Modulation of basophil activity: a novel function of the neuropeptide α-melanocyte-stimulating hormone.

Little is known about the effect of neuropeptides on basophils, which are important effector cells in immune and allergic responses. This study aimed at revealing the role of α-melanocyte-stimulating hormone (α-MSH) on basophil function. Expression of melanocortin receptors and proopiomelanocortin (POMC) was analyzed by means of RT-PCR, Western immunoblotting, fluorescence-activated cell sorting, and double-immunofluorescence analysis. Signal transduction studies included cyclic AMP and Ca(2+) mobilization assays. Basophil activity was assessed based on CD63 surface expression and cytokine release. MC-1R expression was detectable in basophils isolated from human peripheral blood, as well as in basophils within nasal tissue. In isolated basophils from human blood, truncated POMC transcripts were present, but there was no POMC protein. Treatment of basophils with α-MSH increased intracellular Ca(2+) but not cyclic AMP levels. α-MSH at physiologic doses potently suppressed basophil activation induced by N-formyl-methionyl-leucyl-phenylalanine, phorbol 12-myristate 13-acetate, or grass pollen allergen in whole blood of healthy or allergic subjects, respectively. The effect of α-MSH on basophil activation was MC-1R mediated (as shown by blockade with a peptide analogue of agouti-signaling protein) and imitated by adrenocorticotropic hormone but not elicited by the tripeptides KPV and KdPT, both of which lack the central pharmacophore of α-MSH. Moreover, α-MSH at physiologic doses significantly suppressed secretion of 3 proallergic cytokines, IL-4, IL-6, and IL-13, in basophils stimulated with anti-IgE, N-formyl-methionyl-leucyl-phenylalanine, or phorbol 12-myristate 13-acetate. Our findings highlight a novel functional activity of α-MSH, which acts as a natural antiallergic basophil-response modifier. These findings might point to novel therapeutic strategies in treating allergic diseases.

Böhm M ，Apel M ，Sugawara K ，Brehler R ，Jurk K ，Luger TA ，Haas H ，Paus R ，Eiz-Vesper B ，Walls AF ，Ponimaskin E ，Gehring M ，Kapp A ，Raap U ... -  《-》

The melanocortin system in articular chondrocytes: melanocortin receptors, pro-opiomelanocortin, precursor proteases, and a regulatory effect of alpha-melanocyte-stimulating hormone on proinflammatory cytokines and extracellular matrix components.

Grässel S ，Opolka A ，Anders S ，Straub RH ，Grifka J ，Luger TA ，Böhm M ... -  《ARTHRITIS AND RHEUMATISM》

α-MSH modulates cell adhesion and inflammatory responses of synovial fibroblasts from osteoarthritis patients.

The synovium is a target for neuropeptides. Melanocortins have attained particular attention as they elicit antiinflammatory effects. Although synovial fluid from patients with rheumatic diseases contains α-melanocyte-stimulating hormone (α-MSH) it is unknown whether synovial fibroblasts generate α-MSH and respond to melanocortins. Synovial tissue was obtained from osteoarthritis (OA) patients. Cells were isolated and prepared either as primary mixed synoviocytes or propagated as synovial fibroblasts (OASFs). Melanocortin receptor (MC) and proopiomelanocortin (POMC) expression were investigated by endpoint RT-PCR, immunofluorescence and Western immunoblotting. Functional coupling of MC1 was assessed by cAMP and Ca(2+) assays. Cell adhesion was monitored by the xCELLigence system. Secretion of α-MSH, tumour necrosis factor (TNF), interleukin (IL)-6 and IL-8 was determined by ELISA. OASFs in vitro expressed MC1. MC1 transcripts were present in synovial tissue and appropriate immunoreactivity was detected in synovial fibroblasts in situ. OASFs contained truncated POMC transcripts but neither full-length POMC mRNA, POMC protein nor α-MSH were detectable. In accordance with this only truncated POMC transcripts were present in synovial tissue. α-MSH increased cAMP dose-dependently but did not alter calcium in OASFs. α-MSH also enhanced adhesion of OASFs to fibronectin and reduced TNF, IL-6 and IL-8 secretion in primary mixed synoviocyte cultures. In OASFs, α-MSH modulated basal and TNF/IL-1β-mediated secretion of IL-6 and IL-8. Synovial fibroblasts express MC1in vitro and in situ. α-MSH elicits biological effects in these cells suggesting an endogenous immunomodulatory role of melanocortins within the synovium. Our results encourage in vivo studies with melanocortins in OA models.

Böhm M ，Apel M ，Lowin T ，Lorenz J ，Jenei-Lanzl Z ，Capellino S ，Dosoki H ，Luger TA ，Straub RH ，Grässel S ... -  《-》

alpha-melanocyte-stimulating hormone suppresses bleomycin-induced collagen synthesis and reduces tissue fibrosis in a mouse model of scleroderma: melanocortin peptides as a novel treatment strategy for scleroderma?

Kokot A ，Sindrilaru A ，Schiller M ，Sunderkötter C ，Kerkhoff C ，Eckes B ，Scharffetter-Kochanek K ，Luger TA ，Böhm M ... -  《ARTHRITIS AND RHEUMATISM》

Regulation of melanocortin 1 receptor in allergic rhinitis in vitro and in vivo.

α-melanocyte-stimulating hormone (α-MSH) was shown to inhibit allergic airway inflammation and exert suppressive effects on human basophils. This study aims to extend our current knowledge on the melanocortin 1 receptor (MC1R) expression in nasal tissue of patients with allergic rhinitis (AR) and functional effects of α-MSH in human basophils especially from patients with allergic rhinitis. MC1R expression before and after nasal allergen provocation was studied in nasal mucosal tissue of AR patients and in a mouse model of allergic airway inflammation using immunofluorescence. In vitro regulation of the MC1R and CD203c surface expression on whole-blood basophils of patients with AR and controls was assessed with flow cytometry. Functional effects of α-MSH on isolated basophils were analysed regarding apoptosis with flow cytometry and chemotaxis using a Boyden chamber assay. We detected an accumulation of MC1R-positive basophils in nasal mucosa tissue of patients with AR 24 h after nasal allergen provocation. Such accumulation was not present in mucosa sections from healthy controls. In mice with allergic airway inflammation, we found a clear accumulation of MC1R-positive basophils in the nasal tissue compared to control mice. MC1R expression was inducible in AR patients and controls by stimulation with anti-IgE. α-MSH inhibited anti-IgE and grass pollen induced upregulation of CD203c, but had no effect on chemotaxis or apoptosis of basophils in vitro. MC1R-positive basophils accumulate in the nasal mucosa of patients with AR after nasal allergen provocation. Since α-MSH suppresses proinflammatory effector functions in human basophils via the MC1R, it constitutes an interesting novel target for modulating the allergic inflammatory response.

Kleiner S ，Braunstahl GJ ，Rüdrich U ，Gehring M ，Eiz-Vesper B ，Luger TA ，Steelant B ，Seys SF ，Kapp A ，Böhm M ，Hellings PW ，Raap U ... -  《-》