A new isoform of interleukin-32 suppresses IL-8 mRNA expression in the intestinal epithelial cell line HT-29

Interleukin (IL)-32 plays a role in the pathophysiology of inflammatory bowel disease (IBD). We isolated a new isoform of the IL-32 transcript in the process of cloning the full-length IL-32 gene from human colonic subepithelial myofibroblasts (SEMFs). The expression of mRNA in the samples was assessed by RT-PCR and real-time PCR analyses. The PCR products from the IL-32 genes were ligated into the expression vector pIRESneo2. The new isoform of the IL-32 transcript (336 nucleotides) completely lacked exon 4 of the IL-32γ gene, and was 60 bp shorter than IL-32α. TNF-α induced the mRNA expression of the new IL-32 isoform in a dose- and time-dependent manner. Stable transfection of this new isoform significantly decreased TNF-α-induced IL-8 mRNA expression in HT-29 cells, but the expression of the IL-32α gene had no effect. The mRNA expression of this new isoform was significantly elevated in the inflamed mucosa of IBD patients. A new isoform of the IL-32 transcript may play an anti-inflammatory role in the inflamed mucosa of IBD.