Brain endothelial cell enzymes cleave platelet-retained amyloid precursor protein

We have previously demonstrated that thrombin-activated platelets from patients with advanced Alzheimer's disease (AD) retain significantly more surface membrane-bound amyloid precursor protein (mAPP) than platelets from non-demented age-matched individuals (AM). We have studied interactions between these platelets and the cerebrovascular endothelium to which activated platelets adhere in a model system, investigating their involvement in the formation of amyloid beta peptide (Abeta) deposits in AD patients. We report here that there appear to be alpha and beta secretase-like activities in primary human blood brain barrier endothelial cell (BEC) cultures from both AD patients and AM control subjects (AD-BEC and AM-BEC, respectively) as well as a gamma secretase-like activity that appears only in AD-BEC. No such activities were observed in human umbilical vein endothelial cells (HUVECs). Furthermore, there is more penetration of the platelet-released products platelet factor 4 and soluble APP through the BEC layer grown from AD patients than that grown from AM individuals, whereas none penetrate through a HUVEC layer. Thus the interaction between platelets, the APP they have retained or released, and cerebral vascular endothelial cells may be at least partially responsible for amyloidogenic deposits around the cerebral vasculature of AD patients.

Mucosal delivery of murine interleukin-2 (IL-2) and IL-6 by recombinant strains of Lactococcus lactis coexpressing antigen and cytokine

Lactococcus lactis is a nonpathogenic and noncolonizing bacterium which is being developed as a vaccine delivery vehicle for immunization by mucosal routes. To determine whether lactococci can also deliver cytokines to the immune system, we have constructed novel constitutive expression strains of L. lactis which accumulate a test antigen, tetanus toxin fragment C (TTFC), within the cytoplasmic compartment and also secrete either murine interleukin-2 (IL-2) or IL-6. When mice were immunized intranasally with various different expression strains of L. lactis, the anti-TTFC antibody titers increased more rapidly and were substantially higher in mice immunized with the bacterial strains which secreted IL-2 or IL-6 in addition to their production of TTFC. This adjuvant effect was lost when the recombinant strains of L. lactis were killed by pretreatment with mitomycin C and could therefore be attributed to the secretion of IL-2 or IL-6 by the recombinant lactococci. These results provide the first example of the use of a cytokine-secreting, noninvasive experimental bacterial vaccine vector to enhance immune responses to a coexpressed heterologous antigen and point the way to experiments which will test the possible therapeutic efficacy of this mode of cytokine delivery.

Salmonella Contamination Associated with Bacterial Soft Rot of Fresh Fruits and Vegetables in the Marketplace

Wash water from 66% of 401 samples of fresh fruits and vegetables collected in the marketplace and affected by bacterial soft rot were positive for suspected strains of Salmonella, i.e., black, hydrogen sulfide-positive colonies on Salmonella-Shigella agar incubated for 24 h at 37°C. By comparison, 30% of 402 healthy samples were positive. Incidence of suspected Salmonella in broth enrichment cultures was 59% in 533 soft rotted samples and 33% in 781 healthy samples. Thirty percent of 166 representative strains of suspected Salmonella, selected at random from 20 different commodities, were confirmed to be Salmonella by physiological and serological tests. Adjusting incidence values accordingly, Salmonella contamination was potentially present in at least 18 to 20% of soft rotted samples and in 9 to 10% of healthy samples. Wash water from 120 paired healthy and soft rotted fruits and vegetables contained an average of 1.0 × 10⁵ and 3.7 × 10⁶ CFU/ml, respectively, of suspected Salmonella-a ratio of 1:37. Average concentrations of suspected Salmonella in enrichment cultures of healthy and soft rotted samples were 7.5 × 10⁷ and 2.7 × 10⁹ CFU/ml, respectively, also in the ratio of 1:37. Fresh potato, carrot, and pepper disks coinoculated with the soft rot bacterium Erwinia carotovora and with Salmonella typhimurium, and incubated for up to 72 h at room temperature, contained approximately 10 times the concentration of S. typhimurium as did disks inoculated with Salmonella alone. Disks coinoculated with Pseudomonas viridiflava and S. typhimurium contained approximately three times the Salmonella populations as disks inoculated with Salmonella alone.

Oral vaccination of mice against tetanus with recombinant Lactococcus lactis

To determine whether a protective immune response could be elicited by oral delivery of a recombinant bacterial vaccine, tetanus toxin fragment C (TTFC) was expressed constitutively in Lactococcus lactis and administered orally to C57 BL/6 mice. The antibody titers elicited were lower than those following intranasal immunization (a route already known to result in high-level systemic anti-TTFC immune responses) but the protective efficacy was the same order of magnitude. The serum antibody isotypes elicited were predominantly IgG1 and IgG2a. TTFC-specific fecal IgA responses could be detected following oral or intranasal immunization. Chemically killed lactococci administered via the intranasal route were also able to elicit serum antibody responses of similar levels and kinetics to those induced by live bacteria.

Regulated localization confers multiple functions on the protease urokinase plasminogen activator

We have investigated the role of the plasminogen activation cascade in skeletal muscle differentiation. Migrating, undifferentiated myoblasts express urokinase plasminogen activator (uPA) and its cell surface receptor (uPAR). Consequently, uPA is localized predominantly to the cell surface. Preventing uPA from associating with its receptor with a noncatalytic form of uPA (NC-uPA) hinders migration of myoblasts and inhibits differentiation. When myoblasts reach confluence, cease migrating, and start to differentiate, uPAR gets downregulated, and uPA becomes redistributed from the cell surface to the extracellular space. The function of uPA at this stage was tested using the protease inhibitors aprotinin, alpha2-antiplasmin, or plasminogen activator inhibitor-1 (PAI-1). Contrary to the role of cell-associated uPA, inhibition of soluble uPA/plasmin stimulates differentiation of myoblasts. Aprotinin can inhibit activation of latent TGFbeta and stimulates differentiation, suggesting PAI-1 and alpha2-antiplasmin also may stimulate differentiation via this mechanism. These data suggest that regulation of uPA localization allows a dual function for this protease in regulating cell migration and controlling cell differentiation.

Evidence for local production of acute phase response apolipoprotein serum amyloid A in Alzheimer's disease brain

Acute phase serum amyloid A (A-apoSAA), but not constitutive apoSAA (C-apoSAA), was identified by Western blotting experiments in brain protein extracts from eight of nine patients with Alzheimer's disease (AD), one with a brain tumor and one with multiple sclerosis. A-apoSAA was not detected in six subjects with Pick's or Lewy Body disease or three other non-AD brain specimens. Apolipoprotein A-I and albumin were not found in any of the brain protein extracts. A-apoSAA mRNA was detected in AD brain by reverse transcription-polymerase chain reaction (RT-PCR). These data suggest that apoSAA is locally produced in AD brain and that investigation of the neuroinflammatory effects of this injury specific apolipoprotein is warranted.

Protection against tetanus toxin in mice nasally immunized with recombinant Lactococcus lactis expressing tetanus toxin fragment C

Mice inoculated intranasally (i.n.) with a recombinant strain of live Lactococcus lactis expressing tetanus toxin fragment C (TTFC), produced both serum and secretory antibodies to TTFC. Killed bacteria which had accumulated TTFC intracellularly in vitro also elicited protective serum antibody responses. There was no requirement for either colonization or invasion of the mucosa. In addition secretory antibody responses in the lung and nasal tissues were elicited after i.n. inoculation in the presence of an adjuvant.

Moderate and advanced Alzheimer's patients exhibit platelet activation differences

We previously reported that platelets from advanced sporadic Alzheimer's disease (AD) patients exhibit two defects: first, an aberrant signal transduction presenting as a thrombin-induced hyperacidification, which is more severe for donors with the apolipoprotein E4 allele (apoE4), and second, an AD-specific Amyloid Precursor Protein (APP) processing defect that presents as retention of APP on the activated platelets' surface and in independent of the apo E allele. This retention of membrane APP correlates with decreased release of soluble APP. To determine at what stage in the disease progression these defects appear, we performed signal transduction and secretion studies on moderate AD patients. Thrombin-activated platelets from these patients do not exhibit either hyperacidification or APP retention; their APP processing and secretion are normal by Western blotting, suggesting that the two platelet defects appear in the advanced stages of AD.

Activated Alzheimer disease platelets retain more beta amyloid precursor protein

Upon activation, platelet alpha-granules' soluble contents are secreted and membrane-bound contents are translocated to the plasma membrane. Membrane-bound proteins include the beta-amyloid precursor protein (APP) from which the beta-amyloid (A beta) deposits found surrounding the cerebrovasculature of patients with Alzheimer's Disease (AD) may originate. We show here that activated platelets from AD patients exhibit less APP processing, retain more of the protein on their surface, and secrete less as soluble fragments than do controls. Surface labeling demonstrated that there is little APP or CD62 on the surface of resting platelets. Upon activation, control platelets exhibited more of both proteins on their surface, while advanced AD patients exhibited similar amounts of CD62 as controls, but retained significantly more surface APP. AD platelets secreted similar amounts of most soluble alpha-granule contents as controls, but less APP fragments. Together these results suggest a processing defect that may account for greater deposition of A beta-containing products in the vasculature to which activated platelets adhere.

Accumulation of E2F-4.DP-1 DNA binding complexes correlates with induction of dhfr gene expression during the G1 to S phase transition

Previously genomic DNase I footprinting showed changes in protein binding to two overlapping E2F sites correlates with activation of dhfr gene expression at the G1/S boundary of the Chinese hamster cell cycle (Wells, J., Held, P., Illenye, S., and Heintz, N. H. (1996) Mol. Cell. Biol. 16, 634-647). Here gel mobility and antibody supershift assays were used to relate changes in the components of E2F DNA binding complexes in cell extracts to repression and induction of dhfr gene expression. In extracts from log phase cells, E2F complexes contained predominantly E2F-4 and E2F-2 in association with DP-1, and DNA binding assays showed complexes containing E2F-2 preferentially interact with only one of the two overlapping E2F sites. In serum starvation-stimulation experiments, arrest in G1 by low serum was accompanied by decreased levels of dhfr mRNA and the appearance of an E2F-4.DP-1.p130 complex. After serum stimulation, induction of dhfr gene expression was preceded by loss of the p130 complex in mid G1 and coincided with marked increases in two free E2F.DP-1 complexes in late G1, one of which contained E2F-4 and a second which contained an unidentified E2F. We suggest activation of dhfr gene expression after serum stimulation requires at least two temporally distinct processes, relief of p130-mediated repression and subsequent activation of transcription by free E2F.

Transport of GM1 and GM1 inner ester across an in vitro model of the blood-brain barrier

Gangliosides, especially GM1, attenuate the in vivo damage caused by various neurotoxins. The chemically neutral inner ester of GM1 may be a better cytoprotective agent against some neurotoxins than the parent GM1 compound, because it may cross the blood-brain barrier (BBB) more easily than the anionic GM1. Using an in vitro bovine brain endothelial cell model of the BBB, we show the inner ester more readily transverse the tight junction barrier of this model than does GM1. Further, it is demonstrated that the GM1 inner ester is stable for several hours at pH values between 7.0 and 8.2 at 37 degrees C. Finally, the results illustrate that the BBB model may be useful for testing other gangliosides and their various derivatives for increased ability to cross the BBB.

Factors affecting the immunogenicity of tetanus toxin fragment C expressed in Lactococcus lactis

The relative immunogenicity of tetanus toxin fragment C (TTFC) has been determined in three different strains of inbred mice when expressed in Lactococcus lactis as a membrane-anchored protein (strain UCP1054), as an intracellular protein (strain UCP1050), or as a secreted protein which is partly retained within the cell wall (strain UCP1052). Protection against toxin challenge (20 x LD50) could be obtained without the induction of anti-lactococcal antibodies. When compared in terms of the dose of expressed tetanus toxin fragment C required to elicit protection against lethal challenge the membrane-anchored form was significantly (10-20 fold) more immunogenic than the alternative forms of the protein.

The repB gene required for production of extracellular enzymes and fluorescent siderophores in Pseudomonas viridiflava is an analog of the gacA gene of Pseudomonas syringae

Two genes, designated repA and repB, are involved in the regulation of the synthesis of extracellular pectate lyase, protease, and alginate in Pseudomonas viridiflava. The repA gene has been shown to encode a protein highly homologous to several bacterial sensors in the two-component regulator family including the LemA of Pseudomonas syringae. In this study, the repB locus, initially identified in a 6.3-kb EcoRI genomic fragment of P. viridiflava, was further characterized. Results obtained from restriction mapping, deletion subclonings, and mini-Mu-LacZ fusions indicated that the repB gene was contained within a 0.8-kb HindIII-PstI region. Sequence analysis of this repB region revealed the presence of an open reading frame, which was predicted to encode a protein similar or identical to the gacA response regulator found in P. syringae and Pseudomonas fluorescens. The repB gene of P. viridiflava also regulated the production of fluorescent siderophores, in addition to the aforementioned extracellular enzymes and alginate. The repB or gacA homologs were detected in the genomes of nine other strains of P. viridiflava, P. fluorescens, and P. syringae included in the study. The data presented here and earlier indicate that the repA/repB gene regulatory system of P. viridiflava is analogous to the lemA/gacA system of P. syringae and P. fluorescens.

Allele epsilon 4 of apolipoprotein E shows a dose effect on age at onset of Pick disease

Pick disease is a rare progressive dementing illness characterized by severe atrophy of the frontal and temporal lobes. Clinically, Pick disease may be difficult to distinguish from Alzheimer disease (AD). The fact that Pick disease is often familial, and the evidence suggesting that the epsilon 4 allele of apolipoprotein E (ApoE) is a risk factor for AD and possibly other dementias, prompted us to study ApoE isoforms in Pick disease. ApoE genotypes were evaluated in an autopsy series of 21 AD and 12 Pick cases and compared with published data for a large group of adults participating in the Framingham Study. The distributions of ApoE genotypes in the AD and Pick patients and the controls were significantly different from one another. The frequency of epsilon 4 was 50.0, 20.0, and 13.6% in these respective groups. Linear regression analysis showed that the number of epsilon 4 alleles was inversely related to age at onset of Pick disease (P < 0.03) and accounted for 40% of the variation in age at onset. These results suggest that epsilon 4 may be a susceptibility factor for dementia and not specifically for AD. Experiments using a monoclonal antibody against ApoE suggest that neurons and Pick bodies are immunoreactive with ApoE. The dose effect of the epsilon 4 allele on age at onset of dementias other than AD and the association of ApoE immunoreactivity with neurons and Pick bodies support a broader role for ApoE in the pathogenesis of neuronal degeneration through interactions with the neuronal cytoskeleton.

The isolation of lactococcal promoters and their use in investigating bacterial luciferase synthesis in Lactococcus lactis

18 different promoter elements, encompassing a 71-fold range of activity, were isolated from the chromosome of Lactococcus lactis (Ll) MG1363 and from an uncharacterised small isometric bacteriophage of Ll. The Vibrio fischeri (Vf) luciferase-encoding gene (lux) was used as a reporter in Ll, so that the promoters could be identified strictly on the basis of their activity in the homologous host. Sequence and primer extension analysis of six of the promoters has provided a new consensus sequence for the -35 and -10 hexanucleotide motifs present upstream from lactococcal transcription start points. When the nucleotide sequence of the most active promoter (P15) was compared with that of the highly expressed Ll usp45 gene, a novel 8-bp region of homology was identified which corresponded to the newly derived consensus -35 sequence element; this element may therefore be of general importance in Ll gene expression. The isolation of these promoters has also enabled us to investigate the characteristics of the Vf Lux activity in Ll under different physiological conditions using promoters of different strengths. Lux activity in Ll is critically dependent upon the phase of cell growth. Luminescence falls sharply in stationary phase, possibly due to a lack of FMNH2. In contrast to the kinetics of Lux function in Escherichia coli (Ec), Lux activity in Ll declines rapidly after addition of the substrate; the rate of decay is dependent both on the growth phase and on the strength of the promoter. It is apparent that the previously reported thermal instability of Lux is in fact a function of the host organism in which Lux is expressed.(ABSTRACT TRUNCATED AT 250 WORDS)

Progress in the development of Lactococcus lactis as a recombinant mucosal vaccine delivery system

The non-pathogenic, non-colonising Gram-positive organism Lactobacillus lactis is beeing developed as an antigen delivery system for mucosal vaccination. A high level expression system has been developed which allows loading of the bacterium with high levels of a heterologous antigen (TTFC) prior to inoculation. Mucosal inoculation of one such recombinant strain results in a protective serum antibody response and production of TTFC-specific IgA at mucosal sites.

Secretion of biologically active murine interleukin-2 by Lactococcus lactis subsp. lactis

Secretion of functional recombinant murine interleukin-2 (mIL2) by Lactococcus lactis was achieved by fusion of the sequence encoding mature mIL2 to the secretion signal leader of the lactococcal usp45 gene placed under transcriptional control of the phage T7 promoter-T7 RNA polymerase expression system. The recombinant mature mIL2 was one of only a few proteins which accumulated in the growth medium. Sequence analysis revealed correct processing at the first amino acid of the mature protein. A T-cell proliferation assay showed that the recombinant protein has the same specific biological activity as mIL2 obtained from a natural source.

Identification of exopolysaccharides produced by fluorescent pseudomonads associated with commercial mushroom (Agaricus bisporus) production

The acidic exopolysaccharides (EPSs) from 63 strains of mushroom production-associated fluorescent pseudomonads which were mucoid on Pseudomonas agar F medium (PAF) were isolated, partially purified, and characterized. The strains were originally isolated from discolored lesion which developed postharvest on mushroom (Agaricus bisporus) caps or from commercial lots of mushroom casing medium. An acidic galactoglucan, previously named marginalan, was produced by mucoid strains of the saprophyte Pseudomonas putida and the majority of mucoid strains of saprophytic P. fluorescens (biovars III and V) isolated from casing medium. One biovar II strain (J1) of P. fluorescens produced alginate, a copolymer of mannuronic and guluronic acids, and one strain (H13) produced an apparently unique EPS containing neutral and amino sugars. Of 10 strains of the pathogen "P. gingeri," the causal agent of mushroom ginger blotch, 8 gave mucoid growth on PAF. The "P. gingeri" EPS also was unique in containing both neutral sugar and glucuronic acid. Mucoid, weakly virulent strains of "P. reactans" produced either alginate or marginalan. All 10 strains of the pathogen P. tolaasii, the causal agent of brown blotch of mushrooms were nonnmucoid on PAF. Production of EPS by these 10 strains plus the 2 nonmucoid strains of "P. gingeri" also was negative on several additional solid media as well as in two broth media tested. The results support our previous studies indicating that fluorescent pseudomonads are a rich source of novel EPSs.

Effect of temperature on wood decay and translocation of soil-derived phosphorus in mycelial cord systems

Uptake of ³² P phosphorus from soil was investigated at 5-25 °C in mycelial cord systems of Phanerochaete velutina (D.C.: Pers.), Hypholoma fasciculare (Huds.: Fr.) Kummer and Phallus impudiciis (L.) Pers. which extended from 2cm³ beech (Fagus sylvatica) inocula, and which had initially developed at either 10 or 25 °C. Uptake of phosphorus from soil was opportunistic, being unaffected by the presence of additional wood resource units in mycelial cord systems. The magnitude of phosphorus uptake was dependent on species, temperature during uptake and the temperature at which cord systems developed. Phosphorus translocation to newly colonized baits, determined non-destructively, was characterized by an initial rapid flux to a plateau in all three species. Initial rates of phosphorus translocation (up to 18·46 nmol P d^-1 ) generally increased with temperature whilst total translocation was species and temperature dependent. There was evidence that both P. velutina and H. fasciculare displayed temperature acclimation, since phosphorus uptake and translocation at lower temperatures was greater in cord systems which had developed initially at 10° compared with 25 °C. Mycelial extension and wood decay rates also varied with species, initial development temperature and subsequent incubation temperature, but did not correlate with the temperature profiles of phosphorus uptake and translocation. Results are discussed in relation to nutrient acquisition, conservation and cycling in basidiomycete mycelial cord systems.

Cadmium Tolerance in a Metal-contaminated Population of the Grassland Moss Rhytidiadelphus squarrosus

Two populations of Rhytidiadelphus squarrosus, from metal-contaminated and uncontaminated habitats, differed in their intra- and extracellular Cd contents but had similar cellular levels of Cu. Moss shoots were supplied with a pulse of toxic metal by incubating in Cu or Cd nitrate solutions and effects on respiration, photosynthesis and intracellular K loss were monitored with time after initial exposure. Increasing intracellular Cu levels correlated most closely with a concurrent decline in intracellular K. Photosynthesis also declined in proportion to intracellular Cu; significant Cu-induced stimulation of respiration was observed. The most significant effect of Cd treatment was a decline in photosynthesis in proportion to the intracellular concentration of Cd. Apical segments from both populations showed similar sensitivity to Cu, whereas the metal-contaminated population showed increased resistance to Cd. Sensitivity to Cd increased in the more basal portions of moss gametophores, indicating that apparent resistance of Cd might reflect shoot vitality and age effects. After laboratory growth to eliminate differences in the physiological status of apical segments, it was confirmed that the metal-contaminated population of the moss was photosynthetically more tolerant to Cd at intracellular Cd concentrations found to cause considerable photosynthetic inhibition in the uncontaminated population. The metal-contaminated population of the moss that was tolerant to Cd was not co-tolerant to Cu.

Aprotinin, a Kunitz-type protease inhibitor, stimulates skeletal muscle differentiation

Aprotinin, a Kunitz-type inhibitor of serine proteases, stimulates myotube formation by mouse G8-1 and C2C12 skeletal muscle myoblasts. This stimulation of morphological differentiation is accompanied by accumulation of myogenin transcripts and production of muscle-specific proteins. In contrast, active TGF beta prevents differentiation of G8-1 and C2C12 myoblasts. When active TGF beta and aprotinin are both added to myoblast cultures, differentiation is inhibited, suggesting the active growth factor acts downstream of the protease inhibitor. TGF beta is found in serum as a latent, dimeric propolypeptide that is cleaved by limited proteolysis to release the biologically active carboxy-terminal dimer. To address the possibility that aprotinin may effect myogenesis by inhibiting proteolytic activation of latent TGF beta, levels of the endogenous growth factor were measured in differentiating myoblast cultures. Latent TGF beta is rapidly depleted from control cultures within 24 hours of plating, but remains relatively stable in aprotinin-treated cultures. Consistent with this, aprotinin-treated cultures have reduced levels of active TGF beta. These data indicate that Kunitz-domain containing protease inhibitors may help orchestrate the onset of myogenesis, possibly by regulating the activity of TGF beta-like molecules.

A small family of elements with long inverted repeats is located near sites of developmentally regulated DNA rearrangement in Tetrahymena thermophila

Extensive DNA rearrangement occurs during the development of the somatic macronucleus from the germ line micronucleus in ciliated protozoans. The micronuclear junctions and the macronuclear product of a developmentally regulated DNA rearrangement in Tetrahymena thermophila, Tlr1, have been cloned. The intrachromosomal rearrangement joins sequences that are separated by more than 13 kb in the micronucleus with the elimination of moderately repeated micronucleus-specific DNA sequences. There is a long, 825-bp, inverted repeat near the micronuclear junctions. The inverted repeat contains two different 19-bp tandem repeats. The 19-bp repeats are associated with each other and with DNA rearrangements at seven locations in the micronuclear genome. Southern blot analysis is consistent with the occurrence of the 19-bp repeats within pairs of larger repeated sequences. Another family member was isolated. The 19-mers in that clone are also in close proximity to a rearrangement junction. We propose that the 19-mers define a small family of developmentally regulated DNA rearrangements having elements with long inverted repeats near the junction sites. We discuss the possibility that transposable elements evolve by capture of molecular machinery required for essential cellular functions.