Tetrahydrobiopterin enhances apoptotic PC12 cell death following withdrawal of trophic support.

(6R)-Tetrahydro-l-biopterin (BH(4)) is the rate-limiting cofactor in the production of catecholamine and indoleamine neurotransmitters and is also essential for the synthesis of nitric oxide by nitric-oxide synthase. We have previously reported that BH(4) administration induces PC12 cell proliferation and that nerve growth factor- or epidermal growth factor-induced PC12 cell proliferation requires the elevation of intracellular BH(4) levels. We show here that BH(4) accelerates apoptosis in undifferentiated PC12 cells deprived of serum and in differentiated neuron-like PC12 cells after nerve growth factor withdrawal.

Vasoactive intestinal peptide induces both tyrosine hydroxylase activity and tetrahydrobiopterin biosynthesis in PC12 cells.

Vasoactive intestinal peptide plays an important role in the trans-synaptic activation of tyrosine hydroxylase in sympathoadrenal tissues in response to physiological stress. Since tyrosine hydroxylase is thought to be subsaturated with its cofactor, tetrahydrobiopterin, we tested the hypothesis that up-regulation of tyrosine hydroxylase gene expression following vasoactive intestinal peptide treatment is accompanied by a concomitant elevation of intracellular tetrahydrobiopterin biosynthesis. We also investigated the second messenger systems involved in vasoactive intestinal peptide's effects on tetrahydrobiopterin metabolism.

Tetrahydrobiopterin as a mediator of PC12 cell proliferation induced by EGF and NGF.

Epidermal growth factor and nerve growth factor increased the proliferation of rat phaeochromocytoma PC12 cells through obligatory elevation of intracellular (6R)-tetrahydrobiopterin (BH4). Epidermal growth factor and nerve growth factor increased intracellular BH4 by inducing GTP-cyclohydrolase, the rate-limiting enzyme in BH4 biosynthesis. Specific inhibitors of BH4 biosynthesis prevented growth factor-induced increases in BH4 levels and proliferation.