Stress-induced ceramide generation and apoptosis via the phosphorylation and activation of nSMase1 by JNK signaling

Neutral sphingomyelinase (nSMase) activation in response to environmental stress or inflammatory cytokine stimuli generates the second messenger ceramide, which mediates the stress-induced apoptosis. However, the signaling pathways and activation mechanism underlying this process have yet to be elucidated. Here we show that the phosphorylation of nSMase1 (sphingomyelin phosphodiesterase 2, SMPD2) by c-Jun N-terminal kinase (JNK) signaling stimulates ceramide generation and apoptosis and provide evidence for a signaling mechanism that integrates stress- and cytokine-activated apoptosis in vertebrate cells. An nSMase1 was identified as a JNK substrate, and the phosphorylation site responsible for its effects on stress and cytokine induction was Ser-270. In zebrafish cells, the substitution of Ser-270 for alanine blocked the phosphorylation and activation of nSMase1, whereas the substitution of Ser-270 for negatively charged glutamic acid mimicked the effect of phosphorylation. The JNK inhibitor SP600125 blocked the phosphorylation and activation of nSMase1, which in turn blocked ceramide signaling and apoptosis. A variety of stress conditions, including heat shock, UV exposure, hydrogen peroxide treatment, and anti-Fas antibody stimulation, led to the phosphorylation of nSMase1, activated nSMase1, and induced ceramide generation and apoptosis in zebrafish embryonic ZE and human Jurkat T cells. In addition, the depletion of MAPK8/9 or SMPD2 by RNAi knockdown decreased ceramide generation and stress- and cytokine-induced apoptosis in Jurkat cells. Therefore the phosphorylation of nSMase1 is a pivotal step in JNK signaling, which leads to ceramide generation and apoptosis under stress conditions and in response to cytokine stimulation. nSMase1 has a common central role in ceramide signaling during the stress and cytokine responses and apoptosis.

Immune responses to live and inactivated Nocardia seriolae and protective effect of recombinant interferon gamma (rIFN γ) against nocardiosis in ginbuna crucian carp, Carassius auratus langsdorfii

Looking into the fact that substantial mortality and morbidity is associated with intracellular Gram +ve bacterium, Nocardia seriolae infection, an effective vaccine against this pathogen is necessary to control the significant losses in aquaculture practices. Therefore, an attempt was made to evaluate the effect of live (sub-lethal) and inactivated (antigenic form) N. seriolae on cellular and humoral immunity in ginbuna crucian carp, Carassius auratus langsdorfii as well as the therapeutic potency of recombinant interferon gamma (rIFN γ) against N. seriolae infection. Effect of live and inactivated N. seriolae immunisation on the proliferation of CD4(+) T cells, CD8α(+) T cells and surface Ig M(+) cells in peripheral blood leucocytes, spleen, head kidney and trunk kidney of ginbuna was studied after 1st, 3rd, 7th, 15th and 30th day post immunisation. The percentage of CD8α(+) T cells in spleen and head kidney of ginbuna was significantly higher at 3rd day post immunisation. Similarly, surface Ig M(+) cells level was found to increase in both live and inactivated N. seriolae immunised groups. On the contrary, high percentage of CD4(+) T cells was observed in live N. seriolae immunised group in both the head and trunk kidneys at 30th day post immunisation. The humoral immune response to live and inactivated N. seriolae immunised ginbuna showed high antibody titre at 15th day post immunisation but the level declined subsequently in both the immunised groups. On challenge with virulent N. seriolae (1.2 × 10(8) CFU/ml), the relative percent survival was 62.5 and 75 in live and inactivated N. seriolae immunised groups, respectively. Furthermore, we have also studied the therapeutic potency of rIFN γ and found the possible involvement of IFN γ in resistance mechanism in fish. Administration of rIFN γ into ginbuna (at 10 μg/fish) one day before challenge study was found to protect ginbuna. The relative percent survival of ginbuna was 43.75 and 60 when challenged with 2 different doses of N. seriolae i.e., 1.2 × 10(8) CFU/ml and 5 × 10(7) CFU/ml, respectively. In summary, this study indicates that both forms of N. seriolae immunisation as well as rIFN γ indeed elicit an effective protective immunity which will help in designing suitable vaccine and/or adjunct therapy against N. seriolae infection in fish.

Antiviral protection mechanisms mediated by ginbuna crucian carp interferon gamma isoforms 1 and 2 through two distinct interferon gamma-receptors

Fish genomes possess three type II interferon (IFN) genes, ifnγ1, ifnγ2 and ifnγ-related (ifnγrel). The IFNγ-dependent STAT signalling pathway found in humans and mice had not been characterized in fish previously. To identify the antiviral functions and signalling pathways of the type II IFN system in fish, we purified the ifnγ1, ifnγ2 and ifnγrel proteins of ginbuna crucian carp expressed in bacteria and found them to elicit high antiviral activities against crucian carp hematopoietic necrosis virus. We also cloned two distinct ifnγ receptor alpha chain (ifngr1) isoforms, 1 and 2, and stably expressed them in HeLa cells by transfecting the cells with ifngr1-1 or ifngr1-2 cDNA. When receptor transfectants were treated with the ligands in a one-ligand-one-receptor manner (ifnγ1 and ifngr1-2 or ifnγ2 and ifngr1-1), the stat1 protein was phosphorylated at both serine-727 and tyrosine-701 residues. Gel shift mobility analysis and reporter assay clearly showed that the specific ligand-receptor interaction resulted in the binding of the stat1 protein to the GAS element and enhanced transcription. Therefore, the actions of ifnγ1 and ifnγ2 were found to be mediated by a specific receptor for each signalling pathway via a stat1-dependent mechanism.

Cytotoxic T cells in teleost fish

The presence of antigen-specific cytotoxic T cells has been suggested in a number of in vivo and in vitro studies in fish. Acute allograft rejection with an accelerated response on second-set grafts and the presence of graft-versus-host reaction (GVHR) has been reported in teleost. Alloantigen- and virus-specific cytotoxicity has also been demonstrated in ex vivo studies in ginbuna and rainbow trout. In addition, alloantigen-specific cytotoxic T cell clones have been produced in cultures initiated with peripheral blood leukocytes (PBL) from an alloantigen-immunized channel catfish. Over the last decade several fish genomes have been sequenced and genetic information is rapidly accumulating. Thanks to these genome data bases and EST analysis, mRNA expression of T cell surface marker genes in alloantigen- or virus-specific effector cells has been reported in some fish species, e.g. TCR α or β and CD8α in ginbuna and rainbow trout, and TCR α, β or γ in channel catfish. These findings suggest the presence of CD8(+) cytotoxic T lymphocyte (CTL) in fish similar to those of higher vertebrates. Recently, monoclonal antibodies against CD8α and CD4 antigens have been produced in some fish species. Investigation on the characteristics of CTL and cell-mediated immune mechanisms is now possible at defined T cell subsets, although identification of T cell subset is limited in a few fish species at present. In this review, we describe the recent progress in this field focusing on cells involved in antigen specific cytotoxicity.

Kinetics of CD4+ and CD8alpha+ T-cell subsets in graft-versus-host reaction (GVHR) in ginbuna crucian carp Carassius auratus langsdorfii

We have previously demonstrated the presence of graft-versus-host reaction (GVHR) in fish employing a model system of clonal triploid ginbuna and tetraploid ginbuna-goldfish hybrids. To elucidate the role of CD8alpha+ T cells in the induction of GVHR, we investigate the kinetics of CD4+ and CD8+ T-cell subsets in GVHR along with the pathological changes associated with GVH disease (GVHD) in ginbuna. GVHR was not induced with a leukocyte fraction lacking CD8alpha+ T cells separated by magnetic cell sorting. Ploidy and immunofluorescence analysis revealed that CD4+ and CD8alpha+ T cells from sensitized donors greatly increased in the host trunk kidney, constituting more than 80% of total cells 1-2 weeks after donor cell injection, while those from non-sensitized donors constituted less than 50% of cells present. The increase of CD4+ T cells was greater and more rapid than that of CD8alpha+ T cells. The number of donor CD4+ and CD8alpha+ T cells was highest in trunk kidney followed by spleen. Increases in donor CD4+ and CD8alpha+ T cells were also found in liver and PBL, although the percentages were not as high. Pathologic changes similar to those in human and murine acute GVHD were observed in the lymphoid organs as well as target organs such as skin, liver and intestine, including the destruction of cells and tissues and massive leukocyte infiltration. The pathologic changes became more severe with the increase of CD8alpha+ T cells. These results suggest that donor-derived CD8alpha+ T cells play essential roles for the induction of acute GVHR/D in teleosts as in mammals.

Alloantigen-specific killing is mediated by CD8-positive T cells in fish

CD8-positive (CD8(+)) cytotoxic T lymphocytes (CTL) have antigen-specific cytotoxic activity. In fish, however, CTL expressing CD8 on their cell surface have not been identified. In order to characterize the cells involved in specific cell-mediated cytotoxicity in teleosts, we separated and sorted ginbuna kidney leucocytes into CD8alpha(+), CD4(+) and surface IgM (sIgM)(+) cells by magnetic activated cell sorting using monoclonal antibodies and examined their cytotoxic activities. Effector donor ginbuna (OB1 clone) were sensitized by allografting scales from S3N clone fish followed by injection of an allogeneic cell line (CFS) derived from S3N fish. In cytotoxic assays, target cells were labeled with CFSE and cytotoxicity was calculated based on the number of viable target cells using flow cytometry. CD8alpha(+) cells from sensitized OB1 fish showed relatively high cytotoxicity against CFS cells (immunogen) but not against allogeneic CFK cells (third party) nor isogeneic CFO cells. Pre-sensitized sIgM(+) cells exhibited cytotoxicity against not only CFS cells but also CFK cells. However, CD4(+) or CD8alpha(-) CD4(-)sIgM(-) cells as well as cells from non-sensitized fish did not show any significant cytotoxic activity. These results suggest that CD8alpha(+) cells in fish have characteristics similar to those of CTL in mammals, and that the sIgM(+) cells include NK-like cells which non-specifically killed the target cells.

Trisomy 8 and urogenital malformation in the ACI-rat

ACI-rats are considered as a model for studying urogenital abnormalities. In order to recognise cytogenetic changes related to these abnormalities 50 male ACI/Seg rats were examined by means of gross macroscopic, histological, and karyotypical investigations. In six of the examined animals (12%) unilateral agenesis of the kidney and ipsilateral hypoplasia of the testes and seminal vesicles were observed. Isochromosome 8 and trisomy 8 (i8, +8) were observed in 26.5% of karyotypes from the animals with kidney agenesis. Chromosome heteromorphisms such as 1p+, 3p+, 11p+, 12p+ were found in animals with and without apparent pathology. Because of the similarity between the phenotypical changes found in ACI-rats and in patients with familial renal agenesis (Potter's syndrome) and hereditary renal agenesis and aplasia (HRA), rat and human chromosomes associated with manifested renal malformations were examined by comparative cytogenetics and gene mapping.

Hemichrome formation observed in human haemoglobin A under various buffer conditions

AIM

To observe hemichrome formation in human haemoglobin A under various buffer conditions.

METHOD

Hemichrome formation of human oxyhaemoglobin A (HbO2) was studied spectrophotometrically in 0.1 m buffer at various temperatures and pH values.

RESULTS

Following autoxidation in ferrous HbO2, it was evident that formation of hemichrome, which tends to precipitate, occurred at various stages during the course of the autoxidation reaction namely at initial, intermediate or final stages, depending on temperature and pH of the solution. By varying temperature of the solution from 35 to 55 degrees C and pH from 4.5 to 10.5, it is shown here that HbO2 exhibits high susceptibility for hemichrome formation and its occurrence is a function of pH, temperature and progress of autoxidation of HbO2. Unlike HbO2 and its separated haemoglobin chains, monomeric bovine heart myoglobin (MbO2) did not easily form hemichrome.

CONCLUSION

These findings provide a clue on the crucial role of haemoglobin molecule for senescent cell recognition or homeostasis in the blood circulation.

Micro X-ray computed tomography analysis for the evaluation of asymmetrical condylar growth in the rat

OBJECTIVES

To investigate the influence of forced lateral bite on mandibular growth, micro X-ray computed tomography (CT) was used for the purpose evaluating condylar cartilage and cancellous bone formation in 10 male Wister rats (3 weeks of age). SETTINGS AND SAMPLE POPULATION: The rats were divided into two groups--experimental and control. In experimental group, an inclined crown was cemented onto the maxillary incisors to produce 2.5 mm shift toward the left side during mastication. Right-left differences in whole mandibular length, mandibular height, condylar size, trabecular structure of the condylar head and three-dimensional (3-D) finite element analysis were assessed using 3-D images reconstructed from micro X-ray CT scans when the mice had reached 21 weeks.

MEASUREMENTS AND RESULTS

Asymmetrical growth was found in the experimental group, in which the left condylar head became thicker and shorter than the right condylar head during development. When comparing the left and right condyles of the experimental animals, histomorphometric analysis from micro X-ray CT showed that the bone volume (BV) of the cancellous bone, the surface area of the cancellous bone (BS), the BS/BV ratio, the BV fraction (BV/TV), and the trabecular thickness and trabecular number were less for the right condyle than for the left condyle.

CONCLUSIONS

These findings suggested that artificial changes in the mastication do influence the growth of condylar head, condylar bone trabecular structure, and mineralization.

Measurement of mechanical strain on mandibular surface with mastication robot: influence of muscle loading direction and magnitude

OBJECTIVES

To investigate the mechanical effects of mastication on the mandible, we developed computational controlled mastication robot system with human dry skull and analyzed the strain distribution on the mandibular bone surface.

DESIGN

In the mastication robot, the mandible was suspended by eight wires, which simulated masticatory muscles. A non-linear spring damper generated viscoelastic properties, and tension sensors for simulation of jaw reflection to avoid unusual biting force were applied as a biological feedback mechanism. By using this robot system, various patterns of muscle loading (change of wire direction and magnitude) were performed.

RESULTS

From the results, significant differences in the amount of principal strain and its distribution were demonstrated in each condition (ANOVA, post hoc test, and p < 0.05). The value of maximum principal strain ranged from 79.66 x 10(-6) [at anterior border of ramus (Buccal side), 128 N] to -1.42 x 10(-6) [at foramen mentale (Buccal side), 32 N].

CONCLUSION

These results suggested that the muscle loading generated the mechanical strain on the mandibular bone surface and it was affected by the changes in loading direction and magnitude.

Renal blood flow measurement with contrast-enhanced harmonic ultrasonography: evaluation of dopamine-induced changes in renal cortical perfusion in humans

BACKGROUND

An accessible non-invasive method for evaluating renal regional blood flow in real time is highly desirable in the clinical setting. Recent progress in ultrasonography with microbubble contrast has allowed quantification of regional blood flow in animal models.

AIMS

Goal ofthis study was to establish a convenient contrast--enhanced harmonic ultrasonography (CEHU) method for evaluating renal cortical blood flow in humans.

METHODS

We carried out intermittent second harmonic imaging in 9 healthy volunteers. Pulse interval was progressively decreased from 4 s - 0.2 s during continuous venous infusion of the microbubble contrast agent.

RESULTS

Pulse interval versus CEHU-derived acoustic intensity plots provided microbubble velocity (MV) and fractional vascular volume (FVV) during renal cortical perfusion in humans. Low-dose dopamine infusion (2 microg/min/kg) resulted in a significant increase in MV which correlated well with the increase in total renal blood flow (RBF) determined by a conventional study of p-aminohippurate clearance (C(PAH)) (r = 0.956, p < 0.0001). Although FVV was not significantly increased, alterations in CEHU-derived renal cortical blood flow calculated by the products of MV and FVV were also correlated with alterations in total RBF (r = 0.969, p < 0.0001). Thus, low-dose dopamine infusion increases renal cortical blood flow observed in CEHU, mainly by increasing MV.

CONCLUSIONS

The present study shows that renal cortical blood flow in humans can be measured non-invasively by CEHU and that CEHU can be used for quantitatively evaluating changes induced by a therapeutic agent such as dopamine in flow velocity and in FVV.

Convenient synthesis of aliphatic polyesters by distannoxane-catalyzed polycondensation

A convenient synthesis of aliphatic polyesters by the distannoxane-catalyzed polycondensation of aliphatic dicarboxylic acids and aliphatic diols in solvents under azeotropic conditions was developed. To determine the optimum conditions for polycondensation of succinic acid with 1,4-butandiol, the effect of various types of catalyst and their concentration was investigated. By choosing the appropriate solvent, the polymerization was made to proceed in a two-phase system of solvent and molten polymer, and in the presence of 0.001 mol % of 1-chloro-3-hydroxy-1,1,3,3-tetrabutyldistannoxane (CHTD), poly(butylene succinate) (PBS) with a weight-average molecular weight of 277,000 was obtained. This method was then successfully applied to the synthesis of various aliphatic polyesters, such as poly(ethylene succinate), poly(1,4-cyclohexanedimethylene succinate), and poly(ethylene sebacate).

Evaluation of PCR primers to screen for Streptococcus pneumoniae isolates and beta-lactam resistance, and to detect common macrolide resistance determinants

Pneumococcal isolates (n = 148) from various countries (mostly from the USA) were tested by a primer set for PCR. Thirty-eight (86.4%) of the 44 penicillin G-susceptible isolates (MIC < or = 0.06 mg/L) had unaltered pbps, while six isolates (13.6%) had either one or two alterations in pbps. Of 47 penicillin G-resistant strains (MIC > or = 2 mg/L), 41 isolates (87.2%) had all three pbps altered, six isolates (12.8%) had altered pbp1a + 2x. Various combinations of altered pbp were seen in penicillin G-intermediate isolates. Prevalence of macrolide resistance genes mef(A) and erm(B) in isolates was clearly reflected by their MICs. All isolates were positive for lytA. The primers were useful for screening for Streptococcus pneumoniae and beta-lactam resistance, and for detection of common macrolide resistance determinants.

Angiotensin II signaling and HB-EGF shedding via metalloproteinase in glomerular mesangial cells

BACKGROUND

Angiotensin II (Ang II) has been implicated in the development of glomerulosclerosis by stimulating fibronectin (FN) synthesis. The processing and release of heparin binding-endothelin growth factor (HB-EGF) are activated by protein kinase C (PKC) and Ca2+ signaling. We studied the roles of HB-EGF and endothelial growth factor (EGF) receptor (EGFR) in Ang II-induced FN expression using mesangial cells.

METHODS

Mesangial cells were prepared from mouse kidneys by the explant method and cells were used at passages 4 and 5.

RESULTS

Ang II stimulated FN mRNA levels dose-dependently with a maximal increase (3.4-fold) after 12 hours of incubation. This action was completely inhibited by PKC inhibitors and slightly blocked by Ca2+ chelating agents. FN mRNA accumulation by Ang II was abolished by tyrosine kinase inhibitors, a specific inhibitor for EGFR (AG1478) and extracellular signal-regulated kinase (ERK) inactivation. Addition of neutralizing anti-HB-EGF antibody, as well as pretreatment with heparin or the metalloproteinase inhibitor batimastat abolished induction of FN expression by Ang II. In mesangial cells stably transfected with a chimeric construct containing HB-EGF and alkaline phosphatase (ALP) genes, ALP activity in incubation medium was rapidly increased by Ang II (1.7-fold at 0.5 min) and reached a 4.1-fold increase at two minutes. Ang II phosphorylated EGFR (maximal at 2 min) and ERK (maximal at 8 min) in a PKC- and metalloproteinase-dependent manner. Ang II stimulated the expression and release of transforming growth factor-beta (TGF-beta) via EGFR-mediated signaling, and the released TGF-beta also contributed to Ang II-mediated FN expression via EGFR transactivation.

CONCLUSIONS

Ang II-mediated FN expression was regulated by autocrine effects of HB-EGF and TGF-beta, suggesting a novel paradigm for cross-talk between Ang II and growth factor receptor signaling pathways.

Immunolocalization of vacuolar-type H+-ATPase, cathepsin K, matrix metalloproteinase-9, and receptor activator of NFkappaB ligand in odontoclasts during physiological root resorption of human deciduous teeth

To investigate the cellular mechanisms of physiological root resorption in human deciduous teeth, the authors examined the immunocytochemical localization of vacuolar-type H+-ATPase, a lysosomal cysteine proteinase, cathepsin K, matrix metalloproteinase-9 (MMP-9), and receptor activator of NFKB ligand (RANKL) in odontoclasts. H+-ATPase, cathepsin K, and MMP-9 are the most important enzymes for decalcification of apatite crystals and degradation of type-I collagen. In addition, RANKL is one of the key regulatory molecules in osteoclast formation and functions. Odontoclasts developed extensive ruffled borders and clear zones apposed to the resorbing root dentine surfaces. On immunoelectron microscopy, the expression of vacuolar-type H+-ATPase was detected along the limiting membranes of pale vacuoles and the ruffled border membranes of odontoclasts. Cathepsin K in odontoclasts was localized within pale vacuoles, lysosomes, the extracellular canals of ruffled borders, and the underlying resorbing dentine surfaces. MMP-9 localization in odontoclasts was similar to those of cathepsin K. RANKL was detected in both mononuclear stromal cells and odontoclasts located on resorbing dentine surfaces. These results suggest that (1) odontoclasts are directly involved in decalcification of apatite crystals by active extrusion of proton ions mediated by H+-ATPase and (2) extracellular degradation of dentine type-I collagen by both cathepsin K and MMP-9, and (3) odontoclast differentiation and activity are regulated, at least in part, by RANKL, possibly produced by mononuclear stromal cells and odontoclasts themselves in the resorbing tissues. Thus, the cellular mechanisms of physiological root resorption appear to be quite similar to those of osteoclastic bone resorption.