Catalponol enhances dopamine biosynthesis and protects against L-DOPA-induced cytotoxicity in PC12 cells.

The effects of catalponol (1) on dopamine biosynthesis and L-DOPA-induced cytotoxicity in PC12 cells were investigated. Catalponol at concentration ranges of 1-5 microM increased the intracellular levels of dopamine at 12-48 h. Catalponol at concentrations of up to 10 microM did not alter cell viability. Tyrosine hydroxylase (TH) activity was enhanced by 1 at 3 microM in a time-dependent manner, but aromatic L-amino acid decarboxylase activity was not. Catalponol also increased the intracellular levels of cyclic AMP and TH phosphorylation. In addition, catalponol at 3 microM associated with L-DOPA (20-50 microM) further enhanced the increases in dopamine levels induced by L-DOPA (50-100 microM) at 24 h. Catalponol at 2-5 microM inhibited L-DOPA (100-200 microM)-induced cytotoxicity at 48 h. These results suggest that 1 enhanced dopamine biosynthesis by inducing TH activity and protected against L-DOPA-induced cytotoxicity in PC12 cells, which was mediated by the increased levels of cyclic AMP.

Effects of catalpalactone on dopamine biosynthesis and L-DOPA-induced cytotoxicity in PC12 cells.

The effects of catalpalactone on dopamine biosynthesis and L-DOPA-induced cytotoxicity in PC12 cells were investigated. Catalpalactone at 5-30µM decreased intracellular dopamine content with the IC(50) value of 22.1µM. Catalpalactone at 5-20µM, but not 30µM, did not alter cell viability. Catalpalactone at 20µM inhibited tyrosine hydroxylase (TH) and aromatic-l-amino acid decarboxylase (AADC) activities. Catalpalactone also decreased cyclic AMP levels and inhibited TH phosphorylation. In addition, catalpalactone at 20µM reduced the increases in dopamine levels induced by L-DOPA (20-50µM). Catalpalactone (5-30µM) associated with L-DOPA (50-100µM) enhanced L-DOPA-induced cytotoxicity at 48h, which was prevented by N-acetyl-l-cysteine. These results suggest that catalpalactone inhibited dopamine biosynthesis by reducing TH and AADC activities and enhanced L-DOPA-induced cytotoxiciy in PC12 cells.

Effects of (1R,9S)-beta-hydrastine on intracellular calcium concentration in PC12 cells.

(1R,9S)-beta-hydrastine (BHS) decreases the basal intracellular Ca(2+) concentration ([Ca(2+)](i)) in PC12 cells.(5) This study examined the effects of (1R,9S)-BHS on [Ca(2+)](i) in PC12 cells. (1R,9S)-BHS at 10-100 microM in combination with a high extracellular K+ level (56 mM) inhibited the release of dopamine in a concentration-dependent manner with an IC(50) value of 66.5 microM. BHS at 100 microM inhibited the sustained increase in [Ca(2+)](i) induced by a high K+ level (56 mM), and had an inhibitory effect on the 2 microM nifedipine-induced blockage of the K+ -stimulated sustained increase in [Ca(2+)](i). In addition, (1R,9S)-BHS at 100 microM prevented the rapid and sustained increase in [Ca(2+)](i) elicited by 20 mM caffeine, but did not have an effect on the increase induced by 1 microM thapsigargin, in the presence of external Ca(2+). These results suggest that the active sites of (1R,9S)-BHS are mainly L-type Ca(2+) channels and caffeine-sensitive Ca(2+)-permeable channels in PC12 cells.