Extracellular α-synuclein impairs sphingosine 1-phosphate receptor type 3 (S1PR3)-regulated lysosomal delivery of cathepsin D in HeLa cells

α-Synuclein (α-Syn)-positive intracellular fibrillar protein deposits, known as Lewy bodies, are thought to be involved in the pathogenesis of Parkinson's disease (PD). Although recent lines of evidence suggested that extracellular α-Syn secreted from pathogenic neurons contributes to the propagation of PD pathology, the precise mechanism of action remains unclear. We have reported that extracellular α-Syn caused sphingosine 1-phosphate (S1P) receptor type 1 (S1PR1) uncoupled from Gi and inhibited downstream G-protein signaling in SH-SY5Y cells, although its patho/physiological role remains to be clarified. Here we show that extracellular α-Syn caused S1P receptor type 3 (S1PR3) uncoupled from G protein in HeLa cells. Further studies indicated that α-Syn treatment reduced cathepsin D activity while enhancing the secretion of immature pro-cathepsin D into cell culture medium, suggesting that lysosomal delivery of cathepsin D was disturbed. Actually, extracellular α-Syn attenuated the retrograde trafficking of insulin-like growth factor-II/mannose 6-phosphate (IGF-II/M6P) receptor, which is under the regulation of S1PR3. These findings shed light on the understanding of dissemination of the PD pathology, that is, the mechanism underlying how extracellular α-Syn secreted from pathogenic cells causes lysosomal dysfunction of the neighboring healthy cells, leading to propagation of the disease.

Features and mechanisms of propofol-induced protein kinase C (PKC) translocation and activation in living cells

Background and purpose: In this study, we aimed to elucidate the action mechanisms of propofol, particularly those underlying propofol-induced protein kinase C (PKC) translocation. Experimental approach: Various PKCs fused with green fluorescent protein (PKC-GFP) or other GFP-fused proteins were expressed in HeLa cells, and their propofol-induced dynamics were observed using confocal laser scanning microscopy. Propofol-induced PKC activation in cells was estimated using the C kinase activity receptor (CKAR), an indicator of intracellular PKC activation. We also examined PKC translocation using isomers and derivatives of propofol to identify the crucial structural motifs involved in this process. Key results: Propofol persistently translocated PKCα conventional PKCs and PKCδ from novel PKCs (nPKCs) to the plasma membrane (PM). Propofol translocated PKCδ and PKCη of nPKCs to the Golgi apparatus and endoplasmic reticulum, respectively. Propofol also induced the nuclear translocation of PKCζ of atypical PKCs or proteins other than PKCs, such that the protein concentration inside and outside the nucleus became uniform. CKAR analysis revealed that propofol activated PKC in the PM and Golgi apparatus. Moreover, tests using isomers and derivatives of propofol predicted that the structural motifs important for the induction of PKC and nuclear translocation are different. Conclusion and implications: Propofol induced the subtype-specific intracellular translocation of PKCs and activated PKCs. Additionally, propofol induced the nuclear translocation of PKCs and other proteins, probably by altering the permeability of the nuclear envelope. Interestingly, propofol-induced PKC and nuclear translocation may occur via different mechanisms. Our findings provide insights into the action mechanisms of propofol.

Constitutive activation of S1P receptors at the trans-Golgi network is required for surface transport carrier formation

The importance of the G-protein βγ subunits in the regulation of cargo transport from the trans-Golgi network (TGN) to the plasma membrane (PM) is well accepted; however, the molecular mechanism underlying the G-protein activation at the TGN remains unclear. We show here that sphingosine 1-phosphate (S1P) receptors at the PM were trafficked to the TGN in response to a surface transport cargo, temperature-sensitive vesicular stomatitis virus glycoprotein tagged with green fluorescent protein accumulation in the Golgi. The receptor internalization occurred in an S1P-independent manner but required phosphorylation by G-protein receptor kinase 2 and β-arrestin association before internalization. Continuously activated S1P receptors in a manner dependent on S1P at the TGN kept transmitting G-protein signals including the βγ subunits supply necessary for transport carrier formation at the TGN destined for the PM.

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S1P receptors traffic from the PM to Golgi in a surface cargo-dependent manner

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S1PR trafficking follows GRK2-dependent phosphorylation and β-arrestin binding

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S1PRs at the Golgi are continuously activated by S1P while sending G-protein signals

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S1PR/Gβγ signals at the Golgi are indispensable for surface transport carrier formation

Identification of novel OCRL isoforms associated with phenotypic differences between Dent disease-2 and Lowe syndrome

BACKGROUND

Although Lowe syndrome and Dent disease-2 are both caused by OCRL mutations, their clinical severities differ substantially, and their molecular mechanisms remain unclear. Truncating mutations in OCRL exons 1 through 7 lead to Dent disease-2, whereas those in exons 8 through 24 lead to Lowe syndrome. Herein, we identified the mechanism underlying the action of novel OCRL protein isoforms.

METHODS

mRNA samples extracted from cultured urine-derived cells from a healthy control and the Dent disease-2 patient were examined to detect the 5' end of the OCRL isoform. For protein expression and functional analysis, vectors containing (1) the full-length OCRL transcripts, (2) the isoform transcripts, and (3) transcripts with truncating mutations detected in Lowe syndrome and Dent disease-2 patients were transfected into HeLa cells.

RESULTS

We successfully cloned the novel isoform transcripts from OCRL exons 6-24, including the translation-initiation codons present in exon 8. In vitro protein-expression analysis detected proteins of two different sizes (105 and 80 kDa) translated from full-length OCRL, whereas only one protein (80 kDa) was found from the isoform and Dent disease-2 variants. No protein expression was observed for the Lowe syndrome variants. The isoform enzyme activity was equivalent to that of full-length OCRL; the Dent disease-2 variants retained > 50% enzyme activity, whereas the Lowe syndrome variants retained < 20% activity.

CONCLUSIONS

We elucidated the molecular mechanism underlying the two different phenotypes in OCRL-related diseases; the functional OCRL isoform translated starting at exon 8 was associated with this mechanism.

Involvement of Receptor-Mediated S1P Signaling in EGF-Induced Macropinocytosis in COS7 Cells

Macropinocytosis is a highly conserved cellular process of endocytosis by which extracellular fluid and nutrients are taken up into cells through large, heterogeneous vesicles known as macropinosomes. Growth factors such as epidermal growth factor (EGF) can induce macropinocytosis in many types of cells, although precise mechanism underlying EGF-induced macropinocytosis remains unclear. In the present studies we have shown the involvement of S1P signaling in EGF-induced macropinocytosis in COS7 cells. First, EGF-induced macropinocytosis was strongly impaired in sphingosine kinase isozymes, SphK1 or SphK2-depleted cells, which was completely rescued by the expression of the corresponding wild-type isozyme but not the catalytically inactive one, suggesting the involvement of sphingosine 1-phosphate (S1P) in this phenomenon. Next, we observed that EGF-induced macropinocytosis was strongly inhibited in S1P type 1 receptor (S1P1R)-knockdown cells, implying involvement of S1P1R in this event. Furthermore, we could successfully demonstrate EGF-induced trans-activation of S1P1R using one-molecular fluorescence resonance energy transfer (FRET) technique. Moreover, for EGF-induced Rac1 activation, a step essential to F-actin formation and subsequent macropinocytosis, S1P signaling is required for its full activation, as judged by FRET analysis. These findings indicate that growth factors such as EGF utilize receptor-mediated S1P signaling for the regulation of macropinocytosis to fulfil vital cell activity.

Activation of atypical protein kinase C by sphingosine 1-phosphate revealed by an aPKC-specific activity reporter

Atypical protein kinase C (aPKC) isozymes are unique in the PKC superfamily in that they are not regulated by the lipid second messenger diacylglycerol, which has led to speculation about whether a different second messenger acutely controls their function. Here, using a genetically encoded reporter that we designed, aPKC-specific C kinase activity reporter (aCKAR), we found that the lipid mediator sphingosine 1-phosphate (S1P) promoted the cellular activity of aPKC. Intracellular S1P directly bound to the purified kinase domain of aPKC and relieved autoinhibitory constraints, thereby activating the kinase. In silico studies identified potential binding sites on the kinase domain, one of which was validated biochemically. In HeLa cells, S1P-dependent activation of aPKC suppressed apoptosis. Together, our findings identify a previously undescribed molecular mechanism of aPKC regulation, a molecular target for S1P in cell survival regulation, and a tool to further explore the biochemical and biological functions of aPKC.

Essential Role of Sphingosine Kinase 2 in the Regulation of Cargo Contents in the Exosomes from K562 Cells

Sphingosine 1-phosphate (S1P) is a bioactive phosphorylated product of sphingosine catalyzed by sphingosine kinase (SphK) and implicated in diverse cellular functions including vesicular trafficking. In the present study we have shown the importance of one of the subtypes of SphK, SphK2, in the regulation of cargo content in exosomes released from human myeloid leukemia K562 cells. First, SphK2 has been shown to localize with N-Rh-PE-positive late endosomes in the cells. Next, siRNA-mediated knockdown of Sphk2 but not SphK1 resulted in a reduction of cargo content in purified exosomes. The involvement of SphK2 in this phenomenon was further investigated by pharmacological approaches. When cells were treated with N,N-dimethylsphingosine (DMS), one of the most frequently used inhibitors for SphK, cargo contents in purified exosomes were enhanced unexpectedly. Finally, it has been shown that DMS has a potency to stimulate SphK2 activity depending on the substrate sphingosine- and the inhibitor-doses as estimated by in vitro assay systems using a purified SphK2. These findings suggest that SphK2/S1P signaling plays an important role in the regulation of cargo content in exosomes in K562 cells.

Extracellular α-synuclein drives sphingosine 1-phosphate receptor subtype 1 out of lipid rafts, leading to impaired inhibitory G-protein signaling

α-Synuclein (α-Syn)-positive intracytoplasmic inclusions, known as Lewy bodies, are thought to be involved in the pathogenesis of Lewy body diseases, such as Parkinson's disease (PD). Although growing evidence suggests that cell-to-cell transmission of α-Syn is associated with the progression of PD and that extracellular α-Syn promotes formation of inclusion bodies, its precise mechanism of action in the extracellular space remains unclear. Here, as indicated by both conventional fractionation techniques and FRET-based protein-protein interaction analysis, we demonstrate that extracellular α-Syn causes expulsion of sphingosine 1-phosphate receptor subtype 1 (S1P₁R) from the lipid raft fractions. S1P₁R regulates vesicular trafficking, and its expulsion involved α-Syn binding to membrane-surface gangliosides. Consequently, the S1P₁R became refractory to S1P stimulation required for activating inhibitory G-protein (G_i) in the plasma membranes. Moreover, the extracellular α-Syn also induced uncoupling of the S1P₁R on internal vesicles, resulting in the reduced amount of CD63 molecule (CD63) in the lumen of multivesicular endosomes, together with a decrease in CD63 in the released exosomes from α-Syn-treated cells. Furthermore, cholesterol-depleting agent-induced S1P₁R expulsion from the rafts also resulted in S1P₁R uncoupling. Taken together, these results suggest that extracellular α-Syn-induced expulsion of S1P₁R from lipid rafts promotes the uncoupling of S1P₁R from G_i, thereby blocking subsequent G_i signals, such as inhibition of cargo sorting into exosomal vesicles in multivesicular endosomes. These findings help shed additional light on PD pathogenesis.

DHHC5-mediated palmitoylation of S1P receptor subtype 1 determines G-protein coupling

Sphingosine 1-phosphate (S1P) is a pleiotropic lipid mediator involved in the regulation of immune cell trafficking and vascular permeability acting mainly through G-protein-coupled S1P receptors (S1PRs). However, mechanism underlying how S1PRs are coupled with G-proteins remains unknown. Here we have uncovered that palmitoylation of a prototypical subtype S1P₁R is prerequisite for subsequent inhibitory G-protein (Gi) coupling. We have identified DHHC5 as an enzyme for palmitoylation of S1P₁R. Under basal conditions, S1P₁R was functionally associated with DHHC5 in the plasma membranes (PM) and was fully palmitoylated, enabling Gi coupling. Upon stimulation, the receptor underwent internalisation leaving DHHC5 in PM, resulting in depalmitoylation of S1P₁R. We also revealed that while physiological agonist S1P-induced endocytosed S1P₁R readily recycled back to PM, pharmacological FTY720-P-induced endocytosed S1P₁R-positive vesicles became associated with DHHC5 in the later phase, persistently transmitting Gi signals there. This indicates that FTY720-P switches off the S1P signal in PM, while switching on its signal continuously inside the cells. We propose that DHHC5-mediated palmitoylation of S1P₁R determines Gi coupling and its signalling in a spatio/temporal manner.

Involvement of Gβγ subunits of Gi protein coupled with S1P receptor on multivesicular endosomes in F-actin formation and cargo sorting into exosomes

Exosomes play a critical role in cell-to-cell communication by delivering cargo molecules to recipient cells. However, the mechanism underlying the generation of the exosomal multivesicular endosome (MVE) is one of the mysteries in the field of endosome research. Although sphingolipid metabolites such as ceramide and sphingosine 1-phosphate (S1P) are known to play important roles in MVE formation and maturation, the detailed molecular mechanisms are still unclear. Here, we show that Rho family GTPases, including Cdc42 and Rac1, are constitutively activated on exosomal MVEs and are regulated by S1P signaling as measured by fluorescence resonance energy transfer (FRET)-based conformational changes. Moreover, we detected S1P signaling-induced filamentous actin (F-actin) formation. A selective inhibitor of Gβγ subunits, M119, strongly inhibited both F-actin formation on MVEs and cargo sorting into exosomal intralumenal vesicles of MVEs, both of which were fully rescued by the simultaneous expression of constitutively active Cdc42 and Rac1. Our results shed light on the mechanism underlying exosomal MVE maturation and inform the understanding of the physiological relevance of continuous activation of the S1P receptor and subsequent downstream G protein signaling to Gβγ subunits/Rho family GTPases-regulated F-actin formation on MVEs for cargo sorting into exosomal intralumenal vesicles.

MicroRNA Regulation of Human Breast Cancer Stem Cells

MicroRNAs (miRNAs) are involved in virtually all biological processes, including stem cell maintenance, differentiation, and development. The dysregulation of miRNAs is associated with many human diseases including cancer. We have identified a set of miRNAs differentially expressed between human breast cancer stem cells (CSCs) and non-tumorigenic cancer cells. In addition, these miRNAs are similarly upregulated or downregulated in normal mammary stem/progenitor cells. In this review, we mainly describe the miRNAs that are dysregulated in human breast CSCs directly isolated from clinical specimens. The miRNAs and their clusters, such as the miR-200 clusters, miR-183 cluster, miR-221-222 cluster, let-7, miR-142 and miR-214, target the genes and pathways important for stem cell maintenance, such as the self-renewal gene BMI1, apoptosis, Wnt signaling, Notch signaling, and epithelial-to-mesenchymal transition. In addition, the current evidence shows that metastatic breast CSCs acquire a phenotype that is different from the CSCs in a primary site. Thus, clarifying the miRNA regulation of the metastatic breast CSCs will further advance our understanding of the roles of human breast CSCs in tumor progression.

Yasutomi Nishizuka: father of protein kinase C

It is 6 years since we received the tragic news that our great mentor Dr Yasutomi Nishizuka passed away suddenly at the age of 72 years. Dr Nishizuka made several epoch-making discoveries in his life, e.g. the tryptophan metabolism, protein synthesis, ADP-ribosylation, regulation of cAMP-dependent protein kinase and discovery of protein kinase C (PKC). Among them his name will be remembered for a long time as a father of PKC, momentous discoveries in the twentieth century, which are still actively pursued by many laboratories worldwide.

Sphingosine kinase 1 regulates mucin production via ERK phosphorylation

Our previous report showed that inhibition of sphingosine kinase (SphK) ameliorates eosinophilic inflammation and mucin production in a mouse asthmatic model. To clarify the role of SphK in airway mucin production, we utilized the mouse asthmatic model and found that both SphK and MUC5AC expression were increased and co-localized in airway epithelium. Next we cultured normal human bronchial epithelial cells in an air-liquid interface and treated with IL-13 to induce their differentiation into goblet cells. We found that SphK1 and MUC5AC expression was increased by IL-13 treatment at both protein and mRNA levels, whereas SphK2 expression was not changed. N,N-dimethylsphingosine (DMS), a potent SphK inhibitor, decreased MUC5AC expression up-regulated by IL-13 treatment. Furthermore, DMS inhibited IL-13-induced ERK1/2 phosphorylation but neither p38 MAPK nor STAT6 phosphorylation. These results suggest that SphK1 is involved in MUC5AC production induced by IL-13 upstream of ERK1/2 phosphorylation, and independent of STAT6 phosphorylation.

Roles of extracellular and intracellular sphingosine 1-phosphate in cell migration

Sphingosine 1-phosphate (S1P) is an important factor for the regulation of cell motility acting both inside and outside the cells. The precise role of S1P in the control of cell motility, however, remains unclear. Here we describe the roles of S1P in the regulation of cell motility by dissecting them into intracellular and extracellular actions using a liposomal S1P transfer technique. In a Boyden chamber assay free S1P enhanced directional cell movement, whereas liposomal S1P induced nondirectional cell movement. Furthermore, inhibition of sphingosine kinase (SphK) 1 by several inhibitors or knockdown of the enzyme expression by siRNA caused reduced wound-faced cell polarity formation as assessed by wound-healing assay. Moreover, S1P-induced cell migration was strongly inhibited by SphK inhibitors. These results indicate that extracellular S1P acting through S1P receptors facilitates the formation of cell polarity, whereas S1P generated inside the cells functions as an intracellular mediator per se to enhance nondirectional cell movement, thus S1P enhances directional cell movement in a coordinated fashion.

Sphingosine kinase 1 regulates differentiation of human and mouse lung fibroblasts mediated by TGF-beta1

Transforming growth factor beta (TGF-beta) contributes to the progression of pulmonary fibrosis through up-regulation of alpha-smooth muscle actin (alpha-SMA) as lung myofibroblast differentiation. Bioactive sphingosine 1-phosphate (S1P) has been shown to mimic TGF-beta signals; however, the function of S1P in lung fibrotic process has not been well documented. We found, in a mouse model of bleomycin lung fibrosis, that SPHK1 and alpha-SMA were colocalized within lung fibrotic foci and that these expressions were significantly increased in primary cultured fibroblasts. Using human lung fibroblasts WI-38, we explored the rationale of sphingosine kinase (SPHK) with TGF-beta1 stimulation. SPHK inhibitors and small interference RNA (siRNA) targeted SPHK1 decreased alpha-SMA and fibronectin expression up-regulated by TGF-beta1. In the meantime, SPHK1 inhibition did not affect smad2 phosphorylation in response to TGF-beta1. Then we examined whether S1P receptors transactivation may affect TGF-beta signals. siRNA against S1P(2) and S1P(3), but not S1P(1), reduced alpha-SMA expression as well as Y-27632, Rho kinase inhibitor. We also detected activation of Rho GTPase upon stimulation of TGF-beta1 on the cell membrane where S1P(2) or S1P(3) was overexpressed. These data suggested that SPHK1 activation by TGF-beta1 leads to Rho-associated myofibroblasts differentiation mediated by transactivated S1P receptors in the lung fibrogenic process.

Protein kinase D-mediated phosphorylation and nuclear export of sphingosine kinase 2

Sphingosine kinase (SPHK) is a key enzyme producing important messenger sphingosine 1-phosphate and is implicated in cell proliferation and suppression of apoptosis. Because the extent of agonist-induced activation of SPHK is modest, signaling via SPHK may be regulated through its localization at specific intracellular sites. Although the SPHK1 isoform has been extensively studied and characterized, the regulation of expression and function of the other isoform, SPHK2, remain largely unexplored. Here we describe an important post-translational modification, namely, phosphorylation of SPHK2 catalyzed by protein kinase D (PKD), which regulates its localization. Upon stimulation of HeLa cells by tumor promoter phorbol 12-myristate 13-acetate, a serine residue in a novel and putative nuclear export signal, identified for the first time, in SPHK2 was phosphorylated followed by SPHK2 export from the nucleus. Constitutively active PKD phosphorylated this serine residue in the nuclear export signal both in vivo and in vitro. Moreover, down-regulation of PKDs through RNA interference resulted in the attenuation of both basal and phorbol 12-myristate 13-acetate-induced phosphorylation, which was followed by the accumulation of SPHK2 in the nucleus in a manner rescued by PKD over-expression. These results indicate that PKD is a physiologically relevant enzyme for SPHK2 phosphorylation, which leads to its nuclear export for subsequent cellular signaling.

Yasutomi Nishizuka: 12 July 1932 - 4 November 2004

Yasutomi Nizhizuka was born in Seido Village, Muko–gun (now City of Ashiya), Hyogo–Prefecture, on 12 July 1932, as the second son of Yasunobu and Nobuko Nishizuka. His elder brother, Yasuaki (1922–95, pathologist, President of Aichi Cancer Center), was 10 years old, his eldest sister, Hiroko, was aged 8, his elder sister, Fumiko, was 5, and he was a heterozygotic twin with his sister Junko. His mother, Nobuko, was from the Ijichi family, a huge landlord, which traced its roots back to a powerful family of the Heian Era (eleventh century). When Yasutomi was an infant, he was so weak that his parents were not sure that he would survive to adulthood. He had intussusception (ileus) when he was six months old. He barely survived after emergency surgery at Daido Hospital in Osaka. Since then, he frequently suffered from diseases associated with stomach ache. He was always weak and ailing.

Involvement of N-terminal-extended Form of Sphingosine Kinase 2 in Serum-dependent Regulation of Cell Proliferation and Apoptosis

Sphingosine kinase (SPHK) 1 is implicated in the regulation of cell proliferation and anti-apoptotic processes by catalyzing the formation of an important bioactive messenger, sphingosine 1-phosphate. Unlike the proliferative action of SPHK1, another isozyme, SPHK2, has been shown to possess anti-proliferative or pro-apoptotic action. Molecular mechanisms of SPHK2 action, however, are largely unknown. The present studies were undertaken to characterize the N-terminal-extended form of SPHK2 (SPHK2-L) by comparing it with the originally reported form, SPHK2-S. Real-time quantitative PCR analysis revealed that SPHK2-L mRNA is the major form in several human cell lines and tissues. From sequence analyses it was concluded that SPHK2-L is a species-specific isoform that is expressed in human but not in mouse. At the protein level it has been demonstrated by immunoprecipitation studies that SPHK2-L is the major isoform in human hepatoma HepG2 cells. SPHK2-L, when expressed in human embryonic kidney (HEK) 293 cells, did not show any inhibition of DNA synthesis in the presence of serum, whereas it showed marked inhibition in the absence of serum. Moreover, serum deprivation resulted in the translocation of SPHK2-L into the nuclei. In addition, serum deprivation induced SPHK2-L expression in HEK293 cells. Furthermore, suppression of SPHK2 by small interfering RNA treatment prevented serum deprivation- or drug-induced apoptosis in HEK293 cells. Taken together, these results indicate that a major form of SPHK2 splice variant, SPHK2-L, in human cells does not inhibit DNA synthesis under normal conditions and that SPHK2-L accumulation in the nucleus induced by serum deprivation may be involved in the cessation of cell proliferation or apoptosis depending on the cell type.

Identification and characterization of RPK118, a novel sphingosine kinase-1-binding protein

Sphingosine kinase (SPHK) is a key enzyme catalyzing the formation of sphingosine 1 phosphate (SPP), a lipid messenger that is implicated in the regulation of a wide variety of important cellular events through intracellular as well as extracellular mechanisms. However, the molecular mechanism of the intracellular actions of SPP remains unclear. Here we have cloned a novel sphingosine kinase-1 (SPHK1)-binding protein, RPK118, by yeast two-hybrid screening. RPK118 contains several functional domains whose sequences are homologous to other known proteins including the phox homology domain and pseudokinase 1 and 2 domains and is shown to be a member of an evolutionarily highly conserved gene family. The pseudokinase 2 domain of RPK118 is responsible for SPHK1 binding as judged by yeast two-hybrid screening and immunoprecipitation studies. RPK118 is also shown to co-localize with SPHK1 on early endosomes in COS7 cells expressing both recombinant proteins. Furthermore, RPK118 specifically binds to phosphatidylinositol 3-phosphate. These results strongly suggest that RPK118 is a novel SPHK1-binding protein that may be involved in transmitting SPP-mediated signaling into the cell.

Age-related changes in the localization of presenilin-1 in cynomolgus monkey brain

Age-related changes in PS-1 localization were examined in the brains of 22 cynomolgus monkeys ranging in age from embryonic day 87 to 35 years. In embryonic monkey brains, anti-PS-1 antibody N12, which recognizes the PS-1 N-terminal fragment (Ntf) and holo protein, stained immature neuronal cells. In juvenile monkeys, N12 stained large pyramidal neurons, cerebral neocortical neurons, and cerebellar Purkinje's cells. Cytoplasmic staining of these cells was granular in appearance. In aged monkeys, N12 stained neurons in all layers of the neocortex. In contrast, regardless of the age of the animals examined, M5, an anti-PS-1 antibody that specifically recognizes only the PS-1 C-terminal fragment (Ctf), stained neurons in all layers of the neocortex and neurons in the cerebellum. M5 also stained neuropil and white matter, and in aged monkeys, M5 stained swollen neurites of mature senile plaques. Age-related changes in PS-1 expression were further examined using Western blot analysis of mitochondrial, myelin, microsomal, nuclear, synaptosomal, and cytosol fractions isolated from 10 monkey brains ranging in age from embryonic day 87 to 32 years. In all brains, Ntf and Ctf were expressed most abundantly in the microsome fraction. The amount of PS-1 in the nuclear fraction dramatically increased with age. We conclude that the transport of PS-1 diminished with age and that PS-1 fragments accumulated in endoplasmic reticulum (ER) associated with the nuclear membrane.

Effects of zinc deficiency/zinc supplementation on ammonia metabolism in patients with decompensated liver cirrhosis

Hepatic encephalopathy is one of the major complications in decompensated liver cirrhosis. The current study was conducted to clarify the mechanisms of zinc deficiency in liver cirrhosis and its involvement in hepatic encephalopathy via ammonia metabolism. Ten patients each with compensated or decompensated liver cirrhosis and 11 healthy volunteers were enrolled in the study. Serum zinc levels and its daily urinary excretion were measured, an oral zinc-tolerance test was performed to examine zinc malabsorption, and the effects of diuretics on zinc excretion and of zinc supplementation on ammonia metabolism in the skeletal muscle were studied. The mean serum zinc levels in patients with decompensated liver cirrhosis were found to be significantly lower than the levels in controls and patients with compensated liver cirrhosis. The serum zinc levels were inversely correlated with blood ammonia in the fasting state. In the oral zinc-tolerance test, the percent increase in serum zinc levels 120 and 180 min after ingestion was less in cirrhotic patients than in controls. A diuretic administration resulted in a significant reduction in serum zinc levels. An increased uptake of ammonia by and an increased release of glutamine from leg skeletal muscle after oral supplementation of zinc sulfate were evident. Taken together, zinc deficiency in decompensated cirrhotic patients appears to be due to low absorption and to high urinary excretion, for which excessive diuretic administration is, in part, responsible, and zinc supplementation might play an important role in the prevention of hepatic encephalopathy by activating glutamine synthetase.

Actual invasive potential of human hepatocellular carcinoma revealed by in situ gelatin zymography

BACKGROUND

The matrix-degrading proteinases are believed to play an important role in the invasion and metastasis of hepatocellular carcinoma (HCC), but no one has ever seen the in situ matrix-degrading activity in HCCs.

PURPOSE

To demonstrate the cellular localization of actual gelatinolytic activity and to investigate the invasive potential of human HCC.

EXPERIMENTAL DESIGN

HCC cases (30) were subjected to in situ gelatin zymography and SDS-gelatin gel zymogram.

RESULTS

In situ gelatin zymography revealed a heterogeneous gelatinolytic activity in HCC cells, as well as stromal cells of noncancerous livers. The gelatinolytic intensity was stronger in 15 HCC nodules than in the corresponding noncancerous livers and was significantly associated with the cancer invasion to the capsule of the HCCs and to the portal veins. An intense gelatinolytic activity was detected in HCC cells in the front of tumor invasion. SDS-gelatin gel zymogram revealed gelatinases A and B that were mostly in latent forms.

CONCLUSIONS

The present study demonstrates high gelatinolytic activity at the invasive front of HCCs at a cellular level and that HCC has an invasive potential with the gelatin (matrix)-degrading metalloproteinases. Furthermore, it suggests the importance of the activation mechanism of gelatinolytic enzymes in the invasion and metastasis of HCCs.

Frequent allelic imbalance at the ATM locus in DNA multiploid colorectal carcinomas

DNA multiploidy may involve specific DNA ploidy states with respect to genetic alterations such as oncogenes, tumor suppressor gene mutation and microsatellite instability. To clarify the role of DNA multiploidy in colorectal cancer, we analysed allelic imbalance involving the ATM gene, localized to chromosome 11q22-23 and thought to be involved in genetic stability, in a series of multiploid colorectal carcinomas. In addition, p53 gene mutation (exons 5-8) and allelic imbalance at 11q24 loci distal to the ATM locus were also examined. The crypt isolation technique coupled with DNA cytometric sorting and polymerase chain reaction assay using 10 microsatellite markers tightly linked to the ATM gene were used to study ATM allelic imbalance in 55 colorectal carcinomas (15 diploid, 13 aneuploid, 27 multiploid). While allelic imbalance at the ATM locus was rarely observed in diploid and aneuploid carcinomas, multiploid carcinomas exhibited a high frequency of ATM allelic imbalance. In multiploid carcinoma samples, diploid subpopulations showed a smaller range of allelic imbalance at the loci tested compared to aneuploid subpopulations that demonstrated allelic imbalance over a relatively large region. Also, the frequency of AI at 11q24 showed a similar tendency to that at the ATM locus for each DNA ploidy state. An association between p53 gene mutation and ATM allelic imbalance in multiploid carcinoma was also observed. Our results suggest that ATM allelic imbalance and p53 gene mutations occur during the progression from diploid to aneuploid cell populations in multiploid colorectal carcinomas.

Remnant lipoproteins induce proatherothrombogenic molecules in endothelial cells through a redox-sensitive mechanism

BACKGROUND

Triglyceride-rich lipoproteins (TGLs) are atherogenic. However, their cellular mechanisms remain largely unexplained. This study examined the effects of isolated remnant-like lipoprotein particles (RLPs) on the expression of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and tissue factor (TF), proatherothrombogenic molecules, in cultured human endothelial cells.

METHODS AND RESULTS

RLPs were isolated from plasma of hypertriglyceridemic patients by use of the immunoaffinity gel mixture of anti-apoA-1 and anti-apoB-100 monoclonal antibodies. The incubation of cells with RLPs significantly upregulated mRNA and protein expression of these molecules. Total TGLs (d<1.006) and LDL had fewer or minimal effects on expression of these molecules compared with RLPs. RLPs increased intracellular oxidant levels, as assessed with an oxidant-sensitive probe. Combined incubation with alpha-tocopherol or N-acetylcysteine, both antioxidants, suppressed RLP-induced increase in expression of these molecules. In patients with higher plasma levels of RLPs, plasma levels of soluble forms of ICAM-1 and VCAM-1 were significantly higher than in patients with lower RLP levels. Treatment with alpha-tocopherol for 1 month decreased levels of the soluble adhesion molecules concomitantly with an increase in resistance of RLPs to oxidative modification in patients with high RLP levels.

CONCLUSIONS

RLPs upregulated endothelial expression of ICAM-1, VCAM-1, and TF, proatherothrombogenic molecules, partly through a redox-sensitive mechanism. RLPs may have an important role in atherothrombotic complications in hypertriglyceridemic patients.

Immunohistochemical expression of neural tissue markers (neuron-specific enolase, glial fibrillary acidic protein, S100 protein) in ameloblastic fibrodentinoma: a comparative study with ameloblastic fibroma

Formalin-fixed paraffin-embedded sections of three cases of ameloblastic fibrodentinoma (AFD) were studied by the avidin-biotin-peroxidase complex method using antibodies against neuron-specific enolase (NSE), glial fibrillary acidic protein (GFAP) and S100 protein and the results were compared with those in ameloblastic fibroma (AF). A striking histopathological characteristic of AFD was the formation of abortive dentin with various degrees of maturation at the epithelial-mesenchymal tissue interface. Central cells of enamel organ-like epithelia with various stages of abortive dentin induction in AFD were generally positive for NSE. Dental lamina-like epithelial cells also showed positive staining in some areas. No cells were positive for NSE in AF. Positive staining for GFAP was observed in the juxta-epithelial mesenchymal tissue of the formation stage of immature dentin with various numbers of entrapped cells in AFD, but GFAP staining was negative in other mesenchymal and epithelial tissues at other stages. In AF, no GFAP-positive cells were found. There were a few S100 protein-positive cells found in the foci of epithelial components in both AFD and AF. Mesenchymal cells showing a dendritic or spindle shape were positive for S100 protein in some areas of AFD and AF. Although such cells in the mesenchymal component of pigmented AFD were more numerous than in non-pigmented AFD and AF, their distribution pattern in the former condition was basically similar to that in the latter. Although the present results, obtained from conventional immunohistochemical procedures, do not directly reflect the expression of neural crest-derived cells in the dentinogenesis of AFD, such results do not disprove the possibility of the expression of neural proteins probably related to neural crest-derived cells in dentinogenesis under certain pathologic conditions in odontogenic mixed tumors. Such a phenomenon may also occur during dentinogenesis in other odontogenic mixed tumors and in normal tooth differentiation, but at an undetectable level.

Esophageal squamous cell carcinoma characterized by extensive chondroid differentiation

A rare case of carcinoma characterized by extensive chondroid elements at a site of primary esophageal and metastatic lesion is reported. The patient was a 67-year-old man complaining of dysphagia due to an ulcerative lesion at the lower middle esophagus. He underwent irradiation treatment prior to surgery. Histologically, the tumor consisted of both carcinomatous and chondroid elements and had invaded deeply into the esophageal wall. The carcinomatous cells had gradually become chondroid cells embedded within an extensive extracellular matrix. In addition, the metastatic lesion showed findings similar to those of the primary lesion. Immunohistochemistry revealed that both carcinomatous and chondroid elements were immunostained with cytokeratin and epithelial membrane antigen, suggesting an epithelial nature to the chondroid cells. Conversely, only chondroid cells were positively stained for S-100 protein. Furthermore, bone morphogenetic proteins (BMP) were positive for chondroid cells and their surrounding carcinomatous cells. Given the apparent transition between carcinomatous and chondroid cells based on microscopy and immunohistochemical findings in the present case, we concluded that the chondroid cells were derived from carcinomatous cells. In addition, our findings suggest that BMP produced by carcinomatous cells lead to chondroid differentiation of the carcinoma cells.

Microsatellite instability and mutation of mitochondrial and nuclear DNA in gastric carcinoma

BACKGROUND & AIMS

Microsatellite instability (MSI) in mitochondrial DNA (mtDNA) is observed in some colorectal carcinomas. We attempted to determine if mitochondrial MSI (mtMSI) and mutations occur in gastric carcinomas and if the mtMSI phenotype underlies specific clinicopathologic profiles.

METHODS

Sixty-two gastric carcinomas (34 intestinal and 28 diffuse types) were investigated. Coding mutations in 8 different mitochondrial genes, mtMSI in a noncoding (C)n tract, and p53 gene mutations were examined by polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) analysis. MSI in nuclear DNA (nMSI) and loss of the p53 gene were examined using microsatellite markers.

RESULTS

Ten of 62 (16%) carcinomas showed the mtMSI phenotype. Mitochondrial gene mutation was detected in 5 carcinomas, 4 of which also showed the mtMSI phenotype. There was a positive correlation between mtMSI and nMSI status. In intestinal carcinomas, mtMSI, nMSI, and p53 gene alterations were frequently detected from early to advanced stages. In diffuse carcinomas, both kinds of MSI were found in only advanced (subserosal or serosal invasion) carcinomas. Six of 7 carcinomas with the nMSI phenotype and all 5 carcinomas with mitochondrial coding mutations had a considerable intestinal-type tumor cell component.

CONCLUSIONS

Mitochondrial gene mutations, which are associated with the mtMSI phenotype, may play a specific role in the tumorigenesis of intestinal-type gastric carcinomas.

Injury to dorsal root ganglia alters innervation of spinal cord dorsal horn lamina involved in nociception

STUDY DESIGN

A study of the relation between the development of mechanical allodynia and the reorganization of primary afferent terminals in the sensory lamina of the rat spinal cord dorsal horn after partial dorsal root ganglion injury in rats.

OBJECTIVES

To investigate the pathologic mechanisms of mechanical allodynia after partial dorsal root ganglion injury.

SUMMARY OF BACKGROUND DATA

After experimental peripheral nerve injury causing neuropathic pain, myelinated afferent fibers sprout into lamina II of the dorsal horn. This lamina is associated with nociceptive-specific neurons that generally are not stimulated by myelinated fiber input from mechanical receptors. These morphologic changes are suggested to have significance in the pathogenesis of chronic mechanical allodynia, although it is not known whether this kind of morphologic change occurs after dorsal root ganglion injury.

METHODS

After partial dorsal root ganglion crush injury, the mechanical force causing footpad withdrawal was measured with von Frey hairs, and myelinated primary afferents were labeled with cholera toxin B subunit horseradish peroxidase, a selective myelinated fiber tracer that identifies transganglionic synapses.

RESULTS

After partial dorsal root ganglion injury, mechanical allodynia developed in the corresponding footpad within 3 days and persisted throughout the experimental period. At 2 and 4 weeks after the injury, B subunit horseradish peroxidase-positive fibers, presumably myelinated afferents, were observed to be sprouting into lamina II of the dorsal horn on the injured side, but not on the contralateral control side.

CONCLUSIONS

Morphologic change in spinal cord dorsal horn lamina II occurs after partial dorsal root ganglion injury. This change may have significance in the pathogenesis of chronic mechanical allodynia after partial dorsal root ganglion injury.

Usefulness of proliferative activity, DNA ploidy pattern and p53 products as diagnostic adjuncts in colorectal adenomas and intramucosal carcinomas

Although numerous studies have assessed the biologic parameters of tumors, measurement of these parameters has had, to date, little impact on histologic diagnosis. Furthermore, analysis of a single parameter is insufficient to evaluate tumor malignant potential. In the present study, cell proliferation, DNA ploidy and p53 product were analyzed to objectify the tumor malignant potential in colorectal adenomas and intramucosal carcinomas. Sixty-one adenomas and 49 intramucosal carcinomas were studied using immunohistochemical analysis of Ki-67 and p53, silver-staining nucleolar organizer region (AgNOR) stain and DNA ploidy in fresh samples. Intramucosal carcinoma exhibited a greater Ki-67-positive rate and AgNOR count than the adenomas, although these parameters varied widely among samples. The incidence of aneuploidy and p53 over-expression in colorectal intramucosal carcinomas was significantly higher than in colorectal adenomas. These results indicate that DNA aneuploidy and p53 accumulation are the most reliable parameters for distinguishing benign and malignant lesions.

Regional correspondence between the ventral portion of the lumbar intervertebral disc and the groin mediated by a spinal reflex. A possible basis of discogenic referred pain

STUDY DESIGN

Lumbar peripheral nerves were examined to determine whether they were responsive to electrical stimulation of the ventral portion of the lumbar disc in anesthetized rats.

OBJECTIVES

To confirm by electrophysiologic means the neural correspondence between the ventral portion of the lumbar disc and the groin.

SUMMARY OF BACKGROUND DATA

Patients with a degenerated lumbar disc occasionally report groin pain. However, its pathogenesis has not been investigated. The authors of the current study found that chemical stimulation of the ventral portion of rat lumbar disc caused cutaneous plasma extravasation in the groin, and thereby hypothesize the neural relation between the lumbar disc and the groin.

METHODS

The ventral portion of rat L5-L6 disc was electrically stimulated, and the elicited action potentials were recorded from the iliohypogastric, genitofemoral, lateral femoral cutaneous, sural, and sciatic nerves. The roles of the lumbar sympathetic trunks and spinal cord in the generation of the action potentials were examined.

RESULTS

Action potentials were elicited principally in the genitofemoral nerve; the action potentials of the genitofemoral nerve were not influenced by transection of the cervical spinal cord, whereas they disappeared immediately after death, which indicates that they are induced by a spinal reflex. The action potentials were reduced considerably after destruction of the lumbar sympathetic trunks, suggesting that they comprise an afferent path of the reflex.

CONCLUSIONS

The ventral portion of the lumbar disc had spatial relation to the groin area via a spinal reflex. Such a relation suggests that a disorder in the ventral portion of the lumbar disc may be a possible source of groin referred pain.

Gastric plasmacytoma coexistent with plasma cell granuloma in a patient with gastric cancer

We report a rare case of multiple gastric plasmacytomatous lesions at an early stage found incidentally in a stomach resected because of gastric cancer. The three lesions had different macroscopic features, showing depressed, submucosal, and nodular tumor-forming types. The smallest, a depressed lesion, produced IgG of the lambda and kappa types, and had a plasma-cell granuloma-like appearence, whereas the largest, a submucosal tumor, was formed by the monoclonal proliferation of atypical plasma cells containing IgA-kappa type immunoglobulin, and the nodular lesion exhibited histological features intermediate between those of the other two lesions. From their microscopic features and the profile of immunoglobulin production, we believe that these lesions may represent different stages in the possible course of development of plasmacytoma from the early stage of plasma cell granuloma. All three lesions were located far from the gastric carcinoma and it was unclear whether they had any causal relationship with it.

Tumor necrosis factor receptor p55 is essential for intrahepatic granuloma formation and hepatocellular apoptosis in a murine model of bacterium-induced fulminant hepatitis

Accumulating evidence implicates tumor necrosis factor (TNF) and Fas systems in liver injury, although the interaction between these two systems remains to be investigated. In this study, we examined Propionibacterium acnes-primed TNF receptor p55-deficient (TNFRp55-/-) or Fas-deficient MRL/MpJ Lpr/Lpr mice challenged with lipopolysaccharide (LPS). Priming with P. acnes caused mononuclear cell infiltration into the hepatic lobules and granuloma formation in the livers of TNFRp55 wild-type mice. Subsequent LPS challenge caused massive liver injury and a marked increase in transaminase levels, leading to acute lethality in control wild-type mice. In contrast, the same treatment caused few pathological changes in livers of TNFRp55-/- mice, and all animals survived. P. acnes and subsequent LPS challenge induced granuloma formation and apoptotic changes, respectively, in livers of MRL/MpJ Lpr/Lpr mice. However, liver injury was 50% of that in control MRL/MpJ +/+ mice, suggesting some role of the Fas-Fas ligand system in this liver injury model. On the other hand, an agonistic anti-Fas antibody caused massive apoptosis and hemorrhagic changes of the liver without any priming with P. acnes, leading to death in both TNFRp55-/- and control wild-type mice. These results suggest that TNFRp55 but not Fas was involved in P. acnes-induced granuloma formation as well as subsequent LPS-induced liver injury and that TNFRp55 and Fas independently induced apoptosis of hepatocytes in vivo.

True malignant histiocytosis developed during chemotherapy for mediastinal immature teratoma

We report an autopsy case of true malignant histiocytosis that developed during chemotherapy for mediastinal immature teratoma. The patient was a 14-year-old boy who exhibited hepatosplenomegaly while receiving chemotherapy for a mediastinal immature teratoma that had been resected 11 months before. The spleen and liver of the excisional biopsy displayed infiltration of multinucleated giant atypical cells with prominent erythrophagia in massive aggregations. These atypical cells expressed CD68, alpha1-antitrypsin, alpha1-antichymotrypsin, lysozyme, and vimentin, suggesting that the tumor cells may have been derived from macrophages. Immunocytochemistry showed p53 expression in the tumor cells of the malignant histiocytosis, as well as in the elements of the immature teratoma. Direct sequence analysis showed the p53 mutation in the tumor cells of the immature teratoma to be a mutation at codon 175 (exon 5), whereas the mutation in the malignant histiocytosis occurred at codon 285 (exon 8), ie, polyclonality was exhibited and these features suggested that the malignant histiocytosis arose independently from the immature teratoma during the chemotherapy.

The afferent pathways of discogenic low-back pain. Evaluation of L2 spinal nerve infiltration

The afferent pathways of discogenic low-back pain have not been fully investigated. We hypothesised that this pain was transmitted mainly by sympathetic afferent fibres in the L2 nerve root, and in 33 patients we used selective local anaesthesia of this nerve. Low-back pain disappeared or significantly decreased in all patients after the injection. Needle insertion provoked pain which radiated to the low back in 23 patients and the area of skin hypoalgesia produced included the area of pre-existing pain in all but one. None of the nine patients with related sciatica had relief of that component of their symptoms. Our findings show that the main afferent pathways of pain from the lower intervertebral discs are through the L2 spinal nerve root, presumably via sympathetic afferents from the sinuvertebral nerves. Discogenic low-back pain should be regarded as a visceral pain in respect of its neural pathways. Infiltration of the L2 nerve is a useful diagnostic test and also has some therapeutic value.

SOS-inducing activity of chemical carcinogens and mutagens in Salmonella typhimurium TA1535/pSK1002: examination with 151 chemicals

The umu test system is a newly developed method to evaluate genotoxic activities of a wide variety of environmental carcinogens and mutagens (Oda et al., 1985). In the present study, we further examined the abilities of 151 chemicals to induce umu gene expression in Salmonella typhimurium TA1535/pSK1002. Among the chemicals examined, 72 compounds induced umu gene expression, which could be defined on a basis of increased beta-galactosidase activity by 2-fold over the background level. The potent genotoxic compounds without metabolic activation were adriamycin, bleomycin, daunorubicin, 1,3-dinitropyrene, 1,6-dinitropyrene, 1,8-dinitropyrene, N-ethyl-N'-nitro-N-nitrosoguanidine, furylfuramide, methyl methanesulfonate, N-methyl-N'-nitro-N-nitrosoguanidine, mitomycin C, 1-nitropyrene and 4-nitroquino-line-1-oxide. In the presence of S9, aflatoxin B1, 2-aminoanthracene, Glu-P-1, IQ, MeIQ, MeIQx, Trp-P-1 and Trp-P-2 also induced umu gene expression markedly. Several chemicals such as 2-acetylaminofluorene, 9-aminoacridine, azobenzene, benzanthracene, benzidine, diethyl nitrosamine, 1-nitronaphthalene, paraquat, potassium dichromate and sodium nitrite were weakly genotoxic and the induction by these compounds could be detected only when the incubation time was prolonged from 2 h to 5 h. Data are also presented that some of the chemicals such as dimethyl sulfoxide, m-dioxan, 5-fluorouracil and paraquat, which have been reported to be non-mutagenic in Ames/Salmonella assay, were found to be active in inducing umu gene expression, while the known mutagenic compounds including acrylonitrile, 4,4'-dinitrobiphenyl, furfural, methylene chloride, 1-naphthylamine, sodium azide, o-tolidine and o-toluidine were non-genotoxic in the present assay system.

High tyrosine protein kinase activities in soluble and particulate fractions in bone marrow cells

High tyrosine protein kinase activities were detected in soluble and particulate forms from bone marrow cells using synthetic peptide (Glu-Asp-Ala-Glu-Tyr-Ala-Ala-Arg-Arg-Arg-Gly) as a substrate. Total activity of tyrosine protein kinase was 2.4 times higher in the soluble fraction but the specific activity was slightly higher in the particulate one. Mg2+ or Mn2+ requirements of these two enzymes for maximal activity were quite different from each other. Physiological significance of these two forms of enzymes is briefly discussed.