Histone deacetylases inhibitor Trichostatin A ameliorates DNFB-induced allergic contact dermatitis and reduces epidermal Langerhans cells in mice

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Abstract

Background

Histone deacetylases (HDACs) influence chromatin organization, representing a key epigenetic regulatory mechanism in cells. Trichostatin A (TSA), a potent HDAC inhibitor, has anti-tumor and anti-inflammatory effects. Allergic contact dermatitis (ACD) is a T-cell-mediated inflammatory reaction in skin and is regulated by epidermal Langerhans cells (LCs).

Objective

The aim of this study was to investigate if TSA treatment prevents 2,4-dinitrofluorobenzene (DNFB)-induced ACD in mice and regulates epidermal LCs and other immune cells during ACD development.

Methods

ACD was induced by sensitizing and challenging with DNFB topically. Mice were treated intraperitoneally with TSA or vehicle DMSO as a control every other day before and during induction of ACD. The ear swelling response was measured and skin biopsies from sensitized skin areas were obtained for histology. Epidermal cells, thymus, spleen and skin draining lymph nodes were collected for immune staining.

Results

TSA treatment ameliorated skin lesion severity of DNFB-induced ACD. The percentages of epidermal LCs and splenic DCs as well as LC maturation were significantly reduced in TSA-treated mice. However, TSA treatment did not significantly affect the homeostasis of conventional CD4+ and CD8+ T cells, Foxp3+CD4+ regulatory T cells, iNKT cells, and γδ T cells in thymus, spleen and draining lymph nodes (dLNs). Furthermore, there were no significant differences in IL-4 and IFN-γ-producing T cells and iNKT cells between TSA- and DMSO-treated mice.

Conclusion

Our findings suggest that TSA may ameliorate ACD through the regulation of epidermal LCs and HDACs could serve as potential therapeutic targets for ACD and other LCs-related skin diseases.

Introduction

Allergic contact dermatitis (ACD) is one of the leading causes for occupational diseases and it has great socio-economic impact [1]. Knowledge of the pathophysiology of ACD is derived mainly from animal models in which the skin inflammation is induced by painting haptens on the skin. ACD is a T-cell-mediated skin inflammation caused by skin repeated exposure to the haptens, such as 2,4-dinitrofluorobenzene (DNFB). The hapten first penetrates the epidermis and is taken up by skin dendritic cells (DCs), including epidermis-resident DCs, Langerhans cells (LCs) and dermal DCs, which process the allergen internally into a complete antigen. Skin DCs then migrate to the drain lymph nodes (dLNs) and present haptenated peptide to naïve antigen-specific T lymphocytes. As a result, antigen-specific CD4+ and CD8+ T cells are primed [2], [3]. Upon challenging the skin with the same hapten, the haptenated protein is presented by LCs and/or other DCs to recruited hapten-specific T cells to the skin. An inflammatory response is elicited to the skin and the subsequent production of inflammatory cytokines and chemokines [4]. Both DCs and T cells play critical roles in the development of ACD. LCs are members of the heterogenous family of professional antigen presenting cells (APCs), and specifically express Langerin (CD207), a C type lectin [5]. LCs form a contiguous network to detect invading pathogens or antigens in skin, and have classically been thought to play a pivotal role in the initiation and control of skin immunity and allergy [6]. However, more recent studies suggest LCs may have immunoregulatory functions as well [7], [8], [9].

Post-translational modification of histones is an epigenetic regulatory mechanism crucial for the regulation of gene expression. It is widely accepted that densely packed DNA structure is related to histone acetylation status. Histone acetylation status is associated with transcription regulation and controlled by histone acetyltransferases (HATs) and histone deacetylases (HDACs) [10], [11]. HDACs are enzymes that remove acetyl groups from specific lysine residues on histone proteins to regulate chromatin architecture and gene expression [12]. In general, histone acetylation relaxes chromatin structure and promotes gene transcription by allowing transcription factors and regulatory proteins access to DNA [10]. HDAC inhibitors (HDACi) can block HDAC activity and are shown to have anti-tumor and anti-inflammatory effects in a variety of tumors, autoimmune and inflammatory diseases [13], [14], [15]. However, the molecular mechanisms of its effects on these diseases are not very clear. Trichostatin A (TSA) is a well-known potent HDAC inhibitor [16], which has been considered a potential therapeutic agent against inflammatory diseases and autoimmune diseases [17], [18]. We recently reported that TSA reduced the number of LCs in vitro. Moreover, histone deacetylase activity is required for normal LC maturation and phagocytosis [19]. In the present study, we investigated the effects of TSA on DNFB-induced ACD and on the regulation on epidermal LCs and other immune cells during the induction of ACD in TSA treated mice.

Section snippets

Mice

C57BL/6 mice were obtained from the Jackson Laboratory. All experiments were performed with 6–8-wk-old mice. Mice were housed in a specific pathogen-free barrier unit. Handling of mice and experimental procedures were approved by the Institutional Animal Care and Use Committee (IACUC) of the Henry Ford Health System.

Hapten sensitization and elicitation of ACD

Mice were sensitized by applying 25 μl 0.5% DNFB (Sigma–Aldrich, St. Louis, MO, USA) (acetone:olive oil = 4:1) topically on shaved abdominal skin on day 0. On day 5, sensitized mice

TSA ameliorated DNFB-induced allergic contact dermatitis

TSA has demonstrated potent anti-inflammatory effects in experimental animal models of inflammatory diseases. We first investigated whether TSA can inhibit DNFB-induced ACD. The mice were treated with TSA (1 mg/kg) or DMSO alone as the control every other day for 5 times, starting 2 days before DNFB sensitized and ending 1 day after DNFB challenged. Application of DNFB to ears induced severe inflammation, such as, edema and epidermal hyperplasia, which were associated with the infiltration of

Discussion

Posttranslational modifications of histones in chromatin are emerging as an important mechanism in the regulation of gene expression. Histone acetylation plays key role in modulating chromatin structure and function. Recent studies indicate that HDACs play a key role in regulating immune cell development and functions and the alterations in HADC expression and function are related to a number of immune-mediated inflammatory diseases, such as rheumatoid arthritis (RA), systemic lupus

Funding sources

This work was supported in part by grants from National Institutes of Health Grant R21AR059976 and R01Ey017960, the Science and Technology Commission of Shanghai Municipality Grant (09411960600), and the Henry Ford Health System Research Grants for the Immunology Program (T71016 and T71017).

Acknowledgments

We thank the National Institutes of Health tetramer facility for CD1d-Tetramer, Matthew Weiland and Min Liu for maintaining mouse colonies, Xiaofan Mi for her critical reading, and all members from Mi's and Zhou's laboratories for their advice and encouragement.

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