Circulating Levels of Calcitonin Gene-Related Peptide Are Lower in COVID-19 Patients

Untangling the mess of CGRP levels as a migraine biomarker: an in-depth literature review and analysis of our experimental experience

BACKGROUND

Calcitonin gene-related peptide (CGRP) is the most promising candidate to become the first migraine biomarker. However, literature shows clashing results and suggests a methodological source for such discrepancies. We aimed to investigate some of these methodological factors to evaluate the actual role of CGRP as biomarker.

METHODS

Previous to the experimental part, we performed a literature review of articles measuring CGRP in migraine patients. Using our 399 bio-bank sera samples, we performed a series of experiments to test the validity of different ELISA kits employed, time of sample processing, long-term storage, sampling in rest or after moderate exercise. Analysis of in-house data was performed to analyse average levels of the peptide and the effect of sex and age.

RESULTS

Literature review shows the high variability in terms of study design, determination methods, results and conclusions obtained by studies including CGRP determinations in migraine patients. CGRP measurements depends on the method and specific kit employed, also on the isoform detected, showing completely different ranges of concentrations. Alpha-CGRP and beta-CGRP had median with IQR levels of 37.5 (28.2-54.4) and 4.6 (2.4-6.4)pg/mL, respectively. CGRP content is preserved in serum within the 24 first hours when samples are stored at 4°C after clotting and immediate centrifugation. Storages at -80°C of more than 6 months result in a decrease in CGRP levels. Moderate exercise prior to blood extraction does not modulate the concentration of the peptide. Age positively correlates with beta-CGRP content and men have higher alpha-CGRP levels than women.

CONCLUSIONS

We present valuable information for CGRP measurements in serum. ELISA kit suitability should be tested prior to the experiments. Alpha and beta-CGRP levels should be analysed separately as they can show different behaviours even within the same condition. Samples can be processed in a 24-h window if they have been kept in 4°C and should not be stored for more than 6 months at -80°C before assayed. Patients do not need to rest before the blood extraction unless they have performed a high-endurance exercise. For comparative studies, sex and age should be accounted for as these parameters can impact CGRP concentrations.

Calcitonin Gene-Related Peptide Level in Cystic Fibrosis Patients

Calcitonin gene-related peptide (CGRP) has long been implicated in both the physiology and pathophysiology of the respiratory tract. The objective of our study was to determine the serum concentration of alpha CGRP (αCGRP) in cystic fibrosis (CF) that arises from mutations in the gene responsible for encoding the cystic fibrosis transmembrane conductance regulator (CFTR) protein. Currently, there are not many data in the literature about the role of CGRP in CF. The serum level of αCGRP was estimated using the enzyme-linked immunosorbent assay among 64 patients with CF and 31 healthy controls. The αCGRP concentration in the CF group was 62.51 ± 15.45 pg/mL, while in the control group it was 47.43 ± 8.06 pg/mL (p < 0.001). We also compared the level of αCGRP in CF patients according to the type of CFTR mutation. Homozygotes for ΔF508 had higher αCGRP levels than heterozygotes (67.9 ± 10.2 vs. 54.5 ± 18.3 pg/mL, p < 0.01). The level of this neuropeptide was statistically higher in patients with severe disease than in those with mild CF (p = 0.003) when patients were divided into three groups by spirometry results. αCGRP concentration was not correlated with age, sex, clinical parameters, and pulmonary function test results in the study participants. The results of our study suggest a significant increase in the concentration of αCGRP in the serum of patients with CF compared to the control group. This observation opens interesting possibilities for understanding the role of αCGRP in the context of CF pathophysiology.

Neuropathic Corneal Pain after Coronavirus Disease 2019 (COVID-19) Infection

INTRODUCTION

This is a case report of a patient with neuropathic corneal pain after coronavirus disease 2019 (COVID-19) infection.

METHODS

A previously healthy 27-year-old female presented with bilateral eye pain accompanied by increased light sensitivity 5 months after COVID-19 infection. She was diagnosed with neuropathic corneal pain based on clear corneas without fluorescein staining, alongside the presence of microneuromas, dendritic cells, and activated stromal keratocytes identified bilaterally on in vivo confocal microscopy.

RESULTS

The patient's tear nerve growth factor, substance P, and calcitonin gene-related peptide levels were 5.9 pg/mL, 2978.7 pg/mL, and 1.1 ng/mL, respectively, for the right eye and 23.1 pg/mL, 4798.7 pg/mL, and 1.2 ng/mL, respectively, for the left eye, suggesting corneal neuroinflammatory status. After 6 weeks of topical 0.1% flurometholone treatment, decreased microneuroma size, less extensive dendritic cells, and reduced tear nerve growth factor and substance P levels were observed. The scores on the Ocular Pain Assessment Survey showed an improvement in burning sensation and light sensitivity, decreasing from 80% and 70% to 50% for both.

CONCLUSIONS

Neuropathic corneal pain is a potential post-COVID-19 complication that warrants ophthalmologists' and neurologists' attention.

Metabolic and toxicological considerations regarding CGRP mAbs and CGRP antagonists to treat migraine in COVID-19 patients: a narrative review

INTRODUCTION

Migraine pharmacological therapies targeting calcitonin gene-related peptide (CGRP), including monoclonal antibodies and gepants, have shown clinical effect and optimal tolerability. Interactions between treatments of COVID-19 and CGRP-related drugs have not been reviewed.

AREAS COVERED

An overview of CGRP, a description of the characteristics of each CGRP-related drug and its response predictors, COVID-19 and its treatment, the interactions between CGRP-related drugs and COVID-19 treatment, COVID-19 and vaccination-induced headache, and the neurological consequences of Covid-19.

EXPERT OPINION

Clinicians should be careful about using gepants for COVID-19 patients, due to the potential drug interactions with drugs metabolized via CYP3A4 cytochrome. In particular, COVID-19 treatment (especially nirmatrelvir packaged with ritonavir, as Paxlovid) should be considered cautiously. It is advisable to stop or adjust the dose (10 mg atogepant when used for episodic migraine) of gepants when using Paxlovid (except for zavegepant). CGRP moncolconal antibodies (CGRP-mAbs) do not have drug - drug interactions, but a few days' interval between a COVID-19 vaccination and the use of CGRP mAbs is recommended to allow the accurate identification of the possible adverse effects, such as injection site reaction. Covid-19- and vaccination-related headache are known to occur. Whether CGRP-related drugs would be of benefit in these circumstances is not yet known.

The effects of prolactin on the immune system, its relationship with the severity of COVID-19, and its potential immunomodulatory therapeutic effect

Prolactin (PRL) is an endocrine hormone secreted by the anterior pituitary gland that has a variety of physiological effects, including milk production, immune system regulation, and anti-inflammatory effects. Elevated levels of PRL have been found in several viral infections, including 2019 coronavirus disease (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV2), a viral pathogen that has recently spread worldwide. PRL production is increased in SARS-CoV2 infection. While PRL can trigger the production of proinflammatory cytokines, it also has several anti-inflammatory effects that can reduce hyperinflammation. The exact mechanism of PRL's contribution to the severity of COVID-19 is unknown. The purpose of this review is to discuss the interaction between PRL and SARS-CoV2 infection and its possible association with the severity of COVID-19.

Calcitonin Gene-Related Peptide Monoclonal Antibodies and Risk of SARS-CoV-2 Infection and Severe COVID-19 Outcomes Among Veterans With Migraine Disorder

Importance

Calcitonin gene-related peptide (CGRP), a neuropeptide involved in migraine pathophysiology, is also a key neuroimmune modulator. CGRP antagonists may help mitigate the hyperinflammatory response observed in patients with COVID-19; however, findings from the literature are contradictory, and to date, no study has investigated the safety and effectiveness of CGRP antagonists against COVID-19.

Objective

To evaluate the association between CGRP monoclonal antibody (mAb) treatment and risk of SARS-CoV-2 infection and sequela hospitalization, requiring supplemental oxygen, use of mechanical ventilation, or death.

Design, Setting, and Participants

This retrospective cohort study analyzed the electronic health records of US veterans aged 18 to 65 years who were diagnosed with migraine disorder and were at risk of COVID-19 between January 20, 2020, and May 19, 2022.

Exposure

Initiation of CGRP mAbs.

Main Outcomes and Measures

The main outcome was cumulative incidence of SARS-CoV-2 infection. Odds of 30-day hospitalization, requiring supplemental oxygen, use of mechanical ventilation, or death were secondary outcomes.

Results

Among 8 178 652 eligible person-trials (354 294 veterans), 9992 (mean [SD] age, 46.0 [9.5] years; 53.9% male) initiated CGRP mAbs and 8 168 660 (mean [SD] age, 46.6 [10.2] years; 65.7% male) did not initiate CGRP mAbs. Over a 28-month follow-up period, 1247 initiators (12.5%) and 780 575 noninitiators (9.6%) tested positive for SARS-CoV-2. After censoring persons who deviated from treatment, the incidence was 7.4 cases per 1000 person-months among initiators and 6.9 per 1000 person-months among noninitiators. The inverse probability-weighted observational analogs of intention-to-treat and per-protocol hazard ratios were 0.95 (95% CI, 0.89-1.01) and 0.93 (95% CI, 0.86-1.02), respectively. No significant differences in the likelihood of hospitalization (odds ratio [OR], 0.93; 95% CI, 0.62-1.41), requiring supplemental oxygen (OR, 0.77; 95% CI, 0.45-1.30), use of mechanical ventilation (OR, 0.85; 95% CI, 0.26-2.84), or death (OR, 0.67; 95% CI, 0.09-5.23) were observed between CGRP mAb initiators and noninitiators who tested positive for SARS-CoV-2.

Conclusions and Relevance

In this cohort study, CGRP mAb treatment was not associated with positive SARS-CoV-2 test results or risk of severe COVID-19 outcomes, suggesting that CGRP mAbs may be used for migraine prevention during the COVID-19 pandemic. Given the few events of requiring supplemental oxygen, use of mechanical ventilation, and death, replication analysis in a larger sample of patients later in the course of disease is warranted.

COVID-19 Biomarkers at the Crossroad between Patient Stratification and Targeted Therapy: The Role of Validated and Proposed Parameters

Clinical knowledge about SARS-CoV-2 infection mechanisms and COVID-19 pathophysiology have enormously increased during the pandemic. Nevertheless, because of the great heterogeneity of disease manifestations, a precise patient stratification at admission is still difficult, thus rendering a rational allocation of limited medical resources as well as a tailored therapeutic approach challenging. To date, many hematologic biomarkers have been validated to support the early triage of SARS-CoV-2-positive patients and to monitor their disease progression. Among them, some indices have proven to be not only predictive parameters, but also direct or indirect pharmacological targets, thus allowing for a more tailored approach to single-patient symptoms, especially in those with severe progressive disease. While many blood test-derived parameters quickly entered routine clinical practice, other circulating biomarkers have been proposed by several researchers who have investigated their reliability in specific patient cohorts. Despite their usefulness in specific contexts as well as their potential interest as therapeutic targets, such experimental markers have not been implemented in routine clinical practice, mainly due to their higher costs and low availability in general hospital settings. This narrative review will present an overview of the most commonly adopted biomarkers in clinical practice and of the most promising ones emerging from specific population studies. Considering that each of the validated markers reflects a specific aspect of COVID-19 evolution, embedding new highly informative markers into routine clinical testing could help not only in early patient stratification, but also in guiding a timely and tailored method of therapeutic intervention.

Evaluation of serum VIP and aCGRP during pulmonary exacerbation in cystic fibrosis: A longitudinal pilot study of patients undergoing antibiotic therapy

BACKGROUND

Objective monitoring of improvement during treatment of pulmonary exacerbation can be difficulty in children when pulmonary function testing cannot be obtained. Thus, the identification of predictive biomarkers to determine the efficacy of drug treatments is of high priority. The major aim of the current study was to investigate the serum levels of vasoactive intestinal peptide (VIP) and alpha calcitonin gene related peptide (aCGRP) of cystic fibrosis pediatric patients during pulmonary exacerbation and post-antibiotic therapy, and possible associations of their levels with different clinicopathological parameters.

METHODS

21 patients with cystic fibrosis were recruited at onset of pulmonary exacerbation. Serum was collected at time of admission, three days post-antibiotic therapy, and two weeks post-antibiotic therapy (end of antibiotic therapy). Serum VIP and aCGRP levels were measured using ELISA.

RESULTS

Overall least square means of serum aCGRP level but not VIP changed from time of exacerbation to completion of antibiotic therapy (p = 0.005). Serum VIP was significantly associated with the presence of diabetes mellitus (p = 0.026) and other comorbidities (p = 0.013), and with type of antibiotic therapy (p = 0.019). Serum aCGRP level was significantly associated with type of antibiotic therapy (p = 0.012) and positive Staphylococcus aureus microbiology test (p = 0.046).

CONCLUSION

This study could only show significant changes in serum aCGRP levels following treatment of pulmonary exacerbations. Future studies with larger sample size are required to investigate the clinical importance of VIP and aCGRP in cystic fibrosis patients.

5-HT/CGRP pathway and Sumatriptan role in Covid-19

Coronavirus disease 2019 (Covid-19) is a pandemic caused by severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2). In Covid-19, there is uncontrolled activation of immune cells with a massive release of pro-inflammatory cytokines and the development of cytokine storm. These inflammatory changes induce impairment of different organ functions, including the central nervous system (CNS), leading to acute brain injury and substantial changes in the neurotransmitters, including serotonin (5-HT) and calcitonin gene-related peptide (CGRP), which have immunomodulatory properties through modulation of central and peripheral immune responses. In Covid-19, 5-HT neurotransmitters and CGRP could contribute to abnormal and atypical vascular reactivity. Sumatriptan is a pre-synaptic 5-HT (5-HT1D and 5-HT1B) agonist and inhibits the release of CGRP. Both 5-HT and CGRP seem to be augmented in Covid-19 due to underlying activation of inflammatory signaling pathways and hyperinflammation. In virtue of its anti-inflammatory and antioxidant properties with inhibition release of 5-HT and CGRP, Sumatriptan may reduce Covid-19 hyperinflammation. Therefore, Sumatriptan might be a novel potential therapeutic strategy in managing Covid-19. In conclusion, Sumatriptan could be an effective therapeutic strategy in managing Covid-19 through modulation of 5-HT neurotransmitters and inhibiting CGRP.

Neuronal-Immune Cell Units in Allergic Inflammation in the Nose

Immune cells and immune-derived molecules, endocrine glands and hormones, the nervous system and neuro molecules form the combined tridirectional neuroimmune network, which plays a significant role in the communication pathways and regulation at the level of the whole organism and local levels, in both healthy persons and patients with allergic rhinitis based on an allergic inflammatory process. This review focuses on a new research paradigm devoted to neuronal-immune cell units, which are involved in allergic inflammation in the nose and neuroimmune control of the nasal mucociliary immunologically active epithelial barrier. The categorization, cellular sources of neurotransmitters and neuropeptides, and their prevalent profiles in constituting allergen tolerance maintenance or its breakdown are discussed. Novel data on the functional structure of the nasal epithelium based on a transcriptomic technology, single-cell RNA-sequencing results, are considered in terms of neuroimmune regulation. Notably, the research of pathogenesis and therapy for atopic allergic diseases, including recently identified local forms, from the viewpoint of the tridirectional interaction of the neuroimmune network and discrete neuronal-immune cell units is at the cutting-edge.

Calcitonin gene-related peptide: A biomarker for stroke in SARS-CoV-2 infection?

COVID-19 infection was mainly associated with respiratory symptoms, but lately, ischemic stroke (IS) has been reported in several cases. The incidence of IS in SARS-CoV-2 infection is increasing, and its mechanism is still not fully understood. Calcitonin gene-related peptide (CGRP) -the abundantly expressed protein in the peripheral and central nervous system- showed low expression in SARS-CoV-2 patients. This peptide is strongly implicated in regulating cerebral blood flow (CBF) and improving neurological deficits after cerebral arterial occlusion. We assume that a possible interplay between the low circulating levels of CGRP may affect CBF, thus worsening the symptoms of IS in SARS-CoV-2 patients.

Is Persistent Post-COVID Headache Associated With Protein-Protein Interactions Between Antibodies Against Viral Spike Protein and CGRP Receptor?: A Case Report

Background

After the acute pandemic of coronavirus disease 2019 (COVID-19), a wide variety of symptoms are identified under the term post-COVID syndrome, such as persistent headache. Post-COVID headache can be presented in a broad spectrum like headache attributed to systemic infection, chronification of already existing primary headache, or long-lasting, and also late-onset new daily persistent headache. Still, little is known about the pathophysiology of post-COVID headache, but activation of the trigeminovascular system may be one of the players.

Case Report

Here, we present a case with a severe, long-lasting post-COVID headache and its sudden cessation with calcitonin gene-related peptide (CGRP) monoclonal antibody treatment.

Conclusion

In our previous protein mimicry study, we have pointed at mimicry of virus spike protein and CGRP receptors. This mechanism may enlighten the current, common, and yet unsolved post-COVID headache cases.

Can COVID-19 vaccines relieve severe tension-type headache and migraine?

Chronic headache is a frequent disorder that can cause a significant deterioration in the quality of life of the affected person. The COVID-19 pandemic is compelling all countries to develop a complete vaccination protocol for the entire population. In this article, we present 8 clinical cases of patients suffering chronic headache which resolved completely or partially after vaccination. Five patients had migraine, 2 had a post-viral headache typical of COVID-19, and one had a headache induced by sexual activity. Resolution was complete in 3 cases, almost complete in 2 others, and a great improvement was observed in the other 3. We hypothesize that the administration of vaccines for COVID-19 can produce an improvement or the disappearance of symptoms in our patients by inhibiting synthesis of pro-inflammatory cytokines.

The crucial role of prolactin-lactogenic hormone in Covid-19

Prolactin (PRL) is a peptide hormone secreted from anterior pituitary involved in milk production in the females and regulation of sex drive in both sexes. PRL has pro-inflammatory and anti-inflammatory functions. High PRL serum level or hyperprolactinemia is associated with different viral infections. In coronavirus disease 2019 (Covid-19), which caused by positive-sense single-strand RNA virus known as severe acute respiratory distress syndrome coronavirus type 2 (SARS-CoV-2), PRL serum level is increased. PRL in Covid-19 may exacerbate the underlying inflammatory status by induction release of pro-inflammatory cytokines. However, PRL through its anti-inflammatory effects may reduce the hyperinflammatory status in Covid-19. The underlying mechanism of increasing PRL in Covid-19 is poorly understood. Therefore, in this review we try to find the potential anti-inflammatory or pro-inflammatory role of PRL in Covid-19. As well, this review was aimed to discuss the underlying causes and mechanisms for Covid-19-induced hyperprolactinemia.

Innate Receptors Expression by Lung Nociceptors: Impact on COVID-19 and Aging

The lungs are constantly exposed to non-sterile air which carries harmful threats, such as particles and pathogens. Nonetheless, this organ is equipped with fast and efficient mechanisms to eliminate these threats from the airways as well as prevent pathogen invasion. The respiratory tract is densely innervated by sensory neurons, also known as nociceptors, which are responsible for the detection of external stimuli and initiation of physiological and immunological responses. Furthermore, expression of functional innate receptors by nociceptors have been reported; however, the influence of these receptors to the lung function and local immune response is poorly described. The COVID-19 pandemic has shown the importance of coordinated and competent pulmonary immunity for the prevention of pathogen spread as well as prevention of excessive tissue injury. New findings suggest that lung nociceptors can be a target of SARS-CoV-2 infection; what remains unclear is whether innate receptor trigger sensory neuron activation during SARS-CoV-2 infection and what is the relevance for the outcomes. Moreover, elderly individuals often present with respiratory, neurological and immunological dysfunction. Whether aging in the context of sensory nerve function and innate receptors contributes to the disorders of these systems is currently unknown. Here we discuss the expression of innate receptors by nociceptors, particularly in the lungs, and the possible impact of their activation on pulmonary immunity. We then demonstrate recent evidence that suggests lung sensory neurons as reservoirs for SARS-CoV-2 and possible viral recognition via innate receptors. Lastly, we explore the mechanisms by which lung nociceptors might contribute to disturbance in respiratory and immunological responses during the aging process.

Headache as a Symptom of COVID-19: Narrative Review of 1-Year Research

Purpose of Review

Headache is a common symptom of COVID-19 with emerging literature being published on the subject. Although it may seem unspecific, scientific evidence has allowed a better definition of this headache type, revealing relevant associations with other COVID-19 symptoms and prognoses. We therefore sought to highlight the most remarkable findings concerning headache secondary to COVID-19, specifically focusing on epidemiology, characteristics, pathophysiology, and treatments.

Recent Findings

The real prevalence of headache as a symptom of COVID-19 is still unclear ranging from 10 to 70%. Headache mainly has a tension-type-like phenotype, although 25% of individuals present with migraine-like features that also occur in patients without personal migraine history. This finding suggests that a likely pathophysiological mechanism is the activation of the trigeminovascular system. SARS-CoV-2 neurotropism can occur by trans-synaptic invasion through the olfactory route from the nasal cavity, leading to anosmia which has been associated with headache. SARS-CoV-2 protein has been found not only in olfactory mucosa and bulbs but also in trigeminal branches and the trigeminal ganglion, supporting this hypothesis. However, other mechanisms such as brain vessels inflammation due to SARS-CoV-2 damage to the endothelium or systemic inflammation in the context of cytokine storm cannot be ruled out. Interestingly, headache has been associated with lower COVID-19 mortality. No specific treatment for COVID-19 headache is available at present.

Summary

Studies show that investigating COVID-19 headache represents an opportunity not only to better understand COVID-19 in general but also to advance in the knowledge of both secondary and primary headaches. Future research is therefore warranted.

Vasoactive Peptides: Role in COVID-19 Pathogenesis and Potential Use as Biomarkers and Therapeutic Targets

BACKGROUND

The ongoing outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), as the latest threat to global health, causes overwhelming effects for the public healthcare systems worldwide. Of note, in addition to the respiratory complications, some patients with coronavirus disease 2019 (COVID-19) also develop serious cardiovascular injuries. Vasoactive peptides play an important role in a wide range of physiological and pathological conditions.

AIM

With the urgent need for exploring the specific therapeutic targets and biomarkers for the emerging COVID-19, the general aim of this review is to discuss the potentials of the vasoactive peptides including Angiotensin II (Ang II), vasoactive intestinal peptide (VIP), endothelin-1 (ET-1), calcitonin gene-related peptide (CGRP), natriuretic peptides, substance P (SP) and bradykinin (BK) as therapeutic targets and/or prognostic indicators for the COVID-19 pandemic.

CONCLUSION

Based on various observations some authors conclude that the assessment of vasoactive peptides shall be considered a routine part of COVID-19 patient monitoring, and they can serve as potential therapeutic targets for the disease management.

HMGB1, NLRP3, IL-6 and ACE2 levels are elevated in COVID-19 with headache: a window to the infection-related headache mechanism

Background and aim

Pathogenesis of COVID-19 -related headache is unknown, though the induction of the trigeminal neurons through inflammation is proposed. We aimed to investigate key systemic circulating inflammatory molecules and their clinical relations in COVID-19 patients with headache.

Methods

This cross-sectional study enrolled 88 COVID-19 patients, hospitalized on a regular ward during the second wave of the pandemic. Clinical characteristics of COVID-19 patients were recorded, and laboratory tests were studied.

Results

The mean ages of 48 COVID-19 patients with headache (47.71 ± 10.8) and 40 COVID-19 patients without headache (45.70 ± 12.72) were comparable. COVID-19 patients suffered from headache had significantly higher serum levels of HMGB1, NLRP3, ACE2, and IL-6 than COVID-19 patients without headache, whereas CGRP and IL-10 levels were similar in the groups. Angiotensin II level was significantly decreased in the headache group. COVID-19 patients with headache showed an increased frequency of pulmonary involvement and increased D- dimer levels. Furthermore, COVID-19 was more frequently associated with weight loss, nausea, and diarrhea in patients with headache. Serum NLRP3 levels were correlated with headache duration and hospital stay, while headache response to paracetamol was negatively correlated with HMGB1 and positively associated with IL-10 levels.

Conclusion

Stronger inflammatory response is associated with headache in hospitalized COVID-19 patients with moderate disease severity. Increased levels of the circulating inflammatory and/or nociceptive molecules like HMGB1, NLRP3, and IL-6 may play a role in the potential induction of the trigeminal system and manifestation of headache secondary to SARS-CoV-2 infection.