Involvement of beta1 and beta2 integrin stimulation in RNA synthesis in an eosinophilic cell line (EoL-1)

In allergic inflammatory disease, especially in bronchial asthma, eosinophils play important roles as essential inflammatory cells. In the accumulation of eosinophils in airway inflammation, eosinophils receive very diverse stimuli. In this study, we investigated the influences of the signal between beta2 integrin/intercellular adhesion molecule-1 (ICAM-1) or beta1 integrin/fibronectin (FN) and RNA synthesis on proteins in eosinophilic cell line-1 (EoL-1), using recombinant soluble ICAM-1 (r-sICAM-1) as a global response of eosinophils. 3H-thymidine incorporation and 3H-uridine incorporation were used as indices for DNA synthesis and RNA synthesis, respectively. In a comparison of the RNA/DNA ratio with various durations of stimulation of 1 microg/ml of r-sICAM-1 and 100 microg/ml of FN, a time-dependent increase was observed, but the increase induced by FN rose slower than that induced by r-sICAM-1. From this result, a beta2 integrin/ICAM-1 signal induced an increase in the RNA/DNA ratio in EoL-1, implying that the signal promotes RNA synthesis, which suggests that various types of protein synthesis, such as the synthesis of various cytokines, are induced by the beta2 integrin/ICAM-1 signal. Similar results were obtained with a beta1 integrin signal using FN, but there was a difference in the time course between beta2 integrin/ICAM-1 and beta1 integrin/FN signals. This experimental method may be useful for understanding these manifestations as a global response of eosinophils.