Kinase experiment:

The cell based kinase assays for c-Jun and ATF2 phosphorylation carry out by using the LanthaScreen c-Jun (1-79) HeLa and LanthaScreen ATF2 (19-106) A549 cell lines which stably express GFP-c-Jun 1-79 and GFP-ATF2 19-106, respectively. Phosphorylation is determined by measuring the time resolved FRET (TR-FRET) between a terbium labeled phospho-specific antibody and the GFP-fusion protein. The cells are plated in white tissue culture treated 384 well plates at a density of 10,000 cell per well in 32 μl assay medium (supplemented with 1% charcoal/dextran-treated FBS, 100 U/mL Penicillin and 100 μg/mL Streptomycin, 0.1 mM nonessential amino acids, 1 mM sodium pyruvate, 25 mM Hepes, pH 7.3, and lacking phenol red). After overnight incubation, cells are pretreated for 60 min with BI-78D3 (0.001, 0.01, 0.1, 1, 10, and 100 μM) followed by 30 min of stimulation with 2 ng/mL of TNF-α that stimulates both JNK and p38. The medium is then removed by aspiration and the cells are lysed by adding 20 μL of lysis buffer (20 mM TrisoHCl, pH 7.6, 5 mM EDTA, 1% Nonidet P-40 substitute, 5 mM NaF, 150 mM NaCl, and 1:100 protease and phosphatase inhibitor mix, SIGMA P8340 and P2850, respectively). The lysis buffer includs 2 nM of the terbium-labeled anti-pc-Jun (pSer73) or anti-pATF2 (pThr71) detection antibodies. After allowing the assay to equilibrate for 1 h at room temperature, TR-FRET emission ratios are determined on a BMG Pherastar fluorescence plate reader (excitation at 340 nm, emission 520 nm and 490 nm; 100 μs lag time, 200 μs integration time, emission ratio=Em520/Em 490)[1].

Cell experiment:

Mice[1]ConA and BI-78D3 is injected i.v. at 10 mg/kg into 6 to 8 weeks old male BL/6 mice. For partial hepatectomy, mice are anesthetized with isofluorane and subjected to midventral laparotomy followed by removal of the left lateral and median lobes. Animals are killed, blood is collected by cardiac puncture, and livers are surgically removed. Serum is separated and analyzed for alanine-aminotranferase levels[1].Eleven-week-old male BKS.Cg-+Leprdb/+Leprdb/OlaHsd db/db mice are randomized based on blood glucose levels acclimated three days before drug dosing. Blood glucose is read by using a hand-held glucose meter (Mice are fasted 6 h before i.p. (i.p.) administration of 25 mg/kg BI-78D3. Thirty minutes after test article administration, Bovine Insulin (I-0516 at 0.75 mg/kg) is administered via i.p. injection. Blood samples are taken at designated time points and blood glucose levels are measured as described. Food is returned three hours after test article administration[1].

BI-78D3 is a substrate competitive inhibitor of JNK inhibitor [2].

JNK is a member of the MAPK family. JNK is a stress-activated protein kinase that modulates pathways implicated in a variety of disease states. Non-motoric JNK functions may differ between cell types and organs. The JNK is involved in a1-adrenoceptor-mediated contraction of prostate smooth muscle. For non-malignant, epithelial human prostate cells, JNK activation not only has the function of pro-apoptotic and antiproliferative but also related with JNK-dependent survival.[1]

BI-78D3 is competitive with ATF2 for binding to JNK1 with an apparent Ki value of 200 nM. In addition, it has been reported that BI-78D3 does not inhibit the phosphorylation of a short peptide substrate lacking a D-domain. This confirms that BI-78D3 is substrate competitive.[2]

BI-78D3 inhibits both noradrenaline- and phenylephrine-induced contractions. Then it prevents α1-adrenoceptor-mediated contraction of prostate tissue. As an effective JNK inhibitor, BI-78D3 has the ability of abrogating ConA-induced liver damage and restoring insulin sensitivity. [1,2]

References:
[1] Strittmatter F1, Walther S, Gratzke C, etal. , Inhibition of adrenergic human prostate smooth muscle contraction by the inhibitors of c-Jun N-terminal kinase, SP600125 and BI-78D3. Br J Pharmacol. 2012 Jul;166(6):1926-35.
[2] Stebbins JL, De SK, Machleidt T,etal.  , Identification of a new JNK inhibitor targeting the JNK-JIP interaction site. Proc Natl Acad Sci U S A. 2008 Oct 28;105(43):16809-13.