HUMAN LUNG MAST-CELL ACTIVATION LEADS TO IL-13 MESSENGER-RNA EXPRESSION AND PROTEIN RELEASE

Using reverse transcriptase-polymerase chain reaction (RT-PCR) and enz yme-linked immunosorbent assay (ELISA), we studied the generation of t he recently described Th-2 cytokine interleukin-13 (IL-13) by anti-IgE -activated lung fragments (LF), lung mast cells (LMC), and the mast ce ll line HMC-1. We found that IL-13 messenger ribonucleic acid (mRNA) w as constitutively expressed in LF and rapidly increased after anti-IgE challenge, persisting throughout a 16-h period. Quantitative-competit ive PCR (QCPCR) demonstrated an increase from 1.2 fg to 120 fg of IL-1 3 mRNA/mu g LF total cellular RNA. Time-course experiments showed that IL-13 protein was not increased in supernatants at 2 h after activati on, but was upregulated by 8 h. Anti-IgE-activated LF supernatants con tained 592.1 +/- 314.8 pg IL-13/g wet weight of tissue at 24 h (mean /- SE; n = 11). LMC demonstrated upregulation of IL-13 mRNA expression following treatment with A23187 (n = 4), with maximal upregulation by 3 h; anti-IgE or phorbol myristate acetate (PMA) also led to increase d IL-13 mRNA expression. QCPCR analysis of LMC IL-13 mRNA expression a t 4 h after activation showed a 7-, 13.8-, and 13.2-fold increase afte r A23187, anti-IgE, and PMA, respectively. Quantities of IL-13 release d from optimally activated LMC and peripheral blood T cells were compa rable. HMC-1 also showed enhanced IL-13 mRNA beginning 30 min after A2 3187 activation, with peak expression from 1 to 10 h, followed by wani ng over the subsequent 24 h. A23187 stimulation of HMC-1 led to 100-fo ld upregulation of IL-13 mRNA within 4 h and detectable IL-13 in 24-h supernatants. These results demonstrate that activation of LF and LMC through multiple signal-transduction pathways results in increased IL- 13 mRNA and protein expression temporally consistent with a potential role in chronic allergic inflammation.