First and second generation H₁ histamine receptor antagonists produce different sleep-inducing profiles in rats

Effect of second-generation antihistamines on nighttime sleep and daytime sleepiness in patients with allergic rhinitis

BACKGROUND

The daytime tiredness experienced by the vast majority of allergic rhinitis (AR) sufferers is directly related to the fact that they experience disrupted sleep at night. This study compared the effects of recently marketed second-generation H1 antihistamines (SGAs) on nighttime sleep and daytime sleepiness in patients with AR, with patients grouped into those taking non-brain-penetrating antihistamines (NBP group) and those taking brain-penetrating antihistamines (BP group).

METHODS

Patients with AR completed self-administered questionnaire-based surveys to determine Pittsburgh Sleep Quality Index (PSQI) before and after taking SGAs. Statistical analysis was performed on each evaluation item.

RESULTS

Of 53 Japanese patients with AR between 6 and 78 years old, median (SD) age was 37.0 (22.4) years old and 21 were men (40%). Of the 53 patients, 34 were the NBP group and 19 were the BP group. In the NBP group, mean (SD) subjective sleep quality score after medication was 0.76 (0.50), which was significantly lower (better) than the score of 0.97 (0.52) before medication (p = 0.020). In the BP group, mean (SD) subjective sleep quality score after medication was 0.79 (0.54), which was not significantly different from the score of 0.74 (0.56) before medication (p = 0.564). In the NBP group, mean (SD) global PSQI score was 3.47 (1.71) after medication, which was significantly lower (better) than the score of 4.35 (1.92) before medication (p = 0.011). In the BP group, mean (SD) global PSQI score was 2.47 (2.39) after medication, which was not significantly different from the score of 3.00 (2.71) before medication (p = 0.125).

CONCLUSION

Subjective sleep quality and global PSQI score were improved only in the group taking non-brain-penetrating SGAs.

Mast Cell Activation Syndrome Update-A Dermatological Perspective

Mast cells (MCs) are infamous for their role in potentially fatal anaphylaxis reactions. In the last two decades, a more complex picture has emerged, as it has become obvious that MCs are much more than just IgE effectors of anaphylaxis. MCs are defenders against a host of infectious and toxic aggressions (their interactions with other components of the immune system are not yet fully understood) and after the insult has ended, MCs continue to play a role in inflammation regulation and tissue repair. Unfortunately, MC involvement in pathology is also significant. Apart from their role in allergies, MCs can proliferate clonally to produce systemic mastocytosis. They have also been implicated in excessive fibrosis, keloid scaring, graft rejection and chronic inflammation, especially at the level of the skin and gut. In recent years, the term MC activation syndrome (MCAS) was proposed to account for symptoms caused by MC activation, and clear diagnostic criteria have been defined. However, not all authors agree with these criteria, as some find them too restrictive, potentially leaving much of the MC-related pathology unaccounted for. Here, we review the current knowledge on the physiological and pathological roles of MCs, with a dermatological emphasis, and discuss the MCAS classification.

Pathobiology of Second-Generation Antihistamines Related to Sleep in Urticaria Patients

Background: Standard treatment options for urticaria are second-generation antihistamines; however, their effect on sleep is uncertain. This study measures the influence of different antihistamines on the biologic sleep pattern of urticaria patients and the relevance of sleep in urticaria patients. Methods: Ten patients with chronic spontaneous urticaria (CSU) and uncontrolled symptoms under a single dose of second-generation antihistamines were included. Two nights were monitored: the first night after 5 days on single dosage and the second night after 5 days on fourfold dosage. Patient-rated questionnaires were used and sleep was monitored using polygraphy. Results: The patients’ rated daytime sleepiness decreased (p = 0.0319), as did their insomnia severity (p = 0.0349). The urticaria control (UCT) improved (p = 0.0007), as did the quality of life (p < 0.0001). There was no significant change of nightly pruritus (p = 0.1173), but there was an improvement of daytime pruritus (p = 0.0120). A significant increase in rapid eye movement (REM) sleep was seen (p = 0.0002) (from a mean of 3.9% to 14.3%). The deep sleep state (N3) also improved (8.7% to 12.3%) (p = 0.1172). Conclusion: This study has demonstrated an improvement of the sleep pattern in CSU patients under up-dosed second-generation antihistamines, without increased daytime sleepiness, alongside an improvement of urticaria symptoms and quality of life.

Why It Is Important to Consider the Effects of Analgesics on Sleep: A Critical Review

We review the known physiological mechanisms underpinning all of pain processing, sleep regulation, and pharmacology of analgesics prescribed for chronic pain. In particular, we describe how commonly prescribed analgesics act in sleep-wake neural pathways, with potential unintended impact on sleep and/or wake function. Sleep disruption, whether pain- or drug-induced, negatively impacts quality of life, mental and physical health. In the context of chronic pain, poor sleep quality heightens pain sensitivity and may affect analgesic function, potentially resulting in further analgesic need. Clinicians already have to consider factors including efficacy, abuse potential, and likely side effects when making analgesic prescribing choices. We propose that analgesic-related sleep disruption should also be considered. The neurochemical mechanisms underlying the reciprocal relationship between pain and sleep are poorly understood, and studies investigating sleep in those with specific chronic pain conditions (including those with comorbidities) are lacking. We emphasize the importance of further work to clarify the effects (intended and unintended) of each analgesic class to inform personalized treatment decisions in patients with chronic pain. © 2021 American Physiological Society. Compr Physiol 11:1-31, 2021.

A review on α-mangostin as a potential multi-target-directed ligand for Alzheimer's disease

Alzheimer's disease (AD) is an age-related neurodegenerative disease characterized by progressive memory loss, declining language skills and other cognitive disorders. AD has brought great mental and economic burden to patients, families and society. However due to the complexity of AD's pathology, drugs developed for the treatment of AD often fail in clinical or experimental trials. The main problems of current anti-AD drugs are low efficacy due to mono-target method or side effects, especially high hepatotoxicity. To tackle these two main problems, multi-target-directed ligand (MTDL) based on "one molecule, multiple targets" has been studied. MTDLs can regulate multiple biological targets at the same time, so it has shown higher efficacy, better safety. As a natural active small molecule, α-mangostin (α-M) has shown potential multi-factor anti-AD activities in a series of studies, furthermore it also has a certain hepatoprotective effect. The good availability of α-M also provides support for its application in clinical research. In this work, multiple activities of α-M related to AD therapy were reviewed, which included anti-cholinesterase, anti-amyloid-cascade, anti-inflammation, anti-oxidative stress, low toxicity, hepatoprotective effects and drug formulation. It shows that α-M is a promising candidate for the treatment of AD.

A role for mast cells in geographic atrophy

Mast cells (MCs) are the initial responders of innate immunity and their degranulation contribute to various etiologies. While the abundance of MCs in the choroid implies their fundamental importance in the eye, little is known about the significance of MCs and their degranulation in choroid. The cause of geographic atrophy (GA), a progressive dry form of age-related macular degeneration is elusive and there is currently no therapy for this blinding disorder. Here we demonstrate in both human GA and a rat model for GA, that MC degranulation and MC-derived tryptase are central to disease progression. Retinal pigment epithelium degeneration followed by retinal and choroidal thinning, characteristic phenotypes of GA, were driven by continuous choroidal MC stimulation and activation in a slow release fashion in the rat. Genetic manipulation of MCs, pharmacological intervention targeting MC degranulation with ketotifen fumarate or inhibition of MC-derived tryptase with APC 366 prevented all of GA-like phenotypes following MC degranulation in the rat model. Our results demonstrate the fundamental role of choroidal MC involvement in GA disease etiology, and will provide new opportunities for understanding GA pathology and identifying novel therapies targeting MCs.

Cell-based, animal and H1 receptor binding studies relative to the sedative effects of ketotifen and norketotifen atropisomers

OBJECTIVES

Ketotifen (K) and its active metabolite norketotifen (N) exist as optically active atropisomers. They both have antihistaminic and anti-inflammatory properties but the S-atropisomer of N (SN) causes less sedation than K and RN in rodents. This study investigated whether this could be related to a lower concentration of SN in brain or a lower affinity of SN for rat brain H₁ receptors.

METHODS

Ketotifen and norketotifen atropisomers were quantified using a validated chiral HPLC assay. RBE4 and Caco-2 cell monolayers were used in uptake and permeability studies, respectively. Free and total brain-to-plasma (B/P) ratios were determined after injecting racemic K and N into rat tail veins. Affinity for rat brain H₁ receptors (K_I ) was determined using the [³ H]mepyramine binding assay.

KEY FINDINGS

Uptake and permeation studies indicate no stereoselective transport for K or N. B/P ratios reveal the brain concentration of N is lower than K with no stereoselective transport into brain. Finally, the [³ H]mepyramine binding assay shows SN has the lowest affinity for rat brain H₁ receptors.

CONCLUSION

The lower sedative effect of SN in rodents is probably due to a combination of a lower uptake of N than K into the brain and less affinity of SN for CNS H₁ receptors.

Histamine: neural circuits and new medications

Histamine was first identified in the brain about 50 years ago, but only in the last few years have researchers gained an understanding of how it regulates sleep/wake behavior. We provide a translational overview of the histamine system, from basic research to new clinical trials demonstrating the usefulness of drugs that enhance histamine signaling. The tuberomammillary nucleus is the sole neuronal source of histamine in the brain, and like many of the arousal systems, histamine neurons diffusely innervate the cortex, thalamus, and other wake-promoting brain regions. Histamine has generally excitatory effects on target neurons, but paradoxically, histamine neurons may also release the inhibitory neurotransmitter GABA. New research demonstrates that activity in histamine neurons is essential for normal wakefulness, especially at specific circadian phases, and reducing activity in these neurons can produce sedation. The number of histamine neurons is increased in narcolepsy, but whether this affects brain levels of histamine is controversial. Of clinical importance, new compounds are becoming available that enhance histamine signaling, and clinical trials show that these medications reduce sleepiness and cataplexy in narcolepsy.

Sleep and Wakefulness Are Controlled by Ventral Medial Midbrain/Pons GABAergic Neurons in Mice

Sleep-wake behavior is controlled by a wide range of neuronal populations in the mammalian brain. Although the ventral midbrain/pons (VMP) area is suggested to participate in sleep-wake regulation, the neuronal mechanisms have remained unclear. Here, we found that nonspecific cell ablation or selective ablation of GABAergic neurons by expressing diphtheria toxin fragment A in the VMP in male mice induced a large increase in wakefulness that lasted at least 4 weeks. In contrast, selective ablation of dopaminergic neurons in the VMP had little effect on wakefulness. Chemogenetic inhibition of VMP GABAergic neurons also markedly increased wakefulness. The wake-promoting effect of the VMP GABAergic neuron ablation or inhibition was attenuated to varying degrees by the administration of dopamine D1 or D2/3 receptor antagonists and abolished by the administration of both antagonists together. In contrast, chemogenetic activation of VMP GABAergic neurons very strongly increased slow-wave sleep and reduced wakefulness. These findings suggest that VMP GABAergic neurons regulate dopaminergic actions in the sleep-wake behavior of mice.SIGNIFICANCE STATEMENT Current understanding of the neuronal mechanisms and populations that regulate sleep-wake behavior is incomplete. Here, we identified a GABAergic ventral midbrain/pons area that is necessary for controlling the daily amount of sleep and wakefulness in mice. We also found that these inhibitory neurons control wakefulness by suppressing dopaminergic systems. Surprisingly, activation of these neurons strongly induced slow-wave sleep while suppressing wakefulness. Our study reveals a new brain mechanism critical for sleep-wake regulation.

Histamine Regulates Molecular Clock Oscillations in Human Retinal Pigment Epithelial Cells via H1 Receptors

Vertebrate eyes are known to contain circadian clocks, but their regulatory mechanisms remain largely unknown. To address this, we used a cell line from human retinal pigment epithelium (hRPE-YC) with stable coexpression of reporters for molecular clock oscillations (Bmal1-luciferase) and intracellular Ca²⁺ concentrations (YC3.6). We observed concentration-dependent increases in cytosolic Ca²⁺ concentrations after treatment with histamine (1-100 µM) and complete suppression of histamine-induced Ca²⁺ mobilizations by H₁ histamine receptor (H₁R) antagonist d-chlorpheniramine (d-CPA) in hRPE-YC cells. Consistently, real-time RT-PCR assays revealed that H₁R showed the highest expression among the four subtypes (H₁-H₄) of histamine receptors in hRPE-YC cells. Stimulation of hRPE-YC cells with histamine transiently increased nuclear localization of phosphorylated Ca²⁺/cAMP-response element-binding protein that regulates clock gene transcriptions. Administration of histamine also shifted the Bmal1-luciferase rhythms with a type-1 phase-response curve, similar to previous results with carbachol stimulations. Treatment of hRPE-YC cells with d-CPA or with more specific H₁R antagonist, ketotifen, blocked the histamine-induced phase shifts. Furthermore, an H₂ histamine receptor agonist, amthamine, had little effect on the Bmal1-luciferase rhythms. Although the function of the in vivo histaminergic system within the eye remains obscure, the present results suggest histaminergic control of the molecular clock via H₁R in retinal pigment epithelial cells. Also, since d-CPA and ketotifen have been widely used (e.g., to treat allergy and inflammation) in our daily life and thus raise a possible cause for circadian rhythm disorders by improper use of antihistamines.

Investigation of sleep-wake rhythm in non-human primates without restraint during data collection

To understand sleep mechanisms and develop treatments for sleep disorders, investigations using animal models are essential. The sleep architecture of rodents differs from that of diurnal mammals including humans and non-human primates. Sleep studies have been conducted in non-human primates; however, these sleep assessments were performed on animals placed in a restraint chair connected via the umbilical area to the recording apparatus. To avoid restraints, cables, and other stressful apparatuses and manipulations, telemetry systems have been developed. In the present study, sleep recordings in unrestrained cynomolgus monkeys (Macaca fascicularis) and common marmoset monkeys (Callithrix jacchus) were conducted to characterize normal sleep. For the analysis of sleep-wake rhythms in cynomolgus monkeys, telemetry electroencephalography (EEG), electromyography (EMG), and electrooculography (EOG) signals were used. For the analysis of sleep-wake rhythms in marmosets, telemetry EEG and EOG signals were used. Both monkey species showed monophasic sleep patterns during the dark phase. Although non-rapid eye movement (NREM) deep sleep showed higher levels at the beginning of the dark phase in cynomolgus monkeys, NREM deep sleep rarely occurred during the dark phase in marmosets. Our results indicate that the use of telemetry in non-human primate models is useful for sleep studies, and that the different NREM deep sleep activities between cynomolgus monkeys and common marmoset monkeys are useful to examine sleep functions.

Diphenhydramine's role in death investigations: an examination of diphenhydramine prevalence in 2 US geographical areas

PURPOSE

Diphenhydramine (DPH), an over-the-counter first-generation H1 receptor antagonist, is not a common drug of abuse; however, it is encountered in cases of overdose both in the clinical setting and in death investigations. The toxicology laboratories in the Tarrant County Medical Examiner's Office and the District of Columbia Office of The Chief Medical Examiner analyze antemortem and postmortem specimens. Presented are the findings of this evaluation and detailed histories of cases involving DPH.

METHODS

Toxicology reports, autopsy reports, and death investigator narratives were obtained in cases involving DPH at toxic and lethal levels in which this compound was the primary cause or a contributing factor in the death.

RESULTS

Blood concentrations were quantified at a range of 2870 to 21,263 ng/mL. A rare occurrence of DPH abuse via documented intravenous administration leading to death is presented. The cases presented here generally involved much higher concentrations of DPH and an older population than those in previous published data regarding DPH's role in death investigation and abuse.

CONCLUSIONS

As people seek legal alternative drugs to abuse and with the ease of obtaining information via online forums, there is a potential to see an increase in the number of cases involving excessive use of DPH.

Olanzapine and clozapine differently affect sleep in patients with schizophrenia: results from a double-blind, polysomnographic study and review of the literature

Schizophrenia is associated with impaired sleep continuity. The second generation antipsychotics clozapine and olanzapine have been reported to improve sleep continuity but also to rarely induce restless legs syndrome (RLS). The aims of this randomized double-blind study were to compare the effects of clozapine and olanzapine on sleep and the occurrence of RLS. Therefore, polysomnographies were recorded and RLS symptoms were assessed in 30 patients with schizophrenia before and after 2, 4 and 6 weeks of treatment with either clozapine or olanzapine. Treatment with both antipsychotics increased total sleep time, sleep period time and sleep efficiency and decreased sleep onset latency. These changes were similar in both groups, occurred during the first 2 treatment weeks and were sustained. For example, sleep efficiency increased from 83% (olanzapine) and 82% (clozapine) at baseline to 95% at week 2 and 97% at week 6 in both treatment groups. Sleep architecture was differently affected: clozapine caused a significantly stronger increase of stage 2 sleep (44%) than olanzapine (11%) but olanzapine a significantly stronger increase of REM-sleep. Olanzapine caused an 80% increase of slow wave sleep whereas clozapine caused a 6% decrease. No patient reported any of 4 RLS defining symptoms at baseline. During treatment, 1 patient of each group reported at one visit all 4 symptoms, i.e. met the diagnosis of an RLS. In conclusion, sleep continuity similarly improved and sleep architecture changed more physiologically with olanzapine. Neither of the antipsychotics induced RLS symptoms that were clinically relevant.

Histaminergic system in brain disorders: lessons from the translational approach and future perspectives

Histamine and its receptors were first described as part of immune and gastrointestinal systems, but their presence in the central nervous system and importance in behavior are gaining more attention. The histaminergic system modulates different processes including wakefulness, feeding, and learning and memory consolidation. Histamine receptors (H1R, H2R, H3R, and H4R) belong to the rhodopsin-like family of G protein-coupled receptors, present constitutive activity, and are subjected to inverse agonist action. The involvement of the histaminergic system in brain disorders, such as Alzheimer's disease, schizophrenia, sleep disorders, drug dependence, and Parkinson's disease, is largely studied. Data obtained from preclinical studies point antagonists of histamine receptors as promising alternatives to treat brain disorders. Thus, clinical trials are currently ongoing to assess the effects of these drugs on humans. This review summarizes the role of histaminergic system in brain disorders, as well as the effects of different histamine antagonists on animal models and humans.

Insomnia treatment in the third trimester of pregnancy reduces postpartum depression symptoms: a randomized clinical trial

Mental health is an important medical issue in perinatal care, and there is increasing evidence that insomnia during pregnancy is associated with postpartum depression (PPD). Therefore, the present study evaluated the effect of insomnia treatment during the third trimester of pregnancy on PPD symptoms. Fifty-four pregnant women with insomnia were randomly assigned to trazodone, diphenhydramine, or placebo treatment. Sleep quality was measured by actigraphy at baseline, and after 2 and 6 weeks of treatment. In addition, depression was assessed 2 and 6 weeks after delivery. Trazodone and diphenhydramine improved sleep profile compared to placebo after 6 weeks of treatment. Further, depressive symptoms were reduced 2 and 6 weeks after delivery in trazodone and diphenhydramine groups compared to placebo. No differences in depressive symptoms were observed between the trazodone and diphenhydramine groups. These findings indicate that insomnia treatment with trazodone or diphenhydramine during the third trimester of pregnancy may prevent PPD.

Histamine from brain resident MAST cells promotes wakefulness and modulates behavioral states

Mast cell activation and degranulation can result in the release of various chemical mediators, such as histamine and cytokines, which significantly affect sleep. Mast cells also exist in the central nervous system (CNS). Since up to 50% of histamine contents in the brain are from brain mast cells, mediators from brain mast cells may significantly influence sleep and other behaviors. In this study, we examined potential involvement of brain mast cells in sleep/wake regulations, focusing especially on the histaminergic system, using mast cell deficient (W/W^v) mice. No significant difference was found in the basal amount of sleep/wake between W/W^v mice and their wild-type littermates (WT), although W/W^v mice showed increased EEG delta power and attenuated rebound response after sleep deprivation. Intracerebroventricular injection of compound 48/80, a histamine releaser from mast cells, significantly increased histamine levels in the ventricular region and enhanced wakefulness in WT mice, while it had no effect in W/W^v mice. Injection of H1 antagonists (triprolidine and mepyramine) significantly increased the amounts of slow-wave sleep in WT mice, but not in W/W^v mice. Most strikingly, the food-seeking behavior observed in WT mice during food deprivation was completely abolished in W/W^v mice. W/W^v mice also exhibited higher anxiety and depression levels compared to WT mice. Our findings suggest that histamine released from brain mast cells is wake-promoting, and emphasizes the physiological and pharmacological importance of brain mast cells in the regulation of sleep and fundamental neurobehavior.

Sites of action of sleep and wake drugs: insights from model organisms

Small molecules have been used since antiquity to regulate our sleep. Despite the explosion of diverse drugs to treat problems of too much or too little sleep, the detailed mechanisms of action and especially the neuronal targets by which these compounds alter human behavioural states are not well understood. Research efforts in model systems such as mouse, zebrafish and fruit fly are combining conditional genetics and optogenetics with pharmacology to map the effects of sleep-promoting drugs onto neural circuits. Recent studies raise the possibility that many small molecules alter sleep and wake via specific sets of critical neurons rather than through the global modulation of multiple brain targets. These findings also uncover novel brain areas as sleep/wake regulators and indicate that the development of circuit-selective drugs might alleviate sleep disorders with fewer side effects.

Acute enhancement of non-rapid eye movement sleep in rats after drinking water contaminated with cadmium chloride

Cadmium (Cd) is a heavy metal widely used or effused by industries. Serious environmental Cd pollution has been reported over the past two centuries, whereas the mechanisms underlying Cd-mediated diseases are not fully understood. Interestingly, an increase in reactive oxygen species (ROS) after Cd exposure has been shown. Our group has demonstrated that sleep is triggered via accumulation of ROS during neuronal activities, and we thus hypothesize the involvement of Cd poisoning in sleep-wake irregularities. In the present study, we analyzed the effects of Cd intake (1-100 ppm CdCl₂ in drinking water) on rats by monitoring sleep encephalograms and locomotor activities. The results demonstrated that 100 ppm CdCl₂ administration for 28 h was sufficient to increase non-rapid-eye-movement (non-REM) sleep and reduce locomotor activities during the night (the rat active phase). In contrast, free-running locomotor rhythms under constant dim red light and their re-entrainment to 12:12-h light/dark cycles were intact under chronic (1 month) 100 ppm CdCl₂ administrations, suggesting a limited influence on circadian clock movements at this dosage. The relative amount of oxidized glutathione increased in the brain after the 28-h 100 ppm CdCl₂ administrations similar to the levels in cultured astrocytes receiving H₂O₂ or CdCl₂ in culture medium. Therefore, we propose Cd-induced sleep as a consequence of oxidative stress. As oxidized glutathione is an endogenous sleep substance, we suggest that Cd rapidly induces sleepiness and influences activity performance by occupying intrinsic sleep-inducing mechanisms. In conclusion, we propose increased non-REM sleep during the active phase as an index of acute Cd exposure.