Significance and effects of emodin hypo-acid on regulating nitricoxide synthase of melanocyte in skin

Guishu ZHONG; Jiyan CHENG; Liao LI; Deyu CHEN

ABSTRACT

BACKGROUND:

Among multiple signals which affect the function of melanocyte, nitrogen monoxide (NO) has been thought as an important signal molecule. Emodin hypo-acid, effective component of rhubarb, can affect proliferation of melanocyte and regulate activity of tyrosinase in cells.

OBJECTIVE:

To study the effect of emodin hypo-acid on expression of nitricoxide synthase (NOS) of melanocyte in skin of guinea pig and definite the effective concentrations and mechanism of melanocyte in synthesizing melanin in living skin.

DESIGN:

Completely randomized grouping design and controlled study.

SETTING:

Department of Dermatology, Affiliated Hospital of Luzhou Medical College.MATERIALS The experiment was completed at the Infection Laboratory of Affiliated Hospital of Luzhou Medical College and Laboratory of Histology and Embryology of Luzhou Medical College from January to June 2004. A total of 24 adult healthy male guinea pigs were randomly divided into 6 groups control group, 2, 5, 10, 20 and 40 mg/L emodin hypo-acid groups with 4 in each group.

METHODS:

① Emodin hypo-acid was diluted with dimethyl-sulfoxide into 2, 5, 10, 20 and 40 mg/L, then guinea pigs in emodin hypo-acid groups were injected subcutaneously with relevant dosages of emodin hypoacid which was provided by National Institute for the Control of Pharmaceutical and Biological Products into local skins of haunch and back, and the injected volume was 1 mL. Twenty-four hours later, 1 mL emodin hypo-acid of the same concentration was injected once again into one of the places which was injected before. Skin samples were selected after 48 hours and routine paraffin section was made. Skins which were not injected with any drugs were selected from control group and emodin hypoacid groups to regard as experimental control group. ② Expression of NOS was assayed with immunohistochemical method and melanocyte was identified under high-times optic microscope to observe stain and characteristic of cytoplasm. Five sections were randomly selected from each group. Every 20 cells on each section were measured with MLAS-1000 imaging analyzer and computer processing system was used to calculate average absorbency (A) of positive immune product in melanocyte. ③ Measurement data were compared with analysis of variance, and differences among groups were compared with SNK-q.MAIN OUTCOME

MEASURES:

Expression of NOS in melanocyte was assayed with immunohistochemical method and results were obtained with optic microscope and imaging analyzer.

RESULTS:

Average A value of positive immune product in melanocyte was lower in 2, 5, 10, 20 and 40 mg/L emodin hypo-acid groups than that in experimental control group (0.126±0.118, 0.103±0.082, 0.118±0.097,0.122±0.095, 0.112±0.078, 0.196±0.066, P ＜ 0.05). There was no significant difference among emodin hypo-acid groups at various concentrations.

CONCLUSION:

① Emodin hypo-acid can regulate expression of NOS in melanocyte through NO signal transduction pathway. ② Expression of NOS is not changed as the mass concentration of emodin hypo-acid varied from 2 to 40 mg/L.