Anti-psoriatic effects of indigo naturalis on the proliferation and differentiation of keratinocytes with indirubin as the active component.
BACKGROUND
Indigo naturalis has shown efficacy in treating psoriasis in our previous clinical studies.


OBJECTIVE
To investigate the potential effect of indigo naturalis on regulating keratinocyte proliferation and differentiation.


METHODS
Skin samples from six patients were analyzed for proliferating cell nuclear antigen (PCNA) and involucrin expression by immunohistochemical staining. In addition, indigo naturalis extracts from 10 to 500 microg/ml were added to cultured keratinocytes and cell viability determined. Real-time RT-PCR, Western blotting analysis and indirect immunofluorescent labeling were used to investigate the messenger (m)RNA and protein expressions of PCNA and involucrin. Finally, high-performance liquid chromatography (HPLC) was used to identify major components of indigo naturalis and their in vitro effects compared.


RESULTS
Immunohistochemical results demonstrated decreased PCNA and increased involucrin in psoriatic lesions after indigo naturalis treatment. Cultured keratinocytes decreased after indigo naturalis treatment, while G(0)/G(1) arrest was observed to dose-dependently increase. Staining revealed decreased PCNA-stained nuclei and increased cytosolic involucrin in treated keratinocytes. Decreased PCNA and increased involucrin at both the mRNA and protein levels were confirmed. Both major components, indirubin and indigo, could cause G(0)/G(1) phase arrest; however, only indirubin modulated the expressions of PCNA and involucrin similar to indigo naturalis.


CONCLUSIONS
Together, these findings indicate that the anti-psoriatic effects of indigo naturalis are mediated, at least in part, by modulating the proliferation and differentiation of keratinocytes, with indirubin as the major active component.
Lin
Yin-Ku
YK
Department of Traditional Chinese Medicine, Center for Traditional Chinese Medicine, Chang Gung Memorial Hospital, Taoyuan, Taiwan.
Leu
Yann-Lii
YL
Yang
Sien-Hung
SH
Chen
Hsiao-Wen
HW
Wang
Chin-Ting
CT
Pang
Jong-Hwei Su
JH
D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D003879:Dermatologic Agents / Q000494:pharmacology / Q000627:therapeutic use*; D015536:Down-Regulation / Q000235:genetics / Q000502:physiology; D015870:Gene Expression / Q000235:genetics / Q000502:physiology; D006801:Humans; D007203:Indigo Carmine; D029883:Indigofera / Q000737:chemistry*; D007211:Indoles / Q000494:pharmacology / Q000627:therapeutic use*; D015603:Keratinocytes / Q000187:drug effects* / Q000378:metabolism; D008517:Phytotherapy; D010936:Plant Extracts / Q000494:pharmacology / Q000627:therapeutic use; D018809:Proliferating Cell Nuclear Antigen / Q000187:drug effects / Q000378:metabolism; D011498:Protein Precursors / Q000819:agonists / Q000378:metabolism; D011565:Psoriasis / Q000188:drug therapy* / Q000473:pathology
D003879:Dermatologic Agents; D007211:Indoles; D010936:Plant Extracts; D018809:Proliferating Cell Nuclear Antigen; D011498:Protein Precursors; C032253:involucrin; D007203:Indigo Carmine; C027185:indirubin