Elevated sympathetic nervous activity in mice deficient in alphaCGRP

CGRPβ suppresses the pathogenesis of ulcerative colitis via the immunoproteasome

Various factors have been implicated in the pathogenesis of ulcerative colitis (UC), with immune system failure being the most important one. Calcitonin gene-related peptide (CGRP), a neuropeptide with two isoforms, CGRPα and CGRPβ, has been reported to regulate the immune system. In this study, we investigated the role of CGRP isoforms in UC pathogenesis. We induced UC-like symptoms in CGRPα and CGRPβ knockout (KO) mice using dextran sulphate sodium. Compared to wild-type and CGRPα KO mice, CGRPβ-deficient mice exhibited severe symptoms with increased blood in the stool and diarrhoea. Proteome analysis revealed significant up-regulation of immune-related proteins and immunoproteasome components in CGRPβ-deficient mice, suggesting that an enhanced immune response contributes to the severity of this disease. Treatment with ONX-0914, an immunoproteasome inhibitor, markedly improved these symptoms, highlighting the role of the immunoproteasome in exacerbating UC. This study provides the first evidence that CGRPβ protects against UC by modulating immune responses, particularly those mediated by the immunoproteasome. Our findings suggest that functional differences in CGRP isoforms may influence the severity and management of UC. This insight into the neuro-immune mechanism of UC opens avenues for novel therapies that address both the neural and immune aspects of this disease.

Impact of CGRP monoclonal antibody treatment on blood pressure in patients with migraine: A systematic review and potential clinical implications

BACKGROUND

Monoclonal antibodies targeting calcitonin gene-related peptide (CGRP) or the CGRP-receptor have revolutionized the prevention of migraine. Despite their effectiveness, worries have surfaced regarding potential unwanted cardiovascular effects linked to the vasodilation function of CGRP, suggesting a potential influence on blood pressure (BP).

METHODS

Studies were systematically retrieved from PubMed, Cochrane Database of Systematic Reviews, Web of Science, MEDLINE and EMBASE up to 1 May 2024. We focused on randomized controlled trials and observational cohort or case-control studies examining the impact of anti-CGRP(R)-monoclonal antibodies (mAbs) compared to control treatments on BP in patients with migraine. Two reviewers independently conducted study selection, data extraction and risk of bias assessment.

RESULTS

The literature search yielded 693 articles. After removing duplicates and conducting screening, 22 full-text articles were evaluated, with only four studies meeting the inclusion criteria. Among these, only one study had a low risk of bias and reported elevated BP following initiation of anti-CGRP(R)-mAb treatment.

CONCLUSIONS

Although anti-CGRP(R)-mAbs offer substantial benefits for migraine prevention, the potential risk of increased BP requires attention. Despite the current limited evidence, clinicians are urged to monitor BP of migraine patients undergoing treatment with anti-CGRP(R)-mAbs and to remain aware of the increased risk of cardiovascular events in these patients.

Neuropeptide signalling orchestrates T cell differentiation

The balance between T helper type 1 (TH1) cells and other TH cells is critical for antiviral and anti-tumour responses1-3, but how this balance is achieved remains poorly understood. Here we dissected the dynamic regulation of TH1 cell differentiation during in vitro polarization, and during in vivo differentiation after acute viral infection. We identified regulators modulating T helper cell differentiation using a unique TH1-TH2 cell dichotomous culture system and systematically validated their regulatory functions through multiple in vitro and in vivo CRISPR screens. We found that RAMP3, a component of the receptor for the neuropeptide CGRP (calcitonin gene-related peptide), has a cell-intrinsic role in TH1 cell fate determination. Extracellular CGRP signalling through the receptor RAMP3-CALCRL restricted the differentiation of TH2 cells, but promoted TH1 cell differentiation through the activation of downstream cAMP response element-binding protein (CREB) and activating transcription factor 3 (ATF3). ATF3 promoted TH1 cell differentiation by inducing the expression of Stat1, a key regulator of TH1 cell differentiation. After viral infection, an interaction between CGRP produced by neurons and RAMP3 expressed on T cells enhanced the anti-viral IFNγ-producing TH1 and CD8+ T cell response, and timely control of acute viral infection. Our research identifies a neuroimmune circuit in which neurons participate in T cell fate determination by producing the neuropeptide CGRP during acute viral infection, which acts on RAMP3-expressing T cells to induce an effective anti-viral TH1 cell response.

Vagal TRPV1 + sensory neurons regulate myeloid cell dynamics and protect against influenza virus infection

Influenza viruses are a major global cause of morbidity and mortality. Vagal TRPV1 + nociceptive sensory neurons, which innervate the airways, are known to mediate defenses against harmful agents. However, their function in lung antiviral defenses remains unclear. Our study reveals that both systemic and vagal-specific ablation of TRPV1 + nociceptors reduced survival in mice infected with influenza A virus (IAV), despite no significant changes in viral burden or weight loss. Mice lacking nociceptors showed exacerbated lung pathology and elevated levels of pro-inflammatory cytokines. The increased mortality was not attributable to the loss of the TRPV1 ion channel or neuropeptides CGRP or substance P. Immune profiling through flow cytometry and single-cell RNA sequencing identified significant nociceptor deficiency-mediated changes in the lung immune landscape, including an expansion of neutrophils and monocyte-derived macrophages. Transcriptional analysis revealed impaired interferon signaling in these myeloid cells and an imbalance in distinct neutrophil sub-populations in the absence of nociceptors. Furthermore, anti-GR1-mediated depletion of myeloid cells during IAV infection significantly improved survival, underscoring a role of nociceptors in preventing pathogenic myeloid cell states that contribute to IAV-induced mortality. One Sentence Summary : TRPV1 + neurons facilitate host survival from influenza A virus infection by controlling myeloid cell responses and immunopathology.

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.

Activation of Transient Receptor Potential Vanilloid 1 Is Involved in Both Pain and Tumor Growth in a Mouse Model of Cancer Pain

Activation of calcitonin gene-related peptide (CGRP)-positive sensory neurons in the tumor microenvironment has been shown to be involved in tumor growth. However, how CGRP-positive sensory neurons are activated requires elucidation. In this study, we focused on transient receptor potential vanilloid 1 (TRPV1) and examined the contribution of TRPV1 to tumor growth and cancer pain in a mouse cancer model in which Lewis lung carcinoma was subcutaneously inoculated in the left plantar region. Tumor inoculation gradually increased the volumes of the hind paws of wild type (WT) mice over time, but those of both αCGRP knockout mice and TRPV1 knockout mice were significantly smaller than those of WT mice after tumor inoculation. Both TRPV1 and CGRP are therefore suggested to be involved in tumor growth. In an immunohistochemical study, the percentage of phosphorylated cyclic adenosine monophosphate response element-binding protein (p-CREB)-positive profiles in CGRP-positive dorsal root ganglion (DRG) neurons in WT mice was significantly increased after tumor inoculation. The percentage of p-CREB-positive profiles in CGRP-positive DRG neurons in TRPV1 knockout mice was also increased after tumor inoculation, but was significantly lower than that in WT mice, indicating the contribution of TRPV1 to activation of CGRP-positive DRG neurons. Cancer pain in TRPV1 knockout mice was significantly lower than that in WT mice. In conclusion, TRPV1 is involved in both tumor growth and cancer pain, potentially leading to a novel strategy for the treatment of cancer pain and cancer development. Cancer pain is also suggested to facilitate tumor growth.

Neuronal-immune axis alters pain and sensory afferent damage during dental pulp injury

ABSTRACT

Dental pulp tissue is densely innervated by afferent fibers of the trigeminal ganglion. When bacteria cause dental decay near the pulpal tissue, a strong neuronal and immune response occurs, creating pulpitis, which is associated with severe pain and pulp tissue damage. Neuroimmune interactions have the potential to modulate both the pain and pathological outcome of pulpitis. We first investigated the role of the neuropeptide calcitonin gene-related peptide (CGRP), released from peptidergic sensory afferents, in dental pain and immune responses by using Calca knockout (Calca -/- ) and wild-type (Calca +/+ ) mice, in a model of pulpitis by creating a mechanical exposure of the dental pulp horn. We found that the neuropeptide CGRP, facilitated the recruitment of myeloid cells into the pulp while also increasing spontaneous pain-like behavior 20% to 25% at an early time point. Moreover, when we depleted neutrophils and monocytes, we found that there was 20% to 30% more sensory afferent loss and increased presence of bacteria in deeper parts of the tissue, whereas there was a significant reduction in mechanical pain response scores compared with the control group at a later time point. Overall, we showed that there is a crosstalk between peptidergic neurons and neutrophils in the pulp, modulating the pain and inflammatory outcomes of the disease.

A bone to pick-cellular and molecular mechanisms of bone pain in sickle cell disease

The bone is one of the most commonly affected organs in sickle cell disease (SCD). Repeated ischemia, oxidative stress and inflammation within the bone is largely responsible for promoting bone pain. As more individuals with SCD survive into adulthood, they are likely to experience a synergistic impact of both aging and SCD on their bone health. As bone health deteriorates, bone pain will likely exacerbate. Recent mechanistic and observational studies emphasize an intricate relationship between bone remodeling and the peripheral nervous system. Under pathological conditions, abnormal bone remodeling plays a key role in the propagation of bone pain. In this review, we first summarize mechanisms and burden of select bone complications in SCD. We then discuss processes that contribute to pathological bone pain that have been described in both SCD as well as non-sickle cell animal models. We emphasize the role of bone-nervous system interactions and pitfalls when designing new therapies especially for the sickle cell population. Lastly, we also discuss future basic and translational research in addressing questions about the complex role of stress erythropoiesis and inflammation in the development of SCD bone complications, which may lead to promising therapies and reduce morbidity in this vulnerable population.

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.

Nociceptor neurons direct goblet cells via a CGRP-RAMP1 axis to drive mucus production and gut barrier protection

Neuroepithelial crosstalk is critical for gut physiology. However, the mechanisms by which sensory neurons communicate with epithelial cells to mediate gut barrier protection at homeostasis and during inflammation are not well understood. Here, we find that Nav1.8+CGRP+ nociceptor neurons are juxtaposed with and signal to intestinal goblet cells to drive mucus secretion and gut protection. Nociceptor ablation led to decreased mucus thickness and dysbiosis, while chemogenetic nociceptor activation or capsaicin treatment induced mucus growth. Mouse and human goblet cells expressed Ramp1, receptor for the neuropeptide CGRP. Nociceptors signal via the CGRP-Ramp1 pathway to induce rapid goblet cell emptying and mucus secretion. Notably, commensal microbes activated nociceptors to control homeostatic CGRP release. In the absence of nociceptors or epithelial Ramp1, mice showed increased epithelial stress and susceptibility to colitis. Conversely, CGRP administration protected nociceptor-ablated mice against colitis. Our findings demonstrate a neuron-goblet cell axis that orchestrates gut mucosal barrier protection.

An intersegmental single-cell profile reveals aortic heterogeneity and identifies a novel Malat1+ vascular smooth muscle subtype involved in abdominal aortic aneurysm formation

The developmental origin, anatomical location, and other factors contribute to aortic heterogeneity in a physiological state. On this basis, vascular diseases occur at different ratios based on position specificity, even with the same risk factor. However, the continuous intersegmental aortic profile has been rarely reported at the single-cell level. To reveal aortic heterogeneity, we identified 15 cell subtypes from five continuous aortic segments by marker genes and functional definitions. The EC1 subtype highly expressed Vcam1 and Scarb2 genes in the aortic arch, which were reported to be associated with atherosclerosis. The newly identified Fbn1⁺ fibroblasts were found highly expressed in thoracic segments. More importantly, vascular smooth muscle cells (VSMCs) demonstrated a novel composition in which VSMC 4 marked with the gene Malat1 were mainly distributed in the abdominal segment. Malat1 knockout reduced MMPs and inflammatory factor production induced by Ang II in smooth muscle cells, and the Malat1 inhibitor exerted preventive, inhibitory, and reversing effects on AngII-induced abdominal aortic aneurysm (AAA) in vivo revealed by a series of animal experiments. Single-cell analysis of AngII-induced AAA tissues treated with or without the inhibitor further clarified the key role of Malat1⁺VSMC in the occurrence and progression of AAA. In summary, segmental gene expression and cell subtype features in normal aorta associated with different vascular diseases might provide potential therapeutic targets.

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.

[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.

Adverse effects of erenumab on cerebral proliferative angiopathy: A case report

BACKGROUND

Cerebral proliferative angiopathy is a vascular malformation associated with compromised blood-brain barrier and with migraine-like headache. Treating blood-brain barrier-compromised patients with erenumab, an anti-calcitonin gene-related peptide receptor monoclonal antibody, may be risky.

CASE

We describe a case of a 22-year-old chronic migraine patient with cerebral proliferative angiopathy who presented to our hospital in status epilepticus 2 d after his first dose of erenumab. Serial magnetic resonance imaging (MRI) studies demonstrated progressive areas of diffusion restriction including the brain tissue adjacent to the cerebral proliferative angiopathy, bilateral white matter and hippocampi. His 6-month post-presentation magnetic resonance imaging was notable for white matter injury, encephalomalacia surrounding cerebral proliferative angiopathy and bilateral hippocampal sclerosis. He remains clinically affected with residual symptoms, including refractory epilepsy and cognitive deficits.

CONCLUSION

The evidence presented in this case supports further investigation into potential deleterious side effects of erenumab in patients with compromised blood-brain barrier, such as individuals with intracranial vascular malformations.

Ablation of TRPV1 Elevates Nocturnal Blood Pressure in Western Diet-fed Mice

Background: This study tested the hypothesis that genetically ablation of transient receptor potential vanilloid type 1 (TRPV1) exacerbates impairment of baroreflex in mice fed a western diet (WD) and leads to distinct diurnal and nocturnal blood pressure patterns.

Methods: TRPV1 gene knockout (TRPV1^-/-) and wild-type (WT) mice were given a WD or normal diet (CON) for 4 months.

Results: Capsaicin, a selective TRPV1 agonist, increased ipsilateral afferent renal nerve activity in WT but not TRPV1^-/- mice. The sensitivity of renal sympathetic nerve activity and heart rate responses to baroreflex were reduced in TRPV1^-/--CON and WT-WD and further decreased in TRPV1^-/--WD compared to the WT-CON group. Urinary norepinephrine and serum insulin and leptin at day and night were increased in WT-WD and TRPV1^-/--WD, with further elevation at night in TRPV1^-/--WD. WD intake increased leptin, IL-6, and TNF-α in adipose tissue, and TNF-α antagonist III, R-7050, decreased leptin in TRPV1^-/--WD. The urinary albumin level was higher in TRPV1^-/--WD than WT-WD. Blood pressure was not dif-ferent during daytime among all groups, but increased at night in the TRPV1^-/--WD group compared with other groups.

Conclusions: TRPV1 ablation leads to elevated nocturnal but not diurnal blood pressure, which is probably attributed to fur-ther enhancement of sympathetic drives at night.

Transcriptional Atlas of Intestinal Immune Cells Reveals that Neuropeptide α-CGRP Modulates Group 2 Innate Lymphoid Cell Responses

Signaling abnormalities in immune responses in the small intestine can trigger chronic type 2 inflammation involving interaction of multiple immune cell types. To systematically characterize this response, we analyzed 58,067 immune cells from the mouse small intestine by single-cell RNA sequencing (scRNA-seq) at steady state and after induction of a type 2 inflammatory reaction to ovalbumin (OVA). Computational analysis revealed broad shifts in both cell-type composition and cell programs in response to the inflammation, especially in group 2 innate lymphoid cells (ILC2s). Inflammation induced the expression of exon 5 of Calca, which encodes the alpha-calcitonin gene-related peptide (α-CGRP), in intestinal KLRG1⁺ ILC2s. α-CGRP antagonized KLRG1⁺ ILC2s proliferation but promoted IL-5 expression. Genetic perturbation of α-CGRP increased the proportion of intestinal KLRG1⁺ ILC2s. Our work highlights a model where α-CGRP-mediated neuronal signaling is critical for suppressing ILC2 expansion and maintaining homeostasis of the type 2 immune machinery.

Gut-Innervating Nociceptor Neurons Regulate Peyer's Patch Microfold Cells and SFB Levels to Mediate Salmonella Host Defense

Gut-innervating nociceptor sensory neurons respond to noxious stimuli by initiating protective responses including pain and inflammation; however, their role in enteric infections is unclear. Here, we find that nociceptor neurons critically mediate host defense against the bacterial pathogen Salmonella enterica serovar Typhimurium (STm). Dorsal root ganglia nociceptors protect against STm colonization, invasion, and dissemination from the gut. Nociceptors regulate the density of microfold (M) cells in ileum Peyer's patch (PP) follicle-associated epithelia (FAE) to limit entry points for STm invasion. Downstream of M cells, nociceptors maintain levels of segmentous filamentous bacteria (SFB), a gut microbe residing on ileum villi and PP FAE that mediates resistance to STm infection. TRPV1+ nociceptors directly respond to STm by releasing calcitonin gene-related peptide (CGRP), a neuropeptide that modulates M cells and SFB levels to protect against Salmonella infection. These findings reveal a major role for nociceptor neurons in sensing and defending against enteric pathogens.

Calcitonin Gene-Related Peptide Negatively Regulates Alarmin-Driven Type 2 Innate Lymphoid Cell Responses

Neuroimmune interactions have emerged as critical modulators of allergic inflammation, and type 2 innate lymphoid cells (ILC2s) are an important cell type for mediating these interactions. Here, we show that ILC2s expressed both the neuropeptide calcitonin gene-related peptide (CGRP) and its receptor. CGRP potently inhibited alarmin-driven type 2 cytokine production and proliferation by lung ILC2s both in vitro and in vivo. CGRP induced marked changes in ILC2 expression programs in vivo and in vitro, attenuating alarmin-driven proliferative and effector responses. A distinct subset of ILCs scored highly for a CGRP-specific gene signature after in vivo alarmin stimulation, suggesting CGRP regulated this response. Finally, we observed increased ILC2 proliferation and type 2 cytokine production as well as exaggerated responses to alarmins in mice lacking the CGRP receptor. Together, these data indicate that endogenous CGRP is a critical negative regulator of ILC2 responses in vivo.

CGRP in Animal Models of Migraine

With the approval of calcitonin gene-related peptide (CGRP) and CGRP receptor monoclonal antibodies by the Federal Drug Administration, a new era in the treatment of migraine patients is beginning. However, there are still many unknowns in terms of CGRP mechanisms of action that need to be elucidated to allow new advances in migraine therapies. CGRP has been studied both clinically and preclinically since its discovery. Here we review some of the preclinical data regarding CGRP in animal models of migraine.

Protective Effects of TRPV1 Activation Against Cardiac Ischemia/ Reperfusion Injury is Blunted by Diet-Induced Obesity

BACKGROUND

Activation of Transient Receptor Potential Vanilloid Subtype 1 (TRPV1) channels protects the heart from Ischemia/Reperfusion (I/R) injury through releasing Calcitonin Gene-Related Peptide (CGRP) and Substance P (SP). The current study aimed to study the cardioprotective effects of TRPV1 in obesity.

METHODS

TRPV1 gene knockout (TRPV1-/-) and Wild-Type (WT) mice were Fed a High-Fat Diet (HFD) or a control diet or for 20 weeks, and then the hearts were collected for I/R injury ex vivo. The hearts were mounted on a Langendorff apparatus and subjected to ischemia (30 min) and reperfusion (40 min) after incubated with capsaicin (10 nmol/L), CGRP (0.1 μmol/L) and SP (0.1 μmol/L). Then, Coronary Flow (CF), left ventricular peak positive dP/dt (+dP/dt), Left Ventricular Developed Pressure (LVDP) and Left Ventricular End-Diastolic Pressure (LVEDP) were measured.

RESULTS

HFD intake remarkably reduced CF, +dP/dt and LVDP and elevated LVEDP in both strains (P<0.05). Treatment with capsaicin decreased infarct size, increased CF, +dP/dt and LVDP, and decreased LVEDP in WT mice on control diet (P<0.05), but did not do so in other three groups. Treatment with CGRP and SP decreased infarct size in both strains fed with control diet (P<0.05). In contrast, not all the parameters of cardiac postischemic recovery in HFD-fed WT and TRPV1-/- mice were improved by CGRP and SP.

CONCLUSION

These results suggest that HFD intake impairs cardiac postischemic recovery. HFDinduced impairment of recovery is alleviated by CGRP in both strains and by SP only in TRPV1-/- mice, indicating that the effects of CGRP and SP are differentially regulated during HFD intake.

Endogenous calcitonin gene-related peptide suppresses ischemic brain injuries and progression of cognitive decline

BACKGROUND

Calcitonin gene-related peptide (CGRP) is a 37-amino acid peptide and produced by alternative splicing of the transcript of the calcitonin/CGRP gene. Originally identified as a strong vasodilatory and hypotensive peptide, CGRP is now known to be a pleiotropic molecule distributed in various organs, including the brain.

METHOD

In this study, we used CGRP knockout mice (CGRP-/-) to examine the actions of endogenous CGRP during cerebral ischemia. To induce acute and chronic cerebral ischemia, mice were subjected to middle cerebral artery occlusion (MCAO) and bilateral common carotid artery stenosis (BCAS).

RESULTS

In the cerebral cortex of wild-type mice, CGRP expression was upregulated after acute infarction. In CGRP-/- subjected to MCAO or BCAS, recovery of cerebral blood flow was slower and exhibited more extensive neuronal cell death. Expression of the inflammatory cytokines was higher in CGRP-/- than wild type in the acute phase of ischemia. Pathological analysis during the chronic phase revealed more extensive neuronal cell loss and demyelination and higher levels of oxidative stress in CGRP-/- than wild-type. CGRP-/- also showed less compensatory capillary growth. In an eight-arm radial maze test, CGRP-/- exhibited poorer reference memory than wild-type. On the other hand, CGRP administration promoted cerebral blood flow recovery after cerebral ischemia. We also found that CGRP directly inhibited the cell death of primary cortical neurons.

CONCLUSION

These results indicate endogenous CGRP is protective against ischemia-induced neuronal cell injury. CGRP could, thus, be a novel candidate for use in the treatment of both cerebral ischemia and progression of cognitive decline.

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.

TRPV1 protects renal ischemia-reperfusion injury in diet-induced obese mice by enhancing CGRP release and increasing renal blood flow

Background

Obesity is a major risk factor for end-stage renal disease. Using transient receptor potential vanilloid 1 knockout (TRPV1^−/−) mice, we tested the hypothesis that TRPV1 protects against obesity-induced exacerbation of renal ischemia-reperfusion (I/R) injury.

Methods

TRPV1^−/− and wild-type (WT) mice were fed a chow or Western diet (WD) for 22–23 weeks. After that, mice were subjected to renal I/R injury, and renal cortical blood flow (CBF) and medullary blood flow (MBF) were measured.

Results

The Western diet significantly increased body weight and fasting blood glucose levels in both TRPV1^−/− and WT mice. WD-induced impairment of glucose tolerance was worsened in TRPV1^−/− mice compared with WT mice. WD intake prolonged the time required to reach peak reperfusion in the cortex and medulla (both P < 0.05), decreased the recovery rate of CBF (P < 0.05) and MBF (P < 0.05), and increased blood urea nitrogen, plasma creatinine, and urinary 8-isoprostane levels after I/R in both mouse strains, with greater effects in TRPV1^−/− mice (all P < 0.05). Renal I/R increased calcitonin gene-related peptide (CGRP) release in WT but not in TRPV1^−/− mice, and WD attenuated CGRP release in WT mice. Moreover, blockade of CGRP receptors impaired renal regional blood flow and renal function in renal I/R injured WT mice.

Conclusion

These results indicate that TRPV1 plays a protective role in WD-induced exacerbation of renal I/R injury probably through enhancing CGRP release and increasing renal blood flow.

Is calcitonin gene-related peptide a modulator of menopausal vasomotor symptoms?

PURPOSE

Calcitonin gene-related peptide (CGRP) is a neuropeptide widely distributed in the central and peripheral nervous systems, which is known as a potent vasodilator. Postmenopausal women who experience hot flushes have high levels of plasma CGRP, suggesting its involvement in menopausal vasomotor symptoms.

METHODS

In this review, we describe the biochemical aspects of CGRP and its effects associated with deficiencies of sexual hormones on skin temperature, vasodilatation, and sweating as well as the possible peripheral and central mechanisms involved in these events.

RESULTS

Several studies have shown that the effects of CGRP on increasing skin temperature and inducing vasodilatation are potentiated by a deficiency of sex hormones, a common condition of postmenopausal women. Additionally, the medial preoptic area of the hypothalamus, involved in thermoregulation, contains over 25-fold more CGRP-immunoreactive cells in female rodents compared with male rodents, reinforcing the role of female sex hormones on the action of CGRP. Some studies suggest that ovarian hormone deficiency decreases circulating endogenous CGRP, inducing an upregulation of CGRP receptors. Consequently, the high CGRP receptor density, especially in blood vessels, amplifies the stimulatory effects of this neuropeptide to raise skin temperature in postmenopausal women during hot flushes.

CONCLUSIONS

The duration of the perception of each hot flush in a woman is brief, while local reddening after intradermal administration of α-CGRP persists for 1 to 6 h. This contrast remains unclear.

Regulation of cardiovascular development and homeostasis by the adrenomedullin-RAMP system

Adrenomedullin (AM), a member of the calcitonin peptide superfamily, is a peptide involved in both the pathogenesis of cardiovascular diseases and circulatory homeostasis. Its receptor, calcitonin receptor-like receptor (CLR), associates with an accessory protein, receptor activity-modifying protein (RAMP). Depending upon which the three RAMP isoforms (RAMP1-3) it interacts with, CLR functions as a receptor for AM or other calcitonin family peptides. AM knockout mice (-/-) died mid-gestation due to abnormalities in vascular development. We found that phenotypes similar to AM-/- were reproduced only in RAMP2-/- mice. We generated endothelial cell-specific RAMP2 knockout mice (E-RAMP2-/-) and found most E-RAMP2-/- mice died perinatally. In surviving adults, vasculitis and organ fibrosis occurred spontaneously. We next generated drug-inducible cardiac myocyte-specific RAMP2-/- (DI-C-RAMP2-/-) mice, which exhibited dilated cardiomyopathy-like heart failure with cardiac dilatation and myofibril disruption. DI-C-RAMP2-/- hearts also showed changes in mitochondrial structure and downregulation of mitochondria-related genes involved in oxidative phosphorylation and β-oxidation. In contrast to RAMP2-/- mice, RAMP3-/- mice were born with no major abnormalities. In adult RAMP3-/- mice, postnatal angiogenesis was normal, but drainage of subcutaneous lymphatic vessels was delayed. RAMP3-/- mice also showed more severe interstitial edema than in wild-type mice in a tail lymphedema model. These findings show that the AM-RAMP system is a key determinant of cardiovascular integrity and homeostasis from prenatal stages through adulthood. The AM-RAMP2 system mainly regulates vascular development and homeostasis, while the AM-RAMP3 system mainly regulates lymphatic function in adults. The AM-RAMP system may thus have therapeutic potential for the treatment of cardiovascular diseases.

CGRP/CGRP Receptor Antibodies: Potential Adverse Effects Due to Blockade of Neovascularization?

Migraine is a severe neurological disorder in which calcitonin gene-related peptide (CGRP) is a key molecule in pathophysiology. Neuronal system-derived CGRP enhances neovascularization in several important pathological conditions and sends a cue to the vascular system. In 2018, the FDA approved erenumab and fremanezumab, antibodies against CGRP receptor and CGRP, as the first new class of drugs for migraine. Treatment of migraine with these antibodies requires great care because neovascularization-related adverse effects may be induced in some patients. Here, we focus on enhancement of neovascularization by CGRP and discuss possible adverse effects resulting from blocking neovascularization. We also suggest that CGRP antibodies may also be used as novel antitumor agents by suppressing tumor-associated angiogenesis.

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.

Role of calcitonin gene-related peptide in energy metabolism

PURPOSE

Calcitonin gene-related peptide (CGRP) is a neuropeptide produced by alternative tissue-specific splicing of the primary transcript of the CALC genes. CGRP is widely distributed in the central and peripheral nervous system, as well as in several organs and tissues. The presence of CGRP in the liver and brown and white adipose tissue suggests an effect of this neuropeptide on regulation of energy homeostasis.

METHODS

In this review, we summarize the current knowledge of the effect of CGRP on the control of energy metabolism, primarily focusing on food intake, thermoregulation and lipid metabolism in adipose tissue, liver and muscle.

RESULTS

CGRP induces anorexia, stimulating anorexigenic neuropeptide and/or inhibiting orexigenic neuropeptide expression, through cAMP/PKA pathway activation. CGRP also induces energy expenditure, increasing the skin temperature and brown adipose tissue thermogenesis. It has been also suggested that information related to peripheral lipid stores may be conveyed to the brain via CGRP-sensory innervation from adipose tissue. More recently, it was demonstrated that mice lacking αCGRP are protected from obesity induced by high-fat diet and that CGRP regulates the content of lipid in liver, muscle and adipose tissue.

CONCLUSIONS

It is unclear the receptor responsible by CGRP effects, as well as whether this neuropeptide acts directly or indirectly in liver, muscle and adipose tissue.

Essential role of endogenous calcitonin gene-related peptide in pain-associated plasticity in the central amygdala

The role of the neuropeptide calcitonin gene‐related peptide (CGRP) is well established in nociceptive behaviors. CGRP is highly expressed in the projection pathway from the parabrachial nucleus to the laterocapsular region of the central amygdala (CeC), which plays a critical role in relaying nociceptive information. The CeC is a key structure in pain behavior because it integrates and modulates nociceptive information along with other sensory signals. Previous studies have demonstrated that blockade of the amygdalar CGRP‐signaling cascade attenuates nociceptive behaviors in pain models, while CGRP application facilitates amygdalar synaptic transmission and induces pain behaviors. Despite these lines of evidence, it remains unclear whether endogenous CGRP is involved in the development of nociceptive behaviors accompanied with amygdalar plasticity in a peripheral inflammation model in vivo. To directly address this, we utilized a previously generated CGRP knockout (KO) mouse to longitudinally study formalin‐induced plasticity and nociceptive behavior. We found that synaptic potentiation in the right PB‐CeC pathway that was observed in wild‐type mice was drastically attenuated in the CGRP KO mice 6 h post‐inflammation, when acute nociceptive behavior was no longer observed. Furthermore, the bilateral tactile allodynia 6 h post‐inflammation was significantly decreased in the CGRP KO mice. In contrast, the acute nociceptive behavior immediately after the formalin injection was reduced only at 20–25 min post‐injection in the CGRP KO mice. These results suggest that endogenous CGRP contributes to peripheral inflammation‐induced synaptic plasticity in the amygdala, and this plasticity may underlie the exaggerated nociception–emotion linkage in pain chronification.

Endogenous Calcitonin Gene-Related Peptide Regulates Lipid Metabolism and Energy Homeostasis in Male Mice

Calcitonin gene-related peptide (CGRP) is a bioactive peptide produced by alternative splicing of the primary transcript of the calcitonin/CGRP gene. CGRP is largely distributed in the cardiovascular and nervous systems, where it acts as a regulatory factor. CGRP is also expressed in organs and tissues involved in metabolic regulation, including white adipose tissue (WAT), where its function is largely unknown. In this study, we examined the effects of endogenous CGRP on metabolic function. When we administered a high-fat diet to CGRP-specific knockout (CGRP-/-) and wild-type (WT) mice for 10 weeks, we observed that food intake did not differ between the two groups, but body weight and visceral fat weight were significantly lower in CGRP-/- mice. Fatty liver changes were less severe in CGRP-/- mice, which also showed lower serum insulin and leptin levels. Glucose tolerance and insulin sensitivity were better in CGRP-/- than WT mice, and expired gas analysis revealed greater oxygen consumption by CGRP-/- mice. Adipocyte hypertrophy was suppressed in CGRP-/- mice, while expression of β-3-adrenergic receptor, hormone-sensitive lipase and adiponectin was enhanced. Isoproterenol-induced glycerol release from WAT was higher in CGRP-/- than WT mice, and CGRP-/- mice showed elevated sympathetic nervous activity. β-receptor-blockade canceled the beneficial effects of CGRP deletion on obesity. These results suggest that, in addition to its actions in the cardiovascular system, endogenous CGRP is a key regulator of metabolism and energy homeostasis in vivo.

A Novel α-Calcitonin Gene-Related Peptide Analogue Protects Against End-Organ Damage in Experimental Hypertension, Cardiac Hypertrophy, and Heart Failure

Supplemental Digital Content is available in the text.

Research into the therapeutic potential of α-calcitonin gene–related peptide (α-CGRP) has been limited because of its peptide nature and short half-life. Here, we evaluate whether a novel potent and long-lasting (t_½ ≥7 hours) acylated α-CGRP analogue (αAnalogue) could alleviate and reverse cardiovascular disease in 2 distinct murine models of hypertension and heart failure in vivo.

Cardiovascular effects of exogenous adrenomedullin and CGRP in Ramp and Calcrl deficient mice

Adrenomedullin (AM) and calcitonin gene-related peptide (CGRP) are potent vasodilator peptides and serve as ligands for the G-protein coupled receptor (GPCR) calcitonin receptor-like receptor (CLR/Calcrl). Three GPCR accessory proteins called receptor activity-modifying proteins (RAMPs) modify the ligand binding affinity of the receptor such that the CLR/RAMP1 heterodimer preferably binds CGRP, while CLR/RAMP2 and CLR/RAMP3 have a stronger affinity for AM. Here we determine the contribution of each of the three RAMPs to blood pressure control in response to exogenous AM and CGRP by measuring the blood pressure of mice with genetic reduction or deletion of the receptor components. Thus, the cardiovascular response of Ramp1^-/-, Ramp2^+/-, Ramp3^-/-, Ramp1^-/-/Ramp3^-/- double-knockout (dKO), and Calcrl^+/- mice to AM and CGRP were compared to wildtype mice. While under anesthesia, Ramp1^-/- male mice had significantly higher basal blood pressure than wildtype males; a difference which was not present in female mice. Additionally, anesthetized Ramp1^-/-, Ramp3^-/-, and Calcrl^+/- male mice exhibited significantly higher basal blood pressure than females of the same genotype. The hypotensive response to intravenously injected AM was greatly attenuated in Ramp1^-/- mice, and to a lesser extent in Ramp3^-/- and Calcrl^+/- mice. However, Ramp1^-/-/Ramp3^-/- dKO mice retained some hypotensive response to AM. These results suggest that the hypotensive effect of AM is primarily mediated through the CLR/RAMP1 heterodimer, but that AM signaling via CLR/RAMP2 and CLR/RAMP3 also contributes to some hypotensive action. On the other hand, CGRP's hypotensive activity seems to be predominantly through the CLR/RAMP1 heterodimer. With this knowledge, therapeutic AM or CGRP peptides could be designed to cause less hypotension while maintaining canonical receptor-RAMP mediated signaling.

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.

Lactation undernutrition leads to multigenerational molecular programming of hypothalamic gene networks controlling reproduction

Background

Reproductive success is dependent on development of hypothalamic circuits involving many hormonal systems working in concert to regulate gonadal function and sexual behavior. The timing of pubertal initiation and progression in mammals is likely influenced by the nutritional and metabolic state, leading us to the hypothesis that transient malnutrition experienced at critical times during development may perturb pubertal progression through successive generations. To test this hypothesis we have utilized a mouse model of undernutrition during suckling by exposing lactating mothers to undernutrition.

Results

Using a combination of transcriptomic and biological approaches, we demonstrate that molecular programming of hypothalamus may perturb gender specific phenotypes across generations that are dependent on the nutritional environment of the lactation period. Lactation undernutrition in first (F1) generation offspring affected body composition, reproductive performance parameters and influenced the expression of genes responsible for hypothalamic neural circuits controlling reproductive function of both sexes. Strikingly, F2 offspring showed phenotypes similar to F1 progeny; however, they were sex and parental nutritional history specific. Here, we showed that deregulated expression of genes involved in kisspeptin signaling within the hypothalamus is strongly associated with a delay in the attainment of puberty in F1 and F2 male and female offspring.

Conclusion

The early developmental plasticity of hypothalamus when challenged with undernutrition during postnatal development not only leads to altered expression of genes controlling hypothalamic neural circuits, altered body composition, delayed puberty and disturbed reproductive performance in F1 progeny, but also affects F2 offspring, depending on parental malnutrition history and in sexually dimorphic manner.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2615-4) contains supplementary material, which is available to authorized users.

Involvement of Receptor Activity-Modifying Protein 3 (RAMP3) in the Vascular Actions of Adrenomedullin in Rat Mesenteric Artery Smooth Muscle Cells

CALCB, ADM, and ADM2 are potent vasodilators that share a seven-transmembrane GPCR, calcitonin receptor-like receptor (CALCRL), whose ligand specificity is dictated by the presence of one of the three receptor activity-modifying proteins (RAMPs). We assessed the relative pharmacologic potency of these peptides in mesenteric artery smooth muscle cells (VSMCs) and the specific RAMP that mediates the effect of ADM in VSMCs. VSMCs, with or without RAMP knockdown, were treated with CALCB, ADM, or ADM2 in the presence or absence of their antagonists, CALCB8-37, ADM22-52, and ADM217-47, respectively, to assess the relative effect of peptides on cAMP production and their pharmacologic potency. Proximity ligation assay was used to assess the specific RAMP that associates with CALCRL to mediate the actions of ADM in VSMCs. All three peptides induced cAMP generation in VSMCs and the order of their potency is CALCB > ADM > ADM2. Effects of CALCB were blocked by CALCB8-37, ADM effects were blocked by CALCB8-37 and ADM217-47 but not ADM22-52, and ADM2 effects were blocked by all three antagonists. Knockdown of RAMP2 was ineffective, whereas knockdown of RAMP3 inhibited ADM-induced cAMP production in VSMCs, suggesting involvement of RAMP3 with CALCRL to mediate ADM effects. Absence of both RAMP2 and RAMP3 further increased CALCB-induced cAMP synthesis compared to control (P < 0.05). ADM increased CALCRL and RAMP3 association and RAMP3 knockdown inhibited the interaction of ADM with CALCRL.

Non-excitatory electrical stimulation attenuates myocardial infarction via homeostasis of calcitonin gene-related peptide in myocardium

Electrical stimulation has been shown protection of brain, retina, optic nerves and pancreatic β-cells but the effect on cardio-protection is still unknown. Calcitonin gene-related peptide (CGRP) participates in the pathology of injury and protection of myocardium but whether or not electrical stimulation modulates endogenous CGRP is not clear. Male Sprague-Dawley rats were divided into 4 groups: (1) control group, without any treatment. (2) I/R group, animals were subjected to 30 min of myocardial ischemia followed by 60 min reperfusion. (3) NES+I/R group, non-excitatory electrical stimulation (NES) was commenced from 15 min before coronary artery occlusion till the end of reperfusion. (4) I/R+CGRP8-37 group, animals were given with CGRP8-37 (an antagonist of CGRP receptor, 10(-7) mol/L, 0.3 ml, i.v.) at 5 min before reperfusion without any electrical stimulation. The hemodynamics and electrocardiogram were monitored and recorded. Infarct size and troponin I were examined and CGRP expression in the myocardium and serum was analyzed. It was found that the infarct size and TnI were significantly reduced in NES+I/R group, by 45% and 58% respectively, accompanied by an obvious fall back of CGRP in myocardium, compared to I/R group (all p<0.05). Treatment with CGRP8-37 resulted in the same protection on myocardium as NES did. No significant difference in hemodynamics or ventricular tachycardia was detected among the groups (all p>0.05). It can be concluded that NES reduced the infarction size after acute myocardial ischemia and reperfusion, for which the underlying mechanism may be associated with modulation of endogenous CGRP in myocardium.

Calcitonin gene-related peptide is involved in inflammatory pain but not in postoperative pain

BACKGROUND

The aim of this study was to clarify the roles of calcitonin gene-related peptide (CGRP) in postoperative pain and inflammatory pain.

METHODS

αCGRP knockout mice that the authors have developed and wild-type mice were used. Pain behaviors were assessed after incision and complete Freund's adjuvant (CFA) injection. Changes in CGRP and c-Fos expression in the dorsal horn were also examined.

RESULTS

Guarding pain scores in αCGRP knockout mice were lower than those in wild-type mice at 24 h (3.8 ± 1.6 vs. 6.8 ± 1.5, P = 0.044) and 48 h (1.8 ± 1.7 vs. 6.0 ± 1.5, P = 0.001) after CFA injection (n = 8 to 9). Withdrawal latencies to heat stimulation in αCGRP knockout mice were higher than those in wild-type mice at 24 to 72 h after CFA injection (4.9 ± 1.0 vs. 3.4 ± 0.8 at 24 h, P = 0.04; 5.1 ± 0.3 vs. 3.2 ± 0.9 at 48 h, P = 0.047; and 5.4 ± 1.6 vs. 3.5 ± 0.5 s at 72 h, P = 0.045) (n = 11 to 13), but withdrawal thresholds to mechanical stimulation were comparable. CGRP expression was increased at 24 h after CFA injection in wild-type mice, and the c-Fos-positive profile was increased at 4 h after CFA injection (ipsilateral vs. contralateral: 12.3 ± 4.6 vs. 1.3 ± 1.9, P < 0.0001) and maintained at 24 h (10.0 ± 4.1 vs. 0.8 ± 1.3, P < 0.0001) (n = 4 to 6).

CONCLUSION

These results suggest that contribution of the αCGRP system depends on the modality of pain and the stage of inflammation.

Calcitonin gene-related peptide: physiology and pathophysiology

Calcitonin gene-related peptide (CGRP) is a 37-amino acid neuropeptide. Discovered 30 years ago, it is produced as a consequence of alternative RNA processing of the calcitonin gene. CGRP has two major forms (α and β). It belongs to a group of peptides that all act on an unusual receptor family. These receptors consist of calcitonin receptor-like receptor (CLR) linked to an essential receptor activity modifying protein (RAMP) that is necessary for full functionality. CGRP is a highly potent vasodilator and, partly as a consequence, possesses protective mechanisms that are important for physiological and pathological conditions involving the cardiovascular system and wound healing. CGRP is primarily released from sensory nerves and thus is implicated in pain pathways. The proven ability of CGRP antagonists to alleviate migraine has been of most interest in terms of drug development, and knowledge to date concerning this potential therapeutic area is discussed. Other areas covered, where there is less information known on CGRP, include arthritis, skin conditions, diabetes, and obesity. It is concluded that CGRP is an important peptide in mammalian biology, but it is too early at present to know if new medicines for disease treatment will emerge from our knowledge concerning this molecule.

Netrin-1 controls sympathetic arterial innervation

Autonomic sympathetic nerves innervate peripheral resistance arteries, thereby regulating vascular tone and controlling blood supply to organs. Despite the fundamental importance of blood flow control, how sympathetic arterial innervation develops remains largely unknown. Here, we identified the axon guidance cue netrin-1 as an essential factor required for development of arterial innervation in mice. Netrin-1 was produced by arterial smooth muscle cells (SMCs) at the onset of innervation, and arterial innervation required the interaction of netrin-1 with its receptor, deleted in colorectal cancer (DCC), on sympathetic growth cones. Function-blocking approaches, including cell type-specific deletion of the genes encoding Ntn1 in SMCs and Dcc in sympathetic neurons, led to severe and selective reduction of sympathetic innervation and to defective vasoconstriction in resistance arteries. These findings indicate that netrin-1 and DCC are critical for the control of arterial innervation and blood flow regulation in peripheral organs.

Evaluation of cardiovascular parameters in cynomolgus monkeys following IV administration of LBR-101, a monoclonal antibody against calcitonin gene-related peptide

Calcitonin gene-related peptide (CGRP) is a well-validated target for migraine therapy and a known potent systemic vasodilator. LBR-101 is a monoclonal antibody against CGRP in clinical development for the preventive treatment of episodic and chronic migraine. Understanding the hemodynamic and cardiovascular consequences of chronic CGRP inhibition is therefore warranted. Given the conservation in CGRP sequence between monkeys and humans, addressing this question in monkeys is ideal as it allows dosing at super-therapeutic levels. To this end, two independent studies were conducted in monkeys: a single dedicated cardiovascular safety study and a repeat-dose, chronic study, both with electrocardiogram and hemodynamic assessments. LBR-101 was very well tolerated in both studies, with no clinically significant changes noted in any hemodynamic parameter, nor any relevant changes noted in any ECG parameter. In cynomolgus monkeys, cardiovascular and hemodynamic parameters do not appear to be affected by long-term inhibition of CGRP with LBR-101.

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

Calcitonin gene-related peptide (CGRP) is reported to play important roles in cardiovascular regulation in human and animal models. In spite of this, its role remains controversial. We aim to clarify this by studying the autonomic cardiovascular function and vascular structure in CGRP knockout (CGRP(-/-)) mice. Blood pressure (BP) and heart rate (HR) were assessed by telemeters. Urine (24-hour) and blood were collected for catecholamines measurements. Baroreflex sensitivity was assessed using phenylephrine and sodium nitroprusside administered in an acute study. Daytime mean arterial pressure (MAP; 12-hour period) was significantly higher in the CGRP(-/-) mice than in the wild type (WT) mice (114.5 vs. 104.5 mm Hg; P = .04). Norepinephrine was elevated in plasma and 24-hour urine in the knockouts (Urine, 956 vs. 618 pg/mL; P = .004; Plasma, 2505 vs. 1168 pg/mL; P = .04). Paradoxically, cardiovagal baroreflex sensitivity was higher in CGRP(-/-) mice (3.2 vs. 1.4 ms/mm Hg; P = .03). To increase insight, we studied aortic stiffness in CGRP(-/-) mice and found it increased compared with age-matched WT mice, as evidenced by the depression of the compliance curve (P < .05). CGRP(-/-) mice have higher BP due to elevated sympathetic signals and abnormalities in blood vessel structure. Moreover, our data also showed that CGRP plays an important role in the regulation of the cardio-vagal tone.

Expression of transient receptor potential channels TRPC1 and TRPV4 in venoatrial endocardium of the rat heart

The atrial volume receptor reflex arc serves to regulate plasma volume. Atrial volume receptors located in the endocardium of the atrial wall undergo mechanical deformation as blood is returned to the atria of the heart. The mechanosensitive channel(s) responsible for regulating plasma volume remain to be determined. Here we report that the TRP channel family members TRPC1 and TRPV4 were expressed in sensory nerve endings in the atrial endocardium. Furthermore, TRPC1 and TRPV4 were coincident with the nerve ending vesicle marker synaptophysin. Calcitonin gene-related peptide was exclusively confined to the myo- and epicardium of the atria. The small conductance Ca(2+)-activated K(+) channels (SK2 and SK4) were also present, however there was no relationship between SK and TRP channels. SK2 channels were expressed in nerves in the epicardium, while SK4 channels were in some regions of the endocardium but appeared to be present in epithelial cells rather than sensory endings. In conclusion, we have provided the first evidence for TRPC1 and TRPV4 channels as potential contributors to mechanosensation in the atrial volume receptors.

Alpha-calcitonin gene-related peptide is protective against pressure overload-induced heart failure

The sensory neuropeptide, α-calcitonin gene-related peptide (α-CGRP) is protective against hypertension-induced heart damage and cardiac ischemia/reperfusion injury. To determine whether this neuropeptide is also cardioprotective in heart failure, this study examined whether the absence of α-CGRP exacerbated the adverse cardiac remodeling, dysfunction and mortality in pressure overload heart failure induced by transverse aortic constriction (TAC). Male α-CGRP knockout (KO) and wild type (WT) mice had TAC or sham surgery at day 0 and were studied on days 3, 14, 21, and 28. The survival rate of TAC α-CGRP KO mice was lower than the TAC WT mice over the duration of the protocol. Left ventricular α-CGRP content in TAC WT mice was higher at days 3, 14, and 21 than sham WT mice. Echocardiography demonstrated greater adverse cardiac remodeling and dysfunction in the TAC α-CGRP KO compared to the TAC WT mice. The lung/body weight ratios and left ventricular masses were higher in TAC α-CGRP KO compared to the TAC WT mice. While there was increased cardiac fibrosis in the TAC WT mice compared to shams, the TAC α-CGRP KO mice had markedly increased fibrosis above that of the TAC WT mice. TAC WT mice had greater cardiac inflammation, cell death, and adaptive angiogenesis compared to sham mice. Importantly, the TAC α-CGRP KO mice had greater inflammation, cell death, and attenuation of angiogenesis compared to TAC WT hearts. Thus, α-CGRP plays a significant protective role in TAC-induced heart failure which may be mediated by decreased inflammation, cell death, and fibrosis.