The role of H2O2 in the platelet-derived growth factor-induced transcription of the γ-glutamylcysteine synthetase heavy subunit

Abstract.

This study demonstrates that platelet-derived growth factor (PDGF) increases transcription of the γ-glutamylcysteine synthetase (GCS) heavy subunit (GCS-HS) in NIH 3T3 fibroblasts via H₂O₂ and activation of protein kinase C (PKC). The data obtained using catalase, H₂O₂, phorbol-12-myristate 13-acetate (PMA) or a specific inhibitor of PKC demonstrate the possibility of a PDGF up-regulation pathway of GCS synthesis. Moreover, since PDGF mitogenic activity takes place through PKC activation and sphingosine-1-phosphate (S1P) production, the involvement of sphingosine kinase activity in the PDGF effect was also investigated. No clear direct relationship emerged between S1P production and any PDGF- or H₂O₂-induced increase in the GCS-HS mRNA level. However, for the first time, in SIP-stimulated NIH 3T3 cells, increased levels of GCS-HS mRNA were shown to be related to increases in the reduced glutathione synthesis rate similar to those obtained after PMA and PDGF stimulation.