Psoriasis is a common
dermatosis causing considerable inconvenience to 4% of the general population. Traditional
psoriasis treatments often cause
side effects, drug resistance and complications, necessitating development of safer and more effective treatments. In this study, we screened over 600 natural compounds to identify viability inhibitors of human HaCaT keratinocytes cultured in vitro. The results showed that
nitidine chloride was a highly effective inhibitor. Further studies revealed that
nitidine chloride inhibited HaCaT proliferation and induced S phase cell cycle arrest; these effects were associated with reduced
DNA synthesis, decreased Ki67,
cyclin A, and
cyclin D1 levels, and increased p53
protein expression.
Nitidine chloride also significantly downregulated bcl-2 and upregulated bax, cleaved
caspase-9 and cleaved
caspase-3. Mechanistic studies revealed that
nitidine chloride-induced apoptosis involved the
c-Jun N-terminal kinase (JNK) pathway. More importantly, in 12-O-tetradecanoyl-phorbol-13-acetate (TPA)- and
imiquimod (IMQ)-induced epidermal
hyperplasia and
inflammation models,
nitidine chloride inhibited topical
edema in mouse ear and back skin, substantially reducing tissue thickness and weight. In some cases,
nitidine chloride also ameliorated conditions caused by TPA and IMQ, such as angiogenesis and infiltration of large numbers of inflammatory cells around blood vessels. Additionally,
nitidine chloride inhibited the expression of various proinflammatory
cytokines in the two animal models. In conclusion, our results are the first to demonstrate that
nitidine chloride inhibits the proliferation of HaCaT cells, induces apoptosis partly via the JNK signaling pathway in vitro and ameliorates skin lesions and
inflammation in vivo, making it an appropriate candidate for
psoriasis treatment.