Retinoic Acid Negatively Impacts Proliferation and MCTC Specific Attributes of Human Skin Derived Mast Cells, but Reinforces Allergic Stimulability

Abstract

The Vitamin-A-metabolite retinoic acid (RA) acts as a master regulator of cellular programs. Mast cells (MCs) are primary effector cells of type-I-allergic reactions. We recently uncovered that human cutaneous MCs are enriched with RA network components over other skin cells. Yet, direct experimental evidence on the significance of the RA-MC axis is limited. Here, skin-derived cultured MCs were exposed to RA for seven days and investigated by flow-cytometry (BrdU incorporation, Annexin/PI, FcεRI), microscopy, RT-qPCR, histamine quantitation, protease activity, and degranulation assays. We found that while MC size and granularity remained unchanged, RA potently interfered with MC proliferation. Conversely, a modest survival-promoting effect from RA was noted. The granule constituents, histamine and tryptase, remained unaffected, while RA had a striking impact on MC chymase, whose expression dropped by gene and by peptidase activity. The newly uncovered MRGPRX2 performed similarly to chymase. Intriguingly, RA fostered allergic MC degranulation, in a way completely uncoupled from FcεRI expression, but it simultaneously restricted MRGPRX2-triggered histamine release in agreement with the reduced receptor expression. Vitamin-A-derived hormones thus re-shape skin-derived MCs numerically, phenotypically, and functionally. A general theme emerges, implying RA to skew MCs towards processes associated with (allergic) inflammation, while driving them away from the skin-imprinted MCTC (“MCs containing tryptase and chymase”) signature (chymase, MRGPRX2). Collectively, MCs are substantial targets of the skin retinoid network.

Allergic FcεRI‐ and pseudo‐allergic MRGPRX2‐triggered mast cell activation routes are independent and inversely regulated by SCF

“…MC purification was achieved by positive selection with antihuman c‐Kit microbeads and the Auto‐MACS (both from Miltenyi Biotec, Bergisch Gladbach, Germany). MC purity always exceeded 98%, as assessed by acidic toluidine‐blue staining …”

“…Histamine release assay (HRA) was performed according to a method routinely employed in our laboratory . In brief, MCs were stimulated by FcεRI aggregation (antiFcεRIα‐Ab 29C6 at 0.5 μg/mL), c48/80 (at 10 μg/mL), SP (at 30 μ mol/L), c48/80 + SP, or no stimulus (spontaneous) for 30 minutes at 37°C.…”

All‐trans‐retinoic acid activated mast cells via Mas‐related G‐protein‐coupled receptor‐X2 in retinoid dermatitis

“…Some researchers believe that retinoid dermatitis is an inflammatory reaction, with changes in the skin barrier being closely related to skin mast cells, probably mediated by the RA‐degrading enzyme Cyp26b1 affecting ATP receptors of mast cell . Babina et al indicated that ATRA could act on RARα in mast cells, leading to the release of cytokines such as interleukin (IL)‐1β, tumour necrosis factor‐α and IL‐8 from mast cells . However, its mechanism of action is still not fully understood, and further research on retinoid‐induced dermatitis will possibly help to avoid side‐effects in clinical applications.…”

“…4 Babina et al indicated that ATRA could act on RARα in mast cells, leading to the release of cytokines such as interleukin (IL)-1β, tumour necrosis factor-α and IL-8 from mast cells. 5,6 However, its mechanism of action is still not fully understood, and further research on retinoid-induced dermatitis will possibly help to avoid side-effects in clinical applications.…”

Psoriasis and Fat-soluble Vitamins: A Review

“…These include downregulation of inflammatory cytokines, stimulation of alternative binding proteins, and modulation of vitamin A metabolism via synthetic as opposed to endogenous retinoids [8][9][10]. Retinoids also have an inhibitory effect on cutaneous mast cells [11]. In psoriasis, mast cells, key cellular drivers of cytokine expression and perpetuation of lesions, are found activated and in greater number in the papillary dermis [12].…”