Human Lung Mast Cell Activation Leads to IL-13 mRNA Expression and Protein Release

Using reverse transcriptase-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA), we studied the generation of the recently described Th₂ cytokine interleukin-13 (IL-13) by anti-IgE-activated lung fragments (LF), lung mast cells (LMC), and the mast cell line HMC-1. We found that IL-13 messenger ribonucleic acid (mRNA) was constitutively expressed in LF and rapidly increased after anti-IgE challenge, persisting throughout a 16-h period. Quantitative-competitive PCR (QCPCR) demonstrated an increase from 1.2 fg to 120 fg of IL-13 mRNA/μg LF total cellular RNA. Time-course experiments showed that IL-13 protein was not increased in supernatants at 2 h after activation, but was upregulated by 8 h. Anti-IgE-activated LF supernatants contained 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 increased IL-13 mRNA expression. QCPCR analysis of LMC IL-13 mRNA expression at 4 h after activation showed a 7-, 13.8-, and 13.2-fold increase after A23187, anti-IgE, and PMA, respectively. Quantities of IL-13 released from optimally activated LMC and peripheral blood T cells were comparable. HMC-1 also showed enhanced IL-13 mRNA beginning 30 min after A23187 activation, with peak expression from 1 to 10 h, followed by waning over the subsequent 24 h. A23187 stimulation of HMC-I led to 100-fold 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.