The effect of Lu AG09222 on PACAP38- and VIP-induced vasodilation, heart rate increase, and headache in healthy subjects: an interventional, randomized, double-blind, parallel-group, placebo-controlled study.

BACKGROUND: Pituitary adenylate cyclase-activating polypeptide (PACAP), structurally related to vasoactive intestinal peptide (VIP), is one of the important mediators in the pathogenesis of migraine and is known to dilate cranial arteries and induce headache and migraine. Our objective was to determine whether Lu AG09222-an investigational humanized monoclonal antibody directed against PACAP ligand-would inhibit the PACAP-signaling cascade by abolishing its vasodilatory and headache-inducing abilities. METHODS: In a randomized, double-blind, parallel-group, single-dose, placebo-controlled study of Lu AG09222, healthy volunteers aged 18-45 years without history of headache disorders were randomly allocated to three treatment sequences (1:2:2) on two experimental infusion visits with 9 ± 3 days' interval: placebo + saline + saline (n = 5), placebo + PACAP38 + VIP (n = 10), and Lu AG09222 + PACAP38 + VIP (n = 10). The primary outcome measure was area under the curve (AUC) of the change in superficial temporal artery (STA) diameter from 0 to 120 min after start of infusion of PACAP38. The study was conducted at the Danish Headache Center in Copenhagen, Denmark. RESULTS: In participants who received Lu AG09222 + PACAP38 infusion, there was a significantly lower STA diameter (mean (SE) [95% CI] AUC ‒35.4 (4.32) [‒44.6, ‒26.3] mm × min; P < 0.0001) compared to participants who received placebo + PACAP38 infusion. Secondary and explorative analysis revealed that PACAP38 infusion induced an increase in facial blood flow, heart rate and mild headache, and indicated that these PACAP38-induced responses were inhibited by Lu AG09222. CONCLUSIONS: This proof-of-mechanism study demonstrated that Lu AG09222 inhibited PACAP38-induced cephalic vasodilation and increases in heart rate, and reduced concomitant headache. Lu AG09222 may be a potential therapy against migraine and other PACAP-mediated diseases. TRIAL REGISTRATION: ClinicalTrials.gov: NCT04976309. Registration date: July 19, 2021.

Involvement of serotonin 2A receptor activation in modulating medial prefrontal cortex and amygdala neuronal activation during novelty-exposure.

The medial prefrontal cortex (PFC) plays a major role in executive function by exerting a top-down control onto subcortical areas. Novelty-induced frontal cortex activation is 5-HT2A receptor (5-HT2AR) dependent. Here, we further investigated how blockade of 5-HT2ARs in mice exposed to a novel open-field arena affects medial PFC activation and basolateral amygdala (BLA) reactivity. We used c-Fos immunoreactivity (IR) as a marker of neuronal activation and stereological quantification for obtaining the total number of c-Fos-IR neurons as a measure of regional activation. We further examined the impact of 5-HT2AR blockade on the striatal-projecting BLA neurons. Systemic administration of ketanserin (0.5mg/kg) prior to novel open-field exposure resulted in reduced total numbers of c-Fos-IR cells in dorsomedial PFC areas and the BLA. Moreover, there was a positive correlation between the relative time spent in the centre of the open-field and BLA c-Fos-IR in the ketanserin-treated animals. Unilateral medial PFC lesions blocked this effect, ascertaining an involvement of this frontal cortex area. On the other hand, medial PFC lesioning exacerbated the more anxiogenic-like behaviour of the ketanserin-treated animals, upholding its involvement in modulating averseness. Ketanserin did not affect the number of activated striatal-projecting BLA neurons (measured by number of Cholera Toxin b (CTb) retrograde labelled neurons also being c-Fos-IR) following CTb injection in the ventral striatum. These results support a role of 5-HT2AR activation in modulating mPFC and BLA activation during exposure to a novel environment, which may be interrelated. Conversely, 5-HT2AR blockade does not seem to affect the amygdala-striatal projection.

5-HT2A Receptor Binding in the Frontal Cortex of Parkinson's Disease Patients and Alpha-Synuclein Overexpressing Mice: A Postmortem Study.

The 5-HT2A receptor is highly involved in aspects of cognition and executive function and seen to be affected in neurodegenerative diseases like Alzheimer's disease and related to the disease pathology. Even though Parkinson's disease (PD) is primarily a motor disorder, reports of impaired executive function are also steadily being associated with this disease. Not much is known about the pathophysiology behind this. The aim of this study was thereby twofold: (1) to investigate 5-HT2A receptor binding levels in Parkinson's brains and (2) to investigate whether PD associated pathology, alpha-synuclein (AS) overexpression, could be associated with 5-HT2A alterations. Binding density for the 5-HT2A-specific radioligand [(3)H]-MDL 100.907 was measured in membrane suspensions of frontal cortex tissue from PD patients. Protein levels of AS were further measured using western blotting. Results showed higher AS levels accompanied by increased 5-HT2A receptor binding in PD brains. In a separate study, we looked for changes in 5-HT2A receptors in the prefrontal cortex in 52-week-old transgenic mice overexpressing human AS. We performed region-specific 5-HT2A receptor binding measurements followed by gene expression analysis. The transgenic mice showed lower 5-HT2A binding in the frontal association cortex that was not accompanied by changes in gene expression levels. This study is one of the first to look at differences in serotonin receptor levels in PD and in relation to AS overexpression.

Altered α-synuclein, parkin, and synphilin isoform levels in multiple system atrophy brains.

Together with Parkinson's disease (PD) and dementia with Lewy bodies, multiple system atrophy (MSA) is a member of a diverse group of neurodegenerative disorders termed α-synucleinopathies. Previously, it has been shown that α-synuclein, parkin, and synphilin-1 display disease-specific transcription patterns in frontal cortex in PD, dementia with Lewy bodies, and MSA, and thus may mediate the development of α-synucleinopathies. In this study, the differential expression of α-synuclein isoforms on transcriptional and translational levels was ascertained in MSA patients in comparison with PD cases and normal controls using isoform-specific primers and exon-specific antibodies in substantia nigra, striatum, cerebellar cortex, and nucleus dentatus. These regions are severely affected by α-synuclein pathology and neurodegeneration. Furthermore, we have also investigated transcript levels for parkin and synphilin-1 isoforms. In MSA brains, α-synuclein140 and α-synuclein 112 isoform levels were significantly increased, whereas levels of the α-synuclein 126 isoform were decreased in the substantia nigra, striatum, cerebellar cortex, and nucleus dentatus versus controls. Moreover, in MSA cases, we showed increased levels of parkin isoforms lacking the N-terminal ubiquitin-like domain and an aggregation-prone synphilin-1A isoform that causes neuronal toxicity in MSA. In PD brains, parkin transcript variant 3, 7, and 11 were significantly and specifically over-expressed in the striatum and cerebellar cortex, together with synphilin-1A and 1C. The changes of isoform expression profiles in neurodegenerative diseases suggest alterations in the regulation of transcription and/or splicing events, leading to regional/cellular events that may be important for the highly increased aggregation of α-synuclein in the brain. We report differential expression of α-synuclein, parkin, and synphilin-1 isoforms in multiple system atrophy (MSA) versus Parkinson's disease and normal control brains. We have focused on brain regions that are severely affected by α-synuclein pathology and neurodegeneration in MSA. The reported changes of isoform expression profiles suggest alterations in the regulation of transcription that may be important for aggregation of α-synuclein in the brain.