Calcitonin gene-related peptide (CGRP) in autonomic cardiovascular regulation and vascular structure

Lack of alpha CGRP exacerbates the development of atherosclerosis in ApoE-knockout mice

The effects of calcitonin gene-related peptide (CGRP) on atherosclerosis remain unclear. We used apolipoprotein E-deficient (ApoE-/-) mice to generate double-knockout ApoE-/-:CGRP-/- mice lacking alpha CGRP. ApoE-/-:CGRP-/- mice exhibited larger atherosclerotic plaque areas, peritoneal macrophages with enhanced migration functions, and elevated levels of the inflammatory cytokine tumor necrosis factor (TNF)-⍺. Thus, we also explored whether inhibiting TNF-⍺ could improve atherosclerosis in ApoE-/-:CGRP-/- mice by administering etanercept intraperitoneally once a week (5 mg/kg) alongside a high-fat diet for 2 weeks. This treatment led to significant reductions in aortic root lesion size, atherosclerotic plaque area and macrophage migration in ApoE-/-:CGRP-/- mice compared with mice treated with human IgG (5 mg/kg). We further examined whether results observed in ApoE-/-:CGRP-/- mice could similarly be obtained by administering a humanized monoclonal CGRP antibody, galcanezumab, to ApoE-/- mice. ApoE-/- mice were subcutaneously administered galcanezumab at an initial dose of 50 mg/kg, followed by a dose of 30 mg/kg in the second week. Galcanezumab administration did not affect systolic blood pressure, serum lipid levels, or macrophage migration but led to a significant increase in lipid deposition at the aortic root. These findings suggest that alpha CGRP plays a critical role in inhibiting the progression of atherosclerosis.

Migraine as an allostatic reset triggered by unresolved interoceptive prediction errors

Until now, a satisfying account of the cause and purpose of migraine has remained elusive. We explain migraine within the frameworks of allostasis (the situationally-flexible, forward-looking equivalent of homeostasis) and active inference (interacting with the environment via internally-generated predictions). Due to its multimodality, and long timescales between cause and effect, allostasis is inherently prone to catastrophic error, which might be impossible to correct once fully manifest, an early indicator which is elevated prediction error (discrepancy between prediction and sensory input) associated with internal sensations (interoception). Errors can usually be resolved in a targeted manner by action (correcting the physiological state) or perception (updating predictions in light of sensory input); persistent errors are amplified broadly and multimodally, to prioritise their resolution (the migraine premonitory phase); finally, if still unresolved, progressive amplification renders further changes to internal or external sensory inputs intolerably intense, enforcing physiological stability, and facilitating accurate allostatic prediction updating. As such, migraine is an effective 'failsafe' for allostasis, however it has potential to become excessively triggered, therefore maladaptive.

The vascular role of CGRP: a systematic review of human studies

Intravenous infusion of human alpha calcitonin gene-related peptide (h-α-CGRP) has been applied to explore migraine pathogenesis and cerebral hemodynamics during the past three decades. Cumulative data implicate h-α-CGRP in regulating the vascular tone. In this systematic review, we searched PubMed and EMBASE for clinical studies investigating the vascular changes upon intravenous infusion of h-α-CGRP in humans. A total of 386 studies were screened by title and abstract. Of these, 11 studies with 61 healthy participants and 177 participants diagnosed with migraine were included. Several studies reported hemodynamic effects including flushing, palpitation, warm sensation, heart rate (HR), mean arterial blood pressure (MABP), mean blood flow velocity of middle cerebral artery (mean V_MCA), and diameter of superficial temporal artery (STA). Upon the start of h-α-CGRP infusion, 163 of 165 (99%) participants had flushing, 98 of 155 (63%) participants reported palpitation, and 160 of 165 (97%) participants reported warm sensation. HR increased with 14%-58% and MABP decreased with 7%-12%. The mean V_MCA was decreased with 9.5%-21%, and the diameter of the STA was dilated with 41%-43%. The vascular changes lasted from 20 to >120 min. Intravenous infusion of h-α-CGRP caused a universal vasodilation without any serious adverse events. The involvement of CGRP in the systemic hemodynamic raises concerns regarding long-term blockade of CGRP in migraine patients with and without cardiovascular complications.

Serotonergic Modulation of Neurovascular Transmission: A Focus on Prejunctional 5-HT Receptors/Mechanisms

5-Hydroxytryptamine (5-HT), or serotonin, plays a crucial role as a neuromodulator and/or neurotransmitter of several nervous system functions. Its actions are complex, and depend on multiple factors, including the type of effector or receptor activated. Briefly, 5-HT can activate: (i) metabotropic (G-protein-coupled) receptors to promote inhibition (5-HT₁, 5-HT₅) or activation (5-HT₄, 5-HT₆, 5-HT₇) of adenylate cyclase, as well as activation (5-HT₂) of phospholipase C; and (ii) ionotropic receptor (5-HT₃), a ligand-gated Na⁺/K⁺ channel. Regarding blood pressure regulation (and beyond the intricacy of central 5-HT effects), this monoamine also exerts direct postjunctional (on vascular smooth muscle and endothelium) or indirect prejunctional (on autonomic and sensory perivascular nerves) effects. At the prejunctional level, 5-HT can facilitate or preclude the release of autonomic (e.g., noradrenaline and acetylcholine) or sensory (e.g., calcitonin gene-related peptide) neurotransmitters facilitating hypertensive or hypotensive effects. Hence, we cannot formulate a specific impact of 5-HT on blood pressure level, since an increase or decrease in neurotransmitter release would be favoured, depending on the type of prejunctional receptor involved. This review summarizes and discusses the current knowledge on the prejunctional mechanisms involved in blood pressure regulation by 5-HT and its impact on some vascular-related diseases.

Somatosensory innervation of adipose tissues

The increasing prevalence of obesity and type 2 diabetes has led to a greater interest in adipose tissue physiology. Adipose tissue is now understood as an organ with endocrine and thermogenic capacities in addition to its role in fat storage. It plays a critical role in systemic metabolism and energy regulation, and its activity is tightly regulated by the nervous system. Fat is now recognized to receive sympathetic innervation, which transmits information from the brain, as well as sensory innervation, which sends information into the brain. The role of sympathetic innervation in adipose tissue has been extensively studied. However, the extent and the functional significance of sensory innervation have long been unclear. Recent studies have started to reveal that sensory neurons robustly innervate adipose tissue and play an important role in regulating fat activity. This brief review will discuss both historical evidence and recent advances, as well as important remaining questions about the sensory innervation of adipose tissue.

Impairment on Cardiovascular Autonomic Modulation in Women with Migraine

Autonomic dysfunction, such as reduced vagally mediated heart rate variability, has been suggested in headache patients but is still uncertain when considering primary headache disorders. This study aims to compare the heart rate and blood pressure variability and baroreflex sensitivity between women with migraine and controls. A migraine (n = 20) and a control group (n = 20) of age-matched women without headache were evaluated. Heart rate variability was analyzed through frequency-domain using spectral analysis presenting variance, low-frequency (LF; 0.04-0.15 Hz) and high-frequency (HF; 0.15-0.4 Hz) bands and by time domain (root mean square of successive R-R interval differences, RMSSD). Blood pressure variability was analyzed with spectral analysis and baroreflex sensitivity with the sequence method. Migraine group had lower heart rate variability characterized by a reduction in total variance, LF oscillations (sympathetic/vagal modulation) and HF oscillations (vagal modulation), and a reduction in SD and RMSSD compared to control group. No difference was found in the blood pressure variability analysis. Regarding baroreflex sensitivity, migraine group had decreased values of total gain, gain down and up compared to control group. Women with migraine exhibited autonomic modulation alterations, expressed by decreased values of heart rate variability and baroreflex sensitivity, but not by differences in blood pressure variability.

Blood Pressure in Patients With Migraine Treated With Monoclonal Anti-CGRP (Receptor) Antibodies: A Prospective Follow-up Study

BACKGROUND AND OBJECTIVES

Anti-calcitonin gene-related peptide (CGRP) (receptor) antibodies are approved as preventive treatment for migraine. Recent concerns have been raised after a retrospective analysis of postmarketing case reports of elevated blood pressure (BP) associated with erenumab. In this prospective follow-up study, we aimed to assess the safety regarding BP in a real-world setting.

METHODS

All people with migraine who were treated with erenumab and fremanezumab at the Leiden Headache Center between January 2019 and January 2021 were included. BP measurements were collected from baseline (T0) until 12 months of follow-up, with a 3-month interval (T1-T4). Mixed linear models were fitted with time as a fixed effect and the patient as a random effect.

RESULTS

Both systolic and diastolic BP were increased at all time points T1-T4 compared with T0 (p < 0.001). The maximum estimated increase in the mean systolic BP was 5.2 mm Hg (95% CI 3.1-7.5). The maximum estimated increase in the mean diastolic BP was 3.5 mm Hg (95% CI 2.0-4.9). In the erenumab group (n = 109), both systolic and diastolic BP were increased at all time points compared with T0 (all p < 0.001). For fremanezumab (n = 87), systolic but not diastolic BP was increased compared with T0 at T1 (p = 0.006) and T2 (p = 0.004). Four patients (3.7%) with normal BP at T0 required antihypertensive treatment after erenumab was started.

DISCUSSION

The mean systolic and diastolic BP increased after anti-CGRP (receptor) antibodies were started. The majority of patients remained within the normal BP limits, but some patients required antihypertensive treatment. Physicians should be aware that people with migraine may be at risk of developing hypertension when treated with anti-CGRP (receptor) antibodies, and this should be added to (inter)national treatment guidelines.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that anti-CGRP (receptor) antibodies increase BP when used to treat patients with migraine.

The Vascular-Dependent and -Independent Actions of Calcitonin Gene-Related Peptide in Cardiovascular Disease

The treatment of hypertension and heart failure remains a major challenge to healthcare providers. Despite therapeutic advances, heart failure affects more than 26 million people worldwide and is increasing in prevalence due to an ageing population. Similarly, despite an improvement in blood pressure management, largely due to pharmacological interventions, hypertension remains a silent killer. This is in part due to its ability to contribute to heart failure. Development of novel therapies will likely be at the forefront of future cardiovascular studies to address these unmet needs. Calcitonin gene-related peptide (CGRP) is a 37 amino acid potent vasodilator with positive-ionotropic and -chronotropic effects. It has been reported to have beneficial effects in hypertensive and heart failure patients. Interestingly, changes in plasma CGRP concentration in patients after myocardial infarction, heart failure, and in some forms of hypertension, also support a role for CGRP on hemodynamic functions. Rodent studies have played an important role thus far in delineating mechanisms involved in CGRP-induced cardioprotection. However, due to the short plasma half-life of CGRP, these well documented beneficial effects have often proven to be acute and transient. Recent development of longer lasting CGRP agonists may therefore offer a practical solution to investigating CGRP further in cardiovascular disease in vivo. Furthermore, pre-clinical murine studies have hinted at the prospect of cardioprotective mechanisms of CGRP which is independent of its hypotensive effect. Here, we discuss past and present evidence of vascular-dependent and -independent processes by which CGRP could protect the vasculature and myocardium against cardiovascular dysfunction.

Monoaminergic Receptors as Modulators of the Perivascular Sympathetic and Sensory CGRPergic Outflows

Blood pressure is a highly controlled cardiovascular parameter that normally guarantees an adequate blood supply to all body tissues. This parameter is mainly regulated by peripheral vascular resistance and is maintained by local mediators (i.e., autacoids), and by the nervous and endocrine systems. Regarding the nervous system, blood pressure can be modulated at the central level by regulating the autonomic output. However, at peripheral level, there exists a modulation by activation of prejunctional monoaminergic receptors in autonomic- or sensory-perivascular fibers. These modulatory mechanisms on resistance blood vessels exert an effect on the release of neuroactive substances from the autonomic or sensory fibers that modify blood pressure. Certainly, resistance blood vessels are innervated by perivascular: (i) autonomic sympathetic fibers (producing vasoconstriction mainly by noradrenaline release); and (ii) peptidergic sensory fibers [producing vasodilatation mainly by calcitonin gene-related peptide (CGRP) release]. In the last years, by using pithed rats, several monoaminergic mechanisms for controlling both the sympathetic and sensory perivascular outflows have been elucidated. Additionally, several studies have shown the functions of many monoaminergic auto-receptors and hetero-receptors expressed on perivascular fibers that modulate neurotransmitter release. On this basis, the present review: (i) summarizes the modulation of the peripheral vascular tone by adrenergic, serotoninergic, dopaminergic, and histaminergic receptors on perivascular autonomic (sympathetic) and sensory fibers, and (ii) highlights that these monoaminergic receptors are potential therapeutic targets for the development of novel medications to treat cardiovascular diseases (with some of them explored in clinical trials or already in clinical use).

Independent association of palpitation with vasomotor symptoms and anxiety in middle-aged women

OBJECTIVE

Palpitation, or the sensation of rapid or irregular heartbeats, is common in menopausal women; however, the precise underlying mechanisms are unknown. We aimed to investigate factors associated with palpitation in middle-aged women.

METHODS

Medical records of 394 women aged 40 to 59 years (108 premenopausal, 85 perimenopausal, and 201 postmenopausal) were analyzed cross-sectionally. Palpitation severity was estimated based on responses to the Menopausal Symptom Scale. Effects of background characteristics, including age, menopausal status, body composition, cardiovascular parameters, basal metabolism, physical fitness, lifestyle factors, vasomotor, and psychological symptoms on palpitation were assessed using multivariate logistic regression analysis. The association between autonomic nervous system activity and palpitation was also analyzed in 198 participants.

RESULTS

Prevalence of palpitation by severity was as follows: none, 26.4%; mild, 32.7%; moderate, 29.4%; severe, 11.4%. In univariate analyses, the more severely the women were affected by palpitation, 1) the higher their systolic blood pressure, 2) the less exercise they performed, 3) the lower they scored in the sit-and-reach test, 4) the higher their vasomotor symptoms score in the Menopausal Health Related-Quality of Life questionnaire, and 5) the higher their Hospital Anxiety and Depression Scale. Multiple logistic regression analysis revealed that moderate to severe palpitation was independently associated with the vasomotor symptom score (adjusted odds ratio [95% confidence interval]: 1.18 [1.07-1.31]) and Hospital Anxiety and Depression Scale anxiety subscale score (1.19 [1.12-1.27]).

CONCLUSIONS

Rapid or irregular heartbeats are highly prevalent in middle-aged women. It is not associated with age, menopausal status, heart rate, arrhythmia, autonomic nervous system activity, caffeine, or alcohol consumption, but with vasomotor symptoms and anxiety.

[Novel migraine treatment with CGRP-related monoclonal antibodies]

Migraine is a common and debilitating neurological disorder characterized by recurrent attacks of moderate to severe throbbing headache accompanied by nausea, vomiting and photophobia/phonophobia. Because of its high prevalence, migraine causes a considerable financial burden on the society as well as impaired quality of life in individual patients. Scientific evidence shows that migraine is a quite complex neurological disorder that involves not only the trigeminovascular and autonomic systems but also the hypothalamus and cerebral cortex. Calcitonin gene-related peptide (CGRP) was originally discovered as a 37-amino acid neuropeptide derived from a calcitonin gene splicing variant. CGRP is found to be expressed in trigeminal ganglion neurons. Much attention has been attracted to this molecule since CGRP was found to be released from trigeminal terminals in animal migraine models. Subsequent studies demonstrated that CGRP administration induced migraine-like headache attacks specifically in migraineurs, thus highlighting a pivotal role of CGRP in the development of migraine attacks. Several CGRP receptor antagonists were shown to be efficacious for the treatment of acute migraine. Among them, telcagepant, was shown to exert a significant migraine prophylactic action as well. Nevertheless, the development of most of these agents were discontinued due to hepatotoxicity. Currently, newer CGRP receptor antagonists are being developed. On the other hand, monoclonal antibodies targeting CGRP and its receptor showed consistent efficacy for migraine prophylaxis with excellent safety profiles in Phase III clinical trials. Furthermore, emerging data support the long-term safety and efficacy of these antibodies. In this review article, the development and perspective of anti-migraine therapeutic strategies using CGRP-related antibodies are discussed.

Emerging Role of Compartmentalized G Protein-Coupled Receptor Signaling in the Cardiovascular Field

G protein-coupled receptors (GPCRs) are cell surface receptors that for many years have been considered to function exclusively at the plasma membrane, where they bind to extracellular ligands and activate G protein signaling cascades. According to the conventional model, these signaling events are rapidly terminated by β-arrestin (β-arr) recruitment to the activated GPCR resulting in signal desensitization and receptor internalization. However, during the past decade, emerging evidence suggest that many GPCRs can continue to activate G proteins from intracellular compartments after they have been internalized. G protein signaling from intracellular compartments is in general more sustained compared to G protein signaling at the plasma membrane. Notably, the particular location closer to the nucleus is beneficial for selective cellular functions such as regulation of gene transcription. Here, we review key GPCRs that undergo compartmentalized G protein signaling and discuss molecular considerations and requirements for this signaling to occur. Our main focus will be on receptors involved in the regulation of important physiological and pathological cardiovascular functions. We also discuss how sustained G protein activation from intracellular compartments may be involved in cellular functions that are distinct from functions regulated by plasma membrane G protein signaling, and the corresponding significance in cardiovascular physiology.

Renal denervation restrains the inflammatory response in myocardial ischemia-reperfusion injury

Myocardial ischemia-reperfusion (I/R) injury leads to intensive sympathetic nervous system (SNS) activation and inflammatory reactions. Whether renal sympathetic denervation (RDN) could be a new therapeutic strategy to modulate I/R inflammation and reduce infarct size after myocardial I/R injury needs to be explored. First, we investigated the correlation between plasma norepinephrine concentrations and circulating myeloid cell numbers in patients with acute myocardial infarction. And then, C57BL/6 mice underwent a "two-hit" operation, with 10% phenol applied to bilateral renal nerves to abrogate sympathoexcitation, and a 45-min ligation of the left coronary artery to induce myocardial I/R injury. The effects of RDN on the mobilization of immune cells in mice following myocardial I/R injury were explored. We observed a strong association between SNS overactivation and myeloid cell excessive accumulation in patients. In animal experiments, there was a significant reduction in infarct size per area at risk in the denervated-I/R group when compared to that of the innervated-I/R group (39.2% versus 49.8%; p < 0.005), and RDN also improved the left ventricular ejection fraction by 20% after 1 week. Furthermore, the denervated-I/R group showed a decrease in the number of neutrophils and macrophages in the blood and the myocardium as reflected by immunohistochemical staining and flow cytometry analysis (p < 0.05); the decrease was associated with a significant reduction in the circulating production of IL-1, IL-6 and TNF-α (p < 0.05). In summary, our study reveals a novel link between the SNS activity and inflammatory response undergoing myocardium I/R injury and identifies RDN as a potential therapeutic strategy against myocardium I/R injury via preserving the spleen immune cells mobilization.

Characterisation of the calcitonin gene-related peptide receptor antagonists ubrogepant and atogepant in human isolated coronary, cerebral and middle meningeal arteries

BACKGROUND

Migraine has been associated with a dysfunctional activation of the trigeminovascular system. Calcitonin gene-related peptide, a neuropeptide released from the trigeminal nerve fibres, has an important role in the pathophysiology of migraine and is a current therapeutic target for migraine treatment.

METHODS

We examined the effects of two novel calcitonin gene-related peptide receptor antagonists, ubrogepant and atogepant, on the relaxations induced by α calcitonin gene-related peptide in human isolated middle meningeal, cerebral and coronary arteries. Furthermore, the contractile responses to atogepant and ubrogepant per se were studied and compared to the responses elicited by zolmitriptan in proximal and distal human coronary arteries.

RESULTS

In intracranial arteries, both blockers antagonized the calcitonin gene-related peptide-induced relaxations more potently when compared to the inhibition observed in distal human coronary arteries, with atogepant showing a higher potency. When analysing their antagonistic profile in HCA, ubrogepant showed a competitive antagonist profile, while atogepant showed a non-competitive one. Neither of the gepants had vasoconstrictor effect at any of the concentrations studied in human coronary arteries, whereas zolmitriptan elicited concentration-dependent contractions.

CONCLUSION

ubrogepant and atogepant differentially inhibit the calcitonin gene-related peptide-dependent vasodilatory responses in intracranial arteries when compared to distal human coronary arteries. Also, both gepants are devoid of vasoconstrictive properties in human coronary arteries.

Circadian Variation in Vasoconstriction and Vasodilation Mediators and Baroreflex Sensitivity in Hypertensive Rats

The purpose of this study was to evaluate the relationship between the circadian profile of the vasorelaxing substances calcitonin gene-related peptide (CGRP) and epoxyeicosatrienoic acids (EETs) and the vasconstrictive agent endothelin-1 (ET1) and the daily rhythms of cardiac hemodynamic indices (CHI) and baroreflex (BRS) in Wistar rats with 1 kidney-1 clip model of arterial hypertension (1K-1C AH). The animals were divided into 3 groups: I- sham-operated (SO), II- 4-week and III- 8-week 1K-1C AH rats. Plasma concentration of ET1, CGRP and EET’s were investigated every 4 h. In conscious freely moving 1K-1C AH rats unlike SO animals blood pressure (BP), heart period (HP) and BRS underwent significant circadian fluctuations, with more marked increase in mean values of BP in 8-week hypertensive rats in comparison to 4-week hypertensive rats (179 ± 5 vs. 162 ± 4 mm Hg, p < 0.05). These alterations correlated with more significant reduction in HP (138 ± 5 vs. 150 ± 6 ms, p < 0,05) and BRS (0.44 ± 0.04 vs. 0.58 ± 0.04 ms mm Hg^–1, p < 0.05) in 8-week 1K-1C AH rats. The acrophases of BP in 8-week 1K-1C AH rats in comparison with 4-week were shifted to more late night hours (1:58 a.m. vs. 11:32 p.m.) and in both groups of animals corresponded to lowest circadian plasma levels of CGRP and EETs and to greatest level of ET1. SO rats were characterized by lower values of BP (121 ± 3 mm Hg, p < 0,05) and higher indices of HP (158 ± 2 ms, p < 0,05) and BRS (0.86 ± 0.02 ms mmHg^–1, p < 0,001) in comparison with 1K-1C AH rats 4-week duration. The acrophases of BP, HP and BRS in hypertensive animals were revealed at 14.8 ± 0.5 h, 13.6 ± 0.4 h and 13.1 ± 0.2 h, which correlated with maximal circadian contents of ET1 and CGRP at 24:00 h and EETs at 12:00 h and were shifted in comparison to sham-operated group. In rats with 1K-1C AH, plasma levels of ET1, CGRP and EETs undergo circadian fluctuation with corresponding alterations in CHI and BRS which are more markedly expressed on the late stage of diseases and could be used in future for predictive, preventive, and personalized treatment of arterial hypertension.

Functional Characterization of the Prejunctional Receptors Mediating the Inhibition by Ergotamine of the Rat Perivascular Sensory Peptidergic Drive

Calcitonin gene-related peptide (α-CGRP) released from perivascular sensory nerves induces decreases in diastolic blood pressure (DBP). Experimentally, this can be shown by spinal thoracic (T₉-T₁₂) electrical stimulation of these afferent fibers. Because ergotamine inhibits these neurogenic vascular responses and displays affinity for monoaminergic receptors that inhibit neurotransmitter release, we investigated whether this ergotamine-induced inhibition results from activation of serotonin 5-HT_1B/1D, dopamine D₂-like, and α₂-adrenergic receptors. Wistar rats were pithed and, under autonomic ganglion blockade, received intravenous infusions of methoxamine followed by ergotamine (0.1-3.1 μg kg^-1 min^-1). Thoracic T₉-T₁₂ electrical stimulation or an intravenous bolus of α-CGRP resulted in decreases in DBP. Ergotamine inhibited the electrically induced, but not α-CGRP-induced, responses. The vasodilator sensory inhibition by 3.1 μg of ergotamine kg^-1 min^-1 was resistant to simultaneous blockade of 5-HT_1B/1D, D₂-like, and α₂-adrenergic receptors upon addition of antagonists GR127935, haloperidol, and rauwolscine. Moreover, the inhibition by 0.31 μg of ergotamine kg^-1 min^-1 was unaltered by GR127935 and haloperidol, partly blocked by GR127935 and rauwolscine or rauwolscine and haloperidol, and abolished by GR127935, haloperidol, and rauwolscine. These findings imply that prejunctional 5-HT_1B/1D, D₂-like, and α₂-adrenergic receptors mediate the sensory inhibition induced by 0.31 μg of ergotamine kg^-1 min^-1, whereas larger doses may involve other receptors. Thus, ergotamine's ability to inhibit the perivascular sensory peptidergic drive may result in facilitation of its systemic vasoconstrictor properties.

Increased receptor activity-modifying protein 1 in the nervous system is sufficient to protect against autonomic dysregulation and hypertension

Calcitonin gene-related peptide (CGRP) can cause migraines, yet it is also a potent vasodilator that protects against hypertension. Given the emerging role of CGRP-targeted antibodies for migraine prevention, an important question is whether the protective actions of CGRP are mediated by vascular or neural CGRP receptors. To address this, we have characterized the cardiovascular phenotype of transgenic nestin/hRAMP1 mice that have selective elevation of a CGRP receptor subunit in the nervous system, human receptor activity-modifying protein 1 (hRAMP1). Nestin/hRAMP1 mice had relatively little hRAMP1 RNA in blood vessels and intravenous injection of CGRP caused a similar blood pressure decrease in transgenic and control mice. At baseline, nestin/hRAMP1 mice exhibited similar mean arterial pressure, heart rate, baroreflex sensitivity, and sympathetic vasomotor tone as control mice. We previously reported that expression of hRAMP1 in all tissues favorably improved autonomic regulation and attenuated hypertension induced by angiotensin II (Ang II). Similarly, in nestin/hRAMP1 mice, hypertension caused by Ang II or phenylephrine was greatly attenuated, and associated autonomic dysregulation and increased sympathetic vasomotor tone were diminished or abolished. We conclude that increased expression of neuronal CGRP receptors is sufficient to induce a protective change in cardiovascular autonomic regulation with implications for migraine therapy.

CGRP in a gene-environment interaction model for depression: effects of antidepressant treatment

OBJECTIVE

Genetic and environmental factors interact in the development of major depressive disorder (MDD). While neurobiological correlates have only partially been elucidated, altered levels of calcitonin gene-related peptide (CGRP)-like immunoreactivity (LI) in animal models and in the cerebrospinal fluid of depressed patients were reported, suggesting that CGRP may be involved in the pathophysiology and/or be a trait marker of MDD. However, changes in CGRP brain levels resulting from interactions between genetic and environmental risk factors and the response to antidepressant treatment have not been explored.

METHODS

We therefore superimposed maternal separation (MS) onto a genetic rat model (Flinders-sensitive and -resistant lines, FSL/FRL) of depression, treated these rats with antidepressants (escitalopram and nortriptyline) and measured CGRP-LI in selected brain regions.

RESULTS

CGRP was elevated in the frontal cortex, hippocampus and amygdala (but not in the hypothalamus) of FSL rats. However, MS did not significantly alter levels of this peptide. Likewise, there were no significant interactions between the genetic and environmental factors. Most importantly, neither escitalopram nor nortriptyline significantly altered brain CGRP levels.

CONCLUSION

Our data demonstrate that increased brain levels of CGRP are present in a well-established rat model of depression. Given that antidepressants have virtually no effect on the brain level of this peptide, our study indicates that further research is needed to evaluate the functional role of CGRP in the FSL model for depression.

Understanding CGRP and Cardiovascular Risk

Increasing knowledge about the role of calcitonin gene-related peptide (CGRP) in migraine pathophysiology has led to the development of antibodies against this peptide or its receptor. However, CGRP is widely expressed throughout the body, participating not only in pathophysiological conditions but also in several physiological processes and homeostatic responses during pathophysiological events. Therefore, in this chapter, the risks of long-term blockade of the CGRP pathway will be discussed, with focus on the cardiovascular system, as this peptide has been described to have a protective role during ischemic events, and migraine patients present a higher risk of stroke and myocardial infarction.

Effects of capsaicin-induced sensory denervation on early implant osseointegration in adult rats

The presence of nerve endings around implants is well-known, but the interaction between the peripheral nervous system and the osseointegration of implants has not been thoroughly elucidated to date. The purpose of this study was to test the effects of selective sensory denervation on early implant osseointegration. Forty male Sprague-Dawley rats were divided randomly into two groups, group A and group B, and they were treated with capsaicin and normal saline, respectively. One week later, titanium implants were placed in the bilateral femurs of the rats. Three and six weeks after implantation, histological examination, microcomputed tomography and biomechanical testing were performed to observe the effect of sensory denervation on implant osseointegration. At three weeks and six weeks, bone area, trabecular bone volume/total bone volume and bone density were significantly lower in group A than in group B. Similarly, the bone-implant contact rate, trabecular number and trabecular thickness were clearly lower in group A than in group B at three weeks. However, the trabecular separation spacing in group A was greater than that in group B at both time points. Biomechanical testing revealed that the implant-bone binding ability of group A was significantly lower than that in group B. The research demonstrated that sensory innervation played an important role in the formation of osseointegration. Selective-sensory denervation could reduce osseointegration and lower the binding force of the bone and the implant.

Cortical bone is an extraneuronal site of norepinephrine uptake in adult mice

The sympathetic nervous system is a major efferent pathway through which the central nervous system controls the function of peripheral organs. Genetic and pharmacologic evidence in mice indicated that stimulation of the β2 adrenergic receptor (β2AR) in osteoblasts promotes bone loss, leading to the paradigm that high sympathetic nervous activity is deleterious to bone mass. However, considerably less data exist to understand the putative impact of endogenous norepinephrine (NE), released by sympathetic nerves, on bone homeostasis. In this study, we investigated the in vivo expression and activity of the norepinephrine transporter (NET), a membrane pump known to actively uptake NE from the extracellular space in presynaptic neurons. Consistent with previously published in vitro data showing NET uptake activity in differentiated osteoblasts, we were able to detect active NET-specific NE uptake in the mouse cortical bone compartment in vivo. This uptake was the highest in young mice and accordingly with an age-related reduction in NET uptake, NE bone content increased whereas Net RNA and protein expression decreased with age. Histologically, NET expression in adult mouse bones was detected in osteocytes via immunofluorescence. Lastly, taking advantage of tissue-specific fluorescent reporter mice, we used CLARITY imaging and light sheet microscopy to visualize the 3D distribution of sympathetic fibers in whole mount preparations of bone tissues. These analyses allowed us to detect tyrosine hydroxylase (TH)-positive sympathetic nerve fibers penetrating the cortical bone, where NET+ osteocytes reside. Together, these in vitro results support the existence of an age-dependent extraneuronal and osteocytic function of NET with potential to buffer the bone catabolic action of endogenous NE released by sympathetic nerves in vivo.

The Role of Calcitonin Gene Related Peptide (CGRP) in Neurogenic Vasodilation and Its Cardioprotective Effects

Calcitonin gene-related peptide (CGRP) is a highly potent vasoactive peptide released from sensory nerves, which is now proposed to have protective effects in several cardiovascular diseases. The major α-form is produced from alternate splicing and processing of the calcitonin gene. The CGRP receptor is a complex composed of calcitonin like receptor (CLR) and a single transmembrane protein, RAMP1. CGRP is a potent vasodilator and proposed to have protective effects in several cardiovascular diseases. CGRP has a proven role in migraine and selective antagonists and antibodies are now reaching the clinic for treatment of migraine. These clinical trials with antagonists and antibodies indicate that CGRP does not play an obvious role in the physiological control of human blood pressure. This review discusses the vasodilator and hypotensive effects of CGRP and the role of CGRP in mediating cardioprotective effects in various cardiovascular models and disorders. In models of hypertension, CGRP protects against the onset and progression of hypertensive states by potentially counteracting against the pro-hypertensive systems such as the renin-angiotensin-aldosterone system (RAAS) and the sympathetic system. With regards to its cardioprotective effects in conditions such as heart failure and ischaemia, CGRP-containing nerves innervate throughout cardiac tissue and the vasculature, where evidence shows this peptide alleviates various aspects of their pathophysiology, including cardiac hypertrophy, reperfusion injury, cardiac inflammation, and apoptosis. Hence, CGRP has been suggested as a cardioprotective, endogenous mediator released under stress to help preserve cardiovascular function. With the recent developments of various CGRP-targeted pharmacotherapies, in the form of CGRP antibodies/antagonists as well as a CGRP analog, this review provides a summary and a discussion of the most recent basic science and clinical findings, initiating a discussion on the future of CGRP as a novel target in various cardiovascular diseases.

Autonomic nervous system dysfunction and sinonasal symptoms

Background

The autonomic nervous system (ANS) richly innervates the nose and paranasal sinuses, and has a significant role in lower airway diseases, e.g., asthma. Nonetheless, its contribution to sinonasal symptoms is poorly understood. This review aimed to explore the complex relationship between the ANS and sinonasal symptoms, with reference to systemic diseases and triggers of ANS dysfunction.

Methods

A review of articles published in English was conducted by searching medical literature databases with the key words “autonomic nervous system” and (“sinusitis” or “nose” or “otolaryngology”). All identified abstracts were reviewed, and, from these, relevant published whole articles were selected.

Results

The ANS has a significant role in the pathophysiologic mechanisms that produce sinonasal symptoms. There was limited evidence that describes the relationship of the ANS in sinonasal disease with systemic conditions, e.g. hypertension. There was some evidence to support mechanisms related to physical and psychological stressors in this relationship.

Conclusion

The role of ANS dysfunction in sinonasal disease is highly complex. The ANS sits within a web of multiple factors, including personality and psychological distress, that contribute to sinonasal symptoms. Further research will help to clarify the etiology of ANS dysfunction and its contribution to common systemic conditions.

Side effects associated with current and prospective antimigraine pharmacotherapies

INTRODUCTION

Migraine is a neurovascular disorder. Current acute specific antimigraine pharmacotherapies target trigeminovascular 5-HT1B/1D, 5-HT1F and CGRP receptors but, unfortunately, they induce some cardiovascular and central side effects that lead to poor treatment adherence/compliance. Therefore, new antimigraine drugs are being explored. Areas covered: This review considers the adverse (or potential) side effects produced by current and prospective antimigraine drugs, including medication overuse headache (MOH) produced by ergots and triptans, the side effects observed in clinical trials for the new gepants and CGRP antibodies, and a section discussing the potential effects resulting from disruption of the cardiovascular CGRPergic neurotransmission. Expert opinion: The last decades have witnessed remarkable developments in antimigraine therapy, which includes acute (e.g. triptans) and prophylactic (e.g. β-adrenoceptor blockers) antimigraine drugs. Indeed, the triptans represent a considerable advance, but their side effects (including nausea, dizziness and coronary vasoconstriction) preclude some patients from using triptans. This has led to the development of the ditans (5-HT1F receptor agonists), the gepants (CGRP receptor antagonists) and the monoclonal antibodies against CGRP or its receptor. The latter drugs represent a new hope in the antimigraine armamentarium, but as CGRP plays a role in cardiovascular homeostasis, the potential for adverse cardiovascular side effects remains latent.

Calcitonin gene-related peptide has protective effect on brain injury induced by heat stroke in rats

Heat stroke often leads to multiple organ dysfunction syndrome (MODS) with a neurological morbidity of 30%. Current studies suggested that pathophysiological responses to heat stroke may be due to a systemic inflammatory response syndrome and a series of peptidergic nerve reactions. The mechanisms underlying the high neurological morbidity in heat stroke have remained largely elusive. In recent years, calcitonin gene-related peptide (CGRP) has been considered to have a positive role in central nervous system injury. The present study investigated the influence of CGRP on brain injury induced by heat stroke. A rat model of heat stroke was established in a pre-warmed artificial climate chamber with a temperature of 35.5±0.5°C and a relative humidity of 60±5%. The rectal core temperature (Tc) was monitored. Heat stress was halted at a Tc of no more than 41°C A bolus injection of CGRP was administered to each rat in the HS+CGRP group and a bolus injection of CGRP8-37 was administered to each rat in the HS+CGRP8-37 group after heat stress. After 2 h, electroencephalograms were recorded and the pathological morphology of brain tissue as well as brain cell apoptosis and caspase-3 protein levels in the brain were measured. The EEG of rats in the HS+CGRP group was characterized by a short- to long-term α-wave and low-voltage β-waves as well as a large amount of intermittent δ- and θ-waves. Compared with the HS group, the θ-wave decreased and the α-wave increased significantly (P<0.05). Slight pathological damage of nerve cells appeared in the HS+CGRP group. Greater damage was observed in HS+CGRP8-37 group with neural cell shrinkage, volume reduction, nuclear pyknosis, disappearance of part of the nuclear membrane and cell necrosis. In the HS+CGRP group, apoptotic cells and caspase-3 protein in the brain were significantly decreased when compared with those in the HS group (P<0.05), while they were significantly increased in the HS+CGRP8-37 group (P<0.05 vs. HS group). The results of the present study reflected that CGRP has a protective effect on early-stage brain injury induced by heat stroke in rats.

Olcegepant blocks neurogenic and non-neurogenic CGRPergic vasodepressor responses and facilitates noradrenergic vasopressor responses in pithed rats

BACKGROUND AND PURPOSE

Olcegepant (BIBN4096BS) is a selective non-peptide CGRP receptor antagonist with acute antimigraine properties. Since systemic vascular tone is modulated by perivascular (primary sensory CGRPergic and sympathetic) nerves, this randomized study investigated in pithed rats the effect of acute i.v. treatment with olcegepant on the neurogenic and non-neurogenic: (i) CGRPergic vasodepressor responses; and (ii) noradrenergic vasopressor responses. The pithed rat is an experimental model predictive of systemic (cardio) vascular side effects.

EXPERIMENTAL APPROACH

Seventy-five male Wistar rats (divided into 15 groups, n = 5 each) were pithed, artificially ventilated and prepared for: (i) spinal stimulation (T₉ -T₁₂ ; 0.56-5.6 Hz) of the sensory CGRPergic vasodepressor outflow or i.v. bolus injections (0.1-1 μg·kg^-1 ) of α-CGRP, substance P or acetylcholine, which induced frequency-dependent or dose-dependent vasodepressor responses; or (ii) spinal stimulation (T₇ -T₉ ; 0.03-3 Hz) of the sympathetic vasopressor outflow or i.v. bolus injections (0.03-3 μg·kg^-1 ) of noradrenaline, which produced frequency-dependent or dose-dependent vasopressor responses.

KEY RESULTS

Olcegepant (1000 and 3000 μg·kg^-1 , i.v.) dose-dependently blocked the vasodepressor responses to sensory nerve stimulation or i.v. α-CGRP, without affecting those to substance P or acetylcholine. Whereas it potentiated the vasopressor responses to sympathetic nerve stimulation or i.v. noradrenaline.

CONCLUSIONS AND IMPLICATIONS

Olcegepant (i.v.) selectively blocked the neurogenic and non-neurogenic CGRPergic vasodepressor responses. This blockade by olcegepant potentiated the neurogenic and non-neurogenic noradrenergic vasopressor responses in pithed rats, an effect that might result in an increased vascular resistance and, consequently, in a prohypertensive action.

Heteroreceptors Modulating CGRP Release at Neurovascular Junction: Potential Therapeutic Implications on Some Vascular-Related Diseases

Calcitonin gene-related peptide (CGRP) is a 37-amino-acid neuropeptide belonging to the calcitonin gene peptide superfamily. CGRP is a potent vasodilator with potential therapeutic usefulness for treating vascular-related disease. This peptide is primarily located on C- and Aδ-fibers, which have extensive perivascular presence and a dual sensory-efferent function. Although CGRP has two major isoforms (α-CGRP and β-CGRP), the α-CGRP is the isoform related to vascular actions. Release of CGRP from afferent perivascular nerve terminals has been shown to result in vasodilatation, an effect mediated by at least one receptor (the CGRP receptor). This receptor is an atypical G-protein coupled receptor (GPCR) composed of three functional proteins: (i) the calcitonin receptor-like receptor (CRLR; a seven-transmembrane protein), (ii) the activity-modifying protein type 1 (RAMP1), and (iii) a receptor component protein (RCP). Although under physiological conditions, CGRP seems not to play an important role in vascular tone regulation, this peptide has been strongly related as a key player in migraine and other vascular-related disorders (e.g., hypertension and preeclampsia). The present review aims at providing an overview on the role of sensory fibers and CGRP release on the modulation of vascular tone.

Specific endothelial heparin-binding EGF-like growth factor deletion ameliorates renal injury induced by chronic angiotensin II infusion

Transactivation of EGF receptor (EGFR) by angiotensin II (Ang II) plays important roles in the initiation and progression of chronic kidney diseases. Studies suggest that heparin-binding EGF-like factor (HB-EGF) may be a critical mediator in this process, but its role in vivo has not been investigated. In the current study, we found that in response to Ang II infusion, kidneys from endothelial HB-EGF deletion mice had significantly reduced EGFR activation compared with controls. Meanwhile, deletion of endothelial HB-EGF expression decreased Ang II infusion related renal injury, as demonstrated by 1) less albuminuria; 2) less glomerulosclerosis; 3) preserved endothelial integrity and decreased podocyte injury, as shown by greater glomerular tuft area and WT1-positive cells, and fewer apoptotic cells measured by cleaved caspase 3 staining; 4) reduced inflammation in the perivascular area and interstitium measured by F4/80 and CD3 immunostaining; and 5) reduced renal fibrosis. In conclusion, our results suggest that shedding of HB-EGF from endothelium plays an important role in Ang II-induced renal injury by linking Ang II-AT1R with EGFR transactivation. Inhibition of HB-EGF shedding could be a potential therapeutic strategy for chronic kidney disease.