Abstract:

Objective To study the protective mechanism of astragaloside on skin photoaging. Methods　BALB/c mice were randomly divided into four groups: model group irradiated with ultraviolet rays （UV）, model plus matrix group pretreated with the matrix before UV irradiation, model plus astragaloside group pretreated with astragaloside 0.08% cream before UV irradiation, normal control group received no irradiation or pretreatment. After 4-week irradiation, the mice were sacrificed, and skin tissues were resected from the back of these mice. Then, reverse transeription PCR （RT-PCR） and immunohistochemistry were performed to detect the mRNA and protein expression of TGF-βRⅡ and Smad 7, respectively. Gray scale ratio was used to represent the mRNA levels of TGF-βRⅡ and Smad 7. Results There was a significant difference in the mRNA level （F = 80.98, 736.80, respectively, both P < 0.01） and protein positivity rate （F = 45.36,132.25, respectively, both P < 0.01） of TGF-βRⅡand Smad 7 among the 4 groups. The mRNA level and protein positivity rate of TGF-βRⅡwere 0.2588±0.0283 and （28.20 ± 5.24）% respectively in the model group, significantly lower than those in the normal control group［0.5688 ± 0.0439, （53.00 ± 4.72）%, both P < 0.01］ and model plus astragaloside group ［0.3767 ± 0.0374, （41.64 ± 2.59）%, both P < 0.01］; on the contrary, the mRNA level and protein positivity rate of Smad 7 in the model group ［0.8637 ± 0.0514, （82.06 ± 2.18）%］ were significantly higher than those in the normal control group ［0.5900 ± 0.0585, （47.50±3.81）%, both P < 0.01］ and model plus astragaloside group ［0.7131 ± 0.0410, （64.36 ± 2.62）%, both P < 0.01］. In the model plus astragaloside group, the mRNA level and protein positivity rate of TGF-βRⅡ were significantly higher than in the model plus matrix group ［0.2653 ± 0.0456, （28.74 ± 2.28）%, both P < 0.01］, while those of Smad 7 were statistically lower than in the model plus matrix group ［0.8553 ± 0.0575, （82.62 ± 4.02）%, both P < 0.01］. However, no significant difference was observed in the mRNA level or protein positivity rate of TGF-βRⅡ or Smad 7 between the model group and model plus matrix group （all P > 0.01）. Conclusion Astragaloside can prevent skin photoaging by the alteration of TGF-β pathway via up-regulating TGF-βRⅡexpression and down-regulating Smad 7 expression.

Key words: Signal transduction