ABSTRACT: Objectives: Eosinophils cultured with all-trans RA (ATRA) and 9-cis RA showed dramatically induced cell survival, and the efficacy of RAs (10-6 M) was similar to that of IL-5 (1 ng/ml), the most critical cytokine for eosinophil activation. Using a gene microarray, we studied mRNA profile regulated by RAs. Methods: Peripheral venous blood was obtained from subjects with mild eosinophilia. Eosinophils were isolated by sedimentation with 6% dextran followed by centrifugation on 1.088 Percoll (Pharmacia, Uppsala, Sweden) density gradients. The cells were further purified by negative selection using anti-CD16 immunomagnetic beads and a MACS system (Miltenyi Biotec, Bergisch Gladbach, Germany). Purified eosinophils were resuspended in RPMI 1640 medium (Gibco, Grand Island, NY) with 10% FCS, and incubated with vehicle, 10-6 M of 9-cis RA, or ATRA in 1% human serum albumin-coated plates, each 4 × 106 cells, for 4 h. Then cells were lysed, and total RNA was isolated using Isogen (Nippon Gene, Tokyo, Japan) as per the manufacturer’s instructions. RNA was repurified with phenol-chloroform extraction and ethanol precipitation. For each cell culture condition, the total RNA from three donors was pooled, enabling us to acquire adequate amounts of RNA for microarray analysis. Results: There was little variation between the samples treated by 9-cisRA and ATRA. The comparison between vehicle control and 9-cisRA, or vehicle control and ATRA, identified an increase (greater than twofold change over control) in 19 and 11 transcripts, respectively. The number of decreased transcripts (less than 0.5-fold) resulting fromby 9-cisRA or ATRA exposure wasere 19 and 8 transcripts, respectively. In these transcripts, the expression changes relative to vehicle control were smaller in withthe ATRA compared with 9-cis RA, suggesting that 9-cis RA induced gene transcription more effectively rather than ATRA. Of note, among the ten genes with the biggestmost decrease relative tofrom vehicle control, we found an apoptosis- related gene, caspase-3. Conclusions: We screened several genes involved in RA-induced prolonged eosinophil survival.
