Dietary tannic acid attenuates elastase-induced pulmonary inflammation and emphysema in mice

Emphysema is one of the major components of chronic obstructive pulmonary disease (COPD), which is characterised by the destruction and enlargement of air spaces, leading to airflow limitation and dyspnoea, finally progressing to oxygen dependency. The alveolar wall destruction is due to chronic inflammation, oxidative stress, apoptosis, and proteinase/anti-proteinase imbalance. So far, there has been no effective therapy for patients with COPD. We evaluated the therapeutic efficacy of tannic acid (TA), a naturally occurring plant-derived polyphenol in the murine emphysema model. In C57BL/6 J mice, we established emphysema by intratracheal instillation of elastase (EL). Then, mice were treated with TA and evaluated 1 and 21 days post-EL instillation. After 24 h, TA treatment significantly reduced EL-induced histopathological alterations, infiltrating leukocytes, and gene expression of markers of inflammation and apoptosis. Similarly, after 21 days, TA treatment suppressed the mean linear intercept, gene expression of proteinases, and increased elastic fiber contents in the lungs when compared to the EL-alone group. Furthermore, EL induced the activation of p38 mitogen-activated protein kinase (MAPK) and nuclear factor kappa light chain enhancer of activated B cells (NF-kB) p65 pathways in the lungs was suppressed by TA treatment. In summary, TA has the potential to mitigate EL-induced inflammation, apoptosis, proteinase/anti-proteinase imbalance, and subsequent emphysema in mice.