Cardiolipin on the surface of apoptotic cells as a possible trigger for antiphospholipids antibodies

This study provides evidence that cardiolipin (CL) molecules are expressed on the surface of apoptotic cells and are recognized by antiphospholipid antibodies, purified from patients with the antiphospholipid antibody syndrome (APS). CL expression on cell surface was demonstrated by high performance thin layer chromatography analysis of phospholipids from plasma membrane purified fractions and by the positive staining with the CL-specific dye nonyl-acridine orange. This finding was complemented with the observation that aCL IgG purified from patients with APS bind to the surface of apoptotic cells. This staining shows a clustered distribution mostly localized on surface blebs. Interestingly, CL exposure on the cell surface preceded the DNA fragmentation, as shown by cytofluorimetric analysis. These findings demonstrate that exposure of CL molecules on the cell plasma membrane is an early event of the apoptotic cellular program that may represent an in vivo trigger for the generation of aCL.

Prosaposin treatment induces PC12 entry in the S phase of the cell cycle and prevents apoptosis: activation of ERKs and sphingosine kinase

We report that prosaposin treatment induced extracellular signal-regulated kinases (ERKs) and sphingosine kinase activity, increased DNA synthesis, and prevented cell apoptosis. Prosaposin treatment induced pheochromocytoma cells (PC12) to enter the S phase of the cell cycle; this effect was inhibited by the MEK inhibitor PD98059, indicating that prosaposin-induced ERK phosphorylation is required for stimulation of DNA synthesis. The prosaposin effect was also inhibited by pertussis toxin, indicating that the prosaposin receptor is a G-protein-coupled receptor. Prosaposin rescued PC12 cells from apoptosis induced by staurosporine or ceramide. Sphingosine kinase activity was increased by prosaposin treatment. We propose that this effect is a mechanism underlying the proliferative and anti-apoptotic functions of prosaposin. Prosaposin appears to be a key regulatory factor in the ceramide-S-1-P rheostat, which regulates cell fate.

A novel mechanism of CD4 down-modulation induced by monosialoganglioside GM3. Involvement of serine phosphorylation and protein kinase c delta translocation

In this report the molecular mechanism(s) involved in the rapid and selective endocytosis of cell surface glycoprotein CD4 induced by exogenous monosialoganglioside GM3 in human peripheral blood lymphocytes have been investigated. Inhibition of the GM3-induced CD4 down-modulation was observed in the presence of specific protein kinase C (PKC) inhibitors. Scanning confocal microscopy revealed the translocation and clustering on the cell surface of PKC isozymes delta and theta (more evidently than alpha and beta) after GM3 treatment, suggesting the involvement of these isozymes in the ganglioside-induced CD4 down-modulation. Exogenous GM3 induced phosphorylation of CD4 molecule, which then dissociated from p56(lck), as early as after 5 min. Moreover, addition of GM3 resulted in a rapid (1 min) cytosolic phospholipase A2 activation with consequent arachidonic acid release, whereas no phosphatidylinositol-phospholipase C activity was observed. Both PKC translocation and CD4 down-modulation were blocked by the trifluoromethylketone analog of arachidonic acid, a selective inhibitor of cytosolic phospholipase A2 and by mitogen-activated protein kinase inhibitor PD98059. Taken together, these findings strongly suggest that GM3 may trigger a novel mechanism of modulation of the CD4 surface expression through the activation of enzyme(s) involved in the regulation of cellular functions.

Ganglioside expression in human pancreatic islets

Recent biochemical studies have shown that the cytoplasmic islet cell-antibody autoantigen has properties of a monosialoganglioside (GM). To characterize islet glycolipids and ascertain whether islets express unique gangliosides, we determined the pattern of ganglioside expression in whole human pancreas and isolated human islets using high-performance liquid chromatography (HPLC) and high-performance thin-layer chromatography (HPTLC). The major gangliosides detected in glycolipid extracts of whole human pancreas were GM3, GD3 (disialoganglioside), and in a lesser amount, a GD1a-comigrating ganglioside. In contrast to whole human pancreas, isolated human islets were found to predominantly express GM3, an acidic glycolipid comigrating with GM2, and a ganglioside with mobility between GM2 and GM1 by both HPLC and HPTLC. Quantitation of the major ganglioside UV peaks seen on HPLC gave the following results. In whole pancreas, GM3 represented 66.7% of total gangliosides detected; an asialoglycolipid comigrating with GM2, 2.0%; a ganglioside migrating between GM2 and GM1, 2.6%; GD3, 22.6%; and a GD1a-comigrating ganglioside, 6.1%. In isolated islets, these components were found at the following levels: GM3, 14.9%; GM2-comigrating glycolipid, 74.2%; a ganglioside migrating between GM2 and GM1, 9.8%; GD3, 1.1%; and the GD1a-comigrating ganglioside, not detectable.

Colocalization and complex formation between prosaposin and monosialoganglioside GM3 in neural cells

Prosaposin, the precursor of saposins A, B, C, and D, was recently identified as a neurotrophic factor in vitro as well as in vivo. Its neurotrophic activity has been localized to a linear 12-amino acid sequence located in the NH2-terminal portion of the saposin C domain. In this study, we show the colocalization of prosaposin and ganglioside GM3 on NS20Y cell plasma membrane by scanning confocal microscopy. Also, TLC and western blot analyses showed that GM3 was specifically associated with prosaposin in immunoprecipitates; this binding was Ca2+-independent and not disassociated during sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The association of prosaposin-GM3 complexes on the cell surface appeared to be functionally important, as determined by differentiation assays. Neurite sprouting, induced by GM3, was inhibited by antibodies raised against a 22-mer peptide, prosaptide 769, containing the neurotrophic sequence of prosaposin. In addition, pertussis toxin inhibited prosaptide-induced neurite outgrowth, as well as prosaptide-enhanced ganglioside concentrations in NS20Y cells, suggesting that prosaposin acted via a G protein-mediated pathway, affecting both ganglioside content and neuronal differentiation. Our findings revealed a direct and tight GM3-prosaposin association on NS20Y plasma membranes. We suggest that ganglioside-protein complexes are structural components of the prosaposin receptor involved in cell differentiation.

Detection of antiphospholipid antibodies by immunostaining on thin layer chromatography plates

There is increasing interest in the role of antiphospholipid antibodies in the so-called 'antiphospholipid antibody syndrome' (APS). The two major methods currently employed for detecting the autoantibodies are the solid phase ELISA and the LAI test (inhibition of phospholipid dependent coagulation assay). In our study we have tested the possibility of detecting antiphospholipid antibodies by immunostaining on thin layer chromatography (TLC) plates, since this technique permits the use of pure phospholipid molecules as antigen. Sera were collected from 20 patients with SLE without APS, 20 patients with APS, 20 anti-HIV positive subjects, ten patients with signs of APS but antiphospholipid negative (ELISA), 20 patients with syphilis and 40 matched blood donors. Results showed that only 72.3% of sera containing detectable levels of aCL antibodies in solid phase ELISA were also positive for aCL in TLC immunostaining; these discrepancies may be due to the presence of antibodies reacting with a protein complexed with phospholipid (beta 2-glycoprotein-I) or, alternatively, to the different antigenic presentation of phospholipids on chromatograms compared to the surface of microtitre wells. Furthermore, aCL monoclonal antibody CAL-3, as well as nine sera positive for aCL, also reacted with PS and PE. Previous absorption of these sera with CL micelles completely abolished the reactivity with PS and PE, demonstrating cross-reactivity among these three phospholipids. In conclusion, our findings reveal that TLC immunostaining is more specific, but less sensitive, than ELISA for the detection of antiphospholipid antibodies in human sera.

Monosialoganglioside GM3 induces CD4 internalization in human peripheral blood T lymphocytes

Gangliosides modulate the expression of CD4 molecules on the cell surface of T lymphocytes. We report here that treatment of human peripheral blood lymphocytes with exogenous monosialoganglioside GM3 induces a rapid down-modulation of the CD4 molecules on the plasma membrane of CD4+ T lymphocytes, as assessed by cytofluorimetric analysis and quantitative immunoelectron microscopy. The CD4 down-modulation was ganglioside-dose dependent and was already evident after 5 min of treatment, reaching the maximum after 20 min. The expression of other surface antigens was not affected by GM3 treatment. The immunoelectron microscopic analysis showed that, following GM3 addition, gold labelled CD4 molecules were rapidly redistributed on the cell surface, clustered and internalized via endocytic pits and vesicles. These results indicate that CD4 down-modulation induced by GM3 occurs through an endocytic mechanism. A persistent low level of CD4 expression on the cell surface up to 24 h after GM3 treatment, compared with a stable expression of either CD4 in untreated cells and CD3 in GM3-treated cells, suggests intracellular degradation of the internalized CD4 molecules.

GM3 as a target of anti-lymphocytic ganglioside antibodies in AIDS patients

IgG antibodies reacting with the GM3-comigrating band extracted from pooled AIDS lymphocytes were detected in 33.3% of AIDS patients sera, in 8% of asymptomatic anti-HIV-positive subjects, in none of the sera obtained from asymptomatic anti-HIV-negative drug abusers, from patients with acute B and chronic C hepatitis, and from healthy donors. All positive sera reacted selectively with the GM3-comigrating band obtained from AIDS lymphocytes but not with the corresponding band from normal lymphocytes. The lymphocytic ganglioside autoantigen was revealed as GM3. In addition, two main data were shown: (a) AIDS lymphocytes have an increased concentration of GM3 and (b) the ceramide of AIDS lymphocytic GM3 has a different percentual composition of fatty acids in contrast to control cells. It is suggested that these quantitative and qualitative changes might be responsible for the appearance of circulating anti-lymphocytic GM3 antibodies.

Blood leukotrienes in headache: correlation with platelet activity

Platelet hyperactivity, one of the commonest findings associated with migraine, has been related to increased release of biologically active substances such as catecholamines and arachidonic acid metabolites, which seem to play a role in the pathogenesis of migraine. In this study, in vitro platelet aggregation tests were performed on samples from patients with different types of headache. The presence of platelet hyperactivity was clearly demonstrated in 11 patients with classical migraine between attacks, but not in 4 patients between attacks of common migraine. Nevertheless, the presence of a marked platelet hyporesponsivity was found during the attack phase of both classical and common migraine. No difference in platelet aggregability was found between attack and post-attack phases in 5 patients with cluster headache. Blood leukotrienes were analyzed in 8 patients with classical migraine and in the 5 patients with cluster headache. During the attack phase of classical migraine both LTC4 and LTB4 were present in the peripheral blood, while the post-attack phase was characterized by the disappearance of LTC4 and the presence of LTB4 and its transisomer delta 6-trans-LTB4. Blood leukotrienes were constantly absent during both phases of cluster headache. Incubation of normal platelets with LTC4 or delta 6-trans-LTB4 was followed by inhibition of platelet response to epinephrine. delta 6-trans-LTB4, at higher concentrations, induced the opposite effect. A possible role of blood leukotrienes in the changes occurring in platelet aggregability during the different phases of classical migraine, is discussed.

Autoantibodies against ganglioside GM3 represent a portion of anti-lymphocyte antibodies in AIDS patients

In this study we analysed the relationship between anti-lymphocytic ganglioside antibodies and anti-lymphocyte antibodies in AIDS patients. Anti-lymphocytic ganglioside antibodies were detected by thin layer chromatography (TLC) immunostaining; three colour flow cytometry was used to analyse circulating antibodies against different lymphocyte subsets. Anti-lymphocytic ganglioside antibodies were detected in 23 out of 49 AIDS patients sera (46.9%). All positive sera reacted selectively with the GM3 comigrating band from AIDS lymphocytes. Twenty two out of the 23 anti-lymphocytic GM3 positive sera also had antibodies against CD4+T cells, versus 17/26 anti-GM3 negative. Furthermore, patients with lymphocytic GM3 antibodies showed a significantly higher antibody reactivity against CD4+ T cells than patients in which these antibodies were not detected. The absorption tests revealed that preincubation of positive sera with GM3 was followed by a decrease in the reaction with target lymphocytes. These findings suggest that anti-GM3 antibodies are a portion, but not the majority, of antibodies reacting with CD4+ T cells.

Anticardiolipin and Anti-β2-GPI Are Two Distinct Populations of Autoantibodies

This study has been undertaken to assess whether anticardiolipin and anti-(32-GPI are two distinct populations of (auto)antibodies, and to clarify whether the β2-GPI region critical for phospholipid binding is also crucial for anti-β2-GPI reactivity.

Fourteen of the 62 anticardiolipin (aCL) ELISA positive sera (22.6%) were positive for anti-β2-GPI by immunoblotting, 42 (67.7%) for aCL using TLC immunostaining.

IgG fractions from 5 sera gave the same anticardiolipin reactivity detected by TLC immunostaining in the corresponding sera.

All anti-β2-GPI-positive sera were reactive with the phenylthio-carbamyl derivative of the protein, indicating that binding of phe-nylisothiocyanate with lysine residues does not modify the molecule antigenicity. In addition, incubation of IgG fractions with the phospholipid binding site did not modify reactivity with β2-GPI.

These findings demonstrate that: a) “true” antiphospholipid antibodies are detectable in patients sera; b) aCL and anti-β2-GPI have a different immunological profile; c) the β2-GPI phospholipid-binding site is not the region recognized by the antibodies.

Rat pancreatic ganglioside expression: differences between a model of autoimmune islet B cell destruction and a normal strain

Islet cell antibodies (ICA) bind antigens expressed in both human and rat pancreatic islets. Biochemical studies have shown that an ICA-autoantigen has the properties of a monosialo-ganglioside migrating between GM2 and GM1 standards (GM2-1). We therefore aimed to isolate and characterize gangliosides from whole pancreas and isolated islets of bio breeding diabetes-prone (BB-DP), bio breeding diabetes-resistant (BB-DR), and Wistar Furth (WF) rat strains. Gangliosides were characterized by TLC, HPLC, diode array analysis, and ganglioside-specific staining. ICA binding was studied by indirect immunostaining. The GM2-1 fraction was present in BB-DP, BB-DR, and WF rat pancreases (11, 17, and 9.5%, respectively, of total ganglioside content). Substantial differences were found in other fractions: in BB-DP pancreas, in addition to GM2-1, the main fractions were GM3 (49%), GD1a (12%), GT1b (5%), and a ganglioside migrating between GM1 and GD3 standards (23%), while in BB-DR pancreas the above components were 71, 5.5, 2, and 4.5%, respectively; in WF pancreas, the main fractions were GM3, GD3, GD1a, GT1b and a trisialoganglioside (GT*) migrating above the GT1b standard (42.7, 7, 20.2, 13.8, and 6.8, respectively). A different pattern of ganglioside expression was found in isolated islets of BB-DP, BB-DR, and WF rats: the GM2-1 fraction represented, respectively, 29.1, 30.4, and 31.6% of total ganglioside content; GM3 51.1, 66, and 68.4%. A fraction migrating between GM1 and GD3 standards was present only in BB-DP and BB-DR islets (19.8 and 3.6%, respectively). ICA-positive human sera reacted with pancreas of all rat strains studied, with similar end-point titers. In conclusion, (1) the GM2-1 ganglioside, in the same way as a putative target antigen of ICA, is equally expressed in BB-DP, BB-DR, and WF rat pancreata; and (2) the GM1-GD3 is expressed in higher amounts in BB-DP than in BB-DR pancreas and islets and is absent in WF.

Differential evaluation of bronchoalveolar lavage cells and leukotrienes in unilateral acute lung injury and ARDS patients

Patients with unilateral acute lung injury (UALI; n = 6) and ARDS (n = 4) were evaluated by bronchoalveolar lavage, as controls we used 5 patients suffering from cerebral hemorrhage and without pulmonary, cardiac or infectious disease who were mechanically ventilated. For each group of patients two independent bronchoalveolar lavages (BAL) were performed. The BAL fluid recovered from the two lungs was immediately analyzed for leukotrienes (LTS) by means of RP-HPLC and stained for cell counts. The BAL from the control group did not show any LTS and the percentage of neutrophils was within the normal range: 1 +/- 0.2% right lung and 1.2 +/- 0.4% left lung. The BAL fluid from UALI patients showed two different patterns, the injured lung showed high levels of LTS (39.1 +/- 8 ng ml-1 LTB4; 25 +/- 6 ng ml-1 LTD4 and 27.8 +/- 8.2 ng ml-1 11-trans LTC4) and an increased percentage of neutrophils (74.2 +/- 7%) compared to controls. Only 2 out of the 6 patients from the UALI group showed small amounts of LTB4 (4 ng ml-1) and LTD4 (3.2 ng ml-1). The BAL obtained from the "healthy lung" in both cases showed values of LTS almost eight fold lower than those present in the injured lung. The percentage of neutrophils from the unaffected lungs (4.3 +/- 7%) was not significantly different from controls. Lavage fluid from ARDS patients showed a similar picture to that of the affected lung from UALI patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased levels of prostaglandins and nitric oxide in esophageal mucosa of children with reflux esophagitis

BACKGROUND

Prostaglandin E2 (PGE2) is said to be both protective and detrimental for esophageal mucosal integrity. Nitric oxide (NO) controls several esophageal neuromuscular functions, including relaxation of the lower esophageal sphincter. The purpose of this study was to verify PGE2 and NO levels in esophageal mucosa of children with reflux esophagitis.

METHODS

The patients were 10 children, age range 7 to 12 years, affected by reflux esophagitis. The control subjects were 10 children, age range 6 to 11 years, with recurrent abdominal pain. Tissue fragments obtained by esophageal biopsies were placed in a culture medium and processed to obtain a cell suspension. Cells were incubated for 24 hours at 37 degrees C. Thereafter, supernatants were collected and divided into aliquots to determine the amounts of PGE2 and NO metabolites.

RESULTS

Esophageal cells obtained from reflux esophagitis patients synthesize and release a significantly higher (p < 0.01) amount of PGE2 and NO (PGE2 1.9 +/- 0.56 ng/10(6) cells per 24 hours; NO 124.94 +/- 18.36 microM/10(6) cells per 24 hours) than did the control group (PGE2 0.66 +/- 0.14 ng/10(6) cells per 24 hours; NO 68.03 +/- 12.3 microM/10(6) cells per 24 hours).

CONCLUSIONS

These results suggest that in esophageal mucosa, PGE2 and NO, in low concentrations, are protective, whereas, at high doses, they can be harmful. Higher amounts of PGE2 and NO in the esophageal mucosa of reflux esophagitis patients suggest that similar noxious stimuli trigger the inducible forms of the respective enzyme.

Association between GM3 and CD4-Ick complex in human peripheral blood lymphocytes

The aim of this study was to further elucidate our previous observation on molecular interaction of GM3, CD4 and p56Ick in microdomains of human peripheral blood lymphocytes (PBL). We analyzed GM3 distribution by immunoelectron microscopy and the association between GM3 and CD4-p56Ick complex by scanning confocal microscopy and co-immunoprecipitation experiments. Scanning confocal microscopy analysis showed an uneven signal distribution of GM3 molecules over the surface of human lymphocytes. Nearly complete colocalization areas indicated that CD4 molecules were distributed in GM3-enriched plasma membrane domains. Co-immunoprecipitation experiments revealed that CD4 and p56Ick were immunoprecipitated by IgG anti-GM3, demonstrating that GM3 tightly binds to the CD4-p56Ick complex in human PBL. In order to verify whether GM3 association with CD4 molecules may depend on the presence of p56Ick, we analyzed this association in U937, a CD4 + and p56Ick negative cell line. The immunoprecipitation with anti-GM3 revealed the presence of a 58kDa band immunostained with anti-CD4 Ab, suggesting that the GM3-CD4 interaction does not require its association with p56Ick. These findings support the view that GM3 enriched-domains may represent a functional multimolecular complex involved in signal transduction and cell activation.

Influence of labor and oxytocin on in vitro leukotriene release by human fetal membranes and uterine decidua at term gestation

OBJECTIVE

The purpose of this study was to determine whether labor and oxytocin influence in vitro leukotriene release by human fetal membranes and uterine decidua at term gestation.

STUDY DESIGN

All women (N = 21) were studied in an academic clinical research environment. They were delivered either vaginally or before labor by cesarean section. Tissues were incubated with calcium ionophore A23187 alone or with calcium ionophore A23187 after preincubation with either oxytocin, BW755c, or cycloheximide. Leukotrienes in culture medium were determined by high-performance liquid chromatography. Statistical analysis was performed with analysis of variance.

RESULTS

Tissues obtained after vaginal delivery released significantly higher (p less than 0.05) quantities of leukotrienes LTB4, LTD4, and delta-6-trans-LTB4 than did tissues obtained during cesarean section. Leukotriene release was stimulated by oxytocin and was inhibited by both BW755c and cycloheximide.

CONCLUSION

These results suggest an activation of the arachidonate lipoxygenase pathway in these tissues during labor. Oxytocin could play a regulatory role in this process.

Possible involvement of tumour cell membrane gangliosides in platelet-tumour cell interactions

The possible correlation(s) between platelet proaggregating activity, and sialic acid content and ganglioside expression of six human colorectal tumour cell lines (CBS, GEO, HT-29, WiDr, MIP and DLD-1) was evaluated. The three cell lines (HT-29, WiDr and DLD-1) capable of inducing remarkable in vitro platelet aggregation, had significantly higher amounts of lipid-bound sialic acid than those cell lines characterised by a lower platelet proaggregating activity (GEO, CBS and MIP). High performance thin-layer chromatography demonstrated the presence of one band comigrating with GM3 in all cell lines, while GD1a and GT1b comigrating gangliosides were present only in HT-29, WiDr and DLD-1 cells. Finally, an increased platelet pro-aggregating activity of GEO and CBS cell lines was observed after the incorporation of exogenous gangliosides. The present data support the hypothesis that lipid-bound sialic acid may be involved in platelet-tumour cell interactions.

Interleukin-2 in human amniotic fluid during pregnancy and parturition: implications for prostaglandin E2 release by fetal membranes

The potential role of interleukin 2 (IL-2) in human pregnancy was investigated by evaluating the following. (1) The presence and concentrations of IL-2 in amniotic fluid (AF) in 24 women at 16-18 weeks' gestation (Group 1) and in 27 women at term pregnancy, either before the onset of labor (Group 2, n = 10) or during spontaneous active labor (Group 3, n = 17). (2) The production of IL-2 by fetal membranes at term gestation (n = 7). (3) The release of prostaglandin E2 (PGE2) by the above tissues after stimulation with IL-2 (n = 10) or phytohemagglutinin (PHA) (n = 8). Immunoreactive IL-2 was detected only in AF samples obtained from women of Groups 1 and 3; the higher concentration was found in Group 1 samples; IL-2 was not detected in AF samples from women of Group 2. Tissues did not release IL-2. Both IL-2 and PHA exerted a significant stimulatory effect on PGE2 release by tissues. IL-2 stimulated PGE2 release by chorion tissue, but not by amnion tissue. The following conclusions can be drawn: (a) AF IL-2 might play a role in the maternal-fetal immune relationship during early pregnancy and, perhaps, during labor; (b) fetal membranes would not seem to represent a source of AF IL-2 in the absence of labor; (3) IL-2 might influence arachidonic acid metabolism through the cyclooxygenase pathway in the chorion tissue.

Amplification by macrophages of prostaglandin-mediated immunosuppression in mice bearing syngeneic tumors

The role of macrophages in tumor-mediated immunosuppression was examined, using C57B1/6 strain mice bearing four different immunosuppressive transplantable syngeneic tumors (Lewis Lung Carcinoma, B16 Melanoma, and two fibrosarcomas induced by methylcholanthrene in our laboratory). When tested for immunosuppressive activity, in inhibiting the induction of antibody formation by normal spleen cells in response to SRBC in vitro, the splenic and peritoneal macrophages from tumor-bearing mice were all significantly suppressive. The degree of suppression correlated with immunosuppression in tumor-bearing mice challenged in vivo with SRBC. Direct action of tumor cells on normal splenic macrophages in vitro caused them to become suppressive, the extent of suppression dependent on the time of interaction and on the immunosuppressive activity of the tumor cells in vivo. Pretreatment of suppressive splenic macrophages with indomethacin, a potent inhibitor of the synthesis of prostaglandins (PG), reduced significantly their immunosuppressive activity. Also, peritoneal macrophages from tumor-bearing mice produced significantly more PGE in culture than control macrophages. Thus, tumor-activated macrophages, presumably those macrophages that infiltrate the tumor in a host reaction against the tumor, serve to amplify the level of immunosuppression in the host by producing relatively large amounts of PGE that is a key physiological mediator in the activation and function of suppressor T lymphocytes. The stimulation of PGE synthesis in macrophages, as a result of their interaction with syngeneic tumors, is initiated by PGE produced in relatively large amount by the tumor cells.

Release of arachidonic acid metabolites by human fetal membranes: interrelationship between leukotriene B4 and prostaglandin E2

The objective of this study was to ascertain whether human fetal membranes metabolize arachidonic acid preferentially through the lipoxygenase rather than the cyclooxygenase pathway before labor and whether an interaction between lipoxygenase and cyclooxygenase products is present in these tissues. Reflected fetal membranes were obtained from 8 healthy women at term gestation who were delivered by elective repeat cesarean section before the onset of labor. Tissues were cultured either in the presence or in the absence of the calcium ionophore A23187 for 60 minutes. Leukotriene B4 (LTB4) and prostaglandin E2 (PGE2) were measured in culture medium by radioimmunoassays. Moreover, the effect of different concentrations of exogenously added LTB4 on PGE2 release was evaluated. The basal and stimulated output of LTB4 by tissues was significantly higher than that of PGE2. Addition of LTB4 significantly decreased PGE2 release by tissues. These findings suggest that in the above tissues: 1) the arachidonate lipoxygenase pathway is highly active before labor; 2) LTB4 might play a role in the regulation of PGE2 production.

Overexpression of lymphocytic GD3 ganglioside and presence of anti-GD3 antibodies in patients with HIV infection

This study was undertaken to analyze the role of disialoganglioside GD3 in HIV infection and disease progression. We report here the results obtained by both ex vivo and in vitro experiments on (1) surface and cytoplasmic expression and distribution of GD3 in HIV-infected cells, (2) the presence of anti-GD3 antibodies in sera of patients with HIV infection in various stages of the disease, and (3) the association of GD3 expression with HIV-related apoptotic events. GD3 expression was determined by high-performance thin-layer chromatography (HPTLC) and lipid-bound sialic acid and by static and flow cytometric analyses in peripheral blood lymphocytes from 22 AIDS patients, 20 anti-HIV Ab(+) asymptomatic subjects, and 25 healthy donors. Results obtained clearly indicated a significantly higher expression of plasma membrane GD3 content in lymphocytes from HIV-infected patients with respect to healthy controls. These HIV-induced perturbations of glycosphingolipid metabolism could be detected in all stages of the disease, including asymptomatic individuals. In addition, a significant percentage of patients showing disease progression displayed in serum samples an increased presence of anti-GD3 antibodies. Interestingly, ex vivo studies of lymphocytes from patients with HIV infection also indicated that GD3 expression is strictly associated with annexin V binding, an early marker of apoptosis. Moreover, cytofluorimetric analysis showed that virtually all anti-p24 Ab-positive cells were also immunolabeled with anti-GD3 antibodies. Accordingly, in vitro studies showed a significant redistribution and increase in GD3 expression in cultured U937 cells chronically infected with HIV-1 with respect to uninfected counterparts. In conclusion, our data clearly indicate that a significant increase in GD3 content in HIV-infected lymphocytes can occur and that this GD3 overexpression is paralleled by the presence of anti-GD3 antibodies in the plasma of patients. This is the first demonstration that disialoganglioside GD3, independent of the therapeutic schedule employed, can be considered as one of the early markers of HIV infection and can contribute to the early events leading to T cell depletion by apoptosis.

Leukotrienes in human umbilical plasma at birth

The aim of this study was to see whether leukotrienes are present in human umbilical plasma at birth either before or after labour. Plasma concentrations of LTB4 (6.02 ng/ml) and LTD4 (6.11 ng/ml) were significantly higher (P less than 0.01) after spontaneous vaginal delivery than during elective caesarean section before labour (LTB4 = 1.96 ng/ml, LTD4 = 0.18 ng/ml). A possible involvement of leukotrienes in the biochemical and metabolic events of human labour is suggested.

Increased release of interleukin-6 by oesophageal mucosa in children with reflux oesophagitis

OBJECTIVE

To evaluate the release of interleukin-6 (IL-6) by oesophageal mucosa and to establish the serum levels of IL-6 and C-reactive protein (CRP), and plasma fibrinogen in children with reflux oesophagitis.

DESIGN

In a prospective study, IL-6 release by tissue fragments obtained from oesophageal biopsies was determined and serum IL-6 and CRP as well as plasma fibrinogen were analysed.

METHODS

The study population comprised ten children with reflux oesophagitis, diagnosed on the basis of 24 h oesophageal pH monitoring and endoscopy with biopsies. Ten children with recurrent abdominal pain were studied for comparative purposes. Biopsy tissue fragments were processed to obtain a cell suspension and the release of IL-6 was determined in culture medium. Serum IL-6 levels were measured by ELISA, serum CRP by turbidimetry, and plasma fibrinogen by spectrophotometry.

RESULTS

Oesophageal cells obtained from reflux oesophagitis patients synthesize and release in vitro a significantly higher amount of IL-6 than controls (71.26+/-19.5 versus 31.67+/-8.02 pg/10(6) cells; P<0.01). Serum IL-6, serum CRP and plasma fibrinogen levels were not statistically different between patients with reflux oesophagitis and controls.

CONCLUSIONS

These results suggest a short-term action of IL-6 since its effects could be exerted only in the microenvironment of the oesophageal mucosa.