Calcitonin gene-related peptide in pregnancy and its emerging receptor heterogeneity

Neuromodulation Techniques for Headache Management

This narrative review aims to summarize evidence regarding the current utilization and future applications of neuromodulation in patients with headaches, with special attention paid to migraine and chronic cluster headache. A search was conducted in PubMed in August of 2023 to survey the current literature on neuromodulation for the treatment of headache. In total, the search yielded 1989 results, which were further filtered to include only systematic reviews published between 2022 to 2023 to capture the most up-to-date and comprehensive research on this topic. The citation lists of these articles were reviewed to find additional research on neuromodulation and supplement the results presented in this paper with primary literature. Research on the use of neuromodulation for the treatment of headache has predominantly focused on four neuromodulation techniques: peripheral nerve stimulation (PNS), transcranial magnetic stimulation (TMS), deep brain stimulation (DBS), and spinal cord stimulation (SCS). Outcome measures reported in this article include impact on migraine and headache frequency and/or pain intensity, adverse effects of the neuromodulation technique, and associated costs, when available. We found that neuromodulation has developed utility as an alternative treatment for both chronic cluster headaches and migraines, with a reduction in frequency and intensity of headache most elucidated from the articles mentioned in this review.

Calcitonin Gene-Related Peptide Systemic Effects: Embracing the Complexity of Its Biological Roles-A Narrative Review

The calcitonin gene-related peptide (CGRP) is a neuropeptide widely distributed throughout the human body. While primarily recognized as a nociceptive mediator, CGRP antagonists are currently utilized for migraine treatment. However, its role extends far beyond this, acting as a regulator of numerous biological processes. Indeed, CGRP plays a crucial role in vasodilation, inflammation, intestinal motility, and apoptosis. In this review, we explore the non-nociceptive effects of CGRP in various body systems, revealing actions that can be contradictory at times. In the cardiovascular system, it functions as a potent vasodilator, yet its antagonists do not induce arterial hypertension, suggesting concurrent modulation by other molecules. As an immunomodulator, CGRP exhibits intriguing complexity, displaying both anti-inflammatory and pro-inflammatory effects. Furthermore, CGRP appears to be involved in obesity development while paradoxically reducing appetite. A thorough investigation of CGRP's biological effects is crucial for anticipating potential side effects associated with its antagonists' use and for developing novel therapies in other medical fields. In summary, CGRP represents a neuropeptide with a complex systemic impact, extending well beyond nociception, thus offering new perspectives in medical research and therapeutics.

Exposure to medication for neurological disease in pregnancy - time to consider the long-term implications?

A range of long-term neurological conditions may be diagnosed in young adulthood. These conditions are generally not curable, and most people need to take ongoing treatment for symptom control and/or disease modification. When chronic diseases are diagnosed before people have completed their families, there is a need to balance the potential benefits of treatment for the mother against potential risk(s) to the fetus from exposure to medications during pregnancy. Whilst available data regarding short-term fetal outcomes following treatment exposures during pregnancy is rapidly increasing, information regarding longer-term outcomes is more limited. The association of fetal exposure to valproate with serious long-term neurodevelopmental outcomes has highlighted the importance of capturing and evaluating long-term data. In this review we examine available evidence around the long-term effects of treatments used for the most common long-term neurological conditions diagnosed in early adulthood, namely epilepsy, migraine and neuroinflammatory disorders. We draw from existing literature across a range of diseases and discuss strategies to improve future knowledge.

The use of erenumab for migraine prophylaxis during pregnancy: A case report and narrative review

OBJECTIVE

To report a case of a woman who continued erenumab for migraine prophylaxis throughout her pregnancy and to review the literature for pregnancy safety data for the calcitonin gene-related peptide (CGRP) receptor and ligand-directed therapies currently approved for migraine prophylaxis in the United States.

BACKGROUND

Migraine is a common headache disorder that can be significantly disabling. Many people experiencing migraine seek out preventative therapies to improve their quality of life. Unfortunately, currently approved prophylactic agents may not be safe to use during pregnancy, potentially limiting the use of these agents in women of childbearing potential. As the newest class of prophylactic agents for migraine, CGRP agents have limited pregnancy safety data in humans.

METHODS

A review of the literature was conducted through the PubMed database using the terms pregnancy and either erenumab, fremanezumab, galcanezumab, eptinezumab, rimegepant, or atogepant. Additional sources of information such as prescribing information, assessment reports submitted to the European Medicines Agency (EMA), and manufacturer data were sought.

RESULTS

One case report was found in the literature documenting a human pregnancy with no adverse effects in the baby after exposure to erenumab. However, the last dose was administered in the second week of pregnancy and discontinued thereafter. The evaluation of 92 safety reports describing maternal exposure prior to or during pregnancy to either erenumab, galcanezumab, or fremanezumab was located. Incidence of miscarriage and congenital anomalies appear to be similar to rates in the general population.

CONCLUSIONS

The use of erenumab during pregnancy in our patient resulted in no known harm to the child. This case is unique in that the mother continued to receive erenumab throughout the pregnancy. Safety data is lacking regarding the use of these agents during pregnancy, despite their frequent use in women of childbearing potential.

Sex and Gender Considerations in Episodic Migraine

Purpose of Review

We seek to update readers on recent advances in our understanding of sex and gender in episodic migraine with a two part series. In part 1, we examine migraine epidemiology in the context of sex and gender, differences in symptomatology, and the influence of sex hormones on migraine pathophysiology (including CGRP). In part 2, we focus on practical clinical considerations for sex and gender in episodic migraine by addressing menstrual migraine and the controversial topic of hormone-containing therapies. We make note of data applicable to gender minority populations, when available, and summarize knowledge on gender affirming hormone therapy and migraine management in transgender individuals. Finally, we briefly address health disparities, socioeconomic considerations, and research bias.

Recent Findings

Migraine is known to be more prevalent, frequent, and disabling in women. There are also differences in migraine co-morbidities and symptomatology. For instance, women are likely to experience more migraine associated symptoms such as nausea, photophobia, and phonophobia. Migraine pathophysiology is influenced by sex hormones, e.g., estrogen withdrawal as a known trigger for migraine. Other hormones such as progesterone and testosterone are less well studied. Relationships between CGRP (the target of new acute and preventive migraine treatments) and sex hormones have been established with both animal and human model studies. The natural course of migraine throughout the lifetime suggests a contribution from hormonal changes, from puberty to pregnancy to menopause/post-menopause. Treatment of menstrual migraine and the use of hormone-containing therapies remains controversial. Re-evaluation of the data reveals that stroke risk is an estrogen dose- and aura frequency-dependent phenomenon. There are limited data on episodic migraine in gender minorities. Gender affirming hormone therapy may be associated with a change in migraine and unique risks (including ischemic stroke with high dose estrogen).

Summary

There are key differences in migraine epidemiology and symptomatology, thought to be driven at least in part by sex hormones which influence migraine pathophysiology and the natural course of migraine throughout the lifetime. More effective and specific treatments for menstrual migraine are needed. A careful examination of the data on estrogen and stroke risk suggests a nuanced approach to the issue of estrogen-containing contraception and hormone replacement therapy is warranted. Our understanding of sex and gender is evolving, with limited but growing research on the relationship between gender affirming therapy and migraine, and treatment considerations for transgender people with migraine.

Hypervigilance, Allostatic Load, and Migraine Prevention: Antibodies to CGRP or Receptor

Migraine involves brain hypersensitivity with episodic dysfunction triggered by behavioral or physiological stressors. During an acute migraine attack the trigeminal nerve is activated (peripheral sensitization). This leads to central sensitization with activation of the central pathways including the trigeminal nucleus caudalis, the trigemino-thalamic tract, and the thalamus. In episodic migraine the sensitization process ends with the individual act, but with chronic migraine central sensitization may continue interictally. Increased allostatic load, the consequence of chronic, repeated exposure to stressors, leads to central sensitization, lowering the threshold for future neuronal activation (hypervigilance). Ostensibly innocuous stressors are then sufficient to trigger an attack. Medications that reduce sensitization may help patients who are hypervigilant and help to balance allostatic load. Acute treatments and drugs for migraine prevention have traditionally been used to reduce attack duration and frequency. However, since many patients do not fully respond, an unmet treatment need remains. Calcitonin gene-related peptide (CGRP) is a vasoactive neuropeptide involved in nociception and in the sensitization of peripheral and central neurons of the trigeminovascular system, which is implicated in migraine pathophysiology. Elevated CGRP levels are associated with dysregulated signaling in the trigeminovascular system, leading to maladaptive responses to behavioral or physiological stressors. CGRP may, therefore, play a key role in the underlying pathophysiology of migraine. Increased understanding of the role of CGRP in migraine led to the development of small-molecule antagonists (gepants) and monoclonal antibodies (mAbs) that target either CGRP or the receptor (CGRP-R) to restore homeostasis, reducing the frequency, duration, and severity of attacks. In clinical trials, US Food and Drug Administration-approved anti-CGRP-R/CGRP mAbs were well tolerated and effective as preventive migraine treatments. Here, we explore the role of CGRP in migraine pathophysiology and the use of gepants or mAbs to suppress CGRP-R signaling via inhibition of the CGRP ligand or receptor.

DNA Methylation Pattern of CALCA and CALCB in Extremely Premature Infants with Monochorionic Triplets after Single-Embryo Transfer

Compared with full-term peers, premature infants are more likely to suffer from neonatal diseases and death. Variations in DNA methylation may affect these pathological processes. Calcitonin gene-related peptide (CGRP) plays a complex and diversified role in reproduction and chronic inflammation, and participates in the functional maintenance of vascular adaptation and trophoblast cells during pregnancy. Here, premature live births with single-chorionic triple embryos after single-embryo transfer were used as research objects, while full-term infants with double embryos and double-chorionic twins were used as controls. DNA was extracted from umbilical cord tissues for pyrosequencing to detect the methylation level of CpG island in CGRP promoter region. The average values of CGRP methylation in the umbilical cord tissues of very premature fetuses were higher than that of normal controls obtained from the databases. Immunofluorescence results showed that the expression of αCGRP was decreased in the blood vessel wall of the umbilical cord of monozygotic triplets, especially in death cases, while the βCGRP had a compensatory expression. In conclusion, our findings suggest that hypermethylation of CGRP might be considered as an important cause of serious neonatal morbidities.

Safety profile of erenumab, galcanezumab and fremanezumab in pregnancy and lactation: Analysis of the WHO pharmacovigilance database

OBJECTIVE

To assess the safety profile of erenumab, galcanezumab and fremanezumab in pregnancy and lactation.

METHODS

Safety reports of suspected adverse drug reactions were retrieved from VigiBase as of 31 December 2019, for a case-by-case assessment and disproportionality analysis using the reporting odds ratio (ROR).

RESULTS

There were 94 safety reports: 50 (53.2%) on erenumab, 31 (33.0%) on galcanezumab, and 13 (13.8%) on fremanezumab. In five (5.3%) safety reports, drug exposure occurred prior to pregnancy, in 85 (90.4%) during pregnancy, in one (1.1%) during lactation, in one (1.1%) via paternal exposure, and in two (2.1%) the exposure time was unknown. Out of 94 safety reports, 51 (54.3%) consisted only of drug exposure, while 43 (45.7%) additionally reported 47 adverse drug reactions including maternal toxicities (n = 18), poor breastfeeding (n = 1), spontaneous abortion (n = 23), preterm birth/prematurity (n = 3), and birth defects (n = 2). There was no signal of disproportionate reporting for spontaneous abortion compared to the full database (reporting odds ratio 1.46, 95% confidence interval 0.97-2.20). When triptans were used as a comparator group, a signal of disproportionate reporting for spontaneous abortion was detected in association with erenumab, galcanezumab, and fremanezumab (reporting odds ratio 1.86, 95% confidence interval 1.12-3.13), which was not statistically significant after excluding confounded safety reports (reporting odds ratio 1.21, 95% confidence interval 0.67-2.21).

CONCLUSIONS

No specific maternal toxicities, patterns of major birth defects, or increased reporting of spontaneous abortion were found. However, because of the relatively limited number of adverse drug reactions reported and the lack of long-term safety data, continuous surveillance is required in pregnant and lactating women exposed to these drugs.

Changing levels of sex hormones and calcitonin gene-related peptide (CGRP) during a woman's life: Implications for the efficacy and safety of novel antimigraine medications

Migraine is a neurovascular disorder that is three times more prevalent in women than in men and represents a large socio-economic burden. Therefore, the development of new preventive medications is an urgent matter. Currently, calcitonin gene-related peptide (CGRP), a neuropeptide released from trigeminal fibres, is an important target for migraine treatment. Accordingly, antibodies directed against CGRP or its receptor, as well as small-molecule CGRP receptor antagonists, have been developed for the prophylactic and acute treatment of migraine. Results from clinical phase III trials show a significant decrease in migraine days and relatively mild side-effects. However, CGRP is not only present in the trigeminal nerve, but it is also abundant in perivascular nerve fibres. Moreover, CGRP levels and hormones vary between sexes and during different life stages, and hormones affect CGRP, with a seemingly greater role for CGRP in females. In this review we discuss whether these aspects could be associated with differences in response and efficacy of drugs interfering with the CGRP pathway. Furthermore, CGRP has been described as playing a protective role in ischemic events, and CGRP seems to play a larger role in cardiac ischemic events in female patients. As cardiovascular risk is increased in female migraine patients and also increases significantly in females after menopause, further research into the risk of blocking CGRP in these patients is needed.

Managing migraine in pregnancy and breastfeeding

The disproportionate prevalence of migraine among women in their reproductive years underscores the clinical significance of migraine during pregnancy. This paper discusses how migraine evolves during pregnancy, secondary headache disorders presenting in pregnancy and puerperium, and acute and preventive options for migraine management during pregnancy and lactation. Migraine is influenced by rising estrogen levels during pregnancy and their sharp decline in puerperium. Migraine, and migraine aura, can present for the first time during pregnancy and puerperium. There is also a higher risk for the development of preeclampsia and cerebrovascular headache during these periods. New or refractory headache, hypertension, and abnormal neurological signs are important "red flags" to consider. This paper reviews the diagnostic utility of neuroimaging studies and the risks of each during pregnancy. Untreated migraine can itself lead to preterm delivery, preeclampsia, and low birth weight infants. Behavioral interventions and lifestyle modifications are the cornerstone for migraine treatment during pregnancy. In addition, one should consider the risks and efficacy of each treatment during pregnancy on an individual basis. The protective nature of breastfeeding for migraine is debated, but there is no evidence to suggest breastfeeding worsens migraine. Acute and preventive migraine treatment options are available for nursing mothers. Neuromodulation and neurostimulation devices are additional options for treatment during pregnancy and lactation, while the safety of using calcitonin gene-related peptide receptor antagonists during these times remains to be determined.

Menstrual migraine: what it is and does it matter?

The diagnostic criteria of menstrual migraine (MM), migraine related to menstruation and pure menstrual migraine, are placed in the appendix of the International Classification of Headache Disorders and are still primarily considered as research criteria that need validation. Although there is a great wealth of knowledge about the neurobiological processes underlying MM and its symptoms, the mechanisms by which an attack starts during the menstrual cycle remain baffling, and the disease is still undertreated. In this narrative review, we aim to summarize recent data on pathophysiology, epidemiology, burden of disease and treatment of MM. The vast majority of the literature focuses on the relationship between MM and hormonal factors. The role of falling in estrogen levels is believed to increase the susceptibility of blood vessels to prostaglandins, which have been implicated in neurogenic inflammation. Moreover, fluctuations of ovarian steroid hormone levels modulate calcitonin gene-related peptide in the trigeminovascular system. In addition, it has been observed that gonadal hormones modulate cortical spreading depression susceptibility in animal models. Sex hormone influences on MM affect not only the frequency and severity of headache attack but also its treatment. Understanding the mechanisms that contribute to neuroendocrine vulnerability in some women and some menstrual cycles may yield possible marker of the disease opening treatment options specifically targeting MM. An increased interest for future research on the subject will further elucidate how to manage this debilitating type of migraine.

The role of epigenetic changes in preeclampsia

Preeclampsia (PE) is a disorder affecting 2-10% of pregnancies and has a major role for perinatal and maternal mortality and morbidity. PE can be occurred by initiation of new hypertension combined with proteinuria after 20 weeks gestation, as well as various reasons such as inflammatory cytokines, poor trophoblast invasion can be related with PE disease. Environmental factors can cause epigenetic changes including DNA methylation, microRNAs (miRNAs), and histone modification that may be related to different diseases such as PE. Abnormal DNA methylation during placentation is the most important epigenetic factor correlated with PE. Moreover, changes in histone modification like acetylation and also the effect of overregulation or low regulation of miRNAs or long noncoding RNAs on variety signaling pathways can be resulted in PE. The aim of this review is to describe of studies about epigenetic changes in PE and its therapeutic strategies.

CGRP ligand and receptor monoclonal antibodies for migraine prevention: Evidence review and clinical implications

Background: Monoclonal antibodies that target calcitonin gene-related peptide or the canonical calcitonin gene-related peptide receptor have emerged as effective and well tolerated for the preventive treatment of migraine. These large molecules appear ideally suited for migraine prevention. They have an extended biological half-life, are administered either monthly or quarterly either by subcutaneous injection or intravenous infusion, require minimal or no dose-titration and have the potential for a rapid onset of effect compared to conventional oral preventive drugs. There is high selectivity and they target an important mediator in the pathogenesis of migraine. Investigation: Phase II and pivotal phase III studies have all yielded positive results with a favorable adverse event profile. No serious treatment-related adverse outcomes have thus far been reported in controlled or long-term open-label extension studies. This tolerability profile promises to improve adherence and, possibly, long-term outcomes. Conclusions: Calcitonin gene-related peptide monoclonal antibodies are effective and well tolerated for the preventive treatment of migraine. They have distinct advantages over currently available oral preventive drugs. While treatment-related serious adverse events have not been observed in open-label extension studies, long-term outcomes and safety will require broad exposure in heterogeneous patient populations in clinical practice. In addition, their safety in women, especially during pregnancy, will require longitudinal surveillance. Given the overlapping mechanism(s), the effectiveness of existing (triptans) and emerging (calcitonin gene-related peptide receptor antagonists) acute therapies in those using a calcitonin gene-related peptide mAb will require further study.

The Myometrium: From Excitation to Contractions and Labour

We start by describing the functions of the uterus, its structure, both gross and fine, innervation and blood supply. It is interesting to note the diversity of the female's reproductive tract between species and to remember it when working with different animal models. Myocytes are the overwhelming cell type of the uterus (>95%) and our focus. Their function is to contract, and they have an intrinsic pacemaker and rhythmicity, which is modified by hormones, stretch, paracrine factors and the extracellular environment. We discuss evidence or not for pacemaker cells in the uterus. We also describe the sarcoplasmic reticulum (SR) in some detail, as it is relevant to calcium signalling and excitability. Ion channels, including store-operated ones, their contributions to excitability and action potentials, are covered. The main pathway to excitation is from depolarisation opening voltage-gated Ca²⁺ channels. Much of what happens downstream of excitability is common to other smooth muscles, with force depending upon the balance of myosin light kinase and phosphatase. Mechanisms of maintaining Ca²⁺ balance within the myocytes are discussed. Metabolism, and how it is intertwined with activity, blood flow and pH, is covered. Growth of the myometrium and changes in contractile proteins with pregnancy and parturition are also detailed. We finish with a description of uterine activity and why it is important, covering progression to labour as well as preterm and dysfunctional labours. We conclude by highlighting progress made and where further efforts are required.

Unique Populations with Episodic Migraine: Pregnant and Lactating Women

PURPOSE OF REVIEW

Migraine is a disabling and prevalent neurological disease, commonly affecting women during their reproductive years. It is crucial for providers to be able to adequately counsel women who are pregnant, planning pregnancy, or nursing, regarding preventive and abortive treatment options for episodic migraine. This review will discuss (1) the expected course of migraine during pregnancy and the post-partum period, (2) recommended preventive therapies for migraine during pregnancy and lactation, and (3) recommended abortive medications for migraine during pregnancy and lactation.

RECENT FINDINGS

Recent research has indicated safety for triptan use during pregnancy and ibuprofen use during the first trimester of pregnancy. Considerations for use of emerging migraine-preventive treatment, such as non-invasive neurostimulators, are discussed. For clinical decision-making and patient counseling, it is important to understand both the limitations in determining teratogenic effects in humans and the principles affecting medication transmission from mother to breast milk.

Migraine

Migraine is a chronic paroxysmal neurological disorder characterised by multiphase attacks of head pain and a myriad of neurological symptoms. The underlying genetic and biological underpinnings and neural networks involved are coming sharply into focus. This progress in the fundamental understanding of migraine has led to novel, mechanism-based and disease-specific therapeutics. In this Seminar, the clinical features and neurobiology of migraine are reviewed, evidence to support available treatment options is provided, and emerging drug, device, and biological therapies are discussed.

Preeclampsia/Eclampsia candidate genes show altered methylation in maternal leukocytes of preeclamptic women at the time of delivery

OBJECTIVE

To analyze methylation profiles of known preeclampsia/eclampsia (PE) candidate genes in normal (NL) and preeclamptic (PE) women at delivery.

METHODS

A matched case-control study comparing methylation in 79 CpG sites/33 genes from an independent gene set in maternal leukocyte DNA in PE and NL (n = 14 each) on an Illumina BeadChip platform. Replication performed on second cohort (PE = 12; NL = 32).

RESULTS

PE demonstrates differential methylation in POMC, AGT, CALCA, and DDAH1 compared with NL.

CONCLUSION

Differential methylation in four genes associated with PE may represent a potential biomarker or an epigenetic pathophysiologic mechanism altering gene transcription.

Targeting CGRP: A New Era for Migraine Treatment

Migraine is a highly prevalent headache disease that typically affects patients during their most productive years. Despite significant progress in understanding the underlying pathophysiology of this disorder, its treatment so far continues to depend on drugs that, in their majority, were not specifically designed for this purpose. The neuropeptide calcitonin gene-related peptide (CGRP) has been indicated as playing a critical role in the central and peripheral pathways leading to a migraine attack. It is not surprising that drugs designed to specifically block its action are gaining remarkable attention from researchers in the field with, at least so far, a safe risk profile. In this article, we highlight the evolution from older traditional treatments to the innovative CGRP target drugs that are revolutionizing the way to approach this debilitating neurological disease. We provide a brief introduction on pathophysiology of migraine and details on the characteristic, function, and localization of CGRP to then focus on CGRP receptor antagonists (CGRP-RAs) and CGRP monoclonal antibodies (CGRP mAbs).

Alterations in perivascular sympathetic and nitrergic innervation function induced by late pregnancy in rat mesenteric arteries

Background and Purpose

We investigated whether pregnancy was associated with changed function in components of perivascular mesenteric innervation and the mechanism/s involved.

Experimental Approach

We used superior mesenteric arteries from female Sprague-Dawley rats divided into two groups: control rats (in oestrous phase) and pregnant rats (20 days of pregnancy). Modifications in the vasoconstrictor response to electrical field stimulation (EFS) were analysed in the presence/absence of phentolamine (alpha-adrenoceptor antagonist) or L-NAME (nitric oxide synthase-NOS- non-specific inhibitor). Vasomotor responses to noradrenaline (NA), and to NO donor DEA-NO were studied, NA and NO release measured and neuronal NOS (nNOS) expression/activation analysed.

Key Results

EFS induced a lower frequency-dependent contraction in pregnant than in control rats. Phentolamine decreased EFS-induced vasoconstriction in segments from both experimental groups, but to a greater extent in control rats. EFS-induced vasoconstriction was increased by L-NAME in arteries from both experimental groups. This increase was greater in segments from pregnant rats. Pregnancy decreased NA release while increasing NO release. nNOS expression was not modified but nNOS activation was increased by pregnancy. Pregnancy decreased NA-induced vasoconstriction response and did not modify DEA-NO-induced vasodilation response.

Conclusions and Implications

Neural control of mesenteric vasomotor tone was altered by pregnancy. Diminished sympathetic and enhanced nitrergic components both contributed to the decreased vasoconstriction response to EFS during pregnancy. All these changes indicate the selective participation of sympathetic and nitrergic innervations in vascular adaptations produced during pregnancy.

Intermedin/adrenomedullin 2 is associated with implantation and placentation via trophoblast invasion in human pregnancy

RATIONALE

Intermedin (IMD) is a novel peptide expressed in trophoblast cells in human placenta and enhances the invasion, migration, and human leukocyte antigen class I, G (HLA-G) expression in first-trimester HTR-8SV/neo cells. We recently reported that infusion of IMD antagonist in pregnant rats is detrimental to pregnancy outcome, resulting in impaired fetoplacental growth and deformed placental vasculature.

OBJECTIVE

This study was undertaken to assess expression of IMD and its involvement in human implantation and early placentation and assess whether its expression is altered in spontaneous abortion.

FINDINGS AND CONCLUSIONS

We demonstrate for the first time that IMD is present in day 5 embryonic secretome; villous and decidual expression of IMD is higher at 6-8 weeks after a decline as gestation advances toward the second trimester; first-trimester spontaneous abortion is associated with a lower expression of IMD in serum, villi, and decidua; IMD stimulates the invasive capacity of first-trimester primary Extravillous cytotrophoblast cells; and IMD decreases elevated levels of tumor suppressor Kangia-1 in decidual explants from first-trimester spontaneous abortion. In conclusion, this study is the first to demonstrate a potential involvement of IMD in human embryo implantation and placental development via regulation of trophoblast invasion at the maternal-fetal interface and suggests a physiological role for this novel peptide in establishment of human pregnancy.

Upgrading of sea by-products: potential nutraceutical applications

Since many years, numerous kinds of processes based on enzymatic hydrolysis at various pH, involving added plant or bacterial enzymes after inactivation by heating of endogenous enzymes present in the raw material or, alternatively, based on the action of endogenous enzymes, have contributed to the degradation of marine by-product proteins in order to produce fractions exerting biological activities. Peptides obtained by enzymatic hydrolysis of fish proteins exhibit not only nutritional but also biological properties of dietary uses, or even therapeutic potential. In this review, we have focused on the different enzymatic processes able to generate bioactive peptides from marine by-products and exerting high potential in nutraceutical applications to fight against important public health issues like obesity, stress, hypertension, and migraine. Beyond the nutraceutical and pharmaceutical aspects, this way of valorization is also included in the necessary development of by-product fishing industries for economic and ecological reasons in the worldwide context of marine resources depletion.

A whole-genome association study for pig reproductive traits

A whole-genome association study was performed for reproductive traits in commercial sows using the PorcineSNP60 BeadChip and Bayesian statistical methods. The traits included total number born (TNB), number born alive (NBA), number of stillborn (SB), number of mummified foetuses at birth (MUM) and gestation length (GL) in each of the first three parities. We report the associations of informative QTL and the genes within the QTL for each reproductive trait in different parities. These results provide evidence of gene effects having temporal impacts on reproductive traits in different parities. Many QTL identified in this study are new for pig reproductive traits. Around 48% of total genes located in the identified QTL regions were predicted to be involved in placental functions. The genomic regions containing genes important for foetal developmental (e.g. MEF2C) and uterine functions (e.g. PLSCR4) were associated with TNB and NBA in the first two parities. Similarly, QTL in other foetal developmental (e.g. HNRNPD and AHR) and placental (e.g. RELL1 and CD96) genes were associated with SB and MUM in different parities. The QTL with genes related to utero-placental blood flow (e.g. VEGFA) and hematopoiesis (e.g. MAFB) were associated with GL differences among sows in this population. Pathway analyses using genes within QTL identified some modest underlying biological pathways, which are interesting candidates (e.g. the nucleotide metabolism pathway for SB) for pig reproductive traits in different parities. Further validation studies on large populations are warranted to improve our understanding of the complex genetic architecture for pig reproductive traits.

Innervation of the rat uterus at estrus: a study in full-thickness, immunoperoxidase-stained whole-mount preparations

The innervation of the nonpregnant rat uterus has been studied in histological sections, which contain only small samples of nerves and are unlikely to afford a complete picture of uterine innervation. Here we used whole-mount preparations of entire full-thickness uterine horns from nonpregnant rats in estrus to visualize autonomic or sensory nerves with peroxidase immunohistochemistry. Immunoreactivity was studied for tyrosine hydroxylase (TH)-labeled sympathetic nerves; vesicular acetylcholine transporter (VAChT), parasympathetic nerves; and substance P (SP) and calcitonin gene-related peptide (CGRP), sensory nerves. Neuropeptide Y (NPY) and nitric oxide synthase (NOS) identified more than one of these functionally distinct nerve types. Axons of all neurochemical classes entered the uterus at the mesometrium and innervated the uterine smooth muscle. The linea uteri, a dense band of longitudinal muscle opposite the mesometrium, contained more TH-, NPY-, CGRP-, and VAChT-immunoreactive axons than the remaining smooth muscle. Axons immunoreactive for NPY, SP, NOS, and VAChT formed a plexus near the circular muscle-endometrium interface. Rare TH- and NPY-immunoreactive axons and occasional CGRP-immunoreactive axons occurred close to uterine glands. Blood vessels had dense perivascular plexuses of TH- and NPY-containing axons and less dense NOS-, SP-, CGRP-, and VAChT-positive plexuses. The circular muscle plexus and glands were absent opposite the mesometrium. Uterine arterioles formed an interconnected network throughout the uterus. This article provides the first comprehensive description of the autonomic and sensory innervation of the nonpregnant rat uterus and will be a foundation for future studies on changes in uterine innervation caused by normal physiological or pathophysiological challenges.

Calcitonin receptor-like receptor expression in rat skeletal muscle fibers

The calcitonin gene related peptide (CGRP) pathway is important in many processes including several in the central and peripheral nervous systems. CGRP is present in motor neurons and in sensory tracts, with its expression likely regulated by its use. This is supported by the fact that axotomy results in increased CGRP production in the nerve cell body. The target CGRP receptor, produced in part from the calcitonin receptor-like receptor (Calcrl) gene, has been thought to be present in multiple forms based on kinetic studies; however, understanding of the regulation of the expression of the Calcrl gene remains incomplete. CALCRL is an important factor in aging and associated disorders. This study focused on the neuromuscular system where it has been unclear whether different proteins are initially translated and whether higher levels of CALCRL are localized to the endplate regions. Rat gracilis muscle neuromuscular junctions were examined by isolating endplate enriched and non-endplate regions identified by staining for acetylcholine esterase or conjugated α-bungarotoxin binding. The CALCRL protein was detected at approximately 60kDa by Western immunoblotting and, in the isolated extracts, we found that the Calcrl mRNA level was elevated 6 fold in the muscle endplate regions and that there were two distinct Calcrl messages present. Sequence analysis showed that the two different Calcrl forms were due to alternative splicing but in a non-coding region of the transcript such that only one translation product would be generated. This indicates that previously identified pharmacologic heterogeneity is most likely due to post-translational modifications and interactions.

Altered drug metabolism during pregnancy: hormonal regulation of drug-metabolizing enzymes

IMPORTANCE OF THE FIELD

Medication use during pregnancy is prevalent, but pharmacokinetic information of most drugs used during pregnancy is lacking in spite of known effects of pregnancy on drug disposition. Accurate pharmacokinetic information is essential for optimal drug therapy in mother and fetus. Thus, understanding how pregnancy influences drug disposition is important for better prediction of pharmacokinetic changes of drugs in pregnant women.

AREAS COVERED IN THIS REVIEW

Pregnancy is known to affect hepatic drug metabolism, but the underlying mechanisms remain unknown. Physiological changes accompanying pregnancy are probably responsible for the reported alteration in drug metabolism during pregnancy. These include elevated concentrations of various hormones such as estrogen, progesterone, placental growth hormones and prolactin. This review covers how these hormones influence expression of drug-metabolizing enzymes (DMEs), thus potentially responsible for altered drug metabolism during pregnancy.

WHAT THE READER WILL GAIN

The reader will gain a greater understanding of the altered drug metabolism in pregnant women and the regulatory effects of pregnancy hormones on expression of DMEs.

TAKE HOME MESSAGE

In-depth studies in hormonal regulatory mechanisms as well as confirmatory studies in pregnant women are warranted for systematic understanding and prediction of the changes in hepatic drug metabolism during pregnancy.

Effect of cGMP on pharmacomechanical coupling in the uterine artery of near-term pregnant sheep

The present study examined the role of cGMP in the regulation of alpha(1)-adrenoceptor-mediated pharmacomechanical coupling in the uterine artery of near-term pregnant sheep. The cell-permeable cGMP analog 8-bromo-cGMP produced a dose-dependent relaxation of the uterine artery and shifted norepinephrine (NE) dose-response curve to the right with a decreased maximal contraction. Accordingly, 8-bromo-cGMP significantly decreased the potency and the maximal response of NE-induced inositol 1,4,5-trisphosphate (IP(3)) synthesis in the uterine artery. In addition, 8-bromo-cGMP significantly reduced the binding affinity of IP(3) to the IP(3) receptor. The density of IP(3) receptors was not affected. Simultaneous measurement of intracellular Ca2+ concentrations ([Ca2+](i)) and tensions in the same tissue indicated that 8-bromo-cGMP decreased NE-induced contractions by 92% but only blocked 44% [Ca2+](i). In accordance, 8-bromo-cGMP significantly decreased tension generation for a given [Ca2+](i) (g/R(f340/380), 24.87 +/- 3.43 versus 3.10 +/- 0.35). In the absence of extracellular Ca2+, NE produced a transient increase in [Ca2+](i) and contraction, which were inhibited by 8-bromo-cGMP by 47 and 76%, respectively. In contrast to NE-induced responses, 8-bromo-cGMP had no significant effects on KCl-induced [Ca2+](i) and contractions. The results indicate that cGMP suppresses alpha(1)-adrenoceptor-mediated pharmacomechanical coupling in the uterine artery by inhibiting IP(3) synthesis and Ca2+ release from intracellular stores, as well as inhibiting the agonist-mediated Ca2+ sensitization of myofilaments, which is likely to play an important role in the adaptation of uterine artery contractility during pregnancy.

Expression of calcitonin gene-related peptide, adrenomedullin, and receptor modifying proteins in human adipose tissue and alteration in their expression with menopause status

OBJECTIVE

Calcitonin gene-related peptide (CGRP) is a vasoactive, proinflammatory neuropeptide implicated in the pathogenesis of cardiovascular disease. Elevated CGRP levels during hot flushes and pregnancy suggest that reproductive hormones may influence CGRP secretion. CGRP and the related protein adrenomedullin (ADM) may function through adipose tissue-mediated effects, since adipose tissue is an important site of cytokine production and the main site for estrogen production after menopause. This study examined mRNA and protein expression of CGRP, ADM, and the receptor activity-modifying proteins and the effects of menopausal status in human adipose tissue.

DESIGN

Protein/mRNA levels were determined in adipose tissue biopsy samples collected from premenopausal (n = 22: follicle-stimulating hormone, <20 IU/L; estradiol [mean +/- SEM], 434.5 +/- 87.81 pmol/L) and postmenopausal (n = 25: follicle-stimulating hormone, >20 IU/L; estradiol, 43.4 +/- 6.95 pmol/L) women.

RESULTS

Our studies determined that CGRP, ADM, and receptor activity-modifying proteins were expressed in abdominal fat, adipocytes, and preadipocytes. CGRP and ADM mRNA levels were increased in abdominal subcutaneous fat in postmenopausal women compared with premenopausal women (betaCGRP: premenopause Delta cycle threshold [Ct], 31.07 +/- 0.28 vs postmenopause DeltaCt, 30.35 +/- 0.17, P = 0.035; ADM: premenopause subcutaneous fat DeltaCt, 12.41 +/- 0.2 vs postmenopause subcutaneous fat DeltaCt, 11.55 +/- 0.14, P < 0.001) with CGRP differentially expressed in subcutaneous and omental depots. CGRP protein expression was higher in postmenopausal women (P < 0.05) in both fat depots.

CONCLUSIONS

Our findings suggest that adipose tissue represents an important site for CGRP and ADM production and that menopause status alters their expression in abdominal fat. This offers a potential mechanism to explain the role of CGRP in menopausal vasomotor symptoms and the increased risk of cardiovascular disease in postmenopausal women.

Adrenomedullin 2 antagonist infusion to rats during midgestation causes fetoplacental growth restriction through apoptosis

Adrenomedullin 2 (ADM2) is a recently discovered member of the calcitonin/calcitonin gene-related peptide family with an exon-intron structure similar to that of ADM. The mRNA of ADM2 is expressed in several tissues, including uterus and ovary. The present study was designed to assess the effects of ADM2 antagonist (ADM2(17-47)) infusion to pregnant rats on fetal and placental growth. On Day 15 of gestation, rats were implanted s.c. with osmotic minipumps delivering 50 and 200 mug per rat per day of ADM2(17-47) and were killed on Gestational Day 18. In ADM2(17-47)-treated rats, placental weights were significantly inhibited in a dose-related manner, with an 11% reduction in the group of rats receiving 200 microg/day, whereas the fetal weights were reduced by 17% without significant differences between the two doses. 2 In ADM2(17-47)-infused rats, increased apoptosis was demonstrated in the labyrinth and junctional zones of rat placenta by the TUNEL method compared with the control animals. Western blot analysis demonstrated that in ADM2(17-47)-treated rats Bcl-2, mitochondrial cytochrome c, and active caspase-9 and caspase-3 were significantly increased compared with the controls. No significant treatment-associated changes were observed in Bax, Bid, p53, and caspase-8 and caspase-10 proteins in the treated placentas. In addition, infusion of ADM2(17-47) caused a significant decline in the transcripts of nitric oxide synthase 3 (NOS3) and NOS2. These findings show that ADM2(17-47) infusion in rats during midpregnancy cause fetoplacental growth restriction through the activation of mitochondrial apoptotic pathways. This study demonstrates for the first time (to our knowledge) a potential role for ADM2 in placental functions during pregnancy.

Calcitonin gene-related peptide and its role in migraine pathophysiology

Migraine is a common neurological disorder that is associated with an increase in plasma calcitonin gene-related peptide (CGRP) levels. CGRP, a neuropeptide released from activated trigeminal sensory nerves, dilates intracranial blood vessels and transmits vascular nociception. Therefore, it is propounded that: (i) CGRP may have an important role in migraine pathophysiology, and (ii) inhibition of trigeminal CGRP release or CGRP-induced cranial vasodilatation may abort migraine. In this regard, triptans ameliorate migraine headache primarily by constricting the dilated cranial blood vessels and by inhibiting the trigeminal CGRP release. In order to explore the potential role of CGRP in migraine pathophysiology, the advent of a selective CGRP receptor antagonist was obligatory. The introduction of di-peptide CGRP receptor antagonists, namely BIBN4096BS (1-piperidinecarboxamide, N-[2-[[5-amino-1-[[4-(4-pyridinyl)-1-piperazinyl]carbonyl] pentyl] amino]-1-[(3,5-dibromo-4-hydroxyphenyl) methyl]-2-oxoethyl]-4-(1,4-dihydro-2-oxo-3(2H)-quinazolinyl)-, [R-(R*,S*)]-), is a breakthrough in CGRP receptor pharmacology and can be used as a tool to investigate the role of CGRP in migraine headaches. Preclinical investigations in established migraine models that are predictive of antimigraine activity have shown that BIBN4096BS is a potent CGRP receptor antagonist and that it has antimigraine potential. Indeed, a recently published clinical study has reported that BIBN409BS is effective in treating acute migraine attacks without significant side effects. The present review will discuss mainly the potential role of CGRP in the pathophysiology of migraine and the various treatment modalities that are currently available to target this neuropeptide.

CORONARY VASODILATORY RESPONSE TO A NOVEL PEPTIDE, ADRENOMEDULLIN 2

1. Adrenomedullin-2 (AM2) is a novel peptide originally found in a fish and it is structurally related to mammalian AM or fish AM1. Cloning of AM2 cDNA in the mouse, rat and human has been successful. In the present study, the vasodilatory effect of synthetic human AM2 was analysed in isolated artery ring preparations of porcine. 2. Vasodilatory effect of AM2 was the most potent in the coronary artery, followed by the carotid and supramesenteric arteries, but absent in the femoral, pulmonary and renal arteries. 3. The effect of AM2 was equipotent with that of human AM/AM1 in these arteries. 4. AM2-induced relaxation was inhibited by human CGRP (8-37), but not by human AM/AM1 (22-52), suggesting that the vasodilatory response to AM2 is mediated through the CGRP1 receptor. 5. AM2 may share the same receptor (complex) with AM/AM1 for the vasorelaxation. This is the first report of the vasodilatory responses to AM2 in isolated vasculature.

The pharmacology of CGRP-responsive receptors in cultured and transfected cells

Historically, CGRP receptors have been classified as CGRP(1) or CGRP(2) subtypes, chiefly depending on their affinity for the antagonist CGRP(8-37). It has been shown that the complex between calcitonin receptor-like receptor (CRLR or CL) and receptor activity modifying protein (RAMP) 1 provides a molecular correlate for the CGRP(1) receptor; however, this does not explain the range of affinities seen for CGRP(8-37) in isolated tissues. It is suggested that these may largely be explained by a combination of methodological factors and CGRP-responsive receptors generated by CL and RAMP2 or RAMP3 and complexes of RAMPs with the calcitonin receptor.

Novel fish-derived adrenomedullin in mammals: structure and possible function

Adrenomedullin (AM) has been recognized as a member of the calcitonin (CT)/CT gene-related peptide (CGRP) family. However, an independent AM family consisting of five paralogous peptides exists in teleost fish. Among them, the peptide named AM1 is an ortholog of mammalian AM as determined by the linkage analysis of orthologous genes and the presence of proAM N-terminal 20 peptide (PAMP)-like sequence in the prosegment. Since the peptides named AM2 and 3 are distinct from other members with respect to the precursor sequence, tissue distribution of the transcripts, and exon-intron organization, we searched for their mammalian orthologs from genome databases, which resulted in an identification of AM2 in human, rat, and mouse. AM2 was expressed abundantly in the submaxillary gland, kidney, and some vascular and digestive tissues of mice. AM2 injected in vivo induced potent cardiovascular and renal effects in mice. In the heart and kidney of mice, AM2 was localized in endothelial cells of the coronary vessels and in glomeruli and vasa recta, respectively. AM2 increased cAMP accumulation in cells expressing human CT receptor-like receptor (CRLR) and one of receptor activity-modifying proteins (RAMPs), but it was no more potent than CGRP and AM. AM2 was also less potent than CT in cells expressing CT receptor and RAMP. There remains a possibility that a new AM2-specific receptor or an additional RAMP that enables CRLR to be an AM2-specific receptor, exists in mammals.

Studies on the effects of the N-terminal domain antibodies of calcitonin receptor-like receptor and receptor activity-modifying protein 1 on calcitonin gene-related peptide-induced vasorelaxation in rat uterine artery

The vascular relaxation sensitivity to calcitonin gene-related peptide (CGRP) is enhanced during pregnancy, compared with nonpregnant human and rat uterine arteries. In the rat uterine artery, two types of CGRP receptors have been shown to coexist, CGRP-A receptor, which is a complex of calcitonin receptor-like receptor (CRLR), and receptor activity-modifying protein (RAMP(1)) and CGRP-B receptor, which is different from CRLR. In the present study, we hypothesized that: 1) CGRP-induced vasorelaxation in rat uterine artery is mediated through CGRP-A receptor and 2) N-terminal (Nt) domain of CRLR (Nt-CRLR) has a major contribution in ligand binding and mediating CGRP- induced relaxation effects in rat uterine artery. Polyclonal antibodies against Nt-domain of CRLR and RAMP(1) (Nt-RAMP(1)) were raised in rabbits and characterized for their specificity and were used to inhibit CGRP-induced vasorelaxation in rat uterine artery. For vascular relaxation studies, uterine arteries from Day 18 pregnant rats were isolated, and responsiveness of the vessels to CGRP was examined with a small vessel myograph. CGRP (10(-10) to 10(-7) M) produced a concentration-dependent relaxation of norepinephrine-induced contractions in Day 18 pregnant rat uterine arteries. These effects were significantly (P < 0.05) inhibited when uterine arteries were incubated with the antibody raised against Nt-CRLR (PD(2) = 6.75 +/- 0.20) and were totally abolished in presence of antibodies for both Nt-CRLR and Nt-RAMP(1) (PD(2) = 6.14 +/- 0.35). In contrast, a monoclonal antibody for CGRP-B receptor had no effect on CGRP-induced rat uterine artery relaxation. These studies suggest that CGRP effects in rat uterine artery are mediated through CGRP-A receptor and that Nt-domain of CRLR may play a predominant role in CGRP binding and thus in causing CGRP-induced uterine artery relaxation.

Involvement of calcitonin gene-related peptide in control of human fetoplacental vascular tone

Calcitonin gene-related peptide (CGRP), one of the most potent endogenous vasodilators known, has been implicated in vascular adaptations and placental functions during pregnancy. The present study was designed to examine the existence of CGRP-A receptor components, the calcitonin receptor-like receptor (CRLR) and receptor activity-modifying protein 1 (RAMP1), in the human placenta and the vasoactivity of CGRP in the fetoplacental circulation. Immunofluorescent staining of the human placenta in term labor using polyclonal anti-CRLR and RAMP1 antibodies revealed that labeling specifically concentrated in the vascular endothelium and the underlying smooth muscle cells in the umbilical artery/vein, chorionic artery/vein, and stem villous vessels as well as in the trophoblast layer of the placental villi. In vitro isometric force measurement showed that CGRP dose dependently relaxes the umbilical artery/vein, chorionic artery/vein, and stem villous vessels. Furthermore, CGRP-induced relaxation of placental vessels are inhibited by a CGRP receptor antagonist (CGRP8–37), ATP-sensitive potassium (KATP) channel blocker (glybenclamide), and cAMP-dependent protein kinase A inhibitor (Rp-cAMPS) and partially inhibited by a nitric oxide inhibitor ( Nω-nitro-l-arginine methyl ester). We propose that CGRP may play a role in the control of human fetoplacental vascular tone, and the vascular dilations in response to CGRP may involve activation of KATP channels, cAMP, and a nitric oxide pathway.

Identification of novel adrenomedullin in mammals: a potent cardiovascular and renal regulator

We have identified cDNA encoding a new member of the adrenomedullin (AM) family, AM2, for the first time in mammals (mouse, rat and human). The predicted precursor carried mature AM2 in the C-terminus, which had an intramolecular ring formed by an S-S bond and a possibly amidated C-terminus. Phylogenetic analyses clustered AM2 and AM into two distinct but closely related groups. Similarity of exon-intron structure and synteny of neighboring genes showed that mammalian AM2 is an ortholog of pufferfish AM2 and a paralog of mammalian AM. AM2 mRNA was expressed in submaxillary gland, kidney, stomach, ovary, lymphoid tissues and pancreas of mice, but not in adrenal and testis. Intravenous injection of synthetic mature AM2 decreased arterial pressure more potently than AM, and induced antidiuresis and antinatriuresis in mice. These results show that at least two peptides, AM and AM2, comprise an adrenomedullin family in mammals, and that AM2 may play pivotal roles in cardiovascular and body fluid regulation.

Mechanisms involved in calcitonin gene-related Peptide-induced relaxation in pregnant rat uterine artery

Human and rodent studies have demonstrated that calcitonin gene-related peptide (CGRP), a potent vasodilator, relaxes uterine tissue during pregnancy but not during labor. The vascular sensitivity to CGRP is enhanced during pregnancy, compared to nonpregnant human uterine arteries. In the present study, we hypothesized that uterine artery relaxation effects of CGRP are enhanced in pregnant rats compared to nonpregnant diestrus rats (NP-DE) and that several secondary messenger systems are involved in this process. We also hypothesized that the expression of CGRP-A receptor components, calcitonin receptor-like receptor (CRLR), receptor activity-modifying protein (RAMP1), and CGRP-B receptors are greater in pregnant rats. For vascular relaxation studies, uterine arteries from either NP-DE or Day 18 pregnant rats were isolated, and responsiveness of the vessels to CGRP was examined with a small vessel myograph. CGRP-A and CGRP-B receptor expressions were assessed by RT-PCR and Western immunoblotting, respectively. CGRP (10(-10)--10(-7) M) produced a concentration-dependent relaxation of norepinephrine-induced contractions in both NP-DE and Day 18 pregnant rat uterine arteries. Pregnancy increased the vasodilator sensitivity to CGRP significantly (P < 0.05) compared to NP-DE rats. CGRP receptor antagonist, CGRP8-37, inhibited CGRP-induced relaxation of pregnant uterine arteries. The CGRP-induced relaxation was not affected by NG-nitro-l-arginine methyl ester (L-NAME) (nitric oxide inhibitor, 10(-4) M) but was significantly (P < 0.05) attenuated by inhibitors of guanylate cyclase (ODQ, 10(-5) M) and adenylate cyclase (SQ 22536, 10(-5) M). CGRP-induced vasorelaxation was significantly (P < 0.05) attenuated by potassium channel blockers KATP (glybenclamide, 10(-5) M) and K(CA) (tetraethylammonium, 10(-3) M). The expression of CRLR and RAMP1 was significantly (P < 0.05) elevated during pregnancy compared to nonpregnant diestrus state (NP-DE). However, CGRP-B receptor proteins in uterine arteries were not altered with pregnancy compared to those of NP-DE. These studies suggest that CGRP-induced increases in uterine artery relaxation may play a role in regulating blood flow to the uterus during pregnancy and, therefore, in fetal growth and survival.

Changes in the expression of calcitonin receptor-like receptor, receptor activity-modifying protein (RAMP) 1, RAMP2, and RAMP3 in rat uterus during pregnancy, labor, and by steroid hormone treatments

Calcitonin gene-related peptide (CGRP) and its related peptide, adrenomedullin (AM), are potent smooth muscle relaxants in a variety of tissues. The CGRP has been reported to play an important role in maintaining uterine relaxation during pregnancy. We have previously reported that CGRP-induced uterine relaxation was gestationally regulated. Calcitonin receptor-like receptor (CRLR), a seven-domain transmembrane protein functions as CGRP-A receptor, in association with receptor activity-modifying protein (RAMP) 1, a single-domain transmembrane protein, whereas CRLR and RAMP2 or RAMP3 constitute a receptor for AM. In the present investigation, we examined the mRNA expression of CRLR, RAMP1, RAMP2, and RAMP3 in rat uterus (n = 8) by reverse transcriptional analysis and polymerase chain reaction to assess the changes in the expression of CGRP-A- and AM-receptor components during pregnancy and labor and by steroid hormone treatments in adult ovariectomized rats. The changes in mRNA are expressed relative to the 18S mRNA in the uterus of rats at various stages: nonpregnant, pregnant on Day 18, spontaneous labor at term, Day 2 postpartum, and in pregnant rats on treatment with RU486. Ovariectomized rats treated for 3 days twice daily s.c. with estradiol-17beta (2.5 microg/injection), progesterone (2 mg/injection), and the combination of estradiol-17beta and progesterone (same doses as above) were also examined for the expression of various receptor components. Results showed that mRNA expression of the receptor components was significantly higher (P < 0.001 for CRLR, P < 0.01 for RAMP1, P < 0.05 for RAMP2, and P < 0.01 for RAMP3) in pregnant compared to nonpregnant rats. Except for RAMP3, expression of all the other three genes decreased significantly (P < 0.05) during labor. A progesterone antagonist, RU486 significantly decreased (P < 0.01 for CRLR, P < 0.05 for RAMP1, RAMP2, and RAMP3) all the receptor components during pregnancy. In adult ovariectomized rats, progesterone caused significant increases in CRLR (P < 0.001), RAMP1 (P < 0.05), and RAMP2 (P < 0.01). Levels of RAMP3 were unaffected by the progesterone treatment. Estradiol-17beta treatment decreased all of the four receptor components significantly (P < 0.01 for CRLR, P < 0.05 for RAMP1, RAMP2, and RAMP3). Our results demonstrate that both CGRP and AM may play a role in uterine quiescence during pregnancy and that their receptor components are regulated by the steroid hormones.

A role for tachykinins in female mouse and rat reproductive function

Tachykinins may be involved in reproduction. A reverse transcription-polymerase chain reaction assay was used to analyze the expression of tachykinins and tachykinin receptors in different types of reproductive cells from mice. The preprotachykinin (PPT) genes, PPT-A, PPT-B and PPT-C, that encode substance P/neurokinin A, neurokinin B, and hemokinin-1, respectively, and the genes that encode the tachykinin NK1, NK2, and NK3 receptors were all expressed, at different levels, in the uterus of superovulated, unfertilized mice. The mRNA of neprilysin (NEP), the main enzyme involved in tachykinin metabolism, was also expressed in the uterus. Isolated cumulus granulosa cells expressed PPT-A, PPT-B, PPT-C, and NEP and low levels of the tachykinin NK1 and NK2 receptors. Mouse oocytes expressed PPT-A and -B mRNA transcripts. A low expression of the three tachykinin receptors was observed but PPT-C and NEP were undetectable. Two- and 8- to 16-cell mouse embryos expressed only a low-abundance transcript corresponding to the NK1 receptor. However, the mRNAs of PPT-B, PPT-C and NEP appeared in blastocyst-stage embryos. A low-abundance transcript corresponding to the NK2 receptor was the only target gene detected in mice sperm. Female mice or rats treated neonatally with capsaicin showed a reduced fertility. A reduction in litter size was observed in female rats treated in vivo with the tachykinin NK3 receptor antagonist SR 142801. These data show that tachykinins of both neuronal and nonneuronal origin are differentially expressed in various types of reproductive cells and may play a role in female reproductive function.

The effects of pregnancy and estrogen on the expression of calcitonin gene-related peptide (CGRP) in the uterine cervix, dorsal root ganglia and spinal cord

Before parturition the uterine cervix undergoes a ripening process ("softens" and dilates) to allow passage of the fetus at term. The exact mechanism(s) responsible for cervical ripening are unknown, though a role for peptidergic sensory neurons is emerging. Previous work demonstrated that administration of substance P (SP) to ovariectomized rats caused events associated with cervical ripening, that production of SP in cervix-related dorsal root ganglion (DRG) is estrogen responsive, and that release of SP from neurons terminating in the cervix and spinal cord peaks prior to parturition. The present study was designed to test the hypothesis that calcitonin gene-related peptide (CGRP), a neuropeptide co-stored with SP in many sensory neurons, undergoes changes with pregnancy and hormonal environment. Immunohistochemistry, in situ hybridization, reverse transcriptase-polymerase chain reaction (RT-PCR) and radioimmunoassay (RIA) were used to investigate CGRP in L6-S1 DRG, spinal cord and cervix during pregnancy and the role of estrogen in CGRP synthesis. CGRP-immunoreactive primary sensory neurons expressed estrogen receptors (ER-alpha and ER-beta). In the cervix, CGRP concentrations decreased, but in the L6-S1 DRG and the spinal cord segments, CGRP levels increased, with peak effects observed at day 20 of gestation. CGRP mRNA synthesis increased in DRG over pregnancy. Sensory neurons of ovariectomized rats treated with estrogen showed increased CGRP mRNA synthesis in a dose-related manner, an effect blocked by the ER antagonist ICI 182 780. From these results, we postulate that synthesis of CGRP in L6-S1 DRG and utilization in the cervix increase over pregnancy and this synthesis is the under influence of the estrogen-ER system. Collectively, these data are consistent with the hypothesis that CGRP plays a role in cervical ripening and, consequently in the birth process.

Effects of steroid hormones on calcitonin gene-related peptide receptors in cultured human myometrium

OBJECTIVE

This study was designed to examine whether, with the use of human myometrial explants in culture, calcitonin gene-related peptide B receptors are regulated by steroid hormones.

STUDY DESIGN

Myometrial tissues were obtained from the lower uterine segments from women in a nonpregnant state and pregnant women who were not in labor undergoing cesarean delivery (39.1 +/- 0.2 weeks of gestation). Tissues were incubated in Dulbecco's modified Eagle's medium without phenol red, with either 17beta-estradiol (10(-9), 10(-8), 10(-7) mol/L), progesterone (10(-8), 10(-7), 10(-6) mol/L), or in a combination of 17beta-estradiol (10(-8) mol/L) and progesterone (10(-7) mol/L). Reverse transcriptase-polymerase chain reaction was performed to examine the expression of estrogen receptor-alpha, progesterone receptor, and Western blotting was used for calcitonin gene-related peptide B receptor protein measurement in the myometrium.

RESULTS

We found that (1) messenger RNA expression for both estrogen receptor-alpha and progesterone receptor in nonpregnant myometrium significantly declined within 48 hours explant culture; (2) estrogen receptor-alpha messenger RNA levels in the pregnant myometrium were 98.6%, 95.3%, and 89.8% at 12, 24, and 48 hours of incubation, respectively; (3) the levels of messenger RNA for progesterone receptor in the pregnant myometrium were 96.2%, 93.3%, 90.1%, at 12, 24, and 48 hours of incubation, respectively; (4) the 17beta-estradiol dose dependently inhibited calcitonin gene-related peptide B receptor protein in pregnant myometrium explant culture; (5) the progesterone dose dependently increased calcitonin gene-related peptide B receptor expression in pregnant myometrium explant culture; (6) the combined treatment with 17beta-estradiol (10(-8) mol/L) and progesterone (10(-7) mol/L) further enhanced myometrial calcitonin gene-related peptide B receptor protein expression.

CONCLUSION

We conclude from this study that (1) the messenger RNA expression of estrogen receptor-alpha and progesterone receptor in pregnant myometrium were maintained at relatively high levels (>89%) within 48 hours incubation and that this may be useful for in vitro studies that are designed to evaluate the effects of sex steroids on the human myometrium during pregnancy and that (2) estrogen inhibits and progesterone stimulates the expression of calcitonin gene-related peptide B receptors in cultured pregnant myometrial explants. We suggest that steroid hormone-regulated calcitonin gene-related peptide B receptor expression could underlie differential myometrial sensitivity to calcitonin gene-related peptide-induced relaxation.

Evidence for the existence of a new receptor for CGRP, which is not CRLR

Receptors for calcitonin gene-related peptide (CGRP), a neuropeptide known to be the most potent vasodilator, are abundantly expressed in cerebellum. A monoclonal antibody to cerebellar CGRP receptors specifically detects a 66 kDa protein from rat cerebellum and other rat and human tissues, but not from SK-N-MC cells which express calcitonin receptor-like receptor (CRLR), a recently described component of CGRP receptors. In contrast, mRNA expression for CRLR was abundant in SK-N-MC cells, but it was undetectable in rat cerebellum. Furthermore, the antibody could not detect any immunoreactive protein in HEK 293 cells transiently transfected with CRLR and receptor activity-modifying protein 1 (RAMP(1)) indicating the possible existence of another CGRP receptor, which does not involve CRLR. Due to the absence of biochemical or structural data on the existence of a CGRP(2) receptor and the new data provided in this paper, we suggest to identify the two CGRP receptors as CGRP-A and CGRP-B.