Induction of ferritin and heat shock proteins by prostaglandin A1 in human monocytes -: Evidence for transcriptional and post-transcriptional regulation

Prostaglandins of the A type (PGA) exert a cytoprotective activity during hyperthermia and virus infection. This effect is associated with induction of heat shock proteins (HSP) in mammalian cells. We now report that, in human monocytes, PGA(1) is able to induce the synthesis of the iron-binding, redox-regulated protein -ferritin. L-chain ferritin induction is consequent to a substantial increase in the accumulation of L-chain ferritin transcripts in PGA(1)-treated cells, whereas H-chain ferritin is regulated post-transcriptionally, consequently to reduction of iron-regulatory protein binding to iron-responsive elements in ferritin mRNA. Ferritin induction is specific for cyclopentenone prostaglandins (PGA(1), PGA(2), PGJ(2), Delta(12)-PGJ(2)), whereas other arachidonic acid (AA) metabolites have no effect. In human monocytes, PGA(1) also induces heat shock gene transcription via heat shock factor activation, as well as the synthesis of the oxidative-stress protein heme oxygenase (HOS). Differently from HSP, the induction of ferritin by PGA(1) is specific for monocytes. Monocytes/macrophages play a pivotal role in inflammation, controlling iron metabolism and releasing a variety of mediators, including proinflammatory reactive oxygen species (ROS), cytokines and AA metabolites. As ferritin, together with hsp70 and WO, plays a key role in protection from oxidant damage, these results suggest that PGA(1) may have cytoprotective activity also during oxidative injury.