Indirubin is a potent inhibitor of cyclin-dependent kinases (CDKs) (IC50: 50-100nmol/L) and glycogen synthase kinase-3beta (GSK-3β) (IC50: 5-50nmol/L), with oral administration characteristics[1]. Indirubin serves as the primary active ingredient within the traditional Chinese medicine Indigo naturalis and belongs to the bisindole alkaloid category[2]. Indirubin shows promise as a medical treatment against tumors along with inflammatory conditions and neuropathic disorders and is effective against bacterial infections[3].
In vitro, Indirubin showed an IC50 of 12.5μmol/L in glioma U87 and U118 cells for cell proliferation inhibition, and the IC50 in normal astrocytes was 100μmol/L[2]. Indirubin (10μmol/L) activated AhR signaling and inhibited tumor cell proliferation and invasion in clear renal cell carcinoma and osteoma for 24h[4]. Indirubin binds to ATP sites through competitive interactions and suppresses the functions of CDK1/cyclin B, CDK2/cyclin A and CDK2/cyclin E in starfish oocytes at 100μmol/L after 30h treatment[5]. Indirubin increased opsonized zymosan-induced superoxide production in human myelocytic leukaemia HL-60 cells at low concentrations ranging from 10nmol/L to 1μmol/L[6]. Indirubin (1μmol/L, 37 °C for 6 days) suppresses CDK2 expression and Rb protein phosphorylation in HL-60 myeloid leukemia cells while triggering interleukin-8 (IL-8) activity to promote PU.1 activation and neutrophil differentiation[6]. Indirubin (1μmol/L) suppressed KBM-5 human chronic myeloid leukemia cell proliferation by reducing expression levels of NF-κB-dependent protein cyclin D1[6]. Indirubin (1μmol/L, 24h) significantly inhibited the phosphorylation of STAT3 in ovarian cancer cells, and cell apoptosis occurred after treatment of 1μmol/L Indirubin for 72h[7].
In vivo, Indirubin treatment (25-100μmol/L) inhibited the expression of IL-1β, IL-6, and TNF-α in the lipopolysaccharide (LPS)-stimulated mastitis mouse models in a dose-dependent manner[8]. Indirubin（100μmol/L）ameliorated the pathological changes induced by LPS and reduced neutrophils and macrophages in the alveolar space, resulting in a reduction in the thickness of the mammary bleb[8]. Inhibition of intersegmental blood vessel (ISV) formation in zebrafish embryos by treatment with indirubin at 100μmol/L for 24h[9]. Indirubin (100μmol/L) showed mild toxicity in zebrafish embryos[9]. Oral Indirubin (5-10mg/kg, 24h) significantly reduced the anxiety behavior of the male Swiss albino mice and exerted a sedative effect[10].
References:
[1] Leclerc S, Garnier M, Hoessel R, et al. Indirubins Inhibit Glycogen Synthase Kinase-3β and CDK5/P25, Two Protein Kinases Involved in Abnormal Tau Phosphorylation in Alzheimer's Disease: A PROPERTY COMMON TO MOST CYCLIN-DEPENDENT KINASE INHIBITORS?* 210[J]. Journal of Biological Chemistry, 2001, 276(1): 251-260.
[2]Yang L, Li X, Huang W, et al. Pharmacological properties of indirubin and its derivatives[J]. Biomedicine & Pharmacotherapy, 2022, 151: 113112.
[3] Ju Z, Sun J, Liu Y. Molecular structures and spectral properties of natural indigo and indirubin: Experimental and DFT studies[J]. Molecules, 2019, 24(21): 3831.
[4] Ishida M, Mikami S, Shinojima T, et al. Activation of aryl hydrocarbon receptor promotes invasion of clear cell renal cell carcinoma and is associated with poor prognosis and cigarette smoke[J]. International journal of cancer, 2015, 137(2): 299-310.
[5] Hoessel R, Leclerc S, Endicott J A, et al. Indirubin, the active constituent of a Chinese antileukaemia medicine, inhibits cyclin-dependent kinases[J]. Nature cell biology, 1999, 1(1): 60-67.
[6] Suzuki K, Adachi R, Hirayama A, et al. Indirubin, a Chinese anti‐leukaemia drug, promotes neutrophilic differentiation of human myelocytic leukaemia HL‐60 cells[J]. British journal of haematology, 2005, 130(5): 681-690.
[7] Chen L, Wang J, Wu J, et al. Indirubin suppresses ovarian cancer cell viabilities through the STAT3 signaling pathway[J]. Drug design, development and therapy, 2018: 3335-3342.
[8] Lai J, Liu Y, Liu C, et al. Indirubin inhibits LPS-induced inflammation via TLR4 abrogation mediated by the NF-kB and MAPK signaling pathways[J]. Inflammation, 2017, 40: 1-12.
[9] Alex D, Lam I K, Lin Z X, et al. Indirubin shows anti-angiogenic activity in an in vivo zebrafish model and an in vitro HUVEC model[J]. Journal of ethnopharmacology, 2010, 131(2): 242-247.
[10] Disha I J, Hasan R, Bhuia S, et al. Anxiolytic efficacy of Indirubin: in vivo approach along with receptor binding profiling and molecular interaction with GABAergic pathways[J]. ChemistryOpen, 2025, 14(2): e202400290.
Indirubin是强效的周期蛋白依赖性激酶（CDKs）（IC50：50-100nmol/L）和糖原合成酶激酶-3β（GSK-3β）（IC50：5-50nmol/L）抑制剂，具有口服给药特性[1]。Indirubin是中药青黛的主要活性成分，属于双吲哚类生物碱[2]。Indirubin在抗肿瘤、抗炎症及神经病变治疗领域展现出良好前景，同时具有抗细菌感染功效[3]。
在体外，Indirubin对胶质瘤细胞U87和U118的增殖抑制IC50为12.5μmol/L，而在正常星形胶质细胞中IC50达100μmol/L[2]。在透明细胞肾癌和骨瘤模型中，10μmol/L浓度的Indirubin作用24小时可激活AhR信号通路，同时抑制肿瘤细胞增殖与侵袭[4]。100μmol/L浓度的Indirubin处理海星卵母细胞30h后可通过竞争性结合ATP位点，有效抑制CDK1/cyclin B、CDK2/cyclin A 和CDK2/cyclin E的生物学功能[5]。在10nmol/L至1μmol/L的低浓度范围内，Indirubin可增强人髓系白血病HL-60细胞对酵母聚糖诱导的超氧化物生成[6]。Indirubin（1μmol/L，37℃，处理6天）抑制HL-60髓系白血病细胞CDK2表达和Rb蛋白磷酸化，同时激活白细胞介素-8 （IL-8）活性，以促进PU.1活化和中性粒细胞分化[6]。Indirubin（1μmol/L）能通过降低NF-κB依赖性蛋白Cyclin D1的表达，抑制KBM-5人慢性髓系白血病细胞增殖[6]。Indirubin（1μmol/L, 24h）显著抑制卵巢癌细胞STAT3的磷酸化，1μmol/L浓度的Indirubin处理卵巢癌细胞72h后，细胞发生凋亡[7]。
在体内，Indirubin（25-100μmol/L）能够以剂量依赖的方式抑制脂多糖（LPS）诱导的乳腺炎小鼠模型中 IL-1β、IL-6 和 TNF-α 的表达[8]。在100μmol/L浓度下，Indirubin可改善LPS引起的病理损伤，减少肺泡腔中的中性粒细胞和巨噬细胞浸润，降低乳腺泡壁厚度[8]。使用100μmol/L浓度的Indirubin处理斑马鱼胚胎24小时，可抑制斑马鱼胚胎的节间血管（ISV）的形成[9]，100μmol/L浓度的Indirubin对胚胎表现出轻度毒性[9]。口服Indirubin（5-10mg/kg, 24h）能显著缓解瑞士白化雄性小鼠的焦虑行为，发挥镇静作用[10]。