Christine Möller

Expression and function of chemokine receptors in human multiple myeloma

Multiple myeloma (MM) is a B cell tumor characterized by its selective localization in the bone marrow. The mechanisms that contribute to the multiple myeloma cell recruitment to the bone marrow microenvironment are not well understood. Chemokines play a central role for lymphocyte trafficking and homing. In this study we have investigated expression and functional importance of chemokine receptors in MM-derived cell lines and primary MM cells. We found that MM cell lines express functional CCR1, CXCR3 and CXCR4 receptors, and some also CCR6. Although only a minority of the cell lines responded by calcium mobilization after agonist stimulation, a migratory response to the CCR1 ligands RANTES and MIP-1α was obtained in 5/6 and 4/6, respectively, of the cell lines tested. Five out of six cell lines showed a response to the CXCR4 ligand SDF-1. In addition, 3/6 cell lines migrated in response to MIP-3α and IP-10, ligands for CCR6 and CXCR3, respectively. The expression of CXCR4 and CCR1 and the migration to their ligands, SDF-1, and RANTES and MIP-1α, respectively, were also demonstrated in primary MM cells. These findings suggest that chemokine receptor expression and the migratory capacity of MM cells to their ligands are relevant for the compartmentalization of MM cells in the bone marrow.

Mast cell CD30 ligand is upregulated in cutaneous inflammation and mediates degranulation-independent chemokine secretion

Mast cells are involved in many disorders where the triggering mechanism that leads to degranulation and/or cytokine secretion has not been defined. Several chronic inflammatory diseases are associated with increased mast cell numbers and upregulation of the TNF receptor family member CD30, but the role of elevated CD30 expression is poorly understood. Here we report what we believe to be a novel way to activate mast cells with CD30 that leads to degranulation-independent secretion of chemokines. CD30 induced a de novo synthesis and secretion of the chemokines IL-8, macrophage inflammatory protein-1alpha (MIP-1alpha), and MIP-1beta, a process involving the MAPK/ERK pathway. Mast cells were found to be the predominant CD30 ligand-positive (CD30L-positive) cell in the chronic inflammatory skin diseases psoriasis and atopic dermatitis, and both CD30 and CD30L expression were upregulated in lesional skin in these conditions. Furthermore, the number of IL-8-positive mast cells was elevated both in psoriatic and atopic dermatitis lesional skin as well as in ex vivo CD30-treated healthy skin organ cultures. In summary, characterization of CD30 activation of mast cells has uncovered an IgE-independent pathway that is of importance in understanding the entirety of the role of mast cells in diseases associated with mast cells and CD30 expression. These diseases include Hodgkin lymphoma, atopic dermatitis, and psoriasis.

IgE-receptor activation induces survival and Bfl-1 expression in human mast cells but not basophils

Background:  The contribution of mast cells to the pathology of allergic diseases are facilitated by their long life span in tissue and ability to regranulate. Bcl‐2 genes are one of the main regulators of cell death and survival. The aim of this study was to elucidate the mechanisms responsible for mast cell survival in allergy.

Activation of mast cells by immunoglobulin E-receptor cross-linkage, but not through adenosine receptors, induces A1 expression and promotes survival

Background Mast cells are a potent source of mediators that regulate the inflammatory response in allergy and asthma. Mast cells can be activated through different receptors, for example, via cross‐linkage of the high‐affinity IgE receptor (FcɛRI) and by adenosine acting on specific receptors. We have recently described mast cell survival of an IgE receptor activation by up‐regulation of the anti‐apoptotic gene A1.

IgE-receptor activation of mast cells regulates phosphorylation and expression of forkhead and Bcl-2 family members.

Activation of the high‐affinity IgE‐receptor, Fc?RI, expressed on mast cells can result in either enhanced survival or apoptosis depending on the circumstances. In this study, we have analysed signalling pathways involved in the regulation of mast cell survival and apoptosis. Fc?RI cross‐linking induces phosphorylation of Akt and its downstream target forkhead transcription factors. In addition, Bad, GSK‐3β and IκB‐α also become phosphorylated. A1, a prosurvival Bcl‐2 homologue transcriptionally controlled by NFκB transcription factors, is upregulated upon Fc?RI activation. These events have prosurvival effects on the mast cells. Moreover, Fc?RI activation upregulates the levels of the proapoptotic protein Bim and induces a rapid, but transient, phosphorylation of Bim. Thus, Fc?RI activation of mast cells leads to both prosurvival and proapoptotic signalling events where the outcome most likely depends on the balance between these signals.

Coaggregation of FcεRI with FcγRIIB Inhibits Degranulation but Not Induction of Bcl-2 Family Members A1 and Bim in Mast Cells

The aggregation of high-affinity immunoglobulin E (IgE) receptors (FcεRI) on mast cells is a critical event in the initiation of an allergic reaction. Coengagement of FcεRI with immunoglobulin G (IgG) low-affinity receptor FcγRIIB/CD32 inhibits degranulation and the release of inflammatory mediators from mast cells and has therefore been proposed as a new therapeutic approach for the treatment of allergies. In this study, we investigated whether FcγRIIB, besides inhibiting degranulation, negatively regulates other signalling pathways downstream of FcεRI. For this, we determined the phosphorylation and/or expression of proteins involved in the regulation of mast-cell apoptosis. Coaggregation led to an attenuation of Akt phosphorylation but did not inhibit phosphorylation of transcription factor Foxo3a or its proapoptotic target, Bim. Similarly, FcεRI-dependent expression of the prosurvival gene A1 was not affected by coaggregation. Our data demonstrate that coengagement of FcεRI and FcγRIIB inhibits degranulation but not the signalling pathways regulating Bcl-2 family members Bim and A1.

Readministration of IgE Is Required for Repeated Passive Cutaneous Anaphylaxis in Mice

Background: Homologous passive cutaneous anaphylaxis (PCA) is an established technique that provides a useful tool to study local inflammation due to mast cell activation. Since mast cells are responsive to repeated challenge by IgE receptor crosslinking in vitro, we investigated the responsiveness of mice to repeated PCA activation. Methods: Female BALB/c mice were sensitized with intradermal injection of IgE into the ear and provocated through intravenous injection of trinitrophenol-BSA. Repeated provocation was administered, and the outcome was determined by colorimetrical measurement of Evans blue dye leakage. Results: After local IgE injection, mice could be challenged to demonstrate a PCA reaction at least up to 13 days after IgE sensitization. In contrast, passively sensitized mice did not respond to repeated antigen challenge, i.e. a second provocation administered between 1 and 12 days after the first PCA reaction. However, if these mice were intradermally resensitized with IgE at the same site after the first challenge, they became responsive to the repeated challenge. Conclusions: Mast cells become desensitized upon PCA reaction, and resensitization with IgE is critical for mice repeatedly stimulated by PCA activation.