Targeted reduction of CCR4⁺ cells is sufficient to suppress allergic airway inflammation

Role of chemokine-like factor 1 as an inflammatory marker in diseases

Immunoinflammatory mechanisms have been incrementally found to be involved in the pathogenesis of multiple diseases, with chemokines being the main drivers of immune cell infiltration in the inflammatory response. Chemokine-like factor 1 (CKLF1), a novel chemokine, is highly expressed in the human peripheral blood leukocytes and exerts broad-spectrum chemotactic and pro-proliferative effects by activating multiple downstream signaling pathways upon binding to its functional receptors. Furthermore, the relationship between CKLF1 overexpression and various systemic diseases has been demonstrated in both in vivo and in vitro experiments. In this context, it is promising that clarifying the downstream mechanism of CKLF1 and identifying its upstream regulatory sites can yield new strategies for targeted therapeutics of immunoinflammatory diseases.

What does elevated TARC/CCL17 expression tell us about eosinophilic disorders?

Eosinophilic disorders encompass a large spectrum of heterogeneous diseases sharing the presence of elevated numbers of eosinophils in blood and/or tissues. Among these disorders, the role of eosinophils can vary widely, ranging from a modest participation in the disease process to the predominant perpetrator of tissue damage. In many cases, eosinophilic expansion is polyclonal, driven by enhanced production of interleukin-5, mainly by type 2 helper cells (Th2 cells) with a possible contribution of type 2 innate lymphoid cells (ILC2s). Among the key steps implicated in the establishment of type 2 immune responses, leukocyte recruitment toward inflamed tissues is particularly relevant. Herein, the contribution of the chemo-attractant molecule thymus and activation-regulated chemokine (TARC/CCL17) to type 2 immunity will be reviewed. The clinical relevance of this chemokine and its target, C-C chemokine receptor 4 (CCR4), will be illustrated in the setting of various eosinophilic disorders. Special emphasis will be put on the potential diagnostic, prognostic, and therapeutic implications related to activation of the TARC/CCL17-CCR4 axis.

Repeated exposure of house dust mite induces progressive airway inflammation in mice: Differential roles of CCL17 and IL-13

We conducted a systematic evaluation of lung inflammation indued by repeated intranasal exposure (for 10 consecutive days) to a human aeroallergen, house dust mite (HDM) in BALB/c mice. Peak influx of neutrophils, monocytes/lymphocytes, and eosinophils was observed in bronchoalveolar lavage (BAL) on days 1, 7 and 11, respectively, and normalized to baseline by day 21. Peak elevations of Th2, myeloid-derived cytokines/chemokines and serum IgE were seen both in BAL and lung tissue homogenates between days 7 and 11, and declined thereafter; however, IL-33 levels remained elevated from day 7 to day 21. Airway hyperreactivity to inhaled methacholine was significantly increased by day 11 and decreased to baseline by day 21. The lung tissue showed perivascular and peribronchial cuffing, epithelial hypertrophy and hyperplasia and goblet cell formation in airways by day 11, and resolution by day 21. Levels of soluble collagen and tissue inhibitors of metalloproteinases (TIMP) also increased reflecting tissue remodeling in the lung. Microarray analysis demonstrated a significant time-dependent up-regulation of several genes including IL-33, CLCA3, CCL17, CD4, CD10, CD27, IL-13, Foxa3, IL-4, IL-10, and CD19, in BAL cells as well as the lung. Pre-treatment of HDM challenged mice with CCL17 and IL-13 antibodies reduced BAL cellularity, airway hyper-responsiveness (AHR), and histopathological changes. Notably, anti-IL-13, but not anti-CCL17 monoclonal antibodies (mAbs) reduced BAL neutrophilia while both mAbs attenuated eosinophilia. These results suggest that CCL17 has an overlapping, yet distinct profile versus IL-13 in the HDM model of pulmonary inflammation and potential for CCL17-based therapeutics in treating Th2 inflammation.

Sirtuin 2 enhances allergic asthmatic inflammation

Allergic eosinophilic asthma is a chronic condition causing airway remodeling resulting in lung dysfunction. We observed that expression of sirtuin 2 (Sirt2), a histone deacetylase, regulates the recruitment of eosinophils after sensitization and challenge with a triple antigen: dust mite, ragweed, and Aspergillus fumigatus (DRA). Our data demonstrate that IL-4 regulates the expression of Sirt2 isoform 3/5. Pharmacological inhibition of Sirt2 by AGK2 resulted in diminished cellular recruitment, decreased CCL17/TARC, and reduced goblet cell hyperplasia. YM1 and Fizz1 expression was reduced in AGK2-treated, IL-4-stimulated lung macrophages in vitro as well as in lung macrophages from AGK2-DRA-challenged mice. Conversely, overexpression of Sirt2 resulted in increased cellular recruitment, CCL17 production, and goblet cell hyperplasia following DRA challenge. Sirt2 isoform 3/5 was upregulated in primary human alveolar macrophages following IL-4 and AGK2 treatment, which resulted in reduced CCL17 and markers of alternative activation. These gain-of-function and loss-of-function studies indicate that Sirt2 could be developed as a treatment for eosinophilic asthma.

Frequent silencing of RASSF1A by DNA methylation in thymic neuroendocrine tumours

OBJECTIVES

Aberrant methylation of promoter CpG islands (CGIs) of tumour suppressor genes is a common epigenetic mechanism underlying cancer pathogenesis. The methylation patterns of thymic tumours have not been studied in detail since such tumours are rare. Herein, we sought to identify genes that could serve as epigenetic targets for thymic neuroendocrine tumour (NET) therapy.

MATERIALS AND METHODS

Genome-wide screening for aberrantly methylated CGIs was performed in three NET samples, seven thymic carcinoma (TC) samples, and eight type-B3 thymoma samples. The methylation status of thymic epithelial tumours (TETs) samples was validated by pyrosequencing in a larger cohort. The expression status was analysed by quantitative polymerase chain reaction (PCR) and immunohistochemistry.

RESULTS

We identified a CGI on a novel gene, RASSF1A, which was strongly hypermethylated in NET, but not in thymic carcinoma or B3 thymoma. RASSF1A was identified as a candidate gene statistically and bibliographically, as it showed frequent CGI hypermethylation in NET by genome-wide screening. Pyrosequencing confirmed significant hypermethylation of a RASSF1A CGI in NET. Low-grade NET tissue was more strongly methylated than high-grade NET. Quantitative PCR and immunohistochemical staining revealed that RASSF1A mRNA and protein expression levels were negatively regulated by DNA methylation.

CONCLUSIONS

RASSF1A is a tumour suppressor gene epigenetically dysregulated in NET. Aberrant methylation of RASSF1A has been reported in various tumours, but this is the first report of RASSF1A hypermethylation in TETs. RASSF1A may represent an epigenetic therapeutic target in thymic NET.

Interleukin 16 and CCL17/thymus and activation-regulated chemokine in patients with aspirin-exacerbated respiratory disease

BACKGROUND

Interleukin (IL) 16 and thymus and activation-regulated cytokine (TARC) are chemoattractant cytokines for eosinophils and T_H2 cells. Differential levels of these components in aspirin-exacerbated respiratory disease (AERD) and allergic rhinitis with asthma (ARwA) may be related to a different inflammatory response in both asthma phenotypes.

OBJECTIVE

To assess the nasal lavage immunoreactivity of IL-16 and TARC cytokines.

METHODS

We used multienzyme-linked immunosorbent assays to detect IL-5, IL-13, IL-16, IL-33, I-309/CCL1, TARC/CCL17, monocyte-derived chemokine/CCL22, periostin, and eosinophil cationic protein levels in nasal lavages from patients with AERD and patients with ARwA.

RESULTS

The IL-13, IL-16, TARC, and periostin levels were significantly higher in patients with AERD compared with those of patients with ARwA. Correlation analysis of mediator levels in AERD revealed a possible role of IL-16 and TARC in eosinophil recruitment and activation.

CONCLUSION

IL-16, TARC, and periostin distinguish between patients with AERD and those with ARwA. These mediators, taken together rather than individually, may comprise good specific nasal markers in patients with AERD. The effects of IL-16 and TARC on T_H1, T_H2, and T-regulatory cell functions in AERD cannot be disregarded.

Targeting TSLP With shRNA Alleviates Airway Inflammation and Decreases Epithelial CCL17 in a Murine Model of Asthma

Airway epithelium defends the invasion from microorganisms and regulates immune responses in allergic asthma. Thymic stromal lymphopoietin (TSLP) from inflamed epithelium promotes maturation of dendritic cells (DCs) to prime Th2 responses via CCL17, which induces chemotaxis of CD4⁺ T cells to mediate inflammation. However, few studies have investigated the regulation of epithelial CCL17. In this study, we used shRNA against TSLP to clarify the role of TSLP in the airway inflammation and whether TSLP affects the airway inflammation via epithelial CCL17. Specific shTSLP was delivered by lentivirus and selected by the knockdown efficiency. Allergic mice were intratracheally pretreated with the lentivirus and followed by intranasal ovalbumin (OVA) challenges. The sera antibody levels, airway inflammation, airway hyper-responsiveness (AHR), cytokine levels in bronchoalveolar lavage fluids, and CCL17 expressions in lungs were determined. In vivo, TSLP attenuation reduced the AHR, decreased the airway inflammation, inhibited the maturations of DCs, and suppressed the migration of T cells. Furthermore, the expression of CCL17 was particularly decreased in bronchial epithelium. In vitro, CCL17 induction was regulated by TSLP. In conclusion, TSLP might coordinate airway inflammation partially via CCL17-mediated responses and this study provides the vital utility of TSLP to develop the therapeutic approach in allergic airway inflammation.

Diphtheria-toxin based anti-human CCR4 immunotoxin for targeting human CCR4(+) cells in vivo

CC chemokine receptor 4 (CCR4) has attracted much attention as a promising therapeutic drug target for CCR4(+) tumor cells and Tregs. CCR4 is expressed on some tumor cells such as T-cell acute lymphoblastic leukemia (ALL), adult T-cell leukemia/lymphoma (ATLL), adult peripheral T cell lymphoma (PTCL) and cutaneous T cell lymphoma (CTCL). CCR4 is also expressed on majority of Tregs, mainly effector Tregs. In this study we have successfully developed three versions of diphtheria-toxin based anti-human CCR4 immunotoxins (monovalent, bivalent and single-chain fold-back diabody). Binding analysis by flow cytometry showed that all three versions of the anti-human CCR4 immunotoxins bound to the human CCR4(+) tumor cell line as well as CCR4(+) human PBMC. The bivalent isoform bound stronger than its monovalent counterpart and the single-chain foldback diabody isoform was the strongest among the three versions. In vitro efficacy analysis demonstrated that the bivalent isoform was 20 fold more potent in inhibiting cellular proliferation and protein synthesis in human CCR4(+) tumor cells compared to the monovalent anti-human CCR4 immunotoxin. The single-chain fold-back diabody isoform was 10 fold more potent than its bivalent counterpart and 200 fold more potent than its monovalent counterpart. The in vivo efficacy was assessed using a human CCR4(+) tumor-bearing mouse model. The immunotoxin significantly prolonged the survival of tumor-bearing NOD/SCID IL-2 receptor γ(-/-) (NSG) mice injected with human CCR4(+) acute lymphoblastic leukemia cells compared with the control group. This novel anti-human CCR4 immunotoxin is a promising drug candidate for targeting human CCR4(+) tumor cells and Tregs in vivo.

Leukocyte chemoattractant receptors in human disease pathogenesis

Combinations of leukocyte attractant ligands and cognate heptahelical receptors specify the systemic recruitment of circulating cells by triggering integrin-dependent adhesion to endothelial cells, supporting extravasation, and directing specific intratissue localization via gradient-driven chemotaxis. Chemoattractant receptors also control leukocyte egress from lymphoid organs and peripheral tissues. In this article, we summarize the fundamental mechanics of leukocyte trafficking, from the evolution of multistep models of leukocyte recruitment and navigation to the regulation of chemoattractant availability and function by atypical heptahelical receptors. To provide a more complete picture of the migratory circuits involved in leukocyte trafficking, we integrate a number of nonchemokine chemoattractant receptors into our discussion. Leukocyte chemoattractant receptors play key roles in the pathogenesis of autoimmune diseases, allergy, inflammatory disorders, and cancer. We review recent advances in our understanding of chemoattractant receptors in disease pathogenesis, with a focus on genome-wide association studies in humans and the translational implications of mechanistic studies in animal disease models.