Suppression of gene expression and production of interleukin 13 by dexamethasone in human peripheral blood mononuclear cells

Central and Peripheral Inflammation: A Common Factor Causing Addictive and Neurological Disorders and Aging-Related Pathologies

Many diseases and degenerative processes affecting the nervous system and peripheral organs trigger the activation of inflammatory cascades. Inflammation can be triggered by different environmental conditions or risk factors, including drug and food addiction, stress, and aging, among others. Several pieces of evidence show that the modern lifestyle and, more recently, the confinement associated with the COVID-19 pandemic have contributed to increasing the incidence of addictive and neuropsychiatric disorders, plus cardiometabolic diseases. Here, we gather evidence on how some of these risk factors are implicated in activating central and peripheral inflammation contributing to some neuropathologies and behaviors associated with poor health. We discuss the current understanding of the cellular and molecular mechanisms involved in the generation of inflammation and how these processes occur in different cells and tissues to promote ill health and diseases. Concomitantly, we discuss how some pathology-associated and addictive behaviors contribute to worsening these inflammation mechanisms, leading to a vicious cycle that promotes disease progression. Finally, we list some drugs targeting inflammation-related pathways that may have beneficial effects on the pathological processes associated with addictive, mental, and cardiometabolic illnesses.

The hormonal physiology of immune components in breast milk and their impact on the infant immune response

During pregnancy, the maternal body undergoes a considerable transformation regarding the anatomy, metabolism, and immune profile that, after delivery, allows for protection and nourishment of the offspring via lactation. Pregnancy hormones are responsible for the development and functionality of the mammary gland for breast milk production, but little is known about how hormones control its immune properties. Breast milk composition is highly dynamic, adapting to the nutritional and immunological needs that the infant requires in the first months of life and is responsible for the main immune modeling of breastfed newborns. Therefore, alterations in the mechanisms that control the endocrinology of mammary gland adaptation for lactation could disturb the properties of breast milk that prepare the neonatal immune system to respond to the first immunologic challenges. In modern life, humans are chronically exposed to endocrine disruptors (EDs), which alter the endocrine physiology of mammals, affecting the composition of breast milk and hence the neonatal immune response. In this review, we provide a landscape of the possible role of hormones in the control of passive immunity transferred by breast milk and the possible effect of maternal exposure to EDs on lactation, as well as their impacts on the development of neonatal immunity.

Control of immunity by glucocorticoids in health and disease

Animals receive environmental stimuli from neural signals in order to produce hormones that control immune responses. Glucocorticoids (GCs) are a group of steroid hormones produced in the adrenal cortex and well-known mediators for the nervous and immune systems. GC secretion is induced by circadian rhythm and stress, and plasma GC levels are high at the active phase of animals and under stress condition. Clinically, GCs are used for allergies, autoimmunity, and chronic inflammation, because they have strong anti-inflammatory effects and induce the apoptosis of lymphocytes. Glucocorticoid receptor (GR) acts as a transcription factor and represses the expression of inflammatory cytokines, chemokines, and prostaglandins by binding to its motif, glucocorticoid-response element, or to other transcription factors. In mice, GR suppresses the antigen-stimulated inflammation mediated by macrophages, dendritic cells, and epithelial cells, and impairs cytotoxic immune responses by downregulating interferon-γ production and inhibiting the development of type-1 helper T cells, CD8+ T cells, and natural killer cells. These immune inhibitory effects prevent lethality by excessive inflammation, but at the same time increase the susceptibility to infection and cancer. GCs can also activate the immune system. The circadian cycle of GC secretion controls the diurnal oscillations of the distribution and response of T cells, thus supporting T cell maintenance and effective immune protection against infection. Moreover, several reports have shown that GR has the potential to enhance the activities of Th2, Th17, and immunoglobulin-producing B cells. Stress has two different effects on immune responses: immune suppression to cause mortality by infection and cancer, and excessive immune activation to induce chronic inflammation and autoimmune disease. Consistently, stress-induced GCs strongly suppress cell-mediated immunity and cause viral infection and tumor development. They may also enhance the development of pathogenic helper T cells and cause tissue damage through neural and intestinal inflammation. Past studies have reported the positive and negative effects of GCs on the immune system. These opposing properties of GCs may regulate the immune balance between the responsiveness to antigens and excessive inflammation in steady-state and stress conditions.

Immune-enhancing effects of glucocorticoids in response to day-night cycles and stress

Environmental cues such as the day-night cycle or stressors trigger the production of glucocorticoids (GCs) by the adrenal cortex. GCs are well known for their anti-inflammatory effects that suppress the production of inflammatory cytokines and induce the apoptosis of lymphocytes. Recent studies in mice, however, have revealed pro-inflammatory effects. The diurnal oscillation of GCs induces the expression of IL-7 receptor α (IL-7Rα) and C-X-C motif chemokine receptor 4 (CXCR4) at the active phase, which drives the diurnal homing of T cells into lymphoid organs. This accumulation of T cells at the active phase enhances T-cell priming against bacterial infection and antigen immunization, leading to an increase of effector CD8 T cells and antibody production. GCs induced by moderate stress trigger the homing of memory CD8 T cells into the bone marrow and support the maintenance and response of these cells. Thus, endogenous GCs have a self-defense function to enhance adaptive immune responses. By contrast, strong stress induces even higher GC levels and causes chronic inflammation and autoimmunity. Because GCs can enhance the differentiation and function of T-helper 2 (Th2) and Th17 cells, high stress-induced GC levels might enhance inflammation via Th17 cell differentiation. Overall, the positive and negative effects of GCs may regulate the balance between normal immune responses and susceptibility to infections and inflammatory diseases.

Glucocorticoids Regulate Circadian Rhythm of Innate and Adaptive Immunity

Animals have evolved circadian rhythms to adapt to the 24-h day-night cycle. Circadian rhythms are controlled by molecular clocks in the brain and periphery, which is driven by clock genes. The circadian rhythm is propagated from the brain to the periphery by nerves and hormones. Glucocorticoids (GCs) are a class of steroid hormones produced by the adrenal cortex under the control of the circadian rhythm and the stress. GCs have both positive and negative effects on the immune system. Indeed, they are well known for their strong anti-inflammatory and immunosuppressive effects. Endogenous GCs inhibit the expression of inflammatory cytokines and chemokines at the active phase of mice, regulating the circadian rhythm of tissue inflammation. In addition, GCs induce the rhythmic expression of IL-7R and CXCR4 on T cells, which supports T cell maintenance and homing to lymphoid tissues. Clock genes and adrenergic neural activity control the T cell migration and immune response. Taken together, circadian factors shape the diurnal oscillation of innate and adaptive immunity. Among them, GCs participate in the circadian rhythm of innate and adaptive immunity by positive and negative effects.

Estrogen receptor antagonist fulvestrant (ICI 182,780) inhibits the anti-inflammatory effect of glucocorticoids

The glucocorticoid receptor (GR) and estrogen receptor (ER) play important roles in both physiological and pathological conditions involving cell growth and differentiation, lipolysis, control of glucose metabolism, immunity, and inflammation. In fact, recent studies suggest that 17beta-estradiol, like glucocorticoids, may also have anti-inflammatory properties, even if the molecular mechanisms responsible for these activities have not yet been completely clarified. The present study was designed to gain a better understanding of the possible cross-talk between GR and ER in a model of lung inflammation (carrageenan-induced pleurisy). In particular, we have investigated whether fulvestrant (ICI 182,780), a selective ER-alpha antagonist, is able to attenuate the well known anti-inflammatory effect of dexamethasone (DEX), a synthetic glucocorticoid, in ovariectomized rats. We show that ICI 182,780, a selective ER-alpha antagonist, reverses the anti-inflammatory activity exhibited by DEX. Moreover, the coadministration of ICI 182,780 significantly inhibited the ability of DEX to reduce: 1) the degree of lung injury, 2) the rise in myeloperoxidase activity, 3) the increase of poly-(ADP-ribose) polymerase activity, tumor necrosis factor alpha, and interleukin-1beta levels, 4) inducible nitric-oxide synthase, 5) lipid peroxidation, 6) nitrotyrosine formation, 7) cyclooxygenase expression, and 8) the IkappaB-alpha degradation caused by carrageenan administration. In addition, quantitative PCR shows that DEX down-regulates GR and up-regulates glucocorticoid-induced leucine zipper levels, whereas ICI 182,780 does not counteract these effects. In conclusion, these results suggest that the in vivo anti-inflammatory property of DEX is also related to the ER-alpha.

Molecular regulation of interleukin-13 and monocyte chemoattractant protein-1 expression in human mast cells by interleukin-1beta

Mast cells play pivotal roles in immunoglobulin (Ig) E-mediated airway inflammation, expressing interleukin (IL)-13 and monocyte chemoattractant protein-1 (MCP-1), which in turn regulate IgE synthesis and/or inflammatory cell recruitment. The molecular effects of IL-1beta on cytokine expression by human mast cells (HMC) have not been studied well. In this report, we provide evidence that human umbilical cord blood-derived mast cells (CBDMC) and HMC-1 cells express the type 1 receptor for IL-1. We also demonstrate that IL-1beta and tumor necrosis factor-alpha are able to induce, individually or additively, dose-dependent expression of IL-13 and MCP-1 in these cells. The induction of IL-13 and MCP-1 gene expression by IL-1beta was accompanied by the activation of IL-1 receptor-associated kinase and translocation of the transcription factor, nuclear factor (NF) kappaB into the nucleus. Accordingly, Bay-11 7082, an inhibitor of NF-kappaB activation, inhibited IL-1beta-induced IL-13 and MCP-1 expression. IL-1beta also induced IL-13 promoter activity while enhancing the stability of IL-13 messenger RNA transcripts. Dexamethasone, a glucocorticoid, inhibited IL-1beta-induced nuclear translocation of NF-kappaB and also the secretion of IL-13 from mast cells. Our data suggest that IL-1beta can serve as a pivotal costimulus of inflammatory cytokine synthesis in human mast cells, and this may be partly mediated by IL-1 receptor-binding and subsequent signaling via nuclear translocation of NF-kappaB. Because IL-1beta is a ubiquitously expressed cytokine, these findings have important implications for non-IgE-mediated signaling in airway mast cells as well as for innate immunity and airway inflammatory responses, such as observed in extrinsic and intrinsic asthma.

Polyclonal and allergen-induced cytokine responses in adults with asthma: resolution of asthma is associated with normalization of IFN-gamma responses

BACKGROUND

Atopic disease is associated with skewing of immune responses away from a T(H)1 toward a T(H)2 profile. Previous studies have implicated this cytokine imbalance in the development of disease. However, it is not known whether normalization of this imbalance is conversely associated with disease resolution.

OBJECTIVE

To further delineate the role of reduced T(H)1 and increased T(H)2 cytokine production in the pathogenesis of atopic disease and to determine whether disease resolution is associated with alteration of cytokine profiles, we investigated cytokine responses in a cohort of adult patients with asthma followed from childhood.

METHODS

A cohort of wheezy children and control subjects aged 7 to 10 years were recruited from 1964 to 1967. Subjects were reevaluated every 7 years to monitor the outcome of childhood asthma. At the 42-year follow-up, 89 subjects from this cohort were evaluated for mitogen and house dust mite (HDM)-induced T(H)1 (IFN-gamma) and T(H)2 (IL-4, IL-5, and IL-13) cytokine responses. Cytokine responses were compared in patients with ongoing asthma, patients with resolved asthma, and control subjects.

RESULTS

Patients with severe ongoing asthma had significantly reduced HDM-induced IFN-gamma production compared with that of control subjects and patients with resolved asthma. In contrast, HDM-induced IFN-gamma production in patients with resolved asthma was equivalent to that seen in control subjects. Patients with ongoing and resolved asthma produced significantly higher levels of IL-5 in response to HDM compared with that seen in control subjects, with levels being equivalent in patients with active and resolved asthma. HDM-induced IL-13 production was significantly increased in the patients with resolved asthma when compared with that seen in the control subjects. PHA-induced cytokine responses did not parallel HDM-induced responses.

CONCLUSION

Patients with persistent and severe atopic asthma have a reduced HDM-induced T(H)1 response, whereas those with resolved asthma do not. This suggests that reduced HDM-induced IFN-gamma production might be an important factor contributing to ongoing severe asthma and that normalization of allergen-induced T(H)1 responses might be important for disease resolution. The finding that all subjects with a history of asthma displayed increased HDM-induced T(H)2 (IL-5 and IL-13) cytokine responses, irrespective of the presence or absence of asthma, suggests that increased T(H)2 responses reflect the presence of the atopic state per se rather than being specifically linked to asthma.

In vitro effects of fluticasone propionate on IL-13 production by mitogen-stimulated lymphocytes

BACKGROUND

Corticosteroid administration produces multiple immunomodulatory effects, including down-regulation of cytokine production by CD4 T lymphocytes. Fluticasone propionate (FP) (Glaxo Smith&Kline, Greenford, UK), a highly lipophilic topical corticosteroid, has been shown to be safe and effective in the treatment of asthma and of both seasonal and perennial rhinitis.

AIMS

To gain insight into the mechanisms of FP therapeutic effects, we evaluated interleukin (IL)-13 (a type 2 cytokine that seemingly plays a pivotal role in allergic mechanisms) production by mitogen-stimulated peripheral blood mononuclear cells (MNC) in vitro, treated or not with FP.

METHODS

MNC from 10 healthy subjects and 10 asthmatic atopic patients with Parietaria allergy were stimulated v/v with phytohaemagglutinin (PHA) (50 gamma/ml) or with complete medium alone as a control. Culture supernatants, in vitro treated or not with 10(-7) or 10(-8) M FP, were collected after 48 or 72 h incubation. IL-13 production was assessed by enzyme-linked immunosorbent assay. In random selected samples, after 4 or 24 h of cell cultures, RNA was extracted and IL-4 and IL-5 reverse transcriptase-polymerase chain reaction (RT-PCR) products analyzed.

RESULTS

At 48 h, there were no differences in IL-13 concentration in PHA-stimulated cultures between healthy subjects and asthmatic patients (93.6 +/- 18.9 versus 111.0 +/- 25.1 pg/ml). At 72 h, similar results were obtained (63.9 +/- 3.0 versus 73.3 +/- 2.5 pg/ml, respectively). At this time, however, IL-13 concentrations were significantly decreased versus 48 h both in asthmatics (p < 0.001) and in controls (p < 0.001). Treatment with 10(-7) M FP significantly reduced IL-13 production in healthy subjects and asthmatic patients both at 48 h (93.6 +/- 18.9 versus 50.50 +/- 10.6 pg/ml, p < 0.001, and 111.0 +/- 25.1 versus 59.3 +/- 13.6 pg/ml, p < 0.001, respectively) and at 72 h (63.9 +/- 9.6 versus 35.5 +/- 4.4 pg/ml, p < 0.001, and 73.3 +/- 8.0 versus 40.7 +/- 4.5 pg/ml, p < 0.001, respectively). Similar results were obtained with 10(-8) M FP at 48 and 72 h. Accordingly, evaluation of RT-PCR products from selected cell samples showed a FP dosage-dependent inhibition of IL-4 and IL-5 mRNA production both for healthy subjects and asthmatic patients.

CONCLUSIONS

FP in vitro impairs IL-13 production by PHA-stimulated MNC from asthmatic and control subjects. This strengthens previous suggestions that IL-13 inhibition by steroids may, at least in part, account for their therapeutic effects.

Molecular mechanisms of immunomodulatory activity of glucocorticoids

The development and function of cells in the immune system are regulated by many intrinsic and extrinsic factors. One class of molecule that affects immune cells belongs to the neuroendocrine system and the best-studied mediators in this category are glucocorticoids. These are small lypophilic molecules that participate in a wide number of normal and pathologic processes. This paper concentrates on their physiologic and pharmacologic effects on the immune response.

Glucocorticoids in T cell development and function*

Glucocorticoids are small lipophilic compounds that mediate their many biological effects by binding an intracellular receptor (GR) that, in turn, translocates to the nucleus and directly or indirectly regulates gene transcription. Perhaps the most recognized biologic effect of glucocorticoids on peripheral T cells is immunosuppression, which is due to inhibition of expression of a wide variety of activationinduced gene products. Glucocorticoids have also been implicated in Th lineage development (favoring the generation of Th2 cells) and, by virtue of their downregulation of fasL expression, the inhibition of activation-induced T cell apoptosis. Glucocorticoids are also potent inducers of apoptosis, and even glucocorticoid concentrations achieved during a stress response can cause the death of CD4(+)CD8(+ )thymocytes. Perhaps surprisingly, thymic epithelial cells produce glucocorticoids, and based upon in vitro and in vivo studies of T cell development it has been proposed that these locally produced glucocorticoids participate in antigen-specific thymocyte development by inhibiting activation-induced gene transcription and thus increasing the TCR signaling thresholds required to promote positive and negative selection. It is anticipated that studies in animals with tissue-specific GR-deficiency will further elucide how glucocorticoids affect T cell development and function.