Difference in Neutrophil Superoxide Generation During Pregnancy Between Preeclampsia and Essential Hypertension

IsoLGs (Isolevuglandins) Drive Neutrophil Migration in Hypertension and Are Essential for the Formation of Neutrophil Extracellular Traps

BACKGROUND

IsoLGs (isolevuglandins) are electrophilic products of lipid peroxidation formed in the presence of reactive oxygen species. IsoLGs contribute to hypertension by an unknown mechanism. Studies have shown that reactive oxygen species production drives the formation of neutrophil extracellular traps (NETs) and that NETs accumulate within the aorta and kidneys of patients with hypertension. The purpose of this study was to determine the role of isoLGs in neutrophil migration and NET formation (NETosis) in hypertension.

METHODS

Mice were treated with Ang II (angiotensin II) and the specific isoLG scavenger 2-hydroxybenzylamine and examined for tissue neutrophil and NET accumulation by single-cell sequencing and flow cytometry. Isolated human neutrophils were studied to determine the role of isoLGs in NETosis and neutrophil chromatin expansion by immunofluorescence and live cell confocal microscopy.

RESULTS

Single-cell sequencing performed on sham, Ang II, and Ang II+2-hydroxybenzylamine treated mice revealed neutrophils as a primary target of 2-hydroxybenzylamine. Peripheral neutrophil migration, aortic NET accumulation, and renal NET accumulation is blocked with 2-hydroxybenzylamine treatment. In isolated human neutrophils, isoLGs accumulate during NETosis and scavenging of isoLGs prevents NETosis. IsoLGs drive neutrophil chromatin expansion during NETosis and disrupt nucleosome structure.

CONCLUSIONS

These observations identified a critical role of isoLGs in neutrophil migration and NETosis in hypertension and provide a potential therapy for NET-associated diseases including hypertension and associated end organ damage.

The Immune System in Hypertension: a Lost Shaker of Salt 2021 Lewis K. Dahl Memorial Lecture

The seminal observations of Dr Lewis Dahl regarding renal mechanisms of hypertension remain highly relevant in light of more recent experiments showing that immune system dysfunction contributes to hypertension pathogenesis. Dr Dahl established that inappropriate salt retention in the kidney plays a central role via Ohm's Law in permitting blood pressure elevation. Nevertheless, inflammatory cytokines whose expression is induced in the early stages of hypertension can alter renal blood flow and sodium transporter expression and activity to foster renal sodium retention. By elaborating these cytokines and reactive oxygen species, myeloid cells and T lymphocytes can connect systemic inflammatory signals to aberrant kidney functions that allow sustained hypertension. By activating T lymphocytes, antigen-presenting cells such as dendritic cells represent an afferent sensing mechanism triggering T cell activation, cytokine generation, and renal salt and water reabsorption. Manipulating these inflammatory signals to attenuate hypertension without causing prohibitive systemic immunosuppression will pose a challenge, but disrupting actions of inflammatory mediators locally within the kidney may offer a path through which to target immune-mediated mechanisms of hypertension while capitalizing on Dr Dahl's key recognition of the kidney's importance in blood pressure regulation.

Gingival crevicular fluid from pregnant women impairs trophoblast cell function and trophoblast-neutrophil interaction

PROBLEM

A strong association between periodontitis and higher susceptibility to pregnancy complications like preeclampsia has been reported although the mechanisms remain elusive. Trophoblast cells modulate the recruitment and functional shaping of maternal leukocytes at early stages to sustain an antiinflammatory microenvironment and fetal growth. Neutrophil activation with reactive oxygen species (ROS) release is associated with preeclampsia. Our aim was to study the effect of the gingival crevicular fluid (GCF) from pregnant women on trophoblast cell function and trophoblast-neutrophil interaction.

METHOD OF STUDY

Pregnant women at 16-20 weeks of gestation (n = 27) and non-pregnant women (n = 8) as the control group were studied for gingivoperiodontal clinical score evaluation and GCF collection. Total bacteria and common periodontal pathogens were analyzed in GCF samples. The effect of each GCF sample was tested on first trimester trophoblast-derived cells to assess cell migration, cytokine expression and glucose uptake. Also, the effect of GCF on human peripheral neutrophil chemoattraction by trophoblast cells and ROS formation was assessed.

RESULTS

Gingival crevicular fluid from pregnant women reduced trophoblast cell migration, increased proinflammatory marker expression and glucose uptake. A significant correlation between gingivoperiodontal score and trophoblast dysfunction was observed. Upon conditioning of trophoblast cells with GCF, only the GCF from pregnant women stimulated neutrophil chemoattraction. Similarly, GCF from pregnant but not from non-pregnant controls stimulated ROS formation in neutrophils.

CONCLUSIONS

Gingival crevicular fluid from pregnant women is deleterious for first trimester trophoblast cell function. These effects could lead to placental homeostasis disruption underlying a pathogenic mechanism of pregnancy complications associated to periodontal disease.

Myeloperoxidase and Other Markers of Neutrophil Activation Associate With Malaria and Malaria/HIV Coinfection in the Human Placenta

Introduction

Placental malaria (PM) is characterized by accumulation of inflammatory leukocytes in the placenta, leading to poor pregnancy outcomes. Understanding of the underlying mechanisms remains incomplete. Neutrophils respond to malaria parasites by phagocytosis, generation of oxidants, and externalization of Neutrophil Extracellular Traps (NETs). NETs drive inflammation in malaria but evidence of NETosis in PM has not been reported. Neutrophil activity in the placenta has not been directly investigated in the context of PM and PM/HIV-co-infection.

Methods

Using peripheral and placental plasma samples and placental tissue collected from Kenyan women at risk for malaria and HIV infections, we assessed granulocyte levels across all gravidities and markers of neutrophil activation, including NET formation, in primi- and secundigravid women, by ELISA, western blot, immunohistochemistry and immunofluorescence.

Results

Reduced peripheral blood granulocyte numbers are observed with PM and PM/HIV co-infection in association with increasing parasite density and placental leukocyte hemozoin accumulation. In contrast, placental granulocyte levels are unchanged across infection groups, resulting in enhanced placental: peripheral count ratios with PM. Within individuals, PM- women have reduced granulocyte counts in placental relative to peripheral blood; in contrast, PM stabilizes these relative counts, with HIV coinfection tending to elevate placental counts relative to the periphery. In placental blood, indicators of neutrophil activation, myeloperoxidase (MPO) and proteinase 3 (PRTN3), are significantly elevated with PM and, more profoundly, with PM/HIV co-infection, in association with placental parasite density and hemozoin-bearing leukocyte accumulation. Another neutrophil marker, matrix metalloproteinase (MMP9), together with MPO and PRTN3, is elevated with self-reported fever. None of these factors, including the neutrophil chemoattractant, CXCL8, differs in relation to infant birth weight or gestational age. CXCL8 and MPO levels in the peripheral blood do not differ with infection status nor associate with birth outcomes. Indicators of NETosis in the placental plasma do not vary with infection, and while structures consistent with NETs are observed in placental tissue, the results do not support an association with PM.

Conclusions

Granulocyte levels are differentially regulated in the peripheral and placental blood in the presence and absence of PM. PM, both with and without pre-existing HIV infection, enhances neutrophil activation in the placenta. The impact of local neutrophil activation on placental function and maternal and fetal health remains unclear. Additional investigations exploring how neutrophil activation and NETosis participate in the pathogenesis of malaria in pregnant women are needed.

Placenta-derived IL-32β activates neutrophils to promote preeclampsia development

Immune activation at the maternal-fetal interface is a main pathogenic factor of preeclampsia (PE). Neutrophils (PMNs) are activated in PE patients, but the mechanism and consequences of PMN activation need to be further explored. Here, we demonstrated that interleukin-32 (IL-32) expression was significantly upregulated in syncytiotrophoblasts (STBs) and that IL-32β was the major isoform with increased expression in the placenta of severe PE (sPE) patients. Furthermore, the level of IL-32 expression in the placenta was correlated with its level in the serum of sPE patients, indicating that IL-32 in the serum is derived mainly from the placenta. Then, in vitro experiments showed that IL-32β could highly activate PMNs and that these IL-32β-activated PMNs were better able to adhere to endothelial cells (HUVECs) and enhance the expression of vascular cell adhesion molecule-1 (VCAM-1) and intercellular cell adhesion molecule-1 (ICAM-1) in HUVECs, which could be reversed by preincubation with the NADPH oxidase inhibitor VAS 2870. In addition, we showed that IL-32β mainly activated PMNs by binding to proteinase 3. Finally, IL-32β administration induced a PE-like phenotype in a pregnant mouse model. This study provides evidence of the involvement of IL-32β in the pathogenesis of PE.

The Role of Neutrophils in Hypertension

It is well accepted that the immune system and some cells from adaptive and innate immunity are necessary for the initiation/perpetuation of arterial hypertension (AH). However, whether neutrophils are part of this group remains debatable. There is evidence showing that the neutrophil/lymphocyte ratio correlates with AH and is higher in non-dipper patients. On the other hand, the experimental neutrophil depletion in mice reduces basal blood pressure. Nevertheless, their participation in AH is still controversial. Apparently, neutrophils may modulate the microenvironment in blood vessels by increasing oxidative stress, favoring endothelial disfunction. In addition, neutrophils may contribute to the tissue infiltration of immune cells, secreting chemoattractant chemokines/cytokines and promoting the proinflammatory phenotype, leading to AH development. In this work, we discuss the potential role of neutrophils in AH by analyzing different mechanisms proposed from clinical and basic studies, with a perspective on cardiovascular and renal damages relating to the hypertensive phenotype.

Circulating Neutrophils Do Not Predict Subclinical Coronary Artery Disease in Women with Former Preeclampsia

: Introduction: Preeclampsia (PE) represents a hypertensive pregnancy disorder that is associated with increased cardiovascular disease (CVD) risk. This increased risk has been attributed to accelerated atherosclerosis, with inflammation being a major contributor. Neutrophils play an important role in the onset and progression of atherosclerosis and have been associated with vascular damage in the placenta as well as the chronic inflammatory state in women with PE. We therefore investigated whether circulating neutrophil numbers or reactivity were associated with the presence and severity of subclinical atherosclerosis in women with a history of PE.

METHODS

Women aged 45-60 years with a 10 to 20 years earlier history of early onset preeclampsia (delivery <34 weeks of gestation) (n = 90), but without symptomatic CVD burden were screened for the presence of subclinical coronary artery disease (CAD) using both contrast-enhanced and non-contrast coronary CT angiography. Subclinical CAD was defined as a coronary artery calcium (CAC) score ≥100 Agatston Units and/or ≥50% coronary luminal stenosis. We assessed whether the numbers and activity of circulating neutrophils were associated with the presence of subclinical CAD and as secondary outcome measurements, with the presence of any calcium (CAC score > 0 AU) or stenosis, categorized as absent (0%), minimal to mild (>0 and <50%), and moderate to severe (≥50%) narrowing of the coronary artery. Blood was drawn just before CT and neutrophil numbers were assessed by flow cytometry. In addition, the presence of the chemokine receptors CXCR2 and CXCR4, which are known to be instrumental in neutrophil recruitment, and neutrophil activity upon stimulation with the bacterial peptide N-Formylmethionyl-leucyl-phenylalanine (fMLF) was assessed by flow cytometry.

RESULTS

Of the participating women, with an average age of 49 years, 13% (12 out of 90) presented with subclinical signs of CAD (CAC score ≥100 AU and/or ≥50% luminal stenosis), and 37% (33 out of 90) had a positive CAC score (>0). Total white blood cell count and neutrophil counts were not associated with the presence of subclinical CAD or with a positive CAC score. When assessing the presence of the chemokine receptors CXCR4 and CXCR2, we observed a slight decrease of neutrophil CXCR2 expression in women with CAC (median MFI 22.0 [interquartile range (IQR) 20.2-23.8]) compared to women without CAC (23.8 [IQR 21.6-25.6], p = 0.02). We observed no differences regarding neutrophil CXCR4 expression. In addition, expression of the early activity marker CD35 was slightly lower on neutrophils of women with subclinical CAD (median MFI 1.6 [IQR 1.5-1.9] compared to 1.9 [IQR 1.7-2.1] in women without CAD, p = 0.02). However, for all findings, statistical significance disappeared after adjustment for multiple testing.

CONCLUSION

Our findings indicate that neutrophil counts and (re)activity are not directly associated with silent CAD disease burden and as such are not suitable as biomarkers to predict the presence of subclinical CAD in a high-risk population of women with a history of preeclampsia.

Interplay between neutrophils and trophoblast cells conditions trophoblast function and triggers vascular transformation signals

Normal placentation entails highly regulated interactions of maternal leukocytes with vascular and trophoblast cells to favor vascular transformation. Neutrophil activation and neutrophil extracellular trap (NET) formation associate with poor placentation and severe pregnancy complications. To deepen into the mechanisms of trophoblast-neutrophil interaction, we explored the effects of NETs on trophoblast cell function and, conversely, whether trophoblast cell-derived factors condition neutrophils to favor angiogenesis and anti-inflammatory signals required for fetal growth. NETs isolated from activated neutrophils hindered trophoblast cell migration. Trophoblast conditioned media prevented the effect as well as the vasoactive intestinal peptide (VIP) known to regulate trophoblast and neutrophil function. On the other hand, factors released by trophoblast cells and VIP shaped neutrophils to a proangiogenic profile with increased vascular endothelial growth factor synthesis and increased capacity to promote vascular transformation. Results presented here provide novel clues to reconstruct the interaction of trophoblast cells and neutrophils in vivo during placentation in humans.

A combined supplementation of omega-3 fatty acids and micronutrients (folic acid, vitamin B12) reduces oxidative stress markers in a rat model of pregnancy induced hypertension

Objectives

Our earlier studies have highlighted that an altered one carbon metabolism (vitamin B₁₂, folic acid, and docosahexaenoic acid) is associated with preeclampsia. Preeclampsia is also known to be associated with oxidative stress and inflammation. The current study examines whether maternal folic acid, vitamin B₁₂ and omega-3 fatty acid supplementation given either individually or in combination can ameliorate the oxidative stress markers in a rat model of pregnancy induced hypertension (PIH).

Materials and Methods

Pregnant Wistar rats were assigned to control and five treatment groups: PIH; PIH + vitamin B₁₂; PIH + folic acid; PIH + Omega-3 fatty acids and PIH + combined micronutrient supplementation (vitamin B₁₂ + folic acid + omega-3 fatty acids). L-Nitroarginine methylester (L-NAME; 50 mg/kg body weight/day) was used to induce hypertension during pregnancy. Blood Pressure (BP) was recorded during pregnancy and dams were dissected at d20 of gestation.

Results

Animals from the PIH group demonstrated higher (p<0.01 for both) systolic and diastolic BP; lower (p<0.01) pup weight; higher dam plasma homocysteine (p<0.05) and dam and offspring malondialdehyde (MDA) (p<0.01), lower (p<0.05) placental and offspring liver DHA and higher (p<0.01) tumor necrosis factor–alpha (TNF–ά) levels as compared to control. Individual micronutrient supplementation did not offer much benefit. In contrast, combined supplementation lowered systolic BP, homocysteine, MDA and placental TNF-ά levels in dams and liver MDA and protein carbonyl in the offspring as compared to PIH group.

Conclusion

Key constituents of one carbon cycle (folic acid, vitamin B₁₂ and DHA) may play a role in reducing oxidative stress and inflammation in preeclampsia.

Calcineurin expression and activity is regulated by the intracellular redox status and under hypertension in human neutrophils

Calcineurin (protein phosphatase 2B) (CN) comprises a family of serine/threonine phosphatases that play a pivotal role in signal transduction cascades in a variety of cells, including neutrophils. Angiotensin II (Ang II) increases both activity and de novo synthesis of CN in human neutrophils. This study focuses on the role that intracellular redox status plays in the induction of CN activity by Ang II. Both de novo synthesis of CN and activity increase promoted by Ang II were downregulated when cells were treated with L-buthionine-(S,R)-sulfoximine, an inhibitor of synthesis of the antioxidant glutathione. We have also investigated the effect of pyrrolidine dithiocarbamate and phenazine methosulfate, which are antioxidant and oxidant compounds, respectively, and concluded that the intracellular redox status of neutrophils is highly critical for Ang II-induced increase of CN expression and activity. Results obtained in neutrophils from hypertensive patients were very similar to those obtained in these cells on treatment with Ang II. We have also addressed the possible functional implication of CN activation in the development of hypertension. Present findings indicate that downregulation of hemoxygenase-1 expression in neutrophils from hypertensive subjects is likely mediated by CN, which acts by hindering translocation to the nucleus of the transcription factor NRF2. These data support and extend our previous results and those from other authors on modulation of CN expression and activity levels by the intracellular redox status.

[Superoxide-anion production by neutrophil granulocytes in healthy and preeclamptic pregnant women]

Data on respiratory burst activity of granulocytes from healthy and preeclamptic pregnant women are contradictory. To further investigate a possible role of reactive oxygen species in the etiology of preeclampsia, the induced superoxide-anion generation by granulocytes from non-pregnant, healthy pregnant and preeclamptic pregnant women were measured. The reciprocal effects of heat-inactivated and non-inactivated plasma on superoxide production by neutrophils from non-pregnant, healthy pregnant and preeclamptic pregnant subjects were also examined. Superoxide generation was measured by ferricytochrome c reduction. Both phorbol-12.13-dibutirate- and N-formyl-methionyl-leucyl-phenylalanine-induced superoxide production was significantly decreased in normal pregnancy compared to results obtained in non-pregnant and preeclamptic pregnant women. Phorbol-12.13-dibutirate-induced superoxide generation by non-pregnant and preeclamptic neutrophils was significantly inhibited by heat-inactivated and non-inactivated healthy pregnant plasma. N-formyl-methionyl-leucyl-phenylalanine-stimulated superoxide production by non-pregnant and preeclamptic granulocytes was suppressed only by non-inactivated healthy pregnant plasma. Phorbol-12.13-dibutirate-induced superoxide generation of healthy pregnant neutrophils was significantly increased by inactivated and non-inactivated non-pregnant and preeclamptic plasma. N-formyl-methionyl-leucyl-phenylalanine-stimulated superoxide production by healthy pregnant granulocytes was significantly enhanced following treatment of the cells with non-inactivated non-pregnant and preeclamptic pregnant plasma. Deficient superoxide generation in normal pregnancy may be caused by maternal immunosuppressive factors. The failure of reduction in superoxide production in preeclampsia may be partly responsible for endothelial dysfunction. Apart from oxidative stress, a possible role of inefficient maternal immunosuppression should also be considered in the pathogenesis of preeclampsia.

Microparticles of pregnant women and preeclamptic patients activate endothelial cells in the presence of monocytes

PROBLEM

Preeclampsia is a pregnancy-specific disorder that may result from an adverse maternal response to circulating placenta-derived factors, causing a systemic inflammation including endothelial activation. Plasma from preeclamptic patients was shown to induce endothelial activation in the presence of monocytes. We investigated whether microparticles (MP) are the plasma factors causing this activation of endothelial cells.

METHOD OF STUDY

Monocultures and co-cultures of monocytes and endothelial cells were incubated with plasma, MP-poor plasma or isolated MP from non-pregnant and pregnant women and preeclamptic patients (each n = 8). ICAM-1 expression was analyzed with flow cytometry.

RESULTS

The expression of ICAM-1 was significantly increased in monocytes and endothelial cells in co-cultures after the addition of isolated MP from preeclamptic patients (P = 0.017) and to a lesser extent in pregnant women (P = 0.012) compared to non-pregnant controls.

CONCLUSIONS

Microparticles from preeclamptic patients activate endothelial cells in the presence of monocytes. Whether all MP have the same effect on monocytes and endothelial cells or only a specific subgroup is the focus of future research.

Leukocyte activation and circulating leukocyte-derived microparticles in preeclampsia

PROBLEM

Preeclampsia shows characteristics of an inflammatory disease including leukocyte activation. Analyses of leukocyte-derived microparticles (MP) and mRNA expression of inflammation-related genes in leukocytes may establish which subgroups of leukocytes contribute to the development of preeclampsia.

METHOD OF STUDY

Blood samples were obtained from preeclamptic patients, normotensive pregnant and non-pregnant controls. sL-selectin and elastase were measured by ELISA. mRNA was isolated from leukocytes and gene expression was determined by multiplex ligation-dependent probe amplification (MLPA). MP were characterized by flow cytometry.

RESULTS

Altered concentrations of sL-selectin and elastase confirmed leukocyte activation in preeclampsia. These leukocytes showed up-regulation of Nuclear Factor of Kappa light chain gene enhancer in B cells inhibitor (NFkappaB-1A) and cyclin-dependent kinase inhibitor (CDKN)-1A compared with normotensive pregnant women. Interleukin-1 Receptor Antagonist (IL-1RA) and tumor necrosis factor (TNF)-R1 were increased compared with those in non-pregnant controls. Monocyte-derived MP were elevated in preeclamptic patients compared with pregnant women. The numbers of cytotoxic T-cell-derived and granulocyte-derived MP were elevated compared with those of non-pregnant women.

CONCLUSION

Leukocytes are activated in preeclampsia. A pro-inflammatory gene expression profile is not prominent, although differences in mRNA expression can be detected. Increased levels of particular subsets of leukocyte-derived MP reflect activation of their parental cells in preeclampsia.