The effect of dietary octacosanol, a long-chain alcohol, on lipid metabolism was investigated in rats fed on a high-fat diet for 20 d. The addition of octacosanol (10 g/kg diet) to the high-fat diet led to a significant reduction (P < 0.05) in the perirenal adipose tissue weight without decrease of the cell number, suggesting that octacosanol may suppress lipid accumulation in this tissue, whereas no effect was seen in the epididymal adipose tissue weight and in the lipid content in liver. Octacosanol supplementation decreased the serum triacylglycerol concentration, and enhanced the concentration of serum fatty acids, probably through inhibition of hepatic phosphatidate phosphohydrolase (EC 3.1.3.4). Though the activity of hormone-sensitive lipase (EC 3.1.1.3) was not influenced by octacosanol, higher activities of lipoprotein liyase (EC 3.1.1.34) in the perirenal adipose tissue and the total oxidation rate of fatty acid in muscle were observed. Lipid absorption was not affected by the inclusion of octacosanol. Thus, the present results suggest that the dietary incorporation of octacosanol into a high-fat diet affects some aspects of lipid metabolism.

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Osteoclasts are multinucleated cells that play a crucial role in bone resorption, and are formed by the fusion of mononuclear osteoclasts derived from osteoclast precursors of the macrophage lineage. Compounds that specifically target functional osteoclasts would be ideal candidates for anti-resorptive agents for clinical applications. In the present study, we investigated the effects of luteolin, a flavonoid, on the regulation of receptor activator of nuclear factorjB ligand (RANKL)-induced osteoclastogenesis, functions and signaling pathway. Addition of luteolin to a coculture system of mouse bone marrow cells and ST2 cells in the presence of 10 -8 M 1a,25(OH) 2 D 3 caused significant inhibition of osteoclastogenesis. Luteolin had no effects on the 1a,25(OH) 2 D 3 -induced expressions of RANKL, osteoprotegerin and macrophage colony-stimulating factor mRNAs. Next, we examined the direct effects of luteolin on osteoclast precursors using bone marrow macrophages and RAW264.7 cells. Luteolin completely inhibited RANKL-induced osteoclast formation. Moreover, luteolin inhibited the bone resorption by mature osteoclasts accompanied by the disruption of their actin rings, and these effects were reversely induced by the disruption of the actin rings in mature osteoclasts. Finally, we found that luteolin inhibited RANKLinduced osteoclastogenesis through the suppression of ATF2, downstream of p38 MAPK and nuclear factor of activated T-cells, cytoplasmic, calcineurin-dependent 1 (NFATc1) expression, respectively. Taken together, the present results indicate that naturally occurring luteolin has inhibitory activities toward both osteoclast differentiation and functions through inhibition of RANKL-induced signaling pathway as well as actin ring disruption, respectively.

PACE4 (SPC4) is a member of the mammalian subtilisin-like proprotein convertase (SPC) family, which participates in maturation of precursor proteins. PACE4 is expressed at high levels in the anterior pituitary, central nervous system, the developing olfactory bulb, heart, and liver. Recently, we determined the gene structure of human PACE4. [Tsuji et al. (1997) J. Biochem. 122, 438-452]. The 5'-flanking region of PACE4 gene contains 12 E-boxes (E1 to E12) within 1 kb upstream of the transcription initiation site. To examine the function of these E-box elements in the regulation of PACE4 expression, deletion and mutation constructs of the 5'-flanking region were ligated to the luciferase gene and analyzed for promoter activity in HepG2 and GH4C1 cells, which express PACE4 at high level. Some differences were observed in the activity of each promoter construct between HepG2 and GH4C1 cells, although the overall profiles of activity for the promoter fragment series were similar regardless of cell type. We showed that the basal promoter activity of the PACE4 gene is first determined by sequences lying between -315 and -1 bp and further regulated by positive and negative elements in the upstream region. Site-directed mutagenesis of E-boxes in these regulatory elements showed that the E10 E-box act as positive regulator, whereas an E-box cluster (E4-E9) acts as a negative regulator in both cells. E2 E-box acts as a positive regulator only in HepG2 cells. Other E-boxes (E1, E3, and E12) had no effect on the promoter activity. These results indicate that E-box elements play a critical role in controlling PACE4 expression in HepG2 and GH4C1 cells and that PACE4 expression is regulated by a mechanism distinct from that of other SPC family proteases.

Excessive receptor activator of NF-κB ligand (RANKL) signaling causes enhanced osteoclast formation and bone resorption. The downregulation of RANKL expression and its downstream signals may be an effective therapeutic approach to the treatment of bone loss diseases such as osteoporosis. Here, we found that coptisine, one of the isoquinoline alkaloids from Coptidis Rhizoma, exhibited inhibitory effects on osteoclastogenesis in vitro. Although coptisine has been studied for its antipyretic, antiphotooxidative, dampness dispelling, antidote, antinociceptive, and anti-inflammatory activities in vitro and in vivo, its effects on osteoclastogenesis have not been investigated. Therefore, we evaluated the effects of coptisine on osteoblastic cells as well as osteoclast precursors for osteoclastogenesis in vitro. The addition of coptisine to cocultures of mouse bone marrow cells and primary osteoblastic cells with 10(-8) M 1α,25(OH)(2)D(3) caused significant inhibition of osteoclast formation in a dose-dependent manner. Reverse transcriptase polymerase chain reaction (RT-PCR) analyses revealed that coptisine inhibited RANKL gene expression and stimulated the osteoprotegerin gene expression induced by 1α,25(OH)(2)D(3) in osteoblastic cells. Coptisine strongly inhibited RANKL-induced osteoclast formation when added during the early stage of bone marrow macrophage (BMM) cultures, suggesting that it acts on osteoclast precursors to inhibit RANKL/RANK signaling. Among the RANK signaling pathways, coptisine inhibited NF-κB p65 phosphorylations, which are regulated in response to RANKL in BMMs. Coptisine also inhibited the RANKL-induced expression of NFATc1, which is a key transcription factor. In addition, 10 μM coptisine significantly inhibited both the survival of mature osteoclasts and their pit-forming activity in cocultures. Thus, coptisine has potential for the treatment or prevention of several bone diseases characterized by excessive bone destruction.

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Bone homeostasis is maintained by the balance between the bone-forming activity of osteoblasts and the bone-resorbing activity of osteoclasts.1) Excessive osteoclastic bone resorption results in bone destructive disorders such as osteoporosis. Osteoclasts are multinucleated cells that differentiate from hematopoietic precursors and are capable of resorbing mineralized bone.2) Receptor activator of nuclear factorkappa B (NF-kB) ligand (RANKL), a member of the tumor necrosis factor (TNF) family produced by osteoblasts and stromal cells, is an essential factor for osteoclast differentiation and function.3,4) Tartrate-resistant acid phosphatase (TRAP) is a marker enzyme for osteoclasts. RANKL induces the formation of TRAP-positive multinucleated cells (TRAP ϩ MNCs) in cultures of bone marrow cells (BMCs) in the presence of macrophage colony-stimulating factor (M-CSF) without requiring osteoblasts or stromal cells. 5,6) RAW264 cells are also known to differentiate into osteoclasts in the presence of RANKL. 5,7,8) Compounds that inhibit osteoclast differentiation and/or function are useful for treating or preventing bone diseases characterized by excessive bone resorption.We screened various compounds of natural origin for their abilities to affect osteoclast differentiation, and identified honokiol as a promising candidate. Honokiol, a neolignan, is an active ingredient of kouboku (stem bark of Magnolia obovata), an herb used in traditional Chinese medicine. 9)It is known to have many physiological activities, including anti-inflammatory, anti-allergic, anti-platelet, and anti-tumor properties.10-15) However, the effects of honokiol on osteoclastic bone resorption processes have not previously been investigated in detail. In the present study, we evaluated the effects of honokiol on osteoclast differentiation, function and survival, and determined a possible mechanism of action. Agriculture and Technology; Fuchu, MATERIALS AND METHODS Reagents Honokiol Inhibits Osteoclast Differentiation and Function in Vitro

PACE4 is a mammalian subtilisin-like proprotein convertase that activates transforming growth factor (TGF)-beta-related proteins such as bone morphogenetic protein 2 (BMP2), BMP4 and Nodal and exhibits a dynamic expression pattern during embryogenesis. We recently determined that the 1 kb 5'-upstream region of the PACE4 gene contains 12 E-box (E1-E12) elements and that an E-box cluster (E4-E9) acts as a negative regulator [Tsuji, Yoshida, Hasegawa, Bando, Yoshida, Koide, Mori and Matsuda (1999) J. Biochem. (Tokyo) 126, 494-502]. It is known that the mammalian achaete-scute homologue 1 (MASH-1) binds specifically to an E-box (CACCTG) sequence in collaboration with E47, a ubiquitously expressed basic helix-loop-helix (bHLH) factor. To identify the roles of the bHLH factor and E-box elements in regulating PACE4 gene expression in neural development, we analysed the effects of human achaete-scute homologue 1 (hASH-1) on PACE4 gene expression with various neuroblastoma cell lines. The expressions of PACE4 and hASH-1 are correlated inversely in these cell lines. The overexpression of hASH-1 or MASH-1 causes a marked decrease in endogenous PACE4 gene expression but has no effect on the expression of other subtilisin-like proprotein convertases such as furin, PC5/6 and PC7/8. In contrast, other neural bHLH factors (MATH-1, MATH-2, neurogenin 1, neurogenin 2, neurogenin 3 and E47) did not affect PACE4 gene expression. Furthermore, an E-box cluster was a negative regulatory element for the promoter activity in NBL-S cells expressing hASH-1 at high level as determined by a luciferase assay. Binding of hASH-1 to the E-box cluster was confirmed by gel mobility-shift assay. In the present study we identified the PACE4 gene as one of the targets of hASH-1, which is a key factor in the initiation of neural differentiation. These results suggest that the alteration of PACE4 gene expression by hASH-1 causes rapid changes in the biological activities of TGF-beta-related proteins via post-translational modification of these proteins.