IL-6 and IL-22 were from R&D Systems (Minneapolis, MN, USA). IMQ-induced psoriasis-like skin inflammation in mice Female BALB/c mice (8C11 weeks; 20C25?g) were obtained from Vital River Laboratory Animal Technology Co. in psoriatic lesions and it could be induced CID-2858522 by IL-22/STAT3 signaling, a key signaling pathway involved in the pathogenesis of psoriasis, in keratinocytes. Depletion of CDC6 leads to Mouse monoclonal to PRAK decreased proliferation of keratinocytes. We also revealed that berberine (BBR) could inhibit CDK4/6-RB-CDC6 signaling in keratinocytes, leading to reduced proliferation of keratinocytes. The mechanism of antiproliferation effects of BBR is through the repression of JAK1, JAK2, and TYK2, which in turn inhibits activation of STAT3. Finally, we demonstrated that BBR could inhibit imiquimod-induced psoriasis-like skin lesions and upregulation of CDC6 and p-STAT3 in mice. Collectively, our findings indicate that BBR inhibits CDC6 expression and proliferation in human keratinocytes by interfering the JAKCSTAT3 signaling pathway. Thus, BBR may serve as a potential therapeutic option for patients with psoriasis. Introduction Psoriasis is a common chronic, recurring, and immune-mediated inflammatory skin disease, with a worldwide incidence of ~0.09C5.1% and seriously impairs the life quality of the patients1C3. A dysregulated crosstalk between epidermal keratinocytes and immune cells leads to inflammation, abnormal proliferation, and differentiation of keratinocytes, a hallmark of psoriasis4C8. The immune cells, which were mainly dendritic cells and T cells, infiltrating the skin lesions produce a large variety of cytokines such as interleukin (IL)-17, IL-22, IL-23, and IFN- that stimulate CID-2858522 keratinocytes. On the other hand, activated keratinocytes can release numerous proinflammatory cytokines (e.g., IL-1, IL-18, TNF-), chemokines, and antimicrobial peptides (AMPs) that can sustain psoriatic lesions5C7. Therefore, keratinocytes not only respond to psoriatic inflammation but also contribute to the recruitment and activation of immune cells. Thus, targeting keratinocyte proliferation and inflammation pathways can be used as effective therapies against psoriasis. However, the underlying mechanisms regulating these keratinocyte hyperproliferation remain largely elusive. Although the molecular mechanisms involved in the pathogenesis of psoriasis are complex, growing evidence suggests that the activator of transcriptions 1 and 3 (STAT1 and STAT3), and nuclear factor-B (NF-B) is pivotal in the transcriptome network involved in the mechanism of psoriasis. STAT3 is an essential player to be responsible for the antibacterial/fungal type 3 (Th17) immune response and is considered to function as a central player in psoriasis pathogenesis9,10. STAT3 was reported to be active in psoriatic lesions, and suppression of STAT3 could inhibit proliferation and induce apoptosis of psoriatic keratinocytes11. CID-2858522 In particular, expression of constitutively CID-2858522 active STAT3 (STAT3C) in keratinocytes leads to the spontaneous development of psoriasis in transgenic mice12,13. Therefore, the targeting STAT3 pathway has been a promising target for the development of psoriasis therapies. Indeed, it was reported that STAT3 inhibitor not only inhibited the development of psoriasiform lesions in K5.Stat3C mice but also improved psoriatic lesions in psoriasis patients14. CDC6 protein serves as one of the key regulators in DNA replication15,16. Interestingly, the recently published studies showed that CDC6 is also required for proper centrosome duplication17,18. Therefore, CDC6 is important for cell proliferation and is considered to be a specific biomarker of proliferating cells. CDC6 has been shown to be upregulated in tumors and associated with the progression and prognosis in various cancers19,20. However, the role of CDC6 in keratinocytes and psoriasis is unknown. Currently, drug treatments such as retinoids, corticosteroids, and Vit D remain the main option for most psoriasis patients4. However, the efficacy of conventional drugs is limited because of adverse side effects and the development of pharmacoresistance21. Natural products are valuable sources in novel drug development. Berberine (BBR), a plant alkaloid, has been used for treating diarrhea and gastrointestinal disorders, particularly bacterial diarrhea, for thousands of years22. Clinical investigations on BBR revealed that it possesses various pharmacological effects, including antihyperglycemic, anticancer, and antidepressant23. However, the effect and molecular mechanisms of BBR in epidermal hyperplasia in psoriasis CID-2858522 are unknown. In the present study, we examined the expression of CDC6 in lesional skin of psoriasis and investigated its roles in keratinocytes. Our data indicated that CDC6, induced by STAT3 activation in keratinocytes, is upregulated in psoriatic epidermal skin and contributes to proliferation of keratinocytes. Moreover, BBR significantly inhibits CDK4/6-RB-CDC6 signaling, leading to cell cycle arrest and apoptosis in keratinocytes. We further found that BBR exerted its antiproliferation effects through inhibiting the JAK-STAT3 pathway. Importantly, BBR could inhibit the development of imiquimod-induced psoriasiform lesions and STAT3 activation in mice. These findings may have implications in designing therapeutic.