Introduction Parkin (Park2), an E3 ubiquitin ligase, is critical to maintain mitochondrial function by regulating mitochondrial biogenesis and degradation (mitophagy), but recent evidence suggests the involvement of Parkin in promoting inflammation. In the present study, we determined if Parkin regulates airway mitochondrial DNA (mtDNA) release and inflammatory responses to type 2 cytokine interleukin (IL)-13 and allergens.
Methods We measured Parkin mRNA expression in brushed bronchial epithelial cells and mtDNA release in the paired bronchoalveolar lavage fluid (BALF) from normal subjects and asthmatics. Parkin-deficient primary human tracheobronchial epithelial (HTBE) cells generated using the CRISPR-Cas9 system were stimulated with IL-13. To determine the in vivo function of Parkin, Parkin knockout (PKO) and wild-type (WT) mice were treated with IL-13 or allergen (house dust mite, HDM) in the presence or absence of mtDNA isolated from normal mouse lungs.
Results Parkin mRNA expression in asthmatic airway epithelium was upregulated, which positively correlated with the levels of released mtDNA in BALF. IL-13-stimulated HTBE cells increased Parkin expression. Moreover, IL-13 induced mtDNA release in Parkin-sufficient, but not in Parkin-deficient HTBE cells. PKO (vs WT) mice attenuated airway mtDNA release and inflammation following IL-13 or HDM treatments. mtDNA amplified airway inflammation in mice treated with IL-13 or HDM. Notably, Parkin also mediated mtDNA-induced exacerbation of airway inflammation.
Conclusion Our research findings suggest that Parkin promotes mtDNA release and inflammation in airways, thus improving our understanding of the complex role of Parkin and mitochondrial dysfunction in asthma pathogenesis.
- airway epithelium
- asthma mechanisms
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Contributors KGD and HWC drafted the manuscript and designed the experiments. KGD performed the experiments and data analysis. NS helped with the mouse models. RJM, CK and NP provided the human samples. RAG and FH reviewed the manuscript. All authors have read, reviewed and approved the final manuscript.
Funding NIH R01AI106287, R01HL122321, R01HL125128 and U19AI125357 and a grant (BRASS) from the Cohen Family Asthma Institute of National Jewish Health.
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval The study protocol was approved by the Institutional Review Board (HS#2639) at National Jewish Health. Written informed consent was obtained from the study subjects.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement All data relevant to the study are included in the article or uploaded as supplementary information.