Pituitary adenylate-cyclase-activating polypeptide (PACAP): another novel target for treatment of primary headaches?

CGRP physiology, pharmacology, and therapeutic targets: migraine and beyond

Calcitonin gene-related peptide (CGRP) is a neuropeptide with diverse physiological functions. Its two isoforms (α and β) are widely expressed throughout the body in sensory neurons as well as in other cell types, such as motor neurons and neuroendocrine cells. CGRP acts via at least two G protein-coupled receptors that form unusual complexes with receptor activity-modifying proteins. These are the CGRP receptor and the AMY1 receptor; in rodents, additional receptors come into play. Although CGRP is known to produce many effects, the precise molecular identity of the receptor(s) that mediates CGRP effects is seldom clear. Despite the many enigmas still in CGRP biology, therapeutics that target the CGRP axis to treat or prevent migraine are a bench-to-bedside success story. This review provides a contextual background on the regulation and sites of CGRP expression and CGRP receptor pharmacology. The physiological actions of CGRP in the nervous system are discussed, along with updates on CGRP actions in the cardiovascular, pulmonary, gastrointestinal, immune, hematopoietic, and reproductive systems and metabolic effects of CGRP in muscle and adipose tissues. We cover how CGRP in these systems is associated with disease states, most notably migraine. In this context, we discuss how CGRP actions in both the peripheral and central nervous systems provide a basis for therapeutic targeting of CGRP in migraine. Finally, we highlight potentially fertile ground for the development of additional therapeutics and combinatorial strategies that could be designed to modulate CGRP signaling for migraine and other diseases.

Cluster Headache is Still Lurking in the Shadows

Cluster headache, apart from its legendary reputation as the most violent headache that can exist, suffers from an average 60-month delay in diagnosis. The simplicity of the clinical manifestations, although dramatic, makes this delay inexplicable. The education of emergency department physicians and various specialists not specifically dedicated to headaches allows cluster headache to remain in a lurking position with flourishing periods of disease that are often unpredictable in both onset and disappearance. Older drugs have always shown high efficacy but also an equally high rate of adverse events, often discouraging their appropriate use. The availability of a new drug class such as monoclonal antibodies for calcitonin gene-related peptide or its receptor (CGRP_(r)), which have already been efficient for migraine, shows a jeopardized geography of access in the world, and this favors the progression of the episodic form into chronic and of the chronic into refractory.

Protective Effects of PACAP in Peripheral Organs

Pituitary adenylate cyclase activating polypeptide (PACAP) is a neuropeptide widely distributed in the nervous system, where it exerts strong neuroprotective effects. PACAP is also expressed in peripheral organs but its peripheral protective effects have not been summarized so far. Therefore, the aim of the present paper is to review the existing literature regarding the cytoprotective effects of PACAP in non-neuronal cell types, peripheral tissues, and organs. Among others, PACAP has widespread expression in the digestive system, where it shows protective effects in various intestinal pathologies, such as duodenal ulcer, small bowel ischemia, and intestinal inflammation. PACAP is present in both the exocrine and endocrine pancreas as well as liver where it reduces inflammation and steatosis by interfering with hepatic pathology related to obesity. It is found in several exocrine glands and also in urinary organs, where, with its protective effects being mainly published regarding renal pathologies, PACAP is protective in numerous conditions. PACAP displays anti-inflammatory effects in upper and lower airways of the respiratory system. In the skin, it is involved in the development of inflammatory pathology such as psoriasis and also has anti-allergic effects in a model of contact dermatitis. In the non-neuronal part of the visual system, PACAP showed protective effects in pathological conditions of the cornea and retinal pigment epithelial cells. The positive role of PACAP has been demonstrated on the formation and healing processes of cartilage and bone where it also prevents osteoarthritis and rheumatoid arthritis development. The protective role of PACAP was also demonstrated in the cardiovascular system in different pathological processes including hyperglycaemia-induced endothelial dysfunction and age-related vascular changes. In the heart, PACAP protects against ischemia, oxidative stress, and cardiomyopathies. PACAP is also involved in the protection against the development of pre-senile systemic amyloidosis, which is presented in various peripheral organs in PACAP-deficient mice. The studies summarized here provide strong evidence for the cytoprotective effects of the peptide. The survival-promoting effects of PACAP depend on a number of factors which are also shortly discussed in the present review.

Clinical Efficacy and Safety of Electroacupuncture in Migraine Treatment: A Systematic Review and Network Meta-Analysis

Considering the heavy burden of migraine, it is essential to update insufficient and/or outdated clinical evidence supporting electroacupuncture (EA) in migraine therapy. In this study, a literature search of seven medical databases was performed. After data extraction and quality evaluation, 13 randomized controlled trials, including 1559 patients, were assessed in this analysis. Results demonstrated that EA was superior to control treatment (Western medicine, sham-EA, blank control, acupuncture, and acupoint catgut embedding) according to the visual analog scale (VAS) score, frequency of headache attack (Western medicine, sham-EA, blank control), self-rating anxiety scale (SAS [blank control]), self-rating depression score (SDS [Western medicine and blank control]), and clinical efficiency (Western medicine and sham-EA) after treatment ([Formula: see text]). Results of network meta-analysis (for VAS, SAS, and SDS) demonstrated statistically significant differences in VAS scores for EA compared with sham-EA, acupuncture with sham-EA, acupoint catgut embedding with sham-EA, and acupoint catgut embedding with blank control. Rank probability analysis of VAS, SAS, and SDS scores all demonstrated that EA ranked first. Most studies were symmetrically distributed on both sides of the midline in funnel plots for VAS, SAS, and SDS, which indicated a low likelihood of small sample effects. Sensitivity analysis confirmed the stability of the studies included in this research. EA is one of several effective treatments for migraine pain symptoms, and, to some extent, anxiety and depression. Nevertheless, multi-center studies with large sample sizes and/or well-designed randomized controlled trials (RCTs) will be needed in the future.