Runx2 acetylation enhances pulmonary inflammation in chronic obstructive pulmonary disease through activating CDK8.

BACKGROUND: Runt-related transcription factor 2 (Runx2), a transcription factor of the RUNX family, is involved in various inflammatory diseases. However, the role of Runx2 was unclear in chronic obstructive pulmonary disease (COPD). METHODS: Pulmonary Runx2 level was compared in COPD patients and control subjects via a case-control study. Runx2 expression was detected in lung tissues of COPD mice and human bronchial epithelial (BEAS-2B) cells simulated with cigarette smoke extracts (CSE). RESULTS: Pulmonary Runx2 expression was upregulated, and inversely associated with pulmonary function and positively correlated with inflammatory cytokines in COPD patients. Mechanistically, Runx2 activation facilitated the transcription of CDK8, a co-regulator of nuclear factor-κB (NF-κB), and inflammatory cytokines production. Luciferase report gene assay confirmed that CDK8 was the downstream target gene of Runx2. Further analysis found that CSE inhibited Runx2 ubiquitination and proteasomal degradation. Besides, CSE elevated nicotinamide adenine dinucleotide (NAD(+)) consumes and Sirtuin 3 (Sirt3) depletion. Additionally, Runx2 acetylation was increased in CSE-exposed BEAS-2B cells, lungs tissues from COPD mice and patients. Interestingly, Sirt3 overexpression or supplementation with Nicotinamide Riboside (NR), the precursor of NAD(+), abolished CSE-induced Runx2 acetylation and Runx2-CDK8 axis activation. In vivo experiment further confirmed NR supplementation evidently mitigated cigarette smoke-induced a COPD-like phenotype in mice. CONCLUSIONS: These results indicated that Sirt3 depletion-induced Runx2 acetylation contributes to CDK8 activation and pulmonary inflammation in the progression of COPD.