Generation of peroxynitrite and apoptosis in placenta of patients with chorioamnionitis: possible implications in placental abruption

Nitric Oxide Production and Effects in Group B Streptococcus Chorioamnionitis

Intrauterine infection, or chorioamnionitis, due to group B Streptococcus (GBS) is a common cause of miscarriage and preterm birth. To cause chorioamnionitis, GBS must bypass maternal-fetal innate immune defenses including nitric oxide (NO), a microbicidal gas produced by nitric oxide synthases (NOS). This study examined placental NO production and its role in host-pathogen interactions in GBS chorioamnionitis. In a murine model of ascending GBS chorioamnionitis, placental NOS isoform expression quantified by RT-qPCR revealed a four-fold expression increase in inducible NOS, no significant change in expression of endothelial NOS, and decreased expression of neuronal NOS. These NOS expression results were recapitulated ex vivo in freshly collected human placental samples that were co-incubated with GBS. Immunohistochemistry of wild type C57BL/6 murine placentas with GBS chorioamnionitis demonstrated diffuse inducible NOS expression with high-expression foci in the junctional zone and areas of abscess. Pregnancy outcomes between wild type and inducible NOS-deficient mice did not differ significantly although wild type dams had a trend toward more frequent preterm delivery. We also identified possible molecular mechanisms that GBS uses to survive in a NO-rich environment. In vitro exposure of GBS to NO resulted in dose-dependent growth inhibition that varied by serovar. RNA-seq on two GBS strains with distinct NO resistance phenotypes revealed that both GBS strains shared several detoxification pathways that were differentially expressed during NO exposure. These results demonstrate that the placental immune response to GBS chorioamnionitis includes induced NO production and indicate that GBS activates conserved stress pathways in response to NO exposure.

Expression of the Costimulatory Molecule B7-H4 in the Decidua and Placental Tissues in Patients with Placental Abruption

B7 homolog 4 protein (B7-H4), a member of the B7 family, is a immunomodulatory membrane protein. The aim of the study was to evaluate the expression of this protein in the decidua and placental tissues in case of placental abruption (PA) compared to cases of retained placental tissue (RPT) and controls. Tissue samples were obtained from 47 patients with PA, 60 patients with RPT, and 41 healthy controls. The samples were stained for B7-H4 expression, analyzed by an expert pathologist, and a semi-quantitative scale was applied. A statistical analysis revealed that the expression of B7-H4 was significantly higher in the decidua in PA samples compared to samples from patients with RPT (p-value < 0.001) and healthy controls (p-value < 0.001). The expression of B7-H4 in the placental chorionic villus was significantly higher in PA samples in relation to samples from healthy controls (p-value < 0.001) but not in relation to RPT samples (p-value = 0.0853). This finding suggests that B7-H4 might play an important role in mechanisms restoring reproductive tract homeostasis. Further research is necessary in regard to the role of B7-H4 in PA.

Molecular Changes on Maternal-Fetal Interface in Placental Abruption-A Systematic Review

Placental abruption is the separation of the placenta from the lining of the uterus before childbirth. It is an infrequent perinatal complication with serious after-effects and a marked risk of maternal and fetal mortality. Despite the fact that numerous placental abruption risk factors are known, the pathophysiology of this issue is multifactorial and not entirely clear. The aim of this review was to examine the current state of knowledge concerning the molecular changes on the maternal–fetal interface occurring in placental abruption. Only original research articles describing studies published in English until the 15 March 2021 were considered eligible. Reviews, book chapters, case studies, conference papers and opinions were excluded. The systematic literature search of PubMed/MEDLINE and Scopus databases identified 708 articles, 22 of which were analyzed. The available evidence indicates that the disruption of the immunological processes on the maternal–fetal interface plays a crucial role in the pathophysiology of placental abruption. The features of chronic non-infectious inflammation and augmented immunological cytotoxic response were found to be present in placental abruption samples in the reviewed studies. Various molecules participate in this process, with only a few being examined. More advanced research is needed to fully explain this complicated process.

Placental abruption possibly due to parvovirus B19 infection

BACKGROUND

There is concern about the development of anemia-associated fetal hydrops associated with maternal parvovirus B19 infection. Parvovirus B19 infection occurs via the globoside (P antigen) receptor, the main glycolipid of erythroid cells, which induces apoptosis. Similar findings have been reported for the P antigen of globoside-containing placental trophoblast cells.

CASE DESCRIPTION

A 32-year-old woman was infected with human parvovirus B19 at week 32 of pregnancy, and had severe anemia at week 34. At week 37, an emergency cesarean section was performed because of sudden abdominal pain and fetal bradycardia; placental abruption was found. A live male infant was delivered with no sign of fetal hydrops or fetal infection. Placental tissue was positive for parvovirus B19 according to polymerase chain reaction. Immunohistochemical analysis using caspase-related M30 CytoDEATH monoclonal antibody revealed M30 staining of the placental villous trophoblasts.

DISCUSSION AND EVALUATION

Placental trophoblasts and erythroid precursor cells have been reported to express globoside (P antigen), which is necessary for parvovirus B19 infectivity, and to show apoptotic activity as a result of infection. Placentas from three other pregnancies with documented abruption showed no M30 staining.

CONCLUSION

The present case strongly suggests an association between placental abruption and apoptosis resulting from parvovirus B19 infection.

Decrease in 3-nitrotyrosine in the amniotic fluid of women with cytomegalovirus infection

The aim of this study was to assess oxidative stress in pregnant women infected with cytomegalovirus on the basis of 3-nitrotyrosine levels in amniotic fluid (AF). The 3-nitrotyrosine (3-NT) level in AF was measured using the competitive ELISA method. The study groups were as follows: group I consisted of women with IgM and/or IgA; group II were women with only IgG anti-CMV antibodies and group III were seronegative women, used as the control group. Age, gestational age and socioeconomic status were also assessed. The average level of 3-nitrotyrosine in group II and the control group was similar: 53.14 nM 3-NT and 49.78 nM 3-NT, respectively. However, in group I, the lowest level 3-NT in AF was observed - 39.17 nM 3-NT and statistical analysis showed significant differences in levels of 3-NT between group I and the control group (p < 0.01). We conclude that significantly lower levels of 3-nitrotyrosine in pregnant women with CMV infection may indicate an increase in the antioxidant defence mechanisms in these patients.

Histologic evidence of inflammation and risk of placental abruption

OBJECTIVE

The objective of the study was to determine whether placental abruption is associated with an increased incidence of histologic chorioamnionitis among singleton gestations and whether this association is dependent on its severity.

STUDY DESIGN

Data were derived from the New Jersey-Placental Abruption Study, an ongoing, multicenter, case-control study conducted in New Jersey since August 2002. Subjects were women with a clinical diagnosis of abruption, and controls were matched to cases based on parity and maternal race/ethnicity. Two perinatal pathologists, blinded to the case-control status, performed all histologic examination based on standardized protocol. The association between chorioamnionitis and abruption was quantified based on odds ratio (OR) with 95% confidence interval (CI), after adjustment for potential confounders, and all analyses were stratified based on preterm birth (less than 37 weeks) status.

RESULTS

At preterm gestations (n = 141), chorioamnionitis was present in 30.8% and 12.5% of abruption cases and controls, respectively (OR 3.6, 95% CI 1.7 to 10.5). At term gestations (n = 205), the corresponding rates were 34.6% and 20.4%, respectively (OR 2.8, 95% CI 1.3 to 6.1). Severe chorioamnionitis was 7.2 (95% CI 1.6 to 20.1) and 18.3 (95% CI 2.2 to 150.4) times more common in abruption patients at preterm and term gestations, respectively.

CONCLUSION

Histologic chorioamnionitis is associated with placental abruption. The association was strongest in the presence of severe chorioamnionitis at term and, to a lesser extent, at preterm gestations. These observations suggest that the histologic findings in abruption are accompanied by severe inflammation, in both preterm and term gestations.

Accumulation of advanced glycation end products in women with preeclampsia: possible involvement of placental oxidative and nitrative stress

Advanced glycation end products (AGEs) are known to cause oxidative damage in various cells by binding with its receptor, RAGE. We measured the serum level of AGEs and examined the AGEs, RAGE, and the other biomarkers of oxidative stress in the placentas from preeclamptic women. Competitive ELISA was carried out to measure the AGEs in serum. Western blotting was performed to analyze AGEs and RAGE in the placenta. Immunohistochemical analyses were performed to examine the localization of AGEs, RAGE, and other biomarkers of oxidative stress in the placenta. The mean level of serum AGEs in preeclamptic women was significantly higher than that in healthy non-pregnant women or healthy pregnant women. Western blotting revealed that the level of AGEs or RAGE in preeclamptic placenta was significantly higher than that in normal placenta. Immunohistochemical analyses showed that levels of nitrotyrosine and nitroguanosine, which are formed by reactive nitrogen species, in preeclamptic placenta were higher than those in normal placenta. Accumulation of 4-hydroxy-2-nonenal and 8-hydroxy-2'-deoxyguanosine indicated enhanced oxidative modifications of lipids and DNA in preeclamptic placenta. The AGE-RAGE system, which is upregulated in preeclampsia, is likely to be involved in the oxidative stress of preeclampsia.

Placental lesions caused by experimental infection of Sprague-Dawley rats with Mycoplasma pulmonis

PROBLEM

Sprague-Dawley (SD) rats infected during pregnancy with Mycoplasma pulmonis display adverse pregnancy outcomes that are similar to those observed in women with chorioamnionitis and may provide a good model system for this disease. The placental lesions caused by this microorganism, however, have not been thoroughly characterized.

METHOD OF STUDY

Rats were infected with 10(7) colony-forming units (CFU) M. pulmonis or vehicle control on gestation day (gd) 14 and were euthanized on gd 16-18. Tissues were fixed in 10% neutral buffered formalin, embedded in paraffin, sectioned at 4 microm, and stained with hematoxylin and eosin (H & E). The slides were coded and examined by a blinded pathologist using light microscopy.

RESULTS

Infection with M. pulmonis was associated with necrosis of trophoblast giant cells at gd 18. Significantly more neutrophils were observed in the decidual region of the apex of the placenta in M. pulmonis infected animals. The vast majority of neutrophils, however, were observed in the decidua in the lateral regions of the placenta and in the adjacent endometrium.

CONCLUSIONS

Infection of SD rats with M. pulmonis resulted in histological placentitis similar to that described in deciduitis of humans and represents a good model system for investigations into the pathophysiology of intrauterine infection. The influx of neutrophils seems to migrate from the endometrium towards the lateral regions of the placenta near Reichert's membrane and the divergence of the parietal yolk sac.

Nafamostat mesilate suppresses NF-kappaB activation and NO overproduction in LPS-treated macrophages

Nafamostat mesilate (NM), a clinically used serine protease inhibitor, suppressed the overproduction of nitric oxide (NO) and the expression of inducible nitric oxide synthase (iNOS) in RAW264.7 murine macrophages treated with lipopolysaccharide (LPS, 100 ng/ml); however, it had little effect on endothelial NOS (eNOS) in human umbilical vein endothelial cells (HUVEC). Electrophoretic mobility shift assay (EMSA) revealed that LPS activated nuclear factor-kappaB (NF-kappaB) in RAW264.7 cells and that this activation was suppressed by nafamostat mesilate. Western blotting showed that nafamostat mesilate suppressed the phosphorylation and degradation of inhibitor kappaB-alpha (IkappaB-alpha), which holds NF-kappaB in the cytoplasm in an inactivated state. Our observations suggest that nafamostat mesilate is a candidate agent for various diseases such as ischemia-reperfusion, graft rejection, inflammatory diseases, and autoimmune diseases, in which iNOS and/or NF-kappaB are upregulated.

Involvement of peroxynitrite in LPS-induced apoptosis of trophoblasts

OBJECTIVE

To examine whether or not peroxynitrite was involved in trophoblastic apoptosis induced by a bacterial endotoxin, lipopolysaccharide (LPS).

METHODS

Levels of nitrite/nitrate, stable metabolites of nitric oxide (NO), in culture medium of trophoblasts, were determined using Griess reagents. Trophoblastic apoptosis was identified morphologically and confirmed using in situ nick end labeling technique. The amount of nitrotyrosine, a footprint of peroxynitrite, was quantified by dot blotting. Statistical significance was determined by ANOVA.

RESULTS

Treatment of trophoblasts with LPS leads to apoptosis accompanied by formation of NO and nitrotyrosine. Aminoguanidine, an inhibitor of NO synthase (NOS), reduced peroxynitrite formation and prevented apoptosis. Scavengers of peroxynitrite also prevented apoptosis in this culture model.

CONCLUSION

Peroxynitrite was involved in trophoblastic apoptosis induced by LPS. Peroxynitrite scavengers or inhibitors of NOS may thus be candidate therapeutic agents for infectious diseases, which is associated with overproduction of NO and peroxynitrite.

The biological effects of antiadhesion agents on activated RAW264.7 macrophages

The objective of this study is to determine the biological effects of various antiadhesion agents on macrophages, which play an essential role in wound healing and adhesion. To determine these effects, RAW264.7 macrophages were activated with lipopolysaccharide in the presence of antiadhesion agents: oxidized regenerated cellulose (oxyC), sodium hyaluronate (HA), dexamethasone (Dex), or chondroitin sulfate (CS). The release of nitric oxide (NO), vascular endothelial growth factor (VEGF), interleukin-6 (IL-6), or matrix metalloproteinases (MMPs) from RAW264.7 was measured. We found that oxyC reduced the release of NO, IL-6, MMP-2, and MMP-9, whereas it enhanced the release of VEGF. HA reduced the release of MMP-2, whereas it enhanced the release of VEGF and NO. HA exhibited no significant effect on the release of IL-6 or MMP-9. Dex reduced the release of NO, VEGF, IL-6, MMP-2, and MMP-9. CS reduced the release of VEGF, IL-6, and MMP-2, although it had no significant effect on the release of NO and MMP-9. Antiadhesion agents, which have been clinically used as physical barriers, modulated the functions of macrophages.

A long-term transdermal nitric oxide donor improves uteroplacental circulation in women with preeclampsia

OBJECTIVE

To determine the effects of long-term transdermal administration (range, 4-30 days; mean +/- SD, 11.1+/-7.2 days) of isosorbide dinitrate, a nitric oxide donor, in preeclamptic women.

METHODS

We studied uterine and fetoplacental circulation of 12 preeclamptic women with oligohydramnios and an elevated pulsatility index in the uterine arteries.

RESULTS

Transdermal isosorbide dinitrate significantly suppressed the blood pressure of patients. Pulsed Doppler ultrasonography revealed that the average pulsatility index in the uterine arteries was significantly reduced by treatment with isosorbide dinitrate (P < .003). The average pulsatility index in the umbilical artery was also significantly reduced (P < .004). Furthermore, the size of the amniotic fluid pocket increased approximately 4-fold by treatment with isosorbide dinitrate.

CONCLUSIONS

Long-term transdermal administration of isosorbide dinitrate improves fetoplacental circulation and may be effective therapy for avoiding maternal hypertension and oligohydramnios in some preeclamptic women.

Tyrosine nitration: localisation, quantification, consequences for protein function and signal transduction

The nitration of free tyrosine or protein tyrosine residues generates 3-nitrotyrosine the detection of which has been utilised as a footprint for the in vivo formation of peroxynitrite and other reactive nitrogen species. The detection of 3-nitrotyrosine by analytical and immunological techniques has established that tyrosine nitration occurs under physiological conditions and levels increase in most disease states. This review provides an updated, comprehensive and detailed summary of the tissue, cellular and specific protein localisation of 3-nitrotyrosine and its quantification. The potential consequences of nitration to protein function and the pathogenesis of disease are also examined together with the possible effects of protein nitration on signal transduction pathways and on the metabolism of proteins.

Nitrotyrosine immunostaining correlates with increased extracellular matrix: evidence of postplacental hypoxia

Nitrotyrosine residues (NT), an index of oxidative stress arising from peroxynitrite formation and action, are found in placental vasculature of pregnancies complicated by pre-eclampsia (PE) or pregestational insulin-dependent diabetes mellitus (IDDM). This study correlates conventional placental pathology with NT immunostaining in 20 cases of perinatal mortality (13 stillbirths and seven cases of neonatal mortality) associated with PE, IDDM, amniotic fluid infection syndrome (AFIS), or from fetal/neonatal demise not related to these conditions (congenital anomalies) (n = five/group). Patients with PE have more decidual arteriolopathy and Tenney-Parker change, while patients with IDDM and ascending infection have more villous cytotrophoblastic hyperplasia. Archival paraffin-embedded placental sections were immunostained for NT for correlation with clinical features and H&E histological findings. The intensity of immunostaining for NT varied from absent (n = 7) to 1+ (n = 5) or 2+ (n = 8). All eight placentae with 2+ staining showed increased villous extracellular matrix (ECM), compared to none of five with 1+ staining and two of seven with no staining (chi2 = 14.3, P = 0.001). There was no statistically significant difference in the percentage of stem villi with luminal vascular abnormalities (5.7 vs 10 vs 35.7 per cent, F = 2.3, P = 0.1). Our data show that increased production of reactive oxygen species by placental tissue may be associated with increased extracellular matrix, itself produced by fibroblasts under the influence of oxygen. NT immunostaining may therefore help differentiate those cases of perinatal morbidity/mortality associated with post-placental hypoxia provided that the secondary impact of intrauterine fetal death can be excluded by future studies.

Myeloperoxidase-dependent generation of hypochlorite-modified proteins in human placental tissues during normal pregnancy

Myeloperoxidase (MPO), which is released from cytoplasmic granules of activated phagocytes by a degranulation process, reacts with H(2)O(2) (generated during the oxidative burst) and chloride ions to generate hypochlorous acid/hypochlorite (HOCl/OCl(-)). HOCl, a strong oxidant, in turn reacts with proteins to form HOCl-modified proteins. The presence of these cytotoxic chloramines during inflammatory conditions, eg, atherosclerosis and glomerular and tubulointerstitial injury, suggested that chloramines are powerful oxidants that can have profound biologic effects. In the present study, immunoreactive MPO was identified in fetal membranes and the basal plate and in maternal and fetal blood cells of human placental tissues. Monocytes/macrophages represent the major cell source for MPO in human placental tissues. Immunohistochemical findings revealed that HOCl-modified proteins are present in normal human term placenta but not during the first trimester of pregnancy (Weeks 7 to 12). HOCl-modified proteins were localized in areas formed by fetally derived cells as well as maternal decidual tissues, ie, areas where fetal extravillous trophoblast cells invade the maternal tissue and stimulate the maternal immune system. HOCl-modified proteins, products of the MPO-H(2)O(2)-chloride system in vivo, were not present intracellularly, but immunoreactivity for HOCl-modified proteins was cell-associated and/or present in the extracellular matrix. Extravillous trophoblast cells, which may also exert phagocytic activities, showed no intracellular immunoreactivity for MPO or HOCl-modified proteins. The present findings indicate that the generation of HOCl-modified proteins during normal pregnancy is a physiologic rather than a pathophysiologic process.

GnRH agonist-suppressed expression of nitric oxide synthases and generation of peroxynitrite in adenomyosis

Because overproduction of nitric oxide (NO) and peroxynitrite is known to cause tissue injury, the expression of NO synthases (NOS) and generation of peroxynitrite were investigated in adenomyosis. Immunoreactivities to endothelial and inducible NOS demonstrated phase-dependent changes in normal endometrium, and in eutopic endometrium of adenomyosis. However, NOS were expressed throughout the menstrual cycle in ectopic endometrium from the majority of patients with adenomyosis. Nitrotyrosine, a footprint of peroxynitrite, was detected concomitantly with NOS protein. This suggested that high doses of NO and superoxide are produced in the ectopic endometrium, presumably by stimulation with bioactive molecules such as cytokines and growth factors. The expression of NOS and generation of peroxynitrite were markedly reduced by administration of gonadotrophin-releasing hormone agonists (GnRHa). The suppression of serum concentrations of nitrite/nitrate, stable metabolites of NO, by long-term administration of GnRHa was also demonstrated. The suppression of synthesis of NO and/or peroxynitrite may be part of both the therapeutic and adverse effects of GnRHa therapy.

Elevation of total nitrite and nitrate concentration in vaginal secretions as a predictor of premature delivery

We measured the total concentration of nitrite and nitrate, metabolites of nitric oxide, in vaginal secretions from pregnant women at 22 to 32 weeks' gestation. Total nitrite and nitrate concentrations in patients with preterm premature rupture of membranes and in those with preterm labor and subsequent premature delivery were significantly higher than concentrations in patients who were delivered at term. Elevated total nitrite and nitrate concentration may predict premature delivery.