A Study On The Time-Dependent Expression Of Caspase-8in Acute β-irradiated Skin Injury In Rats

Objectives: To investigate the dynamic expression of caspase-8 in acuteβ-irradiation-induced skin ulcers, and to explore the underlying mechanism involved in the retarded wound healing of the ulcer.Methods: 54 female SD rats were divided into 3 groups. Irradiation group, n=24, we established the model of acuteβ-irradiation-induced skin ulcers in rats with the application of 45 Gy electron acceleratorβ-ray to the skin on the buttock of rats; The incision group,n=24, a 15-mm-long incision was made in the skin layer on the central back under sterile condition after the rats were anesthetized by chloral 10%hydrate; The control group, n=6, normal rats were served as control. From different periods skin wounds, the expression of caspase-8 in the wound were respectively assessed by means of immunohistochemical technique and western blot analysis.Results:①The skin on the rats buttock which had been irradiated byβ-ray began to shed in 2 weeks, irritation and blisters appeared in 3 weeks, ulcers formed in 4 weeks and gradually increased in size. The wound would be stable in 5 weeks. The wound of incision group showed normal healing process.②Immunohistochemistry examination showed that the caspase-8 expression was in the epidermis,hair follicles,sebaceous glands and sweat glands. The caspase-8 was stained brown with DAB. 0-3 weeks after wound emerged, the caspase-8 integral absorbance (IA) in the radiation group was much higher than the incision group. 2 week after irradiation the level of caspase-8 expression was the highest. There was significant statistic difference between the two groups(p <0.05).③The western blot showed that 0-3 weeks after wound emerging, the optical density ratio value of caspase-8 active fragments was significantly higher than the incision group. There was statistical difference between the two groups(p <0.05).④The expression of caspase-8 increased evidently with the increment of apoptosis, and it showed a good correlation with apoptosis in the process of wound healing.Conclusions:①It was shown that apoptosis manifested in two typical characteristics, they were high rate and delayed disappearance afterβ-ray irradiation, which might explain the delayed wound healing.②Caspase-8 may play an important role in the regulation of apoptosis and delayed wound healing of acuteβ-irradiation skin injury.③We could estimate theβ-ray irradiation skin injury healing time according to the expression of caspase-8, and arrange clinical treatment properly.