Effect of Topical Application of Black Seed Oil on Imiquimod‐Induced Psoriasis‐like Lesions in the Thin Skin of Adult Male Albino Rats

Psoriasis is a chronic inflammatory skin disease that affects about 1%-3% of the world's population. Black seed oil, i.e., the oil extracted from black seeds (Nigella sativa seeds), possesses a broad spectrum of pharmacological actions including anti-inflammatory, immunostimulatory, and antioxidant properties. This study aimed to investigate the effect of black seed oil on imiquimod (IMQ) induced psoriasis-like skin lesions. To this end, 30 male albino rats were divided into three groups: group I, control group; group II, psoriasis-induced group receiving daily topical applications of IMQ cream (5%) on the shaved back skin for 10 consecutive days; and group III, black seed oil group receiving a daily topical dose of black seed oil 5 mg/kg body weight for 10 days after induction of psoriasis. Animals of all groups were sacrificed and specimens obtained from the skin of the central part of the back were processed for histological and immunohistochemical staining with proliferating cell nuclear antigen (PCNA). IMQ application led to epidermal inflammation, hyperplasia and alterations in the normal appearance of keratinocytes with degenerative changes observed at both light and electron microscopic levels. Collagenous fibers were abundant in the dermis and PCNA-positive cells were detected in all layers of the epidermis. However, topical use of black seed oil strongly inhibited IMQ-induced psoriasis-like inflammation and alleviated all epidermal and dermal changes observed after IMQ application, allowing us to conclude that black seed oil can be used as an adjuvant topical therapy for treating psoriasis. Anat Rec, 2017. © 2017 Wiley Periodicals, Inc. Anat Rec, 301:166-174, 2018. © 2017 Wiley Periodicals, Inc.