Curcumin for propranolol-induced psoriasis-like lesions in guinea pigs: evaluation of therapeutic efficacy and effects on proliferating cell nuclear antigen expression

Abstract

Objective To estimate the influence of curcumin on psoriasis-like lesions and proliferating cell nuclear antigen（PCNA）expression in guinea pigs, so as to investigate the therapeutic effect and mechanism of curcumin in psoriasis. Methods A model of psoriasis-like skin inflammation was established by applying propranolol 5% cream（4 times a day for 3 weeks）to the dorsal skin of ears of 30 guinea pigs , which were then equally classified into 5 groups: model group receiving no treatment, observation group receiving no treatment but observation for 2 weeks, model control group treated with intragastric 25% polyethylene glycol solution（1 ml once a day）for 2 weeks, low-dose and high-dose curcumin groups treated with intragastric curcumin solution at 20 and 40 mg/kg per day respectively once a day for 2 weeks. Six guinea pigs receiving neither induction by propranolol nor treatment by curcumin or polyethylene glycol solution served as the normal control group. Skin specimens were harvested from the ears of guinea pigs in the normal control group after three weeks of breeding, in the model group immediately after the establishment of psoriasis-like model, in the observation group after 2 weeks of observation, and in the other 3 groups after 2 weeks of treatment. Subsequently, haematoxylin-eosin（HE）staining was conducted to observe histopathologic changes, and immunohistochemical assay to detect the expression of proliferating cell nuclear antigen（PCNA）. Results Gross observation of the skin revealed that curcumin attenuated psoriasis-like skin manifestations in guinea pigs. There were significant differences in histopathologic scores（F = 296.14, P < 0.01）and PCNA expression rate among the 6 groups（F= 108.49, P < 0.01）. Least significant difference（LSD）test showed that both histopathologic scores and PCNA expression rate were significantly higher in the model group than in the normal control group（6.42 ± 0.49 vs. 0.92 ± 0.20, 63.17% ± 5.47% vs. 20.83% ± 2.99%, both P < 0.01）. After 2 weeks of treatment, both low-dose and high-dose curcumin groups showed significantly lower histopathologic scores（4.25 ± 0.27 and 1.75 ± 0.42 vs. 6.42 ± 0.49, both P < 0.01）and PCNA expression rate（43.50% ± 2.90% and 25.50% ± 3.74% vs. 63.17% ± 5.47%, both P < 0.01）compared with the model group. Conclusion Curcumin can attenuate pathological manifestations of psoriasis-like lesions, and downregulate PCNA expression in guinea pigs. Key words: Psoriasis; Curcumin; Disease models, animal; Proliferating cell nuclear antigen; Propranolol