acid-phosphatase and 3-methyladenine

Acute primary open angle glaucoma is an optic neuropathy characterized by the elevation of intraocular pressure, which causes retinal ischemia and neuronal death. Rat ischemia/reperfusion enhances endocytosis of both horseradish peroxidase (HRP) or fluorescent dextran into ganglion cell layer (GCL) neurons 24 h after the insult. We investigated the activation of autophagy in GCL-neurons following ischemia/reperfusion, using acid phosphatase (AP) histochemistry and immunofluorescence against LC3 and LAMP1. Retinal I/R lead to the appearance of AP-positive granules and LAMP1-positive vesicles 12 and 24 h after the insult, and LC3 labelling at 24 h, and induced a consistent retinal neuron death. At 48 h the retina was negative for autophagic markers. In addition, Western Blot analysis revealed an increase of LC3 levels after damage: the increase in the conjugated, LC3-II isoform is suggestive of autophagic activity. Inhibition of autophagy by 3-methyladenine partially prevented death of neurons and reduces apoptotic markers, 24 h post-lesion. The number of neurons in the GCL decreased significantly following I/R (I/R 12.21±1.13 vs controls 19.23±1.12 cells/500 µm); this decrease was partially prevented by 3-methyladenine (17.08±1.42 cells/500 µm), which potently inhibits maturation of autophagosomes. Treatment also prevented the increase in glial fibrillary acid protein immunoreactivity elicited by I/R. Therefore, targeting autophagy could represent a novel and promising treatment for glaucoma and retinal ischemia.

Topics: Acid Phosphatase; Adenine; Animals; Apoptosis; Astrocytes; Autophagy; Caspase 3; Cell Count; Drug Design; Endocytosis; Intraocular Pressure; Lysosomes; Male; Microtubule-Associated Proteins; Neurons; Neuroprotective Agents; Rats; Rats, Wistar; Reperfusion Injury; Retina; Retinal Ganglion Cells; Time Factors

Lymphokine-activated killer (LAK) cells can kill several tumor cells. Their killing activity is generally due to cell-cell adhesion. Cell-cell adhesion of the LAK cells to the target cells is essential for LAK lysis. In this report, however, we describe that the LAK cells can also kill the target cells by cell-cell adhesion-independent killing. Killing occurred after the target cells were exposed to the LAK cells. When the LAK cells were added to glioblastoma cell lines T98G and U373MG (which proliferate by adhering to the bottom of a culture flask), the LAK cells killed them by cell-cell adhesion killing within 4 h (early killing). On the other hand, when small numbers of the LAK cells were added, some of the target cells escaped from the early killing. At 4 and 6 h after the adding the LAK cells, when the LAK cells were discarded from the flask by washing with PBS, the escaped cells still adhered and were alive. However, they ultimately died over the next 24-96 h (late killing). The late killing was the cell-cell adhesion-independent killing, because it occurred after the LAK cells were removed. In this killing, numerous granules and vacuoles appeared in the cytoplasm of the cells. The vacuoles enlarged and then the cells died. The cell death was different from apoptosis, because the nucleus was intact until the late stage and no DNA fragment laddering in the degenerated cells was recognized. The vacuoles were stained with acid phosphatase and the cell death was inhibited with 3-methyladenine (an inhibitor of lysosome), suggesting that the late killing may be autophagic cell death due to activated lysosome. Induction of late killing in tumor cells using the LAK cells may become one approach for cancer therapy.

Topics: Acid Phosphatase; Adenine; Apoptosis; Cell Adhesion; Cell Membrane; Cells, Cultured; Dose-Response Relationship, Drug; Glioblastoma; Humans; Killer Cells, Lymphokine-Activated; Lysosomes; Microscopy, Electron; Time Factors; Tumor Cells, Cultured

Bovine parathyroid organoids were maintained for up to 12 days of culture in the presence or absence of insulin. Insulin-treated organoids secreted more PTH and secretory protein-I (SP-I) than did untreated organoids at both 1.4 and 1.8 mM Ca, concentrations chosen to promote partially elevated and suppressed secretion rates, respectively. The insulin effect was dose dependent and reversible. To determine whether insulin might increase secretion by reducing degradation of cellular PTH, its effects on several parameters related to degradative processes were examined. Compared to control cultures maintained at either 1.4 or 1.8 mM Ca, insulin did not induce changes in the relative levels of intact hormone and COOH-terminal peptide fragments secreted into culture medium, nor did it decrease the total cellular levels of three lysosomal enzymes or mute the effects of 3-methyladenine (an agent that decreases formation of autophagosomes) to increase PTH secretion. Thus, insulin did not appear to increase PTH secretion by reducing the latter's cellular degradation. Synthesis of total proteins and of the secreted proteins SP-I and PTH was examined using short incubations of control and insulin-treated organoids with [3H] leucine. Incorporation of 3H into total acid-precipitable proteins was not elevated in insulin-treated organoids; that into PTH/pro-PTH and SP-I, however, was significantly greater in insulin-treated than in control organoids. The results suggested that the insulin-mediated increase in PTH and SP-I secretion is largely due to its regulation of PTH and SP-I biosynthesis.

Topics: Acid Phosphatase; Adenine; Animals; Calcium; Calcium-Binding Proteins; Cathepsin B; Cattle; Cells, Cultured; Chromogranin A; Chromogranins; Glucuronidase; Insulin; Kinetics; Lysosomes; Parathyroid Glands; Parathyroid Hormone; Protein Biosynthesis

[14C]Sucrose, introduced into the cytosol of isolated rat hepatocytes by means of electropermeabilization, was sequestered by sedimentable subcellular particles during incubation of the cells at 37 degrees C. The sedimentation characteristics of particle-associated [14C]sucrose were different from the lysosomal marker enzyme acid phosphatase, suggesting an involvement of organelles of greater size than the average lysosome. Isopycnic banding in isotonic metrizamide/sucrose density gradients resolved two major peaks of radioactivity: a light peak (1.08-1.10 g/ml) coinciding with lysosomal marker enzymes, and a dense peak (1.15 g/ml), coinciding with a mitochondrial marker enzyme. The dense peak was preferentially associated with large-size particles having the sedimentation properties of mitochondria, and it was resistant to the detergent digitonin at a concentration which extracted all of the radioactivity in the light peak. Similarly the autophagy inhibitor 3-methyladenine prevented accumulation of [14C]sucrose in the light peak, while the radioactivity in the dense peak was unaffected. We therefore tentatively conclude that the light peak represents autophagic sequestration of [14C]sucrose into lysosomes (and probably autophagosomes) while the dense peak represents a mitochondrial uptake unrelated to autophagy.

Topics: Acid Phosphatase; Adenine; Animals; Autophagy; Centrifugation, Density Gradient; Chromatography, Gel; Digitonin; In Vitro Techniques; Lysosomes; Male; Metrizamide; Mitochondria, Liver; Rats; Rats, Inbred Strains; Subcellular Fractions; Sucrose; Temperature

Sequestration of the inert cytosolic marker [14C]sucrose by sedimentable organelles was measured in isolated rat hepatocytes made transiently permeable to sucrose by means of electropermeabilization. Lysosomal integrity, protein degradation, autophagic sequestration, and other cellular functions were not significantly impaired by the electric treatment. Hepatocytes sequestered sucrose at an initial rate of approximately 10%/h, which is threefold higher than the estimated rate of autophagic-lysosomal protein degradation. Almost one-third would appear to represent mitochondrial fluid uptake; the rest was nearly completely and specifically inhibited by 3-methyladenine (3MA) and can be regarded as autophagic sequestration. A complete amino acid mixture was somewhat less inhibitory than 3MA, and partially antagonized the effect of the latter. This paradoxical effect, taken together with the high sequestration rate, may suggest heterogeneity as well as selectivity in autophagic sequestration. There was no detectable recycling of sequestered [14C]sucrose between organelles and cytosol. Studies of individual amino acids revealed histidine as the most effective sequestration inhibitor. Leucine may have a regulatory function, as indicated by its unique additive/synergistic effect, and a combination of Leu + His was as effective as the complete amino acid mixture. Asparagine inhibited sequestration only 20%, i.e., its very strong effect on overall (long-lived) protein degradation must partially be due to post-sequestrational inhibition. The lysosomal (amine-sensitive) degradation of short-lived protein was incompletely inhibited by 3MA, indicating a contribution from nonautophagic processes like crinophagy and endocytic membrane influx. The ability of an amino acid mixture to specifically antagonize the inhibition of short-lived protein degradation by AsN + GIN (but not by 3MA) may suggest complex amino acid interactions at the level of fusion between lysosomes and other vesicles in addition to the equally complex interactions at the level of autophagic sequestration.

Topics: Acid Phosphatase; Adenine; Amino Acids; Animals; Carbon Radioisotopes; Cycloheximide; Electric Stimulation; In Vitro Techniques; Liver; Lysosomes; Male; Protein Biosynthesis; Proteins; Rats; Rats, Inbred Strains; Sucrose