Aldehyde dehydrogenase3A1 (ALDH3A1) codes an enzyme that protects the airways from cigarette smoke-induced damage and cytotoxicity. Our previous study of COPD and non-COPD smokers showed that expression of this gene is significantly decreased after 1 year of smoking cessation. In contrast, periostin (POSTN) expression increased after smoking cessation. The latter is essential as periostin regulates airway ECM in lung tissue remodelling and repair.

The effects of ALDH3A1 on POSTN are unknown. We aimed to assess how changes in ALDH3A1 affect POSTN gene expression and the downstream impact on CSE-induced IL6-like cytokine production in airway epithelium.

The ALDH3A1 gene knockouts (KO) were generated using human airway epithelial cells (BEAS-2B). KO and wildtype (WT) cells were then exposed to 10% freshly prepared cigarette smoke extract (CSE) for 6 hrs, and RNA-Seq was performed (n=3). Gene expression differences between WT and KO were assessed at baseline and with CSE exposure with EdgeR and FDR <0.05, and fold change |1.5| defined statistical significance. Then, an ELISA assay quantified the IL6 level at baseline and after 24 hrs of 10% CSE exposure. A paired t-test was done between KO and WT to measure the CSE-induced changes in IL6 (n=7).

We found POSTN expression to be higher in ALDH3A1 KOs at baseline and after 10% CSE exposure. These baseline findings were further validated in A549 dataset which ALDH3A1 was knocked down using si-RNA. Moreover, we observed significantly increased IL6 levels in KO in baseline (P=0.0127) and after 10 % CSE exposure (P= 0.04).

These findings suggest that ALDH3A1 gene plays an important role in suppressing POSTN gene expression.