Phosphorylation of PKCdelta participates in the toxicity of 6-hydroxydopamine on dopaminergic neuroblastoma cell

Abstract

To investigate the role of phosphorylation of protein kinase C (PKC) delta in the toxicity of 6-hydroxydopamine (6-OHDA) to the death of dopaminergic neurons. Human neuroblastoma cells of the line SH-SY5Y were cultured 6-OHDA of the concentrations of 0, 50, 100, 200, and 400 micromol/L was added to observe its toxicity. Rottlerin (PKCdelta inhibitor, 2 micromol/L), bisindolylmaleimide (Bis, general PKC inhibitor, 10 nmol/L), Gö6976 (calcium-dependent PKC inhibitor, 5 nmol/L), and phobol-12-myristate-13-acetate (PMA, PKC activator, 100 nmol/L) were added into the culture fluid of another SH-SY5Y cells respectively, and then (1) culture fluid of equal volume was added for 18 h so as to observe there effects on the survival of the SH-SY5Y cells, or (2) 100 micromol/L 6-OHDA was added to observe the effects of intervention on PKC on the survival of the SH-SY5Y cells by using MTT assay. Cell lysis solution with phosphatase inhibitor was used to lyse the culture cells to extract plasma protein. Western blotting was used to detect the expression of phosphorylated PKCdelta. MTT assay showed that all different concentrations (50 - 400 micromol/L) of 6-OHDA significantly and dose-dependently caused cell death with an EC50 of 92 micromol/L. Pretreatment with rottlerin and Bis alone did not influence the survival of the cells significantly,. However, the survival rate of the cells pretreated by Gö6976 alone was 92.3% +/- 3.2% that of the control group (P < 0.01), and the survival rate of the cells pretreated by PMA was 49.5% +/- 1.0% that of the control group (P < 0.01) Pretreatment of rottlerin decreased the death rate of the cells treated with 6-OHDA to 30.4% +/- 1.6% and conferred significant protection against 6-OHDA neurotoxicity by 57% +/- 6% compared to that of the cells treated by 6-OHDA alone (P < 0.01). However, Bis and Gö6976 did not affect the 6-OHDA-induced cell damage. Pretreatment of PMA increased the death rate of the cells treated with 6-OHDA to 67.1% +/- 2.2% and significantly aggravated 6-OHDA-induced cell toxicity by 66% +/- 9% (P < 0.01). Western blotting showed that 6-OHDA administration increased the expression of phosphorylated PKCdelta, pretreatment with Rottlerin inhibited such increase, PMA promoted such increase, and Bis and Gö6976 did not influence such increase. Inhibition of PKCdelta phosphorylation with rottlerin ameliorates the neurotoxicity evoked by 6-OHDA, and activation of PKCdelta phosphorylation by PMA aggravates neurotoxicity, which implicating that this kinase participates in the 6-OHDA-induced neurotoxicity and Parkinsonian neurodegeneration.