S. John Curnow

Decreased TNF-α synthesis by macrophages restricts cutaneous immunosurveillance by memory CD4+ T cells during aging

Immunity declines during aging, however the mechanisms involved in this decline are not known. In this study, we show that cutaneous delayed type hypersensitivity (DTH) responses to recall antigens are significantly decreased in older individuals. However, this is not related to CC chemokine receptor 4, cutaneous lymphocyte-associated antigen, or CD11a expression by CD4+ T cells or their physical capacity for migration. Instead, there is defective activation of dermal blood vessels in older subject that results from decreased TNF-α secretion by macrophages. This prevents memory T cell entry into the skin after antigen challenge. However, isolated cutaneous macrophages from these subjects can be induced to secrete TNF-α after stimulation with Toll-like receptor (TLR) 1/2 or TLR 4 ligands in vitro, indicating that the defect is reversible. The decreased conditioning of tissue microenvironments by macrophage-derived cytokines may therefore lead to defective immunosurveillance by memory T cells. This may be a predisposing factor for the development of malignancy and infection in the skin during aging.

Inhibition of T Cell Apoptosis in the Aqueous Humor of Patients with Uveitis by IL-6/Soluble IL-6 Receptor trans-Signaling

A fundamental mechanism of immune privilege in the eye is the induction of T lymphocyte apoptosis. Intraocular inflammation in uveitis implies compromise of immune privilege. This study sought to determine whether apoptosis of T cells is actively inhibited in patients with uveitis and by what pathways this may occur. Apoptotic lymphocytes were found to be absent from aqueous humor (AqH) of virtually all patients with recent-onset uveitis. However, T cells removed from the eye were highly susceptible to both spontaneous and Fas ligand-induced apoptosis in vitro. AqH from patients with uveitis had no modulatory effect on Fas ligand-induced apoptosis, but strongly suppressed survival factor deprivation-induced apoptosis. In contrast, noninflammatory AqH from patients undergoing cataract surgery had no modulatory effects on apoptosis at all. These data suggest that triggering of the Fas pathway is diminished in uveitis, and also that homeostatic resolution through survival factor deprivation-induced apoptosis is inhibited by factors present in AqH. The most widely recognized pathways, common γ-chain cytokines and type I IFNs, did not contribute to AqH-mediated T cell survival. High levels of both IL-6 and soluble IL-6R were found in AqH. IL-6 alone did not induce T cell survival, because IL-6R expression on T cells in AqH was too low to facilitate signaling. However, combinations of IL-6 and soluble IL-6R were highly effective inhibitors of T cell apoptosis, suggesting that the trans-signaling pathway is likely to be a key mediator of T cell apoptosis inhibition mediated by uveitis AqH.

The role of chemokines and their receptors in ocular disease.

The migration and infiltration of cells into the eye whether blood-borne leucocytes, endothelial or epithelial cells occurs in many ocular diseases. Dysregulation of this process is apparent in chronic inflammation, corneal graft rejection, allergic eye disease and other sight-threatening conditions. Under normal and inflammatory conditions, chemokines and their receptors are important contributors to cell migration. To date, 47 chemokines and 19 chemokine receptors have been identified and characterised. In recent years, investigations into the role of chemokines and their receptors in ocular disease have generated an increasing number of publications. In the eye, the best understood action of these molecules has arisen from the study of their ability to control the infiltration of leucocytes in uveitis. However, the involvement of chemokines in angiogenesis in several ocular conditions and in the survival of corneal transplants demonstrates the multifaceted nature of their effects. Interestingly, the constitutive expression of chemokines and their receptors in ocular tissues suggests that certain chemokines have a homeostatic function. In this review, we discuss the nature and function of chemokines in health and disease, and describe the role of chemokines in the pathogenesis of different ocular conditions.

A Systems Biology Approach Identifies Molecular Networks Defining Skeletal Muscle Abnormalities in Chronic Obstructive Pulmonary Disease

Chronic Obstructive Pulmonary Disease (COPD) is an inflammatory process of the lung inducing persistent airflow limitation. Extensive systemic effects, such as skeletal muscle dysfunction, often characterize these patients and severely limit life expectancy. Despite considerable research efforts, the molecular basis of muscle degeneration in COPD is still a matter of intense debate. In this study, we have applied a network biology approach to model the relationship between muscle molecular and physiological response to training and systemic inflammatory mediators. Our model shows that failure to co-ordinately activate expression of several tissue remodelling and bioenergetics pathways is a specific landmark of COPD diseased muscles. Our findings also suggest that this phenomenon may be linked to an abnormal expression of a number of histone modifiers, which we discovered correlate with oxygen utilization. These observations raised the interesting possibility that cell hypoxia may be a key factor driving skeletal muscle degeneration in COPD patients.

Distinct Types of Fibrocyte Can Differentiate from Mononuclear Cells in the Presence and Absence of Serum

Background Fibrocytes are bone-marrow derived cells, expressing both haematopoietic and stromal cell markers, which contribute to tissue repair as well as pathological fibrosis. The differentiation of fibrocytes remains poorly characterised and this has limited understanding of their biology and function. In particular two methods are used to generate fibrocytes in vitro that differ fundamentally by the presence or absence of serum. Methodology/Principal Findings We show here that fibrocytes grown in the absence of serum (SF) differentiate more efficiently from peripheral blood mononuclear cells than CD14+ monocytes, and respond to serum by losing their spindle-shaped fibrocyte morphology. Although fibrocytes generated in the presence of serum (SC) express the same range of markers, they differentiate more efficiently from CD14+ monocytes and do not change their morphology in response to serum. Transcriptional analysis revealed that both types of fibrocyte are distinct from each other, fibroblasts and additional monocyte-derived progeny. The gene pathways that differ significantly between SF and SC fibrocytes include those involved in cell migration, immune responses and response to wounding. Conclusions/Significance These data show that SF and SC fibrocytes are distinct but related cell types, and suggest that they will play different roles during tissue repair and fibrosis where changes in serum proteins may occur.

Exploring the pathogenesis of IIH: An inflammatory perspective

Idiopathic intracranial hypertension (IIH) is a common blinding condition amongst the young obese female population (20 per 100,000) characterised by elevated intracranial pressure (ICP). The aetiology of IIH is not known. In this review we explore the literature investigating the pathogenesis of IIH and suggest additional hypotheses. Chronic inflammation is emerging as an aetiological factor in the pathogenesis of obesity and we propose that this may be a feature of IIH. Obesity is also related to dysregulation of cortisol production by the pre-receptor enzyme, 11beta-hydroxysteroid dehydrogenase, and we speculate that this may have a role in the pathogenesis of obesity and raised ICP seen in IIH.

Inflammatory mediators of uveitis: cytokines and chemokines.

Purpose of review The study of uveitis has been restricted by the difficulty in obtaining sufficient intraocular material from both human disease and experimental models. Recent developments in cytokine and chemokine detection have overcome many of these problems. This review presents a summary of the technologic advances in this area. Recent findings Recent advances in cytokine analysis, in particular multiplexed bead immunoassays, have allowed the measurement of an extensive array of cytokines and chemokines from very small sample volumes. This has revolutionized uveitis research, enabling measurement of a large profile of cytokines and chemokines in intraocular fluid, such as aqueous humour. This allows us to recognize complex patterns of cytokines and chemokines from different forms of uveitis and to examine relationships between different molecules. Summary The spectrum of proinflammatory cytokines and chemokines known to be implicated in uveitis has increased over recent years. Many of these molecules have also been found in experimental models of disease and may represent attractive therapeutic targets for the future. With recent advances in cytokine detection, an extension of these techniques with a more detailed analysis of different uveitis conditions may provide useful diagnostic and prognostic information for this potentially blinding group of diseases.

Cytokine and chemokine levels in tears and in corneal fibroblast cultures before and after excimer laser treatment

PURPOSE: To measure multiple cytokine and chemokine production in tears of myopic patients before and after laser in situ keratomileusis (LASIK) and in human corneal fibroblast (HCF) cultures before and after excimer laser treatment. SETTING: Department of Neuroscience, Ophthalmology Unit, University of Padua, Italy and Vissum‐Instituto de Oftalmológico de Alicante, Alicante, Spain METHODS: Tear samples were obtained from 15 myopic patients before LASIK and 1 and 24 hours after LASIK. Quiescent HCF cultures were treated using the same laser energy. Culture medium was collected before treatment and after 1 and 24 hours. Cytokine concentrations were determined using multiplexed bead analysis. RESULTS: Compared with baseline values, interleukin (IL)‐12 tear levels were significantly increased 1 hour after surgery and eotaxin levels were significantly increased at 24 hours (both P<.05). Culture medium of HCF contained high levels of IL‐6, IL‐8, and monocyte chemotactic protein (MCP)‐1 and low levels of IL‐1, eotaxin, and regulated on activation, normal T expressed, and secreted (RANTES) cytokine. One hour after treatment, levels of all cytokines were significantly reduced. At 24 hours, IL‐1, IL‐6, IL‐8, and MCP‐1 levels were significantly increased compared with values at baseline and at 1 hour while RANTES cytokine and eotaxin levels had returned to baseline levels. CONCLUSIONS: In vivo and in vitro studies showed that after excimer laser treatment, cytokines are released to modulate the wound‐healing process; however, they can potentially induce inflammation. However, these types of in vitro studies, although useful for evaluating changes in cytokine profiles before and after treatment, only partially reproduce in vivo corneal behavior.

Topical Glucocorticoid Therapy Directly Induces Up-Regulation of Functional CXCR4 on Primed T Lymphocytes in the Aqueous Humor of Patients with Uveitis

Overexpression of the constitutive chemokine receptor CXCR4 has been shown to contribute to the accumulation of leukocytes at sites of chronic inflammation. Glucocorticoids are widely used to treat inflammatory disorders such as uveitis to considerable effect, yet paradoxically have been reported to increase CXCR4 expression in vitro. We show here that ocular lymphocytes isolated from patients with uveitis who had been treated with topical glucocorticoids expressed highly elevated levels of CXCR4. The up-regulation of CXCR4 could be reproduced in vitro by culture of CD4+ T cells with aqueous humor (AqH), indicating a role for the ocular microenvironment rather than preferential recruitment of CXCR4+ cells. Untreated uveitis and noninflammatory AqH up-regulated CXCR4 to a limited extent; this was dependent on TGF-β2. However, the highest levels of CXCR4 both in vivo and in vitro were found in the glucocorticoid-treated patients. Glucocorticoids appeared to be directly responsible for the induction of CXCR4 in treated patients, as the glucocorticoid receptor antagonist RU38486 inhibited the in vitro up-regulation by AqH from these patients. Dexamethasone selectively up-regulated CXCR4 in vitro, but not any of a wide range of other chemokine receptors. CXCL12, the ligand for CXCR4, was present in AqH under noninflammatory conditions, but the levels were low in untreated uveitis and undetectable in treated uveitis AqH. The importance of these results for the treatment of HIV patients with glucocorticoids is discussed as well as a role for glucocorticoid-induced CXCR4 up-regulation and CXCL12 down-regulation in controlling the migration of lymphocyte populations, resulting in resolution of inflammation.

Endogenous Cortisol and TGF-β in Human Aqueous Humor Contribute to Ocular Immune Privilege by Regulating Dendritic Cell Function

Aqueous humor (AqH) has been shown to have significant immunosuppressive effects on APCs in animal models. We wanted to establish whether, in humans, AqH can regulate dendritic cell (DC) function and to identify the dominant mechanism involved. Human AqH inhibited the capacity of human peripheral blood monocyte-derived DC to induce naive CD4+ T cell proliferation and cytokine production in vitro, associated with a reduction in DC expression of the costimulatory molecule CD86. This was seen both for DC cultured under noninflammatory conditions (immature DC) and for DC stimulated by proinflammatory cytokines (mature DC). DC expression of MHC classes I/II and CD83 was reduced (mature DC only). Myeloid DC from peripheral blood were similarly sensitive to the effects of human AqH, but only under inflammatory conditions. The addition of α-melanocyte stimulating hormone and vasoactive intestinal peptide did not cause significant inhibition at physiological levels. However, the addition of exogenous cortisol at physiological levels recapitulated the AqH-induced reduction in CD86 and inhibition of DC-induced T cell proliferation, and blockade of cortisol in AqH partially reversed its suppressive effects. TGF-β2 had an additional effect with cortisol, and although simultaneous blockade of cortisol and TGF-β2 in AqH reduced its effectiveness, there was still a cortisol- and TGF-β–independent component. In humans, AqH regulates DC maturation and function by the combined actions of cortisol and TGF-β2, a pathway that is likely to contribute to the maintenance of immune privilege in the eye.