated serum Angptl2 is associated with the likelihood of CKD in the general population.

The role of angiopoietin-like protein 2 in pathogenesis of dermatomyositis.

Dermatomyositis (DM) is an autoimmune disease marked by chronic inflammation of skin and muscle tissues and characterized clinically by proximal muscle weakness and skin eruption, including heliotrope rash, and Gottron's sign. Treatment with a non-specific immunosuppressive agent or anti-inflammatory corticosteroids is beneficial, although some patients are resistant to these therapies. Proinflammatory cytokines derived from infiltrating inflammatory cells and activated resident cells within skin and muscle tissues likely promote chronic inflammation in DM pathogenesis; however, molecular mechanisms underlying the disease are not completely defined. Here we show that mRNA and protein levels of angiopoietin-like protein 2 (Angptl2), a recently identified chronic inflammation mediator, are abundant in keratinocytes from DM patients' skin eruptions. To examine whether skin cell-derived Angptl2 promotes DM manifestations, we analyzed transgenic (Tg) mice expressing Angptl2 driven by the keratinocyte specific promoter K14 (K14-Angptl2) and therefore constitutively expressing Angptl2 in skin tissue. We found that K14-Angptl2 Tg mice exhibited skin phenotypes similar to those observed in DM patients. In addition, treatment of keratinocytes with exogenous Angptl2 activated the NF-κB inflammatory cascade, resulting in increased expression of the proinflammatory cytokines IL-1ß and IL-6. We propose that keratinocyte-derived Angptl2 functions in DM pathogenesis by inducing chronic inflammation in skin tissue.

Angiopoietin-like protein 2 and risk of type 2 diabetes in a general Japanese population: the Hisayama study.

OBJECTIVE: To examine, for the first time, the association between a novel inflammatory cytokine, angiopoietin-like protein (ANGPTL) 2, and the development of type 2 diabetes (T2DM). RESEARCH DESIGN AND METHODS: A total of 2,164 community-dwelling Japanese individuals aged 40 to 79 years without diabetes were followed up for 7 years. Serum ANGPTL2 levels were divided into quartile categories at baseline: <2.15, 2.16-2.71, 2.72-3.40, and ≥3.41 ng/mL. During follow-up, 221 participants developed T2DM. RESULTS: In multivariate analyses, after adjusting for comprehensive risk factors and high-sensitivity C-reactive protein (hs-CRP) levels, the risk of developing T2DM was significantly higher in the highest ANGPTL2 quartile than in the lowest quartile (hazard ratio, 1.80; 95% CI, 1.14-2.85; P = 0.01). CONCLUSIONS: Elevated serum ANGPTL2 levels were positively associated with the development of T2DM in a general population, independent of other risk factors including hs-CRP levels.

Nifedipine increases energy expenditure by increasing PGC-1α expression in skeletal muscle.

Nifedipine, an L-type calcium (Ca) channel blocker, is one of the most widely used Ca channel-blocking medications for hypertension. Previous studies have reported an association of nifedipine hypertensive treatment with decreased body weight in obese hypertensive humans and rat models. However, the precise mechanism underlying how nifedipine functions metabolically has not been elucidated. Here, we investigated the long-term effect of a non-hypotensive nifedipine dose using a mildly obese, endothelial NO synthase-deficient mouse model. Treating these mice with nifedipine decreased their body weight gain ratio, and white adipose tissue weight compared with the untreated controls. Metabolic analyses indicated that nifedipine treatment upregulated whole-body energy expenditure through increasing oxygen consumption and reducing the respiratory exchange ratio, suggesting that nifedipine promotes lipid oxidation rather than carbohydrate utilization. Furthermore, nifedipine treatment upregulated the expression of the peroxisome proliferator-activated receptor-γ coactivator -1α (PGC-1α) in skeletal muscle. Overall, these results suggest that a non-hypotensive dose of nifedipine has pleiotropic effects on energy expenditure that could ameliorate obesity.