Date Published: June 20, 2014
Publisher: Public Library of Science
Author(s): Jia-an Zhang, Zhi Yin, Li-wen Ma, Zhi-qiang Yin, Yan-yan Hu, Yang Xu, Di Wu, Felicia Permatasari, Dan Luo, Bing-rong Zhou, Dhyan Chandra.
This study was aimed to evaluate the anti-photoaging effects of baicalin on Ultraviolet B (UVB)-induced photoaging in the dorsal skin of hairless mice and premature senescence in human dermal fibroblasts.
We established in vivo and in vitro photoaging models by repeated exposures to UVB irradiation. By HE staining, masson staining, immunohistostaing and real-time RT-PCR, we analyzed epidermal thickness, collagen expression and the mRNA and protein levels of type I collagen, type III collagen, interstitial collagenase (MMP-1 and MMP-3) in UVB exposed dorsal mice skin. The aging condition in human dermal fibroblasts was determined by senescence-associated β-galactosidase (SA-β-gal) staining. Cell viability was determined using the Cell Counting Kit-8 (CCK-8). The G1 phase cell growth arrest was analyzed by flow cytometry. The senescence-related protein levels of p16INK-4a, p21WAF-1, and p53 and protein levels of phosphorylated histone H2AX were estimated by Western blotting.
Topically application of baicalin treatment reduced UVB-induced epidermal thickening of mouse skin and also result in an increase in the production of collagen I and III, and a decrease in the expression of MMP-1 and MMP-3. Compared with the UVB-irradiated group, we found that the irradiated fibroblasts additionally treated with baicalin demonstrated a decrease in the expression of SA-β-gal, a increase in the cell viability, a decrease in the G1 phase cell proportion, a downregulation in the level of senescence-associated and γ-H2AX proteins. However, Baicalin had no difference in the normal fibroblasts without UVB irradiation and long-term Baicalin incubation of UVB-SIPS fibroblasts gave no effects on the cell proliferation.
Taken together, these results suggest that baicalin significantly antagonizes photoaging induced by UVB in vivo and in vitro, indicating the potential of baicalin application for anti-photoaging treatment.
Skin aging involves intrinsic and extrinsic processes. Environmental factors, primarily ultraviolet (UV) light, cause extrinsic skin aging. Although there are various etiologies of skin photoaging, common points include less dermal type I and III collagen expression . The predominant form of collagen in dermis is type I, followed by small amounts of type III . Type I collagen is characterized by thick fiber that confer stiffness and resistance to perform a crucial function in maintaining the structure of dermis. Whereas collagen type III is characterized by thin fiber that present the resiliency of skin. Collagen fibers arrange parallel to skin surface and are responsible for the high tensile strength and resiliency of skin. The degradation of type I and III fibrillar collagens is initiated by matrix metalloproteinases-1 (MMP-1) and MMP-3 respectively, which belongs to the matrix metalloproteinases (MMPs), a large family of zinc-dependent endo-proteases with a broad range of substrate specificities and the capacity of degrading all extracellular matrix proteins. Fibroblasts regulate production and degradation of the extracellular matrix and make multiple cytokines and glycoproteins. Fibroblasts exposed to UV reduce collagen by both promoting its degradation and interfering with its production . Other studies have reported early senescent changes that were confirmed by measuring β-galactosidase activity, p53, p21 and p16 expressions were detected when human fibroblasts were exposed properly to UVB . In previous reports, fibroblasts could be photoaged by UVB in vitro and in vivo and these experimental models were proven to be applicable in various skin aging studies , , , .
One promising strategy for the prevention of photoaging is the targeting and suppression of collagen degradation using natural phytochemicals. As natural products, these phytochemicals most likely are relatively harmless and possess a variety of beneficial properties. The antioxidant and anti-photodamage properties of baicalin, a naturally occurring flavonoid, have been the subject of much study , , , . However, the specific therapeutic properties and actions of baicalin in the prevention of photoaging are unknown. In the present study, we investigated the potential anti-photoaging effects of baicalin on UVB-exposed mouse dorsal skin and human dermal fibroblasts.