Cell culture
H9c2 (Rat embryonic cardiac myoblast) cell line (C585) obtained from National Cell Bank of Pasteur Institute of Iran. The cells were cultured in Dulbecco’s modified Eagle’s medium (DMEM) (Gibco-BRL, Rockville, IN) containing high level of glucose and 2 mM L-glutamine supplemented with penicillin-streptomycin (Gibco-BRL, Rockville, IN) and fetal bovine serum (FBS) (Gibco-BRL, Rockville, IN) at 37˚C in a humidified incubator with 5% CO2. Compounds A and B were reconstituted in Dimethyl sulfoxide (DMSO) and the final concentration of DMSO was 0.5%. Compounds A and B were synthesized by the Medicinal Chemistry Research Laboratory at the Faculty of Pharmacy, Tehran University of Medical Sciences. Cells without treatment were considered as negative control.
MTT assay
Cell viability was determined by MTT assay. H9c2 cells were plated in 96-well plates at 7000 cells/well for 24 hours and 5000 cells/well for 48 hours of treatment. Cells were exposed to different concentrations of compounds A and B to reach final concentration of 0.1-100 µM at 24 and 48 h. Afterwards, 20 µl of MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide,5 mg/mL) (Sigma-Aldrich, Saint Louis, Missouri, USA) was added for an additional 4 h. The medium was removed and 200 µl of DMSO was added to each well to dissolve formazan crystals. Finally, the absorbance was measured by microplate reader (Epoch2, Biotek, USA)at 545 nm.
Intracellular ROS determination
To determine the intracellular ROS, H9c2 cells were seeded in 6-well plates at a concentration of 25×104 cells per well for 24 h and 15×104 cells for 48 h of incubation. Cells were then treated with 10 and 50 µM of compounds A and B for 24 and 48 hours. Following incubation of cells with 10 µM of DCFH (Sigma-Aldrich, Saint Louis, Missouri, USA) at 37 ºC for 20 min, the cells were washed with PBS (Phosphate Buffered Saline) and then harvested to detect ROS level by flow cytometer.
Mitochondrial membrane potential assay
Mitochondrial dysfunction was assessed using mitochondrial membrane potential (ΔΨ m) assay. Briefly, H9c2 cells were plated in 6-well plates as described above and then trypsinized after treating with 10 and 50 µM of compounds A and B for 24 and 48 h. We used carbonyl 3-chlorophenylhydrazone (CCCP) as a standard control. After washing the cells with PBS, 0.5 ml of PBS buffer containing 10 µg/ml of JC-1 ( Mitoprobe JC1 assay kit, Life technologies, USA, M34152) was added to the suspend cells. Following 15-30 min of incubation at 37˚C, cells were centrifuged to discard the supernatant. Cell pellets were then re-suspended in PBS and analyzed by flow cytometry. A mitochondria-sensitive dye (JC-1) was used to monitor mitochondrial membrane potential alterations by observing the percentage of mitochondrial matrix aggregation. The aggregate JC-1 (red fluorescence) was determined at the emission wavelength of 590 nm, and the monomeric JC-1 (green fluorescence) monitored at 529 nm.
Apoptosis assay
The numbers of apoptotic cells were measured by AnnexinV/PI assay kit (Roche Applied Science, Indianapolis, IN, USA) according to the manufacture’s instruction. To do it, H9c2 cells were washed and then harvested after treatment with 10 and 50 µM of compounds A and B. Doxorubicin was used as a positive control. Next, cells were stained using 100 μl of Annexin V-FLUOS labeling solution containing 2 μl annexin V-FLUOS labeling agent, 2 μl PI solution and 1 ml incubation buffer. Cells were then incubated for 15 minutes at 37ºC and subjected to flow cytometry. The percentages of viable (AnnexinV−/PI−), early apoptotic (AnnexinV+/PI−), late apoptotic (AnnexinV+/PI+) and necrotic (AnnexinV−/PI +) cells were finally analyzed.
Statistical analysis
At least three biological replicates were considered for all experiments and the data were expressed as mean ± SEM. To compare the differences between multiple parameters, one-way ANOVA followed by the Tukey’s post test was applied using GraphPad Prism6.0 Software. A p value lower than 0.05 was considered as significant.