Abstract-The natriuretic peptide (NP) family is involved in the regulation of blood pressure and fluid volume. We isolated the 5Ј-flanking region of the type A human NP receptor gene and identified an insertion/deletion mutation in this region. We then assessed whether there is a genetic association between this mutation and essential hypertension (EH). The deletion allele lacks 8 nucleotides and alters binding sites for the activator protein-2 (AP-2) and Zeste transcriptional factors. We genotyped 200 EH and 200 normotensive (NT) individuals and found 9 subjects with the deletion (8 in the EH group and 1 in the NT group). All 9 individuals were heterozygous. The NT subject with the mutation had left ventricular hypertrophy without hypertension. Transcriptional activity of the deletion allele was Ͻ30% that of the wild-type allele. The plasma levels of brain NP in EH patients with the deleted allele were significantly higher than the levels in the EH patients with the wild-type allele, and plasma brain NP levels were significantly higher in subjects with the deleted allele than in subjects with the wild-type allele, despite comparable blood pressures. These findings suggest that in Japanese individuals, this deletion in the human NP receptor gene reduces receptor activity and may confer increased susceptibility to developing EH or left ventricular hypertrophy. Key Words: natriuretic peptides Ⅲ type A receptors Ⅲ 5Ј-flanking region Ⅲ essential hypertension T hree types of natriuretic peptides (NPs) have been isolated: atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP). The NP family elicits a number of vascular, renal, and endocrine effects that help maintain blood pressure and extracellular fluid volume. 1-3 These effects are mediated by specific binding of NP to cell surface receptors that have been characterized, purified, and cloned from the vasculature, kidney, adrenal gland, and brain. 4 -7 There are 3 subtypes of NP receptors: type A NP receptor (NPRA), 4 type B NP receptor (NPRB), 8 and type C NP receptor (NPRC). 5 All 3 influence cellular second messengers. NPRA and NPRB are guanylyl cyclase receptors, and their activation increases cGMP levels. 9 Activation of NPRC results in the inhibition of adenylyl cyclase activity. 10 Human NPRA (hNPRA) has high structural homology with human NPRB (hNPRB) and also contains a highly conserved guanylyl cyclase domain. 5 ANP and BNP bind primarily to NPRA, which exerts its effect on the vasculature, causing vasodilation and inhibition of the proliferation of vascular smooth muscle cells. 11 Essential hypertension (EH) is thought to be a multifactorial disorder, and there are only a few reports of candidate genes associated with EH. 12 Mice with a targeted deletion of NPRA showed hypertension, cardiac hypertrophy, and sudden death. 13 These findings suggest that NPRA may play key roles in vasodilation, maintenance of blood pressure, and cardiac remodeling and that lack of it may lead to hypertension and other cardiov...

Osteopontin is an RGDS-containing protein that acts as a ligand for the ␣ v ␤ 3 integrin, which is abundantly expressed in osteoclasts, cells responsible for bone resorption in osteopenic diseases such as osteoporosis and hyperparathyroidism. However, the role of osteopontin in the process of bone resorption has not yet been fully understood. Therefore, we investigated the direct function of osteopontin in bone resorption using an organ culture system. The amount of 45 Ca released from the osteopontin-deficient bones was not significantly different from the basal release from wild type bones. However, in contrast to the parathyroid hormone (PTH) enhancement of the 45 Ca release from wild type bones, PTH had no effect on 45 Osteoclastic bone resorption is a key event in the pathophysiology of osteopenic diseases such as osteoporosis and hyperparathyroidism. Osteoclastic bone resorption involves a number of sequential events, including differentiation and activation of osteoclasts. These processes are regulated both by key cytokines and hormones interacting with various cell surface receptors and by interactions of osteoclast precursors with osteoblasts/stromal cells (1-3). The ␣ v ␤ 3 integrin is a major receptor on the osteoclast that can interact with RGD sequence-containing ligands such as osteopontin and vitronectin (4). It possibly promotes osteoclast attachment to bone and, when engaged by either immobilized or soluble ligands, stimulates signaling pathways that regulates osteoclast migration and function. Bone matrix consists of about 90% type I collagen and about 5% noncollagenous proteins. Among these noncollagenous proteins, at least five proteins, osteopontin, bone sialoprotein, thrombospondin, fibronectin, and vitronectin, contain RGD sequences that can be recognized by some integrins (5-8). These noncollagenous bone proteins are candidate ligands for the ␣ v ␤ 3 integrin expressed on the osteoclasts. In vitro data suggest that the ␤ 3 integrin subunit is involved in the attachment of osteoclasts to osteopontin and bone sialoprotein, whereas the ␤ 1 integrin subunit is responsible for the attachment of these cells to fibronectin (9). With regard to osteoclastic bone resorption in vitro, interactions between osteopontin and/or bone sialoprotein and the ␣ v ␤ 3 integrin (10, 11) have been proposed to play a crucial role. The signaling pathways stimulated by the integrin lead to modulation of cytoskeletal reorganization via regulatory molecules such as gelsolin (12). A recent study also indicates that the ␤ 3 integrin is important in osteoclastic bone resorption in vivo. (13) Osteopontin (14), is a mineralized matrix protein and a cytokine that has been suggested to act in several types of organs and systems, including bone (15), the immune system (16), the vascular system (17), and kidney (18). In addition, osteopontin is expressed at sites of inflammation. Osteopontin modifies cell behavior (19,20) and alters gene expression. In mineralized tissues, osteopontin is produced by osteoblasts and osteocla...

Osteopontin has been implicated in the metastasis of tumors, and human tumors with high metastatic activity often express osteopontin at high levels. Osteopontin contains an arginine-glycine-aspartate (RGD) motif that is recognized by integrin family members to promote various cell activities including attachment to substrate and it is abundant in bone, to which certain tumors preferentially metastasize. Therefore, we investigated the role of osteopontin in the experimental metastasis of tumor cells using recently established osteopontindeficient mice. B16 melanoma cells, which produce little osteopontin, were injected into the left ventricle of osteopontin-deficient mice or wild-type mice. Animals were killed 2 weeks after injection. The number of tumors was reduced in the bones of osteopontin-deficient mice compared with the bones in wild-type mice. The number of tumors in the adrenal gland also was reduced. To investigate the osteopontin effect on metastases via a different route, we injected B16 melanoma cells into the femoral vein. Through this route, the number of lung tumors formed was higher than in the intracardiac route and was again less in osteopontin-deficient mice compared with wild-type mice. In conclusion, in an experimental metastasis assay, the number of tumors found in bone (after intracardiac injection) and lung (after left femoral vein injection) was significantly reduced in osteopontin-deficient mice compared with wild-type mice. Tumor numbers in other organs examined were small and not significantly different in the two situations. (J Bone Miner Res 2001;16:652-659)

Hypertension in pregnancy is a multifactorial disorder caused by a complex combination of environmental factors and several predisposing genes. Since estrogen modulates placental vascular development, estrogen synthases are considered plausible candidate genes. The aim of this haplotype-based case-control study was to estimate whether polymorphisms of the maternal estrogen synthesis genes (CYP19A1, HSD3B1 and HSD3B2) are associated with preeclampsia (PE) and gestational hypertension (GH). To examine the genetic markers in 69 PE and 62 GH patients and in 155 age-matched, primiparous, healthy control subjects, genotyping of 5 SNPs for the CYP19A1 gene (rs1870049, rs936306, rs700518, rs700519, and rs4646), 3 SNPs for the HSD3B1 gene (rs3765945, rs6203, and rs1047303), and 2 SNPs for the HSD3B2 gene (rs2854964 and rs1819698) was performed. For rs700158 of CYP19A1, the frequencies of the AG+GG genotype and the G allele were significantly higher in PE as compared to controls (P = 0.037, P = 0.033, respectively). Logistic regression analyses indicated that the AG+GG genotype of rs700158 was a PE risk factor (odds ratio = 2.15, P = 0.026). In addition, the frequency of the G-G haplotype established by rs700518-rs4646 was also significantly higher for PE (P = 0.017). These data suggest that the estrogen synthesis gene, CYP19A1 is associated with PE in the Japanese population.

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