Futoshi Nakagami

Estrogen inhibits vascular calcification via vascular RANKL system: Common mechanism of osteoporosis and vascular calcification

Rationale Arterial calcification and osteoporosis are associated in postmenopausal women. RANK (the receptor activator of nuclear factor &kgr;B), RANKL (RANK ligand), and osteoprotegerin are key proteins in bone metabolism and have been found at the site of aortic calcification. The role of these proteins in vasculature, as well as the contribution of estrogen to vascular calcification, is poorly understood. Objective To clarify the mechanism of RANKL system to vascular calcification in the context of estrogen deficiency. Methods and Results RANKL induced the calcification inducer bone morphogenetic protein-2 by human aortic endothelial cells (HAECs) and decreased the calcification inhibitor matrix Gla protein (MGP) in human aortic smooth muscle cells (HASMCs), as quantified by real-time PCR and Western blot analysis. RANKL also induced bone-related gene mRNA expression and calcium deposition (Alizarin red staining) followed by the osteogenic differentiation of HASMCs. Estrogen inhibited RANKL signaling in HAECs and HASMCs mainly through estrogen receptor &agr;. Apolipoprotein E–deficient mice fed with Western high-fat diet for 3 months presented atherosclerotic calcification (Oil red and Alizarin red staining) and osteoporosis (microcomputed tomographic analysis) after ovariectomy and increased expression of RANKL, RANK, and osteopontin in atherosclerotic lesion, as detected by in situ hybridization. Estrogen replacement inhibited osteoporosis and the bone morphogenetic protein osteogenic pathway in aorta by decreasing phosphorylation of smad-1/5/8 and increasing MGP mRNA expression. Conclusions RANKL contributes to vascular calcification by regulating bone morphogenetic protein-2 and MGP expression, as well as bone-related proteins, and is counteracted by estrogen in a receptor-dependent manner.Rationale: Arterial calcification and osteoporosis are associated in postmenopausal women. RANK (the receptor activator of nuclear factor κB), RANKL (RANK ligand), and osteoprotegerin are key proteins in bone metabolism and have been found at the site of aortic calcification. The role of these proteins in vasculature, as well as the contribution of estrogen to vascular calcification, is poorly understood. Objective: To clarify the mechanism of RANKL system to vascular calcification in the context of estrogen deficiency. Methods and Results: RANKL induced the calcification inducer bone morphogenetic protein-2 by human aortic endothelial cells (HAECs) and decreased the calcification inhibitor matrix Gla protein (MGP) in human aortic smooth muscle cells (HASMCs), as quantified by real-time PCR and Western blot analysis. RANKL also induced bone-related gene mRNA expression and calcium deposition (Alizarin red staining) followed by the osteogenic differentiation of HASMCs. Estrogen inhibited RANKL signaling in HAECs and HASMCs mainly through estrogen receptor α. Apolipoprotein E–deficient mice fed with Western high-fat diet for 3 months presented atherosclerotic calcification (Oil red and Alizarin red staining) and osteoporosis (microcomputed tomographic analysis) after ovariectomy and increased expression of RANKL, RANK, and osteopontin in atherosclerotic lesion, as detected by in situ hybridization. Estrogen replacement inhibited osteoporosis and the bone morphogenetic protein osteogenic pathway in aorta by decreasing phosphorylation of smad-1/5/8 and increasing MGP mRNA expression. Conclusions: RANKL contributes to vascular calcification by regulating bone morphogenetic protein-2 and MGP expression, as well as bone-related proteins, and is counteracted by estrogen in a receptor-dependent manner. # Novelty and Significance {#article-title-42}

Prevention of osteoporosis by angiotensin-converting enzyme inhibitor in spontaneous hypertensive rats

A recent analysis of clinical studies suggests that angiotensin-converting enzyme (ACE) inhibitors might reduce bone fractures. In this study, we examined whether an ACE inhibitor might attenuate osteoporosis in a hypertensive rat model. In spontaneous hypertensive rats (SHRs), estrogen deficiency induced by ovariectomy (OVX) resulted in a significant increase in osteoclast activation as assessed by the tartrate-resistant acid phosphatase (TRAP) activity in the tibia, accompanied by a significant decrease in bone density evaluated by dual-energy X-ray absorptiometry and an increase in urinary deoxypyridinoline. Treatment with an ACE inhibitor, imidapril, attenuated OVX-induced decrease in bone density and increase in TRAP activity and urinary deoxypyridinoline. As ACE inhibitors possess the effects of blockade of the renin–angiotensin system (RAS) and activation of the bradykinin–nitric oxide pathway, we examined the contribution of both pathways in an OVX-induced osteoporosis model. Administration of nitro-L-arginine methylester (L-NAME) did not alter TRAP activity, urinary deoxypyridinoline or bone density, whereas the administration of a subpressor dose of angiotensin II accelerated the increase in TRAP activity in the tibia, accompanied by a significant decrease in bone density and an increase in urinary deoxypyridinoline. Thus, ACE inhibitors prevented osteoporosis, probably because of the inhibition of RAS, but not of nitric oxide. Overall, ACE inhibitors attenuated osteoporosis in a hypertensive rat model through the blockade of RAS.

Cross-Talk of Receptor Activator of Nuclear Factor-κB Ligand Signaling With Renin–Angiotensin System in Vascular Calcification

Objective—Vascular calcification is accelerated by hypertension and also contributes to hypertension; however, it is an enigma why hypertension and vascular calcification are a vicious spiral. The present study elucidates the cross-talk between renin–angiotensin II system and receptor activator of nuclear factor-&kgr;B ligand (RANKL) system in vascular calcification. Approach and Results—Angiotensin (Ang) II (10−7 mol/L) significantly increased calcium deposition as assessed by Alizarin Red staining, associated with a significant increase in the expression of RANKL, RANK, and bone-related genes, such as cbfa1 and msx2, in human aortic vascular smooth muscle cells. Infusion of Ang II (100 ng/kg per minute) in ovariectomized ApoE−/− mice under high-fat diet significantly increased the expression of RANKL system and calcification in vivo, whereas administration of Ang II receptor blocker (olmesartan, 3 mg/kg per day) decreased the calcification and bone markers’ expression. In addition, male OPG−/− mice showed a significant increase in vascular calcification followed by Ang II infusion as compared with wild type. Conversely, RANKL significantly increased Ang II type 1 receptor and angiotensin II–converting enzyme expression in vascular smooth muscle cells via extracellular signal–regulated protein kinase phosphorylation. Conclusions—The present study demonstrated that Ang II significantly induced vascular calcification in vitro and in vivo through RANKL activation. In addition, RANKL activated renin–angiotensin II system, especially angiotensin II–converting enzyme and Ang II type 1 receptor. Cross-talk between renin–angiotensin II system and RANKL system might work as a vicious cycle to promote vascular calcification in atherosclerosis. Further studies to inhibit renin–angiotensin II system and RANKL may provide new therapeutic options to prevent and regress vascular calcification.

Decrease in blood pressure and regression of cardiovascular complications by angiotensin II vaccine in mice.

Vaccines have been recently developed to treat various diseases such as cancer, rheumatoid arthritis and Alzheimer’s disease in addition to infectious diseases. However, before use in the clinical setting, vaccines targeting self-antigens must be demonstrated to be effective and safe, evoking an adequate humoral immune response from B cells while avoiding T cell activation in response to self. Although the vaccine targeting angiotensin II (Ang II) is efficient in rodents and humans, little is known regarding the immunological activation and safety of the vaccine. In this study, we evaluated the efficiency and safety of an Ang II peptide vaccine in mice. Immunization with Ang II conjugated to keyhole limpet hemocyanin (KLH) successfully induced the production of anti-Ang II antibody, which blocked Ang II signaling in human aortic smooth muscle cells. However, Ang II itself did not activate T cells, as assessed by the proliferation and lymphokine production of T cells in immunized mice, whereas KLH activated T cells. In an Ang II-infused model, the non-immunized mice showed high blood pressure (BP), whereas the immunized mice (Ang II-KLH) showed a significant decrease in systolic BP, accompanied by significant reductions in cardiac hypertrophy and fibrosis. Importantly, anti-Ang II antibody titer was not elevated even after the administration of large amounts of Ang II, indicating that Ang II itself boosted antibody production, most likely due to less activation of T cells. In addition, no accumulation of inflammatory cells was observed in immunized mice, because endogenous Ang II would not activate T cells after immunization with Ang II-KLH. Taken together, these data indicate that vaccines targeting Ang II might be effective to decrease high BP and prevent cardiovascular complications without severe side effects.

Estrogen attenuates vascular remodeling in Lp(a) transgenic mice

OBJECTIVE Although it is well known that Lipoprotein(a) (Lp(a)) is an atherogenic lipoprotein and an independent risk factor for cardiovascular disease, there is no confirmed therapy to decrease Lp(a) or prevent atherosclerosis induced by Lp(a). Thus, it is mandatory to develop novel therapy to prevent atherosclerosis in high Lp(a) concentration. Here, we focused on the effect of estrogen on Lp(a) level and Lp(a)-induced vascular remodeling. METHODS We employed Lp(a) transgenic mice (human apo(a) yeast artificial chromosome (YAC) and human apoB double transgenic mice). Vascular remodeling was induced by ligation of the common carotid artery and the effect of estrogen was evaluated in female mice after ovariectomy with or without estrogen replacement. RESULTS Estrogen deficiency caused by ovariectomy increased serum Lp(a), and continuous replacement of 17beta-estradiol (20 microg/kg/day) reversed the change. In the vascular remodeling model induced by carotid artery occlusion, neointima formation was significantly increased in ovariectomized female Lp(a) transgenic mice, but few in male Lp(a) transgenic mice, as compared to wild FVB mice. Importantly, continuous replacement of estrogen in ovariectomized mice significantly attenuated it. In cultured endothelial cells and macrophages, addition of Lp(a) increased mRNA of ICAM-1, VCAM-1, E-selectin and MCP-1 in endothelial cells and TNF-alpha, IL-1beta and MCP-1 in macrophages in a dose-dependent manner. Importantly, pre-treatment with estrogen attenuated these changes in a dose-dependent manner. CONCLUSION Estrogen negatively regulates both plasma Lp(a) level and Lp(a)-induced vascular remodeling, suggesting that estrogen might be a strong candidate to reduce serum Lp(a) concentration.

Therapeutic vaccine against DPP4 improves glucose metabolism in mice

Significance Type 2 diabetes mellitus (T2DM) has become a common disease, and long-term effective drugs have become a necessity. In recent years, dipeptidyl peptidase 4 (DPP4) inhibitors have been commercialized due to its ability to inhibit glucagon-like peptide 1 degradation, a hormone important for enhancing insulin secretion. Despite the availability of efficient drugs, the success of treatment is limited by patients’ inconsistent drug intake and the economic burden included in a lifelong treatment required for T2DM. To alleviate these limitations, in this study an affordable and effective immunotherapeutic method was developed and assessed for T2DM treatment. We selected and designed the appropriate peptide sequences that induce the anti-DPP4 antibody that effectively improves the diabetic phenotype without an adverse autoimmune response. The increasing prevalence of type 2 diabetes mellitus is associated with a significant economic burden. We developed a dipeptidyl peptidase 4 (DPP4)-targeted immune therapy to increase glucagon-like peptide 1 hormone levels and improve insulin sensitivity for the prevention and treatment of type 2 diabetes mellitus. Immunization with the DPP4 vaccine in C57BL/6J mice successfully increased DPP4 titer, inhibited plasma DPP4 activity, and induced an increase in the plasma glucagon-like peptide 1 level. Moreover, this elevated titer was sustained for 3 mo. In mice fed a high-fat diet, DPP4 vaccination resulted in improved postprandial glucose excursions and insulin sensitivity and, in the diabetic KK-Ay and db/db mice strains, DPP4 vaccination significantly reduced glucose excursions and increased both plasma insulin and pancreatic insulin content. Importantly, T cells were not activated following challenge with DPP4 itself, which suggests that this vaccine does not induce cell-mediated autoimmunity. Additionally, no significant immune-mediated damage was detected in cells and tissues where DPP4 is expressed. Thus, this DPP4 vaccine may provide a therapeutic alternative for patients with diabetes.

Development of novel DNA vaccine for VEGF in murine cancer model

We developed DNA vaccine for vascular endothelial growth factor (VEGF), which may provide the therapeutic option instead of anti-VEGF antibody, bevacizumab. Plasmid containing VEGF mini-gene was constructed in the insertion of B-cell epitope of Hepatitis B core protein [HBc-VEGF], which was an epitope carrier. High titer of anti-VEGF antibody was observed in BALB/c mice which were intramuscularly immunized with HBc-VEGF by electropolator. In mice inoculated with colon 26 cells, tumor volume and microvessel density was decreased in HBc-VEGF with a significant prolonged survival. Co-treatment of purified IgG from immunized mice with HBc-VEGF showed in vitro neutralizing activity for VEGF-induced ERK phosphorylation and tube formation in cultured endothelial cells. Furthermore, intravitreally injection of this purified IgG reduced the neovessel formation in the mouse oxygen-induced retinopathy and laser-induced choroidal neovascularization models. These results first provided that DNA vaccine against VEGF possessed the anti-angiogenic effect, leading to prolonged survival in mouse cancer model.

Long-Term Reduction of High Blood Pressure by Angiotensin II DNA Vaccine in Spontaneously Hypertensive Rats

Recent research on vaccination has extended its scope from infectious diseases to chronic diseases, including Alzheimer disease, dyslipidemia, and hypertension. The aim of this study was to design DNA vaccines for high blood pressure and eventually develop human vaccine therapy to treat hypertension. Plasmid vector encoding hepatitis B core-angiotensin II (Ang II) fusion protein was injected into spontaneously hypertensive rats using needleless injection system. Anti-Ang II antibody was successfully produced in hepatitis B core-Ang II group, and antibody response against Ang II was sustained for at least 6 months. Systolic blood pressure was consistently lower in hepatitis B core-Ang II group after immunization, whereas blood pressure reduction was continued for at least 6 months. Perivascular fibrosis in heart tissue was also significantly decreased in hepatitis B core-Ang II group. Survival rate was significantly improved in hepatitis B core-Ang II group. This study demonstrated that Ang II DNA vaccine to spontaneously hypertensive rats significantly lowered high blood pressure for at least 6 months. In addition, Ang II DNA vaccines induced an adequate humoral immune response while avoiding the activation of self-reactive T cells, assessed by ELISPOT assay. Future development of DNA vaccine to treat hypertension may provide a new therapeutic option to treat hypertension.

Cilnidipine, but not amlodipine, ameliorates osteoporosis in ovariectomized hypertensive rats through inhibition of the N-type calcium channel.

Both osteoporosis and high blood pressure are major diseases in aging populations. Recent studies demonstrated that some antihypertensive drugs reduced the risk of bone fracture in elderly patients. Although calcium channel blockers (CCB) are widely used as first-line antihypertensive agents, there is no evidence that they prevent osteoporosis. In this study, we investigated the effects of two types of CCB on bone metabolism: cilnidipine (L-/N-type CCB), which suppresses norepinephrine release from the sympathetic nerve, and amlodipine (L-type CCB). In ovariectomized female spontaneous hypertensive rats, administration of cilnidipine, but not amlodipine, resulted in a significant increase in the ratio of alkaline phosphatase to tartrate-resistant acid phosphatase (TRAP) and a decrease in the number of osteoclasts, as assessed by TRAP staining in the proximal tibia. Bone mineral density, moreover, was significantly higher in the cilnidipine group as compared with the amlodipine group and was associated with a significant decrease in a urinary collagen degradation product (deoxypyridinoline). The degree of prevention of osteoporosis by cilnidipine was similar to that of carvedilol (a β-blocker) because β-blockers reduce fracture risks though the inhibition of osteoclast activation. Interestingly, these effects cannot be attributed to the reduction of blood pressure because all three drugs significantly decreased blood pressure. In contrast, both cilnidipine and carvedilol, but not amlodipine, significantly decreased heart rate, indicating that both cilnidipine and carvedilol suppressed sympathetic nervous activity. Overall, our present data showed that cilnidipine (L-/N-type CCB) ameliorated osteoporosis in ovariectomized hypertensive rats. These pleiotropic effects of antihypertensive drugs such as cilnidipine and carvedilol might provide additional benefits in the treatment of hypertensive postmenopausal women.

Inhibition of Neointima Formation through DNA Vaccination for Apolipoprotein(a): A New Therapeutic Strategy for Lipoprotein(a)

Lipoprotein(a) [Lp(a)] is an unique lipoprotein consisting of the glycoprotein apolipoprotein(a) [apo(a)] in low-density lipoprotein. Although Lp(a) is a well-known independent risk factor for cardiovascular disease; however, there is no drugs to decrease plasma Lp(a) level. Thus, to inhibit the biological activity of Lp(a), we developed DNA vaccine for apo(a) by the targeting to the selected 12 hydrophilic amino acids in the kringle-4 type 2 domain of apo(a). Hepatitis B virus core protein was used as an epitope carrier to enhance the immunogenicity. Intramuscular immunization with apo(a) vaccine resulted in the significant inhibition of neointima formation in carotid artery ligation model using Lp(a) transgenic mice, associated with anti-apo(a) antibody and decrease in vascular Lp(a) deposition. Overall, this study provided the first evidence that the pro-atherosclerotic actions of Lp(a) could be prevented by DNA vaccine directed against apo(a), suggesting a novel therapeutic strategy to treat cardiovascular diseases related to high Lp(a).