Acid phosphatase cytochemistry of mitogen-transformed normal and chronic lymphocytic leukemia lymphocytes

Acid phosphatase cytochemistry was performed on lymphocytes stimulated in vitro with phytohemagglutinin, pokeweed mitogen, or concanavalin A. These electron microscopic studies demonstrated that activated lymphocytes from both normals and patients with chronic lymphocytic leukemia (CLL) had an increased number of lysosomes relative to resting cells. At the time of maximum thymidine incorporation, a reduced number of lysosomes was present in many transformed CLL lymphocytes, mainly medium-sized blast cells, in comparison to transformed normal cells. The findings demonstrate a lysosomal abnormality in phytomitogen transformed CLL lymphocytes which may be related to functional defects of these cells or to an incomplete transformation of a residual population of normal lymphocytes.     

Secretory lysosome biogenesis in cytotoxic T lymphocytes from normal and Chediak Higashi syndrome patients

The lytic proteins mediating target cell killing are stored in the lysosomes of activated cytotoxic T lymphocytes (CTL) and are secreted upon recognition of a target cell. These secretory lysosomes cannot be detected in resting T lymphocytes. Interaction of a resting cell with a target cell activates de novo formation of secretory lysosomes. CTL clones in culture mimic this behaviour, and so provide an ideal system for studying secretory lysosome biogenesis and maturation. In the genetic disease, Chediak Higashi syndrome (CHS), all lysosomes in the cells are enlarged and reduced in number compared with wild-type (WT) cells. We have used CTL from this disease to study secretory lysosome biogenesis and maturation. We show that at early stages after activation the secretory lysosomes are identical in WT and mutant cells, and that delivery of proteins to the secretory lysosome along the biosynthetic and endocytic pathways is normal in the mutant cells. With time, the lysosomes in the mutant cells aggregate, become larger and fewer in number and eventually form giant structures. Our results show that the initial steps of secretory lysosome formation are normal in CHS, but that the organelles subsequently fuse together during cell maturation to form the giant secretory lysosomes.     

HSP70 and lysosomal storage disorders: novel therapeutic opportunities

Lysosomes, with their arsenal of catabolic enzymes and crucial metabolic housekeeping functions are experiencing a revived research interest after having lived a rather quiet life for the last few decades. With the discovery of the interaction of the lysosomes with another ancient component of cellular homoeostasis, the molecular chaperone HSP70 (heat-shock protein 70), the stage seems set for further discoveries of the mechanisms regulating cellular and physiological stress responses to otherwise detrimental challenges.     

N-acetyl-beta-D-glucosaminidase in lymphocytes of patients with diabetes mellitus

In 55 patients with diabetes mellitus the significant quantitative increase in numbers of N-acetyl-beta-D-glucosaminidase-positive lymphocytes in the peripheral blood has been examined by cytochemical methods. The enzyme-positive lymphocytes of these patients were characterized by prevalence of extralysosomal localization of the enzyme and a decrease in the numbers of those cells having intact enzyme-positive lysosomes. No association between these alterations and therapy with insulin or oral hypoglycemic drug and overweight could be stated.     

Toxicity of Copper Oxide (CuO) Nanoparticles on Human Blood Lymphocytes

CuO nanoparticles (CuO-NPs) serve several important functions in human life, particularly in the fields of medicine, engineering, and technology. These nanoparticles have been utilized as catalysts, semiconductors, sensors, gaseous and solid ceramic pigments, and magnet rotatable devices. Further use for CuO-NPs has been employed in the pharmaceutical industry especially in the production of anti-microbial fabric treatments or prevention of infections caused by Escherichia coli and methicillin-resistant Staphylococcus aureus. Two key potential routes of exposure to CuO-NPs exist through inhalation and skin exposure. Toxicity of these nanoparticles has been reported in various studies; however, no study as of yet has investigated the complete cellular mechanisms involved in CuO-NPs toxicity on human cells. The aim of this study was to determine the cytotoxicity of CuO-NPs on human blood lymphocytes. Blood lymphocytes were obtained from healthy male subjects through the use of Ficoll polysaccharide subsequently by gradient centrifugation. The following parameters were assayed in blood lymphocytes after a 6-h incubation with different concentrations of CuO-NPs: cell viability, reactive oxygen species (ROS) formation, lipid peroxidation, cellular glutathione levels, and mitochondrial and lysosomal damage. Our results demonstrate that CuO-NPs, in particular, decreased cell viability in a concentration-dependent manner and the IC50 determined was 382 μM. CuO-NP cytotoxicity was associated with significant increase at intracellular ROS level and loss of mitochondrial membrane potential and lysosomal membrane leakiness. Hence, CuO-NPs are shown to effectively induce oxidative stress in addition to inflict damage on mitochondria and lysosomes in human blood lymphocytes.     

TRPML cation channels regulate the specialized lysosomal compartment of vertebrate B-lymphocytes

B-lymphocytes possess a specialized lysosomal compartment, the regulated transformation of which has been implicated in B-cell antigen presentation. Members of the mucolipin (TRPML) family of cation channels have been implicated in regulated vesicular transport in several tissues, but a role for TRPML function in lymphocyte vesicular transport physiology has not been previously described. To address the role of TRPML proteins in lymphocyte vesicular transport, we analyzed the lysosomal compartment in cultured B-lymphocytes engineered to lack TRPML1 or after expression of N- or C-terminal GFP fusion proteins of TRPML1 or TRPML2. Consistent with previous analyses of lymphocytes derived from human patients with mutations in TRPML1, we were not able to detect abnormalities in the lysosomes of TRPML1-deficient DT40 B-lymphocytes. However, while N-terminal GFP fusions of TRPML2 localized to normal appearing lysosomes, C-terminal GFP fusions of either TRPML1 or TRPML2 acted to antagonize endogenous TRPML function, localizing to large vesicular structures, the histological properties of which were indistinguishable from the enlarged lysosomes observed in affected tissues of TRPML1-deficient humans. Endocytosed B-cell receptors were delivered to these enlarged lysosomes, demonstrating that a TRPML-dependent process is required for normal regulation of the specialized lysosome compartment of vertebrate B-lymphocytes.     

Ultrastructural localization of a lysosomal enzyme in resin-embedded lymphocytes

The intracellular distribution of lysosomal enzymes in lymphocytes has previously been only poorly defined, mainly by cytochemical procedures of low resolution. In the present study we have used a post-embedding immunogold technique to identify the precise ultrastructural localization of a lysosomal enzyme, beta-glucuronidase, in activated lymphocytes embedded in Lowicryl K4M resin. We show that this enzyme is present in the rough endoplasmic reticulum, in the Golgi complex, and in vesicular organelles which probably include lysosomes.     

Changes in lymphocytes following mercury administration in mice. Observations under fluorescence microscopy

Lymphocytes were stained with vital stain acridine orange. The number of lysosomes per lymphocyte was calculated using "score" test. It should be emphasized that the present paper has proved the reliability of the fluorescence microscopy method of identification of lysosomes in the lymphocytes from peripheral blood, employed for studing the toxic effect of metals.     

AGGREGATION AND TRANSFORMATION OF RAT LYMPHOCYTES ON RAT EMBRYO MONOLAYERS

Lymphocytes from Sprague-Dawley rats have been cultured on monolayers of embryo-derived fibroblasts from the same outbred strain. Under these conditions the lymphocytes form aggregates, and transformation of small lymphocytes to lymphoid blast cells occurs within these aggregates. Transformation is characterized cytologically by enlargement of the nucleus, dispersion of nuclear chromatin, and the appearance of a prominent nucleolus. The principal cytoplasmic changes are an increase in cytoplasmic volume, a marked increase in number of ribosomes, and a clustering of ribosomes. These changes parallel those seen in the transformation of lymphocytes caused by a variety of treatments. One apparent difference is the paucity of lysosomes and lipid inclusions in the lymphocytes that transform on the monolayer.     

Ultrastructural investigations on the lysosomal system of lymph node lymphocytes in transplantation immunity.

Activation of the lysosomal system in T lymphocytes is demonstrated in connexion with immune stimulation, by electron microscopic study of the lymph nodes draining skin allografts. The development of primary lysosomes from enlarged Golgi apparatus, their fusion with autophagic and secretory vacuoles forming secondary lysosomes, of the cytolysome and crinophagosome type, were identified by the ultrahistochemical acid phosphatase reaction, suggesting the involvement of these organelles either in blastic transformation or in the effector function of lymphocytes, in connexion with the elaboration of active factors and cytotoxic events.     

Autophagolysosomes exhibiting lysosomophagy in the granular lymphocytes of patients with granular lymphocyte-proliferative disorders

The ultrastructure of granular lymphocytes (GLs) in the peripheral blood of 12 patients with granular lymphocyte-proliferative disorders (GLPDs) was studied. Autophagolysosomes exhibiting so-called “lysosomophagy” were seen in the GLs of four of these patients but not in normal individuals. Because rod-shaped lysosomes beginning to enclose other lysosomes were seen, the autophagolysosomes exhibiting lysosomophagy in GLs were thought to be formed by the same wrapping mechanism. As far as we know, this is the first report of lysosomophagy in lymphocytes.     

BORC coordinates encounter and fusion of lysosomes with autophagosomes

Whereas the mechanisms involved in autophagosome formation have been extensively studied for the past 2 decades, those responsible for autophagosome-lysosome fusion have only recently begun to garner attention. In this study, we report that the multisubunit BORC complex, previously implicated in kinesin-dependent movement of lysosomes toward the cell periphery, is required for efficient autophagosome-lysosome fusion. Knockout (KO) of BORC subunits causes not only juxtanuclear clustering of lysosomes, but also increased levels of the autophagy protein LC3B-II and the receptor SQSTM1. Increases in LC3B-II occur without changes in basal MTORC1 activity and autophagy initiation. Instead, LC3B-II accumulation largely results from decreased lysosomal degradation. Further experiments show that BORC KO impairs both the encounter and fusion of autophagosomes with lysosomes. Reduced encounters result from an inability of lysosomes to move toward the peripheral cytoplasm, where many autophagosomes are formed. However, BORC KO also reduces the recruitment of the HOPS tethering complex to lysosomes and assembly of the STX17-VAMP8-SNAP29 trans-SNARE complex involved in autophagosome-lysosome fusion. Through these dual roles, BORC integrates the kinesin-dependent movement of lysosomes toward autophagosomes with HOPS-dependent autophagosome-lysosome fusion. These findings reveal a requirement for lysosome dispersal in autophagy that is independent of changes in MTORC1 signaling, and identify BORC as a novel regulator of autophagosome-lysosome fusion.     

A role for Rab7 in the movement of secretory granules in cytotoxic T lymphocytes

Cytotoxic T lymphocytes (CTL) are potent killers of virally infected and tumorigenic cells. Upon recognition of target cells, CTL undergo polarized secretion of secretory lysosomes at the immunological synapse (IS) that forms between CTL and target. However, the molecular machinery involved in the polarization of secretory lysosomes is still largely uncharacterized. In this paper, we investigated the role of Rab7 in the polarization of secretory lysosomes. We show that silencing of Rab7 by RNA interference reduces the ability of CTL to kill targets. GTP-bound Rab7 and Rab interacting lysosomal protein, RILP, interact and both localize to secretory lysosomes in CTL. Over-expression of RILP recruits dynein to the membranes of secretory lysosomes and triggers their movement toward the centrosome. Together, these results suggest that Rab7 may play a role in secretory lysosome movement toward the centrosome by interacting with RILP to recruit the minus-end motor, dynein.     

Occurrence of lysosomes and the differentiation of rat liver cells

Summary The occurrence of lysosomes has been investigated electron microscopically and cytochemically in cells of rat liver in the course of ontogenesis.It has been found that primary lysosomes occur during the whole period under investigation and that they originate from the Golgi complex. Some of them assume the appearance of multivesicular bodies. Acid phosphatase activity is lower at the prenatal stage than after the birth. The occurrence of secondary lysosomes proceeds in two stages. Secondary lysosomes appear in a high number at the beginning of differentiation of the liver diverticulum (10–12 day of embryonic life). On the subsequent days they are, with few exceptions, no more present. At the end of the embryonic period (starting with the 20th day) and especially after the birth, they progressively grow in number and move from the region of central cytoplasm peripherally towards the bile capillary.Differences in occurrence of secondary lysosomes are in connexion with reconstruction of the liver primordium at the beginning of liver development and with the change in metabolism of the liver cell after the birth.     

Destination 'lysosome': a target organelle for tumour cell killing?

Lysosomes and lysosome-related organelles constitute a system of acid compartments that interconnect the inside of the cell with the extracellular environment via endocytosis, phagocytosis and exocytosis. In recent decades it has been recognized that lysosomes are not just wastebaskets for disposal of unused cellular constituents, but that they are involved in several cellular processes such as post-translational maturation of proteins, degradation of receptors and extracellular release of active enzymes. By complementing the autophagic process, lysosomes actively contribute to the maintenance of cellular homeostasis. Proteolysis by lysosomal cathepsins has been shown to mediate the death signal of cytotoxic drugs and cytokines, as well as the activation of pro-survival factors. Secreted lysosomal cathepsins have been shown to degrade protein components of the extracellular matrix, thus contributing actively to its re-modelling in physiological and pathological processes. The malfunction of lysosomes can, therefore, impact on cell behaviour and fate. Here we review the role of lysosomal hydrolases in several aspects of the malignant phenotype including loss of cell growth control, altered regulation of cell death, acquisition of chemoresistance and of metastatic potential. Based on these observations, the lysosome is proposed as a potential target organelle for the chemotherapy of tumours. We will also present some recent data concerning the technologies for delivering chemotherapeutic drugs to the endosomal-lysosomal compartment and the strategies to improve their efficacy.     

Ultrastructural localization of a lysosomal enzyme in resin-embedded lymphocytes

Summary The intracellular distribution of lysosomal enzymes in lymphocytes has previously been only poorly defined, mainly by cytochemical procedures of low resolution. In the present study we have used a post-embedding immunogold technique to identify the precise ultrastructural localization of a lysosomal enzyme, -glucuronidase, in activated lymphocytes embedded in Lowicryl K4M resin. We show that this enzyme is present in the rough endoplasmic reticulum, in the Golgi complex, and in vesicular organelles which probably include lysosomes.     

Reaction of human lymphocytes with aggregated IgG columns. Effect on antibody-dependent cytotoxicity and EAC rosette formation.

The origin and life span of long-lived small lymphocytes in the bone marrow of mice have been evaluated by the use of radioautography, scintillation counting, and anti-theta serum. Thymus-deprived BALB/C mice and nude mice had a smaller percentage of long-lived lymphocytes in bone marrow and in thoracic duct lymph than sham-operated or normal littermates. Furthermore, the long-lived lymphocytes in the marrow of nudes have more varied—but generally shorter—life spans than long-lived lymphocytes from mice having a thymus. In thoracic duct lymph of nude mice a more homogeneous long-lived population—according to life span—was found.It was concluded that both long-lived T cells and long-lived B cells are normal residents in the bone marrow. Furthermore, it was concluded that cells of variable life spans comprise the B lymphocyte population: short-lived cells with life spans of 3–5 days and long-lived lymphocytes with life spans of weeks to months.     

Distribution of cytoplasmic vacuoles in blood T and B lymphocytes in two lysosomal disorders.

Distribution of cytoplasmic vacuoles in purified T and B lymphocytes was analyzed in four cases of aspartylglucosaminuria (AGU) and in one case of neuronal ceroid lipofuscinosis (Spielmeyer-Sj?rgren type). In all cases T cells were significantly more vacuolized than B cells. The ultrastructure of the cytoplasmic vacuoles was consistent with the concept of storage lysosomes. The cytoplasmic vacuoles both in T and B cells similar to abnormal lysosomes seen in the visceral organs in these diseases.     

Cyclic endocytic activity and kinetics of lysosomes in Sertoli cells of the rat: a morphometric analysis

Native ferritin was injected into the rete testis of rats, and seminiferous tubules infused with the tracer were collected 6 h later and prepared for electron microscopic analysis. As a result of internalization of the tracer by Sertoli cells, label was found within 12-66% of the secondary lysosomes, depending on the stage of the cycle of the seminiferous epithelium. The Zeiss MOP-3 instrument was used on selected electron microscope photographs to measure a number of morphometric parameters. Applying appropriate formulae and a computerized program, it was possible to determine the absolute numbers of labeled and unlabeled secondary lysosomes per Sertoli cell for each one of the 14 stages of the cycle. Knowing the duration of these stages, it was also possible to evaluate the turnover kinetics and life span of lysosomes for each stage of the cycle. The percentage of ferritin-labeled lysosomes, regarded as an index of the endocytic activity of Sertoli cells, remained low in stages II to VIII, increased abruptly during stage IX, stayed high during stages X to XIV, and decreased to a low level during stage I of the following cycle. Correspondingly, the turnover of secondary lysosomes was relatively slow and their life span relatively long during stages II through VIII, while the turnover of lysosomes was faster and their life span shorter during stages X through XIV-I of the cycle. During stage IX, there was a sharp drop in the number of lysosomes per Sertoli cell associated with a fast rate of disappearance and a remarkably short life span of less than 4 h for the lysosomes. These features, characteristic of stage IX, are explained by the rapid fusion of lysosomes with residual bodies, which are phagocytosed by Sertoli cells at this particular stage of the cycle. The accelerated endocytosis taking place during stages IX through XIV of the cycle may explain the reduction of the surface area of the adluminal plasma membrane of Sertoli cells as well as the reduction in volume of the tubular lumen observed during these stages. Thus, the demonstrated cyclic endocytic activity of Sertoli cells and several other cyclical events taking place within seminiferous tubules correlate well.     

A method for the ultrastructural demonstration of non-specific esterase in human blood and lymphoid tissue

Summary Using the substrate 2-naphthylthiol acetate (NTA), we developed a reproducible method of demonstrating a non-specific esterase while retaining nuclear and cytoplasmic details at the ultrastructural level. The NTA esterase had a distribution and pattern of staining similar to those of esterases demonstrable at the light microscopic level by the -naphthyl acetate or naphthol AS-D acetate esterase reaction.The NTA esterase appeared as intensely electron-dense granules of varying size and shape in the cytoplasm. The granules were most abundant in the cells of the histiomonocytic series. The large number of diffusely scattered granules in the cytoplasm of the histiocytes and monocytes made it possible to separate these cells from other haematopoietic elements. There was usually no direct relationship between the NTA esterase positivity and the amount or the location of lysosomes or mitochondria, although in some histoocytes the granules appeared to the associated with lysosomes. The NTA esterase-positive granules were usually more numerous than lysosomes and were located outside the lysosomal granules. Some of the lymphocytes outside the germinal centres and most of the lymphocytes in the blood showed a punctate positivity in the form of 1–4 electron-dense dots. Plasma cells were usually negative but, in rare cases, contained an occasional single dot-like reaction product similar to that in some of the lymphocytes. Granulocytes were always negative.The method described in this paper can be used effectively for identification and study of human haematopoietic cell lines at the ultrastructural level.