Signal Transduction of Improving Effects of Ibudilast on Methamphetamine Induced Cell Death

Objective: Interaction of methamphetamine and sigma (σ) receptors lead to up-regulation and activation of these receptors. The σ receptors induced apoptosis in some parts of the brain by increasing calcium, dopamine, ROS, mitochondrial pores and caspase activity. Ibudilast is a phosphodiesterase inhibitor and anti-inflammatory drug, which can decrease the inflammatory cytokines. Also, it has a neuroprotective effect. It seems that ibudilast can reduce the methamphetamine-induced cell death due to inhibition of σ receptors. Materials and Methods: There were seven treatments including; control: culture medium, Treatment 1: 1mM methamphetamine, Treatment 2: 1mM methamphetamine and 1nM ibudilast, Treatment 3: 1mM methamphetamine and 10nM ibudilast, Treatment 4: 1mM methamphetamine and 100nM ibudilast, Treatment 5: 1mM methamphetamine and 1uM ibudilast, Treatment 6: 1mM methamphetamine and 10uM ibudilast, and Treatment 7: 1mM methamphetamine and 100uM ibudilast. Finally, for inhibition of PKA, CREB, IP3 receptor, NMDA receptor, Sigma receptor antagonist, sigma receptor agonist, cells were preincubated with adding H89 dihydrochloride, 666-15, Heparin, Ketamine, BMY 14802, and Pentazocine. MTT and LDH tests were performed for cell viability and cytotoxicity measurement, respectively. In continuing, the caspase activity colorimetric assay kit used for caspase 3 activity diagnosis. Rhodamine-123 performed to detection of mitochondrial membrane potential. TUNEL test used to DNA fragmentation and apoptosis, Fura-2 used to Measurement of (Ca2+) ic and (Ca2+) m, and fluorescence microscope used to Measurement of antioxidant enzyme activities. Results: Ibudilast increased the cell viability and the rhodamine-123 absorbance in methamphetamin-treated PC12 cells. It reduced cell cytotoxicity, caspase 3 activity, ic and m Ca2+ concentration, (OH) generation and DNA fragmentation in all concentrations of 1 nM t0 100 μM (p<0.05) by the optimal concentration of 100 μM, between our tested treatments. Conclusion: Ibudilast as a phosphodiesterase inhibitor can reduce the methamphetamine-induced cell death due to inhibition of σ receptors through cAMP production.