The serotonin 2A receptor (5‐HT2AR) is implicated in the pathophysiology and treatment of various psychiatric disorders. 18Faltanserin and 11CCimbi‐36 positron emission tomography (PET) allow for ...high‐resolution imaging of 5‐HT2AR in the living human brain. Cerebral 5‐HT2AR binding is strongly genetically determined, though the impact of specific variants is poorly understood. Candidate gene studies suggest that HTR2A single nucleotide polymorphisms including rs6311/rs6313, rs6314, and rs7997012 may influence risk for psychiatric disorders and mediate treatment response. Although known to impact in vitro expression of 5‐HT2AR or other serotonin (5‐HT) proteins, their effect on human in vivo brain 5‐HT2AR binding has as of yet been insufficiently studied. We thus assessed the extent to which these variants and the commonly studied 5‐HTTLPR predict neocortex in vivo 5‐HT2AR binding in healthy adult humans. We used linear regression analyses and likelihood ratio tests in 197 subjects scanned with 18Faltanserin or 11CCimbi‐36 PET. Although we observed genotype group differences in 5‐HT2AR binding of up to ~10%, no genetic variants were statistically significantly predictive of 5‐HT2AR binding in what is the largest human in vivo 5‐HT2AR imaging genetics study to date. Thus, in vitro and post mortem results suggesting effects on 5‐HT2AR expression did not carry over to the in vivo setting. To any extent these variants might affect clinical risk, our findings do not support that 5‐HT2AR binding mediates such effects. Our observations indicate that these individual variants do not significantly contribute to genetic load on human in vivo 5‐HT2AR binding.
We evaluated whether common HTR2A single nucleotide polymorphisms rs6313, rs6314, rs7997012, and the 5‐HTTLPR predict 5‐HT2AR binding, assessed with 18Faltanserin and 11CCimbi‐36 positron emission tomography in healthy individuals. This is the largest study to date evaluating genetic predictors of a human in vivo serotonin protein (n = 197). Although relative differences of up to 10% were detected, no statistically significant effect was observed. Our results do not support a significant contribution of these individual variants to genetic load on 5‐HT2AR binding.
Abstract
The serotonin transporter (5-HTT) critically shapes serotonin neurotransmission by regulating extracellular brain serotonin levels; it remains unclear to what extent 5-HTT levels in the ...human brain are genetically determined. Here we applied
11
CDASB positron emission tomography to image brain 5-HTT levels and evaluated associations with five common serotonin-related genetic variants that might indirectly regulate 5-HTT levels (
BDNF
rs6265,
SLC6A4
5-HTTLPR,
HTR1A
rs6295,
HTR2A
rs7333412, and
MAOA
rs1137070) in 140 healthy volunteers. In addition, we explored whether these variants could predict in vivo 5-HTT levels using a five-fold cross-validation random forest framework.
MAOA
rs1137070 T-carriers showed significantly higher brain 5-HTT levels compared to C-homozygotes (2–11% across caudate, putamen, midbrain, thalamus, hippocampus, amygdala and neocortex). We did not observe significant associations for the
HTR1A
rs6295 and
HTR2A
rs7333412 genotypes. Our previously observed lower subcortical 5-HTT availability for rs6265 met-carriers remained in the presence of these additional variants. Despite this significant association, our prediction models showed that genotype moderately improved prediction of 5-HTT in caudate, but effects were not statistically significant after adjustment for multiple comparisons. Our observations provide additional evidence that serotonin-related genetic variants modulate adult human brain serotonin neurotransmission.
Women who use oral contraceptives (OCs) may have a higher risk of developing a depression, which is associated with both vulnerability to stress and cognitive dysfunction. OCs disrupt the ...hypothalamic-pituitary-gonadal (HPG) axis by suppressing endogenous sex steroid production including estradiol. The HPG axis and the hypothalamic-pituitary-adrenal (HPA) axis are known to interact, possibly through modulations driven by estradiol. OCs may affect HPA regulation capacity, i.e., disturb cortisol dynamics such as the cortisol awakening response (CAR), and influence cognition such as working memory (WM). We hypothesize that OC use is associated with blunted cortisol dynamics and impaired WM performance relative to non-users.
Data from 78 healthy women in the reproductive age were available from the CIMBI database. We evaluated if CAR and WM differed between OC users (n=25) and non-users (n=53) and if the level of estradiol modulated the OC use effect on CAR or WM in generalized least square models.
We found that OC users had a blunted CAR (p= 0.006) corresponding to a 61% reduction relative to non-users; however, no estradiol-BY-OC use interaction effect was observed on CAR. Also, OC users had higher cortisol levels at awakening compared to non-users (p = 0.03). We observed no effect of OC use or an estradiol-BY-OC use interaction effect on WM. Also, within the OC user group, neither CAR nor WM was associated with suppressed estradiol. CAR was not associated with WM.
Healthy women who use OCs have blunted cortisol dynamics relative to non-users. However, we could not detect OC use effects on working memory in our sample size. We speculate that disrupted cortisol dynamics may be important for the emergence of depressive symptoms in OC users.
Objective
The Cortisol Awakening Response (CAR) measured as the transient increase in cortisol levels following morning awakening appears to be a distinct feature of the HPA axis. Patients with ...bipolar disorder (BD) experience daily stress, mood instability (MI) and studies have shown disrupted HPA-axis dynamics. Aims: to evaluate (1) patient-evaluated stress against the CAR, (2) associations between the CAR and mood symptoms, and (3) the effect of smartphone-based treatment on the CAR.
Methods
Patients with BD (n = 67) were randomized to the use of daily smartphone-based monitoring (the intervention group) or to the control group for six months. Clinically rated symptoms according to the Hamilton Depression Rating Scale 17-items (HDRS), the Young Mania Rating Scale (YMRS), patient-evaluated perceived stress using Cohen’s Perceived Stress Scale (PSS) and salivary awakening cortisol samples used for measuring the CAR were collected at baseline, after three and six months. In the intervention group, smartphone-based data on stress and MI were rated daily during the entire study period.
Results
Smartphone-based patient-evaluated stress (
B: 134.14, 95% CI: 1.35; 266.92, p
=
0.048
) and MI (
B: 430.23, 95% CI: 52.41; 808.04, p
=
0.026
) mapped onto increased CAR. No statistically significant associations between the CAR and patient-evaluated PSS or the HDRS and the YMRS, respectively were found. There was no statistically significant effect of smartphone-based treatment on the CAR.
Conclusion
Our data, of preliminary character, found smartphone-based patient-evaluations of stress and mood instability as read outs that reflect CAR dynamics. Smartphone-supported clinical care did not in itself appear to disturb CAR dynamics.
Positron emission tomography (PET) has become an essential clinical tool for diagnosing neurodegenerative diseases with abnormal accumulation of proteins like amyloid-β or tau. Despite many attempts, ...it has not been possible to develop an appropriate radioligand for imaging aggregated α-synuclein in the brain for diagnosing, e.g., Parkinson's Disease. Access to a large animal model with α-synuclein pathology would critically enable a more translationally appropriate evaluation of novel radioligands. We here establish a pig model with cerebral injections of α-synuclein preformed fibrils or brain homogenate from postmortem human brain tissue from individuals with Alzheimer's disease (AD) or dementia with Lewy body (DLB) into the pig's brain, using minimally invasive surgery and validated against saline injections. In the absence of a suitable α-synuclein radioligand, we validated the model with the unselective amyloid-β tracer
CPIB, which has a high affinity for β-sheet structures in aggregates. Gadolinium-enhanced MRI confirmed that the blood-brain barrier was intact. A few hours post-injection, pigs were PET scanned with
CPIB. Quantification was done with Logan invasive graphical analysis and simplified reference tissue model 2 using the occipital cortex as a reference region. After the scan, we retrieved the brains to confirm successful injection using autoradiography and immunohistochemistry. We found four times higher
CPIB uptake in AD-homogenate-injected regions and two times higher uptake in regions injected with α-synuclein-preformed-fibrils compared to saline. The
CPIB uptake was the same in non-injected (occipital cortex, cerebellum) and injected (DLB-homogenate, saline) regions. With its large brain and ability to undergo repeated PET scans as well as neurosurgical procedures, the pig provides a robust, cost-effective, and good translational model for assessment of novel radioligands including, but not limited to, proteinopathies.
The purinergic P2X3 and P2X2/3 receptors are in the peripheral nervous system almost exclusively confined to afferent sensory neurons, where they are found both at peripheral and central synapses. ...The P2X3 receptor is implicated in both neuropathic and inflammatory pain. However, the role of the P2X3 receptor in chronic cancer-induced bone pain is less known. Here we investigated the effect of systemic acute and chronic administration of the selective P2X3, P2X2/3 receptor antagonist (5-(3-Phenoxyphenyl)methyl(1S)-1,2,3,4-tetrahydro-1-naphthalenylaminocarbonyl-1,2,4-benzenetricarboxylic acid sodium salt hydrate) (A-317491) in a murine model of cancer-induced bone pain. Chronic administration of A-317491 (30μmol/kgs.c., b.i.d.) resulted in a transient attenuation of pain related behaviours in the early stage of the bone cancer model, but had no effect in the late and more progressed stage of bone cancer. Also, acute administration of A-317491 (100μmol/kgs.c.) had no effect in the progressed stage of the bone cancer pain model. Thus, systemically administered A-317491 did not demonstrate a robust effect in the present mouse model of cancer-induced bone pain.
•Tetrahydrobiopterin induces pro-nociceptive effects following peripheral injection.•Local pre-treatment with morphine attenuate tetrahydrobiopterin evoked nociception.•Tetrahydrobiopterin did not ...act through prostaglandin release.•Nitric oxide inhibition does not mediate tetrahydrobiopterin evoked nociception.•TRPV1 activation is not involved in tetrahydrobiopterin evoked nociception.
Tetrahydrobiopterin (BH4) is implicated in the development and maintenance of chronic pain. After injury/inflammation, the biosynthesis of BH4 is markedly increased in sensory neurons, and the pharmacological and genetic inhibition of BH4 shows analgesic effects in pre-clinical animal pain models. Intrathecal injections of BH4 have been shown to induce and enhance pain-like behaviours in rats, suggesting that under chronic pain conditions BH4 may act by facilitating central sensitisation. So far it is unknown whether BH4 acts on peripheral sites of the somatosensory system or whether BH4 per se provokes nociceptive pain behaviours. The purpose of this study was therefore to investigate the acute nociceptive effects of intraplantar injection of BH4. BH4 was found to induce dose-dependent licking/biting of the paw lasting 5min, which was not observed following an injection of biopterin (inactive BH4 metabolite). Paw swelling, measured as paw thickness and weight, was not observed after BH4 injection. To explore possible mechanisms of action of BH4, the effect of local pre-treatment with indomethacin, Nω-nitro-l-arginine methyl ester, Nω-nitro-l-arginine, capsazepine and ruthenium red was tested. Morphine served as a positive control. Intraplantar pre-injection of morphine dose-dependently inhibited BH4-induced nociception, while none of the other compounds showed any statistical significant antinociception. These results suggest that BH4 exhibits nociceptive properties at peripheral sites of the somatosensory system, proposing an as yet unexplored involvement of BH4 in peripheral nociceptive processes. However, this appears not to be mediated through nitric oxide and prostaglandin release or by activation of the transient receptor potential vanilloid 1.
Background
Positron emission tomography (PET) is a molecular imaging technique that can be used to investigate the in vivo pharmacology of drugs. Initial preclinical evaluation of PET tracers is ...often conducted in rodents due to the accessibility of disease models as well as economic considerations. Compared to larger species, rodents display a higher expression and/or activity of efflux transporters such as the P-glycoprotein (P-gp). Low brain uptake could, therefore, be species-specific and uptake in rodents not be predictive for that in humans. We hypothesized that a better prediction from rodent data could be achieved when a tracer is evaluated under P-gp inhibition. Consequently, we compared the performance of eight neuroreceptor tracers in rats with and without P-gp inhibition including a specific binding blockade. This data set was then used to predict the binding of these eight tracers in pigs.
Methods
PET tracers targeting serotonin 5-HT
2A
receptors (
18
FMH.MZ,
18
FAltanserin,
11
CCimbi-36,
11
CPimavanserin), serotonin 5-HT
7
receptors (
11
CCimbi-701,
11
CCimbi-717 and
11
CBA-10) and dopamine D
2/3
receptors (
18
FFallypride) were used in the study. The brain uptake and target-specific binding of these PET radiotracers were evaluated in rats with and without inhibition of P-gp. Rat data were subsequently compared to the results obtained in pigs.
Results
Without P-gp inhibition, the amount of target-specific binding in the rat brain was sufficient to justify further translation for three out of eight evaluated tracers. With P-gp inhibition, results for five out of eight tracers justified further translation. The performance in pigs could correctly be predicted for six out of eight tracers when rat data obtained under P-gp inhibition were used, compared to four out of eight tracers without P-gp inhibition.
Conclusions
P-gp strongly affects the uptake of PET tracers in rodents, but false prediction outcomes can be reduced by evaluating a tracer under P-gp inhibition.
•The hph-1 mouse is a model of BH4 deficiency implicated in affective disorders.•Hph-1 mice display altered anxiety- and depression-like behaviours.•The changes are both sex- and ...test-dependent.•Altered phenotypes possibly reflect reduced monoamine and nitric oxide levels.
Decreased tetrahydrobiopterin (BH4) biosynthesis has been implicated in the pathophysiology of anxiety and depression. The aim of this study was therefore to characterise the phenotype of homozygous hph-1 (hph) mice, a model of BH4 deficiency, in behavioural tests of anxiety and depression as well as determine hippocampal monoamine and plasma nitric oxide levels. In the elevated zero maze test, hph mice displayed increased anxiety-like responses compared to wild-type mice, while the marble burying test revealed decreased anxiety-like behaviour. This was particularly observed in male mice. In the tail suspension test, hph mice of both sexes displayed increased depression-like behaviours compared to wild-type counterparts, whereas the forced swim test showed a trend towards increased depression-like behaviours in male hph mice, but significant decrease in depression-like behaviours in female mice. This study provides the first evidence that congenital BH4 deficiency regulates anxiety- and depression-like behaviours. The altered responses observed possibly reflect decreased hippocampal serotonin and dopamine found in hph mice compared to wild-type mice, but also reduced nitric oxide formation. We propose that the hph-1 mouse may be a novel tool to investigate the role of BH4 deficiency in anxiety and depression.
The cortisol awakening response (CAR) describes the sharp increase in cortisol secretion within 60 min after awakening. A summary of the CAR, the area under the cortisol curve above the awakening ...cortisol value (AUCi) is a widely used biomarker in health research. Estimation of the AUCi rely on a number of collected salivary samples at fixed time intervals (i.e., 5 samples in 15 min intervals) starting from awakening. Little empirical work has been executed to investigate the impact of reducing sampling times on AUCi estimation, which could potentially improve participant compliance and reduce operational costs. This study aimed to assess the reliability and validity of using 3-sample AUCi versus 5-sample AUCi, i.e., systematic and random fluctuations based on a large dataset from healthy and case individuals (total n = 537). We showed that the ideal timing of 3-sampling times was 0–30–60 min with a median difference in AUCi of − 8 nmol*h/L and interquartile range of 65 nmol*h/L among healthy individuals, and − 12 nmol*h/L and 78 nmol*h/L among case individuals. We subsequently validated the 3-sample AUCi by re-analyzing three published association studies. Overall, we obtained similar p-values with 3-sample AUCi when compared to 5-sample AUCi, while smaller effect sizes and standard errors were observed. In conclusion, despite a less precise estimation of the AUCi itself, our data support that the AUC measure of the CAR, based on three samples collected at 0–30–60 min from awakening, provides reliable results in association studies.
•Reducing number of samples to estimate the cortisol awakening response is operable.•Saliva sampled 0–30–60 min from awakening showed highest accuracy and precision.•Sampling across 0–30–60 min was equally valid in both sexes relative to 5 samples.•The 3-sample version replicated previous findings of association studies.•The 3-sample cortisol awakening response estimate exhibited reliable results.
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