Circadian rhythm of cutaneous hypersensitivity reactions in nocturnal asthma

Circadian clock-based therapeutics in chronic pulmonary diseases

The circadian clock is the biochemical oscillator that orchestrates the observable circadian rhythms in physiology and behavior. Disruption of the circadian clock in the lungs during chronic pulmonary diseases is considered one of the key etiological risk factors that drive pathobiology. Preclinical studies support that pharmacological manipulation of the circadian clock is a conceivable approach for the development of novel clock-based therapeutics. Despite recent advances, no effort has been undertaken to integrate novel findings for the treatment and management of chronic lung diseases. We, therefore, recognize the need to discuss the candidate clock genes that can be potentially targeted for therapeutic intervention. Here, we aim to create the first roadmap that will advance the development of circadian- clock-based therapeutics that may provide better outcomes in treating chronic pulmonary diseases.

Diurnal Variations in Skin Prick Testing

Background: Prior research suggests that skin prick testing (SPT) might be larger in the afternoon, with unclear clinical significance. Methods: This retrospective chart review analyzed SPT results from patients between June 2008 and June 2017, organized into 4 time groups for analysis (Group 1: 7:00 AM -10:29 AM, Group 2: 10:30 AM -11:59 AM, Group 3: 12:00 PM -2:29 PM, and Group 4: 2:30 PM -8:15 PM). Results: In total, 12,982 (n) patient test results had positive histamine and were included in final analysis. Histamine wheal size was not significantly increased in the PM compared with AM (P = 0.89). Food allergen and aeroallergen wheal sizes were not significantly increased in PM. Histamine erythema size was increased in the PM compared with AM (P ≤ 0.01). Food allergen and aeroallergen erythema sizes trended toward an increase in the PM. Conclusions: There were not significant differences in SPT wheal size based on time of day for histamine, food allergens, or aeroallergens. SPT can be reliably performed at any time of day.

Effects of constant light exposure on allergic and irritant contact dermatitis in mice reared under constant light conditions

Environmental light levels can affect physiological functions, such as general activity, body temperature and metabolism. Irregular lifestyles, such as those involving exposure to light during the night, can exacerbate the clinical symptoms of several inflammatory skin diseases. However, the effects of constant light exposure on immune responses are not fully understood. This study aimed to elucidate the effects of constant light exposure on two major types of skin reactions, allergic contact dermatitis (ACD) and irritant contact dermatitis (ICD). BALB/c mice were kept under constant light conditions or a normal light and dark cycle, and their ACD and ICD responses were assessed after the topical application of 2,4,6-trinitro-1-chlorobenzene and croton oil, respectively, to the ear skin. Interestingly, in both ACD and ICD, the ear-swelling response and local leukocyte infiltration were aggravated by constant exposure to light, which has previously been shown to severely disturb the behavioural rhythms of mice. In ACD, these findings were accompanied by increases in the numbers of degranulated mast cells and eosinophils. These results suggest that constant light exposure intensifies allergic and non-allergic skin inflammation.

Lentinan Inhibited the Activation of Th2 Cells in Allergic Mice by Reducing the Amplitude of Changes in Biological Rhythm

INTRODUCTION

Biological rhythm is inextricably linked to the physiological mechanisms of allergic diseases, but the exact mechanisms are still poorly understood. Clinical studies have reported rhythmic fluctuations in allergic diseases. The search for natural and harmless active ingredients based on biological rhythm with which to regulate allergic diseases is essential for the control of food allergy.

METHODS

In this study, mice were treated at different time points to determine the link between the severity of allergic reactions and the circadian clock genes. The mice were treated with lentinan, either continuously or discontinuously, to assess their clinical symptoms, vascular permeability, immune cells, cytokines, and clock genes. Specifically, rat basophilic leukemia (RBL-2H3) cells were treated with lentinan and the rhythmic changes of cell degranulation were measured.

RESULTS

The results in different models showed that the allergic reactions in mice treated at different time points were significantly different and thus related to fluctuations in biological rhythm. Treatment with lentinan was found to reduce the amplitude of changes in the clock genes, such as the activation of Per and Cry proteins in allergic mice, as well as to regulate biological rhythm in cells, inhibit the activation of Th2 cells, and alleviate allergic reactions. Furthermore, lentinan changed the rhythm of degranulation in RBL-2H3 cells.

CONCLUSION

Lentinan was, therefore, determined to successfully alleviate allergic reactions by reducing the amplitude of changes in the body's biological rhythm, inhibiting the activation of Th2 cells, and affecting the immune microenvironment.

Constant light exposure impairs immune tolerance development in mice

BACKGROUND

An intrinsic daily physiological rhythm called circadian rhythm has been indicated to affect the immune system and its related diseases. Immune tolerance development is closely associated with the onset of immunological disorders. However, the effect of circadian rhythm in the mechanisms of immune tolerance development has not yet been fully understood.

OBJECTIVE

The purpose of this study was to investigate the effects of circadian rhythm disruption on the development of immune tolerance by the perturbation of light environment, using a mouse model of neonatally induced cutaneous tolerance.

METHODS

Mice were kept under constant light (LL) or light-dark (LD) conditions, and hapten was applied at 2days after birth. Six weeks later, hapten was reapplied to abdominal skin, followed by hapten application to ear skin 5days later.

RESULTS

The ear-swelling responses and cell infiltration into inflamed skin significantly increased in LL mice compared with those in LD mice. Interestingly, the percentage and the number of Foxp3+-regulatory T cells notably decreased in inflamed skin and draining lymph nodes of LL mice compared with that in LD mice. Loss-of-function mutation of a key circadian gene, Bmal1, also exacerbated the ear-swelling responses and cell infiltration into inflamed skin in mice.

CONCLUSION

These results suggest that circadian rhythm may be implicated in immune tolerance development in allergic inflammation.

The circadian clock functions as a potent regulator of allergic reaction

Symptoms and laboratory parameters of allergic diseases exhibit prominent ~24-h variations. For instance, in most allergic rhinitis patients, symptoms worsen overnight or early in the morning. Accordingly, there are benefits to nighttime dosing of anti-allergy medications in such patients. Although the circadian pathophysiology of allergic diseases is well documented, the biological basis of this phenomenon remains poorly understood. Recent studies have begun to reveal that the internal timekeeping system termed the circadian clock plays a key role in temporal regulation of allergic reaction, and may therefore underlie the circadian pathophysiology of allergic diseases. Here, we review new knowledge that highlights the emerging role of the circadian clock as a potent regulator of allergic reactions. Given the strong influence of circadian rhythms on allergic diseases, we believe that research on how the time of day impacts allergic reaction which we may call 'chronoallergology' will provide new insight into previously unknown aspects of the biology of allergies. Such knowledge should facilitate novel strategies for prevention and treatment of these diseases.

Circadian Clocks in the Immune System

The immune system is a complex set of physiological mechanisms whose general aim is to defend the organism against non-self-bodies, such as pathogens (bacteria, viruses, parasites), as well as cancer cells. Circadian rhythms are endogenous 24-h variations found in virtually all physiological processes. These circadian rhythms are generated by circadian clocks, located in most cell types, including cells of the immune system. This review presents an overview of the clocks in the immune system and of the circadian regulation of the function of immune cells. Most immune cells express circadian clock genes and present a wide array of genes expressed with a 24-h rhythm. This has profound impacts on cellular functions, including a daily rhythm in the synthesis and release of cytokines, chemokines and cytolytic factors, the daily gating of the response occurring through pattern recognition receptors, circadian rhythms of cellular functions such as phagocytosis, migration to inflamed or infected tissue, cytolytic activity, and proliferative response to antigens. Consequently, alterations of circadian rhythms (e.g., clock gene mutation in mice or environmental disruption similar to shift work) lead to disturbed immune responses. We discuss the implications of these data for human health and the areas that future research should aim to address.

Circadian clock gene Period2 regulates a time-of-day-dependent variation in cutaneous anaphylactic reaction

BACKGROUND

IgE-mediated immediate-type skin reaction shows a diurnal rhythm, although the precise mechanisms remain uncertain. Period2 (Per2) is a key circadian gene that is essential for endogenous clockworks in mammals.

OBJECTIVE

This study investigated whether Per2 regulates a time-of-day-dependent variation in IgE-mediated immediate-type skin reaction.

METHODS

The kinetics of a passive cutaneous anaphylactic reaction were compared between wild-type mice and mice with a loss-of-function mutation of Per2 (mPer2(m/m) mice). The effects of adrenalectomy, aging, and dexamethasone on the kinetics of a passive cutaneous anaphylactic reaction were also examined. In addition, the extent of IgE-mediated degranulation in bone marrow-derived mast cells (BMMCs) was compared between wild-type and mPer2(m/m) mice.

RESULTS

A time-of-day-dependent variation in a passive cutaneous anaphylactic reaction observed in wild-type mice was absent in mPer2(m/m) mice and in adrenalectomized and aged mice associated with the loss of rhythmic secretion of corticosterone. In addition, mPer2(m/m) mice showed decreased sensitivity to the inhibitory effects of dexamethasone on the passive cutaneous anaphylactic reactions. IgE-mediated degranulation in BMMCs was comparable between wild-type and mPer2(m/m) mice, but Per2 mutation decreased sensitivity to the inhibitory effects of dexamethasone on IgE-mediated degranulation in BMMCs.

CONCLUSION

A circadian oscillator, Per2, regulates a time-of-day-dependent variation in a passive cutaneous anaphylactic reaction in mice. Per2 may do so by controlling the rhythmic secretion of glucocorticoid from adrenal glands and/or by gating the glucocorticoid responses of mast cells to certain times of the day (possibly when Per2 levels are high in mast cells).

Variability of venom skin tests

PURPOSE OF REVIEW

Venom skin tests constitute the cornerstone in establishing the diagnosis of venom allergy. In spite of their fundamental role, data regarding their reproducibility and variability are rather sparse. This paper is an overview of our current knowledge on the extent of variability in venom skin testing, the possible causes for this phenomenon and its clinical implications. It points out certain clinical situations in which this possible variability should be taken into account and anticipates potential venues of expanding our understanding of this debatable subject.

RECENT FINDINGS

A single recent study addressed the reproducibility of skin tests and serum venom-specific immunoglobulin E levels. Using a simple positive-negative or vice versa criterion for all three venoms examined on two different sessions, this study showed an overall 66% reproducibility of the skin test reactions and 59% reproducibility of the venom-specific immunoglobulin E assay results. According to an accompanying editorial, however, the validity of these results needs to be confirmed.

SUMMARY

Determination of the real magnitude of venom skin test variability is required. At present, in specific clinical situations, repeated skin tests and measurement of serum venom-specific immunoglobulin E should be considered before the initiation of venom immunotherapy.

Environmental tobacco smoke exposure and nocturnal symptoms among inner-city children with asthma

BACKGROUND

Environmental tobacco smoke (ETS) is a frequent exposure and is linked to asthma among inner-city children.

OBJECTIVE

We sought to examine the relationship among ETS exposure, select asthma symptoms, and consequences among inner-city children with asthma.

METHODS

Data from interviews with primary caregivers of inner-city elementary school children with asthma were evaluated (n = 590). Caregiver reports of child asthma symptoms, exercise limitations, asthma management, health care use, and ETS exposure were examined.

RESULTS

Smoking in the home was reported by 29.4% of primary caregivers. ETS exposure (yes/no) was not related to frequency of child nocturnal symptoms or other select asthma morbidity markers. However, among children exposed to ETS, the frequency and severity of child nocturnal symptoms were highest among children exposed to moderate-to-heavy levels of ETS. After controlling for child age, anti-inflammatory medication use, asthma primary care, and caregiver's education, exposure to higher levels of ETS was associated with nearly a 3-fold increase in nocturnal symptoms in children (odds ratio, 2.83; 95% CI, 1.22-6.55).

CONCLUSION

Among elementary school inner-city children with asthma, exposure to higher levels of ETS was associated with increased frequency of nocturnal symptoms. Reducing the exposure of children with asthma to ETS should be a clear priority in developing effective asthma management plans for inner-city families.