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.

FHL2 mediates dexamethasone-induced mesenchymal cell differentiation into osteoblasts by activating Wnt/β-catenin signaling-dependent Runx2 expression

Abstract: The differentiation of bone marrow mesenchymal stem cells (MSCs) into osteoblasts is a crucial step in bone formation. However, the mechanisms involved in the early stages of osteogenic differentiation are not well understood. In this study, we identified FHL2, a member of the LIM-only subclass of the LIM protein superfamily, that is up-regulated during early osteoblast differentiation induced by dexamethasone in murine and human MSCs. Gain-of-function studies showed that FHL2 promotes the expression of the osteoblast transcription factor Runx2, alkaline phosphatase, type I collagen, as well as in vitro extracellular matrix mineralization in murine and human mesenchymal cells. Knocking down FHL2 using sh-RNA reduces basal and dexamethasone-induced osteoblast marker gene expression in MSCs. We demonstrate that FHL2 interacts with beta-catenin, a key player involved in bone formation induced by Wnt signaling. FHL2-beta-catenin interaction potentiates beta-catenin nuclear translocation and TCF/LEF transcription, resulting in increased Runx2 and alkaline phosphatase expression, which was inhibited by the Wnt inhibitor DKK1. Reduction of Runx2 transcriptional activity using a mutant Runx2 results in inhibition of FHL2-induced alkaline phosphatase expression in MSCs. These findings reveal that FHL2 acts as an endogenous activator of mesenchymal cell differentiation into osteoblasts and mediates osteogenic differentiation induced by dexamethasone in MSCs through activation of Wnt/beta-catenin signaling- dependent Runx2 expression.

Alkaline Phosphatase: A Marker of Alveolar Type II Cell Differentiation

Abstract: In an effort to identify type II cells by a method independent of staining phospholipid inclusions, we evaluated a histochemical technique for alkaline phosphatase activity in normal rat lung, in freshly isolated type II cells, and in primary culture of type II cells. In the adult rat alveolus, alkaline phosphatase staining selectively identified type II cells, although nonciliated bronchiolar (Clara) cells and loose perivascular connective tissue also stained for alkaline phosphatase activity. In cell suspensions of type II cells and other dissociated lung cells, alkaline phosphatase staining correlated closely with the modified Papanicolaou technique and was particularly useful in distinguishing type II cells from alveolar macrophages. To determine if alkaline phosphatase was related to the differentiated phenotype of type II cells, we studied conditions known to affect other type II cell functions. When type II cells were cultured on plastic substrata, the intensity of alkaline phosphatase staining decreased with increasing time in culture. To quantitate the apparent decrease in alkaline phosphatase activity, we used a biochemical assay to study the expression of alkaline phosphatase by type II cells. The specific activity of alkaline phosphatase in type II cells declined with increasing time in tissue culture on plastic substrata. Alkaline phosphatase activity was maintained, however, by culturing cells on Englebreth-Holm-Swarm (EHS) tumor matrix. Cells that had reduced levels of alkaline phosphatase activity following 48 h of culture on plastic substrata could be "rescued" by removing them from the plastic substratum and reculturing them for 48 h on EHS matrix. Alkaline phosphatase activity was also increased by culturing type II cells in the presence of cAMP or sodium butyrate.(ABSTRACT TRUNCATED AT 250 WORDS)

Phosphatase activity of extra-radical arbuscular mycorrhizal hyphae: A review

Abstract: Phosphatase activity of arbuscular mycorrhizal (AM) fungi has attracted attention in three fairly distinct domains: intracellular enzymes with defined metabolic functions that have been studied in intraradical hyphae, histochemical staining of alkaline phosphatase as an indicator of fungal activity measured both intra- and extraradically, and extracellular activity related to mineralization of organic P (Po) compounds that may enhance mycorrhizal utilization of an important nutrient pool in soil. This review focuses on the latter subjects with emphasis on extraradical mycelium (ERM), while it draws on selected data from the vast material available concerning phosphatases of other organisms. We conclude that histochemical staining of alkaline phosphatase is a sensitive and suitable method for monitoring the effect of adverse conditions encountered by ERM both as a symbiotically functional entity in soil, and in vitro without modifying interference of soil or other solid substrates. Furthermore, the quantitative importance of extracellular enzymes for P nutrition of AM plants is estimated to be insignificant. This is concluded from the low quantitative contribution extracellular hyphae of AM fungi give to the total phosphatase activity in soil, and from estimations of which processes that may be rate limiting in organic P mineralization. Maximum values for the former is in the order of a few percent. As for the latter, solubilization of Po seems to be far more important than Po hydrolysis for utilization of Po by AM fungi and plants, as both endogenous soil phosphatase activity and phosphatases of other soil organisms are ubiquitous and abundant. Our discussion of mycorrhizal phosphatases supports the view that extracellular phosphatases of roots and micro-organisms are to a large extent released incidentally into soil, and that the source has limited benefit from its activity.

Alcohol-induced adipogenesis in bone and marrow: a possible mechanism for osteonecrosis.

Abstract: The effect of alcohol on rabbit bone marrow and on the differentiation of mouse bone marrow stromal cells was investigated Alcohol was administered intragastrically at a dose of 10 mL/kg/day for 1 to 6 months Alcohol induced a significant increase in serum lipid peroxides, triglyceride, and cholesterol, and a reduction in superoxide dismutase activity Fatty infiltration in the liver and adipogenesis in bone marrow were found histologically after alcohol administration Fat cell hypertrophy and proliferation and diminished hematopoiesis in the subchondral area of the femoral head were observed Triglycerides were deposited in osteocytes, which became pyknotic, and the percentage of empty osteocyte lacunae increased None of these abnormal changes were detectable in the control group In the in vitro study, the marrow stromal cells were treated with increasing (003, 009, and 015 mol/L) concentrations of ethanol for 4 to 21 days Alcohol induced the differentiation of the cells into adipocytes The number of adipocytes increased with longer durations of exposure to ethanol and with higher concentrations Cells treated with ethanol also showed diminished alkaline phosphatase activity and expression of osteocalcin These novel findings indicate that alcohol can directly induce adipogenesis, decrease osteogenesis in bone marrow stroma, and produce intracellular lipid deposits resulting in the death of osteocytes, which may be associated with the development of osteonecrosis, especially in patients with long-term and excessive use of alcohol