Pathogenesis of chronic cluster headache and bouts: role of tryptamine, arginine metabolism and α1-agonists

Biomarkers in cluster headache: A systematic review

OBJECTIVE

To systematically investigate previously examined biomarkers in blood, urine, cerebrospinal fluid, tear fluid, and saliva of patients with cluster headache.

BACKGROUND

Cluster headache is a condition with extensive clinical challenges in terms of diagnosis and treatment. Identification of a biomarker with diagnostic implications or as a potential treatment target is highly warranted.

METHODS

We conducted a systematic review including peer reviewed full text of studies that measured biochemical compounds in either blood, urine, cerebrospinal fluid, tear fluid, or saliva of patients with cluster headache diagnosed after the implementation of the International Classification of Headache Disorders (1988) written in English, Danish, Swedish, or Norwegian. Inclusion required a minimum of five participants. The search was conducted in PubMed and EMBASE, in September 2022, and extracted data were screened by two authors. Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines for reporting systematic reviews were followed. The Newcastle-Ottawa Scale was used to assess the risk of bias in case-controlled studies.

RESULTS

We included 40 studies involving 832 patients with cluster headache and 872 controls, evaluating 80 potential biomarkers. The risk of bias for case-controlled studies was a median of 6 (range: 3-8) and 20 studies out of 40 (50%) were of fair or good quality. Most studies were identified within three groups: hypothalamic-regulated hormones, inflammatory markers, and neuropeptides. Among the hypothalamic hormones, cortisol was the most frequently investigated (N = 7) and was elevated in cluster headache in most of the studies. The most frequently examined inflammatory marker was interleukin 1 (N = 3), but findings were divergent. Calcitonin gene-related peptide was the most investigated neuropeptide (N = 9) and all studies found increased levels during attacks.

CONCLUSION

Biomarker findings have been inconsistent and widely non-specific for cluster headache, which explains why none of the previous studies succeeded in identifying a unique biomarker for cluster headache, but instead contributed to substantiating the underlying pathophysiologic mechanisms. Several of the examined biomarkers could hold promise as markers for disease activity but are unfit for a clear distinction from both controls and other headaches.

Migraine signaling pathways: amino acid metabolites that regulate migraine and predispose migraineurs to headache

Migraine is a common, debilitating disorder for which attacks typically result in a throbbing, pulsating headache. Although much is known about migraine, its complexity renders understanding the complete etiology currently out of reach. However, two important facts are clear, the brain and the metabolism of the migraineur differ from that of the non-migraineur. This review centers on the altered amino acid metabolism in migraineurs and how it helps define the pathology of migraine.

Current advances in the management of cluster headaches

Introduction: Cluster headache (CH) is probably the most severe idiopathic pain condition, yet its current medical management remains poor.Areas covered: Only repurpose medicines are currently in use for the prevention of CH, partially because the pathophysiology of the condition is still elusive. In this article we performed a systematic review to evaluate the evidence for efficacy of the currently available or emerging treatments for CH.Expert opinion: We found several ongoing randomized clinical trials testing prophylactic treatments for CH and only few for the standard ones. Recent data from randomized trials with monoclonal antibodies targeting the calcitonin gene related peptide pathway (anti-CGRP mAbs) are controversial, although its role in the pathogenesis of the condition is well documented. This inconsistency may depict inadequacies in clinical trial designing. Anti-CGRP mAbs and antagonists of pituitary adenylate cyclase-activating polypeptide (PACAP) along with neuromodulation techniques, are curing the necessary valuable evidence that could illuminate the therapeutical future for cluster headache. Orexin pathway is another attractive target for CH treatment. To improve the evidence for efficacy, we further propose that the design of the clinical trials for CH needs to be radically reviewed to allow more patients to participate.

Recently available and emerging therapeutic strategies for the acute and prophylactic management of cluster headache: a systematic review and expert opinion

Introduction: Although it causes a huge burden to sufferers, cluster headache (CH), remains an undertreated condition, partly due to the absence of established acute and prophylactic treatment options. New therapeutic approaches providing fast and safe relief from CH are needed. Areas covered: A systematic review was conducted, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) recommendation on recently published (last 5 years) papers on CH treatment. The authors also collected preliminary results from ongoing trials on emerging therapeutic/preventive pharmacological and interventional approaches for CH. Studies and results are reviewed and discussed. Expert opinion: The complexity of CH pathophysiology prevents the definition of reliable acute and preventive treatments. In the real-world clinical setting, several treatments are combined to provide relief to patients and increase their quality of life. Drugs targeting neuropeptides or their receptors within the trigeminovascular network are of particular interest to prevent CH attacks. Calcitonin gene-related peptide (CGRP) blockade seems attractive and promising, but studies on anti-CGRP monoclonal antibodies indicated rather modest or even absence of a prophylactic effect. A deeper insight into CH pathophysiology, and combined approaches may lead the path to new, more effective, and personalized CH therapies.

Pathogenesis of Cluster Headache: From Episodic to Chronic Form, the Role of Neurotransmitters and Neuromodulators

OBJECTIVE

To describe the role of biochemical anomalies of tyrosine (TYR), tryptophan (TRP), and arginine (ARG) metabolism in patients suffering from episodic and chronic cluster headache (CCH).

BACKGROUND

The pathogenesis of cluster headache (CH) and the process that transforms the episodic into the chronic form are unknown. However, the accompanying symptoms suggest a dysfunction of the sympathetic system and hypothalamus along with anomalies of metabolism of catecholamines, elusive amines, and nitric oxide (NO) metabolism.

METHODS

We describe the results obtained from the last papers published on this issue. The level of metabolites were analyzed by different high-performance liquid chromatography methods.

RESULTS

In both episodic and CH patients, the levels of dopamine and elusive amines are very elevated. The only biochemical difference found in studies between episodic and chronic cluster was that norepinephrine levels were significantly lower in episodic cluster in comparison to control and chronic subjects. In addition, the levels of ARG, homoarginine, and citrulline, precursors of synthesis of NO, were significantly lower in chronic cluster.

CONCLUSIONS

All these results suggest that TYR, TRP, and ARG metabolism is abnormal and may constitute a biochemical fingerprint of CH patients. The increased levels of norepinephrine in chronic cluster constitute a possible cause of chronicity of this primary headache. The high levels of tryptamine and its activity on the central serotoninergic system may explain why the length of CH is brief in comparison to migraine and tension-type headache. The low levels of ARG, homoarginine, and citrulline may be the consequence of high circulating levels of α₁ -agonists, such as epinephrine and norepinephrine, and their biochemical interaction with endothelial trace amine-associated receptor 1 that induces activation of NO synthase, resulting in NO synthesis in the circulation, NO release, intense vasodilation, and as a result, the cluster attack.

The role of oxygen in cluster headache

High-flow oxygen inhalation is one of the most effective acute treatments for cluster headache. The therapy was first described for the treatment of cluster headache in 1952 by Horton, and has exhibited some advantages and efficacy compared to other acute medicines. The mechanism is not very clear, but some evidence has demonstrated its relationship to the trigeminovascular system and neuroinflammation. High-flow oxygen inhalation via a non-rebreather mask during cluster headache attacks has been widely recommended. Patients with frequent attacks and/or intolerance to drugs may prefer the oxygen treatment.

The role of neurotransmitters and neuromodulators in the pathogenesis of cluster headache: a review

The pathogenesis underlying cluster headache remains an unresolved issue. Although both the autonomic system and the hypothalamus play a central role, the modality of their involvement remains largely unknown. It is, also, unknown why the duration of the pain attacks is so brief and why their onset and termination are abrupt and extremely painful. This review summarizes the evidence to date accumulated in favor of a possible role of anomalies in the metabolism of tyrosine, tryptophan, and arginine in these unresolved issues.

Diet-Related Metabolic Perturbations of Gut Microbial Shikimate Pathway-Tryptamine-tRNA Aminoacylation-Protein Synthesis in Human Health and Disease

Human gut bacterial Na(+)-transporting NADH:ubiquinone reductase (NQR) sequence is associated with Alzheimer disease (AD). Here, Alzheimer disease-associated sequence (ADAS) is further characterized in cultured spore-forming Clostridium sp. Tryptophan and NQR substrate ubiquinone have common precursor chorismate in microbial shikimate pathway. Tryptophan-derived tryptamine presents in human diet and gut microbiome. Tryptamine inhibits tryptophanyl-tRNA synthetase (TrpRS) with consequent neurodegeneration in cell and animal models. Tryptophanyl-tRNA synthetase inhibition causes protein biosynthesis impairment similar to that revealed in AD. Tryptamine-induced TrpRS gene-dose reduction is associated with TrpRS protein deficiency and cell death. In animals, tryptamine treatment results in toxicity, weight gain, and prediabetes-related hypoglycemia. Sequence analysis of gut microbiome database reveals 89% to 100% ADAS nucleotide identity in American Indian (Cheyenne and Arapaho [C&A]) Oklahomans, of which ~93% being overweight or obese and 50% self-reporting type 2 diabetes (T2D). Alzheimer disease-associated sequence occurs in 10.8% of C&A vs 1.3% of healthy American population. This observation is of considerable interest because T2D links to AD and obesity. Alzheimer disease-associated sequence prevails in gut microbiome of colorectal cancer, which linked to AD. Metabolomics revealed that tryptamine, chorismate precursor quinate, and chorismate product 4-hydroxybenzoate (ubiquinone precursor) are significantly higher, while tryptophan-containing dipeptides are lower due to tRNA aminoacylation deficiency in C&A compared with non-native Oklahoman who showed no ADAS. Thus, gut microbial tryptamine overproduction correlates with ADAS occurrence. Antibiotic and diet additives induce ADAS and tryptamine. Mitogenic/cytotoxic tryptamine cause microbial and human cell death, gut dysbiosis, and consequent disruption of host-microbe homeostasis. Present analysis of 1246 participants from 17 human gut metagenomics studies revealed ADAS in cell death diseases.

Update on the pathophysiology of cluster headache: imaging and neuropeptide studies

OBJECTIVE

Cluster headache (CH) is the most severe primary headache condition. Its pathophysiology is multifaceted and incompletely understood. This review brings together the latest neuroimaging and neuropeptide evidence on the pathophysiology of CH.

METHODS

A review of the literature was conducted by searching PubMed and Web of Science. The search was conducted using the following keywords: imaging studies, voxel-based morphometry, diffusion-tensor imaging, diffusion magnetic resonance imaging, tractography, connectivity, cerebral networks, neuromodulation, central modulation, deep brain stimulation, orexin-A, orexin-B, tract-based spatial statistics, single-photon emission computer tomography studies, positron-emission tomography, functional magnetic resonance imaging, magnetic resonance spectroscopy, trigeminovascular system, neuropeptides, calcitonin gene-related peptide, neurokinin A, substance P, nitric oxide synthase, pituitary adenylate cyclase-activating peptide, vasoactive intestinal peptide, neuropeptide Y, acetylcholine, noradrenaline, and ATP. "Cluster headache" was combined with each keyword for more relevant results. All irrelevant and duplicated records were excluded. Search dates were from October 1976 to May 2018.

RESULTS

Neuroimaging studies support the role of the hypothalamus in CH, as well as other brain areas involved in the pain matrix. Activation of the trigeminovascular system and the release of neuropeptides play an important role in CH pathophysiology. Among neuropeptides, calcitonin gene-related peptide, vasoactive intestinal peptide, and pituitary adenylate cyclase-activating peptide have been reported to be reliable biomarkers for CH attacks, though not specific for CH. Several other neuropeptides are involved in trigeminovascular activation, but the current evidence does not qualify them as reliable biomarkers in CH.

CONCLUSION

CH has a complex pathophysiology and the pain mechanism is not completely understood. Recent neuroimaging studies have provided insight into the functional and structural network bases of CH pathophysiology. Although there has been important progress in neuropeptide studies, a specific biomarker for CH is yet to be found.