Immunomodulatory effect of interleukin-16 on allergic airway inflammation

Interleukin-16 aggravates ovalbumin-induced allergic inflammation by enhancing Th2 and Th17 cytokine production in a mouse model

Asthma is a chronic inflammatory disease that involves a variety of cytokines and cells. Interleukin-16 (IL-16) is highly expressed during allergic airway inflammation and is involved in its development. However, its specific mechanism of action remains unclear. In the present study, we used an animal model of ovalbumin (OVA)-induced allergic asthma with mice harboring an IL-16 gene deletion to investigate the role of this cytokine in asthma, in addition to its underlying mechanism. Increased IL-16 expression was observed during OVA-induced asthma in C57BL/6J mice. However, when OVA was used to induce asthma in IL-16^-/- mice, a diminished inflammatory reaction, decreased bronchoalveolar lavage fluid (BALF) eosinophil numbers, and the suppression of OVA-specific IgE levels in the serum and BALF were observed. The results also demonstrated decreased levels of T helper type 2 (Th2) and Th17 cytokines upon OVA-induced asthma in IL-16^-/- mice. Hence, we confirmed that IL-16 enhances the lung allergic inflammatory response and suggest a mechanism possibly associated with the up-regulation of IgE and the promotion of Th2 and Th17 cytokine production. This work explored the mechanism underlying the regulation of IL-16 in asthma and provides a new target for the clinical treatment of asthma.

Cytokine Diversity in Human Peripheral Blood Eosinophils: Profound Variability of IL-16

Eosinophilic leukocytes develop in the bone marrow and migrate from peripheral blood to tissues, where they maintain homeostasis and promote dysfunction via release of preformed immunomodulatory mediators. In this study, we explore human eosinophil heterogeneity with a specific focus on naturally occurring variations in cytokine content. We found that human eosinophil-associated cytokines varied on a continuum from minimally (coefficient of variation [CV] ≤ 50%) to moderately variable (50% < CV ≤ 90%). Within the moderately variable group, we detected immunoreactive IL-27 (953 ± 504 pg/mg lysate), a mediator not previously associated with human eosinophils. However, our major finding was the distinct and profound variability of eosinophil-associated IL-16 (CV = 103%). Interestingly, eosinophil IL-16 content correlated directly with body mass index (R ² = 0.60, ***p < 0.0001) in one donor subset. We found no direct correlation between eosinophil IL-16 content and donor age, sex, total leukocytes, lymphocytes, or eosinophils (cells per microliter), nor was there any relationship between IL-16 content and the characterized -295T/C IL-16 promoter polymorphism. Likewise, although eosinophil IL-1β, IL-1α, and IL-6 levels correlated with one another, there was no direct association between any of these cytokines and eosinophil IL-16 content. Finally, a moderate increase in total dietary fat resulted in a 2.7-fold reduction in eosinophil IL-16 content among C57BL/6-IL5tg mice. Overall, these results suggest that relationships between energy metabolism, eosinophils, and IL-16 content are not direct or straightforward. Nonetheless, given our current understanding of the connections between asthma and obesity, these findings suggest important eosinophil-focused directions for further exploration.

Pathogenesis of eosinophilic chronic rhinosinusitis

Eosinophilic chronic rhinosinusitis (ECRS) is considered a refractory and intractable disease. Patients with ECRS present with thick mucus production, long-term nasal congestion, loss of sense of smell, and intermittent acute exacerbations secondary to bacterial infections. Despite medical and surgical interventions, there is a high rate of recurrence with significant impairment to quality of life. The recent increasing prevalence of ECRS in south Asian countries and the strong tendency of ECRS to reoccur after surgery should be considered. The majority of cases need repeat surgery, and histological examinations of these cases show eosinophilic-dominant inflammation. The degradation and accumulation of eosinophils, release of cytokines, and mucus secretion have important roles in the pathogenesis of ECRS. ECRS differs from non-ECRS, in which eosinophils are not involved in the pathogenesis of the disease, and also in terms of many clinical characteristics, blood examination and nasal polyp histological findings, clinical features of the disease after surgery, efficacy of medications, and computed tomography findings. This review describes the clinical course, diagnosis, and treatment of ECRS as well as its pathophysiology and the role of eosinophils, mucus, cytokines, and other mediators in the pathogenesis of ECRS.

Human Carotid Plaques With High Levels of Interleukin-16 Are Associated With Reduced Risk for Cardiovascular Events

BACKGROUND AND PURPOSE

Interleukin-16 (IL-16) functions as a regulator of T-cell growth and acts as an inducer of cell migration. The aim of this study was to determine whether IL-16 measured in human carotid plaques was associated with symptoms (eg, stroke, transient ischemic attack, or amaurosis fugax), markers of plaque stability, and postoperative cardiovascular events.

METHODS

Plaques obtained from patients who had ≥1 cerebrovascular ischemic events within 1 month before endarterectomy (n=111) were compared with plaques from patients without symptoms (n=95). Neutral lipids, smooth muscle cell, and macrophage contents were evaluated histologically, and collagen, elastin, and caspase-3 activity were measured biochemically. IL-16, matrix metalloproteinases, and tissue inhibitors of metalloproteinases were measured in plaque homogenates using a multiplex immunoassay. IL-16, CD3, CD4, and FoxP3 mRNA expressions in carotid plaques were analyzed with quantitative real-time polymerase chain reaction.

RESULTS

Carotid plaques from asymptomatic patients had higher levels of IL-16 mRNA. High plaque IL-16 protein levels (above median) were associated with reduced incidence of postoperative cardiovascular events during a mean follow-up of 21 months (hazard ratio, 0.47; 95% confidence interval, 0.22-0.99; P=0.047). IL-16 levels correlated with the plaque-stabilizing components: elastin, collagen, matrix metalloproteinase-2, tissue inhibitors of metalloproteinase-1, tissue inhibitors of metalloproteinase-2 and FoxP3 mRNA.

CONCLUSIONS

This study shows that high levels of IL-16 are associated with asymptomatic carotid plaques, expression of factors contributing to plaque stability, and decreased risk of new cardiovascular events during a 2-year period after surgery, suggesting that IL-16 might have a protective role in human atherosclerotic disease.

Prenatal retinoid deficiency leads to airway hyperresponsiveness in adult mice

There is increasing evidence that vitamin A deficiency in utero correlates with abnormal airway smooth muscle (SM) function in postnatal life. The bioactive vitamin A metabolite retinoic acid (RA) is essential for formation of the lung primordium; however, little is known about the impact of early fetal RA deficiency on postnatal lung structure and function. Here, we provide evidence that during murine lung development, endogenous RA has a key role in restricting the airway SM differentiation program during airway formation. Using murine models of pharmacological, genetic, and dietary vitamin A/RA deficiency, we found that disruption of RA signaling during embryonic development consistently resulted in an altered airway SM phenotype with markedly increased expression of SM markers. The aberrant phenotype persisted postnatally regardless of the adult vitamin A status and manifested as structural changes in the bronchial SM and hyperresponsiveness of the airway without evidence of inflammation. Our data reveal a role for endogenous RA signaling in restricting SM differentiation and preventing precocious and excessive SM differentiation when airways are forming.

CD4+CD25+Foxp3+ regulatory T cells are dispensable for controlling CD8+ T cell-mediated lung inflammation

Every person harbors a population of potentially self-reactive lymphocytes controlled by tightly balanced tolerance mechanisms. Failures in this balance evoke immune activation and autoimmunity. In this study, we investigated the contribution of self-reactive CD8(+) T lymphocytes to chronic pulmonary inflammation and a possible role for naturally occurring CD4(+)CD25(+)Foxp3(+) regulatory T cells (nTregs) in counterbalancing this process. Using a transgenic murine model for autoimmune-mediated lung disease, we demonstrated that despite pulmonary inflammation, lung-specific CD8(+) T cells can reside quiescently in close proximity to self-antigen. Whereas self-reactive CD8(+) T cells in the inflamed lung and lung-draining lymph nodes downregulated the expression of effector molecules, those located in the spleen appeared to be partly Ag-experienced and displayed a memory-like phenotype. Because ex vivo-reisolated self-reactive CD8(+) T cells were very well capable of responding to the Ag in vitro, we investigated a possible contribution of nTregs to the immune control over autoaggressive CD8(+) T cells in the lung. Notably, CD8(+) T cell tolerance established in the lung depends only partially on the function of nTregs, because self-reactive CD8(+) T cells underwent only biased activation and did not acquire effector function after nTreg depletion. However, although transient ablation of nTregs did not expand the population of self-reactive CD8(+) T cells or exacerbate the disease, it provoked rapid accumulation of activated CD103(+)CD62L(lo) Tregs in bronchial lymph nodes, a finding suggesting an adaptive phenotypic switch in the nTreg population that acts in concert with other yet-undefined mechanisms to prevent the detrimental activation of self-reactive CD8(+) T cells.

Histamine 4 receptor activation induces recruitment of FoxP3+ T cells and inhibits allergic asthma in a murine model

Histamine has an important role in regulation of immune response which is mediated by differential expression of four distinct receptors, H1R-H4R. H1R and HR2 have previously been shown to be involved with modulation of lung inflammation. H4R is also expressed on inflammatory cells; therefore, we investigated the potential role of H4R in development of allergic asthma in a murine model. We determined that the H4R agonist 4-methylhistamine when delivered intratracheally before Ag challenge mitigated airway hyperreactivity and inflammation. This was associated with an increase in IL-10 and IFN-gamma, but not TGF-beta or IL-16, as well as a decrease in IL-13 in the bronchoalveolar lavage fluid. We also observed that H4R agonist instillation resulted in accumulation of FoxP3(+) T cells suggesting a direct effect on T regulatory cell recruitment. To investigate this further, we determined the in vitro effect of H4R stimulation on human T cell migration. The H4R agonist induced a 2- to 3-fold increase in T cell migration, similar to that seen for H1R agonists. Cells transmigrating to the H4R agonist, but not H1R, were skewed toward a CD4 cell expressing CD25 and intracellular FoxP3. H4R-responsive cells suppressed proliferation of autologous T cells, an effect that was dependent on IL-10 production. We conclude that H4R stimulation enriches for a regulatory T cell with potent suppressive activity for proliferation. These findings identify a novel function for H4R and suggest a potential therapeutic approach to attenuation of asthmatic inflammation.

Chemokine Receptor CXCR3 Desensitization by IL-16/CD4 Signaling Is Dependent on CCR5 and Intact Membrane Cholesterol

Previous work has shown that IL-16/CD4 induces desensitization of both CCR5- and CXCR4-induced migration, with no apparent effect on CCR2b or CCR3. To investigate the functional relationship between CD4 and other chemokine receptors, we determined the effects of IL-16 interaction with CD4 on CXCR3-induced migration. In this study we demonstrate that IL-16/CD4 induced receptor desensitization of CXCR3 on primary human T cells. IL-16/CD4 stimulation does not result in surface modulation of CXCR3 or changes in CXCL10 binding affinity. This effect does require p56(lck) enzymatic activity and the presence of CCR5, because desensitization is not transmitted in the absence of CCR5. Treatment of human T cells with methyl-beta-cyclodextrin, a cholesterol chelator, prevented the desensitization of CXCR3 via IL-16/CD4, which was restored after reloading of cholesterol, indicating a requirement for intact cholesterol. These studies demonstrate an intimate functional relationship among CD4, CCR5, and CXCR3, in which CCR5 can act as an adaptor molecule for CD4 signaling. This process of regulating Th1 cell chemoattraction may represent a mechanism for orchestrating cell recruitment in Th1-mediated diseases.

Expression of interleukin-16 in allergic rhinitis

BACKGROUND

Interleukin-16 (IL-16) has been characterized as a chemoattractant for a variety of CD4+ T cells. Several inflammatory diseases, including allergic disorders, have been reported to correlate with IL-16. We first examined the IL-16 expression of serum and mucosal tissue in patients with allergic rhinitis.

METHODS

Forty-eight patients with a clinical history of house dust mite (HDM) or pollen-sensitive allergic rhinitis were included in this study. Serum IL-16 was analyzed by enzyme-linked immunosorbent assay (ELISA). IL-16 expression of nasal mucosa was detected by immunohistochemistry.

RESULTS

IL-16 levels were elevated in the serum of patients with allergic rhinitis compared with normal controls. In particular, serum IL-16 levels in HDM-sensitive patients were higher than those in pollen-sensitive patients. IL-16 was significantly correlated with eosinophils in the peripheral blood of allergic rhinitis patients. Histologically, IL-16 was expressed in infiltrated lymphocytes and nasal gland cells.

CONCLUSIONS

Our data indicate that one of the sources of elevated serum IL-16 in allergic patients may be gland cells and lymphocytes in allergic nasal mucosa. This IL-16 cytokine may be strongly associated with the developmental mechanism of allergic rhinitis.

The integration of conventional and unconventional T cells that characterizes cell-mediated responses

This review builds on evidence that cell-mediated immune responses to bacteria, viruses, parasites, and tumors are an integration of conventional and unconventional T-cell activities. Whereas conventional T cells provide clonal antigen-specific responses, unconventional T cells profoundly regulate conventional T cells, often suppressing their activities such that immunopathology is limited. By extrapolation, immunopathologies and inflammatory diseases may reflect defects in regulation by unconventional T cells. To explore the function of unconventional T cells, several extensive gene expression analyses have been undertaken. These studies are reviewed in some detail, with emphasis on the mechanisms by which unconventional T cells may exert their regulatory functions. Highlighting the fundamental nature of T-cell integration, we also review emerging data that the development of conventional and unconventional T cells is also highly integrated.

Effects of different protocol doses of low power gallium–aluminum–arsenate (Ga–Al–As) laser radiation (650 nm) on carrageenan induced rat paw ooedema

The purpose of the present study was to investigate the effect of the low power laser therapy on the acute inflammatory process. Male Wistar rats were used. The rat paw oedema was induced by sub-plantar injection of carrageenan, the paw volume was measured before and 1, 2, 3 and 4 h after the injection using a hydroplethysmometer. To investigate the mechanism action of the Ga-Al-As laser on inflammatory oedema, parallel studies were performed using adrenallectomized rats or rats treated with sodium diclofenac. Different laser irradiation protocols were employed for specific energy densities (EDs), exposure times and repetition rates. The rats were irradiated with the Ga-Al-As laser during 80 s each hour. The ED that produced an anti-inflammatory effect were 1 and 2.5 J/cm(2), reducing the oedema by 27% (P<0.05) and 45.4% (P<0.01), respectively. The ED of 2.5 J/cm(2) produced anti-inflammatory effects similar to those produced by the cyclooxigenase inhibitor sodium diclofenac at a dose of 1 mg/kg. In adrenalectomized animals, the laser irradiation failed to inhibit the oedema. Our results suggest that low power laser irradiation possibly exerts its anti-inflammatory effects by stimulating the release of adrenal corticosteroid hormones.