Chronic mild prenatal stress exacerbates the allergen-induced airway inflammation in rats

Maternal stress increases risk of allergic lung inflammation in adult mice

BACKGROUND

Allergies are increasing worldwide. The presence of atopic diseases in the mother propagates the onset of allergic diseases in the offspring with a considerably stronger penetrance than atopic diseases of the father. Such observation challenges genetic predispositions as the sole cause of allergic diseases. Epidemiological studies suggest that caregiver stress in the perinatal period may predispose offspring to asthma. Only one group has studied the link between prenatal stress and neonatal asthma susceptibility in a murine model.

OBJECTIVES

We aimed to study if the neonatal increased risk of developing allergic lung inflammation persists after puberty and if there are sex differences in susceptibility.

METHODS

Pregnant BALB/c mice were subjected to a single restraint stress exposure at day 15 of gestation. Pups were separated by gender and subjected to a well-known sub-optimal asthma model after puberty.

RESULTS

Adult mice born to stressed dams were more susceptible to developing allergic pulmonary inflammation since an increase in the number of eosinophils in bronchoalveolar lavage (BAL), a greater peribronchial and perivascular infiltrate, a higher proportion of mucus-producing cells, and increased IL-4 and IL-5 levels in BAL were detected compared to control mice. These effects were more profound in females than males. Moreover, only females from stressed dams showed an increase in IgE levels.

CONCLUSIONS

Increased litter susceptibility to develop allergic lung inflammation induced by maternal stress persists after puberty and is more potent in females than in male mice.

Peri-adolescent asthma: Acute impacts on innate immune response, corticosterone, and microglia in mice

Asthma is highly comorbid with anxiety in youth. We investigated the hypothalamic-pituitary-adrenal (HPA) axis and microglia as mechanisms underlying asthma and anxiety comorbidity. We induced asthma symptoms in developing BALB/cJ mice with house dust mite (HDM) for airway inflammation and methacholine (MCH) for bronchoconstriction. On the last day of exposure, we analyzed samples at six timepoints. Lung IL-5 and IL-1β expression peaked 4 h after final HDM exposure. Circulating corticosterone was blunted in a sex- and treatment-specific temporal pattern. Hippocampal IL-1β expression and microglial area were marginally increased 24 h after MCH exposure. These results provide a foundation for further work investigating asthma-anxiety mechanisms.

Ferulic Acid Improves Depressive-Like Behavior in Prenatally-Stressed Offspring Rats via Anti-Inflammatory Activity and HPA Axis

Prenatal stress (PS) can increase the risk of nervous, endocrine and metabolic diseases, and immune dysfunction. Ferulic acid (FA) is a dietary phenolic acid that has pharmacological properties, including potent anti-inflammatory action. We used male, prenatally-stressed offspring rats to investigate the anti-depressive-like effects and possible anti-inflammatory mechanism of FA. We determined the animal behaviors, and the mRNA expression and concentration of inflammatory cytokines, and HPA axis. In addition, we assessed the modulation of hippocampal nuclear factor-κB (NF-κB) activation, neuronal nitric oxide synthase (nNOS) and glucocorticoid receptors (GR) expression via western blotting and immunohistochemistry. Administration of FA (12.5, 25, and 50 mg/kg/day, i.g.) for 28 days markedly increased sucrose intake, and decreased immobility time and total number of crossings, center crossings, rearing, and grooming in the male PS offspring. FA significantly reduced IL-6, IL-1β, and TNF-α concentration and increased IL-10 concentration in male, prenatally-stressed offspring, stimulated by the NF-κB pathway. In addition, FA inhibited interleukin-6 (IL-6), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α), and increased interleukin-10 (IL-10) mRNA and protein expression. Furthermore, FA markedly decreased the serum adrenocorticotropin (ACTH) and corticosterone concentration by the increase of GR protein expression. Taken together, this study revealed that FA has anti-depressive-like effects in male, prenatally-stressed offspring, partially due to its anti-inflammatory activity and hypothalamic-pituitary-adrenal (HPA) axis.

Prenatal Maternal Stress and the Risk of Asthma in Children

Emerging evidence indicate that maternal prenatal stress (MPS) can result in a range of long-term adverse effects in the offspring. The underlying mechanism of MPS is not fully understood. However, its complexity is emphasized by the number of purportedly involved pathways namely, placental deregulated metabolism of maternal steroids, impaired maturation of fetal HPA axis, imbalanced efflux of commensal bacteria across the placenta, and skewed immune development toward Th2. Fetal programming probably exerts a pivotal role in the end result of the above pathways through the modulation of gene expression. In this review, we highlight the current knowledge from epidemiological and experimental studies regarding the effects of MPS on asthma development in the offspring.

The effects of prenatal "psychological" stressor exposure on lung inflammation and hyperresponsiveness in adult rat offspring

The aim of this study was to establish whether exposure of pregnant rats to uncontrollable (psychological) stressors might change the likelihood of their offspring to exhibit functional and histopathological abnormalities suggestive of asthma in adulthood. Pregnant rats (n = 16) underwent one of three treatments: electric shocks of a maximum duration of 10 s that could be escaped (controllable group; C) those that could not be escaped (uncontrollable group; U) or no shocks (control group; N). The offspring (n = 54) were kept in animal house under standard conditions until 3 months of age, when lung hyperresponsiveness, histopathology, immunohistochemical measurements of the cytokines interleukin (IL) 2, IL-4, IL-5, and IL-13 and actin as well as oxidative stress based on iNOS-positive cell counts and isoprostane PGF2α contents were assessed. The results showed that prenatal exposure to physical stressors (shocks) caused lung hyperresponsiveness and increased cytokine expression; exposure to uncontrollable shock (group U) had a differential effect on the expression of IL-2, IL-5, and IL-13 in inflammatory cells compared to exposure to controllable shock (group C), which characterizes the "psychological" aspect of stress. The results show that not only stress but also its uncontrollability during gestation might increase the likelihood that the offspring will exhibit functional and histopathological abnormalities suggestive of asthma. These findings strengthen the importance of psychological control with regard to environmental stimuli for the occurrence of several illnesses, suggesting the desirability of integration among various fields of science.

Maternal stress during pregnancy increases neonatal allergy susceptibility: role of glucocorticoids

We sought to test experimentally whether maternal stress can promote susceptibility to development of asthma-like allergic airways disease in offspring. Normal pregnant mice (day 15) were subjected to a single restraint stress exposure. We subsequently tested their offspring for the development of airway hyperreactivity (AHR) and allergic airway inflammation (AI), after an intentionally suboptimal sensitization protocol. The offspring of stressed mothers showed levels of AI and enhanced airway responses to methacholine comparable to those seen in fully sensitized and challenged positive control animals; in contrast, minimal effects were seen in control offspring. Restraint stress caused a rapid and large increase in plasma corticosterone levels. Maternal treatment with dexamethasone on day 15 of pregnancy mimicked the stress effect and reproduced the AI and AHR outcomes, whereas blockade of the stress-induced corticosterone surge with metyrapone pretreatment of pregnant mice abrogated the effect. We conclude that stress-triggered glucocorticoids during pregnancy can increase susceptibility to allergy in offspring. Because inflammation typically includes a stress hormone response, the results also suggest a common pathway by which various injurious exposures during pregnancy might increase offspring susceptibility to asthma.

Prenatal maternal stress exposure and immune function in the offspring

The intra-uterine environment provides the first regulatory connection for the developing fetus and shapes its physiological responses in preparation for postnatal life. Psychological stress acts as a programming determinant by setting functional parameters to abnormal levels, thus inducing postnatal maladaptation. The effects of prenatal maternal stress (PNMS) on the developing immune system have been documented mostly through animal studies, but inconsistent results and methodological differences have hampered the complete understanding of these findings. As the immune system follows a similar ontogenic pattern in all mammals, a translational framework based on the developmental windows of vulnerability proposed by immunotoxicology studies was created to integrate these findings. The objective of this review is to examine the available literature on PNMS and immune function in the offspring through the above framework and gain a better understanding of these results by elucidating the moderating influence of the stressor type, timing and duration, and the offspring species, sex and age at assessment. The evaluation of the literature through this framework showed that the effects of PNMS are parameter specific: the moderating effects of timing in gestation were relevant for lymphocyte population numbers, Natural Killer cell function and mitogen-induced proliferation. The presence of an important and directional sexual dimorphism was evident and the influence of the type or duration of PNMS paralleled that of stress in non-pregnant animals. In conclusion, PNMS is a relevant factor in the programming of immune function. Its consequences may be related to disorders with an important immune component such as allergies.

Stress-related programming of autonomic imbalance: role in allergy and asthma

Evidence linking psychological stress to allergy has grown with our increased understanding of the natural history and pathophysiology of these disorders and the neurobiology of stress vulnerability. However, the specific pathways that increase vulnerability to developing allergy and associated disorders remain to be elucidated. Autonomic nervous system functioning (autonomic balance) has been implicated in allergy for some time albeit links between autonomic balance and immune function in early development have been under studied. Starting in utero, stress may influence the programming of brain neurotransmitter systems, sympathetic and parasympathetic nervous system functioning, and the hypothalamic-pituitary-adrenal axis, which in turn may alter neural regulation of immune function. Epigenetic dysregulation of gene expression may be a fundamental mechanism for programming of early neural-immune processes.

Prenatal and postnatal maternal stress and wheeze in urban children: effect of maternal sensitization

RATIONALE

Critical periods for programming early wheeze risk may include pregnancy and infancy. Effects of timing remain poorly understood.

OBJECTIVES

Associations among prenatal and postnatal maternal stress and children's wheeze were prospectively examined in 653 families. Effect modification by maternal sensitization was also examined.

METHODS

Stress was indexed by a maternal negative life events (NLEs) score (range, 0-9) ascertained during pregnancy and between 1 and 2 years postpartum. Mothers reported child wheeze every 3 months up to age 2 years. Relationships of prenatal and postnatal maternal NLEs with repeated wheeze (≥2 episodes) were examined using logistic regression adjusting for covariates. Penalized splines were implemented to explore possible nonlinear associations. We also examined the interaction between prenatal stress and maternal sensitization indexed by allergen-specific IgE from maternal prenatal serum.

MEASUREMENTS AND MAIN RESULTS

Adjusted models considering prenatal or postnatal NLEs alone both showed an exposure-response relationship between higher stress and child wheeze. When considering prenatal and postnatal stress concurrently, only children of mothers with high stress in both periods were significantly more likely to wheeze (adjusted odds ratio, 3.04; 95% confidence interval, 1.67-5.53) than children of mothers reporting low stress in both periods. Associations between high prenatal stress and wheeze were significant in children born to nonsensitized mothers (any IgE <0.35 kU/L) but not in the sensitized group (P for interaction = 0.03).

CONCLUSIONS

Although children have heightened sensitivity to maternal stress in utero and in early childhood, those with higher stress in both periods were particularly at risk for wheeze. The prenatal maternal immune milieu modified effects.

Prenatal negative life events increases cord blood IgE: interactions with dust mite allergen and maternal atopy

BACKGROUND

Prenatal exposure to both stress and aeroallergens (dust mite) may modulate the fetal immune system. These exposures may interact to affect the newborn immune response. We examined associations between prenatal maternal stress and cord blood total IgE in 403 predominately low-income minority infants enrolled in the Asthma Coalition on Community, Environment, and Social Stress (ACCESS) project. We also examined potential modifying effects of maternal atopy and maternal dust mite exposure.

METHODS

The Crisis in Family Systems survey was administered to mothers prenatally, and a negative life event domain score was derived to characterize stress. Dust mite allergen was quantified in dust from pregnant mothers' bedrooms. Cord blood was analyzed for total IgE. Using linear regression, we modeled the relationship of stress with cord blood IgE and interactions of stress with dust mite and/or maternal atopy, adjusting for potential confounders.

RESULTS

Higher prenatal maternal stress (β = 0.09; P = 0.01) was associated with increased cord blood IgE. The interactive effects between stress and dust mite groups (high vs low) were significantly different for children of atopic vs nonatopic mothers (P for three-way interaction = 0.005). Among children of atopic mothers, the positive association between stress and IgE was stronger in the high dust mite group. In children of mothers without a history of atopy, the positive association between stress and IgE was most evident in the low allergen group.

CONCLUSIONS

Prenatal stress was independently associated with elevated cord blood IgE. Mechanisms underlying stress effects on fetal immunomodulation may differ based on maternal atopic status.

Epidemiology of stress and asthma: from constricting communities and fragile families to epigenetics

Several epidemiologic frameworks, exemplified through extant research examples, provide insight into the role of stress in the expression of asthma and other allergic disorders. Biologic, psychological, and social processes interact throughout the life course to influence disease expression. Studies exploiting a child development framework focus on critical periods of exposure, including the in utero environment, to examine the influence of stress on disease onset. Early stress effects that alter the normal course of morphogenesis and maturation that affect both structure and function of key organ systems (eg, immune, respiratory) may persist into adult life underscoring the importance of a life course perspective. Other evidence suggests that maternal stress influences programming of integrated physiologic systems in their offspring (eg, neuroendocrine, autonomic, immune function) starting in pregnancy; consequently stress effects may be transgenerational. A multilevel approach that includes an ecological perspective may help to explain heterogeneities in asthma expression across socioeconomic and geographic boundaries that to date remain largely unexplained. Evolving studies incorporating psychological, behavioral, and physiologic correlates of stress more specifically inform underlying mechanisms operating in these critical periods of development. The role of genetics, gene by environment interactions, and epigenetic mechanisms of gene expression have been sparsely examined in epidemiologic studies on stress and asthma although overlapping evidence provides proof of concept for such studies in the future.

Perinatal stress and early life programming of lung structure and function

Exposure to environmental toxins during critical periods of prenatal and/or postnatal development may alter the normal course of lung morphogenesis and maturation, potentially resulting in changes that affect both structure and function of the respiratory system. Moreover, these early effects may persist into adult life magnifying the potential public health impact. Aberrant or excessive pro-inflammatory immune responses, occurring both locally and systemically, that result in inflammatory damage to the airway are a central determinant of lung structure-function changes throughout life. Disruption of neuroendocrine function in early development, specifically the hypothalamic-pituitary-adrenal (HPA) axis, may alter functional status of the immune system. Autonomic nervous system (ANS) function (sympathovagal imbalance) is another integral component of airway function and immunity in childhood. This overview discusses the evidence linking psychological factors to alterations in these interrelated physiological processes that may, in turn, influence childhood lung function and identifies gaps in our understanding.

Moving towards making social toxins mainstream in children's environmental health

PURPOSE OF REVIEW

Although traditional disciplinary research theory and methods have focused separately on how social and physical environmental factors affect children's health, evolving research underscores important integrated effects.

RECENT FINDINGS

This review outlines the specific reasons why social determinants should be considered mainstream in children's environmental health research with particular focus on interactive effects between social and physical hazards. These include sensitivity of overlapping physiological systems, via epigenesis, programming, and plasticity to social and physical environmental moderation that may impact health across the life span; ways in which social environmental vulnerabilities moderate the effects of physical environmental factors, providing specific examples related to respiratory health and neurodevelopment; overlapping exposure distribution profiles; and relevance to pediatric health disparities.

SUMMARY

Because of the covariance across exposures, and evidence that social stress and other environmental toxins (e.g., pollutants, tobacco smoke) may influence common physiological pathways (e.g., oxidative stress, proinflammatory immune pathways, autonomic disruption), understanding the potential synergistic effects promises to more completely inform children's environmental health risk. Although this discussion focuses around the respiratory and neurological systems, these concepts extend more broadly to children's psychological and physical development.

Effects of stress and neuropeptides on airway responses in ovalbumin-sensitized rats

OBJECTIVE

The aim of this study was to investigate the influence of stress and neuropeptides on airway responses in ovalbumin (OVA)-sensitized rats.

METHODS

Three experimental conditions were employed: neonatal capsaicin treatment, foot shock stress and OVA sensitization. For neuropeptide depletion, male Wistar rats were neonatally treated with capsaicin (50 mg/kg) or with control solution 2 days after birth. Ninety days later, they were injected with OVA and aluminum hydroxide (ED0) or no injection. Thereafter, rats of the stressed groups were individually placed in a shuttle box where they received 50 mild escapable foot shocks/day; the stressful stimuli were repeated until ED14, when the animals received OVA aerosol. Pulmonary mechanic function was measured before and after OVA challenge in anesthetized and mechanically ventilated rats.

RESULTS

Data on ultrasonic vocalizations and corticosterone showed high levels of anxiety in stressed animals. As expected, a significant increment in airway elastance and resistance after the OVA challenge was found in sensitized rats compared to non-sensitized ones. Capsaicin treatment decreased the values of elastance in sensitized and non-stressed rats; however, after the OVA challenge, elastance was increased in stressed animals. No differences were found in the levels of resistance among sensitized and non-stressed rats; however, a reduced increment in resistance was verified in capsaicin-treated, stressed animals.

CONCLUSIONS

Our results suggest that neurokinin depletion and stress may affect smooth muscle tonus around the airways during an anaphylactic reaction. These data suggest that stress and neuropeptides play a significant role in pulmonary function in OVA-sensitized rats.

Early-life psychological stress exacerbates adult mouse asthma via the hypothalamus-pituitary-adrenal axis

RATIONALE

Despite accumulating evidence that psychological stress has a short-lasting detrimental effect on asthma, little is known about the way stress in childhood predisposes to adult asthma.

OBJECTIVES

Using a communication box, we investigated the long-lasting effect of early psychological and physical stress on adult asthma in mice.

METHODS

Male BALB/c mice were exposed to either psychological stress or physical stress three times (every other day) during their fourth week of life. The mice were sensitized to ovalbumin at 8 and 10 weeks, and an ovalbumin airway challenge was conducted at the age of 11 weeks.

RESULTS

Twenty-four hours after ovalbumin challenge, both psychological and physical stress-exposed mice exhibited a significant acceleration in the number of total mononuclear cells and eosinophils and airway hyperresponsiveness compared with control mice. No differences in serum anti-OVA-specific immunoglobulin E levels were found between stress-exposed and control animals after antigen sensitization. In the psychological stress group, but not in the physical stress group, an elevation of the serum corticosterone levels during ovalbumin challenge was significantly attenuated in comparison with the control group. Moreover, pretreatment with RU-486, a glucocorticoid receptor antagonist, before ovalbumin challenge completely inhibited a psychological stress-induced exacerbation of asthma. However, pretreatment with GR-82334, a neurokinin-1 receptor antagonist, failed to affect physical stress-induced augmentation of airway inflammation.

CONCLUSION

Early psychological and physical stresses aggravated adult asthma via hyporesponsiveness of the hypothalamic-pituitary-adrenal axis during antigen challenge and via a pathway(s) distinct from the hypothalamic-pituitary-adrenal axis or neurokinin-1 receptors.

Stress induces substance P in vagal sensory neurons innervating the mouse airways

BACKGROUND

Tachykinins-like substance P (SP) have been shown to play an important role in initiating and perpetuating airway inflammation. Furthermore, they are supposed to be released into tissues in response to stress.

OBJECTIVE

The aim of this study was to investigate the effects of stress alone or in combination with allergic airway inflammation on SP expression in sensory neurons innervating the mouse airways.

METHODS

Balb/c mice were systemically sensitized to ovalbumin (OVA), followed by allergen aerosol exposure, and compared with non-sensitized controls. Additionally, OVA-sensitized and -challenged and non-sensitized mice were exposed to sound stress. SP expression in airway-specific and overall vagal sensory neurons of the jugular and nodose ganglion complex was analysed using retrograde neuronal tracing in combination with immunohistochemistry. Preprotachykinin A (PPT-A) mRNA, the precursor for SP, was quantified in lung tissue by real-time PCR. Bronchoalveolar lavage (BAL) fluid was obtained, and cell numbers and differentiation were determined.

RESULTS

Stress and/or allergic airway inflammation significantly increased SP expression in retrograde-labelled vagal sensory neurons from the mouse lower airways compared with controls [stress: 15.7+/-0.8% (% of retrograde-labelled neurons, mean+/-SEM); allergen: 17.9+/-0.4%; allergen/stress: 13.1+/-0.7% vs. controls: 6.3+/-0.3%]. Similarly, SP expression increased in overall vagal sensory neurons identified by the neuronal marker protein gene product (PGP) 9.5 [stress: 9.3+/-0.6% (% of PGP 9.5-positive neurons, means+/-SEM); allergen: 12.5+/-0.4%; allergen/stress: 10.2+/-0.4% vs. controls: 5.1+/-0.3%]. Furthermore, stress significantly increased PPT-A mRNA expression in lung tissue from OVA-sensitized and -challenged animals, and immune cells were identified as an additional source of SP in the lung by immunohistochemistry. Associated with enhanced neuronal SP expression, a significantly higher number of leucocytes were found in the BAL following allergen exposure. Further, stress significantly increased allergen-induced airway inflammation identified by increased leucocyte numbers in BAL fluids.

CONCLUSION

The central event of sound stress leads to the stimulation of SP expression in airway-specific neurons. However, in sensitized stressed mice an additional local source of SP (probably inflammatory cells) might enhance allergic airway inflammation.

Upregulation of tumor necrosis factor-alpha by stress and substance p in a murine model of allergic airway inflammation

OBJECTIVE

Clinical observation has suggested that stress and asthma morbidity are associated, though underlying mechanisms are not clearly understood. After having established a mouse model of stress-exacerbated allergic airway inflammation, we demonstrated a stress-mediating role for neurokinin-1 receptor, the main substance P (SP) receptor. Here, our aim was to investigate the influence of stress or exogenously applied SP on airway inflammation and on the local cytokine production of immune cells.

METHODS

BALB/c mice were systemically sensitized to ovalbumin (OVA) and repeatedly challenged with OVA aerosol. Sound stress was applied to the animals for 24 h, starting with the first airway challenge. Alternatively, one group of non-stressed mice received intranasal SP before airway challenges. Cell numbers were determined in bronchoalveolar lavage (BAL) fluid. Leukocytes from mediastinal lymph nodes were analyzed by flow cytometry to determine the percentages of T cells producing interleukin-4, interferon-gamma and tumor necrosis factor-alpha.

RESULTS

In BAL fluids of stressed or SP-treated animals, significantly higher total cell counts were found compared to non-stressed mice. In lymph nodes, the percentage of TNF-alpha-positive T cells was higher in stressed mice and mice after application of SP. In contrast, the influence of stress did not increase the percentages of interferon-gamma-positive CD3+ cells, meanwhile the application of SP increased the percentages of T cells positive for this cytokine.

CONCLUSION

Our data provide further evidence for a stress-mediating neuroimmunological pathway that, putatively via SP, is able to influence the composition of immune cells in different compartments of allergic airway inflammation.

Chronic mild stress (CMS) revisited: consistency and behavioural-neurobiological concordance in the effects of CMS

The chronic mild stress (CMS) model of depression has high validity but has in the past been criticized for being difficult to replicate. However, a large number of recent publications have confirmed that CMS causes behavioural changes in rodents that parallel symptoms of depression. This review summarizes studies from over sixty independent research groups that have reported decreases in reactivity to rewards, and a variety of other depression-like behaviours, in rats or mice, following exposure to CMS. Together, these changes are referred to as a 'depressive' behavioural profile. Almost every study that has examined the effects of chronic antidepressant treatment in these procedures has reported that antidepressants were effective in reversing or preventing these 'depressive' behavioural changes. (The single exception is a study in which the duration of treatment was too brief to constitute an adequate trial.) There are also a handful of reports of CMS causing significant effects in the opposite direction, termed here an 'anomalous' behavioural profile. There are six neurobiological parameters that have been studied in both 'anhedonic' and 'anomalous' animals: psychostimulant and place-conditioning effects of dopamine agonists; dopamine D2 receptor number and message; inhibition of dopamine turnover by quinpirole, and beta-adrenergic receptor binding. On all six measures, CMS caused opposite effects in animals displaying 'depressive' and 'anomalous' profiles. Thus, there is overwhelming evidence that under appropriate experimental conditions, CMS can cause antidepressant-reversible depressive-like effects in rodents; however, the 'anomalous' profile that is occasionally reported appears to be a genuine phenomenon, and these two sets of behavioural effects appear to be associated with opposite patterns of neurobiological changes.

Opposing effects of short- and long-term stress on airway inflammation

Between 20% and 35% of subjects with asthma experience asthma exacerbations during periods of stress. The biological mechanisms underlying these exacerbations are not clearly understood, and the role of psychologic factors in the pathophysiology of asthma remains controversial. We investigated the ability of psychologic stress to modulate airway inflammation and airway hyperresponsiveness (AHR) to methacholine in a murine model of asthma. Animals were exposed to a stressor daily for 3 (short-term stress) or 7 (long-term stress) days. After allergen challenge, AHR was assessed through plethysmography, and bronchoalveolar lavage cells were counted as a measure of inflammation. After short-term stress, inflammatory cell number was decreased compared with unstressed animals, whereas levels of interleukin (IL)-6, IL-9, and IL-13 were increased. Administration of a corticosteroid receptor antagonist, before stress, prevented the decrease in inflammatory cell numbers. In contrast, animals stressed for 7 consecutive days showed a significant increase in inflammatory cell numbers, which was independent of the glucocorticoid response, but no change in cytokine levels. AHR was not altered in stressed animals. Our results indicate that repeated exposure to stress over the long term engages different mechanisms than short-term stress and can exacerbate the chronic inflammatory responses of the airway.

Influence of chronic unpredictable stress on the allergic responses in rats

The effects of chronic unpredictable stress on airway leukocyte infiltration and plasma extravasation in female rats have been investigated. The chronic stress lasted for 14 days and consisted of transitory and variable changes in the living conditions of the animals. Concomitant to the stress procedure, the animals were sensitized (Day 0) and challenged with ovalbumin (OVA; 200 microg) at Day 14. Bronchoalveolar lavage (BAL) was performed 48 h after intratracheal challenge with OVA (0.4 ml of a 0.25% solution). The increase in plasma extravasation was assessed by the rat paw oedema induced by OVA (0.1 mg/paw) or the mast cell degranulator compound 48/80 (5 microg/paw). A significant increase (P < .05) in the total leukocyte influxes into the airways was observed in the stressed (sensitized) group compared to nonstressed (sensitized) animals, and this was associated with a marked recruitment of eosinophils and mononuclear cells in the BAL fluid. In OVA-sensitized rats, intraplantar injection of OVA induced a marked paw oedema that was significantly higher in stressed compared to nonstressed groups. In contrast to OVA, the compound 48/80 (5 microg/paw)-induced oedema did not significantly differ between nonstressed and stressed groups. Our results indicate that chronic unpredictable stress exacerbates the vascular and cellular inflammatory responses.

Effect of prenatal stress on the hormonal response to acute and chronic stress and on immune parameters in the offspring

The effect of prenatal stress on the time course of the corticosterone response to acute and chronic stress and on hematological and immunological parameters in the offspring were analized in the present study. Pregnant Sprague-Dawley rats were stressed daily for 2 hours during the last week of gestation, and female and male off-spring were studied during adulthood. Corticosterone response to acute immobilization stress was not significantly different in either control or prenatally stressed rats. However, after 10 days of immobilization stress the corticosterone response completely disappeared in the control animals but not in the prenatally stressed group: high levels of corticosterone were found during the first hour of stress, although they were lower than those found in acutely stressed rats. Adrenal hypertrophy in response to prenatal stress was observed in females but not in male offspring, and chronic stress only increased adrenal weights in the male control group. Prenatal stress decreased the total peripheral leukocyte count, altered its diferential count decreasing lymphocytes and increasing neutrophil and eosinhophil counts, and significantly reduced the percentage of peripheral lymphocyte T CD8+ subset in male offspring. Chronic stress also reduced the percentage of the peripheral T CD8+ lymphocyte subset in the control group but not in the prenatally stressed group. These results suggest that the exposure to stress during pregnancy alters the adaptative response of the hypothalamus-pituitary-adrenocortical axis to chronic stress and presumably the immune competence in the offspring.

Effects of diazepam and stress on lung inflammatory response in OVA-sensitized rats

The influence of stress and diazepam treatment on airway inflammation was investigated in ovalbumin (OVA)-sensitized rats. Animals were injected with OVA plus aluminum hydroxide intraperitoneally (day 0) and boosted with OVA subcutaneously (day 7). From the first to 13th day after sensitization, rats were treated with diazepam, and 1 h later they were placed in a shuttle box where they received 50 mild escapable foot shocks/day preceded by a sound signal (S). Response during the warning (S) canceled shock delivery and terminated the S. On day 14, rats were submitted to a single session of 50 inescapable foot shocks preceded by S and then were challenged with OVA. High levels of stress were detected in shocked animals, manifested as ultrasonic vocalizations. Morphometric analysis of stressed animals revealed a significant increase in both edema and lymphomononucleated cells in airways compared with controls. Diazepam treatment reduced edema in stressed and nonstressed rats. No differences were found in polymorphonucleated cell infiltration. Diazepam treatment reduced lymphomononucleated cell infiltration in stressed animals. These data suggest that stress and diazepam treatment play relevant roles in edema and lymphomononucleated airway inflammation in OVA-sensitized rats.

Effects of maternal stress on development and behaviour in rat offspring

Retrospective studies suggest that gestational stress in humans can delay the attainment of developmental milestones, increase the incidence of allergic reactions and respiratory infections and cause behavioural abnormalities in the children. Our studies and others have shown that prenatal stress in rats can mimic several of these developmental and behavioural alterations. These include a suppression of immune function, but also enhanced sensitivity to allergens. Prenatally-stressed rats, like children, show a reduced propensity for social interaction and increased anxiety in intimidating or novel situations. They have physiological and behavioural alterations consistent with depressive symptoms, including a phase-shift in their circadian rhythm for corticosterone, sleep abnormalities, and greater acquisition of learned helplessness under appropriate conditions. Prenatally-stressed male rats also show demasculinisation and feminisation of their sexual behaviour. The developmental and behavioural abnormalities in prenatally-stressed offspring may be mediated by alterations in the activity of endogenous opioids or neurosteroids, since several of them can be corrected by maternal administration of an opioid antagonist or by drugs like diazepam and allopregnanolone that modulate GABA transmission.

Evidence that behavioral depression does not influence airway cell influx in allergic rats

This study was designated to evaluate the influence of behavioral depression on the airway leukocyte recruitment in allergic animals. To achieve this, total and differential cell counts in bronchoalveolar (BAL) fluid of ovalbumin (OVA)-sensitized and depressed rats was evaluated. Inescapable electric footshock, applied on day 0, 7 and 13 after OVA sensitization, was used as a model to induce depression. In both nondepressed and depressed groups, the number of total and differential cells (eosinophils and mononuclear cells) in BAL fluid was significantly larger in sensitized compared with non-sensitized animals. However, no statistical differences were found between these groups with respect to the number of total and differential leukocytes, irrespective of the day inescapable shock was applied. Thus, behavioral depression does not influence the pattern of cell infiltration into the airways of allergen-induced airway inflammation.

Stress and the Gastrointestinal Tract IV. Modulation of intestinal inflammation by stress: basic mechanisms and clinical relevance

The stress response in a healthy organism is generally viewed as a warning and thus a protective reaction to a threat. However, the response may be deleterious if it is linked to an inflammatory stimulus or if it proceeds an inflammatory event. Prior stress enhances the response to an inflammatory stimulus by a mechanism that is independent of the release of hypothalamic corticotropin-releasing factor (CRF) or arginine vasopressin. Putative mechanisms include an increase in intestinal permeability as well as the release of the proinflammatory neuropeptide substance P. Stress may also reactivate previous inflammation when applied in conjunction with a small luminal stimulus. This reactivation involves increased permeability and requires the presence of T lymphocytes. Inflammatory mediators activate hypothalamic pathways, and a negative feedback loop, mediated by CRF release, has been proposed because animals with impaired hypothalamic CRF responses are more susceptible to inflammatory stimuli. Together, these experimental observations provide insights into the expression of inflammatory disorders in humans, including inflammatory bowel disease and postinfective irritable bowel syndrome.

Stress-induced increment on total bronchoalveolar cell count in OVA-sensitized rats

The influence of stress on total leukocyte count from bronchoalveolar lavage (BAL) was investigated in rats sensitized and challenged with ovalbumin (OVA). The animals were injected intraperitoneally with a suspension of OVA plus aluminum hydroxide in 0.9% NaCl (Day 0) and boosted at Day 7 with an identical OVA solution, administered subcutaneously. From the first to the 13th day after sensitization, rats were placed individually in a shuttle box where they received 50 escapable footshocks per day, always preceded by a sound signal (S); the responses that occurred during both S and shocks canceled the stressful stimulation. On Day 14, animals were submitted to a single session of 50 inescapable footshocks, preceded by the same S; immediately after, the animals were submitted to a 1% OVA-inhalation challenge. Results showed high levels of stress in the shocked animals as detected through both ultrasonic vocalizations (UVs) and social interaction test in an open field. Total leukocyte count in BAL from stressed animals (24 h post-OVA challenge) revealed a significant increase in the number of inflammatory cells in comparison to that measured in sensitized, nonstressed challenged rats. These data demonstrate that stress plays a relevant and important role on total bronchoalveolar cell count in OVA-sensitized rats.