Gasdermin D maintains bone mass by rewiring the endo-lysosomal pathway of osteoclastic bone resorption

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Oxygen free radicals induced release of lysosomal enzymes in vitro

Summary The effect of oxygen free radicals, generated by xanthine and xanthine oxidase, was studied on the release of lysosomal hydrolase from rat liver lysosomes in vitro. A lysosomal enriched subcellular fraction was prepared, using differential centrifugation technique, from the homogenate of rat liver. The biochemical purity of the lysosomal fraction was established by using the markers of different cellular organelles. Oxygen free radicals were generated in vitro by the addition of xanthine and xanthine oxidase. The release of lysosomal hydrolase (-glucuronidase) from the lysosomal fraction was measured. There was a 3 to 4 fold increase in the release of -glucuronidase activity in the presence of xanthine and xanthine oxidase when compared to that in the absence of xanthine and xanthine oxidase. In the presence of superoxide dismutase (SOD), a scavenger of oxygen free radicals, the xanthine and xanthine oxidase system was unable to induce the release of -glucuronidase activity from the lysosomes. Sonication (2 bursts for 15 sec each) and Lubrol (2 mg/10 mg lysosomal protein) treatment, which are known to cause membrane disruption, also induced the release of -glucuronidase from lysosomal fraction. This release of -glucuronidase by sonication and lubrol treatment was not prevented by SOD. These data indicate that lysosomal disruption is a consequence of oxygen free radicals, generated by xanthine and xanthine oxidase.Abbreviations HEPES N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid - EGTA Ethylene Glycol Bis-(-aminoethyl ether)N,N,-N,N-tetracetic acid - Tris Tris (hydroxymethyl) aminomethane - SOD Superoxide Dismutase     

Ultrastructural analysis of pathologic lesions in sterol-deficient Nippostrongylus brasiliensis larvae

A variety of cellular lesions were manifested by the free-living larval stages of Nippostrongylus brasiliensis cultured axenically in medium lacking cholesterol. Pathologic changes developed rapidly and were most apparent in intestinal cells which displayed generalized degradation of membranous organelles. Mitochondria, endoplasmic reticulum, and Golgi complexes became disassociated and vacuolated. Autophagosomes appeared within intestinal cells and contained a wide variety of cellular components. By the 5th day gross vacuolization and degeneration of intestinal cells occurred and the hypodermis and lateral cords displayed lysed cytoplasmic regions. The latter structures are concerned with synthesis of cuticle and their degeneration correlates with the suppression of molting and the abnormal molts that occurred.     

Species variations amongst proteinases in liver lysosomes

Cathepsin B, H, L and D activities in liver lysosomes were compared between species. Although cathepsin B and D were detected in bovine, pig, chicken and rat liver, striking species differences were evident for cathepsin H and L. Cathepsin L activity was particularly high in chicken lysosomal extracts, but could not be detected in bovine and pig extracts. Whereas there was no significant cathepsin H activity in bovine extracts, rat liver lysosomal extracts contained large amounts of cathepsin H activity.     

Kurloff cell lysosomal arylsulphatases: Presence of both cationic and highly anionic isoforms of the sole B class

Following the previous ultrastructural demonstration of the presence of arylsulphatase (Asase) activities in Kurloff cells (KC) and of their quasi-exclusive localization in the Kurloff body (KB), this work investigates their biochemical and zymographic properties after extraction from purified KC suspensions. Using the discriminative inhibitory conditions of both the Baum or LeeVaupel and Conzelmann methods, nitrocatechol sulphate hydrolyzing enzymes of the KC were assumed to belong to the B class of the type II Asase alone. After electrophoretic separation under non-denaturing conditions in a 4–23% polyacrylamide gel, they were characterized by 55 kDa and 62 kDa zymographic bands. After isoelectric focusing, ‘classical’ cationic isoforms (pI 8.5) and two anionic isoforms (pI 4.4 and 4.6) were observed on zymograms. As expected for class B Asase, the different zymographic forms of KC Asase were only recovered in the unadsorbed fraction after anion-exchange chromatography on DEAE-cellulose column equilibrated with high ionic strength buffer. Their K_m (2.1 mM), their optimum pH (5.8) and their inhibitions by sulfite, phosphate, sulphate and ascorbic acid as well as their slight stimulation by AgNO₃ were also characteristic of this class of Asase. Finally, chondroitin4-sulphate was shown to potentially be a physiological substrate for these lysosomal enzymes.     

Purification and Characterization of Phospholipase C Preferentially Hydrolysing Phosphatidylcholine in Tetrahymena Membranes

A phospholipase C (PLC) activity that preferentially hydrolyses phosphatidylcholine to diacylglycerol and phosphorylcholine was found to be present in Tetrahymena pyriformis, strain W and most of its activity was recovered in the membrane fraction. This enzyme was extracted with 1% Triton X-100 from the membrane fraction and purified to apparent homogeneity by sequential chromatographies on Fast Q-Sepharose, hydroxyapatite HCA-100S, Mono Q and Superose 12 gel filtration columns. The purified enzyme had specific activity of 2083 nmol of diacylglycerol released/mg of protein/min for dipalmitoylphosphatidylcholine hydrolysis. Its apparent molecular mass was 128 kDa as determined by SDS-polyacrylamide gel electrophoresis and was 127 kDa by gel filtration chromatography, indicating that the enzyme is present in a monomeric form. The enzyme exhibited an optimum pH 7.0 and the apparent K_m value was determined to be 166 μM for dipalmitoylphosphatidylcholine. A marked increase was observed in phosphatidylcholine hydrolytic activity in the presence of 0.05% (1.2 mM) deoxycholate. Ca²⁺ but not Mg²⁺ enhanced the activity at a concentration of 2 mM. This purified phospholipase C exhibited a preferential hydrolytic activity for phosphatidylcholine but much less activity was observed for phosphatidylinositol (～ 9%) and phosphatidylethanolamine (～ 2%).     

Selective intra-lysosomal concentration of niobium in kidney and bone marrow cells: a microanalytical study

Niobium is used as an alloy in the industrial and biomedical fields. The concentration of the toxic element in organs of a number of animal species has been defined by using radioactive niobium (⁹⁵Nb). However, tissue lesions induced by niobium have only been studied at the light microscopy level. In this study, we used an electron probe X-ray analyzer equipped with a transmission electron microscope to define the localization of this element in kidney and bone marrow cells. Results demonstrated that niobium is located in the lysosome and that this element coprecipitates with phosphate. In kidney, lysosomes and precipitates are eliminated in the tubular lumen. In contrast, precipitates appear to be eliminated more slowly from the lysosomes of bone marrow macrophages. These processes therefore correspond to one of the mechanisms by which lysosomes eliminate certain toxic mineral elements and thus play a role in the more general process of the body's defenses.