Molecular mechanisms of leukocyte trafficking in T-cell-mediated skin inflammation: insights from intravital imaging

Hyaluronic acid-cyclodextrin encapsulating paeonol for treatment of atopic dermatitis

The cyclodextrin (CD) was grafted onto hyaluronic acid (HA) to form a topical delivery carrier (HACD) in which Paeonol was loaded in its CD cavity and self-assemble into the polymeric micelles (HACD-PAE) for the treatment of atopic dermatitis. Fluorescence microscope observed that HACD could fast penetrate into the skin and remain stable within 12 h. In vitro penetration test (IVPT) results showed the PAE retentions of HACD-PAE group in the stratum corneum and dermis were 3.35 and 1.78 times improvement than that of PAE group. ATR-FTIR and H&E staining assays indicated HACD could increase the gap of keratinocytes by interacting with corneum lipids and loosening the keratin. Furthermore, HACD-PAE showed the best therapeutic effect on atopic dermatitis mice. Thus HACD could be a promising skin-specific delivery carrier, not only promoting the drug penetrating but increasing its remaining in the skin and play the skin disease therapy and skin-care role.

Anti-Atopic Dermatitis Effect of Seaweed Fulvescens Extract via Inhibiting the STAT1 Pathway

Seaweed fulvescens (SF) is a green alga rich in chlorophyll with unique flavor and taste. It is also called Maesaengi which has antioxidant and other physiological activities. In the present study, we evaluated the therapeutic effects of SF in a mouse model of Dermatophagoides farinae body-induced atopic dermatitis (AD) and in tumor necrosis factor-α and interferon-γ-stimulated HaCaT keratinocytes. SF treatment (200 mg/mouse) inhibited the development of AD symptoms, compared to that in the control group, as evidenced from the improved dorsal skin lesion, reduced thickness and infiltration of inflammatory cells and smaller lymph nodes, and reduced levels of proinflammatory cytokines. In HaCaT keratinocytes, SF (10, 25, and 50 μg/mL) suppressed the production of proinflammatory cytokines in a dose-dependent manner. In addition, SF reduced the phosphorylation of signal transducer and activator of transcription 1, which is one of the major signaling molecules involved in cellular inflammation. These results suggested that SF could be a potential therapeutic alternative for the treatment of AD.

Intravital microscopy in historic and contemporary immunology

In this review, we discuss intravital microscopy of immune cells, starting from its historic origins to current applications in diverse organs. It is clear from a quantitative review of the literature that intravital microscopy is a key tool in both historic and contemporary immunological research, providing unique advances in our understanding of immune responses. We have chosen to focus this review on how intravital microscopy methodologies are used to image specific organs or systems and we present recent descriptions of fundamental immunological processes that could not have been achieved by other methods. The following target organs/systems are discussed in more detail: cremaster muscle, skin (ear and dorsal skin fold chamber), lymph node, liver, lung, mesenteric vessels, carotid artery, bone marrow, brain, spleen, foetus and lastly vessels of the knee joint.

HPV16 E7 expression in skin induces TSLP secretion, type 2 ILC infiltration and atopic dermatitis-like lesions

Atopic dermatitis is a common pruritic and inflammatory skin disorder with unknown etiology. Most commonly occurring during early childhood, atopic dermatitis is associated with eczematous lesions and lichenification, in which the epidermis becomes hypertrophied resulting in thickening of the skin. In this study, we report an atopic dermatitis-like pathophysiology results in a murine model following the expression of the high-risk Human Papillomavirus (HPV) 16 oncoprotein E7 in keratinocytes under the Keratin 14 promoter. We show that HPV 16 E7 expression in the skin is associated with skin thickening, acanthosis and light spongiosis. Locally, HPV 16 E7 expressing skin secreted high levels of TSLP and contained increased numbers of ILCs. High levels of circulating IgE were associated with increased susceptibility to skin allergy in a model of cutaneous challenge, and to airway bronchiolar inflammation, enhanced airway goblet cell metaplasia and mucus production in a model of atopic march. Surprisingly, skin pathology occurred independently of T-cells and mast cells. Thus, our findings suggest that the expression of a single HPV oncogene in the skin can drive the onset of atopic dermatitis-like pathology through the induction of TSLP and type 2 ILC infiltration.

Regulatory T cells dynamically regulate selectin ligand function during multiple challenge contact hypersensitivity

Regulatory T cells (Tregs) play critical roles in restricting T cell-mediated inflammation. In the skin, this is dependent on expression of selectin ligands required for leukocyte rolling in dermal microvessels. However, whether there are differences in the molecules used by Tregs and proinflammatory T cells to undergo rolling in the skin remains unclear. In this study, we used spinning disk confocal microscopy in Foxp3-GFP mice to visualize rolling of endogenous Tregs in dermal postcapillary venules. Tregs underwent consistent but low-frequency rolling interactions under resting and inflamed conditions. At the early stage of the response, Treg adhesion was minimal. However, at the peak of inflammation, Tregs made up 40% of the adherent CD4(+) T cell population. In a multiple challenge model of contact hypersensitivity, rolling of Tregs and conventional CD4(+) T cells was mostly dependent on overlapping contributions of P- and E-selectin. However, after a second challenge, rolling of Tregs but not conventional CD4(+) T cells became P-selectin independent, and Tregs showed reduced capacity to bind P-selectin. Moreover, inhibition of E-selectin at this time point resulted in exacerbation of inflammation. These findings demonstrate that in this multiple challenge model of inflammation, Treg selectin binding capacity and the molecular basis of Treg rolling can be regulated dynamically.

Immunosuppressive effects of fisetin against dinitrofluorobenzene-induced atopic dermatitis-like symptoms in NC/Nga mice

Atopic dermatitis (AD) is a multifactorial chronic skin disorder that is increasing in prevalence globally. In NC/Nga mice, repetitive epicutaneous applications of 2-4-dinitrofluorobenzene (DNFB) induces AD-like clinical symptoms. Bioflanonol fisetin (3,7,3',4'-tetrahydroxyflavone) is a dietary component found in plants, fruits and vegetables. Fisetin has various physiological effects that include anti-oxidation, anti-angiogenesis, anti-carcinogenesis and anti-inflammation. In this study, we investigated whether fisetin relieves AD-like clinical symptoms induced by repeated DNFB treatment in NC/Nga mice. Fisetin significantly inhibited infiltration of inflammatory cells including eosinophils, mast cells and CD4(+) T and CD8(+) T cells, and suppressed the expressions of cytokines and chemokines associated with dermal infiltrates in AD-like skin lesions. Total serum immunoglobulin E (IgE) levels and the ratio of phospho-NF-κB p65 to total NF-κB p65 were markedly reduced by fisetin. Fisetin also reduced the production of interferon-gamma and interleukin-4 by activated CD4(+) T cells in a dose-dependent manner, whereas the anti-inflammatory cytokine, interleukin-10 was increased. These results implicate fisetin as a potential therapeutic for AD.

Multi-scale optical imaging of the delayed type hypersensitivity reaction attenuated by rapamycin

Neutrophils and monocytes/macrophages (MMs) play important roles in the development of cell-mediated delayed type hypersensitivity (DTH). However, the dynamics of neutrophils and MMs during the DTH reaction and how the immunosuppressant rapamycin modulates their behavior in vivo are rarely reported. Here, we take advantage of multi-scale optical imaging techniques and a footpad DTH reaction model to non-invasively investigate the dynamic behavior and properties of immune cells from the whole field of the footpad to the cellular level. During the classic elicitation phase of the DTH reaction, both neutrophils and MMs obviously accumulated at inflammatory foci at 24 h post-challenge. Rapamycin treatment resulted in advanced neutrophil recruitment and vascular hyperpermeability at an early stage (4 h), the reduced accumulation of neutrophils (> 50% inhibition ratio) at 48 h, and the delayed involvement of MMs in inflammatory foci. The motility parameters of immune cells in the rapamycin-treated reaction at 4 h post-challenge displayed similar mean velocities, arrest durations, mean displacements, and confinements as the classic DTH reaction at 24 h. These results indicate that rapamycin treatment shortened the initial preparation stage of the DTH reaction and attenuated its intensity, which may be due to the involvement of T helper type 2 cells or regulatory T cells.

The integrin coactivator Kindlin-3 is not required for lymphocyte diapedesis

Kindlin-3 is an integrin-binding focal adhesion adaptor absent in patients with leukocyte and platelet adhesion deficiency syndrome and is critical for firm integrin-dependent leukocyte adhesion. The role of this adaptor in leukocyte diapedesis has never been investigated. In the present study, the functions of Kindlin-3 in this process were investigated in effector T lymphocytes trafficking to various lymphoid and nonlymphoid tissues. In vitro, Kindlin-3-deficient T cells displayed severely impaired lymphocyte function antigen-1-dependent lymphocyte adhesion but partially conserved very late antigen-4 adhesiveness. In vivo, the number of adoptively transferred Kindlin-3-deficient T effectors was dramatically elevated in the circulating pool compared with normal effectors, and the Kindlin-3 mutant effectors failed to enter inflamed skin lesions. The frequency of Kindlin-3-deficient T effectors arrested on vessel walls within inflamed skin-draining lymph nodes was also reduced. Strikingly, however, Kindlin-3-deficient effector T cells accumulated inside these vessels at significantly higher numbers than their wild-type lymphocyte counterparts and successfully extravasated into inflamed lymph nodes. Nevertheless, on entering these organs, the interstitial motility of these lymphocytes was impaired. This is the first in vivo demonstration that Kindlin-3-stabilized integrin adhesions, although essential for lymphocyte arrest on blood vessels and interstitial motility, are not obligatory for leukocyte diapedesis.

Deficiency of annexin A1 in CD4+ T cells exacerbates T cell-dependent inflammation

Annexin A1 (AnxA1) is recognized as an endogenous anti-inflammatory molecule. However, its effects on the adaptive immune response and, in particular, on T cells remain unclear. In this study, we investigated the actions of AnxA1 in three distinct models of T cell-mediated inflammation. In contact hypersensitivity, collagen-induced arthritis, and inflammation induced by OT-II TCR transgenic T cells responding to OVA, AnxA1 deficiency significantly increased Ag-induced T cell proliferation and the resultant level of inflammation. In the contact hypersensitivity model, this was associated with increased adhesion of CD4(+) T cells, CD8(+) T cells, and neutrophils in the dermal microvasculature, as well as increased T cell expression of RORγt and IL-17A. In collagen-induced arthritis, deficiency of endogenous AnxA1 increased susceptibility to arthritis and Ag-specific T cell activation. Deficiency of AnxA1 also increased OVA-induced cutaneous delayed-type hypersensitivity and IFN-γ and IL-17 release. Transfer experiments using CD4(+) T cells from AnxA1(-/-) mice demonstrated that the absence of AnxA1 solely in T cells resulted in increased inflammatory responses in wild-type recipients. Similarly, experiments using AnxA1(-/-) OT-II CD4(+) T cells demonstrated that the absence of AnxA1 in T cells was sufficient to induce increased Ag-specific CD4(+) T cell proliferation in vivo, augment T cell production of IFN-γ, IL-17, TNF, and IL-6, and increase Akt, ERK, and p38 activation. Together, these findings indicate that T cell-expressed AnxA1 functions to attenuate T cell-driven inflammatory responses via T cell-intrinsic effects on intracellular signaling, proliferation, and Th1/Th17 cytokine release.

Imaging of cell adhesion events in 3D matrix environments

Cell adhesion plays an essential role in development and homeostasis, but is also a key regulator of many diseases such as cancer and immune dysfunction. Numerous studies over the past three decades have revealed a wealth of information detailing signalling molecules required for cell adhesion to two-dimensional surfaces. However, in vivo many cells are completely surrounded by matrix and this will very likely influence the size, composition and dynamics of adhesive structures. The study of adhesion in cells within three-dimensional environments is still in its infancy, thus the role and regulation of adhesions in these complex environments remains unclear. The recent development of new experimental models coupled with significant advances in cell imaging approaches have provided platforms for researchers to begin to dissect adhesion signalling in cells in 3D matrices. Here we summarise the recent insights in cell adhesion formation and regulation in 3D model systems and the imaging approaches used to analyse these events.

Is exposure to formaldehyde in air causally associated with leukemia?--A hypothesis-based weight-of-evidence analysis

Recent scientific debate has focused on the potential for inhaled formaldehyde to cause lymphohematopoietic cancers, particularly leukemias, in humans. The concern stems from certain epidemiology studies reporting an association, although particulars of endpoints and dosimetry are inconsistent across studies and several other studies show no such effects. Animal studies generally report neither hematotoxicity nor leukemia associated with formaldehyde inhalation, and hematotoxicity studies in humans are inconsistent. Formaldehyde's reactivity has been thought to preclude systemic exposure following inhalation, and its apparent inability to reach and affect the target tissues attacked by known leukemogens has, heretofore, led to skepticism regarding its potential to cause human lymphohematopoietic cancers. Recently, however, potential modes of action for formaldehyde leukemogenesis have been hypothesized, and it has been suggested that formaldehyde be identified as a known human leukemogen. In this article, we apply our hypothesis-based weight-of-evidence (HBWoE) approach to evaluate the large body of evidence regarding formaldehyde and leukemogenesis, attending to how human, animal, and mode-of-action results inform one another. We trace the logic of inference within and across all studies, and articulate how one could account for the suite of available observations under the various proposed hypotheses. Upon comparison of alternative proposals regarding what causal processes may have led to the array of observations as we see them, we conclude that the case for a causal association is weak and strains biological plausibility. Instead, apparent association between formaldehyde inhalation and leukemia in some human studies is better interpreted as due to chance or confounding.

Off-target serine/threonine kinase 10 inhibition by erlotinib enhances lymphocytic activity leading to severe skin disorders

Skin disorders are among the most common adverse events related to treatment with epidermal growth factor receptor (EGFR) kinase inhibitors, and of these, erlotinib is known to cause more frequent and severe skin disease than other agents in this class. Although previous reports have shown that cutaneous manifestations are triggered by the inhibition of multiple EGFR-related homeostatic functions of the skin, this mechanism alone cannot explain the differences in frequency and severity of skin disorders caused by different kinase inhibitors. In this study, we focused on the relationship between the off-target kinase inhibition and aggravation of skin disorders. Based on calculations using reported K(d) values and plasma drug concentrations, serine/threonine kinase 10 (STK10) and Ste20-like kinase (SLK) were selected as candidates preferentially inhibited by erlotinib over gefitinib. In vitro experiments confirmed that STK10 and SLK kinase activity are inhibited by erlotinib at clinical concentrations, whereas only STK10 is slightly inhibited by gefitinib. It was also shown that erlotinib up-regulated lymphocytic responses such as interleukin (IL)-2 secretion and cell migration at clinical concentrations, whereas gefitinib did not affect lymphocyte activity. Moreover, small interfering RNA experiments revealed that STK10 plays a major role in up-regulation of the lymphocytic responses induced by erlotinib treatment. Finally, the role of erlotinib-induced lymphocyte activation was assessed in vivo using irritant hypersensitivity models. The results indicated that erlotinib aggravates cutaneous inflammatory reactions through the activation of lymphocytic responses such as IL-2 secretion and cell migration. These results demonstrated that off-target inhibition of STK10 by erlotinib enhances lymphocytic responses, which lead to the aggravation of skin inflammation.

Advances in imaging cell-matrix adhesions

Adhesion is fundamental to the survival and function of many different cell types, and regulates basic events such as mitosis, cell survival and migration, in both embryonic and adult organisms. Cell-matrix adhesion also regulates the dynamic interplay between cells and surrounding tissues during processes such as immune cell recruitment, wound healing and cancer cell metastasis. The study of cell adhesion has gained momentum in recent years, in large part because of the emergence of imaging techniques that have facilitated detailed analysis of the molecular composition and dynamics of the structures involved. In this Commentary, we discuss the recent application of different imaging techniques to study cell-matrix adhesions, emphasising common strategies used for the analysis of adhesion dynamics both in cells in culture and in whole organisms.

The histone deacetylase inhibitor, trichostatin A, inhibits the development of 2,4-dinitrofluorobenzene-induced dermatitis in NC/Nga mice

Repetitive skin contact with a chemical hapten like 2,4-dinitrofluorobenzene (DNFB) evokes an atopic dermatitis (AD)-like dermatitis reaction in NC/Nga mice maintained under specific pathogen-free (SPF) conditions. The histone deacetylase (HDAC) inhibitor, trichostatin A (TSA), modulates the expression of several genes by inhibiting the activity of HDACs. Furthermore, TSA has been reported to suppress inflammatory cytokine expression and to induce T cell-suppression by increasing regulatory T cell (T reg cell) numbers. In addition, histone deacetylase inhibitors (HDACi) are currently undergoing clinical trials for the treatment of inflammatory disorders. In the present study, we examined whether treatment with TSA suppresses AD-like skin lesions in NC/Nga mice treated with DNFB under SPF conditions. Intraperitoneal (i.p.) administration of TSA to DNFB-treated NC/Nga mice was found to inhibit ear thickness increases and the skin lesions induced by DNFB. Furthermore, IL-4 production by CD4+ T cells from the lymph nodes of DNFB-treated NC/Nga mice was significantly inhibited by TSA, although levels of IFN-γ were not. Flow cytometric analysis of lymphocytes showed an increase in CD4+ CD25+ T cell proportions in mice given TSA-i.p. These findings suggest that TSA suppresses the development of AD-like dermatitis in DNFB-treated NC/Nga mice by reducing IL-4 production and increasing the T reg cell population.

Expression of chemokine receptor CCR6 as a molecular determinant of adrenal metastatic relapse in patients with primary lung cancer

BACKGROUND

Recent studies suggest that chemokines are involved in organ-specific metastatic relapse. We evaluated the potential implications of chemokine receptors in the development of adrenal metastasis after complete resections of primary non-small-cell lung cancer.

PATIENTS AND METHODS

We studied a unique cohort of 21 primary lung cancers with matched adrenal metastases for the expression of CX3CR1, CXCR4, CCR6, and CCR7, using immunohistochemistry.

RESULTS

Although CXCR4, CX3CR1, and CCR7 were independently expressed in primary and corresponding metastases, CCR6 was clearly overexpressed in adrenal metastases, compared with corresponding primary tumors. Moreover, CCL20, the ligand of CCR6, was preferentially expressed in adrenal tissues that developed metastases.

CONCLUSION

We report for the first time (to the best of our knowledge) a potential role for the CCR6 receptor in the organ orientation of the development of metastases in lung cancer. We demonstrated a statistically significant overexpression of CCR6 in adrenal metastases compared with primary lung tumors, indicating that the increased production of CCL20 in adrenal glands might contribute to the selective recruitment of CCR6-expressing cancer cells in lung cancer. This study, in concordance with the data obtained in animal models, suggests that the chemokine receptor family constitutes a biologic support of the "seed and soil" theory.

Down-regulation of IL-6, IL-8, TNF-α and IL-1β by glucosamine in HaCaT cells, but not in the presence of TNF-α

There is considerable evidence that glucosamine exerts an inhibitory effect on inflammatory cytokine expression in cells. Glucosamine has been recommended as a promising anti-inflammatory modulator, which has been applied in clinical trials for attenuation of the inflammatory process. However, it is unknown whether glucosamine reduces the expression of TNF-α-induced inflammatory cytokines in HaCaT cells. The anti-inflammatory effects of curcumin in HaCaT cells have been extensively investigated in several studies. Thus, in this study we investigated the expression of IL-6, IL-8, TNF-α and IL-1β in glucosamine-treated HaCaT cells, and the effects of glucosamine were compared to those of curcumin-treated HaCaT cells. Our data showed that the expression of IL-6, IL-8, TNF-α and IL-1β was decreased by glucosamine treatment in the HaCaT cells. In contrast, the expression of IL-6, IL-8, TNF-α and IL-1β was not attenuated by glucosamine treatment in the TNF-α-treated HaCaT cells. Notably, curcumin induced an increased expression of IL-8 and IL-1β in the HaCaT cells, but not that of IL-6 and TNF-α. On the other hand, curcumin attenuated the expression of IL-6 and IL-8 in the TNF-α-treated HaCaT cells. Our data indicated that glucosamine induced the down-regulation of IL-6, IL-8, TNF-α and IL-1β expression in the HaCaT cells. However, the stimulation of TNF-α abolished the inhibitory effects of glucosamine on the expression of inflammatory cytokines in the HaCaT cells. Thus, even though glucosamine induces the down-regulation of inflammatory cytokines in HaCaT cells, the anti-inflammatory role of glucosamine in TNF-α-mediated inflammatory skin diseases should be investigated.

New insights into the dynamics of cell adhesions

Adhesion to the extracellular matrix (ECM) and to adjacent cells is a fundamental requirement for survival, differentiation, and migration of numerous cell types during both embryonic development and adult homeostasis. Different types of adhesion structures have been classified within different cell types or tissue environments. Much is now known regarding the complexity of protein composition of these critical points of cell contact with the extracellular environment. It has become clear that adhesions are highly ordered, dynamic structures under tight spatial control at the subcellular level to enable localized responses to extracellular cues. However, it is only in the last decade that the relative dynamics of these adhesion proteins have been closely studied. Here, we provide an overview of the recent data arising from such studies of cell-matrix and cell-cell contact and an overview of the imaging strategies that have been developed and implemented to study the intricacies and hierarchy of protein turnover within adhesions.