Effects of Betulinic Acid on the Proliferation, Cellular Senescence, and Type 1 Interferon-Related Signaling Pathways in Human Dermal Fibroblasts.

Pentacyclic triterpenoids, including betulinic acid (BA), and their glycosides are abundant in fruits such as Zizyphus sp., Dillenia sp., and Azanza sp. These compounds exhibit various pharmacological activities in human cells. Here, we investigated the effects of BA on the cellular proliferation and senescence of cultured normal human dermal fibroblasts (NHDFs). BA treatment for 24-48 h increased the proliferation of low-passage young fibroblasts. Furthermore, BA reduced the proportion of senescent cells, as determined via the ß-galactosidase assay of high-passage NHDFs. DNA microarray analysis and subsequent validations via quantitative real-time polymerase chain reaction revealed that BA downregulates interferon (IFN)-inducible genes, including IFIT1, IFITM1, IFI6, MX1, and OAS2, which are upregulated in replicative senescent cells compared with the low-passage young cells (control). Enrichment analysis based on the microarray data predicted BA-induced suppression of the type I IFN signaling pathway. BA downregulated the expression of the IRF9 transcriptional factor downstream of the type 1 IFN signaling pathway. IFN-inducible genes were downregulated via IRF9 silencing using siRNA compared with the negative control treated with siRNA. Consistently, BA treatment reduced the proportion of senescent cells and IFN-inducible genes in etoposide-treated fibroblasts. Hence, BA alleviates cellular senescence via the inhibition of the type 1 IFN signaling pathway in dermal fibroblasts.

Puerarin blocks the aging phenotype in human dermal fibroblasts.

Dermal fibroblast aging contributes to aging-associated functional defects in the skin since dermal fibroblasts maintain skin homeostasis by interacting with the epidermis and extracellular matrix. Here, we found that puerarin, an isoflavone present in Pueraria lobata (Kudzu), can prevent the development of the aging-phenotype in human dermal fibroblasts. Normal human dermal fibroblasts (NHDFs) were subcultivated and high-passage cells were selected as senescent cells, whereas low-passage cells were selected as a young cell control. Puerarin treatment increased cell proliferation and decreased the proportion of senescence-associated beta-galactosidase-positive cells in a high-passage culture of NHDFs. Moreover, puerarin treatment reduced the number of smooth muscle actin (SMA)-positive myofibroblasts and the expression of a reticular fibroblast marker, calponin 1 (CNN1), which were induced in high-passage NHDFs. Fulvestrant, an estrogen receptor antagonist, blocked the puerarin-mediated downregulation of SMA and CNN1. Our results suggest that puerarin may be a useful functional food that alleviates aging-related functional defects in dermal fibroblasts.