Molecular cloning and characterization of CHM1L, a novel membrane molecule similar to chondromodulin-I.

Chondromodulin-I (ChM-I) is a cartilage-specific glycoprotein that stimulates the growth of chondrocytes and inhibits the tube formation of endothelial cells. In the present study, we identified a novel ChM-I like molecule, designated ChM1L. Cloning of full length cDNAs of human, mouse, and rat ChM1L revealed that ChM1L encodes 317 amino acids novel type II transmembrane protein. ChM1L protein was expressed on the cell surface as N-glycosylated and non-N-glycosylated protein with molecular mass of 45 and 40 kDa, respectively. In adult mouse tissues, ChM1L mRNA was highly expressed in eye, skeletal muscle, and whole rib. The temporal pattern of ChM1L mRNA was examined using whole embryo at day 10 to 19 of gestation. After day 11, ChM1L mRNA was detected and its level was progressively elevated in association with development of mouse embryo. These data suggest that ChM1L is a novel membrane molecule which is similar to ChM-I that plays a regulatory role in eye, skeletal muscle, and development of embryo.

Comparison of hemorrhagic effect of heparin and human activated protein C with use of Thrombostat 4000.

The importance of bleeding as a complication of anticoagulant therapy is clearly recognized. We previously reported that amelioration of hemorrhage associated with disseminated intravascular coagulation by the human activated protein C (APC) was greater than that by heparin. In this study, we compared the bleeding complication of intravenously administered APC and heparin in rabbits, and also estimated primary hemostasis. When both anticoagulants were intravenously infused, the bleeding time from a punctured ear vein was prolonged dose-dependently. However, at doses which prolonged the activated partial thromboplastin time nearly equally, the prolongation of bleeding was greater in heparin-administered rabbits. Blood withdrawn from heparin-administered animals showed increases in in vitro bleeding parameters which correlated with the in vivo bleeding time. However, only small changes were observed in the blood withdrawn from APC-administered animals. Both drugs induced either no change or only a slight decrease in the platelet count, hematocrit and fibrinogen content. These observations suggest that APC may be a more useful anticoagulant than heparin since it causes less bleeding tendency.

Species specificity of anticoagulant activity of activated human protein C: involvement of factor V as well as protein S.

Activated protein C (APC) possesses species specificity in its anticoagulant activity. Human APC exerts only weak activity in rat plasma compared with that in human plasma. The present study was undertaken to estimate the difference in interaction of human and rat factors with human APC and to assess the cause of the species specificity. Human or rat protein S (PS), factor V, or factor VIII was used to supplement human plasma depleted of each respective factor, and the anticoagulant activity of human APC was measured in term of the elongation of activated partial thromboplastin time (APTT). The activity of human APC in rat PS- or factor V-supplemented plasma was weaker than that in the human PS- or factor V-supplemented plasma. Furthermore, using purified human and rat factor V, human APC showed weaker inactivation of rat factor V than human factor V. Equal anticoagulant activity was observed in human or rat factor VIII-supplemented plasma. And there was a little difference in the interaction of APC with its inhibitors in human or rat plasma during a few minutes of incubation as judged by measurement of residual activity by an enzyme capture assay. From these results factor V as well as PS seems to play a major role in the species specificity of APC.

TEI-3313, a novel prostaglandin A1 derivative, prevents bone loss and enhances bone formation in immobilized male rats.

The effect of a novel prostaglandin A1 derivative, TEI-3313, with the chemical structure 5-[(Z,2E)-4,7-dihydroxy-2-heptenyridene]-4-hydroxy- 2-methylthio-4-(4-phenoxybutyl)-2-cyclopentenone, on bone mineral content was investigated. Seven-week-old Sprague-Dawley rats in which the right hindlimbs were immobilized by sciatic nerve dissection received 1, 10, 100 or 500 micrograms of TEI-3313/kg/day, i.p., for 6 weeks. Control animals were operated on but received vehicle only. Bone mineral content of the femur was measured by single-photon absorptiometry, and biochemical parameters were analyzed. Histomorphometric observations were performed on the proximal metaphysial sections of the tibiae. The administration of up to 500 micrograms/kg of TEI-3313 to rats had no effect on body weight or on serum calcium, inorganic phosphorus and 1 alpha,25 dihydroxy vitamin D3 levels. Immobilization decreased the ash content, calcium content and total bone mineral content of the femur compared with nonimmobilization (unoperated femur). With TEI-3313 administration, changes in these parameters in the immobilized femur were prevented almost to the levels of the nonimmobilized femur, in a dose-dependent manner. The enhancement of bone mineral content was remarkable in the midshaft of the femur. TEI-3313 enhanced ash and calcium content and total bone mineral content in nonimmobilized femurs. Microradiograms showed that TEI-3313, unlike pamidronate and 17 beta-estradiol, had little inhibitory effect on trabecular bone resorption in the proximal portion of the tibia. TEI-3313 not only prevented the bone loss induced by immobilization but also increased bone mass in the nonimmobilized femurs without affecting the levels of 1 alpha,25 dihydroxy vitamin D3.(ABSTRACT TRUNCATED AT 250 WORDS)

Alendronate distributed on bone surfaces inhibits osteoclastic bone resorption in vitro and in experimental hypercalcemia models.

Alendronate is an aminobisphosphonate that acts as a potent inhibitor of osteoclastic bone resorption. To understand the mechanism of action of alendronate in vivo, in this study we investigated the relationship between distribution of [14C]-alendronate in rat bone and its effects on bone resorption in vitro or in rat hypercalcemic models. A single IV dose of 0.05 approximately 1.25 mg/kg inhibited the increase in plasma calcium level induced by bovine PTH or 1 alpha(OH)D3. The minimal effective dose of pamidronate (1.25 mg/kg) and etidronate (over 31.25 mg/kg) were at least 5 times and 25 times, respectively, higher than the dose of alendronate in the rat hypercalcemic model prepared by 1 alpha(OH)D3. The relative potencies of compounds in the hypercalcemic rat models reflected those of inhibitory effects on bone resorption in vitro. We conducted the ivory-slice assay under two conditions: (a) addition of a given bisphosphonate after adherence of the osteoclasts; and (b) preincubation of the ivory slices with a given bisphosphonate. The inhibitory IC50 values of alendronate under condition (b) were similar to those under condition (a). To evaluate the interaction between osteoclasts and alendronate in bone, we investigated the localization of [14C]-alendronate in the tibia of growing rats (4-day-old rats). Alendronate did not distribute uniformly in the tibia. At 1 day after injection (0.05 mg SC), dense labeling was seen primarily under osteoclasts. We injected 0.05 mg/kg of [14C]-alendronate (single i.v.) into rats [14C]-alendronate was rapidly eliminated from plasma, and mainly distributed to the bone in rats. These data suggest that alendronate which distributed on bone surface mainly contributed to the antihypercalcemic action in vivo.

Alendronate modulates osteogenesis of human osteoblastic cells in vitro.

The bisphosphonates, which are carbon-substituted pyrophosphates, have been studied extensively both in vivo and in vitro to elucidate their effects on bone tissues and cells. However, because these agents were shown to have a potent inhibitory effect on bone resorption, the majority of studies have focused on only this aspect of bone metabolism. There appears to be less information regarding the direct effect of bisphosphonates on bone formation, so thus we undertook experiments to investigate the effects of bisphosphonates, especially alendronate, on the mineralization and matrix protein synthesis of human osteoblastic cells in vitro. The data show that the bisphosphonates, alendronate, etidronate and pamidronate, suppressed 1,25-dihydroxycholecalciferol (1,25(OH)2D3)-stimulated mineralization of human osteoblastic cells at high concentrations, while relatively lower concentrations of alendronate and etidronate potentiated mineralization of the cells in the presence of 1,25(OH)2D3. The potentiation of mineralization with alendronate was accompanied by increased synthesis of bone matrix proteins, osteocalcin and collagen, and the mRNA of pro alpha(I) collagen. These findings show that in addition to their well-known effects on bone resorption, bisphosphonates have significant and direct effects on osteogenesis in osteoblasts in vitro. The actual mechanism remains to be further investigated.

Secretion of osteocalcin and its propeptide from human osteoblastic cells: dissociation of the secretory patterns of osteocalcin and its propeptide.

Specific immunoassay systems for intact human osteocalcin (I-OC) and its 26-residue propeptide have been newly developed to assess their usefulness as biochemical markers of bone metabolism. Using human cultured osteoblastic periosteal cells, we monitored 24 h secretion of these molecules from the osteoblastic cells and also examined the deposition of Ca, P, and I-OC on the extracellular matrix. At day 5, both I-OC and its propeptide were secreted by osteoblastic cells in a concentration-dependent manner by treatment with 1,25-(OH)2D3. This propeptide was not detected in the serum of adult subjects but was detected in the serum of normal children, which confirmed this in vitro result of propeptide secretion. The secretion of I-OC into medium transiently decreased at day 11, when the rapid accumulation of I-OC, Ca, and P, namely mineralization, was observed on the extracellular matrix of osteoblastic cells, although secretion of the propeptide constantly increased throughout the culture period. Therefore, the ratio of the amount of propeptide to I-OC in the supernatant markedly increased when mineralization started. These data demonstrate the superior specificity of propeptide as a marker of osteoblastic function in vitro compared with I-OC and that monitoring the changes in propeptide to I-OC ratios in the culture supernatant may be useful for predicting the timing of mineralization on the extracellular matrix of osteoblastic cells.

Chlorpromazine alters bone metabolism of rats in vivo.

The acute effect of chlorpromazine (CPZ) on metabolic changes in rats was investigated. CPZ was found to markedly suppress 45Ca incorporation into the calvarium and ileum in vitro. According to the serum and/or urinary levels of certain markers for bone metabolism, the increases of Ca and P in the serum and Ca, P, and gamma-carboxyglutamate (Gla) in the urine were observed in rats given 10 mg CPZ/kg of their body weight, whereas the amount of alkaline phosphatase (ALP) activity, ionized Ca, calcitonin, 25-hydroxyvitamin D3 (25(OH)D3), 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), and 24,25-dihydroxyvitamin D3 (24,25(OH)2D3) as clearly or slightly reduced, suggesting the inhibitory effect of their bone formation. This was well supported since only bone type ALP was detected in the urine and loss of the vertebral bone density from rats given daily CPZ administration for a week. Moreover, in this case, there is little if any difference in the levels of mid-molecule parathyroid hormone (mid-PTH), osteocalcin, and urinary cAMP for the nontreated and CPZ-treated animals, resulting in the fact that CPZ may mainly inhibit the hydroxylase for active vitamin D3.