Transcriptome analysis in HepG2 cells revealed multiple activity mechanisms of a Tibetan polyherbal formula

Background: Transcriptome analysis in combination with pathway-focused bioassays is considered as a helpful approach to gain deeper insight into the complex mechanisms of action of multicomponent herbal preparations in living cells. Tibetan medicine relies on the concept of polyherbalism, however, it is difficult to explain multifactorial molecular signatures. Therefore, a polyherbal Tibetan preparation, that has been approved by the Swiss drug authorities (Padma 28, Swissmedic Nr.58436), was applied to a more detailed dissection of mechanism of action in human hepatoma HepG2 cells.

Methods: Cell-free as well as cell-based assays were used to evaluate the antioxidant capacity, and genome-wide expression profiling was applied to identify differenzially expressed genes. Pathway- and network-oriented analysis was used to elucidate the affected biological processes. The obtained results were validated using reporter gene assays and quantitative real-time PCR.

Results: Direct radical scavenging effects could be confirmed for an aqueous-ethanolic extract of the Tibetan formula by an in vitro oxygen radical absorbance capacity assay and by the potential to decrease peroxyd-radical induced formation of intracellular reactive oxygen species in HepG2 cells. Integrated transcriptome analysis revealed a major influence on detoxification and oxidative stress response. In addition, the expression of cytoprotective genes such as heme oxygenase 1 (HO-1) was induced.

Conclusions: Although extrapolation of these findings obtained in HepG2 cells to the in vivo situation is not directly possible, the study demonstrates the potential of the combination of focused and unbiased research strategies in the mode of action analysis of multicomponent herbal mixtures.