OBJECTIVETo observe the reconstruction features of adventitia in senescent rats, and to explore the intervention mechanism of Chinese herbs (CH, extracts from Radix Ginseng, Radix Notoginseng, and Rhizoma Chuanxiong).

METHODSTotally 85 20-month senescent rats were randomly divided into 5 groups according to body weight, i.e., the aging model group, the high dose CH group, the middle dose CH group, the low dose CH group, the Losartan group, 17 in each group. Another 14 2-month old Wistar rats were selected as a young group. Extracts of CH at the daily dose of 1493. 4, 746. 7, and 373. 4 mg/kg were administered to rats in the 3 CH groups respectively by gastrogavage. Losartan suspension at the daily dose of 10 mg/kg was administered to rats in the Losartan group by gastrogavage. Equal volume of distilled water was administered to rats in the aging model group and the young group. All medication was performed once daily. After 15-week intervention, morphological changes of thoracic aorta were observed by HE staining. The types, distribution, and contents of vessel wall collagens were determined using picric acid picrosirius red staining. The plasma renin activity (PRA) , the concentration of rennin angiotensin II (Ang II), and the content of Ang II in adventitia were detected by radioimmunoassay. The content of hydroxyproline ( Hyp) was detected by biochemical analysis. mRNA contents and protein expressions of angiotensin II receptor 1 (AT1R) and angiotensin II receptor 2 (AT2R) were detected by real-time PCR (RT-PCR) and Western blot.

RESULTSCompared with the young group, thickened adventitia, increased adventitia thickness/caliber, accumulated collagen fiber, increased area of type I collagen, decreased area of type III collagen, decreased type III/I collagen area ratio (P <0. 05), decreased plasma PRA and Ang II (P < 0.01, P < 0.05), increased contents of Ang II and Hyp in adventitia, down-regulated mRNA and protein expressions of AT1R, and up-regulated mRNA and protein expression of AT2R could be seen in the aging model group (P < 0.05). Compared with the aging model group, morphological changes could be improved in the 3 CH groups. Adventitia thickness/caliber was reduced in middle and high dose CH groups, as well as the Losartan group. The area of type I collagen was reduced and the area of type III collagen was enlarged, type III/I collagen area ratio obviously increased, contents of adventitia Hyp was obviously lowered in the high dose CH groups and the Losartan group (P < 0.05, P < 0.01). Ang II levels in adventitia decreased in middle and high dose CH groups and the Losartan group (P < 0.05, P < 0.01). There was no statistical difference in PAR among all groups (P > 0.05). Compared with the aging model group, mRNA expression of AT1R all increased in each treatment group (P < 0.01); mRNA expression of AT2R also increased in middle and high dose CH groups (P < 0.05). Protein expression of AT1R increased in the high dose CH group and the Losartan group (P < 0.01, P < 0.05); protein expression of AT2R also increased in middle and high dose CH groups (P < 0.05).

CONCLUSIONSAdventitia remodeling occurred in aged rats, manifested as thickened adventitia and accumulated collagens, disordered ratios of collagen I and III. Its mechanism might be possibly associated with aactivation of renin-angiotensin system (RAS). Extracts from Radix Ginseng, Radix Notoginseng, and Rhizoma Chuanxiong could improve adventitial remodeling possibly by interfering multi-targets, such as Ang II and AT1R, thereby delaying vascular aging.