Epidermis‐to‐dermis migration of immature Langerhans cells upon topical irritant exposure is dependent on CCL2 and CCL5

Abstract

Skin irritation is generally not considered to be an immunological event; however, alterations in the density of Langerhans cells (LC) in the epidermis do occur, which is indicative of LC migration. In this study, we investigated the migration of LC out of the epidermis after skin exposure to contact irritants and identified the chemokines involved. With the aid of ex vivo-intact human skin and epidermal sheets we show that dermal fibroblasts play a role in mediating LC migration towards the dermis. Exposure of ex vivo-intact human skin to a panel of seven irritants (SDS, salicylic acid, phenol, isopropanol, DMSO, TritonX, or benzalkonium chloride) resulted in decreased numbers of CD1a 1 cells in the epidermis and the accumulation of CD1a 1 cells in the dermis. In contrast to allergen exposure, neutralizing antibodies to either CXCL12 or CCL19/CCL21 did not inhibit LC migration out of the epidermis. Exposure of epidermal sheets to the prototypical irritant SDS resulted in a TNF-a-dependent LC migration towards dermal fibroblasts. This was a result of CCL2/MCP-1 and CCL5/RANTES chemokine secretion by fibroblasts: injection of CCL2-and CCL5-neutralizing antibodies into intact human skin totally inhibited LC migration into the dermis. We have thus identified a novel role for TNF-a-inducible dermis-derived CCL2 and CCL5 in initiating migration of irritant-exposed human LC out of the epidermis.Key words: Chemokine . DC . Irritant-contact dermatitis IntroductionEpidermal Langerhans cells (LC) are known to be capable of taking up and presenting antigenic chemicals to T lymphocytes and to be directly involved in the induction of allergic-contact dermatitis (ACD). In contrast, irritant-contact dermatitis (ICD) is considered to be an immunologically non-specific, local inflammatory reaction caused by substances found in, e.g. the workplace or consumer products that come into direct contact with the skin. Irritant substances penetrate the outer layer of the skin, whereupon they cause a localized acute inflammation. Morphologic studies have demonstrated that, despite ICD's supposed independence of adaptive immunity, alterations in the density and morphology of LC do occur concomitant with the clinical manifestation of inflammation. Several groups showed that upon irritant exposure, LC residing in the epidermis migrate into the dermis [1][2][3][4]. Whereas relatively much is known about allergeninduced migration of maturing LC out of the epidermis, very little is known about the underlying mechanisms of migration of LC exposed to non-maturing stimuli, such as irritants, out of the epidermis. Irritancy may result from perturbation or disruption of the lipid bilayers of the epidermis together with increased hydration [5,6]. Disruption of the skin barrier leads to the release of 2026cytokines such as IL-1a, . TNF-a is described to be one of the key cytokines in irritant dermatitis. Upon its release by keratinocytes, it induces strong gelatinolytic activity and down-regulates E-cadherin, which in turn decreases the attachment o...

MUTZ-3 Langerhans Cell maturation and CXCL12 independent migration in reconstructed human gingiva

“…For blocking experiments 7 μg/ml goat anti-human CXCL12 (AF-310-NA, R&D Systems, Minneapolis, MN, USA) was added to the culture medium of SE-LC or GE-LC 30 min prior to chemical exposure (optimal blocking concentration was previously determined) (Ouwehand et al, 2008(Ouwehand et al, , 2010, according to the manufacturer's data sheet. Isotype control to assess non-specific reactions was added at 7 μg/ml goat IgG (6-001-F, R&D Systems).…”

“…With regards to skin, a number of in vitro models are available to investigate DC biology, in particular in the area of human safety and risk assessment of chemicals, and for testing novel drugs and therapeutic strategies (Roggen, 2014;dos Santos et al, 2009;Gibbs et al, 2013). Since large pieces of skin are regularly available from routine surgical procedures (e.g., abdominal dermolipectomy), fresh human skin explants provide a very relevant model to study Langerhans cell (LC) biology in situ (Ouwehand et al, 2008(Ouwehand et al, , 2010Jacobs et al, 2006;Lindenberg et al, 2013;Oosterhoff et al, 2013). Even so, the logistics around getting fresh tissue to the laboratory, the short viability of the tissue ex vivo (48 h) and the extremely limited size of oral mucosa (gingiva) biopsies, which are also often infected with microorganisms, provide profound limitations to implementing these tissues directly as a research tool.…”

In Vitro Approaches for Detection of Chemical Sensitization

“…Fibroblasts play a key role both as advisors helping the KCs and Langerhans cells (LCs) to discriminate irritants from sensitizers, which in many cases are irritants themselves, and as guides helping the LCs out of the epidermis into the dermis and further towards lymphatic vessels (Fig. 4) [42]. Using a full-thickness tissue-engineered skin model containing fully functional MUTZ-3-derived LCs (MUTZ-LC), the MUTZ-LCs were demonstrated to mature and to acquire the ability to migrate towards C-X-C motif ligand (CXCL)12 and C-C motif ligand (CCL)19/21 in a comparable manner with primary LCs in skin explants [43].…”

“…Primary T-cell responses in lymph nodes require contact-dependent information exchange [41]. Fibroblasts play a key role both as advisors helping the keratinocytes (KCs) and LCs to discriminate irritants from sensitizers, which in many cases are irritants themselves, and as guides helping the LCs out of the epidermis into the dermis and further towards lymphatic vessels [42]. Transient serial encounters during the first activation phase (T-cell activation) are followed by a second phase of stable contacts culminating in cytokine production antigen-driven T-cell proliferation, which triggers a transition into a third phase of high motility and rapid proliferation (antigen-independent and IL-12-driven proliferation) [45,46].…”

Advanced tests for skin and respiratory sensitization assessment

“…This step is simulated in the MUTZ-LC migration assay (Ouwehand et al, 2008(Ouwehand et al, , 2010. the model is based on MUTZ-3 human cell lines that are differentiated for 7 days toward cells that closely resemble langerhans cells.…”