Mental stress in atopic dermatitis--neuronal plasticity and the cholinergic system are affected in atopic dermatitis and in response to acute experimental mental stress in a randomized controlled pilot study

Abstract

Rationale: In mouse models for atopic dermatitis (AD) hypothalamus pituitary adrenal axis (HPA) dysfunction and neuropeptide-dependent neurogenic inflammation explain stress-aggravated flares to some extent. Lately, cholinergic signaling has emerged as a link between innate and adaptive immunity as well as stress responses in chronic inflammatory diseases. Here we aim to determine in humans the impact of acute stress on neuro-immune interaction as well as on the non-neuronal cholinergic system (NNCS).

Methods: Skin biopsies were obtained from 22 individuals (AD patients and matched healthy control subjects) before and after the Trier social stress test (TSST). To assess neuro-immune interaction, nerve fiber (NF)-density, NF-mast cell contacts and mast cell activation were determined by immunohistomorphometry. To evaluate NNCS effects, expression of secreted mammal Ly-6/urokinase-type plasminogen activator receptor-related protein (SLURP) 1 and 2 (endogenous nicotinic acetylcholine receptor ligands) and their main corresponding receptors were assessed by quantitative RT-PCR.

Results: With respect to neuro-immune interaction we found higher numbers of NGF+ dermal NF in lesional compared to non-lesional AD but lower numbers of Gap43+ growing NF at baseline. Mast cell-NF contacts correlated with SCORAD and itch in lesional skin. With respect to the NNCS, nicotinic acetylcholine receptor α7 (α7nAChR) mRNA was significantly lower in lesional AD skin at baseline. After TSST, PGP 9.5+ NF numbers dropped in lesional AD as did their contacts with mast cells. NGF+ NF now correlated with SCORAD and mast cell-NF contacts with itch in non-lesional skin. At the same time, SLURP-2 levels increased in lesional AD skin.

Conclusions: In humans chronic inflammatory and highly acute psycho-emotional stress interact to modulate cutaneous neuro-immune communication and NNCS marker expression. These findings may have consequences for understanding and treatment of chronic inflammatory diseases in the future.

Figure 1. Epidermal thickness and NF in healthy, non-lesional and lesional AD skin.

Epidermal thickness and number of IR NF were determined per microscopic field in stained cryo-sections of full thickness skin as described before . Participants per group (control, non-lesional AD, lesional AD): epidermal thickness N = 9, 8, 11; NGF+ NF N = 11, 11, 11; PGP 9.5+ NF N = 4, 5, 6; Gap43+ NF N = 8, 3, 5. Corresponding raw data is provided as Data S1. P-values: <0.10 =  (*), <0.05 = *, <0.01 = **. Abbreviations: conH – healthy control skin, conAD – non-lesional AD skin, lesAD – lesional AD skin.

Figure 2. SLURP and selected SLURP receptor levels in healthy, non-lesional and lesional AD skin.

Quantitative RT-PCR was performed on full thickness skin biopsies. Participants per group: eight (six male, two female). Corresponding raw data is provided as Data S1. P-values: <0.10 = (*), <0.05 = *, <0.01 = **. Abbreviations: conH – healthy control skin, conAD – non-lesional AD skin, lesAD – lesional AD skin.

Figure 3. Stress response during TSST.

During TSST salivary cortisol levels (HPA), pulse (beats per min, SA) and tension assessment (Likert scale, psychoemotional stress perception) were obtained 7 times. Time points: 1 =  after rest before biopsy, 2 =  immediately after biopsy, 3 = 30 min after rest following biopsy, 4 =  after instruction and preparation for TSST, 5 =  after TSST, 6 = 10 min after TSST, 7 = 30 min after TSST. Corresponding raw data is provided as Data S1. P-values: <0.05 = *.

Figure 4. TSST induced neuro-immune changes in healthy control, non-lesional and lesional AD skin.

Changes to baseline obtained as described in Figure 1 were determined 24 h after TSST. Number of participants per evaluation (NGF+ NF, PGP 9.5+ NF, PGP 9.5+ NF-mast cell contacts, degranulated mast cells [MC]): control: N = 11, 4, 4, 4; non-lesional AD: N = 11, 4, 4, 4; lesional AD: N = 11, 6, 6, 5. Corresponding raw data is provided as Data S1. P-values: <0.10 = (*), <0.05 = *. Abbreviations: conH – healthy control skin, conAD – non-lesional AD skin, lesAD – lesional AD skin, preS – prior to TSST, postS – 24 h after TSST.

Figure 5. TSST induced changes in SLURP and SLURP receptor levels in healthy, non-lesional and lesional AD skin.

Changes to baseline as given in Figure 2 were determined 24 h after TSST. Participants per group: eight (six male, two female). Corresponding raw data is provided as Data S1. P-values: <0.10 = (*), <0.05 = *. Abbreviations: conH – healthy control skin, conAD – non-lesional AD skin, lesAD – lesional AD skin, preS – prior to TSST, postS – 24 h after TSST.