Prenatal exposure to endotoxin in rats attenuates the allergic airways eosinophil infiltration in the adult offspring: role of inducible nitric oxide synthase activation

Neuroscience and treatment of asthma, new therapeutic strategies and future aspects

AIMS

Asthma is an airway inflammatory disease that is affected by neurological and psychological factors. The aim of present review is to investigating the relationship between neural functions and neurobiological changes and asthma symptoms.

MAIN METHODS

The information in this article is provided from articles published in English and reputable database using appropriate keywords from 1970 to October 2020.

KEY FINDINGS

The symptoms of asthma such as cough, difficult breathing, and mucus secretion get worse when a person is suffering from stress, anxiety, and depression. The function of the insula, anterior cingulate cortex, and hypothalamic-pituitary-adrenal axis changes in response to stress and psychological disease; then the stress hormones are produced from neuroendocrine system, which leads to asthma exacerbation. The evidence represents that psychological therapies or neurological rehabilitation reduces the inflammation through modulating the activity of neurocircuitry and the function of brain centers involved in asthma. Moreover, the neurotrophins and neuropeptides are the key mediators in the neuro-immune interactions, which secrete from the airway nerves in response to brain signals, and they could be the target of many new therapies in asthma.

SIGNIFICANCE

This review provides an insight into the vital role of the central and peripheral nervous system in development and exacerbation of asthma and provides practical approaches and strategies on neural networks to improve the airway inflammation and asthma severity.

Environmental exposures during pregnancy: Mechanistic effects on immunity

In human studies, it is well established that exposures during embryonic and fetal development periods can influence immune health. Coupled with genetic predisposition, these exposures can alter lifetime chronic and infectious disease trajectory, and, ultimately, life expectancy. Fortunately, as research advances, mechanisms governing long-term effects of prenatal exposures are coming to light and providing the opportunity for intervention and risk reduction. For instance, human association studies have provided a foundation for the association of prenatal exposure to particulate matter with early immunosuppression and later allergic disease in the offspring. Only recently, the mechanisms mediating this response have been revealed and there is much we have yet to discover. Although cellular immune response is understood for many exposure scenarios, molecular pathways are still unidentified. This review will provide commentary and synthesis of the current literature regarding environmental exposures during pregnancy and mechanisms determining immune outcomes. Shared mechanistic features and current gaps in the state of the science are identified and discussed. To such purpose, we address exposures by their immune effect type: immunosuppression, autoimmunity, inflammation and tissue damage, hypersensitivity, and general immunomodulation.

Immunity and ultrasonic vocalization in rodents

Ultrasonic vocalizations (USVs) serve important communicative functions in rodents. Different types of USVs can be triggered in the sender, for example, by maternal separation, social interactions, or exposure to predators, and they evoke affiliative or alarming behaviors in recipients. This review focusses on studies evaluating possible links between immunity and USVs. Most studies have been performed in a murine model of maternal immune activation and subsequent evaluation of effects in the offspring. This model has received large attention in recent years because it mimics behavioral abnormalities observed in certain human neuropsychiatric disorders, including autism spectrum disorder. Although there is still some controversy, the results indicate that stimulation of the immune system of mice and rats during pregnancy affects ultrasonic calling in pups. Few studies are available on immunization during adulthood and USVs. In most cases, immune stimulation led to disease, complicating conclusions about a possible direct link between vocalization and immunity. Although much work is still needed, this is certainly a rather new and promising aspect of interactions between the immune system and behavior.

The effect of maternal Inflammation on foetal programming of metabolic disease

Maternal obesity during pregnancy increases the child's risk of developing obesity and obesity-related diseases later in life. Key components in foetal programming of metabolic risk remain to be identified; however, chronic low-grade inflammation associated with obesity might be responsible for metabolic imprinting in the offspring. We have therefore surveyed the literature to evaluate the role of maternal obesity-induced inflammation in foetal programming of obesity and related diseases. The literature on this topic is limited, so this review also includes animal models where maternal inflammation is mimicked by single injections with lipopolysaccharide (LPS). An LPS challenge results in an immunological response that resembles the obesity-induced immune profile, although LPS injections provoke a stronger response than the subclinical obesity-associated response. Maternal LPS or cytokine exposures result in increased adiposity and impaired metabolic homeostasis in the offspring, similar to the phenotype observed after exposure to maternal obesity. The cytokine levels might be specifically important for the metabolic imprinting, as cytokines are both transferable from maternal to foetal circulation and have the capability to modulate placental nutrient transfer. However, the immune response associated with obesity is moderate and therefore potentially weakened by the pregnancy-driven immune modulation, dominated by anti-inflammatory Treg and Th2 cells. We know from other low-grade inflammatory diseases, such as rheumatoid arthritis, that pregnancy can improve disease state. If pregnancy is also capable of suppressing the obesity-associated inflammation, the immunological markers might be less likely to affect metabolic programming in the developing foetus than otherwise implied.

Inter- and transgenerational epigenetic inheritance: evidence in asthma and COPD?

Evidence is now emerging that early life environment can have lifelong effects on metabolic, cardiovascular, and pulmonary function in offspring, a concept also known as fetal or developmental programming. In mammals, developmental programming is thought to occur mainly via epigenetic mechanisms, which include DNA methylation, histone modifications, and expression of non-coding RNAs. The effects of developmental programming can be induced by the intrauterine environment, leading to intergenerational epigenetic effects from one generation to the next. Transgenerational epigenetic inheritance may be considered when developmental programming is transmitted across generations that were not exposed to the initial environment which triggered the change. So far, inter- and transgenerational programming has been mainly described for cardiovascular and metabolic disease risk. In this review, we discuss available evidence that epigenetic inheritance also occurs in respiratory diseases, using asthma and chronic obstructive pulmonary disease (COPD) as examples. While multiple epidemiological as well as animal studies demonstrate effects of 'toxic' intrauterine exposure on various asthma-related phenotypes in the offspring, only few studies link epigenetic marks to the observed phenotypes. As epigenetic marks may distinguish individuals most at risk of later disease at early age, it will enable early intervention strategies to reduce such risks. To achieve this goal further, well designed experimental and human studies are needed.

Microorganism-induced suppression of allergic airway disease: novel therapies on the horizon?

Allergic airway disease is a major global health burden, and novel treatment options are urgently needed. Numerous epidemiological and experimental studies suggest that certain helminths and bacteria protect against respiratory allergies. These microorganisms are strong regulators of the immune system, and various potential regulatory mechanisms by which they protect against allergic airway inflammation have been proposed. Whereas early studies addressed the beneficial effect of natural infections, the focus now shifts toward identifying the dominant protective molecules and exploring their efficacy in models of allergic airway disease. In this article, we will review the evidence for microbe-mediated protection from allergic airway disease, the potential modes of action involved and discuss advances as well as limitations in the translation of this knowledge into novel treatment strategies against allergic airway disease.

Single early prenatal lipopolysaccharide exposure prevents subsequent airway inflammation response in an experimental model of asthma

AIMS

There has been emerging interest in the prenatal determinants of respiratory disease. In utero factors have been reported to play a role in airway development, inflammation, and remodeling. Specifically, prenatal exposure to endotoxins might regulate tolerance to allergens later in life. The present study investigated whether prenatal lipopolysaccharide (LPS) administration alters subsequent offspring allergen-induced inflammatory response in adult rats.

MAIN METHODS

Pregnant Wistar rats were treated with LPS (100 μg/kg, i.p.) on gestation day 9.5 and their ovariectomized female offspring were sensitized and challenged with OVA later in adulthood. The bronchoalveolar lavage (BAL) fluid, peripheral blood, bone marrow leukocytes and passive cutaneous anaphylaxis were evaluated in these 75-day-old pups.

KEY FINDINGS

OVA sensitized pups of NaCl treated rats showed an increase of leucocytes in BAL after OVA challenge. This increase was attenuated, when mothers were exposed to a single LPS injection early in pregnancy. Thus, LPS prenatal treatment resulted in (1) lower increased total and differential (macrophages, neutrophils, eosinophils and lymphocytes) BAL cellularity count; (2) increased number of total, mononuclear and polymorphonuclear cells in the peripheral blood; and (3) no differences in bone marrow cellularity or passive cutaneous anaphylaxis.

SIGNIFICANCE

In conclusion, female pups treated prenatally with LPS presented an attenuated response to experimentally-induced asthma. We observed reduced immune cell migration from peripheral blood to the lungs, with no effect on the production of bone marrow cells or antibodies. It was suggested that inflammatory events such as exposure to LPS in early fetal life can attenuate allergic inflammation in the lung, which is a common symptom in asthma.