Phospholipase D2 in prostate cancer: protein expression changes with Gleason score

BACKGROUND

Phospholipases D1 and D2 (PLD1/2) are implicated in tumorigenesis through their generation of the signalling lipid phosphatidic acid and its downstream effects. Inhibition of PLD1 blocks prostate cell growth and colony formation. Here a role for PLD2 in prostate cancer (PCa), the major cancer of men in the western world, is examined.

METHODS

PLD2 expression was analysed by immunohistochemistry and western blotting. The effects of PLD2 inhibition on PCa cell viability and cell motility were measured using MTS, colony forming and wound-healing assays.

RESULTS

PLD2 protein is expressed about equally in luminal and basal prostate epithelial cells. In cells from different Gleason-scored PCa tissue PLD2 protein expression is generally higher than in non-tumorigenic cells and increases in PCa tissue scored Gleason 6-8. PLD2 protein is detected in the cytosol and nucleus and had a punctate appearance. In BPH tissue stromal cells as well as basal and luminal cells express PLD2. PLD2 protein co-expresses with chromogranin A in castrate-resistant PCa tissue. PLD2 inhibition reduces PCa cell viability, colony forming ability and directional cell movement.

CONCLUSIONS

PLD2 expression correlates with increasing Gleason score to GS8. PLD2 inhibition has the potential to reduce PCa progression.

Relative contribution of cell contact pattern, specific PKC isoforms and gap junctional communication in tight junction assembly in the mouse early embryo

In mouse early development, cell contact patterns regulate the spatial organization and segregation of inner cell mass (ICM) and trophectoderm epithelium (TE) during blastocyst morphogenesis. Progressive membrane assembly of tight junctional (TJ) proteins in the differentiating TE during cleavage is upregulated by cell contact asymmetry (outside position) and suppressed within the ICM by cell contact symmetry (inside position). This is reversible, and immunosurgical isolation of the ICM induces upregulation of TJ assembly in a sequence that broadly mimics that occurring during blastocyst formation. The mechanism relating cell contact pattern and TJ assembly was investigated in the ICM model with respect to PKC-mediated signaling and gap junctional communication. Our results indicate that complete cell contact asymmetry is required for TJ biogenesis and acts upstream of PKC-mediated signaling. Specific inhibition of two PKC isoforms, PKCdelta and zeta, revealed that both PKC activities are required for membrane assembly of ZO-2 TJ protein, while only PKCzeta activity is involved in regulating ZO-1alpha+ membrane assembly, suggesting different mechanisms for individual TJ proteins. Gap junctional communication had no apparent influence on either TJ formation or PKC signaling but was itself affected by changes of cell contact patterns. Our data suggest that the dynamics of cell contact patterns coordinate the spatial organization of TJ formation via specific PKC signaling pathways during blastocyst biogenesis.

Specific PKC isoforms regulate blastocoel formation during mouse preimplantation development

During early mammalian development, blastocyst morphogenesis is achieved by epithelial differentiation of trophectoderm (TE) and its segregation from the inner cell mass (ICM). Two major interrelated features of TE differentiation required for blastocoel formation include intercellular junction biogenesis and a directed ion transport system, mediated by Na+/K+ ATPase. We have examined the relative contribution of intercellular signalling mediated by protein kinase C (PKC) and gap junctional communication in TE differentiation and blastocyst cavitation. The distribution pattern of four (delta, theta, iota/lambda, zeta) PKC isoforms and PKCmicro/PKD1 showed partial colocalisation with the tight junction marker ZO-1alpha+ in TE and all four PKCs (delta, theta, iota/lambda, zeta) showed distinct TE/ICM staining patterns (predominantly at the cell membrane within the TE and cytoplasmic within the ICM), indicating their potential contribution to TE differentiation and blastocyst morphogenesis. Specific inhibition of PKCdelta and zeta activity significantly delayed blastocyst formation. Although modulation of these PKC isoforms failed to influence the already established programme of epithelial junctional differentiation within the TE, Na+/K+ ATPase alpha1 subunit was internalised from membrane to cytoplasm. Inhibition of gap junctional communication, in contrast, had no influence on any of these processes. Our results demonstrate for the first time that distinct PKC isotypes contribute to the regulation of cavitation in preimplantation embryos via target proteins including Na+/K+ ATPase.

Phorbol ester-induced translocation of PKC epsilon to the nucleus in fibroblasts: identification of nuclear PKC epsilon-associating proteins

We show that phorbol ester treatment of NIH 3T3 fibroblasts induces rapid translocation of PKC from a perinuclear site to the nucleus, extending findings in PC12 and NG108-15 cells and in myocytes. We have immunoprecipitated the PKC from nuclei isolated from phorbol ester-treated fibroblasts and identified six proteins which associate with nuclear PKC. These have been characterised as matrin 3, transferrin, Rac GTPase activating protein 1, vimentin, beta-actin and annexin II by MALDI-TOF-MS. We have confirmed that these proteins associate with PKC by gel overlay and/or dot blotting assays. The role of these PKC-associating proteins in the nucleus and their interaction with PKC are considered.

PKC signalling regulates tight junction membrane assembly in the pre-implantation mouse embryo

Epithelial differentiation including tight junction (TJ) formation occurs exclusively within the trophectoderm (TE) lineage of the mouse blastocyst. Here we examine mechanisms by which TJ protein membrane assembly might be regulated by protein kinase C (PKC) in the embryo. To overcome the inherent staging asynchrony of individual blastomeres within intact embryos, we have used isolated inner cell masses (ICMs) from early blastocysts to induce epithelial differentiation in their outer cells responding to their new cell contact pattern. Two TJ proteins examined retain their order of membrane assembly in isolated ICMs in culture as during normal development (early-assembling ZO-2 and late-assembling ZO-1α+), but this process is highly accelerated. Using six chemical modulators of PKC activity, we show here that PKC signalling is involved in the regulation of TJ membrane assembly. While indolactam-mediated PKC activation stimulates membrane assembly of both TJ proteins, TPA-mediated PKC activation stimulates only that of ZO-1α+. The PKC inhibitors Ro-31-8220, Ro-31-8425 and Gö 6983 suppress the stimulatory effect of both PKC activators on membrane assembly to varying extents according to inhibitor and TJ protein examined. Gö 6983 similarly inhibits ZO-2 and ZO-1α+membrane assembly. PKC inhibition by Gö 6976 appeared to stimulate TJ membrane assembly. Despite the broad PKC isotype specificity of the inhibitors used, these data suggest that the two TJ proteins are differently regulated by PKC isotypes or subfamilies. As Gö 6983 uniquely affects aPKC (particularly PKCζ) and we find that both PKCδ and ζ relocate upon activator treatment to colocalise partially with the TJ proteins in isolated ICMs, we suggest that at least PKCδ and ζ may play a central role in regulating TJ membrane assembly.

Intestinal sugar absorption is regulated by phosphorylation and turnover of protein kinase C betaII mediated by phosphatidylinositol 3-kinase- and mammalian target of rapamycin-dependent pathways

Stimulation of intestinal fructose absorption by phorbol 12-myristate 13-acetate (PMA) results from rapid insertion of GLUT2 into the brush-border membrane and correlates with protein kinase C (PKC) betaII activation. We have therefore investigated the role of phosphatidylinositol 3 (PI3)-kinase and mammalian target of rapamycin in the regulation of fructose absorption by PKC betaII phosphorylation. In isolated jejunal loops, stimulation of fructose absorption by PMA was inhibited by preperfusion with wortmannin or rapamycin, which blocked GLUT2 activation and insertion into the brush-border membrane. Antibodies to the last 18 and last 10 residues of the C-terminal region of PKC betaII recognized several species differentially in Western blots. Extensive cleavage of native enzyme (80/78 kDa) to a catalytic domain product of 49 kDa occurred. PMA and sugars provoked turnover and degradation of PKC betaII by dephosphorylation to a 42-kDa species, which was converted to polyubiquitylated species detected at 180 and 250+ kDa. PMA increased the level of the PKC betaII 49-kDa species, which correlates with the GLUT2 level; wortmannin and rapamycin blocked these effects of PMA. Rapamycin and wortmannin inhibited PKC betaII turnover. PI3-kinase, PDK-1, and protein kinase B were present in the brush-border membrane, where their levels were increased by PMA and blocked by the inhibitors. We conclude that GLUT2-mediated fructose absorption is regulated through PI3-kinase and mammalian target of rapamycin-dependent pathways, which control phosphorylation of PKC betaII and its substrate-induced turnover and ubiquitin-dependent degradation. These findings suggest possible mechanisms for short term control of intestinal sugar absorption by insulin and amino acids.

The 5' untranslated region of protein kinase Cdelta directs translation by an internal ribosome entry segment that is most active in densely growing cells and during apoptosis

Protein kinase Cdelta (PKCdelta) is a member of the PKC family of phospholipid-dependent serine/threonine kinases and is involved in cell proliferation, apoptosis, and differentiation. Previous studies have suggested that different PKC isoforms might be translationally regulated. We report here that the 395-nt-long 5' untranslated region (5' UTR) of PKCdelta is predicted to form very stable secondary structures with free energies (deltaG values) of around -170 kcal/mol. The 5' UTR of PKCdelta can significantly repress luciferase translation in rabbit reticulocyte lysate but does not repress luciferase translation in a number of transiently transfected cell lines. By using a bicistronic luciferase reporter, we show that the 5' UTR of PKCdelta contains a functional internal ribosome entry segment (IRES). The activity of the PKCdelta IRES is greatest in densely growing cells and during apoptosis, when total protein synthesis and levels of full-length eukaryotic initiation factor 4G are reduced. However, the IRES activity of the 5' UTR of PKCdelta is not enhanced during serum starvation, another condition shown to inhibit cap-dependent translation, suggesting that its potency is dependent on specific cellular conditions. Accumulating data suggest that PKCdelta has a function as proliferating cells reach high density and in early and later events of apoptosis. Our studies suggest a mechanism whereby PKCdelta synthesis can be maintained under these conditions when cap-dependent translation is inhibited.

The 5' UTR of protein kinase C epsilon confers translational regulation in vitro and in vivo

We have examined translational regulation conferred by the 5' untranslated region (UTR) of PKCepsilon on expression of the luciferase reporter gene in vitro, using rabbit reticulocyte lysates and in vivo, in contact-inhibiting mouse Swiss 3T3 fibroblasts and non-contact-inhibiting Swiss 3T6 fibroblasts. In rabbit reticulocyte lysates, the 5' UTR of PKCepsilon significantly represses translation. In 3T3 and 3T6 cells, the 5' UTR of PKCepsilon reduces luciferase activity, but not to the same extent as it does in vitro. In rabbit reticulocyte lysate, the degree of repression mediated by different PKCepsilon 5' UTR-deletion constructs correlates with the free energy (DeltaG) of their predicted secondary structures. However, in cells, secondary structure is not the only determinant of repression; an internal region of the 5' UTR is both necessary and sufficient for repression. Mutation of an upstream AUG (uAUG) motif in this region partially relieves repression. We conclude that the 5' UTR of PKCepsilon can mediate translational regulation and that translation inhibition in vivo involves the uAUG motif. Our findings also suggest that there are factors present in fibroblasts, but not in rabbit reticulocyte lysates that substantially overcome the repressive qualities of the long, structured 5' UTR. Thus, we have identified a potential new level of regulation of PKC in mammalian cells.

Changes in protein kinase C epsilon phosphorylation status and intracellular localization as 3T3 and 3T6 fibroblasts grow to confluency and quiescence: a role for phosphorylation at ser-729?

Protein kinase C (PKC) epsilon in 3T3 and 3T6 fibroblasts and in C6 glioma cells migrated on SDS/PAGE predominantly as a doublet with molecular masses of 87 and 95 kDa (PKC epsilon(87) and PKC epsilon(95) respectively). PKC epsilon(95) predominates when cells reach confluency but PKC epsilon(87) was the main form detected within 15 min when confluent cells were passaged at low cell density into fresh medium containing serum and allowed to adhere. Matrix-assisted laser-desorption ionization-time-of-flight MS analysis and experiments with phosphospecific antibodies revealed that PKC epsilon(87) is phosphorylated at Thr-566 and Ser-703, and PKC epsilon(95) is additionally phosphorylated at Ser-729. Cell fractionation studies revealed that PKC epsilon(95) is associated with the nuclear fraction, whereas PKC epsilon(87) was found in the 100,000 g cytosol fraction. Immunofluorescence studies confirmed these findings and showed that PKC epsilon(95) had a perinuclear, probably Golgi, localization and PKC epsilon(87) was distributed in the cytosol. It is proposed that phosphorylation at Ser-729 may be important for determining the intracellular localization of PKC epsilon, and that a specific Ser-729 phosphatase may be activated on cell passage to convert PKC epsilon(95) to PKC epsilon(87).

Phage display identifies thioredoxin and superoxide dismutase as novel protein kinase C-interacting proteins: thioredoxin inhibits protein kinase C-mediated phosphorylation of histone

Using phage display we identify the redox proteins thioredoxin and superoxide dismutase (SOD) as novel protein kinase C (PKC)-interacting proteins. Overlay assays demonstrated that PKC bound to immobilized thioredoxin, providing supporting evidence for the phage display results. Kinase assays demonstrated that SOD and thioredoxin were not direct substrates for PKC but that both proteins blocked autophosphorylation of PKC. Moreover, thioredoxin inhibited PKC-mediated phosphorylation of histone (IC(50) of approx. 20 ng/ml).

Protein kinases and multidrug resistance

The role of protein kinases in the multidrug resistance phenotype of cancer cell lines is discussed with an emphasis on protein kinase C and protein kinase A. Evidence that P-glycoprotein is phosphorylated by these kinases is summarised and the relationship between P-glycoprotein phosphorylation and the multidrug-resistant phenotype discussed. Results showing that protein kinase C, particularly the alpha subspecies, is overexpressed in many MDR cell lines are described: this common but by no means universal finding seems to be drug- and cell line-dependent and in only in a few cases is there a direct correlation between protein kinase C activity and multidrug resistance. From co-immunoprecipitation results it is suggested that P-glycoprotein is a specific protein kinase C receptor, as well as being a substrate. Revertant experiments provide conflicting results as to a direct relationship between expression of P-glycoprotein and protein kinase C. Evidence that protein kinase A influences P-glycoprotein expression at the gene level is well documented and the mechanisms by which this occurs are becoming clarified. Results on the relationship between protein kinase C and multidrug resistance using many inhibitors and phorbol esters are difficult to interpret because such compounds bind to P-glycoprotein. In spite of huge effort, a direct involvement of protein kinase C in regulating multidrug resistance has not yet been firmly established. However, evidence that PKC regulates a Pgp-independent mechanism of drug resistance is accumulating.

Monensin and verapamil do not alter intracellular localisation of daunorubicin in multidrug resistant human KB cells

The effects of monensin, verapamil and several inhibitors of membrane transport processes on the accumulation of [3H] daunorubicin by human KB-A1 cells have been investigated to determine the role of subcellular vesicular transport in the multidrug resistance phenotype. The Golgi inhibitor, brefeldin A, had no effect on drug accumulation, which suggests that vesicular transport is not a significant factor in drug resistance in these cells. KB-A1 cells were collaterally sensitive to both monensin and verapamil. Both of these compounds reduced drug efflux but did not alter subcellular distribution of daunorubicin, consistent with the view that monensin, like verapamil, acts directly on P-glycoprotein.

Rat brain glial cells in primary culture and subculture contain the delta, epsilon and zeta subspecies of protein kinase C as well as the conventional subspecies

We raised polyclonal antibodies against the C-terminal peptides of protein kinase C (PkC) subspecies alpha, beta 1, beta 2, gamma, delta, epsilon, and zeta and checked their specificity against brain extracts using Western immunoblot analysis. With equal amounts of protein applied to gels PkC subspecies beta 1, delta, epsilon and zeta were detected in primary cultures of mixed glial cells: bands for the alpha and beta 2 subspecies were less prominent. PkC gamma was not detected in primary glial cultures. The epsilon and zeta subspecies of PkC were detected in subcultures of type 1 astrocytes with weaker bands for the alpha, beta 1 and beta 2 subspecies. Blots of O-2A-lineage glia contained PkCs delta and zeta as prominent bands: the alpha, beta 1 and epsilon subspecies were also present. All PkC subspecies including PkC gamma were detected in C6 glioma cells.

Susceptibility of myelin glycerophospholipids and sphingolipids to oxidative attack by hydroxyl free radicals as measured by the thiobarbituric acid test

Glycerophospholipids and sphingolipids typical of the myelin sheath have been examined for the formation of thiobarbituric acid reactive materials after attack by hydroxyl free radicals. Thiobarbituric acid (TBA) reactive materials are formed following exposure of phosphatidylcholine (PC), phosphatidylserine (PS) and phosphatidylethanolamine (PE) to hydroxyl radical attack in the order PS > PC > PE while the sphingolipids, sphingomyelin and cerebroside and the sterol cholesterol, did not form TBA reactive materials. Inclusion of cholesterol into PC vesicles reduced the formation of TBA reactive materials on hydroxyl radical attack while with PS there was an increase. In mixed glycerophospholipid systems inclusion of cerebroside reduced formation of TBA reactive materials following hydroxyl radical attack on phosphatidylcholine and phosphatidylserine, but not phosphatidylethanolamine. The findings are discussed in relation to the oxidative damage we have observed in the central nervous system at different stages of chronic relapsing experimental allergic encephalomyelitis [Brett R. and Rumsby M. G. Neurochem. Int. 23, 35-44 (1993)].

A role for protein kinase C subtypes alpha and epsilon in phorbol-ester-enhanced K(+)- and carbachol-evoked noradrenaline release from the human neuroblastoma SH-SY5Y

Protein kinase C (PKC) consists of a family of closely related subtypes which differ in their localization and activation properties. Our previous studies have suggested a role for PKC in the regulation of noradrenaline (NA) release from the human neuroblastoma SH-SY5Y. Here we have used two approaches to characterize the PKC subtypes present in SH-SY5Y cells. Firstly, the PCR was used to show that SH-SY5Y cells contain mRNA encoding PKC subtypes alpha, beta, gamma, delta, epsilon and zeta. Secondly, immunoblotting showed that SH-SY5Y cells express PKC subtypes alpha, epsilon and zeta at the protein level. Prolonged (48 h) exposure of cells to the phorbol ester phorbol 12-myristate 13-acetate (PMA; 100 nM) resulted in a marked decrease in the amounts of PKC-alpha and PKC-epsilon, with no change in levels of PKC-zeta. Prolonged PMA treatment had no significant effect on K(+)-evoked NA release from SH-SY5Y cells, whereas carbachol-evoked release was increased 2.2-fold. However, prolonged exposure to PMA completely inhibited the ability of acute (12 min) PMA treatment to enhance both K(+)- and carbachol-evoked NA release. The specific PKC inhibitor RO 31-7459 (10 microM) was found to inhibit K(+)- and carbachol-evoked release by 27% and 68% respectively. RO 31-7549 also completely inhibited the ability of acute PMA treatment to enhance release. These data suggest that PKC-alpha and/or PKC-epsilon play an essential role in the regulation of PMA-enhanced K(+)- and carbachol-evoked NA release in SH-SY5Y cells.

Evidence of free radical damage in the central nervous system of guinea-pigs at the prolonged acute and early relapse stages of chronic relapsing experimental allergic encephalomyelitis

Central nervous system tissue from guinea-pigs in various stages of chronic relapsing experimental allergic encephalomyelitis (CR-EAE) has been analysed for evidence of free radical damage using the thiobarbituric acid test as an indicator of oxidative changes. Levels of thiobarbituric acid-reactive materials in brain and spinal cord regions from prolonged acute and early relapse phases of CR-EAE were significantly higher than in central nervous system tissue from Freund's adjuvant control and normal uninoculated animals. In the late relapse phase of CR-EAE, levels of thiobarbituric acid-reactive materials in CNS samples were at control values. Fluorescence analysis of central nervous system tissue confirmed evidence of increased free radical damage in prolonged acute and early relapse stages of CR-EAE. The increased oxidative damage observed in the central nervous system in CR-EAE is discussed in relation to the role of macrophages and their oxidative burst.

The protein kinase C, calcium-independent and calcium-dependent kinase activities of glial cells in primary culture and subculture

The activity of calcium-independent, calcium-dependent and calcium + phospholipid-dependent (protein kinase C) kinases in cytosol fractions from rat brain glial cells in primary culture and from subcultured astrocytes and in oligodendrocyte-type 2 astrocyte lineage glia has been measured with histone Type IIIS as substrate. Accurate measurement of protein kinase C activity was achieved only after chromatography of glial cytosols on DE-52 anion exchange columns to remove an endogenous inhibitor, identified tentatively as a phosphatase possibly of the protein phosphatase 2A class. The specific activity of protein kinase C in glial cell cytosol increased from 7.5 +/- 0.8 to 37.9 +/- 0.9 nmol32P incorporated/mg protein/10 min with increasing culture age. Protein kinase C activity in glial cytosol was significantly higher when primary cultures were grown in a defined medium lacking serum. Astrocyte-conditioned medium and phorbol esters caused a rapid translocation of glial cell protein kinase C activity from cytosol to membrane compartments. Myelin basic protein and protamine have been compared with histone as substrates for measurement of calcium-independent, calcium-dependent and calcium + phospholipid-dependent kinase activities in glial cytosol.

Ethanolamine is released from glial cells in primary culture on stimulation with foetal calf serum and phorbol ester

Ethanolamine is released to the external medium at increased rates over basal levels when [3H]ethanolamine-labelled glial cells in primary culture, subcultures of astrocytes and O-2A lineage glia or C6 glioma cells are treated with phorbol ester or foetal calf serum. On equilibrium labelling of mixed glial cultures 90-95% of incorporated [3H]ethanolamine was in ethanolamine-containing phospholipids and 2% in the phosphatidylcholine component. On stimulation of glia with phorbol ester or foetal calf serum ethanolamine, and not phosphoethanolamine or choline, was released to the medium suggesting that a phospholipase D-mediated turnover of lipid, perhaps partially linked to protein kinase C, is involved. The results show that cells in primary culture behave similarly to cell lines in that signal transduction pathways involve a stimulated turnover of ethanolamine-phospholipids with the external release of ethanolamine.

The origin and specificity of intrathecal IgG in chronic relapsing experimental allergic encephalomyelitis

The source of IgG in the cerebrospinal fluid (CSF) in guinea pigs with chronic relapsing experimental allergic encephalomyelitis (CR-EAE) was investigated using quotient analysis of total IgG and albumin concentrations and by computing CSF-plasma ratios of specific IgG concentrations. Increased blood-CSF barrier (B-CSFB) permeability was shown by elevated albumin quotients in both relapse and remission phases of CR-EAE and intrathecal production of IgG was indicated by raised ratios of IgG to albumin in the CSF. Intrathecal IgG synthesis was greatest in guinea pigs which had little B-CSFB damage. When enzyme-linked immunosorbent assays (ELISA) for whole cord, myelin basic protein (MBP) or Mycobacterium tuberculosis were performed with CSF and plasma adjusted to the concentration of total IgG, the CSF/plasma ratios of ELISA results for specific antibodies were less then unity and ratios for whole cord and MBP were lower than those for M. tuberculosis. There was thus no evidence for a selective increase in the CSF of antibody specific either for the neuroantigens tested or for adjuvant components. The CSF-plasma ratios for each specific antibody were inversely correlated with the extent of total IgG intrathecal synthesis, suggesting that much of the antibody production within the CNS is the result of polyclonal B cell activation.

Autoantibody responses in the cerebrospinal fluid of guinea pigs with chronic relapsing experimental allergic encephalomyelitis

We report the use of the ELISA technique to measure IgG specific for whole cord, myelin, myelin basic protein and Mycobacterium tuberculosis in the cerebrospinal fluid (CSF) of Strain 13 guinea pigs in different stages of chronic relapsing experimental allergic encephalomyelitis (CR-EAE). Specific antibody levels to all 4 antigen preparations were related to the severity of clinical signs, with the highest levels of IgG in the CSF of guinea pigs in relapse or in stable chronic disease. Total IgG levels in the CSF, though elevated throughout the course of CR-EAE, did not show any association with the category of disease. Control animals inoculated with complete Freund's adjuvant (CFA) alone showed CSF IgG levels specific for M. tuberculosis that were not significantly different from those in animals with chronic EAE, indicating that CFA may itself induce a late-acting increase in blood-brain barrier permeability.

Plasma immunoglobulin responses and disease severity in chronic relapsing experimental allergic encephalomyelitis

Plasma IgG, IgA and IgM responses in various stages of chronic relapsing experimental allergic encephalomyelitis (CR-EAE) were investigated by ELISA and rocket immunoelectrophoresis. Autoantibody levels were elevated in acute EAE but immunoglobulin responses were maximal in chronic disease. Plasma IgG and IgA specific for the whole cord, myelin and MBP correlated closely with the clinical signs of post-acute disease; in age-matched groups, levels were lower in animals in remission or with no further disease than in those in relapse or with a stable chronic disease course. Sequential sampling revealed a significant increase in neuroantigen-specific IgG (with MBP as the dominant autoantigen) during the onset of a relapse. Lipid-specific antibody levels were raised throughout CR-EAE but constituted only a small proportion of the total response against neural antigens. Determination of total immunoglobulin concentrations suggested a general suppression of IgG responses in guinea pigs in remission. The strong correlations found between antibody levels and the severity of chronic disease provide further evidence that antibody-mediated mechanisms can play a major role in the pathogenesis of CR-EAE.

Stimulation of protein phosphorylation in mixed glial cell primary cultures and subcultures by the phorbol ester 12-O-tetradecanoylphorbol-13-acetate

Glial cell primary cultures consisting of protoplasmic and fibrous astrocytes, oligodendrocytes and progenitor glial cells incubated in medium containing 0.5% foetal calf serum and treated with 25 nM 12-o-tetradecanoylphorbol-13-acetate (TPA) for periods between 15 and 60 min showed a stimulation of protein phosphorylation which was most prominent in a polypeptide with a molecular weight of about 80,000 Da. Glial subcultures consisting mainly of Type 2 astrocytes, oligodendrocytes and progenitor glia showed a similar TPA stimulation of 80,000 Da protein phosphorylation detectable within 1 min of phorbol ester addition. TPA treatment of primary glial cultures led to an enhancement of phospholipid turnover but exposure of primary glial cultures to concentrations of TPA up to 250 nM caused no morphological change in protoplasmic astrocytes. 4-Phorbol (4-PH) or dimethylsulfoxide (DMSO) was without effect on protein phosphorylation or lipid turnover in glial cultures.

Protein kinase C activity in soluble fractions from glial cells in primary culture and subcultures

Protein kinase C (calcium + phospholipid-dependent kinase) activity has been measured in soluble 100,000 g fractions from mixed glial cells in primary culture; in 12 day cultures the specific activity (mean +/- S.D.) was 184 +/- 10 pmol 32P incorporated/10 min/mg protein. In glial cell subcultures lacking protoplasmic astrocytes protein kinase C specific activity was lower. An inhibitor of protein kinase C in 100,000 g supernatants was removed by chromatography through DE-52 anion exchange resin increasing the specific activity of the calcium + phospholipid-dependent kinase about 20 times. Protein kinase C was also associated with membrane fractions from glial cells; the membrane-associated enzyme had a higher specific activity than in the cytoplasm.

Cerebrospinal fluid interleukin 1 like activity during chronic relapsing experimental allergic encephalomyelitis

Cerebrospinal fluid (CSF) and plasma samples were taken from strain 13 guinea pigs in various stages of chronic relapsing experimental allergic encephalomyelitis (CREAE). The samples were assayed for interleukin 1 (IL-1) in the C3H/Hej mouse thymocyte assay. After removal of inhibitors, IL-1 was detectable in low amounts in plasma (5 U/ml) throughout the course of the disease but was raised in the acute phase (12 U/ml). CSF IL-1 was, however, only present in low amounts (6 U/ml) during the acute phase but was elevated (18 U/ml) during the chronic stages of CREAE. During the relapse phase levels of IL-1 correlated with the total leucocyte count in the CSF. On gel filtration of CSF, IL-1 activity eluted at approximately 15 kD and could not be attributed to leakage of plasma IL-1 during CSF puncture or IL-2 activity.

Lymphocytic activation in peripheral blood and cerebrospinal fluid during the course of chronic relapsing experimental allergic encephalomyelitis

A monoclonal antibody against the human interleukin-2 receptor (anti-Tac) has been found to cross-react with an antigen on the surface of guinea pig leucocytes. Cells marking with anti-Tac and with an anti-pan T cell monoclonal antibody have been quantitated in the peripheral blood and cerebrospinal fluid (CSF) of guinea pigs with chronic relapsing experimental allergic encephalomyelitis (CR-EAE). T cells account for about 90% of peripheral blood leucocytes in all animals whilst in the CSF, T cells are the major contributor only when there is a pleocytosis. The proportion of T cells marking with anti-Tac, a measure of T cell activation, in blood and CSF of control animals is 12%, rising to 23% in blood in the post-acute phase of the disease. However, a fall in the blood Tac/T ratio to 13% occurs during the first 10 days of relapse with a subsequent rise to 30-35%. This change is related to the time after onset of relapse irrespective of the subsequent course of the disease. From first relapse onwards CSF lymphocytes show a greater level of activation than lymphocytes from paired peripheral blood samples but the proportion of Tac+ cells in CSF does not increase with increasing CSF pleocytosis. The data is consistent with migration of activated T cells from blood to CSF at the onset of relapse.

Activated T-cells and macrophages in the cerebrospinal fluid and the spinal meningeal exudate in chronic relapsing experimental allergic encephalomyelitis

An analysis has been made of the cell types which mark with monoclonal antibodies against T cells, macrophages and the IL-2 receptor (anti-Tac) in the blood, cerebrospinal fluid (CSF) and spinal meningeal exudates taken from guinea pigs in the relapse and remission stages of chronic relapsing experimental allergic encephalomyelitis (CR-EAE). Whilst the T-cell and macrophage content of blood remained unchanged throughout the course of CR-EAE, T cells accounted for the majority of the CSF pleocytosis associated with relapsing disease but both T cells and macrophages populated the meningeal exudate in substantial numbers. Activated T cells (Tac+) rose in number in blood only after the onset of relapse but formed a far higher proportion of the CSF pleocytosis or meningeal exudate than in paired blood samples. Meningeal exudate cells from Freund's adjuvant-inoculated, but not uninoculated animals, also showed an increase in Tac+ cell levels. In addition, the meningeal exudate contained a substantial number of cells which did not label with anti-T or anti-macrophage antibodies and which did not vary in absolute numbers throughout the course of disease.

IgG subclass responses and immediate skin sensitivity in guinea-pigs with chronic relapsing experimental allergic encephalomyelitis

In strain-13 guinea-pigs inoculated for chronic relapsing experimental allergic encephalomyelitis (CR-EAE), IgG1 and IgG2 subclass antibody responses were investigated using single radial immunodiffusion and enzyme-linked immunosorbent assays (ELISA) for IgG1 and IgG2 specific for whole cord, myelin, myelin basic protein and Mycobacterium tuberculosis. The early acute stage revealed no increase in IgG1 but was associated with increased levels of IgG2 specific for neural and adjuvant components. Throughout the chronic phase of the disease, there were increased levels of IgG of both subclasses specific for the antigens tested but a preferential synthesis of IgG1. Levels of both IgG1 and IgG2 specific for neuroantigens were lowest in those guinea-pigs which did not develop signs of chronic disease. Immediate skin sensitivity against a wide range of neural antigens was not demonstrated though positive results may have been masked by the ability of myelin basic protein to induce non-specific mast cell degranulation and by altered histamine responsiveness in disease. Guinea-pigs with chronic paralysis had a lower skin sensitivity to histamine, compound 48/80 and M. tuberculosis than those in remission.

Chronic relapsing experimental allergic encephalomyelitis. Inhibition of lymphocyte mitogenesis by disease-related serum factors

Peripheral blood mononuclear cells (PBMC) from strain 13 guinea pigs at various stages of chronic relapsing experimental allergic encephalomyelitis (CREAE) showed significantly reduced reactivity to the polyclonal T cell mitogens, phytohaemagglutinin and concanavalin A. Serum taken at the same time revealed an increase in inhibitors of lymphocyte mitogenesis. The factors identified appeared to inhibit the initial stages of lymphocyte proliferation: they were not cytotoxic for lymphocytes nor were they complement-dependent.

Quantitative analysis of the cellular constituents of the cerebrospinal fluid in chronic relapsing experimental allergic encephalomyelitis

Cerebrospinal fluid (CSF) was taken from guinea pigs in various stages of chronic relapsing experimental allergic encephalomyelitis (CR-EAE). The leucocytes in CSF samples were counted and subjected to immunocytochemical analysis using monoclonal antibodies selectively recognising guinea pig T cells, macrophages or Ia antigens. The results showed that total leucocyte numbers and the proportion of macrophages in CSF were elevated in the acute phase of CR-EAE but samples of CSF from animals in early relapse did not show a significant elevation in leucocyte count or macrophage content. In addition the level of T cell activation was higher in CSF than in peripheral blood during disease and was highest in the acute and immediately post-acute phases of the CR-EAE.

Immunocytochemical demonstration of glial-neuronal interactions and myelinogenesis in subcultures of rat brain cells

Subcultures have been established from primary rat brain cell cultures and have been characterised with a range of cell-specific immunocytochemical markers. The subcultures are mainly composed of fibrous astrocytes, oligodendrocytes and neurones. The cells do not divide to any great extent giving a system where it is possible to follow culture development at the cellular level for a number of weeks. During this time oligodendrocytes colonise subpopulations of neurones, differentiate further showing the presence of myelin basic protein and elaborate myelin-like membrane; the fibrous astrocytes remain scattered uniformly throughout the cultures. Radially oriented processes emerge from the oligodendrocyte-neurone aggregates which subsequently coalesce to form fascicles that link the clusters of cells together. These fascicles react with antibodies for both neurofilament protein and myelin basic protein. The subcultures provide a straightforward system that is composed of cells derived entirely from the CNS, is free from mitotic inhibitors and yet retains a sufficiently low cell density to allow immunocytochemical identification of the cell types present. The subcultures should be useful for the study of trophic interactions between oligodendrocytes and neurones as well as the early events associated with myelinogenesis.

Immunocytochemical characterisation of cell cultures grown from dissociated 1-2-day post-natal rat cerebral tissue. A developmental study

A range of cell-specific markers have been employed with immunocytochemical methods to characterise and quantitate the cell types present in mixed brain cell cultures derived from dissociated 1-2-day post-natal rat cerebral hemispheres and grown in the presence of FCS. Protoplasmic astrocytes (GFAP+, A2B5-) were the major cell type to develop in culture, a confluent monolayer forming in 5-8 days. A population of smaller round cells of oligodendrocyte-like morphology appeared on this astrocyte layer. Greater than 70% of these smaller cells were GC- and thus were not oligodendrocytes. The GC- cells were A2B5+ and, in early cultures, may therefore be progenitor glial cells. Examination of GFAP and A2B5 co-expression by these smaller cells was difficult due to the dense underlying GFAP+ astrocyte layer. In less dense areas of older cultures these smaller cells with processes were GFAP+ and A2B5+: these are Type 2, fibrous astrocytes. GC+ oligodendrocytes, comprising 5-10% of the total identified cell population, were initially distributed over the astrocyte monolayer; in older cultures (after about 8 days) GC+ cells were observed in clumps over places where NF+ cells were identifiable. Such GC+ cells mostly became MBP+. Neurones accounted for about 6% of the identifiable cells in early cultures but a lower percentage in older cultures. Minor populations of ependymal cells and macrophages were present; cells displaying fibronectin, fibroblasts, were rarely identified. Use of horse serum in place of FCS gave lower yields of GC+ cells in cultures, slowed down astrocyte development, and resulted in the formation of trunks of GFAP+ cells throughout cultures. Other sera gave lower numbers of GC+ cells.

Infection of rat brain primary cell cultures with an avirulent A7 strain of Semliki Forest virus

The ability of A7 Semliki Forest Virus (SFV) to infect primary brain cell cultures has been examined using cultures prepared from 1-2-day neonatal rat cerebral hemispheres. These cultures, characterised immunocytochemically using cell-specified markers, contain mainly GFAP+ protoplasmic astrocytes and smaller multiprocessed A2B5+ cells, probably fibrous astrocytes. 10% of the cells are GC+ oligodendrocytes and some neurones are also present. These cultures support virus growth and a cytopathic effect was observed. Using double labelling techniques with the cell-specific markers and anti-SFV antibody A7 has been shown to readily infect cells which carry either the A2B5+ antigen or galactocerebroside marker. Protoplasmic astrocytes (GFAP+/A2B5-) are not readily infected under the conditions used. The protein labelling studies using [35S]methionine show that host cell protein synthesis is not completely shut off and continues in the astrocyte protein region. These results suggest that cells derived from a common A2B5+, GFAP-, GC- progenitor glial cell, i.e. GC+ oligodendrocytes and A2B5+/GFAP+ fibrous astrocytes, are more readily infected than other brain cell types including the protoplasmic astrocytes.

The effect of Freund's adjuvants on blood-cerebrospinal fluid barrier permeability

In guinea pigs with experimental allergic encephalomyelitis induced by spinal cord homogenate--complete Freund's adjuvant (CFA) emulsions an increase in the albumin permeability of the blood--cerebrospinal fluid barrier occurred from day 10 post-inoculation (p.i.) onward. In animals inoculated with CFA alone an increased albumin permeability was also demonstrated but only between days 5 and 10 after inoculation; by day 14-16 p.i. the barrier permeability had returned to control values. A similar change was seen in animals inoculated with incomplete Freund's adjuvant (IFA) only. However, both CFA and CFA-cord induced a strong humoral immune response which was not seen in animals inoculated with IFA alone. These results may have important consequences for the understanding of the development of inflammatory diseases of the central nervous system.

Chronic relapsing experimental allergic encephalomyelitis. The presence in the cerebrospinal fluid of factors chemotactic for monocytes

Cerebrospinal fluid (CSF) was removed from guinea pigs with chronic relapsing experimental allergic encephalomyelitis (CR-EAE) and control inoculated animals by puncture of the cisterna magna. The fluid from 7/8 animals in relapse and 2/4 animals in remission phases of CR-EAE was found to promote the migration of peripheral blood monocytes through a 5-micron pore diameter polycarbonate membrane filter. Monocytes were also found to orient towards the migration-stimulating CSF in a gradient formed between such fluid and CSF derived from a control animal, thereby indicating the presence of a chemotactic factor. The factor responsible for promoting monocyte migration had a molecular weight of between 50 000 and 300 000 as defined by ultrafiltration. The results are discussed in relation to the known pathohistological features of the chronic relapsing disease.

Chronic relapsing experimental allergic encephalomyelitis: cerebrospinal fluid cytology and a comparison with meningeal and spinal cord pathology

Cerebrospinal fluid (CSF) was taken from strain 13 guinea pigs in various stages of chronic relapsing experimental allergic encephalomyelitis, the spinal cords removed for histological examination and meningeal stretch preparations made. CSF cells were counted and characterized by morphological studies, anti-IgG and alpha-naphthyl acetate esterase (ANAE) staining. Approximately 65% of normal CSF lymphocytes were ANAE positive and 10% stained with anti-IgG. No polymorphonuclear leucocytes were seen. Five out of eight relapsing animals had raised cell counts (up to 152/microliters) as did three animals in remission. There was no change in the proportion of various types of CSF cells where increased numbers were recorded. Infiltrating cells in spinal cord sections and meningeal preparations were similarly characterized and the results compared with CSF cells findings. Animals in relapse which had, in addition, macroscopically visible cord plaques showed the most severe infiltrative changes in spinal cord tissue and in the meninges. There were differences between the proportion of various types of CSF cells and meningeal infiltrate cells on ANAE staining reaction. In general there were far more lymphocyte-type cells in the CSF but more monocyte-type cells in meningeal infiltrates.

Chronic relapsing experimental allergic encephalomyelitis. Immunological and blood--cerebrospinal fluid barrier-dependent changes in the cerebrospinal fluid

Cerebrospinal fluid (CSF) and plasma were taken from strain 13 guinea pigs in various stages of chronic relapsing experimental allergic encephalomyelitis using techniques which allowed repeated sampling from the same animal. Samples were assayed for albumin and IgG and the corresponding CSF/plasma quotients evaluated graphically using a method which could discriminate between blood-CSF barrier dysfunction and local IgG synthesis in the central nervous system (CNS). During the disease a 2-3-fold increase in plasma IgG concentration developed and an increase in blood-CSF permeability was noted. Isoelectric focusing revealed an oligoclonal IgG pattern identical in both plasma and CSF. The results provided no evidence for a local production of IgG in the CNS like that which is known to occur in multiple sclerosis.

A syringe modification for the simple and rapid dissociation of post-natal rat cerebral tissue for preparing primary cultures of mixed glial cells

Mechanical disruption of 2-day post-natal rat cerebral tissue without enzyme pretreatment through 21-gauge and 23-gauge hypodermic needles on a 1 ml disposable plastic syringe, gives dissociated preparations which contain between 1.7 and 2.1 X 10(7) cells/100 mg wet tissue. At a plating density of between 7.1 and 9.2 X 10(5)/cm2 in culture, between 2 X 10(5) and 2 X 10(6) cells are recovered after 7 days. Use of needles finer than 23-gauge resulted in lower cell yields and loss of galactocerebroside-positive oligodendrocytes. The method described is convenient for the routine preparation of mixed primary glial cultures on a regular basis where many cerebra need to be processed.

Effect of Co2+-substitution on the substrate specificity of phospholipase C from Bacillus cereus during attack on two membrane systems

Phospholipid degradation by native phospholipase C from Bacillus cereus and enzyme forms where one or both of the Zn2+ prosthetic groups had been replaced with Co2+ was studied in human erythrocyte membranes (ghosts) and resuspended freeze-dried bovine brain myelin. The rate of total phospholipid degradation was 2-9-fold more rapid with erythrocytes than with myelin. With both membrane systems the activity decreased in the order ZnZn-enzyme greater than ZnCo-enzyme greater than CoCo-enzyme. For all three enzyme forms with either membrane system, phosphatidylethanolamine (or the ethanolamine-containing phosphoglycerides) and phosphatidylcholine were hydrolysed most rapidly and sphingomyelin least. The relative rate of sphingomyelin degradation was highest with the ZnCo-enzyme. In myelin at low ionic strength there seemed to be a core of phospholipid that was very resistant to degradation by native phospholipase C but which was much more accessible to the Co2+-substituted forms. It is suggested that ZnCo-phospholipase C has potential applications in membrane studies.