Background: Asthma is a chronic inflammatory disease characterized by airway inflammation and airway hyperresponsiveness (AHR). IL-33 is considered as one of the most critical molecules in asthma pathogenesis. IL-33 is stored in nucleus and passively released during necrosis. But little is known about whether living cells can release IL-33 and how this process is regulated.
Objective: We sought to investigate the role of polymerase I and transcript release factor (PTRF) in IL-33 release and asthma pathogenesis.
Methods: Ovalbumin (OVA)-induced asthma model in PTRF+/- mice were employed to dissect the role of PTRF in vivo. Then, further in vitro experiments were carried out to unwind the potential mechanism involved.
Results: In OVA asthma model with challenge phase, PTRF+/- mice showed a greater airway hyper-reaction, with an intense airway inflammation and more eosinophils in bronchoalveolar lavage fluid (BALF). Consistently, more acute type 2 immune response in lung and a higher IL-33 level in BALF were found in PTRF+/- mice. In OVA asthma model without challenge phase, airway inflammation and local type 2 immune responses were comparable between control mice and PTRF+/- mice. Knockdown of PTRF in 16HBE led to a significantly increased level of IL-33 in cell culture supernatants in response to LPS or HDM. Immunoprecipitation assay clarified Y158 as the major phosphorylation site of PTRF, which was also critical for the interaction of IL-33 and PTRF. Overexpression of dephosphorylated mutant Y158F of PTRF sequestered IL-33 in nucleus together with PTRF and limited IL-33 extracellular secretion.
Conclusion: Partial loss of PTRF led to a greater AHR and potent type 2 immune responses during challenge phase of asthma model, without influencing the sensitization phase. PTRF phosphorylation status determined subcellular location of PTRF and, therefore, regulated IL-33 release.
[1]Shanghai Jiao Tong Univ, Rui Jin Hosp, Dept Pulm & Crit Care Med, Sch Med, Shanghai, Peoples R China.
[2]Shanghai Jiao Tong Univ, Inst Resp Dis, Sch Med, Shanghai, Peoples R China.
[3]Chinese Acad Sci, Lab Cell Biol, Shanghai Inst Biol Sci, Inst Biochem & Cell Biol, Shanghai, Peoples R China.
[4]Shanghai Jiao Tong Univ, Sch Med, Dept Immunol & Microbiol, Shanghai Inst Immunol, Shanghai, Peoples R China.
[5]Shanghai Univ Tradit Chinese Med, Sch Pharm, Shanghai, Peoples R China.
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