Progesterone-induced blocking factor (PIBF) and trophoblast invasiveness

Cytokines, NK cells and regulatory T cell functions in normal pregnancy and reproductive failures

PURPOSE OF THE REVIEW

Pregnancy brings about an intricate assortment of dynamic changes, which causes proper connection of genetically discordant maternal and foetal tissues. Uterine NK cells are immune cells populating the endometrium and play a major role in implantation and also regulate placentation. This review mainly aims explore the role of uterine NK cells in implantation and how it is affecting in adverse pregnancy outcomes.

RECENT FINDINGS

Though the functions of uterine NK (uNK) cells are not clearly understood, NK cell activity plays a vital role during immunomodulation which is the main step in implantation and sustaining the early pregnancy. Cytokines, cell surface receptors of NK cells and hormones such as progesterone modulate the NK cell activity in turn affect the implantation of the embryo. Altered NK cell activity (number and functionality) would be an important attributing factor in adverse pregnancy outcomes. Furthermore, T regulatory cells and cytokines also modulate the immune responses in the decidua which in turn contributes to successful implantation of embryos.

SUMMARY

Immunological responses and interactions in the Foetus-maternal interface is crucial in the successful implantation of allogenic foetus resulting in a healthy pregnancy. NK cells, Treg cells and cytokines play a major role in successful implantation which remains an enigma. Comprehending pregnancy-induced immunological changes at the foetus-maternal interface will allow newer therapeutic strategies to improve pregnancy outcomes.

A Hypothetical Model Suggesting Some Possible Ways That the Progesterone Receptor May Be Involved in Cancer Proliferation

Cancer and the fetal-placental semi-allograft share certain characteristics, e.g., rapid proliferation, the capacity to invade normal tissue, and, related to the presence of antigens foreign to the host, the need to evade immune surveillance. Many present-day methods to treat cancer use drugs that can block a key molecule that is important for one or more of these characteristics and thus reduce side effects. The ideal molecule would be one that is essential for both the survival of the fetus and malignant tumor, but not needed for normal cells. There is a potential suitable candidate, the progesterone induced blocking factor (PIBF). The parent 90 kilodalton (kDa) form seems to be required for cell-cycle regulation, required by both the fetal-placental unit and malignant tumors. The parent form may be converted to splice variants that help both the fetus and tumors escape immune surveillance, especially in the fetal and tumor microenvironment. Evidence suggests that membrane progesterone receptors are involved in PIBF production, and indeed there has been anecdotal evidence that progesterone receptor antagonists, e.g., mifepristone, can significantly improve longevity and quality of life, with few side effects.

Cytokines, Hormones and Cellular Regulatory Mechanisms Favoring Successful Reproduction

Its semi-allogeneic nature renders the conceptus vulnerable to attack by the maternal immune system. Several protective mechanisms operate during gestation to correct the harmful effects of anti-fetal immunity and to support a healthy pregnancy outcome. Pregnancy is characterized by gross alterations in endocrine functions. Progesterone is indispensable for pregnancy and humans, and it affects immune functions both directly and via mediators. The progesterone-induced mediator - PIBF - acts in favor of Th2-type immunity, by increasing Th2 type cytokines production. Except for implantation and parturition, pregnancy is characterized by a Th2-dominant cytokine pattern. Progesterone and the orally-administered progestogen dydrogesterone upregulate the production of Th2-type cytokines and suppress the production of Th1 and Th17 cytokine production in vitro. This is particularly relevant to the fact that the Th1-type cytokines TNF-α and IFN-γ and the Th17 cytokine IL-17 have embryotoxic and anti-trophoblast activities. These cytokine-modulating effects and the PIBF-inducing capabilities of dydrogesterone may contribute to the demonstrated beneficial effects of dydrogesterone in recurrent spontaneous miscarriage and threatened miscarriage. IL-17 and IL-22 produced by T helper cells are involved in allograft rejection, and therefore could account for the rejection of paternal HLA-C-expressing trophoblast. Th17 cells (producing IL-17 and IL-22) and Th22 cells (producing IL-22) exhibit plasticity and could produce IL-22 and IL-17 in association with Th2-type cytokines or with Th1-type cytokines. IL-17 and IL-22 producing Th cells are not harmful for the conceptus, if they also produce IL-4. Another important protective mechanism is connected with the expansion and action of regulatory T cells, which play a major role in the induction of tolerance both in pregnant women and in tumour-bearing patients. Clonally-expanded Treg cells increase at the feto-maternal interface and in tumour-infiltrating regions. While in cancer patients, clonally-expanded Treg cells are present in peripheral blood, they are scarce in pregnancy blood, suggesting that fetal antigen-specific tolerance is restricted to the foeto-maternal interface. The significance of Treg cells in maintaining a normal materno-foetal interaction is underlined by the fact that miscarriage is characterized by a decreased number of total effector Treg cells, and the number of clonally-expanded effector Treg cells is markedly reduced in preeclampsia. In this review we present an overview of the above mechanisms, attempt to show how they are connected, how they operate during normal gestation and how their failure might lead to pregnancy pathologies.

A Brief Analysis of Tissue-Resident NK Cells in Pregnancy and Endometrial Diseases: The Importance of Pharmacologic Modulation

NK cells are lymphocytes involved in the innate and adaptative immune response. These cells are located in peripheral blood and tissues with ample functions, from immune vigilant to tolerogenic reactions. In the endometrium, NK cell populations vary depending on age, hormones, and inflammation. When pregnancy occurs, tissue-resident NK cells and conventional NK cells are recruited to protect the fetus, a tolerogenic response. On the contrary, in the inflamed endometrium, various inflammatory cells down-regulate NK tolerance and impair embryo implantation. Therefore, NK cells’ pharmacological modulation is difficult to achieve. Several strategies have been used, from progesterone, lipid emulsions to steroids; the success has not been as expected. However, new therapeutic approaches have been proposed to decrease the endometrial inflammatory burden and increase pregnancy success based on understanding NK cell physiology.

Natural killer cells in recurrent miscarriage: An overview

Recurrent Miscarriage is an early pregnancy complication which affects about 1-3 % of child-bearing couples. The mechanisms involved in the occurrence of recurrent miscarriages are not clearly understood. In the last decade Natural Killer cells have been studied in peripheral blood and uterus in order to determine if there are specific characteristics of Natural Killer cells associated with miscarriage. Different authors have described an increased number of uterine and peripheral blood Natural Killer cells in women with recurrent miscarriages compared to control women. However, its relationship with miscarriage has not been confirmed. In patients with recurrent miscarriage a lack of inhibition of decidua Natural Killer cells can be observed, which leads to a more activated state characterized by higher levels of proinflammatory cytokines. In peripheral blood, it has been also reported a dysfunctional cytokine production by Natural Killer cells, with an increase of interferon-γ levels and a decrease of Interleukin-4. Significant progress has been made in the last decade in understanding the biology of Natural Killer cells, including the identification of new receptors that also contribute to the activation and regulation of Natural Killer cells. In this review, we summarize the current progress in the study of Natural Killer cells in recurrent miscarriage.

The immunolocalization of Galectin-1 and Progesterone-Induced Blocking Factor (PIBF) in equine trophoblast: Possible roles in trophoblast invasion and the immunological protection of pregnancy

INTRODUCTION

The proteins galectin-1 and Progesterone Induced Blocking Factor (PIBF) are present on human and murine trophoblast and are thought to influence both immunomodulation and trophoblast invasion. In equids, the invasive component of the placenta, the endometrial cups, stimulate maternal cell-mediated and humoral immune responses. It was therefore of interest to know if galectin-1 or PIBF could be immunolocalised to the invasive and/or non-invasive components of the equine placenta.

MATERIALS

Horse and mule (♀ horse X ♂ donkey) embryos and placental tissues between Days 12 and 124 of gestation were stained immunohistochemically with antibodies raised against galectin-1 and PIBF.

RESULTS

Galectin-1 stained the non-invasive trophoblast between Days 15 and 20 but thereafter stained only the invasive trophoblast cells of the chorionic girdle, both before and after they invaded the endometrium to form the endometrial cups. PIBF, on the other hand, stained both the invasive and non-invasive trophoblast throughout the period of gestation studied. Of particular interest was the relative lack of staining of the endometrial cup cells in mule compared to horse pregnancies for galectin-1 and PIBF prior to the earlier and more rapid death and desquamation of the mule cup cells.

DISCUSSION

The expression of galectin-1 and PIBF proteins in equine trophoblast and the marked difference in lifespan between the endometrial cups in intraspecies horse versus interspecies mule pregnancies support a likely role for these two proteins protecting the fetal trophoblast from maternal immune attack and/or modulation of the invasiveness of endometrial cup cells.

Progestogens and immunology

Fifty percent of fetal antigens are of paternal origin. These are recognized by the maternal immune system, thereby resulting in lymphocyte activation and the induction of progesterone receptors (PRs) in immune cells. Upon binding of progesterone to PRs on lymphocytes, a downstream mediator called progesterone-induced blocking factor (PIBF) is produced. The full-length PIBF is a 90 kDa protein; however, because of alternative splicing, several smaller isoforms are also produced. While the 90 kDa molecule plays a role in cell cycle regulation, the small isoforms are localized in the cytoplasm, and after secretion, they bind to their receptors on other cells and act in a cytokine-like manner. The communication between the embryo and the maternal immune system is established through PIBF-containing extracellular vesicles. PIBF induces an increased production of Th2 cytokines and inhibits degranulation of NK cells, and by regulating the maternal immune response, it contributes to successful implantation and maintenance of pregnancy.

Embryonic extracellular vesicles as informers to the immune cells at the maternal-fetal interface

Extracellular vesicle (EV) exchange is emerging as a novel method of communication at the maternal-fetal interface. The presence of the EVs has been demonstrated in the preimplantation embryo culture medium from different species, such as bovines, porcines and humans. Preimplantation embryo-derived EVs have been shown to carry molecules potentially able to modulate the local endometrial immune system. The non-classical major histocompatibility complex (MHC) class I molecule human leucocyte antigen (HLA)-G, the immunomodulatory molecule progesterone-induced blocking factor and some regulatory miRNAs species are contained in embryo-derived EV cargo. The implanted syncytiotrophoblasts are also well known to secrete EVs, with microvesicles exerting a mainly proinflammatory effect while exosomes in general mediate local immunotolerance. This review focuses on the current knowledge on the potential role of EVs released by the embryo in the first weeks of pregnancy on the maternal immune cells. Collectively, the data warrant further exploration of the dialogue between the mother and the embryo via EVs.

The involvement of the progesterone receptor in PIBF and Gal-1 expression in the mouse endometrium

PROBLEM

The progesterone-regulated genes, PIBF and Gal-1, are key players in the feto-maternal immunological interaction. This study aims to investigate the expression of PIBF and Gal-1 in WT and progesterone receptor KO models as well as subsequent effects of PIBF on decidualization of stromal cells.

METHOD OF THE STUDY

PRAKO, PRBKO and PRKO BALB/c mice were used for assessing the role of PR isoforms in PIBF induction. PIBF- and Gal-1 mRNA expression in the uterus was tested by real-time PCR. The effect of PIBF on decidualization of endometrial stromal cells was verified by anti-desmin immunofluorescence. Immunohistochemistry was used for testing PIBF expression in the uterus. Gal-1, ERα and PR positive decidual NK cells were detected by immunofluorescence.

RESULTS

PIBF mRNA was significantly increased in progesterone-treated WT mice, but not in PRKO and PRAKO mice. PIBF protein expression was reduced in the endometria of PRKO and PRAKO, but not in PRBKO mice. During a 6-day culture, PIBF induced decidual transformation of endometrial stromal cells. PIBF expression in the mouse uterus was highest during the implantation window, while Gal-1 mRNA expression continuously increased between day 2.5 and day 11.5 of gestation. Decidual NK cells express Gal-1 and ERα, but not PR at day 7.5 murine pregnancy.

CONCLUSION

PIBF produced via engagement of PRA, is highly expressed in the endometrium during the implantation window, and plays a role in decidualization. The concerted action of PIBF and Gal-1 might contribute to the low cytotoxic activity of decidual NK cells.

The Role of Extracellular Vesicles and PIBF in Embryo-Maternal Immune-Interactions

Pregnancy represents a unique immunological situation. Though paternal antigens expressed by the conceptus are recognized by the immune system of the mother, the immune response does not harm the fetus. Progesterone and a progesterone induced protein; PIBF are important players in re-adjusting the functioning of the maternal immune system during pregnancy. PIBF expressed by peripheral pregnancy lymphocytes, and other cell types, participates in the feto-maternal communication, partly, by mediating the immunological actions of progesterone. Several splice variants of PIBF were identified with different physiological activity. The full length 90 kD PIBF protein plays a role in cell cycle regulation, while shorter splice variants are secreted and act as cytokines. Aberrant production of PIBF isoforms lead to the loss of immune-regulatory functions, resulting in and pregnancy failure. By up regulating Th2 type cytokine production and by down-regulating NK activity, PIBF contributes to the altered attitude of the maternal immune system. Normal pregnancy is characterized by a Th2-dominant cytokine balance, which is partly due to the action of the smaller PIBF isoforms. These bind to a novel form of the IL-4 receptor, and induce increased production of IL-3, IL-4, and IL-10. The communication between the conceptus and the mother is established via extracellular vesicles (EVs). Pre-implantation embryos produce EVs both in vitro, and in vivo. PIBF transported by the EVs from the embryo to maternal lymphocytes induces increased IL-10 production by the latter, this way contributing to the Th2 dominant immune responses described during pregnancy.

The Role of Progesterone in Feto-Maternal Immunological Cross Talk

This review aims to provide a brief historical overview of the feto-maternal immunological relationship, which profoundly influences the outcome of pregnancy. The initial question posed in the 1950s by Medawar [Symp Soc Exp Biol. 1953; 7: 320-338] was based on the assumption that the maternal immune system recognizes the fetus as an allograft. Indeed, based on the association between HLA-matching and spontaneous miscarriage, it became obvious that immunological recognition of pregnancy is required for a successful gestation. The restricted expression of polymorphic HLA antigens on the trophoblast, together with the presence of nonpolymorphic MHC products, excludes recognition by both T and NK cells of trophoblast-presented antigens; however, γδ T cells, which constitute the majority of decidual T cells, are likely candidates. Indeed, a high number of activated, progesterone receptor-expressing γδ T cells are present in the peripheral blood of healthy pregnant women and, in the presence of progesterone, these cells secrete an immunomodulatory protein called progesterone-induced blocking factor (PIBF). As early as in the peri-implantation period, the embryo communicates with the maternal immune system via PIBF containing extracellular vesicles. PIBF contributes to the dominance of Th2-type reactivity which characterizes normal pregnancy by inducing increased production of Th2 cytokines. The high expression of this molecule in the decidua might be one of the reasons for the low cytotoxic activity of decidual NK cells.

Intrauterine trophoblast migration: A comparative view of humans and rodents

Trophoblast migration and invasion through the decidua and maternal uterine spiral arteries are crucial events in placentation. During this process, invasive trophoblast replace vascular endothelial cells as the uterine arteries are remodeled to form more permissive vessels that facilitate adequate blood flow to the growing fetus. Placentation failures resulting from either extensive or shallow trophoblastic invasion can cause pregnancy complications such as preeclampsia, intrauterine growth restriction, placenta creta, gestational trophoblastic disease and even maternal or fetal death. Consequently, the use of experimental animal models such as rats and mice has led to great progress in recent years with regards to the identification of mechanisms and factors that control trophoblast migration kinetics. This review aims to perform a comparative analysis of placentation and the mechanisms and factors that coordinate intrauterine trophoblast migration in humans, rats and mice under physiological and pathological conditions.

The endocrine function of human placenta: an overview

During pregnancy, several tightly coordinated and regulated processes take place to enable proper fetal development and gestational success. The formation and development of the placenta is one of these critical pregnancy events. This organ plays essential roles during gestation, including fetal nourishment, support and protection, gas exchange and production of several hormones and other mediators. Placental hormones are mainly secreted by the syncytiotrophoblast, in a highly and tightly regulated way. These hormones are important for pregnancy establishment and maintenance, exerting autocrine and paracrine effects that regulate decidualization, placental development, angiogenesis, endometrial receptivity, embryo implantation, immunotolerance and fetal development. In addition, because they are released into maternal circulation, the profile of their blood levels throughout pregnancy has been the target of intense research towards finding potential robust and reliable biomarkers to predict and diagnose pregnancy-associated complications. In fact, altered levels of these hormones have been associated with some pathologies, such as chromosomal anomalies or pre-eclampsia. This review proposes to revise and update the main pregnancy-related hormones, addressing their major characteristics, molecular targets, function throughout pregnancy, regulators of their expression and their potential clinical interest.

Progesterone Inhibits Leptin-Induced Invasiveness of BeWo Cells

BACKGROUND

This study investigated the roles of progesterone and leptin in placenta invasion, which is closely related to pregnancy prognosis. We examined the effects of leptin and progesterone on the invasion of BeWo cells, a human trophoblastic cell line, and the effect of concurrent treatment.

METHODS

Cells were treated with leptin (0, 5, 50, or 500 ng/mL) or progesterone (0, 2, 20, or 200 µM) and cultured in an invasion assay. Cells treated with 500 ng/mL leptin were also treated with progesterone (0, 2, 20, or 200 µM) in the invasion assay for 48 h. The number of cells that invaded the lower surface was counted in five randomly chosen fields using a light microscope with a 200× objective. The mRNA expression levels of MMP-9, TIMP1, TIMP2, and E-cadherin were detected by semi-quantitative PCR.

RESULTS

Invasion of BeWo cells was promoted by leptin and influenced by both leptin concentration and treatment duration. Invasion was most effective at 500 ng/mL leptin and 48 h culture. Leptin-induced invasiveness was suppressed by progesterone in a dose-dependent manner. Leptin significantly decreased the expression levels of TIMP1 and E-cadherin, whereas progesterone significantly decreased expression of MMP-9 and significantly increased levels of TIMP1, TIMP2, and E-cadherin.

CONCLUSIONS

Leptin promotes invasion of BeWo cells, and progesterone suppresses leptin-induced invasion by regulating the expressions of MMP-9, TIMP1, TIMP2, and E-cadherin. The balance between leptin and progesterone may play an important role in human placenta formation during early pregnancy.

Maternal thyroid dysfunction affects placental profile of inflammatory mediators and the intrauterine trophoblast migration kinetics

The objective of the present study was to evaluate the gene and immunohistochemical expression of inflammatory mediators involved in the immune activity and the intrauterine trophoblast migration of the placentas in hypothyroid and L-thyroxine (L-T4)-treated rats. A total of 144 adult female rats were divided equally into hypothyroid, l-T4-treated, and euthyroid (control) groups. Hypothyroidism was induced by daily administration of propylthiouracil. Rats were killed at 0, 10, 14, 15, 16, 17, 18, and 19 days of gestation. We evaluated the depth of interstitial and endovascular intrauterine trophoblast invasion and the immunohistochemical expression of interferon γ (INFy), migration inhibitory factor (MIF), and inducible nitric oxide synthase (NOS2 (iNOS)). The gene expression of Toll-like receptor 2 (Tlr2) and Tlr4, Infy, Mif, tumor necrosis factor (Tnf (Tnfα)), Il10, Nos2, matrix metalloproteinase 2 (Mmp2) and Mmp9, and placental leptin was also measured in placental disks by real-time RT-PCR. The data were analyzed using an Student-Newman-Keuls (SNK) test. Hypothyroidism reduced the endovascular and interstitial trophoblast migration, and the expression of TLR4, INFy, MIF, interleukin 10 (IL10), NOS2, MMP2 and MMP9, and placental leptin, while increased the expression of TLR2 (P<0.05). T4-treated rats not only increased the expression of IL10 and NOS2 but also reduced the expression of TNF and MIF at 10 days of gestation (P<0.05). However, at 19 days of gestation, expression of INFy and MIF was increased in T4-treated group (P<0.05). Excess of T4 also increased the gene expression of Mmp2 at 10 days of gestation (P<0.05), but reduced the endovascular trophoblast migration at 18 days of gestation (P<0.05). Hypothyroidism and excess of T4 differentially affect the immune profile and the intrauterine trophoblast migration of the placenta, and these effects are dependent on the gestational period.

Cells isolated from human glioblastoma multiforme express progesterone-induced blocking factor (PIBF)

Glioblastoma multiforme (GBM) is the most common and malignant tumor in the central nervous system. One of the contemporary hypotheses postulates that its pathogenesis is associated with the cancer stem cells (CSCs) which originate from mutations in the normal neural stem cells residing in their specific "niches." Simultaneously with its aggressive development the tumor suppresses the local immune system by different secreted and/or cell expressed factors. Progesterone-induced blocking factor (PIBF) is an immunomodulatory protein with known role in the regulation of the immune response in the reproductive system. Expression of PIBF has been described in some tumors as one of the factors suppressing the anti-tumor immunity. The aim of the present study was to check for the expression of PIBF from cells isolated from six GBMs. To characterize the cultured cells and to study the PIBF expression confocal microscopy, flow cytometry, ELISA, and real-time PCR were used. The results obtained showed expression of markers typical for cancer CSCs and secretion of interleukin 6 by the GBM-derived cultured cells. The results convincingly prove that PIBF is intracellularly expressed by the cultured cells from the all six GBM samples, and this fact is confirmed by three different methods-flow cytometry, confocal microscopy, and real-time PCR. This paper reports for the first time the expression of PIBF by GBM-derived cells cultured in vitro and reveals a new aspect of the immunosuppressive mechanism used by GBM in escaping the immune control.

Progesterone-induced blocking factor differentially regulates trophoblast and tumor invasion by altering matrix metalloproteinase activity

Invasiveness is a common feature of trophoblast and tumors; however, while tumor invasion is uncontrolled, trophoblast invasion is strictly regulated. Both trophoblast and tumor cells express high levels of the immunomodulatory progesterone-induced blocking factor (PIBF), therefore, we aimed to test the possibility that PIBF might be involved in invasion. To this aim, we used PIBF-silenced or PIBF-treated trophoblast (HTR8/Svneo, and primary trophoblast) and tumor (HT-1080, A549, HCT116, PC3) cell lines. Silencing of PIBF increased invasiveness as well as MMP-2,-9 secretion of HTR8/SVneo, and decreased those of HT-1080 cells. PIBF induced immediate STAT6 activation in both cell lines. Silencing of IL-4Rα abrogated all the above effects of PIBF, suggesting that invasion-related signaling by PIBF is initiated through the IL-4Rα/PIBF-receptor complex. In HTR-8/SVneo, PIBF induced fast, but transient Akt and ERK phosphorylation, whereas in tumor cells, PIBF triggered sustained Akt, ERK, and late STAT3 activation. The late signaling events might be due to indirect action of PIBF. PIBF induced the expression of EGF and HB-EGF in HT-1080 cells. The STAT3-activating effect of PIBF was reduced in HB-EGF-deficient HT-1080 cells, suggesting that PIBF-induced HB-EGF contributes to late STAT3 activation. PIBF binds to the promoters of IL-6, EGF, and HB-EGF; however, the protein profile of the protein/DNA complex is different in the two cell lines. We conclude that in tumor cells, PIBF induces proteins, which activate invasion signaling, while-based on our previous data-PIBF might control trophoblast invasion by suppressing proinvasive genes.

Genome-wide association study identifies 8 novel loci associated with blood pressure responses to interventions in Han Chinese

BACKGROUND

Blood pressure (BP) responses to dietary sodium and potassium intervention and cold pressor test vary considerably among individuals. We aimed to identify novel genetic variants influencing individuals' BP responses to dietary intervention and cold pressor test.

METHODS AND RESULTS

We conducted a genome-wide association study of BP responses in 1881 Han Chinese and de novo genotyped top findings in 698 Han Chinese. Diet-feeding study included a 7-day low-sodium (51.3 mmol/d), a 7-day high-sodium (307.8 mmol/d), and a 7-day high-sodium plus potassium supplementation (60 mmol/d). Nine BP measurements were obtained during baseline observation and each intervention period. The meta-analyses identified 8 novel loci for BP phenotypes, which physically mapped in or near PRMT6 (P=7.29 × 10(-9)), CDCA7 (P=3.57 × 10(-8)), PIBF1 (P=1.78 × 10(-9)), ARL4C (P=1.86 × 10(-8)), IRAK1BP1 (P=1.44 × 10(-10)), SALL1 (P=7.01 × 10(-13)), TRPM8 (P=2.68 × 10(-8)), and FBXL13 (P=3.74 × 10(-9)). There was a strong dose-response relationship between the number of risk alleles of these independent single-nucleotide polymorphisms and the risk of developing hypertension during the 7.5-year follow-up in the study participants. Compared with those in the lowest quartile of risk alleles, odds ratios (95% confidence intervals) for those in the second, third, and fourth quartiles were 1.39 (0.97, 1.99), 1.72 (1.19, 2.47), and 1.84 (1.29, 2.62), respectively (P=0.0003 for trend).

CONCLUSIONS

Our study identified 8 novel loci for BP responses to dietary sodium and potassium intervention and cold pressor test. The effect size of these novel loci on BP phenotypes is much larger than those reported by the previously published studies. Furthermore, these variants predict the risk of developing hypertension among individuals with normal BP at baseline.