Harumichi Seguchi

Cerium-based cytochemical method for detection of ouabain-sensitive, potassium-dependent p-nitrophenylphosphatase activity at physiological pH.

We have developed a new cytochemical method for detecting the ouabain-sensitive, potassium-dependent p-nitrophenylphosphatase (K-NPPase) activity of the sodium-potassium-activated adenosine triphosphatase (Na-K ATPase) complex. The incubation medium contains p-nitrophenylphosphate (p-NPP) as substrate, cerium chloride as capture agent, Tricine buffer, MgCl2, and KCl. Tricine buffer protected against the medium turbidity caused by non-enzymatic reaction at pH 7.5. Biochemically, the accumulation of p-nitrophenol and phosphate in the reaction precipitate was proportionally related to the enzyme concentration. Ultracytochemically, the reaction products of the K-NPPase activity were localized as fine and uniform electron-dense deposits in the cytoplasmic side of specialized basolateral plasma membranes of cells of kidney distal convoluted tubules, secretory cells of salt gland, and marginal cells of stria vascularis. This method has the advantage of being useful at physiological pH.

Superoxide production at phagosomal cup/phagosome through βI protein kinase C during FcγR-mediated phagocytosis in microglia

Protein kinase C (PKC) plays a prominent role in immune signaling. To elucidate the signal transduction in a respiratory burst and isoform-specific function of PKC during FcγR-mediated phagocytosis, we used live, digital fluorescence imaging of mouse microglial cells expressing GFP-tagged molecules. βI PKC, εPKC, and diacylglycerol kinase (DGK) β dynamically and transiently accumulated around IgG-opsonized beads (BIgG). Moreover, the accumulation of p47phox, an essential cytosolic component of NADPH oxidase and a substrate for βI PKC, at the phagosomal cup/phagosome was apparent during BIgG ingestion. Superoxide (O2−) production was profoundly inhibited by Gö6976, a cPKC inhibitor, and dramatically increased by the DGK inhibitor, R59949. Ultrastructural analysis revealed that BIgG induced O2− production at the phagosome but not at the intracellular granules. We conclude that activation/accumulation of βI PKC is involved in O2− production, and that O2− production is primarily initiated at the phagosomal cup/phagosome. This study also suggests that DGKβ plays a prominent role in regulation of O2− production during FcγR-mediated phagocytosis.

Evaluation of the process for superoxide production by NADPH oxidase in human neutrophils: evidence for cytoplasmic origin of superoxide

Abstract We present an up-to-date insight into the function of NADPH oxidase in human neutrophils, the signalling pathways involved in activation of this enzyme and the process of association of its components with the cytoskeleton. We also discuss the functional implications of morphological studies revealing localization of the sites of NADPH oxidase activity. An original model of the process of superoxide (O2) production in human neutrophils is shown. Organization of NADPH oxidase is associated with several components. Upon stimulation, tri-phox cytosolic components of NADPH oxidase (p40-phox, p47-phox and p67-phox) bind to actin filaments. This process involves other actin-binding proteins, such as cofilin and coronin. Activated protein kinase C, translocated from the plasma membrane, phosphorylates cytosolic components at a scaffold of cytoskeleton. Subsequently, p40-phox, responsible for maintaining the resting state of NADPH oxidase, is separated from other two cytosolic phox proteins following an attachment of the active form of small GTP-binding protein Rac to p67-phox. Cytosolic duo-phox proteins (p47-phox and p67-phox) conjugate with membrane components (gp91-phox, p22-phox and Rap1a) of NADPH oxidase residing within membranes of intracellular compartments. This chain of events triggers production of O2. Then, oxidant-producing intracellular compartments associate with the plasma membrane. Eventually, intracellularly produced O2 is released to the extracellular environment through the orifice formed by fusion of oxidant-producing compartments with the plasma membrane. Intracellular movement of the oxidant-producing compartments may be regulated by myosin light chain kinase. The review emphasizes that functional assembly of NADPH oxidase and, therefore, generation of O2 is accomplished essentially within the intracellular compartments. Upon neutrophil stimulation, intracellularly generated O2 is transported to the plasma membrane to be released and to ensure host defense against infection.

Detection of Oxidant Producing-sites in Glutaraldehyde-fixed Human Neutrophils and Eosinophils Stimulated with Phorbol Myristate Acetate

The aim of the present study was to detect oxidant-producing sites, and to elucidate their dynamic reorganization in human polymorphonuclear leukocytes (PMNs) fixed with glutaraldehyde which preserves cell structure. In biochemical analyses, the detectable O2− generation in unfixed PMNs upon stimulation with phorbol 12-myristate 13-acetate (PMA) in the presence of cytochalasin B was characterized by a lag period of approximately 10 sec followed by O2− production. The maximal rate reached was 3.18±0.07 n mol/min/1×106 cells (mean±S.D.; n=4) after 30 sec of stimulation. PMNs exposed to PMA and cytochalasin B followed by fixation with glutaraldehyde generated O2− without a lag period at a rate of 0.35±0.05 n mol/min/1×106 cells (mean±S.D.) by the addition of NADPH as substrate to the cell suspension. In the cytochemical assays, we employed both cells exposed to PMA and cytochalasin B, and then fixed with glutaraldehyde followed by incubation in the cytochemical reaction medium (pre-fixed cells) and cells incubated in the medium containing PMA and cytochalasin B followed by fixation with glutaraldehyde (post-fixed cells). Oxidant reaction in the pre-fixed cells was detected by the addition of NADPH and FAD to the reaction medium. No oxidant-reaction product was seen in pre-fixed cells stimulated for 10 sec whereas the oxidant reaction was visualized in intracellular compartments of pre-fixed PMNs stimulated for 20 sec. The fact that the pre-fixed PMNs stimulated for 30 sec showed increased numbers of oxidant-producing structures compared to those seen in the pre-fixed cells stimulated for 20 sec, demonstrates that the amount of the reaction product and the number of oxidant-producing intracellular compartments increases between 20 and 30 sec after start of stimulation with PMA. These cytochemical results using the pre-fixed cells coincided with the findings obtained from the biochemical assays in the pre-fixed cells exposed to PMA and cytochalasin B. The oxidant reaction was observed in elongated tubular structures that were arranged in a radial fashion, and were associated with the plasma membrane in the pre-fixed PMNs, whereas post-fixed PMNs exhibited slender spherical or rod-shaped structures of various lengths. The present results indicate that the pre-fixed PMNs can be employed for elucidating the dynamic reorganization of oxidant-producing sites in human PMNs.

Evaluation of neutrophil structure and function by electron microscopy: cytochemical studies

Methods for studying human neutrophils at the ultrastructural level by enzyme cytochemistry and immunocytochemistry are presented. The focus of these methods is on the analysis of the alkaline phosphatase-positive secretory organelle of these cells. These methods provide unique information which, when coupled with biochemical studies, provide for the most complete analysis of neutrophil structure and function.

Ecto-ATPase activity in cerebellum: implication to the function of synaptic transmission

The involvement of ATP in synaptic transmission was examined in synapses on granule cells of the rat cerebellum using ecto-ATPase activity. Reaction product was found in a majority but not all synapses between axodendritic, axoaxonic, and dendrodendritic appositions of granule cells and was associated with extracellular surface of both pre- and postsynaptic membranes. Specificity of the detection was justified by using diethyl pyrocarbonate, specific inhibitor of ecto-ATPase activity. These observations provide direct morphological evidence in support of the view that ATP participates in synaptic transmission and indicate functional heterogeneity of synapses in cerebellum.

Changes in the Ki-67 Labeling Rates of Head and Neck Squamous Cell Carcinomas during Preoperative Radiation Therapy

Immunostaining with Ki-67 monoclonal antibody was performed on frozen sections of biopsy specimens obtained before and during preoperative radiation therapy from 21 patients with head and neck squamous cell carcinoma. The Ki-67 labeling rates before radiation therapy and at radiation doses of 10 and 20 Gy ranged from 21 to 71% (mean: 35.0%), from 7 to 49% (mean: 25.8%) and from 1 to 44% (mean: 14.8%), respectively. One of the 2 patients whose tumors showing Ki-67 labeling rates of greater than 48% (mean +1 SD) before radiation therapy suffered local relapse shortly after the treatment. Moreover, tumors with rapidly decreased Ki-67 labeling rates (lower than 3%) at radiation doses of 20 Gy were related to poor clinical outcome: 4 out of 6 patients whose tumors showed Ki-67 labeling rates below 3% (mean -1 SD) at 20 Gy of irradiation had local relapses or showed distant metastases. These findings indicate that immunostaining with Ki-67 monoclonal antibody of biopsy specimens of head and neck squamous cell carcinoma, before and during radiation therapy, is very useful in assessing the clinical outcome of the patients.

Mitochondrial transmembrane potential is diminished in phorbol myristate acetate-stimulated peritoneal resident macrophages isolated from wild-type mice, but not in those from gp91-phox-deficient mice

Macrophages produce superoxide (O2−) during phagocytosis or upon stimulation with a variety of agents including phorbol myristate acetate (PMA) through the activation of NADPH oxidase, and the formed O2− is converted to other reactive oxygen species (ROS) such as hydrogen peroxide (H2O2). The aim of the present study was to elucidate the effect of the intracellularly produced ROS on mitochondrial transmembrane potential (MTP) in mouse (C57BL/6) peritoneal resident macrophages stimulated with PMA. Using a fluorescent dye, succinimidyl ester of dichlorodihydrofluorescein (H2DCFDA), O2− was visualized in intracellular compartments in a certain subpopulation of macrophages isolated from wild-type mice. Cells deficient in gp91-phox, one of the membrane components of NADPH oxidase, were negative for the fluorescence. When cells were loaded with both H2DCFDA and MitoCapture, a fluorescent dye for mitochondria, mitochondrial fluorescence was diminished in O2−-producing cells, but not in O2−-deficient cells. Flow cytometry also revealed the decrease of mitochondrial fluorescence in wild-type cells, but not in gp91-phox-deficient cells. The loss of mitochondrial fluorescence was prevented by microinjection of catalase into cells. The present findings demonstrate that MTP is diminished by ROS, including the H2O2 dismutated from O2−, produced intracellularly by activation of the NADPH oxidase in mouse peritoneal resident macrophages stimulated with PMA.

ML-7 inhibits exocytosis of superoxide-producing intracellular compartments in human neutrophils stimulated with phorbol myristate acetate in a myosin light chain kinase-independent manner

ML-7, (5-iodonaphthalene-1-sulfonyl) homopiperazine, is commonly employed as a myosin light chain kinase (MLCK) inhibitor. In the present study, we demonstrated that ML-7 affects the superoxide (O2−)-producing system of human neutrophils in an MLCK-independent manner. Human neutrophils were stimulated with phorbol myristate acetate (PMA), which does not activate MLCK. ML-7 inhibited extracellular release, but not intracellular production of O2− in the stimulated cells. Fluorescence microscopy revealed the generation of O2− at intracellular compartments in the stimulated cells exposed to ML-7. At the electron microscopic level, the reaction product of NADPH oxidase activity was found in intracellular compartments. ML-7 strongly inhibited the association of the oxidant-producing intracellular compartments with the plasma membrane. Furthermore, the upregulation of alkaline phosphatase activity, a marker enzyme of the oxidant-producing intracellular compartments, was also inhibited by ML-7. These findings indicate that ML-7 inhibits the fusion of the oxidant-producing intracellular compartments to the plasma membrane resulting in the inhibition of the extracellular release of O2− in PMA-stimulated human neutrophils in an MLCK-independent manner.

Amyotrophic lateral sclerosis and parkinsonism in Papua, Indonesia: 2001–2012 survey results

Objective Only one previous follow-up study of amyotrophic lateral sclerosis (ALS) and parkinsonism in Papua, Indonesia has been carried out since a survey undertaken in 1962–1981 by Gajdusek and colleagues. Therefore, to clarify the clinical epidemiology of ALS and parkinsonism in the southern coastal region of Papua, the clinical characteristics and prevalence of the diseases in this region were examined and assessed. Methods Cases of ALS and parkinsonism were clinically examined during a 2001–2012 survey in Bade and other villages along the Ia, Edera, Dumut and Obaa rivers in Papua, Indonesia. Possible, probable and definite ALS was diagnosed clinically by certified neurologists based on El Escorial criteria. The criteria for a diagnosis of parkinsonism were the presence of at least two of the four following signs: tremor, rigidity, bradykinesia and postural impairment with a progressive course. Results During the survey, 46 cases of ALS and/or parkinsonism were diagnosed within a population range of 7000 (2001–2002) to 13 900 (2007–2012). The 46 cases consisted of 17 probable-definite cases of ALS, including three with cognitive impairment (CI), 13 cases of overlapping possible, probable or definite ALS and parkinsonism, including five with CI, and 16 cases of parkinsonism, including one with CI. The crude point prevalence rate of pure ALS was estimated to be at least 73 (95% CI 0 to 156) to 133 (27 to 240)/100 000 people and that of overlapping ALS and parkinsonism at least 53 (0 to 126) to 98 (2 to 193)/100 000 in 2007, or 2010 in some regions. Conclusions While the prevalence of ALS in Papua has decreased over the past ∼30–35 years, it remains higher than the global average. There was a high prevalence of overlapping ALS, parkinsonism and CI, which has also been previously reported in Guam and Kii.