Neurotrophins act as neuroendocrine regulators of skin homeostasis in health and disease

Neurotrophins regulate cutaneous innervation, act as growth and motility factors on structural skin cells such as keratinocytes and fibroblasts, modulate cutaneous immune function and even serve as stress mediators in skin biology. The multilayered neurotrophin interaction with skin biology through high affinity specific tyrosinekinase receptors and the Janus-faced p75 receptor, which depending on ligand and co-receptor expression can serve as a low-affinity pan-neurotrophin receptor or a high affinity proneurotrophin receptor, guaranties this neuroendocrine peptide family a central position in the control of skin homeostasis in health and disease. It is a challenging task for future research efforts to integrate our knowledge on differential neurotrophin expression patterns and signaling pathways into complex concepts of neuroendocrine tissue remodeling and pathogenetic processes. In addition, we need to improve our understanding of the role of neurotrophin processing enzymes, associated co-receptors and intracellular adaptor molecules in specific cutaneous cell populations to design precise interaction tools for research and treatment. Such tools will allow us to utilize this ancient growth factor family in the management of neurotrophin responsive pathogenetic pathways and cutaneous diseases such as neurogenic inflammation, peripheral nerve degeneration, wound healing, atopic dermatitis or psoriasis.

Exotic food allergy: anaphylactic reaction to lychee

There are very few reports on allergic reactions to lychee fruit in the literature. We describe the case of a 26-year-old man who developed pruritus, generalized urticaria, and severe angioedema of his lips and tongue with dyspnea within 15 minutes after lychee fruit intake. Although we found no lychee-specific immunoglobulin E antibodies, a basophil activation test (BAT) and a cellular antigen stimulation test (CAST) to lychee were both positive, as was a prick-to-prick test with fresh lychee fruit. The patient also suffered from an oral food allergy syndrome to parsley and was sensitized to mugwort but not to latex or profilin. BAT and CAST are helpful tools in the diagnostic workup for exotic food allergy. Mugwort is suggested as the allergen responsible for,the cross-reactivity presented by this patient, as he had no sensitization to latex or profilin.

Circulating levels of brain-derived neurotrophic factor correlate with disease severity in the intrinsic type of atopic dermatitis

BACKGROUND

Recent studies have shed light on the complex regulation of genetic, environmental, immunologic and pharmacologic factors, which contribute to the development of atopic dermatitis (AD). However, it is still unclear to which extent neuroimmune mediators have a role in AD.

AIMS OF THE STUDY

To assess peripheral neurotrophin levels and their correlation with scoring atopic dermatitis (SCORAD) scores in both the intrinsic and extrinsic types of AD compared with patients with psoriasis and nonatopic healthy subjects.

METHODS

Levels of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) were assessed in peripheral blood with enzyme-linked immunosorbent assay. Based on IgE-mediated sensitization, AD was divided into the extrinsic and intrinsic type. Severity of AD was assessed with SCORAD score and with psoriasis area and severity index (PASI) in patients with psoriasis.

RESULTS

Brain-derived neurotrophic factor and NGF were detectable in all the subjects studied. However, the levels of both neurotrophins were significantly higher in patients with extrinsic and intrinsic types of AD compared with patients with psoriasis and nonatopic healthy subjects (NGF: P < 0.001, BDNF: P < 0.001). NGF and BDNF levels were similar in the intrinsic and extrinsic type of AD. There was a significant correlation between BDNF and SCORAD score only in patients with the intrinsic type of AD (r = 0.57, P < 0.05).

CONCLUSIONS

This study shows for the first time that NGF and BDNF are increased in both, the extrinsic type and the intrinsic type of AD. This finding points to a similar pathophysiologic background implicating a neuroimmune network in both variants of this chronic inflammatory skin disease. Future studies are needed to show the direct mechanisms of neurotrophin action in chronic inflammatory skin.

Neurophysiologie des Pruritus

Neurophysiologic studies indicate that pruritus is a distinct sensation with its own neuronal pathways in the peripheral and central nervous system which are different from that of pain. Pruritus is a very disturbing sensation and most common skin-related symptom. Histamine was long considered to be the only mediator of pruritus. However, it has become evident that - besides histamine - a variety of neuromediators such as neurotrophins and neuropeptides as well as their receptors play an important role in pruritus. Neuromediators are produced by mast cells, keratinocytes and eosinophil granulocytes which are in close contact to sensory nerves. The discovery of these neurophysiological interactions opens new and promising therapeutic options for the treatment of pruritus.

Erfolgreiche Therapie des IgA-Pemphigus vom subkorneal pustul�sen Typ

IgA pemphigus is a rare autoimmune intraepidermal blistering disease characterized by in vivo bound, and circulating IgA autoantibodies that target cell surface components (cadherins) of epidermal keratinocytes. The average age of onset is approximately 50 years. Histological hallmarks of IgA pemphigus are epidermal acantholysis, subcorneal or intraepidermal pustulosis, and neutrophilic infiltration. The main clinical characteristics are erythematous skin lesions with vesiculopustules, erosions, crusts and desquamation, favoring the trunk, groins, auxiliaries, and proximal extremities. The drug of choice for treating IgA pemphigus is diaminodiphenylsulfone. In this case study, we describe a patient who suffered from IgA pemphigus and responded well to diaminodiphenylsulfone.

[Chronic urticaria in childhood]

Chronic urticaria in children occurs more often than it might be supposed, but its management is not part of the usual daily routine. While acute urticaria in children can be treated symptomatically without further investigations, chronic urticaria requires a search for trigger factors. Autoimmune urticaria can occasionally be documented in children. The treatment of chronic urticaria depends on the suspected trigger, always keeping in mind that medications may need to be adjusted to meet pediatric requirements.

Neue Therapieoptionen der Urtikaria und ihrer Subtypen

Urticaria is one of the most common skin diseases. It is divided into several categories including acute and chronic urticaria as well as physical urticaria and special subtypes such as cholinergic and autoimmune urticaria. The causes of urticaria are multiple. In more than 80%, urticaria is triggered by an inflammatory focus, a subclinical infection or autoimmune actions. In addition, non-specific pharmacological or toxin-mediated release of inflammatory mediators from basophils or mast cells can also trigger urticaria. These new aspects in the pathophysiology of urticaria suggest new and promising therapeutic strategies. The first line treatment of urticaria still consists of non-sedating H1-antihistamines. Since urticaria has a profound impact on quality of life, effective treatment is very important. We consider new therapeutic options based on our long-term experience in treating patients with urticaria.

[Atopic dermatitis and psychological stress]

Atopic dermatitis (AD) is a chronic relapsing inflammatory skin disease. Its main features are eczematous skin lesions with a typical distribution and severe pruritus. Allergens, skin irritants, systemic or local infections, environmental pollutants and hormonal changes have a role in the pathophysiology of AD. A further important trigger factor for both intrinsic and extrinsic AD is emotional stress. Recently published observations point to direct psychoneuroimmunological and -endocrinological mechanisms: Psychological stress causes a transient increase of peripheral blood eosinophil count and an increase in both CD8+/CD11b+ and CLA+ T-cells. In addition, stress changes the cytokine and the hormone profile with increased levels of IFN-gamma and IL-5, and decreased levels of cortisol in AD patients in contrast to healthy controls. These findings underline the role of immunological changes and a possible suppressed hypothalamic-pituitary-adrenal (HPA) axis closing the loop for the final aggravation of AD.

IL-4-induced apoptosis in peripheral blood eosinophils

BACKGROUND

The regulation of eosinophil survival and apoptosis may play a major role in diseases demonstrating increased numbers of circulating and tissue eosinophils such as allergic reactions. Because few promoters of eosinophil apoptosis have been described so far, the objective of this study was to elucidate the role of endogenous factors on eosinophil survival and apoptosis.

METHODS AND RESULTS

Highly purified peripheral blood eosinophils were analyzed in the time course from 24 up to 144 hours in culture. Eosinophil survival was assessed with trypan blue dye exclusion and apoptosis was determined by DNA fragmentation gel analysis and ELISA technique with anti-histone antibodies. We confirmed previous results demonstrating prolonged eosinophil survival and inhibited apoptosis by IL-3, IL-5, and GM-CSF. In contrast, eosinophil apoptosis was significantly enhanced by corticosteroids, particularly dexamethasone and hydrocortisone. However, IL-1beta, IL-8, IL-12, platelet-activating factor, TNF-alpha, and eotaxin had no effect on eosinophil survival or apoptosis when compared with culture medium alone. In contrast, IL-4 at concentrations of 100 U/mL or more inhibited eosinophil survival and induced apoptosis. This effect was time dependent and abrogated by preincubation with neutralizing anti-IL-4 antibodies. However, after 96 hours in coincubation, IL-4 did overcome the survival-prolonging effect of IL-3, IL-5, and GM-CSF. IL-4 did not enhance eosinophil surface expression of APO-1/Fas antigen (CD95). In assessing IL-4-mediated effects on eosinophil function, we found no response by means of the release of eosinophil cationic protein or reactive oxygen species.

CONCLUSIONS

Taken together, our data present direct evidence for the presence of functional IL-4 receptors on human eosinophils and indicate that IL-4 may lead to resolution of chronic inflammation by induction of eosinophil apoptosis.

Delayed eosinophil programmed cell death in vitro: a common feature of inhalant allergy and extrinsic and intrinsic atopic dermatitis

The present studies were undertaken to characterize the potential role of eosinophil programmed cell death (PCD) in atopic diseases. Peripheral blood eosinophil PCD was found to be delayed in inhalant allergy (p < 0.05) and delayed to an even greater extent in atopic dermatitis (AD) (p < 0.0001) when compared to nonatopic subjects. There was no difference in the occurrence of PCD between the extrinsic and the intrinsic type of AD, pointing to a secondary role of specific sensitization. Blockade of eosinophil PCD was not responsible for peripheral blood eosinophilia, because we found no obvious relationship of eosinophil survival to blood eosinophil count. Eosinophil supernatants of more patients with AD than of patients with inhalant allergy dose-dependently inhibited PCD in nonatopic eosinophils, and it was shown that this effect was possibly due to autocrine production of granulocyte-macrophage-colony stimulating factor, probably IL-5. Eosinophil expression of CD95 (Fas antigen) did not change over time in culture and was not modulated by cytokines prolonging eosinophil survival. In contrast, IL-3, IL-5, and granulocyte-macrophage-colony stimulating factor caused an upregulated expression of CD69. However, in AD, CD69 on eosinophils was upregulated without the need of exogenous growth factor or factors over time in culture, thus confirming an autocrine production of proeosinophilic cytokines. In conclusion, our data clearly indicate that eosinophil PCD is markedly delayed in the so-called atopic diseases irrespective of allergen sensitization and suggest that this effect is mediated by the autocrine production of growth factors by eosinophils.