Modulation of the activation of endothelial nitric oxide synthase and nitrosative stress biomarkers by aspirin triggered lipoxins: A possible mechanism of action of aspirin in the antiphospholipid syndrome

PROBLEM

Antiphospholipid syndrome (APS) is characterized by the clinical manifestation of vascular thrombosis (VT) or pregnancy morbidity (PM) and antiphospholipid antibodies (aPL) that can modify the nitric oxide production. Low-dose aspirin is used in the prevention and treatment of diverse alterations of pregnancy. One of the mechanisms of action of aspirin is to induce the production of aspirin-triggered-lipoxins (ATL). The aim of this study was to evaluate the modulatory effect of ATL over the activation of endothelial nitric oxide synthase (eNOS) and nitrosative stress biomarkers induced by aPL.

METHODS

We used polyclonal IgG and sera from women with aPL and PM/VT or VT only, and from women with PM only and positive for non-criteria aPL (SN-OAPS). In these sera, biomarkers of nitrosative stress (nitrites and nitrotyrosine) were measured. The protein expression of nitrotyrosine and the phosphorylation of eNOS (at Ser1177) were estimated in human umbilical vein endothelial cells (HUVECs) stimulated with polyclonal IgG with or without ATL.

RESULTS

Women with SN-OAPS showed increased circulating levels of nitrites and nitrotyrosine. Likewise, polyclonal IgG from either SN-OAPS or VT patients stimulated nitrotyrosine expression in HUVECs. ATL decreased the nitrotyrosine expression induced by polyclonal IgG from the SN-OAPS group. ATL also recovered the reduced eNOS phosphorylation at Ser1177 in HUVECs stimulated with polyclonal IgG from women with PM/VT or SN-OAPS.

CONCLUSIONS

Increased nitrosative stress present in serum of women with SN-OAPS is associated with IgG-mediated impaired endothelial NO synthesis in endothelial cells. ATL prevent these cellular changes.

Antiphospholipid Antibodies From Women With Pregnancy Morbidity and Vascular Thrombosis Induce Endothelial Mitochondrial Dysfunction, mTOR Activation, and Autophagy

Antiphospholipid syndrome (APS) is an autoimmune disease characterized by thrombosis and pregnancy morbidity (PM) obstetric events together with persistent high titers of circulating antiphospholipid antibodies (aPL). Several mechanisms that explain the development of thrombosis and PM in APS include the association of aPL with alterations in the coagulation cascade and inflammatory events. Other mechanisms disturbing cellular homeostases, such as mitochondrial dysfunction, autophagy, and cell proliferation, have been described in other autoimmune diseases. Therefore, the objective of this study was to investigate the impact of aPL from different patient populations on endothelial cell mitochondrial function, activation of the mammalian target of rapamycin (mTOR) and autophagy pathways, and cellular growth. Using an in vitro model, human umbilical vein endothelial cells (HUVECs) were treated with polyclonal immunoglobulin G (IgG) purified from the serum of women with both PM and vascular thrombosis (PM/VT), with VT only (VT), or with PM and non-criteria aPL (seronegative-obstetric APS, SN-OAPS). We included IgG from women with PM without aPL (PM/aPL-) and healthy women with previous uncomplicated pregnancies (normal human serum, NHS) as control groups. Mitochondrial function, mTOR activation, autophagy, and cell proliferation were evaluated by Western blotting, flow cytometry, and functional assays. IgG from women with PM/VT increased HUVEC mitochondrial hyperpolarization and activation of the mTOR and autophagic pathways, while IgG from patients with VT induced endothelial autophagy and cell proliferation in the absence of elevated mTOR activity or mitochondrial dysfunction. IgG from the SN-OAPS patient group had no effect on any of these HUVEC responses. In conclusion, aPL from women with PM and vascular events induce cellular stress evidenced by mitochondrial hyperpolarization and increased activation of the mTOR and autophagic pathways which may play a role in the pathogenesis of obstetric APS.

Effects of anti-beta 2-glycoprotein 1 antibodies and its association with pregnancy-related morbidity in antiphospholipid syndrome

Antiphospholipid syndrome (APS) is an autoimmune disease characterized by venous, arterial, or small-vessel thrombosis and/or pregnancy-related morbidity, associated with persistent positivity of antiphospholipid antibodies (aPL). Pregnancy-related morbidity in APS patients is characterized by unexplained fetal deaths, premature birth of morphologically normal newborns, and/or consecutive pregnancy losses before the 10^th week of gestation. Beta 2-glycoprotein 1 (ß2GP1) is the main antigen recognized by aPL and plays an essential role in the pathogenesis of APS. Antibodies against ß2GP1 (aß2GP1) are involved in damage-generating mechanisms in APS due to their interaction with trophoblasts, decidua, and endothelial cells. aß2GP1 might be used as a prognostic tool for obstetric risk stratification and ß2GP1 could be a target for molecular-targeted treatment to prevent pregnancy morbidity in APS. This review describes these aspects of aß2GP1, including effects on different cellular targets, its association with the severity of obstetric manifestations and the potential of ß2GP1-targeted therapies for APS.

Aspirin: The Mechanism of Action Revisited in the Context of Pregnancy Complications

Aspirin is one of the most frequently used and cheapest drugs in medicine. It belongs to the non-steroidal anti-inflammatory drugs with a wide range of pharmacological activities, including analgesic, antipyretic, and antiplatelet properties. Currently, it is accepted to prescribe a low dose of aspirin to pregnant women who are at high risk of preeclampsia (PE) because it reduces the onset of this complication. Another pregnancy alteration in which a low dose of aspirin is recommended is the obstetric antiphospholipid syndrome (APS). The most recognized mechanism of action of aspirin is to inhibit the synthesis of prostaglandins but this by itself does not explain the repertoire of anti-inflammatory effects of aspirin. Later, another mechanism was described: the induction of the production of aspirin-triggered lipoxins (ATLs) from arachidonic acid by acetylation of the enzyme cyclooxygenase-2. The availability of a stable analog of ATL has stimulated investigations on the use of this analog and it has been found that, similar to endogenously produced lipoxins, ATL resolves inflammation and acts as antioxidant and immunomodulator. If we consider that in PE and in the obstetric APS, there is an underlying inflammatory process, aspirin might be used based on the induction of ATL. The objective of this review is to revisit the old and new mechanisms of action of aspirin. In particular, it intends to show other potential uses of this drug to prevent certain pregnancy complications in the light of its ability to induce anti-inflammatory and pro-resolving lipid-derived mediators.

Modulation of antiphospholipid antibodies-induced trophoblast damage by different drugs used to prevent pregnancy morbidity associated with antiphospholipid syndrome

PROBLEM

Women with antiphospholipid antibodies (aPLs) present a risk of pregnancy morbidity (PM), vascular thrombosis (VT), or both (PM/VT). aPLs affect trophoblast function, and the aim of this study was to determine the modulation of this aPL-induced damage by different drugs.

METHOD OF STUDY

IgG was obtained from women with PM and PM/VT positive to aPLs. Binding of IgG to trophoblastic cells, proliferation, mitochondrial membrane integrity, and trophoblast invasion were assessed. The effect of enoxaparin, aspirin, and aspirin-triggered lipoxin (ATL) were evaluated as well as signal transducer and activator of transcription 3 (STAT3) phosphorylation.

RESULTS

IgG from women with aPLs strongly binds to trophoblastic cells. Integrity of mitochondrial membrane was reduced, and proliferation was increased by IgG-PM/VT. Both IgG-PM and IgG-PM/VT decreased trophoblast invasion, which was restored by enoxaparin, aspirin, and ATL. IgG-PM triggered reduction in STAT3 phosphorylation.

CONCLUSION

Some drugs used to prevent aPL-induced PM modulated the alteration of trophoblast function.

Aspirin-triggered lipoxin prevents antiphospholipid antibody effects on human trophoblast migration and endothelial cell interactions

OBJECTIVE

Antiphospholipid antibodies (aPL) interfere with several physiologic functions of human trophoblasts, including reducing their ability to migrate, decreasing their production of angiogenic factors, and inducing an inflammatory response. This may provide the underlying mechanism by which aPL responses lead to recurrent pregnancy loss or preeclampsia in women with obstetric antiphospholipid syndrome (APS). Although treatment with heparin may reduce the rate of recurrent pregnancy loss, the risk of preeclampsia remains high. Therefore, alternative treatments are needed for the management of pregnant patients with APS. Since aspirin-triggered lipoxins (ATLs) have immune and angiogenic modulatory properties, the objective of this study was to determine the effects of the ATL 15-epi-lipoxin A4 on the function of aPL-altered human trophoblasts in the first trimester of pregnancy.

METHODS

A first-trimester human trophoblast cell line (HTR8) was treated with mouse anti-human β2 -glycoprotein I monoclonal antibodies (aPL) in the presence or absence of the ATL 15-epi-lipoxin A4 . Trophoblast migration and interactions with endometrial endothelial cells were measured using Transwell and coculture assays. Trophoblast secretion of cytokines and angiogenic factors was measured by enzyme-linked immunosorbent assay.

RESULTS

Treatment of HTR8 cells with ATL reversed the aPL-induced decrease in trophoblast migration, an effect that appeared to be regulated through restoration of interleukin-6 production. Using a model of spiral artery transformation, aPL and sera from APS patients with pregnancy morbidity disrupted trophoblast-endothelial cell interactions, and treatment with ATL restored the stability of the cocultures. In contrast, ATL treatment did not resolve the proinflammatory and antiangiogenic responses of trophoblasts induced by aPL.

CONCLUSION

These findings indicate that ATLs may have some benefits in terms of preventing the effects of aPL on trophoblast function, which raises the possibility of the use of ATLs as an adjuvant therapy in women with aPL.

Exogenous vascular endothelial growth factor supplementation can restore the podocyte barrier-forming capacity disrupted by sera of preeclamptic women

AIM

To determine whether exogenous vascular endothelial growth factor (VEGF) supplementation to sera from women with preeclampsia can restore the podocyte barrier-forming capacity disrupted after stimulation with sera from these women.

MATERIAL AND METHODS

Enzyme-linked immunosorbent assays (ELISAs) for sFlt-1 (soluble VEGF receptor 1) and VEGF were performed in the sera of preeclamptic and healthy pregnant women. VEGF-enriched preeclamptic serum was used to evaluate the capacity of such sera to restore the diminished podocyte barrier capacity secondary to stimulation with untreated preeclamptic sera.

RESULTS

Two groups, preeclampsia (n=15) and healthy (n=15) pregnant women, were established. Median serum levels (pg/mL) of sFlt-1 and VEGF were significantly different between groups: 3987 versus 1432 and 6 versus 15.6 (P<0.001). Altered resistance values of podocytes stimulated with sera from women with preeclampsia were recovered after exogenous VEGF supplementation.

CONCLUSION

The mean resistance value of cultured podocytes, an indicator of the integrity of the cytoskeleton and the capacity of these cells to form layers, is altered in women with preeclampsia. High levels of sFlt-1, an inhibitor of VEGF observed in high concentrations in the serum of these patients, could be the underlying cause of this alteration. We provide evidence that exogenous VEGF supplementation of the sera of these women could recover this indicator.

[Evaluation of atypical semen parameters in individuals whose couples had a history of early recurrent embryo death: in search for a reference value]

INTRODUCTION

Previous studies related alterations in non-conventional seminal parameters with recurrent early embryonic death for one couple. A reference standard of clinical assessment is required for the management of these kinds of patients.

OBJECTIVE

Normal semen parameters were established based on functional tests including lipid peroxidation of sperm membranes, antioxidant capacity of seminal plasma and integrity of sperm chromatin to compare with men whose partners have recurrent early embryonic death. These parameters set reference values to identify subfertile individuals whose condition can be attributed to altered semen parameters.

MATERIALS AND METHODS

The conventional and non-conventional semen parameters of 47 samples of semen were evaluated. Thirty-six samples were from subfertile individuals whose partners had a history of early recurrent embryo death, and 11 samples were from individuals with recent evidence of normal fertility.

RESULTS

By discriminant analysis, the two groups were classified as follows: a value below 0.50 for 86.1% of individuals in the group of recurrent early embryonic death, and a value above 0.50 to classify 81.8% of individuals in the group of recent fertility.

CONCLUSIONS

This reference value of 0.5 based on the results of sperm tests can identify infertile male patients whose partners have a history of early embryonic death. This will aid the physician to suggest treatments more focused on the possible cause of subfertility.

Prevention and treatment of allergic asthma in pregnancy: from conventional drugs to new therapeutical approaches

Different conventional anti-asthmatic and anti-allergic drugs are commonly used in pregnancy, including inhaled corticosteroids, long- and short-acting β-agonists, leukotriene modifiers, cromolyn, and theophylline. Alternatively, immunotherapy with allergens before and during pregnancy is accepted as a causal treatment of allergies, but the allergy specifity and severity in combination with a variety of application protocols and procedures cause wide heterogenity of this treatment principle. Furthermore, the pharmacokinetic characteristics and the US Food and Drug Administration (FDA) classification of conventional anti-allergic drugs and immunological implications of immunotherapy are summarized in this review, and insights on fetal programming of allergies are introduced. We propose a potential perspective of treatment with anti-inflammatory and pro-resolving mediators, such as lipoxins, resolvins and protectins; these are lipid mediators physiologically generated during the immune response from arachidonic acid, eicosapentaenoic acid and docosahexaenoic acid. This proposal fits with the recently appreciated approaches to allergy prevention for the newborn child by a balanced maternal nutrition and omega-3 long-chain polyunsaturated fatty acid consumption.

Preeclamptic sera directly induce slit-diaphragm protein redistribution and alter podocyte barrier-forming capacity

BACKGROUND/AIMS

Podocytes are critical in maintaining the filtration barrier of the glomerulus and are dependent on the slit diaphragm. We hypothesized that disturbances of podocyte biology contribute to proteinuria in women with preeclampsia (PE).

METHODS

A human podocyte cell line was stimulated with serum from women with PE (patients) and healthy pregnant women (controls); the main changes in 3 important podocyte proteins: podocin, CD2AP and actin were established by immunofluorescence and Western blot; we also searched for changes in cell plasticity by measuring the resistance of cultured podocytes.

RESULTS

Different distributions of CD2AP, podocin and actin were observed in the podocytes stimulated with patient sera compared to podocytes stimulated with control sera. We also found that the mean resistance value of podocytes cultured with serum from women with PE was significantly lower than podocytes cultured with serum from controls. There was no difference in the protein expression level of podocin and CD2AP between patients and controls.

CONCLUSIONS

We present evidence that there are differences in podocytes when stimulated with sera from women with PE compared to those stimulated with healthy pregnancy sera. This is the first time that podocyte alterations have been directly related to PE; these descriptive findings could be considered as an interesting beginning for further studies relating podocytes and PE.

The role of mannose receptor on HIV-1 entry into human spermatozoa

In this opinion article we consider the possibility that human spermatozoa have receptors for human immunodeficiency virus-1 (HIV-1). It is clear that sperm cells have the potential for transmitting HIV-1, but the mechanisms responsible for spreading or the virus by this vector are not known. In contrast to the traditional HIV-1 target cells, spermatozoa do not express CD4 receptors or the CCR5/CXCR4 co-receptors. Recent evidence indicates that astrocytes, which also do not express these molecules, can be infected with HIV-1 through the mannose receptor. Furthermore, a 160-kDa sperm receptor that interacts with the HIV gp 120 has been described. Therefore, we hypothesize that the mannose receptor, of 165-175 kDa, is the receptor that HIV-1 uses to invade spermatozoa, which could lead to both vertical and horizontal transmission of HIV-1.

Evaluación de la reacción acrosomal en espermatozoides humanos inducida por los monosacáridos manosa y N-acetilglucosamina

OBJECTIVE

The aim of this investigation was to evaluate the role of the monosaccharides, mannose and N-acetylglucosamine in the induction of the acrosome reaction in human spermatozoa.

METHODS

Each individual gave a semen sample, the samples were capacitated using bovien serum albumin; the analysis of the mannose and N-acetylglucosamine induced acrosome reaction was evaluated for fluorescence microscopy and flow cytometry.

RESULTS

The results obtained in the acrosomal reaction in the 10 samples evaluated by flow cytometry showed that only calcium ionophore A23187 induced acrosomal reaction (p < 0.001); in contrast, by fluorescence microscopy, was observed a statistically significant increase in the induced acrosomal reaction with mannose and N-acetylglucosamine (p < 0.001).

CONCLUSIONS

The monosaccharides mannose and N-acetylglucosamine induces partial acrosomal reaction and it does not complete, therefore the spermatozoa due to partial acrosomal reaction and the morphologics modifications that suffer during that process is able to fertilize the oocyte.

[Sperm parameters in 113 subjects after recent fatherhood did not correlate with WHO standards]

OBJECTIVES

This is a descriptive prospective study of semen analysis in 113 men who were candidates for vasectomy as an option for fertility control after a recent event of fertility.

METHODS

Each subject provided a semen sample for the analysis of volume, pH, spermatozoid concentration, mobility, and morphology. The results were compared with the reference values established by WHO.

RESULTS

Different from what was expected, a great proportion of these fertile subjects, 54.9%, showed at least one altered parameter in comparison to minimal values established by WHO. Generally, median values for the whole group were normal: volume 2.4 ml, spermatozoid concentration measured in Makler and Neubauer chambers 89 and 91 millions/ml, respectively; sperm mobility (A + B) 56%; vitality 78%; and normal morphology 79%.

CONCLUSIONS

In this group of fertile subjects we found a high probability to have altered semen parameters, which argues questions the real value and significance of sperm analysis in the diagnosis of a subfertile patient.

The production of MLR-blocking factors after lymphocyte immunotherapy for RSA does not predict the outcome of pregnancy

PROBLEM

The questions of whether production of mixed lymphocyte reaction-blocking factors (MLR-BFs) after immunotherapy with lymphocytes for recurrent spontaneous abortion (RSA) has prognostic value and whether cytotoxic antibodies are also involved were tested.

METHOD OF STUDY

A prospective study with 33 patients who had a history of two or more abortions, lacking MLR-BFs, was carried out. The patients received immunizations with lymphocytes and 6 weeks or later were tested for seroconversion of MLR-BFs. Seventeen of these thirty-three patients were evaluated for antipaternal cytotoxic antibodies. The results were correlated with the outcome of the next pregnancy after treatment.

RESULTS

Eighty percent of the 33 patients had a live child. Of those patients having success, only 50% produced MLR-BFs. Of those patients having a new loss, five did and two did not produce MLR-BF (P > 0.05). Regarding the 17 patients tested for cytotoxic antibodies, 4 of the 5 patients who tested positive had a new abortion, whereas only 1 of 12 whose tests remained negative did not have gestational success (P < 0.01).

CONCLUSION

The presence of MLR-BFs is not a prognostic criterium for the outcome of pregnancy after alloimmunotherapy, and, consequently, it is not a good diagnostic tool for RSA of alloimmune cause.

Human cytotrophoblastic cells absorb the NK blocking activity of monoclonal BA11

PROBLEM

R80K is a polymorphic alloantigeneic protein present on human placental trophoblast and on paternal B lymphocytes and monocytes. This protein, unlike the former candidate TLX antigen, stimulates a protective maternal immune response in vivo. A murine monoclonal BA11 antibody, directed against R80K, prevents abortion in three murine pregnancy-failure models and inhibits human and murine NK activity. We attempted to define the target of BA11 in the human NK assay system.

METHODS

A CELISA method was used to detect R80K antigen on the surface of different cells using the BA11 antibody. The effect, on human peripheral blood NK activity against K562, by BA11 before and after absorption by different cells, including the K562 target, was determined.

RESULTS

R80K was detected on term placental syncytio and cytotrophoblast and on BeWo cells, by CELISA. BA11 suppressed NK lysis of K562 cell sin a dose-dependent manner. Absorption of the BA11 by BeWo and by cytotrophoblastic cells significantly decreased the NK-inhibitory activity. There was minimal absorption by K562 and BA11-pretreateed K562 cells remained susceptible to NK lysis. By contrast, BA11-pretreated peripheral blood cells lost all NK activity.

CONCLUSIONS

The inhibition of NK killing of K562 cells by BA11 is more complex than simple masking of a trophoblast cell-associated molecule in K562 necessary for recognition in NK cells.

Is the immune system necessary for placental reproduction? A hypothesis on the mechanisms of alloimmunotherapy in recurrent spontaneous abortion

Recurrent spontaneous abortion is being treated with alloimmunotherapy which consists of the inoculation of allogeneic mononuclear cells. However the mechanisms explaining the benefits of this therapy are not clear yet. Taking the immunotrophic hypothesis as the paradigm of the field of reproductive immunology, hereby we present a hypothesis to propose a role for the immune system in reproduction and at the same time to explain how alloimmunotherapy may work. We base our view on several facts: first, immunodeficient mice reproduce--albeit their progeny may not be as robust and numerous as that from normal individuals. Second, maternal lymphocytes cross the placenta and may induce graft versus host disease. Third, graft versus host disease in newborn F1 mice inoculated with paternal lymphocytes can be prevented by inoculation of the mother with the same paternal lymphocytes before and during pregnancy. We propose that: 1) the immune system by itself is not necessary for placental reproduction; 2) the immune system plays its major role in reproduction by counteracting the allogeneic response generated against the fetus; 3) recurrent spontaneous abortion represents a type of graft versus host disease induced by maternal cells infiltrating the fetus; and 4) alloimmunotherapy induces an antiidiotypic response necessary to counteract the graft versus host reaction in the fetus.

Prevalence of anti-Toxoplasma gondii antibodies in Cebus spp in the Santa Fe Zoological Park of Medellín, Colombia

The prevalence of anti-Toxoplasma gondii antibodies was studied in 47 nonhuman primates of the Cebus species in the Santa Fe Zoological Park in Medellín, Colombia. Specific IgG titers (greater than 1/64) were detected in 40.9% of C. albifrons studied (n = 22), 13.3% of C. capucinus (n = 15), and 0% of C. apella (n = 10). Specific IgM was not detected in any of the animals studied.