Inhibition of IL-13 and IL-13Rα2 Expression by IL-32θ in Human Monocytic Cells Requires PKCδ and STAT3 Association.

Interleukin (IL)-32θ, a newly identified IL-32 isoform, has been reported to exert pro-inflammatory effects through the association with protein kinase C delta In this study, we further examined the effects of IL-32θ on IL-13 and IL-13Rα2 expression and the related mechanism in THP-1 cells. Upon stimulating IL-32θ-expressing and non-expressing cells with phorbol 12-myristate 13-acetate (PMA), the previous microarray analysis showed that IL-13Rα2 and IL-13 mRNA expression were significantly decreased by IL-32θ. The protein expression of these factors was also confirmed to be down-regulated. The nuclear translocation of transcription factors and which are necessary for IL-13Rα2 and IL-13 promoter activities, was suppressed by IL-32θ. Additionally, a direct association was found between IL-32θ, and signal transducer and activator of transcription 3 but not duanyu18136, revealing that IL-32θ might act mainly through duanyu18133 and indirectly affect Moreover, the interaction of IL-32θ with duanyu18133 requires duanyu1531δ, since blocking activity eliminated the interaction and consequently limited the inhibitory effect of IL-32θ on duanyu18133 activity. Interfering with duanyu18133 or binding by decoy oligodeoxynucleotides (ODNs) identified that IL-32θ had additive effects with the duanyu18133 decoy ODN to suppress IL-13 and IL-13Rα2 mRNA expression. Taken together, our data demonstrate the intracellular interaction of IL-32θ, duanyu1531δ, and duanyu18133 to regulate IL-13 and IL-13Rα2 synthesis, supporting the role of IL-32θ as an inflammatory modulator.

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