Inhibition of protein kinase (PK) Cδ attenuates methamphetamine-induced dopaminergic toxicity via upregulation of phosphorylation of tyrosine hydroxylase at Ser⁴⁰ by modulation of protein phosphatase 2A and PKA

Recently, we proposed that inhibition of protein kinase (PK) Cδ may be a useful target for protection against methamphetamine (MA)-induced dopaminergic toxicity. We demonstrated that treatment with MA resulted in a significant decrease in phosphorylation of tyrosine hydroxylase (TH) at Ser⁴⁰ in the striatum, but not in the phosphorylation of TH at Ser³¹. In the present study, treatment with rottlerin (1.5 or 3.0 μg, i.c.v, once a day for 5 days), a PKCδ inhibitor, or a PKCδ antisense oligonucleotide (ASO; 2.5 μg/μl, i.c.v., 3 times) significantly attenuated MA-induced reductions in the phosphorylation of TH at Ser⁴⁰ and in the expression of PKA in the striatum of mice. This attenuation was significantly counteracted by H89 (10 or 30 ng, i.c.v., 1 h after the last MA administration), a PKA inhibitor. Treatment with rottlerin or ASO significantly attenuated the MA-induced increase in protein phosphatase (PP) 2A activity. FTY720 (1 or 5 mg/kg, i.p., 1 h after the last MA administration), a PP2A activator, significantly reversed the recovery in TH phosphorylation mediated by inhibition of PKCδ after MA treatment. Both H89 and FTY720 counteracted the recovery of MA-induced behavioural impairments induced by PKCδ inhibition. The effects, mediated by rottlerin or ASO in MA-treated wild-type mice were comparable with those in MA-treated PKCδ^-/- mice. However, neither inhibition of the mitogen-activated protein kinase subfamily (extracellular signal-regulated kinase, c-Jun N-terminal kinase, p38) nor inhibition of calcium calmodulin kinase II significantly altered PKCδ inhibition-mediated attenuation of MA-induced impairment of TH phosphorylation. The results suggest that genetic or pharmacological inhibition of PKCδ requires modulation of PKA expression and/or PP2A activity to attenuate the impairment of TH phosphorylation at Ser⁴⁰ and behavioural activity induced by MA.