Bacterial lipoprotein and lipopolysaccharide act synergistically to induce lethal shock and proinflammatory cytokine production

Septic shock is a major cause of death in the world. Although much is known about the role of LPS in septic shock, little is known about the role of other bacterial components. Lipoprotein (LP) is a major component of bacteria in the family Enterobacteriaceae. LP purified from Escherichia coli was shown to induce TNF-alpha and IL-6 production in peritoneal exudate macrophages obtained from LPS-responsive (C3H/HeOuJ) and LPS-nonresponsive (C3H/HeJ) mice. LP and LPS acted synergistically to induce cytokine production not only in C3H/HeOuJ macrophages but also in C3H/HeJ macrophages. These results suggest that LPS can induce cellular signaling in C3H/HeJ macrophages, and that LPS and LP activate macrophages via different receptors and/or signaling pathways. The role LP plays in septic shock was investigated using the mouse D-galactosamine model. LP induced lethal shock and in vivo production of TNF-alpha and IL-6 in both LPS-responsive and LPS-nonresponsive mice. LPS failed to induce lethal shock or in vivo cytokine production in C3H/HeJ mice. However, LP and LPS acted synergistically in inducing lethal shock and in vivo cytokine production in both LPS-responsive and LPS-nonresponsive mice. Finally, a heat-killed preparation of an E. coli mutant strain that lacked LP was shown to be less efficient than heat-killed wild-type E. coli at inducing lethal shock in C3H/HeJ mice. Collectively, these results suggest that LP and LPS induce cytokine production via different mechanisms and that LP plays an important role in septic shock induced by bacteria in the family Enterobacteriaceae.

Bacterial lipoprotein and lipopolysaccharide act synergistically to induce lethal shock and proinflammatory cytokine production

Septic shock is a major cause of death in the world. Although much is known about the role of LPS in septic shock, little is known about the role of other bacterial components. Lipoprotein (LP) is a major component of bacteria in the family Enterobacteriaceae. LP purified from Escherichia coli was shown to induce TNF-alpha and IL-6 production in peritoneal exudate macrophages obtained from LPS-responsive (C3H/HeOuJ) and LPS-nonresponsive (C3H/HeJ) mice. LP and LPS acted synergistically to induce cytokine production not only in C3H/HeOuJ macrophages but also in C3H/HeJ macrophages. These results suggest that LPS can induce cellular signaling in C3H/HeJ macrophages, and that LPS and LP activate macrophages via different receptors and/or signaling pathways. The role LP plays in septic shock was investigated using the mouse D-galactosamine model. LP induced lethal shock and in vivo production of TNF-alpha and IL-6 in both LPS-responsive and LPS-nonresponsive mice. LPS failed to induce lethal shock or in vivo cytokine production in C3H/HeJ mice. However, LP and LPS acted synergistically in inducing lethal shock and in vivo cytokine production in both LPS-responsive and LPS-nonresponsive mice. Finally, a heat-killed preparation of an E. coli mutant strain that lacked LP was shown to be less efficient than heat-killed wild-type E. coli at inducing lethal shock in C3H/HeJ mice. Collectively, these results suggest that LP and LPS induce cytokine production via different mechanisms and that LP plays an important role in septic shock induced by bacteria in the family Enterobacteriaceae.

Hyperproduction, purification, and mechanism of action of the cytotoxic enterotoxin produced by Aeromonas hydrophila

A gene encoding the cytotoxic enterotoxin (Act) from Aeromonas hydrophila was hyperexpressed with the pET, pTRX, and pGEX vector systems. Maximum toxin yield was obtained with the pTRX vector. Approximately 40 to 60% of Act was in a soluble form with the pTRX and pET vector systems. The toxin protein was purified to homogeneity by a combination of ammonium sulfate precipitation and fast protein liquid chromatography-based column chromatographies, including hydrophobic, anion-exchange, sizing, and hydroxylapatite chromatographies. Purified mature toxin migrated as a 52-kDa polypeptide on a sodium dodecyl sulfate (SDS)polyacrylamide gel that reacted with Act-specific antibodies in immunoblots. The minimal amount of toxin needed to cause fluid secretion in rat ileal loops was 200 ng, and the 50% lethal dose for mice was 27.5 ng when injected intravenously. Binding of the toxin to erythrocytes was temperature dependent, with no binding occurring at 4 degrees C. However, at 37 degrees C the toxin bound to erythrocytes within 1 to 2 min. It was determined that the mechanism of action of the toxin involved the formation of pores in erythrocyte membranes, and the diameter of the pores was estimated to be 1.14 to 2.8 nm, as determined by the use of saccharides of different sizes and by electron microscopy. Calcium chloride prevented lysis of erythrocytes by the toxin; however, it did not affect the binding and pore-forming capabilities of the toxin. A dose-dependent reduction in hemoglobin release from erythrocytes was observed when Act was preincubated with cholesterol, but not with myristylated cholesterol. With 14C-labeled cholesterol and gel filtration, the binding of cholesterol to Act was demonstrated. None of the other phospholipids and glycolipids tested reduced the hemolytic activity of Act. The toxin also appeared to undergo aggregation when preincubated with cholesterol, as determined by SDS-polyacrylamide gel electorphoresis. As a result of this aggregation, Act's capacity to form pores in the erythrocyte membrane was inhibited.

Melittin binds to secretory phospholipase A2 and inhibits its enzymatic activity

Synthetic melittin inhibited the enzymatic activity of secretory phospholipase A2 (PLA2) from various sources, including bee and snake venoms, bovine pancreas, and synovial fluid from rheumatoid arthritis patients, irrespective of substrate (e.g., [14C]-phosphatidylcholine or phosphatidylethanolamine vesicles and [3H]-oleic acid-labeled E.coli). A Lineweaver-Burk analysis showed that melittin was a noncompetitive inhibitor of bee venom PLA2, causing a change in Vmax from 200 to 50 units/min/mg of protein. The Km remained unchanged (0.75 nmole). Melittin inhibited approximately 50% of purified bee venom PLA2 activity in a 30:1 molar ratio (melittin:enzyme). Because the enzyme kinetics indicated a PLA2-melittin interaction, a melittin-sepharose affinity column was used to purify a PLA2 from human serum. Further, an enzyme-linked assay was developed to quantitate PLA2 activity in biological fluids using avidin-peroxidase and ELISA plates coated with biotinylated melittin. These observations may have potential therapeutic significance, as well as provide a convenient basis for the isolation and quantitation of PLA2.

Lipoprotein from Yersinia enterocolitica contains epitopes that cross-react with the human thyrotropin receptor

Yersinia enterocolitica has recently been shown to produce a low molecular mass envelope protein that contains an epitope(s) that is cross-reactive with the extracellular domain of the human thyrotropin receptor (ETSHR). In this study, we have generated mAb to this cross-reactive protein and have obtained amino acid sequences for peptide fragments obtained from Lys-c digestion of the protein. The amino acid sequences of these peptides were identical to sequences present in bacterial lipoprotein (LP). All bacteria of the Enterobacteriaceae family produce LP as a major outer membrane protein. However, the ETSHR cross-reactive epitope(s) was shown to be unique to LP produced by Yersinia species. This was shown by Western blot analysis using a mAb specific for LP and with affinity-purified Ab specific for either LP or ETSHR and obtained from mouse antiserum generated to Y. enterocolitica. LPs from different Gram-negative bacteria were shown to be mitogenic for C3H/HeJ spleen cells and induced production and secretion of significant levels of Ig. Production of Ab that recognized the ETSHR was only induced in spleen cells stimulated with the LP obtained from Yersinia. In contrast, LP was not mitogenic for either human PBMC or human B cells. However, LP did induce IL6 and IL8 production in human monocytes at levels equivalent to that seen after LPS activation. These results identify, for the first time, the Yersinia envelope protein that is cross-reactive with the ETSHR and show that it can activate human monocytes. These findings are potentially important for advancing our understanding of the role molecular mimicry plays in the induction of autoimmunity to the thyrotropin receptor.

Lipoprotein from Yersinia enterocolitica contains epitopes that cross-react with the human thyrotropin receptor

Yersinia enterocolitica has recently been shown to produce a low molecular mass envelope protein that contains an epitope(s) that is cross-reactive with the extracellular domain of the human thyrotropin receptor (ETSHR). In this study, we have generated mAb to this cross-reactive protein and have obtained amino acid sequences for peptide fragments obtained from Lys-c digestion of the protein. The amino acid sequences of these peptides were identical to sequences present in bacterial lipoprotein (LP). All bacteria of the Enterobacteriaceae family produce LP as a major outer membrane protein. However, the ETSHR cross-reactive epitope(s) was shown to be unique to LP produced by Yersinia species. This was shown by Western blot analysis using a mAb specific for LP and with affinity-purified Ab specific for either LP or ETSHR and obtained from mouse antiserum generated to Y. enterocolitica. LPs from different Gram-negative bacteria were shown to be mitogenic for C3H/HeJ spleen cells and induced production and secretion of significant levels of Ig. Production of Ab that recognized the ETSHR was only induced in spleen cells stimulated with the LP obtained from Yersinia. In contrast, LP was not mitogenic for either human PBMC or human B cells. However, LP did induce IL6 and IL8 production in human monocytes at levels equivalent to that seen after LPS activation. These results identify, for the first time, the Yersinia envelope protein that is cross-reactive with the ETSHR and show that it can activate human monocytes. These findings are potentially important for advancing our understanding of the role molecular mimicry plays in the induction of autoimmunity to the thyrotropin receptor.

Induction of apoptosis in multi-drug resistant (MDR) human glioblastoma cells by SN-38, a metabolite of the camptothecin derivative CPT-11

The overexpression of the multidrug resistance (mdr1) gene and its product, P-glycoprotein (P-gp), is thought to limit the successful chemotherapy of human tumors. Recent studies demonstrate that SN-38, a metabolite of the camptothecin (CPT) derivative CPT-11, has antitumor effects on several tumors, but the mechanisms responsible for its cytotoxicity remain unclear. We therefore determined whether SN-38 has cytotoxic effects on MDR human glioblastoma GB-1 cells and non-MDR human glioblastoma U87-MG cells. Furthermore, we determined what role SN-38 plays in the induction of cytotoxicity in these tumor cells. In this study, we demonstrated that SN-38 had significantly stronger antitumor effects on GB-1 and U-87MG cells than did CPT (P < 0.01 and P < 0.05, respectively). In addition, findings obtained using a DNA fragmentation assay, Hoechst 33258 staining, in situ end-labeling and cell cycle analysis demonstrated that SN-38 induced apoptosis in these tumors. Our results suggest that SN-38 has a stronger antitumor effect on malignant glioma cells regardless of MDR expression than does CPT, and therefore can be considered a new chemotherapeutic agent potentially effective in the treatment of human primary or recurrent malignant gliomas resistant to chemotherapy.

Amyloid load and neural elements in Alzheimer's disease and nondemented individuals with high amyloid plaque density

The amyloid burden and relationship between amyloid deposits and neural elements were investigated in sections of prefrontal neocortex from eight Alzheimer's disease (AD) patients and four age-matched nondemented controls with high amyloid plaque density (HPND). Computer-based image analysis revealed that the total area occupied by betaA4 immunoreactivity was significantly greater (P < 0.031) in AD (27.1%) than in HPND (14.5%) sections. The total betaA4-positive area occupied by nondiffuse plaques was significantly greater (P < 0.05) in AD (13.6%) than in HPND (5.2%) sections. The percentage of diffuse (DPs) and nondiffuse plaques (NDPs) which contained neurons, astrocytes, microglia, dystrophic neurites, and amyloid precursor protein (APP) was also determined. The frequency of association between betaA4 and these neural elements was similar between AD and HPND cases in both diffuse and nondiffuse plaques. Forty percent of DPs in AD and HPND sections contained neuronal perikarya. Microglia, dystrophic neurites, and APP were detected in most nondiffuse plaques in both AD and HPND sections. While astrocyte cell bodies were not present in either diffuse or nondiffuse plaques, their processes were detected in most. These findings indicate that amyloid deposition and nondiffuse plaques are greater in AD than in HPND sections. The association between microglia and nondiffuse plaques supports the hypothesis that these resident immune cells participate in aggregation and redistribution of amyloid deposits and possibly formation of dystrophic neurites.

Molecular and biochemical characterization of a heat-labile cytotonic enterotoxin from Aeromonas hydrophila

We report herein the DNA sequence analysis of the heat-labile cytotonic enterotoxin gene (alt) from Aeromonas hydrophila and the biological function of the purified hyperproduced toxin (Alt). One large open-reading frame (ORF), comprised of 1104 bp, was detected at positions 804 to 1907 bp on a 4.0-kb Sa/l DNA fragment from Aeromonas. This ORF encodes for a protein having 368 amino acids (aa) with a computed molecular weight of 38 kDa. The aa sequence of the first 15 NH2-terminal residues of the mature native Alt from A. hydrophila matched with the DNA-derived aa sequence of the alt gene expressed in E. coli starting at position 19, which was leucine. The first 18aa residues of the Alt represented a putative signal sequence with alanine at its carboxy terminus. A BLAST search of the entire database showed 45-51% identity of the Alt, starting at position 158 with the carboxy half of the phospholipase C (PLC) and lipase from A. hydrophila; however, the purified Alt had no lipase/PLC activity. The alt gene was hyperexpressed using gene fusion expression vector systems, and the recombinant Alt exhibited a size of 35-40 kDa. The pure recombinant Alt elongated Chinese hamster ovary cells and elicited fluid secretion in rats ligated intestinal loops, indicating its enterotoxicity. Immunization of mice with recombinant Alt resulted in a reduced fluid secretory response when challenged with Aeromonas. The biological activity of the recombinant Alt in E. coli was about 10-fold less, compared to native Alt from Aeromonas, indicating differential processing of the toxin. The antibodies to native Alt neutralized the biological activity of the recombinant toxin, and these antibodies reacted with the same specificity to the native and recombinant Alt in immunoblots. The role of cyclic adenosine monophosphate and prostaglandins in causing a fluid secretory response by Alt also was demonstrated.

Phospholipase A2 activating protein and idiopathic inflammatory bowel disease

BACKGROUND

Crohn's disease and ulcerative colitis are idiopathic inflammatory bowel diseases (IBD) involving synthesis of eicosanoids from arachidonic acid (AA), which is released from membrane phospholipids by phospholipase A2 (PLA2). A potentially important regulator of the production of these mediators is a protein activator of PLA2, referred to as PLA2 activating protein (PLAP).

AIMS

The purpose of this investigation was to discover if PLAP values might be increased in the inflamed intestinal tissue of patients with IBD and in intestinal tissue of mice with colitis.

PATIENTS

Biopsy specimens were taken from patients with ulcerative colitis and Crohn's disease undergoing diagnostic colonoscopy, and normal colonic mucosa was obtained from patients without IBD after surgical resection.

METHODS

Immunocytochemistry with affinity purified antibodies to PLAP synthetic peptides was used to locate PLAP antigen in sections of intestinal biopsy specimens from IBD patients compared with that of normal intestinal tissue. Northern blot analysis with a murine [32P] labelled plap cDNA probe was performed on RNA extracted from the colons of mice fed dextran sulphate sodium (DSS) and cultured HT-29 cells exposed to lipopolysaccharide (LPS).

RESULTS

PLAP antigen was localised predominantly within monocytes and granulocytes in intestinal tissue sections from IBD patients, and additional deposition of extracellular PLAP antigen was associated with blood vessels and oedema fluid in the inflamed tissues. In contrast, tissue sections from normal human intestine were devoid of PLAP reactive antigen, except for some weak cytoplasmic reaction of luminal intestinal epithelial cells. Similarly, colonic tissue from DSS treated mice contained an increased amount of PLAP antigen compared with controls. The stroma of the lamina propria of the colonic mucosa from the DSS treated mice reacted intensely with antibodies to PLAP synthetic peptides, while no reaction was observed with control mouse colons. These data were supported by northern analysis which showed that PLAP mRNA was increased in the colons of DSS treated mice and cultured HT-29 cells exposed to LPS.

CONCLUSIONS

As PLAP values were increased in the intestinal mucosa of IBD patients and mice with colitis, as well as in LPS treated cultured HT-29 cells, a role was postulated for PLAP in increasing PLA2 activity, which leads to the increased synthesis of eicosanoids in intestinal tissues of patients with these inflammatory diseases.

The transforming activities of MDM2 in cultured neonatal rat astrocytes

Although the molecular events regulating the pathogenesis of malignant astrocytomas remains unclear, the inactivation of tumor suppressor genes may be a key factor. The inactivation of p53 by mutation or deletion, however, is not the only obligatory step in astrocytoma genesis. The MDM2 protein has been shown to bind to and downmodulate p53 function, and to have oncogenic capacity. The MDM2 gene is also amplified and overexpressed in a subset of malignant astrocytomas without p53 mutation. Here we show that overexpression of MDM2 promoted the DNA synthesis of cultured neonatal rat astrocytes (RNB cells), abrogated the transcriptional activity of wild-type p53, conferred invasive activity, and subsequently induced the transformation from astrocytes to high-grade astrocytomas. Intriguingly, MDM2 enhanced the expression of angiogenic mitogens; basic fibroblast growth factor (bFGF) and platelet-derived growth factor (PDGF) in RNB cells. These results indicate that MDM2 may play an important role in the progression of astrocytomas, by not only conferring invasive activity but also stimulating the expression of angiogenic growth factors.

mdm2 gene mediates the expression of mdr1 gene and P-glycoprotein in a human glioblastoma cell line

The overexpression of the multidrug resistance (mdr1) gene and its product, P-glycoprotein (P-gp), is thought to limit the successful chemotherapy of human tumours. The mechanism by which mdr1 gene and P-gp are overexpressed in human tumours, however, is not yet clear. In this report, we show that the mdm2 (murine double minute 2) gene induced the expression of the mdr1 gene and P-gp in human glioblastoma U87-MG cells, which did not express the MDM2 protein or P-gp. The mdm2 gene, in addition, conferred the resistance of U87-MG cells to the apoptotic cell death induced by etoposide (VP-16) or doxorubicin. Furthermore, treatment with mdm2 antisense oligonucleotides inhibited the expression of P-gp in MDM2-expressing U87-MG cells. These findings suggest that the mdm2 gene may play an important role in the development of MDR phenotype in human tumours.

Distribution of immunoglobulin superfamily members ICAM-1, -2, -3, and the beta 2 integrin LFA-1 in multiple sclerosis lesions

To identify potential molecular substrates for leukocyte trafficking and activation in multiple sclerosis (MS) brain, we determined the immunocytochemical distribution of the beta, integrin lymphocyte-function-associated antigen-1 (LFA-1) and its major ligands, intercellular adhesion molecule (ICAM)-1, ICAM-2, and ICAM-3 in MS tissue. Colocalization of these adhesion molecules with lineage-specific markers was analyzed by dual-labeling immunocytochemistry and confocal microscopy. ICAM-1 and ICAM-2 were detected on endothelial cells, and ICAM-3 immunoreactivity was restricted to infiltrating leukocytes. In control brain, 10% of glucose transporter-1 positive vessels contained ICAM-1 immunoreactivity on their luminal surface and 21% were ICAM-2-positive. A significant increase in ICAM-1-positive vessels was found in MS brains. This increase was greater in MS lesions (81% of vessels) than in nonlesion areas (37% of vessels). A significant increase in ICAM-1-positive vessels was found in encephalitis (55% of vessels) but not in Parkinson's (17% of vessels) brains. The percentage of vessels expressing ICAM-2 was not increased in MS, encephalitis, or Parkinson's brains. Both ICAM-3 and LFA-1 were detected on the vast majority of infiltrating lymphocytes and monocytes in and near MS lesions, and these cells were often closely apposed to each other. In addition, LFA-1 was detected on activated microglia located close to the edge of demyelinating lesions. ICAM-3-positive leukocytes were often closely apposed to LFA-1-positive microglia. These results suggest a role for ICAM-1, -2, and LFA-1 in the transendothelial migration of leukocytes into MS brain and a role for ICAM 3/LFA-1 interactions in the activation of lymphocytes, monocytes, and microglia in MS lesions.

WAF1/CIP1 increases the susceptibility of p53 non-functional malignant glioma cells to cisplatin-induced apoptosis

Induction of apoptosis in tumor cells is an important determinant in the outcome of therapy. Molecular details of the apoptosis pathway, however, are still poorly defined. The recently discovered WAF1/CIP1 gene is a potent inhibitor of cyclin-dependent kinases and a mediator of tumor-suppressor p53-dependent apoptosis by DNA damage. In addition, WAF1/CIP1 expression is shown to be triggered through the p53-independent pathway. The relationship between WAF1/CIP1 and p53-independent apoptosis by DNA damage, however, remains unclear. In this study, we show that WAF1/CIP1 was induced in p53-dependent apoptosis of U87-MG glioma cells by cis-diamminedichloroplatinum (cisplatin), and overexpression of WAF1/CIP1 induced apoptosis in U87-MG cells without cisplatin treatment. In contrast, the p53-independent apoptosis of GB-1 glioma cells by cisplatin did not express WAF1/CIP1. Overexpression of WAF1/CIP1 inhibited DNA synthesis in GB-1 cells, but did not induce apoptosis. Interestingly, WAF1/CIP1 increased the susceptibility of GB-1 cells to cisplatin-induced apoptosis. These results suggest that overexpression of WAF1/CIP1 may have potential for the treatment of tumors with non-functional p53.

Vascular hypertrophy is an early finding in essential hypertension and is related to arterial pressure waveform contour

The effects of hypertension on the arterial vasculature were examined in a study group of 20 patients with newly diagnosed essential hypertension, 18 patients with chronic essential hypertension, and 32 control subjects with normal blood pressure. Left ventricular mass was determined echocardiographically. Carotid artery intimal-medial thickness was measured by means of B-mode ultrasound imaging, and carotid arterial waveforms were obtained by applanation tonometry. Compared with that in control subjects, carotid intimal-medial thickness was increased in patients with chronic hypertension (0.74 +/- 0.17 mm vs 0.61 +/- 0.15 mm in control subjects; p < 0.01) and in patients with newly diagnosed hypertension (0.66 +/- 0.12 mm vs 0.61 +/- 0.15 mm in control subjects; p < 0.05). Left ventricular mass was also higher in patients with chronic hypertension than in control subjects but was very similar between control subjects and those with newly diagnosed hypertension. Both the group with early hypertension and the group with chronic hypertension had an increased incidence of early waveform reflection evident on carotid arterial waveform examination. By multiple regression analysis, independent predictors of increased carotid intimal-medial thickness were age, systolic arterial pressure, and Murgo class of arterial waveform. Conduit arterial wall thickening precedes left ventricular remodeling in essential hypertension and is significantly related to the degree of pressure elevation and the arterial waveform contour.

Involvement of interleukin-1 beta-converting enzyme in apoptosis of bFGF-deprived murine aortic endothelial cells

Apoptosis (programmed cell death) is an essential physiological process that is genetically regulated and contributes to the balance between cell growth, differentiation, and the maintenance of normal cells. Recent studies show that deprivation of growth factor induces apoptosis in endothelial cells. However, the molecular mechanisms regulating apoptosis remain unclear. In this study, we demonstrate that deprivation of basic fibroblast growth factor (bFGF) increased the expression of interleukin-1 beta-converting enzyme (ICE) protein, and subsequently induced apoptosis in murine aortic endothelial (MAE) cells. In contrast, the proteins of the tumor suppressor p53 and c-myc were undetected during apoptosis. This apoptosis was suppressed by the tetrapeptide ICE inhibitor, Ac-YVAD-CMK. Overexpression of murine ICE, in addition, induced apoptosis in MAE cells using gene transfer techniques. These results strongly suggest that ICE may mediate apoptosis in bFGF-deprived endothelial cells, and the suppression of ICE function could represent a novel approach for the protection of endothelial cells from damages.-Kondo, S., Kondo, Y., Yin, D., Barnett, G. H., Kaakaji, R., Peterson, J. W., Morimura, T., Kubo, H., Takeuchi, J., Barna, B. P. Involvement of interleukin-1 beta converting enzyme in apoptosis of bFGF-deprived murine aortic endothelial cells.

Yersinia enterocolitica envelope proteins that are crossreactive with the thyrotropin receptor (TSHR) also have B-cell mitogenic activity

Autoantibodies to the thyrotropin receptor (TSHR) have been shown to mediate the hyperthyroidism associated with Graves' disease (GD). A number of hypotheses have been proposed which link an infectious agent to the mechanism(s) involved in the induction of GD. Several studies have suggested that the development of GD may be linked to infection with the enteric pathogen Yersinia enterocolitica. We have recently identified two low molecular weight (5.5 and 8 kDa) envelope proteins of Y. enterocolitica that are cross-reactive with the extracellular domain of human TSHR (ETSHR). In this study, we have purified these ETSHR-crossreactive Yersinia proteins (TSHR-CRP) and have further characterized their immunoreactivity. Both the 5.5 and 8 kDa TSHR-CRPs were shown to be mitogenic for mouse spleen cells. This mitogenic activity was specific for B cells and was not due to lipopolysaccharide (LPS) contamination. TSHR-CRPs were mitogenic for LPS-non-responsive spleen cells obtained from C3H/Hej mice, and polymyxin B did not inhibit the mitogenic activity of the TSHR-CRPs. TSHR-CRPs also induced high levels of IL-6 production in B cells and induced production and secretion of significant levels of IgG and IgM. Finally, culture supernatants from TSHR-CRP-stimulated spleen cells were shown by Western blot analysis to contain antibodies that recognized the ETSHR These results identify for the first time two envelope proteins of Yersinia that have mitogenic activity and therefore could represent important proteins involved in the pathogenesis of Yersinia infections. Because these mitogenic proteins also contain epitopes crossreactive with the TSHR, they are potentially important for advancing our understanding of the role molecular mimicry plays in the induction of autoimmunity to the TSHR.

Neutrophil infiltration, glial reaction, and neurological disease in transgenic mice expressing the chemokine N51/KC in oligodendrocytes

Chemokines (pro-inflammatory chemoattractant cytokines) are expressed in pathological conditions of the central nervous system (CNS). Previous studies suggested that the CNS is relatively resistant to leukocyte diapedesis after chemokine injection, leaving their functional role unresolved. The CNS function of N51/KC, a neutrophil-selective chemokine, was addressed by expressing N51/KC under control of the myelin basic protein (MBP) promoter in transgenic (tg) mice (MBP-N51/KC mice). CNS-specific N51/KC expression produced remarkable neutrophil infiltration into perivascular, meningeal, and parenchymal sites, demonstrating that this chemokine exerts the multiple functions in vivo required to recruit leukocytes into the CNS. MBP-N5 1/KC mice represent an incisive model for the molecular dissection of neutrophil entry into the CNS. Unexpectedly, MBP-N51/KC mice developed a neurological syndrome of pronounced postural instability and rigidity at high frequency beginning at 40 days of age, well after peak chemokine expression. 68/182 mice in one tg fine were found dead before one year of age, with prominent neurological symptoms premortem in 26 (38%). Florid microglial activation and blood-brain barrier disruption without dysmyelination were the major neuropathological alterations. Late-onset neurological symptoms in MBP-N51/KC mice may indicate unanticipated consequences of CNS chemokine expression.

Cholera toxin induces synthesis of phospholipase A2-activating protein

The mechanism of cholera toxin (CT)-stimulated arachidonate metabolism was evaluated. CT caused rapid in vitro synthesis of prostaglandin E2 (PGE2) in murine smooth muscle-like cells (BC3H1), reaching maximal levels within 3 to 4 min. In comparison, cyclic AMP (cAMP) levels were unchanged, and addition of dibutyryl cAMP did not affect PGE2 synthesis. CT-induced PGE2 synthesis was prevented by actinomycin D or cycloheximide, indicating a need for de novo protein synthesis. Northern blot analysis of total RNA from BC3H1 cells revealed that exposure to CT resulted in an increase in abundance of mRNA encoding phospholipase A2 (PLA2)-activating protein (PLAP). PLAP is a regulatory protein that increases the enzymatic activity of cellular PLA(2), which in turn causes increased hydrolysis of arachidonate from membrane phospholipids. Furthermore, CT evoked the accumulation of PLAP mRNA in J774 (murine monocyte/macrophage) and Caco-2 (human intestinal epithelial) cells in vitro, but the responses were more delayed than that of BC3H1 cells. A protein band of approximately 35 kDa, which corresponded to the size of PLAP, was observed in sodium dodecyl sulfate extracts of Caco-2 cells by Western blot (immunoblot) analysis using affinity-purified antibodies to PLAP synthetic peptides. Synthesis of PLAP protein was increased after 2 h of exposure to CT. Exposure of mouse intestinal loops to either CT or live Salmonella typhimurium for 3 h increased mucosal PLAP mRNA levels. The role of PLAP in CT-induced PGE2 synthesis provides an attractive explanation for the reported suppression of CT-induced intestinal secretion by inhibitors of protein synthesis.

Comparison of thickness and distensibility in the carotid artery and descending thoracic aorta: in vivo ultrasound assessment

Early atherosclerotic changes in the carotid artery and thoracic aorta have been examined by high-frequency ultrasound measuring of intimal-medial thickness and stiffness. Whether changes in stiffness and thickness occur in parallel and whether the determinants of stiffness and thickness in the two vessels are similar is unknown. To examine the relation between ultrasonographic measures of atherosclerosis in the carotid and the thoracic aorta, 146 patients aged 20 to 84 years (mean 54 years) were studied by both transesophageal echocardiography (TEE) and carotid duplex scanning. From two-dimensionally derived M-mode recordings of the thoracic aorta and high-frequency B-mode imaging of the common carotid, the intimal-medial thickness was measured along with diastolic and systolic diameters for calculation of stiffness. Interobserver and intraobserver variability of carotid and aortic intimal-medial thickness and diameter were low. There was a good relation between carotid and aortic intimal-medial thickness (r = 0.69; p=0.0001). Age was the major independent determinant of thickness in both vessels. Carotid and aortic stiffness, as measured by Peterson's elastic modulus, were less closely related (r=0.51; p=0.0001). Age was the only independent predictor of stiffness in both vessels. In conclusion, structural ultrasonographic manifestations of early atherosclerosis in the carotid artery and thoracic aorta are closely related. Large population studies measuring only carotid intimal-medial two-thickness may reflect atherosclerotic changes occurring throughout the vascular bed.

Intracellular calcium, myosin light chain phosphorylation, and contractile force in experimental cerebral vasospasm

It remains unknown what proportion of delayed arterial narrowing after subarachnoid hemorrhage depends on ongoing metabolic activity within arterial smooth muscle cells versus changes in the passive structural properties of the arterial wall. To determine this, vasospasm was induced by the double subarachnoid hemorrhage model. Anterior spinal artery segments were harvested from control dogs and from dogs with vasospasm. The segments were suspended in a force transducer and stretched to an optimal length for contraction. The difference in tension between 37 and 0 degrees C was defined as the intrinsic tone, and the residual tension at 0 degrees C was defined as the passive tension. The segments taken from dogs with vasospasm had increased intrinsic tone and passive tension (the differences were 3.8 kN/m2 [P < 0.05] and 14.8 kN/m2 [P < 0.025], respectively). Hence, the passive component accounted for 79.6% of the increased tension in vasospastic arterial segments. The intracellular calcium concentration was measured in these segments, using the luminescent calcium indicator, aequorin. The vasospastic segments had increased basal intracellular calcium concentration (398 versus 258 nmol/L, P < 0.025). In parallel experiments, control and vasospastic vessels were immediately excised when the animals were killed, and the vessels were quick-frozen. Subsequently, using two-dimensional gel electrophoresis to measure percent myosin light chain phosphorylation, vasospastic vessels were found to have increased myosin light chain phosphorylation (37 versus 2%, P < 0.05). The increased intracellular calcium concentration and increased percent myosin light chain phosphorylation in vasospastic segments implicate a role for the Ca(2+)-dependent pathway of smooth muscle cell contraction in vasospasm.

A nontoxic cholera enterotoxin (CT) analog is chimeric with regard to both epitypes of CT-B subunits, CT-B-1 and CT-B-2

The gene encoding a nontoxic analog, CT-2*, of cholera enterotoxin (CT) with attenuating codon substitutions in the A subunit was introduced into the attenuated Vibrio cholerae classical biotype mutant candidate vaccine strain CVD103, which produces the B subunit (but not the A subunit) of CT-1. The recombinant strain produces a chimeric nontoxic analog holotoxin containing both CT-B-1 and CT-B-2 subunits. This offers potential advantages over CVD103 in the induction of immunity against E1 Tor biotype and V. cholerae O139 strains which produce CT-B-2. The recombinant protein may also be useful in polysaccharide-protein conjugate vaccines against both O1 and O139 serovars of V. cholerae.