This study aims to dissect the mechanism of traditional Chinese medicinal herbs against asthma; we chose to first focus on the main chemical components of licorice to investigate their contribution to asthmatic inflammation inhibition.
Production of cellular nucleotide molecules such as cAMP, cGMP, and cGAMP was examined by using enzyme-linked immunosorbent assay (ELISA). Enzyme-encoding genes were tested using quantitative real-time PCR and protein level was detected by Western blotting analysis. In addition, co-culturing of murine dendritic cells together with T cells was conducted to examine the expression of cytokine genes and host immune response.
We found that one of the components within licorice, named liquiritigenin (LR), could efficiently enhance cAMP production in different cell lines. The augmentation of such molecules was linked to the high expression of cAMP synthesis genes and repressed expression of cAMP breaking down genes. In addition, the downstream immune response was also alleviated by the increase in cAMP levels by LR, suggesting the great potential of this molecule against inflammation. Subsequent immunological tests showed that LR could efficiently inhibit the expression of several cytokines and alter the NF-κB pathway and T cell polarization.
Altogether, we have identified a promising antiasthmatic agent LR that could exhibit immunosuppressive function by elevating the cAMP level.