Nataliya M. Kushnir-Sukhov

5-Hydroxytryptamine Induces Mast Cell Adhesion and Migration

The neurotransmitter serotonin (5-hydroxytryptamine (5-HT)) is implicated in enhancing inflammatory reactions of skin, lung, and gastrointestinal tract. To determine whether 5-HT acts, in part, through mast cells (MC), we first established that mouse bone marrow-derived MC (mBMMC) and human CD34+-derived MC (huMC) expressed mRNA for multiple 5-HT receptors. We next determined the effect of 5-HT on mouse and human MC degranulation, adhesion, and chemotaxis. We found no evidence that 5-HT degranulates MC or modulates IgE-dependent activation. 5-HT did induce mBMMC and huMC adherence to fibronectin; and immature and mature mBMMC and huMC migration. Chemotaxis was accompanied by actin polymerization. Using receptor antagonists and pertussis toxin, we identified 5-HT1A as the principal receptor mediating the effects of 5-HT on MC. mBMMC from the 5-HT1A receptor knockout mouse (5-HT1AR−/−) did not respond to 5-HT. 5-HT did induce accumulation of MC in the dermis of 5-HT1AR+/+ mice, but not in 5-HT1AR−/− mice. These studies are the first to demonstrate an effect of 5-HT on MC. Furthermore, both mouse and human MC respond to 5-HT through the 5-HT1A receptor. Our data are consistent with the conclusion that 5-HT promotes inflammation by increasing MC at the site of tissue injury.

Bone marrow stromal cells inhibit mast cell function via a COX2‐dependent mechanism

Cite this as: J. M. Brown, K. Nemeth, N. M. Kushnir‐Sukhov, D. D. Metcalfe and E. Mezey, Clinical & Experimental Allergy, 2011 (41) 526–534.

Elevated Tryptase Levels Are Associated with Greater Bone Density in a Cohort of Patients with Mastocytosis

Background: Mastocytosis is associated with a pathological increase in tissue mast cells. Associated skeletal problems include a decrease in bone density and pathological fractures. Methods: In order to explore the relationship between bone density and the severity of mastocytosis, 21 patients with mastocytosis who underwent dual-energy X-ray absorptiometry were entered into this study. Correlation coefficients were computed between Z-scores and demographic, clinical and laboratory data. Femoral neck Z-scores correlated with serum tryptase levels when all the patients were considered (p = 0.029). Results and Conclusion: Patients with less severe disease had significantly lower values at the L1–L4 spine (p = 0.046) and femoral neck (p = 0.029) Z-scores compared to patients with more severe disease. Most patients who had low Z-scores (between –1 and –2.5) were under 50 years of age, had less severe disease and had lower serum tryptase levels. A history of gastroesophageal reflux disease and a history of hypotensive episodes correlated with lower L1–L4 spine Z-scores (p < 0.05). Thus, patients with less severe disease and lower serum tryptase levels should in particular have their bone density determined with treatment appropriate to the findings.

Effects of Gamma Radiation on FcεRI and TLR-Mediated Mast Cell Activation

Ionizing gamma radiation has several therapeutic indications including bone marrow transplantation and tumor ablation. Among immune cells, susceptibility of lymphocytes to gamma radiation is well known. However, there is little information on the effects of gamma radiation on mast cells, which are important in both innate and acquired immunity. Previous studies have suggested that mast cells may release histamine in response to high doses of gamma radiation, whereas other reports suggest that mast cells are relatively radioresistant. No strong link has been established between gamma radiation and its effect on mast cell survival and activation. We examined both human and murine mast cell survival and activation, including mechanisms related to innate and acquired immune responses following gamma radiation. Data revealed that human and murine mast cells were resistant to gamma radiation-induced cytotoxicity and, importantly, that irradiation did not directly induce β-hexosaminidase release. Instead, a transient attenuation of IgE-mediated β-hexosaminidase release and cytokine production was observed which appeared to be the result of reactive oxygen species formation after irradiation. Mast cells retained the ability to phagocytose Escherichia coli particles and respond to TLR ligands as measured by cytokine production after irradiation. In vivo, there was no decrease in mast cell numbers in skin of irradiated mice. Additionally, mast cells retained the ability to respond to Ag in vivo as measured by passive cutaneous anaphylaxis in mice after irradiation. Mast cells are thus resistant to the cytotoxic effects and alterations in function after irradiation and, despite a transient inhibition, ultimately respond to innate and acquired immune activation signals.

Clinical correlates of blood serotonin levels in patients with mastocytosis.

Background  Mastocytosis is a clonal disorder associated with an increased mast cell burden. We have recently demonstrated the ability of human mast cells to express and be activated through multiple serotonin receptors; to synthesize and release serotonin; and that mastocytosis patients may have abnormal serotonin levels. As serotonin has been implicated in the genesis of clinical symptoms found in association with some chronic diseases, we have now determined the whole blood serotonin levels in 29 patients diagnosed with mastocytosis, and correlated these levels with multiple clinical and laboratory parameters.