Blockage of heme oxygenase-1 abrogates the protective effect of regulatory T cells on murine pregnancy and promotes the maturation of dendritic cells

Immunological Indicators of Recurrent Pregnancy Loss: A Mendelian Randomization Study

Recurrent pregnancy loss (RPL) is thought to be related to maternal-fetal immune tolerance disorders. Immune monitoring of RPL patients mainly involves two aspects: inflammatory factors and immune cells. However, most observational studies have reported controversial findings. This study aimed to confirm whether abnormal inflammatory factors and immune cells in peripheral blood may lead to RPL, and guide clinical immune monitoring. We demonstrated causality using two-sample Mendelian randomization. Sensitivity analysis, reverse Mendelian randomization and meta-analysis were used to enhance the effectiveness of the results. There was a causal relationship between the level of IL-12 (OR = 1.78, 95% CI = 1.25-2.55; P = 0.00149) and RPL for 41 inflammatory factors. We screened 5 groups of immune cell subtypes that were causally associated with RPL: switched memory B-cell absolute count (OR = 0.66, 95% CI = 0.49-0.87, P = 0.00406), IgD + CD24 + B-cell absolute count (OR = 0.69, 95% CI = 0.53-0.88, P = 0.00319), CD39 + resting CD4 regulatory T-cell %CD4 regulatory T-cell (OR = 0.86, 95% CI = 0.78-0.95, P = 0.00252), activated & resting CD4 regulatory T-cell %CD4 regulatory T-cell (OR = 0.89, 95% CI = 0.82-0.97, P = 0.00938) and CD45 RA + CD28-CD8 + T-cell %CD8 + T-cell (OR = 0.99, 95% CI = 0.98-1.00, P = 0.01231). In terms of inflammatory factors, a causal relationship between IL-12 and RPL in peripheral blood was confirmed. We also identified five immune cell phenotypes that play a protective role. This suggests that there may be protective B cells and CD8 + T-cell subsets in peripheral blood, and the protective effect of Tregs was proved again. Immune monitoring of peripheral blood in patients with RPL seems to be necessary and the foundation for precision medicine.

Single-cell transcriptomics of Treg reveals hallmarks and trajectories of immunological aging

Age-related immunosenescence is characterized by progressive dysfunction of adaptive immune response and increased autoimmunity. Nevertheless, the impact of aging on CD4+ regulatory T cells that are master regulators of the immune system remains largely unclear. Here, we report cellular and molecular hallmarks of regulatory T cells derived from murine lymphoid and adipose tissues at 3, 18, and 24 mo of age, respectively, by analyzing their heterogeneity that displays dynamic changes in transcriptomic effector signatures at a single-cell resolution. Although the proportion of regulatory T cells among total Cd4+ T cells, as well as their expression levels of Foxp3, did not show any global change with time, we have identified 6 transcriptomically distinct clusters of regulatory T cells with cross-tissue conserved hallmarks of aging, including increased numbers of proinflammatory regulatory T cells, reduced precursor cells, increased immature and mature T follicular regulatory cells potentially supported by a metabolic switch from oxidative phosphorylation to glycolysis, a gradual loss of CD150hi regulatory T cells that support hematopoiesis, and increased adipose tissue-specific regulatory T cells that are associated with metabolic disease. To dissect the impact of immunosenescence on humoral immunity, we propose some potential mechanisms underlying T follicular regulatory cell-mediated dysfunction by interactome analysis on T follicular regulatory cells, T follicular helper cells, and B cells during aging. Lastly, spatiotemporal analysis further revealed trajectories of regulatory T-cell aging that demonstrate the most significant changes in marrow and adipose tissues that might contribute to the development of age-related immunosenescence and type 2 diabetes. Taken together, our findings could provide a better understanding of age-associated regulatory T-cell heterogeneity in lymphoid and adipose tissues, as well as regulatory T-cell hallmarks during progressive adaptation to aging that could be therapeutically targeted for rejuvenating the aging immune system in the future.

Beneficial or detrimental activity of regulatory T cells, indoleamine 2,3-dioxygenase, and heme oxygenase-1 in the lungs is influenced by the level of virulence of Mycobacterium tuberculosis strain infection

Tuberculosis (TB) caused by the complex Mycobacterium tuberculosis (Mtb) is the main cause of death by a single bacterial agent. Last year, TB was the second leading infectious killer after SARS-CoV-2. Nevertheless, many biological and immunological aspects of TB are not completely elucidated, such as the complex process of immunoregulation mediated by regulatory T cells (Treg cells) and the enzymes indoleamine 2,3-dioxygenase (IDO) and heme oxygenase 1 (HO-1). In this study, the contribution of these immunoregulatory factors was compared in mice infected with Mtb strains with different levels of virulence. First Balb/c mice were infected by intratracheal route, with a high dose of mild virulence reference strain H37Rv or with a highly virulent clinical isolate (strain 5186). In the lungs of infected mice, the kinetics of Treg cells during the infection were determined by cytofluorometry and the expression of IDO and HO-1 by RT-PCR and immunohistochemistry. Then, the contribution of immune-regulation mediated by Treg cells, IDO and HO-1, was evaluated by treating infected animals with specific cytotoxic monoclonal antibodies for Treg cells depletion anti-CD25 (PC61 clone) or by blocking IDO and HO-1 activity using specific inhibitors (1-methyl-D,L-tryptophan or zinc protoporphyrin-IX, respectively). Mice infected with the mild virulent strain showed a progressive increment of Treg cells, showing this highest number at the beginning of the late phase of the infection (28 days), the same trend was observed in the expression of both enzymes being macrophages the cells that showed the highest immunostaining. Animals infected with the highly virulent strain showed lower survival (34 days) and higher amounts of Treg cells, as well as higher expression of IDO and HO-1 one week before. In comparison with non-treated animals, mice infected with strain H37Rv with depletion of Treg cells or treated with the enzymes blockers during late infection showed a significant decrease of bacilli loads, higher expression of IFN-g and lower IL-4 but with a similar extension of inflammatory lung consolidation determined by automated morphometry. In contrast, the depletion of Treg cells in infected mice with the highly virulent strain 5186 produced diffuse alveolar damage that was similar to severe acute viral pneumonia, lesser survival and increase of bacillary loads, while blocking of both IDO and HO-1 produced high bacillary loads and extensive pneumonia with necrosis. Thus, it seems that Treg cells, IDO and HO-1 activities are detrimental during late pulmonary TB induced by mild virulence Mtb, probably because these factors decrease immune protection mediated by the Th1 response. In contrast, Treg cells, IDO and HO-1 are beneficial when the infection is produced by a highly virulent strain, by regulation of excessive inflammation that produced alveolar damage, pulmonary necrosis, acute respiratory insufficiency, and rapid death.

Innate and Adaptive Immune Systems in Physiological and Pathological Pregnancy

The dynamic immunological changes occurring throughout pregnancy are well-orchestrated and important for the success of the pregnancy. One of the key immune adaptations is the maternal immune tolerance towards the semi-allogeneic fetus. In this review, we provide a comprehensive overview of what is known about the innate and adaptive immunological changes in pregnancy and the role(s) of specific immune cells during physiological and pathological pregnancy. Alongside this, we provided details of remaining questions and challenges, as well as future perspectives for this growing field of research. Understanding the immunological changes that occur can inform potential strategies on treatments for the optimal health of the neonate and pregnant individual both during and after pregnancy.

Dominant immune cells in pregnancy and pregnancy complications: T helper cells (TH1/TH2, TH17/Treg cells), NK cells, MDSCs, and the immune checkpoints

Pregnancy problems including recurrent pregnancy loss, repeated implantation failure and pre-eclampsia  are common problems in the reproductive ages. Different reasons such as genetic, immunological, and environmental agents and also infections could develop these complications. In those cases in which the cause of the abortion is diagnosed, the chance of a successful pregnancy is increased by eliminating defective factors. However, in patients with unknown causes, there may be an imbalance in immune cells pattern. As a matter of fact, an inappropriate immune response is often associated with a failed pregnancy. Hence, the focus of treatment is to increase tolerance, not to suppress maternal immune system. These findings are linked to an elevated number of Treg cells and immune checkpoints through normal pregnancy. The present review discusses the balance of myeloid-derived suppressor cells, natural killer cells, T cells, and immune checkpoints, and also targeting them to maintain pregnancy and prevent associated complications.

Breast cancers co-opt normal mechanisms of tolerance to promote immune evasion and metastasis

Normal developmental processes, such as those seen during embryonic development and postpartum mammary gland involution, can be reactivated by cancer cells to promote immune suppression, tumor growth, and metastatic spread. In mammalian embryos, paternal-derived antigens are at risk of being recognized as foreign by the maternal immune system. Suppression of the maternal immune response toward the fetus, which is mediated in part by the trophoblast, is critical to ensure embryonic survival and development. The postpartum mammary microenvironment also exhibits immunosuppressive mechanisms accompanying the massive cell death and tissue remodeling that occurs during mammary gland involution. These normal immunosuppressive mechanisms are paralleled during malignant transformation, where tumors can develop neoantigens that may be recognized as foreign by the immune system. To circumvent this, tumors can dedifferentiate and co-opt immune-suppressive mechanisms normally utilized during fetal tolerance and postpartum mammary involution. In this review, we discuss those similarities and how they can inform our understanding of cancer progression and metastasis.

Immune–Metabolic Interactions and T Cell Tolerance in Pregnancy

Pregnancy depends on a state of maternal immune tolerance mediated by CD4+ regulatory T (Treg) cells. Uterine Treg cells release anti-inflammatory factors, inhibit effector immunity, and support adaptation of the uterine vasculature to facilitate placental development. Insufficient Treg cells or inadequate functional competence is implicated in infertility and recurrent miscarriage, as well as pregnancy complications preeclampsia, fetal growth restriction, and preterm birth, which stem from placental insufficiency. In this review we address an emerging area of interest in pregnancy immunology–the significance of metabolic status in regulating the Treg cell expansion required for maternal–fetal tolerance. We describe how hyperglycemia and insulin resistance affect T cell responses to suppress generation of Treg cells, summarize data that implicate a role for altered glucose metabolism in impaired maternal–fetal tolerance, and explore the prospect of targeting dysregulated metabolism to rebalance the adaptive immune response in women experiencing reproductive disorders.

The different facets of heme-oxygenase 1 in innate and adaptive immunity

Heme oxygenase (HO) enzymes are responsible for the main oxidative step in heme degradation, generating equimolar amounts of free iron, biliverdin and carbon monoxide. HO-1 is induced as a crucial stress response protein, playing protective roles in physiologic and pathological conditions, due to its antioxidant, anti-apoptotic and anti-inflammatory effects. The mechanisms behind HO-1-mediated protection are being explored by different studies, affecting cell fate through multiple ways, such as reduction in intracellular levels of heme and ROS, transcriptional regulation, and through its byproducts generation. In this review we focus on the interplay between HO-1 and immune-related signaling pathways, which culminate in the activation of transcription factors important in immune responses and inflammation. We also discuss the dual interaction of HO-1 and inflammatory mediators that govern resolution and tissue damage. We highlight the dichotomy of HO-1 in innate and adaptive immune cells development and activation in different disease contexts. Finally, we address different known anti-inflammatory pharmaceuticals that are now being described to modulate HO-1, and the possible contribution of HO-1 in their anti-inflammatory effects.

Dependence of Retinal Pigment Epithelium Integrity on the NRF2-Heme Oxygenase-1 Axis

Purpose

Tight junctions (TJs) form the structural basis of retinal pigment epithelium (RPE) barrier functions. Although oxidative stress contributes to age-related macular degeneration, it is unclear how RPE TJ integrity is controlled by redox balance. In this study, we investigated the protective roles of nuclear factor erythroid 2–related factor 2 (NRF2), a transcription factor, and heme oxygenase-1 (HO1), a heme-degrading enzyme encoded by the NRF2 target gene HMOX1.

Methods

ARPE19 cell cultures and mice, including wild-type, Nrf2^−/−, and RPE-specific NRF2-deficient mice, were treated with chemicals that impose oxidative stress or impact heme metabolism. In addition, NRF2 and HO1 expression in ARPE19 cells was knocked down by siRNA. TJ integrity was examined by anti–zonula occludens-1 staining of cultured cells or flatmount RPE tissues from mice. RPE barrier functions were evaluated by transepithelium electrical resistance in ARPE19 cells and immunofluorescence staining for albumin or dextran in eye histological sections.

Results

TJ structures and RPE barrier functions were compromised due to oxidant exposure and NRF2 deficiency but were rescued by HO1 inducer. Furthermore, treatment with HO1 inhibitor or heme precursor is destructive to TJ structures and RPE barrier properties. Interestingly, both NRF2 and HO1 were upregulated under oxidative stress, probably as an adaptive response to mitigate oxidant-inflicted damages.

Conclusions

Our data indicate that the NRF2–HO1 axis protects TJ integrity and RPE barrier functions by driving heme degradation.

Carbon monoxide mechanism of protection against renal ischemia and reperfusion injury

Carbon monoxide is quickly moving past its historic label as a molecule once feared, to a therapeutic drug that modulates inflammation. The development of carbon monoxide releasing molecules and utilization of heme oxygenase-1 inducers have shown carbon monoxide to be a promising therapy in reducing renal ischemia and reperfusion injury and other inflammatory diseases. In this review, we will discuss the developments and application of carbon monoxide releasing molecules in renal ischemia and reperfusion injury, and transplantation. We will review the anti-inflammatory mechanisms of carbon monoxide in respect to mitigating apoptosis, suppressing dendritic cell maturation and signalling, inhibiting toll-like receptor activation, promoting anti-inflammatory responses, and the effects on renal vasculature.

Immune determinants of endometrial receptivity: a biological perspective

Immune cells are essential for endometrial receptivity to embryo implantation and early placental development. They exert tissue-remodeling and immune regulatory roles-acting to promote epithelial attachment competence, regulate the differentiation of decidual cells, remodel the uterine vasculature, control and resolve inflammatory activation, and suppress destructive immunity to paternally inherited alloantigens. From a biological perspective, the endometrial immune response exerts a form of "quality control"-it promotes implantation success when conditions are favorable but constrains receptivity when physiological circumstances are not ideal. Women with recurrent implantation failure and recurrent miscarriage may exhibit altered numbers or disturbed function of certain uterine immune cell populations-most notably uterine natural killer cells and regulatory T cells. Preclinical and animal studies indicate that deficiencies or aberrant activation states in these cells can be causal in the pathophysiological mechanisms of infertility. Immune cells are, therefore, targets for diagnostic evaluation and therapeutic intervention. However, current diagnostic tests are overly simplistic and have limited clinical utility. To be more informative, they need to account for the full complexity and reflect the range of perturbations that can occur in uterine immune cell phenotypes and networks. Moreover, safe and effective interventions to modulate these cells are in their infancy, and personalized approaches matched to specific diagnostic criteria will be needed. Here we summarize current biological understanding and identify knowledge gaps to be resolved before the promise of therapies to target the uterine immune response can be fully realized.

Prevention of mastitis in multiparous dairy cows with a previous history of mastitis by oral feeding with probiotic Bacillus subtilis

Mastitis is a very common inflammatory disease of the mammary gland of dairy cows, resulting in a reduction of milk production and quality. Probiotics may serve as an alternative to antibiotics to prevent mastitis, and the use of probiotics in this way may lessen the risk of antibiotic resistant bacteria developing. We investigated the effect of oral feeding of probiotic Bacillus subtilis (BS) C‐3102 strain on the onset of mastitis in dairy cows with a previous history of mastitis. BS feeding significantly decreased the incidence of mastitis, the average number of medication days and the average number of days when milk was discarded, and maintained the mean SCC in milk at a level substantially lower than the control group. BS feeding was associated with lower levels of cortisol and TBARS and increased the proportion of CD4⁺ T cells and CD11c⁺ CD172a^high dendritic cells in the blood by flow cytometry analysis. Parturition increased the migrating frequency of granulocytes toward a milk chemoattractant cyclophilin A in the control cows, however, this was reduced by BS feeding, possibly indicating a decreased sensitivity of peripheral granulocytes to cyclophilin A. These results reveal that B. subtilis C‐3102 has potential as a probiotic and has preventative capacity against mastitis in dairy cows.

Cellular immune responses in the pathophysiology of preeclampsia

Preeclampsia, defined as new-onset hypertension accompanied by proteinuria occurring at 20 weeks of gestation or later, is a leading cause of perinatal morbidity and mortality worldwide. The pathophysiology of this major multi-systemic syndrome includes defective deep placentation, oxidative stress, endothelial dysfunction, the presence of an anti-angiogenic state, and intravascular inflammation, among others. In this review, we provide a comprehensive overview of the cellular immune responses involved in the pathogenesis of preeclampsia. Specifically, we summarize the role of innate and adaptive immune cells in the maternal circulation, reproductive tissues, and at the maternal-fetal interface of women affected by this pregnancy complication. The major cellular subsets involved in the pathogenesis of preeclampsia are regulatory T cells, effector T cells, NK cells, monocytes, macrophages, and neutrophils. We also summarize the literature on those immune cells that have been less characterized in this clinical condition, such as γδ T cells, invariant natural killer T cells, dendritic cells, mast cells, and B cells. Moreover, we discuss in vivo studies utilizing a variety of animal models of preeclampsia to further support the role of immune cells in this disease. Finally, we highlight the existing gaps in knowledge of the immunobiology of preeclampsia that require further investigation. The goal of this review is to promote translational research leading to clinically relevant strategies that can improve adverse perinatal outcomes resulting from the obstetrical syndrome of preeclampsia.

Heme Oxygenase 1 in Vertebrates: Friend and Foe

HO-1 is the inducible form of the enzyme heme-oxygenase. HO-1 catalyzes heme breakdown, reducing the levels of this important oxidant molecule and generating antioxidant, anti-inflammatory, and anti-apoptotic byproducts. Thus, HO-1 has been described as an important stress response mechanism during both physiologic and pathological processes. Interestingly, some findings are demonstrating that uncontrolled levels of HO-1 byproducts can be associated with cell death and tissue destruction as well. Furthermore, HO-1 can be located in the nucleus, influencing gene transcription, cellular proliferation, and DNA repair. Here, we will discuss several studies that approach HO-1 effects as a protective or detrimental mechanism in different pathological conditions. In this sense, as the major organs of vertebrates will deal specifically with distinct types of stresses, we discuss the HO-1 role in each of them, exposing the contradictions associated with HO-1 expression after different insults and circumstances.

Immunomodulatory Effects of Heme Oxygenase-1 in Kidney Disease

Kidney disease is a general term for heterogeneous damage that affects the function and the structure of the kidneys. The rising incidence of kidney diseases represents a considerable burden on the healthcare system, so the development of new drugs and the identification of novel therapeutic targets are urgently needed. The pathophysiology of kidney diseases is complex and involves multiple processes, including inflammation, autophagy, cell-cycle progression, and oxidative stress. Heme oxygenase-1 (HO-1), an enzyme involved in the process of heme degradation, has attracted widespread attention in recent years due to its cytoprotective properties. As an enzyme with known anti-oxidative functions, HO-1 plays an indispensable role in the regulation of oxidative stress and is involved in the pathogenesis of several kidney diseases. Moreover, current studies have revealed that HO-1 can affect cell proliferation, cell maturation, and other metabolic processes, thereby altering the function of immune cells. Many strategies, such as the administration of HO-1-overexpressing macrophages, use of phytochemicals, and carbon monoxide-based therapies, have been developed to target HO-1 in a variety of nephropathological animal models, indicating that HO-1 is a promising protein for the treatment of kidney diseases. Here, we briefly review the effects of HO-1 induction on specific immune cell populations with the aim of exploring the potential therapeutic roles of HO-1 and designing HO-1-based therapeutic strategies for the treatment of kidney diseases.

Using ultrasound to define the time point of intrauterine growth retardation in a mouse model of heme oxygenase-1 deficiency†

The enzyme heme oxygenase-1 (HO-1), encoded by the HMOX1 gene, mediates heme catabolism by cleaving free heme. We have previously revealed the importance of HO-1 in pregnancy. Here, we determined the impact of maternal or paternal HO-1 deficiency on fetal growth and placental parameters throughout gestation. We mated Hmox1-sufficient (WT), partial (HET)-, or total (KO)-deficient BALB/c female mice with Hmox1-WT or -KO BALB/c males and performed ultrasound analysis to monitor placental and fetal growth. Doppler measurements were used to determine maternal blood flow parameters. Offspring weights and feto-placental indices (FPI) were also determined. We found a significantly increased number of underdeveloped fetuses at gd10 in HET females that were mated with WT males compared with WT × WT pairings. At the same gestational age, underdeveloped placentas could be detected in HET females mated with KO males. Many fetuses from the KO × KO combination died in utero between gd12 and gd14. At gd14, abnormal placental parameters were found in surviving fetuses, which had significant reduced weights. Moreover, only 3.11% female and 5.33% male KO pups resulted from 10 HET × HET breeding pairs over 1 year. Our results show that HO-1 from both maternal and paternal origins is important for proper placental and fetal growth. Placental growth restriction and occurrence of abortions in mice that were partially or totally deficient in HO-1 were recorded in vivo from gd10 onwards. Future studies will focus on elucidating the cellular and molecular mechanisms behind these observations.

The Role and Function of Regulatory T Cells in Toxoplasma gondii-Induced Adverse Pregnancy Outcomes

Infection with Toxoplasma gondii (T. gondii) during the pregnant period and its potentially miserable outcomes for the fetus, newborn, and even adult offspring continuously occur worldwide. People acquire infection through the consumption of infected and undercooked meat or contaminated food or water. T. gondii infection in pregnant women primarily during the gestation causes microcephaly, mental and psychomotor retardation, or death. Abnormal pregnancy outcomes are mainly associated with regulatory T cell (Treg) dysfunction. Tregs, a special subpopulation of T cells, function as a vital regulator in maintaining immune homeostasis. Tregs exert a critical effect on forming and maintaining maternal-fetal tolerance and promoting fetal development during the pregnancy period. Forkhead box P3 (Foxp3), a significant functional factor of Tregs, determines the status of Tregs. In this review, we summarize the effects of T. gondii infection on host Tregs and its critical transcriptional factor, Foxp3.

Regulation of inflammation by the antioxidant haem oxygenase 1

Haem oxygenase 1 (HO-1), an inducible enzyme responsible for the breakdown of haem, is primarily considered an antioxidant, and has long been overlooked by immunologists. However, research over the past two decades in particular has demonstrated that HO-1 also exhibits numerous anti-inflammatory properties. These emerging immunomodulatory functions have made HO-1 an appealing target for treatment of diseases characterized by high levels of chronic inflammation. In this Review, we present an introduction to HO-1 for immunologists, including an overview of its roles in iron metabolism and antioxidant defence, and the factors which regulate its expression. We discuss the impact of HO-1 induction in specific immune cell populations and provide new insights into the immunomodulation that accompanies haem catabolism, including its relationship to immunometabolism. Furthermore, we highlight the therapeutic potential of HO-1 induction to treat chronic inflammatory and autoimmune diseases, and the issues faced when trying to translate such therapies to the clinic. Finally, we examine a number of alternative, safer strategies that are under investigation to harness the therapeutic potential of HO-1, including the use of phytochemicals, novel HO-1 inducers and carbon monoxide-based therapies.

5-aminolevulinic acid combined with sodium ferrous citrate ameliorated lupus nephritis in a mouse chronic graft-versus-host disease model

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by the abnormal activation of immune cells and hypersecretion of autoantibodies and causes irreversible chronic damage, such as lupus nephritis. Chronic graft-versus-host-disease (cGvHD) in mice induced by the injection of parental mouse lymphocytes into F1 hybrids leads to a disease similar to SLE. 5-aminolevulinic acid (5-ALA) is a key progenitor of heme, and its combination with sodium ferrous citrate (SFC) can up-regulate the heme oxygenase (HO-1) expression, resulting in an anti-inflammatory effect. While HO-1 had been reported to be involved in T cell activation and can limit immune-based tissue damage through Treg suppression, which promotes effector response. Thus, we hypothesized that treatment with 5-ALA/SFC could ameliorate lupus nephritis in a mouse cGvHD model. Our results showed that 5-ALA/SFC-treatment significantly decreased the anti-double-stranded DNA (ds-DNA) autoantibodies, blood urea nitrogen (BUN) and creatinine (Cre) levels, reduced kidney inflammatory dendritic cells (DCs) and B cell activation, and increased the regulatory T cells (Tregs) at nine weeks. Furthermore, 5-ALA/SFC suppressed mRNA expression of TNF-α, IL-1β, IFN-γ and markers on DCs. In addition, we also found that 5-ALA/SFC treatment increased the HO-1 expression on donor-derived DCs and Tregs concurrently, increased the number of Tregs, and reduced the population of activated DCs, B cells and CD8+ T cells at three weeks (early stage of the disease). We thus identified a novel role of 5-ALA/SFC for therapeutically improving the symptoms of lupus nephritis in a mouse cGvHD model and expanded the current understanding of how this immunoregulatory agent can be used to generate beneficial immune responses and treat autoimmune disease.

Haem oxygenases play a pivotal role in placental physiology and pathology

BACKGROUND

Haem oxygenases (HO) catabolise haem, which is the prosthetic group of numerous haemoproteins. Thus, multiple primary cellular pathways and functions rely on haem availability. HO exists in two isoforms, both expressed in the placenta, namely HO-1 and HO-2, the first being inducible. Haem oxygenases, particularly HO-1, have garnered specific interest in the field of physiological and pathological placental function. These enzymes mediate haem degradation by cleaving the alpha methene bridge to produce biliverdin, which is subsequently converted to bilirubin, carbon monoxide and iron. HO-1 has anti-inflammatory and antioxidant activities.

SEARCH METHODS

An initial literature analysis was performed using PubMed on 3 October 2018 using key terms such as 'haem oxygenase and pregnancy', 'haem oxygenase and placenta', 'HO-1 and pregnancy', 'HO-1 and placenta', 'HO and placenta', 'HO and pregnancy', 'genetic variant and HO', 'CO and pregnancy', 'CO and placenta', 'Bilirubin and pregnancy', 'Iron and pregnancy' and 'PPAR and Haem', selecting consensus conferences, recommendations, meta-analyses, practical recommendations and reviews. A second literature analysis was performed, including notable miscarriages, foetal loss and diabetes mellitus, on 20 December 2019. The three authors studied the publications independently to decipher whether they should be included in the manuscript.

OBJECTIVE AND RATIONALE

This review aimed to summarise current pieces of knowledge of haem oxygenase location, function and regulation in the placenta, either in healthy pregnancies or those associated with miscarriages and foetal loss, pre-eclampsia, foetal growth restriction and diabetes mellitus.

OUTCOMES

HO-1 exerts some protective effects on the placentation, probably by a combination of factors, including its interrelation with the PGC-1α/PPAR pathway and the sFlt1/PlGF balance, and through its primary metabolites, notably carbon monoxide and bilirubin. Its protective role has been highlighted in numerous pregnancy conditions, including pre-eclampsia, foetal growth restriction, gestational diabetes mellitus and miscarriages.

WIDER IMPLICATIONS

HO-1 is a crucial enzyme in physiological and pathological placentation. This protective enzyme is currently considered a potential therapeutic target in various pregnancy diseases.

Adoptive transfer of Tregs: A novel strategy for cell-based immunotherapy in spontaneous abortion: Lessons from experimental models

Since half of the genes are inherited from the paternal side, the maternal immune system has to tolerate the presence of foreign paternal antigens. Regulatory T cells facilitate the development and maintenance of peripheral tissue tolerance of the fetus during pregnancy. Reduction in regulatory T cells is associated with complications of pregnancy, including spontaneous abortion. Recent studies in mouse models have shown that the adoptive transfer of Tregs can prevent spontaneous abortion in mouse models through improving maternal tolerance. Thus, adoptive cell therapy using autologous Tregs could potentially be a novel therapeutic approach for cell-based immunotherapy in women with unexplained spontaneous abortion. Besides, strategies for activating and expanding antigen-specific Tregs ex vivo and in vivo based on pharmacological agents can pave the foundation for an approach incorporating immunotherapy and pharmacotherapy. This review aims to elaborate on the current understanding of the therapeutic potential of the adoptive transfer of Tregs in the treatment of spontaneous abortion disease.

Dendritic cells in pregnancy and pregnancy-associated diseases

Dendritic cells (DCs) play a critical immuno-modulating role in pregnancy, which requires the maternal immune system to tolerate semiallogeneic fetus and at the same time to maintain adequate defense against pathogens. DCs interact closely with other immune components such as T cells, natural killer cells and macrophages, as well as the endocrine system to keep a pregnancy-friendly environment. Aberrant DC activities have been related to various pregnancy-associated diseases such as recurrent spontaneous abortion, preterm birth, pre-eclampsia, peripartum cardiomyopathy and infectious pregnancy complications. These findings make DCs an attractive candidate for prevention or therapy on the pregnancy-associated diseases. Here, we review recent findings that provide new insights into the roles of DCs in pregnancy and the related diseases. We also discuss the medical potentials to manipulate DCs in clinics. Whereas this is an emerging area with much work remaining, we anticipate that a better understanding of the role of DCs in maternal-fetal immunotolerance and a therapeutic manipulation of DCs will help women suffering from the pregnancy-associated diseases.

Mesenchymal stromal cell-derived extracellular vesicle therapy prevents preeclamptic physiology through intrauterine immunomodulation†

Human umbilical cord-derived mesenchymal stromal cells (MSCs) are a widely recognized treatment modality for a variety of preclinical disease models and have been transitioned to human clinical trials. We have previously shown in neonatal lung disease that the therapeutic capacity of MSCs is conferred by their secreted extracellular vesicles (MEx), which function primarily through immunomodulation. We hypothesize that MEx have significant therapeutic potential pertinent to immune-mediated gestational diseases. Of particular interest is early-onset preeclampsia, which can be caused by alterations of the maternal intrauterine immune environment. Using a heme-oxygenase-1 null mouse model of pregnancy loss with preeclampsia-like features, we examined the preventative effects of maternal MEx treatment early in pregnancy. Heme oxygenase-1 null females (Hmox1-/-) or wild-type control females were bred in homozygous matings followed by evaluation of maternal and fetal parameters. A single dose of MEx was administered intravenously on gestational day (GD)1 to Hmox1-/- females (Hmox1-/- MEx). Compared with untreated Hmox1-/- females, Hmox1-/- MEx-treated pregnancies showed significant improvement in fetal loss, intrauterine growth restriction, placental spiral artery modification, and maternal preeclamptic stigmata. Biodistribution studies demonstrated that MEx localize to a subset of cells in the preimplantation uterus. Further, mass cytometric (CyTOF) evaluation of utero-placental leukocytes in Hmox1-/- MEx versus untreated pregnancies showed alteration in the abundance, surface marker repertoire, and cytokine profiles of multiple immune populations. Our data demonstrate the therapeutic potential of MEx to optimize the intrauterine immune environment and prevent maternal and fetal sequelae of preeclamptic disease.

CXCL12-CXCR4 Interplay Facilitates Palatal Osteogenesis in Mice

Cranial neural crest cells (CNCCs), identified by expression of transcription factor Sox9, migrate to the first branchial arch and undergo proliferation and differentiation to form the cartilage and bone structures of the orofacial region, including the palatal bone. Sox9 promotes osteogenic differentiation and stimulates CXCL12-CXCR4 chemokine-receptor signaling, which elevates alkaline phosphatase (ALP)-activity in osteoblasts to initiate bone mineralization. Disintegration of the midline epithelial seam (MES) is crucial for palatal fusion. Since we earlier demonstrated chemokine-receptor mediated signaling by the MES, we hypothesized that chemokine CXCL12 is expressed by the disintegrating MES to promote the formation of an osteogenic center by CXCR4-positive osteoblasts. Disturbed migration of CNCCs by excess oxidative and inflammatory stress is associated with increased risk of cleft lip and palate (CLP). The cytoprotective heme oxygenase (HO) enzymes are powerful guardians harnessing injurious oxidative and inflammatory stressors and enhances osteogenic ALP-activity. By contrast, abrogation of HO-1 or HO-2 expression promotes pregnancy pathologies. We postulate that Sox9, CXCR4, and HO-1 are expressed in the ALP-activity positive osteogenic regions within the CNCCs-derived palatal mesenchyme. To investigate these hypotheses, we studied expression of Sox9, CXCL12, CXCR4, and HO-1 in relation to palatal osteogenesis between E15 and E16 using (immuno)histochemical staining of coronal palatal sections in wild-type (wt) mice. In addition, the effects of abrogated HO-2 expression in HO-2 KO mice and inhibited HO-1 and HO-2 activity by administrating HO-enzyme activity inhibitor SnMP at E11 in wt mice were investigated at E15 or E16 following palatal fusion. Overexpression of Sox9, CXCL12, CXCR4, and HO-1 was detected in the ALP-activity positive osteogenic regions within the palatal mesenchyme. Overexpression of Sox9 and CXCL12 by the disintegrating MES was detected. Neither palatal fusion nor MES disintegration seemed affected by either HO-2 abrogation or inhibition of HO-activity. Sox9 progenitors seem important to maintain the CXCR4-positive osteoblast pool to drive osteogenesis. Sox9 expression may facilitate MES disintegration and palatal fusion by promoting epithelial-to-mesenchymal transformation (EMT). CXCL12 expression by the MES and the palatal mesenchyme may promote osteogenic differentiation to create osteogenic centers. This study provides novel evidence that CXCL12-CXCR4 interplay facilitates palatal osteogenesis and palatal fusion in mice.

Gasotransmitters in pregnancy: from conception to uterine involution

Gasotransmitters are endogenous small gaseous messengers exemplified by nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S or sulfide). Gasotransmitters are implicated in myriad physiologic functions including many aspects of reproduction. Our objective was to comprehensively review basic mechanisms and functions of gasotransmitters during pregnancy from conception to uterine involution and highlight future research opportunities. We searched PubMed and Web of Science databases using combinations of keywords nitric oxide, carbon monoxide, sulfide, placenta, uterus, labor, and pregnancy. We included English language publications on human and animal studies from any date through August 2018 and retained basic and translational articles with relevant original findings. All gasotransmitters activate cGMP signaling. NO and sulfide also covalently modify target protein cysteines. Protein kinases and ion channels transduce gasotransmitter signals, and co-expressed gasotransmitters can be synergistic or antagonistic depending on cell type. Gasotransmitters influence tubal transit, placentation, cervical remodeling, and myometrial contractility. NO, CO, and sulfide dilate resistance vessels, suppress inflammation, and relax myometrium to promote uterine quiescence and normal placentation. Cervical remodeling and rupture of fetal membranes coincide with enhanced oxidation and altered gasotransmitter metabolism. Mechanisms mediating cellular and organismal changes in pregnancy due to gasotransmitters are largely unknown. Altered gasotransmitter signaling has been reported for preeclampsia, intrauterine growth restriction, premature rupture of membranes, and preterm labor. However, in most cases specific molecular changes are not yet characterized. Nonclassical signaling pathways and the crosstalk among gasotransmitters are emerging investigation topics.

Heme Oxygenase Protects against Placental Vascular Inflammation and Abortion by the Alarmin Heme in Mice

Both infectious as non-infectious inflammation can cause placental dysfunction and pregnancy complications. During the first trimester of human gestation, when palatogenesis takes place, intrauterine hematoma and hemorrhage are common phenomena, causing the release of large amounts of heme, a well-known alarmin. We postulated that exposure of pregnant mice to heme during palatogenesis would initiate oxidative and inflammatory stress, leading to pathological pregnancy, increasing the incidence of palatal clefting and abortion. Both heme oxygenase isoforms (HO-1 and HO-2) break down heme, thereby generating anti-oxidative and -inflammatory products. HO may thus counteract these heme-induced injurious stresses. To test this hypothesis, we administered heme to pregnant CD1 outbred mice at Day E12 by intraperitoneal injection in increasing doses: 30, 75 or 150 μmol/kg body weight (30H, 75H or 150H) in the presence or absence of HO-activity inhibitor SnMP from Day E11. Exposure to heme resulted in a dose-dependent increase in abortion. At 75H half of the fetuses where resorbed, while at 150H all fetuses were aborted. HO-activity protected against heme-induced abortion since inhibition of HO-activity aggravated heme-induced detrimental effects. The fetuses surviving heme administration demonstrated normal palatal fusion. Immunostainings at Day E16 demonstrated higher numbers of ICAM-1 positive blood vessels, macrophages and HO-1 positive cells in placenta after administration of 75H or SnMP + 30H. Summarizing, heme acts as an endogenous “alarmin” during pregnancy in a dose-dependent fashion, while HO-activity protects against heme-induced placental vascular inflammation and abortion.

Functional significance of lymphocytes in pregnancy and lymphocyte immunotherapy in infertility: A comprehensive review and update

During pregnancy, the fetal-maternal interface underlies several dynamic alterations to permit the fetus to be cultivated and developed in the uterus, in spite of being identifies by the maternal immune system. A large variety of decidual leukocyte populations, including natural killer cells, NKT cells, innate lymphoid cells, dendritic cells, B cells, T cells, subpopulations of helper T cells play a vital role in controlling the trophoblast invasion, angiogenesis as well as vascular remodeling. In contrast, several regulatory immunosuppressive mechanisms, including regulatory T cells, regulatory B cells, several cytokines and mediators are involved in maintain the homeostasis of immune system in the fetal-maternal interface. Nonetheless, aberrant alterations in the balance of immune inflammatory or immunosuppressive arms have been associated with various pregnancy losses and infertilities. As a result, numerous strategies have been developed to revers dysregulated balance of immune players to increase the chance of successful pregnancy. Lymphocyte immunotherapy has been developed through utilization of peripheral white blood cells of the husband or others and administered into the mother to confer an immune tolerance for embryo's antigens. However, the results have not always been promising, implying to further investigations to improve the approach. This review attempts to clarify the involvement of lymphocytes in contributing to the pregnancy outcome and the potential of lymphocyte immunotherapy in treatment of infertilities with dysregulated immune system basis.

A Role of the Heme Degradation Pathway in Shaping Prostate Inflammatory Responses and Lipid Metabolism

The molecular mechanisms of prostate inflammation are unclear. We hypothesized that heme oxygenase 1 (HMOX1; HO-1), an enzyme responsible for degradation of heme to carbon monoxide, bilirubin, and iron, is an important regulator of inflammation and epithelial responses in the prostate. Injection of non-uropathogenic Escherichia coli (MG1655 strain) or phosphate-buffered saline into the urethra of mice led to increased numbers of CD45⁺ leukocytes and mitotic markers (phosphorylated histone H₃ and phosphorylated ERK1/2) in the prostate glands. Leukocyte infiltration was elevated in the prostates harvested from mice lacking HO-1 in myeloid compartment. Conversely, exogenous carbon monoxide (250 ppm) increased IL-1β levels and suppressed cell proliferation in the prostates. Carbon monoxide did not affect the number of infiltrating CD45⁺ cells in the prostates of E. coli- or phosphate-buffered saline-treated mice. Interestingly, immunomodulatory effects of HO-1 and/or carbon monoxide correlated with early induction of the long-chain acyl-CoA synthetase 1 (ACSL1). ACSL1 levels were elevated in response to E. coli treatment, and macrophage-expressed ACSL1 was in part required for controlling of IL-1β expression and prostate cancer cell colony growth in soft agar. These results suggest that HO-1 and/or carbon monoxide might play a distinctive role in modulating prostate inflammation, cell proliferation, and IL-1β levels in part via an ACSL1-mediated pathway.

Immune checkpoint molecules in pregnancy: Focus on regulatory T cells

Regulatory T (Treg) cells are a specialized subpopulation of T cells that plays critical roles in the maintenance of immune homeostasis. Although efforts have been done, their role in human pregnancy is not fully understood. Numerous studies reported the presence of Treg cells throughout gestation by promoting maternal-fetal tolerance and fetal development. Furthermore, Treg population is heterogeneous as it is expressing different immune checkpoint molecules favoring immune suppressive function. Therefore, better understanding of the heterogeneity and function of Treg cells during pregnancy is critical for an effective immune intervention. Latest evidence has shown that several immune checkpoint molecules are closely associated with pregnancy outcome via multiple inhibitory mechanisms. Majority of these studies demonstrated the modulatory effects of immune checkpoint molecules on effector T-cell immunity, but their effects on Treg activation and function are still an enigma. In this review, we emphasize the potential influence of multiple immune checkpoint molecules, including CTLA-4, PD-1, Tim-3, LAG-3, and TIGIT, either in membrane or soluble form, on the function of decidual and peripheral Treg cells during pregnancy. Additionally, we discuss the promising future of targeting Treg cells via immune checkpoint molecules for pregnancy maintenance and prevention of complicated pregnancies.

Heme-Oxygenase-1 Is Decreased in Circulating Monocytes and Is Associated With Impaired Phagocytosis and ROS Production in Lupus Nephritis

Lupus nephritis (LN) is one of the most serious manifestations of systemic lupus erythematosus (SLE). Based on studies showing the potential role of heme oxygenase-1 (HO-1), an enzyme that catalyzes the degradation of heme and has anti-inflammatory properties in SLE development, we decided to explore HO-1 in LN. Accordingly, we evaluated HO-1 levels and function in circulating and infiltrating monocytes and neutrophils of LN patients. HO-1 levels were assessed in peripheral monocytes of LN patients and controls by flow cytometry and immunofluorescence microscopy. Phagocytosis and the production of reactive oxygen species (ROS) were evaluated to determine the effect of HO-1 in monocyte function. In addition, renal biopsies with proliferative LN were used to identify HO-1 in infiltrating cells and renal tissue by immunofluorescence and immunohistochemistry. Biopsies of healthy controls (HC) and patients who underwent nephrectomy were included as controls. Circulating pro-inflammatory monocytes and activated neutrophils were increased in LN patients. HO-1 levels were decreased in all subsets of monocytes and in activated neutrophils. LN monocytes showed increased phagocytosis and higher production of ROS than those of HC. When HO-1 was induced, phagocytosis and ROS levels became similar to those of HC. HO-1 was mostly expressed in renal tubular epithelial cells (RTEC). Renal tissue of LN patients showed lower levels of HO-1 than HC, whereas infiltrating immune cells of LN showed lower levels of HO-1 than biopsies of patients who had renal surgery. HO-1 is decreased in circulating monocytes and activated neutrophils of LN patients. HO-1 levels modulate the phagocytosis of LN monocytes and ROS production. HO-1 expression in RTEC might be an attempt of self-protection from inflammation.

Human chorionic gonadotropin promotes recruitment of regulatory T cells in endometrium by inducing chemokine CCL2

Human chorionic gonadotropin (hCG) can attract regulatory T cells (Tregs) into the fetal-maternal interface regulating maternal immune tolerance in pregnancy. The objective of this study was to investigate whether hCG recruits the Tregs into endometrium by inducing chemokines. The number of Tregs in the endometrium was analyzed by immunohistochemistry. The expression of CCL2 was analyzed in vivo and in vitro with hCG stimulation. CD4⁺CD25⁺ Tregs were isolated from peripheral blood for Tregs migration assay with hCG, CCL2 siRNA and CCR2 antagonist stimulation. Our results showed that the number of endometrial Tregs in RIF patients was significantly decreased (9.4 ± 5.3 vs. 23.1 ± 3.1, P < 0.01), while intrauterine infusion of 2000 IU hCG increased the endometrial Tregs (18.6 ± 9.8 vs. 9.4 ± 5.3, P < 0.05) and CCL2 expression (0.21 ± 0.01 vs. 0.17 ± 0.01, P < 0.01). Horn injecting with 10 IU hCG also increased the endometrial Tregs in pseudopregnant mice (46 ± 16.8 vs. 7 ± 4.3, P < 0.01). Furthermore, the CCL2 protein and mRNA levels were significantly increased in human endometrial stromal cells (hESCs) with the stimulation of hCG. Migration assays showed that hESCs with hCG stimulation promoted Tregs migration (2597 ± 833.2 vs. 1115 ± 670.7, P < 0.05), while the number of migrated Tregs significantly decreased with CCL2 siRNA (1061 ± 105.4 vs. 2598 ± 294.7, P < 0.05) or CCR2 antagonist (356.7 ± 138.8 vs. 2597 ± 833.2, P < 0.05) treatment. In conclusion, intrauterine perfusion of hCG might promote the recruitment of Tregs into endometrium by inducing chemokine CCL2.

The Tolerogenic Function of Regulatory T Cells in Pregnancy and Cancer

Regulatory T cells, a subpopulation of suppressive T cells, are potent mediators of self-tolerance and essential for the suppression of triggered immune responses. The immune modulating capacity of these cells play a major role in both transplantation, autoimmune disease, allergy, cancer and pregnancy. During pregnancy, low numbers of regulatory T cells are associated with pregnancy failure and pregnancy complications such as pre-eclampsia. On the other hand, in cancer, low numbers of immunosuppressive T cells are correlated with better prognosis. Hence, maternal immune tolerance toward the fetus during pregnancy and the escape from host immunosurveillance by cancer seem to be based on similar immunological mechanisms being highly dependent on the balance between immune activation and suppression. As regulatory T cells hold a crucial role in several biological processes, they may also be promising subjects for therapeutic use. Especially in the field of cancer, cell therapy and checkpoint inhibitors have demonstrated that immune-based therapies have a very promising potential in treatment of human malignancies. However, these therapies are often accompanied by adverse autoimmune side effects. Therefore, expanding the knowledge to recognize the complexities of immune regulation pathways shared across different immunological scenarios is extremely important in order to improve and develop new strategies for immune-based therapy. The intent of this review is to highlight the functional characteristics of regulatory T cells in the context of mechanisms of immune regulation in pregnancy and cancer, and how manipulation of these mechanisms potentially may improve therapeutic options.

Therapeutic Potential of Regulatory T Cells in Preeclampsia-Opportunities and Challenges

Inflammation is a central feature and is implicated as a causal factor in preeclampsia and other hypertensive disorders of pregnancy. Inflammatory mediators and leukocytes, which are elevated in peripheral blood and gestational tissues, contribute to the uterine vascular anomalies and compromised placental function that characterize particularly the severe, early onset form of disease. Regulatory T (Treg) cells are central mediators of pregnancy tolerance and direct other immune cells to counteract inflammation and promote robust placentation. Treg cells are commonly perturbed in preeclampsia, and there is evidence Treg cell insufficiency predates onset of symptoms. A causal role is implied by mouse studies showing sufficient numbers of functionally competent Treg cells must be present in the uterus from conception, to support maternal vascular adaptation and prevent later placental inflammatory pathology. Treg cells may therefore provide a tractable target for both preventative strategies and treatment interventions in preeclampsia. Steps to boost Treg cell activity require investigation and could be incorporated into pregnancy planning and preconception care. Pharmacological interventions developed to target Treg cells in autoimmune conditions warrant consideration for evaluation, utilizing rigorous clinical trial methodology, and ensuring safety is paramount. Emerging cell therapy tools involving in vitro Treg cell generation and/or expansion may in time become relevant. The success of preventative and therapeutic approaches will depend on resolving several challenges including developing informative diagnostic tests for Treg cell activity applicable before conception or during early pregnancy, selection of relevant patient subgroups, and identification of appropriate windows of gestation for intervention.

Regulatory T cells in embryo implantation and the immune response to pregnancy

At implantation, the embryo expresses paternally derived alloantigens and evokes inflammation that can threaten reproductive success. To ensure a robust placenta and sustainable pregnancy, an active state of maternal immune tolerance mediated by CD4+ regulatory T cells (Tregs) is essential. Tregs operate to inhibit effector immunity, contain inflammation, and support maternal vascular adaptations, thereby facilitating trophoblast invasion and placental access to the maternal blood supply. Insufficient Treg numbers or inadequate functional competence are implicated in idiopathic infertility and recurrent miscarriage as well as later-onset pregnancy complications stemming from placental insufficiency, including preeclampsia and fetal growth restriction. In this Review, we summarize the mechanisms acting in the conception environment to drive the Treg response and discuss prospects for targeting the T cell compartment to alleviate immune-based reproductive disorders.

Reversal of Triple-Negative Breast Cancer EMT by miR-200c Decreases Tryptophan Catabolism and a Program of Immunosuppression

Tryptophan-2,3-dioxygenase (TDO2), a rate-limiting enzyme in the tryptophan catabolism pathway, is induced in triple-negative breast cancer (TNBC) by inflammatory signals and anchorage-independent conditions. TNBCs express extremely low levels of the miR-200 family compared with estrogen receptor-positive (ER⁺) breast cancer. In normal epithelial cells and ER⁺ breast cancers and cell lines, high levels of the family member miR-200c serve to target and repress genes involved in epithelial-to-mesenchymal transition (EMT). To identify mechanism(s) that permit TNBC to express TDO2 and other proteins not expressed in the more well-differentiated ER⁺ breast cancers, miRNA-200c was restored in TNBC cell lines. The data demonstrate that miR-200c targeted TDO2 directly resulting in reduced production of the immunosuppressive metabolite kynurenine. Furthermore, in addition to reversing a classic EMT signature, miR-200c repressed many genes encoding immunosuppressive factors including CD274/CD273, HMOX-1, and GDF15. Restoration of miR-200c revealed a mechanism, whereby TNBC hijacks a gene expression program reminiscent of that used by trophoblasts to suppress the maternal immune system to ensure fetal tolerance during pregnancy. IMPLICATIONS: Knowledge of the regulation of tumor-derived immunosuppressive factors will facilitate development of novel therapeutic strategies that complement current immunotherapy to reduce mortality for patients with TNBC.

Naturally derived Heme-Oxygenase 1 inducers attenuate inflammatory responses in human dendritic cells and T cells: relevance for psoriasis treatment

Psoriasis is a chronic autoimmune disease mediated by dysregulated immune responses in dendritic cells (DC) and T cells. The stress-response enzyme heme oxygenase-1 (HO-1) has been described as protective in animal models of psoriasis, however, implementation of HO-1-based therapies is hindered by the lack of clinically-suitable HO-1 inducers. The plant-derived polyphenols, carnosol and curcumin, have been identified as candidate HO-1 inducers however there has been little investigation into their effects on human immune cells. We demonstrate that treatment of human DC with these polyphenols limits DC maturation, reduces pro-inflammatory cytokine production, and prevents induction of allospecific T cell responses, in a manner partially dependent on carbon monoxide (CO). We also characterised their effects in ex-vivo psoriasis PBMC and report that curcumin, but not carnosol, strongly reduces T cell proliferation and cytokine poly-functionality, with reduced expression of psoriatic cytokines IFNγ, IL-17, GM-CSF and IL-22. This study therefore supports reports highlighting the therapeutic potential of curcumin in psoriasis by providing insight into its immunological effects on healthy human DC and psoriasis PBMC. We also demonstrate, for the first time, the anti-inflammatory effects of carnosol in human immune cells.

HO-1 regulates the function of Treg: Association with the immune intolerance in vitiligo

In vitiligo, cutaneous depigmentation is accompanied by increased T cell cytolytic activity targeting melanocytes, indicating that autoimmune tolerance is disrupted. The inhibited amount and function of Tregs have been indicated to be involved in the autoimmune intolerance in vitiligo, however, with the conclusion still controversial and the involved mechanism unknown. In this study, we explored the molecular and cellular alterations accounting for the impaired Treg response in vitiligo. Our results showed that the amount of Tregs was drastically reduced in peripheral blood of active vitiligo patients. Furthermore, the immunoregulatory function of Tregs was attenuated, with lower expression of CTLA4, IL‐10 and TGF‐β. Moreover, the expression of HO‐1, a functional modulator of Tregs, was decreased in vitiligo Tregs, and the concentrations of HO‐1 metabolites, including bilirubin, CoHb and iron, were correspondingly decreased in serum of vitiligo patients. In addition, we treated the Tregs from vitiligo patients with Hemin, an agonist of HO‐1, and found that enhanced HO‐1 expression restored the function of Tregs by up‐regulating IL‐10 expression. Our study demonstrates the essential role of HO‐1 in the impaired Treg response in vitiligo and indicates the potential of HO‐1 as a therapeutic target in vitiligo management.

Phenotypic and functional analysis of bovine peripheral blood dendritic cells before parturition by a novel purification method

Dendritic cells (DCs) are specialized antigen presenting cells specializing in antigen uptake and processing, and play an important role in the innate and adaptive immune response. A subset of bovine peripheral blood DCs was identified as CD172a⁺/CD11c⁺/MHC (major histocompatibility complex) class II⁺ cells. Although DCs are identified at 0.1%–0.7% of peripheral blood mononuclear cells (PBMC), the phenotype and function of DCs remain poorly understood with regard to maintaining tolerance during the pregnancy. All cattle used in this study were 1 month before parturition. We have established a novel method for the purification of DCs from PBMC using magnetic‐activated cell sorting, and purified the CD172a⁺/CD11c⁺DCs, with high expression of MHC class II and CD40, at 84.8% purity. There were individual differences in the expressions of CD205 and co‐stimulatory molecules CD80 and CD86 on DCs. There were positive correlations between expression of cytokine and co‐stimulatory molecules in DCs, and the DCs maintained their immune tolerance, evidenced by their low expressions of the co‐stimulatory molecules and cytokine production. These results suggest that before parturition a half of DCs may be immature and tend to maintain tolerance based on the low cytokine production, and the other DCs with high co‐stimulatory molecules may already have the ability of modulating the T‐cell linage.

Distinct pattern of Th17/Treg cells in pregnant women with a history of unexplained recurrent spontaneous abortion

The aim of the current study was to determine the pattern of immune cells and related functional molecules in peripheral blood and at the maternal-fetal interface in women with unexplained recurrent spontaneous abortion (URSA). In part I, 155 women were included and divided into four groups: non-pregnant controls with no history of URSA (NPCs), pregnant controls with no history of URSA (PCs), non-pregnant women with a history of URSA (NPUs), and pregnant women with a history of URSA (PUs). Venous blood samples were collected and analyzed. In part II, 35 subjects with URSA and 40 subjects in the early stage of normal pregnancy who chose to undergo an abortion were recruited. Samples of the decidua were collected, and the proportion of immune cells and the expression of related molecules were evaluated. Peripheral regulatory T cells (Treg cells) increased in PCs compared to NPCs, but in women with URSA the flux of Treg cells disappeared when pregnancy occurred. Levels of interleukin-10 (IL-10), cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), and IL-17 and the ratio of Th17/Treg cells in peripheral blood remained stable among the four groups. At the maternal-fetal interface, the percentage of Treg cells, the level of CTLA-4 of CD4⁺CD25⁺CD127^lo cells and CD4⁺Foxp3⁺ cells were significantly lower in women with URSA compared to controls, respectively. Levels of transforming growth factor-β1 (TGF-β1) mRNA and protein in the decidua significantly decreased in URSA while levels of IL-6 and tumor necrosis factor-ɑ (TNF-ɑ) and the Th17/Treg ratio significantly increased. In conclusion, peripheral Treg cells did not increase in pregnant women with URSA. The decrease in Treg cells and levels of CTLA-4 and TGF-β1 and as well as the increase in levels of IL-6 and TNF-ɑ, and the Th17/Treg ratio at the maternal-fetal interface might contribute to inappropriate maternal-fetal immune tolerance in URSA.

Heme oxygenase-1 promoter region (GT)n polymorphism associates with increased neuroimmune activation and risk for encephalitis in HIV infection

BACKGROUND

Heme oxygenase-1 (HO-1) is a critical cytoprotective enzyme that limits oxidative stress, inflammation, and cellular injury within the central nervous system (CNS) and other tissues. We previously demonstrated that HO-1 protein expression is decreased within the brains of HIV+ subjects and that this HO-1 reduction correlates with CNS immune activation and neurocognitive dysfunction. To define a potential CNS protective role for HO-1 against HIV, we analyzed a well-characterized HIV autopsy cohort for two common HO-1 promoter region polymorphisms that are implicated in regulating HO-1 promoter transcriptional activity, a (GT)n dinucleotide repeat polymorphism and a single nucleotide polymorphism (A(-413)T). Shorter HO-1 (GT)n repeats and the 'A' SNP allele associate with higher HO-1 promoter activity.

METHODS

Brain dorsolateral prefrontal cortex tissue samples from an autopsy cohort of HIV-, HIV+, and HIV encephalitis (HIVE) subjects (n = 554) were analyzed as follows: HO-1 (GT)n polymorphism allele lengths were determined by PCR and capillary electrophoresis, A(-413)T SNP alleles were determined by PCR with allele specific probes, and RNA expression of selected neuroimmune markers was analyzed by quantitative PCR.

RESULTS

HIV+ subjects with shorter HO-1 (GT)n alleles had a significantly lower risk of HIVE; however, shorter HO-1 (GT)n alleles did not correlate with CNS or peripheral viral loads. In HIV+ subjects without HIVE, shorter HO-1 (GT)n alleles associated significantly with lower expression of brain type I interferon response markers (MX1, ISG15, and IRF1) and T-lymphocyte activation markers (CD38 and GZMB). No significant correlations were found between the HO-1 (GT)n repeat length and brain expression of macrophage markers (CD163, CD68), endothelial markers (PECAM1, VWF), the T-lymphocyte marker CD8A, or the B-lymphocyte maker CD19. Finally, we found no significant associations between the A(-413)T SNP and HIVE diagnosis, HIV viral loads, or any neuroimmune markers.

CONCLUSION

Our data suggest that an individual's HO-1 promoter region (GT)n polymorphism allele repeat length exerts unique modifying risk effects on HIV-induced CNS neuroinflammation and associated neuropathogenesis. Shorter HO-1 (GT)n alleles increase HO-1 promoter activity, which could provide neuroprotection through decreased neuroimmune activation. Therapeutic strategies that induce HO-1 expression could decrease HIV-associated CNS neuroinflammation and decrease the risk for development of HIV neurological disease.

Heme oxygenase-1 deficiency results in splenic T-cell dysregulation in offspring of mothers exposed to late gestational inflammation

PROBLEM

Infection during pregnancy can disrupt regulatory/effector immune system balance, resulting in adverse pregnancy and fetal-neonatal outcomes. Heme oxygenase-1 (HO-1) is a major regulatory enzyme in the immune system. We observed maternal immune response dysregulation during late gestational inflammation (LGI), which may be mediated by HO-1. Here, we extend these studies to examine the immune response of offspring.

METHOD OF STUDY

Pregnant wild-type (Wt) and HO-1 heterozygote (Het) dams were treated with lipopolysaccharide (LPS) or vehicle at E15.5. Pups' splenic immune cells were characterized using flow cytometry.

RESULTS

CD3⁺ CD4⁺ CD25⁺ (Tregs) and CD3⁺ CD8⁺ (Teffs) T cells in Wt and Het were similar in control neonates and increased with age. We showed not only age- but also genotype-specific and long-lasting T-cell dysregulation in pups after maternal LGI. The persistent immune dysregulation, mediated by HO-1 deficiency, was reflected as a decrease in Treg FoxP3 and CD3⁺ CD8⁺ T cells, and an increase in CD4⁺ /CD8⁺ T-cell and Treg/Teff ratios in Hets compared with Wt juvenile mice after maternal exposure to LGI.

CONCLUSION

Maternal exposure to LGI can result in dysregulation of splenic T cells in offspring, especially in those with HO-1 deficiency. We speculate that these immune alterations are the basis of adverse outcomes in neonates from mothers exposed to low-grade (subclinical) infections.

HO-1/EBP interaction alleviates cholesterol-induced hypoxia through the activation of the AKT and Nrf2/mTOR pathways and inhibition of carbohydrate metabolism in cardiomyocytes

Heme oxygenase-1 (HO-1) is an inducible and cytoprotective enzyme that provides a defense against oxidant damage. The present study screened 137 HO-1/interacting proteins using a profound co-immunoprecipitation (Co-IP) coupled with proteomics, and profiled the global HO-1 interactome network, including oxidative phosphorylation, endoplasmic reticulum and transport vesicle functions. Among these molecules, we observed that a novel interactor, emopamil-binding protein (EBP), is closely related to the cholesterol metabolism process. This study demonstrated that cholesterol promotes excessive oxidative stress and alters the energy metabolism in cardiomyocytes, further triggering numerous cardiovascular diseases. We observed that cholesterol caused the overexpression of EBP and HO-1 by the activation of AKT and Nrf2/mTOR pathways. In addition, HO-1 and EBP performed a myocardial protective function. The overexpression of HO-1 alleviated the cholesterol-induced excessive oxidative stress status by inhibition of the carbohydrate metabolism. Notably, we also confirmed that the loss of partial HO-1 activity aggravated the oxidative damage and cardiac systolic function induced by a high-fat diet in HO-1 heterozygous (HO-1^+/−) mice. These findings indicate that the HO-1/EBP interaction plays a protective role in alleviating the dysfunction of oxidative stress and cardiac systolic function induced by cholesterol stimulation.

Hydrogen-rich water protects against inflammatory bowel disease in mice by inhibiting endoplasmic reticulum stress and promoting heme oxygenase-1 expression

AIM

To investigate the therapeutic effect of hydrogen-rich water (HRW) on inflammatory bowel disease (IBD) and to explore the potential mechanisms involved.

METHODS

Male mice were randomly divided into the following four groups: control group, in which the mice received equivalent volumes of normal saline (NS) intraperitoneally (ip); dextran sulfate sodium (DSS) group, in which the mice received NS ip (5 mL/kg body weight, twice per day at 8 am and 5 pm) for 7 consecutive days after IBD modeling; DSS + HRW group, in which the mice received HRW (in the same volume as the NS treatment) for 7 consecutive days after IBD modeling; and DSS + HRW + ZnPP group, in which the mice received HRW (in the same volume as the NS treatment) and ZnPP [a heme oxygenase-1 (HO-1) inhibitor, 25 mg/kg] for 7 consecutive days after IBD modeling. IBD was induced by feeding DSS to the mice, and blood and colon tissues were collected on the 7^th d after IBD modeling to determine clinical symptoms, colonic inflammation and the potential mechanisms involved.

RESULTS

The DSS + HRW group exhibited significantly attenuated weight loss and a lower extent of disease activity index compared with the DSS group on the 7^th d (P < 0.05). HRW exerted protective effects against colon shortening and colonic wall thickening in contrast to the DSS group (P < 0.05). The histological study demonstrated milder inflammation in the DSS + HRW group, which was similar to normal inflammatory levels, and the macroscopic and microcosmic damage scores were lower in this group than in the DSS group (P < 0.05). The oxidative stress parameters, including MDA and MPO in the colon, were significantly decreased in the DSS + HRW group compared with the DSS group (P < 0.05). Simultaneously, the protective indicators, superoxide dismutase and glutathione, were markedly increased with the use of HRW. Inflammatory factors were assessed, and the results showed that the DSS + HRW group exhibited significantly reduced levels of TNF-α, IL-6 and IL-1β compared with the DSS group (P < 0.05). In addition, the pivotal proteins involved in endoplasmic reticulum (ER) stress, including p-eIF2α, ATF4, XBP1s and CHOP, were dramatically reduced after HRW treatment in contrast to the control group (P < 0.05). Furthermore, HRW treatment markedly up-regulated HO-1 expression, and the use of ZnPP obviously reversed the protective role of HRW. In the DSS + HRW + ZnPP group, colon shortening and colonic wall thickening were significantly aggravated, and the macroscopic damage scores were similar to those of the DSS + HRW group (P < 0.05). The histological study also showed more serious colonic damage that was similar to the DSS group.

CONCLUSION

HRW has a significant therapeutic potential in IBD by inhibiting inflammatory factors, oxidative stress and ER stress and by up-regulating HO-1 expression.

Heme oxygenase/carbon monoxide in the female reproductive system: an overlooked signalling pathway

For a long time, carbon monoxide (CO) was known for its toxic effect on organisms. But there are still many things left to discover on that molecule. CO is formed directly in the body by the enzymatic activity of heme oxygenase (HO). CO plays an important role in many physiological processes, such as cell protections (against various stress factors), and the regulation of metabolic processes. Recent research proves that CO also operates in the female reproductive system. At the centre of interest is the importance of CO for gestation. During the gestation period, CO is an important element affecting the proper function of the feto-placental unit and generally affects fetal survivability rates. Gestation is one of the most important processes of successful reproduction, although there are more relevant processes that need to be researched. While already proven that CO influences steroidogenesis and the corpus luteum survivability rate, our knowledge concerning the function and importance of CO in the reproductive system is still relatively limited. As an example, our knowledge of CO function in an oocyte, the most important cell for reproduction, is almost non-existent. The aim of this review is to summarize our current knowledge concerning the function of CO in the female reproductive system.

Immune regulatory network in successful pregnancy and reproductive failures

Maternal immune system must tolerate semiallogenic fetus to establish and maintain a successful pregnancy. Despite the existence of several strategies of trophoblast to avoid recognition by maternal leukocytes, maternal immune system may react against paternal alloantigenes. Leukocytes are important components in decidua. Not only T helper (Th)1/Th2 balance, but also regulatory T (Treg) cells play an important role in pregnancy. Although the frequency of Tregs is elevated during normal pregnancies, their frequency and function are reduced in reproductive defects such as recurrent miscarriage and preeclampsia. Tregs are not the sole population of suppressive cells in the decidua. It has recently been shown that regulatory B10 (Breg) cells participate in pregnancy through secretion of IL-10 cytokine. Myeloid derived suppressor cells (MDSCs) are immature developing precursors of innate myeloid cells that are increased in pregnant women, implying their possible function in pregnancy. Natural killer T (NKT) cells are also detected in mouse and human decidua. They can also affect the fetomaternal tolerance. In this review, we will discuss on the role of different immune regulatory cells including Treg, γd T cell, Breg, MDSC, and NKT cells in pregnancy outcome.

Heme Oxygenase-1-Expressing Dendritic Cells Promote Foxp3+ Regulatory T Cell Differentiation and Induce Less Severe Airway Inflammation in Murine Models

Dendritic cells (DCs) are critical for instructing immune responses toward inflammatory or anti-inflammatory status. Heme oxygenase-1 (HO-1) is known for its cytoprotective effect against oxidative stress and inflammation, suggesting its immune regulatory role in allergic lung inflammation. HO-1 has been implicated in affecting DC maturation; however, its role in DC-mediated T-cell differentiation is unclear. In this study, we demonstrated that HO-1-expressing bone marrow-derived dendritic cells (BM-DCs) displayed tolerogenic phenotypes, including their resistance to lipopolysaccharide (LPS)-induced maturation, high level expression of IL-10, and low T-cell stimulatory activity. In addition, HO-1-expressing DCs were able to induce antigen-specific Foxp3⁺ regulatory T cells (Treg) differentiation in vitro and in vivo. Also, HO-1-expressing DCs modulated the severity of lung inflammatory responses in two murine models of airway inflammation. This study provided evidence supporting the role of HO-1-expressing DCs in tolerance induction and as a potential therapeutic target for allergic asthma as well as other inflammatory diseases.