Kinase experiment:

GSK-3β is expressed in and purified from insect Sf9 cells. It is assayed, following a 1/100 dilution in 1 mg/mL BSA, 10 mM DTT, with 5 μL of 40 μM GS-1 peptide as a substrate, in buffer A, in the presence of 15 μM[γ-32P]ATP (3000 Ci/mmol; 1 mCi/mL) in a final volume of 30 μL. After 30-min incubation at 30℃, 25-μL aliquots of supernatant are spotted onto 2.5×3-cm pieces of Whatman P81 phosphocellulose paper, and, 20 s later, the filters are washed five times (for at least 5 min each time) in a solution of 10 mL of phosphoric acid/liter of water. The wet filters are counted in the presence of 1 mL of ACS scintillation fluid[1].

Cell experiment:

Cytotoxicity of Indirubin-3'-monoxime in monocytes is analysed by MTT assay in a 96-well format using a multi-well scanning spectrophotometer. Neutrophils (5×106 cells/mL) or monocytes (2×106 cells/mL) are incubated for 30 min with Indirubin-3'-monoxime, and the viability of the cells is analysed by MTT assay. Compared with vehicle (0.3% DMSO), no significant acute cytotoxicity is observed (neutrophils: 103.9±4.4%; monocytes: 129.4±5.4%; n=3, each)[3].

Animal experiment:

Male mice (5-6 weeks old) are randomLy assigned into five groups (n=10). Group 1: receive normal pellet diet (NPD); Group 2: receive a HFD; Group 3-5 receive HFD for 8 weeks followed by Indirubin-3'-monoxime treatment (0.1, 0.2 and 0.4 mg/kg i.p, respectively) once daily for 1 week. Indirubin-3'-monoxime is dissolved in (2.5% v/v) DMSO in saline. The mice in NPD and HFD groups receive an equivalent volume of vehicle (2.5% v/v DMSO in saline). Doses of Indirubin-3'-monoxime are selected. Mice are kept under standard husbandry conditions (22±1℃ and 60% humidity) and maintained on a 12/12-h light/dark schedule with free access to food and water for 8 weeks. Body weight is recorded weekly throughout the experimental period[2].

Indirubin-3'-monoxime is a potent GSK-3β inhibitor, and weakly inhibits 5-Lipoxygenase, with IC50s of 22 nM and 7.8-10 μM, respectively; Indirubin-3'-monoxime also shows inhibitory activities against CDK5/p25 and CDK1/cyclin B, with IC50s of 100 and 180 nM.
Indirubin-3'-monoxime inhibits GSK-3β by competing with ATP, with Ki of 0.85 μM, and Km of 110 μM. Indirubin-3'-monoxime also inhibits tau phosphorylation by GSK-3β, with an IC50 value of around 100 nM. Indirubin-3'-monoxime completely inhibits the phosphorylation of the AT100 epitope[1]. Indirubin-3'-monoxime inhibits vascular smooth muscle cell (VSMC) proliferation with IC50 of ~2 μM. Indirubin-3'-monoxime blunts migration of VSMC stimulated with the PDGF. Indirubin-3'-monoxime interferes with the migratory response in VSMC, and also suppresses the production of pro-migratory LT in monocytes. Moreover, Indirubin-3'-monoxime inhibits 5-lipoxygenase (5-LO) product synthesis in monocytes and neutrophils, with the same potency (IC50=5.0±1.1 and 3.7±1.2 μM, respectively). Indirubin-3'-monoxime is an inhibitor of 5-LO, with IC50 of 7.8-10 μM in cell-free assay[3].
Indirubin-3'-monoxime (0.1, 0.2 and 0.4 mg/kg, i.p) dose dependently reverses the cognitive impairment and combats the elevated oxidative stress markers in HFD fed mice. Indirubin-3'-monoxime also dose dependently lowers the serum glucose, TGs, TC and insulin levels, and improves the β-cell functioning in HFD fed mice. Moreover, Indirubin-3'-monoxime treatment significantly decreases HOMA-IR levels compared to HFD group. Indirubin-3'-monoxime (0.4 mg/kg) significantly attenuates the increased EL in the HFD group[2].
Reference:
[1]. Leclerc S, et al. Indirubins inhibit glycogen synthase kinase-3 beta and CDK5/p25, two protein kinases involved in abnormal tau phosphorylation in Alzheimer's disease. A property common to most cyclin-dependent kinase inhibitors? J Biol Chem. 2001 Jan 5;276(1):251-60.
[2]. Sharma S, et al. Neuroprotective role of Indirubin-3'-monoxime, a GSKβ inhibitor in high fat diet induced cognitive impairment in mice. Biochem Biophys Res Commun. 2014 Oct 3;452(4):1009-15.
[3]. Blazevic T, et al. Indirubin-3'-monoxime exerts a dual mode of inhibition towards leukotriene-mediated vascular smooth muscle cell migration. Cardiovasc Res. 2014 Mar 1;101(3):522-32.