Alkaline phosphatase

About: Alkaline phosphatase is a research topic. Over the lifetime, 20218 publications have been published within this topic receiving 540547 citations. The topic is also known as: Alkaline_phosphatase & IPR001952.

Phosphohexosyl recognition is a general characteristic of pinocytosis of lysosomal glycosidases by human fibroblasts.

Abstract: We recently presented data showing that mannose-6-phosphate was a potent competitive inhibitor of pinocytosis of human platelet beta-glucuronidase, and that treatment of "high-uptake" forms of the enzyme with alkaline phosphatase destroyed the high-uptake property of the enzyme without diminishing its catalytic activity. These data indicate that phosphate is a necessary component of the recognition marker on the enzyme for pinocytosis by human fibroblasts, and suggest that the phosphate on high-uptake forms of the enzyme is present as a phosphohexosyl moiety. Results presented here show that mannose-6-phosphate is also a potent inhibitor of pinocytosis of the following enzyme preparations: (a) beta-glucuronidase from human spleen, liver, placenta, and urine; (b) beta-hexosaminidase and beta-galactosidase from human platelets; (c) beta-hexosaminidase from human fibroblast secretions. Alkaline phosphatase treatment of all these enzymes except beta-galactosidase, which was unstable to the incubation conditions and could not be tested, greatly diminished the uptake activity of the enzymes without diminishing their catalytic activity. These results suggest that phosphohexosyl recognition is a general characteristic of pinocytosis of lysosomal glycosidases.

Degranulation of leukocytes in chronic granulomatous disease

Abstract: Quantitative chemical analyses of the subcellular distribution patterns for acid and alkaline phosphatase, beta glucuronidase and peroxidase were obtained for human peripheral blood leukocytes of four patients with chronic granulomatous disease (CGD). Five young adults with acute infections served as controls. The observations were made on fractions obtained by homogenization and centrifugation of leukocytes previously incubated with or without particles for ingestion. Distributions in resting CGD and normal cells were very similar for acid and alkaline phosphatase and peroxidase, but the proportion of beta glucuronidase in the granule fraction of CGD cells was depressed, with an increased proportion in the soluble fraction. Release of granule-bound enzymes during phagocytosis of a variety of particles was the same for CGD and control cells, except that release of beta glucuronidase was less marked in CGD cells. Total enzymatic activity of CGD cells for the hydrolases studied was normal. The data indicated that granular enzymes are released in a normal fashion in phagocytizing CGD cells. Supportive evidence of release of enzymes into the phagocytic vacuole of CGD cells was obtained by an electron microscopic study of myeloperoxidase.

Cytokine-stimulated expression of inducible nitric oxide synthase by mouse, rat, and human osteoblast-like cells and its functional role in osteoblast metabolic activity

Abstract: Recent evidence suggests that the production of nitric oxide (NO) may have important roles in the regulation of osteoblast and osteoclast metabolism. The present study was performed to investigate the effects of interleukin-1 beta (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha), and interferon-gamma (IFN-gamma) on the expression of inducible NO-synthase (iNOS) and to measure high-output production of NO by primary rat osteoblasts and osteoblastic cell lines ROS 17/2.8, MC3T3-E1 and MG-63. In addition, we have investigated if NO may mediate some of the effects of these cytokines on osteoblast metabolism. Northern blots and immunocytochemistry revealed time-dependent iNOS messenger RNA and protein expression in primary rat osteoblasts in response to cytokine treatment. Reverse transcription polymerase chain reaction amplified an 807-base pair (bp) product from ROS 17/2.8 cells, which had a size and restriction enzyme-cut pattern identical to that predicted for authentic rat iNOS. Nitrite accumulation in culture medium was induced by IFN-gamma in a time- and dose-dependent manner and inhibited by cotreatment with inhibitors of NOS activity and by dexamethasone. IL-1 beta, TNF-alpha, and bacterial lipopolysaccharide were found to have weak stimulatory effects on nitrite production on their own. However, IL-1 beta and TNF-alpha showed strong synergy with IFN-gamma, but, surprisingly, lipopolysaccharide was found to exert potent inhibitory effects on IFN-gamma-induced nitrite synthesis. Basal production of nitrite and induction of its synthesis was similarly observed with primary rat osteoblasts as well as ROS 17/2.8, MC3T3-E1, and MG-63 cell lines. Cytokine-induced NO production significantly reduced osteoblast activity, as was evidenced by inhibition of DNA synthesis, cell proliferation, alkaline phosphatase activity, and osteocalcin production. The results provide evidence for a basal expression of iNOS activity and show that the iNOS messenger RNA, protein, and enzyme activity are all induced by cytokines across the species. The data further suggest that osteoblast-derived NO may have an important role in mediation of localized bone destruction associated with inflammatory bone diseases such as rheumatoid arthritis.

Modulation of Dickkopf-1 Attenuates Glucocorticoid Induction of Osteoblast Apoptosis, Adipocytic Differentiation, and Bone Mass Loss

Abstract: Long-term glucocorticoid treatment impairs the survival and bone formation of osteogenic cells, leading to bone mass loss. The Wnt inhibitor Dickkopf-1 (DKK1) acts as a potent bone-remodeling factor that mediates several types of skeletal disorders. Whereas excess glucocorticoid is known to disturb Wnt signaling in osteogenic cells, modulation of the skeletally deleterious effects of DKK1 to alleviate glucocorticoid induction of bone loss has not been tested. In this study, knockdown of DKK1 expression by end-capped phosphorothioate DKK1 antisense oligonucleotide (DKK1-AS) abrogated dexamethasone suppression of alkaline phosphatase activity and osteocalcin expression in MC3T3-E1 preosteoblasts. Exogenous DKK1-AS treatment alleviated dexamethasone suppression of mineral density, trabecular bone volume, osteoblast surface, and bone formation rate in bone tissue and ex vivo osteogenesis of primary bone-marrow mesenchymal cells. The DKK1-AS inhibited adipocyte volume in the marrow cavity of steroid-treated bo...