Transcription Elongation Factor P-TEFb Is Involved in IL-17F Signaling in Airway Smooth Muscle Cells

Abstract

Background: IL-17F is involved in the pathogenesis of several inflammatory diseases, including asthma and COPD. However, the effects of steroids on the function of IL-17F signaling mechanisms are largely unknown. One of the transcription elongation factors, positive transcription elongation factor b (P-TEFb) composed of cyclin T1 and cyclin-dependent kinase 9 (CDK9), is known as a novel checkpoint regulator of gene expression via bromodomain-containing protein 4 (Brd4). Methods: Human airway smooth muscle cells were stimulated with IL-17F and the expression of IL-8 was evaluated by real-time PCR and ELISA. Next, the phosphorylation of CDK9 was determined by Western blotting. The CDK9 inhibitor and short interfering RNAs (siRNAs) targeting Brd4, cyclin T1, and CDK9 were used to identify the effect on IL-17F-induced IL-8 expression. Finally, the effect of steroids and its signaling were evaluated. Results: IL-17F markedly induced the transcription of the IL-8 gene and the expression of the protein. Pretreatment of CDK9 inhibitor and transfection of siRNAs targeting CDK9 markedly abrogated IL-17F-induced IL-8 production. Transfection of siRNAs targeting Brd4 and cyclin T1 diminished IL-17F-induced phosphorylation of CDK9 and IL-8 production. Moreover, budesonide decreased CDK9 phosphorylation and markedly inhibited IL-17F-induced IL-8 production. Conclusions: This is the first report that P-TEFb is involved in IL-17F-induced IL-8 expression and that steroids diminish it via the inhibition of CDK9 phosphorylation. IL-17F and P-TEFb might be novel therapeutic targets for airway inflammatory diseases.

Extracellular acidification-induced CXCL8 production through a proton-sensing receptor OGR1 in human airway smooth muscle cells: a response inhibited by dexamethasone

“…CXCL8 is secreted by ASMCs following various stimuli, such as TNF-α and cigarette smoke [7, 26–34]. Our previous study showed that extracellular acidification induced ASMCs to generate IL-6 and CTGF via OGR1 [18, 19].…”

“…However, elevated concentrations of CXCL8 are found in sputum, bronchoalveolar lavage fluid, and bronchial tissue of patients with respiratory diseases such as severe asthma, occupational asthma, cystic fibrosis, and COPD [22, 23]. CXCL8 is secreted by different cell types including alveolar macrophages [24], airway epithelial cells [25], and ASMCs [7, 26–34] following stimulation by viruses, various cytokines, hypoxia, reactive oxygen species, and bacterial particles.…”

BRD4 as a Therapeutic Target in Pulmonary Diseases

“…IL-17F induces the production of CXCL8 (IL-8) and the latter potentially contributes to neutrophilic infiltration into the airway. BRD4 has been reported to mediate CXCL8 production and CDK9 phosphorylation by IL-17F in human ASMCs [70], suggesting that BRD4 may be involved in neutrophilic infiltration by modulating IL-17F/CXCL8 signaling.…”

Chemokines in COPD: From Implication to Therapeutic Use

“…Indeed, IL-17F stimulation of human bronchial smooth muscle cells induces the transcription of the CXCL8 gene via the positive transcription elongation factor b (P-TEFb) composed of cyclin T1 and cyclin-dependent kinase 9 (CDK9). IL-17F is able to trigger CDK9 phosphorylation, thus enhancing the production of CXCL8 [107]. This sheds light on different mechanisms by which CXCL8 expression is activated during an exacerbation.…”