Postnatal life events affect the severity of asthmatic airway inflammation in the adult rat

Major stress in early childhood strengthens the association between peripheral inflammatory activity and corticostriatal responsivity to reward

BACKGROUND

Severe, chronic stress during childhood accentuates vulnerability to mental and physical health problems across the lifespan. To explain this phenomenon, the neuroimmune network hypothesis proposes that childhood stressors amplify signaling between peripheral inflammatory cells and developing brain circuits that support processing of rewards and threats. Here, we conducted a preliminary test of the basic premises of this hypothesis.

METHODS

180 adolescents (mean age = 19.1 years; 68.9 % female) with diverse racial and ethnic identities (56.1 % White; 28.3 % Hispanic; 26.1 % Asian) participated. The Childhood Trauma Interview was administered to quantify early adversity. Five inflammatory biomarkers were assayed in antecubital blood - C-reactive protein, tumor necrosis factor-a, and interleukins-6, -8, and -10 - and were averaged to form a composite score. Participants also completed a functional MRI task to measure corticostriatal responsivity to the anticipation and acquisition of monetary rewards.

RESULTS

Stress exposure and corticostriatal responsivity interacted statistically to predict the inflammation composite. Among participants who experienced major stressors in the first decade of life, higher inflammatory activity covaried with lower corticostriatal responsivity during acquisition of monetary rewards. This relationship was specific to participants who experienced major stress in early childhood, implying a sensitive period for exposure, and were evident in both the orbitofrontal cortex and the ventral striatum, suggesting the broad involvement of corticostriatal regions. The findings were independent of participants' age, sex, racial and ethnic identity, family income, and depressive symptoms.

CONCLUSIONS

Collectively, the results are consistent with hypotheses suggesting that major stress in childhood alters brain-immune signaling.

Porcine blood cell and brain tissue energy metabolism: Effects of "early life stress"

Background: Early Life Stress (ELS) may exert long-lasting biological effects, e.g., on PBMC energy metabolism and mitochondrial respiration. Data on its effect on brain tissue mitochondrial respiration is scarce, and it is unclear whether blood cell mitochondrial activity mirrors that of brain tissue. This study investigated blood immune cell and brain tissue mitochondrial respiratory activity in a porcine ELS model. Methods: This prospective randomized, controlled, animal investigation comprised 12 German Large White swine of either sex, which were weaned at PND (postnatal day) 28-35 (control) or PND21 (ELS). At 20-24 weeks, animals were anesthetized, mechanically ventilated and surgically instrumented. We determined serum hormone, cytokine, and "brain injury marker" levels, superoxide anion (O₂ ^•¯) formation and mitochondrial respiration in isolated immune cells and immediate post mortem frontal cortex brain tissue. Results: ELS animals presented with higher glucose levels, lower mean arterial pressure. Most determined serum factors did not differ. In male controls, TNFα and IL-10 levels were both higher than in female controls as well as, no matter the gender in ELS animals. MAP-2, GFAP, and NSE were also higher in male controls than in the other three groups. Neither PBMC routine respiration and brain tissue oxidative phosphorylation nor maximal electron transfer capacity in the uncoupled state (ETC) showed any difference between ELS and controls. There was no significant relation between brain tissue and PBMC, ETC, or brain tissue, ETC, and PBMC bioenergetic health index. Whole blood O₂ ^•¯ concentrations and PBMC O₂ ^•¯ production were comparable between groups. However, granulocyte O₂ ^•¯ production after stimulation with E. coli was lower in the ELS group, and this effect was sex-specific: increased O₂ ^•¯ production increased upon stimulation in all control animals, which was abolished in the female ELS swine. Conclusion: This study provides evidence that ELS i) may, gender-specifically, affect the immune response to general anesthesia as well as O₂ ^•¯ radical production at sexual maturity, ii) has limited effects on brain and peripheral blood immune cell mitochondrial respiratory activity, and iii) mitochondrial respiratory activity of peripheral blood immune cells and brain tissue do not correlate.

Lung development and immune status under chronic LPS exposure in rat pups with and without CD26/DPP4 deficiency

Dipeptidyl-peptidase IV (CD26), a multifactorial integral type II protein, is expressed in the lungs during development and is involved in inflammation processes. We tested whether daily LPS administration influences the CD26-dependent retardation in morphological lung development and induces alterations in the immune status. Newborn Fischer rats with and without CD26 deficiency were nebulized with 1 µg LPS/2 ml NaCl for 10 min from days postpartum (dpp) 3 to 9. We used stereological methods and fluorescence activated cell sorting (FACS) to determine morphological lung maturation and alterations in the pulmonary leukocyte content on dpp 7, 10, and 14. Daily LPS application did not change the lung volume but resulted in a significant retardation of alveolarization in both substrains proved by significantly lower values of septal surface and volume as well as higher mean free distances in airspaces. Looking at the immune status after LPS exposure compared to controls, a significantly higher percentage of B lymphocytes and decrease of CD4⁺CD25⁺ T cells were found in both subtypes, on dpp7 a significantly higher percentage of CD4 T⁺ cells in CD26⁺ pups, and a significantly higher percentage of monocytes in CD26⁻ pups. The percentage of T cells was significantly higher in the CD26-deficient group on each dpp. Thus, daily postnatal exposition to low doses of LPS for 1 week resulted in a delay in formation of secondary septa, which remained up to dpp 14 in CD26⁻ pups. The retardation was accompanied by moderate parenchymal inflammation and CD26-dependent changes in the pulmonary immune cell composition.

Unbiased Screening Identifies Functional Differences in NK Cells After Early Life Psychosocial Stress

Early Life Adversity (ELA) is closely associated with the risk for developing diseases later in life, such as autoimmune diseases, type-2 diabetes and cardiovascular diseases. In humans, early parental separation, physical and sexual abuse or low social-economic status during childhood are known to have great impact on brain development, in the hormonal system and immune responses. Maternal deprivation (MD) is the closest animal model available to the human situation. This paradigm induces long lasting behavioral effects, causes changes in the HPA axis and affects the immune system. However, the mechanisms underlying changes in the immune response after ELA are still not fully understood. In this study we investigated how ELA changes the immune system, through an unbiased analysis, viSNE, and addressed specially the NK immune cell population and its functionality. We have demonstrated that maternal separation, in both humans and rats, significantly affects the sensitivity of the immune system in adulthood. Particularly, NK cells’ profile and response to target cell lines are significantly changed after ELA. These immune cells in rats are not only less cytotoxic towards YAC-1 cells, but also show a clear increase in the expression of maturation markers after 3h of maternal separation. Similarly, individuals who suffered from ELA display significant changes in the cytotoxic profile of NK cells together with decreased degranulation capacity. These results suggest that one of the key mechanisms by which the immune system becomes impaired after ELA might be due to a shift on the senescent state of the cells, specifically NK cells. Elucidation of such a mechanism highlights the importance of ELA prevention and how NK targeted immunotherapy might help attenuating ELA consequences.

Selective inflammatory propensities in adopted adolescents institutionalized as infants

This study examined whether early life adversity (ELA) limited to infancy was associated with an increase in circulating levels of proinflammatory cytokines and cellular cytokine responses to three stimulants [lipopolysaccharide (LPS), phytohemagglutinin (PHA), and phorbol myristate acetate plus ionomycin (PMA/IO)]. Participants were previously institutionalized (PI) youth (N = 45, 56 % female) who had spent their first years in institutional care (e.g., orphanages, baby homes) before being adopted into well-resourced homes (median age at adoption = 13 mos) and non-adopted comparisons (NA; N = 38, 55 % female). Their age range was 13.3-21.2 years (M = 16.3 years). This analysis followed up an earlier report on these youth (Reid et al., 2019a) that identified an increase in terminally differentiated CD8 + CD57 T cells among the PI relative to the NA youth. Cytokine levels in circulation were not highly correlated and thus examined separately. PI youth had higher circulating levels of Tumor Necrosis Factor-alpha (TNFα), but not Interleukin-1β (IL-1β) or Interleukin-6 (IL-6). Cytokine responses to in vitro activation within each stimulant condition were highly correlated and were thus combined to generate an index of the inflammatory reaction to each stimulant. Using Multivariate Analysis of Covariance, there was a highly significant multivariate effect of group, which was carried primarily by the PMA/IO condition, with PI youth exhibiting a larger inflammatory response than NA youth. Tests of mediation showed that both the early rearing effects on circulating TNFα and the composite inflammatory index of PMA/IO responsiveness were mediated in the statistical model by the percentage of CD8 + CD57+ TEMRA cells in circulation, a marker of replicative senescence in T cells. Sex differences were also found in circulating levels of IL-6 and TNFα, with males having higher levels than females.

Early-life stress and inflammation: A systematic review of a key experimental approach in rodents

Repeated maternal separation is the most widely used pre-clinical approach to investigate the relationship between early-life chronic stress and its neuropsychiatric and physical consequences. In this systematic review, we identified 46 studies that conducted repeated maternal separation or single-episode maternal separation and reported measurements of interleukin-1b, interleukin-6, interleukin-10, tumour necrosis factor-alpha, or microglia activation and density. We report that in the short-term and in the context of later-life stress, repeated maternal separation has pro-inflammatory immune consequences in diverse tissues. Repeated maternal separation animals exhibit greater microglial activation and elevated pro-inflammatory cytokine signalling in key brain regions implicated in human psychiatric disorders. Notably, repeated maternal separation generally has no long-term effect on cytokine expression in any tissue in the absence of later-life stress. These observations suggest that the elevated inflammatory signalling that has been reported in humans with a history of early-life stress may be the joint consequence of ongoing stressor exposure together with potentiated neural and/or immune responsiveness to stressors. Finally, our findings provide detailed guidance for future studies interrogating the causal roles of early-life stress and inflammation in disorders such as major depression.

The effect of neonatal maternal separation on short-chain fatty acids and airway inflammation in adult asthma mice

BACKGROUND

To investigate neonatal maternal separation (NMS) effects on airway inflammation of asthma and potential mechanism using a mouse model.

METHODS

80 Balb/c neonatal male mice were randomly assigned to NMS and non-NMS groups. Feces were collected on PND21, 28, 35 and 42 to analyze microbiota and short-chain fatty acids (SCFAs). Non-NMS group were then divided into control (group A) and asthma groups (group B), while NMS group was assigned to NMS+asthma (group C) and NMS+SCFAs+asthma groups (group D). Inflammatory cells and eosinophils (EOS) in bronchoalveolar lavage fluid (BALF) were assessed. Pathological changes and cytokines in lung tissue were observed. Protein expression of Occludin and E-cadherin in airway epithelial was examined.

RESULTS

The number of S', diversity index H' and dominance index D', as well as content butyric acid in NMS group C were significantly lower than non-NMS group B (p<0.05). Mice in group C had a higher level of inflammatory cells and EOS compared with group A, B and D. EOS moderate infiltration was found in mice of group B, C and D. Mice in group C had significantly higher levels of cytokines and showed slightly increased bronchial epithelium goblet cells and a small amount of visceral secretions. Occludin and E-cadherin expression in lung in B, C and D groups was depressed, and protein level in group C was significantly lower than group B and D.

CONCLUSIONS

NMS is associated with exacerbated inflammation of adult asthma by changing intestinal microflora resulting in butanoic acid decline and airway epithelial barrier damage.

Divergent transcriptional profiles in pediatric asthma patients of low and high socioeconomic status

AIM

There are marked socioeconomic disparities in pediatric asthma control, but the molecular origins of these disparities are not well understood. To fill this gap, we performed genome-wide expression profiling of monocytes and T-helper cells from pediatric asthma patients of lower and higher socioeconomic status (SES).

METHOD

Ninety-nine children with asthma participated in a cross-sectional assessment. Out of which 87% were atopic, and most had disease of mild (54%) or moderate (29%) severity. Children were from lower-SES (n = 49; household income <$50 000) or higher-SES (n = 50; household income >$140 000) families. Peripheral blood monocytes and T-helper cells were isolated for genome-wide expression profiling of mRNA.

RESULTS

Lower-SES children had worse asthma quality of life relative to higher-SES children, by both their own and their parents' reports. Although the groups had similar disease severity and potential confounds were controlled, their transcriptional profiles differed notably. The monocytes of lower-SES children showed transcriptional indications of up-regulated anti-microbial and pro-inflammatory activity. The T-helper cells of lower-SES children also had comparatively reduced expression of genes encoding γ-interferon and tumor necrosis factor-α, cytokines that orchestrate Type 1 responses. They also showed up-regulated activity of transcription factors that polarize cells towards Type 2 responses and promote Th17 cell maturation.

CONCLUSION

Collectively, these patterns implicate pro-inflammatory monocytes and Type 2 cytokine activity as mechanisms contributing to worse asthma control among lower-SES children.

Social and physical environments early in development predict DNA methylation of inflammatory genes in young adulthood

Chronic inflammation contributes to a wide range of human diseases, and environments in infancy and childhood are important determinants of inflammatory phenotypes. The underlying biological mechanisms connecting early environments with the regulation of inflammation in adulthood are not known, but epigenetic processes are plausible candidates. We tested the hypothesis that patterns of DNA methylation (DNAm) in inflammatory genes in young adulthood would be predicted by early life nutritional, microbial, and psychosocial exposures previously associated with levels of inflammation. Data come from a population-based longitudinal birth cohort study in metropolitan Cebu, the Philippines, and DNAm was characterized in whole blood samples from 494 participants (age 20-22 y). Analyses focused on probes in 114 target genes involved in the regulation of inflammation, and we identified 10 sites across nine genes where the level of DNAm was significantly predicted by the following variables: household socioeconomic status in childhood, extended absence of a parent in childhood, exposure to animal feces in infancy, birth in the dry season, or duration of exclusive breastfeeding. To evaluate the biological significance of these sites, we tested for associations with a panel of inflammatory biomarkers measured in plasma obtained at the same age as DNAm assessment. Three sites predicted elevated inflammation, and one site predicted lower inflammation, consistent with the interpretation that levels of DNAm at these sites are functionally relevant. This pattern of results points toward DNAm as a potentially important biological mechanism through which developmental environments shape inflammatory phenotypes across the life course.

Postnatal treatment with metyrapone attenuates the effects of diet-induced obesity in female rats exposed to early-life stress

Experimental studies in rodents have shown that females are more susceptible to exhibiting fat expansion and metabolic disease compared with males in several models of fetal programming. This study tested the hypothesis that female rat pups exposed to maternal separation (MatSep), a model of early-life stress, display an exacerbated response to diet-induced obesity compared with male rats. Also, we tested whether the postnatal treatment with metyrapone (MTP), a corticosterone synthase inhibitor, would attenuate this phenotype. MatSep was performed in WKY offspring by separation from the dam (3 h/day, postnatal days 2-14). Upon weaning, male and female rats were placed on a normal (ND; 18% kcal fat) or high-fat diet (HFD; 60% kcal fat). Nondisturbed littermates served as controls. In male rats, no diet-induced differences in body weight (BW), glucose tolerance, and fat tissue weight and morphology were found between MatSep and control male rats. However, female MatSep rats displayed increased BW gain, fat pad weights, and glucose intolerance compared with control rats (P < 0.05). Also, HFD increased plasma corticosterone (196 ± 51 vs. 79 ± 18 pg/ml, P < 0.05) and leptin levels (1.8 ± 0.4 vs. 1.3 ± 0.1 ng/ml, P < 0.05) in female MatSep compared with control rats, whereas insulin and adiponectin levels were similar between groups. Female control and MatSep offspring were treated with MTP (50 µg/g ip) 30 min before the daily separation. MTP treatment significantly attenuated diet-induced obesity risk factors, including elevated adiposity, hyperleptinemia, and glucose intolerance. These findings show that exposure to stress hormones during early life could be a key event to enhance diet-induced obesity and metabolic disease in female rats. Thus, pharmacological and/or behavioral inflection of the stress levels is a potential therapeutic approach for prevention of early life stress-enhanced obesity and metabolic disease.

Harsh parent-child conflict is associated with decreased anti-inflammatory gene expression and increased symptom severity in children with asthma

Asthma is a chronic respiratory disorder that affects over 7 million children in the United States. Evidence indicates that family stressors are associated with worsening of asthma symptoms, and some research suggests that these stressful experiences engender changes in children's immune systems in ways that exacerbate airway inflammation and contribute to both acute and chronic asthma symptoms. We examined the association between observed experiences of parent-child conflict and the expression of signaling molecules involved in the transduction of anti-inflammatory signals that regulate airway inflammation and obstruction. Fifty-seven children and their parents participated in a conflict task, and coders rated interactions for evidence of harsh and supportive behaviors. Children reported on their perceptions of parental support and reported on their daily asthma symptoms for 2 weeks. We collected peripheral blood in children to measure leukocyte expression of messenger RNA for the glucocorticoid receptor and the β2-adrenergic receptor. Analyses revealed that harsh conflict behaviors were associated with decreased expression of both messenger RNAs and more severe asthma symptoms. Neither supportive behaviors nor perceived parental support was associated with gene expression or asthma symptoms. These findings suggest that harsh interactions with parents are associated with downregulation of key anti-inflammatory signaling molecules and difficulties breathing in children with asthma. Children with asthma who are also victims of maltreatment may be particularly susceptible to transcriptional changes in immune cells that could worsen asthma over time.

Exposure to gun violence and asthma among children in Puerto Rico

BACKGROUND AND OBJECTIVES

Although community violence may influence asthma morbidity by increasing stress, no study has assessed exposure to gun violence and childhood asthma. We examined whether exposure to gun violence is associated with asthma in children, particularly in those reporting fear of leaving their home.

METHODS

Case-control study of 466 children aged 9-14 years with (n = 234) and without (n = 232) asthma in San Juan, Puerto Rico. Lifetime exposure to gun violence was defined as hearing a gunshot more than once. We also assessed whether the child was afraid to leave his/her home because of violence. Asthma was defined as physician-diagnosed asthma and wheeze in the prior year. We used logistic regression for the statistical analysis. All multivariate models were adjusted for age, gender, household income, parental asthma, environmental tobacco smoke, prematurity and residential distance from a major road.

RESULTS

Cases were more likely to have heard a gunshot more than once than control subjects (n = 156 or 67.2% vs. n = 122 or 52.1%, P < 0.01). In a multivariate analysis, hearing a gunshot more than once was associated with asthma (odds ratio [OR] = 1.8, 95% confidence interval [CI] = 1.1-1.7, P = 0.01). Compared with children who had heard a gunshot not more than once and were not afraid to leave their home because of violence, those who had heard a gunshot more than once and were afraid to leave their home due to violence had 3.2 times greater odds of asthma (95% CI for OR = 2.2-4.4, P < 0.01).

CONCLUSIONS

Exposure to gun violence is associated with asthma in Puerto Rican children, particularly in those afraid to leave their home. Stress from such violence may contribute to the high burden of asthma in Puerto Ricans.

Stress and asthma: novel insights on genetic, epigenetic, and immunologic mechanisms

In the United States the economically disadvantaged and some ethnic minorities are often exposed to chronic psychosocial stressors and disproportionately affected by asthma. Current evidence suggests a causal association between chronic psychosocial stress and asthma or asthma morbidity. Recent findings suggest potential mechanisms underlying this association, including changes in the methylation and expression of genes that regulate behavioral, autonomic, neuroendocrine, and immunologic responses to stress. There is also evidence suggesting the existence of susceptibility genes that predispose chronically stressed youth to both post-traumatic stress disorder and asthma. In this review we critically examine published evidence and suggest future directions for research in this field.

The behavioral and immunological impact of maternal separation: a matter of timing

Maternal separation (MS), an early life stressful event, has been demonstrated to trigger neuropsychiatric disorders later in life, in particular depression. Experiments using rodents subjected to MS protocols have been very informative for the establishment of this association. However, the mechanism by which MS leads to neuropsychiatric disorders is far from being understood. This is probably associated with the multifactorial nature of depression but also with the fact that different research MS protocols have been used (that vary on temporal windows and time of exposure to MS). In the present study, MS was induced in rats in two developmental periods: for 6 h per day for 14 days between postnatal days 2-15 (MS2-15) and 7-20 (MS7-20). These two periods were defined to differ essentially on the almost complete (MS2-15) or partial (MS7-20) overlap with the stress hypo-responsive period. Behavioral, immunological, and endocrine parameters, frequently associated with depressive-like behavior, were analyzed in adulthood. Irrespectively from the temporal window, both MS exposure periods led to increased sera corticosterone levels. However, only MS2-15 animals displayed depressive and anxious-like behaviors. Moreover, MS2-15 was also the only group presenting alterations in the immune system, displaying decreased percentage of CD8(+) T cells, increased spleen T cell CD4/CD8 ratio, and thymocytes with increased resistance to dexamethasone-induced cell death. A linear regression model performed to predict depressive-like behavior showed that both corticosterone levels and T cell CD4/CD8 ratio explained 37% of the variance observed in depressive-like behavior. Overall, these findings highlight the existence of "critical periods" for early life stressful events to exert programing effects on both central and peripheral systems, which are of relevance for distinct patterns of susceptibility to emotional disorders later in life.

Neonatal stress modulates sickness behavior: role for proinflammatory cytokines

Neonatal stress increased the duration and augmented symptoms of sickness behavior induced by influenza virus infection or endotoxin challenge in mice. Since proinflammatory cytokines were implicated in sickness behavior, the present study sought to determine the effect of neonatal stress on cytokines-induced sickness behavior and on proinflammatory cytokine secretion. Data indicate that separation of mouse pups from the dams at an early age (maternal separation, MSP) increased the duration and augmented some of the symptoms of sickness behavior induced by proinflammatory cytokines. In addition, MSP partially suppressed cytokine and corticosterone secretion in response to endotoxin administration. These data may suggest that MSP increased sensitivity to the effects of proinflammatory cytokines on sickness behavior following an immune challenge.

The Biological Residue of Childhood Poverty

Children raised in poverty are prone to physical health problems late in life. To understand these findings and address the scientific challenge they represent, we must formulate integrative conceptual frameworks at the crossroads of behavioral and biomedical science, with a strong developmental emphasis. In this article, we outline such a framework and discuss research bearing on its validity. We address how childhood poverty gets under the skin, at the level of tissues and organs, in a manner that affects later disease risks. We also tackle questions about resilience; Even with lengthy exposure to childhood poverty, why do only a subset of people acquire diseases? Why are some individuals protected while others remain vulnerable? Maternal nurturance might be a source of resilience, buffering children from the long-term health consequences of poverty. We conclude with research priorities.

Pathways to resilience: maternal nurturance as a buffer against the effects of childhood poverty on metabolic syndrome at midlife

Children raised in families with low socioeconomic status (SES) go on to have high rates of chronic illness in adulthood. However, a sizable minority of low-SES children remain healthy across the life course, which raises questions about the factors associated with, and potentially responsible for, such resilience. Using a sample of 1,205 middle-aged Americans, we explored whether two characteristics--upward socioeconomic mobility and early parental nurturance--were associated with resilience to the health effects of childhood disadvantage. The primary outcome in our analyses was the presence of metabolic syndrome in adulthood. Results revealed that low childhood SES was associated with higher prevalence of metabolic syndrome at midlife, independently of traditional risk factors. Despite this pattern, half the participants raised in low-SES households were free of metabolic syndrome at midlife. Upward social mobility was not associated with resilience to metabolic syndrome. However, results were consistent with a buffering scenario, in which high levels of maternal nurturance offset the metabolic consequences of childhood disadvantage.

Synthetic double-stranded RNA enhances airway inflammation and remodelling in a rat model of asthma

Respiratory viral infections are frequently associated with exacerbations of asthma. Double-stranded RNA (dsRNA) produced during viral infections may be one of the stimuli for exacerbation. We aimed to assess the potential effect of dsRNA on certain aspects of chronic asthma through the administration of polyinosine-polycytidylic acid (poly I:C), synthetic dsRNA, to a rat model of asthma. Brown Norway rats were sensitized to ovalbumin and challenged three times to evoke airway remodelling. The effect of poly I:C on the ovalbumin-induced airway inflammation and structural changes was assessed from bronchoalveolar lavage fluid and histological findings. The expression of cytokines and chemokines was evaluated by real-time quantitative reverse transcription PCR and ELISA. Ovalbumin-challenged animals showed an increased number of total cells and eosinophils in bronchoalveolar lavage fluid compared with PBS-challenged controls. Ovalbumin-challenged animals treated with poly I:C showed an increased number of total cells and neutrophils in bronchoalveolar lavage fluid compared with those without poly I:C treatment. Ovalbumin-challenged animals showed goblet cell hyperplasia, increased airway smooth muscle mass, and proliferation of both airway epithelial cells and airway smooth muscle cells. Treatment with poly I:C enhanced these structural changes. Among the cytokines and chemokines examined, the expression of interleukins 12 and 17 and of transforming growth factor-β(1) in ovalbumin-challenged animals treated with poly I:C was significantly increased compared with those of the other groups. Double-stranded RNA enhanced airway inflammation and remodelling in a rat model of bronchial asthma. These observations suggest that viral infections may promote airway remodelling.

Psychological stress in childhood and susceptibility to the chronic diseases of aging: moving toward a model of behavioral and biological mechanisms

Among people exposed to major psychological stressors in early life, there are elevated rates of morbidity and mortality from chronic diseases of aging. The most compelling data come from studies of children raised in poverty or maltreated by their parents, who show heightened vulnerability to vascular disease, autoimmune disorders, and premature mortality. These findings raise challenging theoretical questions. How does childhood stress get under the skin, at the molecular level, to affect risk for later diseases? And how does it incubate there, giving rise to diseases several decades later? Here we present a biological embedding model, which attempts to address these questions by synthesizing knowledge across several behavioral and biomedical literatures. This model maintains that childhood stress gets "programmed" into macrophages through epigenetic markings, posttranslational modifications, and tissue remodeling. As a consequence these cells are endowed with proinflammatory tendencies, manifest in exaggerated cytokine responses to challenge and decreased sensitivity to inhibitory hormonal signals. The model goes on to propose that over the life course, these proinflammatory tendencies are exacerbated by behavioral proclivities and hormonal dysregulation, themselves the products of exposure to early stress. Behaviorally, the model posits that childhood stress gives rise to excessive threat vigilance, mistrust of others, poor social relationships, impaired self-regulation, and unhealthy lifestyle choices. Hormonally, early stress confers altered patterns of endocrine and autonomic discharge. This milieu amplifies the proinflammatory environment already instantiated by macrophages. Acting in concert with other exposures and genetic liabilities, the resulting inflammation drives forward pathogenic mechanisms that ultimately foster chronic disease.

A rat model of exercise-induced asthma: a nonspecific response to a specific immunogen

Exercise-induced bronchoconstriction (EIB) is common; however, key aspects of its pathogenesis are still unclear. We investigated the feasibility of adapting an established animal model of asthma to investigate the earliest stages of EIB. The hypothesis was that a single exposure to a normally innocuous, and brief, exercise challenge could trigger EIB symptoms in rats previously sensitized to ovalbumin (OVA) but otherwise unchallenged. Brown-Norway rats were sensitized by intraperitoneal injection of OVA at 0 and 2 wk. At week 3, animals were exposed to either aerosolized OVA (SS) or exercise (EXS). A trained, blinded, clinical observer graded EIB by respiratory sounds. Plasma and lung cytokine levels were analyzed. No control rats with or without exercise (EX, CON) showed evidence of EIB. Eighty percent of the SS group demonstrated abnormal breath sounds upon exposure to aerosolized OVA. Approximately 30% of EXS rats sensitized to OVA but exposed only to exercise had abnormal breath sounds. Lung tissue levels of TNF-α, IL-1α, growth-related oncogene/keratinocyte/chemoattractant, and IFN-γ were significantly higher (P < 0.001) in the SS group, relative to all other groups. Changes in most of these cytokines were not notable in the EXS rats, suggesting a different mechanism of EIB. Remarkably, IFN-γ, but not the other cytokines measured, was significantly elevated following brief exercise in both sensitized and unsensitized rats. Exercise led to detectable breathing sound abnormalities in sensitized rats, but less severe than those observed following classical OVA challenge. Precisely how this immune crossover occurs is not known, but this model may be useful in elucidating essential mechanisms of EIB.

Increased rat neonatal activity influences adult cytokine levels and relative muscle mass

Little is known about the effect of physical activity in early life on subsequent growth and regulation of inflammation. We previously reported that exposure of muscles in growing rats to IL-6 results in decreased muscle growth apparently because of a state of resistance to growth factors such IGF-I and that running exercise could ameliorate this growth defect. Herein, we hypothesized that increased activity, for a brief period during neonatal life, would pattern the adult rat toward a less inflammatory phenotype. Neonatal rats were induced to move about their cage for brief periods from d 5 to d 15 postpartum. Additional groups were undisturbed controls (CONs) and handled (HAND). Subgroups of rats were sampled at the age of 30 and 65 d. Relative to CON and HAND groups, the neonatal exercise (EX) group demonstrated a decrease in circulating levels of TNFα, IL-6, and IL-1β in adulthood, primarily in male rats. In addition, adult male EX rats had lower body mass and increased skeletal muscle mass suggesting a leaner phenotype. The results of this study suggest that moderate increases in activity early in life can influence the adult toward a more healthy phenotype with regard to inflammatory mediators and relative muscle mass.

Neonatal stress modulates sickness behavior

The quality of the early environment, especially during the neonatal period, influences the development of individual differences in resistance to stress and illness in adulthood. A previous study demonstrated that neonatal stress augmented proinflammatory cytokine expression and viral replication in influenza virus-infected adult mice. The goal of the following study was to examine the lifelong effects of neonatal stress on the behavioral response to an immune challenge. Neonatal stress consisted of separating mouse pups from their dams (maternal separation, MSP) at critical points of their development. In the first study, pups were separated from the dam daily for 6h between postnatal day 1 and 14. As adults, these mice were infected with influenza A/PR8 virus. In a second study, a similar paradigm of MSP was employed, and as adults mice were injected with lipopolysaccharide (LPS) (ip). In a third study pups were separated from the dam for 24h on postnatal day 4 or 9. As adults, these mice received ip injections of LPS. In all three studies, changes in body weight, food and sweet solution consumption were examined following immune challenge. As previously described, activation of the immune system using influenza virus infection or LPS administration resulted in sickness behavior that consisted of body weight loss, anorexia and reduced consumption of a sweet solution. Furthermore, neonatal stress induced more rapid kinetics of sickness behavior and augmented several aspects of these symptoms. Together with previous studies, these findings suggest that neonatal stress disrupted the regulation of innate resistance to an immune challenge resulting in enhanced immunological and behavioral responses to immune activation. Thus, long lasting effects of early stress events may be the basis for individual differences in health and susceptibility to disease.

Ozone and allergen exposure during postnatal development alters the frequency and airway distribution of CD25+ cells in infant rhesus monkeys

The epidemiologic link between air pollutant exposure and asthma has been supported by experimental findings, but the mechanisms are not understood. In this study, we evaluated the impact of combined ozone and house dust mite (HDM) exposure on the immunophenotype of peripheral blood and airway lymphocytes from rhesus macaque monkeys during the postnatal period of development. Starting at 30 days of age, monkeys were exposed to 11 cycles of filtered air, ozone, HDM aerosol, or ozone+HDM aerosol. Each cycle consisted of ozone delivered at 0.5 ppm for 5 days (8 h/day), followed by 9 days of filtered air; animals received HDM aerosol during the last 3 days of each ozone exposure period. Between 2-3 months of age, animals co-exposed to ozone+HDM exhibited a decline in total circulating leukocyte numbers and increased total circulating lymphocyte frequency. At 3 months of age, blood CD4+/CD25+ lymphocytes were increased with ozone+HDM. At 6 months of age, CD4+/CD25+ and CD8+/CD25+ lymphocyte populations increased in both blood and lavage of ozone+HDM animals. Overall volume of CD25+ cells within airway mucosa increased with HDM exposure. Ozone did not have an additive effect on volume of mucosal CD25+ cells in HDM-exposed animals, but did alter the anatomical distribution of this cell type throughout the proximal and distal airways. We conclude that a window of postnatal development is sensitive to air pollutant and allergen exposure, resulting in immunomodulation of peripheral blood and airway lymphocyte frequency and trafficking.

Early childhood stress is associated with elevated antibody levels to herpes simplex virus type 1

It is well known that children need solicitous parenting and a nurturing rearing environment to ensure their normal behavioral development. Early adversity often negatively impacts emotional and mental well-being, but it is less clearly established how much the maturation and regulation of physiological systems is also compromised. The following research investigated the effect of 2 different types of adverse childhood experiences, early deprivation through institutionalization and physical abuse, on a previously unexplored outcome: the containment of herpes simplex virus (HSV). The presence of HSV-specific antibody in salivary specimens was determined in 155 adolescents, including 41 postinstitutionalized, 34 physically-abused, and 80 demographically-similar control youth. Across 4 school and home days, HSV antibody was higher in both postinstitutionalized and physically-abused adolescents when compared with control participants. Because the prevalence of HSV infection was similar across the groups, the elevated antibody was likely indicative of viral recrudescence from latency. Total secretory Ig-A secretion was associated with HSV, but did not account for the group differences in HSV-specific antibody. These findings are likely caused by a failure of cellular immune processes to limit viral reactivation, indicating a persistent effect of early rearing on immune functioning. The fact that antibody profiles were still altered years after adoption into a more benevolent setting with supportive families suggests these results were not caused by contemporaneous factors, but rather reflect a lingering influence of earlier life experiences.

Dysregulation of the stress response in asthmatic children

The stress system co-ordinates the adaptive responses of the organism to stressors of any kind. Inappropriate responsiveness may account for increased susceptibility to a variety of disorders, including asthma. Accumulated evidence from animal models suggests that exogenously applied stress enhances airway reactivity and increases allergen-induced airway inflammation. This is in agreement with the clinical observation that stressful life events increase the risk of a new asthma attack. Activation of the hypothalamic-pituitary-adrenal (HPA) axis by specific cytokines increases the release of cortisol, which in turn feeds back and suppresses the immune reaction. Data from animal models suggest that inability to increase glucocorticoid production in response to stress is associated with increased airway inflammation with mechanical dysfunction of the lungs. Recently, a growing body of evidence shows that asthmatic subjects who are not treated with inhaled corticosteroids (ICS) are likely to have an attenuated activity and/or responsiveness of their HPA axis. In line with this concept, most asthmatic children demonstrate improved HPA axis responsiveness on conventional doses of ICS, as their airway inflammation subsides. Few patients may experience further deterioration of adrenal function, a phenomenon which may be genetically determined.