The inhibitory receptor <scp>CD</scp>300a is up‐regulated by hypoxia and <scp>GM</scp>‐<scp>CSF</scp> in human peripheral blood eosinophils

Abstract

BACKGROUND: Eosinophils are involved in several inflammatory processes including allergic inflammation. It has been shown that eosinophil functions may be regulated by activating or inhibitory receptors. Hypoxia is a feature of inflamed tissues and has recently been shown to regulate eosinophil viability and pro-angiogenic potential. In this study, the effect of hypoxia and GM-CSF on the inhibitory receptor CD300a in human peripheral blood eosinophils was investigated. METHODS: CD300a expression on eosinophils was analyzed by flow cytometry and evaluated by immuno-fluorescence; mRNA levels were evaluated by RT-PCR. RESULTS: An increase in the expression of CD300a was observed in hypoxic eosinophils compared to the normoxic ones. GM-CSF strongly induced CD300a increase also after 3 h in culture. In addition, hypoxia augmented mRNA levels of CD300a. Inhibition of hypoxia-inducible factor (HIF)-1 abolished the hypoxia-/GM-CSF-induced CD300a increase. CONCLUSION: CD300a expression is up-regulated by hypoxia, and GM-CSF where HIF-1 might play an important role. These results are important for the understanding of eosinophils behavior in inflamed tissue and suggest a new effect on their function in allergic inflammation. Taken together our data point out CD300a as a novel target for the treatment of allergy.