6R-Tetrahydrobiopterin induces dopamine synthesis in a human neuroblastoma cell line, LA-N-1. A cellular model of DOPA-responsive dystonia.

Dopa-responsive dystonia (DRD) is an extrapyramidal disorder caused by deficit of 5,6,7,8-tetrahydrobiopterin (BH4), cofactor for tyrosine hydroxylase (TH). In these patients the nigrostriatal dopaminergic neurons normally express TH and the cellular machinery for the dopamine uptake. LA-N-1 is a human neuroblastoma cell line expressing tyrosine hydroxylase. Here we show that LA-N-1 cells are able to take up exogenous dopamine (DA) by an high-affinity mechanism; significant amounts of serotonin and its metabolite 5HIAA, but neither DA nor its metabolites, DOPAC and HVA, could be measured in the cell culture homogenate. 5,6,7,8-Tetrahydrobiopterin, cofactor for both tyrosine and tryptophan hydroxylases, is able to activate dopamine synthesis and also decreases the content of 5HIAA by 50%, indicating that LA-N-1 might be a useful model for studying dopamine-serotonin interaction in cultured cells and the neuronal mechanism of DRD.